Autoregulation and Autoinhibition of the Main NO Synthase Isoforms (Brief Review)

Nitric oxide (II) (NO) is the most important mediator of a wide range of physiological and pathophysiological processes. It is synthesized by NO synthases (NOSs), which have three main isoforms differing from each other in terms of activation and inhibition features, levels of NO production, subcellular localization, etc. At the same time, all isoforms are structurally very similar, and these differences are determined by NOS autoregulatory elements. The article presents an analysis of the autoregulatory and autoinhibitory mechanisms of the NOS reductase domain that determine differences in the productivity of isoforms, as well as their dependence on the concentration of Ca2+ ions. The main regulatory elements in NOS that modulate the electron transfer from flavin to heme include calmodulin (CaM), an autoinhibitory insert (AI), and the C-terminal tail (C-tail). Hydrophobic interactions of CaM with the surface of the NOS oxidase domain are assumed to facilitate electron transfer from flavin mononucleotide (FMN). CaM binding causes a change in the inter-domain distances, a shift of AI and the C-tail, and, as a result, a decrease in their inhibitory effect. CaM also shifts the conformational equilibrium of the reductase domain towards more open conformations, reduces the lifetime of conformations, their stereometric distribution, and accelerates the flow of electrons through the reductase domain. The AI element, apparently, induces a conformational change that hinders electron transfer within the reductase domain, similar to the hinge domain in cytochrome P450. Together with CaM, the C-tail regulates the electron flow between flavins, the distance and relative orientation of isoalloxane rings, and also modulates the electron flow from FMN to the terminal acceptor. Together with the C-tail, AI also predetermines the dependence of neuronal and endothelial forms of NOS on the concentration of Ca2+ ions, and the C-tail length affects differences in the productivity of NO synthesis. The inhibitory effect of the C-tail is likely to be reduced by CaM binding due to the C-tail shift due to the electrostatic repulsive forces of the negatively charged phosphate and aspartate residues. The autoregulatory elements of NOS require further study, since the mechanisms of their interaction are complex and multidirectional, and hence provide a wide range of characteristics of the observed isoforms.

[Effect of Usnic Acid-Derived Tyrosyl-DNA Phosphodiesterase 1 Inhibitor Used as Monotherapy or in Combination with Olaparib on Transplanted Tumors In Vivo]

Tyrosyl-DNA phosphodiesterase 1 (Tdp1) is a DNA repair enzyme that removes various adducts from the 3' end of DNA. Such adducts are formed by enzymes that introduce single-strand breaks in DNA during catalysis (for example, topoisomerase 1) and a number of anticancer drugs with different mechanisms of action. Poly(ADP-ribose) polymerase 1 (PARP1) is an enzyme that catalyzes posttranslational modification (PARylation) of various targets and thus controls many cell processes, including DNA repair. Tdp1 is a PARP1 target, and its PARylation attracts Tdp1 to the site of DNA damage. Olaparib is a PARP1 inhibitor used in clinical practice to treat homologous recombination-deficient tumors. Olaparib inhibits PARylation and, therefore, DNA repair. The Tdp1 inhibitor OL7-43 was used in combination with olaparib to increase the antitumor effect of the latter. Olaparib cytotoxicity was found to increase in the presence of OL7-43 in vitro. OL7-43 did not exert a sensitizing effect, but showed its own antitumor and antimetastatic effects in Lewis and Krebs-2 carcinoma models.

Experimental Study of Antitumor Activity of Pefagtal Addressed to αvβ3 Integrins

We studied the effect of a new targeted drug Pefagtal that represents a conjugate in which the MS2 phage filled with a substance toxic to cells (thallium salts) is covalently linked to peptides containing the RGD motif. The antitumor and pronounced antimetastatic effects of Pefagtal were demonstrated on transplanted mouse tumors differing in histological type and status of metastasis: Krebs-2 ascites adenocarcinoma of the mammary gland, Lewis lung adenocarcinoma, hepatoma-29, and lung adenocarcinoma. It is assumed that the RGD motif mediates primary binding of the construct to αvβ3 and αvβ5 integrins that are predominantly overexpressed in the endothelial cells of tumor blood vessels and in tumor and metastatic cells.

[Identification and chromatemass- spectrometry quantification of toxic chemicals (N-nitrosamines, phthalates) in baby foods]

Currently, assessing exposure to toxic chemicals detected in foodstuffs is a vital issue, especially regarding foods for babies and toddlers. The research goal was to identify and quantify toxic chemicals (N-nitrosamines, phthalates) in baby foods. Material and methods. Our research objects were 21 samples of canned meat and vegetable purees; 30 samples of juices. All samples were bought in retail outlets. We applied solid phase extraction to prepare the samples for the chromatographic analysis. Chemicals were identified in samples by a hybrid technique, gas chromatography and quadrupole mass spectrometry (GC-MS). The components were classified by comparing the mass spectra we obtained with spectra of specific chemicals and data from the following libraries: NIST 08.L, WILEY275.L and PMW_TOX2.L, AMDIS, USEPA (US Environmental Protection Agency) database with identification numbers of environmental pollutants; libraries containing mass spectra of narcotics, drugs, toxic pollutants and pesticides. Quantitative determination of phthalates in juice products by HPLC/MS was performed. Results. We identified three toxic chemicals in the analyzed canned meat and vegetable purees for babies. They belonged to the 1-3 hazard category and to different classes of organic compounds. Specifically, we identified nitrogen-containing chemicals (N-nitrosamines within a range of concentrations being 0.00077-0.0015 mg/kg with a 73% probability that a mass spectrum would match one taken from a library) in 52.9% of samples. These chemicals are not allowed in canned meat purees for babies by the Technical Regulations TR CU 021/2011 (<0.001 mg/kg). Next, we identified dibutyl phthalate and diethyl phthalate in 30.0% of samples; contents of these organic compounds in canned meat purees for babies are not stipulated by the TR CU 021/2011. We also identified an aromatic compound, namely furfural in 21.7% of samples, and a food additive, 2-butenoic acid (E570) in 5.3% of samples; their contents are regulated by the Technical Regulations TR CU 029/2012. Three toxic chemicals were identified in the analyzed juice samples. First, N-nitrosodiethylamine and N-nitrosodimethylamine were identified in 56.7% of samples (with a 73% probability that a mass spectrum would match one taken from a library, over a concentration range of 0.00045- 0.00077 mg/kg). Second, we identified phthalates (dibutyl phthalate, diethyl phthalate, and diisobutyl phthalate) in 30% of samples (in the concentration range from 0.4 to 59.26 mg/l). The contents of these compounds in juices for babies are not regulated by the TR CU 021/2011. We also detected furfural in 56.7% of samples (with a value of the coefficient of coincidence with library data of 90%), the use of which is regulated in TR CU 029/2012. Conclusion. We have developed and experimentally substantiated an algorithm of an analytical study with its focus on preparing food samples for further identification of chemicals in them. The algorithm involves using a complex technique that combines distillation, solid phase extraction, gas chromatography and mass spectrometry. This technique provides an opportunity to identify a component structure of complex chemical mixtures in food samples with high probability and reliability. It also provides solid evidence that organic compounds occur in food samples based on comparing analytical mass spectra with those taken from mass spectral libraries.

The influence of an enamine usnic acid derivative (a tyrosyl-DNA phosphodiesterase 1 inhibitor) on the therapeutic effect of topotecan against transplanted tumors in vivo

Tyrosyl-DNA phosphodiesterase 1 (Tdp1) is a repair enzyme for 3'-end DNA lesions, predominantly stalled DNA-topoisomerase 1 (Top1) cleavage complexes. Tdp1 is a promising target for anticancer therapy based on DNA damage caused by Top1 poisoning. Earlier, we have reported about usnic acid enamine derivatives that are Tdp1 inhibitors sensitizing tumor cells to the action of Top1 poison (Zakharenko in J Nat Prod 79:2961-2967, 2016). In the present work, we showed a sensitizing effect of an enamine derivative of usnic acid (when administered intragastrically) on Lewis lung carcinoma in mice in combination with topotecan (TPT, Top1 poison used in the clinic). In the presence of the usnic acid derivative, both the volume of the primary tumor and the number of metastases significantly diminished. The absence of acute toxicity of this compound was demonstrated, as was the importance of the method of its administration for the manifestation of the sensitizing properties.

[Antitumor Activity of the Combination of Topotecan and Tyrosyl-DNA-Phosphodiesterase 1 Inhibitor on Model Krebs-2 Mouse Ascite Carcinoma]

Topotecan is a cytostatic drug from the camptothecin group, it acts by inhibiting topoisomerase 1 (TOP1). Tyrosyl-DNA phosphodiesterase 1 (TDP1) is capable of interfering with the action of TOP1 inhibitors, reducing their therapeutic efficacy. Suppression of TDP1 activity may enhance the effects of topotecan. In this work, we investigated the effect of the antitumor drug topotecan alone and in combination with a TDP1 inhibitor, a hydrazinothiazole derivative of usnic acid, on Krebs-2 mouse ascites tumors. We have previously shown that this derivative efficiently inhibits TDP1. In the present work, we show that both topotecan and the TDP1 inhibitor have an antitumor effect when evaluated separately. The combination of topotecan and the TDP1 inhibitor additively reduces both the weight of the ascites tumor and the number of cells in ascites. In mice, the TDP1 inhibitor alone or in combination with topotecan eliminated the tumor cells. After the combined intraperitoneal administration of these two compounds, we observed cells in which lipid droplets occupied almost the entire cytoplasm and the accumulation of cell detritus, which was absent in the samples collected from mice treated with each compound separately.

[Characteristic of the active substance of the Saccharomyces cerevisiae preparation having radioprotective properties]

The paper describes some biological features of the radioprotective effect of double-stranded RNA preparation. It was found that yeast RNA preparation has a prolonged radioprotective effect after irradiation by a lethal dose of 9.4 Gy. 100 % of animals survive on the 70th day of observation when irradiated 1 hour or 4 days after 7 mg RNA preparation injection, 60 % animals survive when irradiated on day 8 or 12. Time parameters of repair of double-stranded breaks induced by gamma rays were estimated. It was found that the injection of the RNA preparation at the time of maximum number of double-stranded breaks, 1 hour after irradiation, reduces the efficacy of radioprotective action compared with the injection 1 hour before irradiation and 4 hours after irradiation. A comparison of the radioprotective effect of the standard radioprotector B-190 and the RNA preparation was made in one experiment. It has been established that the total RNA preparation is more efficacious than B-190. Survival on the 40th day after irradiation was 78 % for the group of mice treated with the RNA preparation and 67 % for those treated with B-190. In the course of analytical studies of the total yeast RNA preparation, it was found that the preparation is a mixture of single-stranded and double-stranded RNA. It was shown that only double-stranded RNA has radioprotective properties. Injection of 160 μg double-stranded RNA protects 100 % of the experimental animals from an absolutely lethal dose of gamma radiation, 9.4 Gy. It was established that the radioprotective effect of double-stranded RNA does not depend on sequence, but depends on its double-stranded form and the presence of "open" ends of the molecule. It is supposed that the radioprotective effect of double-stranded RNA is associated with the participation of RNA molecules in the correct repair of radiation-damaged chromatin in blood stem cells. The hematopoietic pluripotent cells that have survived migrate to the periphery, reach the spleen and actively proliferate. The newly formed cell population restores the hematopoietic and immune systems, which determines the survival of lethally irradiated animals.

Antimetastatic Activity of Combined Topotecan and Tyrosyl-DNA Phosphodiesterase-1 Inhibitor on Modeled Lewis Lung Carcinoma

The antimetastatic activity of combined or individual administration of topotecan and tyrosyl-DNA phosphodiesterase 1 (Tdp1) inhibitor was examined under various administration schedules in mice with Lewis lung carcinoma modeled by intravenous injection of 200,000 clone/mouse. The greatest antimetastatic effect was observed after combined use of topotecan and Tdp1 inhibitor as documented by macroscopic study of the lungs that revealed the decreased metastatic scores by 76, 91, or 74% at the respective inhibitor doses of 2, 4, or 6 mg/mouse, respectively, in parallel with inhibition of metastasis up to 98% (at inhibitor dose of 4 mg/mouse) and morphological and morphometric analyses of the lung sections, which revealed elevation of metastasis growth delay index to 86 and 63% at the respective inhibitor doses of 4 and 6 mg/mouse, respectively. The combined administration of topotecan and Tdp1 inhibitor is viewed as the most effective way to eliminate the metastatic formations with possible restitution of focal lesions.

[Development and application of gas chromatographymass spectrometry method for quantitive determination of volatile N-nitrosamines in smoked meat products]

The article presents the results of experimental studies on the development of highly sensitive and selective chromatography-mass spectrometry technique for the determination of 9 N-nitrosamines in food samples (sausage products) using distillation and an automatic solid-phase extraction system on Coconut cartridges for sample preparation. In the elaborated conditions of sample preparation (distillation and solid-phase extraction) and chromatography-mass spectrometric analysis, we achieved a high recovery and efficiency of the separation of nine N-nitrosamines. The quantitation limit was at level of 0.0002 mg/kg with maximum error not exceeding 19%. The complex use of the distillation of N-nitrosamines with the addition of potassium hydroxide in combination with the optimal elution scheme for solid-phase extraction and concentrating the distillate into a Coconut carbon cartridge of 6 ml ensures the recovery of N-nitrosamines from the food product sample (sausage products) up to 93.2-100%. The process of approbation of the chromatography-mass spectrometric method in the samples of food products (sausage products) of various manufacturers revealed the content of N-nitrosamines in the concentration range 0.00029±0.000055÷0.350±0.05 mg/kg. The conducted studies of the content of the sum of highly toxic N-nitrosamines (N-nitrosodimethylamine, N-nitrosodiethylamine) made it possible to disclose that in sample No. 5 the maximum allowable concentration was exceeded by 47 times, in samples No. 2 and 16, to 57.5 and 22.9 times and in sample No. 4 to 88 times, respectively.

Novel tyrosyl-DNA phosphodiesterase 1 inhibitors enhance the therapeutic impact of topoteсan on in vivo tumor models

The druggability of the tyrosyl-DNA phosphodiesterase 1 (Tdp1) enzyme was investigated in conjunction with topoisomerase 1 inhibition. A novel class of thiazole, aminothiazole and hydrazonothiazole usnic acid derivatives was synthesized and evaluated as Tdp1 inhibitors and their ability to sensitize tumors to topotecan, a topoisomerase inhibitor in clinical use. Of all the compounds tested, four hydrazinothiazole derivatives, 20c, 20d, 20h and 20i, inhibited the enzyme in the nanomolar range. The activity of the compounds was verified by affinity experiments as well as supported by molecular modelling. The most effective Tdp1 inhibitor, 20d, was ton-toxic and increased the effect of topotecan both in vitro and in vivo in the Lewis lung carcinoma model. Furthermore, 20d showed significant increase in the antitumor and antimetastatic effect of topotecan in mice. The results presented here justify compound 20d to be considered as a drug lead for antitumor therapy.

Correction to Comparative Study of Toxicity of Alkoxyamines In Vitro and In Vivo

The author name M. V. Edeeva should read M. V. Edeleva.

Antimetastatic Effect of Liposomal Recombinant Lactaptin

Antimetastatic effect of the liposomal form of recombinant lactaptin RL2 (a proteolytic fragment of human breast milk κ-casein; 8.6 kDa) was studied in A/Sn mice after intravenous transplantation of GA-1 tumor with high rate of liver metastases. Tumor growth in the liver was found in all mice. In animals dying early, the tumors were presented by multiple nodes of about the same size; in mice dying later, the tumors in the liver were presented by just few large nodes formed by cells that survived chemotherapy. A single intravenous injection of RL2 lactaptin in liposomes prolonged lifespan of animals with liver metastases of GA-1 tumor by 1.5 times in comparison with that in untreated animals.

Comparative Study of Toxicity of Alkoxyamines In Vitro and In Vivo

Effect of alkoxyamines on normal and tumor cells was studied in vitro and in vivo. In vitro experiments showed that alkoxyamines produce a dose-dependent toxic effect on cells of human breast tumor MCF7 line. Transplantation of Krebs-2 ascites carcinoma cells preincubated with alkoxyamines to mice did not induce tumor growth. An opposite effect was observed in normal mouse cells: functional activity of peritoneal macrophages increased. The possibility of using alkoxyamines as theranostic agents is discussed.

[Determination of N-nitrosodiphenylamine in meat canned food for children by the method of chromato-massspectrometry]

This study demonstrates the results obtained from the GC/MS experimental determination of low concentrations of N-nitrosodiphenylamine in meat canned baby food in the concentration range of 0.027-3.89 mg/kg. The perfect conditions of sample preparation (extraction with organic solvent and solid phase extraction) as well as the application of the chromatography-mass spectrometry allowed us to detect N-nitrosodiphenylamine in samples of the meat canned baby food with high selectivity in concentrations ranged from 0.016 to 5 mg/kg when an error of 23% was assumed. The use of the reaction of transesterification of fatty acids by potassium methylate, the removal of the ester generated from the samples of canned meat by organic solvent (hexane), concentrating of N-nitrosodiphenylamine in the aqueous layer on the cartridges of an automatic solid-phase extraction system provided 99.94% extraction of N-nitrosodiphenylamine from the canned meat samples. The experiment has made evident the presence of N-nitrosodiphenylamine in the samples of canned meat (beef + chicken) with the help of mass-spectrometry method in the mode of full ion scanning using the AMDIS automatic mass-spectral identification system.

Difficulties of diagnosing acute intermittent porphyria in clinical practice

Acute intermittent porphyria is an inherited metabolic disease with autosomal dominant inheritance pattern. The pathogenesis of the disease includes disturbed function of vegetative regulation. Attacks of acute intermittent porphyria are rare, sometimes are fatal, but in practice they often remain undiagnosed. Significant difficulties are attributed to unspecific clinical manifistations of acute intermittent porphyria. The patients initially visit surgeons with a clinical presentation of acute abdomen. As a result porphyrinogenic diagnostic and remedial procedures are administered including anesthetics and laparoscopy with anesthesia, which worsen the attack and prognosis. Porphyria being an orphan disease and polymorphism of clinical presentation, absence of medications for its treatment in health care facilities in Russian Federation cause challenges for physicians. The article deals with clinical observation of two patients with a diagnosis of acute intermittent porphyria first made in the neurology department. A 53-year old female was brought in to the neurology department by an ambulance in obtundation after a series of generalized tonoclonic spasms with hyperthermia. A 21-year old female was admitted to the surgical department due to intensive epigastric pain, nausea, repeated episodes of vomiting, an episode of diarrhea and significant general fatigue causing impossibility to move. Presented clinical cases reflect a general situation when for a long period of time the patients were wrongfully admitted to different departments, and cover a problem of late and untimely diagnosis of the disease.

[Evaluation of contamination levels of serum and expired air of mechanical rubber production workers exposed to acrylonitrile at work]

To evaluate occupational hazards for workers engaged into mechanical rubber production, the authors determined contents of acrylonitrile in serum and expired air, during occupational exposure and in reference group. Findings are that depending on occupation, age and length of service, acrylonitrile contamination level of expired air has intermittent effect. Main occupations workers are exposed to continuous inhalation of acrylonitrile vapors, with its average concentration of 0.01-0.015 mg/m3 in air of workplace. Acrylonitrile concentration in expired air of this group ranged from 0.0001-0.0009 mg/M3 - that is reliably (p <0.05) higher (5.5 times) than in expired air of the reference group members. Serum levels of acrylonitrile did not differ significantly between the main group and the reference group members.

Effect of Paclitaxel on Antitumor Activity of Cyclophosphamide: Study on Two Transplanted Tumors in Mice

Antitumor effect of paclitaxel used as the monotherapy or in combination with cyclophosphamide was studied on CBA/LacSto mice with transplanted LS and RLS tumors characterized by high (LS) and low (RLS) sensitivity to cyclophosphamide. The therapeutic effects of cyclophosphamide and paclitaxel were summed in animals with drug-resistant RLS tumor, while combined use of these drugs in LS tumor highly sensitive to the apoptogenic effect of cyclophosphamide was no more effective than cyclophosphamide alone.

[Effect of Hepatic P450 2e1 Activity Modulation on the Toxicity and Carcinogenicity of Diethylnitrosamine in Mice]

In this paper, the biological effects of diethylnitrosamine have been studied under controlled conditions of its metabolism in mice of different ages. The data presented indicate that diethylnitrosamine in a non-metabolized form exerts general toxic and hepatocarcinogenic effects while alkylating agents of this compound produce toxic liver injury. To our knowledge, the data presented impel to revise the general notion of an exceptional role of mutagenic activation in the carcinogenic effect of chemicals.

[THE DEVELOPMENT AND VALIDATION OF THE GAS CHROMATOGRAPHY METHOD AND VALIDATION DEVELOPMENT FOR THE ORGANIC CYANIDE (CYANOETHYLENE) DETERMINATION IN EXPIRED AIR]

There are presented results of experimental studies on the development of gas chromatography method for the cyan ethylene determination in expired air During the process of the study there was chosen and proved the capillary gas chromatography method; there were investigated and elaborated optimal parameters of the gas chromatography separation of cyanoethylene with associated hydrocarbons together with the sample preparation and quantitative measurement methods. There was achieved the optimal level of gas chromatography quantification method for the cyan ethylene determination at 0, 00012 mg/m3, with the method uncertainty not more than 25%. The method was tried during the medical and biological examination of groups of 6-8 years old children, living in the territory of exposition from the moment of the birth and in the control territory.

PT/Y Mice Are Sensitive to the Inhibitory Effect of o-Aminoazotoluene on Glucocorticoid Induction of Tyrosine Aminotransferase and Its Hepatocarcinogenic Effect

PT/Y mice used for studies of the effects of mutagens are characterized by the absence of spontaneous tumors of the liver, but often develop these tumors in response to chronic oaminoazotoluene treatment. The level of glucocorticoid induction of adaptive hepatic enzyme tyrosine aminotransferase decreases by more than 70% 24 h after acute injection of o-aminoazotoluene to these animals. These mice can serve as a model for studies of the relationship between the effect of carcinogens on the regulation of activity of adaptive hepatic enzymes and their capacity to induce the development of liver tumors.

[Features of the immune proteasome expression in ascite Zajdela hepatoma after implantation into Brattleboro rats with the hereditary defect of arginine-vasopressin synthesis]

The expression of the total proteasome pool, immune proteasome subunits LMP2 and LMP7, TAP1 and TAP2 transporters, as well as RT1A molecule of MHC class I was investigated in the ascite Zajdela hepatoma at the 10th day after implantation into Brattleboro rats with the hereditary defect of hypothalamic arginine-vasopressin synthesis (AVP) and into WAG rats with normal AVP expression. In Zajdela hepatoma cells implanted into Brattleboro rats the 3-fold increase of the total proteasome pool and LMP2 level and 8-fold increase of the LMP7 level was detected by Western blotting as compared to those in WAG rats. Differences in the LMP2 and LMP7 expression suggest variations in their functions, namely the important role of LMP7 in anti-tumor immunity. The growth of Zajdela hepatoma in WAG rats was accompanied by the decreased level of total proteasome pool as well as immune proteasome expression as compared to those in Brattleboro rats during the regression of tumor. The analysis of TAP1 and TAP2 revealed the pronounced expression of these peptide transporters in Zajdela hepatoma cells implanted into Brattleboro and WAG rats. The expression level of RT1A molecule of MHC class I was increased 3 times in Zajdela hepatoma cells implanted into Brattleboro rats as compared to WAG rats. Moreover, flow cytometric analysis of CD4- and CD8-lymphocytes number in the spleen of Brattleboro and WAG rats was performed at the 10th day after implantation of Zajdela hepatoma. The increased number of CD4- and CD8-lymphocytes was observed in the spleen of Brattleboro as compared to WAG. The increased subpopulations of cytotoxic T-lymphocytes and T-helpers might promote the tumor regression in Brattleboro rats. The reduced populations of CD4- and CD8-lymphocytes in the spleen of WAG rats were accompanied by the splenomegaly and tumor progression. The data obtained suggest that AVP deficiency in Brattleboro rats leads to the increase of the immune proteasome and MHC class I expression in Zajdela hepatoma cells, resulting in tumor immunogenicity and its elimination by the adaptive immunity.

Dual effects of indoleamine 2,3-dioxygenase inhibitors on the therapeutic effects of cyclophosphamide and cycloplatam on Ehrlich ascites tumor in mice

Ethyl pyruvate, an inhibitor of indoleamine 2,3-dioxygenase, slightly suppressed the growth of transplantable Ehrlich tumor in mice and significantly potentiated the therapeutic effect of cyclophosphamide. Another inhibitor amidoxime produced a similar effect. However, both ethyl pyruvate and amidoxime significantly reduced the effect of cycloplatam therapy. The observed changes can be stipulated by different effects of cyclophosphamide and cycloplatam on the subpopulations of lymphoid cells taking part in the formation of antitumor immunity and resistance to tumors.

Suppression of sulfoconjugation reduces the protective effect of ortho-aminoazotoluene on hepatocarcinogenesis induced by diethylnitrosamine in mice

The effects of ortho-aminoazotoluene on carcinogenic activity of diethylnitrosamine were studied in CBA and ICR mice. Injection of ortho-aminoazotoluene before and after diethylnitrosamine led to a significant reduction of its anticarcinogenic effect, judging from significantly lower level of liver tumors. Pentachlorophenol, inhibitor of sulfotransferase (catalyzing the terminal stage of ortho-aminoazotoluene metabolic activity), stimulated its carcinogenic effect on mouse liver. On the other hand, pentachlorophenol reduced the protective effect of ortho-aminoazotoluene on diethylnitrosamine-induced hepatocarcinogenesis in mice. Presumably, the carcinogenic and anticarcinogenic effects of ortho-aminoazotoluene were realized by its initial form or intermediate (non-sulfated) metabolites.

[Inhibitory effect of ortho-aminoazotoluene on diethylnirtosamine hepatocarcinogenesis in suckling mice. Phenomenon and possible mechanism]

The modifying effect of the one compound on carcinogenicity of the other in the combined application is attributed usually to some changes in the carcinogen metabolism, i.e. its activation or inactivation. In this paper, when used separately, diethylnitrosamine (DENA) induced 4-6 times more neoplastic lesions in the liver of suckling mice than ortho-aminoazotoluene (OAT) did. However, after combined treatment with both carcinogens the total number of hepatic lesions was significantly lower than that in mice treated with DENA only. Similar effect was observed when OAT was administered 3 days before or 3 days after DENA injection. The observed protective effect is not mediated at metabolic level, because OAT has no effect on metabolism of DENA in mouse liver. Our findings can be unequivocally explained by the competition of the carcinogens for target protein molecules, presumably transcription factors, participating in hepatocyte differentiation, which differently interact with and are diversely impaired by different compounds.

[The elaboration of gas chromatographic method of the determination of N-nitrosamines (N-nitrosodimethylamine, N-nitrosodiethylamine) in biological samples (urine)]

The issues of the elaboration of a method for the determination of N-nitrosamines (N-nitrosodimethylamine, N-nitrosodiethylamine) in urine by means of the method of capillary gas chromatography with the use of a thermionic detector are considered. There were performed investigations on the study of the efficacy of the extraction of N-nitrosamines from the urine by steam distillation and gas chromatographic detection of headspace. With the aim of the maximal recovery of N-nitrosamines from the urine and setting parameters of the extraction two method were used to prepare the bioassay for the analysis the alkalization with potassium hydroxide and the addition of salting out reagent--neutral salts of alkali and alkaline earth metals. During the process of performed studies there was found that the greatest degree of extraction of N-nitrosamines from the urine by the method of headspace analysis is achieved if using the salting-out agent in an amount of 16 g of sodium sulfate and for N-nitrosodimethylamine is 99%, for N-nitrosodiethylamine--100%.

[Mutagenic activation and carcinogenicity of aminoazo dyes of ortho-aminoazotoluene and 3'-methyl-4-dimethylaminoazobenzene in experiments on suckling mice]

It is found that after administration of 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB,) which was hepatocarcinogenic to rats, in suckling mice, the number of neoplastic lesions in the liver of mice was 3 times higher than after analogous administration of equimolar dose of ortho-aminoazotoluene (OAT)). However, in the Ames test (TA-98 strain of Salmonella typhimurium) with activation by hepatic enzymes (S-9 fraction) of both intact and Aroclor-1254-induced mice and rats OAT contributed by an order of magnitude to revertant colonies compared to 3'-Me-DAB. In vivo inhibition of sulfotransferase activity, the enzyme which catalyzes the final stage of the mutagenic activation of aminoazo dyes, had no effect on carcinogenicity of 3'-Me-DAB but more than 4 times elevated that of OAT. It was concluded that the mechanism of carcinogenic action of aminoazo dyes studied is not genotoxic and that the carcinogenic potential of OAT is lost in the process of mutagenic activation.

Immunomodulating effect of ethyl pyruvate on nonsyngenic transplanted tumor in mice

Indolamine-2,3-dioxygenase, a tryptophan-catabolizing enzyme, creates local conditions suppressing immune lymphocytes. Expression of this enzyme in tumors protects them from immune mechanisms, while its inhibition partially reduces tumor immunoresistance. This effect is attained by multiple subcutaneous or intraperitoneal injections of ethyl pyruvate, an indolamine-2,3-dioxygenase inhibitor. Experiments on mouse nonsyngenic tumor have demonstrated the immunomodulating effect of chronic oral ethyl pyruvate administered with drinking water.

[The effect of psychoemotional state on Lewis lung carcinoma metastasis]

The effect of a depression-like status formed by chronic stress on development of Lewis lung carcinoma metastases in C57Bl/6J mice was investigated. Two types of acute stress (restraint and social stress) were used for comparison. The depression-like status was induced by eight-week exposure to repeated but unpredictable stressors (chronic mild stress model) and was assessed in the forced swim test. Tumor cells were inoculated an hour after the onset of social stressor or immediately after physical or chronic stressor impacts. The number of metastases was counted 17 days after the inoculation. The results indicate that chronic mild stress provokes the development of a depression-like state in mice and causes a twofold increase in the number of metastases in the lungs, while both types of acute stress have no such effects. Thus, a depression-like psychoemotional status of animals enhances the metastasis of Lewis lung carcinoma.

Cyclophosphamide metabolite inducing apoptosis in RLS mouse lymphosarcoma cells is a substrate for P-glycoprotein

RLS lymphosarcoma characterized by enhanced expression of mdr1a and mdr1b genes encoding P-glycoprotein is insensitive to low doses of cyclophosphamide, but is susceptible to its high doses approximating the maximum tolerated doses. Induction of apoptotic death of RLS cells by high doses of cyclophosphamide was demonstrated by cytofluorometry and electrophoresis. Experiments on RLS(40) tumor cells derived from RLS lymphosarcoma and characterized by more intensive expression of mdr1a/1b genes showed that the therapeutic effects of cyclophosphamide increased under conditions of simultaneous suppression of these genes by specific small interfering RNA (siRNA). These findings suggest that active cyclophosphamide metabolite can be a substrate for P-glycoprotein.

Accelerated rejection of the second transplants of immunogenic tumor in mice under inhibition of indoleamine 2,3-dioxygenase activity by ethyl pyruvate

AIM

A recently discovered enzyme, indoleamine 2,3-dioxygenase (IDO), is expressed in placenta, dendritic cells and also in many kinds of tumors and in tumor-infiltrating macrophages. By catabolizing tryptophan, IDO causes local depletion of this essential amino acid and excess of kinurenin, and suppresses in situ proliferation and functioning of T lymphocytes. Thus, immune resistance of tumors can be overcome by inhibiting IDO activity.

MATERIALS AND METHODS

C3HA mice immunized with non-syngeneic H-29 tumor were used to study the effect of the IDO inhibitor ethyl pyruvate, under systemic or local (at site of tumor cells localization) administration, on the occurrence and rate of rejection of the second transplants of this tumor.

RESULTS

Both systemic and local administration of ethyl pyruvate increases the incidence of and substantially accelerates tumor regression as compared with control.

CONCLUSION

IDO inhibitors impairing immune resistance of tumors may appear useful in leveraging the efficacy of antitumor therapy.

Depressive-like psychoemotional state versus acute stresses enhances Lewis lung carcinoma metastasis in C57BL/6J mice

AIM

The effect of a depression-like status formed by chronic stress on the development of Lewis lung carcinoma metastases in C57Bl/6J mice was investigated. Two types of acute stress (restraint and social stress) were used for comparison.

METHODS

The depression-like status was induced by eight-week exposure to repeated but unpredictable stressors (chronic mild stress model) and was assessed in the forced swim test. Tumor cells were inoculated an hour after the onset of social stressor or immediately after physical or chronic stressor impacts. The number of metastases was counted 17 days after the inoculation.

RESULTS

Chronic mild stress provokes the development of a depression-like state in mice and causes a twofold increase in the number of metastases in the lungs, while both types of acute stress have no such effects.

CONCLUSION

Depressive-like psychoemotional state of animals enhances the metastasis of Lewis lung carcinoma.

Effect of vasopressin V1b receptor antagonist, SSR149415, on anxiety-like behavior and Lewis lung carcinoma metastasis in mice

AIM

To study the effect of new vasopressin V1b receptor antagonist, SSR149415, on anxiety-like behavior and Lewis lung carcinoma metastasis in the anxious adult male mice of C57Bl/6J strain. This type of receptors was thought to act as potential targets mediating the effect of negative psychoemotional state on tumor progression.

METHODS

Anxiety-like psychoemotional state of the animals was produced using chronic social conflict model. Used behavioral tests were elevated plus-maze, social interaction test and open field test. Tumor cells were administrated on background of double or sixfold SSR149415 injections and the number of metastases in the lung were calculated 17 days later.

RESULTS

SSR149415 reduced the anxiety-like behavior measured in the elevated plus-maze and social interaction tests and did not affect locomotor activity in the open field test. Double and sixfold administration of the compound to such mice before and after inoculation of the tumor cells produced no effect on the metastasis rate.

CONCLUSION

vasopressin V1b receptor is involved in the mediation of anxious behavior of animals but is not involved in the mechanism underlying the influence of negative psychoemotional state on Lewis lung carcinoma metastasis.