Combined mechanical trauma and metabolic impairment in vitro induces NMDA receptor-dependent neuronal cell death and caspase-3-dependent apoptosis

Neuronal necrosis and apoptosis occur after traumatic brain injury (TBI) in animals and contribute to subsequent neurological deficits. In contrast, r elatively little apoptosis is found after mechanical injury in vitro, Becau se in vivo trauma models and clinical head injury have associated cerebral ischemia and/or metabolic impairment, we transiently impaired cellular meta bolism after mechanical trauma of neuronal-glial cultures by combining 5-ni tropropionic acid treatment with concurrent glucose deprivation, This produ ced greater neuronal cell death than mechanical trauma alone. Such injury w as attenuated by the NMDA receptor antagonist dizocilpine (MK801), In addit ion, this injury significantly increased the number of apoptotic cells over that accruing from mechanical injury alone. This apoptotic cell. death was accompanied by DNA fragmentation, attenuated by cycloheximide, and associa ted with an increase in caspase-3-like but not caspase-1-like activity, Cel l death was reduced by the pan-caspase inhibitor BAF or the caspase-3 selec tive inhibitor z-DEVD-fmk, whereas the caspase-1 selective inhibitor z-YVAD -fmk had no effect; z-DEVD-fmk also reduced the number of apoptotic cells a fter combined injury. Moreover, cotreatment with MK801 and BAF resulted in greater neuroprotection than either drug alone. Thus, in vitro trauma with concurrent metabolic inhibition parallels in vivo TBI, showing both NMDA-se nsitive necrosis and caspase-3-dependent apoptosis.