Over the last decade, hydrogen sulfide (H
2
S) has emerged as an important endogenous gasotransmitter in mammalian cells and tissues. Similar to the previously characterized gasotransmitters nitric ...oxide and carbon monoxide, H
2
S is produced by various enzymatic reactions and regulates a host of physiologic and pathophysiological processes in various cells and tissues. H
2
S levels are decreased in a number of conditions (e.g., diabetes mellitus, ischemia, and aging) and are increased in other states (e.g., inflammation, critical illness, and cancer). Over the last decades, multiple approaches have been identified for the therapeutic exploitation of H
2
S, either based on H
2
S donation or inhibition of H
2
S biosynthesis. H
2
S donation can be achieved through the inhalation of H
2
S gas and/or the parenteral or enteral administration of so-called fast-releasing H
2
S donors (salts of H
2
S such as NaHS and Na
2
S) or slow-releasing H
2
S donors (GYY4137 being the prototypical compound used in hundreds of studies in vitro and in vivo). Recent work also identifies various donors with regulated H
2
S release profiles, including oxidant-triggered donors, pH-dependent donors, esterase-activated donors, and organelle-targeted (e.g., mitochondrial) compounds. There are also approaches where existing, clinically approved drugs of various classes (e.g., nonsteroidal anti-inflammatories) are coupled with H
2
S-donating groups (the most advanced compound in clinical trials is ATB-346, an H
2
S-donating derivative of the non-steroidal anti-inflammatory compound naproxen). For pharmacological inhibition of H
2
S synthesis, there are now several small molecule compounds targeting each of the three H
2
S-producing enzymes cystathionine-
β
-synthase (CBS), cystathionine-
γ
-lyase, and 3-mercaptopyruvate sulfurtransferase. Although many of these compounds have their limitations (potency, selectivity), these molecules, especially in combination with genetic approaches, can be instrumental for the delineation of the biologic processes involving endogenous H
2
S production. Moreover, some of these compounds (e.g., cell-permeable prodrugs of the CBS inhibitor aminooxyacetate, or benserazide, a potentially repurposable CBS inhibitor) may serve as starting points for future clinical translation. The present article overviews the currently known H
2
S donors and H
2
S biosynthesis inhibitors, delineates their mode of action, and offers examples for their biologic effects and potential therapeutic utility.
Vascular biology of hydrogen sulfide Kanagy, Nancy L; Szabo, Csaba; Papapetropoulos, Andreas
American Journal of Physiology: Cell Physiology,
05/2017, Letnik:
312, Številka:
5
Journal Article
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Odprti dostop
Hydrogen sulfide (H
S) is a ubiquitous signaling molecule with important functions in many mammalian organs and systems. Observations in the 1990s ascribed physiological actions to H
S in the nervous ...system, proposing that this gasotransmitter acts as a neuromodulator. Soon after that, the vasodilating properties of H
S were demonstrated. In the past decade, H
S was shown to exert a multitude of physiological effects in the vessel wall. H
S is produced by vascular cells and exhibits antioxidant, antiapoptotic, anti-inflammatory, and vasoactive properties. In this concise review, we have focused on the impact of H
S on vascular structure and function with an emphasis on angiogenesis, vascular tone, vascular permeability and atherosclerosis. H
S reduces arterial blood pressure, limits atheromatous plaque formation, and promotes vascularization of ischemic tissues. Although the beneficial properties of H
S are well established, mechanistic insights into the molecular pathways implicated in disease prevention and treatment remain largely unexplored. Unraveling the targets and downstream effectors of H
S in the vessel wall in the context of disease will aid in translation of preclinical observations. In addition, acute regulation of H
S production is still poorly understood and additional work delineating the pathways regulating the enzymes that produce H
S will allow pharmacological manipulation of this pathway. As the field continues to grow, we expect that H
S-related compounds will find their way into clinical trials for diseases affecting the blood vessels.
The physiological functions of hydrogen sulfide (H ₂S) 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 H ₂S-producing enzyme cystathionine-β-synthase (CBS) in colon cancer, resulting in an increased rate of H ₂S production. Similarly, colon cancer-derived epithelial cell lines (HCT116, HT-29, LoVo) exhibited selective CBS up-regulation and increased H ₂S 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 H ₂S 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, H ₂S 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 H ₂S as a tumor growth factor and anticancer drug target.
It is well established that exposure of mammalian cells to hydrogen sulfide (H2S) suppresses mitochondrial function by inhibiting cytochrome‐c oxidase (CcOX; complex IV). However, recent experimental ...data show that administration of H2S to mammalian cells can serve as an electron donor and inorganic source of energy. The aim of our study was to investigate the role of endogenously produced H2S in the regulation of mitochondrial electron transport and oxidative phosphorylation in isolated liver mitochondria and in the cultured murine hepatoma cell line Hepa1c1c7. Low concentrations of H2S (0.1–1 μM) elicited a significant increase in mitochondrial function, while higher concentrations of H2S (3–30 μM) were inhibitory. The positive bioenergetic effect of H2S required a basal activity of the Krebs cycle and was most pronounced at intermediate concentrations of succinate. 3‐mercaptopyruvate (3‐MP), the substrate of the mitochondrial enzyme 3‐mercaptopyruvate sulfurtransferase (3‐MST) stimulated mitochondrial H2S production and enhanced mitochondrial electron transport and cellular bioenergetics at low concentrations (10–100 nM), while at higher concentrations, it inhibited cellular bioenergetics. SiRNA silencing of 3‐MST reduced basal bioenergetic parameters and prevented the stimulating effect of 3‐MP on mitochondrial bioenergetics. Silencing of sulfide quinone oxidoreductase (SQR) also reduced basal and 3‐MP‐stimulated bioenergetic parameters. We conclude that an endogenous intramitochondrial H2S‐producing pathway, governed by 3‐MST, complements and balances the bioenergetic role of Krebs cycle‐derived electron donors. This pathway may serve a physiological role in the maintenance of mitochondrial electron transport and cellular bioenergetics.—Módis, K., Coletta, C., Erdélyi, K., Papapetropoulos, A., Szabo, C. Intramitochondrial hydrogen sulfide production by 3‐mercaptopyruvate sulfurtransferase maintains mitochondrial electron flow and supports cellular bioenergetics. FASEB J. 27, 601–611 (2013). www.fasebj.org
The Concise Guide to PHARMACOLOGY 2021/22 is the fifth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of nearly ...1900 human drug targets with an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes over 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point‐in‐time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/bph.15542. Enzymes are one of the six major pharmacological targets into which the Guide is divided, with the others being: G protein‐coupled receptors, ion channels, nuclear hormone receptors, catalytic receptors and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid‐2021, and supersedes data presented in the 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC‐IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.
Glioblastoma and other brain or CNS malignancies (like neuroblastoma and medulloblastoma) are difficult to treat and are characterized by excessive vascularization that favors further tumor growth. ...Since the mean overall survival of these types of diseases is low, the finding of new therapeutic approaches is imperative. In this review, we discuss the importance of the interaction between the endothelium and the tumor cells in brain and CNS malignancies. The different mechanisms of formation of new vessels that supply the tumor with nutrients are discussed. We also describe how the tumor cells (TC) alter the endothelial cell (EC) physiology in a way that favors tumorigenesis. In particular, mechanisms of EC-TC interaction are described such as (a) communication using secreted growth factors (i.e., VEGF, TGF-β), (b) intercellular communication through gap junctions (i.e., Cx43), and (c) indirect interaction via intermediate cell types (pericytes, astrocytes, neurons, and immune cells). At the signaling level, we outline the role of important mediators, like the gasotransmitter nitric oxide and different types of reactive oxygen species and the systems producing them. Finally, we briefly discuss the current antiangiogenic therapies used against brain and CNS tumors and the potential of new pharmacological interventions that target the EC-TC interaction.
Hydrogen sulfide (H₂S) is a unique gasotransmitter, with regulatory roles in the cardiovascular, nervous, and immune systems. Some of the vascular actions of H₂S (stimulation of angiogenesis, ...relaxation of vascular smooth muscle) resemble those of nitric oxide (NO). Although it was generally assumed that H₂S and NO exert their effects via separate pathways, the results of the current study show that H₂S and NO are mutually required to elicit angiogenesis and vasodilatation. Exposure of endothelial cells to H₂S 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 H₂S-stimulated angiogenic response, and attenuated H₂S-stimulated vasorelaxation, demonstrating the requirement of NO in vascular H₂S signaling. Conversely, silencing of the H₂S-producing enzyme cystathionme-γ-lyase abolishes NO-stimulated cGMP accumulation and angiogenesis and attenuates the acetylcholine-induced vasorelaxation, indicating a partial requirement of H₂S in the vascular activity of NO. The actions of H₂S and NO converge at cGMP; though H₂S does not directly activate soluble guanylyl cyclase, it maintains a tonic inhibitory effect on PDE5, thereby delaying the degradation of cGMP. H₂S 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. H₂S-induced wound healing and microvessel growth in matrigel plugs is suppressed by pharmacological inhibition or genetic ablation of eNOS. Thus, NO and H₂S are mutually required for the physiological control of vascular function.
This report identifies mitochondrial DNA (mtDNA) as a target and active mediator that links low-level oxidative stress to inflammatory response in pulmonary epithelial cells. Extrusion of mtDNA into ...the bronchoalveolar lavage fluid occurs as an early event in mice subjected to cigarette smoke injury, concomitantly with the depletion of mtDNA in the lung tissue. In cultured lung epithelial cells, prolonged, low-level oxidative stress damages the mtDNA, without any detectable damage to the nuclear DNA. In turn, cellular depletion of the mtDNA occurs, together with a transient remodeling of cellular bioenergetics and morphology - all without any detectable impairment in overall cell viability. Damaged mtDNA first enters the cytoplasm, where it binds to Z-DNA binding protein 1 (ZBP1) and triggers inflammation via the TANK-binding kinase 1 /interferon regulatory factor 3 signaling pathway. Fragments of the mtDNA are subsequently released into the extracellular space via exosomes. MtDNA-containing exosomes are capable of inducing an inflammatory response in naïve (non-oxidatively stressed) epithelial cells. In vivo, administration of isolated mtDNA into the in lungs of naïve mice induces the production of pro-inflammatory mediators, without histopathologic evidence of tissue injury. We propose that mtDNA-specific damage, and subsequent activation of the ZBP1 pathway, is a mechanism that links prolonged, low-level oxidative stress to autocrine and paracrine inflammation during the early stages of inflammatory lung disease.
The goal of the current study was to investigate the role of exogenous and endogenous hydrogen sulfide (H₂S) on neovascularization and wound healing in vitro and in vivo. Incubation of endothelial ...cells (ECs) with H₂S enhanced their angiogenic potential, evidenced by accelerated cell growth, migration, and capillary morphogenesis on Matrigel. Treatment of chicken chorioallantoic membranes (CAMS) with H₂S increased vascular length. Exposure of ECs to H₂S resulted in increased phosphorylation of Akt, ERK, and p38. The KATP channel blocker glibenclamide or the p38 inhibitor SB203580 abolished H₂S-induced EC motility. Since glibenclamide inhibited H₂S-triggered p38 phosphorylation, we propose that KATP channels lay upstream of p38 in this process. When CAMs were treated with H₂S biosynthesis inhibitors dl-propylargylglycine or beta-cyano-L-alanine, a reduction in vessel length and branching was observed, indicating that H₂S serves as an endogenous stimulator of the angiogenic response. Stimulation of ECs with vascular endothelial growth factor (VEGF) increased H₂S release, while pharmacological inhibition of H₂S production or KATP channels or silencing of cystathionine gamma-lyase (CSE) attenuated VEGF signaling and migration of ECs. These results implicate endothelial H₂S 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 H₂S enhanced wound healing in a rat model, while wound healing was delayed in CSE⁻/⁻ mice. We conclude that endogenous and exogenous H₂S stimulates EC-related angiogenic properties through a KATP channel/MAPK pathway.
OBJECTIVE—Recent studies have demonstrated that hydrogen sulfide (H2S) is produced within the vessel wall from l-cysteine regulating several aspects of vascular homeostasis. H2S generated from ...cystathione γ-lyase (CSE) contributes to vascular tone; however, the molecular mechanisms underlying the vasorelaxing effects of H2S are still under investigation.
METHODS AND RESULTS—Using isolated aortic rings, we observed that addition of l-cysteine led to a concentration-dependent relaxation that was prevented by the CSE inhibitors dl-propargylglyicine (PAG) and β-cyano-l-alanine (BCA). Moreover, incubation with PAG or BCA resulted in a rightward shift in sodium nitroprusside-and isoproterenol-induced relaxation. Aortic tissues exposed to PAG or BCA contained lower levels of cGMP, exposure of cells to exogenous H2S or overexpression of CSE raised cGMP concentration. RNA silencing of CSE expression reduced intracellular cGMP levels confirming a positive role for endogenous H2S on cGMP accumulation. The ability of H2S to enhance cGMP levels was greatly reduced by the nonselective phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine. Finally, addition of H2S to a cell-free system inhibited both cGMP and cAMP breakdown.
CONCLUSION—These findings provide direct evidence that H2S acts as an endogenous inhibitor of phosphodiesterase activity and reinforce the notion that this gasotransmitter could be therapeutically exploited.
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