Activation of the Mitf promoter by lipid-stimulated activation of p38-stress signalling to CREB

Whitening and Anti-Inflammatory Activities of Exosomes Derived from Leuconostoc mesenteroides subsp. DB-21 Strain Isolated from Camellia japonica Flower

In the present study, we investigated the anti-inflammatory and anti-melanogenic effects of Leuconostoc mesenteroides subsp. DB-21-derived exosomes (DB-21 exosomes), isolated from Camellia japonica flower in lipopolysaccharide (LPS)-induced RAW 264.7 macrophage cells and melanocyte-stimulating hormone (α-MSH)-induced B16F10 melanoma cells. We confirmed that DB-21 exosomes were not toxic to LPS-induced RAW 264.7 macrophage cells and α-MSH-induced B16F10 melanoma cells. Moreover, we confirmed that DB-21 exosomes inhibit the pro-inflammatory cytokines IL-6, IL-1β, TNF-α, PGE2, and the expression of inflammatory factors iNOS and COX-2. We also found that DB-21 exosomes have a concentration-dependent ability to inhibit melanin, TRP-1, TRP-2, tyrosinase, and MITF, which are factors involved in melanogenesis. Additionally, it inhibits the phosphorylation of Akt and GSK-3β, and MAP kinase pathway proteins such as ERK, JNK, and p38. We confirmed that DB-21 exosomes inhibit melanin synthesis in B16F10 cells through various pathways, and based on previous results, they may be used as a functional cosmetic material with anti-inflammatory and anti-melanogenic activities.

Nigella sativa L. seed extract alleviates oxidative stress-induced cellular senescence and dysfunction in melanocytes

Nigella sativa L. seeds have been traditionally utilized in Chinese folk medicine for centuries to treat vitiligo. This study revealed that the ethanolic extract of Nigella sativa L. (HZC) enhances melanogenesis and mitigates oxidative stress-induced cellular senescence and dysfunction in melanocytes. In accordance with established protocols, the ethanol fraction from Nigella sativa L. seeds was extracted, concentrated, and lyophilized to evaluate its herbal effects via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, tyrosinase activity evaluation, measurement of cellular melanin contents, scratch assays, senescence-associated β-galactosidase (SA-β-gal) staining, enzyme-linked immunosorbent assay (ELISA), and Western blot analysis for expression profiling of experimentally relevant proteins. The results indicated that HZC significantly enhanced tyrosinase activity and melanin content while notably increasing the protein expression levels of Tyr, Mitf, and gp100 in B16F10 cells. Furthermore, HZC effectively mitigated oxidative stress-induced cellular senescence, improved melanocyte condition, and rectified various functional impairments associated with melanocyte dysfunction. These findings suggest that HZC increases melanin synthesis in melanocytes through the activation of the MAPK, PKA, and Wnt signaling pathways. In addition, HZC attenuates oxidative damage induced by H2O2 therapy by activating the nuclear factor E2-related factor 2-antioxidant response element (Nrf2-ARE) pathway and enhancing the activity of downstream antioxidant enzymes, thus preventing premature senescence and dysfunction in melanocytes.

Post-translational modification in the pathogenesis of vitiligo

Vitiligo is a chronic dermatological condition marked by the loss of skin pigmentation. Its complex etiology involves multiple factors and has not been completely elucidated. Protein post-translational modification pathways have been proven to play a significant role in inflammatory skin diseases, yet research in the context of vitiligo remains limited. This review focuses on the role of post-translational modifications in vitiligo pathogenesis, especially their impact on cellular signaling pathways related to immune response and melanocyte survival. Current therapeutic strategies targeting these pathways are discussed, emphasizing the potential for novel treatments in vitiligo management.

Exposure to Radiofrequency Electromagnetic Fields Enhances Melanin Synthesis by Activating the P53 Signaling Pathway in Mel-Ab Melanocytes

The skin is the largest body organ that can be physiologically affected by exposure to radiofrequency electromagnetic fields (RF-EMFs). We investigated the effect of RF-EMFs on melanogenesis; Mel-Ab melanocytes were exposed to 1760 MHz radiation with a specific absorption rate of 4.0 W/kg for 4 h/day over 4 days. Exposure to the RF-EMF led to skin pigmentation, with a significant increase in melanin production in Mel-Ab melanocytes. The phosphorylation level of cAMP response element binding protein (CREB) and the expression of microphthalmia-associated transcription factor (MITF), which regulate the expression of tyrosinase, were significantly increased in Mel-Ab after RF-EMF exposure. Interestingly, the expression of tyrosinase was significantly increased, but tyrosinase activity was unchanged in the RF-EMF-exposed Mel-Ab cells. Additionally, the expression of p53 and melanocortin 1 receptor (MC1R), which regulate MITF expression, was significantly increased. These results suggest that the RF-EMF induces melanogenesis by increasing phospho-CREB and MITF activity. Importantly, when Mel-Ab cells were incubated at 38 °C, the melanin production and the levels of tyrosinase significantly decreased, indicating that the increase in melanin synthesis by RF-EMF exposure is not due to a thermal effect. In conclusion, RF-EMF exposure induces melanogenesis in Mel-Ab cells through the increased expression of tyrosinase via the activation of MITF or the phosphorylation of CREB, which are initiated by the activation of p53 and MC1R.

A gain-of-function variant in SREBF1 causes generalized skin hyperpigmentation with congenital cataracts

BACKGROUND

Lipid metabolism has essential roles in skin barrier formation and the regulation of skin inflammation. Lipid homeostasis regulates skin melanogenesis, although the underlying mechanism remains largely unknown. Sterol regulatory element binding protein 1 (SREBP-1) is a key transcription factor essential for cellular lipid metabolism. Loss-of-function variants in SREBF1 are responsible for autosomal-dominant ichthyosis follicularis, alopecia and photophobia syndrome, emphasizing the significance of lipid homeostasis in skin keratinization.

OBJECTIVES

To identify the genetic basis of a new entity featuring diffuse skin hyperpigmentation with congenital cataracts, and to unravel the underlying mechanism for the pathogenesis of the SREBF1 variant.

METHODS

Whole-exome sequencing was performed to identify underlying genetic variants. Quantitative polymerase chain reaction, Western blot and immunofluorescence staining were used to assess the expression and the subcellular localization of the SREBF1 variant. The transcriptional activity of mutant SREBP-1 was determined by a luciferase reporter assay. A transgenic zebrafish model was constructed.

RESULTS

Two unrelated patients presented with generalized skin hyperpigmentation with skin xerosis, congenital cataracts and extracutaneous symptoms. We identified a de novo nonsense variant c.1289C>A (p.Ser430*) in SREBF1 in both patients. The variant encoded a truncated protein that showed preferential nucleus localization, in contrast to wild-type SREBP-1 which - in sterol-sufficient conditions - is mainly localized in the cytoplasm. The luciferase reporter assay revealed that the p.Ser430* mutant exhibited enhanced transcriptional activity. Cultured patient primary melanocytes showed increased melanin synthesis vs. those from healthy controls. At 35 days postfertilization, the p.Ser430* transgenic zebrafish model exhibited more black spots, along with upregulated expression of melanogenic genes.

CONCLUSIONS

We demonstrated that a gain-of-function variant of SREBF1 causes a previously undescribed disorder characterized by generalized skin hyperpigmentation and congenital cataracts. Our study reveals the involvement of SREBP-1 in melanogenesis and lens development, and paves the way for the development of novel therapeutic targets for skin dyspigmentation or cataracts.

CREB Is Critically Implicated in Skin Mast Cell Degranulation Elicited via FcεRI and MRGPRX2

Skin mast cells (MCs) mediate acute allergic reactions in the cutaneous environment and contribute to chronic dermatoses, including urticaria, and atopic or contact dermatitis. The cAMP response element binding protein (CREB), an evolutionarily well conserved transcription factor (TF) with over 4,000 binding sites in the genome, was recently found to form a feedforward loop with KIT, maintaining MC survival. The most selective MC function is degranulation with its acute release of prestored mediators. Herein, we asked whether CREB contributes to the expression and function of the degranulation-competent receptors FcεRI and MRGPRX2. Interference with CREB by pharmacological inhibition (CREBi, 666-15) or RNA interference only slightly affected the expression of these receptors, while KIT was strongly attenuated. Interestingly, MRGPRX2 surface expression moderately increased following CREB-knockdown, whereas MRGPRX2-dependent exocytosis simultaneously decreased. FcεRI expression and function were regulated consistently, although the effect was stronger at the functional level. Preformed MC mediators (tryptase, histamine, β-hexosaminidase) remained comparable following CREB attenuation, suggesting that granule synthesis did not rely on CREB function. Collectively, in contrast to KIT, FcεRI and MRGPRX2 moderately depend on unperturbed CREB function. Nevertheless, CREB is required to maintain MC releasability irrespective of stimulus, insinuating that CREB may operate by safeguarding the degranulation machinery. To our knowledge, CREB is the first factor identified to regulate MRGPRX2 expression and function in opposite direction. Overall, the ancient TF is an indispensable component of skin MCs, orchestrating not only survival and proliferation but also their secretory competence.

Resveratrol-Enriched Rice Callus Extract Inhibits Oxidative and Cellular Melanogenic Activities in Melan-A Cells

The excessive production of melanin can cause skin diseases and hyperpigmentation. In this study, resveratrol contained in Dongjin rice seed (DJ526) was increased through callus induction. The antioxidant capacity of resveratrol-enriched rice callus was evaluated using the ABTS radical scavenging method and was equivalent to that of vitamin C. DJ526 rice callus extract significantly increased antioxidant activities in a concentration-dependent manner. The anti-melanogenesis effects of DJ526 rice callus extract were also evaluated in melan-a cells. Resveratrol-enriched rice callus extract significantly (i) decreased the size and number of melanin-containing cells, (ii) suppressed the activity of cellular tyrosinase and melanin content, (iii) downregulated the expression of microphthalmia-associated transcription factor, tyrosinase, tyrosinase-related protein-1, and tyrosinase-related protein-2, (iv) increased the expression of phosphorylated extracellular signal-regulated kinase 1/2 and protein kinase B, and (v) inhibited the activation of phosphorylated p38 in melan-a cells. From the above observations, DJ526 rice callus extract showed strong antioxidant and anti-melanogenesis activity at the concentration test. These findings indicate the potential of resveratrol-enriched rice callus as a novel agent for controlling hyperpigmentation.

(2-Methylbutyryl)shikonin Naturally Occurring Shikonin Derivative Ameliorates the α-MSH-Induced Melanogenesis via ERK1/2 and p38 MAP Kinase-Mediated Down-Regulation of the MITF Transcription Factor

Cutaneous pigmentation is an important phenotypic trait whose regulation, despite recent advances, has yet to be completely elucidated. Melanogenesis, a physiological process of melanin production, is imperative for organism survival as it provides protection against the environmental insults that majorly involve sunlight-induced skin photodamage. However, immoderate melanin synthesis can cause pigmentation disorders associated with a psychosocial impact. In this study, the hypopigmentation effect of (2-methylbutyryl)shikonin, a natural product present in the root extract of Lithospermum erythrorhizon, and the underlying mechanisms responsible for the inhibition of melanin synthesis in α-MSH-stimulated B16F10 cells and C57BL/6J mice was studied. Non-cytotoxic concentrations of (2-methylbutyryl)shikonin significantly repressed cellular tyrosinase activity and melanin synthesis in both in vitro and in vivo models (C57BL/6J mice). (2-Methylbutyryl)shikonin remarkably abolished the protein expression of MITF, tyrosinase, tyrosinase-related protein 1, and tyrosinase-related protein 2, thereby blocking the production of pigment melanin via modulating the phosphorylation status of MAPK proteins, viz., ERK1/2 and p38. In addition, specific inhibition of ERK1/2 attenuated the inhibitory effects of (2-methylbutyryl)shikonin on melanin synthesis, whereas selective inhibition of p38 augmented the inhibitory effect of BSHK on melanin synthesis. Moreover, topical application of (2-methylbutyryl)shikonin on C57BL/6J mouse tails remarkably induced tail depigmentation. In conclusion, with these findings, we, for the first time, report the hypopigmentation effect of (2-methylbutyryl)shikonin via inhibition of cellular tyrosinase enzyme activity, subsequently ameliorating the melanin production, thereby indicating that (2-methylbutyryl)shikonin is a potential natural therapy for hyperpigmentation disorders.

Anti-Melanogenic Effects of Lilium lancifolium Root Extract via Downregulation of PKA/CREB and MAPK/CREB Signaling Pathways in B16F10 Cells

Hyperpigmentation disorders causing emotional distress require the topical use of depigmenting agents of natural origin. In this study, the anti-melanogenic effects of the Lilium lancifolium root extract (LRE) were investigated in B16F10 cells. Consequently, a non-cytotoxic concentration of the extract reduced intracellular melanin content and tyrosinase activity in a dose-dependent manner, correlating with the diminished expression of core melanogenic enzymes within cells. LRE treatment also inhibited cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB)/microphthalmia-associated transcription factor signaling, which regulates the expression of tyrosinase-related genes. Upon examining these findings from a molecular mechanism perspective, LRE treatment suppressed the phosphorylation of protein kinase A (PKA), p38, and extracellular signal-related kinase (ERK), which are upstream regulators of CREB. In addition, L-phenylalanine and regaloside A, specifically identified within the LRE using liquid chromatography-mass spectrometry, exhibited inhibitory effects on melanin production. Collectively, these results imply that LRE potentially suppresses cAMP-mediated melanogenesis by downregulating PKA/CREB and mitogen-activated protein kinase (MAPK)/CREB signaling pathways. Therefore, it can be employed as a novel therapeutic ingredient of natural origin to ameliorate hyperpigmentation disorders.

Anhydrous Alum Inhibits α-MSH-Induced Melanogenesis by Down-Regulating MITF via Dual Modulation of CREB and ERK

Melanogenesis, the intricate process of melanin synthesis, is central to skin pigmentation and photoprotection and is regulated by various signaling pathways and transcription factors. To develop potential skin-whitening agents, we used B16F1 melanoma cells to investigate the inhibitory effects of anhydrous alum on melanogenesis and its underlying molecular mechanisms. Anhydrous alum (KAl(SO4)2) with high purity (>99%), which is generated through the heat-treatment of hydrated alum (KAl(SO4)2·12H2O) at 400 °C, potentiates a significant reduction in melanin content without cytotoxicity. Anhydrous alum downregulates the master regulator of melanogenesis, microphthalmia-associated transcription factor (MITF), which targets key genes involved in melanogenesis, thereby inhibiting α-melanocyte-stimulating hormone (α-MSH)-induced melanogenesis. Phosphorylation of the cAMP response element-binding protein, which acts as a co-activator of MITF gene expression, is attenuated by anhydrous alum, resulting in compromised MITF transcription. Notably, anhydrous alum promoted extracellular signal-regulated kinase phosphorylation, leading to the impaired nuclear localization of MITF. Overall, these results demonstrated the generation and mode of action of anhydrous alum in B16F1 cells, which constitutes a promising option for cosmetic or therapeutic use.

A Comprehensive Review of Mammalian Pigmentation: Paving the Way for Innovative Hair Colour-Changing Cosmetics

The natural colour of hair shafts is formed at the bulb of hair follicles, and it is coupled to the hair growth cycle. Three critical processes must happen for efficient pigmentation: (1) melanosome biogenesis in neural crest-derived melanocytes, (2) the biochemical synthesis of melanins (melanogenesis) inside melanosomes, and (3) the transfer of melanin granules to surrounding pre-cortical keratinocytes for their incorporation into nascent hair fibres. All these steps are under complex genetic control. The array of natural hair colour shades are ascribed to polymorphisms in several pigmentary genes. A myriad of factors acting via autocrine, paracrine, and endocrine mechanisms also contributes for hair colour diversity. Given the enormous social and cosmetic importance attributed to hair colour, hair dyeing is today a common practice. Nonetheless, the adverse effects of the long-term usage of such cosmetic procedures demand the development of new methods for colour change. In this context, case reports of hair lightening, darkening and repigmentation as a side-effect of the therapeutic usage of many drugs substantiate the possibility to tune hair colour by interfering with the biology of follicular pigmentary units. By scrutinizing mammalian pigmentation, this review pinpoints key targetable processes for the development of innovative cosmetics that can safely change the hair colour from the inside out.

Anti-melanogenic effect of Moju through inhibition of tyrosinase activity

Background

Moju is a traditional rice beverage local to Jeonju with an alcohol content of 1–2%. Moju is made by boiling makgeolli with several kinds of medicinal herbs, such as ginger, jujube and cinnamon. The raw materials used in Moju are well known for their physiological and functional effects. Although Moju is made with functional raw materials, the operational role of Moju has not yet been reported.

Objectives

The aim of this study was to identify the anti-melanogenic effects of Moju in B16F10 melanoma cells and explore the potential mechanisms.

Results

In this study, we investigated the antioxidant activity and anti-melanogenic effect of Moju. Moju showed no toxicity to HEK293T or B16F10 cells. The antioxidant activity of Moju was confirmed by its ability to increase radical scavenging activity. Moju decreased tyrosinase activity in a concentration-dependent manner. At the cellular level, Moju reduced melanin synthesis and the expression of proteins involved in melanin synthesis at concentrations of 100, 250, and 500 μg/mL in B16F10 cells. In addition, Moju inhibited the phosphorylation of extracellular signal-regulated kinase (ERK).

Conclusions

These results provide evidence that Moju has antioxidant activity and anti-melanogenic effect that occur through regulation of the ERK pathway. Although further research is needed to elucidate the specific mechanism and functional components, the ability of Moju to inhibit melanin synthesis by altering tyrosinase activation suggest that it can be used as a functional whitening ingredient.

MiR-585-5p impedes gastric cancer proliferation and metastasis by orchestrating the interactions among CREB1, MAPK1 and MITF

BACKGROUND

Gastric cancer (GC) is one of the most malignant and lethal cancers worldwide. Multiple microRNAs (miRNAs) have been identified as key regulators in the progression of GC. However, the underlying pathogenesis that miRNAs govern GC malignancy remains uncertain. Here, we identified a novel miR-585-5p as a key regulator in GC development.

METHODS

The expression of miR-585-5p in the context of GC tissue was detected by in situ hybridization for GC tissue microarray and assessed by H-scoring. The gain- and loss-of-function analyses comprised of Cell Counting Kit-8 assay and Transwell invasion and migration assay. The expression of downstream microphthalmia-associated transcription factor (MITF), cyclic AMP-responsive element-binding protein 1 (CREB1) and mitogen-activated protein kinase 1 (MAPK1) were examined by Immunohistochemistry, quantitative real-time PCR and western blot. The direct regulation between miR-585-5p and MITF/CREB1/MAPK1 were predicted by bioinformatic analysis and screened by luciferase reporter assay. The direct transcriptional activation of CREB1 on MITF was verified by luciferase reporter assay, chromatin immunoprecipitation (ChIP) and electrophoretic mobility shift assays (EMSAs). The interaction between MAPK1 and MITF was confirmed by co-immunoprecipitation (Co-IP) and immunofluorescent double-labelled staining.

RESULTS

MiR-585-5p is progressively downregulated in GC tissues and low miR-585-5p levels were strongly associated with poor clinical outcomes. Further gain- and loss-of-function analyses showed that miR-585-5p possesses strong anti-proliferative and anti-metastatic capacities in GC. Follow-up studies indicated that miR-585-5p targets the downstream molecules CREB1 and MAPK1 to regulate the transcriptional and post-translational regulation of MITF, respectively, thus controlling its expression and cancer-promoting activity. MiR-585-5p directly and negatively regulates MITF together with CREB1 and MAPK1. According to bioinformatic analysis, promotor reporter gene assays, ChIP and EMSAs, CREB1 binds to the promotor region to enhance transcriptional expression of MITF. Co-IP and immunofluorescent double-labelled staining confirmed interaction between MAPK1 and MITF. Protein immunoprecipitation revealed that MAPK1 enhances MITF activity via phosphorylation (Ser73). MiR-585-5p can not only inhibit MITF expression directly, but also hinder MITF expression and pro-cancerous activity in a CREB1-/MAPK1-dependent manner indirectly.

CONCLUSIONS

In conclusion, this study uncovered miR-585-5p impedes gastric cancer proliferation and metastasis by orchestrating the interactions among CREB1, MAPK1 and MITF.

The Function of Autophagy as a Regulator of Melanin Homeostasis

Melanosomes are melanocyte-specific organelles that protect cells from ultraviolet (UV)-induced deoxyribonucleic acid damage through the production and accumulation of melanin and are transferred from melanocytes to keratinocytes. The relatively well-known process by which melanin is synthesized from melanocytes is known as melanogenesis. The relationship between melanogenesis and autophagy is attracting the attention of researchers because proteins associated with autophagy, such as WD repeat domain phosphoinositide-interacting protein 1, microtubule-associated protein 1 light chain 3, autophagy-related (ATG)7, ATG4, beclin-1, and UV-radiation resistance-associated gene, contribute to the melanogenesis signaling pathway. Additionally, there are reports that some compounds used as whitening cosmetics materials induce skin depigmentation through autophagy. Thus, the possibility that autophagy is involved in the removal of melanin has been suggested. To date, however, there is a lack of data on melanosome autophagy and its underlying mechanism. This review highlights the importance of autophagy in melanin homeostasis by providing an overview of melanogenesis, autophagy, the autophagy machinery involved in melanogenesis, and natural compounds that induce autophagy-mediated depigmentation.

Fuzhuan Brick Tea Boosts Melanogenesis and Prevents Hair Graying through Reduction of Oxidative Stress via NRF2-HO-1 Signaling

The anti-graying effect of the hexane fraction of Fuzhuan brick tea is investigated in Melan-A cells and C57BL/6 mice. As a result, it is found that reactive oxygen species-induced damage is associated with the reduction of melanogenesis in hair bulb melanocytes when reactive oxygen species generation in Melan-A cells occurred. The results revealed that the hexane fraction of Fuzhuan brick tea could remarkably reduce reactive oxygen species generation in Melan-A cells; meanwhile, it could increase the cellular tyrosinase and melanin content, as well as up-regulate the expression of tyrosinase, tyrosinase related protein-1, tyrosinase related protein-2, and microphthalmia-associated transcription factor, and activate the MAP-kinase pathway through activating the phosphorylation of p38 c-Jun N terminal kinase/extracellular signal-regulated kinase. Furthermore, high-pressure liquid chromatography analysis reveals that the tea's major ingredients in hexane fraction include gallic acid, theaflavin, theobromine, caffeine, epicatechin, and quercetin. Together, the current results suggest that Fuzhuan brick tea proves to protect from the damage of hydroquinone, which induces hair pigment loss.

Mechanisms of 4-Dimethylamino-4'-Methoxy Chalcone in Promoting Melanin Synthesis

Background and aims: Vitiligo, a pigmentation-associated disease, affects 1–2% of the global population andis difficult to treat. The pathogenetic mechanism of vitiligo remains unclear. Vernonia anthelmintica (L.) Willd. extract for vitiligo treatment was initially recorded 300 years ago. Itschalcone compounds are believed to play essential roles in this treatment. In a previous study, chalcones were shown to enhance melanin production and tyrosinase activity inmouse B16 cells. Materials and methods: In this study, the effects were investigated of 4-dimethylamino-4'-methoxy chalcone (DMC) on theexpression of tyrosinase (TYR), tyrosinase-related protein (TRP)-1, tyrosinase-relatedprotein (TRP)-2, and microphthalmia-associated transcription factor (MITF)on murine B16 cells. Moreover, the signaling pathways of melanogenesis regulation,and the effects of DMCon the AC/cAMP/PKA/CREB (CREB and p-CREB), p38mitogen-activated protein kinase (MAPK) (MAPK, p-p38 MAPK, ERK andp-ERK), Wnt/β-catenin (β-catenin), and SWI/SNF pathways (SOX-10) proteinexpression levels were examined by Western blot. Results: The data showed that DMCcould promote melanin production by upregulating the p-CREB, p-p38,p-ERK and β-catenin proteins.

Sulforaphane induces cell differentiation, melanogenesis and also inhibit the proliferation of melanoma cells

Sulforaphane (SFN) is an organosulfur compound extracted from cruciferous vegetables and has biological effects. The effect of SFN has been studied in different types of cancers, as this compound incites various cytotoxic mechanisms to stunt cancer proliferation. However, the role of SFN activity in melanoma is yet to be known. The current study has been devised to elucidate the effects induced by SFN treatment in the B16F10 melanoma cell line and zebrafish model. Cells were treated with SFN reduced cell proliferation and increased tyrosinase production. Moreover, microscopic and immunofluorescence analysis confirmed the elongated appearance of melanoma cells due to cytoskeletal reorganization induced by SFN. Western blotting showed that SFN regulates the protein expression of Microphthalmia-associated transcription factor (MITF), Protein kinase C beta 1 (PKCβ1), and tyrosinase. The relationship between melanin biosynthesis and changes in the actin cytoskeleton encouraged by SFN on melanoma was determined by treating it with Cytochalasin D (CD) and Jasplakinolide (JAS). Co-treatment of SFN with CD increased more tyrosinase expression than SFN alone whereas with JAS, slightly reduced the expression. Immature zebrafish were pretreated with phenylthiourea (PTU) and then exposed to different SFN concentrations yielded the same results by upregulating the melanin levels despite the presence of melanin inhibitor (PTU). These study results show that SFN induces the biosynthesis of melanin in the B16F10 melanoma cell line, which occurs through changes in actin.

Diarylpropionitrile inhibits melanogenesis via protein kinase A/cAMP-response element-binding protein/microphthalmia-associated transcription factor signaling pathway in α-MSH-stimulated B16F10 melanoma cells

Diarylpropionitrile (DPN), a selective agonist for estrogen receptor β (ERβ), has been reported to regulate various hormonal responses through activation of ERβ in tissues including the mammary gland and brain. However, the effect of DPN on melanogenesis independent of ERβ has not been studied. The aim of this study is to examine the possibility of anti-melanogenic effect of DPN and its underlying mechanism. Melanin contents and cellular tyrosinase activity assay indicated that DPN inhibited melanin biosynthesis in alpha-melanocyte stimulating hormone-stimulated B16F10 melanoma cell line. However, DPN had no direct influence on in vitro tyrosinase catalytic activity. On the other hand, 17β-estradiol had no effect on inhibition of melanogenesis, suggesting that the DPN-mediated suppression of melanin production was not related with estrogen signaling pathway. Immunoblotting analysis showed that DPN down-regulated the expression of microphthalmia-associated transcription factor (MITF), a central transcription factor of melanogenesis and its down-stream genes including tyrosinase, tyrosinase-related protein (TRP)-1, and TRP-2. Also, DPN attenuated the phosphorylation of protein kinase A (PKA) and cAMP-response element-binding protein (CREB). Additionally, DPN suppressed the melanin synthesis in UVB-irradiated HaCaT conditioned media culture system suggesting that DPN has potential as an anti-melanogenic activity in physiological conditions. Collectively, our data show that DPN inhibits melanogenesis via down-regulation of PKA/CREB/MITF signaling pathway.

The Expression Pattern of Genes Related to Melanogenesis and Endogenous Opioids in Psoriasis

The melanocortin system is a major regulator of stress responses in the skin and is responsible for the induction of melanin synthesis through activation of melanogenesis enzymes. The expression of both melanocortin system genes and melanogenesis enzyme genes is altered in psoriasis, and the focus here was on twelve genes related to the signal transduction between them. Additionally, five endogenous opioid system genes that are involved in cutaneous inflammation were examined. Quantitative real-time-PCR was utilized to measure mRNA expression in punch biopsies from lesional and non-lesional skin of psoriasis patients and from the skin of healthy control subjects. Most of the genes related to melanogenesis were down-regulated in patients (CREB1, MITF, LEF1, USF1, MAPK14, ICAM1, PIK3CB, RPS6KB1, KIT, and ATRN). Conversely, an up-regulation occurred in the case of opioids (PENK, PDYN, and PNOC). The suppression of genes related to melanogenesis is in agreement with the reported reduction in pigmentation signaling in psoriatic skin and potentially results from the pro-inflammatory environment. The increase in endogenous opioids can be associated with their involvement in inflammatory dysregulation in psoriasis.

Hinokitiol-induced decreases of tyrosinase and microphthalmia-associated transcription factor are mediated by the endoplasmic reticulum-associated degradation pathway in human melanoma cells

Tyrosinase (TYR) is a key enzyme for melanin production. We previously showed that hinokitiol, a naturally occurring seven-membered ring terpenoid, potently inhibits human TYR activity. Interestingly, hinokitiol was recently reported to decrease expression of TYR and microphthalmia-associated transcription factor (MITF), which is a main transcription factor of the TYR gene, in murine melanoma cells. However, the mechanisms by which hinokitiol decreases the intracellular levels of TYR and MITF have not been fully elucidated. Here, we investigated the underlying mechanisms of the decreases using cultured human melanoma cells. As a result, hinokitiol treatment decreased TYR protein level in a time- and dose-dependent manner in G361 human melanoma cells, while MITF protein level was decreased only at higher concentrations after 3 days treatment. Notably, the mRNA levels of TYR and MITF were slightly increased by hinokitiol treatment. Therefore, we focused on the degradation of TYR and MITF in endoplasmic reticulum (ER)-associated protein degradation (ERAD) pathway. Importantly, co-treatment of ERAD inhibitor with hinokitiol restored the protein levels of TYR and MITF to approximately 30% and 20% of total those in untreated control cells, respectively. Hinokitiol affected the ER homeostasis as well as degradation of TYR and MITF in two human melanoma cell lines, G361 and HT-144, but the changes of ER-stress markers under the hinokitiol treatment were different in the two human melanoma cell lines. Taken together, these observations indicate that hinokitiol may induce ER stress and trigger the degradation of unfolded newly synthesizing TYR and MITF via the ERAD pathway.

microRNAs in the Regulation of Melanogenesis

Melanogenesis is the process leading to the synthesis of melanin, the main substance that influences skin color and plays a pivotal role against UV damage. Altered melanogenesis is observed in several pigmentation disorders. Melanogenesis occurs in specialized cells called melanocytes, physically and functionally related by means of autocrine and paracrine interplay to other skin cell types. Several external and internal factors control melanin biosynthesis and operate through different intracellular signaling pathways, which finally leads to the regulation of microphthalmia-associated transcription factor (MITF), the key transcription factor involved in melanogenesis and the expression of the main melanogenic enzymes, including TYR, TYRP-1, and TYRP-2. Epigenetic factors, including microRNAs (miRNAs), are involved in melanogenesis regulation. miRNAs are small, single-stranded, non-coding RNAs, of approximately 22 nucleotides in length, which control cell behavior by regulating gene expression, mainly by binding the 3′ untranslated region (3′-UTR) of target mRNAs. This review collects data on the miRNAs involved in melanogenesis and how these miRNAs can modulate target gene expression. Bringing to light the biological function of miRNAs could lead to a wider understanding of epigenetic melanogenesis regulation and its dysregulation. This knowledge may constitute the basis for developing innovative treatment approaches for pigmentation dysregulation.

Anti-Melanogenic Effects of Paederia foetida L. Extract via MAPK Signaling-Mediated MITF Downregulation

In this study, in order to explore the anti-melanogenic effect of PFE (Paederia foetida L. extract) and suggest its availability, B16F10 cells, which are murine melanoma cells, were stimulated with alpha-Melanocyte-stimulating hormone (α-MSH) to conduct an in vitro experiment. Treatment with PFE in B16F10 cells with activated melanogenesis due to stimulants showed that PFE significantly inhibits melanin content as well as intracellular tyrosinase activity within a range that does not cause cytotoxicity. In addition, Western blot assay demonstrated that PFE strongly inhibited the protein expression of not only tyrosinase-related protein (TRP)-1, -2, and tyrosinase, but also microphthalmia-associated transcription factor (MITF). Moreover, mechanism studies have shown that PFE processing inhibited the activation of melanin production by regulating the phosphorylation of each mitogen-activated protein kinase (MAPK) family in the MAPK signaling pathway. To test the biocompatibility of PFE on human skin, a primary skin irritation test was performed. The results revealed that PFE did not have any side effects on human skin. These findings suggest that PFE holds great potential as a skin whitening agent and in the prevention of hyperpigmentation disorders.

The Anti-Melanogenesis Effect of 3,4-Dihydroxybenzalacetone through Downregulation of Melanosome Maturation and Transportation in B16F10 and Human Epidermal Melanocytes

The biosynthesis pathway of melanin is a series of oxidative reactions that are catalyzed by melanin-related proteins, including tyrosinase (TYR), tyrosinase-related protein-1 (TRP-1), and tyrosinase-related protein-2 (TRP-2). Reagents or materials with antioxidative or free radical-scavenging activities may be candidates for anti-melanogenesis. 3,4-Dihydroxybenzalacetone (DBL) is a polyphenol isolated from fungi, such as Phellinus obliguus (Persoon) Pilat and P. linteus. In this study, we investigated the effects and mechanisms of DBL on antioxidation and melanogenesis in murine melanoma cells (B16F10) and human epidermal melanocytes (HEMs). The results indicated that DBL scavenged 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radicals, and exhibited potent reducing power, indicating that it displays strong antioxidative activity. DBL also inhibited the expression of TYR, TRP-1, TRP-2, and microphthalmia-related transcription factor (MITF) in both the cells. In addition, DBL inhibited hyperpigmentation in B16F10 and HEMs by regulating the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA), v-akt murine thymoma viral oncogene homolog (AKT)/glycogen synthase kinase 3 beta (GSK3β), and mitogen-activated protein kinase kinase (MEK)/extracellular regulated protein kinase (ERK) signaling pathways. DBL not only shortened dendritic melanocytes but also inhibited premelanosome protein 17 (PMEL17) expression, slowing down the maturation of melanosome transportation. These results indicated that DBL promotes anti-melanogenesis by inhibiting the transportation of melanosomes. Therefore, DBL is a potent antioxidant and depigmenting agent that may be used in whitening cosmetics.

The underestimated role of the microphthalmia-associated transcription factor (MiTF) in normal and pathological haematopoiesis

Haematopoiesis, the process by which a restrained population of stem cells terminally differentiates into specific types of blood cells, depends on the tightly regulated temporospatial activity of several transcription factors (TFs). The deregulation of their activity or expression is a main cause of pathological haematopoiesis, leading to bone marrow failure (BMF), anaemia and leukaemia. TFs can be induced and/or activated by different stimuli, to which they respond by regulating the expression of genes and gene networks. Most TFs are highly pleiotropic; i.e., they are capable of influencing two or more apparently unrelated phenotypic traits, and the action of a single TF in a specific setting often depends on its interaction with other TFs and signalling pathway components. The microphthalmia-associated TF (MiTF) is a prototype TF in multiple situations. MiTF has been described extensively as a key regulator of melanocyte and melanoma development because it acts mainly as an oncogene. Mitf-mutated mice show a plethora of pleiotropic phenotypes, such as microphthalmia, deafness, abnormal pigmentation, retinal degeneration, reduced mast cell numbers and osteopetrosis, revealing a greater requirement for MiTF activity in cells and tissue. A growing amount of evidence has led to the delineation of key roles for MiTF in haematopoiesis and/or in cells of haematopoietic origin, including haematopoietic stem cells, mast cells, NK cells, basophiles, B cells and osteoclasts. This review summarizes several roles of MiTF in cells of the haematopoietic system and how MiTFs can impact BM development.

7,3',4'-Trihydroxyisoflavone, a Metabolite of the Soy Isoflavone Daidzein, Suppresses α-Melanocyte-Stimulating Hormone-Induced Melanogenesis by Targeting Melanocortin 1 Receptor

7,3',4'-Trihydroxyisoflavone (7,3',4'-THIF) is a metabolite of daidzein which is a representative isoflavone found in soybean. Recent studies suggested that 7,3',4'-THIF exerts a hypopigmentary effect in B16F10 cells, however, its underlying molecular mechanisms and specific target protein remain unknown. Here, we found that 7,3',4'-THIF, but not daidzein, inhibited α-melanocyte-stimulating hormone (MSH)-induced intracellular and extracellular melanin production in B16F10 cells by directly targeting melanocortin 1 receptor (MC1R). Western blot data showed that 7,3',4'-THIF inhibited α-MSH-induced tyrosinase, tyrosinase-related protein-1 (TYRP-1), and tyrosinase-related protein-2 (TYRP-2) expressions through the inhibition of Microphthalmia-associated transcription factor (MITF) expression and cAMP response element-binding (CREB) phosphorylation. 7,3',4'-THIF also inhibited α-MSH-induced dephosphorylation of AKT and phosphorylation of p38 and cAMP-dependent protein kinase (PKA). cAMP and Pull-down assays indicated that 7,3',4'-THIF strongly inhibited forskolin-induced intracellular cAMP production and bound MC1R directly by competing with α-MSH. Moreover, 7,3',4'-THIF inhibited α-MSH-induced intracellular melanin production in human epidermal melanocytes (HEMs). Collectively, these results demonstrate that 7,3',4'-THIF targets MC1R, resulting in the suppression of melanin production, suggesting a protective role for 7,3',4'-THIF against melanogenesis.

Melanogenesis Effect of 7-acetoxy-4-methylcoumarin in B16F10 Melanoma Cells

The increased interest in anti-whitening dyes has enhanced the research interest to identify efficient melanogenic activators. Melanogenesis is the process of melanin production by melanocytes in the hair follicles and skin, which is mediated by several enzymes, such as microphthalmia-associated transcription factor (MITF), tyrosinase (TYR), tyrosinase-related protein (TRP)-1, and TRP-2. This study investigated the melanogenesis-stimulating effect of 4-Methylumbelliferone (4MUMB) and its synthetic derivatives, 7-acetoxy-4-methylcoumarin (7A4MC) and 4-methylheriniarin (4MH) in B16F10 melanoma cells. The cytotoxicity of these compounds was investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, followed by the assessment of the melanin content and the intracellular TYR activity. Finally, the expression levels of the key enzymes involved in melanogenesis were investigated. 7A4MC increased melanin production in B16F10 cells relative to that by 4MUMB and 4MH treated cells in a dose-dependent manner without significant cytotoxicity. Concomitantly, 7A4MC significantly increased TYR activity and enhanced the expression of MITF, which significantly induced the expression of TRP-1, TRP-2, and TYR. Furthermore, 7A4MC stimulated melanogenesis via increased phosphorylation of c-Jun N-terminal kinases (JNK) and reduced phosphorylation of protein kinase B (AKT). These results confirmed the melanogenesis-inducing effects of 7A4MC and indicated its potential use as an anti-hair bleaching agent in cosmetics industries.

Essential Oils of Alpinia nantoensis Retard Forskolin-Induced Melanogenesis via ERK1/2-Mediated Proteasomal Degradation of MITF

The anti-melanogenic activity of essential oils of Alpinia nantoensis and their bioactive ingredients were investigated in vitro. Treatment with leaf (LEO) and rhizome (REO) essential oils of A. nantoensis, significantly reduced forskolin-induced melanin production followed by down-regulation of tyrosinase (TYR) and tyrosinase related protein-1 (TRP-1) expression at both transcriptional and translational levels. Further studies revealed that down-regulation TYR and TRP-1 were caused by LEO/REO-mediated suppression of Microphthalmia-associated transcription factor (MITF), as evidenced by reduced nuclear translocation of MITF. Also, we found that LEO/REO induce the sustained activation of ERK1/2, which facilitate subsequent proteasomal degradation of MITF, as confirmed by that LEO/REO failed to inhibits MITF activity in ERK1/2 inhibitor treated cells. In addition, a significant increase of ubiquitinated MITF was observed after treatment with LEO and REO. Furthermore, the chemical composition of LEO and REO were characterized by gas chromatography-mass spectrometry (GC-MS) resulted that camphor, camphene, α-pinene, β-pinene, isoborneol and _D-limonene were the major compounds in both LEO and REO. Further studies revealed that α-pinene and _D-limonene were the active components responsible for the anti-melanogenic properties of LEO and REO. Based on the results, this study provided a strong evidence that LEO and REO could be promising natural sources for the development of novel skin-whitening agents for the cosmetic purposes.

Carvone Decreases Melanin Content by Inhibiting Melanoma Cell Proliferation via the Cyclic Adenosine Monophosphate (cAMP) Pathway

Melanin, which determines the color of the skin and hair, is initially synthesized to protect the skin from ultraviolet light; however, excessive melanin pigmentation caused by abnormal cell proliferation can result in various melanocytic lesions. Cyclic adenosine monophosphate (cAMP) is known to regulate cell cycle progression and consequently to inhibit the division of abnormally proliferating cells. In this work, we aimed to test whether carvone, a scent compound from plants, inhibits proliferation and subsequently reduces melanin content of melanoma cells and to determine whether its beneficial effects are mediated by the cAMP pathway. We found that carvone decreases melanin content and inhibits melanoma cell proliferation in a concentration-dependent manner. Meanwhile, it inhibited the activation of cell cycle-associated proteins such as cyclin-dependent kinase 1 (CDK1). Of note, the beneficial effects of carvone were abrogated by cAMP inhibition. Our findings indicate potential benefits of carvone for the treatment of melanomas and presumably other hyperpigmentation-related dermatological disorders such as melasmas, lentigines, and excessive freckles.

What turns CREB on? And off? And why does it matter?

Altered expression and function of the transcription factor cyclic AMP response-binding protein (CREB) has been identified to play an important role in cancer and is associated with the overall survival and therapy response of tumor patients. This review focuses on the expression and activation of CREB under physiologic conditions and in tumors of distinct origin as well as the underlying mechanisms of CREB regulation by diverse stimuli and inhibitors. In addition, the clinical relevance of CREB is summarized, including its use as a prognostic and/or predictive marker as well as a therapeutic target.

Inhibitory Effects of Pinostilbene Hydrate on Melanogenesis in B16F10 Melanoma Cells via ERK and p38 Signaling Pathways

Melanin protects our skin from harmful ultraviolet (UV) radiation. However, when produced in excess, it can cause hyperpigmentation disorders, such as melanoma, freckles, lentigo, and blotches. In this study, we investigated the effects of pinostilbene hydrate (PH) on melanogenesis. We also examined the underlying mechanisms of PH on melanin production in B16F10 cells. Our findings indicated that PH significantly inhibits melanin content and cellular tyrosinase activity in cells without causing cytotoxicity. In addition, Western blot analysis showed that PH downregulated the protein levels of microphthalmia-associated transcription factor (MITF), tyrosinase, and other melanogenic enzymes, such as tyrosinase-related protein-1 (TRP-1) and tyrosinase-related protein-2 (TRP-2). Although PH activated the phosphorylation of extracellular signal-regulated kinase (ERK), it inhibited p38 mitogen-activated protein kinases (p38). Furthermore, the inhibition of tyrosinase activity by PH was attenuated by treatment with PD98059 (a specific ERK inhibitor). Additionally, p-AKT was upregulated by PH treatment. Finally, the inhibitory effects of PH on melanin content and tyrosinase activity were confirmed in normal human melanocytes. These results suggest PH downregulates melanogenesis via the inhibition of MITF expression, followed by the MAPKase signaling pathways. Thus, PH may be used to treat or prevent hyperpigmentation disorders and in functional cosmetic agents for skin whitening.

Mutated SASH1 promotes Mitf expression in a heterozygous mutated SASH1 knock‑in mouse model

The SAM and SH3 domain‑containing 1 (SASH1) genes have been identified as the causal genes of dyschromatosis universalis hereditaria (DUH); these genes cause the pathological phenotypes of DUH, and SASH1 variants have been shown to regulate the abnormal pigmentation phenotype in human skin in various genodermatoses. However, investigations into the mutated SASH1 gene have been limited to in vitro studies. In the present study, to recapitulate the molecular pathological phenotypes of individuals with DUH induced by SASH1 mutations, a heterozygous BALB/c mouse model, in which the human SASH1 c.1654 T>G (p. Tyr 551Asp, Y551D) mutation was knocked in was first generated. The in vivo functional experiments on Y551D SASH1 indicated that the increased expression of microphthalmia‑associated transcription factor (Mitf) was uniformly induced in the tails of heterozygous BALB/c mice, and an increased quantity of Mitf‑positive epithelial cells was also detected. An increased expression of Mitf‑ and Mitf‑positive cells was also demonstrated in the epithelial tissues of Y551D‑SASH1 affected individuals. In the present study, Mitf expression was also found to be increased by Y551D SASH1 in vitro. Taken together, these findings indicate that the upregulation of Mitf is the bona fide effector of the Y551D SASH1‑mediated melanogenesis signaling pathway in vivo. SASH1 may function as a scaffold molecule for the assembly of a SASH1‑Mitf molecular complex to regulate Mitf expression in the cell nucleus and thus to promote the hyperpigmented phenotype in the pathogenesis of DUH and other genodermatoses related to pigment abnormalities.

MicroRNA-379 mediates pigmentation, migration and proliferation of melanocytes by targeting the insulin-like growth factor 1 receptor

Melanogenesis, migration and proliferation of melanocytes are important factors that determine the hair colours of mammals. MicroRNAs (miRNAs) have been shown to be closely related to these processes. In melanocytes of alpacas, insulin-like growth factor 1 (IGF1) has been shown to improve melanogenesis through the cyclic AMP (cAMP) pathway. miR-379 was predicted to target insulin-like growth factor (IGF) receptor 1 (IGF1R), which binds to IGF1. Therefore, we hypothesized that miR-379 could mediate melanogenesis, migration and proliferation of melanocytes. Here, we report that miR-379 was highly expressed in alpaca melanocytes. Subsequent overexpression of miR-379 in alpaca melanocytes led to the generation of the phenotype of melanogenesis, proliferation and migration. In addition, the expression of genes related to these phenotypes in melanocytes was detected. Our results showed that miR-379 targets IGF1R in melanocytes. The overexpression of miR-379 stimulated dendrite extension or elongation and limited the perinuclear distribution of melanin, but inhibited melanogenesis via cAMP response element (CRE)-binding protein (CREB)/microphthalmia-associated transcription factor (MITF) pathway. miR-379 attenuated melanocyte migration by downregulating the focal adhesion kinase (FAK) and enhanced melanocyte proliferation by upregulating protein kinase B (AKT). These observations suggest the involvement of miR-379 in the physiological regulation of melanocytes, mediated by targeting IGF1R on insulin receptor (IR) compensation and subsequent crosstalk.

Induction of Melanogenesis by Fosfomycin in B16F10 Cells Through the Upregulation of P-JNK and P-p38 Signaling Pathways

Fosfomycin disodium salt (FDS), which is a water-soluble extract, is a bactericidal drug used to inhibit the synthesis of cells. Moreover, it has been found to be effective in the treatment of urinary tract infections. The present study was conducted to investigate the melanogenesis-stimulating effect of FDS in B16F10 cells. Several experiments were performed on B16F10 cells: the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, the melanin content assay, the cellular tyrosinase activity assay, and Western blotting. FDS upregulated the activity of tyrosinase in a dose-dependent manner at a wide concentration range of 0–1 mg/mL, which showed no cytotoxicity. It also increased the melanin content and the activity of the microphthalmia-associated transcription factor (MITF), tyrosinase related protein 1 (TRP-1), and tyrosinase related protein 2 (TRP-2) enzymes in a dose-dependent manner. Western blotting results showed that FDS clearly upregulated the phosphorylation of c-Jun N-terminal kinases (JNK) and p38 pathways. These data are clear evidence of the melanogenesis-inducing effect of FDS in B16F10 murine melanoma cells.

CREBBP and WDR 24 Identified as Candidate Genes for Quantitative Variation in Red-Brown Plumage Colouration in the Chicken

Plumage colouration in birds is important for a plethora of reasons, ranging from camouflage, sexual signalling, and species recognition. The genes underlying colour variation have been vital in understanding how genes can affect a phenotype. Multiple genes have been identified that affect plumage variation, but research has principally focused on major-effect genes (such as those causing albinism, barring, and the like), rather than the smaller effect modifier loci that more subtly influence colour. By utilising a domestic × wild advanced intercross with a combination of classical QTL mapping of red colouration as a quantitative trait and a targeted genetical genomics approach, we have identified five separate candidate genes (CREBBP, WDR24, ARL8A, PHLDA3, LAD1) that putatively influence quantitative variation in red-brown colouration in chickens. By treating colour as a quantitative rather than qualitative trait, we have identified both QTL and genes of small effect. Such small effect loci are potentially far more prevalent in wild populations, and can therefore potentially be highly relevant to colour evolution.

Ethanolic Extract of Hippocampus abdominalis Exerts Anti-Melanogenic Effects in B16F10 Melanoma Cells and Zebrafish Larvae by Activating the ERK Signaling Pathway

The big belly seahorse (Hippocampus abdominalis), a well-known ingredient of traditional medicine, possesses anti-inflammatory, anti-aging, anti-fatigue, and anti-thrombotic properties, and also increases male fertility. This study demonstrates that the ethanolic extract of dried H. abdominalis (EEHA) has anti-melanogenic effects in B16F10 melanoma cells and zebrafish larvae. EEHA significantly reduced the α-melanocyte-stimulating hormone (α-MSH)-induced melanogenesis in B16F10 melanoma cells without causing cytotoxicity. At a concentration of 200 µg/mL, EEHA had significant anti-melanogenic activity in zebrafish larvae, accompanied by a severe reduction in the heart rate (118 ± 17 heartbeats/min) compared to that of the untreated group (185 ± 8 heartbeats/min), indicating that EEHA induces cardiotoxicity at high concentrations. Below 100 µg/mL, EEHA significantly reduced melanogenesis in zebrafish larvae in the presence or absence of α-MSH, while the heart rate remained unaltered. Additionally, EEHA downregulated the release of cyclic adenosine monophosphate (cAMP) and the phosphorylation of cAMP response element-binding protein (CREB) in B16F10 melanoma cells, which inhibited microphthalmia-associated transcription factor (MITF), leading to the inhibition of tyrosinase activity. EEHA also increased the phosphorylation of extracellular-signal regulated kinase (ERK). The ERK inhibitor PD98059 interfered with the anti-melanogenic activity of EEHA in B16F10 melanoma cells and zebrafish larvae, indicating that the ERK signaling pathway might regulate the anti-melanogenic properties of EEHA. Altogether, we conclude that EEHA represses the cAMP–CREB–MITF axis, which consequently inhibits tyrosinase-mediated melanogenesis. We propose that at low concentrations, EEHA can serve as a promising anti-melanogenic agent that could be used to prepare whitening cosmetics and for treating melanogenic disorders.

Sjogren-Larsson syndrome associated hypermelanosis

BACKGROUND/OBJECTIVES

Sjogren - Larsson syndrome (SLS) is a rare autosomal recessive disease of the mutation ALDH3A2 that identifies a part of fatty acids for fatty aldehyde dehydrogenase: NAD-oxidoreductase enzyme complex. This study aimed to access variant ALDH3A2 gene coded for FALDH and products regulating pathogenic melanogenesis owing to increased oxidative stress and reactive oxygen species resulting in DNA harm in SLS. By turning them into fatty acids, FALDH avoids the accumulation of toxic fatty aldehydes. The mutation results in the accumulation of aldehyde-modified lipids or fatty alcohols that may interfere with skin and brain function.

METHODS

In Nov 2018, we performed a literature search in PubMed for clinical studies, clinical trials, case reports, controlled trials, randomized controlled trials, and systemic reviews. The search terms we used were "SJOGREN-LARSSON SYNDROME" AND "HYPERMELANNOSIS" OR "FALDH" (from 1985). The search resulted in 1,289 articles, out of these 95 articles met our inclusion exclusion criteria. Our inclusion criteria included relevant original articles relevant, critical systemic reviews, and crucial referenced articles, ex-clusion criteria included duplicates and articles not published in English language.

RESULTS

Toxicity of long-chain aldehydes to FALDH-deficient cells owing to accumulation under the profound epidermis layer improves oxidative stress in the cell resulting in keratinocyte hyperproliferation.

CONCLUSION

While it continues to be determined whether accumulated fatty alcohol and fatty aldehydes obtained from ether glycerolipids and sphingolipids improve the susceptibility of melanocytes and their element accountable for skin hyperpigmentation to biological colour.

Diazepam enhances melanogenesis, melanocyte dendricity and melanosome transport via the PBR/cAMP/PKA pathway

Diazepam is a medicament of the benzodiazepine family and it typically produces a sedative effect. Researchers have revealed that diazepam can induce melanogenesis and produce dendrite-like structures in B16 melanoma cells. However, the associated mechanisms of melanogenesis and phenotypic alterations have mostly remained unknown. In this study, we determined the effects of diazepam on melanogenesis, cellular phenotypic alterations, the location of melanosomes and the expression of relevant proteins in melanocytes using Masson-Fontana ammoniacal silver staining, scanning electron microscopy, immunocytochemistry and western blot analysis. Our results collectively indicated that diazepam had a pivotal role in melanocytes by enhancing melanin synthesis, melanocyte dendricity, melanosome trafficking, and capture at the dendrite tips. These functions might be attributed to the fact that diazepam activated the peripheral benzodiazepine receptor (PBR). This increased intracellular levels of cAMP, which stimulated the phosphorylation of cAMP response element-binding (CREB). As a result, this increased the tyrosinase, microphthalmia-associated transcription factor (MITF), Rab27a, Myosin Va, Rab17 and Cdc42 expression. This caused melanogenesis and melanosome transport. Therefore, our findings may provide a potential strategy for treating anti-hypopigmentation disorders.

Enhancing the Efficacy of Melanocortin 1 Receptor-Targeted Radiotherapy by Pharmacologically Upregulating the Receptor in Metastatic Melanoma

Melanocortin 1 receptor (MC1R) is under investigation as a target for drug delivery for metastatic melanoma therapy and imaging. The purpose of this study was to determine the potential of using BRAF inhibitors (BRAF_i) and histone deacetylase inhibitors (HDAC_i) to enhance the delivery of MC1R-targeted radiolabeled peptide ([²¹²Pb]DOTA-MC1L) by pharmacologically upregulating the MC1R expression in metastatic melanoma cells and tumors. MC1R expression was analyzed in de-identified melanoma biopsies by immunohistochemical staining. Upregulation of MC1R expression was determined in BRAF^V600E cells (A2058) and BRAF wild-type melanoma cells (MEWO) by quantitative real-time polymerase chain reaction, flow cytometry, and receptor-ligand binding assays. The role of microphthalmia-associated transcription factor (MITF) in the upregulation of MC1R was also examined in A2058 and MEWO cells. The effectiveness of [²¹²Pb]DOTA-MC1L α-particle radiotherapy in combination with BRAF_i and/or HDAC_i was determined in athymic nu/nu mice bearing A2058 and MEWO human melanoma xenografts. High expression of MC1R was observed in situ in clinical melanoma biopsies. BRAF_i and HDAC_i significantly increased the MC1R expression (up to 10-fold in mRNA and 4-fold in protein levels) via MITF-dependent pathways, and this increase led to enhanced ligand binding on the cell surface. Inhibition of MITF expression antagonized the upregulation of MC1R in both BRAF^V600E and BRAF^WT cells. Combining [²¹²Pb]DOTA-MC1L with BRAF_i and/or HDAC_i improved the tumor response by increasing the delivery of ²¹²Pb α-particle emissions to melanoma tumors via augmented MC1R expression. These data suggest that FDA-approved HDAC_i and BRAF_i could improve the effectiveness of MC1R-targeted therapies by enhancing drug delivery via upregulated MC1R.

Gynostemma pentaphyllum saponins induce melanogenesis and activate cAMP/PKA and Wnt/β-catenin signaling pathways

BACKGROUND

Melanogenesis is a physiological process of melanin production in response to UV exposure, which is modulated through multi-signaling pathways including cAMP/PKA, Wnt/β-catenin and MAPK signaling cascades.

HYPOTHESIS/PURPOSE

The present study aims to investigate the molecular mechanism of hyperpigmentation induced by Gynostemma pentaphyllum saponins.

STUDY DESIGN/METHODS

In this study, we investigated the melanogenic effects of triterpenoid saponins of Gynostemma pentaphyllum (GpS), a medicinal plant. Two mouse melanogenic cell lines B16 and B16F10 were employed for the current study.

RESULTS

The results showed that non-toxic doses of GpS markedly increased melanin formation in both B16 and B16F10 cells. Western blot analysis showed that GpS treatment significantly up-regulated the expression levels of the key melanogenic proteins, including tyrosinase (TYR), microphthalmia-associated transcription factor (MITF), TRP-1 and TRP-2 in a dose-dependent manner. The phospho-CREB, which is the downstream target of PKA is also elevated upon GpS treatment. We further observed that H89, a PKA inhibitor, attenuated the GpS induced tyrosinase activity, melanin content, the expression of phospho-CREB. In addition to the cAMP/PKA signaling pathway, GpS treatment also up-regulated the β-catenin of the Wnt signaling pathway which is involved in the transcriptional activation of MITF in melanogensis. We further demonstrated that treatment with GpS markedly enhance mRNA expression of MITF, along with the downstream target molecules, TYR, TRP-1 and TRP-2. Knock-down MITF with siMITF inhibited the expression of MITF mRNA by 63%, and the melanin content was reduced 70% in the siMITF-transfected cells compared to untransfected or scramble siRNA control cells.

CONCLUSION

These findings demonstrated strong melanogenic activities of GpS, and the MITF is essential for the melanogenesis stimulated by GpS.

Liquiritin and Liquiritigenin Induce Melanogenesis via Enhancement of p38 and PKA Signaling Pathways

Background: Liquiritin (LQ) and its aglycone, liquiritigenin (LQG), are major flavonoids in licorice root (Glycyrrhiza spp.). Our preliminary screening identified LQ and LQG, which promote melanin synthesis in the melanoma cells. In this study, we investigated the molecular mechanism of melanin synthesis activated by LQ and LQG. Methods: Murine (B16-F1) and human (HMVII) melanoma cell lines were treated with LQ or LQG. After incubation, melanin contents, intracellular tyrosinase activity, and cell viability were evaluated. Protein levels were determined using Western blotting. Results: LQ and LQG activated melanin synthesis and intracellular tyrosinase activity. The induction of melanin and intracellular tyrosinase activity by LQG was higher than that by LQ. LQ and LQG induced the expression of tyrosinase, tyrosinase-related protein (TRP)-1, and TRP-2. LQ and LQG also enhanced microphthalmia-associated transcription factor (MITF) expression, and cyclic AMP-responsive element-binding protein (CREB) phosphorylation. The phosphorylation of p38 and extracellular signal-regulated kinase (ERK), but not Akt, was significantly increased by LQ or LQG. Furthermore, LQ- or LQG-mediated melanin synthesis was partially blocked by p38 inhibitor (SB203580) and protein kinase A (PKA) inhibitor (H-89); however, ERK kinase (MEK) inhibitor (U0126) and phosphatidylinositol-3-kinase (PI3K) inhibitor (LY294002) had no effect. Conclusions: The results suggest that LQ and LQG enhance melanin synthesis by upregulating the expression of melanogenic enzymes, which were activated by p38 and PKA signaling pathways, leading to MITF expression and CREB phosphorylation.

Anti-melanogenic effects of oyster hydrolysate in UVB-irradiated C57BL/6J mice and B16F10 melanoma cells via downregulation of cAMP signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Pacific oyster (Crassostrea gigas) has been used to treat pigmentary disorders such as freckles, melasma, and moles in Korea.

AIM OF THE STUDY

We aimed to investigate the inhibitory effects of oyster hydrolysate (OH) on melanogenesis in B16F10 melanoma cells and UVB-irradiated C57BL/6J mice.

MATERIAL AND METHODS

The molecular weight distribution and peptide sequences of OH were detected using MALDI-TOF and UHPLC. To evaluate the anti-melanogenic effects of OH, cell viability, melanin content, tyrosinase activity, intracellular cyclic adenosine monophosphate (cAMP) and protein expressions levels were measured in B16F10 cells. In addition, OH was orally administered to UVB-irradiated mice for 9 weeks. After sacrificing the mice, the whitening effects of OH were evaluated based on histological observations and protein expression levels.

RESULTS

In B16F10 cells, OH decreased melanin content and tyrosinase activity in a dose-dependent manner. OH exhibited anti-melanogenic activities via downregulation of cAMP signaling pathway, which consequently decreased melanin synthesis. In UVB-irradiated mice groups, OH decreased the number of active melanocytes and melanin granules. The expression of tyrosinase-related proteins and microphthalmia-associated transcription factor (MITF) decreased in the OH-administered groups.

CONCLUSIONS

These results show that OH inhibits melanin synthesis in B16F10 cells via downregulation of cAMP signaling pathway and in UVB-irradiated mice, by decreasing the number of active melanocytes and melanin granules.

Leathesia difformis Extract Inhibits α-MSH-Induced Melanogenesis in B16F10 Cells via Down-Regulation of CREB Signaling Pathway

Leathesia difformis (L.) Areschoug (L. difformis) is a species of littoral brown algae of the class Phaeophyceae. Only a few studies on the apoptotic, antiviral, and antioxidant properties of L. difformis have been reported, and its inhibitory effect on melanin synthesis has not been studied. The aim of this study was to investigate the anti-melanogenic effect of L. difformis extract on α-melanocyte-stimulating hormone (α-MSH)-induced B16F10 melanocytes and its mechanism of action. L. difformis was extracted using 80% ethanol (LDE) and then fractioned between ethyl acetate (LDE-EA) and water (LDE-A). Our data demonstrated that LDE-EA significantly inhibited melanin level and cellular tyrosinase activity in α-MSH-stimulated B16 cells. In addition, the expression of genes associated with melanin synthesis, such as microphthalmia-associated transcription factor (Mitf), tyrosinase (Tyr), tyrosinase-related protein-1 (Trp-1), dopachrome tautomerase (Dct), and melanocortin 1 receptor (Mc1r) was down-regulated by LDE-EA treatment. Moreover, LDE-EA decreased p-CREB levels, which suggests that the inhibition of the cAMP/PKA/CREB pathways may be involved in the anti-melanogenic effect of LDE-EA. Thus, this study revealed that LDE-EA is an effective inhibitor of hyperpigmentation through inhibition of CREB pathways and may be considered as a potential therapeutic agent for hyperpigmentation disorders.

Effect of polysaccharide FMP-1 from Morchella esculenta on melanogenesis in B16F10 cells and zebrafish

Polysaccharides from Morchella esculenta are known to exhibit diverse bioactivities, while an anti-melanogenesis effect has been barely addressed. Herein, the anti-melanogenesis activity of a heteropolysaccharide from M. esculenta (FMP-1) was investigated in vitro and in vivo. FMP-1 had no significant cytotoxic effect on B16F10 melanoma cells as well as zebrafish larvae, but did reduce melanin contents and tyrosinase activities in both of them. Treatment with FMP-1 also effectively suppressed the expression of melanogenesis-related proteins, including MC1R, MITF, TRP-1 and TRP-2, through decreasing the phosphorylation of cyclic adenosine monophosphate response element-binding protein (CREB). Moreover, the mitogen-activated protein kinase (MAPK) pathway was observed mediating FMP-1's inhibitory effect against melanin production. Specifically, FMP-1 treatment markedly inhibited the activation of phosphorylation of p38 mitogen-activated protein kinase. These results suggested that FMP-1's inhibitory effect against melanogenesis is mediated by the inhibition of CREB and p38 signaling pathways, thereby resulting in the downstream repression of melanogenesis-related proteins and the subsequent melanin production. These data provide insight into FMP-1's potential anti-melanogenesis effect in food and cosmetic industries.