Oestrogen receptor β Ligand acts on CD11c ^+ Cells to mediate protection in experimental autoimmune encephalomyelitis

Oestrogen treatments are neuroprotective in a variety of neurodegenerative disease models. Selective oestrogen receptor modifiers are needed to optimize beneficial effects while minimizing adverse effects to achieve neuroprotection in chronic diseases. Oestrogen receptor beta (ERb) ligands are potential candidates. In the multiple sclerosis model chronic experimental autoimmune encephalomyelitis, ERb-ligand treatment is neuroprotective, but mechanisms underlying this neuroprotection remain unclear. Specifically, whether there are direct effects of ERb-ligand on CD11c + microglia, myeloid dendritic cells or macrophages in vivo during disease is unknown. Here, we generated mice with ERb deleted from CD11c + cells to show direct effects of ERb-ligand treatment in vivo on these cells to mediate neuroprotection during experimental autoimmune encephalomyelitis. Further, we use bone marrow chimeras to show that ERb in peripherally derived myeloid cells, not resident microglia, are the CD11c + cells mediating this protection. CD11c + dendritic cell and macrophages isolated from the central nervous system of wild-type experimental autoimmune encephalomyelitis mice treated with ERb-ligand expressed less iNOS and T-bet, but more IL-10, and this treatment effect was lost in mice with specific deletion of ERb in CD11c + cells. Also, we extend previous reports of ERb-ligand's ability to enhance remyelination through a direct effect on oligodendrocytes by showing that the immunomodulatory effect of ERb-ligand acting on CD11c + cells is necessary to permit the maturation of oligodendrocytes. Together these results demonstrate that targeting ERb signalling pathways in CD11c + myeloid cells is a novel strategy for regulation of the innate immune system in neurodegenerative diseases. To our knowledge, this is the first report showing how direct effects of a candidate neuroprotective treatment on two distinct cell lineages (bone marrow derived myeloid cells and oligodendrocytes) can have complementary neuroprotective effects in vivo.