Figure 6. Microglial C1q knockdown prevents radiation-induced neuroinflammation.

Immunofluorescence staining, confocal microscopy and 3D algorithm-based, volumetric quantification for the CD68 (A) and C5aR1 (B) immunoreactivity (CD68 and C5aR1, red, blue, DAPI nuclear counter stain; a1-a4 and b1-b4 respectively) show that cranial irradiation (IRR) significantly elevated CD68 (P = 0.001, A) and C5aR1 (P = 0.002, B) in the WT hippocampus (DH, dentate hilus; DG, dentate gyrus) compared to unirradiated controls. Exposure of C1q-Flox mice to the cranial IRR did not elevate CD68 or C5aR1 immunoreactivity indicating prevention of inflammation (A and B). Similarly, volumetric analysis for C3-GFAP (C, c1-c4) and IBA1-TLR4 co-localization (D, d1-d4) showed radiation-induced elevation in the co-labeling of GFAP⁺ astrocytic surfaces with C3 (GFAP surface rendering, magenta and C3 spot rendering, yellow, c1-c4) and, IBA1⁺ microglial surfaces with TLR4 (IBA1, green; red, TLR4 and blue, DAPI, d1-d4) in the hippocampal DH. Irradiated C1q-Flox brains did not show elevated C3-GFAP or IBA-TLR4 indicating reduced neuroinflammation. Data are presented as mean ± SEM (N = 6 to 8 observations per group). P values were derived from ANOVA and Bonferroni’s post hoc test. Scale bars, 40 μm (a1-a4, b1-b4) and 5 μm (c1-c4, d1-d4).