Mrp4-/- mice have an impaired cytoprotective response in obstructive cholestasis.
Mrp4 is a member of the multidrug resistance-associated gene family that is expressed on the basolateral membrane of hepatocytes and undergoes adaptive upregulation in response to cholestatic injury or bile acid feeding. However, the relative importance of Mrp4 in a protective adaptive response to cholestatic injury is not known. To address this issue, common bile duct ligation (CBDL) was performed in wild-type and Mrp4-/- mice and animals followed for 7 days. Histological analysis and serum aminotransferase levels revealed more severe liver injury in the absence of Mrp4 expression. Western analyses revealed that Mrp4, but not Mrp3, was significantly increased after CBDL in wild-type mice. Serum bile acid levels were significantly lower in Mrp4-/- mice than in wild-type CBDL mice, whereas serum bilirubin levels were the same, suggesting that Mrp4 was required to effectively extrude bile acids from the cholestatic liver. Mrp3 and Ostalpha-Ostbeta were upregulated in Mrp4-/- mice but were unable to compensate for the loss of Mrp4. High-performance liquid chromatography analysis on liver extracts revealed that taurine tetrahydroxy bile acid/beta-muricholic acid ratios were increased twofold in Mrp4-/- mice. In conclusion, hepatic Mrp4 plays a unique and essential protective role in the adaptive response to obstructive cholestatic liver injury.
Mennone
Albert
A
Liver Center and Department of Medicine, Yale University School of Medicine, New Haven, CT, USA.
Soroka
Carol J
CJ
Cai
Shi-Ying
SY
Harry
Kathy
K
Adachi
Masashi
M
Hagey
Lee
L
Schuetz
John D
JD
Boyer
James L
JL
D000818:Animals; D002779:Cholestasis / Q000473:pathology / Q000503:physiopathology*; D019610:Cytoprotection; D008099:Liver / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000172:deficiency* / Q000235:genetics
D027425:ATP-Binding Cassette, Sub-Family C Proteins; C489540:Abcc4 protein, mouse