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Cytosolic Ca 2+ movements of endothelial cells exposed to reactive oxygen intermediates: Role of hydroxyl radical‐mediated redox alteration of cell‐membrane Ca 2+ channels
Author(s) -
Azma Toshiharu,
Saeki Noboru,
Yuge Osafumi
Publication year - 1999
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0702438
Subject(s) - chemistry , dithiothreitol , xanthine oxidase , cytosol , channel blocker , extracellular , intracellular , reactive oxygen species , biophysics , biochemistry , calcium , biology , enzyme , organic chemistry
The mode of action of reactive oxygen intermediates in cysosolic Ca 2+ movements of cultured porcine aortic endothelial cells exposed to xanthine/xanthine oxidase (X/XO) was investigated. Cytosolic Ca 2+ movements provoked by X/XO consisted of an initial Ca 2+ release from thapsigargin‐sensitive intracellular Ca 2+ stores and a sustained Ca 2+ influx through cell‐membrane Ca 2+ channels. The Ca 2+ movements from both sources were inhibited by catalase, cell‐membrane permeable iron chelators (o‐phenanthroline and deferoxamine), a • OH scavenger (5,5‐dimethyl‐1‐pyrroline‐N‐oxide), or an anion channel blocker (disodium 4, 4′‐diisothiocyano‐2, 2′‐stilbenedisulphonic acid), suggesting that • O 2 − influx through anion channels was responsible for the Ca 2+ movements, in which • OH generation catalyzed by intracellular transition metals (i.e., Haber‐Weiss cycle) was involved. After an initial Ca 2+ elevation provoked by X/XO, cytosolic Ca 2+ concentration decreased to a level higher than basal levels. Removal of X/XO slightly enhanced the Ca 2+ decrease. Extracellular addition of sulphydryl (SH)‐reducing agents, dithiothreitol or glutathione, after the removal of X/XO accelerated the decrement. A Ca 2+ channel blocker, Ni 2+ , abolished the sustained increase in Ca 2+ , suggesting that Ca 2+ influx through cell‐membrane Ca 2+ channels was extracellularly regulated by the redox state of SH‐groups. The X/XO‐provoked change in cellular respiration was inhibited by Ni 2+ or dithiothreitol as well as inhibitors of Haber‐Weiss cycle, suggesting that Ca 2+ influx was responsible for • OH‐mediated cytotoxicity. We concluded that intracellular • OH generation was involved in the Ca 2+ movements in endothelial cells exposed to X/XO. Cytosolic Ca 2+ elevation was partly responsible for the oxidants‐mediated cytotoxicity.British Journal of Pharmacology (1999) 126 , 1462–1470; doi: 10.1038/sj.bjp.0702438