Tyrosinase stabilization by Tyrp1 (the brown locus protein)

Sesamol Inhibited Melanogenesis by Regulating Melanin-Related Signal Transduction in B16F10 Cells

Melanin is synthesized through a series of interactions catalyzed by melanogenic enzymes such as tyrosinase, dopachrome tautomerase (tyrosinase-related protein-2; TRP-2), and tyrosinase-related protein-1 (TRP-1). Tyrosinase plays a key role in catalysing the initial and limiting steps of melanogenesis. The melanin that results from melanogenesis has the protective effect of absorbing ultraviolet radiation. However, overproduction of melanin, in addition to altering the appearance of skin, may lead to skin disorders such as melasma, solar lentigo, and postinflammatory hyperpigmentation. Previous studies have revealed that sesamol is a strong antioxidant and a free radical scavenger. In this study, we investigated the effects of sesamol on the regulation of melanogenesis and related mechanisms in B16F10 cells. The results indicated that sesamol inhibited tyrosinase activity and melanogenesis induced by α-melanocyte-stimulating hormone (α-MSH) in B16F10 melanoma cells. Sesamol decreased the protein level of melanocortin 1 receptor (MC1R), microphthalmia-associated transcription factor (MITF), tyrosinase, and TRP-1 by downregulating cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathways that had been activated by α-MSH. Sesamol increased glycogen synthase kinase 3 beta (GSK3β), protein kinase B (AKT), and extracellular signal-related kinase (ERK) phosphorylation, thus inhibiting the transcription of MITF. Sesamol also inhibited melanin synthesis and tyrosinase expression by modulating ERK, phosphoinositide 3-kinase (PI3K)/AKT, p38, and c-Jun amino-terminal kinase (JNK) signalling pathways. These results indicate that sesamol acted as a potent depigmenting agent.

Molecular cloning and expression analysis of tyr and tyrp1 genes in normal and albino yellow catfish Tachysurus fulvidraco

The full-length complementary DNA of two genes related to vertebrate albinism, the tyrosinase gene tyr and tyrosinase-related protein 1 gene tyrp1, were cloned and analysed from normal and albino yellow catfish Tachysurus fulvidraco. The open reading frames (ORF) of tyr and tyrp1 encode putative peptides of 533 and 526 amino acids (amino-acid), both of which possess two conserved copper binding sites. The homologous identities of deduced amino-acid sequences showed that both Tyr and Tyrp1 of T. fulvidraco share considerable similarity with that of channel catfish Ictalurus punctatus. Both tyr and tyrp1 were expressed in a wide range of adult tissues. Tyr gene had the highest expression level in the brain of both normal and albino T. fulvidraco. Tyrp1 had the highest expression level in the skin of normal groups, and the fin of albino groups. The messenger (m)RNA expressions of tyr and tyrp1 were detectable at different early developmental stages and varied with embryonic and larval growth. Tyr and tyrp1 mRNA have obvious tissue specificity both in normal and albino T. fulvidraco and higher expression levels were detected in the normal group revealing that tyr and tyrp1 may have an important role in pigmentation. These results will provide useful data for understanding the molecular mechanism of melanin formation and the occurrence of albinism in T. fulvidraco.

Molecular Genetics of Pigment Dispersion Syndrome and Pigmentary Glaucoma: New Insights into Mechanisms

We explore the ideas and advances surrounding the genetic basis of pigment dispersion syndrome (PDS) and pigmentary glaucoma (PG). As PG is the leading cause of nontraumatic blindness in young adults and current tailored interventions have proven ineffective, a better understanding of the underlying causes of PDS, PG, and their relationship is essential. Despite PDS being a subclinical disease, a large proportion of patients progress to PG with associated vision loss. Decades of research have supported a genetic component both for PDS and conversion to PG. We review the body of evidence supporting a genetic basis in humans and animal models and reevaluate classical mechanisms of PDS/PG considering this new evidence.

On the Metal Cofactor in the Tyrosinase Family

The production of pigment in mammalian melanocytes requires the contribution of at least three melanogenic enzymes, tyrosinase and two other accessory enzymes called the tyrosinase-related proteins (Trp1 and Trp2), which regulate the type and amount of melanin. The last two proteins are paralogues to tyrosinase, and they appeared late in evolution by triplication of the tyrosinase gene. Tyrosinase is a copper-enzyme, and Trp2 is a zinc-enzyme. Trp1 has been more elusive, and the direct identification of its metal cofactor has never been achieved. However, due to its enzymatic activity and similarities with tyrosinase, it has been assumed as a copper-enzyme. Recently, recombinant human tyrosinase and Trp1 have been expressed in enough amounts to achieve for the first time their crystallization. Unexpectedly, it has been found that Trp1 contains a couple of Zn(II) at the active site. This review discusses data about the metal cofactor of tyrosinase and Trps. It points out differences in the studied models, and it proposes some possible points accounting for the apparent discrepancies currently appearing. Moreover, some proposals about the possible flexibility of the tyrosinase family to uptake copper or zinc are discussed.

A novel anti-melanogenic agent, KDZ-001, inhibits tyrosinase enzymatic activity

BACKGROUND

The demand for anti-melanogenic agents is increasing due to the unwanted side effects of current treatments. To find an effective anti-melanogenic agent, we used zebrafish as a whole animal model for phenotype-based drug and cosmetic discovery screening.

OBJECTIVES

The aim of this study was to identify and explore a small molecule that could be used for skin-whitening cosmetics.

METHODS

Using zebrafish embryos, we examined the effects of 1000 compounds on zebrafish development and pigmentation. Pigmentation production was assessed by tyrosinase (TYR) enzymatic activity and melanin contents. Pigmentation marker expression in the human melanoma cell line HMV-II was analyzed by western blot. We also tested reconstituted human skin tissue and analyzed KDZ-001 with computational molecular modeling.

RESULTS

We identified three compounds that affected the pigmentation of developing melanophores in zebrafish. Among them, we identified KDZ-001, a novel anti-melanogenic agent, which strongly inhibits melanin synthesis in the developing melanophores of zebrafish, HMV-II cells, and reconstituted human skin with no toxicity. We found that KDZ-001 directly inhibits TYR enzymatic activity. Notably, computational molecular modeling of KDZ-001 suggested that its interaction with copper ions in the active site of TYR is essential for melanin synthesis, further demonstrating that KDZ-001 mainly acts as a TYR inhibitor to synthesize melanin.

CONCLUSION

KDZ-001 inhibits melanin synthesis and has a potential for use in skin-whitening cosmetics.

Whitening and anti-wrinkle activities of ferulic acid isolated from Tetragonia tetragonioides in B16F10 melanoma and CCD-986sk fibroblast cells

Ferulic acid isolated from Tetragonia tetragonioides was tested for its whitening effect on the B16F10 mouse melanoma cell line and its anti-wrinkle activity on the CCD-986sk human dermal fibroblast cell line. Ferulic acid, one of the primary phenolic compounds that can be isolated from T. tetragonioides, has been reported to show potential as a functional food, for its whitening effect and anti-wrinkle activity. To measure its whitening and anti-wrinkle activities, cells were treated with ferulic acid isolated from T. tetragonioides at concentrations between 5 and 20 μM. Ferulic acid showed no cytotoxicity at concentrations up to 20 μM. Ferulic acid inhibited melanin synthesis, tyrosinase expression, and microphthalmia transcription factor expression in B16F10 cells stimulated with α-melanocyte stimulating hormone. Ferulic acid induced procollagen synthesis, hyaluronic acid synthesis, tissue inhibitor of metalloproteinase synthesis, and inhibited matrix metalloproteinase (MMP)-1 and MMP-9 expression in CCD-986sk cells stimulated with UV-B. On the basis of these results, we conclude that ferulic acid isolated from T. tetragonioides shows potential for use as a functional food, with whitening and anti-wrinkle activities.

Soyasaponin Ag inhibits α‑MSH‑induced melanogenesis in B16F10 melanoma cells via the downregulation of TRP‑2

Saponins, which are glycosylated, represent a diverse group of biologically functional products in plants. In the present study, we investigated the effects of soyasaponin Ag, a secondary metabolite extracted from soybean, on α‑melanocyte-stimulating hormone (α‑MSH)‑induced melanin synthesis in B16F10 mouse melanoma cells and the underlying molecular mechanisms. To elucidate the mechanisms through which soyasaponin Ag inhibits melanin synthesis, we performed cellular tyrosinase activity assays and analyzed the expression of the melanogenesis‑related genes, tyrosinase, tyrosinase‑related protein (TRP)‑1 and TRP‑2. We demonstrated that soyasaponin Ag inhibited α‑MSH‑induced melanin synthesis in melanoma cells. Of note, soyasaponin Ag had no inhibitory effect on intracellular tyrosinase activity. However, soyasaponin Ag inhibited TRP‑2 expression in a dose‑dependent manner. Therefore, the depigmenting effect of soyasaponin Ag may be due to the inhibition of tyrosinase expression or the enhancement of tyrosinase degradation. Moreover, soyasaponin Ag did not exert any toxic on B16F10 mouse melanoma cells, suggesting that soyasaponin is a safe component for use in skin care cosmetic formulations that are used for skin whitening.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Ocular Albinism Type 1 Regulates Melanogenesis in Mouse Melanocytes

To investigate whether ocular albinism type 1 (OA1) is differentially expressed in the skin of mice with different coat colors and to determine its correlation with coat color establishment in mouse, the expression patterns and tissue distribution characterization of OA1 in the skin of mice with different coat colors were qualitatively and quantitatively analyzed by real-time quantitative PCR (qRT-PCR), immunofluorescence staining and Western blot. The qRT-PCR analysis revealed that OA1 mRNA was expressed in all mice skin samples tested, with the highest expression level in brown skin, a moderate expression level in black skin and the lowest expression level in gray skin. Positive OA1 protein bands were also detected in all skin samples by Western blot analysis. The relative expression levels of OA1 protein in both black and brown skin were significantly higher than that in gray skin, but there was no significant difference between black and brown mice. Immunofluorescence assays revealed that OA1 was mainly expressed in the hair follicle matrix, the inner and outer root sheath in the skin tissues with different coat colors. To get further insight into the important role of OA1 in the melanocytes’ pigmentation, we transfected the OA1 into mouse melanocytes and then detected the relative expression levels of pigmentation-related gene. Simultaneously, we tested the melanin content of melanocytes. As a result, the overexpression of OA1 significantly increased the expression levels of microphthalmia-associated transcription factor (MITF), tyrosinase (TYR), tyrosinase-related protein 1 (TRP1) and premelanosome protein (PMEL). However, the tyrosinase-related protein 2 (TRP2) level was attenuated. By contrast, the level of glycoprotein non-metastatic melanoma protein b (GPNMB) was unaffected by OA1 overexpression. Furthermore, we observed a significant increase in melanin content in mouse melanocyte transfected OA1. Therefore, we propose that OA1 may participate in the formation of coat color by regulating the level of MITF and the number, size, motility and maturation of melanosome.

Differential expression of TYRP1 in adult human retinal pigment epithelium and uveal melanoma cells

Uveal melanoma (UM) is the most frequently occurring primary intraocular malignancy in adults. Tyrosinase (TYR) is a copper-containing enzyme and a type I membrane protein that is involved in the generation of melanin, the main pigment in vertebrates. TYR-related protein 1 (TYRP1) is regarded to have a crucial role in the immunotherapy of melanoma. As biomarkers, the TYR-related proteins, TYRP1 and TYRP2, exhibit specific expression in melanocytes, while also contributing to melanin synthesis within melanosomes. In the present study, the differential expression of TYRP1 was investigated at the mRNA, protein and morphological levels in four human UM cell lines (SP6.5, OM431, OCM1 and OCM290) and the human retinal pigment epithelium (RPE) cell line, using polymerase chain reaction, western blotting, immunocytochemistry and immunofluorescence staining. It was found that SP6.5 cells expressed the highest level of TYRP1, in comparison to SP6.5 OCM1 and OM431 cells, which produced less TYRP1, and OCM290 cells, which produced almost no TYRP1. No TYRP1 protein expression was identified in the RPE cell line. These findings indicate the potential use of TYRP1 in the development of therapy for UM.

Mechanistic Studies on the Use of Polygonum multiflorum for the Treatment of Hair Graying

Polygonum multiflorum is a traditional Chinese medicine with a long history in hair growth promotion and hair blackening. The purpose of the study was to examine the effect and the mechanism of Polygonum multiflorum in hair blackening. C57BL/6 mice hair fade was induced with H2O2 and used in this research. Hair pigmentogenesis promotion activities of Polygonum Multiflorum Radix (PMR, raw crude drug), Polygonum Multiflorum Radix Preparata (PMRP, processed crude drug), and their major chemical constituent TSG were investigated. The regulation effects of several cytokines and enzymes such as POMC, α-MSH, MC1R, ASIP, MITF, TYR, TRP-1, and TRP-2 were investigated. PMR group gave out the most outstanding black hair among all groups with the highest contents of total melanin, α-MSH, MC1R, and TYR. Promotion of hair pigmentogenesis was slightly decreased after processing in the PMRP group. TSG as the major constituent of PMR showed weaker hair color regulation effects than both PMR and PMRP. PMR, but not PMRP, should be used to blacken hair. The α-MSH, MC1R, and TYR were the major targets in the medicinal use of PMR in hair graying. Chemical constituents other than TSG may contribute to the hair color regulation activity of PMR.

Association of Tyrosinase (TYR) and Tyrosinase-related Protein 1 (TYRP1) with Melanic Plumage Color in Korean Quails (Coturnix coturnix)

TYR (Tyrosinase) and TYRP1 (Tyrosinase-related protein 1) play crucial roles in determining the coat color of birds. In this paper, we aimed to characterize the relationship of TYR and TYRP1 genes with plumage colors in Korean quails. The SNPs were searched by cDNA sequencing and PCR-SSCP in three plumage color Korean quails (maroon, white and black plumage). Two SNPs (367T→C and 1153C→T) were found in the coding region of TYRP1 gene, but had no significant association with plumage phenotype in Korean quails. The expression of TYR was higher in black plumage quails than that in maroon plumage quails. In contrast, the expression of TYRP1 was lower in black plumage quails than that in maroon plumage quails. This study suggested that the melanic plumage color in Korean quails may be associated with either increased production of TYR or decreased production of TYRP1.

The Expression of Melanogenic Proteins in Korean Skin after Ultraviolet Irradiation

For proper melanin production, several specific enzymes such as tyrosinase, tyrosinase-related protein 1 (TRP-1) and dopachrome tautomerase are required. Their expressions are increased after exposure to UVB. However, it is not known how long tyrosinase and TRP-1 activities continue after UV irradiation in vivo. The purpose of this study is to measure the changes in expressions of tyrosinase, TRP1, and MITF after exposure to UV on skin in a Korean population. We established an immunohistochemical staining protocol for specimens which were obtained from UV-irradiated skin in five healthy Korean males on the 2nd, 5th, 7th, 28th, and 56th days after UV irradiation. Tyrosinase, TRP-1, and MITF expressions increased until 7 days after UV irradiation and then dropped to the basal constitutive level 4 and 8 weeks later. Interestingly, tyrosinase increased prior to TRP-1. This study reveals the time-sequence of melanin-synthesized enzymes and provides important information for the clinical evaluation of the effectiveness of whitening agents.

Mutational analysis of oculocutaneous albinism: a compact review

Oculocutaneous albinism (OCA) is an autosomal recessive disorder caused by either complete lack of or a reduction of melanin biosynthesis in the melanocytes. The OCA1A is the most severe type with a complete lack of melanin production throughout life, while the milder forms OCA1B, OCA2, OCA3, and OCA4 show some pigment accumulation over time. Mutations in TYR, OCA2, TYRP1, and SLC45A2 are mainly responsible for causing oculocutaneous albinism. Recently, two new genes SLC24A5 and C10orf11 are identified that are responsible to cause OCA6 and OCA7, respectively. Also a locus has been mapped to the human chromosome 4q24 region which is responsible for genetic cause of OCA5. In this paper, we summarized the clinical and molecular features of OCA genes. Further, we reviewed the screening of pathological mutations of OCA genes and its molecular mechanism of the protein upon mutation by in silico approach. We also reviewed TYR (T373K, N371Y, M370T, and P313R), OCA2 (R305W), TYRP1 (R326H and R356Q) mutations and their structural consequences at molecular level. It is observed that the pathological genetic mutations and their structural and functional significance of OCA genes will aid in development of personalized medicine for albinism patients.

Melanosome-autonomous regulation of size and number: the OA1 receptor sustains PMEL expression

Little is known as to how cells ensure that organelle size and number are coordinated to correctly couple organelle biogenesis to the demands of proliferation or differentiation. OA1 is a melanosome-associated G-protein-coupled receptor involved in melanosome biogenesis during melanocyte differentiation. Cells lacking OA1 contain fewer, but larger, mature melanosomes. Here, we show that OA1 loss of function reduces both the basal expression and the α-melanocyte-stimulating hormone/cAMP-dependent induction of the microphthalmia-associated transcription factor (MITF), the master regulator of melanocyte differentiation. In turn, this leads to a significant reduction in expression of PMEL, a major melanosomal structural protein, but does not affect tyrosinase and melanin levels. In line with its pivotal role in sensing melanosome maturation, OA1 expression rescues melanosome biogenesis, activates MITF expression and thereby coordinates melanosome size and number, providing a quality control mechanism for the organelle in which resides. Thus, resident sensor receptors can activate a transcriptional cascade to specifically promote organelle biogenesis.

The mouse brown (b/Tyrp1(b) ) allele does not affect pheomelanin synthesis in mice

B (Tyrp1 (+)), the wild type allele at the mouse brown locus, produces black eumelanin, while b (Tyrp1(b) ), the recessive allele, produces brown eumelanin and exhibits lower tyrosinase (Tyr)-related protein 1 (Tyrp1) activity. However, it is unknown whether melanocyte proliferation and differentiation are affected by the Tyrp1(b) mutation. The proliferation rate of brown (C57BL/10JHir (B10)-Tyrp1(b) / Tyrp1(b) ) melanocytes cultured in a serum-free melanocyte proliferation medium (MDMD) was similar to that of black (B10-Tyrp1(+)/Tyrp1(+) ) melanocytes. Although brown melanocytes exhibited normal morphology, their pigmentation was lower than that of black melanocytes. However, Tyr activity in brown melanocytes was increased both in vivo and in vitro. Melanosomes of cultured brown melanocytes were mostly spherical stage III melanosomes with granular depositions of pigments, whereas those of cultured black melanocytes were mostly stage IV ellipsoidal melanosomes with pigment depositions in intraluminal fibrils. Chemical analysis of melanin present in dorsal hairs of 5-week-old mice from the F2 generation between brown and recessive yellow (B10-Mc1r(e)/Mc1r(e) ) or agouti (B10-A/A) mice showed that eumelanin content was greatly decreased in brown and brown agouti (cinnamon) mice, whereas pheomelanin contents in brown recessive yellow and cinnamon mice did not differ from the corresponding Tyrp1(+)/- mice. These results suggest that the brown allele greatly inhibits eumelanin, but not pheomelanin synthesis.

Determining immune components necessary for progression of pigment dispersing disease to glaucoma in DBA/2J mice

Background

The molecular mechanisms causing pigment dispersion syndrome (PDS) and the pathway(s) by which it progresses to pigmentary glaucoma are not known. Mutations in two melanosomal protein genes (Tyrp1^b and Gpnmb^R150X) are responsible for pigment dispersing iris disease, which progresses to intraocular pressure (IOP) elevation and subsequent glaucoma in DBA/2J mice. Melanosomal defects along with ocular immune abnormalities play a role in the propagation of pigment dispersion and progression to IOP elevation. Here, we tested the role of specific immune components in the progression of the iris disease and high IOP.

Results

We tested the role of NK cells in disease etiology by genetically modifying the B6.D2-Gpnmb^R150XTyrp1^b strain, which develops the same iris disease as DBA/2J mice. Our findings demonstrate that neither diminishing NK mediated cytotoxic activity (Prf1 mutation) nor NK cell depletion (Il2rg mutation) has any influence on the severity or timing of Gpnmb^R150XTyrp1^b mediated iris disease. Since DBA/2J mice are deficient in CD94, an important immune modulator that often acts as an immune suppressor, we generated DBA/2J mice sufficient in CD94. Sufficiency of CD94 failed to alter either the iris disease or the subsequent IOP elevation. Additionally CD94 status had no detected effect on glaucomatous optic nerve damage.

Conclusion

Our previous data implicate immune components in the manifestation of pigment dispersion and/or IOP elevation in DBA/2J mice. The current study eliminates important immune components, specifically NK cells and CD94 deficiency, as critical in the progression of iris disease and glaucoma. This narrows the field of possible immune components responsible for disease progression.

In silico screening and molecular dynamics simulation of disease-associated nsSNP in TYRP1 gene and its structural consequences in OCA3

Oculocutaneous albinism type III (OCA3), caused by mutations of TYRP1 gene, is an autosomal recessive disorder characterized by reduced biosynthesis of melanin pigment in the hair, skin, and eyes. The TYRP1 gene encodes a protein called tyrosinase-related protein-1 (Tyrp1). Tyrp1 is involved in maintaining the stability of tyrosinase protein and modulating its catalytic activity in eumelanin synthesis. Tyrp1 is also involved in maintenance of melanosome structure and affects melanocyte proliferation and cell death. In this work we implemented computational analysis to filter the most probable mutation that might be associated with OCA3. We found R326H and R356Q as most deleterious and disease associated by using PolyPhen 2.0, SIFT, PANTHER, I-mutant 3.0, PhD-SNP, SNP&GO, Pmut, and Mutpred tools. To understand the atomic arrangement in 3D space, the native and mutant (R326H and R356Q) structures were modelled. Finally the structural analyses of native and mutant Tyrp1 proteins were investigated using molecular dynamics simulation (MDS) approach. MDS results showed more flexibility in native Tyrp1 structure. Due to mutation in Tyrp1 protein, it became more rigid and might disturb the structural conformation and catalytic function of the structure and might also play a significant role in inducing OCA3. The results obtained from this study would facilitate wet-lab researches to develop a potent drug therapies against OCA3.

Skin transcriptome profiles associated with coat color in sheep

Background

Previous molecular genetic studies of physiology and pigmentation of sheep skin have focused primarily on a limited number of genes and proteins. To identify additional genes that may play important roles in coat color regulation, Illumina sequencing technology was used to catalog global gene expression profiles in skin of sheep with white versus black coat color.

Results

There were 90,006 and 74,533 unigenes assembled from the reads obtained from white and black sheep skin, respectively. Genes encoding for the ribosomal proteins and keratin associated proteins were most highly expressed. A total of 2,235 known genes were differentially expressed in black versus white sheep skin, with 479 genes up-regulated and 1,756 genes down-regulated. A total of 845 novel genes were differentially expressed in black versus white sheep skin, consisting of 107 genes which were up-regulated (including 2 highly expressed genes exclusively expressed in black sheep skin) and 738 genes that were down-regulated. There was also a total of 49 known coat color genes expressed in sheep skin, from which 13 genes showed higher expression in black sheep skin. Many of these up-regulated genes, such as DCT, MATP, TYR and TYRP1, are members of the components of melanosomes and their precursor ontology category.

Conclusion

The white and black sheep skin transcriptome profiles obtained provide a valuable resource for future research to understand the network of gene expression controlling skin physiology and melanogenesis in sheep.

Genetic modulation of the iris transillumination defect: a systems genetics analysis using the expanded family of BXD glaucoma strains

We investigated the contributions of Tyrp1 and Gpnmb to the iris transillumination defect (TID) in five age cohorts of BXD mice. Using systems genetics, we also evaluated the role of other known pigmentation genes (PGs). Mapping studies indicate that Tyrp1 contributes to the phenotype at all ages, yet the TID maps to Gpnmb only in the oldest cohort. Composite interval mapping reveals secondary loci viz. Oca2, Myo5a, Prkcz, and Zbtb20 that modulate the phenotype in the age groups up to 10–13 months. The contributions of Tyrp1 and Gpnmb were highly significant in all age cohorts. Moreover, in young mice, all six gene candidates had substantial interactions in our model. Our model accounted for 71–88% of the explained variance of the TID phenotype across the age bins. These results demonstrate that along with Tyrp1 and Gpnmb, Oca2, Myo5a, Prkcz, and Zbtb20 modulate the TID in an age-dependent manner.

Tyrosinase-related protein 1 mRNA expression in lymph node metastases predicts overall survival in high-risk melanoma patients

Background:

Clinical outcome of high-risk melanoma patients is not reliably predicted from histopathological analyses of primary tumours and is often adjusted during disease progression. Our study aimed at extending our previous findings in skin metastases to evaluate the prognostic value of tyrosinase-related protein 1 (TYRP1) in lymph node metastases of stages III and IV melanoma patients.

Methods:

TYRP1 mRNA expression in 104 lymph node metastases was quantified by real-time PCR and normalised to S100 calcium-binding protein B (S100B) mRNA expression to correct for tumour load. TYRP1/S100B ratios were calculated and median was used as cutoff value. TYRP1/S100B mRNA values were correlated to clinical follow-up and histopathological characteristics of the primary lesion.

Results:

A high TYRP1/S100B mRNA ratio significantly correlated with reduced disease-free (DFS) and overall survival (OS; Cox regression analysis, P=0.005 and 0.01, respectively), increased Breslow thickness (Spearman's rho test, P<0.001) and the presence of ulceration (Mann–Whitney test, P=0.02) of the primaries. Moreover, high TYRP1/S100B was of better prognostic value (lower P-value) for OS than Breslow thickness and ulceration. Finally, it was well conserved during disease progression with respect to high/low TYRP1 groups.

Conclusion:

High TYRP1/S100B mRNA expression in lymph node metastases from melanoma patients is associated with unfavourable clinical outcome. Its evaluation in lymph node metastases may refine initial prognosis for metastatic patients, may define prognosis for those with unknown or non-evaluable primary lesions and may allow different management of the two groups of patients.

Cyclohexanediol bis-ethylhexanoate inhibits melanogenesis of murine B16 melanoma and UV-induced pigmentation in human skin

The role of cyclohexane diester analogues in the formation of melanin has been recently reported. In the present study, we investigated the inhibitory effect of cyclohexanediol bis-ethylhexanoate (CHEH) on melanogenesis in B16 melanoma cells and on UV-B-induced pigmentation in human skin. CHEH significantly reduced the melanin content in a dose-dependent manner, without cytotoxic effects at the effective concentrations. Moreover, CHEH dose-dependently inhibited tyrosinase activity in B16 melanoma cells, as confirmed by Western blot analysis of the tyrosinase protein levels. However, tyrosinase transcript levels remained unchanged under the same experimental conditions. These results indicate that CHEH inhibited melanogenesis in B16 melanoma cells by regulating tyrosinase activity at the post-transcriptional level. On the other hand, in a cell-free system, CHEH did not inhibit tyrosinase activity. This indicated that CHEH suppressed the pigmentation of melanocytes by indirectly regulating tyrosinase activity. Finally, in a clinical trial, a cream containing 1.0% CHEH showed good whitening effect on UV-induced pigmented human skin without adverse effects. In conclusion, we suggest that CHEH may be an effective inhibitor of melanogenesis and useful effects in the treatment of hyperpigmented disorders.

The genetics of pigment dispersion syndrome and pigmentary glaucoma

We review the inheritance patterns and recent genetic advances in the study of pigment dispersion syndrome (PDS) and pigmentary glaucoma (PG). Both conditions may result from combinations of mutations in more than one gene or from common variants in many genes, each contributing small effects. We discuss the currently known genetic loci that may be related with PDS/PG in humans, the role of animal models in expanding our understanding of the genetic basis of PDS, the genetic factors underlying the risk for conversion from PDS to PG and the relationship between genetic and environmental--as well as anatomical--risk factors.

Inhibitory effects of Asterina pectinifera extracts on melanin biosynthesis through tyrosinase activity

The control of melanogenesis is an important strategy in the treatment of abnormal skin pigmentation for cosmetic purposes. The aim of the present study was to investigate the anti-melanogenic effect of Asterina pectinifera (A. pectinifera) extracts by cell-free mushroom tyrosinase assay, cellular tyrosinase assay, melanin content assay and the analysis of related protein expression in melan-a cells. A. pectinifera was extracted with 80% methanol (80-MAP) and further fractionated with hexane (He-AP) and ethyl acetate (EA-AP). In addition, the enzyme extract (En-AP) of A. pectinifera, to which protease was added, was processed. EA-AP and En-AP among A. pectinifera extracts showed strong inhibitory activity against the cell-free mushroom tyrosinase activity. EA-AP and En-AP induced significant inhibition of melanin production and cellular tyrosinase activity. In the action of EA-AP and En-AP on melanogenesis, they reduced the expression of melanogenic genes and proteins including tyrosinase, tyrosinase-related protein-1 (TRP-1) and dopachrome tautomerase (Dct). These results showed that EA-AP and En-AP inhibited melanogenesis by reducing tyrosinase activity and melanin production via subsequent downregulation of tyrosinase-related proteins. The overall results suggest that EA-AP and En-AP among A. pectinifera extracts may be promising candidates for the treatment of hyperpigmentation disorder and useful for self-tanning cosmetic products.

Mechanisms of protein delivery to melanosomes in pigment cells

Vertebrate pigment cells in the eye and skin are useful models for cell types that use specialized endosomal trafficking pathways to partition cargo proteins to unique lysosome-related organelles such as melanosomes. This review describes current models of protein trafficking required for melanosome biogenesis in mammalian melanocytes.

New insights into the evolution of metazoan tyrosinase gene family

Tyrosinases, widely distributed among animals, plants and fungi, are involved in the biosynthesis of melanin, a pigment that has been exploited, in the course of evolution, to serve different functions. We conducted a deep evolutionary analysis of tyrosinase family amongst metazoa, thanks to the availability of new sequenced genomes, assessing that tyrosinases (tyr) represent a distinctive feature of all the organisms included in our study and, interestingly, they show an independent expansion in most of the analyzed phyla. Tyrosinase-related proteins (tyrp), which derive from tyr but show distinct key residues in the catalytic domain, constitute an invention of chordate lineage. In addition we here reported a detailed study of the expression territories of the ascidian Ciona intestinalis tyr and tyrps. Furthermore, we put efforts in the identification of the regulatory sequences responsible for their expression in pigment cell lineage. Collectively, the results reported here enlarge our knowledge about the tyrosinase gene family as valuable resource for understanding the genetic components involved in pigment cells evolution and development.

Evidence for positive selection on a number of MicroRNA regulatory interactions during recent human evolution

MicroRNA (miRNA)–mediated gene regulation is of critical functional importance in animals and is thought to be largely constrained during evolution. However, little is known regarding evolutionary changes of the miRNA network and their role in human evolution. Here we show that a number of miRNA binding sites display high levels of population differentiation in humans and thus are likely targets of local adaptation. In a subset we demonstrate that allelic differences modulate miRNA regulation in mammalian cells, including an interaction between miR-155 and TYRP1, an important melanosomal enzyme associated with human pigmentary differences. We identify alternate alleles of TYRP1 that induce or disrupt miR-155 regulation and demonstrate that these alleles are selected with different modes among human populations, causing a strong negative correlation between the frequency of miR-155 regulation of TYRP1 in human populations and their latitude of residence. We propose that local adaptation of microRNA regulation acts as a rheostat to optimize TYRP1 expression in response to differential UV radiation. Our findings illustrate the evolutionary plasticity of the microRNA regulatory network in recent human evolution.

MicroRNAs (miRNAs) are endogenous small RNAs that bind to their target mRNAs to post-transcriptionally repress protein production. miRNA–mediated gene regulation is usually considered to be strongly conserved among and within species, and thus alteration of such regulations is usually considered as detrimental. However, it is likely that evolutionary divergence of miRNA regulation may actually be selectively advantageous and could even serve as a genetic reservoir for innovation and adaptation. Towards this goal, we identified a number of polymorphic miRNA binding sites that display extreme population differentiation and show evidence of positive selection. We experimentally validated 3 regulations, including a regulation by miR-155 on TYRP1, a melanosomal enzyme associated with human pigmentation. We found that the two alternate alleles on the 3′ UTR of TYRP1, either inducing or disrupting repression by miR-155, are under opposite selections among human populations. This results in a strong negative correlation between the degree of fixation of miR-155–mediated repression of TYRP1 in a population and the population's latitude of residence. These observations collectively suggest miR-155 acts a rheostat to optimize TYRP1 expression for local adaptation to differential UV radiation along the latitudes. Our findings demonstrate the plasticity of miRNA regulation in recent human evolution.

Diversity of human hair pigmentation as studied by chemical analysis of eumelanin and pheomelanin

Hair colour is one of the most conspicuous phenotypes in humans, ranging from black, brown, blond to red. This diversity arises mostly from the quantity and ratio of the black-dark brown eumelanin and the reddish-brown pheomelanin. To study the chemical basis underlying the diversity of hair colour, we have developed several chemical methods to quantify those two pigments. Alkaline H(2) O(2) oxidation affords pyrrole-2,3,5-tricarboxylic acid (PTCA) as a eumelanin marker and thiazole-2,4,5-tricarboxylic acid (TTCA) as a pheomelanin marker. Pheomelanin can also be analysed as 4-amino-3-hydroxyphenylalanine (4-AHP) after hydroiodic acid hydrolysis. Using those methods, we evaluated the contents of eumelanin and pheomelanin (the 'chemical' phenotype) in human hairs of black, dark brown, brown, light brown, blond and red colour (the 'visual' phenotype). Eumelanin contents decrease in that order, with a trace but constant level of pheomelanin, except for red hair which contains about equal levels of pheomelanin and eumelanin. Thus, the chemical phenotype correlates well with the visual phenotype. The genotype of melanocortin-1 receptor (MC1R), a gene regulating the red hair phenotype, is predictive of hair melanin expressed as the log value of eumelanin to pheomelanin ratio, with a dosage effect evident. Hair melanin contents were also analysed in patients with various hypopigmentary disorders including Hermansky-Pudlak syndrome, Menkes disease, proopiomelanocortin deficiency, cystinosis, malnutrition and trace metal deficiency. The chemical phenotype helped evaluate the precise effects of each disease on pigmentation. In studies of human hair, the chemical phenotype will find more and more application as an objective measure of pigmentation.

Diethylstilbestrol enhances melanogenesis via cAMP-PKA-mediating up-regulation of tyrosinase and MITF in mouse B16 melanoma cells

BACKGROUND

It is well known that melanin synthesis in melanoma cells is controlled by melanogenic enzymes, which regulate the cAMP-PKA signaling pathway. Estrogen was previously reported to upregulate melanogenesis that is associated with human skin pigmentation.

OBJECTIVE

To investigate the influence and mechanism of diethylstilbestrol (DES) on melanogenesis in mouse B16 melanoma cells.

METHODS

The effects of diethylstilbestrol on cell viability, melanin content, tyrosinase activity, cAMP level, expression of the tyrosinase family and microphthalmia related transcription factor (MITF) were measured in B16 melanoma. Estrogen receptor (ER) expression were detected in B16 melanoma and A375 melanoma. Diethylstilbestrol-induced melanin synthesis were evaluated in the presence and absence of H89 (a PKA-specific inhibitor) and ICI182, 780 (a pure ER antagonist). Tyrosinase activity, the mRNA levels of tyrosinase and MITF were evaluated in the presence and absence of H89.

RESULTS

In B16 cells, diethylstilbestrol increased cell proliferation, melanin synthesis, tyrosinase activity and expression of the tyrosinase family and MITF. ER expression have not difference in human and mouse melanoma. When ER were inhibited by ICI182, 780, DES-induced melanogenesis was significantly reduced. Diethylstilbestrol enhanced the level of cAMP. The upregulation of melanin content and tyrosinase activity stimulated by diethylstilbestrol was significantly attenuated in the presence of H89. Further, diethylstilbestrol-induced upregulation of tyrosinase and MITF were significantly attenuated when the PKA pathway was blocked.

CONCLUSIONS

Diethylstilbestrol can enhance melanin synthesis in melanoma cells. This effect is associated with activation of the cAMP-PKA pathway and upregulation of expression and activity of the melanogenesis-related enzyme tyrosinase and MITF.

Inactivation of Pmel alters melanosome shape but has only a subtle effect on visible pigmentation

PMEL is an amyloidogenic protein that appears to be exclusively expressed in pigment cells and forms intralumenal fibrils within early stage melanosomes upon which eumelanins deposit in later stages. PMEL is well conserved among vertebrates, and allelic variants in several species are associated with reduced levels of eumelanin in epidermal tissues. However, in most of these cases it is not clear whether the allelic variants reflect gain-of-function or loss-of-function, and no complete PMEL loss-of-function has been reported in a mammal. Here, we have created a mouse line in which the Pmel gene has been inactivated (Pmel^−/−). These mice are fully viable, fertile, and display no obvious developmental defects. Melanosomes within Pmel^−/− melanocytes are spherical in contrast to the oblong shape present in wild-type animals. This feature was documented in primary cultures of skin-derived melanocytes as well as in retinal pigment epithelium cells and in uveal melanocytes. Inactivation of Pmel has only a mild effect on the coat color phenotype in four different genetic backgrounds, with the clearest effect in mice also carrying the brown/Tyrp1 mutation. This phenotype, which is similar to that observed with the spontaneous silver mutation in mice, strongly suggests that other previously described alleles in vertebrates with more striking effects on pigmentation are dominant-negative mutations. Despite a mild effect on visible pigmentation, inactivation of Pmel led to a substantial reduction in eumelanin content in hair, which demonstrates that PMEL has a critical role for maintaining efficient epidermal pigmentation.

Pigmentation has since long constituted a prime model to study how genes act and interact. The PMEL gene encodes a protein exclusively found in the melanosomes of pigment-producing cells. Mutations in PMEL underlie some spectacular color phenotypes in animals including Dominant white color in chickens, Silver in horses, and Merle in dogs, but no spontaneous mutation causing a complete inactivation of this gene has yet been found in mammals. We have now developed a PMEL knockout mouse to further study the function of this protein. We show that mice lacking PMEL have almost normal visible pigmentation. However, loss of PMEL has a dramatic effect on the morphology of the melanosomes in skin, hair, and eye, such that the normally rod-shaped melanosomes in wild-type animals are spherical in the knockout mice. The knockout animals also have a substantial reduction in the content of black pigment in hair. The study establishes that PMEL has a critical role for maintaining normal pigment production.

Ethnic and mouse strain differences in central corneal thickness and association with pigmentation phenotype

The cornea is a transparent structure that permits the refraction of light into the eye. Evidence from a range of studies indicates that central corneal thickness (CCT) is strongly genetically determined. Support for a genetic component comes from data showing significant variation in CCT between different human ethnic groups. Interestingly, these studies also appear to show that skin pigmentation may influence CCT. To validate these observations, we undertook the first analysis of CCT in an oculocutaneous albinism (OCA) and Ugandan cohort, populations with distinct skin pigmentation phenotypes. There was a significant difference in the mean CCT of the OCA, Ugandan and Australian-Caucasian cohorts (Ugandan: 517.3±37 µm; Caucasian: 539.7±32.8 µm, OCA: 563.3±37.2 µm; p<0.001). A meta-analysis of 53 studies investigating the CCT of different ethnic groups was then performed and demonstrated that darker skin pigmentation is associated with a thinner CCT (p<0.001). To further verify these observations, we measured CCT in 13 different inbred mouse strains and found a significant difference between the albino and pigmented strains (p = 0.008). Specific mutations within the melanin synthesis pathway were then investigated in mice for an association with CCT. Significant differences between mutant and wild type strains were seen with the nonagouti (p<0.001), myosin VA (p<0.001), tyrosinase (p = 0.025) and tyrosinase related protein (p = 0.001) genes. These findings provide support for our hypothesis that pigmentation is associated with CCT and identifies pigment-related genes as candidates for developmental determination of a non-pigmented structure.

Human hair melanins: what we have learned and have not learned from mouse coat color pigmentation

Hair pigmentation is one of the most conspicuous phenotypes in humans. Melanocytes produce two distinct types of melanin pigment: brown to black, indolic eumelanin and yellow to reddish brown, sulfur-containing pheomelanin. Biochemically, the precursor tyrosine and the key enzyme tyrosinase and the tyrosinase-related proteins are involved in eumelanogenesis, while only the additional presence of cysteine is necessary for pheomelanogenesis. Other important proteins involved in melanogenesis include P protein, MATP protein, α-MSH, agouti signaling protein (ASIP), MC1R (the receptor for MSH and ASIP), and SLC7A11, a cystine transporter. Many studies have examined the effects of loss-of-function mutations of those proteins on mouse coat color pigmentation. In contrast, much less is known regarding the effects of mutations of the corresponding proteins on human hair pigmentation except for MC1R polymorphisms that lead to pheomelanogenesis. This perspective will discuss what we have/have not learned from mouse coat color pigmentation, with special emphasis on the significant roles of pH and the level of cysteine in melanosomes in controlling melanogenesis. Based on these data, a hypothesis is proposed to explain the diversity of human hair pigmentation.

Colours of domestication

During the last decade, coat colouration in mammals has been investigated in numerous studies. Most of these studies addressing the genetics of coat colouration were on domesticated animals. In contrast to their wild ancestors, domesticated species are often characterized by a huge allelic variability of coat-colour-associated genes. This variability results from artificial selection accepting negative pleiotropic effects linked with certain coat-colour variants. Recent studies demonstrate that this selection for coat-colour phenotypes started at the beginning of domestication. Although to date more than 300 genetic loci and more than 150 identified coat-colour-associated genes have been discovered, which influence pigmentation in various ways, the genetic pathways influencing coat colouration are still only poorly described. On the one hand, similar coat colourations observed in different species can be the product of a few conserved genes. On the other hand, different genes can be responsible for highly similar coat colourations in different individuals of a species or in different species. Therefore, any phenotypic classification of coat colouration blurs underlying differences in the genetic basis of colour variants. In this review we focus on (i) the underlying causes that have resulted in the observed increase of colour variation in domesticated animals compared to their wild ancestors, and (ii) the current state of knowledge with regard to the molecular mechanisms of colouration, with a special emphasis on when and where the different coat-colour-associated genes act.

Tyrosinase related protein 1 (TYRP1/gp75) in human cutaneous melanoma

Melanoma prognosis is based on specific pathological features at the primary lesion. In metastatic patients, the extent of lymph node involvement is also an important prognosis indicator. Many progression markers both in tissues and serum, including circulating tumor cells, have been studied and new molecular markers are awaited from high-throughput screenings to discriminate between clinical stages and predict disease progression. The present review focuses on human tyrosinase related protein 1 also known as gp75 glycoprotein (Tyrp1/gp75), a melanosomal protein involved in the pigmentary machinery of the melanocyte and often used as differentiation marker, with a special emphasis on its emerging roles in the malignant melanocyte and melanoma progression.

Update on the regulation of mammalian melanocyte function and skin pigmentation

Melanogenesis is the unique process of producing pigmented biopolymers that are sequestered within melanosomes, which provides color to the skin, hair and eyes of animals and, in the case of human skin, also protects the underlying tissues from UV damage. We review the current understanding of melanogenesis, focusing on factors important to the biochemistry of pigment synthesis, the biogenesis of melanosomes, signaling pathways and factors that regulate melanogenesis, intramelanosomal pH, transport and transfer of melanosomes, and pigmentary disorders related to the dysfunction of melanosome-related proteins. Although it has been known for some time that many of the factors that affect melanogenesis are derived from keratinocytes, fibroblasts, endothelial cells, hormones, inflammatory cells and nerves, a number of new factors that are involved in that regulation have recently been reported, such as factors that regulate melanosome pH and ion transport.

New insights into the active site structure and catalytic mechanism of tyrosinase and its related proteins

Tyrosinases are widely distributed in nature. They are copper-containing oxidases belonging to the type 3 copper protein family, together with catechol oxidases and haemocyanins. Tyrosinases are essential enzymes in melanin biosynthesis and therefore responsible for pigmentation of skin and hair in mammals, where two more enzymes, the tyrosinase-related proteins (Tyrps), participate in the pathway. The structure and catalytic mechanism of mammalian tyrosinases have been extensively studied but they are not completely understood because of the lack of information on the tertiary structure. The availability of crystallographic data of one plant catechol oxidase and one bacterial tyrosinase has improved the model of the three-dimensional structure of the active site of the enzyme. Furthermore, sequence comparison of tyrosinase and the Tyrps reveals that the three orthologue proteins share many key structural features, because of their common origin from an ancestral gene, although the specific residues responsible for their different catalytic capabilities have not been identified yet. This review summarizes our current knowledge of tyrosinase and Tyrps structure and function and describes the catalytic mechanism of tyrosinase and Dct/Tyrp2, which are better characterized.

Pigmentary function and evolution of tyrp1 gene duplicates in fish

The function of the tyrosinase-related protein 1 (Tyrp1) has not yet been investigated in vertebrates basal to tetrapods. Teleost fishes have two duplicates of the tyrp1 gene. Here, we show that the teleost tyrp1 duplicates have distributed the ancestral gene expression in the retinal pigment epithelium (RPE) and melanophores in a species-specific manner. In medaka embryos, tyrp1a expression is found in the RPE and in melanophores while tyrp1b is only expressed in melanophores. In zebrafish embryos, expression of tyrp1 paralogs overlaps in the RPE and in melanophores. Knockdown of each zebrafish tyrp1 duplicate alone does not show pigmentary defects, but simultaneous knockdown of both tyrp1 genes results in the formation of brown instead of black eumelanin accompanied by severe melanosome defects. Our study suggests that the brown melanosome color in Tyrp1-deficient vertebrates is an effect of altered eumelanin synthesis. Black eumelanin formation essentially relies on the presence of Tyrp1 and some of its function is most likely conserved from the common ancestor of bony vertebrates.

ESCRT-I function is required for Tyrp1 transport from early endosomes to the melanosome limiting membrane

Melanosomes are lysosome-related organelles that coexist with lysosomes within melanocytes. The pathways by which melanosomal proteins are diverted from endocytic organelles toward melanosomes are incompletely defined. In melanocytes from mouse models of Hermansky-Pudlak syndrome that lack BLOC-1, melanosomal proteins such as tyrosinase-related protein 1 (Tyrp1) accumulate in early endosomes. Whether this accumulation represents an anomalous pathway or an arrested normal intermediate in melanosome protein trafficking is not clear. Here, we show that early endosomes are requisite intermediates in the trafficking of Tyrp1 from the Golgi to late stage melanosomes in normal melanocytic cells. Kinetic analyses show that very little newly synthesized Tyrp1 traverses the cell surface and that internalized Tyrp1 is inefficiently sorted to melanosomes. Nevertheless, nearly all Tyrp1 traverse early endosomes since it becomes trapped within enlarged, modified endosomes upon overexpression of Hrs. Although Tyrp1 localization is not affected by Hrs depletion, depletion of the ESCRT-I component, Tsg101, or inhibition of ESCRT function by dominant-negative approaches results in a dramatic redistribution of Tyrp1 to aberrant endosomal membranes that are largely distinct from those harboring traditional ESCRT-dependent, ubiquitylated cargoes such as MART-1. The lysosomal protein content of some of these membranes and the lack of Tyrp1 recycling to the plasma membrane in Tsg101-depleted cells suggests that ESCRT-I functions downstream of BLOC-1. Our data delineate a novel pathway for Tyrp1 trafficking and illustrate a requirement for ESCRT-I function in controlling protein sorting from vacuolar endosomes to the limiting membrane of a lysosome-related organelle.

Anemonin is a natural bioactive compound that can regulate tyrosinase-related proteins and mRNA in human melanocytes

BACKGROUND

Melanin is the pigment responsible for skin color. Melanin synthesis occurs with the participation of the tyrosinase (TYR) family of proteins including TYR, tyrosinase-related protein 1 (TRP1), and tyrosinase-related protein 2(TRP2/DCT).

OBJECTIVE

The effect of a newly isolated natural compound that inhibits hyperpigmentation on the regulation of the TYR family of proteins was examined.

METHODS

The natural compound, anemonin, was isolated from Clematis crassifolia Benth and was used to inhibit cellular TYR activity; it was found to have a low cytotoxicity (cell viability > 80%) in human melanocytes.

RESULTS

In human melanocytes, anemonin showed both time- and dose-dependent inhibition (IC(50) 43.5 microM) of TYR. Western blot analysis and immunocytochemical staining revealed that expression of TYR, TRP1, and TRP2 was decreased in anemonin-treated melanocytes. Additionally, reverse transcription and quantitative real-time polymerase chain reaction analyses revealed that expression of mRNAs for MITF, TYR, TYRP1, and TYRP2 was also suppressed by anemonin.

CONCLUSION

The natural compound, anemonin, an active compound of C. crassifolia, inhibits pigmentation synthesis in human melanocytes. Anemonin inhibits melanin synthesis by inhibiting the transcription of the genes encoding MITF, TYR, TRP1, and TRP2. This natural compound may be a candidate for cosmetic use.