Duodenogastric reflux and foregut carcinogenesis: analysis of duodenal juice in a rodent model of cancer

Abstract

The incidence of esophageal adenocarcinoma is increasing rapidly. In rats, surgically induced duodenoesophageal reflux is carcinogenic. One proposed mechanism of carcinogenesis is based on the reaction of physiological bile acids with nitrite to produce carcinogenic N:-nitroso amides. To test this hypothesis, duodenal juice was analyzed for endogenously formed N:-nitroso bile acids and its genotoxicity was determined. Esophagojejunostomy was performed on 15 Sprague-Dawley rats to produce duodeno-esophageal reflux. At the time of surgery and 2 and 6 weeks later, duodenal contents were aspirated and analyzed immediately. High performance liquid chromatography coupled to tandem mass spectrometry was used to detect bile acids and their nitroso derivates. Genotoxicity was assessed using a micronucleus test. The characteristic pattern of bile acid derivatives, with taurocholic acid (TCA) and glycocholic acid (GCA) as the predominant conjugates, was detected in all samples. However, even selective reaction monitoring experiments failed to demonstrate the presence of any N:-nitroso-TCA or N:-nitroso-GCA. In addition, other nitroso derivatives could not be detected in any of the samples by neutral loss experiments monitoring the loss of nitric oxide (detection limit 0.1% of the concentration of TCA). All samples were cytotoxic, but neither the preoperative nor the postoperative samples were genotoxic. Duodenal juice was cytotoxic but not genotoxic. Tumorigenesis of esophageal adenocarcinoma in the rodent model could not be linked to a specific carcinogen, especially not to nitroso bile acids. Chronic inflammation is likely to be the mechanism of carcinogenesis by duodenogastric reflux.

Mechanisms of oxidant production in esophageal squamous cell and Barrett's cell lines

“…A number of animal models for GERD have linked the generation of ROS with the development of reflux esophagitis, Barrett's esophagus, and esophageal adenocarcinoma (5,6,10,11,14,27). In normal human bronchial epithelial cells, oxidative stress has been shown to induce the expression of the MUC5AC and acetylated tubulin, proteins that characterize the intestinal metaplasia of Barrett's esophagus (2).…”

Barrett's esophagus and animal models

“…Barrett's esophagus (BE), the precursor of EAC, results from chronic injury to the esophagus from acid and bile 17,18 . The Levrat's surgical model of esophago‐duodenal anatomosis in rats has been shown to induce gastroduodenojejunal reflux 4,19,20 . This in vivo model reproduces the sequence of histologic and molecular events that lead to the development of BE and EAC in humans and, as such, provides a realistic and translatable model for development of therapeutics for EAC 21 …”

Activation of MUC1 mucin expression by bile acids in human esophageal adenocarcinomatous cells and tissues is mediated by the phosphatidylinositol 3-kinase

“…Bile acids, amphophilic derivatives of cholesterol, have been shown to enhance cellular transformation in vitro and are known promoters of gastrointestinal neoplasia in vivo. 42 Moreover, conjugated bile acids exacerbate esophageal mucosa injury either in combination with acid or alone, both in vitro or in animals 8,43,44 and humans. 45 Wide variations in biologic activity have been reported for individual bile acid fractions, and minor changes in the structure of bile acids dramatically alter their biologic effects.…”