A novel mechanism of acid and bile acid-induced DNA damage involving Na+/H+ exchanger: implication for Barrett's oesophagus.

TitleA novel mechanism of acid and bile acid-induced DNA damage involving Na+/H+ exchanger: implication for Barrett's oesophagus.
Publication TypeJournal Article
Year of Publication2010
AuthorsGoldman A, Shahidullah M, Goldman D, Khailova L, Watts G, Delamere N, Dvorak K
JournalGut
Volume59
Issue12
Pagination1606-16
Date Published2010 Dec
ISSN1468-3288
KeywordsBarrett Esophagus, Bile Acids and Salts, Cation Transport Proteins, Cell Line, DNA Damage, Dose-Response Relationship, Drug, Drug Synergism, Enzyme Activation, Esophagus, Humans, Hydrochloric Acid, Hydrogen-Ion Concentration, Nitric Oxide, Nitric Oxide Synthase, Reverse Transcriptase Polymerase Chain Reaction, RNA, Messenger, Sodium-Hydrogen Antiporter
Abstract

OBJECTIVE: Barrett's oesophagus is a premalignant disease associated with oesophageal adenocarcinoma. The major goal of this study was to determine the mechanism responsible for bile acid-induced alteration in intracellular pH (pH(i)) and its effect on DNA damage in cells derived from normal oesophagus (HET1A) or Barrett's oesophagus (CP-A).

DESIGN: Cells were exposed to bile acid cocktail (BA) and/or acid in the presence/absence of inhibitors of nitric oxide synthase (NOS) or sodium-hydrogen exchanger (NHE). Nitric oxide (NO), pH(i) and DNA damage were measured by fluorescent imaging and comet assay. Expression of NHE1 and NOS in cultured cells and biopsies from Barrett's oesophagus or normal squamous epithelium was determined by RT-PCR, immunoblotting or immunohistochemistry.

RESULTS: A dose dependent decrease in pH(i) was observed in CP-A cells exposed to BA. This effect of BA is the consequence of NOS activation and increased NO production, which leads to NHE inhibition. Exposure of oesophageal cells to acid in combination with BA synergistically decreased pH(i). The decrease was more pronounced in CP-A cells and resulted in >2-fold increase in DNA damage compared to acid treatment alone. Examination of biopsies and cell lines revealed robust expression of NHE1 in Barrett's oesophagus but an absence of NHE1 in normal epithelium.

CONCLUSIONS: The results of this study identify a new mechanism of bile acid-induced DNA damage. We found that bile acids present in the refluxate activate immediately all three isoforms of NOS, which leads to an increased NO production and NHE inhibition. This consequently results in increased intracellular acidification and DNA damage, which may lead to mutations and cancer progression. Therefore, we propose that in addition to gastric reflux, bile reflux should be controlled in patients with Barrett's oesophagus.

DOI10.1136/gut.2010.213686
Alternate JournalGut
PubMed ID20876775
PubMed Central IDPMC3087378
Grant ListP30 CA023074 / CA / NCI NIH HHS / United States
T32 CA009213-33 / CA / NCI NIH HHS / United States
P50 CA095060-09 / CA / NCI NIH HHS / United States
CA95060 / CA / NCI NIH HHS / United States
P30 ES006694 / ES / NIEHS NIH HHS / United States
CA023074-26 / CA / NCI NIH HHS / United States
EY06951 / EY / NEI NIH HHS / United States
P50 CA095060 / CA / NCI NIH HHS / United States
T32 CA009213 / CA / NCI NIH HHS / United States
R01 EY006915-22 / EY / NEI NIH HHS / United States
R01 EY006915 / EY / NEI NIH HHS / United States
Faculty Member Reference: 
George Watts, Ph.D.