Effect of chitosan on epithelial cell tight junctions.
OBJECTIVE
Chitosan has been proposed as a novel excipient for transepithelial drug-delivery systems. Chitosan is thought to disrupt intercellular tight junctions, thus increasing the permeability of an epithelium. The effect of chitosan on tight junction complex was investigated at the molecular level.


METHODS
Changes in barrier properties of Caco-2 cell monolayers, including transepithelial electrical resistance and permeability to horseradish peroxidase (HRP), were assessed in response to chitosan treatment. Changes in subcellular localization of the tight junction proteins zona occludens 1 (ZO-1) and occludin by immunofluorescence and Western blotting of cellular fractions were also assessed.


RESULTS
Chitosan was found to cause a dose-dependent reduction in transepithelial electrical resistance of Caco-2 monolayers of up to 83%. A corresponding increase in horseradish peroxidase permeability of up to 18 times greater than the control was also observed across the monolayer. Immunofluorescent localization of ZO-1 revealed loss of membrane-associated ZO-1 from discrete areas. Analysis of cellular fractions revealed a dose-dependent loss of ZO-1 and occludin from the cytosolic and membrane fractions into the cytoskeletal fraction. These changes did not occur because of chitosan-mediated ATP depletion.


CONCLUSIONS
Chitosan-mediated tight junction disruption is caused by a translocation of tight junction proteins from the membrane to the cytoskeleton.
Smith
Jennifer
J
School of Biochemistry and Molecular Biology, University of Leeds, Mount Preston Street, Leeds, LS2 9JT, United Kingdom.
Wood
Edward
E
Dornish
Michael
M
D018938:Caco-2 Cells; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002686:Chitin / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology*; D048271:Chitosan; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D019108:Tight Junctions / Q000187:drug effects* / Q000378:metabolism
D002686:Chitin; D048271:Chitosan