Role And Mechanism Of MiR-24-3p/STING Pathway Regulating Neuroinflammation In Alzheimer’s Disease Model Mice

Background: Micro RNAs(miRNAs)are a class of endogenous small RNAs of approximately 20-24 nucleotides in length that can play an important role in the regulation of gene expression in cells,including Alzheimer’s disease(AD).A variety of neurodegenerative diseases are closely related.Alzheimer’s disease is a progressive degenerative disease in which the etiology has not been known.The pathological features of AD are plaques formed by extracellularly produced β-amyloid(Aβ)and neurofibrillary tangles(NFT)with hyperphosphorylated tau,and most studies focus on these two Classical pathological features.However,more and more studies have shown that neuroinflammation plays an important role in the pathogenesis of Alzheimer’s disease.In this study,we found that the classical inflammatory pathway STING pathway is over-activated in microglia in the brain of Alzheimer’s disease model mice,prompting microglia to produce a variety of inflammatory factors,leading to neuroinflammation.We screened micro RNAs that may regulate STING through bioinformatics analysis.Finally,through a series of experiments,we found miR-24-3p,a micro RNA that mediates neuroinflammatory responses by regulating STING expression.The miR-124/STING pathway may be a new target for the treatment of AD patients.Objective: To investigate the neuroinflammation in the brain of Alzheimer’s disease by regulating the miR-24-3p/STING pathway in microglia.Methods: This experiment used 9-month-old AD model mouse APP/PS1 and wild type C57/BL6 mice.Western blot was used to detect the activation of STING pathway n hippocampus of mice,and the content of various inflammatory factors in brain was detected by ELISA.Primary microglia were cultured and treated with Aβ in vitro to simulate Aβ lesions in AD brain.The P301 S mice and control mouse at 9 months old were detected by western blot to detect the activation of STING pathway in hippocampus.Overexpression of tau protein in cells detects the effect on STING.The bioinformatics method was used to screen miro RNA which can regulate STING,and further screening by q PCR.After determining miR-24-3p,its expression in the brain of AD model mouse was confirmed by FISH.Binding of miR-24-3p to STING was verified by dual luciferase.Transfection of miR-24-3p mimic and inhibitor and corresponding controls to verify its regulation of STING.The mimic of miR-24-3p was administered to primary microglia,and the transcription and expression of inflammatory factors were detected by q PCR and ELISA.Through the above experiments,it was confirmed that the miR-24-3p/STING pathway can regulate neuroinflammation in the brain of AD mice.Results: The STING pathway in the 9-month-old AD model APP/PS1 brain was significantly activated,and the levels of various inflammatory factors including IFN-β,TNF-α,IL-6 and IL-1β were significantly increased.In the brain of APP/PS1 mice,STING co-localized with microglia.Primary microglia were cultured.After Aβtreatment in vitro,the STING pathway was activated and the content of downstream inflammatory factors was significantly increased.There was no significant activation of the STING pathway in the brain of P301 S mice at 9 months of age.Overexpression of tau protein in N2 a cells had no significant effect on the content of STING.Dual luciferase assays confirm that miR-24-3p binds to STING.Transfected with miR-24-3p mimic in N2 a cells down-regulated the expression of STING,while the transfection of the inhibitor up-regulated the expression of STING.The mimic of miR-24-3p was administered to primary microglia,and the levels of various inflammatory factors were significantly reduced.Through the above experiments,it was confirmed that the miR-24-3p/STING pathway can regulate neuroinflammation n the brain of AD mice.Conclusion: Aβ can down-regulate the expression of miR-24-3p in microglia,which leads to the excessive activation of STING pathway,and the expression of inflammatory factors IFN-β,TNF-α,IL-6 and IL-1β are increased,triggering neuroinflammation.Up-regulation of miR-24-3p expression can reduce the production of inflammatory factors and play a neuroprotective role.The results of this study show that the miR-24-3p/STING pathway plays an important role in AD-related neuroinflammation.