Deletion of FHL2 in fibroblasts attenuates fibroblasts activation and kidney fibrosis via restraining TGF-beta 1-induced Wnt/beta-catenin signaling

摘要

Four-and-a-half LIM domains protein 2 (FHL2) has been proposed involving in beta-catenin activity. We previously reported that FHL2 mediates TGF-beta 1-induced tubular epithelial-to-mesenchymal transition through activating Wnt/beta-catenin signaling. However, the potential role and mechanism for FHL2 in TGF-beta 1-induced fibroblast activation and kidney fibrosis remains unknown. Here, we initially observed higher levels of FHL2 expression in fibrotic kidneys from both patients and mice, especially in alpha-smooth muscle actin (alpha-SMA)-positive cells in the interstitium. In cultured interstitial fibroblasts, FHL2 expression was induced by TGF-beta 1. Knockdown of FHL2 remarkably suppressed TGF-beta 1-induced alpha-SMA, type I collagen, and fibronectin expression, while overexpression of FHL2 was sufficient to activate fibroblasts. In mice, fibroblast-specific deletion of FHL2 diminished renal induction of alpha-SMA, type I collagen, and fibronectin and interstitial extracellular matrix deposition at 2 weeks after ureteral obstruction. We next investigated Wnt/beta-catenin activity and found that beta-catenin was activated in most FHL2-positive cells in renal interstitium from mice with obstructive nephropathy. In vitro, TGF-beta 1 induced a physical interaction between FHL2 and beta-catenin, especially in the nucleus. Downregulation of FHL2 inhibited TGF-beta 1-induced active beta-catenin upregulation, beta-catenin nuclear translocation, and beta-catenin-mediated transcription, whereas overexpression of FHL2 was able to activate Wnt/beta-catenin signaling. FHL2 overexpression-induced beta-catenin-mediated gene transcription could be hindered by ICG-001, but FHL2 overexpression-induced upregulation of active beta-catenin could not be. Collectively, this study reveals that the signal regulatory effect of FHL2 on beta-catenin plays an important role in TGF-beta 1-induced fibroblast activation and kidney fibrosis.