Neuropeptide Y mitigates ER stress-induced neuronal cell death by activating the PI3K-XBP1 pathway

The unfolded protein response (UPR) is an evolutionarily conserved adaptive reaction that increases cell survival under endoplasmic reticulum (ER) stress conditions. ER stress-associated neuronal cell death pathways play roles in the pathogenesis of neurodegenerative diseases, including Alzheimer's, Parkinson's, and Huntington's disease. Neuropeptide Y (NPY) has an important role in neuroprotection against neurodegenerative diseases. In this study, we investigated whether NPY has a protective role in ER stress-induced neuronal cell death in SK-N-SH human neuroblastoma cells. An ER stress-inducing chemical, tunicamycin, increased the activities of caspase-3 and -4, whereas pretreatment with NPY decreased caspase-3 and -4 activities during the ER stress response. In addition, NPY suppressed the activation of three major ER stress sensors during the tunicamycin-induced ER stress response. NPY-mediated activation of PI3K increased nuclear translocation of XBP1s, which in turn induced expression of Grp78/BiP. Taken together, our data indicated that NPY plays a protective role in ER stress-induced neuronal cell death through activation of the PI3K-XBP1 pathway, and that NPY signaling can serve as therapeutic target for ER stress-mediated neurodegenerative diseases.