title: Enhancement of apoptosis by nitric oxide released from alpha-phenyl-tert-butyl nitrone under hyperthermic conditions.
abstract: The aim of this study was to examine whether a neuroprotector, PBN (alpha-phenyl-tert-butyl nitrone), enhances apoptosis induced by hyperthermia, which generates superoxide (O2-) intracellularly, since the release of nitric oxide (NO) from PBN under oxidative stress has been reported. When human myelomonocytic lymphoma U937 cells were treated with hyperthermia (44 degrees C, 10 min) and PBN, an increase in the concentration of nitrite in the culture medium, and a decrease in the hyperthermia-induced production of O2- was observed. Imaging using a fluorescence dye for intracellular NO, diaminofluorescein-2 diacetate (DAF-2 DA), revealed the formation of NO in the apoptotic cells treated with hyperthermia and PBN combined. Apoptotic endpoints were significantly enhanced by the combined treatment: a decrease in mitochondrial trans-membrane potential, cleavage of Bid, release of cytochrome c, and activation of caspase-8 and -3. An increase in the intracellular Ca2+ concentration ([Ca2+]i), externalization of Fas, and decrease in Hsp70 and phosphorylated HSF1 were observed following the combined treatment. Furthermore, scavengers of NO an d ONOO- significantly inhibited the enhancement of apoptosis, the externalization of Fas and the increase in [Ca2+]i. These results suggest that, (1) NO is released from PBN by hyperthermia, and subsequently reacts with O2- to form ONOO-, (2) NO and ONOO- are involved in the enhancement of apoptosis through Fas-mitochondria-caspase and [Ca2+]i-dependent pathways, and (3) a decrease in Hsp70 and phosphorylated HSF1 also contributed to the enhancement of apoptosis.
authors.affiliation: Department of Radiological Sciences, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Sugitani, Toyama, Japan.
authors.forename: Zheng-Guo
authors.initials: ZG
authors.lastname: Cui
authors.forename: Takashi
authors.initials: T
authors.lastname: Kondo
authors.forename: Hideki
authors.initials: H
authors.lastname: Matsumoto
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D003497:Cyclic N-Oxides; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005110:Extracellular Space / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D000076249:Heat Shock Transcription Factors; D006358:Hot Temperature; D006801:Humans; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D009569:Nitric Oxide / Q000378:metabolism / Q000494:pharmacology*; D009589:Nitrogen Oxides / Q000737:chemistry / Q000494:pharmacology*; D015398:Signal Transduction; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D020298:U937 Cells
chemical_list: D003497:Cyclic N-Oxides; D004268:DNA-Binding Proteins; C000619706:HSF1 protein, human; D018840:HSP70 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D009589:Nitrogen Oxides; D014157:Transcription Factors; D009569:Nitric Oxide; C029217:phenyl-N-tert-butylnitrone; D020169:Caspases; D002118:Calcium