Involvement of the p38 MAPK and ERK signaling pathway in the anti-melanogenic effect of methyl 3,5-dicaffeoyl quinate in B16F10 mouse melanoma cells

Miglitol, an Oral Antidiabetic Drug, Downregulates Melanogenesis in B16F10 Melanoma Cells through the PKA, MAPK, and GSK3β/β-Catenin Signaling Pathways

Hyperpigmentation is a common condition that causes darker spots or patches on the skin, which often look brown, black, gray, red, or pink. This results in unresolved psychological impact due to high anxiety, depression, and somatoform disorder. We aimed to repurpose an antidiabetic drug, miglitol, as an effective compound against hyperpigmentation when applied as a cosmeceutical agent. The present study investigated the antimelanogenic effects of miglitol and the trehalase inhibitor validamycin A. Miglitol in isolation exhibited no cytotoxicity and significantly reduced the melanin production and intracellular tyrosinase activity in B16F10 melanoma cells. The Western blotting results showed that miglitol reduces the expression of melanogenic regulatory factors, including tyrosinase, tyrosinase-related protein (TRP)-1, TRP-2, and microphthalmia-associated transcription factor (MITF). Mechanistically, miglitol appears to suppress melanin synthesis through cAMP-dependent protein kinase (PKA)-dependent downregulation of MITF, a master transcription factor in melanogenesis. The antimelanogenic effects of miglitol was mediated by downregulation of the p38 signaling pathway and upregulation of extracellular signal-regulated kinase (ERK). Moreover, miglitol decreases P-GSK3β and β-catenin levels compared to those in the untreated group. However, miglitol activated P-β-catenin expression compared to that in the untreated group. Finally, we tested the potential of miglitol in topical application through primary human skin irritation tests on the normal skin (upper back) of 33 volunteers. In these assays, miglitol (125 and 250 μM) did not induce any adverse reactions. Taken together, these findings suggest that the regulation of melanogenesis by miglitol may be mediated by the PKA, MAPK, and GSK3β/β-Catenin signaling pathways and that miglitol might provide new insights into drug repurposing for the treatment of hyperpigmentation symptoms.

Anti-Inflammatory Effects of (9Z,11E)-13-Oxooctadeca-9,11-dienoic Acid (13-KODE) Derived from Salicornia herbacea L. on Lipopolysaccharide-Stimulated Murine Macrophage via NF-kB and MAPK Inhibition and Nrf2/HO-1 Signaling Activation

Glasswort (Salicornia herbacea L.) is a halophyte that exhibits antioxidant and antidiabetic effects. Only a few studies have been conducted on its antioxidant effects. Here, we isolated an antioxidant using an activity-based purification method, and the resulting compound was identified as (9Z,11E)-13-Oxooctadeca-9,11-dienoic acid (13-KODE). We investigated its ability to suppress inflammatory responses and the molecular mechanisms underlying these abilities using lipopolysaccharide-stimulated RAW 264.7 macrophage cells. We studied the anti-inflammatory effects of 13-KODE derived from S. herbacea L on RAW 264.7 macrophages. 13-KODE inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO) production by suppressing inducible NO synthase and suppressed LPS-induced tumor necrosis factor and interleukin-1β expression in RAW 264.7 macrophages. LPS-mediated nuclear localization of NF-κB and mitogen-activated protein kinase activation were inhibited by 13-KODE. 13-KODE significantly reduced LPS-induced production of reactive oxygen species and increased the expression of nuclear factor erythroid-2 like 2 (Nfe2I2) and heme oxygenase 1. Overall, our results indicate that 13-KODE may have potential for treating inflammation.

The Ethanol Extract of Musa sapientum Linn. Peel Inhibits Melanogenesis through AKT Signaling Pathway

Hyperpigmentation caused by melanin overproduction can be induced by UV radiation. The quest for effective depigmenting agents continues because many anti-melanin agents have restricted use and/or produce side-effects. The present study was aimed to investigate the inhibitory activity of Musa sapientum Linn. (AA group) peel ethanol extracts (MPE) on α-melanocyte stimulating hormone (α-MSH)-induced melanin production. In addition, the molecular mechanism related to this process was examined in B16F10 mouse melanoma cells. The results indicated that MPE remarkably inhibited melanogenesis in α-MSH-stimulated B16F10 cells. Microphthalmia-associated transcription factor (MITF) and tyrosinase expressions were suppressed by MPE in a concentration-dependent manner. In addition, MPE significantly decreased the expression of melanosome transfer protein markers (Rab27a and Pmel17) in a dose-dependent manner. This study found that the elevated phosphorylation of AKT in the B16F10 cells was diminished by MPE treatment. Furthermore, microtubule-associated protein 1 light chain 3 (LC3)-II and p62 (autophagy markers) were affected after the B16F10 cells were treated with MPE. This study demonstrated that MPE might be an effective agent for anti-melanogenesis through the AKT pathway, subsequently diminishing MITF expression and tyrosinase enzyme family production. The findings indicated that MPE could potentially serve as a depigmenting agent in cosmeceuticals.

Chemical Structure and Biological Activities of Secondary Metabolites from Salicornia europaea L

Salicornia europaea L. is a halophyte that grows in salt marshes and muddy seashores, which is widely used both as traditional medicine and as an edible vegetable. This salt-tolerant plant is a source of diverse secondary metabolites with several therapeutic properties, including antioxidant, antidiabetic, cytotoxic, anti-inflammatory, and anti-obesity effects. Therefore, this review summarizes the chemical structure and biological activities of secondary metabolites isolated from Salicornia europaea L.

Anti-Melanogenesis Effects of Lotus Seedpod In Vitro and In Vivo

Melanogenesis has many important physiological functions. However, abnormal melanin production causes various pigmentation disorders. Melanin synthesis is stimulated by α-melanocyte stimulating hormone (α-MSH) and ultraviolet (UV) irradiation. Lotus seedpod extract (LSE) has been reported as possessing antioxidative, anti-aging, and anticancer activities. The present study examined the effect of LSE on melanogenesis and the involved signaling pathways in vitro and in vivo. Results showed that non-cytotoxic doses of LSE and its main component epigallocatechin (EGC) reduced both tyrosinase activity and melanin production in the α-MSH-induced melanoma cells. Western blotting data revealed that LSE and EGC inhibited expressions of tyrosinase and tyrosinase-related protein 1 (TRP-1). Phosphorylation of p38 and protein kinase A (PKA) stimulated by α-MSH was efficiently blocked by LSE treatment. Furthermore, LSE suppressed the nuclear level of cAMP-response element binding protein (CREB) and disturbed the activation of melanocyte inducing transcription factor (MITF) in the α-MSH-stimulated B16F0 cells. The in vivo study revealed that LSE inhibited melanin production in the ear skin of C57BL/6 mice after exposure to UVB. These findings suggested that the anti-melanogenesis of LSE involved both PKA and p38 signaling pathways. LSE is a potent novo natural depigmenting agent for cosmetics or pharmaceutical applications.

Anti-Melanogenic Effects of Ethanol Extracts of the Leaves and Roots of Patrinia villosa (Thunb.) Juss through Their Inhibition of CREB and Induction of ERK and Autophagy

Patrinia villosa (Thunb.) Juss is a traditional herb commonly used in East Asia including Korea, Japan, and China. It has been administered to reduce and treat inflammation in Donguibogam, Korea. The mechanism for its anti-inflammatory effects has already been reported. In this study, we confirmed the efficacy of Patrinia villosa (Thunb.) Juss ethanol extract (Pv-EE) for inducing autophagy and investigate its anti-melanogenic properties. Melanin secretion and content were investigated using cells from the melanoma cell line B16F10. Pv-EE inhibited melanin in melanogenesis induced by α-melanocyte-stimulating hormone (α-MSH). The mechanism of inhibition of Pv-EE was confirmed by suppressing the mRNA of microphthalmia-associated transcription factor (MITF), decreasing the phosphorylation level of CREB, and increasing the phosphorylation of ERK. Finally, it was confirmed that Pv-EE induces autophagy through the autophagy markers LC3B and p62, and that the anti-melanogenic effect of Pv-EE is inhibited by the autophagy inhibitor 3-methyl adenine (3-MA). These results suggest that Pv-EE may be used as a skin protectant due to its anti-melanin properties including autophagy.

Coriolic Acid (13-(S)-Hydroxy-9Z, 11E-octadecadienoic Acid) from Glasswort (Salicornia herbacea L.) Suppresses Breast Cancer Stem Cell through the Regulation of c-Myc

Cancer stem cells have certain characteristics, such as self-renewal, differentiation, and drug resistance, which are related to tumor progression, maintenance, recurrence, and metastasis. In our study, we targeted breast cancer stem cells (BCSCs) using a natural compound, coriolic acid, from Salicornia herbacea L. This compound was isolated by mammosphere formation inhibition bioassay-guided fractionation and identified by using NMR spectroscopy and electrospray ionization mass spectrometry. Coriolic acid inhibited the formation of mammospheres and induced BCSC apoptosis. It also decreased the subpopulation of CD44^high/CD24^low cells, a cancer stem cell (CSC) phenotype, and specific genes related to CSCs, such as Nanog,Oct4, and CD44. Coriolic acid decreased the transcriptional and translational levels of the c-Myc gene, which is a CSC survival factor. These results indicated that coriolic acid could be a novel compound to target BCSCs via regulation of c-Myc.

Collagen/Chitosan Complexes: Preparation, Antioxidant Activity, Tyrosinase Inhibition Activity, and Melanin Synthesis

Bioactive collagen/chitosan complexes were prepared by an ion crosslinking method using fish skin collagen and chitosan solution as raw materials. Scanning electron microscopy observation confirmed that the collagen/chitosan complexes were of a uniform spherical shape and uniform particle size. The complexes were stable at different pH values for a certain period of time through swelling experiments. Differential scanning calorimetry (DSC) showed the collagen/ chitosan complexes were more stable than collagen. X-ray diffraction (XRD) showed that the complexes had a strong crystal structure, and Fourier transform infrared spectroscopy (FTIR) data revealed the changes in the secondary structure of the protein due to chitosan and TPP crosslinking. The content of malondialdehyde (MDA) in the complex treatment group was considerably lower, but the content of SOD was significantly higher than that of the collagen group or chitosan group. In addition, the collagen/chitosan complexes could considerably reduce melanin content, inhibit tyrosinase activity, and down-regulate tyrosinase mRNA expression. In conclusion, the collagen/chitosan complexes were potential oral protein preparation for antioxidant enhancement and inhibiting melanin synthesis.

Resveratrol-mediated inhibition of cyclooxygenase-2 in melanocytes suppresses melanogenesis through extracellular signal-regulated kinase 1/2 and phosphoinositide 3-kinase/Akt signalling

Resveratrol (3,5,4'-trihydroxy-trans-stilbene), has been reported to exert a variety of important pharmacological effects including anti-inflammatory, anticancer, and direct inhibition of tyrosinase. This study aimed to examine the expression of melanogenic molecules following down-regulation of cyclooxygenase (COX)-2 expression by resveratrol and the related signal transduction pathways in mouse B16F10 melanoma cells and zebrafish larvae. We report that resveratrol suppressed COX-2 in melanocytes and decreased the expressions of tyrosinase and microphthalmia-associated transcription factor (MITF). Furthermore, inhibition of COX-2 with NS398 enhanced resveratrol-reduced tyrosinase and MITF expression. Resveratrol also induced phosphorylation of extracellular signal-regulated 1/2 (ERK1/2) and phosphoinositide-3 (PI-3)-kinase/Akt. Inhibition of ERK1/2 or PI-3K/Akt by PD98059 and LY294002 restored the decreased tyrosinase activity and MITF expression via resveratrol-mediated down-regulation of COX-2. Additionally, resveratrol inhibited body pigmentation in zebrafish. These results indicated that resveratrol inhibited melanogenesis by down-regulating COX-2 via ERK1/2 and PI-3K/Akt pathways in B16F10 cells.

Antiphotoaging and Antimelanogenic Effects of Penthorum chinense Pursh Ethanol Extract due to Antioxidant- and Autophagy-Inducing Properties

Ethnopharmacological Relevance. Penthorum chinense Pursh (Penthoraceae) is a traditional herbal plant that has been used in China for the treatment of jaundice, cholecystitis, edema, and infectious hepatitis. In addition, the Korea Medicinal Plant Dictionary states that Penthorum chinense Pursh can be used to treat contusions and skin bruises by improving blood flow. Recent studies have shown that Penthorum chinense Pursh ethanol extract (Pc-EE) exhibits strong antioxidant effects. In this study, we examined the effects of Pc-EE on UVB-induced or H₂O₂-induced oxidative stress, as well as its antimelanogenic properties. Cell viability, matrix metalloproteinase (MMP) expression, cyclooxygenease-2 (COX-2), and interleukin-6 (IL-6) expression and moisturizing factors were investigated in keratinocytes. Collagen synthesis induction was measured in HEK293T cells. For melanogenesis, the effects of Pc-EE on melanin content and tyrosinase activity were measured. Additionally, the antimelanogenic- and autophagy-inducing activities of Pc-EE were examined using immunoblotting and confocal microscopy. Pc-EE protected HaCaT cells against death from UVB irradiation- or H₂O₂-induced oxidative stress. Pc-EE increased the promoter activity of the type 1 procollagen gene Col1A1 and decreased the expression of MMPs, COX-2, IL-6, and hyaluronidase induced by UVB irradiation- or H₂O₂-induced oxidative stress. Pc-EE showed a strong antioxidant effect in the DPPH assay. In α-melanocyte-stimulating hormone- (α-MSH-) stimulated B16F10 cells, Pc-EE reduced melanin production, decreased tyrosinase expression and microphthalmia-associated transcription factor (MITF) protein levels, and decreased the phosphorylation levels of p38 and JNK. In HEK293T cells, Pc-EE promoted the expression of GFP-LC3B. In B16F10 cells, the LC3B and melanin contents were reduced by Pc-EE and were restored by the autophagy inhibitor 3-methyladenine (3-MA). These results suggest that Pc-EE can be used as a skin protection agent due to its antiapoptotic, antiaging, anti-inflammatory, and antimelanogenic properties.

A chemical compound from fruit extract of Juglans mandshurica inhibits melanogenesis through p-ERK-associated MITF degradation

BACKGROUND

Trials for regulation of abnormal hyperpigmentation from the use of natural products have been going on for years. Leaf and root extracts from Juglans mandshurica are reported to function as antioxidants and to suppress allergic dermatitis. However, studies evaluating its fruit extract and the chemical compounds from the fruit extract are lacking in dermatology fields, including melanogenesis.

PURPOSE

The aim of this study is to understand the effect of the fruit extract from J. mandshurica on pigmentation and to search for specific chemical compounds that affect melanogenesis.

METHODS

After screening out any anti-melanotic effects of the fruit extract from J. mandshurica in B16F10 melanoma cells, three major phenolic compounds isolated from the fruit extract were tested by western blot analysis for expression of microphthalmia-associated transcription factor (MITF) and tyrosinase. Their effect on B16F10 melanoma cells with regard to melanogenesis was also confirmed in primary human epidermal melanocytes (PHEMs). PD98059 was tested to observe the compounds' signaling role in the extracellular signal-regulated protein kinase (ERK)-pathway.

RESULTS

Fruit extract from J. mandshurica showed anti-melanotic effects in B16F10 melanoma cells. After chemical compounds were isolated from the fruit extracts, three phenolic compounds were evaluated for anti-melanotic effects. 2-[4-(3-hydroxypropyl)-2-methoxyphenoxy]-1,3-propanediol (compound 1) showed the highest suppression effect among the three compounds. In B16F10 melanoma cells and PHEMs, reduced melanin contents were observed after treatment with the compound (1). Experiments using a blocker of ERK showed that the inhibitory effect of the compound (1) on melanogenesis was dependent on ERK-associated MITF degradation.

CONCLUSION

A chemical constituent of Juglans mandshurica Maxim. induces an inhibitory mechanism to melanogenesis. It has the potential to become a whitening agent in the medical field, though this requires further clinical investigation.

Effect of Sucrier Banana Peel Extracts on Inhibition of Melanogenesis through the ERK Signaling Pathway

Hyperpigmentation is a type of pigmentary disorder induced by overexpression of melanin content activated severe esthetic problems as melasma, freckle, ephelides, lentigo and other forms on human skin. Several whitening agents have restricted use because of their side effects or stability such as kojic acid, ascorbic acid and hydroquinone can act as cytotoxic substance which associated to dermatitis and skin cancer. To find for the safe substance, this study aimed to find for the ability of several components in Sucrier banana peel (SBP) extracts to inhibit melanogenesis process through p38 signaling pathway in B16F10 mouse melanoma cells. Tyrosinase activity and the cellular melanin content were dose dependent manner decreasing after SBP treatment. Furthermore, SBP decreased the expression of melanogenesis relate protein as microphthalmia-associated transcription factor (MITF) and tyrosinase protein after 24 hours incubation with α-melanocyte stimulating hormones (MSH) stimulating. The findings demonstrated that SBP contained an effective agent for hyperpigmentation inhibitor through p38 signaling pathways without any effect to ERK pathway, and subsequent down-regulate MITF expression and tyrosinase enzyme family production.

MicroRNA-23a inhibits melanoma cell proliferation, migration, and invasion in mice through a negative feedback regulation of sdcbp and the MAPK/ERK signaling pathway

Melanoma is the main cause of death associated with skin cancer. Surgical resection and adjuvant therapy are currently effective treatments, but the recurrence rate is very high. The understanding of microRNA (miR) dynamics after surgical resection of melanoma is essential to accurately explain the changes in the recurrence of melanoma. In this study, we hypothesized that microRNA-23a (miR-23a) affects the cell proliferation, migration, and invasion of melanoma with a mechanism related to SDCBP and the MAPK/ERK signaling pathway. To validate this, we performed a series of experiments in cells of melanoma modeled. Initially, positive expression of SDCBP and morphology of normal and melanoma tissues and cells were observed. Expression of miR-23a, SDCBP, and MAPK/ERK signaling pathway-related genes was identified in melanoma tissues. Melanoma cells transfected with mimic or inhibitor of miR-23a or si-SDCBP were detected to validate effect of miR-23a on SDCBP and the MAPK/ERK signaling pathway. MTT assay, scratch test, transwell assay, and flow cytometry were performed to evaluate cell viability, invasion, metastasis, and apoptosis in vitro, respectively. Tumorigenicity assay in nude mice was conducted to test the tumorigenesis of the transfected cells in vivo. High positive expression of SDCBP and abnormal morphology were observed in melanoma tissues and cells. Reduced expression of miR-23a and increased expression of SDCBP and MAPK/ERK signaling pathway-related genes were identified in the melanoma tissues of melanoma mice. Overexpressed miR-23a dampened SDCBP and the MAPK/ERK signaling pathway. The melanoma cells with overexpressed miR-23a presented ascended cell apoptosis and descended cell proliferation, migration, invasion as well as tumor size. Taken together, our study demonstrated that miR-23a could inhibit the development of melanoma in mice through a negative feedback regulation of SDCBP and the MAPK/ERK signaling pathway. © 2018 IUBMB Life, 71(5):587-600, 2019.

Potential anti-vitiligo properties of cynarine extracted from Vernonia anthelmintica (L.) Willd

Vitiligo is a depigmentation disorder of the skin. It is primarily caused by the destruction of melanocytes or obstruction of the melanin synthesis pathway. Melanin is a type of skin pigment that determines skin color. The seeds of Vernonia anthelmintica (L.) Willd (Kaliziri) are used for treating skin diseases including vitiligo in traditional Uyghur medicine. 1,5‑Dicaffeoylquinic acid (1,5‑diCQA) is a natural polyphenolic compound widely distributed in plants and extracted from Kaliziri seeds. Therefore, in the present study, the effect of 1,5‑diCQA on melanin synthesis in B16 cell was evaluated, and its molecular mechanism was explored. The results indicated that 1,5‑diCQA treatment of B16 cells stimulated an increase of intracellular melanin level and tyrosinase (TYR) activity without cytotoxicity. Reverse transcription quantitative polymerase chain reaction results also indicated that 1,5‑diCQA may markedly improve the protein expression and RNA transcription of microphthalmia‑associated transcription factor (MITF), melanogenic enzyme Tyr, tyrosinase‑related protein 1 (TRP 1) and tyrosinase‑related protein 2 (TRP 2). Additional results identified that 1,5‑diCQA may promote the phosphorylation of p38 mitogen‑activated protein kinase (p38 MAPK) and extracellular signal‑regulated kinase (ERK) MAPK. Notably, the increased levels of intracellular melanin synthesis and tyrosinase expression induced by 1,5‑diCQA treatment were significantly attenuated by the protein kinase A (PKA) inhibitor H‑89. Intracellular cyclic adenosine monophosphate (cAMP) concentration and phosphorylation of cAMP‑response element binding protein was increased following 1,5‑diCQA treatment. These results indicated that 1,5‑diCQA stimulated melanogenesis via the MAPK and cAMP/PKA signaling pathways in B16 cells, which has potential therapeutic implications for vitiligo.

A novel psoralen derivative-MPFC enhances melanogenesis via activation of p38 MAPK and PKA signaling pathways in B16 cells

As an active compound, psoralen is present in various Chinese herbal medicines and has exhibited significant activity in skin disease treatment. Its derivative 8-methoxypsoralan (8-MOP) is the most commonly used drug to induce repigmentation of vitiligo. In our previous screening assays, 4-methyl-6-phenyl-2H-furo[3,2-g]chromen-2-one (MPFC), a psoralen derivative, was identified as more effective tyrosinase and melanin activator than the positive control 8-MOP in consideration of low doses, as well as low toxicity. The overall purpose of this study was to characterize the melanogenic effect and mechanisms of MPFC in B16 cells. The melanin biosynthesis effects of MPFC were determined by examination of cellular melanin contents, tyrosinase activity assay, cyclic adenosinemonophosphate (cAMP) assay, and western blotting of MPFC-stimulated B16 mouse melanoma cells. Our results showed that MPFC enhanced both melanin synthesis and tyrosinase activity in a concentration-dependent manner as well as significantly activated the expression of melanogenic proteins such as tyrosinase, tyrosinase-related protein-1 and tyrosinase-related protein-2. Western blot analysis showed that MPFC increased the phosphorylation of p38 mitogen-activated protein kinase and cAMP response element-binding protein (CREB) as well as the expression of microphthalmia-associated transcription factor (MITF). Moreover, MPFC stimulated intracellular cAMP levels and induced tyrosinase activity and melanin synthesis were attenuated by H89, a protein kinase A inhibitor. These results indicated that MPFC-mediated activation of the p38 MAPK and the protein kinase A (PKA) pathway may shed light on a novel approach for an effective therapy for vitiligo.

Effects of volatile oil from ginger on the murine B16 melanoma cells and its mechanism

In this study, the inhibitory effects of volatile oil from ginger on melanogenesis and its antioxidant characteristics were investigated. The effects of volatile oil from ginger on cell proliferation, melanin content and tyrosinase activity were determined using a microplate reader. In addition, the expression of melanogenesis-related protein was determined by western blotting. The results indicate that the tested concentrates of volatile oil from ginger showed inhibitory effects on cell proliferation and melanogenesis. This revealed that volatile oil from ginger exhibited apparent capacities for scavenging ROS and lipid peroxidation. Furthermore, volatile oil from ginger improved the activities of GSH, SOD and CAT in B16 melanoma cells. These results demonstrated that volatile oil from ginger suppressed melanin synthesis through its antioxidant properties and the inhibitory effects on tyrosinase activity and melanogensis-related proteins. Hence, volatile oil from ginger could be used as an effective skin-whitening agent applied in food industry.

An Isoxazole Chalcone Derivative Enhances Melanogenesis in B16 Melanoma Cells via the Akt/GSK3β/β-Catenin Signaling Pathways

Plants or plant-derived products have been routinely used in several traditional medicine systems for vitiligo treatment. It is well-known that melanogenesis can be promoted by certain flavonoid compounds isolated from the traditional Uyghur medicinal plant, Kaliziri. Therefore, Chalcones, one class of flavonoid compounds, has become an interesting target for the development of anti-vitiligo agents. A series of novel isoxazole chalcone derivatives have been designed, synthesized, and evaluated for biological activities by our group. Among them, derivative 1-(4-((3-phenylisoxazol-5-yl)methoxy)phenyl)-3-phenylprop-2-en-1-one (PMPP) was identified as a potent tyrosinase activator with better activity and lower toxicity than the positive control 8-methoxypsoralen (8-MOP) in this study. Further investigations revealed that Akt and GSK3β were the signaling pathways involved in the hyperpigmentation of PMPP. Overall, these studies may provide a convenient and novel approach for the further development of anti-vitiligo agents.

Anti-melanogenic effects of Aster spathulifolius extract in UVB-exposed C57BL/6J mice and B16F10 melanoma cells through the regulation of MAPK/ERK and AKT/GSK3β signalling

OBJECTIVES

Pharmacological studies of Aster spathulifolius Maxim(AS) have demonstrated its anti-allergy, anti-viral and anti-obesity effects, however, its anti-melanogenic effects is still unclear. In this study, the effects of AS extract (ASE) on the inhibition of melanin synthesis were investigated in vitro and in vivo.

METHODS

To perform this study, the contents of melanin and tyrosinase activity were analysed in B16F10 melanoma cells. Western blotting was carried out to determine the underlyling mechanism. Additionally, we investigated the effect of this extract on hyperpigmentation in C57bL/6J mice induced by 3, 6 and 9 weeks of UVB irradiation.

KEY FINDINGS

AS extract led to reduced melanin synthesis through the regulation of MITF and its downstream signals. Furthermore, ASE increased the phosphorylation of MAPK/ERK and Akt/GSK3β signalling pathway components. In vivo study, hypopigmentation effects were also observed. The melanocyte activity and the distribution of melanin granules were decreased in UVB-irradiated mice treated with ASE.

CONCLUSIONS

These results suggest that the ASE may be promising as an active anti-melanogenic component, and further investigations should be performed regarding its potential as a whitening agent in the field of cosmetics.

Modulation effects of sweroside isolated from the Lonicera japonica on melanin synthesis

In the course of screening for the melanogenesis inhibitors, sweroside was isolated from Lonicera japonica. Its chemical structure was determined on the basis of spectroscopic analysis, including mass spectroscopy and nuclear magnetic resonance analysis. Sweroside inhibited potent melanogenesis in melan-a cells at 300μM without cytotoxicity. Also, sweroside decreased tyrosinase, tyrosinase-related protein-1 (TRP-1) and TRP-2 protein production in melan a cells. To identify the signaling pathway of sweroside, the ability of sweroside to influence Akt and extracellular signal-regulated protein kinase (ERK) activation was investigated. Sweroside induced Akt and ERK in a dose-dependent manner. In addition, the specific inhibition of the Akt and ERK signaling pathways were studied by specific inhibitor LY294002 and U0126, respectively and it was causing the increased melanin synthesis. Furthermore, sweroside presented inhibition of the body pigmentation and tyrosinase activity in zebrafish in vivo model. These results suggest that sweroside isolated from L. japonica may be an effective skin-whitening agent through the regulates the expression of MAP kinase and melanogenic enzymes.

Ophiopogonin-D suppresses MDA-MB-435 cell adhesion and invasion by inhibiting matrix metalloproteinase-9

Ophiopogonin-D is one of steroidal saponins isolated from the root of the Chinese medicinal plant Ophiopogon japonicas. It has been claimed to possess anti-inflammatory and anti-oxidant properties. The present study was the first to examine the anti-tumor metastasis properties of ophiopogonin-D. An MTT assay showed that ophiopogonin-D inhibited the proliferation of MDA-MB-435 melanoma cells, and decreased invasion was demonstrated using a Transwell invasion assay. Furthermore, adhesion of MDA-MB-435 cells to human umbilical vascular endothelial cells and to fibronectin was inhibited by ophiopogonin-D. Gelatin zymography and western blot analysis showed that ophiopogonin-D inhibited the expression and secretion of matrix metalloproteinase-9 (MMP-9), but not that of MMP-2. Inhibition of phosphorylation of p38 by ophiopogonin-D indicated its inhibition of the mitogen-activated protein kinase pathway. Overall, the results suggested that ophiopogonin-D may be considered as a candidate drug for treating or preventing tumor metastasis.

Lipoteichoic acid isolated from Lactobacillus plantarum inhibits melanogenesis in B16F10 mouse melanoma cells

Lipoteichoic acid (LTA) is a major component of the cell wall of Gram-positive bacteria. Its effects on living organisms are different from those of lipopolysaccharide (LPS) found in Gram-negative bacteria. LTA contributes to immune regulatory effects including anti-aging. In this study, we showed that LTA isolated from Lactobacillus plantarum (pLTA) inhibited melanogenesis in B16F10 mouse melanoma cells. pLTA reduced the cellular activity of tyrosinase and the expression of tyrosinase family members in a dose-dependent manner. The expression of microphthalmia-associated transcription factor (MITF), a key factor in the synthesis of melanin, was also decreased by pLTA. Further, we showed that pLTA activated melanogenesis signaling, such as extracellular signal-regulated kinase (ERK) and phosphatidylinositol 3-kinse (PI3K)/AKT. In addition, the expression of heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) and HuR, which are important RNA-binding proteins (RBPs), was reduced. pLTA likely degrades MITF via regulation of melanogenic signaling and RNA stability of melanogenic proteins, resulting in the reduction of melanin. Thus, our data suggest that pLTA has therapeutic potential for treating hyperpigmentation disorders and can also be used as a cosmetic whitening agent.

Microarray-based analysis of the differential expression of melanin synthesis genes in dark and light-muzzle Korean cattle

The coat color of mammals is determined by the melanogenesis pathway, which is responsible for maintaining the balance between black-brown eumelanin and yellow-reddish pheomelanin. It is also believed that the color of the bovine muzzle is regulated in a similar manner; however, the molecular mechanism underlying pigment deposition in the dark-muzzle has yet to be elucidated. The aim of the present study was to identify melanogenesis-associated genes that are differentially expressed in the dark vs. light muzzle of native Korean cows. Using microarray clustering and real-time polymerase chain reaction techniques, we observed that the expression of genes involved in the mitogen-activated protein kinase (MAPK) and Wnt signaling pathways is distinctively regulated in the dark and light muzzle tissues. Differential expression of tyrosinase was also noticed, although the difference was not as distinct as those of MAPK and Wnt. We hypothesize that emphasis on the MAPK pathway in the dark-muzzle induces eumelanin synthesis through the activation of cAMP response element-binding protein and tyrosinase, while activation of Wnt signaling counteracts this process and raises the amount of pheomelanin in the light-muzzle. We also found 2 novel genes (GenBank No. NM-001076026 and XM-588439) with increase expression in the black nose, which may provide additional information about the mechanism of nose pigmentation. Regarding the increasing interest in the genetic diversity of cattle stocks, genes we identified for differential expression in the dark vs. light muzzle may serve as novel markers for genetic diversity among cows based on the muzzle color phenotype.

Extracts of Artocarpus communis decrease α-melanocyte stimulating hormone-induced melanogenesis through activation of ERK and JNK signaling pathways

Artocarpus communis is an agricultural plant that is also used in folk medicine to prevent skin diseases, including acne and dermatitis. Extracts of A. communis have been used to effectively inhibit melanogenesis; however, the antimelanogenesis mechanism of these extracts has not yet been investigated. The present study utilized a cell-free tyrosinase assay as well as α-melanocyte stimulating hormone- (-MSH-) induced tyrosinase assay conducted in B16F10 cells, performed a cytotoxicity assay, and determined cellular melanin content to examine the effects of a methanolic extract of A. communis (ACM) and various organic partition fractions of A. communis on melanogenesis. In addition, we performed western blot analysis to elucidate the mechanism of their antimelanogenesis effect. Our results indicated that, except for the n-hexane extract, ACM and the various partition extracts at noncytotoxic concentrations effectively decreased melanin content and tyrosinase activity by downregulating microphthalmia-associated transcription factor (MITF) and phosphorylated cAMP response element-binding protein (p-CREB). Moreover, ACM and the partition fractions activated phosphorylation of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) to inhibit the synthesis of MITF and finally to decrease melanin production. In conclusion, we suggest that noncytotoxic concentrations of ACM and the various partition fractions may be useful as references for developing skin-lighting agents for use in medicines or cosmetics.

Octaphlorethol A isolated from Ishige foliacea inhibits α-MSH-stimulated induced melanogenesis via ERK pathway in B16F10 melanoma cells

In this study, the potent skin-whitening effects of Octaphlorethol A (OPA) isolated from Ishige foliacea was investigated through inhibitory effect of melanin synthesis and tyrosinase activity in alpha-melanocyte stimulating hormone (α-MSH) induced B16F10 melanoma cells. OPA markedly inhibited melanin synthesis and tyrosinase activity in a concentration-dependent manner. We also found that OPA decreased microphthalmia-associated transcription factor (MITF), tyrosinase, tyrosinase-related protein-1 and -2 (TRP-1 and TRP-2) protein expressions. Moreover, OPA reduces p38 MAPK protein levels and activates extracellular signal-regulated kinase (ERK) and c-jun N-terminal kinases (JNKs) protein expressions in B16F10 cells. A specific ERK inhibitor PD98059 significantly blocks OPA-inhibited melanin synthesis and tyrosinase activity, whereas a p38MAP and JNK inhibitor had no effect. These findings provide evidence demonstrating that the anti-melanogenic effect of OPA is mediated through the activation of ERK signal pathway in B16F10 cells. These results indicate that OPA has the potential to be used as a melanogenesis inhibitor in the food and cosmetics industry.

Natural Melanogenesis Inhibitors Acting Through the Down-Regulation of Tyrosinase Activity

Melanogenesis is a biosynthetic pathway for the formation of the pigment melanin in human skin. A key enzyme, tyrosinase, catalyzes the first and only rate-limiting steps in melanogenesis, and the down-regulation of enzyme activity is the most reported method for the inhibition of melanogenesis. Because of the cosmetically important issue of hyperpigmentation, there is a big demand for melanogenesis inhibitors. This encourages researchers to seek potent melanogenesis inhibitors for cosmetic uses. This article reviews melanogenesis inhibitors that have been recently discovered from natural sources. The reaction mechanisms of the inhibitors on tyrosinase activity are also discussed.