title: Hydrogen peroxide overproduction in megamitochondria of troglitazone-treated human hepatocytes.
abstract: Troglitazone has been withdrawn from therapeutic options for diabetes mellitus because of its severe hepatocyte toxicity of unknown pathogenesis. The aim of the present study was to assess both morphologic and functional alterations in the mitochondria of troglitazone-treated hepatocytes. A polarized human hepatocyte cell line, OUMS-29, was used in this study. The mitochondrial volume and the mitochondrial transmembrane potential (DeltaPsi(m)) were examined using flow cytometry with nonylacridine orange (NAO) and rhodamine-123, respectively. An ultrastructural examination of the troglitazone-treated OUMS-29 cells was performed using transmission electron microscopy (TEM). Reactive oxygen species (ROS) production was assessed using flow cytometry with dihydroethidium and 2',7'-dichlorodihydrofluorescein diacetate. A significant increase in the mitochondrial volume of the troglitazone-treated cells was found by the NAO analysis, in comparison with pioglitazone-treated and ciglitazone-treated cells. The increase in volume was due to a marked enlargement in the mitochondria. The markedly enlarged mitochondria with intramitochondrial electron-dense deposits were confirmed on TEM, which showed myelin-like structures, indicating degraded membrane constituents. The troglitazone-treated cells showed a significant decline in the DeltaPsi(m) per unit mitochondrial volume but resulted in no clear cell death. ROS analysis revealed a significant production of hydrogen peroxide in the troglitazone-treated hepatocytes. This production was attenuated using an antioxidant, N-acetyl-L-cysteine. In conclusion, troglitazone caused overproduction of hydrogen peroxide, which deteriorated both mitochondrial membrane structures and mitochondrial function, leading to a possible priming for the severe hepatocyte toxicity.
authors.affiliation: Second Department of Medicine, and the Research Center for Innovative Cancer Therapy, Kurume University School of Medicine, Japan.
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Shishido
authors.forename: Hironori
authors.initials: H
authors.lastname: Koga
authors.forename: Masaru
authors.initials: M
authors.lastname: Harada
authors.forename: Hiroto
authors.initials: H
authors.lastname: Kumemura
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Hanada
authors.forename: Eitaro
authors.initials: E
authors.lastname: Taniguchi
authors.forename: Ryukichi
authors.initials: R
authors.lastname: Kumashiro
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Ohira
authors.forename: Yukio
authors.initials: Y
authors.lastname: Sato
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Namba
authors.forename: Takato
authors.initials: T
authors.lastname: Ueno
authors.forename: Michio
authors.initials: M
authors.lastname: Sata
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000418:Albumins / Q000032:analysis; D000975:Antioxidants / Q000633:toxicity*; D002461:Cell Line, Transformed; D016764:Cell Polarity; D002839:Chromans / Q000633:toxicity*; D003574:Cytochrome c Group / Q000032:analysis; D016166:Free Radical Scavengers / Q000494:pharmacology; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008024:Ligands; D008854:Microscopy, Electron; D008928:Mitochondria / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D017382:Reactive Oxygen Species / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000032:analysis; D013844:Thiazoles / Q000633:toxicity*; D045162:Thiazolidinediones; D014157:Transcription Factors / Q000032:analysis; D000077288:Troglitazone
chemical_list: D000418:Albumins; D000975:Antioxidants; D002839:Chromans; D003574:Cytochrome c Group; D016166:Free Radical Scavengers; D008024:Ligands; D017382:Reactive Oxygen Species; D018160:Receptors, Cytoplasmic and Nuclear; D013844:Thiazoles; D045162:Thiazolidinediones; D014157:Transcription Factors; D006861:Hydrogen Peroxide; D000077288:Troglitazone; D000111:Acetylcysteine