Among
oxysterols oxidized at C7 (7alpha-, 7beta-hydroxycholesterol, and 7-ketocholesterol)
7beta-hydroxycholesterol and
7-ketocholesterol are potent inducers of cell death and probably play central roles in
atherosclerosis. As suggested by our previous investigations,
7-ketocholesterol might be a causative agent of vascular damage by inducing apoptosis and enhancing
superoxide anion (O2*-) production. To determine the precise relationships between cytotoxicity and oxidative stress, the ability of
oxysterols oxidized at C7 to induce apoptosis, to stimulate O2*- production and to promote lipid peroxidation was compared with different pro-apoptotic chemicals: antitumoral drugs (VB,
Ara-C, CHX, and
VP-16) and STS. All compounds, except
7alpha-hydroxycholesterol, induced apoptosis characterized by the occurrence of cells with fragmented and/or condensed nuclei, loss of mitochondrial potential,
caspase-3 activation, PARP degradation, and internucleosomal DNA fragmentation. The highest proportion of apoptotic cells was found with antitumoral drugs and STS, whereas the highest overproduction of O2*- detected before and after the loss of mitochondrial potential was obtained with
7beta-hydroxycholesterol and
7-ketocholesterol. Overproduction of O2*- was always correlated with enhanced lipid peroxidation. Vit E was only capable to significantly counteract apoptosis and oxidative stress induced by
7beta-hydroxycholesterol,
7-ketocholesterol, VB and STS. By electron and fluorescence microscopy, myelin figures evocating autophagic vacuoles were barely observed under treatment with
7beta-hydroxycholesterol and
7-ketocholesterol, and their formation occurring before the loss of mitochondrial potential was reduced by Vit E. In the presence of
7alpha-hydroxycholesterol, no enhancement of O2*- production, no lipid peroxidation, and no formation of myelin figures were observed. Collectively, our data demonstrate, that there can be a more or less important stimulation of oxidative stress during apoptosis. They also suggest that enhancement of O2*- production associated with lipid peroxidation during
7beta-hydroxycholesterol and 7-ketocholesterol-induced apoptosis could contribute to in vivo
vascular injury, and that myelin figures could constitute suitable markers of
oxysterol-induced cell death.