Activation of G protein‐coupled estrogen receptor 1 (GPER) induced coronary vasodilation by activation of MLCP via cAMP/PKA pathway

Abstract

Activation of GPER exerts a protective effect in hypertension and ischemia‐reperfusion models, and relaxes arteries in vitro. However, our understanding of the mechanisms of GPER‐mediated vascular regulation is far from completed. We have investigated whether GPER‐mediated relaxation of porcine coronary arteries involves cAMP/PKA signaling. In these vessels, the selective GPER agonist, G‐1, increased cAMP production in a concentration‐dependent manner. Myograph studies demonstrated that inhibiting the activity of adenylyl cyclase (AC) with100 μM SQ‐22538 inhibited 0.3–3 μM G‐1‐induced relaxation of coronary arteries preconstricted with 1 μM PGF2α. Activating AC with forskolin also induced a concentration‐dependent relaxation. Furthermore, G‐1‐induced coronary vasodilation was attenuated by inhibiting PKA with either 5μM Rp‐8‐CPT‐cAMPS or 5μM PKI. To determine downstream signals of the cAMP/PKA cascade, we measured myosin light chain phosphatase (MLCP) activity in these artery rings and cultured smooth muscle cells with Western blot by detecting phosphorylation of myosin‐targeting subunit protein‐1 (pMYPT‐1), the MLCP regulatory subunit. Treatment with G‐1 decreased pMYPT‐1induced by PGF2α. Both Rp‐8‐CPT‐cAMPS and PKI attenuated the decrease of pMYPT‐1 by G‐1. These findings demonstrate that cAMP/PKA signaling is involved in GPER‐mediated coronary vasodilation by activating MLCP.