The goal of the current study was to investigate the role of exogenous and endogenous hydrogen sulfide (H ₂ S) on neovascularization and wound healing in vitro and in vivo. Incubation of endothelial cells (ECs) with H ₂ S enhanced their angiogenic potential, evidenced by accelerated cell growth, migration, and capillary morphogenesis on Matrigel. Treatment of chicken chorioallantoic membranes (CAMS) with H ₂ S increased vascular length. Exposure of ECs to H ₂ S resulted in increased phosphorylation of Akt, ERK, and p38. The K _ATP channel blocker glibenclamide or the p38 inhibitor SB203580 abolished H ₂ S-induced EC motility. Since glibenclamide inhibited H ₂ S-triggered p38 phosphorylation, we propose that K _ATP channels lay upstream of p38 in this process. When CAMs were treated with H ₂ S biosynthesis inhibitors dl-propylargylglycine or beta-cyano-L-alanine, a reduction in vessel length and branching was observed, indicating that H ₂ S serves as an endogenous stimulator of the angiogenic response. Stimulation of ECs with vascular endothelial growth factor (VEGF) increased H ₂ S release, while pharmacological inhibition of H ₂ S production or K _ATP channels or silencing of cystathionine gamma-lyase (CSE) attenuated VEGF signaling and migration of ECs. These results implicate endothelial H ₂ S synthesis in the pro-angiogenic action of VEGF. Aortic rings isolated from CSE knockout mice exhibited markedly reduced microvessel formation in response to VEGF when compared to wild-type littermates. Finally, in vivo, topical administration of H ₂ S enhanced wound healing in a rat model, while wound healing was delayed in CSE ^−/− mice. We conclude that endogenous and exogenous H ₂ S stimulates EC-related angiogenic properties through a K _ATP channel/MAPK pathway.

The physiological functions of hydrogen sulfide (H₂S) include vasorelaxation, stimulation of cellular bioenergetics, and promotion of angiogenesis. Analysis of human colon cancer biopsies and patient-matched normal margin mucosa revealed the selective up-regulation of the H₂S-producing enzyme cystathionine-β-synthase (CBS) in colon cancer, resulting in an increased rate of H₂S production. Similarly, colon cancer-derived epithelial cell lines (HCT116, HT-29, LoVo) exhibited selective CBS up-regulation and increased H₂S production, compared with the nonmalignant colonic mucosa cells, NCM356. CBS localized to the cytosol, as well as the mitochondrial outer membrane. ShRNA-mediated silencing of CBS or its pharmacological inhibition with aminooxyacetic acid reduced HCT116 cell proliferation, migration, and invasion; reduced endothelial cell migration in tumor/endothelial cell cocultures; and suppressed mitochondrial function (oxygen consumption, ATP turnover, and respiratory reserve capacity), as well as glycolysis. Treatment of nude mice with aminooxyacetic acid attenuated the growth of patient-derived colon cancer xenografts and reduced tumor blood flow. Similarly, CBS silencing of the tumor cells decreased xenograft growth and suppressed neovessel density, suggesting a role for endogenous H₂S in tumor angiogenesis. In contrast to CBS, silencing of cystathionine-γ-lyase (the expression of which was unchanged in colon cancer) did not affect tumor growth or bioenergetics. In conclusion, H₂S produced from CBS serves to (i) maintain colon cancer cellular bioenergetics, thereby supporting tumor growth and proliferation, and (ii) promote angiogenesis and vasorelaxation, consequently providing the tumor with blood and nutritients. The current findings identify CBS-derived H₂S as a tumor growth factor and anticancer drug target.

Hydrogen sulfide (H ₂ S) is a unique gasotransmitter, with regulatory roles in the cardiovascular, nervous, and immune systems. Some of the vascular actions of H ₂ S (stimulation of angiogenesis, relaxation of vascular smooth muscle) resemble those of nitric oxide (NO). Although it was generally assumed that H ₂ S and NO exert their effects via separate pathways, the results of the current study show that H ₂ S and NO are mutually required to elicit angiogenesis and vasodilatation. Exposure of endothelial cells to H ₂ S increases intracellular cyclic guanosine 5′-monophosphate (cGMP) in a NO-dependent manner, and activated protein kinase G (PKG) and its downstream effector, the vasodilator-stimulated phosphoprotein ( VASP ). Inhibition of endothelial isoform of NO synthase (eNOS) or PKG-I abolishes the H ₂ S-stimulated angiogenic response, and attenuated H ₂ S-stimulated vasorelaxation, demonstrating the requirement of NO in vascular H ₂ S signaling. Conversely, silencing of the H ₂ S-producing enzyme cystathionine-γ-lyase abolishes NO-stimulated cGMP accumulation and angiogenesis and attenuates the acetylcholine-induced vasorelaxation, indicating a partial requirement of H ₂ S in the vascular activity of NO. The actions of H ₂ S and NO converge at cGMP; though H ₂ S does not directly activate soluble guanylyl cyclase, it maintains a tonic inhibitory effect on PDE5, thereby delaying the degradation of cGMP. H ₂ S also activates PI3K/Akt, and increases eNOS phosphorylation at its activating site S1177. The cooperative action of the two gasotransmitters on increasing and maintaining intracellular cGMP is essential for PKG activation and angiogenesis and vasorelaxation. H ₂ S-induced wound healing and microvessel growth in matrigel plugs is suppressed by pharmacological inhibition or genetic ablation of eNOS. Thus, NO and H ₂ S are mutually required for the physiological control of vascular function.

Over the last two decades, hydrogen sulfide (H₂S) has emerged as an endogenous regulator of a broad range of physiological functions. H₂S belongs to the class of molecules known as gasotransmitters, which typically include nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H₂S in various cells and tissues: cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS), and 3-mercaptopyruvate sulfurtransferase (3-MST). The present article reviews the regulation of these enzymes as well as the pathways of their enzymatic and nonenzymatic degradation and elimination. The multiple interactions of H₂S with other labile endogenous molecules (e.g., NO) and reactive oxygen species are also outlined. Next, the various biological targets and signaling pathways are outlined, with special reference to H₂S or oxidative posttranscriptional modification (persulfidation or sulfhydration) of proteins and the effect of H₂S on various channels and intracellular second messenger pathways, the regulation of gene transcription and translation, and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H₂S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H₂S in the regulation of various physiological and cellular functions is reviewed, including the regulation of membrane potential, endo- and exocytosis, regulation of various cell organelles (endoplasmic reticulum, Golgi, mitochondria), regulation of cell movement, cell cycle, cell differentiation, and physiological aspects of regulated cell death. Next, the physiological roles of H₂S in various cell types and organ systems are overviewed, including the role of H₂S in red blood cells, immune cells, the central and peripheral nervous systems (with focus on neuronal transmission, learning, and memory formation), and regulation of vascular function (including angiogenesis as well as its specialized roles in the cerebrovascular, renal, and pulmonary vascular beds) and the role of H₂S in the regulation of special senses, vision, hearing, taste and smell, and pain-sensing. Finally, the roles of H₂S in the regulation of various organ functions (lung, heart, liver, kidney, urogenital organs, reproductive system, bone and cartilage, skeletal muscle, and endocrine organs) are presented, with a focus on physiology (including physiological aging) but also extending to some common pathophysiological conditions. From these data, a wide array of significant roles of H₂S in the physiological regulation of all organ functions emerges and the characteristic bell-shaped biphasic effects of H₂S are highlighted. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified.