Association of beta-catenin with P-Smad3 but not LEF-1 dissociates in vitro profibrotic from anti-inflammatory effects of TGF-beta 1

Transforming growth factor beta 1 (TGF-beta 1) is known to be both anti-inflammatory and profibrotic. Cross-talk between TGF-beta/Smad and Wnt/beta-catenin pathways in epithelial-mesenchymal transition (EMT) suggests a specific role for beta-catenin in profibrotic effects of TGF-beta 1. However, no such mechanistic role has been demonstrated for beta-catenin in the anti-inflammatory effects of TGF-beta 1. In the present study, we explored the role of beta-catenin in the profibrotic and anti-inflammatory effects of TGF-beta 1 by using a cytosolic, but not membrane, beta-catenin knockdown chimera (F-TrCP-Ecad) and the beta-catenin/CBP inhibitor ICG-001. TGF-beta 1 induced nuclear Smad3/beta-catenin complex, but not beta-catenin/LEF-1 complex or TOP-flash activity, during EMT of C1.1 (renal tubular epithelial) cells. F-TrCP-Ecad selectively degraded TGF-beta 1-induced cytoplasmic beta-catenin and blocked EMT of C1.1 cells. Both F-TrCP-Ecad and ICG-001 blocked TGF-beta 1-induced Smad3/beta-catenin and Smad reporter activity in C1.1 cells, suggesting that TGF-beta 1-induced EMT depends on beta-catenin binding to Smad3, but not LEF-1 downstream of Smad3, through canonical Wnt. In contrast, in J774 macrophages, the beta-catenin level was low and was not changed by interferon-c (IFN-gamma) or lipopolysaccharide (LPS) with or without TGF-beta 1. TGF-beta 1 inhibition of LPS-induced TNF-alpha and IFN-gamma-stimulated inducible NO synthase (iNOS) expression was not affected by F-TrCP-Ecad, ICG-001 or by overexpression of wild-type beta-catenin in J774 cells. Inhibition of beta-catenin by either F-TrCP-Ecad or ICG-001 abolished LiCl-induced TOP-flash, but not TGF-beta 1-induced Smad reporter, activity in J774 cells. These results demonstrate for the first time that beta-catenin is required as a co-factor of Smad in TGF-beta 1-induced EMT of C1.1 epithelial cells, but not in TGF-beta 1 inhibition of macrophage activation. Targeting beta-catenin may dissociate the TGF-beta 1 profibrotic and anti-inflammatory effects.