Huntington's disease (HD) is a monogenic inherited polyglutamine-mediated neurodegenerative disorder for which effective therapies are currently unavailable. Neuropeptide Y (NPY) has been implicated as a potential therapeutic target in several neurodegenerative diseases, including HD. However, its mechanisms of action in the context of HD pathology remain unknown. Here, we investigated the beneficial effects of Y2 receptor (Y2R) activation with NPY or Y2R selective agonist NPY13–36 in the R6/2 mouse and PC12 cell models of HD. Also, we explored the effects of selective pharmacological blockage of Y2R using selective non-peptide small molecule Y2R antagonist SF31 in vivo and in vitro.
Our results showed that activation of Y2R with intranasal NPY or NPY13–36 led to an improved motor function in R6/2 mice as revealed by rotarod performance, vertical pole test, and hindlimb clasping behaviour. Also, intranasal NPY or NPY13–36 led to a decrease in aggregated mHtt and mediated increase in dopamine and cAMP-regulated phosphoprotein, 32 kDa (DARPP-32), brain-derived neurotrophic factor (BDNF), and activated extracellular signal-regulated protein kinases (pERK1/2) levels in R6/2 mice. Intranasal NPY or NPY13–36 had no effect on body weight but showed positive effects on survival in R6/2 mice. Furthermore, intranasal NPY or NPY13–36 attenuated induction of proinflammatory cytokine and inflammatory mediators in R6/2 mice. In contrast, antagonizing by using SF31 exacerbates phenotypic severity in R6/2 mice and treatment effects with either intranasal NPY or NPY13–36 were significantly blocked.In vitro, using inducible PC12/HttQ103-EGFP cells, treatment with NPY or NPY13–36 protected against mHtt-mediated neuromorphological defects (neurite length and soma area) and neurotoxicity but had no effect on mHtt inclusion body formation. Conversely, co-treatment with SF31 significantly inhibited these effects. Together, our findings extend previous evidence of the beneficial effects of NPY in R6/2 mice, and more importantly, suggest that targeted activation of Y2R receptor might be a promising disease-modifying target for HD and other neurodegenerative diseases.