Involvement of caspases and calpains in cerebrocortical neuronal cell death is stimulus-dependentd

1 Caspases and calpains are mediators of apoptotic cell death. The objective of this study was to determine the role of caspases and calpains in primary cerebrocortical neuronal (CCN) death in response to a range of stimuli which reportedly induce neuronal apoptosis. 2 Cell death of primary cultures of rat CCN was induced by staurosporine (STS), C2-ceramide (CER), camptothecin (CMT), hydrogen peroxide (H2O2) or N-methyl-D-aspartate (NMDA). Caspase and calpain activity were assessed by cleavage of a-fodrin or fluorogenic substrates. Cell death was analysed by lactate dehydrogenase (LDH) assay in the absence or presence of the pan-caspase inhibitor Boc-Asp-(OMe)-Fluoromethylketone (Baf) and/or the calpain inhibitor calpeptin (CP). 3 Cell death induced by STS, CER or CMT was accompanied by chromatin condensation and activation of multiple caspases, particularly caspase-3-type proteases. Hydrogen peroxide (H2O2) treatment was accompanied by activation of caspases -1, -6 and -8, but not -3, whereas none of the caspases tested were activated in response to NMDA. 4 With the exception of H2O2, when cell death was accompanied by caspase activation, it was significantly suppressed by Baf. 5 All stimuli also induced calpain activation, but calpeptin only suppressed cell death induced by H2O2. Furthermore, co-treatment with Baf and calpeptin did not alter the cell death relative to either inhibitor alone. 6 These findings suggest the existence of stimulus-dependent routes for the activation of caspases and calpains during death of cortical neurones and imply that although caspases and calpains are activated, their involvement in the execution of cell death varies with the stimulus.