High density lipoproteins downregulate basic fibroblast growth factor production and release in minimally oxidated-LDL treated smooth muscle cells

Increase in plasma low density lipoprotein (LDL) levels and/or decrease in high density lipoprotein (HDL) levels are major risk factors for the development of atherosclerosis. An oxidative modification of LDL represents a key process in atherogenesis. It is well known that the LDL/HDL ratio is more important than the individual LDL and HDL levels to predict atherosclerosis. The purpose of our study was to investigate the effects of mildly oxidized LDL (minimally modified LDL: MM-LDL) and HDL, administrated alone or in combination, on the production and release of basic fibroblast growth factor (bFGF) by bovine aortic smooth muscle cells (SMCs) in culture. MM-LDL and HDL have opposite effects on aortic SMCs: MM-LDL increases both bFGF production and release and SMC proliferation, while HDL decreases both bFGF production and release and SMC proliferation. The effects of either MM-LDL or HDL on SMCs are mediated through a Gi-protein-coupled receptor. The simultaneous treatment of SMCs with MM-LDL and HDL (MM-LDL/HDL ratio = 4.0) produced the inhibition of MM-LDL effects. Our data suggest that the protective role of HDL could also be exerted through the inhibition of the pro-atherosclerotic effects of MM-LDL on SMCs.