CALL FOR PAPERS Cell Signaling: Proteins, Pathways and Mechanisms 3-Adrenoceptor activation relieves oxidative inhibition of the cardiac Na -K pump in hyperglycemia induced by insulin receptor blockade

Karimi Galougahi K, Liu CC, Garcia A, Fry NA, Hamilton EJ, Figtree GA, Rasmussen HH. 3-Adrenoceptor activation relieves oxidative inhibition of the cardiac Na -K pump in hyperglycemia induced by insulin receptor blockade. Am J Physiol Cell Physiol 309: C286 –C295, 2015. First published June 10, 2015; doi:10.1152/ajpcell.00071.2015.—Dysregulated nitric oxide (NO)and superoxide (O2 )-dependent signaling contributes to the pathobiology of diabetes-induced cardiovascular complications. We examined if stimulation of 3-adrenergic receptors ( 3-ARs), coupled to endothelial NO synthase (eNOS) activation, relieves oxidative inhibition of eNOS and the Na -K pump induced by hyperglycemia. Hyperglycemia was established in male New Zealand White rabbits by infusion of the insulin receptor antagonist S961 for 7 days. Hyperglycemia increased tissue and blood indexes of oxidative stress. It induced glutathionylation of the Na -K pump 1-subunit in cardiac myocytes, an oxidative modification causing pump inhibition, and reduced the electrogenic pump current in voltage-clamped myocytes. Hyperglycemia also increased glutathionylation of eNOS, which causes its uncoupling, and increased coimmunoprecipitation of cytosolic p47 and membranous p22 NADPH oxidase subunits, consistent with NADPH oxidase activation. Blocking translocation of p47 to p22 with the gp91ds-tat peptide in cardiac myocytes ex vivo abolished the hyperglycemia-induced increase in glutathionylation of the Na -K pump 1-subunit and decrease in pump current. In vivo treatment with the 3-AR agonist CL316243 for 3 days eliminated the increase in indexes of oxidative stress, decreased coimmunoprecipitation of p22 with p47, abolished the hyperglycemia-induced increase in glutathionylation of eNOS and the Na -K pump 1-subunit, and abolished the decrease in pump current. CL316243 also increased coimmunoprecipitation of glutaredoxin-1 with the Na -K pump 1-subunit, which may reflect facilitation of deglutathionylation. In vivo 3-AR activation relieves oxidative inhibition of key cardiac myocyte proteins in hyperglycemia and may be effective in targeting the deleterious cardiac effects of diabetes.