Inhibition of transforming growth factor (TGF)-beta1-induced extracellular matrix with a novel inhibitor of the TGF-beta type I receptor kinase activity: SB-431542.
Transforming growth factor beta1 (TGF-beta1) is a potent fibrotic factor responsible for the synthesis of extracellular matrix. TGF-beta1 acts through the TGF-beta type I and type II receptors to activate intracellular mediators, such as Smad proteins, the p38 mitogen-activated protein kinase (MAPK), and the extracellular signal-regulated kinase pathway. We expressed the kinase domain of the TGF-beta type I receptor [activin receptor-like kinase (ALK)5] and the substrate, Smad3, and determined that SB-431542 is a selective inhibitor of Smad3 phosphorylation with an IC50 of 94 nM. It inhibited TGF-beta1-induced nuclear Smad3 localization. The p38 mitogen-activated protein kinase inhibitors SB-203580 and SB-202190 also inhibit phosphorylation of Smad3 by ALK5 with IC50 values of 6 and 3 microM, respectively. This suggests that these p38 MAPK inhibitors must be used at concentrations of less than 10 microM to selectively address p38 MAPK mechanisms. However, the p38 MAPK inhibitor SB-242235 did not inhibit ALK5. To evaluate the relative contribution of Smad signaling and p38 MAPK signaling in TGF-beta1-induced matrix production, the effect of SB-431542 was compared with that of SB-242235 in renal epithelial carcinoma A498 cells. All compounds inhibited TGF-beta1-induced fibronectin (FN) mRNA, indicating that FN synthesis is mediated in part via the p38 MAPK pathway. In contrast, SB-431542, but not the selective p38 MAPK inhibitor SB-242235, inhibited TGF-beta1-induced collagen Ialpha1 (col Ialpha1). These data indicate that some matrix markers that are stimulated by TGF-beta1 are mediated via the p38 MAPK pathway (i.e., FN), whereas others seem to be activated via ALK5 signaling independent of the p38 MAPK pathway (i.e., col Ialpha1).
Laping
N J
NJ
Department of Renal and Urology Research, GlaxoSmithKline Pharmaceuticals, King of Prussia, Pennsylvania 19406, USA. nicholas_j_laping@sbphrd.com
Grygielko
E
E
Mathur
A
A
Butter
S
S
Bomberger
J
J
Tweed
C
C
Martin
W
W
Fornwald
J
J
Lehr
R
R
Harling
J
J
Gaster
L
L
Callahan
J F
JF
Olson
B A
BA
D030201:Activin Receptors, Type I / Q000378:metabolism; D001549:Benzamides / Q000494:pharmacology*; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D004149:Dioxoles / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D019700:Thrombospondin 1 / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors*; D053773:Transforming Growth Factor beta1; D014407:Tumor Cells, Cultured; D048051:p38 Mitogen-Activated Protein Kinases
C459179:4-(5-benzo(1,3)dioxol-5-yl-4-pyridin-2-yl-1H-imidazol-2-yl)benzamide; D001549:Benzamides; D024042:Collagen Type I; D004149:Dioxoles; D004791:Enzyme Inhibitors; D005353:Fibronectins; D007093:Imidazoles; D017395:Plasminogen Activator Inhibitor 1; D011725:Pyridines; D012333:RNA, Messenger; D018125:Receptors, Transforming Growth Factor beta; C403289:SB 242235; C508960:TGFB1 protein, human; D019700:Thrombospondin 1; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625841:TGFBR1 protein, human