Bile salts disrupt human esophageal squamous epithelial barrier function by modulating tight junction proteins

Area of Science:

• Gastroenterology
• Cell Biology
• Tissue Engineering

Background:

• Gastro-esophageal reflux disease (GERD) involves acid and bile acid reflux, causing esophageal injury.
• The precise impact of refluxed substances on human esophageal stratified epithelial barrier function and tight junction (TJ) proteins remains incompletely understood.

Purpose of the Study:

• To investigate the effects of acid and bile acids on esophageal epithelial barrier function and TJ protein distribution.
• To validate a novel air-liquid interface (ALI) in vitro culture model using primary human esophageal epithelial cells (HEECs).

Main Methods:

• Developed an ALI in vitro culture model using primary HEECs.
• Assessed epithelial barrier integrity via transepithelial electrical resistance (TEER) and paracellular permeability.
• Analyzed TJ protein distribution (claudin-1, claudin-4, occludin) using immunofluorescence and biochemical fractionation.

Main Results:

• ALI-cultured HEECs formed stratified squamous epithelium with established TJs by day 7.
• Exposure to acid (pH 2), taurocholic acid (TCA, pH 3), and glycocholic acid (GCA, pH 3) significantly impaired barrier function (reduced TEER, increased permeability).
• Acid and bile acids altered TJ protein distribution, reducing insoluble fractions of claudin-1 and -4, while deoxycholic acid and pepsin also disrupted barrier function.

Conclusions:

• The ALI-cultured HEEC model is a robust in vitro system for studying esophageal epithelial barrier function.
• Acid, bile acids, and pepsin disrupt the esophageal squamous epithelial barrier, at least partly, through modulation of TJ proteins.
• These findings offer new insights into the role of TJ proteins in the pathogenesis of esophagitis.