Suppressed Signaling of Interleukine 27, a Novel Immunosuppressive Cytokine, in Experimental Allergic Conjunctivitis Induced by Short Ragweed Pollen

Abstract

Purpose : While most studies focused on pro-allergic cytokines, the protective role of immunosuppressive cytokines in allergic inflammation is largely unknown. This study was to explore a novel anti-inflammatory role and molecular mechanism of IL-27 in allergic inflammation induced by short ragweed pollen.

Methods : A murine model of experimental allergic conjunctivitis (EAC) was induced in BALB/c or IL-27Rα deficient (WSX-1^-/-) mice by short ragweed (SRW) pollen, which was first immunized with 50µg in 5 mg Imject Alum by footpad injection on day 1, followed by topical challenge of 1.5mg SRW in 10µl PBS into each eye once a day from days 11 to 13. Mice without treatment (UT) or treated with PBS along will be used as controls. The serum, eyeballs, conjunctiva and cervical lymph nodes (CLN) were collected on days 14 for evaluation. The mRNA expression was determined by RT-qPCR. The protein production was evaluated by immunostaining, ELISA, Western blotting and/or flow cytometry.

Results : Typical allergic signs, stimulated TSLP signaling and Th2 cytokine overproduction were observed in ocular surface of BALB/c mice with EAC induced by SRW. The decrease of IL-27 at mRNA (IL-27A/EBI3 two chains) and protein levels, accompanied by suppressed levels of IL-10 and signaling molecules STAT1, C-Maf, ICOS and PD-L1 with increased STAT6 and GATA3, was observed in conjunctiva and draining CLN tissues of SRW-EAC mice when compared with UT or PBS control mice, as evaluated by RT-qPCR, immunofluorescent staining, ELISA and/or Western blotting. IL-27 was identified to be produced mainly by dendritic cells (DCs) and macrophages, but not epithelial or T cells by flow cytometry and immunostaining with specific cell surface markers CD11c, F4/80 and CD4. Furthermore, EAC model induced by SRW in WSX-1^-/- mice showed more severe allergic signs with significantly higher expression of TSLP by corneal and conjunctival epithelial cells, OX40L by DCs, and Th2 cytokines IL-4, IL-5 and IL-13 by CD4⁺ T cells than EAC-BALB/c mice.

Conclusions : Our findings for the first time uncovered a novel mechanism by which SRW pollen triggers Th2-dominant allergic inflammation by suppressing IL-27 anti-allergic signaling pathway. These findings shed light on the understanding of pollen-induced allergic inflammation, and may create new therapeutic targets to treat allergic diseases.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.