Alteration of intestinal mucosal immunity and metabolites in mice exposed to chronic restraint stress

Depression is greatly impacted by stress. Individuals with depression are more susceptible to developing gastrointestinal disorders. Chronic restraint stress (CRS) can induce depression-like behaviors in animals. However, the effects of CRS on intestinal mucosal immunity and metabolism, which may play roles in modulating depression-like behaviors, are not yet fully understood. A C57/BL6J mouse model of CRS was established to induce depression-like behaviors. Histopathological and cell biology techniques were used to assess intestinal mucosal changes. Transcriptome sequencing of ileum and colon tissues and nontargeted metabolomics of colonic contents were performed to analyze gene and metabolite alterations after CRS. The study findings revealed that CRS mice had disturbed mucosal microenvironments, as evidenced by increased crypt depths and inflammation scores, enhanced intestinal permeability, and reduced expression of defensins. At the mucosal effector sites, the proportion of TCRαβ⁺CD8αβ⁺ intraepithelial lymphocytes (IELs) in the epithelium and innate lymphoid cells type 3 (ILC3s) in the lamina propria was notably reduced. Transcriptome sequencing revealed the enrichment of differential genes in lipid metabolic processes, particularly in steroid metabolism. Metabolomic analysis further revealed that 28-homobrassinolide, 1α,25-dihydroxy-11α-phenylcholecalciferol, and 2α-α(benzyloxy)-1α,25-dihydroxy-19-norcholecalciferol, all belonging to steroid hormones, were significantly decreased after CRS. Given that the latter two are side chain-modified 1,25-dihydroxyvitamin D3 (1,25D3), intervention with 1,25D3 was implemented in CRS mice. The results were promising as 1,25D3 treatment not only improved the depression-like behavior but also enhanced the intestinal mucosal immune milieu. Notably, 1,25D3 intervention significantly increased the proportion of TCRαβ⁺CD8αβ⁺ IELs in CRS mice, which may be the inner cause to enhance mucosal defense. Additionally, microbiota sequencing provided valuable evidence for the resource and regulation of differential metabolites. Hence, our study suggests a potential role of steroid metabolism in chronic stress-induced intestinal mucosal disorders and provides preliminary evidence supporting the therapeutic effects of 1,25D3 on depression combined with gastrointestinal disorders.