Activation of the interleukin-6/STAT3 antiapoptotic pathway in esophageal cells by bile acids and low pH: relevance to barrett's esophagus.
OBJECTIVE
The molecular factors contributing to the development of Barrett's esophagus (BE) are unclear. Our previous studies showed that BE tissues secrete interleukin-6 (IL-6) and express proteins associated with IL-6 signaling, including IL-6 receptor, activated signal transducer and activators of transcription 3 (STAT3), and antiapoptotic proteins Bcl-x(L) and Mcl-1. Here, we test the hypothesis that bile acids and gastric acids, two components of refluxate associated with gastresophageal reflux disease, activate the IL-6/STAT3 pathway.


METHODS
Immunohistochemistry was used to assess levels of phosphorylated STAT3 in esophageal tissue samples from BE patients with different grades of dysplasia. Seg-1 esophageal adenocarcinoma cells were evaluated for STAT3 activation and IL-6 and Bcl-x(L) expression by molecular biology techniques, including Western blot, reverse transcription-PCR, and ELISA after exposure to control media (pH 7.4), media supplemented with a 0.1 mmol/L bile acid cocktail with media at pH 4 or media at pH 4 with bile acid cocktail.


RESULTS
Immunohistochemical analysis showed that activated, phosphorylated STAT3 is expressed in nuclei of dysplastic BE and cancer tissues. Treatment of Seg-1 cells with media containing bile acid cocktail and acidified to pH 4 resulted in increased activation of STAT3, IL-6 secretion, and increased expression of Bcl-x(L). Inhibition of the STAT3 pathway using STAT3 small interfering RNA or Janus-activated kinase inhibitor resulted in increased apoptosis.


CONCLUSIONS
The IL-6/STAT3 antiapoptotic pathway is induced by short exposure to bile acid cocktail and low pH. This alteration, if persistent in vivo, may underlie the development of dysplastic BE and tumor progression.
Dvorak
Katerina
K
Department of Cell Biology and Anatomy, College of Medicine, The University of Arizona, Tucson, Arizona 85724, USA. kdvorak@email.arizona.edu
Chavarria
Melissa
M
Payne
Claire M
CM
Ramsey
Lois
L
Crowley-Weber
Cara
C
Dvorakova
Barbora
B
Dvorak
Bohuslav
B
Bernstein
Harris
H
Holubec
Hana
H
Sampliner
Richard E
RE
Bernstein
Carol
C
Prasad
Anil
A
Green
Sylvan B
SB
Garewal
Harinder
H
D000230:Adenocarcinoma / Q000737:chemistry / Q000378:metabolism / Q000473:pathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis; D001471:Barrett Esophagus / Q000378:metabolism* / Q000473:pathology; D001647:Bile Acids and Salts / Q000378:metabolism* / Q000494:pharmacology; D004938:Esophageal Neoplasms / Q000737:chemistry / Q000378:metabolism / Q000473:pathology; D004947:Esophagus / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D005260:Female; D005744:Gastric Acid / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein / Q000235:genetics / Q000378:metabolism
D001647:Bile Acids and Salts; D015850:Interleukin-6; D012333:RNA, Messenger; D050796:STAT3 Transcription Factor; D051020:bcl-X Protein