Interplay between MRP Inhibition and Metabolism of MRP Inhibitors:  The Case of Curcumin

Abstract

The multidrug resistance proteins MRP1 and MRP2 are efflux transporters with broad substrate specificity, including glutathione, glucuronide, and sulfate conjugates. In the present study, the interaction of the dietary polyphenol curcumin with MRP1 and MRP2 and the interplay between curcumin-dependent MRP inhibition and its glutathione-dependent metabolism were investigated using two transport model systems. In isolated membrane vesicles of MRP1- and MRP2-expressing Sf9 cells, curcumin clearly inhibited both MRP1- and MRP2-mediated transport with IC(50) values of 15 and 5 microM, respectively. In intact monolayers of MRP1 overexpressing Madin-Darby canine kidney (MDCKII-MRP1) cells, curcumin also inhibited MRP1-mediated activity, although with a 3-fold higher IC(50) value than the one observed in the vesicle model. Interestingly, MRP2-mediated activity was hardly inhibited in intact monolayers of MRP2-overexpressing MDCKII (MDCKII-MRP2) cells upon exposure to curcumin, whereas the IC(50) value in the vesicle incubations was 5 microM. The difference in extent of inhibition of the MRPs by curcumin in isolated vesicles as compared to intact cells, observed especially for MRP2, was shown to be due to a swift metabolism of curcumin to two glutathione conjugates in the MDCKII cells. Formation of both glutathione conjugates was about six times higher in the MDCKII-MRP2 cells as compared with the MDCKII-MRP1 cells, a phenomenon that could be ascribed to the significantly lower glutathione levels in the cell line. The efflux of both conjugates, identified in the present study as monoglutathionyl curcumin conjugates, was demonstrated to be mediated by both MRP1 and MRP2. From dose-response curves with Sf9 membrane vesicles, glutathionylcurcumin conjugates appeared to be less potent inhibitors of MRP1 and MRP2 than their parent compound curcumin. In conclusion, curcumin clearly inhibits both MRP1- and MRP2-mediated transport, but the glutathione-dependent metabolism of curcumin plays a crucial role in the ultimate level of inhibition of MRP-mediated transport that can be achieved in a cellular system. This complex interplay between MRP inhibition and metabolism of MRP inhibitors, the latter affecting the ultimate potential of a compound for cellular MRP inhibition, may exist not only for a compound like curcumin but also for many other MRP inhibitors presently or previously developed on the basis of vesicle studies.

The Molecular Basis for the Pharmacokinetics and Pharmacodynamics of Curcumin and Its Metabolites in Relation to Cancer

“…The last notable type of processes that contributes to the low systemic bioavailability of curcumin and/or the generation of curcumin metabolites entails the association of curcumin with intestinal nondetoxification proteins. In some instances the binding of curcumin to a protein relays an inhibitory effect, as has been shown for several ATP-binding cassette (ABC) transporters (Wortelboer et al, 2003(Wortelboer et al, , 2005Shukla et al, 2009) and CYP isozymes (Volak et al, 2008), whereas in other instances the binding can be both antagonistic and biotransformative, as is the case for, e.g., SULTs (Eaton et al, 1996;Ireson et al, 2002;Volak et al, 2008;Fong et al, 2012), UGTs (Volak et al, 2008;Berginc et al, 2012;Dempe et al, 2012;Fong et al, 2012), and GSTs (Awasthi et al, 2000). With respect to nondetoxifying enzymes, the combined antagonistic and catalytic effects have been demonstrated for curcumin-COX-2 (Hong et al, 2004;Selvam et al, 2005;Griesser et al, 2011) and curcumin-lipoxygenase complexes (Skrzypczak-Jankun et al, 2000;Toth et al, 2000;Hong et al, 2004;Prasad et al, 2004), which result in the formation of 6-hydroxy-1-(4-hydroxy-3-methoxyphenoxy)-3-(4-hydroxy-3-methoxyphenyl)-1,3,3a,6a-tetrahydro-4H-cyclopenta[c]furan-4-one (Fig.…”

“…Several studies have demonstrated that curcumin is capable of inhibiting various ABC transporters (Wortelboer et al, 2003(Wortelboer et al, , 2005Shukla et al, 2009), which is likely to affect the transport kinetics of curcumin and its metabolites in, e.g., enterocytes and hepatocytes, because these cells are replete with multiple ABC transporters (section III.C.2.f). Cancer cells also overexpress multiple ABC transporters (Brozik et al, 2011) that confer multidrug resistance (Tiwari et al, 2011).…”

Curcumin as “Curecumin”: From kitchen to clinic

“…It binds to and inhibits the activity of enzymes, growth factor receptors, metals, albumin, and other molecules. It binds proteins such as P-glycoprotein [68,69], multidrug resistance proteins 1 and 2 (MRP1 and MRP2) [59], glutathione [59], protein kinase C, ATPase [52,53], ErbB2 [61], and alpha1-acid glycoprotein (AGP) [50]. By directly binding small b-amyloid species, curcumin blocks aggregation and fibril formation in vitro and in vivo [51].…”

Biliary Excretion of Curcumin Is Mediated by Multidrug Resistance-Associated Protein 2

“…Although there are no data examining whether curcumin is a substrate of Mrp2, curcumin is known to interact with Mrp2 as an inhibitor. 18,19) Thus, we hypothesized that Mrp2 could be involved in the hepatobiliary excretion of curcumin.…”