Cell Membrane Polarization Research Articles

Cyclo(Pro-Tyr) elicits conserved cellular damage in fungi by targeting the [H+]ATPase Pma1 in plasma membrane domains

Bioactive metabolites play a crucial role in shaping interactions among diverse organisms. In this study, we identified cyclo(Pro-Tyr), a metabolite produced by Bacillus velezensis, as a potent inhibitor of Botrytis cinerea and Caenorhabditis elegans, two potential cohabitant eukaryotic organisms. Based on our investigation, cyclo(Pro-Tyr) disrupts plasma membrane polarization, induces oxidative stress and increases membrane fluidity, which compromises fungal membrane integrity. These cytological and physiological changes induced by cyclo(Pro-Tyr) may be triggered by the destabilization of membrane microdomains containing the [H+]ATPase Pma1. In response to cyclo(Pro-Tyr) stress, fungal cells activate a transcriptomic and metabolomic response, which primarily involves lipid metabolism and Reactive Oxygen Species (ROS) detoxification, to mitigate membrane damage. This similar response occurs in the nematode C. elegans, indicating that cyclo(Pro-Tyr) targets eukaryotic cellular membranes.

Membrane-Targeting Amphiphilic Honokiol Derivatives Containing an Oxazole Moiety as Potential Antibacterials against Methicillin-Resistant Staphylococcus aureus.

Infections with methicillin-resistant Staphylococcus aureus (MRSA) are becoming increasingly serious, making the development of novel antimicrobials urgent. Here, we synthesized some amphiphilic honokiol derivatives bearing an oxazole moiety and investigated their antibacterial and hemolytic activities. Bioactivity evaluation showed that E17 possessed significant in vitro antibacterial activity against S. aureus and MRSA, along with low hemolytic activity. Moreover, E17 exhibited rapid bactericidal properties and was not susceptible to resistance. Mechanistic studies indicated that E17 interacts with phosphatidylglycerol and cardiolipin of bacterial cell membranes, leading to changes in cell membrane permeability and polarization, increased intracellular ROS, and leakage of DNA and proteins, thus accelerating bacterial death. Transcriptome analysis further demonstrated that E17 has membrane-targeting effects, affecting the expression of genes related to cell membranes and ABC transporter proteins. Notably, in vivo activity showed that E17 has prominent anti-MRSA efficacy, comparable to vancomycin, and is expected to be a new anti-MRSA drug candidate.

Dietary potassium and cold acclimation additively increase cold tolerance in Drosophila melanogaster

In the cold, chill susceptible insects lose the ability to regulate ionic and osmotic gradients. This leads to hemolymph hyperkalemia that drives a debilitating loss of cell membrane polarization, triggering cell death pathways and causing organismal injury. Biotic and abiotic factors can modulate insect cold tolerance by impacting the ability to mitigate or prevent this cascade of events. In the present study, we test the combined and isolated effects of dietary manipulations and thermal acclimation on cold tolerance in fruit flies. Specifically, we acclimated adult Drosophila melanogaster to 15 or 25 °C and fed them either a K+-loaded diet or a control diet. We then tested the ability of these flies to recover from and survive a cold exposure, as well as their capacity to protect transmembrane K+ gradients, and intracellular Na+ concentration. As predicted, cold-exposed flies experienced hemolymph hyperkalemia and cold-acclimated flies had improved cold tolerance due to an improved maintenance of the hemolymph K+ concentration at low temperature. Feeding on a high-K+ diet improved cold tolerance additively, but paradoxically reduced the ability to maintain extracellular K+ concentrations. Cold-acclimation and K+-feeding additively increased the intracellular K+ concentration, aiding in maintenance of the transmembrane K+ gradient during cold exposure despite cold-induced hemolymph hyperkalemia. There was no effect of acclimation or diet on intracellular Na+ concentration. These findings suggest intracellular K+ loading and reduced muscle membrane K+ sensitivity as mechanisms through which cold-acclimated and K+-fed flies are able to tolerate hemolymph hyperkalemia.

The biophysical and biochemical polarization of the epithelial cell plasma membrane

The biophysical and biochemical polarization of the epithelial cell plasma membrane

Ratiometric NIR cell membrane-targeted probe for monitoring cell membrane polarity and tumor application

The investigation of cell membrane polarity is critical to determining cell physiological states and related disease for diagnosis and treatment. Herein, a ratiometric NIR cell membrane-targeted fluorescent probe, Cy-C12-MpN, was designed and synthesized to assess cell membrane polarity, which has an amphiphilic structure consisting of a dodecyl unit and a quaternary ammonium unit. It exhibited changes in emission wavelength and fluorescence intensity with the changes in polarity of the solution. It can use the ratio signal of the two peaks to report the polarity difference in its environment. The self-tuning of the probe internal system ensures the reliability of the test results and can be a semi-quantitative detection method. Indeed, in vitro polarity test, the ratio signal reported by Cy-C12-MpN had an optimal linear range with respect to polarity. Cell imaging illustrated the excellent cell membrane-targeted ability of Cy-C12-MpN, as it can rapidly target the cell membrane within 30 s and still anchor at it well after 1 hr. Moreover, Cy-C12-MpN showed that cell membrane polarity decreases after cells become cancerous, and observed the changes in cell membrane polarity caused by homeostatic membrane response stimulated by polyunsaturated fatty acids firstly. Imaging in vivo demonstrated the ability of Cy-C12-MpN to distinguish between tumor cells and normal cells, and further demonstrated that tumor cells have lower cell membrane polarity. In summary, the accuracy of the ratio detection of the probe Cy-C12-MpN and its excellent cell membrane targeting ability reveal reliable results that can provide very useful insights for cancer research.

Cell membrane targetable NIR fluorescent polarity probe for selective visualization of cancer cells and early tumor

The development of a sensitive method for early cancer diagnosis is very important because the early diagnosis of cancer is crucial in preventing the spread of cancer cells and improving patient survival rates. Recent studies showed that cancer cell membranes have lower polarity than normal cell membranes, which provides a new approach for cancer diagnosis at the cell membrane level. We developed herein a highly sensitive cell membrane polarity probe (Cal-M) for early diagnosis of cancer. This probe has low cytotoxicity, good photostability, near-infrared (NIR) fluorescence emission (>700 nm), large Stokes shift, high sensitivity for polarity, excellent cell membrane localization performance, and the ability to selectively light up cancer cells. Using this probe staining, the fluorescence of cancer cells is ∼63 times higher than that of normal cells, demonstrating excellent sensitivity and selectivity of Cal-M. This probe was also successfully used to detect polarity changes on cancer cell membranes and selectively visualize tumors in mice. Notably, the tumor could be visualized sensitively with a size as small as 1.37 mm3, indicating that Cal-M is promising for early diagnosis of tumors.

Pyroelectric Janus nanomotors to promote cell internalization and synergistic tumor therapy

The tumor diffusion and cell internalization are the major obstacles to improving delivery efficacy of therapeutic agents. External electric fields have shown strong effect on the cell membrane polarization and fluidity, but usually need complicated power management circuits. Herein, in situ generation of microelectric field on nanoparticles (NPs) is proposed to overcome these delivery barriers. Janus tBT@PDA-CPT NPs were developed through partially coating of polydopamine (PDA) caps on pyroelectric tetragonal BaTiO3 (tBT) NPs and then camptothecin (CPT) conjugation via disulfide linkages. For comparison, cBT@PDA-CPT NPs were prepared from non-pyroelectric cubic BaTiO3 (cBT) as control. Near-infrared (NIR) illumination on PDA caps of the Janus NPs produces asymmetric thermophoretic force to drive NP motion for tumor accumulation, deep tissue penetration and effective cell interaction. Photothermally created temperature variations on tBT NPs build pyroelectric potentials to selectively change the membrane potential of tumor cells other than normal cells and exhibit a dominated role in enhancing tumor cell internalization and cytotoxicity. The combination index analysis confirms the synergistic effect of pyroelectric dynamic therapy (PEDT), chemotherapy and photothermal therapy (PTT), leading to full inhibition of tumor growth and noticeable extension of animal survival at significant lower CPT doses. The mild PTT/PEDT, the reduced CPT dose and the selective toxicity to tumor cells have achieved favorable treatment safety after tBT@PDA-CPT/NIR treatment. Therefore, in response to the differences in membrane potentials and glutathione levels between tumor and normal cells, we have demonstrated a concise design to achieve thermophoresis-driven motion, pyroelectric potential-enhanced cell internalization and PTT/PEDT/chemotherapy-synergized antitumor treatment.

Antimicrobial Peptide Cec4 Eradicates Multidrug-Resistant Acinetobacter baumannii in vitro and in vivo.

Acinetobacter baumannii has become a major difficulty in the treatment of bacteria-associated infection. The previously reported antimicrobial peptide Cec4 exhibited good and stable activity against A. baumannii in vitro, but the mechanisms and effects in vivo are elusive. The effects of Cec4 on bacterial membrane permeability, membrane potential and bacterial reactive oxygen species were measured. The cell membrane localization of antimicrobial peptides was studied by fluorescence labelling. The ability of bacteria to develop resistance to antimicrobial peptides was studied by continuous induction, and transcriptome difference was analysed. The in vivo toxicity of Cec4 against nematodes and mice was studied, and the in vivo therapeutic potential of Cec4 against A. baumannii was assessed. Cec4 effectively cleared multidrug-resistant A. baumannii by altering bacterial cell membrane permeability, changing bacterial cell membrane polarity, and increasing bacterial intracellular reactive oxygen species. Cec4 affected the expression of the secretion system, outer membrane, and efflux pump genes of A. baumannii. In addition, the bacteria did not acquire stable drug-resistant ability. Cec4 at 1.024 mg/mL did not affect the proliferation of HeLa and HepG2 cells, and Cec4 at 45 mg/kg had little effect on the mortality of Caenorhabditis elegans, even the liver and kidney tissues of mouse. Most importantly, Cec4 could effectively improve the survival rates and reduce the bacterial load of various tissues in the mouse model of infection. In conclusion, Cec4 can damage the cell membrane of bacteria, and the bacteria is not easy to produce resistance to Cec4. Besides, Cec4 has good potential for the treatment of multidrug-resistant A. baumannii infections.

Lipid Membrane Alterations in Tumor Spheroids Revealed by Fluorescence Lifetime Microscopy Imaging.

Three-dimensional (3D) cultured tumor spheroid models, as one type of in vitro model, have been proven to have more physiological similarities to in vivo animal models than cells in 2D cultures. Tumor spheroids have been widely used in preclinical experiments of anticancer drug treatments, providing reliable data in pathogenetic research. Currently, different 3D cell culture conditions, even in the same cell line, generate heterogeneous spheroids in morphology and size, resulting in different growth rates or drug-killing responses. Therefore, the measurement and evaluation of the properties of tumor spheroids have become highly demanding tasks with huge challenges. For functional characterization of tumor spheroids, the microenvironment sensitivity and quantitative properties of the fluorescence lifetime microscopy imaging (FLIM) technique have great advantages for improving the reliability of cell physiological testing. In this paper, we have proposed a FLIM-based approach to observe the lipid components labeled with Nile red of cells in both 3D and 2D cultures. The imaging data and analysis provided basic information on the sizes, morphologies, and cell membrane fluorescence lifetime values of the tumor spheroids. FLIM data showed that the microenvironment of the cell membrane in the 3D model was largely altered compared to that in the 2D culture. Next, a series of parameters that may influence the lipid components of tumor cells and tumor spheroids were tested by FLIM, including pH, viscosity, and polarity. The results showed that pH and viscosity contributed little to the change in fluorescence lifetime values, while the change in cell membrane polarity was the main cause of the alterations in fluorescence lifetime data, suggesting that cell membrane polarity should be considered a marker in distinguishing tumor spheroids from cellular physiological status. In conclusion, this FLIM-based testing process has been proven to be a quantitative method for measuring the differences between the cells of the 3D model from the 2D cultured cells with satisfactory sensitivity and accuracy, providing a high potential standard assay in the quality evaluation and control of tumor spheroids for future anticancer drug development.

Sensitization of KPC and NDM Klebsiella pneumoniae To Rifampicin by the Human Lactoferrin-Derived Peptide hLF1-11.

A synergistic effect of non-bactericidal concentrations of the human lactoferrin (hLF)-derived peptide hLF1-11 and rifampicin against multidrug-resistant KPC (Klebsiella pneumoniae carbapenemase)-producing K. pneumoniae has been previously shown. The present study focuses on the mechanism(s) underlying this synergistic effect. The contribution of hLF1-11 and rifampicin to the synergistic effect was evaluated by killing assays with KPC K. pneumoniae cells incubated with hLF1-11 and, after washing, with rifampicin, or vice versa. Cell membrane permeability and polarization upon exposure to hLF1-11 and/or rifampicin were evaluated by ethidium bromide (EtBr) and DiBAC4(3) (bis-1,3-dibutylbarbituric acid trimethine oxonol) permeability, respectively. The effect of carbonyl cyanide m-chlorophenyl hydrazone (CCCP), an uncoupler of oxidative phosphorylation, was also evaluated. KPC K. pneumoniae cells were effectively killed after prior exposure to rifampicin for 30 to 60 min followed by treatment with hLF1-11, while no antibacterial activity was observed when cells were incubated with hLF1-11 first and then with rifampicin. EtBr accumulation increased upon exposure to hLF1-11 or the combination of hLF1-11 and rifampicin, but not upon exposure to rifampicin alone. Moreover, hLF1-11 induced a dose-dependent membrane depolarization. As expected, the antibacterial activity of hLF1-11 alone or combined with rifampicin was significantly reduced in the presence of CCCP. Furthermore, hLF1-11 and rifampicin were synergistic also against a colistin-resistant NDM (New Delhi metallo-β-lactamase)-producing K. pneumoniae strain. The results suggest that rifampicin was accumulated by KPC cells during the 30-to-60-min incubation and that the addition of hLF1-11 sensitized bacterial cells to rifampicin by inducing a transient loss of membrane potential and increased cell membrane permeability, thus facilitating the entrance and retention of rifampicin into the cytoplasm. IMPORTANCE The present study describes a synergistic effect between rifampicin, an impermeable hydrophobic antibiotic with an intracellular target, and an hLF1-11, an antimicrobial peptide derived from human lactoferrin, against multidrug-resistant Klebsiella pneumoniae. Carbapenem-resistant K. pneumoniae has recently caused an outbreak in Tuscany, Italy, thus pressing the need for the development of new treatment options. The mechanisms underlying such a synergistic effect have been studied. The results suggest that the synergistic effect was due to the transient loss of membrane potential induced by hLF1-11 and the subsequent increase in cell membrane permeability which allowed rifampicin to enter the bacterial cell. Therefore, it is likely that a sub-inhibitory concentration of hLF1-11 can efficiently permeabilize K. pneumoniae cells to rifampicin, allowing the antibiotic to reach its intracellular target. These results encourage further exploration of possible applications of this synergistic combination in the treatment of K. pneumoniae infections.

Effect of Lipid Raft Disruptors on Cell Membrane Fluidity Studied by Fluorescence Spectroscopy.

Lipid rafts are specialized microdomains in cell membranes, rich in cholesterol and sphingolipids, and play an integrative role in several physiological and pathophysiological processes. The integrity of rafts can be disrupted via their cholesterol content-with methyl-β-cyclodextrin (MCD) or with our own carboxamido-steroid compound (C1)-or via their sphingolipid content-with sphingomyelinase (SMase) or with myriocin (Myr). We previously proved by the fluorescent spectroscopy method with LAURDAN that treatment with lipid raft disruptors led to a change in cell membrane polarity. In this study, we focused on the alteration of parameters describing membrane fluidity, such as generalized polarization (GP), characteristic time of the GP values change-Center of Gravity (τCoG)-and rotational mobility (τrot) of LAURDAN molecules. Myr caused a blue shift of the LAURDAN spectrum (higher GP value), while other agents lowered GP values (red shift). MCD decreased the CoG values, while other compounds increased it, so MCD lowered membrane stiffness. In the case of τrot, only Myr lowered the rotation of LAURDAN, while the other compounds increased the speed of τrot, which indicated a more disordered membrane structure. Overall, MCD appeared to increase the fluidity of the membranes, while treatment with the other compounds resulted in decreased fluidity and increased stiffness of the membranes.

Phenolic-rich extracts from acerola, cashew apple and mango by-products cause diverse inhibitory effects and cell damages on enterotoxigenic Escherichia coli

This study aimed to evaluate the inhibitory effects of phenolic‐rich extracts from acerola (Malpighia emarginata D.C., PEA), cashew apple (Anacardium occidentale L., PEC) and mango (Mangifera indica L., PEM) by‐products on distinct enterotoxigenic Escherichia coli (ETEC) strains. The capability of PEA and PEC of impairing various physiological functions of ETEC strains was investigated with multiparametric flow cytometry. Procyanidin B2, myricetin and p‐coumaric acid were the major phenolic compounds in PEA, PEC and PEM, respectively. PEA and PEC had lower minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) (MIC: 31·25 mg ml−1; MBC: 62·5 mg ml−1) on ETEC strains than PEM (MIC and MIC: >1000 mg ml−1). PEA and PEC (15·6, 31·2, 62·5 mg ml−1) caused viable count reductions (P < 0·05) on ETEC strains after 24 h of exposure, notably the ≥3 log reductions caused by 62·5 mg ml−1. The 24 h exposure of ETEC strains to PEA and PEC (31·2, 62·5 mg ml−1) led to high sizes of cell subpopulations with concomitant impairments in cell membrane polarization and permeability, as well as in enzymatic, respiratory and efflux activities. PEA and PEC are effective in inhibiting ETEC through a multi‐target action mode with disturbance in different physiological functions.

Two Water-Soluble and Wash-Free Fluorogenic Probes for Specific Lighting Up Cancer Cell Membranes and Tumors.

The construction of microenvironment-sensitive probes with good cell membrane-targetability can reveal the fundamental properties of cell membranes. Herein, two polarity-sensitive probes, termed MEMs were reported for the first time to specifically light up cancer cell membranes. Both probes were designed with tetrahydroquinoxaline coumarin amide as the fluorophore, and quaternary ammonium groups were appended to increase water solubility and target cell membranes. In vitro studies showed that the fluorescence of both probes displayed strong polarity dependence and had a wide linear range to polarity (Δf). MEMs also displayed excellent cell membrane targeting ability and could long-term light up cell membranes with red fluorescence and a wash-free process. More excitingly, MEMs could specifically light up cancer cell membranes, revealing that cancer cells might have lower cell membrane polarity than normal cells. In vivo studies showed that MEMs could also effectively distinguish tumors from normal tissues. Overall, this work has not only developed two polarity-sensitive probes with good cell membrane targetability, but also provided new insights and methods for an in-depth understanding of cancer cells and cancer diagnosis.

Proliferation and Differentiation of Intestinal Caco-2 Cells Are Maintained in Culture with Human Platelet Lysate Instead of Fetal Calf Serum

Cell lines are widely used as in vitro model systems and substitute for animal experiments. The frequently used Caco-2 cell line is considered to reflect characteristics of differentiated intestinal epithelium. However, the need to culture the cells with fetal calf serum (FCS) induces a high variability, risk of contamination and is ethically disputed. We tested the culture of Caco-2 cells with human platelet lysate (PL) instead of FCS. We compared cell viability and differentiation by measuring ATP levels, gene and protein expression of specific markers in total cell extracts, brush border membrane vesicles (BBM) and lipid rafts (LR). Cell viability was slightly enhanced in cells grown with PL compared to FCS. The cells differentiated to an intestinal phenotype like the cells cultured in FCS, as indicated by the similar gene expression levels of hexose and protein transport proteins and the structural protein VILLIN. BBM showed a comparable distribution of the intestinal hydrolases, indicating a maintained cell membrane polarity. The distribution of the marker protein FLOTILLIN-2 in LR was also similar. We conclude that PL is an exquisite and suitable replacement for FCS in the culture of Caco-2 cells that can eliminate many disadvantages incurred due to the use of FCS.

A bioelectric model of carcinogenesis, including propagation of cell membrane depolarization and reversal therapies

As the main theory of carcinogenesis, the Somatic Mutation Theory, increasingly presents difficulties to explain some experimental observations, different theories are being proposed. A major alternative approach is the Tissue Organization Field Theory, which explains cancer origin as a tissue regulation disease instead of having a mainly cellular origin. This work fits in the latter hypothesis, proposing the bioelectric field, in particular the cell membrane polarization state, and ionic exchange through ion channels and gap junctions, as an important mechanism of cell communication and tissue organization and regulation. Taking into account recent experimental results and proposed bioelectric models, a computational model of cancer initiation was developed, including the propagation of a cell depolarization wave in the tissue under consideration. Cell depolarization leads to a change in its state, with the activation and deactivation of several regulation pathways, increasing cell proliferation and motility, changing its epigenetic state to a more stem cell-like behavior without the requirement of genomic mutation. The intercellular communication via gap junctions leads, in certain circumstances, to a bioelectric state propagation to neighbor cells, in a chain-like reaction, till an electric discontinuity is reached. However, this is a reversible process, and it was shown experimentally that, by implementing a therapy targeted on cell ion exchange channels, it is possible to reverse the state and repolarize cells. This mechanism can be an important alternative way in cancer prevention, diagnosis and therapy, and new experiments are proposed to test the presented hypothesis.

ZxNPF7.3/NRT1.5 from the xerophyte Zygophyllum xanthoxylum modulates salt and drought tolerance by regulating NO3−, Na+ and K+ transport

The Nitrate Transporter1/Peptide Transporter family member NPF7.3/NRT1.5 is responsible for long-distance transport of NO3− and involved in affecting salt and drought tolerance in plants. However, current studies have only focused on AtNRT1.5 from the stress-sensitive glycophyte Arabidopsis. In this study, the function of the NRT1.5 homolog ZxNRT1.5 from the typical xerophyte Zygophyllum xanthoxylum in ion transport and plants’ salt and drought tolerance was analyzed. The results indicated that ZxNRT1.5 was mainly expressed in the root stele, and its expression level was significantly induced by salt treatments and osmotic stress. Overexpression of ZxNRT1.5 in Arabidopsis showed that ZxNRT1.5 mediated root-to-shoot NO3− transport and contributed to enhancing NO3− uptake. Overexpression of ZxNRT1.5 increased Na+ accumulation by decreasing the expression of AtHKT1;1 in roots, and promoted root-to-shoot transport of K+ probably by changing polarization of cell membrane under salt stress. Meanwhile, ZxNRT1.5-overexpressing lines exhibited stronger tolerance to mannitol-induced osmotic stress, resulted from an increased accumulation of NO3− and the accumulation of a small quantity of Na+ that was beneficial for plant growth. These findings suggest that ZxNRT1.5 is not only essential for long-distance transport and accumulation of NO3−, but also involved in regulating Na+ and K+ transport, thereby modulating salt and drought tolerance.

Toxicity of Carbon, Silicon, and Metal-Based Nanoparticles to the Hemocytes of Three Marine Bivalves.

Simple SummaryThe growing nanotechnology industry disposes of a variety of nanoparticles with different physiochemical properties in everyday life. However, the dependence of the safety and toxicity of nanoparticles on their physicochemical properties remains unclear. Bivalve molluscs represent an efficient model for the investigation of nanoparticle toxicity owing to their filtrating ability and feeding on particles suspended in the water. Moreover, the blood cells of bivalve molluscs, the hemocytes, have been suggested as a good analog test-object to mammalian immune cells, phagocytes. In this study, we used hemocytes of three marine bivalve species, namely, Crenomytilus grayanus, Modiolus modiolus, and Arca boucardi, to evaluate and compare the toxic effects of 10 different types of nanoparticles. We gave short-term exposure of the nanoparticles to the hemocytes and registered viability and changes in their cell membrane polarization by employing flow cytometry. Metal-based nanoparticles were the most toxic to the cells of all three tested bivalve mollusc species. However, the sensitivity to different nanoparticle types varied between species. Moreover, the registered cell membrane depolarization indicated an early toxic response and raised concern that chronic long-term exposure of nanoparticles (even if they were previously declared as safe) is a serious threat for aquatic organisms.Nanoparticles (NPs) have broad applications in medicine, cosmetics, optics, catalysis, environmental purification, and other areas nowadays. With increasing annual production of NPs, the risks of their harmful influence on the environment and human health are also increasing. Currently, our knowledge about the mechanisms of the interaction between NPs and living organisms is limited. The marine species and their habitat environment are under continuous stress owing to the anthropogenic activities, which result in the release of NPs in the aquatic environment. We used a bioassay model with hemocytes of three bivalve mollusc species, namely, Crenomytilus grayanus, Modiolus modiolus, and Arca boucardi, to evaluate the toxicity of 10 different types of NPs. Specifically, we compared the cytotoxic effects and cell-membrane polarization changes in the hemocytes exposed to carbon nanotubes, carbon nanofibers, silicon nanotubes, cadmium and zinc sulfides, Au-NPs, and TiO2 NPs. Viability and the changes in hemocyte membrane polarization were measured by the flow cytometry method. The highest aquatic toxicity was registered for metal-based NPs, which caused cytotoxicity to the hemocytes of all the studied bivalve species. Our results also highlighted different sensitivities of the used tested mollusc species to specific NPs.

PRESOWING STIMULATION OF ECHINACEA AND VALERIAN SEEDS WITH ULTRA-HIGH FREQUENCY ELECTROMAGNETIC FIELD

The article presents the results obtained by testing the previously proposed physical and mathematical model of the temperature distribution in the layer of poured seeds when irradiated with a high-frequency electromagnetic field. It has been proven that temperature is one of the factors influencing the consequences of pre-sowing seed treatment. We have found out that, along with heating, other physical processes occur in the seed structure at the level of cell membranes and membrane transport of substances. The transformation of protein structures, the polarization of cell membranes, and the intensification of metabolic processes under the influence of irradiation can lead to changes in the electrical properties of seeds and, as a consequence, can impact on the physiological state, germinability and growth energy of plants. The result of the seed exposure to high-frequency electromagnetic field depends on the electrical characteristics of the seeds. We have developed a technology for the pre-sowing treatment of Echinacea and Valerian seeds in order to obtain more ecologically pure raw materials for pharmacological industry. The study has demonstrated positive thermal and oscillation effects produced by the electromagnetic field on the structural elements of seeds. Based on the method of presowing stimulation of the seeds with a high-frequency electromagnetic field, the optimal modes for irradiation of Echinacea and Valerian seeds have been elaborated. It has been established that boosting the overall resistance of biological tissue, an increase in the polarization of cell membranes indicates an enhancement of metabolic processes and, as a result, stimulates the process of seed germination and rapid vegetation in the early stages of plant development. Theoretical calculations and experimental studies have evidenced positive results doe to implementation of the described technology.

Radio-frequency dielectric relaxation behavior of selected vegetable tissues: Spectra analysis with logarithmic derivative method and simulation with double-shell model

The dielectric relaxation behaviors in the radio-frequency range, where β- relaxation is predominant, of flesh tissues of several vegetables are studied in this work. By taking advantage of the logarithmic derivative method, three sub -β- relaxations were revealed for all vegetable tissues under study, and their relaxation characteristics were accurately determined. The relaxation behaviors were further simulated by means of the double-shell model. With reasonable values of involved morphological and physiological parameters, fairly satisfying simulations were achieved, where the simulated relaxations have consistent relaxation times to those of the measured relaxations. The simulation suggests that the low-frequency sub -β- relaxation arises from polarization of plasma membrane, while the middle- and high-frequency sub -β- relaxations are due to interfacial polarization at interfaces of tonoplast/protoplasm and cell sap/tonoplast, respectively.

The Mechanisms Linking Relative Hypercortisolism - The Common Feature Across COVID-19 Risks - To ARDS, Septic Shock, and Cytokine Dysregulation

Covid-19 mortality risk factors share a common feature: a high ratio of cortisol to DHEA, referred to as relative hypercortisolism (RHC).Starting from a low just after age 25, adult COVID-19 mortality rates rise in tandem with this ratio as DHEA levels fall by over 80% by age 70. Conversely, juvenile COVID-19 morbidity rates _fall_ with this ratio as DHEA rises to pre-adolescent levels after age 6. Moreover, RHC predicts the severity and likelihood of death for both community acquired pneumonia and septic shock, the primary COVID-19 modes of death. Consistent with this finding, DHEA prevents cytokinedysregulation in a murine leukemia retrovirus model. DHEA, byinhibiting the PI3K/AKT pathway, also inhibits viral replication.DHEA, antagonized by cortisol, maintains intracellular calciumhomeostasis, a critical function during viral infections. The cortisol to DHEA ratio determines the exon splicing of the calcium-sensitive big potassium (BKCa) channel, which exerts predominate control over cell and inner mitochondrial membrane polarization. DHEA increases BKCa calcium sensitivity, and thereby reduces calcium influx into the cell and mitochondrial matrix. This effect–together with vitamin D3/calcitriol promoted calbindin-D9k/28k, magnesium, andubiquinone–protects against mitochondrial calcium overload. Absent these key factors, the COVID-19 virus, SARS-CoV-2, like other viruses disrupts intracellular calcium homeostasis to trigger mitochondrial calcium overload in susceptible hosts. The virus then hijacks the inflammatory ER stress and unfolded protein response (UPR) for its own replication.UPR underlies the virus’s lethality. It splices X-box protein 1(XBP-1) to its active form, which in turn activates the transcription regulator SNAI1. sXBP-1 and SNAI1 shift cellular metabolism from the pentose phosphate pathway to the hexosamine biosynthesis pathway and induce insulin resistance. SNAI1 also causes epidermal-to-mesenchymal transition (EMT). In this process, SNAI1 represses transcription of epithelial and vascular endothelial cadherins along with othercritical proteins forming the tight junction barriers in the lung and vasculature. UPR also inhibits expression of the epithelial sodium channel (ENaC), which maintains alveolar fluid balance. DHEAdose-dependently reduces XBP-1 mRNA splicing in cultured hepatocytes treated with the ER stress/UPR inducer tunicamycin.RHC and insulin resistance also produce a pathological immuneresponse. Insulin resistance via mTORC1 inhibits the cell energy sensor AMPK and, consequently, the first line of defense against the virus, autophagy. Severe mitochondrial calcium overload associated with RHC oxidizes phospholipids and predisposes the cell to necrosis.Upon cell lysis, the oxidized phospholipids trigger sterileinflammation, drawing cytokine-secreting neutrophils and macrophages to the site. Further exacerbating inflammation, insulin resistance and its inhibition of PPAR-γ skews macrophage polarization to thepro-inflammatory M1 phenotype. Meanwhile, RHC promotes glucocorticoid recycling via 11β-HSD1 in thymocytes. This recycling causesactivation-induced cell death, suppresses lymphocyte countproliferation, and leads to IL-1β hypersecretion and worsening RHC.Ultimately, this cytokine storm and severe RHC induce autoimmunity.Evidence suggests this pathological state can be avoided by restoring calcium homeostasis using a combination of DHEA, vitaminD3/calcitriol, magnesium, ubiquinone, and the AMPK/SIRT1 activators, acetyl L-carnitine and alpha lipoic acid.