title: Characterization of phosphine complexes of technetium(III) as transport substrates of the multidrug resistance P-glycoprotein and functional markers of P-glycoprotein at the blood-brain barrier.
abstract: The multidrug resistance (MDR1) P-glycoprotein functions as a broad specificity efflux transporter of structurally diverse natural product and xenobiotic compounds. P-glycoprotein also is an important component of the functional blood-brain barrier. To enable further studies of function and modulation of MDR1 P-glycoprotein in vitro and in vivo, two novel phosphine technetium(III) complexes were designed and characterized: trans-[2,2'-(1, 2-ethanediyldiimino)bis(1, 5-methoxy-5-methyl-4-oxo-hexenyl)]bis[methylbis(3-methoxy-1- propyl)ph osphine]Tc(III) (Tc-Q58) and trans-[5,5'-(1,2-ethanediyl diimino)bis(2-ethoxy-2-methyl-3-oxo-4-pentenyl)]bis[dimethyl(3- methox y-1-propyl)phosphine)]Tc(III) (Tc-Q63). In human drug-sensitive KB 3-1 cells and multidrug-resistant KB 8-5 and 8-5-11 derivative cell lines, expressing nonimmunodetectable, low, and high levels of MDR1 P-glycoprotein, respectively, accumulation of Tc-Q58 and Tc-Q63 was inverse to expression of the transporter. Differences between drug-sensitive and multidrug-resistant cells, while detectable at picomolar concentrations of each radiopharmaceutical, were independent of tracer concentration. Ratios of tracer accumulation in KB 3-1 and 8-5 cells were 62.3 and 48.1 for Tc-Q58 and Tc-Q63, respectively. Cell contents of Tc-Q58 and Tc-Q63 were enhanced up to 60-fold in MDR cells by known modulators of MDR1 P-glycoprotein, while drugs not in the multidrug-resistant phenotype had no effect on their accumulation. In KB 8-5 cells, potency of modulators was GF120918 >> cyclosporin A > verapamil. Accumulation of Tc-Q58 and Tc-Q63 in Sf9 insect cells infected with a recombinant baculovirus containing human MDR1 P-glycoprotein was reduced in a GF120918-reversible manner (EC50 </= 70 nM) compared with cells infected with a wild-type baculovirus. By contrast, cell contents of Tc-Q58 or Tc-Q63 in Sf9 cells expressing the homologous MDR3 P-glycoprotein did not differ from wild-type virus. Demonstrating molecular targeting of these complexes in vivo, distribution and retention of Tc-Q58 in brain tissue of FVB mice treated with a saturating dose of GF120918 and mice deficient in the mdr1a gene [mdr1a (-/-)] were enhanced 180% and 520% over control, respectively. Exploiting the gamma-emission spectrum of 99mTc, increased uptake of Tc-Q58 in brain tissue of mdr1a (-/-) mice was readily detected noninvasively by scintigraphic imaging. Thus, both Tc-Q58 and Tc-Q63 are demonstrated to be substrates for transport by MDR1 P-glycoprotein, broadening the specificity of this transporter to include phosphine-containing metal complexes. As shown with Tc-Q58, these Q complexes can be used to detect transport activity and modulation of MDR1 P-glycoprotein in vitro and to directly monitor the functional status of P-glycoprotein at the blood-brain barrier in vivo.
authors.affiliation: Laboratory of Molecular Radiopharmacology, Department of Radiology, Washington University Medical School, St. Louis, Missouri 63110, USA.
authors.forename: G D
authors.initials: GD
authors.lastname: Luker
authors.forename: V V
authors.initials: VV
authors.lastname: Rao
authors.forename: C L
authors.initials: CL
authors.lastname: Crankshaw
authors.forename: J
authors.initials: J
authors.lastname: Dahlheimer
authors.forename: D
authors.initials: D
authors.lastname: Piwnica-Worms
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D018528:ATP-Binding Cassette Transporters / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D000166:Acridines / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D001812:Blood-Brain Barrier / Q000502:physiology*; D001921:Brain / Q000000981:diagnostic imaging; D007546:Isoquinolines / Q000494:pharmacology; D051379:Mice; D008817:Mice, Mutant Strains; D015335:Molecular Probes; D009943:Organophosphorus Compounds / Q000378:metabolism*; D015609:Organotechnetium Compounds / Q000378:metabolism*; D011877:Radionuclide Imaging / Q000379:methods; D011994:Recombinant Proteins / Q000378:metabolism; D044005:Tetrahydroisoquinolines; D014407:Tumor Cells, Cultured
chemical_list: C109250:(2,2'-(1,2-ethanediyldimino)bis(1,5-dimethoxy-5-methyl-4-oxohexenyl))bis(methylbis(3-methoxy-1-propyl)phosphine)technetium(III); C109251:(5,5'-(1,2-ethanediyldimino)bis(2-ethoxy-2-methyl-3-oxo-4-pentenyl)bis(dimethyl(3-methoxy-1-propyl)phosphine))technetium(III); D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D000166:Acridines; D007546:Isoquinolines; D015335:Molecular Probes; D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D011994:Recombinant Proteins; D044005:Tetrahydroisoquinolines; C095122:multidrug resistance protein 3; C083501:Elacridar