Curcumin blocks multiple sites of the TGF-beta signaling cascade in renal cells.
BACKGROUND
Over-expression of transforming growth factor-beta (TGF-beta) contributes greatly to fibrotic kidney disease. The activator protein-1 (AP-1) inhibitor curcumin, a polyphenolic compound derived from Curcuma longa, has been shown to reduce collagen accumulation in experimental pulmonary fibrosis. Here, we investigate curcumin's ability to modulate TGF-beta's profibrotic actions in vitro.


METHODS
NRK49F rat renal fibroblasts were stimulated with TGF-beta (5 ng/mL), and the effects of curcumin on TGF-beta-regulated genes, TGF-beta receptors, and phosphorylated SMAD isoforms were analyzed by Northern blotting, enzyme-linked immunosorbent assay (ELISA), and Western blotting. The effects of c-jun depletion on TGF-beta-regulated gene and protein expression were analyzed with RNAi.


RESULTS
When applied 30 minutes before TGF-beta, curcumin dose dependently and dramatically reduced TGF-beta-induced increases in plasminogen activator inhibitor-1 (PAI-1), TGF-beta1, fibronectin (FN) and collagen I (Col I) mRNA, and in PAI-1 and fibronectin protein. Prolonged curcumin treatment (>6 h) significantly reduced TGF-beta receptor type II levels and SMAD2/3 phosphorylation in response to added TGF-beta. Depletion of cellular c-jun levels with a RNAi method mimicked the effects of curcumin on expression of TGF-beta1, FN, and Col I, but not PAI-1.


CONCLUSIONS
Curcumin blocks TGF-beta's profibrotic actions on renal fibroblasts through down-regulation of TbetaRII, and through partial inhibition of c-jun activity. These in vitro data suggest that curcumin might be an effective antifibrotic drug in the treatment of chronic kidney disease.
Gaedeke
Jens
J
Fibrosis Research Laboratory, Division of Nephrology, University of Utah, Salt Lake City, Utah, USA.
Noble
Nancy A
NA
Border
Wayne A
WA
D000818:Animals; D002478:Cells, Cultured; D003474:Curcumin / Q000008:administration & dosage / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D005347:Fibroblasts / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism; D005355:Fibrosis; D015870:Gene Expression / Q000187:drug effects; D005920:Glomerular Mesangium / Q000187:drug effects; D007668:Kidney / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D051381:Rats; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000037:antagonists & inhibitors; D015398:Signal Transduction / Q000187:drug effects*; D051899:Smad2 Protein; D051900:Smad3 Protein; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism* / Q000494:pharmacology
D004268:DNA-Binding Proteins; D005353:Fibronectins; D017395:Plasminogen Activator Inhibitor 1; D016755:Proto-Oncogene Proteins c-jun; D018125:Receptors, Transforming Growth Factor beta; D051899:Smad2 Protein; C497784:Smad2 protein, rat; D051900:Smad3 Protein; C497787:Smad3 protein, rat; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; D003474:Curcumin