Department of Nephroimmunology, Children's Hospital of Chongqing Medical University, 136 Zhongshan Er Road, Yu Zhong District, Chongqing, 400014, People's Republic of China.
Mol Cell Biochem. 2011 Jan;346(1-2):197-204. doi: 10.1007/s11010-010-0605-4. Epub 2010 Oct 10.
The aim of this article is to investigate whether interleukin-1β (IL-1β) could regulate the intracellular accumulation of cholesterol and the expression of lipid-metabolism-related regulators in podocytes in vitro and the potential mechanisms. Podocytes were treated with 200 μg/ml of low-density protein (LDL), 20 ng/ml of IL-1β, or 200 μg/ml of LDL plus 5-20 ng/ml of IL-1β for 24 h in vitro. The contents of intracellular cholesterol were determined by enzymatic assays and Oil Red O staining. The levels of LDL receptor (LDLr), 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, sterol regulatory element binding protein 2 (SREBP-2), SREBP cleavage activating protein (SCAP), and insulin-induced gene-1 (Insig-1) expression were characterized by real-time polymerase chain reaction (RT-PCR) and Western blot assays. Treatment with IL-1β or LDL alone increased the contents of intracellular cholesterol (P < 0.05 for both) and lipid droplets, and treatment with both IL-1β and LDL further increased the accumulation of intracellular cholesterol in podocytes (P < 0.05 vs. LDL alone). While loading with LDL significantly inhibited the expression of LDLr, HMG-CoA reductase, nuclear SREBP-2 (nSREBP-2), SCAP, and Insig-1 by 40-62% treatment with IL-1β enhanced the expression of LDLr, HMG-CoA reductase and nSREBP-2, but not Insig-1, in podocytes (P < 0.05 vs. control). Treatment with both LDL and IL-1β significantly increased the levels of LDLr and HMG-CoA reductase expression and the ratio of SCAP to Insig-1, as compared with that in the LDL-treated podocytes (P < 0.05 vs. LDL alone). Our data indicated that IL-1β mitigated the LDL-triggered SCAP-SREBP-2-mediated feedback inhibition on the expression of LDLr and HMG-CoA reductase, leading to the intracellular accumulation of LDL-cholesterol in podocytes in vitro.
本文旨在研究白细胞介素-1β（IL-1β）是否可以调节体外足细胞内胆固醇的积累以及脂质代谢相关调节剂的表达，并探讨其潜在机制。体外将足细胞分别用 200μg/ml 低密度脂蛋白（LDL）、20ng/ml IL-1β、200μg/ml LDL 加 5-20ng/ml IL-1β处理 24 小时。采用酶法和油红 O 染色检测细胞内胆固醇含量。实时聚合酶链反应（RT-PCR）和 Western blot 检测 LDL 受体（LDLr）、3-羟-3-甲基戊二酰辅酶 A（HMG-CoA）还原酶、固醇调节元件结合蛋白 2（SREBP-2）、SREBP 切割激活蛋白（SCAP）和胰岛素诱导基因-1（Insig-1）的表达水平。结果显示，单独使用 IL-1β 或 LDL 均可增加细胞内胆固醇含量（两者均 P<0.05）和脂滴形成，而同时使用 IL-1β 和 LDL 进一步增加了足细胞内胆固醇的积累（与 LDL 单独处理相比 P<0.05）。LDL 处理显著抑制 LDLr、HMG-CoA 还原酶、核 SREBP-2（nSREBP-2）、SCAP 和 Insig-1 的表达，而 IL-1β 处理增强了 LDLr、HMG-CoA 还原酶和 nSREBP-2 的表达，但不影响 Insig-1（与对照组相比 P<0.05）。同时使用 LDL 和 IL-1β 显著增加了 LDLr 和 HMG-CoA 还原酶的表达水平，以及 SCAP 与 Insig-1 的比值，与 LDL 单独处理的足细胞相比（与 LDL 单独处理相比 P<0.05）。综上所述，IL-1β 减轻了 LDL 触发的 SCAP-SREBP-2 介导的对 LDLr 和 HMG-CoA 还原酶表达的反馈抑制，导致体外足细胞内 LDL 胆固醇的积累。
