Effect of chitosan on epithelial cell tight junctions

Area of Science:

• Biomaterials Science
• Cell Biology
• Drug Delivery Systems

Background:

• Chitosan is a promising excipient for enhancing drug delivery across epithelial tissues.
• It is hypothesized that chitosan increases epithelial permeability by disrupting intercellular tight junctions.

Purpose of the Study:

• To investigate the molecular mechanisms by which chitosan affects the tight junction complex.
• To evaluate the impact of chitosan on epithelial barrier function at the cellular level.

Main Methods:

• Caco-2 cell monolayers were treated with chitosan to assess changes in transepithelial electrical resistance (TEER) and permeability to horseradish peroxidase (HRP).
• Immunofluorescence microscopy and Western blotting were used to analyze the subcellular localization of tight junction proteins, specifically zona occludens 1 (ZO-1) and occludin.

Main Results:

• Chitosan induced a dose-dependent decrease in TEER (up to 83%) and a significant increase in HRP permeability (up to 18-fold).
• Immunofluorescence revealed a loss of membrane-associated ZO-1. Western blot analysis showed a dose-dependent translocation of ZO-1 and occludin from membrane and cytosolic fractions to the cytoskeletal fraction.
• These effects were independent of chitosan-induced ATP depletion.

Conclusions:

• Chitosan disrupts tight junctions by causing a redistribution of key tight junction proteins (ZO-1 and occludin) from the cell membrane to the cytoskeleton.
• This molecular mechanism underlies chitosan's ability to enhance transepithelial drug delivery.