abstract
Tackling microbial resistance requires continuous efforts for the development of new molecules with novel mechanisms of action and potent antimicrobial activity. Our group has previously identified metal-based compounds, [Ag(1,10-phenanthroline-5,6-dione)(2)]ClO4 (Ag-phendione) and [Cu(1,10-phenanthroline-5,6-dione)(3)](ClO4)(2).4H(2)O (Cu-phendione), with efficient antimicrobial action against multidrug-resistant species. Herein, we investigated the ability of Ag-phendione and Cu-phendione to bind with double-stranded DNA using a combination of in silico and in vitro approaches. Molecular docking revealed that both phendione derivatives can interact with the DNA by hydrogen bonding, hydrophobic and electrostatic interactions. Cu-phendione exhibited the highest binding affinity to either major (- 7.9 kcal/mol) or minor (- 7.2 kcal/mol) DNA grooves. In vitro competitive quenching assays involving duplex DNA with Hoechst 33258 or ethidium bromide demonstrated that Ag-phendione and Cu-phendione preferentially bind DNA in the minor grooves. The competitive ethidium bromide displacement technique revealed Cu-phendione has a higher binding affinity to DNA (K-app = 2.55 x 10(6) M-1) than Ag-phendione (K-app = 2.79 x 10(5) M-1) and phendione (K-app = 1.33 x 10(5) M-1). Cu-phendione induced topoisomerase I-mediated DNA relaxation of supercoiled plasmid DNA. Moreover, Cu-phendione was able to induce oxidative DNA injuries with the addition of free radical scavengers inhibiting DNA damage. Ag-phendione and Cu-phendione avidly displaced propidium iodide bound to DNA in permeabilized Pseudomonas aeruginosa cells in a dose-dependent manner as judged by flow cytometry. The treatment of P. aeruginosa with bactericidal concentrations of Cu-phendione (15 mu M) induced DNA fragmentation as visualized by either agarose gel or TUNEL assays. Altogether, these results highlight a possible novel DNA-targeted mechanism by which phendione-containing complexes, in part, elicit toxicity toward the multidrug-resistant pathogen P. aeruginosa. [GRAPHICS] .
keywords
IN-VITRO; METAL-COMPLEXES; 1,10-PHENANTHROLINE-5,6-DIONE; BINDING; DAMAGE; CHEMOTHERAPY; ANTICANCER; PHTHALATE; DESIGN; OXYGEN
subject category
Biochemistry & Molecular Biology; Chemistry
authors
Galdino, ACM; Viganor, L; Pereira, MM; Devereux, M; McCann, M; Branquinha, MH; Molphy, Z; O'Carroll, S; Bain, C; Menounou, G; Kellett, A; dos Santos, ALS
our authors
Matheus M. Pereira
Researcheracknowledgements
Open Access funding provided by the IReL Consortium. This study was supported by grants and fellowships from the Brazilian Agencies: Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Fundacao de Amparo a Pesquisa no Estado do Rio de Janeiro (FAPERJ) and Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES-Financial code 001). Andrew Kellett and Zara Molphy acknowledge funding from Science Foundation Ireland Career Development Award (SFI-CDA) [15/CDA/3648]. This publication has emanated from research supported in part by a research grant from Science Foundation Ireland (SFI) and is co-funded under the European Regional Development Fund under Grant Number 12/RC/2275_P2.