Secreted phospholipase A2 induces vascular endothelial cell migration

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Abstract
Secreted phospholipase A2 (sPLA2) regulates a variety of cellular functions. The present investigation was undertaken to elucidate the potential role of sPLA2 in endothelial cell (EC) migration. Bovine aortic endothelial cells (BAECs) exposed to sPLA2 placed in the lower compartment of a modified Boyden chamber displayed increased migration compared to cells exposed to vehicle. The effect of sPLA2 on EC migration was time and dose dependent. Migration of BAECs was observed at 30 minutes, increased over 1 to 2 hours, and declined thereafter. At 2 hours of stimulation, sPLA2 (0.01-2 μmol/L) induced 1.2- to 3-fold increased cell migration compared with media alone. Among the different sPLA2s tested, bee venom, Naja naja, and porcine and human pancreatic PLA2s all evoked a migratory response in ECs. Moreover, human synovial fluid, obtained from patients with arthritis and containing sPLA2 activity, induced EC migration. Migration of ECs was significantly reduced after exposure to a catalytic site mutant of pancreatic sPLA2with decreased lipolytic activity as compared to wild-type sPLA2. Similarly, pretreatment of human synovial fluid withp-bromophenacyl bromide, an irreversible inhibitor of sPLA2, markedly decreased the ability of human synovial fluid to stimulate EC migration. Moreover, migration of ECs was stimulated on exposure to hydrolytic products of sPLA2activity including arachidonic acid, lysophosphatidic acid, and lysophosphatidylcholine. These findings suggest that sPLA2plays a physiologic role in induction of EC migration. Moreover, the effects of sPLA2 on EC migration are mediated, at least in part, by its catalytic activity.