In vitro cellular and molecular plus in silico studies of a substituted bipyridine-coordinated Zn(II) ion: cytotoxicity, ROS-induced apoptosis, anti-metastasis, and BAX/BCL2 genes expression.

Abstract

A new dimethyl-substituted bipyridine-Zn(II) complex (^2Mebpy-Zn) was synthesized and structurally characterized. Single-crystalline structure of the complex was elucidated as [Zn(^2Mebpy)₃](ClO₄)₂∙1.5(dioxane) by X-ray diffraction, where ^2Mebpy is 4,4'-dimethyl-2,2'-bipyridine. The three-dimensional electrostatic potential maps (3D ESP) were plotted for [Zn(^2Mebpy)₃]²⁺ cation and [Zn(^2Mebpy)₃](ClO₄)₂ molecule. In vitro cytotoxicity studies indicated significant cytotoxicity of ^2Mebpy-Zn against both breast (MCF-7) and glioblastoma (U-87) cancer cells relative to normal murine embryo cells (NIH/3T3). The results are indicative of a superior selectivity toward MCF-7 over the other cell lines as confirmed by IC₅₀ value of 5.1 ± 0.5 µM after 48 h. Interestingly, MCF-7 and U-87 cells death induced by ^2Mebpy-Zn mostly proceed through an apoptotic pathway which probably associates with the overproduction of reactive oxygen species (ROS). The Zn(II) complex suppressed the metastatic affinity of MCF-7 cells by blocking migration as well as formation of colonies. Also, the expression of two opponent apoptosis-relevant genes (BAX and BCL2) measured by real-time polymerase chain reaction (qPCR) experiments indicated that ^2Mebpy-Zn could potentially trigger apoptotic cell death. Moreover, ^2Mebpy-Zn could cleave hydrolytically the pUC19 DNA without the need to add any external agent. Finally, the binding affinity of two enantiomers of ^2Mebpy-Zn toward cancer therapeutic targets, such as anti-apoptotic proteins, estrogen receptor α, tubulin, and topoisomerase II, was studied by in silico molecular docking. In conclusion, ^2Mebpy-Zn can be introduced as a potential therapeutic agent in breast cancer and indicates that other metal complexes with bipyridine derivatives can also exhibit promising anticancer effects.