Targeting prohibitin with small molecules to promote melanogenesis and apoptosis in melanoma cells.

Prohibitins 1 and 2 (PHB1/2) are scaffold proteins that are involved in both melanogenesis and oncogenic pathways. We hypothesized that a PHB1 ligand, melanogenin, may display anti-cancer effects in addition to its known melanogenic activity in melanocytes. Here, we disclose a convenient synthesis of melanogenin, and its analogs. We found that, among 57 new melanogenin analogs, two (Mel9 and Mel41) significantly promoted both melanogenesis in melanocytes by activating one of the PHB2-interacting proteins, microtubule-associated protein light chain 3 (LC3), and upregulating the expression of microphthalmia associated transcription factor (MITF). These analogs also activate ERK. Besides, in addition to their promelanogenic activities, we uncovered that melanogenin and its active analogs induce apoptosis in several cancer cell lines, including melanoma cells, and that this effect is caused by an inhibition of AKT survival pathway. Our findings present a new putative function for PHBs as regulators of LC3/ERK/MITF melanogenic signaling, and suggest that Mel9 and Mel41 may provide the basis for the development of new drugs candidates to treat melanoma and other types of cancers.

First-in-Class Combination Therapy of a Copper(II) Metallo-Phosphorus Dendrimer with Cytotoxic Agents.

The metallo-phosphorus dendrimer 1G3-Cu (generation 3 dendrimer bearing 48 conjugated copper(II) on its surface) has antiproliferative activity related to its capacity to activate Bax translocation. In the present study, we evaluate the activity of an association of 1G3-Cu with 5 cytotoxic agents used in chemotherapy having different modes of action. Data show no additive effect with camptothecin and cisplatin, additivity with paclitaxel and MG132, and synergy with doxorubicin. Results suggest that the multivalent Cu-conjugated dendrimer 1G3-Cu (activator of Bax translocation) plays an important role in boosting the clinical impact of Bax accumulation stimulated by the proteasome inhibitor MG132, antimitotic taxanes, and the topo II inhibitor doxorubicin.

Original Multivalent Gold(III) and Dual Gold(III)-Copper(II) Conjugated Phosphorus Dendrimers as Potent Antitumoral and Antimicrobial Agents.

Original metallophosphorus dendrimers (generation 3, 48 terminal groups) have been prepared via the complexation of phosphorus dendrimers bearing imino-pyridino end groups with Au(III) or with both Au(III) and Cu(II). The complexation of the dendrimer with Au(III), leading to 1G3-[Au48][AuCl4]48, strongly increased the antiproliferative activities against both KB and HL-60 tumoral cell lines, showing IC50s in the low nanomolar range. It can be noticed also that this gold conjugated phosphorus dendrimer displayed low activity on the quiescent cell line EPC versus its potent antiproliferative activity against actively dividing cells. In order to evaluate the potential synergistic effect between Au(III) and Cu(II) and the influence of the number of Au(III) moieties on the surface of dendrimer against the proliferative activities, nine other original dendrimers with several surface modifications have been prepared. Whatever the number of Au(III) moieties introduced on the surface of dendrimers, all the dendrimers prepared displayed similar potency (nanomolar range) to 1G3-[Au48][AuCl4]48 against KB and HL60. In marked contrast synergistic effects on the antimicrobial activity of some of these phosphorus dendrimers are observed when both Au(III) and Cu(II) are present on the dendritic structure.

Benzylphenylpyrrolizinones with Anti-amyloid and Radical Scavenging Effects, Potentially Useful in Alzheimer's Disease Treatment.

Herein we describe the drug design steps developed to increase the radical scavenging and ß-amyloid aggregation inhibitory activities of a previously described series of benzylidenephenylpyrrolizinones. Among the newly synthesized derivatives, some benzylphenylpyrrolizinones exhibited interesting results in regard to those activities. Initial druggability parameters were measured, and suggest these compounds as a suitable starting point for potential alternatives in treating Alzheimer's disease.

Anticancer copper(II) phosphorus dendrimers are potent proapoptotic Bax activators.

A multivalent phosphorus dendrimer 1G3 and its corresponding Cu-complex, 1G3-Cu have been recently identified as agents retaining high antiproliferative potency. This antiproliferative capacity was preserved in cell lines overexpressing the efflux pump ABC B1, whereas cross-resistance was observed in ovarian cancer cell lines resistant to cisplatin. Theoretical 3D models were constructed: the dendrimers appear as irregularly shaped disk-like nano-objects of about 22 Å thickness and 49 Å diameter, which accumulated in cells after penetration by endocytosis. To get insight in their mode of action, cell death pathways have been examined in human cancer cell lines: early apoptosis was followed by secondary necrosis after multivalent phosphorus dendrimers exposure. The multivalent plain phosphorus dendrimer 1G3 moderately activated caspase-3 activity, in contrast with the multivalent Cu-conjugated phosphorus dendrimer 1G3-Cu which strikingly reduced the caspase-3 content and activity. This decrease of caspase activity is not related to the presence of copper, since inorganic copper has no or little effect on caspase-3. Conversely the potent apoptosis activation could be related to a noticeable translocation of Bax to the mitochondria, resulting in the release of AIF into the cytosol, its translocation to the nucleus and a severe DNA fragmentation, without alteration of the cell cycle. The multivalent Cu-conjugated phosphorus dendrimer is more efficient than its non-complexed analog to activate this pathway in close relationship with the higher antiproliferative potency. Therefore, this multivalent Cu-conjugated phosphorus dendrimer 1G3-Cu can be considered as a new and promising first-in-class antiproliferative agent with a distinctive mode of action, inducing apoptosis tumor cell death through Bax activation pathway.

A novel class of ethacrynic acid derivatives as promising drug-like potent generation of anticancer agents with established mechanism of action.

The well-known diuretic Ethacrynic acid (EA, Edecrin), showing low anti-proliferative activities, was chemically modified at different positions. The new EA derivatives have been tested in vitro in anti-proliferative assays on both tumor KB (epidermal carcinoma) and leukemia HL60 (promyelocytic) cells suitable targets for anticancer activity. Reduction of the α-ß double bond of EA completely abolished anti-cancer activities, whereas introduction of either 2-(4-substituted phenyl)ethanamine (series A) or 4-(4-substituted phenyl)piperazine (series B) moieties generated compounds showing moderate to strong anti-proliferative activities against human cancer cell lines. Several substitutions on the phenyl of these two moieties are tolerated. The mechanism of action of the EA derivatives prepared in this study is more complex than the inhibition of glutathione S-transferase π ascribed as unique effect to EA and might help to overcome tumor resistances.

Novel benzylidenephenylpyrrolizinones with pleiotropic activities potentially useful in Alzheimer's disease treatment.

This work describes the synthesis and the biological evaluation of novel benzylidenephenylpyrrolizinones as potential antioxidant, metal chelating or amyloid ß (ßA) aggregation inhibitors. Some derivatives exhibited interesting results in regard to several of the performed evaluations and appear as valuable Multi-Target Directed Ligands with potential therapeutic interest in Alzheimer's disease. Among them, compound 29 particularly appears as a valuable radical and NO scavenger, a Cu(II) and Fe(II) chelating agent and exhibits moderate ßA aggregation inhibition properties. These activities, associated to a good predictive bioavailability and a lack of cytotoxicity, design it as a promising hit for further in vivo investigation.

Linking of Antitumor trans NHC-Pt(II) Complexes to G-Quadruplex DNA Ligand for Telomeric Targeting.

G-quadruplex structures (G4) are promising anticancerous targets. A great number of small molecules targeting these structures have already been identified through biophysical methods. In cellulo, some of them are able to target either telomeric DNA and/or some sequences involved in oncogene promotors, both resulting in cancer cell death. However, only a few of them are able to bind to these structures G4 irreversibly. Here we combine within the same molecule the G4-binding agent PDC (pyridodicarboxamide) with a N-heterocyclic carbene-platinum complex NHC-Pt already identified for its antitumor properties. The resulting conjugate platinum complex NHC-Pt-PDC stabilizes strongly G-quadruplex structures in vitro, with affinity slightly affected as compared to PDC. In addition, we show that the new conjugate binds preferentially and irreversibly the quadruplex form of the human telomeric sequence with a profile in a way different from that of NHC-Pt thereby indicating that the platination reaction is oriented by stacking of the PDC moiety onto the G4-structure. In cellulo, NHC-Pt-PDC induces a significant loss of TRF2 from telomeres that is considerably more important than the effect of its two components alone, PDC and NHC-Pt, respectively.

Antidiabetic potential of two medicinal plants used in Gabonese folk medicine.

BACKGROUND: Diabetes mellitus is a metabolic disorder which is rising globally in rich and developing countries. In the African region this rate is the highest, with 20 million diagnosed diabetics. Despite a noticeable progress in the treatment of diabetes mellitus by synthetic drugs, the search for new natural anti-diabetic agents is going on. Nauclea diderrichii (De Wild.) Merr. (ND) and Sarcocephalus pobeguinii Hua ex Pellegr. (SP) are used as traditional medicines in Gabon for the treatment of different diseases, especially in the case of diabetes. The aim of this study was to evaluate the antidiabetic potential of these two medicinal plants traditionally used in Gabon. METHODS: Pharmacological (inhibitory action on α and ß-glucosidases) and toxicological (effect on human T cell proliferation) studies were conducted on aqueous extracts of ND (leaves and bark) and SP (bark) collected in Gabon. All raw extracts were analyzed by HPTLC and their content in phenolic compounds was determined by using standard method. The most active extracts were submitted to preparative HPLC in order to evidence the most efficient subfractions by biological evaluation. RESULTS: The results showed that two extracts from ND were potent α-glucosidase inhibitors, the leaf extract being more active that the bark extract: the first one was more than 60 fold more active than Acarbose, which is an oral medication used to treat type 2 diabetes; the extract from SP bark was less efficient. The HPLC subfractions of the extracts of ND leaves and SP bark were tested in the same experimental conditions. In each case, the most active subfractions still show very potent inhibitory effect on α-glucosidase (80-90% inhibition at 0.1 mg/mL). The most efficient extract, from ND leaves, was also characterized by the highest percentage of phenolic compounds, which suggests a relationship between its inhibitory potential on α-glucosidase and its content in phenolic compounds. Conversely, only a moderate inhibitory activity of the three extracts was observed on ß-glucosidase. CONCLUSION: These results clearly indicated that active compounds present in N. diderrichii and S. pobeguinii leaves or/and bark were selective and highly potent inhibitors of α-glucosidase and validate their popular use for the treatment of diabetes.

Boronic species as promising inhibitors of the Staphylococcus aureus NorA efflux pump: study of 6-substituted pyridine-3-boronic acid derivatives.

In response to the extensive use of antibiotics, bacteria have evolved numerous mechanisms of defense against antimicrobial agents. Among them, extrusion of the antimicrobial agents outside the bacterial cell through efflux pumps is a major cause of concern. At first limited to one or few structurally-related antibiotics, bacterial resistance have then progressed towards cross-resistance between different classes of antibiotics, leading to multidrug-resistant microorganisms. Emergence of these pathogens requires development of novel therapeutic strategies and inhibition of efflux pumps appears to be a promising strategy that could restore the potency of existing antibiotics. NorA is the most studied chromosomal efflux pump of Staphylococcus aureus; it is known to be implied in resistance of Methicillin-resistant S. aureus (MRSA) strains against a wide range of unrelated substrates, including hydrophilic fluoroquinolones. Starting from 6-benzyloxypyridine-3-boronic acid I that we previously identified as a potential inhibitor of the NorA efflux pump against the NorA-overexpressing S. aureus 1199B strain (SA1199B), we describe here the synthesis and biological evaluation of a series of 6-(aryl)alkoxypyridine-3-boronic acids. 6-(3-Phenylpropoxy)pyridine-3-boronic acid 3i and 6-(4-phenylbutoxy)pyridine-3-boronic acid 3j were found to potentiate ciprofloxacin activity by a 4-fold increase compared to the parent compound I. In addition, it has been shown that both compounds promote Ethidium Bromide (EtBr) accumulation in SA1199B, thus corroborating their potential mode of action as NorA inhibitors.

Investigations on dendrimer space reveal solid and liquid tumor growth-inhibition by original phosphorus-based dendrimers and the corresponding monomers and dendrons with ethacrynic acid motifs.

The well-known reactive diuretic ethacrynic acid (EA, Edecrin), with low antiproliferative activities, was chemically modified and grafted onto phosphorus dendrimers and the corresponding simple branched phosphorus dendron-like derivatives affording novel nanodevices showing moderate to strong antiproliferative activities against liquid and solid tumor cell lines, respectively.

α-Glucosidase inhibitory activity of marine sponges collected in Mauritius waters.

This report describes the use of α-glucosidase to evaluate the anti-diabetic potential of extracts from marine sponges collected in the Mauritius waters. Initial screening at 1.0 mg/mL of 141 extracts obtained from 47 sponge species revealed 10 extracts with inhibitory activity greater than 85%. Seven of the 10 extracts were further tested at 0.1 and 0.01 mg/mL and only the methanol extract of two sponges namely Acanthostylotella sp. (ASSM) and Echinodictyum pykei (EPM) showed inhibition activity greater than 60% at 0.1 mg/mL with an IC50 value of 0.16 ± 0.02 and 0.04 ± 0.01 mg/mL, respectively, while being inactive at 0.01 mg/mL.

Synthesis of 2,3-di- and 2,2,3-trisubstituted-3-methoxycarbonyl-γ-butyrolactones as potent antitumor agents.

Various 2,3-substituted γ-butyrolactones have been synthesized by three-component reaction of aryl bromides, dimethyl itaconate and carbonyl compounds. The in vitro cytotoxic activity of these products was evaluated against a representative panel of cancer cell lines (KB, HCT116, MCF7, MCF7R, PC3, SK-OV3, HL60 and HL60R). One compound (4x) displays a good anti-proliferative activity with IC50 in the sub-micromolar range. The mechanism of action has been investigated using flow cytometry.

Design of donecopride, a dual serotonin subtype 4 receptor agonist/acetylcholinesterase inhibitor with potential interest for Alzheimer's disease treatment.

RS67333 is a partial serotonin subtype 4 receptor (5-HT4R) agonist that has been widely studied for its procognitive effect. More recently, it has been shown that its ability to promote the nonamyloidogenic cleavage of the precursor of the neurotoxic amyloid-ß peptide leads to the secretion of the neurotrophic protein sAPPα. This effect has generated great interest in RS67333 as a potential treatment for Alzheimer's disease (AD). We show herein that RS67333 is also a submicromolar acetylcholinesterase (AChE) inhibitor and therefore, could contribute, through this effect, to the restoration of the cholinergic neurotransmission that becomes altered in AD. We planned to pharmacomodulate RS67333 to enhance its AChE inhibitory activity to take advantage of this pleiotropic pharmacological profile in the design of a novel multitarget-directed ligand that is able to exert not only a symptomatic but also, a disease-modifying effect against AD. These efforts allowed us to select donecopride as a valuable dual (h)5-HT4R partial agonist (Ki = 10.4 nM; 48.3% of control agonist response)/(h)AChEI (IC50 = 16 nM) that further promotes sAPPα release (EC50 = 11.3 nM). Donecopride, as a druggable lead, was assessed for its in vivo procognitive effects (0.1, 0.3, 1, and 3 mg/kg) with an improvement of memory performances observed at 0.3 and 1 mg/kg on the object recognition test. On the basis of these in vitro and in vivo activities, donecopride seems to be a promising drug candidate for AD treatment.

Design, synthesis and biological evaluation of Pontin ATPase inhibitors through a molecular docking approach.

A virtual screening strategy, through molecular docking, for the elaboration of an electronic library of Pontin inhibitors has resulted in the identification of two original scaffolds. The chemical synthesis of four candidates allowed extensive biological evaluations for their anticancer activity. Two compounds displayed an effect on Pontin ATPase activity, and one of them also exhibited a noticeable effect on cell growth. Further biological studies revealed that the most active compound induced apoptotic cell death together with necrosis, this latter effect being likely related to the cellular balance of ATP regulation.

Evaluation of hexane and ethyl acetate extracts of the sponge Jaspis diastra collected from Mauritius Waters on HeLa cells.

OBJECTIVES: Based on previous screening results, the cytotoxic effect of the hexane (JDH) and ethyl acetate extracts (JDE) of the marine sponge Jaspis diastra were evaluated on HeLa cells and the present study aimed at determining their possible mechanism of cell death. METHODS: Nuclear staining, membrane potential change, flow cytometry analysis of cell cycle distribution and annexin V staining were undertaken to investigate the effects of JDE and JDH. Electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance were used to characterize an isolated bioactive molecule. KEY FINDINGS: JDE displayed an IC50 25 times more significant than the JDH. Flow cytometry analysis revealed JDE induced apoptosis in HeLa cells accompanied by the collapse of mitochondrial membrane potential. Fractionation of JDE resulted in the isolation of the known cytotoxic cyclodepsipeptide, Jaspamide. CONCLUSIONS: Taking our results together suggest that JDE can be valuable for the development of anticancer drugs, especially for cervical cancer. Further investigations are currently in progress with the aim to determine and isolate other bioactive compounds from this extract.

First identification of boronic species as novel potential inhibitors of the Staphylococcus aureus NorA efflux pump.

Overexpression of efflux pumps is an important mechanism of bacterial resistance that results in the extrusion of antimicrobial agents outside the bacterial cell. Inhibition of such pumps appears to be a promising strategy that could restore the potency of existing antibiotics. The NorA efflux pump of Staphylococcus aureus confers resistance to a wide range of unrelated substrates, such as hydrophilic fluoroquinolones, leading to a multidrug-resistance phenotype. In this work, approximately 150 heterocyclic boronic species were evaluated for their activity against susceptible and resistant strains of S. aureus. Twenty-four hit compounds, although inactive when tested alone, were found to potentiate ciprofloxacin activity by a 4-fold increase at concentrations ranging from 0.5 to 8 µg/mL against S. aureus 1199B, which overexpresses NorA. Boron-free analogues showed no biological activity, thus revealing that the boron atom is crucial for biological activity. This work describes the first reported efflux pump inhibitory activity of boronic acid derivatives.

A concise formation of N-substituted 3,4-diarylpyrroles--synthesis and cytotoxic activity.

A short synthesis of N-substituted 3,4-diarylpyrroles by condensation of a phenacyl halide with a primary amine and a phenylacetaldehyde is reported. The key step is an intramolecular cyclization of an in situ generated enamine onto a ketone. Using differently substituted aromatic reactants and N-(3-aminopropyl)azatricyclodecane as the amine component, the preparation of analogs of the cytotoxic marine alkaloid halitulin could be achieved. The cytotoxicity of some of the compounds obtained by this method was studied, and one of them proved to be a very potent derivative, acting at a nanomolar concentration, in a caspase-independent cell death mechanism.

Synthesis and evaluation of cytotoxic activities of new guanidines derived from carbazoles.

Several new alkylguanidines derived from carbazole have been synthesized in a simple one-pot reaction starting from 3-aminocarbazole derivatives. The aminocarbazoles were reacted with ethoxycarbonylisothiocyanate, to give thiourea intermediates, followed by the addition of an alkylamine and HgCl2 to give ethoxycarbonylguanidine intermediates. The reaction mixture was then heated at 160 °C to give the N-(1,4-dimethyl-9H-carbazol-3-yl)-N'-alkylguanidines. The cytotoxic activity of all the synthesized guanidines was evaluated against different cell lines.

Synthesis and evaluation of 3-deoxy and 3-deoxy-3-fluoro derivatives of gluco- and manno-configured tetrahydropyridoimidazole glycosidase inhibitors.

Three tetrahydropyridoimidazole-type glycosidase inhibitors have been synthesized with the 3-deoxy ribo- and arabino-, and 3-deoxy-3-fluoro gluco-configurations and two of them screened for activity against α- and ß-gluco- and mannosidase enzymes. Only one substance, the 3-deoxy-3-fluoro-derivative of the gluco-configured tetrahydropyridoimidazole was found to have any activity against a single enzyme, sweet almond ß-glucosidase, and even then at a level 100-fold lower than that of the corresponding simple gluco-configured tetrahydropyridoimidazole thereby underlining the importance of the 3-hydroxy group in the key substrate-enzyme interactions.