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...

Long recognized as a malodorous and highly toxic gas, recent experimental studies have revealed that hydrogen sulfide (H2S) is produced enzymatically in all mammalian species including man and exerts a number of critical actions to promote cardiovascular homeostasis and health. During the past 15 years, scientists have determined that H2S is produced by three endogenous enzymes and exerts powerful effects on endothelial cells, smooth muscle cells, inflammatory cells, mitochondria, endoplasmic reticulum, and nuclear transcription factors. These effects have been reported in multiple organ systems and the vast majority of data clearly indicate that H2S produced by the endogenous enzymes exerts cytoprotective actions. Recent preclinical studies investigating cardiovascular diseases have demonstrated that the administration of physiological or pharmacological levels of H2S attenuates myocardial injury, protects blood vessels, limits inflammation, and regulates blood pressure. H2S has emerged as a critical cardiovascular signaling molecule similar to nitric oxide (NO) and carbon monoxide (CO) with a profound impact on the heart and circulation (Figure 1). Our improved understanding of how H2S elicits protective actions, coupled with the very rapid development of novel H2S releasing agents, has resulted in heightened enthusiasm for the clinical translation of this ephemeral gaseous molecule. This review will examine our current state of knowledge regarding the actions of H2S within the cardiovascular system with an emphasis on the therapeutic potential and molecular crosstalk between H2S, NO, and CO.

Background Trimethylamine N-oxide (TMAO), a gut microbe dependent metabolite of dietary choline and other trimethylamine containing nutrients, is both elevated in the circulation of patients suffering from heart failure (HF) and heralds worse overall prognosis. In animal studies, dietary choline or TMAO significantly accelerate atherosclerotic lesion development in ApoE deficient mice, and reduction in TMAO levels inhibits atherosclerosis development in the LDL receptor knockout mouse. Methods and Results C57BL6/J mice were fed either a control diet, a diet containing choline (1.2%) or a diet containing TMAO (0.12%) starting 3 weeks prior to surgical TAC. Mice were studied for 12 weeks following TAC. Cardiac function and left ventricular structure were monitored at 3-week intervals using echocardiography. Twelve weeks post-TAC myocardial tissues were collected to evaluate cardiac and vascular fibrosis, and blood samples were evaluated for cardiac BNP, choline, and TMAO levels. Pulmonary edema, cardiac enlargement, and left ventricular ejection fraction (LVEF) were significantly (p < 0.05, each) worse in mice fed either TMAO or choline supplemented diets compared to the control diet. In addition, myocardial fibrosis was also significantly greater (p < 0.01, each) in the TMAO and choline groups relative to controls. Conclusions Heart failure severity is significantly enhanced in mice fed diets supplemented in either choline or the gut microbe-dependent metabolite TMAO. The present results suggest that further studies are warranted examining whether gut microbiota and the dietary choline -> TMAO pathway contribute to increased heart failure susceptibility.

Background Hydrogen sulfide (H2S) has been shown to induce angiogenesis in in vitro models and to promote vessel growth in the setting of hind-limb ischemia. The goal of the present study was to determine the therapeutic potential of a stable, long-acting H2S donor, diallyl trisulfide (DATS), in a model of pressure-overload heart failure and to assess the effects of chronic H2S therapy on myocardial vascular density and angiogenesis. Methods and Results Transverse aortic constriction (TAC) was performed in mice (C57BL/6J, 8-10 weeks of age). Mice received either vehicle or DATS (200 μg/kg) starting 24 hours after TAC and were followed for 12 weeks using echocardiography. H2S therapy with DATS improved left ventricular remodeling and preserved LV function in the setting of TAC. H2S therapy also increased the expression of the pro-angiogenic factor, vascular endothelial cell growth factor, while decreasing the angiogenesis inhibitor, angiostatin. Further studies revealed that H2S therapy increased the expression of the proliferation marker, Ki67, as well as increased the phosphorylation of endothelial nitric oxide synthase and increased the bioavailability of nitric oxide. Importantly, these changes were associated with an increase in vascular density within the H2S-treated hearts. Conclusions These results suggest that H2S therapy attenuates LV remodeling and dysfunction in the setting of heart failure by creating a pro-angiogenic environment for the growth of new vessels.

SummaryRecent studies demonstrate robust molecular cross talk and signaling between hydrogen sulfide (H2S) and nitric oxide (NO). Heart failure (HF) patients are deficient in both H2S and NO, two molecules that are critical for cardiovascular homeostasis. A phase I clinical trial of a novel H2S prodrug (SG1002) was designed to assess safety and changes in H2S and NO bioavailability in healthy and HF subjects. Healthy subjects (n = 7) and heart failure patients (n = 8) received oral SG1002 treatment in escalating dosages of 200, 400, and 800 mg twice daily for 7 days for each dose. Safety and tolerability were assessed by physical examination, vital signs, and ECG analysis. Plasma samples were collected during a 24‐h period each week for H2S and NO analysis. BNP and glutathione levels were analyzed as markers of cardiac health and redox status. Administration of SG1002 resulted in increased H2S levels in healthy subjects. We also observed increased H2S levels in HF subjects following 400 mg SG1002. Nitrite, a metabolite of NO, was increased in both healthy and HF patients receiving 400 mg and 800 mg SG1002. HF subjects treated with SG1002 displayed stable drug levels over the course of the trial. SG1002 was safe and well tolerated at all doses in both healthy and HF subjects. These data suggest that SG1002 increases blood H2S levels and circulating NO bioavailability. The finding that SG1002 attenuates increases in BNP in HF patients suggests that this novel agent warrants further study in a larger clinical study.

Hydrogen sulfide (H 2 S)—a potent gaseous signaling molecule—has emerged as a critical regulator of cardiovascular homeostasis. H 2 S is produced enzymatically by 3 constitutively active endogenous enzymes in all mammalian species. Within the past 2 decades, studies administering H 2 S-donating agents and the genetic manipulation of H 2 S-producing enzymes have revealed multiple beneficial effects of H 2 S, including vasodilation, activation of antiapoptotic and antioxidant pathways, and anti-inflammatory effects. More recently, the heightened enthusiasm in this field has shifted to the development of novel H 2 S-donating agents that exert favorable pharmacological profiles. This has led to the discovery of novel H 2 S-mediated signaling pathways. This review will discuss recently developed H 2 S therapeutics, introduce signaling pathways that are influenced by H 2 S-dependent sulfhydration, and explore the dual-protective effect of H 2 S in cardiorenal syndrome.

Background Bone marrow cell-based treatment for critical limb ischemia (CLI) in diabetic patients yielded a modest therapeutic effect due to cell dysfunction. Therefore, approaches that improve diabetic stem/progenitor cell functions may provide therapeutic benefits. Here, we tested the hypotheses that restoration of hydrogen sulfide (H2S) production in diabetic bone marrow cells (BMCs) improves their reparative capacities. Methods Mouse BMCs were isolated by density-gradient centrifugation. Unilateral hind limb ischemia (HLI) was conducted in 12- to 14-week old db/+ and db/db mice by ligation of left femoral artery. H2S level was measured by either gas chromatography or staining with florescent dye sulfidefluor 7AM. Results Both H2S production and cystathionine γ-lyase (CSE), an H2S enzyme, levels were significantly decreased in BMCs from diabetic db/db mice. Administration of H2S donor diallyl trisulfide (DATS) or overexpression of CSE restored H2S production and enhanced cell survival and migratory capacity in high glucose (HG)-treated BMCs. Immediately after HLI surgery, the db/+ and db/db mice were administrated with DATS orally and/or local intramuscular injection of GFP-labeled BMCs or RFP-CSE-overexpressing BMCs (CSE-BMCs). Mice with HLI were divided into six groups: 1) db/+; 2) db/db; 3) db/db+BMCs; 4) db/db+DATS; 5) db/db+DATS+BMCs; 6) db/db+CSE-BMCs. DATS and CSE overexpression greatly enhanced diabetic BMCs retention in ischemic hind limbs (IHL) followed by improved blood perfusion, capillary/arteriole density, skeletal muscle architecture and cell survival, and decreased perivascular CD68+ cell infiltration in IHL of diabetic mice. Interestingly, DATS or CSE overexpression rescued HG-impaired migration, tube formation and survival of BMCs or mature human cardiac microvascular endothelial cells (HCMVECs). Mechanistically, DATS restored nitric oxide production and decreased eNOS-pT495 levels in HCMVECs, and improved BMC angiogenic activity under HG condition. Finally, silencing CSE by siRNA significantly increased eNOS-pT495 levels in HCMVECs. Conclusions Decreased CSE-mediated H2S bioavailability is an underlying source of BMC dysfunction in diabetes. Our data indicate that H2S and overexpression of CSE in diabetic BMCs may rescue their dysfunction and open novel avenues for cell-based therapeutics of CLI in diabetic patients.

It has now become universally accepted that hydrogen sulfide (H2S), previously considered only as a lethal toxin, has robust cytoprotective actions in multiple organ systems. The diverse signaling profile of H2S impacts multiple pathways to exert cytoprotective actions in a number of pathological states. This paper will review the recently described cardioprotective actions of hydrogen sulfide in both myocardial ischemia/reperfusion injury and congestive heart failure.