Inhibition of gene markers of fibrosis with a novel inhibitor of transforming growth factor-beta type I receptor kinase in puromycin-induced nephritis.
SB-525334 (6-[2-tert-butyl-5-(6-methyl-pyridin-2-yl)-1H-imidazol-4-yl]-quinoxaline) has been characterized as a potent and selective inhibitor of the transforming growth factor-beta1 (TGF-beta1) receptor, activin receptor-like kinase (ALK5). The compound inhibited ALK5 kinase activity with an IC(50) of 14.3 nM and was approximately 4-fold less potent as an inhibitor of ALK4 (IC(50) = 58.5 nM). SB-525334 was inactive as an inhibitor of ALK2, ALK3, and ALK6 (IC(50) > 10,000 nM). In cell-based assays, SB-525334 (1 microM) blocked TGF-beta1-induced phosphorylation and nuclear translocation of Smad2/3 in renal proximal tubule cells and inhibited TGF-beta1-induced increases in plasminogen activator inhibitor-1 (PAI-1) and procollagen alpha1(I) mRNA expression in A498 renal epithelial carcinoma cells. In view of this profile, SB-525334 was used to investigate the role of TGF-beta1 in the acute puromycin aminonucleoside (PAN) rat model of renal disease, a model of nephritis-induced renal fibrosis. Orally administered doses of 1, 3, or 10 mg/kg/day SB-525334 for 11 days produced statistically significant reductions in renal PAI-1 mRNA. Also, the compound produced dose-dependent decreases in renal procollagen alpha1(I) and procollagen alpha1(III) mRNA, which reached statistical significance at the 10-mg/kg/day dose when compared with vehicle-treated PAN controls. Furthermore, PAN-induced proteinuria was significantly inhibited at the 10-mg/kg/day dose level. These results provide further evidence for the involvement of TGF-beta1 in the profibrotic changes that occur in the PAN model and for the first time, demonstrate the ability of a small molecule inhibitor of ALK5 to block several of the markers that are predictive of fibrosis and renal injury in this model.
Grygielko
Eugene T
ET
Urogenital Biology, GlaxoSmithKline, King of Prussia, PA 19406, USA. eugene_t_grygielko@gsk.com
Martin
William M
WM
Tweed
Christopher
C
Thornton
Peter
P
Harling
John
J
Brooks
David P
DP
Laping
Nicholas J
NJ
D029404:Activin Receptors / Q000037:antagonists & inhibitors; D000818:Animals; D015415:Biomarkers; D045744:Cell Line, Tumor; D024042:Collagen Type I / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D005355:Fibrosis; D006801:Humans; D007668:Kidney / Q000473:pathology*; D009393:Nephritis / Q000378:metabolism / Q000473:pathology*; D010766:Phosphorylation; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D011691:Puromycin / Q000633:toxicity*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors* / Q000502:physiology; D053773:Transforming Growth Factor beta1
D015415:Biomarkers; D024042:Collagen Type I; D017395:Plasminogen Activator Inhibitor 1; D012333:RNA, Messenger; D018125:Receptors, Transforming Growth Factor beta; C508960:TGFB1 protein, human; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D011691:Puromycin; D017346:Protein Serine-Threonine Kinases; D029404:Activin Receptors; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625841:TGFBR1 protein, human; C000625843:Tgfbr1 protein, rat