title: Caffeine potentiation of allyl alcohol-induced hepatotoxicity. II. In vitro study.
abstract: We examined the effects of caffeine (C) on allyl alcohol (AA)- and acrolein (A)-induced hepatotoxicity on freshly-isolated, rat hepatocytes obtained from livers of adult, male, Sprague-Dawley rats. Isolated rat hepatocytes in suspension were incubated in each test with one of the following: 0, 1.0, or 2.5 mM of AA alone; or with 0, 2.5, or 5 mM of C alone; or a combination of AA and C at the same range of concentrations as used alone, for 15, 30, 60, 90, and 120 minutes at 37 degrees C. A dose- and time-dependent potentiation of cytotoxicity as measured by cellular viability (using trypan blue exclusion) were observed. The AA (2.5 mM)-induced lactate dehydrogenase (LDH) leakage observed after 60 minutes incubation was completely prevented when pretreated for 15 minutes with 4-methylpyrazole (MP) (0.5 mM). Such pretreatment, even with a double dose of 4-MP, only partially, and not significantly, prevented LDH leakage when the hepatocytes were incubated with a mixture of 2.5 mM AA and 5 mM C. The depletion of hepatocyte nonprotein sulfhydryl (NPSH) content caused by AA was further enhanced in the presence of C, as early as 15 minutes after their exposure. The AA-induced increase in lipid peroxidation was also potentiated by C; however, potentiation started later, and only after sufficient depletion of NPSH (mostly glutathione) occurred resulting from the presence of AA plus C. A significant loss of protein sulfhydryls in rat hepatocytes could be noted following a 60-minute incubation period with either AA (1 mM) or AA (1 mM) plus C (5 mM). Similarly, C produced a dose-and time-dependent potentiation of A-induced liver cytotoxicity, which was preceded by severe loss of NPSH content within 15 minutes of exposure, whereas the potentiation of lipid peroxidation (LPO) resulting from A plus C was found to be a relatively late event, as with AA plus C. Furthermore, combined treatment with AA and C produced a significantly higher cytotoxicity (as measured by cellular viability) than that due to the combined treatment with A plus C based on equimolar concentration. These results suggest that two increased bioactivation pathways of AA involving the P-450 mixed-function oxidase system resulting from C may be involved in the potentiation of AA hepatotoxicity.
authors.affiliation: Hĵpital du Sacré-Coeur de Montréal, Quebec, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Karas
authors.forename: S K
authors.initials: SK
authors.lastname: Chakrabarti
mesh_terms: D000171:Acrolein / Q000378:metabolism / Q000633:toxicity*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D000077604:Fomepizole; D005978:Glutathione / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D066298:In Vitro Techniques; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008099:Liver / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D020005:Propanols / Q000378:metabolism / Q000633:toxicity*; D011720:Pyrazoles / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013438:Sulfhydryl Compounds; D013997:Time Factors
chemical_list: D020005:Propanols; D011720:Pyrazoles; D013438:Sulfhydryl Compounds; D002110:Caffeine; C006463:allyl alcohol; D008315:Malondialdehyde; D000171:Acrolein; D000077604:Fomepizole; D007770:L-Lactate Dehydrogenase; D005978:Glutathione