Mitochondrial ATP-sensitive potassium channel activation protects cerebellar granule neurons from apoptosis induced by oxidative stress.
OBJECTIVE
Mitochondrial ATP-sensitive potassium (mitoK(ATP)) channels are present in the brain, and several reports have shown that mitoK(ATP) channel openers protect the brain against ischemic injury. However, the precise mechanisms of this protection are not well established. We hypothesized that mitoK(ATP) channel openers prevent apoptosis by preserving mitochondrial membrane potential.


METHODS
We investigated the effect of mitoK(ATP) channel openers on apoptosis induced by oxidative stress using cultured cerebellar granule neurons.


RESULTS
The mitoK(ATP) channel opener diazoxide (100 micromol/L) significantly suppressed the number of cells with terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive nuclei and the increase in caspase-3 activity induced by 20 micromol/L H2O2. Diazoxide and another opener, pinacidil, prevented the loss of mitochondrial inner membrane potential (Delta(Psi)m) induced by H2O2. These effects were abolished by 5-hydroxydecanoate (500 micromol/L), a mitoK(ATP) channel blocker. Cyclosporin A and bongkrekic acid, inhibitors of the mitochondrial permeability transition pore, also prevented Delta(Psi)m loss, confirming the involvement of the mitochondrial permeability transition in the apoptotic cascade in neurons. Furthermore, diazoxide prevented the increase in extracellular glutamate concentration induced by H2O2, but this effect was not attributable to activation of surface K(ATP) channels.


CONCLUSIONS
MitoK(ATP) channel openers inhibited apoptosis by preserving mitochondrial inner membrane potential. These beneficial effects may suggest a possible new target for neuroprotection.
Teshima
Yasushi
Y
Institute of Molecular Cardiobiology, The Johns Hopkins University, Baltimore, MD 21205, USA.
Akao
Masaharu
M
Li
Ronald A
RA
Chong
Tae H
TH
Baumgartner
William A
WA
Johnston
Michael V
MV
Marbán
Eduardo
E
D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001865:Bongkrekic Acid / Q000494:pharmacology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology; D016572:Cyclosporine / Q000494:pharmacology; D003981:Diazoxide / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D007473:Ion Channels; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D016877:Oxidants; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D001865:Bongkrekic Acid; D018698:Glutamic Acid; D016572:Cyclosporine; D000255:Adenosine Triphosphate; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D003981:Diazoxide