Bile acids but not acidic acids induce Barrett's esophagus

Abstract

Barrett's esophagus (BE) is associated with the development of esophageal adenocarcinoma (EAC). Bile acids (BAs) refluxing into the esophagus contribute to esophageal injury, which results in BE and subsequent EAC. We developed two animal models to test the role of BAs in the pathogenesis of BE. We surgically generated BA reflux, with or without gastric acid, in rats. In a second experiment, we fed animals separately with BAs and gastric acid. Pathologic changes were examined and the expression of Muc2 and Cdx2 in BE tissue was tested by immunostaining. Inflammatory factors in the plasma, as well as differentiation genes in BE were examined through highly sensitive ELISA and semi-quantitative RT-PCR techniques. We found that BAs are sufficient for the induction of esophagitis and Barrett's-like metaplasia in the esophagus. Overexpression of inflammatory cells, IL-6, and TNF-α was observed both in animals fed with BAs and surgically generated BA reflux. Furthermore, elevated levels of Cdx2, Muc2, Bmp4, Kit19, and Tff2 (differentiation genes in BE) were found in BA-treated rats. In conclusion, BAs, but not gastric acid, are a major causative factor for BE. We confirmed that BAs contribute to the development of BE by inducing the inflammatory response in the esophagus. Inhibiting BAs may be a promising therapy for BE.

Keywords: Barrett’s esophagus; bile acids; esophageal adenocarcinoma; esophageal reflux.

Figures

Figure 1

Appearance of esophagus after 6 month of surgery. C/H show the gross appearance of the intact esophagus. A/F and B/G display the apperance of that suffered from 6 months of reflux due to surgical procedues (A/F, duodenoesophageal reflux; B/G, duodenogastroesophageal reflux). Surgical group rats show abnormally dilated esophagus, and esophageal inner surface displays nodular patches (arrow in G) and ulcers (arrow in F). D/I and E/J show the esophagus of animals fed with exogenous chemicals (D/I, bile acids feeding; E/J, acidic water feeding). The mucosa of these two groups become thick and nodular patches occur (arrow in G).

Figure 2

Histopathology of esophageal. The sham group A/C show the nomal squamous epithelium. Barrett’s epithelium, B/D intestinal type mucosa is present and bound on either side by squamous epithelium. Arrows indicate goblet cells in metaplastic epithelium.

Figure 3

Representative results of Muc2 and Cdx2 immunohistochemical staining on esophageal specimens. A. Marked positive staining for Muc2 (brown) in the glandular component of BE (200 ×). B. Expression of Cdx2 (brown) in the nuclei of BE areas (200 ×).

Figure 4

The inflammatory cytokines in the plasma of rats were checked for IL-6 (A) and TNF-α (B). Both surgeries and compounds increased the plasma level of IL-6 and TNF-α. However, no obvious difference between group A and group B in IL-6 and TNF-α levels was observed. Meanwhile, more inflammatory cytokines were observed in group D than in group E. (*P < 0.05 data are represented as the mean ± SEM).

Figure 5

mRNA expression (RT-qPCR) of Muc2, Cdx2, Bmp4, Krt19, and Tff2 in the tissue of BA-treated rats and acidic acid-treated rats (*P < 0.05 data are represented as the mean ± SEM).