Abstract 33: Impaired Mitochondrial Metabolism Contributes To Endothelial Dysfunction And Hypertension Independently From Oxidative Stress

Abstract

Metabolic disorders contribute to pathogenesis of endothelial dysfunction, and mitochondrial deacetylase Sirt3 is critical in regulation of metabolic and antioxidant functions, but the role of Sirt3 has been largely ignored. We have recently shown that Sirt3 level is reduced in human hypertension. We propose Sirt3 as a novel target to improve the treatment of endothelial dysfunction and hypertension. Oxidative stress promotes metabolic dysregulation while metabolic conditions increase production of reactive oxygen species. In this work we have discerned the pathological role of impaired mitochondrial metabolism and oxidative stress using our new SOD2K68R deacetylation mimic mouse model. SOD2K68R mice are protected from oxidative stress because mutation of lysine 68 to arginine prevents SOD2 inactivation by acetylation. To define the specific role of impaired mitochondrial metabolism in endothelial dysfunction and hypertension, we have crossed SOD2K68R with Sirt3 -/- mice. Resultant SOD2K68R-Sirt3 -/- mice are protected from mitochondrial oxidative stress but have impaired Sirt3-mediated mitochondrial metabolism. We have tested the hypothesis that impaired Sirt3-mediated mitochondrial metabolism in SOD2K68R-Sirt3 -/- mice promotes vascular dysfunction and hypertension. SOD2K68R-Sirt3 -/- mice are protected from AngII-induced superoxide measured by mitoSOX and DHE. Meanwhile, systolic blood pressure in AngII-infused SOD2K68R-Sirt3 -/- mice was substantially higher than in SOD2K68R mice but lower than in Sirt3 -/- mice. To define the role of mitochondrial metabolism in vascular homeostasis we analyzed metabolic, inflammatory, and cellular pathways. LCAD hyperacetylation and increased HIF1α in SOD2K68R-Sirt3 -/- mice indicates impaired mitochondrial fatty acid oxidation and increased glycolysis which were further exacerbated by AngII-infusion and NFkB/ICAM increase promoting vascular inflammation. The loss of VeCAD in SOD2K68R-Sirt3 -/- Sham mice was further aggravated in AngII-infusion supporting alteration of endothelial phenotype in SOD2K68R-Sirt3 -/- mice. These data indicate that impaired mitochondrial metabolism contributes to endothelial dysfunction and hypertension independently from oxidative stress.