Effects of endogenous sulfur dioxide on monocrotaline-induced pulmonary hypertension in rats

Pyrrolidine dithiocarbamate attenuates the development of monocrotaline-induced pulmonary arterial hypertension

We aimed to demonstrate the potential protective effects of pyrrolidine dithiocarbamate (PDTC) on monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH). Adult male rats were randomly assigned to 4 groups: control group, MCT-treated rats only, MCT-injected rats treated with PDTC, and PDTC-treated rats only. Blood and tissue samples were collected after the sacrifice. Levels of malondialdehyde (MDA) were measured by using the thiobarbituric acid method. Total antioxidant status (TAS) was determined using a commercially available ImAnOx kit. A histopathological evaluation was accomplished by scoring the degree of severity. Endothelial damage of the main pulmonary artery was evaluated by immunohistochemical labeling of endothelial cells using anti-rat endothelial cell antigen 1 (RECA-1) antibody. MCT-induced right ventricular hypertrophy (RVH) was reduced significantly in the MCT+PDTC-treated group. MDA levels were significantly lowered in the MCT+PDTC-treated group. TAS was significantly higher in the MCT+PDTC-treated group when compared with the rats with PAH. Histopathological examination demonstrated that PDTC treatment reduced the development of inflammation, hemorrhage and congestion, and collagen deposition. In conclusion, PDTC attenuated PAH and protected pulmonary endothelium in rats administered MCT. These findings suggest that PDTC treatment may provide a new effective therapeutic approach in the treatment of PAH.

Sulfur dioxide preconditioning increases antioxidative capacity in rat with myocardial ischemia reperfusion (I/R) injury

BACKGROUND

The study was designed to explore if sulfur dioxide (SO2) preconditioning increased antioxidative capacity in rat with myocardial ischemia reperfusion (I/R) injury.

METHODS

The myocardial I/R model was made by left coronary artery ligation for 30min and reperfusion for 120min in rats. Myocardial infarct size and plasma lactate dehydrogenase (LDH) and creatine kinase (CK) activities, plasma superoxide dismutase (SOD), malondialdehyde (MDA), glutathione peroxidase (GSH-Px) and glutathione (GSH) changes were detected for the rats. The contents of myocardial hydrogen sulfide (H2S) and nitric oxide (NO) were measured. Myocardial protein expressions of SOD1, SOD2, cystathionine γ-lyase (CSE) and iNOS were tested using Western blot.

RESULTS

Myocardial infarction developed and plasma CK and LDH activities were significantly increased in I/R group compared with those in control group, but SO2 preconditioning significantly reduced myocardial infarct size, and plasma CK and LDH activities. SO2 preconditioning successfully increased plasma SOD, GSH and GSH-Px levels and myocardial SOD1 protein expression, but decreased MDA level in rats of I/R group. Compared with controls, the myocardial H2S level and CSE expression were decreased after I/R, but myocardial NO level and iNOS expression were increased. With the treatment of SO2, myocardial H2S level and CSE expression were increased, but myocardial NO level and iNOS expression were decreased compared with those in I/R group.

CONCLUSIONS

SO2 preconditioning could significantly reduce I/R-induced myocardial injury in vivo in association with increased myocardial antioxidative capacity, upregulated myocardial H2S/CSE pathway but downregulated NO/iNOS pathway.

Sulfur dioxide upregulates the inhibited endogenous hydrogen sulfide pathway in rats with pulmonary hypertension induced by high pulmonary blood flow

Pulmonary hypertension (PH) is an important pathophysiological process in the development of many diseases. However, the mechanism responsible for the development of PH remains unknown. The objective of the study was to explore the possible impact of sulfur dioxide (SO2) on the endogenous hydrogen sulfide (H2S) pathway in rats with PH induced by high pulmonary blood flow. Compared with sham group, the systolic pulmonary artery pressure (SPAP) in the shunt group was significantly increased, along with the increased percentage of muscularized arteries and partially muscularized arteries of small pulmonary arteries. Compared with the shunt group, SPAP in the shunt+SO2 group was significantly decreased, and the percentage of muscularized pulmonary arteries was also decreased. Additionally, rats that developed PH had significantly lower levels of SO2 concentration, aspartate aminotransferase (AAT) activity, protein and mRNA expressions of AAT2 in pulmonary tissues. Administration of an SO2 donor could alleviate the elevated pulmonary arterial pressure and decrease the muscularization of pulmonary arteries. At the same time, it increased the H2S production, protein expression of cystathionine-γ-lyase (CSE), mRNA expression of CSE, mercaptopyruvate transsulphurase (MPST) and cystathionine-β-synthase (CBS) in the pulmonary tissue of the rats. The results suggested that endogenous SO2/AAT2 pathway and the endogenous H2S production were downregulated in rats with PH induced by high pulmonary blood flow. However, SO2 could reduce pulmonary arterial pressure and improve the pulmonary vascular pathological changes in association with upregulating endogenous H2S pathway.

Protective effects of methylsulfonylmethane on hemodynamics and oxidative stress in monocrotaline-induced pulmonary hypertensive rats

Methylsulfonylmethane (MSM) is naturally occurring organic sulfur that is known as a potent antioxidant/anti-inflammatory compound. The aim of this study was to investigate the effect of MSM on hemodynamics functions and oxidative stress in rats with monocrotaline- (MCT-) induced pulmonary arterial hypertension (PAH). Wistar rats were randomly assigned to 38-days treatment. MSM was administered to rats at 100, 200, and 400 mg/kg/day doses 10 days before a single dose of 60 mg/kg, IP, MCT. Hemodynamics of ventricles were determined by Powerlab AD instrument. Blood samples were obtained to evaluate changes in the antioxidative system including activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and the level of reduced glutathione (GSH) and malondialdehyde (MDA). Improvements in cardiopulmonary hemodynamics were observed in the MSM-treated pulmonary arterial hypertensive rats, with a significant reduction in right ventricular systolic pressure (RSVP) and an increase in the mean arterial pressure (MAP). The values of CAT, SOD, GSH-px activities, and GSH were significantly lower in MCT-induced PAH (P < 0.01), but they were recovered to control levels of MSM-treated groups. Our present results suggest that long-term administration of the MSM attenuates MCT-induced PAH in rats through modulation of oxidative stress and antioxidant defense.

Sulfur dioxide attenuates LPS-induced acute lung injury via enhancing polymorphonuclear neutrophil apoptosis

AIM

We speculated that the enhanced apoptosis of polymorphonuclear neutrophil (PMN) might be responsible for the inhibition of PMN infiltration in the lung. This study was designed to investigate the effects of sulfur dioxide (SO(2)) on PMN apoptosis in vivo and in vitro, which may mediate the protective action of SO(2) on pulmonary diseases.

METHODS

Acute lung injury (ALI) was induced by intratracheally instillation of lipopolysaccharide (LPS, 100 μg/100 g, in 200 μL saline) in adult male SD rats. SO(2) solution (25 μmol/kg) was administered intraperitoneally 30 min before LPS treatment. The rats were killed 6 h after LPS treatment. Lung tissues were collected for histopathologic study and SO(2) concentration assay. Bronchoalveolar lavage fluid (BALF) was collected for the measurement of PMN apoptosis. For in vitro experiments, rat peripheral blood PMNs were cultured and treated with LPS (30 mg/L) and SO(2) (10, 20 and 30 μmol/L) for 6 h, and apoptosis-related protein expression was detected by Western blotting, and apoptosis rate was measured with flow cytometry.

RESULTS

LPS treatment significantly reduced the SO(2) concentrations in the lung tissue and peripheral blood, as compared with the control group. Pretreatment with SO(2) prevented LPS-induced reduction of the SO(2) concentration in the lung tissue and peripheral blood. LPS treatment significantly reduced PMN apoptosis both in vivo and in vitro, which could be prevented by the pretreatment with SO(2). The protein levels of Caspase-3 and Bax was significantly increased, but Bcl-2 was decreased by the pretreatment with SO(2), as compared with LPS administration alone.

CONCLUSION

SO(2) plays an important role as the modulator of PMN apoptosis during LPS-induced ALI, which might be one of the mechanisms underlying the protective action of SO(2) on pulmonary diseases.

Regulatory effects of sulfur dioxide on the development of atherosclerotic lesions and vascular hydrogen sulfide in atherosclerotic rats

OBJECTIVE

This study was designed to examine the effect of sulfur dioxide (SO(2)) on atherosclerotic progression and endogenous vascular hydrogen sulfide (H(2)S) in rats with atherosclerosis (AS).

METHODS

Twenty-eight male rats were randomly divided into control, AS and AS+SO(2) groups. Rats were given a single dose of vitamin D(3) and fed a high-cholesterol diet for 8 weeks to induce AS. Plasma lipids, aortic ultrastructure, and atherosclerotic lesions were detected at the termination of experiment. Plasma and aortic SO(2) were measured using high-performance liquid chromatography, and aspartate aminotransferase (AAT) 1 and AAT2 mRNAs were detected by real-time PCR. Plasma and aortic H(2)S levels were determined with a sulfide-sensitive electrode. Cystathionine-γ-lyase (CSE) mRNA and protein expression was detected. Plasma glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) activities, malondialdehyde (MDA) and nitric oxide (NO) contents, inducible NO synthase (iNOS) and eNOS activities, and aortic SOD1 and SOD2 expressions were detected.

RESULTS

Marked atherosclerotic lesions with elevated levels of TC and LDL-C were observed in AS rats. While, there were decreased plasma SO(2) levels and aortic SO(2) production, with a reduced aortic AAT activity in atherosclerotic rats. Plasma GSH-Px and SOD activities were decreased but MDA level increased. Plasma NO content and iNOS activity were also increased. SO(2) donor, however, significantly decreased the atherosclerotic lesions with an increased aortic H(2)S/CSE pathway. It elevated plasma GSH-Px and SOD activities, reduced plasma MDA level, and increased NO/NOS pathway.

CONCLUSIONS

SO(2) has a marked anti-atherogenic effect with an increase in endogenous H(2)S production in rats with AS.

Endogenous sulfur dioxide protects against isoproterenol-induced myocardial injury and increases myocardial antioxidant capacity in rats

Recently, sulfur dioxide (SO(2)) was discovered to be produced in the cardiovascular system and to influence important biological processes. Here, we investigated changes in endogenous SO(2)/glutamic oxaloacetic transaminase (GOT) pathway in the development of isoproterenol (ISO)-induced myocardial injury in rats and the regulatory effect of SO(2) on cardiac function, myocardial micro- and ultrastructure, and oxidative stress. Wistar male rats were divided into control, ISO-treated, ISO+SO(2), and SO(2) groups. At the termination of the experiment, parameters of cardiac function and hemodynamics were measured and the micro- and ultrastructure of myocardium and stereological ultrastructure of mitochondria were analyzed. Myocardial SO(2) content was detected by high-performance liquid chromatography. GOT (key enzyme for endogenous SO(2) production) activity and gene (GOT1 and GOT2) expressions were measured, and superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), hydrogen peroxide, and superoxide radical levels were assayed. SOD (SOD1 and SOD2) and GSH-Px (GSH-Px1) gene expressions were also detected. The results showed that SO(2) donor at a dose of 85 mg/(kg day) did not impact the cardiac function and structure of rats, but exerted a subtle influence on myocardial redox status. ISO-treated rats exhibited decreased cardiac function, damaged myocardial structures, and downregulated endogenous SO(2)/GOT pathway. Meanwhile, myocardial oxidative stress increased, whereas antioxidative capacity downregulated. Administration of SO(2) markedly improved cardiac function and ISO-induced myocardial damage by ameliorating the pathological structure of the myocardium and the mitochondria. At the same time, myocardial products of oxidative stress decreased, whereas antioxidative capacity increased. These results suggest that downregulation of the endogenous SO(2)/GOT pathway is likely involved in the pathogenesis of ISO-induced myocardial injury. SO(2) protects against ISO-induced myocardial injury associated with increased myocardial antioxidant capacity in rats.

Kinetic and thermodynamic resolution of the interactions between sulfite and the pentahaem cytochrome NrfA from Escherichia coli

NrfA is a pentahaem cytochrome present in a wide-range of γ-, δ- and ε-proteobacteria. Its nitrite and nitric oxide reductase activities have been studied extensively and contribute to respiratory nitrite ammonification and nitric oxide detoxification respectively. Sulfite is a third substrate for NrfA that may be encountered in the micro-oxic environments where nrfA is expressed. Consequently, we have performed quantitative kinetic and thermodynamic studies of the interactions between sulfite and Escherichia coli NrfA to provide a biochemical framework from which to consider their possible cellular consequences. A combination of voltammetric, spectroscopic and crystallographic analyses define dissociation constants for sulfite binding to NrfA in oxidized (~54 μM), semi-reduced (~145 μM) and reduced (~180 μM) states that are comparable with each other, and the Km (~70 μM) for sulfite reduction at pH 7. Under comparable conditions Km values of ~22 and ~300 μM describe nitrite and nitric oxide reduction respectively, whereas the affinities of nitrate and thiocyanate for NrfA fall more than 50-fold on enzyme reduction. These results are discussed in terms of the nature of sulfite co-ordination within the active site of NrfA and their implications for the cellular activity of NrfA.

Endogenous sulfur dioxide aggravates myocardial injury in isolated rat heart with ischemia and reperfusion

BACKGROUND

Ischemia-reperfusion (I/R) injury is an important clinical problem. This article investigated the role of sulfur dioxide (SO2) in the regulation of cardiac function and in the pathogenesis of cardiac I/R injury in isolated rat heart.

METHODS

Rat hearts isolated on a Langendorff apparatus were divided into control, I/R, I/R+SO2, and I/R+hydroxamate groups. Hydroxamate is an inhibitor of SO2 synthetase. I/R treatment was ischemia for 2 hr in hypothermic solution (4 degrees C), then reperfusion/rewarming (37 degrees C) for 60 min. Cardiac function was monitored by MacLab analog to a digital converter. Determination of sulfite content involved reverse-phase high performance liquid chromatography with fluorescence detection. Myoglobin content of coronary perfusate was determined at 410 nm. Myocardial malondialdehyde (MDA) was determined by thiobarbituric acid method, and conjugated diene (CD) was extracted by chloroform. 5,50-Dithiobis-2-nitrobenzoic acid was used to determine glutathione (GSH).

RESULTS

The results showed that I/R treatment obviously increased myocardial sulfite content, and sulfite content of myocardium was negatively correlated with the recovery rate of left-ventricle developed pressure and positively correlated with the leakage of myoglobin. In postreperfusion, myocardial function recovery was decreased by SO2. During reperfusion, myocardium-released enzymes, MDA and CD level were increased but myocardial GSH content was depressed with the treatment of SO2 donor. Incubation of myocardial tissue with SO2 significantly increased MDA and CD generation.

CONCLUSIONS

Endogenous SO2 might be involved in the pathogenesis of myocardial I/R injury, and its mechanism might be associated with an increase in lipid peroxide level and a decrease in GSH generation.