Indole-3-Carbinol–Dependent Aryl Hydrocarbon Receptor Signaling Attenuates the Inflammatory Response in Experimental Necrotizing Enterocolitis

Abstract

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 (AhRΔCD11c) 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 and Marco, 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 AhRΔCD11c 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 AhRΔCD11c 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.

Untargeted Metabolomic Analysis of Human Milk from Mothers of Preterm Infants

“…Differences in the aromatic amino acids tyrosine or tryptophan metabolites may alter infant microbial composition and activity, affecting breast milk nutritional content and contributing to NEC development. Anaerobic fermentation of tyrosine and tryptophan by intestinal bacteria results in the derivation of phenols as well as indoles, which have recently shown benefit in attenuating intestinal inflammation in NEC [ 6 , 7 ]. The metabolism of tryptophan by intestinal bacteria along the kynurenine pathway results in metabolites that are implicated in microbial defense, immunoregulation and antioxidant activity in the intestine [ 23 , 49 , 50 ].…”

“…This is a promising approach for metabolic fingerprinting and phenotyping of maternal milk to highlight variations in composition related to maternal health and diet and the resulting impact on the infant. Variations in the bioactive components of human milk have been shown to influence neonatal health outcomes, including growth, development, protection from disease development, neurodevelopment, and immunological development [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ].…”

A protocol for the induction of experimental necrotizing enterocolitis in neonatal mice

“…Fecal samples should be snap-frozen in a 1.5 ml microcentrifuge tube and stored at −80°C for later 16s rRNA microbial sequencing ( Mihi et al., 2021 ). Mouse pups subjected to experimental NEC will exhibit an intestinal microbiome with an overabundance of Gammaproteobacteria species similar to human infants with NEC ( Mihi et al., 2021 ; Nolan et al., 2021 ).…”

Necrotizing enterocolitis: Bench to bedside approaches and advancing our understanding of disease pathogenesis

“…Another study by Nolan and colleagues investigated the role of aryl hydrocarbon receptor (AhR) signaling in DCs during experimental NEC, as this signaling pathway helps regulate intestinal immunity and homeostasis. They found that a lack of AhR signaling in DCs increased NEC-mediated intestinal inflammation, and that this effect was associated with an increase in a specific subset of macrophages in the small intestinal lamina propria ( 111 ).…”