OXYGEN-INDUCED APOPTOSIS IN PC12 CELLS WITH SPECIAL REFERENCE TO THE ROLE OF BCL-2

We previously reported that PC12h cells are killed by a high oxygen at mosphere. in this study, we further characterized this oxygen-induced cell death and found apoptotic features, as follows. Firstly, chromati n condensation was observed in cells cultured in a 50% O-2 atmosphere. Secondly, cycloheximide and cordycepin, protein and RNA synthesis inh ibitors, respectively, prevented the oxygen-induced cell death in PC12 h cells, suggesting that it is mediated by an intracellular death prog ram. Thirdly, NGF, CPT-cAMP and depolarization by high potassium mediu m also effectively inhibited this apoptotic cell death in PC12h cells. The effect of high K+ is thought to be mediated by the influx of Ca2 into cells through voltage-dependent Ca2+ channels, because nifedipin e, an L-type Ca2+ channel blocker, inhibited the effect of high K+. In addition, since the oxygen-induced apoptosis was blocked by the antio xidant vitamin E, this oxygen toxicity is suggested to be mediated by reactive oxygen species. To further characterize this oxygen-induced a poptosis at the molecular level, we used PC12 cells overexpressing the proto-oncogene bcl-2. Although a large number of PC12 cells transfect ed with the control vector died in a 50% O-2 atmosphere within 6 days, bcl-2-transfected PC12 cells survived and proliferated. These finding s suggested that our system using PC12 cells will be a useful model wi th which to analyze the molecular mechanisms of apoptosis induced by o xidative stress in neuronal cells.