Journal
LIVER INTERNATIONAL
Volume 33, Issue 2, Pages 312-320Publisher
WILEY
DOI: 10.1111/liv.12049
Keywords
antimitochondrial antibody; autophagy; biliary epithelial cell; cellular senescence; primary biliary cirrhosis
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Funding
- Ministry of Education, Culture, Sports and Science and Technology of Japan [21590366, 24590409]
- Grants-in-Aid for Scientific Research [24590409, 21590366] Funding Source: KAKEN
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Background/Aims We have reported the involvement of deregulated autophagy and subsequent cellular senescence in biliary epithelial lesions in primary biliary cirrhosis (PBC). Given that mitochondria are a major target of autophagy, we hypothesized that deregulated autophagy of mitochondria may be involved in autoimmune pathogenesis in PBC. Methods We examined immunohistochemically the expression of pyruvate dehydrogenase complex-E2 component (PDC-E2) and cytochrome c oxidase, subunit I (CCO), in livers taken from patients with PBC (n = 42) and control livers (n = 76). The colocalization of mitochondrial antigens with an autophagy marker microtubule-associated protein-light chain 3 beta (LC3), a deregulated autophagy marker p62/sequestosome-1 (p62) and a lysosomal marker LAMP-1 was examined by double immunofluorescence. We examined the colocalization of mitochondrial antigens with LC3, p62 and LAMP-1 and the cell-surface expression of PDC-E2 in cultured biliary epithelial cells (BECs) treated with various stresses. Results Intense granular expression of PDC-E2 and CCO was seen in the damaged small bile ducts (SBDs) in PBC and the expression was significantly more frequent in PBC than in control livers (P < 0.01). The granular expression of mitochondrial antigens was colocalized with LC3 in damaged SBDs in PBC. The accumulation of LC3-expressing punctae colocalized with PDC-E2 and CCO was significantly more increased in cultured BECs treated with various stresses. The cell-surface expression of PDC-E2 was induced by various stresses in BECs. Conclusion Deregulated autophagy may contribute to the abnormal expression of mitochondrial antigens and may be involved in the autoimmune pathogenesis of bile duct lesions in PBC.
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