Effect of nitric oxide donors on NADPH oxidase signaling pathway in human neutrophils in vitro

The production of reactive oxygen species (ROS) in activated neutrophils is catalyzed by NADPH oxidase, a multiproteins complex. Various protein kinases including protein kinase C (PKC) and mitogen activated protein kinases (MAPKs) are involved in NADPH oxidase phosphorylation and activation. The main step in the NADPH oxidase activation is phosphorylation of its cytosolic protein p47phox. We found previously that nitric oxide (NO) donors such as metabolite of molsidomine-SIN-1 and diethylamine/NO significantly impaired the ROS production in activated human neutrophils. In this study, we investigated the effects of both NO donors on NADPH oxidase-linked signaling proteins in activated neutrophils. We found that NO donors decreased the phosphorylation of p47phox on tyrosine and serine/threonine residues and PKC on serine residues in neutrophils. Both NO donors did not affect the phosphorylation of MAPKs. NO donors partially but significantly lost their ability to reduce ROS production in the presence of PKC but not MAPKs inhibitors. We show that whereas NO donors have no effect on MAPKs activity, they do decrease PMA- and/or fMLP-induced phosphorylation of p47phox and PKC as well as PMA- and fMLP-induced ROS production.