Alterations in manganese superoxide dismutase expression in the progression from reflux esophagitis to esophageal adenocarcinoma.

BACKGROUND: Comprehensive understanding of the basic mechanisms in the progression of esophagitis, Barrett esophagus (BE), and esophageal adenocarcinoma (EAC) is urgently needed to develop a management strategy for an effective screening of BE and management of EAC. The aim of this study is to provide a detailed insight of the histology and the cellular and molecular events associated with the genesis of BE and EAC under the esophagoduodenal reflux conditions. METHODS: Esophagoduodenal anastomosis (EDA) was performed on rats. Animals were weighed weekly and killed after 1, 2, 3, 4, 5, and 6 months. The entire esophagi were examined for macroscopic and microscopic changes and for manganese superoxide dismutase (MnSOD) expression, and TUNEL (terminal deoxynucleotidyl transferase dUTP nick-end labeling) assay was performed. RESULTS: Morphological transformation from esophagitis (100% of animals) to BE (66% of animals) to EAC was observed after 3 months. There was marked loss of MnSOD expression in animals with esophagitis and BE at 1 and 2 months, with an increase in expression during the transformation to dysplasia and EAC. Increased proliferation and apoptosis was observed and reached a peak at months 1 and 2. Greatly increased levels of 8-hydroxy-deoxyguanosine was found during the progression to EAC. CONCLUSIONS: The morphological transformation of the esophageal mucosa is an adaptive process, and it is an important foundation for the transdifferentiation of BE and cancer. The significant loss of MnSOD expression to achieve BE and then the adaptive increase in expression to achieve dysplasia and EAC during this transformation may represent a predictive marker in identifying patients who will progress from BE to EAC.

Loss of manganese superoxide dismutase expression and activity in rat esophagus with external esophageal perfusion.

BACKGROUND: Manganese superoxide dismutase (MnSOD), the primary antioxidant enzyme that scavenges superoxide radicals found in the mitochondria, has been shown to protect oxygen-utilizing cells from the toxicity of the reactive oxygen species (ROS). Current studies in the animal esophageal reflux model are limited, and the reports on the relevance of protein expression level and enzymatic antioxidative activity of MnSOD in esophageal mucosal defense are controversial. Thus, the aim of this study is to investigate the role of MnSOD expression and activity in rats with esophageal perfusion injury. METHODS: We have established a novel external esophageal perfusion (EEP) animal model that allows for esophageal reflux injury. We used the model with 0.5% bovine bile as the perfusion agent in one group of rats and used saline in another group to serve as controls. The esophageal mucosal was isolated for MnSOD expression and activity analysis. RESULTS: Severe esophagitis was observed in the mucosa at 1, 2, and 4 week(s) after bile perfusion. A significant decrease in MnSOD expression with bile perfusion was demonstrated by Western blotting and immunohistochemical evaluation. Similarly, a reduction in MnSOD enzyme activity was observed in bile-perfused rats compared with the saline-perfused controls; no decrease in copper/zinc SOD enzyme activity was observed. CONCLUSIONS: MnSOD expression and activity is decreased in bile-induced esophagitis. This decrease in MnSOD expression and activity is associated with esophagitis and cell death. This study suggests that the loss of MnSOD protein contributes to the reduced level of its enzymatic activity and plays a key role in the induction of esophagitis.

Cyclooxygenase-2 and epithelial growth factor receptor up-regulation during progression of Barrett's esophagus to adenocarcinoma.

AIM: To investigate the expression of cyclooxygenase-2 (COX-2) and epithelial growth factor receptor (EGFR) throughout the progression of Barretts esophagus (BE). METHODS: COX-2 and EGFR protein expressions were detected by using immunohistochemical method. A detailed cytomorphological changes were determined. Areas of COX-2 and EGFR expression were quantified by using computer Imaging System. RESULTS: The expressions of both COX-2 and EGFR increased along with the progression from BE to esophagus adenocarcinoma (EAC). A positive correlation was found between COX-2 expression and EGFR expression. CONCLUSION: COX-2 and EGFR may be cooperative in the stepwise progression from BE to EAC, thereby leading to carcinogenesis.

Esophageal injury with external esophageal perfusion.

BACKGROUND: External esophageal perfusion (EEP) with the idea that esophageal perfusion can be controlled with a single ingredient at a constant rate and concentration, might be used to dissect the injurious role of gastro-duodenal secretions for the progression from esophagitis to Barrett's esophagus (BE) and esophageal adenocarcinoma (EAC). This study is to evaluate the EEP rat model for esophagitis induced by using a micro-osmotic pump with bile perfusion. METHODS: Eighteen adult rats underwent the EEP procedure. Bile (0.5% bovine bile, pH 7.4) was used as perfusion agent and three types of perfusions were performed: 1 week perfusion, 2 weeks perfusion, and 4 weeks perfusion compared to saline perfusion and sham operation. Histological changes, cell proliferation, apoptosis, 8-hydroxy-deoxyguanosine (8-OH-dG) and Manganese superoxide dismutase (MnSOD) were observed after perfusion and compared. RESULTS: The bile perfusion for 1 week, 2 weeks, and 4 weeks induced mucosa infiltration of inflammatory cells, basal cell hyperproliferation, and papillae hypertrophy in all animals. Histopathology and cellular changes consistent with the findings associated with reflux esophagitis. The apoptotic index, the proliferating index, and expression of 8-OH-dG were significantly increased in the esophageal mucosa compared to controls. MnSOD expression was decreased with bile perfusion compared to saline controls. CONCLUSIONS: The external esophageal perfusion model enabled precise control of the injurious agent. It induced the typical histological injury and cellular changes seen in severe reflux esophagitis. The cellular changes in apoptosis, proliferation and anti-oxidant defense make this model unique for reflux esophagitis studies. Further studies are needed to induce Barrett's esophagus and esophageal adenocarcinoma.