Effects of chloride and potassium channel blockers on apoptotic cell shrinkage and apoptosis in cortical neurons.
K+ and Cl- homeostasis have been implicated in cell volume regulation and apoptosis. We addressed the hypothesis that K+ and Cl- efflux may contribute to apoptotic cell shrinkage and apoptotic death in cultured cortical neurons. CLC-2 and CLC-3 chloride channels were detected in cultured cortical neurons. The Cl- channel blockers 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS) and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) inhibited the outwardly rectifying Cl- current, prevented apoptotic cell shrinkage, and mildly attenuated cell death induced by staurosporine, C2-ceramide, or serum deprivation. Cl- channel blockers, however, at concentrations that prevented cell shrinkage had no significant effects on caspase activation and/or DNA fragmentation. Cell death in the presence of a Cl- channel blocker was still sensitive to blockade by the caspase inhibitor z-Val-Ala-Asp(OMe)-fluoromethyl ketone (z-VAD-fmk). Electron microscopy revealed that, although DIDS prevented apoptotic cell shrinkage, certain apoptotic ultrastructural alterations still took place in injured neurons. On the other hand, the K+ channel blocker tetraethylammonium (TEA), clofilium, or the caspase inhibitor z-VAD-fmk prevented cell shrinkage as well as caspase activation and/or DNA damage, and showed stronger neuroprotection against apoptotic alterations and cell death. The results indicate that neurons may undergo apoptotic process without cell shrinkage and imply distinct roles for Cl- and K+ homeostasis in regulating different apoptotic events.
Wei
Ling
L
Department of Pathology, Medical University of South Carolina, Charleston, SC 29425, USA.
Xiao
Ai Ying
AY
Jin
Chun
C
Yang
Aizhen
A
Lu
Zhong Yang
ZY
Yu
Shan Ping
SP
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D046529:Microscopy, Electron, Transmission; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D009579:Nitrobenzoates / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*
D018118:Chloride Channels; D004791:Enzyme Inhibitors; D009579:Nitrobenzoates; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D020169:Caspases; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid