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Objective: Exposure of the oesophageal mucosa to gastric acid and bile acids leads to the accumulation of reactive oxygen species (ROS), a known risk factor for Barrett's oesophagus and progression to oesophageal adenocarcinoma (OAC). This study investigated the functions of glutathione peroxidase 7 (GPX7), frequently silenced in OAC, and its capacity in regulating ROS and its associated oxidative DNA damage., Design: Using in-vitro cell models, experiments were performed that included glutathione peroxidase (GPX) activity, Amplex UltraRed, CM-H(2)DCFDA, Annexin V, 8-oxoguanine, phospho-H2A.X, quantitative real-time PCR and western blot assays., Results: Enzymatic assays demonstrated limited GPX activity of the recombinant GPX7 protein. GPX7 exhibited a strong capacity to neutralise hydrogen peroxide (H(2)O(2)) independent of glutathione. Reconstitution of GPX7 expression in immortalised Barrett's oesophagus cells, BAR-T and CP-A led to resistance to H(2)O(2)-induced oxidative stress. Following exposure to acidic bile acids cocktail (pH4), these GPX7-expressing cells demonstrated lower levels of H(2)O(2), intracellular ROS, oxidative DNA damage and double-strand breaks, compared with controls (p<0.01). In addition, these cells demonstrated lower levels of ROS signalling, indicated by reduced phospho-JNK (Thr183/Tyr185) and phospho-p38 (Thr180/Tyr182), and demonstrated lower levels of apoptosis following the exposure to acidic bile acids or H(2)O(2)-induced oxidative stress. The knockdown of endogenous GPX7 in immortalised oesophageal squamous epithelial cells (HET1A) confirmed the protective functions of GPX7 against pH4 bile acids by showing an increase in the levels of H(2)O(2), intracellular ROS, oxidative DNA damage, double-strand breaks, apoptosis, and ROS-dependent signalling (p<0.01)., Conclusion: The dysfunction of GPX7 in oesophageal cells increases the levels of ROS and oxidative DNA damage, which are common risk factors for Barrett's oesophagus and OAC.

Background: Although prostaglandin E2 (PGE2), cyclooxygenase 2 (COX-2), and microsomal prostaglandin E synthase 1 (mPGES-1) are known to play a role in various inflammatory events, their roles in the pathogenesis of gastro-oesophageal reflux disease are not known., Aims: We examined the dynamics of COX-1, COX-2, mPGES-1, mPGES-2, cytosolic PGES (cPGES), and PGE2 synthetic activity in rat acid reflux oesophagitis and the effects of COX-2 inhibitors on the severity of oesophagitis., Methods: Acid reflux oesophagitis was induced by ligating the transitional region between the forestomach and the glandular portion and wrapping the duodenum near the pylorus. Rats were killed on day 3 (acute phase) or day 21 (chronic phase) after induction of oesophagitis., Results: Expression of COX-2 and mPGES-1 was markedly increased in oesophagitis while modest changes in COX-1, cPGES, and mPGES-2 expression were observed. COX-2 and mPGES-1 were colocalised in epithelial cells of the basal layer, as well as inflammatory and mesenchymal cells in the lamina propria and submucosa. COX-2 inhibitors significantly reduced the severity of chronic oesophagitis but did not affect acute oesophageal lesions. COX-2 inhibitors significantly inhibited the increase in PGE2 synthesis in oesophageal lesions on both days 3 and 21. Epithelial proliferation was significantly increased in the basal layer on day 21. Inflammatory cells and epithelial cells of the basal layer exhibited reactions for EP4 in oesophagitis., Conclusion: PGE2 derived from COX-2 and mPGES-1 plays a significant role in the pathogenesis of chronic acid reflux oesophagitis, and possibly in basal hyperplasia and persistent inflammatory cell infiltration.

Background: Cancer of the oesophagus has so far eluded every attempt at pharmacological treatment. The recent advent of somatic gene therapy offers a new therapeutic approach to malignant tumours., Aim: To investigate whether and how gene transfer into the oesophagus can be achieved., Methods: A LacZ reporter gene was used as marker and transferred into the oesophagus of rats using cationic liposomes. Gene transfer was achieved by either luminal instillation into a closed segment using a double balloon catheter, or by intramural injection through a needle. Expression of beta-galactosidase was monitored in the oesophagus and various control tissues by histochemistry, polymerase chain reaction (PCR), reverse transcriptase PCR, and Southern blotting., Results: Up to 100 days after in vivo gene transfer beta-galactosidase activity could be demonstrated in the oesophagus. Following luminal application, the transgene was expressed in epithelial cells whereas intramural injection induced preferential expression in fibroblasts., Conclusion: In vivo gene transfer into the esophagus is feasible and safe, and the route of administration largely determines cell type specificity. This novel approach will enable in vivo studies of growth, differentiation, and malignant transformation in the oesophagus, and may open new avenues to the confinement of oesophageal malignancies.

The human CYP3A subfamily is of interest due to its multiplicity, activity toward known carcinogens, and extrahepatic expression. In situ hybridisation analysis of formalin fixed, routinely processed biopsy specimens was used to localise CYP3A mRNA in human gastrointestinal tissues from several individuals. CYP3A mRNA is abundant in human liver and in mucosal epithelial cells of all segments of the human small intestine. RNA blot analyses showed that the mRNA species observed in most livers and in human small intestine represent CYP3A3/3A4 transcripts. This was confirmed at the protein level by immunoblot comparison of small intestine microsomes to in vitro expressed CYP3A4 and CYP3A5 proteins. In liver and small intestine, CYP3A mRNA is not uniformly distributed, with grain density highest in cells within the respective non-proliferative compartments. CYP3A mRNA was also observed in human oesophagus and colon. RNA blot analysis of multiple colons showed heterogeneity in the CYP3A mRNAs present. Two CYP3A mRNAs (CYP3A3/3A4 and CYP3A5) were detected in colon samples from several individuals. In addition to those localisation studies, the capacity of expressed CYP3A4 and CYP3A5 to activate the dietary heterocyclic amine MeIQ in the presence of alpha-naphthoflavone was shown. These results show that there is considerable heterogeneity in the expression of the CYP3A subfamily in human gastrointestinal tissues.

The cytochrome P450 superfamily of enzymes play a central part in the metabolism of carcinogens and anti-cancer drugs. The expression, cellular localisation, and distribution of different forms of P450 and the functionally associated enzymes epoxide hydrolase and glutathione S-transferases have been investigated in oesophageal cancer and non-neoplastic oesophageal tissue using immunohistochemistry. Expression of the different enzymes was confined to epithelial cells in both non-neoplastic samples and tumour samples except the CYP3A was also identified in mast cells and glutathione S-transferase pi was present in chronic inflammatory cells. CYP1A was present in a small percentage of non-neoplastic samples but both CYP2C and CYP3A were absent. Epoxide hydrolase was present in half of the non-neoplastic samples and the different classes of glutathione S-transferase were present in a low number of samples. In carcinomas CYP1A, CYP3A, epoxide hydrolase, and glutathione S-transferase pi were expressed in at least 60% of samples. The expression of glutathione S-transferases alpha and mu were significantly less in adenocarcinoma compared with squamous carcinoma.

The distribution of carbonic anhydrase isoenzymes I, II, and VI was studied in the human alimentary tract using specific antibodies to human isoenzymes in conjunction with the immunoperoxidase technique to elucidate the physiological role and possible functional interplay of carbonic anhydrases (CAs) in alimentary canal functions. From the isoenzymes studied, CA II was found to be the most widely distributed in the various epithelia throughout the alimentary canal. In addition to the acinar cells of the parotid and submandibular glands and the duodenal Brunner's glands, it was present in the mucosal epithelium of the oesophagus, stomach, duodenum, and colon. The epithelial cells of the hepatic bile ducts, gall bladder, and pancreatic ducts also contained CA II in abundance. In contrast, CA VI was present only in the serous acinar and ductal cells of the parotid and submandibular glands, and CA I in the mucosal epithelium of the colon and the A cells of the pancreatic Langerhans's islets. These results suggest that CA II as a widely distributed isoenzyme in the epithelia of the alimentary canal and CA VI as secreted into saliva, may form a mutually complementary system protecting oesophageal, gastric, and intestinal mucosa from acidity.

Oesophageal biopsies were obtained from 74 patinets undergoing upper gastrointestinal fibreoptic endoscopy. Thirteen patients with histological evidence of inflammation had a raised alkaline phosphatase activity (2.7 +/- 1.6 nmol/mg protein/min) compared with 49 normal controls (1.2 +/- 0.68 nmol/mg protein/min: P less than 0.001). The acid phosphatase level was lower (8.4+/- 4.0 vs. 5.8 +/- 2.2 nmol/mg protein/min: P less than 0.05) and the glucuronidase activity raised (0.44 +/- 0.17 vs 0.81 +/- 0.32 nmol/mg protein/min: P less than 0.001) and their ratio declined (24.0 +/- 1.9 nmol/mg protein/min: P less than 0.001) in patients with oesophagitis. This may be due to differential secretion of membrane coating granules, a form of lysosome found isophagitis--was assessed by point counting. The volume density rose from 10.9 +/- 4.25% in normal biopsies to 46.4+/-12.5% (P less than 0.001) in oesophagitis. These results show a consistent pattern that possibly indicates an intermediate stage between the clinically, histologically, and biochemically normal oesophagus and one that is inflamed on endoscopy.