Pro-Inflammatory Activation Suppresses TRAIL-induced Apoptosis of Acute Myeloid Leukemia Cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo2L) is a promising agent for treatment of AML due to its specific apoptosis-inducing effect on tumor cells but not normal cells. However, emergence of resistance to TRAIL in the AML cells limits its potential as an antileukemic agent. Previously, we revealed increase in the resistance of the human AML THP-1 cells to the TRAIL-induced death during their LPS-dependent proinflammatory activation and in the in vitro model of LPS-independent proinflammatory activation - in a long-term high-density cell culture. In this study, we investigated mechanisms of this phenomenon using Western blot analysis, caspase 3 enzymatic activity analysis, quantitative reverse transcription-PCR, and flow cytometry. The results showed that the increased resistance to the TRAIL-induced cell death of AML THP-1 cells during their pro-inflammatory activation is associated with the decrease in the surface expression of the proapoptotic receptors TRAIL-R1/DR4 and TRAIL-R2/DR5, as well as with the increased content of members of the IAPs family - Livin and cIAP2. The results of this article open up new insights into the role of inflammation in formation of the resistance of AML cells to the action of mediators of antitumor immunity, in particular TRAIL.

[The Redox-Catalytic Properties of Cobalamins]

Vitamin B12, or cobalamin, is essential for normal body function and is used in the therapies of different diseases. Vitamin B12 has anti-inflammatory and antioxidant properties that can play an important role in the prevention of some diseases. On the other hand, it has been reported that vitamin B12 in combination with such reducing agents as ascorbate (vitamin C) and thiols showed prooxidant activity. This review provides information on the roles of vitamin B12 in diseases accompanied by inflammation and oxidative stress and the effects of vitamin B12 administrated alone and in combinations with different reducing agents such as ascorbate and thiols on oxidative stress. In addition, the mechanisms of prooxidant actions of combinations of vitamin B12 with these reducing agents depending on the form of vitamin B12 (hydroxocobalamin and cyanocobalamin) are discussed. Understanding the mechanisms of prooxidant action of vitamin B12 is necessary for developing strategies for therapeutic administration of vitamin B12.

Soft Biomimetic Approach for the Development of Calcinosis-Resistant Glutaraldehyde-Fixed Biomaterials for Cardiovascular Surgery

Pathological aseptic calcification is the most common form of structural valvular degeneration (SVD), leading to premature failure of heart valve bioprostheses (BHVs). The processing methods used to obtain GA-fixed pericardium-based biomaterials determine the hemodynamic characteristics and durability of BHVs. This article presents a comparative study of the effects of several processing methods on the degree of damage to the ECM of GA-fixed pericardium-based biomaterials as well as on their biostability, biocompatibility, and resistance to calcification. Based on the assumption that preservation of the native ECM structure will enable the creation of calcinosis-resistant materials, this study provides a soft biomimetic approach for the manufacture of GA-fixed biomaterials using gentle decellularization and washing methods. It has been shown that the use of soft methods for preimplantation processing of materials, ensuring maximum preservation of the intactness of the pericardial ECM, radically increases the resistance of biomaterials to calcification. These obtained data are of interest for the development of new calcinosis-resistant biomaterials for the manufacture of BHVs.

Improving the Stability and Effectiveness of Immunotropic Squalene Nanoemulsion by Adding Turpentine Oil

Turpentine oil, owing to the presence of 7-50 terpenes, has analgesic, anti-inflammatory, immunomodulatory, antibacterial, anticoagulant, antioxidant, and antitumor properties, which are important for medical emulsion preparation. The addition of turpentine oil to squalene emulsions can increase their effectiveness, thereby reducing the concentration of expensive and possibly deficient squalene, and increasing its stability and shelf life. In this study, squalene emulsions were obtained by adding various concentrations of turpentine oil via high-pressure homogenization, and the safety and effectiveness of the obtained emulsions were studied in vitro and in vivo. All emulsions showed high safety profiles, regardless of the concentration of turpentine oil used. However, these emulsions exhibited dose-dependent effects in terms of both efficiency and storage stability, and the squalene emulsion with 1.0% turpentine oil had the most pronounced adjuvant and cytokine-stimulating activity as well as the most pronounced stability indicators when stored at room temperature. Thus, it can be concluded that the squalene emulsion with 1% turpentine oil is a stable, monomodal, and reliably safe ultradispersed emulsion and may have pleiotropic effects with pronounced immunopotentiating properties.

Conjugation of Triterpenic Acids of Ursane and Oleanane Types with Mitochondria-Targeting Cation F16 Synergistically Enhanced Their Cytotoxicity against Tumor Cells

The present work shows the cytotoxic effects of novel conjugates of ursolic, oleanolic, maslinic, and corosolic acids with the penetrating cation F16 on cancer cells (lung adenocarcinoma A549 and H1299, breast cancer cell lines MCF-7 and BT474) and non-tumor human fibroblasts. It has been established that the conjugates have a significantly enhanced toxicity against tumor-derived cells compared to native acids and also demonstrate selectivity to some cancer cells. The toxic effect of the conjugates is shown to be due to ROS hyperproduction in cells, induced by the effect on mitochondria. The conjugates caused dysfunction of isolated rat liver mitochondria and, in particular, a decrease in the efficiency of oxidative phosphorylation, a decrease in the membrane potential, and also an overproduction of ROS by organelles. The paper discusses how the membranotropic- and mitochondria-targeted effects of the conjugates may be related to their toxic effects.

Biomimetic Remineralized Three-Dimensional Collagen Bone Matrices with an Enhanced Osteostimulating Effect

Bone grafts with a high potential for osseointegration, capable of providing a complete and effective regeneration of bone tissue, remain an urgent and unresolved issue. The presented work proposes an approach to develop composite biomimetic bone material for reconstructive surgery by deposition (remineralization) on the surface of high-purity, demineralized bone collagen matrix calcium phosphate layers. Histological and elemental analysis have shown reproduction of the bone tissue matrix architectonics, and a high-purity degree of the obtained collagen scaffolds; the cell culture and confocal microscopy have demonstrated a high biocompatibility of the materials obtained. Adsorption spectroscopy, scanning electron microscopy, microcomputed tomography (microCT) and infrared spectroscopy, and X-ray diffraction have proven the efficiency of the deposition of calcium phosphates on the surface of bone collagen scaffolds. Cell culture and confocal microscopy methods have shown high biocompatibility of both demineralized and remineralized bone matrices. In the model of heterotopic implantation in rats, at the term of seven weeks, an intensive intratrabecular infiltration of calcium phosphate precipitates, and a pronounced synthetic activity of osteoblast remodeling and rebuilding implanted materials, were revealed in remineralized bone collagen matrices in contrast to demineralized ones. Thus, remineralization of highly purified demineralized bone matrices significantly enhanced their osteostimulating ability. The data obtained are of interest for the creation of new highly effective osteoplastic materials for bone tissue regeneration and augmentation.

Comparative Study of Cytotoxic and Membranotropic Properties of Betulinic Acid-F16 Conjugate on Breast Adenocarcinoma Cells (MCF-7) and Primary Human Fibroblasts

The present study evaluates the cytotoxicity of a previously synthesized conjugate of betulinic acid (BA) with the penetrating cation F16 on breast adenocarcinoma (MCF-7) and human fibroblast (HF) cell lines, and also shows the mechanism underlying its membranotropic action. It was confirmed that the conjugate exhibits higher cytotoxicity compared to native BA at low doses also blocking the proliferation of both cell lines and causing cell cycle arrest in the G₀/G₁ phase. We show that the conjugate indeed has a high potential for accumulation in mitochondria, being visualized in these organelles, which is most pronounced in cancer cells. The effect of the conjugate was observed to be accompanied by ROS hyperproduction in both cancerous and healthy cells, despite the lower base level of ROS in the latter. Along with this, using artificial liposomes, we determined that the conjugate is able to influence the phase state of lipid membranes, make them more fluid, and induce nonspecific permeabilization contributing to the overall cytotoxicity of the tested agent. We conclude that the studied BA-F16 conjugate does not have significant selective cytotoxicity, at least against the studied breast cancer cell line MCF-7.

Effect of Morphogenetic Protein BMP-2 on X-Ray Density of Bone Defect in the Experiment

In experiments on Wistar rats, a simulated defect in the flat bones of the skull was filled with a collagen sponge of animal origin impregnated with BMP-2 or pure sponge; in control rats, the defect was left open. During follow-up, X-ray density of the collagen sponge in the experimental groups differed significantly. The results attest to the absence of spontaneous remodeling of the bone tissue under conditions modeled focal defect. Moreover, stimulation of reparative processes by the collagen matrix did not lead to positive dynamics. Saturation of the collagen sponge with BMP-2 in a concentration of 0.05 mg/ml allowed increasing Xray density of the bone starting from week 4.

Study of Biointegration and Elastic-Strength Properties of a New Xenopericardium-Based Biomaterial for Reconstructive Cardiovascular Surgery

We analyzed biocompatibility, elastic-strength properties, and biointegration potential of a new biomaterial made of xenopericardium for reconstructive cardiovascular surgery. The biomaterial manufactured by the proposed technology demonstrated high biocompatibility and biointegration potential and its elastic-strength properties 2-4-fold surpassed that of native pericardium. The obtained results attested to good prospects of using the proposed technology for preparing biomaterials for reconstructive cardiovascular surgery.

Hydroxycobalamin catalyzes the oxidation of diethyldithiocarbamate and increases its cytotoxicity independently of copper ions

It is known that some metals (Cu, Zn, Cd, Au) markedly increase the toxic effect of thiocarbamates. It was shown in the present study that hydroxycobalamin (a form of vitamin B12, HOCbl), which incorporates cobalt, significantly enhances the cytotoxicity of diethyldithiocarbamate (DDC), decreasing its IC50 value in tumor cells three to five times. The addition of HOCbl to aqueous DDC solutions accelerated the reduction of oxygen. No hydrogen peroxide accumulation was observed in DDC + HOCbl solutions; however, catalase slowed down the oxygen reduction rate. Catalase as well as the antioxidants N-acetylcysteine (NAC) and glutathione (GSH) partially inhibited the cytotoxic effect of DDC + HOCbl, whereas ascorbate, pyruvate, and tiron, a scavenger of superoxide anion, had no cytoprotective effect. The administration of HOCbl into DDC solutions (> 1 mM) resulted in the formation of a crystalline precipitate, which was inhibited in the presence of GSH. The data of UV and NMR spectroscopy and HPLC and Mass Spectrometry (LC/MS) indicated that the main products of the reaction of DDC with HOCbl are disulfiram (DSF) and its oxidized forms, sulfones and sulfoxides. The increase in the cytotoxicity of DDC combined with HOCbl occurred both in the presence of Cu2+ in culture medium and in nominally Cu-free solutions, as well as in growth medium containing the copper chelator bathocuproine disulfonate (BCS). The results indicate that HOCbl accelerates the oxidation of DDC with the formation of DSF and its oxidized forms. Presumably, the main cause of the synergistic increase in the toxic effect of DDC + HOCbl is the formation of sulfones and sulfoxides of DSF.

[Inhibition of NF-kB Activation Decreases Resistance in Acute Myeloid Leukemia Cells to TRAIL-induced Apoptosis in Multicellular Aggregates]

Suppression of resistance in acute myeloid leukemia cells to TRAIL-induced apoptosis in multicellular aggregates, was studied using small molecule inhibitors of the activation of the transcription factor NF-kB - NF-k9 Activation Inhibitor IV and JSH-23 at non-toxic concentrations. NF-kB Activation Inhibitor IV and JSH-23 reduced resistance in the acute myeloid leukemia cells in multicellular aggregates to cytotoxic action of recombinant protein izTRAIL. It is shown that the use of these inhibitors decreased the phosphorylation of the RelA (p65) as a main marker activation of the transcription factor NF-kB. We discuss a possible reason for increasing resistance in acute myeloid leukemia cells to TRAIL-induced apoptosis in multicellular aggregates.

Thiol antioxidants in combination with vitamin B12 induce apoptotic death of human lymphocytic leukemia cells by destabilization of lysosomes with the involvement of iron ions

The extensively used thiol antioxidants (dithiothreitol, glutathione, and N-acetylcysteine) in combination with hydroxycobalamine (vitamin B12) gain toxic activity in relation to human lymphocytic leukemia cell line HL60. Combined treatment with thiol and vitamin B12 was followed by early destabilization of lysosomes and apoptotic death of cells. The cytotoxic effect was abolished by caspase inhibitors. An iron-chelating agent deferoxamine partly prevented cell death, while lysosomal protease inhibitor pepstatin produced no protective effect.

Oleic acid is a key cytotoxic component of HAMLET-like complexes

HAMLET is a complex of α-lactalbumin (α-LA) with oleic acid (OA) that selectively kills tumor cells and Streptococcus pneumoniae. To assess the contribution of the proteinaceous component to cytotoxicity of HAMLET, OA complexes with proteins structurally and functionally distinct from α-LA were prepared. Similar to HAMLET, the OA complexes with bovine β-lactoglobulin (bLG) and pike parvalbumin (pPA) (bLG-OA-45 and pPA-OA-45, respectively) induced S. pneumoniae D39 cell death. The activation mechanisms of S. pneumoniae death for these complexes were analogous to those for HAMLET, and the cytotoxicity of the complexes increased with OA content in the preparations. The half-maximal inhibitory concentration for HEp-2 cells linearly decreased with rise in OA content in the preparations, and OA concentration in the preparations causing HEp-2 cell death was close to the cytotoxicity of OA alone. Hence, the cytotoxic action of these complexes against HEp-2 cells is induced mostly by OA. Thermal stabilization of bLG upon association with OA implies that cytotoxicity of bLG-OA-45 complex cannot be ascribed to molten globule-like conformation of the protein component. Overall, the proteinaceous component of HAMLET-like complexes studied is not a prerequisite for their activity; the cytotoxicity of these complexes is mostly due to the action of OA.

[Multikinase inhibitor sorafenib and HDAC inhibitor suberoylanilide hydroxamic acid suppress confluent resistance of cancer cells to recombinant protein izTRAIL]

Suppression of human tumor cell resistance to TRAIL-induced apoptosis in confluent cultures, using molecular target drugs (sorafenib and SAHA) at non-toxic concentrations was studied. Sorafenib, a multikinase inhibitor, and SAHA, an inhibitor of histone deacetylase, effectively suppressed resistance of confluent human cells derived from the skin carcinoma (A431 cell line) and fibrosarcoma (HT-1080 cell line). The effectiveness of suppression of confluent resistance with these inhibitors for human carcinoma A431 cells was significantly higher than that for the human ovarian carcinoma OVCAR-3 cells. For all cell lines studied, suppression of confluent resistance with SAHA was more effective than when sorafenib was used. The possible reason for increasing tumor cell resistance in confluent cultures and the importance of this phenomenon for understanding drug resistance of cells in the tumor tissue are discussed.

[Increase in resistance of A431 cancer cells to TRAIL-induced apoptosis in confluent cultures]

It was shown that cancer cells acquired resistance to TRAIL-induced apoptosis in confluent cultures. Recombinant protein izTRAIL induced apoptosis of human carcinoma A431 cells in the first hours after cell plating at a concentration of 3-10 ng/ml, while in confluent cultures these cells acquire resistance to protein izTRAIL even at the concentration of 2 mkg/ml. Detachment and suspending of the cells of confluent cultures immediately suppressed the resistance to izTRAIL. The cells of confluent cultures, being resistant to TRAIL-induced apoptosis continue progression through the cell cycle, as evidenced by the DNA cytograms and the Ki67p-GFP reporter system. Thus, the results showed that tumor A431 cells can acquire resistance to TRAIL-induced apoptosis in confluent cultures, while continue progression through the cell cycle, keeping the proliferative potential.

A novel method for preparation of HAMLET-like protein complexes

Some natural proteins induce tumor-selective apoptosis. α-Lactalbumin (α-LA), a milk calcium-binding protein, is converted into an antitumor form, called HAMLET/BAMLET, via partial unfolding and association with oleic acid (OA). Besides triggering multiple cell death mechanisms in tumor cells, HAMLET exhibits bactericidal activity against Streptococcus pneumoniae. The existing methods for preparation of active complexes of α-LA with OA employ neutral pH solutions, which greatly limit water solubility of OA. Therefore these methods suffer from low scalability and/or heterogeneity of the resulting α-LA - OA samples. In this study we present a novel method for preparation of α-LA - OA complexes using alkaline conditions that favor aqueous solubility of OA. The unbound OA is removed by precipitation under acidic conditions. The resulting sample, bLA-OA-45, bears 11 OA molecules and exhibits physico-chemical properties similar to those of BAMLET. Cytotoxic activities of bLA-OA-45 against human epidermoid larynx carcinoma and S. pneumoniae D39 cells are close to those of HAMLET. Treatment of S. pneumoniae with bLA-OA-45 or HAMLET induces depolarization and rupture of the membrane. The cells are markedly rescued from death upon pretreatment with an inhibitor of Ca(2+) transport. Hence, the activation mechanisms of S. pneumoniae death are analogous for these two complexes. The developed express method for preparation of active α-LA - OA complex is high-throughput and suited for development of other protein complexes with low-molecular-weight amphiphilic substances possessing valuable cytotoxic properties.

[The role of recipient cells in the mechanism of pathological calcification of heart valve and vascular transplants]

It was found using the model of subcutaneous implantation in rats that the calcification of the aorta wall occurs by two mechanisms of which one is dependent on, and the other independent of the migration of recipient cells to the transplant.

Vitamin B12b enhances the cytotoxicity of dithiothreitol

It has been found previously that vitamin B12b amplifies significantly the cytotoxic effects of ascorbic acid by catalyzing the formation of reactive oxygen species, and the antioxidant dithiothreitol (DTT), in contrast to catalase, does not prevent the cytotoxicity. Therefore, in this study we examined whether B12b is able to enhance the cytotoxicity of DTT. It was revealed that B12b strongly increases the cytotoxic effect of DTT. Vitamin B12b added to DTT catalyzed the generation and drastic accumulation of hydrogen peroxide in culture medium to a concentration of 260 microM within 7 min. The extracellular oxidative burst induced by the combination of B12b and DTT (DTT + B12b) was accompanied by intracellular oxidative stress, the destabilization of lysosomes, and damage to DNA. The accumulation of DNA lesions led to the initiation of apoptotic cell death, including the activation of caspase-3 and the release of cytochrome c. The antioxidants pyruvate and catalase completely prevented the DTT + B12b-induced oxidative stress and cell death. The iron chelators desferrioxamine and phenanthroline prevented the geno- and cytotoxic action of the combination although they did not reduce the exogenous oxidative burst, indicating a key role for intracellular iron in the cytotoxicity of the combination. Thus, vitamin B12b dramatically enhances the cytotoxicity of DTT, catalyzing the generation of hydrogen peroxide and inducing extra- and intracellular oxidative stress, early destabilization of lysosomes, and iron-dependent DNA damage.

Vitamin B12b increases the cytotoxicity of short-time exposure to ascorbic acid, inducing oxidative burst and iron-dependent DNA damage

It has been found previously that hydroxycobalamine (vitamin B12b) amplifies significantly the cytotoxic effect of ascorbic acid (vitamin C) added to cells for small a, Cyrillic long period of time (48 h). However, according to pharmacokinetics, the concentration of vitamin C in vivo decreases to a physiological value within a short period of time (2-3 h) after the injection. Therefore, in this study we examined the cytotoxic effect of a short-time (up to 2 h) exposure of human larynx carcinoma HEp-2 cells to a combination of vitamins B12b and C (B12b+C). The kinetics of the B12b+C-caused extracellular oxidative burst in this time interval was also explored. Vitamin B12b combined with ascorbic acid provoked a rapid accumulation of extracellular hydrogen peroxide followed by intracellular oxidative stress, DNA single-strand breaks, and the initiation of apoptosis. The chelators of iron phenanthroline and desferrioxamine prevented B12b+C-induced DNA single-strand breaks and cell death but not the accumulation of H2O2 in culture medium. The nonthiol antioxidants pyruvate and catalase were effective in preventing the prooxidant and cytotoxic effects of B12b+C. Thiols, when added simultaneously with the combined vitamins, inhibited these effects only partially (N-acetylcysteine, GSH) or even amplified them (dithiothreitol). The results obtained point to the determining role of oxidative burst and iron-dependent DNA damage in the cytotoxic effect of short-time exposure to B12b+C combination.

Improving biocompatibility of heart valve and vascular transplants by their devitalization and repopulation by recipient cells

Inoculation of cells derived from the aorta of Wistar rats on devitalized porcine aortic walls 2-4-fold reduced their calcinosis after subcutaneous implantation to Wistar rats. Inoculation of Wistar rat bone marrow mesenchymal cells selected by adhesion activity did not reduce tissue calcinosis. The results indicate good prospects of repopulation of devitalized heart valve and vessel transplants by recipient vascular cells for reducing transplant calcinosis and improvement of their biocompatibility.

[Prooxidant and cytotoxic action of N-acetylcysteine and glutathione combined with vitamin Bl2b]

We studied the prooxidant and cytotoxic action of thiols N-acetylcystein (NAC) and glutathione (GSH) combined with vitamin Bl2b. The synergism of action of the thiols and Bl2b resulted in human carcinoma cell damage was found. It was shown that GSH and NAC in physiological doses combined with Bl2b caused the initiation of apoptosis. It was established that prooxidant action of the thiols combined with vitamin Bl2b, i. e. generation and accumulation of hydrogen peroxide in culture medium, led to intracellular oxidative stress and injury of cell redox system. These effects were completely abolished by nonthiol antioxidants catalase and pyruvate. The chelators of iron phenanthroline and deferoxamine did not suppress the H2O2 accumulation in culture medium but significantly inhibited the cell death induced by the thiols combined with Bl2b. Therefore, the thiols GSH and NAC widely used as antioxidants, in combination with vitamin Bl2b show prooxidant characteristics and induce, with the participation of intracellular iron, apoptotic HEp-2 cell death.

Apoptotic death of human lympholeukemia HL-60 cells resultant from combined effect of cobalt octa-4,5-carboxyphthalocyanine propylenglycol ether and ascorbate

Cobalt octa-4,5-carboxyphthalocyanine propylenglycol ether proposed for antitumor therapy potentiates the cytotoxic effect of ascorbate on HL-60 human leukemia cells. Combination of these substances caused the formation of H2O2 in the medium and initiated apoptotic death of cells. Catalase abolished the cytotoxic effect of this combination. The results indicate that binary catalytic system of this combination can be regarded as a potential antitumor agent.

Both PA63 and PA83 are endocytosed within an anthrax protective antigen mixed heptamer: A putative mechanism to overcome a furin deficiency

Anthrax toxin consists of protective antigen (PA), and lethal (LF) and edema (EF) factors. A 83 kDa PA monomer (PA83) precursor binds to the cell receptor. Furin-like proprotein convertases (PCs) cleave PA83 to generate cell-bound 63 kDa protein (PA63). PA63 oligomerizes to form a ring-shaped heptamer that binds LF-EF and facilitates their entry into the cells. Several additional PCs, as opposed to furin alone, are capable of processing PA83. Following the incomplete processing of the available pool of PA83, the functional heptamer includes both PA83 and PA63. The available structures of the receptor-PA complex imply that the presence of either one or two molecules of PA83 will not impose structural limitations on the formation of the heptamer and the association of either the (PA83)(1)(PA63)(6) or (PA83)(2)(PA63)(5) heteroheptamer with LF-EF. Our data point to the intriguing mechanism of anthrax that appears to facilitate entry of the toxin into the cells which express limiting amounts of PCs and an incompletely processed PA83 pool.

Oxidative Stress in HEp-2 Human Laryngeal Carcinoma Cells Induced by Combination of Vitamins B12b and C

Incubation of human laryngeal epidermoid carcinoma HEp-2 cells with hydroxocobalamin (vitamin B12b) and ascorbic acid (vitamin C) for 1 h initiated oxidative stress accompanied by damage to mitochondria and increase in intracellular oxidative activity. Studies of the kinetics of these processes showed that the increase in intracellular H2O2 activity and mitochondrial damage are more likely a result, but not the cause of cell apoptosis during the first hour of their incubation with vitamins B12b and C.

Small Heat Shock Protein hsp27 as a Possible Mediator of Intercellular Adhesion-Induced Drug Resistance in Human Larynx Carcinoma HEp-2 Cells

The confluence-dependent resistance of human larynx carcinoma HEp-2 cells to hydrogen peroxide and a new antitumor drug based on the combination of vitamins C and B12b was studied. It was found that this resistance in growing cells is suppressed by the disruption of intercellular contacts by EGTA and is related neither to the activity of P-glycoprotein nor to the content of intracellular glutathione and the activities of glutathione S-transferases, glutathione peroxidase and glutathionine reductase. Here we showed that the level of expression of the small heat shock protein hsp27, which is known to protect cells from a variety of stresses associated with apoptosis, in growing confluent cells both in the presence and absence of the vitamins B12b and C is much higher (about 20–25 times) than in nonconfluent cells. Taken together, the results suggest that the confluence-dependent resistance of cells to the combination of vitamins C and B12b and to hydrogen peroxide is mediated by hsp27 overexpression, which is activated via cell-cell adhesion.

[Antitumor effect of combined treatment with ionizing radiation and vitamin B12-C complex]

The combined effect of ionizing radiation (0.5-4 Gy) and the vitamin B12-C complex on life-span of mice with Ehrlich carcinomas was studied. It was shown that antitumor effect of the combined treatment strictly depends on the sequence of the agent applying and on the time interval between them. For example, the combined treatment increased essentially the life-span of mice if the vitamins were used 24 h after irradiation but with the reverse order of influences, the antitumor effect was less than that of the vitamin complex only. It was supposed that the discovered regularities are due to tumor cell synchronization or division stimulation with the first influence.

[DNA degradation and repair in human laryngeal carcinoma HEp-2 cells after combined exposure to vitamin B12b and ascorbic acid]

The formation and accumulation of DNA fragments containing no more than 23,000 pairs of bases were observed under exposure of human larynx epidermoid carcinoma cells (Hep-2) to "chemical nuclease", oxycobalamin (vitamin B12b) and ascorbic acid (vitamin C). The obtained DNA damages were repaired more slowly than those induced by gamma-irradiation in the dose adequate to the level of DNA damages. DNA reparation was not revealed after washing the cells from vitamin B12b and ascorbic acid, and in the course of cell incubation with ascorbic acid. Vitamin B12b and ascorbic acid separately did not induce degradation of DNA. DNA damages induced by "chemical nuclease" action precede the cell death observed later.

Combined treatment with vitamin B12b and ascorbic acid causes in vitro DNA degradation in tumor cells

Incubation of Ehrlich ascites carcinoma and HEp-2 human epidermoid laryngeal carcinoma cells with hydroxycobalamin (vitamin B12b) and ascorbic acid induced generation and accumulation of double-stranded DNA fragments (23,000 b.p. and longer) in cells. The same vitamins alone in the same concentrations produced no such effects. DNA degradation in HEp-2 cells caused by long-term (4 h) incubation with 5-25 microM hydroxycobalamin and ascorbic acid (1:10-1:40 molar ratio) at 37 degrees C was comparable with that induced by gamma-irradiation in a dose of 150 Gy at 4 degrees C.

Combined vitamins Bl2b and C induce the glutathione depletion and the death of epidermoid human larynx carcinoma cells HEp-2

The combination of hydroxocobalamin (vitamin B12b) and ascorbic acid (vitamin C) can cause the death of tumor cells at the concentrations of the components at which they are nontoxic when administered separately. This cytotoxic action on epidermoid human larynx carcinoma cells HEp-2 in vitro is shown to be due to the hydrogen peroxide generated by the combination of vitamins B12b and C. The drop in the glutathione level preceding cell death was found to be the result of combined action of the vitamins. It is supposed that the induction of cell death by combined action of vitamins B12b and C is connected to the damage of the cell redox system.

Functional activity of hepatocytes in tissue fragments in a new bioreactor biological artificial liver

Functional activity of hepatocytes in a new bioreactor designed for culturing of liver tissue fragments under perfusion conditions was tested. Specific hepatic functions such as ammonium detoxification, urea and protein synthesis, and P-450-dependent metabolism of p-nitroanisole were maintained for 1.5 days. The bioreactor can be used as a bioartificial liver support apparatus.

[Migration of fibroblasts into heart valve leaflet tissue in vitro]

Heart valve allografts are widely used for surgical treatment of the heart. In recent years a new field of research has emerged dealing with allograft modification by cells of recipient by means of tissue engineering. This method involves culturing fibroblasts and endothelial cells, using recipient tissue, followed by introduction of the fibroblasts into tissues of allograft and coating its surface by the endothelial cells. This modification is expected to ensure the structural maintenance of implanted tissues and to reduce its thrombogenecity. This procedure may promote the allograft adhering to the recipient tissues, thus prolonging the terms of the valve normal functioning after implantations. For this purpose, methods of luminescent microscopy are suggested using double staining of tissue with fluorescent dyes Hoechst 33,342 and ethidium bromide, or with fluorescein diacetate and ethidium bromide. Experimental results are presented indicative of fibroblast migration from the surface to the human heart valve leaflets.

[The role of intracellular pH in regulation of NS/O myeloma cell growth and death]

Measurements of intracellular pH (pHi) were taken in the course of NS/O myeloma cell proliferation, growth arrest and death. Cell proliferation was shown to take place within a wide range of various pHi values (6.8-7.2), in which cell death could also occur. In dense cultures, after ceasing proliferation the apoptosis pathway of cell death was activated practically without pHi changes. Both proliferation and cell death stimulation were noticed in serum-free medium with apoptosis prevalence up to 72 h. Apoptotic death occurred at various intracellular pH values within the range from 6.5 to 7.2. The data obtained provide the ground to suppose that in contrast to normal cells, the pHi value in NS/O myeloma tumor cells was not a regulator of their proliferation and death. The decrease of cell growth and increase of cell death can take place with put pHi alteration.

[Mechanism of cell death in myeloma NS(O) in culture]

We studied in vitro myeloma cell death in a serum-free medium. Spectrophotometric assessment of DNA fragmentation, flow cytometry, and staining by Hoechst dye and ethidium bromide indicate that by the beginning of the third day cell death largely followed the apoptotic pathway. We studied dynamics of intracellular pH (pHi) during the cell death and the relationship between the pHi and apoptosis induction during cultivation in media with different pH. We have shown that decreasing pHi in the course of cell death is a consequence rather than the cause of myeloma cell death. Apoptosis took place at cultivation in the media with pH 6.3 and 8.1; the corresponding pHi values were 6.5 and 7.2, respectively. In the presence of Ca-ionophore A23187 we observed appearance of the cells with aberrant distribution of chromatin and fragmented nucleus; however calcium binding in the media with 5-10 mM EDTA induced even more pronounced nuclei fragmentation. This may indicate that both increased and decreased concentration of intracellular calcium induce NS(O) myeloma cell apoptosis.

Low pH value of pericellular medium as a factor limiting cell proliferation in dense cultures

An attempt was made to determine the role of metabolic acidification of pericellular medium in regulating cell proliferation. A method of measuring the pH of pericellular medium at a distance exceeding a Debye radius of 5-10 A from the cell surface (pHp) was developed. The values of pHp and pH measured in the medium at a distance of greater than 1 cm from cells (pHm) were found to differ, depending on the cell population density. At a density of at least 7 X 10(5) cells/cm2 (maximum saturation density) and at pHm 7.4-7.6, pHp reached a value of approximately 6.5. It was found that pHm 6.5 was unfavorable for cell proliferation in sparse cultures, where pHm and pHp were equal. Based on these findings, low pHp as revealed in the present work using dense cultures at optimal pHm can be considered to be a limiting factor for cell multiplication.

[Fibroblast adhesion to glass and the dynamics of pH change in the medium in the pericellular space]

A study was made of dynamics of pH changes in the pericellular space of the Chinese hamster fibroblasts after the completion of cell sedimentation in three media. With the first medium, the cells were spread over the glass, with the second one they were attached to the glass without spreading and with the third medium the cells were not attached to the glass at all. The pH value of the medium surrounding the cells decreased, mainly, within the first 6 hours after sedimentation was completed, this depended on the cell population density on the glass surface. The outlook of this dependence was different for the three media. Based on the analysis of the results obtained it is concluded that the attachment of cells to glass may lead to the increased efflux of acid metabolic products from the cell.

[Change in cell adhesiveness to glass at a constant density of their surface-bound charges]

It has been investigated whether there exists a correlation between the adhesiveness of Chinese hamster fibroblasts to glass and the density of surface-bound charges of the cells and the glass. The adhesiveness of the cells to glass was shown to vary appreciably at constant density of their surface-bound charges.

[Controlled cell cultivation. IX. Dynamic study of pH changes of the medium in the pericellular area]

The dynamics of pH changes occurring near the cells has been studied after the sedimentation of cells and after the culture medium replacement. For this purpose, cells were situated on the H+-selective membrane of the electrode. The pH fall in the space hear the cells took place mainly within the first 6 hours after sedimentation or medium replacement. The magnitude of this change depends on the cell population density and reaches 1.2 units of pH, if the density value was higher than 10(6) cell/cm2. It has been shown that there are two stages in the dynamics of pH changes near the cells during the first 6 hours after sedimentation and the mean rate of pH changes depends on the cell population density. Based on the results obtained, a possibility to explain the inhibition of cell growth in the monolayer by diffuse limitations of outflowing metabolic products is discussed.

[Study of animal cell adhesion to glass by means of the frustrated total internal reflection method]

The method for studying the adhesion of mammalian cells to glass in vivo is presented. It is based on the effect of frustrated total reflection. It permits one to measure the index of refraction of hydroplasma situated near the site of cell-glass contact, to evaluate the distance between glass surface and cell surface membrane and to study the kinetics of flattening of the cell surface facing the glass.

[Use of the effect of impaired complete internal reflection for studying the adhesion of animal cells to glass. II. Kinetics of flattening of the cell surface facing the glass]

The kinetics of form change (flattening) of Chinese hamster fibroblast cell surface facing the glass has been studied during attachment of fibroblasts to the glass using the effect of frustrated total reflection. Two stages of the process were shown to exist. The first one is characterized by a rapid (5 min) partial flattening and requires no serum in the medium. The second stage occurs only in the presence of serum in the medium, it lasts no longer than one hour and ends in a complete flattening. After the second stage is completed, spreaded cells appear.

[Use of the effect of impaired complete internal reflection for studying the adhesion of animal cells to glass. III. Measurement of the refractive index of hyaloplasm and determination of the distance between cell membrane surface and glass]

The kinetics of form change (flattening) of Chinese hamster fibroblast cell surface facing the glass has been studied during attachment of fibroblasts to the glass using the effect of frustrated total reflection. Two stages of the process were shown to exist. The first one is characterized by a rapid (5 min) partial flattening and requires no serum in the medium. The second stage occurs only in the presence of serum in the medium, it lasts no longer than one hour and ends in a complete flattening. After the second stage is completed, spreaded cells appear.

[Use of the disordered total internal reflection effect to study the adhesion of animal cells to glass. I. Results of a theoretical analysis]

Theoretical analysis data have been presented on the effect of frustrated total reflection due to light scatterring on cells situated near the glass surface. A conclusion is made that using this effect it is possible to measure the index of refraction of the cytoplasm, to determine the distance between the glass and the cytoplasmic membrane of monolayer cells, and to study the kinetics of changes in the cell surface on contacting the glass.