Antioxidant vitamins C, E and beta-carotene reduce DNA damage before as well as after gamma-ray irradiation of human lymphocytes in vitro

The protective effect of Vitamins C, E and beta-carotene against gamma-ray-induced DNA damage in human lymphocytes in vitro was investigated. Cultured lymphocytes were exposed to increasing concentration of these vitamins either before or after irradiation with 2Gy of gamma-rays and DNA damage was estimated using micronucleus assay. A radioprotective effect was observed when antioxidant vitamins were added to cultured cells before as well after irradiation; the strongest effect was observed when they were added no later than 1h after irradiation. The radioprotective effect of vitamins also depended on their concentration; Vitamins C added at low concentration (1 microg/ml) before exposure of the cells to radiation prevented induction of micronuclei. Vitamin E at the concentration above 2 microg/ml decreased the level of radiation-induced micronuclei when compared to the cells irradiated without vitamin treatment. beta-Carotene was effective at all tested concentrations from 1 to 5 microg/ml and reduced the number of micronuclei in irradiated cells. The vitamins had no effect on radiation-induced cytotoxicity as measured by nuclear division index. The radioprotective action of antioxidant Vitamins C, E and beta-carotene was dependent upon their concentration as well as time and sequence of application.     

Pro-carcinogenic activity of beta-carotene, a putative systemic photoprotectant.

Beta-carotene is a strong singlet oxygen quencher and antioxidant. Epidemiologic studies have implied that an above average intake of the carotenoid might reduce cancer risks. Earlier studies found that the carotenoid, when added to commercial closed-formula rodent diets, provided significant photoprotection against UV-carcinogenesis in mice. Clinical intervention trials found that beta-carotene supplementation evoked no change in incidence of nonmelanoma skin cancer. However, when smokers were supplemented with the carotenoid a significant increase in lung cancer resulted. Recently, employing a beta-carotene supplemented semi-defined diet, not only was no photoprotective effect found, but significant exacerbation of UV-carcinogenesis occurred. Earlier, a mechanism, based upon redox potential of interacting antioxidants, was proposed in which beta-carotene participated with vitamins E and C to efficiently repair oxy radicals and, thus, thought to provide photoprotection. In this schema, alpha-tocopherol would first intercept an oxy radical. In terminating the radical-propagating reaction, the tocopherol radical cation is formed which, in turn, is repaired by beta-carotene to form the carotenoid radical cation. This radical is repaired by ascorbic acid (vitamin C). As the carotenoid radical cation is a strongly oxidizing radical, unrepaired it could contribute to the exacerbating effect on UV-carcinogenesis. Thus, vitamin C levels could influence the levels of the pro-oxidant carotenoid radical cation. However, when hairless mice were fed beta-carotene supplemented semi-defined diet with varying levels of vitamin C (0-5590 mg kg(-1) diet) no effect on UV-carcinogenesis was observed. Lowering alpha-tocopherol levels did result in further increase of beta-carotene exacerbation, suggesting beta-carotene and alpha-tocopherol interaction. It was concluded that the non-injurious or protective effect of beta-carotene found in the closed-formula rations might depend on interaction with other dietary factors that are absent in the semi-defined diet. At present, beta-carotene use as a dietary supplement for photoprotection should be approached cautiously.     

Photoprotective potential of lycopene,beta-carotene,vitamin E,vitamin C and carnosic acid in UVA-irradiated human skin fibroblasts

The photoprotective potential of the dietary antioxidants vitamin C, vitamin E, lycopene, beta-carotene, and the rosemary polyphenol, carnosic acid, was tested in human dermal fibroblasts exposed to ultraviolet-A (UVA) light. The carotenoids were prepared in special nanoparticle formulations together with vitamin C and/or vitamin E. Nanoparticle formulations, in contrast to dimethylsulphoxide, stablized lycopene in the cell culture medium and allowed efficient cellular uptake. The presence of vitamin E in the formulation further increased the stability and cellular uptake of lycopene. UVA irradiation of the human skin fibroblasts led to a 10-15-fold rise in metalloproteinase 1 (MMP-1) mRNA. This rise was suppressed in the presence of low microM concentrations of vitamin E, vitamin C, or carnosic acid but not with beta-carotene or lycopene. Indeed, in the presence of 0.5-1.0 microM beta-carotene or lycopene, the UVA-induced MMP-1 mRNA was further increased by 1.5-2-fold. This increase was totally suppressed when vitamin E was included in the nanoparticle formulation. Heme-oxygenase 1 (HO-1) mRNA expression was strongly induced by UVA irradiation but none of the antioxidants inhibited this effect at the concentrations used in this study. Indeed, beta-carotene or lycopene (0.5-1.0 microM) led to a further 1.5-fold rise in the UVA-induced HO-1 mRNA levels. In conclusion, vitamin C, vitamin E, and carnosic acid showed photoprotective potential. Lycopene and beta-carotene did not protect on their own but in the presence of vitamin E, their stability in culture was improved and the rise in MMP-1 mRNA expression was suppressed, suggesting a requirement for antioxidant protection of the carotenoids against formation of oxidative derivatives that can influence the cellular and molecular responses.     

Comparative investigation of vitamins and their analogues on terminal differentiation, from preadipocytes to adipocytes, of 3T3-L1 cells

1. The effects of 20 kinds of vitamins or their analogues on the growth rate of preadipocytes and the terminal differentiation of preadipocytes to adipocytes was systematically compared in 3T3-L1 cells. 2. The addition of vitamin C markedly increased the growth rate of preadipocytes at over 50 microM. 3. The addition of vitamin K3 slowed down the growth rate at over 0.1 microM. 4. In water soluble vitamins and their analogues tested, the vitamin B6 group and vitamin C significantly stimulated the differentiation, and consequently increased the glycerophosphate dehydrogenase activity and triglyceride accumulation, to a concentration of over 10 microM. 5. Many fat soluble vitamins and their analogues (the vitamin A group, including beta-carotene, the vitamin D group, vitamin E and the vitamin K group) strongly inhibited the adipose conversion of 3T3-L1 cells at microM level.     

Effects of beta-carotene,vitamin C and E on antioxidant status in hyperlipidemic smokers

Smoking can accelerate the consumption of the stored antioxidant vitamins and increase the oxidative stress in the hyperlipidemic patients. The study investigated the effects of combined beta-carotene, vitamin C, and vitamin E on plasma antioxidant levels, erythrocyte antioxidative enzyme activities, and LDL lipid peroxides. Male hyperlipidemic smokers (35-78 years old) were randomly divided into two antioxidant supplemented groups: intervention 1 (I1, n = 22) (15 mg beta-carotene/day, 500 mg vitamin C/day, and 400 mg alpha-tocopherol equivalent/day) and intervention 2 (I2, n = 20) (30 mg beta-carotene/day, 1000 mg vitamin C/day, and 800 mg alpha-tocopherol equivalent/day). After 6-week supplementation, plasma beta-carotene, vitamin C, vitamin E, and erythrocyte glutathione levels increased significantly by 200%, 98%, 129%, and 39%, respectively, in the I1 group, and by 209%, 216%, 197%, and 32%, respectively, in the I2 group. Plasma Fe(+2) concentrations and Fe(+2)/Fe(+3) decreased significantly in both groups. Except erythrocyte glutathione peroxidase activity in the I1 group, erythrocyte catalase, glutathione peroxidase, and superoxide dismutase activities increased significantly in both groups. Lipid peroxides in LDL decreased significantly by 56% and 72% in the I1 and I2 groups, respectively. However, the levels of plasma iron, erythrocyte glutathione, and LDL lipid peroxides, and the activities of erythrocyte antioxidative enzymes did not differ between two groups. In conclusion, combined antioxidant supplements increased plasma antioxidant levels and antioxidative enzyme activities, and lowered LDL lipid peroxides in male hyperlipidemic smokers. Higher dosage of the supplements did not have an additive effect.     

Effects of vitamin C and vitamin E on lipid peroxidation, blood serum metabolites, and mineral concentrations of laying hens reared at high ambient temperature

This study was conducted to determine the effects of vitamin C (L-ascorbic acid) and vitamin E (alpha-tocopherol acetate) on serum concentrations of lipid peroxidation (MDA) and triiodothyronine (T3), thyroxine (T4), adrenocorticotropic hormone (ACTH), and some metabolite and mineral in laying hens reared at high ambient temperatures ranging from 25 degrees C to 35 degrees C. One hundred twenty laying hens (18 wk old; Hy-Line) were divided into 4 groups, 30 hens per group. The laying hens were fed either a basal diet (control) or the basal diet supplemented with either 250 mg of L-ascorbic acid/kg of diet (vitamin C), 250 mg of alpha-tocopherol acetate/kg of diet (vitamin E), or 250 mg of L-ascorbic acid plus 250 mg alpha-tocopherol acetate/kg of diet (combination). Separately or as a combination vitamins C and E increased serum vitamin C and vitamin E concentrations (p < 0.001) but decreased serum MDA concentration (p < 0.05). Serum concentrations of vitamin E and vitamin C were found highest but serum MDA concentration was lowest in the combination group. Supplemental vitamins C and E either separately or in a combination increased serum T3 and T4 concentrations (p < 0.05), whereas decreased serum ACTH concentration (p < 0.01). Serum glucose and cholesterol concentrations decreased, whereas serum protein concentration increased (p < 0.05) when vitamins C and E singly or together were added to the diet. Vitamin C and vitamin E supplementation resulted in an increase in serum concentrations of Ca, P, and K (p < 0.01) but a decrease in serum concentration of Na (p < 0.05). The results of the present study suggest that supplemental vitamin C and vitamin E alter serum lipid peroxidation, vitamin C, vitamin E and metabolite status, and diets supplemented with a combination of these two vitamins offer a good management practice in laying hens reared at high temperatures. In addition, the results suggest that dietary vitamin C and vitamin E act synergistically.     

Mitomycin C-activity effected by vitamins B1, C,E and beta-carotene under irradiation with gamma-rays

Vitamin B1 (thiamine) can essentially effect the activity of mitomycin C (MMC), added individually or in combination with antioxidant vitamins (C, E-acetate, beta-carotene) as found in experiments in vitro (Escherichia coli bacteria, AB 1157) under irradiation with gamma-rays. The environment plays a crucial role. In airfree media vitamin B1 leads to a 2-fold increase of the MMC-efficiency, but adding vitamin C it decreases. In the presence of all vitamins (B1, C, E-ac., and beta-carotene) the MMC-action increases about 1.8-fold. In aerated media vitamin B1 causes an about 4-times increase of the MMC-efficiency, but by adding vitamin B1 and C the MMC-activity decreases by a factor of two, whereas in the presence of B1, C, E-ac., and beta-carotene it rises again to 2.6-fold. In environment saturated with N2O (conversion of e(-)aq into OH radicals) a different picture is observed. The presence of vitamin B1 or vitamin B1 + C causes a strong decrease of the MMC-efficiency, but the addition of all vitamins (B1, C, E-ac., and beta-car.) leads to a small increase of the cytostatic action. The results demonstrate the influence of vitamin B1 used individually or in combination with other antioxidants on the MMC-efficiency and the strong effect of the environment. The results are of interest for the application of MMC in radiotherapy.     

Physiological levels of tea catechins increase cellular lipid antioxidant activity of vitamin C and vitamin E in human intestinal caco-2 cells

Oxidative stress has been linked to the development of various chronic diseases. Vegetables and fruits, which contain polyphenols, were shown to have protective effects. (-)-Epigallocatechin-3-gallate (EGCG), a polyphenol abundant in tea, has been shown to have antioxidant activities in cell-free conditions and this study focused on the effect of cellular EGCG. Using an intestinal cell model to examine the oxidative stress induced by hydroxyl radicals, we report here that physiological concentrations (0.1-1 microM) of EGCG have dose- and incubation duration-dependent cell-associated lipid antioxidant activity (measuring malondialdehyde production). Vitamin E and vitamin C at 10-40 microM also showed cell-associated lipid antioxidant activities under shorter incubation durations. When EGCG was included in the incubation with vitamin E or C, more antioxidant activities were consistently observed than when vitamins were added alone. Catechin (widely present in fruits and vegetables) at 1 microM also significantly increased the antioxidant activity of vitamins E and C. Previous studies examining cell-associated activity of EGCG mainly focused on the 10-100 microM concentration range. Our results suggest that although the physiological level (0.1-1 microM) of dietary catechins is much lower than that of vitamins, they further contribute to the total antioxidant capacity even in the presence of vitamins.     

Genotoxicity of idarubicin and its modulation by vitamins C and E and amifostine

Idarubicin is an anthracycline anticancer drug used in haematological malignancies. The main side effect of idarubicin is free-radicals based cardiotoxicity. Using the comet assay we showed that the drug at concentrations from the range 0.001 to 10 microM induced DNA damage in normal human lymphocytes, measured as the increase in percentage of DNA in the tail (% tail DNA). The effect was dose-dependent. Treated cells were able to recover within a 120-min incubation. Recognised cell protector, amifostine at 14 mM decreased the mean % tail DNA of the cells exposed to idarubicin at all tested concentrations of the drug. So did vitamin C at 10 microM, but vitamin E (alpha-tocopherol) at 50 microM increased the % tail DNA. Lymphocytes exposed to idarubicin and treated with endonuclease III, formamidopyrimidine-DNA glycosylase and 3-methyladenine-DNA glycosylase II, enzymes recognizing oxidized and alkylated bases, displayed greater extent of DNA damage than those not treated with these enzymes. Pretreatment of lymphocytes with nitrone spin traps, N-tert-butyl-alpha-phenylnitrone and alpha-(4-pyridil-1-oxide)-N-tert-butylnitrone decreased the extent of DNA damage evoked by idarubicin. To discuss the influence of vitamins and amifostine in cancer cells we used also murine pro-B lymphoid BaF3 transformed with BCR/ABL oncogene. These cells can be treated as model cells of human acute myelogenous leukemia. The response of these cells to vitamin E was quantitatively the same as human lymphocytes. However, vitamin C did not exert any effect on DNA damage and amifostine, in spite to normal lymphocytes, potentiated this effect. The results obtained suggest that reactive oxygen species, including free radicals, may be involved in the formation of DNA lesions induced by idarubicin. The drug can also methylate DNA bases. Our results indicate that not only cardiotoxicity but also genotoxicity and in consequence induction of secondary malignancies should be taken into account as diverse side effects of idarubicin. Amifostine may potentate DNA-damage effect of idarubicin in cancer cells and decrease this effect in normal cells. Vitamin C can be considered as protective agents against DNA damage in normal cells in persons receiving idarubicin-based chemotherapy, but the use of vitamin E cannot be recommended and at least needs further research.     

Background level of 8-oxo-2'-deoxyguanosine in lymphocyte DNA does not correlate with the concentration of antioxidant vitamins in blood plasma.

Antioxidant vitamins, being effective free radical scavengers, can protect cellular DNA from oxidative damage. Therefore, in the present study we report on the relationship between basal level of 8-oxo-2'-deoxyguanosine in human lymphocyte DNA and the concentration of antioxidant vitamins (A, C and E). The average level of 8-oxo-2'-deoxyguanosine in lymphocytes of the studied group (15 males and 20 females) was 9.57 per 10(6) dG molecules. The endogenous level of ascorbic acid (vitamin C) in the plasma was, on average, 56.78 microM, while the mean concentrations of retinol (vitamin A) and alpha-tocopherol (vitamin E) were 1.24 uM and 25.74,uM, respectively. No correlations were found between individual 8-oxo-2 micro-deoxyguanosine levels in lymphocyte DNA and endogenous concentration of the vitamins.     

UVB induced oxidative stress in human keratinocytes and protective effect of antioxidant agents

This study aims at exploring the oxidative stress in keratinocytes induced by UVB irradiation and the protective effect of nutritional antioxidants. Cultured Colo-16 cells were exposed to UVB in vitro followed by measurement of reactive oxygen species (ROS), endogenous antioxidant enzyme activity, as well as cell death in the presence or absence of supplementation with vitamin C, vitamin E, or Ginsenoside Panoxatriol. Intracellular ROS content was found significantly reduced 1 h after exposure, but increased at later time points. After exposure to 150–600 J m⁻² UVB, reduction of ROS content was accompanied by increased activity of catalase and CuZn-superoxide dismutase at early time points. Vitamins C and E, and Ginsenoside Panoxatriol counteracted the increase of ROS in the Colo-16 cells induced by acute UVB irradiation. At the same time, Ginsenoside Panoxatriol protected the activity of CuZn-superoxide dismutase, while vitamin E showed only a moderate protective role. Vitamins C and E, and Ginsenoside Panoxatriol in combination protected the Colo-16 cells from UVB-induced apoptosis, but not necrosis. These findings suggest that vitamins C and E as well as Ginsenoside Panoxatriol are promising protective agents against UVB-induced damage in skin cells.     

Lipoxygenase-catalysed degradation of carotenoids from tomato in the presence of antioxidant vitamins

Carotenoid extract from ripe tomato fruit was subjected to a lipoxygenase-catalysed co-oxidation in the presence of vitamin C and vitamin E at different concentrations. Relative retention (%) of major carotenoids by the experimental mixture was used as an index of their degradation and interaction with the antioxidants. Oxidation-prevention activity of each antioxidant against pigment co-oxidation as impacted by their molar concentration was studied. beta-Carotene was found to be the most sensitive pigment, followed by lycoxanthin and lycopene. Ascorbic acid when added in the range of 0-1.8 mM interacted with the different carotenoids by different modes. Evidence was given on regeneration, by ascorbic acid, of lycopene during the course of co-oxidation. The concentration required for alpha-tocopherol acetate to exhibit antioxidative effect was 10 times higher than that of ascorbic acid. beta-Carotene was prevented, by alpha-tocopherol acetate, faster than lycoxanthin and lycopene. The latter carotenoids differed substantially in their interaction with the lipophilic antioxidant at only the lowest concentration (0.3 mM). It was established that under the given conditions there is no synergism between vitamin C and vitamin E that improves their oxidation prevention against co-oxidation of carotenoids. Moreover, the combined use of antioxidants caused more oxidative degradation of beta-carotene.     

The inhibition of radical-initiated peroxidation of microsomal lipids by both alpha-tocopherol and beta-carotene.

Rat liver microsomal lipids in hexane solution were exposed to the lipid-soluble radical initiator, azobis-isobutyronitrile (AIBN), and the antioxidant activities of alpha-tocopherol and beta-carotene have been compared. Lipid peroxidation was monitored both by conjugated diene formation at 233 nm, and by malondialdehyde (MDA) formation in the thiobarbituric acid assay at 535 nm. Diene formation was continuous for at least 120 min in the presence of 85 micrograms/ml lipid and 4 mM AIBN. Both alpha-tocopherol and beta-carotene acted as chain-breaking antioxidants, suppressing lipid peroxidation and producing an induction period at concentrations as low as 0.5 and 8 microM, respectively. When both of these lipid-soluble antioxidants were present together, the oxidation was strongly suppressed and the induction period was the sum of the individual antioxidants, alpha-Tocopherol and beta-carotene also inhibited MDA generation. In the presence of 170 micrograms/ml lipid and 8 mM AIBN, beta-carotene exhibited an IC50 of 1.1 microM and inhibited completely at 15 microM. Using beta-carotene, an induction period was observed, although much less pronounced than with alpha-tocopherol. Furthermore, beta-carotene inhibited MDA production in a concentration-dependent manner and exhibited an IC50 of 50 microM. In addition, added beta-carotene delayed the radical-initiated destruction of the endogenous alpha-tocopherol and gamma-tocopherol in this system.     

Studies on the effects of x-ray on erythrocyte zinc and copper concentrations in rabbits after treatment with antioxidants

The aim of this study was to investigate the effect of supplemental antioxidant vitamins and minerals on the erythrocyte concentrations of zinc and copper in rabbits after exposure to X-rays. The animals were divided into two experimental and one control group (CG). The first group (VG) was given daily oral doses of vitamins E and C; supplemental amounts of managanese, zinc, and copper were mixed with the feed and given to the second group of experimental animals (MG). Blood samples were taken from all groups before and after 4 wk of vitamin and mineral administration and after irradiation with a total dose of 550-rad X-rays. The administration of minerals caused the most significant increases of Zn and Cu. Even after irradiation, the zinc levels in the irradiated animals were higher than in the nonirradiated vitamin-supplemented animals (p<0.05). The results suggest that supplementation with antioxidant vitamins and minerals may have a protective effect against X-ray-induced damage.     

In vitro manipulations of vitamin C and vitamin E concentrations alter intracellular O2- production of hybrid striped bass (Morone chrysops x Morone saxatilis) head-kidney cells

To examine the mechanism by which vitamins C and E alter phagocyte function, a series of in vitro manipulations were conducted with cells isolated from the head-kidney of hybrid striped bass (average weight 680 g) fed a diet supplemented with minimum requirement levels of vitamins C and E for 2 weeks. Head-kidney phagocytes were cultured in media containing physiologically deficient (23 microM, adequate (45 microM) or excessive (182 microM) concentrations of vitamin C, and physiologically deficient (5 microM), adequate (9 microM) or excessive (32 microM) concentrations of vitamin E for 18 h. Following culture and stimulation, levels of reactive oxygen intermediates and hydrogen peroxide were determined. There were no effects of vitamin C or vitamin E concentrations on hydrogen peroxide or extracellular O2- generation. Intracellular O2- production, however, was significantly (P < or = 0.05) affected. When vitamin C was supplied at deficient levels to the medium, vitamin E elevated O2- production to levels not different from those of cells incubated with requirement levels of both vitamins. Similarly, when vitamin E was deficient in the media, vitamin C supplementation at requirement levels normalised intracellular O2- production. This data provides support for the presence of a vitamin C and vitamin E sparing mechanism in phagocytic head-kidney cells of hybrid striped bass and yield some insight into the mechanisms by which vitamin C and vitamin E function in immunomodulation.     

Modulation of gamma-ray-induced apoptosis in human peripheral blood leukocytes by famotidine and vitamin C

To study the radioprotective effects of vitamin C and famotidine against radiation-induced apoptosis in human peripheral blood leukocytes, peripheral blood was obtained from six healthy volunteers including three males and three females. Twelve microlitres of blood sample diluted in 1 ml complete RPMI-1640 medium was irradiated with various doses of gamma-rays (4, 8 and 12 Gy) in the presence or absence of various doses of vitamin C and famotidine. After 48 and 72 h incubation in a 37 degrees C CO(2) incubator, neutral comet assay was performed for all samples. At least 1000 cells were analyzed for each sample for presence of apoptosis. Data were statistically evaluated using Mann-Whitney non-parametric and ANOVA tests. Results show a significant increase in apoptosis induction following gamma-irradiation with a dose dependent manner compared to controls (p<0.001). Presence of famotidine at 200 microg/ml produced a significant protective effect against radiation-induced apoptosis for various doses of radiation. Similar effects were observed for vitamin C at much lower doses (10 microg/ml). Dose reduction factor (DRF) calculated for famotidine treatment was about 1.5, and above 2 for vitamin C treatment. These results suggest that both vitamin C and famotidine suppresses radiation-induced apoptosis when used with various doses of gamma-irradiation (4-12 Gy) probably via *OH radical scavenging and an intracellular antioxidation mechanism.     

beta-Carotene: interactions with alpha-tocopherol and ascorbic acid in microsomal lipid peroxidation

beta-Carotene, alpha-tocopherol, and ascorbic acid were tested for their ability to inhibit, enhance, or react synergistically with O(2) (15, 150, 760 torr) and, 2,2'-azobis (2-amidino-propane) dihydrochloride (AAPH) or 1,1'-azobis (cyclohexane-carbonitrile) (ACCN) in isolated rat liver microsomes. beta-Carotene did not protect against lipid peroxidation, i.e., malondialdehyde (MDA) formation, in microsomal samples incubated at 37 degrees C with aqueous soluble AAPH at all added beta-carotene concentrations and oxygen tensions. More MDA (16%, p < 0.001) was produced at 15 torr of O(2,) and 160 nmol/mg protein of beta-carotene compared to respective vehicle control. Individually, alpha-tocopherol and ascorbic acid exhibited antioxidant protection (ascorbic acid &z.Gt; alpha-tocopherol); however, a mixture of both compounds was no more protective than ascorbic acid alone. beta-Carotene demonstrated a concentration-dependent antioxidant affect at 15 torr O(2) (p < 0.01); but a prooxidant effect at higher O(2) at 150 and 760 torr (>57%, p < 0.001) by lipid-soluble ACCN. alpha-Tocopherol exhibited concentration-dependent inhibitory effects on microsomal MDA formation at all oxygen tensions, but was most effective under 150 torr. Ascorbic acid demonstrated a concentration-dependent antioxidant effect only at 150 torr. ACCN-induced lipid peroxidation was no greater for the combination of the three compounds than ascorbic acid added alone. Thus, antioxidant or prooxidant activities for beta-carotene, alpha-tocopherol, and ascorbic acid in microsomal suspensions are related to O(2) tension, solubility, antioxidant concentrations and are governed by complex interactions. Differences between AAPH- and ACCN-induced lipid peroxidation are related to differences in lipid solubility.     

Effect of vitamin C and vitamin E on prostaglandin synthesis by fibroblasts and squamous carcinoma cells.

Dietary levels of vitamins C and E have been associated with cancer prevention and to a lesser extent with therapeutic enhancement of cancer treatment. Inhibition of prostaglandins (PGs) by pharmacological agents has been demonstrated to enhance immunocompetence, and to suppress growth of tumors in animals and humans. We report here on the effect of vitamins C and E on PGE2 production by human gingival fibroblasts and SCC-25 oral squamous carcinoma cells. The results indicate: 1. vitamins C and E exert a dose-dependent effect on arachidonic acid (AA) release and PGE2 synthesis; 2. vitamin E has a biphasic effect which is stimulatory at 1 and 10 microM and inhibitory at 100 microM; 3. vitamin E is considerably more potent than vitamin C in its inhibitory effect on AA and PGE2 in both cell types; 4. a combination of the two vitamins has a consistent dose-dependent inhibitory effect on AA and PGE2; 5. vitamin C stimulates PGE2 synthesis from exogenous AA in fibroblasts, and inhibits it in SCC-25 cells. The in vivo significance of these findings requires further investigation.     

Beta-carotene inhibits growth of human colon carcinoma cells in vitro by induction of apoptosis

Epidemiological studies suggest that beta-carotene is able to modulate the risk of cancer. A number of in vitro studies reported that beta-carotene inhibits the growth of cancer cells; however, so far little is known about the molecular mechanisms of the antiproliferative effect of beta-carotene. Here we have investigated the effects of two beta-carotene preparations, (i) beta-carotene dissolved in tetrahydrofuran (final concentration in cell culture medium: 0.5%) and (ii) beta-carotene incorporated in a water dispersible bead form, on cultured human colon carcinoma cells HT29. The treatment of cells with beta-carotene up to 30 microM for 72 h led to a significant increase in the cellular beta-carotene concentration and formation of retinol. Beta-Carotene showed only low cytotoxicity for confluent cells tested up to 30 microM, but at dietary relevant concentrations for the intestinal tract (10, 30 microM) beta-carotene was strongly cytotoxic for growing cells and induced apoptosis in HT29 cells as assessed by the Annexin-V assay (the maximal effect was observed 15 h after treatment with beta-carotene). Exposure of cells to retinol at concentrations yielding cellular retinol levels similar to those observed by beta-carotene treatment had no antiproliferative or cytotoxic effect. Furthermore, beta-carotene did not affect the activation of the extracellular signal-regulated kinases (ERK1 and ERK2) that are essential for cellular growth. In summary, beta-carotene can inhibit growth of human colon carcinoma cells in vitro by induction of apoptosis in proliferating cells.     

In vitro effects of singular or combined anti-oxidative vitamins and/or minerals on tilapia (Oreochromis hybrids) peripheral blood monocyte-derived, anterior kidney-derived, and spleen-derived macrophages

The present study was to determine the in vitro effects of singular or combined anti-oxidative vitamins (A, C, and E) and/or minerals (Se, Zn, Cu, Mn, and Fe) on the immune functions of tilapia, Oreochromis hybrids, peripheral blood monocyte-derived, anterior kidney-derived, and spleen-derived macrophages. An optimal dose of vitamins and minerals increased cell viability and lysozyme activity. On the other hand, the above activities decreased at the high doses of combined vitamins (A+C+E group, each 300 microg mL(-1)) or single mineral (Se, Zn, Cu, Mn, and Fe groups, each 200, 800 or 1000 microg mL(-1)). Combining two of the aforementioned vitamins (A+C, A+E, and C+E groups, each 100 microg mL(-1)) was able to prolong cell viable time up to 72 h compared with singular vitamin addition. Before or after adding vitamins or minerals during infection, addition of vitamins decreased the percentage of dead cells and a greater effect was observed for mineral (each 40 or 80 microg mL(-1)) and vitamin (each 100 microg mL(-1)) combinations. A low dose of vitamins increased nitric oxide production and decreased superoxide production, but high dose of vitamins decreased superoxide and nitric oxide productions. Furthermore, minerals also decreased nitric oxide production at concentrations of 40, 80, 200, 800 or 1000 microg mL(-1). The threshold concentrations for cell death by necrosis and/or apoptosis were >1000 and >800 microg mL(-1) for vitamins and minerals, respectively. In conclusion, appropriate concentration of vitamins or minerals can increase tilapia macrophage immunity; nevertheless, extreme concentrations of vitamins or minerals are lethal to cells.