Archive for the ‘Hematology’ Category

Targeting hematopoietic stem cells

Larry H. Bernstein, MD, FCAP, Curator



New technology uncovered the stem cell niche in the bone marrow

HSCs, Stem cells, hematopoiesis

Hematopoietic stem cells (HSCs) are so rare that it’s difficult to comprehensively localize dividing and non-dividing HSCs. Thus, there has controversy about their specific location in the bone marrow. A recent Nature publication reported that the HSCs resides mainly in perisinusoidal niches through out the bone marrow and there are no spatially distinct niches for dividing and non-dividing blood-forming stem cells. This group of researchers at UT Southwestern Medical Center started the generation of a GFP knock-in for the gene Ctnnal1, a generic marker for HSCs in mice (α-catulinGFP mice) and confirmed that α-catulin-GFP+c-kit+ cells represent blood-forming HSCs by showing that α-catulin-GFP+c-kit+ cells gave long term multi-lineage reconstitution of irradiated mice. Using a tissue-clearing technique and deep confocal imaging, they were able to image thousands of α-catulin-GFP+c-kit+ cells and see their relation to other cells. This publication improved the understanding of the microenvironment of HSCs in the bone marrow, which would significantly improve the safety and effectiveness of bone marrow transplantation.

Melih Acar, etc. (October 2015) Deep imaging of bone marrow shows non-dividing stem cells are mainly perisinusoidal. Nature


Deep imaging of bone marrow shows non-dividing stem cells are mainly perisinusoidal

AcarKS. KocherlakotaMM. MurphyJG. PeyerH OguroCN. InraC JaiyeolaZ ZhaoK Luby-Phelps & Sean J. Morrison
Nature526,126–130(01 October 2015)


Haematopoietic stem cells (HSCs) reside in a perivascular niche but the specific location of this niche remains controversial1. HSCs are rare and few can be found in thin tissue sections2, 3 or upon live imaging4, making it difficult to comprehensively localize dividing and non-dividing HSCs. Here, using a green fluorescent protein (GFP) knock-in for the gene Ctnnal1 in mice (hereafter denoted as αcatulinGFP), we discover that αcatulinGFP is expressed by only 0.02% of bone marrow haematopoietic cells, including almost all HSCs. We find that approximately 30% of αcatulin−GFP+c-kit+ cells give long-term multilineage reconstitution of irradiated mice, indicating thatαcatulin−GFP+c-kit+ cells are comparable in HSC purity to cells obtained using the best markers currently available. We optically cleared the bone marrow to perform deep confocal imaging, allowing us to image thousands of αcatulin–GFP+c-kit+ cells and to digitally reconstruct large segments of bone marrow. The distribution of αcatulin–GFP+c-kit+ cells indicated that HSCs were more common in central marrow than near bone surfaces, and in the diaphysis relative to the metaphysis. Nearly all HSCs contacted leptin receptor positive (Lepr+) and Cxcl12high niche cells, and approximately 85% of HSCs were within 10 μm of a sinusoidal blood vessel. Most HSCs, both dividing (Ki-67+) and non-dividing (Ki-67), were distant from arterioles, transition zone vessels, and bone surfaces. Dividing and non-dividing HSCs thus reside mainly in perisinusoidal niches with Lepr+Cxcl12high cells throughout the bone marrow.


Figure 1: Deep imaging of αcatulin−GFP+ HSCs in digitally reconstructed bone marrow.close


Deep imaging of [agr]-catulin-GFP+ HSCs in digitally reconstructed bone marrow.

a, Only 0.021 ± 0.006% of αcatulinGFP/+ bone marrow cells were GFP+ (n = 14 mice in 11 independent experiments). b, Nearly allαcatulin−GFP+c-kit+ bone marrow cells were CD150+CD48 (n = 9 mice in 3 independent experiments;


Extended Data Figure 3: αcatulin−GFP expression among haematopoietic cells is highly restricted to HSCs.


[agr]-catulin-GFP expression among haematopoietic cells is highly restricted to HSCs.


a, The frequency of αcatulin−GFP+ bone marrow cells in negative control αcatulin+/+ (WT) mice and α-catulinGFP/+ mice (n = 14 mice per genotype in 11 independent experiments). In all cases in this figure, percentages refer to the frequency of each population as a percentage of WBM cells. b, αcatulin−GFP+c-kit+ cells from Fig. 1b are shown (blue dots) along with all other bone marrow cells in the same sample (red dots). c, CD150+CD48LSK HSCs express αcatulin−GFP but CD150CD48LSK MPPs do not (n = 17 mice in 12 independent experiments). A minority of the αcatulin−GFP+c-kit+ cells had high forward scatter, lacked reconstituting potential, and were gated out when isolating HSCs by flow cytometry and when identifying HSCs during imaging (see Extended Data Fig. 5for further explanation). d, Linc-kitlowSca-1lowCD127+CD135+ common lymphoid progenitors (CLPs), Linc-kit+Sca-1CD34+CD16/32 common myeloid progenitors (CMPs), Linc-kit+Sca-1CD34+CD16/32+ granulocyte-macrophage progenitors (GMPs), and Linc-kit+Sca-1CD34CD16/32 megakaryocyte-erythroid progenitors (MEPs) did not express αcatulin−GFP. αcatulinGFP/+ and control cell populations had similar levels of background GFP signals that accounted for fewer than 1% of the cells in each population (n = 9 mice per genotype in 2 independent experiments).


Extended Data Figure 7: HSC density is higher in the diaphysis as compared to the metaphysis.

HSC density is higher in the diaphysis as compared to the metaphysis.

a, Schematic of a femur showing the separation of epiphysis/metaphysis from diaphysis. We divided metaphysis from diaphysis at the point where the central sinus branched (see red line in panels a, f,and i). This is also the point at wh…



Extended Data Figure 9: Bone marrow blood vessel types can be distinguished based on vessel diameter, continuity of basal lamina, morphology, and position; and no difference in the distribution of HSCs in the bone marrow of male and female mice was detected.close

Bone marrow blood vessel types can be distinguished based on vessel diameter, continuity of basal lamina, morphology, and position; and no difference in the distribution of HSCs in the bone marrow of male and female mice was detected.

a, b, Schematic (a) and properties (b) of blood vessels in the bone marrow. Blood enters the marrow through arterioles that branch as they become smaller in diameter and approach the endosteum, where they connect to smaller diameter tra…

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Immunopathogenesis Advances in Diabetes and Lymphomas

Larry H Bernstein, MD, FCAP, Curator




 Science team says they’ve taken another step toward a potential cure for diabetes

Wednesday, January 27, 2016 | By John Carroll
Building on years of work on developing new insulin-producing cells that could one day control glucose levels and cure diabetes, a group of investigators led by scientists at MIT and Boston Children’s Hospital say they’ve developed a promising new gel capsule that protected the cells from an immune system assault.

Dr. Jose Oberholzer, a professor of bioengineering at the University of Illinois at Chicago, tested a variety of chemically modified alginate hydrogel spheres to see which ones would be best at protecting the islet cells created from human stem cells.

The team concluded that 1.5-millimeter spheres of triazole-thiomorphine dioxide (TMTD) alginate were best at protecting the cells and allowing insulin to seep out without spurring an errant immune system attack or the development of scar tissue–two key threats to making this work in humans.

They maintained healthy glucose levels in the rodents for 174 days, the equivalent to decades for humans.

“While this is a very promising step towards an eventual cure for diabetes, a lot more testing is needed to ensure that the islet cells don’t de-differentiate back toward their stem-cell states or become cancerous,” said Oberholzer.

Millions of diabetics have effectively controlled the chronic disease with existing therapies, but there’s still a huge unmet medical need to consider. While diabetes companies like Novo ($NVO) like to cite the fact that a third of diabetics have the disease under control, a third are on meds but don’t control it well and a third haven’t been diagnosed. An actual cure for the disease, which has been growing by leaps and bounds all over the world, would be revolutionary.

Their study was published in Nature Medicine.

– here’s the release
– get the journal abstract


Long-term glycemic control using polymer-encapsulated human stem cell–derived beta cells in immune-competent mice

Arturo J Vegas, Omid Veiseh, Mads Gürtler,…, Robert Langer & Daniel G Anderson

Nature Medicine (2016)   http://dx.doi.org:/10.1038/nm.4030

The transplantation of glucose-responsive, insulin-producing cells offers the potential for restoring glycemic control in individuals with diabetes1. Pancreas transplantation and the infusion of cadaveric islets are currently implemented clinically2, but these approaches are limited by the adverse effects of immunosuppressive therapy over the lifetime of the recipient and the limited supply of donor tissue3. The latter concern may be addressed by recently described glucose-responsive mature beta cells that are derived from human embryonic stem cells (referred to as SC-β cells), which may represent an unlimited source of human cells for pancreas replacement therapy4. Strategies to address the immunosuppression concerns include immunoisolation of insulin-producing cells with porous biomaterials that function as an immune barrier56. However, clinical implementation has been challenging because of host immune responses to the implant materials7. Here we report the first long-term glycemic correction of a diabetic, immunocompetent animal model using human SC-β cells. SC-β cells were encapsulated with alginate derivatives capable of mitigating foreign-body responses in vivo and implanted into the intraperitoneal space of C57BL/6J mice treated with streptozotocin, which is an animal model for chemically induced type 1 diabetes. These implants induced glycemic correction without any immunosuppression until their removal at 174 d after implantation. Human C-peptide concentrations and in vivo glucose responsiveness demonstrated therapeutically relevant glycemic control. Implants retrieved after 174 d contained viable insulin-producing cells.

Subject terms: Regenerative medicine  Type 1 diabetes

Figure 1: SC-β cells encapsulated with TMTD alginate sustain normoglycemia in STZ-treated immune-competent C57BL/6J mice.close

(a) Top, schematic representation of the last three stages of differentiation of human embryonic stem cells to SC-β cells. Stage 4 cells (pancreatic progenitors 2) co-express pancreatic and duodenal homeobox 1 (PDX-1) and NK6 homeobox 1…


Potential Cure for Diabetes Discovered  
http://www.rdmag.com/news/2016/01/potential-cure-diabetes-discovered   01/27/2016

Two new scientific papers published on Monday demonstrated tools that could result in potential therapies for patients diagnosed with type 1 diabetes, a condition in which the immune system limits the production of insulin, typically in adolescents.  See —

Bubble Technique Could Create Type 1 Diabetes Therapy


Two new scientific papers published on Monday demonstrated tools that could result in potential therapies for patients diagnosed with type 1 diabetes, a condition in which the immune system limits the production of insulin, typically in adolescents.

Previous treatments for this disease have involved injecting beta cells from dead donors into patients to help their pancreas generate healthy-insulin cells, writes STAT. However, this method has resulted in the immune system targeting these new cells as “foreign” so transplant recipients have had to take immune-suppressing medications for the rest of their lives.

The first paper published in the journal Nature Biotechnology explained how scientists analyzed a seaweed extract called alginate to gauge its effectiveness in supporting the flow of sugar and insulin between cells and the body. An estimated 774 variations were tested in mice and monkeys in which results indicated only a handful could reduce the body’s response to foreign invaders, explains STAT.

The other paper in the journal Nature Medicine detailed a process where scientists developed small capsules infused with alginate and embryonic stem cells. A six-month observation period revealed this “protective bubble” technique “began to produce insulin in response to blood glucose levels” after transplantation in mice subjects with a condition similar to type 1 diabetes, reports Gizmodo.

Essentially, this cured the mice of their diabetes, and the beta cells worked as well as the body’s own cells, according to the researchers. Human trials could still be a few years away, but this experiment could yield a safer alternative to insulin injections.


Combinatorial hydrogel library enables identification of materials that mitigate the foreign body response in primates

Arturo J Vegas, Omid Veiseh, Joshua C Doloff, et al.

Nature Biotechnology (2016)    http://dx.doi.org:/10.1038/nbt.3462

The foreign body response is an immune-mediated reaction that can lead to the failure of implanted medical devices and discomfort for the recipient1, 2, 3, 4, 5, 6. There is a critical need for biomaterials that overcome this key challenge in the development of medical devices. Here we use a combinatorial approach for covalent chemical modification to generate a large library of variants of one of the most widely used hydrogel biomaterials, alginate. We evaluated the materials in vivo and identified three triazole-containing analogs that substantially reduce foreign body reactions in both rodents and, for at least 6 months, in non-human primates. The distribution of the triazole modification creates a unique hydrogel surface that inhibits recognition by macrophages and fibrous deposition. In addition to the utility of the compounds reported here, our approach may enable the discovery of other materials that mitigate the foreign body response.


Video 1: Intravital imaging of 300 μm SLG20 microcapsules.

Video 2: Intravital imaging of 300 μm Z2-Y12 microcapsules.

Video 3: NHP Laparoscopic procedure for the retrieval of Z2-Y12 spheres.


Clinical Focus on Follicular Lymphoma: CAR T-Cells Active in Relapsed Blood Cancers

MedPage Today

CAR T-Cells Active in Relapsed Blood Cancers

Complete responses in half of patients

by Charles Bankhead

Patients with relapsed and refractory B-cell malignancies have responded to treatment with modified T-cells added to conventional chemotherapy, data from an ongoing Swedish study showed.

Six of the first 11 evaluable patients achieved complete responses with increasing doses of chimeric antigen receptor (CAR)-modified T-cells that target the CD19 antigen, although two subsequently relapsed.

Five of the six responding patients received preconditioning chemotherapy the day before CAR T-cell infusion, in addition to chemotherapy administered up to 90 days before T-cell infusion to reduce tumor-cell burden. The remaining five patients received only the earlier chemotherapy, according to a presentation at the inaugural International Cancer Immunotherapy Conference in New York City.

“The complete responses in lymphoma patients despite the fact that they received only low doses of preconditioning compared with other published data surprised us,” Angelica Loskog, PhD, of Uppsala University in Sweden, said in a statement. “The strategy of both providing tumor-reductive chemotherapy for weeks prior to CAR T-cell infusion combined with preconditioning just before CAR T-cell infusion seems to offer promise.

CAR T-cells have demonstrated activity in a variety of studies involving patients with B-cell malignancies. Much of the work has focused on patients with leukemia, including trials in the U.S. B-cell lymphomas have proven more difficult to treat with CAR T-cells because the diseases are associated with higher concentration of immunosuppressive cells that can inhibit CAR T-cell activity, said Loskog. Moreover, blood-vessel abnormalities and accumulation of fibrotic tissue can hinder tumor penetration by therapeutic T-cells.

Each laboratory has its own process for modifying T-cells. Loskog and colleagues in Sweden and at Baylor College of Medicine in Houston have developed third-generation CAR T-cells that contain signaling domains for CD28 and 4-1BB, which act as co-stimulatory molecules. In preclinical models, third-generation CAR T-cells have demonstrated increased activation and proliferation in response to antigen challenge. Additionally, they have chosen to experiment with tumor burden-reducing chemotherapy, a preconditioning chemotherapy to counter the higher immunosuppressive cell count in lymphoma patients.

Loskog reported details of an ongoing phase I/IIa clinical trial involving patients with relapsed or refractory CD19-positive B-cell malignancies. Altogether, investigators have treated 12 patients with increasing doses (2 x 107 to 2 x 108 cells/m2) of CAR T-cells. One patient (with mixed follicular/Burkitt lymphoma) has yet to be evaluated for response. The remaining 11 included three patients with diffuse large B-cell lymphoma (DLBCL), one with follicular lymphoma transformed to DLBCL, two with chronic lymphocytic leukemia, two with mantle cell lymphoma, and three with acute lymphoblastic leukemia.

All of the patients with lymphoma received standard tumor cell-reducing chemotherapy, beginning 3 to 90 days before administration of CAR T-cells. Beginning with the sixth patient in the cohort, patients also received preconditioning chemotherapy (cyclophosphamide/fludarabine) 1 to 2 days before T-cell infusion to reduce the number and activity of immunosuppressive cells.

Cytokine release syndrome is a common effect of CAR T-cell therapy and occurred in several patients treated. In general, the syndrome has been manageable and has not interfered with treatment or response to the modified T-cells.

On the basis of the data produced thus far, the investigators have proceeded with patient evaluation and enrollment. They have already begun cell production for the next patient that will be treated with autologous CAR T-cells.

Although laboratories have their own cell production techniques, the treatment strategy has broad applicability to the treatment of B-cell malignancies, said Loskog.

“The results using different CARs and different techniques for manufacturing them is very similar in the clinic, in terms of initial complete response,” she told MedPage Today. “By using 4-1BB as a co-stimulator in the CAR intracellular region, it seems possible to achieve long-term complete responses in some patients. However, preconditioning of the patients with chemotherapy to reduce the regulatory immune cells seems crucial for effect.”

In an effort to manage the effect of patients’ immunosuppressive cells, the investigators have begun studying each the immune profile before and after treatment. Preliminary results suggest that the population of immunosuppressive cells increases over time, which has the potential to interfere with CAR T-cell responses.

“Especially for lymphoma, it may be crucial to deplete such cells prior to CAR infusion,” said Loskog. “It may even be necessary with supportive treatment for some time after CAR T-cell infusion. A supportive treatment needs to specifically regulate the suppressive cells while sparing the effect of CARs.”

The immunotherapy conference is jointly sponsored by the American Association for Cancer Research, the Cancer Research Institute, the Association for Cancer Immunotherapy, and the European Academy of Tumor Immunology.


PET-CT Best for FL Response Assessment

PET-CT associated with better progression-free and overall survival rates in follicular lymphoma.

Kay Jackson

PET-CT (PET) rather than contrast-enhanced CT scanning should be considered the new gold standard for response assessment after first-line rituximab therapy for high-tumor burden follicular lymphoma (FL), a pooled analysis of a central review in three multicenter studies indicated.

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Monitoring AML with “cell specific” blood test

Larry H. Bernstein, MD, FCAP, Curator



‘Liquid Biopsy’ Blood Test Replaces Painful Bone Marrow Biopsy for Leukemia

Mon, 01/11/2016  by BioFluidica, Inc.  http://www.mdtmag.com/news/2016/01/liquid-biopsy-blood-test-replaces-painful-bone-marrow-biopsy-leukemia


BioFluidica, Inc. has released the clinical data for minimal residual disease detection in Acute Myeloid Leukemia (AML) patients using circulating leukemic cells selected from blood. The data was published in the peer reviewed journal the Analyst (141 (2016) 640). AML is a rapidly developing leukemic disease with ~20,000 cases reported in 2015 with a 5-year survival rate of only 25%.

The goal of this study was to detect early stages of disease relapse following stem cell transplantation. Currently AML relapse is detected using bone marrow biopsy samples that are painful for the patient and using existing commercial tests, limits the frequency of testing and thus resulting in poor outcomes for AML patients. The paper describes that using BioFluidica’s analytical technology relapse could be detected nearly 2 months earlier than conventional tests. In addition, test frequency could be significantly increased using BioFluidica’s technology compared to tests requiring bone marrow biopsies.

Professor Steven A. Soper, the scientific founder of BioFluidica and co-author of the paper with Dr. Paul Armistead, a hematologist, both at the University of North Carolina states that “the use of a blood test compared to a bone marrow biopsy would be a tremendous advancement in diagnostic capability that can dramatically improve the survival rate of patients with AML.”

BioFluidica is developing innovative technologies for the isolation and analysis of rare, circulating biomarkers in the blood. The company’s first platform has the capacity to isolate circulating tumor cells, exosomes and cfDNA from the blood with unprecedented recovery and purity. The technology is based on patented microfluidics designs which has been clinically validated for 6 different cancer types including Colorectal, Pancreatic Ductal Adenocarcinoma, Ovarian, Breast, Multiple Myeloma and AML. Additionally, stroke detection and infectious disease identification have also obtained clinical validation using the BioFluidica test. The company was cofounded by Dr. Soper who is currently a Professor in Biomedical Engineering and Chemistry at the University of North Carolina at Chapel Hill (UNC-CH). He is also Director of a new center on the UNC-CH campus, Center for BioModular Multi-scale Systems for Precision Medicine, focused on developing new tools for the molecular analysis of circulating biomarkers.

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Larry H. Bernstein, MD, FCAP, Curator



Hematopoietic Stem Cells Use a Simple Heirarchy





These papers challenge this model by arguing that the CMP does not exist. Let me say that again – the CMP, a cell that has been identified several times in mouse and human bone marrow isolates, does not exist. When CMPs were identified from mouse and human none marrow extracts, they were isolated by means of flow cytometry, which is a very powerful technique, but relies on the assumption that the cell type you want to isolate is represented by the cell surface protein you have chosen to use for its isolation. Once the presumptive CMP was isolated, it could recapitulate the myeloid lineage when implanted into the bone marrow of laboratory animals and it could also produce all the myeloid cells in cell culture. Sounds convincing doesn’t it?

In a paper in Science magazine, Faiyaz Notta and colleagues from the University of Toronto beg to differ. By using a battery of antibodies to particular cell surface molecules, Notta and others identified 11 different cell types from umbilical cord blood, bone marrow, and human fetal liver that isolates that would have traditionally been called the CMP. It turns out that the original CMP isolate was a highly heterogeneous mixture of different cell types that were all descended from the HSC, but had different developmental potencies.


Notta and others used single-cell culture assays to determine what kinds of cells these different cell types would make. Almost 3000 single-cell cultures later, it was clear that the majority of the cultured cells were unipotent (could differentiate into only one cell type) rather than multipotent. In fact, the cell that makes platelets, the megakarocyte, seems to derive directly from the MPP, which jives with the identification of megakarocyte progenitors within the HSC compartment of bone marrow that make platelets “speedy quick” in response to stress (see R. Yamamoto et al., Cell 154, 1112 (2013); S. Haas, Cell Stem Cell 17, 422 (2015)).

Another paper in the journal Cell by Paul and others from the Weizmann Institute of Science, Rehovot, Israel examined over 2700 mouse CMPs and subjected these cells to gene expression analyses (so-called single-cell transriptome analysis). If the CMP is truly multipotent, then you would expect it to express genes associated with lots of different lineages, but that is not what Paul and others found. Instead, their examination of 3461 genes revealed 19 different progenitor subpopulations, and each of these was primed toward one of the seven myeloid cell fates. Once again, the presumptive CMPs looked very unipotent at the level of gene expression.

One particular subpopulation of cells had all the trappings of becoming a red blood cell and there was no indication that these cells expressed any of the megakarocyte-specific genes you would expect to find if MEPS truly existed. Once again, it looks as though unipotency is the main rule once the MPP commits to a particular cell lineage.

Thus, it looks as though either the CMP is a very short-lived state or that it does not exist in mouse and human bone marrow. Paul and others did show that cells that could differentiate into more than one cell type can appear when regulation is perturbed, which suggests that under pathological conditions, this system has a degree of plasticity that allows the body to compensate for losses of particular cell lineages.

 A model of the changes in human My-Er-Mk differentiation that occur across developmental time points. Graphical depiction of My-Er-Mk cell differentiation that encompasses the predominant lineage potential of progenitor subsets; the standard model is shown for comparison. The redefined model proposes a developmental shift in the progenitor cell architecture from the fetus, where many stem and progenitor cell types are multipotent, to the adult, where the stem cell compartment is multipotent but the progenitors are unipotent. The grayed planes represent theoretical tiers of differentiation.
A model of the changes in human My-Er-Mk differentiation that occur across developmental time points.
Graphical depiction of My-Er-Mk cell differentiation that encompasses the predominant lineage potential of progenitor subsets; the standard model is shown for comparison. The redefined model proposes a developmental shift in the progenitor cell architecture from the fetus, where many stem and progenitor cell types are multipotent, to the adult, where the stem cell compartment is multipotent but the progenitors are unipotent. The grayed planes represent theoretical tiers of differentiation.

Fetal HSCs, however, are a bird of a different feather, since they divide quickly and reside in fetal liver.  Also, these HSCs seem to produce CMPs, which is more in line with the classical model.  Does the environmental difference or fetal liver and bone marrow make the difference?  In adult bone marrow, some HSCs nestle next to blood vessels where they encounter cells that hang around blood vessels known as “pericytes.”  These pericytes sport a host of cell surface molecules that affect the proliferative status of HSCs (e.g., nestin, NG2).  What about fetal liver?  That’s not so clear – until now.

In the same issue of Science magazine, Khan and others from the Albert Einstein College of Medicine in the Bronx, New York, report that fetal liver also has pericytes that express the same cell surface molecules as the ones in bone marrow, and the removal of these cells reduces the numbers of and proliferative status of fetal liver HSCs.

Now we have a conundrum, because the same cells in bone marrow do not drive HSC proliferation, but instead drive HSC quiescence.  What gives? Khan and others showed that the fetal liver pericytes are part of an expanding and constantly remodeling blood system in the liver and this growing, dynamic environment fosters a proliferative behavior in the fetal HSCs.

When umbilical inlet is closed at birth, the liver pericytes stop expressing Nestin and NG2, which drives the HSCs from the fetal liver to the other place were such molecules are found in abundance – the bone marrow.

These models give us a better view of the inner workings of HSC differentiation.  Since HSC transplantation is one of the mainstays of leukemia and lymphoma treatment, understanding HSC biology more perfectly will certainly yield clinical pay dirt in the future.


Distinct routes of lineage development reshape the human blood hierarchy across ontogeny

In a classical view of hematopoiesis, the various blood cell lineages arise via a hierarchical scheme starting with multipotent stem cells that become increasingly restricted in their differentiation potential through oligopotent and then unipotent progenitors. We developed a cell-sorting scheme to resolve myeloid (My), erythroid (Er), and megakaryocytic (Mk) fates from single CD34+ cells and then mapped the progenitor hierarchy across human development. Fetal liver contained large numbers of distinct oligopotent progenitors with intermingled My, Er, and Mk fates. However, few oligopotent progenitor intermediates were present in the adult bone marrow. Instead, only two progenitor classes predominate, multipotent and unipotent, with Er-Mk lineages emerging from multipotent cells. The developmental shift to an adult “two-tier” hierarchy challenges current dogma and provides a revised framework to understand normal and disease states of human hematopoiesis.

Transcriptional Heterogeneity and Lineage Commitment in Myeloid Progenitors

Franziska Paul, et al.
Cell Dec 2015; Volume 163, Issue 7:1663–1677   http://dx.doi.org/10.1016/j.cell.2015.11.013
Figure thumbnail fx1
  • Transcriptionally primed single-cell subpopulations in early myeloid progenitors
  • Transcription factors and epigenetic landscapes that regulate myeloid priming
  • Mixed lineage states are not observed but appear when regulation is perturbed
  • New reference model for studying hematopoiesis at single-cell resolution



Within the bone marrow, stem cells differentiate and give rise to diverse blood cell types and functions. Currently, hematopoietic progenitors are defined using surface markers combined with functional assays that are not directly linked with in vivo differentiation potential or gene regulatory mechanisms. Here, we comprehensively map myeloid progenitor subpopulations by transcriptional sorting of single cells from the bone marrow. We describe multiple progenitor subgroups, showing unexpected transcriptional priming toward seven differentiation fates but no progenitors with a mixed state. Transcriptional differentiation is correlated with combinations of known and previously undefined transcription factors, suggesting that the process is tightly regulated. Histone maps and knockout assays are consistent with early transcriptional priming, while traditional transplantation experiments suggest that in vivo priming may still allow for plasticity given strong perturbations. These data establish a reference model and general framework for studying hematopoiesis at single-cell resolution.



Fetal liver hematopoietic stem cell niches associate with portal vessels

Jalal A. Khan, et al.   Science  08 Jan 2016; 351(6269):176-180   http://dx.doi.org:/10.1126/science.aad0084
How HSCs populate the fetal liver

Hematopoietic stem cells (HSCs) undergo dramatic expansion in the fetal liver before migrating to their definitive site in the bone marrow. Khan et al. identify portal vessel–associated Nestin+NG2+ pericytes as critical HSC niche components (see the Perspective by Cabezas-Wallscheid and Trumpp). The portal vessel niche and HSCs expand according to fractal geometries, suggesting that niche cells—rather than factors expressed by the niche—drive HSC proliferation. After birth, arterial portal vessels transform into portal veins, and lose Nestin+NG2+pericytes. When this happens, the niche is lost and HSCs migrate away from the neonatal liver.

Science, this issue p. 176; see also p. 126


Whereas the cellular basis of the hematopoietic stem cell (HSC) niche in the bone marrow has been characterized, the nature of the fetal liver niche is not yet elucidated. We show that Nestin+NG2+ pericytes associate with portal vessels, forming a niche promoting HSC expansion. Nestin+NG2+ cells and HSCs scale during development with the fractal branching patterns of portal vessels, tributaries of the umbilical vein. After closure of the umbilical inlet at birth, portal vessels undergo a transition from Neuropilin-1+Ephrin-B2+ artery to EphB4+ vein phenotype, associated with a loss of periportal Nestin+NG2+ cells and emigration of HSCs away from portal vessels. These data support a model in which HSCs are titrated against a periportal vascular niche with a fractal-like organization enabled by placental circulation.



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Monoclonal antibody treatment of Multiple Myeloma

Larry H. Bernstein, MD, FCAP, Curator









A SLAMF7-directed immunostimulatory antibody used to treat multiple myeloma.






Elotuzumab (brand name Empliciti, previously known as HuLuc63) is ahumanized monoclonal antibody used in relapsed multiple myeloma.[1] The package insert denotes its mechanism as a SLAMF7-directed (also known as CD 319) immunostimulatory antibody.[2]

Approvals and indications

In May 2014, it was granted “Breakthrough Therapy” designation by the FDA.[3] On November 30, 2015, FDA approved elotuzumab as a treatment for patients with multiple myeloma who have received one to three prior medications.[1] Elotuzumab was labeled for use with lenalidomide anddexamethasone. Each intravenous injection of elotuzumab should be premedicated with dexamethasone, diphenhydramine, ranitidine andacetaminophen.[2]


Elotuzumab is APPROVED for safety and efficacy in combination with lenalidomide and dexamethasone.

Monoclonal antibody therapy for multiple myeloma, a malignancy of plasma cells, was not very clinically efficacious until the development of cell surface glycoprotein CS1 targeting humanized immunoglobulin G1 monoclonal antibody – Elotuzumab. Elotuzumab is currently APPROVED in relapsed multiple myeloma.

Elotuzumab (HuLuc63) binds to CS1 antigens, highly expressed by multiple myeloma cells but minimally present on normal cells. The binding of elotuzumab to CS1 triggers antibody dependent cellular cytotoxicity in tumor cells expressing CS1. CS1 is a cell surface glycoprotein that belongs to the CD2 subset of immunoglobulin superfamily (IgSF). Preclinical studies showed that elotuzumab initiates cell lysis at high rates. The action of elotuzumab was found to be enhanced when multiple myeloma cells were pretreated with sub-therapeutic doses of lenalidomide and bortezomib. The impressive preclinical findings prompted investigation and analysis of elotuzumab in phase I and phase II studies in combination with lenalidomide and bortezomib.

Elotuzumab As Part of Combination Therapy: Clinical Trial Results

Elotuzumab showed manageable side effect profile and was well tolerated in a population of relapsed/refractory multiple myeloma patients, when treated with intravenous elotuzumab as single agent therapy. Lets’ take a look at how elotuzumab fared in combination therapy trials,

In phase I trial of elotuzumab in combination with Velcade/bortezomib in patients with relapsed/refractory myeloma, the overall response rate was 48% and activity was observed in patients whose disease had stopped responding to Velcade previously. The trial results found that elotuzumab enhanced Velcade activity.
A phase I/II trial in combination with lenalidomide and dexamethasone in refractory/relapsed multiple myeloma patients showed that 82% of patients responded to treatment with a partial response or better and 12% of patients showed complete response. Patients who had received only one prior therapy showed 91% response rate with elotuzumab in combination with lenalidomide and dexamethasone.



Phase I/II trials of the antibody drug has been very impressive and the drug is currently into Phase III trials. Two phase III trials are investigating whether addition of elotuzumab with Revlimid and low dose dexamethasone would increase the time to disease progression. Another phase III trial (ELOQUENT 2) is investigating and comparing safety and efficacy of lenalidomide plus low dose dexamethasone with or without 10mg/kg of elotuzumab in patients with relapsed/refractory multiple myeloma.

Elotuzumab is being investigated in many other trials too. It is being evaluated in combination with Revlimid and low-dose dexamethasone in multiple myeloma patients with various levels of kidney functions, while another phase II study is investigating elotuzumab’s efficacy in patients with high-risk smoldering myeloma.

The main target of multiple myeloma drug development is to satisfy the unmet need for drugs that would improve survival rates. Elotuzumab is an example that mandates much interest in this area and should be followed with diligence.



1 “Press Announcement—FDA approves Empliciti, a new immune-stimulating therapy to treat multiple myeloma”. U.S. Food and Drug Administration. Retrieved 3 December 2015.

2“Empliciti (elotuzumab) for Injection, for Intravenous Use. Full Prescribing Information” (PDF). Empliciti (elotuzumab) for US Healthcare Professionals. Bristol-Myers Squibb Company, Princeton, NJ 08543 USA.

3 “Bristol-Myers Squibb and AbbVie Receive U.S. FDA Breakthrough Therapy Designation for Elotuzumab, an Investigational Humanized Monoclonal Antibody for Multiple Myeloma” (Press release). Princeton, NJ & North Chicago, IL: Bristol-Myers Squibb. 2014-05-19. Retrieved 2015-02-05.

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Neutrophil Serine Proteases in Disease and Therapeutic Considerations

Larry H. Bernstein, MD, FCAP, Curator



SERPINB1 Regulates the activity of the neutrophil proteases elastase, cathepsin G, proteinase-3, chymase,
chymotrypsin, and kallikrein-3. Belongs to the serpin family. Ov-serpin subfamily. Note: This description may
include information from UniProtKB.
Chromosomal Location of Human Ortholog: 6p25
Cellular Component: extracellular space; membrane; cytoplasm
Molecular Function: serine-type endopeptidase inhibitor activity
Reference #:  P30740 (UniProtKB)
Alt. Names/Synonyms: anti-elastase; EI; ELANH2; ILEU; LEI; Leukocyte elastase inhibitor; M/NEI; MNEI; Monocyte/neutrophil elastase inhibitor; Peptidase inhibitor 2; PI-2; PI2; protease inhibitor 2 (anti-elastase), monocyte/neutrophil derived; serine (or cysteine) proteinase inhibitor, clade B (ovalbumin), member 1; Serpin B1; serpin peptidase inhibitor, clade B (ovalbumin), member 1; SERPINB1
Gene Symbols: SERPINB1
Molecular weight: 42,742 Da


Alternative titles; symbols
HGNC Approved Gene Symbol: SERPINB1
Cloning and Expression
Monocyte/neutrophil elastase inhibitor (EI) is a protein of approximately 42,000 Mr with serpin-like functional properties.
Remold-O’Donnell et al. (1992) cloned EI cDNA and identified 3 EI mRNA species of 1.5, 1.9, and 2.6 kb in monocyte-like cells
and no hybridizing mRNA in lymphoblastoid cells lacking detectable EI enzymatic activity. The cDNA open reading frame encoded
a 379-amino acid protein. Its sequence established EI as a member of the serpin superfamily. Sequence alignment indicated that
the reactive center P1 residue is cys-344, consistent with abrogation of elastase inhibitory activity by iodoacetamide and making
EI a naturally occurring cys-serpin.



In the course of studying 4 closely linked genes encoding members of the ovalbumin family of serine proteinase inhibitors
(Ov-serpins) located on 18q21.3, Schneider et al. (1995) investigated the mapping of elastase inhibitor. They prepared PCR
primer sets of the gene, and by using the NIGMS monochromosomal somatic cell hybrid panel, showed that the EI gene maps
to chromosome 6.

By amplifying DNA of a somatic cell hybrid panel, Evans et al. (1995) unambiguously localized ELANH2 to chromosome 6.
With the use of a panel of radiation and somatic cell hybrids specific for chromosome 6, they refined the localization to
the short arm telomeric of D6S89, F13A (134570), and D6S202 at 6pter-p24.




Evans, E., Cooley, J., Remold-O’Donnell, E. Characterization and chromosomal localization of ELANH2, the gene encoding human
monocyte/neutrophil elastase inhibitor. Genomics 28: 235-240, 1995. [PubMed: 8530031related citations] [Full Text]
Remold-O’Donnell, E., Chin, J., Alberts, M. Sequence and molecular characterization of human monocyte/neutrophil elastase inhibitor.
Proc. Nat. Acad. Sci. 89: 5635-5639, 1992. [PubMed: 1376927related citations][Full Text]
Schneider, S. S., Schick, C., Fish, K. E., Miller, E., Pena, J. C., Treter, S. D., Hui, S. M., Silverman, G. A. A serine proteinase inhibitor locus at
18q21.3 contains a tandem duplication of the human squamous cell carcinoma antigen gene. Proc. Nat. Acad. Sci. 92: 3147-3151, 1995.
[PubMed: 7724531,related citations] [Full Text]


Leukocyte elastase inhibitor (serpin B1) (IPR015557)

Short name: Serpin_B1

Family relationships

  • Serpin family (IPR000215)
    • Leukocyte elastase inhibitor (serpin B1) (IPR015557)


Leukocyte elastase inhibitor is also known as serpin B1. Serpins (SERine Proteinase INhibitors) belong to MEROPS inhibitor family I4 (clan ID)
[PMID: 14705960].

Serpin B1 regulates the activity of neutrophil serine proteases such as elastase, cathepsin G and proteinase-3 and may play a regulatory role to
limit inflammatory damage due to proteases of cellular origin [PMID: 11747453]. It also functions as a potent intracellular inhibitor of granzyme
H [PMID: 23269243]. In mouse, four different homologues of human serpin B1 have been described [PMID: 12189154].


The neutrophil serine protease inhibitor SerpinB1 protects against inflammatory lung injury and morbidity in influenza virus infection

Dapeng Gong1,2, Charaf Benarafa1,2, Kevan L Hartshorn3 and Eileen Remold-O’Donnell1,2
J Immunol April 2009; 182(Meeting Abstract Supplement) 43.10

SerpinB1 is an efficient inhibitor of neutrophil serine proteases. SerpinB1-/- mice fail to clear bacterial lung infection with increased inflammation and neutrophil death. Here, we investigated the role of serpinB1 in influenza virus infection, where infiltrating neutrophils and monocytes facilitate virus clearance but can also cause tissue injury. Influenza virus (H3N2 A/Phil/82) infection caused greater and more protracted body weight loss in serpinB1-/- vs. WT mice (20% vs. 15%; nadir on day 4 vs. day 3). Increased morbidity was not associated with defective virus clearance. Cytokines (IFN, TNF, IL-17, IFN, G-CSF) and chemokines (MIP-1, KC, MIP-2) were increased in serpinB1-/- mice vs. WT on days 2-7 post-infection but not on day 1. In WT mice, histology indicated large infiltration of neutrophils peaking on day 1 and maximal airway injury on day 2 that resolved on day 3 coincident with the influx of monocytes/macrophages. In serpinB1-/- mice, neutrophils also peaked on day 1; epithelial injury was severe and sustained with accumulation of dead cells on day 2 and 3. Immunophenotyping of lung digests on day 2 and 3 showed delayed recruitment of monocytes, macrophages and DC in serpinB1-/- mice, but increase of activated CD4 (day 2-3) and CD8 (day 3) T cells. Our findings demonstrate that serpinB1 protects against morbidity and inflammatory lung injury associated with influenza infection.


The neutrophil serine protease inhibitor serpinb1 preserves lung defense functions in Pseudomonas aeruginosainfection

Charaf Benarafa 1 , 2 Gregory P. Priebe 3 , 4 , and Eileen Remold-O’Donnell 1 , 2
JEM July 30, 2007; 204(8): 1901-1909   http://dx.doi.org:/10.1084/jem.20070494

Neutrophil serine proteases (NSPs; elastase, cathepsin G, and proteinase-3) directly kill invading microbes. However, excess NSPs in the lungs play a central role in the pathology of inflammatory pulmonary disease. We show that serpinb1, an efficient inhibitor of the three NSPs, preserves cell and molecular components responsible for host defense against Pseudomonas aeruginosa. On infection, wild-type (WT) and serpinb1-deficient mice mount similar early responses, including robust production of cytokines and chemokines, recruitment of neutrophils, and initial containment of bacteria. However, serpinb1−/− mice have considerably increased mortality relative to WT mice in association with late-onset failed bacterial clearance. We found that serpinb1-deficient neutrophils recruited to the lungs have an intrinsic defect in survival accompanied by release of neutrophil protease activity, sustained inflammatory cytokine production, and proteolysis of the collectin surfactant protein–D (SP-D). Coadministration of recombinant SERPINB1 with the P. aeruginosa inoculum normalized bacterial clearance inserpinb1−/− mice. Thus, regulation of pulmonary innate immunity by serpinb1 is nonredundant and is required to protect two key components, the neutrophil and SP-D, from NSP damage during the host response to infection.


Neutrophils are the first and most abundant phagocytes mobilized to clear pathogenic bacteria during acute lung infection. Prominent among their antimicrobial weapons, neutrophils carry high concentrations of a unique set of serine proteases in their granules, including neu trophil elastase (NE), cathepsin G (CG), and proteinase-3. These neutrophil serine proteases (NSPs) are required to kill phagocytosed bacteria and fungi (12). Indeed, neutrophils lacking NE fail to kill phagocytosed pathogens, and mice deficient for NE and/or CG have increased mortality after infection with pulmonary pathogens (34). However, NSPs in the lung airspace can have a detrimental effect in severe inflammatory lung disease through degradation of host defense and matrix proteins (57). Thus, understanding of the mechanisms that regulate NSP actions during lung infections associated with neutrophilia will help identify strategies to balance host defense and prevent infection-induced tissue injury.


SERPINB1, also known as monocyte NE inhibitor (8), is an ancestral serpin super-family protein and one of the most efficient inhibitors of NE, CG, and proteinase-3 (910). SERPINB1 is broadly expressed and is at particularly high levels in the cytoplasm of neutrophils (1112). SERPINB1 has been found complexed to neutro phil proteases in lung fluids of cystic fibrosis patients and in a baboon model of bronchopulmonary dysplasia (1314). Although these studies suggest a role for SERPINB1 in regulating NSP activity, it is unclear whether these complexes reflect an important physiological role for SERPINB1 in the lung air space.


To define the physiological importance of SERPINB1 in shaping the outcome of bacterial lung infection, we generated mice deficient for serpinb1 (serpinb1−/−) by targeted mutagenesis in embryonic stem (ES) cells (Fig. 1, A–C). Crossings of heterozygous mice produced WT (+/+), heterozygous (+/−), and KO (−/−) mice for serpinb1 at expected Mendelian ratios (25% +/+, 51% +/−, and 24% −/−; n = 225; Fig. 1 D), indicating no embryonic lethality. Bone marrow neutrophils of serpinb1−/− mice lacked expression of the protein, whereas heterozygous serpinb1+/− mice had reduced levels compared with WT mice (Fig. 1 E). Importantly, levels of the cognate neutrophil proteases NE and CG, measured as antigenic units, were not altered by deletion of serpinb1 (Fig. 1 F). When maintained in a specific pathogen-free environment, serpinb1−/− mice did not differ from WT littermates in growth, litter size, or life span (followed up to 12 mo), and no gross or histopathological defects were observed at necropsy in 8-wk-old mice.

6–8-wk-old animals were intranasally inoculated with the nonmucoid Pseudomonas aeruginosa strain PAO1. Using two infection doses (3 × 106 and 7 × 106 CFU/mouse),serpinb1−/− mice had a significantly lower survival probability and a shorter median survival time compared with WT mice (Fig. 2 A). Further groups of infected mice were used to evaluate bacterial clearance. At 6 h after infection, the bacteria were similarly restricted in mice of the two genotypes, suggesting that the serpinb1−/− mice have a normal initial response to infection. At 24 h, the median bacterial count in the lungs of serpinb1−/− mice was five logs higher than that of the WT mice (P < 0.001), and the infection had spread systemically in serpinb1−/− mice but not in WT mice, as shown by high median CFU counts in the spleen (Fig. 2 B). Histological examination at 24 h after infection revealed abundant neutrophil infiltration in the lungs of both WT and serpinb1−/− mice, and consistent with the bacteriological findings, numerous foci of bacterial colonies and large areas of alveolar exudates were found in serpinb1−/− mice only (Fig. 2 C). When challenged with the mucoid P. aeruginosa clinical strain PA M57-15 isolated from a cystic fibrosis patient, WT mice cleared >99.9% of the inoculum within 24 h, whereas serpinb1-deficient mice failed to clear the infection (Fig. 2 D). Thus, the NSP inhibitor serpinb1 is essential for maximal protection against pneumonia induced by mucoid and nonmucoid strains of P. aeruginosa.

Figure 2.

Serpinb1−/− mice fail to clear P. aeruginosalung infection. (A) Kaplan-Meier survival curves of WT (+/+) and serpinb1-deficient (−/−) mice intranasally inoculated with nonmucoid P. aeruginosa strain PAO1. Increased mortality of serpinb1−/− mice was statistically significant (P = 0.03 at 3 × 106CFU/mouse; P < 0.0001 at 7 × 106CFU/mouse). (B) CFUs per milligram of lung (left) and splenic (right) tissue determined 6 and 24 h after inoculation with 3 × 106 CFUP. aeruginosa PAO1 in WT (+/+, filled circles) and serpinb1−/− (−/−, open circles) mice. Each symbol represents a value for an individual mouse. Differences between median values (horizontal lines) were analyzed by the Mann-Whitney U test. Data below the limit of detection (dotted line) are plotted as 0.5 CFU × dilution factor. (C) Lung sections stained with hematoxylin and eosin show bacterial colonies (arrowheads) and alveolar exudate in lungs of serpinb1−/− mice 24 h after infection with P. aeruginosa PAO1. Bars, 50 μm. (D) Total CFUs in the lung and spleen 24 h after inoculation with 2 × 108 CFU of the mucoid P. aeruginosa strain PA M57-15 in WT (+/+, filled circles) and serpinb1−/− (−/−, open circles) mice. Differences between median values (horizontal lines) were analyzed by the Mann-Whitney U test.

To verify specificity of the gene deletion, we tested whether delivering rSERPINB1 would correct the defective phenotype. Indeed, intranasal instillation of rSERPINB1 to serpinb1−/− mice at the time of inoculation significantly improved clearance of P. aeruginosa PAO1 from the lungs assessed at 24 h and reduced bacteremia compared with infectedserpinb1−/− mice that received PBS instead of the recombinant protein (Fig. S1 A, available at http://www.jem.org/cgi/content/full/jem.20070494/DC1). We have previously demonstrated that rSERPINB1 has no effect on the growth of P. aeruginosa in vitro (15) and does not induce bacterial aggrega tion (16). Also, rSERPINB1 mixed with PAO1 had no effect on adherence of the bacteria to human bronchial epithelial and corneal epithelial cell lines (unpublished data). Therefore, the improved bacterial clearance in treated serpinb1−/− mice is not related to a direct antibacterial role for rSERPINB1 but rather to reducing injury induced by excess neutrophil proteases. In addition, previous in vivo studies in WT rats showed that rSERPINB1 can protect against elastase-induced lung injury (17) and accelerate bacterial clearance two- to threefold in the Pseudomonas agar bead model (15).

Evidence of excess NSP action was examined in the lungs of infected serpinb1−/− mice by measuring surfactant protein–D (SP-D). SP-D, a multimeric collagenous C-type lectin produced by alveolar epithelial cells, is highly relevant as a host defense molecule, because it functions as an opsonin in microbial clearance (18) and acts on alveolar macrophages to regulate pro- and antiinflammatory cytokine production (19). SP-D is also relevant as an NSP target because it is degraded in vitro by trace levels of each of the NSPs (1620). SP-D levels in lung homogenates of WT and serpinb1−/− mice were similar 6 h after P. aeruginosa infection. At 24 h, SP-D levels were reduced in the lungs ofserpinb1−/− mice compared with WT mice, as indicated by immunoblots. A lower molecular mass band indicative of proteolytic degradation is also apparent (Fig. 3 A). Densitometry analysis of the 43-kD SP-D band relative to β-actin indicated that the reduction of SP-D level was statistically significant (+/+, 45 ± 6 [n = 8]; −/−, 10 ± 2 [n = 8]; P < 0.0001 according to the Student’s t test). Furthermore, rSERPINB1 treatment ofP. aeruginosa–infected serpinb1−/− mice partly prevented the degradation of SP-D in lung homogenates compared with nontreated mice (Fig. S1 B). As a further test of the impact of serpinb1 deletion on NSP activity, isolated neutrophils of serpinb1−/− mice were treated with LPS and FMLP and tested for their ability to cleave recombinant rat SP-D (rrSP-D) in vitro. The extent of rrSP-D cleavage by serpinb1−/− neutrophils was fourfold greater than by WT neutrophils, as determined by densitometry. The cleavage was specific for NSPs because it was abrogated by rSERPINB1 and diisopropyl fluorophosphate (Fig. 3 B). Collectively, these findings indicate a direct role for serpinb1 in regulating NSP activity released by neutrophils and in preserving SP-D, an important-host defense molecule.

Efficient clearance of P. aeruginosa infection requires an early cytokine and chemokine response coordinated by both resident alveolar macrophages and lung parenchymal cells (2122). The IL-8 homologue keratinocyte-derived chemokine (KC) and the cytokines TNF-α, IL-1β, and G-CSF were measured in cell-free bronchoalveolar (BAL) samples. Although the tested cytokines were undetectable in sham-infected mice of both genotypes (unpublished data), comparable induc tion of these cytokines was observed in BAL of WT and serpinb1−/− mice at 6 h after infection, demonstrating that there is no early defect in cytokine production in serpinb1−/− mice. At 24 h, levels of TNF-α, KC, and IL-1β were sustained or increased in serpinb1−/− mice and significantly higher than cytokine levels in WT mice. G-CSF levels at 24 h were elevated to a similar extent in BAL of WT and KO mice (Fig. 3 C). However, G-CSF levels were significantly higher in the serum of serpinb1−/− mice (WT, 336 ± 80 ng/ml; KO, 601 ± 13 ng/ml; n = 6 of each genotype; P < 0.01). In addition, serpinb1−/− mice that were treated at the time of infection with rSERPINB1 had cytokine levels in 24-h lung homogenates that were indistinguishable from those of infected WT mice (Fig. S1 C). The increased cytokine production in the lungs of infected serpinb1−/− mice may be caused by failed bacterial clearance but also by excess NSPs, which directly induce cytokine and neutrophil chemokine production in pulmonary parenchymal cells and alveolar macrophages (2324).

Neutrophil recruitment to the lungs was next examined as a pivotal event of the response to P. aeruginosa infection (25). Lung homogenates were assayed for the neutrophil-specific enzyme myeloperoxidase (MPO) to quantify marginating, interstitial, and alveolar neutrophils. Neutrophils in BAL fluid were directly counted as a measure of neutrophil accumulation in the alveolar and airway lumen. MPO in lung homo genates was undetectable in uninfected mice and was comparably increased in mice of both genotypes at 6 h, suggesting normal early serpinb1−/− neutrophil margination and migration into the interstitium. However, by 24 h after infection, MPO levels in lung homogenates remained high in WT mice but were significantly decreased in serpinb1−/− mice (Fig. 4 A). Importantly, the content of MPO per cell was the same for isolated neutrophils of WT andserpinb1−/− mice (+/+, 369 ± 33 mU/106 cells; −/−, 396 ± 27 mU/106 cells). The numbers of neutrophils in BAL were negligible in uninfected mice and were similarly increased in WT and serpinb1−/− mice at 6 h after infection. Neutrophil counts in BAL further increased at 24 h, but the mean BAL neutrophil numbers were significantly lower in serpinb1−/− mice compared with WT mice (Fig. 4 B). The evidence from the 6-h quantitation of MPO in homogenates and neutrophils in BAL strongly suggests that neutrophil recruitment is not defective in infected serpinb1−/− mice. Moreover, the high levels of cytokines and neutrophil chemoattractant KC in serpinb1−/− mice at 24 h (Fig. 3 C) also suggest that, potentially, more neutrophils should be recruited. Therefore, to examine neutrophil recruitment in serpinb1−/− mice, we used a noninfectious model in which neutrophils are mobilized to migrate to the lung after intranasal delivery of P. aeruginosa LPS. MPO levels in lung homogenate and neutrophil numbers in BAL were not statistically different in WT and serpinb1−/− mice 24 h after LPS instillation (Fig. 4, C and D). Furthermore, the number of circulating blood neutrophils and recruited peritoneal neutrophils after injection of sterile irritants glycogen and thioglycollate did not differ in WT and serpinb1−/− mice (unpublished data). Alveolar macrophage numbers were similar in uninfected mice of both genotypes (∼5 × 105 cells/mouse) and did not substantially change upon infection. Collectively, these findings show that neutrophil recruitment to the lungs in response to P. aeruginosa infection is not defective in serpinb1−/− mice, and therefore, the recovery of lower numbers of serpinb1−/− neutrophils at 24 h after infection suggests their decreased survival.

To examine the putative increased death of serpinb1−/− neutrophils in the lungs after P. aeruginosa infection, lung sections were analyzed by immunohistochemistry. Caspase-3–positive leukocytes were more relevant in the alveolar space of serpinb1−/− mice compared with WT mice at 24 h after infection, suggesting increased neutrophil apoptosis (Fig. 5 A). The positive cells were counted in 50 high power fields (hpf’s), and mean numbers of caspase-3–stained cells were increased in the lungs of serpinb1/− mice (1.8 ± 0.2 cells/hpf) compared with WT mice (0.4 ± 0.1 cells/hpf; P < 0.0001). To characterize neutrophils in the alveoli and airways, neutrophils in BAL were identified in flow cytometry by forward scatter (FSC) and side scatter and were stained with annexin V (AnV) and propidium iodide (PI). At 24 h after infection, the proportion of late apoptotic/necrotic neutrophils (AnV+PI+) was increased at the expense of viable neutrophils (AnVPI) in the BAL of serpinb1−/− mice compared with WT mice (Fig. 5 B). Neutrophil fragments in BAL were also identified in flow cytometry by low FSC (FSClow) within the neutrophil population defined by the neutrophil marker Gr-1. The number of neutrophil fragments (FSClow, Gr-1+) relative to intact neutrophils was increased two- to threefold at 24 h after infection for serpinb1−/− compared with WT mice (Fig. 5 C). Moreover, free MPO in BAL supernatants was increased in serpinb1−/− mice compared with WT mice at 24 h after infection, indicating increased PMN lysis or degranulation (Fig. 5 D).

Finally, we questioned whether the enhanced death of serpinb1−/− pulmonary neutrophils was a primary effect of gene deletion or a secondary effect caused by, for example, bacteria or components of inflammation. To address this, neutrophils were collected using the noninfectious LPS recruitment model and were cultured in vitro to allow for spontaneous cell death. After 24 h, the percentages of apoptotic and necrotic neutrophils evaluated by microscopy were increased in serpinb1−/− neutrophils compared with WT neutrophils (Fig. 6, A–C). A similar increase in apoptotic cells was observed using AnV/PI staining and measurements of hypodiploid DNA (unpublished data). Moreover, live cell numbers from serpinb1−/− mice remaining in culture after 24 h were significantly decreased compared with WT mice (Fig. 6 D). The in vitro findings indicate that enhanced death of pulmonary neutrophils of infected serpinb1−/− mice is at least in part a cell-autonomous defect likely mediated by unchecked NSP actions.


In this paper, we have demonstrated that serpinb1, an intracellular serpin family member, regulates the innate immune response and protects the host during lung bacterial infection. Serpinb1 is among the most potent inhibitors of NSPs and is carried at high levels within neutrophils. Serpinb1-deficient mice fail to clear P. aeruginosa PAO1 lung infection and succumb from systemic bacterial spreading. The defective immune function in serpinb1−/− mice stems at least in part from an increased rate of neutrophil necrosis, reducing the number of phagocytes and leading to increased NSP activity in the lungs with proteolysis of SP-D. In addition, serpinb1-deficient mice also have impaired clearance of the mucoid clinical strain PA M57-15. Interestingly, mucoid strains of P. aeruginosa are cleared with a very high efficiency from the lungs of WT and cystic fibrosis transmembrane conductance regulator–deficient mice (26). The phenotype of serpinb1−/− mice reproduces major pathologic features of human pulmonary diseases characterized by excessive inflammation, massive neutrophil recruitment to the air space, and destruction of cellular and molecular protective mechanisms. Importantly, serpinb1 deficiency may be helpful as an alternative or additional model of the inflammatory lung pathology of cystic fibrosis.

The present study documents a key protective role for serpinb1 in regulating NSP actions in the lung. This role has previously been attributed to the NSP inhibitors α1-antitrypsin and secretory leukocyte protease inhibitor, which are found in the airway and alveolar lining fluid (2728). However, patients with α1-antitrypsin deficiency do not present with pulmonary infection secondary to innate immune defects despite increased NSP activity that leads to reduced lung elasticity and emphysema. Moreover, there is so far no evidence that deficiency in secretory leukocyte protease inhibitor results in failure to clear pulmonary infection. Because synthesis and storage of NSPs in granules is an event that exclusively takes place in bone marrow promyelocytes (29), the regulation of NSPs in the lung relies entirely on NSP inhibitors. Thus, the extent of the innate immune defect inserpinb1−/− mice and the normalization of bacterial clearance with topical rSERPINB1 treatment indicate that serpinb1 is required to regulate NSP activity in the airway fluids and that, during acute lung infection associated with high neutrophilic recruitment, there is insufficient compensation by other NSP inhibitors. The devastating effects of NSPs when released in the lungs by degranulating and necrotic neutrophils are well documented in human pulmonary diseases (5630). Therefore, our findings clearly establish a physiological and nonredundant role for serpinb1 in regulating NSPs during pulmonary infection.

NSPs also cleave molecules involved in apoptotic cell clearance, including the surfactant protein SP-D and the phosphatidylserine receptor on macrophages (3132), thereby tipping the balance further toward a detrimental outcome. The increased numbers of leukocytes with active caspase-3 in the alveolar space of P. aeruginosa–infectedserpinb1−/− mice suggest that the removal of apoptotic cells may be inadequate during infection. SP-D has been shown to stimulate phagocytosis of P. aeruginosa by alveolar macrophages in vitro (33), and SP-D–deficient mice were found to have defective early (6-h) clearance of P. aeruginosa from the lung (34). Although the destruction of SP-D alone may not entirely account for the defective phenotype of serpinb1−/− mice, loss of SP-D likely diminishes bacterial clearance and removal of apop totic neutrophils.

Given that NSPs also mediate bacterial killing, why would NSP excess lead to a failed bacterial clearance? In the NE KO mice, the decreased killing activity of neutrophils is a direct consequence of the loss of the bactericidal activity of NE. The absence of an early bacterial clearance defect at 6 h after infection in serpinb1−/− mice suggests that there is initially normal bacterial killing. The current understanding is that the compartmentalization of the NSPs is crucial to the outcome of their actions: on the one hand, NSPs are protective when killing microbes within phagosomes, and on the other hand, extracellular NSPs destroy innate immune defense molecules such as lung collectins, immunoglobulins, and complement receptors. We have shown that the regulation of NSP activity is essential and that cytoplasmic serpinb1 provides this crucial shield. Neutrophils undergoing cell death gradually transition from apoptosis, characterized by a nonpermeable plasma membrane, to necrosis and lysis, where cellular and granule contents, including NSPs, are released. The increased pace of serpinb1−/− neutrophil cell death strongly suggests that unopposed NSPs may precipitate neutrophil demise and, therefore, reduce the neutrophil numbers leading to a late-onset innate immune defect. High levels of G-CSF, a prosurvival cytokine for neutrophils, also indicate that increased cell death is likely independent or downstream of G-CSF.

In conclusion, serpinb1 deficiency unleashes unbridled proteolytic activity during inflammation and thereby disables two critical components of the host response to bacterial infection, the neutrophil and the collectin SP-D. The phenotype of the infectedserpinb1-deficient mouse, characterized by a normal early antibacterial response that degenerates over time, highlights the delicate balance of protease–antiprotease systems that protect the host against its own defenses as well as invading microbes during infection-induced inflammation.



Proteinase 3 and neutrophil elastase enhance inflammation in mice by inactivating antiinflammatory progranulin

K Kessenbrock,1 LFröhlich,2 M Sixt,3 …., A Belaaouaj,5 J Ring,6,7 M Ollert,6 R Fässler,3 and DE. Jenne1
J Clin Invest. 2008 Jul 1; 118(7): 2438–2447.   http://dx.doi.org:/10.1172/JCI34694

Neutrophil granulocytes form the body’s first line of antibacterial defense, but they also contribute to tissue injury and noninfectious, chronic inflammation. Proteinase 3 (PR3) and neutrophil elastase (NE) are 2 abundant neutrophil serine proteases implicated in antimicrobial defense with overlapping and potentially redundant substrate specificity. Here, we unraveled a cooperative role for PR3 and NE in neutrophil activation and noninfectious inflammation in vivo, which we believe to be novel. Mice lacking both PR3 and NE demonstrated strongly diminished immune complex–mediated (IC-mediated) neutrophil infiltration in vivo as well as reduced activation of isolated neutrophils by ICs in vitro. In contrast, in mice lacking just NE, neutrophil recruitment to ICs was only marginally impaired. The defects in mice lacking both PR3 and NE were directly linked to the accumulation of antiinflammatory progranulin (PGRN). Both PR3 and NE cleaved PGRN in vitro and during neutrophil activation and inflammation in vivo. Local administration of recombinant PGRN potently inhibited neutrophilic inflammation in vivo, demonstrating that PGRN represents a crucial inflammation-suppressing mediator. We conclude that PR3 and NE enhance neutrophil-dependent inflammation by eliminating the local antiinflammatory activity of PGRN. Our results support the use of serine protease inhibitors as antiinflammatory agents.


Neutrophils belong to the body’s first line of cellular defense and respond quickly to tissue injury and invading microorganisms (1). In a variety of human diseases, like autoimmune disorders, infections, or hypersensitivity reactions, the underlying pathogenic mechanism is the formation of antigen-antibody complexes, so-called immune complexes (ICs), which trigger an inflammatory response by inducing the infiltration of neutrophils (2). The subsequent stimulation of neutrophils by C3b-opsonized ICs results in the generation of ROS and the release of intracellularly stored proteases leading to tissue damage and inflammation (3). It is therefore important to identify the mechanisms that control the activation of infiltrating neutrophils.

Neutrophils abundantly express a unique set of neutrophil serine proteases (NSPs), namely cathepsin G (CG), proteinase 3 (PR3; encoded by Prtn3), and neutrophil elastase (NE; encoded by Ela2), which are stored in the cytoplasmic, azurophilic granules. PR3 and NE are closely related enzymes, with overlapping and potentially redundant substrate specificities different from those of CG. All 3 NSPs are implicated in antimicrobial defense by degrading engulfed microorganisms inside the phagolysosomes of neutrophils (48). Among many other functions ascribed to these enzymes, PR3 and NE were also suggested to play a fundamental role in granulocyte development in the bone marrow (911).

While the vast majority of the enzymes is stored intracellularly, minor quantities of PR3 and NE are externalized early during neutrophil activation and remain bound to the cell surface, where they are protected against protease inhibitors (1213). These membrane presented proteases were suggested to act as path clearers for neutrophil migration by degrading components of the extracellular matrix (14). This notion has been addressed in a number of studies, which yielded conflicting results (1517). Thus, the role of PR3 and NE in leukocyte extravasation and interstitial migration still remains controversial.

Emerging data suggest that externalized NSPs can contribute to inflammatory processes in a more complex way than by simple proteolytic tissue degradation (18). For instance, recent observations using mice double-deficient for CG and NE indicate that pericellular CG enhances IC-mediated neutrophil activation and inflammation by modulating integrin clustering on the neutrophil cell surface (1920). Because to our knowledge no Prtn3–/– mice have previously been generated, the role of this NSP in inflammatory processes has not been deciphered. Moreover, NE-dependent functions that can be compensated by PR3 in Ela2–/–animals are still elusive.

One mechanism by which NSPs could upregulate the inflammatory response has recently been proposed. The ubiquitously expressed progranulin (PGRN) is a growth factor implicated in tissue regeneration, tumorigenesis, and inflammation (2123). PGRN was previously shown to directly inhibit adhesion-dependent neutrophil activation by suppressing the production of ROS and the release of neutrophil proteases in vitro (23). This antiinflammatory activity was degraded by NE-mediated proteolysis of PGRN to granulin (GRN) peptides (23). In contrast, GRN peptides may enhance inflammation (23) and have been detected in neutrophil-rich peritoneal exudates (24). In short, recent studies proposed PGRN as a regulator of the innate immune response, but the factors that control PGRN function are still poorly defined and its relevance to inflammation needs to be elucidated in vivo.

In the present study, we generated double-deficient Prtn3–/–Ela2–/– mice to investigate the role of these highly similar serine proteases in noninfectious neutrophilic inflammation. We established that PR3 and NE are required for acute inflammation in response to subcutaneous IC formation. The proteases were found to be directly involved in early neutrophil activation events, because isolated Prtn3–/–Ela2–/– neutrophils were poorly activated by ICs in vitro. These defects in Prtn3–/–Ela2–/– mice were accompanied by accumulation of PGRN. We demonstrated that PGRN represents a potent inflammation-suppressing factor that is cleaved by both PR3 and NE. Our data delineate what we believe to be a previously unknown proinflammatory role for PR3 and NE, which is accomplished via the local inactivation of antiinflammatory PGRN.


Generation of Prtn3–/–Ela2–/– mice.

To analyze the role of PR3 and NE in neutrophilic inflammation, we generated a Prtn3–/–Ela2–/– mouse line by targeted gene disruption in embryonic stem cells (see Supplemental Figure 1; supplemental material available online with this article; doi: 10.1172/JCI34694DS1). Positive recombination of the Prtn3/Ela2locus was proven by Southern blotting of embryonic stem cell clones (Figure ​(Figure1A).1A). Prtn3–/–Ela2–/– mice showed no expression of mRNA for PR3 and NE in bone marrow cells, as assessed by RT-PCR (Figure ​(Figure1B).1B). The successful elimination of PR3 and NE was confirmed at the level of proteolytic activity in neutrophil lysates using a PR3/NE-specific chromogenic substrate (Supplemental Figure 3) as well as by casein zymography (Figure ​(Figure1C).1C). The substantially reduced casein degradation by heterozygous neutrophils indicates gene-dosage dependence of PR3/NE activities. Furthermore, PR3 and NE deficiency was proven by Western blotting using cell lysates from bone marrow–derived neutrophils, while other enzymes stored in azurophilic granula, such as CG and myeloperoxidase (MPO), were normally detected (Figure ​(Figure1D).1D). Crossing of heterozygous Prtn3+/–Ela2+/– mice resulted in regular offspring of WT, heterozygous, and homozygous genotype according to the Mendelian ratio. Despite the absence of 2 abundant serine proteases, and in contrast to expectations based on previous reports (911), we found unchanged neutrophil morphology (Figure ​(Figure1E)1E) and regular neutrophil populations in the peripheral blood of the mutant mice, the latter as assessed via flow cytometry to determine the differentiation markers CD11b and Gr-1 (Figure ​(Figure1F)1F) (2526). Moreover, Prtn3–/–Ela2–/– mice demonstrated normal percentages of the leukocyte subpopulations in the peripheral blood, as determined by the Diff-Quick staining protocol and by hemocytometric counting (Supplemental Figure 2, A and B). Hence, the proteases are not crucially involved in granulopoiesis, and ablating PR3 and NE in the germ line represents a valid approach to assess their biological significance in vivo.


Figure 1

Generation and characterization of Prtn3–/–Ela2–/– mice.

PR3 and NE are dispensable for neutrophil extravasation and interstitial migration.

To examine neutrophil infiltration into the perivascular tissue, we applied phorbol esters (croton oil) to the mouse ears. At 4 h after stimulation, we assessed the neutrophil distribution in relation to the extravascular basement membrane (EBM) by immunofluorescence microscopy of fixed whole-mount specimens (Figure ​(Figure2A).2A). We found that Prtn3–/–Ela2–/– neutrophils transmigrated into the interstitium without retention at the EBM (Figure ​(Figure2B),2B), resulting in quantitatively normal and widespread neutrophil influx compared with WT mice (Figure ​(Figure2C).2C). Moreover, we analyzed chemotactic migration of isolated neutrophils through a 3-dimensional collagen meshwork in vitro (Supplemental Video 1) and found unhampered chemotaxis toward a C5a gradient, based on the directionality (Figure ​(Figure2D)2D) and velocity (Figure ​(Figure2E)2E) of Prtn3–/–Ela2–/–neutrophils. These findings led us to conclude that PR3 and NE are not principally required for neutrophil extravasation or interstitial migration.


Figure 2

PR3 and NE are not principally required for neutrophil extravasation and interstitial migration.

Reduced inflammatory response to ICs in Prtn3–/–Ela2–/– mice.

The formation of ICs represents an important trigger of neutrophil-dependent inflammation in many human diseases (2). To determine the role of PR3 and NE in this context, we induced a classic model of subcutaneous IC-mediated inflammation, namely the reverse passive Arthus reaction (RPA) (27). At 4 h after RPA induction, we assessed the cellular inflammatory infiltrates by histology using H&E-stained skin sections (Figure ​(Figure3A).3A). Neutrophils, which were additionally identified by Gr-1 immunohistochemistry, made up the vast majority of all cellular infiltrates (Figure ​(Figure3A).3A). We found that neutrophil infiltration to the sites of IC formation was severely diminished in Prtn3–/–Ela2–/– mice. Indeed, histological quantification revealed significantly reduced neutrophil influx in Prtn3–/–Ela2–/– mice compared with WT mice, while Ela2–/– mice showed marginally reduced neutrophil counts (Figure ​(Figure3B).3B). These results indicate that PR3 and NE fulfill an important proinflammatory function during IC-mediated inflammation.


Figure 3

Impaired inflammatory response to locally formed ICs inPrtn3–/–Ela2–/– mice.

(A) Representative photomicrographs of inflamed skin sections 4 h after IC formation. Neutrophils were identified morphologically (polymorphic nucleus) in H&E stainings and by Gr-1 staining (red). The cellular infiltrates were located to the adipose tissue next to the panniculus carnosus muscle (asterisks) and were primarily composed of neutrophil granulocytes. Scale bars: 200 μm. (B) Neutrophil infiltrates in lesions from Prtn3–/–Ela2–/– mice were significantly diminished compared with Ela2–/– mice and WT mice. Neutrophil influx in Ela2–/–mice was slightly, but not significantly, diminished compared with WT mice. Results are mean ± SEM infiltrated neutrophils per HPF. *P < 0.05.

PR3 and NE enhance neutrophil activation by ICs in vitro.

PR3 and NE enhance neutrophil activation by ICs in vitro.

Because PR3 and NE were required for the inflammatory response to IC (Figure ​(Figure3),3), but not to phorbol esters (Figure ​(Figure2),2), we considered the enzymes as enhancers of the neutrophil response to IC. We therefore assessed the oxidative burst using dihydrorhodamine as a readout for cellular activation of isolated, TNF-α–primed neutrophils in the presence of ICs in vitro. While both WT and Prtn3–/–Ela2–/– neutrophils showed a similar, approximately 20-min lag phase before the oxidative burst commenced, the ROS production over time was markedly reduced, by 30%–40%, in the absence of PR3 and NE (Figure ​(Figure4A).4A). In contrast, oxidative burst triggered by 25 nM PMA was not hindered in Prtn3–/–Ela2–/– neutrophils (Figure ​(Figure4B),4B), which indicated no general defect in producing ROS. We also performed a titration series ranging from 0.1 to 50 nM PMA and found no reduction in oxidative burst activity in Prtn3–/–Ela2–/– neutrophils at any PMA concentration used (Supplemental Figure 4). These data are consistent with our in vivo experiments showing that neutrophil influx to ICs was impaired (Figure ​(Figure3),3), whereas the inflammatory response to phorbol esters was normal (Figure ​(Figure2,2, A–C), in Prtn3–/–Ela2–/– mice. To compare neutrophil priming in WT and Prtn3–/–Ela2–/–neutrophils, we analyzed cell surface expression of CD11b after 30 min of incubation at various concentrations of TNF-α and found no difference (Supplemental Figure 5). Moreover, we observed normal neutrophil adhesion to IC-coated surfaces (Supplemental Figure 6A) and unaltered phagocytosis of opsonized, fluorescently labeled E. coli bacteria (Supplemental Figure 6, B and C) in the absence of both proteases. We therefore hypothesized that PR3 and NE enhance early events of adhesion-dependent neutrophil activation after TNF-α priming and binding of ICs. It is important to note that Ela2–/– neutrophils were previously shown to react normally in the same setup (20). Regarding the highly similar cleavage specificities of both proteases, we suggested that PR3 and NE complemented each other during the process of neutrophil activation and inflammation.


Figure 4

Impaired oxidative burst and PGRN degradation by IC-activatedPrtn3–/–Ela2–/– neutrophils.

Oxidative burst as the readout for neutrophil activation by ICs was measured over time. (A) While no difference was observed during the initial 20-min lag phase of the oxidative burst, Prtn3–/–Ela2–/– neutrophils exhibited diminished ROS production over time compared with WT neutrophils. (B) Bypassing receptor-mediated activation using 25 nM PMA restored the diminished oxidative burst of Prtn3–/–Ela2–/–neutrophils. Results are presented as normalized fluorescence in AU (relative to maximum fluorescence produced by WT cells). Data (mean ± SD) are representative of 3 independent experiments each conducted in triplicate. (C) Isolated mouse neutrophils were activated by ICs in vitro and tested for PGRN degradation by IB. In the cellular fraction, the PGRN (~80 kDa) signal was markedly increased in Prtn3–/–Ela2–/–cells compared with WT and Ela2–/– neutrophils. Intact PGRN was present in the supernatant (SN) of IC-activated Prtn3–/–Ela2–/–neutrophils only, not of WT or Ela2–/– cells. (D and E) Exogenous administration of 100 nM PGRN significantly reduced ROS production of neutrophils activated by ICs (D), but not when activated by PMA (E). Data (mean ± SD) are representative of 3 independent experiments each conducted in triplicate.

Antiinflammatory PGRN is degraded by PR3 and NE during IC-mediated neutrophil activation.

PGRN inhibits neutrophil activation by ICs in vitro.

Both PR3 and NE process PGRN in vitro.

Figure 5

PR3 and NE are major PGRN processing enzymes of neutrophils.

PGRN inhibits IC-mediated inflammation in vivo.

Figure 6

PGRN is a potent inhibitor of IC-stimulated inflammation in vivo.

PR3 and NE cleave PGRN during inflammation in vivo.

Finally, we aimed to demonstrate defective PGRN degradation in Prtn3–/–Ela2–/– mice during neutrophilic inflammation in vivo. For practical reasons, we harvested infiltrated neutrophils from the inflamed peritoneum 4 h after casein injection and subjected the lysates of these cells to anti-PGRN Western blot. Intact, inhibitory PGRN was detected in Prtn3–/–Ela2–/– neutrophils, but not in WT cells (Figure ​(Figure6D).6D). These data prove that neutrophilic inflammation is accompanied by proteolytic removal of antiinflammatory PGRN and that the process of PGRN degradation is essentially impaired in vivo in the absence of PR3 and NE.


Chronic inflammatory and autoimmune diseases are often perpetuated by continuous neutrophil infiltration and activation. According to the current view, the role of NSPs in these diseases is mainly associated with proteolytic tissue degradation after their release from activated or dying neutrophils. However, recent observations suggest that NSPs such as CG may contribute to noninfectious diseases in a more complex manner, namely as specific regulators of inflammation (18). Here, we demonstrate that PR3 and NE cooperatively fulfilled an important proinflammatory role during neutrophilic inflammation. PR3 and NE directly enhanced neutrophil activation by degrading oxidative burst–suppressing PGRN. These findings support the use of specific serine protease inhibitors as antiinflammatory agents.

Much attention has been paid to the degradation of extracellular matrix components by NSPs. We therefore expected that ablation of both PR3 and NE would cause impaired neutrophil extravasation and interstitial migration. Surprisingly, we found that the proteases were principally dispensable for these processes:Prtn3–/–Ela2–/– neutrophils migrated normally through a dense, 3-dimensional collagen matrix in vitro and demonstrated regular extravasation in vivo when phorbol esters were applied (Figure ​(Figure2).2). This finding is in agreement with recent reports that neutrophils preferentially and readily cross the EBM through regions of low matrix density in the absence of NE (28).

Conversely, we observed that PR3 and NE were required for the inflammatory response to locally formed ICs (Figure ​(Figure3).3). Even isolated Prtn3–/–Ela2–/– neutrophils were challenged in performing oxidative burst after IC stimulation in vitro (Figure ​(Figure4A),4A), showing that the proteases directly enhanced the activation of neutrophils also in the absence of extracellular matrix. However, when receptor-mediated signal transduction was bypassed by means of PMA, neutrophils from Prtn3–/–Ela2–/– mice performed normal oxidative burst (Figure ​(Figure4B),4B), indicating that the function of the phagocyte oxidase (phox) complex was not altered in the absence of PR3 and NE. These findings substantiate what we believe to be a novel paradigm: that all 3 serine proteases of azurophilic granules (CG, PR3, and NE), after their release in response to IC encounter, potentiate a positive autocrine feedback on neutrophil activation.

In contrast to CG, the highly related proteases PR3 and NE cooperate in the effacement of antiinflammatory PGRN, leading to enhanced neutrophil activation. Previous studies already demonstrated that PGRN is a potent inhibitor of the adhesion-dependent oxidative burst of neutrophils in vitro, which can be degraded by NE (23). Here, we showed that PR3 and NE play an equally important role in the regulation of PGRN function. Ela2–/– neutrophils were sufficiently able to degrade PGRN. Only in the absence of both PR3 and NE was PGRN degradation substantially impaired, resulting in the accumulation of antiinflammatory PGRN during neutrophil activation in vitro (Figure ​(Figure4C)4C) and neutrophilic inflammation in vivo (Figure ​(Figure6D).6D). Moreover, we provided in vivo evidence for the crucial role of PGRN as an inflammation-suppressing mediator, because administration of recombinant PGRN potently inhibited the neutrophil influx to sites of IC formation (Figure ​(Figure6,6, A–C). Hence, the cooperative degradation of PGRN by PR3 and NE is a decisive step for the establishment of neutrophilic inflammation.

The molecular mechanism of PGRN function is not yet completely understood, but it seems to interfere with integrin (CD11b/CD18) outside-in signaling by blocking the function of pyk2 and thus dampens adhesion-related oxidative burst even when added after the initial lag phase of oxidase activation (23). PGRN is produced by neutrophils and stored in highly mobile secretory granules (29). It was recently shown that PGRN can bind to heparan-sulfated proteoglycans (30), which are abundant components of the EBM and various cell surfaces, including those of neutrophils. Also, PR3 and NE are known to interact with heparan sulfates on the outer membrane of neutrophils, where the enzymes appear to be protected against protease inhibitors (121331). These circumstantial observations support the notion that PGRN cleavage by PR3 and NE takes place at the pericellular microenvironment of the neutrophil cell surface.

Impaired outside-in signaling most likely reduced the oxidative burst in Prtn3–/–Ela2–/– neutrophils adhering to ICs. In support of this hypothesis, we excluded an altered response to TNF-α priming (Supplemental Figure 5) as well as reduced adhesion to immobilized ICs and defective endocytosis of serum-opsonized E. coli in Prtn3–/–Ela2–/– neutrophils (Supplemental Figure 6). MPO content and processing was also unchanged in Prtn3–/–Ela2–/– neutrophils (Figure ​(Figure1D);1D); hence, the previously discussed inhibitory effect of MPO on phox activity (3233) does not appear to be stronger in neutrophils lacking PR3 and NE. Because there was no difference in the lag phase of the oxidative burst, initial IC-triggered receptor activation was probably not affected by either PRGN or PR3/NE. Our concept is consistent with all these observations and takes into account that PGRN unfolds its suppressing effects in the second phase, when additional membrane receptors, endogenous PGRN, and some PR3/NE from highly mobile intracellular pools are translocated to the cell surface. The decline and cessation of ROS production suggested to us that outside-in signaling was not sustained and that active oxidase complexes were no longer replenished in the absence of PR3 and NE. Our present findings, however, do not allow us to exclude other potential mechanisms, such as accelerated disassembly of the active oxidase complex.



Proposed function of PR3 and NE in IC-mediated inflammation.

TNF-α–primed neutrophils extravasate from blood vessels, translocate PR3/NE to the cellular surface, and discharge PGRN to the pericellular environment (i). During transmigration of interstitial tissues (ii), neutrophil activation is initially suppressed by relatively high pericellular levels of antiinflammatory PGRN (green shading), which is also produced locally by keratinocytes and epithelial cells of the skin. Until IC depots are reached, neutrophil activation is inhibited by PGRN. Surface receptors (e.g., Mac-1) recognize ICs, which results in signal transduction (black dotted arrow) and activation of the phox. The molecular pathway of PGRN-mediated inhibition is not completely understood, but it may interfere with integrin signaling after IC encounter (green dotted line inside the cell). Adherence of neutrophils to ICs (iii) further increases pericellular PR3 and NE activity. PR3 and NE cooperatively degrade PGRN in the early stage of neutrophilic activation to facilitate optimal neutrophil activation (red shading), resulting in sustained integrin signaling (red arrow) and robust production of ROS by the phox system. Subsequently, neutrophils release ROS together with other proinflammatory mediators and chemotactic agents, thereby enhancing the recruitment of further neutrophils and establishing inflammation (iv). In the absence of PR3/NE, the switch from inflammation-suppressing (ii) to inflammation-enhancing (iii) conditions is substantially delayed, resulting in diminished inflammation in response to ICs (iv).


NSPs are strongly implicated as effector molecules in a large number of destructive diseases, such as emphysema or the autoimmune blistering skin disease bullous pemphigoid (143537). Normally, PR3/NE activity is tightly controlled by high plasma levels of α1-antitrypsin. This balance between proteases and protease inhibitors is disrupted in patients with genetic α1-antitrypsin deficiency, which represents a high risk factor for the development of emphysema and certain autoimmune disorders (38). The pathogenic effects of NSPs in these diseases have so far been associated with tissue destruction by the proteases after their release from dying neutrophils. Our findings showed that PR3 and NE were already involved in much earlier events of the inflammatory process, because the enzymes directly regulated cellular activation of infiltrating neutrophils by degrading inflammation-suppressing PGRN. This concept is further supported by previous studies showing increased inflammation in mice lacking serine protease inhibitors such as SERPINB1 or SLPI (3940). Blocking PR3/NE activity using specific inhibitors therefore represents a promising therapeutic strategy to treat chronic, noninfectious inflammation. Serine protease inhibitors as antiinflammatory agents can interfere with the disease process at 2 different stages, because they attenuate both early events of neutrophil activation and proteolytic tissue injury caused by released NSPs.





Editorial: Serine proteases, serpins, and neutropenia

David C. Dale

J Leuko Biol July 2011;  90(1): 3-4   http://dx.doi.org:/10.1189/jlb.1010592

Cyclic neutropenia and severe congenital neutropenia are autosomal-dominant diseases usually attributable to mutations in the gene for neutrophil elastase orELANE. Patients with these diseases are predisposed to recurrent and life-threatening infections [1]. Neutrophil elastase, the product of the ELANE gene, is a serine protease that is synthesized and packaged in the primary granules of neutrophils. These granules are formed at the promyelocytes stage of neutrophil development. Synthesis of mutant neutrophil elastase in promyelocytes triggers the unfolded protein response and a cascade of intracellular events, which culminates in death of neutrophil precursors through apoptosis [2]. This loss of cells causes the marrow abnormality often referred to as “maturation arrest” [34].

Neutrophil elastase is one of the serine proteases normally inhibited by serpinB1. In this issue of JLB, Benarafa and coauthors [5] present their intriguing studies of serpinB1 expression in human myeloid cells and their extensive investigations ofSERPINB1−/− mice. They observed that serpinB1 expression parallels protease expression. The peak of serpinB1 expression occurs in promyelocytes. Benarafa et al. [5] found that SERPINB1−/− mice have a deficiency of postmitotic neutrophils in the bone marrow. This change was accompanied by an increase in the plasma levels of G-CSF. The decreased supply of marrow neutrophils reduced the number of neutrophils that could be mobilized to an inflammatory site. Using colony-forming cell assays, they determined that the early myeloid progenitor pool was intact. Separate assays showed that maturing myeloid cells were being lost through accelerated apoptosis of maturing neutrophils in the marrow. The authors concluded that serpinB1 is required for maintenance of a healthy reserve of marrow neutrophils and a normal acute immune response [5].

This paper provides new and fascinating insights for understanding the mechanism for neutropenia. It also suggests opportunities to investigate potential therapies for patients with neutropenia and prompts several questions. As inhibition of the activity of intracellular serine proteases is the only known function of serpinB1, the findings reported by Benarafa et al. [5] suggest that uninhibited serine proteases perturbed neutrophil production severely. The SERPINB1−/− mice used in their work have accelerated apoptosis of myeloid cells, a finding suggesting that uninhibited serine proteases or mutant neutrophil elastase perturb myelopoiesis by similar mechanisms. It is now important to determine whether the defect in the SERPINB1−/− mice is, indeed, attributable to uninhibited activity of normal neutrophil elastase, other neutrophil proteases, or another mechanism. ″Double-knockout″ studies in mice deficient in neutrophil elastase and serpinB1 might provide an answer.

This report provides evidence regarding the intracellular mechanisms for the apoptosis of myeloid cells and indicates that other studies are ongoing. The key antiapoptotic proteins, Mcl-1, Bcl-XL, and A1/Bfl-I, are apparently not involved. A more precise understanding of the mechanisms of cell death is important for development of targeted therapies for neutropenia. It is also important to discover whether only cells of the neutrophil lineage are involved or whether monocytes are also affected. In cyclic and congenital neutropenia, patients failed to produce neutrophils, but they can produce monocytes; in fact, they overproduce monocytes and have significantly elevated blood monocyte counts. Neutropenia with monocytosis is probably attributable to differences in the expression of ELANE in the two lineages. Benarafa et al. [5] reported that human bone marrow monocytes contain substantially less serpinB1 than marrow neutrophils, suggesting that the expression of serpinB1 and the serine proteases are closely coordinated.

This report shows the importance of the marrow neutrophil reserves in the normal response to infections. Compared with humans, healthy mice are always neutropenic, but they have a bigger marrow neutrophil reserve, and their mature neutrophils in the marrow and blood look like human band neutrophils. These differences are well known, but they are critical for considering the clinical inferences that can be made from this report. For example, although theSERPINB1−/− mice were not neutropenic, human SERPINB1−/− might cause neutropenia because of physiological differences between the species. If some but not all mutations in SERPINB1 cause neutropenia, we might gain a better understanding about how serpinB1 normally inhibits the neutrophil’s serine proteases.

We do not know if some or all of the mutant neutrophil elastases can be inhibited by serpinB1. We do not know whether cyclic or congenital neutropenia are attributable to defects in this interaction. However, we do know that there are chemical inhibitors of neutrophil elastase that can abrogate apoptosis of myeloid cells in a cellular model for congenital neutropenia [6]. It would be interesting to see if these chemical inhibitors can replace the natural inhibitor and normalize neutrophil production in the SERPINB1−/− mice. This would provide evidence to support use of chemical protease inhibitors as a treatment for cyclic and congenital neutropenia.

Concerns with the use of G-CSF for the treatment of cyclic and congenital neutropenia are how and why some of these patients are at risk of developing leukemia. Are the SERPINB1−/− mice with a hyperproliferative marrow and high G-CSF levels also at risk of developing myeloid leukemia?

This is a very provocative paper, and much will be learned from further studies of the SERPINB1−/− mice.


SerpinB1 is critical for neutrophil survival through cell-autonomous inhibition of cathepsin G

Mathias Baumann1,2, Christine T. N. Pham3, and Charaf Benarafa1

Blood May 9, 2013; 121(19)   http://www.bloodjournal.org/content/121/19/3900

Key Points

  • Serine protease inhibitor serpinB1 protects neutrophils by inhibition of their own azurophil granule protease cathepsin G.
  • Granule permeabilization in neutrophils leads to cathepsin G–mediated death upstream and independent of apoptotic caspases.


Bone marrow (BM) holds a large reserve of polymorphonuclear neutrophils (PMNs) that are rapidly mobilized to the circulation and tissues in response to danger signals. SerpinB1 is a potent inhibitor of neutrophil serine proteases neutrophil elastase (NE) and cathepsin G (CG). SerpinB1 deficiency (sB1−/−) results in a severe reduction of the BM PMN reserve and failure to clear bacterial infection. Using BM chimera, we found that serpinB1 deficiency in BM cells was necessary and sufficient to reproduce the BM neutropenia ofsB1−/− mice. Moreover, we showed that genetic deletion of CG, but not NE, fully rescued the BM neutropenia in sB1−/− mice. In mixed BM chimera and in vitro survival studies, we showed that CG modulates sB1−/− PMN survival through a cell-intrinsic pathway. In addition, membrane permeabilization by lysosomotropic agent L-leucyl-L-leucine methyl ester that allows cytosolic release of granule contents was sufficient to induce rapid PMN death through a CG-dependent pathway. CG-mediated PMN cytotoxicity was only partly blocked by caspase inhibition, suggesting that CG cleaves a distinct set of targets during apoptosis. In conclusion, we have unveiled a new cytotoxic function for the serine protease CG and showed that serpinB1 is critical for maintaining PMN survival by antagonizing intracellular CG activity.


Polymorphonuclear neutrophil (PMN) granulocytes are essential components of the innate immune response to infection. PMNs are relatively short-lived leukocytes that originate from hematopoietic stem cells in the bone marrow (BM) in a process called granulopoiesis. Granulopoiesis proceeds through a proliferative phase followed by a maturation phase. After maturation, the BM retains a large reserve of mature PMNs, which includes over 90% of the mature PMNs in the body while only a small proportion (1%-5%) is in the blood.1,2 Even in noninflammatory conditions, granulopoiesis is remarkable as >1011 PMNs are produced daily in an adult human, only to be disposed of, largely unused, a few hours later.3 There is evidence that the majority of PMNs produced never reach circulation and die within the BM.4 Congenital or acquired forms of neutropenia are associated with the highest risks of bacterial and fungal infection,5 indicating a strong evolutionary pressure to maintain granulopoiesis at high levels and sustain a large mobilizable pool of PMNs in the BM.

In steady state, PMNs die by apoptosis, a form of programmed cell death that allows for the safe disposal of aging PMNs and their potentially toxic cargo. Like in other cells, caspases participate in the initiation, amplification, and execution steps of apoptosis in PMNs.6,7 Interestingly, noncaspase cysteine proteases calpain and cathepsin D were reported to induce PMN apoptosis through activation of caspases.811 In addition, PMNs carry a unique set of serine proteases (neutrophil serine proteases [NSPs]) including elastase (NE), cathepsin G (CG), and proteinase-3 (PR3) stored active in primary granules. There is strong evidence for a role of NSPs in killing pathogens and inducing tissue injury when released extracellularly.1214 In contrast, the function of NSPs in PMN homeostasis and cell death remains elusive. In particular, no defects in granulopoiesis or PMN homeostasis have been reported in mice deficient in cathepsin G (CG−/−),15 neutrophil elastase (NE−/−),16,17 or dipeptidylpeptidase I (DPPI−/−), which lack active NSPs.18 We have recently shown that mice lacking the serine protease inhibitor serpinB1 (sB1−/−) have reduced PMN survival in the lungs following Pseudomonas infection and that these mice have a profound reduction in mature PMN numbers in the BM.19,20SerpinB1, also known as monocyte NE inhibitor, is expressed at high levels in the cytoplasm of PMNs and is one of the most potent inhibitors of NE, CG, and PR3.21,22 In this study, we tested the hypothesis that serpinB1 promotes PMN survival by inhibiting 1 or several NSPs, and we discovered a novel regulatory pathway in PMN homeostasis in vivo.



Figure 1

Defective PMN reserve in BM chimera depends on serpinB1 deficiency in the hematopoietic compartment. Flow cytometry analysis of major BM leukocyte subsets of lethally irradiated mice was performed 8 to 10 weeks after BM transfer. (A) Irradiated WT (CD45.1) mice were transferred with WT (●) or sB1−/− (○) BM cells. (B) Irradiated WT (●) andsB1−/− (○) mice both CD45.2 were transferred with WT (CD45.1) BM cells. Each circle represents leukocyte numbers for 1 mouse and horizontal line indicates the median. Median subsets numbers were compared by the Mann-Whitney test (*P < .05; ***P < .001).

CG regulates neutrophil numbers in the BM

Because serpinB1 is an efficient inhibitor of NE, CG, and PR3, we then examined PMN numbers in mice deficient in 1 or several NSPs in combination with serpinB1 deletion. As expected, sB1−/− mice had significantly reduced numbers and percentage of mature PMNs in the BM compared with WT and heterozygous sB1+/− mice. In addition, PMN numbers were normal in mice deficient in either DPPI, NE, or CG (Figure 2A). DPPI is not inhibited by serpinB1 but is required for the activation of all NSPs, and no NSP activity is detectable in DPPI−/− mice.18,23 PMN counts in DPPI−/−.sB1−/− BM were significantly higher than in sB1−/− BM, suggesting that 1 or several NSPs contribute to the PMN survival defect. To examine the role of NSPs in this process, we crossed several NSP-deficient strains with sB1−/− mice. We found that NE.CG.sB1−/− mice had normal PMN numbers indicating that these NSPs play a key role in the defective phenotype of sB1−/− PMNs (Figure 2A). Furthermore, CG.sB1−/− mice showed normal PMN numbers whereasNE.sB1−/− mice retained the BM neutropenia phenotype indicating that CG, but not NE, plays a significant role in the death of sB1−/− PMNs (Figure 2A). In addition, the double-deficient NE.sB1−/− mice had significantly lower BM myelocyte numbers than sB1−/− mice while the myelocyte numbers in singly deficient NE−/− and sB1−/− BM were normal (Figure 2B). These results suggest that NE may promote myeloid cell proliferation, an activity that is revealed only when serpinB1 is absent. This complex interaction between sB1 and NE requires further investigation. On the other hand, B-cell and monocyte numbers and relative percentage in the BM were largely similar in all genotypes (supplemental Figure 2). Total numbers of blood leukocytes, erythrocytes, and platelets were normal in mice deficient in NSPs and/or serpinB1 (supplemental Figure 3). PMN numbers in blood were normal insB1−/− mice in steady state and combined deficiency of NSPs did not significantly alter these numbers (Figure 2C). Taken together, our results indicate that serpinB1 likely sustains the survival of postmitotic PMNs through its interaction with CG.

Figure 2

PMN and myelocyte numbers in BM and blood of mice deficient in NSPs and serpinB1.


CG-mediated PMN death proceeds independent of caspase activity

Figure 4

sB1−/− PMN death mediated by CG does not require caspase activity


Granule membrane permeabilization induces CG-mediated death in PMNs

To test whether granule disruption contributes to the serpinB1-regulated CG-dependent cell death, BM cells were treated with the lysosomotropic agent LLME. LLME accumulates in lysosomes where the acyl transferase activity of DPPI generates hydrophobic (Leu-Leu)n-OMe polymers that induce lysosomal membrane permeabilization (LMP) and cytotoxicity in granule-bearing cells such as cytotoxic T lymphocytes, NK cells, and myeloid cells.29,30

Figure 5

LMP induces CG-mediated death in PMNs


G-CSF therapy increases sB1−/− PMN numbers via enhanced granulopoiesis

G-CSF therapy is an effective long-term treatment in many cases of severe congenital neutropenia and it is also used to prevent chemotherapy-induced febrile neutropenia by enhancing PMN production. In addition, G-CSF delays neutrophil apoptosis by differentially regulating proapoptotic and antiapoptotic factors.10 To test whether G-CSF could rescue sB1−/− PMN survival defect, WT and sB1−/− mice were treated with therapeutic doses of G-CSF or saline for 5 days and BM and blood PMNs were analyzed 24 hours after the last injection. Total counts of myelocytes and PMNs were significantly increased in the BM of treated mice compared with their respective untreated genotype controls (Figure 6A-B). The increase in myelocyte numbers was identical in G-CSF–treated WT and sB1−/− mice, indicating that G-CSF–induced granulopoiesis proceeds normally in sB1−/−myeloid progenitors (Figure 6B).

Figure 6

In vivo G-CSF therapy increases PMN numbers in BM of sB1−/− mice.


SerpinB1 is a member of the clade B serpins, a subfamily composed of leaderless proteins with nucleocytoplasmic localization. Clade B serpins are often expressed in cells that also carry target proteases, which led to the hypothesis that intracellular serpins protect against misdirected granule proteases and/or protect bystander cells from released proteases.31 We previously reported that deficiency in serpinB1 is associated with reduced PMN survival in the BM and at inflammatory sites.19,20 The evidence presented here demonstrates that the cytoprotective function of serpinB1 in PMNs is based on the inhibition of granule protease CG. Deficiency in CG was sufficient to rescue the defect of sB1−/− mice as illustrated by normal PMN counts in the BM of double knockout CG.sB1−/− mice. We also showed that the protease-serpin interaction occurred within PMNs. Indeed, WT PMNs had a greater survival over sB1−/− PMNs in mixed BM chimera, whereas the survival of CG.sB1−/− PMNs was similar to WT PMNs after BM transfer. SerpinB1 is an ancestral clade B serpin with a conserved specificity determining reactive center loop in all vertebrates.32 Furthermore, human and mouse serpinB1 have the same specificity for chymotrypsin-like and elastase-like serine proteases.21,22 Likewise, human and mouse CG have identical substrate specificities and the phenotype of CG−/− murine PMN can be rescued by human CG.33 Therefore, it is highly likely that the antagonistic functions of CG and serpinB1 in cellular homeostasis observed in mice can be extended to other species.

Extracellular CG was previously reported to promote detachment-induced apoptosis (anoikis) in human and mouse cardiomyocytes.34 This activity is mediated through the shedding and transactivation of epidermal growth factor receptor and downregulation of focal adhesion signaling.35,36 In our study, exogenous human CG also induced PMN death in vitro but these effects were not enhanced in sB1−/− PMNs and the neutropenia associated with serpinB1 deficiency was principally cell intrinsic. How intracellular CG induces PMN death remains to be fully investigated. However, our studies provide some indications on the potential pathways. Like other NSPs, the expression of CG is transcriptionally restricted to the promyelocyte stage during PMN development and NSPs are then stored in active form in primary azurophil granules.37 Because serpinB1 is equally efficient at inhibiting NE, CG, and PR3, it was surprising that deletion of CG alone was sufficient to achieve a complete reversal of the PMN survival defect in CG.sB1−/− mice. A possible explanation would be that CG gains access to targets more readily than other granule proteases. There is evidence that binding to serglycin proteoglycans differs between NE and CG resulting in altered sorting of NE but not CG into granules of serglycin-deficient PMNs.38 Different interactions with granule matrix may thus contribute to differential release of CG from the granules compared with other NSPs. However, because sB1−/− PMNs have similar levels of CG and NE as WT PMNs20 and because LLME-induced granule permeabilization likely releases all granule contents equally, we favor an alternative interpretation where CG specifically targets essential cellular components that are not cleaved by the other serpinB1-inhibitable granule proteases. Upon granule permeabilization, we found that CG can induce cell death upstream of caspases as well as independent of caspases. CG was previously shown to activate caspase-7 in vitro and it functions at neutral pH, which is consistent with a physiological role in the nucleocytoplasmic environment.39 Cell death induced by lysosomal/granule membrane permeabilization has previously been linked to cysteine cathepsins in other cell types. However, these proteases appear to depend on caspase activation to trigger apoptosis and they function poorly at neutral pH, questioning their potential role as regulators of cell death.40 In contrast, CG-mediated cell death is not completely blocked by caspase inhibition, which is a property reminiscent of granzymes in cytotoxic T cells.41 In fact, CG is phylogenetically most closely related to serine proteases granzyme B and H.42 Granzymes have numerous nuclear, mitochondrial, and cytoplasmic target proteins leading to cell death41 and we anticipate that this may also be the case for CG.


G-CSF therapy is successfully used to treat most congenital and acquired neutropenia through increased granulopoiesis, mobilization from the BM, and increased survival of PMNs. Prosurvival effects of G-CSF include the upregulation of antiapoptotic Bcl-2 family members, which act upstream of the mitochondria and the activation of effector caspases. In sB1−/− mice, G-CSF levels in serum are fourfold higher than in WT mice in steady state and this is accompanied by an upregulation of the antiapoptotic Bcl-2 family member Mcl-1 in sB1−/− PMNs.19 Here, G-CSF therapy significantly increased granulopoiesis in both WT and sB1−/− mice. However, the PMN numbers in treated sB1−/− BM and blood were significantly lower than those of treated WT mice, indicating only a partial rescue of the survival defect. This is consistent with our findings that CG-mediated death can proceed independent of caspases and can thus bypass antiapoptotic effects mediated by G-CSF.

CG has largely been studied in association with antimicrobial and inflammatory functions due to its presence in PMNs.1214,49 In this context, we have previously shown that serpinB1 contributes to prevent increased mortality and morbidity associated with production of inflammatory cytokines upon infection with Pseudomonas aeruginosa and influenza A virus.20,50 In this study, we demonstrate that serpinB1 inhibition of the primary granule protease CG in PMNs is essential for PMN survival and this ultimately regulates PMN numbers in vivo. Our findings also extend the roles of CG from antimicrobial and immunoregulatory functions to a novel role in inducing cell death.


Neutrophil Elastase, Proteinase 3, and Cathepsin G as Therapeutic Targets in Human Diseases

Brice KorkmazMarshall S. HorwitzDieter E. Jenne and Francis Gauthier
Pharma Rev Dec 2010; 62(4):726-759  http://dx.doi.org:/10.1124/pr.110.002733

Polymorphonuclear neutrophils are the first cells recruited to inflammatory sites and form the earliest line of defense against invading microorganisms. Neutrophil elastase, proteinase 3, and cathepsin G are three hematopoietic serine proteases stored in large quantities in neutrophil cytoplasmic azurophilic granules. They act in combination with reactive oxygen species to help degrade engulfed microorganisms inside phagolysosomes. These proteases are also externalized in an active form during neutrophil activation at inflammatory sites, thus contributing to the regulation of inflammatory and immune responses. As multifunctional proteases, they also play a regulatory role in noninfectious inflammatory diseases. Mutations in the ELA2/ELANE gene, encoding neutrophil elastase, are the cause of human congenital neutropenia. Neutrophil membrane-bound proteinase 3 serves as an autoantigen in Wegener granulomatosis, a systemic autoimmune vasculitis. All three proteases are affected by mutations of the gene (CTSC) encoding dipeptidyl peptidase I, a protease required for activation of their proform before storage in cytoplasmic granules. Mutations of CTSC cause Papillon-Lefèvre syndrome. Because of their roles in host defense and disease, elastase, proteinase 3, and cathepsin G are of interest as potential therapeutic targets. In this review, we describe the physicochemical functions of these proteases, toward a goal of better delineating their role in human diseases and identifying new therapeutic strategies based on the modulation of their bioavailability and activity. We also describe how nonhuman primate experimental models could assist with testing the efficacy of proposed therapeutic strategies.


Human polymorphonuclear neutrophils represent 35 to 75% of the population of circulating leukocytes and are the most abundant type of white blood cell in mammals (Borregaard et al., 2005). They are classified as granulocytes because of their intracytoplasmic granule content and are characterized by a multilobular nucleus. Neutrophils develop from pluripotent stem cells in the bone marrow and are released into the bloodstream where they reach a concentration of 1.5 to 5 × 109 cells/liter. Their half-life in the circulation is only on the order of a few hours. They play an essential role in innate immune defense against invading pathogens and are among the primary mediators of inflammatory response. During the acute phase of inflammation, neutrophils are the first inflammatory cells to leave the vasculature, where they migrate toward sites of inflammation, following a gradient of inflammatory stimuli. They are responsible for short-term phagocytosis during the initial stages of infection (Borregaard and Cowland, 1997Hampton et al., 1998Segal, 2005). Neutrophils use complementary oxidative and nonoxidative pathways to defend the host against invading pathogens (Kobayashi et al., 2005).

The three serine proteases neutrophil elastase (NE1), proteinase 3 (PR3), and cathepsin G (CG) are major components of neutrophil azurophilic granules and participate in the nonoxidative pathway of intracellular and extracellular pathogen destruction. These neutrophil serine proteases (NSPs) act intracellularly within phagolysosomes to digest phagocytized microorganisms in combination with microbicidal peptides and the membrane-associated NADPH oxidase system, which produces reactive oxygen metabolites (Segal, 2005). An additional extracellular antimicrobial mechanism, neutrophil extracellular traps (NET), has been described that is made of a web-like structure of DNA secreted by activated neutrophils (Papayannopoulos and Zychlinsky, 2009) (Fig. 1). NETs are composed of chromatin bound to positively charged molecules, such as histones and NSPs, and serve as physical barriers that kill pathogens extracellularly, thus preventing further spreading. NET-associated NSPs participate in pathogen killing by degrading bacterial virulence factors extracellularly (Brinkmann et al., 2004;Papayannopoulos and Zychlinsky, 2009).


Fig. 1.

Polymorphonuclear neutrophil. Quiescent (A) and chemically activated (B) neutrophils purified from peripheral blood. C, PMA-activated neutrophils embedded within NET and neutrophil spreading on insoluble elastin.

In addition to their involvement in pathogen destruction and the regulation of proinflammatory processes, NSPs are also involved in a variety of inflammatory human conditions, including chronic lung diseases (chronic obstructive pulmonary disease, cystic fibrosis, acute lung injury, and acute respiratory distress syndrome) (Lee and Downey, 2001Shapiro, 2002Moraes et al., 2003Owen, 2008b). In these disorders, accumulation and activation of neutrophils in the airways result in excessive secretion of active NSPs, thus causing lung matrix destruction and inflammation. NSPs are also involved in other human disorders as a consequence of gene mutations, altered cellular trafficking, or, for PR3, autoimmune disease. Mutations in the ELA2/ELANE gene encoding HNE are the cause of human cyclic neutropenia and severe congenital neutropenia (Horwitz et al., 19992007). Neutrophil membrane-bound proteinase 3 (mPR3) is the major target antigen of anti-neutrophil cytoplasmic autoantibodies (ANCA), which are associated with Wegener granulomatosis (Jenne et al., 1990). All three proteases are affected by mutation of the gene (CTSC) encoding dipeptidyl peptidase I (DPPI), which activates several granular hematopoietic serine proteases (Pham and Ley, 1999Adkison et al., 2002). Mutations of CTSC cause Papillon-Lefèvre syndrome and palmoplantar keratosis (Hart et al., 1999Toomes et al., 1999).


Fully processed mature HNE, PR3, and CG isolated from azurophilic granules contain, respectively, 218 (Bode et al., 1986Sinha et al., 1987), 222 (Campanelli et al., 1990b), and 235 (Salvesen et al., 1987Hof et al., 1996) residues. They are present in several isoforms depending on their carbohydrate content, with apparent mass of 29 to 33 kDa upon SDS-polyacrylamide gel electrophoresis (Twumasi and Liener, 1977Watorek et al., 1993). HNE and PR3 display two sites of N-glycosylation, whereas CG possesses only one. NSPs are stored mainly in neutrophil azurophilic granules, but HNE is also localized in the nuclear envelope, as revealed by immunostaining and electron microscopy (Clark et al., 1980;Benson et al., 2003), whereas PR3 is also found in secretory vesicles (Witko-Sarsat et al., 1999a). Upon neutrophil activation, granular HNE, PR3, and CG are secreted extracellularly, although some molecules nevertheless remain at the cell surface (Owen and Campbell, 1999Owen, 2008a). The mechanism through which NSPs are sorted from the trans-Golgi network to the granules has not been completely defined, even though an intracellular proteoglycan, serglycin, has been identified as playing a role in elastase sorting and packaging into azurophilic granules (Niemann et al., 2007). Unlike HNE and CG, PR3 is constitutively expressed on the membranes of freshly isolated neutrophils (Csernok et al., 1990Halbwachs-Mecarelli et al., 1995). Stimulation of neutrophils at inflammatory sites triggers intracytoplasmic granules to translocate to the phagosomes and plasma membrane, thereby liberating their contents. The first step of the translocation to the target membrane depends on cytoskeleton remodeling and microtubule assembly (Burgoyne and Morgan, 2003). This is followed by a second step of granule tethering and docking, which are dependent on the sequential intervention of SNARE proteins (Jog et al., 2007).


Exposure of neutrophils to cytokines (TNF-α), chemoattractants (platelet-activating factor, formyl-Met-Leu-Phe, or IL-8), or bacterial lipopolysaccharide leads to rapid granule translocation to the cell surface with secretion of HNE, PR3, and CG into the extracellular medium (Owen and Campbell, 1999). A fraction of secreted HNE, PR3, and CG is detected at the surface of activated neutrophils (Owen et al., 1995a1997Campbell et al., 2000). Resting purified neutrophils from peripheral blood express variable amounts of PR3 on their surface. A bimodal, apparently genetically determined, distribution has been observed with two populations of quiescent neutrophils that express or do not express the protease at their surface (Halbwachs-Mecarelli et al., 1995Schreiber et al., 2003). The percentage of mPR3-positive neutrophils ranges from 0 to 100% of the total neutrophil population within individuals. Furthermore, the percentage of mPR3-positive neutrophils remains stable over time and is not affected by neutrophil activation (Halbwachs-Mecarelli et al., 1995).

The mechanism through which HNE and CG are associated with the outer surface of the plasma membrane of neutrophils mainly involves electrostatic interactions with the sulfate groups of chondroitin sulfate- and heparan sulfate-containing proteoglycans (Campbell and Owen, 2007). These two proteases are released from neutrophil cell surfaces by high concentrations of salt (Owen et al., 1995b1997;Korkmaz et al., 2005a) and after treatment with chondroitinase ABC and heparinase (Campbell and Owen, 2007). Membrane PR3 is not solubilized by high salt concentrations, which means that its membrane association is not charge dependant (Witko-Sarsat et al., 1999aKorkmaz et al., 2009). Unlike HNE and CG, PR3 bears at its surface a hydrophobic patch formed by residues Phe166, Ile217, Trp218, Leu223, and Phe224 that is involved in membrane binding (Goldmann et al., 1999Hajjar et al., 2008) (Fig. 3B). Several membrane partners of PR3 have been identified, including CD16/FcγRIIIb (David et al., 2005Fridlich et al., 2006), phospholipid scramblase-1, a myristoylated membrane protein with translocase activity present in lipid rafts (Kantari et al., 2007), CD11b/CD18 (David et al., 2003), and human neutrophil antigen NB1/CD177 (von Vietinghoff et al., 2007Hu et al., 2009), a 58- to 64-kDa glycosyl-phosphatidylinositol anchored surface receptor belonging to the urokinase plasminogen activator receptor superfamily (Stroncek, 2007). NB1 shows a bimodal distribution that superimposes with that of PR3 on purified blood neutrophils (Bauer et al., 2007). Active, mature forms of PR3 but not pro-PR3 can bind to the surface of NB1-transfected human embryonic kidney 293 cells (von Vietinghoff et al., 2008) and Chinese hamster ovary cells (Korkmaz et al., 2008b). Interaction involves the hydrophobic patch of PR3 because specific amino acid substitutions disrupting this patch in the closely related gibbon PR3 prevent binding to NB1-transfected cells (Korkmaz et al., 2008b). Decreased interaction of pro-PR3 with NB1-transfected cells is explained by the topological changes affecting the activation domain containing the hydrophobic patch residues. Together, these results support the hydrophobic nature of PR3-membrane interaction.


Roles in Inflammatory Process Regulation

NSPs are abundantly secreted into the extracellular environment upon neutrophil activation at inflammatory sites. A fraction of the released proteases remain bound in an active form on the external surface of the plasma membrane so that both soluble and membrane-bound NSPs are able to proteolytically regulate the activities of a variety of chemokines, cytokines, growth factors, and cell surface receptors. Secreted proteases also activate lymphocytes and cleave apoptotic and adhesion molecules (Bank and Ansorge, 2001Pham, 2006Meyer-Hoffert, 2009). Thus, they retain pro- and anti-inflammatory activities, resulting in a modulation of the immune response at sites of inflammation.


Processing of Cytokines, Chemokines, and Growth Factors.

Processing and Activation of Cellular Receptors.

Induction of Apoptosis by Proteinase 3.

Physiological Inhibitors of Elastase, Proteinase 3, and Cathepsin G

During phagocytosis and neutrophil turnover, HNE, PR3, and CG are released into the extracellular space as active proteases. The proteolytic activity of HNE, PR3, and CG seems to be tightly regulated in the extracellular and pericellular space to avoid degradation of connective tissue proteins including elastin, collagen, and proteoglycans (Janoff, 1985). Protein inhibitors that belong to three main families, the serpins, the chelonianins, and the macroglobulins, ultimately control proteolytic activity of HNE, PR3, and CG activities. The individual contributions of these families depend on their tissue localization and that of their target proteases. The main characteristics of HNE, PR3, and CG physiological inhibitors are presented in Table 2.


Serine Protease Inhibitors

Serpins are the largest and most diverse family of protease inhibitors; more than 1000 members have been identified in human, plant, fungi, bacteria, archaea, and certain viruses (Silverman et al., 2001Mangan et al., 2008). They share a similar highly conserved tertiary structure and similar molecular weight of approximately 50 kDa. Human serpins belong to the first nine clades (A–I) of the 16 that have been described based on phylogenic relationships (Irving et al., 2000Silverman et al., 2001Mangan et al., 2008). For historical reasons, α1-protease inhibitor (α1-PI) was assigned to the first clade. Clade B, also known as the ov-serpin clan because of the similarity of its members to ovalbumin (a protein that belongs to the serpin family but lacks inhibitory activity), is the second largest clan in humans, with 15 members identified so far. Ov-serpin clan members are generally located in the cytoplasm and, to a lesser extent, on the cell surface and nucleus (Remold-O’Donnell, 1993).

Serpins play important regulatory functions in intracellular and extracellular proteolytic events, including blood coagulation, complement activation, fibrinolysis, cell migration, angiogenesis, and apoptosis (Potempa et al., 1994). Serpin dysfunction is known to contribute to diseases such as emphysema, thrombosis, angioedema, and cancer (Carrell and Lomas, 1997Lomas and Carrell, 2002). Most inhibitory serpins target trypsin-/chymotrypsin-like serine proteases, but some, termed “cross-class inhibitors,” have been shown to target cysteine proteases (Annand et al., 1999). The crystal structure of the prototype plasma inhibitor α1-PI revealed the archetype native serpin fold (Loebermann et al., 1984). All serpins typically have three β-sheets (termed A, B, and C) and eight or nine α-helices (hA–hI) arranged in a stressed configuration. The so-called reactive center loop (RCL) of inhibitory molecules determines specificity and forms the initial encounter complex with the target protease (Potempa et al., 1994Silverman et al., 2001). Serpins inhibit proteases by a suicide substrate inhibition mechanism. The protease initially recognizes the serpin as a potential substrate using residues of the reactive center loop and cleaves it between P1 and P1′ This cleavage allows insertion of the cleaved RCL into the β-sheet A of the serpin, dragging the protease with it and moving it over 71 Å to the distal end of the serpin to form a 1:1 stoichiometric covalent inhibitory complex (Huntington et al., 2000). Such cleavage generates a ∼4-kDa C-terminal fragment that remains noncovalently bound to the cleaved serpin. Displacement of the covalently attached active site serine residue from its catalytic partner histidine explains the loss of catalytic function in the covalent complex. The distortion of the catalytic site structure prevents the release of the protease from the complex, and the structural disorder induces its proteolytic inactivation (Huntington et al., 2000). Covalent complex formation between serpin and serine proteases triggers a number of conformational changes, particularly in the activation domain loops of the bound protease (Dementiev et al., 2006).


Pathophysiology of Elastase, Proteinase 3 and Cathepsin G in Human Diseases

In many instances, the initiation and propagation of lung damage is a consequence of an exaggerated inappropriate inflammatory response, which includes the release of proteases and leukocyte-derived cytotoxic products (Owen, 2008b;Roghanian and Sallenave, 2008). Inflammation is a physiological protective response to injury or infection consisting of endothelial activation, leukocyte recruitment and activation, vasodilation, and increased vascular permeability. Although designed to curtail tissue injury and facilitate repair, the inflammatory response sometimes results in further injury and organ dysfunction. Inflammatory chronic lung diseases, chronic obstructive pulmonary disease, acute lung injury, acute respiratory distress syndrome, and cystic fibrosis are syndromes of severe pulmonary dysfunction resulting from a massive inflammatory response and affecting millions of people worldwide. The histological hallmark of these chronic inflammatory lung diseases is the accumulation of neutrophils in the microvasculature of the lung. Neutrophils are crucial to the innate immune response, and their activation leads to the release of multiple cytotoxic products, including reactive oxygen species and proteases (serine, cysteine, and metalloproteases). The physiological balance between proteases and antiproteases is required for the maintenance of the lung’s connective tissue, and an imbalance in favor of proteases results in lung injury (Umeki et al., 1988Tetley, 1993). A number of studies in animal and cell culture models have demonstrated a contribution of HNE and related NSPs to the development of chronic inflammatory lung diseases. Available preclinical and clinical data suggest that inhibition of NSP in lung diseases suppresses or attenuates the contribution of NSP to pathogenesis (Chughtai and O’Riordan, 2004Voynow et al., 2008Quinn et al., 2010). HNE could also participate in fibrotic lung remodeling by playing a focused role in the conversion of latent transforming growth factor-β into its biologically active form (Chua and Laurent, 2006Lungarella et al., 2008).

Anti-Neutrophil Cytoplasmic Autoantibody-Associated Vasculitides

ANCA-associated vasculitides encompasses a variety of diseases characterized by inflammation of blood vessels and by the presence of autoantibodies directed against neutrophil constituents. These autoantibodies are known as ANCAs (Kallenberg et al., 2006). In Wegener granulomatosis (WG), antibodies are mostly directed against PR3. WG is a relatively uncommon chronic inflammatory disorder first described in 1931 by Heinz Karl Ernst Klinger as a variant of polyarteritis nodosa (Klinger, 1931). In 1936, the German pathologist Friedrich Wegener described the disease as a distinct pathological entity (Wegener, 19361939). WG is characterized by necrotizing granulomatous inflammation and vasculitis of small vessels and can affect any organ (Fauci and Wolff, 1973Sarraf and Sneller, 2005). The most common sites of involvement are the upper and lower respiratory tract and the kidneys. WG affects approximately 1 in 20,000 people; it can occur in persons of any age but most often affects those aged 40 to 60 years (Walton, 1958Cotch et al., 1996). Approximately 90% of patients have cold or sinusitis symptoms that fail to respond to the usual therapeutic measures and that last considerably longer than the usual upper respiratory tract infection. Lung involvement occurs in approximately 85% of the patients. Other symptoms include nasal membrane ulcerations and crusting, saddle-nose deformity, inflammation of the ear with hearing problems, inflammation of the eye with sight problems, and cough (with or without hemoptysis).

Hereditary Neutropenias

Neutropenia is a hematological disorder characterized by an abnormally low number of neutrophils (Horwitz et al., 2007). The normal neutrophil count fluctuates across human populations and within individual patients in response to infection but typically lies in the range of 1.5 to 5 × 109 cells/liter. Neutropenia is categorized as severe when the cell count falls below 0.5 × 109 cells/liter. Hence, patients with neutropenia are more susceptible to bacterial infections and, without prompt medical attention, the condition may become life-threatening. Common causes of neutropenia include cancer chemotherapy, drug reactions, autoimmune diseases, and hereditary disorders (Berliner et al., 2004Schwartzberg, 2006).

Papillon-Lefèvre Syndrome


New Strategies for Fighting Neutrophil Serine Protease-Related Human Diseases

Administration of therapeutic inhibitors to control unwanted proteolysis at inflammation sites has been tested as a therapy for a variety of inflammatory and infectious lung diseases (Chughtai and O’Riordan, 2004). Depending on the size and chemical nature of the inhibitors, they may be administered orally, intravenously, or by an aerosol route. Whatever the mode of administration, the access of therapeutic inhibitors to active proteases is often hampered by physicochemical constraints in the extravascular space and/or by the partitioning of proteases between soluble and solid phases.


Concluding Remarks

NSPs were first recognized as protein-degrading enzymes but have now proven to be multifunctional components participating in a variety of pathophysiological processes. Thus, they appear as potential therapeutic targets for drugs that inhibit their active site or impair activation from their precursor. Overall, the available preclinical and clinical data suggest that inhibition of NSPs using therapeutic inhibitors would suppress or attenuate deleterious effects of inflammatory diseases, including lung diseases. Depending on the size and chemical nature of inhibitors, those may be administered orally, intravenously, or by aerosolization. But the results obtained until now have not been fully convincing because of the poor knowledge of the biological function of each protease, their spatiotemporal regulation during the course of the disease, the physicochemical constraints associated with inhibitor administration, or the use of animal models in which NSP regulation and specificity differ from those in human. Two different and complementary approaches may help bypass these putative problems. One is to target active proteases by inhibitors at the inflammatory site in animal models in which lung anatomy and physiology are close to those in human to allow in vitro and in vivo assays of human-directed drugs/inhibitors. The other is to prevent neutrophil accumulation at inflammatory sites by impairing production of proteolytically active NSPs using an inhibitor of their maturation protease, DPPI. Preventing neutrophil accumulation at the inflammatory sites by therapeutic inhibition of DPPI represents an original and novel approach, the exploration of which has just started (Méthot et al., 2008). Thus pharmacological inactivation of DPPI in human neutrophils could well reduce membrane binding of PR3 and, as a consequence, neutrophil priming by pathogenic auto-antibodies in WG. In addition, it has been recognized that the intracellular level of NSPs depends on their correct intracellular trafficking. In the future, pharmacological targeting of molecules specifically involved in the correct intracellular trafficking of each NSP could possibly regulate their production and activity, a feature that could be exploited as a therapeutic strategy for inflammatory diseases.










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P13K delta-gamma anticancer agent

Larry H. Bernstein, MD, FCAP, Curator



RP 6350, Rhizen Pharmaceuticals S.A. and Novartis tieup for Rhizen’s inhaled dual Pl3K-delta gamma inhibitor



(A)           and                         (Al)                  and                (A2)

(S)-2-(l-(9H-purin-6-ylamino)propyl)-3-(3-fluorophenyl)-4H-chromen-4-one (Compound A1 is RP 6350).




RP 6350, RP6350, RP-6350


mw 415

Rhizen Pharmaceuticals is developing RP-6530, a PI3K delta and gamma dual inhibitor, for the potential oral treatment of cancer and inflammation  In November 2013, a phase I trial in patients with hematologic malignancies was initiated in Italy ]\. In September 2015, a phase I/Ib study was initiated in the US, in patients with relapsed and refractory T-cell lymphoma. At that time, the study was expected to complete in December 2016

PATENTS……..WO 11/055215 ,  WO 12/151525.

  • Antineoplastics; Small molecules
  • Mechanism of Action Phosphatidylinositol 3 kinase delta inhibitors; Phosphatidylinositol 3 kinase gamma inhibitors
  • Phase I Haematological malignancies
  • Preclinical Multiple myeloma


Swaroop K. V. S. Vakkalanka,
COMPANY Rhizen Pharmaceuticals Sa



PI3K delta/gamma inhibitor RP6530 An orally active, highly selective, small molecule inhibitor of the delta and gamma isoforms of phosphoinositide-3 kinase (PI3K) with potential immunomodulating and antineoplastic activities. Upon administration, PI3K delta/gamma inhibitor RP6530 inhibits the PI3K delta and gamma isoforms and prevents the activation of the PI3K/AKT-mediated signaling pathway. This may lead to a reduction in cellular proliferation in PI3K delta/gamma-expressing tumor cells. In addition, this agent modulates inflammatory responses through various mechanisms, including the inhibition of both the release of reactive oxygen species (ROS) from neutrophils and tumor necrosis factor (TNF)-alpha activity. Unlike other isoforms of PI3K, the delta and gamma isoforms are overexpressed primarily in hematologic malignancies and in inflammatory and autoimmune diseases. By selectively targeting these isoforms, PI3K signaling in normal, non-neoplastic cells is minimally impacted or not affected at all, which minimizes the side effect profile for this agent. Check for active clinical trials using this agent. (NCI Thesaurus)

Company Rhizen Pharmaceuticals S.A.
Description Dual phosphoinositide 3-kinase (PI3K) delta and gamma inhibitor
Molecular Target Phosphoinositide 3-kinase (PI3K) delta ; Phosphoinositide 3-kinase (PI3K) gamma
Mechanism of Action Phosphoinositide 3-kinase (PI3K) delta inhibitor; Phosphoinositide 3-kinase (PI3K) gamma inhibitor
Therapeutic Modality Small molecule


Dual PI3Kδ/γ Inhibition By RP6530 Induces Apoptosis and Cytotoxicity In B-Lymphoma Cells
 Swaroop Vakkalanka, PhD*,1, Srikant Viswanadha, Ph.D.*,2, Eugenio Gaudio, PhD*,3, Emanuele Zucca, MD4, Francesco Bertoni, MD5, Elena Bernasconi, B.Sc.*,3, Davide Rossi, MD, Ph.D.*,6, and Anastasios Stathis, MD*,7
 1Rhizen Pharmaceuticals S A, La Chaux-de-Fonds, Switzerland, 2Incozen Therapeutics Pvt. Ltd., Hyderabad, India, 3Lymphoma & Genomics Research Program, IOR-Institute of Oncology Research, Bellinzona, Switzerland, 4IOSI Oncology Institute of Southern Switzerland, Bellinzona, Switzerland, 5Lymphoma Unit, IOSI-Oncology Institute of Southern Switzerland, Bellinzona, Switzerland, 6Italian Multiple Myeloma Network, GIMEMA, Italy, 7Oncology Institute of Southern Switzerland, Bellinzona, Switzerland

RP6530 is a potent and selective dual PI3Kδ/γ inhibitor that inhibited growth of B-cell lymphoma cell lines with a concomitant reduction in the downstream biomarker, pAKT. Additionally, the compound showed cytotoxicity in a panel of lymphoma primary cells. Findings provide a rationale for future clinical trials in B-cell malignancies.

Blood 2013 122:4411; published ahead of print December 6, 2013
Swaroop Vakkalanka, Srikant Viswanadha, Eugenio Gaudio, Emanuele Zucca, Francesco Bertoni, Elena Bernasconi, Davide Rossi, Anastasios Stathis
  • Dual PI3K delta/gamma Inhibition By RP6530 Induces Apoptosis and Cytotoxicity
  • RP6530, a novel, small molecule PI3K delta/gamma
  • Activity and selectivity of RP6530 for PI3K delta and gamma isoforms

Introduction Activation of the PI3K pathway triggers multiple events including cell growth, cell cycle entry, cell survival and motility. While α and β isoforms are ubiquitous in their distribution, expression of δ and γ is restricted to cells of the hematopoietic system. Because these isoforms contribute to the development, maintenance, transformation, and proliferation of immune cells, dual targeting of PI3Kδ and γ represents a promising approach in the treatment of lymphomas. The objective of the experiments was to explore the therapeutic potential of RP6530, a novel, small molecule PI3Kδ/γ inhibitor, in B-cell lymphomas.

Methods Activity and selectivity of RP6530 for PI3Kδ and γ isoforms and subsequent downstream activity was determined in enzyme and cell-based assays. Additionally, RP6530 was tested for potency in viability, apoptosis, and Akt phosphorylation assays using a range of immortalized B-cell lymphoma cell lines (Raji, TOLEDO, KG-1, JEKO, OCI-LY-1, OCI-LY-10, MAVER, and REC-1). Viability was assessed using the colorimetric MTT reagent after incubation of cells for 72 h. Inhibition of pAKT was estimated by Western Blotting and bands were quantified using ImageJ after normalization with Actin. Primary cells from lymphoid tumors [1 chronic lymphocytic leukemia (CLL), 2 diffuse large B-cell lymphomas (DLBCL), 2 mantle cell lymphoma (MCL), 1 splenic marginal zone lymphoma (SMZL), and 1 extranodal MZL (EMZL)] were isolated, incubated with 4 µM RP6530, and analyzed for apoptosis or cytotoxicity by Annexin V/PI staining.

Results RP6530 demonstrated high potency against PI3Kδ (IC50=24.5 nM) and γ (IC50=33.2 nM) enzymes with selectivity over α (>300-fold) and β (>100-fold) isoforms. Cellular potency was confirmed in target-specific assays, namely anti-FcεR1-(EC50=37.8 nM) or fMLP (EC50=39.0 nM) induced CD63 expression in human whole blood basophils, LPS induced CD19+ cell proliferation in human whole blood (EC50=250 nM), and LPS induced CD45R+ cell proliferation in mouse whole blood (EC50=101 nM). RP6530 caused a dose-dependent inhibition (>50% @ 2-7 μM) in growth of immortalized (Raji, TOLEDO, KG-1, JEKO, REC-1) B-cell lymphoma cells. Effect was more pronounced in the DLBCL cell lines, OCI-LY-1 and OCI-LY-10 (>50% inhibition @ 0.1-0.7 μM), and the reduction in viability was accompanied by corresponding inhibition of pAKT with EC50 of 6 & 70 nM respectively. Treatment of patient-derived primary cells with 4 µM RP6530 caused an increase in cell death. Fold-increase in cytotoxicity as evident from PI+ staining was 1.6 for CLL, 1.1 for DLBCL, 1.2 for MCL, 2.2 for SMZL, and 2.3 for EMZL. Cells in early apotosis (Annexin V+/PI-) were not different between the DMSO blank and RP6530 samples.

Conclusions RP6530 is a potent and selective dual PI3Kδ/γ inhibitor that inhibited growth of B-cell lymphoma cell lines with a concomitant reduction in the downstream biomarker, pAKT. Additionally, the compound showed cytotoxicity in a panel of lymphoma primary cells. Findings provide a rationale for future clinical trials in B-cell malignancies.

Disclosures:Vakkalanka:Rhizen Pharmaceuticals, S.A.: Employment, Equity Ownership; Incozen Therapeutics Pvt. Ltd.: Employment, Equity Ownership.Viswanadha:Incozen Therapeutics Pvt. Ltd.: Employment. Bertoni:Rhizen Pharmaceuticals SA: Research Funding.


PI3K Dual Inhibitor (RP-6530)

Therapeutic Area Respiratory , Oncology – Liquid Tumors , Rheumatology Molecule Type Small Molecule
Indication Peripheral T-cell lymphoma (PTCL) , Non-Hodgkins Lymphoma , Asthma , Chronic Obstructive Pulmonary Disease (COPD) , Rheumatoid Arthritis
Development Phase Phase I Rt. of Administration Oral


Rhizen is developing dual PI3K gamma/delta inhibitors for liquid tumors and inflammatory conditions.

Situation Overview

Dual Pl3K inhibition is strongly implicated as an intervention treatment in allergic and non-allergic inflammation of the airways and autoimmune diseases manifested by a reduction in neutrophilia and TNF in response to LPS. Scientific evidence for PI3-kinase involvement in various cellular processes underlying asthma and COPD stems from inhibitor studies and gene-targeting approaches, which makes it a potential target for treatment of respiratory disease. Resistance to conventional therapies such as corticosteroids in several patients has been attributed to an up-regulation of the PI3K pathway; thus, disruption of PI3K signaling provides a novel strategy aimed at counteracting the immuno-inflammatory response. Given the established criticality of these isoforms in immune surveillance, inhibitors specifically targeting the ? and ? isoforms would be expected to attenuate the progression of immune response encountered in most variations of airway inflammation and arthritis.

Mechanism of Action

While alpha and beta isoforms are ubiquitous in their distribution, expression of delta and gamma is restricted to circulating hematogenous cells and endothelial cells. Unlike PI3K-alpha or beta, mice lacking expression of gamma or delta do not show any adverse phenotype indicating that targeting of these specific isoforms would not result in overt toxicity. Dual delta/gamma inhibition is strongly implicated as an intervention strategy in allergic and non-allergic inflammation of the airways and other autoimmune diseases. Scientific evidence for PI3K-delta and gamma involvement in various cellular processes underlying asthma and COPD stems from inhibitor studies and gene-targeting approaches. Also, resistance to conventional therapies such as corticosteroids in several COPD patients has been attributed to an up-regulation of the PI3K delta/gamma pathway. Disruption of PI3K-delta/gamma signalling therefore provides a novel strategy aimed at counteracting the immuno-inflammatory response. Due to the pivotal role played by PI3K-delta and gamma in mediating inflammatory cell functionality such as leukocyte migration and activation, and mast cell degranulation, blocking these isoforms may also be an effective strategy for the treatment of rheumatoid arthritis as well.

Given the established criticality of these isoforms in immune surveillance, inhibitors specifically targeting the delta and gamma isoforms would be expected to attenuate the progression of immune response encountered in airway inflammation and rheumatoid arthritis.




Clinical Trials

Rhizen has identified an orally active Lead Molecule, RP-6530, that has an excellent pre-clinical profile. RP-6530 is currently in non-GLP Tox studies and is expected to enter Clinical Development in H2 2013.

In December 2013, Rhizen announced the start of a Phase I clinical trial. The study entitled A Phase-I, Dose Escalation Study to Evaluate Safety and Efficacy of RP6530, a dual PI3K delta /gamma inhibitor, in patients with Relapsed or Refractory Hematologic Malignancies is designed primarily to establish the safety and tolerability of RP6530. Secondary objectives include clinical efficacy assessment and biomarker response to allow dose determination and potential patient stratification in subsequent expansion studies.


Partners by Region

Rhizen’s pipeline consists of internally discovered (with 100% IP ownership) novel small molecule programs aimed at high value markets of Oncology, Immuno-inflammtion and Metabolic Disorders. Rhizen has been successful in securing critical IP space in these areas and efforts are on for further expansion in to several indications. Rhizen seeks partnerships to unlock the potential of these valuable assets for further development from global pharmaceutical partners. At present global rights on all programs are available and Rhizen is flexible to consider suitable business models for licensing/collaboration.

In 2012, Rhizen announced a joint venture collaboration with TG Therapeutics for global development and commercialization of Rhizen’s Novel Selective PI3K Kinase Inhibitors. The selected lead RP5264 (hereafter, to be developed as TGR-1202) is an orally available, small molecule, PI3K specific inhibitor currently being positioned for the treatment of hematological malignancies.


This scheme provides a synthetic route for the preparation of compound of formula wherein all the variables are as described herein in above

Figure imgf000094_0001

15 14 10 12 12a

April 2015, preclinical data were presented at the 106th AACR Meeting in Philadelphia, PA. RP-6530 had GI50 values of 17,028 and 22,014 nM, respectively
December 2014, data were presented at the 56th ASH Meeting in San Francisco, CA.
December 2013, preclinical data were presented at the 55th ASH Meeting in New Orleans, LA.
June 2013, preclinical data were presented at the 18th Annual EHA Congress in Stockholm, Sweden. RP-6530 inhibited PI3K delta and gamma isoforms with IC50 values of 24.5 and 33.2 nM, respectively.
  • 01 Sep 2015 Phase-I clinical trials in Hematological malignancies (Second-line therapy or greater) in USA (PO) (NCT02567656)
  • 18 Nov 2014 Preclinical trials in Multiple myeloma in Switzerland (PO) prior to November 2014
  • 18 Nov 2014 Early research in Multiple myeloma in Switzerland (PO) prior to November 2014


WO2011055215A2 Nov 3, 2010 May 12, 2011 Incozen Therapeutics Pvt. Ltd. Novel kinase modulators
WO2012151525A1 May 4, 2012 Nov 8, 2012 Rhizen Pharmaceuticals Sa Novel compounds as modulators of protein kinases
WO2013164801A1 May 3, 2013 Nov 7, 2013 Rhizen Pharmaceuticals Sa Process for preparation of optically pure and optionally substituted 2- (1 -hydroxy- alkyl) – chromen – 4 – one derivatives and their use in preparing pharmaceuticals
US20110118257 May 19, 2011 Rhizen Pharmaceuticals Sa Novel kinase modulators
US20120289496 May 4, 2012 Nov 15, 2012 Rhizen Pharmaceuticals Sa Novel compounds as modulators of protein kinases
WO 2011055215



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von Willebrand Factor

Larry H. Bernstein, MD, FCAP, Curator



FDA approves first recombinant von Willebrand factor to treat bleeding episodes

Dr. Anthony Melvin Castro



12/08/2015 02:44
The U.S. Food and Drug Administration today approved Vonvendi, von Willebrand factor (Recombinant), for use in adults 18 years of age and older who have von Willebrand disease (VWD). Vonvendi is the first FDA-approved recombinant von Willebrand factor, and is approved for the on-demand (as needed) treatment and control of bleeding episodes in adults diagnosed with VWD.
Company Baxalta Inc.
Description Recombinant human von Willebrand factor (vWF)
Molecular Target von Willebrand factor (vWF)
Mechanism of Action
Therapeutic Modality Biologic: Protein
Latest Stage of Development Registration
Standard Indication Bleeding
Indication Details Treat and prevent bleeding episodes in von Willebrand disease (vWD) patients; Treat von Willebrand disease (vWD)
Regulatory Designation U.S. – Orphan Drug (Treat and prevent bleeding episodes in von Willebrand disease (vWD) patients);
EU – Orphan Drug (Treat and prevent bleeding episodes in von Willebrand disease (vWD) patients);
Japan – Orphan Drug (Treat and prevent bleeding episodes in von Willebrand disease (vWD) patients)


The U.S. Food and Drug Administration today approved Vonvendi, von Willebrand factor (Recombinant), for use in adults 18 years of age and older who have von Willebrand disease (VWD). Vonvendi is the first FDA-approved recombinant von Willebrand factor, and is approved for the on-demand (as needed) treatment and control of bleeding episodes in adults diagnosed with VWD.

VWD is the most common inherited bleeding disorder, affecting approximately 1 percent of the U.S. population. Men and women are equally affected by VWD, which is caused by a deficiency or defect in von Willebrand factor, a protein that is critical for normal blood clotting. Patients with VWD can develop severe bleeding from the nose, gums, and intestines, as well as into muscles and joints. Women with VWD may have heavy menstrual periods lasting longer than average and may experience excessive bleeding after childbirth.

“Patients with heritable bleeding disorders should meet with their health care provider to discuss appropriate measures to reduce blood loss,” said Karen Midthun, M.D., director of the FDA’s Center for Biologics Evaluation and Research. “The approval of Vonvendi provides an additional therapeutic option for the treatment of bleeding episodes in patients with von Willebrand disease.”

The safety and efficacy of Vonvendi were evaluated in two clinical trials of 69 adult participants with VWD. These trials demonstrated that Vonvendi was safe and effective for the on-demand treatment and control of bleeding episodes from a variety of different sites in the body. No safety concerns were identified in the trials. The most common adverse reaction observed was generalized pruritus (itching).

The FDA granted Vonvendi orphan product designation for these uses.Orphan product designation is given to drugs intended to treat rare diseases in order to promote their development.

Vonvendi is manufactured by Baxalta U.S., Inc., based in Westlake Village, California.


von Willebrand Disease

Author: Eleanor S Pollak; Chief Editor: Srikanth Nagalla

Von Willebrand disease (vWD) is a common, inherited, genetically and clinically heterogeneous hemorrhagic disorder caused by a deficiency or dysfunction of the protein termed von Willebrand factor (vWF). Consequently, defective vWF interaction between platelets and the vessel wall impairs primary hemostasis.

vWF, a large, multimeric glycoprotein, circulates in blood plasma at concentrations of approximately 10 mg/mL. In response to numerous stimuli, vWF is released from storage granules in platelets and endothelial cells. It performs two major roles in hemostasis. First, it mediates the adhesion of platelets to sites of vascular injury. Second, it binds and stabilizes the procoagulant protein factor VIII (FVIII). (See Etiology.)

vWD is divided into three major categories: (1) partial quantitative deficiency (type I), (2) qualitative deficiency (type II), and (3) total deficiency (type III). vWD type II is further divided into four variants (IIA, IIB, IIN, IIM), based on characteristics of dysfunctional vWF. These categories correspond to distinct molecular mechanisms, with corresponding clinical features and therapeutic recommendations.

For discussion of vWD in children, see Pediatric Von Willebrand Disease.




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Understanding the Stem Cell Niche: A Webinar by The Scientist

Reporter: Stephen J. Williams, Ph.D.


The Scientist

nature stem cell

Schematic diagram showing some of the factors implicated in each process. Haematopoietic stem cells (HSCs) bound to the bone-marrow niche are mobilized in response to granulocyte colony-stimulating factor (G-CSF) or cyclophosphamide, or after peripheral myeloablation following treatment with 5-fluorouracil (5-FU). After extravasation from the bone-marrow cords into the microvasculature, HSCs enter the circulation and are distributed to peripheral tissues such as the spleen or liver. HSCs locate close to endothelial cells in the splenic red pulp. They home to the bone-marrow cords through the circulation, a process that is controlled by a number of adhesion molecules such as very late antigen 4 (VLA4), VLA5, lymphocyte function-associated antigen 1 (LFA1) or selectins. After entering the bone marrow, HSCs specifically lodge in the niche, a process requiring membrane-bound stem-cell factor (SCF), CXC-chemokine ligand 12 (CXCL12), osteopontin (OPN), hyaluronic acid, and their corresponding receptors. CXCR4, CXC-chemokine receptor 4; E-selectin, endothelial-cell selectin; P-selectin, platelet selectin; PSGL1, P-selectin glycoprotein ligand 1.


Understanding the Stem Cell Niche

  This presentation will begin on Tuesday, December 01, 2015 at 02:30 PM Eastern Standard Time.

Free Webinar
Tuesday December 1, 2015
2:30 – 4:00 PM EST

Stem cells provide an attractive model to study human physiology and disease. However, technical challenges persist in the biological characterization and manipulation of stem cells in their native microenvironment. The Scientist brings together a panel of experts to discuss interactions between stem cells and external cues, and the role of the stem cell niche in development and disease. Topics to be covered include the molecular mechanisms of hematopoietic stem cell niche interactions and techniques for engineering 3-D stem-cell microenvironments. Following the presentations, attendees will have an opportunity to ask questions concerning their specific applications and receive answers in real-time.


Dr. Jon Hoggatt, Assistant Professor of Medicine, Cancer Center and Center for Transplantation Sciences, Harvard Medical School/Massachusetts General Hospital.

Dr. Todd McDevitt, Senior Investigator, Gladstone Institute of Cardiovascular Disease, Professor, Department of Bioengineering & Therapeutic Sciences, UCSF.


Understanding the Stem Cell Niche
Click Here To Watch The Video

To find out about our upcoming events follow us on Twitter @LabMgrEvents


Notes from Webinar:

Hematopoetic stem cells good model since now we have liquid biopsies (as a result field has skyrocketed).

Two processes involved with stem cells finding their niche

  1. Homing; CXCR4-SDK1 dependent process into the bone marrow.
  2. Mobilization: stem cells moving from bone into blood (found that GMCSF main factor responsible for this process)

Dr. Raymond Schofield was one of the first to propose the existence of this stem cell niche (each progenitor will produce a unique factor {possibly a therapeutic target} for example leptin+ receptor target perivascular cells so one target is good for only a small subset of stem cells)

Therefore it may be possible or advantageous to target the whole stem cell milieu. One such possible target they are investigating is CD26 (dipeptyl peptidase). The diabetes drug Januvia is an inhibitor of CD26.

It was also noticed if inhibit the GMCSF receptor complex can inhibit the whole stem cell niche.

Prostoglandins and stem cell niche

  • Indomethacin blocks the mobilization step
  • Prostaglandin E increases homing
  • GMCSF and malaxocam (COX2 inhibitor) flattens osteoblast cells and may be a mechanism how inhibition of prostaglandin synthesis blocks mobilization
  • Found that the PGE4 receptor is ultimately responsible for the NSAID effect

The niche after G-CSF

Dr. Hoggat found that macrophages are supplying the factors that support the niche. He will be presenting the findings at 2015 Hematology conference. (See information about his conference presentation here).

From the 57th Annual American Society of Hematology Meeting (2015) please see Dr. Hoggat’s moderated section Hematopoiesis and Stem Cells: Microenvironment, Cell Adhesion and Stromal Stem Cells: Hematopoietic Stem Cell Niche


Relevant articles from Dr. Hoggat

Anti-CD47 Therapy Is More Than a Dinner Bell October 19, 2015

Dr. Hoggatt looks at the therapeutic effects of blocking CD47 aside from alerting macrophages to devour tumor cells.

Hematopoietic Stem Cells Should Hold Their Breath August 12, 2015

Dr. Hoggatt and Hannah Rasmussen discuss new approaches to the use of hematopoietic stem cells considering observer effects that emerge due to our experimental systems for HSCs.

Prostaglandin E2 enhances hematopoietic stem cell homing, survival, and proliferation. Hoggatt J, Singh P, Sampath J, Pelus LM. Blood. 2009 May 28;113(22):5444-55. doi: 10.1182/blood-2009-01-201335. Epub 2009 Mar 26.


Prostaglandin E2 enhances long-term repopulation but does not permanently alter inherent stem cell competitiveness. Hoggatt J, Mohammad KS, Singh P, Pelus LM. Blood. 2013 Oct 24;122(17):2997-3000. doi: 10.1182/blood-2013-07-515288. Epub 2013 Sep 18.


Pharmacologic increase in HIF1α enhances hematopoietic stem and progenitor homing and engraftment. Speth JM, Hoggatt J, Singh P, Pelus LM. Blood. 2014 Jan 9;123(2):203-7. doi: 10.1182/blood-2013-07-516336. Epub 2013 Oct 28.


Blockade of prostaglandin E2 signaling through EP1 and EP3 receptors attenuates Flt3L-dependent dendritic cell development from hematopoietic progenitor cells. Singh P, Hoggatt J, Hu P, Speth JM, Fukuda S, Breyer RM, Pelus LM. Blood. 2012 Feb 16;119(7):1671-82. doi: 10.1182/blood-2011-03-342428. Epub 2011 Nov 22.


Recovery from hematopoietic injury by modulating prostaglandin E(2) signaling post-irradiation. Hoggatt J, Singh P, Stilger KN, Plett PA, Sampson CH, Chua HL, Orschell CM, Pelus LM. Blood Cells Mol Dis. 2013 Mar;50(3):147-53. doi: 10.1016/j.bcmd.2012.11.006. Epub 2012 Nov 30.


Pulse exposure of haematopoietic grafts to prostaglandin E2 in vitro facilitates engraftment and recovery. Pelus LM, Hoggatt J, Singh P. Cell Prolif. 2011 Apr;44 Suppl 1:22-9. doi: 10.1111/j.1365-2184.2010.00726.x.


Pleiotropic effects of prostaglandin E2 in hematopoiesis; prostaglandin E2 and other eicosanoids regulate hematopoietic stem and progenitor cell function. Pelus LM, Hoggatt J. Prostaglandins Other Lipid Mediat. 2011 Nov;96(1-4):3-9. doi: 10.1016/j.prostaglandins.2011.06.004. Epub 2011 Jun 21. Review.


Differential stem- and progenitor-cell trafficking by prostaglandin E2. Hoggatt J, Mohammad KS, Singh P, Hoggatt AF, Chitteti BR, Speth JM, Hu P, Poteat BA, Stilger KN, Ferraro F, Silberstein L, Wong FK, Farag SS, Czader M, Milne GL, Breyer RM, Serezani CH, Scadden DT, Guise TA, Srour EF, Pelus LM. Nature. 2013 Mar 21;495(7441):365-9. doi: 10.1038/nature11929. Epub 2013 Mar 13.


Eicosanoid regulation of hematopoiesis and hematopoietic stem and progenitor trafficking.Hoggatt J, Pelus LM. Leukemia. 2010 Dec;24(12):1993-2002. doi: 10.1038/leu.2010.216. Epub 2010 Sep 30. Review.


Hematopoietic stem cell mobilization with agents other than G-CSF. Hoggatt J, Pelus LM. Methods Mol Biol. 2012;904:49-67. doi: 10.1007/978-1-61779-943-3_4.


Mobilization of hematopoietic stem cells from the bone marrow niche to the blood compartment. Hoggatt J, Pelus LM. Stem Cell Res Ther. 2011 Mar 14;2(2):13. doi: 10.1186/scrt54. Review.


Engineering 3D Pluripotent Stem Cell Microenvironments by Todd McDevitt, Ph.D.

In recent years, it has finally been shown how to produce centrally derived (self assembling) organoids (microtissues).


How to specifically deliver specific morphogens in 3D organoids


  1. Microparticle (MP)-mediated delivery (can do in mouse and human): reduces the amount needed to be delivered



What are other effects of introduced MP in ES (embryonic stem cell) aggregates?

  1. a) physiocomechanical changes –mechanical effects of materials
  2. b) how changes in local presentation of factors affect bioavailbility and binding properties







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Ebola therapy breakthrough

Larry H. Bernstein, MD, FCAP, Curator



Updated 11/23/2015

Giant Molecules Inhibit Ebola Infection

Nov 11, 2015   http://www.technologynetworks.com/medchem/news.aspx?ID=185080

European researchers have designed a “giant” molecule formed by thirteen fullerenes covered by carbohydrates which, by blocking this receptor, are able to inhibit the cell infection by an artificial ebola virus model.


Different studies have demonstrated that the ebola virus infection process starts when the virus reaches the cellular DC-SIGN receptor to infect the dendritic cells (of the immune system).

In this study researchers from the Universidad Complutense de Madrid/IMDEA-Nanociencia, the Instituto de Investigación Sanitaria Hospital 12 de Octubre (Madrid), and the Instituto de Investigaciones Químicas del CSIC-Universidad de Sevilla have collaborated, together with three european research groups (CNRS/Université de Strasbourg, France and Université de Namur, Belgium).

“Fullerenes are hollow cages exclusively formed by carbon atoms”, explains Nazario Martín, Professor of Organic Chemistry in the UCM and main author of the study. In this work, scientists have employed C60 fullerene, which is formed by 60 carbon atoms and has the shape of a truncated icosahedron, which resembles a football ball.


These molecules decorated with specific carbohydrates (sugars) present affinity by the receptor used as an entry point to infect the cell and act blocking it, thus inhibiting the infection.

Researchers employed an artificial ebola virus by expressing one of its proteins, envelope protein GP1, responsible of its entry in the cells. In a model in vitro, this protein is covering a false virus, which is able of cell infection but not of replication.

“We have employed a cell model previously described in our lab which consists in a cell line of human lymphocytes expressing DC-SIGN receptor, which facilitates the entry of the virus in Dendritic Cells”, points out Rafael Delgado, researcher of the Hospital 12 de Octubre, and other of the authors of the study.

By blocking this receptor and inhibiting the virus infection, the authors think that the dissemination of the virus would decrease and the immune response increase, but this idea has still to be developed with in vivo studies.

The biggest fullerene system in the lab

The system designed by the chemists, based on carbon nanostructures developed in the UCM, mimic the presentation of carbohydrates surrounding virus like ebola or VIH.

The team has achieved an unprecedented success in fullerene chemistry and dendritic growth: connecting in one synthetic step twelve fullerene units, each with ten sugars, to other central fullerene, creating a globular superstructure with 120 sugar moieties on its surface, “this is the fastest dendrimeric growth developed in a laboratory up to now” says Beatriz Illescas, Professor in the UCM and coauthor of the work.

According to scientists, the results highlight the potential of these giant molecules as antiviral agents. “This work open the door to the design and preparation of new systems to inhibit the pathogens infection in cases where the current therapies are not effective or are inexistent, as occurs with the ebola virus”, clarifies Martín.

After these experiments on the cellular level, researchers will study the behavior of these systems in animal models, starting with mice. “We will study, on the one hand, the pharmacokinetics and, on the other, the antiviral activity in vivo” explains Javier Rojo, researcher of the Instituto de Investigaciones Químicas del CSIC and other of the authors of the study. Once the most effective compound has been identified, studies using the true ebola virus could be carried out.




DCSIGN, which is abundantly expressed by DC both in vitro and in vivo, … Whereas ICAM-3 binding by monocytes is for the greater part LFA-1 … The specificity of this adhesion receptor on DC for ICAM-3 is demonstrated by the ….



This subset coexpresses CD14, CD16, and CD33 and is thus of myeloid origin. In contrast to. CD14 monocytes, DCSIGN blood cells.



Mar 1, 2002 Several receptors expressed by immature DCs belong to the C-type lectin superfamily, … Here, DCSIGN efficiently transmits the virus to T lymphocytes



Jul 14, 2006 Although B cells that express DCSIGN do not replicate HIV-1, they serve as … receptors [12–15], with conflicting reports on expression of DCSIGN[16,17]. …..
human herpesvirus 8 infects DC and macrophages via DCSIGN …



Results. The effect of human milk on direct HIV-1 infection of CD4+ T lymphocytesexpressing the DCSIGN receptor (Raji-DCSIGN) (8).



An indictment of Ebola response  

Panel calls for reform of global public health system in wake of epidemic

By B. D. Colen, Harvard Staff Writer




“The most egregious failure was by WHO in the delay in sounding the alarm,” said Harvard’s Ashish Jha.

An independent group of 19 international experts, convened by theHarvard Global Health Institute and the London School of Hygiene and Tropical Medicine (LSHTM), today issued a scathing analysis of the global response to the 2014-15 Ebola outbreak in West Africa.

The members of the Harvard-LSHTM Independent Panel on the Global Response to Ebola said that while the 2014-15 Ebola outbreak “engendered acts of understanding, courage, and solidarity,” it also caused “immense human suffering, fear and chaos, largely unchecked by high-level political leadership or reliable and rapid institutional responses.”

The report, published in the prestigious British medical journal The Lancet, is especially hard on the World Health Organization (WHO), which the panel contends failed to provide the leadership and support needed to deal properly with the outbreak of hemorrhagic fever that infected more than 28,000 people and claimed more than 11,000 lives.

The authors of the report, who were affiliated with, but functioned independently from, such disparate organizations as the Council on Foreign Relations, Médecins Sans Frontières, Indiana University law school, and theAIDS Health Care Foundation, reminded readers that the Ebola epidemic “brought national health systems to their knees, rolled back hard-won social and economic gains in a region recovering from civil wars, sparked worldwide panic, and cost at least several billion dollars in short-term control efforts and economic losses.”

“The most egregious failure was by WHO in the delay in sounding the alarm,” said Ashish Jha, director of the Harvard Global Health Institute, K.T. Li Professor of International Health at the Harvard T.H. Chan School of Public Health, and a professor of medicine at Harvard Medical School. “People at WHO were aware that there was an Ebola outbreak that was getting out of control by spring … and it took until August to declare a public health emergency … Those were precious months,” said Jha.

The panel was co-chaired by Professor Peter Piot, director of the LSHTM and co-discoverer of the Ebola virus. Piot said, “We need to strengthen core capacities in all countries to detect, report, and respond rapidly to small outbreaks, in order to prevent them from becoming large-scale emergencies. Major reform of national and global systems to respond to epidemics are not only feasible, but also essential so that we do not witness such depths of suffering, death, and social and economic havoc in future epidemics. The AIDS pandemic put global health on the world’s agenda. The Ebola crisis in West Africa should now be an equal game-changer for how the world prevents and responds to epidemics.”

Liberian Mosoka Fallah of Action Contre la Faim International and a member of the panel said, “The human misery and deaths from the Ebola epidemic in West Africa demand a team of independent thinkers to serve as a mirror of reflection on how and why the global response to the greatest Ebola calamity in human history was late, feeble, and uncoordinated. The threat of infectious disease anywhere is the threat of infectious disease everywhere. The world has become one big village.”

The global response to Ebola is being examined by a number of different panels, Jha said, including a group at WHO and another at the United Nations. During the height of the epidemic in fall, 2014, Jha met with Julio Frenk, then the dean of the Harvard Chan School, and Suerie Moon, research director and co-chair of the Harvard Kennedy School’s Forum on Global Governance for Health, and a Harvard Chan faculty member. Together, they “decided this deserves independent examination; we can’t let this happen again,” Jha said.

“The Ebola outbreak is a stark reminder of the fragility of health security in an interdependent word,” the report reads, “and of the importance of building a more robust global system to protect all people from such risks.

“A more humane, competent, and timely response to future outbreaks requires greater willingness to assist affected populations, and systematic investments to enable the global community to perform four key functions: strengthen core capacities within and among countries to prevent, detect, and respond to outbreaks when and where they occur; mobilize faster and more effective external assistance when countries are unable to prevent an outbreak from turning into a crisis alone; rapidly produce and widely share relevant knowledge, from community mobilization strategies to protective measures for health workers, from rapid diagnostic tools to vaccines; [and] provide stewardship over the whole system, entailing strong leadership, coordination, priority setting, and robust accountability from all involved actors.”

Though it pulls no punches in its criticism of the ways institutions and nations responded to the Ebola crisis, the Harvard-LSHTM report is also a positive document, offering 10 concrete recommendations to strengthen public health systems and future responses.

Those recommendations fall into four areas: preventing major disease outbreaks; responding to outbreaks; producing and sharing data, knowledge, and technologies; and improving the governance of the global health system, “with a focus on the World Health Organization.”

One recommendation is that WHO create a dedicated center “for outbreak response, with strong technical capacity, protected budget, and clear lines of accountability,” and that that center be governed by a separate board independent of the WHO bureaucracy.

“Our primary goal is to convince the high-level political leaders, north and south, to seize the moment to make necessary and enduring changes to better prepare for future outbreaks, while memories of the human health costs of inaction remain vivid and fresh,” the report said.

“There is a high risk here of not learning our lessons,” said Jha. “We’ve had outbreaks like this before, and often you get thoughtful reviews, and august bodies that look at it, and people say, ‘We will get to this right away,’ and then other things draw our attention. I think we owe it to the more than 11,000 people who died in West Africa to see that that doesn’t happen this time.”


The Lancet 2015


Ebola—lessons learned: Authors from Harvard’s Global Health Institute and the London School of Hygiene and Tropical Medicine outline 10 proposals to help prevent future health catastrophes, based on experiences from the 2014-15 Ebola outbreak in west Africa.

Timeline infographic

Illustration demonstrating pathogenesis of vascular leak in Ebola virus disease - Copyright: Elsevier

The current outbreak of Ebola in west Africa is both a public health emergency of international concern and a human tragedy.

The Lancet Ebola Resource Centre contains all related resources from The Lancet family of journals offered with free access to assist health workers and researchers in their important work to bring this outbreak to a close a quickly as possible.

Find out more about Ebola in The Lancet’s Seminar.


Expert panel slams WHO’s poor showing against Ebola
John Maurice
The Lancet, July 13, 2015;Vol. 386, No. 9990, e1

Criticism of WHO’s response to the west African Ebola crisis spawned an expert review that this week proposed several solutions to restore the agency’s performance. John Maurice reports.

WHO suffers from an incapacity “to deliver a full emergency public health response” against a severe epidemic. So concluded a panel of six international health experts in a damning report released on July 7. They prescribed 21 actions aimed at restoring WHO’s “pre-eminence as the guardian of global public health”.

The panel was commissioned by WHO Director-General Margaret Chan in response to widespread criticism that WHO had mishandled its response to the west African Ebola epidemic. The panel corroborated many of the criticisms. Chief among them was the “unjustifiable” time it took WHO to declare the outbreak a “public health emergency of international concern”. Chan made this declaration 5 months after the escalating spread of Ebola had become evident. WHO officials claim that the delay in making the official declaration did not affect its operations involving some 100 staff in the field in the early months of the epidemic.

WHO’s Member States also drew sharp criticism from the panel. Many applied travel bans during the epidemic without WHO authorisation, thereby contravening the International Health Regulations (IHR) and “causing negative political, economic and social consequences for the affected countries”. Perhaps the most damning criticism of WHO came from Médecins sans Frontières (MSF), whose teams were among the first to arrive at the scene of the outbreak in March, 2014. An MSF reportpublished in March, 2015, describes how MSF was unable to convince WHO that the epidemic was out of control. “WHO officials”, the report notes, “called us alarmists”.

Four of the panel’s recommendations stand out: countries should be given incentives to comply with the IHR and disincentives, such as sanctions, when they flout them; a brand-new WHO Centre for Emergency Preparedness and Response should be created; a contingency fund of US$100 million to be used solely to finance outbreak responses should be established; and an intermediate trigger should be set up to alert the health community to a health crisis before it becomes an emergency.

Asked whether the panel’s report meets her concerns, MSF president Joanne Liu tells The Lancet: “It has many strong points for us. But how they will translate into real action on the ground” is unclear. Liu is particularly pleased with the panel’s call for greater community engagement in epidemic response efforts. “As regards an intermediate alert”, she says, “it should be based on the needs of the affected communities, not just on a perceived security risk for other countries. MSF didn’t wait for an official declaration before going into the field.”

David Heymann, head and senior fellow at the Centre on Global Health Security in Chatham House, London, wonders whether the panel’s recommendations for fundamental changes in the decision-making processes can be implemented. “WHO has a flawed structure and I’m not sure its Member States have the will to change that.” He commends the panel’s call for strengthening existing emergency response mechanisms, such as the Global Outbreak Alert and Response Network (GOARN). “This is an agile, sustainable network of epidemiologists, logisticians, and other field-support experts from WHO Member States. It goes immediately into action to prevent outbreaks from becoming emergencies of international concern and has worked extremely well in previous Ebola outbreaks and in the 2003 SARS epidemic.” He believes that the existence of GOARN, with an added external advisory group, obviates the need for the new WHO emergency response centre proposed by the panel.

Will WHO implement the recommendations? “If it doesn’t implement them now”, says Jeremy Farrar, director of the Wellcome Trust, “it will never do so, because the Ebola epidemic has really shocked people and has exposed the structural weaknesses in WHO. Reforming its emergency response capabilities means reducing the bureaucracy and speeding up its capacity to respond. And that means appointing the very best people.” Farrar is enthusiastic about the proposed creation of a new WHO emergency response body. “It should be overseen by an independent board and needs to be outside the influence of politics and truly independent. It also needs to be given the right authority, the right budget, and the right mandate in order to attract the right leadership.”

Rick Brennan, director of WHO’s emergency operations, found the panel’s report constructive. “Work has already begun on several of the recommendations, such as increasing staff and funds for emergency operations and integrating our health security and humanitarian work. I’m convinced that we will implement the rest of the recommendations, including the creation of a new WHO health emergency centre.”

Experts were unanimous on one point made in the report. With 20–30 cases occurring every week, Ebola in west Africa is not over and many eyes are now on WHO’s role in ending it.

A plan to protect the world—and save WHO
The Lancet July 11, 2015
The Lancet, Vol. 386, No. 9989, p103

“WHO must reestablish its pre-eminence as the guardian of global public health.” These words resonate throughout the final report of the Ebola Interim Assessment Panel, requested by WHO’s Executive Board, chaired by Dame Barbara Stocking, and published this week. The findings of the panel present a devastating critique of WHO and the chronic inaction of its member states, which together created the conditions for an Ebola virus disease outbreak of unprecedented ferocity and human tragedy. The Stocking Report, as it will come to be known, sets out in agonising detail how the entire global health system fatally let down the people of west Africa.

Stocking reserves her harshest criticism for WHO. The delays in announcing a Public Health Emergency of International Concern (it took 5 months from announcing an “unprecedented outbreak” in April, 2014, to declaring a public health emergency on August 8) was “unjustifiable”. The agency’s culture is unfit to manage an emergency response. Independent and courageous decision-making by the Director-General of WHO and her team “was absent in the early months of the Ebola crisis”. The agency was slow and reactive to events. WHO has lost its position as the authoritative body on health emergencies. It thought it could manage Ebola through polite behind-the-scenes international diplomacy. It failed to recognise that Ebola was a health emergency, not a diplomatic puzzle. And WHO’s communication strategy for Ebola simply “failed”. The agency failed to communicate proactively and it failed to establish itself as the authoritative voice on the Ebola outbreak. Member States of WHO are not spared. They have persistently failed to take the International Health Regulations (IHR, 2005) seriously—a position that is “irresponsible” and “untenable” for global health security. They should adopt the notion of “shared sovereignty”. They need to invest in WHO (the Panel proposes a modest 5% increase in assessed contributions in 2016).

The Panel’s recommendations are clear and forthright. Although WHO was severely criticised, Stocking argues that the agency should still take the lead for emergency health responses. But to do so, WHO must undergo “significant transformation”—not least, adequate funding and a change in culture. It must provide costed plans for establishing core public health capacities as set out in the IHR (2005). It should establish a new WHO Centre for Emergency Preparedness and Response, with an independent board that publishes a report on Global Health Security annually. WHO country and regional offices should be strengthened. The agency should take its role in accelerating the research and development of diagnostics, vaccines, and medicines more seriously. And WHO should do more to coordinate its activities with other parts of the humanitarian community. The IHR Review Committee should examine the value of an intermediate alert for a public health emergency, lowering the threshold at which the world can be warned of a new health risk. And sanctions against countries that violate the IHR should be considered.

The Panel makes clear that global health must be put at the centre of the global security agenda. But while its recommendations are cogent, there are three important omissions that deserve attention. First, the Panel does not address the vicious cycle within which WHO is caught. The reason why WHO is so poorly resourced is that it lacks the confidence of donors. As the agency continues to underperform because of chronic underinvestment, so that lack of confidence (and the resultant unwillingness to invest) only worsens. The Panel presents no way out of this endless circle of failure. Second, one of the most important responsibilities for governments is the preservation of public order and national security. In the context of Ebola (indeed, any health crisis), this means creating resilient health systems to protect populations from unexpected shocks, as explained by Mosoka Fallah and colleagues in a letter from Liberia’s Ministry of Health this week. Universal health coverage should have been emphasised as a crucial instrument in building global health security. Finally, the Panel rightly notes that, “While WHO has already accepted the need for transformation of its organisational culture and delivery, it will need to be held accountable to ensure that this transformation is achieved”. However, nowhere does the Panel recommend the accountability mechanism to monitor and review the implementation of its recommendations. Our fear is that the unique opportunity presented by the Stocking Report will be squandered. We have little confidence that the governing bodies of WHO will deliver on the expectations of Stocking and her team. The responsibility for action therefore falls to WHO’s Director-General. Dr Margaret Chan has 20 months to save her agency from further and possibly irreversible reputational damage.

ReEBOV Antigen Rapid Test kit for point-of-care and laboratory-based testing for Ebola virus disease: a field validation study
Mara Jana Broadhurst, John Daniel Kelly, Ann Miller, Amanda Semper, Daniel Bailey, et al.

The Lancet, June 25, 2015; Vol. 386, No. 9996, p867–874    http://dx.doi.org/10.1016/S0140-6736(15)61042-X    
Background  At present, diagnosis of Ebola virus disease requires transport of venepuncture blood to field biocontainment laboratories for testing by real-time RT-PCR, resulting in delays that complicate patient care and infection control efforts. Therefore, an urgent need exists for a point-of-care rapid diagnostic test for this disease. In this Article, we report the results of a field validation of the Corgenix ReEBOV Antigen Rapid Test kit.
Methods   We performed the rapid diagnostic test on fingerstick blood samples from 106 individuals with suspected Ebola virus disease presenting at two clinical centres in Sierra Leone. Adults and children who were able to provide verbal consent or assent were included; we excluded patients with haemodynamic instability and those who were unable to cooperate with fingerstick or venous blood draw. Two independent readers scored each rapid diagnostic test, with any disagreements resolved by a third. We compared point-of-care rapid diagnostic test results with clinical real-time RT-PCR results (RealStar Filovirus Screen RT-PCR kit 1·0; altona Diagnostics GmbH, Hamburg, Germany) for venepuncture plasma samples tested in a Public Health England field reference laboratory (Port Loko, Sierra Leone). Separately, we performed the rapid diagnostic test (on whole blood) and real-time RT-PCR (on plasma) on 284 specimens in the reference laboratory, which were submitted to the laboratory for testing from many clinical sites in Sierra Leone, including our two clinical centres.
Findings   In point-of-care testing, all 28 patients who tested positive for Ebola virus disease by RT-PCR were also positive by fingerstick rapid diagnostic test (sensitivity 100% [95% CI 87·7–100]), and 71 of 77 patients who tested negative by RT-PCR were also negative by the rapid diagnostic test (specificity 92·2% [95% CI 83·8–97·1]). In laboratory testing, all 45 specimens that tested positive by RT-PCR were also positive by the rapid diagnostic test (sensitivity 100% [95% CI 92·1–100]), and 214 of 232 specimens that tested negative by RT-PCR were also negative by the rapid diagnostic test (specificity 92·2% [88·0–95·3]). The two independent readers agreed about 95·2% of point-of-care and 98·6% of reference laboratory rapid diagnostic test results. Cycle threshold values ranged from 15·9 to 26·3 (mean 22·6 [SD 2·6]) for the PCR-positive point-of-care cohort and from 17·5 to 26·3 (mean 21·5 [2·7]) for the reference laboratory cohort. Six of 16 banked plasma samples from rapid diagnostic test-positive and altona-negative patients were positive by an alternative real-time RT-PCR assay (the Trombley assay); three (17%) of 18 samples from individuals who were negative by both the rapid diagnostic test and altona test were also positive by Trombley.
Interpretation   The ReEBOV rapid diagnostic test had 100% sensitivity and 92% specificity in both point-of-care and reference laboratory testing in this population (maximum cycle threshold 26·3). With two independent readers, the test detected all patients who were positive for Ebola virus by altona real-time RT-PCR; however, this benchmark itself had imperfect sensitivity.
Malaria morbidity and mortality in Ebola-affected countries caused by decreased health-care capacity, and the potential effect of mitigation strategies: a modelling analysis
Patrick G T Walker, Michael T White, Jamie T Griffin, Alison Reynolds, Neil M Ferguson, Azra C Ghani
The Lancet Infectious Diseases, April 23, 2015; Vol. 15, No. 7, p825–832  http://dx.doi.org/10.1016/S1473-3099(15)70124-6    
Background  The ongoing Ebola epidemic in parts of west Africa largely overwhelmed health-care systems in 2014, making adequate care for malaria impossible and threatening the gains in malaria control achieved over the past decade. We quantified this additional indirect burden of Ebola virus disease.
Methods  We estimated the number of cases and deaths from malaria in Guinea, Liberia, and Sierra Leone from Demographic and Health Surveys data for malaria prevalence and coverage of malaria interventions before the Ebola outbreak. We then removed the effect of treatment and hospital care to estimate additional cases and deaths from malaria caused by reduced health-care capacity and potential disruption of delivery of insecticide-treated bednets. We modelled the potential effect of emergency mass drug administration in affected areas on malaria cases and health-care demand.
Findings  If malaria care ceased as a result of the Ebola epidemic, untreated cases of malaria would have increased by 45% (95% credible interval 43–49) in Guinea, 88% (83–93) in Sierra Leone, and 140% (135–147) in Liberia in 2014. This increase is equivalent to 3·5 million (95% credible interval 2·6 million to 4·9 million) additional untreated cases, with 10 900 (5700–21 400) additional malaria-attributable deaths. Mass drug administration and distribution of insecticide-treated bednets timed to coincide with the 2015 malaria transmission season could largely mitigate the effect of Ebola virus disease on malaria.
Interpretation  These findings suggest that untreated malaria cases as a result of reduced health-care capacity probably contributed substantially to the morbidity caused by the Ebola crisis. Mass drug administration can be an effective means to mitigate this burden and reduce the number of non-Ebola fever cases within health systems.

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