Hepatic Mrp4 induction following acetaminophen exposure is dependent on Kupffer cell function

Abstract

During acetaminophen (APAP) hepatotoxicity, increased expression of multidrug resistance-associated proteins 2, 3, and 4 (Mrp2-4) occurs. Mrp4 is the most significantly upregulated transporter in mouse liver following APAP treatment. Although 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 iv) to deplete Kupffer cells and then challenged with APAP (500 mg/kg ip). 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. Although 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 h 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-alpha and IL-1beta 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.

Xenobiotic, Bile Acid, and Cholesterol Transporters: Function and Regulation

“…Functional studies to dissect the role of Mrp4 in APAP hepatotoxicity are under way, although it is purported that Mrp4 may reduce hepatotoxicity by removing byproducts of cellular injury and/or facilitating hepatocyte recovery by exporting signaling molecules to adjacent hepatocytes and nonparenchymal cells. This hypothesis is supported by the fact that Kupffer cells participate not only in protecting the liver from APAP toxicity but also in upregulating hepatocellular Mrp4 protein (Campion et al, 2008). Work by Ghanem et al (2005) has provided an additional explanation for APAP autoprotection in rodents.…”

“…Protein expression patterns mirror mRNA changes. Livers from APAP-treated mice exhibit reduced Oatp1a1, Oatp1b2, and Ntcp and increased Mrp2, Mrp3, and Mrp4 protein expression Campion et al, 2008). It is noteworthy that Mrp3 and Mrp4 proteins are selectively up-regulated in hepatocytes surrounding the central vein and adjacent to regions of hepatic damage .…”

Alcohol Cirrhosis Alters Nuclear Receptor and Drug Transporter Expression in Human Liver

“…Homogenates were centrifuged at 100,000g for 60 minutes at 4°C. The resulting pellet is a typical fraction used to detect transporter expression as described in our previous publications, as well as by multiple other research groups (Trauner et al, 1997;Aleksunes et al, 2006;Campion et al, 2008;Cheng et al, 2008;Maher et al, 2008). The supernatant was saved as a cytosolic fraction to measure NQO1 and glutathione peroxidase 1 (GPX1) protein expression.…”

TGF-β-SMAD3 signaling mediates hepatic bile acid and phospholipid metabolism following lithocholic acid-induced liver injury

“…In addition, TNF ␣ upregulates multidrug resistanceassociated protein 3 (MRP3; basolateral bile salt export transporter, also called ABCC3) and can protect from liver injury that results from obstructive cholestasis ( 19 ). Kupffer cell activation mediates induction of hepatic multidrug resistance-associated protein 4 (MRP4; basolateral bile salt export transporter, also called ABCC4) expression ( 20 ), which is involved in basolateral BA export. The TGF ␤ signal regulates expression of CYP7A1 gene ( 21 ), the ratelimiting enzyme of the BA synthesis.…”