Increased IL-10 expression by the inhibition of KCa3.1 in CD4+CD25+ regulatory T cells in the recovery phase in an inflammatory bowel disease mouse model.

Inflammatory bowel diseases (IBD) are chronic inflammatory diseases of the gastrointestinal tract arising from abnormal responses of the innate and adaptative immune systems. Interleukin-10 (IL-10)-producing CD4+CD25+ regulatory T (Treg) cells play a protective role in the recovery phase of IBD. In the present study, the effects of the administration of the selective Ca2+-activated K+ channel KCa3.1 inhibitor TRAM-34 on disease activities were examined in chemically-induced, semi-chronic IBD (scIBD) model mice. IBD disease severity, as assessed by diarrhea, visible fecal blood, inflammation, and crypt damage in the colon, was significantly lower in mice administered 1 mg/kg TRAM-34 than in vehicle-administrated mice. Quantitative real-time PCR examinations showed that IL-10 expression levels in the recovery phase were markedly increased by the inhibition of KCa3.1 in mesenteric lymph node (mLN) Treg cells of scIBD model mice compared with in vehicle-administered mice. Among several positive and negative transcriptional regulators (TRs) for IL-10, three positive TRs, E4BP4, KLF4, and Blimp1 were up-regulated by the inhibition of KCa3.1 in the mLN Treg cells of scIBD model mice. In mouse peripheral CD4+CD25+ Treg cells induced by a lectin stimulation, IL-10 expression and secretion were enhanced by the treatment with TRAM-34, together with the up-regulation of E4BP4, KLF4, and Blimp1. Collectively, the present results demonstrated that the pharmacological inhibition of KCa3.1 decreased IBD symptoms in scIBD model by increasing IL-10 production in peripheral Treg cells, and that IL-10high Treg cells produced by the treatment with KCa3.1 inhibitor may contribute to efficient Treg therapy for chronic inflammatory disorders, including IBD. Significance Statement Pharmacological inhibition of Ca2+-activated K+ channel KCa3.1 increased IL-10 expression in peripheral Treg cells, together with the up-regulation of the transcriptional regulators of IL-10: KLF4, E4BP4, and/or Blimp1. The manipulation of IL-10high-producing Treg cells by the pharmacological inhibition of KCa3.1 may be beneficial in the treatment of chronic inflammatory diseases like IBD.