Radiation induced oxidative stress: II Studies in liver as a distant organ of tumor bearing mice

Since the radiation dose tolerance of normal tissues/organs away from the site of tumor influences the success of radiation therapy of cancer, and antioxidant status is likely to be one of the factors to determine the tolerance; the radioresponse of antioxidant enzymes has been examined in the liver as a representative distant organ in the tumorbearing mice.Swiss albino male mice (7–8 weeks old) with Ehrlich solid tumor in the thigh pad were irradiated with different doses of radiation (0–9 Gy) at a dose rate of 0.0153 Gy/s and the specific activities of enzymes involved in the free radical metabolism were determined in the liver. Except GST, the activities of SOD, DTD and Gly I as well as the GSH content were found to be higher in the liver of tumorbearing mice compared to the nontumor bearing mice. The catalase activity progressively decreased with dose in both the groups of mice. However, the activity was relatively higher in the liver of tumor bearing mice than the control. Thus, the radioresponse of antioxidant enzymes seemed to be significantly different in the liver of tumorburdened mice compared to controls. The enhanced activities might be due to relatively more damage caused by radiation. The higher levels of NO· and peroxidative damage in the liver of tumorbearing mice probably suggest this possibility. These findings of the present work might have some serious implications as the increased radiationdamage of the distant normal organs (due to tumor burden) is likely to adversely affect the therapeutic gain.     

Effect of beta-Carotene on the development of the solid Ehrlich tumor in mice

The effect of beta-Carotene on the development of the solid Ehrlich tumor in BALB/c mice was investigated. Male mice received orally, on alternate days, three different doses of beta-Carotene (1, 3.5 or 7 mg/100 g) or corn oil as the control. This protocol started 14 days before tumor inoculation (1.75 x 10(5) cells) into mouse footpad and lasted until 10 days after. The tumor growth was evaluated by daily measurement of the footpad thickness, and the tumor mass was evaluated morphometrically. The proliferation rate of tumor was investigated by counting PCNA (proliferating cell nuclear antigen) positive nuclei in the 10th day of the tumor development. Histopathological examination of the lymphoid tissue: thymus, spleen and popliteal lymph node were also performed. beta-Carotene treatment, at dose 3.5 mg/100 g, increased the tumor growth, proliferative rate and the relative weight of popliteal lymph nodes, showing up an adverse effect only when this intermediate dose was used. No effects were obtained when the smaller (1,0 mg/100 g) or the higher (7.0 mg/100 g) doses were used. These results suggest that depending on the dose, beta-Carotene may determine an undesirable effect upon the tumor growth. This should be taken into account in chemopreventive experiments and human applications.     

Ascitic and solid Ehrlich tumor inhibition by Chenopodium ambrosioides L. treatment

The leaves of Chenopodium ambrosioides L. [Chenopodiaceae] ('mastruz') have been indicated for the treatment of several diseases, among which the cancer. There are no results focusing the effect of C. ambrosioides treatment on tumor development in vivo. The aim of this study was to investigate the effect of treatment with C. ambrosioides on Ehrlich tumor development. Swiss mice were treated by intraperitoneal route (i.p.) with hydroalcoholic extract from leaves of C. ambrosioides (5 mg/kg) or with PBS (control group) 48 h before or 48 h later the Ehrlich tumor implantation. The tumor cells were implanted on the left footpad (solid tumor) or in the peritoneal cavity (ascitic tumor). To determine the solid tumor growth, footpad was measured each 2 days until the fourteenth day, when the feet were weighed. Ascitic tumor development was evaluated after 8 days of tumor implantation by quantification of the ascitic fluid volume and tumor cell number. The i.p. administration of C. ambrosioides extract before or after the tumor implantation significantly inhibited the solid and ascitic Ehrlich tumor forms. This inhibition was observed in ascitic tumor cell number, in the ascitic volume, in the tumor-bearing foot size and foot weight when compared to control mice. The treatments also increased the survival of tumor-bearing mice. In conclusion, C. ambrosioides has a potent anti-tumoral effect which was evident with a small dose and even when the treatment was given two days after the tumor implantation. This effect is probably related with anti-oxidant properties of C. ambrosioides.     

Walker-256 tumor growth causes oxidative stress in rat brain

The elevated rate of oxygen consumption and high amount of polyunsaturated fatty acids make the central nervous system vulnerable to oxidative stress. The effect of Walker-256 tumor growth on oxi-reduction indexes in the hypothalamus (HT), cortex (CT), hippocampus (HC) and cerebellum (CB) of male Wistar rats was investigated. The presence of the tumor caused an increase in thiobarbituric acid reactant substances (TBARs) in the HT, CB and HC. Due to tumor growth, the activity of glucose-6-phosphate dehydrogenase increased in the HT and CB, whereas citrate synthase activity was reduced in the HT, CT and CB. Therefore, the potential for generation of reducing power is increased in the cytosol and decreased in the mitochondria of various brain regions of Walker-256 tumor-bearing rats. These changes occurred concomitantly with an unbalance in the brain enzymatic antioxidant system. The tumor decreased the activities of catalase in the HT and CB and of glutathione peroxidase in the HT, CB and HC, and raised the CuZn-superoxide dismutase activity in the HT, CB and HC. These combined findings indicate that Walker-256 tumor growth causes oxidative stress in the brain.     

Mitochondrial glutathione protects against cell death induced by oxidative and nitrative stress in astrocytes

The major cellular antioxidant, glutathione, is mostly localized in the cytosol but a small portion is found in mitochondria. We have recently shown that highly selective depletion of mitochondrial glutathione in astrocytes in culture markedly increased cell death induced by the peroxynitrite donor, 3-morpholino-syndnonimine. The present study was aimed at characterizing the increase in susceptibility arising from mitochondrial glutathione loss and testing the possibility that elevating this metabolite pool above normal values could be protective. The increased vulnerability of astrocytes with depleted mitochondrial glutathione to Sin-1 was confirmed. Furthermore, these cells showed marked increases in sensitivity to hydrogen peroxide and also to high concentrations of the nitric oxide donor, S-nitroso-N-acetyl-penicillamine. The increase in cell death was mostly due to necrosis as indicated by substantially increased release of lactate dehydrogenase and staining of nuclei with propidium iodide but little change in annexin V staining and caspase 3 activation. The enhanced cell loss was blocked by prior restoration of the mitochondrial glutathione content. It was also essentially fully inhibited by treatment with cyclosporin A, consistent with a role for the mitochondrial permeability transition in the development of cell death. Susceptibility to the classical apoptosis inducer, staurosporine, was only affected to a small extent in contrast to the response to the other substances tested. Incubation of normal astrocytes with glutathione monoethylester produced large and long-lasting increases in mitochondrial glutathione content with much smaller effects on the cytosolic glutathione pool. This treatment reduced cell death on exposure to 3-morpholino-syndnonimine or hydrogen peroxide but not S-nitroso-N-acetyl-pencillamine or staurosporine. These findings provide evidence for an important role for mitochondrial glutathione in preserving cell viability during periods of oxidative or nitrative stress and indicate that increases in this glutathione pool can confer protection against some of these stressors.     

Glycyrrhizin exhibits potential chemopreventive activity on 12-O-tetradecanoyl phorbol-13-acetate-induced cutaneous oxidative stress and tumor promotion in swiss albino mice

Glycyrrhizin and its aglycone, glycyrrhetic acid has been found useful for various therapeutic purposes. Glycyrrhizin has been shown to possess many physiological functions like anti-inflammatory activity, detoxification and inhibition of carcinogenic promoters. 12-O-Tetradecanoyl phorbol-13-acetate (TPA), a well-known phorbal ester is known for its tumor promotion activity. The induction of inflammation in skin mediated by TPA is believed to be governed by cyclooxygenase (COX), lipoxygenase and ornithine decarboxylase (ODC). These markers of inflammatory responses are important for skin tumor promotion. In our present study, we studied the chemopreventive effect of glycyrrhizin on TPA (20 nmol/0.2 mL acetone/animal, topically)-induced oxidative stress and hyperproliferation markers in skin. TPA enhanced lipid peroxidation with reduction in the level of catalase, glutathione, glutathione peroxidase, glutathione reductase and glutathione-s-transferase. TPA treatment also enhanced ODC activity and [³H] thymidine incorporation into cutaneous DNA. Prophylactic treatment of mice with glycyrrhizin (2.0 & 4.0 mg/0.2 mL acetone/animal, topically) resulted in a significant decrease in cutaneous microsomal lipid peroxidation (P < 0.001) and recovery of cutaneous glutathione content (P < 0.001) and its dependent enzymes. A significant inhibition in ODC activity and DNA synthesis (P < 0.001) was also observed. Thus, the results demonstrate that pretreatment with glycyrrhizin is protective against TPA-induced oxidative stress and tumor promotion in Swiss albino mice.     

Binucleate cells in the Ehrlich ascites tumor. Autoradiographic labeling

An autoradiographic study was performed on binucleate and mitotic cells in the Ehrlich ascites tumor (EAT) untreated and after treatment with 5-fluorouracil (FU). The number of binucleate cells was greater in the treated tumor than in the controls. It was also observed that the number of labeled mitoses was greater in the Fu-treated tumor. Autoradiographic labeling showed that the cells that proved to be binucleate had previously passed through S-phase; thus, these cells belonged to the proliferative compartment.     

Diazepam effects on Ehrlich tumor growth and macrophage activity in mice

Besides the central gabaergic receptors described for benzodiazepines, peripheral type binding sites (PBR) were also identified for these molecules in endocrine steroidogenic tissues, immune organs and cells, such as macrophages and lymphocytes. PBR activation was reported to decrease innate immunity and host defense. The present experiment was designed to analyze the effects of diazepam on Ehrlich tumor growth, and on macrophage activity of Ehrlich tumor bearing mice. Results showed that diazepam (3.0 mg/kg/day, for 7 days) increased the number of Ehrlich tumor cells and the volume of tumor-induced ascitic fluid. These effects were not observed after smaller doses of diazepam, suggesting a dose-dependant effect. Furthermore, our results show that 3.0 mg/kg of diazepam, administered daily, for 2 days, decreased (1) the number of peritoneal leukocytes retrieved after injection of the Ehrlich tumor, (2) the percents of macrophage spreading, and (3) the levels of macrophage NO production. Diazepam (3.0 mg/kg/day for 2 days) had no effect on macrophage phagocytosis or on H2O2 production. The present data is discussed based on a direct and/or indirect action of diazepam. Particularly, our findings might be due to a direct effect of diazepam on PBRs present on macrophages and tumor cells, or could still be mediated by PBR stimulation within the hypothalamus-pituitary-adrenal (HPA) axis.     

Antioxidant activities of seabuckthorn (Hippophae rhamnoides) during hypoxia induced oxidative stress in glial cells

The present study reports the cytoprotective and antioxidant properties of alcoholic leaf extract of seabuckthorn (SBT) against hypoxia induced oxidative stress in C-6 glioma cells. Exposure of cells to hypoxia for 12 h resulted in a significant increase in cytotoxicity and decrease in mitochondrial transmembrane potential compared to the controls. Further an appreciable increase in nitric oxide and reactive oxygen species (ROS) production was noted which in turn was responsible for fall in intracellular antioxidant levels and GSH/GSSG ratio. There was a significant increase in DNA damage during hypoxia as revealed by comet assay. Pretreatment of cells with alcoholic leaf extract of SBT at 200 μg/ml significantly inhibited cytotoxicity, ROS production and maintained antioxidant levels similar to that of control cells. Further, the leaf extract restored the mitochondrial integrity and prevented the DNA damage induced by hypoxia. These results indicate that the leaf extract of SBT has strong antioxidant and cytoprotective activity against hypoxia induced oxidative injury. (Mol Cell Biochem 278: 9–14, 2005)     

Leukotriene-D4 induced cell shrinkage in Ehrlich ascites tumor cells

Summary The nature of the leukotriene-D₄ (LTD₄) induced cell shrinkage in Ehrlich ascites tumor cells has been investigated. LTD₄ treatment of Ehrlich cells induces net loss of cellular KCl and cell shrinkage independent of the initial cell volume. LTD₄ also produces water loss and reduction in cell volume when all extracellular and all intracellular Cl has been replaced by NO₃. On the other hand, LTD₄ fails to produce any significant changes in cell volume in the presence of the K-channel blocker quinine, suggesting that LTD₄ in Ehrlich cells induces Cl-independent K loss through the Ca²⁺-dependent K channels. However, the effect of physiological doses of LTD₄ on cell volume seems not to be as potent in Cl-free, NO₃ cells when compared to Cl-containing cells, indicating that LTD₄ in Ehrlich cells also provokes Cl-dependent K loss. LTD₄ seems not to produce K loss through an electroneutral K⁺/H⁺ exchange system. LTD₄ still produces Cl-independent K loss and cell shrinkage in the presence of the anticalmodulin drug pimozide but not in the presence of the LTD₄ receptor antagonist L-649,923 or the 5-lipoxygenase inhibitor NDGA. Pretreatment of the cells with pertussis toxin, which inactivates inhibitory guanine nucleotide binding proteins (G-proteins), leads to partial inhibition of the LTD₄-induced shrinkage. It is suggested that the LTD₄-induced activation of K and Cl transporting systems in Ehrlich ascites tumor cells is mediated via a G-protein coupled receptor and that LTD₄ might exert its effect through another lipoxygenase product. The Ca²⁺-calmodulin complex is not involved in the LTD₄-induced activation of K and Cl transporting systems.     

Effects of exogenous nitric oxide donor on antioxidant metabolism in wheat leaves under aluminum stress

With the enhancement of aluminum stress, the content of chlorophyll in wheat seedlings (Triticum aestivum L.) decreased dramatically. At 0.2 mM AlCl₃, the chlorophyll content halved. The aluminum-induced decrease in chlorophyll content could be alleviated by exogenous nitric oxide donor, sodium nitroprusside (SNP) in a dose-dependent manner. Treatment with SNP dramatically promoted the activities of superoxide dismutase, catalase, ascorbate peroxidase and increased the proline content, whereas it decreased hydrogen peroxide and malondialdehyde and maintained the level of soluble protein as compared with water controls. Therefore, NO donor enhanced the antioxidant capacity in wheat seedlings under aluminum stress.     

Further studies on the charge-related alterations of methotrexate transport in Ehrlich ascites tumor cells by ionic liposomes: Correlation with liposome-cell association

Summary Interaction of positively (phosphatidylcholine/stearylamine 51) or negatively (phosphatidylcholine/stearic acid 51) charged liposomes with Ehrlich ascites tumor cells for 1–5 min increases or decreases, respectively, the bidirectional fluxes of the folic acid analog, methotrexate. These effects on influx and efflux appear to be symmetrical since the liposomes do not change the intracellular level of methotrexate at the steady state. Influx kinetics show that these alterations result from an increase or decrease in theV _max with no change in theK _m ⁱⁿ . These effects appear to be specific for the methotrexate-tetrahydrofolate carrier system since the transport of other compounds which utilize this carrier, aminopterin, 5-methyltetrahydrofolate, and 5-formyltetrahydrofolate, is affected similarly to methotrexate, whereas, the transport of folic acid, a compound similar in structure and charge but not significantly transported by this carrier is unaffected by liposomes. Once cells are exposed to charged liposomes, the effects on methotrexate transport cannot be reversed by washing the cells free of the extracellular liposomes. If, however, cells are exposed to liposomes of one charge, washed and then exposed to liposomes of the opposite charge, methotrexate influx is reversed to control rates. The effects of charged liposomes on methotrexate influx were not abolished by treating the cells with neuraminidase, metabolic inhibitors or lowering the temperature to 4°C. Studies on the uptake of [¹⁴C] liposomes show that these effects are not proportional to the total amount of lipid associated with the cell but result from an initial rapid liposome-cell association that is not dependent on temperature or energy metabolism nor related to cell surface charge.     

Protective effect of quercetin on hyperglycemia,oxidative stress and DNA damage in alloxan induced type 2 diabetic mice

Aims

Quercetin is a natural polyphenolic flavonoid and acts as a quencher for reactive oxygen species generated by any physical or chemical action. In type 2 diabetes mellitus (T2DM) the basic characteristic feature is hyperglycemia which leads to complications involving oxidative stress. In view of this, the present study was conducted to examine the effect of quercetin in T2DM.

Main methods

A total of 18 mice were divided into three groups, vis control, diabetic and diabetic treated with quercetin. Fasting blood glucose (FBG) levels and anti-oxidant enzyme activity were assayed. Creatinine, urea, lipid peroxidation, GLUT4 expression and DNA damage were also measured.

Key findings

A significant decrease in FBG level and liver and kidney marker enzymes was observed in the quercetin treated group as compared to the diabetic one. Glutathione, SOD, catalase, and glutathione-S-transferase levels were also found to be increased on quercetin supplementation. Thiobarbituric acid-reactive substance level was decreased while GLUT4 expression levels were increased in the treated group. DNA damage was also affected positively by quercetin when subjected with single cell alkaline gel electrophoresis. Thus, we may suggest an anti-oxidant potential and protective effect of quercetin in T2DM mice.

Significance

From this study, we conclude that quercetin ameliorates hyperglycemia and oxidative stress, by blunting free radical induced toxicity in T2DM.     

The protective effects of nutritional antioxidant therapy on Ehrlich solid tumor-bearing mice depend on the type of antioxidant therapy chosen: histology, genotoxicity and hematology evaluations

Strong evidence indicates that reactive oxygen species (ROS) play an important role in the initiation as well as the promotion phase of carcinogenesis. Studies support the role of ROS in cancer, in part, by showing that dietary antioxidants act as cancer-preventive agents. Although results are promising, the research on this topic is still controversial. Thus, the aim of this study was to investigate whether vitamins C, E and pequi oil can, individually, provide prevention and/or be used afterward as an adjuvant in cancer therapy. Ehrlich solid tumor-bearing mice received antioxidant as follows: before tumor inoculation, before and after tumor inoculation (continuous administration), and after tumor inoculation; morphometric analyses of tumor, genotoxicity and hematology were then carried out. Antioxidant administrations before tumor inoculation effectively inhibited its growth in the three experimental protocols, but administrations after the tumor's appearance accelerated tumor growth and favored metastases. Continuous administration of pequi oil inhibited the tumor's growth, while the same protocol with vitamins E and C accelerated it, favoring metastasis and increasing oxidative stress on erythrocytes. Except for continuous administration with vitamin E, the development of ascites tumor metastases was linked with increased inflammation. Results suggest that the efficiency and applicability of antioxidants in the medical clinic can depend not only on the nature of the antioxidant, the type and stage of cancer being treated and the prevailing oxygen partial pressure in the tissues, but also on the type of antioxidant therapy chosen.     

Ameliorative effect of an oxovanadium (IV) complex against oxidative stress and nephrotoxicity induced by cisplatin

Objective: The present study was designed to investigate the chemoprotective efficacy of an L-cysteine-based oxovanadium (IV) complex, namely, oxovanadium (IV)-L-cysteine methyl ester complex (VC-IV) against cisplatin (CDDP)-induced renal injury in Swiss albino mice.

Methods: CDDP was administered intraperitoneally (5 mg/kg body weight) and VC-IV was administered orally (1 mg/kg body weight) in concomitant and 7 days pre-treatment schedule.

Results: CDDP-treated mice showed marked kidney damage and renal failure. Administration of VC-IV caused significant attenuation of renal oxidative stress and elevation of antioxidant status. VC-IV also significantly decreased serum levels of creatinine and blood urea nitrogen, and improved histopathological lesions. Western blot analysis of the kidneys showed that VC-IV treatment resulted in nuclear translocation of nuclear factor E2-related factor 2 (Nrf2) through modulation of cytosolic Kelch-like ECH-associated protein 1. Thus, VC-IV stimulated Nrf2-mediated activation of antioxidant response element (ARE) pathway and promoted expression of ARE-driven cytoprotective proteins, heme oxygenase 1 and NAD(P)H:quinone oxidoreductase 1, and enhanced activity of antioxidant enzymes. Interestingly, VC-IV did not alter the bioavailability and renal accumulation of CDDP in mice.

Discussion: In this study, VC-IV exhibited strong nephroprotective efficacy by restoring antioxidant defense mechanisms and hence may serve as a promising chemoprotectant in cancer chemotherapy.     

Salicylic acid increases tolerance to oxidative stress induced by hydrogen peroxide accumulation in leaves of cadmium-exposed flax (Linum usitatissimum L.)

The aim of this study is to investigate the impacts of exogenous salicylic acid (SA) pretreatments on hydrogen peroxide (H₂O₂) accumulation, protein oxidation, and H₂O₂-scavenging enzymes in leaves of Cd-treated flax seedlings. Cd-enhanced H₂O₂ levels were related to increased activities of guaiacol peroxidase (POX, EC 1.11.1.7) and ascorbate peroxidase (APX, EC 1.11.1.11), and were independent of changes in catalase (CAT, EC 1.11.1.6) and superoxide dismutase (SOD, EC 1.15.1.1) activities. In control flax seedlings, exogenous SA pretreatments inhibited the activity of CAT, resulted in an enhanced production of H₂O₂ suggesting that SA requires H₂O₂ to initiate an oxidative stress. However, although leaves of Cd-free flax seedlings pretreated with SA accumulated in vivo H₂O₂ by 1.2-fold compared with leaves of Cd-only exposed ones; the damage to growth and proteins after the exposure to Cd was significantly less, indicating that SA can regulate the Cd-induced oxidative stress. Moreover, the Cd-treated seedlings primed with SA exhibited a higher level of total antioxidant capacities and increased activities of H₂O₂-detoxifying enzymes.     

Involvement of protein tyrosine phosphorylation and reduction of cellular sulfhydryl groups in cell death induced by 1' -acetoxychavicol acetate in Ehrlich ascites tumor cells

Elucidation of the mechanisms underlying potential anticancer drugs continues and unraveling these mechanisms would not only provide a conceptual framework for drug design but also promote use of natural products for chemotherapy. To further evaluate the efficacy of the anticancer activity of 1'-acetoxychavicol acetate (ACA), this study investigates the underlying mechanisms by which ACA induces death of Ehrlich ascites tumor cells. ACA treatment induced loss of cell viability, and Western blotting analysis revealed that the compound stimulated tyrosine phosphorylation of several proteins with 27 and 70 kDa proteins being regulated in both dose- and time-dependent manner prior to loss of viability. Protein tyrosine kinase inhibitor herbimycin A moderately protected cells from ACA-induced toxicity. In addition, cellular glutathione and protein sulfydryl groups were also significantly reduced both dose- and time-dependently during evidence of cell death. Replenishing thiol levels by antioxidant, N-acetylcysteine (NAC), an excellent supplier of glutathione and precursor of glutathione, substantially recovered the viability loss, but the recovery being time-dependent, as late addition of NAC (at least 30 min after ACA addition to cultures) was, however, ineffective. Addition of NAC to ACA treated cultures also abolished tyrosine phosphorylation of the 27 kDa protein. These results, at least partly, identify cellular sulfhydryl groups and protein tyrosine phosphorylation as targets of ACA cytotoxicity in tumor cells.     

外源NO对南方红豆杉幼苗光合色素及抗氧化酶的影响

以4年生南方红豆杉幼苗为实验材料,通过对南方红豆杉幼苗喷施不同浓度外源一氧化氮（NO）供体硝普钠溶液（0、0.01、0.1、0.5和1 mmol·L^-1SNP）,测定光合色素含量、抗氧化酶活性、丙二醛（MDA）含量和过氧化氢（H₂O₂）含量等生理指标,以探讨不同浓度外源NO对南方红豆杉叶片光合色素和抗氧化酶的影响。结果表明：喷施低浓度（0.01、0.1 mmol·L^-1）SNP可显著提高南方红豆杉叶片的叶绿素a、叶绿素b、类胡萝卜素和总叶绿素含量,增加叶绿素a/b的比值,而喷施高浓度（0.5、1 mmol·L^-1）SNP降低了叶片的光合色素含量。随着外源NO供体浓度的增加,叶片过氧化氢酶(CAT)活性显著增加,过氧化物酶(POD)活性先增加后降低。此外,处理前期,低浓度SNP处理明显提高了抗坏血酸过氧化物酶(APX)活性,而高浓度SNP处理显著降低了APX活性,处理后期APX活性随SNP浓度的增加而显著下降。喷施低浓度SNP可有效提高超氧化物歧化酶(SOD)活性和增加可溶性蛋白含量,降低MDA和H₂O₂的含量,而喷施高浓度SNP显著增加了MDA和H₂O₂的含量。因此,低浓度的SNP（<0.5 mmol·L^-1）处理南方红豆杉幼苗,可增加其叶绿素含量,提高抗氧化酶活性,降低MDA和H₂O₂的含量,而高浓度的SNP（≥0.5 mmol·L^-1）处理会降低叶绿素含量,提高H₂O₂含量,增加细胞膜质过氧化程度,从而对南方红豆杉幼苗造成一定伤害。     

NO在CCK—8减轻肿瘤坏死因子诱导兔肺动脉反应性变化中的作用

为探讨八肽胆囊收缩素（CCK－8）缓解内毒素休克时肺动脉高压的作用机制,应用离体血管环张力测定技术及一氧化氮合酶（NOS）检测方法,观察了一氧化氮（NO）在CCK－8减轻肿瘤坏死因子－α（tumor necrosis factor-al-pha,TNF-α）的抑制肺动脉内皮依赖性舒张反应中的作用。结果显示：TNF－α（4000U／ml）孵育2h时,肺动脉对10^-6mol/L苯肾上腺素(phenylephrine,PE）和10^-6mol/L乙酰胆碱（ACh）的收缩反应及内皮依赖性舒张反应均无明显变化。TNF－α孵育7或14h时,肺动脉对10^-6mol/L ACh介导的内皮依赖性舒张反应降低,CCK－8（0.5μg/ml）可逆转TNF－α的上述作用,CCK－8本身对正常肺动脉反应性无明显影响。TNF－α、CCK－8对PE引起的收缩反应无显著影响。L－精氨酸（L－Arg）可使TNF－α7h内皮依赖性舒张作用恢复。氨基胍（AG）不影响各组肺动脉对10^-6mol/L ACh的内皮依赖性舒张反应,而使TNF－α组肺动脉环对10^-6mol/L PE的收缩反应显著增加。L－硝基精氨酸（L－NNA）使各组肺动脉环对10^-6mol/L ACh反应由舒张变为收缩,对10^-6mol/L PE的收缩反应显著增强。检测7h各组NOS活性,TNF－α组、TNF－α＋CCK－8组均较对照组显著增加,CCK－8组与对照组比较无显著差异。上述结果提示,CCK－8可逆转TNF－α对内皮依赖性舒张反应的抑制作用,此作用可能与NO有关。     

Involvement of polyamines in evening primrose extract-induced apoptosis in Ehrlich ascites tumor cells

Summary. We previously demonstrated that evening primrose extract (EPE) induced apoptosis and inhibited the DNA synthesis in Ehrlich ascites tumor cells (EATC) and suggested that EPE-induced inhibition of the growth of EATC are via at least two pathway differentially modulated by reactive oxygen species, notably intracellular peroxides. These are (a) the EPE-induced apoptosis pathway which is dependent on increases in hydrogen peroxide and (b) the EPE-induced inhibition of cell proliferation which is hydrogen peroxide independent. In this study, EPE brought about a significant decrease in intracellular polyamine levels. Furthermore, the addition of polyamines reversed the EPE-induced decrease in cell viability and suppressed the EPE-induced increase in intracellular hydrogen peroxides. However, the addition of polyamines did not reverse EPE-induced decrease in DNA synthesis and phosphorylation of Rb protein, and EPE-induced translocation of AIF. These results suggest the involvement of polyamines in the EPE-induced apoptosis pathway which is dependent on increase in hydrogen peroxide.