Oxidized LDL Exposure Induces Morphological Change Independent of Rac and Ras Expression But May Involve Intracellular Ca[fec7]in Vascular Endothelial Cells

Abstract

氧化態低密度脂蛋白(Ox-LDL)被認為與動脈粥狀硬化的發生有關，可發現於動脈粥狀硬化斑中,先前的研究發現氧化態低密度脂蛋白可誘導血管內皮細胞產生波浪狀並增加胞飲活性。報導指出,這種現象與增加一些小分子GTP結合蛋白，例如Ras、Rac蛋白質表現量或/和提升細胞內的鈣離子濃度有關。本研究利用免疫沈澱和西方墨點法，以偵測n-LDL或x-LDL處理後的血管內皮細胞，表現Ras、Rac蛋白質量，利用Fura-2螢光劑以偵測n-LDL或ox-LDL急性處理血管內皮細胞內鈣離子濃度變化，結果發現血管內皮細胞暴露在氧化態低密度脂蛋白減低Ras和Rac蛋白質表現，提高細胞內鈣離子濃度。這種結果顯示，血管內皮細胞暴露在氧化態低密度脂蛋白誘發形態改變，可能牽涉細胞內鈣離子濃度提高，與Ras和Rac蛋白質表現無關;進一步研究,氧化態低密度脂蛋白使得細胞的Ras蛋白質表現量減少而減弱其下游作用者MAP kinase的活性,導致血管內皮細胞生長延遲。

Oxidized low density lipoprotein (ox-LDL) has been detected in atherosclerotic lesions and was thought to be involved in atherogenesis. Our previous study showed that ox-LDL induced membrane ruffling and increased the pinocytotic activity in vascular endothelial cell (EC). It has been shown that increased the expression of small GTP-binding proteins (such as Ras and Rac) and increased [Ca2+]i might induce cell membrane ruffling and promote the pinocytotic activity. In this study, we directly assayed Ras and Rac proteins expressions by immunoprecipitation blot and Western blot in n-LDL or ox-LDL treated EC. Using Fura-2 to determine the intracellular calcium elicited by ox-LDL or n-LDL acute exposure in EC. We showed ox-LDL exposure reduced Ras and Rac proteins expressions and elevated [Ca2+]i levels in cultured EC. These results suggested ox-LDL exposed EC induced morphological change were independent of the expression of Rac and Ras proteins, but might involve in the elevation of [Ca2+]i. Ox-LDL exposure induced growth retardation might be related to reduction Ras protein expressions and attenuation of its downstream effector, the MAP (ERK1/ERK2) kinase activity in vascular ECs.