LncRNA XIST modulates 5-hydroxytrytophan-induced visceral hypersensitivity by epigenetic silencing of the SERT gene in mice with diarrhea-predominant IBS

Diarrhea-predominant irritable bowel syndrome (IBS-D) is a prevalent gastrointestinal disorder with a high incidence in children. The role of long non-coding RNAs (lncRNAs) in gastrointestinal diseases has been previously highlighted. Nevertheless, the underlying regulatory mechanism of lncRNA X inactivate-specific transcript (XIST) in IBS-D requires further studies. Thus, the present study was conducted with the main objective of elucidating the underlying mechanism of lncRNA XIST in visceral hypersensitivity in IBS-D. An in vivo mouse model of IBS-D was constructed via rectal perfusion of acetic acid. Next, in order to evaluate the effect of lncRNA XIST on the development of visceral hypersensitivity in IBS-D, different vector plasmids were injected into mice along with rectal mucosal epithelial cells, followed by the measurement of abdominal withdrawal reflex (AWR) score, counts of peristaltic wave, abdominal wall contraction and defecation particles. Furthermore, luciferase reporter assay, FISH, RIP and ChIP assays were conducted to determine the interactions between lncRNA XIST and SERT. Subsequently, MS-PCR was adopted to test the methylation level of SERT promoter. 5-hydroxytrytophan (HT) content in rectal tissues was detected using immunohistochemistry. The IBS-D mouse models presented with a high expression of lncRNA XIST along with low expression of SERT. LncRNA XIST was observed to recruit methylase DNMT1, DNMT3A and DNMT3B to promote SERT promoter methylation, reducing its expression. Restoration of lncRNA XIST resulted in increased AWR score, counts of peristaltic wave, abdominal wall contraction and defecation particles along with stimulated 5-HT expression and SERT methylation level, while downregulation of lncRNA XIST reversed these effects. In conclusion, the key findings from our study indicated that lncRNA XIST acts as a regulator in 5-HT-induced visceral hypersensitivity in mice with IBS-D, providing a new insight into the regulatory effect of lncRNA XIST and its epigenetic diagnostic and therapeutic properties in IBS-D.