Experimental Necrotizing Enterocolitis Signaling Attenuates the Inflammatory Response in Dependent Aryl Hydrocarbon Receptor

Necrotizing enterocolitis (NEC) causes significant morbidity and mortality in premature infants; therefore, the identification of therapeutic and preventative strategies against NEC remains a high priority. The ligand-dependent transcription factor aryl hydrocarbon receptor (AhR) is well known to contribute to the regulation of intestinal microbial communities and amelioration of intestinal inflammation. However, the role of AhR signaling in NEC is unclear. Experimental NEC was induced in 4-d-old wild-type mice or mice lacking AhR expression in the intestinal epithelial cells or AhR expression in CD11c cells (AhR) by subjecting animals to twice daily hypoxic stress and gavage feeding with formula supplemented with LPS and enteric bacteria. During NEC, compared with wild-type mice treated with vehicle, littermates treated with an AhR proligand, indole-3-carbinol, had reduced expression of Il1b andMarco, a scavenger receptor that mediates dendritic cell activation and the recognition and clearance of bacterial pathogens by macrophages. Furthermore, indole-3-carbinol treatment led to the downregulation of genes involved in cytokine and chemokine, as revealed by pathway enrichment analysis. AhR expression in the intestinal epithelial cells and their cre-negative mouse littermates were similarly susceptible to experimental NEC, whereas AhR mice with NEC exhibited heightened inflammatory responses compared with their cre-negative mouse littermates. In seeking to determine the mechanisms involved in this increased inflammatory response, we identified the Tim-4 monocyte--dependent subset of macrophages as increased in AhR mice compared with their cre-negative littermates. Taken together, these findings demonstrate the potential for AhR ligands as a novel immunotherapeutic approach to the management of this devastating disease. ImmunoHorizons, 2021, 5: 193–209. Received for publication March 1, 2021. Accepted for publication March 1, 2021. Address correspondence and reprint requests to: Dr. Misty Good, Division of Newborn Medicine, Department of Pediatrics, Washington University School of Medicine, St. Louis Children’s Hospital, 660 South Euclid Avenue, Campus Box 8208, St. Louis, MO 63110. E-mail: mistygood@wustl.edu ORCIDs: 0000-0002-4185-2686 (L.S.N.); 0000-0002-9952-4888 (P.A.); 0000-0002-9871-1737 (M.G.); 0000-0002-1331-7424 (J.K.B.); 0000-0002-3971-8795 (Z.H.); 0000-0002-5082-0336 (M.L.L.); 0000-0002-0264-5721 (M.G.). This work was supported by the National Institutes of Health (NIH) R01DK118568 (to M.G.), R03DK111473 (to M.G.), K08DK101608 (to M.G.), and 5T32HD043010 (to L.S.N.); March of Dimes Foundation Grant 5-FY17-79 (to M.G.); the American Academy of Pediatrics Marshall Klaus Award (to L.S.N.), the St. Louis Children’s Hospital Foundation (to M.G.); the Children’s Discovery Institute (CDI) of Washington University School of Medicine (WUSM); and the St. Louis Children’s Hospital (SLCH) and the Department of Pediatrics at WUSM. Contributions from the Genome Technology Access Center in the Department of Genetics at WUSM are partially supported by National Cancer Institute Cancer Center Support Grant P30 CA91842 to the Siteman Cancer Center, by the Institute for Clinical and Translational Science Clinical and Translational Sciences Award, National Center for Research Resources of the NIH Grant UL1TR000448, and the NIH Roadmap for Medical Research. Contributions from the WUSM Digestive Disease Research Core Center are supported by NIH Grant P30DK052574. Imaging contributions were performed in part through the use of the Washington University Center for Cellular Imaging supported by WUSM, the CDI of WUSM and SLCH (CDI-CORE-2015-505 and CDI-CORE-2019-813), and the Foundation for Barnes-Jewish Hospital (3770 and 4642). None of the funding sources had any role in the manuscript. The sequences presented in this article have been submitted to the Gene Expression Omnibus (https://www.ncbi.nlm.nih.gov/geo/) under accession number