UVB-induced Hyperpigmentation Research Articles

The amino acid transporter SLC16A10 promotes melanogenesis by facilitating the transportation of phenylalanine.

Phenylalanine is a crucial amino acid in the process of melanogenesis. However, the exact mechanism by which it is transported into melanocytes has not been disclosed. The aim of this study was to identify and examine the key transporters that are responsible for phenylalanine transportation and evaluate their significance in melanogenesis. The amino acid transporter SLC16A10 was found to be up-regulated in both melasma (GSE72140) and sun-exposed skin (GSE67098). The protein levels of SLC16A10 were proportional to the melanin content in melanocytic nevi, indicating that SLC16A10 was related to melanogenesis. After SLC16A10 overexpression, melanin increased significantly in MNT1 cells. Meanwhile, the expression of melanogenesis-related proteins such as TYR and TYRP1 increased, while their RNA levels did not change. Transcriptomics data indicated that SLC16A10 can enhance the function of ribosome. Furthermore, targeted metabolomics data and ELISA results demonstrated SLC16A10 mainly affected the transport of phenylalanine into the cells. Then, phenylalanine was added to the cell culture medium after SLC16A10 overexpression, melanin synthesis in cells furtherly increased, which verified that SLC16A10 enhances melanogenesis by promoting the uptake of phenylalanine. Finally, we found that SLC16A10 expression increased after UVB irradiation. Knockdown SLC16A10 reduced UVB-induced melanin production and phenylalanine uptake by cells. In summary, SLC16A10 enhances melanogenesis by promoting the uptake of phenylalanine, and upregulation SLC16A10 is likely responsible for the UVB-induced hyperpigmentation as well.

Fast freezing inhibits melanin synthesis of melanocytes by modulating the Wnt/β-catenin signalling pathway.

Skin hyperpigmentation is mainly caused by excessive synthesis of melanin; however, there is still no safe and effective therapy for its removal. Here, we found that the dermal freezer was able to improve UVB-induced hyperpigmentation of guinea pigs without causing obvious epidermal damage. We also mimic freezing stimulation at the cellular level by rapid freezing and observed that freezing treatments <2.5 min could not decrease cell viability or induce cell apoptosis in B16F10 and Melan-A cells. Critically, melanin content and tyrosinase activity in two cells were greatly reduced after freezing treatments. The dramatic decrease in tyrosinase activity was associated with the downregulation of MITF, TYR, TRP-1 and TRP-2 protein expression in response to freezing treatments for two cells. Furthermore, our results first demonstrated that freezing treatments significantly reduced the levels of p-GSK3β and β-catenin and the nuclear accumulation of β-catenin in B16F10 and Melan-A cells. Together, these data suggest that fast freezing treatments can inhibit melanogenesis-related gene expression in melanocytes by regulating the Wnt/β-catenin signalling pathway. The inhibition of melanin production eventually contributed to the improvement in skin hyperpigmentation induced by UVB. Therefore, fast freezing treatments may be a new alternative of skin whitening in the clinic in the future.

Alternative approach for delivery of a depigmenting agent via dissolving microneedle arrays: Formulations and in vivo efficacy

Dissolving microneedle (DMN) arrays have gained attention as a carrier for cosmetic or pharmaceutical active compounds since they can bypass the stratum corneum to ensure delivery beyond the epidermis. In this study, we were curious whether using sodium hyaluronate (HYA) alone would be enough to fabricate DMN arrays that could yield the effective intradermal delivery and we aimed to fabricate a new concept to deliver a depigmenting agent for anti-hyperpigmentation. Thus, DMN arrays were cast by HYA with different molecular weights (MWs) and loaded with ethyl ascorbic acid (EAA). Mechanical and biological performances of DMN arrays were investigated both in vitro, ex vivo, and in vivo. The results showed that combinations of two types of HYA provided adjustable mechanical characteristics. The DMN arrays contained low MW HYA, medium MW HYA, and EAA at 70:30:20 gave the optimal in vitro properties and were selected to examine further in UVB-induced hyperpigmentation guinea pigs. The delivery of EAA, whether through the EAA-loaded DMN or the EAA solution on the pretreated skin with blank DMN, resulted in an increase in the whitening index. Hence, these two intradermal approaches demonstrated great promise and effectiveness in combating hyperpigmentation.

Incobotulinum Toxin Type A for Treatment of Ultraviolet-B-Induced Hyperpigmentation: A Prospective, Randomized, Controlled Trial.

Incobotulinum toxin A (IncoBoNT-A) is effective in preventing ultraviolet B (UVB)-induced hyperpigmentation. This prospective, randomized, controlled study aimed to evaluate the effect of IncoBoNT-A on the treatment of UVB-induced hyperpigmentation in 15 volunteers. Five hyperpigmentation squares (2 × 2 cm) were induced by local UVB on the abdomen at baseline. At Day 7, each site was randomized to receive no treatment (control), normal saline, or intradermal IncoBoNT-A injection with 1:2.5, 1:5, and 1:7.5 dilutions (12, 6, and 4 units, respectively). The mean lightness index (L*), hyperpigmentation improvement score evaluated by blinded dermatologists, and participant satisfaction scores were obtained at Days 21, 28, and 35. At Day 21, improvements in mean L* of 1:2.5, 1:5, and 1:7.5 IncoBoNT-A-treated, saline-treated, and control sites were 14.30%, 12.28%, 6.62%, 0.32%, and 4.98%, respectively (p = 0.86). At Day 28, the improvement in mean L* in IncoBoNT-A-treated groups was superior to that in the other groups. In terms of the hyperpigmentation improvement score, 12 participants (80%) experienced better outcomes with the IncoBoNT-A-injected site compared with the other sites. IncoBoNT-A, especially at higher concentrations, showed some positive effects on the treatment of UVB-induced hyperpigmentation. This may serve as an adjuvant treatment for hyperpigmentary conditions that are aggravated by UVB.

UVB-Induced Secretion of IL-1β Promotes Melanogenesis by Upregulating TYR/TRP-1 Expression In Vitro.

Purpose Ultraviolet radiation (UVR) is one of the exogenous stimuli increasing melanogenesis. UV light, especially UVB, is also a potent inducer of epidermal cytokine release. This study is aimed at determining the underlying mechanisms by which UVB-induced cytokines in keratinocytes regulate melanin production in vitro. Methods Expression levels of mRNA for interleukin- (IL-) 1, IL-1β, IL-6, IL-10, IL-17, and tumor necrosis factor-alpha (TNF-α) were measured using RT-qPCR at various time points after UVB irradiation in C57BL/6 mice and HaCaT cells. NaOH lysis and L-dihydroxyphenylalanine (L-DOPA) oxidation method were used to measure melanin content and tyrosinase (TYR) activity, respectively, in melanoma B16 cells. RT-qPCR and Western blot were used to assess mRNA and protein levels of microphthalmia-associated transcription factor (MITF), TYR, tyrosine-related protein-1 (TRP-1), and tyrosine-related protein-2 (TRP-2) in B16 cells. Finally, expression levels of cyclooxygenase-2 (COX-2) mRNA and stem cell factor (SCF) in HaCaT cells were measured following knockdown of IL-1β using siRNA (siIL-1β). Results UVB irradiation increased IL-1β mRNA expression levels in both C57BL/6 mice and HaCaT cells. The melanin content, TYR activity, and expression levels of TYR and TRP-1 were all raised when B16 cells were treated with 4 pg/l of IL-1. Moreover, IL-1β also upregulated the expression levels of SCF and COX-2 in nonirradiated HaCaT cells. Conversely, knockdown of IL-1β attenuated UVB irradiation-induced upregulation of SCF and COX-2 expression in keratinocytes. Conclusions UVB-induced melanogenesis is mediated in part by IL-1β, leading to upregulation of the TYR/TRP1 expression in melanoma B16 cells. IL-1β can also stimulate the expression of COX-2 and SCF in HaCaT cells, which in turn increase melanin synthesis in melanocytes. These results suggest that anti-inflammatory approaches could possibly mitigate UVB-induced hyperpigmentation.

Study of botulinum toxin type A for the treatment of ultraviolet B-induced hyperpigmentation: A prospective, randomized, controlled trial.

Botulinum toxin type A (BTX-A) has been used experimentally under various dermatological conditions. Recent studies have revealed a preventive effect of BTX-A against ultraviolet B (UVB)-induced skin hyperpigmentation. We examined the effect of BTX-A for the treatment of UVB-induced hyperpigmentation in humans. A prospective, double-blind, randomized controlled trial was conducted. UVB irradiation induced five separate hyperpigmented squares on the abdomen. Seven days after irradiation, all squares were randomly assigned to five intervention groups: control, 0.9% normal saline injection, 12 units (1:2.5), 6 units (1:5), and 4 units (1:7.5) of onabotulinum toxin injections. The lightness index (L*), hyperpigmentation improvement score rated by a blinded physician, and participant satisfaction scores were obtained at 14, 21, and 28days after injection. Fifteen participants (mean age 36.9years, Fitzpatrick skin types III-IV) completed the study. The BTX-A (1:2.5)-treated site had a lower degree of hyperpigmentation at all time points, as measured by mean L* and hyperpigmentation improvement scores. However, there were no statistically significant differences between the groups. Participants were most satisfied with the control site. Intradermal BTX-A injection had no therapeutic effect on UVB-induced hyperpigmentation. However, the role of BTX-A injections in the treatment of other hyperpigmentary conditions requires further elucidation.

A Role for NRF2-Signaling in the Treatment and Prevention of Solar Lentigines

Photoaging is premature skin aging resulting from oxidative stress generated by exposure to solar radiation. A key clinical feature is solar lentigines, areas of hyperpigmentation on sun-exposed skin. Skin pigmentation is determined by cross-talk between keratinocytes and melanocytes, which is exquisitely sensitive to oxidative stress. Toll-like receptor (TLR) signaling and NF-E2-related factor 2 (NRF2) signaling, an endogenous antioxidant system, serve as a bridge between the oxidative stress response and immune regulation. Moreover, TLR-mediated induction of IL-6 production has been shown to prevent ultraviolet (UV)-induced hyperpigmentation. Shave biopsies of solar lentigines were obtained from 14 individuals. An additional 7 subjects applied broccoli sprout extract (BSE) containing sulforaphane daily or vehicle on photodamaged skin. Immunofluorescence staining was used to determine total and phosphorylated NRF2 in the lentiginous skin. Dermoscopy and Fontana & Masson staining were used to assess the effect of topical BSE on UV-induced pigmentation. Similar topical treatments were performed in a mouse model of UVB-induced hyperpigmentation utilizing WT, Nrf2-/-, or K14-Cre-ERT2IL-6Rαfl/fl C57BL/6 mice. NRF2 expression is altered in solar lentigines, and UV-induced skin pigmentation in humans could be ameliorated with topical BSE. Corresponding mouse models replicated the authors' clinical findings and identified a potential mechanistic link to IL-6Rα signaling in keratinocytes. The authors' findings suggest that dysregulation of NRF2 signaling is involved in the pathogenesis of UV-induced skin pigmentation and pharmacological activation of NRF2 may represent a potential therapeutic target in photoaging.

The Inhibitory Effect of Curcumin Derivative J147 on Melanogenesis and Melanosome Transport by Facilitating ERK-Mediated MITF Degradation.

The therapeutic use of curcumin and chemically modified curcumin (CMC) for suppressing melanogenesis and tyrosinase activity have been recognized. J147 is a modified version of curcumin with superior bioavailability and stability. However, there is no report about the effects of J147 on pigmentation in vitro and in vivo. In our studies, we investigated the hypopigmentary effects of J147 treatment on melanocytes and explored the underlying mechanism. The present studies suggested that J147 suppressed both basal and α-MSH-induced melanogenesis, as well as decreased melanocyte dendricity extension and melanosome transport. J147 played these roles mainly by activating the extracellular signal-regulated protein kinase (ERK) pathway. Once activated, it resulted in MITF degradation and further down-regulated the expression of tyrosinase, TRP-1, TRP-2, Myosin Va, Rab27a and Cdc42, ultimately inhibited melanin synthesis and melanosome transport. Furthermore, the hypopigmentary effects of J147 were demonstrated in vivo in a zebrafish model and UVB-induced hyperpigmentation model in brown guinea pigs. Our findings also suggested that J147 exhibited no cytotoxicity in vitro and in vivo. Taken together, these data confirmed that J147 may prove quite useful as a safer natural skin-whitening agent.

A single‐blinded, randomized, controlled trial comparing efficacy between low‐fluence alexandrite 755‐nm picosecond laser and low‐fluence neodymium‐doped yttrium aluminum garnet (Nd:YAG) 1064‐nm picosecond laser for the treatment of ultraviolet B‐induced hyperpigmentation

Hyperpigmentation is a common concern of patients in dermatology clinics. Although there are many treatment options, lasers are considered a promising therapy for various hyperpigmentary conditions. This study aims to evaluate the efficacy of alexandrite 755-nm picosecond and neodymium-doped yttrium aluminum garnet (Nd:YAG) 1064-nm picosecond lasers for the treatment of ultraviolet B (UVB)-induced hyperpigmentation in Asians. A randomized, single-blinded study was conducted. UVB-induced hyperpigmentation was performed in three spots by narrowband UVB. After 2weeks, these three spots were allocated into 755-treated, 1064-treated, and control sites. Patients received weekly laser treatments for five sessions. Follow-ups were scheduled at 1 and 2months after the last session. Twenty patients attended the study. Overall, 755-nm and 1064-nm picosecond lasers showed a significant improvement in the mean lightness index (L*) compared to the control site, which started at Day49 and Day77, respectively. The mean L* of the 755-nm-treated site was also higher than that of the 1064-nm-treated site at Day105 (p≤0.001). Initially, the mean L*, physician's visual analog scale (VAS), and patient satisfaction with the 1064-nm picosecond laser were better than those with the 755-nm picosecond laser. Nevertheless, an inversion of the mean L* and VAS was noted at Day49, whereas the mean patient satisfaction was noted at Day77. In the subgroup analysis, a 755-nm picosecond laser effectively treated Fitzpatrick skin types (FPTs) III and IV. However, the mean L* of the 1064-nm picosecond laser was not significantly different from that of the control for FPT4. The alexandrite 755-nm picosecond and Nd:YAG 1064-nm picosecond lasers appear to be effective and safe modalities for treating UVB-induced hyperpigmentation. With the setting employed in this study, the outcome after the 755-nm picosecond laser treatment seemed superior to that of the 1064-nm picosecond laser treatment, especially for FPT4.

Human amniotic stem cells-derived exosmal miR-181a-5p and miR-199a inhibit melanogenesis and promote melanosome degradation in skin hyperpigmentation, respectively

BackgroundHyperpigmentation of skin is caused by an imbalance between the melanosome/melanin synthesis in melanocytes and the melanosome/melanin degradation in keratinocytes. Although studies showed that stem cells play a role in hypopigmentation, the underlying mechanisms are far not elucidated. Human amniotic stem cells (hASCs) including human amniotic mesenchymal stem cells (hAMSCs) and human amniotic epithelial stem cells (hAESCs) were considered to be a promising cell source for stem cells-based therapy of many diseases clinically due to their pluripotent potential, no tumorigenesis and immunogenicity, no ethical issues, and potent paracrine effects. Here, we reported that both hASCs and their conditional medium (CM) had a potent anti-hyperpigmentation in skin in vivo and in vitro.MethodshAESCs and hAMSCs were identified by RT-PCR, flow cytometric analysis and immunofluorescence. Effects of hASCs and hASC-CM on pigmentation were evaluated in B16F10 cells stimulated with α-melanocyte-stimulating hormone (α-MSH), and mouse ears or human skin substitutes treated with ultraviolet radiation B (UVB). Expressions of the key proteins related with melanogenesis and autophagic flux were detected by western blot in B16F10 cells for further exploring the effects and the underlying mechanisms of hAESC-CM and hAMSC-CM on melanogenesis and melanosome degradation. The hAMSCs exosomes-derived miRNAs were determined by sequencing. RT-PCR, western blot, melanin content analysis and luciferase activity assay were used to determine the hypopigmentation of miR-181a-5p and miR-199a.ResultsIn our study, we observed that both hASCs and their CM significantly alleviated the α-MSH in B16F10 cells or UVB-induced hyperpigmentation in mouse ears or human skin substitutes by suppressing melanin synthesis and promoting melanosome degradation in vivo and in vitro. Furthermore, we demonstrated that miR-181a-5p and miR-199a derived from hASCs exosomes remarkably inhibited melanogenesis by suppressing MITF (microphthalmia-associated transcription factor) which is a master regulator for governing melanogenesis and promoting melanosome degradation through activating autophagy, respectively.ConclusionsOur studies provided strong evidence that the conditional medium and exosomes derived from hAMSCs inhibit skin hyperpigmentation by suppressing melanogenesis and promoting melanosome degradation, indicating that the hASCs exosomes or their released microRNAs might be as reagents for cell-free therapy in hyperpigmented disorders clinically.

Marliolide Derivative Induces Melanosome Degradation via Nrf2/p62-Mediated Autophagy.

Nuclear factor erythroid 2-related factor 2 (Nrf2), which is linked to autophagy regulation and melanogenesis regulation, is activated by marliolide. In this study, we investigated the effect of a marliolide derivative on melanosome degradation through the autophagy pathway. The effect of the marliolide derivative on melanosome degradation was investigated in α-melanocyte stimulating hormone (α-MSH)-treated melanocytes, melanosome-incorporated keratinocyte, and ultraviolet (UV)B-exposed HRM-2 mice (melanin-possessing hairless mice). The marliolide derivative, 5-methyl-3-tetradecylidene-dihydro-furan-2-one (DMF02), decreased melanin pigmentation by melanosome degradation in α-MSH-treated melanocytes and melanosome-incorporated keratinocytes, evidenced by premelanosome protein (PMEL) expression, but did not affect melanogenesis-associated proteins. The UVB-induced hyperpigmentation in HRM-2 mice was also reduced by a topical application of DMF02. DMF02 activated Nrf2 and induced autophagy in vivo, evidenced by decreased PMEL in microtubule-associated proteins 1A/1B light chain 3B (LC3)-II-expressed areas. DMF02 also induced melanosome degradation via autophagy in vitro, and DMF02-induced melanosome degradation was recovered by chloroquine (CQ), which is a lysosomal inhibitor. In addition, Nrf2 silencing by siRNA attenuated the DMF02-induced melanosome degradation via the suppression of p62. DMF02 induced melanosome degradation in melanocytes and keratinocytes by regulating autophagy via Nrf2-p62 activation. Therefore, Nrf2 activator could be a promising therapeutic agent for reducing hyperpigmentation.

A Study of Botulinum Toxin A for Ultraviolet-Induced Hyperpigmentation: A Randomized Controlled Trial.

Ultraviolet (UV) exposure contributes to skin hyperpigmentation. Recently, botulinum neurotoxin type A (BoNT-A) showed a promising protective effect on UVB-induced hyperpigmentation in both in vitro and animal models. The study aimed to investigate the preventive effect of BoNT-A against UVB-induced hyperpigmentation in human subjects. A prospective, double-blinded, randomized controlled trial was performed in 15 healthy participants. Four separate square areas on the abdomen were randomly injected intradermally with different dilutions of BoNT-A (1:2.5, 1:5, 1:7.5) and normal saline (control). Two weeks after injection, hyperpigmented spots were induced by UVB irradiation at the experimental sites. The lightness index and hyperpigmentation scores from blinded physician and participants were evaluated. Fifteen participants completed the study. One week after UVB irradiation, all BoNT-A-treated sites had a significantly lower degree of hyperpigmentation than the control site in lightness index and hyperpigmentation scores from blinded physician and participants (p < .05). However, no statistically significant difference was observed between different concentrations of BoNT-A. No side effects were observed throughout the study period. Intradermal BoNT-A injection provided a protective effect from UVB-induced hyperpigmentation. It may be used for other hyperpigmentation disorders that are aggravated by UVB.

Combination and efficiency: preparation of dissolving microneedles array loaded with two active ingredients and its anti-pigmentation effects on guinea pigs

Hyperpigmentation is a common skin disorder caused by excessive melanogenesis and uneven dispersion of melanin in the skin. To combine multiple active agents with an efficient transdermal drug delivery system is an effective strategy to combat UV induced skin pigmentation. In this work, Arbutin (Arb) and Vitamin C (Vc) mixed in 1:1 were found to have the greatest inhibition effects on melanogenesis and tyrosinase activity in B16 murine melanoma cells. And hyaluronic acid (HA) based dissolving microneedles array (DMNA) was employed to overcome the skin barriers for improved topical drug delivery, which exhibited the most desirable features, including morphology, mechanical properties, dissolving ability, and the highest drug loading. Furthermore, DMNA could greatly increase the stability of Vc during storage without adding any antioxidant which is an important issue for Vc administration. Pharmacodynamics study showed that DMNA loaded with Arb and Vc could synergistically suppress UVB-induced hyperpigmentation in guinea pig skin. This work provides a promising treatment strategy and solution for skin pigmentation and other skin problems.

Seven traditional Chinese herbal extracts fermented by Lactobacillus rhamnosus provide anti-pigmentation effects by regulating the CREB/MITF/tyrosinase pathway.

Skin pigmentation is resulted from several processes, such as melanin synthesis transportation and abnormal melanin accumulation in keratinocytes. Various studies have suggested that seven traditional Chinese herbal extracts from Atractylodes macrocephala, Paeonia lactiflora, Bletilla striata, Poria cocos, Dictamnus dasycarpus, Ampelopsis japonica and Tribulus terrestris (which we collectively named ChiBai), show several protective effects toward skin-related diseases. Lactobacillus rhamnosus, a lactic acid bacterium, has been reported to treat skin inflammation and atopic dermatitis. In this study, the broth produced by the cofermentation of ChiBai with Lactobacillus rhamnosus was studied for its effects on skin pigmentation through in vitro and in vitro experiments. In the in vitro experiments, we found that the fermented broth of ChiBai (FB-ChiBai) suppressed alpha-melanocyte stimulating hormone (α-MSH)-induced melanogenesis in B16F0 murine melanoma cells without any cytotoxicity at a concentration of 0.5%. FB-ChiBai significantly attenuated melanin production, tyrosinase activities and melanogenesis-related signaling pathways. Treatment with FB-ChiBai also reduced the nuclear translocation and promoter binding activities of MITF. In the in vivo experiments, FB-ChiBai was topically applied to the dorsal skin of C57BL/6J nude mice and concurrently irradiated with UVB, three times a week for 8 weeks. The results indicated that FB-ChiBai alleviated UVB-induced hyperpigmentation by reducing epidermal hyperplasia and inhibiting the CREB/MITF/tyrosinase pathway. In conclusion, our data indicated that the anti-melanogenic effects of FB-ChiBai are mediated by the inhibition of CREB/MITF/tyrosinase signaling pathway. The findings suggest that FB-ChiBai can protect against UV-B irradiation and that it might be used as an agent in cosmetic products to protect against UVB-induced hyperpigmentation.

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.

The regulation of protein kinase casein kinase II by apigenin is involved in the inhibition of ultraviolet B-induced macrophage migration inhibitory factor-mediated hyperpigmentation.

Ultraviolet (UV) radiation elicits melanogenesis and pigmentation in the skin. Apigenin (4',5,7-trihydroxyflavone [AGN]) is a plant flavone contained in various herbs, fruits, and vegetables. We herein investigated antimelanogenic properties of AGN and the molecular mechanisms of the action of AGN. In UVB-treated mice, AGN inhibited cutaneous hyperpigmentation and macrophage migration inhibitory factor (MIF) expression as a melanogenesis-related key factor. In mouse keratinocytes, AGN inhibited the expression of MIF and also the related factors (e.g., stem cell factor and proteinase-activated receptor 2) induced by MIF. In addition to ellagic acid as a casein kinase II (CK2) inhibitor, AGN suppressed CK2 enzymatic activity and UVB-induced CK2 expression and subsequent phosphorylation of IκB and MIF expression. These results suggest that AGN inhibits UVB-induced hyperpigmentation through the regulation of CK2-mediated MIF expression in keratinocytes.

A study of efficacy and safety of high-intensity focused ultrasound for the treatment of melasma in Asians: A single-blinded, randomized, split-face, pilot study.

A recent report suggested potential of high-intensity focused ultrasound in improving UVB-induced hyperpigmentation in patients with Fitzpatrick skin type IV, but reports regarding its efficacy in other hyperpigmented conditions including melasma are lacking. To investigate efficacy and safety of high-intensity focused ultrasound for the treatment of melasma in Asians. Each side of the face of 25 melasma patients was randomized to receive 3-monthly sessions of high-intensity focused ultrasound treatment or serve as control. Lightness index, Melasma Area and Severity Index of malar area (MASIm ) by blinded dermatologists, self-evaluated improvement and satisfaction scales by patients, and side effects were assessed every 4weeks for 20weeks. Twenty-one patients with Fitzpatrick skin type III and IV completed the study. There was a greater reduction of relative lightness index and MASIm after treatment in high-intensity focused ultrasound-treated side. However, there were no statistically significant differences between both sides. More than 50% improvement on treatment side was rated in 11 patients (52.4%). Side effects were minimal. None had worsening of melasma. High-intensity focused ultrasound may be an adjuvant for treatment of melasma. Further studies with larger sample size and proper parameter settings are recommended to determine its efficacy.

766 NRF2-mediated inhibition of UVB-induced hyperpigmentation by topical sulforaphane is dependent on upregulation of IL6Rα expression on keratinocytes

Oxidative stress underlies many hyperpigmentation conditions, such as solar lentigines, melasma, and postinflammatory melanoderma. We previously reported that nuclear factor erythroid 2-related factor 2 (NRF2) signaling, a key redox regulator, is impaired in solar lentigines and topical application of NRF2 agonist sulforaphane (SF) improves hyperpigmentation in photodamaged human skin. Experiments in a mouse model of UVB-induced hyperpigmentation replicated clinical findings and provided evidence for an additional preventative benefit of SF. Interleukin 6 (IL-6) is a pleiotropic cytokine that is rapidly produced by keratinocytes and fibroblasts following UVB exposure. Furthermore, IL-6-/- mice are more sensitive to UVB irradiation. Herein, we report that topical application of 1 μmole SF daily for 5 days a week for a total of 4 weeks upregulated IL-6Rα expression on keratinocytes in C57BL/6 WT mouse skin. To investigate the impact of IL-6Rα signaling on NRF2 mediated prevention of UVB-induced hyperpigmentation, we utilized a tamoxifen-inducible keratinocyte specific IL-6Rα knock out mouse model (K14-Cre-ERT2IL-6Rαfl/fl). Ears of WT (n=14) and K14-Cre-ERT2IL-6Rαfl/fl (n=10) mice were exposed to UVB (80 mJ/cm2) once daily 5 times a week for 2 to 4 weeks. Prior to each UVB treatment, SF was topically applied to one ear and the other received vehicle or no treatment. In K14-Cre-ERT2IL-6Rαfl/fl mice, skin darkness increased by two-fold in half the time required for WT controls (2 versus 4 weeks). Notably, in contrast to WT controls, topical SF failed to prevent UVB-induced hyperpigmentation in K14-Cre-ERT2IL-6Rαfl/fl mice. Taken together, this suggests that the interplay between NRF2 and IL-6Rα signaling is a potential therapeutic target for hyperpigmentation disorders that are induced or exacerbated by UV exposure.

In vitro and in vivo evaluation of MHY908-loaded nanostructured lipid carriers for the topical treatment of hyperpigmentation

Hyperpigmentation disorder, caused by the immoderate performance of tyrosinase, is a major abnormality of human skin. Downregulation of tyrosinase enzyme through tyrosinase inhibitors has emerged as an effective strategy for hyperpigmentation therapy. In this study, a newly synthesized tyrosinase inhibitor (MHY908) was loaded into a nanostructured lipid carrier (MHY908/NLC) for the topical treatment of hyperpigmentation. MHY908/NLCs were prepared by a reverse instilling technique of melt and ultrasonication. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), and transmission electron microscopy (TEM) analyses showed that MHY908 was highly dispersed and encapsulated in NLC in an amorphous state. MHY908/NLCs exhibited a dual drug release kinetic (initial burst release followed by prolonged drug release), higher skin permeation, and significant occlusion effect (in vitro and ex vivo) than MHY908 solution. The anti-melanogenesis activity of MHY908/NLCs in a mouse model of UVB-induced hyperpigmentation was significantly higher than that of MHY908 solution. Furthermore, the in vitro cytotoxicity test revealed the non-toxicity of MHY908/NLCs to healthy fibroblast cells. Therefore, MHY908/NLC could serve as a promising topical delivery system for the treatment of hyperpigmentation.

Osmanthus fragrans Flower Aqueous Extract and its Enriched Acteoside inhibit Melanogenesis and Ultraviolet-induced Pigmentation

The Osmanthus fragrans flower (OFF) is commonly used as an additive for tea in China and as a traditional medicine to treat dysentery, asthma and hepatitis. In the current study, we have acquired the aqueous extract of the dried OFF (OFFE) and determined its enriched acteoside contents. However, whether OFFE and acteoside can modulate melanogenesis and pigmentation has yet to be determined. We here provide novel data revealing that OFFE and acteoside inhibit melanogenesis induced by α-MSH in B16 melanoma cells via the MITF-tyrosinase signaling pathway. Treatment with α-MSH (1μM) enhanced melanin levels and tyrosinase activity, up-regulated the mRNA levels of MITF and tyrosinase and increased the dendritic number in B16 melanoma cells, effects all being intervened by OFFE and acteoside. Of interest, OFFE and acteoside showed no direct inhibition of tyrosinase activity as revealed by our ex vivo tyrosinase activity assay. In addition, OFFE produced a depigmenting action on UVB-induced hyperpigmentation in guinea pigs, as shown by the improved skin brightness and the decreased melanin staining. Our data have demonstrated that OFFE can alter melanogenesis via modulating the MITF-tyrosinase signaling thereby leading to its depigmenting action in the in vivo model. OFFE could be a substitute for acteoside as a promising skin-whitening agent.