Effects of proteasome inhibitors on rat renal fibrosis in vitro and in vivo.

Abstract

AIM:

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.

CONCLUSION:

Proteasome inhibitors attenuate TGF-β signalling by blocking Smad signal transduction in vitro, but do not inhibit renal interstitial fibrosis in vivo.

• Authors: Toru Sakairi, Keiju Hiromura, Satoshi Takahashi, Hiroko Hamatani, Shigeru Takeuchi, Mai Tomioka, Akito Maeshima, Takashi Kuroiwa, Yoshihisa Nojima
• Journal: Nephrology (Carlton, Vic.) (Nephrology (Carlton)) Vol. 16 Issue 1 Pg. 76-86 (Jan 2011) ISSN: 1440-1797 [Electronic] Australia
• PMID: 21175982 (Publication Type: Journal Article)
• Copyright: © 2011 The Authors. Nephrology © 2011 Asian Pacific Society of Nephrology.

Chemical References

• Actins
• Cysteine Proteinase Inhibitors
• Leupeptins
• Nerve Tissue Proteins
• RNA, Messenger
• Skil_v1 protein, rat
• Smad Proteins, Receptor-Regulated
• Smad2 Protein
• Smad2 protein, rat
• Smad3 Protein
• Smad3 protein, rat
• Smad4 Protein
• Smad4 protein, rat
• Transcription Factors
• Transforming Growth Factor beta
• smooth muscle actin, rat
• lactacystin
• benzyloxycarbonylleucyl-leucyl-leucine aldehyde
• Acetylcysteine

Topics

• Acetylcysteine (analogs & derivatives, pharmacology)
• Actins (genetics, metabolism)
• Animals
• Cells, Cultured
• Cysteine Proteinase Inhibitors (pharmacology)
• Disease Models, Animal
• Epithelial Cells (cytology, metabolism)
• Epithelial-Mesenchymal Transition (drug effects)
• Fibroblasts (cytology, metabolism)
• Fibrosis (genetics, metabolism)
• Kidney Diseases (metabolism, pathology)
• Leupeptins (pharmacology)
• Male
• Nerve Tissue Proteins (metabolism)
• RNA, Messenger (metabolism)
• Rats
• Rats, Wistar
• Signal Transduction (drug effects, genetics)
• Smad Proteins, Receptor-Regulated (metabolism)
• Smad2 Protein (metabolism)
• Smad3 Protein (metabolism)
• Smad4 Protein (metabolism)
• Transcription Factors (metabolism)
• Transcription, Genetic (drug effects)
• Transforming Growth Factor beta (drug effects, metabolism)
• Ureteral Obstruction (metabolism, pathology)