title: Naringenin enhances intestinal barrier function through the expression and cytoskeletal association of tight junction proteins in Caco-2 cells.
abstract: METHODS
  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.
  
  
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, Japan.
authors.forename: Sakino
authors.initials: S
authors.lastname: Noda
authors.forename: Soichi
authors.initials: S
authors.lastname: Tanabe
authors.forename: Takuya
authors.initials: T
authors.lastname: Suzuki
mesh_terms: D018938:Caco-2 Cells; D062445:Claudin-1 / Q000235:genetics / Q000378:metabolism; D062506:Claudin-4 / Q000235:genetics / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism*; D003911:Dextrans; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D044950:Flavanones / Q000494:pharmacology*; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives; D005786:Gene Expression Regulation; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D007422:Intestines / Q000187:drug effects*; D062793:Occludin / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D062725:Tight Junction Proteins / Q000235:genetics / Q000378:metabolism*; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism; D062827:Zonula Occludens-2 Protein / Q000235:genetics / Q000378:metabolism
chemical_list: C568108:CLDN1 protein, human; C568157:CLDN4 protein, human; D062445:Claudin-1; D062506:Claudin-4; D003911:Dextrans; D044950:Flavanones; D018840:HSP70 Heat-Shock Proteins; C568985:OCLN protein, human; D062793:Occludin; D016329:Sp1 Transcription Factor; D062725:Tight Junction Proteins; D062827:Zonula Occludens-2 Protein; C015219:fluorescein isothiocyanate dextran; C005273:naringenin; D016650:Fluorescein-5-isothiocyanate
keywords: Caco-2 cell; Intestinal barrier; Intestinal cell; Naringenin; Tight junction