TY - JOUR
T1 - TGF-β induces proangiogenic and antiangiogenic factors via parallel but distinct Smad pathways
AU - Nakagawa, Takahiko
AU - Li, Jin H.
AU - Garcia, Gabriela
AU - Mu, Wei
AU - Piek, Ester
AU - Böttinger, Erwin P.
AU - Chen, Yan
AU - Zhu, Hong J.
AU - Kang, Duk Hee
AU - Schreiner, George F.
AU - Lan, Hui Y.
AU - Johnson, Richard J.
N1 - Funding Information:
Support for these studies was provided by National Kidney Fellowship grant (to Takahiko Nakagawa) by NIH DK-52121 (R.J.), and by a George O'Brien Center grant (P50D4-064233–01) (H.Y.L. and R.J.).
PY - 2004/8
Y1 - 2004/8
N2 - 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-β1 (TGF-β1), but the mechanism remains unclear. Methods. We examined the role of TGF-β1 and its signaling pathways in mediating expression of these two molecules. Rat proximal tubular cells (NRK52E) were stimulated with TGF-β1 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 Fit-1 regulation in response to TGF-β1 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-β1 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-β1. Conditioned media from NRK52E, which was stimulated by TGF-β1 for 24 hours, did not induce endothelial cell proliferation. However, conditioned media from Smad2 knock-out 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-β1.
AB - 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-β1 (TGF-β1), but the mechanism remains unclear. Methods. We examined the role of TGF-β1 and its signaling pathways in mediating expression of these two molecules. Rat proximal tubular cells (NRK52E) were stimulated with TGF-β1 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 Fit-1 regulation in response to TGF-β1 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-β1 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-β1. Conditioned media from NRK52E, which was stimulated by TGF-β1 for 24 hours, did not induce endothelial cell proliferation. However, conditioned media from Smad2 knock-out 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-β1.
KW - Endothelial cell proliferation
KW - Smad KO cell
KW - TSP-1
KW - VEGF
KW - sFlt-1
UR - http://www.scopus.com/inward/record.url?scp=3242757526&partnerID=8YFLogxK
U2 - 10.1111/j.1523-1755.2004.00780.x
DO - 10.1111/j.1523-1755.2004.00780.x
M3 - Article
C2 - 15253713
AN - SCOPUS:3242757526
SN - 0085-2538
VL - 66
SP - 605
EP - 613
JO - Kidney International
JF - Kidney International
IS - 2
ER -