Delayed recovery from ulcerative colitis is mainly due to impaired healing of the intestinal epithelium after inflammation. The circadian rhythm controls cell proliferation and energy metabolism. However, the role of circadian genes in inflammatory bowel disease is largely unknown. The purpose of this study was to investigate whether disrupting the circadian rhythm in mice can worsen colitis by altering mitochondrial energy metabolism. Mice in the experimental groups were under physiologic stress with an 8-h light shift jet-lag schedule every 3 days, whereas those in the control group were not. Subsequently, half of the mice in the control and jet-lagged groups were given dextran sodium sulfate (DSS) to induce colitis. Mice in each group were euthanized at zeitgeber time (ZT)0, ZT4, ZT8, ZT12, ZT16, and ZT20. To investigate the effects of jet lag on the mice, colon specimens were subjected to hematoxylin and eosin staining to analyse mRNA and protein expression of core circadian clock genes (Bmal1, Clock, Per1, Per2, Cry1, Cry2, and Nr1d1). We analysed the mitochondrial morphology, adenosine triphosphate (ATP) levels, and the expression of dynamin-related protein 1 (Drp1) and ser637-phosphorylated (p)-Drp1, which are closely related to ATP production. We further investigated the effect of PER2 knock-down in the colon epithelial cells (CCD 841 CoN) by measuring ATP and cell proliferation levels. Disrupting the circadian rhythm changed the oscillation of clock genes in the colon of mice, altered the mitochondrial morphology of the colon specimens, decreased the expression of p-Drp1, reduced ATP production, and exacerbated inflammatory responses in mice with DSS-induced colitis. Additionally, silencing of PER2 in the colon epithelial cells reduced ATP production and cell proliferation. Disrupting the circadian rhythm in mice decreases mitochondrial energy metabolism in the colon and exacerbates symptoms of colitis.

Background: Ulcerative colitis (UC) is a chronic, incurable condition characterized by mucosal inflammation and intestinal epithelial cell (IEC) damage. The circadian clock gene NR1D1, implicated in UC and the critical mitophagy process for epithelial repair, needs further exploration regarding its role in mitophagy regulation in UC. Methods: We created a jet lag mouse model and induced colitis with dextran sulfate sodium (DSS), investigating NR1D1’s role. Intestinal-specific Nr1d1 knockout mice were also generated. RNA sequencing, chromatin immunoprecipitation (ChIP), and dual-luciferase reporter assays helped ascertain NR1D1’s regulatory effect on BNIP3 expression. The mitochondrial state in IECs was assessed through transmission electron microscopy, while confocal microscopy evaluated mitophagy-associated protein expression in colon tissue and CCD841 cells. Cell apoptosis and reactive oxygen species (ROS) were measured via flow cytometry. Results: We observed reduced NR1D1 expression in the IECs of UC patients, accentuated under jet lag and DSS exposure in mice. NR1D1 ablation led to disrupted immune homeostasis and declined mitophagy in IECs. NR1D1, usually a transcriptional repressor, was a positive regulator of BNIP3 expression, leading to impaired mitophagy, cellular inflammation, and apoptosis. Administering the NR1D1 agonist SR9009 ameliorated colitis symptoms, primarily by rectifying defective mitophagy. Conclusions: Our results suggest that NR1D1 bridges the circadian clock and UC, controlling BNIP3-mediated mitophagy and representing a potential therapeutic target. Its agonist, SR9009, shows promise in UC symptom alleviation.

Background: Intestinal fibrosis, a complex complication of colitis, is characterized by excessive extracellular matrix (ECM) deposition. Estrogen receptor (ER) β may play a role in regulating this process. Methods: Intestinal tissue samples from stenotic and nonstenotic regions were collected from Crohn’s disease (CD) patients. RNA sequencing was conducted on a mouse model to identify differentially expressed mRNAs. Histological, immunohistochemical, and semiquantitative Western blotting analyses were employed to assess ECM deposition and fibrosis. The roles of relevant pathways in fibroblast transdifferentiation, activity, and migration were examined. Results: Estrogen receptor β expression was found to be downregulated in the stenotic intestinal tissue of CD patients. Histological fibrosis score, collagen deposition, and profibrotic molecules in the colon of an intestinal fibrosis mouse model were significantly decreased after activation of ERβ. In vitro, ERβ activation alleviated transforming growth factor (TGF)-β-induced fibroblast activation and migration, as evidenced by the inhibition of col1α1, fibronectin, α-smooth muscle actin (α-SMA), collagen I, and N-cadherin expression. RNA sequencing showed that ERβ activation affected the expression of genes involved in ECM homeostasis and tissue remodeling. Enrichment analysis of differentially expressed genes highlighted that the downregulated genes were enriched in ECM-receptor interaction, TGF-β signaling, and Toll-like receptor (TLR) signaling. Western blotting confirmed the involvement of TGF-β/Smad and TLR4/MyD88/NF-κB signaling pathways in modulating fibrosis both in vivo and in vitro. The promoter activity of TGF-β1 and TLR4 could be suppressed by ERβ transcription factor. Conclusion: Estrogen receptor β may regulate intestinal fibrosis through modulation of the TGF-β/Smad and TLR4/MyD88/NF-κB signaling pathways. Targeting ERβ activation could be a promising therapeutic strategy for treating intestinal fibrosis.

Background. Clinical data suggest that enteral nutrition (EN) effectively decreases disease activity and maintains remission in patients with inflammatory bowel disease (IBD). However, the modulatory effects of EN on the intestinal mucosal immune system remain unclear. Aims. This study first aimed at comparing the therapeutic effects of three EN formulas on ameliorating dextran sulfate sodium- (DSS-) induced chronic colitis; with the most effective formula, we then examined its influence on the mucosal inflammatory response and epithelial barrier function. Methods. The effect of EN formulas on colitis in mice was assessed by body weight, disease activity index scores, colon length, and H&E staining for pathological examination. Colonic and circulating cytokine expression levels and the frequencies of immune cells were also analyzed. Intestinal epithelial barrier function was evaluated by detecting tight junction proteins. Results. We found that among the three EN formulas, an elemental diet (ED) containing enriched amino acids restored the colitis-related reduction in body weight better than the other two EN formulas. ED amino acids suppressed the release of colonic proinflammatory mediators and maintained the expression of tight junction proteins in these mice. ED amino acid treatment mitigated the colitis-induced increase in CD103⁺CD11b⁺ dendritic cells and CD4⁺ and CD8⁺ T cells and inhibited the predominant Th1/Th17 responses particularly in the colonic mucosal lamina propria of mice with colitis. Conclusions. We showed that ED amino acids can be an effective immunomodulatory agent to reduce colitis-related inflammation by inhibiting proinflammatory mediators and Th1/Th17 cell responses and by repairing the disrupted epithelial barrier.

Background: Ulcerative colitis (UC), a major type of inflammatory bowel disease, is characterized by chronic inflammation of the colonic mucosa and submucosa. Estrogen receptor β (ERβ) predominates in the colon and exerts anti-inflammatory effects. Ferroptosis, a recently discovered form of iron-dependent programmed cell death, is implicated in the pathogenesis of several diseases, including UC. However, the link between ferroptosis and the anti-inflammatory actions of ERβ in UC remains to be elucidated. Methods: We analyzed colonic mucosal samples from inflammatory and non-inflammatory regions of UC patients to assess ferroptosis levels. Experimental colitis was induced in wild-type C57BL/6 mice and intestinal epithelial cell-specific ERβ knockout (ERβ^−/−) mice using dextran sulfate sodium (DSS). We measured body weight, colon length, disease activity index (DAI), and histopathological scores. RNA sequencing was performed to identify differentially expressed genes and related signaling pathways, with additional ferroptosis assessment in vivo and in vitro through biochemical markers and cellular assays. Results: In UC patients, ferroptosis was significantly elevated in inflammatory mucosal regions compared to non-inflammatory areas. Compared to the wild-type counterparts, ERβ^−/− mice exacerbated DSS-induced experimental colitis, including reduced body weight, shortened colon length, and higher DAI scores. RNA sequencing showed enrichment of inflammatory and immune response pathways, with significant activation of JAK/STAT, NF-κB, and TNF signaling in ERβ^−/− mice. ERβ deficiency induced ferroptosis in both in vitro and in vivo models. Ferroptosis indicators such as PTGS2 were upregulated, GPX4 expression was downregulated, and there were increases in malondialdehyde, iron content, reactive oxygen species, and mitochondrial damage. Conclusion: Our findings demonstrate that ERβ deficiency exacerbates colitis and enhances ferroptosis in IECs. ERβ positively regulates GPX4 transcription, thereby inhibiting ferroptosis and alleviating colitis. These insights suggest that modulation of ERβ and its regulation of ferroptosis may represent a novel therapeutic strategy for UC.

Autoimmune diseases (AIDs) are characterized by a breakdown in immune tolerance, wherein the patient’s immune system fails to recognize self‐tissues and subsequently attacks the body’s organs and tissues. Although there are many therapeutic medicines targeting the pathogenic mechanisms, there is currently a lack of curative or long‐term symptom control options. Chimeric antigen receptor (CAR) cells are engineered cells that express multifunctional synthetic receptors. These CAR cells specifically target killer pathogenic immune cells and offer a novel approach to treating AIDs by modulating the immune microenvironment. Recent studies have demonstrated satisfactory outcomes with this method in managing autoimmune conditions. In our review paper, we provide a comprehensive summary of previous cases utilizing CAR cell therapy for AIDs. We hope that our review will provide clinicians with more options for the treatment of AIDs.