P0135 Effect of human recombinant IL-33 on fibrosis markers in colonic fibroblasts
Authors: Ratel L , Leboutte M , Hermoso M A , Savoye G , Marion-Letellier R 
Published: January 2025

Abstract

Background
IBD is frequently complicated by intestinal fibrosis and strictures formation, occurring in more than 50% of Crohn’s disease (CD) and 5% of ulcerative colitis. Intestinal fibrosis leads to surgery in CD and strictures frequently recur leading to repeated surgeries1. There is currently no specific therapy to prevent or inhibit intestinal fibrosis and this therefore constitutes a major treatment challenge. Intestinal fibrosis is characterized by excessive deposition of extracellular matrix (ECM) synthesized by intestinal myofibroblasts1. Interleukin-33 (IL-33) is a pleiotropic nuclear cytokine involved in immunoregulation and tissue repair2. Following cellular injury, IL-33 is released by epithelial, endothelial or fibroblast cells. Binding to the ST2 (suppressor of tumorigenicity 2) receptor, it induces translocation of the transcription factor NF-□□□□B, which regulates the expression of pro-inflammatory genes2. IBD patients have increased colonic expression of IL-33 and ST2 in epithelial cells compared to control patients3. Neutralization of IL-33 enables the repair of lung epithelial cells by limiting the release of pro-inflammatory cytokines such as IL-6, IL-8 and TNF-α in a mouse model of pulmonary epithelial lesions4. We hypothesized that IL-33 may be involved in IBD-associated intestinal fibrosis. We therefore aimed to understand the role of IL-33 in a human colonic fibroblast cell line (CCD-18Co).

Methods
First, we measured IL-33 and ST2 mRNA expression in CCD-18Co in response to TGF-ß1 (10 ng/mL) and/or TNF-ɑ (100 ng/mL) for 24h. Then, CCD-18Co were induced by increasing doses of IL-33 treatment (10, 50, 100 ng/mL) for 24h and inflammatory and fibrosis markers were measured.

Results
TGF-ß1 significantly induced mRNA levels encoding ECM-associated proteins such as α-SMA (***p&lt;0.001) or COL1A1 (*p&lt;0.05, Figure 1).Treatment with TGF-ß1 and/or TNF-α had no effect on the expression of mRNAs encoding IL-33 and ST2 in CCD-18Co in our experimental conditions. IL-33 treatment significantly increased mRNA levels for IL-1ß and ECM-associated proteins (COL3A1, CTGF and VIM) (*p&lt;0.05, Figure 1) in CCD-18Co but these effects are abolished in presence of TGF-ß1 and/or TNF-α treatment.

Conclusion
Treatment with TGF-ß1 and/or TNF-α had no significative impact on IL-33 mRNA levels in the CCD-18Co in our experimental conditions. IL-33 treatment increased ECM-associated proteins in CCD-18Co line under basal conditions but not in TGF-ß1 and/or TNF-α conditions.

References
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2.Schmitz J, Owyang A, Oldham E, et al. IL-33, an interleukin-1-like cytokine that signals via the IL-1 receptor-related protein ST2 and induces T helper type 2-associated cytokines. Immunity. 2005;23(5):479-490. doi:10.1016/j.immuni.2005.09.015
3.Beltrán CJ, Núñez LE, Díaz-Jiménez D, et al. Characterization of the novel ST2/IL-33 system in patients with inflammatory bowel disease. Inflamm Bowel Dis. 2010;16(7):1097-1107. doi:10.1002/ibd.21175 4.
4.England E, Rees DG, Scott IC, et al. Tozorakimab (MEDI3506): an anti-IL-33 antibody that inhibits IL-33 signalling via ST2 and RAGE/EGFR to reduce inflammation and epithelial dysfunction. Sci Rep. 2023;13(1):9825. doi:10.1038/s41598-023-36642-y