CHOLECYSTOKININ MITIGATES INFLAMMATION-INDUCED IMPAIRMENT OF DENDRITOGENESIS IN NORMAL AND ENGRAILED-2 OVEREXPRESSING PURKINJE CELLS

Autism spectrum disorder (ASD) is a neurodevelopmental condition with high genetic susceptibility and extrinsic risk factors such as maternal immune activation. A growing body of evidence implicates the cerebellum in ASD pathology, and a genetic predisposition within the transcription factor Engrailed-2 (En2) gene, which is required for normal cerebellar development, has been associated with ASD-like phenotypes. Previously, we showed that prolonged En2 expression and immune activation cooperate to disrupt normal Purkinje cell (PC) differentiation in mice, and that the gut peptide cholecystokinin-8 (CCK-8) is downregulated in PCs upon En2 overexpression. In addition, we have shown that expression of the gut peptide cholecystokinin-8 is inhibited in mice overexpressing En2 in PCs. Here, we asked whether CCK-8 impacts on PC differentiation under physiological and inflammatory conditions in a moue model overexpressing En2.
Using cerebellar slice cultures prepared from 6-day-old mice, we can show that lipopolysaccharide (LPS) treatment impaired PC dendritogenesis, resulting in shorter dendrites, and reduced arbor complexity. Blocking TNF-α receptor signalling and inhibiting microglial proliferation restored dendritic growth, indicating that microglia are key mediators of the inflammatory response. In wild-type mice, CCK-8 alleviated LPS-induced dendritic impairments, but this effect was reduced in PCs lacking CCK receptor A and B expression. In addition, CCK-8 significantly reduced PC arborization deficits induced by En2 overexpression and mitigated impairments caused by both LPS treatment and En2 overexpression. Together, these findings indicate that CCK-8 has a strong anti-inflammatory, partly receptor-mediated protective effect on PC differentiation, including in PCs with an ASD-like genetic background.