Norepinephrine (NE) Increases Production of Superoxide (O2• ‐) in Cultured Peripheral Blood Mononuclear Cells (PBMCs) and Splenocytes Isolated from Rats

Abstract

Physiological/pathophysiological states with increased sympathetic nerve activity (SNA) are associated with oxidative stress. It is known that increased O2• ‐ in specific brain regions results in increased efferent SNA. Recently we found that NE increased intracellular O2• ‐ production (Dihydroethidium, DHE) and mRNA for NADPH oxidase (NOX‐2) subunits in cultured PBMCs from humans suggesting elevated SNA may increase systemic O2• ‐ production. Current experiments tested whether the rat is a good experimental model of humans to further study the interaction between sympathoexcitation and PBMC‐derived O2• ‐. Primary PBMCs and splenocytes were isolated from male rats and incubated at 37°C for 36 hr with either vehicle (Veh), 50 pcg/ml, 50 ng/ml, or 50 µg/ml NE. Similar to human PBMCs, relative to Veh, NE increased intracellular O2• ‐ production in rat PBMCs (50 µg/ml NE = 11± 5 fold; P< 0.05) and tended to increase mRNA for NOX‐2 subunits (50 ng/ml NE: gp 91phox = 1.8 ± 0.4; p22phox = 1.6± 0.5). NE also increased O2• ‐ in rat splenocytes (50 µg/ml NE = 11± 6 fold; P< 0.05). Thus, results in rat PBMCs and splenocytes are similar to human PBMCs, and are consistent with a positive feedback system whereby increased NE promotes increased O2• ‐ in circulating PBMCs which in turn could activate CNS sites to promote further increases in SNA. Using the rat as a model, future experiments will evaluate a potential role of circulating PBMCs on activation of brain regions involved in the control of sympathetic outflow. R01 HL091164