Geier Andreas, Dietrich Christoph G, Voigt Sebastian, Kim Suk-Kyum, Gerloff Thomas, Kullak-Ublick Gerd A, Lorenzen Johann, Matern Siegfried, Gartung Carsten
Department of Internal Medicine III, University of Technology Aachen, Aachen, Germany.
Hepatology. 2003 Aug;38(2):345-54. doi: 10.1053/jhep.2003.50317.
Hepatobiliary transporters are down-regulated in toxic and cholestatic liver injury. Cytokines such as tumor necrosis factor alpha (TNF-alpha) and interleukin 1 beta (IL-1 beta) are attributed to mediate this regulation, but their particular contribution in vivo is still unknown. Thus, we studied the molecular mechanisms by which Ntcp, Oatp1, Oatp2, and Mrp2 are regulated by proinflammatory cytokines during liver injury. Rats were injected intraperitoneally with either carbon tetrachloride or endotoxin. Inactivation of TNF-alpha and IL-1 beta was achieved by repetitive intraperitoneal injection of etanercept and anakinra, respectively. Messenger RNA (mRNA) levels of transporters and binding activities as well as nuclear protein levels of Ntcp, Oatp2, and Mrp2 transactivators were determined 20 to 24 hours later. In contrast to IL-1 beta, TNF-alpha inactivation alone fully prevented down-regulation of Ntcp, Oatp1, and Oatp2 mRNA as well as reduced binding activity of hepatocyte nuclear factor 1 (HNF-1) in CCl(4)-induced toxic injury. In endotoxemia, down-regulation of Mrp2, and partially in case of Ntcp, could be prevented by IL-1 beta but not TNF-alpha blockade. However, inactivation of either cytokine led to preservation of HNF1 and partially of retinoid X receptor/retinoic acid receptor (RXR/RAR) binding activity. No effect of anticytokines was seen on pregnane X receptor (PXR) and constitutive androstane receptor (CAR) binding activity as well as nuclear protein mass. In conclusion, TNF-alpha represents the master cytokine responsible for HNF1-dependent down-regulation of Ntcp, Oatp1, and Oatp2 in CCl(4)-induced toxic liver injury. IL-1 beta predominates in a complex signaling network of Ntcp and Mrp2 regulation in cholestatic liver injury. In contrast to in vitro studies, HNF1 and RXR/RAR-independent mechanisms appear to be more important in regulation of Mrp2 and Ntcp gene expression in endotoxemia.
肝胆转运体在中毒性和胆汁淤积性肝损伤中表达下调。诸如肿瘤坏死因子α（TNF-α）和白细胞介素1β（IL-1β）等细胞因子被认为介导了这种调节作用，但其在体内的具体作用仍不清楚。因此，我们研究了在肝损伤过程中促炎细胞因子调节Ntcp、Oatp1、Oatp2和Mrp2的分子机制。给大鼠腹腔注射四氯化碳或内毒素。分别通过重复腹腔注射依那西普和阿那白滞素来使TNF-α和IL-1β失活。20至24小时后测定转运体的信使核糖核酸（mRNA）水平、结合活性以及Ntcp、Oatp2和Mrp2反式激活因子的核蛋白水平。与IL-1β不同，单独使TNF-α失活可完全阻止CCl4诱导的中毒性损伤中Ntcp、Oatp1和Oatp2 mRNA的下调以及肝细胞因子1（HNF-1）结合活性的降低。在内毒素血症中，IL-1β可阻止Mrp2的下调，对于Ntcp则部分阻止其下调，但TNF-α阻断无效。然而，任一细胞因子失活均可使HNF1以及部分视黄醇X受体/视黄酸受体（RXR/RAR）结合活性得以保留。抗细胞因子对孕烷X受体（PXR）和组成型雄甾烷受体（CAR）结合活性以及核蛋白量未见影响。总之，TNF-α是CCl4诱导的中毒性肝损伤中负责HNF1依赖性下调Ntcp、Oatp1和Oatp2的主要细胞因子。在胆汁淤积性肝损伤中，IL-1β在Ntcp和Mrp2调节的复杂信号网络中起主导作用。与体外研究不同，在内毒素血症中，HNF1和RXR/RAR非依赖性机制在Mrp2和Ntcp基因表达调节中似乎更为重要。
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