Abstract 1687: AMP-Activated Kinase induces Mitochondrial Biogenesis and promotes Endothelial Cell Survival in a PGC-1alpha Dependent Manner
AMP-activated Kinase (AMPK) is a key enzyme in cellular energy homeostasis and adaptation to environmental stress. We recently found that chronic activation of AMPK protects endothelial cells of oxidative stress and promotes cell survival in a mitochondrial-dependent manner. Since peroxisome proliferator co-activator (PGC)-1alpha has been implicated as a downstream AMPK target, we therefore sought to determine the role of PGC-1alpha on the endothelial cell response to oxidative stress. Human umbilical vein endothelial cells (HUVEC) were incubated with AICAR or Metformin to activate AMPK. We found dose- and time-dependent upregulation of PGC-1alpha by AICAR and Metformin in an AMPK-dependent manner. This resulted in an increase in mitochondrial mass after 24 h, as determined by an increase in cytochrome c expression as well as by the fluorescence intensity of the mitochondrial-specific dyes Nonyl-Acridine Orange (NAO) (p<0.05) and MitoTracker Green FM (p<0.01). We also found upregulation of mitochondrial transcription factor A (mtTFA, 75% increase) and its downstream targets such as beta-ATP-Synthase (20% increase), Thioredoxin-2 (25% increase) or SOD-2 (25% increase). These changes appeared due to PGC-1alpha as they were recapitulated by overexpression of PGC-1alpha and inhibited with siRNA-mediated silencing of AMPK or PGC-1alpha. To confirm that increasing mitochondrial mass is cytoprotective, we overexpressed PGC-1alpha and observed inhibition of H2O2-mediated cell death that was quantitatively similar to that with chronic AMPK activation (66% vs. 74%, respectively). Thus, upregulation of PGC-1alpha and increased mitochondrial mass is responsible for the attenuation of oxidative stress-induced cytotoxicity observed with chronic AMPK activation. These data highlight PGC-1alpha as a potential target for improving endothelial function and ameliorating vascular disease.