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Archive for the ‘Cardiac and Cardiovascular Surgical Procedures’ Category


Post TAVR: Management of conduction disturbances and number of valve recapture and/or repositioning attempts – Optimize self-expanding transcatheter aortic valve replacement (TAVR) positioning reduced the need for permanent pacemaker (PPM) implants down the road

Reporter: Aviva Lev-Ari, PhD, RN

  • The PPM rate dropped from 9.7% to 3.0% (P=0.035), according to a team led by Hasan Jilaihawi, MD, of NYU Langone Health in New York City.
  • the PARTNER 3 and CoreValve Low Risk trials in patients at low surgical risk showed PPM implant rates of 17.4% with the Evolut line, 6.6% with the balloon-expandable Sapien 3, and 4.1%-6.1% with surgery.

 

  • “The His bundle passes through the membranous septum, a few millimeters beneath the non-coronary/right coronary cusps. It is therefore not surprising that a deeper valve implantation increases the likelihood of mechanical damage of the His bundle leading to a transient or persistent conduction disturbance,” according to Rodés-Cabau.

To capture factors that contributed to need for PPM implantation, Jilaihawi and colleagues performed a detailed restrospective analysis on 248 consecutive Evolut recipients at Langone treated with the standard TAVR approach — aiming for 3-4 mm implant depth (in relation to the non-coronary cusp) and recapturing and repositioning when the device landed considerably lower. Patients with prior PPM implantation were excluded. Devices used were Medtronic’s Evolut R, Evolut Pro, and Evolut 34XL.

This analysis revealed that use of the large Evolut 34XL (OR 4.96, 95% CI 1.68-14.63) and implant depth exceeding membranous septum length (OR 8.04, 95% CI 2.58-25.04) were independent predictors of later PPM implantation.

From there, operators came up with the MIDAS technique and applied it prospectively to another 100 consecutive patients.

Besides bringing down the PPM implant rate to 3.0%, there were no more cases of valve embolization, dislocation, or need for a second valve.

The standard and MIDAS groups shared similar membranous septum lengths but diverged in average actual device depth, such that the standard group tended to have Evolut devices positioned deeper (3.3 mm vs 2.3 mm, P<0.001).

SOURCE

https://www.medpagetoday.com/cardiology/pci/81849

 

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Digital Therapeutics: A Threat or Opportunity to Pharmaceuticals


Digital Therapeutics: A Threat or Opportunity to Pharmaceuticals

Reporter and Curator: Dr. Sudipta Saha, Ph.D.

 

Digital Therapeutics (DTx) have been defined by the Digital Therapeutics Alliance (DTA) as “delivering evidence based therapeutic interventions to patients, that are driven by software to prevent, manage or treat a medical disorder or disease”. They might come in the form of a smart phone or computer tablet app, or some form of a cloud-based service connected to a wearable device. DTx tend to fall into three groups. Firstly, developers and mental health researchers have built digital solutions which typically provide a form of software delivered Cognitive-Behaviour Therapies (CBT) that help patients change behaviours and develop coping strategies around their condition. Secondly there are the group of Digital Therapeutics which target lifestyle issues, such as diet, exercise and stress, that are associated with chronic conditions, and work by offering personalized support for goal setting and target achievement. Lastly, DTx can be designed to work in combination with existing medication or treatments, helping patients manage their therapies and focus on ensuring the therapy delivers the best outcomes possible.

 

Pharmaceutical companies are clearly trying to understand what DTx will mean for them. They want to analyze whether it will be a threat or opportunity to their business. For a long time, they have been providing additional support services to patients who take relatively expensive drugs for chronic conditions. A nurse-led service might provide visits and telephone support to diabetics for example who self-inject insulin therapies. But DTx will help broaden the scope of support services because they can be delivered cost-effectively, and importantly have the ability to capture real-world evidence on patient outcomes. They will no-longer be reserved for the most expensive drugs or therapies but could apply to a whole range of common treatments to boost their efficacy. Faced with the arrival of Digital Therapeutics either replacing drugs, or playing an important role alongside therapies, pharmaceutical firms have three options. They can either ignore DTx and focus on developing drug therapies as they have done; they can partner with a growing number of DTx companies to develop software and services complimenting their drugs; or they can start to build their own Digital Therapeutics to work with their products.

 

Digital Therapeutics will have knock-on effects in health industries, which may be as great as the introduction of therapeutic apps and services themselves. Together with connected health monitoring devices, DTx will offer a near constant stream of data about an individuals’ behavior, real world context around factors affecting their treatment in their everyday lives and emotional and physiological data such as blood pressure and blood sugar levels. Analysis of the resulting data will help create support services tailored to each patient. But who stores and analyses this data is an important question. Strong data governance will be paramount to maintaining trust, and the highly regulated pharmaceutical industry may not be best-placed to handle individual patient data. Meanwhile, the health sector (payers and healthcare providers) is becoming more focused on patient outcomes, and payment for value not volume. The future will say whether pharmaceutical firms enhance the effectiveness of drugs with DTx, or in some cases replace drugs with DTx.

 

Digital Therapeutics have the potential to change what the pharmaceutical industry sells: rather than a drug it will sell a package of drugs and digital services. But they will also alter who the industry sells to. Pharmaceutical firms have traditionally marketed drugs to doctors, pharmacists and other health professionals, based on the efficacy of a specific product. Soon it could be paid on the outcome of a bundle of digital therapies, medicines and services with a closer connection to both providers and patients. Apart from a notable few, most pharmaceutical firms have taken a cautious approach towards Digital Therapeutics. Now, it is to be observed that how the pharmaceutical companies use DTx to their benefit as well as for the benefit of the general population.

 

References:

 

https://eloqua.eyeforpharma.com/LP=23674?utm_campaign=EFP%2007MAR19%20EFP%20Database&utm_medium=email&utm_source=Eloqua&elqTrackId=73e21ae550de49ccabbf65fce72faea0&elq=818d76a54d894491b031fa8d1cc8d05c&elqaid=43259&elqat=1&elqCampaignId=24564

 

https://www.s3connectedhealth.com/resources/white-papers/digital-therapeutics-pharmas-threat-or-opportunity/

 

http://www.pharmatimes.com/web_exclusives/digital_therapeutics_will_transform_pharma_and_healthcare_industries_in_2019._heres_how._1273671

 

https://www.mckinsey.com/industries/pharmaceuticals-and-medical-products/our-insights/exploring-the-potential-of-digital-therapeutics

 

https://player.fm/series/digital-health-today-2404448/s9-081-scaling-digital-therapeutics-the-opportunities-and-challenges

 

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Immunoediting can be a constant defense in the cancer landscape


Reporter and Curator: Dr. Sudipta Saha, Ph.D.

 

There are many considerations in the cancer immunoediting landscape of defense and regulation in the cancer hallmark biology. The cancer hallmark biology in concert with key controls of the HLA compatibility affinity mechanisms are pivotal in architecting a unique patient-centric therapeutic application. Selection of random immune products including neoantigens, antigens, antibodies and other vital immune elements creates a high level of uncertainty and risk of undesirable immune reactions. Immunoediting is a constant process. The human innate and adaptive forces can either trigger favorable or unfavorable immunoediting features. Cancer is a multi-disease entity. There are multi-factorial initiators in a certain disease process. Namely, environmental exposures, viral and / or microbiome exposure disequilibrium, direct harm to DNA, poor immune adaptability, inherent risk and an individual’s own vibration rhythm in life.

 

When a human single cell is crippled (Deranged DNA) with mixed up molecular behavior that is the initiator of the problem. A once normal cell now transitioned into full threatening molecular time bomb. In the modeling and creation of a tumor it all begins with the singular molecular crisis and crippling of a normal human cell. At this point it is either chop suey (mixed bit responses) or a productive defensive and regulation response and posture of the immune system. Mixed bits of normal DNA, cancer-laden DNA, circulating tumor DNA, circulating normal cells, circulating tumor cells, circulating immune defense cells, circulating immune inflammatory cells forming a moiety of normal and a moiety of mess. The challenge is to scavenge the mess and amplify the normal.

 

Immunoediting is a primary push-button feature that is definitely required to be hit when it comes to initiating immune defenses against cancer and an adaptation in favor of regression. As mentioned before that the tumor microenvironment is a “mixed bit” moiety, which includes elements of the immune system that can defend against circulating cancer cells and tumor growth. Personalized (Precision-Based) cancer vaccines must become the primary form of treatment in this case. Current treatment regimens in conventional therapy destroy immune defenses and regulation and create more serious complications observed in tumor progression, metastasis and survival. Commonly resistance to chemotherapeutic agents is observed. These personalized treatments will be developed in concert with cancer hallmark analytics and immunocentrics affinity and selection mapping. This mapping will demonstrate molecular pathway interface and HLA compatibility and adaptation with patientcentricity.

References:

 

https://www.linkedin.com/pulse/immunoediting-cancer-landscape-john-catanzaro/

 

https://www.cell.com/cell/fulltext/S0092-8674(16)31609-9

 

https://www.researchgate.net/publication/309432057_Circulating_tumor_cell_clusters_What_we_know_and_what_we_expect_Review

 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4190561/

 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5840207/

 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5593672/

 

https://www.frontiersin.org/articles/10.3389/fimmu.2018.00414/full

 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5593672/

 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4190561/

 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4388310/

 

https://www.linkedin.com/pulse/cancer-hallmark-analytics-omics-data-pathway-studio-review-catanzaro/

 

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Mitralign and Corvia, Tewksbury, Mass – Investment and Acquisition by Edwards Lifesciences

 

Reporter: Aviva Lev-Ari, PhD, RN

 

Edwards LifesciencesEdwards Lifesciences (NYSE:EW) said today that it made a pair of strategic bets on the structural heart space, paying $35 million for the right to acquire Corvia Medical and paying an unspecified amount for some of mitral valve repair device maker Mitralign‘s assets.

Tewksbury, Mass.-based Corvia is developing an interatrial shunt to treat heart failure by creating a small opening between the left and right atria to lower blood pressure in the left atrium and lungs. The device has CE Mark approval in the European Union and a pivotal U.S trial aimed at winning a nod from the FDA is under way, Edwards said.

“We are extremely pleased to have the support of the global leader in patient-focused innovations for structural heart disease as we continue to advance this novel treatment for heart failure,” Corvia president & CEO George Fazio said in prepared remarks. “We are proud of our accomplishments to date and look forward to completing the pivotal study with the support of our global clinical investigators.”

The Irvine, Calif.-based company also said it bought “certain” Mitralign assets, including intellectual property and associated clinical and regulatory experience. Mitralign, also based in Tewksbury, is developing an annuloplasty system for treating functional mitral and tricuspid regurgitation.

Edwards said the transactions are not expected to affect its financial outlook for 2019.

SOURCE

https://www.massdevice.com/edwards-lifesciences-gets-in-on-corvia-mitralign/?spMailingID=1958&puid=370787

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Reporter: Gail S. Thornton

This article appeared on the website of Cardiovascular Business

‘Patient No. 1’ from a Hep C heart transplant study shares his story

By the time three transplant physicians approached Tom Giangiulio Jr. about being the first patient in a new clinical trial to accept a heart from a Hepatitis C-positive donor, Giangiulio didn’t have much of a choice.

He had already been on the heart transplant waitlist for more than two years, he was a live-in at the Hospital of the University of Pennsylvania and he had a body size (6-foot-2, 220 pounds) and blood type (O-positive) that was difficult to match to a donor.

It took Giangiulio less than 24 hours to speak to his previous cardiologist and his family and decide to enroll in the program. The doctors at Penn explained to him that because of new medications that can cure Hepatitis C, they were confident the virus could be eradicated post-transplant.

“There was no hesitation at all, not with me,” said Carin Giangiulio, Tom’s wife of 33 years. “Because I knew what the alternative was and we didn’t have too much choice except for going on a VAD (ventricular assist device) … and he didn’t want to do that. I said, ‘If they have a cure, then it’s a no-brainer. Let’s just do it.’ And I’m glad we did because I don’t think he would’ve been here today.”

Tom, 59, is set to celebrate his second anniversary with his new heart in June. He received the heart the day after Father’s Day in 2017 and subsequently contracted Hepatitis C, which was promptly wiped out with a 12-week regimen of elbasvir/grazoprevir (Zepatier).

Some of Giangiulio’s doctors at Penn published in February their experience with the first 10 patients in the clinical trial, called USHER, in the American Journal of Transplantation. All nine patients who survived were cured of Hepatitis C thanks to the antiviral therapy.

The implications of the research are massive, said Rhondalyn McLean, MD, MHS, the medical director of Penn’s heart transplant program and lead author of the recently published study. For the past two decades, the U.S. has struggled to increase the number of heart transplants above about 3,000 per year. And every year, patients die waiting for a heart transplant or become too sick to handle a transplant surgery.

McLean estimated 700 hearts from donors with Hepatitis C are discarded each year in the U.S. If even half of those are suitable for transplant, it would increase by 10 percent the number of organs that are available for implantation.

“There are so many people who have end-stage heart failure who die waiting for transplant, so anytime that we can increase our access to organs then I think we’re all going to be happy about that,” McLean said. “I think the people believe in the medicine, they believe that Hepatitis C is curable, so the risk to these folks is low. With the results of the study, I think we’ve proven that we can do this safely and the medications have great efficacy.”

Transplanting Hepatitis C-positive hearts isn’t a new idea, McLean explained.

“We used to do this all the time (with) the thinking that Hepatitis C usually doesn’t cause a problem for many, many years, so if hearts are only going to last 13 years or so and Hepatitis C doesn’t usually cause a problem for 30 years in someone, it should be an OK thing to do,” she said.

But then a study published in the 1990s found Hepatitis C-negative patients who accepted a heart from a donor with Hepatitis C actually had an increased risk of death compared to those who received normal hearts, and the practice of using these organs ceased.

However, with the new medications—the first commercially available treatment for Hepatitis C was approved by the FDA in 2014—McLean and her team are systematically studying the safety of implanting these hearts and then wiping out the virus once it’s contracted. And they’re optimistic about the program, which showed the first 10 patients had no evidence of the virus after their 12-week medication regimens.

“That met the criteria for sustained virologic response and those patients are deemed to be cured,” she said. “There’s no reason to think that this population would be any different than your normal, nontransplant population (in terms of Hepatitis C reappearing) so I think it was a pretty successful study.”

Penn researchers are also studying a similar approach in kidney and lung transplant candidates, which could help patients stuck on waitlists for those organs as well.

McLean described the increasing availability of these organs as an “unfortunate benefit” of the opioid epidemic. Through sharing needles, many opioid users are contracting Hepatitis C and dying young. Organs from young donors tend to perform better and often have no other problems, so solving the Hep C issue through medication could have a huge impact if this strategy is eventually rolled out on a broader scale.

“It’s hard when you have single-center studies,” McLean said. “They’re always promising, but in order to get a better assessment of what we’re doing and how the drug is doing I think you need to combine numbers so there has to be a registry that looks at all of the patients who have received these drugs and then using numbers to determine whether this is a successful strategy for us. And I believe that it will be.”

Those are the large-scale implications of this research. Tom Giangiulio can share the personal side.

Patient No. 1

Giangiulio said he feels “extremely gifted” to be Patient No. 1 in the USHER program. He knows he may not be alive if he wasn’t.

He recalls going into ventricular tachycardia about a week before his transplant and said it “scared the daylights” out of him.

“The amount of red tape, meetings and research, technology, and things that had to happen at a very precise moment in time for me to be the first … it’s mind-boggling to think about it,” he said. “But for all that to happen and for it to happen when it happened—and for me to get the heart when I got it—there was a lot of divine intervention along with a lot of people that were involved.”

Giangiulio has also experienced some powerful moments since receiving the transplant. After a bit of written correspondence with his donor’s family, he met the young man’s family one weekend in December of 2018.

He said riding over to the meeting was probably the most tense he’s ever been, but once he arrived the experience far exceeded his expectations.

“We were there for 2 ½ hours and nobody wanted to leave,” Giangiulio said.

The donor’s mother got Giangiulio a gift, a ceramic heart with a photograph of her son. A fellow transplant patient had told Giangiulio about a product called Enso, a kidney-shaped object you can hold in your hand which plays a recording of a user’s heartbeat.

Giangiulio decided to give it to her.

“I was very cautious at the advice of the people here at Penn,” he said. “Nobody knew how she would react to it. It might bother her, she could be thrilled to death. And she was, she was thrilled to death with it and she sleeps with it every night. She boots up the app and she listens to my heartbeat on that app every night.”

Another moment that sticks out to Giangiulio is meeting Patient No. 7 in the USHER program, who he remains in touch with. They ran into each other while waiting to get blood work done, and began talking about their shared experience as transplant recipients.

The clinical trial came up and Giangiulio slow-played his involvement, asking Patient No. 7 about the trial and not letting on that he was ultra-familiar with the program.

When Giangiulio finally told him he was Patient No. 1, Patient No. 7 “came launching out of his chair” to hug him.

“He said, ‘I owe you my life,’” Giangiulio recalled.

After Giangiulio responded that it was the doctors he really owed, Patient No. 7 said he had specifically asked how Patient No. 1 was doing when McLean first offered the program to him.

“She explained that I was going to be No. 7. … I didn’t care about 6, 5, 4, 3 or 2. I wanted to know how No. 1 was doing,” Giangiulio recalled of the conversation. “He said, ‘That was you. … They told me how well you were doing and that if I wanted you’d come here and talk to me, so I owe you.’”

Giangiulio feels strongly about giving back and reciprocating the good fortune he’s had. That’s why he talks to fellow patients and the media to share his story—because it could save other people’s lives, too.

He can’t do as much physical labor as he used to, but he remains involved in the excavating company he owns with his brothers and is the Emergency Management Coordinator for Waterford Township, New Jersey. He also serves on the township’s planning board and was previously Director of Public Safety.

“To me, he’s Superman,” Carin Giangiulio said. “It was insane, completely insane what the human body can endure and still survive.”

That now includes being given a heart with Hepatitis C and then wiping out the virus with the help of modern medicine.

“I would tell (other transplant candidates) to not fear it, especially if you’re here at Penn,” Giangiulio said. “I know there’s a lot of good hospitals across the country, but my loyalty kind of lies here for understandable reasons.”

Other related articles were published in this Open Access Online Scientific Journal include the following:

2016

People with blood type O have been reported to be protected from coronary heart disease, cancer, and have lower cholesterol levels.

https://pharmaceuticalintelligence.com/2016/01/11/people-with-blood-type-o-have-been-reported-to-be-protected-from-coronary-heart-disease-cancer-and-have-lower-cholesterol-levels/

2015

A Patient’s Perspective: On Open Heart Surgery from Diagnosis and Intervention to Recovery

https://pharmaceuticalintelligence.com/2015/05/10/a-patients-perspective-on-open-heart-surgery-from-diagnosis-and-intervention-to-recovery/

No evidence to change current transfusion practices for adults undergoing complex cardiac surgery: RECESS evaluated 1,098 cardiac surgery patients received red blood cell units stored for short or long periods

https://pharmaceuticalintelligence.com/2015/04/08/no-evidence-to-change-current-transfusion-practices-for-adults-undergoing-complex-cardiac-surgery-recess-evaluated-1098-cardiac-surgery-patients-received-red-blood-cell-units-stored-for-short-or-lon/

2013

ACC/AHA Guidelines for Coronary Artery Bypass Graft Surgery

https://pharmaceuticalintelligence.com/2013/11/05/accaha-guidelines-for-coronary-artery-bypass-graft-surgery/

On Devices and On Algorithms: Arrhythmia after Cardiac SurgeryPrediction and ECG Prediction of Paroxysmal Atrial Fibrillation Onset

https://pharmaceuticalintelligence.com/2013/05/07/on-devices-and-on-algorithms-arrhythmia-after-cardiac-surgery-prediction-and-ecg-prediction-of-paroxysmal-atrial-fibrillation-onset/

 

Editor’s note:

I wish to encourage the e-Reader of this Interview to consider reading and comparing the experiences of other Open Heart Surgery Patients, voicing their private-life episodes in the ER that are included in this recently published volume, The VOICES of Patients, Hospital CEOs, Health Care Providers, Caregivers and Families: Personal Experience with Critical Care and Invasive Medical Procedures.

https://pharmaceuticalintelligence.com/2017/11/21/the-voices-of-patients-hospital-ceos-health-care-providers-caregivers-and-families-personal-experience-with-critical-care-and-invasive-medical-procedures/

 

I also wish to encourage the e-Reader to consider, if interested, reviewing additional e-Books on Cardiovascular Diseases from the same Publisher, Leaders in Pharmaceutical Business Intelligence (LPBI) Group, on Amazon.com.

  • Perspectives on Nitric Oxide in Disease Mechanisms, on Amazon since 6/2/12013

http://www.amazon.com/dp/B00DINFFYC

  • Cardiovascular, Volume Two: Cardiovascular Original Research: Cases in Methodology Design for Content Co-Curation, on Amazon since 11/30/2015

http://www.amazon.com/dp/B018Q5MCN8

  • Cardiovascular Diseases, Volume Three: Etiologies of Cardiovascular Diseases: Epigenetics, Genetics and Genomics, on Amazon since 11/29/2015

http://www.amazon.com/dp/B018PNHJ84

  • Cardiovascular Diseases, Volume Four: Regenerative and Translational Medicine: The Therapeutics Promise for Cardiovascular Diseases, on Amazon since 12/26/2015

http://www.amazon.com/dp/B019UM909A

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The Golden Hour of Stroke Intervention

Reporter: Irina Robu, PhD

The removal of thrombus under the image guidance, endovascular thrombectomy is preferred for an arterial embolism which is characteristic for an arterial blockage frequently caused by atrial fibrillation, a heart rhythm disorder. An arterial embolism causes restricted blood supply which leads to pain in the affected area. A thrombectomy can too be used to treat conditions in your organs which is usually associated with less benefit and more risk, a large retrospective study found.

Alejandro Spiotta, MD from Medical University of South Carolina in Charleston stated that functional independence rates were 45% for those treated in less than 30 minutes, 33% with procedures 30 to 60 minutes long, and 27% when procedures took more than 60 minutes. The results indicate that complications double after 50 minutes and the mortality risk is significantly for the over 60-minute group than in those treated in 30 to 60 minutes.

Earlier research has shown that when it comes to mechanical thrombectomy, procedure time has a noteworthy effect on patient outcomes. Based on these findings, it seems reasonable to conclude that at 60 minutes, one should consider the futility of continuing the procedure. However, procedures that last longer were connected with increased cost, worse outcomes, and increased incidence of complications, the investigators noted. Yet, the findings underscore the importance of timely recanalization and suggest there’s a point at which continuing to manipulate the intracranial artery may not be helpful for the patient.

Spiotta’s group evaluated 1,357 participants at seven U.S. medical centers, but only 12% out of the patients showed signs of posterior circulation stroke and 46% of cases received IV tissue-type plasminogen activator. The scientists use a prospectively-maintained database which consists of clinical and technical outcomes and baseline variables and can evaluate patients that underwent endovascular thrombectomy with direct aspiration as first pass technique or a stent retriever.

They collected their experience with the benefit of hindsight and joint it together, so there’s always a chance of case ascertain bias or other bias in the collection of the cases. One limitation is the fact that these are quality, busy centers, and the results might even worse if less experienced centers were included. It’s a little bit like getting the cream of the crop and analyzing their data. Upcoming studies should gather data on the relationship between specific thrombectomy devices and techniques and the success of recanalization procedures for patients with AIS.

SOURCE
https://www.medpagetoday.com/cardiology/strokes/78251

 

 

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Lesson 3 Cell Signaling & Motility: G Proteins, Signal Transduction: Curations and Articles of reference as supplemental information: #TUBiol3373

Curator: Stephen J. Williams, Ph.D.

Updated 7/15/2019

Lesson 3 Powerpoint (click link below):

cell signaling and motility 3 finalissima sjw

Four papers to choose from for your February 11 group presentation:

Structural studies of G protein Coupled receptor

Shapiro-2009-Annals_of_the_New_York_Academy_of_Sciences

G protein as target in neurodegerative disease

fish technique

 

 

Today’s lesson 3 explains how extracellular signals are transduced (transmitted) into the cell through receptors to produce an agonist-driven event (effect).  This lesson focused on signal transduction from agonist through G proteins (GTPases), and eventually to the effectors of the signal transduction process.  Agonists such as small molecules like neurotransmitters, hormones, nitric oxide were discussed however later lectures will discuss more in detail the large growth factor signalings which occur through receptor tyrosine kinases and the Ras family of G proteins as well as mechanosignaling through Rho and Rac family of G proteins.

Transducers: The Heterotrimeric G Proteins (GTPases)

An excellent review of heterotrimeric G Proteins found in the brain is given by

Heterotrimeric G Proteins by Eric J Nestler and Ronald S Duman.

 

 

from Seven-Transmembrane receptors – Scientific Figure on ResearchGate. Available from: https://www.researchgate.net/figure/Examples-of-heterotrimeric-G-protein-effectors_tbl1_11180073 [accessed 4 Feb, 2019] and see references within

 

 

See below for the G Protein Cycle

 

 

 

 

 

 

 

 

<a href=”https://www.researchgate.net/figure/32-The-G-protein-cycle-In-the-absence-of-agonist-A-GPCRs-are-mainly-in-the-low_fig2_47933733″><img src=”https://www.researchgate.net/profile/Veli_Pekka_Jaakola/publication/47933733/figure/fig2/AS:669499451781133@1536632516635/32-The-G-protein-cycle-In-the-absence-of-agonist-A-GPCRs-are-mainly-in-the-low.ppm&#8221; alt=”.3.2: The G protein cycle. In the absence of agonist (A), GPCRs are mainly in the low affinity state (R). After agonist binding, the receptor is activated in the high affinity state (R*), and the agonist-GPCR-G protein complex is formed. GTP replaces GDP in Gα. After that the G protein dissociates into the Gα subunit and the Gβγ heterodimer, which then activate several effector proteins. The built-in GTPase activity of the Gα subunit cleaves the terminal phosphate group of GTP, and the GDP bound Gα subunit reassociates with Gβγ heterodimer. This results in the deactivation of both Gα and Gβγ. The G protein cycle returns to the basal state. RGS, regulator of G protein signalling.”/></a>

 

From Citation: Review: A. M. Preininger, H. E. Hamm, G protein signaling: Insights from new structures. Sci. STKE2004, re3 (2004)

 

For a tutorial on G Protein coupled receptors (GPCR) see

https://www.khanacademy.org/test-prep/mcat/organ-systems/biosignaling/v/g-protein-coupled-receptors

 

 

 

cyclic AMP (cAMP) signaling to the effector Protein Kinase A (PKA)

from https://courses.washington.edu/conj/gprotein/cyclicamp.htm

Cyclic AMP is an important second messenger. It forms, as shown, when the membrane enzyme adenylyl cyclase is activated (as indicated, by the alpha subunit of a G protein).

 

The cyclic AMP then goes on the activate specific proteins. Some ion channels, for example, are gated by cyclic AMP. But an especially important protein activated by cyclic AMP is protein kinase A, which goes on the phosphorylate certain cellular proteins. The scheme below shows how cyclic AMP activates protein kinase A.

Updated 7/15/2019

Additional New Studies on Regulation of the Beta 2 Adrenergic Receptor

We had discussed regulation of the G protein coupled beta 2 adrenergic receptor by the B-AR receptor kinase (BARK)/B arrestin system which uncouples and desensitizes the receptor from its G protein system.  In an article by Xiangyu Liu in Science in 2019, the authors describe another type of allosteric modulation (this time a POSITIVE allosteric modulation) in the intracellular loop 2.  See below:

Mechanism of β2AR regulation by an intracellular positive allosteric modulator

Xiangyu Liu1,*, Ali Masoudi2,*, Alem W. Kahsai2,*, Li-Yin Huang2, Biswaranjan Pani2Dean P. Staus2, Paul J. Shim2, Kunio Hirata3,4, Rishabh K. Simhal2, Allison M. Schwalb2, Paula K. Rambarat2, Seungkirl Ahn2, Robert J. Lefkowitz2,5,6,Brian Kobilka1

Positive reinforcement in a GPCR

Many drug discovery efforts focus on G protein–coupled receptors (GPCRs), a class of receptors that regulate many physiological processes. An exemplar is the β2-adrenergic receptor (β2AR), which is targeted by both blockers and agonists to treat cardiovascular and respiratory diseases. Most GPCR drugs target the primary (orthosteric) ligand binding site, but binding at allosteric sites can modulate activation. Because such allosteric sites are less conserved, they could possibly be targeted more specifically. Liu et al. report the crystal structure of β2AR bound to both an orthosteric agonist and a positive allosteric modulator that increases receptor activity. The structure suggests why the modulator compound is selective for β2AR over the closely related β1AR. Furthermore, the structure reveals that the modulator acts by enhancing orthosteric agonist binding and stabilizing the active conformation of the receptor.

Abstract

Drugs targeting the orthosteric, primary binding site of G protein–coupled receptors are the most common therapeutics. Allosteric binding sites, elsewhere on the receptors, are less well-defined, and so less exploited clinically. We report the crystal structure of the prototypic β2-adrenergic receptor in complex with an orthosteric agonist and compound-6FA, a positive allosteric modulator of this receptor. It binds on the receptor’s inner surface in a pocket created by intracellular loop 2 and transmembrane segments 3 and 4, stabilizing the loop in an α-helical conformation required to engage the G protein. Structural comparison explains the selectivity of the compound for β2– over the β1-adrenergic receptor. Diversity in location, mechanism, and selectivity of allosteric ligands provides potential to expand the range of receptor drugs.

 

Recent structures of GPCRs bound to allosteric modulators have revealed that receptor surfaces are decorated with diverse cavities and crevices that may serve as allosteric modulatory sites (1). This substantiates the notion that GPCRs are structurally plastic and can be modulated by a variety of allosteric ligands through distinct mechanisms (2-7). Most of these structures have been solved with negative allosteric modulators (NAMs), which stabilize receptors in their inactive states (1). To date, only a single structure of an active GPCR bound to a small-molecule positive allosteric modulator (PAM) has been reported, namely, the M2 muscarinic acetylcholine receptor with LY2119620 (8). Thus, mechanisms of PAMs and their potential binding sites remain largely unexplored.

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Fig 1. Structure of the active state T4L-B2AR in complex with the orthosteric agonist BI-167107, nanobody 689, and compound 6FA.  (A) The chemical structure of compound-6FA (Cmpd-6FA). (B) Isoproterenol (ISO) competition binding with 125I-cyanopindolol (CYP) to the β2AR reconstituted in nanodisks in the presence of vehicle (0.32% dimethylsulfoxide; DMSO), Cmpd-6, or Cmpd-6FA at 32 μM. Values were normalized to percentages of the maximal 125I-CYP binding level obtained from a one-site competition binding–log IC50 (median inhibitory concentration) curve fit. Binding curves were generated by GraphPad Prism. Points on curves represent mean ± SEM obtained from five independent experiments performed in duplicate. (C) Analysis of Cmpd-6FA interaction with the BI-167107–bound β2AR by ITC. Representative thermogram (inset) and binding isotherm, of three independent experiments, with the best titration curve fit are shown. Summary of thermodynamic parameters obtained by ITC: binding affinity (KD = 1.2 ± 0.1 μM), stoichiometry (N = 0.9 ± 0.1 sites), enthalpy (ΔH = 5.0 ± 1.2 kcal mol−1), and entropy (ΔS =13 ± 2.0 cal mol−1 deg−1). (D) Side view of T4L-β2AR bound to the orthosteric agonist BI-167107, nanobody 6B9 (Nb6B9), and Cmpd-6FA. The gray box indicates the membrane layer as defined by the OPM database. (E) Close-up view of Cmpd-6FA binding site. Covering Cmpd-6FA is 2Fo– Fc electron density contoured at 1.0 σ (green mesh).From Science  28 Jun 2019:
Vol. 364, Issue 6447, pp. 1283-1287

 

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Fig 3. Fig. 3 Mechanism of allosteric activation of the β2AR by Cmpd-6FA.

(A) Superposition of the inactive β2AR bound to the antagonist carazolol (PDB code: 2RH1) and the active β2AR bound to the agonist BI-167107, Cmpd-6FA, and Nb6B9. Close-up view of the Cmpd-6FA binding site is shown. The residues of the inactive (yellow) and active (blue) β2AR are depicted, and the hydrogen bond formed between Asp1303.49and Tyr141ICL2 in the active state is indicated by a black dashed line. (B) Topography of Cmpd-6FA binding surface on the active β2AR (left, blue) and the corresponding surface of the inactive β2AR (right, yellow) with Cmpd-6FA (orange sticks) docked on top. Molecular surfaces are of only those residues involved in interaction with Cmpd-6FA. Steric clash between Cmpd-6FA and the surface of inactive β2AR is represented by a purple asterisk. (C) Overlay of the β2AR bound to BI-167107, Nb6B9, and Cmpd-6FA with the β2AR–Gscomplex (PDB code: 3SN6). The inset shows the position of Phe139ICL2 relative to the α subunit of Gs. (D) Superposition of the active β2AR bound to the agonist BI-167107, Nb6B9, and Cmpd-6FA (blue) with the inactive β2AR bound to carazolol (yellow) (PDB code: 2RH1) as viewed from the cytoplasm. For clarity, Nb6B9 and the orthosteric ligands are omitted. The arrows indicate shifts in the intracellular ends of the TM helices 3, 5, and 6 upon activation and their relative distances.

 

 

 

 

Allosteric sites may not face the same evolutionary pressure as do orthosteric sites, and thus are more divergent across subtypes within a receptor family (2426). Therefore, allosteric sites may provide a greater source of specificity for targeting GPCRs.

 

 

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Additional information on Nitric Oxide as a Cellular Signal

Nitric oxide is actually a free radical and can react with other free radicals, resulting in a very short half life (only a few seconds) and so in the body is produced locally to its site of action (i.e. in endothelial cells surrounding the vascular smooth muscle, in nerve cells). In the late 1970s, Dr. Robert Furchgott observed that acetylcholine released a substance that produced vascular relaxation, but only when the endothelium was intact. This observation opened this field of research and eventually led to his receiving a Nobel prize. Initially, Furchgott called this substance endothelium-derived relaxing factor (EDRF), but by the mid-1980s he and others identified this substance as being NO.

Nitric oxide is produced from metabolism of endogenous substances like L-arginine, catalyzed by one of three isoforms of nitric oxide synthase (for link to a good article see here) or release from exogenous compounds like drugs used to treat angina pectoris like amyl nitrate or drugs used for hypertension such as sodium nitroprusside.

The following articles are a great reference to the chemistry, and physiological and pathological Roles of Nitric Oxide:

46. The Molecular Biology of Renal Disorders: Nitric Oxide – Part III

Curator and Author: Larry H Bernstein, MD, FACP

https://pharmaceuticalintelligence.com/2012/11/26/the-molecular-biology-of-renal-disorders/

47. Nitric Oxide Function in Coagulation – Part II

Curator and Author: Larry H. Bernstein, MD, FCAP

https://pharmaceuticalintelligence.com/2012/11/26/nitric-oxide-function-in-coagulation/

48. Nitric Oxide, Platelets, Endothelium and Hemostasis

Curator and Author: Larry H Bernstein, MD, FACP

https://pharmaceuticalintelligence.com/2012/11/08/nitric-oxide-platelets-endothelium-and-hemostasis/

49. Interaction of Nitric Oxide and Prostacyclin in Vascular Endothelium

Curator and Author: Larry H Bernstein, MD, FACP

https://pharmaceuticalintelligence.com/2012/09/14/interaction-of-nitric-oxide-and-prostacyclin-in-vascular-endothelium/

50. Nitric Oxide and Immune Responses: Part 1

Curator and Author:  Aviral Vatsa PhD, MBBS

https://pharmaceuticalintelligence.com/2012/10/18/nitric-oxide-and-immune-responses-part-1/

51. Nitric Oxide and Immune Responses: Part 2

Curator and Author:  Aviral Vatsa PhD, MBBS

https://pharmaceuticalintelligence.com/2012/10/28/nitric-oxide-and-immune-responses-part-2/

56. Nitric Oxide and iNOS have Key Roles in Kidney Diseases – Part II

Curator and Author: Larry H Bernstein, MD, FACP

https://pharmaceuticalintelligence.com/2012/11/26/nitric-oxide-and-inos-have-key-roles-in-kidney-diseases/

57. New Insights on Nitric Oxide donors – Part IV

Curator and Author: Larry H Bernstein, MD, FACP

https://pharmaceuticalintelligence.com/2012/11/26/new-insights-on-no-donors/

59. Nitric Oxide has a ubiquitous role in the regulation of glycolysis -with a concomitant influence on mitochondrial function

Curator and Author: Larry H Bernstein, MD, FACP

https://pharmaceuticalintelligence.com/2012/09/16/nitric-oxide-has-a-ubiquitous-role-in-the-regulation-of-glycolysis-with-         a-concomitant-influence-on-mitochondrial-function/

Biochemistry of the Coagulation Cascade and Platelet Aggregation: Nitric Oxide: Platelets, Circulatory Disorders, and Coagulation Effects

Nitric Oxide Function in Coagulation – Part II

Nitric oxide is implicated in many pathologic processes as well.  Nitric oxide post translational modifications have been attributed to nitric oxide’s role in pathology however, although the general mechanism by which nitric oxide exerts its physiological effects is by stimulation of soluble guanylate cyclase to produce cGMP, these post translational modifications can act as a cellular signal as well.  For more information of NO pathologic effects and how NO induced post translational modifications can act as a cellular signal see the following:

Nitric Oxide Covalent Modifications: A Putative Therapeutic Target?

58. Crucial role of Nitric Oxide in Cancer

Curator and Author: Ritu Saxena, Ph.D.

https://pharmaceuticalintelligence.com/2012/10/16/crucial-role-of-nitric-oxide-in-cancer/

Note:  A more comprehensive ebook on Nitric Oxide and Disease Perspectives is found at

Cardiovascular Diseases, Volume One: Perspectives on Nitric Oxide in Disease Mechanisms

available on Kindle Store @ Amazon.com

http://www.amazon.com/dp/B00DINFFYC

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