The Lipid Research Laboratory, Technion Faculty of Medicine, The Rappaport Family Institute for Research in the Medical Sciences, and Rambam Medical Center, Haifa 31096, Israel.
The Lipid Research Laboratory, Technion Faculty of Medicine, The Rappaport Family Institute for Research in the Medical Sciences, and Rambam Medical Center, Haifa 31096, Israel.
Atherosclerosis. 2014 Mar;233(1):11-8. doi: 10.1016/j.atherosclerosis.2013.11.070. Epub 2013 Dec 25.
The aim of the present study was to investigate the effect of urokinase-type plasminogen activator (uPA) on the expression of the scavenger receptor class B type I (SR-BI) in hepatocytes, and its impact on the removal of HDL-cholesteryl ester (CE) in the liver.
Huh7 hepatoma cell lines were incubated with increasing concentrations of uPA. uPA dose-dependently decreased SR-BI protein expression, as determined by flow cytometry (FACS) and by Western blot assays, and down-regulated SR-BI gene expression. Functionally, uPA decreased both the cellular binding of HDL to Huh7 hepatocytes, and the selective uptake of CE from HDL, as determined by several methods including BODIPY staining, cellular cholesterol determination and chasing radio-labeled CE transfer from HDL to the cells. These results were further confirmed using primary rat hepatocytes. The effect of uPA on hepatic SR-BI expression was mediated via binding to the uPA receptor (uPAR). In vivo, SR-BI protein and gene expressions were found to be increased in hepatocytes derived from the uPAR-KO mice compared to C57Bl/6 mice, and in parallel HDL-cholesterol levels in plasma derived from uPAR-KO mice were decreased. Moreover, deficiency of uPAR significantly accelerated the plasma decay of injected HDL-[(3)H]CE.
The results of this study suggest that uPA decreases the removal of HDL-CE in the liver via suppression of the hepatic SR-BI expression. Impaired reverse cholesterol transport (RCT) may result in atherogenic dysfunctional HDL metabolism and may contribute to atherosclerosis development.
本研究旨在探讨尿激酶型纤溶酶原激活物（uPA）对肝细胞中清道夫受体 B 类 I 型（SR-BI）表达的影响，及其对肝脏清除高密度脂蛋白胆固醇酯（HDL-CE）的影响。
用不同浓度的 uPA 孵育 Huh7 肝癌细胞系。流式细胞术（FACS）和 Western blot 检测结果表明，uPA 呈剂量依赖性降低 SR-BI 蛋白表达，并下调 SR-BI 基因表达。功能实验表明，uPA 降低了 HDL 与 Huh7 肝细胞的细胞结合，以及从 HDL 摄取 CE 的选择性，这些结果通过几种方法进一步证实，包括 BODIPY 染色、细胞胆固醇测定和放射性标记的 CE 从 HDL 转移到细胞的追踪。uPA 对肝 SR-BI 表达的影响是通过与 uPA 受体（uPAR）结合介导的。在体内，与 C57Bl/6 小鼠相比，uPAR-KO 小鼠来源的肝细胞中 SR-BI 蛋白和基因表达增加，同时来自 uPAR-KO 小鼠的血浆 HDL 胆固醇水平降低。此外，uPAR 缺乏显著加速了注射的 HDL-[(3)H]CE 的血浆衰变。
本研究结果表明，uPA 通过抑制肝 SR-BI 表达降低肝脏对 HDL-CE 的清除。受损的胆固醇逆向转运（RCT）可能导致致动脉粥样硬化功能失调的 HDL 代谢，并可能导致动脉粥样硬化的发展。
