diethyl-maleate and Necrosis

Sustained activation of the c-Jun NH(2)-terminal kinase (JNK) signaling pathway mediates the development and progression of experimental diet-induced nonalcoholic fatty liver disease (NAFLD). Delineating the mechanism of JNK overactivation in the setting of a fatty liver is therefore essential to understanding the pathophysiology of NAFLD. Both human and experimental NAFLD are associated with oxidative stress and resultant lipid peroxidation, which have been proposed to mediate the progression of this disease from simple steatosis to steatohepatitis. The ability of oxidants and the lipid peroxidation product 4-hydroxynonenal (HNE) to activate JNK signaling suggested that these two factors may act synergistically to trigger JNK overactivation. The effect of HNE on hepatocyte injury and JNK activation was therefore examined in cells under chronic oxidant stress from overexpression of the prooxidant enzyme cytochrome P450 2E1 (CYP2E1), which occurs in NAFLD. CYP2E1-generated oxidant stress sensitized a rat hepatocyte cell line to death from normally nontoxic concentrations of HNE. CYP2E1-overexpressing cells underwent a more profound depletion of glutathione (GSH) in response to HNE secondary to decreased gamma-glutamylcysteine synthetase activity. GSH depletion led to overactivation of JNK/c-Jun signaling at the level of mitogen-activated protein kinase kinase 4 that induced cell death. Oxidant stress and the lipid peroxidation product HNE cause synergistic overactivation of the JNK/c-Jun signaling pathway in hepatocytes, demonstrating that HNE may not be just a passive biomarker of hepatic oxidant stress but rather an active mediator of hepatocellular injury through effects on JNK signaling.

Topics: Aldehydes; Animals; Apoptosis; Catalase; Cell Death; Cell Line, Transformed; Cytochrome P-450 CYP2E1; Extracellular Signal-Regulated MAP Kinases; Glutamate-Cysteine Ligase; Glutathione; Glutathione Transferase; Heat-Shock Response; Hepatocytes; Hydrogen Peroxide; JNK Mitogen-Activated Protein Kinases; Maleates; Malondialdehyde; MAP Kinase Kinase 4; Necrosis; Oxidative Stress; Phosphorylation; Proto-Oncogene Proteins c-jun; Rats; Reactive Oxygen Species; Signal Transduction; Transcription Factor AP-1; Transfection

Hypothermia induces injury in its own right, but the mechanisms involved in the cell damage are still unclear. The aim of this study was to test the effects that glutathione (GSH) depletion induces on cell death in isolated rat hepatocytes, kept at 4 degrees C for 20 h, by modulating intracellular GSH concentration with diethylmaleate and buthionine sulfoximine (DEM and BSO). Untreated hepatocytes showed Annexin V stained cells (AnxV(+)), scarce propidium iodide stained cells (PI(+)) and presented a low level of lactate dehydrogenase (LDH) leakage after 20 h at 4 degrees C and rewarming at 37 degrees C. When DEM and BSO were added before cold storage, we observed a few AnXV(+) cells and an increase in PI(+) cells associated with LDH release in the incubation medium. Conversely, the addition of DEM and BSO only during rewarming caused a marked increase in cell death by apoptosis. Production of reactive oxygen species (ROS) and thiobarbituric acid species (TBARS), associated with a decrease in GSH concentrations, was higher when DEM and BSO were added before cold storage. Cells treated with DEM and BSO before cold storage showed lower ATP energy stores than hepatocytes treated with DEM and BSO only during rewarming. Pretreatment of hepatocytes with deferoxamine protected against apoptotic and necrotic morphology in conditions of GSH depletion. These results suggest that pretreatment of hepatocytes with DEM and BSO before cold storage induces necrosis, while the treatment of hepatocytes only during rewarming increases apoptosis. In both conditions, iron represents a crucial mediator of cell death.

Topics: Analysis of Variance; Animals; Annexin A5; Apoptosis; Buthionine Sulfoximine; Cell Count; Deferoxamine; Glutathione; Hepatocytes; L-Lactate Dehydrogenase; Male; Maleates; Necrosis; Propidium; Rats; Rats, Wistar; Reactive Oxygen Species; Rewarming; Thiobarbituric Acid Reactive Substances; Time Factors

The effect of reduced glutathione (GSH) depletion by acetaminophen (APAP), diethylmaleate (DEM), or phorone on the mode of cell death and susceptibility to tumor necrosis factor (TNF)-induced cell death was studied in cultured mouse hepatocytes. Dose-dependent necrosis was the exclusive mode of cell death with APAP alone, but the addition of TNF-alpha induced a switch to about half apoptosis without changing total loss of viability. This effect was seen at 1 and 5 mmol/L but was inhibited at 10 and 20 mmol/L APAP. The switch to apoptosis was associated with increased caspase activities, release of cytochrome c, and DNA laddering and was inhibited by caspase inhibitors. DEM and phorone also induced dose-dependent necrosis. Treatment with TNF-alpha under these conditions lead to incremental cell death in the form of apoptosis at 0.25 and 0.5 mmol/L DEM and 0.1 and 0.2 mmol/L phorone. At 1.0 and 2.0 mmol/L DEM and 0.5 mmol/L phorone, 90% to 100% necrosis was observed with resistance to TNF-alpha effects. The apoptosis with TNF-alpha plus DEM was confirmed by DNA laddering and inhibition by caspase inhibitors. However, in the presence of caspase inhibitors, the increment in cell death induced by TNF-alpha persisted as an increase in necrosis. A combination of antioxidants, vitamin E, and butylated hydroxytoluene (BHT) markedly inhibited necrosis induced by APAP or DEM alone, but the sensitization to TNF-alpha-induced apoptosis was unaffected. GSH monoethylester (GSH-EE) protected against necrosis and apoptosis. In conclusion, depletion of GSH by APAP, DEM, or phorone causes oxidative stress-induced necrosis and sensitizes to an oxidative stress independent TNF-alpha-induced apoptosis.

Topics: Acetaminophen; Animals; Antioxidants; Apoptosis; Butylated Hydroxytoluene; Caspase Inhibitors; Caspases; Cells, Cultured; Cytochrome c Group; DNA Fragmentation; Glutathione; Hepatocytes; Ketones; Maleates; Mice; Mice, Inbred C57BL; Necrosis; NF-kappa B; Oxidative Stress; Tumor Necrosis Factor-alpha; Vitamin E

Manipulation of the intracellular redox state has been shown to alter cell activation pathways with resultant changes in cellular function. Previous studies have suggested that thiol oxidation, using the glutathione-depleting agent diethyl maleate (DEM), was able to inhibit endothelial cell activation. We hypothesized that this agent might exert beneficial effects following endotoxemia in the rat, a model in which transendothelial migration of neutrophils is central to the development of hepatocellular injury. Sprague-Dawley rats treated intraperitoneally with lipopolysaccharide (LPS) (200 microg/kg) plus D-galactosamine (GalN) (600 mg/kg) developed hepatocellular necrosis, as evidenced by liver enzyme release and morphological changes. Pretreatment with DEM abrogated this injury in a dose-dependent fashion. Histology revealed reduced neutrophil accumulation in both the parenchyma and sinusoids, consistent with reduced neutrophil sequestration and transendothelial migration. This effect appeared to be related to the ability of DEM to prevent LPS-induced up-regulation of both vascular cell adhesion molecule-1 (VCAM-1) mRNA and intercellular adhesion molecule-1 (ICAM-1) mRNA in the liver, as well as reducing tumor necrosis factor (TNF) mRNA expression. In addition, DEM prevented hepatocyte apoptosis following LPS treatment. The effect was reproduced when TNF was used as an inflammatory stimulus, suggesting a direct protective effect on the hepatocyte. Taken together, these studies show that redox manipulation through thiol oxidation may represent a novel approach to preventing liver necrosis and apoptosis in inflammatory conditions.

Topics: Alanine Transaminase; Animals; Apoptosis; Endotoxemia; Glutathione; Intercellular Adhesion Molecule-1; Liver; Male; Maleates; Necrosis; NF-kappa B; Oxidation-Reduction; Rats; Rats, Sprague-Dawley; Tumor Necrosis Factor-alpha; Vascular Cell Adhesion Molecule-1

We have shown that urinary taurine level may be used as a biomarker of pathological and biochemical lesions. Detection of changes in the urinary concentration of this low molecular weight metabolite indicates biochemical lesions which may also be associated with pathological damage. Hepatotoxic compounds such as CCl4, galactosamine and thioacetamide that cause hepatic necrosis and compounds such as hydrazine and ethionine that cause fatty liver all result in elevated urinary taurine levels in rats. However compounds which do not cause liver damage, such as cycloheximide, also raise urinary taurine levels. All of these substances are known to or are believed to inhibit protein synthesis. Conversely, compounds which increase protein synthesis, such as phenobarbital and clenbuterol, significantly decrease urinary taurine levels. Compounds which interfere with hepatic GSH synthesis will also change urinary taurine levels. Thus, depletion of GSH with diethyl maleate or phorone decreases urinary taurine whereas inhibition of GSH synthesis with compounds such as buthionine sulphoximine increases urinary taurine levels. In isolated hepatocytes in vitro, leakage of taurine occurs in response to cytotoxic compounds such as hydrazine and allyl alcohol. However, total taurine levels were increased by the hepatotoxicant CCl4. Taurine synthesis is decreased by depletion of GSH with allyl alcohol in isolated hepatocytes. Therefore taurine levels are an important potential biomarker for biochemical lesions induced by chemicals both in vivo and in vitro, in particular changes in protein and GSH synthesis.

Topics: Animals; Biomarkers; Carbon Tetrachloride; Carbon Tetrachloride Poisoning; Cells, Cultured; Clenbuterol; Galactosamine; Glutathione; Ketones; Liver; Liver Diseases; Male; Maleates; Necrosis; Phenobarbital; Rats; Rats, Sprague-Dawley; Taurine; Thioacetamide

Selenium and glutathione have interrelated oxidant defense roles in vivo. Experiments were carried out to determine the effect of glutathione depletion in selenium-deficient rats.. Selenium-deficient and control rats were injected with phorone to deplete glutathione. Histologic assessment of liver and kidney injury was performed at 24 hours. In another experiment, glutathione depletion, lipid peroxidation, and liver injury were measured for 12 hours after phorone administration to determine their relationships with one another. In a final experiment, selenoproteins were correlated with protection against lipid peroxidation and liver necrosis. Selenium-deficient rats were injected with vehicle alone and with 5, 10, or 25 micrograms of selenium/kg. Twelve hours later, selenoproteins were measured in some of the rats, and phorone was injected into others. Liver injury and lipid peroxidation were assessed 6 hours after the phorone injection.. Twenty-four hours after phorone administration (125 mg/kg), centrilobular hepatic necrosis and renal tubular necrosis were evident in selenium-deficient rats but not in controls. The time-course experiment revealed that phorone (250 mg/kg) caused sharp decreases in liver and kidney glutathione levels in both groups within 2 to 4 hours. Lipid peroxidation, as assessed by F2 isoprostane concentrations, in selenium-deficient animals. Liver necrosis, indicated by a rise in plasma ALT, took place in selenium-deficient rats but not in controls. Selenium injections into selenium-deficient rats increased selenoprotein P concentrations from 4% of control to as high as 39% but had little effect on glutathione peroxidase activities. Six hours after phorone administration, rats that had received selenium had no rise in ALT, and the rises in F2 isoprostanes were abolished or attenuated.. We conclude that depletion of glutathione in selenium-deficient liver and kidney leads to necrosis in those organs associated with evidence of lipid peroxidation. Protection against this injury by selenium correlates with selenoprotein P concentration in plasma but not with glutathione peroxidase activity in tissues or in plasma. These findings raise the possibility that selenoprotein P protects cell membranes against oxidant injury and that glutathione is involved in that protection.

Topics: Animals; Buthionine Sulfoximine; Dinoprost; Glutathione; Ketones; Kidney; Lipid Peroxides; Liver; Male; Maleates; Methionine Sulfoximine; Necrosis; Osmolar Concentration; Proteins; Rats; Rats, Sprague-Dawley; Selenium; Selenoprotein P; Selenoproteins

Conjugation with glutathione (GSH) is a mechanism of detoxification of acrylamide (ACR); hence, prior depletion of GSH might be expected to exacerbate ACR's neurotoxicity. GSH levels in female rats were reduced by ip administration of styrene oxide (SO; 250 mg/kg), diethylmaleate (DEM; 0.5 ml/kg), or 2-vinylpyridine (VP; 100 mg/kg) 1.5 or 2 hr prior to a single dose of ACR (100 mg/kg). The time course of GSH depletion following treatment with SO/ACR, DEM/ACR, or VP/ACR showed that all three regimens were equally effective in reducing GSH in liver, cerebellum, cerebral cortex, and hippocampus. GSH levels in the liver were reduced to 4-22% of control levels between 2 and 4 hr after treatment and to 38-57% of control levels in all brain regions between 4 and 8 hr. ACR alone (100 mg/kg) reduced both brain and liver GSH to about 60% of normal. The administration of a second dose of ACR (also 100 mg/kg) 12 hr later further depleted brain and liver GSH to 33% of control. Brains were examined 2, 4, 7, 14, and 30 days after treatment by light and electron microscopy. The administration of SO plus ACR (in either order) produced lesions consisting of pyknotic granule cells confined to the anterior portions of the cerebellum and some of the small neurons of lamina II and III of the cerebral cortex. Electron microscopy revealed condensation of the granule cell chromatin and dissolution of the cytoplasm with the formation of large pericellular spaces. The granule cell lesion was not produced when the time between SO and ACR injections was either 4 or 24 hr. No pathology was observed following treatment with DEM/ACR, VP/ACR, ACR/ACR, vehicle (peanut oil), SO, or ACR alone. It appears that the neurotoxicity in animals treated with SO plus ACR is not directly the result of reduced cellular GSH levels per se, but may involve other detoxification pathways of ACR and SO.

Topics: Acrylamide; Acrylamides; Animals; Cerebellum; Drug Synergism; Epoxy Compounds; Female; Ganglia, Spinal; Glutathione; Glutathione Transferase; Maleates; Necrosis; Pyridines; Rats; Rats, Sprague-Dawley

The mechanisms of the liver damage produced by three glutathione (GSH) depleting agents, bromobenzene, allyl alcohol and diethylmaleate, was investigated. The change in the antioxidant systems represented by alpha-tocopherol (vitamin E) and ascorbic acid were studied under conditions of severe GSH depletion. With each toxin liver necrosis was accompanied by lipid peroxidation that developed only after severe depletion of GSH. The hepatic level of vitamin E was decreased whenever extensive lipid peroxidation developed. In the case of bromobenzene intoxication, vitamin E decreased before the onset of lipid peroxidation. Changes in levels of the ascorbic and dehydroascorbic acid indicated a redox cycling of vitamin C with the oxidative stress induced by all the three agents. Such a change of the redox state of vitamin C (increase of the oxidized over the reduced form) may be an index of oxidative stress preceding lipid peroxidation in the case of bromobenzene. In the other cases, such a change is likely to be a consequence of lipid peroxidation. Experiments carried out with vitamin E deficient or supplemented diets indicated that the pathological phenomena occurring as a consequence of GSH depletion depend on hepatic levels of vitamin E. In vitamin E deficient animals, lipid peroxidation and liver necrosis appeared earlier than in animals fed the control diet. Animals fed a vitamin E supplemented diet had an hepatic vitamin E level double that obtained with a commercial pellet diet. In such animals, bromobenzene and allyl alcohol had only limited toxicity and diethylmaleate none in spite of comparable hepatic GSH depletion. Thus, vitamin E may largely modulate the expression of the toxicity by GSH depleting agents.

Topics: 1-Propanol; Animals; Antioxidants; Ascorbic Acid; Bromobenzenes; Chromatography, High Pressure Liquid; Glutathione; Lipid Peroxidation; Liver; Male; Maleates; Malondialdehyde; Mice; Necrosis; Propanols; Time Factors; Vitamin E

Loxistatin is a possible therapeutic agent of muscular dystrophy. A single oral administration of loxistatin to male rats caused focal necrosis of the liver with inflammatory cell infiltration. The severity of the lesions was dose-dependent up to 200 mg/kg and also manifest by an increase in serum alanine aminotransferase and aspartate aminotransferase activities. Hepatic glutathione (GSH) levels decreased with a maximum 20% depletion within 5 hr after the oral administration of loxistatin. Pretreatment with diethyl maleate did not potentiate the loxistatin-induced hepatic injury. On the other hand, the hepatoprotective effect of cysteamine was observed when cysteamine was administered 24 hr before loxistatin dosing, but the effect was not observed when the antidote was administered concomitantly with loxistatin. Pretreatment of rats with phenobarbital or trans-stilbene oxide provided partial protection against the hepatotoxic effect of loxistatin. Pretreatment with SKF-525A resulted in increased hepatic injury, while pretreatment with piperonyl butoxide, cimetidine, or 3-methylcholanthrene had no effect on hepatic damage by loxistatin. Five hours after [14C]loxistatin administration to rats, the covalent binding of the radioactivity to proteins was greatest in the liver, followed by the kidney, then muscle and blood to a lesser extent. [14C]Loxistatin acid, the pharmacologically active form of loxistatin, irreversibly bound to rat liver microsomal proteins; more binding occurred when the NADPH-generating system was omitted and when the microsomes were boiled first. GSH did not alter the extent of irreversible binding, whereas N-ethylmaleimide decreased the binding of [14C]loxistatin acid to rat liver microsomal proteins by 75%. Unlike the rat, administration of loxistatin to hamsters caused neither hepatic injury nor hepatic GSH depletion even at a high dose (500 mg/kg). Both the distribution and covalent binding of radioactivity in the hamster liver were one-third of those in rats following [14C]loxistatin dosing. These results suggest that loxistatin causes species-specific hepatotoxicity and that, at least in part, some of the toxic effects of loxistatin are mediated by the nonenzymatic covalent binding of loxistatin acid to thiol residues on cellular macromolecules.

Topics: Alanine Transaminase; Animals; Aspartate Aminotransferases; Chemical and Drug Induced Liver Injury; Cricetinae; Cysteamine; Cysteine Proteinase Inhibitors; Drug Interactions; Glutathione; In Vitro Techniques; Leucine; Liver Diseases; Male; Maleates; Mesocricetus; Necrosis; Protein Binding; Rats; Rats, Inbred Strains; Species Specificity; Tissue Distribution

Studies were undertaken to determine if the toxicity and pathology of rubratoxin B, a nephrotoxic and hepatotoxic mycotoxin, could be altered by increasing or decreasing the tissue concentrations of nonprotein sulfhydryls in the liver and kidneys. Rubratoxin B dissolved in DMSO was administered ip to weanling male Syrian hamsters and Mongolian gerbils at doses of 0.4 mg/kg and 2.0 mg/kg, respectively. Rubratoxin B caused a 70% decrease in hepatic and a 60% decrease in renal cortical nonprotein sulfhydryl (NPSH) concentration, an index of tissue reduced glutathione concentration, in both species. Treatment with cysteine prior to rubratoxin B administration did not greatly alter the decreases in NPSH concentration, but did decrease the severity of renal lesions. Treatment with diethyl maleate prior to rubratoxin B administration caused an 80% reduction in hepatic and a 70% reduction in renal NPSH concentration, which was prolonged by rubratoxin B treatment. The incidence and severity of renal lesions was increased in rubratoxin B-treated hamsters and gerbils given diethyl maleate compared to animals given rubratoxin B alone. Additionally, hepatic lesions were seen in hamsters and were more frequent and severe in gerbils that were treated with diethyl maleate prior to rubratoxin B dosing compared to animals given rubratoxin B alone. Renal and hepatocellular NPSH concentration appears to decrease during rubratoxin B toxicosis in the hamster and gerbil, and appears to be contributory in lesion development, since lesions in the liver and kidneys were more severe in animals in which NPSH concentrations were reduced by treatment with diethyl maleate.

Topics: Animals; Cricetinae; Cysteine; Gerbillinae; Kidney; Kidney Tubules; Liver; Male; Maleates; Mesocricetus; Mycotoxins; Necrosis; Sulfhydryl Compounds

Chlorobenzene (CB) was less hepatotoxic to trout than to rats. This difference could not be totally accounted for by reduced absorption in the trout and CB was metabolized in the trout. Glutathione concentrations in trout livers were 1/3 of those of the rat and prior depletion of the tripeptide led to irreversible binding of CB to trout liver protein equivalent to that of rats suffering extensive necrosis. No consistent correlation between glutathione content or protein binding and liver damage was seen in either species.

Topics: Alanine Transaminase; Animals; Benzoflavones; beta-Naphthoflavone; Chlorobenzenes; Glutathione; Liver; Male; Maleates; Necrosis; Neurons; Phenobarbital; Protein Binding; Rats; Rats, Inbred Strains; Salmonidae; Species Specificity; Time Factors; Trout

Acrylonitrile [vinyl cyanide (VCN)] induces acute hemorrhagic focal superficial gastric mucosal necrosis or gastric erosions. In this report the authors have studied the mechanism of the VCN-induced gastric erosions. VCN-induced gastric lesions are coupled with a marked decrease of gastric reduced glutathione (GSH) concentration. Pretreatment of rats with various metabolic modulators (cytochrome P-450 monooxygenase and GSH) before VCN demonstrated that there is an inverse and highly significant correlation between gastric GSH concentration and the VCN-induced gastric erosions. Pretreatment of rats with sulfhydryl-containing compounds protected against the VCN-induced gastric necrosis and blocked the VCN-induced gastric GSH depletion. Furthermore, pretreatment of rats with atropine, which blocks muscarinic receptors, protected rats against the VCN-induced gastric erosions. The working hypothesis is that depletion and/or inactivation of critical endogenous sulfhydryl groups causes configurational changes of cholinergic receptors and increases agonist binding affinity, which, among other actions, leads to the causation of gastric mucosal erosions.

Topics: Acrylonitrile; Animals; Cysteamine; Cytochrome P-450 Enzyme System; Gastric Mucosa; Glutathione; Male; Maleates; Necrosis; Nitriles; Rats; Rats, Inbred Strains

The mechanisms of bromobenzene and iodobenzene hepatotoxicity in vivo were studied in mice. Both the intoxications caused a progressive decrease in hepatic glutathione content. In both instances liver necrosis was evident only when the hepatic glutathione depletion reached a threshold value (3.5-2.5 nmol/mg protein). The same threshold value was evident for the occurrence of lipid peroxidation. Similar results were obtained in a group of mice sacrificed 15-20 hours after the administration of diethylmaleate, a drug which is mainly conjugated with hepatic glutathione without previous metabolism. The correlation between lipid peroxidation and liver necrosis was much more significant than that between covalent binding and liver necrosis. This fact supports the view that lipid peroxidation is the major candidate for the liver cell death produced by bromobenzene intoxication. Moreover, a dissociation of liver necrosis from covalent binding was observed in experiments in which Trolox C (a lower homolog of vitamin E) was administered after bromobenzene poisoning. The treatment with Trolox C, in fact, almost completely prevented both liver necrosis and lipid peroxidation, while not changing at all the extent of the covalent binding of bromobenzene metabolites to liver protein.

Topics: Alanine Transaminase; Animals; Aspartate Aminotransferases; Bromobenzenes; Chemical and Drug Induced Liver Injury; Chromans; Glutathione; Iodobenzenes; Lipid Peroxides; Liver; Liver Diseases; Male; Maleates; Mice; Necrosis; Proteins; Rats; Rats, Inbred Strains

Acute administration of 5 g/kg ethanol resulted in a 35% reduction of glutathione levels but not in increases in lipoperoxidation as measured by diene conjugate levels in mitochondria or in microsomes. Administration of diethylmaleate which markedly decreased glutathione levels by 85% did not render the livers susceptible to lipoperoxidation after ethanol administration. Chronic alcohol administration did not result in detectable changes in diene conjugates with respect to isocaloric sucrose treatment. Liver necrosis when induced by anemia in rats chronically treated with ethanol was not accompanied by increases in diene conjugate levels.

Topics: Animals; Ethanol; Female; Glutathione; Lipid Peroxides; Liver; Maleates; Necrosis; Rats; Rats, Inbred Strains

NMRI Albino mice, in which the hepatic glutathione (GSH) content was decreased by nearly 50% by either the administration of a pure glucose diet or by starvation, were intoxicated with aryl halides, bromobenzene, and iodobenzene (13 and 9 mmol/kg body weight, respectively, p.o.). After both intoxications, the hepatic glutathione content decreased rapidly to very low values, and liver necrosis, as assessed by serum transaminase levels, occurred in about 45 or 60% of the animals (in the case of bromobenzene or iodobenzene, respectively) after a lag phase of 9 or 6 hr. In both instances liver necrosis was evident only when the hepatic GSH depletion reached a threshold value (3.5-2.5 nmols/mg protein). The same threshold value was evident for the occurrence of lipid peroxidation (measured as both carbonyl functions and conjugated dienes in liver phospholipids). The possibility that the depletion in hepatic GSH level is capable of inducing lipid peroxidation and necrosis could be supported by the fact that similar results were obtained after the administration of inethylmaleate (12 mmol/kg, p.o.), a drug which is expected to conjugate directly with GSH without previous metabolism. The covalent binding of reactive metabolites to cellular macromolecules was determined in the case of bromobenzene poisoning. A dissociation between liver necrosis and covalent binding was observed in experiments in which Trolox C, a lower homolog of vitamin E, was administered (270 mumol/kg) 9 and 13 hr after bromobenzene poisoning. The treatment with Trolox C, in fact, almost completely prevented both liver necrosis and lipid peroxidation, while the extent of the covalent binding of bromobenzene metabolites to liver proteins was not altered.

Topics: Animals; Bromobenzenes; Glutathione; Iodobenzenes; Lipid Peroxides; Liver; Male; Maleates; Mice; Mice, Inbred Strains; Necrosis

Exogenous thiol compounds have been reported to protect the stomach from ethanol-induced necrotic lesions. The gastric mucosa contains high levels of an endogenous thiol, glutathion (GSH). Because of the known role of glutathione in protecting against hepatic injury, its role in gastric mucosal cytoprotection was of interest. By use of an animal model for acute gastric injury from ethanol, a close parallel relation between depletion of endogenous mucosal GSH and induction of mucosal protection was demonstrated. Surprisingly, mucosal protection varied inversely with the level of mucosal GSH obtained after treatment with specific GSH-depleting agents (diethyl maleate and cyclohexene-1-one). Depletion of gastric mucosal GSH was associated with an increase in the mucosal content of prostaglandins 6-keto F1 alpha and F2 alpha but not E2. The protective effect induced by GSH-depleting agents was partially reversed by indomethacin in some but not all studies. Although GSH depletors increased gastric juice volume, protection with these agents persisted after the volume and mucosal GSH had returned to control levels and also was not reversed by increasing the dose of ethanol threefold to overcome a possible dilutional effect. We conclude that, contrary to apparent predictions, depletion of endogenous gastric GSH protects the stomach from acute ethanol-induced injury. Although the mechanism of this protection is unknown, a mediation by endogenous release of prostaglandins seems to play a minor role since diethyl maleate was protective even in indomethacin-treated animals.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Cyclohexanones; Dinoprost; Dinoprostone; Ethanol; Gastric Mucosa; Glutathione; Indomethacin; Male; Maleates; Necrosis; Prostaglandins E; Prostaglandins F; Rats; Rats, Inbred Strains

Intraperitoneal administration of the volatile hydrocarbon, naphthalene, resulted in severe bronchiolar epithelial cell necrosis in mice, while hepatic or renal necrosis was not observed. Pulmonary damage and mortality by naphthalene were increased by prior treatment with diethyl maleate and decreased by prior treatment with piperonyl butoxide (1600 mg/kg). SKF 525A pretreatment had no effect on naphthalene-induced pulmonary damage. Administration of [14C]naphthalene resulted in the covalent binding of radiolabel to tissue macromolecules. Highest levels of binding occurred in lung, liver and kidney. Levels of covalent binding reached a maximum 2--4 h after treatment and corresponded to rapid glutathione depletion in lung and liver. Covalent binding was dose-dependent and showed a threshold between 200 and 400 mg/kg which coincided with almost total depletion of tissue glutathione levels. Covalent binding of reactive metabolites was increased 3--4-fold by prior treatment with diethyl maleate, and was decreased 3--4-fold by pretreatment with piperonyl butoxide. These studies support the view that naphthalene-induced pulmonary damage is mediated by the cytochrome P-450-dependent metabolism of naphthalene and that glutathione plays an important role in the detoxification of the lung damaging metabolite(s).

Topics: Animals; Bronchi; Cytochrome P-450 Enzyme System; Glutathione; Lung; Male; Maleates; Mice; Mice, Inbred Strains; Naphthalenes; Necrosis; Piperonyl Butoxide; Proadifen; Tissue Distribution