Colitis induced destruction of the tight junction (TJ) protein ZO-1 is IL-4/Stat6 dependent

Abstract

Introduction: The TJ, which helps regulate the intestinal permeability (IP) barrier, is composed of both cytosolic proteins such as ZO-1 and transmembrane proteins such as claudin-1. Increased IP is present in intestinal inflammation. Stat6 regulates cytokine induced gene expression through the IL-4-Stat6 signaling pathway and may be involved in intestinal inflammation. Hypothesis: TJ expression is decreased in dextran sodium sulfate (DSS) induced colitis. Methods: Balb/c and Stat6 knockout (Stat6)- mice were fed 3–4% DSS in their water. Control animals received water. Animals were weighed and stool was checked for blood. On day 7 animals were sacrificed, the colon measured, and segments embedded in paraffin for histology. Colonic mucosa was harvested and assayed quantitatively by Western blot using a monoclonal antibody to ZO-1 and claudin-1. Results: DSS treated animals had heme positive stools, colitis by histology, significant weight loss and colon shortening (table). TABLE—ABSTRACT 87Control Balb/cControl Stat6-DSS Balb/cDSS Stat6-% Wt gain2.0 ± 0.5−0.8 ± 1.0−11.9 ± 1.8∗−14.8 ± 2.1∗Colon (cm)8.37 ± 0.149.83 ± 0.226.44 ± 0.35∗6.52 ± 0.27∗Mean ± standard error,∗P < 0.001 vs. appropriate control by ANOVA. There were no differences between Balb/c and Stat6- DSS treated animals. There was an absence of ZO-1 in the Balb/c DSS treated animals but normal levels in the Stat6- DSS treated animals (figure). There were no changes in claudin-1 expression with DSS treatment in either mouse type. Conclusions: 1: DSS ingestion caused weight loss, colonic shortening, bloody diarrhea and colitis. 2: These findings were the same in both the Balb/c and Stat6- mice. 3: ZO-1, but not claudin-1, was absent in the DSS treated Balb/c mice suggesting that the inflammatory process destroyed ZO-1. 4: An intact IL-4-stat6 activation pathway is necessary for colitis induced disruption of ZO-1 because Stat6- DSS treated mice did not show a decrease in ZO-1. IL-4 may be responsible for the disruption of ZO-1 in this model.