title: Role of acid-sensitive outwardly rectifying anion channels in acidosis-induced cell death in human epithelial cells.
abstract: Recently, a novel type of anion channel activated by extracellular acidification has been found in a variety of mammalian cell types. However, the role of this acid-sensitive outwardly rectifying (ASOR) anion channel is not known. In human epithelial HeLa cells, reduction in extracellular pH below 5 rapidly activated anion-selective whole-cell currents. The currents exhibited strong outward rectification, activation kinetics at positive potentials, low-field anion selectivity, and sensitivity to 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) and phloretin. When outside-out patches were exposed to acidic bathing solution, single-channel events of the anion channel could be observed. The unitary conductance was 4.8 pS in the voltage range between -80 and +80 mV. The single-channel activity prominently increased with depolarization and was suppressed by DIDS or phloretin. After 1-h incubation in acidic solution (pH 4.5), a significant population of HeLa cells suffered from necrotic cell injury characterized by stainability with propidium iodide and lack of caspase-3 activation. Upon exposure to acidic solution, HeLa cells exhibited immediate, persistent swelling. Both the necrotic volume increase and cell injury induced by extracellular acidification were inhibited by DIDS or phloretin. Therefore, it is concluded that the ASOR anion channel is involved in the genesis of necrotic cell injury induced by acidosis in human epithelial cells.
authors.affiliation: Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan.
authors.forename: Hai-Yan
authors.initials: HY
authors.lastname: Wang
authors.forename: Takahiro
authors.initials: T
authors.lastname: Shimizu
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Numata
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Okada
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000138:Acidosis / Q000378:metabolism / Q000503:physiopathology*; D000838:Anions / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D048429:Cell Size / Q000187:drug effects; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000502:physiology; D004594:Electrophysiology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D009336:Necrosis / Q000378:metabolism; D010693:Phloretin / Q000494:pharmacology
chemical_list: D000838:Anions; D018118:Chloride Channels; D007473:Ion Channels; D053148:Caspase 3; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D010693:Phloretin