Melanocyte-stimulating properties of arachidonic acid metabolites: possible role in postinflammatory pigmentation

Updates in clinical trial-explored chemopreventive agents for cutaneous melanoma: mechanisms affecting melanocytes

Cutaneous melanoma is a highly aggressive skin cancer with rising incidence, driven by risk factors such as ultraviolet exposure, genetic predisposition, and immunosuppression. While surgical excision remains the primary treatment, interest in chemoprevention strategies is growing. Numerous natural and synthetic agents have shown preclinical promise, but evaluating their effectiveness is challenging due to their systemic effects on multiple cell types. This review provides a focused examination of the melanocyte-specific mechanisms of select agents that have been tested in clinical trials for melanoma chemoprevention. We discuss various molecular and cellular mechanisms driving the anti-melanoma properties of nonsteroidal anti-inflammatory drugs, statins, sulforaphane, vitamin D, and N-acetylcysteine. Despite promising preclinical and early clinical data, challenges remain regarding precise mechanisms, optimal dosing, long-term safety, and patient selection. Future research should focus on refining melanoma prevention strategies through well-designed clinical trials and personalized approaches integrating genetic and molecular risk factors.

Comparative Efficacy of Skin-Lightening Formulations in Suppressing Ultraviolet B (UVB)-Induced Arachidonic Acid, Alpha-Melanocyte-Stimulating Hormone (α-MSH), and Melanin Expression: An In Vitro Keratinocyte-Melanocyte Co-culture Study

BACKGROUND

Melasma is a chronic hyperpigmentary disorder exacerbated by sun exposure, characterized by asymptomatic hyperpigmented macules and patches. Its pathogenesis involves ultraviolet B (UVB)-induced activation of melanogenesis pathways, including arachidonic acid (AA) metabolism, alpha-melanocyte-stimulating hormone (α-MSH) secretion, and melanin synthesis. This study aimed to evaluate the efficacy of a multi-ingredient skin-lightening formulation (3% tranexamic acid, 2% ascorbyl glucoside, 2.5% arbutin, and 5% niacinamide) compared to a 10% vitamin C preparation and 4% hydroquinone (HQ) in suppressing UVB-induced AA, α-MSH, and melanin production in a keratinocyte-melanocyte co-culture model.

METHODS

Keratinocyte-melanocyte co-cultures were pretreated with the multi-ingredient formulation, 10% vitamin C, or 4% HQ before UVB irradiation (150 mJ/cm2). Distilled water served as the negative control. Biomarkers (AA, α-MSH, and melanin) were quantified using enzyme-linked immunosorbent assay (ELISA) and fluorometric assay.

RESULTS

UVB irradiation significantly increased AA (4.3-fold), α-MSH (3.7-fold), and melanin (2.6-fold) levels compared to unirradiated cells (all p < 0.001). All tested formulations reduced AA levels compared to the negative control (p < 0.001), with the multi-ingredient formulation demonstrating superior efficacy over both 10% vitamin C and 4% HQ (p < 0.001). Only the multi-ingredient formulation significantly suppressed α-MSH levels (p < 0.001). Regarding melanin reduction, the multi-ingredient formulation achieved comparable efficacy to 4% HQ but outperformed 10% vitamin C (p < 0.05).

CONCLUSION

The multi-ingredient formulation demonstrated superior efficacy in reducing UVB-induced AA and α-MSH levels while achieving comparable melanin reduction to 4% HQ. These results are consistent with the prevailing consensus that effective melasma management necessitates a multifaceted approach that concurrently targets multiple mechanisms.

Inhibitory Effect on the Tyrosinase Activity and Low Cytotoxicity of Monounsaturated Long-Chain Chelating Fatty Ester

In the present study, 5-Hydroxy-2-(Oleoyloxymethyl) -4H-pyran-4-one (KMO 3), and their chelated with Cu(II) and Fe(III) ions were synthesized to explore their inhibitory activity against tyrosinase and cytotoxicity. To this end, the structures of the obtained compounds were confirmed by ATR/FT-IR, 13C and 1H-NMR, and UV-vis techniques. The results show that chelating fatty ester presents the bands at 1567m, 1511w cm-1 attributed to the coordinated carbonyl (Cu(II)←[O=C]2), and the bands at 1540m, 1519m cm-1 which were attributed to the coordinated carbonyl (Fe(III)←[O=C]3). The inhibitory effect of chelating Oleic acid 2 (inhibition 68.3% ± 4.5) showed a factor of 19 times higher than free fatty acid (3.6% ± 3.2). IC50 Anti-tyrosinase activity of the Kojic acid 1 and KMO 3 compounds were 62.8 ± 6.6 µM and 77.6 ± 4.3 µM. The IC50 and IC90 values for tyrosinase inhibitory activity for chelating fatty ester and their complexes are values > 400 µM. Finally, the assay with the series showed no hemolytic activity (EC50> 250 μg mL-1), and not cytotoxic to B16F10, ACP-02, and human dermal fibroblast cells at 100 µM and showed no hemolytic potential at the concentration of IC50 250 µM.

Postoperative risk assessment of post-inflammatory hyperpigmentation and the efficacy of delayed prevention following 532 nm Q-switched Nd:YAG laser treatment of solar lentigines: a randomized controlled study

BACKGROUND

Although post-inflammatory hyperpigmentation (PIH) is a common adverse event following laser procedures, studies evaluating its risk remain limited.

OBJECTIVE

To analyze PIH risk after 532 nm Q-switched Nd:YAG laser (QSNYL) treatment for solar lentigines and examine the efficacy of triple combination cream (TCC) for its prevention.

METHODS

In this single center, investigator-blinded, randomized controlled study, participants with solar lentigo either received TCC or emollient from 2 weeks post-QSNYL treatment. The occurrence of PIH was determined by three independent and blinded dermatologists. In vivo skin measurements and sun exposure questionnaires were examined to evaluate the risk of PIH.

RESULTS

A total of 28 patients with 67 solar lentigines were included in the analysis. In the control group, PIH occurred in 55.3% of the lesions. Risk factors for the occurrence of PIH were the increased erythema at weeks 2 (OR, 1.32; p = 0.035) and outdoor activity during 1-5 pm (OR, 8.10; p = 0.038). Treatment with TCC from 2 weeks post-QSNYL treatment significantly decreased the incidence of PIH (31.0% vs. 55.3%, p = 0.048).

CONCLUSION

Post-laser erythema and outdoor activity at the daytime are prognostic factors for the occurrence of PIH. Administering TCC could be considered for the prevention of PIH in high-risk patients.

Tokishakuyakusan alleviates ultraviolet-induced skin pigmentation by decreasing the expression of melanogenesis-related enzymes

ETHNOPHARMACOLOGICAL RELEVANCE

Tokishakuyakusan (TSS), a traditional Kampo medicine, can effectively alleviate symptoms unique to women, such as menstrual pain and menopausal symptoms, and this effect is believed to be related to its ability to increase the secretion of female hormones. TSS is also believed to be effective against skin pigmentation. However, no studies have examined the effect of TSS on pigmentation.

AIM OF THE STUDY

In this study, we conducted basic research to determine the effects of TSS on pigmentation.

MATERIALS AND METHODS

Female HRM-2 mice were given free access to a normal diet or a TSS-containing diet for 7 weeks. For 3 weeks starting from the 4th week of treatment, the back of the skin was irradiated with ultraviolet (UV) light, and the melanin level was measured. The expression levels of melanogenesis-related genes and inflammatory markers in the skin were analyzed.

RESULTS

The melanin level in the skin of the mice exposed to UV radiation was approximately three times greater than that in the skin of the mice in the non-UV-irradiated group, confirming pigmentation due to UV irradiation. The protein expression levels of tyrosinase (Tyr), tyrosinase-related protein-1 (Tyrp1), and dopachrome tautomerase (Dct), which are important for melanin production, were significantly greater in the UV irradiation group than in the non-UV irradiation group. In contrast, the amount of skin melanin in the mice treated with TSS was significantly lower than that in the UV-irradiated group, and the expression levels of melanogenesis-related enzymes were also lower. Furthermore, TSS significantly decreased the expression of microphthalmia transcription factor (Mitf), a transcription factor for melanogenesis-related enzymes, and the inflammatory cytokines interleukin-1β and interleukin-6.

CONCLUSIONS

TSS inhibits melanin production in melanocytes by suppressing the increase in the expression of melanogenesis-related enzymes caused by UV irradiation. These findings suggested that this effect of TSS is exerted through the combined regulation of MITF expression and anti-inflammatory responses.

A novel liquid plasma derivative inhibits melanogenesis through upregulation of Nrf2

Non-thermal plasma (NTP) is an emerging technology with extensive applications in biomedicine, including treatment of abnormal pigmentation. However, very few studies have investigated how plasma induces anti-melanogenesis. Here, liquid plasma was prepared by treating an NTP jet with helium and oxygen (as carrier gases) for 15 min in serum-free culture media. In the zebrafish model, pigmentation ratio was observed with or without liquid plasma. The anti-melanogenic effect of liquid plasma was evaluated in human melanocytes by assessing the expression of melanogenesis-related genes using western blotting, RT-PCR, and immunohistochemistry. Liquid plasma reduced pigmentation in the zebrafish model and inhibited melanin synthesis in primary human melanocytes. Intracellular reactive oxygen species levels decreased and Nrf2 expression increased in liquid plasma-treated melanocytes. Liquid plasma affected microphthalmia-associated transcription factor (MITF) and tyrosinase mRNA and protein levels, tyrosinase activity, and melanin content. Considering the role of Wnt/β-catenin and PI3K/Akt pathways in melanogenesis, the effect of liquid plasma on this pathway was determined; liquid plasma decreased active β-catenin, LEF1/TCF4, MITF, and tyrosinase levels in a time-dependent manner and inhibited the nuclear translocation of β-catenin. This inhibition subsequently suppressed melanogenesis by downregulating MITF and tyrosinase. These results suggest that liquid plasma may be used for treating pigmentary disorders.

Secondary glaucoma: Toward interventions based on molecular underpinnings

Glaucoma is a heterogeneous group of progressive diseases that leads to irreversible blindness. Secondary glaucoma refers to glaucoma caused by a known underlying condition. Pseudoexfoliation and pigment dispersion syndromes are common causes of secondary glaucoma. Their respective deposits may obstruct the trabecular meshwork, leading to aqueous humor outflow resistance, ocular hypertension, and optic neuropathy. There are no disease-specific interventions available for either. Pseudoexfoliation syndrome is characterized by fibrillar deposits (pseudoexfoliative material) on anterior segment structures. Over a decade of multiomics analyses taken together with the current knowledge on pseudoexfoliative glaucoma warrant a re-think of mechanistic possibilities. We propose that the presence of nucleation centers (e.g., vitamin D binding protein), crosslinking enzymes (e.g., transglutaminase 2), aberrant extracellular matrix, flawed endocytosis, and abnormal aqueous-blood barrier contribute to the formation of proteolytically resistant pseudoexfoliative material. Pigment dispersion syndrome is characterized by abnormal iridolenticular contact that disrupts iris pigment epithelium and liberates melanin granules. Iris melanogenesis is aberrant in this condition. Cytotoxic melanogenesis intermediates leak out of melanosomes and cause iris melanocyte and pigment epithelium cell death. Targeting melanogenesis can likely decrease the risk of pigmentary glaucoma. Skin and melanoma research provides insights into potential therapeutics. We propose that specific prostanoid agonists and fenofibrates may reduce melanogenesis by inhibiting cholesterol internalization and de novo synthesis. Additionally, melatonin is a potent melanogenesis suppressor, antioxidant, and hypotensive agent, rendering it a valuable agent for pigmentary glaucoma. In pseudoexfoliative glaucoma, where environmental insults drive pseudoexfoliative material formation, melatonin's antioxidant and hypotensive properties may offer adjunct therapeutic benefits. This article is categorized under: Neurological Diseases > Molecular and Cellular Physiology.

Serotonin/5-HT7 receptor provides an adaptive signal to enhance pigmentation response to environmental stressors through cAMP-PKA-MAPK, Rab27a/RhoA, and PI3K/AKT signaling pathways

Serotonin (5-HT), a neurotransmitter, is essential for normal and pathological pigmentation processing, and its receptors may be therapeutical targets. The effect and behavior of the 5-HT7 receptor (5-HT7R) in melanogenesis in high vertebrates remain unknown. Herein, we examine the role and molecular mechanism of 5-HT7R in the pigmentation of human skin cells, human tissue, mice, and zebrafish models. Firstly, 5-HT7R protein expression decreased significantly in stress-induced depigmentation skin and vitiligo epidermis. Stressed mice received transdermal serotonin 5-HT7R selective agonists (LP-12, 0.01%) for 12 or 60 days. Mice might recover from persistent stress-induced depigmentation. The downregulation of tyrosinase (Tyr), microphthalmia-associated transcription factor (Mitf) expression, and 5-HT7R was consistently restored in stressed skin. High-throughput RNA sequencing showed that structural organization (dendrite growth and migration) and associated pathways were activated in the dorsal skin of LP-12-treated animals. 5-HT7R selective agonist, LP-12, had been demonstrated to enhance melanin production, dendrite growth, and chemotactic motility in B16F10 cells, normal human melanocytes (NHMCs), and zebrafish. Mechanistically, the melanogenic, dendritic, and migratory functions of 5-HT7R were dependent on the downstream signaling of cAMP-PKA-ERK1/2, JNK MAPK, RhoA/Rab27a, and PI3K/AKT pathway activation. Importantly, pharmacological inhibition and genetic siRNA of 5-HT7R by antagonist SB269970 partially/completely abolished these functional properties and the related activated pathways in both NHMCs and B16F10 cells. Consistently, htr7a/7b genetic knockdown in zebrafish could blockade melanogenic effects and abrogate 5-HT-induced melanin accumulation. Collectively, we have first identified that 5-HT7R regulates melanogenesis, which may be a targeted therapy for pigmentation disorders, especially those worsened by stress.

Post-Inflammatory Hyperpigmentation in Dark Skin: Molecular Mechanism and Skincare Implications

Human skin is characterized by significant diversity in color and tone, which are determined by the quantity and distribution of melanin pigment in the epidermis. Melanin absorbs and reflects ultraviolet radiation (UVR), preventing the damage to genomic DNA in the epidermis and degradation of collagen in the dermis; therefore, darker skin types are thought to be well protected from the photodamage because of the high melanin content. However, increased content of melanin in combination with the extrinsic stress factors causing inflammation such as excess UVR, allergic reactions, or injury can also frequently lead to cosmetic problems resulting in discoloration and scarring. This review summarizes current knowledge on histopathology and likely molecular signatures of one of the most common problems, post-inflammatory hyperpigmentation (PIH). The mechanisms proposed so far are subsequently discussed in the context of other factors characterizing darker skin types. This includes the common cellular features, organization of upper skin layers, and major biomarkers, with particular emphasis on increased propensities to systemic and localized inflammation. Enhanced or prolonged inflammatory responses can not only affect the process of melanogenesis but also have been implicated in injury-related skin pathologies and aging. Finally, we summarize the major cosmetic treatments for PIH and their known anti-inflammatory targets, which can be beneficial for darker skin tones and combined with broad-spectrum filters against UVR.

Mechanism of Action of Topical Tranexamic Acid in the Treatment of Melasma and Sun-Induced Skin Hyperpigmentation

Tranexamic acid (TXA) has anti-plasmin activity and has been shown when administered orally to be effective against melasma, for which it is considered first-line pharmacotherapy. Several studies have shown that topically applied TXA is also effective against melasma and skin hyperpigmentation caused by sunburn and inflammation. The TXA concentration in the epidermis and dermis/vasculature has been estimated from its distribution in the skin after closed application, and topically applied TXA has thus been shown to act on neutrophils and mast cells in the dermis and on the vascular system. It is unlikely that topically applied TXA acts on dermal neutrophils or mast cells or on the vascular system to form thrombi. As discussed in the present review, studies on the effects of topical TXA on the hyperpigmentation process indicate that the resulting skin-lightening mechanism involves the suppression of cytokine/chemical mediator production, which stimulates melanin production via the keratinocyte-derived urokinase-type plasminogen activator and plasminogen derived from dermal vascular in the basal layer of the epidermis, thereby suppressing the production of excessive melanin to prevent hyperpigmentation.

Treatment of hyperpigmentation after burn: A literature review

OBJECTIFY

Skin pigmentation disorders are one of the most frequent sequelae after burn injury. While these conditions often improve over time, some are permanent and cause severe psychological disorders (especially on the face). Given the frequency of these disorders and their benign nature, the scientific community has great difficulty postponing these patient follow-ups. Publications on their management are rare, and there is no consensus on the gold standard treatment for skin dyschromia. Herein, we performed a literature review including the various treatments currently proposed to manage these hyperpigmentations.

METHODS

All reported articles up to February 2021 were reviewed on Pubmed. Studies on the treatment of hyperpigmented scars were included if they were secondary to burn injuries. Excluded articles evaluated transient treatments, such as makeup, and articles on inflammatory hyperpigmentation without etiological details or not secondary to burns.

RESULTS

201 articles were identified, and 13 studies were included. Topical creams used in inflammatory hyperpigmented lesions such as hydroquinone and first-line retinoids are controversial due to their inconstant efficacy. Various types of laser and pulsed light treatments have shown their effectiveness but can also aggravate pigmentation.

CONCLUSION

Dyschromia after burn remains a therapeutic challenge. Hyperpigmentations after burn should be treated on a case-by-case basis, using data from the literature, clinical experience and measuring the risk/benefit ratio.

Timeline of the Development of Skin-Lightening Active Ingredients in Japan

Japanese pharmaceutical cosmetics, often referred to as quasi-drugs, contain skin-lightening active ingredients formulated to prevent sun-induced pigment spots and freckles. Their mechanisms of action include suppressing melanin production in melanocytes and promoting epidermal growth to eliminate melanin more rapidly. For example, arbutin and rucinol are representative skin-lightening active ingredients that inhibit melanin production, and disodium adenosine monophosphate and dexpanthenol are skin-lightening active ingredients that inhibit melanin accumulation in the epidermis. In contrast, oral administration of vitamin C and tranexamic acid in pharmaceutical products can lighten freckles and melasma, and these products are more effective than quasi-drugs. On the basis of their clinical effectiveness, skin-lightening active ingredients can be divided into four categories according to their effectiveness and adverse effects. This review discusses academic research and development regarding skin-lightening ingredients in Japan.

Solamargine Alleviated UVB-Induced Inflammation and Melanogenesis in Human Keratinocytes and Melanocytes via the p38 MAPK Signaling Pathway, a Promising Agent for Post-inflammatory Hyperpigmentation

Post-inflammatory hyperpigmentation (PIH) is a common acquired pigmentary disorder occurring after skin inflammation or injury. Ultraviolet B irradiation could exaggerate PIH clinically due to its effect on promoting cutaneous inflammation and melanogenesis in keratinocytes and melanocytes, respectively. Solamargine (SM), a steroidal alkaloid glycoside extracted from Solanum undatum, significantly inhibits Ultraviolet B (UVB)-induced pro-inflammatory cytokines IL-1α, IL-1β, IL-8, and IFN-γ, as well as paracrine melanogenic factors ET-1, α-MSH, and bFGF in human keratinocytes. Additionally, SM significantly attenuated UVB-induced melanin synthesis in human epidermal melanocytes through down-regulation of tyrosinase activity and expression of MITF, TRP-1, TRP-2, and tyrosinase. SM exerted an anti-inflammatory effect in UVB-irradiated keratinocytes through the p38 MAPK/Nrf2/HO-1 signaling pathway. With its anti-inflammatory and whitening effect, SM may improve PIH through paracrine regulations of keratinocytes and direct action on melanocytes, making it a promising agent for PIH.

A Focused review on the pathophysiology of post-inflammatory hyperpigmentation

Post-inflammatory hyperpigmentation (PIH) is one of the most common disorders of acquired hyperpigmentation. It often develops following cutaneous inflammation and is triggered by various stimuli, from inflammatory and autoimmune conditions to iatrogenic causes and mechanical injuries. While it is well established that an increase in melanin production and distribution within the epidermis and dermis is a hallmark feature of this condition, the exact mechanisms underlying PIH are not completely understood. This article aims to review the current evidence on the pathophysiology of PIH as the cellular and molecular mechanism of PIH represents a promising avenue for the development of novel, targeted therapies.

Bilateral periareolar hyperpigmentation after augmentation mammoplasty: a case report and literature review

Complications arising from breast augmentation procedures are broadly categorized as either surgery-related or prosthesis-related. Many reports have described complications associated with breast augmentation. However, to date, periareolar post-inflammatory hyperpigmentation (PIH) after breast augmentation has not been reported. Herein, we report a case of PIH after augmentation mammoplasty using a silicone implant through the periareolar approach. A 35-year-old woman, who underwent bilateral breast augmentation using a periareolar approach, presented with bilateral periareolar tissue changes, with dark brown, irregular macules appearing 6 weeks postoperatively. Based on clinical symptoms and histological examination, the lesion was diagnosed as PIH. Topical hydroquinone and retinoic acid were applied for 8 weeks after the pigmentation appeared. After 6 months of observation, the pigmentation faded. To summarize, we report a case of pigmentation around the bilateral nipples after periareolar breast augmentation along with a literature review.

Keratinocytes take part in the regulation of substance P in melanogenesis through the HPA axis

BACKGROUND

Clinical findings have shown that skin depigmentation disorder such as vitiligo may be closely associated with the release of central and peripheral substance P (SP) resulted from chronic psychological stress or sudden mental blow. But the regulatory role of SP and its receptor, tachykinin receptor in the pathogenesis of vitiligo is unclear.

OBJECTIVES

To investigate the function and mechanism of SP in melanogenesis.

METHODS

The chronic mental stress was used to explore the intrinsic association between psychological factors, SP and melanogenesis disorder. The effect of SP on melanogenesis through hypothalamic pituitary adrenocortical (HPA) axis was studied by skin culture in vitro. The conditioned medium experiment demonstrated the indirect effect of SP on melanogenesis of B16F10 cells through HaCaT cells. The ability to produce melanin was evaluated by detecting melanin and tyrosinase activity. qRT-PCR, western blotting and immunohistochemistry were used to detect the expression of related genes and proteins in melanogenesis and HPA axis.

RESULTS

Increased SP expression and reduction of melanogenesis in the skin of mice were observed under mental stress. Melanogenesis was suppressed in the cultured human skin treated with SP due to the down-regulation of melanin-related proteins and HPA axis genes. The melanogenesis of B16F10 cells was inhibited by the conditioned medium of HaCaT cells treated with SP.

CONCLUSIONS

Overall, these results indicate that excess SP originated from mental stress interferes with melanogenesis through keratinocytes in the skin. The HPA axis is the key downstream to perceive the SP signaling and furtherly regulate the melanogenesis.

Sebocytes contribute to melasma onset

Melasma is a hyperpigmentary disorder with photoaging features, whose manifestations appear on specific face areas, rich in sebaceous glands (SGs). To explore the SGs possible contribution to the onset, the expression of pro-melanogenic and inflammatory factors from the SZ95 SG cell line exposed to single or repetitive ultraviolet (UVA) radiation was evaluated. UVA up-modulated the long-lasting production of α-MSH, EDN1, b-FGF, SCF, inflammatory cytokines and mediators. Irradiated SZ95 sebocyte conditioned media increased pigmentation in melanocytes and the expression of senescence markers, pro-inflammatory cytokines, and growth factors regulating melanogenesis in fibroblasts cultures. Cocultures experiments with skin explants confirmed the role of sebocytes on melanogenesis promotion. The analysis on sebum collected from melasma patients demonstrated that in vivo sebocytes from lesional areas express the UVA-activated pathways markers observed in vitro. Our results indicate sebocytes as one of the actors in melasma pathogenesis, inducing prolonged skin cell stimulation, contributing to localized dermal aging and hyperpigmentation.

Radiofrequency Irradiation Mitigated UV-B-Induced Skin Pigmentation by Increasing Lymphangiogenesis

Dermal macrophages containing melanin increase skin pigmentation since dermal melanin removal is slower than epidermal melanin removal. Lymphatic vessels are also involved in melanin clearance. We evaluated whether radiofrequency (RF) irradiation induced an increase in HSP90, which promotes lymphangiogenesis by activating the BRAF/MEK/ERK pathway and decreasing tyrosinase activity, in the UV-B exposed animal model. The HSP90/BRAF/MEK/ERK pathway was upregulated by RF. Tyrosinase activity and the VEGF-C/VEGFR 3/PI3K/pAKT1/2/pERK1/2 pathway, which increase lymphangiogenesis, as well as the expression of the lymphatic endothelial marker LYVE-1, were increased by RF. Additionally, the number of melanin-containing dermal macrophages, the melanin content in the lymph nodes, and melanin deposition in the skin were decreased by RF. In conclusion, RF increased HSP90/BRAF/MEK/ERK expression, which decreased tyrosinase activity and increased lymphangiogenesis to eventually promote the clearance of dermal melanin-containing macrophages, thereby decreasing skin pigmentation.

Features of Common Skin Disorders in Pediatric Patients with Skin of Color

Many dermatologic conditions common in the pediatric population may have unique presentations in skin of color or occur with greater incidence. This may be due to ethnic origin, socioeconomic factors, or other influences. Awareness of the potential variations in skin of color may enhance prompt diagnosis, appropriate treatment, and/or reassurance as indicated.

Post-acne hyperpigmentation: Evaluation of risk factors and the use of artificial neural network as a predictive classifier

Acne is common among young individuals. People with dark skin have a higher risk for developing pigmentary complications. Inflammation is an important factor in post-acne hyperpigmentation however other factors are also involved in developing this complication however these factors are not well studied. The aim of this study is to identify risk factors involved in post-acne hyperpigmentation. Clinical data related to acne, acne- related hyperpigmentation were collected. Data was analyzed for risk factors associated with acne pigmentation. Artificial neural network was used as predictive disease classifier for the outcome of pigmentation. Majority of patients in this study (339 patients) had dark skin phototypes (3 and 4). Post- acne hyperpigmentation was seen in more than 80% of patients. Females, darker skin color, severe acne, facial sites, and excessive sunlight exposure, squeezing or scratching lesions are important risk factors for post-acne hyperpigmentation. Post-acne hyperpigmentation is multifactorial. Several factors implicated in PAH are modifiable by adequate patient education (lesion trauma, excessive sunlight exposure). The use of ANN was helpful in predicting appearance of post-acne hyperpigmentation based on identified risk factors.

An in vivo model of postinflammatory hyperpigmentation and erythema: clinical, colorimetric and molecular characteristics

BACKGROUND

Postinflammatory hyperpigmentation (PIH) is a common, acquired pigmentary disorder of the skin associated with significant quality-of-life impairment, especially in individuals with skin of colour. Current treatment for PIH is limited, largely due to a poor understanding of disease pathogenesis and the lack of a representative disease model.

OBJECTIVES

This study is intended to further develop, update and validate our previously designed in vivo model of acne-induced PIH/postinflammatory erythema (PIE) using different concentrations of trichloroacetic acid (TCA), a medium-depth chemical peel.

METHODS

Twenty-nine patients with skin types II-VI and clinician-confirmed presence of two or more truncal acne pustules and PIH/PIE were included. On the basis of Investigator's Global Assessment (IGA), clinical polarized photography (CPP), colorimetry and Skindex, we experimentally determined an optimum TCA concentration and assessed our model's ability to exhibit a dose-response relationship between degree of inciting insult and severity of resulting pigmentation. We also performed differential microRNA profiling and pathway analysis to explore the potential of microRNAs as molecular adjuncts to our model.

RESULTS

Application of TCA 30% produced lesions indistinguishable from acne-induced PIH and PIE lesions on the basis of colorimetry data without causing epidermal necrosis. Application of progressively increasing TCA doses from 20% to 30% resulted in concentration-dependent increases in CPP, IGA and colorimetry scores at all timepoints during the study. miRNA-31 and miRNA-23b may play a role in PIH pathogenesis, although further validation is required.

CONCLUSIONS

Our TCA-based in vivo model, using TCA concentrations between 20% and 30% with an optimum of 30%, enables the quantitative assessment of the pigmentary response to varying degrees of cutaneous inflammation in a fashion that mirrors natural acne-induced PIH and PIE.

Topical Cyperus rotundus essential oil for treatment of axillary hyperpigmentation: a randomized, double-blind, active- and placebo-controlled study

BACKGROUND

The oil of the grass Cyperus rotundus (purple nutsedge) is an effective and safe treatment option for a variety of conditions. It has anti-inflammatory and antipigmenting properties. There have been no clinical trials comparing topical C. rotundus oil with skin-lightening treatments for axillary hyperpigmentation.

AIM

To assess the efficacy of C. rotundus essential oil (CREO) in treating axillary hyperpigmentation, and compare with another active treatment hydroquinone (HQ) and a placebo (cold cream) in this study.

METHODS

The study included 153 participants, who were assigned to one of three study groups: CREO, HQ group or placebo group. A tri-stimulus colorimeter was used to assess pigmentation and erythema. Two independent experts completed the Physician Global Assessment, and the patients completed a self-assessment questionnaire.

RESULTS

CREO had significantly (P < 0.001) better depigmenting effects than HQ. CREO and HQ did not differ significantly in terms of depigmentation effects (P > 0.05); however, there were statistically significant differences in anti-inflammatory effects and decrease in hair growth (P < 0.05) in favour of CREO.

CONCLUSIONS

CREO is a cost-effective and safe treatment for axillary hyperpigmentation.

Topical treatment for postinflammatory hyperpigmentation: a systematic review

BACKGROUND

Topical measures are the mainstay treatment for postinflammatory hyperpigmentation (PIH). Numerous studies have assessed the efficacy of topical medications for the treatment of PIH, but few have evaluated the quality of evidence supporting these topical therapies. We performed a systematic review to evaluate the evidence of topical treatments for PIH.

METHODS

We included English-language studies that evaluated topical medications for PIH. We searched PubMed, MEDLINE, and EMBASE from conception to March 29 2021. We used the modified Grading of Recommendations, Assessment, Development and Evaluation scale (GRADE) scale to assess quality of evidence.

RESULTS

Forty-seven of 1,224 studies with 1,853 subjects were included. Topical agents with high-quality studies included retinoids, hydroxy acids, corticosteroids, thiamidol, niacinamide and plant-derived products. Sunscreens with SPF30 or greater was recommended in almost every study. Common side effects included desquamation, burning, stinging, dryness, and pruritus.

CONCLUSIONS

Retinoids, hydroxy acids and broad-spectrum sunscreen were supported by the greatest number of high-quality studies. Ongoing inflammation may be subtle, especially in darker skin phenotypes. Herein, we proposed an evidence-based algorithm for PIH based on the high-quality studies. There is a need to adopt a validated outcome measure for PIH to better compare efficacy between various treatments in future studies.

Identification of the fate and regenerative mechanism of zebrafish melanocyte progenitor cells and melanocytes after laser-induced pigment ablation

BACKGROUND AND OBJECTIVES

Lasers are known to be the most effective treatment modality for pigmentary skin diseases. However, melanocytes and melanin pigment often recur or leave post-inflammatory hyperpigmentation after the laser procedure. Studies have reported on the role of progenitor cells in pigment cell regeneration, which can be constantly replenished through mitosis. However, the response of unpigmented melanocyte progenitor cells to laser treatment is poorly understood. In this study, we used adult zebrafish skin as the melanocyte regenerative system and examined the response of melanocyte progenitor cells to laser photothermolysis.

MATERIALS AND METHODS

The two groups of adult zebrafish were irradiated with 1064 nm wavelength laser system of Q-switched neodymium:yttrium-aluminum-garnet (Nd:YAG) laser with 0.3 or 0.7 J·cm^-2 . We compared the regeneration of pigment at different energy levels by measuring new melanocyte counts and pigment area. We traced and quantitatively compared the melanocyte lineage cells by immunohistochemical staining using specific markers such as sox10, mitfa, and dct during the regeneration process. Three repetitive laser ablations were also held to test the postinflammatory hyperpigmentation.

RESULTS

After the laser ablation of melanocytes, most of the new melanocytes appeared between Days 5 and 10. In high-energy irradiation of 0.7 J·cm^-2 , the unpigmented mitfa-expressing cells showed significant decrease (p < 0.05) and showed delay in the differentiation process of melanocyte lineage cells. After repeated laser irradiation, hyperpigmentation did not appear and the final recovery ratio of the pigmented area was 87.5% and 75.3% at the 0.3 and 0.7 J·cm^-2 energy levels, respectively.

CONCLUSION

We suggest that laser treatment overcoming the recurrence should be planned based on the adequate energy level targeting the melanocyte progenitor cells. High-energy irradiation may induce apoptosis of progenitor cells and delay their process of differentiation. Short-term repetitive sessions of laser therapy can reduce the pigmentation in the long-term observation.

Participation of keratinocyte- and fibroblast-derived factors in melanocyte homeostasis, the response to UV, and pigmentary disorders

Human epidermal melanocytes play a central role in sensing the environment and protecting the skin from the drastic effects of solar ultraviolet radiation and other environmental toxins or inflammatory agents. Melanocytes survive in the epidermis for decades, which subjects them to chronic environmental insults. Melanocytes have a poor self-renewal capacity; therefore, it is critical to ensure their survival with genomic stability. The function and survival of melanocytes is regulated by an elaborate network of paracrine factors synthesized mainly by epidermal keratinocytes and dermal fibroblasts. A symbiotic relationship exists between epidermal melanocytes and keratinocytes on the one hand, and between melanocytes and dermal fibroblasts on the other hand. Melanocytes protect epidermal keratinocytes and dermal fibroblasts from the damaging effects of solar radiation, and the latter cells synthesize biochemical mediators that maintain the homeostasis, and regulate the stress response of melanocytes. Disruption of the paracrine network results in pigmentary disorders, due to abnormal regulation of melanin synthesis, and compromise of melanocyte survival or genomic stability. This review provides an update of the current knowledge of keratinocyte- and fibroblast-derived paracrine factors and their contribution to melanocyte physiology, and how their abnormal production is involved in the pathogenesis of common pigmentary disorders.

Prophylaxis of Post-Inflammatory Hyperpigmentation From Energy-Based Device Treatments: A Review

Post-inflammatory hyperpigmentation (PIH) is an acquired hypermelanosis that can result from inflammatory dermatologic disease, trauma, or iatrogenesis from procedures. This condition disproportionately affects individuals with skin of color, and it can place a significant psychosocial burden on affected patients. The management of PIH is, therefore, of great interest to clinicians, especially dermatologists. The treatment of established PIH has long been a principal focus within the literature, with publications on the topic outnumbering publications on prophylaxis of PIH. Prophylaxis strategies to prevent PIH vary greatly in clinical practice, likely due to the absence of an evidence-based consensus. Published approaches to PIH prophylaxis include pretreatment (topical alpha hydroxy acids, retinoids, hydroquinone, and brimonidine) and post-treatment strategies (photoprotection, corticosteroids, and tranexamic acid). This review will examine the current literature on prophylaxis of PIH from energy-based device treatments.

FGIN-1-27 Inhibits Melanogenesis by Regulating Protein Kinase A/cAMP-Responsive Element-Binding, Protein Kinase C-β, and Mitogen-Activated Protein Kinase Pathways

FGIN-1-27 is a synthetic mitochondrial diazepam binding inhibitor receptor (MDR) agonist that has demonstrated pro-apoptotic, anti-anxiety, and steroidogenic activity in various studies. Here we report, for the first time, the anti-melanogenic efficacy of FGIN-1-27 in vitro and in vivo. FGIN-1-27 significantly inhibited basal and α-melanocyte-stimulating hormone (α-MSH)-, 1-Oleoyl-2-acetyl-sn-glycerol (OAG)- and Endothelin-1 (ET-1)-induced melanogenesis without cellular toxicity. Mushroom tyrosinase activity assay showed that FGIN-1-27 did not directly inhibit tyrosinase activity, which suggested that FGIN-1-27 was not a direct inhibitor of tyrosinase. Although it was not capable of modulating the catalytic activity of mushroom tyrosinase in vitro, FGIN-1-27 downregulated the expression levels of key proteins that function in melanogenesis. FGIN-1-27 played these functions mainly by suppressing the PKA/CREB, PKC-β, and MAPK pathways. Once inactivated, it decreased the expression of MITF, tyrosinase, TRP-1, TRP-2, and inhibited the tyrosinase activity, finally inhibiting melanogenesis. During in vivo experiments, FGIN-1-27 inhibited the body pigmentation of zebrafish and reduced UVB-induced hyperpigmentation in guinea pig skin, but not a reduction of numbers of melanocytes. Our findings indicated that FGIN-1-27 exhibited no cytotoxicity and inhibited melanogenesis in both in vitro and in vivo models. It may prove quite useful as a safer skin-whitening agent.

Q-Switched Nd:YAG (532 nm) Laser Versus Intra-Dermal Tranexamic Acid for Treatment of Facial Ephelides: A Split Face, Randomized, Comparative Trial

BACKGROUND AND OBJECTIVES

To compare the efficacy and safety of intradermal injection of tranexamic acid (TXA) versus Q switched (QS) KTP (532 nm) in the treatment of facial ephelides.

STUDY DESIGN/MATERIALS AND METHODS

A randomized comparative split-face study included a total of 30 female patients with bilateral facial ephelides. One cheek was treated by intra-dermal TXA injections and the other was treated by QS-KTP (532 nm). Patient assessment was performed by photography, pigmentation area, severity index and spectrophotometry at baseline, 1 week after treatment, and 2 months after treatment.

RESULTS

A significant difference was found between both sides regarding the percentage change of pigmentation area, severity score (PSI) and melanin index (MI) after treatment and during follow up, favoring laser (P = 0.001). PSI decreased after treatment by 66.5% and 15.4% (laser and TXA sides respectively), further decrease after follow-up was 69.4% with laser and 26.1% with TXA. MI improved by 3.7% after KTP laser to 7.7% after follow-up and by 2.4% after TXA injections to 6.5% after follow-up. Four patients developed post-inflammatory hyperpigmentation following QS-KTP.

CONCLUSION

QS-KTP laser is superior to intradermal TXA injection in the treatment of facial ephelides. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Isoliquiritigenin inhibits melanogenesis, melanocyte dendricity and melanosome transport by regulating ERK-mediated MITF degradation

Isoliquiritigenin (ISL), a flavonoid component from the hydrolysis products of licorice root. It has been reported that ISL inhibited melanogenesis by suppressing the tyrosinase activity in human melanocytes. Recently, ISL was found to induce melanin degradation in human epidermal keratinocytes. However, the role of ISL in pigmentation is not fully understood. In the current study, we aimed to investigate the effects of ISL on pigmentation, and further explored the underlying mechanism. Our results suggested that ISL suppressed basal and α-MSH-, ACTH- and UV-induced melanin synthesis, in addition to inhibiting melanocyte dendricity and melanosome transport. ISL played these roles mainly by activating the extracellular signal-regulated protein kinase pathway. Once activated, it induced microphthalmia-associated transcription factor degradation and decreased the expression of tyrosinase, TRP-1, DCT, Rab27a and Cdc42, finally inhibited melanogenesis, melanocyte dendricity and melanosome transport. Our findings suggested that ISL exhibited no cytotoxicity in our research, it may prove quite useful as a safer natural skin-whitening agent.

IFN-γ inhibits 5-HT-induced melanin biosynthesis via downregulation of 5-HT receptors in vivo/in vitro

Hypopigmentation disorders, such as vitiligo, are difficult for treatment due to complicated pathogenesis, resulting from multiple factors including neural and immune elements. 5-HT and IFN-γ both play crucial roles in these skin diseases. However, the interactions between 5-HT and IFN-γ in regulation of melanogenesis is still unknown. Our study aimed at exploring whether IFN-γ affects 5-HT-induced melanogenesis and searching the mechanism. In our study, IFN-γ attenuated 5-HT-induced pigmentation and green fluorescent protein (GFP) expression in zebrafishes. In addition, we found that IFN-γ decreased serum serotonin levels as well as the cutaneous expression of tryptophan hydroxylase 1 (TPH1), 5-HT1A receptor (5-HT1AR) and 5-HT1B receptor (5-HT1BR) in C57BL/6 mice. Moreover, IFN-γ attenuated 5-HT-induced melanin biosynthesis as well as the expression of 5-HT1AR, 5-HT1BR and 5-HT2A receptor (5-HT2AR) in B16F10 cells, which blocked by interferon-γ receptor 1 and interferon-γ receptor 2 (IFNGR1/IFNGR2) antibodies. In summary, IFN-γ not only affects melanogenesis alone, but also inhibits 5-HT response on melanin biosynthesis. Mediated by IFNGR1/IFNGR2, IFN-γ downregulated 5-HT receptors expression, which directly affect 5-HT-induced melanin biosynthesis. Our work may give insights into the drug development of hypopigmentation disorders with neuro-immune derangement.

The physiology of melanin deposition in health and disease

Eumelanin is the major pigment responsible for human skin color. This black/brown pigment is localized in membrane-bound organelles (melanosomes) found in specialized cells (melanocytes) in the basal layer of the epidermis. This review highlights the steps involved in melanogenesis in the epidermis and the disorders in skin pigmentation that occur when specific steps critical for this process are defective. Melanosomes, which contain tyrosinase, a major enzyme involved in melanin synthesis, develop through a series of steps in the melanocyte. They are donated from the melanocyte dendrites to the surrounding keratinocytes in the epidermis. In the keratinocytes, the melanosomes are found singly or packaged into groups, and as the keratinocytes move upward in the epidermis, the melanosomes start to degrade. This sequence of events is critical for melanin pigmentation in the skin and can be influenced by genetic, hormonal, and environmental factors, which all play a role in levels of melanization of the epidermis. The effects these factors have on skin pigmentation can be due to different underlying mechanisms involved in the melanization process leading to either hypo- or hyperpigmentary disorders. These disorders highlight the importance of mechanistic studies on the specific steps involved in the melanization process.

The ultraviolet B inflammation model: Postinflammatory hyperpigmentation and validation of a reduced UVB exposure paradigm for inducing hyperalgesia in healthy subjects

Background

Pain models are commonly used in drug development to demonstrate analgesic activity in healthy subjects and should therefore not cause long‐term adverse effects. The ultraviolet B (UVB) model is a model for inflammatory pain in which three times the minimal erythema dose (3MED) is typically applied to induce sensitization. Based on reports of long‐lasting postinflammatory hyperpigmentation (PIH) associated with 3MED, it was decided to investigate the prevalence of PIH among subjects who were previously exposed to 3MED at our research centre. In addition, re‐evaluation of the UVB inflammation model using a reduced exposure paradigm (2MED) was performed in healthy subjects.

Methods

In the first study, all 142 subjects previously exposed to 3MED UVB were invited for a clinical evaluation of PIH. In the second study, 18 healthy subjects were exposed to 2MED UVB, and heat pain detection threshold (PDT) and PIH were evaluated.

Results

In total, 78 of the 142 subjects responded. The prevalence of PIH among responders was 53.8%. In the second study, we found a significant and stable difference in PDT between UVB‐exposed and control skin 3 hr after irradiation; 13 hr post‐irradiation, the least squares mean estimate of the difference in PDT ranged from −2.6°C to −4.5°C (p < 0.0001). Finally, the prevalence of PIH was lower in the 2MED group compared to the 3MED group.

Conclusions

The 3MED model is associated with a relatively high prevalence of long‐lasting PIH. In contrast, 2MED exposure produces stable hyperalgesia and has a lower risk of PIH and is therefore recommended for modelling inflammatory pain.

Significance

Postinflammatory hyperpigmentation is an unwanted long‐term side effect associated with the UVB inflammation model using the 3× minimal erythema dose (3MED) paradigm. In contrast, using a 2MED paradigm results in hyperalgesia that is stable for 36 hr and has a lower risk of inducing postinflammatory hyperpigmentation.

R-Fluoxetine Increases Melanin Synthesis Through a 5-HT1A/2A Receptor and p38 MAPK Signaling Pathways

Fluoxetine, a member of the class of selective serotonin reuptake inhibitors, is a racemic mixture and has an anxiolytic effect in rodents. Previously, we have shown that fluoxetine can up-regulate melanin synthesis in B16F10 melanoma cells and normal human melanocytes (NMHM). However, the role of r-fluoxetine and s-fluoxetine, in the regulation of melanin synthesis, is still unknown. Here, we show how r-fluoxetine plays a critical role in fluoxetine enhancing melanogenesis, both in vivo and vitro, by up-regulating tyrosinase (TYR) and the microphthalmia-associated transcription factor (MITF) expression, whereas, s-fluoxetine does not show any effect in the vivo and vitro systems. In addition, we found that r-fluoxetine induced melanin synthesis through the serotonin1A receptor (5-HT1A) and serotonin 2A receptor (5-HT2A). Furthermore, r-fluoxetine increased the phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK), without affecting the phosphorylation of extracellularly responsive kinase (ERK1/2) and c-Jun N-terminal kinase (JNK). These data suggest that r-fluoxetine may be used as a drug for skin hypopigmentation disorders.

A Newly Authenticated Compound from Traditional Chinese Medicine Decoction Induces Melanogenesis in B16-F10 Cells by Increasing Tyrosinase Activity

Vitiligo is a kind of skin dysfunction on melanogenesis. The highly prevalent, chronic, and distinctive complexion changes on patients have imposed enormous psychic and economic burden on both individuals and society. Traditional Chinese Medicine (TCM) is a kind of precious source on chronic disease treatment, including skin dysfunctional diseases. In our previous study, a new compound named apigenin-7-butylene glucoside has been authenticated and purified from a prescription of Chinese traditional medicine formula which has been used clinically in vitiligo treatment. The aim of this work is to evaluate the effects of this compound on melanogenesis using melanoma cell B16-F10 in vitro. The results showed that apigenin-7-butylene glucoside had almost no cytotoxicity on B16-F10 cells within a lower dose of 5.0 μg ml⁻¹ and enhanced the melanin level to about 41% and tyrosinase activity to 1.32-fold when compared with controls. The compound showed minor cytotoxicity to B16-F10 cells at the higher concentration of 10 μg ml⁻¹ and 50 μg ml⁻¹, the inhibition rate was 8.4% and 11.8%, and the melanin level and tyrosinase activity showed a decreased trend because of the lower cell number at the higher concentrations. The results indicated that apigenin-7-butylene glucoside was safe to B16-F10 cells within a lower concentration, <5.0 μg ml⁻¹. Incubated with 5.0 ug ml⁻¹of apigenin-7-butylene glucoside for 48 hours, the mRNA and protein levels of Tyr, Trp-1, and Trp-2 genes were all increased except Mitf in B16-F10 cells. The stimulation of apigenin-7-butylene glucoside on melanogenesis of B16-F10 cells through Tyr, Trp-1, and Trp-2 pathway highlighted the potential usage of the compound in vitiligo treatment.

Vesicular carriers containing phenylethyl resorcinol for topical delivery system; liposomes, transfersomes and invasomes

Topical administration of phenylethyl resorcinol (PR) has attracted much attention as skin lightening agent with potent anti-tyrosinase activity. Two novel types of elastic carriers were developed to overcome the limitation of PR as topical delivery by increasing the solubility, stability and decreasing skin irritation compared to conventional liposomes. In addition, it also promotes skin penetration of PR to reach deep skin layer at the target site. The lead formulations were obtained from the invasomes containing 1% (w/v) d-limonene mixed with 10% (v/v) absolute ethanol as the skin enhancer, and transfersomes containing 15% (w/w) sodium deoxycholate (SDC) as edge activator. All formulations gave a vesicle size < 500 nm, polydispersity index (PDI) < 0.3, high zeta potential, entrapment efficiency > 50%, and good stability on storage at 30 °C at 75% RH for 4 months. Transfersomes have a lower degree of deformability (6.63%) than invasomes (25.26%). In contrast, the liposomes as rigid vesicles do not show a deformable property. This characteristic affects the skin permeation, and thus, transfersomes with high elastic property provided a significantly higher cumulative amount, steady state flux (J ss) and permeability coefficient (Kp ) compared to other formulations. However, in vitro PR accumulation in full-thickness newborn pig skin demonstrated that the application of elastic carrier formulations gave significantly higher accumulation than liposomes, and gave anti-tyrosinase activity up to 80%. These results are straightforwardly related to the results of cellular level study. Transfersomes and invasomes showed higher tyrosinase inhibition activity and melanin content reduction when compared to liposomes in B16 melanoma cells. In addition, acute irritation test in rabbits confirmed that these formulations are safe for skin application. Therefore, elastic vesicle carriers have the efficiency to deliver PR into the deep skin in both quantity and effectiveness which are better than conventional liposomes and appropriate for a skin lightening product.

Effect of Aurea Helianthus stem extract on anti-melanogenesis

Aurea Helianthus (AH), also known as wild confederate rose or golden sunflower, is a curative herb. It has been used as a medicinal material in China due to its anti-inflammatory, immune regulatory, and anti-oxidant activities. However, its melanogenic effect on skin has not been sufficiently investigated. In this study, we tested whether AH has melanogenic inhibitory activities for the development of effective skin whitening agent. The extract showed inhibition of melanin synthesis and reduced the oxidation of 3, 4-dihydroxyphenilalanine (DOPA) to o-dopaquinone. Additionally, AH downregulated the levels of microphthalmia-associated transcription factor (MITF), tyrosinase and tyrosinase related proteins (TRPs), suggesting that AH has inhibitory effects on melanogenesis. Analysis of the components of AH showed that it contained paprazine and trans-N-feruloyltyramine (FA). We confirmed that the effect of AH resulted from paprazine and FA. Therefore, AH might have potential as an effective candidate for skin whitening.

Postinflammatory Hyperpigmentation: Epidemiology, Clinical Presentation, Pathogenesis and Treatment

Postinflammatory hyperpigmentation (PIH) is a reactive hypermelanosis that develops following cutaneous inflammation. Common causes of PIH include intrinsic skin conditions (e.g., acne and eczema) as well as external insults to the skin, such as burn injuries and dermatologic procedures. PIH more commonly occurs in individuals with darker skin, for whom it is often a source of significant psychological distress. Several therapeutic modalities are available for the treatment of PIH, including topical agents, chemical peels, and energy-based devices. We review the epidemiology, clinical presentation, pathogenesis, and treatment of PIH.

Melanopsin and rhodopsin mediate UVA-induced immediate pigment darkening: Unravelling the photosensitive system of the skin

The mammalian skin has a photosensitive system comprised by several opsins, including rhodopsin (OPN2) and melanopsin (OPN4). Recently, our group showed that UVA (4.4 kJ/m²) leads to immediate pigment darkening (IPD) in murine normal and malignant melanocytes. We show the role of OPN2 and OPN4 as UVA sensors: UVA-induced IPD was fully abolished when OPN4 was pharmacologically inhibited by AA9253 or when OPN2 and OPN4 were knocked down by siRNA in both cell lines. Our data, however, demonstrate that phospholipase C/protein kinase C pathway, a classical OPN4 pathway, is not involved in UVA-induced IPD in either cell line. Nonetheless, in both cell types we have shown that: a) intracellular calcium signal is necessary for UVA-induced IPD; b) the involvement of CaMK II, whose inhibition, abolished the UVA-induced IPD; c) the role of CAMK II/NOS/sGC/cGMP pathway in the process since inhibition of either NOS or sGC abolished the UVA-induced IPD. Taken altogether, we show that OPN2 and OPN4 participate in IPD induced by UVA in murine normal and malignant melanocytes through a conserved common pathway. Interestingly, upon knockdown of OPN2 or OPN4, the UVA-driven IPD is completely lost, which suggests that both opsins are required and cooperatively signal in murine both cell lines. The participation of OPN2 and OPN4 system in UVA radiation-induced response, if proven to take place in human skin, may represent an interesting pharmacological target for the treatment of depigmentary disorders and skin-related cancer.

Interleukin-22 participates in the inflammatory process of vitiligo

Vitiligo is an acquired depigmentary skin inflammatory disorder. The pathogenesis of inflammatory skin disease involves the release of cytokines from keratinocytes, including interleukin (IL)-1β. IL-22 belongs to a family of cytokines structurally related to IL-10, including IL-19, IL-20, IL-24, and IL-26. In contrast to IL-10, IL-22 has proinflammatory activities. Among skin cell populations only keratinocytes are the major targets of IL-22. In the present study, we demonstrated that IL-22 promoting IL-1β secretion from keratinocytes via the Reactive oxygen species (ROS)-NOD-like receptor family, pyrin domain containing 3 (NLRP3)-caspase-1 pathway. It inhibited the expression of protease-activated receptor-2 (PAR-2) of keratinocytes. However, IL-22 had no direct effect on normal human foreskin-derived epidermal melanocytes (NHEM). Considering the closely connection between keratinocytes and melanocytes, and the ability of keratinocytes to produce a plethora of cytokines, in the present work, we examined whether IL-22 could regulate melanocytes functions by keratinocytes participation. Keratinocytes were exposed to IL-22 and the conditional medium was collected. The effect of conditional medium on melanocytes was studied. The expressions of relative proteins were assessed by western blot. Influence of conditional medium on NHEM migration was assessed by Transwell method and the apoptosis by flow cytometry analysis. The IL-22-treating keratinocytes conditional medium inhibited melanogenesis and restrained the expressions of Rab GTPases of NHEM. In addition, the conditional medium suppressed melanocytes migration and induced apoptosis. Our results collectively indicated that IL-22 may potentiate IL-1β-mediated skin inflammation and result in participating in the inflammatory pathogenesis of vitiligo.

Investigation of the pro-apoptotic effects of arbutin and its acetylated derivative on murine melanoma cells

Arbutin, a natural polyphenol isolated from the bearberry plant Arctostaphylos uvaursi, possesses whitening and anticancer properties. The effects of arbutin on melanogenesis and its pro-apoptotic effect on B16 murine melanoma cells have not yet been reported. In the present study, acetylated arbutin was prepared in order to improve the biological effects of arbutin, and it was found to significantly inhibit the biosynthesis of melanin and tyrosinase activity compared with parent arbutin in B16 murine melanoma cells. Interestingly, only acetylated arbutin strongly inhibited B16 murine melanoma cell migration in a dose-dependent manner. Both arbutin and acetylated arbutin significantly reduced cell viability, promoted cell apoptosis, caused G1 cell cycle arrest and induced mitochondrial disruption in B16 murine melanoma cells. Furthermore, reduced expression of B-cell lymphoma‑extra large (Bcl-xL) and Bcl-2 were observed in arbutin- and acetylated arbutin-treated cells. Therefore, arbutin and acetylated arbutin were found to exert pro-apoptotic effects on B16 murine melanoma cells, mediated through the mitochondrial pathway. The findings of the present study also support the use of acetylated arbutin as a new potential candidate agent for skin whitening and melanoma treatment.

Medical and Maintenance Treatments for Vitiligo

Medical treatments alone, or in combination with phototherapy, are key approaches for treating nonsegmental vitiligo and, to a lesser extent, segmental vitiligo. The treatments are useful for halting disease progression and have been proven effective for inducing repigmentation and decreasing risk of relapses. Although the treatments have side effects and limitations, vitiligo often induces a marked decrease in quality of life and in most cases the risk:benefit ratio is in favor of an active approach. Systemic and topical agents targeting the pathways involved in loss of melanocytes and in differentiation of melanocyte stem cells should provide more effective approaches in the near future.

Postinflammatory hyperpigmentation: A comprehensive overview: Epidemiology, pathogenesis, clinical presentation, and noninvasive assessment technique

Postinflammatory hyperpigmentation (PIH) commonly occurs after various endogenous and exogenous stimuli, especially in dark-skinned individuals. PIH is one of the most common complications of procedures performed using laser and other light sources. The severity of PIH is determined by the inherent skin color, degree and depth of inflammation, degree of dermoepidermal junction disruption, inflammatory conditions, and the stability of melanocytes, leading to epidermal and dermal melanin pigment deposition. The depth of melanin pigment is the key factor to predict prognosis and treatment outcome. Epidermal hyperpigmentation fades more rapidly than dermal hyperpigmentation. Various inflammatory disorders can eventually result in PIH. The evaluation of pigmentation using noninvasive tools helps define the level of pigmentation in the skin, pigmentation intensity, and guides therapeutic approaches. This first article in this 2-part series discusses the epidemiology, pathogenesis, etiology, clinical presentation, differential diagnoses, and investigation using noninvasive assessment techniques that objectively determine the details of pigmentation.