Smad3 deficiency attenuates renal fibrosis, inflammation,and apoptosis after unilateral ureteral obstruction.
BACKGROUND: Transforming growth factor-beta (TGF-beta) has been implicated in the development of renal fibrosis induced by unilateral ureteral obstruction (UUO). However, there is little information on signaling pathways mediating TGF-beta activity involved in molecular and cellular events leading to renal fibrosis induced by UUO. In this study, we sought to determine whether Smad3, a major signaling component of TGF-beta, mediated renal fibrosis induced by UUO. METHODS: Renal fibrosis, inflammation, and apoptosis induced by UUO were macroscopically and histologically compared between wild-type mice and Smad3 null mice. RESULTS: Gross appearance of the kidney after UUO showed relatively intact kidney in Smad3 null mice [Smad3(-/-) mice] when compared with that of wild-type mice [Smad3(+/+) mice]. Renal interstitial fibrosis based on the interstitial area stained with Aniline-blue or Sirius red solution was significantly attenuated in the obstructed kidney of Smad3(-/-) mice when compared with that of Smad3(+/+) mice. Deposition of type I and type III collagens were also significantly reduced in the obstructed kidney of Smad3(-/-) mice. In addition, the numbers of myofibroblasts, macrophages, and CD4/CD8 T cells infiltrated into the kidney after UUO were significantly attenuated in the obstructed kidney of Smad3(-/-) mice when compared with that of Smad3(+/+) mice. Furthermore, terminal deoxynucleotidyltransferase- mediated deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL) staining after UUO showed significantly reduced number of tubular apoptotic cells in the obstructed kidney of Smad3(-/-) mice when compared with that of Smad3(+/+) mice. Endogenous Smad pathway was activated in the obstructed kidney after UUO in wild-type mice as judged by the increase of phosphorylated Smad2 or phosphorylated Smad2/3-positive cells in renal interstitial area. CONCLUSION: Smad3 deficiency attenuated renal fibrosis, inflammation, and apoptosis after UUO, suggesting that Smad3 was a key molecule mediating TGF-beta activity leading to real fibrosis after UUO.[1]References
- Smad3 deficiency attenuates renal fibrosis, inflammation,and apoptosis after unilateral ureteral obstruction. Inazaki, K., Kanamaru, Y., Kojima, Y., Sueyoshi, N., Okumura, K., Kaneko, K., Yamashiro, Y., Ogawa, H., Nakao, A. Kidney Int. (2004) [Pubmed]
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