Vascular Endothelial σ₁-Receptor Stimulation With SA4503 Rescues Aortic Relaxation via Akt/eNOS Signaling in Ovariectomized Rats With Aortic Banding

Abstract

Background: We previously reported that σ₁-receptor (σ₁R) expression in the thoracic aorta decreased after pressure overload (PO) induced by abdominal aortic banding in ovariectomized (OVX) rats. Here, we asked whether stimulation of σ₁R with the selective agonist SA4503 elicits functional recovery of aortic vasodilation and constriction following vascular injury in OVX rats with PO. Methods and Results: SA4503 (0.3–1.0mg/kg) and NE-100 (a σ₁R antagonist, 1.0mg/kg) were administered orally for 4 weeks (once daily) to OVX-PO rats. Vascular functions of isolated descending aorta were measured following phenylephrine (PE)- or endothelin-1 (ET-1)-induced vasoconstriction and acetylcholine (ACh)- or clonidine-induced vasodilation. SA4503 administration rescued PO-induced σ₁R decreases in aortic smooth muscle and endothelial cells. SA4503 treatment also rescued PO-induced impairments in ACh- and clonidine-induced vasodilation without affecting PE- and ET-1-induced vasoconstriction. Ameliorated ACh- and clonidine-induced vasodilation was closely associated with increased Akt activity and in turn endothelial nitric oxide synthase (eNOS) phosphorylation. The SA4503-mediated improvement of vasodilation was blocked by NE-100 treatment. Conclusions: σ₁R is downregulated following PO-induced endothelial injury in OVX rats. The selective σ₁R agonist SA4503 rescues impaired endothelium-dependent vasodilation in the aorta from OVX-PO rats through σ₁R stimulation, enhancing eNOS-cGMP signaling in vascular endothelial cells. These observations encourage development of novel therapeutics targeting σ₁R to prevent vascular endothelial injury in vascular diseases.  (Circ J 2013; 77: 2831–2840)