Selenium-dependent and -independent transport of arsenic by the human multidrug resistance protein 2 (MRP2/ABCC2): implications for the mutual detoxification of arsenic and selenium

Abstract

Simultaneous exposure of lab animals to toxic doses of the human carcinogen arsenic (As) and the essential trace element selenium (Se) results in a remarkable mutual detoxification. A likely basis for this is the in vivo formation and biliary excretion of seleno-bis(S-glutathionyl) arsinium ion [(GS)(2)AsSe](-); however, the transport protein responsible for the biliary efflux of [(GS)(2)AsSe](-) has not been identified. The multidrug resistance protein 2 (MRP2/ABCC2) is an adenosine triphosphate (ATP)-binding cassette transporter expressed at the canalicular membrane of hepatocytes. Rat Mrp2 is known to excrete the As glutathione (GSH/GS-) conjugates arsenic triglutathione [As(GS)(3)] and monomethyl arsenic diglutathione [CH(3)As(GS)(2)] into bile, and in vitro studies have established As(GS)(3) as a substrate for human MRP2. In the present study, membrane vesicles prepared from human embryonic kidney (HEK293T) cells transfected with human MRP2 were used to demonstrate that MRP2 transports [(GS)(2)AsSe](-). In addition, the characteristics of MRP2 transport of As(GS)(3) and [(GS)(2)AsSe](-) were investigated. As(GS)(3) and [(GS)(2)AsSe](-) are chemically labile and have the potential to dissociate. However, arsenite (As(III)) +/- selenite (Se(IV)) transport was not detected in the absence of GSH or in the presence of the non-reducing GSH analog, ophthalmic acid, suggesting that the conjugates are the transported forms. The apparent K(m) values for [(GS)(2)AsSe](-) and As(GS)(3) were 1.7 and 4.2 microM, respectively, signifying high relative affinities. Membrane vesicles prepared from human erythrocytes, which express the MRP2-related MRP1/ABCC1, MRP4/ABCC4 and MRP5/ABCC5, transported As(GS)(3) in an MRP1- and ATP-dependent manner but did not transport [(GS)(2)AsSe](-). These results have important implications for the Se-dependent and -independent disposition of As.

Molecular characterization and functions of zebrafish ABCC2 in cellular efflux of heavy metals

“…To survive various toxic environments, vertebrates including fish have developed defensive mechanisms against toxicants and MRP transporters appears to be the main factors involved in the multi-xenobiotic resistance developed during the evolution of aquatic organisms (Sauerborn Klobucar et al, 2010). Mammalian ABCC2s have been shown to be critical in the detoxification and elimination of heavy metals, including mercury (Aleo et al, 2005;Zalups and Bridges, 2010), arsenite (Carew and Leslie, 2010;Kala et al, 2000) and platinum (Guminski et al, 2006;Surowiak Livers and intestines were taken from 4 females, and kidneys were taken from 4 females and 4 males. Same tissues from different fish were mixed for isolation of total RNA and subjected to qRT-PCR analysis of abcc2 mRNA levels relative to the control.…”

“…Previous studies have demonstrated that heavy metals can be detoxified and eliminated from cells by some of MRP transporters after conjugation to glutathione (Aleo et al, 2005;Chen et al, 1997;Ishikawa et al, 1994;Preveral et al, 2009). ABCC2/MRP2 has been shown to play important roles in the detoxification of heavy metals, including mercury (Aleo et al, 2005;Zalups and Bridges, 2010), arsenite (Carew and Leslie, 2010;Kala et al, 2000) and platinum (Guminski et al, 2006;Surowiak et al, 2006).…”

A Novel Pathway for Arsenic Elimination: Human Multidrug Resistance Protein 4 (MRP4/ABCC4) Mediates Cellular Export of Dimethylarsinic Acid (DMAV) and the Diglutathione Conjugate of Monomethylarsonous Acid (MMAIII)

“…For stable expression of MRP3, MRP4, MRP5, and empty pcDNA3.1(1), 2.5 Â 10 5 HEK293 cells were seeded in each well of a six-well plate, and 24 hours later DNA (1 mg) was transfected using either 3 ml FuGENE 6 transfection reagent (Roche Diagnostics Co., Mannheim, Germany), according to the manufacturer's instructions, or the calcium phosphate transfection method as described previously (Carew and Leslie, 2010). Forty-eight hours later, cells were subcultured (1:24) onto six-well plates and medium was replaced with Dulbecco's modified Eagle's medium containing 1000 mg/ml G418 (Invitrogen) and 10% fetal bovine serum.…”

“…In vivo studies of Mrp2 (Abcc2)-deficient (TR 2 ) Wistar rats show that Mrp2 is responsible for the biliary excretion of As(GS) 3 and MMA(GS) 2 (Kala et al, 2000). As(GS) 3 and the seleno-bis (S-glutathionyl) arsinium ion [(GS) 2 AsSe] 2 are substrates for human MRP2 in vitro (Carew and Leslie, 2010). Despite the important roles MRP1 and MRP2 play in protecting cells and tissues from arsenic, neither protein is localized to the basolateral surface of human hepatocytes.…”

Effect of the ARG1 gene on arsenic resistance of 293T cells

“…Previous reports showed that arsenic in combination with glutathione can be excreted by MRPs and PGPs (Li et al, 2007;Drobna et al, 2010;Carew and Leslie, 2010). Li et al (2007) have shown that when cells subjected to long-term exposure to a low-dose arsenic environment are subjected to acute arsenic exposure their sensitivity to arsenic reduces significantly.…”