Angiotensin II stimulates alpha3(IV) collagen production in mouse podocytes via TGF-beta and VEGF signalling: implications for diabetic glomerulopathy

Nephrol Dial Transplant. 2005 Jul;20(7):1320-8. doi: 10.1093/ndt/gfh837. Epub 2005 Apr 19.


Background: The podocyte is bathed in an angiotensin II (AngII)-rich ultrafiltrate, but the impact of AngII on podocyte pathobiology is not well known. Because podocytes play a direct role in the glomerular basement membrane (GBM) thickening of diabetes, the alpha3(IV) collagen chain was examined. Podocyte expression of alpha3(IV) collagen may involve the transforming growth factor-beta (TGF-beta) and vascular endothelial growth factor (VEGF) systems.

Methods: Cultured mouse podocytes were treated with various doses of AngII for selected periods of time, with or without inhibitors of TGF-beta and VEGF signalling, SB-431542 and SU5416, respectively. TGF-beta1 and VEGF were assayed by enzyme-linked immunosorbent assay (ELISA); alpha3(IV) collagen, TGF-beta type II receptor and phospho-Smad2 were assayed by immunoblotting.

Results: AngII >or=10(-10) M was found to stimulate the production of alpha3(IV) collagen significantly in as short a time as 3 h. The expression of alpha3(IV) collagen was influenced by the TGF-beta system, but AngII did not increase the podocyte's production of TGF-beta1 ligand; rather, it increased the expression of the TGF-beta type II receptor and activated the TGF-beta signalling system through Smad2. Despite the TGF-beta receptor upregulation, synergy between AngII and TGF-beta1 to boost alpha3(IV) collagen production was not observed. However, blockade of TGF-beta signalling with SB-431542 prevented AngII from stimulating alpha3(IV) collagen production. Podocyte expression of alpha3(IV) collagen was also increased by the autocrine activity of VEGF. Podocytes were stimulated to secrete VEGF by 10(-10) M or higher AngII after 48 h. Blockade of the endogenous VEGF activity by SU5416 prevented AngII-stimulated alpha3(IV) collagen production.

Conclusions: AngII stimulates the podocyte to produce alpha3(IV) collagen protein via mechanisms involving TGF-beta and VEGF signalling. Alterations in alpha3(IV) collagen production may contribute to GBM thickening and perhaps proteinuria in diabetes.

Publication types

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

MeSH terms

  • Angiotensin II / administration & dosage
  • Angiotensin II / pharmacology*
  • Animals
  • Autoantigens / biosynthesis
  • Autoantigens / drug effects*
  • Cell Culture Techniques
  • Collagen Type IV / biosynthesis
  • Collagen Type IV / drug effects*
  • Dose-Response Relationship, Drug
  • Epithelial Cells / drug effects*
  • Epithelial Cells / metabolism
  • Kidney Glomerulus / cytology
  • Kidney Glomerulus / drug effects*
  • Mice
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • Time Factors
  • Transforming Growth Factor beta / drug effects
  • Transforming Growth Factor beta / physiology
  • Vascular Endothelial Growth Factor A / drug effects
  • Vascular Endothelial Growth Factor A / physiology
  • Vasoconstrictor Agents / administration & dosage
  • Vasoconstrictor Agents / pharmacology*


  • Autoantigens
  • Collagen Type IV
  • Transforming Growth Factor beta
  • Vascular Endothelial Growth Factor A
  • Vasoconstrictor Agents
  • type IV collagen alpha3 chain
  • vascular endothelial growth factor A, mouse
  • Angiotensin II