Protective role for bcl-2 in experimentally induced cell death of bovine corneal endothelial cells

To characterize the pattern of cell death and to investigate the potential role of bcl-2 in a death paradigm of corneal endothelial cells, primary cultures of bovine corneal endothelial (BCEN) cells were first established and treated with 0.01-1 microM staurosporine, a nonspecific protein kinase inhibitor. The pattern of BCEN cell death induced by staurosporine was apoptotic in nature, characterized by shrinkage of the cytoplasmic membrane, nuclear condensation and DNA fragmentation. Cotreatment of BCEN cells with Z-VAD-fmk (a caspase inhibitor) but not cycloheximide (a protein synthesis inhibitor) prevented staurosporine-induced cell death. To investigate the potential role of bcl-2, BCEN cells were transferred with a eukaryotic expression vector containing anti-apoptotic bcl-2 cDNA and characterized by reverse transcription-polymerase chain reaction (RT-PCR; BCEN/bcl-2). As measured by the MTT reduction assay after treatment with staurosporine, the survival rate of BCEN/bcl-2 cells was 48.0 +/- 4.8% compared to 7.4 +/- 2.1% in control BCEN cells. As determined by light microscopy, apoptotic changes such as nuclear condensation and apoptotic bodies were largely attenuated in BCEN/bcl-2 cells after staurosporine treatment although arborization of processes and rounding up of the cell body were not affected by overexpression of bcl-2. These results suggest that staurosporine induces apoptosis in a cycloheximide-independent but caspase-dependent manner and bcl-2 acts as a negative regulator in staurosporine-induced apoptosis of BCEN cells.