Cholangiocyte endothelin 1 and transforming growth factor beta1 production in rat experimental hepatopulmonary syndrome.
OBJECTIVE
Hepatic production and release of endothelin 1 plays a central role in experimental hepatopulmonary syndrome after common bile duct ligation by stimulating pulmonary endothelial nitric oxide production. In thioacetamide-induced nonbiliary cirrhosis, hepatic endothelin 1 production and release do not occur, and hepatopulmonary syndrome does not develop. However, the source and regulation of hepatic endothelin 1 after common bile duct ligation are not fully characterized. We evaluated the sources of hepatic endothelin 1 production after common bile duct ligation in relation to thioacetamide cirrhosis and assessed whether transforming growth factor beta1 regulates endothelin 1 production.


METHODS
Hepatopulmonary syndrome and hepatic and plasma endothelin 1 levels were evaluated after common bile duct ligation or thioacetamide administration. Cellular sources of endothelin 1 were assessed by immunohistochemistry and laser capture microdissection of cholangiocytes. Transforming growth factor beta1 expression and signaling were assessed by using immunohistochemistry and Western blotting and by evaluating normal rat cholangiocytes.


RESULTS
Hepatic and plasma endothelin 1 levels increased and hepatopulmonary syndrome developed only after common bile duct ligation. Hepatic endothelin 1 and transforming growth factor beta1 levels increased over a similar time frame, and cholangiocytes were a major source of each peptide. Transforming growth factor beta1 signaling in cholangiocytes in vivo was evident by increased phosphorylation and nuclear localization of Smad2, and hepatic endothelin 1 levels correlated directly with liver transforming growth factor beta1 and phosphorylated Smad2 levels. Transforming growth factor beta1 also stimulated endothelin 1 promoter activity, expression, and production in normal rat cholangiocytes.


CONCLUSIONS
Cholangiocytes are a major source of hepatic endothelin 1 production during the development of hepatopulmonary syndrome after common bile duct ligation, but not in thioacetamide-induced cirrhosis. Transforming growth factor beta1 stimulates cholangiocyte endothelin 1 expression and production. Cholangiocyte-derived endothelin 1 may be an important endocrine mediator of experimental hepatopulmonary syndrome.
Luo
Bao
B
Department of Internal Medicine and Liver Center, University of Alabama at Birmingham, 35294, USA.
Tang
Liping
L
Wang
Zhishan
Z
Zhang
Junlan
J
Ling
Yiqun
Y
Feng
Wenguang
W
Sun
Ju-Zhong
JZ
Stockard
Cecil R
CR
Frost
Andra R
AR
Chen
Yiu-Fai
YF
Grizzle
William E
WE
Fallon
Michael B
MB
D000818:Animals; D001483:Base Sequence; D015415:Biomarkers / Q000032:analysis; D001707:Biopsy, Needle; D001784:Blood Gas Analysis; D015152:Blotting, Northern; D015153:Blotting, Western; D002478:Cells, Cultured; D004195:Disease Models, Animal; D019332:Endothelin-1 / Q000032:analysis / Q000378:metabolism*; D020065:Hepatopulmonary Syndrome / Q000378:metabolism* / Q000473:pathology*; D007150:Immunohistochemistry; D008111:Liver Function Tests; D008297:Male; D008969:Molecular Sequence Data; D011336:Probability; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D016212:Transforming Growth Factor beta / Q000032:analysis / Q000378:metabolism*; D053773:Transforming Growth Factor beta1
D015415:Biomarkers; D019332:Endothelin-1; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1