Loss of mitochondrial membrane potential is dependent on the apoptotic program activated: prevention by R-2HMP.
Recent evidence suggests that the mitochondrial membrane potential begins to decrease well before the cells commit to apoptotic death. By using cultured cerebellar granule cells, two types of apoptosis can be induced, one by adding cytosine arabinoside (Ara-c; p53-dependent apoptosis) and one by lowering the K(+) concentrations of the medium (p53-independent apoptosis). Cultures show clear signs of increased apoptosis (chromatin condensation as visualized with bis-benzamide) after 12 hr which increases with time up to 24 hr. A fluorescent probe, chloromethyl-tetramethylrhodamine methyl ester (CMTMR), a lipophilic, potentiometric dye, which when introduced into the media accumulates within mitochondria in proportion to the mitochondrial membrane potential, was added at various time points after the induction of apoptosis. In Ara-c-induced apoptosis, there was a shift in the distribution of cell populations towards low-intensity CMTMR fluorescence, whereas in control and low-K(+) cultures, there was no such shift. This effect was observed as early as 6 hr after adding Ara-c. The antiapoptotic drug R-N-2-heptyl-N-methylpropargylamine hydrochloride (R-2HMP) reversed this loss of mitochondrial membrane potential in Ara-c-induced apoptosis; the effect was antagonized by the S-2HMP.
Zhang
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D
Neuropsychiatry Research Unit, Department of Psychiatry, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. daz212@mail.usask.ca
Berry
M D
MD
Paterson
I A
IA
Boulton
A A
AA
D000480:Alkynes / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects; D003561:Cytarabine / Q000494:pharmacology; D005260:Female; D007425:Intracellular Membranes / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D013237:Stereoisomerism
D000480:Alkynes; C402679:N-2-heptyl-N-methylpropargylamine; D003561:Cytarabine