Abstract
Background and AimsMounting evidence supports an association between cholestatic liver disease and changes in the composition of the microbiome. Still, the role of the microbiome in the pathogenesis of this condition remains largely undefined.Approach and ResultsTo address this, we have used two experimental models, administering alpha‐naphtylisocyanate or feeding a 0.1% 3,5‐diethoxycarbonyl‐1,4‐dihydrocollidine diet, to induce cholestatic liver disease in germ‐free mice and germ‐free mice conventionalized with the microbiome from wild‐type, specific pathogen‐free animals. Next, we have inhibited macrophage activation by depleting these cells using clodronate liposomes and inhibiting the inflammasome with a specific inhibitor of NOD‐, LRR‐, and pyrin domain‐containing protein 3. Our results demonstrate that cholestasis, the accumulation of bile acids in the liver, fails to promote liver injury in the absence of the microbiome in vivo. Additional in vitro studies supported that endotoxin sensitizes hepatocytes to bile‐acid–induced cell death. We also demonstrate that during cholestasis, macrophages contribute to promoting intestinal permeability and to altered microbiome composition through activation of the inflammasome, overall leading to increased endotoxin flux into the cholestatic liver.ConclusionsWe demonstrate that the intestinal microbiome contributes to cholestasis‐mediated cell death and inflammation through mechanisms involving activation of the inflammasome in macrophages.
Highlights
AND AIMS: Mounting evidence supports an association between cholestatic liver disease and changes in the composition of the microbiome
We demonstrate that during cholestasis, macrophages contribute to promoting intestinal permeability and to altered microbiome composition through activation of the inflammasome, overall leading to increased endotoxin flux into the cholestatic liver
We demonstrate that the intestinal microbiome contributes to cholestasis-mediated cell death and inflammation through mechanisms involving activation of the inflammasome in macrophages. (Hepatology 2020;72:2090-2108)
Summary
Germ-free (GF) mice were generated on a C57/ B6J background in the Disease Modelling Unit (University of East Anglia, UK). A subset of GF mice was conventionalized with the microbiome obtained from specific pathogen-free (SPF) wildtype (WT) mice by administration of fecal matter by gavage 3 weeks before initiation of the experiments (GF + WT). The NOD-, LRR-, and pyrin domain-containing protein 3 (Nrlp3)-specific inhibitor, MCC950 (20 mg/kg), was administered to GF + WT mice in parallel to the administration of ANIT and 24 hours after. All experimental procedures were conducted in male mice from 8 to 12 weeks of age that were held in isolators in the germ-free facility at the Disease Modelling Unit (University of East Anglia, UK). All experiments were previously approved by the Animal Welfare and Ethical Review Body (University of East Anglia, Norwich, UK) and were performed following the guidelines of the National Academy of Sciences (National Institutes of Health publication 86-23, revised 1985) and were conducted within the provisions of the Animals (Scientific Procedures) Act (1986) and the LASA Guiding Principles for Preparing for and Undertaking Aseptic Surgery (2010) under UK Home Office approval (70/8929)
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