ABSTRACT
BACKGROUND & AIMS: Liver tight junctions (TJs) establish tissue barriers that isolate bile from the blood circulation. TJP2/ZO-2-inactivating mutations cause progressive cholestatic liver disease in humans. Because the underlying mechanisms remain elusive, we characterized mice with liver-specific inactivation of Tjp2. METHODS: Tjp2 was deleted in hepatocytes, cholangiocytes, or both. Effects on the liver were assessed by biochemical analyses of plasma, liver, and bile and by electron microscopy, histology, and immunostaining. TJ barrier permeability was evaluated using fluorescein isothiocyanate-dextran (4 kDa). Cholic acid (CA) diet was used to assess susceptibility to liver injury. RESULTS: Liver-specific deletion of Tjp2 resulted in lower Cldn1 protein levels, minor changes to the TJ, dilated canaliculi, lower microvilli density, and aberrant radixin and bile salt export pump (BSEP) distribution, without an overt increase in TJ permeability. Hepatic Tjp2-defcient mice presented with mild progressive cholestasis with lower expression levels of bile acid transporter Abcb11/Bsep and detoxification enzyme Cyp2b10. A CA diet tolerated by control mice caused severe cholestasis and liver necrosis in Tjp2-deficient animals. 1,4-Bis[2-(3,5-dichloropyridyloxy)]benzene ameliorated CA-induced injury by enhancing Cyp2b10 expression, and ursodeoxycholic acid provided partial improvement. Inactivating Tjp2 separately in hepatocytes or cholangiocytes showed only mild CA-induced liver injury. CONCLUSION: Tjp2 is required for normal cortical distribution of radixin, canalicular volume regulation, and microvilli density. Its inactivation deregulated expression of Cldn1 and key bile acid transporters and detoxification enzymes. The mice provide a novel animal model for cholestatic liver disease caused by TJP2-inactivating mutations in humans.
Subject(s)
Bile Canaliculi/metabolism , Chemical and Drug Induced Liver Injury/genetics , Cholestasis/genetics , Tight Junctions/metabolism , Zonula Occludens-2 Protein/genetics , ATP Binding Cassette Transporter, Subfamily B, Member 11/genetics , ATP Binding Cassette Transporter, Subfamily B, Member 11/metabolism , Animals , Aryl Hydrocarbon Hydroxylases/metabolism , Bile Acids and Salts/metabolism , Bile Canaliculi/pathology , Chemical and Drug Induced Liver Injury/drug therapy , Cholagogues and Choleretics/therapeutic use , Cholic Acid , Claudin-1/metabolism , Cytochrome P450 Family 2/metabolism , Cytoskeletal Proteins/metabolism , Epithelial Cells , Female , Fibrosis , Genetic Predisposition to Disease , Hepatocytes , Male , Membrane Proteins/metabolism , Mice , Mice, Knockout , Mutation , Oxazoles/therapeutic use , Permeability , Protective Factors , RNA, Messenger/metabolism , Steroid Hydroxylases/metabolism , Tight Junctions/ultrastructure , Ursodeoxycholic Acid/therapeutic use , Zonula Occludens-2 Protein/deficiencyABSTRACT
Epstein-Barr virus (EBV) is associated with a variety of tumors and nonmalignant conditions. Latent EBV genomes in cells, including tumor cells, are often CpG methylated, whereas virion DNA is not CpG methylated. We demonstrate that methyl CpG binding magnetic beads can be used to fractionate among sources of EBV DNA (DNA extracted from laboratory-purified virions vs DNA extracted from latently infected cell lines). We then applied the technique to plasma specimens and showed that this technique can distinguish EBV DNA from patients with EBV-associated tumors (nasopharyngeal carcinoma, Hodgkin lymphoma) and viral DNA from patients without EBV-associated tumors, including immunocompromised patients and patients with EBV(-) Hodgkin lymphoma.