title: Involvement of the multidrug resistance P-glycoprotein in acetaminophen-induced toxicity in hepatoma-derived HepG2 and Hep3B cells.
abstract: Acetaminophen overdose causes severe hepatic failure. Although the mechanisms of acetaminophen hepatotoxicity have been well investigated, little is known about the involvement of the P-glycoprotein in acetaminophen transport and toxicity. P-Glycoprotein is a membrane efflux pump, playing a significant role in regulating absorption, excretion, and tissue distribution of many drugs. To evaluate the contribution of P-glycoprotein transporter in the course of acetaminophen-induced toxicity, HepG2 and Hep3B cells with different P-glycoprotein expression and activity, were treated by acetaminophen (1-10 mM) for different time periods, with or without the P-glycoprotein inhibitor verapamil. P-Glycoprotein activity was determined by rhodamine 123 efflux assay and western blot analysis. To assess the acetaminophen-induced toxicity and effect of verapamil, we investigated cellular redox status, phosphatidylserine externalization, nuclear fragmentation and ultrastructural changes. Verapamil markedly enhanced acetaminophen-induced oxidative damage and cell death. Moreover, verapamil revealed acetaminophen toxicity even at subtoxic levels. High acetaminophen concentrations increased P-glycoprotein activity and content in both HepG2 and Hep3B cells. These observations suggest the involvement of P-glycoprotein in acetaminophen transport. Notwithstanding the differences of the investigated hepatoma cell lines in P-glycoprotein function, acetaminophen-induced toxicity was similar, possibly due to different functions of drug-metabolizing systems. We conclude that acetaminophen is a P-glycoprotein substrate and P-glycoprotein is involved in acetaminophen transport and toxicity in HepG2 and Hep3B cells. This study establishes the fact that acetaminophen can modulate P-glycoprotein in tumour cells, suggesting that its routine use in cancer patients in combination with anticancer drugs, may influence the result of chemotherapy.
authors.affiliation: Paediatric Research and Electron Microscopy Unit, Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel. irmanov@tx.technion.ac.il
authors.forename: Irena
authors.initials: I
authors.lastname: Manov
authors.forename: Yulia
authors.initials: Y
authors.lastname: Bashenko
authors.forename: Mark
authors.initials: M
authors.lastname: Hirsh
authors.forename: Theodore C
authors.initials: TC
authors.lastname: Iancu
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000082:Acetaminophen / Q000378:metabolism / Q000633:toxicity*; D000970:Antineoplastic Agents / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000378:metabolism* / Q000473:pathology*; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004351:Drug Resistance; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D018384:Oxidative Stress / Q000187:drug effects; D014700:Verapamil / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D000082:Acetaminophen; D014700:Verapamil