title: Ginkgolide A contributes to the potentiation of acetaminophen toxicity by Ginkgo biloba extract in primary cultures of rat hepatocytes.
abstract: The present cell culture study investigated the effect of Ginkgo biloba extract pretreatment on acetaminophen toxicity and assessed the role of ginkgolide A and cytochrome P450 3A (CYP3A) in hepatocytes isolated from adult male Long-Evans rats provided ad libitum with a standard diet. Acetaminophen (7.5-25 mM for 24 h) conferred hepatocyte toxicity, as determined by the lactate dehydrogenase (LDH) assay. G. biloba extract alone increased LDH leakage in hepatocytes at concentrations > or =75 mug/ml and > or =750 mug/ml after a 72 h and 24 h treatment period, respectively. G. biloba extract (25 or 50 mug/ml once every 24 h for 72 h) potentiated LDH leakage by acetaminophen (10 mM for 24 h; added at 48 h after initiation of extract pretreatment). The effect was confirmed by a decrease in [(14)C]-leucine incorporation. At the level present in a modulating concentration (50 mug/ml) of the extract, ginkgolide A (0.55 mug/ml), which increased CYP3A23 mRNA levels and CYP3A-mediated enzyme activity, accounted for part but not all of the potentiating effect of the extract on acetaminophen toxicity. This occurred as a result of CYP3A induction by ginkgolide A because triacetyloleandomycin (TAO), a specific inhibitor of CYP3A catalytic activity, completely blocked the effect of ginkgolide A. Ginkgolide B, ginkgolide C, ginkgolide J, quercetin, kaempferol, isorhamnetin, and isorhamnetin-3-O-rutinoside did not alter the extent of LDH leakage by acetaminophen. In summary, G. biloba pretreatment potentiated acetaminophen toxicity in cultured rat hepatocytes and ginkgolide A contributed to this novel effect of the extract by inducing CYP3A.
authors.affiliation: Faculty of Pharmaceutical Sciences, The University of British Columbia, 2146 East Mall, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Ganesh
authors.initials: G
authors.lastname: Rajaraman
authors.forename: Jie
authors.initials: J
authors.lastname: Chen
authors.forename: Thomas K H
authors.initials: TK
authors.lastname: Chang
mesh_terms: D000082:Acetaminophen / Q000633:toxicity*; D018712:Analgesics, Non-Narcotic / Q000633:toxicity*; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D051544:Cytochrome P-450 CYP3A / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004365:Drugs, Chinese Herbal / Q000737:chemistry / Q000633:toxicity*; D004790:Enzyme Induction / Q000187:drug effects; D020441:Ginkgo biloba; D046934:Ginkgolides / Q000032:analysis / Q000633:toxicity*; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D007783:Lactones / Q000032:analysis / Q000633:toxicity*; D008297:Male; D014176:Protein Biosynthesis / Q000187:drug effects; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D020318:Rats, Long-Evans; D013997:Time Factors
chemical_list: D018712:Analgesics, Non-Narcotic; D004365:Drugs, Chinese Herbal; D046934:Ginkgolides; D007783:Lactones; D012333:RNA, Messenger; D000082:Acetaminophen; D007770:L-Lactate Dehydrogenase; D001189:Aryl Hydrocarbon Hydroxylases; C465138:Cyp3a23-3a1 protein, rat; D051544:Cytochrome P-450 CYP3A; C477042:ginkgolide A