title: Effects of proteasome inhibitors on rat renal fibrosis in vitro and in vivo.
abstract: OBJECTIVE
  Transforming growth factor-β (TGF-β) is involved in renal tubulointerstitial fibrosis. Recently, the ubiquitin proteasome system was shown to participate in the TGF-β signalling pathway. The aim of this study was to examine the effects of proteasome inhibitors on TGF-β-induced transformation of renal fibroblasts and tubular epithelial cells in vitro and on unilateral ureteral obstruction (UUO) in vivo.
  
  
  METHODS
  Rat renal fibroblasts NRK-49F cells and tubular epithelial cells, NRK-52E, were treated with TGF-β in the presence or absence of a proteasome inhibitor, MG132 or lactacystin. Rats were subjected to UUO and received MG132 i.p. for 7 days.
  
  
  RESULTS
  In cultured renal cells, both MG132 and lactacystin inhibited TGF-β-induced α-smooth muscle actin (α-SMA) protein expression according to both western blotting and immunofluorescent study results. MG132 also suppressed TGF-β-induced mRNA expression of α-SMA and upregulation of Smad-response element reporter activity. However, MG132 did not inhibit TGF-β-induced phosphorylation and nuclear translocation of Smad2. In contrast, MG132 increased the protein level of Smad co-repressor SnoN, demonstrating that SnoN is one of the target molecules by which MG132 blocks the TGF-β signalling pathway. Although the proteasome inhibitor suppressed TGF-β-induced transformation of cultured fibroblasts and tubular epithelial cells, MG132 treatment did not ameliorate tubulointerstitial fibrosis in the rat UUO model.
  
  
  CONCLUSIONS
  Proteasome inhibitors attenuate TGF-β signalling by blocking Smad signal transduction in vitro, but do not inhibit renal interstitial fibrosis in vivo.
authors.affiliation: Department of Medicine and Clinical Science, Gunma University Graduate School of Medicine, Maebashi, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Sakairi
authors.forename: Keiju
authors.initials: K
authors.lastname: Hiromura
authors.forename: Satoshi
authors.initials: S
authors.lastname: Takahashi
authors.forename: Hiroko
authors.initials: H
authors.lastname: Hamatani
authors.forename: Shigeru
authors.initials: S
authors.lastname: Takeuchi
authors.forename: Mai
authors.initials: M
authors.lastname: Tomioka
authors.forename: Akito
authors.initials: A
authors.lastname: Maeshima
authors.forename: Takashi
authors.initials: T
authors.lastname: Kuroiwa
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Nojima
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D004195:Disease Models, Animal; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005355:Fibrosis / Q000235:genetics / Q000378:metabolism*; D007674:Kidney Diseases / Q000378:metabolism* / Q000473:pathology; D007976:Leupeptins / Q000494:pharmacology; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics; D051896:Smad Proteins, Receptor-Regulated / Q000378:metabolism; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D051901:Smad4 Protein / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000187:drug effects / Q000378:metabolism*; D014517:Ureteral Obstruction / Q000378:metabolism / Q000473:pathology
chemical_list: D000111:Acetylcysteine; D000199:Actins; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D051896:Smad Proteins, Receptor-Regulated; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; C511209:Skil_v1 protein, rat; C497784:Smad2 protein, rat; C497787:Smad3 protein, rat; C490811:Smad4 protein, rat; C498862:Acta2 protein, rat; C067713:lactacystin; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde