Erythrocyte Plasma Membrane Research Articles

Beta-adrenergic reactivity of erythrocytes and the progression of heart failure in patients after myocardial infarction

Aim. To identify the associations between beta-adrenergic reactivity of erythrocytes and the progression of heart failure (HF) in patients after myocardial infarction (MI).Material and methods. The study included 50 patients with HF and history of MI 6 months ago. To determine the level of sympathoadrenal system activity, we analyzed beta-adrenergic reactivity by changing the osmotic resistance of erythrocytes by use of adrenoceptor blocking agent.Results. The frequency of HF progression after index MI was 26% (n=13). All patients were divided into 2 groups depending on the presence/absence of HF progression in the postinfarction period. When determining beta-adrenergic reactivity, it was found that patients with HF progression compared with patients without it had the higher level of beta-adrenergic reactivity of membrane (β-ARM) of erythrocytes: 58,8 (50,9; 78,0) CU and 46,8 (38,0; 66,3) CU, p=0,025). A ROC analysis made it possible to establish the β-ARM level ≥49,53 CU a cut-off point, which can be considered as a marker of HF progression in patients after MI (sensitivity 92,3%, specificity 62,2%). This level of β-ARM is associated with a more than five-fold increase of HF progression risk in patients after MI (OR 5,48; 95% CI 1,28-23,37; p=0,024).Conclusion. In patients with HF and MI history, there is a decrease in the adrenergic reactivity of erythrocyte cell membrane, which is reflected by an increase of β-ARM above normal range of 20 CU. At the same time, β-ARM in patients with HF progression compared with patients without it is significantly increased. Established cut-off point of β-ARM (≥49,53 CU) allows predicting the HF progression with high sensitivity and specificity.

Dietary supplementation with annatto food-coloring extracts increases the resistance of human erythrocytes to hemolysis

Erythrocytes exhibit high susceptibility to hemolysis in several pathologies due to the oxidation of cellular components. We hypothesized that annatto carotenoids improve the redox status of erythrocyte plasma membranes and promote a consequent increase in human erythrocyte resistance to hemolysis. The objective of this study was to evaluate whether food-grade annatto carotenoids can increase human erythrocyte resistance to hemolysis in vitro and ex vivo. For the in vitro experiment, erythrocytes from healthy volunteers were isolated and coincubated with bixin (BIX) or norbixin (NBIX) and 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH), glucose, or sodium nitrite (NaNO2) as hemolysis inducers. In the ex vivo study, healthy volunteers consumed a capsule containing BIX or NBIX (0.05 mg/kg body weight per day) or placebo for 7 days before blood sample collection. Their erythrocytes were isolated and incubated with AAPH, glucose, or NaNO2. In both the ex vivo and in vitro studies, erythrocytes were subjected to osmotic fragility tests. The activity of antioxidant enzymes, and reduced glutathione and lipid peroxidation levels in erythrocytes were also evaluated ex vivo. In vitro BIX and NBIX not only reduced erythrocyte membrane fragility induced by AAPH, glucose, or NaNO2 but also improved basal osmotic resistance in the micromole-per-liter range (P < .05). BIX and NBIX supplementation increased erythrocyte membrane resistance (P < .05), with BIX being more effective. Also, BIX and NBIX protected erythrocytes from lipid peroxidation and improved the cellular redox environment (P < .05). These results support the hypothesis that annatto carotenoids supplementation exerts antihemolytic properties by preventing the oxidative damage of human erythrocytes.

Inhibition of Tolaasin Hemolytic Activity by Increase in GD3+-Induced Membrane Rigidity

Tolaasin molecule multimerizes and forms a membrane pore, causing brown blotch disease of the cultivated mushrooms. The peptide is a pore-forming bacterial toxin produced by Pseudomonas tolaasii. The pores destroy plasma membrane by interrupting cellular osmotic pressure. Cytotoxicity of tolaasin can be evaluated by measuring hemolytic activity using erythrocytes and blotch formations on the mushroom tissue. Previous studies showed that divalent cations, such as Zn2+, Ni2+, and Cd2+, inhibit tolaasin-induced hemolysis. In this study, Gadolinium ion, Gd3+, known to inhibit the mechanosensitive ion channels, also inhibits the tolaasin activity as a dose-dependent manner. The inhibition of tolaasin-induced hemolysis was observed at 200 μM Gd3+ and completed at 1 mM. Mechanism of Gd3+ action has not been clearly demonstrated; however, it has been known that Gd3+ decreases membrane fluidity. Inhibition of hemolytic activity by Gd3+ was reversible similar to that of Zn2+, but the action mechanisms of these two ions seem to be very different. Although Zn2+ inhibits the ion channel by plugging into the entrance of tolaasin pore, Gd3+ may inhibit the formation of tolaasin channel by changing membrane fluidity. To investigate the effect of Gd3+ on the plasma membrane of erythrocyte, a fluorescent probe, 1,6-diphenyl-1,3,5-hexatriene (DPH), was inserted into the membrane and the changes in fluorescence intensity were measured. The maximum fluorescence intensity of DPH was measured at 360 nm in excitation and at 456 nm in emission. In the presence of Gd3+, the fluorescence intensity of DPH was increased, suggesting that Gd3+ made the membrane more rigid. Therefore, the Gd3+-mediated increase in membrane rigidity reduces the rate of molecular diffusion in the membrane and may inhibit the multimerization and orientation of tolaasin molecules requiring for membrane pore formation.

An efficient delivery of photosensitizers and hypoxic prodrugs for a tumor combination therapy by membrane camouflage nanoparticles.

Photodynamic therapy (PDT) is an oxygen-dependent, non-invasive cancer treatment. The hypoxia in the tumor environment limits the therapeutic effects of PDT. The combined delivery of photosensitizers and hypoxic prodrugs is expected to improve the efficacy of tumor treatment. In this paper, an erythrocyte and tumor cell membrane camouflage nanocarrier co-loaded with a photosensitizer (indocyanine green) and a hypoxic prodrug (tirapazamine) were used to combine PDT with chemotherapy. The system achieved less macrophage clearance through erythrocyte membranes and tumor-targeted tumor cell membranes, thereby inducing cell death and increasing tumor environment hypoxia by NIR irradiation of photosensitizers. Furthermore, the hypoxic environment activated TPZ to kill more tumor cells. In vivo results showed that the tumor inhibition rate of the drug-loaded nanoparticles increased from 34% to 64% after membrane modification. Moreover, the tumor inhibition rate of the photodynamic treatment group alone was only 47%, and the tumor inhibition rate after the combination was 1.3 times that of photodynamic therapy alone. Our platform is expected to contribute to the further application of cancer combination therapy.

Assessment of the intensity of lipid peroxidation and catalase activity in the blood-erythrocyte serum system in patients with laryngeal cancer

Aim: To evaluate the intensity of lipid peroxidation and the activity of catalase in patients with laryngeal cancer. Materials and Methods: Samples of blood serum and erythrocytes from 40 patients with laryngeal cancer of stages II and III and 20 healthy volunteers were investigated. Results: The level of TBA-positive products and diene conjugates in blood serum samples of stage II and III patients with laryngeal cancer was increased than that of control. In the same time catalase activity was significantly reduced. In the erythrocytes of patients in both groups the level of diene conjugates and catalase activity was higher than that of control. The level of TBA-positive products increased only in patients with III stage disease. Our results indicate the intensification of free-radical oxidation against the background of the functional stress of the antioxidant defense system in patients with laryngeal cancer, as well as the violation of the structural and functional state of erythrocyte plasma membranes, which is manifested in the activation of lipid peroxidation. This indicates about the formation of a complex of disorders, which can play a significant role in the development and deepening of the pathological process.

Erythrocyte plasma membrane potential: past and current methods for its measurement.

The plasma membrane functions both as a natural insulator and a diffusion barrier to the movement of ions. A wide variety of proteins transport and pump ions to generate concentration gradients that result in voltage differences, while ion channels allow ions to move across the membrane down those gradients. Plasma membrane potential is the difference in voltage between the inside and the outside of a biological cell, and it ranges from ~- 3 to ~- 90 mV. Most of the most significant discoveries in this field have been made in excitable cells, such as nerve and muscle cells. Nevertheless, special attention has been paid to some events controlled by changes in membrane potential in non-excitable cells. The origins of several blood disorders, for instance, are related to disturbances at the level of plasma membrane in erythrocytes, the structurally simplest red blood cells. The high simplicity of erythrocytes, in particular, made them perfect candidates for the electrophysiological studies that laid the foundations for understanding the generation, maintenance, and roles of membrane potential. This article summarizes the methodologies that have been used during the past decades to determine Δψ in red blood cells, from seminal microelectrodes, through the use of nuclear magnetic resonance or lipophilic radioactive ions to quantify intra and extracellular ions, to continuously renewed fluorescent potentiometric dyes. We have attempted to highlight the advantages and disadvantages of each methodology, as well as to provide a description of the technical aspects involved.

Effect of Triclosan on the Functioning of Liver Mitochondria and Permeability of Erythrocyte Membranes of Marsh Frog (Pelophylax ridibundus (Pallas, 1771)).

The paper examines the effects of the antimicrobial agent triclosan on the functioning of the liver mitochondria of marsh frog (Pelophylax ridibundus (Pallas, 1771)). It was established that triclosan inhibits DNP-stimulated respiration of mitochondria and decreases respiratory control ratio. In addition, triclosan causes the collapse of the mitochondrial membrane potential on both types of substrates. Such an action of triclosan can be mediated by both a protonophore effect and suppression of the activity of complex II and combined activity of complexes II + III (and, to a lesser degree, the combined activity of complexes I + III) of the mitochondrial respiratory chain. It is shown that high concentrations of triclosan enhance the production of hydrogen peroxide during the oxidation of substrates of the complex I by mitochondria, and decrease it in the case of succinate oxidation. It is found that triclosan is able to induce nonspecific permeability of the liver mitochondria of these amphibians, as well as the plasma membrane of erythrocytes. The possible mechanisms of triclosan effect on marsh frog liver mitochondria and red blood cells are discussed.

Complex assessment of blood pressure regulation system in hypertension patients

Introduction: There are almost no studies characterizing the integrative level of blood pressure (BP) regulation.&#x0D; Materials and methods: 277 people of both genders aged 58.6±6.4 with stage II hypertension disease were randomized into six groups. The monotherapy of hypertension disease was conducted in five groups, using nebivolol, lisinopril, indapamide, amlodipine, and losartan. The sixth group had a combined therapy (lisinopril/indapamide). The therapy effectiveness was assessed at four levels of blood pressure regulation, using the following methods: 1) laser Doppler flowmetry, determination of the level of tumor necrosis factor-α and interleukin-10; 2) echocardiography and Doppler sonography, ultrasound examination of the renal blood flow, ECG, Holter monitoring of ECG; 3) an examination of the heart rate variability level and a quantitative assessment of beta-adrenoreception of erythrocyte cell membranes; 4) the regulatory and adaptive status was assessed, using the method of cardio-respiratory synchronism.&#x0D; Results and discussion: A more significant BP decrease was revealed during a combination therapy (by 20.4% of the baseline daily value). At the integrative level, an index of the regulatory and adaptive status (iRAS) increased in the treatment with lisinopril/indapamide combination (by 40.5%), amlodipine (by 40.5%), losartan (by 35.3%), and lisinopril (by 30.2%). Nebivolol administration resulted in a 13.5% decrease in iRAS. Indapamide therapy had no significant effect on iRAS.&#x0D; Conclusion: A comprehensive assessment of the blood pressure regulation system makes it possible to control the effectiveness of the therapy not only on a target organ or function, but also on the condition of the organism as an integral system.

The Physicochemical Characteristics of Serum Albumin and Erythrocyte Cell Membranes under Normal and Heart Failure Symptom Conditions

Abstract—Spin labeling EPR spectroscopy was used to study the structural and conformational characteristics of human serum albumin and human erythrocyte membranes under normal conditions and with symptoms of heart failure. 5-Doxyl stearic acid and 16-doxyl stearic acid were used as spin labels, whose paramagnetic NO fragments are bound to different sites of the hydrocarbon chain. The EPR spectra of 16-doxyl stearic acid indicate that in the physiological temperature range serum albumin molecules are characterized by several types of fatty acid binding sites, which differ in parameters of spin-label rotational diffusion. This distribution of fatty-acid binding sites was typical for the blood serum of all patients who participated in our study, regardless of deviations from the normal blood parameters. The microviscosity of erythrocyte membranes from patient blood was measured using both 5-doxyl stearic and 16-doxyl stearic spin labels, whose paramagnetic fragments are located at different depths inside the lipid bilayer. It was found that in patients with an increased erythrocyte distribution width, the membrane lipid microviscosity is statistically significantly higher than under normal conditions.

Molecular Simulations of Intact Anion Exchanger 1 Reveal Specific Domain and Lipid Interactions

Anion exchanger 1 (AE1) is responsible for the exchange of bicarbonate and chloride across the erythrocyte plasma membrane. Human AE1 consists of a cytoplasmic and a membrane domain joined by a 33-residue flexible linker. Crystal structures of the individual domains have been determined, but the intact AE1 structure remains elusive. In this study, we use molecular dynamics simulations and modeling to build intact AE1 structures in a complex lipid bilayer that resembles the native erythrocyte plasma membrane. AE1 models were evaluated using available experimental data to provide an atomistic view of the interaction and dynamics of the cytoplasmic domain, the membrane domain, and the connecting linker in a complete model of AE1 in a lipid bilayer. Anionic lipids were found to interact strongly with AE1 at specific amino acid residues that are linked to diseases and blood group antigens. Cholesterol was found in the dimeric interface of AE1, suggesting that it may regulate subunit interactions and anion transport.

Effect of Hyperglycemia on the Total Surface Charge of the Erythrocyte Membrane in Patients with Metabolic Syndrome

Aim. To study the effect of hyperglycemia on the total surface charge of the erythrocyte membrane (SCEM) in patients with metabolic syndrome (MS).Material and methods. 112 MS patients were examined (45 men and 67 women) (mean age 61.4±7.2 years, average MS duration 8.7±5.2 years). The level of SCEM was determined by adsorption of a positive cationic dye (cationic blue O) on the surface of the plasma membrane of erythrocytes to completely neutralize their negative charge, followed by photometry of the solution and calculation of the number of charges on the cell surface of erythrocytes.Results. In the main group of patients with MS, abdominal obesity was observed in 100% of patients, arterial hypertension – in 73%, hyperglycemia – in 75%, dyslipidemia – in 80%. The level of glycated hemoglobin (HbA1c) was determined in all patients with MS, which was 7.3±1.9%. Patients with MS were conditionally divided according to the level of HbA1c into 2 groups (group 1 – HbA1c from 6.6 to 7.8%, group 2 – more than 7.8%). In MS patients with hyperglycemia, the SCEM values were significantly lower than in the group of patients without hyperglycemia (1.58±0.05×107 and 1.64±0.03×107, respectively; p=0.001)., Significant negative correlations between SCEM and the fasting blood glucose level, hyperglycemia duration, HbA1c level were found in patients with MS.Conclusion. SCEM indices reliably depended on the presence, severity and duration of hyperglycemia, which indicated the effect of impaired carbohydrate metabolism on the state of electric charge of erythrocyte membranes and, therefore, on the mechanisms of microvascular blood flow, thereby contributing to the development of vascular changes in patients with MS.

Bioevaluation of Ranatuerin-2Pb from the Frog Skin Secretion of Rana pipiens and its Truncated Analogues.

Antimicrobial peptides (AMPs) are considered as a promising agent to overcome the drug-resistance of bacteria. Large numbers of AMPs have been identified from the skin secretion of Rana pipiens, including brevinins, ranatuerins, temporins and esculentins. In this study, the cDNA precursor of a broad-spectrum antimicrobial peptide, ranatuerin-2Pb, was cloned and identified. Additionally, two truncated analogues, RPa and RPb, were synthesised to investigate the structure-activity relationship of ranatuerin-2Pb. RPa lost antimicrobial activity against Candida albicans, MRSA, Enterococcus faecalis and Pseudomonas aeruginosa, while RPb retained its broad-spectrum antimicrobial activity. Additionally, ranatuerin-2Pb, RPa and RPb demonstrated inhibition and eradication effects against Staphylococcus aureus biofilm. RPb showed a rapid bacterial killing manner via membrane permeabilization without damaging the cell membrane of erythrocytes. Moreover, RPb decreased the mortality of S. aureus infected Galleria mellonella larvae. Collectively, our results suggested that RPb may pave a novel way for natural antimicrobial drug design.

Differentiation of erythroblast requires the dimeric form of acetylcholinesterase: Interference with erythropoietin receptor

Acetylcholinesterase (AChE) hydrolyzes acetylcholine at cholinergic synapses, and which has various isoforms of AChE, i.e. AChER, AChEH and AChET, deriving from single gene. AChEH exists as a glycophosphatidylinositol (GPI)-linked dimer (G2), presents mainly in plasma membrane of mammalian erythrocyte. Transgenic mice with ACHE gene depletion were employed here to investigate the possible role of AChE in blood cell formation. ACHE knock-out mice were found to suffer normocytic anemia. In erythrocyte of ACHE−/− mice, the amount of hemoglobin, especially α-globin, was found to be markedly reduced. In addition, the number of erythrocyte and hematocrit of ACHE−/− mice were significantly lowered. To probe the role of AChE isoforms in erythroid differentiation, erythroblast-like cells (TF-1) over-expressed with different AChE isoforms were induced to differentiate by erythropoietin (EPO): this differentiation induced the expression of each AChE isoform. Only in the TF-1 cells over-expressed with AChEH, the EPO-induced transcriptions and protein expressions of α- and β-globins could be significantly enhanced, which therefore suggested that AChEH might regulate the responsiveness of TF-1 cells to EPO. The alternation of EPO-induced downstream signaling might be accounted by association of AChE with EPO receptor in cell surface. The findings indicated the significance of AChE in erythroblast maturation, which provided an insight in elucidating possible mechanisms in regulating erythropoiesis.

Alterations to plasma membrane lipid contents affect the biophysical properties of erythrocytes from individuals with hypertension

Genetic and environmental factors may contribute to high blood pressure, which is termed essential hypertension. Hypertension is a major independent risk factor for cardiovascular disease, stroke and renal failure; thus, elucidation of the etiopathology of hypertension merits further research. We recently reported that the platelets and neutrophils of patients with hypertension exhibit altered biophysical characteristics. In the present study, we assessed whether the major structural elements of erythrocyte plasma membranes are altered in individuals with hypertension. We compared the phospholipid (phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, sphingosine) and cholesterol contents of erythrocytes from individuals with hypertension (HTN) and healthy individuals (HI) using LC/MS-MS. HTN erythrocytes contained higher phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine contents and a lower cholesterol content than HI erythrocytes. Furthermore, atomic force microscopy revealed important morphological changes in HTN erythrocytes, which reflected the increased membrane fragility and fluidity and higher levels of oxidative stress observed in HTN erythrocytes using spectrophotofluorometry, flow cytometry and spectrometry. This study reveals that alterations to the lipid contents of erythrocyte plasma membranes occur in hypertension, and these alterations in lipid composition result in morphological and physiological abnormalities that modify the dynamic properties of erythrocytes and contribute to the pathophysiology of hypertension.

A Multi-Ingredient Nutritional Supplement in Combination With Resistance Exercise and High-Intensity Interval Training Improves Cognitive Function and Increases N-3 Index in Healthy Older Men: A Randomized Controlled Trial

We aimed to evaluate the effect of multi-ingredient nutritional supplementation, with and without exercise training, on cognitive function in healthy older men. Forty-nine sedentary men [age: 73 ± 6 years (mean ± SD); body mass index: 28.5 ± 3.6 kg/m2] were randomized to consume a supplement (SUPP n = 25; 1500 mg n-3 polyunsaturated fatty acids, 30 g whey protein, 2.5 g creatine, 500 IU vitamin D, and 400 mg calcium) or control beverage (CON n = 24; 22 g maltodextrin) twice daily for 20 weeks consisting of Phase 1: SUPP/CON followed by Phase 2: 12-week resistance exercise training plus high-intensity interval training, while continuing to consume the study beverages (SUPP/CON + EX). At baseline, 6 weeks, and 19 weeks we assessed cognitive function [Montréal Cognitive Assessment (MOCA)], memory [word recall during the Rey Auditory Verbal Learning Test (RAVLT)], executive functions (working memory inhibition control), and nutrient bioavailability. We did not observe changes to any aspect of cognitive function after Phase 1; however, significant improvements in the following cognitive function outcomes were detected following Phase 2: MOCA scores increased (6 weeks: 23.5 ± 3.3 vs. 19 weeks: 24.4 ± 2.5, p = 0.013); number of words recalled during the RAVLT increased (6 weeks: 6.6 ± 3.6 vs. 19 weeks: 7.6 ± 3.8, p = 0.047); and reaction time improved (6 weeks: 567 ± 49 ms vs. 19 weeks: 551 ± 51 ms, p = 0.002). Although between-group differences in these outcomes were not significant, we observed within-group improvements in composite cognitive function scores over the course of the entire study only in the SUPP group (Δ = 0.58 ± 0.62, p = 0.004) but not in the CON group (Δ = 0.31 ± 0.61, p = 0.06). We observed a progressive increase in n-3 index, and a concomitant decrease in the ratio of arachidonic acid (ARA) to eicosapentaenoic acid (EPA) within erythrocyte plasma membranes, in the SUPP group only. At week 19, n-3 index (r = 0.49, p = 0.02) and the ARA:EPA ratio (r = -0.44, p = 0.03) were significantly correlated with composite cognitive function scores. Our results show that 12 weeks of RET + HIIT resulted in improved MOCA scores, word recall, and reaction time during an executive functions task; and suggest that a multi-ingredient supplement combined with this exercise training program may improve composite cognitive function scores in older men possibly via supplementation-mediated alterations to n-3 PUFA bioavailability.Clinical Trial Registration: http://www.ClinicalTrials.gov, identifier NCT02281331.

Anodic Behavior of Erythrocytes and Erythrocytes Ghosts on the Carbon Paste Electrode

Electrochemical investigations of processes occurring when blood cells come into contact with foreign conductive materials provide important fundamental and application-specific information. Indeed, the mechanism of blood cell interaction with foreign surfaces is not well understood at the present time. On the other hand, the results of such studies have the potential of underpinning the development of new physicochemical methods for assessment of the traumatic ability of the material towards blood cells. While charge transfer between metal bodies and erythrocytes has long been hypothesized, only recently was experimental (coulometric) evidence of electron transfer obtained during the interaction of erythrocytes with the platinum electrode [1]; it should be noted that this phenomenon was observed both in the cathodic and the anodic potential ranges. Electron transfer may be rationalized as a result of electrochemical transformations of functional groups located on the erythrocyte membrane. To elucidate the localization of electrochemical processes between the erythrocyte and the electrode, it is important to rule out the occurrence of numerous vital processes in a whole cell that could greatly complicate the interpretation of results. Therefore, erythrocytes ghosts, or lysed erythrocyte membranes that fully or partially retain the surface functional groups of whole red blood cells but no longer contain physiologically functional components of an erythrocyte, are an especially suitable model for studying such electrochemical processes on the membrane surface. In the present work, the electrochemical behavior of erythrocytes and erythrocytes ghosts on a carbon paste electrode (CPE) in phosphate buffered saline (PBS) was investigated. With a highly developed surface area compared to traditional solid electrodes, CPE possesses an increased sensitivity of measurements. Polarization measurements were performed using a three-electrode cell and an IPC Pro L potentiostat in the potential range between 0 mV and 1000 mV with a potential scan rate of 10 mV/s. A CPE working electrode (d = 2 mm) utilized was made from Super P carbon black (TIMCAL, Belgium) with paraffin oil as the binder. The mass ratio of carbon black to binder was 1:0.3 (w/w). Thermally expanded graphite foil was used as the auxiliary electrode, and saturated Ag/AgCl served as the reference electrode. In the resulting voltammograms recorded in a suspension of erythrocytes, two electrooxidation peaks are present, with maximums at potentials of +400 mV and +700 mV (Fig. 1a). The height of the oxidation peaks was dependent on the concentration of cells in the suspension. Thus, erythrocytes were shown to possess electrochemical activity on CPE in the anodic range of potentials. It is noteworthy that earlier work [1] did not discover any polarization peaks on the platinum electrode in the anodic potential range. However, the electrooxidation process was observed on the platinum electrode via coulometry at potentials more positive than +200 mV. This can be rationalized by considering the increase in sensitivity when using coulometry on a smooth platinum electrode as compared with the polarization measurement method. At the same time the voltammogram for the suspension of erythrocytes ghosts on a CPE is characterized by an electrooxidation peak with a maximum at +700 mV, with the peak maximum height being dependent upon the concentration of ghosts in the suspension (Fig. 1b). Evidence of electrochemical activity for both whole erythrocytes and erythrocytes ghosts corroborates the hypothesis that electrochemical processes (i.e., electron transport between the blood cell membrane and foreign material) are localized on certain functional groups present on the cell membrane. Differences in the anodic behavior of erythrocytes and erythrocytes ghosts may be attributed to erythrocytes ghosts not being a full-fledged cell, as well as to differences in the chemical composition of functional groups on cell membranes of erythrocytes vs. ghosts. The observed charge transfer phenomena provide experimental corroboration of the hypothesis about the involvement of cell-membrane functional group electrochemistry in the process of electron transport between erythrocytes (or erythrocytes ghosts) and a foreign surface. References Yu. Tsivadze, M.Sh. Khubutiya, I.V. Goroncharovskaya, A.K. Evseev, Michael M. Goldin, N.V. Borovkova, O.V. Batishchev and Mark M. Goldin, Mendeleev Commun., 27, 183 (2017). Figure 1

Possible contribution of erythrocytes to the purinergic regulation of tissue oxygen delivery

ATP release occurs in virtually all cell types and tissues. It is considered to be a key component of a ubiquitous, evolutionary ancient cell-to-cell communication system. The regulated release of ATP is also believed to be a part of a mechanism which facilitates matching tissue oxygen supply with demand. In this paper, ATP signaling is reviewed, regulation of tissue oxygen supply is outlined, and a concept attributing a role in this process to erythrocytes releasing ATP is discussed. Oxygen saturation of hemoglobin in erythrocytes traveling through a tissue reflects the level of oxygen utilization of that tissue. Therefore, erythrocytes can serve as local oxygen sensors. In the proposed mechanism, upon hemoglobin deoxygenation, Gi protein in the erythrocyte plasma membrane is activated. The activation of Gi protein initiates a cAMP-dependent pathway, leading to ATP efflux through pannexin channels. Extracellular ATP triggers vasodilatation via P2Y receptors on the surface of vascular endothelial cells, increasing blood flow in tissue regions of elevated oxygen consumption. Despite the abundance of compelling evidence in support of this concept, some details remain elusive, in particular, the process of Gi protein activation in response to hemoglobin desaturation. Furthermore, the involvement of cAMP, as well as the final conduit of ATP release from erythrocytes, remains controversial. Finally, the actual physiological relevance of the proposed regulatory mechanism will require further in vivo research.

Biological Investigations and Spectroscopic Studies of New Moxifloxacin/Glycine-Metal Complexes.

Two novel ligand-metal complexes were prepared through the reaction of Zn(II) and Sn(II) with moxifloxacin (MOX) in the presence of glycine (Gly) to investigate their biological activities. IR, UV/VIS and 1 H-NMR analysis have been carried out for insuring the chelation process. Results suggested that MOX and Gly react with the metal ions through the carbonyl oxygen atom and the oxygen atom of the carboxylic group of MOX and Gly. The antimicrobial activity was carried out against some common bacterial and fungal pathogens and the radical scavenging activity (RSA%) was evaluated using DPPH and ABTS methods. Phytotoxic effect of the prepared complexes was evaluated in vitro against Raphanus raphanistrum and Lepidium sativum. Hemolytic activity was tested against cell membrane of erythrocytes. Results showed that the two prepared complexes exhibited high antimicrobial activity against all tested phytopathogens and no significant phytotoxic effect has been observed. Only MOX-Zn(II) complex showed moderate hemolysis at 100 % concentration.

Acute toxicity and antiproliferative and procoagulant activities of fractions derived from Thymus satureioides of the Moroccan High Atlas

This study aimed to determine the effects of crude extract (CE) and fractions derived from the Moroccan endemic plant Thymus satureioides (T. satureioides) on inflammation, coagulation and viability of a cell cancer line. The crude extract and fractions from the leaves of T. satureioides were analysed using HPLC and examined for their antioxidant capacity using mineral and biological substrates. The anti-inflammatory activity of the extracts was evaluated using croton oil- and carrageenan-induced oedema. The effect on blood coagulation in normal rat plasma was also determined using prothrombin time (PT) and activated partial thromboplastin time (APTT) assays. Furthermore, the oral acute toxicity and antiproliferative effects on the MCF-7 cell line of the CE were evaluated. The major identified polyphenol in the CE and polar fractions was rosmarinic acid. No mortalities due to acute toxicity were observed at 5 g/kg. All plant preparations protected the cell membranes of erythrocytes against oxidative damage and showed high scavenging activity, as measured using DPPH and FRAP. Moreover, the hydrophobic fractions demonstrated significant inhibitory effects against croton oil-induced oedema. The methanol fraction (60 mg/kg) significantly reduced oedema induced by carrageenan during the first phase. During the APTT and PT assays, the CE and fractions caused plasma coagulation even at low concentrations. An antiproliferative assay (MTT) showed a significant decrease in the number of viable cells in culture medium supplemented with CE at different concentrations. These results suggest that extracts from the leaves of T. satureioides constitute a valuable source of anti-inflammatory and anti-cancer metabolites.

Does Membrane Asymmetry Affect Nanoparticle-Membrane Interactions

Plasma membrane damage is one of the primary mechanisms through which engineered nanomaterials cause cytotoxicity. Despite a number of studies, the role of the structural features of the plasma membrane, in particular membrane phospholipid asymmetry in regulating nanoparticle-membrane interactions has remained obscure. In the current study, the role of membrane phospholipid asymmetry, differences in the lipid composition of exofacial and cytofacial leaflet of the plasma membrane in regulating nanoparticle-membrane interactions was investigated. Vesicles mimicking the exofacial (Vexo) and cytofacial leaflets (Vcyto) of the plasma membrane of erythrocytes were exposed to silica nanoparticles (50 nm), with different surface functional groups, plain, or carboxyl-, amine-, and polyethylene glycol (PEG)-modified and the effect of particles on vesicle integrity was examined. Symmetric and asymmetric vesicles with similar outer leaflet, but different inner leaflet lipid compositions, as well as live erythrocytes, were also used to elucidate the role of membrane asymmetry and individual leaflets in regulating nanoparticle-membrane interaction. Vexo and Vcyto vesicles showed significant difference in their interactions with nanoparticles. Vexo vesicles showed drastic leakage of intravesicular content after exposure to plain and amine-modified particles while none of the particles caused significant leakage in Vcyto vesicles. FRET experiments revealed that nanoparticle-induced disruption by plain and amine-modified particles occurs via pore formation. In agreement, FRET assay and GUV images revealed significant localization of plain and amine-modified particles at the surface of the Vexo vesicles. However, no localization was observed with the Vcyto vesicles. Interestingly, symmetric and asymmetric vesicles were disrupted similarly by plain and amine-modified particles. Importantly, hemolysis was observed after the incubation of erythrocytes with plain and amine-modified particles, consistent with leakage assays using Vexo vesicles. In conclusion, these results suggest that the exofacial leaflet of the plasma membrane is the primary regulator of nanoparticle-induced membrane damage in erythrocytes.