Helicobacter pylori Induces Apoptosis in Barrett's Derived Human Esophageal Adenocarcinoma
Abstracts
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Background: It has been proposed that colonization with cagA+ Helicobacter pylori (Hp) strains may actually be protective against the development of dysplasia in Barrett's epithelium of patients with gastroesophageal reflux disease (GERD). The specific mechanism behind this Hp-protective effect in GERD is not entirely known. The aim of the present study was to investigate whether one of the Hp protective effects in GERD may be due to the direct effects of Hp by increasing apoptosis in Barrett's esophageal cells. Methods: A Barrett's-derived adenocarcinoma cell line (OE33) was grown on plastic dishes. Hp wild-type (WT) 60190, 84-183 strains, 60190-v1 (isogenic VacA-negative mutant), and 84-183M22 (isogenic CagA-negative mutant) strains were grown on agar plates. Hp were harvested and used as intact bacteria or as bacterial sonicates to treat OE33 cells for 24 or 48 hrs. Western immunoblotting was used to detect FAS protein expression, and Hoechst-dye binding to measure apoptosis. Results: The addition of intact Hp WT strains to OE33 cells produced significant (P < 0.05) dose-dependent increases in OE33 apoptosis, with a maximal 19.6 ±0.7% (WT 60190) and 18.7 ±0.8% (WT 84-183) apoptosis over controls at 1x108 cfu/ml. Heat-killed Hp produced no apoptosis. The addition of Hp WT sonicates (0-30 µg/ml) also produced dose- and time-dependent changes in OE33 apoptosis. Relative to the camptothecin control, OE33 cells treated for 24 hrs with sonicates (30 µg/ml) of WT, cagA-, and vacA- had significantly (P < 0.05) increased apoptosis over controls by 21 ±0.3%, 13 ±0.3%, and 7.0 ±0.3%, respectively. The addition of WT Hp strains produced no change in OE33 FAS expression at 24-hrs. Conclusions: 1) H. pylori can induce apoptosis in Barrett's-derived adenocarcinoma that was not dependent on Fas expression; and 2) wild-type H. pylori was more effective than H. pylori cagA- and vacA- strains in producing apoptosis in these cells. |
