Endogenous thiols and MRP transporters contribute to Hg2+ efflux in HgCl2-treated tubular MDCK cells.
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.
Aleo
Maria Francesca
MF
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
Morandini
Fausta
F
Bettoni
Francesca
F
Giuliani
Roberta
R
Rovetta
Francesca
F
Steimberg
Nathalie
N
Apostoli
Pietro
P
Parrinello
Giovanni
G
Mazzoleni
Giovanna
G
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
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