Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.6.1.2 (alanine aminotransferase)
26,722 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pretreatment of fasted rats with aminooxyacetic acid (AOAA, 0.25 mmol kg-1, i.p.), methimazole (MTZ, 0.35 mmol kg-1, i.p.) and acivicin (AT-125, 56 mumol kg-1, i.p.) 30 min prior to a 4-h inhalation exposure to 180-200 ppm or 150-180 ppm vinylidene chloride (VDC) was used to study the role of cysteine beta-lyase, cysteine conjugate S-oxidase and gamma-glutamyltranspeptidase (gamma-GT) in VDC-induced liver and kidney toxicity. Pretreatment with AOAA reduced by 65-95% those increases in serum alanine aminotransferase (ALAT), glutamate dehydrogenase (GLDH) and sorbitol dehydrogenase (SDH) caused by exposure to 180-200 ppm VDC. This pretreatment also prevented VDC-induced increases in aspartate aminotransferase (ASAT) and N-acetyl-beta-d-glucosaminidase (NAG) activities and in the concentration of beta 2-microglobulin (beta 2-m) in 24-h urine samples. There was only a slight potentiation of VDC-induced liver and renal toxicities by MTZ given before exposure to 180-200 ppm VDC, but potentiation became significant (40-80%) when MTZ was administered before a slightly lower level of exposure (150-180 ppm). Pretreatment with AT-125 did not significantly change the liver and renal effects of exposure to 180-200 ppm VDC. These results suggest that the formation of a cysteine conjugate may be involved in the renal and liver toxicity of VDC in fasted rats.
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PMID:Role of cysteine conjugation in vinylidene chloride-induced nephrotoxicity and hepatotoxicity in fasted rats. 893 83

Long-term exposure to trichloroethylene can cause kidney cancer in experimental animals and humans. In addition, dichloroacetylene (a breakdown product of trichloroethylene) is nephrotoxic and neurotoxic. Both trichloroethylene and dichloroacetylene are metabolized in part to the corresponding cysteine S-conjugate (i.e. S-(1,2-dichlorovinyl)-L-cysteine) which is toxic. Cysteine S-conjugate beta-lyases convert S-(1,2,dichlorovinyl)-L-cysteine to pyruvate, ammonia and a reactive fragment that adds to macromolecules, depletes cellular thiols and causes lipid peroxidation. We now show that S-(1,2-dichlorovinyl)-L-cysteine and another nephrotoxic cysteine S-conjugate, S-(1,1,2,2-tetrafluoroethyl)-L-cysteine, inactive purified cytosolic aspartate aminotransferase and purified alanine aminotransferase. These cysteine S-conjugates also inactive aspartate aminotransferase in cytosolic and mitochondrial fractions of rat brain and kidney. The present results suggest that some halogenated xenobiotics may be toxic in part through their conversion to the corresponding cysteine S-conjugate which inactivates key pyridoxal 5'-phosphate-containing enzyme.
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PMID:Inactivation of brain and kidney aspartate aminotransferases by S-(1,2,-dichlorovinyl)-L-cysteine and by S-(1,1,2,2,-tetrafluoroethyl)-L-cysteine. 894 Jun 25

The two conjugates, S-[N-(2-hydroxyethyl)carbamoylmethyl]glutathione (GSAAE), and its corresponding mercapturic derivative N-acetyl-S-[N-(2-hydroxyethyl)carbamoylmethyl]cysteine (NCySAAE) were administered to fasted Sprague-Dawley rats as putative metabolites of vinylidene chloride (VDC). Methylthioacetylaminoethanol (MAAE) was identified in the urine of GSAAE- or NCySAAE-treated rats (0.5-2.0 mmol/kg, i.p.), as well as in the urine of VDC-treated rats (0.5-2.0 mmol/kg, p.o.). The effects of VDC, GSAAE and NCySAAE on the kidney and liver were also examined using aspartate aminotransferase (ASAT). N-acetyl-beta-D-glucosaminidase (NAG) and beta 2-microglobulin (beta 2-m) as urinary parameters of nephrotoxicity, and glutamate dehydrogenase (GLDH), sorbitol dehydrogenase (SDH) and alanine aminotransferase (ALAT) as serum parameters of hepatotoxicity. Unlike treatment with VDC, treatment with both GSAAE and NCySAAE failed to cause kidney and liver toxicity. The results support the hypothesis that MAAE originates from the formation of GSAAE and further metabolization to NCySAAE, and that MAAE excretion does not reveal a pathway of reactive intermediates.
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PMID:Formation of GSH-derivatives as a pathway for inactive intermediates in vinylidene chloride-treated rats. 900 91

We have recently observed that S-(2-hydroxyethylmercapto)-L-cysteine (L-CySSME), the mixed disulfide of L-cysteine and 2-mercaptoethanol, prevented cataracts induced in mice by acetaminophen (ACP) by functioning as a prodrug of L-cysteine and protecting the liver. This prompted the evaluation of the more lipophilic N-acetyl (Ac-CySSME) and ethyl ester (Et-CySSME) derivatives of L-CySSME as proprodrug forms, as well as the "D" enantiomer, as hepatoprotective agents. Serum ALT levels were measured at 24 hours after a toxic but nonlethal dose of ACP that insured 48 hour survival of the animals. Since the increases in ALT produced were highly variable (even after log transformation) and complicated the statistical analyses, we calculated confidence intervals for the mean ALT levels for each treatment group. This enabled comparisons to be made of the efficacy of L-CySSME as well as Ac-CySSME and Et-CySSME with other representative prodrugs of L-cysteine, namely, 2(RS)-methylthiazolidine-4(R)-carboxylic acid (MTCA), L-2-oxothiazolidine-4-carboxylic acid (OTCA), and N-acetyl-L-cysteine (NAC), in protecting the liver. It was shown that L-CySSME and MTCA administered intraperitoneally at 2.5 mmol/kg were superior to the other cysteine prodrugs at equimolar doses in protecting mice from hepatotoxicity elicited by a 400 mg/kg (2.65 mmol/kg) dose of ACP given i.p. 30 minutes prior to the prodrugs. The "D" form of CySSME was totally without protective effect. Oral doses of the prodrugs even at 2x the i.p. dose were less effective, although MTCA was the most protective.
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PMID:Protection against acetaminophen-induced hepatotoxicity by L-CySSME and its N-acetyl and ethyl ester derivatives. 917 40

Phenethyl isothiocyanate (PEITC), a compound derived from cruciferous and other vegetables, is a potent inhibitor of cytochrome P450 2E1. This enzyme catalyzes the bioactivation of acetaminophen (APAP) and many other xenobiotics. The present study investigated the effects of PEITC on APAP metabolism and associated hepatotoxicity in Swiss-Webster mice. When PEITC (19-150 micromol/kg) was given to mice intragastrically 1 hr before or immediately prior to a toxic dose of APAP, the APAP-induced hepatotoxicity was significantly decreased or was completely prevented. The extent of toxicity was evaluated by mortality, serum levels of glutamic-pyruvic transaminase, lactate dehydrogenase, and liver histopathology. Pretreatment of mice with ethanol enhanced APAP hepatotoxicity; this enhanced toxicity could also be prevented by the administration of PEITC. PEITC treatment prevented the depletion of hepatic glutathione levels caused by oxidized APAP metabolites. PEITC treatment also significantly decreased the plasma levels of oxidized APAP metabolites (analyzed as APAP-glutathione, APAP-cysteine, and APAP-N-acetylcysteine) and reduced the urinary excretion of APAP-cysteine. In microsomal incubations, PEITC effectively inhibited the rate of APAP-glutathione formation from APAP as well as the P450 2E1-dependent N-nitrosodimethylamine demethylase and the P450 1A2-dependent ethoxyresorufin O-deethylase activities. The protective action of PEITC against APAP toxicity is attributed to the blocking of APAP activation through inhibition of P450 enzymes.
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PMID:Effects of phenethyl isothiocyanate on acetaminophen metabolism and hepatotoxicity in mice. 919 14

Because current standard therapy of chronic hepatitis C with alpha interferon is less than ideal, numerous other approaches have been studied. Iron in the liver, particularly that found in vascular endothelial cells of portal tracts, has been associated with decreased responsiveness to alpha interferon therapy. Iron reduction alone, generally achieved by therapeutic phlebotomy, regularly has been associated with biochemical improvement (decrease in serum alanine aminotransferase), but not with virological improvement. Iron reduction has been reported to increase the therapeutic response to alpha interferon. Most studies of this combination have been conducted in patients who had not responded to interferon alone; in these patients, improved responsiveness has been observed in some, but not all studies. In patients not previously treated, iron reduction was found in a recent trial to improve the sustained biochemical and virological response rate from 5% to 29%. Hepatic iron and chronic hepatitis C increase oxidative stress in the liver and are associated with decreases in hepatic glutathione levels. In one report, administration of N-acetyl cysteine, a sulfhydryl donor, led to improved response to interferon in chronic hepatitis C. Several cytokines and immunomodulators have undergone limited study; perhaps the most promising of these is thymosin alpha-1. In one small study, amantadine was found to produce some response in patients who previously had failed to respond to interferon. Ursodiol improves serum aminotransferase levels in chronic hepatitis C but has no antiviral effect, nor has it been found to improve histologic abnormalities. The future of therapy of chronic hepatitis C will likely include measures to decrease oxidative stress and injury and multidrug combinations, including inhibitors of the hepatitis C viral protease and RNA polymerase.
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PMID:Therapy of hepatitis C: other options. 930 80

cis-Diamminedichloroplatinum (cisplatin) is an important anticancer drug used to treat solid tumors. The nephrotoxicity of cisplatin is recognized as the most important dose-limiting factor, but high doses of cisplatin also produce hepatotoxicity. However, little is known about cisplatin-induced liver injury and the role of metallothionein, a cysteine-rich, metal-binding protein, in modulating its hepatotoxicity. This study was designed to examine cisplatin hepatotoxicity in control and metallothionein-I/II knockout (MT-null) mice. Animals were given a single injection of cisplatin (50-200 mumol/kg i.p.), and liver injury was evaluated 3-16 h later. Cisplatin produced dose- and time-dependent liver injury, as evidenced by increased serum activity of alanine aminotransferase (ALT), as well as by histopathology. Apoptosis, rather than necrosis, predominates in cisplatin-induced liver injury, as indicated by increased numbers of apoptotic cells (hematoxylin and eosin staining), in situ apoptotic DNA detection, and DNA fragmentation on agarose gel electrophoresis. MT-null mice were more sensitive than controls to cisplatin-induced hepatotoxicity. Cisplatin (200 mumol/kg) was lethal to 12% of control mice, but 60% of MT-null mice died within 16 h. At the dose of 150 mumol/kg, serum ALT activities were increased 2-fold in control mice compared to 6.5-fold in MT-null mice. Apoptotic lesions were more pronounced in MT-null than in control mice. MT-null mice were also more susceptible than controls to cisplatin-induced nephrotoxicity, as evidenced by having higher blood urea nitrogen concentrations. Furthermore, cultured MT-null hepatocytes were more sensitive than control cells to the cytotoxicity of cisplatin (50-200 microM), as indicated by lactate dehydrogenase leakage into the medium. These results demonstrate that (1) high doses of cisplatin produce hepatotoxicity, with apoptosis as the major lesion, and (2) MT protects against cisplatin-induced liver injury.
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PMID:Metallothionein (MT)-null mice are sensitive to cisplatin-induced hepatotoxicity. 951 23

We examined the effect of gamma-glutamylcysteinylethyl ester (gamma-GCE), which is readily transported into hepatocytes and increases hepatocellular reduced glutathione (GSH) levels, on the progression of carbon tetrachloride (CCl4)-induced liver injury in mice in comparison with that of GSH. Administration of more than 160 micromol/kg of gamma-GCE, but not GSH, to mice at 3 h after intraperitoneal injection of CCl4 (1 ml/kg) significantly attenuated increases in serum aspartate aminotransferase and alanine aminotransferase activities at 24 h after the CCl4 injection. Increases in hepatic lipid peroxide (LPO) concentrations and decreases in hepatic GSH concentrations after the CCl4 injection were significantly diminished by the gamma-GCE (160 micromol/kg) administration, but not by the same dose of GSH. Gamma-GCE, gamma-glutamylcysteine, and cysteine acted as substrates for glutathione peroxidases much less efficiently than GSH in the post-mitochondrial fraction of normal mouse liver cells. These results indicate that gamma-GCE attenuates the progression of CCl4-induced acute liver injury in mice through the maintenance of hepatic GSH levels, leading to inhibition of hepatic LPO formation, which could be due to an efficient utilization of GSH converted from gamma-GCE in the liver cells.
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PMID:Gamma-glutamylcysteinylethyl ester attenuates progression of carbon tetrachloride-induced acute liver injury in mice. 958 92

Cisplatin [cis-dichlorodiammineplatinum (II)] is a widely used chemotherapeutic drug that is toxic to the kidney. Concurrent administration of cysteine together with vitamin E, Crocus sativus and Nigella sativa reduced the toxicity of cisplatin in rats. When administered i.p. for 5 alternate days with 3 mg/kg cisplatin, cysteine (20 mg/kg) together with vitamin E (2 mg/rat) an extract of Crocus sativus stigmas (50 mg/kg) and Nigella sativa seed (50 mg/kg) significantly reduced blood urea nitrogen (BUN) and serum creatinine levels as well as cisplatin-induced serum total lipids increases. In contrast, the protective agents given together with cisplatin led to an even greater decrease in blood glucose than that seen with cisplatin alone. The serum activities of alkaline phosphatase, lactate dehydrogenase, malate dehydrogenase, aspartate aminotransferase and alanine aminotransferase of cisplatin-treated rats were significantly decreased, whereas the activities of glutathione reductase and isocitrate dehydrogenase were significantly increased. Addition of cysteine and vitamin E, Crocus sativus and Nigella sativa in combination with cisplatin partially prevented many changes in the activities of serum enzymes. In cisplatin-treated rats, the liver activities of isocitrate dehydrogenase and aspartate aminotransferase were significantly increased, whereas much greater changes were found in the kidneys, with increased activity of glucose-6-phosphate dehydrogenase and decreased activities of alkaline phosphatase, isocitrate dehydrogenase, malate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, sorbitol dehydrogenase and gamma-glutamyl transferase, as well as a decreased phosphorylation to oxidation ratio in the mitochondria, indicating reduced adenosine triphosphate production. Also, administration of cysteine and vitamin E, Crocus sativus and Nigella sativa together with cisplatin partially reversed many of the kidney enzymes changes induced by cisplatin. Cysteine together with vitamin E, Crocus sativus and Nigella sativa tended to protect from cisplatin-induced falls in leucocyte counts, haemoglobin levels and mean osmotic fragility of erythrocytes and also prevented the increase in haematocrit. The results of this study indicate a basis for the toxic effects of cisplatin, and suggest a possible way of counteracting the toxicity by introducing protective agents such sulphydryl compounds, other antioxidants and extracts of natural products. It also appears that cells adapt to the effects of cisplatin through the induction of systems that produce NADPH, which in turn compensates the decrease of free sulphydryl groups. We conclude that cysteine and vitamin E, Crocus sativus and Nigella Sativa may be a promising compound for reducing cisplatin-toxic side effects including nephrotoxicity.
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PMID:Protective effect of cysteine and vitamin E, Crocus sativus and Nigella sativa extracts on cisplatin-induced toxicity in rats. 960 69

Treatment of mice with a toxic dose of acetaminophen (300 mg/kg, ip) significantly increased hepatotoxicity at 4 h, as evidenced by histological necrosis in the centrilobular areas of the liver, and increased serum levels of alanine aminotransferase (ALT) (from 8 +/- 1 IU/L in saline-treated mice to 3226 +/- 892 IU/L in the acetaminophen-treated mice). Serum levels of nitrate plus nitrite (a marker of nitric oxide synthesis) were also increased from 62 +/- 8 microM in saline-treated mice to 110 +/- 14 microM in acetaminophen-treated mice (P < 0.05). Regression analysis of serum ALT levels to serum nitrate plus nitrite levels in individual mice revealed a positive, linear relationship between serum ALT levels and serum nitrate plus nitrite levels with a correlation coefficient of 0.9 (P < 0.05). The y intercept value (nitrate plus nitrite level) was 63 +/- 15 microM. Immunohistochemical analysis of liver sections from acetaminophen-intoxicated mice using an anti-3-nitrotyrosine antibody indicated tyrosine nitration in the proteins of the centrilobular cells. Tyrosine nitration has been shown to occur by peroxynitrite, a reactive intermediate formed by an extremely rapid reaction of nitric oxide and superoxide and a species which also has hydroxyl radical-like activity. Analysis of liver sections using an anti-acetaminophen antiserum indicated the centrilobular cells also contained acetaminophen-protein adducts, a reaction of the metabolite N-acetyl-p-benzoquinone imine with cysteine residues on proteins. These data are consistent with acetaminophen metabolic activation leading to increased synthesis of nitric oxide and superoxide and to peroxynitrite as an important intermediate in the toxicity.
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PMID:Nitrotyrosine-protein adducts in hepatic centrilobular areas following toxic doses of acetaminophen in mice. 962 27


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