The Role of Phospho‐Adenosine Monophosphate‐Activated Protein Kinase and Vascular Endothelial Growth Factor in a Model of Chronic Heart Failure

Abstract

We established a stable and reproducible animal model of chronic heart failure (CHF) in sheep to investigate biomolecular changes. Therefore, two biomarkers, adenosine monophosphate-activated protein kinase (AMPK) and vascular endothelial growth factor-A (VEGF-A) were examined to reveal their role during chronic ischemic conditions of the heart. AMPK was studied because it plays an important role in cellular energy homeostasis and its upregulation is associated with myocardial ischemia, whereas VEGF-A was studied because it acts as an important signaling protein for neoangiogenesis. We examined 15 juvenile sheep (mean weight, 78±4kg; control, n=3; ShamOP, n=2; coronary microembolization [CME], n=10). CHF was induced under fluoroscopic guidance by multiple sequential microembolizations (MEs) through bolus injection of polysterol microspheres (90µm, n=25.000) into the left main coronary artery. CME was repeated up to three times at 2- to 3-week intervals until animals started to develop stable signs of CHF. All animals were followed for 3 months. Phosphorylation of AMPK, marking the activated protein form, was detected by Western blotting. VEGF-A and vascular endothelial growth factor-receptor 2 (VEGF-R2) mRNA were detected by real-time polymerase chain reaction. Glyceraldehyde-3-phosphate-dehydrogenase (GAPDH) was used as a reference housekeeping gene. All 10 CHF animals developed clinical signs of CHF as indicated by a significant decrease of cardiac output, decreased ejection fraction, as well as occurrence of tachycardia and tachypnoea. Western blots showed significant phosphorylation of AMPK in CME animals compared to the control group (phospho-adenosine monophosphate-activated protein kinase α) (GAPDH control: 0.0, CME left ventricle [LV]: 0.39±0.20, CME right ventricle [RV]: 0.53±0.30; P<0.05). VEGF-A and VEGF-R2 expression in CME animal myocardium was within the range of the control group, but this data did not reach statistical significance due to the small size of this group. While microinjection was performed into the left main coronary artery, phosphorylation of AMPK and expression of VEGF-A and VEGF-R2 were significantly higher in the RV than in the LV. Multiple sequential intracoronary MEs can effectively induce myocardial dysfunction with clinical and biomolecular signs of chronic ischemic cardiomyopathy. Quantitative analysis of biomolecular markers showed a significantly higher phosphorylation of AMPK in CHF animals compared with control myocardium.