Abstract 4077: Exposure to bile acids alters intracellular expression of MnSOD in Barrett's esophagus

Abstract

Abstract Introduction: Oxidative stress secondary to bile acid exposure has been associated with metaplastic degeneration of normal esophageal mucosa into Barrett's Esophagus cells and eventually Esophageal Adenocarcinoma. We have previously reported that the macromolecular response of BE cells to this stress is largely regulated by the expression of Manganese Superoxide Dismutase (MnSOD). As the mitochondrion plays a vital role in MnSOD activation, the purpose of this study was to determine the location and activity of MnSOD within the BE cell after exposure to oxidative stress. Methods: BE cells were cultured to 80-90% confluence in 75ml flasks. The cells were then exposed for four hours to 0.4mM concentrations of taurocholic acid (TCA) or a 0.4mM 1:1 mixture of bile salts including sodium cholate (CA), sodium deoxycholate (DCA), sodium glycocholate (GCA), and sodium taurocholate (TCA) to mimic natural biliary refluxate. Proteins were extracted and separated into mitochondrial, nuclear, and cytoplasmic fragments followed by western blot analysis. Enzymatic Activity of MnSOD was determined by silencing of other SOD molecules with potassium cyanate. Lethality testing of biliary exposure was performed with MTT assays. Results: Mitochondrial expression of MnSOD was significantly increased in the cells exposed to a mixture of bile acids vs. TCA and control. This was present on both qualitative and quantitative analyses of Western blots. Cytoplasmic expression of MnSOD was also present and conserved between treated and untreated cells. Control cells lines showed no significant change in baseline MnSOD expression. This expression was confirmed by increased MnSOD activity in the mitochondria of cells exposed to mixed bile. The lethality of mixed bile for Barrett's cells was confirmed by MTT assay, with isolated bile salts and controls having a significantly higher fraction of living cells. Conclusion: This is the first study to evaluate microcellular MnSOD expression which is increased in BE cells in response to the oxidative stress of bile exposure, specifically in the mitochondrion. Mitochondrial MnSOD activity is increased within the BE cell after exposure to bile. Further investigation is required to determine the potential correlation between bile exposure and BE to adenocarcinoma progression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4077. doi:10.1158/1538-7445.AM2011-4077