Impact of Cadmium on Intracellular Zinc Levels in HepG2 Cells: Quantitative Evaluations and Molecular Effects.
Cadmium is classified as a human carcinogen, and its disturbance in zinc homeostasis has been well established. However, its extent as well as molecular mechanisms involved in cadmium carcinogenesis has yet to be fully clarified. To this end, we used the zinc specific probe Zinquin to visualize and to quantitatively evaluate changes in the concentration of labile zinc, in an in vitro model of human hepatic cells (HepG2) exposed to cadmium. A very large increase (+93%) of intracellular labile zinc, displaced by cadmium from the zinc proteome, was measured when HepG2 were exposed to 10 µM cadmium for 24 hrs. Microarray expression profiling showed that in cells, featuring an increase of labile zinc after cadmium exposure, one of the top regulated genes is Snail1 (+3.6), which is included in the adherens junction pathway and linked to cancer. In the same pathway MET, TGF-βR, and two members of the Rho-family GTPase, Rac, and cdc42 all implicated in the loss of adherence features and acquisition of migratory and cancer properties were regulated, as well. The microRNAs analysis showed a downregulation of miR-34a and miR-200a, both implicated in the epithelial-mesenchymal transition. These microRNAs results support the role played by zinc in affecting gene expression at the posttranscriptional level.
Department of Earth and Environmental Sciences, University of Milan Bicocca, Piazza della Scienza 1, 20126 Milan, Italy.
Chiara
C
Urani
Department of Earth and Environmental Sciences, University of Milan Bicocca, Piazza della Scienza 1, 20126 Milan, Italy.
Pasquale
P
Melchioretto
Department of Earth and Environmental Sciences, University of Milan Bicocca, Piazza della Scienza 1, 20126 Milan, Italy.
Maurizio
M
Bruschi
Department of Clinical and Experimental Medicine, University of Insubria, 21100 Varese, Italy.
Marco
M
Fabbri
Molecular Biology and Genomics Unit, Institute for Health and Consumer Protection, DG JRC, European Commission, Via Enrico Fermi 2749, 21027 Ispra, Italy.
Maria Grazia
MG
Sacco
Chemical Assessment and Testing Unit (CAT), Institute for Health and Consumer Protection, DG JRC, European Commission, Via Enrico Fermi 2749, 21027 Ispra, Italy.
Laura
L
Gribaldo
D002104:Cadmium / Q000633:toxicity*; D063646:Carcinogenesis / Q000187:drug effects / Q000235:genetics*; D003593:Cytoplasm / Q000187:drug effects / Q000235:genetics; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects*; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D056945:Hep G2 Cells; D006801:Humans; D035683:MicroRNAs / Q000096:biosynthesis; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000096:biosynthesis; D015032:Zinc / Q000302:isolation & purification / Q000378:metabolism*
C533896:MIRN200 microRNA, human; C522425:MIRN34 microRNA, human; D035683:MicroRNAs; C000604407:SNAI1 protein, human; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D002104:Cadmium; D015032:Zinc