title: Endogenous thiols and MRP transporters contribute to Hg2+ efflux in HgCl2-treated tubular MDCK cells.
abstract: Tubular epithelium represents the primary target of mercuric ions (Hg(2+)) nephrotoxicity. Although widely investigated, the mechanisms of Hg(2+) cell uptake, accumulation and excretion all along the nephron remain largely unknown. In the present study, native distal tubular-derived Madin-Darby canine kidney (MDCK) cells exposed to subcytotoxic (micromolar) HgCl(2) concentrations were used for investigating specific mechanisms involved in the tubular response to toxic metals. Inductively coupled plasma-mass spectrometry (ICP-MS) was firstly used for assessing HgCl(2) solubility and then for quantifying Hg(2+) cell uptake. Exposed to HgCl(2), MDCK cells showed a rapid, but transient, Hg(2+) accumulation. The metallic cation was found to affect cell density and morphology, being these effects related to the dose and the time of exposure. In parallel, an Hg(2+)-induced up-regulation of endogenous MRP1 and MRP2 export pumps, a significant HgCl(2)-dependent induction of protective cellular thiols and an increase in the glutathione conjugates metabolism were also observed. The functional suppression of MRPs activity, obtained by MK-571 treatment, increased the Hg(2+) cell content and the sensitivity of MDCK cells to HgCl(2). Our results demonstrate that, in MDCK cells, inorganic Hg(2+) promotes the activation of specific detoxifying pathways that may, at least partly, depend on the activity of MRP transporters.
authors.affiliation: Unit of Biochemistry, Department of Biomedical Sciences and Biotechnologies, School of Medicine, University of Brescia, viale Europa, 11, 25123 Brescia, Italy. aleo@med.unibs.it
authors.forename: Maria Francesca
authors.initials: MF
authors.lastname: Aleo
authors.forename: Fausta
authors.initials: F
authors.lastname: Morandini
authors.forename: Francesca
authors.initials: F
authors.lastname: Bettoni
authors.forename: Roberta
authors.initials: R
authors.lastname: Giuliani
authors.forename: Francesca
authors.initials: F
authors.lastname: Rovetta
authors.forename: Nathalie
authors.initials: N
authors.lastname: Steimberg
authors.forename: Pietro
authors.initials: P
authors.lastname: Apostoli
authors.forename: Giovanni
authors.initials: G
authors.lastname: Parrinello
authors.forename: Giovanna
authors.initials: G
authors.lastname: Mazzoleni
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D000818:Animals; D015152:Blotting, Northern; D002413:Cations, Divalent / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004285:Dogs; D005978:Glutathione / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007684:Kidney Tubules / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D049990:Membrane Transport Modulators; D026901:Membrane Transport Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D008627:Mercuric Chloride / Q000378:metabolism / Q000633:toxicity*; D008628:Mercury / Q000378:metabolism*; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D011422:Propionates / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002413:Cations, Divalent; D005978:Glutathione; D005982:Glutathione Transferase; D049990:Membrane Transport Modulators; D026901:Membrane Transport Proteins; D008627:Mercuric Chloride; D008628:Mercury; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D011422:Propionates; D011804:Quinolines; D013438:Sulfhydryl Compounds; C000715087:ABCC2 protein, human; C059141:verlukast