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Baicalein ameliorates ulcerative colitis by improving intestinal epithelial barrier via AhR/IL-22 pathway in ILC3s

Abstract

Ulcerative colitis (UC) is a chronic inflammatory disease of the gastrointestinal tract, which is closely related to gut barrier dysfunction. Emerging evidence shows that interleukin-22 (IL-22) derived from group 3 innate lymphoid cells (ILC3s) confers benefits on intestinal barrier, and IL-22 expression is controlled by aryl hydrocarbon receptor (AhR). Previous studies show that baicalein protects the colon from inflammatory damage. In this study we elucidated the molecular mechanisms underlying the protective effect of baicalein on intestinal barrier function in colitis mice. Mice were administered baicalein (10, 20, 40 mg·kg−1·d−1, i.g.) for 10 days; the mice freely drank 3% dextran sulfate sodium (DSS) on D1–D7 to induce colitis. We showed that baicalein administration simultaneously ameliorated gut inflammation, decreased intestinal permeability, restored tight junctions of colons possibly via promoting AhR/IL-22 pathway. Co-administration of AhR antagonist CH223191 (10 mg/kg, i.p.) partially blocked the therapeutic effects of baicalein in colitis mice, whereas AhR agonist FICZ (1 μg, i.p.) ameliorated symptoms and gut barrier function in colitis mice. In a murine lymphocyte line MNK-3, baicalein (5–20 μM) dose-dependently increased the expression of AhR downstream target protein CYP1A1, and enhanced IL-22 production through facilitating AhR nuclear translocation, these effects were greatly diminished in shAhR-MNK3 cells, suggesting that baicalein induced IL-22 production in AhR-dependent manner. To further clarify that, we constructed an in vitro system consisting of MNK-3 and Caco-2 cells, in which MNK-3 cell supernatant treated with baicalein could decrease FITC-dextran permeability and promoted the expression of tight junction proteins ZO-1 and occluding in Caco-2 cells. In conclusion, this study demonstrates that baicalein ameliorates colitis by improving intestinal epithelial barrier via AhR/IL-22 pathway in ILC3s, thus providing a potential therapy for UC.

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Fig. 1: Baicalein ameliorated DSS-induced mice and the effect was dependent on AhR.
Fig. 2: Baicalein improved the intestinal barrier structure and function in colitis mice.
Fig. 3: Baicalein regulated AhR/IL-22 pathway in ILC3s of colitis mice.
Fig. 4: Baicalein activated AhR/IL-22 pathway in MNK-3 cells in vitro.
Fig. 5: Establishment of shAhR-MNK3 stable transfected cell line.
Fig. 6: Baicalein had little effect on the AhR/IL-22 pathway in shAhR-MNK3 cells in vitro.
Fig. 7: Protective effect of baicalein on Caco-2 cells was mediated by IL-22 that MNK-3 cells secreted.
Fig. 8: Mechanisms of protection against colitis by baicalein via activation of the AhR/IL-22 pathway in ILC3s.

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant No. 82074092), Characteristic Innovation Project of Guangdong Provincial Universities (Grant No. 2020KTSCX026), “Double First-class” and High-level University Discipline Collaborative Innovation Team Project of Guangzhou University of Chinese Medicine (Grant No. 2021xk81), Natural Science Foundation of Guangdong Province (Grant no. 2021A1515012219) and Guangdong Provincial Bureau of Traditional Chinese Medicine (Grant no. 20181076).

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YYL performed experiments and wrote the article. XJW, YLS, QW, SWH, ZFP contributed to establishment and treatment of colitis mice model. YPC, JJL, MLZ, XQX, ZYW performed some cell studies. JYC analyzed and organized the data. LZ and XL designed ideas and edited the paper.

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Correspondence to Lian Zhou or Xia Luo.

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The authors declare no competing interests.

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Li, Yy., Wang, Xj., Su, Yl. et al. Baicalein ameliorates ulcerative colitis by improving intestinal epithelial barrier via AhR/IL-22 pathway in ILC3s. Acta Pharmacol Sin (2021). https://doi.org/10.1038/s41401-021-00781-7

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Keywords

  • ulcerative colitis
  • baicalein
  • epithelial barrier
  • group 3 innate lymphoid cells
  • interleukin-22
  • aryl hydrocarbon receptor
  • CH223191
  • FICZ

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