Sulfide Donor Research Articles

A Hydrogen Sulfide Donor, JK1, Preserves Endothelial Function and Improves Exercise Capacity in Pressure Overload ‐ Induced Heart Failure

Background and HypothesisHydrogen sulfide (H2S) protects against heart failure by ameliorating oxidative stress, improving mitochondrial function, and attenuating apoptosis. At present there is a lack of data demonstrating the protective actions of H2S in the late stages of heart failure. And the effects of H2S on exercise intolerance, the clinical hallmark of heart failure, has not been evaluated in preclinical models. In current study, we tested the efficacy of delayed therapy with a novel H2S donor, JK1, on cardiac function, endothelial function, and exercise capacity in a murine model of pressure overload‐induced heart failure.MethodsMale C57/BL6J mice at 10 weeks (wks) of age were subjected to transverse aortic constriction (TAC) for 18 weeks. JK1 (200 μg/kg/d, n=20) or the H2S deficient control compound (200 μg/kg/d, n=18) was administered via i.p. injection twice per day starting at 10 wks post TAC, in which time all mice had EF lower than 45%. Echocardiography was performed at baseline and tri‐weekly to assess LV structure and function. LV hemodynamics, cardiac fibrosis, vascular reactivity (isolated thoracic aorta), and exercise capacity were measured at the endpoint, 18 wks post TAC.ResultsDelayed treatment with JK1 initiated at 10 wks post TAC reduced LV dilation (p < 0.01) and attenuated eccentric hypertrophy (p < 0.01). However, no significant difference was noted in LV ejection fraction and cardiac fibrosis. JK1 treated mice displayed lower LV end‐diastolic pressure (LVEDP 17.8 ± 1.8 mmHg vs. 22.9 ± 1.23 mmHg, p < 0.05) and improved relaxation time constant (Tau 8 ± 0.27 ms vs. 10.05 ± 0.58 ms, p < 0.01). In addition, aortic vasorelaxation in response to acetylcholine treatment was markedly improved in mice received JK1 treatment (Max. Relaxation 51.8 ± 4.2% vs. 31.5 ± 3.6%, p < 0.01). More importantly, mice received JK1 treatment exhibited improved exercise capacity (Distance 312 ± 13.4 m vs. 89 ± 6.3 m, p < 0.05) as compared to those received control.ConclusionThese results demonstrate that delayed administration of a novel H2S donor, JK1, improves exercise capacity in severe heart failure following TAC. JK1 treatment initiated at 10 weeks post TAC did not improve systolic function or reduce cardiac fibrosis, suggesting that the beneficial effects of 10‐wks‐delayed H2S therapy in pressure overload heart failure are a result of the improved vascular function and LV hemodynamics.Support or Funding Information

Delayed Therapy with A Hydrogen Sulfide Donor, JK1, Protects against Pressure Overload ‐ Induced Heart Failure

Background and HypothesisHydrogen sulfide (H2S) protects against heart failure by ameliorating oxidative stress, improving mitochondrial function, increasing nitric oxide bioavailability, and attenuating apoptosis. However, at present there is insufficient evidence supporting the cardioprotective effects of H2S in delayed‐treatment settings which more closely mimics the heart failure in human. In current study, we tested the efficacy of delayed therapy with a novel H2S donor, JK1, in a murine model of transverse aortic constriction (TAC) induced heart failure (HF).MethodsMale C57/BL6J mice at 10 weeks (wks) of age were subjected to TAC for 18 weeks. JK1 (200 μg/kg/d, n=20) or the control compound that is devoid of H2S (200 μg/kg/d, n=18) was administered via i.p. injection twice per day starting at 3 wks post TAC. Echocardiography was performed at baseline and tri‐weekly for 18 weeks post TAC to assess LV structure and function. LV hemodynamics, cardiac fibrosis, vascular reactivity (isolated thoracic aorta), and exercise capacity were measured at the endpoint.ResultsDelayed treatment with JK1 preserved left ventricular (LV) ejection fraction (LVEF 54.6 ± 1.4% vs. 29.7 ± 2.9%, p < 0.01), reduced LV dilation (p < 0.01), and attenuated eccentric hypertrophy (p < 0.01). JK1 treated mice displayed lower LV end‐diastolic pressure (LVEDP 11.4 ± 0.8 mmHg vs. 22.9 ± 1.2 mmHg, p < 0.01) and improved relaxation time constant (Tau 7.2 ± 0.4 ms vs. 10.05 ± 0.6 ms, p < 0.01). Global cardiac fibrosis was markedly reduced in mice received JK1 treatment (5.8 ± 1.5% vs. 17.1 ± 2.4%, p < 0.01). In addition, acetylcholine‐mediated vasorelaxation was significantly improved in mice received JK1 treatment (Max. Relaxation, 66.1 ± 4.6% vs. 31.5 ± 3.6%, p < 0.01; EC50, 605.3 ± 115.9 nM vs. 161.8 ± 31.5 nM, p < 0.01). More importantly, mice received JK1 treatment had greater exercise capacity when compared to those received control (Distance, 0.520 ± 0.083 km vs. 0.089 ± 0.006 km, p < 0.05).ConclusionThese results demonstrate that delayed administration of a novel H2S donor, JK1, significantly preserves systolic LV function, attenuates fibrotic remodeling, and improves LV hemodynamics. JK1 treatment provides benefits beyond the heart as it significantly ameliorates the damage to endothelium caused by HF. In addition, JK1 treatment markedly enhances the exercise capacity in HF. Studies are currently underway to define the molecular mechanisms involved in JK1‐induced cardiovascular protection.Support or Funding Information

Role of Cranial Temperature in Neuroprotection by Sodium Hydrogen Sulfide After Cardiac Arrest in Mice.

The hydrogen sulfide donor sodium hydrogen sulfide (NaHS) is recognized as a neuroprotective agent, which induces a hibernation-like metabolic state and hypothermia. However, it remains unclear whether it is the sulfide itself or the hypothermia induced by the sulfide that mediates treatment outcomes following cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). We therefore tested whether NaHS improved outcomes following CA/CPR in mice maintained at 35.0°C by active warming during recovery. Adult male mice were subjected to 8 minutes CA/CPR and randomly treated intraperitoneally with either implantation of miniosmotic pump with NaHS (50 μmol/kg/day) for 3 days or vehicle 30 minutes after CPR. A normothermia group had cranial temperatures kept >35.0°C for 6 hours with a heat pad, and a hypothermia group was allowed to spontaneous hypothermia at room temperature (26.0°C). Behavioral testing and histological evaluation of neurons in the CA1 hippocampal region and striatum were performed on days 4 and 12 after CA/CPR. Both cranial and body temperature decreased following CA/CPR in the hypothermia group, and this was enhanced by NaHS treatment. In the active warming (normothermia) group, NaHS protected striatal neurons and improved long-term survival, which was comparable to the hypothermia groups. No differences were found in the CA1 region. Following CA/CPR, NaHS treatment decreased the heart rate, but not the mean arterial pressure. Our study demonstrated that post-CPR treatment with NaHS exerted neuroprotection in mice while maintaining a normal cranial temperature, indicating that NaHS-related neuroprotection is independent of the known protective effect of spontaneous hypothermia.

GYY4137 protects against myocardial ischemia/reperfusion injury via activation of the PHLPP-1/Akt/Nrf2 signaling pathway in diabetic mice

BackgroundThis study explores the protective effects of a hydrogen sulfide donor, morpholin-4-ium 4-methoxyphenyl-morpholino-phosphinodithioate (GYY4137), in the hearts of diabetic mice that had been subjected to myocardial ischemia/reperfusion injury. Diabetes impairs the Akt pathway, in which the Akt protein is dephosphorylated and inactivated by PH domain leucine-rich repeat protein phosphatase-1 (PHLPP-1). However, the function of PHLPP-1 and molecular mechanism that underlies the cardiac protection exerted by GYY4137 remains unknown. MethodsDiabetic or nondiabetic mice were subjected to 45 min of coronary artery occlusion followed by 2 h of reperfusion. H9c2 cells were cultured with normal or high glucose and then subjected to 3 h of hypoxia followed by 6 h of reoxygenation. Pretreatment with GYY4137 was performed in a randomized manner before ischemia/reperfusion or hypoxia/reoxygenation. The infarct size, cardiomyocyte apoptosis, and oxidative stress were measured. Western blotting was conducted to elucidate the protective mechanism. ResultsDiabetic mice or H9c2 cells exposed to high glucose displayed a larger infarct size, more severe cardiomyocyte apoptosis, lower cell viability, and increased oxidative stress, which were associated with increased levels of PHLPP-1 and reduced levels of p-Akt and nuclear factor-erythroid-2-related factor 2 (Nrf2) protein expression. These changes were prevented/reversed by GYYG4137 pretreatment. At the cellular level, PHLPP-1 siRNA attenuated cellular injury, and this was associated with increased p-Akt and nuclear Nrf2 protein, whereas the decrement of Akt phosphorylation induced by LY294002 augmented cellular injury and decreased nuclear Nrf2. ConclusionsGYY4137 activates the PHLPP-1/Akt/Nrf2 pathway to protect against diabetic myocardial ischemia/reperfusion injury.

Post-treatment with a Hydrogen Sulfide Donor Limits Neuronal Injury and Modulates Potassium Voltage-gated Channel Subfamily D Member 2 (Kv4.2) and Potassium Channel Interacting Protein 3 (KChIP3) During Transient Global Cerebral Ischemia.

Although the neuroprotective effect of sodium hydrosulfide (NaHS, a hydrogen sulfide donor) pretreatment has been revealed, the effect of NaHS post-conditioning remains largely unknown. We aimed to investigate the neuroprotective effect of NaHS post-conditioning against transient Global Cerebral Ischemia (tGCI)-induced hippocampal CA1 injury and its underlying molecular mechanism. A tGCI rat model was established using the four-vessel occlusion method for 15 min of ischemia. The survival of hippocampal neurons was determined by Nissl staining and NeuN immunostaining. Protein expression of potassium voltage-gated channel subfamily D member 2 (Kv4.2) and potassium channel interacting protein 3 (KChIP3) was assessed by Immunohistochemistry (IHC) and Western blot. Decreased concentrations (12 and 24 µmol/kg) of NaHS post-conditioning significantly increased the numbers of survival neurons and NeuN-positive neurons in the hippocampal CA1 region at 7 days post-tGCI (all P<0.05). NaHS post-conditioning (24 µmol/kg) at 12 and 24 hr posttGCI can achieve the best protective effect (both P<0.05). IHC data demonstrated that NaHS postconditioning (24 µmol/kg) markedly attenuated tGCI-induced down-regulation of Kv4.2 protein in the hippocampal CA1 region at 26 hr post-tGCI. Confocal images showed that Kv4.2 did not express in the neuronal nuclei but predominantly express in the neuronal dendrites. In addition, NaHS post-conditioning significantly up-regulated Kv4.2 and down-regulated KChIP3 in tGCI rats at 26 and 168 hr post- tGCI (all P<0.05). Decreased concentrations of NaHS post-conditioning at 12-24 hr post-tGCI effectively protected hippocampal CA1 neurons from tGCI-induced injury, which may be through regulating the expression of Kv4.2 and KChIP3.

Light triggered uncaging of hydrogen sulfide (H2S) with real-time monitoring.

An ESIPT based light activated hydrogen sulfide (H2S) donor using a p-hydroxyphenacyl phototrigger has been developed. The unique feature of our H2S donor system is that it provides real-time monitoring of H2S release by a non-invasive fluorescence colour change approach.

Cysteine-activated hydrogen sulfide (H2S) delivery through caged carbonyl sulfide (COS) donor motifs.

Hydrogen sulfide (H2S) is an important biomolecule, and controllable H2S donors are needed to investigate H2S biological functions. Here we utilize cysteine-mediated addition/cyclization chemistry to unmask an acrylate-functionalized thiocarbamate and release carbonyl sulfide (COS), which is quickly converted to H2S by carbonic anhydrase (CA).

GYY4137, an Extended-Release Hydrogen Sulfide Donor, Reduces NMDA-Induced Neuronal Injury in the Murine Retina.

We previously reported that systemic administration with sodium hydrogen sulfide, a rapid-release donor compound of hydrogen sulfide (H2S), protected retinal neurons against N-methyl-D-aspartic acid (NMDA)-induced injury. For clinical application of H2S donors for retinal neurodegeneration, topical administration with an extended-release donor compound will be better. In the present study, we histologically investigated whether GYY4137, an extended-release hydrogen sulfide donor, had a protective effect on NMDA-induced retinal injury in the mice in vivo. Male and female B6.Cg-Tg(Thy1-CFP)23Jrs/J and C57BL/6J mice anesthetized with a mixture of ketamine and xylazine were subjected to intravitreal NMDA injection (80 nmol/eye). GYY4137 was intravitreally administered with NMDA simultaneously. Morphometric evaluation was carried out seven days after NMDA injection. Intravitreal NMDA induced retinal ganglion cell loss. GYY4137 (1, 10 and 100 nmol/eye) significantly reduced retinal ganglion cell loss seven days after NMDA injection. GYY4137 (10 nmol/eye) decreased the numbers of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL)-positive and 8-hydroxy-2'-deoxyguanosine (8-OHdG)-positive cells 12 h after NMDA injection. These results suggest that extended release donor compounds of H2S protect retinal neurons against excitotoxicity induced by intravitreal NMDA in the mice in vivo through its anti-oxidative activity.

Вторичный метаболизм проростков secale cereale при действии донора сероводорода и холодового закаливания

Вторичный метаболизм проростков secale cereale при действии донора сероводорода и холодового закаливания

Effect of Magnetic Field on Blood Oxygen Transport Function during a Hydrogen Sulfide Donor Introduction

Gas transmitters (hydrogen sulfide, H2S, nitric oxide, NO) belong to gaseous signaling compounds, which are important for transduction of physiological signals. However, contribution of hydrogen sulfide to effects of magnetic field (MF) on oxygen transport function is still poorly understood. So, the effect of magnetic field on oxygen transport function of the blood upon the administration of a hydrogen sulfide donor was evaluated in the work. The tail artery of outbred white male rats was exposed to MF, and the drugs affecting hydrogen sulfide formation, namely, sodium hydrosulfide (NaHS); L-arginine; NG -nitro-L-arginine methyl ester (L-NAME), a nonselective inhibitor of NO synthase; and DL-propargylglycine (PAG), an irreversible inhibitor of cystathionine-γ-lyase were injected intraperitoneally for 10 days. Oxygen transport function of the blood, the contents of hydrogen sulfide and nitrate/nitrite anions (NO2− /NO3−) were determined in the blood plasma. It has been shown that an exposure of rats to MF and administration of either NaHS or amino acid L-arginine leads to a decrease in the affinity of hemoglobin for oxygen and is accompanied by an increase in the content of gas transmitters (NO and H2S) in the blood. With the introduction of L-NAME and PAG, the effect of MF on the affinity of hemoglobin for oxygen is not manifested. Thus, MF realizes its effect through the hydrogen sulfide and nitric oxide.

Hydrogen Sulfide Donor NaHS Improves Metabolism and Reduces Muscle Atrophy in Type 2 Diabetes: Implication for Understanding Sarcopenic Pathophysiology

Sarcopenia, a loss of muscle mass and functionality, constitutes a major contributor to disability in diabetes. Hydrogen sulfide (H2S) dynamics and muscle mass regulatory signaling were studied in GK rats, a model for type 2 diabetes (T2D). GK rats exhibited a number of features that are consistent with sarcopenia and T2D including loss of muscle mass and strength, in addition to glucose intolerance, insulin resistance, and impaired β-cell responsiveness to glucose. Mechanistically, activation levels of Akt, a key modulator of protein balance, were decreased in T2D. Consequently, we confirmed reduced activity of mTOR signaling components and higher expression of atrophy-related markers typified by FoxO1/atrogin-1/MuRF1 and myostatin-Smad2/3 signaling during the course of diabetes. We observed in GK rat reduced antioxidant capacity (↓GSH/GSSG) and increased expression and activity of NADPH oxidase in connection with augmented rate of oxidation of lipids, proteins, and DNA. H2S bioavailability and the expression of key enzymes involved in its synthesis were suppressed as a function of diabetes. Interestingly, GK rats receiving NaHS displayed increased muscle Akt/mTOR signaling and decreased expression of myostatin and the FoxO1/MuRF1/atrogin-dependent pathway. Moreover, diabetes-induced heightened state of oxidative stress was also ameliorated in response to NaHS therapy. Overall, the current data support the notion that a relationship exists between sarcopenia, heightened state of oxidative stress, and H2S deficiency at least in the context of diabetes. Moreover, treatment with a potent H2S donor at an early stage of diabetes is likely to mitigate the development of sarcopenia/frailty and predictably reduces its devastating sequelae of amputation.

Role of reactive oxygen species and sulfide-quinone oxoreductase in hydrogen sulfide-induced contraction of rat pulmonary arteries.

Application of H2S (“sulfide”) elicits a complex contraction in rat pulmonary arteries (PAs) comprising a small transient contraction (phase 1; Ph1) followed by relaxation and then a second, larger, and more sustained contraction (phase 2; Ph2). We investigated the mechanisms causing this response using isometric myography in rat second-order PAs, with Na2S as a sulfide donor. Both phases of contraction to 1,000 μM Na2S were attenuated by the pan-PKC inhibitor Gö6983 (3 μM) and by 50 μM ryanodine; the Ca2+ channel blocker nifedipine (1 μM) was without effect. Ph2 was attenuated by the mitochondrial complex III blocker myxothiazol (1 μM), the NADPH oxidase (NOX) blocker VAS2870 (10 μM), and the antioxidant TEMPOL (3 mM) but was unaffected by the complex I blocker rotenone (1 μM). The bath sulfide concentration, measured using an amperometric sensor, decreased rapidly following Na2S application, and the peak of Ph2 occurred when this had fallen to ~50 μM. Sulfide caused a transient increase in NAD(P)H autofluorescence, the offset of which coincided with development of the Ph2 contraction. Sulfide also caused a brief mitochondrial hyperpolarization (assessed using tetramethylrhodamine ethyl ester), followed immediately by depolarization and then a second more prolonged hyperpolarization, the onset of which was temporally correlated with the Ph2 contraction. Sulfide application to cultured PA smooth muscle cells increased reactive oxygen species (ROS) production (recorded using L012); this was absent when the mitochondrial flavoprotein sulfide-quinone oxoreductase (SQR) was knocked down using small interfering RNA. We propose that the Ph2 contraction is largely caused by SQR-mediated sulfide metabolism, which, by donating electrons to ubiquinone, increases electron production by complex III and thereby ROS production.

Reduced Expression of Hydrogen Sulfide–Generating Enzymes Down-Regulates 15-Hydroxyprostaglandin Dehydrogenase in Chorion during Term and Preterm Labor

Chorionic NAD-dependent 15-hydroxyprostaglandin dehydrogenase (PGDH) plays a pivotal role in controlling the amount of prostaglandins in the uterus and has been implicated in the process of labor. Prior studies identified hydrogen sulfide-generating enzymes cystathionine-β-synthetase (CBS) and cystathionine-γ-lyase (CSE) in fetal membranes. We investigated whether hydrogen sulfide is involved in the regulation of PGDH expression in the chorion during labor. The chorionic tissues were obtained from pregnant women at preterm in labor and at term in labor or not in labor at term. Levels of CSE and CBS and hydrogen sulfide production rate were down-regulated in term in labor and preterm in labor groups compared with not in labor at term group. The CBS level correlated to PGDH expression in the chorion. Hydrogen sulfide donor NaHS and precursor l-cysteine dose-dependently stimulated PGDH expression and activity in cultured chorionic trophoblasts. The effect of l-cysteine was blocked by CBS inhibitor and CBS siRNA but not by CSE inhibitor and CSE siRNA. Hydrogen sulfide treatment suppressed miR-26b and miR-199a expression in chorionic trophoblasts. miR-26b and miR-199a mimics blocked hydrogen sulfide upregulation of PGDH expression. Our results indicate that hydrogen sulfide plays pivotal roles in maintenance of PGDH expression in the chorion during human pregnancy. Reduced expression of hydrogen sulfide-generating enzymes contributes to an increased amount of prostaglandins in the uterus during labor.

The role of aspirin, heparin, and other interventions in the prevention and treatment of fetal growth restriction.

Fetal growth restriction and related placental pathologies such as preeclampsia, stillbirth, and placental abruption are believed to arise in early pregnancy when inadequate remodeling of the maternal spiral arteries leads to persistent high-resistance and low-flow uteroplacental circulation. The consequent placental ischaemia, reperfusion injury, and oxidative stress are associated with an imbalance in angiogenic/antiangiogenic factors. Many interventions have centered on the prevention and/or treatment of preeclampsia with results pertaining to fetal growth restriction and small-for-gestational-age pregnancy often included as secondary outcomes because of the common pathophysiology. This renders the study findings less reliable for determining clinical significance. For the prevention of fetal growth restriction, a recent large-study level meta-analysis and individual patient data meta-analysis confirm that aspirin modestly reduces small-for-gestational-age pregnancy in women at high risk (relative risk, 0.90, 95% confidence interval, 0.81-1.00) and that a dose of ≥100 mg should be recommended and to start at or before 16 weeks of gestation. These findings support national clinical practice guidelines. Invitro and invivo studies suggest that low-molecular-weight heparin may prevent fetal growth restriction; however, evidence from randomized control trials is inconsistent. A meta-analysis of multicenter trial data does not demonstrate any positive preventative effect of low-molecular-weight heparin on a primary composite outcome of placenta-mediated complications including fetal growth restriction (18% vs 18%; absolute risk difference, 0.6%; 95% confidence interval, 10.4-9.2); use of low-molecular-weight heparin for the prevention of fetal growth restriction should remain in the research setting. There are even fewer treatment options once fetal growth restriction is diagnosed. At present the only management option if the risk of hypoxia, acidosis, and intrauterine death is high is iatrogenic preterm birth, with the use of peripartum maternal administration of magnesium sulphate for neuroprotection and corticosteroids for fetal lung maturity, to prevent adverse neonatal outcomes. The pipeline of potential therapies use different strategies, many aiming to increase fetal growth by improving poor placentation and uterine blood flow. Phosphodiesterase type 5 inhibitors that potentiate nitric oxide availability such as sildenafil citrate have been extensively researched both in preclinical and clinical studies; results from the Sildenafil Therapy In Dismal Prognosis Early-Onset Intrauterine Growth Restriction consortium of randomized control clinical trials are keenly awaited. Targeting the uteroplacental circulation with novel therapeutics is another approach, the most advanced being maternal vascular endothelial growth factor gene therapy, which is being translated into the clinic via the doEs Vascular endothelial growth factor gene therapy safEly impRove outcome in seveRe Early-onset fetal growth reSTriction consortium. Other targeting approaches include nanoparticles and microRNAs to deliver drugs locally to the uterine arterial endothelium or trophoblast. Invitro and invivo studies and animal models have demonstrated effects of nitric oxide donors, dietary nitrate, hydrogen sulphide donors, statins, and proton pump inhibitors on maternal blood pressure, uteroplacental resistance indices, and angiogenic/antiangiogenic factors. Data from human pregnancies and, in particular, pregnancies with fetal growth restriction remain very limited. Early research into melatonin, creatine, and N-acetyl cysteine supplementation in pregnancy suggests they may have potential as neuro- and cardioprotective agents in fetal growth restriction.

Editorial

Editorial

Evidences of ultraviolet visible spectra of hydrogen sulfide scavenging trans-crotonaldehyde induced by hydrogen peroxide through mitochondria of rat heart

ABSTRACTEvidences of ultraviolet visible spectra of hydrogen sulfide scavenging trans-crotonaldehyde (TCA) induced by hydrogen peroxide through mitochondria were probed for the first time. TCA was induced by hydrogen peroxide through mitochondria. When sodium hydrosulfide as hydrogen sulfide donor, comparison with control, ultraviolet visible spectra of TCA decrease were clear. Hydrogen sulfide released by garlic was detected by ultraviolet visible spectroscopy. When garlic as hydrogen sulfide donors, the ultraviolet visible spectra of TCA decrease were very obvious. The findings are strongly recommended that garlic as safe, stable, and controllable hydrogen sulfide donor become a promising drug which is worthy of further study.

Colonic hydrogen sulfide produces portal hypertension and systemic hypotension in rats

Hydrogen sulfide, a toxic gas, at low concentrations is also a biological mediator in animals. In the colon, hydrogen sulfide is produced by intestinal tissues and gut sulfur bacteria. Gut-derived molecules undergo liver metabolism. Portal hypertension is one of the most common complications contributing to the high mortality in liver cirrhosis. We hypothesized that the colon-derived hydrogen sulfide may affect portal blood pressure. Sprague-Dawley rats were maintained either on tap water (controls) or on water solution of thioacetamide to produce liver cirrhosis (CRH-R). Hemodynamics were measured after administration of either saline or Na2S, a hydrogen sulfide donor, into (1) the colon, (2) the portal vein, or (3) the femoral vein. Expression of enzymes involved in hydrogen sulfide metabolism was measured by RT-PCR. CRH-R showed a significantly higher portal blood pressure but a lower arterial blood pressure than controls. Saline did not affect hemodynamic parameters. In controls, intracolonic hydrogen sulfide decreased arterial blood pressure and portal blood flow but increased portal blood pressure. Similarly, hydrogen sulfide administered into the portal vein decreased arterial blood pressure but increased portal blood pressure. In contrast, hydrogen sulfide administered into the systemic vein decreased both arterial and portal blood pressures. CRH-R showed significantly greater responses to hydrogen sulfide than controls. CRH-R had a significantly higher liver concentration of hydrogen sulfide but lower expression of rhodanese, an enzyme converting hydrogen sulfide to sulfate. In conclusion, colon-administered hydrogen sulfide increases portal blood pressure while decreasing the systemic arterial blood pressure. The response to hydrogen sulfide is more pronounced in cirrhotic rats which show reduced hydrogen sulfide liver metabolism. Therefore, colon-derived hydrogen sulfide may be involved in the regulation of portal blood pressure, and may contribute to portal hypertension. Impact statement Accumulating evidence suggests that gut-derived molecules affect the control of the circulatory system. Mechanisms controlling liver circulation have been profoundly studied; however, the effects of gut bacteria-derived molecules on portal blood pressure have not been established. In the colon, hydrogen sulfide is produced by intestinal tissues and gut sulfur bacteria. We found that colon-administered hydrogen sulfide increases portal blood pressure while decreasing the systemic arterial blood pressure. The hemodynamic response to hydrogen sulfide was more pronounced in cirrhotic rats which showed reduced hydrogen sulfide liver metabolism, i.e. lower expression of rhodanese, an enzyme converting hydrogen sulfide to sulfate. We propose that colon-derived hydrogen sulfide may affect the regulation of portal and arterial blood pressures and may be involved in portal hypertension.

1,2,4-Thiadiazolidin-3,5-diones as novel hydrogen sulfide donors

Hydrogen sulfide (H2S) is an endogenous modulator that plays significant physio-pathological roles in several biological systems. In this research field there is a large interest in developing selective CBS and CSE inhibitors and H2S releasing moieties, that could be either used as therapeutic agents or linked to known drugs. One of the major problem is the limited availability of chemicals that ensure a controlled release of H2S in vitro as well in vivo. Aiming to obtain novel H2S donors, whose release properties could be appropriately modulated, we have synthesized a series of 1,2,4-thiadiazolidine-3,5-diones (THIA 1–10) as innovative donors that could release H2S in controlled manner. All the synthesized compounds were evaluated for their H2S releasing properties by an amperometric approach and for their vasorelaxant ability on aorta rings. In order to rationalize the obtained results, a detailed study on the release mechanism has been performed using the most efficient H2S donor, THIA 3 (Cmax 65.4 μM and EC50 1.7 μM).

Investigations into the carbonic anhydrase inhibition of COS-releasing donor core motifs

Carbonyl sulfide (COS) releasing scaffolds are gaining popularity as hydrogen sulfide (H2S) donors through exploitation of the carbonic anhydrase (CA)-mediated hydrolysis of COS to H2S. The majority of compounds in this emerging class of donors undergo triggerable decomposition (often referred to as self-immolation) to release COS, and a handful of different COS-releasing structures have been reported. One benefit of this donation strategy is that numerous caged COS-containing core motifs are possible and are poised for development into self-immolative COS/H2S donors. Because the intermediate release of COS en route to H2S donation requires CA, it is important that the COS donor motifs do not inhibit CA directly. In this work, we investigate the cytotoxicity and CA inhibition properties of different caged COS donor cores, as well as caged CO2 and CS2 motifs and non-self-immolative control compounds. None of the compounds investigated exhibited significant cytotoxicity or enhanced cell proliferation at concentrations up to 100 μM in A549 cells, but we identified four core structures that function as CA inhibitors, thus providing a roadmap for the future development of self-immolative COS/H2S donor motifs.

Vasoconstriction triggered by hydrogen sulfide: Evidence for Na+,K+,2Cl-cotransport and L-type Ca2+ channel-mediated pathway

ObjectivesThis study examined the dose-dependent actions of hydrogen sulfide donor sodium hydrosulphide (NaHS) on isometric contractions and ion transport in rat aorta smooth muscle cells (SMC). MethodsIsometric contraction was measured in ring aortas segments from male Wistar rats. Activity of Na+/K+-pump and Na+,K+,2Cl-cotransport was measured in cultured endothelial and smooth muscle cells from the rat aorta as ouabain-sensitive and ouabain-resistant, bumetanide-sensitive components of the 86Rb influx, respectively. ResultsNaHS exhibited the bimodal action on contractions triggered by modest depolarization ([K+]o=30mM). At 10−4 M, NaHS augmented contractions of intact and endothelium-denuded strips by ~ 15% and 25%, respectively, whereas at concentration of 10−3M it decreased contractile responses by more than two-fold. Contractions evoked by 10−4M NaHS were completely abolished by bumetanide, a potent inhibitor of Na+,K+,2Cl-cotransport, whereas the inhibition seen at 10−3M NaHS was suppressed in the presence of K+ channel blocker TEA. In cultured SMC, 5×10−5M NaHS increased Na+,K+,2Cl- - cotransport without any effect on the activity of this carrier in endothelial cells. In depolarized SMC, 45Ca influx was enhanced in the presence of 10−4M NaHS and suppressed under elevation of [NaHS] up to 10−3M. 45Ca influx triggered by 10−4M NaHS was abolished by bumetanide and L-type Ca2+ channel blocker nicardipine. ConclusionsOur results strongly suggest that contractions of rat aortic rings triggered by low doses of NaHS are mediated by activation of Na+,K+,2Cl-cotransport and Ca2+ influx via L-type channels.