Metformin inhibits TNF-alpha-induced IkappaB kinase phosphorylation, IkappaB-alpha degradation and IL-6 production in endothelial cells through PI3K-dependent AMPK phosphorylation

Int J Cardiol. 2009 May 15;134(2):169-75. doi: 10.1016/j.ijcard.2008.04.010. Epub 2008 Jul 1.

Abstract

Background: Metformin has been reported to reduce cardiovascular complications in diabetic patients. The purpose of the present study was to investigate the anti-inflammatory effects of metformin on endothelial cells and the related molecular mechanisms.

Methods: Human umbilical vein endothelial cells (HUVEC) were used for the experiments. The effects of metformin on TNF-alpha-induced IL-6 production were investigated. Modulation of AMPK and related signal transduction pathways were also performed.

Results: TNF-alpha increased IL-6 secretion by HUVEC in a dose-dependent manner but inhibitors of NF-kappaB abolished the TNF-alpha-induced IL-6 production. Pre-treatment with metformin (100-1000 micromol/L) also inhibited TNF-alpha-induced IL-6 production, phosphorylation of IkappaB kinase (IKK) alpha/beta and IkappaB-alpha degradation. Metformin increased phosphorylation of AMP-activated kinase (AMPK) but wortmannin, a PI3K inhibitor, negated its effects on AMPK phosphorylation and TNF-alpha-induced IkappaB-alpha degradation. AICAR, a direct AMPK activator, had inhibitory effects on TNF-alpha-induced IL-6 production, similar to that of metformin. Transfection of siRNA against alpha1-AMPK eradicated the inhibitory effects of metformin on TNF-alpha-induced IL-6, implying the essential role of AMPK.

Conclusions: Metformin had anti-inflammatory effects on endothelial cells and inhibited TNF-alpha-induced IKKalpha/beta phosphorylation, IkappaB-alpha degradation and IL-6 production in HUVEC. This effect was related to PI3K-dependent AMPK phosphorylation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • AMP-Activated Protein Kinases / genetics
  • AMP-Activated Protein Kinases / metabolism*
  • Anti-Inflammatory Agents / pharmacology
  • Atherosclerosis / drug therapy
  • Atherosclerosis / metabolism
  • Atherosclerosis / pathology
  • Cells, Cultured
  • Endothelial Cells / cytology
  • Endothelial Cells / drug effects*
  • Endothelial Cells / metabolism
  • Enzyme Activation / drug effects
  • Humans
  • Hypoglycemic Agents / pharmacology
  • I-kappa B Kinase / metabolism*
  • Interleukin-6 / metabolism*
  • Metformin / pharmacology*
  • NF-kappa B / metabolism
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphorylation / drug effects
  • RNA, Small Interfering
  • Signal Transduction / drug effects
  • Tumor Necrosis Factor-alpha / metabolism
  • Umbilical Veins / cytology

Substances

  • Anti-Inflammatory Agents
  • Hypoglycemic Agents
  • IL6 protein, human
  • Interleukin-6
  • NF-kappa B
  • RNA, Small Interfering
  • Tumor Necrosis Factor-alpha
  • Metformin
  • Phosphatidylinositol 3-Kinases
  • PRKAA1 protein, human
  • I-kappa B Kinase
  • AMP-Activated Protein Kinases