Ruboxistaurin attenuates diabetic nephropathy via modulation of TGF-β1/Smad and GRAP pathways

J Pharm Pharmacol. 2016 Feb;68(2):219-32. doi: 10.1111/jphp.12504. Epub 2016 Jan 28.


Objective: To investigate whether ruboxistaurin (a selective PKC-β inhibitor) mediates renoprotective effect via interference with TGF-β1/Smad-GRAP cross-signalling.

Method: Diabetes was induced in rats by a single intraperitoneal injection of streptozotocin (55 mg/kg). Then, the diabetic rats were treated with ruboxistaurin (10 mg/kg, p.o) for 6 weeks. Valsartan (15 mg/kg, p.o) was used as a positive control. After 6 weeks of treatment, diabetic nephropathy biomarkers were assessed. TGF-β1, Smad2, and Smad3 mRNA and protein levels were detected using qPCR and western blot analysis.

Key findings: Data showed that serum creatinine, kidney/body weight ratio and urinary albumin excretion significantly increased in diabetic rats. These changes were significantly attenuated by treatment with ruboxistaurin. A significant up-regulation of TGF-β1, Smad2 and Smad3 mRNA expression was observed in diabetic rats, which was alleviated by administration of ruboxistaurin. Furthermore, immunoblotting showed a significant improvement in protein levels of TGF-β1 (P < 0.01), Smad2/3 (P < 0.01) and p-Smad3 (P < 0.001) in diabetic rats treated with ruboxistaurin compared to untreated. Importantly, the reduction in GRAP protein expression in diabetic kidney was prevented by treatment with ruboxistaurin.

Conclusion: These data suggest that the renoprotective effect of ruboxistaurin is possibly due to down-regulation of TGF-β1/Smad pathway and normalization of GRAP protein expression.

Keywords: GRAP; TGF-β1; diabetic nephropathy; ruboxistaurin; smad.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Diabetes Mellitus, Experimental / complications
  • Diabetes Mellitus, Experimental / drug therapy
  • Diabetic Nephropathies / metabolism
  • Diabetic Nephropathies / pathology
  • Diabetic Nephropathies / prevention & control*
  • GRB2 Adaptor Protein / metabolism*
  • Indoles / administration & dosage
  • Indoles / therapeutic use*
  • Kidney Function Tests
  • Male
  • Maleimides / administration & dosage
  • Maleimides / therapeutic use*
  • Protein Kinase C beta / antagonists & inhibitors*
  • Rats, Wistar
  • Signal Transduction
  • Smad2 Protein / metabolism*
  • Smad3 Protein / metabolism*
  • Transforming Growth Factor beta1 / metabolism*


  • GRB2 Adaptor Protein
  • Grb2 protein, rat
  • Indoles
  • Maleimides
  • Smad2 Protein
  • Smad2 protein, rat
  • Smad3 Protein
  • Smad3 protein, rat
  • Transforming Growth Factor beta1
  • ruboxistaurin
  • Protein Kinase C beta