title: The differential role of Smad2 and Smad3 in the regulation of pro-fibrotic TGFbeta1 responses in human proximal-tubule epithelial cells.
abstract: In chronic renal diseases, progressive loss of renal function correlates with advancing tubulo-interstitial fibrosis. TGFbeta1-Smad (transforming growth factor-beta1-Sma and Mad protein) signalling plays an important role in the development of renal tubulo-interstitial fibrosis. Secretion of CTGF (connective-tissue growth factor; CCN2) by PTECs (proximal-tubule epithelial cells) and EMT (epithelial-mesenchymal transdifferentiation) of PTECs to myofibroblasts in response to TGFbeta are critical Smad-dependent events in the development of tubulo-interstitial fibrosis. In the present study we have investigated the distinct contributions of Smad2 and Smad3 to expression of CTGF, E-cadherin, alpha-SMA (alpha-smooth-muscle actin) and MMP-2 (matrix-metalloproteinase-2) in response to TGFbeta1 treatment in an in vitro culture model of HKC-8 (transformed human PTECs). RNA interference was used to achieve selective and specific knockdown of Smad2 and Smad3. Cellular E-cadherin, alpha-SMA as well as secreted CTGF and MMP-2 were assessed by Western immunoblotting. TGFbeta1 treatment induced a fibrotic phenotype with increased expression of CTGF, MMP-2 and alpha-SMA, and decreased expression of E-cadherin. TGFbeta1-induced increases in CTGF and decreases in E-cadherin expression were Smad3-dependent, whereas increases in MMP-2 expression were Smad2-dependent. Increases in alpha-SMA expression were dependent on both Smad2 and Smad3 and were abolished by combined knockdown of both Smad2 and Smad3. In conclusion, we have demonstrated distinct roles for Smad2 and Smad3 in TGFbeta1-induced CTGF expression and markers of EMT in human PTECs. This can be of therapeutic value in designing targeted anti-fibrotic therapies for tubulo-interstitial fibrosis.
authors.affiliation: South West Thames Institute For Renal Research, St. Helier Hospital, Carshalton, Surrey SM5 1AA, UK. m.phanish@btinternet.com
authors.forename: Mysore K
authors.initials: MK
authors.lastname: Phanish
authors.forename: Nadia A
authors.initials: NA
authors.lastname: Wahab
authors.forename: Paul
authors.initials: P
authors.lastname: Colville-Nash
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Hendry
authors.forename: Mark E C
authors.initials: ME
authors.lastname: Dockrell
mesh_terms: D015415:Biomarkers; D002460:Cell Line; D055513:Connective Tissue Growth Factor; D015536:Down-Regulation; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology*; D034622:RNA Interference; D051899:Smad2 Protein / Q000235:genetics / Q000378:metabolism*; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1; D015854:Up-Regulation
chemical_list: D015415:Biomarkers; C526317:CCN2 protein, human; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; C508960:TGFB1 protein, human; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D055513:Connective Tissue Growth Factor