New Analogs of Polyamine Toxins from Spiders and Wasps: Liquid Phase Fragment Synthesis and Evaluation of Antiproliferative Activity

Polyamine toxins (PATs) are conjugates of polyamines (PAs) with lipophilic carboxylic acids, which have been recently shown to present antiproliferative activity. Ten analogs of the spider PATs Agel 416, HO-416b, and JSTX-3 and the wasp PAT PhTX-433 were synthesized with changes in the lipophilic head group and/or the PA chain, and their antiproliferative activity was evaluated on MCF-7 and MDA-MB-231 breast cancer cells, using Agel 416 and HO-416b as reference compounds. All five analogs of PhTX-433 were of very low activity on both cell lines, whereas the two analogs of JSTX-3 were highly active only on the MCF-7 cell line with IC50 values of 2.63–2.81 μΜ. Of the remaining three Agel 416 or HO-416b analogs, only the one with the spermidine chain was highly active on both cells with IC50 values of 3.15–12.6 μM. The two most potent compounds in this series, Agel 416 and HO-416b, with IC50 values of 0.09–3.98 μΜ for both cell lines, were found to have a very weak cytotoxic effect on the MCF-12A normal breast cells. The present study points out that the structure of both the head group and the PA chain determine the strength of the antiproliferative activity of PATs and their selectivity towards different cells.

Functions and Mechanisms of SAC Phosphoinositide Phosphatases in Plants

Phosphatidylinositol (PtdIns) is one type of phospholipid comprising an inositol head group and two fatty acid chains covalently linked to the diacylglycerol group. In addition to their roles as compositions of cell membranes, phosphorylated PtdIns derivatives, termed phosphoinositides, execute a wide range of regulatory functions. PtdIns can be phosphorylated by various lipid kinases at 3-, 4- and/or 5- hydroxyls of the inositol ring, and the phosphorylated forms, including PtdIns3P, PtdIns4P, PtdIns5P, PtdIns(3,5)P2, PtdIns(4,5)P2, can be reversibly dephosphorylated by distinct lipid phosphatases. Amongst many other types, the SUPPRESSOR OF ACTIN (SAC) family of phosphoinositide phosphatases recently emerged as important regulators in multiple growth and developmental processes in plants. Here, we review recent advances on the biological functions, cellular activities, and molecular mechanisms of SAC domain-containing phosphoinositide phosphatases in plants. With a focus on those studies in the model plant Arabidopsis thaliana together with progresses in other plants, we highlight the important roles of subcellular localizations and substrate preferences of various SAC isoforms in their functions.

Stabilizing Na-bentonite by Poly(Diallyl Dimethyl Ammonium Chloride) Adsorption

Clay minerals have been modified by polymers for different applications. The polymer addition affects not only the surface propertiesbut also the rheological properties and the stability of the clay-polymer suspension as a whole. In the current study, the electro-chemical properties of bentonite particles in presence of poly diallyl dimethyl ammonium chloride (PDDACl) were investigated. Theseproperties were characterized by as zeta potential, adsorption isotherm, Fourier transform infrared (FTIR) and the apparent viscosityat different solid percent. The results indicated that the viscosity of the bentonite-PDDACl suspension not only increases by raising thepolymer concentration but also by increasing solids %. Adsorption of PDDACl polymer increases the positivity of bentonite surfaceas a function of polymer concentration, which could be explained mainly by electrostatic interaction of deficient metal ions at theoctahedral sheets of bentonite with the cationic head group of the polymer. The PDDACl adsorption isotherm on bentonite fits moreprobably Langmuir than Freundlich isotherm

Phosphonodithioester–Amine Coupling as a Key Reaction Step for the Design of Cationic Amphiphiles Used for Gene Delivery

A convergent synthesis of cationic amphiphilic compounds is reported here with the use of the phosphonodithioester–amine coupling (PAC) reaction. This versatile reaction occurs at room temperature without any catalyst, allowing binding of the lipid moiety to a polar head group. This strategy is illustrated with the use of two lipid units featuring either two oleyl chains or two-branched saturated lipid chains. The final cationic amphiphiles were evaluated as carriers for plasmid DNA delivery in four cell lines (A549, Calu3, CFBE and 16HBE) and were compared to standards (BSV36 and KLN47). These new amphiphilic derivatives, which were formulated with DOPE or DOPE-cholesterol as helper lipids, feature high transfection efficacies when associated with DOPE. The highest transfection efficacies were observed in the four cell lines at low charge ratios (CR = 0.7, 1 or 2). At these CRs, no toxic effects were detected. Altogether, this new synthesis scheme using the PAC reaction opens up new possibilities for investigating the effects of lipid or polar head groups on transfection efficacies.

The Synthesis of Malonganenone Analogues for Antiparasitic Structure-Activity Relationship Analyses

<p>The most lethal causative species of malaria, Plasmodium falciparum, has been reported as developing resistance against current antimalarial drugs in South-East Asia. New antimalarial drugs, especially those with novel modes of action, need to be established before resistance spreads. The marine natural products malonganenones A, B, and C, isolated from the gorgonian Leptogorgia gilchristi, have recently been shown to inhibit P. falciparum parasite growth. Therefore, a library of malonganenone analogues were synthesised for structure activity relationship analysis. A range of purines, purinones, and pyrimidines were alkylated with simple terpenoid chains to generate malonganenone A and B analogues, while malonganenone C analogues were made by acetylation or formylation, then methylation of terpenoid amines. The compounds were moderately active against P. falciparum infected red blood cells, but exhibited significant activity against Trypanosoma brucei, the parasite responsible for African sleeping sickness. Off target activity was assessed by assay against Escherichia coli, Staphylococcus aureus, Steptococcus uberis and HeLa cells. The overall structureactivity relationship analysis resulted in the identification of lead candidate, geranylgeranyl imidazole (146), which had IC50 values of 10.2 μM and 3.4 μM against P. falciparum and T. brucei, respectively. In addition, the minimum inhibitory concentration of 146 against S. uberis and S. aureus was 16 – 32 μM and 128 μM, respectively. Compound 146 was inactive against E. coli and was also non-toxic to HeLa cells. In addition, a geometric mixture of E and Z isomers at the alkene closest to the imidazole head group was more active than just the E isomer as for 146, which suggested the Z isomer was more active than the E isomer. Therefore, the lead compound identified within this project was the 2Z isomer of geranylgeranyl imidazole.</p>

The Synthesis of Malonganenone Analogues for Antiparasitic Structure-Activity Relationship Analyses

<p>The most lethal causative species of malaria, Plasmodium falciparum, has been reported as developing resistance against current antimalarial drugs in South-East Asia. New antimalarial drugs, especially those with novel modes of action, need to be established before resistance spreads. The marine natural products malonganenones A, B, and C, isolated from the gorgonian Leptogorgia gilchristi, have recently been shown to inhibit P. falciparum parasite growth. Therefore, a library of malonganenone analogues were synthesised for structure activity relationship analysis. A range of purines, purinones, and pyrimidines were alkylated with simple terpenoid chains to generate malonganenone A and B analogues, while malonganenone C analogues were made by acetylation or formylation, then methylation of terpenoid amines. The compounds were moderately active against P. falciparum infected red blood cells, but exhibited significant activity against Trypanosoma brucei, the parasite responsible for African sleeping sickness. Off target activity was assessed by assay against Escherichia coli, Staphylococcus aureus, Steptococcus uberis and HeLa cells. The overall structureactivity relationship analysis resulted in the identification of lead candidate, geranylgeranyl imidazole (146), which had IC50 values of 10.2 μM and 3.4 μM against P. falciparum and T. brucei, respectively. In addition, the minimum inhibitory concentration of 146 against S. uberis and S. aureus was 16 – 32 μM and 128 μM, respectively. Compound 146 was inactive against E. coli and was also non-toxic to HeLa cells. In addition, a geometric mixture of E and Z isomers at the alkene closest to the imidazole head group was more active than just the E isomer as for 146, which suggested the Z isomer was more active than the E isomer. Therefore, the lead compound identified within this project was the 2Z isomer of geranylgeranyl imidazole.</p>

Transgene expression in mice of the Opa1 mitochondrial transmembrane protein through bicontinuous cubic lipoplexes containing gemini imidazolium surfactants

Background Lipoplexes are non-viral vectors based on cationic lipids used to deliver DNA into cells, also known as lipofection. The positively charge of the hydrophilic head-group provides the cationic lipids the ability to condensate the negatively charged DNA into structured complexes. The polar head can carry a large variety of chemical groups including amines as well as guanidino or imidazole groups. In particular, gemini cationic lipids consist of two positive polar heads linked by a spacer with different length. As for the hydrophobic aliphatic chains, they can be unsaturated or saturated and are connected to the polar head-groups. Many other chemical components can be included in the formulation of lipoplexes to improve their transfection efficiency, which often relies on their structural features. Varying these components can drastically change the arrangement of DNA molecules within the lamellar, hexagonal or cubic phases that are provided by the lipid matrix. Lipofection is widely used to deliver genetic material in cell culture experiments but the simpler formulations exhibit major drawbacks related to low transfection, low specificity, low circulation half-life and toxicity when scaled up to in vivo experiments. Results So far, we have explored in cell cultures the transfection ability of lipoplexes based on gemini cationic lipids that consist of two C16 alkyl chains and two imidazolium polar head-groups linked with a polyoxyethylene spacer, (C16Im)2(C4O). Here, PEGylated lipids have been introduced to the lipoplex formulation and the transgene expression of the Opa1 mitochondrial transmembrane protein in mice was assessed. The addition of PEG on the surface of the lipid mixed resulted in the formation of Ia3d bicontinuous cubic phases as determined by small angle X-ray scattering. After a single intramuscular administration, the cubic lipoplexes were accumulated in tissues with tight endothelial barriers such as brain, heart, and lungs for at least 48 h. The transgene expression of Opa1 in those organs was identified by western blotting or RNA expression analysis through quantitative polymerase chain reaction. Conclusions The expression reported here is sufficient in magnitude, duration and toxicity to consolidate the bicontinuous cubic structures formed by (C16Im)2(C4O)-based lipoplexes as valuable therapeutic agents in the field of gene delivery. Graphical Abstract

The exploration of Thermococcus barophilus lipidome reveals the widest variety of phosphoglycolipids in Thermococcales.

One of the most distinctive characteristics of Archaea is their unique lipids. While the general nature of archaeal lipids has been linked to their tolerance to extreme conditions, little is known about the diversity of lipidic structures Archaea are able to synthesize, which hinders the elucidation of the physicochemical properties of their cell membrane. In an effort to widen the known lipid repertoire of the piezophilic and hyperthermophilic model archaeon Thermococcus barophilus, we comprehensively characterized its intact polar lipid (IPL), core lipid (CL), and polar head group compositions using a combination of cutting-edge liquid chromatography and mass spectrometric ionization systems. We tentatively identified 82 different IPLs based on five distinct CLs and 10 polar head group derivatives of phosphatidylhexoses, including compounds reported here for the first time, e.g., di-N-acetylhexosamine phosphatidylhexose-bearing lipids. Despite having extended the knowledge on the lipidome, our results also indicate that the majority of T. barophilus lipids remain inaccessible to current analytical procedures and that improvements in lipid extraction and analysis are still required. This expanded yet incomplete lipidome nonetheless opens new avenues for understanding the physiology, physicochemical properties, and organization of the membrane in this archaeon as well as other Archaea.