Lysophosphatidylcholine protects cerebellar granule neurons from apoptotic cell death

Abstract

Cultured cerebellar granule neurons (CGNs) undergo apoptosis when deprived of depolarizing stimulation and provide an in vitro model system with which to study the effects of neurotrophic substances. Our previous results showed that secretory phospholipases A(2) (sPLA(2)s) protect CGNs from apoptotic cell death under the nondepolarizing condition. In this study, we further analyzed the mechanism whereby sPLA(2) exhibits this effect. Among the primary metabolites of sPLA(2) tested, lysophosphatidylcholine (LPC), but not other lysophospholipids, remarkably rescued CGNs from apoptosis. In contrast, neither arachidonic nor oleic acids displayed neurotrophic effect. Release of LPC into the culture media occurred in response to sPLA(2) treatment, and degradation or sequestration of LPC attenuated the survival-promoting effects of sPLA(2) and LPC. The neurotrophic effect of LPC required the presence of extracellular Ca(2+) and L-type Ca(2+) channel activity, suggesting that Ca(2+) influx across the plasma membrane is evoked by LPC. sPLA(2)- or LPC-induced promotion of CGN survival was suppressed by inhibitors of protein kinase A and phospholipase C, suggesting that they play a role in mediating survival-promoting signal of sPLA(2). The results presented here demonstrate a novel, unexpected neurotrophin-like effect of LPC in the central nervous system.