Fig. 4: Reactive microglia mediate PV-INs depopulation to impair motor behaviors.

a Immunofluorescent staining of microglial cells (Iba1+) and its phagocytosis toward SNCA-expressing cells (mCherry labeled) in M1 from SNCA model mice. Scale bare, 50 μm or 25 μm (enlarged views only). b The number of microglial cells in the given field was increased by SNCA overexpression. Two-sample unpaired t-test, t(7) = 3.419, P = 0.0112. N = 5 and 4 mice from mCherry and SNCA group, respectively. c Representative blotting bands of Iba1 and CD68 from M1 extracts. d Quantification of relative protein expression of Iba1 and CD68. Multiple t-test showed significant difference between groups. P = 0.038 for Iba1 and P = 0.030 for CD68. N = 4 mice in each group. e Contours of sampled microglial morphology. Scale bar, 15 μm. f Microglial cells of model mice also had larger soma size compared to control group. D = 0.9420, P < 0.0001. g SNCA model mice presented more cell processes of microglia on average. Non-parametric Kolmogorov–Smirnov test, D = 0.7429, P < 0.0001, n = 30 and 35 cells from 4 mice in each group, in (f, g). h Graphic illustration of microglial ablation assays. SNCA-overexpressed mice were fed with PLX5622-containing food chows for 2 weeks, in contrast with a control group receiving normal (ANI76) diet. Behavioral phenotyping was performed later. i Representative immunofluorescent staining images of microglial cells and PV-INs. Although PLX5622 did not change the level of α-synuclein, PV-IN population was maintained. Scale bar, 150 μm in upper panels and 50 μm in lower panels. j Oral PLX5622 administration remarkably decreased microglial cell density. Two-sample unpaired t-test, t(13) = 12.61, P < 0.001. k Ablation of microglial cells increased PV-INs density. t(13) = 9.071, P < 0.001. N = 7 and 8 mice in ANI76 and PLX5622 group, respectively, in (j, k). l PLX5622 treatment recovered mouse performance on the accelerating rotarod. Two-way ANOVA with respect to group factor, F(1117) = 34.80, P < 0.0001. Sidak’s multiple comparison test of post hoc comparison at each time point. m Microglia ablation improved the performance on vertical pole climbing task. Two-way ANOVA with respect to group factor, F(139) = 21.88, P < 0.0001. Sidak’s multiple comparison test of post hoc comparison at each time point. n PLX5622 intervention rescued impairment on the walking beam. F(1,39) = 45.28, P < 0.0001. Sidak’s multiple comparison test of post hoc comparison at each time point. N = 7 and 8 mice from ANI76 and PLX5622 group, respectively, in (l–n). *P < 0.05, **P < 0.01, ***P < 0.001. All data were presented as mean ± SEM.