Sigma-1 receptor stimulation with fluvoxamine activates Akt-eNOS signaling in the thoracic aorta of ovariectomized rats with abdominal aortic banding

In the present study, we investigated the vasculoprotective effect of sigma-1 receptor stimulation with fluvoxamine on pressure overload hypertrophy-induced vascular injury in the thoracic aorta and defined mechanisms underlying that activity. Wistar rats underwent bilateral ovariectomy, and two weeks later were further treated with abdominal aortic stenosis. To confirm the vasculoprotective role of sigma-1 receptor signaling, we treated rats with the agonist fluvoxamine (at 0.5 and 1.0 mg/kg) and with the antagonist NE-100 (at1.0 mg/kg) for 4 weeks orally once a day after the onset of aortic banding. Interestingly, sigma-1 receptor expression in the thoracic aorta decreased significantly 4 weeks after pressure overload-induced hypertrophy in vehicle treated ovariectomized rats. Fluvoxamine administration significantly attenuated pressure overload-induced vascular injury with concomitant increase in receptor expression and subsequent decrease in IP3 receptor expression. Fluvoxamine treatment also significantly restored pressure overload-induced impaired Akt phosphorylation and stimulated eNOS protein expression as well as Akt-mediated eNOS phosphorylation (Ser1177). Fluvoxamine's vasculoprotective effect was nullified by co-administration of a sigma-1 receptor antagonist. No changes in phosphorylation of ERK1/2 or PKCα in the aorta were observed following pressure overload and after fluvoxamine treatment. Our findings confirm, for the first time, a potential role for sigma-1 receptor expression and signaling in the thoracic aorta in attenuating hypertrophy-induced vascular injury in ovariectomized rats. Thus, we demonstrate, for the first time, a potential role in the thoracic aorta for sigma-1 receptor expression and signaling via Akt-eNOS in attenuating hypertrophy-induced vascular injury in ovariectomized rats.