Induction of mitochondrial permeability transition and cytochrome C release in the absence of caspase activation is insufficient for effective apoptosis in human leukemia cells

作者：Jayshree L. Hirpara, Mohamed Ali‐Seyed, Kok W. Loh, Hui Dong, R. Manjunatha Kini, Shazib Pervaiz · 发表于：Blood · 年份：2000 · DOI：10.1182/blood.v95.5.1773.005k17_1773_1780 · 被引用次数：51 · 研究领域：Cell death mechanisms and regulation、Mitochondrial Function and Pathology、ATP Synthase and ATPases Research

Induction of mitochondrial permeability transition (MPT) and cytosolic translocation of cytochrome C are considered essential components of the apoptotic pathway. Hence, there is the realization that mitochondrial-specific drugs could have potential for use as chemotherapeutic agents to trigger apoptosis in tumor cells. Recently, we showed that photoproducts of merocyanine 540 (pMC540) induced tumor cell apoptosis. In this study, we focused on identifying mitochondrial-specific compounds from pMC540 and studied their apoptotic potential. One purified fraction, C5, induced a drop in mitochondrial transmembrane potential and cytosolic translocation of cytochrome C in HL60 human leukemia cells. Moreover, the addition of C5 to purified rat liver mitochondria induced MPT as indicated by mitochondrial matrix swelling, which was completely inhibited by cyclosporin A, an inhibitor of the inner-membrane pore. Supernatant of C5-treated mitochondria showed a dose-dependent increase in cytochrome C, which was also inhibited in the presence of cyclosporin A, strongly indicating a direct effect on the inner-membrane pore. Despite the strong mitochondrial reactivity, C5 elicited minimal cytotoxicity (less than 25%) against HL60 leukemia and M14 melanoma cells because of inefficient caspase activation. However, prior exposure to C5 significantly enhanced the apoptotic response to etoposide or the CD95 receptor. Thus, we demonstrate that MPT induction and cytochrome C release by the novel com...