β3 Adrenergic Stimulation Restores Nitric Oxide/Redox Balance and Enhances Endothelial Function in Hyperglycemia.

Background-Perturbed balance between NO and O-2(center dot-). (ie, NO/redox imbalance) is central in the pathobiology of diabetes-induced vascular dysfunction. We examined whether stimulation of beta(3) adrenergic receptors (beta(3) ARs), coupled to endothelial nitric oxide synthase (eNOS) activation, would re-establish NO/redox balance, relieve oxidative inhibition of the membrane proteins eNOS and Na+-K+ (NK) pump, and improve vascular function in a new animal model of hyperglycemia. Methods and Results-We established hyperglycemia in male White New Zealand rabbits by infusion of S961, a competitive high-affinity peptide inhibitor of the insulin receptor. Hyperglycemia impaired endothelium-dependent vasorelaxation by "uncoupling" of eNOS via glutathionylation (eNOS-GSS) that was dependent on NADPH oxidase activity. Accordingly, NO levels were lower while O-2(center dot-) levels were higher in hyperglycemic rabbits. Infusion of the beta(3) AR agonist CL316243 (CL) decreased eNOS-GSS, reduced O-2(center dot-), restored NO levels, and improved endothelium-dependent relaxation. CL decreased hyperglycemia-induced NADPH oxidase activation as suggested by co-immunoprecipitation experiments, and it increased eNOS co-immunoprecipitation with glutaredoxin-1, which may reflect promotion of eNOS de-glutathionylation by CL. Moreover, CL reversed hyperglycemia-induced glutathionylation of the beta(1) NK pump subunit that causes NK pump inhibition, and improved K+-induced vasorelaxation that reflects enhancement in NK pump activity. Lastly, eNOS-GSS was higher in vessels of diabetic patients and was reduced by CL, suggesting potential significance of the experimental findings in human diabetes. Conclusions-beta(3) AR activation restored NO/redox balance and improved endothelial function in hyperglycemia. beta(3) AR agonists may confer protection against diabetes-induced vascular dysfunction.