Submitted on April 13, 2005
Accepted on October 15, 2005
Bile Salt Exposure Increases Proliferation Through p38 and ERK-MAPK Pathways in a Non-Neoplastic Barrett's Cell Line
Kshama Jaiswal1, Christie Lopez-Guzman1, Rhonda F. Souza1, Stuart J. Spechler1, and George A. Sarosi, Jr.1*
1 Department of Surgery, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA; Department of Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA; Gastroenterology, University of Texas Health Center, Dallas, TX, USA
* To whom correspondence should be addressed. E-mail: George.Sarosi{at}utsouthwestern.edu.
Introduction: Bile reflux has been implicated in the neoplastic progression of Barrett's esophagus (BE). Bile salts increase proliferation in a Barrett's-associated adenocarcinoma cell line (SEG-1) by activating ERK and p38- MAPK pathways. However, it is not clear that these findings in cancer cells are applicable to the non-neoplastic cells of benign Barrett's esophagus. We examined the effect of bile salts on three human cell lines: normal esophageal squamous (NES), non-neoplastic Barrett's cells (BAR), and a Barrett's derived adenocarcinoma cell line, SEG-1. We hypothesized that bile salt exposure activates pro-proliferative and anti-apoptotic pathways to promote increased growth in BE. Methods: NES, BAR, and SEG-1 cells were exposed to glycochenodeoxycholic acid (GCDA) at a neutral pH for 5 minutes. Proliferation was measured by Coulter counter cell counts and BrdU incorporation assay. GCDA-induced MAPK activation was examined by Western blot for phosphorylated ERK and p38. Apoptosis was measured by TUNEL and Annexin-V staining after GCDA and UV-B exposure. Statistical significance was determined by ANOVA. Results: NES cells exposed to 5 minutes of GCDA did not increase cell number. In BAR cells, GCDA exposure increased cell number by 31%, increased phosphorylated p38 and ERK levels by 2-3 fold, increased BrdU incorporation by 30%, and decreased UV-induced apoptosis by 15-20%. Conclusion: In a non-neoplastic Barrett's cell line, GCDA exposure induces proliferation by activation of both the ERK and p38 MAPK pathways. These findings suggest a potential mechanism whereby bile reflux may facilitate the neoplastic progression of Barrett's esophagus.
