Effects of Catechin on Activity of Angiotensin-Converting Enzyme and Generation of Reactive Oxygen Species in Rat Aorta.

Activity of angiotensin-converting enzyme (ACE) and intensity of ROS generation in the aorta were studied in male Wistar rats intraperitoneally injected with a mixture of (+) and (-) stereoisomers of catechin. ACE activity in aortal segments was evaluated by hydrolysis of hippuryl-histidine-leucine; ROS generation was measured by oxidation of dichlorodihydrofluorescein. The dynamics of ACE activity and intensity of ROS generation in the aorta after catechin administration and their dependence on the catechin dose were studied. The effects of dihydroquercetin and fucoidin on the studied parameters were analyzed. Catechin increased ACE activity; the maximum increase was achieved in 3 h after administration. Catechin dose producing a half-maximum increase in ACE activity was 0.04 µg/kg. The effects of catechin on ACE activity was attenuated by dihydroquercetin and completely abolished by fucoidin. Catechin did not enhance ROS production in the aorta, and in a dose of 0.1 µg/kg even inhibited this process. It is hypothesized that isomers of catechin produce opposite effects on ROS generation in the aorta.

Blood Pressure Changes After Exposures Increasing Angiotensin-Converting Enzyme Activity and After Its Normalization with Dihydroquercetin in Male Wistar Rats.

Changes in BP and HR were assessed after exposures increasing activity of angiotensin-converting enzyme: ionizing radiation, NO synthase inhibitor (L-NAME), and dexamethasone. Effects of dihydroquercetin and angiotensin-converting enzyme inhibitor enalapril on activity of this enzyme, BP, and HR were also evaluated under these exposures. Wistar male rats were subjected to X-ray irradiation in a dose of 2.5 Gy. Angiotensin-converting enzyme activity in the aorta sections was determined by Hip-His-Leu hydrolysis. BP and HR were recorded using a non-invasive tail-cuff method and PowerLab 8/35 software. BP and HR were not altered with the increase in activity of angiotensin-converting enzyme after irradiation. In case of prolonged (7 days) treatment with NO synthase inhibitor and dexamethasone, the increase in enzyme activity was accompanied by elevation of BP and, in the case of NO synthase inhibitor, HR reduction. Dihydroquercetin normalized the enzyme activity and lowered BP, but not to the normal level. Enalapril normalized BP, increased by NO synthase inhibitor solution intake; at the same time, the angiotensinconverting enzyme activity decreased more than 2-fold in comparison with the normal.

Dihydroquercetin and Fucoidin Inhibit the Increase of Angiotensin-Converting Enzyme Activity in the Rat Aorta after Irradiation.

The time course of angiotensin-converting enzyme activity in the rat aorta after fractionated exposure to ionizing radiation and the effects of dihydroquercetin and fucoidin on this parameter were studied. Male Wistar rats were exposed to single or repeated (fractionated) X-ray radiation in a dose of 2.5 Gy at 200 kV. Activity of angiotensin-converting enzyme in aorta segments was evaluated 2 h after the last exposure by hydrolysis of hippuryl-histidineleucin substrate. Enzyme activity in the rat aorta was higher than normally after all the studied doses of fractionated exposure (2.5 Gy per fraction) with the maximum effect after the total dose of 7.5 Gy (3 fractions). Fucoidin, a blocker of endothelium receptors realizing the leukocyte adhesion to the endothelium, and flavonoid dihydroquercetin inhibiting expression of adhesion molecules in the endothelium abolished the increase in activity of angiotensinconverting enzyme in the rat aorta after single exposure; moreover, dihydroquercetin reduced significantly the effect of fractionated exposure. These data indicate that leukocyte adhesion to the endothelium is an important factor contributing to the increase of angiotensin-converting enzyme activity in the aorta.

Ionizing Radiation Enhances Activity of Angiotensin-Converting Enzyme in Rat Aorta.

We analyzed changes in angiotensin-converting enzyme activity in rat aorta at the early terms after irradiation in doses equal to one fraction dose used in tumor radiotherapy. Male Wistar rats were exposed to whole body or local (chest) X-ray irradiation (200 kV, 1-7.5 Gy). The activity of the enzyme in aorta segments was measured in 1-48 h after irradiation by hydrolysis of hippuryl-histidine-leucine. Activity of angiotensin-converting enzyme in rat aorta was increased 1-24 h after whole body irradiation in a dose of 2.5 Gy with a peak in 2 h after exposure. After local exposure, enzyme activity also increased in 2 h, but returned to the control level in 24 h. In 2 h after whole-body irradiation in doses >2.5 Gy, the increase in enzyme activity was less pronounced and after exposure to 7.5 Gy, it did not differ from the control. During local exposure, the effect did not decrease with increasing the irradiation dose. The fraction of blood monocytes adherent to plastic in rats subjected to whole body irradiation decreases with increasing the dose. In rats subjected to local irradiation in a dose of 7.5 Gy, monocyte adhesion to plastic did not differ from the control. These data suggest that the increase in activity of angiotensin-converting enzyme in the aorta after irradiation is determined by monocyte adhesion to the endothelium; the decrease in this effects with increasing the dose can be explained by radiation damage of monocytes.

Lipoxygenase Inhibitors Nordihydroguaiaretic Acid and Fungus Lecanicillum lecanii Extract Induce Death of Lymphoid Leukemia Cells.

We studied the effect of lipoxygenase inhibitors nordihydroguaiaretic acid (NDGA) and fungus Lecanicillum lecanii extract on lymphatic leukemia P388 cells. The cells grown in the abdominal cavity of DBA2 mice for 7 days were transferred into a nutrient medium. The effect of lipoxygenase inhibitors was evaluated by changes in cell number, trypan blue staining, nucleus damage, and changes in cell distribution by DNA content after 22-h incubation. NDGA and fungus extract induced apoptotic death of lymphatic leukemia cells, which was seen from nucleus damage and reduced DNA content in cells. IC50 for NDGA and fungus extract was 0.66 and 5.5 µg/ml, respectively.

Dihydroquercetin Does Not Affect Age-Dependent Increase in Blood Pressure and Angiotensin-Converting Enzyme Activity in the Aorta of Hypertensive Rats.

We analyzed changes in angiotensin-converting enzyme activity in the aorta of hypertensive SHR rats against the background of age-related BP increase (from week 7 to 14) and the effect of dihydroquercetin on BP rise and angiotensin-converting enzyme activity. Normotensive WKY rats of the same age were used as the control. BP and activity of angiotensin-converting enzyme in the aorta of SHR rats increased with age. Dihydroquercetin in doses of 100 and 300 µg/kg per day had no effect on the increase of these parameters; dihydroquercetin administered to 14-week-old WKY rats in a dose of 300 µg/kg reduced activity of the angiotensin-converting enzyme. Thus, the early (7-14 weeks) increase in BP and angiotensin-converting enzyme activity in the aorta of SHR rats was not modified by flavonoids (dihydroquercetin) in contrast to other rat strains and humans, which is indicative of specificity of hypertension mechanism in SHR rats.

Taxifolin and Fucoidin Abolish the Irradiation-Induced Increase in the Production of Reactive Oxygen Species in Rat Aorta.

We studied changes in ROS content in the aorta of Wistar rats at early terms after irradiation in doses equal to single fraction used in tumor radiotherapy and the effects of taxifolin and fucoidin, blockers of leukocyte adhesion to endothelium, on ROS content. Male rats were exposed to X-rays (200 kW) in doses of 1-7.5 Gy. ROS production in aorta segments was measured in 1-48 h after irradiation by dichlorodihydrofluorescein oxidation. The content of ROS in the aorta of rats exposed to radiation in doses of 1-2.5 Gy increased in 1-24 h after irradiation, the peak ROS content was found in 2 h after irradiation. Taxifolin (100 µg/kg dihydroquercetin once a day with drinking water) and fucoidin (10 mg/kg, i.v.) abolished ROS accumulation. The content of ROS in rat aorta increased in 1-24 h after irradiation in doses used for tumor radiotherapy and this increase can be determined by leukocyte adhesion to the endothelium.

[Change of Tumor Cell Multiple Drug Resistance Inhibitory Activity of Oligomycins in Complexes with Lithium and Zinc].

Oligomycins and their complexes with lithium and zinc were shown to be less active vs. cyclosporin A in inhibition of transport proteins responsible for multiple drug resistance of lymphoid leukosis P388VR cells, while certain oligomycin complexes were tens or hundreds times more active than cyclosporin A by inhibition of transport proteins in another type of tumor cells, i.e. human larynx cancer Hep-2, that makes possible the use of the oligomycins complexes with lithium and zinc for inhibition of multiple drug resistance of certain tumor types.

Camel thorn extract reduces activity of angiotensin-converting enzyme in rat aorta increased during aging and treatment with NO-synthase inhibitor.

We studied the effect of camel thorn extract on activity of angiotensin-converting enzyme in rat aorta increased in animals during aging or treatment with NO-synthase inhibitor. Intake of camel thorn extract with drinking water reduced activity of angiotensin-converting enzyme; the effect increased with increasing the dose of the extract. Angiotensin-converting enzyme activity in older rats and animals treated with NO-synthase inhibitor decreased to the values observed in young control rats at extract concentration of 0.2%. Comparison of the effects of camel thorn extract with those of flavonoid taxifolin showed that the extract was not inferior to taxifolin in preventing the early stages of aortic atherosclerosis caused by increased activity of angiotensin-converting enzyme.

Effects of high-salt diet on the activity of angiotensin-converting enzyme and generation of reactive oxygen species in rat aorta.

The dynamics of angiotensin-converting enzyme activity in the aorta and blood plasma and generation of ROS in the aorta were studied in rats subjected to two high-salt diets (0.4% and 1% NaCl solutions). During high-salt diets, activity of angiotensin-converting enzyme in the aorta progressively decreased to the minimal during week 1 and remained lower than control level for 1 month. Both diets were followed by a decrease in ROS concentration in the aorta, and this effect was more pronounced when the dosage of salt increased. ROS level in the aorta varied similarly during both diets, but the amplitude of the response was significantly higher in rats receiving 0.4% salt solution. ROS amount in the aorta during high-salt diets differed from the control level and depended from salt dosage and the duration of administration.

[Antitumor effect of low-intensity extremely high-frequency electromagnetic radiation on a model of solid Ehrlich carcinoma].

The influence of different exposure regimes of low-intensity extremely high-frequency electromagnetic radiation on the growth rate of solid Ehrlich carcinoma in mice has been studied. It was shown that, at an optimum repetition factor of exposure (20 min daily for five consecutive days after the tumor inoculation), there is a clearly pronounced frequency dependence of the antitumor effect. The analysis of experimental data indicates that the mechanisms of antitumor effects of the radiation may be related to the modification of the immune status of the organism. The results obtained show that extremely high-frequency electromagnetic radiation at a proper selection of exposure regimes can result in distinct and stable antitumor effects.

[Antitumor effect of natural avermectins]. / Protivoopukholevoe deistvie prirodnykh avermektinov.

The effects of the natural avermectin complex, aversectin C and individual avermectin B1 on the growth of ascitic and solid transplantable tumors in animals were studied. The results showed for the first time that both aversectin C and avermectin B1 possessed marked antitumor activity. In subtoxic doses aversectin C significantly inhibited the growth of P388 lymphoid leukemia and Ehrlich carcinoma, both ascitic and solid ones. In some administration regimens aversectin C inhibited the tumor growth by 70 to 80%. The highest effect of aversectin C was observed after its intraperitoneal administration. Avermectin B1 inhibited the growth of solid Ehrlich carcinoma and carcinoma 755.

[Analysis of 15-lipoxygenase activity in irradiated thymocytes]. / Issledovanie aktivnosti 15-lipoksigenazy v timotsitakh posle oblucheniia.

We studied the effect of gamma-radiation on 15-lipoxygenase activity in rat thymocytes. The enzyme activity was determined as the rate of linoleic acid oxidation by the protein fraction isolated from the control and irradiated thymocytes under standard conditions. We demonstrate lipoxygenase activation immediately after irradiation of thymocytes. High lipoxygenase activity is observed in the cells for no more than an hour after irradiation. No high lipoxygenase activity later indicates that its synthesis is not directly induced by irradiation. Irradiation-induced generation of lipid peroxides can be the factor of lipoxygenase activation.

[A study of the role of lipoxygenases in radiation-induced apoptosis of thymocytes. Inhibitory analysis]. / Issledovanie roli lipoksigenaz v radiatsionnom apoptoze timotsitov. Ingibitornyi analiz.

The radiation-induced apoptosis of thymocytes is suppressed by the common inhibitor of lipoxygenases nordihydroguaiaretic acid but not the inhibitors of cyclooxygenases or cytochrome P-450, which indicates the key role of lipoxygenases in apoptosis. However, the specific inhibitors of 5-lipoxygenase (AA861) and of 12-lipoxygenase (baicalein) do not suppress apoptosis and even enhance it. This effect can be explained by an increase in the yield of the 15-lipoxygenase product upon inhibition of 5- and 12-lipoxygenases. Indeed, the addition of 15-hydroxyecosotetraenic acid, a product of 15-lipoxygenase, into the incubation medium induces apoptosis in thymocytes. The results obtained suggest that 15-lipoxygenase is one of the enzymes involved in radiation-induced apoptosis of thymocytes.

[Modification of antitumor effect of vincristine by natural avermectins]. / Modifikatsiia protivoopukhlevogo effekta vinkristina prirodnymi avermektinami.

The effect of avermectins (aversectin C, aversectin C1 and avermectin B1) on the vincristine antitumor action with respect to murine transplantable tumors was studied. It was shown that both the natural avermectins mixtures and the individual avermectin B1 potentiated the antitumor action of vincristine on Ehrlich carcinoma, melanoma B16 and P388 lymphoid leukemia, including the vincristine resistant strain P388. Such an effect of the avermectins was observed only when they were administered after vincristine.

[Antitumor effect of combined treatment with ionizing radiation and vitamin B12-C complex]. / Protivoopukholevyi éffekt sochetannogo primeneniia ioniziruiushchei radiatsii s kompleksom vitaminov B12 i C.

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.

[Growth inhibition and induction of tumor cell death by phospholipase A2 and lipoxygenase inhibitors]. / Podavlenie rosta i induktsiia gibeli opukholevykh kletok ingibitorami fosfolipazy A2 i lipoksigenazy.

We studied the effect of arachidonic acid metabolism inhibitors in a wide concentration range on the proliferation and death of lympholeukemia cells P-388. Proliferation of the cells was estimated by metaphase frequency and the proportion of cells in S phase; cellular death was determined by their lysis, trypan blue staining, damaged nuclei, the proportion of cells with subdiploid DNA content, and DNA fragmentation. Low concentrations of phospholipase A2 and lipoxygenase inhibitors were shown to stimulate cell division, while higher concentrations inhibited it by blocking G1-S transition and inducing apoptotic cellular death. Indomethacin, a cyclooxygenase inhibitor, had no effect on proliferation and induced no cell death at concentrations up to 10 microM. Inhibitors of phospholipase A2 and lipoxygenase also inhibited tumor growth in mice.

[Cytotoxic and cytostatic effect of avermectines on tumor cells in vitro]. / [Tsitostaticheskoe i tsitotoksicheskoe deistvie avermektinov na opukholevye kletki in vitro]

Effect of natural avermectin complex (aversectin C) and separate avermectins A1, A2, B1 and B2 in the cell culture of murine myeloma Ns/o, Erlich carcinoma ascites and human larynx carcinoma Hep-2 was investigated. It was shown that aversectin C within the concentrations of 0.1 to 1.0 mcg/ml inhibited proliferation of tumor cells and induced their death. Proliferation inhibition was due to the delay of the cells cycle start (lag-phase prolongation) and blocking of mitotic cycle. Ns/o cells death had apoptosis signs: chromatin condensation and fragmentation, DNA fragmentation. It was demonstrated that only avermectin A1 has cytotoxic activity within the concentrations used, avermectins A2 and B2 had cytostatic activity, avermectin B1 showed no activity under the experimental conditions.