Subliminal Fas stimulation increases the hepatotoxicity of acetaminophen and bromobenzene in mice.

The hepatotoxicity of several drugs is increased by mild viral infections. During such infections, death receptor ligands are expressed at low levels, and most parenchymal cells survive. We tested the hypothesis that subliminal death receptor stimulation may aggravate the hepatotoxicity of drugs, which are transformed by cytochrome P-450 cytochrome P-450 into glutathione-depleting reactive metabolites. Twenty-four-hour-fasted mice were pretreated with a subtoxic dose of the agonistic Jo2 anti-Fas antibody (1 microg per mouse) 3 hours before acetaminophen (500 mg/kg) or 1 hour before bromobenzene (400 mg/kg) administration. Administration of Jo2 alone increased hepatic inducible nitric oxide synthase nitric oxide synthase but did not modify serum alanine aminotransferase (ALT), hepatic adenosine triphosphate (ATP), glutathione (GSH), cytochrome P-450, cytosolic cytochrome c, caspase-3 activity or hepatic morphology. However, pretreating mice with Jo2 further decreased both hepatic GSH and ATP by 40% 4 hours after acetaminophen administration, and further increased serum ALT and the area of centrilobular necrosis at 24 hours. In mice pretreated with the Jo2 antibody before bromobenzene administration, hepatic GSH 4 hours after bromobenzene administration was 51% lower than in mice treated with bromobenzene alone, and serum ALT activity at 24 hours was 47-fold higher. In conclusion, administration of a subtoxic dose of an agonistic anti-Fas antibody before acetaminophen or bromobenzene increases metabolite-mediated GSH depletion and hepatotoxicity. Subliminal death receptor stimulation may be one mechanism whereby mild viral infections can increase drug-induced toxicity.

Comparison of hepatotoxicity of 1,2-, 1,3- and 1,4-dibromobenzenes: the dynamics of changes of selected parameters of liver necrosis in acute poisoning in mice.

Various doses of dibromobenzene isomers (1,2-dBB, 1,3-dBB, 1,4-dBB) were administered (i.p.) to BALB mice. The levels of reduced glutathione (GSH) and malondialdehyde (MDA) in the liver, and glutamate-pyruvate transaminase (GPT) (EC.2.6.1.2) gamma-glutamyltransferase (gamma-GT) (EC.2.3.2.2) and triglycerides (TG) in the serum were estimated. A considerable decrease of GSH was observed between 2 and 12 h after administration of the compounds. Increases in serum GPT activity (up to 100-fold) and gamma-GT (three-to fivefold) were observed after treatment using 1,2- and 1,3-dibromobenzenes; TG decreased in concentration initially and then slightly increased. Histopathological examination confirmed the strong necrotic effect of 1,2- and 1,3-dBB isomers. No such changes (elevation of serum GPT activity and necrosis) were noticed after 1,4-dBB.

[Antioxidant effect of metallothioneins in acute bromobenzene poisoning in mice]. / Antioksidantnyi éffekt metallotioneinov pri ostroi intoksikatsii brombenzolom u myshei.

An increase in the content of malondialdehyde (MDA) and endogenous metallothioneins (MT) in the liver of mice 1 day after intraperitoneal injection of bromobenzene (0.5-2 g/kg) has been found. An exogenic zinc-MT polymer injected to mice decreases the basal and xenobiotic-induced MDA level in the liver and blood plasma and decreases the acute toxicity of bromobenzene. The mixture modelling zinc-MT composition (albumin, cysteine and zinc) possesses no such properties. A conclusion is made that the protective effect is specific for the MT structure and is induced by antioxidant properties of MT.

Beta-N-acetylhexosaminidase in the urine, kidney and serum of bromobenzene-intoxicated mice.

beta-N-Acetylhexosaminidase isoenzymes were separated from the kidney, serum and urine of normal mice and mice intoxicated with bromobenzene, using DEAE-cellulose chromatography. Both mouse serum and urine showed hexosaminidase profiles similar to the human counterparts with the presence of B (basic), I (intermediate) and A (acidic) isoenzymes. A notable feature was the presence of a high proportion of an intermediate form in mouse urine which is not always present in human urine. Hexosaminidase activity increased significantly in urine of mice intoxicated with bromobenzene. Its increase was time-dependent and due to kidney damage with a release in the urine of hexosaminidase A, I and, in higher proportion, B. No significant differences were observed in mouse kidney and serum profiles following intoxication with bromobenzene. The total activity of hexosaminidase, using 4-methylumbelliferyl-2-acetamido-2-deoxy-beta-D-glucopyranoside as substrate, did not increase in the serum of mice intoxicated with bromobenzene. Both hexosaminidase activity and the isoenzyme pattern in urine can be used as indicators of kidney damage by bromobenzene intoxication.

Measurement of lipid peroxidation in vivo: a comparison of different procedures.

A study was undertaken to investigate whether some of the methods commonly used to detect lipid peroxidation of cellular membranes in vivo correlate with each other. The study was performed with the livers of bromobenzene-intoxicated mice, in which lipid peroxidation develops when the depletion of glutathione (GSH) reaches a threshold value. The methods tested and compared were the following: i) measurement of the malondialdehyde (MDA) content of the liver; ii) detection of diene conjugation absorption in liver phospholipids; iii) measurement of the loss of polyunsaturated fatty acids in liver phospholipids; and iv) determination of carbonyl functions formed in acyl residues of membrane phospholipids as a result of the peroxidative breakdown of phospholipid fatty acids. Correlations among the values obtained with these methods showed high statistical significances, indicating that the procedures measure lipid peroxidation in vivo with comparable reliability. Analogously, the four methods appeared also to correlate when applied to in vitro microsomal lipid peroxidation.

Lipid peroxidation and cellular damage in extrahepatic tissues of bromobenzene-intoxicated mice.

The mechanisms of bromobenzene toxicity in extrahepatic tissues of mice were studied. Kidney, lung, heart and brain were examined. As observed in this as well as in a previous report for the liver, bromobenzene intoxication caused a progressive decrease in the glutathione content of all the tissues examined. Cellular damage (as assessed by both biochemical determinations and histologic observations) appeared after 6 hours in the case of the kidney and the heart and after 15 hours in the case of the lung. Lipid peroxidation (as assessed by the tissue content of malonic dialdehyde, a parameter correlating with both the diene conjugation absorption and the amount of carbonyl functions in cellular phospholipids) was found to occur at the same times at which cellular damage was observed or even before. As in the case of bromobenzene-induced liver injury, when the individual values for cell damage obtained at 15-20 hours were plotted against the corresponding glutathione contents, a severe cellular damage was generally observed when the glutathione levels reached a threshold value (3.0-0.5 nmol/mg protein). Such a glutathione threshold was also observed for the onset of lipid peroxidation. Glutathione depletion and lipid peroxidation are therefore general phenomena occurring not only in the liver but in all the tissues as a consequence of bromobenzene poisoning. The possibility that lipid peroxidation is the cause of bromobenzene-induced damage to liver and extrahepatic tissues is discussed.

The effect of some hepatotoxins on the sulphoxidation of cimetidine in rat.

Sulphoxidation of cimetidine was investigated in male and female rats after pretreatment with the hepatotoxins allyl alcohol, dl-ethionine, thioacetamide and carbon tetrachloride. There was a marked sex difference in cimetidine sulphoxidation in response to the hepatotoxin pretreatment. All the hepatotoxins enhanced cimetidine sulphoxidation in the male rat (P less than 0.01). Carbon tetrachloride and thioacetamide inhibited cimetidine sulphoxidation in the female rat (P less than 0.01) but dl-ethionine and allyl alcohol had no effect on this metabolic pathway.

Liver glutathione depletion induced by bromobenzene, iodobenzene, and diethylmaleate poisoning and its relation to lipid peroxidation and necrosis.

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.

[Glutathione depletion and lipid peroxidation in the mouse brain after bromobenzene poisoning]. / Deplezione di glutatione e perossidazione lipidica nell'encefalo di topo in seguito ad intossicazione con bromobenzene.

Intoxication of NMRI Albino mice with bromobenzene is often followed by the appearance of neurological symptoms. The possibility was investigated that the intoxication results in glutathione (GSH) depletion in central nervous systems as seen in other tissues, and that such a depletion is followed by the development of lipid peroxidation. 18-20 hours after bromobenzene administration (15 mmoles/Kg, p.o.) GSH content of prosencephalic and metencephalic regions was depleted by 39 and 55%, respectively. Lipid peroxidation (measured by the tissue content of malonildialdehyde) was observed only when GSH content reached a threshold value, which was different for prosencephalon as compared to metencephalon (2-1.5 mumoles GSH/g and 1.2-0.7 mumoles GSH/g, respectively). Possible mechanisms underlying the phenomenon are discussed.

Decreased acute hepatotoxicity of carbon tetrachloride and bromobenzene by cholestyramine in the rat.

Numerous factors are known to increase or decrease drug-induced liver injury. The aim of this study was to test the effect of cholestyramine. Cholestyramine, and anion exchange resin binding in the gut substances taken up and metabolized by the liver such as bile salts, vitamins, endotoxins, etc., could indirectly modify drug-induced toxicity. Two groups of animals were studied: cholestyramine-fed and pair-fed controls. Five days after feeding, carbon tetrachloride or corn oil was injected intraperitoneally. Liver function and histology were normal after corn oil injection in both groups. One day after carbon tetrachloride injection liver weight/body weight ratio was lower in the cholestyramine-fed than in the pair-fed group (4.0 +/- 0.4 mean +/- SD vs. 4.4 +/- 0.3, p less than 0.05). Alanine and aspartate aminotransferases were lower (618 +/- 782 IU and 242 +/- 147 IU vs. 8245 +/- 8189 and 1966 +/- 1524 IU, p less than 0.001), as was necrosis (p less than 0.05). Steatosis and inflammatory reaction were similar in both groups. Two and four days later there were no significant differences between the two groups, because necrosis was no longer a major feature in the pair-fed group. Similar experiments were performed with bromobenzene. Here too cholestyramine prevents necrosis but to a much lesser extent. These results confirm that steatosis and necrosis are independent toxic effects of carbon tetrachloride. Cholestyramine, a widely used drug in cholestasis, could provide a potentially clinically important hepatocellular resistance to toxicity from environmental agents.

The influence of ethanol pretreatment on the effects of nine hepatotoxic agents.

The hepatotoxic effects of carbon tetrachloride (0.01 ml/kg i.p.), thioacetamide (50 mg/kg intraperitoneally), paracetamol (0.5 g/kg intraperitoneally), and allyl alcohol (0.05 ml/kg intraperitoneally) as estimated by determination of serum enzyme activities (GOT, GPT, SDH) were enhanced in mice treated with one oral dose of 4.8 g/kg ethanol 16 hrs. previously. Pretreatment of mice with ethanol did not increase the hepatotoxic actions of bromobenzene (0.25 ml/kg intraperitoneally), phalloidin (1.5 mg/kg intraperitoneally), alpha-amanitin (0.75 mg/kg intraperitoneally), and praseodymium (12 mg/kg intravenously) though there was a trend to higher enzyme activities in the case of bromobenzene. In guinea-pigs ethanol also aggravated CCl4-induced liver damage, but only strengthened the hepatotoxic activity of D-galactosamine (150 mg/kg intraperitoneally). Treatment with 4.8 g/kg ethanol did not influence liver glutathione levels in mice but increased aniline hydroxylation in the 9000 x g liver homogenate supernatant of mice and guinea-pigs. A dose of 2.4 g/kg ethanol, on the other hand, neither increased aniline hydroxylase activity nor enhanced carbon tetrachloride-induced hepatotoxicity in mice. It is assumed that the enhanced sensitivity to hepatotoxic agents after treatment with ethanol may be due to an enhanced microsomal activation of these substances.