5‐Hydroxytryptamine Evokes Endothelial Nitric Oxide Synthase Activation in Bovine Aortic Endothelial Cell Cultures

Abstract

Activation of endothelial nitric oxide synthase (eNOS) results in the production of nitric oxide (NO) that mediates the vasorelaxing properties of endothelial cells. The goal of this project was to address the possibility that 5-hydroxytryptamine (5-HT) stimulates eNOS activity in bovine aortic endothelial cell (BAEC) cultures. Here, we tested the hypothesis that 5-HT receptors mediate eNOS activation by measuring agonist-stimulated [3H]L-citrulline ([3H]L-Cit) formation in BAEC cultures. We found that 5-HT stimulated the conversion of [3H]L-arginine ([3H]L-Arg) to [3H]L-Cit, indicating eNOS activation. The high affinity 5-HT1B receptor agonist, 5-nonyloxytryptamine (5-NOT)-stimulated [3H]L-Cit turnover responses were concentration-(0.01 nM to 100 microM) and time-dependent. Maximal responses were observed within 10 min following agonist exposures. These responses were effectively blocked by the 5-HT1B receptor antagonist, isamoltane, the 5-HT1B/5-HT2 receptor antagonist, methiothepin, and the eNOS selective antagonists (0.01-10 microM): L-Nomega -monomethyl-L-arginine (L-NMMA) and L-N omega-iminoethyl-L-ornithine (L-NIO). Pretreatment of BAEC cultures with pertussis toxin (PTX; 1-100 ng/ml) for 16 hr resulted in significant inhibition of the agonist-stimulated eNOS activity, indicating the involvement of Gi proteins. These findings lend evidence of a 5-HT1B receptor/eNOS pathway, accounting in part for the activation of eNOS by 5-HT. Further investigation is needed to determine the role of other vascular 5-HT receptors in the stimulation of eNOS activity.

5‐HT moduline: an endogenous inhibitor of 5‐HT1B/1D‐mediated contraction in pulmonary arteries

“…It is possible that nitric oxide or cGMP in some way interacts with the 5‐HT 1B receptor to keep it in a conformation or state that enables 5‐HTm to bind. Indeed, the 5‐HT 1B receptor has been shown to activate endothelial nitric oxide synthase and nitric oxide production (McDuffie et al ., 1999; Ishida et al ., 1998) which may normally facilitate binding of 5‐HTm. It has been shown that there are two interacting sites for 5‐HTm, probably corresponding to different conformations of the 5‐HT 1B receptor.…”

Contemporary Approaches to Modulating the Nitric Oxide–cGMP Pathway in Cardiovascular Disease

“…caveolin-1 (CAV1) 12 or heat shock protein 90 (HSP90) 13 ] and other assorted regulators 14 . NO production is stimulated by various vasoactive factors including catecholamines 15 , bradykinin 16 , and serotonin 17 as well as physical factors such as fluid shear stress 18 . At physiological levels, NO can buffer reactive oxygen species and its lipophilic character allows it to freely permeate membranes to reach circulating cells in the lumen such as neutrophils and platelets and traverse abluminally into the professional contractile cells of blood vessels, vascular smooth muscles cells (VSMC).…”

Antagonism of nitrous oxide-induced anxiolytic-like behavior in the mouse light/dark exploration procedure by pharmacologic disruption of endogenous nitric oxide function

“…SMTC is considered a selective nNOSinhibitor, being 10-fold more potent against nNOS than eNOS and 28-fold more potent against nNOS than iNOS (Furfine et al 1994). l-NIO is reported to selectively inhibit eNOS, being 8-fold more potent against eNOS than nNOS and 4-fold more potent against eNOS than iNOS (Rees et al 1990;McCall et al 1991;McDuffie et al 1999). However, AMT is a selective inhibitor of iNOS, being 10-fold more potent against iNOS than nNOS and 42-fold more potent against iNOS than eNOS Tracey et al 1995).…”