The Effect Of A20 On OxLDL-mediated Cell Proliferation And Apoptosis And Related Molelar Mechanisms In Macrophages And Vascular Smooth Muscle Cells

Atherosclerosis (AS) is the principal cause of heart attack, stroke. AS is a disease of multiple etiologies resulting from a series of molecular and cellular changes that begin in the intima of the arterial wall. An elevated plasma level of low-density lipoprotein (LDL) is clearly a major risk factor for cardiovascular disease. An increase in plasma LDL levels lead to an increased rate of entry of LDL into the intima. Where the LDL can undergo oxidative modification catalyzed by any of the major cell type found in artery. OxLDL exhibit a variety of biology properties potentially involved in atherosclerosis. Such as induction of adhesion protein expression and subsequent entry of mononuclear cells, formation of foam cells and fatty streak, induction of macrophages apoptosis and smooth muscle cell (SMC) migration and proliferation and changes in the extracellular matrix.Previous studies showed that A20 possessed anti-apoptosis effect as evidence in inhibition of the activation of NF-kB. Thus we presumed that A20 might also have anti-apoptosis effect mediated by OxLDL in macrophages and might inhibit VSMC proliferation and migration. Therefore, the effect of A20 on OxLDL-induced damages of RAW264.7 macrophages and VSMC as well as their effects on related signal transduction were studied. The results are described as follows:In vitro experiments as well as histological studies suggest that OxLDL can cause macrophages damages. The protective effect of A20 was investigated in RAW264.7 cells. RAW264.7 cells were infected with AdGFP, 10-100μg/mL OxLDL can decrease cell viability in a time-and dose-dependent manners. Analysis of the mount of the sub Gl DNA and morphological changes as well as DNA fragmentation, consistently revealed OxLDL-induced apoptosis in RAW264.7 cells. We found a similar pattern with apoptotic effects of OxLDL when the degree of apoptosis was examined by Hoechst 33342 staining visualizing the presence of apoptotic nuclei and DNA laddering visualizing the degree of nucleosomal DNA fragmentation. In the same experimental condition, nLDL was not shown to have significant cytotoxicity. In contrast, macrophages infected with AdA20 were significantly protected from OxLDL-mediated cytotoxicity and apoptosis.