Search

Lindane-induced seizure in rats is a model of refractory generalized epilepsy. Hydrogen sulfide (H2S) is a gasotransmitter with different physiological and pathological roles. Cystathionine-?-synthase (CBS) is a major enzyme responsible for H2S production in the brain. The aim of this study was to investigate the effects of H2S production inhibition using aminooxyacetate (a CBS inhibitor) on behavioral and EEG manifestations of lindane-induced seizures. Male Wistar rats with previously implanted EEG electrodes were intraperitoneally (i.p.) treated with 4 mg/kg lindane and observed for convulsive behavior and EEG manifestations during the next 30 min. Aminooxyacetate (5, 15 and 25 mg/kg, i.p.) or saline, was injected 30 min prior to lindane. Convulsive behavior was assessed by seizure incidence, latency time and severity (grades 0-4). The number and duration of ictal periods in the EEG were also analyzed. Seizure incidence was higher in rats treated with aminooxyacetate (AOA) before lindane, but not significantly when compared with those treated only with lindane. However, AOA significantly decreased the latency time and augmented the severity of lindane-induced seizures in a dose-dependent manner. EEG analysis revealed an increased number and duration of ictal periods in rats receiving AOA prior to lindane. H2S production inhibition aggravated lindane-induced seizures, which showed a functional relationship between H2S and the effects of lindane.

Diabetes dramatically increases the risk of cardiovascular complications. The endothelial dysfunction and diastolic heart dysfunction are associated with a decreasing level of hydrogen sulfide (H2S) and inhibition of the activity of endothelial nitric oxide synthase (NOS) in diabetes. The aim of this study is to investigate the effect of modulation of H2S synthesis on heart functions and vasorelaxation in diabetes. The dl-propargylglycine and l-cysteine were administered intraperitoneally. H2S content in the heart tissue, markers of oxidative stress, inducible NOS and constitutive NOS (cNOS) activities, endothelium-dependent vasorelaxation of the aortic rings, and heart function were studied. We demonstrate that our combination increased H2S synthesis 13 times and cNOS activity 5 times in the heart tissue of diabetic rats. Increasing NO and H2S production caused improvement and restoration of endothelium-dependent relaxation of aorta, effective arterial elastance, and diastolic heart function in diabetic rats. The endothelium-dependent relaxation increased 2.4 times; effective arterial elastance decreased by 47%. The end-diastolic myocardial stiffness decreased 2.2 times. Thus, modulation of H2S synthesis leads to increased cNOS activity by up to 5 times in the cardiovascular system. Increasing NO and H2S production restored endothelium-dependent relaxation of aorta and improved heart function in diabetes.

Background/Aims: Overproliferation of mesangial cells was believed to play an important role in the progress of diabetic nephropathy, one of the primary complications of diabetes. Hydrogen sulfide (H2S), a well-known and pungent gas with the distinctive smell of rotten eggs, was discovered to play a protective role in diabetic nephropathy. Methods: MTT assay was used to examine the viability of mesangial cells. Small interfering RNA was used to knock down the expression of TLR4 while specific inhibitor LY294002 to suppress the function of PI3K. H2S generation rate was determined by a H2S micro-respiration sensor. Results: Glucose of 25mM induced significant mesangial cells proliferation, which was accomplished by significantly inhibited endogenous H2S synthesis. And exogenous H2S treatment by NaHS markedly mitigated the overproliferation of mouse mesangial cells. Furthermore, it was found that H2S deficiency could result in TLR4 activation. And H2S supplementation remarkably inhibited TLR4 expression and curbed the mesangial cell overproliferation. Besides, PI3K/Akt pathway inhibition also significantly ameliorated the cell overproliferation. Conclusion: High glucose (HG) induces mouse mesangial cell overproliferation via inhibition of hydrogen sulfide synthesis in a TLR-4-dependent manner. And PI3K/Akt pathway might also play a vital part in the HG-induced mesangial cell overproliferation.

Hydrogen sulfide (H2S) is an endogenous gas transmitter with profound effects on the cardiovascular system. We hypothesized that stimulation of H2S synthesis might alleviate age-associated changes in vascular reactivity. Pyridoxal-5-phosphate (PLP), the coenzyme of H2S-synthesizing enzymes, was administrated to old male Wistar rats per os at a dose of 0.7 mg/kg body mass once a day for 2 weeks. H2S content in the aortic tissue, markers of oxidative stress, inducible nitric oxide synthase (iNOS) and constitutive nitric oxide synthase (cNOS), arginase activities, and endothelium-dependent vasorelaxation of the aortic rings were studied. Our results showed that PLP restored endogenous H2S and low molecular weight S-nitrosothiol levels in old rat aorta to the levels detected in adults. PLP significantly reduced diene conjugate content, hydrogen peroxide and peroxynitrite generation rates, and iNOS and arginase activity in the aortic tissue of old rats. PLP also greatly improved acetylcholine-induced relaxation of old rat aorta (47.7% ± 4.8% versus 18.4% ± 4.1% in old rats, P < 0.05) that was abolished by NO inhibition with N-nitro-l-arginine methyl ester hydrochloride (L-NAME) or H2S inhibition with O-carboxymethylhydroxylamine (O-CMH). Thus, PLP might be used for stimulation of endogenous H2S synthesis and correction of oxidative and nitrosative stress and vessel tone dysfunction in aging and age-associated diseases.

Poster presentation

The effects of hydrogen sulfide (H2S) and acute hypoxia are similar in isolated pulmonary arteries from various species. However, the involvement of H2S in hypoxic pulmonary vasoconstriction (HPV) has not been studied in the intact lung. The present study used an intact, isolated, perfused rat lung preparation to examine whether adding compounds essential to H2S synthesis or to its inhibition would result in a corresponding increase or decrease in the magnitude of HPV. Western blots performed in lung tissue identified the presence of the H2S-synthesizing enzymes, cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfur transferase (3-MST), but not cystathionine β-synthase (CBS). Adding three H2S synthesis precursors, cysteine and oxidized or reduced glutathione, to the perfusate significantly increased peak arterial pressure during hypoxia compared with control ( P < 0.05). Adding α-ketoglutarate to enhance the 3-MST enzyme pathway also resulted in an increase ( P < 0.05). Both aspartate, which inhibits the 3-MST synthesis pathway, and propargylglycine (PPG), which inhibits the CSE pathway, significantly reduced the increases in arterial pressure during hypoxia. Diethylmaleate (DEM), which conjugates sulfhydryls, also reduced the peak hypoxic arterial pressure at concentrations >2 mM. Finally, H2S concentrations as measured with a specially designed polarographic electrode decreased markedly in lung tissue homogenate and in small pulmonary arteries when air was added to the hypoxic environment of the measurement chamber. The results of this study provide evidence that the rate of H2S synthesis plays a role in the magnitude of acute HPV in the isolated perfused rat lung.

Hydrogen sulfide (H 2S) is a biological mediator produced by enzyme-regulated pathways from L-cysteine, which is a substrate for cystathionine-γ-lyase (CSE). In myocardium, endogenously and exogenously administered H2S has been shown to protect against ischemia-reperfusion injury. We hypothesized that L-cysteine exerts its protective action through stimulation of H2S production. Rat isolated hearts were Langendorff-perfused and underwent 35-minute regional ischemia and 120-minute reperfusion. L-cysteine perfusion from 10 minutes before ischemia until 10 minutes after reperfusion limited infarct size in a concentration-dependent manner, maximal at 1 mmol/L (control 36.4% ± 2.4% vs L-cysteine 24.3% ± 3.4%, P < .05). This protective action was attenuated by the CSE inhibitor, DL-propargylglycine (PAG) 1 mmol/L (31.4 ± 5.9%, not significant vs control) but administration of the CSE cofactor pyridoxal-5′-phosphate (PLP) 50 μmol/L did not enhance the effect of L-cysteine. Ten minutes normoxic perfusion with L-cysteine 1 mmol/L caused a 3-fold increase in myocardial H2S concentration (0.64 ± 0.16 vs 2.01 ± 0.07 μmol/g protein, P < .01), an effect that was significantly attenuated by PAG (1.17 ± 0.15 μmol/g protein). These data provide evidence that exogenous L-cysteine administration limits ischemia-reperfusion injury through a mechanism that appears to be at least partially dependent on H2S synthesis.

Cystathionine β-synthase (CBS) is a key enzyme in human (patho)physiology with a central role in hydrogen sulfide metabolism. The enzyme is composed of a pyridoxal 5'-phosphate-binding catalytic domain, flanked by the following two domains: a heme-binding N-terminal domain and a regulatory C-terminal domain binding S-adenosyl-l-methionine (AdoMet). CO or NO(•) binding at the ferrous heme negatively modulates the enzyme activity. Conversely, AdoMet binding stimulates CBS activity. Here, we provide experimental evidence for a functional communication between the two domains. We report that AdoMet binding significantly enhances CBS inhibition by CO. Consistently, we observed increased affinity (∼5-fold) and faster association (∼10-fold) of CO to the ferrous heme at physiological AdoMet concentrations. NO(•) binding to reduced CBS was also enhanced by AdoMet, although to a lesser extent (∼2-fold higher affinity) as compared with CO. Importantly, CO and NO(•) binding was unchanged by AdoMet in a truncated form of CBS lacking the C-terminal regulatory domain. These unprecedented observations demonstrate that CBS activation by AdoMet puzzlingly sensitizes the enzyme toward inhibition by exogenous ligands, like CO and NO(•). This further supports the notion that CBS regulation is a complex process, involving the concerted action of multiple physiologically relevant effectors.

Hydrogen sulfide, like nitric oxide, was best known as a toxic pollutant before becoming recognized as a key regulator of several physiologic processes. In recent years, evidence has accumulated to suggest important roles for hydrogen sulfide as a mediator of several aspects of gastrointestinal and liver function. Moreover, alterations in hydrogen sulfide production could contribute to disorders of the gastrointestinal tract and liver. For example, nonsteroidal anti-inflammatory drugs can reduce production of hydrogen sulfide in the stomach, and this has been shown to contribute to the generation of mucosal injury. Hydrogen sulfide has also been shown to play a key role in modulation of visceral hyperalgesia. Inhibitors of hydrogen sulfide synthesis and drugs that can generate safe levels of hydrogen sulfide in vivo have been developed and are permitting interventional studies in experimental models and, in the near future, humans.

Hydrogen sulfide (H2S) is an important modulator of many aspects of digestive function, both in health and disease. Colonic tissue H2S synthesis increases markedly during injury and inflammation and appears to contribute to resolution. Some of the bacteria residing in the colon can also produce H2S. The extent to which bacterial H2S synthesis contributes to what is measured as colonic H2S synthesis is not clear. Using conventional and germ-free mice, we have delineated the eukaryotic vs. prokaryotic contributions to colonic H2S synthesis, both in healthy and colitic mice. Colonic tissue H2S production is entirely dependent on the presence of the cofactor pyridoxal 5′-phosphate (vitamin B6), while bacterial H2S synthesis appears to occur independent of this cofactor. As expected, approximately one-half of the H2S produced by feces is derived from eukaryotic cells. While colonic H2S synthesis is markedly increased when the tissue is inflamed, and, in proportion to the extent of inflammation, fecal H2S synthesis does not change and tissue granulocytes do not appear to be the source of the elevated H2S production. Rats fed a B vitamin-deficient diet for 6 wk exhibited significantly diminished colonic H2S synthesis, but fecal H2S synthesis was not different from that of rats on the control diet. Our results demonstrate that H2S production by colonic bacteria does not contribute significantly to what is measured as colonic tissue H2S production, using the acetate trapping assay system employed in this study.

Hydrogen sulfide is one of three gases involved in biological functions and synthesized in vivo. Like NO and CO, it seems to act as a neuromodulator: it modulates NMDA glutamate receptor function. CBS seems to be the only source of hydrogen sulfide in the brain, whereas the liver synthesizes hydrogen sulfide via cystathionase. In the heart, the third pathway for the hydrogen sulfide synthesis, the 3-mercaptopyruvate pathway is used. Only two diseases characterized by alterations of hydrogen sulfide metabolism have been described: decreased hydrogen sulfide synthesis in the brains of Alzheimer's disease patients and increased hydrogen sulfide synthesis due to the overexpression of CBS in Down syndrome patients.