Therapeutic potential of endogenous hydrogen sulfide inhibition in breast cancer (Review).

Hydrogen sulfide (H2S), the third gas signal molecule, is associated with the modulation of various physiological and pathological processes. Recent studies have reevealed that endogenous H2S may promote proliferation, induce angiogenesis and inhibit apoptosis, thereby stimulating oncogenesis. Conversely, decreased endogenous H2S release suppresses growth of various tumors including breast cancer. This observation suggests an alternative tumor therapy strategy by inhibiting H2S­producing enzymes to reduce the release of endogenous H2S. Breast cancer is the most common type of cancer in women. Due to the lack of approved targeted therapy, its recurrence and metastasis still affect its clinical treatment. In recent years, significant progress has been made in the control of breast cancer by using inhibitors on H2S­producing enzymes. This review summarized the roles of endogenous H2S­producing enzymes in breast cancer and the effects of the enzyme inhibitors on anticancer and anti­metastasis, with the aim of providing new insights for the treatment of breast cancer.

Pharmacological induction of mesenchymal-epithelial transition via inhibition of H2S biosynthesis and consequent suppression of ACLY activity in colon cancer cells.

Hydrogen sulfide (H2S) is an important endogenous gaseous transmitter mediator, which regulates a variety of cellular functions in autocrine and paracrine manner. The enzymes responsible for the biological generation of H2S include cystathionine-ß-synthase (CBS), cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST). Increased expression of these enzymes and overproduction of H2S has been implicated in essential processes of various cancer cells, including the stimulation of metabolism, maintenance of cell proliferation and cytoprotection. Cancer cell identity is characterized by so-called "transition states". The progression from normal (epithelial) to transformed (mesenchymal) state is termed epithelial-to-mesenchymal transition (EMT) whereby epithelial cells lose their cell-to-cell adhesion capacity and gain mesenchymal characteristics. The transition process can also proceed in the opposite direction, and this process is termed mesenchymal-to-epithelial transition (MET). The current project was designed to determine whether inhibition of endogenous H2S production in colon cancer cells affects the EMT/MET balance in vitro. Inhibition of H2S biosynthesis in HCT116 human colon cancer cells was achieved either with aminooxyacetic acid (AOAA) or 2-[(4-hydroxy-6-methylpyrimidin-2-yl)sulfanyl]-1-(naphthalen-1-yl)ethan-1-one (HMPSNE). These inhibitors induced an upregulation of E-cadherin and Zonula occludens-1 (ZO-1) expression and downregulation of fibronectin expression, demonstrating that H2S biosynthesis inhibitors can produce a pharmacological induction of MET in colon cancer cells. These actions were functionally reflected in an inhibition of cell migration, as demonstrated in an in vitro "scratch wound" assay. The mechanisms involved in the action of endogenously produced H2S in cancer cells in promoting (or maintaining) EMT (or tonically inhibiting MET) relate, at least in part, in the induction of ATP citrate lyase (ACLY) protein expression, which occurs via upregulation of ACLY mRNA (via activation of the ACLY promoter). ACLY in turn, regulates the Wnt-ß-catenin pathway, an essential regulator of the EMT/MET balance. Taken together, pharmacological inhibition of endogenous H2S biosynthesis in cancer cells induces MET. We hypothesize that this may contribute to anti-cancer / anti-metastatic effects of H2S biosynthesis inhibitors.

Acute acrylonitrile exposure inhibits endogenous H2S biosynthesis in rat brain and liver: The role of CBS/3-MPST-H2S pathway in its astrocytic toxicity.

Hydrogen sulfide (H2S) as the third gasotransmitter molecule serves various biological regulatory roles in health and disease. Acrylonitrile (AN) is a common occupational toxicant and environmental pollutant, causing brain and liver damage in mammals. The biotransformation of AN is dependent-upon reduced glutathione (GSH), cysteine and other sulfur-containing compounds. However, the effects of AN on the endogenous H2S biosynthesis pathway have yet to be determined. Herein, we demonstrated that a single exposure to AN (at 25, 50, or 75 mg/kg for 1, 6 or 24 h) decreased the endogenous H2S content and H2S-producing capacity in a dose-dependent manner, both in the cerebral cortex and liver of rats in vivo. In addition, the inhibitory effects of AN (1, 2.5, 5, 10 mM for 12 h) on the H2S content and/or the expression of H2S-producing enzymes were also found both in primary rat astrocytes and rat liver cell line (BRL cells). Impairment in the H2S biosynthesis pathway was also assessed in primary rat astrocytes treated with AN. It was found that inhibition of the cystathionine-ß-synthase (CBS)/3-mercaptopyruvate sulfurtransferase (3-MPST)-H2S pathway with the CBS inhibitor or 3-MPST-targeted siRNA significantly increased the AN-induced (5 mM for 12 h) cytotoxicity in astrocytes. In turn, CBS activation or 3-MPST overexpression as well as exogenous NaHS supplementation significantly attenuated AN-induced cytotoxicity. Taken together, endogenous H2S biosynthesis pathway was disrupted in rats acutely exposed to AN, which contributes to acute AN neurotoxicity in primary rat astrocytes.

Effects of endogenous H2S production inhibition on the homeostatic responses induced by acute high-salt diet consumption.

The gaseous modulator hydrogen sulfide (H2S) is synthesized, among other routes, by the action of cystathionine-γ-lyase (CSE) and importantly participates in body fluid homeostasis. Therefore, the present study aimed to evaluate the participation of H2S in behavioral, renal and neuroendocrine homeostatic responses triggered by the acute consumption of a high Na+ diet. After habituation, adult male Wistar rats were randomly distributed and maintained for seven days on a control [CD (0.27% of Na+)] or hypersodic diet [HD (0.81% of Na+)]. CD and HD-fed animals were treated with DL-Propargylglycine (PAG, 25 mg/kg/day, ip) or vehicle (0.9% NaCl in equivalent volume) for the same period. At the end of the experiment, animals were euthanized for blood and tissue collection. We demonstrated that a short-term increase in dietary Na+ intake, in values that mimic the variations in human consumption (two times the recommended) significantly modified hydroelectrolytic homeostasis, with repercussions in the hypothalamic-neurohypophysial system and hypothalamic-pituitary-adrenal axis function. These findings were accompanied by the development of a clear inflammatory response in renal tubular cells and microvascular components. On the other hand, the inhibition of the endogenous production of H2S by CSE provided by PAG treatment prevented the inflammation induced by HD. In the kidney, PAG treatment induced the overexpression of inducible nitric oxide synthase in animals fed with HD. Taken together, these data suggest, therefore, that HD-induced H2S production plays an important proinflammatory role in the kidney, apparently counter regulating nitric oxide actions in renal tissue.

Cyanidin-3-O-Glucoside Improves Colonic Motility During Severe Acute Pancreatitis by Inhibiting the H2S-Regulated AMPK/mTOR Pathway.

BACKGROUND: Cyanidin-3-O-glucoside (C3G) is an important anthocyanin that can modulate digestive system functioning. Inflammation associated with severe acute pancreatitis (SAP) induces H2S production, which impairs the gastrointestinal (GI) system. We investigated the effects of C3G in attenuating SAP-associated colonic motility loss by examining the H2S level and activity of AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway. METHODS: A rat model of SAP was induced using sodium taurocholate, and the effect of C3G on colonic mobility, H2S production, and the inflammatory response was investigated. AMPK/mTOR pathway changes were detected to assess the pathways by which H2S influences colonic mobility in SAP-model rats. The mechanism underlying H2S function was further examined by subjecting colonic muscle cells (CMCs) to C3G, SAP plasma and an AMPK activator. RESULTS: Administering C3G improved colonic motility but suppressed the inflammatory response and H2S production in the SAP-model rats, which was associated with inhibiting the AMPK/mTOR pathway. Furthermore, activating the AMPK/mTOR pathway in CMCs promoted inflammation but suppressed Ca2+ levels, even after administering C3G. CONCLUSION: Administering C3G may improve SAP-associated colonic mobility by inhibiting the H2S-mediated AMPK/mTOR pathway.

Inhibition of endogenous hydrogen sulfide biosynthesis enhances the anti-cancer effect of 3,3'-diindolylmethane in human gastric cancer cells.

AIMS: 3,3'-Diindolylmethane (DIM) has limited anti-cancer effects in gastric cancer. Hydrogen sulfide (H2S) plays an important role in the tumor development and therapy, cystathionine-ß-synthase (CBS) and cystathionine-γ-lyase (CSE), two key endogenous H2S biosynthesis enzymes, can affect endogenous H2S levels and alter cancer treatment. Our main objective was to investigate whether the aminooxyacetic acid (AOAA) and DL-Propargylglycine (PAG), two specific inhibitors of CBS and CSE, could assist DIM to exert a stronger anti-cancer effects in gastric cancer BGC-823 and SGC-7901 cells. MATERIALS AND METHODS: Cell proliferation was assayed by MTT and cell colony-forming assay. Apoptosis and migration were detected by Hoechst staining and scratch test respectively. Western blot was used to evaluate the expression of proteins related to proliferation, apoptosis and migration. KEY FINDINGS: Combination of AOAA or PAG with DIM synergistically inhibited proliferation and migration, increased apoptosis in gastric cancer cells. The p38-p53 axis was also further activated by the combination of AOAA or PAG with DIM. Exogenous H2S from sodium hydrosulfide, attenuated the efficacy of DIM in cancer cells by reducing the activation level of p38-p53 axis. Taken together, AOAA or PAG inhibited the expression of endogenous H2S biosynthesis enzymes and effectively enhanced susceptibility of gastric cancer to DIM through activating p38-p53 axis. SIGNIFICANCE: The current study highlight more precise requirements for the clinical application of sulfur-containing anti-cancer drugs, and open a new way to enhance the sensitivity of DIM in chemotherapy of gastric cancer.

Endogenous hydrogen sulfide sulfhydrates IKKß at cysteine 179 to control pulmonary artery endothelial cell inflammation.

BACKGROUND: Pulmonary artery endothelial cell (PAEC) inflammation is a critical event in the development of pulmonary arterial hypertension (PAH). However, the pathogenesis of PAEC inflammation remains unclear. METHODS: Purified recombinant human inhibitor of κB kinase subunit ß (IKKß) protein, human PAECs and monocrotaline-induced pulmonary hypertensive rats were employed in the study. Site-directed mutagenesis, gene knockdown or overexpression were conducted to manipulate the expression or activity of a target protein. RESULTS: We showed that hydrogen sulfide (H2S) inhibited IKKß activation in the cell model of human PAEC inflammation induced by monocrotaline pyrrole-stimulation or knockdown of cystathionine γ-lyase (CSE), an H2S generating enzyme. Mechanistically, H2S was proved to inhibit IKKß activity directly via sulfhydrating IKKß at cysteinyl residue 179 (C179) in purified recombinant IKKß protein in vitro, whereas thiol reductant dithiothreitol (DTT) reversed H2S-induced IKKß inactivation. Furthermore, to demonstrate the significance of IKKß sulfhydration by H2S in the development of PAEC inflammation, we mutated C179 to serine (C179S) in IKKß. In purified IKKß protein, C179S mutation of IKKß abolished H2S-induced IKKß sulfhydration and the subsequent IKKß inactivation. In human PAECs, C179S mutation of IKKß blocked H2S-inhibited IKKß activation and PAEC inflammatory response. In pulmonary hypertensive rats, C179S mutation of IKKß abolished the inhibitory effect of H2S on IKKß activation and pulmonary vascular inflammation and remodeling. CONCLUSION: Collectively, our in vivo and in vitro findings demonstrated, for the first time, that endogenous H2S directly inactivated IKKß via sulfhydrating IKKß at Cys179 to inhibit nuclear factor-κB (NF-κB) pathway activation and thereby control PAEC inflammation in PAH.

Mental retardation in Down syndrome: Two ways to treat.

Mental retardation is a progressive condition in Down syndrome: intelligence starts to decline linearly within the first year. This phenomenon could be related to the overproduction of a toxic compound, hydrogen sulfide. Indeed, a gene located on chromosome 21 controls the production of cystathionine-ß-synthase, an enzyme involved in hydrogen sulfide production in the central nervous system. It has recently been demonstrated that excess cystathionine-ß-synthase levels are needed and sufficient to induce cognitive phenotypes in mouse models of Down syndrome. Thus, two therapeutic options might be used in Down syndrome patients: the use of a specific cystathionine ß-synthase inhibitor and the use of an effective antidote to reduce hydrogen sulfide toxicity. Prenatal treatment of Down syndrome fetuses is also suggested.

Data-Driven Identification of Hydrogen Sulfide Scavengers.

Hydrogen sulfide (H2 S) is an important signaling molecule whose up- and down-regulation have specific biological consequences. Although significant advances in H2 S up-regulation, by the development of H2 S donors, have been achieved in recent years, precise H2 S down-regulation is still challenging. The lack of potent/specific inhibitors for H2 S-producing enzymes contributes to this problem. We expect the development of H2 S scavengers is an alternative approach to address this problem. Since chemical sensors and scavengers of H2 S share the same criteria, we constructed a H2 S sensor database, which summarizes key parameters of reported sensors. Data-driven analysis led to the selection of 30 potential compounds. Further evaluation of these compounds identified a group of promising scavengers, based on the sulfonyl azide template. The efficiency of these scavengers in in vitro and in vivo experiments was demonstrated.

Angiotensin II downregulates vascular endothelial cell hydrogen sulfide production by enhancing cystathionine γ-lyase degradation through ROS-activated ubiquitination pathway.

The interactions between vasoactive peptides and gasotransmitters have attracted considerable attention from scientists. However, the impact of angiotensin II (AngII) on the endogenous hydrogen sulfide/cystathionine γ-lyase (H2S/CSE) pathway in vascular endothelial cells remains unclear. In this study, we found, for the first time, that AngII downregulated the endogenous H2S/CSE pathway in a time-dependent manner. Mechanistically, AngII accelerated the degradation of the CSE protein and shortened its half-life in endothelial cells. AngII significantly induced Lys48 (K48)-linked CSE ubiquitination and subsequent CSE degradation but did not affect Lys63 (K63)-linked CSE ubiquitination in vascular endothelial cells. Treatment with the proteasome inhibitor MG132 and mutation of Lys48 to Arg in ubiquitin successfully blunted the inhibitory effects of AngII on the endogenous H2S/CSE pathway in vascular endothelial cells. Furthermore, we found that superoxide anion levels were significantly increased in AngII-treated endothelial cells compared with controls and that the ROS scavenger N-acetyl-l-cysteine (NAC) significantly abolished CSE ubiquitination. Taken together, our data suggested that AngII inhibited endogenous H2S generation through ubiquitination-mediated CSE degradation via the ROS pathway in vascular endothelial cells.

Central administration of aminooxyacetate, an inhibitor of H2S production, affects thermoregulatory but not cardiovascular and ventilatory responses to hypercapnia in spontaneously hypertensive rats.

Hydrogen sulfide (H2S) is classically known for its toxic effects. More recently H2S has been documented as a neuromodulator. Here we investigated the central effects of aminooxyacetate (AOA; inhibitor of the H2S-synthesizing enzyme cystathionine ß-synthase, CBS) on cardiovascular, respiratory and thermoregulatory responses to hypercapnia in spontaneously hypertensive rats (SHR). To attain this goal we measured mean arterial pressure (MAP), heart rate (HR), ventilation (VE), and deep body temperature (Tb) of SHR and (normotensive) Wistar Kyoto (WKY) rats before and after microinjection of AOA (9 nmol/µL) or saline into the fourth ventricle immediately followed by 30-min hypercapnia exposure (7% inspired CO2). In saline-treated WKY rats, hypercapnia caused an increase in MAP accompanied by bradycardia, an increase in VE, and a drop in Tb. In AOA-treated WKY rats exposed to hypercapnia, the drug did not affect the increased MAP, potentiated the bradycardic response, attenuated the increased VE, and potentiated the drop in Tb. In saline-treated SHR, in comparison to the saline-treated WKY rats, hypercapnia elicited a minor, shorter-lasting increase in MAP with no changes in HR, evoked a greater increase in VE, and did not induce a drop in Tb. In AOA-treated SHR exposed to hypercapnia, the drug did not change the hypercapnia-induced cardiovascular and ventilatory responses while permitted a drop in Tb. Our findings indicate that AOA, an inhibitor of H2S production, modulates cardiorespiratory and thermoregulatory responses to hypercapnia in normotensive rats, whereas hypertension development in SHR is accompanied by suppression of the AOA effect on the cardiovascular and respiratory responses.

Hydrogen Sulfide in Physiological and Pathological Mechanisms in Brain.

BACKGROUND & OBJECTIVE: Hydrogen sulfide [H2S] has been widely known as a toxic gas for more than 300 years in the scientific community. However, the understanding about this small molecule has changed after the discovery of involvement of H2S in physiological and pathological mechanisms in brain. H2S is a third gasotransmitter and neuromodulator after carbon monoxide [CO] and nitric oxide [NO]. H2S plays an important role in memory and cognition by regulating long-term potentiation [LTP] and calcium homeostasis in neuronal cells. The disturbances in endogenous H2S levels and trans-sulfuration pathway have been implicated in neurodegenerative disorders like Alzheimer's disease, Parkinson disease, stroke and traumatic brain injury. According to the results obtained from various studies, H2S not only behaves as neuromodulator but also is a potent antioxidant, anti-inflammatory and anti-apoptotic molecule suggesting its neuroprotective potential. CONCLUSION: Recently, there is an increased interest in developing H2S releasing pharmaceuticals to target various neurological disorders. This review covers the information about the involvement of H2S in neurodegenerative diseases, its molecular targets and its role as potential therapeutic molecule.

Transcriptome-Based Analysis in Lactobacillus plantarum WCFS1 Reveals New Insights into Resveratrol Effects at System Level.

SCOPE: This study was undertaken to expand our insights into the mechanisms involved in the tolerance to resveratrol (RSV) that operate at system-level in gut microorganisms and advance knowledge on new RSV-responsive gene circuits. METHODS AND RESULTS: Whole genome transcriptional profiling was used to characterize the molecular response of Lactobacillus plantarum WCFS1 to RSV. DNA repair mechanisms were induced by RSV and responses were triggered to decrease the load of copper, a metal required for RSV-mediated DNA cleavage, and H2 S, a genotoxic gas. To counter the effects of RSV, L. plantarum strongly up- or downregulated efflux systems and ABC transporters pointing to transport control of RSV across the membrane as a key mechanism for RSV tolerance. L. plantarum also downregulated tRNAs, induced chaperones, and reprogrammed its transcriptome to tightly control ammonia levels. RSV induced a probiotic effector gene and a likely deoxycholate transporter, two functions that improve the host health status. CONCLUSION: Our data identify novel protective mechanisms involved in RSV tolerance operating at system level in a gut microbe. These insights could influence the way RSV is used for a better management of gut microbial ecosystems to obtain associated health benefits.

Exogenous hydrogen sulfide inhibits oral mucosal wound-induced macrophage activation via the NF-κB pathway.

OBJECTIVE: This study includes exploring (i) the production of endogenous hydrogen sulfide (H2 S) after mucosal wound generation and (ii) the role of compensating the change in H2 S level postmucosal wound generation. METHODS AND MATERIALS: A mucosal wound model was established in female C57BL/6J mice. Wound tissues were collected to examine the change in the endogenous H2 S level. To examine the effect of decreased H2 S, GYY4137 was intraperitoneally injected into mice at 50 mg kg-1  day-1 before mucosal wounding to compensate for the decreased endogenous H2 S. Finally, we confirmed the role of GYY4137 in inhibiting the M1 phenotype macrophage activation induced by LPS in peritoneal macrophages and RAW264.7. RESULTS: The production of endogenous H2 S and the expression of cystathionine b-synthase and cystathionine g-lyase in vivo were reduced significantly in early stage after wound. GYY4137 significantly inhibited the activation of the M1 phenotype induced by mucosal wound inflammation in vivo and LPS in vitro. Finally, we confirmed that GYY4137 inhibited iNOS expression via the NF-κB signaling pathway. CONCLUSION: The exogenous H2 S donor GYY4137 compensated for the reduced endogenous H2 S postmucosal wound generation and inhibited the induced M1 macrophage activation. Thus, appropriate H2 S supplementation may aid in controlling inflammation associated with mucosal wounds.

Two mechanisms of oral malodor inhibition by zinc ions.

The aim of this study was to reveal the mechanisms by which zinc ions inhibit oral malodor. The direct binding of zinc ions to gaseous hydrogen sulfide (H2S) was assessed in comparison with other metal ions. Nine metal chlorides and six metal acetates were examined. To understand the strength of H2S volatilization inhibition, the minimum concentration needed to inhibit H2S volatilization was determined using serial dilution methods. Subsequently, the inhibitory activities of zinc ions on the growth of six oral bacterial strains related to volatile sulfur compound (VSC) production and three strains not related to VSC production were evaluated. Aqueous solutions of ZnCl2, CdCl2, CuCl2, (CH3COO)2Zn, (CH3COO)2Cd, (CH3COO)2Cu, and CH3COOAg inhibited H2S volatilization almost entirely. The strengths of H2S volatilization inhibition were in the order Ag+ > Cd2+ > Cu2+ > Zn2+. The effect of zinc ions on the growth of oral bacteria was strain-dependent. Fusobacterium nucleatum ATCC 25586 was the most sensitive, as it was suppressed by medium containing 0.001% zinc ions. Zinc ions have an inhibitory effect on oral malodor involving the two mechanisms of direct binding with gaseous H2S and suppressing the growth of VSC-producing oral bacteria.

Endogenous peripheral hydrogen sulfide is propyretic: its permissive role in brown adipose tissue thermogenesis in rats.

NEW FINDINGS: What is the central question of this study? In fever, the most striking response in the acute phase reaction of systemic inflammation, plasma H2 S concentration increases. However, the role of endogenous peripheral H2 S in fever is unknown. What is the main finding and its importance? Endogenous peripheral H2 S is permissive for increased brown adipose tissue thermogenesis to maintain thermal homeostasis in cold environments as well as to mount fever. This finding expands the physiological role of the gaseous modulator as a key regulator of thermal control in health (thermal homeostasis) and disease (fever in systemic inflammation). ABSTRACT: In recent years, hydrogen sulfide (H2 S) has been reported as a gaseous modulator acting in several tissues in health and disease. In animal models of systemic inflammation, the plasma H2 S concentration increases in response to endotoxin (bacterial lipopolysaccharide, LPS). The most striking response in the acute phase reaction of systemic inflammation is fever, but we found no reports of the peripheral action of H2 S on this thermoregulatory response. We aimed at investigating whether endogenous systemic H2 S modulates LPS-induced fever. A temperature datalogger capsule was inserted in the abdominal cavity of male Wistar rats (220-270 g) to record body core temperature. These animals received an i.p. injection of a systemic H2 S inhibitor (propargylglycine; 50 or 75 mg kg-1 ), immediately followed by an i.p. injection of LPS (50 or 2500 µg kg-1 ), and were exposed to different ambient temperatures (16, 22 or 27°C). At 22°C, but not at 27°C, propargylglycine at 75 mg kg-1 significantly attenuated (P < 0.0001) the fever induced by LPS (50 µg kg-1 ), indicating a modulatory (permissive) action of endogenous peripheral H2 S on brown adipose tissue (BAT) thermogenesis. Evidence on the modulatory role of peripheral H2 S in BAT thermogenesis was strengthened when we discarded (i) the possible influence of the gas on febrigenic signalling (when measuring plasma cytokines), and (ii) its interaction with the nitric oxide pathway, and mainly when (iii) we carried out physiological and pharmacological activations of BAT. Endogenous peripheral H2 S modulates (permits) BAT activity not only in fever but also during maintenance of thermal homeostasis in cold environments.

Two mechanisms of oral malodor inhibition by zinc ions

Abstract Objectives The aim of this study was to reveal the mechanisms by which zinc ions inhibit oral malodor. Material and Methods The direct binding of zinc ions to gaseous hydrogen sulfide (H2S) was assessed in comparison with other metal ions. Nine metal chlorides and six metal acetates were examined. To understand the strength of H2S volatilization inhibition, the minimum concentration needed to inhibit H2S volatilization was determined using serial dilution methods. Subsequently, the inhibitory activities of zinc ions on the growth of six oral bacterial strains related to volatile sulfur compound (VSC) production and three strains not related to VSC production were evaluated. Results Aqueous solutions of ZnCl2, CdCl2, CuCl2, (CH3COO)2Zn, (CH3COO)2Cd, (CH3COO)2Cu, and CH3COOAg inhibited H2S volatilization almost entirely. The strengths of H2S volatilization inhibition were in the order Ag+ > Cd2+ > Cu2+ > Zn2+. The effect of zinc ions on the growth of oral bacteria was strain-dependent. Fusobacterium nucleatum ATCC 25586 was the most sensitive, as it was suppressed by medium containing 0.001% zinc ions. Conclusions Zinc ions have an inhibitory effect on oral malodor involving the two mechanisms of direct binding with gaseous H2S and suppressing the growth of VSC-producing oral bacteria.

International Union of Basic and Clinical Pharmacology. CII: Pharmacological Modulation of H2S Levels: H2S Donors and H2S Biosynthesis Inhibitors.

Over the last decade, hydrogen sulfide (H2S) has emerged as an important endogenous gasotransmitter in mammalian cells and tissues. Similar to the previously characterized gasotransmitters nitric oxide and carbon monoxide, H2S is produced by various enzymatic reactions and regulates a host of physiologic and pathophysiological processes in various cells and tissues. H2S 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 H2S, either based on H2S donation or inhibition of H2S biosynthesis. H2S donation can be achieved through the inhalation of H2S gas and/or the parenteral or enteral administration of so-called fast-releasing H2S donors (salts of H2S such as NaHS and Na2S) or slow-releasing H2S donors (GYY4137 being the prototypical compound used in hundreds of studies in vitro and in vivo). Recent work also identifies various donors with regulated H2S 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 H2S-donating groups (the most advanced compound in clinical trials is ATB-346, an H2S-donating derivative of the non-steroidal anti-inflammatory compound naproxen). For pharmacological inhibition of H2S synthesis, there are now several small molecule compounds targeting each of the three H2S-producing enzymes cystathionine-ß-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 H2S 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 H2S donors and H2S biosynthesis inhibitors, delineates their mode of action, and offers examples for their biologic effects and potential therapeutic utility.

Endogenous hydrogen sulphide attenuates NLRP3 inflammasome-mediated neuroinflammation by suppressing the P2X7 receptor after intracerebral haemorrhage in rats.

BACKGROUND: Emerging studies have demonstrated the important physiological and pathophysiological roles of hydrogen sulphide (H2S) as a gasotransmitter for NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome-associated neuroinflammation in the central nervous system. However, the effects of H2S on neuroinflammation after intracerebral haemorrhage (ICH), especially on the NLRP3 inflammasome, remain unknown. METHODS: We employed a Sprague-Dawley rat of collagenase-induced ICH in the present study. The time course of H2S content and the spatial expression of cystathionine-ß-synthase (CBS) after ICH, the effects of endogenous and exogenous H2S after ICH, the effects of endogenous and exogenous H2S on NLRP3 inflammasome activation under P2X7 receptor (P2X7R) overexpression after ICH, and the involvement of the P2X7R in the mechanism by which microglia-derived H2S prevented NLRP3 inflammasome activation were investigated. RESULTS: We found ICH induced significant downregulation of endogenous H2S production in the brain, which may be the result of decreasing in CBS, the predominant cerebral H2S-generating enzyme. Administration of S-adenosyl-L-methionine (SAM), a CBS-specific agonist, or sodium hydrosulfide (NaHS), a classical exogenous H2S donor, not only restored brain and plasma H2S content but also attenuated brain oedema, microglial accumulation and neurological deficits at 1 day post-ICH by inhibiting the P2X7R/NLRP3 inflammasome cascade. Endogenous H2S production, which was derived mainly by microglia and above treatments, was verified by adenovirus-overexpressed P2X7R and in vitro primary microglia studies. CONCLUSIONS: These results indicated endogenous H2S synthesis was impaired after ICH, which plays a pivotal role in the P2X7R/NLRP3 inflammasome-associated neuroinflammatory response in the pathogenesis of secondary brain injury. Maintaining appropriate H2S concentrations in the central nervous system may represent a potential therapeutic strategy for managing post-ICH secondary brain injury and associated neurological deficits.

[Research progress of the association of hydrogen sulfide with colorectal cancer and its associated anti-tumor drugs].

As the third confirmed gaseous transmitters, hydrogen sulfide was found to play a vital role in the eternal milieu both physiologically and pathologically. What's intriguing is that, there exists a debate about the role of hydrogen sulfide in the pathogenesis of cancer, especially colorectal cancer. In this manuscript, progress of the effect of low and high dose hydrogen sulfide on the tumorigenesis of colorectal cancer and research on the antitumor new drugs stemmed from the function of hydrogen sulfide is summarized. Recently, the "bell-shape" model of the action of hydrogen sulfide illustrated that hydrogen sulfide was able to promote the progression of tumor in low dose and inhibit the progression of tumor in high dose. Based on these results, both hydrogen sulfide synthesis inhibitors and hydrogen sulfide donors(chimeras with NSAIDs) have been widely studied as potential anti-tumor novel drugs. According to the actual results of present studies, hydrogen sulfide synthesis inhibitors featured by aminooxyacetic acid (AOA) is more promising as a novel kind of drug. The future research based on the relationship between hydrogen sulfide and rectal cancer may bring insights into the development of novel anti-tumor drugs, thus producing tremendous potential clinical value.