The Fas antigen (CD95, APO-1) is a transmembrane cell surface receptor that mediates apoptosis of many cell types when bound by Fas ligand or cross-linked by agonist antibody. The cellular factors regulating Fas-induced apoptosis have not been well defined. Here we show that basal nitric-oxide synthase (NOS) activity in human leukocytes inhibits Fas-induced apoptosis via a cGMP-independent mechanism. Further, NOS inhibits Fas-induced cleavage of poly(ADP-ribose) polymerase by members of the caspase family of cysteine proteases. These data suggest that Fas activity is under the control of the NO signaling pathway. NOS regulating the function of this member of the tumor necrosis factor receptor family suggests a new role for nitric oxide (or related molecules) in the human immune response.
Abstract mTOR inhibition extends lifespan and ameliorates aging-related pathologies including declining immune function in model organisms. The objective of this Phase 2a clinical trial was to determine if low dose mTOR inhibitor therapy enhanced immune function and thereby decreased infection rates in elderly subjects. The results indicate that 6 weeks of treatment with a low dose combination of a catalytic (BEZ235) plus an allosteric (RAD001) mTOR inhibitor (that selectively inhibits TORC1 downstream of mTOR) was safe, significantly decreased the rate of infections reported by elderly subjects for a year following study drug initiation, upregulated antiviral gene expression, and significantly improved influenza vaccination response. Thus selective TORC1 inhibition with a combination of BEZ235 and RAD001 may be efficacious as immunotherapy to reduce infections, a leading cause of death in the elderly. One Sentence Summary Treatment of elderly subjects with a low dose mTOR inhibitor regimen that selectively inhibits TORC1 significantly decreased infection rates
Using a modified Delphi process, we engaged 28 experts in clinical trials, geriatrics, and research translation to determine if there were consensus around what clinical endpoints should be used for trials evaluating the efficacy of interventions to prevent or treat multiple age-related conditions. Four focus groups developed themes. Statements related to those themes were circulated back to participants in a survey. There was consensus (more than 66% agreed or disagreed) that outcome measures should include multiple health dimensions including-age-related disease, function and patient reported outcomes that reflect participants goals; and be tailored to population characteristics. Experts felt that blood-based biomarkers would be unlikely to be accepted as primary endpoints of efficacy trials. Plausible components mentioned as part of a composite endpoint included mortality, mobility function and the onset of multiple age-related diseases. Our findings provide guidance on acceptable approaches to endpoint selection guiding the design of future geroscience trials.
Abstract S‐nitrosylation is the binding of an NO group to a cysteine or other thiol. Like phosphorylation, S‐nitrosylation is a precisely targeted and rapidly reversible post‐translational modification that serves as an on/off switch for protein function during cell signaling. However, unlike phosphorylation, S‐nitrosylation of proteins occurs nonenzymatically, mediated, at least in part, by redox‐regulated chemical reactions in cells. Alterations in pH, pO 2 , cellular reductants, transition metals, and UV light lead to the loss and/or gain of S‐NO bonds. Due to the redox‐sensitive nature of the modification, analysis of protein S‐nitrosylation is technically difficult, the S‐NO bond formation being easily disrupted during sample preparation. In addition, the level of S‐nitrosylated proteins in cells approaches the limit of detection of currently available technology. Despite these technical challenges, several useful methods have been developed recently to measure protein S‐nitrosylation in biologic samples, and these are described in this unit.
Protein nitrosylation is emerging as a key mechanism by which nitric oxide regulates cell signaling. Nitrosylation is the binding of a NO group to a metal or thiol (-SH) on a peptide or protein. Like phosphorylation, nitrosylation is a precisely targeted and rapidly reversible posttranslational modification that allows cells to flexibly and specifically respond to changes in their environment. An increasing number of proteins have been identified whose activity is regulated by intracellular nitrosylation. This review focuses on proteins regulated by endogenous nitrosylation, the chemistry underlying nitrosylation, the specificity and reversibility of nitrosylation reactions, methods to detect protein nitrosylation, and the role of coordinated protein nitrosylation/denitrosylation in cell signaling.
Caspase-3 is a cysteine protease located in both the cytoplasm and mitochondrial intermembrane space that is a central effector of many apoptotic pathways. In resting cells, a subset of caspase-3 zymogens is S-nitrosylated at the active site cysteine, inhibiting enzyme activity. During Fas-induced apoptosis, caspases are denitrosylated, allowing the catalytic site to function. In the current studies, we sought to identify the subpopulation of caspases that is regulated by S-nitrosylation. We report that the majority of mitochondrial, but not cytoplasmic, caspase-3 zymogens contain this inhibitory modification. In addition, the majority of mitochondrial caspase-9 is S-nitrosylated. These studies suggest that S-nitrosylation plays an important role in regulating mitochondrial caspase function and that the S-nitrosylation state of a given protein depends on its subcellular localization.
Abstract For many years, it was believed that the aging process was inevitable and that age‐related diseases could not be prevented or reversed. The geroscience hypothesis, however, posits that aging is, in fact, malleable and, by targeting the hallmarks of biological aging, it is indeed possible to alleviate age‐related diseases and dysfunction and extend longevity. This field of geroscience thus aims to prevent the development of multiple disorders with age, thereby extending healthspan, with the reduction of morbidity toward the end of life. Experts in the field have made remarkable advancements in understanding the mechanisms underlying biological aging and identified ways to target aging pathways using both novel agents and repurposed therapies. While geroscience researchers currently face significant barriers in bringing therapies through clinical development, proof‐of‐concept studies, as well as early‐stage clinical trials, are underway to assess the feasibility of drug evaluation and lay a regulatory foundation for future FDA approvals in the future.
