Mechanism of toxicity of the antimelanoma drug 4-hydroxyanisole in mouse hepatocytes.
To elucidate the mechanism of the hepatotoxicity of 4-hydroxyanisole (4-HA), its effect on the viability of mouse hepatocytes in suspension was investigated. Cell viability was assessed by measurement of release of lactate dehydrogenase into the medium. 4-HA was cytotoxic in a concentration-dependent and time-dependent fashion with an IC50 of 0.26 mmol/l after 4 h incubation. Almost all cells were killed after exposure to 4-HA for 4 h at 0.5 mmol/l or for 2 h at 1.0 mmol/l. At 5 and 10 mmol/l, 4-HA caused less cytotoxicity and 1 mmol/l or below. On coincubation with the P450 inhibitor octylamine, 4-HA cytotoxcity was reduced, which suggests the involvement of cytochrome P450 in the hepatocytotoxicity of this drug. Induction of P450 isoenzymes IA, IIB and IIE1 by pretreatment of mice with phenobarbitone, 3-methylcholanthrene or acetone had no significant effect on the toxicity of 4-HA towards hepatocytes. Depletion of hepatic glutathione by pretreatment of mice with buthionine sulphoximine (1.6 g/kg, intraperitoneally) 4 h before cell isolation led to an increase in 4-HA cytotoxicity. Incubation with N-acetylcysteine (10 mmol/l) abolished the cytotoxicity of 4-HA (1 mmol/l). Both these results are consistent with the intermediacy of a reactive metabolite of 4-HA. Production of hydroquinone by oxidative demethylation of 4-HA as toxication mechanism can be excluded as formation of formaldehyde was not observed on incubation of 4-HA with mouse liver microsomes. 3,4-diacetoxyanisole, a prodrug of the known 4-HA metabolite 3,4-dihydroxyanisole, was not more cytotoxic towards hepatocytes than 4-HA.(ABSTRACT TRUNCATED AT 250 WORDS)
Schiller
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Department of Pharmaceutical Sciences, Aston University, Birmingham, U.K.
Gescher
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Jheeta
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D000082:Acetaminophen / Q000037:antagonists & inhibitors; D000588:Amines / Q000494:pharmacology; D000818:Animals; D000840:Anisoles / Q000633:toxicity*; D002470:Cell Survival / Q000187:drug effects; D065607:Cytochrome P-450 Enzyme Inhibitors; D004305:Dose-Response Relationship, Drug; D005978:Glutathione / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008099:Liver / Q000187:drug effects* / Q000201:enzymology; D051379:Mice; D013997:Time Factors
D000588:Amines; D000840:Anisoles; D065607:Cytochrome P-450 Enzyme Inhibitors; D000082:Acetaminophen; C009760:mequinol; D007770:L-Lactate Dehydrogenase; D005978:Glutathione; C008699:octylamine