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

Two-dimensional imaging of spontaneous ultra-weak photon emission from the human skin: role of reactive oxygen species

In the human skin, reactive oxygen species (ROS) produced continuously during oxidative metabolic processes (cellular respiration, oxidative burst) are essential for various cellular processes such as defense against infection, cellular signaling and apoptosis. On the other hand, when the formation of ROS exceeds a capacity of the non-enzymatic and the enzymatic antioxidant defense system, ROS cause the damage to the human skin known to initiate premature skin aging and skin cancer. In this study, two-dimensional spontaneous ultra-weak photon emission from the human skin has been measured using a highly sensitive charged coupled device (CCD) camera. It is demonstrated here that two-dimensional ultra-weak photon emission from the human skin increases with the topical application of exogenous ROS in the following order: hydrogen peroxide (H₂O₂) < superoxide anion radical (O₂•⁻) < hydroxyl radical (HO•). We propose here that the two-dimensional ultra-weak photon emission can be used as a non-invasive tool for the spatial and temporal monitoring of oxidative stress in the human skin.

Skin penetration enhancement of core-multishell nanotransporters and invasomes measured by electron paramagnetic resonance spectroscopy

In order to cross the skin barrier several techniques and carrier systems were developed to increase skin penetration of topical dermatics and to reduce systemic adverse effects by avoiding systemic application. Ultra-flexible vesicles, e.g. invasomes and core-multishell (CMS) nanotransporters are efficient drug delivery systems for dermatological applications. Electron paramagnetic resonance (EPR) spectroscopic techniques were used for the determination of localization and distribution of the spin label 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (PCA; logP=-1.7) within the carrier systems and the ability of the carriers to promote penetration of PCA into the skin. The results show an exclusive localization of PCA in the hydrophilic compartments of the invasome dispersion and the CMS nanotransporter solution. PCA penetration was enhanced 2.5 fold for CMS and 1.9 fold for invasomes compared to PCA solution. Investigation of penetration depth by step-wise removal of the stratum corneum by tape stripping revealed deepest PCA penetration for invasomes. UV-irradiation of PCA-exposed skin samples revealed that the spin label is still reactive. In conclusion novel polymer-based CMS nanotransporters and invasomes can favor the penetration of PCA or hydrophilic drugs. This offers possibilities for e.g. improved photodynamic therapy.

Main approaches for delivering antioxidant vitamins through the skin to prevent skin ageing

INTRODUCTION

One of the major contributions to skin photoageing and diseases is oxidative stress, caused by UV radiation inducing reactive oxygen and nitrogen species. Successful prophylaxis and therapy would necessitate control of the oxidant/antioxidant balance at the affected site, which can be achieved through the external supply of endogenous antioxidants.

AREAS COVERED

This review discusses possible strategies for dermal delivery of the antioxidant vitamins E and C, as oral supplementation has proved insufficient. These antioxidants have low skin bioavailability, owing to their poor solubility, inefficient skin permeability, or instability during storage. These drawbacks can be overcome by various approaches, such as chemical modification of the vitamins and the use of new colloidal drug delivery systems. New knowledge is included about the importance of: enhancing the endogenous skin antioxidant defense through external supply; the balance between various skin antioxidants; factors that can improve the skin bioavailability of antioxidants; and new delivery systems, such as microemulsions, used to deliver vitamins C and E into the skin simultaneously.

EXPERT OPINION

A promising strategy for enhancing skin protection from oxidative stress is to support the endogenous antioxidant system, with antioxidants containing products that are normally present in the skin.

Determination of the antioxidative capacity of the skin in vivo using resonance Raman and electron paramagnetic resonance spectroscopy

BACKGROUND

Non-invasive measurements are of major interest for investigating the effects of stress, nutrition, diseases or pharmaceuticals on the antioxidative capacity of the human skin. However, only a few non-invasive methods are available.

MATERIAL AND METHODS

The resonance Raman spectroscopy is well established to monitor carotenoids in the skin, but correlations with other antioxidants have not yet been described. Electron paramagnetic resonance spectroscopy used for measurements of free radicals has already been used elsewhere to investigate the reduction of applied long-living nitroxide radicals, caused by skin antioxidants and UV irradiation, but only a single or up to four volunteers were included in these studies. Therefore, in this study, the two methods were applied in parallel on 17 volunteers, and the rate constant of the nitroxide decrease was correlated with the cutaneous carotenoid concentration.

RESULTS AND DISCUSSION

A correlation with R = 0.65 was found, supporting the thesis that different antioxidants protect each other and build an antioxidative network in the skin. The results also give first indications that the carotenoids serve as marker substances for the antioxidative capacity, if the nutrition is well balanced.

Kinetics of carotenoid distribution in human skin in vivo after exogenous stress: disinfectant and wIRA-induced carotenoid depletion recovers from outside to inside

The human organism has developed a protection system against the destructive effect of free radicals. The aim of the present study was to investigate the extent of exogenous stress factors such as disinfectant and IR-A radiation on the skin, and their influence on the kinetics of carotenoids distribution during the recovery process. Ten healthy volunteers were assessed with resonance spectroscopy using an Argon-laser at 488 nm to excite the carotenoids in vivo. Additionally, Raman-confocal-micro-spectroscopy measurements were performed using a model 3510 Skin Composition Analyzer with spatially resolved measurements down to 30 μm. The measurements were performed at a baseline of 20, 40, 60, and 120 min after an external stressor consisting either of water-filtered infrared A (wIRA) with 150 mW∕cm(2) or 1 ml∕cm(2) of an alcoholic disinfectant. Both Raman methods were capable to detect the infrared-induced depletion of carotenoids. Only Raman-microspectroscopy could reveal the carotenoids decrease after topical disinfectant application. The carotenoid-depletion started at the surface. After 60 min, recovery starts at the surface while deeper parts were still depleted. The disinfectant- and wIRA-induced carotenoid depletion in the epidermis recovers from outside to inside and probably delivered by sweat and sebaceous glands. We could show that the Raman microscopic spectroscopy is suited to analyze the carotenoid kinetic of stress effects and recovery.

Unleashing the untold and misunderstood observations on vitamin E

Paradoxically, meta-analysis of human randomized controlled trials revealed that natural but not synthetic α-tocopherol supplementation significantly increases all-cause mortality at 95% confidence interval. The root cause was that natural α-tocopherol supplementation significantly depressed bioavailability of other forms of vitamin E that have better chemo-prevention capability. Meta-analysis outcome demonstrated flaws in the understanding of vitamin E. Reinterpretation of reported data provides plausible explanations to several important observations. While α-tocopherol is almost exclusively secreted in chylomicrons, enterocytes secrete tocotrienols in both chylomicrons and small high-density lipoproteins. Vitamin E secreted in chylomicrons is discriminately repacked by α-tocopherol transfer protein into nascent very low-density lipoproteins in the liver. Circulating very low-density lipoproteins undergo delipidation to form intermediate-density lipoproteins and low-density lipoproteins. Uptake of vitamin E in intermediate-density lipoproteins and low-density lipoproteins takes place at various tissues via low-density lipoproteins receptor-mediated endocytosis. Small high-density lipoproteins can deliver tocotrienols upon maturation to peripheral tissues independent of α-tocopherol transfer protein action, and uptake of vitamin E takes place at selective tissues by scavenger receptor-mediated direct vitamin E uptake. Dual absorption pathways for tocotrienols are consistent with human and animal studies. α-Tocopherol depresses the bioavailability of α-tocotrienol and has antagonistic effect on tocotrienols in chemo-prevention against degenerative diseases. Therefore, it is an undesirable component for chemo-prevention. Future research directions should be focused on tocotrienols, preferably free from α-tocopherol, for optimum chemo-prevention and benefits to mankind.

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.

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.

Selenoproteins are essential for proper keratinocyte function and skin development

Dietary selenium is known to protect skin against UV-induced damage and cancer and its topical application improves skin surface parameters in humans, while selenium deficiency compromises protective antioxidant enzymes in skin. Furthermore, skin and hair abnormalities in humans and rodents may be caused by selenium deficiency, which are overcome by dietary selenium supplementation. Most important biological functions of selenium are attributed to selenoproteins, proteins containing selenium in the form of the amino acid, selenocysteine (Sec). Sec insertion into proteins depends on Sec tRNA; thus, knocking out the Sec tRNA gene (Trsp) ablates selenoprotein expression. We generated mice with targeted removal of selenoproteins in keratin 14 (K14) expressing cells and their differentiated descendents. The knockout progeny had a runt phenotype, developed skin abnormalities and experienced premature death. Lack of selenoproteins in epidermal cells led to the development of hyperplastic epidermis and aberrant hair follicle morphogenesis, accompanied by progressive alopecia after birth. Further analyses revealed that selenoproteins are essential antioxidants in skin and unveiled their role in keratinocyte growth and viability. This study links severe selenoprotein deficiency to abnormalities in skin and hair and provides genetic evidence for the role of these proteins in keratinocyte function and cutaneous development.

Unraveling the mystery of vernix caseosa

Vernix caseosa is a white, creamy, naturally occurring biofilm covering the skin of the fetus during the last trimester of pregnancy. Vernix coating on the neonatal skin protects the newborn skin and facilitates extra-uterine adaptation of skin in the first postnatal week if not washed away after birth. It consists of water-containing corneocytes embedded in a lipid matrix. The strategic location of the vernix on the fetal skin surface suggests participation in multiple overlapping functions required at birth, such as barrier to water loss, temperature regulation, and innate immunity. Vernix seems to perform various integral roles during transition of the fetus from intra-uterine to extra-uterine life. It has also found various interesting diagnostic and prognostic implications in this arena. Thus, it continues to be an intriguing topic of interest among the medical fraternity to understand its detailed biology and function in the fetus and also to put its naturally endowed characteristics to use in the adult population.

Cellular and sub-cellular responses to UVA in relation to carcinogenesis

PURPOSE

UVA radiation (315-400 nm) contributes to skin aging and carcinogenesis. The aim of this review is to consider the mechanisms that underlie UVA-induced cellular damage, how this damage may be prevented or repaired and the signal transduction processes that are elicited in response to it.

RESULTS

Exposure to ultraviolet (UV) light is well-established as the causative factor in skin cancer. Until recently, most work on the mechanisms that underlie skin carcinogenesis focused on shorter wavelength UVB radiation (280-315 nm), however in recent years there has been increased interest in the contribution made by UVA. UVA is able to cause a range of damage to cellular biomolecules including lipid peroxidation, oxidized protein and DNA damage, such as 8-oxoguanine and cyclobutane pyrimidine dimers. Such damage is strongly implicated in both cell death and malignant transformation and cells have a number of mechanisms in place to mitigate the effects of UVA exposure, including antioxidants, DNA repair, and stress signalling pathways.

CONCLUSIONS

The past decade has seen a surge of interest in the biological effects of UVA exposure as its significance to the process of photo-carcinogenesis has become increasingly evident. However, unpicking the unique complexity of the cellular response to UVA, which is only now becoming apparent, will be a major challenge for the field of photobiology in the 21st century.

Change of biophysical properties of the skin caused by ultraviolet radiation-induced photodamage in Koreans

BACKGROUND/PURPOSE

Ultraviolet (UV) irradiation affects the function and complexion of the skin by inducing changes in physical properties through formation of erythema, proliferation of epithelial cells, DNA damage, activation or inactivation of various enzymes and proteins, and free radical formation. In this study, the authors intended to observe the overall course of changes in barrier function and reflectance of the skin induced by photodamage, and healing reaction in the course of time, and alteration of the skin complexion.

METHODS

The subjects were chosen from 15 healthy Korean men 20-35 in age, that fall into the category of Fitzpatrick's skin types II, III, and IV without history of recent exposure to sunlight, photosensitivity, or having taken any drugs that induce phototoxicity or photoallergic reactions. The subjects were artificially exposed to suberythemogenic dose [0.5 minimal erythemal dose (MED), 0.75 MED], 1 MED and high dose (2.5 MED) by solar simulator, and changes in skin barrier function and skin reflectance were assessed with a Tewameter, a Corneometer, and a Colorimeter for 4 weeks.

RESULTS

Transepidermal water loss (TEWL) increased abruptly at Day 1 of single solar UV (SSUV) exposure, and slowly returned to the original level from Day 2/Day 3. In the case of exposure with 0.75 MED, it returned to the original level at Day 4 of exposure, and at Days 7 and 28 in the cases of 1 MED and 2.5 MED exposure, respectively. Water-holding capacity sharply declined at Day 1 of exposure, hitting the lowest point at Day 2, and then slowly recovered starting on Day 3. In the case of exposure with 0.75 MED and 1 MED, it returned to the original level at Days 7 and 28 in the case of 2.5 MED exposure. The a(*) values abruptly increased and reached the peak at Day 1 and slowly returned to the original level at Day 2, while the b(*) values slowly increased at Day 3, peaking at Day 7 and slowly returning to the original level thereafter. The L(*) values abruptly declined at Day 1, maintaining plateau through Day 7 and slowly returning to the baseline level thereafter. The individual typology angle (ITA degrees ) were compatible with L(*) values change. The erythema index increased abruptly at Day 1 of SSUV exposure, peaking at Day 2 and slowly returned to the original level starting at Day 3. Melanin index slowly started to increase on Day 3 of SSUV exposure, peaking at Day 7 and gradually returned to the original level thereafter. However, L(*), a(*), b(*), erythema index, and melanin index did not return to the original level during the 28-day course of this study.

CONCLUSION

This study shows that in the skin of Korean subjects, changes in skin barrier function and delayed melanization do occur even in exposure to a suberythemogenic dose of SSUV. Also, given the fact that restoration of barrier function occurs as the process of melanization begins, melanization is considered to be a useful predictive indicator of the restoration of the skin barrier function after sunburn.

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.

A simple and non-invasive visualization for assessment of carbonylated protein in the stratum corneum

BACKGROUND/PURPOSE

Stratum corneum (SC) is the interface of body and environment and is continuously exposed to oxidative stress, resulting in oxidative modification of proteins. Consequent carbonylated proteins (CPs) have so far been labeled with 2,4-dinitrophenyl (DNP) hydrazine and subsequently detected with anti-DNP antibody. We developed a simpler, non-invasive method to assess CP level in the SC and applied it to following research.

METHODS

SC was collected by adhesive tape stripping and its carbonyl groups were labeled with fluorescein-5-thiosemicarbazide (FTZ). The staining image was observed by fluorescence microscopy and the average fluorescence intensity of the SC extracted from the image was calculated as stratum corneum carbonylated protein (SCCP) level.

RESULTS

By reaction with FTZ, carbonyl groups in the SC could be detected easily. Relatively strong fluorescence was observed in exfoliating scales. Lipid removal from the SC in vitro or in vivo did not show any change in fluorescence intensity, suggesting that carbonyl groups were mainly derived from proteins, not from lipids. SCCP level was higher in the upper layer than the lower layer, and higher in the cheek (sun-exposed) than the inside of upper arm (unexposed), positively correlated with age especially in male cheek, positively correlated with transepidermal water loss, negatively correlated with water content, and showed a subtle correlation with sebum level. On the other hand, SC collected by cyanoacrylate resin and labeled with FTZ revealed strong fluorescence around the pores in the cheek and on the grooves in the upper arm, suggesting the role of sebum in the generation of SCCP.

CONCLUSION

SCCP was assessed in a simple and non-invasive method, and suggested to be a novel indicator that reflects some aspect of skin condition.

Vitamin E metabolism

The aim of this paper is to provide an overview of vitamin E metabolism. The topics covered include: major classes of vitamin E metabolites; their production pathways and route of excretion; possible biological activities of vitamin E metabolites; and use of vitamin E metabolites as markers of oxidant generation. Recent investigations into vitamin E metabolism have also highlighted important new areas of research, such as the potential for high dose vitamin E supplementation to interfere with drug metabolism, as well as alternative methods to alter vitamin E bioavailability in vivo. These issues will also be discussed in the review.

Generation and distribution of reactive oxygen species in the skin of hairless mice under UVA: studies on in vivo chemiluminescent detection and tape stripping methods

Although the formation of reactive oxygen species (ROS) in the skin induced by the ultraviolet (UV) light has been shown to lead to many cutaneous disorders, skin cancer and photoageing, the mechanism and distribution of ROS generation has not yet been definitively determined. In the present study, we examined the distribution of UVA-induced ROS in the skin of live hairless mice, using our proposed in vivo imaging chemiluminescent (CL) method to detect ROS combined with a CL probe (cypridina hilgendorfii luciferin analogue; CLA) and tape stripping (TS) technique. The CL intensities in the skin of live hairless mice were confirmed to significantly increase by UVA exposure. When TS was conducted five times in a maximum level after CL measurement following UVA exposure and subsequent CLA application, CL intensities due to UVA-induced ROS generation in the residual skin decreased to 10% of the original levels; and those in the stripped skin on each tape decreased in the stripped order such as 52%, 16%, 11%, 6% and 5%. Next, CLA was applied and then CL intensities were measured in the residual skin after advance 1, 3 and 5 tape strippings, and CL intensities due to ROS were detected primarily in the outer layer of the skin. On the basis of these results, we concluded that ROS induced by UVA exposure occurs and distributes in the outermost layer of the stratum corneum.

Skin bioavailability of dietary vitamin E, carotenoids, polyphenols, vitamin C, zinc and selenium

Dietary bioactive compounds (vitamin E, carotenoids, polyphenols, vitamin C, Se and Zn) have beneficial effects on skin health. The classical route of administration of active compounds is by topical application direct to the skin, and manufacturers have substantial experience of formulating ingredients in this field. However, the use of functional foods and oral supplements for improving skin condition is increasing. For oral consumption, some dietary components could have an indirect effect on the skin via, for example, secondary messengers. However, in the case of the dietary bioactive compounds considered here, we assume that they must pass down the gastrointestinal tract, cross the intestinal barrier, reach the blood circulation, and then be distributed to the different tissues of the body including the skin. The advantages of this route of administration are that the dietary bioactive compounds are metabolized and then presented to the entire tissue, potentially in an active form. Also, the blood continuously replenishes the skin with these bioactive compounds, which can then be distributed to all skin compartments (i.e. epidermis, dermis, subcutaneous fat and also to sebum). Where known, the distribution and mechanisms of transport of dietary bioactive compounds in skin are presented. Even for compounds that have been studied well in other organs, information on skin is relatively sparse. Gaps in knowledge are identified and suggestions made for future research.

Iron chelators may help prevent photoaging

For years, cosmetic ingredients for anti-aging treatments have attracted consumers. Skin aging is accelerated by reactive oxygen species (ROS), generated by exposure to solar ultraviolet radiation (UVR), in a process known as photoaging. Because cutaneous iron catalyses ROS generation, it is thought to play a key role in photoaging. Iron is essential to almost all forms of life. However, excess iron is potentially toxic as its catalytic activity induces the generation of ROS. Iron-catalysed ROS generation is involved in numerous pathological conditions, including cutaneous damage. When skin is directly exposed to UVR, cutaneous intracellular catalytic iron levels increase because of the release of iron from iron-binding proteins such as ferritin. Consequently, the subsequent ROS generation may overwhelm cutaneous defense systems such as the cellular iron sequestration and ROS scavenging capacity. The harmful role of excess cutaneous iron implies that there may be a potential for topical iron chelator treatments. We now consider cutaneous photodamage skin photoaging as the result of iron-catalysed ROS generation and discuss preventative strategies based on iron chelators.

Evaluation of the Antioxidant Capacity and Preventive Effects of a Topical Emulsion and Its Vehicle Control on the Skin Response to UV Exposure

Supplying topical exogenous antioxidants to the skin may prevent or minimize free radical-induced damaging. This study determines antioxidative capacity of a topical skin care emulsion (an oil-in-water vitamin E-containing formulation) versus its vehicle on human skin that was exposed to ultraviolet radiation (UVR) by utilizing a photochemiluminescence device and biophysical methods. Ten healthy Caucasians (3 male and 7 female; mean age 47 +/- 10 years) were enrolled. In a randomized and double-blind manner, a pH-balanced vitamin E emulsion or its vehicle control was applied onto predesignated forearm prior to UVR exposure. Thirty minutes after application, these test sites were exposed to a UV light to induce the minimal erythema dose. One untreated site served as a blank control. Visual scoring and instrumental measurements were recorded at baseline and at 24 h and 48 h thereafter. At day 3, after completing instrumental measurements, each test site was stripped three times in a consecutive manner with a proprietary adhesive tape disc. These tapes were quantified for antioxidant capacity using a photochemiluminescence device. Vitamin E emulsion and vehicle control significantly (p < 0.05) suppressed visual scores when compared with blank control at day 2 and day 3 after UV exposure. However, vitamin E emulsion showed significantly (p < 0.05) lower visual scores when compared with vehicle control at day 2 and day 3 after UV exposure.Also,vitamin E emulsion and its vehicle control significantly (p < 0.05) diminished skin color measurement (a*) values when compared with blank control at day 2 and day 3 after UV exposure. At day 2 after UV exposure, only vitamin E emulsion significantly (p < 0.05) reduced skin blood flow volume when compared with blank control. Vitamin E emulsion and its vehicle control showed significant (p < 0.05) reduction of blood flow volume when compared with blank control at day 3 after UV exposure. Vitamin E emulsion and its vehicle control proved effective in preventing induction of erythema and reducing inflammatory damage caused by UV exposure. The effect of vitamin E emulsion exceeded that of an 'active control'.

Vernix caseosa in neonatal adaptation

OBJECTIVES

To characterize vernix caseosa in newborn infants with respect to factors that influence vernix distribution on the skin surface, vernix effects on thermal stability, skin hydration, acid mantle development, and vernix antioxidant properties.

STUDY DESIGN

Vernix distribution was determined for 430 infants. Thermal stability was assessed in parallel groups following vernix retention (n=66) and removal (n=64). The effects of vernix retention on skin hydration, pH, erythema, and dryness/scaling were determined. Samples were analyzed for vitamin E before and after UV exposure.

RESULTS

Vernix distribution depended upon gestational age, delivery mode, gender, race, and meconium exposure. Retention had no effect on axillary temperatures. Skin hydration was significantly higher for vernix-retained skin. Skin pH and erythema were significantly lower with retention. Vitamin E levels were decreased by ultraviolet radiation.

CONCLUSIONS

Vernix is a naturally occurring barrier cream with multiple salubrious effects, which support its retention on the skin surface at birth.

Oral supplementation with all-Rac- and RRR-alpha-tocopherol increases vitamin E levels in human sebum after a latency period of 14-21 days

In human skin, highest alpha-tocopherol levels are found in facial sebum. We hypothesized that the bioavailability of vitamin E in human skin is, at least in part, dependent on sebaceous gland secretion. To test this, 24 volunteers were subjected to a randomized daily supplementation with either 400 mg RRR-alpha-tocopheryl acetate (RRR-alpha-toc) or 400 mg all-rac-alpha-tocopheryl acetate (all-rac-alpha-toc) for 14 days. Fasting blood samples, facial sebum samples, and lower-arm skin-surface lipids (SSL) were taken at time-points between 0-21 days. Samples were analyzed by HPLC for alpha-tocopherol and squalene concentrations. Increased serum alpha-tocopherol levels were detectable as early as 12 h after supplementation of RRR-alpha-toc or all-rac-alpha-toc and peaked on day 7. No significant changes were observed in lower-arm SSL. Remarkably, while unchanged until day 14, alpha-tocopherol sebum levels were increased on day 21 in both the RRR-alpha-toc and the all-rac-alpha-toc group by 87% and 92%, respectively. With respect to dietary supplementation of vitamin E and its bioavailability in human skin, these results suggest that (1) sebaceous gland secretion is a relevant delivery mechanism; (2) the bioavailabilities of RRR-alpha-toc and the all-rac-alpha-toc are similar; and (3) significant accumulation requires a daily supplementation period of at least 2-3 weeks.

Alpha-tocopherol pro-vitamins: synthesis, hydrolysis and accumulation in rabbit ear skin

We synthesized esters of alpha-tocopherol (VE) with the aim to develop new pro-vitamins, easily reconverted by enzymes in the skin and able to release another active moiety such as an amino acid, in order to obtain a synergic effect. In particular, the attention was dedicated to the amino acids glycine and alanine and to pyroglutamic acid. The sensitivity of pro-vitamins to enzymatic hydrolysis was evaluated in vitro using porcine liver esterase. Permeation experiments were performed using rabbit ear skin, for the quantification of pro-vitamins and derived VE in the epidermis and dermis. The new derivatives synthesized, and in particular the glycine and alanine derivatives, accumulated in rabbit skin in a significant extent and originated substantial amounts of alpha-tocopherol. In comparison with the acetate derivative (VEAc), the amounts accumulated are comparable or higher. Moreover, the new derivatives, being more hydrophilic, allow the use of vehicles such as the mixture water/propylene glycol/ethanol widely employed for the preparation of creams and gels. Finally, the enzymatic metabolism of these new derivatives generates not only VE, but also components that can have a further advantageous action on skin.

Allergic contact dermatitis is accompanied by severe abnormal changes in antioxidativity of blood

We investigated whether the oxidative stress (OS) caused by skin inflammation could reflect in the blood, in a 21-year-old female student sensitized to nickel, colophony and abitole with often relapsing allergic contact dermatitis (ACD). As glutathione redox ratio was increased in the blood not only during the relapse but also in the beginning of remission phase, we prescribed natural medical preparations of d-alpha-tocopherol (in the first week 100 mg three times a day followed by 100 mg/day) and ascorbic acid (200 mg/day) for 25 days to her. After using antioxidants in the remission period, one of the principal OS markers-the glutathione redox ratio reached the normal physiological level. In this report, we showed that during acute extensive ACD OS is expressed in the blood and simultaneous supplementation of d-alpha-tocopherol and ascorbic acid might reduce systemic OS.

Vitamin E Delivery to Human Skin by a Rinse-Off Product: Penetration of α-Tocopherol versus Wash-Out Effects of Skin Surface Lipids

alpha-Tocopherol, the major biologically active form of vitamin E, represents a frequently added lipophilic compound of skin care products. Despite its emerging use in rinse-off formulations, little is known on its efficacy with respect to its deposition or its antioxidant potential in human skin. The objective of this study was to investigate whether the single use of an alpha-tocopherol-enriched rinse-off product provides effective deposition of alpha-tocopherol on human stratum corneum. To test this, forearm skin of 13 volunteers was washed either with an alpha-tocopherol-enriched rinse-off product (test product, TP) or with an alpha-tocopherol-free vehicle control (control product, CP) (contralateral arm) using a standardized wash protocol. Thereafter, skin surface lipids were extracted with pure ethanol after the wash procedure as well as after 24 h. Additionally, one group of volunteers was subjected to irradiation of their forearms with low-dose UVA (8 J/cm(2)) prior to lipid extraction. Skin lipid extracts were analyzed by high performance liquid chromatography using electrochemical detection for vitamin E and UV detection for squalene (SQ) and squalene monohydroperoxide. The results of this in vivo study demonstrated that (1) while CP treatment lowers, TP treatment strongly increases alpha-tocopherol levels of skin barrier lipids; (2) increased vitamin E deposition levels were maintained for a period of at least 24 h, and (3) TP treatment significantly inhibited photooxidation of SQ. In conclusion, the use of alpha-tocopherol-enriched rinse-off products may help to maintain the integrity of the skin barrier by providing protection against photooxidative stress at the level of skin surface lipids.

Nutritional protection against skin damage from sunlight

The concept of systemic photoprotection by dietary means is gaining momentum. Skin is continuously exposed to ultraviolet (UV) radiation, the major cause of skin disorders such as sunburn, photodamage, and nonmelanoma skin cancer. Most of the erythemal annual UV dose is encountered under nonvacation conditions, when no sunscreen is applied. In the absence of topically added compounds, skin protection depends solely on endogenous defense. Micronutrients can act as UV absorbers, as antioxidants, or can modulate signaling pathways elicited upon UV exposure. UV-induced erythema is a suitable parameter to assess photoprotection. Dietary protection is provided by carotenoids, tocopherols, ascorbate, flavonoids, or n-3 fatty acids, contributing to maintenance resistance as part of lifelong protection.

Wipe-test and patch-test for alcohol misuse based on the concentration ratio of fatty acid ethyl esters and squalene CFAEE/CSQ in skin surface lipids

Fatty acid ethyl esters (FAEE) are known to be formed in blood and almost all human tissues after alcohol consumption and to be incorporated from sebum into hair where they can be used as long-term markers for excessive alcohol consumption. In order to examine whether skin surface lipids which consist mainly of sebum are an equally useful matrix for measurement of FAEE as alcohol abuse markers, samples were collected by a wipe-test from the forehead of 13 teetotallers, 16 social drinkers, 10 death cases with known recent alcohol misuse and five death cases without indications of alcohol misuse. The samples were analysed by headspace solid-phase microextraction and gas chromatography-mass spectrometry for ethyl myristate, ethyl palmitate, ethyl oleate and ethyl stearate and by high performance liquid chromatography with photodiode array detector for squalene, (SQ), as a natural reference substance which the FAEE concentrations were related to. The ratio mFAEE/mSQ ranged between 0.16 and 1.12 ng/microg (mean 0.34 ng/microg) for the teetotallers and between 0.08 and 0.94 ng/microg (mean 0.37 ng/microg) for the social drinkers with no significant difference between both groups. For the alcoholics 2.4-24.2 ng/microg (mean 13.1 ng/microg) were found. For two volunteers the course of mFAEE/mSQ 2 weeks before and 3 weeks after a single high alcohol dose was pursued by daily wipe tests. A strong increase of mFAEE/mSQ occurred between 7 and 12 days after the drinking event. This delay can be explained by the transition time of about 8 days between sebum production and its appearance on the skin surface known from literature. For seven social drinkers skin surface lipid samples were also collected using drug of abuse patches of the firm PharmCheck. The ratios mFAEE/mSQ in these samples were in the same range as from the wipe-test. The comparison with the self-reported ethanol amounts consumed the week before and during the test gave no good correlation (R2 = 0.42). It can be concluded from the results that FAEE in skin surface lipids can be used for medium-term retrospective detection of heavy drinking.

Role of oxidative stress and the antioxidant network in cutaneous carcinogenesis

Melanoma and nonmelanoma skin cancers are among the most prevalent cancers in the human population. Solar ultraviolet radiation is considered a major etiological factor but the relationship between dose, timing, and nature of exposure to tumor development is still unclear. Free radicals are generated by normal physiologic processes, including aerobic metabolism and inflammatory response, but may inflict cellular damage when generation is increased and antioxidant defense mechanisms are overwhelmed. Important findings supporting the free radical hypothesis in skin carcinogenesis are: (1) Reactive oxygen species (ROS) are generated in UVA- and UVB-irradiated skin in excessive doses, (2) the natural cutaneous antioxidant defense is impaired upon UV-exposure, (3) free radicals are involved in all steps of carcinogenesis, (4) supplementation with antioxidants can inhibit skin carcinogenesis, and (5) conditions that increase ROS generation enhance photocarcinogenesis. These findings provide a promising rationale for the development of powerful new antioxidant strategies in the prevention and therapy of skin cancer.

Antioxidant activity of topically applied lycopene

BACKGROUND

Ultraviolet (UV) rays cause depletion of the antioxidant substances contained in the epidermis. This is the rationale for the use of topical antioxidant substances.

METHODS

We studied the protective activity against UV radiation of a product based on lycopene and a product containing a mixture of vitamins E and C. Photostimulation was applied with a solar simulator and the cutaneous response was evaluated instrumentally.

RESULTS

The lycopene-based product had a much greater protective ability than the product containing the mixture of vitamins.

CONCLUSIONS

Lycopene has suitable characteristics to be used successfully in the prevention of cutaneous damage by free radicals. Its antioxidant ability is probably due to its high reductive power.

Impact of ultraviolet radiation and ozone on the transepidermal water loss as a function of skin temperature in hairless mice

Exposure to ultraviolet radiation or ozone leads to skin damage including oxidation of skin biomolecules, as well as to depletion of constitutive antioxidants. The highly organized stratum corneum forming the main barrier against most xenobiotics is particularly susceptible to such damage and possible barrier perturbation may be the consequence. Whereas ample evidence exists for an increased permeability for different solutes including water after exposure to ultraviolet radiation, such an effect has not yet been reported for ozone. This study reports on the effect of such oxidative stressors using the hairless mouse as the skin model and measuring temperature-controlled transepidermal water loss (TEWL) as an indicator for skin barrier integrity. First, a strong dependency of the TEWL on skin temperature was observed, an effect that was clearly more pronounced than that found in man. Given this temperature dependency in untreated animals, we proceeded to determine the effects of both ultraviolet radiation and ozone on TEWL over a relevant physiological skin temperature range. Solar-simulated ultraviolet radiation (0.75-3 minimal erythemal dose) resulted in a delayed and dose-dependent skin barrier disruption over the entire temperature range investigated. Conversely, daily ozone exposure at 2 ppm for 1 week, however, did not significantly alter TEWL up to 72 h after the last exposure. The results demonstrate a differential response of the epidermis to two environmental stressors associated with oxidative damage; they suggest that chronic ozone exposure at relevant environmental levels does not lead to a detectable skin barrier defect, while solar UV exposure was demonstrated to increase epidermal water loss. Furthermore, experimental evidence clearly suggests that future studies applying TEWL measurements in animal models should be performed under carefully controlled skin temperature conditions.

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.

Antioxidants in dermocosmetology: from the laboratory to clinical application

Oxygen situated in cutaneous cells can be activated by light. This makes the integumentary apparatus particularly vulnerable to oxidative damage and is responsible for the immediate cutaneous damage that is the basis of late phenomena, such as photo-induced ageing and tumours. Thus, the cosmetic industry has undertaken research and development into antioxidant-based products able to protect the skin from the effect of pro-oxidizing noxae. This review re-examines both antioxidants suitable for dermatological application and skin care products with antioxidant capacity, as well as the laboratory methods used to evaluate the effects and in vivo efficacy of antioxidants.

Induction of stress proteins and MMP-9 by 0.8 ppm of ozone in murine skin

Ozone (O(3)) is among the most reactive environmental oxidant pollutants to which cutaneous tissues are exposed. O(3) exposure has been shown to induce antioxidant depletion as well as the oxidation of lipids and proteins within the outermost skin layer, the stratum corneum. However, relatively little is known regarding the potential effects of O(3) on the cellular constituents of the underlying skin epidermis and dermis. In the present study, hairless mice exposed for 6 h to 0.8 ppm O(3) showed increases in lipid peroxidation, as quantitated by increases in 4-hydroxynonenal-protein adducts. O(3) exposure caused an induction of the stress proteins HSP27 and heme oxygenase-1 (HO-1), starting at 6 h and increasing up to 18 h after O(3) exposure. This was accompanied by an increase in matrix metalloproteinase-9 (MMP-9) mRNA and activity levels, indicative of possible injurious-reparative processes. Collectively, our data demonstrate that skin exposure to O(3) not only affects antioxidant levels and oxidation markers in the outermost stratum corneum layer, but also induces cellular stress responses in the deeper cellular layers of the skin.

Ultraviolet a induces generation of squalene monohydroperoxide isomers in human sebum and skin surface lipids in vitro and in vivo

At the outermost surface of human skin, skin surface lipids are first-line targets of solar ultraviolet radiation. Therefore, we hypothesized that ultraviolet A and ultraviolet B irradiation induce photo-oxidation of skin surface lipids. To test this, sebum samples were collected from facial skin of 17 healthy volunteers, weighed, and immediately irradiated with either ultraviolet B or ultraviolet A. Squalene, the major sebum lipid, as well as photo-oxidation products were identified in sebum lipid extracts by high-performance liquid chromatography analysis. Upon ultraviolet A exposures squalene was depleted in a concentration-dependent manner, whereas an unidentified sebum lipid photo-oxidation product was detected. Using high-performance thin layer chromatography, high-performance liquid chromatography, atmospheric pressure chemical ionization mass spectrometry, and nuclear magnetic resonance, unidentified sebum lipid photo-oxidation product was identified as a mixture of squalene monohydroperoxide isomers. Squalene monohydroperoxide isomers purified from sebum were identical with squalene monohydroperoxide isomers synthesized by preparative photo-oxidation of squalene. Squalene monohydroperoxide isomers were formed even after small suberythematogenic doses of ultraviolet A (5 J per cm2). Whereas physiologic baseline levels of squalene monohydroperoxide isomers in human skin were only slightly above detection limits, squalene monohydroperoxide isomer levels were strongly increased by suberythematogenic doses of ultraviolet A both in vitro and in vivo. High-performance liquid chromatography results could be complemented by a straightforward thin layer chromatography method for rapid screening of lipid peroxide formation in human sebum/skin surface lipids. In conclusion, specific squalene monohydroperoxide isomers were identified as highly ultraviolet A sensitive skin surface lipid breakdown products that may serve as a marker for photo-oxidative stress in vitro and in vivo.

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.

The role of H2O2 as a mediator of UVB-induced apoptosis in keratinocytes

Apoptosis is an active form of cell death that is initiated by a variety of stimuli, including reactive oxygen species (ROS) and ultraviolet (UV) radiation. Previously, it has been reported that UVB-irradiation of keratinocytes leads to intracellular generation of hydrogen peroxide (H2O2) and that antioxidants can inhibit ROS-induced apoptosis. Although both UVB-irradiation and H2O2-incubation led to increased intracellular H2O2 levels, the antioxidants catalase and glutathione monoester (GME), inhibited apoptosis only when induced by H2O2, not by UVB. Furthermore, extracellular signal-regulated kinase (ERK), a prominent member of the mitogen-activated protein kinase (MAPK) family, was found to be activated by treatment with both UVB and H2O2. Inhibition of ERK phosphorylation by pre-treatment with PD98059 resulted in enhanced apoptosis after H2O2-exposure. However,no significant difference of apoptosis was observed between cells with and without inhibitor pre-treatment upon UVB-irradiation. DNA damage in the form of cyclobutane pyrimidine dimers was observed after exposure to UVB, but no photoproducts were found in H2O2-treated cells. These results suggest a ROS-independent pathway of UVB-induced apoptosis. Although UVB-irradiation causes moderate increase in H2O2, the generation of H2O2 does not contribute to the induction of apoptosis. Moreover, activation of ERK only blocks H2O2-dependent apoptosis but has no impact on UVB-induced apoptosis.

Antioxidant enzyme activity in human stratum corneum shows seasonal variation with an age-dependent recovery

The stratum corneum, as the body's principal barrier to the environment, is continuously exposed to environmental sources of reactive oxygen species like ultraviolet light, ozone, and pollution. Reactive oxygen species are believed to be involved in cancer, aging, and inflammatory skin disorders. We have developed a method to measure catalase and superoxide dismutase activity on tape strippings from the human stratum corneum and demonstrated a gradient of antioxidant enzyme activity across the stratum corneum with decreasing levels towards the skin surface. Sun exposure resulted in a seasonal variation of the catalase activity in stratum corneum, with low activities in summer and higher activities in winter for the same person, whereas superoxide dismutase activity in stratum corneum did not seem to vary in those conditions. Exposure of human skin to broadband ultraviolet-A resulted in a dose-dependent deactivation of the catalase activity in stratum corneum within 24 h, whereas exposure to ultraviolet-B had no effect. Superoxide dismutase activity in stratum corneum was not affected by ultraviolet-A or ultraviolet-B irradiation within 24 h. After exposure to a dose of 15 J per cm2 broadband ultraviolet-A, full recovery of the catalase activity occurred in 3-4 wk at an age-dependent rate. We conclude that sun exposure results in a disturbed catalase to superoxide dismutase ratio in the stratum corneum. This may lead to an increased vulnerability to oxidative damage in stratum corneum barrier components. These results therefore stress the importance of providing efficient protection for this internal defense mechanism in sun-exposed areas of the skin.

Topical alpha-tocotrienol supplementation inhibits lipid peroxidation but fails to mitigate increased transepidermal water loss after benzoyl peroxide treatment of human skin

Benzoyl peroxide (BPO) is a commonly used drug in the treatment of acne vulgaris, but it induces unwanted side effects related to stratum corneum (SC) function. Since it has been recently shown to oxidize SC antioxidants, it was hypothesized that antioxidant supplementation may mitigate the BPO-induced SC changes. To test this, 11 subjects were selected to be topically supplemented with alpha-tocotrienol (5% w/vol) for 7 d on defined regions of the upper back, while the contralateral region was used for vehicle-only controls. Starting on day 8, all test sites were also treated with BPO (10%) for 7 d; the alpha-tocotrienol supplementation was continued throughout the study. A single dose of BPO depleted 93.2% of the total vitamin E. While continuing the BPO exposure for 7 d further depleted vitamin E in both vehicle-only and alpha-tocotrienol-treated sites, significantly more vitamin E remained in the alpha-tocotrienol-treated areas. Seven BPO applications increased lipid peroxidation. Alpha-tocotrienol supplementation significantly mitigated the BPO-induced lipid peroxidation. The transepidermal water loss was increased 1.9-fold by seven BPO applications, while there was no difference between alpha-tocotrienol treatment and controls. The data suggest that alpha-tocotrienol supplementation counteracts the lipid peroxidation but not the barrier perturbation in the SC induced by 10% BPO.