Pyridoxal-5-phosphate induced cardioprotection in aging associated with up-expression of cystathionine-γ-lyase, 3-mercaptopyruvate sulfurtransferase, and ATP-sensitive potassium channels.

BACKGROUND: In the present work, we investigated the cardioprotective potential of pyridoxal-5-phosphate (PLP) in old rats as a cofactor of enzymes that synthesize hydrogen sulphide (H2 S). MATERIALS AND METHODS: PLP was administered per os in a dose of 0.7 mg per kg daily for 2 weeks. Rats were divided into three groups (adult, old and old +PLP) of 20 animals. The cardiac mRNA levels of genes encoding H2 S-synthesizing enzymes cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST), uncoupling proteins (UCP3), subunits of ATP-sensitive potassium (KATP ) channels were determined using real-time polymerase chain reaction analysis. We also studied the effect of PLP-administration on the content of H2 S, oxidative stress, the activities of inducible and constitutive NO-synthase (iNOS, cNOS), arginase and nitrate reductase in the heart homogenates as well as cardiac resistance to ischemia-reperfusion in Langendorff-isolated heart model. RESULTS: It was shown that PLP restored mRNA levels of CSE, 3-MST and UCP3 genes, and H2 S content and also significantly increased the expression of SUR2 and Kir6.1 (2.2 and 3.3 times, respectively) in the heart of old rats. PLP significantly reduced the formation of superoxide, malondialdehyde, diene conjugates as well as the activity of iNOS and arginase. PLP significantly increased constitutive synthesis of NO and prevented reperfusion disturbances of the heart function after ischemia. CONCLUSIONS: Thus, PLP-administration in old rats was associated with up-expression of CSE, 3-MST, UCP3 and SUR2 and Kir6.1 subunits of KATP channels, and also increased cNOS activity and reduced oxidative stress and prevented reperfusion dysfunction of the heart in ischemia-reperfusion.

Zofenopril Protects Against Myocardial Ischemia-Reperfusion Injury by Increasing Nitric Oxide and Hydrogen Sulfide Bioavailability.

BACKGROUND: Zofenopril, a sulfhydrylated angiotensin-converting enzyme inhibitor (ACEI), reduces mortality and morbidity in infarcted patients to a greater extent than do other ACEIs. Zofenopril is a unique ACEI that has been shown to increase hydrogen sulfide (H2S) bioavailability and nitric oxide (NO) levels via bradykinin-dependent signaling. Both H2S and NO exert cytoprotective and antioxidant effects. We examined zofenopril effects on H2S and NO bioavailability and cardiac damage in murine and swine models of myocardial ischemia/reperfusion (I/R) injury. METHODS AND RESULTS: Zofenopril (10 mg/kg PO) was administered for 1, 8, and 24 hours to establish optimal dosing in mice. Myocardial and plasma H2S and NO levels were measured along with the levels of H2S and NO enzymes (cystathionine ß-synthase, cystathionine γ-lyase, 3-mercaptopyruvate sulfur transferase, and endothelial nitric oxide synthase). Mice received 8 hours of zofenopril or vehicle pretreatment followed by 45 minutes of ischemia and 24 hours of reperfusion. Pigs received placebo or zofenopril (30 mg/daily orally) 7 days before 75 minutes of ischemia and 48 hours of reperfusion. Zofenopril significantly augmented both plasma and myocardial H2S and NO levels in mice and plasma H2S (sulfane sulfur) in pigs. Cystathionine ß-synthase, cystathionine γ-lyase, 3-mercaptopyruvate sulfur transferase, and total endothelial nitric oxide synthase levels were unaltered, while phospho-endothelial nitric oxide synthase(1177) was significantly increased in mice. Pretreatment with zofenopril significantly reduced myocardial infarct size and cardiac troponin I levels after I/R injury in both mice and swine. Zofenopril also significantly preserved ischemic zone endocardial blood flow at reperfusion in pigs after I/R. CONCLUSIONS: Zofenopril-mediated cardioprotection during I/R is associated with an increase in H2S and NO signaling.

A novel mercaptopyruvate sulfurtransferase thioredoxin-dependent redox-sensing molecular switch: a mechanism for the maintenance of cellular redox equilibrium.

An intermolecular disulfide bond serves as a thioredoxin-dependent redox-sensing switch for the regulation of the enzymatic activity of 3-mercaptopyruvate sulfurtransferase (MST, EC.2.8.1.2). A cysteine residue on the surface of each subunit was oxidized to form an intersubunit disulfide bond so as to decrease MST activity, and thioredoxin-specific conversion of a dimer to a monomer increased MST activity. Further, a low redox potential sulfenate was reversibly formed at a catalytic site cysteine so as to inhibit MST, and thioredoxin-dependent reduction of the sulfenate restored the MST activity. Concludingly, MST partly contributes to the maintenance of cellular redox homeostasis via exerting control over cysteine catabolism.

In vitro and in vivo comparison of sulfur donors as antidotes to acute cyanide intoxication.

Antidotes for cyanide (CN) intoxication include the use of sulfane sulfur donors (SSDs), such as thiosulfate, which increase the conversion of CN to thiocyanate by the enzyme rhodanese. To develop pretreatments that might be useful against CN, SSDs with greater lipophilicity than thiosulfate were synthesized and assessed. The ability of SSDs to protect mice against 2LD50 of sodium cyanide (NaCN) administered either 15 or 60 min following administration of an SSD was assessed. To study the mechanism of action of the SSD, the candidate compounds were examined in vitro for their effect on rhodanese and 3-mercaptopyruvate sulfurtransferase (MST) activity under increasing SSD concentrations. Tests were conducted on nine candidate SSDs: ICD1021 (3-hydroxypyridin-2-yl N-[(N-methyl-3-aminopropyl)]-2-aminoethyl disulfide dihydrochloride), ICD1022, (3-hydroxypyridin-2-yl N-[(N-methyl-3-aminopropyl)]-2-aminoethyl disulfide trihydrochloride), ICD1584 (diethyl tetrasulfide), ICD1585 (diallyl tetrasulfide), ICD1587 (diisopropyl tetrasulfide); ICD1738 (N-(3-aminopropyl)-2-aminoethyl 2-oxopropyl disulfide dihydrochloride), ICD1816 (3,3'-tetrathiobis-N-acctyl-L-alanine), ICD2214 (2-aminoethyl 4-methoxyphenyl disulfide hydrochloride) and ICD2467 (bis(4-methoxyphenyl) disulfide). These tests demonstrated that altering the chemical substituent of the longer chain sulfide modified the ability of the candidate SSD to protect against CN toxicity. At least two of the SSDs at selected doses provided 100% protection against 2LD50 of NaCN, normally an LD99. All compounds were evaluated using locomotor activity as a measure of potential adverse behavioral effects. Positive hypoactivity relationships were found with several disulfides but none was found with ICD1584, a tetrasulfide. Separate studies suggest that the chemical reaction of potassium cyanide (KCN) and cystine forms the toxic metabolite 2-iminothiazolidine-4-carboxylic acid. An alternative detoxification pathway, one not primarily involving the sulfur transferases. may be important in pretreatment for CN intoxication. Although studies to elucidate the precise mechanisms are needed. it is clear that these newly synthesized compounds provide a new rationale for anti-CN drugs, with fewer side-effects than the methemoglobin formers.

Involvement of protein kinase C in the regulation of glycolipid sulfotransferase activity levels in renal cell carcinoma cells.

Accumulation of sulfolipids associated with elevated levels of glycolipid sulfotransferase activities has previously been demonstrated in renal cell carcinoma cells. To investigate the role of protein kinase C in the synthesis of sulfolipids, the effects of 12-O-tetradecanoylphorbol-13-acetate and protein kinase C inhibitors on glycolipid sulfotransferase activity levels were examined in a human renal cell carcinoma cell line, SMKT-R3. Continuous treatment of the cells with 12-O-tetradecanoylphorbol-13-acetate caused a dose- and time-dependent reduction of the sulfotransferase activity levels. Similarly, protein kinase C inhibitors, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride and staurosporine, reduced the enzyme activities in a dose-dependent manner. These observations suggest that the glycolipid sulfotransferase activity levels are regulated by protein kinase C in SMKT-R3 cells. Furthermore, long-term 12-O-tetradecanoylphorbol-13-acetate treatment resulted in a reduction of sulfolipid synthesis and a decrease of the expression of sulfolipids on the cell surface. Taken together, it is suggested that protein kinase C is involved in the synthesis of sulfolipids through the regulation of the glycolipid sulfotransferase activity levels in renal cell carcinoma cells.