ROS-production-mediated activation of AP-1 but not NFκB inhibits glutamate-induced HT4 neuronal cell death

Aside from their deleterious effect, reactive oxygen species (ROS) can function as small messenger molecules during physiologic processes. ROS have been shown to activate the transcription nuclear factor kappa B (NFκB) and activator protein 1 (AP-1). Exposure of HT4 neuronal cells to 10 mM glutamate results in cell death after 12 h. Here we show that glutamate treatment leads to an increase in ROS production and activation of AP-1, but not NFκB. 12-O-Tetradecanoylphorbol 13-acetate (TPA), an activator of protein kinase C and an inducer of NFκB and AP-1, protected the cells. This protective effect was preceded by increased production of ROS compared with glutamate alone, which was accompanied by a synergistic increase in AP-1, but not NFκB activity. We used all-trans-retinoic acid (ATRA), overexpression of retinoic acid receptor α (RARα) and a decoy oligonucleotide inclusion assay to suppress AP-1 activity. NFκB was inhibited by using a super suppressor (IκBαδN-transfected cells). Inhibition of AP-1, but not NFκB resulted in increased cellular vulnerability to glutamate. Inhibition of AP-1 activity was coincident with a decrease in ROS production. Thus, although ROS are significant to the cell-death effect induced by glutamate, they also activate protective pathways mediated by increasing AP-1 activity, and not that of NFκB.