The protective role of melanin against UV damage in human skin

Redox properties of LDH microcrystals coated with a catechol-bearing phosphonate derived from dopamine

The surface of Zn–Al-chloride LDH microcrystals (LDH = Layered Double Hydroxides) was activated by grafting a redox active catechol bearing bis-phosphonate obtained by dopamine derivatization.

UV light and skin aging

This article reviews current data about the relationship between sun radiation and skin, especially with regards ultraviolet light and the skin aging process. The benefits of sun exposition and the photoaging process are discussed. Finally, the authors present a review of photoprotection agents that are commercially available nowadays.

Benzylidene-linked thiohydantoin derivatives as inhibitors of tyrosinase and melanogenesis: importance of the β-phenyl-α,β-unsaturated carbonyl functionality

The “β-phenyl-α,β-unsaturated carbonyl” group might serve as a key pharmacophore for high tyrosinase inhibition.

Norartocarpetin from a folk medicine Artocarpus communis plays a melanogenesis inhibitor without cytotoxicity in B16F10 cell and skin irritation in mice

Background

Many natural products used in preventive medicine have also been developed as cosmeceutical ingredients in skin care products, such as Scutellaria baicalensis and Gardenia jasminoides. Norartocarpetin is one of the antioxidant and antityrosinase activity compound in Artocarpus communis; however, the cytotoxicity, skin irritation and antimelanogenesis mechanisms of norartocarpetin have not been investigated yet.

Methods

In the present study, cell viability in vitro and skin irritation in vivo are used to determine the safety of norartocarpetin. The melanogenesis inhibition of norartocarpetin was determined by cellular melanin content and tyrosinase in B16F10 melanoma cell. Moreover, we examined the related-melanogenesis protein by western blot analysis for elucidating the antimelanogenesis mechanism of norartocarpin.

Results

The result of the present study demonstrated that norartocarpetin not only present non-cytotoxic in B16F10 and human fibroblast cells but also non-skin irritation in mice. Moreover, our result also first found that norartocarpetin downregulated phospho-cAMP response element-binding (phospho-CREB) and microphthalmia-associated transcription factor (MITF) expression, which in turn decreased both synthesis of tyrosinases (TRP-1 and TRP-2) and cellular melanin content. This process is dependent on norartocarpetin phosphorylation by mitogen-activated protein kinases such as phospho-JNK and phospho-p38, and it results in decreased melanogenesis.

Conclusion

The present study suggests that norartocarpetin could be used as a whitening agent in medicine and/or cosmetic industry and need further clinical study.

Occupational sun exposure and risk of melanoma according to anatomical site

Although sunburn and intermittent sun exposures are associated with increased melanoma risk, most studies have found null or inverse associations between occupational (more continuous pattern) sun exposure and melanoma risk. The association of melanoma with occupational sun exposure may differ according to anatomical site, with some studies finding a positive association with melanoma on the head and neck. We examined the association between occupational sun exposure (self-reported weekday sun exposure) and melanoma risk according to anatomical site, using data from two multicentre population-based case-control studies: the Australian Melanoma Family Study (588 cases, 472 controls) and the Genes, Environment and Melanoma study (GEM; 1079 cases, 2,181 controls). Unconditional logistic regression was used to estimate odds ratios (OR) and their 95% confidence intervals, adjusting for potential confounders. Occupational sun exposure was not positively associated with melanoma risk overall or at different body sites in both studies. The GEM study found inverse associations between occupational sun exposure and melanoma on the head and neck [OR for highest vs. lowest quartile: 0.56, 95% confidence intervals (CI) 0.36-0.86, ptrend 0.02], and between the proportion of total sun exposure occurring on weekdays and melanoma on the upper limbs (OR for highest vs. lowest quartile: 0.66, 95% CI 0.42-1.02, ptrend 0.03). Our results suggest that occupational sun exposure does not increase risk of melanoma, even of melanomas situated on the head and neck. This finding seemed not to be due to negative confounding of occupational sun exposure by weekend sun.

Eupafolin, a skin whitening flavonoid isolated from Phyla nodiflora, downregulated melanogenesis: Role of MAPK and Akt pathways

ETHNOPHARMACOLOGICAL RELEVANCE

In hyperpigmentation disorders marked by melanin overproduction in the skin, including melisma and freckles, melanogenesis is caused by tyrosinase overexpression. Natural medicinal resources, like Phyla nodiflora, a traditional Chinese herbal medicine, have been used for a long time to management of dermatological conditions, such as skin inflammation and melanogenesis. Eupafolin, a functional flavonoid isolated from Phyla nodiflora, is an herbal tea constituent and possesses anti-inflammatory and anticancer activities. However, molecular mechanisms of eupafolin-mediated antimelanogenesis remain unknown. We thus focused on its antimelanogenesis effects in B16F10 mouse melanoma cells.

MATERIAL AND METHODS

B16F10 cells were treated with eupafolin (0.01, 0.1, 1, and 10μM) in a dose-escalation-dependent manner for the determination of melanin, tyrosinase activity and melanogenesis protein levels by ELISA or western blot analysis.

RESULTS

Eupafolin treatment significantly reduced cellular melanin content and tyrosinase activity in a dose-dependent manner (P<0.05), and no cytotoxic effects were observed. Eupafolin was associated with reduction in the levels of phospho-cAMP response element-binding protein and microphthalmia-associated transcription factor (MITF), and downregulation of tyrosinase synthesis and tyrosinase-related protein expression, leading to inhibit melanin production. In addition, eupafolin significantly induced the phosphorylation of ERK1/2 and p38 MAPK, whereas the decreased effect was observed in the phosphorylation of Akt. Moreover, inhibitors of these signals recovered or attenuated the inhibitory effects of eupafolin on melanogenesis.

CONCLUSIONS

Our results seem that inhibition of Akt and activation of phospho-ERK or p38 MAPK may lead to the suppression of melanogenesis in eupafolin-treated B16F10 mouse melanoma cells.

Sociodemographic and Psychological Correlates of Sun Protection Behaviors among Outdoor Workers: A Review

Outdoor workers are at a higher risk for developing skin cancer due to their increased sun exposure. The primary objective of this review was to synthesize the current research literature that addresses sociodemographic and psychological factors related to sun protection behaviors in outdoor workers. Two additional purposes were to provide an overview of sun exposure and describe sun protection behaviors of outdoor workers. To identify the studies for this review, a methodical search was performed in the PubMed, PsycInfo, MEDLINE, and ERIC databases. Fifteen studies met the review criteria. Despite regular and prolonged sun exposure, many outdoor workers fail to engage in sufficient sun protection behaviors. Correlates of outdoor workers' sun protection behaviors include being female, older age, being white, personal skin cancer history, time (hours/years) spent at work, sun safety training, perceived prioritization of sun protection, concern about sun exposure, workplace support, families' expectations, and familial information giving. However, limited attention is given to designing theoretically grounded studies to identify factors to inform future research. There is a need to conduct research based on solid theoretical foundations that explains the relationships among the factors in this domain.

Essential role of the molecular chaperone gp96 in regulating melanogenesis

Through a process known as melanogenesis, melanocyte produces melanin in specialized organelles termed melanosomes, which regulates pigmentation of the skin, eyes, and hair. Gp96 is a constitutively expressed heat shock protein in the endoplasmic reticulum whose expression is further upregulated upon ultraviolet irradiation. However, the roles and mechanisms of this chaperone in pigmentation biology are unknown. In this study, we found that knockdown of gp96 by RNA interference significantly perturbed melanin synthesis and blocked late melanosome maturation. Gp96 knockdown did not impair the expression of tyrosinase, an essential enzyme in melanin synthesis, but compromised its catalytic activity and melanosome translocation. Further, mice with melanocyte-specific deletion of gp96 displayed decreased pigmentation. A mechanistic study revealed that the defect in melanogenesis can be rescued by activation of the canonical Wnt pathway, consistent with the critical roles of gp96 in chaperoning Wnt-coreceptor LRP6. Thus, this work uncovered the essential role of gp96 in regulating melanogenesis.

Tissue-engineered skin substitutes: an overview

Extensive skin loss and chronic wounds are still a significant challenge to clinicians: even if injured epidermis is normally able to self-renew, deep injuries can cause negative regulation of the wound healing cascade, leading to chronic wound formation. Skin-autografting surgical procedures are often limited by the poor availability of healthy tissue, whereas the use of non-self-tissues for allografts presents some severe risks. Tissue-engineered skin substitutes have recently become viable as a suitable alternative to auto- and allografts. However, biologists, biochemists, and technical engineers are still struggling to produce complex skin substitutes that can readily be transplanted in large quantities. The ambitious goal is now to construct a dermoepidermal substitute that rapidly vascularizes and optimally supports a stratifying epidermal graft on a biodegradable matrix. This review analyzes these aspects in light of the available literature and the authors' experience.

Effect of serum folate status on total folate and 5-methyltetrahydrofolate in human skin

BACKGROUND

It has been suggested that human skin color adapts to balance the need for vitamin D synthesis in comparison with the protection of DNA and folate from photodegradation. However, the folate content of human skin is unknown and may affect the effectiveness of the antifolate methotrexate for the treatment of psoriasis.

OBJECTIVES

We examined whether total folate and 5-methyl-(6S)-tetrahydrofolate (5-MTHF) in human skin can be predicted by serum concentrations and whether there are differences in the proportion of 5-MTHF in dermis compared with epidermis.

DESIGN

Total folate (by using a microbiological assay) and 5-MTHF (by using high-pressure liquid chromatography) were measured in fasting serum and fresh skin obtained at surgery by using a recovery validated extraction method.

RESULTS

Total folate in human epidermis was shown to be low compared with in many other tissues, and dermal folate was an order-of-magnitude even lower. These concentrations were directly and linearly linked to serum folate status. Although the percentage of 5-MTHF of the total in the dermis was similar to that in other organs, it was especially high in the epidermis and increased to >65% as serum folate decreased.

CONCLUSIONS

The high proportion of 5-MTHF in the epidermis, which is further emphasized in subjects with a lower (10-20-nmol/L) serum folate status, points to a special role for this form of folate in skin, perhaps as a protectant from ultraviolet-induced photosensitization reactions. 5-MTHF may also maintain methylation reactions that influence the proliferative activity. These results may help to individualize the treatment of psoriasis patients with methotrexate and folate.

Anti-melanogenic effect of (Z)-5-(2,4-dihydroxybenzylidene) thiazolidine-2,4-dione, a novel tyrosinase inhibitor

We synthesized (Z)-5-(2,4-dihydroxybenzylidene)thiazolidine-2,4-dione (MHY498) as a potential tyrosinase inhibitor. MHY498 potently inhibited mushroom tyrosinase activity (mean IC50 = 3.55 μM) in a dose-dependent manner. MHY498 was more potent than the well-known tyrosinase inhibitor, kojic acid (mean IC50 = 22.79 μM). When tested in B16F10 melanoma cells treated with α-melanocyte stimulating hormone (α-MSH), MHY498 inhibited murine tyrosinase activity and decreased melanin production without inducing cytotoxicity. Docking models showed that the binding affinity of MHY498 to tyrosinase was higher than that of kojic acid, and docking simulation results indicated that the tyrosinase binding moieties of MHY498 and kojic acid were similar. Western blotting showed that tyrosinase inhibition by MHY498 partly resulted from the expressional modulations of tyrosinase and its transcription factor, microphthalmia-associated transcription factor, via the cAMP-PKA-CREB pathway. These findings suggest that MHY498 could be useful as an antimelanogenic agent for the prevention and treatment of diseases associated with skin pigmentation.

Geranylgeranylacetone inhibits melanin synthesis via ERK activation in Mel-Ab cells

AIMS

Geranylgeranylacetone (GGA) has shown cytoprotective activity through induction of a 70-kDa heat shock protein (HSP70). Although HSP70 is reported to regulate melanogenesis, the effects of GGA on melanin synthesis in melanocytes have not been previously studied. Therefore, this study investigated the effects of GGA on melanogenesis and the related signaling pathways.

MAIN METHODS

Melanin content and tyrosinase activities were measured in Mel-Ab cells. GGA-induced signal transduction pathways were investigated by western blot analysis.

KEY FINDINGS

Our results showed that GGA significantly decreased melanin content in a concentration-dependent manner. Similarly, GGA reduced tyrosinase activity dose-dependently, but it did not directly inhibit tyrosinase. Western blot analysis indicated that GGA downregulated microphthalmia-associated transcription factor (MITF) and tyrosinase protein expression, whereas it increased the phosphorylation of extracellular signal-regulated kinase (ERK) and mammalian target of rapamycin (mTOR). Furthermore, a specific ERK pathway inhibitor, PD98059, blocked GGA-induced melanin reduction and then prevented downregulation of MITF and tyrosinase by GGA. However, a specific mTOR inhibitor, rapamycin, only slightly restored inhibition of melanin production by GGA, indicating that mTOR signaling is not a key mechanism regulating the inhibition of melanin production.

SIGNIFICANCE

These findings suggest that activation of ERK by GGA reduces melanin synthesis in Mel-Ab cells through downregulation of MITF and tyrosinase expression.

Photodermatoses in pigmented skin

Photodermatoses are a group of skin diseases primarily caused by, or exacerbated by exposure to ultraviolet and or visible radiation. The effect of sunlight on skin depends on a number of factors including skin colour, skin phototype and the content and type of melanin in the skin. There are only a few studies describing photodermatoses in populations with dark skin. A PubMed search was conducted to summarize currently available information on differences in biology of melanin in dark and light skin and photodermatoses in dark skin. Dark skin is characterised by higher content of melanin, higher eumelanin to pheomelanin ratio, lower tyrosinase activity, and more effective distribution of melanin for protection against ultraviolet light. Photodermatoses are common in dark skinned patients with some variation in the spectrum of photodermatoses. Polymorphous light eruption (PMLE) is the commonest, followed by chronic actinic dermatitis. Pin-point papular and lichenoid variants of PMLE and actinic lichen planus are more frequent in dark skin whereas actinic prurigo, solar urticaria and hydroa vacciniforme are uncommon. Photodermatoses are common in dark skinned patients despite better natural photoprotection. It is proposed that lichenoid photodermatoses may be added to the classification of photodermatoses in dark skin.

Photoaging of human retinal pigment epithelium is accompanied by oxidative modifications of its eumelanin

Although photodegradation of the retinal pigment epithelium (RPE) melanin may contribute to the etiology of age-related macular degeneration, the molecular mechanisms of this phenomenon and the structural changes of the modified melanin remain unknown. Recently, we found that the ratio of pyrrole-2,3,4,5-tetracarboxylic acid (PTeCA) to pyrrole-2,3,5-tricarboxylic acid (PTCA) is a marker for the heat-induced cross-linking of eumelanin. In this study, we examined UVA-induced changes in synthetic eumelanins to confirm the usefulness of the PTeCA/PTCA ratio as an indicator of photo-oxidation and compared changes in various melanin markers and their ratios in human melanocytes exposed to UVA, in isolated bovine RPE melanosomes exposed to strong blue light and in human RPE cells from donors of various ages. The results indicate that the PTeCA/PTCA ratio is a sensitive marker for the oxidation of eumelanin exposed to UVA or blue light and that eumelanin and pheomelanin in human RPE cells undergo extensive structural modifications due to the life-long exposure to blue light.

Computational model for pathway reconstruction to unravel the evolutionary significance of melanin synthesis

Melanogenesis is a complex multistep process of high molecular weight melanins production by hydroxylation and polymerization of polyphenols. Melanins have a wide range of applications other than being a sun - protection pigment. Melanogenesis pathway exists from prokaryotes to eukaryotes. It has evolved over years owing to the fact that the melanin pigment has different roles in diverse taxa of organisms. Melanin plays a pivotal role in the existence of certain bacteria and fungi whereas in higher organisms it is a measure of protection against the harmful radiation. We have done a detailed study on various pathways known for melanin synthesis across species. It was divulged that melanin production is not restricted to tyrosine but there are other secondary metabolites that synthesize melanin in lower organisms. Furthermore the phylogenetic study of these paths was done to understand their molecular and cellular development. It has revealed that the melanin synthesis paths have co-evolved in several groups of organisms. In this study, we also introduce a method for the comparative analysis of a metabolic pathway to study its evolution based on similarity between enzymatic reactions.

Depigmentation effect of kadsuralignan F on melan-a murine melanocytes and human skin equivalents

The development of melanogenic inhibitors is important for the prevention of hyperpigmentation, and, recently, consideration has been given to natural materials or traditionally used ingredients such as Chinese medicine. The aim of this study is the evaluation of a new anti-melanogenic candidate, kadsuralignan F, from the natural plant Kadsura coccinea, as well as the determination of mechanisms of melanogenesis inhibition at a molecular level. Kadsuralignan F significantly reduced melanin synthesis in a dose-dependent manner in a murine melanocyte cell line and human skin equivalents. There was no direct inhibition on mushroom tyrosinase or cell-extract tyrosinase activity, and mRNA expression of tyrosinase and other melanogenic genes such as tyrosinase-related protein-1 (trp-1) or trp-2 were not affected by kadsuralignan F. Interestingly, the protein level of tyrosinase was dramatically downregulated with kadsuralignan F treatment. We found that a decrease of tyrosinase protein by kadsuralignan F was fully recovered by MG132, a proteasome inhibitor, but not by chloroquine, a lysosome inhibitor. In this study, we found that kadsuralignan F, a lignan from an extract of Kadsura coccinea, has an inhibitory activity on melanin synthesis through tyrosinase degradation. These findings suggest that kadsuralignan F can be used as an active ingredient for hyperpigmentation treatment.

Identification of miR-145 as a key regulator of the pigmentary process

The current treatments for hyperpigmentation are often associated with a lack of efficacy and adverse side effects. We hypothesized that microRNA (miRNA)-based treatments may offer an attractive alternative by specifically targeting key genes in melanogenesis. The aim of this study was to identify miRNAs interfering with the pigmentary process and to assess their functional role. miRNA profiling was performed on mouse melanocytes after three consecutive treatments involving forskolin and solar-simulated UV (ssUV) irradiation. Sixteen miRNAs were identified as differentially expressed in treated melan-a cells versus untreated cells. Remarkably, a 15-fold downregulation of miR-145 was detected. Overexpression or downregulation of miR-145 in melan-a cells revealed reduced or increased expression of Sox9, Mitf, Tyr, Trp1, Myo5a, Rab27a, and Fscn1, respectively. Moreover, a luciferase reporter assay demonstrated direct targeting of Myo5a by miR-145 in mouse and human melanocytes. Immunofluorescence tagging of melanosomes in miR-145-transfected human melanocytes displayed perinuclear accumulation of melanosomes with additional hypopigmentation of harvested cell pellets. In conclusion, this study has established an miRNA signature associated with forskolin and ssUV treatment. The significant down- or upregulation of major pigmentation genes, after modulating miR-145 expression, suggests a key role for miR-145 in regulating melanogenesis.

Evaluation of melanogenesis in A-375 melanoma cells treated with 5,7-dimethoxycoumarin and valproic acid

Malignant melanoma (melanoma malignum) is one of the most dangerous types of tumor. It is very difficult to cure. In recent years, a lot of attention has been given to chemoprevention. This method uses natural and synthetic compounds to interfere with and inhibit the process of carcinogenesis. In this study, a new treatment strategy was proposed consisting of a combination of 5,7-dimethoxycoumarin (DMC), an activator of melanogenesis, and valproic acid (VPA), a well-known drug that is one of the histone deacetylase inhibitors (HDACis). In conjunction with 1 mM VPA, all of the tested concentrations of DMC (10-150 μM) significantly decreased the proliferation of A-375 cells. VPA and DMC also induced the synthesis of melanin and the formation of dendrite and star-shaped cells. Tyrosinase gene expression and tyrosinase activity significantly increased in response to VPA treatment. Pyrolysis with gas chromatography and mass spectrometry (Py-GC/MS) was used to investigate the structure of the isolated melanin. This showed that the quantitative and qualitative components of melanin degradation products are dependent on the type of applied melanogenesis inductor. Products derived from eumelanin were detected in the pyrolytic profile of melanin isolated from A-375 cells stimulated with DMC. Thermal degradation of melanin isolated from melanoma cells after exposure to VPA or a mixture of VPA and DMC revealed the additional presence of products derived from pheomelanin.

Effects of solar radiation on the skin

No one would underestimate the importance of sunlight to the evolution of life on the earth and its role in human development. However, all humans - especially individuals who are lightly pigmented or whose occupation or lifestyle exposes them to excessive amounts of sunlight - are potentially susceptible to its deleterious effects. These effects can range from acute biological responses, such as sunburn and skin tanning, to conditions resulting from chronic exposure such as photoaged skin and potentially life-threatening conditions such as skin cancer. The objective of this review is to present a concise and up-to-date perspective on the effects of UVB, UVA, visible, and infrared radiation on cutaneous biochemistry and physiology.

Melanogenesis Inhibitor(s) from Phyla nodiflora Extract

Overexpression of tyrosinase can cause excessive production of melanin and lead to hyperpigmentation disorders, including melasma and freckles. Recently, agents obtained from plants are being used as alternative medicines to downregulate tyrosinase synthesis and decrease melanin production. Phyla nodiflora Greene (Verbenaceae) is used as a folk medicine in Taiwanese for treating and preventing inflammatory diseases such as hepatitis and dermatitis. However, the antimelanogenesis activity and molecular biological mechanism underlying the activity of the methanolic extract of P. nodiflora (PNM) have not been investigated to date. Our results showed that PNM treatment was not cytotoxic and significantly reduced the cellular melanin content and tyrosinase activity in a dose-dependent manner (P < 0.05). Further, PNM exhibited a significant antimelanogenesis effect (P < 0.05) by reducing the levels of phospho-cAMP response element-binding protein and microphthalmia-associated transcription factor (MITF), inhibiting the synthesis of tyrosinase, tyrosinase-related protein-1 (TRP-1), and TRP-2, and decreasing the cellular melanin content. Moreover, PNM significantly activated the phosphorylation of mitogen-activated protein kinases, including phospho-extracellular signal-regulated kinase, c-Jun N-terminal kinase, and phospho-p38, and inhibited the synthesis of MITF, thus decreasing melanogenesis. These properties suggest that PNM could be used as a clinical and cosmetic skin-whitening agent to cure and/or prevent hyperpigmentation.

UVA-induced oxidative degradation of melanins: fission of indole moiety in eumelanin and conversion to benzothiazole moiety in pheomelanin

Eumelanin is photoprotective while pheomelanin is phototoxic to pigmented tissues. Ultraviolet A (UVA)-induced tanning seems to result from the photooxidation of pre-existing melanin and contributes no photoprotection. However, data available for melanin biodegradation remain limited. In this study, we first examined photodegradation of eumelanin and pheomelanin in human black hairs and found that the ratio of Free (formed by peroxidation in situ) to Total (after hydrogen peroxide oxidation) pyrrole-2,3,5-tricarboxylic acid (PTCA) increases with hair aging, indicating fission of the dihydroxyindole moiety. In red hair, the ratio of thiazole-2,4,5-tricarboxylic acid (TTCA) to 4-amino-3-hydroxyphenylalanine (4-AHP) increases with aging, indicating the conversion from benzothiazine to benzothiazole moiety. These photodegradation of melanins were confirmed by UVA (not UVB) irradiation of melanins from mice and human hairs and synthetic eumelanin and pheomelanin. These results show that both eumelanin and pheomelanin degrade by UVA and that Free/Total PTCA and TTCA/4-AHP ratios serve as sensitive indicators of photodegradation.

Human pigmentation genes under environmental selection

Genome-wide association studies and comparative genomics have established major loci and specific polymorphisms affecting human skin, hair and eye color. Environmental changes have had an impact on selected pigmentation genes as populations have expanded into different regions of the globe.

The infant skin barrier: can we preserve, protect, and enhance the barrier?

Infant skin is different from adult in structure, function, and composition. Despite these differences, the skin barrier is competent at birth in healthy, full-term neonates. The primary focus of this paper is on the developing skin barrier in healthy, full-term neonates and infants. Additionally, a brief discussion of the properties of the skin barrier in premature neonates and infants with abnormal skin conditions (i.e., atopic dermatitis and eczema) is included. As infant skin continues to mature through the first years of life, it is important that skin care products (e.g., cleansers and emollients) are formulated appropriately. Ideally, products that are used on infants should not interfere with skin surface pH or perturb the skin barrier. For cleansers, this can be achieved by choosing the right type of surfactant, by blending surfactants, or by blending hydrophobically-modified polymers (HMPs) with surfactants to increase product mildness. Similarly, choosing the right type of oil for emollients is important. Unlike some vegetable oils, mineral oil is more stable and is not subject to oxidation and hydrolysis. Although emollients can improve the skin barrier, more studies are needed to determine the potential long-term benefits of using emollients on healthy, full-term neonates and infants.

Involvement of the p38 MAPK and ERK signaling pathway in the anti-melanogenic effect of methyl 3,5-dicaffeoyl quinate in B16F10 mouse melanoma cells

Methyl 3,5-dicaffeoyl quinate (MDQ), an active compound present in Kalopanax pictus, Salicornia herbacea L., Aster oharai and Solidago virga-aurea var. gigantean, is a dicaffeoylquinic acid derivative esterified by methanol. Recent studies have revealed that MDQ possesses multiple pharmacological activities, such as antitumor, antioxidative and cytoprotective activities. To date, there has been no attempt to test the action of MDQ in melanocytes. In this study, we investigated the effect of MDQ on melanogenesis in B16F10 mouse melanoma cells. MDQ inhibited melanin production and tyrosinase activity in B16F10 mouse melanoma cells without a direct inhibitory effect on mushroom tyrosinase activity. Furthermore, we also found that MDQ decreased protein expression levels of microphthalmia-associated transcription factor (MITF) and tyrosinase in B16F10 melanin cells. Meanwhile, phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) was significantly reduced after 6h MDQ treatment, and this expression recovered at 48 h. The phosphorylation of extracellular signal-regulated kinase (ERK) was significantly enhanced at 12-48 h, whereas no effect was observed in the phosphorylation of Akt. In addition, MDQ treatment did not significantly alter the expression levels of total p38 MAPK, ERK, and Akt. Thus, it seems that inhibition of phospho-p38 MAPK and activation of phospho-ERK may lead to the suppression of melanogenesis in MDQ-treated B16F10 mouse melanoma cells.

Human skin pigmentation, migration and disease susceptibility

Human skin pigmentation evolved as a compromise between the conflicting physiological demands of protection against the deleterious effects of ultraviolet radiation (UVR) and photosynthesis of UVB-dependent vitamin D(3). Living under high UVR near the equator, ancestral Homo sapiens had skin rich in protective eumelanin. Dispersals outside of the tropics were associated with positive selection for depigmentation to maximize cutaneous biosynthesis of pre-vitamin D(3) under low and highly seasonal UVB conditions. In recent centuries, migrations and high-speed transportation have brought many people into UVR regimes different from those experienced by their ancestors and, accordingly, exposed them to new disease risks. These have been increased by urbanization and changes in diet and lifestyle. Three examples-nutritional rickets, multiple sclerosis (MS) and cutaneous malignant melanoma (CMM)-are chosen to illustrate the serious health effects of mismatches between skin pigmentation and UVR. The aetiology of MS in particular provides insight into complex and contingent interactions of genetic and environmental factors necessary to trigger lethal disease states. Low UVB levels and vitamin D deficiencies produced by changes in location and lifestyle pose some of the most serious disease risks of the twenty-first century.

Skin tissue engineering--in vivo and in vitro applications

Significant progress has been made over the years in the development of in vitro-engineered substitutes that mimic human skin, either to be used as grafts for the replacement of lost skin or for the establishment of human-based in vitro skin models. This review summarizes these advances in in vivo and in vitro applications of tissue-engineered skin. We further highlight novel efforts in the design of complex disease-in-a-dish models for studies ranging from disease etiology to drug development and screening.

The prevalence of actinic cheilitis in farmers in a semi-arid northeastern region of Brazil

BACKGROUND

Actinic cheilitis (AC) is a potentially malignant disorder of the lip caused by chronic exposure to solar radiation. Despite being a relatively common lesion in tropical countries, the data related to AC prevalence in Brazil are sparse, particularly in regions with high levels of ultraviolet radiation.

OBJECTIVE

To estimate AC prevalence among farmers in a semiarid northeastern Brazil.

METHODS

Cross-sectional study was carried out involving a representative sample (n = 240) of the farm workers. Sociodemographic, clinical, and histopathological variables were analyzed.

RESULTS

AC prevalence was 16.7% [95% confidence interval (CI): 12.0% to 21.4%]. The disease was more prevalent in males [prevalence ratio (PR) = 2.72; 95% CI: 1.52-4.90], fair-skinned farmers (PR = 2.07; 95% CI: 1.00-4.30), age over 50 years (PR = 2.91; 95% CI: 1.40-6.04), daily exposure time more than eight hours (PR = 1.84; 95% CI: 1.03-3.27), and among smokers/ex-smokers (PR = 2.17; 95% CI: 1.22-3.87). Mantel-Haenszel test showed a positive relationship between cumulative exposure time and development of AC (P < 0.001). Two cases were diagnosed as microinvasive squamous cell carcinoma.

CONCLUSIONS

Our results suggest that farmers in this semiarid area have a high risk of lip cancer and indicate the need for health public programs in the early detection of AC and education to teach the population about precautions to be taken during sun exposure.

The skin ivory spot. A possible indicator for skinfield photo-carcinogenesis in recreational sunbed addicts

Introduction: For a decade or so, artificial sources of restricted light wavelengths, particularly sunbeds, have progressively gained popularity among adolescents and young adults. Warnings were raised focusing on the risk of accelerated photoaging and photocarcinogenesis. The ULEV (ultraviolet light-enhanced visualization) method is a convenient noninvasive way identifying subtle pigmentary changes presenting as a mottled subclinical melanoderma (MSM). Of note, rare spotty amelanotic macules presenting as skin ivory spots (SIS) was reported on any part of the body. Subjects and method: This work is the first attempt at evaluating the changes in the MSM and SIS spots developed on the skin of 33 phototype III young women designated as avid users involved in frequent exposures to sunshine and sunbeds for lifestyle purposes for a duration of at least 120 months. Results: MSM was markedly heterogeneous and was distinctly obvious in the majority of adepts of frequent natural and artificial photoexposures. SIS was particularly developed in subjects presenting with severe MSM patterns. Discussion: MSM and SIS are more severe in subjects frequently exposed to sunbeds and sun exposures. These signs possibly represent a risk marker for field photocarcinogenesis.

Characterization of a novel tyrosinase inhibitor, (2RS,4R)-2-(2,4-dihydroxyphenyl)thiazolidine-4-carboxylic acid (MHY384)

BACKGROUND

We synthesized (2RS,4R)-2-(2,4-dihydroxyphenyl)thiazolidine-4-carboxylic acid (MHY384) as a potential tyrosinase inhibitor and investigated its antityrosinase activity.

METHODS

The structure of MHY384 was established using (1)H and (13)C NMR spectroscopy and mass spectral analyses. To investigate dual mechanisms of action of MHY384 for the inhibition of melanin synthesis, we confirmed the inhibitory effect of tyrosinase catalytic activity of MHY384. Then, we confirmed the inhibitory effect of MHY384 on transcription of tyrosinase mRNA through alpha-MSH-induced cAMP-PKA-MITF signaling. In addition, we supported the inhibitory mechanism of MHY384 against tyrosinase using a kinetic study and docking programs.

RESULTS

To determine how MHY384 regulates melanogenesis, we measured melanin levels and expression of the genes for microphthalmia-associated transcription factor (MITF) and tyrosinase in α-melanocyte-stimulating hormone (α-MSH)-induced B16F10 melanoma cells. MHY384 potently inhibited tyrosinase activity and melanin production in B16F10 melanoma cells. Through docking models, we were able to construct the tertiary structure of mushroom tyrosinase and simulate its docking with MHY384. The result supports that MHY384 strongly interacts with tyrosinase residues in the active site and it can directly inhibit tyrosinase. To investigate additional mechanisms of action of MHY384, we confirmed that the inhibition of tyrosinase activity was found to be due to the modulation of the expression of tyrosinase and its transcription factor, MITF, through cAMP, which regulates protein kinase A.

CONCLUSIONS

This study strongly indicates that the depigmenting effect of MHY384 results from the down-regulation of MITF and tyrosinase through direct tyrosinase inhibition.

GENERAL SIGNIFICANCE

Our findings suggest that MHY384 can be an effective skin-whitening agent.

Melanoma in adolescents and young adults (ages 15-39 years): United States, 1999-2006

BACKGROUND

Invasive melanoma of the skin is the third most common cancer diagnosed among adolescents and young adults (aged 15-39 years) in the United States. Understanding the burden of melanoma in this age group is important to identifying areas for etiologic research and in developing effective prevention approaches aimed at reducing melanoma risk.

METHODS

Melanoma incidence data reported from 38 National Program of Cancer Registries and/or Surveillance Epidemiology and End Results statewide cancer registries covering nearly 67.2% of the US population were used to estimate age-adjusted incidence rates for persons 15-39 years of age. Incidence rate ratios were calculated to compare rates between demographic groups.

RESULTS

Melanoma incidence was higher among females (age-adjusted incidence rates = 9.74; 95% confidence interval 9.62-9.86) compared with males (age-adjusted incidence rates = 5.77; 95% confidence interval 5.68-5.86), increased with age, and was higher in non-Hispanic white compared with Hispanic white and black, American Indians/Alaskan Natives, and Asian and Pacific Islanders populations. Melanoma incidence rates increased with year of diagnosis in females but not males. The majority of melanomas were diagnosed on the trunk in all racial and ethnic groups among males but only in non-Hispanic whites among females. Most melanomas were diagnosed at localized stage, and among those melanomas with known histology, the majority were superficial spreading.

LIMITATIONS

Accuracy of melanoma cases reporting was limited because of some incompleteness (delayed reporting) or nonspecific reporting including large proportion of unspecified histology.

CONCLUSIONS

Differences in incidence rates by anatomic site, histology, and stage among adolescents and young adults by race, ethnicity, and sex suggest that both host characteristics and behaviors influence risk. These data suggest areas for etiologic research around gene-environment interactions and the need for targeted cancer control activities specific to adolescents and young adult populations.

UV-sensitive photoreceptor protein OPN5 in humans and mice

A variety of animal species utilize the ultraviolet (UV) component of sunlight as their environmental cues, whereas physiological roles of UV photoreception in mammals, especially in human beings, remain open questions. Here we report that mouse neuropsin (OPN5) encoded by the Opn5 gene exhibited an absorption maximum (λmax) at 380 nm when reconstituted with 11-cis-retinal. Upon UV-light illumination, OPN5 was converted to a blue-absorbing photoproduct (λmax 470 nm), which was stable in the dark and reverted to the UV-absorbing state by the subsequent orange light illumination, indicating its bistable nature. Human OPN5 also had an absorption maximum at 380 nm with spectral properties similar to mouse OPN5, revealing that OPN5 is the first and hitherto unknown human opsin with peak sensitivity in the UV region. OPN5 was capable of activating heterotrimeric G protein Gi in a UV-dependent manner. Immuno-blotting analyses of mouse tissue extracts identified the retina, the brain and, unexpectedly, the outer ears as the major sites of OPN5 expression. In the tissue sections of mice, OPN5 immuno-reactivities were detected in a subset of non-rod/non-cone retinal neurons as well as in the epidermal and muscle cells of the outer ears. Most of these OPN5-immuno-reactivities in mice were co-localized with positive signals for the alpha-subunit of Gi. These results demonstrate the first example of UV photoreceptor in human beings and strongly suggest that OPN5 triggers a UV-sensitive Gi-mediated signaling pathway in the mammalian tissues.

The specificity of UVA-induced DNA damage in human melanocytes

Exposure to solar UV radiation is the origin of most skin cancers, including deadly melanomas. Melanomas are quite different from keratinocyte-derived tumours and exhibit a different mutation spectrum in the activated oncogenes, possibly arising from a different class of DNA damage. In addition, some data suggest a role for UVA radiation in melanomagenesis. To get further insight into the molecular mechanisms underlying induction of melanoma, we quantified a series of UV-induced DNA damage in primary cultures of normal human melanocytes. The results were compared with those obtained in keratinocytes from the same donors. In the UVB range, the frequency and the distribution of pyrimidine dimers was the same in melanocytes and keratinocytes. UVA was also found to produce thymine cyclobutane dimer as the major DNA lesion with an equal efficiency in both cell types. In contrast, following UVA-irradiation a large difference was found for the yield of 8-oxo-7,8-dihydroguanine; the level of this product was 2.2-fold higher in melanocytes than in keratinocytes. The comet assay showed that the induction of strand breaks was equally efficient in both cell types but that the yield of Fpg-sensitive sites was larger in melanocytes. Our data show that, upon UVA irradiation, oxidative lesions contribute to a larger extent to DNA damage in melanocytes than in keratinocytes. We also observed that the basal level of oxidative lesions was higher in the melanocytes, in agreement with a higher oxidative stress that may be due to the production of melanin. The bulk of these results, combined with qPCR and cell survival data, may explain some of the differences in mutation spectrum and target genes between melanomas and carcinomas arising from keratinocytes.