Effect of Antioxidant Vitamins on Radiation-Induced Apoptosis in Cells of a Human Lymphoblastic Cell Line

Antioxidant Supplementation: A Linchpin in Radiation-Induced Enteritis

Radiation enteritis is one of the most feared complications of abdominal and pelvic regions. Thus, radiation to abdominal or pelvic malignancies unavoidably injures the intestine. Because of rapid cell turnover, the intestine is highly sensitive to radiation injury, which is the limiting factor in the permissible dosage of irradiation. Bowel injuries such as fistulas, strictures, and chronic malabsorption are potentially life-threatening complications and have an impact on patient quality of life. The incidence of radiation enteritis is increasing because of the current trend of combined chemotherapy and radiation. The consequences of radiation damage to the intestine may result in considerable morbidity and even mortality. The observed effects of ionizing radiation are mediated mainly by oxygen-free radicals that are generated by its action on water and are involved in several steps of signal transduction cascade, leading to apoptosis. The oxyradicals also induce DNA strand breaks and protein oxidation. An important line of defense against free radical damage is the presence of antioxidants. Therefore, administration of antioxidants may ameliorate the radiation-induced damage to the intestine.

Effect of antioxidant supplementation on digestive enzymes in radiation induced intestinal damage in rats

PURPOSE

Intestinal mucosa, a rapidly proliferating tissue, is highly sensitive to radiation and undergoes apoptosis as a consequence of over generation of oxidative free radicals and the lack of the antioxidants. Thus the present study was designed to investigate the intestinal damage induced by radiation and to study if supplementation of the diet with antioxidant vitamins could ameliorate the intestinal damage and its digestive activity, as determined by the expression of various border enzymes.

MATERIALS AND METHODS

Swiss Albino rats (150-200 g body weight) were divided into six groups. Group I: Control untreated; Group II: Irradiated; Group III: Irradiated + vitamin A; Group IV: Irradiated + vitamin C; Group V: Irradiated + vitamin E; and Group VI: Irradiated + lycopene. Animals were exposed to whole body γ-radiation from (60)Co at the rate of 8 Gy for 15 min/rat. Intestinal morphology and changes in various digestive enzymes together with, DNA damage was studied in six groups and each group consisted of 18 animals.

RESULTS

The gastrointestinal toxicity resulted in malabsorption, diarrhoea, weight loss, loss of appetite, abdominal haemorrhage and hair loss. The activities of sucrase and alkaline phosphatase were elevated and those of lactase, leucine aminopeptidase (LAP) and gamma-glutamyl transpeptidase or tranferase (γ-GTP) were markedly reduced. Antioxidant vitamin A, C or E supplementations prevented changes in brush border enzyme activities as compared to lycopene administration in rat intestine by radiation exposure. Intestinal histology showed that the vitamin supplementation to irradiated rats minimized the intestinal damage in rats.

CONCLUSION

These findings suggest that the epithelial lining of the intestine is highly sensitive to radiation exposure and supplementation of antioxidant vitamins is helpful in minimizing the intestinal damage and supplementation by vitamin E was most potent in ameliorating the intestinal aberrations.

Radioprotective agents for the prevention of side effects induced by radioiodine-131 therapy

Radioiodine 131 (131I) has been used worldwide for the ablation of remnant thyroidal tissue after surgery or as the first-line treatment for Graves’ disease. Although the use of 131I is becoming increasingly prevalent, there is evidence suggesting that this treatment is associated with side effects such as salivary gland dysfunction and an increased risk of leukemia. This article aims to review the potential use of radioprotective agents and the side effects induced by 131I therapy. Several synthetic and natural compounds have been investigated in preclinical and clinical studies. The protective agents reduced the toxicity of 131I, mainly in the salivary glands, and mitigated the genetic damage through different mechanisms. There are limited clinical studies evaluating the use of radioprotective agents in patients undergoing radioiodine therapy. However, lemon candies, lemon juice and sugarless chewing gum have been proposed to be beneficial for minimizing the side effects of radioiodine within the salivary glands.

Vitamin-induced intracellular electrons are the mechanism for their well-known beneficial effects: a review

A new conception of the action mechanisms of vitamins and some other compounds without a vitamin status is briefly presented. It is based on results obtained through pulse radiolysis, molecular radiation biological investigations, and in vitro studies. The data clearly show that antioxidant vitamins (C, E, β-carotene) and B vitamins and related compounds possess the capability to emit "solvated electrons" in aqueous solutions or polar media. In consequence, the well-known vitamin effects are attributed to the action of the emitted solvated electrons and the resulting vitamin free radicals rather than the vitamin molecules per se, as generally accepted.

Investigation of cytotoxic and mutagenic effects of Malpighia glabra L. (barbados cherry) fruit pulp and vitamin C on plant and animal test systems

Fruits are important sources of nutrients in human diet, and Barbados Cherry (Malpighia glabra L.) is of particular interest due to its high content of antioxidants. Diets rich in fruits and vegetables protect individuals against diseases and cancer, but excessive intake of vitamins may act as pro-oxidant and generate changes in DNA. To evaluate the effect of different in natura (BAN) and frozen (BAF) Barbados Cherry pulp concentrations and synthetic vitamin C in liquid form (VC) on the chromosome level and the cell cycle division, root meristeme cells of Allium cepa L. and bone marrow cells of Wistar rats Rattus norvegicus, were used as test system. In Allium cepa L., BAN, at the highest concentration (0.4 mg.mL-1) and BAF, at the lowest concentration (0.2 mg.mL-1), inhibited cell division, and there was recovery of cell division after the recovery period in water only for BAN. In the Wistar rats, all treatments with Barbados Cherry, either acute or subchronic, were not cytotoxic or mutagenic; only the highest concentration of VC increased significantly the rate of chromosomal abnormalities. The data obtained are important to reinforce the use of Barbados Cherry fruit in the diet.

Bioaccumulation and lack of oxidative stress response in the ragworm H. diversicolor following exposure to 226Ra in sediment

The main effluent from oil and gas production, produced water, from some platforms in the North Sea contains elevated concentrations of (226)Ra. The aim of this study was to investigate whether (226)Ra in sediment would accumulate in and affect sediment-dwelling organisms. In addition, we wanted to determine if the bioavailability would be modulated by the presence of a scale inhibitor which is used during oil and gas production. Hediste diversicolor was therefore exposed to different levels of (226)Ra (30-6600 Bq kg(-1)) in combination with scale inhibitor in the sediments in a flow through system. The levels of radioactivity in the exposures were close to levels that can be measured in proximity to oil/gas production facilities. (226)Ra spiked to natural sediment partitioned into pore water and accumulated in the sediment-dwelling polychaete following a four-week exposure period. The results suggest that (226)Ra did not bind strongly to sediment (low sediment:water partitioning coefficient), but it was not shown to bioaccumulate in any great extent (bioaccumulation factors of 0.019-0.022). Exposure of H. diversicolor in sediments with up to 6600 Bq kg(-1)(226)Ra had no measurable effect on the total oxyradical scavenging capacity of the organisms compared to control. So although they accumulated the alpha-emitter, the treatments did not appear to cause oxidative stress in polychaete tissues.

Dietary antioxidants protect hematopoietic cells and improve animal survival after total-body irradiation

The purpose of this study was to determine whether a dietary supplement consisting of L-selenomethionine, vitamin C, vitamin E succinate, alpha-lipoic acid and N-acetyl cysteine could improve the survival of mice after total-body irradiation. Antioxidants significantly increased the 30-day survival of mice after exposure to a potentially lethal dose of X rays when given prior to or after animal irradiation. Pretreatment of animals with antioxidants resulted in significantly higher total white blood cell and neutrophil counts in peripheral blood at 4 and 24 h after 1 Gy and 8 Gy. Antioxidants were effective in preventing peripheral lymphopenia only after low-dose irradiation. Antioxidant supplementation was also associated with increased bone marrow cell counts after irradiation. Supplementation with antioxidants was associated with increased Bcl2 and decreased Bax, caspase 9 and TGF-beta1 mRNA expression in the bone marrow after irradiation. Maintenance of the antioxidant diet was associated with improved recovery of the bone marrow after sublethal or potentially lethal irradiation. Taken together, oral supplementation with antioxidants appears to be an effective approach for radioprotection of hematopoietic cells and improvement of animal survival, and modulation of apoptosis is implicated as a mechanism for the radioprotection of the hematopoietic system by antioxidants.

Effects of N-acetylcysteine amide (NACA), a thiol antioxidant on radiation-induced cytotoxicity in Chinese hamster ovary cells

Ionizing radiation is known to cause tissue damage in biological systems, mainly due to its ability to produce reactive oxygen species (ROS) in cells. Many thiol antioxidants have been used previously as radioprotectors, but their application has been limited by their toxicity. In this investigation, we have explored the possible radioprotective effects of a newly synthesized thiol antioxidant, N-acetylcysteine amide (NACA), in comparison with N-acetylcysteine (NAC), a commonly used antioxidant. Protective effects of NACA and NAC were assessed using Chinese hamster ovary (CHO) cells, irradiated with 6 gray (Gy) radiation. Oxidative stress parameters, including levels of reduced glutathione (GSH), cysteine, malondialdehyde (MDA), and activities of antioxidant enzymes like glutathione peroxidase, glutathione reductase, and catalase, were measured. Results indicate that NACA was capable of restoring GSH levels in irradiated cells in a dose dependent manner. In addition, NACA prevented radiation-induced loss in cell viability. NACA further restored levels of malondialdehyde, caspase-3 activity, and antioxidant enzyme activities to control levels. Although NAC affected cells in a similar manner to NACA, its effects were not as significant. Further, NAC was also found to be cytotoxic to cells at higher concentrations, whereas NACA was non-toxic at similar concentrations. These results suggest that NACA may be able to attenuate radiation-induced cytotoxicity, possibly by its ability to provide thiols to cells.

The bystander effect-induced formation of micronucleated cells is inhibited by antioxidants, but the parallel induction of apoptosis and loss of viability are not affected

X-rays induce various DNA damages including strand breaks that lead to formation of micronuclei and chromosomal aberrations as well as increased number of apoptotic cells. Similar effects appear when non-irradiated cells are treated with medium collected from cultures of irradiated cells (irradiation conditioned medium - ICM). This phenomenon was termed "bystander effect". A number of studies suggest that bystander effect appears to be associated with up-regulation of oxidative metabolism. We thus compared the effects of antioxidant Vitamins C and E on the frequency of micronuclei and apoptotic cells in both directly irradiated cell cultures and in cultures exposed to ICM. Addition of Vitamins C or E (1-40 microg/ml) to culture medium after exposure to radiation or ICM reduced the frequency of micronuclei in a concentration-dependent manner. These vitamins had no effect on cell viability, clonogenic survival or the frequency of apoptotic cells under both conditions tested. These results show that the bystander effect causes micronucleation in addition to other known effects and suggest that the factors causing micronucleation by X-irradiation, oxidative DNA damage and incomplete repair, are regulated by apoptosis-independent pathways.

The relation between sphingomyelinase activity, lipid peroxide oxidation and NO-releasing in mice liver and brain

We used animal models to study connection between oxidating system and sphingomyelin signaling cascade, because this models are more close related to people disease. Activation of n-sphingomyelinase (n-SMase) in mice liver and brain is coincided in time with increased level of peroxide products (conjugated dienes) after injection of tumor necrosis factor alpha (TNF-alpha). We found that ceramide can induce peroxide oxidation and lead to accumulation of TNF-alpha in animal organs. Nitric oxide (NO) donors (S-nitrosoglutathione and dinitrosyl iron complex) reversibly inhibited activity of n-SMase and decreased level of lipid peroxidation products. This data proposed that both SMase and messengers of oxidative systems could be targets for NO-derived oxidants.

Radical mediators and mitogen-activated protein kinase signaling in oxygen-dependent radiosensitivity of human tumor cell lines

Oxygen enhancement of tumor radiosensitivity is attributed to DNA damage by reactive oxygen species. The mechanism remains unclear but may involve mitochondria as major sources of oxygen and nitrogen radicals as well as central effectors of energy homeostasis and apoptosis. Here we used dihydrorhodamine and 2',7'-dichlorodihydrofluorescein to compare mitochondrial and total cell generation, respectively, of reactive oxygen or nitrogen species in cells irradiated at 5 Gy. Irradiation in the presence of oxygen selectively stimulated mitochondrial radical production in HeLa and MeWo cells, but in MCF7 cells radical production was more generalized. In all three cell lines oxygen impaired cell proliferation as measured by resazurin reduction 7 days after irradiation. Antioxidants N-acetylcysteine, ascorbic acid, and melatonin largely prevented dye oxidation during normoxic irradiation yet had no effect on oxygen-dependent irradiation injury. However, NO synthase inhibitor N(G)-monomethyl-L-arginine protected HeLa and MCF7 though not MeWo cells, consistent with their different levels of constitutive NO generation. SB203580 inhibition of p38 MAPK appreciably protected HeLa and marginally protected MCF7 cells against oxygen-dependent irradiation injury, while the less specific JNK/SAPK inhibitor SP600125 and ERK inhibitor U0126 had no effect. None of the inhibitors affected MeWo radiosensitivity. Therefore oxygen-enhanced radiosensitivity in these tumor cell lines does not depend on extensive production of oxygen radicals and is cell-type dependent. NO mediates oxygen-dependent injury in HeLa and MCF7 cells, by p38-dependent and MAPK-independent mechanisms, respectively. In MeWo cells this oxygen-enhanced radiosensitivity is independent of both NO and MAPK signaling.

Can β-carotene regulate cell growth by a redox mechanism? An answer from cultured cells

Many studies suggest a protective role of beta-carotene against cancer. However, the ATBC and the CARET trials have shown that beta-carotene increases the incidence of lung cancer in heavy smokers and asbestos workers. To explain this paradox, it can be hypothesized that beta-carotene modulates intracellular redox status and through this mechanism, it affects redox-sensitive molecular pathways involved in the regulation of cell cycle progression and apoptosis. Studies conducted in cultured cells seem to confirm such a hypothesis. At low concentrations, the carotenoid may serve as an antioxidant, inhibiting free radical production, while at relatively high concentrations and/or in the presence of a chronic oxidative stress (i.e. smoke), it may behave as a prooxidant, propagating free radical-induced reactions, consuming endogenous antioxidants and inducing DNA oxidative damage. In this context, it may regulate cell growth and death by the modulation of redox-sensitive genes and transcription factors.