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Y. Iizuka, K.S. Park, H.Y. Yeom, S.J. Ha, Y.J. Hong, G.J. Seong; Effect of Brimonidine on Expression of Fibronectin and SMAD Signaling Pathway in Subconjuctival Fbroblasts Activated by TGF–ß . Invest. Ophthalmol. Vis. Sci. 2006;47(13):44.
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Transforming growth factor–ß (TGF–ß) have been shown to play a key role in wound healing after trabeculectomy and they use SMAD pathway for signaling. In this study we examine the effect of brimonidine, relative alpha 2 agonist, on expression of fibronectin and phospho SMAD in subconjuctival fibroblasts (SCFs) activated by TGF– ß.
We stimulated the human cultured SCFs for 48hrs with various concentrations of TGF–ß and immunoblotted the stimulated cells with anti–fibronectin antibody. In order to determine whether TGF–ß–stimulated expression of fibronectin may be affected by brimonidine, SCFs treated with or without TGF–ß were cultured in the presence of various concentrations of brimonidine (10 nM, 100 nM, 1uM, 10 uM) and examined by western blot analysis. In order to know the effect of brimonidine on SMAD signaling pathway, SCFs stimulated with TGF–ß were cultured in the presence of brimonidine 100nM and immunoblotted the stimulated cells with anti–phospho SMAD antibody. Cell viability was detected by MTT assay.
SCFs expressed alpha 2 receptors. SCFs activated by TGF– ß enhanced the expression of fibronectin. Brimonidine reduced the expression of fibronectin in SCFs activated by TGF– ß. Brimonidine reduced the expression of phospho SMAD in early period. TGF– ß stimulated the proliferation of SCFs and brimonidine inhibited the proliferation of SCFs.
These results may indicate that brimonidine inhibit the expression of fibronectin via reduction of phosphorylation of SMAD. Further study will be needed to find out the mechanism that brimonidine inhibit the phosphorylation of SMAD.
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