title: Sodium nitroprusside induces autophagic cell death in glutathione-depleted osteoblasts.
abstract: Previous studies reported that high levels of nitric oxide (NO) induce apoptotic cell death in osteoblasts. We examined molecular mechanisms of cytotoxic injury induced by sodium nitroprusside (SNP), a NO donor, in both glutathione (GSH)-depleted and control U2-OS osteoblasts. Cell viability was reduced by much lower effective concentrations of SNP in GSH-depleted cells compared to normal cells. The data suggest that the level of intracellular GSH is critical in SNP-induced cell death processes of osteoblasts. The level of oxidative stress due to SNP treatments doubled in GSH-depleted cells when measured with fluorochrome H2DCFDA. Pretreatment with the NO scavenger PTIO preserved the viability of cells treated with SNP. Viability of cells treated with SNP was recovered by pretreatment with Wortmannin, an autophagy inhibitor, but not by pretreatment with zVAD-fmk, a pan-specific caspase inhibitor. Large increases of LC3-II were shown by immunoblot analysis of the SNP-treated cells, and the increase was blocked by pretreatment with PTIO or Wortmannin; this implies that under GSH-depleted conditions SNP induces different molecular signaling that lead to autophagic cell death. The ultrastructural morphology of SNP-treated cells in transmission electron microscopy showed numerous autophagic vacuoles. These data suggest NO produces oxidative stress and cellular damage that culminate in autophagic cell death of GSH-depleted osteoblasts.
authors.affiliation: Department of Biochemistry, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea.
authors.forename: Min Jeong
authors.initials: MJ
authors.lastname: Son
authors.forename: Seong-Beom
authors.initials: SB
authors.lastname: Lee
authors.forename: Yu Jeong
authors.initials: YJ
authors.lastname: Byun
authors.forename: Hwa Ok
authors.initials: HO
authors.lastname: Lee
authors.forename: Ho-Shik
authors.initials: HS
authors.lastname: Kim
authors.forename: Oh-Joo
authors.initials: OJ
authors.lastname: Kwon
authors.forename: Seong-Whan
authors.initials: SW
authors.lastname: Jeong
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology; D001343:Autophagy / Q000502:physiology; D016923:Cell Death / Q000502:physiology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors; D009599:Nitroprusside / Q000633:toxicity*; D010006:Osteoblasts / Q000166:cytology* / Q000502:physiology* / Q000648:ultrastructure; D018384:Oxidative Stress / Q000502:physiology; D012509:Sarcoma; D013778:Tetrazolium Salts / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D020030:Nitric Oxide Donors; D013778:Tetrazolium Salts; D013844:Thiazoles; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D009599:Nitroprusside; D009569:Nitric Oxide; C022616:thiazolyl blue; D005978:Glutathione