Sunscreens Inadequately Protect Against Ultraviolet-A-Induced Free Radicals in Skin: Implications for Skin Aging and Melanoma?

Assessment of In vitro Sun Protection Factor of Calendula Officinalis L. (Asteraceae) Essential Oil Formulation

The present study was undertaken to study the sunscreen activity of herbal formulation. There is no evidence of the sun protection factor (SPF) studies on essential oil of Calendula flowers (Calendula officinalis L., Asteraceae). The study investigates the in vitro SPF by ultraviolet specrtophotometry method of Calendula flower oil in a cream formulation. Calendula oil was isolated by Clavenger's apparatus, compositions were identified by GC–MS and the cream of calendula flower oil was prepared by homogenization method followed by evaluation for physical parameters. The sun protection factor of cream was evaluated by in vitro method employing UV–visible spectrophotometer (Shimazdu-1600). The SPF of Calendula oil in cream formulation exhibited good activity (SPF = 14.84 ± 0.16). Finding of this study suggested that calendula oil cream can be used to protect the skin from UV radiations in form of sunscreen cream and to maintain the natural pigmentation of the skin.

The role of antioxidants in photoprotection: a critical review

Free radicals have long been studied as a contributor to aging and disease processes. Endogenous production of radicals from cellular metabolism and exogenous sources from ultraviolet radiation and pollution can damage the skin on the cellular and tissue levels. Although the body possesses an elegant defense system to prevent radical damage, this innate system can be overwhelmed and lead to a state of oxidative stress or immunosuppression, and can even trigger carcinogenesis. Topical supplementation of antioxidants can provide additional protection to neutralize reactive oxygen species from both endogenous and exogenous sources. This review will discuss our current understanding of the mechanisms of free radical damage and evaluate the potential benefit of topical antioxidants in sunscreens and skin care products.

Ellagic acid protects human keratinocyte (HaCaT) cells against UVA-induced oxidative stress and apoptosis through the upregulation of the HO-1 and Nrf-2 antioxidant genes

UV radiation from the sun is a potent environmental risk factor in the pathogenesis of skin damage. Much of the skin damage caused by ultraviolet A (UVA) irradiation from the sun is associated with oxidative stress. The aim of this study was to investigate the protective role of ellagic acid (25-75 μM), a natural antioxidant, against UVA (5-20 J/cm(2))-induced oxidative stress and apoptosis in human keratinocyte (HaCaT) cells and to reveal the possible mechanisms underlying this protective efficacy. Ellagic acid pre-treatment markedly increased HaCaT cell viability and suppressed UVA-induced ROS generation and MDA formation. Moreover, ellagic acid pre-treatment prevented UVA-induced DNA damage as evaluated by the comet assay. Ellagic acid treatment also significantly inhibited the UVA-induced apoptosis of HaCaT cells, as measured by a reduction of DNA fragmentation, mitochondria dysfunction, ER stress, caspase-3 activation, and Bcl-2/Bax deregulation. Notably, the antioxidant potential of ellagic acid was directly correlated with the increased expression of HO-1 and SOD, which was followed by the downregulation of Keap1 and the augmented nuclear translocation and transcriptional activation of Nrf2 with or without UVA irradiation. Nrf2 knockdown diminished the protective effects of ellagic acid. Therefore, ellagic acid may be useful for the treatment of UVA-induced skin damage.

Nitroxides and a nitroxide-based UV filter have the potential to photoprotect UVA-irradiated human skin fibroblasts against oxidative damage

BACKGROUND

Antioxidants are now being incorporated into sunscreens as additional topical measure for delaying the aging process and reducing photo-damage to skin induced by excessive UVA exposure. UVA radiation reaching the skin leads to the generation of ROS (reactive oxygen species) implicated in DNA damage and activation of matrix metalloproteinase-1 (MMP-1) responsible for collagen damage and photo-aging. Nitroxides are a class of compounds endowed with versatile antioxidant activity and recently, nitroxide-based UV filters in which a nitroxide moiety has been attached to the most popular UV filter present in sunscreens have been developed.

OBJECTIVE

This study explores the potential photo-protective effects of these compounds on ROS production and induction of MMP-1 in cultured human dermal fibroblasts exposed to UVA. For comparison, vitamin E was also tested.

METHODS

The effects were assessed by measuring intracellular ROS production using a ROS-index probe and MMP-1 mRNA expression levels using quantitative real-time PCR (qPCR).

RESULTS

Exposure of fibroblasts to 18J/cm(2) UVA lead to a two-fold increase in ROS production which was reduced to non-irradiated control levels in the presence of 50μM nitroxide compounds and vitamin E. Under the same conditions, a ten-fold increase in MMP-1 mRNA expression levels was observed 24h post-UVA treatment which was significantly reduced by all nitroxide compounds but not vitamin E.

CONCLUSION

The results of this study support the potential use of nitroxide compounds, including novel nitroxide-based UV filters, as a useful and alternative strategy for improving the efficacy of topical formulations against photo-aging and possibly photo-carcinogenesis.

Skin cell protection against UVA by Sideroxyl, a new antioxidant complementary to sunscreens

Oxidative stress resulting from photosensitized ROS production in skin is widely accepted as the main contributor to the deleterious effects of UVA exposure. Among the mechanisms known to be involved in UVA-induced oxidative damage, iron plays a central role. UVA radiation of skin cells induces an immediate release of iron, which can then act as a catalyst for uncontrolled oxidation reactions of cell components. Such site-specific damage can scarcely be counteracted by classical antioxidants. In contrast, iron chelators potentially offer an effective way to protect skin against UVA insults. However, iron chelation is very difficult to achieve without disturbing iron homeostasis or inducing iron depletion. A novel compound was developed to avoid these potentially harmful side effects. Sideroxyl was designed to acquire its strong chelating capability only during oxidative stress according to an original process of intramolecular hydroxylation. Herein, we describe in vitro results demonstrating the protective efficiency of Sideroxyl against deleterious effects of UVA at the molecular, cellular, and tissular levels. First, the Sideroxyl diacid form protects a model protein against UVA-induced photosensitized carbonylation. Second, intracellular ROS are dose-dependently decreased in the presence of Sideroxyl in both human cultured fibroblasts and human keratinocytes. Third, Sideroxyl protects normal human fibroblasts against UVA-induced DNA damage as measured by the comet assay and MMP-1 production. Finally, Sideroxyl provides protection against UVA-induced alterations in human reconstructed skin. These results suggest that Sideroxyl may prevent UVA-induced damage in human skin as a complement to sunscreens, especially in the long-wavelength UVA range.

Solar radiation induced skin damage: review of protective and preventive options

PURPOSE

Solar energy has a number of short- and long-term detrimental effects on skin that can result in several skin disorders. The aim of this review is to summarise current knowledge on endogenous systems within the skin for protection from solar radiation and present research findings to date, on the exogenous options for such skin photoprotection.

RESULTS

Endogenous systems for protection from solar radiation include melanin synthesis, epidermal thickening and an antioxidant network. Existing lesions are eliminated via repair mechanisms. Cells with irreparable damage undergo apoptosis. Excessive and chronic sun exposure however can overwhelm these mechanisms leading to photoaging and the development of cutaneous malignancies. Therefore exogenous means are a necessity. Exogenous protection includes sun avoidance, use of photoprotective clothing and sufficient application of broad-spectrum sunscreens as presently the best way to protect the skin. However other strategies that may enhance currently used means of protection are being investigated. These are often based on the endogenous protective response to solar light such as compounds that stimulate pigmentation, antioxidant enzymes, DNA repair enzymes, non-enzymatic antioxidants.

CONCLUSION

More research is needed to confirm the effectiveness of new alternatives to photoprotection such as use of DNA repair and antioxidant enzymes and plant polyphenols and to find an efficient way for their delivery to the skin. New approaches to the prevention of skin damage are important especially for specific groups of people such as (young) children, photosensitive people and patients on immunosuppressive therapy. Changes in public awareness on the subject too must be made.

Complementary effects of antioxidants and sunscreens in reducing UV-induced skin damage as demonstrated by skin biomarker expression

BACKGROUND

UV-exposure of the skin causes oxidative stress, leading to inflammatory reactions and premature skin aging. Sunscreens protect by absorbing or reflecting UV on the skin surface. Antioxidants provide protection by quenching UV-induced reactive oxygen species inside skin.

OBJECTIVE

To evaluate the complementary photoprotective benefits of formulas containing either an antioxidant complex of Cassia alata leaf extract or a combination of the antioxidant complex and sunscreens on normal healthy volunteers using biomarkers of skin damage.

METHODS

Each formula and a placebo control were applied separately to selected areas on the lower back of 10 individuals for 4 consecutive days. On Day 4, the control and three test sites were exposed to 5 x MED (minimal erythemal dose) of solar-simulated UV-irradiation (UVR). On Day 5, 4-mm punch biopsies were collected from the four exposed sites and a control site (untreated, unexposed) for immunohistochemistry.

RESULTS

Exposure to 5 x MED demonstrated significant damage as assessed by thymine dimer formation, MMP-9 and p53 protein expression on untreated exposed skin. The formula containing sunscreens + the antioxidant complex was the most protective, followed by the formula with the antioxidant alone.

CONCLUSION

The study demonstrated that a combination of antioxidants and sunscreens complement each other, resulting in superior photoprotection.

Molecular mechanisms of inhibition of photocarcinogenesis by silymarin, a phytochemical from milk thistle (Silybum marianum L. Gaertn.) (Review)

Changes in life style over the past several decades including much of the time spent outdoors and the use of tanning devices for cosmetic purposes by individuals have led to an increase in the incidence of solar ultraviolet (UV) radiation-induced skin diseases including the risk of skin cancers. Solar UV radiations are considered as the most prevalent environmental carcinogens, and chronic exposure of the skin to UV leads to squamous and basal cell carcinoma and melanoma in human population. A wide variety of phytochemicals have been reported to have substantial anti-carcinogenic activity because of their antioxidant and anti-inflammatory properties. Silymarin is one of them and extensively studied for its skin photoprotective capabilities. Silymarin, a flavanolignan, is extracted from the fruits and seeds of milk thistle (Silybum marianum L. Gaertn.), and has been shown to have chemopreventive effects against photocarcinogenesis in mouse tumor models. Topical treatment of silymarin inhibited photocarcinogenesis in mice in terms of tumor incidence, tumor multiplicity and growth of the tumors. Wide range of in vivo mechanistic studies conducted in a variety of mouse models indicated that silymarin has anti-oxidant, anti-inflammatory and immunomodulatory properties which led to the prevention of photocarcinogenesis in mice. This review summarizes and updates the photoprotective potential of silymarin with the particular emphasis on its in vivo mechanism of actions. It is suggested that silymarin may favorably supplement sunscreen protection, and may be useful for skin diseases associated with solar UV radiation-induced inflammation, oxidative stress and immunomodulatory effects.

Nutritional approach to sun protection: a suggested complement to external strategies

The increasing incidence of skin cancer despite the use of externally applied sun protection strategies, alongside research showing that nutrients reduce photo-oxidative damage, suggest nutritional approaches could play a beneficial role in skin cancer prevention. Penetrating photo-oxidative ultraviolet A radiation reduces skin and blood antioxidants and damages cell components, including DNA. Dietary antioxidant vitamins, minerals, and phytochemicals in addition to n-3 polyunsaturated fatty acids, n-9 monounsaturated fatty acids, and low pro-inflammatory n-6 polyunsaturated fatty acids, have demonstrated protective properties. The presence of these elements in the traditional Greek-style Mediterranean diet may have contributed to the low rates of melanoma in the Mediterranean region despite high levels of solar radiation. This suggests a potentially relevant model for studying dietary/nutritional supplementation for lifelong internal support of sun-protection mechanisms, which could complement external strategies.

Synergistic damage by UVA radiation and pollutants

Not only is skin cancer by far the most common human cancer but also the incidence of skin cancer has been increasing at an alarming rate in recent decades. Fortunately, most people now realize that sun exposure causes unattractive photoaging and skin cancer, so they do apply sunscreens conscientiously. However, until recently, most sunscreens did not adequately protect against ultraviolet A (UVA) radiation. Although UVA is indeed less erythrogenic and less carcinogenic than UVB, UVA directly causes photoaging and enhances UVB-induced skin cancer. Furthermore, recent research demonstrates that UVA combined with environmental pollutants (including cigarette smoke) significantly increases the risk of skin cancer. Similarly, previous research demonstrated another synergy between environmental pollutants and UV: When ozone exposure precedes UV exposure, there is enhancement of UV-induced depletion of protective vitamin E from the skin's stratum corneum. This article reviews experimental evidence that environmental pollutants (such as benzo[a]pyrene (BaP), a commonly used index of environmental pollution) are photosensitizers that generate reactive oxygen species (ROS) when exposed to UVA radiation. This in turn causes oxidative and genetic damage, leading to unattractive photodamage and carcinogenesis.

Synthesis and application of a novel sunscreen-antioxidant

Background information on the inefficacy of sunscreens to provide free radical protection in skin, despite their usefulness in preventing sunburn/erythema, prompted us to synthesize a compound which would display in the same molecule both UV-absorbing and antioxidant capacities. For this purpose, the UVB absorber, 2-ethylhexyl-4-methoxycinnamate (OMC) was combined with the piperidine nitroxide TEMPOL, which has antioxidant properties. The spectral properties of the new nitroxide-based sunscreen (MC-NO) as well as its efficacy to prevent photo-oxidative damage to lipids induced by UVA, natural sunlight and 4-tert-butyl-4-methoxydibenzoylmethane (BMDBM), a photo-unstable sunscreen which generates free radicals upon UV radiation, was studied. The results obtained demonstrate that MC-NO: (a) absorbs in the UVB region even after UVA irradiation; (b) acts as free radical scavenger as demonstrated by EPR experiments; (c) strongly reduces both UVA-, sunlight- and BMDBM-induced lipid peroxidation in liposomes, measured as reduced TBARS levels; and (d) has comparable antioxidant activity to that of commonly used vitamin E and BHT in skin care formulations. These results suggest that the use of the novel sunscreen-antioxidant or of other nitroxide-based sunscreens in formulations aimed at reducing photoinduced skin damage may be envisaged.

[Photosensitivity in lupus erythematosus]

Photosensitivity is one of the ARA diagnostic criteria of systemic lupus erythematosus. Sun exposure can also induce extracutaneous manifestations of the disease. Photosensitivity may be difficult to prove by history taking in lupus patients, as the delay between sun exposure and the onset of specific skin lesions is rather long. Photo-induction of lupus can occur by ultraviolet A (UVA) radiation in the shadow or behind window glass, so that the relationship between radiation exposure and exacerbation of the disease may not seem obvious to the patient. Phototesting procedures for lupus erythematosus have been described, but they are not used in routine practice. Both UVB and UVA play a role in the pathogenesis of lupus erythematosus: in the epidermis they induce DNA damage, they expose nuclear antigens and photo-induced neo-antigens at the cell surface, they lead to an accumulation of apoptotic material, and they induce several pro-inflammatory cytokines. In the dermis, UV radiation triggers skin infiltration by inflammatory cells by modulation of microvascular flow rates and by upregulation of white blood cell migration from dermal capillaries to the skin. Photodistribution of skin lesions and a delay of their onset of more than 48 hours after sun exposure are clinical hallmarks of cutaneous lupus erythematosus that are usually completed by histological confirmation. Photoprotection is essential in the treatment of lupus patients: it comprises sun avoidance suitable for both UVB and UVA radiation, protective clothing, and topical broad-spectrum filters.

In vitro photostability and photoprotection studies of a novel 'multi-active' UV-absorber

This paper reports on the synthesis and properties of a new UV-absorber (OC-NO) based on the most popular UV filter worldwide, ethylhexyl methoxycinnamate (OMC) in which the methoxy group has been replaced with a pyrrolidine nitroxide bearing antioxidant activity. This sunscreen active has therefore both UV-absorbing and antioxidant properties which could ideally address both the UV-B and UV-A skin photo-damage. For broad-spectrum coverage, the combinations of OC-NO with two commonly used UV-A absorbers (BMDBM and DHHB) were also studied. The results obtained reveal that OC-NO: (a) is as photostable as OMC after UV-A exposure; (b) acts as free radical scavenger as demonstrated by EPR and chemical studies; (c) reduces UV-A and UV-A+BMDBM induced lipid peroxidation in liposomes and cells, measured as reduced TBARS levels and increased C11-BODIPY red fluorescence, respectively; (d) has comparable antioxidant activity to that of vitamin E and BHT commonly used in skin care formulations; (e) is non-cytotoxic to human skin fibroblasts as assessed with the MTT assay when exposed to increasing doses of UV-A; and (f) OC-NO+DHHB is a promising, photostable broad spectrum UV-filter combination that concomitantly reduces UV-induced free radical damage. These results suggest that nitroxide/antioxidant-based UV-absorbers may pave the way for the utilization of 'multi-active' ingredients in sunscreens thereby reducing the number of ingredients in these formulations.

A topical antioxidant solution containing vitamins C and E stabilized by ferulic acid provides protection for human skin against damage caused by ultraviolet irradiation

BACKGROUND

Skin cancer and photoaging changes result from ultraviolet (UV)-induced oxidative stress. Topical antioxidants may protect skin from these effects.

OBJECTIVE

We sought to determine whether a stable topical formulation of 15% L-ascorbic acid, 1% alpha-tocopherol, and 0.5% ferulic acid (CEFer) could protect human skin in vivo from substantial amounts of solar-simulated UV radiation.

METHODS

CEFer and its vehicle were applied to separate patches of normal-appearing human skin for 4 days. Each patch was irradiated with solar-simulated UV, 2 to 10 minimal erythema doses, at 2-minimal erythema dose intervals. One day later, skin was evaluated for erythema and sunburn cells, and immunohistochemically for thymine dimers and p53. UV-induced cytokine formation, including interleukin (IL)-1alpha, IL-6, IL-8, and IL-10, and tumor necrosis factor-alpha, were evaluated by real-time polymerase chain reaction.

RESULTS

CEFer provided significant and meaningful photoprotection for skin by all methods of evaluation.

LIMITATIONS

The number of patients evaluated was relatively small.

CONCLUSION

CEFer provided substantial UV photoprotection for skin. It is particularly effective for reducing thymine dimer mutations known to be associated with skin cancer. Its mechanism of action is different from sunscreens and would be expected to supplement the sun protection provided by sunscreens.

Protein, lipid, and DNA radicals to measure skin UVA damage and modulation by melanin

Afro-Caribbeans have a lower incidence of skin cancer than Caucasians, but the effectiveness of melanin as a photoprotective pigment is debated. We investigated the UVA and solar irradiation of ex vivo human skin and DMPO using electron spin resonance spectroscopy, to determine whether pigmented skin is protected by melanin against free radical damage. Initial ascorbate radicals in Caucasian skin were superseded by lipid and/or protein radical adducts with isotropic (a(H)=1.8 mT) and anisotropic spectra comparable to spectra in irradiated pig fat (a(H)=1.9 mT) and BSA. DNA carbon-centered radical adducts (a(H)=2.3 mT) and a broad singlet were detected in genomic DNA/melanin but were not distinguishable in irradiated Caucasian skin. Protein and lipid radicals (n=6 in Caucasian skin) were minimal in Afro-Caribbean skin (n=4) and intermediate skin pigmentations were variable (n=3). In irradiated Afro-Caribbean skin a shoulder to the melanin radical (also in UVA-irradiated pigmented melanoma cells and genomic DNA/melanin and intrinsic to pheomelanin) was detected. In this sample group, protein (but not lipid) radical adducts decreased directly with pigmentation. ESR/spin trapping methodology has potential for screening skin susceptibility to aging and cancer-related radical damage and for measuring protection afforded by melanin, sunscreens, and antiaging creams.

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.

Flavonolignans from Silybum marianum moderate UVA-induced oxidative damage to HaCaT keratinocytes

BACKGROUND

UV radiation from sunlight is a very potent environmental risk factor in the pathogenesis of skin cancer. Exposure to UV light, especially the UVA part, provokes the generation of reactive oxygen species (ROS), which induce oxidative stress in exposed cells. Topical application of antioxidants is a successful strategy for protecting the skin against UV-caused oxidative damage.

OBJECTIVE

In this study, silybin (SB) and 2,3-dehydrosilybin (DS) (1-50 micromol/l), flavonolignan components of Silybum marianum, were tested for their ability to moderate UVA-induced damage.

METHODS

Human keratinocytes HaCaT were used as an appropriate experimental in vitro model, to monitor the effects of SB and DS on cell viability, proliferation, intracellular ATP and GSH level, ROS generation, membrane lipid peroxidation, caspase-3 activation and DNA damage.

RESULTS

Application of the flavonolignans (1-50 micromol/l) led to an increase in cell viability of irradiated (20 J/cm(2)) HaCaT keratinocytes. SB and DS also suppressed intracellular ATP and GSH depletion, ROS production and peroxidation of membrane lipids. UVA-induced caspases-3 activity/activation was suppressed by treatment with SB and DS. Lower concentrations of both compounds (10 micromol/l) significantly reduced cellular DNA single strand break formation.

CONCLUSION

Taken together, the results suggest that these flavonolignans suppress UVA-caused oxidative stress and may be useful in the treatment of UVA-induced skin damage.

Ultraviolet light induced alteration to the skin

Solar light is the primary source of UV radiation for all living systems. UV photons can mediate damage through two different mechanisms, either by direct absorption of UV via cellular chromophores, resulting in excited states formation and subsequent chemical reaction, or by phosensitization mechanisms, where the UV light is absorbed by endogenous (or exogenous) sensitizers that are excited and their further reactions lead to formation of reactive oxygen species (ROS). These highly reactive species can interact with cellular macromolecules such as DNA, proteins, fatty acids and saccharides causing oxidative damage. Direct and indirect injuries result in a number of harmful effects such as disrupted cell metabolism, morphological and ultrastructural changes, attack on the regulation pathways and, alterations in the differentiation, proliferation and apoptosis of skin cells. Processes like these can lead to erythema, sunburn, inflammation, immunosuppression, photoaging, gene mutation, and development of cutaneous malignancies. The endogenous and exogenous mechanisms of skin photoprotection are discussed.

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.

Melanoma, long wavelength ultraviolet and sunscreens: Controversies and potential resolutions

Although sunlight is known to cause melanoma, there has been considerable controversy as to the importance of short (UVB) and long (UVA) ultraviolet (UV) wavelengths in causing melanoma, leading to uncertainty in how best to prevent this cancer. This uncertainty has been compounded by the difficulties in assaying the UVA protection abilities of sunscreens, as compared to widely accepted measures of UVB screening by the sun protection factor (SPF). This review discusses the controversies surrounding UVA causation of melanoma in both human and animal models and the use of sunscreens to prevent melanoma. In addition, it details the development of an electron paramagnetic resonance (EPR) technique, initially used to determine the wavelength dependence (or action spectrum) of intramelanocyte radical generation to resolve these controversies in the Xiphophorus model. It is shown how this EPR technique allows a sunscreen protection factor to be determined, that is weighted to the melanocyte, and how this also allows study of the wavelength-dependent screening ability of sunscreens.

Travellers to high UV-index countries: Sun-exposure behaviour in 7822 French adults

BACKGROUND

Travel health information includes warning on sun exposure, particularly for fair-skinned individuals travelling to tropical countries.

METHOD

A self-completed questionnaire on sun exposure behaviour was sent to the 12,741 French adults enrolled in the SU.VI.MAX cohort. Among the 7822 participants, 196 (110 women and 86 men) declared at least one visit to a high UV-index country over the past year for more than 1 month, subsequently referred to as long-term travellers. The remaining 7626 participants (non-travellers) accounted for 4862 women and 2764 men.

RESULTS

Women travellers declared more frequently skin exposure to the sun over the past year, practised tanning in high UV-index areas more than 2h daily, experienced intensive sun exposure than non-travellers. Moreover, they asserted that basking in the sun is very important. Comparable results were found in men. The use of sun protection products was similar in travellers and non-travellers, but women tended to use sunscreen products more often, more regularly and with a higher sun protection factor (SPF) than men.

CONCLUSIONS

Specific health education campaigns and pre-travel advice aiming to reduce sun exposure and to improve protective measures against ultraviolet (UV) radiation should be addressed to travellers to countries with high UV-index.

Determination of Wavelength-Specific UV Protection Factors of Sunscreens in Intact Skin by EPR Measurement of UV-Induced Reactive Melanin Radical

There remains an unmet need for skin tissue-based assays for the measurement of the UVA protection and efficacy of sunscreens. Here we describe development of a novel electron paramagnetic resonance assay that uses the photogeneration of reactive melanin radical as a measure of UV light penetration to melanocytes in situ in skin. We have used areas of focal melanocytic hyperplasia in the skin of Monodelphis domestica to model the human nevus. We show that we are able to use this assay to determine the monochromatic protection factors (mPF) of research and commercial sunscreens at specific narrow wavebands of UVB, UVA and blue visible light. Both commercial sunscreens, a sun protection factor (SPF) 4 and an SPF 30 product, had mPFs in the UVB range that correlated well with their claimed SPF. However, their mPF in the UVA ranges were only about one-third of claimed SPF. This technique can be used to design and assay sunscreens with optimally balanced UVA and UVB protection.

Expatriates in high-UV index and tropical countries: sun exposure and protection behavior in 9,416 French adults

BACKGROUND

Overexposure to sunlight during long stays in tropical countries can reveal short- and long-term harmful effects on the skin of Caucasian residents, especially for fair-skinned subjects. The aim of this study was to describe sun exposure and sun protection behaviors during lifetime among French adults who declared having experienced at least one expatriation period in tropical or high-sun index areas for a duration of more than three consecutive months.

METHODS

A self-reported questionnaire on sun exposure behavior was addressed two times, in 1997 and 2001, to the 12,741 French adult volunteers enrolled in the SU.VI.MAX cohort. A total of 8,084 subjects answered to the first survey and 1,332 additional responders answered to the second. Among the 9,416 individuals, 1,594 (652 women and 942 men) corresponded to expatriates and the remaining 7,822 to nonexpatriates (4,972 women and 2,850 men). A descriptive analysis of sun exposure and sun protection behaviors during lifetime of expatriates and nonexpatriates was performed by gender.

RESULTS

Among women, 39% of expatriates belonged to the 50 to 60 class of age at inclusion, versus 33% in nonexpatriates (72 and 55% in men, respectively). In women, expatriates declared more frequently having during lifetime exposed voluntarily their skin to the sun, practiced tanning between 11 a.m. and 4 p.m., less gradually exposed their skin, experienced intensive sun exposure, and exposed their skin during nautical sports and practiced naturism. In men, expatriates declared more frequently having experienced intensive sun exposure and exposed their skin during outdoor occupations and during nautical and mountain sports.

CONCLUSIONS

Although expatriates are aware of travel health advices concerning the countries where they planned to stay, they are usually poorly informed about sun exposure risk factors. Such individuals who planned to expatriate in countries with a high ultraviolet index should benefit from a visit to a travel clinic including specific health care information for risk related to sun exposure, ie, skin cancers and photoaging.

Photostability of commercial sunscreens upon sun exposure and irradiation by ultraviolet lamps

Background

Sunscreens are being widely used to reduce exposure to harmful ultraviolet (UV) radiation. The fact that some sunscreens are photounstable has been known for many years. Since the UV-absorbing ingredients of sunscreens may be photounstable, especially in the long wavelength region, it is of great interest to determine their degradation during exposure to UV radiation. Our aim was to investigate the photostability of seven commercial sunscreen products after natural UV exposure (UVnat) and artificial UV exposure (UVart).

Methods

Seven commercial sunscreens were studied with absorption spectroscopy. Sunscreen product, 0.5 mg/cm², was placed between plates of silica. The area under the curve (AUC) in the spectrum was calculated for UVA (320–400 nm), UVA1 (340–400 nm), UVA2 (320–340 nm) and UVB (290–320 nm) before (AUC_before) and after (AUC_after) UVart (980 kJ/m² UVA and 12 kJ/m² of UVB) and before and after UVnat. If theAUC Index (AUCI), defined as AUCI = AUC_after/AUC_before, was > 0.80, the sunscreen was considered photostable.

Results

Three sunscreens were unstable after 90 min of UVnat; in the UVA range the AUCI was between 0.41 and 0.76. In the UVB range one of these sunscreens was unstable with an AUCI of 0.75 after 90 min. Three sunscreens were photostable after 120 min of UVnat; in the UVA range the AUCI was between 0.85 and 0.99 and in the UVB range between 0.92 and 1.0. One sunscreen showed in the UVA range an AUCI of 0.87 after UVnat but an AUCI of 0.72 after UVart. Five of the sunscreens were stable in the UVB region.

Conclusion

The present study shows that several sunscreens are photounstable in the UVA range after UVnat and UVart. There is a need for a standardized method to measure photostability, and the photostability should be marked on the sunscreen product.

Design of a photostabilizer having built-in antioxidant functionality and its utility in obtaining broad-spectrum sunscreen formulations

Di-2,2'-diethylhexyl-3,5-dimethoxy-4-hydroxy-benzylidenemalonate (INCI name diethylhexyl syringylidene malonate, DESM), the target photostabilizer, was synthesized in one step by condensation of 3,5-dimethoxy-4-hydroxy benzaldehyde (Syringaldehyde) with di-2,2'-diethylhexyl malonate. Photostability data in sunscreen formulations showed that DESM is photostable and improves the photostability of avobenzone significantly when compared to control (without a photostabilizer). Photostable broad-spectrum sunscreen formulations with high SPF (>30) have been achieved by combining avobenzone, DESM and UV-B sunscreens, such as homosalate, octisalate or other UV-B sunscreens. It seems that (a) triplet-state energy transfer from avobenzone to DESM and (b) scavenging of reactive species are responsible for the observed stabilization of avobenzone. In vitro study of the two formulations containing DESM clearly showed critical wavelength of well over 370 nm and can thus be categorized as broad-spectrum sunscreens. DESM does not have any contribution to in vivo SPF; instead it boosts SPF by about 5 units in high-SPF products. DESM was found to be an excellent singlet-oxygen quencher, thereby reducing photodegradation of avobenzone caused by singlet oxygen. In short, the multiplicity of effects and formulation benefits seen with DESM makes it an ideal choice as a unique antioxidant photostabilizer for a variety of cosmetic products targeting young and mature skin alike.

Prevention and treatment of skin aging

Skin aging is a complex biological process that is a consequence of both intrinsic or genetically programmed aging that occurs with time, and extrinsic aging caused by environmental factors. The dramatic increase in the aging population and the psychosocial impact of skin aging has created a demand for effective interventions. The advances that have been made in the past 25 years in our understanding of the clinical, biochemical, and molecular changes associated with aging have led to the development of many different approaches to reduce, postpone, and in some cases, repair the untoward effects of intrinsic programmed aging and extrinsic environmental injury.

Photoaging: Mechanisms and repair

Aging is a complex, multifactorial process resulting in several functional and esthetic changes in the skin. These changes result from intrinsic as well as extrinsic processes, such as ultraviolet radiation. Recent advances in skin biology have increased our understanding of skin homeostasis and the aging process, as well as the mechanisms by which ultraviolet radiation contributes to photoaging and cutaneous disease. These advances in skin biology have led to the development of a diversity of treatments aimed at preventing aging and rejuvenating the skin. The focus of this review is the mechanism of photoaging and the pathophysiology underlying the treatments specifically designed for its prevention and treatment.

LEARNING OBJECTIVES

At the conclusion of this learning activity, participants should be familiar with the mechanism of photoaging, the treatments for photoaging, and the data that supports the use of these treatments.

The repair enzyme peptide methionine-S-sulfoxide reductase is expressed in human epidermis and upregulated by UVA radiation

Recently, we reported that photoaging correlates well with the amount of oxidized protein accumulated in the upper dermis, while protein oxidation levels in the viable epidermis are very low. We hypothesized that this might be due to epidermal expression of the repair enzymes methionine sulfoxide reductases (MSRs). The expression of human methionine sulfoxide reductase A (MSRA) was investigated in HaCaT cells, primary human keratinocytes, and in human skin. High MSRA mRNA and protein levels as well as MSR activity were found in cultured human keratinocytes. MSRA was expressed in human epidermis, as shown by immunohistochemistry in healthy human skin. Repetitive in vivo exposure of human skin to solar-simulated light on 10 consecutive days (n=10 subjects) significantly increased epidermal MSRA expression. To further assess the functional relevance of the enzyme, its expression in response to UVB, UVA, and H(2)O(2) was investigated in HaCaT cells. While UVB lowered protein expression of MSRA, an upregulation was observed in response to low doses of UVA and H(2)O(2). In summary, MSRA represents the only enzyme so far identified in human skin that is capable of repairing oxidative protein damage. In addition to melanogenesis and DNA repair systems, a wavelength-specific activation of epidermal MSRA may be involved in epidermal photoprotection.

Role of Sun Exposure in Melanoma

BACKGROUND

Malignant melanoma is the third most common skin cancer in the United States. It is commonly thought that sun exposure is causative in these tumors. Recently, however, the significance of the role of sun exposure in melanoma has come into question. Some have suggested that other factors, such as genetics, play a larger role, and that sun protection may even be harmful.

OBJECTIVE AND METHODS

To investigate the role of sun exposure in melanoma etiology. An extensive review of basic science and clinical literature on this subject was conducted.

RESULTS

Although exceptions exist, sun exposure likely plays a large role in most melanomas. The pattern of this exposure, however, is not fully known, and controversy exists, especially in the use of sunscreens. Sun exposure may interact with genetic factors to cause melanomas, and sun protective measures appear to be prudent.

CONCLUSIONS

The cause of melanoma is probably variable and multifactorial. Sun exposure may play a primary or supporting role in most melanoma tumors.

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.

Changes in ultraviolet absorbance and hence in protective efficacy against lipid peroxidation of organic sunscreens after UVA irradiation

Owing to the spectral distribution of solar UV, the UVA component of sunlight is now believed to be the main cause of photoaging and photocarcinogenesis and is much more effective than UVB in inducing peroxidative damage. Consequently, most skin care cosmetic products now include UVA filters in their formulations along with UVB filters. These modern sunscreens should provide and maintain their initial absorbance, hence protection, throughout the entire period of exposure to sunlight. However, not all UVA and UVB filters are sufficiently photostable. In this study, we examine the correlation between the photochemical degradation of sunscreen agents under UVA irradiation, with particular reference to the UVA-absorber 4-tert-butyl-4'-methoxydibenzoylmethane, alone and in combination with other organic UV filters (2-ethylhexyl 4 methoxycinnamate and 2-ethylhexyl 2-cyano-3,3-diphenylacrylate) and their ability to prevent UVA-induced lipid peroxidation. Since antioxidants are also added to formulations to deactivate free radicals generated during UVA exposure, vitamin E and the synthetic antioxidant, bis(2,2,6,6-tetramethyl-1-oxyl-piperidine-4-yl)sebacate, a nitroxide derivative, were also included in this study. By using simple in vitro tests, the results show that a decrease in spectral absorbance of the UV filters correlates in most cases with increased UVA-induced lipid peroxidation; this depends on the specific UV absorber analysed and also on whether they are alone or in combination. Furthermore, the combined presence or absence of antioxidants has a profound effect on this oxidative event. In particular, the nitroxide appears to be a more efficient photo-antioxidant than vitamin E. Similar experiments were also performed under natural sunlight and the results obtained did not differ substantially from those performed under UVA. The results presented and discussed in this work may help in understanding the effects of UVA/UVB absorbers and antioxidants upon the level of UV-induced ROS generated under UVA exposure and in natural sunlight which could be relevant for improving the photoprotection and efficacy of skin care cosmetic formulations.

Relevance of Sunscreen Application Method, Visible Light and Sunlight Intensity to Free-radical Protection: A Study of ex vivo Human Skin

With the continued rise in skin cancers worldwide there is a need for effective skin protection against sunlight damage. It was shown previously that sunscreens, which claimed UVA protection (SPF 20+), provided limited protection against UV-induced ascorbate radicals in human skin. Here the results of an electron spin resonance (ESR) investigation to irradiate ex vivo human skin with solar-simulated light are reported. The ascorbate radical signal in the majority of skin samples was directly proportional to the irradiance over relevant sunlight intensities (0.9-2.9 mW cm(-2)). Radical production (substratum-corneum) by UV (wavelengths < 400 nm) and visible components (> 400 nm) was approximately 67% and 33% respectively. Ascorbate radicals were in steady state concentration at low irradiance (approximately 1 mW cm(-2) equivalent to UK sunlight), but at higher irradiance (approximately 3 mW cm(-2)) decreased with time, suggesting ascorbate depletion. Radical protection by a four star-rated sunscreen (with UVA protection) was optimal when applied as a thin film (40-60% at 2 mg cm(-2)) but less so when rubbed into the skin (37% at 4 mg cm(-2) and no significant protection at 2 mg cm(-2)), possibly due to cream filling crevices, which reduced film thickness. This study validates ESR determinations of the ascorbate radical for quantitative protection measurements. Visible light contribution to radical production, and loss of protection when sunscreen is rubbed into skin, has implications for sunscreen design and use for the prevention of free-radical damage.