An organogold compound as potential antimicrobial agent against drug resistant bacteria:Initial mechanistic insights

The rise of antimicrobial resistance has necessitated novel strategies to efficiently combat pathogenic bacteria. Metal‐based compounds have been proven as a possible alternative to classical organic drugs. Here, we have assessed the antibacterial activity of seven gold complexes of different families. One compound, a cyclometalated Au(III) C^N complex, showed activity against Gram‐positive bacteria, including multi‐drug resistant clinical strains. The mechanism of action of this compound was studied in Bacillus subtilis. Overall, the studies point towards a complex mode of antibacterial action, which does not include induction of oxidative stress or cell membrane damage. A number of genes related to metal transport and homeostasis were upregulated upon short treatment of the cells with gold compound. Toxicity tests conducted on precision‐cut mouse tissue slices ex vivo revealed that the organogold compound is poorly toxic to mouse liver and kidney tissues, and may thus, be treated as an antibacterial drug candidate

Identifying and validating the presence of Guanine-Quadruplexes (G4) within the blood fluke parasite Schistosoma mansoni

Schistosomiasis is a neglected tropical disease that currently affects over 250 million individuals worldwide. In the absence of an immunoprophylactic vaccine and the recognition that mono-chemotherapeutic control of schistosomiasis by praziquantel has limitations, new strategies for managing disease burden are urgently needed. A better understanding of schistosome biology could identify previously undocumented areas suitable for the development of novel interventions. Here, for the first time, we detail the presence of G-quadruplexes (G4) and putative quadruplex forming sequences (PQS) within the Schistosoma mansoni genome. We find that G4 are present in both intragenic and intergenic regions of the seven autosomes as well as the sex-defining allosome pair. Amongst intragenic regions, G4 are particularly enriched in 3´ UTR regions. Gene Ontology (GO) term analysis evidenced significant G4 enrichment in the wnt signalling pathway (p<0.05) and PQS oligonucleotides synthetically derived from wnt-related genes resolve into parallel and anti-parallel G4 motifs as elucidated by circular dichroism (CD) spectroscopy. Finally, utilising a single chain anti-G4 antibody called BG4, we confirm the in situ presence of G4 within both adult female and male worm nuclei. These results collectively suggest that G4-targeted compounds could be tested as novel anthelmintic agents and highlights the possibility that G4-stabilizing molecules could be progressed as candidates for the treatment of schistosomiasi

Exploring the Anticancer Activity of Tamoxifen-Based Metal Complexes Targeting Mitochondria

Two new 'hybrid' metallodrugs of Au(III)(AuTAML)and Cu(II) (CuTAML) were designed featuring a tamoxifen-derived pharmacophoreto ideally synergize the anticancer activity of both the metal centerand the organic ligand. The compounds have antiproliferative effectsagainst human MCF-7 and MDA-MB 231 breast cancer cells. Moleculardynamics studies suggest that the compounds retain the binding activityto estrogen receptor (ER & alpha;). In vitro and in silico studies showed that the Au(III) derivative isan inhibitor of the seleno-enzyme thioredoxin reductase, while theCu(II) complex may act as an oxidant of different intracellular thiols.In breast cancer cells treated with the compounds, a redox imbalancecharacterized by a decrease in total thiols and increased reactiveoxygen species production was detected. Despite their different reactivitiesand cytotoxic potencies, a great capacity of the metal complexes toinduce mitochondrial damage was observed as shown by their effectson mitochondrial respiration, membrane potential, and morphology

On the mechanism of Gold/NHC compounds binding to DNA G-quadruplexes: combined metadynamics and biophysical methods

The binding modes and free‐energy landscape of two AuI/N‐heterocyclic carbene complexes interacting with G‐quadruplexes, namely a human telomeric (hTelo) and a promoter sequence (C‐KIT1), are studied here for the first time by metadynamics. The theoretical results are validated by FRET DNA melting assays and provide an accurate estimate of the absolute gold complex/DNA binding free energy. This advanced in silico approach is valuable to achieve rational drug design of selective G4 binders

Exploring the reactivity and biological effects of heteroleptic N-Heterocyclic carbene gold(I)-Alkynyl complexes

Two families of heteroleptic N‐heterocyclic carbene gold(I)‐alkynyl complexes have been synthesized and characterized by different methods. Their reactivity with model thiols has been studied by NMR spectroscopy and DFT calculations. Moreover, preliminary studies on the compounds' reactivity with DNA and antiproliferative effects have been conducted

Mechanisms of irreversible aquaporin-10 inhibition by organogold compounds studied by combined biophysical methods and atomistic simulations

The inhibition of glycerol permeation via human aquaporin-10 (hAQP10) by organometallic gold complexes has been studied by stopped-flow fluorescence spectroscopy, and its mechanism has been described using molecular modelling and atomistic simulations. The most effective hAQP10 inhibitors are cyclometalated Au(III) C^N compounds known to efficiently react with cysteine residues leading to the formation of irreversible C–S bonds. Functional assays also demonstrate the irreversibility of the binding to hAQP10 by the organometallic complexes. The obtained computational results by metadynamics show that the local arylation of Cys209 in hAQP10 by one of the gold inhibitors is mapped into a global change of the overall free energy of glycerol translocation across the channel. Our study further pinpoints the need to understand the mechanism of glycerol and small molecule permeation as a combination of local structural motifs and global pore conformational changes, which are taking place on the scale of the translocation process and whose study, therefore, require sophisticated molecular dynamics strategies

Isoxazolo[3,4-d]pyridazin-7(6H)-one derivatives endowed with anti-proliferative Activity.

Isoxazolo[3,4-d]pyridazin-7(6H)-one derivatives endowed with antiproliferative Activity B. Maggio1, G. Cancemi1, D. Raffa1, M. V. Raimondi1, F. Plescia1, A. D’Anneo2,M. Lauricella3, G. Barone4, R. Bonsignore4, G. Daidone1 1. Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, Medicinal Chemistry and Pharmaceutical Technologies Section, University of Palermo, ViaArchirafi 32, 90123, Palermo, Italy 2. Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, Laboratory of Biochemistry, University of Palermo. 3.Department of Experimental Biomedicine and Clinical Neurosciences, Laboratory of Biochemistry, University of Palermo. 4. Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, University of Palermo. [email protected] A screening carried out by NCI (Bethesda, USA) on compounds available in our laboratory,in order to ascertain their antiproliferative activity against a panel of 60 human tumor cell lines, allowed to discovery the 3,4-diphenylisoxazolo[3,4-d]pyridazin-7(6H)-one 1a [1] as an hit compound, often showing GI50values at sub-micromolar level. We synthesized some analogs of 1a, i.e.1b-gand other derivatives in which the NHgroup is variably alkylated, with the aim to obtain more active compounds as well as to perform structure-activity relationship(SAR) studies. We obtained a quite active antiproliferative compound, the 3,4-di-p-tolylisoxazolo[3,4-d]pyridazin-7(6H)- one 1d, and verified the importance for the antiproliferative activity of the aril, and not alkyl, groups linked to the isoxazolo-pyridazinone moiety. Studies performed on the cell cycle progression and on some cellular target (ATM, procaspase-2 proteins and H2AX histone) demonstrated that 1d produces an increase of the cell population in pre-G0/G1 and induces cellular death by apoptosis, damaging the DNA by double strand breaks. UV-vis titration and viscosity measurement showed that the compound is able to give an interaction with the B-DNA. 1. Renzi G., Dal Piaz V. (2004)Gazz. Chim. It.95: 1478–149

Exploring the chemoselectivity towards cysteine arylation by cyclometalated Au(III) compounds: new mechanistic insights

To gain more insight into the factors controlling the efficient cysteine arylation by cyclometalated Au(III) complexes, the reaction between selected gold compounds and different peptides was investigated by high‐resolution liquid chromatography electrospray ionization mass spectrometry (HR‐LC‐ESI‐MS). The deducted mechanisms of C–S cross‐coupling, also supported by density functional theory (DFT) and quantum mechanics/molecular mechanics (QM/MM) calculations, evidenced the key role of secondary peptidic gold binding sites in favouring the process of reductive elimination