Our laboratory has also assessed the anti-inflammatory actions of PPARδ following irradiation in vivo. One week following a single dose of 10 Gy 137Cs γ WBI, young adult male C57Bl/6 mice exhibited a significant increase in the number of activated microglia (CD68+ cells) in the dentate gyrus (DG). GW0742 administered prior to, during, and after WBI prevented this radiation-induced increase in activated microglia. Interestingly, radiation did not induce an increase in activated microglia in the DG of PPARδ-null mice at one week or two months after WBI. These results suggest that PPARδ deficiency leads to an inhibition of microglial activation (unpublished results). These findings are surprising and quite different from those observed in PPARα-null mice, where PPARα deficiency resulted in a sustained increase in activated microglia seen at one week and two months after WBI [81]. This indicates that the effect of PPAR deficiency is subtype-dependent.
