The evaluation of oesophageal function in patients with different types of oesophageal metaplasia

Role of ion transporters in the bile acid-induced esophageal injury

Barrett's esophagus (BE) is considered to be the most severe complication of gastro-esophageal reflux disease (GERD), in which the prolonged, repetitive episodes of combined acidic and biliary reflux result in the replacement of the squamous esophageal lining by columnar epithelium. Therefore, the acid-extruding mechanisms of esophageal epithelial cells (EECs) may play an important role in the defense. Our aim was to identify the presence of acid/base transporters on EECs and to investigate the effect of bile acids on their expressions and functions. Human EEC lines (CP-A and CP-D) were acutely exposed to bile acid cocktail (BAC) and the changes in intracellular pH (pHi) and Ca(2+) concentration ([Ca(2+)]i) were measured by microfluorometry. mRNA and protein expression of ion transporters was investigated by RT-PCR, Western blot, and immunohistochemistry. We have identified the presence of a Na(+)/H(+) exchanger (NHE), Na(+)/HCO3 (-) cotransporter (NBC), and a Cl(-)-dependent HCO3 (-) secretory mechanism in CP-A and CP-D cells. Acute administration of BAC stimulated HCO3 (-) secretion in both cell lines and the NHE activity in CP-D cells by an inositol triphosphate-dependent calcium release. Chronic administration of BAC to EECs increased the expression of ion transporters compared with nontreated cells. A similar expression pattern was observed in biopsy samples from BE compared with normal epithelium. We have shown that acute administration of bile acids differently alters ion transport mechanisms of EECs, whereas chronic exposure to bile acids increases the expression of acid/base transporters. We speculate that these adaptive processes of EECs represent an important mucosal defense against the bile acid-induced epithelial injury.

Lifetime risk of esophageal adenocarcinoma in patients with Barrett's esophagus

AIM: To investigate the lifetime risk of development of esophageal adenocarcinoma and/or high-grade dysplasia in patients diagnosed with Barrett’s esophagus.

METHODS: Data were extracted from the United Kingdom National Barrett’s Oesophagus Registry on date of diagnosis, patient age and gender of 7877 patients from who had been registered from 35 United Kingdom centers. Life expectancy was evaluated from United Kingdom National Statistics data based upon gender and age at year at diagnosis. These data were then used with published estimates of annual adenocarcinoma and high-grade dysplasia incidences from meta-analyses and large population-based studies to estimate overall lifetime risk of development of these study endpoints.

RESULTS: The mean age at diagnosis of Barrett’s esophagus was 61.6 years in males and 67.3 years in females. The mean life expectancy at diagnosis was 23.1 years in males, 20.7 years in females and 22.2 years overall. Using data from published meta-analyses, the lifetime risk of development of adenocarcinoma was between 1 in 8 and 1 in 14 and the lifetime risk of high-grade dysplasia or adenocarcinoma was 1 in 5 to 1 in 6. Using data from 3 large recent population-based cohort studies the lifetime risk of adenocarcinoma was between 1 in 10 and 1 in 37 and of the combined end-point of high-grade dysplasia and adenocarcinoma was between 1 in 8 and 1 in 20. Age at Barrett’s esophagus diagnosis is reducing and life expectancy is increasing, which will partially counter-balance lower annual cancer incidence.

CONCLUSION: There is a significant lifetime risk of development of high-grade dysplasia and adenocarcinoma in Barrett’s esophagus.