Hydroxy-Methylglutaryl–Coenzyme A Reductase Inhibition Promotes Endothelial Nitric Oxide Synthase Activation Through a Decrease in Caveolin Abundance

Abstract

Background —Hypercholesterolemia is causally associated with defects of endothelial nitric oxide (NO)–dependent vasodilation. Increased uptake of cholesterol by endothelial cells (ECs) upregulates the abundance of the structural protein caveolin-1 and impairs NO release through the stabilization of the inhibitory heterocomplex between caveolin-1 and endothelial NO synthase (eNOS). Therefore, we examined whether the hydroxy-methylglutaryl–coenzyme A reductase inhibitor atorvastatin modulates caveolin abundance, eNOS activity, and NO release through a reduction in endogenous cholesterol levels. Methods and Results —ECs were incubated with increasing doses of atorvastatin in the absence or in the presence of human LDL cholesterol (LDL-Chol) fractions in the presence of antioxidants. Our results show that atorvastatin (10 nmol/L to 1 μmol/L) reduced caveolin-1 abundance in the absence (−75%) and in the presence (−20% to 70%) of LDL-Chol. This was paralleled by a decreased inhibitory interaction between caveolin-1 and eNOS and a restoration and/or potentiation of the basal (+45%) and agonist-stimulated (+107%) eNOS activity. These effects were observed in the absence of changes in eNOS abundance and were reversed with mevalonate. In the presence of LDL-Chol, atorvastatin also promoted the agonist-induced association of eNOS and the chaperone Hsp90, resulting in the potentiation of eNOS activation. Conclusions —We provide biochemical and functional evidence that atorvastatin promotes NO production by decreasing caveolin-1 expression in ECs, regardless of the level of extracellular LDL-Chol. These findings highlight the therapeutic potential of inhibiting cholesterol synthesis in peripheral cells to correct NO-dependent endothelial dysfunction associated with hypercholesterolemia and possibly other diseases.