Acid and bile salts induce different effects on cell proliferation in human esophageal keratinocytes and Barrett's esophagus cells.

A222

Barrett's esophagus is a pre-malignant condition that develops in the context of mucosal injury from chronic gastro-esophageal reflux disease (GERD). This condition develops in 10-15% of patients with GERD. BE patients are at an elevated risk (30 to 45 times greater than the normal population) of developing esophageal adenocarcinoma. Barrett's esophagus occurs when the normal stratified squamous epithelium of the esophagus is replaced with a single layer of specialized columnar epithelium. The aim of this study is to determine if pulses of acid and bile, both alone and together, have different effects on cell proliferation of squamous cells and Barrett's esophagus cells both individually and in competition. A normal squamous cell line, EPC2, and four Barrett's Esophagus-derived columnar cell lines were used. In monoculture, total cells were counted at the end of each exposure, either to acidic media (pH 3.5) (n=4) for three minutes or bile salts (pH 7.4) (n=3) for 6 minutes and 1 hour daily for three days. The bile salt mixture was 1mM total of sodium glycocholate hydrate, taurocholic acid, glycocholic acid, and taurochenodeoxycholate. Multiple exposures of each treatment had a different effect on each cell line. Acid affected the cell lines differently, having a more dramatic effect on total cell number of squamous cells than the BE cells (p < 0.05). In the early BE cell line derived from non-dysplastic metaplasia, KR-42421, daily treatment with acid over 3 days did not reduce growth rate after the initial decline observed from the first acid exposure. EPC2 cells were equally affected from 1 to 3 days of acid pulses. However, the remaining BE cell lines, derived from high-grade dsyplasia, did demonstrate a decrease in growth rate after 3 days of acid pulses. In experiments with pulsed conjugated bile acids, 60 minutes of bile affected all cell lines approximately equally. However, with multiple pulses of bile for 6 minutes, EPC2's were more affected than some (KR-42421 and CP-52731, p<0.05) but not all of the BE cell lines. Some of the BE cell lines were equally susceptible as the squamous cells to bile's effects on cell proliferation (CP-94921 and CP18821). Most of the cell lines decreased growth rate compared with their respective controls over three days, with exception of EPC2 and CP18821. BE cell lines are more resistant to acid and bile exposure than normal esophageal squamous cells, in vitro. These differences suggest that BE cells are able to out compete squamous cells in the esophageal environment of acid-bile reflux. Our bile exposure results may also explain why the suppression of acid in patients, without suppressing bile reflux, generally does not lead to regression of BE.