Transforming growth factor-beta1 inhibition of vascular smooth muscle cell activation is mediated via Smad3.
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.
Feinberg
Mark W
MW
Division of Cardiovascular Medicine and Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
Watanabe
Masafumi
M
Lebedeva
Maria A
MA
Depina
Ana S
AS
Hanai
Jun-ichi
J
Mammoto
Tadanori
T
Frederick
Joshua P
JP
Wang
Xiao-Fan
XF
Sukhatme
Vikas P
VP
Jain
Mukesh K
MK
D000818:Animals; D001161:Arteriosclerosis / Q000209:etiology / Q000378:metabolism; D051743:CCAAT-Enhancer-Binding Protein-delta; D022762:CCAAT-Enhancer-Binding Proteins / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D007249:Inflammation / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D051900:Smad3 Protein; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D053773:Transforming Growth Factor beta1
D022762:CCAAT-Enhancer-Binding Proteins; C497254:Cebpd protein, rat; D004268:DNA-Binding Proteins; D051900:Smad3 Protein; C497787:Smad3 protein, rat; C508962:Tgfb1 protein, rat; D015534:Trans-Activators; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D051743:CCAAT-Enhancer-Binding Protein-delta; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat