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* = Presenting author

P002 Beneficial effects of blocking EphBs-ephrinBs forward signalling in a murine Crohn’s sisease (CD) model

A. Grandi, I. Zini, M. Tognolini, V. Ballabeni, E. Barocelli, S. Bertoni*

University of Parma, Department of Pharmacy, Parma, Italy

Background

Eph receptors, the largest family of tyrosine kinase receptors in mammals, comprise A and B classes based on sequence homology and preferences for cell-bound ephrin ligands. Receptor-ligand interactions generate a bidirectional signalling affecting the receptor bearing (forward) or the ligand bearing cells (reverse). The Eph-ephrins system was primarily related to carcinogenesis and developmental biology; yet, its involvement in the regulation of inflammatory and immune responses, such as endothelial cell activation, leukocyte migration, and T-cell maturation, as well as in gut epithelial tissue remodelling, is gradually emerging. Interestingly, some evidence is provided that EphBs-ephrinBs are overexpressed in the gut epithelium in CD and that stimulation of ephrinB reverse signalling up regulates epithelial cells wound-healing genes in vitro.

Our study aims at investigating the role of EphBs-ephrinBs in the local and systemic inflammatory responses induced in a murine model of CD. To this end, the effects produced by unidirectional activation of reverse signalling (administration of chimeric protein EphB1-Fc), of forward signalling (ephrinB1-Fc) or inhibition of both signals (monomeric EphB4) were studied.

Methods

Colitis was induced in C57BL/6 mice by enema administration of 5 mg/mouse 2,4,6-Trinitrobenzene sulfonic acid (TNBS) in 50% ethanol. Subcutaneous pharmacological treatments started 8 hours after induction of colitis and were applied daily until the sacrifice, 3 days later; control mice (CTR) received only vehicle. Disease Activity Index (DAI), colonic macroscopic score (MS), colon length and colon and lung myeloperoxidase (MPO) activity, and index of leukocyte recruitment were determined. Splenic CD3+, CD3+CD4+, and CD3+CD8+ T-cells were counted by flow cytometry. All experiments were performed according to the guidelines for the Care and Use of Animals (DL26/2014).

Results

EphB1-Fc 30μg/kg and equimolar EphB4 20μg/kg dramatically reduced DAI (p < 0.001) and MS (p < 0.05), minimised colon shortening (p < 0.05), and curtailed local (p < 0.05) and systemic (p < 0.01) neutrophil infiltration by about 80% compared with CTR. Treatment with ephrinB1-Fc 17μg/kg lowered only DAI and lung MPO levels (p < 0.05), whereas equimolar Fc had no effect on colitis parameters. No treatments significantly modified T-cells subpopulations compared with CTR.

Conclusion

These preliminary findings are the first evidence that endogenous EphBs-ephrinBs forward signalling promotes the local inflammatory response in TNBS-induced colitis, seemingly in a T-cell–independent way: pharmacological agents selectively disrupting this pathway might represent a novel strategy for the treatment of intestinal inflammatory conditions such as CD.