Deubiquitinase inhibitor PR-619 reduces Smad4 expression and suppresses renal fibrosis in mice with unilateral ureteral obstruction.

Deubiquitinating enzymes (DUBs) remove ubiquitin from their substrates and, together with ubiquitin ligases, play an important role in the regulation of protein expression. Although transforming growth factor (TGF)-ß1-Smad signaling is a central pathway of renal fibrosis, the role of DUBs in the expression of TGF-ß receptors and Smads during the development of renal fibrosis remains unknown. In this study, we investigated whether PR-619, a pan-DUB inhibitor, suppresses fibrosis in mice with unilateral ureteral obstruction (UUO) and TGF-ß1-stimulated normal rat kidney (NRK)-49F cells, a rat renal fibroblast cell line. Either the vehicle (dimethyl sulfoxide) or PR-619 (100 µg) was intraperitoneally administered to mice after UUO induction once a day for 7 days. Administration of PR-619 attenuated renal fibrosis with downregulation of mesenchymal markers, extracellular matrix proteins, matrix metalloproteinases, apoptosis, macrophage infiltration, and the TGF-ß1 mRNA level in UUO mice. Although type I TGF-ß receptor (TGF-ßRI), Smad2, Smad3, and Smad4 protein expression levels were markedly increased in mice with UUO, administration of PR-619 suppressed only Smad4 expression but not TGF-ßRI, Smad2, or Smad3 expression. PR-619 also had an inhibitory effect on TGF-ß1-induced α-smooth muscle actin expression and reduced Smad4 levels in NRK-49F cells. Our results indicate that PR-619 ameliorates renal fibrosis, which is accompanied by the reduction of Smad4 expression.

Efficacy of add-on therapy of aliskiren to an angiotensin II receptor blocker on renal outcomes in advanced-stage chronic kidney disease: a prospective, randomized, open-label study.

BACKGROUND: Combination therapy of aliskiren and an angiotensin II receptor blocker (ARB) has been reported to be effective for reducing the level of proteinuria. However, it remains unclear whether this combination therapy contributes to suppression of kidney disease progression. The aim of this study was to investigate the effect of aliskiren on hard renal endpoints, when added to an ARB, in patients with advanced chronic kidney disease (CKD). METHODS: The study design was a prospective, randomized open-label design. 83 CKD patients (52 men and 31 women) were enrolled and assigned randomly to an aliskiren add-on group (n = 42) or control group (n = 41). Entry criteria included elevated serum creatinine ≥ 1.5 mg/dl, urine protein excretion (≥ 1+ on urine dipstick test), and hypertension. All participants were treated with an ARB. The follow-up period was 12 months. 12 participants were withdrawn during the study period and the study was terminated in January 2012 as a consequence of the results of the interim analysis of the ALTITUDE study. RESULTS: Nine patients in the aliskiren group and seven patients in the control group started dialysis. Doubling of the serum creatinine level occurred in one patient in the control group. A Cox proportional hazards test showed that dual blockade of the renin-angiotensin-aldosterone system with aliskiren and ARB was not associated with improvement in hard renal endpoints. CONCLUSION: We conclude that aliskiren add-on therapy to an ARB may not give any benefit and, therefore, should not be recommended in CKD patients.