Mitochondrial Ca(2+)homeostasis in the regulation of apoptotic and necrotic cell deaths.
Using distinct models of apoptosis and necrosis, we have investigated the effect of mitochondrial Ca(2+)(Ca(m)) homeostasis in the regulation of cell death in neuroblastoma cells as well as cardiac myocytes. The steady state level of Ca(m)was determined as the FCCP-releasable Ca(2+). Culturing cells with low concentration of extracellular Ca(2+)(Ca(o)) or with EGTA triggered an early reduction in both the Ca(m)store and the membrane potential (DeltaPsi(m)). This was followed by the detection of cytochrome c release, caspase activation, and apoptosis. Inhibitors of the mitochondrial permeability transition pore such as cyclosporin A and Bcl-2 blocked the release of Ca(m)and inhibited apoptosis. In contrast, mitochondrial Ca(2+)overload resulted in necrotic cell death. Culturing cells in the presence of excess Ca(o)led to increased Ca(m)load together with a decrease of DeltaPsi(m)that reached maximum at 1 h, with necrosis occurring at 2 h. While the decline of Ca(m)and DeltaPsi(m)was a coupled reaction for apoptosis, this relationship was uncoupled during necrosis. Clonazepam, a relatively specific inhibitor of the mitochondrial Na/Ca exchanger, was able to protect the cells from necrosis by reducing Ca(m)overload. Importantly, combination of clonazepam and cyclosporin showed a cooperative effect in further reducing the Ca(m)overload and abolished cell death. The data imply the participation of Ca(m)homeostasis in the regulation of apoptosis and necrosis.
Zhu
L P
LP
Department of Pathology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
Yu
X D
XD
Ling
S
S
Brown
R A
RA
Kuo
T H
TH
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D020013:Calcium Signaling; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002998:Clonazepam / Q000494:pharmacology; D016572:Cyclosporine / Q000494:pharmacology; D006706:Homeostasis; D006801:Humans; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism / Q000473:pathology; D009336:Necrosis; D009447:Neuroblastoma; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014407:Tumor Cells, Cultured
D019253:Proto-Oncogene Proteins c-bcl-2; D002998:Clonazepam; D016572:Cyclosporine; D002118:Calcium