Catecholamines facilitate VEGF-dependent angiogenesis via β2-adrenoceptor-induced Epac1 and PKA activation

// Jaspal Garg 1 , Yu-Xi Feng 1 , Sepp R. Jansen 1 , Julian Friedrich 2 , Frank Lezoualc'h 3 , Martina Schmidt 4 and Thomas Wieland 1 1 Institute of Experimental and Clinical Pharmacology and Toxicology, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany 2 5th Medical Clinic, University Hospital Mannheim, Heidelberg University, Mannheim, Germany 3 Institute of Cardiovascular and Metabolic Diseases, Inserm UMR-1048, Université Toulouse -Paul Sabatier, Toulouse, France 4 Department of Molecular Pharmacology, Center of Pharmacy, University of Groningen, Groningen, The Netherlands Correspondence to: Thomas Wieland, email: thomas.wieland@medma.uni-heidelberg.de Keywords: angiogenesis, cAMP, VEGF, EPAC, PKA Received: March 24, 2017      Accepted: March 30, 2017      Published: April 20, 2017 ABSTRACT Chronic stress has been associated with the progression of cancer and antagonists for β-adrenoceptors (βAR) are regarded as therapeutic option. As they are also used to treat hemangiomas as well as retinopathy of prematurity, a role of endothelial β 2 AR in angiogenesis can be envisioned. We therefore investigated the role of β 2 AR-induced cAMP formation by analyzing the role of the cAMP effector molecules exchange factor directly activated by cAMP 1 (Epac1) and protein kinase A (PKA) in endothelial cells (EC). Epac1-deficient mice showed a reduced amount of pre-retinal neovascularizations in the model of oxygen-induced retinopathy, which is predominantly driven by vascular endothelial growth factor (VEGF). siRNA-mediated knockdown of Epac1 in human umbilical vein EC (HUVEC) decreased angiogenic sprouting by lowering the expression of the endothelial VEGF-receptor-2 (VEGFR-2). Conversely, Epac1 activation by β 2 AR stimulation or the Epac-selective activator cAMP analog 8-p-CPT-2’-O-Me-cAMP (8-pCPT) increased VEGFR-2 levels and VEGF-dependent sprouting. Similar to Epac1 knockdown, depletion of the monomeric GTPase Rac1 decreased VEGFR-2 expression. As Epac1 stimulation induces Rac1 activation, Epac1 might regulate VEGFR-2 expression through Rac1. In addition, we found that PKA was also involved in the regulation of angiogenesis in EC since the adenylyl cyclase (AC) activator forskolin (Fsk), but not 8-pCPT, increased sprouting in Epac1-depleted HUVEC and this increase was sensitive to a selective synthetic peptide PKA inhibitor. In accordance, β 2 AR- and AC-activation, but not Epac1 stimulation increased VEGF secretion in HUVEC. Our data indicate that high levels of catecholamines, which occur during chronic stress, prime the endothelium for angiogenesis through a β 2 AR-mediated increase in endothelial VEGFR-2 expression and VEGF secretion.