Tyrosinase Protein Levels Research Articles

Depigmentation of α-melanocyte-stimulating hormone-treated melanoma cells by β-mangostin is mediated by selective autophagy.

Melanogenesis is a key pathway for the regulation of skin pigmentation and the development of skin-lightening/skin-whitening drugs or cosmetics. In this study, we found that β-mangostin from seedcases of Garcinia mangostana inhibited α-melanocyte-stimulating hormone (α-MSH)-mediated melanogenesis in B16F10 melanoma cells and a three-dimensional human skin model. β-Mangostin significantly inhibited the protein level of tyrosinase induced by α-MSH in UPS (ubiquitin proteasome system)-independent and lysosome-dependent manner. The inhibition of autophagy by 3-methyladenine treatment or ATG5 knockdown effectively recovered premelanosome protein as well as tyrosinase degraded by the β-mangostin treatment. However, rapamycin, a representative non-selective autophagy inducer, triggered autophagy in α-MSH-stimulated cells, which was characterized by a considerable decrease in p62, but it was unable to inhibit melanogenesis. Melanosome-engulfing autophagosomes were observed using transmission electron microscopy. Furthermore, previously formed melanin could be degraded effectively in an autophagy-dependent manner in β-mangostin-treated cells. Taken together, our results suggest that β-mangostin inhibits the melanogenesis induced by α-MSH via an autophagy-dependent mechanism, and thus, the depigmentation effect of β-mangostin may depend on autophagy targeted at the melanosome rather than non-selective autophagy.

4-n-butylresorcinol enhances proteolytic degradation of tyrosinase in B16F10 melanoma cells.

4-n-butylresorcinol is a competitive inhibitor of tyrosinase and has been used as an antimelanogenic agent. However, its inhibition mechanism in intact cells is not fully understood. To elucidate the cellular mechanism, we compared in vitro and in vivo inhibitory effects of 4-n-butylresorcinol on tyrosinase activity. B16F10 melanoma cells were cultured in media containing α-MSH in the presence or absence of 4-n-butylresorcinol. Tyrosinase mRNA levels, protein levels and activity in B16F10 cells were compared by real-time PCR, immunostaining combined with western blot and colorimetric analysis, respectively. Melanin concentration was measured by colorimetry both in the cells and in the media. Tyrosinase glycosylation and proteolytic degradation were analysed by immunoblotting after cells were treated with Endo H/PNGase F and E64/proteasome inhibitors, respectively. 4-n-butylresorcinol inhibited tyrosinase activity and melanin synthesis more effectively in intact cells than in cell lysates. Western blotting and real-time RT-PCR showed that 4-n-butylresorcinol reduced protein levels, but not mRNA levels, of tyrosinase in B16F10 cells. 4-n-butylresorcinol showed no effect on the processing of tyrosinase glycosylation or on trafficking to melanosomes. However, treatment of B16F10 cells with E64 or proteasome inhibitor abrogated the 4-n-butylresorcinol-induced decrease of tyrosinase. Moreover, 4-n-butylresorcinol activated p38 MAPK, resulting in increased ubiquitination of tyrosinase. 4-n-butylresorcinol inhibits melanogenesis by enhancing proteolytic degradation of tyrosinase as well as competitive binding to tyrosinase. These findings will help to develop new, effective and safe chemicals for the treatment of hyperpigmentation disorders.

Novel Anti-Melanogenesis Properties of Polydeoxyribonucleotide, a Popular Wound Healing Booster.

Polydeoxyribonucleotide (PDRN), a deoxyribonucleotide polymer, is popularly used for faster healing of cutaneous wounds and boosting of neocollagenesis of photoaged skin among current dermatologic practitioners. Some patients receiving PDRN injection treatment also reported improvement of photoaging-associated mottled pigmentation (PMP). To investigate the effect of PDRN on cutaneous melanogenesis, we examined the effect of PDRN and an available product (Placentex®) containing PDRN on melanogenesis using human melanocytes-keratinocytes cocultures and mouse melanocytes. Melanin content, tyrosinase activity, and levels of microphthalmia-associated transcription factor (MITF), tyrosinase, and tyrosinase-related protein (TRP-1) were determined. Intracellular signaling pathways were assessed by Western blotting. PDRN and Placentex® led to decreases in melanin content, tyrosinase activity, and MITF and TRP-1 expression with concomitant increases in phosphorylated forms of extracellular signal-regulated protein kinase (ERK) and AKT in mouse melanocytes. More importantly, both PDRN and Placentex® significantly suppressed the melanin content in human melanocyte–keratinocyte cocultures. Clinical evaluation of six female patients with facial hyperpigmentation after three sessions of intradermal PDRN injections using a 5-point scale revealed that PDRN led to more than noticeable improvements in hyperpigmented lesions. This is the first study to demonstrate that PDRN, which is known for its wound-healing properties, may have novel anti-melanogenesis and potential skin whitening properties.

1-Phenyl-3-(2-thiazolyl)-2-thiourea inhibits melanogenesis via a dual-action mechanism.

1-Phenyl-3-(2-thiazolyl)-2-thiourea (PTTU) is a well-characterized dopamine β-hydroxylase inhibitor that prevents 6-hydroxydopamine-induced degenerative neuronal disease. However, the effect of PTTU on melanogenesis has not been reported. In this study, we examined the effect of PTTU on melanogenesis and studied its mechanism of action. We found that PTTU decreased melanin biosynthesis in a dose-dependent manner in normal human epidermal melanocytes (NHEMs). PTTU also inhibited tyrosinase catalytic activity in NHEMs. Moreover, PTTU treatment led to reduced protein levels of tyrosinase in NHEMs, while the protein levels of tyrosinase-related protein-1, tyrosinase-related protein-2, and microphthalmia-associated transcription factor were not affected. However, PTTU treatment did not affect the mRNA expression of tyrosinase. We found that PTTU-accelerated tyrosinase degradation via the ubiquitin-dependent proteasome pathway. In summary, we found that PTTU decreased melanin biosynthesis by decreasing the enzymatic activity and stability of tyrosinase. Our results indicate that PTTU could be used as a depigmentation agent for hyperpigmentation disorder.

MR molecular imaging of tumors based on an optimal hTERT promoter tyrosinase expression system

The early diagnosis and treatment of tumors is of vital significance to increase patient survival. Therefore, we constructed a lentiviral vector expressing tyrosinase (TYR) driven by an optimized human telomerase reverse transcriptase (hTERT) promoter or a cytomegalovirus(CMV) promoter in the hopes of performing noninvasive and real-time tumor-specific imaging. First, hTERT-TYR and CMV-TYR were constructed to infect cancer cell lines (telomerase-negative cell line: U2OS; telomerase-positive cell lines: SGC-7901, SW480 and HepG2). Subsequently, stable tyrosinase-expressing cell lines were sorted by flow cytometry out of these infected cancer cell lines. Then, the mRNA and protein levels of tyrosinase were analyzed. Thetyrosinase activity, melanin production and ferric ion adsorption were measured followed by an MR scan. Consequently the results showed that tyrosinase was only expressed in telomerase-positive tumor cells infected by hTERT-TYR, whereas tyrosinase was expressed in both telomerase-negative and telomerase-positive tumor cells infected by CMV-TYR. Finally, we performed in vivo tumor MR using a clinical 3T MR scanner and found increased signals at T1W1 from telomerase-positive cells infected by hTERT-TYR, which revealed that MR scanning could distinguish cells with hTERT -positive cells from hTERT-negative cells infected with the optimized lentivirus. The mechanism underlying this effect is that tyrosinase promotes melanin production and ferric ion adsorption only in hTERT-expressing cells. Taken together, these data show that this optimized hTERT promoter-driving tyrosinase expression system might be a useful diagnostic tool for the detection of tumors using MR imaging.

Afzelin positively regulates melanogenesis through the p38 MAPK pathway

Melanogenesis refers to synthesis of the skin pigment melanin, which plays a critical role in the protection of skin against ultraviolet irradiation and oxidative stressors. We investigated the effects of afzelin on melanogenesis and its mechanisms of action in human epidermal melanocytes. In this study, we found that afzelin increased both melanin content and tyrosinase activity in a concentration-dependent manner. While the mRNA levels of microphthalmia-associated transcription factor (MITF), tyrosinase, and tyrosinase-related protein (TRP)-1 increased following afzelin treatment, the mRNA levels of TRP-2 were not affected by afzelin. Likewise, afzelin increased the protein levels of MITF, TRP-1, and tyrosinase but not TRP-2. Mechanistically, we found that afzelin regulated melanogenesis by upregulating MITF through phosphorylation of p38 mitogen-activated protein kinase (MAPK), independent of cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) signaling. Taken together, these findings indicate that the promotion of melanogenesis by afzelin occurs through increased MITF gene expression, which is mediated by activation of p38 MAPK, and suggest that afzelin may be useful as a protective agent against ultraviolet irradiation.

Two new lignans and melanogenesis inhibitors from Schisandra nigra.

An acetone extract from the stems of Schisandra nigra MAX. (Schisandraceae) exhibited significant inhibition of 3-isobutyl-1-methylxanthine (IBMX)-stimulated melanogenesis in murine B16 melanoma F10 cells. Fractionation and purification of the extract led to the isolation of two new tetrahydrofuran-type lignans, (+)-5-methoxyzuonin A (2) and kadlongirin C (3), along with eight known compounds (1, 4-10). The structures of the new compounds were determined by spectroscopic analyses. Of the isolated compounds (1,3 -10), (+)-zuonin A (1) showed remarkable inhibition of melanogenesis at concentrations without cytotoxicity in B16 melanoma F10 cells. (+)-Zuonin A (1) did not inhibit tyrosinase; however, Western blot analysis revealed that it decreased protein levels of tyrosinase and tyrosinase-related proteins (TRP)-1 and TRP-2 without changing phosphorylation level of cAMP response element-binding protein.

Toll-like receptor 9 regulates melanogenesis through NF-κB activation.

Toll-like receptors play essential roles in the modulation of melanogenesis, which has been implicated in the pathogenesis of hyper- or hypopigmentation-related diseases. However, little is currently known regarding the role of TLR9 in human melanocytes. TLR9 recognizes unmethylated cytosine-phosphate-guanine motif-containing oligodeoxynucleotides, and cytosine-phosphate-guanine ODN2006 acts as an hTLR9 agonist. The aim of the present study was to investigate the effect of cytosine-phosphate-guanine ODN2006 on melanogenesis in the human melanocyte cells. MTT assay and enzyme-linked immunosorbent assay indicated that ODN2006 stimulation (0, 1, 5, 10 µM) dose-dependently reduced cell viability and promoted the production of TNF-α, IL-6, and IL-8 in PIG1 melanocytes. The mRNA and protein levels of PMEL and TYRosinase were elevated at 6 h, and then decreased 24 h later, but were significantly augmented 72 h later following ODN2006 stimulation; whereas, TLR9 expressions were time-dependently increased in PIG1 melanocytes. Moreover, ultraviolet B irradiation combined with ODN2006 stimulation induced much more significant enhancement of PMEL, TYRosinase, and TLR9 mRNA and protein after three days in PIG1 melanocytes, and the similar results were obtained using the primary human melanocytes. The expression of TLR9 protein was down-regulated by TLR9 siRNA transfection. ODN2006 had an additive effect on ultraviolet B-induced melanogenesis and PMEL expression, as well as NF-κB activation, which could be blocked by TLR9 knockdown, the NF-κB specific inhibitor PDTC, or the TBK1 inhibitor BX795. Collectively, we concluded that TLR9 regulates melanogenesis through NF-κB activation, suggesting that TLR9 may play a role in microbial-induced melanogenesis.

Inhibitory effects of N,N,N-trimethyl phytosphingosine-iodide on melanogenesis via ERK activation-mediated MITF degradation.

N,N,N-trimethyl phytosphingosine-iodide (TMP) was recently developed as an antitumor agent. We examined the effects of TMP on melanogenesis and its related signaling pathways in normal human melanocytes. Our results showed that melanin is significantly reduced in a dose-dependent manner in both cells following liposomal TMP treatment. We also investigated changes in the phosphorylation of extracellular signal-regulated kinase (ERK), which is related to the degradation of microphthalmia-associated transcription factor (MITF). Our results indicated that liposomal TMP treatment leads to the phosphorylation of ERK, which reduces both MITF and tyrosinase protein levels. Treatment with PD98059, an ERK pathway-specific inhibitor, restored liposomal TMP-induced reductions in melanin, abrogated reductions in tyrosinase activity, and downregulated MITF and tyrosinase protein. In conclusion, these results suggest that the inhibitory effects of TMP on melanogenesis are due to MITF and tyrosinase downregulation via ERK activation.

(Z)-5-(2,4-Dihydroxybenzylidene)thiazolidine-2,4-dione Prevents UVB-Induced Melanogenesis and Wrinkle Formation through Suppressing Oxidative Stress in HRM-2 Hairless Mice.

Background. Uncontrolled melanogenesis and wrinkle formation are an indication of photoaging. Our previous studies demonstrated that (Z)-5-(2,4-dihydroxybenzylidene)thiazolidine-2,4-dione (MHY498) inhibited tyrosinase activity and melanogenesis in vitro. Objective. To examine in vivo effects of MHY498 as an antiaging compound on UVB-induced melanogenesis and wrinkle formation, we topically applied MHY498 on dorsal skin of HRM-2 hairless mice. Methods. Using histological analysis, we evaluated effects of MHY498 on melanogenesis and wrinkle formation after UVB exposure. In addition, related molecular signaling pathways were examined using western blotting, fluorometric assay, and enzyme-linked immunosorbent assay. Results. MHY498 suppressed UVB-induced melanogenesis by inhibiting phosphorylation of CREB and translocation of MITF protein into the nucleus, which are key factors for tyrosinase expression. Consistently, tyrosinase protein levels were notably reduced in the dorsal skin of the hairless mice by MHY498 treatment. Furthermore, MHY498 inhibited UVB-induced wrinkle formation and collagen fiber destruction by increasing type 1 procollagen concentration and decreasing protein expression levels of MMPs, which play an essential role in collagen fiber degradation. As a mechanism, MHY498 notably ameliorated UVB-induced oxidative stress and NF-κB activation in the dermal skin of the hairless mice. Conclusion. Our study suggests that MHY498 can be used as a therapeutic or cosmetic agent for preventing uncontrolled melanogenesis and wrinkle formation.

Chaetocin inhibits IBMX-induced melanogenesis in B16F10 mouse melanoma cells through activation of ERK

Chaetocin is a natural product isolated from Chaetomium species that has anti-bacterial and anti-myeloma activities. In this study, we investigated the inhibitory effect of chaetocin on melanogenesis and the underlying mechanisms in B16F10 mouse melanoma cells. In the present study, chaetocin significantly inhibited IBMX-induced melanin production and tyrosinase activity without any cytotoxicity. Furthermore, chaetocin down-regulated both the protein and mRNA levels of tyrosinase, which is a specific enzyme that catalyzes the conversion of tyrosine to melanin. We also observed that the protein level of MITF was significantly reduced by chaetocin treatment. In addition, we found that the anti-melanogenic effect of chaetocin was suppressed by treatment with the specific ERK inhibitor (PD98059). Accordingly, chaetocin inhibited melanogenesis via suppressing the protein level of MITF followed by activation of the ERK signaling pathway. These data suggest that chaetocin may be a potential anti-melanogenic agent for use in skin-whitening cosmetics and a topical agent for treatment of hyperpigmentation disorders.

Role of gap junctions between keratinocyte and melanocyte in melanogenesis

The process of melanogenesis in melanocytes and the transport of melanin in the form of melanosomes to the neighboring keratinocytes are the key steps in human skin pigmentation. Keratinocytes and melanocytes interact in intricate manner to maintain the homeostasis. The present study was designed to understand the role of cell-cell interaction through the gap junctions between melanocytes and keratinocytes on melanogenesis. We show that, inhibition of the gap junctional activity between human keratinocytes and melanocytes in a coculture system using gap junction blocker lowers the expression of key regulatory genes of melanogenesis such as tyrosinase and microphthalmiaassociated transcription factor (MITF). This was followed by concurrent decrease in tyrosinase protein levels and activity. Our results show the preliminary evidence for the regulation of melanogenesis in melanocytes through direct gap junctional communication by keratinocytes. Deciphering the mechanism and factors involved in the process would uncover the significance of gap junctions in melanogenesis.

Whitening Effects of Solvent Fractions Isolated from Vitex rotundifolia

Recently many effort focused to understand the mechanical insights of melanogenesis to develop the agent for hyper-pigmentation. So this study was performed to investigate the depigmentation of Vitex rotundifolia. With B16F10 mouse melanoma cell, we have seen inhibition of the tyrosinase, MITF, TRP-1, TRP-2, and melanin synthesis, which eventually were dose dependently decreased by Vitex rotundifolia. Specially, Vitex rotundifolia decreased the protein levels of tyrosinase and TRP-1. In conclusion, Vitex rotundifolia showed the whitening activity in all the experiments mentioned above and we expect that it can be used for preventing melanin synthesis.

Hesperidin, A Popular Antioxidant Inhibits Melanogenesis via Erk1/2 Mediated MITF Degradation.

Regulation of melanogenesis has been the focus of treatment for hyperpigmentary skin disorders. Although hesperidin is one of the most well-known, naturally occurring flavonoids with antioxidant and anti-inflammatory effect, its anti-melanogenic effect is not known. The present study aims to determine the anti-melanogenic effect of hespiridin as well as its underlying molecular mechanisms. Melanin contents were measured in normal human melanocytes and B16F10 melanoma cells. Protein and mRNA levels of tyrosinase, microphthalmia-associated transcription factor (MITF), tyrosinase related protein-1 (TRP-1) and TRP-2 were determined. Melanogenesis-regulating signals were examined. In results, hesperidin strongly inhibited melanin synthesis and tyrosinase activity. Hesperidin decreased tyrosinase, TRP-1, and TRP-2 protein expression but increased phospho-extracellular signal-regulated kinase 1/2 (p-Erk1/2) expression. Specific inhibitor of Erk1/2 or proteasome inhibitor reversed the inhibition of melanogenesis induced by hesperidin. Taken together, hesperidin, a popular antioxidant, stimulated Erk1/2 phosphorylation which subsequently degraded MITF which resulted in suppression of melanogenic enzymes and melanin synthesis.

STAP-2 Protein Expression in B16F10 Melanoma Cells Positively Regulates Protein Levels of Tyrosinase, Which Determines Organs to Infiltrate in the Body

Melanoma is the most serious type of skin cancer, with a highly metastatic phenotype. In this report, we show that signal transducing adaptor protein 2 (STAP-2) is involved in cell migration, proliferation, and melanogenesis as well as chemokine receptor expression and tumorigenesis in B16F10 melanoma cells. This was evident in mice injected with STAP-2 shRNA (shSTAP-2)-expressing B16F10 cells, which infiltrated organs in a completely different pattern from the original cells, showing massive colonization in the liver, kidney, and neck but not in the lung. The most important finding was that STAP-2 expression determined tyrosinase protein content. STAP-2 colocalized with tyrosinase in lysosomes and protected tyrosinase from protein degradation. It is noteworthy that B16F10 cells with knocked down tyrosinase showed similar cell characteristics as shSTAP-2 cells. These results indicated that tyrosinase contributed to some cellular events beyond melanogenesis. Taken together, one possibility is that STAP-2 positively regulates the protein levels of tyrosinase, which determines tumor invasion via controlling chemokine receptor expression.

Baicalin-induced Akt activation decreases melanogenesis through downregulation of microphthalmia-associated transcription factor and tyrosinase

Scutellaria baicalensis has been used topically to treat inflammatory skin diseases in traditional East Asian medicine. Because post-inflammatory hyperpigmentation of the skin is difficult to manage, we investigated the effects of baicalin, a major component of S. baicalensis, on melanin synthesis in Mel-Ab cells. Our data showed that baicalin significantly inhibited melanin production and tyrosinase activity in a dose-dependent fashion, but it did not directly influence tyrosinase activity. Moreover, baicalin treatment triggered decreases in both mRNA and protein levels of microphthalmia-associated transcription factor (MITF) and tyrosinase. Although AMP-activated protein kinase (AMPK) and extracellular signal-regulated kinase (ERK) activation were induced in baicalin-treated Mel-Ab cells, they were not responsible for baicalin-induced hypopigmentation. Because the Akt pathway is also known to be involved in regulation of melanogenic protein expression and melanin synthesis, we examined the effects of baicalin on the Akt pathway. Our results showed that baicalin treatment stimulated Akt activation. Treatment with LY294002, a specific Akt inhibitor, restored baicalin-induced melanogenesis inhibition and abolished MITF and tyrosinase downregulation by baicalin. Taken together, our data suggest that Akt activation by baicalin inhibits melanin production via downregulation of MITF and tyrosinase in Mel-Ab cells.

Cellular Anti-Melanogenic Effects of a Euryale ferox Seed Extract Ethyl Acetate Fraction via the Lysosomal Degradation Machinery.

The aim of this study was to investigate the effect of ethyl acetate fraction of Euryale ferox seed extracts (Efse-EA) on melanogenesis in immortalized mouse melanocyte cell line, melan-a. Efse-EA showed strong dose-dependent mushroom tyrosinase inhibitory activity. Treatment of melan-a cells with 30 μg/mL Efse-EA produced strong inhibition of cellular tyrosinase and melanin synthesis. Efse-EA significantly reduced the levels of melanogenesis-related proteins, such as tyrosinase, tyrosinase-related proteins 1 and 2, and microphthalmia-associated transcription factor. Because Efse-EA treatment reduced tyrosinase protein levels without changing its mRNA expression, we investigated whether this decrease was related to proteasomal or lysosomal degradation of tyrosinase. We found that chloroquine, a lysosomal proteolysis inhibitor, almost completely abolished both the down-regulation of tyrosinase and the inhibition of melanin synthesis induced by Efse-EA. These results suggested that Efse-EA may contribute to the inhibition of melanogenesis by altering lysosomal degradation of tyrosinase, and that this extract may provide a new cosmetic skin-whitening agent.

Melia azedarach extract stimulates melanogenesis through increase of tyrosinase-related protein 1 expression in B16F10 mouse melanoma cells.

Melia azedarach (MA) has been used in folk medicine in Asia for the treatment of several diseases. Several constituents from MA possess anti-herpetic, anti-angiogenic and anticancer properties. The aim of the present study was to investigate the effect of a 70% ethanol extract of MA on melanogenesis and the underlying mechanisms involved. A B16F10 mouse melanoma cell line was used in our experiments. Treatment of B16F10 cells with the MA extract (10, 20 and 40 µg/ml) increased melanin content in a concentration-dependent manner without cytotoxicity at 24 h. Further experiments indicated that the MA extract (20 µg/ml) increased melanin content as early as at 4 h after treatment. Additionally, although the MA extract did not affect intracellular tyrosinase activity and the protein levels of tyrosinase and tyrosinase-related protein-2 (TRP-2) at 2 and 4 h after treatment, the MA extract increased TRP-1 protein expression at both time points. However, no significant effect of the MA extract treatment on TRP-1 mRNA level at the time points measured was observed. In conclusion, the results from the present study demonstrate that the MA extract increases melanogenesis through the upregulation of TRP-1 protein expression by post-transcriptional control in B16F10 cells and suggest that the MA extract can be viewed as a rapid inducer of melanogenesis, thus rendering it a potential treatment for hypopigmentation diseases including vitiligo.

Melanogenesis-inhibitory activity and cancer chemopreventive effect of glucosylcucurbic acid from shea (Vitellaria paradoxa) kernels.

Two jasmonate derivatives, glucosylcucurbic acid (1) and methyl glucosylcucurbate (2), were isolated from the MeOH extract of defatted shea (Vitellaria paradoxa; Sapotaceae) kernels. These and their deglucosylated derivatives, cucurbic acid (3) and methyl cucurbate (4), were evaluated for their melanogenesis-inhibitory and cancer chemopreventive potencies. Compounds 1, 3, and 4 exhibited potent melanogenesis-inhibitory activities in α-melanocyte-stimulating hormone (α-MSH)-stimulated B16 melanoma cells. Western-blot analysis revealed that compounds 1 and 3 reduced the protein levels of MITF (=microphthalmia-associated transcription factor), tyrosinase, TRP-1 (=tyrosine-related protein 1), and TRP-2 mostly in a concentration-dependent manner. In addition, compound 1 exhibited inhibitory effects against Epstein-Barr virus early antigen (EBV-EA) activation induced with 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells, against TPA-induced inflammation in mice, and against skin tumor promotion in an in vivo two-stage mouse skin carcinogenesis test based on 7,12-dimethylbenz[a]anthracene (DMBA) as initiator, and with TPA as promoter.

Antimelanogenic effect of ginsenoside Rg3 through extracellular signal-regulated kinase-mediated inhibition of microphthalmia-associated transcription factor

BackgroundPanax ginseng has been used to prolong longevity and is believed to be useful for improving skin complexion. Ginsenosides are the most active components isolated from ginseng, and ginsenoside Rg3 (G-Rg3) in particular has been demonstrated to possess antioxidative, antitumorigenic, and anti-inflammatory properties. The aim of this study was to examine the ability of G-Rg3 to inhibit melanogenesis. MethodsThe effects of G-Rg3 on melanin contents and the protein levels of tyrosinase, microphthalmia-associated transcription factor (MITF), and tyrosinase-related protein 1 (TRP1) were evaluated. Melanogenesis-regulating signaling molecules such as Akt and extracellular signal-regulated kinase (ERK) were also examined to explore G-Rg3-induced antimelanogenic mechanisms. ResultsG-Rg3 was found to significantly inhibit the synthesis of melanin in normal human epidermal melanocytes and B16F10 cells in a dose-dependent manner. The activity of cellular tyrosinase and the expression of MITF, tyrosinase, and TRP1 were all reduced, whereas ERK was strongly activated. PD98059 (a specific inhibitor of ERK) attenuated the G-Rg3-induced inhibition of melanin synthesis and tyrosinase activity. ConclusionTaken together, these results showed that G-Rg3 induces the activation of ERK, which accounts for its antimelanogenic effects. G-Rg3 may be a promising safe skin-whitening agent, adding to the long list of uses of P. ginseng for the enhancement of skin beauty.