Dissociation and Dispersion of Claudin-3 From Tight Junction is a Most Sensitive Diagnostic Indicator of Reflux Esophagitis in a Rat Model

Abstract

Background: Tight junction (TJ) is considered to be an important contributor to the epithelial defense system. However, TJ in the esophagus has not been well elucidated. Claudins are a family of TJ transmembrane proteins. They are both structurally and functionally essential components of TJ strands, and play a critical role in the TJ barrier In a previous study, we reported altered location pattern of epithelial claudin-1, -3, -4 proteins in a rat chronic acid esophagitis model using immunofluorescence analysis. The aim of this study is to characterize pathological lesions of the esophageal epithelial tight junction complex in a rat reflux esophagitis model in a search for a reliable diagnostic indicator. Methods: Rats underwent the operation to induce reflux esophagitis with or without Rabeprazole treatment (1.0mg/ kg/day and 10.0mg/kg/day). Sham-operated rats served as a control. Each group comprising more than 3 animals in each experiment. Fourteen days after the operation, esophagi were isolated from the rats and subjected to double-label confocal immunofluorescent microscopy, and biochemical analyses. Results: Immunofluorescent microscopy revealed claudins-1, -3, and -4 were located on the surface of epithelial cells in normal esophagus, although there were differences in the distribution patterns between claudin-3 and claudins-1 or -4 in the epithelial layer. However, in reflux esophagitis, the immunoreactivity of claudin-3 on the cell surface was significantly decreased, and it appeared instead as a faint granular pattern within the epithelial cytoplasm. Claudin-3 expression in the entire esophageal epithelium was also decreased. Expression and location of claudin-1 and -4 in epithelial cells were basically unaffected in reflux esophagitis. Gastric acid-induced dissociation of claudin-3 elicited instability of the epithelial tight junction complex, which was confirmed by sedimentation analysis using centrifugation in a sucrose density gradient. Rabeprazole (10.0mg/ kg/day) significantly attenuated these alterations. Conclusions: Our data indicate that dispersion of claudin-3 from esophageal epithelial plasmamembranes to cytoplasm and the resulting instability of the tight junction complex is a most specific and sensitive indicator for monitoring inflammatory and recovery processes in reflux esophagitis.