Published online before print March 23, 2006, doi: 10.1161/01.RES.0000218782.52610.dc
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Submitted on October 12, 2005
Revised on March 3, 2006
Accepted on March 13, 2006
Essential Role of Smad3 in Angiotensin II-Induced Vascular Fibrosis
Wansheng Wang ;
From the Departments of Medicine and Molecular and Cellular Biology (W.W., X.R.H., E.C., K.O., H.Y.L.), Baylor College of Medicine, Houston, Tex; Department of Pathology (L.D.T.), Methodist Hospital, Houston, Texas; Genetics of Development and Disease Branch (C.D.), Digestive and Kidney Diseases, National Cancer Institute, National Institutes of Health, Bethesda, Md; Vanderbilt-Ingram Cancer Center (N.A.B.), Vanderbilt University School of Medicine, Nashville, Tenn; and Department of Medicine-Renal Division (E.P.B.), Mount Sinai Medical School, New York, NY.
* To whom correspondence should be addressed. E-mail: hlan{at}bcm.tmc.edu.
Angiotensin II (Ang II) plays a pivotal role in vascular fibrosis, which leads to serious complications in hypertension and diabetes. However, the underlying signaling mechanisms are largely unclear. In hypertensive patients, we found that arteriosclerosis was associated with the activation of Smad2/3. This observation was further investigated in vitro by stimulating mouse primary aorta vascular smooth muscle cells (VSMCs) with Ang II. There were several novel findings. First, Ang II was able to activate an early Smad signaling pathway directly at 15 to 30 minutes. This was extracellular signal-regulated kinase 1/2 (ERK1/2) mitogen-activated protein kinase (MAPK) dependent but transforming growth factor-
(TGF-) independent because Ang II-induced Smad signaling was blocked by addition of ERK1/2 inhibitor and by dominant-negative (DN) ERK1/2 but not by DN-TRII or conditional deletion of TRII. Second, Ang II was also able to activate the late Smad2/3 signaling pathway at 24 hours, which was TGF- dependent because it was blocked by the anti-TGF- antibody and DN-TRII. Finally, activation of Smad3 but not Smad2 was a key and necessary mechanism of Ang II-induced vascular fibrosis because Ang II induced Smad3/4 promoter activities and collagen matrix expression was abolished in VSMCs null for Smad3 but not Smad2. Thus, we concluded that Ang II induces vascular fibrosis via both TGF--dependent and ERK1/2 MAPK-dependent Smad signaling pathways. Activation of Smad3 but not Smad2 is a key mechanism by which Ang II mediates arteriosclerosis.
Key words: angiotensin • TGF-
•
Smads •
vascular fibrosis
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