RESUMO
Astrocytes, the major glial cells in the central nervous system (CNS), can express vascular cell adhesion molecule-1(VCAM-1) in response to cytokines, such as TNF-alpha. In CNS, an increased VCAM-1 expression may contribute to inflammatory processes. We, in the present study, have examined the effect of human plasma High Density Lipoproteins (HDL) and other lipoproteins on VCAM-1 expression in astroglioma cells since astrocytes secrete HDL-like lipoprotein particles which contain apo E and cholesterol, phospholipid. The exposure of astroglioma cells to the major plasma lipoprotein fractions (VLDL, LDL and HDL) had no effect on the VCAM-1 expression. However, TNF-alpha-induced VCAM-l was inhibited by HDL in a dose-dependent manner, but not by VLDL or LDL. The inhibitory effect of HDL on TNF-alpha-induced VCAM-l was reversed by the inclusion of Apo A-I antibody, the major apolipoprotein of HDL, demonstrating the specificity of this response. Reconstituted HDL (discoidal complex of apo HDL and DMPC), but not apo HDL or DMPC, was effective in suppressing the VCAM-1 expression. RNase protection assay (RPA) revealed that TNF-alpha- induced VCAM-l mRNA expression was markedly inhibited by HDL (500 microgram cholesterol/mL). These results indicate that HDL-like particles in the CNS may function as an immunosuppressive molecule in pathologic conditions of CNS.