Transforming growth factor-beta1 inhibition of vascular smooth muscle cell activation is mediated via Smad3

J Biol Chem. 2004 Apr 16;279(16):16388-93. doi: 10.1074/jbc.M309664200. Epub 2004 Feb 1.


Activation of vascular smooth muscle cells (VSMCs) by proinflammatory cytokines is a key feature of atherosclerotic lesion formation. Transforming growth factor (TGF)-beta1 is a pleiotropic growth factor that can modulate the inflammatory response in diverse cell types including VSMCs. However, the mechanisms by which TGF-beta1 is able to mediate these effects remains incompletely understood. We demonstrate here that the ability of TGF-beta1 to inhibit markers of VSMC activation, inducible nitric-oxide synthase (iNOS) and interleukin (IL)-6, is mediated through its downstream effector Smad3. In reporter gene transfection studies, we found that among a panel of Smads, Smad3 could inhibit iNOS induction in an analogous manner as exogenous TGF-beta1. Adenoviral overexpression of Smad3 potently repressed inducible expression of endogenous iNOS and IL-6. Conversely, TGF-beta1 inhibition of cytokine-mediated induction of iNOS and IL-6 expression was completely blocked in Smad3-deficient VSMCs. Previous studies demonstrate that CCAAT/enhancer-binding protein (C/EBP) and NF-kappaB sites are critical for cytokine induction of both the iNOS and IL-6 promoters. We demonstrate that the inhibitory effect of Smad3 occurs via a novel antagonistic effect of Smad3 on C/EBP DNA-protein binding and activity. Smad3 mediates this effect in part by inhibiting C/EBP-beta and C/EBP-delta through distinct mechanisms. Furthermore, we find that Smad3 prevents the cooperative induction of the iNOS promoter by C/EBP and NF-kappaB. These data demonstrate that Smad3 plays an essential role in mediating TGF-beta1 anti-inflammatory response in VSMCs.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Arteriosclerosis / etiology
  • Arteriosclerosis / metabolism
  • CCAAT-Enhancer-Binding Protein-delta
  • CCAAT-Enhancer-Binding Proteins / biosynthesis
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Inflammation / metabolism
  • Muscle, Smooth, Vascular / physiology*
  • Nitric Oxide Synthase / biosynthesis
  • Nitric Oxide Synthase Type II
  • Rats
  • Signal Transduction / physiology
  • Smad3 Protein
  • Trans-Activators / genetics
  • Trans-Activators / metabolism*
  • Transcription Factors*
  • Transforming Growth Factor beta / metabolism*
  • Transforming Growth Factor beta1


  • CCAAT-Enhancer-Binding Proteins
  • Cebpd protein, rat
  • DNA-Binding Proteins
  • Smad3 Protein
  • Smad3 protein, rat
  • Tgfb1 protein, rat
  • Trans-Activators
  • Transcription Factors
  • Transforming Growth Factor beta
  • Transforming Growth Factor beta1
  • CCAAT-Enhancer-Binding Protein-delta
  • Nitric Oxide Synthase
  • Nitric Oxide Synthase Type II
  • Nos2 protein, rat