Thymosin β4 released by mast cells under stress conditions impairs intestinal epithelial barrier via IL22RA1/JAK1/STAT3 signaling in irritable bowel syndrome.

BACKGROUND: Mast cells (MCs) under stress conditions contribute to the development of irritable bowel syndrome (IBS), yet their precise mechanisms in IBS remain unclear. AIM: To investigate the role of MC-derived thymosin β4 (Tβ4) in stress-induced intestinal barrier dysfunction. METHODS: The colonic mucus Tβ4 levels in IBS patients were determined and their effects on the epithelial barrier were assessed in vitro and in vivo. Specifically, rats genetically deficient in Tβ4 (Tβ4 (-/-)) or mice deficient in MCs (Kit (w-sh/w-sh)) were used to observe the effects of reintroducing Tβ4 or wild-type peritoneal MCs (wt-PMCs) into these animals. Additionally, the regulatory mechanism underlying Tβ4 secretion in MCs was investigated. RESULTS: We demonstrated that high levels of Tβ4 in IBS mucus and intestinal MCs mediate stress-associated disruptive changes to the epithelial barrier. Moreover, Tβ4 treatment of wild-type or MC-deficient Kit (w-sh/w-sh) mice caused a reduction in tight junction proteins and the interleukin 22 receptor A1 (IL22RA1)/Reg3γ cascade, but an increase in myosin light chain kinase. Furthermore, Tβ4 (-/-) rats were resistant to stress, though reintroduction of Tβ4 or wt-PMCs restored stress or corticotropin-releasing hormone (CRH)-induced barrier disturbance. Consistently, Tβ4 release from MCs was dependent on the CRH receptor 1, but not degranulation. The effect of Tβ4 was accompanied by IL22RA1/Janus kinase 1 (JAK1)/signal transducer and activation of transcription 3 (STAT3) pathway inhibition, suggesting a mechanism for physical and immune barrier suppression. CONCLUSION: Collectively, these results suggest that Tβ4, which is abundant in IBS mucus and the secretome of MCs, plays a crucial role in the pathogenesis of IBS via IL22RA1/JAK1/STAT3 signaling, with potential implications for diagnostic and therapeutic targeting.