Nitrite augments tolerance to ischemia/reperfusion injury via the modulation of mitochondrial electron transfer

Nitrite (NO2−) is an intrinsic signaling molecule that is reduced to NO during ischemia and limits apoptosis and cytotoxicity at reperfusion in the mammalian heart, liver, and brain. Although the mechanism of nitrite-mediated cytoprotection is unknown, NO is a mediator of the ischemic preconditioning cell-survival program. Analogous to the temporally distinct acute and delayed ischemic preconditioning cytoprotective phenotypes, we report that both acute and delayed (24 h before ischemia) exposure to physiological concentrations of nitrite, given both systemically or orally, potently limits cardiac and hepatic reperfusion injury. This cytoprotection is associated with increases in mitochondrial oxidative phosphorylation. Remarkably, isolated mitochondria subjected to 30 min of anoxia followed by reoxygenation were directly protected by nitrite administered both in vitro during anoxia or in vivo 24 h before mitochondrial isolation. Mechanistically, nitrite dose-dependently modifies and inhibits complex I by posttranslational S-nitrosation; this dampens electron transfer and effectively reduces reperfusion reactive oxygen species generation and ameliorates oxidative inactivation of complexes II–IV and aconitase, thus preventing mitochondrial permeability transition pore opening and cytochrome c release. These data suggest that nitrite dynamically modulates mitochondrial resilience to reperfusion injury and may represent an effector of the cell-survival program of ischemic preconditioning and the Mediterranean diet

A Unifying Mechanism for Mitochondrial Superoxide Production during Ischemia-Reperfusion Injury.

Ischemia-reperfusion (IR) injury occurs when blood supply to an organ is disrupted--ischemia--and then restored--reperfusion--leading to a burst of reactive oxygen species (ROS) from mitochondria. It has been tacitly assumed that ROS production during IR is a non-specific consequence of oxygen interacting with dysfunctional mitochondria upon reperfusion. Recently, this view has changed, suggesting that ROS production during IR occurs by a defined mechanism. Here we survey the metabolic factors underlying IR injury and propose a unifying mechanism for its causes that makes sense of the huge amount of disparate data in this area and provides testable hypotheses and new directions for therapies.Work in our laboratories is supported by the Medical Research Council (UK) and the British Heart Foundation. E.T.C. is supported by a Human Frontiers Science Program fellowship.This is the author accepted manuscript. The final version is available from Cell Press via http://dx.doi.org/10.1016/j.cmet.2015.12.00

Identification of Mitochondrial S-nitrosothiols and Determination of the Protective Effect of Mitochondrial S-nitrosation in Cardiac Ischemia Reperfusion Injury

Thesis (Ph.D.)--University of Rochester. School of Medicine and Dentistry. Dept. of Biochemistry and Biophysics, 2008.Mitochondrial dysfunction is a pathological hallmark of cardiac ischemia reperfusion (IR) injury. Mitochondrial pathology contributes to the oxidative damage and death of cardiac tissue subjected to a prolonged ischemic insult. Preservation of mitochondria, resulting in attenuation of mitochondrial reactive oxygen species (ROS) generation and inhibition of mitochondria dependent cell death cascades, has proven to be an effective cardioprotective strategy against IR injury. Mitochondria are preserved in the endogenous cardioprotective pathways initiated by ischemic preconditioning (IPC), where the myocardium is exposed to brief periods of ischemia prior to a long-term ischemic insult. Mitochondria are also preserved in the exogenous cardioprotective pathways elicited by pharmacological preconditioning (PPC). Nitric oxide (NO•) is one molecule that is important in both IPC and PPC, and to date most of the cardioprotective effects of NO• have been attributed to the activation of soluble guanylate cyclase signaling. However, it is apparent that NO• can also regulate biological systems independent of this signaling mechanism, via post-translational protein modifications, such as S-nitrosation. Work herein has centered on addressing the hypothesis that mitochondrial proteins are S-nitrosated under cardioprotective conditions, and that S-nitrosation regulates mitochondria to protect the heart during IR injury. Chemiluminescence and biotin switch methods were developed to monitor mitochondrial S-nitrosation. Perfused hearts, isolated cardiomyocytes and isolated mitochondria were used to model IR injury. Mitochondrial function was monitored using respirometry, isolated enzyme activities, ROS assays, Ca2+ handling and membrane potential measurements. It was found that mitochondrial proteins, including respiratory complex I (NADH dehydrogenase), were S-nitrosated under cardioprotective conditions. Enhancing mitochondrial protein S-nitrosation was found to elicit cardioprotection in IR injury and preserve mitochondrial function. Mitochondrial protein S-nitrosation was found to attenuate mitochondrial ROS overproduction and excessive Ca2+ uptake, which are pathological hallmarks of ischemic injury at the mitochondrial level. In addition, the mechanisms linking S-nitrosation of mitochondrial proteins to the prevention of these pathologic events were investigated. In conclusion, it was determined mitochondrial proteins are S-nitrosated under cardioprotective conditions and S-nitrosation attenuates two key mitochondrial events (ROS generation and Ca2+ accumulation) known to trigger heart dysfunction in IR injury

Effect of long-term vitamin E and selenium supplementation on urine F2-isoprostanes, a biomarker of oxidative stress

BackgroundCigarette smoking generates reactive oxidant species and contributes to systemic oxidative stress, which plays a role in the pathophysiology of chronic diseases. Nutrients with antioxidant properties, including vitamin E and selenium, are proposed to reduce systemic oxidative burden and thus to mitigate the negative health effects of reactive oxidant species.ObjectiveOur objective was to determine whether long-term supplementation with vitamin E and/or selenium reduces oxidative stress in smokers, as measured by urine 8-iso-prostaglandin F2-alpha (8-iso-PGF2α).DesignWe measured urine 8-iso-PGF2α with competitive enzyme linked immunoassay (ELISA) in 312 male current smokers after 36 months of intervention in a randomized placebo-controlled trial of vitamin E (400IU/d all rac-α-tocopheryl acetate) and/or selenium (200µg/d L-selenomethionine). We used linear regression to estimate the effect of intervention on urine 8-iso-PGF2α, with adjustments for age and race.ResultsCompared to placebo, vitamin E alone lowered urine 8-iso-PGF2α by 21% (p=0.02); there was no effect of combined vitamin E and selenium (intervention arm lower by 9%; p=0.37) or selenium alone (intervention arm higher by 8%; p=0.52).ConclusionsLong-term vitamin E supplementation decreases urine 8-iso-PGF2α among male cigarette smokers, but we observed little to no evidence for an effect of selenium supplementation, alone or combined with vitamin E

Erythritol is a pentose-phosphate pathway metabolite and associated with adiposity gain in young adults.

Metabolomic markers associated with incident central adiposity gain were investigated in young adults. In a 9-mo prospective study of university freshmen (n = 264). Blood samples and anthropometry measurements were collected in the first 3 d on campus and at the end of the year. Plasma from individuals was pooled by phenotype [incident central adiposity, stable adiposity, baseline hemoglobin A1c (HbA1c) > 5.05%, HbA1c 5.05% had 21-fold (95% CI: 19.84, 21.41) higher blood erythritol compared with participants with lower HbA1c (P < 0.001, FDR = 0.00016). Erythritol was shown to be synthesized endogenously from glucose via the pentose-phosphate pathway (PPP) in stable isotope-assisted ex vivo blood incubation experiments and through in vivo conversion of erythritol to erythronate in stable isotope-assisted dried blood spot experiments. Therefore, endogenous production of erythritol from glucose may contribute to the association between erythritol and obesity observed in young adults