VEGF stimulation of endothelial cell PAF synthesis is mediated by group V 14 kDa secretory phospholipase A 2

Vascular endothelial growth factor (VEGF) is a potent inducer of inflammation, and we have shown that this latter effect is mediated through endothelial cell (EC) PAF synthesis. Since the phospholipid remodelling pathway enzymes (CoA‐independent transacylase, CoA‐IT; phospholipase A 2 , PLA 2 ; and lyso‐PAF acetyltransferase, lyso‐PAF‐AT) may participate in PAF synthesis, we assessed their contribution to VEGF‐induced PAF synthesis in bovine aortic EC (BAEC) and human umbilical vein EC (HUVEC). VEGF enhanced BAEC and HUVEC PAF synthesis by up to 28 and 4 fold above basal levels respectively. A pretreatment with a CoA‐IT and lyso‐PAF‐AT inhibitor (Sanguinarin; 500 n M ) blocked VEGF‐induced PAF synthesis by 95%, a specific CoA‐IT inhibitor (SKF45905; 10 – 50 μ M ) was without effect, confirming the crucial role of the PLA 2 and lyso‐PAF‐AT. Treatment with secreted PLA 2 (sPLA 2 ) inhibitors which have been shown to inhibit both groups IIA and V sPLA 2 (SB203347; 10 μ M and LY311727; 100 μ M ) blocked EC PAF synthesis by up to 90%, whereas selective inhibition of group IIA sPLA 2 (LY311727; 1 μ M ) had no significant effect. RT – PCR and Western blot analyses demonstrated the presence of group V sPLA 2 whereas group IIA sPLA 2 was undetected in EC. Treatment with cytosolic and calcium‐independent PLA 2 inhibitors (Arachidonyl trifluoromethyl ketone, Bromoenol lactone, Methyl arachydonyl fluorophosphate, up to 50 μ M ) did not prevent but rather potentiated the VEGF effect on EC PAF synthesis. These results provide evidence that with VEGF activation of EC cells, the group V sPLA 2 provides substrate for EC PAF formation.British Journal of Pharmacology (2001) 134 , 197–205; doi: 10.1038/sj.bjp.0704215