Impaired NO release by phosphorylation of neuronal nitric oxide synthase in interactions between trophoblast and cytokines generating preeclampsia

초록

Impairment of the endothelial nitric oxide (NO) production in pregnancy has been suggested as a major cause of the incidence of preeclampsia (PE), which is associated with maternal hypertension in pregnancy, proteinuria, edema, fetal growth restriction and premature birth, and also with increases of placental inflammatory cytokines. However, NO is also synthesized by peripheral non-adrenergic non-cholinergic (NANC) nerves in teh vessels, thereby mediating vasodilation. In this study, we investigated the effects of inflammatory mediators, such as cytokines (TNF-a, IL-1b and INF-r) and LPS endotoxin, which are differentially changed in PE, on the expression and the modification of neuronal NO synthase (nNOS) in human term trophoblast cells (HT-1). Treatment of cells with cytokines and/or LPS stimulated at least three different protein kinase activities (PKC, PKA and CaMK-II) with an increase in Ca++ influx, and a decrease in the nNOS activity by phosphorylation. Cytokines and/or LPS caused an increase in phosphorylation of the nNOS probably via CaMK-II and PKA pathways, as the phosphorylation of the nNOS was inhibited by their specific inhibitors KN-93 and H-89, respectively. In addition, calcium inophore (10uM) also enhanced phosphorylation of nNOS via CaMK-II activity, which led to a decrease in NOS activity. Thus, we suggest that the increase of placental cytokines may enhance calcium influx, leading to an activation of CaMK-II, which, in turn, phosphorylates nNOS to inactivate the NOS in trophoblast cells. This result may provide a causative mechansism for the impaired NOS activity by interactions between trophoblast and cytokines generated in preeclampsia.