BASHY Dyes Are Highly Efficient Lipid Droplet-Targeting Photosensitizers that Induce Ferroptosis through Lipid Peroxidation.

Ferroptosis is an iron-dependent lipid-peroxidation-driven mechanism of cell death and a promising therapeutic target to eradicate cancer cells. In this study, we discovered that boronic acid-derived salicylidenehydrazone (BASHY) dyes are highly efficient singlet-oxygen photosensitizers (PSs; ΦΔ up to 0.8) that induce ferroptosis triggered by photodynamic therapy. The best-performing BASHY dye displayed a high phototoxicity against the human glioblastoma multiform U87 cell line, with an IC50 value in the low nanomolar range (4.40 nM) and a remarkable phototoxicity index (PI > 22,700). Importantly, BASHY dyes were shown to accumulate in lipid droplets (LDs) and this intracellular partition was found to be essential for the enhanced phototoxicity and the induction of ferroptosis through lipid peroxidation. The safety and phototoxicity of this platform were validated using an in vivo zebrafish model (Danio rerio).

Sodium Tetraphenylborate Displays Selective Bactericidal Activity against Neisseria meningitidis and N. gonorrhoeae and Is Effective at Reducing Bacterial Infection Load.

Neisseria meningitidis and Neisseria gonorrhoeae, two highly related species that might have emerged from a common commensal ancestor, constitute major human threats. Vaccines are available to prevent N. meningitidis infection, whereas there are only a limited number of antibiotics available for N. gonorrhoeae Unfortunately, some strains of these species are rapidly evolving and capable of escaping human interventions. Thus, it is now urgent to develop new avenues to fight these bacteria. This study reports that a boron-based salt, sodium tetraphenylborate (NaBPh4), displays high bactericidal activity and remarkable specificity against N. meningitidis and N. gonorrhoeae Other closely related commensal species such as Neisseria lactamica, which is found in the normal flora of healthy individuals, were found to be less affected even at 5-fold higher doses of NaBPh4 This specificity was further observed when much lower sensitivity was found for more distant Neisseriaceae species (such as Neisseria elongata or Kingella oralis) and completely unrelated species. Significant boron uptake by N. meningitidis cells was observed after incubation with 5 µM NaBPh4, as measured by inductively coupled plasma mass spectrometry, suggesting that this drug candidate's target(s) could be located intracellularly or within the cell envelope. Furthermore, mutants with slightly decreased susceptibility displayed alterations in genes coding for cell envelope elements, which reduced their virulence in an animal model of infection. Finally, a single dose of NaBPh4 resulted in a significant reduction in bacterial burden in a mouse model of N. meningitidis bacteremia. Although numerous boron-containing species were previously reported for their complex biological activities, the observation of this narrow selectivity is unprecedented and of potential importance from a therapeutic standpoint.

Cationic RuII Cyclopentadienyl Complexes with Antifungal Activity against Several Candida Species.

Fungal infections, including those caused by antifungal-resistant Candida, are a very challenging health problem worldwide. Whereas different ruthenium complexes were previously studied for their anti-Candida potential, Ru-cyclopentadienyl complexes were overlooked. Here, we report an antifungal activity assessment of three Ru-cyclopentadienyl complexes with some insights into their potential mode of action. Among these complexes, only the cationic species [Ru-ACN]+ and [Ru-ATZ]+ displayed a significant antifungal activity against different Candida strains, notably against the ones that did not respond to one of the most currently used antifungal drugs fluconazole (FCZ). However, no apparent activity was observed for the neutral species, Ru-Cl, thus indicating the important role of the cationic backbone of these complexes in their biological activity. We suggest that reactive oxygen species (ROS) generation might be involved in the mechanism of action of these complexes as, unlike neutral Ru-Cl, [Ru-ACN]+ and [Ru-ATZ]+ could generate intracellular concentration-dependent ROS. We also observed a correlation between the ruthenium cellular uptake, ROS generation and fungal growth inhibitory activity of the compounds. Furthermore, docking simulations showed that the CYP51 enzyme can form more energetically favorable complexes with [Ru-ATZ]+ than fluconazole (FCZ); this suggests that CYP51 inhibition could also be considered as a potential mode of action.

Rationally Designed Ruthenium Complexes for Breast Cancer Therapy.

Since the discovery of the anticancer potential of ruthenium-based complexes, several species were reported as promising candidates for the treatment of breast cancer, which accounts for the greatest number of new cases in women every year worldwide. Among these ruthenium complexes, species containing bioactive ligand(s) have attracted increasing attention due to their potential multitargeting properties, leading to anticancer drug candidates with a broader range of cellular targets/modes of action. This review of the literature aims at providing an overview of the rationally designed ruthenium-based complexes that have been reported to date for which ligands were carefully selected for the treatment of hormone receptor positive breast cancers (estrogen receptor (ER+) or progesterone receptor (PR+)). In addition, this brief survey highlights some of the most successful examples of ruthenium complexes reported for the treatment of triple negative breast cancer (TNBC), a highly aggressive type of cancer, regardless of if their ligands are known to have the ability to achieve a specific biological function.

Anticancer Activity and Catalytic Potential of Ruthenium(II)-Arene Complexes with N,O-Donor Ligands.

The special ability of organometallic complexes to catalyze various transformations might offer new effective mechanisms for the treatment of cancer. Studies that report both the biological properties and the ability of metallic complexes to promote therapeutically relevant catalytic reactions are limited. Herein, we report the anticancer activity and catalytic potential of some ruthenium(II)-arene complexes bearing bidentate Schiff base ligands (2a and 2b) and their reduced analogues (5a and 5b, respectively). In comparison to their Schiff base counterparts 2a and 2b, we demonstrate that amine complexes 5a and 5b display (i) a higher in vitro antiproliferative activity on different human cancer cell lines, (ii) a lower rate of hydrolysis, and (iii) an improved initial catalytic rate for the reduction of NAD+ to NADH. In contrast to their imine analogues 2a and 2b, we also show that amine complexes 5a and 5b induce the generation of intracellular reactive oxygen species (ROS) in MCF-7 breast cancer cells. Our results highlight the impact that a simple ligand modification such as the reduction of an imine moiety can have on both the catalytic and biological activities of metal complexes. Moreover, the ruthenium complexes reported here display some antiproliferative activity against T47D breast cancer cells, known for their cis-platin resistance.

Engagement of the GABA to KCC2 signaling pathway contributes to the analgesic effects of A3AR agonists in neuropathic pain.

More than 1.5 billion people worldwide suffer from chronic pain, yet current treatment strategies often lack efficacy or have deleterious side effects in patients. Adenosine is an inhibitory neuromodulator that was previously thought to mediate antinociception through the A1 and A2A receptor subtypes. We have since demonstrated that A3AR agonists have potent analgesic actions in preclinical rodent models of neuropathic pain and that A3AR analgesia is independent of adenosine A1 or A2A unwanted effects. Herein, we explored the contribution of the GABA inhibitory system to A3AR-mediated analgesia using well-characterized mouse and rat models of chronic constriction injury (CCI)-induced neuropathic pain. The deregulation of GABA signaling in pathophysiological pain states is well established: GABA signaling can be hampered by a reduction in extracellular GABA synthesis by GAD65 and enhanced extracellular GABA reuptake via the GABA transporter, GAT-1. In neuropathic pain, GABAAR-mediated signaling can be further disrupted by the loss of the KCC2 chloride anion gradient. Here, we demonstrate that A3AR agonists (IB-MECA and MRS5698) reverse neuropathic pain via a spinal mechanism of action that modulates GABA activity. Spinal administration of the GABAA antagonist, bicuculline, disrupted A3AR-mediated analgesia. Furthermore, A3AR-mediated analgesia was associated with reductions in CCI-related GAD65 and GAT-1 serine dephosphorylation as well as an enhancement of KCC2 serine phosphorylation and activity. Our results suggest that A3AR-mediated reversal of neuropathic pain increases modulation of GABA inhibitory neurotransmission both directly and indirectly through protection of KCC2 function, underscoring the unique utility of A3AR agonists in chronic pain.

Microglia disrupt mesolimbic reward circuitry in chronic pain.

Chronic pain attenuates midbrain dopamine (DA) transmission, as evidenced by a decrease in opioid-evoked DA release in the ventral striatum, suggesting that the occurrence of chronic pain impairs reward-related behaviors. However, mechanisms by which pain modifies DA transmission remain elusive. Using in vivo microdialysis and microinjection of drugs into the mesolimbic DA system, we demonstrate in mice and rats that microglial activation in the VTA compromises not only opioid-evoked release of DA, but also other DA-stimulating drugs, such as cocaine. Our data show that loss of stimulated extracellular DA is due to impaired chloride homeostasis in midbrain GABAergic interneurons. Treatment with minocycline or interfering with BDNF signaling restored chloride transport within these neurons and recovered DA-dependent reward behavior. Our findings demonstrate that a peripheral nerve injury causes activated microglia within reward circuitry that result in disruption of dopaminergic signaling and reward behavior. These results have broad implications that are not restricted to the problem of pain, but are also relevant to affective disorders associated with disruption of reward circuitry. Because chronic pain causes glial activation in areas of the CNS important for mood and affect, our findings may translate to other disorders, including anxiety and depression, that demonstrate high comorbidity with chronic pain.

Efficacy of synaptic inhibition depends on multiple, dynamically interacting mechanisms implicated in chloride homeostasis.

Chloride homeostasis is a critical determinant of the strength and robustness of inhibition mediated by GABA(A) receptors (GABA(A)Rs). The impact of changes in steady state Cl(-) gradient is relatively straightforward to understand, but how dynamic interplay between Cl(-) influx, diffusion, extrusion and interaction with other ion species affects synaptic signaling remains uncertain. Here we used electrodiffusion modeling to investigate the nonlinear interactions between these processes. Results demonstrate that diffusion is crucial for redistributing intracellular Cl(-) load on a fast time scale, whereas Cl(-)extrusion controls steady state levels. Interaction between diffusion and extrusion can result in a somato-dendritic Cl(-) gradient even when KCC2 is distributed uniformly across the cell. Reducing KCC2 activity led to decreased efficacy of GABA(A)R-mediated inhibition, but increasing GABA(A)R input failed to fully compensate for this form of disinhibition because of activity-dependent accumulation of Cl(-). Furthermore, if spiking persisted despite the presence of GABA(A)R input, Cl(-) accumulation became accelerated because of the large Cl(-) driving force that occurs during spikes. The resulting positive feedback loop caused catastrophic failure of inhibition. Simulations also revealed other feedback loops, such as competition between Cl(-) and pH regulation. Several model predictions were tested and confirmed by [Cl(-)](i) imaging experiments. Our study has thus uncovered how Cl(-) regulation depends on a multiplicity of dynamically interacting mechanisms. Furthermore, the model revealed that enhancing KCC2 activity beyond normal levels did not negatively impact firing frequency or cause overt extracellular K(-) accumulation, demonstrating that enhancing KCC2 activity is a valid strategy for therapeutic intervention.

Exploiting exo and endo furan-maleimide Diels-Alder linkages for the functionalization of organoruthenium complexes.

Diels-Alder cycloadditions involving furans and maleimides are extensively used in organic chemistry and materials synthesis. Given the promising advances of organoruthenium complexes in therapy, we explored the possibility of exploiting such Diels-Alder linkages as a mean to modulate their biological properties.

Microglia-mediated degradation of perineuronal nets promotes pain.

Activation of microglia in the spinal cord dorsal horn after peripheral nerve injury contributes to the development of pain hypersensitivity. How activated microglia selectively enhance the activity of spinal nociceptive circuits is not well understood. We discovered that after peripheral nerve injury, microglia degrade extracellular matrix structures, perineuronal nets (PNNs), in lamina I of the spinal cord dorsal horn. Lamina I PNNs selectively enwrap spinoparabrachial projection neurons, which integrate nociceptive information in the spinal cord and convey it to supraspinal brain regions to induce pain sensation. Degradation of PNNs by microglia enhances the activity of projection neurons and induces pain-related behaviors. Thus, nerve injury-induced degradation of PNNs is a mechanism by which microglia selectively augment the output of spinal nociceptive circuits and cause pain hypersensitivity.

Note of Caution for the Aqueous Behaviour of Metal-Based Drug Candidates.

Poor aqueous solubility is one of the recurrent drawbacks of many compounds in medicinal chemistry. To overcome this limitation, the dilution of drug candidates from stock solutions of an organic solvent is common practice. However, the precise characterisation of these compounds in aqueous solutions is often neglected, leading to some uncertainties regarding the nature of the actual active species. In this communication, we demonstrate that two ruthenium complexes previously reported by our group for their chemotherapeutic potential against cancer, namely [Ru(DIP)2 (sq)](PF6 ) and [Ru(DIP)2 (3-methoxysq)](PF6 ), where DIP is 4,7-diphenyl-1,10-phenanthroline, sq=semiquinonate and 3-methoxysq=3-methoxysemiquinonate, form colloids in water-DMSO (1 % v/v) mixtures that are invisible to the naked eyes. [Ru(DIP)2 (3-methoxysq)](PF6 ) was found to form a highly stable and monodispersed colloid with nanoaggregates of ∼25 nm. In contrast, [Ru(DIP)2 (sq)](PF6 ) was found to form large reticulates of mostly spherical aggregates which size was found to increase over time. The difference in size and shape distribution of drug candidates is of tremendous significance as the study of their biological activity might be severely affected. Overall, we strongly believe that these observations should be taken into account by the scientific community working on the development of metal-based drugs with poor water solubility.

Cu-catalyzed click conjugation of cobalamin to a BODIPY-based fluorophore: A versatile tool to explore the cellular biology of vitamin B12.

The Cu-catalyzed click conjugation of an azide-functionalized vitamin B12 (cobalamin) and an alkyne-labeled 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) led to the formation of a highly stable fluorescent BODIPY-labeled vitamin B12 (λex/λem = 495/508 nm). The formation of what has been identified as an iodine adduct of the conjugate was also observed as a side-product during this reaction and could be removed using HPLC. BODIPY-labeled vitamin B12 was characterized by NMR and HR-ESI-MS. In vitro studies on wild-type human fibroblasts indicated that BODIPY-labeled vitamin B12 could internalize in a manner similar to that of untagged vitamin B12. ATP-binding cassette sub-family D member 4 (ABCD4) is a lysosomal localized transporter required to export vitamin B12 from the lysosomal lumen to the cytosol. Mutations in this transporter result in the accumulation of vitamin B12 in lysosomes. In human fibroblasts harbouring a mutation in ABCD4, BODIPY-labeled vitamin B12 accumulated in the lumen of lysosomes. Our data suggests the potential use of BODIPY-labeled vitamin B12 to investigate the intracellular behavior of the vitamin in the context of disorders related to the abnormal cellular utilization of the vitamin. Moreover, results presented here demonstrate that click chemistry could be exploited for the conjugation of vitamin B12 to various other fluorophores.

Differential chloride homeostasis in the spinal dorsal horn locally shapes synaptic metaplasticity and modality-specific sensitization.

GABAA/glycine-mediated neuronal inhibition critically depends on intracellular chloride (Cl-) concentration which is mainly regulated by the K+-Cl- co-transporter 2 (KCC2) in the adult central nervous system (CNS). KCC2 heterogeneity thus affects information processing across CNS areas. Here, we uncover a gradient in Cl- extrusion capacity across the superficial dorsal horn (SDH) of the spinal cord (laminae I-II: LI-LII), which remains concealed under low Cl- load. Under high Cl- load or heightened synaptic drive, lower Cl- extrusion is unveiled in LI, as expected from the gradient in KCC2 expression found across the SDH. Blocking TrkB receptors increases KCC2 in LI, pointing to differential constitutive TrkB activation across laminae. Higher Cl- lability in LI results in rapidly collapsing inhibition, and a form of activity-dependent synaptic plasticity expressed as a continuous facilitation of excitatory responses. The higher metaplasticity in LI as compared to LII differentially affects sensitization to thermal and mechanical input. Thus, inconspicuous heterogeneity of Cl- extrusion across laminae critically shapes plasticity for selective nociceptive modalities.

Synthesis and biological assessment of a ruthenium(II) cyclopentadienyl complex in breast cancer cells and on the development of zebrafish embryos.

Ruthenium-based complexes currently attract great attention as they hold promise to replace platinum-based drugs as a first line cancer treatment. Whereas ruthenium arene complexes are some of the most studied species for their potential anticancer properties, other types of ruthenium complexes have been overlooked for this purpose. Here, we report the synthesis and characterization of Ru(II) cyclopentadienyl (Cp), Ru(II) cyclooctadienyl (COD) and Ru(III) complexes bearing anastrozole or letrozole ligands, third-generation aromatase inhibitors currently used for the treatment of estrogen receptor positive (ER +) breast cancer. Among these complexes, Ru(II)Cp 2 was the only one that displayed a high stability in DMSO and in cell culture media and consequently, the only complex for which the in vitro and in vivo biological activities were investigated. Unlike anastrozole alone, complex 2 was considerably cytotoxic in vitro (IC50 values < 1 µM) in human ER + breast cancer (T47D and MCF7), triple negative breast cancer (TNBC) (MBA-MB-231), and in adrenocortical carcinoma (H295R) cells. Theoretical (docking simulation) and experimental (aromatase catalytic activity) studies suggested that an interaction between 2 and the aromatase enzyme was not likely to occur and that the bulkiness of the PPh3 ligands could be an important factor preventing the complex to reach the active site of the enzyme. Exposure of zebrafish embryos to complex 2 at concentrations around its in vitro cytotoxicity IC50 value (0.1-1 µM) did not lead to noticeable signs of toxicity over 96 h, making it a suitable candidate for further in vivo investigations. This study confirms the potential of Ru(II)Cp complexes for breast cancer therapy, more specifically against TNBCs that are usually not responsive to currently used chemotherapeutic agents.

Exome Sequencing Implicates Impaired GABA Signaling and Neuronal Ion Transport in Trigeminal Neuralgia.

Trigeminal neuralgia (TN) is a common, debilitating neuropathic face pain syndrome often resistant to therapy. The familial clustering of TN cases suggests that genetic factors play a role in disease pathogenesis. However, no unbiased, large-scale genomic study of TN has been performed to date. Analysis of 290 whole exome-sequenced TN probands, including 20 multiplex kindreds and 70 parent-offspring trios, revealed enrichment of rare, damaging variants in GABA receptor-binding genes in cases. Mice engineered with a TN-associated de novo mutation (p.Cys188Trp) in the GABAA receptor Cl- channel γ-1 subunit (GABRG1) exhibited trigeminal mechanical allodynia and face pain behavior. Other TN probands harbored rare damaging variants in Na+ and Ca+ channels, including a significant variant burden in the α-1H subunit of the voltage-gated Ca2+ channel Cav3.2 (CACNA1H). These results provide exome-level insight into TN and implicate genetically encoded impairment of GABA signaling and neuronal ion transport in TN pathogenesis.

Coordination-mode control of bound nitrile radical complex reactivity: intercepting end-on nitrile-Mo(III) radicals at low temperature.

Variable temperature equilibrium studies were used to derive thermodynamic data for formation of eta(1) nitrile complexes with Mo(N[(t)Bu]Ar)(3), 1. (1-AdamantylCN = AdCN: DeltaH(degrees) = -6 +/- 2 kcal mol(-1), DeltaS(degrees) = -20 +/- 7 cal mol(-1) K(-1). C(6)H(5)CN = PhCN: DeltaH(degrees) = -14.5 +/- 1.5 kcal mol(-1), DeltaS(degrees) = -40 +/- 5 cal mol(-1) K(-1). 2,4,6-(H(3)C)(3)C(6)H(2)CN = MesCN: DeltaH(degrees) = -15.4 +/- 1.5 kcal mol(-1), DeltaS(degrees) = -52 +/- 5 cal mol(-1) K(-1).) Solution calorimetric studies show that the enthalpy of formation of 1-[eta(2)-NCNMe(2)] is more exothermic (DeltaH(degrees) = -22.0 +/- 1.0 kcal mol(-1)). Rate and activation parameters for eta(1) binding of nitriles were measured by stopped flow kinetic studies (AdCN: DeltaH(on)(++) = 5 +/- 1 kcal mol(-1), DeltaS(on)(++) = -28 +/- 5 cal mol(-1) K(-1); PhCN: DeltaH(on)(++) = 5.2 +/- 0.2 kcal mol(-1), DeltaS(on)(++) = -24 +/- 1 cal mol(-1) K(-1); MesCN: DeltaH(on)(++) = 5.0 +/- 0.3 kcal mol(-1), DeltaS(on)(++) = -26 +/- 1 cal mol(-1) K(-1)). Binding of Me(2)NCN was observed to proceed by reversible formation of an intermediate complex 1-[eta(1)-NCNMe(2)] which subsequently forms 1-[eta(2)-NCNMe(2)]: DeltaH(++)(k1) = 6.4 +/- 0.4 kcal mol(-1), DeltaS(++)(k1) = -18 +/- 2 cal mol(-1) K(-1), and DeltaH(++)(k2) = 11.1 +/- 0.2 kcal mol(-1), DeltaS(++)(k2) = -7.5 +/- 0.8 cal mol(-1) K(-1). The oxidative addition of PhSSPh to 1-[eta(1)-NCPh] is a rapid second-order process with activation parameters: DeltaH(++) = 6.7 +/- 0.6 kcal mol(-1), DeltaS(++) = -27 +/- 4 cal mol(-1) K(-1). The oxidative addition of PhSSPh to 1-[eta(2)-NCNMe(2)] also followed a second-order rate law but was much slower: DeltaH(++) = 12.2 +/- 1.5 kcal mol(-1) and DeltaS(++) = -25.4 +/- 5.0 cal mol(-1) K(-1). The crystal structure of 1-[eta(1)-NC(SPh)NMe(2)] is reported. Trapping of in situ generated 1-[eta(1)-NCNMe(2)] by PhSSPh was successful at low temperatures (-80 to -40 degrees C) as studied by stopped flow methods. If 1-[eta(1)-NCNMe(2)] is not intercepted before isomerization to 1-[eta(2)-NCNMe(2)] no oxidative addition occurs at low temperatures. The structures of key intermediates have been studied by density functional theory, confirming partial radical character of the carbon atom in eta(1)-bound nitriles. A complete reaction profile for reversible ligand binding, eta(1) to eta(2) isomerization, and oxidative addition of PhSSPh has been assembled and gives a clear picture of ligand reactivity as a function of hapticity in this system.

New derivatives of PCP-type pincer complexes of nickel.

The pincer-type complexes (PC(sp3)P(i-Pr))NiR (PC(sp3)P(i-Pr) = (i-Pr(2)PCH(2)CH(2))(2)CH) react with HBF(4) (R = C[triple bond]CMe, Ph, Me) or AgBF(4) (R = Br) to give (PC(sp3)P(i-Pr))Ni(BF(4)), 1, which was found to involve fluxional Ni-F-BF(3) interactions. Competition experiments revealed that the relative ease of protonation of the Ni-hydrocarbyl moiety follows the order Ni-Me > Ni-C[triple bond]CMe > Ni-Ph. Complex 1 reacts with water to give [(PC(sp3)P(i-Pr))Ni(H(2)O)][BF(4)], 2, that in turn undergoes H(2)O exchange with CH(3)CN, i-PrNH(2), and CO to give the corresponding cationic adducts 3, 4, and 5; alternatively, 3-5 can also be obtained directly from the reaction of 1 with CH(3)CN, i-PrNH(2), and CO, respectively. Deprotonation of complex 2 gives the neutral hydroxo complex (PC(sp3)P(i-Pr))Ni(OH), 6. All complexes have been characterized by NMR spectroscopy and, in the case of 2-6, by X-ray crystallography.

Novel 'Bacteriospray' Method Facilitates the Functional Screening of Metagenomic Libraries for Antimicrobial Activity.

Metagenomic techniques, notably the cloning of environmental DNA (eDNA) into surrogate hosts, have given access to the genome of uncultured bacteria. However, the determination of gene functions based on DNA sequences alone remains a significant challenge. The functional screening of metagenomic libraries represents an interesting approach in the discovery of microbial metabolites. We describe here an optimized screening approach that facilitates the identification of new antimicrobials among large metagenomic libraries. Notably, we report a detailed genomic library construction protocol using Escherichia coli DH10B as a surrogate host, and demonstrate how vector/genomic DNA dephosphorylation, ligase inactivation, dialysis of the ligation product and vector/genomic DNA ratio greatly influence clone recovery. Furthermore, we describe the use of an airbrush device to screen E. coli metagenomic libraries for their antibacterial activity against Staphylococcus aureus, a method we called bacteriospray. This bacterial spraying tool greatly facilitates and improves the functional screening of large genomic libraries, as it conveniently allows the production of a thinner and more uniform layer of target bacteria compared to the commonly used overlay method, resulting in the screening of 5-10 times more clones per agar plate. Using the Burkholderia thailandensis E264 genomic DNA as a proof of concept, four clones out of 70,000 inhibited the growth of S. aureus and were found to each contain a DNA insert. Analysis of these chromosomic fragments revealed genomic regions never previously reported to be responsible for the production of antimicrobials, nor predicted by bioinformatics tools.

Synthesis, characterization and biological evaluation of cationic organoruthenium(ii) fluorene complexes: influence of the nature of the counteranion.

In this study, five ruthenium arene complexes with fluorene-bearing N,N-(1) and N,O-(2) donor Schiff base ligands were synthesized and fully characterized. Cationic ruthenium complexes 3[X], ([Ru(η6-C6H6)(Cl)(fluorene-N[double bond, length as m-dash]CH-pyridine)][X] (where X = BF4, PF6, BPh4), were obtained by reacting ligand 1 with [Ru(η6-C6H6)Cl2]2 in the presence of NH4X salts, whereas neutral complex 4, Ru(η6-C6H6)(Cl)(fluorene-N[double bond, length as m-dash]CH-naphtholate), was isolated by reacting ligand 2 with the same precursor. It was possible to obtain a cationic version of the latter, 5[BF4], by reacting 4 with AgBF4 in the presence of pyridine. All compounds were fully characterized by NMR and HR-ESI-MS whereas some of them were also analyzed by single crystal X-ray analysis. Their in vitro antiproliferative activity was also assessed in human breast cancer cell lines, notably MCF-7 and T47D. Complex 4 and its cationic counterpart 5[BF4] were found to be the most cytotoxic compounds of the series (IC50 = 6.2-16.2 µM) and displayed higher antiproliferative activities than cisplatin in both cell lines. It was found that 5[BF4] undergoes a ligand exchange reaction and readily converts to 4 in the presence of 0.1 M NaCl, explaining the similarity in their observed cytotoxicities. Whereas 3[BF4] and 3[PF6] were found inactive at the tested concentrations, 3[BPh4] displayed a considerable cytotoxicity (IC50 = 16.7-27.8 µM). Notably, 3[BPh4], 4 (and 5[BF4]) were active against T47D, a cisplatin resistant cell line. Interestingly, 4 (16.4 µM) was found to be less cytotoxic than 3[BPh4] and cisplatin (6.6 and 7.9 µM, respectively) in breast healthy cells (MCF-12A). However, in comparison to 4 and cisplatin (at 10 µM), a lower in vivo toxicity was observed for complex 3[BPh4] on the development of zebrafish (Danio rerio) embryos.