Abstract 920: Depletion of AMPK Alpha 2 Subunits Accentuates Oxidant Stress and Atherosclerosis in vivo
AMP-activated kinase (AMPK) is a serine/threonine protein kinase involved in the regulation of cellular and organismal metabolism. AMPK is activated by a large number of stimuli including oxidant stresses. The aim of the study is to determine the effects of AMPK activation in the development of atherosclerosis. Exposure of human aortic endothelial cells (HAEC) to palmitate (0.1 mM) for 2 to 24 hours significantly increased superoxide, impaired nitric oxide bioactivity, and increased tyrosine nitration of prostacyclin synthase while increasing AMPK-Thr172 phosphorylation. Overexpression of AMPK dominant negative mutants markedly increased palmitate-induced oxidant stress. Conversely, activation of AMPK by either the AMPK activator AICAR, or with adenoviruses overexpressing constitutively active AMPK, attenuated palmitate-driven oxidant stress in HAEC, suggesting that AMPK activation might reduce palmitate-induced oxidant stress. To explore the physiological function of AMPK, 5 weeks old male AMPK alpha-2 /ApoE double knockout mice were fed with a high-cholesterol diet (0.21% cholesterol) for 15 weeks. There were no significant differences in body weight (33.3±4.3 g vs. 32.4±2.3 g), non-fasting blood glucose (210.3±12.4 mg/dL vs. 233.3±7.3 mg/dL), and cholesterol (18.5±1.0 mmol/L vs. 18.9±1.4 mol/L) between ApoE-KO (n=10) and AMPK-α2-KO/ApoE-KO mice (n=9). Serum triglycerides in double knockout mice were significantly higher compared to those in Apo-E KO mice (1.64 ± 0.07 mol/L vs. 1.22±0.05 mol/L; p<0.01). Interestingly, compared with ApoE-KO mice, the atherosclerotic lesion areas in the aortic root were significantly increased in AMPK-α2-KO/ApoE-KO mice (29.8±1.2% vs. 45.4±2.7%; p<0.01, n=4). Also, aortic arch lesion areas were considerably larger in AMPK-α2-KO/ApoE-KO mice than those from ApoE-KO mice (21.2%±1.0 vs. 13.0±2.1%; p<0.05, n=4). Finally, the immunostainings of 3-nitrotyrosine (a biomarker of reactive nitrogen species) were markedly increased in thoracic aortas of double knockout mice. Taken together, our results indicate that the depletion of AMPK α2 increased oxidant stress and atherosclerosis and, AMPK activation might delay atherosclerosis by inhibiting the processes that generate oxidants in vivo.