Figure 3. Caspase-8 is activated in viable CD16/32-immunolabeled microglia in substantia nigra in response to intranigral LPS injection, which is associated to higher key proinflammatory microglial markers. Panel (a) shows an illustration of dual immunofluorescence of cleaved caspase-8 and CD16/32 in substantia nigra in response to intranigral LPS in Casp8fl/fl mice and CreLysMCasp8fl/fl mice. Note how cleaved caspase-8 labeling is mostly associated to CD16/32-labeled microglia, which is dramatically decreased in CreLysMCasp8fl/fl mice. Panel (b) shows higher magnification photograph of that shown in panel (a) demonstrating active caspase-8 within viable CD16/32-immunolabeled microglia in Casp8fl/fl mice after LPS. Panel (c) shows the effect of LPS on mRNA expression of inducible nitric oxide synthase (iNOS), tumour necrosis factor α (TNF- α), interleukin 6 (IL-6) and interleukin-1β in substantia nigra of Casp8fl/fl mice and CreLysMCasp8fl/fl mice. mRNA levels were measured by quantitative PCR. Results are mean ± SD of at least four independent experiments and are expressed as relative quantification (RQ), calculated using the delta Ct method. Statistical significance was calculated by one-way analysis of variance followed by the least significant difference post hoc test for multiple range (p <0.05). As expected, LPS injection increased the expression levels of mRNA in Casp8fl/fl mice (WT). This induction was highly prevented in CreLysMCasp8fl/fl mice (KO). Note the extremely low levels of IL-1β in CreLysMCasp8fl/fl mice. Scale bar: a: 30 μm; b: 10 μm.