Abstract 1150: Activation Of AMPK During Angiotensin II Induced Hypertension Improves Endothelial Function By Inhibition Of NADPH Oxidase And Xanthine Oxidase Activity.
Background: AMP-activated protein kinase (AMPK) mediates cellular adaptation to metabolic stress, but its role in vascular disease is less clear. Here we tested if AMPK modulation in vivo may affect vascular function and oxidative stress in a murine model of angiotensin II (AT-II) induced hypertension.
Methods: C57Bl6 mice were devided into 4 groups (Ctr, Aicar, AT-II, AT-II/Aicar). Hypertension was induced by continuous AT-II infusion (0,8mg/kg/d) via osmotic minipump, the AMPK activator Aicar was administrated by a daily subcutaneous injection (200mg/kg/d). After 7 days, we determined vascular function by isometric tension studies, activity of AMPK by phosphorylation of AMPK and its downstream target ACC, reactive oxygen species (ROS) formation by dihydroethidium fluorescence, NADPH oxidase activity in heart membrane fractions (lucigenin 5μM) and serum xanthine oxidase activity by cytochrome C reduction.
Results: In mice treated with AT II for 7 days we observed a 30% decrease of AMPK activity. Parallel administration of the AMPK activator Aicar restored AMPK activity and improved endothelial function in AT-II treated animals. At the same time, vascular oxidative stress in AT-II infused mice was significantly reduced by concomitant Aicar treatment assessed by dihydroethdium fluorescence in aortic sections. We identified NADPH oxidase (Ctr 124455±12255, AT-II 217552±20868, AT-II&Aicar 139766±11077 counts/mg/min; p<0.05) as well as serum xanthine oxidase (Ctr 150±13, Ctr Aicar 82±11, AT-II 158±14, AT-II&Aicar 81±16 nmol O2−/min; p<0.05 AT-II vs. AT-II&Aicar, Ctr vs. AT-II n.s.) as possible AMPK-sensitive ROS-sources, since their activity was diminished by concomitant AICAR treatment in AT-II infused mice. In contrast, knockout of the major vascular AMPK-isoform (alpha1AMPK −/−) lead to a marked increase in NADPH-oxidase activity in control and AT-II treated animals (WT Ctr 4316±175, WT AT-II 24021±843, AMPK ko 6559±385, AMPK ko AT-II 36006±1400 counts/mg/min; p<0.05).
Conclusion: Restoration of AMPK activity during AT II hypertension improves vascular function by inhibition of NADPH-oxidase and xanthine oxidase activity, suggesting AMPK as a possible pharmacological target in vascular disease.