title: Metalloprobes: Fluorescence imaging of multidrug resistance (MDR1) P-Glycoprotein (Pgp)-mediated functional transport activity in cellulo.
abstract: Radiolabeled metalloprobes offer sensitive tools for evaluating quantitative accumulation of chemical entities within pooled cell populations. Although beneficial in translational nuclear imaging, this method precludes interrogation of effects resulting from variations at a single cell level, within the same segment of cell population. Compared with radiotracer bioassays, fluorescence imaging offers a cost-efficient technique to assess accumulation of metalloprobes at a single cell level, and determine their intracellular localization under live cell conditions. To evaluate, whether or not radiotracer assay and fluorescence imaging provide complementary information on utility of metalloprobes to assess functional expression of P-glycoprotein (Pgp) on plasma membrane of tumor cells, imaging studies of fluorescent cationic Ga(III)-ENBDMPI (bis(3-ethoxy-2-hydroxy-benzylidene)-N,N'-bis(2,2-dimethyl-3-amino-propyl)ethylenediamine) and its neutral counterpart Zn(II)-ENBDMPI are performed. While the uptake profiles of the cationic metalloprobe are inversely proportional to expression of Pgp in tumor cells, the accumulation profiles of the neutral Zn(II)-ENBDMPI in non-MDR and MDR cells are not significantly impacted. The cationic Ga(III)-ENBDMPI maps with Mito-Tracker Red, thereby confirming localization within mitochondria of non-MDR (Pgp-) cells. Depolarization of both plasmalemmal and mitochondrial potentials decreased retention of the cationic Ga(III)-ENBDMPI within the mitochondria. Additionally, LY335979, an antagonist-induced accumulation of the cationic Ga(III) metalloprobe in MDR (Pgp+) cells indicated specificity of the agent. Compared with traits of Ga(III)-ENBDMPI as a Pgp recognized substrate, Zn(II)-ENBDMPI demonstrated uptake in both MDR and non-MDR cells thus indicating the significance of overall molecular charge in mediating Pgp recognition profiles. Combined data indicate that live cell imaging can offer a cost-effective methodology for monitoring functional Pgp expression.
authors.affiliation: ICCE Institute, Molecular Imaging Center, Mallinckrodt Institute of Radiology, United States.
authors.forename: G S M
authors.initials: GS
authors.lastname: Sundaram
authors.affiliation: Department of Neurology, Washington University School of Medicine, St. Louis, MO 63110, United States; Students and Teachers As Research Scientists, Washington University School of Medicine, St. Louis, MO 63110, United States.
authors.forename: Monica
authors.initials: M
authors.lastname: Sharma
authors.affiliation: ICCE Institute, Molecular Imaging Center, Mallinckrodt Institute of Radiology, United States; Students and Teachers As Research Scientists, Washington University School of Medicine, St. Louis, MO 63110, United States.
authors.forename: Daniel
authors.initials: D
authors.lastname: Kaganov
authors.affiliation: ICCE Institute, Molecular Imaging Center, Mallinckrodt Institute of Radiology, United States; Students and Teachers As Research Scientists, Washington University School of Medicine, St. Louis, MO 63110, United States.
authors.forename: Junsang
authors.initials: J
authors.lastname: Cho
authors.affiliation: ICCE Institute, Molecular Imaging Center, Mallinckrodt Institute of Radiology, United States.
authors.forename: Scott E
authors.initials: SE
authors.lastname: Harpstrite
authors.affiliation: ICCE Institute, Molecular Imaging Center, Mallinckrodt Institute of Radiology, United States; Department of Neurology, Washington University School of Medicine, St. Louis, MO 63110, United States; Students and Teachers As Research Scientists, Washington University School of Medicine, St. Louis, MO 63110, United States; Department of Biomedical Engineering, School of Engineering & Applied Science, Washington University, St. Louis 63105, United States. Electronic address: sharmav@wustl.edu.
authors.forename: Vijay
authors.initials: V
authors.lastname: Sharma
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000378:metabolism; D001693:Biological Transport, Active / Q000502:physiology; D045744:Cell Line, Tumor; D005456:Fluorescent Dyes / Q000737:chemistry / Q000494:pharmacology; D005708:Gallium / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D008856:Microscopy, Fluorescence / Q000379:methods; D015032:Zinc / Q000737:chemistry / Q000494:pharmacology
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D005456:Fluorescent Dyes; D005708:Gallium; D015032:Zinc