Figure 4

Glial response in the subacute MPTP animal model and in MyD88-/- mice. (A) Real-time imaging of the TLR2 response during the course of MPTP injections and 14 days following the last injection. Representative photographs of a saline- and an MPTP-treated mouse across time, showing significant brain TLR2 signal following the third MPTP injection, as compared to saline. The data is illustrated using pseudocolor images representing light intensity as indicated by the color scale, which were superimposed over gray-scale reference photographs. (B) (Left graph) Quantification of the total photon emission in the brain of saline- and MPTP-treated TLR2-luc/gfp mice at each time point assessed. (Right graph) Quantification of the areas under the curves in the two groups of animals. Statistical analyses were performed using student's t-tests. (C) Stereological count of iba1+ cells in the SNpc revealed a trend towards increased microglial expression in MPTP-treated mice 24 h following the last injection, which was significantly different from saline-treated animals at 7 (p < 0.05) and 14 days (p < 0.01), and from MPTP-treated mice at 14 days following the end of treatment (p < 0.05). (D) Photomicrograph of iba1 immunofluorescence staining of saline- and MPTP-treated animals at the level of SNpc, which has been outlined with a solid line. (E) 3 h following the last MPTP injection, similar microglial counts in the SNpc were seen in both saline- and MPTP-injected WT and MyD88-/- mice. (F) Western blot analysis of striatal GFAP protein levels revealed a strong increase in the MPTP-treated mice 24 h following the last injection, which had declined significantly 14 days following the end of treatment (p < 0.01) but still remained significantly increased compared to saline-controls at the 7-(p < 0.05) and 14-day time point (p < 0.05). (G) MPTP treatment induced a significant increase in GFAP striatal expression of similar magnitude in both WT (p < 0.01) and MyD88-/- mice (p < 0.001). Statistical analyses were performed using one-way ANOVA. *p < 0.05, **p < 0.01, ***p < 0.001 in comparison to saline-controls; ^##p < 0.01 in comparison to MPTP-treated mice sacrificed at 24 h. Scale bar in D = 150 μm. Abbreviation: AUC: areas under curves; SNpc: substantia nigra pars compacta; SNr: substantia nigra reticulata; VTA: ventral tegmental area; WT: wild type.