Valinomycin induces apoptosis of ascites hepatoma cells (AH-130) in relation to mitochondrial membrane potential.
Valinomycin is a potassium ionophore, and is well known to cause the collapse of the mitochondrial membrane potential. It has been reported that loss of mitochondrial membrane potential is observed in the early stages of apoptosis induced by various agents. Thus, the effects of valinomycin on tumor cells were examined. Valinomycin induced uncoupling of respiration and depolarization of isolated mitochondria. Depolarization of intact mitochondria in AH-130 rat ascites hepatoma cells was also induced by valinomycin. Valinomycin induced apoptosis revealing the typical apoptotic characteristics such as fragmentation and ladder formation of DNA, shrinkage of cells, and formation of pycnotic nucleus. There was a correlation between the depolarization of mitochondria and DNA fragmentation. After depolarization of mitochondria, the activity of caspase-3-like protease but not caspase-1-like protease increased markedly. In contrast, this apoptosis did not involve the release of reactive oxygen species from mitochondria, increase in intracellular calcium concentration, or protein synthesis. In addition, anti-apoptotic members of the Bcl-2 family (Bcl-xL and Bcl-2) were not correlated with apoptosis. These results indicate that valinomycin might induce apoptosis through degradation of the mitochondrial membrane potential. Taken together, these observations suggest that there may be a mechanism that transmits the signal from mitochondrial depolarization to subsequent apoptosis execution steps.
Inai
Y
Y
Department of Cell Chemistry, Okayama University Medical School, Japan.
Yabuki
M
M
Kanno
T
T
Akiyama
J
J
Yasuda
T
T
Utsumi
K
K
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001201:Ascites / Q000473:pathology; D006528:Carcinoma, Hepatocellular / Q000473:pathology* / Q000648:ultrastructure; D020170:Caspase 1; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D004273:DNA, Neoplasm / Q000302:isolation & purification; D007476:Ionophores / Q000494:pharmacology*; D008113:Liver Neoplasms / Q000473:pathology* / Q000648:ultrastructure; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects*; D010101:Oxygen Consumption / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D014407:Tumor Cells, Cultured; D014634:Valinomycin / Q000494:pharmacology*; D051020:bcl-X Protein
C494813:Bcl2l1 protein, rat; D004273:DNA, Neoplasm; D007476:Ionophores; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D014634:Valinomycin; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases; D020170:Caspase 1