Interleukin-1β enhances the intracellular accumulation of cholesterol by up-regulating the expression of low-density lipoprotein receptor and 3-hydroxy-3-methylglutaryl coenzyme A reductase in podocytes

Mol Cell Biochem. 2011 Jan;346(1-2):197-204. doi: 10.1007/s11010-010-0605-4. Epub 2010 Oct 10.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Cholesterol / metabolism*
  • DNA Primers
  • Humans
  • Hydroxymethylglutaryl CoA Reductases / metabolism*
  • Interleukin-1beta / physiology*
  • Mice
  • Mice, Transgenic
  • Podocytes / enzymology
  • Podocytes / metabolism*
  • Receptors, LDL / metabolism*
  • Up-Regulation*

Substances

  • DNA Primers
  • Interleukin-1beta
  • Receptors, LDL
  • Cholesterol
  • Hydroxymethylglutaryl CoA Reductases