Phospholipid Bilayer Of Cell Membrane Research Articles

Early-stage mapping of macromolecular content in APPNL-F mouse model of Alzheimer's disease using nuclear Overhauser effect MRI.

Non-invasive methods of detecting early-stage Alzheimer's disease (AD) can provide valuable insight into disease pathology, improving the diagnosis and treatment of AD. Nuclear Overhauser enhancement (NOE) MRI is a technique that provides image contrast sensitive to lipid and protein content in the brain. These macromolecules have been shown to be altered in Alzheimer's pathology, with early disruptions in cell membrane integrity and signaling pathways leading to the buildup of amyloid-beta plaques and neurofibrillary tangles. We used template-based analyzes of NOE MRI data and the characteristic Z-spectrum, with parameters optimized for increase specificity to NOE, to detect changes in lipids and proteins in an AD mouse model that recapitulates features of human AD. We find changes in NOE contrast in the hippocampus, hypothalamus, entorhinal cortex, and fimbria, with these changes likely attributed to disruptions in the phospholipid bilayer of cell membranes in both gray and white matter regions. This study suggests that NOE MRI may be a useful tool for monitoring early-stage changes in lipid-mediated metabolism in AD and other disorders with high spatial resolution.

Potential Benefits of Omega-3 Polyunsaturated Fatty Acids (N3PUFAs) on Cardiovascular Health Associated with COVID-19: An Update for 2023.

The accumulating literature demonstrates that omega-3 polyunsaturated fatty acid (n-3 polyunsaturated fatty acid, N3PUFA) can be incorporated into the phospholipid bilayer of cell membranes in the human body to positively affect the cardiovascular system, including improving epithelial function, decreasing coagulopathy, and attenuating uncontrolled inflammatory responses and oxidative stress. Moreover, it has been proven that the N3PUFAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are precursors of some potent endogenous bioactive lipid mediators that mediate some favorable effects attributed to their parent substances. A dose-response relationship between increased EPA and DHA intake and reduced thrombotic outcomes has been reported. The excellent safety profile of dietary N3PUFAs makes them a prospective adjuvant treatment for people exposed to a higher risk of cardiovascular problems associated with COVID-19. This review presented the potential mechanisms that might contribute to the beneficial effects of N3PUFA and the optimal form and dose applied.

REDOX STATUS AND CELL MEMBRANE ALTERATIONS OF CIRCULATING LEUKOCYTES AND ERYTHROCYTES IN ABNORMAL UTERINE BLEEDING

Aim. To analyze the eryptosis degree, the state of cell membranes and redox status of circulating red blood cells and leukocytes in patients with abnormal uterine bleeding and its combination with hypothyroidism. Materials and methods. Patients, 74 women aged 18 to 49 years, were examined, which were divided into 3 groups: group I - women with abnormal uterine bleeding (AUB) (24 patients); group II - with AUB and thyroid pathology (30 patients, of whom 18 women had primary hypothyroidism and 2 - secondary hypothyroidism); group III - control group (20 healthy women, who had never had menstrual irregularities). Eryptosis of circulating erythrocytes was assessed by flow cytometry using annexin V staining and 2′,7′-dichlorodihydrofluorescein diacetate (H2DCFDA) staining. Fluorescent probes O1O (2-(2¢-hydroxy-phenyl)-5-phenyl-1,3-oxazole) and PH7 (2-(2¢-hydroxy-phenyl)-phenanthro[9,10-d]-1,3-oxazole) were used to characterize changes in phospholipid bilayers of circulating erythrocytes and leukocytes. Lysed blood samples were stained with antibodies to CD45, 7-aminoactinomycin D and H2DCFDA to analyze the redox status of circulating viable leukocytes. Results. Annexin V staining revealed eryptosis activation in females with abnormal uterine bleeding combined with hypothyroidism. In addition, in these patients, oxidative stress developed in red blood cells, evidenced by an increase in intracellular reactive oxygen species (ROS) levels. Oxidative stress was accompanied by changes in the physico-chemical properties of erythrocyte membranes, namely a decrease in membrane hydration and an increase in lipid order, which can indicate enhanced lipid peroxidation. These changes were observed in women with abnormal uterine bleeding alone, however, to a lesser extent. In this study, the redox state of leukocytes and phospholipid bilayers of their cell membranes were not affected in the patients from both groups. Conclusions. Abnormal uterine bleeding combined with hypothyroidism is associated with eryptosis activation, oxidative stress development in erythrocytes and changes in the physico-chemical properties of phospholipid bilayer of cell membranes in red blood cells.

Misfolded protein oligomers induce an increase of intracellular Ca2+ causing an escalation of reactive oxidative species

Alzheimer's disease is characterized by the accumulation in the brain of the amyloid β (Aβ) peptide in the form of senile plaques. According to the amyloid hypothesis, the aggregation process of Aβ also generates smaller soluble misfolded oligomers that contribute to disease progression. One of the mechanisms of Aβ oligomer cytotoxicity is the aberrant interaction of these species with the phospholipid bilayer of cell membranes, with a consequent increase in cytosolic Ca2+ levels, flowing from the extracellular space, and production of reactive oxygen species (ROS). Here we investigated the relationship between the increase in Ca2+ and ROS levels immediately after the exposure to misfolded protein oligomers, asking whether they are simultaneous or instead one precedes the other. Using Aβ42-derived diffusible ligands (ADDLs) and type A HypF-N model oligomers (OAs), we followed the kinetics of ROS production and Ca2+ influx in human neuroblastoma SH-SY5Y cells and rat primary cortical neurons in a variety of conditions. In all cases we found a faster increase of intracellular Ca2+ than ROS levels, and a lag phase in the latter process. A Ca2+-deprived cell medium prevented the increase of intracellular Ca2+ ions and abolished ROS production. By contrast, treatment with antioxidant agents prevented ROS formation, did not prevent the initial Ca2+ flux, but allowed the cells to react to the initial calcium dyshomeostasis, restoring later the normal levels of the ions. These results reveal a mechanism in which the entry of Ca2+ causes the production of ROS in cells challenged by aberrant protein oligomers.

Role of S protein transmembrane domain mutations in the development of occult hepatitis B virus infection

ABSTRACT Occult HBV infection (OBI) is a special infection status during Hepatitis B virus (HBV) infection. The underlying mechanism of its occurrence remains unclear. This study conducted sequencing analysis on 104 OBI plasma samples and 524 HBsAg positive samples from 29 blood centres, and searched for high-frequency mutations in transmembrane domain (TMD) of S protein in the OBI population. Plasmids with TMD high-frequency mutations were constructed, in vivo and in vitro functional experiments were performed to investigate possible molecular mechanisms of OBI occurrence. We found 22 high-frequency TMD mutations in genotype B OBI strains. Among them, five mutations can lead to impairment of HBsAg secretion; seven mutations had accumulated intracellular HBsAg while extracellular HBsAg didn’t decrease compared to wildtype. This study chose C85R from TMD2, F220C, and F220Y from TMD4 for further exploration. Protein structure predication showed these three mutant HBsAg displayed changed hydrophilic properties and tended to accumulate in the phospholipid bilayer of cell membrane. Mutant HBsAg’s secretion disorder may induce OBI. On the other hand, V168A + V177A from TMD3 expressed increased HBsAg both in intracellular and extracellular levels. This mutation had most unstable natural conformation and may be inclined to transition into V177A or V168A + S174N + V177A. These three mutations were more prone to mixed infection, presenting a state of coexistence, thus approaching the impaired secretion pattern of OBI. This study demonstrated TMD mutations could contribute to the occurrence of OBI and provided a theoretical basis for OBI study and the functional cure of chronic hepatitis B virus infection.

The study of phospholipid bilayer of cell membranes in leukocytes incubated with high concentrations of the food additive E407a

The aim of the study was to assess the impact of semi-refined carrageenan (E407a) on the hydrophobic region of phospholipid bilayer in cell membranes of leukocytes exposed to the solution with high concentrations of this food additive. Materials and methods. Fluorescent probe (2-phenyl-phenanthro[9,10-d]-1,3-oxazole) was used to investigate the influence of E407a on the state of lipid bilayer in leukocytes extracted from rats and treated with a 5% solution of the food additive E407a during 4 hours. Results. The shapes of the probe fluorescence spectra did not differ in leukocytes of rats treated with the 5% solution of semi-refined carrageenan and white blood cells of control samples. Such findings suggest that exposure to the E407a solution causes no changes in the proton-donor ability of the media in the lipid membranes of leukocytes in the region where the probe locates. Conclusion. Exposure of white blood cell suspensions to the semi-refined carrageenan solution does not affect the membrane hydration of the hydrophobic region of leukocyte phospholipid bilayer.

P1088BRAND NEW METHOD TO CALCULATE THE VOLUME OF EXTRA CELLULAR FLUID IN HEMODIALYSIS PATIENT ONLY FROM REGULAR BLOOD TEST

Abstract Background and Aims Uric acid is a small molecule with molecular weight 168, but has an electrical pole which enables pass through the phospholipid bilayers of cell membranes by simple diffusion. Urate transport proteins of cell membranes (URAT1, GLUT9, OAT, MRP4, MCT9, NPT4, ABCG2) are expressed only in uric acid-excreting tissues. These findings suggest that uric acid does not pass through the cell membrane, either by diffusion or active transport. Since uric acid does not pass through cell membranes, the uric acid distribution volume (UDiV) would reflect the extracellular volume (ECV). At ASN 2018, we reported that UDiV significantly correlated with ECV predicted by the bio-impedance method measured by InBody, S 20 (Biospace Co., Ltd, Korea). However, both data were correlated, there was a large fixed error. This time, we examined the correlation with the UDiV again using the Fresenius BCM (Fresenius Medical Care, Bad Homberg, Germany), which is trusted worldwide. Method We calculated UDiV from regular blood test results by uric acid kinetic modeling. This study was performed in Yokohama Minami Clinic. One hundred nine patient under hemodialysis was consented and enrolled in this study. The HD patients were 59males and 50females. 68.0±10.9years old. We performed UDiV calculation from blood samples obtained before and after hemodialysis. Then, after the hemodialysis session, 30minutes interval was made to measure the BIA-ECV using BCM. Then, we compared UDiV with BIA-ECV . We used least squares regression analysis and Bland–Altman analysis to compare the UDiV method and the BIA-ECV method, and the Steel test for multiple comparisons of UDiV and symptoms. All analyses were performed using JMP 9.0.2 (SAS Institute, Inc., Cary, NC, USA). Results There was a significant correlation between UDiV(x) and BIA-ECFV (y): (y = 0.70x +3.02, r-square = 0.61, p < 0.0001, Figure 1a). The regression line closely coincided with the line of identity. Bland–Altman analysis showed a systematic error for UDiVvs. BIA-ECV (Figure 1b). There was a significant difference between UDiVand BIA-ECV (mean difference 1.32 L, 95% CI -2.6 to 5.2 L). Conclusion UdiV could be a viable alternative marker of BIA-ECV for the assessment of hydration status of patients with HD.

Rapid detection of pathogens using lyotropic liquid crystals.

Lyotropic liquid crystals play an important role in many biological environments, such as micelles, liposomes, and phospholipid bilayers of cell membranes. In this work, we explore the performance of lyotropic liquid crystals as biosensors for macromolecules, proteins and whole microorganisms in hydrophilic media, i.e., the natural media where these specimens exist. The aim is to detect specific targets employing simple, unpowered sensors that can be used in the field, with minimum additional equipment. A number of different structures have been explored. The novelty in this work is the inclusion of a new optical effect, flow enhanced amplification, that allows for the semiquantitative detection of microscopic targets in lyotropic liquid crystal cells using the naked eye only.

Systemic membrane-destabilizing distress syndrome in surgery: concept, pathogenesis, diagnosis

To justify the concept of systemic membrane-destabilizing distress syndrome in surgery via analysis of phospholipid bilayer of cell membranes of various organs in urgent surgical abdominal diseases. Experimental research on dogs (n=90) included modeling of peritonitis, pancreatitis, intestinal obstruction, obstructive jaundice, and post-hemorrhagic anemia. Clinical and laboratory studies were performed in patients (n=119) with acute peritonitis, severe pancreatitis, intestinal obstruction, post-hemorrhagic anemia, acute cholecystitis, gastrointestinal bleeding, benign mechanical jaundice. Lipid profile in tissues and blood cells was determined by extraction, fractionation and densitometry. Moreover, we assessed intensity of lipid peroxidation and phospholipase activity, endogenous intoxication, functional state of organs and blood cells. It was revealed that all above-mentioned acute abdominal diseases are followed by significant changes of lipid bilayer and dysfunction of tissues in target organs, blood cells and other organs (liver, kidney, colon and small intestine, heart, lungs, spleen, brain). Changes of phospholipid bilayer are correlated with severity and course of the disease. These data were used to determine a new complex in surgery - systemic membrane-destabilizing distress syndrome. Its concept, pathogenesis, and diagnosis are presented. It was analyzed its role in development and progression of dysregulation pathology and thanatogenesis. Evidence of its importance in the pathogenesis of surgical aggression was obtained.

Evaluation of Aculeatin and Toddaculin Isolated from Toddalia asiatica as Anti-inflammatory Agents in LPS-Stimulated RAW264 Macrophages.

Anti-inflammatory activity of aculeatin and toddaculin, which are coumarins with a similar structure isolated from Toddalia asiatica (L.) LAM., was evaluated using lipopolysaccharide (LPS)-stimulated RAW264 mouse macrophage cells. Both aculeatin and toddaculin significantly inhibited mRNA expression of inflammatory mediators and nitric oxide production. Furthermore, Toddaculin suppressed LPS-induced phosphorylation of p38 and extracellular signal-regulated kinase (ERK)1/2 and inhibited LPS-induced activation of nuclear factor-kappaB (NF-κB). However, aculeatin did not exhibit such effects, suggesting that aculeatin and toddaculin suppress LPS-induced inflammation of RAW264 cells via different mechanisms. The cellular uptake of these compounds was also evaluated. Toddaculin was detected in RAW264 cells after 4 and 24 h. However, aculeatin levels were not observed in RAW264 cells at all incubation intervals. These results indicate that de-epoxidation of a prenyl group can increase hydrophobicity of molecule and is thought to accelerate cellular uptake and/or interactions with the phospholipid bilayers of cell membranes.

Electrochemical sensor based on phospholipid modified glassy carbon electrode - determination of paraquat

Electrochemical sensor based on glassy carbon electrode modified with asolectin (mixture of soybean phospholipids) was developed. Properties of phospholipid layer, such as thickness and compactness, were investigated using atomic force microscopy and X-ray photoelectron spectroscopy. Phospholipids completely cover whole surface and the thickness of the layer 7.1±1.2nm corresponds to the value of the phospholipid bilayer of cell membranes. Due to the accumulation of paraquat in the phospholipid layer, square wave voltammetry with asolectin modified electrode exhibits three times higher sensitivity, measured as a slope of calibration dependence, and better linearity in comparison to unmodified glassy carbon electrode. Limit of detection 2.2nmolL−1 and recoveries higher than 88% were achieved in model samples of water. The method was used for determination of paraquat in real sample of river water and results were compared with high performance liquid chromatography and differential pulse voltammetry on hanging mercury drop electrode giving 0.071±0.010, 0.050±0.010 and 0.061±0.008μmolL−1, respectively.

The development of activatable lytic peptides for targeting triple negative breast cancer

Cytolytic peptides are an emerging class of promising cancer therapeutics shown to overcome drug resistance. They eliminate cancer cells via disruption of the phospholipid bilayer of cell membranes, a mechanism that differentiates it from traditional treatments. However, applications of lytic peptides via systematic administration are hampered by nonspecific toxicity. Here, we describe activatable, masked lytic peptides that are conjugated with anionic peptides via a cleavable linker sensitive to matrix metalloproteinases (Ac-w-βA-e8-XPLG*LAG-klUklUkklUklUk-NH2; lower case letters in the sequences represent D-amino-acids, U=Aib, α-aminoisobutyric acid, *cleavage site). The peptides were activated upon being introduced into the triple negative breast cancer cell line MDA-MB-231, which overexpresses secreted matrix metalloproteinases, to selectively cleave the peptide linker. Our results indicate that the activatable design could be applied to improve the targeting ability of lytic peptides.

α-Tocopherol incorporation in mitochondria and microsomes upon supranutritional vitamin E supplementation

Vitamin E (α-tocopherol) is a major lipid-soluble chain-breaking antioxidant in humans and mammals and plays an important role in normal development and physiology. The localization of α-tocopherol within the highly unsaturated phospholipid bilayer of cell membranes provides a means of controlling lipid oxidation at the initiation site. Mitochondria are the site for major oxidative processes and are important in fat oxidation and energy production, but a side effect is leakage of reactive oxygen species. Thus, incorporation of α-tocopherol and other antioxidants into mitochondria and other cellular compartments is important in order to maintain oxidative stability of the membrane-bound lipids and prevent damage from the reactive oxygen species. Many studies regarding mitochondrial disease and dysfunction have been performed in relation to deficiency of vitamin E and other antioxidants, whereas relatively sparse information is available regarding the eventual beneficial effects of antioxidant-enriched mitochondria in terms of health and function. This may be due to the fact that only little scientific information is available concerning the effect of supranutritional supplementation with antioxidants on their incorporation into mitochondria and other cellular membranes. The purpose of this review is therefore to briefly summarize experimental data performed with dietary vitamin E treatments in relation to the deposition of α-tocopherol in mitochondria and microsomes.

ω-3 polyunsaturated fatty acids and the cardiovascular system

ω-3 polyunsaturated fatty acids (PUFAs) (alpha-linolenic, eicosapentaenoic, and decosahexaenoic acids) are classified with essential fatty acids and are structural components of the phospholipid bilayer of cell membranes. ω-3 PUFAs incorporated into the phospholipid domain of cell membranes are metabolized to prostaglandins and thromboxanes (PGI3, PGE3, TxA, etc.), which significantly differ in biological activity from those formed in the arachidonic acid cascade (PGI2, PGE2, TxA2, etc.) and to which the antiaggregatory, antiatherogenic, and vasodilating effects of ω-3 PUFAs can largely be attributed. In addition, ω-3 PUFAs incorporated into cardiomyocyte cell membranes considerably modify the functional activity of transmembrane voltage-gated ion channels by causing a dose-dependent inhibition of the outward transmembrane sodium current, slowing down the work of transmembrane voltage-gated slow L-type calcium channels, and partially blocking the efflux of potassium ions from cardiomyocytes, thus showing the properties of class I, III, and IV antiarrhythmic drugs according to the Vaughnan Williams classification. Several clinical trials have supported experimental data that ω-3 PUFAs have membrane-stabilizing (antiarrhythmogenic) effects. For example, in the GISSI-Prevenzione trial, a large-scale, randomized, placebo-controlled study conducted in more than 9.5 thousand patients with left ventricular systolic dysfunction after myocardial infarction, ω-3 PUFA regular consumption significantly reduced the risk of sudden cardiac death by more than 50% in these patients. In our review, the mechanisms underlying the membrane-stabilizing, antiaggregatory, antiatherogenic, and vasodilating effects of ω-3 PUFAs and the clinical effectiveness of ω-3 PUFAs have been analyzed in terms of evidencebased pharmacology.

Dynamic structure of phospholipid bilayers on the path for oxygen diffusion in the ox lung.

The dynamic properties of the phospholipid bilayer of cell membranes were studied with a nanosecond fluorometer to obtain information on the microstructure of the path for oxygen diffusion in the ox lung. The viscosity in membranes of pneumocytes, endothelial cells from pulmonary artery, and erythrocytes was 47, 54 and 162 mPa . sec respectively. The wobbling angle representing the oscillation of phospholipid molecules was 47, 44 and 38 degrees, respectively.