Aging modulates microglia phenotypes in neuroinflammation of MPTP-PD mice

Abstract As the crucial etiological factor, aging-related microglia activation promotes the development of Parkinson's disease (PD). However, the molecular and functional changes of aged-microglia and their contribution to neurodegeneration in PD are only partially understood, which was investigated in our study. Female C57BL/6 mice were randomly divided into four groups, included young-control group, young-MPTP group, aged-control group and aged-MPTP group. Pole test and adhesive removal test were firstly performed. ELISA assay was used to detect the content of interleukin-1β (IL-1β) and tumor necrosis factor alpha (TNF-α) in brain tissue. Then we tested the expression of tyrosine hydroxylase (TH), p-nuclear transcription factor (NF-κB), toll-like receptor2 (TLR2), arginase-1 (arg-1), inducible nitric oxide synthase (iNOS) by western blot and immunofluorescence analysis. Our results showed that aging promoted M1 microglia activation and inhibited M2 microglia activation in SN in MPTP-PD model, accompanied by the elevation of proinflammatory cytokine (TNF-α and IL-1β). Consequently, aging significantly aggravated motor dysfunction and dopaminergic neuron loss in SN. Besides, compared with young-MPTP group, the protein expression of TLR2 and p-NF-κB-p65 increased obviously in aged-MPTP group. The results revealed that aging aggravated inflammatory response by modulated microglia phenotypes transition in SN in PD, and contributed to further understand the pathogenesis of PD.