Anti-Leishmania braziliensis activity of 1,10-phenanthroline-5,6-dione and its Cu(II) and Ag(I) complexes

Metalloenzyme Inhibitors against Zoonotic Infections: Focus on Leishmania and Schistosoma

The term "zoonosis" denotes diseases transmissible among vertebrate animals and humans. These diseases constitute a significant public health challenge, comprising 61% of human pathogens and causing an estimated 2.7 million deaths annually. Zoonoses not only affect human health but also impact animal welfare and economic stability, particularly in low- and middle-income nations. Leishmaniasis and schistosomiasis are two important neglected tropical diseases with a high prevalence in tropical and subtropical areas, imposing significant burdens on affected regions. Schistosomiasis, particularly rampant in sub-Saharan Africa, lacks alternative treatments to praziquantel, prompting concerns regarding parasite resistance. Similarly, leishmaniasis poses challenges with unsatisfactory treatments, urging the development of novel therapeutic strategies. Effective prevention demands a One Health approach, integrating diverse disciplines to enhance diagnostics and develop safer drugs. Metalloenzymes, involved in parasite biology and critical in different biological pathways, emerged in the last few years as useful drug targets for the treatment of human diseases. Herein we have reviewed recent reports on the discovery of inhibitors of metalloenzymes associated with zoonotic diseases like histone deacetylases (HDACs), carbonic anhydrase (CA), arginase, and heme-dependent enzymes.

Manganese(II), copper(II) and silver(I) complexes containing 1,10-phenanthroline/1,10-phenanthroline-5,6-dione against Candida species

Background: New chemotherapeutics are urgently required to treat Candida infections caused by drug-resistant strains. Methods: The effects of 16 1,10-phenanthroline (phen)/1,10-phenanthroline-5,6-dione/dicarboxylate complexed with Mn(II), Cu(II) and Ag(I) were evaluated against ten different Candida species. Results: Proliferation of Candida albicans, Candida dubliniensis, Candida famata, Candida glabrata, Candida guilliermondii, Candida kefyr, Candida krusei, Candida lusitaniae, Candida parapsilosis and Candida tropicalis was inhibited by three of six Cu(II) (MICs 1.52-21.55 μM), three of three Ag(I) (MICs 0.11-12.74 μM) and seven of seven Mn(II) (MICs 0.40-38.06 μM) complexes. Among these [Mn2(oda)(phen)4(H2O)2][Mn2(oda)(phen)4(oda)2].4H2O, where oda = octanedioic acid, exhibited effective growth inhibition (MICs 0.4-3.25 μM), favorable activity indexes, low toxicity against Vero cells and good/excellent selectivity indexes (46.88-375). Conclusion: [Mn2(oda)(phen)4(H2O)2][Mn2(oda)(phen)4(oda)2].4H2O represents a promising chemotherapeutic option for emerging, medically relevant and drug-resistant Candida species.

The Lung Microbiome in COPD and Lung Cancer: Exploring the Potential of Metal-Based Drugs

Chronic obstructive pulmonary disease (COPD) and lung cancer 17 are two of the most prevalent and debilitating respiratory diseases worldwide, both associated with high morbidity and mortality rates. As major global health concerns, they impose a substantial burden on patients, healthcare systems, and society at large. Despite their distinct aetiologies, lung cancer and COPD share common risk factors, clinical features, and pathological pathways, which have spurred increasing research interest in their co-occurrence. One area of particular interest is the role of the lung microbiome in the development and progression of these diseases, including the transition from COPD to lung cancer. Exploring novel therapeutic strategies, such as metal-based drugs, offers a potential avenue for targeting the microbiome in these diseases to improve patient outcomes. This review aims to provide an overview of the current understanding of the lung microbiome, with a particular emphasis on COPD and lung cancer, and to discuss the potential of metal-based drugs as a therapeutic strategy for these conditions, specifically concerning targeting the microbiome.

Silver(I) and Copper(II) 1,10-Phenanthroline-5,6-dione Complexes as Promising Antivirulence Strategy against Leishmania: Focus on Gp63 (Leishmanolysin)

Leishmaniasis, caused by protozoa of the genus Leishmania, encompasses a group of neglected diseases with diverse clinical and epidemiological manifestations that can be fatal if not adequately and promptly managed/treated. The current chemotherapy options for this disease are expensive, require invasive administration and often lead to severe side effects. In this regard, our research group has previously reported the potent anti-Leishmania activity of two coordination compounds (complexes) derived from 1,10-phenanthroline-5,6-dione (phendione): [Cu(phendione)₃].(ClO₄)₂.4H₂O and [Ag(phendione)₂].ClO₄. The present study aimed to evaluate the effects of these complexes on leishmanolysin (gp63), a virulence factor produced by all Leishmania species that plays multiple functions and is recognized as a potential target for antiparasitic drugs. The results showed that both Ag-phendione (-74.82 kcal/mol) and Cu-phendione (-68.16 kcal/mol) were capable of interacting with the amino acids comprising the active site of the gp63 protein, exhibiting more favorable interaction energies compared to phendione alone (-39.75 kcal/mol) or 1,10-phenanthroline (-45.83 kcal/mol; a classical gp63 inhibitor) as judged by molecular docking assay. The analysis of kinetic parameters using the fluorogenic substrate Z-Phe-Arg-AMC indicated V_max and apparent K_m values of 0.064 µM/s and 14.18 µM, respectively, for the released gp63. The effects of both complexes on gp63 proteolytic activity were consistent with the in silico assay, where Ag-phendione exhibited the highest gp63 inhibition capacity against gp63, with an IC₅₀ value of 2.16 µM and the lowest inhibitory constant value (K_i = 5.13 µM), followed by Cu-phendione (IC₅₀ = 163 µM and K_i = 27.05 µM). Notably, pretreatment of live L. amazonensis promastigotes with the complexes resulted in a significant reduction in the expression of gp63 protein, including the isoforms located on the parasite cell surface. Both complexes markedly decreased the in vitro association indexes between L. amazonensis promastigotes and THP-1 human macrophages; however, this effect was reversed by the addition of soluble gp63 molecules to the interaction medium. Collectively, our findings highlight the potential use of these potent complexes in antivirulence therapy against Leishmania, offering new insights for the development of effective treatments for leishmaniasis.

Peptidases Are Potential Targets of Copper(II)-1,10-Phenanthroline-5,6-dione Complex, a Promising and Potent New Drug against Trichomonas vaginalis

Trichomonas vaginalis is responsible for 156 million new cases per year worldwide. When present asymptomatically, the parasite can lead to serious complications, such as development of cervical and prostate cancer. As infection increases the acquisition and transmission of HIV, the control of trichomoniasis represents an important niche for the discovery and development of new antiparasitic molecules. This urogenital parasite synthesizes several molecules that allow the establishment and pathogenesis of infection. Among them, peptidases occupy key roles as virulence factors, and the inhibition of these enzymes has become an important mechanism for modulating pathogenesis. Based on these premises, our group recently reported the potent anti-T. vaginalis action of the metal-based complex [Cu(phendione)₃](ClO₄)₂.4H₂O (Cu-phendione). In the present study, we evaluated the influence of Cu-phendione on the modulation of proteolytic activities produced by T. vaginalis by biochemical and molecular approaches. Cu-phendione showed strong inhibitory potential against T. vaginalis peptidases, especially cysteine- and metallo-type peptidases. The latter revealed a more prominent effect at both the post-transcriptional and post-translational levels. Molecular Docking analysis confirmed the interaction of Cu-phendione, with high binding energy (-9.7 and -10.7 kcal·mol^-1, respectively) at the active site of both TvMP50 and TvGP63 metallopeptidases. In addition, Cu-phendione significantly reduced trophozoite-mediated cytolysis in human vaginal (HMVII) and monkey kidney (VERO) epithelial cell lineages. These results highlight the antiparasitic potential of Cu-phendione by interaction with important T. vaginalis virulence factors.

Antibacterial activity of metal-phenanthroline complexes against multidrug-resistant Irish clinical isolates: a whole genome sequencing approach

Antimicrobial resistance (AMR) is one of the serious global health challenges of our time. There is now an urgent need to develop novel therapeutic agents that can overcome AMR, preferably through alternative mechanistic pathways from conventional treatments. The antibacterial activity of metal complexes (metal = Cu(II), Mn(II), and Ag(I)) incorporating 1,10-phenanthroline (phen) and various dianionic dicarboxylate ligands, along with their simple metal salt and dicarboxylic acid precursors, against common AMR pathogens were investigated. Overall, the highest level of antibacterial activity was evident in compounds that incorporate the phen ligand compared to the activities of their simple salt and dicarboxylic acid precursors. The chelates incorporating both phen and the dianion of 3,6,9-trioxaundecanedioic acid (tdda) were the most effective, and the activity varied depending on the metal centre. Whole-genome sequencing (WGS) was carried out on the reference Pseudomonas aeruginosa strain, PAO1. This strain was exposed to sub-lethal doses of lead metal-tdda-phen complexes to form mutants with induced resistance properties with the aim of elucidating their mechanism of action. Various mutations were detected in the mutant P. aeruginosa genome, causing amino acid changes to proteins involved in cellular respiration, the polyamine biosynthetic pathway, and virulence mechanisms. This study provides insights into acquired resistance mechanisms of pathogenic organisms exposed to Cu(II), Mn(II), and Ag(I) complexes incorporating phen with tdda and warrants further development of these potential complexes as alternative clinical therapeutic drugs to treat AMR infections.

The Anti-Leishmania amazonensis and Anti-Leishmania chagasi Action of Copper(II) and Silver(I) 1,10-Phenanthroline-5,6-dione Coordination Compounds

Leishmaniasis is a neglected disease caused by protozoa belonging to the Leishmania genus. Notably, the search for new, promising and potent anti-Leishmania compounds remains a major goal due to the inefficacy of the available drugs used nowadays. In the present work, we evaluated the effects of 1,10-phenanthroline-5,6-dione (phendione) coordinated to silver(I), [Ag(phendione)₂]ClO₄ (Ag-phendione), and copper(II), [Cu(phendione)₃](ClO₄)₂·4H₂O (Cu-phendione), as potential drugs to be used in the chemotherapy against Leishmania amazonensis and Leishmania chagasi. The results showed that promastigotes treated with Ag-phendione and Cu-phendione presented a significant reduction in the proliferation rate. The IC₅₀ values calculated to Ag-phendione and Cu-phendione, respectively, were 7.8 nM and 7.5 nM for L. amazonensis and 24.5 nM and 20.0 nM for L. chagasi. Microscopical analyses revealed several relevant morphological changes in promastigotes, such as a rounding of the cell body and a shortening/loss of the single flagellum. Moreover, the treatment promoted alterations in the unique mitochondrion of these parasites, inducing significant reductions on both metabolic activity and membrane potential parameters. All these cellular perturbations induced the triggering of apoptosis-like death in these parasites, as judged by the (i) increased percentage of annexin-positive/propidium iodide negative cells, (ii) augmentation in the proportion of parasites in the sub-G₀/G₁ phase and (iii) DNA fragmentation. Finally, the test compounds showed potent effects against intracellular amastigotes; contrarily, these molecules were well tolerated by THP-1 macrophages, which resulted in excellent selective index values. Overall, the results highlight new selective and effective drugs against Leishmania species, which are important etiological agents of both cutaneous (L. amazonensis) and visceral (L. chagasi) leishmaniasis in a global perspective.

In Vivo Activity of Metal Complexes Containing 1,10-Phenanthroline and 3,6,9-Trioxaundecanedioate Ligands against Pseudomonas aeruginosa Infection in Galleria mellonella Larvae

Drug-resistant Pseudomonas aeruginosa is rapidly developing resulting in a serious global threat. Immunocompromised patients are specifically at risk, especially those with cystic fibrosis (CF). Novel metal complexes incorporating 1,10-phenanthroline (phen) ligands have previously demonstrated antibacterial and anti-biofilm effects against resistant P. aeruginosa from CF patients in vitro. Herein, we present the in vivo efficacy of {[Cu(3,6,9-tdda)(phen)₂]·₃H₂O·EtOH}_n (Cu-tdda-phen), {[Mn(3,6,9-tdda)(phen)₂]·₃H₂O·EtOH}_n (Mn-tdda-phen) and [Ag₂(3,6,9-tdda)(phen)₄]·EtOH (Ag-tdda-phen) (tddaH₂ = 3,6,9-trioxaundecanedioic acid). Individual treatments of these metal-tdda-phen complexes and in combination with the established antibiotic gentamicin were evaluated in vivo in larvae of Galleria mellonella infected with clinical isolates and laboratory strains of P. aeruginosa. G. mellonella were able to tolerate all test complexes up to 10 µg/larva. In addition, the immune response was affected by stimulation of immune cells (hemocytes) and genes that encode for immune-related peptides, specifically transferrin and inducible metallo-proteinase inhibitor. The amalgamation of metal-tdda-phen complexes and gentamicin further intensified this response at lower concentrations, clearing a P. aeruginosa infection that were previously resistant to gentamicin alone. Therefore this work highlights the anti-pseudomonal capabilities of metal-tdda-phen complexes alone and combined with gentamicin in an in vivo model.