Interaction between carbon dots from folic acid and their cellular receptor: a qualitative physicochemical approach.

According to the World Health Organization, the number of cancers (all cancers, both sexes, all ages and worldwide) in 2020 reached a total of 19 292 789 new cases leading to 9 958 133 deaths during the same period. Many cancers could be cured if detected early. Preventing cancer and detecting it early are two essential strategies for controlling this pathology. For this purpose, several strategies have been described for imaging cancer cells. One of them is based on the use of carbon nanoparticles called carbon dots, tools of physical chemistry. The literature describes that cancer cells can be imaged using carbon dots obtained from folic acid and that the in cellulo observed photoluminescence probably results from the interaction of these nanoparticles with the folic acid-receptor, a cell surface protein overexpressed in many malignant cells. However, this interaction has never been directly demonstrated yet. We investigated it, for the first time, using (i) freshly synthesized and fully characterized carbon dots, (ii) folate binding protein, a folic acid-receptor model protein and (iii) fluorescence spectroscopy and isothermal titration calorimetry, two powerful methods for detecting molecular interactions. Our results even highlight a selective interaction between these carbon made nano-objects and their biological target.

Modified Fluoroquinolones as Antimicrobial Compounds Targeting Chlamydia trachomatis.

Chlamydia trachomatis causes the most common sexually transmitted bacterial infection and trachoma, an eye infection. Untreated infections can lead to sequelae, such as infertility and ectopic pregnancy in women and blindness. We previously enhanced the antichlamydial activity of the fluoroquinolone ciprofloxacin by grafting a metal chelating moiety onto it. In the present study, we pursued this pharmacomodulation and obtained nanomolar active molecules (EC50) against this pathogen. This gain in activity prompted us to evaluate the antibacterial activity of this family of molecules against other pathogenic bacteria, such as Neisseria gonorrhoeae and bacteria from the ESKAPE group. The results show that the novel molecules have selectively improved activity against C. trachomatis and demonstrate how the antichlamydial effect of fluoroquinolones can be enhanced.

Electronic spectroscopic characterization of the formation of iron(III) metal complexes: The 8-HydroxyQuinoline as ligand case study.

Synthetic siderophores derivated from 8-HydroxyQuinoline (HQ) present various biological and pharmacological activities, such as anti-neurodegenerative or anti-oxydative. However, their affinity towards iron(III) seems to depend on the position (i.e., 7 or 2) of the HQ substitution by an electron withdrawing group. Two ester-derivatives of HQ at 2- and 7-position are synthesized and their respective iron-complexation is characterized by a joined experimental and theoretical work. By investigating the stability of all the possible accessible spin states of the iron(III) complexes at density-functional theory (DFT) level, we demonstrate that the high-spin (HS) state is the most stable one, and leads to a UV/vis absorption spectrum in perfect match with experiments. From this DFT protocol, and in agreement with the experimental results, we show that the ester functionalization of HQ in 2-position weakens the formation of the iron(III) complex while its substitution in 7-position allows a salicylate coordination of the metal very close to the ideal octahedral environment.

In vitro activities of a new fluoroquinolone derivative highly active against Chlamydia trachomatis.

Chlamydia trachomatis is a bacterial human pathogen responsible for the development of trachoma, an infection leading to blindness, and is also the cause of the main bacterial sexually transmitted infection worldwide. We designed a new inhibitor of this bacterium with, however, some prerequisites using (i) the iron dependency of the bacterium, (ii) a commercially available broad-spectrum antibiotic and (iii) a short synthetic pathway. The corresponding 8-hydroxyquinoline-ciprofloxacin conjugate was evaluated against a panel of pathogenic bacteria, including C. trachomatis but also the ESKAPE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter species). Its anti-Chlamydia activity is higher than that of ciprofloxacin and seems to be related to the fluoroquinolone moiety of the molecule, which is also responsible for the complexation of iron(III), as demonstrated by spectrophotometric titration.

Inhibition of Chlamydia trachomatis Growth During the Last Decade: A Mini-Review.

Chlamydia trachomatis is responsible for the most frequent sexually transmitted bacterial infection in the world and for trachoma, the world's leading infectious cause of blindness. Genital chlamydial infection is very common among sexually active young people, and when untreated, leads to serious complications. No vaccine is yet available for this bacterial infection. Although Chlamydia resistance to antibiotics is rarely observed in vivo, studies showed that 10-20% of patients remain infected at the end of antibiotherapy, without being reinfected. The present review gives a global and comprehensive overview of the different targets and the related inhibitors proposed during the last decade, with a view to limiting the growth of this human pathogen. Metallic and polymeric nanoparticles in this field are also briefly presented.

Targeted Delivery of Amoxicillin to C. trachomatis by the Transferrin Iron Acquisition Pathway.

Weak intracellular penetration of antibiotics makes some infections difficult to treat. The Trojan horse strategy for targeted drug delivery is among the interesting routes being explored to overcome this therapeutic difficulty. Chlamydia trachomatis, as an obligate intracellular human pathogen, is responsible for both trachoma and sexually transmitted diseases. Chlamydia develops in a vacuole and is therefore protected by four membranes (plasma membrane, bacterial inclusion membrane, and bacterial membranes). In this work, the iron-transport protein, human serum-transferrin, was used as a Trojan horse for antibiotic delivery into the bacterial vacuole. Amoxicillin was grafted onto transferrin. The transferrin-amoxicillin construct was characterized by mass spectrometry and absorption spectroscopy. Its affinity for transferrin receptor 1, determined by fluorescence emission titration [KaffTf-amox = (1.3 ± 1.0) x 108], is very close to that of transferrin [4.3 x 108]. Transmission electron and confocal microscopies showed a co-localization of transferrin with the bacteria in the vacuole and were also used to evaluate the antibiotic capability of the construct. It is significantly more effective than amoxicillin alone. These promising results demonstrate targeted delivery of amoxicillin to suppress Chlamydia and are of interest for Chlamydiaceae and maybe other intracellular bacteria therapies.

Is the conformational flexibility of piperazine derivatives important to inhibit HIV-1 replication?

The conserved binding site of HIV-1 gp120 envelope protein, an essential component in the viral entry process, provides an attractive antiviral target. The structural similarities between two piperazine derivatives: PMS-601, showing a dual activity for anti-PAF and anti-HIV activity, and BMS-378806, known to inhibit HIV-1 gp120, motivated us to merge important structural features of the two compounds. Novel piperazine derivatives were synthesized and evaluated in vitro concerning their ability to inhibit HIV-1 replication in in vitro infected lymphocytes. We described an approach that combines molecular docking, molecular dynamics, MM-PBSA calculations and conformational analysis to rationally predict piperazine derivatives binding mode with HIV-1 gp120. We also inquired about the conformational adaptability of the molecules, upon complex formation, and its importance to their respective inhibitory activity. The analysis suggested that the impact of the flexibility of these molecules revealed to be more important, in the context of drug design, than it has generally been assumed. These new insights at the atomic level might be useful to design inhibitors with improved antiviral activity.

Transferrin receptor-1 iron-acquisition pathway - synthesis, kinetics, thermodynamics and rapid cellular internalization of a holotransferrin-maghemite nanoparticle construct.

BACKGROUND: Targeting nanoobjects via the iron-acquisition pathway is always reported slower than the transferrin/receptor endocytosis. Is there a remedy? METHODS: Maghemite superparamagnetic and theragnostic nanoparticles (diameter 8.6nm) were synthesized, coated with 3-aminopropyltriethoxysilane (NP) and coupled to four holotransferrin (TFe2) by amide bonds (TFe2-NP). The constructs were characterized by X-ray diffraction, transmission electron microscopy, FTIR, X-ray Electron Spectroscopy, Inductively Coupled Plasma with Atomic Emission Spectrometry. The in-vitro protein/protein interaction of TFe2-NP with transferrin receptor-1 (R1) and endocytosis in HeLa cells were investigated spectrophotometrically, by fast T-jump kinetics and confocal microscopy. RESULTS: In-vitro, R1 interacts with TFe2-NP with an overall dissociation constant KD=11nM. This interaction occurs in two steps: in the first, the C-lobe of the TFe2-NP interacts with R1 in 50µs: second-order rate constant, k1=6×10(10)M(-1)s(-1); first-order rate constant, k-1=9×10(4)s(-1); dissociation constant, K1d=1.5µM. In the second step, the protein/protein adduct undergoes a slow (10,000s) change in conformation to reach equilibrium. This mechanism is identical to that occurring with the free TFe2. In HeLa cells, TFe2-NP is internalized in the cytosol in less than 15min. CONCLUSION: This is the first time that a nanoparticle-transferrin construct is shown to interact with R1 and is internalized in time scales similar to those of the free holotransferrin. GENERAL SIGNIFICANCE: TFe2-NP behaves as free TFe2 and constitutes a model for rapidly targeting theragnostic devices via the main iron-acquisition pathway.

PMS1077 sensitizes TNF-α induced apoptosis in human prostate cancer cells by blocking NF-κB signaling pathway.

Our previous studies have demonstrated that PMS1077, a platelet-activating factor (PAF) antagonist, could induce apoptosis of Raji cells. However, the mechanism of action has not yet been determined. The nuclear transcription factor-kappa B (NF-κB) signaling pathway plays a critical role in tumor cell survival, proliferation, invasion, metastasis, and angiogenesis, so we determined the effects of PMS1077 and its structural analogs on tumor necrosis factor-α (TNF-α) induced activation of NF-κB signaling. In this study, we found that PMS1077 inhibited TNF-α induced expression of the NF-κB regulated reporter gene in a dose dependent manner. Western blot assay indicated that PMS1077 suppressed the TNF-α induced inhibitor of κB-α (IκB-α) phosphorylation, IκB-α degradation, and p65 phosphorylation. PMS1077 consistently blocked TNF-α induced p65 nuclear translocation as demonstrated in the immunofluorescence assay used. Docking studies by molecular modeling predicted that PMS1077 might interact directly with the IκB kinase-ß (IKK-ß) subunit. These results suggested that PMS1077 might suppress the activation of NF-κB by targeting IKK-ß involved in the NF-κB signaling pathway. Finally, we showed that PMS1077 sensitized cells to TNF-α induced apoptosis by suppressing the expression of NF-κB regulated anti-apoptotic genes. Our results reveal a novel function of PMS1077 on the NF-κB signaling pathway and imply that PMS1077 can be considered as an anti-tumor lead compound.

Synthesis of gatifloxacin derivatives and their biological activities against Mycobacterium leprae and Mycobacterium tuberculosis.

Novel 3'-piperazinyl derivatives of the 8-hydrogeno and 8-methoxy-6-fluoro-1-cyclopropyl-4-quinolone-3-carboxylic acid scaffolds were designed, synthesized and characterized by (1)H, (13)C and (19)F NMR, and HRMS. The activity of these derivatives against pathogenic mycobacteria (M. leprae and M. tuberculosis), wild-type (WT) strains or strains harboring mutations implicated in quinolone resistance, were determined by measuring drug concentrations inhibiting cell growth (MIC) and/or DNA supercoiling by DNA gyrase (IC(50)), or inducing 25% DNA cleavage by DNA gyrase (CC(25)). Compound 4 (with a methoxy in R(8) and a secondary carbamate in R(3)') and compound 5 (with a hydrogen in R(8) and an ethyl ester in R(3)') displayed biological activities close to those of ofloxacin but inferior to those of gatifloxacin and moxifloxacin against M. tuberculosis and M. leprae WT DNA gyrases, whereas all of the compounds were less active in inhibiting M. tuberculosis growth and M. leprae mutant DNA gyrases. Since R(3)' substitutions have been poorly investigated previously, our results may help to design new quinolone derivatives in the future.

PMS-1077, a PAF antagonist, induced differentiation of HL-60 cells with its novel activity.

The cell differentiation-inducing effect of 2-N,N-diethylaminocarbonyloxymethyl-1-diphenylmethyl-4-(3,4,5-trimethoxybenzoyl) piperazine, hydrochloride (PMS-1077) was determined in human leukaemic HL-60 cells with profiling of cell proliferation, analysis of cell cycling, characterization of expression of various CD molecules and determination of phagocytotic activity of differentiated HL-60 cells. After treatment with PMS-1077, HL-60 cells exhibited a decreased cell viability during which cell cycle was arrested in G0-/G1-phase. Flow cytometric analysis showed CD11b and CD14 were up-regulated, whereas CD15 was unaffected. Together with the finding that PMS-1077-treated HL-60 cells exhibited activities of differentiation by examining their ability of phagocytosing latex beads, an antiproliferative effect and a differentiation-inducing role were determined for PMS-1077 in HL-60 cells.

Development of a platelet-activating factor antagonist for HIV-1 associated neurocognitive disorders.

The neuroregulatory activities of PMS-601, a platelet activating factor antagonist, were investigated in laboratory and animal models of HIV-1 encephalitis (HIVE). For the former, PMS-601 reduced monocyte-derived macrophage pro-inflammatory secretions, multinucleated giant cell (MGC) formation, and neuronal loss independent of antiretroviral responses. PMS-601 treatment of HIVE severe combined immunodeficient mice showed reduced microgliosis, MGCs and neurodegeneration. These observations support the further development of PMS-601 as an adjunctive therapy for HIV-1 associated neurocognitive disorders.

Structure-activity relationships in platelet-activating factor. Part 14: synthesis and biological evaluation of piperazine derivatives with dual anti-PAF and anti-HIV-1 activity.

As HIV-associated dementia prevalence has risen with the lifespan of HIV-infected individuals, there is an important need for antiretroviral and anti-inflammatory drugs targeting the central nervous system. Platelet-activating factor, a mediator of inflammation, is an HIV-induced neurotoxin secreted in the infected brain. In this work, we developed piperazine derivatives bearing a heterocyclic moiety as PAF-antagonists and HIV-1 replication inhibitors with micromolar potency.

Structure-activity relationships in platelet-activating factor. Part 13: synthesis and biological evaluation of piperazine derivatives with dual anti-PAF and anti-HIV-1 or pure antiretroviral activity.

HIV-1 infection of the brain and PAF neurotoxicity are implicated in AIDS dementia complex. We previously reported that a trisubstituted piperazine derivative is able to diminish both HIV-1 replication in monocyte-derived macrophages and PAF-induced platelet aggregation. We report in this work new compounds obtained by modifying its piperazine substituents. The structure-activity relationship study shows that a better dual activity or even pure antiretroviral compounds can be obtained in this series.

Structure-activity relationships in platelet-activating factor. 12. Synthesis and biological evaluation of platelet-activating factor antagonists with anti-HIV-1 activity.

The HIV-1 central nervous system infection leads to the onset of neurological impairments called AIDS dementia complex (ADC). PAF plays an important role in this pathology, as it is an HIV-1-induced neurotoxin produced by infected or activated macrophages and microglia, in the brain. We previously reported that PAF-antagonists bearing a trisubstituted piperazine presented in vitro anti-HIV-1 activity in human macrophages. To improve the pharmacological activities of our lead compound, 1a, we modified its carbamate function and evaluated both its antiretroviral and anti-PAF activities. One carbamate derivative (10c) demonstrated a similar antiviral activity but a higher anti-PAF potency, whereas 4a, with an ureide function, presents an increased antiviral activity and can be considered as a pure antiretroviral drug, as it does not present PAF-antagonism. Moreover, we measured the ability of 1a to cross the blood-brain barrier, using the in situ mouse brain perfusion method and its plasmatic concentrations after iv and po administration. The transport parameter measured (K(in)) proves that 1a is able to cross this biological barrier, but a pharmacokinetic study reveals its weak bioavailability in rats.

Stereodefined and polyunsaturated inhibitors of histone deacetylase based on (2E,4E)-5-arylpenta-2,4-dienoic acid hydroxyamides.

Syntheses of (2E,4E)-5-arylpenta-2,4-dienoic acid hydroxyamides are described, some of which are potent inhibitors of histone deacetylase, a double bond conferring more than a 10-fold increase in potency compared with the triple bond analogue oxamflatin. Variation of substituents on the aromatic ring has a marked effect on potency, in vitro IC(50) values down to 50 nM being obtained.