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.

Abstract

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).

• Authors: N J Laping, E Grygielko, A Mathur, S Butter, J Bomberger, C Tweed, W Martin, J Fornwald, R Lehr, J Harling, L Gaster, J F Callahan, B A Olson
• Journal: Molecular pharmacology (Mol Pharmacol) Vol. 62 Issue 1 Pg. 58-64 (Jul 2002) ISSN: 0026-895X [Print] United States
• PMID: 12065755 (Publication Type: Journal Article)

Chemical References

• 4-(5-benzo(1,3)dioxol-5-yl-4-pyridin-2-yl-1H-imidazol-2-yl)benzamide
• Benzamides
• Collagen Type I
• Dioxoles
• Enzyme Inhibitors
• Fibronectins
• Imidazoles
• Plasminogen Activator Inhibitor 1
• Pyridines
• RNA, Messenger
• Receptors, Transforming Growth Factor beta
• SB 242235
• TGFB1 protein, human
• Thrombospondin 1
• Transforming Growth Factor beta
• Transforming Growth Factor beta1
• Protein Serine-Threonine Kinases
• Mitogen-Activated Protein Kinases
• p38 Mitogen-Activated Protein Kinases
• Activin Receptors, Type I
• Receptor, Transforming Growth Factor-beta Type I
• TGFBR1 protein, human

Topics

• Activin Receptors, Type I (metabolism)
• Benzamides (pharmacology)
• Collagen Type I (genetics, metabolism)
• Dioxoles (pharmacology)
• Enzyme Inhibitors (pharmacology)
• Extracellular Matrix (drug effects, metabolism)
• Fibronectins (metabolism)
• Humans
• Imidazoles (pharmacology)
• Mitogen-Activated Protein Kinases (antagonists & inhibitors)
• Plasminogen Activator Inhibitor 1 (genetics, metabolism)
• Protein Serine-Threonine Kinases (antagonists & inhibitors)
• Pyridines (pharmacology)
• RNA, Messenger (drug effects, metabolism)
• Receptor, Transforming Growth Factor-beta Type I
• Receptors, Transforming Growth Factor beta (metabolism)
• Thrombospondin 1 (genetics, metabolism)
• Transforming Growth Factor beta (antagonists & inhibitors)
• Transforming Growth Factor beta1
• Tumor Cells, Cultured
• p38 Mitogen-Activated Protein Kinases