TGF-beta induces proangiogenic and antiangiogenic factors via parallel but distinct Smad pathways

Kidney Int. 2004 Aug;66(2):605-13. doi: 10.1111/j.1523-1755.2004.00780.x.


Background: Angiogenesis has a key role in numerous disease processes. One of the most important angiogenic factors is vascular endothelial growth factor (VEGF-A), whereas thrombospondin-1 (TSP-1) is a major antiangiogenic factor. Recent studies have shown that VEGF-A as well as TSP-1 is regulated by transforming growth factor-beta1 (TGF-beta1), but the mechanism remains unclear.

Methods: We examined the role of TGF-beta1 and its signaling pathways in mediating expression of these two molecules. Rat proximal tubular cells (NRK52E) were stimulated with TGF-beta1 to induce VEGF-A and TSP-1 synthesis. To clarify roles of receptor-activated Smads (R-Smads), we blocked Smad signaling using overexpression of the inhibitory Smad, Smad7, and by using fibroblasts from wild-type or knockout mice. To confirm the antiantigenic role of Smads, soluble Flt-1 regulation in response to TGF-beta1 was also examined. In addition, the effect of conditioned media from NRK52E and Smad knockout cells was examined on endothelial cell proliferation.

Results: Induction of VEGF-A and TSP-1 by TGF-beta1 in NRK52E cells was associated with activation of pathway-restricted R-Smads (Smad2 and 3) and blocking these Smads by overexpression of Smad7 blocked their induction. By using of Smad knockout cells, Smad3 was shown to have a key role in the stimulation of VEGF-A expression whereas Smad2 was critical for TSP-1 expression. Consistent with the hypothesis that Smad2 has an antiangiogenic function, we also demonstrated that Smad2, but not Smad3, mediated the expression of VEGF-A antagonist, soluble VEGF-A receptor sFlt-1, in response to TGF-beta1. Conditioned media from NRK52E, which was stimulated by TGF-beta1 for 24 hours, did not induce endothelial cell proliferation. However, conditioned media from Smad2 knockout induced endothelial cell proliferation, whereas endothelial cell proliferation was inhibited by Smad3 knockout-derived conditioned media.

Conclusion: R-Smads have distinct roles in mediating the expression of pro- and antiangiogenic growth factors in response to TGF-beta1.

Publication types

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

MeSH terms

  • Animals
  • Cell Line
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Dose-Response Relationship, Drug
  • Gene Expression / drug effects
  • Kidney Tubules, Proximal / cytology
  • Kidney Tubules, Proximal / drug effects
  • Kidney Tubules, Proximal / metabolism*
  • Neovascularization, Physiologic / drug effects*
  • Neovascularization, Physiologic / physiology
  • RNA, Messenger / analysis
  • Rats
  • Signal Transduction / drug effects*
  • Signal Transduction / physiology
  • Smad2 Protein
  • Smad3 Protein
  • Smad7 Protein
  • Thrombospondin 1 / genetics
  • Trans-Activators / genetics
  • Trans-Activators / metabolism*
  • Transforming Growth Factor beta / pharmacology*
  • Transforming Growth Factor beta1
  • Vascular Endothelial Growth Factor A / genetics


  • DNA-Binding Proteins
  • RNA, Messenger
  • Smad2 Protein
  • Smad2 protein, rat
  • Smad3 Protein
  • Smad3 protein, rat
  • Smad7 Protein
  • Smad7 protein, rat
  • Tgfb1 protein, rat
  • Thrombospondin 1
  • Trans-Activators
  • Transforming Growth Factor beta
  • Transforming Growth Factor beta1
  • Vascular Endothelial Growth Factor A
  • vascular endothelial growth factor A, rat