Cytosolic phospholipase A2α upregulation mediates apoptotic neuronal death induced by aggregated amyloid-β peptide1-42

Increased cytosolic phospholipase A(2)alpha (cPLA(2)alpha) immunoreactivity and transcript were observed in Alzheimer's disease (AD) brain associated with amyloid deposits. Thus, the present study examined whether cPLA(2)alpha upregulation participate in cortical neuron damage induced by aggregated A beta(1-42) and determined its role in the signaling events leading to damage, using an antisense technology. Exposure of primary cortical neurons to 1 mu M aggregated A beta(1-42) for 24 h induced up-regulation and activation of cPLA(2)alpha and apoptotic cell death of about 30% as detected by: cell count, MTT reduction, caspases-3 and -8 activation, DAPI and TUNEL staining, that were prevented by inhibition of cPLA2 alpha up-regulation and activity in the presence of antisense against cPLA(2)alpha, (AS). cPLA(2)alpha, was rapidly activated upon addition of aggregated A beta(1-42), as determined by its phosphorylated form on serine 505, and this activity was dependent on NADPH oxidase activity. NOX2- and NOX4-NADPH oxidase upregulation at 24 h of aggregated A beta(1-42) exposure was not affected by the presence of AS, but superoxide production was reduced, probably due to NOX2 inhibition. cPLA(2)alpha upregulation led to activation of neutral sphingomyelinase (N-SMase) as its activity was inhibited in the presence of AS, and could be restored by addition of arachidonic acid. Addition of ceramide analog induced caspase-8 activation leading to caspase-3 activation and apoptotic neuronal death. In conclusion, our results suggest that cPLA2 alpha activity plays a crucial role in the signaling cascade leading to apoptotic neuronal death by aggregated A beta(1-42) probably via activation of N-SMase, ceramide production and caspases-3 and -8. (C) 2013 Elsevier Ltd. All rights reserved.