DOP117 Innate lymphoid cells control colitis and intestinal fibrosis via cellular stress response in mice and human

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Abstract Background Group 2 innate lymphoid cells (ILC2s) are increased in peripheral blood and intestinal samples from IBD patients and mice with colitis. ILC2s are major producers of type 2 cytokines including IL-5 and IL-13 and growth factor AREG that induce goblet cell hyperplasia and mitigate acute inflammation in the gut. On the other hand, prolonged or uncontrolled ILC2 activation may contribute to chronic inflammation and tissue fibrosis, although the role of ILC2s in stricturing/fibrostenotic Crohn’s disease (CD) has been unknown. In this study, we investigated the function of IRE1a-XBP1 pathway, a regulatory hub of cellular stress response, in colitis and fibrosis in mice and CD patients. Methods We generated conditional knockout Ire1aflo/floxIl5-Cre (Ire1aΔIl5) and Rag-/-Ire1aΔIl5 mice with Ire1a deleted in ILC2s. Dextran sodium sulfate (DSS)-induced and T-cell transfer colitis models were used. Human peripheral ILC2s were collected for flow cytometry and ex vivo stimulations. Results Mouse intestinal ILC2s express high level of Ire1a. The number of ILC2s increased in colon, small intestine (SI), and esophagus of Ire1aΔIl5 mice with elevated proliferation marker Ki67. Additionally, SI and colonic Ire1aΔIl5 ILC2s produced more IL-5, IL-13, and AREG after ex vivo stimulation with IL-33 or IL-25. Consistently, selective IRE1 inhibitor 4u8C enhanced production of IL-13, while selective IRE1 activator IXA4 suppressed IL-13 in sort-purified human ILC2s ex vivo (Figure 1). Bulk RNA-seq of SI Ire1aΔIl5 ILC2s showed reduced Rxrg and elevated fatty acid transport by pathway analysis, which may lead to the increased proliferation and cytokine production in Ire1aΔIl5 ILC2s. Upon DSS challenge, Ire1aΔIl5 mice exhibited milder signs of disease including weight loss, clinical scores as well as colon shortening and histology, which was accompanied by elevations in ILC2-derived cytokines and AREG as well as heightened goblet cell differentiation and mucin production. In contrast, upon adoptive T-cell transfer, Rag-/-Ire1aΔIl5 mice developed worsened chronic colitis and intestinal fibrosis, which was reversed by intraperitoneal injection of neutralizing antibody against IL-13 or AREG. Furthermore, CD patients with intestinal strictures expressed higher level of IL-13 in ILC2s in the blood (Figure 2). Conclusion IRE1a-XBP1 constrains cytokine production by intestinal ILC2s during inflammation. IRE1a deficiency in ILC2s protected against acute colitis with heightened type 2 cytokines and AREG; while loss of IRE1a exacerbated chronic colitis and fibrosis. The presence of CD strictures was associated with elevated IL-13 in peripheral ILC2s . We identified IRE1a and ILC2s as potential biomarkers and therapeutic targets for stricturing CD.