Membranotropic Activity Research Articles

Structure-activity correlation for new phosphorylated quaternary ammonium salts: To antimicrobial activity via self-organization

The impact of the hydrocarbon tail length on the physicochemical properties of N-((diisopropoxyphosphoryl)methyl)-N,N-dimethyl-N-alkylammonium bromides (CnPN+Br-, where n = 10, 12, 14, 16, 18) was studied through surface tension, electrical conductivity, and spectral characteristics of hydrophobic probes (Orange OT, pyrene) measurements. In homologous series, the values of the critical micelle concentration (cmс) decrease and reach the micromolar range for hexadecyl and octadecyl derivatives. Surface tension isotherms were used to determine the maximum surface excess (Γmax), the minimum area per surfactant molecule at the air/water interface (Amin), and the Gibbs free energy of micelle formation (∆Gmic) and adsorption (∆Gad). Thermodynamic parameters (ΔGmic, ΔHmic, ΔSmic) and counterion binding degree values (β) were calculated from the temperature dependences of specific electrical conductivity on the CnPN+Br- concentration. It was established that micellization is a spontaneous and entropy-driven process. Additionally, aggregation numbers of CnPN+Br- were obtained from steady-state fluorescence quenching and dye solubilization techniques. It was established that the investigated cationic surfactants exhibit membranotropic activity against gram-positive bacteria Staphylococcus aureus, caused by depolarization of bacterial cytoplasmic membrane.

Terpene-functionalized macrocyclic amphiphiles on pillar[5]arene platform as a bioimaging system: Synthesis, membranotropic activity and complexation with azo dye

For the first time, terpene-functionalized pillar[5]arenes containing geranyl, perillyl or farnesyl fragments were synthesized. The obtained compounds did not have a pronounced cytotoxic effect on A549 cells in the studied concentration range (0.025–1 mg/mL). The ability of the obtained compounds to self-assemble in aqueous solutions was evaluated by DLS method. It was shown that the synthesized compounds are formed monodisperse nanosized aggregates with a diameter of 87–180 nm (PDI 0.18–0.33). The morphology of the formed aggregates was studied by transmission electron microscopy. The incorporation of the obtained amphiphilic macrocycles into the lipid bilayer of model lipid biomembranes was definitely confirmed by turbidimetry. Synthesized pillar [5]arenes form a complex with the aza dye methyl orange in a 1:2 ratio (logK11 = 2.12, logK12 = 8.63) This complex retains stability both in neutral (pH 7.4) and in an acidic environment (pH 2.7).

Computational Methods Reveal a Series of Cyclic and Linear Lichenysins and Surfactins from the Vietnamese Marine Sediment-Derived Streptomyces Strain G222.

The Streptomyces strain G222, isolated from a Vietnamese marine sediment, was confidently identified by 16S rRNA gene sequencing. Its AcOEt crude extract was successfully analyzed using non-targeted LC-MS/MS analysis, and molecular networking, leading to a putative annotation of its chemical diversity thanks to spectral libraries from GNPS and in silico metabolite structure prediction obtained from SIRIUS combined with the bioinformatics tool conCISE (Consensus Annotation Propagation of in silico Elucidations). This dereplication strategy allowed the identification of an interesting cluster of a series of putative cyclic and linear lipopeptides of the lichenysin and surfactin families. Lichenysins (3-7) were isolated from the sub-fraction, which showed significant anti-biofilm activity against Pseudomonas aeruginosa MUC-N1. Their structures were confirmed by detailed 1D and 2D NMR spectroscopy (COSY, HSQC, HMBC, TOCSY, ROESY) recorded in CD3OH, and their absolute configurations were determined using the modified Marfey's method. The isolated lichenysins showed anti-biofilm activity at a minimum concentration of 100 µM. When evaluated for antibacterial activity against a panel of Gram-positive and Gram-negative strains, two isolated lichenysins exhibited selective activity against the MRSA strain without affecting its growth curve and without membranotropic activity. This study highlights the power of the MS/MS spectral similarity strategy using computational methods to obtain a cross-validation of the annotated molecules from the complex metabolic profile of a marine sediment-derived Streptomyces extract. This work provides the first report from a Streptomyces strain of combined cyclic and linear lichenysins and surfactins, known to be characteristic compounds of the genus Bacillus.

Introduction of constrained Trp analogs in RW9 modulates structure and partition in membrane models

Over the past decades, many cell-penetrating peptides (CPP) have been studied for their capacity to cross cellular membranes, mostly in order to improve cellular uptake of therapeutic agents. Even though hydrophobic and anionic CPPs have been described, many of them are polycationic, due to the presence of several arginine (Arg) residues. Noteworthy, however, the presence of aromatic amino acids such as tryptophan (Trp) within CPPs seems to play an important role to reach high membranotropic activity. RW9 (RRWWRRWRR) is a designed CPP derived from the polyarginine R9 presenting both features. In general, when interacting with membranes, CPPs adopt an optimal conformation for membrane interactions – an amphipathic helical secondary structure in the case of RW9. Herein, we assumed that the incorporation of a locally constrained amino acid in the peptide sequence could improve the membranotropic activity of RW9, by facilitating its structuration upon contact with a membrane, while leaving a certain plasticity. Therefore, two cyclized Trp derivatives (Tcc and Aia) were synthesized to be incorporated in RW9 as surrogates of Trp residues. Thus, a series of peptides containing these building blocks has been synthesized by varying the type, position, and number of modifications. The membranotropic activity of the RW9 analogs was studied by spectrofluorescence titration of the peptides in presence of liposomes (DMPG), allowing to calculate partition coefficients (Kp). Our results indicate that the partitioning of the modified peptides depends on the type, the number and the position of the modification, with the best sequence being [Aia4]RW9. Interestingly, both NMR analysis and molecular dynamic (MD) simulations indicate that this analog presents an extended conformation similar to the native RW9, but with a much-reduced structural flexibility. Finally, cell internalization properties were also confirmed by confocal microscopy.

Towards potential antifungal agents: synthesis, supramolecular self-assembly and in vitro activity of azole mono-, sesqui- and diterpenoids.

Terpenes and their derivatives are natural antifungal and antimicrobial agents. In this paper, potential antifungal agents were developed on the basis of farnesol, geraniol, myrtenol, perillyl alcohol, cedrol and phytol. The synthesized compounds exist in aqueous solutions as stable associates (D = 142-216 nm, PDI 0.04-0.16, Z = +0.9-+46 mV). Formation of stable associates of the compounds in solution promotes compaction and dosed release of the drug. The membranotropic activity of the compounds was also investigated to open up their possible application in the treatment of skin diseases. The relationship between membranotropism and lipophilicity coefficient (log P) has been established. The antifungal and antimicrobial activities of the obtained compounds were studied in vitro on the clinical isolate of Candida sp., Candida albicans, yeast Saccharomyces cerevisiae, Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus, Bifidobacterium bifidum) bacteria. Candida sp. (0.0781 mg mL-1) and Saccharomyces cerevisiae (0.0049 mg mL-1) showed the highest sensitivity to the agents.

Mechanism of Action and Therapeutic Potential of the β-Hairpin Antimicrobial Peptide Capitellacin from the Marine Polychaeta Capitella teleta.

Among the most potent and proteolytically resistant antimicrobial peptides (AMPs) of animal origin are molecules forming a β-hairpin structure stabilized by disulfide bonds. In this study, we investigated the mechanism of action and therapeutic potential of the β-hairpin AMP from the marine polychaeta Capitella teleta, named capitellacin. The peptide exhibits a low cytotoxicity toward mammalian cells and a pronounced activity against a wide range of bacterial pathogens including multi-resistant bacteria, but the mechanism of its antibacterial action is still obscure. In view of this, we obtained analogs of capitellacin and tachyplesin-inspired chimeric variants to identify amino acid residues important for biological activities. A low hydrophobicity of the β-turn region in capitellacin determines its modest membranotropic activity and slow membrane permeabilization. Electrochemical measurements in planar lipid bilayers mimicking the E. coli membrane were consistent with the detergent-like mechanism of action rather than with binding to a specific molecular target in the cell. The peptide did not induce bacterial resistance after a 21-day selection experiment, which also pointed at a membranotropic mechanism of action. We also found that capitellacin can both prevent E. coli biofilm formation and destroy preformed mature biofilms. The marked antibacterial and antibiofilm activity of capitellacin along with its moderate adverse effects on mammalian cells make this peptide a promising scaffold for the development of drugs for the treatment of chronic E. coli infections, in particular those caused by the formation of biofilms.

Membranotropic and biological activities of the membrane fusion peptides from SARS-CoV spike glycoprotein: The importance of the complete internal fusion peptide domain.

Fusion peptides (FP) are prominent hydrophobic segments of viral fusion proteins that play critical roles in viral entry. FPs interact with and insert into the host lipid membranes, triggering conformational changes in the viral protein that leads to the viral-cell fusion. Multiple membrane-active domains from the severe acute respiratory syndrome (SARS) coronavirus (CoV) spike protein have been reported to act as the functional fusion peptide such as the peptide sequence located between the S1/S2 and S2’ cleavage sites (FP1), the S2’-adjacent fusion peptide domain (FP2), and the internal FP sequence (cIFP). Using a combined biophysical approach, we demonstrated that the α-helical coiled-coil-forming internal cIFP displayed the highest membrane fusion and permeabilizing activities along with membrane ordering effect in phosphatidylcholine (PC)/phosphatidylglycerol (PG) unilamellar vesicles compared to the other two N-proximal fusion peptide counterparts. While the FP1 sequence displayed intermediate membranotropic activities, the well-conserved FP2 peptide was substantially less effective in promoting fusion, leakage, and membrane ordering in PC/PG model membranes. Furthermore, Ca2+ did not enhance the FP2-induced lipid mixing activity in PC/phosphatidylserine/cholesterol lipid membranes, despite its strong erythrocyte membrane perturbation. Nonetheless, we found that the three putative SARS-CoV membrane-active fusion peptide sequences here studied altered the physical properties of model and erythrocyte membranes to different extents. The importance of the distinct membranotropic and biological activities of all SARS-CoV fusion peptide domains and the pronounced effect of the internal fusion peptide sequence to the whole spike-mediated membrane fusion process are discussed.

Синтетические меротерпеноиды на основе терпеновых спиртов: синтез, самосборка и мембранотропные свойства

Currently, targeted drug delivery is of great interest in the field of medicine. The study of compounds capable of permeating cell membranes is a major problem in this area. The synthesis of pharmacologically active compounds includes the formation of structures with various combinations of pharmacophore fragments and properties. Amphiphilic compounds tend to exhibit membranotropic activity. From this point of view, the modification of natural products, especially terpenoids, is of particular interest. Terpenoid structures are used as membrane anchors in the development of modulators for membrane-integrated proteins or structures for creating nanocontainers. In this paper we synthesized a number of water-soluble amphiphilic meroterpenoids containing a charged pyridinium fragment on the basis of acyclic terpene alcohols. Residue of terpene alcohols – geraniol (monoterpenol), farnesol (sesquiterpenol), and phytol (diterpenol) – were used as the hydrophobic part of the amphiphilic structure. Linear acyclic alcohols are commercially available reagents and have a structure similar to that of polyprenols in archaeal lipids, which made it possible to obtain synthetic lipid-like meroterpenoids capable of self-assembly in aqueous solutions. The charged pyridinium fragment, which is included in numerous natural compounds, was of interest as a polar component. This meroterpenoids are synthetic analogs of archaeal lipids. It was shown that the studied meroterpenoids form nanosized aggregates in aqueous solutions by the method of dynamic light scattering and the Doppler microelectrophoresis method. Turbidimetric titration on model dipalmitoylphosphatidylcholine vesicles revealed that the synthesized compounds are embedded into the bilayer membrane without destroying it. Self-assembled aggregates of synthesized compounds in water can find application for drug delivery – in the creation of nanocontainers containing membrane anchors capable of interacting with the outer surface of the cell (lipid membrane).

Similarities and differences for membranotropic action of three unnatural antimicrobial peptides.

Previously, we described the design and synthesis of three nine-residue AMPs, P9Nal(SS), P9Trp(SS), and P9Nal(SR), showing high stability in serum and broad spectrum antimicrobial activity. The peptides P9Trp(SS) and P9Nal(SR) differ from P9Nal(SS) for the replacement of the two 2Nal residues with Trp residues and for the replacement of the two Cys (StBu) with Cys (tBu) residues, respectively. These changes led to peptides with a lower hydrophobicity respect to the P9Nal(SS). Interestingly, the three peptides have very similar activity against Gram-negative bacteria. Instead, they exhibit a significant difference towards Gram-positive bacteria, being P9Nal(SS) the most active. In order to evaluate the impact of amino acids substitution on membranotropic activity and rationalize the observed effects in vivo, here, we report the detailed biophysical characterization of the interaction between P9Nal(SR) and P9Trp(SS) and liposomes by combining differential scanning calorimetry, circular dichroism, and fluorescence spectroscopy. The comparison with the results for the previously characterized P9Nal(SS) peptide reveals similarities and differences on the interaction process and perturbation activities. It was found that the three peptides can penetrate at different extent inside the bilayer upon changing their conformation and inducing lipid domains formation, revealing that the formation of lipid domains is fundamental for the activity against Gram-negative bacteria. On the contrary, the dissimilar activity against Gram-positive bacteria well correlate with the different affinity of peptides for the lipoteichoic acid, a component selectively present in the cell wall of Gram-positive bacteria.

Mechanisms of Immunomodulatory and Membranotropic Activity of Trehalolipid Biosurfactants (a Review)

Of the glycolipid biosurfactants with possible medical applications, trehalolipids produced by the actinobacteria in the Rhodococcus genus are intensively studied due to their lower toxicity as compared to mycobacterial trehalose di- and monomycolates. The immunomodulatory activity of trehalolipids is based on their interaction with surface receptors on the membrane of immune cells, which trigger the signal system. This leads to the activation of cytokine, reactive oxygen species, and antibody production. Being amphiphilic, trehalose lipids can interact with the lipid bilayer and change its permeability. The discussed molecular mechanisms of the interaction between trehalolipids and immune system cells are important for the development of new immunotherapy approaches.

Membranotropic activity of taurine derivatives

The aim of the work. To evaluate the effect of n-phenylalkyl derivatives of taurine on changes in transmembrane ion currents of potential-controlled ion channels of isolated neurons.
 Materials and methods. The method of intracellular dialysis and fixation of membrane potential on isolated neurons of the great pond truncatula (Lymnaea stagnalis) and hornbill (Planorbarius corneus) was used. The n-phenylalkyl derivatives of taurine (1-phenyl-2-isopropylaminoethanesulfonic acid; benzylaminoethane sulfonic acid isopropylamide; phenethylaminoethane sulfonic acid isopropylamide) or the comparison drug taurine was dissolved in external solutions and studied at concentrations of 1, 10, 100 and 1000 M.
 Results. The results demonstrate that n-phenilalkyl derivatives of taurine in low concentrations (1; 10 M) have a modulating effect on electrically excitable cells, and in high concentrations (100; 1000 M) reduce the sodium-calcium influx and potassium efflux ionic currents, have a channel blocking effect.
 Conclusion. N-phenylalkyl derivatives of taurine reduces the excitability of cells contribute to the suppression of synaptic potentials, ion gradients of the cells.

Studies of membranotropic and fusogenic activity of two putative HCV fusion peptides

Over the past decades, membranotropic peptides such as positively charged cell-penetrating peptides (CPPs) or amphipathic antimicrobial peptides (AMPs) have received increasing interest in order to improve therapeutic agent cellular uptake.As far as we are concerned, we were interested in studying HCV fusion peptides as putative anchors. Two peptides, HCV6 and HCV7, were identified and conjugated to a fluorescent tag NBD and tested for their interaction with liposomes as model membranes. DSC and spectrofluorescence analyses demonstrate HCV7 propensity to insert or internalize in vesicles containing anionic lipids DMPG whereas no activity was observed with zwitterionic DMPC. This behavior could be explained by the peptide sequence containing a cationic arginine residue. On the contrary, HCV6 did not exhibit any membranotropic activity but was the only sequence able to induce liposomes' fusion or aggregation monitored by spectrofluorescence and DLS. This two peptides mild activity was related to their inefficient structuration in contact with membrane mimetics, which was demonstrated by CD and NMR experiments.Altogether, our data allowed us to identify two promising membrane-active peptides from E1 and E2 HCV viral proteins, one fusogenic (HCV6) and the other membranotropic (HCV7). The latter was also confirmed by fluorescence microscopy with CHO cells, indicating that HCV7 could cross the plasma membrane via an endocytosis process. Therefore, this study provides new evidences supporting the identification of HCV6 as the HCV fusion peptide as well as insights on a novel membranotropic peptide from the HCV-E2 viral protein.

C60 Fullerenes Diminish Muscle Fatigue in Rats Comparable to N-acetylcysteine or β-Alanine.

The aim of this study is to detect the effects of C60 fullerenes, which possess pronounced antioxidant properties, in comparison with the actions of the known exogenous antioxidants N-acetylcysteine (NAC) and β-Alanine in terms of exercise tolerance and contractile property changes of the m. triceps surae (TS) during development of the muscle fatigue in rats. The electrical stimulation of the TS muscle during four 30 min series in control rats led to total reduction of the muscle contraction force. Furthermore, the effects of prior intraperitoneal (i.p.) or oral C60FAS application and preliminary i.p. injection of NAC or β-Alanine on muscle contraction force under fatigue development conditions is studied. In contrast to control rats, animals with C60FAS, NAC, or β-Alanine administration could maintain a constant level of muscle effort over five stimulation series. The accumulation of secondary products and changes in antioxidant levels in the muscle tissues were also determined after the fatigue tests. The increased levels of lactic acid, thiobarbituric acid reactive substances and H2O2 after stimulation were statistically significant with respect to intact muscles. In the working muscle, there was a significant (p < 0.05) increase in the activity of endogenous antioxidants: reduced glutathione, catalase, glutathione peroxidase, and superoxide dismutase. Treated animal groups showed a decrease in endogenous antioxidant activity relative to the fatigue-induced animals (P < 0.05). Oral C60FAS administration clearly demonstrated an action on skeletal muscle fatigue development similar to the effects of i.p. injections of the exogenous antioxidants NAC or β-Alanine. This creates opportunities to oral use of C60FAS as a potential therapeutic agent. Due to the membranotropic activity of C60 fullerenes, non-toxic C60FAS has a more pronounced effect on the prooxidant-antioxidant homeostasis of muscle tissues in rats.

Membrane Crossing and Membranotropic Activity of Cell-Penetrating Peptides: Dangerous Liaisons?

Living organisms have to maintain a stable balance in molecules and ions in the changing environment in which they are living, a process known as homeostasis. At the level of cells, the plasma membrane has a major role in homeostasis, since this hydrophobic film prevents passive diffusion of large and hydrophilic molecules between the extracellular and intracellular milieu. Living organisms have evolved with highly sophisticated transport systems to control exchanges across this barrier: import of nutrients and fuel essential for their survival; recognition of chemical or physical messengers allowing information interchanges with surrounding cells. Besides specialized proteins, endocytosis mechanisms at the level of the lipid bilayer can transport molecules from the outside across the cell membrane, in an energy-dependent manner. The cell membrane is highly heterogeneous in its molecular composition (tens of different lipids, proteins, polysaccharides, and combinations of these) and dynamic with bending, deformation, and elastic properties that depend on the local composition of membrane domains. Many viruses, microorganisms, and toxins exploit the plasma membrane to enter into cells. Chemists develop strategies to target the plasma membrane with molecules capable of circumventing this hydrophobic barrier, in particular to transport and deliver nonpermeable drugs in cells for biotechnological or pharmaceutical purposes. Drug delivery systems are numerous and include lipid-, sugar-, protein-, and peptide-based delivery systems, since these biomolecules generally have good biocompatibility, biodegradability, environmental sustainability, cost effectiveness, and availability. Among those, cell-penetrating peptides (CPPs), reported for the first time in the early 1990s, are attracting major interest not only as potential drug delivery systems but also at the level of fundamental research. It was indeed demonstrated very early that these peptides, which generally correspond to highly cationic sequences, can still cross the cell membrane at 4 °C, a temperature at which all active transport and endocytosis pathways are totally inhibited. Therefore, how these charged hydrophilic peptides cross the hydrophobic membrane barrier is of utmost interest as a pure basic and physicochemical question. In this Account, we focus on cationic cell-penetrating peptides (CPPs) and the way they cross cell membranes. We summarize the history of this field that emerged around 20 years ago. CPPs were indeed first identified as protein-transduction domains from the human immunodeficiency virus (HIV) TAT protein and the Antennapedia homeoprotein, a transcription factor from Drosophila. We highlight our contribution to the elucidation of CPP internalization pathways, in particular translocation, which implies perturbation and reorganization of the lipid bilayer, and endocytosis depending on sulfated glycosaminoglycans. We show a particular role of Trp (indole side chain) and Arg (guanidinium side chain), which are essential amino acids for CPP internalization. Interactions with the cell-surface are not only Coulombic; H-bonds and hydrophobic interactions contribute also significantly to CPP entry. The capacity of CPPs to cross cell membrane is not related to their strength of membrane binding. Finally, we present optimized methods based on mass spectrometry and fluorescence spectroscopy that allow unequivocal quantification of CPPs inside cells or bound to the outer leaflet of the membrane, and discuss some limitations of the technique of flow cytometry that we have recently highlighted.

A study of the antioxidant and membranotropic activities of equinochrome a using different model systems

Echinochrome A (6-ethyl-2,3,5,7,8-pentahydroxy-1,4-naphthoquinone) isolated from the body of sand dollar Scaphechinus mirabilis is an active substance of cardioprotective medication Histochrome and exerts a wide spectrum of anti-inflammatory activities. In the present paper, we conducted a comparative study of the antioxidant (radical-scavengering) properties of echinochrome A in 2,2′-azobis(2-methylpropionamidine) dihydrochloride−luminol and hemoglobin−hydrogen peroxide−luminol systems and assessed its impact on permeability of planar bilayer lipid membranes. Trolox was used as a reference antioxidant and ascorbic acid and dihydroquercetin are taken as standards. Echinochrome A shows moderate antioxidant activity, possessing higher antioxidant capacity than Trolox and ascorbic acid, but exhibiting lower antioxidant potential compared with dihydroquercetin in tests for antioxidant activity in both investigated systems. The test substances can be arranged in the following order according to the effectiveness of the antioxidant effect: dihydroquercetin > echinochrome A > Trolox > ascorbic acid. Echinochrome A does not lead to significant changes in the permeability of planar bilayer membranes in a dose range of 1.5 to 30 μМ. Our data indicate that echinochrome A has a rather high level of radical-scavengering activity without a primary membranotropic effect. It is thought that the high levels of the cardioprotective and anti-inflammatory activities of echinochrome A may be due not only to the ability of this substance to neutralize reactive oxygen species, but also to its capacity to generate physiological concentrations of hydrogen peroxide molecules in biological systems as signaling messengers of various metabolic processes and biochemical pathways. The suspected mechanisms of the biological activity of echinochrome A are discussed.

A study of the antioxidant and membranotropic activities of luteolin using different model systems

Luteolin, a water-insoluble 3′,4′,5,7-tetrahydroxyflavon, is one of the best-studied representatives of bioflavonoids. Luteolin is an essential food component for humans and other mammals that possesses a wide spectrum of biological activities by affecting the activities of various metabolic enzymes, target receptors, and signal transduction pathways. In this study, we conducted a comparative study of the antioxidant (free-radical scavenging) properties of luteolin in 2,2′-azobis(2-methylpropionamidine) dihydrochloride–luminol and hemoglobin–hydrogen peroxide–luminol systems and assessed its effect on the permeability of planar lipid bilayer membranes. Trolox was used as a reference antioxidant, while ascorbic acid and dihydroquercetin were taken as standards. Luteolin shows moderate antioxidant activity, exhibiting a higher antioxidant capacity than trolox and ascorbic acid, but it was less effective than dihydroquercetin in tests for antioxidant activity in the studied systems. The studied compounds can be ranked according to the effectiveness of their antioxidant action: dihydroquercetin > luteolin > trolox > ascorbic acid. It should be noted that the antioxidant activity of a water-soluble form of luteolin, luteolin disulfate, is comparable with that of luteolin. Luteolin does not cause significant changes in the permeability of planar bilayer membranes in the dose range from 1.5 to 30 μM. Our findings indicate the presence of a high level of free-radical scavenging activity and the absence of a primary membranotropic effect for luteolin. It can be assumed that the multiple pleiotropic nature of luteolin activity towards a variety of biological systems is associated not only with a neutralizing effect in regard to reactive oxygen species, but also with the ability of luteolin to block and modulate different cell-signaling processes and biochemical pathways. The presumed mechanisms of the biological activity of luteolin and luteolin disulfate are discussed.

Changes in intracellular potentials and ionic currents of the mollusk and activity of Cl--channels under exposure to some inhibitory amino acids and new litium-containing compounds of them

The Changes of membrane rest potential (RP), action potential (AP), impulse activity (IA) as well as sodium, calcium and potassium ionic currents in neurons of isolated central nervous system of the Planorbarius corneus mollusk (pedal ganglia) under the extracellular action of inhibitory amino acids GABA, glycine and β-alanine and their litium-containing derivatives (LCD) in 0.1, 1 and 5 mM concentrations have been studied using a microelectrode technique. They induced the same dose-dependent and irreversible depolarization of neurons on 2-10 mV accompanied by increase of AP frequency, prolongation of their duration and decrease of summmerized ionic currents (dV/dt). According to degree of depolarization, the drugs were placed in the following range in decreasing activity: compound 3 &gt; compound 2 &gt; compound 1. In identified pedal ganglion neurons (PPed1), compound 3 in contrast to other compounds induced hyperpolarization by 2-10 mV and blocked impulse activity. The amplitude of sodium and calcium channels was decreased by 7-15 %, in the same degree after application of all compounds exposed in concentration of 5 mM. Efflux potassium ionic currents were increased in dose-dependent manner and irreversibly about by 3-7 % assessed on amplitude indexes without changes in kinetic parameters after application of LCD. Therefore, the decrease of ionic current amplitudes was due to both depolarization of neurons and direct action of LCD on ionic channels. Thus, LCD possess membranotropic activity and can modulate functional state of neurons. In the study of chloride channels in cells culture of rat glioma C6 in vitro by patch-clamp method, GABA, glycine, β-alanine and their LCD 10 µM/l activated chloride channels, shifting equiliblium membrane potential of glioma cells from -90… -70 mV to -55... -60 mV. All compounds (transmitters and LCD) were placed in the following range: glycine &gt; GABA &gt; β-alanine and compound 1 &gt; compound 3 &gt; compound 2 according to descending activity. Therefore, the most active compounds activating Cl--channels were glycine and compound 1 (LCD). Glycine was shown to be coagonist GABA receptors and its litium salt possessed significant membranotropic activity.

Hematin loses its membranotropic activity upon oligomerization into malaria pigment

Malaria is an infectious disease caused by Plasmodium type parasites transmitted by the bites of infected female anopheles mosquitoes. The malaria parasite multiplies in red blood cells where it degrades hemoglobin. This degradation of hemoglobin proteins releases hematin, an iron-containing porphyrin, which provokes membrane disruption and lysis. The malaria parasite blocks hematin-induced lysis by biocrystallization, a process that converts hematin into insoluble and chemically inert crystals. Hematin molecules are especially prone to self-assembly as dimers, oligomers and aggregates depending on environmental conditions (pH, solvent, temperature, concentration, ionic strength). Considering the different forms of hematin-based assemblies, it is still unclear which are the ones able to interact with membranes. We have prepared hematin under different conditions to form hematin-based assemblies and to measure their ability to interact and to disorganize membranes. Our results show that different forms of hematin molecules are able to penetrate lipid membranes. Interestingly, this membrane activity is spontaneously inhibited at acidic pH and it can be restored under neutral pH. By contrast, the oligomers of β-hematin were found to be completely harmless toward lipid membranes. Finally, the AFM visualization of hematin interaction with supported lipid bilayers showed for the first time its preferential interaction with defaults in membranes, at the boundaries between two distinct lipid phases. The superficial adsorption of aggregates on membranes and the absence of effect due to oligomers were also confirmed with AFM.

Investigation of the antioxidant and membranotropic activity of the quinozaline alkaloid triptantrin in different model systems

A comparative study of antioxidant (radical-scavenging) properties of triptantrin, which is a quinazoline alkaloid with anti-inflammatory activity that occurs in many species of higher plants and microorganisms, including the human microbiome, in systems containing 2,2’-azobis (2-methylpropionamidin) dihydrochloride and luminol, or hemoglobin, hydrogen peroxide, and luminol was performed and the impact of the alkaloid on the permeability of planar bilayer lipid membranes was assessed. Trolox was used as a reference antioxidant, and ascorbic acid and dihydroquercetin were used as standards. The antioxidant activity of triptantrin in both systems was much lower than that of the reference and standard antioxidants. The substances formed the following series according to antioxidant activity: dihydroquercetin > trolox > ascorbic acid > triptantrin, with the antioxidant potential of the latter being 1000 times lower than that of trolox and 3000 times lower than that of the bioflavonoid dihydroquercetin. Triptantrin did not cause significant changes in permeability of planar bilayer membranes when applied at concentrations of 0.5–10 μg/mL. The data show that triptantrin lacks considerable radical-scavenging and membranotropic activities; therefore one can assume that the high antiinflammatory activity that has been reported for triptantrin is neither related to an ability to neutralize reactive oxygen species nor to effects on cell membrane permeability. The putative mechanisms that underlie the biological effects of triptantrin are discussed.

Competing intermolecular interactions of artemisinin-type agents and aspirin with membrane phospholipids: Combined model mass spectrometry and quantum-chemical study

Study of intermolecular interactions of antimalarial artemisinin-type drugs and aspirin with membrane phospholipids is important in term of elucidation of the drugs activity modification under their joint usage. Combined experimental and computational study of the interaction of dihydroartemisinin, α-artemether, and artesunate with aspirin (ASP) and dipalmitoylphosphatidylcholine (DPPC) is performed by electrospray ionization (ESI) mass spectrometry and by DFT B3LYP/aug-cc-pVDZ methods. The results of the ESI investigation of systems containing artemisinin-type agent, ASP and DPPC, reveal a competition between the antimalarial agents and ASP for binding with DPPC molecules. The complexation between the antimalarial drugs and ASP is also found. Observed phenomena suggest that membranotropic activity of artemisin-type agents and aspirin is modified under their combined usage. To elucidate structure-energy characteristics of the non-covalent complexes studied the model DFT calculations are performed for dihydroartemisinin·ASP complex and complexes of the each drug with phosphatidylcholine head of DPPC in neutral and cationized forms.