Deo SH, Jenkins NT, Padilla J, Parrish AR, Fadel PJ. Norepinephrine increases NADPH oxidase-derived superoxide in human peripheral blood mononuclear cells via ␣-adrenergic receptors. Am J Physiol Regul Integr Comp Physiol 305: R1124 -R1132, 2013. First published September 25, 2013 doi:10.1152/ajpregu.00347.2013.-Many diseases associated with sympathoexcitation also exhibit elevated reactive oxygen species (ROS). A recent animal study indicated that exogenous administration of the sympathetic neurotransmitter norepinephrine (NE) increased systemic ROS via circulating leukocytes. The mechanisms contributing to this effect of NE and whether these findings can be translated to humans is unknown. Thus we tested the hypothesis that NE increases superoxide production in human peripheral blood mononuclear cells (PBMCs) via NADPH oxidase. Primary human PBMCs were freshly isolated from healthy young men and placed in culture. After NE (50 pg/ml, 50 ng/ml, and 50 g/ml concentrations) or control treatments, NADPH oxidase mRNA expression (gp91 phox , p22 phox , and p67 phox ) was assessed using realtime RT-PCR, and intracellular superoxide production was measured using dihydroethidium fluorescence. PBMCs were also treated with selective adrenergic agonists-antagonists to determine the receptor population involved. In addition, CD14ϩ monocyte-endothelial cell adhesion was determined using a fluorescent-based assay. NE significantly increased NADPH oxidase gene expression and intracellular superoxide production in a time-dependent manner (superoxide: 0.9 Ϯ 0.2 fold, 6 h vs. 3.0 Ϯ 0.3 fold, 36 h; NE, 50 g/ml; P Ͻ 0.05). The sustained increase in NE-induced superoxide production was primarily mediated via ␣-adrenergic receptors, preferentially ␣ 2-receptors. The NADPH oxidase blocker diphenylene iodonium and protein kinase C inhibitor Staurosporine significantly attenuated NE-induced increases in superoxide production. Importantly, NE treatment increased CD14ϩ monocyte-endothelial cell adhesion. These findings indicate for the first time that NE increases superoxide production in freshly isolated primary human PBMCs via NADPH oxidase through ␣-adrenergic receptors, an effect facilitating monocyte adhesion to the endothelium. sympathetic nerve activity; reactive oxygen species; oxidative stress CHRONICALLY ELEVATED SYMPATHETIC NERVE ACTIVITY is a hallmark characteristic of several cardiovascular diseases (14,17,29). Recently, many of these diseases have also been shown to exhibit elevated systemic oxidative stress (9,19,38). However, it is unclear whether elevated oxidative stress causes sympathoexcitation or vice versa.Numerous studies performed in animals have convincingly shown that an increase in central superoxide levels induces activation of key brain areas, such as the rostral ventrolateral medulla, to cause sympathoexcitation (4,33,44,53,54). In contrast, to our knowledge, little consideration has been given to the potential ability of the sympathetic neurotransmitter norepinephrine (NE) to increase oxidative stress. In...