Substituted bifunctional Au(III)-2.2'-bipyridine complexes as potential PARP inhibitors

Abstract

Cancer represents one of the most serious diseases today, with a high mortality rate. Chemotherapy is a primary therapeutic method for the treatment of many cancers. In the middle of the last century, following the discovery that cis-diaminedichloroplatinum (III) (cisplatin) inhibited Escherichia coli cell division, platinum chemotherapeutics played a key role in the treatment of a wide range of malignancies. Although the use of these drugs in chemotherapy has shown success, it has been proven that platinum-based therapy shows many side effects, including severe neurotoxicity. Inhibition of poly(ADP-ribose) polymerase (PARP), a nuclear enzyme activated upon DNA damage, represents one of the basic approaches to cancer treatment by applying targeted therapy. Platinum complexes are also widely used for this purpose. Finding new, less toxic drugs based on metal complexes would make a significant contribution to the treatment of malignancies. In this sense, the potential of the bifunctional Au(III) complexes to inhibit PARP was examined. For that purpose, [AuCl2(bipy)]+ (bipy = 2.2'-bipyridine) complex, then complexes in which one and both Cl-atoms are substituted with L-cysteine are examined. The mentioned Au(III) complexes have been previously synthesized and experimentally investigated, but their theoretical study using molecular docking analysis was done here for the first time. The inhibitory activity of these gold complexes was compared with the inhibitory activity of cisplatin and oxyplatinum. Applied molecular docking analysis performed using AutoDock 4.0 program indicated that the highest inhibition potency possess monosubstituted Au(III)(bipy) complex (ΔGbind= -8.74 kcal/mol, Ki= 0.40 μM), while somewhat lower inhibition potency has disubstituted Au(III)(bipy) complex (ΔGbind= -7.19 kcal/mol, Ki= 5.40 μM) and initial [AuCl2(bipy)]+ complex (ΔGbind= -6.84 kcal/mol, Ki= 9.73 μM). The appropriate thermodynamical parameters that illustrates the inhibition potency of oxyplatinum are ΔGbind= -7.12 kcal/mol, Ki= 6.01 μM, and of cisplatin those are ΔGbind= -4.46 kcal/mol, Ki= 535.61 μM. Here performed theoretical study indicates that the investigated Au(III) complexes have the potential to be used for targeted therapy and that it would be important to investigate their biological activity in vitro and in vivo in detail.