title: Fucoidan enhances intestinal barrier function by upregulating the expression of claudin-1.
abstract: OBJECTIVE
  To evaluate the protective effects of fucoidan on oxidative stress-induced barrier disruption in human intestinal epithelial cells.
  
  
  METHODS
  In Caco-2 cell monolayer models, the disruption of barrier function by oxidative stress is mediated by H₂O₂. The integrity of polarized Caco-2 cell monolayers was determined by measuring the transepithelial resistance (TER) and permeability was estimated by measuring the paracellular transport of FITC-labeled 4-kDa dextran (FD4). The protective effects of fucoidan on epithelial barrier functions on polarized Caco-2 cell monolayers were evaluated by TER and FD4 flux. The expression of tight junction (TJ) proteins was assessed using reverse-transcription polymerase chain reaction (RT-PCR) and immunofluorescence staining.
  
  
  RESULTS
  Without H₂O₂ treatment, fucoidan significantly increased the TER compared to control (P < 0.05), indicating a direct enhancement of intestinal epithelial barrier function. Next, H₂O₂ disrupted the epithelial barrier function in a time-dependent manner. Fucoidan prevented the H₂O₂-induced destruction in a dose-dependent manner. Fucoidan significantly decreased H₂O₂-induced FD4 flux (P < 0.01), indicating the prevention of disruption in paracellular permeability. RT-PCR showed that Caco-2 cells endogenously expressed claudin-1 and -2, and occludin and that H₂O₂ reduced the mRNA expression of these TJ proteins. Treatment with fucoidan attenuated the reduction in the expressions of claudin-1 and claudin-2 but not occludin. Immunofluorescence staining revealed that the expression of claudin-1 was intact and high on the cell surface. H₂O₂ disrupted the integrity of claudin-1. Treatment with fucoidan dramatically attenuated the expression of claudin-1.
  
  
  CONCLUSIONS
  Fucoidan enhanced intestinal epithelial barrier function by upregulating the expression of claudin-1. Thus, fucoidan may be an appropriate therapy for the treatment of inflammatory bowel diseases.
authors.affiliation: Atsushi Iraha, Akira Hokama, Kazuto Kishimoto, Tetsuo Hirata, Futoshi Higa, Masao Tateyama, Jiro Fujita, Department of Infectious, Respiratory, and Digestive Medicine, Faculty of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Iraha
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Chinen
authors.forename: Akira
authors.initials: A
authors.lastname: Hokama
authors.forename: Takumi
authors.initials: T
authors.lastname: Yonashiro
authors.forename: Tetsu
authors.initials: T
authors.lastname: Kinjo
authors.forename: Kazuto
authors.initials: K
authors.lastname: Kishimoto
authors.forename: Manabu
authors.initials: M
authors.lastname: Nakamoto
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Hirata
authors.forename: Nagisa
authors.initials: N
authors.lastname: Kinjo
authors.forename: Futoshi
authors.initials: F
authors.lastname: Higa
authors.forename: Masao
authors.initials: M
authors.lastname: Tateyama
authors.forename: Fukunori
authors.initials: F
authors.lastname: Kinjo
authors.forename: Jiro
authors.initials: J
authors.lastname: Fujita
mesh_terms: D000897:Anti-Ulcer Agents / Q000494:pharmacology* / Q000627:therapeutic use; D018938:Caco-2 Cells; D062445:Claudin-1 / Q000378:metabolism*; D004353:Drug Evaluation, Preclinical; D004847:Epithelial Cells / Q000187:drug effects; D006801:Humans; D006861:Hydrogen Peroxide; D015212:Inflammatory Bowel Diseases / Q000188:drug therapy; D007413:Intestinal Mucosa / Q000187:drug effects*; D011134:Polysaccharides / Q000494:pharmacology* / Q000627:therapeutic use; D019108:Tight Junctions / Q000187:drug effects*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D000897:Anti-Ulcer Agents; C568108:CLDN1 protein, human; D062445:Claudin-1; D011134:Polysaccharides; C007789:fucoidan; D006861:Hydrogen Peroxide
keywords: Fucoidan; Inflammatory bowel diseases; Intestinal epithelial cells; Oxidative stress; Tight junction
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