The effect of inflammation on the in vivo expression and activity of P-glycoprotein and multidrug resistance-associated protein-2 in mice.
Published: 2005
Language: eng
Number of pages: 176
Description: The drug-transporting proteins P-glycoprotein/Multidrug Resistance Protein-1 (PGP/Mdr1/ABCA1) and Multidrug Resistance-Associated Protein-2/Canalicular Multispecific Organic Anion Transporter (Mrp2/cMOAT/ABCC2) play an important role in the disposition of xenobiotics. In the liver, these transporters mediate the efflux of substrates into bile. Acute inflammation is known to suppress the hepatic expression and activity of PGP and Mrp2 in rodents. Using a murine model of endotoxin (LPS)-induced inflammation and Hepal-6 mouse hepatoma cells, we investigated the role of inflammatory cytokines in regulating the expression and activity of hepatic PGP/Mdr1 and Mrp2. Furthermore we delineated the effect of inflammation on the in vivo disposition of the PGP substrate doxorubicin (DOX) in mice. LPS, interleukin (IL)-1beta, IL-6 and tumor necrosis factor (TNF)-alpha were administered in vivo to mice or  in vitro to Hepal-6 cells. The expression of Mdr1a, Mdr1b, Mrp2 and the related transporters Mdr2, Mrp1, Mrp3, and the Bile Salt Export Pump (Bsep) was measured using Western blotting and Reverse Transcriptase-Polymerase Chain Reaction. Plasma concentrations of DOX in mice were analyzed by high-performance liquid chromatography.In vivo, LPS treatment profoundly suppressed the mRNA levels of Mdr1a, Mdr1b, Mrp2, Mrp3 and Bsep to 15--60% of controls (p &lt; 0.05), without significantly altering  Mrp1 expression. Likewise, IL-6 administration suppressed  Mdr1a, Mdr1b, Mrp2 and Bsep expression to 30--60% of control levels. Similar effects were seen for the levels of Organic Anion Transporting Polypeptides (Oatp) 1 and 2. The suppressive effects of IL-1beta and TNF-alpha on transporter expression were less pronounced, moreover TNF-alpha induced Mdr1b mRNA 6-fold. Significantly lower Mrp2 mRNA levels with a corresponding decrease in cellular efflux of 5-carboxyfluorescein were seen in vitro  in cytokine-treated Hepal-6 cells. As compared to controls, LPS-treated mice exhibited 40% decreased biliary excretion, and 3-fold increased renal excretion of DOX, associated with reduced hepatic and increased renal PGP expression. In conclusion, cytokines are key regulators of hepatic PGP and Mrp2 in inflammation. Moreover, inflammation causes PGP expression in the liver and kidney to be differentially regulated, thus altering the clearance profile of DOX.
Notes: Thesis (Ph.D.)--University of Toronto, 2005.

Electronic version licensed for access by U. of T. users.

Source: Dissertation Abstracts International, Volume: 66-06, Section: B, page: 3079.