Mechanisms Underlying Dysregulation of Electrolyte Absorption in Inflammatory Bowel Disease-Associated Diarrhea

Yu Shi An Chang Fang Ameliorates TNBS-Induced Colitis in Mice by Reducing Inflammatory Response and Protecting the Intestinal Mucosal Barrier

Ulcerative colitis (UC) is an inflammatory bowel disease that is related to the occurrence of colon cancer. This study aimed to investigate the underlying mechanism by which Yu Shi An Chang Fang (YST) treated UC. 2, 4, 6-trinitrobenzene sulfonic acid (TNBS) was used to construct the UC model. The body weight, fecal viscosity, and fecal bleeding of all mice were recorded every day to calculate the DAI value. The pathological changes in colon tissues were observed by hematoxylin-eosin (H&E) staining. The levels of tumor necrosis factor-α (TNF-α), interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and myeloperoxidase (MPO) reflecting inflammation and the levels of malondialdehyde (MDA), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD) reflecting oxidative stress in colon tissues were all measured by their assay kits. The mRNA expression of TNF-α, IL-1β, and IL-6 in colon tissues was detected by quantitative reverse transcription-PCR (qRT-PCR). The expression of proteins related to pyroptosis and the colonic mucosal barrier was analyzed by Western blot. As a result, TNBS caused decreases in body weight and colon lengths, triggered serious histological damage, promoted inflammation, oxidative stress, and pyroptosis, and destroyed the colonic mucosal barrier. The above changes caused by TNBS in colitis mice could be partially reversed by YST. In conclusion, YST ameliorates TNBS-induced UC in mice by reducing the inflammatory response and protecting the intestinal mucosal barrier.

Xinhuang Tablets Improve Intestinal Barrier Function via Regulating Epithelial Tight Junctions in Dextran Sulfate Sodium-Induced Ulcerative Colitis Mice

Intestinal mucosal barrier dysfunction is involved in the pathogenesis of inflammatory bowel disease, including ulcerative colitis (UC). Xinhuang tablets (XHTs) have been prescribed for several kinds of inflammatory diseases, including UC, whereas its possible underlying molecular mechanisms had never been explored. Mouse model of UC was constructed by DSS treatment and followed by XHT treatment. Disease activity index, histopathological of colonic tissue, tumor necrosis factor-alpha (TNF-α), and serum amyloid A (SAA) levels in serum were further assessed. The underlying mechanism was further explored by determination of the expression of epithelial tight junction-related protein. XHT administration ameliorated dextran sulfate sodium (DSS)-induced clinical symptoms, colonic histological injury, and decreased the circulating levels of TNF-α and SAA. Moreover, XHT treatment significantly increased the protein levels of zona occludens (ZO)-1, whereas decreased the levels of phosphorylation of Elk-1. In conclusion, this study confirmed the therapeutic effects of XHT treatment on UC in a DSS-induced mouse model, and indicated that by increasing expression of epithelial tight junctions and decreasing phosphorylation of Elk-1 might be one of the underlying mechanisms of XHT treatment on UC.

Functional characterization of SLC26A3 c.392C>G (p.P131R) mutation in intestinal barrier function using CRISPR/CAS9-created cell models

Background

Congenital chloride diarrhea (CCD) in a newborn is a rare autosomal recessive disorder with life-threatening complications, requiring early diagnostics and treatment to prevent severe dehydration and infant mortality. SLC26A3 rs386833481 (c.392C>G; p.P131R) gene polymorphism is an important genetic determinant of CCD. Here, we report the influence of the non-synonymous SLC26A3 variant rs386833481 gene polymorphism on the function of the epithelial barrier and the potential mechanisms of these effects.

Results

We found that P131R-SLC26A3 increased dysfunction of the epithelial barrier compared with wild type SLC26A3 in human colonic Caco-2 and mouse colonic CMT-93 cells. When P131R-SLC26A3 was subsequently reverted to wild type, the epithelial barrier function was restored similar to wild type cells. Further study demonstrated that variant P131R-SLC26A3 disrupts function of epithelial barrier through two distinct molecular mechanisms: (a) decreasing SLC26A3 expression through a ubiquitination pathway and (b) disrupting a key interaction with its partner ZO-1/CFTR, thereby increasing the epithelial permeability.

Conclusion

Our study provides an important insight of SLC26A3 SNPs in the regulation of the epithelial permeability and indicates that SLC26A3 rs386833481 is likely a causative mutation in the dysfunction of epithelial barrier of CCD, and correction of this SNP or increasing SLC26A3 function could be therapeutically beneficial for chronic diarrhea diseases.