Oxysterols and Tr1 · Oxysterols and IL-27-induced Type 1 regulatory T cells in Experimental Autoimmune Encephalomyelitis

Oxysterols and IL-27-induced Type 1 regulatory T cells in Experimental Autoimmune Encephalomyelitis

The behaviors of lymphocytes and other leukocytes is controlled on many levels by internal metabolic properties such as lipid metabolism. Perturbation of steroids pathways has been shown to modulate inflammation and potentially promotes a variety of diseases. However the impact of lipid metabolism on autoimmune diseases development and lymphocytes biology is still largely unraveled. We focused our attention on studying the role of the cholesterol metabolites oxysterol during lymphocytes differentiation and their implication in multiple sclerosis (MS) pathogenesis. In this project, we investigated the function of the enzyme cholesterol 25-hydroxylase (Ch25h) during CD4+ T cell differentiation as well as its role during MS, using the animal model experimental autoimmune encephalomyelitis (EAE). Cholesterol 25-hydroxylase (Ch25h) converts cholesterol into 25-hydroxycholesterol (25-OHC) which is further metabolized into 7 alpha, 25-dihydroxycholesterol (7α,25-OHC). We focused our attention on this pathway as both 25-OHC and 7α,25-OHC are implicated in the immune response: 25-OHC suppresses IgA production by B cells and has broad anti-viral properties while 7α,25-OHC guides B cell and macrophages within the germinal follicules of the spleen and lymph nodes. However how oxysterols modulate adaptive immunity and participate to T lymphocytes biology is largely unknown and their role in autoimmunity has not been explored. We first investigated the expression of oxysterol converting enzymes on subset of T helper CD4+ T cells activated in vitro with αCD3 and αCD28 and polarized in T subset with different cytokines: TH0 (no cytokines), TH1 (IL-12), TH2 (IL-4), TH17 (TGF-β and IL6), Foxp3Tregs (TGF-β) or TR1 cells (IL-27). We found Ch25h to be highly and specifically induced by IL-27 in TR1 cells during CD4+ T cell differentiation in vitro. IL-27, a member of IL-12 family cytokine, promotes the generation of regulatory T cells that are characterized by their suppressive activity and by IL-10, INF-γ and Granzyme B production. We observed that CD4+ T cells differentiated in the presence of IL-27 induced the expression of Ch25h as early as 14 hours after culture initiation. Ch25h converts cholesterol into its metabolite 25-OHC. In cell cultured in the presence of IL-27, 25-OHC can be measured by Mass spectrometry both intracellular (in the cell pellet) and in culture supernatant. This points toward a dual role of 25-OHC during CD4+ T cell differentiation. We further observe that 25-OHC inhibits IL-27-induced secretion of IL-10 and Granzyme B and thus contributes to a pro-inflammatory response. Because signal transducer and activator of transcription factor 1 (Stat1) is activated by IL-27 though its receptor and is involved in Ch25h expression in macrophages, we next tested the ability of IL-27 to activate Ch25h mRNA levels in Stat1−/− cells. Interestingly, we observed that Ch25h expression was entirely dependent on Stat1 signaling, an important signaling pathway during inflammation. Finally, we showed that Tr1 cells differentiated in vivo with αCD3 expressed higher levels of IL-10 in the absence of Ch25h. Furthermore, we investigated the role of ch25h during experimental autoimmune encephalomyelitis (EAE). In the MOG35-55-induced EAE model, we found that Ch25h-/- mice depict a delayed EAE onset and reduced disease severity compared to wild-type mice. Surprisingly the specific antigen response to MOG is preserved. However, we observed that IL-17A+ but not IFNγ+ CD4+T cells are enriched in the draining lymph nodes of immunized mice. This led us to hypothesize that 25-hydroxycholesterol could control TH17 T cells migration in the draining lymph nodes. Mechanistically, we show a critical involvement for oxysterols in recruiting leukocytes into inflamed tissues and propose that 7α,25-OHC preferentially promotes the migration of activated CD44+CD4+ T cells by binding the G protein-coupled receptor called Epstein-Barr virus induced gene 2 (EBI2). Collectively, our results support a pro-inflammatory role for oxysterols during EAE and identify oxysterols as a potential therapeutic target to treat autoimmune diseases. Altogether our studies highlights Ch25h pathway as proinflammatory mediators that contribute to the immune response in a dual way: first by inhibiting the generation of IL-27-induced regulatory T cells and second by promoting trafficking of pathogenic CD4+ T cell during autoimmune diseases. Website address: http://pathology.unige.ch/group-pot.html

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз