Ser9p-GSK3β Modulation Contributes to the Protective Effects of Vitamin C in Neuroinflammation

Background. The prolonged activation of microglia and excessive production of pro-inflammatory cytokines can lead to chronic neuroinflammation, which is an important pathological feature of Parkinson's disease (PD). We have previously reported the protective effect of Vitamin C (Vit C) on a mouse model of PD. However, its effect on microglial functions in neuroinflammation remains to be clarified. Glycogen synthase kinase 3 beta (GSK3 beta) is a serine/threonine kinase having a role in driving inflammatory responses, making GSK3 beta inhibitors a promising target for anti-inflammatory research. Methods. In this study, we investigated the possible involvement of GSK3 beta in Vit C neuroprotective effects by using a well-known 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced animal model of PD and a cellular model of neuroinflammation, represented by Lipopolysaccharide (LPS)-activated BV-2 microglial cells. Results. We demonstrated the ability of Vit C to decrease the expression of different mediators involved in the inflammatory responses, such as TLR4, p-IKB alpha, and the phosphorylated forms of p38 and AKT. In addition, we demonstrated for the first time that Vit C promotes the GSK3 beta inhibition by stimulating its phosphorylation at Ser9. Conclusion. This study evidenced that Vit C exerts an anti-inflammatory function in microglia, promoting the upregulation of the M2 phenotype through the activation of the Wnt/beta-catenin signaling pathway.