Background & aims: Mitochondria are the major organelles for the formation of reactive oxygen species (ROS) in the cell, and mitochondrial dysfunction has been described as a key factor in the pathogenesis of cholestatic liver disease. The methylation-controlled J-protein (MCJ) is a mitochondrial protein that interacts with and represses the function of complex I of the electron transport chain. The relevance of MCJ in the pathology of cholestasis has not yet been explored.
Methods: We studied the relationship between MCJ and cholestasis-induced liver injury in liver biopsies from patients with chronic cholestatic liver diseases, and in livers and primary hepatocytes obtained from WT and MCJ-KO mice. Bile duct ligation (BDL) was used as an animal model of cholestasis, and primary hepatocytes were treated with toxic doses of bile acids. We evaluated the effect of MCJ silencing for the treatment of cholestasis-induced liver injury.
Results: Elevated levels of MCJ were detected in the liver tissue of patients with chronic cholestatic liver disease when compared with normal liver tissue. Likewise, in mouse models, the hepatic levels of MCJ were increased. After BDL, MCJ-KO animals showed significantly decreased inflammation and apoptosis. In an in vitro model of bile-acid induced toxicity, we observed that the loss of MCJ protected mouse primary hepatocytes from bile acid-induced mitochondrial ROS overproduction and ATP depletion, enabling higher cell viability. Finally, the in vivo inhibition of the MCJ expression, following BDL, showed reduced liver injury and a mitigation of the main cholestatic characteristics.
Conclusions: We demonstrated that MCJ is involved in the progression of cholestatic liver injury, and our results identified MCJ as a potential therapeutic target to mitigate the liver injury caused by cholestasis.
Lay summary: In this study, we examine the effect of mitochondrial respiratory chain inhibition by MCJ on bile acid-induced liver toxicity. The loss of MCJ protects hepatocytes against apoptosis, mitochondrial ROS overproduction, and ATP depletion as a result of bile acid toxicity. Our results identify MCJ as a potential therapeutic target to mitigate liver injury in cholestatic liver diseases.
Keywords: ALP, alkaline phosphatase; ALT, alanine aminotransferase; AMA-M2, antimitochondrial M2 antibody; ANA, antinuclear antibodies; APRI, AST to platelet ratio index; AST, aspartate aminotransferase; Abs, antibodies; BA, bile acid; BAX, BCL2 associated X; BCL-2, B-cell lymphoma 2; BCL-Xl, B-cell lymphoma-extra large; BDL, bile duct ligation; Bile duct ligation; CLD, cholestatic liver disease; Ccl2, C-C motif chemokine ligand 2; Ccr2, C-C motif chemokine receptor 2; Ccr5, C-C motif chemokine receptor 5; Cholestasis; Cxcl1, C-X-C motif chemokine ligand 1; Cyp7α1, cholesterol 7 alpha-hydroxylase; DCA, deoxycholic acid; ETC, electron transport chain; Ezh2, enhancer of zeste homolog 2; Fxr, farnesoid X receptor; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GCDCA, glycochenodeoxycholic acid; HSC, hepatic stellate cells; Hif-1α, hypoxia-inducible factor 1-alpha; JNK, c-Jun N-terminal kinase; KO, knockout; LSM, liver stiffness; MAPK, mitogen-activated protein kinase; MCJ; MCJ, methylation-controlled J; MLKL, mixed-lineage kinase domain-like pseudokinase; MMP, mitochondrial membrane potential; MPO, myeloperoxidase; MPT, mitochondrial permeability transition; Mitochondria; Nrf1, nuclear respiratory factor 1; PARP, poly (ADP-ribose) polymerase; PBC, primary biliary cholangitis; PSC, primary sclerosing cholangitis; Pgc1α, peroxisome proliferator-activated receptor gamma coactivator 1-alpha; Pgc1β, peroxisome proliferator-activated receptor gamma coactivator 1-beta; ROS; ROS, reactive oxygen species; RT, room temperature; SDH2, succinate dehydrogenase; TNF, tumour necrosis factor; Tfam, transcription factor A mitochondrial; Trail, TNF-related apoptosis-inducing ligand; UDCA, ursodeoxycholic acid; Ucp2, uncoupling protein 2; VCTE, vibration-controlled transient elastography; WT, wild-type; mRNA, messenger ribonucleic acid; p-JNK, phosphor-JNK; p-MLKL, phosphor-MLKL; shRNA, small hairpin RNA; siRNA, small interfering RNA; tBIL, total bilirubin; α-SMA, alpha-smooth muscle actin.
© 2021 The Author(s).