The protonophore CCCP induces mitochondrial permeability transition without cytochrome c release in human osteosarcoma cells

Mitochondrial permeability transition (MPT) and cytochrome c redistribution from mitochondria are two events associated with apoptosis. We investigate d whether an MPT event obligatorily leads to cytochrome c release in vivo. We have previously shown that treatment of human osteosarcoma cells with th e protonophore m-chlorophenylhydrazone (CCCP) for 6 h induces MPT and mitoc hondrial swelling without significant cell death. Here we demonstrate that release of cytochrome c does not occur and the cells remain viable even aft er 72 h of treatment with CCCP. Bax is not mobilized to mitochondria under these conditions. However, subsequent exposure of CCCP-treated cells to eto poside or staurosporine for 48 h results in rapid cell death and cytochrome c release that is accompanied by Bax association with mitochondria, demons trating competency of these mitochondria to release cytochrome c with addit ional triggers. Our findings suggest that MPT is not a sufficient condition , in itself, to effect cytochrome c release. ((C) 2001 Federation of Europe an Biochemical Societies. Published by Elsevier Science B.V.. All rights re served.