Induced oxidative stress and cell death in the A549 lung adenocarcinoma cell line by ionizing radiation is enhanced by supplementation with docosahexaenoic acid

Both ionizing radiation and docosahexaenoic acid (DHA), an n-3 polyunsaturated fatty acid (PUFA), have been shown to inhibit tumor cell growth at least in part by increasing oxidative stress. In this study, the effects of ionizing radiation, DHA, or a combination of the two on cell proliferation, anchorage-independent growth, apoptosis, and lipid peroxidation in A549 lung adenocarcinoma cells were examined. In this study, significant decreases in cell proliferation and colony formation were noted for ionizing radiation or DHA treatments, whereas a combination of the two showed significant reductions over either treatment alone. Conversely, lipid peroxidation and apoptotic cell death showed significant increases with ionizing radiation and DHA treatments, whereas cells receiving both treatments demonstrated further significant increases. Moreover, addition of vitamin E, an antioxidant, was able to completely reverse lipid peroxidation and cell death due to ionizing radiation and partially reverse these changes in DHA treatments. Finally, the preferential incorporation of DHA into lung and xenograft compared to liver tissue is demonstrated in an in vivo model. These findings confirm the potential of DHA supplementation to enhance the treatment of lung cancer using ionizing radiation by increasing oxidative stress and enhancing tumor cell death.     

Docosahexaenoic acid abundance in the brain: a biodevice to combat oxidative stress

Docosahexaenoic acid (DHA) (22:6) is a polyunsaturated fatty acid of the n - 3 series which is believed to be a molecular target for lipid peroxides (LPO) formation. Its ubiquitous nature in the nervous tissue renders it particularly vulnerable to oxidative stress, which is high in brain during normal activity because of high oxygen consumption and generation of reactive oxygen species (ROS). Under steady state conditions potentially harmful ROS and LPO are maintained at low levels due to a strong antioxidant defense mechanism, which involves several enzymes and low molecular weight reducing compounds. The present review emphasizes a paradox: a discrepancy between the expected high oxidability of the DHA molecule due to its high degree of unsaturation and certain experimental results which would indicate no change or even decreased lipid peroxidation when brain tissue is supplied or enriched with DHA. The following is a critical review of the experimental data relating DHA levels in the brain to lipid peroxidation and oxidative damage there. A neuroprotective role for DHA, possibly in association with the vinyl ether (VE) linkage of plasmalogens (pPLs) in combating free radicals is proposed.     

Gallic acid, an antioxidant, exhibits antiapoptotic potential in normal human lymphocytes: A Bcl-2 independent mechanism

Oxidative stress, produced as a consequence of normal metabolism or induced by extraneous stimuli, has been proved to be a mediator of cell death. The inherent antioxidant defense system and exogenous antioxidants can help the body to combat this oxidative stress-induced cell death. In this study, we explored the antiapoptotic potential of gallic acid, a dietary phenolic having antioxidative and anticarcinogenic properties, in normal human peripheral blood lymphocytes (PBLs). Incubation of PBLs with 100 microM H2O2 for 1.5-2.0 h induced phosphatidyl serine externalisation, lipid peroxidation and high molecular weight DNA fragmentation. Pretreatment of lymphocytes with gallic acid for 18 h could effectively inhibit lipid peroxidation and apoptosis induced by oxidative stress. Treatment of PBLs with gallic acid failed to induce any change in the expression of Bcl-2, an antiapoptotic protein. It seems that the protection provided by gallic acid was due to its direct action in the scavenging of free radicals as it was found to be a stronger antiradical than trolox, a water- soluble analogue of vitamin E.     

Antioxidants in dietary oils: their potential role in breast cancer prevention

Edible oils contain variable amounts of natural antioxidants such as vitamin E. Antioxidants act not only to prevent lipid peroxidation and free-radical production, but also display potent anticancer activity. The vitamin E family of compounds is divided into two subgroups called tocopherols and tocotrienols, but only tocotrienols display potent anticancer activity at treatment doses that have little or no effect on normal cell growth or viability. Palm oil contains the highest concentrations of natural tocotrienols. Tocotrienols induced apoptosis or programmed cell death in breast cancer cells. Morphological and biochemical characteristics of apoptosis, such as nuclear and cytoplasmic condensation and DNA fragmentation, are mediated by the activation of cysteine proteases called caspases. Apoptosis is triggered by the activation of initiator caspases (caspase-8 or 9) that subsequently activate effector caspases (caspase-3, 6, and 7). Studies were conducted using the highly malignant +SA mouse mammary epithelial cell line to determine if tocotrienol-induced programmed cell death is mediated through the caspase-8 or caspase-9 pathway. Treatment with cytotoxic doses of tocotrienol resulted in a large increase in caspase-8 and caspase-3, but not caspase-9 activity. Combined treatment of tocotrienol with selective caspase-8 or caspase-3 inhibitors completely blocked tocotrieno-linduced apoptosis and activation of caspase-8 and caspase-3, respectively. These findings demonstrate that tocotrienol-induced apoptosis in highly malignant mammary epithelial cells is mediated through caspase-8 activation, and may provide essential information necessary for understanding the potential health benefits of these compounds in preventing and/or reducing the risk of breast cancer in women.     

Antioxidant, antimutagenic, and antitumor effects of pine needles (Pinus densiflora)

Pine needles (Pinus densiflora Siebold et Zuccarini) have long been used as a traditional health-promoting medicinal food in Korea. To investigate their potential anticancer effects, antioxidant, antimutagenic, and antitumor activities were assessed in vitro and/or in vivo. Pine needle ethanol extract (PNE) significantly inhibited Fe(2+)-induced lipid peroxidation and scavenged 1,1-diphenyl- 2-picrylhydrazyl radical in vitro. PNE markedly inhibited mutagenicity of 2-anthramine, 2-nitrofluorene, or sodium azide in Salmonella typhimurium TA98 or TA100 in Ames tests. PNE exposure effectively inhibited the growth of cancer cells (MCF-7, SNU-638, and HL-60) compared with normal cell (HDF) in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. In in vivo antitumor studies, freeze-dried pine needle powder supplemented (5%, wt/wt) diet was fed to mice inoculated with Sarcoma-180 cells or rats treated with mammary carcinogen, 7,12-dimethylbenz[a]anthracene (DMBA, 50 mg/kg body weight). Tumorigenesis was suppressed by pine needle supplementation in the two model systems. Moreover, blood urea nitrogen and aspartate aminotransferase levels were significantly lower in pine needle-supplemented rats in the DMBA-induced mammary tumor model. These results demonstrate that pine needles exhibit strong antioxidant, antimutagenic, and antiproliferative effects on cancer cells and also antitumor effects in vivo and point to their potential usefulness in cancer prevention.     

γ-亚麻酸对人癌细胞蛋白质合成和脂质过氧化的影响

本文报告γ-亚麻酸对体外培养人癌细胞生长、蛋白质合成和脂质过氧化的影响。结果表明,γ-亚麻酸抑制人癌细胞生长和20、30kD蛋白质合成,并增强培养人结肠癌细胞的脂质过氧化,α-生育酚则部分抵消γ-亚麻酸的作用。上述结果提示,γ-亚麻酸的抗肿瘤效果可能是由于其对蛋白质合成的抑制作用,而蛋白质合成的抑制则可能是由增强的脂质过氧化所致。     

Chronic exposure to high levels of dietary iron fortification increases lipid peroxidation in the mucosa of the rat large intestine.

There is increasing evidence that excess dietary iron may be a risk factor for colorectal cancer. However, the majority of animal studies looking at possible mechanism have used unrealistically high concentrations of iron. The current study was designed to test whether chronic exposure to high levels of iron fortification affects the free radical generating capacity of the lumenal contents, mucosal lipid peroxidation and crypt cell proliferation. Rats were fed diets containing either 29 mg/kg or 102 mg/kg of elemental iron for 6 mo. The free radical generating capacity of lumenal contents was assessed using an in vitro assay. Crypt cell proliferation rate was measured in tissues taken from the cecum and colon, with the remaining tissue being used for the assessment of lipid peroxidation. Chronic feeding of iron did not increase crypt cell proliferation rate in either the colon or cecum, but it was associated with an increase in free radical generating capacity in the colon and increased lipid peroxidation, particularly in the cecum. These results may be relevant to epidemiological evidence showing that dietary iron is associated with the risk of proximal colon cancer in humans.     

Induced Oxidative Stress and Cell Death in the A549 Lung Adenocarcinoma Cell Line by Ionizing Radiation Is Enhanced by Supplementation With Docosahexaenoic Acid

Both ionizing radiation and docosahexaenoic acid (DHA), an n-3 polyunsaturated fatty acid (PUFA), have been shown to inhibit tumor cell growth at least in part by increasing oxidative stress. In this study, the effects of ionizing radiation, DHA, or a combination of the two on cell proliferation, anchorage-independent growth, apoptosis, and lipid peroxidation in A549 lung adenocarcinoma cells were examined. In this study, significant decreases in cell proliferation and colony formation were noted for ionizing radiation or DHA treatments, whereas a combination of the two showed significant reductions over either treatment alone. Conversely, lipid peroxidation and apoptotic cell death showed significant increases with ionizing radiation and DHA treatments, whereas cells receiving both treatments demonstrated further significant increases. Moreover, addition of vitamin E, an antioxidant, was able to completely reverse lipid peroxidation and cell death due to ionizing radiation and partially reverse these changes in DHA treatments. Finally, the preferential incorporation of DHA into lung and xenograft compared to liver tissue is demonstrated in an in vivo model. These findings confirm the potential of DHA supplementation to enhance the treatment of lung cancer using ionizing radiation by increasing oxidative stress and enhancing tumor cell death.     

Iron in neoplastic disease

Promotion of chemically induced esophageal cancer by ethanol may include the generation of highly reactive free radicals and thus may be preventable by the antioxidant vitamin E. In the present study, female C57BL/6 mice received N‐nitrosomethylbenzylamine (NMBzA, 0.2 mg/kg ig) three times a week for three weeks. After this esophageal carcinogenic treatment, mice were fed a nutritionally adequate liquid diet with 30% of the calories supplied by ethanol or an isocaloric carbohydrate with or without supplemental α‐tocopherol (142 mg/kg diet). As a marker of in vivo lipid peroxidation, exhaled ethane was collected and measured 24 hours “before”; the mice were killed after 20 weeks of dietary treatment. Hepatic malondial‐dehyde, lipid fluorescence, and conjugated dienes were determined as markers of products of lipid peroxidation and serum aminotransferases as indexes of liver toxicity. Hepatic liver concentrations of vitamins A and E and the size and frequency of esophageal tumors were also assessed. Ethanol consumption after NMBzA administration significantly increased (p < 0.05) the size and frequency of esophageal tumors. These ethanol‐promoted effects were accompanied by increases in indexes of in vivo and accumulated products of lipid peroxidation. Similarly treated animals that received supplemental dietary vitamin E showed significant reductions (p < 0.05) in mean tumor size and frequency of tumors as well as a decrease in the indexes of hepatic lipid peroxidation. The results suggest that promotion of NMBzA‐induced esophageal tumors by ethanol may in part result from increased lipid peroxidation and that vitamin E reduces carcinogenicity of NMBzA or ethanol promoter effects by inhibiting lipid peroxidation.     

Linoleic acid suppresses colorectal cancer cell growth by inducing oxidant stress and mitochondrial dysfunction

Some polyunsaturated fatty acids (PUFAs), if not all, have been shown to have tumoricidal action, but their exact mechanism(s) of action is not clear. In the present study, we observed that n-6 PUFA linoleic acid (LA) inhibited tumor cell growth at high concentrations (above 300 μM); while low concentrations (100-200 μM) promoted proliferation. Analysis of cell mitochondrial membrane potential, reactive oxygen species (ROS) formation, malondialdehyde (MDA) accumulation and superoxide dismutase (SOD) activity suggested that anti-cancer action of LA is due to enhanced ROS generation and decreased cell anti-oxidant capacity that resulted in mitochondrial damage. Of the three cell lines tested, semi-differentiated colorectal cancer cells RKO were most sensitive to the cytotoxic action of LA, followed by undifferentiated colorectal cancer cell line (LOVO) while the normal human umbilical vein endothelial cells (HUVEC) were the most resistant (the degree of sensitivity to LA is as follows: RKO > LOVO > HUVEC). LA induced cell death was primed by mitochondrial apoptotic pathway. Pre-incubation of cancer cells with 100 μM LA for 24 hr enhanced sensitivity of differentiated and semi-differentiated cells to the subsequent exposure to LA. The relative resistance of LOVO cells to the cytotoxic action of LA is due to a reduction in the activation of caspase-3. Thus, LA induced cancer cell apoptosis by enhancing cellular oxidant status and inducing mitochondrial dysfunction.     

Accelerating effect of 12-keto oleic acid on lipid peroxide and fluorescent productions in mouse liver homogenate.

12-Keto oleic acid is generally considered to be a secondary degradation product of peroxides produced by lipid peroxidation. The acid was added to a mouse liver homogenate or to a bovine serum albumin and its influences on lipid peroxidation and fluorescent production were investigated and compared with other acids. Just as with vitamin E deficiency, 12-keto oleic acid was shown to increase lipid peroxide formation and fluorescence productiod directly and indirectly. The increase of lipid peroxide formation was caused directly through the increase of the free radical production, and indirectly through change of the biomembrane structure. The fluorescence production increase was caused directly by reaction of the 12-keto oleic acid itself, and indirectly by acceleration of the lipid peroxidation.     

Punicic Acid Triggers Ferroptotic Cell Death in Carcinoma Cells

Plant-derived conjugated linolenic acids (CLnA) have been widely studied for their preventive and therapeutic properties against diverse diseases such as cancer. In particular, punicic acid (PunA), a conjugated linolenic acid isomer (C18:3 c9t11c13) present at up to 83% in pomegranate seed oil, has been shown to exert anti-cancer effects, although the mechanism behind its cytotoxicity remains unclear. Ferroptosis, a cell death triggered by an overwhelming accumulation of lipid peroxides, has recently arisen as a potential mechanism underlying CLnA cytotoxicity. In the present study, we show that PunA is highly cytotoxic to HCT-116 colorectal and FaDu hypopharyngeal carcinoma cells grown either in monolayers or as three-dimensional spheroids. Moreover, our data indicate that PunA triggers ferroptosis in carcinoma cells. It induces significant lipid peroxidation and its effects are prevented by the addition of ferroptosis inhibitors. A combination with docosahexaenoic acid (DHA), a known polyunsaturated fatty acid with anticancer properties, synergistically increases PunA cytotoxicity. Our findings highlight the potential of using PunA as a ferroptosis-sensitizing phytochemical for the prevention and treatment of cancer.     

Interaction between ascorbic acid and acetylsalicylic acid and their effects on nutritional status in man

Healthy adults were given four diets, each one for one week: Low ascorbic acid diet, low ascorbic acid diet plus acetylsalicylic acid (3 g/d), high ascorbic acid diet (1 g/d) and high ascorbic acid diet plus acetylsalicylic acid. At low ascorbic acid intake, acetylsalicylic acid increased urinary ascorbic acid, but at high ascorbic acid intake, acetylsalicylic acid instead decreased urinary ascorbic acid. The latter effect was probably due to an inhibited intestinal absorbtion of ascorbic acid, and the former effect may reflect decreased protein binding and tissue uptake of ascorbic acid caused by acetylsalicylic acid. In no instance, acetylsalicylic acid affected plasma ascorbic acid. The effect of ascorbic acid on substances related to lipid peroxidation was investigated. The high ascorbic acid diets decreased plasma lipoperoxide and retinol binding protein. No change was observed in serum tocopherol, iron status, erythrocyte lipid fluorescence, plasma ceruloplasmin, urinary and plasma selenium and glutathione peroxidase activity. Thus, one-week supplementation of ascorbic acid seems to have only marginal effects on lipid peroxidation and antioxidant status.     

Docosahexaenoic Acid Abundance in the Brain: A biodevice to Combat Oxidative Stress

Abstract

Docosahexaenoic acid (DHA) (22:6) is a polyunsaturated fatty acid of the n?3 series which is believed to be a molecular target for lipid peroxides (LPO) formation. Its ubiquitous nature in the nervous tissue renders it particularly vulnerable to oxidative stress, which is high in brain during normal activity because of high oxygen consumption and generation of reactive oxygen species (ROS). Under steady state conditions potentially harmful ROS and LPO are maintained at low levels due to a strong antioxidant defense mechanism, which involves several enzymes and low molecular weight reducing compounds. The present review emphasizes a paradox: a discrepancy between the expected high oxidability of the DHA molecule due to its high degree of unsaturation and certain experimental results which would indicate no change or even decreased lipid peroxidation when brain tissue is supplied or enriched with DHA. The following is a critical review of the experimental data relating DHA levels in the brain to lipid peroxidation and oxidative damage there. A neuroprotective role for DHA, possibly in association with the vinyl ether (VE) linkage of plasmalogens (pPLs) in combating free radicals is proposed.     

High intakes of vegetables,berries, and apples combined with a high intake of linoleic or oleic acid only slightly affect markers of lipid peroxidation and lipoprotein metabolism in healthy subjects

BACKGROUND: A high consumption of vegetables and fruit is associated with decreased risk of ischemic heart disease and several cancers. The pathophysiology of these diseases involves free radical mechanisms. Diet may either enhance or diminish oxidative stress in the body. OBJECTIVE: We studied the effects of high and low intakes of vegetables, berries, and apples on markers of lipid peroxidation and lipoprotein metabolism in subjects consuming diets high in linoleic or oleic acid. DESIGN: For 6 wk, healthy men and women (n = 77; aged 19-52 y) consumed 1 of 4 controlled isoenergetic diets rich in either linoleic acid (11% of energy) or oleic acid (12% of energy) and containing either 815 or 170 g vegetables, berries, and apples/10 MJ. Nineteen healthy volunteers served as control subjects. Several markers of dietary compliance (plasma fatty acids, vitamin C, carotenoids, and quercetin), lipid peroxidation [ex vivo LDL oxidation, plasma and LDL thiobarbituric acid-reactive substances, paraoxonase (EC 3.1.8.1), and urinary 8-iso-prostaglandin F(2)(alpha)], and lipoprotein metabolism (plasma lipids, apolipoproteins, and lipid transfer protein activities) were measured from samples collected before and at the end of the experimental period. RESULTS: Plasma fatty acid composition and antioxidant concentrations showed that compliance with the diets was good. However, there were no significant differences between the diets in the markers of lipid peroxidation and lipoprotein metabolism. CONCLUSIONS: In healthy volunteers with adequate vitamin intakes, 6-wk diets differing markedly in the amounts of linoleic and oleic acid and vegetables, berries, and apples did not differ in their effects on lipid peroxidation or lipoprotein metabolism.     

Fatty acids as a potentially helpful supplement in cancer therapy

This review presents pro- and anticancer effects of fatty acids in vitro and in vivo. The epidemiological and experimental data indicate that short-chain saturated and long-chain unsaturated omega-3 fatty acids exert protective effects against some cancers. In the contrary, omega-6 fatty acids are rather procancerous and can increase tumour proliferation. The possible mechanisms are still not fully understood and are very variable including: suppression of neoplastic transformation, direct cytotoxicity, apoptosis induction, antiangiogenicity etc. Experimental data indicate that fatty acid composition of cancer cells in cultures or in animals can be modified to make the cells more susceptible to lipid peroxidation, increasing the cell damage due to oxidant stress and make the cells more sensitive to chemotherapy. It is reasonable to suppose that fatty acids supplementation can make an enrichment of traditional tools for modern anticancer strategies.     

Vitamin E inhibition of lipid peroxidation and ethanol-mediated promotion of esophageal tumorigenesis.

Promotion of chemically induced esophageal cancer by ethanol may include the generation of highly reactive free radicals and thus may be preventable by the antioxidant vitamin E. In the present study, female C57BL/6 mice received N-nitrosomethylbenzylamine (NMBzA, 0.2 mg/kg ig) three times a week for three weeks. After this esophageal carcinogenic treatment, mice were fed a nutritionally adequate liquid diet with 30% of the calories supplied by ethanol or an isocaloric carbohydrate with or without supplemental alpha-tocopherol (142 mg/kg diet). As a marker of in vivo lipid peroxidation, exhaled ethane was collected and measured 24 hours "before" the mice were killed after 20 weeks of dietary treatment. Hepatic malondialdehyde, lipid fluorescence, and conjugated dienes were determined as markers of products of lipid peroxidation and serum aminotransferases as indexes of liver toxicity. Hepatic liver concentrations of vitamins A and E and the size and frequency of esophageal tumors were also assessed. Ethanol consumption after NMBzA administration significantly increased (p less than 0.05) the size and frequency of esophageal tumors. These ethanol-promoted effects were accompanied by increases in indexes of in vivo and accumulated products of lipid peroxidation. Similarly treated animals that received supplemental dietary vitamin E showed significant reductions (p less than 0.05) in mean tumor size and frequency of tumors as well as a decrease in the indexes of hepatic lipid peroxidation. The results suggest that promotion of NMBzA-induced esophageal tumors by ethanol may in part result from increased lipid peroxidation and that vitamin E reduces carcinogenicity of NMBzA or ethanol promoter effects by inhibiting lipid peroxidation.     

血清对DHA抑制肺癌A549细胞生长的影响及DHA的抗癌机制

目的研究血清对体外培养条件下二十二碳六稀酸(DHA)抑癌作用的影响及DHA的抗癌机制。方法采用MTT法观察血清刺激和无血清情况下DHA对体外培养的肺癌A549细胞的生长抑制作用,同时采用免疫印迹方法检测DHA对血清诱导的蛋白激酶B(Akt)磷酸化的影响。结果在无血清和低浓度血清(<2%)下,DHA明显抑制A549细胞的生长;在高浓度血清下,DHA则呈现促进A549生长的作用。无血清下,DHA对血清诱导的Akt的活化具有抑制作用。结论体外培养条件下,培养基中无血清时DHA可能通过脂质过氧化降低Akt的活化、抑制A549细胞的生长;高血清含量则明显干扰DHA的抗癌活性。     

Genotoxic effect of chronic exposure to DDT on lymphocytes, oral mucosa and breast cells of female rats

The genotoxicity of some environmental contaminants may affect human health directly by damaging genetic material and thus plays an important role in cancer development. Xenoestrogens are one kind of environmental pollutants that may alter hormonal routes or directly affect DNA. The number of available biomarkers used to assess genetic risk and cancer is very extensive. The present study evaluated genotoxicity produced by the pesticide DDT on systemic and mammary gland cells obtained from adult female Wistar rats. Oral mucosa cells micronuclei were assessed; the comet assay in peripheral blood-isolated lymphocytes and mammary epithelial cells was also carried out. Additionally, oxidative stress was studied in mammary tissue through a lipid peroxidation assay. Our data showed an increase in lipid peroxidation, product of an increase in free oxygen radical levels, which leads to an oxidative stress status. Our results suggest that DDT is genotoxic, not only for lymphocytes but also to mammary epithelial cells.