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Epithelial RXRα activity induced by Westernization of diet instigates enteritis in Crohn’s disease

ABSTRACT: Westernization of diet, partly characterised by excess of long-chain fatty acids, provides a risk for developing Crohn’s disease (CD), and perturbs the function of specialized intestinal epithelium termed Paneth cells. The lack of a cellular and molecular framework of lipid sensing in intestinal inflammation poses a constraint to understanding detrimental effects of Western diets. Here, we report how Paneth cell sensing of lipid excess in a Western diet is translated into CD-like intestinal inflammation. Small intestinal transcriptional profiling of CD patients from three independent cohorts identified increased activity of the transcription factor retinoid x receptor alpha (RXRα) specifically in intestinal epithelium. Intestinal epithelial RXRα activity was induced by polyunsaturated fatty acid (PUFA) excess in a Western diet in mice with CD-like enteritis. PUFA-induced RXRα activity in Paneth cells governed chronic transmural enteritis by enabling the expression of the interleukin 8 homologue CXCL1. Blockade of PUFA-induced RXRα activity by 9-cis retinoic acid ameliorated CXCL1 production and enteritis, and patients receiving isotretinoin therapy (a precursor for 9-cis retinoic acid) displayed reduced odds of developing CD. Collectively, we identify Paneth cells as gatekeepers of lipid stress that exploit RXRα to sense and translate PUFA excess into enteritis, which could be targeted to prevent or treat CD.

ORGANISM(S): Mus musculus

PROVIDER: GSE284139 | GEO | 2025/12/12

REPOSITORIES: GEO

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Project description:Crohn’s disease (CD) is associated with multiple Paneth cell dysfunctions such as altered antimicrobial secretion that relies on autophagy - an essential process controlling the turnover of cellular components. Genome-wide association studies have linked CD to mutations in the ATG16l1 gene, encoding an important component of the autophagy machinery. Patients carrying the ATG16l1 CD risk allele have Paneth cell abnormalities, as reproduced in Atg16l1-deficient mouse models. However, the direct effect of the ATG16L1-deficiency and autophagy-impairment in Paneth cells has not been analysed in detail. To investigate this, we generated a mouse model lacking ATG16L1 specifically in intestinal epithelial cells (Atg16l1△IEC) making these cells impaired in autophagy. Using a 3D small intestinal organoid culture model, which we enriched for Paneth cells and compared the proteomic profiles of organoids derived from the wild-type (WT) and the Atg16l1△IEC mice. We used an integrated computational approach combining protein-protein interaction networks, list of proteins potentially targeted by autophagy and functional information on the proteins with altered protein levels to identify the mechanistic link between autophagy-impairment and disrupted cellular process. 198 (70%) of the 284 altered proteins were more abundant in autophagy-impaired organoids than WT organoids that could be due to a reduced protein turnover. Combining the proteomic dataset with the potential target proteins of selective autophagy proteins revealed that 116 (41%) of the differentially abundant proteins could rely on autophagy-mediated turnover. Taken together, our results suggest that proteins with increased levels in autophagy-impaired background require an autophagy-mediated turnover mechanism, and that their altered levels in CD could affect key cellular processes. Consequently, we pointed out the importance of autophagy in controlling the turnover of proteins relevant in key Paneth cell functions such as exocytosis, apoptosis and DNA damage repair. Our study unravels autophagy-dependent cellular processes of Paneth cells that not directly relies on the autophagy process, rather than a selective protein turnover mechanism. The identified proteins and processes open new avenues for targeted, cell type-specific therapeutic interventions in CD.

Project description:This UH2/UH3 demonstration project entitled "Effects of Crohn's disease risk alleles on enteric microbiota" is focused on characterizing intestinal associated microbiota in patients with ileal Crohn's disease (ileal CD), ulcerative colitis (UC) and control patients without inflammatory bowel diseases (non-IBD). We hypothesize that genetic factors that affect Paneth cell function, contribute to compositional changes in intestinal microbiota. These changes in microbiota may lead to reduction of protective commensal organisms and increased numbers of aggressive organisms that incite intestinal inflammation. This hypothesis is being tested by high throughput 16S rRNA sequence analysis of de-identified ileal and colonic tissues that have been archived at Washington University St. Louis, University of North Carolina, Mount Sinai Hospital and the Cleveland Clinic. Multivariate analysis of the metagenomic data will be conducted with genotyping metadata (highly reproducible CD risk alleles, including NOD2 and ATG16L1) and phenotyping metadata (e.g. age, gender, race, body mass index, medications and smoking.) Shotgun sequencing will be performed on selected fecal specimens linked to ileal tissues to identify additional, or auxiliary, or synergistic pathogenic factors or other functional changes in the microbiome. Because members of this research team have observed that a chronic viral infection is required for the Paneth cell defect in Atg16l1 hypomorphic mice, a major focus of these studies will be towards identifying potential viral triggers for the defective Paneth cell phenotype in individuals harboring the ATG16L1 risk allele. Novel genetic probes for protective and aggressive organisms will be developed by mining bacterial genome and shotgun sequencing data. Genomic sequences will be produced for candidate protective and aggressive strains (e.g. adherent-invasive strains of E. coli) isolated from human intestinal tissues where there is limited existing genome information. Quantitative qPCR assays using the novel as well as established genetic probes will be conducted to test the hypothesis that an imbalance between protective and aggressive organisms is associated with genetic factors that affect Paneth cell function. Our combined expertise in multiple disciplines across multiple institutions, our demonstrated ability to collect a large number of well-phenotyped samples with longitudinal clinical information that will be linked to host response and morphologic studies, and our consortium's capacity for high-throughput sequencing will be used to investigate how alterations in human microbiome relate to CD risk alleles and CD pathogenesis.

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Epithelial RXRα activity induced by Westernization of diet instigates enteritis in Crohn’s disease

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