The antiatherogenic and antiinflammatory effect of HDL-associated lysosphingolipids operates via Akt → NF-kappaB signalling pathways in human vascular endothelial cells

Adhesion of mononuclear cells to the vascular endothelium and their subsequent transmigration into the arterial wall represent key events in the pathogenesis of arteriosclerosis. In previous studies we have shown that high density lipoproteins (HDL) and the HDL–associated sphingosylphosphorylcholine (SPC) have the ability to suppress the TNF–alpha–induced expression of endothelial cell E–selectin. However, the current understanding of the mechanism by which HDL reduces the expression of E–selectin is still incomplete. In the present study we show that interaction of the HDL–associated sphingosylphosphorylcholine and sphingosylgalactosyl–3–sulfate (lysosulfatide, LSF) with the G–protein–coupled EDG receptor initiates a signalling cascade that activates the protein kinase Akt and reduces the E–selectin, ICAM–1 and VCAM–1 expression on protein and mRNA level. This signalling cascade is consistently associated with a reduced translocation of TNF–alpha–activated NF–kappaB into the cell nucleus. The suppressor effect of SPC and LSF is completely reverted by inhibition of the phosphatidylinositol– 3–kinase/Akt pathway. We conclude that the antiatherogenic/antiinflammatory effect of lysosphingolipids depends on a competitive interaction of EDG receptor–induced inhibition and TNF–alpha–initiated stimulation of NF–kappaB translocation into the cell nucleus thereby preventing or stimulating inflammatory events in atherogenesis.