肝X受体介导肾小球系膜细胞胆固醇外流

目的:探讨肝X受体在肾系膜细胞脂质代谢中的作用及机制.方法:肝X受体两种亚型的表达运用反转录-多聚酶链式反应和蛋白印迹实验方法证实.ATP结合盒蛋白(ATP-binding cassette,ABC)A1和G1的表达水平用实时荧光定量多聚酶链式反应及转染荧光素酶报告基因方法研究.胆固醇的外流量用3H]标记胆固醇方法测量.结果:肝X受体两种亚型在肾、肾小球、系膜细胞中均有表达.肝X受体人工合成配体TO901317处理系膜细胞后,不仅ABCA1表达上调,而且ABCG1的表达也增高,并导致游离胆固醇外流增加.结论:在小鼠肾系膜细胞中存在肝X受体两种亚型的表达,肝X受体能够通过上调ABCA1和ABCG1的表达,增加系膜细胞中游离胆固醇的外流,减轻脂质负荷和细胞损伤.

Liver X receptors mediate cholesterol efflux in mouse glomerular mesangial cells

OBJECTIVE: To examine the role of liver X receptors (LXRs) in lipid metabolism in cultured mouse mesangial cells. METHODS: To determine whether LXRalpha and LXRbeta are expressed in the kidney, RT-PCR and western blot assay were utilized. Cultured mesangial cells were treated with either vehicle or LXR agonist TO901317(10 micromol/L) for 24 hours. Real-time PCR analysis was used to detect ABCA1 and ABCG1 expressions. Cells were also transfected with a human ABCA1 promoter driven luciferase reporter plasmid and then stimulated with or without TO901317 for 24 hours. In order to determine the effect of TO901317 on protein expression of ABCA1, LXRalpha adenovirus was used to overexpress LXRalpha in the cultured cells. Finally, 3H] cholesterol efflux assay was performed to evaluate the efflux of cholesterol upon TO901317 stimulation. RESULTS: Both LXRalpha and LXRbeta were expressed in the kidney, freshly isolated glomeruli and mesangial cells. After treatment with TO901317, both ABCA1 and ABCG1 expressions were induced. Moreover, ABCA1 protein level was increased after the cells were simultaneously treated with LXRalpha-adenovirus and TO901317. The cholesterol efflux was also significantly enhanced after TO901317 treatment. CONCLUSION: LXRalpha and LXRbeta were functionally expressed in mouse mesangial cells. Activation of LXRs enhanced cholesterol efflux possibly through upregulating ABCA1 and ABCG1 expressions in mesangial cells. Therefore, LXR agonist might ameliorate lipid accumulation and reduce related cell injury in mesangial cells.