Activation of AMP-Activated Protein Kinase Prevents TGF-β1–Induced Epithelial-Mesenchymal Transition and Myofibroblast Activation

• DOI: 10.1016/j.ajpath.2015.04.014
• Publication Date: 2015-06-12T04:34:54Z
• Authors: Sachin Thakur; Suryavathi Viswan...; Jeffrey B. Kopp; Qian Shi; Jeffrey L. Barnes; Karen Block; Yves Gorin; Hanna E. Abboud
• Keywords: Mice, Knockout; 0301 basic medicine; 0303 health sciences; Epithelial-Mesenchymal Transition; AMP-Activated Protein Kinases; Aminoimidazole Carboxamide; Cadherins; Fibronectins; 3. Good health; Kidney Tubules, Proximal; Transforming Growth Factor beta1; Mice; 03 medical and health sciences; Animals; Humans; Ribonucleosides; Phosphorylation; Myofibroblasts

Transforming growth factor (TGF)-β contributes to tubulointerstitial fibrosis. We investigated the mechanism by which TGF-β exerts its profibrotic effects and specifically the role of AMP-activated protein kinase (AMPK) in kidney tubular epithelial cells and interstitial fibroblasts. In proximal tubular epithelial cells, TGF-β1 treatment causes a decrease in AMPK phosphorylation and activation together with increased fibronectin and α-smooth muscle actin expression and decreased in E-cadherin. TGF-β1 causes similar changes in interstitial fibroblasts. Activation of AMPK with 5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside, metformin, or overexpression of constitutively active AMPK markedly attenuated TGF-β1 functions. Conversely, inhibition of AMPK with adenine 9-β-d-arabinofuranoside or siRNA-mediated knockdown of AMPK (official name PRKAA1) mimicked the effect of TGF-β1 and enhanced basal and TGF-β1-induced phenotypic changes. Importantly, we found that tuberin contributed to the protective effects of AMPK and that TGF-β1 promoted cell injury by blocking AMPK-mediated tuberin phosphorylation and activation. In the kidney cortex of TGF-β transgenic mice, the significant decrease in AMPK phosphorylation and tuberin phosphorylation on its AMPK-dependent activating site was associated with an increase in mesenchymal markers and a decrease in E-cadherin. Collectively, the data indicate that TGF-β exerts its profibrotic action in vitro and in vivo via inactivation of AMPK. AMPK and tuberin activation prevent tubulointerstitial injury induced by TGF-β. Activators of AMPK provide potential therapeutic strategy to prevent kidney fibrosis and progressive kidney disease.