(867.1) Wnt signaling promotes IL-33 expression in the colonic epithelium

Poster Board Number: E202

Michael Schumacher (University of Southern California, University of Southern California), Megan Thai (Childrens Hospital Los Angeles), Mark Frey (University of Southern California, University of Southern California)

Background:  Interleukin-33 (IL-33) released from the colonic epithelium promotes type 2 innate lymphoid cell activity as part of the colonic injury response. We have previously shown that the intracellular signaling regulator, Sprouty2, restrains colonic IL-33 via a GSK3β-dependent mechanism. GSK3β can regulate canonical Wnt signaling, but the role of Wnt signaling and the specific components of this pathway involved in driving IL-33 are unknown. We tested the hypothesis that activation of discrete arms of Wnt signaling induce epithelial IL-33 expression.

Methods:  Bulk RNA sequencing was performed on colons from mice with an intestinal epithelial-specific Sprouty2 deletion (Spry2IEKO) or littermate controls to determine the effect of Sprouty2 on Wnt targets. Colonoid and young adult mouse colon (YAMC) epithelial cell cultures were treated with Wnt ligands. Small molecule inhibitors were used to inhibit CBP- or p300-mediated Wnt signaling arms (ICG-001 or IQ-1 respectively), in YAMC cells. IL-33 levels were assayed by qPCR and ELISA.

Results:   Spry2IEKO mice have increased colonic transcript levels of the Wnt target genes Mmp7 (plt;0.01), Irx3 (plt;0.05), Mapk10 (plt;0.05), and Jag1 (plt;0.05), correlating with the increased expression of IL-33 that we have previously reported in these mice. Pathway analysis suggests specifically altered CBP/p300-mediated Wnt signaling in Spry2IEKO colons. Treatment of wild-type colonoids or YAMC cells with the Wnt ligands Wnt3a and R-spondin induced IL-33 expression by 2.1-fold and 2.3-fold respectively (plt;0.05). Pre-treatment of cells with ICG-001 blocked the Wnt-induced increase in IL-33 at both the RNA and protein level, whereas IQ-1 had no effect.

Conclusion:  CBP-mediated Wnt signaling promotes colonic epithelial expression of IL-33 in vitro. Elevated Wnt activity in Spry2IEKO mice is associated with elevated IL-33 levels. Dysregulated Wnt signaling may result in impairment of the injury response in inflammatory disease.

Crohns and Colitis Foundation Career Development Award (MAS)