Peroxisome proliferator-activated receptor delta (PPARδ) limits Th1 inflammation through effects on interferon (IFN)-γ transcription and lymphocyte homeostasis (IRM7P.480)

Abstract

Abstract PPARδ is a nuclear receptor that functions as a transcriptional regulator of various processes including metabolic homeostasis, cell proliferation and differentiation. We previously reported that mice deficient in PPARδ (KO) exhibit more severe experimental autoimmune encephalomyelitis than wild type (WT) mice. This more severe inflammation correlated with an increased expansion of myelin-reactive IFNγ-producing cells in the spinal cord, suggesting that PPARδ may act to limit Th1 inflammatory responses. However, the mechanism of how PPARδ accomplishes this is not clear. Characterization of the spleen and thymus compartments revealed that KO mice exhibit reduced spleen and thymus cellularity as compared to WT mice. The resultant lymphopenia in KO mice associated with a higher frequency of memory CD4+ T cells in the periphery. Radiation bone marrow chimeras were generated and the defect in thymocyte development was found to map to the radio-resistant compartment, suggesting that PPARδ may operate in stromal cells to regulate thymocyte development. This was furthered confirmed by the finding that mice with T cell-restricted deficiency of PPARδ did not exhibit defective thymocyte homeostasis. Furthermore, we observed that naïve CD4+ T cell from both KO and T cell-restricted PPARδ-deficient mice had a higher propensity to produce IFNγ upon stimulation. Thus PPARδ appears to limit Th1 inflammation both through the control of lymphocyte homeostasis and IFNγ production.