Activation of nitric oxide synthase by β₂‐adrenoceptors in human umbilical vein endothelium in vitro

Abstract

1 Some animal studies suggest that b-adrenoceptor-mediated vasorelaxation is in part mediated through nitric oxide (NO) release. Furthermore, in humans, we have recently shown that forearm blood¯ow is increased by infusion of b 2 -adrenergic agonists into the brachial artery, and the nitric oxide synthase (NOS) inhibitor N G -monomethyl-L-arginine (L-NMMA) inhibits this response. 2 The purpose of the present study was to determine whether stimulation of human umbilical vein endothelial b-adrenoceptors causes vasorelaxation and nitric oxide generation, and whether this might be mediated by cyclic adenosine-3',5'-monophosphate (cyclic AMP). 5 Isoprenaline relaxed umbilical vein rings, and this vasorelaxation was abolished by b 2 -(but not b 1 -) adrenergic blockage, and by endothelium removal or 1 mM L-NMMA. In addition, vasorelaxant responses to dibutyryl cyclic AMP were inhibited by 1 mM L-NMMA, with a reduction in E max from 90.0+9.3% to 50.5+9.9% (P50.05). 6 Isoprenaline 1 mM increased NOS activity in HUVEC (34.0+5.9% above basal, P50.001). Furthermore, isoprenaline increased adenylyl cyclase activity in a concentration-dependent manner; this response was inhibited by b 2 (but not b 1 -) adrenergic blockade. Forskolin 1 mM and dibutyryl cyclic AMP 1 mM each increased NOS activity in HUVEC, to a degree similar to isoprenaline 1 mM. The increase in L-arginine to L-citrulline conversion observed with each agent was abolished by coincubation with NOS inhibitors. 7 These results indicate that endothelial b 2 -adrenergic stimulation and cyclic AMP elevation activate the L-arginine/NO system, and give rise to vasorelaxation, in human umbilical vein.

Nitric oxide generation mediated by ?-adrenoceptors is impaired in platelets from patients with Type 2 diabetes mellitus

“…An alternative explanation for the findings must therefore be sought. Alterations in Ca 2+ signalling have been described in diabetes [36,37], although this is unlikely to affect βAR-mediated NOS3 activation, as this activation has been shown to occur without detectable changes in intracellular Ca 2+ either in human vascular endothelial cells [38] or in platelets [6]. It has been reported that sheer stress can activate NOS3 in a Ca 2+ -independent manner [39].…”

β 2 -Adrenergic Receptor Gene Delivery to the Endothelium Corrects Impaired Adrenergic Vasorelaxation in Hypertension

“…In umbilical vein endothelial cells, it has been demonstrated that ␤ 2 AR stimulates eNOS activation. 4 However, most studies in other preparations have failed to demonstrate an active release of NO in response to ␤AR agonists. 21 Therefore, we first confirmed that ISO in normotensive rat aorta endothelial cells can induce eNOS activation and also demonstrated that AD␤ 2 AR treatment can enhance this response.…”

“…1,2 Indeed, both ␤ 1 ARs and ␤ 2 ARs are expressed on endothelial cells, 3 and stimulation of endothelial ␤ 2 ARs causes endothelial nitric oxide synthase (eNOS) activation and NO release in human umbilical vein endothelium. 4 In hypertension, ␤AR control of vasorelaxation is impaired, and this impairment seems to be involved in high blood pressure. 5 There are two alternative hypotheses to explain this alteration.…”

Changes in vascular reactivity following administration of isoproterenol for 1 week: a role for endothelial modulation

“…b-adrenoceptors change endothelial function eNOS in isolated endothelial cells (Ferro et al, 1999, Isenovic et al, 2002 and iNOS in cultured vascular smooth cells (Koide et al, 1993) following b-adrenoceptor stimulation. In addition, we found a significant increase in protein concentrations for both eNOS and nNOS in aortas from ISO-treated rats.…”

“…In addition, activation of b-adrenoceptors on the endothelium produces vasodilatation (Gray & Marshall, 1992;Brawley et al, 2000) that is mediated by the synthesis of nitric oxide (NO) (Ferro et al, 1999). It is possible that chronic b-adrenergic stimulation could induce adaptive alterations of vascular b-adrenoceptor signalling pathways resulting in endothelial dysfunction, impaired peripheral vasodilatation and/or inappropriate vasoconstriction.…”