The control and consequences of AMP-activated protein kinase (AMPK) activation in endothelial cells is not well understood, however, we have previously shown that it can be activated by fluid shear stress and modulate the expression of a number of genes including the 3-hydroxy 3-methylglutaryl-coenzymeA reductase and angiopoietin 2.

To determine the spectrum of genes affected by the AMPK in endothelial cells we performed gene array analysis using endothelial cells overexpressing either a dominant negative or a constitutively active AMPKa subunit. Overexpression of the constitutive active AMPK in endothelial cells increased Krüppel-like factor-2 (KLF-2) mRNA expression as well as that of its downstream target eNOS. Indeed, AMPK overexpression was associated with a significant increase in eNOS mRNA and protein expression as well as in the basal formation of cyclic GMP. In contrast, the loss of AMPK activity was associated with an increase in the endothelial expression of E-selectin and monocyte adherence to endothelial cells. Moreover, eNOS expression in the aorta and in endothelial cells isolated from AMPK-/- mice was markedly lower than in tissues from wild-type littermates. As the expression of KLF-2 is regulated by the myocyte enhancer factor 2A (MEF2A) we determined the consequences of MEF2A on eNOS and the potential interaction with the AMPK. The constitutively active AMPK resulted in the nuclear translocation of MEF2A and overexpression of MEF2A in turn increased eNOS mRNA expression, an effect abolished by the overexpression of a DN-AMPK mutant. In addition to affecting the nuclear translocation of MEF2A, the AMPK was able to phosphorylate the histone acetylase p300 in vitro; the latter is also involved in the regulation of MEF2 acetylation and activity.

Taken together, our data indicated that the activation of the AMPK can regulate the expression of eNOS and thus affect endothelial cell activation by modulating the intracellular localisation and activity of MEF2A and expression of KLF2. Together with the increase in NO availability this mechanism contributes to the anti-inflammatory effect of AMPK.