ABSTRACT
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.
ABSTRACT
The aim of this study was to evaluate the preventive role of epigallocatechin-3 gallate (EGCG, a derivative of green tea) in ischemia/reperfusion (I/R) injury of isolated rat hearts. It has been suggested that EGCG has beneficial health effects, including prevention of cancer and heart disease, and it is also a potent antioxidant. Rat hearts were subjected to 20 min of normoxia, 20 min of zero-flow ischemia and then 50 min of reperfusion. EGCG was perfused 10 min before ischemia and during the whole reperfusion period. EGCG significantly increased left ventricular developed pressure (LVDP) and increased maximum positive and negative dP/dt (+/-dP/dtmax). EGCG also significantly increased the coronary flow (CF) at baseline before ischemia and at the onset of the reperfusion period. Moreover, EGCG decreased left ventricular end diastolic pressure (LVEDP). This study showed that lipid peroxydation was inhibited and Mn-SOD and catalase expressions were increased in the presence of EGCG. In addition, EGCG increased levels of Bcl-2, Mn-superoxide dismutase (SOD), and catalase expression and decreased levels of Bax and increased the ratio of Bcl-2/Bax in isolated rat hearts. Cleaved caspase-3 was decreased after EGCG treatment. EGCG markedly decreased the infarct size while attenuating the increase in lactate dehydrogenase (LDH) levels in the effluent. In summary, we suggest that EGCG has a protective effect on I/R-associated hemodynamic alteration and injury by acting as an antioxidant and anti-apoptotic agent in one.