Diet and Hydrogen Sulfide Production in Mammals.

Significance: In recent times, it has emerged that some dietary sulfur compounds can act on mammalian cell signaling systems via their propensity to release hydrogen sulfide (H2S). H2S plays important biochemical and physiological roles in the heart, gastrointestinal tract, brain, kidney, and immune systems of mammals. Reduced levels of H2S in cells and tissues correlate with a spectrum of pathophysiological conditions, including heart disease, diabetes, obesity, and altered immune function. Recent Advances: In the last decade, researchers have now begun to explore the mechanisms by which dietary-derived sulfur compounds, in addition to cysteine, can act as sources of H2S. This research has led to the identified several compounds, organic sulfides, isothiocyanates, and inorganic sulfur species including sulfate that can act as potential sources of H2S in mammalian cells and tissues. Critical Issues: We have summarised progress made in the identification of dietary factors that can impact on endogenous H2S levels in mammals. We also describe current research focused on how some sulfur molecules present in dietary plants, and associated chemical analogues, act as sources of H2S, and discuss the biological properties of these molecules as studied in a range of in vitro and in vivo systems. Future Directions: The identification of sulfur compounds in edible plants that can act as novel H2S releasing molecules is intriguing. Research in this area could inform future studies exploring the impact of diet on H2S levels in mammalian systems. Despite recent progress, additional work is needed to determine the mechanisms by which H2S is released from these molecules following ingestions of dietary plants in humans, whether the amounts of H2S produced is of physiological significance following the metabolism of these compounds in vivo, and if diet could be used to manipulated H2S levels in humans. Importantly, this will lead to a better understanding of the biological significance of H2S generated from dietary sources, and this information could be used in the development of plant breeding initiatives to increase the levels of H2S releasing sulfur compounds in crops, or inform dietary intervention strategies that could be used to alter the levels of H2S in humans.

Lifespan and healthspan benefits of exogenous H2S in C. elegans are independent from effects downstream of eat-2 mutation.

Caloric restriction (CR) is one of the most effective interventions to prolong lifespan and promote health. Recently, it has been suggested that hydrogen sulfide (H2S) may play a pivotal role in mediating some of these CR-associated benefits. While toxic at high concentrations, H2S at lower concentrations can be biologically advantageous. H2S levels can be artificially elevated via H2S-releasing donor drugs. In this study, we explored the function of a novel, slow-releasing H2S donor drug (FW1256) and used it as a tool to investigate H2S in the context of CR and as a potential CR mimetic. We show that exposure to FW1256 extends lifespan and promotes health in Caenorhabditis elegans (C. elegans) more robustly than some previous H2S-releasing compounds, including GYY4137. We looked at the extent to which FW1256 reproduces CR-associated physiological effects in normal-feeding C. elegans. We found that FW1256 promoted healthy longevity to a similar degree as CR but with fewer fitness costs. In contrast to CR, FW1256 actually enhanced overall reproductive capacity and did not reduce adult body length. FW1256 further extended the lifespan of already long-lived eat-2 mutants without further detriments in developmental timing or fertility, but these lifespan and healthspan benefits required H2S exposure to begin early in development. Taken together, these observations suggest that FW1256 delivers exogenous H2S efficiently and supports a role for H2S in mediating longevity benefits of CR. Delivery of H2S via FW1256, however, does not mimic CR perfectly, suggesting that the role of H2S in CR-associated longevity is likely more complex than previously described.

An Appraisal of Developments in Allium Sulfur Chemistry: Expanding the Pharmacopeia of Garlic.

Alliums and allied plant species are rich sources of sulfur compounds that have effects on vascular homeostasis and the control of metabolic systems linked to nutrient metabolism in mammals. In view of the multiple biological effects ascribed to these sulfur molecules, researchers are now using these compounds as inspiration for the synthesis and development of novel sulfur-based therapeutics. This research has led to the chemical synthesis and biological assessment of a diverse array of sulfur compounds representative of derivatives of S-alkenyl-l-cysteine sulfoxides, thiosulfinates, ajoene molecules, sulfides, and S-allylcysteine. Many of these synthetic derivatives have potent antimicrobial and anticancer properties when tested in preclinical models of disease. Therefore, the current review provides an overview of advances in the development and biological assessment of synthetic analogs of allium-derived sulfur compounds.

Garlic and Gaseous Mediators.

Garlic (Allium sativum) and allied plant species are rich sources of sulfur compounds. Major roles for garlic and its sulfur constituents include the regulation of vascular homeostasis and the control of metabolic systems linked to nutrient metabolism. Recent studies have indicated that some of these sulfur compounds, such as diallyl trisulfide (DATS), alter the levels of gaseous signalling molecules including nitric oxide (NO), hydrogen sulfide (H2S), and perhaps carbon monoxide (CO) in mammalian tissues. These gases are important in cellular processes associated with the cardiovascular system, inflammation, and neurological functions. Importantly, these studies build on the known biological effects of garlic and associated sulfur constituents. This review highlights our current understanding of the health benefits attributed to edible plants like garlic.

Is there a role of H2S in mediating health span benefits of caloric restriction?

Caloric restriction (CR) is a dietary regimen that aims to reduce the intake of total calories while maintaining adequate supply of key nutrients so as to avoid malnutrition. CR is one of only a small number of interventions that show promising outcomes on health span and lifespan across different species. There is growing interest in the development of compounds that might replicate CR-related benefits without actually restricting food intake. Hydrogen sulfide (H2S) is produced inside the bodies of many animals, including humans, by evolutionarily conserved H2S synthesizing enzymes. Endogenous H2S is increasingly recognized as an important gaseous signalling molecule involved in diverse cellular and molecular processes. However, the specific role of H2S in diverse biological processes remains to be elucidated and not all its biological effects are beneficial. Nonetheless, recent evidence suggests that the biological functions of H2S intersect with the network of evolutionarily conserved nutrient sensing and stress response pathways that govern organismal responses to CR. Induction of H2S synthesizing enzymes appears to be a conserved and essential feature of the CR response in evolutionarily distant organisms, including nematodes and mice. Here we review the evidence for a role of H2S in CR and lifespan modulation. H2S releasing drugs, capable of controlled delivery of exogenous H2S, are currently in clinical development. These findings suggest such H2S releasing drugs as a promising novel avenue for the development of CR mimetic compounds.

A novel slow-releasing hydrogen sulfide donor, FW1256, exerts anti-inflammatory effects in mouse macrophages and in vivo.

Exogenous hydrogen sulfide (H2S) is known to exert anti-inflammatory effects both in macrophages and in animal models. In this study, we first showed that NaHS caused a concentration dependent reduction in TNFα and IL-6 secretion in LPS-stimulated RAW264.7 macrophages in the absence of cell death. Thereafter, we screened a series of novel slow H2S donors for similar activity. One such compound, FW1256, concentration dependently decreased TNFα, IL-6, PGE2 and NO generation in LPS-stimulated RAW264.7 macrophages and BMDMs. FW1256 also significantly reduced IL-1ß, COX-2 and iNOS mRNA and protein in LPS-stimulated RAW264.7 macrophages. Mechanistically, FW1256 decreased NFκB activation as evidenced by reduced cytosolic phospho-IκBα levels and reduced nuclear p65 levels in LPS-stimulated RAW264.7 macrophages treated with FW1256. Using a H2S fluorescent probe in FW1256-treated RAW264.7 macrophages, H2S release from FW1256 was apparent over a period of 24h in these cells. Moreover, the effect of FW1256 on TNFα and IL-6 by FW1256 in LPS-stimulated RAW264.7 macrophages was reversed by treatment with the H2S scavenger, vitamin B12a. FW1256 had no cytotoxic effect on LPS-stimulated RAW264.7 macrophages or BMDMs. In vivo, FW1256 administration also reduced IL-1ß, TNFα, nitrate/nitrite and PGE2 levels in LPS-treated mice. We show here a novel slow H2S-releasing compound that exerts anti-inflammatory effects in macrophages and in vivo. FW1256 may be a useful tool to study the biological effects of exogenous H2S and could also have future therapeutic value in inflammatory conditions.

Energy crisis precedes global metabolic failure in a novel Caenorhabditis elegans Alzheimer Disease model.

Alzheimer Disease (AD) is a progressive neurological disorder characterized by the deposition of amyloid beta (Aß), predominantly the Aß1-42 form, in the brain. Mitochondrial dysfunction and impaired energy metabolism are important components of AD pathogenesis. However, the causal and temporal relationships between them and AD pathology remain unclear. Using a novel C. elegans AD strain with constitutive neuronal Aß1-42 expression that displays neuromuscular defects and age-dependent behavioural dysfunction reminiscent of AD, we have shown that mitochondrial bioenergetic deficit is an early event in AD pathogenesis, preceding dysfunction of mitochondrial electron transfer chain (ETC) complexes and the onset of global metabolic failure. These results are consistent with an emerging view that AD may be a metabolic neurodegenerative disease, and also confirm that Aß-driven metabolic and mitochondrial effects can be reproduced in organisms separated by large evolutionary distances.

H2S Synthesizing Enzymes: Biochemistry and Molecular Aspects.

Hydrogen sulfide (H2S) is a biologically active gas that is synthesized naturally by three enzymes, cystathionine γ-lyase (CSE), cystathionine ß-synthetase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). These enzymes are constitutively present in a wide array of biological cells and tissues and their expression can be induced by a number of disease states. It is becoming increasingly clear that H2S is an important mediator of a wide range of cell functions in health and in disease. This review therefore provides an overview of the biochemical and molecular regulation of H2S synthesizing enzymes both in physiological conditions and their modulation in disease states with particular focus on their regulation in asthma, atherosclerosis and diabetes. The importance of small molecule inhibitors in the study of molecular pathways, the current use of common H2S synthesizing enzyme inhibitors and the relevant characteristics of mice in which these enzymes have been genetically deleted will also be summarized. With a greater understanding of the molecular regulation of these enzymes in disease states, as well as the availability of novel small molecules with high specificity targeted towards H2S producing enzymes, the potential to regulate the biological functions of this intriguing gas H2S for therapeutic effect can perhaps be brought one step closer.

Hydrogen sulfide promotes adipogenesis in 3T3L1 cells.

The effect of hydrogen sulfide (H2S) on differentiation of 3T3L1-derived adipocytes was examined. Endogenous H2S was increased after 3T3L1 differentiation. The expression of the H2S-synthesising enzymes, cystathionine γ-lyase (CSE), cystathionine ß-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST), was increased in a time-dependent manner during 3T3L1 differentiation. Expression of genes associated with adipogenesis related genes including fatty acid binding protein 4 (FABP4/aP2), a key regulator of this process, was increased by GYY4137 (a slow-releasing H2S donor compound) and sodium hydrosulfide (NaHS, a classical H2S donor) but not by ZYJ1122 or time-expired NaHS. Furthermore expression of these genes were reduced by aminooxyacetic acid (AOAA, CBS inhibitor), DL-propargylglycine (PAG, CSE inhibitor) as well as by CSE small interference RNA (siCSE) and siCBS. The size and number of lipid droplets in mature adipocytes was significantly increased by both GYY4137 and NaHS, which also impaired the ability of CL316,243 (ß3-agonist) to promote lipolysis in these cells. In contrast, AOAA and PAG had the opposite effect. Taken together, we show that the H2S-synthesising enzymes CBS, CSE and 3-MST are endogenously expressed during adipogenesis and that both endogenous and exogenous H2S modulate adipogenesis and adipocyte maturation.

The slow-releasing hydrogen sulfide donor, GYY4137, exhibits novel anti-cancer effects in vitro and in vivo.

The slow-releasing hydrogen sulfide (H2S) donor, GYY4137, caused concentration-dependent killing of seven different human cancer cell lines (HeLa, HCT-116, Hep G2, HL-60, MCF-7, MV4-11 and U2OS) but did not affect survival of normal human lung fibroblasts (IMR90, WI-38) as determined by trypan blue exclusion. Sodium hydrosulfide (NaHS) was less potent and not active in all cell lines. A structural analogue of GYY4137 (ZYJ1122) lacking sulfur and thence not able to release H2S was inactive. Similar results were obtained using a clonogenic assay. Incubation of GYY4137 (400 µM) in culture medium led to the generation of low (<20 µM) concentrations of H2S sustained over 7 days. In contrast, incubation of NaHS (400 µM) in the same way led to much higher (up to 400 µM) concentrations of H2S which persisted for only 1 hour. Mechanistic studies revealed that GYY4137 (400 µM) incubated for 5 days with MCF-7 but not IMR90 cells caused the generation of cleaved PARP and cleaved caspase 9, indicative of a pro-apoptotic effect. GYY4137 (but not ZYJ1122) also caused partial G2/M arrest of these cells. Mice xenograft studies using HL-60 and MV4-11 cells showed that GYY4137 (100-300 mg/kg/day for 14 days) significantly reduced tumor growth. We conclude that GYY4137 exhibits anti-cancer activity by releasing H2S over a period of days. We also propose that a combination of apoptosis and cell cycle arrest contributes to this effect and that H2S donors should be investigated further as potential anti-cancer agents.

Hydrogen sulfide: regulatory role on blood pressure in hyperhomocysteinemia.

Hyperhomocysteinemia (HHcy) is a metabolic disorder marked by an excess amount of the amino acid homocysteine (Hcy) in the blood stream. Hcy is a H(2)S precursor-formed from the metabolism of methionine. Elevated Hcy levels have been associated with higher blood pressure. However, the precise contribution of H(2)S to blood pressure in HHcy is not known. In the current study, we have examined a novel link between H(2)S, blood pressure and HHcy. Male Sprague-Dawley rats were injected with PAG, NaHS, L-NAME+PAG and saline. HHcy condition was induced by providing methionine (1 g/kg) in drinking water for 8 weeks. After 8 weeks, plasma Hcy and H(2)S were measured. The treated rats were anaesthetized with a mixture of ketamine hydrochloride and medetomidine. Blood pressures were measured by intra-carotid artery catheterization and to further investigate the immediate effect of NO and H(2)S, exogenous drugs namely NaHS, SNP, Ach and NA were administered. Plasma Hcy levels were higher in HHcy groups and this group exhibited hypertension. We observed high blood pressure at low levels of H(2)S and vice versa. Endogenous H(2)S in HHcy condition facilitated a mild decrease in MAP (Mean Arterial Pressure). Exogenous SNP (NO donor) showed a greater pressure decrease in HHcy group. The underlying mechanism is yet to be exploited. High levels of Hcy play an important role in the pathogenesis of hypertension. The results suggest that both endogenous and exogenous H(2)S may play a vital role in regulating blood pressure in HHcy.

Effect of S-diclofenac, a novel hydrogen sulfide releasing derivative inhibit rat vascular smooth muscle cell proliferation.

S-diclofenac (2-[(2,6-dichlorophenyl) amino] benzene acetic acid 4-(3H-1,2,dithiol-3-thione-5-yl) phenyl ester) is a novel molecule comprising a hydrogen sulfide (H2S)-releasing dithiol-thione moiety attached by an ester linkage to diclofenac. Effect of S-diclofenac (H2S donor) on cell proliferation was investigated on the primary and immortalized rat aortic vascular smooth muscle cells (SMC). Smooth muscle cell proliferation has been considered as a key event in vascular injury in diseases such as atherosclerosis and restenosis after invasive intervention. Clonogenic cell survival assay showed a dose dependent (10-100 microM) decrease in cell survival. Flow cytometric analysis showed that the asynchronized cells are more sensitive than the cells that are synchronized and revealed that the cells in G1 phase are not affected by the treatment of the S-diclofenac. Asynchronized smooth muscle cells treated with the S-diclofenac showed an increase in apoptotic cell death. S-diclofenac treatment also resulted in stabilization of p53 coupled with the induction of downstream proteins such as p21, p53AIP1 and Bax. S-diclofenac did not up-regulate cell levels of the antiapoptotic protein Bcl-2. However, when the cells are synchronized a stimulatory effect of cell growth with the decrease in apoptosis, p53 and p21 was evident. S-diclofenac inhibits smooth muscle cell growth and may play a role in the lesion formation at sites of the vascular injury. The present results suggest that S-diclofenac may be useful for the prevention of smooth muscle cell proliferation in diseases such as vascular obstructive and restenosis.

The novel proangiogenic effect of hydrogen sulfide is dependent on Akt phosphorylation.

OBJECTIVE: Hydrogen sulfide (H(2)S) has been reported to be a gasotransmitter which regulates cardiovascular homeostasis. The present study aims to examine the hypothesis that hydrogen sulfide is able to promote angiogenesis. METHODS: Angiogenesis was assessed using in vitro parameters (i.e. endothelial cell proliferation, adhesion, transwell migration assay, scratched wound healing and formation of tube-like structure) and in vivo by assessing neovascularization in mice. Phosphorylation of Akt was measured using Western blot analysis. RESULTS: Exogenously administered NaHS (H(2)S donor) concentration-dependently (10-20 micromol/l) increased cell growth, migration, scratched wound healing and tube-like structure formation in cultured endothelial cells. These effects of NaHS on endothelial wound healing and tube-like structure formation were prevented by either the phosphatidylinositol 3-kinase (PI3K) inhibitor LY 294002 (5 micromol/l) or transfection of a dominant-negative mutant of Akt. NaHS increased Akt phosphorylation and this effect was also blocked by either LY 294002 or wortmannin (25 nmol/l). NaHS did not significantly alter the levels of vascular endothelial growth factor, mRNA expression of fibroblast growth factor and angiopoietin-1, or nitric oxide metabolites. NaHS treatment (10 and 50 micromol kg(-1) day(-1)) significantly promoted neovascularization in vivo in mice. CONCLUSION: The present study reports a novel proangiogenic role of H(2)S which is dependent on activation of Akt.

Chronic sodium hydrosulfide treatment decreases medial thickening of intramyocardial coronary arterioles, interstitial fibrosis, and ROS production in spontaneously hypertensive rats.

Hydrogen sulfide (H(2)S) is a gasotransmitter that regulates cardiovascular functions. The present study aimed to examine the hypothesis that chronic treatment with sodium hydrosulfide (NaHS, an H(2)S donor) is able to prevent left-ventricular remodeling in spontaneously hypertensive rats (SHR). Four-week-old SHR were treated with NaHS (10, 30, and 90 micromol x kg(-1) x day(-1)), a combination of NaHS (30 micromol x kg(-1) x day(-1)) and glibenclamide (5 mg x kg(-1) x day(-1)), glibenclamide alone (5 mg x kg(-1) x day(-1)), hydralazine alone (10 mg x kg(-1) x day(-1)), and placebo for 3 mo. At the end of the treatment period, variables such as cardiac geometry and function, intramyocardial arterioles ranging in diameter from 25 to 100 microm, perivascular and interstitial collagen content, reactive oxygen species (ROS), thiol groups, conjugated dienes, and DNA base modification were examined. The novel finding of the present study is that chronic NaHS treatment prevented the hypertrophy of intramyocardial arterioles and ventricular fibrosis, as well as decreased myocardial ROS and conjugated diene levels. The cardioprotective effects were blunted by coadministration of glibenclamide, suggesting a role of ATP-sensitive potassium channels in mediating the action of NaHS. Hydralazine caused a comparable reduction of blood pressure compared with NaHS treatment; however, it exerted no effect on the remodeling process or on ROS and conjugated diene levels. Moreover, NaHS treatment caused an increase in myocardial thiol group levels, whereas DNA base modification was not altered by NaHS treatment. In conclusion, the superior cardioprotective effects of NaHS treatment are worthy to be further explored to develop novel therapeutic approaches for the treatment of cardiac remodeling in hypertension.

Endogenous hydrogen sulfide regulates leukocyte trafficking in cecal ligation and puncture-induced sepsis.

Hydrogen sulfide (H(2)S) is recognized increasingly as a proinflammatory mediator in various inflammatory conditions. Here, we have investigated the role of H(2)S in regulating expression of some endothelial adhesion molecules and recruitment of leukocytes to inflamed sites in sepsis. Male Swiss mice were subjected to cecal ligation and puncture (CLP)-induced sepsis and treated with saline (i.p.), DL-propargylglycine (PAG; 50 mg/kg, i.p.), an inhibitor of H(2)S formation or NaHS (10 mg/kg, i.p.), an H(2)S donor. PAG was administered 1 h before or after the induction of sepsis, and NaHS was given at the same time of CLP. Using intravital microcopy, we found that in sepsis, prophylactic and therapeutic administration of PAG reduced leukocyte rolling and adherence significantly in mesenteric venules coupled with decreased mRNA and protein levels of adhesion molecules (ICAM-1, P-selectin, and E-selectin) in lung and liver. In contrast, injection of NaHS up-regulated leukocyte rolling and attachment significantly, as well as tissue levels of adhesion molecules in sepsis. Conversely, normal mice were given NaHS (10 mg/kg, i.p.) to induce lung inflammation, with or without NF-kappaB inhibitor BAY 11-7082 pretreatment. NaHS treatment enhanced the level of adhesion molecules and neutrophil infiltration in lung. These alterations were reversed by pretreatment with BAY 11-7082. Moreover, expression of CXCR2 in neutrophils obtained from H(2)S-treated mice was up-regulated significantly, leading to an obvious elevation in MIP-2-directed migration of neutrophils. Therefore, H(2)S acts as an important endogenous regulator of leukocyte activation and trafficking during an inflammatory response.

Anti-inflammatory and gastrointestinal effects of a novel diclofenac derivative.

S-diclofenac (2-[(2,6-dichlorophenyl)amino]benzeneacetic acid 4-(3H-1,2,dithiol-3-thione-5-yl)phenyl ester; ACS 15) is a novel molecule comprising a hydrogen sulfide (H2S)-releasing dithiol-thione moiety attached by an ester linkage to diclofenac. S-diclofenac administration inhibited lipopolysaccharide-induced inflammation (as evidenced by reduced lung and liver myeloperoxidase activity) and caused significantly less gastric toxicity than diclofenac. S-diclofenac did not affect blood pressure or heart rate of the anesthetized rat. S-diclofenac administration downregulated expression of genes encoding enzymes which synthesize nitric oxide, prostanoids, and H2S; reduced plasma IL-1beta/TNF-alpha; and elevated plasma IL-10. Reduced liver NF-kappaB p65 and AP-1/c-fos DNA-binding activity was also observed. These effects were mimicked in large part by a combination of diclofenac plus an H2S-releasing moiety (ADT-OH). Incubation of S-diclofenac (100 microM) with rat plasma or liver homogenate caused a time-dependent release of H2S, which was inhibited by sodium fluoride (10 mM). Administration of S-diclofenac (47.2 micromol/kg, i.p.) to conscious rats significantly increased plasma H2S concentration (at 45 min and 6 h). We propose that H2S release from S-diclofenac in vivo contributes to the observed effects.

Hydrogen sulfide-induces DNA damage and changes in apoptotic gene expression in human lung fibroblast cells.

Hydrogen sulfide (H2S) has been shown previously to exert proapoptotic activity. However, the mechanism(s) by which H2S affects cell growth and function have not been addressed adequately. In this study, cultured human lung fibroblasts were treated with the H2S donor NaHS (10-75 microM; 12-48 h). NaHS caused a concentration-dependent increase in micronuclei formation (indicating DNA damage) and cell cycle arrest (G1 phase). NaHS increased expression of ku 70 and ku 80 but did not affect the expression of other DNA repair proteins such as proliferating cell nuclear antigen (PCNA) or replication protein A (rNase protection assay). NaHS treatment also resulted in stabilization of p53 coupled with induction of downstream proteins such as p21, Bax, and cytochrome c, as well as translocation of Bax from the cytosol to the mitochondria and release of cytochrome c from mitochondria. NaHS did not up-regulate cell levels of the antiapoptotic protein, Bcl-2. We propose that the genotoxic action of H2S propels the cell toward apoptotic death triggered initially by stabilization of p53 and subsequently involving a cascade of downstream products. These results are of significance as they uncover a hitherto unknown and very fundamental role for H2S in determining cell fate.

The role of urotensin II in cardiovascular and renal physiology and diseases.

Urotensin II (U-II) is a cyclic neuropeptide that was first isolated from teleost fish some 35 years ago. Mammalian U-II is a powerful vasoconstrictor with a potency greater than that of endothelin-1.Nevertheless, unlike endothelin-1, which constricts all or nearly all vascular beds, the vasoactive effects of U-II are reported to be dependent both on the species and on the regional vascular bed examined. Typical regional variability occurs in the rat in which vasoconstriction to U-II is most robust in thoracic aorta proximal to the aortic arch and decreases gradually towards the distal peripheral arteries. As small peripheral arteries but not larger arteries such as the aorta play a major role in regulating peripheral resistance and consequent blood pressure as well as workload on the heart, doubts have been raised concerning the importance of this peptide in cardiovascular physiology. Moreover, an interaction between U-II and other endogenous vasoactive molecules may add a level of complexity to the vascular actions of U-II.On the other hand, recent experimental and clinical studies have revealed increased expression of U-II and urotensin receptor (UT receptor) in animals with experimentally induced myocardial infarction, heart failure, and in patients with hypertension, atherosclerosis, and diabetic nephropathy, which suggests a potential role for U-II in both cardiovascular and renal diseases. A series of peptidic and nonpeptidic UT receptor ligands have been shown to be effective in antagonizing the effects of U-II in the cardiorenal system. This article aims to review recent advances in our understanding of the physiology and pathophysiology of U-II with particular references to its role in cardiovascular health and disease.

Role of hydrogen sulfide in the cardioprotection caused by ischemic preconditioning in the rat heart and cardiac myocytes.

Endogenous H(2)S is synthesized mainly by cystathionine gamma-lyase in the heart. The present study investigated the role of H(2)S in cardioprotection induced by ischemic preconditioning. We have examined the effect of endogenous H(2)S and exogenous application of NaHS (H(2)S donor) on cardiac rhythm in the isolated rat heart subjected to low-flow ischemia insults as well as cell viability and function in isolated myocytes exposed to simulated ischemia solution. Preconditioning with NaHS (SP) or ischemia (IP) for three cycles (3 min each cycle separated by 5 min of recovery) significantly decreased the duration and severity of ischemia/reperfusion-induced arrhythmias in the isolated heart while increasing cell viability and the amplitude of electrically induced calcium transients after ischemia/reperfusion in cardiac myocytes. Both IP and SP also significantly attenuated the decreased H(2)S production during ischemia. Moreover, decreasing endogenous H(2)S production significantly attenuated the protective effect of IP in both the isolated heart and isolated cardiac myocytes. Blockade of protein kinase C with chelerythrine or bisindolylmaleimide I as well as ATP-sensitive K(+) (K(ATP)) channel with glibenclamide (a nonselective K(ATP) blocker) and HMR-1098 (1-[[5-[2-(5-Chloro-o-anisamido)ethyl]-2-methoxyphenyl]sulfonyl]-3-methylthiourea) (a sarcolemmal K(ATP) channel blocker) reversed the cardioprotection induced by SP or IP. However, blockade of mitochondrial K(ATP) channels with 5-hydroxydecanoic acid had no effect on the cardioprotection of SP, suggesting that, unlike the mechanism involved in IP, mitochondrial K(ATP) channels most probably do not play a major role in the cardioprotection of SP. Our findings suggest that endogenous H(2)S contributes to cardioprotection induced by IP, which effect may involve protein kinase C and sarcolemmal K(ATP) channels.