Fig. 4: Metronidazole reduces amyloid plaques and modulates central and peripheral immunity.

Female 5xFAD and wild type (WT) mice were treated with metronidazole (MTZ) in their drinking water between 9 and 12 months of age. Amyloid plaques were assessed with histology, cortical gene expression with the NanoString neuropathology panel and microglia gene expression with RNA sequencing. A The amyloid-β (Aβ) plaque burden in cortex. Plaque burden was defined as the percent of the cortex area that were covered with plaques and the number of plaques per square millimeter in the cortex. The p-values were calculated with a two-sided Student’s t test, n = 5 mice/group. B Volcano plot of differentially expressed genes in the cortical tissue of 5xFAD-MTZ mice vs. 5xFAD-H₂0 mice and the normalized counts of Ide mRNA (coding for Insulin degrading enzyme), the p-value was generated with Nsolver Advanced Analysis (two-sided test), n = 3 mice/group. C Volcano plot showing the adjusted two-sided p-value and fold change (FC) of microglia genes modulated by MTZ in 5xFAD mice. D Heatmap of homeostatic microglia gene signature with an unadjusted two-sided p-value of <0.05 (5xFAD-H₂O vs. 5xFAD-MTZ), n = 5 mice/group. E Microglia pathways altered by MTZ in 5xFAD mice identified by Ingenuity Pathway Analysis (IPA). Genes with a FC > ±0.2 and a two-sided unadjusted p-value < 0.05 were included in the analysis. Circles are shaded according to the z-score indicating activation (red) or inhibition (blue) or no presumed direction (gray). *p-value < 0.05, n = 5 mice/group. F Frequency of GM-CSF + T cells, the T cells were isolated from the spleen and stimulated for 3 h with PMA/ionomycin. One outlier was removed from the AD-MTZ group with the Grubb’s test in GraphPad Prism. The p-values were calculated with one-way ANOVA, n = 5 mice/group. Violin plots represent min, max, interquartile range and median, the dots represent individual mice. Source data are provided as a Source Data file.