Air pollution-induced tanning of human skin.

BACKGROUND: Melanism is more frequent in animals living in polluted areas on urban-industrial sites. Given that an increasing number of people are exposed to elevated air pollution levels, it is possible that environmental pollutants affect melanogenesis in human skin. Epidemiological studies have shown that exposure to traffic-related air pollutants such as diesel exhaust particles (DEP) is associated with more clinical signs of hyperpigmentation. However, mechanistic evidence linking DEP exposure to pigmentation has been elusive. OBJECTIVES: To develop an ex␣vivo skin model to allow for repetitive topical application of relevant ambient DEP, and to provide proof of concept in humans. METHODS: We measured skin pigmentation, melanin and pigmentation-associated gene expression, and evaluated oxidative stress. RESULTS: Repetitive exposure of ex␣vivo skin to DEP at nontoxic concentrations increased skin pigmentation. This increase was visible to the naked eye, time dependent, and associated with an increase in melanin content and the transcription of genes involved in de novo melanin synthesis. Similarly, in healthy participants (n = 76), repetitive topical application of DEP at nontoxic concentrations increased skin pigmentation. DEP-induced pigmentation was mediated by an oxidative stress response. After the application of DEP, epidermal antioxidants were depleted, lipid peroxidation and oxidative DNA damage were enhanced, and in a vehicle-controlled, double-blind clinical study DEP-induced pigmentation was prevented by the topical application of an antioxidant mixture. CONCLUSIONS: Similar to solar radiation, air pollutants cause skin tanning. As eumelanin is an antioxidant, it is proposed that this response serves to protect human skin against air pollution-induced oxidative stress.

EPR Technology as Sensitive Method for Oxidative Stress Detection in Primary and Secondary Keratinocytes Induced by Two Selected Nanoparticles.

Exogenous factors can cause an imbalance in the redox state of biological systems, promoting the development of oxidative stress, especially reactive oxygen species (ROS). To monitor the intensity of ROS production in secondary keratinocytes (HaCaT) by diesel exhaust particles and thermoresponsive nanogels (tNG), electron paramagnetic resonance (EPR) spectroscopy after 1 and 24 h of incubation, respectively, was applied. Their cytotoxicity was analyzed by a cell viability assay (XTT). For tNG an increase in the cell viability and ROS production of 10% was visible after 24 h, whereas 1 h showed no effect. A ten times lower concentration of diesel exhaust particles exhibited no significant toxic effects on HaCaT cells for both incubation times, thus normal adult human keratinocytes (NHK) were additionally analyzed by XTT and EPR spectroscopy. Here, after 24 h a slight increase of 18% in metabolic activity was observed. However, this effect could not be explained by the ROS formation. A slight increase in the ROS production was only visible after 1 h of incubation time for HaCaT (9%) and NHK (14%).

Molecular evidence that oral supplementation with lycopene or lutein protects human skin against ultraviolet radiation: results from a double-blinded, placebo-controlled, crossover study.

BACKGROUND: Increasing evidence suggests photoprotection by oral supplementation with ß-carotene and lycopene. OBJECTIVES: To examine the capacity of lycopene-rich tomato nutrient complex (TNC) and lutein, to protect against ultraviolet (UV)A/B and UVA1 radiation at a molecular level. METHODS: In a placebo-controlled, double-blinded, randomized, crossover study two active treatments containing either TNC or lutein were assessed for their capacity to decrease the expression of UVA1 the radiation-inducible genes HO1, ICAM1 and MMP1. Sixty-five healthy volunteers were allocated to four treatment groups and subjected to a 2-week washout phase, followed by two 12-week treatment phases separated by another 2 weeks of washout. Volunteers started either with active treatment and were then switched to placebo, or vice versa. At the beginning and at the end of each treatment phase skin was irradiated and 24 h later biopsies were taken from untreated, UVA/B- and UVA1-irradiated skin for subsequent reverse transcriptase polymerase chain reaction analysis of gene expression. Moreover, blood samples were taken after the washout and the treatment phases for assessment of carotenoids. RESULTS: TNC completely inhibited UVA1- and UVA/B-induced upregulation of heme-oxygenase 1, intercellular adhesion molecule 1 and matrix metallopeptidase 1 mRNA, no matter the sequence (anova, P < 0·05). In contrast, lutein provided complete protection if it was taken in the first period but showed significantly smaller effects in the second sequence compared with TNC. CONCLUSIONS: Assuming the role of these genes as indicators of oxidative stress, photodermatoses and photoageing, these results might indicate that TNC and lutein could protect against solar radiation-induced health damage.

[Environmentally induced (extrinsic) skin aging]. / Umweltinduzierte (extrinsische) Hautalterung.

Chronic exposure to ultraviolet light, particularly as a component of natural sunlight, is a major cause of environmentally induced aging of the skin. In addition, other environmental factors for premature skin aging include longer wavelength radiation in the visible light region and in particular in the shortwave infrared radiation region. Furthermore, particulate and gaseous components of air pollution significantly contribute to the aging process.

Pycnogenol® effects on skin elasticity and hydration coincide with increased gene expressions of collagen type I and hyaluronic acid synthase in women.

INTRODUCTION AND OBJECTIVES: In recent years there has been an increasing interest in the use of nutritional supplements to benefit human skin. Molecular evidence substantiating such effects, however, is scarce. In the present study we investigated whether nutritional supplementation of women with the standardized pine bark extract Pycnogenol® will improve their cosmetic appearance and relate these effects to expression of corresponding molecular markers of their skin. MATERIALS AND METHODS: For this purpose 20 healthy postmenopausal women were supplemented with Pycnogenol for 12 weeks. Before, during and after supplementation, their skin condition was assessed (i) by employing non-invasive, biophysical methods including corneometry, cutometry, visioscan and ultrasound analyses and (ii) by taking biopsies and subsequent PCR for gene expression analyses related to extracellular matrix homeostasis. RESULTS: Pycnogenol supplementation was well tolerated in all volunteers. Pycnogenol significantly improved hydration and elasticity of skin. These effects were most pronounced in women presenting with dry skin conditions prior to the start of supplementation. The skin-physiological improvement was accompanied by a significant increase in the mRNA expression of hyaluronic acid synthase-1 (HAS-1), an enzyme critically involved in the synthesis of hyaluronic acid, and a noticeable increase in gene expression involved in collagen de novo synthesis. CONCLUSIONS: This study provides skin-physiological and for the first time molecular evidence that Pycnogenol supplementation benefits human skin by increasing skin hydration and skin elasticity. These effects are most likely due to an increased synthesis of extracellular matrix molecules such as hyaluronic acid and possibly collagen. Pycnogenol supplementation may thus be useful to counteract the clinical signs of skin aging.

[Adipose tissue. Cellular and molecular principles]. / Fettgewebe. Zelluläre und molekulare Grundlagen.

For many decades, cutaneous biology research has primarily focused on the dermis and epidermis. In recent years the subcutaneous far has attracted the attention of basic science, cosmetology and industry. Numerous new approaches are in the process of development, enabling us to better understand assembly, differentiation and function of adipose tissue. To understand these developments a background in the cellular and molecular basics of adipose tissue is indispensable. This state-of the art article provides the needed information.

[Urea plus ceramides and vitamins: improving the efficacy of a topical urea preparation by addition of ceramides and vitamins]. / Harnstoff plus Ceramide und Vitamine: Untersuchungen zur Verbesserung eines harnstoffhaltigen Externums durch Zusatz von Ceramiden und Vitaminen.

Topical urea preparations containing urea have been used successfully to improve the barrier function of the skin. We investigated whether the efficacy of an urea-containing topical preparation could be improved by the addition of vitamins and ceramides. For this an intra-individual comparative study was conducted on 10 subjects with healthy skin. The application of the combination preparation containing urea, vitamins and ceramides for 2 weeks was significantly superior to the urea-only preparation in respect to reduction of transepidermal water loss and skin hydration levels. This improved efficacy was associated with a stronger up-regulation of the transcriptional expression of differentiation genes in keratinocytes in the treated skin areas. While both preparations caused an increased expression of the genes encoding transglutaminase-1, involucrin, loricrin and filaggrin, this increase was significantly greater in those skin areas treated with the combination preparation. This study indicates that the efficacy of topical preparations containing urea can be enhanced by the incorporation of ceramides and vitamins.

[Topical application of vitamins, phytosterols and ceramides. Protection against increased expression of interstital collagenase and reduced collagen-I expression after single exposure to UVA irradiation]. / Topische Applikation von Vitaminen, Phytosterolen und Ceramiden. Schutz vor vermehrter Expression der interstitiellen Kollagenase und verminderter Kollagen-I-Expression nach 1-maliger UVA-Bestrahlung.

Photoaged skin is characterized by a decrease of dermal collagen fibers, resulting from an increased breakdown and a diminished de novo synthesis. The increased breakdown results from an increased expression of matrix metalloproteinases (MMPs). The main building blocks involved in de novo synthesis of collagen fibers are collagen 1A1 and 1A2, the expression of which is reduced in photoaged skin. We studied the effect of topical application of vitamins, phytosterols and ceramides on UV-induced up-regulation of the expression of MMP-1 and on UV-induced down-regulation of COL1A1 and COL1A2. The study was conducted with 10 subjects with healthy skin who were comparatively treated for 10 days with (i) a basic preparation containing jojoba oil, (ii) the basic preparation supplemented with vitamins, (iii) the basic preparation supplemented with phytosterols and ceramides, and (iv) the basic preparation supplemented with vitamins, phytosterols and ceramides. All four preparations inhibited the UV induced up-regulation of MMP-1. Neither the basic product nor that supplemented with vitamins inhibited down-regulation of COL1A1 and COL1A2, but addition of phytosterols and ceramides caused a decreased down-regulation of the expression of these genes. Our results indicate that phytosterols and ceramides are effective in blocking the reduced collagen synthesis after UV irradiation and even stimulating synthesis. They may be useful additions to anti-aging products.

Ceramide and raft signaling are linked with each other in UVA radiation-induced gene expression.

Solar ultraviolet A (UVA) (320-400 nm) radiation-induced gene expression in keratinocytes is initiated at the level of the cell membrane via generation of singlet oxygen and subsequent formation of ceramide from sphingomyelin. We now report that the UVA response also involves raft signaling and that ceramide and raft signaling are linked with each other. Upon UVA irradiation, the lipid composition of rafts decreased 40% in sphingomyelin and 60% in cholesterol (Chol). Also, decrease of Chol increased the susceptibility towards UVA-induced gene expression, whereas increase of Chol completely abolished their capacity to generate signaling ceramides and to mount the subsequent UVA response. This inhibition was not associated with UVA-induced Chol oxidation and was also seen after treatment of cells with plant sterols. The UVA responsiveness depended on the ratio of Chol versus ceramide in rafts. A ratio smaller than 1 permitted initiation and transduction of the signaling response, whereas a ratio greater than 1, for example, upon sterol pretreatment, abolished this response, indicating that UVA radiation-induced ceramide signaling is controlled by the lipid composition of rafts.

Evaluation of the capacity of sunscreens to photoprotect lupus erythematosus patients by employing the photoprovocation test.

Although sunscreens are widely used to photoprotect patients with photosensitive lupus erythematosus (LE), standardized controlled studies that can prove their efficacy for this indication have been lacking. Therefore, in the present study, the capacity of three different, commercially available sunscreens to prevent the development of skin lesions that have been induced in LE patients under standardized, reproducible conditions by employing a provocative phototest was assessed. In a double blind, intraindividual comparative study, 11 patients with LE were photoprovoked according to a standard protocol. All patients developed LE-specific skin lesions upon photoprovocation with a combination of UVA plus UVB radiation. Each of the sunscreens tested prevented the development of skin lesions in this assay, but to various extents. Suncreen A (UVB: Octocrylene; UVA: Mexoryl SX, Mexoryl XL, Parsol 1789; TiO2) was by far the most effective by protecting in 11/11 patients. This protective capacity was corroborated by studies in which strong ICAM-1 mRNA expression was found in unprotected test areas, but not in sunscreen A pretreated sites. In contrast to sunscreen A, sunscreen B (UVB: Eusolex 6300, Parsol MCX, Uvinul T150, Neohelipan; UVA: Parsol 1789; TiO2) protected in 5 patients and sunscreen C (Eusolex 6300, Parsol MCX, Uvinul T150; UVA: Parsol 1789; TiO2) in 3 out of 11 patients. These studies indicate that the use of sunscreens is beneficial to LE patients because it can prevent the development of UV radiation-induced skin lesions. Effective protection, however, might vary considerably between different sunscreens.

Non-enzymatic triggering of the ceramide signalling cascade by solar UVA radiation.

Ceramide is a key component of intracellular stress responses. Evidence is provided for a novel mechanism of ceramide formation that mediates solar ultraviolet (UV) A radiation-induced expression of the intercellular adhesion molecule (ICAM)-1. Similarly to UVA radiation, ceramide stimulation of human keratinocytes induced ICAM-1 mRNA expression and activated the ICAM-1 promoter through transcription factor AP-2. Ceramide-activated AP-2 and ceramide-induced ICAM-1 reporter gene activation were abrogated through deletion of the AP-2 binding site. UVA radiation increased the level of ceramide in keratinocytes and inhibition of sphingomyelin synthesis prevented UVA radiation-induced ICAM-1 expression. Hitherto, two pathways have been identified for ceramide accumulation: hydrolysis from sphingomyelin through neutral and acid sphingomyelinases, and de novo synthesis by ceramide synthase. UVA radiation did not activate any of these enzymes. Ceramide generation in UVA-irradiated cells, however, was inhibited by singlet oxygen quenchers and mimicked in unirradiated cells by a singlet oxygen-generating system. In addition, UVA radiation and singlet oxygen both generated ceramide in protein-free, sphingomyelin-containing liposomes. This study indicates that singlet oxygen triggers a third, non-enzymatic mechanism of ceramide formation.

Enzyme plus light therapy to repair DNA damage in ultraviolet-B-irradiated human skin.

Ultraviolet-B (UVB) (290-320 nm) radiation-induced cyclobutane pyrimidine dimers within the DNA of epidermal cells are detrimental to human health by causing mutations and immunosuppressive effects that presumably contribute to photocarcinogenesis. Conventional photoprotection by sunscreens is exclusively prophylactic in nature and of no value once DNA damage has occurred. In this paper, we have therefore assessed whether it is possible to repair UVB radiation-induced DNA damage through topical application of the DNA-repair enzyme photolyase, derived from Anacystis nidulans, that specifically converts cyclobutane dimers into their original DNA structure after exposure to photoreactivating light. When a dose of UVB radiation sufficient to induce erythema was administered to the skin of healthy subjects, significant numbers of dimers were formed within epidermal cells. Topical application of photolyase-containing liposomes to UVB-irradiated skin and subsequent exposure to photoreactivating light decreased the number of UVB radiation-induced dimers by 40-45%. No reduction was observed if the liposomes were not filled with photolyase or if photoreactivating exposure preceded the application of filled liposomes. The UVB dose administered resulted in suppression of intercellular adhesion molecule-1 (ICAM-1), a molecule required for immunity and inflammatory events in the epidermis. In addition, in subjects hypersensitive to nickel sulfate, elicitation of the hypersensitivity reaction in irradiated skin areas was prevented. Photolyase-induced dimer repair completely prevented these UVB radiation-induced immunosuppressive effects as well as erythema and sunburn-cell formation. These studies demonstrate that topical application of photolyase is effective in dimer reversal and thereby leads to immunoprotection.

Singlet oxygen mediates the UVA-induced generation of the photoaging-associated mitochondrial common deletion.

Mutations of mitochondrial (mt) DNA accumulate during normal aging. The most frequent mutation is a 4,977-base pair deletion also called the common deletion, which is increased in photoaged skin. Oxidative stress may play a major role in the generation of large scale mtDNA deletions, but direct proof for this has been elusive. We therefore assessed whether the common deletion can be generated in vitro through UV irradiation and whether reactive oxygen species are involved in this process. Normal human fibroblasts were repetitively exposed to sublethal doses of UVA radiation and assayed for the common deletion employing a semiquantitative polymerase chain reaction technique. There was a time/dose-dependent generation of the common deletion, attributable to the generation of singlet oxygen, since the common deletion was diminished when irradiating in the presence of singlet oxygen quenchers, but increased when enhancing singlet oxygen half-life by deuterium oxide. The induction of the common deletion by UVA irradiation was mimicked by treatment of unirradiated cells with singlet oxygen produced by the thermodecomposition of an endoperoxide. These studies provide evidence for the involvement of reactive oxygen species in the generation of aging-associated mtDNA lesions in human cells and indicate a previously unrecognized role of singlet oxygen in photoaging of human skin.

Evidence that singlet oxygen-induced human T helper cell apoptosis is the basic mechanism of ultraviolet-A radiation phototherapy.

Ultraviolet A (UVA) irradiation is effectively used to treat patients with atopic dermatitis and other T cell mediated, inflammatory skin diseases. In the present study, successful phototherapy of atopic dermatitis was found to result from UVA radiation-induced apoptosis in skin-infiltrating T helper cells, leading to T cell depletion from eczematous skin. In vitro, UVA radiation-induced human T helper cell apoptosis was mediated through the FAS/FAS-ligand system, which was activated in irradiated T cells as a consequence of singlet oxygen generation. These studies demonstrate that singlet oxygen is a potent trigger for the induction of human T cell apoptosis. They also identify singlet oxygen generation as a fundamental mechanism of action operative in phototherapy.

Photocarcinogenesis and inhibition of intercellular adhesion molecule 1 expression in cells of DNA-repair-defective individuals.

Cells from patients with xeroderma pigmentosum complementation group D (XP-D) and most patients with trichothiodystrophy (TTD) are deficient in excision repair of ultraviolet (UV) radiation-induced DNA damage. Although in both syndromes this defect is based on mutations in the same gene, XPD, only XP-D, not TTD, individuals have an increased risk of skin cancer. Since the reduction in DNA repair capacity is similar in XP-D and TTD patients, it cannot account for the difference in skin cancer risk. The features of XP-D and TTD might therefore be attributable to differences in the immune response following UV-irradiation, a factor which is presumed to be important for photocarcinogenesis. We have measured the capacity of UVB radiation to inhibit expression of the immunological key molecule intercellular adhesion molecule 1 (ICAM-1) in cells from three healthy individuals in comparison to cells from three XP-D and three TTD patients. Cells from XP-D patients, but not from TTD patients, exhibited an increased susceptibility to UVB radiation-induced inhibition of ICAM-1 expression. Transfection of XP-D cells with the wild-type XPD cDNA, but not with XPC cDNA, corrected this abnormal phenotype. Thus, the skin cancer risk in DNA repair-defective individuals correlated with the susceptibility of their cells to UVB radiation-induced inhibition of ICAM-1 expression, rather than with their defect in DNA repair. The XPD protein has dual roles: in DNA repair and transcription. The transcriptional role might be important for the control of expression of immunologically relevant genes and thereby contribute to the skin cancer risk of a DNA-repair-deficient individual.