Curator/Reporter Aviral Vatsa PhD, MBBS
Based on: A review by (Wink et al., 2011)
This post is in continuation to Part 1 by the same title.
In part one I covered the basics of role of redox chemistry in immune reactions, the phagosome cauldron, and how bacteria bacteria, virus and parasites trigger the complex pathway of NO production and its downstream effects. While we move further in this post, the previous post can be accessed here.
REDOX REGULATION OF IMMUNE FUNCTION
Regulation of the redox immunomodulators—NO/RNS and ROS
In addition to eradicating pathogens, NO/RNS and ROS and their chemical interactions act as effective immunomodulators that regulate many cellular metabolic pathways and tissue repair and proinflammatory pathways. Figure 3 shows these pathways.
Figure 3. Schematic overview of interactive connections between NO and ROS-mediated metabolic pathways. Credit: (Wink et al., 2011)
Regulation of iNOS enzyme activity is critical to NO production. Factors such as the availability of arginine, BH4, NADPH, and superoxide affect iNOS activity and thus NO production. In the absence of arginine and BH4 iNOS becomes a O2_/H2O2 generator (Vásquez-Vivar et al., 1999). Hence metabolic pathways that control arginine and BH4 play a role in determining the NO/superoxide balance. Arginine levels in cells depend on various factors such as type of uptake mechanisms that determine its spatial presence in various compartments and enzymatic systems. As shown in Fig3 Arginine is the sole substrate for iNOS and arginase. Arginase is another key enzyme in immunemodulation. AG is also regulated by NOS and NOX activities. NOHA, a product of NOS, inhibits AG, and O2–increases AG activity. Importantly, high AG activity is associated with elevated ROS and low NO fluxes. NO antagonises NOX2 assembly that in turn leads to reduction in O2_ production. NO also inhibits COX2 activity thus reducing ROS production. Thus, as NO levels decline, oxidative mechanisms increase. Oxidative and nitrosative stress can also decrease intracellular GSH (reduced form) levels, resulting in a reduced antioxidant capability of the cell.
Immune-associated redox pathways regulate other important metabolic cell functions that have the potential for widespread impact on cells, organs, and organisms. These pathways, such as mediated via methionine and polyamines, are critical for DNA stabilization, cell proliferation, and membrane channel activity, all of which are also involved in immune-mediated repair processes.
NO levels dictate the immune signaling pathway
NO/RNS and ROS actively control innate and adaptive immune signaling by participating in induction, maintenance, and/or termination of proinflammatory and anti-inflammatory signaling. As in pathogen eradication, the temporal and spatial concentration profiles of NO are key factors in determining immune-mediated processes.
Brune and coworkers (Messmer et al., 1994) first demonstrated that p53 expression was associated with the concentrations of NO that led to apoptosis in macrophages. Subsequent studies linked NO concentration profiles with expression of other key signaling proteins such as HIF-1α and Akt-P (Ridnour et al., 2008; Thomas et al., 2008). Various levels of NO concentrations trigger different pathways and expectedly this concentration-dependent profile varies with distance from the NO source.NO is highly diffucible and this characteristic can result in 1000 fold reduction in concentration within one cell length distance travelled from the source of production. Time course studies have also shown alteration in effects of same levels of NO over time e.g. NO-mediated ERK-P levels initially increased rapidly on exposure to NO donors and then decreased with continued NO exposure (Thomas et al., 2004), however HIF-1α levels remained high as long as NO levels were elevated. Thus some of the important factors that play critical role in NO effects are: distance from source, NO concentrations, duration of exposure, bioavailability of NO, and production/absence of other redox molecules.
Figure and legend credits: (Wink et al., 2011)
Fig 4: The effect of steady-state flux of NO on signal transduction mechanisms.
This diagram represents the level of sustained NO that is required to activate specific pathways in tumor cells. Similar effects have been seen on endothelial cells. These data were generated by treating tumor or endothelial cells with the NO donor DETANO (NOC-18) for 24 h and then measuring the appropriate outcome measures (for example, p53 activation). Various concentrations of DETANO that correspond to cellular levels of NO are: 40–60 μM DETANO = 50 nM NO; 80–120 μM DETANO = 100 nM NO; 500 μM DETANO = 400 nM NO; and 1 mM DETANO = 1 μM NO. The diagram represents the effect of diffusion of NO with distance from the point source (an activated murine macrophage producing iNOS) in vitro (Petri dish) generating 1 μM NO or more. Thus, reactants or cells located at a specific distance from the point source (i.e., iNOS, represented by star) would be exposed to a level of NO that governs a specific subset of physiological or pathophysiological reactions. The x-axis represents the different zone of NO-mediated events that is experienced at a specific distance from a source iNOS producing >1 μM. Note: Akt activation is regulated by NO at two different sites and by two different concentration levels of NO.
Species-specific NO production
The relationship of NO and immunoregulation has been established on the basis of studies on tumor cell lines or rodent macrophages, which are readily available sources of NO. However in humans the levels of protein expression for NOS enzymes and the immune induction required for such levels of expression are quite different than in rodents (Weinberg, 1998). This difference is most likely due to the human iNOS promotor rather than the activity of iNOS itself. There is a significant mismatch between the promoters of humans and rodents and that is likely to account for the notable differences in the regulation of gene induction between them. The combined data on rodent versus human NO and O2– production strongly suggest that in general, ROS production is a predominant feature of activated human macrophages, neutrophils, and monocytes, and the equivalent murine immune cells generate a combination of O2– and NO and in some cases, favor NO production. These differences may be crucial to understanding how immune responses are regulated in a species-specific manner. This is particularly useful, as pathogen challenges change constantly.
The next post in this series will cover the following topics:
The impact of NO signaling on an innate immune response—classical activation
NO and proinflammatory genes
NO and regulation of anti-inflammatory pathways
NO impact on adaptive immunity—immunosuppression and tissue-restoration response
NO and revascularization
Acute versus chronic inflammatory disease
Bibliography
Further reading on NO:
Nitric Oxide in bone metabolism July 16, 2012
Author: Aviral Vatsa PhD, MBBS
Nitric Oxide production in Systemic sclerosis July 25, 2012
Curator: Aviral Vatsa, PhD, MBBS
Nitric Oxide Signalling Pathways August 22, 2012 by
Curator/ Author: Aviral Vatsa, PhD, MBBS
Nitric Oxide: a short historic perspective August 5, 2012
Author/Curator: Aviral Vatsa PhD, MBBS
http://pharmaceuticalintelligence.com/2012/08/05/nitric-oxide-a-short-historic-perspective-7/
Nitric Oxide: Chemistry and function August 10, 2012
Curator/Author: Aviral Vatsa PhD, MBBS
Nitric Oxide and Platelet Aggregation August 16, 2012 by
Author: Dr. Venkat S. Karra, Ph.D.
The rationale and use of inhaled NO in Pulmonary Artery Hypertension and Right Sided Heart Failure August 20, 2012
Author: Larry Bernstein, MD
Nitric Oxide: The Nobel Prize in Physiology or Medicine 1998 Robert F. Furchgott, Louis J. Ignarro, Ferid Murad August 16, 2012
Reporter: Aviva Lev-Ari, PhD, RN
Coronary Artery Disease – Medical Devices Solutions: From First-In-Man Stent Implantation, via Medical Ethical Dilemmas to Drug Eluting Stents August 13, 2012
Author: Aviva Lev-Ari, PhD, RN
Nano-particles as Synthetic Platelets to Stop Internal Bleeding Resulting from Trauma
August 22, 2012
Reported by: Dr. V. S. Karra, Ph.D.
Cardiovascular Disease (CVD) and the Role of agent alternatives in endothelial Nitric Oxide Synthase (eNOS) Activation and Nitric Oxide Production July 19, 2012
Curator and Research Study Originator: Aviva Lev-Ari, PhD, RN
Macrovascular Disease – Therapeutic Potential of cEPCs: Reduction Methods for CV Risk
July 2, 2012
An Investigation of the Potential of circulating Endothelial Progenitor Cells (cEPCs) as a Therapeutic Target for Pharmacological Therapy Design for Cardiovascular Risk Reduction: A New Multimarker Biomarker Discovery
Curator: Aviva Lev-Ari, PhD, RN
Bone remodelling in a nutshell June 22, 2012
Author: Aviral Vatsa, Ph.D., MBBS
http://pharmaceuticalintelligence.com/2012/06/22/bone-remodelling-in-a-nutshell/
Targeted delivery of therapeutics to bone and connective tissues: current status and challenges- Part, September
Author: Aviral Vatsa, PhD, September 23, 2012
Calcium dependent NOS induction by sex hormones: Estrogen
Curator: S. Saha, PhD, October 3, 2012
http://pharmaceuticalintelligence.com/2012/10/03/calcium-dependent-nos-induction-by-sex-hormones/
Nitric Oxide and Platelet Aggregation,
Author V. Karra, PhD, August 16, 2012
http://pharmaceuticalintelligence.com/2012/08/16/no-and-platelet-aggregation/
Curator: Aviva Lev-Ari, PhD, July 16, 2012
http://pharmaceuticalintelligence.com/?s=Nebivolol
Endothelin Receptors in Cardiovascular Diseases: The Role of eNOS Stimulation
Author: Aviva Lev-Ari, PhD, 10/4/2012
Inhibition of ET-1, ETA and ETA-ETB, Induction of NO production, stimulation of eNOS and Treatment Regime with PPAR-gamma agonists (TZD): cEPCs Endogenous Augmentation for Cardiovascular Risk Reduction – A Bibliography
Curator: Aviva Lev-Ari, 10/4/2012.
Nitric Oxide Nutritional remedies for hypertension and atherosclerosis. It’s 12 am: do you know where your electrons are?
Author and Reporter: Meg Baker, 10/7/2012.
[…] a) regulation of glycolysis b) NO in cardiovascular disease c) NO and Immune responses Part I and Part II d) NO signaling pathways (Also, please see Source for more articles on NO and its […]
Dr. A viral
Great post, great illustrations, great plan for future posts on the subject of Innumerable Responses
Thank you Aviva…yeah we wish to cover as many subtopics as possible with NO. I am also looking into elaborating a few of these subtopics in subsequent posts.
I think that the difference between rodent and man is in some part explained by the dietary source of methionine as a sulfur containing amino acid. This is shown in upper right. The rodent relies on plant as primary source of protein. The plant source has a S:N ratio of 1:20, whereas the animal sourced protein has a S:N ratio of 1:12.5. Even if the experiments are done in vitro, the strong effect of the metabolic profile is operative. This is also behind the development of CVD in strict vegans, who because of limited food source by choice or by circumstance have inadequate methionine.
If the methionine is inadequate, then the formation of SAM is low, and this results in increased homocysteine, which is predictive. SAM can feed into protein synthesis or into DNA synthesis. In this circumstance protein methylation becomes rate limiting, and ADMA declines. Thus, ADMA is the inhibitor of iNOS, and the Arginine feed into NO production prevails. This excess of NO generation is unbalanced in ROS, which is uncompensated by the SAM, and it has to have an effect on the Krebs Cycle and OX-PHOS. I would think that the oxidative stress would impair mitochondrial regulatory function, and the cell would have to rely on skeletal muscle proteolysis to provide gluconeogenic precursors.
In both cases, rodent and man, the oxidative stress is very high with the rapid generation of NO by the neutrophils and monocytes. If you are using Rodent tumor cells (fast or slow growing hepatoma), then you also have a vell that is already on track with a redirected mitochondria.
This was in part covered in the UPS, but it was by no means direct. Remember the effects of starvation as well as oxidative stress on mitochondrial regulatory function, as 90% of the cell’s energy is provided by the mitochondria. The organelle has to receive nutrients for its support from an outside source.
Dr. Larry
Thank you for your comment
Please NO abbreviations that are not common, UPS? SAM??
ALL MUST BE SPELLED OUT
Thank you
[…] a) regulation of glycolysis b) NO in cardiovascular disease c) NO and Immune responses Part I and Part II d) NO signaling pathways. The effects of NO in diseased states have been reviewed by the articles […]
[…] Nitric Oxide and Immune Responses: Part 2 (pharmaceuticalintelligence.com) […]
[…] of glycolysis b) NO in cardiovascular disease c) NO and Immune responses Part I and Part II d) NO signaling pathways. The effects of NO in diseased states have been reviewed by the […]
[…] Nitric Oxide and Immune Responses: Part 2 (pharmaceuticalintelligence.com) […]
[…] Nitric Oxide and Immune Responses: Part 2 (pharmaceuticalintelligence.com) […]
[…] Nitric Oxide and Immune Responses: Part 2 (pharmaceuticalintelligence.com) […]
PUT IT IN CONTEXT OF CANCER CELL MOVEMENT
The contraction of skeletal muscle is triggered by nerve impulses, which stimulate the release of Ca2+ from the sarcoplasmic reticuluma specialized network of internal membranes, similar to the endoplasmic reticulum, that stores high concentrations of Ca2+ ions. The release of Ca2+ from the sarcoplasmic reticulum increases the concentration of Ca2+ in the cytosol from approximately 10-7 to 10-5 M. The increased Ca2+ concentration signals muscle contraction via the action of two accessory proteins bound to the actin filaments: tropomyosin and troponin (Figure 11.25). Tropomyosin is a fibrous protein that binds lengthwise along the groove of actin filaments. In striated muscle, each tropomyosin molecule is bound to troponin, which is a complex of three polypeptides: troponin C (Ca2+-binding), troponin I (inhibitory), and troponin T (tropomyosin-binding). When the concentration of Ca2+ is low, the complex of the troponins with tropomyosin blocks the interaction of actin and myosin, so the muscle does not contract. At high concentrations, Ca2+ binding to troponin C shifts the position of the complex, relieving this inhibition and allowing contraction to proceed.
Figure 11.25
Association of tropomyosin and troponins with actin filaments. (A) Tropomyosin binds lengthwise along actin filaments and, in striated muscle, is associated with a complex of three troponins: troponin I (TnI), troponin C (TnC), and troponin T (TnT). In (more ) Contractile Assemblies of Actin and Myosin in Nonmuscle Cells
Contractile assemblies of actin and myosin, resembling small-scale versions of muscle fibers, are present also in nonmuscle cells. As in muscle, the actin filaments in these contractile assemblies are interdigitated with bipolar filaments of myosin II, consisting of 15 to 20 myosin II molecules, which produce contraction by sliding the actin filaments relative to one another (Figure 11.26). The actin filaments in contractile bundles in nonmuscle cells are also associated with tropomyosin, which facilitates their interaction with myosin II, probably by competing with filamin for binding sites on actin.
Figure 11.26
Contractile assemblies in nonmuscle cells. Bipolar filaments of myosin II produce contraction by sliding actin filaments in opposite directions. Two examples of contractile assemblies in nonmuscle cells, stress fibers and adhesion belts, were discussed earlier with respect to attachment of the actin cytoskeleton to regions of cell-substrate and cell-cell contacts (see Figures 11.13 and 11.14). The contraction of stress fibers produces tension across the cell, allowing the cell to pull on a substrate (e.g., the extracellular matrix) to which it is anchored. The contraction of adhesion belts alters the shape of epithelial cell sheets: a process that is particularly important during embryonic development, when sheets of epithelial cells fold into structures such as tubes.
The most dramatic example of actin-myosin contraction in nonmuscle cells, however, is provided by cytokinesisthe division of a cell into two following mitosis (Figure 11.27). Toward the end of mitosis in animal cells, a contractile ring consisting of actin filaments and myosin II assembles just underneath the plasma membrane. Its contraction pulls the plasma membrane progressively inward, constricting the center of the cell and pinching it in two. Interestingly, the thickness of the contractile ring remains constant as it contracts, implying that actin filaments disassemble as contraction proceeds. The ring then disperses completely following cell division.
Figure 11.27
Cytokinesis. Following completion of mitosis (nuclear division), a contractile ring consisting of actin filaments and myosin II divides the cell in two.
http://www.ncbi.nlm.nih.gov/books/NBK9961/
This is good. I don’t recall seeing it in the original comment. I am very aware of the actin myosin troponin connection in heart and in skeletal muscle, and I did know about the nonmuscle work. I won’t deal with it now, and I have been working with Aviral now online for 2 hours.
I have had a considerable background from way back in atomic orbital theory, physical chemistry, organic chemistry, and the equilibrium necessary for cations and anions. Despite the calcium role in contraction, I would not discount hypomagnesemia in having a disease role because of the intracellular-extracellular connection. The description you pasted reminds me also of a lecture given a few years ago by the Nobel Laureate that year on the mechanism of cell division.
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