Leonid Livshits

Dielectric spectroscopy study of specific glucose influence on human erythrocyte membranes

Time domain dielectric spectroscopy has been used to study spherical erythrocytes, suspended in diluted phosphate buffered saline (PBS) buffers at varying concentrations of D- and L-glucose at 25°C. The osmolarity for each glucose solution was adapted, equalling that of a 63% PBS (183 mOsm). The strong effect of the electrode polarization was corrected using the fractal approach in time domain. For analysis of the dielectric properties of suspensions of erythrocytes, the Maxwell–Wagner model is used for small volume fractions. Values of the permittivity and conductivity of the cell membrane were obtained from a fitting procedure according to the one-shell model. The non-monotonic and specific response of membrane electric properties on D-glucose concentrations were observed, with a dramatic decrease around 12 mM. No changes of membrane properties have been observed in the presence of increasing concentrations of L-glucose, the biologically inactive enantiomer of D-glucose. The effect is thus specific to D-glucose. The possible mechanism of specific cell reaction to D-glucose is discussed in this paper.

Dielectric response of biconcave erythrocyte membranes to D- and L-Glucose

In this paper, we report on the influence of D- and L-glucose on the dielectric properties of native shaped (biconcave) human erythrocytes using time domain dielectric spectroscopy. The dielectric spectra of biconcave cells were analysed using a modified form of the model originally reported for spheroid particle suspensions (Asami and Yonezawa 1995 Biochim. Biophys. Acta. 1245 317–24) The observed increase in the specific membrane capacitance of the biconcave erythrocytes was correlated with an increase in the concentration of D-glucose. In contrast, no associated correlation was found to changes in the membrane capacitance with increasing concentrations of L-glucose. A similar analysis of the dielectric response of osmotically swollen erythrocytes to changes in D-glucose concentration revealed a significantly different calculated specific cell membrane capacitance at elevated (>12 mM) D-glucose concentrations. The paper outlines and discusses the possible biochemical mechanisms that could be responsible for the measured dielectric properties of the erythrocyte membrane capacitances.

The role of GLUT1 in the sugar-induced dielectric response of human erythrocytes.

We propose a key role for the glucose transporter 1 (GLUT1) in mediating the observed changes in the dielectric properties of human erythrocyte membranes as determined by dielectric spectroscopy. Cytochalasin B, a GLUT1 transport inhibitor, abolished the membrane capacitance changes in glucose-exposed red cells. Surprisingly, D-fructose, known to be transported primarily by GLUT5, exerted similar membrane capacitance changes at increasing D-fructose concentrations. In order to evaluate whether the glucose-mediated membrane capacitance changes originated directly from intracellularly bound adenosine triphosphate (ATP) or other components of the glycolysis process, we studied the dielectric responses of swollen erythrocytes with a decreased ATP content and of nucleotide-filled ghosts. Resealed ghosts containing physiological concentrations of ATP yielded the same glucose-dependent capacitance changes as biconcave intact red blood cells, further supporting the finding that ATP is the effector of the glucose-mediated dielectric response where the ATP concentration is also the mediating factor in swollen red blood cells. The results suggest that ATP binding to GLUT1 elicits a membrane capacitance change that increases with the applied concentration gradient of D-glucose. A simplified model of the membrane capacitance alteration with glucose uptake is proposed.

The dark-colour-inducing neurohormone of locusts in relation to an albino mutant of Schistocerca gregaria

In the albino mutant of an Okinawa strain of Locusta migratoria (L.) (Orthoptera: Acrididae), albinism is caused by the absence of the dark‐colour‐inducing neurohormone (DCIN), which is present in the corpora cardiaca (CC) of normally coloured phenotypes. This study tests whether the absence of DCIN is responsible for albinism in an albino mutant of another locust, Schistocerca gregaria (Forsk.) (Orthoptera: Acrididae). This seemed feasible because a single Mendelian unit controls albinism in both species. However, implantation of CC, or injection of an extract of CC, from albino donors of S. gregaria, induce dark coloration in crowded nymph recipients of the Okinawa albino mutant of L. migratoria, as effectively as do implanted CC, or injections of extract of CC, from normal phenotype donors of S. gregaria. Therefore, DCIN is present in the albino mutant of S. gregaria, and consequently, the albinism in this mutant is not caused by its absence.

Diabetic foot disease is associated with reduced erythrocyte deformability.

The pathogenesis of diabetic foot disease is multifactorial and encompasses microvascular and macrovascular pathologies. Abnormal blood rheology may also play a part in its development. Using a cell flow analyser (CFA), we examined the association between erythrocyte deformability and diabetic foot disease. Erythrocytes from diabetic patients with no known microvascular complications (n = 11) and patients suffering from a diabetic foot ulcer (n = 11) were isolated and their average elongation ratio (ER) as well as the ER distribution curve were measured.

D-Glucose-Induced Second Harmonic Generation Response in Human Erythrocytes

The first experimental results of the nonresonant second harmonic generation (SHG) studies of human erythrocytes membrane exposed to various glucose concentrations in phosphate buffered saline (PBS solution) are presented in this article. It is shown that the SHG signal from the membrane can be altered as a function of glucose concentration. The link between the variation of the SHG intensity and the membrane dielectric permittivity with glucose is established both theoretically and experimentally by comparison with time domain dielectric spectroscopy (TDDS) measurement data.

Mechanisms of defense against products of cysteine catabolism in the nematode Caenorhabditis elegans

ABSTRACT Cysteine catabolism presents cells with a double‐edged sword. On the one hand, cysteine degradation provides cells with essential molecules such as taurine and sulfide. The formation of sulfide in cells is thought to regulate important and diverse physiological processes including blood circulation, synaptic activity and inflammation. On the other hand, the catabolism of cysteine by gut microbiota can release high levels of sulfide that may underlie the development or relapse of ulcerative colitis, an inflammatory bowel disease affecting millions of people worldwide. Here, we have used the nematode C. elegans to explore how cells tolerate high levels of sulfide produced by cysteine degradation in bacteria. We have identified mutations in genes coding for thioredoxin family proteins, mitochondrial proteins, and collagens that confer tolerance to sulfide toxicity. Exposure to sulfide induces the unfolded protein response in the endoplasmic reticulum and mitochondria. Moreover, our results suggest that sulfide toxicity is mediated by reactive oxygen species (ROS). Indeed, pre‐treatment of worms with antioxidants increases their tolerance to sulfide toxicity. Intriguingly, sub‐toxic levels of the superoxide generator paraquat can also increase the tolerance of worms to sulfide. Therefore, it appears that activation of ROS detoxification pathway prior to the exposure to sulfide, can increase the tolerance to sulfide toxicity. Our results suggest that these detoxification pathways are mediated by the hypoxia inducible factor HIF‐1. Finally, we show that sulfide resistance varies among wild C. elegans and other nematode species, suggesting that tolerance to sulfide was naturally selected in certain habitats. HIGHLIGHTSThiol oxidation and mitochondrial inhibition protect against sulfide toxicity.Sulfide toxicity induces oxidative stress in C. elegans.Antioxidants and sublethal levels of paraquat protect against sulfide toxicity.Sulfide tolerance varies among wild nematodes.

A method for measuring sulfide toxicity in the nematode Caenorhabditis elegans

Graphical abstract

Characterization of gene expression associated with the adaptation of the nematode C. elegans to hypoxia and reoxygenation stress reveals an unexpected function of the neuroglobin GLB-5 in innate immunity

Abstract Oxygen (O2) is a double‐edged sword to cells, for while it is vital for energy production in all aerobic animals and insufficient O2 (hypoxia) can lead to cell death, the reoxygenation of hypoxic tissues may trigger the generation of reactive oxygen species (ROS) that can destroy any biological molecule. Indeed, both hypoxia and hypoxia‐reoxygenation (H/R) stress are harmful, and may play a critical role in the pathophysiology of many human diseases, such as myocardial ischemia and stroke. Therefore, understanding how animals adapt to hypoxia and H/R stress is critical for developing better treatments for these diseases. Previous studies showed that the neuroglobin GLB‐5(Haw) is essential for the fast recovery of the nematode Caenorhabditis elegans (C. elegans) from H/R stress. Here, we characterize the changes in neuronal gene expression during the adaptation of worms to hypoxia and recovery from H/R stress. Our analysis shows that innate immunity genes are differentially expressed during both adaptation to hypoxia and recovery from H/R stress. Moreover, we reveal that the prolyl hydroxylase EGL‐9, a known regulator of both adaptation to hypoxia and the innate immune response, inhibits the fast recovery from H/R stress through its activity in the O2‐sensing neurons AQR, PQR, and URX. Finally, we show that GLB‐5(Haw) acts in AQR, PQR, and URX to increase the tolerance of worms to Pseudomonas aeruginosa pathogenesis. Together, our studies suggest that innate immunity and recovery from H/R stress are regulated by overlapping signaling pathways. Graphical abstract Figure. No Caption available. HighlightsHypoxia‐reoxygenation stress activates the innate immune response in C. elegans.Globin 5 increases the tolerance of C. elegans to Pseudomonas aeruginosa toxicity.HIF‐1 is essential for the function of globin 5 in innate immunity.EGL‐9 activity attenuates the recovery from Hypoxia‐reoxygenation stress.Fast neuronal recovery from Hypoxia‐reoxygenation stress is mediated by HIF‐1.

Polystyrene Nanoparticles Activate Erythrocyte Aggregation and Adhesion to Endothelial Cells

Nanoparticles (NPs) are drawing an increasing clinical interest because of their potential use as drug carriers. Recently, a new strategy for elevation of NPs in vivo circulation time has been proposed, specifically, utilizing red blood cells (RBCs) as a carrier for NPs, that are loaded with a drug, by interaction (in vitro) of human RBCs with NPs (RBCNP). This class of delivery set-up, combines advantages of natural RBCs and synthetic biomaterials. Previous studies demonstrated that NPs initiated hemolysis of RBC and activated cells aggregation. In the present study, we examined the effect of RBCNP on the aggregation of RBC and their adhesion to endothelial cells (EC). Red cells were treated with polystyrene NPs (PS-NP), and following their washing, were added to suspension of untreated cells at various concentrations. We observed that the PS-NP and RBCNP initiated the formation of red cells aggregates and markedly elevated RBC adhesion to EC. These effects were augmented with (a) increasing concentration of NPs or RBCNP, and (b) with decreasing NP size. This implies that RBCNP are cells with a stronger intercellular interaction, and may thereby induce the formation of large and strong aggregates with untreated RBC, as well as strong RBC/EC interaction.