AMP-activated protein kinase inhibits TGF-beta1 induced matrix accumulation in NRK-49F cells

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 758-775-Beta Cells, Glucose Control & Complications
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-760
Suryavathi Viswanadhapalli* and Hanna E Abboud
University of Texas Health Science Center at San Antonio, San Antonio, TX
Accumulation of interstitial extracellular matrix is a common feature of progressive kidney diseases that lead to fibrosis and loss of kidney function. Interstitial fibroblasts are activated in progressive kidney diseases including diabetes and acquire myofibroblast phenotype characterized by increased expression of alpha smooth muscle actin (alpha-SMA) and increased production of matrix proteins that lead to fibrosis. TGF-beta is a potent inducer of fibroblast activation in vitro by mechanisms that are incompletely characterized. In this study, we investigated the effect of TGF-beta1 and high glucose (HG) on AMPK in cultured rat kidney interstitial fibroblast cells (NRK-49F). We provide the first evidence that TGF-beta1 and HG induce matrix accumulation through inactivation of AMPK. NRK-49F cells were treated with TGF-beta1 (1ng/ml) or HG (25mM) in short or long term incubations and also in the absence or presence of AMPK activators/inhibitors for 24 hrs. The expression of fibronectin and alpha-SMA were analyzed by immunofluorescence staining and western blotting. Here, we report that, in NRK-49F cells, TGF-beta1 or HG treatment causes a decrease in AMP-activated protein kinase (AMPK) phosphorylation on its activating site (Thr172) that is associated with increased fibronectin and alpha-SMA expression. Activation of AMPK with 5-aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside (AICAR) or metformin or infection of the cells with constitutively active AMPK, markedly attenuated the phenotypic changes induced by TGF-beta1 or HG. Conversely, inhibition of AMPK with adenine 9-β-d-arabinofuranoside (ARA) or siRNA-mediated knockdown or infection of the cells with dominant negative AMPK, enhanced basal as well as TGF-beta1/HG-induced phenotypic changes. Collectively, our data indicate that TGF-beta1 or HG exert profibrotic action though inactivation of AMPK and that activation of AMPK is protective. Our data suggest that AMPK activation represents a potential therapeutic strategy to prevent interstitial fibrosis in progressive kidney disease.

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