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Cytokine‐independent repression of rodent Ntcp in obstructive cholestasis
Author(s) -
Geier Andreas,
Zollner Gernot,
Dietrich Christoph G.,
Wagner Martin,
Fickert Peter,
Denk Helmut,
van Rooijen Nico,
Matern Siegfried,
Gartung Carsten,
Trauner Michael
Publication year - 2005
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1002/hep.20594
Subject(s) - endocrinology , cholestasis , downregulation and upregulation , cytokine , medicine , proinflammatory cytokine , tumor necrosis factor alpha , bile acid , biology , chemistry , inflammation , biochemistry , gene
Cholestatic liver injury is associated not only with accumulation of bile acids but also with activation of proinflammatory cytokines. Common bile duct ligation (CBDL) induces sustained downregulation of the Na + /taurocholate cotransporter (Ntcp) in rodent liver. Although repression of Ntcp during endotoxemia is cytokine mediated, it is unclear whether inflammatory cytokines contribute to this downregulation in obstructive cholestasis. Cytokine inactivation in CBDL rats and mice was either performed directly with tumor necrosis factor alpha (etanercept) or interleukin 1 beta inactivation (anakinra/AMG 719) or indirectly Kupffer cell depletion via intraperitoneal administration of liposome‐encapsulated dichloromethylene bisphosphonate. Protein and messenger RNA (mRNA) expression of Ntcp and short heterodimer partner (SHP) were analyzed via Western and Northern blotting. Key regulators of Ntcp (hepatocyte nuclear factor 1 alpha [HNF‐1α], HNF‐4α, retinoid X receptor alpha [RXRα]:retinoic acid receptor alpha [RARα]) were studied via electrophoretic mobility shift analysis and nuclear Western blot analysis. Both methods of cytokine inactivation failed to maintain Ntcp protein or mRNA expression within 3 days after CBDL in either rats or mice (20%‐40% of sham controls), while SHP mRNA expression increased three‐ to five‐fold. Decreased nuclear HNF‐1α and HNF‐4α protein levels (45% and 60% of sham controls, respectively) and HNF‐1α binding activity (32% of sham controls) were not restored during cytokine inactivation after CBDL, indicating cytokine‐independent mechanisms of Ntcp regulation. RXRα:RARα binding remained unchanged in all experimental conditions. In conclusion , during obstructive cholestasis accumulating bile acids per se , without major contribution of cytokines, leads to downregulation of Ntcp via repression of HNF‐1α and HNF‐4α. (H EPATOLOGY 2005;41:470–477.)