Bile acids in combination with low pH induce oxidative stress and oxidative DNA damage: relevance to the pathogenesis of Barrett's oesophagus.
BACKGROUND
Barrett's oesophagus is a premalignant condition associated with an increased risk for the development of oesophageal adenocarcinoma (ADCA). Previous studies indicated that oxidative damage contributes to the development of ADCA.


OBJECTIVE
To test the hypothesis that bile acids and gastric acid, two components of refluxate, can induce oxidative stress and oxidative DNA damage.


METHODS
Oxidative stress was evaluated by staining Barrett's oesophagus tissues with different degrees of dysplasia with 8-hydroxy-deoxyguanosine (8-OH-dG) antibody. The levels of 8-OH-dG were also evaluated ex vivo in Barrett's oesophagus tissues incubated for 10 min with control medium and medium acidified to pH 4 and supplemented with 0.5 mM bile acid cocktail. Furthermore, three oesophageal cell lines (Seg-1 cells, Barrett's oesophagus cells and HET-1A cells) were exposed to control media, media containing 0.1 mM bile acid cocktail, media acidified to pH 4, and media at pH 4 supplemented with 0.1 mM bile acid cocktail, and evaluated for induction of reactive oxygen species (ROS).


RESULTS
Immunohistochemical analysis showed that 8-OH-dG is formed mainly in the epithelial cells in dysplastic Barrett's oesophagus. Importantly, incubation of Barrett's oesophagus tissues with the combination of bile acid cocktail and acid leads to increased formation of 8-OH-dG. An increase in ROS in oesophageal cells was detected after exposure to pH 4 and bile acid cocktail.


CONCLUSIONS
Oxidative stress and oxidative DNA damage can be induced in oesophageal tissues and cells by short exposures to bile acids and low pH. These alterations may underlie the development of Barrett's oesophagus and tumour progression.
Dvorak
Katerina
K
Department of Cell Biology and Anatomy, PO Box 245044, University of Arizona, Tucson, AZ 85724, USA. kdvorak@email.arizona.edu.
Payne
Claire M
CM
Chavarria
Melissa
M
Ramsey
Lois
L
Dvorakova
Barbora
B
Bernstein
Harris
H
Holubec
Hana
H
Sampliner
Richard E
RE
Guy
Naihsuan
N
Condon
Amanda
A
Bernstein
Carol
C
Green
Sylvan B
SB
Prasad
Anil
A
Garewal
Harinder S
HS
D000080242:8-Hydroxy-2'-Deoxyguanosine; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis / Q000187:drug effects; D001471:Barrett Esophagus / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D001647:Bile Acids and Salts / Q000494:pharmacology / Q000502:physiology*; D001706:Biopsy; D003470:Culture Media; D004249:DNA Damage; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism; D018450:Disease Progression; D004947:Esophagus / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D018384:Oxidative Stress / Q000187:drug effects; D014407:Tumor Cells, Cultured
D001647:Bile Acids and Salts; D003470:Culture Media; D000080242:8-Hydroxy-2'-Deoxyguanosine; D003849:Deoxyguanosine