title: Rosiglitazone inhibits transforming growth factor-β1 mediated fibrogenesis in ADPKD cyst-lining epithelial cells.
abstract: BACKGROUND
  Interstitial fibrosis plays an important role in progressive renal dysfunction in autosomal dominant polycystic kidney disease (ADPKD). In our previous studies, we confirmed that PPAR-γ agonist, rosiglitazone could protect renal function and prolong the survival of a slowly progressive ADPKD animal model by reducing renal fibrosis. However, the mechanism remains unknown.
  
  
  METHODS
  Primary culture epithelial cells pretreated with TGF-β1 were incubated with rosiglitazone. Extracellular matrix proteins were detected using real-time PCR and Western blotting. MAPK and Smad2 phosphorylation were measured with western blot. ERK1/2 pathway and P38 pathway were inhibited with the specific inhibitors PD98059 and SB203580. The Smad2 pathway was blocked with the siRNA. To address whether PPAR-γ agonist-mediated inhibition of TGF-β1-induced collagen type I expression was mediated through a PPAR-γ dependent mechanism, genetic and pharmaceutical approaches were used to block the activity of endogenous PPARγ.
  
  
  RESULTS
  TGF-β1-stimulated collagen type I and fibronectin expression of ADPKD cyst-lining epithelia were inhibited by rosiglitazone in a dosage-dependent manner. Smad2, ERK1/2 and P38 pathways were activated in response to TGF-β1; however, TGF-β1 had little effect on JNK pathway. Rosiglitazone suppressed TGF-β1 induced Smad2 activation, while ERK1/2 and P38MAPK signals remained unaffected. Rosiglitazone could also attenuate TGF-β1-stimulated collagen type I and fibronectin expression in primary renal tubular epithelial cells, but had no effect on TGF-β1-induced activation of Smad2, ERK1/2 and P38 pathways. There was no crosstalk between the Smad2 and MAPK pathways in ADPKD cyst-lining epithelial cells. These inhibitory effects of rosiglitazone were reversed by the PPARγ specific antagonist GW9662 and PPARγ siRNA.
  
  
  CONCLUSIONS
  ADPKD cyst-lining epithelial cells participate in TGF-β1 mediated fibrogenesis. Rosiglitazone could suppress TGF-β1-induced collagen type I and fibronectin expression in ADPKD cyst-lining epithelia through modulation of the Smad2 pathway. Our study may provide therapeutic basis for clinical applications of rosiglitazone in retarding the progression of ADPKD.
authors.affiliation: Division of Nephrology, Nephrology Institute of PLA, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai, China.
authors.forename: Yawei
authors.initials: Y
authors.lastname: Liu
authors.forename: Bing
authors.initials: B
authors.lastname: Dai
authors.forename: Chenggang
authors.initials: C
authors.lastname: Xu
authors.forename: Lili
authors.initials: L
authors.lastname: Fu
authors.forename: Zhenhao
authors.initials: Z
authors.lastname: Hua
authors.forename: Changlin
authors.initials: C
authors.lastname: Mei
mesh_terms: D002478:Cells, Cultured; D024042:Collagen Type I / Q000378:metabolism; D003560:Cysts / Q000473:pathology*; D004789:Enzyme Activation / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D005260:Female; D005353:Fibronectins / Q000378:metabolism; D005355:Fibrosis; D006801:Humans; D007684:Kidney Tubules / Q000187:drug effects / Q000473:pathology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D047495:PPAR gamma / Q000378:metabolism; D016891:Polycystic Kidney, Autosomal Dominant / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D034741:RNA, Small Interfering / Q000378:metabolism; D000077154:Rosiglitazone; D051899:Smad2 Protein / Q000378:metabolism; D045162:Thiazolidinediones / Q000494:pharmacology*; D013997:Time Factors; D053773:Transforming Growth Factor beta1 / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D024042:Collagen Type I; D005353:Fibronectins; D047495:PPAR gamma; D034741:RNA, Small Interfering; C497782:SMAD2 protein, human; D051899:Smad2 Protein; D045162:Thiazolidinediones; D053773:Transforming Growth Factor beta1; D000077154:Rosiglitazone