ET‐1‐induced Superoxide‐dependent NFATc3 Activation

Abstract

Endothelin‐1 (ET‐1)‐induced activation of Nuclear Factor of Activated T‐cells isoform c3 (NFATc3) is necessary for the progression of chronic hypoxia (CH)‐induced pulmonary hypertension. Reactive oxygen species (ROS) levels are elevated in CH. ET‐1 increases ROS in pulmonary artery smooth muscle cells (PASMC). ROS participates in NFAT activation in cancer cells. However, it is unknown whether ROS mediates ET‐1‐induced NFATc3 activation in PASMC. Using human PASMC electroporated with a NFATc3‐GFP plasmid, we tested the hypothesis that increased ROS participates in ET‐1‐induced NFATc3 activation. Cells were pretreated with vehicle, a superoxide dismutase mimetic (tempol), a superoxide dismutase inhibitor (diethyldithiocarbamate, DDC) or H2O2. Nuclear fluorescence was measured before and during ET‐1 treatment. To prevent NFATc3 nuclear export, the CRM1 exportin inhibitor leptomycin B was present in all experiments.Our results show that pretreatment with both tempol and H2O2 inhibited ET‐1‐induced NFATc3 nuclear import. On the other hand, DDC enhanced ET‐1‐induced NFATc3 nuclear import.To determine the intracellular source of ROS, cells were pretreated with a xanthine oxidase inhibitor, allopurinol (Allo), or a NADPH oxidase inhibitor, apocynin (Apo). Allo but not Apo inhibited ET‐1‐induced NFATc3 nuclear import.Our results suggest that in human PASMC, ET‐1‐induced NFATc3 nuclear import is dependent on xanthine oxidase‐derived superoxide and/or a reduction in H2O2 levels. Therefore, it is possible that elevated superoxide levels in CH contribute to NFATc3 activation.Funding source: R01 HL088151