Naringenin enhances intestinal barrier function through the expression and cytoskeletal association of tight junction proteins in Caco-2 cells

Authors

  • Sakino Noda,

    1. Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Japan
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  • Soichi Tanabe,

    1. Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Japan
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  • Takuya Suzuki

    Corresponding author
    1. Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Japan
    • Correspondence: Professor Takuya Suzuki, Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, 1-4-4, Kagamiyama, Higashi-Hiroshima, 739-8528, Japan

      E-mail: takuya@hiroshima-u.ac.jp

      Fax: +81-82-424-7916

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Abstract

Scope

We have previously reported that naringenin promotes the tight junction (TJ) integrity in intestinal Caco-2 cells. This study investigated the naringenin-mediated effect in Caco-2 cells with a particular focus on the modulation of TJ structure and claudin-4 transcriptional regulation.

Methods and results

Naringenin (10∼100 μM) dose-dependently enhanced TJ barrier integrity of Caco-2 cells, indicated by transepithelial electrical resistance and FITC-dextran flux. Immunoblot analysis showed that naringenin increased the cytoskeletal association of TJ proteins, zonula occludens-2, occludin, claudin-1, and claudin-4, simultaneously with increased occludin phosphorylation. The total expression of claudin-4 was also increased by naringenin. Quantitative RT-PCR and luciferase reporter assay revealed that naringenin transcriptionally increased the claudin-4 expression with activation of claudin-4 promoter. The mutation of the binding site of the transcriptional factor Sp1 in the claudin-4 promoter sequence and the pharmacological inhibition of Sp1 partially suppressed the naringenin-mediated activation of the claudin-4 promoter. Further, naringenin induced the heat shock protein 70 expression in the cells.

Conclusion

Naringenin enhances barrier integrity through the assembly and expression of TJ proteins in intestinal epithelial cells. Naringenin-mediated claudin-4 expression occurs, at least partially, through Sp1-dependent transcriptional regulation. The induction of heat shock protein 70 may be also involved in the increased claudin-4 expression.

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