Impairment with various antioxidants of the loss of mitochondrial transmembrane potential and of the cytosolic release of cytochrome C occuring during 7-ketocholesterol-induced apoptosis

Previous investigations of our laboratory have shown that 7-ketocholesterol was a potent inducer of apoptosis involving a release of cytochrome c into the cytosol, and a lipid peroxidation process that could be the consequenc e of a production of radical oxygen species. According to these considerati ons, we asked whether some antioxidants were able to counteract 7-ketochole sterol-induced apoptosis, and whether prevention of cell death was associat ed with the impairment of mitochondrial events implied in the commitment to apoptosis, i.e., opening of the mitochondrial megachannels leading to the loss of the mitochondrial transmembrane potential (Delta Psi m), and releas e of cytochrome c from mitochondria into the cytosol. To this end, we studi ed the effects of glutathione (15 mM), N-acetylcysteine (15 mM), vitamin E (100 mu M), vitamin C (50 ELM) and melatonin (1 mM) on U937 cells treated w ith 7-ketocholesterol (40 mu g/ml). Only glutathione, N-acetylcysteine, and vitamin E prevented apoptosis measured by the occurrence of cells with con densed and/or fragmented nuclei, as well as the loss of Delta Psi m, and th e release of cytochrome c. However, all the antioxidants used were potent i nhibitors of the production of O-2(.) occuring under treatment with 7-ketoc holesterol. Collectively, our data demonstrate that impairment of apoptosis by glutathione, N-acetylcysteine, and vitamin E correlates with the preven tion of mitochondrial dysfunctions, and they underline that the ability of antioxidants to counteract 7-ketocholesterol-induced apoptosis does not onl y depend on their capability to inhibit the production of O-2(.). (C) 2000 Elsevier Science Inc.