Submitted on November 19, 2007
Accepted on June 9, 2008
Hepatic Mrp4 Induction Following Acetaminophen Exposure is Dependent on Kupffer Cell Function
Sarah N. Campion1, Rachel Johnson1, Lauren M. Aleksunes1, Michael J. Goedken2, Nico van Rooijen3, George L. Scheffer4, Nathan J. Cherrington5, and Jose E Manautou1*
1 Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut, United States
2 Department of Pathology, Schering Plough Research Institute, Lafayette, New Jersey, United States
3 Department of Molecular Cell Biology, Vrije Universiteit Medical Center, Amsterdam, Netherlands
4 Department of Pathology, Vrije Universiteit Medical Center, Amsterdam, Netherlands
5 Department of Pharmacology and Toxicology, University of Arizona, Tucson, Arizona, United States
* To whom correspondence should be addressed. E-mail: jose.manautou{at}uconn.edu.
During acetaminophen (APAP) hepatotoxicity, increased expression of multidrug resistance-associated proteins 2, 3 and 4 (Mrp2-4) occurs. Mrp4 is the most significantly up-regulated transporter in mouse liver following APAP treatment. While the expression profiles of liver transporters following APAP hepatotoxicity are well characterized, the regulatory mechanisms contributing to these changes remain unknown. We hypothesized that Kupffer cell-derived mediators participate in the regulation of hepatic transporters during APAP toxicity. To investigate this, C57BL/6J mice were pretreated with clodronate liposomes (0.1 ml i.v.) to deplete Kupffer cells and then challenged with APAP (500mg/kg i.p.). Liver injury was assessed by plasma alanine aminotransferase and hepatic transporter protein expression was determined by western blot and immunohistochemistry. Depletion of Kupffer cells by liposomal clodronate increased susceptibility to APAP hepatotoxicity. While increased expression of several efflux transporters was observed after APAP exposure, only Mrp4 was found to be differentially regulated following Kupffer cell depletion. At 48 and 72 hrs after APAP dosing, Mrp4 levels were increased by 10- and 33-fold, respectively, in mice receiving empty liposomes. Immunohistochemistry revealed Mrp4 staining confined to centrilobular hepatocytes. Remarkably, Kupffer cell depletion completely prevented Mrp4 induction by APAP. Elevated plasma levels of TNF-
and IL-1
were also prevented by Kupffer cell depletion. These findings show that Kupffer cells protect the liver from APAP toxicity and that Kupffer cell mediators released in response to APAP are likely responsible for the induction of Mrp4.
