Angiotensin II induces connective tissue growth factor and collagen I expression via transforming growth factor-beta-dependent and -independent Smad pathways: the role of Smad3

Hypertension. 2009 Oct;54(4):877-84. doi: 10.1161/HYPERTENSIONAHA.109.136531. Epub 2009 Aug 10.

Abstract

Connective tissue growth factor (CTGF) plays a critical role in angiotensin II (Ang II)-mediated hypertensive nephropathy. The present study investigated the mechanisms and specific roles of individual Smads in Ang II-induced CTGF and collagen I expression in tubular epithelial cells with deletion of transforming growth factor (TGF)-beta1, overexpression of Smad7, or knockdown of Smad2 or Smad3. We found that Ang II-induced tubular CTGF and collagen I mRNA and protein expressions were regulated positively by phosphorylated Smad2/3 but negatively by Smad7 because overexpression of Smad7-abolished Ang II-induced Smad2/3 phosphorylation and upregulation of CTGF and collagen I in vitro and in a rat model of remnant kidney disease. Additional studies revealed that, in addition to a late (24-hour) TGF-beta-dependent Smad2/3 activation, Ang II also induced a rapid activation of Smad2/3 at 15 minutes and expression of CTGF and collagen I in tubular epithelial cells lacking the TGF-beta gene, which was blocked by the addition of an Ang II type 1 receptor antagonist (losartan) and inhibitors to extracellular signal-regulated kinase 1/2 (PD98059) and p38 (SB203580) but not by inhibitors to Ang II type 2 receptor (PD123319) or c-Jun N-terminal kinase (SP600125), demonstrating a TGF-beta-independent, Ang II type 1 receptor-mediated extracellular signal-regulated kinase/p38 mitogen-activated protein kinase cross-talk pathway in Ang II-mediated CTGF and collagen I expression. Importantly, the ability of knockdown of Smad3, but not Smad2, to inhibit Ang II-induced CTGF and collagen I expression further revealed an essential role for Smad3 in Ang II-mediated renal fibrosis. In conclusion, Ang II induces tubular CTGF expression and renal fibrosis via the TGF-beta-dependent and -independent Smad3 signaling pathways, suggesting that targeting Smad3 may have therapeutic potential for hypertensive nephropathy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Angiotensin II / physiology*
  • Animals
  • Cell Line
  • Collagen Type I / metabolism*
  • Connective Tissue Growth Factor / metabolism*
  • Disease Models, Animal
  • Epithelial Cells / cytology
  • Epithelial Cells / drug effects
  • Epithelial Cells / metabolism
  • Hypertension / complications
  • Hypertension / metabolism
  • Hypertension / pathology
  • Kidney Diseases / etiology
  • Kidney Diseases / metabolism
  • Kidney Diseases / pathology
  • Kidney Tubules / cytology
  • Kidney Tubules / drug effects
  • Kidney Tubules / metabolism*
  • Male
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Phosphorylation
  • Rats
  • Rats, Sprague-Dawley
  • Signal Transduction / physiology*
  • Smad2 Protein / metabolism
  • Smad3 Protein / metabolism*
  • Smad7 Protein / metabolism
  • Transforming Growth Factor beta / metabolism*
  • Up-Regulation
  • p38 Mitogen-Activated Protein Kinases / metabolism

Substances

  • Collagen Type I
  • Smad2 Protein
  • Smad2 protein, rat
  • Smad3 Protein
  • Smad3 protein, rat
  • Smad7 Protein
  • Smad7 protein, rat
  • Transforming Growth Factor beta
  • Angiotensin II
  • Connective Tissue Growth Factor
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • p38 Mitogen-Activated Protein Kinases