Study of the decorporation efficacy and toxicity of tetradentate 3-hydroxy- 2-pyridinone ligands at the cellular level

Objective:A series of experiments were carried out to study the comparative decorporation efficacy and toxicity of three tetradentate hydroxypyridinone ligands(3LI-1-Cm-3,2-HOPO,5LIO-1-Cm-3,2-HOPO,and 7LIO-1-Cm-3,2-HOPO)with the variation of the linker length and the substituents.Methods:Three ligands were obtained from a 4-step synthesis via the amidation of HOPO unit and different backbones.Potentiometric titrations were carried out to evaluate the formation constants of their corresponding uranyl complexes.CCK-8 and colony formation assays were used to compare the cytotoxicity of the three ligands and uranyl using renal proximal tubular epithelial(NRK-52E)cells.In vitro uranium removal assays were performed to assess decorporation efficiencies of those ligands by co-incubating uranium and chelators with NRK-52E cells for 48 h.Results:Among the three ligands,5LIO-1-Cm-3,2-HOPO exhibits the highest uranyl affinity(logβ110?18.6(7))in comparison to the other two ligands(logβ110?14.9(2)for 3LI-1-Cm-3,2-HOPO and logβ110?16.7(1)for 7LIO-1-Cm-3,2-HOPO).The results of CCK-8 tests and colony formation assays further elucidate that 5LIO-1-Cm-3,2-HOPO and 7LIO-1-Cm-3,2-HOPO both show a similar level of cytotoxicity compared with ZnNa3-DTPA at relatively low ligand concentrations.In contrast,in the 3LI-1-Cm-3,2-HOPO treated group,the cell viability decreased markedly with the increase of the ligand concentrations,and the colony formation capability of NRK-52E cells was inhibited.Furthermore,the comparative decorporation efficacy of the three ligands was obtained from in vitro uranium removal assays,suggesting that these ligands could significantly inhibit the cellular uptake and prompt the cellular release of uranium from NRK-52E cells by the level of 81.9%,91.8%,and 87.1%,respectively.Conclusion:Our current results demonstrate that the linker/backbone species would significantly affect the decorporation efficacy and toxicity of the tetradentate 3-hydroxy-2-pyridinone ligands,which is informative for the future design and modification of novel decorporation ligands.