Porcine pancreatic group IB secretory phospholipase A2potentiates Ca2+ influx through L-type voltage-sensitive Ca2+ channels

Secretory phospholipase A(2) (sPLA(2)) exhibits neurotoxicity in the central nervous system. There are high-affinity binding sites of the porcine pancreatic group IB sPLA(2) (s PLA(2)-IB) in the brain. sPLA(2)-IB causes neuronal cell death via apoptosis in the rat cerebral cortex. Although apoptosis is triggered by an influx Of Ca2+ into neurons, it has not yet been ascertained whether the Ca2+ influx is associated with the neurotoxicity of sPLA(2)-IB, We thus examined the possible involvement of Ca2+ in the neurotoxicity of sPLA(2)-IB in the primary culture of rat cortical neurons. sPLA(2)-IB induced neuronal cell death in a concentration-and time-dependent manner. This death was accompanied by condensed chromatin and fragmented DNA, exhibiting apoptotic features. Before apoptosis, sPLA(2)-IB markedly enhanced the influx of Ca2+ into neurons. A calcium chelator suppressed neurons from sPLA(2)-IB-induced neuronal cell death in a concentration-dependent manner. An L-type voltage-sensitive Ca2+ channel (L-VSCC) blocker significantly protected the sPLA(2)-IB-potentiated influx of Ca2+. On the other hand, blockers of N-VSCC and P/Q-VSCC did not. An L-VSCC blocker protected neurons from sPLA(2)-IB-induced neuronal cell death. In addition, the L-VSCC blocker ameliorated the apoptotic features of sPLA(2)-IB -treated neurons. Neither an N-VSCC blocker nor P/Q-VSCC blockers affected the neurotoxicity of the enzyme. In conclusion, these findings demonstrate that the influx of Ca2+ into neurone play an important role in the neurotoxicity of sPLA(2)-IB. Furthermore. the present study suggests that L-VSCC contribute to the sPLA(2)-IB-potentiated influx of Ca2+ into neurons. (C) 2002 Elsevier Science B.V. All rights reserved.