Exploring the Process of Neutrophil Transendothelial Migration Using Scanning Ion-Conductance Microscopy

The dynamics of neutrophil transendothelial migration was investigated in a model of experimental septicopyemia. Scanning ion-conductance microscopy allowed us to determine changes in morphometric characteristics of endothelial cells during this process. In the presence of a pyogenic lesion simulated by Staphylococcus aureus, such migration was accompanied by both compensatory reactions and alteration of both neutrophils and endothelial cells. Neutrophils demonstrated crawling along the contact sites between endothelial cells, swarming phenomenon, as well as anergy and formation of neutrophil extracellular traps (NETs) as a normergic state. Neutrophil swarming was accompanied by an increase in the intercellular spaces between endothelial cells. Endothelial cells decreased the area of adhesion to the substrate, which was determined by a decrease in the cell projection area, and the cell membrane was smoothed. However, endothelial cell rigidity was paradoxically unchanged compared to the control. Over time, neutrophil migration led to a more significant alteration of endothelial cells: first, shallow perforations in the membrane were formed, which were repaired rather quickly, then stress fibrils were formed, and finally, endothelial cells died and multiple perforations were formed on their membrane.

ROS Production by a Single Neutrophil Cell and Neutrophil Population upon Bacterial Stimulation

The reactive oxygen species (ROS) production by a single neutrophil after stimulation with S. aureus and E. coli was estimated by an electrochemical amperometric method with a high time resolution. This showed significant variability in the response of a single neutrophil to bacterial stimulation, from a "silent cell" to a pronounced response manifested by a series of chronoamperometric spikes. The amount of ROS produced by a single neutrophil under the influence of S. aureus was 5.5-fold greater than that produced under the influence of E. coli. The response of a neutrophil granulocyte population to bacterial stimulation was analyzed using luminol-dependent biochemiluminescence (BCL). The stimulation of neutrophils with S. aureus, as compared to stimulation with E. coli, caused a total response in terms of ROS production that was seven-fold greater in terms of the integral value of the light sum and 13-fold greater in terms of the maximum peak value. The method of ROS detection at the level of a single cell indicated the functional heterogeneity of the neutrophil population, but the specificity of the cellular response to different pathogens was the same at the cellular and population levels.

S. aureus and E. coli change the force and work of adhesion between P- and E-selectins of endothelial cells and ligands of neutrophil granulocytes

Thanks to the modification of the force spectroscopy method, when a neutrophil is fixed on the tip, and an endotheliocyte culture is grown on the substrate, the exact indicators of the adhesion force and adhesion work between cells have been investigated. The high variability of adhesion contacts in different donors associated with different expression profiles of neutrophils. It was found by flow cytometry that the EA.hy926 cell line actively expresses VCAM-1, as well as P- and E-selectin under the Staphylococcus aureus influence after 60 min of co-incubation. At the same time, the integral indicators of the adhesion force and adhesion work in the "neutrophil - endothelial cell" interaction were significantly inhibited by S. aureus in all studied donors. Since the VCAM-1 receptor is not involved in the adhesion bonds between neutrophils and endothelial cells, the suppression of the interaction is associated with the inhibition of P- and E-selectins, but direct receptors removal from the endothelial cells surface of the EA.hy926 cell line does not occur. Escherichia coli causes multidirectional effects in the system of interaction "neutrophil - endothelial cell", depending on the expression profile of the donor's neutrophils. However, the cumulative effect of interaction from all donors shows that in general, under the influence of E. coli, there is an increase in adhesion force and a suppression of adhesion work.

Influence of Quantum Dots Protein Crown on the Morphology and Morphometric Characteristics of Lymphocytes

The incubation of quantum dots with lymphocytes induced significant changes in all morphometric characteristics of these cells. Protein crown formed on the surface of quantum dots after incubation with the serum consists mainly of transport proteins, immunoglobulins, blood coagulation proteins, and kininogens. Protein crown changes the morphometric characteristics of cells: in the case of incubation with quantum dots that have low-molecular-weight coating, a shift towards control parameters (cells without exposure) was observed; on the contrary, after incubation with quantum dots that have a high-molecular-weight coating, the differences from the control became more pronounced. It can be hypothesized that protein crown provokes autoagression of lymphocytes against each other and against platelets.

Serum Protein Corona Abolishes Changes in the Expression of Proinflammatory Genes Induced by Quantum Dots in Human Blood Mononuclear Cell

We studied changes in the transcription of genes encoding cytokines (TNF, IL-6, IL-10, and IL-32), cell activation markers (ICAM1, CD38, Fas, and FCGRIII), ROS production catalyst (NOX2), autophagy (Beclin 1, LC3B, and p62) and apoptosis (BAX, BCL2) regulators in peripheral blood mononuclear cells upon contact with quantum dots CdSe/ZnS-MPA and CdSe/CdSeZnS/ZnS-PTVP. Up-regulation of TNF, ICAM1, Fas, p62 mRNA and down-regulation of the FCGRIII and NOX2 mRNA in response to the presence of quantum dots were revealed. The formation of serum protein corona on the surface of quantum dots abolished this effect.

Conditioning adhesive contacts between the neutrophils and the endotheliocytes by Staphylococcus aureus

We have developed a model for evaluating the integral intercellular interactions in the "endotheliocyte-neutrophil" system and have shown the high variability of adhesion contacts in different donors associated with different expression profiles of neutrophils. Two methods (forсe spectroscopy-spectroscopy and scanning ion-conductance microscopy) showed a decrease in the rigidity of the membrane-cytoskeletal complex of neutrophils under the influence of Staphylococcus aureus 2879 M. Adding this strain to the "endotheliocyte-neutrophil" system caused a statistically significant decrease in the adhesion force and adhesion work, which indicates a change in the expression profile and physicochemical properties of membranes of both types of interacting cells (neutrophils and endotheliocytes).

Differences between Neutrophilic Granulocytes and Lymphocytes in Fixation of Quantum Dots of Different Composition

Studies by flow cytometry, scanning electron microscopy, and X-ray microanalysis have shown that fixation/internalization of quantum dots differ in lymphocytes and neutrophilic granulocytes. Punctate fixation of quantum dots to cell surface is characteristic of lymphocytes, while phagocytosis with perinuclear location of quantum dot aggregations is characteristic of neutrophils. The presence of complex functional groups on the surface of quantum dots can inhibit significantly the fixation/internalization of quantum dots by blood cells.

[CHARACTERIZATION OF THE DIFFERENCE IN THE MORPHOLOGY OF DETERGENT RESISTANT MEMBRANES DOMAINS ISOLATED FROM DIFFERENT CELL TYPES BY ATOMIC FORCE MICROSCOPY]

Planar raft and caveolae are specific membrane clusters with high concentration of cholesterol and lipids with saturated fatty acid. These clasters are resistant to detergents and are denoted as detergent resistant membranes domains (DRMs). Their morphology and size have been studied by atomic force microscopy. The size of planar rafts isolated by Librol from monocytes of healthy volunteers was 150.6 ± 68.6 nm--diameters and 5.7 ± 2.9 nm--height, the size of caveolae was 87.3 ± 46.1 nm--diameters and 9.4 ± 5.4 nm--height. Significant difference have been found morphology and size of DRMs isolated from monocytes of healthy volunteers and patients suffering from myocardial infarction as well as between DRMs isolated from endothelial cells. The study of time-dependent changes in the morphology of isolated planar rafts and caveolae has shown that they quickly aggregate during keeping. Therefore, to asses the actual size and morphology of the DRMS, they should be investigated immediately after isolation.

[Low doses of ionizing radiation-induced apoptotic nature of erythrocyte hemolysis]

It is established that exposure of the red blood cells of the rats to low doses of ionizing radiation (0.04; 0.08; 0.16; 0.25 and 0.33 mGr) leads to non-linear changes in the processes of lipid peroxidation in the membrane of erythrocytes, their electrophoretic mobility, osmotic resistance. In a dose range from 0.08 to 0.16 mGr with ionizing radiation apoptosis that determines a temporary slowing of the process of hemolysis and stabilization of erythrocytes that is confirmed by morphological changes in erythrocytes is most likely triggered.

Interactions of quantum dots with donor blood erythrocytes in vitro

The effects of quantum dots CdSe/ZnS-mercaptopropionic acid, (CdSe/CdZnS)ZnS-polyT, and CdSeCdSZnS/polyT/SiO2-NH2 on human erythrocytes were studied. The nanomaterials reduced signifi cantly the erythrocyte sedimentation rate and modified the erythrocyte membrane resistance to induced (acid and hypo-osmotic) hemolysis. Evaluation of the erythrocyte morphology by atomic force microscopy in the control and after exposure to quantum dots showed significant differences in erythrocyte size and changes in their morphology as a result of exposure to the nanomaterials.

[Comparative morphofunctional description of planar rafts and caveolae]

Recently, redefining of the role of the membrane lipids and the formation of a new look at the morphology, organization and functioning of membranes occurred due to the study of specific membrane clusters--rafts. The present review summarizes the current data concerning the morphology, the biophysical and biochemical properties of rafts, describes the structure, form and basic functional microdomains marking proteins.

[Research of biocompatibility of nanoparticles with fluorescent domen Er/Yb in the neutrophilic granulocytes system]

Fluorescent tags are extensively used for the diagnostic, labeling and marking in vivo and in vitro systems. In this study, fluorescent nanoparticles with Er/Yb lightning center were tested on neutrophilic granulocytes. The main purpose was to idenfity possible toxic effect. The negative impact of fluorophores on the metabolism of neutrophilic and their enzyme systems, on the receptor-mediated cell responses and on the rigidity of cell membranes was shown. The viability of neutrophils (estimated with the use of propidium iodide) after 2 hours of incubation with the fluorescent nanoparticles in concentrations of 10(-4) and 10(-3) mM was 27.0 +/- 6.6 and 19.07 +/- 3.34 %, respectively.

[Photoinduced bactericidal activity of TiO2 films]

A decline in CFU of gram-positive and gram-negative bacteria on the surface of UV illuminated TiO2 films (wavelength of 380 nm) is shown. A 29, 45, and 47% decrease in bacterial viability of Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli, respectively, was seen following a 12-min exposition. It was first discovered that the reuse of TiO2 films to test a bacterial suspension for viability removes UV-induced bactericidal activity. However, annealing of TiO2 at a temperature above 400 degrees C restores the photoinduced bactericidal activity to its initial state.

[Differences in the functional activity of human neutrophilic granulocytes in their interactions with semiconductor quantum dots]

The uptake of quantum dots (QD-5 nm particles of CdSe/ZnS-mercaptoacetic acid) by human neutrophilic granulocytes was studied using the methods of scanning laser and scanning probe microscopy. The results show that the neutrophilic granulocytes may be subdivided into three subpopulations: (1) the cells with no uptake of QD (10.0 +/- 2.0%); (2) cells that accumulate QD in their volume (28.0 +/- 1.9%), and (3) cells, surrounded by a halo of QD (59.0 +/- 2.2%). The dispersion of these characteristics may suggest the differences in neutrophilic granulocyte plasma membrane permeability.

Study of morphology and rigidity of neutrophilic granulocyte membrane in the real time mode by scanning probe microscopy

The rigidity of neutrophilic granulocyte membrane was determined: 2.1+/-0.7 kPa. Scanning in the contact mode did not modify cell morphology, while spectroscopy caused nonspecific swelling reaction and a 3-fold increase in cell volume. Spectroscopy had no effect on rigidity of neutrophilic granulocyte membrane.

[Scanning probe microscopy for the study of morphological parameters of neutrophilic granulocytes]

Morphological parameters of human blood neutrophilic granulocytes were studied by scanning probe microscopy. The basic morphological characteristics of the living (unfixed) and fixed cells were compared. It was found that using the method described, the dimensions of the cells changed substantially and significantly depending upon the mode of fixation applied. The methanol fixation allowed to demonstrate the internal structure of a cell, though it sharply deformed the object of study. After glutaraldehyde fixation cells possessed the morphological characteristics similar to those of the living cells, but the diameter and height of the fixed cells were again different from those of living cells. The resolution of a scanning probe microscope was higher when the fixed cells were studied, permitting the visualization of a detailed cell structure, including the nucleus and cytoplasmic granules (in particular, when methanol fixation was used). However, this method of study is unreliable for the determination of cell dimensions (diameter and height).