METTL3/IGF2BP2/IκBα axis participates in neuroinflammation in Alzheimer's disease by regulating M1/M2 polarization of microglia.

Abstract

Background: Microglia-mediated neuroinflammation is closely related to the development of Alzheimer's disease (AD). This study further elucidated the regulatory mechanism of microglia polarization in AD.

Method: Microglia polarization was assessed using RT-qPCR, ELISA, and immunofluorescence (IF). Western blot (WB) analyzed inflammation-related, p-tau, and apoptosis-related proteins. Neuronal damage was evaluated by immunofluorescence, and neuronal apoptosis by flow cytometry and TUNEL assay. METTL3 and IκBα expression were detected using RT-qPCR and WB. N⁶-methyladenosine (m⁶A) levels were quantified with a colorimetric assay. RNA pull-down assay examined METTL3, IGF2BP2, and IκBα mRNA binding. IGF2BP expression was assessed by RT-qPCR. Learning and memory abilities were evaluated using morris water maze (MWM) test and novel object recognition (NOR) test. Inflammation-related proteins were detected using IF.

Results: Stimulation with Aβ_1-42 led to microglia M1 polarization, upregulation of inflammation-related proteins, and exacerbation of neuronal injury and apoptosis, along with increased p-tau expression in neurons. METTL3/IGF2BP2 modulated IκBα m⁶A modification through binding to IκBα mRNA, enhancing its expression. Enhanced METTL3 or IGF2BP2 expression suppressed M1 polarization, inflammation, and neuronal apoptosis in microglia, reversed by knockdown of IκBα. AD model mice exhibited cognitive impairments, neuroinflammation, and elevated M1 polarization. METTL3 or IGF2BP2 overexpression improved cognitive function, reduced neuroinflammation, and inhibited M1 polarization, and this effect was similarly reversed by knockdown of IκBα.

Conclusion: Our study demonstrates that the METTL3/IGF2BP2/IκBα axis is involved in neuroinflammation in AD by modulating microglia M1/M2 polarization, which sheds light on the treatment of AD.