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Bile acid-induced Mallory body formation in drug-primed mouse liver
Peter Fickert1, Michael Trauner, Andrea Fuchsbichler
1Department of Medicine, Karl-Franzens University, Auenbruggerplatz 25, A-8036 Graz, Austria.
Abstract:
Chronic cholestasis is associated with retention of bile acids and profound cytoskeletal alterations in hepatocytes including Mallory body (MB) formation. The mechanisms responsible for MB formation in cholestatic liver diseases are unclear. The aim of our study was to determine the relevance of cholestasis and bile acids for MB formation. For this purpose mice received a 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-supplemented diet for 2.5 months to induce MB formation. After recovery from DDC intoxication for 4 weeks followed by disappearance of MBs, these drug-primed mice were subjected to DDC refeeding, common bile duct ligation (CBDL), and feeding of a cholic acid (CA)-supplemented diet for 7 days, respectively. Cytokeratin (CK) 8 and CK 18 expression was studied by competitive reverse transcriptase-polymerase chain reaction and Western blot analysis. Cytoskeletal alterations of hepatocytes and MB formation were monitored by immunofluorescence microscopy and immunohistochemistry using CK-, ubiquitin-, and MB-specific antibodies. Like DDC refeeding, both CBDL and CA feeding of drug-primed mice significantly increased CK 8 and CK 18 mRNA and protein levels (with excess of CK 8) and resulted in ubiquitination and abnormal phosphorylation of CKs. Furthermore, CBDL and CA feeding resulted in rapid neoformation of MBs in drug-primed mice. It is concluded that MB formation in cholestatic liver diseases may be triggered by the action of potentially toxic bile acids.
Insights
Chronic cholestasis causes bile acid buildup and liver cell damage, leading to Mallory body formation. This study shows bile acids, not just cholestasis, can trigger Mallory body formation in liver cells.
Area of Science:
- Hepatology
- Cell Biology
- Biochemistry
Background:
- Chronic cholestasis leads to bile acid retention and liver cell cytoskeletal changes, including Mallory body (MB) formation.
- The precise mechanisms driving MB formation in cholestatic liver diseases remain largely unknown.
Purpose of the Study:
- To investigate the roles of cholestasis and bile acids in the pathogenesis of Mallory body formation.
- To elucidate the molecular mechanisms underlying MB formation in response to cholestatic conditions.
Main Methods:
- Mice were administered a 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet to induce MB formation, followed by recovery.
- Drug-primed mice underwent refeeding with DDC, common bile duct ligation (CBDL), or a cholic acid (CA)-supplemented diet.
- Cytokeratin (CK) expression, phosphorylation, and ubiquitination were analyzed using molecular and microscopic techniques.
Main Results:
- Both CBDL and CA feeding in drug-primed mice significantly elevated CK 8 and CK 18 mRNA and protein levels.
- These cholestatic conditions induced abnormal CK phosphorylation and ubiquitination, hallmarks of MB formation.
- CBDL and CA feeding rapidly triggered new MB formation in previously DDC-treated mice.
Conclusions:
- Mallory body formation in cholestatic liver diseases can be triggered by the direct action of bile acids.
- Bile acids play a critical role in the cytoskeletal pathology observed in cholestatic conditions, contributing to MB formation.