Cholestasis protects the liver from ischaemic injury and post-ischaemic inflammation in the mouse

Swiss Hepato-Pancreato-Biliary Centre, Department of Visceral and Transplantation Surgery, University Hospital of Zurich, Zürich, Switzerland.
Gut (Impact Factor: 14.66). 02/2007; 56(1):121-8. DOI: 10.1136/gut.2006.097170
Source: PubMed


Cholestasis is associated with high morbidity and mortality in patients undergoing major liver surgery, but the mechanisms responsible remain elusive. Increased ischaemic liver injury and inflammation may contribute to the poor outcome.
Common bile duct ligation (biliary obstruction with hyperbilirubinaemia) or selective ligation of the left hepatic duct (biliary obstruction without hyperbilirubinaemia) was performed in C57BL/6 mice before 1 h of hepatic ischaemia and 1, 4 or 24 h of reperfusion. Infection with the intracellular hepatic pathogen Listeria monocytogenes for 12 and 48 h was used to study ischaemia-independent hepatic inflammation.
Cholestatic mice showed considerable protection from ischaemic liver injury as determined by transaminase release, histological liver injury and neutrophil infiltration. In cholestatic mice, reduced injury correlated with a failure to activate nuclear factor kappaB (NFkappaB) and tumour necrosis factor alpha (TNFalpha) mRNA synthesis, two key mediators of post-ischaemic liver inflammation. After selective bile duct ligation, both the ligated and the non-ligated lobes showed blocked activation of NFkappaB as well as reduced induction of TNFalpha mRNA synthesis and neutrophil infiltration. By contrast, infection with L monocytogenes showed comparable activation of NFkappaB and hepatic recruitment of neutrophils 12 h after infection.
Cholestasis does not increase but rather dramatically protects the liver from ischaemic injury and inflammation. This effect is mediated by a systemic factor, but not bilirubin, and is associated with a preserved capacity to trigger an inflammatory response to other stimuli such as a bacterial pathogen.

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    ABSTRACT: Hepatocyte growth factor (HGF), its receptor c-Met and Interleukin-6 (IL-6) together with its signalling transducer gp130 are important mediators of liver regeneration and mediate hepatoprotective effects. C-Met and HGF are essential for liver development during embryogenesis and it was shown that HGF/c-Met mediated signalling is essential for the regeneration of the liver after an injury. IL-6/gp130 mediated signalling is important for the regulation of the acute phase response after an acute liver injury, the modulation of liver regeneration and immune cell homeostasis. The aim of this thesis is to define the effects of HGF/c-Met and IL-6/gp130 dependent signalling in the model of bile duct ligation (BDL) that induces a chronic cholestatic liver injury, which leads to liver fibrosis. In this thesis, wildtype-mice (c-Met/gp130loxP/loxP), conditional c-Met knockout mice (c-Met Delta hepa), conditional gp130-deficient mice (gp130 Delta hepa) and conditional c-Met/gp130-double-deficient mice (c-Met/gp130 Delta hepa) were subjected to BDL for up to 4 weeks. The conditional knockout-mice where generated by using the cre-loxP-system under the control of a hepatocyte-specific albumin-promoter. The first efforts to generate hepatocyte specific c-Met knockouts with a pre-natal activated albumin promoter resulted in embryonic lethality. The change to a post-natal, hepatocyte-specific albumin promoter allowed the generation of viable offspring carrying a hepatocyte specific c-Met deficiency. It was shown that depletion of c-Met results in a higher grade of liver injury, which is ascribed to a greater sensitivity to FAS-induced apoptosis by lack of c-Met mediated anti-apoptotic gene-expression. 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Both, c-Met and gp130, do contribute to liver protection and play an important role for the regulation and modulation of the acute phase response as well. They participate in specific signalling pathways like anti-apoptotic signalling in the case of c-Met and anti-bacterial signalling in the case of gp130 in pathway and ligand specific manner. These findings lead to a further and more detailed understanding of the signalling specific effects mediated by c-Met and gp130 during chronic cholestatic liver disease. Those findings can support the eforts to find a cure against fibrosis and helps to improve the treatment of bacterial induced sepsis. Hepatocyte growth factor (HGF), sein Rezeptor c-Met und Interleukin-6 (IL-6), gemeinsam mit seinem Signaltransduktor gp130, sind wichtige Mediatoren der Leberregeneration und leberprotektiver Effekte. C-Met und HGF sind für die Leberentwicklung während der Embryogenese als auch, für die Leberregeneration, nach einer Schädigung essentiell. IL-6/gp130 vermittelte Signalwege sind wichtig für die Regulation der Akut-Phase-Antwort im Rahmen einer akuten Leberschädigung, ebenso wie die Modulation der Leberregeneration und der Immunzellhomöostase. Ziel dieser Arbeit ist die Untersuchung der Effekte der von HGF/c-Met und IL-6/gp130 vermittelten Signalwege im Gallengangsligaturmodell (BDL), welches eine chronisch-cholestatische Leberschädigung induziert und in deren Verlauf ein fibrotischer Prozess in Gang gesetzt wird. In dieser Thesis wurden Wildtyp-Mäuse (c-Met/gp130loxP/loxP), konditionale c-Met knockout Mäuse, konditionale gp130 defiziente Mäuse (gp130 Delta hepa) und konditionale c-Met/gp130 Doppelknockout Mäuse 4 Wochen lang der Gallengangsligatur unterzogen. Die konditionalen Knockout-Tiere wurden mit dem Cre-LoxP-System generiert. Ein erster Versuch der hepatozytenspezifischen Deletion von c-Met mittels eines prä-natalen Albuminpromoters führte zu embryonaler Lethalität. 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Sie partizipieren in spezifischen Signalwegen, wie der Anti-apoptotischen Genexpression, so im Fall von c-Met und den antibakteriellen Signalwegen im Fall von gp130, in Signalwegen, wie auch Liganden spezifischer Art und Weise. Die hier beschriebenen Ergebnisse ermöglichen ein tieferes Verständnis der signalwegsspezifischen Effekte, welche durch c-Met und gp130 im Rahmen der chronischen Cholestatischen Lebererkrankung vermittelt werden. Dies unterstützt die Anstrengungen der Suche nach einer Behandlung der Leberfibrose und ermöglicht die bessere Behandlung von bakteriellen Sepsen.
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