G Protein‐Coupled Estrogen Receptor (GPER)‐Mediated Relaxation of Coronary Arteries is Mitigated by Phosphorylation of ERK1/2

Abstract

GPER is a membrane‐bound estrogen receptor, distinct from ERα or ERβ, and exerts genomic and non‐genomic effects. GPER's effect on the cardiovascular system has been controversial; evidence indicate it relaxes arteries, whereas other findings suggest it contracts arteries. Our objective is to better understand the dual nature of GPER. Previously, our work demonstrated that G‐1 stimulates cAMP production. We hypothesize GPER mediates relaxation response through cAMP and constriction via ERK1/2. Isometric tension studies were used to measure GPER‐mediated coronary tone response in porcine coronary arteries. Western blots were applied to detect pERK1/2 in primary cell culture of smooth muscle cells. The identity of smooth muscle cells was validated by immunohistochemistry techniques using α actin as a marker. Under adenylate cyclase inhibition by SQ22536, G‐1 stimulated phosphorylation of ERK1/2. The effect of G‐1 was blocked by G36, a GPER inhibitor. A time course of G‐1 (1 nM) demonstrated that detection of pERK1/2 peaked at 2 and 5 min, decreased at 15 min, and returned below baseline by 30 min. Similar results were found for a time course of E2 (1 nM) detecting pERK1/2, however, under no adenylate cyclase inhibition. Tension studies demonstrated that G‐1 caused concentration‐dependent relaxation of PGF2α (1 μM) precontracted, endothelium denuded coronary arteries. PD98059, a MEK 44/42 inhibitor which blocks the phosphorylation of ERK1/2, led to further relaxation than G‐1 alone. We conclude that phosphorylation of ERK1/2 lessens the coronary artery relaxation caused by GPER.Support or Funding InformationAmerican Heart Association