Effect of beta-carotene on spontaneous and X-ray-induced chromosomal damage in bone marrow cells of mice

Low folate status increases chromosomal damage by X-ray irradiation

PURPOSE

To examine how folate status influences chromosomal damage following X-ray irradiation.

MATERIAL AND METHODS

In an animal study, mice were fed either a low, basal, or high folic acid diet (0, 2, or 40 mg/kg diet, respectively) for 4 weeks, and then given total body irradiation (TBI) at 0.5 Gy. In a human study, subjects were supplemented with folic acid (800 microg/day) for 2 weeks and their peripheral blood was irradiated at 0.5 Gy in vitro. Chromosomal damage was determined by micronucleus assay.

RESULTS

In an animal study, TBI-induced chromosomal damage was higher and folate concentration was lower in the bone marrow of the low folic acid group compared to the other two diet groups. The chromosomal damage and folate concentration were comparable between the basal and high folic acid groups. TBI administered to mice decreased folate in the plasma, erythrocyte and bone marrow. In a human study, supplementation with folic acid increased plasma folate, but did not influence either plasma homocysteine or X-ray-induced chromosomal damage in lymphocytes.

CONCLUSION

Low folate status increases susceptibility to X-ray-induced chromosomal damage, but excessive folic acid supplementation under normal conditions yields no further protection due to folate saturation in the target tissue.

Dicamba-induced genotoxicity in Chinese hamster ovary (CHO) cells is prevented by vitamin E

In the present study the cytogenetic and genotoxic effect of benzoic herbicide dicamba and its Argentinean commercial formulation banvel (57.71% dicamba) was evaluated and whether this effect is mediated through oxidative damage or not. The protective role of vitamin E was also studied. Sister chromatid exchange (SCE) frequency, cell-cycle progression, and cell viability analyses in CHO cells were used as in vitro end-points. Treatments with the test compounds were performed either during 24h (Protocol A) or 12h (Protocol B) before harvesting. Protocol A showed that vitamin E decreased pesticide SCE induction, corrected the cell-cycle delay and partially protected cell-death only in 500 microg/ml dicamba-treated cultures. A similar trend was found in banvel-treated cultures. Protocol B revealed similar protective role of vitamin E only for dicamba-induced geno- and cytotoxicity. Based on these observations it could be suggested that dicamba injures DNA by delivering reactive oxygen species rather than by another type of mechanism/s. Although banvel mimics the effect observed by dicamba, its formulation contains other xenobiotic/s agents able to induce cellular and DNA damage by a different mechanism/s. Further investigations are needed to acquire a comprehensive knowledge of the possible mechanism/s through dicamba and banvel exert their toxic effects.

Low folate status enhanced benzene-induced cytogenetic damage in bone marrow of mice: a relationship between dietary intake and tissue levels of folate

We examined the protective effect of dietary folate on benzene-induced chromosomal damage in bone marrow of mice regarding folate levels in diet and tissue. Male mice were fed either a deficient, basal, or high folate diet (0, 2, or 8 mg/kg diet, respectively) for 4 wk followed by a single dose of benzene. Plasma folate levels corresponded to those of dietary intake. Meanwhile, bone marrow, erythrocyte, and liver folate were decreased to 40% in the deficient group and almost saturated in the high group. Plasma homocysteine levels negatively correlated to levels of tissue folate. Chromosomal damage, evaluated by micronucleus assay, was not affected by folate status alone but was markedly enhanced by benzene, particularly in the deficient group (P < 0.05 vs. the basal and high groups). The activities of hepatic drug-metabolizing enzymes did not enhance benzene metabolism in the deficient groups, indicating that enhanced chromosomal damage was solely due to the low folate status. These results suggest that a low folate status can increase the risk of benzene-induced chromosomal damage in bone marrow, but excess folate intake does not enhance protection, as it is saturated in tissue.

Vitamin E and immunity

Vitamin E is a potent antioxidant and has an ability to modulate host immune functions. This chapter consists of five parts: (1) vitamin E deficiency and immunity, (2) vitamin E supplementation and immunity, (3) vitamin E and the decreased cellular immunity with aging, (4) vitamin E and T-cell differentiation in the thymus, and (5) vitamin E and acquired immune deficiency syndrome (AIDS). In vitamin E deficiency most of the immune parameters show a downward trend, which is associated with increased infectious diseases and the incidence of tumors. In contrast, vitamin E supplementation has various beneficial effects on the host immune system. The decreased cellular immunity with aging or during the development of AIDS is markedly improved by the intake of a high vitamin E diet. In addition, vitamin E plays an important role in the differentiation of immature T cells in thymus. Vitamin E deficiency induces the decreased differentiation of immature T cells, which results in the early decrease of cellular immunity with aging in spontaneously hypertensive rats. Conversely, vitamin E supplementation induces a higher differentiation of immature T cells via increased positive selection by thymic epithelial cells, which results in the improvement of decreased cellular immunity in the aged. Furthermore, vitamin E supplementation induces the early recovery of thymic atrophy following X-ray irradiation. Taken together, these results suggest that vitamin E is an important nutrient for maintaining the immune system, especially in the aged.

Transplacental inhibitory effect of carrot juice on the clastogenicity of cyclophosphamide in mice

Genetic damage during the prenatal period can provoke important neoplastic alterations and other diseases in postnatal life. Beta-carotene (ßC) is considered to be one of the most important anticarcinogens in the diet and can protect mammalian cells against genotoxic events. As carrots are important dietary source of ßC, we decided to test the effect of fresh carrot juice (CaJ) on cyclophosphamide (CP)-induced genotoxicity in maternal and fetal erythropoietic tissues. The treatment with CaJ started on the 7th day of the pregnancy of BALB/c female mice. We observed, on the 16th gestational day, that this treatment did not modify the spontaneous frequency of micronucleated polychromatic erythrocytes (mPCE) in the bone marrow of the females nor in the livers of their fetuses. The mPCE frequency observed 24 h after an intraperitoneal injection of CP (40 mg/kg) on the 15th day was significantly lower in CaJ-pretreated pregnant female bone marrow and in the liver of their fetuses than those observed in the group treated with CP only. These results demonstrate the presence of natural anticlastogens in carrots.

The role of vitamin E in T-cell differentiation and the decrease of cellular immunity with aging

The purpose of this study is to investigate the effects of vitamin E on both the decrease of cellular immunity with aging (Section 2) and the differentiation of T-cells in thymus (Section 3). In Section 2, spontaneously hypertensive rats (SHR) as a model for aging were used in this experiment and fed regular (50 IU/kg diet) or a high vitamin E (500 IU/kg diet) diet for 6 weeks. At 12 weeks old, they were killed and assayed. Although proliferation of thymic lymphocytes was significantly decreased in SHR fed the regular diet compared to that of Wistar Kyoto rats (WKY) fed the same diet, the high vitamin E diet induced higher proliferation of thymic lymphocytes in SHR, which was almost the same as that of WKY fed the regular diet. In addition, the expressions of both CD4 and CD8 antigens on CD4+ CD8+ T-cells were also decreased in SHR, which was significantly improved by a high vitamin E diet. These results suggest that a high vitamin E diet enhances thymic lymphocyte proliferation through increased T-cell differentiation in the thymus. Then, the effect of vitamin E on T-cell differentiation in the thymus was investigated by using male Fisher rats. Rats were divided into three groups; vitamin E-free, regular and high vitamin E groups and fed a diet containing various levels of vitamin E (0, 50 and 500 IU/kg diet) for 7 weeks. Although the proportions of CD4+ CD8- and CD4- CD8+ T-cells in thymocytes were significantly greater in the high vitamin E group, the proportion of CD4+ CD8- T-cells inversely decreased in the vitamin E-free group compared to that of the regular group. We have tried to investigate the mechanism on the increased T-cell differentiation in the thymus of rats fed the high vitamin E diet through cytokine production, thymic epithelial cell (TEC) and macrophage functions. As their results, we have found that vitamin E enhances T-cell differentiation through the increase of not macrophage but TEC function in the thymus, which is associated with the increased binding capacity of TEC to immature T-cells via increased expression of the adhesion molecule, ICAM-1. These results suggest that vitamin E is a potent nutrient for promoting health in the aged via the improvement of cellular immunity decreased with aging.

Effects of alpha-tocopherol and beta-carotene on hepatic lipid peroxidation and blood lipids in rats with dietary iron overload

The ability of dietary antioxidants to reduce lipid peroxidation induced by iron overload was examined in weanling male Sprague-Dawley rats. Animals were fed ad libitum a modified AIN-76A diet (control) or control diet with 0.5% alpha-tocopherol acid succinate, 0.5% crystalline trans-beta-carotene, or 0.5% alpha-tocopherol acid succinate + 0.5% trans-beta-carotene for four weeks. In the following four-week period, the animals received the above diets with 10,000 micrograms Fe/g; a control group continued to receive 35 micrograms Fe/g, and a high-iron group received 10,000 micrograms Fe/g with no antioxidants. After four weeks of dietary supplementation with alpha-tocopherol. Beta-carotene or alpha-tocopherol + beta-carotene, liver concentrations of alpha-tocopherol and beta-carotene increased significantly (p < 0.001). Liver lipid peroxidation, measured by the lipid-conjugated diene assay, increased significantly from 0.012 mumol/mg of lipid in the controls to 0.021 mumol/mg of lipid in animals receiving the high-iron diet. However, lipid peroxidation was significantly reduced in all animals fed the antioxidants, with the group fed alpha-tocopherol + beta-carotene having a lower level than the high-iron group. Total serum cholesterol was elevated in animals fed a high-iron diet and in animals fed the high-iron diet with alpha-tocopherol. In contrast, total serum cholesterol levels in the two groups of animals receiving the diets containing high iron with beta-carotene alone or high iron with beta-carotene + alpha-tocopherol were significantly reduced to the level of the control group. High-density lipoprotein cholesterol also decreased to baseline in the animals receiving beta-carotene alone. Modulation of lipid peroxidation by alpha-tocopherol or beta-carotene may be an important mechanism for reducing oxidative stress.