Activity Of Melanocytes Research Articles

Effects of broadband ultraviolet B on non-canonical Wnt pathways in human epidermal melanocytes

Objective To investigate the effects of broadband ultraviolet B (BB-UVB) on the proliferation of, tyrosinase activity and melanogenesis in melanocytes. Methods Melanocytes isolated from human foreskin were subjected to primary culture. Some cultured primary melanocytes were irradiated with BB-UVB at 10, 20, 30, 40, 50, 100, 200 and 300 mJ/cm2. Then, CCK-8 assay was performed to evaluate the proliferative activity of melanocytes, dopa oxidation assay to estimate the activity of tyrosinase, and sodium hydroxide (NaOH) -lysis method was used to determine melanin content. Real-time fluorescence-based quantitative PCR was conducted to measure the mRNA expressions of genes involved in non-canonical Wnt pathways in melanocytes after irradiation with BB-UVB at 30, 50 and 100 mJ/cm2. Western blot was carried out to determine the expressions of proteins involved in non-canonical Wnt pathways in melanocytes before and after irradiation with BB-UVB of 100 mJ/cm2. The melanocytes receiving no treatment served as the control group. Statistical analysis was carried out by one-way analysis of variance followed by least significant difference (LSD) -t test for multiple group comparisons and by the independent sample t test for two-group comparisons. Results After irradiation with BB-UVB at 10-300 mJ/cm2, the proliferative activity of melanocytes was gradually reduced compared with the control group (all P< 0.05) , and the survival rate of melanocytes was less than 50% when the irradiation dose of BB-UVB was higher than 100 mJ/cm2. Furthermore, tyrosinase activity gradually increased in melanocytes after irradiation with BB-UVB at 10-100 mJ/cm2 compared with the control group, and the increase was statistically significant at the radiation dose of 100 mJ/cm2 (P< 0.05). Compared with the control group, the WIF-1 mRNA expression level decreased, while c-Jun N-terminal kinase (JNK) , microphthalmia-associated transcription factor (MITF) , Ras-related C3 botulinum toxin substrate1 (RAC1) and tyrosinase (TYR) mRNA expression levels increased in melanocytes after irradiation with BB-UVB at 30, 50 and 100 mJ/cm2 (all P< 0.05) ; the WNT5A mRNA expression significantly decreased in melanocytes irradiated with 30 and 50 mJ/cm2 BB-UVB, but increased in those irradiated with 100 mJ/cm2 BB-UVB (all P< 0.05). The radiation with 100 mJ/cm2 BB-UVB significantly decreased the expression of WIF-1 protein, but enhanced the expressions of WNT5A, JNK, MITF, RAC1 and TYR proteins in melanocytes compared with the control group (all P< 0.05) . Conclusions BB-UVB can decelerate the proliferation of, elevate tyrosinase activity and melanin level in, melanocytes. The WIF-1 gene may inhibit melanogenesis, and the decrease in its expression may promote melanogenesis by activating the JNK/MITF/TYR pathway through the combined effects of proteins involved in non-canonical Wnt pathways. Key words: Melanocytes; Ultraviolet rays; Wnt signaling pathway; Cell proliferation; Melanin synthesis

L-tyrosine induces melanocyte differentiation in novel pink-eyed dilution castaneus mouse mutant showing age-related pigmentation

BackgroundThe mouse pink-eyed dilution (oculocutaneous albinism II; p/Oca2p) locus is known to control tyrosinase activity, melanin content, and melanosome development in melanocytes. Pink-eyed dilution castaneus (pcas/Oca2p−cas) is a novel mutant allele on mouse chromosome 7 that arose spontaneously in Indonesian wild mice, Mus musculus castaneus. Mice homozygous for Oca2p−cas usually exhibit pink eyes and beige-colored coat on nonagouti C57BL/6 (B6) background. Recently, a novel spontaneous mutation occurred in the progeny between this mutant and B6 mice. The eyes of this novel mutant progressively become black from pink and the coat becomes dark gray from beige with aging. ObjectiveThe aim of this study is to clarify whatever differences exist in melanocyte proliferation and differentiation between the ordinary (pink-eyed) and novel (black-eyed) mutant using serum-free primary culture system. MethodsThe characteristics of melanocyte proliferation and differentiation were investigated by serum-free primary culture system using melanocyte-proliferation medium (MDMD). ResultsThe proliferation of melanoblasts in MDMD did not differ between the two mice. However, when the epidermal cell suspensions were cultured with MDMD supplemented with l-tyrosine (Tyr), the differentiation of black-eyed melanocytes was greatly induced in a concentration-dependent manner compared with pink-eyed melanocytes. Immunocytochemistry demonstrated that the expression of tyrosinase and tyrosinase-related protein-1 (Tyrp1) was greatly induced or stimulated both in pink-eyed and black-eyed melanocytes, whereas the expression of microphthalmia-associated transcription factor (Mitf) was stimulated only in black-eyed melanocytes. ConclusionThese results suggest that the age-related coat darkening in black-eyed mutant may be caused by the increased ability of melanocyte differentiation dependent on l-Tyr through the upregulation of tyrosinase, Tyrp1, and Mitf. This mutant mouse may be useful for animal model to clarify the mechanisms of age-related pigmentation in human skin, such as melasma and solar lentigines.

Pigmented lesions of the nail unit.

Longitudinal melanonychia originates from pigmented and/or melanocytic lesions of the nail unit. It may be a less-common entity encountered in dermatologic practice, but it is often a vexing one. Lesions occurring at this location present particular problems due to the unfamiliarity with clinical assessment, their relative inaccessibility, requiring more surgical finesse, and the lack of experience with histopathologic examination. Obtaining a specimen sufficient for interpretation is one of the main impediments to successful diagnosis in this setting. Most pigmented bands are benign, due to more common entities such as melanocytic activation, lentigo, and/or a nevus; however, deciding which ones are due to melanoma is of the utmost importance and can be difficult. Some examples of melanoma at this site are amelanotic, which are more challenging to recognize clinically, and usually lead to significant delays in diagnosis. In order to provide optimal patient care in this setting, it is very important that the physician has an understanding of the unique clinical, surgical, and pathologic issues relating to diagnosis of melanocytic neoplasms at this site, and there is communication between the clinician and the pathologist.

Free-Radical-Scavenging, Antityrosinase, and Cellular Melanogenesis Inhibitory Activities of Synthetic Isoflavones.

In this study, we examined the potential of synthetic isoflavones for application in cosmeceuticals. Twenty-five isoflavones were synthesized and their capacities of free-radical-scavenging and mushroom tyrosinase inhibition, as well as their impact on cell viability of B16F10 murine melanoma cells and HaCaT human keratinocytes were evaluated. Isoflavones that showed significant mushroom tyrosinase inhibitory activities were further studied on reduction of cellular melanin formation and antityrosinase activities in B16F10 melanocytes in vitro. Among the isoflavones tested, 6-hydroxydaidzein (2) was the strongest scavenger of both ABTS(.+) and DPPH(.) radicals with SC50 values of 11.3 ± 0.3 and 9.4 ± 0.1 μM, respectively. Texasin (20) exhibited the most potent inhibition of mushroom tyrosinase (IC50 14.9 ± 4.5 μM), whereas retusin (17) showed the most efficient inhibition both of cellular melanin formation and antityrosinase activity in B16F10 melanocytes, respectively. In summary, both retusin (17) and texasin (20) exhibited potent free-radical-scavenging capacities as well as efficient inhibition of cellular melanogenesis, suggesting that they are valuable hit compounds with potential for advanced cosmeceutical development.

Effects of diethylstilbestrol on the proliferation and tyrosinase activity of cultured human melanocytes.

The aim of the present study was to observe the effects of different exogenous estrogen diethylstilbestrol (DES) concentrations on the human melanocyte proliferation and tyrosinase activity. Skin specimens were obtained following blepharoplasty, and the melanocytes were primary cultured and passaged to the third generation. The melanocytes were seeded in 96-well plates, each well had 5×103 cells. The medium was changed after 24 h, and contained 10-4-10-8 M DES. After the melanocytes were incubated, the proliferation and tyrosinase activity were detected by the MTT assay and L-DOPA reaction. DES (10-8-10-6 M) enhanced the proliferation of cultured melanocytes. The intensity was positively correlated with the concentration of drug. DES, >10-5 M, inhibited the melanocytes proliferation or even produced the toxicity effect. Following the addition of 10-6 M DES to the medium, the tyrosinase activity of melanocytes was significantly increased, with P<0.05. In conclusion, a certain concentration of DES promoted the proliferation of melanocytes, enhanced the activity of tyrosinase and promoted pigment synthesis of melanocytes, with the optimal concentration of 10-6 M.

The Peripheral Clock Regulates Human Pigmentation

Although the regulation of pigmentation is well characterized, it remains unclear whether cell-autonomous controls regulate the cyclic on-off switching of pigmentation in the hair follicle (HF). As human HFs and epidermal melanocytes express clock genes and proteins, and given that core clock genes (PER1, BMAL1) modulate human HF cycling, we investigated whether peripheral clock activity influences human HF pigmentation. We found that silencing BMAL1 or PER1 in human HFs increased HF melanin content. Furthermore, tyrosinase expression and activity, as well as TYRP1 and TYRP2 mRNA levels, gp100 protein expression, melanocyte dendricity, and the number gp100+ HF melanocytes, were all significantly increased in BMAL1 and/or PER1-silenced HFs. BMAL1 or PER1 silencing also increased epidermal melanin content, gp100 protein expression, and tyrosinase activity in human skin. These effects reflect direct modulation of melanocytes, as BMAL1 and/or PER1 silencing in isolated melanocytes increased tyrosinase activity and TYRP1/2 expression. Mechanistically, BMAL1 knockdown reduces PER1 transcription, and PER1 silencing induces phosphorylation of the master regulator of melanogenesis, microphthalmia-associated transcription factor, thus stimulating human melanogenesis and melanocyte activity in situ and in vitro. Therefore, the molecular clock operates as a cell-autonomous modulator of human pigmentation and may be targeted for future therapeutic strategies.

When the Circadian Clock Meets the Melanin Pigmentary System

Silencing of BMAL1 and PER1 stimulates melanogenic activity of follicular and epidermal melanocytes, indicating a novel role for peripheral circadian clock processes in the regulation of melanin pigmentation. Linking the expression levels of BMAL1/PER1 with changes in melanogenesis opens exciting opportunities to study the role of the local molecular clock in modulation of melanocyte functions in the hair follicle and the epidermis with attendant effects on epidermal barrier functions in general.

Hesperetin induces melanin production in adult human epidermal melanocytes

One of the major sources of flavonoids for humans are citrus fruits, hesperidin being the predominant flavonoid. Hesperetin (HSP), the aglycon of hesperidin, has been reported to provide health benefits such as antioxidant, anti-inflammatory and anticarcinogenic effects. However, the effect of HSP on skin pigmentation is not clear. Some authors have found that HSP induces melanogenesis in murine B16-F10 melanoma cells, which, if extrapolated to in vivo conditions, might protect skin against photodamage. Since the effect of HSP on normal melanocytes could be different to that observed on melanoma cells, the described effect of HSP on murine melanoma cells has been compared to the effect obtained using normal human melanocytes. HSP concentrations of 25 and 50 µM induced melanin synthesis and tyrosinase activity in human melanocytes in a concentration-dependent manner. Compared to control melanocytes, 25 µM HSP increased melanin production and tyrosinase activity 1.4-fold (p < 0.01) and 1.1-fold (p < 0.01), respectively, and the corresponding increases in the case of 50 µM HSP were 1.9-fold (p < 0.001) and 1.3-fold (p < 0.001). Therefore, HSP could be considered a valuable photoprotective substance if its capacity to increase melanin production in human melanocyte cultures could be reproduced on human skin.

In vivo time-sequential histological study focused on melanocytes: suggestion of golden time for intervention to prevent post-laser pigmentary changes.

Post-inflammatory pigmentary changes after laser treatments are challenging adverse effect. To suggest an ideal time period with regard to intervention to prevent post-laser pigmentary changes, an in vivo time-sequential histological study focused on melanocytes was performed. The back skin of four volunteers was irradiated with Q-switched alexandrite laser (QSAL). In one subject (subject 4), topical corticosteroid was applied onto the irradiated skin from the time of irradiation to day 28. In all subjects, time-sequential skin biopsies were performed at baseline, an immediate time after irradiation, day 2, day 7, and day 28. Histological and immunohistochemical analyses were conducted. Q-switched alexandrite laser led to the successful removal of pigments and most melanocytes from the epidermis in all subjects. At day 28, there was increased epidermal pigmentation in the skin of the subjects 1-3. It was noted that numerous activated melanocytes appeared on day 7, continued to be observed until day 28. However, in the subject 4, the melanocyte activation and post-laser pigmentary changes were not observed. In regard to intervene melanocyte activation, at least 1 week after laser treatment is suggested as a 'golden' time period to prevent pigmentary changes.

A multimodal assessment of melanin and melanocyte activity in abnormally pigmented hypertrophic scar.

Using a validated swine model of human scar formation, hyperpigmented and hypopigmented scar samples were examined for their histological and optical properties to help elucidate the mechanisms and characteristics of dyspigmentation. Full-thickness wounds were created on the flanks of red Duroc pigs and allowed to heal. Biopsies from areas of hyperpigmentation, hypopigmentation, and uninjured tissue were fixed and embedded for histological examination using Azure B and primary antibodies to S100B, HMB45, and α-melanocyte-stimulating hormone (α-MSH). Spatial frequency domain imaging (SFDI) was then used to examine the optical properties of scars. Hyperpigmentation was first noticeable in healing wounds around weeks 2 to 3, gradually becoming darker. There was no significant difference in S100B staining for the presence of melanocytes between hyperpigmented and hypopigmented scar samples. Azure B staining of melanin was significantly greater in histological sections from hyperpigmented areas than in sections from both uninjured skin and hypopigmented scar (P < .0001). There was significantly greater staining for α-MSH in hyperpigmented samples compared with hypopigmented samples (P = .0121), and HMB45 staining was positive for melanocytes in hyperpigmented scar. SFDI at a wavelength of 632 nm resulted in an absorption coefficient map correlating with visibly hyperpigmented areas of scars. In a red Duroc model of hypertrophic scar formation, melanocyte number is similar in hyperpigmented and hypopigmented tissues. Hyperpigmented tissues, however, show a greater amount of melanin and α-MSH, along with immunohistochemical evidence of stimulated melanocytes. These observations encourage further investigation of melanocyte stimulation and the inflammatory environment within a wound that may influence melanocyte activity. Additionally, SFDI can be used to identify areas of melanin content in mature, pigmented scars, which may lead to its usefulness in wounds at earlier time points before markedly apparent pigmentation abnormalities.

A Case of Sporadic Dyschromatosis Universalis Hereditaria.

Dear Editor: Dyschromatosis universalis hereditaria (DUH) is a rare genodermatosis characterized by hypo- and hyper-pigmented macules with a reticulated pattern, giving an overall impression of mottling, over the trunk and limbs. It is generally an autosomal dominant disorder but recessive inheritance and patients without a family history of dyschromatosis have been reported, implying a sporadic origin1,2. The etiology of this disorder is unknown. It was recently suggested to be a disorder of melanosome synthesis rate or melanocyte activity and not a disorder of melanocyte number3. A 57-year-old man presented with generalized hypo- and hyper-pigmented macules in mottled pattern on the whole body (Fig. 1). The skin lesions developed on 100th day after his birth. He had moderate pruritus and dry skin with scaling. Potassium hydroxide preparation from the scale produced a negative result. The hair, nails, and oral mucosa as well as mental and developmental status were normal. He had no family history of similar lesions, but his son was diagnosed with X-linked ichthyosis at birth. The patient had a history of diabetes mellitus and hypertension. Systemic examination revealed no abnormalities. Routine blood test results were unremarkable. Skin biopsy specimens taken from both hypo- and hyper-pigmented lesions on his arms revealed markedly reduced and slightly increased melanin in the basal layer in hypoand hyper-pigmented lesions, respectively (Fig. 2). Therefore, we diagnosed the skin lesions as a sporadic form of dyschromatosis universalis. Fig. 1 Generalized reticulated hyper- and hypo-pigmented macules with scales on the whole body. Fig. 2 Skin biopsies were collected from hyper- and hypopigmented lesions on the upper arm (HE ×200). (A) Marked decreased basal pigmentation in a hypopigmented lesion. (B) Slightly increased melanin content in the basal layer of a hyperpigmented ... Dyschromatosis is variation of skin pigmentation, consisting of asymptomatic well-demarcated and irregular brown macules admixed with hypo-pigmented macules of varying size2. There are three major categories of dyschromatosis: DUH, dyschromatosis symmetrica hereditaria (also termed acropigmentation of Dohi), and unilateral dermatomal pigmentary dermatosis. Since its first description by Toyamo in Japan in 1929, subsequent cases of DUH have been reported in Europe, South America, and India. The phenotype seems to be heterogeneous. It is characterized by the presence of both hyper- and hypopigmented small irregular macules uniformly distributed all over the body. The trunk and extremities are the predominantly affected sites, while the face, palms, soles, and mucous membranes are less affected. The skin lesions usually develop in the first few months after birth and do not progress with age. Histopathologically, hyperpigmented lesions exhibit increased melanin content in the basal layer as well as melanin incontinence, while hypopigmented lesions exhibit relatively decreased melanin deposition in the basal layer2. On electron microscopy, hyperchromic macules contain numerous fully melanized melanosomes forming melanosome complexes, but melanosomes are absent from both keratinocytes and melanocytes in achromic macules3. The pathogenesis of DUH remains unknown. However, the DUH locus was recently mapped to chromosome 6q24.2-q25.2 and 12q21-q23, and the ABCB6 gene was identified as the pathogenic gene4. Most cases of DUH have been reported in Japan while only a few have been reported in Korea5. Furthermore, the sporadic form has rarely been reported in the Korean literature. In summary, we report a rare case of the sporadic form of dyschromatosis universalis in a middle-aged man who had no family history.

Different Advanced Therapeutic Approaches to Treat Vitiligo.

Vitiligo is a hypopigmentation disorder that is caused by the loss of melanocyte activity for melanin pigment generation. Vitiligo is distinguished by the existence of white macules. Vitiligo affects 0.1%-2% of individuals of different populations, irrespective of skin color, ethnic origin, race, or age. Although the actual mechanism behind this disease is not yet known, it is thought to be caused by a cumulative effect of various mechanisms (e.g., neurohormonal, genetic, cytotoxic, oxidative stress, autoimmune, and biochemical). This article reviews the published literature on various treatment modalities that might be effective in successfully treating patients with vitiligo, including phototherapies or some photochemotherapies, vitamin D analogs, topical and systemic corticosteroids, zinc treatment, anti-tumor necrosis factor agents, calcineurin inhibitors (tacrolimus, pimecrolimus), and surgical methods. This critical review also discusses a few herbal medications that may be worthy of future investigation because they have no significant side effects.

Antioxidant, cell-protective, and anti-melanogenic activities of leaf extracts from wild bitter melon (Momordica charantia Linn. var. abbreviata Ser.) cultivars.

BackgroundSeveral wild bitter melon (WBM; Momordica charantia Linn. var. abbreviata Ser.) cultivars were developed in Taiwan. However, little information is available regarding biological function of WBM leaf. Therefore, the objectives of this study were to investigate the nutrient content, antioxidant, cell protection and anti-melanogenic properties of wild bitter melon leaf.ResultsMethanolic leaf extracts were prepared from a variety and two cultivars of WBM. All extracts exerted potent nitric oxide and hydroxyl radical scavenging capacities. Furthermore, all extracts effectively reduce the production of reactive oxygen species and prevent cell death in UVB-irradiated HaCaT keratinocytes. The cell protective effect of leaf extract was also investigated by the prevention of HaCaT cells from sodium nitroprusside or menadione-induced toxicity, and significant cyto-protective activities were observed for all of them. Additionally, all extracts significantly suppressed tyrosinase activity and melanin levels in B16-F10 melanocytes.ConclusionsWBM leaf extract showed significant antioxidant, cyto-protective and anti-melanogenic activities. These findings suggested that WBM leaves may be beneficial for preventing the photo-oxidative damage and melanogenesis of skin.Electronic supplementary materialThe online version of this article (doi:10.1186/s40529-014-0078-y) contains supplementary material, which is available to authorized users.

Effect of norfloxacin and moxifloxacin on melanin synthesis and antioxidant enzymes activity in normal human melanocytes.

Fluoroquinolone antibiotics provide broad-spectrum coverage for a number of infectious diseases, including respiratory as well as urinary tract infections. One of the important adverse effects of these drugs is phototoxicity which introduces a serious limitation to their use. To gain insight the molecular mechanisms underlying the fluoroquinolones-induced phototoxic side effects, the impact of two fluoroquinolone derivatives with different phototoxic potential, norfloxacin and moxifloxacin, on melanogenesis and antioxidant enzymes activity in normal human melanocytes HEMa-LP was determined. Both drugs induced concentration-dependent loss in melanocytes viability. The value of EC50 for these drugs was found to be 0.5 mM. Norfloxacin and moxifloxacin suppressed melanin biosynthesis; antibiotics were shown to inhibit cellular tyrosinase activity and to reduce melanin content in melanocytes. When comparing the both analyzed fluoroquinolones, it was observed that norfloxacin possesses greater inhibitory effect on tyrosinase activity in melanocytes than moxifloxacin. The extent of oxidative stress in cells was assessed by measuring the activity of antioxidant enzymes: SOD, CAT, and GPx. It was observed that norfloxacin caused higher depletion of antioxidant status in melanocytes when compared with moxifloxacin. The obtained results give a new insight into the mechanisms of fluoroquinolones toxicity directed to pigmented tissues. Moreover, the presented differences in modulation of biochemical processes in melanocytes may be an explanation for various phototoxic activities of the analyzed fluoroquinolone derivatives in vivo.

Biocompatibility of carboxymethyl chitosan membranes with human skin melanocytes

Objective To study the biocompatibility of carboxymethyl chitosan (CMCS) membrane with melanocytes from healthy human skin,and to investigate the feasibility to transport and carry melanocytes by using CMCS membrane.Methods CMCS membrane was prepared by a casting method combined with a glutaraldehydebased cross-linking method.Melanocytes were isolated from the foreskin of healthy men,and subjected to primary culture and subculture.The third-passage melanocytes were classified into two groups to be cultured on the CMCS membrane (test group) or traditional culture plates (control group).Methyl thiazolyl tetrazolium (MTT) assay was performed to evaluate the proliferative activity of melanocytes,and a sodium hydroxide-based lysis method to determine melanin content.HMB45 staining was conducted,and tyrosinase activity was estimated for melanocytes.Results Inverted microscopy showed that melanocytes were evenly distributed on the CMCS membrane with a normal shape.The melanocytes adherent to the CMCS membrane stained positive for anti-HMB45 monoclonal antibody.The growth curve of the melanocytes on the CMCS membrane,which was obtained from MTT assay,demonstrated that CMCS membrane could support the normal growth of melanocytes.No significant difference was observed between the test group and control group in melanin content (0.083 ± 0.015 vs.0.066 ± 0.008,t =2.38,P ＞ 0.01) or tyrosinase activity (0.234 ± 0.083 vs.0.241 ± 0.061,t =0.23,P ＞ 0.05).Conclusion CMCS membrane can maintain the normal biological activity of melanocytes and have good biocompatibility with skin melanocytes. Key words: Melanocytes; Chitosan; Membranes, artificial; Biocompatible materials

Melanogenesis and antioxidant defense system in normal human melanocytes cultured in the presence of chlorpromazine

Chlorpromazine is used in the treatment of schizophrenia and psychotic disorders and belongs to phenothiazine class of neuroleptic drugs. It shows severe side effects such as extrapyramidal symptoms as well as ocular and skin disorders, but the mechanism is still not fully established. The aim of this study was to examine the effect of chlorpromazine on cell viability, melanogenesis and antioxidant defense system in normal human melanocytes. It has been demonstrated that chlorpromazine induces concentration-dependent loss in cell viability. The value of EC50 was calculated to be 2.53μM. Chlorpromazine in lower concentrations (0.0001, 0.001 and 0.01μM) increased the melanin and microphthalmia-associated transcription factor (MITF) content and tyrosinase activity, while changes of antioxidant enzymes activity were not observed. It suggests that long-term chlorpromazine therapy, even with low drug doses, may lead to hyperpigmentation disorders in skin and/or eye. The use of the analyzed drug in higher concentrations (0.1 and 1.0μM) caused significant alterations of antioxidant enzymes activity in normal melanocytes, what may explain a potential role of chlorpromazine in the depletion of cellular antioxidant status leading to other adverse effects associated with the high-dose and/or long-term therapy.

When all you have is a dermatoscope- start looking at the nails.

Pigmented and non-pigmented nail alterations are a frequent challenge for dermatologists. A profound knowledge of clinical and dermatoscopic features of nail disorders is crucial because a range of differential diagnoses and even potentially life-threatening diseases are possible underlying causes. Nail matrix melanocytes of unaffected individuals are in a dormant state, and, therefore, fingernails and toenails physiologically are non-pigmented. The formation of continuous, longitudinal pigmented streaks (longitudinal melanonychia) may either be caused by a benign activation of matrix melanocytes (e.g., as a result of trauma, inflammation, or adverse drug reactions) or by a true melanocytic proliferation (e.g., in a nevus or melanoma). In general, non-continuous nail alterations, affecting only limited parts of the nail apparatus, are most frequently of non-melanocytic origin. Important and common differential diagnoses in these cases are subungual hemorrhage or onychomycosis. In addition, foreign bodies, bacterial infections, traumatic injuries, or artificial discolorations of the nail unit may less frequently cause non-continuous nail alterations. Many systemic diseases that may also show involvement of the nails (e.g., psoriasis, atopic dermatitis, lichen planus, alopecia areata) tend to induce alterations in numerous if not all nails of the hands and feet. A similar extensive and generalized alteration of nails has been reported after treatment with a number of systemic drugs, especially antibiotics and cytostatics. Benign or malignant neoplasms that may also affect the nail unit include glomus tumor, Bowen’s disease, squamous cell carcinoma, and rare collision tumors. This review aims to assist clinicians in correctly evaluating and diagnosing nail disorders with the help of dermatoscopy.

Melatonin and its metabolites accumulate in the human epidermis in vivo and inhibit proliferation and tyrosinase activity in epidermal melanocytes in vitro

Melatonin and its metabolites including 6-hydroxymelatonin (6(OH)M), N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK) and 5-methoxytryptamine (5MT) are endogenously produced in human epidermis. This production depends on race, gender and age. The highest melatonin levels are in African-Americans. In each racial group they are highest in young African-Americans [30–50 years old (yo)], old Caucasians (60–90 yo) and Caucasian females. AFMK levels are the highest in African-Americans, while 6(OH)M and 5MT levels are similar in all groups. Testing of their phenotypic effects in normal human melanocytes show that melatonin and its metabolites (10−5 M) inhibit tyrosinase activity and cell growth, and inhibit DNA synthesis in a dose dependent manner with 10−9 M being the lowest effective concentration. In melanoma cells, they inhibited cell growth but had no effect on melanogenesis, except for 5MT which enhanced L-tyrosine induced melanogenesis. In conclusion, melatonin and its metabolites [6(OH)M, AFMK and 5MT] are produced endogenously in human epidermis and can affect melanocyte and melanoma behavior.

Melanocyte migration is influenced by E-cadherin-dependent adhesion of keratinocytes in both two- and three-dimensional in vitro wound models.

During wound healing, melanocytes are required to migrate into the wounded area that is still in the process of re-construction. The role and behaviour of melanocytes during this process is poorly understood, that is, whether melanocyte migration into the wound is keratinocyte-dependent or not. This paper attempts, through the use of both two- and three-dimensional in vitro models, to understand the role and behaviour of melanocytes during the process of wound healing. In addition, it sheds light on whether keratinocytes influence/contribute toward melanocyte migration and ultimately wound healing. Scratch assays were performed to analyse migration and Western blot analyses measured cellular E-cadherin expression. Immunohistochemistry was used to analyse the in vivo 3D wound healing effect. Scratch assays performed on co-cultures of melanocytes and keratinocytes demonstrated that melanocytes actively migrated, with the use of their dendrites, into the scratch ahead of the proliferating keratinocyte sheet. Migration of the melanocyte into the wound bed was accompanied by loss of attachment to keratinocytes at the wound front with concomitant downregulation of E-cadherin expression as observed through immunocytochemistry. This result suggests that, in vitro, melanocyte migration occurs independently of keratinocytes but that the migration is influenced by keratinocyte E-cadherin expression. We now demonstrate that melanocyte migration during re-pigmentation is an active process, and suggest that targeting of mechanisms involved in active melanocyte migration (e.g. the melanocyte dendrite) may enhance the re-pigmentation process.

Tranexamic acid suppresses ultraviolet B eye irradiation-induced melanocyte activation by decreasing the levels of prohormone convertase 2 and alpha-melanocyte-stimulating hormone.

Tranexamic acid (trans-4-aminomethylcyclohexanecarboxylic acid) is a medicinal amino acid used in skin whitening care. This study examined the effects of tranexamic acid on the melanocyte activation of the skin induced by an ultraviolet (UV) B eye irradiation. The eye or ear was locally exposed to UVB at a dose of 1.0 kJ/m(2) using a 20SE sunlamp after covering the remaining body surface with aluminum foil. UVB eye irradiation induced melanocyte activation of the skin, similar to that observed following UVB ear irradiation, which was suppressed by the administration of tranexamic acid treatment. The plasma α-melanocyte-stimulating hormone (α-MSH) content was increased by UVB irradiation of the eye; however, the increase in α-MSH was suppressed by tranexamic acid treatment. In addition, UVB eye irradiation induced the up-regulation of prohormone convertase (PC) 2 in the pituitary gland. Meanwhile, the increase in PC2 induced by UVB eye irradiation was suppressed by tranexamic acid treatment. These results clearly indicate that tranexamic acid decreases the expression of PC2, which cleavages from proopiomelanocortin to α-MSH in the pituitary gland, thereby suppressing melanocyte activation.