Apoptotic cell death is induced in SH-SY5Y neuroblastoma cells following exposure to the protein kinase inhibitors staurosporine (100 nM) and 1-(5-Isoquinolinesulfonyl)-2-methylpiperazine: H-7 (100 microM). This is associated with reduced levels of PARP 117 kDa and with the concomitant formation of PARP-cleaved products of 89 kDa that result from caspase-3 activation. The process is inhibited with DEVD-fmk, a potent caspase-3 (and caspase-8) inhibitor, thus indicating that staurosporine- and H-7-induced cell death in SH-SY5Y is mediated by caspase activation. Increased caspase-2- and caspase-3-like activities, but not caspase-9-like activity, were demonstrated by monitoring proteolysis of the corresponding colorimetric substrates. Caspase-2 activity peaked at 6 h, whereas caspase-3 peaked at 12 h in parallel with the maximal loss of cell viability. No modifications in the expression levels of Fas and Fas-L were observed by Western blotting. Furthermore, no activation of caspase-8 was elicited by colorimetric assays through the process of apoptosis of neuroblastoma cells. These findings indicate that the Fas/Fas-L-caspase-8 pathway of cell death signaling is not involved in staurosporine- and H-7-induced apoptosis in SH-SY5Y neuroblastoma cells.