The influence of topical and systemic vitamin E on ultraviolet light-induced skin damage in hairless mice

Impact of coconut kernel extract on carcinogen-induced skin cancer model: Oxidative stress, C-MYC proto-oncogene and tumor formation

This study aimed at analysing the effects of coconut (Cocos nucifera L.) kernel extract (CKE) on oxidative stress, C-MYC proto-oncogene, and tumour formation in a skin cancer model. Tumorigenesis was induced by dimethylbenz[a]anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA). In vitro antioxidant activity of CKE was assessed using 2, 2-diphenyl-1-picrylhydrazyl (DPPH), hydrogen peroxide (H2O2), total phenolic and flavonoid content assays. CKE showed a higher antioxidant activity then ascorbic acid (*P < 0.05, ****P < 0.0001). HPLC and NMR study of the CKE revealed the presence of lauric acid (LA). Following the characterization of CKE, mice were randomly assigned to receive DMBA/TPA Induction and CKE treatment at different doses (50, 100, and 200 mg/kg) of body weight. LA 100 mg/kg of body weight used as standard. Significantly, the CKE200 and control groups' mice did not develop tumors; however, the CKE100 and CKE50 treated groups did develop tumors less frequently than the DMBA/TPA-treated mice. Histopathological analysis revealed that the epidermal layer in DMBA-induced mice was thicker and had squamous pearls along with a hyperplasia/dysplasia lesion, indicating skin squamous cell carcinoma (SCC), whereas the epidermal layers in CKE200-treated and control mice were normal. Additionally, the CKE treatment demonstrated a significant stimulatory effect on the activities of reactive oxygen species (ROS), glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD), as well as an inhibitory effect on lipid peroxidase (*P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001) and c-MYC protein expression (*P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001). In conclusion, CKE prevents the growth of tumors on mouse skin by reducing oxidative stress and suppressing c-MYC overexpression brought on by DMBA/TPA induction. This makes it an effective dietary antioxidant with anti-tumor properties.

Evidence of Potential Natural Products for the Management of Hypertrophic Scars

Hypertrophic scarring is an aberrant wound-healing response to reestablish dermal integrity after an injury and can cause significant abnormalities in physical, aesthetic, functional, and psychological symptoms, impacting the patient's quality of life. There is currently no gold standard for preventing and treating hypertrophic scars. Therefore, many researchers have attempted to search for antihypertrophic scar agents with greater efficacy and fewer side effects. Natural therapeutics are becoming attractive as potential alternative anti-scarring agents because of their high efficacy, safety, biocompatibility, low cost, and easy accessibility. This review demonstrates various kinds of natural product-based therapeutics, including onion, vitamin E, Gotu kola, green tea, resveratrol, emodin, curcumin, and others, in terms of their mechanisms of action, evidence of efficacy and safety, advantages, and disadvantages when used as anti-scarring agents. We reviewed the literature based on data from in vitro, in vivo, and clinical trials. A total of 23 clinical trials were identified in this review; most clinical trials were ranked as having uncertain results (level of evidence 2b; n = 16). Although these natural products showed beneficial effects in both in vitro and in vivo studies of potential anti-scarring agents, there was limited clinical evidence to support their efficacy due to the limited quality of the studies, with individual flaws including small sample sizes, poor randomization, and blinding, and short follow-up durations. More robust and well-designed clinical trials with large-scale and prolonged follow-up durations are required to clarify the benefits and risks of these agents.

Uniform titania-supported Ce(iii) carbonate cluster catalysts for degradation of reactive oxygen species

We report the synthesis of uniform 2.5 ± 0.4 nm diameter Ce(iii) carbonate clusters deposited on the surface of TiO₂ nanoparticles and characterize them using HAADF-STEM and EELS, as well as UV-Vis and FTIR spectroscopies. This material is a highly proficient catalytic antioxidant for the degradation of photocatalytically generated reactive oxygen species (ROS). We observed an unusual U-shaped pH-dependence in its photoprotection catalytic activity, with an optimum function in the near-neutral pH range of 7.7 ± 0.7. This sharp pH dependence is not observed in previously reported bulk Ce(iii) carbonate materials, and it is also not a consequence of Ce(iii) carbonate cluster decomposition. However, it is consistent with a tandem reaction sequence consisting of a biomimetic superoxide dismutase and catalase function, which is dependent on a balance of protons and hydroxide anions for function. Our dissolution-deposition approach for synthesizing nanoscale Ce(iii) carbonate clusters on TiO₂ should be generalizable to other carbonates and metal-oxide supports.

Vitamin E inhibits the UVAI induction of "light" and "dark" cyclobutane pyrimidine dimers, and oxidatively generated DNA damage, in keratinocytes

Solar ultraviolet radiation (UVR)-induced DNA damage has acute, and long-term adverse effects in the skin. This damage arises directly by absorption of UVR, and indirectly via photosensitization reactions. The aim of the present study was to assess the effects of vitamin E on UVAI-induced DNA damage in keratinocytes in vitro. Incubation with vitamin E before UVAI exposure decreased the formation of oxidized purines (with a decrease in intracellular oxidizing species), and cyclobutane pyrimidine dimers (CPD). A possible sunscreening effect was excluded when similar results were obtained following vitamin E addition after UVAI exposure. Our data showed that DNA damage by UVA-induced photosensitization reactions can be inhibited by the introduction of vitamin E either pre- or post-irradiation, for both oxidized purines and CPD (including so-called "dark" CPDs). These data validate the evidence that some CPD are induced by UVAI initially via photosensitization, and some via chemoexcitation, and support the evidence that vitamin E can intervene in this pathway to prevent CPD formation in keratinocytes. We propose the inclusion of similar agents into topical sunscreens and aftersun preparations which, for the latter in particular, represents a means to mitigate on-going DNA damage formation, even after sun exposure has ended.

Melanogenesis-Inhibitory and Antioxidant Activities of Phenolics from Periploca forrestii

Two new tetrahydrofuran-type lignans, (-)-gentioluteol 9-O-β-d-glucopyranoside (1), (-)-berchemol 9-O-β-d-apiofuranosyl-(1→6)-O-β-d-glucopyranoside (2), along with sixteen known compounds 3 - 18 were isolated from the 95% EtOH extract of the stems of Periploca forrestii. The structures of the new tetrahydrofuran-type lignans were determined by HR-ESI-MS and various NMR techniques in combination with CD method. Then, their antioxidant abilities were evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, and ferric-reducing antioxidant power (FRAP) assays. Meanwhile, a similar trend was obtained in tripartite antioxidant assays, which compounds 7 - 9 and 11 exhibited potent abilities. Subsequently, the evaluation of all compounds against the α-melanocyte-stimulating hormone (α-MSH) induced melanogenesis on the B16F10 cell line, compounds 5 - 11, 15, and 16 exhibited inhibitory effects with no or weak toxicity at low concentration. Of these, compound 8 exhibited the strongest inhibition melanogenesis ability. Furthermore, Western blot analysis suggested that compound 8 could inhibit melanogenesis by suppressing the protein expression of microphthalmia-associated transcription factor (MITF) and tyrosinase.

Curcumin Stimulates the Antioxidant Mechanisms in Mouse Skin Exposed to Fractionated γ-Irradiation

Fractionated irradiation is one of the important radiotherapy regimens to treat different types of neoplasia. Despite of the immense therapeutic gains accrued by delivering fractionated irradiation to tumors, the radiation burden on skin increases significantly. Low doses of irradiation to skin adversely affect its molecular and metabolic status. The use of antioxidant/s may help to alleviate the radiation-induced changes in the skin and allow delivering a higher dose of radiation to attain better therapeutic gains. Curcumin is an antioxidant and a free radical scavenging dietary supplement, commonly used as a flavoring agent in curries. Therefore, the effect of 100 mg/kg body weight curcumin was studied on the antioxidant status of mice skin exposed to a total dose of 10, 20 and 40 Gy γ-radiation below the rib cage delivered as a single fraction of 2 Gy per day for 5, 10 or 20 days. Skin biopsies from both the curcumin treated or untreated irradiated groups were collected for the biochemical estimations at various post-irradiation times. The irradiation of animals caused a dose dependent decline in the glutathione concentration, glutathione peroxidase, and superoxide dismutase activities and increased the lipid peroxidation in the irradiated skin. Curcumin treatment before irradiation resulted in a significant rise in the glutathione concentration and activities of both the glutathione peroxidase and superoxide dismutase enzymes in mouse skin, whereas lipid peroxidation declined significantly. The present study indicates that curcumin treatment increased the antioxidant status of mouse exposed to different doses of fractionated γ-radiation.

Oxidative stress and skin cancer: an overview

Skin is the largest body organ that serves as an important environmental interface providing a protective envelope that is crucial for homeostasis. On the other hand, it is a major target for toxic insult by a broad spectrum of physical and chemical agents that are capable of altering its structure and function. There are a large number of dietary contaminants and drugs can manifest their toxicity in skin. These environmental toxicants or their metabolites are inherent oxidants and/or directly or indirectly drive the production of a variety of reactive oxidants also known as reactive oxygen species. These are short-lived entities that are continuously generated at low levels during the course of normal aerobic metabolism. These are believed to activate proliferative and cell survival signaling that can alter apoptotic pathways that may be involved in the pathogenesis of a number of skin disorders. The skin possesses an array of antioxidant defense mechanisms that interact with toxicants to obviate their deleterious effect. The "antioxidant power" of a food is an expression of its capability both to defend the human organism from the action of the free radicals and to prevent degenerative disorders. Plants like olive trees have their own built-in protection against the oxidative damage of the sun, and these built-in protectors function as cell protectors in our own body. Although many antioxidants have shown substantive efficacy in cell culture systems and in animal models of oxidant injury, unequivocal confirmation of their beneficial effects in human populations has proven elusive.

Evaluation of the antioxidative capability of commonly used antioxidants in dermocosmetics by in vivo detection of protein carbonylation in human stratum corneum

We present an in vivo test platform to evaluate the antioxidative capability of seven frequently used dermocosmetic antioxidants on the human stratum corneum (SC). It has been reported that the protein carbonylation could be used as a biomarker for oxidative stress. The current study detects the change of the level of exposed protein carbonyl group in the most outer layer of human SC. The concentration of the antioxidant in each subject emulsion formulation was 0.5% (w/w). The data indicated that alpha-tocopherol (α-Vit E) and ascorbic acid (Vit C) have excellent antioxidative capability and α-Vit E-acetate possesses better than the average antioxidative capability. The bioconversion of α-Vit E-acetate to α-Vit E may occur in the human SC during a less than 2 weeks time course test. Lipoic acid possessed moderate antioxidative capability. Ascorbyl 6-palmitate had a low antioxidative capability. Ascorbic acid 2-glucoside represented an insignificant antioxidative capability. Glutathion (GSH) had no effect on reducing oxidative damage to human SC proteins, implying that the GSH recycling system could be absent in human SC. This test platform is an useful tool to evaluate the antioxidative efficiency of antioxidants on human SC proteins.

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.

Anti-photoaging and photoprotective compounds derived from marine organisms

Marine organisms form a prominent component of the oceanic population, which significantly contribute in the production of cosmeceutical and pharmaceutical molecules with biologically efficient moieties. In addition to the molecules of various biological activities like anti-bacterial, anti-cancerous, anti-inflammatory and anti-oxidative etc., these organisms also produce potential photoprotective or anti-photoaging agents, which are attracting present day researchers. Continuous exposure to UV irradiation (both UV-A and UV-B) leads to the skin cancer and other photoaging complications, which are typically mediated by the reactive oxygen species (ROS), generated in the oxidative pathways. Many of the anti-oxidative and anti-photoaging compounds have been identified previously, which work efficiently against photodamage of the skin. Recently, marine originated photoprotective or anti-photoaging behavior was observed in the methanol extracts of Corallina pilulifera (CPM). These extracts were found to exert potent antioxidant activity and protective effect on UV-A-induced oxidative stress in human dermal fibroblast (HDF) cells by protecting DNA and also by inhibiting matrix metalloproteinases (MMPs), a key component in photoaging of the skin due to exposure to UV-A. The present review depicts various other photoprotective compounds from algae and other marine sources for further elaborative research and their probable use in cosmeceutical and pharmaceutical industries.

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.

The cosmetic treatment of wrinkles

Wrinkles now have a greater social impact because people live longer. Science and hedonism overlap in the search for causes, treatments and prevention of wrinkles. The cosmetic approach to wrinkles includes: i Cleansing ii Photoprotection iii Active ingredients Active ingredients go well beyond simple moisturisers and exert a more complex activity in protecting skin from external injuries, nourishing it and removing its superficial layers. Transport systems and excipients are increasingly effective. Functional agents currently include alpha hydroxy acids (AHAs), poly-AHAs, complex poly-AHAs, retinoids, fish polysaccharides, anti-enzymatic agents, antioxidants (including ascorbic acid, pycnogenol, ursolic acid, vegetable isoflavones, vitamin E, coenzyme Q10, lipoic acid, resveratorol, l-carnosine and taurine) as well as agaricic acid and various plant extracts. All are reviewed in this text. Most are topical, some can be given by mouth, even as food supplements. Cosmetics are becoming closer to drugs in preventing and treating wrinkles. Included amongst the cosmeceuticals are the anti-wrinkle agents described herein.

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.

Role of novel delivery systems in developing topical antioxidants as therapeutics to combat photoageing

Ageing proceeds by highly complicated biochemical processes, in which the involvement of the reactive oxygen species (ROS) and free radicals has been implicated. Reactive oxygen species are dramatically enhanced by exposure to the ultraviolet radiation. Free radical scavengers and antioxidants can thus provide a long-term protection against these changes. Currently, dermaceutical and cosmetic industry is growing immensely with its main focus on packaging the active into a suitable/novel delivery system. This not only enhances the customer acceptance but offers better targeting to the upper skin layer, with faster onset, at a lower concentration of the active. Later also counter toxic or adverse effects observed with large doses especially when administered orally. Several of the antioxidant molecules are labile to degradation in the presence of oxygen, water and light, hence it becomes all the more appropriate to use a delivery system which will augment their stability and hence enhance the performance. In the present review, we focus on the pioneering research on novel delivery systems which can promote the therapeutic value of antioxidants for combating UV-induced photoageing.

The effect of vitamin E on acute skin reaction caused by radiotherapy

Ionizing radiation affects healthy organs and tissues as well as diseased tissues during radiation therapy. Skin reactions varying from acute erythema to necrosis can be seen. It has been found that vitamin E can prevent mutagenic and/or carcinogenic effects of ionizing radiation in both animals and cell cultures. This study investigated the preventative effect of antioxidant vitamin E on irradiation-induced acute skin reactions. No protective effect of vitamin E was demonstrated. It is possible that the vehicle induced free radical exposure in the irradiated skin.

Vitamin E in human skin: organ-specific physiology and considerations for its use in dermatology

Vitamin E has been used for more than 50 years in experimental and clinical dermatology. While a large number of case reports were published in this time, there is still a lack of controlled clinical studies providing a rationale for well defined dosages and clinical indications. In contrast, advances in basic research on the physiology, mechanism of action, penetration, bioconversion and photoprotection of vitamin E in human skin has led to the development of numerous new formulations for use in cosmetics and skin care products. This article reviews basic mechanisms and possible cosmetic as well as clinical implications of the recent advances in cutaneous vitamin E research. Experimental evidence suggests that topical and oral vitamin E has antitumorigenic, photoprotective, and skin barrier stabilizing properties. While the current use of vitamin E is largely limited to cosmetics, controlled clinical studies for indications such as atopic dermatitis or preventions of photocarcinogenesis are needed to evaluate the clinical benefit of vitamin E.

Development and evaluation of sesamol as an antiaging agent

Aging comprises various changes that occur in living organisms with the passage of time, leading to increased system entropy, loss of homeostasis and eventually death. Of the various theories proposed, the free radical theory of aging states that it is the shift in antioxidant/pro-oxidant balance that leads to increased oxidative stress, dysregulation of cellular function and aging. It has been proved that accumulated damage by free radicals produced by exposure to ultraviolet (UV) radiation results in extensive damage to the soft skin tissues, which is commonly known as "photoaging". Although the human body has built-in antioxidant mechanisms to suppress uncontrolled free radicals, these mechanisms may at times fail due to overwhelming production of toxic radicals. This is where supplemental antioxidants can play a vital role in restoring the balance, lack of which produces visible wrinkling and premature aging. Sesamol, a highly acclaimed antioxidant, was selected as a suitable antioxidant to investigate in this study, and is for the first time shown to counter UV-induced oxidative stress (in terms of both biochemical and histopathological changes) in mouse skin. The source of radiation was a 300-W UV lamp, and mice of the lacca strain were chosen as an animal model for this study. Free radical levels generated were estimated using the Ohkawa method for estimation of lipid peroxidation in animal tissues. The results from biochemical and histopathological investigations clearly confirm that the sesamol formulation is effective in preventing photodamage (lesions, ulcers and changes in skin integrity) due to chronic UV exposure.

Vitamin E: Critical Review of Its Current Use in Cosmetic and Clinical Dermatology

BACKGROUND AND OBJECTIVE

The lipophilic antioxidant vitamin E has been used for more than 50 years in clinical and experimental dermatology. However, although a large number of case reports were published, there is still a lack of controlled clinical studies providing a rationale for clinical indications and dosage. In contrast, advances in basic research on the physiology, mechanism of action, penetration, bioconversion, and photoprotection of vitamin E in human skin have led to the development of numerous new formulations for use in cosmetics and skin care products.

RESULTS

This article reviews the basic mechanisms and possible cosmetical and clinical implications of the recent advances in cutaneous vitamin E research. Experimental evidence suggests that topical and oral vitamin E has anticarcinogenic, photoprotective, and skin barrier-stabilizing properties.

CONCLUSION

Although its current use is largely limited to cosmetics, controlled clinical studies for indications such as atopic dermatitis or prevention of photocarcinogenesis are needed to evaluate the clinical benefit of vitamin E.

Prevention of UV Radiation–Induced Premature Skin Aging in Hairless Mice by the Novel Compound Melanocin A

Repetitive exposure of the skin to UV radiation induces various harmful changes, such as thickening, wrinkle formation, inflammation and carcinogenesis. A variety of natural compounds and synthetic compounds have been studied to determine whether they can prevent UV-induced harmful effects. In this study, we investigated the effect of a novel compound, Melanocin A, which was isolated from Eupenicillium shearii F80695, on UV-induced premature skin aging. First, we studied the effect of Melanocin A on UV-induced matrix metalloproteinase (MMP)-9 expression in an immortalized human keratinocyte cell line, HaCaT, in vitro. Acute UV irradiation induced MMP-9 expression at both the mRNA and protein levels and Melanocin A suppressed this expression in a dose-dependent manner. We then investigated the effect of Melanocin A on UV-induced skin changes in hairless mice in vivo. Chronic exposure of hairless mouse dorsal skin to UV increased skin thickness and induced wrinkle formation and the gelatinase activities of MMP-2 and MMP-9. Moreover, Melanocin A significantly suppressed UV-induced morphologic skin changes and MMP-2 and MMP-9 expression. Taken together, these results show that Melanocin A can prevent the harmful effects of UV that lead to skin aging. Therefore, we suggest that Melanocin A should be viewed as a potential therapeutic agent for preventing and/or treating premature skin aging.

Antioxidants and basal cell carcinoma of the skin: a nested case-control study

OBJECTIVE

To investigate the relationship between basal cell carcinoma (BCC) and antioxidant nutrients, specifically carotenoids, vitamin E and selenium.

METHODS

The Nambour Skin Cancer Study is an ongoing, community-based study of randomly selected adult residents of a township in sub-tropical Queensland, Australia. Using a nested case-control design, incident cases of BCC (n=90) were compared with age and sex matched controls (n=90). Dietary exposure was measured using food frequency questionnaire estimates of intake as well as serum biomarkers. Other determinants of skin cancer including sun exposure were also considered. Dietary intakes were adjusted for energy intake, and serum carotenoids and vitamin E were adjusted for serum cholesterol. Odds ratios were calculated across quartiles of dietary intake and serum biomarkers and linear trends were assessed using logistic regression, adjusting for age, sex and supplement use.

RESULTS AND CONCLUSIONS

In this prospective study no significant associations were found between BCC and carotenoids, vitamin E or selenium, as measured by serum biomarkers or dietary intake, although there was a suggestion of a positive association with lutein intake.

Ultraviolet B-induced DNA damage in human epidermis is modified by the antioxidants ascorbic acid and D-alpha-tocopherol

DNA damage caused by ultraviolet (UV) irradiation is considered the main etiologic factor contributing to the development of skin cancer. Systemic or topical application of antioxidants has been suggested as a protective measure against UV-induced skin damage. We investigated the effect of long-term oral administration of a combination of the antioxidants ascorbic acid (vitamin C) and D-alpha-tocopherol (vitamin E) in human volunteers on UVB-induced epidermal damage. The intake of vitamins C and E for a period of 3 mo significantly reduced the sunburn reaction to UVB irradiation. Detection of thymine dimers in the skin using a specific antibody revealed a significant increase of this type of DNA damage following UVB exposure. After 3 mo of antioxidant administration, significantly less thymine dimers were induced by the UVB challenge, suggesting that antioxidant treatment protected against DNA damage.

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.

Immediate effects of UV radiation on the skin: modification by an antioxidant complex containing carotenoids

BACKGROUND/AIMS

The ultraviolet (UV) portion of sunlight is involved in the induction and development of skin cancers against which a limited photoprotection may be provided by reduced time of exposure, clothing, and sunscreen applications. The concept of an effective, safe, systemic photoprotection will circumvent many of the shortcomings. The UV-induced oxidative stress is a cause of DNA damage and a few publications have shown, in humans, minimal benefits, if any, of the oral intake of antioxidant complex, contrasting with the large literature showing beneficial effects in vitro or in animal models.

METHODS

We investigated, in 25 healthy individuals, the capacity of an antioxidant complex (AOC) - vitamins (lycopene, beta-carotene, alpha-tocopherol), selenium - to reduce UV-induced damages. The AOC was administered orally, daily during 7 weeks. Before and after irradiations, before and after the intake of the product, six parameters were studied: skin color by chromametry, minimal erythemal dose and, on skin biopsies, sunburn cells (SBCs), p53 detected by immunohistochemistry, pigmentation index, and levels of lipoperoxides (thiobarbituric acid reaction).

RESULTS

After the oral intake of AOC, we observed an elevation of the actinic erythema threshold (+20%, P=0.01) and a general reduction of the UV-induced erythemas, a reduction of the UV-induced p53 expression (P<0.05) and of SBCs (P<0.01), and a parallel reduction of the lipoperoxide levels (P<0.01). The pigmentation was increased (P<0.01).

CONCLUSION

After the oral intake of an antioxidant complex, many parameters of the epidermal defense against UV-induced damages are significantly improved. The oral intake of AOC could provide a safe, daylong and efficient complement to photo-protective measures provided by topical and physical agents and may contribute to reduce the DNA damages leading to skin aging and skin cancers.

Protective effect of alpha-tocopherol-6-O-phosphate against ultraviolet B-induced damage in cultured mouse skin

The ability of the novel water-soluble provitamin E, alpha-tocopherol-6-O-phosphate, to protect against ultraviolet B-induced damage in cultured mouse skin was investigated and compared with the protectiveness of alpha-tocopherol acetate in cultured mouse skin. Pretreatment of skin with 0.5% (9.4 mM) alpha-tocopherol-6-O-phosphate in medium for 3 h significantly prevented such photodamage as sunburn cell formation, DNA degradation, and lipid peroxidation, which were induced in control cultured skin by a single dose of ultraviolet B irradiation at 0 to 40 kJ per m2 (290-380 nm, maximum 312 nm). This protection was greater than that seen with alpha-tocopherol acetate, the most common provitamin E that is used in commercial human skin care products. The concentration of alpha-tocopherol in cultured skin pretreated with 0.5% alpha-tocopherol-6-O-phosphate rose to approximately two to three times that found in the control skin and the reduction in cutaneous alpha-tocopherol that was induced by ultraviolet irradiation was significantly inhibited. In the group pretreated with 0.5% alpha-tocopherol acetate, however, conversion of alpha-tocopherol acetate to alpha-tocopherol was not observed, although the level of provitamin incorporated into the cultured skin was the same as that for alpha-tocopherol-6-O-phosphate. These findings indicated that the enhanced ability of alpha-tocopherol-6-O-phosphate to protect against ultraviolet B-induced skin damage compared with alpha-tocopherol acetate may have been due to alpha-tocopherol-6-O-phosphate's conversion to alpha-tocopherol. Moreover, following pretreatment with a 0.5% alpha-tocopherol-6-O-phosphate, alpha-tocopherol-6-O-phosphate was incorporated into the human skin in a three-dimensional model and 5% of the incorporated alpha-tocopherol-6-O-phosphate was converted to alpha-tocopherol. These results suggest that treatment with the novel provitamin E, alpha-tocopherol-6-O-phosphate may be useful in preventing ultraviolet-induced human skin damage.

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.

Photoaging in Asians

The aging process of the skin can be divided into intrinsic and photoaging. Clinically, naturally aged skin is smooth, pale and finely wrinkled. In contrast, photoaged skin is coarsely wrinkled and associated with dyspigmentation and telangiectasia. Although the population of Asia is more than half the population of the Earth, no well-designed study has been undertaken to investigate the characteristics of cutaneous photodamage in Asian skin. As Asian skin is more pigmented, the acute and chronic cutaneous responses to UV irradiation seen in brown skin differ from those in white skin. The clinical characteristics of photoaging in Asian skin, such as pigmentary changes and wrinkle patterns, differ from those of Caucasian skin. This review provides an outline of the characteristic features of photoaging on the brown skin of Asians.

UV photoprotection by combination topical antioxidants vitamin C and vitamin E

BACKGROUND

Virtually all plants and animals protect themselves from the sun using vitamins C and E.

OBJECTIVE

The purpose of this study was to see if a combination of topical vitamins C and E is better for UV protection to skin than an equivalent concentration of topical vitamin C or E alone.

METHODS

We developed a stable aqueous solution of 15% L-ascorbic acid (vitamin C) and 1% alpha-tocopherol (vitamin E). We applied antioxidant or vehicle solutions to pig skin daily for 4 days. We irradiated (1-5x minimal erythema dose) control- and antioxidant-treated skin using a solar simulator with a 295-nm band-pass filter. On day 5, we measured antioxidant protection factor, erythema, sunburn cells, and thymine dimers.

RESULTS

The combination of 15% L-ascorbic acid and 1% alpha-tocopherol provided significant protection against erythema and sunburn cell formation; either L-ascorbic acid or 1% alpha-tocopherol alone also was protective but the combination was superior. Application during 4 days provided progressive protection that yielded an antioxidant protection factor of 4-fold. In addition, the combination of vitamins C and E provided protection against thymine dimer formation.

CONCLUSION

Appreciable photoprotection can be obtained from the combination of topical vitamins C and E. We suggest that these natural products may protect against skin cancer and photoaging.

Interaction of tocopherols and phenolic compounds with membrane lipid components: evaluation of their antioxidant activity in a liposomal model system

This paper describes the use of complex liposomes as real membrane models to evaluate the potential benefits of several antioxidants in relation to lipid peroxidation. The xanthine oxidase/Fe(3+)-ADP-EDTA and the Fe(2+)/H2O2 systems have been used to generate hydroxyl radicals and the water soluble azo-compound 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) to generate carbon centered radicals (A*) by thermal decomposition. The antioxidant behavior of the rosemary and citrus plant extracts and vitamin-E and vitamin-E acetate alpha-tocopherols have been analyzed. The order of effectiveness in avoiding radical chain reactions has been established by using the colorimetric thiobarbituric acid reaction and the fluorescent probe DPH-PA. ESR spectroscopy has been used to carry out the pursuit of the oxidation processes on the basis of the identification of the radical species resulting from the oxidant system and the ability of the antioxidants to act as scavengers for hydroxyl and AAPH-derived radicals. The modification of the main transition temperature for the lipid mixture and the splitting of the calorimetric peak in the presence of the antioxidants were demonstrated by differential scanning calorimetry. The results obtained showed that the phenols-containing plant extracts and alpha-tocopherols perturb the phase behavior of the BBE lipid bilayer and have a fluidifying effect that could favor the known antioxidant capability and scavenging characteristics of these compounds. 31P-NMR results could be interpreted as, after the incorporation of these antioxidants, those lipid molecules interacting with antioxidants give rise to lamellar phase spectral components with resonance position at lower fields or to isotropic signals in accordance with a higher motion of their phosphate groups.

Protective effect of vitamin E on ultraviolet B light-induced damage in keratinocytes

Ultraviolet (UV) B radiation is the most common environmental factor in the pathogenesis of skin cancer. Exposure of human skin to UVB radiation leads to the depletion of cutaneous antioxidants, the activation of nuclear factor kappa B (NF-kappaB), and programmed cell death (apoptosis). Although antioxidant supplementation has been shown to prevent UVB-induced photooxidative damage, its effect on components of cell signaling pathways leading to gene expression has not been clearly established. In the present study, the effect of the antioxidant vitamin, alpha-tocopherol (alpha-T), and its acetate analog, alpha-tocopherol acetate (alpha-TAc), on UVB-induced damage in primary and neoplastic mouse keratinocytes was investigated. The ability of both vitamins to modulate UVB-induced apoptosis and activation of the transcription factor NF-kappaB were studied. Treatment of normal and neoplastic mouse epidermal keratinocytes (308 cells) with 30-60 mJ/cm(2) UVB markedly decreased viable cell number and was accompanied by DNA fragmentation. When both vitamins were applied to cells at times before and after UVB radiation, a significant increase in the percentage of viable cells and concomitant decrease in the number of apoptotic cells was noted, with vitamin pretreatment providing a better protection than posttreatment. Simultaneous posttreatment of irradiated cells with alpha-TAc abolished the cytotoxic effects of UVB and restored cell viability to control levels. In addition, simultaneous posttreatment of irradiated cells with alpha-T reduced the number of apoptotic cells by half, indicating a synergistic effect of two such treatments compared with any single one. Flow cytometry analysis indicated that vitamin treatment suppressed both an increase in pre-G0 cells and a decrease in cycling cells by UVB exposure. In addition, NF-kappaB activation was detected 2 h after UV exposure and was maintained for up to 8 h. Pretreatment with vitamins significantly inhibited NF-kappaB activation at 4 and 8 h. These results indicate that vitamin E and its acetate analog can modulate the cellular response to UVB partly through their action on NF-kappaB activation. Thus, these antioxidant vitamins are potential drugs for the protection from or the reduction of UVB-associated epidermal damage.

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.

Aging- and photoaging-dependent changes of enzymic and nonenzymic antioxidants in the epidermis and dermis of human skin in vivo

This is a comprehensive study of the changes in major antioxidant enzymes and antioxidant molecules during intrinsic aging and photoaging processes in the epidermis and dermis of human skin in vivo. We show that the activities of superoxide dismutase and glutathione peroxidase are not changed during these processes in human skin in vivo. Interestingly, the activity of catalase was significantly increased in the epidermis of photoaged (163%) and naturally aged (118%) skin (n = 9), but it was significantly lower in the dermis of photoaged (67% of the young skin level) and naturally aged (55%) skin compared with young (n = 7) skin. The activity of glutathione reductase was significantly higher (121%) in naturally aged epidermis. The concentration of alpha-tocopherol was significantly lower in the epidermis of photoaged (56% of young skin level) and aged (61%) skin, but this was not found to be the case in the dermis. Ascorbic acid levels were lower in both epidermis (69% and 61%) and dermis (63% and 70%) of photoaged and naturally aged skin, respectively. Gluta thione concentrations were also lower. Uric acid did not show any significant changes. Our results suggest that the components of the antioxidant defense system in human skin are probably regulated in a complex manner during the intrinsic aging and photoaging processes.

Tannins protect against skin tumor promotion induced by ultraviolet-B radiation in hairless mice

We recently showed that Tarapod tannic acid (TA), a hydrolyzable tannin extracted from the pods of the Tara tree (Caesalpinia spinosa), was more effective than other tannins tested at inhibiting ultraviolet-B (UV-B)-stimulated hydrogen peroxide activity (an indirect measure of free radicals) in the skin of hairless mice. We also found that Tarapod TA inhibited UV-B-induced ornithine decarboxylase activity and UV-B-stimulated DNA synthesis, two biochemical markers linked to the skin tumor-promoting ability of this physical carcinogen. For this reason, we examined the effect of topical application, force feeding (gavage), and intraperitoneal injections of Tarapod TA on mouse skin chronically treated with UV-B light. Mice were initiated by a single topical application of 7,12-dimethylbenz[a]anthracene (50 nmol) and promoted by two weekly treatments with UV-B light (250 mJ/cm2) for 25 weeks. Topical application of Tarapod TA, 20 minutes before irradiation, resulted in a dose-dependent inhibition of tumor incidence (number of mice with tumors) and tumor yield (number of tumors/mouse), with 8 mg of TA inhibiting tumor yield by 70% at Week 25. Intraperitoneal injections of low doses (10 mg/kg mouse body wt), but not of high doses (25 mg/kg body wt), of TA afforded protection against UV-B-induced papillomas. However, the protection by intraperitoneal injection was lower than that observed by topical application: 10 mg/kg body wt of TA reduced tumor yield by 55%. The force feeding of 10 mg of Tarapod TA before irradiation failed to significantly inhibit the yield of tumors at the end of the experiment but delayed tumor appearance by six weeks. These results suggest that plant tannins administered topically or injected intraperitoneally reduce the tumor-promoting effects of UV-B radiation and thus could be useful photoprotectants.

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.

The effects of radicals compared with UVB as initiating species for the induction of chronic cutaneous photodamage

There is substantial evidence that ultraviolet radiation induces the formation of reactive oxygen species which are implicated as toxic intermediates in the pathogenesis of photoaging. The aim of this study was to determine whether repeated topical treatment with benzoyl peroxide, a source of free radicals, produced the same cutaneous effects as chronic ultraviolet B radiation. Three concentrations of benzoyl peroxide (0.1, 1.5, 5.0% wt/wt) and three cumulative fluences of ultraviolet B radiation (0.9, 2.2, 5.1 J per cm2) used alone and in all combinations along with appropriate controls. Female SKH1 (hr/hr) albino hairless mice were treated 5 d per wk for 12 wk. Extracellular matrix molecules and histologic parameters were assessed. Ultraviolet B radiation induced a fluence-dependent and time-dependent increase in skin-fold thickness. Fluence dependence was seen for epidermal thickness, sunburn cell numbers, dermal thickness, glycosaminoglycan content, mast cell numbers, and skin-fold thickness. Benzoyl peroxide treatment alone caused less marked increases in epidermal and dermal measures compared with ultraviolet B under the conditions used. A benzoyl peroxide concentration-dependent increase was only observed for elastin content, although the highest concentration of benzoyl peroxide increased epidermal thickness and glycosaminoglycan content. A synergistic interaction between ultraviolet B and benzoyl peroxide was not found. These results indicate that repeated administration of benzoyl peroxide produces skin changes in the hairless mouse that qualitatively resemble those produced by ultraviolet B and suggest that common mechanisms may be involved. In addition, any potential synergistic effect of ultraviolet B and benzoyl peroxide was below the level of detection used in this study.

Prevention of topical and ocular oxidative stress by positively charged submicron emulsion

A positively charged submicron emulsion with zeta potential values ranging from 35 to 45 mV and mean droplet size around 150-250 nm has recently been developed and characterized. This formulation is based on three surface-active agents, an egg yolk phospholipid mixture, poloxamer 188, and stearylamine, a cationic lipid with a pKa of 10.6. The emulsion toxicity was evaluated in three animal studies. The results of the ocular tolerance study in the rabbit eye indicated that hourly administration of one droplet of the positively charged emulsion vehicle was well tolerated without any toxic or inflammatory response to the ocular surface during the five days of the study. No marked acute toxicity was observed when 0.6 mL of positively charged emulsion was injected intravenously to BALB/c mice. Furthermore, no difference was noted between this group of animals and the group injected with the marketed and clinically well accepted negatively charged Intralipid emulsion. These observations were further confirmed in a four week toxicity study following intravenous administration to rats of 1 mL/kg of the positively charged emulsion as compared to Intralipid. No toxic effect was noted in any of the various organs examined, whereas the results of the hematological and blood chemistry tests remained in the normal range for both emulsions, confirming the preliminary safety study findings. In addition, it was demonstrated by means of a non-invasive technique that alpha-tocopherol positively charged emulsions prevented oxidative damage in rat skin subjected to UVA irradiation. The intrinsic ability of positively charged emulsified oil droplets to protect against reactive oxygen species cannot be excluded, and could act synergistically with the antioxidant alpha-tocopherol itself. The effect of blank and piroxicam positively charged emulsions on rabbit eye following alkali burn was also evaluated. The blank emulsion showed a very rapid healing rate during the first three days with a breakdown in day 14. Complete re-epithelialization was observed in day 28. The same behavior (albeit less pronounced), was noted in piroxicam emulsion, although piroxicam is known to inhibit the epithelial healing process. It can therefore be deduced that the positively charged emulsion vehicle prevented piroxicam from interfering with the epithelial healing process due to the intrinsic free radical scavenger ability of the positively charged submicron emulsion previously demonstrated. Finally, the efficacy of this promising emulsion vehicle containing effective cosmetic ingredients in preventing skin damage and aging following oxidative stress is evaluated.

Modulation of UV-light-induced skin inflammation by D-alpha-tocopherol and L-ascorbic acid: a clinical study using solar simulated radiation

OBJECTIVE

In this clinical trial we studied whether oral supplementation with D-alpha-tocopherol (alpha-Toc), L-ascorbic acid (Asc), or alpha-Toc combined with Asc influenced the solar simulated radiation (SSR) induced skin inflammation in healthy volunteers.

METHODS

We investigated the following groups in a prospective, randomized and placebo controlled study: Group (1) alpha-Toc 2 g/day, group (2) Asc 3 g/day, group (3) alpha-Toc 2 g/day combined with Asc 3 g/day, and group (4) placebo. Before and 50 days after supplementation we analyzed alpha-Toc and Asc concentrations in keratinocytes. The dose response curve of UV erythema was determined by reflectance spectrophotometry and the minimal erythema dose (MED) by visual grading before and after supplementation.

RESULTS

50 days after supplementation alpha-Toc keratinocyte levels were increased in groups (1) and (3), Asc concentrations were elevated in groups (2) and (3), and the a/gamma-Toc ratio increased in groups (1) and (3). The dose response curve of UVR induced erythema showed a significant flattening and the MED increased from 103 +/- 29 mJ/cm2 (before supplementation) to 183 +/- 35 mJ/cm2 (after supplementation) in group (3), while there were no significant changes in groups (1) and (2) after vitamin supplementation.

CONCLUSION

Alpha-Toc and Asc act synergistically in suppression of the sunburn reaction.

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.

Potentials and limitations of the natural antioxidants RRR-alpha-tocopherol, L-ascorbic acid and beta-carotene in cutaneous photoprotection

Sun exposure has been linked to several types of skin damage including sun burn, photoimmunosuppression, photoaging and photocarcinogenesis. In view of the increasing awareness of the potentially detrimental long term side effects of chronic solar irradiation there is a general need for safe and effective photoprotectants. One likely hypothesis for the genesis of skin pathologies due to solar radiation is the increased formation of reactive oxidants and impairment of the cutaneous antioxidant system. Consequently, oral antioxidants that scavenge reactive oxidants and modulate the cellular redox status may be useful; systemic photoprotection overcomes some of the problems associated with the topical use of sunscreens. Preclinical studies amply illustrate the photoprotective properties of supplemented antioxidants, particularly RRR-alpha-tocopherol, L-ascorbate and beta-carotene. However, clinical evidence that these antioxidants prevent, retard or slow down solar skin damage is not yet convincing. The purpose of this review is to provide the reader with current information on cutaneous pathophysiology of photoxidative stress, to review the literature on antioxidant photoprotection and to discuss the caveats of the photo-oxidative stress hypothesis.

Depletion of human stratum corneum vitamin E: an early and sensitive in vivo marker of UV induced photo-oxidation

As the outermost barrier of the body, the stratum corneum (SC) is frequently and directly exposed to a pro-oxidative environment, including ultraviolet solar radiation (UVR). Therefore, we hypothesized that the SC is susceptible to UVR induced depletion of vitamin E, the major lipophilic antioxidant. To test this, we investigated (i) the susceptibility of SC tocopherols to solar simulated UVR in hairless mice, (ii) the baseline levels and distribution patterns of tocopherols in human SC, and (iii) the impact of a suberythemogenic dose of solar simulated UVR on human SC tocopherols. SC tocopherol levels were measured by high performance liquid chromotography analysis of SC extracts from tape strippings. In murine SC, overall tocopherol concentrations were determined, whereas in human SC, 10 consecutive layers were analyzed for each individual. The results on SC tocopherols demonstrated (i) their concentration dependent depletion by solar simulated UVR in hairless mice; (ii) a gradient distribution within untreated human SC, with the lowest levels at the surface (alpha-tocopherol 6.5 +/- 1.4 pmol per mg, and gamma-tocopherol 2.2 +/- 1.3 pmol per mg) and the highest levels in the deepest layers (alpha-tocopherol 76 +/- 12 pmol per mg, and gamma-tocopherol 7.9 +/- 3.7 pmol per mg, n = 10; p < 0.0001); and (iii) the depletion of tocopherols in human SC by a single suberythemogenic dose of solar simulated UVR (alpha-tocopherol by 45%, and gamma-tocopherol by 35% as compared with controls; n = 6; both p < 0.01). These results demonstrate that the SC is a remarkably susceptible site for UVR induced depletion of vitamin E.

Topical application of alpha-tocopherol modulates the antioxidant network and diminishes ultraviolet-induced oxidative damage in murine skin

The aim of this study was to investigate the effects of topical alpha-tocopherol application on epidermal and dermal antioxidants and its ability to prevent ultraviolet (UV)-induced oxidative damage. Hairless mice received topical applications of alpha-tocopherol 24 h before a single, acute UV irradiation (10 x minimal erythemal dose). The four major antioxidant enzymes (catalase, superoxide dismutase, glutathione reductase and glutathione peroxidase), hydrophilic and lipophilic antioxidants, and lipid hydroperoxides, markers of oxidative damage, were assayed in both epidermis and dermis of hairless mice. Topical alpha-tocopherol treatment increased dermal superoxide dismutase activity by 30% (P < 0.01) and protected epidermal glutathione peroxidase and superoxide dismutase from depletion after UV irradiation. Total and reduced glutathione levels in the epidermis increased by 50% after the topical treatment (P < 0.05), as did dermal ascorbate levels (by 40%: P < 0.01). The topical treatment increased alpha-tocopherol levels both in the epidermis (62-fold) and the dermis (22-fold: P < 0.001 in each layer). Furthermore, alpha-tocopherol treatment significantly reduced the formation of epidermal lipid hydroperoxides after UV irradiation (P < 0.05). These results demonstrate that topical administration of alpha-tocopherol protects cutaneous tissues against oxidative damage induced by UV irradiation in vivo, and suggest that the underlying mechanism of this effect involves the up-regulation of a network of enzymatic and non-enzymatic antioxidants.

Protective effect against sunburn of combined systemic ascorbic acid (vitamin C) and d-alpha-tocopherol (vitamin E)

BACKGROUND

UV radiation causes acute adverse effects like sunburn, photosensitivity reactions, or immunologic suppression, as well as long-term sequelae like photoaging or malignant skin tumors. UV radiation induces tissues to produce reactive oxygen species, eicosanoids and cytokines. Inhibition of these mediators might reduce skin damage. Antioxidants such as ascorbic acid and d-alpha-tocopherol have been found to be photoprotective in some in vitro studies and animal experiments.

OBJECTIVE

Our purpose was to assess the protective effect of systemic vitamins C and E against sunburn in human beings.

METHODS

In a double-blind placebo-controlled study, each of 10 subjects took daily either 2 gm of ascorbic acid (vitamin C) combined with 1000 IU of d-alpha-tocopherol (vitamin E) or placebo. The sunburn reaction before and after 8 days of treatment was assessed by determination of the threshold UV dose for eliciting sunburn (minimal erythema dose [MED]) and by measuring the cutaneous blood flow of skin irradiated with incremental UV doses against that of nonirradiated skin.

RESULTS

The median MED of those taking vitamins increased from 80 to 96.5 mJ/cm2 (p < 0.01), whereas it declined from 80 to 68.5 mJ/cm2 in the placebo group. Cutaneous blood flow changed significantly (p < 0.05) for most irradiation doses with decreases in those given vitamins and increases in the placebo group.

CONCLUSION

Combined vitamins C and E reduce the sunburn reaction, which might indicate a consequent reduced risk for later sequelae of UV-induced skin damage. The increase of sunburn reactivity in the placebo group could be related to "priming" by the previous UV exposure.