Macrophage-Derived GX Secretory Phospholipase A2 and Atherosclerosis

"4IIJ Secretory phospholipases have been implicated in several inflammatory diseases including atherosclerosis. Our model is that sPLA2 hydrolyzes LDL retained in the subendothelial extracellular matrix (ECM) resulting in the release of pro-inflammatory factors and modified LDL. Hydrolyzed LDL is small, dense and susceptible to aggregation and further modification leading to enhanced lipid uptake by macrophages. Lipid uptake by macrophages causes the formation of foam cells, which is a key event in atherosclerosis. GX sPLA2 is a recently discovered phospholipase believed to playa role in atherosclerosis. GX sPLA2 has been shown to have a higher affinity for LDL than other phospholipases and has been shown to promote m,i;1crophagefoam cell formation in vitro. We propose that GX sPLA2 promotes atherosclerosis by interaction with LDL in the subendothelial extracellular matrix (ECM). We plan to test whether macrophage-derived GX sPLA2 is pro-atherogenic. To accomplish this we will use retrovirus-mediated gene transfer to over-express GX sPLA2 in hematopoietic stem cells in an atherosclerosis mouse model. We also propose to examine whether the effect of GX sPLA2 on atherosclerosis is localized in the subendothelium or due to a systemic effect. To accomplish this aim we will mutate GX sPLA2 and insert a proteoglycan-binding motif. A catalytically inactive GX sPLA2 mutant will also be created. These mutants will also be over-expressed in hematopoietic stem cells using retrovirus-mediated gene transfer in an atherosclerosis mouse model. We expect that the results from our aims will support our model that GX sPLA2 promotes atherosclerosis and that it does so by acting within tt'l,esubendothelial ECM.