Membrane Microviscosity Research Articles

Carotenoids Assist in Cyanobacterial Photosystem II Assembly and Function.

Carotenoids (carotenes and xanthophylls) are ubiquitous constituents of living organisms. They are protective agents against oxidative stresses and serve as modulators of membrane microviscosity. As antioxidants they can protect photosynthetic organisms from free radicals like reactive oxygen species that originate from water splitting, the first step of photosynthesis. We summarize the structural and functional roles of carotenoids in connection with cyanobacterial Photosystem II. Although carotenoids are hydrophobic molecules, their complexes with proteins also allow cytoplasmic localization. In cyanobacterial cells such complexes are called orange carotenoid proteins, and they protect Photosystem II and Photosystem I by preventing their overexcitation through phycobilisomes (PBS). Recently it has been observed that carotenoids are not only required for the proper functioning, but also for the structural stability of PBSs.

The effect of prolonged simvastatin application on serotonin uptake, membrane microviscosity and behavioral changes in the animal model

Simvastatin and other statins (HMG-CoA (3-hydroxy-3-methylglutaryl coenzyme A) reductase inhibitors) are extensively used in clinical practices and are very effective in decreasing serum low-density lipoprotein cholesterol. However, their effect on cholesterol synthesis in central nervous system and its behavioral consequences have not been fully understood yet. We have studied selected biologic traits potentially affected by statin treatment — serotonin (5-HT) uptake in platelets, membrane microviscosity in erythrocytes, cholesterol level in the brain (amygdala; hippocampus and prefrontal cortex), as well as behavioral changes in an elevated plus maze and open field test in male Long-Evans rats, which were treated by simvastatin (30mg/kg per day) for 2 or 4weeks.We demonstrated: 1) a decrease in both serotonin transporter (SERT) activity and membrane microviscosity after treatment with simvastatin, 2) lower cholesterol content in all tested brain regions in animals from the simvastatin treated group, and 3) longer time spent in the open arms and a higher number of entrances to the closed arms in the elevated plus maze by animals from the simvastatin group compared to animals from the control group, but no differences in behavior in the open field test.Taken together, our results confirmed complex alterations, including behavioral changes, after the cholesterol lowering treatment. Furthermore, we discuss the possibility that the behavioral changes, traditionally interpreted as an anxiolytic effect, may be interpreted as increased impulsivity. We also confirmed that such behavioral changes may be attributed to changes in serotonergic neurotransmission.

Peroxidation of Lipoprotein and of Certain Liposomal Lipids Depend Similarly on the Physico-Chemical Properties of the Aggregated Lipids

In view of the complexity of biological membranes, the dependence of peroxidation on the physicochemical properties of membranes and on different antioxidants have been studied in liposomes made of different compositions, under different conditions. low molecular weight antioxidants and the dependence of these effects on various factors have also been studied. In 007, we reviewed the literature regarding these issues. Recent information clarifies several aspects of the peroxidation in these model membranes, including the promotion of copper-induced peroxidation by inclusion of negatively charged phospholipids (PA and PS), inhibition of the peroxidation of PS-containing liposomes by nano-molar concentrations of Tocopherol and other 12 (out of 37 tested) phenols of possible semi-quinone structures and promotion of copper induced peroxidation by soluble “antioxidants. Several new studies support our previous interpretation that the dependence of peroxidation on the packing of the PUFA in the bilayer (and the microviscosity of the liposomal membranes) is due to the consequent change of the rate of lateral diffusion of the PUFA-bearing phospholipids. Recent study ruled out this interpretation on the basis of the similar effects of “fluidizing” and “rigidifying” non-oxidizable phospholipids. Nonetheless, the data is insufficient to rule out the previous interpretation because both the propagation and termination of the free radical chain reaction depend similarly on the micro-viscosity (and the rate of lateral diffusion), while the results of a change in the rate of these two reactions are opposite. New data also show how peroxidation affect continuous peroxidation and demonstrate that liposomes are affected by antioxidants similar to LDL only when they contain PS.

A Possible Interconnection of Cholesterol Overloading and Phagocytic Activityof the Monocytes in the Prone to Rheumatoid Arthritis Individuals

Background: The abnormalities of lipid metabolism were demonstrated in the individuals, who later develop rheumatoid arthritis (RA). Trivial infections are known to contribute to atherosclerosis. We showed that first degree relatives of RA patients suffer from frequent and lingering trivial infections. The interconnection between the disturbance of lipid metabolism and the increased trivial infection burden is hypothesized in this group. Mononuclear phagocytes (MP) are the important players in RA pathogenesis, antiinfectious defense and atherosclerosis. The aim was to investigate the interconnection between the involvement of MPs in cholesterol metabolism, their phagocytic activity and the burden of trivial infections in the RA patients, their relatives and healthy individuals without autoimmune diseases in family history. Methods: The following parameters were studied: intracellular cholesterol content (colorimetric), membrane cholesterol content and microviscosity (fluorescent), engulfment and digestion (radioisotope); reactive oxygen species generation (chemiluminescence). Results: In relatives MPs and their cell membranes were overloaded with cholesterol; microviscosity of cell membranes and membrane annular lipid regions was increased, cholesterol accumulation in the cells being in strong correlation with the incidence and duration of the trivial infections. In RA group only increased microviscosity of annular lipid regions was revealed. In the patient and relative groups the delayed engulfment and the slowed down time to reach the peak of reactive oxygen species generation after MP stimulation were revealed. Conclusion: We speculate that the abnormalities in monocyte – cholesterol interaction can exacerbate the insufficiency of antiinfectious defense and promote the aggravation of the infectious syndrome, which is known to be a risk factor of RA.

CALCIUM SIGNALING IN TUMOR CELLS

The objective. The objective of this study was to investigate change in calcium maintenance of Ehrlich ascite adenocarcinoma cells in the course of tumor growth. Materials and methods. Cell viability was determined by counting apoptotic and necrotic cells under the fluorescence microscope. Intracellular calcium concentration was determined with the fluorescent probe 2,5 mM Fura-2AM. Relative microviscosity of membranes was estimated by fluorescence method using Pyrene. The activity of Ca-ATPase was assessed by the amount of inorganic phosphate produced during ATP hydrolysis. Results and discussions. We revealed that dynamics of Ehrlich ascite adenocarcinoma growth in our experiments was different from the commonly observed one. We noticed one peculiarity. The quantity of cells decreased on the day 12 after the tumor transplantation. This diminution was caused by mitotic activity lowering and by increase of apoptotic cell quantity the day before. Ehrlich ascite adenocarcinoma growth was accompanied by change in intracellular calcium maintenance which was independent of Ca-ATPase and cell membrane microviscosity. Conclusions. Thus, our experiments have shown the change in calcium concentration. Apparently Ca2+ activated proliferation. However calcium maintenance was settled by ROS. Possibly ROS supression in tumour on the day 12 was able to put down proliferative processes stimulation.

Influence of Lipid Composition, pH, and Temperature on Physicochemical Properties of Liposomes with Curcumin as Model Drug.

The physicochemical properties of large unilamellar vesicles (LUVs) were assessed with respect to lipid composition, pH, time, and temperature by monitoring their size, zeta potential, drug payload, and thermal behavior. A conventional thin film hydration technique was employed to prepare liposomes from soy phosphatidylcholine (SPC), dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylglycerol (DPPG), and a 7:3 (M/M) mixture of DPPC+DPPG along with 30 mole% cholesterol in each combination. While the size of liposomes depended on lipid composition, pH and temperature, the zeta potential was found to be independent of the pH of the medium, although it varied with liposome type. Spherical morphology and bilayer were observed by electron microscopy. The phase transition temperature increased with decreasing pH. Membrane micro-viscosity showed the highest value for SPC, and membrane rigidity increased with increasing pH. The entrapment efficiency of liposomes with reference to curcumin was as follows: DPPC>DPPC+DPPG>DPPG>SPC. Sustained release of curcumin was observed for all liposomes. Curcumin-loaded liposomes exhibited substantial antibacterial activity against the gram-positive bacteria Bacillus amyloliquefaciens. Additional studies are needed to improve the understanding of the effect of formulation variables on the physicochemical stability of liposomes.

Structural characterization of β-carotene-incorporated nanovesicles produced with non-purified phospholipids

The technical feasibility of obtaining β-carotene-incorporated phospholipid nanovesicles using non-purified soybean lecithins was studied. For this purpose, three lecithin-types were evaluated. Nanovesicles were characterized by average hydrodynamic diameter, particle size distribution, polydispersity index, ζ-potential, transmission electron microscopy, membrane microviscosity, small angle X-ray scattering and capacity of lipid peroxidation inhibition. In general, the β-carotene incorporation did not promote a significant increase on average hydrodynamic diameter, but vesicles produced from lecithins containing triglycerides showed lower polydispersity. The lecithin-type used to produce nanovesicles did not influence the β-carotene loading capacity, but significantly influenced the microviscosity of liposomal membrane and lipid peroxidation inhibition capacity. Non-enzymatically modified lecithin (containing or not triglycerides) showed similar efficiency and peroxidation inhibition capacity considering β-carotene incorporation. Therefore, low-cost non-purified lecithin can be employed for production of liposomal systems as an encapsulating and/or delivery system to be used in food products.

Membrane Interactions of Phytochemicals as Their Molecular Mechanism Applicable to the Discovery of Drug Leads from Plants.

In addition to interacting with functional proteins such as receptors, ion channels, and enzymes, a variety of drugs mechanistically act on membrane lipids to change the physicochemical properties of biomembranes as reported for anesthetic, adrenergic, cholinergic, non-steroidal anti-inflammatory, analgesic, antitumor, antiplatelet, antimicrobial, and antioxidant drugs. As well as these membrane-acting drugs, bioactive plant components, phytochemicals, with amphiphilic or hydrophobic structures, are presumed to interact with biological membranes and biomimetic membranes prepared with phospholipids and cholesterol, resulting in the modification of membrane fluidity, microviscosity, order, elasticity, and permeability with the potencies being consistent with their pharmacological effects. A novel mechanistic point of view of phytochemicals would lead to a better understanding of their bioactivities, an insight into their medicinal benefits, and a strategic implication for discovering drug leads from plants. This article reviews the membrane interactions of different classes of phytochemicals by highlighting their induced changes in membrane property. The phytochemicals to be reviewed include membrane-interactive flavonoids, terpenoids, stilbenoids, capsaicinoids, phloroglucinols, naphthodianthrones, organosulfur compounds, alkaloids, anthraquinonoids, ginsenosides, pentacyclic triterpene acids, and curcuminoids. The membrane interaction’s applicability to the discovery of phytochemical drug leads is also discussed while referring to previous screening and isolating studies.

Association of resistin with impaired membrane fluidity of red blood cells in hypertensive and normotensive men: an electron paramagnetic resonance study.

Abnormalities in physical properties of the cell membranes may strongly be linked to hypertension. Recent evidence indicates that resistin may actively participate in the pathophysiology of insulin resistance, diabetes mellitus, hypertension and other circulatory disorders. The present study was undertaken to investigate the possible relationships among plasma resistin, oxidative stress and membrane fluidity (a reciprocal value of membrane microviscosity) in hypertension. We measured the membrane fluidity of red blood cells (RBCs) in hypertensive and normotensive men using an electron paramagnetic resonance (EPR) and spin-labeling method. The order parameter (S) for the spin-label agents (5-nitroxide stearate) in EPR spectra of red blood cell (RBC) membranes was significantly higher in hypertensive men than in normotensive men, indicating that membrane fluidity was decreased in hypertension. Plasma resistin levels were correlated with systolic blood pressure and 8-iso-prostaglandin F2α levels (an index of oxidative stress). Furthermore, the order parameter (S) of RBCs significantly correlated with plasma resistin and plasma 8-isoPG F2α, suggesting that reduced membrane fluidity of RBCs might be associated with hyperresistinemia and increased oxidative stress. Multivariate regression analysis showed that, after adjustment for confounding factors, plasma resistin might be an independent determinant of membrane fluidity of RBCs. The EPR study suggests that resistin might have a close correlation with impaired rheologic behavior of RBCs and microcirculatory dysfunction in hypertension, at least in part, via an oxidative stress-dependent mechanism.

The effect of NT-1505 on the structure of endoplasmic reticulum membranes in vivo

The effect of NT-1505 on the membranes of the endoplasmic reticulum was studied. It is shown that the dynamics of changes in the microviscosity of lipid and near-protein regions of endoplasmic reticulum membranes with the administration of the preparation is antibate in character, which indicates the absence of pathological changes in the membrane structure. The microviscosity of membranes was measured by electron paramagnetic resonance of 2,2,6,6-tetramethyl-4-capryloyl-oxylpiperidine-1-oxyl (lipid probe) and 5,6-benzo-2,2,6,6-tetramethyl-1,2,3,4-tetrahydro-γ-carboline-3-oxyl (near-protein probe) spin probes. In order to obtain more information about the changes in the structure of membranes under the action of the NT-1505 neuroprotector, the temperature dependence of the correlation time of rotational diffusion was measured in the temperature range of 283–317 K (10–44°C). In the control group, two structural transitions in the temperature ranges of 16–20 and 32–38°C were characterized for both areas of membranes, which remained following the introduction of NT-1505. Thus, NT-1505 does not significantly affect the structure of the endoplasmic reticulum membrane.

Azadircta indica as a modulator of membrane stability parameters and surface changes during 1,2 dimethylhydrazine-induced colorectal carcinogenesis

ObjectiveThe aim of the present study was to study the modulatory potential of Azadirta indica on colonic surface abnormalities and membrane fluidity changes following 1,2 dimethylhydrazine-induced [DMH] colon carcinogenesis. Materials and methodsBrush border membranes [BBM] were isolated from the colon of rats and the viscosity as well as fluidity parameters were assessed by using the membrane extrinsic fluorophore pyrene. ResultsDMH treatment resulted in a significant increase in lipid peroxidation [LPO]. Reduced glutathione levels [GSH] and the activities of glutathione reductase [GR], glutathione transferase [GST], superoxide dismutase [SOD], catalase [CAT] and glutathione peroxidase [GPx] were found to be significantly decreased following DMH treatment. On the other hand, supplementation with AI, DMH-treated rats resulted in a significant decrease in the levels of lipid peroxidation but caused a significant increase in the levels of GSH as well in the activities of GR, GST, SOD, CAT and GPx. The results further demonstrated a marked decrease in membrane microviscosity following DMH treatment. On the other hand, a significant increase was observed in the excimer/monomer ratio and fluidity parameter of DMH-treated rats when compared to normal control rats. However, the alterations in membrane microviscosity and the fluidity parameters were significantly restored following A. indica treatment. Further, histological as well as colon surface alterations were also observed following DMH treatment, which however were greatly prevented upon AI co-administration. ConclusionsThe study, therefore, concludes that A. indica proves to be useful in modulating the colonic surface abnormalities and membrane stability following DMH-induced colon carcinogenesis.

The in vitro influence of external electrostatic field on the lipid-protein interactions in membranes of rat erythrocytes

Purpose – The purpose of this paper is to investigate the in vitro influence of 200 kV/m electrostatic fields (ESF) on the microviscosity, viscosity and polarity of rat erythrocyte membranes for revealing the possible changes in lipid-protein interactions due to the field influence. Design/methodology/approach – The investigation of the parameters of erythrocyte membranes and their ghosts, particularly, their microviscosity, the amount and immersion degree of membrane proteins in lipid bilayer, polarity in depth of membrane and its viscosity carried out by the spectrofluorimetric method using the hydrophobic fluorescent probe pyrene. Findings – The carried out investigations shown that the in vitro influence of ESF changes membrane microviscosity, the quantity of membrane peripheral proteins and their immersion degree in the lipid bilayer, if the ghosts have prepared from erythrocytes previously exposed in the field. The analysis of the same parameters for previously prepared erythrocyte ghosts exposed to the 200 kV/m ESF during an hour did not reveal any changes. Originality/value – Data obtained and their comparison with the results of the previous works allow authors to conclude that the in vitro influence of ESF leads to the changes in the lipid-protein interactions in erythrocyte membranes.

Trans–Cis Isomerization of Lipophilic Dyes Probing Membrane Microviscosity in Biological Membranes and in Live Cells

Membrane environment and fluidity can modulate the dynamics and interactions of membrane proteins and can thereby strongly influence the function of cells and organisms in general. In this work, we demonstrate that trans-cis isomerization of lipophilic dyes is a useful parameter to monitor packaging and fluidity of biomembranes. Fluorescence fluctuations, generated by trans-cis isomerization of the thiocarbocyanine dye Merocyanine 540 (MC540), were first analyzed by fluorescence correlation spectroscopy (FCS) in different alcohol solutions. Similar isomerization kinetics of MC540 in lipid vesicles could then also be monitored, and the influence of lipid polarity, membrane curvature, and cholesterol content was investigated. While no influence of membrane curvature and lipid polarity could be observed, a clear decrease in the isomerization rates could be observed with increasing cholesterol contents in the vesicle membranes. Finally, procedures to spatially map photoinduced and thermal isomerization rates on live cells by transient state (TRAST) imaging were established. On the basis of these procedures, MC540 isomerization was studied on live MCF7 cells, and TRAST images of the cells at different temperatures were found to reliably detect differences in the isomerization parameters. Our studies indicate that trans-cis isomerization is a useful parameter for probing membrane dynamics and that the TRAST imaging technique can provide spatial maps of photoinduced isomerization as well as both photoinduced and thermal back-isomerization, resolving differences in local membrane microviscosity in live cells.

Microviscosity of erythrocyte membranes during chronic heart failure in patients of middle and senior age groups

Microviscosity coefficients were studied in the area of integrated and annular lipids of erythrocyte membranes in the peripheral blood of patients aged 35–50 and 60–75 with chronic coronary heart disease (CHD), as well as healthy donors of corresponding age. It was found in healthy donors that the microviscosity coefficients in the area of integrated and of annular lipids are significantly higher in the senior age group (60–75 years). In CHD, both an increase and a decrease in the microviscosity parameters in the area of lipid–lipid interactions can be characteristic for erythrocyte membranes, regardless of the patient age. In the protein–lipid contacts, an increase in microviscosity parameters is characteristic for patients aged 35–50 and, in contrast, a decrease in the microviscosity coefficient was observed in 60- to 75-year-old patients. It was concluded that the indicators of erythrocyte membrane microviscosity in patients of different age groups reflect both the implementation of general mechanisms of adaptive changes in cell membranes and the individual characteristics determined by their lipid and protein composition during the development of chronic CHD.

Оценка влияния углеродных нанотрубок на микровязкость мембран эритроцитов методом спиновых зондов

Оценка влияния углеродных нанотрубок на микровязкость мембран эритроцитов методом спиновых зондов

Evaluation of Cell Membrane-Modulating Properties of Non-Ionic Surfactants with the use of Atomic Force Spectroscopy

Analytical possibilities of atomic force spectroscopy (AFS) in liquid were studied upon interaction of membranotropic polymers with the plasma membrane of human cells. Topographical visualization of tightly adherent dermal fibroblasts, but not relatively soft prostate cancer (PC-3) cells, was achieved using a conventional triangular cantilever. A microsphere-based probe has been developed and applied for AFS analysis of micromechanical properties of PC-3 cells. Non-ionic block copolymers of ethylene oxide and propylene oxide, bi-functional Pluronic® L61, and glycerol-based tri-functional copolymer (TFC) were studied as potential modulators of cellular membranes and drug delivery systems as reported by Bondar et al. (Int. J. Pharm. 461(97), 104, 2014). As indicated by dynamic light scattering and fluorescent techniques, Pluronic® L61 and TFC were adsorbed onto the cell surface and inserted into the plasma membrane in different extent. Analysis of AFS curves for surfactant-treated PC-3 cells showed that both Pluronic® L61 and TFC decreased the Young’s modulus of cellular surface by almost 1.6 and 2 times, respectively. This is in accordance with the ability of amphiphilic polymers of decreasing the microviscosity of cellular membrane and promoting intracellular drug uptake as shown previously by Bondar et al. (Int. J. Pharm. 461(97), 104, 2014). Our results are of particular interest for the characterization of interaction of living cells with amphiphilic polymer-based nanocarriers and drug formulations using AFS and other surface-sensitive techniques.

The action of stress hormones on the structure and function of erythrocyte membrane.

The action of a mixture of hormones (cortisol and adrenaline) on erythrocyte membrane during their binding was investigated. Changes in the membrane structure were elucidated by atomic force microscopy; microviscosity of the lipid bilayer and changes in the activity of Na(+),K(+)-ATPase at different concentrations of the hormones in erythrocyte suspension were estimated by the fluorescence method. Cortisol and adrenaline were shown to compete for the binding sites. A hormone that managed to bind nonspecifically to the membrane hindered the binding of another hormone. In a mixture of these hormones, cortisol won a competition for the binding sites; therewith, microviscosity of the membranes increased by 25%, which corresponds to a change in microviscosity produced by the action of cortisol alone. The competitive relationships affected also the Na(+),K(+)-ATPase activity, which was indicated by appearance of the second maximum of enzyme activity. It is assumed that an increase in microviscosity of erythrocyte membrane first raises the Na(+),K(+)-ATPase activity due to a growth of the maximum energy of membrane phonons, and then decreases the activity due to hindering of conformational transitions in the enzyme molecule.

Simvastatin Effects On Brain and Behavior in Animal Model

Introduction Simvastatin and other HMG-CoA (3-hydroxy-3-methylglutaryl coenzyme A) reductase inhibitors (statins) have been demonstrated to reduce mortality and the risk of major cardiovascular events. However, their neuropsychiatric adverse effects have not been sufficiently studied. The aim of our study is to elucidate effect of long term application of simvastatin on cholesterol level in the brain, serotonin uptake, microviscosity of membranes, and behavior in animal model. Methods We have studied cholesterol content in amygdala; hippocampus and prefrontal cortex, serotonin (5-HT) uptake and mitochondrial respiration in platelets, membrane microviscosity in erythrocytes, and behavioral changes in elevated plus maze in 6 male Long Evans rats in the control group and 6 rats in the simvastatin-treated group (30 mg/kg per day) after 2 and 4 weeks of treatment. Results Our results show: 1) lower cholesterol content in all tested brain regions in simvastatin treated group 2) decrease of SERT aktivity after 2 weeks of treatment compared to 4 weeks treatment 3) disturbed mitochondrial respiration and 4) higher number of entrances and the time spent in the closed arms in simvastatin group. Conclusion These results confirmed cholesterol-lowering effect of simvastatin in brain and harmful effect on cellular energy metabolism and further supported the hypothesis that lowering of plasma cholesterol after simvastatin treatments affects membrane fluidity and transmembrane transport of serotonin. Effects on behavior require additional testing to better explain observed changes in experimental tasks.

Microviscosity of erythrocyte membranes in chronic coronary insufficiency in patients of middle and older age groups

We examined the ratios microviscosity in the area of integral and annularly lipid membranes of erythrocytes of peripheral blood in patients of 35-50 and 60-75 years with chronic ischemic heart disease, as well as age-matched healthy controls. In healthy donors coefficients microviscosity in the area of integral and annularly lipids proved to be significantly higher in the older age group (60-75 years). In CHD, regardless of the age of the patients, erythrocyte membranes can be characterized as raising and lowering the parameters microviscosity of lipid-lipid interactions. In the protein-lipid contacts for patients aged 35-50 years an increase is typical, while for patients of 60-75 years, on the contrary, a decrease of the coefficient of microviscosity. It is concluded that the values of the microviscosity of erythrocyte membranes in patients of different age groups in the development of chronic ischemic heart disease, reflect both the implementation of the general mechanisms of adaptive changes of cell membranes, and the specifics of an individual, determined by their lipid and protein composition.

Partitioning of Hydrophobic Molecules to Liposome Membranes Can Induce Variations in their Micro-Polarity and Micro-Viscosity

The micro-polarity and micro-viscosity of liposome membranes were evaluated to develop a platform for the localization of hydrophobic substrates in aqueous solution. The distribution ratios of benzaldoxime (BO) onto the zwitterionic 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) liposome and onto the cationic 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) liposome were almost the same, while those of benzonitrile oxide (BNO) onto DOTAP liposomes were higher than those of BO. Through the analysis of a polarity-sensitive 6-lauroyl-2-dimethylaminonaphthalene, the membrane surface of the DOTAP liposome was found to be dehydrated in the presence of substrates. Using a fluorescent probe 1,6-diphenyl-1,3,5-hexatriene, we found that the micro-viscosity of the DOTAP liposome membrane increased with BNO. These results indicate that the interaction of hydrophobic substrates induce variations in the microscopic membrane environment.