P-130 Production of Inflammatory Cytokines Is Regulated by mPGES-1-Dependent PGE2 in T Cells. (March 2016) - Maseda, Damian
Abstract : Background: The integration of inflammatory signals is paramount in controlling the intensity and duration of immune responses. Eicosanoids, particularly prostaglandin E2 (PGE2), are critical molecules in the initiation and resolution of inflammation and in the transition from innate to acquired immune responses. Additionally, PGE2 is associated with modulating autoimmune features through altering the IL-23/IL-17 axis and regulatory T cell development, whose balance is critical for keeping potential pathogenic T cell responses under control. PGE2 has pleiotropic effects on many cell types, but it is still unclear how it affects T cell differentiation and function. Microsomal prostaglandin E synthase 1 (mPGES-1) is a membrane enzyme that controls local PGE2 levels and is highly expressed at sites of inflammation. mPGES-1 is part of the PGE2 biosynthetic pathway and, due to its inducible nature, it controls PGE2 concentrations during activation of the inflammatory program. We hypothesize that mPGES1 plays a role in lymphoid and non-lymphoid intestinal tissues in controlling inflammatory responses, especially in controlling regulatory and pathogenic T cell responses. Methods: We performed magnetic bead isolation of T cells and subsequent Treg and Th17 polarization assays with freshly isolated naïve T cells (CD4 + CD44 − CD62L + ). We also sorted different T cell populations from primary lymphoid organs and analyzed markers for inflammation, T cell fate decision and PGE2-receptors by Real Time-PCR. Using LC-MS and ELISA we analyzed prostaglandin production by different T cells upon activation. The Rag −/− transfer model of T-cell driven colitis was used to examine regulatory T cell function and T cell tropism to the intestinal tissues by flow cytometry. Results: Different T cell populations were analyzed for receptors involved in inflammatory responses. We found that mPGES1 −/− naïve T cells showed a significant decrease in tgfbr1, ptger2 and ptger4 (PGE2 receptors EP2 and EP4) expression compared with WT naive T cells. Since TGF-b is a key cytokine for the generation of both regulatory and Th17 cells we addressed the effect of mPGES-1 deficiency during in vitro T cell polarization. We observed that mPGES1 −/− naive CD4 + T cells generate more IL-17A+ cells under Th17 polarizing conditions, but exogenous addition of PGE2 shifted the production of IL-17A to IFNg. In vitro activation of purified T cells showed that mPGES1 −/− CD4 + CD25 − cells were less capable of secreting PGE2 than their WT counterparts, and CD4 + CD25 + T cells produced less PGE2 than CD4 + CD25 − cells overall. Furthermore, in the Rag-/- transfer colitis model, mice that received mPGES1 −/− CD4 + CD25 + cells showed an increased percentage of CD4 + FoxP3 + cells in the colonic lamina propria but not in the mesenteric lymph nodes when compared to mice transferred with WT CD4 + CD25 + cells, although colitis incidence was not different between groups. Conclusions: Endogenous mPGES-1-mediated production of PGE2 by T cells modulates IL-17A and IFNg responses. T cell deficiency of mPGES-1 also reduces regulatory T cell seeding of the colonic lamina propria, which might have implications during colitis.