Alexander Sapozhnikov - Academia.edu (original) (raw)

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Papers by Alexander Sapozhnikov

Bulletin of Experimental Biology and Medicine, 1990

Influence of concentration of aggregated immunoglobulins with varying molecular weights on the el... more Influence of concentration of aggregated immunoglobulins with varying molecular weights on the electrophoretic mobility of ram erythrocytes has been explored. It was shown, that electrophoretic mobility of ram erythrocytes depend on the quantity and the size of adsorption complexes.

Bulletin of Experimental Biology and Medicine, 2011

We studied activity and dynamics of apoptosis of peripheral blood lymphocytes in patients with my... more We studied activity and dynamics of apoptosis of peripheral blood lymphocytes in patients with myocardial infarction and analyzed the relationship of these processes with expression of heat shock proteins with a molecular weight of 70 kDa playing an essential role in preventing cell death. Thus, we first demonstrated activation of apoptosis in peripheral blood cells of patients with myocardial infarction compared to the control (healthy individuals) and revealed the expected negative correlation between the expression of heat shock proteins with a molecular weight of 70 kDa by lymphocytes and intensity of their death. The observed dynamics of mononuclear cell apoptosis in the peripheral blood of patients with myocardial infarction can reflect activity of programmed cardiomyocyte death in the focus of ischemic injury.

Bulletin of Experimental Biology and Medicine, 2009

For evaluation of the stress-protective influence of delta-sleep inducing peptide we studied its ... more For evaluation of the stress-protective influence of delta-sleep inducing peptide we studied its effects on the system of heat-shock proteins in immune cells using the method of flow cytometry. The peptide affected the expression of heat-shock protein 70 kDa in cultured human myeloleukemia K562 cells. Delta-sleep-inducing peptide reduces accumulation of intracellular heat shock proteins 70 kDa in cells cultured under conditions of high density.

Russian Journal of Bioorganic Chemistry, 2004

An experimental model system involving the modification of carbohydrate composition of the target... more An experimental model system involving the modification of carbohydrate composition of the target cell surface with neoglycolipids was developed for studying the role of surface carbohydrates of target cells in the NK-cell-mediated cytotoxicity. The polymeric glycoconjugates of the Glyc–PAA–PEA and Glyc–PAA(Flu)–PEA types (where Glyc was an oligosaccharide residue, PAA poly(acrylamide) polymer, PEA the phosphatidylethanolamine residue, and Flu fluorescein residue) capable of incorporating into the cell membrane were synthesized. The optimum structures of neoglycoconjugates and the conditions for their incorporation into K562 and Raji cell lines, which differ in their sensitivity to the NK-cell-mediated lysis were selected. The mechanism of association of glycoconjugates with the plasma cell membrane and the kinetics of their elimination from the cell surface were investigated using the fluorescent-labeled Glyc–PAA(Flu)–PEA derivatives. The spatial accessibility of the carbohydrate ligands for the interaction with human NK cells was demonstrated. The target cells modified with the Lex trisaccharide were shown to be more sensitive to the cytotoxic effect of human NK cells than the intact cells.

Immunology Letters, 2000

Heat shock proteins (HSPs) are intracellular proteins which function as molecular chaperones. At ... more Heat shock proteins (HSPs) are intracellular proteins which function as molecular chaperones. At the same time, translocation of HSPs to the cell surface has been observed in stressed, infected and transformed cells. It seems plausible that surface HSPs may represent molecular targets for recognition and elimination of 'altered' cells by cytotoxic lymphocytes. Previously we demonstrated that EL-4 mouse lymphoma cells growing in vitro express HSPs on their plasma membrane. In this study, we tested the hypothesis that surface HSPs present on EL-4 cells may mediate their recognition and killing by cytotoxic lymphocytes. We have found that susceptibility of culture-adapted EL-4 cells to in vitro lysis by syngeneic and allogeneic splenocytes correlated with the expression of HSP70 on EL-4 cells. Moreover, cytotoxicity was blocked by pretreatment of EL-4 target cells with anti-HSP70 antibody, whereas antibodies to MHC class I molecules and Thy1 did not have such effect. Cytotoxicity against EL-4 lymphoma was not MHC class I-restricted, and was not decreased after depletion of CD8 + cells from the effector cell population. We conclude that in vitro killing of EL-4 cells is mediated, at least in part, by NK cells via recognition of HSPs present on the surface of tumor cells. Thus, cytotoxic response against EL-4 lymphoma should serve as a good model to study the role of HSPs in anti-tumor immunity.

Cell Proliferation, 2002

Heat shock proteins (HSPs) are involved in a variety of intracellular processes and can have both... more Heat shock proteins (HSPs) are involved in a variety of intracellular processes and can have both pro-and anti-apoptotic action. However, little is known about the role of HSPs in the progression of apoptosis. Translocation of HSPs to the surface of apoptotic cells is a previously observed phenomenon demonstrating participation of these proteins in execution of the terminal stages of apoptosis. In a previous study we showed that development of EL-4 lymphoma cell apoptosis in vitro is accompanied by elevation of surface HSP expression. In this study we used this model to analyse the relationship of HSP70 expression and its translocation to the cell surface during apoptosis with some key intracellular events. Our data demonstrate a synchronization of surface and intracellular HSP70 expression with bcl-2 expression, intracellular reactive oxygen species (ROS) concentration and caspase-3 activity. A maximum level of surface and intracellular HSP70 expression was observed at an irreversible phase of EL-4 cell apoptosis after mitochondrial potential depolarization. In addition, an enhancement of the relative level of cytoplasmic HSP70 translocation to the cell surface was concomitant with EL-4 cell apoptosis. However, the size of surface and intracellular pools of HSP70, increasing for initial and intermediate stages of cell death, decreased at the terminal phase of apoptosis. Western blot analysis of HSP70 in conditioned supernatant obtained from EL-4 cell tissue showed that the observed decrease of HSP70 cell content might be due to surface HSP70 shedding into the intercellular space.

Doklady Biological Sciences, 2006

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Doklady Biological Sciences, 2002

In recent years, there were reports in the literature that inhibitors of chlorine channels (ICCs)... more In recent years, there were reports in the literature that inhibitors of chlorine channels (ICCs) of plasma membranes are capable of preventing programmed cell death . This effect of ICCs is attributed to the ability of these inhibitors to block the cell volume decrease caused by cell dehydration, an early stage of apoptosis. It was shown in many models that, during the development of apoptosis, ICCs prevent release of potassium and chloride ions from the intracellular space. This release is typical of the early stage of cell death, and it decreases the osmotic pressure in cells, thereby causing cell shrinkage . The ICC-mediated blockage of cell volume decrease is thought to prevent the development of the processes required to implement the cell death program . On the other hand, it is well known that ICCs are polyfunctional molecules. In addition to inhibition of transmembrane transport of chlorine ions, ICCs are able to modify many other intracellular processes . This suggests that the antiapoptotic effect of ICCs can be attributed not only to the stage of blockage of cell volume decrease, but also to the ICC-induced activation of the specific protective functions of cells that prevent cell death. For example, this may include activation of the biosynthesis of heat shock proteins (HSPs). To test this hypothesis, we studied the correlation of the ICC-induced effects in a model of programmed cell death with the effects of these inhibitors on the expression of the HSP species capable of protecting the cell against apoptosis . The effects of 4-acetamido-4-isothiocyanostilbene-2,2-disulphonic acid (SITS) and 4,4-diisothiocyanostilbene-2,2-disulphonic acid (DIDS), two ICC species, on the programmed death of EL-4 mouse lymphoma cells in vitro and on the level of HSP70 expression in these cells were studied. It should be noted that HSP70 is a protein with a well-studied protective function . It was demonstrated earlier in our experiments that the EL-4 cell culture in vitro is characterized by the presence of a broad range of HSPs. For instance, the surface of the cultured cells was shown to contain representatives of the HSP70 family, the main family of protective proteins . The amount of HSP70 molecules exposed at the surface of live cells in this model represents the rate of intracellular biosynthesis of these proteins. Flow cytometry can be used as a simple method of analysis of changes in the level of HSP70 expression in EL-4 cells.

Histochemistry and Cell Biology, 2007

Membrane-associated oligosaccharides are known to take part in interactions between natural kille... more Membrane-associated oligosaccharides are known to take part in interactions between natural killer (NK) cells and their targets and modulate NK cell activity. A model system was therefore developed using synthetic glycoconjugates as tools to modify the carbohydrate pattern on NK target cell surfaces. NK cells were then assessed for function in response to synthetic glycoconjugates, using both cytolysis-associated caspase 6 activation measured by flow cytometry and IFN-γ production. Lipophilic neoglycoconjugates were synthesized to provide their easy incorporation into the target cell membranes and to make carbohydrate residues available for cell–cell interactions. While incorporation was successful based on fluorescence monitoring, glycoconjugate incorporation did not evoke artifactual changes in surface antigen expression, and had no negative effect on cell viability. Glycoconjugates contained Lex, sulfated Lex, and Ley sharing the common structure motif trisaccharide Lex were revealed to enhance cytotoxicity mediated specifically by CD16 +CD56+NK cells. The glycoconjugate effects were dependent on saccharide presentation in a polymeric form. Only polymeric, or clustered, but not monomeric glycoconjugates resulted in alteration of cytotoxicity in our system, suggesting that appropriate presentation is critical for carbohydrate recognition and subsequent biological effects.

Cell Proliferation, 1999

Abstract. The expression of heat-shock proteins (HSPs) is enhanced in stressed cells and can prot... more Abstract. The expression of heat-shock proteins (HSPs) is enhanced in stressed cells and can protect cells from stress-induced injury. However, existing data about the relationship between apoptosis and HSP expression is contradictory. In this paper, a mouse lymphoma cell death model system is used to detect simultaneously both the process of apoptosis and the level of HSP expression. The model was established after discovering that spontaneous apoptosis and spontaneous cell surface HSP expression occurs in EL-4 mouse lymphoma cells during normal optimal culture conditions. The data show that apoptotic EL-4 cells had higher levels of hsp25, hsp60, hsp70 and hsp90 exposed on the plasma membrane surface than viable cells. The level of surface HSPs was found to increase through several stages of early and late apoptotic death as measured by flow cytometry, with the highest levels observed during the loss of cell membrane phospholipid asymmetry. Heat shock and actinomycin D significantly increased the proportion of apoptotic cells in culture. However, hyperthermia only stimulated a weak and temporary increase in surface HSP expression, whereas actinomycin D strongly elevated the level of surface and intracellular HSPs, particularly in live cells. These results show an associative relationship between apoptosis and HSP expression. The relationship between the progression of cell death and HSP expression suggests a role for membrane HSP expression in programmed cell death.

Doklady Biological Sciences, 2000

Immunology Letters, 1997

introduction: The recently discovered cytokine interleukin (IL)-15 shares several biological acti... more introduction: The recently discovered cytokine interleukin (IL)-15 shares several biological activities with IL-2 and both cytokines use IL-2 receptor B and y for binding, and signaling. Furthermore an IL-15 specific receptor chain (IL-15&) has been described which is structurally related to IL-2Ra chain by the presence of a "sushi" domain involved In cytokine binding. This domain is encoded by exon 2 in both a receptor genes. Three differentially spliced human IL-15% variants have been already identified. Here, we investigated the regulation of expression of the alternative splice variants during T cell activation.

Natural killer (NK) cells have been shown to play a regulatory role in sepsis. According to the c... more Natural killer (NK) cells have been shown to play a regulatory role in sepsis. According to the current view, NK cells become activated via macrophages or dendritic cells primed by lipopolysaccharide (LPS). Recently, TLR4 gene expression was detected in human NK cells suggesting the possibility of a direct action of LPS on NK cells. In this study, effects of LPS on NK cell cytokine production and cytotoxicity were studied using highly purified human NK cells. LPS was shown to induce IFN-γ production in the presence of IL-2 in NK cell populations containing >98% CD56 + cells. Surprisingly, in the same experiments LPS decreased NK cell degranulation. No significant expression of markers related to blood dendritic cells, monocytes or T or B lymphocytes in the NK cell preparations was observed; the portions of HLA-DR bright , CD14 + , CD3 + , and CD20 + cells amounted to less than 0.1% within the cell populations. No more than 0.2% of NK cells were shown to be slightly positive for surface TLR4 in our experimental system, although intracellular staining revealed moderate amounts of TLR4 inside the NK cell population. These cells were negative for surface CD14, the receptor participating in LPS recognition byTLR4. Incubation of NK cells with IL-2 or/and LPS did not lead to an increase in TLR4 surface expression. TLR4 − CD56 + NK cells isolated by cell sorting secreted IFN-γ in response to LPS. Antibody to TLR4 did not block the LPS-induced increase in IFN-γ production. We have also shown that R e -form of LPS lacking outer core oligosaccharide and O-antigen induces less cytokine production in NK cells than full-length LPS. We speculate that the polysaccharide fragments of LPS molecule may take part in LPS-induced IFN-γ production by NK cells. Collectively our data suggest the existence of a mechanism of LPS direct action on NK cells distinct from established TLR4-mediated signaling.