Prevention of photocarcinogenesis by dietary vitamin E

Understanding Active Photoprotection: DNA-Repair Enzymes and Antioxidants

The detrimental effects of ultraviolet radiation (UVR) on human skin are well-documented, encompassing DNA damage, oxidative stress, and an increased risk of carcinogenesis. Conventional photoprotective measures predominantly rely on filters, which scatter or absorb UV radiation, yet fail to address the cellular damage incurred post-exposure. To fill this gap, antioxidant molecules and DNA-repair enzymes have been extensively researched, offering a paradigm shift towards active photoprotection capable of both preventing and reversing UV-induced damage. In the current review, we focused on "active photoprotection", assessing the state-of-the-art, latest advancements and scientific data from clinical trials and in vivo models concerning the use of DNA-repair enzymes and naturally occurring antioxidant molecules.

Dietary antioxidant supplements and risk of keratinocyte cancers in women: a prospective cohort study

PURPOSE

Experimental studies suggested that antioxidants could protect against skin carcinomas. However, epidemiological studies on antioxidant supplement use in relation to basal-cell carcinoma (BCC) and squamous-cell carcinoma (SCC) risks yielded inconsistent findings, and few prospective studies have been conducted to date. We aimed to investigate the associations between antioxidant supplement intake and keratinocyte cancer (KC) risk.

METHODS

E3N is an ongoing prospective cohort initiated in 1990 and involving 98,995 French women aged 40-65 years at recruitment. Intakes of dietary antioxidants were estimated via a validated dietary questionnaire in 1993 and self-reported antioxidant supplement use was collected in 1995. We used Cox models to compute hazard ratios (HRs) and 95% confidence intervals (CIs) adjusted for age and skin cancer risk factors.

RESULTS

Over 1995-2014, 2426 BCC and 451 SCC cases were diagnosed among 63,063 women. We found positive relationships between vitamin A supplement use and KC risk (HR = 1.37, 95% CI 1.15-1.62), particularly with BCC (HR = 1.40, 95% CI 1.17-1.69); and between vitamin E supplement use and risks of both BCC (HR = 1.21, 95% CI 1.03-1.52) and SCC (HR = 1.43, 95% CI 1.03-1.99). Intake of beta-carotene supplements was associated with an increased SCC risk (HR = 1.59, 95% CI 1.00-2.54). Vitamin C supplement use was not associated with KC risk. We found similar results when considering total antioxidant intake.

CONCLUSIONS

Intakes of vitamin A or E supplements were associated with an increased KC risk in women. Further studies with information on doses and duration of supplement use and the ability to examine their underlying mechanisms are needed.

Does Photosensitivity Predict Photococarcinogenicity?

Assessment of short-term and long-term effects of light (pho—totesting) is part of the safety evaluation of drugs. Results are incorporated into drug package inserts to advise patients and health care providers about the use of drug products on sun—exposed skin. We undertook an exhaustive literature search and a search of archived studies at the Center for Drug Evaluation and Research (CDER), Food and Drug Administration (FDA), in order to evaluate the potential of short—term photoassays to predict long—term effects of drugs used in sunlight (280–700 nm). The correlation between the findings from the photococarcinogenicity assays in mice that used exposure to simulated sunlight and those from photogenotoxicity and photosensitivity studies was examined. Results indicated that photosensitivity and photogenotoxicity assays did not necessarily predict effects in photococarcinogenicity studies in mice. Effects of drugs on skin that are not due to photoactivation of drug can be important factors in enhancement of UV—induced skin carcinogenesis.

Vitamin E in dermatology

Vitamin E is an important fat-soluble antioxidant and has been in use for more than 50 years in dermatology. It is an important ingredient in many cosmetic products. It protects the skin from various deleterious effects due to solar radiation by acting as a free-radical scavenger. Experimental studies suggest that vitamin E has antitumorigenic and photoprotective properties. There is a paucity of controlled clinical studies providing a rationale for well-defined dosages and clinical indications of vitamin E usage in dermatological practice. The aim of this article is to review the cosmetic as well as clinical implications of vitamin E in dermatology.

The role of phytonutrients in skin health

Photodamage is known to occur in skin with exposure to sunlight, specifically ultraviolet (UV) radiation. Such damage includes inflammation, oxidative stress, breakdown of the extracellular matrix, and development of cancer in the skin. Sun exposure is considered to be one of the most important risk factors for both nonmelanoma and melanoma skin cancers. Many phytonutrients have shown promise as photoprotectants in clinical, animal and cell culture studies. In part, the actions of these phytonutrients are thought to be through their actions as antioxidants. In regard to skin health, phytonutrients of interest include vitamin E, certain flavonoids, and the carotenoids, β-carotene, lycopene and lutein.

Relevance of vitamins C and E in cutaneous photoprotection

Ultraviolet (UV) radiation-induced oxidative stress may result in acute and chronic photodamage. Based on the endogenous antioxidant system, the administration of antioxidants for scavenging reactive oxygen species might be a promising strategy in the prevention of UV-induced skin reactions. The relevance of the most common antioxidants, vitamins E and C, is reviewed focusing on topical and systemic photoprotective effects in animals and humans. Topically applied vitamin C induced significant photoprotective effects at concentrations of at least 10% in animals and humans, whereas a photoprotective effect has not been demonstrated by oral administration even at high doses in humans. Topical vitamin E reduced erythema, sunburn cells, chronic UV-B-induced skin damage, and photocarcinogenesis in the majority of the published studies, whereas only high doses of oral vitamin E may affect the response to UV-B in humans. Combination of vitamins C and E, partly with other photoprotective compounds, did increase the photoprotective effects dramatically compared to monotherapies. This synergistic interplay of several antioxidants should be taken into consideration in future research on cutaneous photoprotection.

Interaction of vitamins C and E as better cosmeceuticals

Although many cosmeceutical formulations contain vitamin C and/or vitamin E, very few are actually effective in topical application. First because there is only a low concentration, second because the stability is compromised as soon as the product is opened and exposed to air and light, and third because the form of the molecule (an ester or a mixture of isomers) is not absorbed or metabolized effectively by the skin. However, when a stable formulation delivers a high concentration of the nonesterified, optimal isomer of the antioxidant, vitamins C and E do indeed inhibit the acute ultraviolet (UV) damage of erythema, sunburn, and tanning as well as chronic UV photoaging and skin cancer. Both are highly effective depigmenting agents. Topical vitamin C also increases collagen synthesis in both young and old fibroblasts. Because vitamin C regenerates oxidized vitamin E, the combination in a cosmeceutical formulation is synergistic - particularly in UV protection.

Dietary chromium and nickel enhance UV-carcinogenesis in skin of hairless mice

The skin cancer enhancing effect of chromium (in male mice) and nickel in UVR-irradiated female Skh1 mice was investigated. The dietary vitamin E and selenomethionine were tested for prevention of chromium-enhanced skin carcinogenesis. The mice were exposed to UVR (1.0 kJ/m(2) 3 x weekly) for 26 weeks either alone, or combined with 2.5 or 5.0 ppm potassium chromate, or with 20, 100 or 500 ppm nickel chloride in drinking water. Vitamin E or selenomethionine was added to the lab chow for 29 weeks beginning 3 weeks before the start of UVR exposure. Both chromium and nickel significantly increased the UVR-induced skin cancer yield in mice. In male Skh1 mice, UVR alone induced 1.9+/-0.4 cancers/mouse, and 2.5 or 5.0 ppm potassium chromate added to drinking water increased the yields to 5.9+/-0.8 and 8.6+/-0.9 cancers/mouse, respectively. In female Skh1 mice, UVR alone induced 1.7+/-0.4 cancers/mouse, and the addition of 20, 100 or 500 ppm nickel chloride increased the yields to 2.8+/-0.9, 5.6+/-0.7 and 4.2+/-1.0 cancers/mouse, respectively. Neither vitamin E nor selenomethionine reduced the cancer yield enhancement by chromium. These results confirm that chromium and nickel, while not good skin carcinogens per se, are enhancers of UVR-induced skin cancers in Skh1 mice. Data also suggest that the enhancement of UVR-induced skin cancers by chromate may not be oxidatively mediated since the antioxidant vitamin E as well as selenomethionine, found to prevent arsenite-enhanced skin carcinogenesis, failed to suppress enhancement by chromate.

Vitamin E and organoselenium prevent the cocarcinogenic activity of arsenite with solar UVR in mouse skin

Arsenic-induced carcinogenesis is a worldwide problem for which there is currently limited means for control. Recently, we showed that arsenite in drinking water greatly potentiates solar ultraviolet radiation (UVR) induced skin cancer in mice, at concentrations as low as 1.25 mg/l. In this study, we examined the protective efficacy of vitamin E and 1,4-phenylenebis(methylene)selenocyanate (p-XSC) against tumors induced by UVR and UVR + arsenite. Hairless mice were exposed to UVR alone (1.0 kJ/m(2) x 3 times weekly) or UVR + sodium arsenite (5 mg/l in drinking water) and fed lab chow supplemented or not with vitamin E (RRR-alpha-tocopheryl acetate, 62.5 IU/kg diet) or p-XSC (10 mg/kg) for 26 weeks. The tumor yield for mice receiving UVR alone was 3.6 tumors/mouse and the addition of arsenite to the drinking water increased the yield to 7.0 tumors/mouse (P < 0.005). Vitamin E and p-XSC reduced the tumor yield in mice given UVR + arsenite by 2.1-fold (P < 0.001) and 2-fold (P < 0.002), respectively. Vitamin E, but not p-XSC, reduced the tumor yield induced by UVR alone by 30% (P < 0.05). No significant difference in tumor types or grade of malignancy was observed in mice treated with or without chemopreventives. Immunostaining of mouse skin for 8-oxo-2'-deoxyguanosine (8-oxo-dG) revealed a significant reduction of 8-oxo-dG formation in mice treated with vitamin E or p-XSC compared with those treated with UVR + arsenite. These results show that vitamin E and p-XSC protect strongly against arsenite-induced enhancement of UVR carcinogenesis.

Effects of oral vitamin E and beta-carotene supplementation on ultraviolet radiation-induced oxidative stress in human skin

BACKGROUND

Ultraviolet radiation (UVR) generates reactive oxygen species in skin that can play a role in skin damage, but reports about the photoprotective properties of oral antioxidant supplements are conflicting.

OBJECTIVE

We examined the ability of 2 lipid-soluble antioxidants, vitamin E and beta-carotene, to reduce markers of oxidative stress and erythema in human skin exposed to UVR.

DESIGN

Sixteen healthy subjects took either alpha-tocopherol (n = 8; 400 IU/d) or beta-carotene (n = 8; 15 mg/d) for 8 wk. Biopsy samples before and after supplementation were taken from unexposed skin and skin 6 h after 120 mJ/cm(2) UVR. The effects of supplements on markers of oxidative stress in skin and the minimal erythema dose to UVR were assessed.

RESULTS

Supplementary vitamin E was bioavailable, the plasma concentration increased from 14.0 +/- 0.66 (x +/- SEM) to 18.2 +/- 0.64 mug/mL (P < 0.01), and the skin concentration increased from 0.55 +/- 0.09 to 1.6 +/- 0.19 ng/mg protein (P < 0.01). Supplementary beta-carotene increased plasma concentrations from 1 +/- 0.3 to 2.25 +/- 0.3 mug/mL (P < 0.05), but skin concentrations were undetectable. Before vitamin E supplementation, UVR increased the skin malondialdehyde concentration from 0.42 +/- 0.07 to 1.24 +/- 0.16 nmol/mg protein (P < 0.01), whereas oxidized or total glutathione increased from 9.98 +/- 0.4% to 12.0 +/- 1.0% (P < 0.05). Vitamin E supplementation significantly decreased the skin malondialdehyde concentration, but neither vitamin E nor beta-carotene significantly influenced other measures of oxidation in basal or UVR-exposed skin.

CONCLUSIONS

Vitamin E or beta-carotene supplementation had no effect on skin sensitivity to UVR. Although vitamin E supplements significantly reduced the skin malondialdehyde concentration, neither supplement affected other measures of UVR-induced oxidative stress in human skin, which suggested no photoprotection of supplementation.

Photodamage of the skin: protection and reversal with topical antioxidants

Controversy exists as to whether topical antioxidants can be effective in protecting against and reversing photodamage to the skin. Topical vitamins C and E, as well as topical selenium, protect skin against sunburn, suntan and skin cancer and also reverse the mottled pigmentation and wrinkles of photoageing. However, only certain forms of these labile antioxidants are stable and active after percutaneous absorption. For effective topical application, vitamin C must be non-esterified, acidic and optimally at 20% concentration; vitamin E must be the non-esterified isomer d-alpha-tocopherol at 2-5% concentration. Selenium is only percutaneously absorbed and active when applied topically as l-selenomethionine, optimally at 0.02-0.05%. There are two great advantages in applying an active formulation of topical antioxidants to the skin. First, the skin attains far higher levels of each antioxidant than can be achieved by only taking these vitamins orally. The level of vitamin C attained in the skin by topical application is 20-40 times that achievable with oral vitamin C. With topical application, the concentration of vitamin E in the skin increases by a factor of 10.6 and selenium by a factor of 1.7. Second, topical application arms the skin with a reservoir of antioxidants that cannot be washed or rubbed off, a protection which stays in the skin for several days after application.

Effects of topical L-selenomethionine with topical and oral vitamin E on pigmentation and skin cancer induced by ultraviolet irradiation in Skh:2 hairless mice

BACKGROUND

The antioxidants selenium and vitamin E can be effective in reducing acute and chronic ultraviolet (UV)-induced skin damage.

OBJECTIVE

This study investigated whether topical L-selenomethionine with topical RRR-alpha-tocopherol (Eol) or oral RRR-alpha-tocopheryl acetate (Eac) can reduce the incidence of UV-induced skin damage more than treatment with each alone.

METHODS

Skh:2 hairless pigmented mice were treated with lotion vehicle, L-selenomethionine lotion, Eol lotion, oral Eac, L-selenomethionine plus Eol lotion, or L-selenomethionine lotion plus oral Eac and exposed to UVB. Skin pigmentation was scored, and the number of skin tumors per animal was counted weekly.

RESULTS

Mice treated with selenium and vitamin E had significantly less acute and chronic UV-induced skin damage.

CONCLUSION

Topical L-selenomethionine alone and combined with vitamin E gave the best protection against UV-induced blistering and pigmentation. In protecting against skin cancer, topical Eol and topical L-selenomethionine plus oral Eac were best. Significant synergy of L-selenomethionine with vitamin E was not observed.

Dietary lutein/zeaxanthin decreases ultraviolet B-induced epidermal hyperproliferation and acute inflammation in hairless mice

Lutein and zeaxanthin are carotenoids found in green leafy vegetables with interesting antioxidant properties. They are present in high concentrations in the fovea centralis of the human retina and their role in the prevention of age-related macula degeneration has been reported. We have investigated the effect of orally administered lutein and zeaxanthin in the cutaneous response to ultraviolet B irradiation. Female hairless SKh-1 mice receiving 0.4% and 0.04% lutein plus zeaxanthin-enriched diet for 2 wk were exposed to single doses of ultraviolet B radiation. Skin biopsies were taken at 24 and 48 h after irradiation and analyzed for the presence of apoptotic cells, proliferating cells, and expression of proliferating cell nuclear antigen. Our results show a clear ultraviolet-induced dose-dependent inflammatory response. Orally administered 0.4% lutein and zeaxanthin decreased significantly the edematous cutaneous response (p<0.01) as determined by the reduction of the UVB-induced increase of ear bifold thickening. Additionally, dietary carotenoids were efficient in reducing the ultraviolet B-induced increases in the percentage of proliferating cell nuclear antigen (p<0.05), bromodeoxyuridine (p<0.05), and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling-positive cells (p<0.01). These data demonstrate that oral supplementation of lutein and zeaxanthin diminishes the effects of ultraviolet B irradiation by reducing acute inflammatory responses and ultraviolet-induced hyperproliferative rebound.

Cancer chemopreventive effects of oral feeding alpha-tocopherol on ultraviolet light B induced photocarcinogenesis of hairless mouse

Ultraviolet light is the most common cause of skin cancers in humans and several effects of ultraviolet light B (UVB: 290-320 nm) are thought to contribute to skin photocarcinogenesis. The generation of free radicals and related oxidants produced by UVB exposure, result in photocarcinogenesis by directly damaging DNA. On the other side, activating of transcription factor, activator protein 1 (AP-1) induced by UVB exposure causes tumor promotion. alpha-tocopherol has two principal physiological activities and one is an antioxidant activity through which alpha-tocopherol protects unsaturated fatty acids, protein and DNA from oxidation. The other activity is to stabilize the structure of the biomembrane. In addition to these two activities, it has been recently established that alpha-tocopherol plays important roles in cell signal transduction. In course of these studies, we examined such effects of alpha-tocopherol on UVB induced skin photocarcinogenesis in hairless mice. These results indicate that oral feeding of alpha-tocopherol including diet exhibited a marked inhibitory effects on both tumor incidence and multiplicity in UVB induced mouse skin photocarcinogenesis.

Turkish Tombul hazelnut (Corylus avellana L.). 1. Compositional characteristics

The quality of Tombul (Round) hazelnut, grown in the Giresun province of Turkey, was determined by measuring proximate composition, minerals, vitamins, dietary fiber, amino acids, and taste active components (free amino acids, sugars, and organic acids). Fat was the predominant component in Tombul hazelnut (approximately 61%). The major minerals were potassium, phosphorus, calcium, magnesium, and selenium. Hazelnut was also found to serve as an excellent source of vitamin E (24 mg/100 g) and a good source of water soluble (B complex) vitamins and dietary fiber. The major amino acids were glutamic acid, arginine, and aspartic acid. The three nonessential amino acids and the essential amino acids contributed 44.9 and 30.9% to the total amino acids present, respectively, while lysine and tryptophan were the limiting amino acids in Tombul hazelnut. Twenty-one free amino acids, six sugars, and six organic acids were positively identified; among these, arginine, sucrose, and malic acid predominated, respectively. These taste active components may play a significant role in the taste and flavor characteristics of hazelnut. Thus, the present results suggest that Tombul hazelnut serves as a good source of vital nutrients and taste active components.

Final report on the safety assessment of Tocopherol, Tocopheryl Acetate, Tocopheryl Linoleate, Tocopheryl Linoleate/Oleate, Tocopheryl Nicotinate, Tocopheryl Succinate, Dioleyl Tocopheryl Methylsilanol, Potassium Ascorbyl Tocopheryl Phosphate, and Tocophersolan

Tocopherol and its several ester and ether derivatives all function as antioxidants in cosmetic formulations; they also have other functions, such as skin conditioning. Tocopheryl Acetate, Tocopherol, and Tocopheryl Linoleate are used in 2673 formulations, generally at concentrations of up to 36%, 5%, and 2%, respectively, although Tocopheryl Acetate is 100% of vitamin E oil. Tocophersolan, Tocopheryl Linoleate/Oleate, Tocopheryl Nicotinate, Tocopheryl Succinate, Dioleyl Tocopheryl Methylsilanol, and Potassium Ascorbyl Tocopheryl Phosphate, combined, are used in 36 formulations at concentrations lower than those reported for the frequently used ingredients. Tocopherol may be isolated from vegetable oils or synthesized using isophytol and methylhydroquinone. Tocopherol, Tocopheryl Acetate, Tocopheryl Linoleate, and Tocopheryl Succinate all were absorbed in human skin. In rat skin, Tocopheryl Acetate is hydrolyzed to Tocopherol. Tocopherol is a natural component of cell membranes thought to protect against oxidative damage. Tocopherol, Tocopheryl Acetate, and Tocopheryl Succinate each were reported to protect against ultraviolet radiation-induced skin damage. These ingredients are generally not toxic in animal feeding studies, although very high doses (>2 g/kg/day) have hemorrhagic activity. These ingredients are generally not irritating or sensitizing to skin or irritating to eyes, although a Tocopheryl Acetate did produce sensitization in one animal test, and Tocophersolan was a slight eye irritant in an animal test. Reproductive and developmental toxicity tests in animals using Tocopherol, Tocopheryl Acetate, Tocopheryl Succinate, and Tocophersolan were all negative or showed some effect of reducing toxicity. Tocopherol, Tocopheryl Acetate, Tocopheryl Succinate, and Dioleyl Tocopheryl Methylsilanol were almost uniformly negative. These ingredients exhibit antimutagenic activity consistent with their antioxidant properties. Tocopherol was not carcinogenic. The ability of Tocopherol, Tocopheryl Acetate, and Tocopheryl Succinate to modulate the carcinogenic effect of other agents (e.g., tumor promotion) has been extensively studied. One study showing tumor promotion in mice may be discounted as not reproducible and not consistent with the large volume of data suggesting that the antioxidant properties of these agents protect against tumor induction. Specifically, the frequent use of Tocopherol as a negative control in other tumor promotion studies suggests that Tocopherol is not a tumor promoter. Tocopherol has been shown to reduce the photocarcinogenic effect of ultraviolet radiation in mice. Similar studies with Tocopheryl Acetate and Tocopheryl Succinate, however, demonstrated some enhancement of photocarcinogenesis, although the effect was not dose related. In clinical studies, Tocopherol, Tocopheryl Acetate, and Tocopheryl Nicotinate were not irritants or sensitizers. A report of a large number of positive patch-tests to Tocopheryl Linoleate in one cosmetic product were considered to result from a contaminant or metabolite. The Cosmetic Ingredient Review Expert Panel considered that these data provide an adequate basis on which to conclude that Tocopherol, Tocophersolan, Tocopheryl Acetate, Tocopheryl Linoleate, Tocopheryl Linoleate/Oleate, Tocopheryl Nicotinate, Tocopheryl Succinate, Dioleyl Tocopheryl Methylsilanol, and Potassium Ascorbyl Tocopheryl Phosphate are safe as used in cosmetic formulations. Although there were no inhalation toxicity data, these ingredients are used at such low concentrations in hair sprays that no inhalation toxicity risk was considered likely. Because methylhydroquinone is used in the chemical synthesis of Tocopherol, there was concern that hydroquinone may be present as an impurity. In such cases, residual levels of hydroquinone would be expected to be limited to those achieved by good manufacturing practices.

Dietary, but not topical, alpha-linolenic acid suppresses UVB-induced skin injury in hairless mice when compared with linoleic acids

Peroxidizability of fatty acids in the air is roughly proportional to the number of double bonds, but in vivo peroxidation proceeds in a more complex manner. Here, we compared the effects of dietary and topically applied oils enriched with linoleic acid (LA, 18:2n-6) or alpha-linolenic acid (ALA, 18:3n-3) on UV-induced skin injury in a strain of hairless mice. The UVB-induced erythema score was significantly lower in mice with topically applied creams containing LA and ALA than in mice with the basal cream; no significant increase in the score was detected in the ALA group compared with the LA group. However, dietary ALA inhibited the increase in erythema score after UVB irradiation compared with LA. The peroxidizability index of the skin total lipids was significantly higher, but UVB-induced prostaglandin E2 (PGE2) production was significantly lower in the group fed an ALA-rich diet compared with the group fed an LA-rich diet. The levels of thiobarbituric acid-reactive substances, estimated in the presence of butylated hydroxytoluene in the assay mixture, were not affected by UVB treatment or by the dietary fatty acids, but the severity of the skin lesion was associated with PGE2 levels. These results indicate that the type of fatty acids, n-6 or n-3, is critical for the suppression of UVB-induced skin lesion when the skin fatty acids are modified by dietary manipulation. Anti-inflammatory activity of dietary flaxseed oil with relatively high ALA and low LA contents was demonstrated in UVB-irradiated hairless mice.

Vitamin E protection from/potentiation of the cytogenetic toxicity of cisplatin in Swiss mice

Possible protection from or potentiation of the cytogenetic toxic effects of cisplatin (CP) 5 mg/kg b.w. in mouse bone marrow, spermatogonia by three different doses of alpha-tocopheryl acetate (vitamin E) 100, 200 and 300 mg/kg, and the transmission of such effects in the male germline, were assessed. CP-induced chromosomal aberrations (CAs) in bone marrow were decreased in vitamin E pretreated mice, but significantly (P < or = 0.05) only with vitamin E 300 mg/kg. The percentages of dividing cells in bone marrow were increased in vitamin E-pretreated groups of mice, but not significantly. However, the frequency of CP-induced micronuclei (MN) in polychromatic erythrocytes (PCEs) declined significantly (P < or = 0.01) in all the vitamin E-pretreated groups of mice. In spermatogonia the CP-induced CAs were also decreased significantly by vitamin E 200 mg/kg (P < or = 0.01), and 100 and 300 mg/kg (P < or = 0.05). However, transmission of CP-induced cytogenetic toxic effects from spermatogonia to spermatocyte, resulting in the formation of aberrant primary spermatocytes, was enhanced significantly in the mice pretreated with vitamin E 100 mg/kg (P < or = 0.05) and 200 mg/kg (P < or = 0.01). But the enhancement in the transmission of such effects was not significant in the mice pretreated with vitamin E 300 mg/kg. Besides, there was no significant change in vitamin E-pretreated groups of mice in the transmission of cytogenetic toxicity of CP from spermatogonia to sperm with the manifestation of abnormal sperm morphology. Thus, vitamin E protected bone marrow and spermatogonia from the cytogenetic toxic effects of CP, particularly efficiently at the highest tested dose (300 mg/kg), but it failed to protect from the transmission of such effects in the male germline of mouse and rather potentiated them to some extent. Treatment with vitamin E, an antioxidant, might be capable of protecting noncancerous cells from the oxidative damage caused by cisplatin but it might also reduce the effects of cisplatin on cancerous cells. Thus, the benefits of antioxidant treatment during cancer chemotherapy is yet to be demonstrated clearly.

Effects of topical and oral vitamin E on pigmentation and skin cancer induced by ultraviolet irradiation in Skh:2 hairless mice

This study investigates whether supplementation with topical RRR-alpha-tocopherol (Eol), topical RRR-alpha-tocopheryl succinate, and oral RRR-alpha-tocopheryl acetate can reduce the incidence of acute and chronic damage to the skin (i.e., sunburn and pigmentation and skin cancer, respectively) induced by ultraviolet (UV) irradiation to mice. Groups of twenty Skh:2 female hairless pigmented mice were treated with 1) lotion vehicle, 2) 5% Eol lotion, 3) 5% topical RRR-alpha-tocopheryl succinate lotion, or 4) lotion vehicle and oral RRR-alpha-tocopheryl acetate. Within each group, 15 mice were exposed to 0.24 J/cm2 of UV-B radiation three times per week. The animals' weights and food intakes were monitored, and the vitamin E concentrations of skin, liver, and adipose tissue were measured to determine whether the topical Eol resulted in significant tissue levels. Skin pigmentation was scored, and the total number of clinically detectable skin tumors per animal was counted weekly. Results showed that the skin concentrations of Eol, as well as levels in the adipose tissue, were increased after topical application. Mice treated with each form of vitamin E showed no signs of toxicity and had significantly less acute and chronic skin damage induced by UV irradiation, as indicated by reduced inflammation and pigmentation and by later onset and lesser incidence of skin cancer.

An electrophoretic study of vitamin E status and expression of heat shock proteins in alveolar type II and liver cells

Vitamin E is the most important lipophilic antioxidant. Oxidative injuries are prevented or minimized by vitamin E supplementation. Various physiological and pathological situations are accompanied by vitamin E deficiency. However, it is not clear whether alimentary vitamin E deficiency in itself constitutes oxidant stress that induces appropriate responses, which, in turn, can be avoided by adequate vitamin E supplies, or whether the remaining cellular antioxidants compensate a temporary vitamin E deficiency. We studied effects of the dietary vitamin E status on cellular vitamin E levels and on the expression of heat shock proteins (HSPs) in alveolar type II cells and liver. The expression of HSPs, representing an early and very sensitive marker of cellular stress, was compared with the activity of antioxidative enzymes. Vitamin E depletion caused a substantial increase in HSP32 in alveolar type II cells, whereas in liver there was a marked increase in HSP70. The activity of the antioxidant enzymes, however, did not change significantly. A reversal of HSP expression to almost normal levels was seen after vitamin E resupplementation. These results indicate that, under normal conditions, a suboptimal supply of vitamin E to rats exposes the alveolar type II cells and the liver to reversible cellular stress.

Photoprotective actions of topically applied vitamin E

Topical application of vitamin E has been shown to decrease the incidence of ultraviolet (UV)-induced skin cancer in mice. Vitamin E provides protection against UV-induced skin photodamage through a combination of antioxidant and UV absorptive properties. Topical application of alpha-tocopherol on mouse skin inhibits the formation of cyclobutane pyrimidine photoproducts. However, topically applied alpha-tocopherol is rapidly depleted by UVB radiation in a dose-dependent manner. The photooxidative fate of the alpha-tocopherol depends on the local environment of the vitamin E. alpha-Tocopherol quinone and alpha-tocopherol quinone epoxides are principal photoproducts of vitamin E that has penetrated into the epidermal layer of the skin, whereas tocopherol dimers and trimers are formed from alpha-tocopherol in a bulk phase at the skin surface. Dimer and trimer products may participate in prevention of UV-induced photodamage.

Inhibitory effects of deferoxamine on UVB-induced AP-1 transactivation

Production of reactive oxygen species (ROS) by iron can contribute directly to DNA and protein damage and may contribute to cell signaling and proliferation. We have examined the effects of the iron(III) chelator deferroxamine (DFO) and iron (FeCl(3)) on UVB (290-320 nm)-induced activator protein 1 (AP-1) signaling. The ability of DFO to inhibit UVB-induced AP-1 transactivation was tested in a human keratinocyte cell line stably transfected with a luciferase reporter driven by a single AP-1 element. DFO treatment 24 h prior to UVB irradiation reduced UVB-induced AP-1 transactivation by approximately 80%, with the effect of DFO diminishing as pre-treatment time was shortened. Treatment with FeCl(3) a minimum of 6 h prior to UVB potentiated the UVB induction of AP-1 transactivation by 2-3-fold. DFO was able to ablate both the UVB induction of AP-1 transactivation as well as the potentiation by FeCl(3). The antioxidants Trolox and N-acetyl cysteine were both able to inhibit UVB-induced AP-1 transactivation and Trolox was able to inhibit the potentiation of UVB-induced AP-1 by FeCl(3). These results indicate that UVB-induced AP-1 activation may be in part due to oxidant effects of UVB and intercellular iron.

Do vitamin E supplements in diets for laboratory animals jeopardize findings in animal models of disease?

Vitamin E has been supplemented to the diets of farm animals to improve fertility, health, growth rates and quality of animal products. Because of the positive experience obtained in farm animals, vitamin E has been added in increasing amounts to the diets of laboratory animals. Today, vitamin E levels in standard rodent maintenance diets range from 30 mg/kg (France, United States), 90-120 mg/kg (Netherlands, United Kingdom) to as much as 200 mg/kg (Germany). While increasing fertility and health of laboratory animals, these vitamin E supplements affect diverse pathophysiological conditions and thus the outcome of animal models of disease. Because of the large variability of vitamin E levels between laboratories within and between different countries, results obtained in established animal models may no longer be comparable and/or reproducible. Researchers should be aware of these vitamin E supplements and carefully control for potential effects in their respective animal models that involve--or may involve--the generation of reactive oxygen species.

Protection by black tea and green tea against UVB and UVA + B induced skin cancer in hairless mice

The effects of green and black tea consumption on the early indices of UVB and UVA + B skin damage in hairless mice have been studied in the absence of any chemical tumour initiators or promoters. Black tea consumption was associated with a reduction in the number of sunburn cells in the epidermis of mice 24 h after UVA + B irradiation, although there was no effect of green tea. Other indices of early damage such as necrotic cells or mitotic figures were not affected. Neutrophil infiltration as a measure of skin redness was slightly lowered by tea consumption in the UVB group. Consumption of either green or black tea resulted in significantly fewer skin papillomas and tumours induced by UVA + B light, however black tea provided better protection against UVB-induced tumours than green tea. This study confirms earlier reports that tea consumption can reduce the incidence of skin cancer in hairless mice, and indicates that black tea may afford more protection against simulated solar irradiation than green tea.

The effect of vitamin E acetate on ultraviolet-induced mouse skin carcinogenesis

Despite the benefits of sunscreens, ultraviolet (UV) exposure can still lead to skin cancer. In this study we investigated the effect of topical application of the antioxidant vitamin E acetate (VEA) on the inhibition of UV-induced carcinogenesis. Hairless SKH-1 mice received 5.2 mg of VEA 30 min before (VEA/UV) or after (UV/ VEA) a single minimal erythemic dose of UV light. Vehicle-control animals received acetone 30 min before UV exposure (Ace/UV). After 24 h, cyclobutane dimer repair was twofold and 1.5-fold greater in the UVNEA and VEA/UV groups, respectively. Expression of p53 protein in the UV/VEA group was maximum at 12 h after UV exposure, whereas in the Ace/UV- and VEA/UV-treated mice, maximum p53 immunostaining was statistically higher at 15 h (P = 0.03). DNA synthesis as determined by 5-bromo-2'-deoxyuridine incorporation was twofold higher after 15 h in all groups but was not statistically different among treatment groups. Protein levels of cyclin D1 and p21 were increased in both VEA groups by 6 h. In addition, VEA treatments delayed tumor formation and yield for the first 20 wk, although this difference was lost by 30 wk. The telomerase activity of carcinomas from the UV/VEA-treated mice was statistically lower than that of the Ace/UV-treated mice (P = 0.05). This study showed that although VEA may mitigate some of the initial events associated with UV irradiation such as DNA damage and p53 expression, it has limited potential in preventing UV-induced proliferation and tumor formation.

Content of alpha-tocopherol in blood serum of human Papillomavirus-infected women with cervical dysplasias

The studies were carried out in a group of 228 female patients with normal cytological smear and 324 patients with cervical intraepithelial neoplasia. The applied method of identification, i.e., the human Papillomavirus (HPV) digene hybrid capture system, made it possible to select a control group consisting of 168 HPV-negative patients with normal Pap smear, as well as a group of 228 HPV-positive patients with cervical intraepithelial neoplasia. The high-performance liquid chromatography method was employed to evaluate the level of alpha-tocopherol in the blood serum of the patients who were examined. A statistically significantly lower level of alpha-tocopherol was observed in the blood serum of HPV-positive patients with cervical intraepithelial neoplasia. The risk of dysplasia was four times higher for an alpha-tocopherol level < 7.95 mumol/l.

Modulation of ultraviolet light-induced epidermal damage: beneficial effects of tocopherol

Oxygen free radicals have been shown to result from and mediate deleterious effects of ultraviolet radiation on the skin. The purpose of this study was to determine if topical DL-alpha-tocopherol (vitamin E) could reduce ultraviolet-induced damage to the epidermis. Twenty mice were treated with either ethanol or a 1:1 mixture of tocopherol and ethanol. Treatments consisted of once-daily 0.1-ml topical applications for 1 week, followed by irradiation with 0.30 mW/cm2 of ultraviolet B irradiation. A statistically significant decrease in Schiff base formation was noted between tocopherol-treated animals and their controls. Histologic study revealed a statistically significant increase in epidermal thickness in tocopherol-treated skin versus controls or vehicle alone. The thicker epidermis was accompanied by the presence of parakeratosis, implicating increased proliferation as the cause of the increasing thickness. The number of sunburn cells was decreased by tocopherol treatment. Tocopherol protection from ultraviolet irradiation may have been due to both direct protection from free radicals and indirect protection by means of increased epidermal thickness. The demonstration of beneficial effects of tocopherol administration suggests that further studies in clinically relevant models to define optimal dosage, frequency of administration, vehicle, and quantitation of the possible protective effects afforded to Langerhans cells may be useful.

Photocarcinogenesis: an overview

Photocarcinogenesis represents the sum of a complex of simultaneous and sequential biochemical events that ultimately lead to the occurrence of skin cancer. These events, initiated by UV radiation of appropriate wavelength, include the formation of DNA photoproducts: DNA repair; mutation of proto-oncogenes and tumor suppressor genes; UV-production of radical species with subsequent effects on mutation and extra-nuclear function; and other epigenetic events that influence the course of carcinogenesis. The epigenetic influences may include immunological responses, antioxidant defenses, and dietary factors. This review represents an effort to provide current research results in the aforementioned areas and an attempt to meld these events into a comprehensive overview of photocarcinogenesis. If effective prevention and intervention strategies for skin cancer are to developed, a more thorough understanding of the disease process is imperative.

Vitamin E modulation of hepatic focal lesion growth in mice

The effect of DL-alpha-tocopherol acetate (vitamin E) on hepatic focal lesion growth in male B6C3F1 mice previously treated with diethylnitrosamine (DEN) was investigated. After hepatic focal lesions were formed, mice were placed into one of the following dose groups: 0 mg vitamin E/kg NIH-07 diet, 50 mg vitamin E/kg NIH-07 diet (control diet), 250 mg vitamin E/kg NIH-07 diet, and 450 mg vitamin E/kg NIH-07 diet. Mice were euthanized after either 30 or 60 days of dietary treatment. In normal (nonlesion) liver, vitamin E deficiency (0 mg/kg diet) increased hepatic DNA synthesis. In addition, vitamin E supplementation (450 mg/kg diet) decreased the incidence of hepatic apoptosis, while vitamin E deficiency (0 mg/kg diet) increased the incidence of hepatic apoptosis. The effect of vitamin E-induced lesion growth was examined by measuring the number of focal lesions per liver and the relative focal lesion volume. High-dose vitamin E supplementation (450 mg/kg diet) appeared to enhance the growth of hepatic focal lesions. In particular, basophilic lesions appeared to be the most sensitive to high-dose vitamin E modulation (450 mg/kg diet) as evidenced by increased number, volume, and labeling index of hepatic focal lesions. Vitamin E deficiency also appeared to enhance the growth of hepatic focal lesions, though to a lesser extent than vitamin E supplementation (450 mg/kg diet). In the present study, both vitamin E supplementation (450 mg/kg diet) and deficiency (0 mg/kg diet) appeared to enhance focal lesion growth albeit neither treatment enhanced lesion growth as dramatically as known nongenotoxic hepatocarcinogens (e.g., phenobarbital and dieldrin). The data presented here suggest that oxidative stress in focal hepatocytes may be a component of the liver tumor promotion process.

Decrease in vitamin E levels in the bone marrow of mice receiving whole-body X-ray irradiation

Mice were subjected to whole-body x-ray irradiation, and changes in vitamin E content and lipid peroxide levels in various tissues were examined. When mice were irradiated with 6 Gy, vitamin E content (per mg protein) in the bone marrow began to decrease 3 h later and a marked decrease to the level of 30% of that of the controls was observed on day 2. Concomitant with the decrease of vitamin E, an increase of lipid peroxide levels was also observed in the bone marrow. On day 2 after an exposure to doses ranging from 1 to 10 Gy, a dose-dependent decrease of vitamin E and an increase of lipid peroxide levels were observed in the bone marrow with a dose of 3 Gy or more. In contrast, neither a decrease of vitamin E nor an increase of lipid peroxide levels was observed in the liver, kidney, spleen, and testes even with an exposure of up to 10 Gy. After the irradiation, glutathione in the bone marrow decreased, while that in the liver increased. These results suggest that the bone marrow is more highly susceptible to oxidative damage induced by radiation than other tissues.

Vitamin E: molecular and biological function

There is a growing body of evidence implicating free radicals in a wide variety of medical diseases and conditions, especially the diseases of ageing, such as cancer and cardiovascular disease, which appear to be ultimate expressions of long-term, cumulative and sustained cellular damage. Vitamin E is an excellent lipid-soluble, chain-breaking antioxidant in the presence of other co-operative antioxidants such as vitamin C or ubiquinol, but it can act as a pro-oxidant in their absence. Epidemiological findings and animal studies support the belief that vitamin E is protective against cardiovascular disease and possibly cancer. The wide range of symptoms associated with vitamin E deficiency is consistent with a loss of antioxidant protection in those long-lived cells in which there is sufficient opportunity for accumulation of free radical damage. The cellular damage is proposed to arise from the generation of free radicals during normal aerobic metabolism. Some susceptible tissues may have enhanced levels of radicals that are produced, for example, by the action of cytochrome P-450 enzymes in steroidogenic tissues, or by the generation of NO in neural tissues.