The dose makes the poison: Hydrogen sulfide is an important gasotransmitter for which rapid detection agents are needed. A hydrogen sulfide probe, which allows for fast (within seconds), selective, and quantitative detection in buffer solution, serum, and whole blood is designed, synthesized, and used for detection of hydrogen sulfide (see picture).

Previous studies have demonstrated that hydrogen sulfide (H 2 S) protects against multiple cardiovascular disease states in a similar manner as nitric oxide (NO). H 2 S therapy also has been shown to augment NO bioavailability and signaling. The purpose of this study was to investigate the impact of H 2 S deficiency on endothelial NO synthase (eNOS) function, NO production, and ischemia/reperfusion (I/R) injury. We found that mice lacking the H 2 S-producing enzyme cystathionine γ-lyase (CSE) exhibit elevated oxidative stress, dysfunctional eNOS, diminished NO levels, and exacerbated myocardial and hepatic I/R injury. In CSE KO mice, acute H 2 S therapy restored eNOS function and NO bioavailability and attenuated I/R injury. In addition, we found that H 2 S therapy fails to protect against I/R in eNOS phosphomutant mice (S1179A). Our results suggest that H 2 S-mediated cytoprotective signaling in the setting of I/R injury is dependent in large part on eNOS activation and NO generation.eNOS uncoupling | myocardial infarction | cystathionase | Cth | nitrite H ydrogen sulfide (H 2 S), historically known for its odorous smell and toxicity at high concentrations, has recently been classified as a physiological signaling molecule with robust cytoprotective actions in multiple organ systems (1-3). H 2 S is produced enzymatically in mammalian tissues by three different enzymes: cystathionine γ-lyase (CSE), cystathionine beta-synthase (CBS), and 3-mercatopyruvate sulfurtransferase (3-MST). CSE, involved in the cysteine biosynthesis pathway, coordinates with L-cystine to produce H 2 S within the vasculature and is known to regulate blood pressure, modulate cellular metabolism, promote angiogenesis, regulate ion channels, and mitigate fibrosis and inflammation (4). Endothelial nitric oxide synthase (eNOS) catalyzes the production of nitric oxide (NO) from L-arginine within the endothelium to regulate vascular tone via cGMP signaling in vascular smooth muscle, mitochondrial respiration, platelet function, inflammation, and angiogenesis. The biological profiles of H 2 S and NO are similar, and both molecules are known to protect cells against various injurious states that result in organ injury. Although H 2 S and NO are thought to modulate independent signaling pathways, there is limited evidence of cross-talk between these two molecules (5, 6).H 2 S therapeutics and endogenous overexpression of CSE have been shown to attenuate ischemia/reperfusion (I/R) injury (7,8). Similarly, NO therapy and eNOS gene overexpression are also protective in ischemic disease states (9). Given the potent antioxidant actions of H 2 S (10, 11) and the effects of exogenous H 2 S therapy on NO bioavailability (5, 8), we investigated the effects of genetic deletion of the cystathionase gene (Cth, i.e., CSE KO) on the regulation of eNOS function and NO bioavailability. ResultsSulfide Levels are Reduced in CSE KO Mice. Whole blood and heart specimens were collected from WT and CSE KO mice to measure H 2 S levels using a high-sensitivity gas chromato...

Introduction Cystathionine gamma-lyase (CSE) produces H2S via enzymatic conversion of L-cysteine and plays a critical role in cardiovascular homeostasis. We investigated the effects of genetic modulation of CSE and exogenous H2S therapy in the setting of pressure overload-induced heart failure. Methods and Results Transverse aortic constriction (TAC) was performed in wild-type (WT), CSE knockout (KO), and cardiac specific CSE transgenic (CS-CSE Tg) mice. In addition, C57BL/6J or CSE KO mice received a novel–H2S donor (SG-1002). Mice were followed for 12 weeks using echocardiography. We observed a >60% reduction in myocardial and circulating H2S levels following TAC. CSE KO mice exhibited cardiac dilatation and dysfunction significantly greater than WT mice following TAC and CS-CSE Tg mice maintained cardiac structure and function following TAC. H2S therapy with SG-1002 resulted in cardioprotection during TAC via upregulation of the VEGF-Akt-eNOS-nitric oxide-cGMP pathway with preserved mitochondrial function, attenuated oxidative stress, and increased myocardial vascular density. Conclusions Our results demonstrate that H2S levels are decreased in mice in the setting of heart failure. Moreover, CSE plays a critical role in the preservation of cardiac function in heart failure and oral H2S therapy prevents the transition from compensated to decompensated heart failure in part via upregulation of endothelial nitric oxide synthase (eNOS) and increased NO bioavailability.

Fatty liver disease associated with chronic alcohol consumption or obesity/type 2 diabetes has emerged as a serious public health problem. Steatosis, accumulation of triglyceride in hepatocytes, is now recognized as a critical "first-hit" in the pathogenesis of liver disease. It is proposed that steatosis "primes" the liver to progress to more severe liver pathologies when individuals are exposed to subsequent metabolic and/or environmental stressors or "second-hits". Genetic risk factors can also influence the susceptibility and severity of fatty liver disease. Furthermore, oxidative stress, disrupted nitric oxide (NO) signaling, and mitochondrial dysfunctional are proposed to be key molecular events that accelerate or worsen steatosis and initiate progression to steatohepatitis and fibrosis. This review article will discuss the following topics regarding the pathobiology and molecular mechanisms responsible for fatty liver disease: 1) the "two-hit" or "multi-hit" hypothesis; 2) the role of mitochondrial bioenergetic defects and oxidant stress; 3) interplay between NO and mitochondria in fatty liver disease; 4) genetic risk factors and oxidative stress responsive genes; and 5) the feasibility of antioxidants for treatment.

NAFLD (non-alcoholic fatty liver disease), associated with obesity and the cardiometabolic syndrome, is an important medical problem affecting up to 20% of western populations. Evidence indicates that mitochondrial dysfunction plays a critical role in NAFLD initiation and progression to the more serious condition of NASH (non-alcoholic steatohepatitis). Herein we hypothesize that mitochondrial defects induced by exposure to a HFD (high fat diet) contribute to a hypoxic state in liver and this is associated with increased protein modification by RNS (reactive nitrogen species). To test this concept, C57BL/6 mice were pair-fed a control diet and HFD containing 35% and 71% total calories (1 cal≈4.184 J) from fat respectively, for 8 or 16 weeks and liver hypoxia, mitochondrial bioenergetics, NO (nitric oxide)-dependent control of respiration, and 3-NT (3-nitrotyrosine), a marker of protein modification by RNS, were examined. Feeding a HFD for 16 weeks induced NASH-like pathology accompanied by elevated triacylglycerols, increased CYP2E1 (cytochrome P450 2E1) and iNOS (inducible nitric oxide synthase) protein, and significantly enhanced hypoxia in the pericentral region of the liver. Mitochondria from the HFD group showed increased sensitivity to NO-dependent inhibition of respiration compared with controls. In addition, accumulation of 3-NT paralleled the hypoxia gradient in vivo and 3-NT levels were increased in mitochondrial proteins. Liver mitochondria from mice fed the HFD for 16 weeks exhibited depressed state 3 respiration, uncoupled respiration, cytochrome c oxidase activity, and mitochondrial membrane potential. These findings indicate that chronic exposure to a HFD negatively affects the bioenergetics of liver mitochondria and this probably contributes to hypoxic stress and deleterious NO-dependent modification of mitochondrial proteins.