The dermal stem cell factor and c-kit are overexpressed in melasma

Astaxanthin and withaferin A block paracrine cytokine interactions between UVB-exposed human keratinocytes and human melanocytes via the attenuation of endothelin-1 secretion and its downstream intracellular signaling

BACKGROUND

Paracrine interactions between keratinocytes and melanocytes via cytokines play an essential role in regulating pigmentation in epidermal hyperpigmentary disorders. There is an urgent need for a human epidermal model in which melanogenic paracrine interactions between UVB-exposed keratinocytes and melanocytes can be precisely evaluated because human epidermal equivalents consisting of multilayered keratinocytes and melanocytes have significant limitations in this respect.

OBJECTIVE

To resolve this challenge, we established a co-culture system with cell inserts using human keratinocytes and human melanocytes that serves as an appropriate new model for UVB-induced hyperpigmentation. Using that new model, we examined the blocking effects of two natural chemicals, astaxanthin and withaferin A, on paracrine cytokine interactions between UVB-exposed keratinocytes and melanocytes and characterized their mechanisms of action.

METHODS AND RESULTS

RT-PCR analysis showed that co-culture of human keratinocytes that had been exposed to UVB significantly stimulated human melanocytes to increase their expression of genes encoding microphthalmia-associated transcription factor, tyrosinase and tyrosinase-related protein 1. The catalytic activity of tyrosinase was also increased. ELISA assays revealed that UVB significantly increased the secretion of interleukin-1α, interleukin-6/8, granulocyte macrophage stimulatory factor and endothelin-1 but not α-melanocyte stimulating hormone. The addition of an endothelin-1 neutralizing antibody significantly abrogated the increase of tyrosinase activity. Post-irradiation treatment with astaxanthin or withaferin A significantly abolished the up-regulation of tyrosinase activity induced by UVB. Treatment with astaxanthin or withaferin A significantly reduced the increased levels of interleukin-1α, interleukin-6/8, granulocyte macrophage stimulatory factor and endothelin-1. Withaferin A but not astaxanthin also significantly abrogated the endothelin-1-stimulated activity of tyrosinase in melanocytes. Western blot analysis of intracellular signaling factors revealed that withaferin A but not astaxanthin significantly abolished the endothelin-1-stimulated phosphorylation of Raf-1, MEK, ERK, MITF and CREB in human melanocytes.

CONCLUSIONS

These results demonstrate that this co-culture system is an appropriate model to characterize melanogenic paracrine interactions and that astaxanthin and withaferin A serve as potent inhibitors of those interactions. Their effects are caused not only by down-regulating the increased secretion of an intrinsic melanogenic cytokine, endothelin-1, by UVB-exposed human keratinocytes, but also by interrupting the endothelin-1-triggered downstream intracellular signaling between protein kinase C and Raf-1 in human melanocytes (only for withaferin A).

Retreatment using a dual mode of low-fluence Q-switched and long-pulse Nd:YAG laser in patients with melasma aggravation after previous therapy

BACKGROUND

Aggravated melasma after treatment is vulnerable to stimulation, can easily deteriorate, and may be distressing without proper management.

OBJECTIVE

To retrospectively assess the effectiveness and safety of combination therapy using low-fluence Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (QSNY) and long-pulse Nd:YAG laser (LPNY) (dual toning) in patients with rebound melasma.

MATERIALS AND METHODS

A total of 30 patients with aggravated melasma after previous therapy who were treated with dual toning were enrolled. A total of 10 sessions were conducted at 1-week intervals, followed by maintenance treatment. The results were evaluated using the modified Melasma Area and Severity Index (mMASI) and the physician's global assessment (PGA) before and 2 months after completing the 10 treatment sessions.

RESULTS

The baseline mMASI was 10.48 ± 3.64, which significantly decreased to 3.22 ± 1.45 2 months after completing the 10 treatment sessions (p < 0.001). Twenty-four patients (80%) had PGA grade 4 (76-100% improvement) and 6 patients (20%) had PGA grade 3 (51-75% improvement).

CONCLUSION

Dual toning may be a safe and effective salvage treatment for patients with aggravated melasma after previous treatment. LPNY may stabilize melasma activity to prevent rebound hyperpigmentation via dermal remodeling.

Inhibitors of intracellular signaling pathways that lead to stimulated epidermal pigmentation: perspective of anti-pigmenting agents

Few anti-pigmenting agents have been designed and developed according to their known hyperpigmentation mechanisms and corresponding intracellular signaling cascades. Most anti-pigmenting agents developed so far are mechanistically involved in the interruption of constitutional melanogenic mechanisms by which skin color is maintained at a normal and unstimulated level. Thus, owing to the difficulty of confining topical application to a specific hyperpigmented skin area, potent anti-pigmenting agents capable of attenuating the natural unstimulated pigmentation process have the risk of leading to hypopigmentation. Since intracellular signaling pathways within melanocytes do not function substantially in maintaining normal skin color and are activated only by environmental stimuli such as UV radiation, specifically down-regulating the activation of melanogenesis to the constitutive level would be an appropriate strategy to develop new potent anti-pigmenting agents with a low risk of hypopigmentation. In this article, we review the hyperpigmentation mechanisms and intracellular signaling pathways that lead to the stimulation of melanogenesis. We also discuss a screening and evaluation system to select candidates for new anti-melanogenic substances by focusing on inhibitors of endothelin-1 or stem cell factor-triggered intracellular signaling cascades. From this viewpoint, we show that extracts of the herbs Withania somnifera and Melia toosendan and the natural chemicals Withaferin A and Astaxanthin are new candidates for potent anti-pigmenting substances that avoid the risk of hypopigmentation.

Hypopigmented macules secondary to imatinib for the treatment of chronic myeloid leukemia: a histopathologic and immunohistochemical study

BACKGROUND

A few series addressing the cutaneous side effects related to imatinib in the skin have been published, but only one described scarce histopathologic information in seven patients.

OBJECTIVE

To characterize these lesions and compare the number of melanocytes between hypopigmented lesions and normal appearing skin.

METHODS

We retrieved clinical data of the patients and performed 24 skin biopsies (13 from hypopigmented skin and 11 from normal-appearing skin) within a cohort of 41 patients with chronic myeloid leukemia treated with imatinib. We classified the biopsies into three patterns.

RESULTS

About 45% of patients presented with periocular hypopigmentation. Perifollicular fibrosis was observed in hypopigmented skin biopsies (76.9%) and in normal-appearing skin (45.5%). Epidermal melanin, as determined with Masson-Fontana staining, and melanocyte number, as evaluated with MiTF, Melan A and c-kit immunostains, were lower in hypopigmented skin.

CONCLUSIONS

Histopathologic study of hypopigmented macules demonstrates the presence of melanin with a statistically significant decrease in the number of melanocytes. Therefore, these findings differ from vitiligo, as melanocytes are present. Three histopathological patterns may be found, namely (a) perifollicular fibrosis, (b) lichen planopilaris-like and (c) apparently normal skin. One of the most striking histopathologic finding consisted of the presence of perifollicular fibrosis in both hypopigmented lesions and apparently normal skin.

Treatment of melasma in Caucasian patients using a novel 694-nm Q-switched ruby fractional laser

Background

Melasma is a common hypermelanosis of the face. The use of a classical Q-switched ruby laser (QSRL) to treat melasma is discussed controversially and is associated with frequent adverse effects, such as hyper- or hypopigmentation. Recently a fractional-mode (FRx) QSRL was developed to minimize the adverse effects of classical QSRL. The objective of this research was to evaluate the efficacy and safety of a novel FRx-QSRL in the treatment of melasma in Caucasian patients.

Methods

We performed a retrospective study of 25 Caucasian melasma patients (Fitzpatrick skin types I to III). Patients received one to three FRx-QSRL treatments (Tattoostar FRx, Asclepion Laser Technologies, Jena, Germany) at pulse energies of 4 to 8 J/cm². Three blinded investigators independently evaluated the melasma area and severity index (MASI) score before treatment and at the four- to six-week follow-ups. At additional three-month follow-ups, patients evaluated subjective improvement, pain and over-all satisfaction with the treatment according to a numeric analogue score (NAS). Side effects were documented.

Results

At four to six weeks post laser treatment for a mean of 1.4 sessions, we observed a significant (P = 0.0001) reduction of the MASI score from 6.54 to 1.98 (72.3%). Patients rated the pain of the intervention at a mean 2.46 points (0 = no pain; 10 = maximum pain), the improvement at a mean 5.55 points (0 = no improvement; 10 = maximum improvement) and the overall satisfaction at a mean 4.66 points (0 = not satisfied; 10 = maximum satisfaction). After three months, post-inflammatory hyperpigmentation (PIH) and/or recurring melasma were observed in 7 (28%) and 11 (44%) patients, respectively.

Conclusion

The 694-nm FRx-QSRL is a safe and effective option for treating melasma in Caucasian patients. Over periods of >3 months, PIH and/or recurring melasma may develop at significant rates and may reduce patient satisfaction. Multiple treatment sessions with lower pulse energies and/or a post-interventional therapy with hypopigmenting ointments and UV protection may help to minimize these complications.

The dual toning technique for melasma treatment with the 1064 nm Nd: YAG laser: A preliminary study

BACKGROUND AND AIMS

Melasma is a treatment-resistant and acquired pigmentary facial skin condition of uncertain etiology particularly prevalent in the older Asian female. Traditional bleaching agents have offered some success. Intense pulsed light (IPL), fractionated nonablative and more recently ablative laser technology have also been used, but were associated with postoperative hyperpigmentation in the Asian skin. The present study examined the consecutive application of 2 modes of the 1064 nm Nd:YAG laser in the 'dual toning' process.

SUBJECTS AND METHODS

Thirty females, mean age 41.4 ± 11.96 yr, Fitzpatrick skin type IV, participated in the prospective uncontrolled study. All subjects were treated with the 1064 nm Nd:YAG laser, first with the 5 ns Q-switched mode, 1.2 J/cm(2), 8 mm collimated handpiece with multiple passes and then immediately after with the micropulsed mode, 300 µs, 7.0 J/cm(2), 5 mm handpiece, multiple passes. Mild and even erythema was the endpoint. Treatments were given every other week until maximum improvement was obtained. Improvement was rated at a final assessment 6 weeks after the final treatment on a 5 point scale where 1 was little or no improvement and 5 was maximum improvement.

RESULTS

At the final treatment session and at the 6-week assessment, 20 of the 30 patients (67%) saw a fair to excellent degree of improvement, 7 (23%) had visible improvement and little or no improvement was seen in 3 (10%) patients. There were no unexpected side effects in any patients.

CONCLUSIONS

The dual toning technique using the 1064 nm Nd:YAG laser was safe and effective, and well-tolerated by all patents without anesthesia. Larger controlled studies are merited with more objective measurement techniques to confirm the results of this preliminary study.

Melasma in men

Melasma is an acquired hypermelanosis that results in localized hyperpigmentation, commonly found on the face. This condition is much more common in women than men. There are some features of melasma in men that seem to differ from those seen in women. However, there is a paucity of data on this topic. The aim of this article is to review the etiology, clinical presentation, and treatment of melasma in men. It is important for dermatologists to understand some unique aspects of melasma in this group to provide appropriate care for patients who suffer from this frustrating condition.

Melasma: a comprehensive update: part I

Melasma is a common disorder of hyperpigmentation affecting millions of people worldwide. While it is thought to be triggered or exacerbated by sun exposure and hormones, much remains to be understood about its pathogenesis. A thorough understanding of the etiology of melasma and the research tools available to study this condition are crucial to enhancing management and developing novel targeted therapies of this often frustrating condition.

Defective barrier function in melasma skin

BACKGROUND

Melasma is characterized by increased pigmentation and photodamaged features, which include solar elastosis. Recently, we detected the downregulation of the genes most associated with lipid metabolism using microarray analysis in melasma. These findings suggested that lesional skin may have different biophysical characteristics, and, in particular, an altered skin barrier function.

OBJECTIVE

To determine the cutaneous biophysical characteristics of melasma.

METHODS

The melanin index, erythema index, stratum corneum hydration, sebum content and transepidermal water loss (TEWL) were measured for lesional and perilesional normal skin of 16 melasma patients and then compared. In addition, a skin biopsy was performed on 11 of the 16 study subjects to measure stratum corneum thickness and to study the protein expressions of PPAR-α and ALOX15B.

RESULTS

Melanin index, erythema index and stratum corneum hydration were significantly higher in lesional skin than in perilesional normal skin. No significant difference was found between lesional and normal skin in terms of basal TEWL level or sebum content. However, the rate of TEWL after barrier perturbation was significantly higher for lesional skin, and the barrier recovery rate was significantly delayed. Furthermore, a trend towards thinned stratum corneum was observed for lesional skin, and this was correlated with barrier recovery rate. The expressions of PPAR-α and ALOX15B were variable in the samples.

CONCLUSIONS

Melasma skin is characterized by impaired stratum corneum integrity and a delayed barrier recovery rate.

Histochemical and immunohistochemical study in melasma: evidence of damage in the basal membrane

The pathogenesis of melasma has not been clearly elucidated. Using Fontana Masson; diastase-resistant periodic acid-Schiff stains; and immunohistochemistry to stem cell factor (SCF), its receptor c-kit, anti-mast cell tryptase, and anti-collagen type IV antibody, we evaluated melasma lesions and compared them with perilesional skin and photoprotected skin. Samples were taken from lesional and photoprotected nonlesional skin in 24 patients. In other 24 patients, we took biopsies of lesional and perilesional skin. With Fontana Masson, we observed many pigmented basal cells protruding into the dermis of the melasma skin. Periodic acid-Schiff stain and anti-collagen type IV showed damage on the basal membrane in 95.5% and 83%, respectively, in melasma lesion. The immunoreactivity of SCF and the prevalence of mast cells were increased in the dermis of melasma compared with perilesional dermis. The expression of c-kit was significantly increased at lesional epidermis; a frequent protrusion of c-kit-positive basal cells into the dermis was evident in 70% versus that in 29% of perilesional skin. The expression of c-kit was increased at lesional dermis of melasma compared with perilesional skin. We found a low correlation between c-kit expression and prevalence of mast cells; these were increased in melasma skin. The results may suggest a role of SCF, c-kit, and mast cells in the pathogenesis of melasma. We were surprised by the unexpected evidence of damage to basal membrane (BM), which could facilitate the fall or the migration of active melanocytes and melanin into the dermis allowing the constant hyperpigmentation in melasma.

The genetic determination of skin pigmentation: KITLG and the KITLG/c-Kit pathway as key players in the onset of human familial pigmentary diseases

Cutaneous pigmentation is regulated by a complex melanogenic network in which skin cells synthesize growth factors and cytokines. Mutations in genes encoding these regulators modify their expression and/or functionality, leading to altered signaling pathways and contributing to altered skin phenotypes. In this issue, Amyere et al. report a genome-wide analysis of seven families with familial progressive hyperpigmentation and hypopigmentation, identifying three new mutations in KITLG. The study underlines the relevance of investigating candidate genes implicated in the onset of pigmentary disorders. Furthermore, Amyere et al. suggest that different pigmentary diseases can result from the same mutation or different mutations in the same gene, and they offer hope for the development of new and efficacious treatment strategies.

Natural options for the management of hyperpigmentation

Facial hyperpigmented disorders are a common complaint in the adult population of all races. First-line topical treatments are usually hydroquinone or topical retinoids, which can cause irritant reactions. The need for better tolerated, yet effective, skin lightening agents that could be utilized by a wider population has led to the investigation of several potential botanical/natural compounds. There are currently many topical cosmetic formulations claiming skin depigmenting effects. A few of the ingredients (e.g. soy) are supported not only by in vitro results but also by a body of controlled clinical efficacy studies; other ingredients, instead, are backed mostly by in vitro data and a few small uncontrolled clinical studies. In this review, we describe the most common natural ingredients used for skin depigmentation and their major published studies: soy, licorice extracts, kojic acid, arbutin, niacinamide, N-acetylglucosamine, COFFEEBERRY(™) and green tea.

Transcriptional profiling shows altered expression of wnt pathway- and lipid metabolism-related genes as well as melanogenesis-related genes in melasma

Melasma is a commonly acquired hyperpigmentary disorder of the face, but its pathogenesis is poorly understood and its treatment remains challenging. We conducted a comparative histological study on lesional and perilesional normal skin to clarify the histological nature of melasma. Significantly, higher amounts of melanin and of melanogenesis-associated proteins were observed in the epidermis of lesional skin, and the mRNA level of tyrosinase-related protein 1 was higher in lesional skin, indicating regulation at the mRNA level. However, melanocyte numbers were comparable between lesional and perilesional skin. A transcriptomic study was undertaken to identify genes involved in the pathology of melasma. A total of 279 genes were found to be differentially expressed in lesional and perilesional skin. As was expected, the mRNA levels of a number of known melanogenesis-associated genes, such as tyrosinase, were found to be elevated in lesional skin. Bioinformatics analysis revealed that the most lipid metabolism-associated genes were downregulated in lesional skin, and this finding was supported by an impaired barrier function in melasma. Interestingly, a subset of Wnt signaling modulators, including Wnt inhibitory factor 1, secreted frizzled-related protein 2, and Wnt5a, were also found to be upregulated in lesional skin. Immunohistochemistry confirmed the higher expression of these factors in melasma lesions.

Acquired bilateral naevus of Ota-like macules: an immunohistological analysis of dermal melanogenic paracrine cytokine networks

BACKGROUND

Acquired bilateral naevus of Ota-like macules (ABNOM) is similar to melasma with regard to their clinical features, including female predominance, acquired onset, and predominant involvement of the malar area. The similar clinical features suggest the possibility of a shared pathogenesis. Dermal factors including vascularity and melanogenic paracrine networks such as the stem cell factor (SCF)/c-kit pathway have recently been suggested to play an important role in the pathogenesis of melasma. However, the role of dermal factors in ABNOM remains unknown.

OBJECTIVES

To provide a novel view on the pathogenesis of ABNOM, we studied the expression of melanogenic paracrine cytokines such as SCF/c-kit, and assessed dermal vascularity.

METHODS

Thirty-seven patients with ABNOM and 20 patients with melasma were enrolled in this study. Skin samples were obtained from lesional and perilesional normal skin. Immunohistochemistry was performed.

RESULTS

Solar elastosis was slightly more intense in the lesional skin of ABNOM. In contrast to dermal pigmentation and melanocytes, the amounts of epidermal pigmentation and melanocytes were not increased in the lesional skin of patients with ABNOM. The expression of dermal SCF and c-kit was increased; however, the expression of epidermal SCF and c-kit and dermal factor VIII-related antigen was not increased in the lesional skin of ABNOM.

CONCLUSIONS

These results suggest that the increased expression of the SCF/c-kit pathway between dermal fibroblasts and dermal melanocytes may play an important role in the pathogenesis of ABNOM.

What should be considered in treatment of melasma

Melasma is a common acquired hyperpigmentary skin disorder characterized by light to dark brown macules and patches occurring in the sun-exposed areas of the face. Melasma lesional skin is characterized by epidermal hyperpigmentation through increased melanogenesis in epidermal melanocytes. Some patients have dermal melanin but its amount is not significant and its distribution is very heterogeneous in the whole melasma lesional skin. Melasma is not homogeneous disease and there are personal characteristics of patients with melasma. The pathogenesis of melasma is not fully understood, but several hypotheses have been suggested. Increased vascularity in melasma lesions has suggested the role of increased number of enlarged vessels in the development of melasma. Endogeneous and exogeneous stimuli such as sex hormones and ultraviolet irradiation respectively may stimulate the microenvironment leading to the release of various mediators that cause activation of melanocytes and/or these stimuli may directly activate the melanocytes. Melasma patients may have specialized melanocytes with an intrinsic sensitivity to these stimuli.

[Physiopathology of melasma]

Melasma is a common dermatosis that involves changes in normal skin pigmentation, resulting from the hyperactivity of epidermal melanocytes. The consequent hyperpigmentation is mostly induced by ultraviolet radiation. Clinically, melasma is characterized by light to dark brown macules that usually occur on the face, although they can also affect the cervical and anterior thoracic regions and upper members.Fertile age women and those with intermediate skin phototypes are most likely to develop melasma. Most of its physiopathogenics is not yet fully understood, but there is a relation with genetic and hormonal factors, drugs and cosmetics use, endocrinopathies and sun exposure. The authors discuss the main aspects associated with skin pigmentation and the development of melasma.

Management of hyperpigmentation in darker racial ethnic groups

Dyschromias, in particular hyperpigmentation, are major issues of concern for people of color. Pigmentary disorders such as melasma and postinflammatory hyperpigmentation (PIH) can cause psychological and emotional distress and can pose a negative impact on a person's health-related quality of life. The precise etiology of these conditions is unknown. Therapies for melasma and PIH target various points during the cycle of melanin production and degradation. Therapies for these conditions include topical agents and resurfacing procedures. Hydroquinone remains the gold standard of topical agents. Other efficacious agents include kojic acid, azelaic acid, mequinol, and retinoids. Cosmeceutical agents include licorice, arbutin, soy, N-acetyl glucosamine, and niacinamide. Resurfacing procedures that have been used to treat melasma and PIH include chemical peels, microdermabrasion, lasers, and intense pulsed light. These procedures are best used in combination with topical bleaching agents. Given the propensity of darker skin to hyperpigment, resurfacing procedures should be used with care and caution. Maximal results are best achieved with repetitive, superficial, resurfacing modalities. In addition, ultraviolet protective measures such as broad-spectrum sunscreens are fundamental to the successful management of these conditions.

Solar elastosis and presence of mast cells as key features in the pathogenesis of melasma

Melasma is an acquired hypermelanosis on sun-exposed areas. Its pathogenesis has not been clearly elucidated. Using histochemistry (Giemsa, Verhoeff-van Gieson and Fontana-Masson staining), we evaluated melasma lesions and compared them with nonlesional skin. Skin samples were obtained from lesional and nonlesional facial skin of 27 patients with melasma, and biopsies were also taken from normal control subjects. Mast cells and solar elastosis areas were evaluated using a computer-assisted image-analysis program. Lesional skin had abundant elastotic material compared with nonaffected skin (13.3 +/- 2.8% vs. 10.2 +/- 2.9%, P < 0.001). Mast cells were more prominent in the elastotic areas of melasma skin (173 +/- 57% vs. 145 +/- 57%, P = 0.04). Melasma could be a result of a cumulative sun exposure, in a microenvironment of cutaneous photoageing in which inflammatory cells, particularly mast cells, play a key role.

Latest insights into skin hyperpigmentation

Hyperpigmentary problems, including postinflammatory hyperpigmentation, solar lentigos, and melasma, occur widely in the human population and are thus of broad interest for control. On the basis of genomic and proteomic understanding of the melanocyte and melanogenesis, there are potentially hundreds of proteins and other effectors involved in pigmentation. This knowledge, although complex, should prove most useful in identifying specific abnormalities that lead to the hyperpigmentary problems. Also available are new laboratory screening methods and skin color measurement tools that are increasing the pace at which materials can be screened and evaluated clinically for their effectiveness. Combined with a clear consumer need for effective pigmentation control agents, advanced pigmentary system understanding and new research capabilities are setting the stage for future technological advancements.

[4-t-butylphenyl]-N-(4-imidazol-1-yl phenyl)sulfonamide (ISCK03) inhibits SCF/c-kit signaling in 501mel human melanoma cells and abolishes melanin production in mice and brownish guinea pigs

It is well known that c-kit is related to pigmentation as well as to the oncology target protein. The objective of this study was to discover a skin-whitening agent that regulates c-kit activity. We have developed a high-throughput screening system using recombinant human c-kit protein. Approximately 10,000 synthetic compounds were screened for their effect on c-kit activity. Phenyl-imidazole sulfonamide derivatives showed inhibitory activity on c-kit phosphorylation in vitro. The effects of one derivative, [4-t-butylphenyl]-N-(4-imidazol-1-yl phenyl)sulfonamide (ISCK03), on stem-cell factor (SCF)/c-kit cellular signaling in 501mel human melanoma cells were examined further. Pretreatment of 501mel cells with ISCK03 inhibited SCF-induced c-kit phosphorylation dose dependently. ISCK03 also inhibited p44/42 ERK mitogen-activated protein kinase (MAPK) phosphorylation, which is known to be involved in SCF/c-kit downstream signaling. However ISCK03 did not inhibit hepatocyte growth factor (HGF)-induced phosphorylation of p44/42 ERK proteins. To determine the in vivo potency of ISCK03, it was orally administered to depilated C57BL/6 mice. Interestingly, oral administration of ISCK03 induced the dose-dependent depigmentation of newly regrown hair, and this was reversed with cessation of ISCK03 treatment. Finally, to investigate whether the inhibitory effect of ISCK03 on SCF/c-kit signaling abolished UV-induced pigmentation, ISCK03 was applied to UV-induced pigmented spots on brownish guinea pig skin. The topical application of ISCK03 promoted the depigmentation of UV-induced hyperpigmented spots. Fontana-Masson staining analysis showed epidermal melanin was diminished in spots treated with ISCK03. These results indicate that phenyl-imidazole sulfonamide derivatives are potent c-kit inhibitors and might be used as skin-whitening agents.

The vascular characteristics of melasma

BACKGROUND

The pathogenesis of melasma is not yet fully understood. Previous studies indicate that dermal environment such as fibroblasts may have an important role in the development of melasma. Recently, it has been suggested that interactions between the cutaneous vasculature and melanocytes might have an influence on the development of pigmentation.

OBJECTIVES

We investigated the vascular characteristics in melasma lesions. The expression of vascular endothelial growth factor (VEGF), a major angiogenic factor of the skin, was also investigated in melasma.

METHODS

Erythema intensity was quantified by the increase of the a* parameter using a colorimeter. Skin samples were obtained from lesional and non-lesional facial skin of 50 Korean women with melasma. Immunohistochemistry was performed to determine the expression of factor VIIIa-related antigen and VEGF in melasma.

RESULTS

The values of a* was significantly higher in the melasma lesion than that of perilesional normal skin. Computer-assisted image analyses of factor VIIIa-related antigen-stained sections revealed a significant increase of both the number and the size of dermal blood vessels in the lesional skin. There was significant relationship between the number of vessels and pigmentation in melasma. The expression of VEGF was significantly increased in melasma

CONCLUSIONS

These data suggest that increased vascularity is one of the major findings in melasma. VEGF may be a major angiogenic factor for altered vessels in melasma.