Cytokine-independent repression of rodent Ntcp in obstructive cholestasis
Cytokine-independent repression of rodent Ntcp in obstructive cholestasis
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DOI：
10.1002/hep.20594
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发表时间：
2005-03-01
期刊：
影响因子：
13.5
通讯作者：
Trauner, M
中科院分区：
文献类型：
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作者：
Geier, A;Zollner, G;Trauner, M
胆汁淤积性肝损伤不仅与胆汁酸的积累有关，而且与促炎细胞因子的激活有关。胆总管结扎（CBDL）诱导Na+/牛磺胆酸共转运蛋白（Ntcp）在啮齿动物肝脏中的持续下调。虽然内毒素血症期间Ntcp的抑制是细胞因子介导的，但目前尚不清楚炎症细胞因子是否有助于梗阻性胆汁淤积的下调。CBDL大鼠和小鼠的细胞因子失活可以直接通过肿瘤坏死因子α（依那西普）或白细胞介素1 β失活（阿那白/AMG 719）进行，也可以通过脂质体包裹的二氯甲基二膦酸盐腹腔注射间接库普弗细胞失活。Western和Northern blotting分析Ntcp和短异源二聚体伴侣（short heterodimer partner， SHP）蛋白和信使RNA （mRNA）的表达。通过电泳迁移位移分析和核Western blot分析研究Ntcp的关键调控因子（肝细胞核因子1 α [hnf - 1α]、hnf - 4α、类视黄X受体α [rxrα]：视黄酸受体α [rar α]）。两种细胞因子失活方法都未能在CBDL后3天内维持大鼠或小鼠（20%-40%的假对照组）Ntcp蛋白或mRNA的表达，而SHP mRNA的表达增加了3至5倍。在CBDL后细胞因子失活期间，核hnf -1 α和hnf -4 α蛋白水平（分别为假手术对照组的45%和60%）和hnf -1 α结合活性（假手术对照组的32%）的降低并未恢复，这表明Ntcp的调节机制不依赖于细胞因子。RXRalpha: RXRalpha结合在所有实验条件下均保持不变。总之，在梗阻性胆汁淤积过程中，胆汁本身的积累，而不是细胞因子的主要贡献，通过抑制hnf -1 α和hnf -4 α导致Ntcp的下调。
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-1alpha], HNF-4alpha, retinoid X receptor alpha [RXRalpha]:retinoic acid receptor alpha [RARalpha]) 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-1alpha and HNF-4alpha protein levels (45% and 60% of sham controls, respectively) and HNF-1alpha binding activity (32% of sham controls) were not restored during cytokine inactivation after CBDL, indicating cytokine-independent mechanisms of Ntcp regulation. RXRalpha:RARalpha binding remained unchanged in all experimental conditions. In conclusion, during obstructive cholestasis accumulating bile adds per se, without major contribution of cytokines, leads to downregulation of Ntcp via repression of HNF-1alpha and HNF-4alpha.