title: Heme oxygenase-1 protects HepG2 cells against cytochrome P450 2E1-dependent toxicity.
abstract: The inducible form of heme oxygenase (HO-1) is increased during oxidative injury and HO-1 is believed to be an important defense mechanism against such injury. Arachidonic acid (AA) and l-buthionine-(S,R)-sulfoximine (BSO), which lowers GSH levels, cause cytochrome P450 2E1 (CYP2E1)-dependent oxidative injuries in HepG2 cells (E47 cells). Treatment of E47 cells with 50 microM AA or 100 microM BSO for 48 h was recently shown to increase HO-1 mRNA, protein, and activity. The possible functional significance of this increase in protecting against CYP2E1-dependent toxicity was evaluated in the current study. The treatment with AA and BSO caused loss of cell viability (40 and 50%, respectively) in E47 cells. Chromium mesoporphyrin (CrMP), an inhibitor of HO activity, significantly potentiated this cytotoxicity. ROS production, lipid peroxidation, and the decline in mitochondrial membrane potential produced by AA and BSO were also enhanced in the presence of CrMP in E47 cells. Infection with an adenovirus expressing rat HO-1 protected E47 cells from AA toxicity, increasing cell viability and reducing LDH release. HO catalyzes formation of CO, bilirubin, and iron from the oxidation of heme. Bilirubin was not protective whereas iron catalyzed the AA toxicity. The carbon monoxide (CO) scavenger hemoglobin enhanced AA toxicity in E47 cells analogous to CrMP, whereas exposure to exogenous CO partially reduced AA toxicity and the enhanced AA toxicity by CrMP. Addition of exogenous CO to the cells inhibited CYP2E1 catalytic activity, as did overexpression of the rat HO-1 adenovirus. These results suggest that induction of HO-1 protects against CYP2E1-dependent toxicity and this protection may be mediated in part via production of CO and CO inhibition of CYP2E1 activity.
authors.affiliation: Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, New York, NY 10029, USA.
authors.forename: Pengfei
authors.initials: P
authors.lastname: Gong
authors.forename: Arthur I
authors.initials: AI
authors.lastname: Cederbaum
authors.forename: Natalia
authors.initials: N
authors.lastname: Nieto
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D016718:Arachidonic Acid / Q000037:antagonists & inhibitors / Q000633:toxicity; D019328:Buthionine Sulfoximine / Q000037:antagonists & inhibitors / Q000633:toxicity; D002460:Cell Line; D019392:Cytochrome P-450 CYP2E1 / Q000187:drug effects / Q000378:metabolism*; D006419:Heme Oxygenase (Decyclizing) / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D051547:Heme Oxygenase-1; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D015227:Lipid Peroxidation / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D008565:Membrane Proteins; D008652:Mesoporphyrins / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D009336:Necrosis; D020011:Protective Agents / Q000494:pharmacology*; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D008565:Membrane Proteins; D008652:Mesoporphyrins; D020011:Protective Agents; D017382:Reactive Oxygen Species; C427471:chromium mesoporphyrin; D016718:Arachidonic Acid; D019328:Buthionine Sulfoximine; D019392:Cytochrome P-450 CYP2E1; C496541:HMOX1 protein, human; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1