Viscum album agglutinin-induced aggregation of blood cells and the lectin effects on neutrophil function

Extracts from mistletoe enjoy a large popularity in central Europe as an unconventional treatment modality for cancer, warranting scientific efforts with defined components to delineate any potential benefit. The galactose-specific lectin from Viscum album (VAA), known to exhibit immunomodulatory and ensuing antitumoral capacities in animal model systems, was shown to aggregate human blood cells in the following order: neutrophils, mononuclear cells--thrombocytes and erythrocytes. To contribute to the analysis of lectin effects on individual aspects of the host defence system, two parameters of neutrophils were quantitatively assessed, namely the aggregating activity of VAA as a measure of strength of interaction with cell surface ligands and the effect of lectin on oxidative metabolism (H2O2 release) of these cells. It was found that whole lectin and its carbohydrate-binding B-subunit possessed the capacity to induce cell aggregation and H2O2 release, which were blocked by D-galactose and lactose. Both effects displayed similar dependence on the lectin concentration in the range 0.1-25 micrograms/ml. The toxic A-subunit displayed detectable activity only in high doses (50 micrograms/ml) while the bovine heart galaptin (14 kDa; galectin-1) failed to affect neutrophils. The role of oxidative metabolism in regulation of neutrophil aggregation induced by VAA was studied using metabolic inhibitors and controlled heating at 46 degrees C leading to inhibition of plasma membrane NADPH-oxidase system. Trifluoperazine and menadione inhibited the neutrophil aggregation in a dose-dependent manner in comparison with such inhibitors as amiloride and theophylline.(ABSTRACT TRUNCATED AT 250 WORDS)

[The effect of hyperthermia (45 C) on lymphoid cell aggregation]

Hyperthermia (45 degrees C) has found to decrease the rate of rat thymocytes as well as splenocytes aggregation induced by lectins (concanavalin A, wheat germ agglutinin) and sulphated polysaccharides (heparin, dextran sulphate-500) and to increase those induced by cationic dye alcian blue. Shedding of plasma membrane glycoproteins and changes of surface charge are supposed to affect the aggregation.

[Aggregation of neutrophils and their generation of active forms of oxygen as affected by lectins]

It was shown that neutrophil aggregation is caused by all lectins with different specificity for carbohydrates but generation of active oxygen forms is induced only by some lectins. Polyspecific lectins-erythroagglutinin and phytohemagglutinins have the greatest activity in relation to both processes.

[The effect of metabolic inhibitors on resistance of mannose-specific contacts of Escherichia coli K12 and human neutrophils]

Human neutrophil aggregation induced by Escherichia coli K12 cells has been studied. D-mannose has been found to inhibit the process in the dose-dependent way causing the full blockage at 10 mM concentration. The process of disaggregation induced by the concentration is significantly higher at 10 degrees C than at 37 degrees C. The inhibitors of cellular oxygenation such as N-ethylmaleimide, nordihydroguaiaretic acid, trifluoperazine, and colchicine did not affect the aggregation process. Cellular aggregation was concomitant with production of H2O2, and this reaction was also blocked by D-mannose and depended on the number of bacteria present. The nordihydroguaiaretic acid and N-ethylmaleimide inhibited production of H2O2, while sodium azide enhanced the process. The results show the mannose-specific contact of bacteria and neutrophils to depend on the functional activity of phagocytes including their ability to produce H2O2.

[The effect of recombinant interleukin-1 beta on concanavalin A-induced lymphocyte reactions]

As revealed by investigations made by the use of the method of luminol-dependent chemiluminescence and light dispersion, the addition of concanavalin A (ConA) to the suspension of human peripheral blood lymphocytes and subsequent incubation with recombinant interleukin-1 beta leads to a sharp increase in the yield of chemiluminescence and the rate of cell aggregation in comparison with similar parameters obtained for cells, not treated with interleukin-1 beta. The study revealed the potentiating action of recombinant interleukin-1 beta on ConA-induced proliferative response of thymocytes in the culture. The mechanisms of the priming action of recombinant interleukin-1 beta on ConA-induced reaction of lymphocytes are discussed.

[The free-radical mechanisms of the cytotoxic action of 1,2-benzoquinone derivatives]

The authors examined the interaction of 1,2-benzoquinone derivatives with HeLa cell cultures and ascite Ehrlich's cancer cells. 4-N (anilino)-5-methoxy-1,2-benzoquinone was found to produce a marked toxic effects against tumor cells. The cytotoxic effect is oxygen dependent and associated with the formation of oxygen radicals in quinone's redox cyclization reactions. The inhibitory analysis was used to show that the major mediators of the toxic action of the agent are superoxide radical-anion and hydrogen peroxide. It is concluded that the interaction of highly toxic oxygen radicals, which are generated in quinone redox cyclization, with plasma membrane cells is likely to be the mechanism responsible for cellular destruction when quinones act on tumor cells.

[A comparative study of the reactions of the peripheral blood neutrophils from donors and from lymphogranulomatosis patients to arachidonate stimulation of the cells]

Arachidonate-induced aggregation and generalization of active oxygen forms (OAF) by peripheral blood neutrophils in donors were studied in donors and Hodgkin's disease patients. Leukocytes of the latter had incomplete ability to produce AOF in response to cell stimulation with arachidonic acid. The study of arachidonate-induced aggregation of neutrophils indicated no differences in the speed of the process in the patients and donors. AOF catchers did not act on the rate of leukocyte aggregation in the patients though accelerated the process in the donors. It is inferred that Hodgkin's disease is associated with dysfunction of oxygen activation by neutrophils. The findings suggest that defects in leukocytes ability to activate oxygen in Hodgkin's disease may entail deranged regulation of other processes essential for functional activity of polymorphonuclear leukocytes.

Photodynamic activity of chlorin e6 and chlorin e6 ethylenediamide in vitro and in vivo

Several parameters of chlorin e6 and its derivative chlorin e6 ethylenediamide have been investigated as these compound are potential sensitizers for photodynamic therapy. A study carried out to compare the cellular uptake of the pigments indicates that chlorin e6 ethylenediamide possesses an enhanced affinity for tumour cells and cellular membranes. Comparison of the uptake in induced sarcoma shows that chlorin e6 ethylenediamide is a much better tumour localizer than chlorin e6. The efficiency of phototherapy with chlorin e6 ethylenediamide is higher than that with chlorin e6. These data show the influence of the substitution of the carboxyl groups in chlorin e6 by ester and amide groups on the photosensitizing properties of the pigments.

[Photodamage of gram-positive and gram-negative bacterial cells in the presence of chlorin e6 derivatives]

The kinetics of photoinduced damage sensitized by chlorine e6 and its derivatives was studied in Escherichia coli and Bacillus subtilis. The effectiveness of E. coli photoinactivation in the presence of chlorines was 100-200 times lower as compared with that of B. subtilis. The structural organisation of bacterial cell walls apparently played an essential role in the penetration of tetrapyrrole pigments into the cell and in their binding.

[Chlorine e6-sensitized photoinhibition of thrombocyte aggregation. Participation of active oxygen forms]

It has been shown that photosensitized action of chlorin e6 (Che6) on platelet-rich plasma leads to platelet aggregation inhibition. Che6-sensitized photoinactivation of platelets was intensified in the presence of singlet oxygen interceptor. The aggregation rate of light-irradiated platelets in the presence of Che6 in D2O buffer was higher than in H2O buffer. The participation of active oxygen forms in the determination of platelet function has been considered.

[The chlorine e6-photosensitized inhibition of human thrombocyte aggregation]

ADP-induced aggregation of platelets in the presence of chlorin E6 under the action of visible light depending on the pigment concentration and the time of light action was studied. It was shown that the photosensitized effect of chlorin E6 on the platelet-enriched plasma results in platelet aggregation inhibition.

[Oxygen activation by lymphocytes during interaction of HLA antibodies with HLA antigens]

The method of luminol-dependent chemiluminescence was used to detect oxygen activation during interaction of HLA antibodies with HLA antigens expressed on lymphocyte surface. Introduction of specific anti-HLA serum into the lymphocyte suspension leads to a rapid decrease of intensity in chemiluminescence intensity follows. The maximum yield of induced chemiluminescence in case of using a specific antiserum is significantly lower than in the control. The method could be used for detection of HLA antigens on lymphocyte surface.

[The role of active forms of oxygen in platelet aggregation and deaggregation]

The effect of hydrogen peroxide on ADP-induced platelet aggregation in the presence of active oxygen species scavengers was studied. It was shown that the superoxide radical and singlet oxygen, alongside with hydrogen peroxide, may play a role in platelet interactions.

[Arachidonic acid-induced aggregation of human peripheral blood neutrophils in the presence of interceptors of active forms of oxygen]

Arachidonate-induced aggregation of human peripheral blood neutrophils and the influence of certain interreceptors of oxygen active forms (OAF) on its rate were studied. The results obtained have shown that OAF play an important role in the processes of interaction between arachidonate and leucocytes. Regulation of the process of leucocyte aggregation may be realized during arachidonate-induced aggregation of neutrophils, due to interaction of cell-generated OAF with arachidonic acid and its lipoxygenase metabolites.

[Modification of redox properties of cells by ortho-benzoquinones]

Ortho-benzoquinones have been studied for their effect on the processes of methemoglobin formation in the rabbit erythrocytes and reduction of potassium ferricyanide by the HeLa cells. It is established that the incubation of cells in the presence of lipophilic quinone OBQ-1 results in the formation of the intracellular methemoglobin in erythrocytes and the intensification of the ferricyanide reduction by HeLa cells. OBQ-2 differing in the presence of the polar sulphogroup does not react with the intracellular oxyhemoglobin and exerts no effect on the ferricyanide reduction. It is supposed that OBQ-1 may change the ratio of the oxidized and reduced metabolites in a cell, thus inducing in it a state of the oxidative stress. A conclusion is drawn hat ortho-benzoquinones are able to modify the redox properties of cells, the efficiency of modification depending on the chemical structure of the compounds.

[The distribution of chlorine e6 and its derivatives in HeLa cells studied using luminescence microscopy]

The influence of the chemical structure of porphyrin pigments on their accumulation and localization in HeLa cells has been examined by the scanning fluorescence microphotometry. It has been found that the replacement of carboxyl groups of chlorine e6 for methyl and amino groups has no influence on the pigment distributions in cells. All the pigments are bound by cell membrane structures. The chemical modification of chlorine e6 structure is essential for the ability of pigment to be accumulated by cells that can be used to increase the efficiency of cancer phototherapy. The charge and hydrophobic properties of pigment molecules are of great importance for accumulating porphyrin sensitizers by cells.

[Structural-functional state of platelets at the initial stage of aggregation]

ADP-induced changes of light transmission of platelet suspension were studied with a laser aggregometer at concentration variation of both cells and aggregation agents. It was shown that a decrease of light transmission of platelet suspension was due to structure-morphological changes of platelets and pseudopodia formation. An investigation method of platelet aggregation with a small content of cells in the solution permits to fix distinctly the stages of the platelet structural states in the processes of stimulation and aggregation.

[Single ion channels and macroscopic conductivity of bilayer lipid membranes]

The dynamic conductivity of bilayer lipid membranes unmodified by ionophores in current ranges of 10(-12)-10(-10) A was studied. On the current voltage characteristics the jumps of dynamic conductivity in the voltage ranges near zero and disruption value were observed. The lifetime of these jumps was 1-5 s. It was shown that these effects were due to electrostriction phenomena and defects in the bilayer lipid structure correspondingly. Apparently, lipid peroxidation products participate in the building of defects in lipid bilayers.

[Damage photosensitized by chlorine e6 in bacteria with various defects of the DNA repair system]

The goal of the work was to study the sensitivity of isogenic Escherichia coli cells differing in their ability to mediate DNA repair steps to the action of visible light sensitized by chlorine e6. Cells incapable of excision repair as well as those deficient in post-replicative recombination DNA repair were found to be much more sensitive to the combined action of visible light and chlorine e6 as compared to cells whose genes responsible for DNA repair were not damaged. The results indicate that visible light damages bacterial DNA in the presence of chlorine e6.

[Mechanisms of the interaction of the leukemic cell with endogenous regulators of the proliferation of hematopoietic tissue]

A substance inhibiting DNA synthesis in mouse leukemic cells was isolated from the regenerating calf spleen. When added to a suspension of leukaemic cells, this substance is adsorbed on their surface. The following changes in cell features being noticed: 1) a minute decrease in electrophoretic cell motility, 2) a decrease in esterase activity of the cells, 3) an increase in microviscosity of membrane lipids, 4) an increase in the intracellular pH values. With a longer contact with this substance, changes in nuclear chromatin structure were noticed, with special reference to weakened bonds between DNA and proteins. The data obtained are of significance for revealing molecular mechanisms of hematopoietic mediator action on target cells.

[Photosensitization by chlorine and porphyrin causing structural damage of erythrocytes]

Kinetics of hemolysis of human erythrocytes photosensitized by porphyrin and chlorin derivatives was investigated by small angle light scattering method. The compounds used were arranged in the following order of photosensitizing activity decrease: ethylendiamide of chlorine e6, chlorine e6 dimethylester chlorine e6 haematoporphyrin diacetate tetracarboxyphenylporphyn. The substances having a greater number of binding sites with liposomes (chlorine e6 dimethylester) or with albumin (ethylendiamide of chlorine e6) showed the greatest photohemolytic activity. The photohemolytic activity of porphyrins was suggested to depend on the number of the pigment molecules bound by erythrocytes membranes.

[Effect of concanavalin A on the level of sulfhydryl groups in thymocytes]

Fluorescein mercury acetate (FMA), a fluorescent probe, is used for the investigation of SH-groups of thymocytes' plasma membrane. It is found that mitogenic lectin Con A decreases the amount of membrane SH-groups and increases the fluorescence polarization degree of FMA (PFMA). The value of PFMA increases also during the incubation of cells with potassium ferricyanide and H2O2 but it decreases in the presence of NADH. The analysis of the data permits a conclusion that the thymocyte activation by Con A results in the selective oxidation of certain SH-groups with the formation of disulphide cross-linking between the plasma membrane receptors bound with the lectin molecules.