taurochenodeoxycholic-acid and Gastroesophageal-Reflux

Oesophageal exposure to duodenogastroesophageal refluxate is implicated in the development of Barrett's metaplasia (BM), with increased risk of progression to oesophageal adenocarcinoma. The literature proposes that reflux exposure activates NF-κB, driving the aberrant expression of intestine-specific caudal-related homeobox (CDX) genes. However, early events in the pathogenesis of BM from normal epithelium are poorly understood. To investigate this, our study subjected a 3D model of the normal human oesophageal mucosa to repeated, pulsatile exposure to specific bile components and examined changes in gene expression. Initial 2D experiments with a range of bile salts observed that taurochenodeoxycholate (TCDC) impacted upon NF-κB activation without causing cell death. Informed by this, the 3D oesophageal model was repeatedly exposed to TCDC in the presence and absence of acid, and the epithelial cells underwent gene expression profiling. We identified ~300 differentially expressed genes following each treatment, with a large and significant overlap between treatments. Enrichment analysis (Broad GSEA, DAVID and Metacore™; GeneGo Inc) identified multiple gene sets related to cell signalling, inflammation, proliferation, differentiation and cell adhesion. Specifically NF-κB activation, Wnt signalling, cell adhesion and targets for the transcription factors PTF1A and HNF4α were highlighted. Our data suggest that HNF4α isoform switching may be an early event in Barrett's pathogenesis. CDX1/2 targets were, however, not enriched, suggesting that although CDX1/2 activation reportedly plays a role in BM development, it may not be an initial event. Our findings highlight new areas for investigation in the earliest stages of BM pathogenesis of oesophageal diseases and new potential therapeutic targets.

Topics: Adenocarcinoma; Barrett Esophagus; Bile Acids and Salts; Bile Reflux; Cell Line; Cells, Cultured; Epithelial Cells; Esophageal Neoplasms; Esophagus; Gastroesophageal Reflux; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Hepatocyte Nuclear Factor 4; Humans; Hydrogen-Ion Concentration; Mucous Membrane; NF-kappa B; Oligonucleotide Array Sequence Analysis; Protein Isoforms; Taurochenodeoxycholic Acid; Transcription Factors

The pathogenesis of alkaline reflux esophagitis was investigated in an experimental model by assessing individually the influence of different bile salt moieties and trypsin on esophageal mucosa. An isolated segment of rabbit esophagus was perfused at pH 7 with a solution containing the test agent under study, and the severity of mucosal damage was assessed by using as indicators of mucosal integrity transmucosal potential difference, net flux of Na+, and mucosal permeability to two neutral molecules of different sizes, 3H-H2O and 14C-erythritol. The data indicate that the secondary dihydroxy bile salt, deoxycholate, in its deconjugated form was highly injurious to esophageal mucosa; it was the only test agent that caused gross mucosal lesions during the experiment. The respective conjugated bile salt moiety, taurodeoxycholate, had a weaker effect. Also the primary dihydroxy bile salt, chenodeoxycholate, in its deconjugated form caused moderate damage to the mucosa, whereas its conjugated form, taurochenodeoxycholate, had no effect. The effect of the other three bile salts tested--cholate, taurocholate, and taurolithocholate--was negligible. Trypsin also adversely affected the mucosa, but its effect was weaker than that of deoxycholate. The results suggest that the deconjugated bile salts deoxycholate and chenodeoxycholate (which are formed following bacterial colonization of the upper gastrointestinal tract in the absence of gastric acid), the conjugated bile salt taurodeoxycholate, and the proteolytic enzyme trypsin may have significant roles in the pathogenesis of alkaline reflux esophagitis.

Topics: Alkalies; Animals; Bile Acids and Salts; Chenodeoxycholic Acid; Cholic Acids; Deoxycholic Acid; Esophagus; Gastroesophageal Reflux; Rabbits; Taurochenodeoxycholic Acid; Taurocholic Acid; Taurodeoxycholic Acid; Taurolithocholic Acid; Trypsin