Membranotropic Action Research Articles

Modifying Membranotropic Action of Antimicrobial Peptide Gramicidin S by Star-like Polyacrylamide and Lipid Composition of Nanocontainers.

Gramicidin S (GS), one of the first discovered antimicrobial peptides, still shows strong antibiotic activity after decades of clinical use, with no evidence of resistance. The relatively high hemolytic activity and narrow therapeutic window of GS limit its use in topical applications. Encapsulation and targeted delivery may be the way to develop the internal administration of this drug. The lipid composition of membranes and non-covalent interactions affect GS's affinity for and partitioning into lipid bilayers as monomers or oligomers, which are crucial for GS activity. Using both differential scanning calorimetry (DSC) and FTIR methods, the impact of GS on dipalmitoylphosphatidylcholine (DPPC) membranes was tested. Additionally, the combined effect of GS and cholesterol on membrane characteristics was observed; while dipalmitoylphosphatydylglycerol (DPPG) and cerebrosides did not affect GS binding to DPPC membranes, cholesterol significantly altered the membrane, with 30% mol concentration being most effective in enhancing GS binding. The effect of star-like dextran-polyacrylamide D-g-PAA(PE) on GS binding to the membrane was tested, revealing that it interacted with GS in the membrane and significantly increased the proportion of GS oligomers. Instead, calcium ions affected GS binding to the membrane differently, with independent binding of calcium and GS and no interaction between them. This study shows how GS interactions with lipid membranes can be effectively modulated, potentially leading to new formulations for internal GS administration. Modified liposomes or polymer nanocarriers for targeted GS delivery could be used to treat protein misfolding disorders and inflammatory conditions associated with free-radical processes in cell membranes.

Alcoholic cardiomyopathy: aspects of pathogenesis and clinic

Alcoholic cardiomyopathy is the most common form of myocardial damage caused by ethanol. Ethanol and its main active metabolite acetaldehyde have a direct toxic effect on the myocardium. The mechanisms of the cardiotoxic effect of ethanol are diverse and include membranotropic action, damage to cellular organelles, activation of lipid peroxidation, and a number of others. Dissolving in the lipids of biological membranes, ethanol changes their physico-chemical properties, disrupts the activity of membrane receptors, eventually disconnecting the connection of excitation with the contraction of cardiomyocytes. Particular importance in the pathogenesis of alcoholic cardiomyopathy is attached to the ability of ethanol to cause structural and functional changes in mitochondria, which is directly related to the violation of oxidative processes and energy supply of the myocardium as a whole. Under the influence of alcohol, free-radical lipid oxidation products content increases and antioxidants activity decreases, which indicates oxidative stress development. The deterioration of myocardial contractility due to chronic alcohol intoxication triggers a cascade of compensatory mechanisms in the form of cardiomyocyte hypertrophy and progressive fibrosis, while adaptive reactions become a factor in further pathological changes. Ethanol causes myocardial damage in a dose-dependent manner.The probability of alcoholic cardiomyopathy occurrence is a derivative of the total accumulated dose of alcohol and individual predisposition. Alcoholic cardiomyopathy is considered as a variant of secondary dilated cardiomyopathy with all its clinical manifestations and consequences: dilation of the heart chambers, low left ventricular ejection fraction, progressive circulatory insufficiency, and cardiac arrhythmias. A relatively favorable prognosis in alcoholic cardiomyopathy is provided due to partial reversibility of myocardial damage under the condition of abstinence from alcohol consumption. Specific drugs for the treatment of alcoholic cardiomyopathy have not been developed. New treatment strategies include the use of myocardial growth and regulation factors synthesized by cardiomyocytes, as well as the stimulation of heart muscle regeneration and repair processes.

Kinetic biopharmaceutical studies of a new paracetamol–glucosamine analgetic drug

Background: Intercomponent drug interactions could play important role for drug release, membrane permeability and membranotropic action. Therefore, newly developed drugs need for checking their biopharmaceutical characteristics. A new analgetic drug based on paracetamol (Actimask® Acetaminoprofen) and a hepatoprotector N-acetyl-D-glucosamine has been developed, with increased safety and potentiation of the analgesic effect (Ruban O., 2022). Multibilayer lipid membranes were chosen as promising testing medium due to their proved appropriation and sensitivity for study multi-compound drug-membrane interactions. It is the basis for a kinetic approach allowing elucidation of biopharmaceutical interactions in model membrane medium. Objectives: Revealing changes of paracetamol release and membrane penetration in the new paracetamol-glucosamine analgetic drug as well as estimation the rationale of the approach developed to trace biopharmaceutical interactions in model membrane medium. Materials and Methods: L-a-dimyristoyl phosphatidylcholine (DMPC) multibilayer membrane was used as a model biomimetic testing medium. Differential scanning calorimetry (DSC) was applicated to trace kinetics of drug-membrane interactions. Results: Gelatin as a part of Actimask® increased the characteristic time of paracetamol diffusion about threefold, but it had no pronounced effect on the equilibrium paracetamol penetration into the membrane. Sole glucosamine manifested no membranotropic effect under the experimental conditions, however, in combination with gelatin, it sufficiently reduced equilibrium paracetamol penetration while paracetamol diffusion remained within the experimental error. The full drug formulation increased membrantoropic effect by 34 % in compared with sole paracetamol. Conclusions: Glucosamine and gelatin can affect both kinetic and equilibrium parameters of paracetamol-membrane interactions, while the full set of the drug components is able to increase the effect which correlates well with the previously established enhancement of analgetic effect of the drugs. The approach developed allows accurate tracing of drug release and membrane penetration depending on a set of drug components. Generally, the results obtained prove the rationale of applying the approach to pre-clinical drug examination.

Effect of Fusidic Acid and Some Nitrogen-Containing Derivatives on Liposomal and Mitochondrial Membranes.

The paper assesses the membranotropic action of the natural antibiotic fusidic acid (FA) and its derivatives. It was found that a FA analogue with ethylenediamine moiety (derivative 2), in contrast to native FA and 3,11-dioxime analogue (derivative 1), is able to increase the mobility of the lipid bilayer in the zone of lipid headgroups, as well as to induce permeabilization of lecithin liposome membranes. A similar effect of derivative 2 is also observed in the case of rat liver mitochondrial membranes. We noted a decrease in the microviscosity of the mitochondrial membrane and nonspecific permeabilization of organelle membranes in the presence of this agent, which was accompanied by a decrease in mitochondrial Δψ and OXPHOS efficiency. This led to a reduction in mitochondrial calcium retention capacity. The derivatives also reduced the production of H2O2 by mitochondria. The paper considers the relationship between the structure of the tested compounds and the observed effects.

Comparative Study of Cytotoxic and Membranotropic Properties of Betulinic Acid-F16 Conjugate on Breast Adenocarcinoma Cells (MCF-7) and Primary Human Fibroblasts.

The present study evaluates the cytotoxicity of a previously synthesized conjugate of betulinic acid (BA) with the penetrating cation F16 on breast adenocarcinoma (MCF-7) and human fibroblast (HF) cell lines, and also shows the mechanism underlying its membranotropic action. It was confirmed that the conjugate exhibits higher cytotoxicity compared to native BA at low doses also blocking the proliferation of both cell lines and causing cell cycle arrest in the G0/G1 phase. We show that the conjugate indeed has a high potential for accumulation in mitochondria, being visualized in these organelles, which is most pronounced in cancer cells. The effect of the conjugate was observed to be accompanied by ROS hyperproduction in both cancerous and healthy cells, despite the lower base level of ROS in the latter. Along with this, using artificial liposomes, we determined that the conjugate is able to influence the phase state of lipid membranes, make them more fluid, and induce nonspecific permeabilization contributing to the overall cytotoxicity of the tested agent. We conclude that the studied BA-F16 conjugate does not have significant selective cytotoxicity, at least against the studied breast cancer cell line MCF-7.

The Structural Changes in the Membranes of Staphylococcus aureus Caused by Hydrolysable Tannins Witness Their Antibacterial Activity.

Polyphenols, including tannins, are phytochemicals with pronounced antimicrobial properties. We studied the activity of two hydrolysable tannins, (i) gallotannin-1,2,3,4,5-penta-O-galloyl-β-D-glucose (PGG) and (ii) ellagitannin-1,2-di-O-galloyl-4,6-valoneoyl-β-D-glucose (dGVG), applied alone and in combination with antibiotics against Staphylococcus aureus strain 8324-4. We also evaluated the effect of these tannins on bacterial membrane integrity and fluidity and studied their interaction with membrane proteins and lipids. A correlation between the antimicrobial activity of the tannins and their membranotropic action depending on the tannin molecular structure has been demonstrated. We found that the antibacterial activity of PGG was stronger than dGVG, which can be associated with its larger flexibility, dipole moment, and hydrophobicity. In addition, we also noted the membrane effects of the tannins observed as an increase in the size of released bacterial membrane vesicles.

Structure-Activity Relationships of Holothuroid's Triterpene Glycosides and Some In Silico Insights Obtained by Molecular Dynamics Study on the Mechanisms of Their Membranolytic Action.

The article describes the structure-activity relationships (SAR) for a broad series of sea cucumber glycosides on different tumor cell lines and erythrocytes, and an in silico modulation of the interaction of selected glycosides from the sea cucumber Eupentacta fraudatrix with model erythrocyte membranes using full-atom molecular dynamics (MD) simulations. The in silico approach revealed that the glycosides bound to the membrane surface mainly through hydrophobic interactions and hydrogen bonds. The mode of such interactions depends on the aglycone structure, including the side chain structural peculiarities, and varies to a great extent. Two different mechanisms of glycoside/membrane interactions were discovered. The first one was realized through the pore formation (by cucumariosides A1 (40) and A8 (44)), preceded by bonding of the glycosides with membrane sphingomyelin, phospholipids, and cholesterol. Noncovalent intermolecular interactions inside multimolecular membrane complexes and their stoichiometry differed for 40 and 44. The second mechanism was realized by cucumarioside A2 (59) through the formation of phospholipid and cholesterol clusters in the outer and inner membrane leaflets, correspondingly. Noticeably, the glycoside/phospholipid interactions were more favorable compared to the glycoside/cholesterol interactions, but the glycoside possessed an agglomerating action towards the cholesterol molecules from the inner membrane leaflet. In silico simulations of the interactions of cucumarioside A7 (45) with model membrane demonstrated only slight interactions with phospholipid polar heads and the absence of glycoside/cholesterol interactions. This fact correlated well with very low experimental hemolytic activity of this substance. The observed peculiarities of membranotropic action are in good agreement with the corresponding experimental data on hemolytic activity of the investigated compounds in vitro.

Elimination of the toxic effect of copper sulfate is accompanied by the normalization of liver function in fibrosis

The search for biologically active compounds that regulate liver function in fibrosis is an urgent medical and biological problem. A working hypothesis was tested, according to which low molecular weight biologically active compounds from Pleurotus ostreatus and Sacharamirses cerevisiae are capable of exerting immunomodulatory and antitoxic effects after intoxication of the body with ions of heavy metals, in particular copper sulfate. Elimination of the toxic effect caused by copper sulfate can also ensure the normalization of liver function in various pathologies, in particular with liver fibrosis. When determining toxicity, a study was carried out on Wistar rats, and when studying the effect of low molecular weight biologically active compounds on liver function, clinical trials were carried out on volunteers. The activity of alanine aminotransferase, aspartate aminotransferase, actonitase and glutathione peroxidase, as well as the content of bilirubin and lipid hydroperoxides were determined. It was shown that preliminary administration of biologically active compounds to rats at a dose of 0.05 mL/100 g of body weight provided the formation in some animals (up to 80%) of resistance to the toxic effect of copper sulfate (dose 2.5 mg/100 g of body weight). Such stability is associated with a shift in the balance of “prooxidants-antioxidants” towards antioxidants. The data obtained in the clinic on volunteers with liver fibrosis and hepatitis also testify in favour of the membranotropic action of biologically active compounds. Biologically active compounds provided a decrease or complete restoration of the activity of transferases (ALT and AST) in the blood serum of these patients, with the exception of one patient out of 20 examined. Our experiment has shown the relationship between the elimination of toxicity to the action of copper sulfate and the normalization of liver function in patients. The results obtained indicate that it will be promising to use a complex of low molecular weight components from P. ostreatus and S. cerevisiae as an antidote and hepatoprotective agent.

State of antioxidant system in urogenital trichomoniasis and membranotropic effect of metronidazole

The objective of this work was to study the activity of glutathione peroxidase, glutathione reductase and the level of sulfhydryl groups in erythrocytes of patients with urogenital trichomoniasis and the effect of metronidazole on the degree of osmotic and peroxide resistance of erythrocytes from healthy donors. We examined 15 patients with urogenital trichomoniasis and 20 healthy volunteers. We studied native preparations, and also carried out a culture method using the Johnson-Trussel nutrient medium (CPLM) to identify Trichomona vaginalis. The activity of glutathione reductase, glutathione peroxidase and the level of total sulfhydryl groups were determined in erythrocytes of peripheral blood. The membrane effect of metronidazole was evaluated in in vitro experiment by the degree of osmotic and peroxide resistance of erythrocytes from healthy people. It has been established that a significant decrease in glutathione reductase and glutathione peroxidase activities in erythrocytes is observed, which indicates a violation of the antioxidant system in this pathology. It was shown in vitro experiment, that metronidazole in low concentration (80 μmol /l) has the ability to inhibit erythrocyte hypotonic hemolysis, and high concentration (250 μmol/l) leads to a decrease in osmotic and peroxide resistance of erythrocytes. Thus, inhibition of the activity of the enzymatic link of the antioxidant defense is observed in urogenital trichomoniasis, which is one of the mechanisms for the development of pathology at the cellular level in this disease. It has been shown that the isolated membranotropic action of metronidazole depends on its concentration – the drug at low concentration is able to inhibit hypotonic hemolysis of erythrocytes, and high concentration makes them more sensitive to the osmotic and peroxide hemolysis. The obtained results should be taken into account in the development of complex methods of therapy for urogenital trichomoniasis.

ТЕХНОЛОГИЯ ПОЛУЧЕНИЯ НОВЫХ БИОЛОГИЧЕСКИ АКТИВНЫХ ПЕКТИНОВЫХ МАТЕРИАЛОВ, МОДИФИЦИРОВАННЫХ L - ТРИПТОФАНОМ

New polymer complexes of copper (II) were obtained on the basis of apple pectin modified with the amino acid L-tryptophan. The stoichiometry of the complexes formed was determined by spectrophotometric methods, and the stability constants and standard thermodynamic characteristics of the complexation process (Hº; Gº; Sº) were calculated. It was found that the interaction of pectin modified with an amino acid with Cu (II) cations leads to the formation of enthalpy - entropy stabilized metal complex compounds. The IR spectral method showed that the coordination interaction of copper (II) cations with tryptophan-modified pectin involves not only carboxyl groups, but also the hydroxyl functions of the polymer matrix. The obtained polymer metal complexes in the future can be proposed for the production of new generation drugs, which, in addition to the specific properties of the amino acid introduced into the polysaccharide, also have membranotropic, immunomolulatory properties and prolonged action.

INFLUENCE OF NEUROTROPIC AND METABOLIC DRUGS ON STRUCTURAL AND FUNCTIONAL STATE OF LIPID MATRIX OF THE CELL MEMBRANE

Lately, more and more often to stimulate the reproductive function of animals people use biochemical products, which are based on neurotropic and metabolic compounds and trace elements of nanobiotechnological origin. In order to new biotechnical drugs search and development, and more effective and safe combinations of dietary supplements in them, one should know Biochemical mechanisms of membranotropic action of these substances on a cell. Since these substances can lead to physiological changes in the cell and trigger nonspecific toxic effects on the body of animals depending on dose and period of action. The article presents the results of studies on the effects of neurotropic and metabolic drugs on structural and functional state of lipid matrix of the cell membrane. In experiment were used four drugs: hlutam 1-M (Sodium Glutaminate), stymulin (Sodium Glutaminate, Sodium Succinate), nanovulin-VHR (Sodium Glutaminate, Sodium Succinate, Copper Citrate), nanovulin-R (Sodium Glutaminate, Sodium Succinate, L-arginine, Copper Citrate). The main task of the experiment was to investigate the concentration effects and primary mechanisms of membranotropic influence of the components of investigated drugs in the range of physiological concentrations of the active substance on the structural and functional state of the lipid matrix of cell membranes. According to research results, it was found that Sodium Glutaminate, which is part of all the investigational drugs, affects the polarity of the hydrophobic zone of the membrane and increases the polarity of the lipid surround. An application of Sodium glutaminate with Succinate in same drug (stimulin, nanovulin-VHR, nanovulin-R) reduces the destructive effects of Sodium Glutamate on the lipid membrane of cells. Also, it should be noted that Copper Citrate in combination with Glutaminate and Succinate (nanovulin-VHR, nanovolin-R) excludes the membrane-stabilizing and membrane-disruptive effects of their influence on the structure of lipid packing in the bilayer. From the results of the research we can suggest, that aquachelates penetrate the hydrophobic lipid bilayer zone, as evidenced by the total fluorescence quenching of pyrene.

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.

Implementation of the method of acidic erythrograms to reveal the membranotropic effect of biologically active peptides

The method of acidic erythrograms was used to study the membranotropic effect of biologically active peptides (BAP). The air exposure of erythrocyte suspension in isotonic sodium chloride solution caused a decrease in their resistance to acid hemolysis: the time of hemolysis decreased, the integral indicator of erythrocyte resistance decreased too. The air exposure of erythrocyte suspension with the BAP solutions (10-8M) changed the hemolytic resistance of erythrocytes. It was found out that a non-opiate analogue of leu-enkephalin (NALE – Phe-D-Ala-Glu-Phe-Leu-Arg), Selank (Thr-Lys-Pro-Arg-ProGly-Pro) and Semax (Met-Glu -His-Phe-Pro-Gly-Pro) increase the resistance of erythrocyte membranes to acid hemolysis, and the Arg-Gly-Arg-Pro-Gly-Pro peptide decreases the resistance of erythrocyte membranes to acid hemolysis. Membranotropic action can determine the nonspecific effects of BAP and the range of their clinical use. Acidic erythrograms can be used as a screening method for the selection of BAP with membranotropic effects.

Formation of antibiotic cycloserine complexes with stearic acid and its calcium and magnesium salts: from quantum mechanical modeling to studies of membranotropic action

Formation of antibiotic cycloserine complexes with stearic acid and its calcium and magnesium salts: from quantum mechanical modeling to studies of membranotropic action

Model lipid bilayers as sensor bionanomaterials for characterization of membranotropic action of water-soluble substances

Model lipid bilayers as sensor bionanomaterials for characterization of membranotropic action of water-soluble substances

Impact of surface properties of branched polyacrylamides onto model lipid membranes of various compositions

Branched dextran-graft-polyacrylamide copolymers with different surface properties (charged and uncharged, pure and loaded by Ag or Au nanoparticles) were created in order to drug delivery usage. By means of differential scanning calorimetry, membranotropic action of the polymers was revealed in a set of model lipid membranes, both charged and uncharged. It was observed that negatively charged membranes were more sensitive to the polymers introduction then uncharged one. The most pronounced membrantoropic effects resulted from membrane surface disturbance, which is due to significant contribution and specificity of surface interaction in the systems studied.

Membranotropic action of lauric acid, fenspiride and kaoline in model lipid membranes: role of lipid composition

Background: Model lipid membranes are widely used nowadays to elucidate membranotropic action (MA) of pharmaceuticals as well as for development of liposomal drugs. Meanwhile, membrane lipid composition could substantially affect a drug-membrane interaction. Objectives: Comparision of MA of certain pharmaceuticals on model membranes with various lipid compositions. Materials and methods: By means of differential scanning calorimetry (DSC) lauric acid, fenspiride and kaolin were studied with respect of their effects on phase transitions of model membranes based on hydrated phospholipids. Along with “standard” membrane based on L-α-dipalmitoyl­phos­pha­ti­dyl­choline (DPPC), a membrane containing cerebrosides (DPPC-C) was used, as well as one composed of DPPC, L-α-dipalmitoyl­phospha­tidylethanolamine and cholesterol (DPPC-DPPE-Chol). According to literature, DPPC and DPPC-C membranes are characterized by lipid phase homogeneity, as distinct from membrane DPPC-DPPE-Chol, where two different lipid phases coexist both below and above phase transition region. Results: It was shown that fenspiride manifested similar MA on membranes of all three types. MA of lauric acid in DPPC and DPPC-C membranes were qualitatively similar, whereas, in DPPC-DPPE-Chol membrane, different effects were observed. As to kaolin, distinctions in its MA were observed even between DPPC and DPPC-C membranes, namely, elevation of phase transition temperatures in DPPC-C membrane and a tendency to their reduction in DPPC one. In DPPC-DPPE-Chol membrane, kaolin markedly lowered phase transition temperatures coupled with opposite changes in cooperativity. Conclusions: By the examples of separated substances it was shown that strong disordering MA may be practically independent on lipid composition of membrane. Lipid rearrangement and cooperativity changes in membrane can be induced not only by incorporation of guest substances in the bulk, but also by their adsorption on membrane surface.The obtained results could be useful in adjustment of model membrane composition for MA studies of different pharmaceuticals.

Biochemical markers of safety of nano-particles of metals on the model of isolated subcultural fractions of eukaryotes

Unique sizes and a high level of bioavailability allow nanoparticles of metals (NPMe) to come into direct contact with biological systems, with infectious agents, toxins, as well as with different chemical compounds and separate cell structures (proteins, lipids, nucleic acids). Other biological effects, including less toxicity than in microscopic substances, require attention to be paid to the study of the potential risk of using nanoparticles of each type in a particular way, therefore scientific support is absolutely necessary in this direction. It is believed that the cytotoxicity of nanomaterials is due to genomic and mutagenic effects, but the mechanical forces of interaction of NPMе with cells, obviously, will change not only cytological but also their metabolic reactions. Therefore, the purpose of this research was to determine the biochemical markers of safety (potential toxicity) of NPMe (Au, Ag, Cu, Fe, Co, GFCo, Zn, MnO2) on the model of isolated membrane and cytosolic fractions of eukaryotic test cells of CHO-K1 and U937 lines. Under conditions of preincubation of experimental samples of NPMe at a final concentration of 1 μg/cm3 by the metal with preparations of subcellular fractions of CHO-K1 and U937 (in the final amount of protein 150–200 μg/cm3) for 3 minutes at 37 ± 1 ºС, there was determined the magnitude of membrane ATP-ase and cytosolic LDH-ase activity compared to intact cells ("control"). According to the results of the research, colloidal dispersions of NPAg average size ~30 nm, NPFe ~100 nm, NPCu ~70 nm, and NPMnO2 ~50 nm are safe and biocompatible by their membranotropic effect on subcellular fractions of eukaryotic test cells, as evidenced by an increase in the level of membrane ATPase and cytosolic LDHase of test-cells CHO-K1, and the experimental samples NPCo, NPGFCo and NPZn average size of ~100 nm are membrane-toxic, that is, dangerous. By the nature of the changes in the enzymatic activity of the test cells U937, the discrete dimensions of the membranotropic action of NPAu have been demonstrated: nanoparticles of size ~10 nm caused the inhibition of the membrane Na+,K+-ATPase, and the size of ~30 nm and ~45 nm – its induction; nanoparticles of size ~10, ~20 and ~30 nm induced cytosolic LDHase and the size of ~45 nm – its inhibition relative to the control level of enzymes, so NPAu ~10 and ~45 nm can be considered membrane toxic, and size ~30 nm – safe and biocompatible for eukaryotic cells. Based on the hypothesis about the involvement of metabolism-dependent mechanisms of contact interaction of colloidal dispersions of experimental samples of NPMe with cells through membranotropic properties, the study of their potential danger or biocompatibility in further research can be carried out by determining the intensity of oxidation of the main structural components of biomembranes of cells – lipids and proteins and indicators of their AO-regulation.

Study of the Combined Effect of Ibuprofen and Cholesterol on the Microviscosity and Ordering of Model Lipid Membranes by Timeresolved Measurement of Fluorescence Anisotropy Decay

The timeresolved fluorescence anisotropy decay of perylene incorporated into the lipid Ladipalmitoylphosphatidylch oline (DPPC) membrane has been studied to evaluate the membranotropic action of the nonsteroidal antiinflammatory drug, ibuprofen, and the combined effect of ibuprofen and cholesterol. The rotation correlation times (φ) and limiting anisotropy (r∞ ) permit an independent estimation of the effects of these additives on the microviscosity and ordering of model lipid membranes in different phase states. Ibuprofen was shown to cause a significant decrease in the DPPC membrane microviscosity in the gel phase with hardly any effect on the liquidcrystal phase. However, in both phases, ibuprofen diminishes the ordering of the lipid hydrophobic chains. A marked additive effect is noted when ibuprofen is embedded in the liquid membrane enriched with cholesterol, which manifests itself in substantial fluidization and disordering or the liquid membrane by the action of the components on the lipid membrane. Ibuprofen in the liquidcrystal phase causes leveling of the fluidizing and ordering effects of cholesterol.

Anticancer activity of sea cucumber triterpene glycosides.

Triterpene glycosides are characteristic secondary metabolites of sea cucumbers (Holothurioidea, Echinodermata). They have hemolytic, cytotoxic, antifungal, and other biological activities caused by membranotropic action. These natural products suppress the proliferation of various human tumor cell lines in vitro and, more importantly, intraperitoneal administration in rodents of solutions of some sea cucumber triterpene glycosides significantly reduces both tumor burden and metastasis. The anticancer molecular mechanisms include the induction of tumor cell apoptosis through the activation of intracellular caspase cell death pathways, arrest of the cell cycle at S or G2/M phases, influence on nuclear factors, NF-κB, and up-down regulation of certain cellular receptors and enzymes participating in cancerogenesis, such as EGFR (epidermal growth factor receptor), Akt (protein kinase B), ERK (extracellular signal-regulated kinases), FAK (focal adhesion kinase), MMP-9 (matrix metalloproteinase-9) and others. Administration of some glycosides leads to a reduction of cancer cell adhesion, suppression of cell migration and tube formation in those cells, suppression of angiogenesis, inhibition of cell proliferation, colony formation and tumor invasion. As a result, marked growth inhibition of tumors occurs in vitro and in vivo. Some holothurian triterpene glycosides have the potential to be used as P-gp mediated MDR reversal agents in combined therapy with standard cytostatics.