Neutralization of IL‐17 rescues amyloid‐β‐induced neuroinflammation and memory impairment

Background and purpose Alzheimer's disease (AD) is a common neurodegenerative disease characterized by a neuroinflammatory state, and to date, there is no cure and its treatment represents a large unmet clinical need. The involvement of Th17 cells in the pathogenesis of AD‐related neuroinflammation has been reported in several studies. However, the role of the cytokine, IL‐17 has not been well addressed. Herein, we investigate the effects of IL‐17 neutralizing antibody (IL‐17Ab) injected by i.c.v. or intranasal (IN) routes on amyloid‐β (Aβ)‐induced neuroinflammation and memory impairment in mice. Experimental approach Aβ1–42 was injected into cerebral ventricles of adult CD1 mice. These mice received IL‐17Ab via i.c.v. either at 1 h prior to Aβ1–42 injection or IN 5 and 12 days after Aβ1–42 injection. After 7 and 14 days of Aβ1–42 administration, we evaluated olfactory, spatial and working memory and performed biochemical analyses on whole brain and specific brain areas. Key results Pretreatment with IL‐17Ab, given, i.c.v., markedly reduced Aβ1–42‐induced neurodegeneration, improved memory function, and prevented the increase of pro‐inflammatory mediators in a dose‐dependent manner at 7 and 14 days. Similarly, the double IN administration of IL‐17Ab after Aβ1–42 injection reduced neurodegeneration, memory decline, and the levels of proinflammatory mediators and cytokines. Conclusion and implications These findings suggest that the IL‐17Ab reduced neuroinflammation and behavioural symptoms induced by Aβ. The efficacy of IL‐17Ab IN administration in reducing Aβ1–42 neurodegeneration points to a possible future therapeutic approach in patients with AD. Linked Articles This article is part of a themed section on Therapeutics for Dementia and Alzheimer's Disease: New Directions for Precision Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.18/issuetoc