Role of SERCA3-dependent calcium signaling in mouse aortic function

Abstract

Calcium homeostasis has a major role in vascular reactivity. The Sarco/Endoplasmic Reticulum Ca2+-ATPases (SERCAs) contribute to generate intracellular Ca2+-stores that are mobilized during functional responses. The SERCA2 family is described as the most important in vascular cells, but SERCA3 has been reported to be co-expressed, with SERCA3a mainly at the endothelial level and SERCA3b at the smooth muscle level. Our objective is to evaluate the role of the SERCA3-dependent calcium pathway in vascular reactivity. For experiments, aortic rings were collected from wild-type (WT) and SERCA3-deficient (SERCA3-KO) mice (2–3 month-old male) and mounted in an organ bath system. Contractile and relaxant agents were applied to compare the in vitro aortic reactivity in both animal groups. The contractile responses to a depolarizing high-potassium solution or to cumulative increasing concentrations of serotonin (a 5-HT agonist, 10-9 to 10-5 M) or U46619 (a TXA2 analog, 10-10 to 3.10-6 M) were similar in SERCA3-KO and WT aorta. By contrast the response to phenylephrine (an α1-adrenergic agonist, 10-9 to 3.10-5 M) was significantly decreased in SERCA3-KO compared to WT aorta (N = 8-8; P < 0.05, 2-way ANOVA). However, in aorta denuded from endothelium, the contractile response to phenylephrine was similar in SERCA3-KO and WT vessels. In phenylephrine-precontracted aorta, the relaxant responses to acetylcholine (a muscarinic agonist, 10-9 to 3.10-5 M) or to isoproterenol (a b-adrenergic agonist, 10-10 to 10-5 M) were similar in both groups. The concentration-response curve to DEA-NOate (a NO donor, 10-11 to 10-5 M) was shifted to the right in SERCA3-KO compared to WT aortas, with a slight increase in EC50 (N = 9-8; P < 0.05, t -test). When the endothelium was removed, the effect to DEA-NOate was similar in both groups. We observed that SERCA3-KO aorta exhibit a major decrease in the amplitude of the α1-adrenergic contractile response, and in the sensitivity to the relaxant NO donor. These alterations are abolished in the absence of a functional endothelium. These preliminary data suggest that there is an influence of SERCA3 protein on the NO signaling pathway in mouse aorta.