#33 Semaphorin 3E reduces the activation of splenic CD11c+ cells and T cell priming in active colitis
Laëtitia Kermarrec, University of Manitoba; Nour Eissa, University of Manitoba; Omar Elgazzar, University of Manitoba; Charles N Bernstein, University of Manitoba; Jean-Eric Ghia, University of Manitoba
Inflammatory bowel diseases (IBD) involve an increase of dendritic cells (DC) infiltration and cytokines production. Semaphorins have emerged as an essential axis in DC immune responses. Previously, we demonstrated that Sema3E regulates colitis via the modulation of DC-IL-12p40 release. This study aims to determine the role of Sema3E on colitis and on DC regulation and T-cell priming.
mRNA expression level of Sema3E in active UC patients using RT-qPCR, and its correlation analysis with pro- and anti-inflammatory markers were determined. Colitis was induced by dextran sulfate sodium (DSS 5%) for 5 days in Sema3E-/- and Sema3E+/+ mice treated or not with recombinant-Sema3E-Fc. Disease severity, colonic, Sema3E, INF-γ, TNF-α, IL-4, IL-17, IL-23, IL-12p70 and IL-12p40 were quantified. IL-12p70, p40 and IL-23 levels in isolated splenic DCs were determined in presence of Nk-B-inhibitor (BAY-11-7082) or activator (betulinic-acid). IFN-γ, IL-17 levels from DC/CD4+CD25-T cell co-culture were determined in the presence of anti-p19-mAb or p35-mAb.
In active UC biopsies, Sema3E mRNA was significantly decreased and negatively and positively correlated with pro-and anti-inflammatory cytokines respectively. In colitic Sema3E+/+ mice, Sema3E level was significantly decreased. In colitic Sema3E-/- mice, clinical score, IL-17, IL-12p40, p70, IL-23, IFN-γ were significantly increased compared to Sema3E+/+ with no effect on IL-4. Colitic SemaE-/- splenic CD11c+ cells showed an increased production of IL-12p70, p40 and IL-23, with no effect on CD11c+ proliferation; Sema3E-Fc decreased the cytokines production as much as BAY 11-7082 whereas betulinic acid abrogated Sema3E-Fc effect. Colitic SemaE-/- splenic CD11c+ cells showed higher effective T-cell priming reflected by an increase of IFN-γ and IL-17 release by CD4+CD25- T cells. Addition of the anti p19-mAb in the medium abolished the production of IL-17 in DCs/CD4+CD25- T cells co-cultures; and anti p35-mAb the IFN- production.
Sema3E reduces colitis and may lead to improved therapeutic strategies in IBD.