AMP-activated protein kinase (AMPK) activation has been shown to protect against fibrosis. However, the underlying mechanism remains unclear. Here we explored the effect of AMPK activation on transforming growth factor-β1 (TGFβ1) production induced by angiotensin II (AngII) in cardiac fibroblasts and the underlying mechanisms. Adult mouse cardiac fibroblasts were isolated. TGFβ1 and AMPK activity were determined by ELISA and Western blots, respectively. Pretreatment of AMPK activator AICAR inhibited TGFβ1 production induced by AngII in cardiac fibroblasts, which was reversed by AMPK inhibitor compound C. Furthermore, bioinformatics predicted a potential CCAAT/enhancer-binding protein β (C/EBPβ) binding site in the promoter region of the mouse Tgfb1 gene. Luciferase reporter with wild type, but not deleted, C/EBPβ binding sites transfection in mouse embryonic fibroblasts showed increased TGFβ1 transcriptional activity induced by AngII, indicating that C/EBPβ mediates AngII-induced TGFβ1 transcript expression. Pretreatment of AICAR inhibited C/EBPβ expression induced by AngII. In conclusion, AMPK activation inhibited TGFβ1 production induced by AngII in cardiac fibroblasts through targeting C/EBPβ. This finding provides a new mechanism underlying the anti-fibrogenic effects of AMPK activation.
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