L. N. Kublik

The effect of inhibitors of arachidonic acid metabolism on proliferation and death of tumor cells

The effect of inhibitors of arachidonic acid metabolism on proliferation and death of tumor P‐388 cells in a broad concentration range was studied. Cell proliferation was estimated by the metaphase frequency and the proportion of cells in S phase; cell death was determined from lysis, staining of cells with trypan blue, nuclear damage, percentage of cells with subdiploid DNA and the type of DNA fragmentation. It was shown that low concentrations of phospholipase A2 and lipoxygenase inhibitors stimulated the proliferation of P‐388 cells. At higher concentrations, the inhibitors suppressed cell proliferation by blocking the G1‐S transition and induced cell death of the apoptosis type. Indomethacin, an inhibitor of cyclooxygenase, did not initiate cell death, nor did it affect the proliferation of P‐388 cells at concentrations of up to 10 μM.

The effect of low-dose irradiation on proliferation of mammalian cells in vitro

The effect of low doses of gamma radiation on proliferation of Raji lymphoma cells and Chinese hamster fibroblasts in vitro has been investigated. It is shown that irradiation in the dose range between 2 and 20 cGy (maximum at 10 cGy) stimulates growth of cultured cells due to the shortening of the lag phase of cell growth, with the duration of the doubling time being unchanged. Preirradiation of growth medium in this dose range also stimulates cell proliferation, though to a lesser extent than irradiation of cells and the medium does. The stimulatory effect manifests itself in an increase in the cell number as well as in the size and number of colonies.

Distribution of the activity of the angiotensin-converting enzyme in the rat aorta and changes in the activity with aging and by the action of l-NAME

The activity of the angiotensin-converting enzyme (ACE) of the inner surface (the endothelium surface) of rat aorta sections has been studied depending on their distance from the aortic arch, age of rats, and the duration of treatment of rats with the NO synthase inhibitor, Nω-nitro-l-arginine (l-NAME). The activity of ACE of aorta sections was determined by measuring the hydrolysis of hippuryl-l-histidyl-l-leucine and was expressed as picomoles of Hip–His–Leu hydrolyzed per minute per square millimeter of the endothelium surface. It was found that the ACE activity considerably varies along the aorta of young rats. This variability decreases with increasing age of rats and by the action of l-NAME. The average ACE activity in the aorta increases with the age of rats and with increasing time of l-NAME treatment. Enalapril normalizes the distribution of the ACE activity along the aorta and decreases the average ACE activity. The changes in the distribution of the ACE activity along the aorta and in the average ACE activity in the aorta with increasing age of the rat and by the action of l-NAME may play a role in the development of atherosclerosis of vessels on aging and the inhibition of formation of nitric oxide.

Opposite Effects of Low Oligomycin Concentrations on the Apoptosis of Normal and Tumor Cells

Oligomycin is widely used in laboratory studies as an ATPase inhibitor. It binds to F 0 F 1 ATPase and inhibits the mitochondrial proton pump [1], which results in respiration suppression and a decrease in the cell ATP content. Oligomycin concentrations completely inhibiting respiration vary from 80 to 300 nmol/l for different cell types [2]. A decrease in ATP concentration has been previously assumed to be the only cause of the toxic effect of oligomycin on cells. Recent data suggest, however, that some oligomycin effects do not depend on ATP. For example, the inhibition of Baxinduced apoptosis does not depend on ATP [1]. It is supposed [1] that, in this case, a blockage of mitochondrial pore opening accounts for the oligomycin effect.

Dependence of Radioprotective Effect of Chemical Modifying Agents on Their Intracellular Concentrations

SummaryRegularities of the radioprotective effect of chemical modifying agents cysteamine, caffeine benzoate, thioglycolic acid, and caffeine, all weak electrolytes, have been studied in cultured Chinese hamster cells. Efficiency of protection is shown to be dependent on pH and concentrations of the drug inside the cells and in the medium. Based on the theory of the dissociation of weak electrolytes and their distribution between the cells and the medium a strong correlation between the efficiency of modification of the radiation response and intracellular concentration of a modifying agent is shown.

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.

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.

The Hexapeptide Immunofan Inhibits the MRP-dependent Multidrug Resistance of Tumor Cells

The phenomenon of resistance to a broad range of drugs is widely known for many biological objects: bacteria, protists, fungi, and mammalian cells. The fact that plasma membrane contains transport proteins capable of using the energy of ATP for exporting various compounds out of cells against the concentration gradient is one of the main factors of multidrug resistance (MDR) [1]. The transport of various compounds out of cells causes a substantial decrease in the efficacy of remedies used in therapy of bacterial, parasitic, and fungal diseases, as well as malignant neoplasms. MDR makes it difficult or even impossible to treat a broad spectrum of diseases. Therefore, it is necessary to find effective inhibitors of MDR. Transport proteins of two types are mainly responsible for MDR in mammalian cells: multidrug resistance associated protein (MRP) and P-glycoprotein (P-gp) [1]. Both MRP and P-gp have been found in tumors of various origin: lymphomas, sarcomas, carcinomas, and neuroblastomas [1]. A broad range of antitumor drugs are substrates of transport proteins of the two types: anthracyclines, Etoposide, Vincristine, Taxol, etc. [1]. However, in contrast to P-gp, MRP mediates the transport of various compounds out of cells in a modified form, namely, as conjugates with gluthatione or glucuronic acid [1].

Growth Inhibition and Death Induction in Tumor Cells by Inhibitors of Phospholipase A2 and Lipoxygenase

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 μM. Inhibitors of phospholipase A2 and lipoxygenase also inhibited tumor growth in mice.