HSP90 and Akt modulate Ang-1-induced angiogenesis via NO in coronary artery endothelium

Abstract

This study examines the notion that heat shock protein (HSP) 90 binding to nitric oxide (NO), endothelial NO synthase (eNOS), and PI3K-Akt regulate angiopoietin (Ang)-1-induced angiogenesis in porcine coronary artery endothelial cells (PCAEC). Exposure to Ang-1 (250 ng/ml) for periods up to 2 h resulted in a time-dependent increase in eNOS phosphorylation at Ser 1177 that occurred by 5 min and peaked at 60 min. This was accompanied by a gradual increase in NO release. Ang-1 also led to stimulation of HSP90 binding to eNOS and a significant increase in Akt phosphorylation. Thirty minutes of pretreatment of cells with either 1 μg/ml geldanamycin (a specific inhibitor of HSP90) or 500 nM wortmannin [a specific phosphatidylinositol 3 (PI3)-kinase (PI3K) inhibitor] significantly attenuated Ang-1-stimulated eNOS phosphorylation and NO production. Exposure to Ang-1 caused an increase in endothelial cell migration, tube formation, and sprouting from PCAEC spheroids, and pharmacological blockage of HSP90 function or inhibition of PI3K-Akt pathway completely abolished these effects. Inhibition of nitric oxide synthase by NG-nitro-l-arginine methyl ester (2.5 mM) also resulted in a significant decrease in Ang-1-induced angiogenesis. We conclude that stimulated HSP90 binding to eNOS and activation of the PI3-Akt pathway contribute to Ang-1-induced eNOS phosphorylation, NO production, and angiogenesis in PCAEC.