Normal Human Epidermal Melanocytes Research Articles

Identification of L-Cysteinamide as a Potent Inhibitor of Tyrosinase-Mediated Dopachrome Formation and Eumelanin Synthesis.

The purpose of this study is to identify amino acid derivatives with potent anti-eumelanogenic activity. First, we compared the effects of twenty different amidated amino acids on tyrosinase (TYR)-mediated dopachrome formation in vitro and melanin content in dark-pigmented human melanoma MNT-1 cells. The results showed that only L-cysteinamide inhibited TYR-mediated dopachrome formation in vitro and reduced the melanin content of cells. Next, the antimelanogenic effect of L-cysteinamide was compared to those of other thiol compounds (L-cysteine, N-acetyl L-cysteine, glutathione, L-cysteine ethyl ester, N-acetyl L-cysteinamide, and cysteamine) and positive controls with known antimelanogenic effects (kojic acid and β-arbutin). The results showed the unique properties of L-cysteinamide, which effectively reduces melanin content without causing cytotoxicity. L-Cysteinamide did not affect the mRNA and protein levels of TYR, tyrosinase-related protein 1, and dopachrome tautomerase in MNT-1 cells. L-Cysteinamide exhibited similar properties in normal human epidermal melanocytes (HEMs). Experiments using mushroom TYR suggest that L-cysteinamide at certain concentrations can inhibit eumelanin synthesis through a dual mechanism by inhibiting TYR-catalyzed dopaquinone synthesis and by diverting the synthesized dopaquinone to the formation of DOPA-cysteinamide conjugates rather than dopachrome. Finally, L-cysteinamide was shown to increase pheomelanin content while decreasing eumelanin and total melanin contents in MNT-1 cells. This study suggests that L-cysteinamide has an optimal structure that can effectively and safely inhibit eumelanin synthesis in MNT-1 cells and HEMs, and will be useful in controlling skin hyperpigmentation.

Antimelanogenesis Effects of Theasinensin A.

Theasinensin A (TSA) is a major group of catechin dimers mainly found in oolong tea and black tea. This compound is also manufactured with epigallocatechin gallate (EGCG) as a substrate and is refined after the enzyme reaction. In previous studies, TSA has been reported to be effective against inflammation. However, the effect of these substances on skin melanin formation remains unknown. In this study, we unraveled the role of TSA in melanogenesis using mouse melanoma B16F10 cells and normal human epidermal melanocytes (NHEMs) through reverse transcription polymerase chain reaction (RT-PCR), Western blotting analysis, luciferase reporter assay, and enzyme-linked immunosorbent assay analysis. TSA inhibited melanin formation and secretion in α-melanocyte stimulating hormone (α-MSH)-induced B16F10 cells and NHEMs. TSA down-regulated the mRNA expression of tyrosinase (Tyr), tyrosinase-related protein 1 (Tyrp1), and Tyrp2, which are all related to melanin formation in these cells. TSA was able to suppress the activities of certain proteins in the melanocortin 1 receptor (MC1R) signaling pathway associated with melanin synthesis in B16F10 cells: cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB), protein kinase A (PKA), tyrosinase, and microphthalmia-associated transcription factor (MITF). We also confirmed α-MSH-mediated CREB activities through a luciferase reporter assay, and that the quantities of cAMP were reduced by TSA in the enzyme linked immunosorbent assay (ELISA) results. Based on these findings, TSA should be considered an effective inhibitor of hyperpigmentation.

Learning from Embryogenesis-A Comparative Expression Analysis in Melanoblast Differentiation and Tumorigenesis Reveals miRNAs Driving Melanoma Development.

Malignant melanoma is one of the most dangerous tumor types due to its high metastasis rates and a steadily increasing incidence. During tumorigenesis, the molecular processes of embryonic development, exemplified by epithelial–mesenchymal transition (EMT), are often reactivated. For melanoma development, the exact molecular differences between melanoblasts, melanocytes, and melanoma cells are not completely understood. In this study, we aimed to identify microRNAs (miRNAs) that promote melanoma tumorigenesis and progression, based on an in vitro model of normal human epidermal melanocyte (NHEM) de-differentiation into melanoblast-like cells (MBrCs). Using miRNA-sequencing and differential expression analysis, we demonstrated in this study that a majority of miRNAs have an almost equal expression level in NHEMs and MBrCs but are significantly differentially regulated in primary tumor- and metastasis-derived melanoma cell lines. Further, a target gene analysis of strongly regulated but functionally unknown miRNAs yielded the implication of those miRNAs in many important cellular pathways driving malignancy. We hypothesize that many of the miRNAs discovered in our study are key drivers of melanoma development as they account for the tumorigenic potential that differentiates melanoma cells from proliferating or migrating embryonic cells.

Intense Pulsed Light Attenuates UV-Induced Hyperimmune Response and Pigmentation in Human Skin Cells.

The skin of an organism is affected by various environmental factors and fights against aging stress via mechanical and biochemical responses. Photoaging induced by ultraviolet B (UVB) irradiation is common and is the most vital factor in the senescence phenotype of skin, and so, suppression of UVB stress-induced damage is critical. To lessen the UVB-induced hyperimmune response and hyperpigmentation, we investigated the ameliorative effects of intense pulsed light (IPL) treatment on the photoaged phenotype of skin cells. Normal human epidermal keratinocytes and human epidermal melanocytes were exposed to 20 mJ/cm2 of UVB. After UVB irradiation, the cells were treated with green (525–530 nm) and yellow (585–592 nm) IPL at various time points prior to the harvest step. Subsequently, various signs of excessive immune response, including expression of proinflammatory and melanogenic genes and proteins, cellular oxidative stress level, and antioxidative enzyme activity, were examined. We found that IPL treatment reduced excessive cutaneous immune reactions by suppressing UVB-induced proinflammatory cytokine expression. IPL treatment prevented hyperpigmentation, and combined treatment with green and yellow IPL synergistically attenuated both processes. IPL treatment may exert protective effects against UVB injury in skin cells by attenuating inflammatory cytokine and melanogenic gene overexpression, possibly by reducing intracellular oxidative stress. IPL treatment also preserves antioxidative enzyme activity under UVB irradiation. This study suggests that IPL treatment is a useful strategy against photoaging, and provides evidence supporting clinical approaches with non-invasive light therapy.

α-Mangostin suppressed melanogenesis in B16F10 murine melanoma cells through GSK3β and ERK signaling pathway

Mangosteen (Garcinia mangostana L) fruit contains many xanthones in its pericarp, such as α-mangostin. Here, we aimed to elucidate the physiological effect of α-mangostin and the mechanism on melanogenesis in mouse B16F10 cells. The melanin production in B16F10 cells was decreased by α-mangostin treatment. α-Mangostin also suppressed the enzymatic activity of tyrosinase, the critical enzyme for melanin synthesis. Furthermore, Western blot analysis revealed that α-mangostin down-regulated the protein quantity of tyrosinase, tyrosinase relative protein (TRP)-2, and microphthalmia-associated transcription factor (MITF). We also used inhibitors of the extracellular signal-regulated kinase (ERK), and glycogen synthase kinase 3 (GSK-3β) to identify the upstream signaling cascade of MITF. Results showed us GSK3β plays a more important role in α-mangostin regulated melanogenesis. Further, the de-pigmentation effect on normal human epidermal melanocytes (NHEMs) of α-mangostin was also confirmed. These results suggested that α-mangostin is a reagent for depigmentation and it has the potential to be applied as a component of cosmetics or pharmaceuticals for the therapy of spots, chloasma, or melanosis.

The BH3 mimetic (\xb1) gossypol induces ROS-independent apoptosis and mitochondrial dysfunction in human A375 melanoma cells in vitro

A major challenge in current cancer therapy is still the treatment of metastatic melanomas of the skin. BH3 mimetics represent a novel group of substances inducing apoptosis. In this study, we investigated the cytotoxic effect of (±) gossypol (GP), a natural compound from cotton seed, on A375 melanoma cells and the underlying biochemical mechanisms. To prevent undesired side effects due to toxicity on normal (healthy) cells, concentrations only toxic for tumor cells have been elaborated. Viability assays were performed to determine the cytotoxicity of GP in A375 melanoma and normal (healthy) cells. For the majority of experiments, a concentration of 2.5 µM GP was used resulting in a ROS-independent but caspase-dependent cell death of A375 melanoma cells. At this level, GP was non-toxic for normal human epidermal melanocytes. GP has a very short half-life, however, it was demonstrated that only the “parent” compound and not decomposition products are responsible for the cytotoxic effect in A375 melanoma cells. GP significantly decreased mitochondrial membrane potential accompanied by a Drp1-dependent loss of mitochondrial integrity (fragmentation) in tumor cells. Taken together, GP induced a ROS-independent intrinsic apoptosis leading to the conclusion that within a specific concentration range, GP may work as effective anticancer drug without harmful side effects.

Expression of histidine decarboxylase in melanocytes of the human skin

Histamine-producing cells include storage-type cells (e.g., mast cells and basophils), which store histamine intracellularly, and inducible-type cells (e.g., keratinocytes and macrophages), which induce histidine decarboxylase (HDC, a key enzyme for histamine biosynthesis) activity but do not have a storage pool of histamine. Most of the studies focused on identifying HDC-expressing cells by using cultured cells, and few on investigating the localization of HDC by using skin tissues. Hence, this study conducted immunohistochemical studies using human healthy skin samples. HDC-positive and cytokeratin 14 (a marker of basal keratinocytes)-negative cells were present around the basal layer of the epidermis. These cells did not immunohistochemically react with mast cell tryptase but expressed tyrosinase (a key enzyme for melanin biosynthesis) and microphthalmia-associated transcription factor (MITF, a transcription factor controlling the expression of tyrosinase genes). Melanin granules were clearly observed around HDC-positive and MITF-positive cells. Moreover, HDC mRNA and protein were both detected in cultured normal human epidermal melanocytes. In conclusion, HDC-positive and cytokeratin 14-negative cells around the basal layer of the epidermis are melanocytes.

Exogenous pyruvate alleviates UV-induced hyperpigmentation via restraining dendrite outgrowth and Rac1 GTPase activity

BackgroundMelanin is synthesized in melanocytes and transferred to keratinocytes through dendrites. Endogenous pyruvate is a key metabolite for ATP production in glycolysis, and the tricarboxylic acid (TCA) cycle and exogenous pyruvate provide protection against oxidative stress and acidosis in the intercellular space. The function of pyruvate in the regulation of dendrite outgrowth remains to be elucidated. ObjectiveWe examined the effect of pyruvate on dendritic elongation and skin pigmentation MethodsMurine B16F10 melanoma cells and human primary melanocytes were used for in vitro analysis. Melanin quantitation and histochemical staining were performed in a 3D pigmented human skin model. ResultsWe demonstrated the participation of monocarboxylate transporters (MCTs) responsible for the membrane transport of pyruvate in B16F10 melanoma cells. The accumulation of pyruvate occurred in a pH-dependent manner, which was highly sensitive to a specific MCT inhibitor (α-cyano-4-hydroxycinnamic acid). α-MSH-induced morphological changes, including dendrite elongation and growth-cone-like structure, were diminished in B16F10 cells upon treatment with pyruvate. In addition, the number of dendrite branches was reduced in normal human epidermal melanocytes. As the Rho-subfamily of monomeric GTP-binding proteins modulates dendrite formation, we subsequently examined the suppression of Rac1 activation by pyruvate, but not RhoA and Cdc42. Furthermore, pyruvate showed anti-melanogenic effects against UV-induced pigmentation in reconstructed pigmented epidermis, established by co-seeding autologous melanocytes and keratinocytes, which act similar to in vivo skin tissue. ConclusionThese results suggest that pyruvate treatment may be an alternative or additive therapeutic strategy to prevent hyperpigmentation.

UP256 Inhibits Hyperpigmentation by Tyrosinase Expression/Dendrite Formation via Rho-Dependent Signaling and by Primary Cilium Formation in Melanocytes.

Skin hyperpigmentation is generally characterized by increased synthesis and deposition of melanin in the skin. UP256, containing bakuchiol, is a well-known medication for acne vulgaris. Acne sometimes leaves dark spots on the skin, and we hypothesized that UP256 may be effective against hyperpigmentation-associated diseases. UP256 was treated for anti-melanogenesis and melanocyte dendrite formation in cultured normal human epidermal melanocytes as well as in the reconstituted skin and zebrafish models. Western blot analysis and glutathione S-transferase (GST)-pull down assays were used to evaluate the expression and interaction of enzymes related in melanin synthesis and transportation. The cellular tyrosinase activity and melanin content assay revealed that UP256 decreased melanin synthesis by regulating the expression of proteins related on melanogenesis including tyrosinase, TRP-1 and -2, and SOX9. UP256 also decreased dendrite formation in melanocytes via regulating the Rac/Cdc42/α-PAK signaling proteins, without cytotoxic effects. UP256 also inhibited ciliogenesis-dependent melanogenesis in normal human epidermal melanocytes. Furthermore, UP256 suppressed melanin contents in the zebrafish and the 3D human skin tissue model. All things taken together, UP256 inhibits melanin synthesis, dendrite formation, and primary cilium formation leading to the inhibition of melanogenesis.

MiR-143 acts as an inhibitor of migration and proliferation as well as an inducer of apoptosis in melanoma cancer cells in vitro.

Melanoma is a serious form of skin cancers begins in the melanocyte. Micro-RNAs are small noncoding RNA with 19 to 25 nucleotides in length involves in the regulation of a wide range of biological processes. MicroRNAs are affected by an aberrant epigenetic alteration in the tumors that may lead to their dysregulation and formation of cancer. Recently, dysregulation of numerous microRNAs has been reported in different types of cancer. The present study focused on the role of miR-143 in carcinogenesis of melanoma cancer. Here, we evaluated the expression level of miR-143 in three melanoma cell lines in comparison with the normal human epidermal melanocyte cell line. Then, miR-143 gene plasmid transfected into the WM115 cell line, for having the lowest expression of miR-143. In addition, the effect of miR-143 transfection on mRNA and protein levels of metastasis-related genes was performed along with MTT assay, wound healing assay, and flow cytometry. The results showed that mRNA and protein expression levels of metastasis-related genes including MMP-9, E-cadherin, Vimentin, and CXCR4 have been reduced following transfection of miR-143. Moreover, the results of the scratch test showed that miR-143 re-expression inhibited cell migration. Also, the role of miR-143 in the induction of apoptosis and inhibition of proliferation by flow cytometry and MTT was confirmed. As a result, the present study showed that miR-143 was involved in metastatic and apoptotic pathways, suggesting that miR-143 acts as a tumor-suppressor microRNA in melanoma cancer.

Bromodomain Epigenetic Protein Promotes Metastatic Potential in Melanoma Cells through Increased Invasiveness and Decreased Macrophage-Mediated Phagocytosis

Bromodomain Epigenetic Protein Promotes Metastatic Potential in Melanoma Cells through Increased Invasiveness and Decreased Macrophage-Mediated Phagocytosis

Dysfunction of ATG7-dependent autophagy dysregulates the antioxidant response and contributes to oxidative stress-induced biological impairments in human epidermal melanocytes

Autophagy is a process involving the self-digestion of components that participates in anti-oxidative stress responses and protects cells against oxidative damage. However, the role of autophagy in the anti-oxidative stress responses of melanocytes remains unclear. To investigate the role of autophagy in human epidermal melanocytes, we knocked down and overexpressed ATG7, the critical gene of autophagy, in normal human epidermal melanocytes. We demonstrated that ATG7-dependent autophagy could affect melanin content of melanocytes by regulating melanogenesis. Moreover, suppression of ATG7-dependent autophagy inhibits proliferation and promotes oxidative stress-induced apoptosis of melanocytes, whereas enhancement of ATG7-dependent autophagy protects melanocytes from oxidative stress-induced apoptosis. Meanwhile, deficiency of ATG7-dependent autophagy results in premature senescence of melanocytes under oxidative stress. Notably, we verified that ATG7-dependent autophagy could alter oxidative stress homeostasis by regulating reactive oxygen species (ROS) production, nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidant pathway, and the activity of several antioxidant enzymes in melanocytes. In conclusion, our study suggested that ATG7-dependent autophagy is indispensable for redox homeostasis and the biological functions of melanocytes, such as melanogenesis, proliferation, apoptosis, and senescence, especially under oxidative stress.

The Polyamine Putrescine Promotes Human Epidermal Melanogenesis

Hyperpigmentary conditions can arise when melanogenesis in the epidermis is misregulated. Understanding the pathways underlying melanogenesis is essential for the development of effective treatments. Here, we report that a group of metabolites called polyamines are important in the control of melanogenesis in human skin. Polyamines are cationic molecules present in all cells and are essential for cellular function. We report that polyamine regulator ODC1 is upregulated in melanocytes from melasma lesional skin. We report that the polyamine putrescine can promote pigmentation in human skin explants and primary normal human epidermal melanocytes through induction of tyrosinase which is rate-limiting for the synthesis of melanin. Putrescine supplementation on normal human epidermal melanocytes results in the activation of polyamine catabolism, which results in increased intracellular H2O2. Polyamine catabolism is also increased in human skin explants that have been treated with putrescine. We further report that inhibition of polyamine catabolism prevents putrescine-induced promotion of tyrosinase levels and pigmentation in normal human epidermal melanocytes, showing that polyamine catabolism is responsible for the putrescine induction of melanogenesis. Our data showing that putrescine promotes pigmentation has important consequences for hyperpigmented and hypopigmented conditions. Further understanding of how polyamines control epidermal pigmentation could open the door for the development of new therapeutics.

Identification of photodegraded derivatives of usnic acid with improved toxicity profile and UVA/UVB protection in normal human L02 hepatocytes and epidermal melanocytes

This study focused on the investigation of photodegradation of usnic acid (UA) which is a natural UV absorbing agent in lichens. Despite years of historical use in food supplement, traditional medicine or cosmetic products in many countries, liver toxicity has been found to be one of the severe and life threatening adverse effects in early 2000's. Such severe side effect has limited UA or its synthesized derivatives for further use clinically or commercially. In this study, extracted UA from Usnea longissima in methanol was exposed to natural sunlight for 21 days. Five photodegraded derivatives (1 to 5) with two new and three previously explored compounds were isolated and purified by column chromatography and preparative liquid chromatography. The structures of these derivatives were identified based on the data of nuclear magnetic resonance spectrum, mass spectrum, optical rotation, infrared spectrum, X-ray crystallography and/or electronic circulation dichroism. The cytotoxicity of (+)-UA and 2 to 5 in liver L02 cells and melanocytes were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Experimental results indicated that IC50 of (+)-UA in liver L02 cells and melanocytes were 24.4 and 6.9 μM respectively, while compound 2 to 5 have lower cytotoxicity with IC50 of 326.7, 1085.0, 62.7 and 152.4 μM in L02 cells and 87.7, 297.7, 60.2 and 85.0 μM in melanocytes respectively. Besides, (+)-UA and these derivatives were exposed to fix dosed of UVA or UVB. The anti-UVA/UVB activity was determined via Hoechst33342/propidium iodide double staining method, and quantified by computer linked fluorescence microscope equipped with CellsSense Dimension system. Based on analysis, Compound 2 to 5 captured prominent UVA/UVB protection capacity in both hepatocytes and melanocytes (p < .001). In addition, the effects of chemicals on tyrosinase were evaluated via Western Blot analysis. In terms of tyrosinase expression, only 2 showed significant stimulating effect (p < .05). However, the safe use of these derivatives cutaneously should be further studied. In conclusion, the photodegraded derivatives (2 to 5) of extracted UA have lower hepatotoxicity than (+)-UA and captured significant UV protection activities.

Astragaloside IV Enhances Melanogenesis via the AhR-Dependent AKT/GSK-3β/β-Catenin Pathway in Normal Human Epidermal Melanocytes.

Astragalus membranaceus root has been widely used for repigmentation treatment in vitiligo, but its mechanism is poorly understood. We sought to investigate the effect of astragaloside IV (AS-IV), a main active extract of the Astragalus membranaceus root, on melanin synthesis in normal human epidermal melanocytes (NHEMs) and to elucidate its underlying mechanisms. Melanin content, tyrosinase activity, qPCR, western blot, and immunofluorescence were employed. Specific inhibitors and small interfering RNA were used to investigate the possible pathway. AS-IV stimulated melanin synthesis and upregulated the expression of melanogenesis-related genes in a concentration-dependent manner in NHEMs. AS-IV could activate the aryl hydrocarbon receptor (AhR), and AS-IV-induced melanogenesis was inhibited in si-AhR-transfected NHEMs. In addition, we showed that AS-IV enhanced the phosphorylation of AKT and GSK-3β and nuclear translocation of β-catenin. AS-IV-induced MITF expression upregulation and melanin synthesis were decreased in the presence of β-catenin inhibitor FH353. Furthermore, AhR antagonist CH223191 inhibited the activation of AKT/GSK-3β/β-catenin signaling, whereas the expression of CYP1A1 (marker of AhR activation) was not affected by the AKT inhibitor in AS-IV-exposed NHEMs. Our findings show that AS-IV induces melanogenesis through AhR-dependent AKT/GSK-3β/β-catenin pathway activation and could be beneficial in the therapy for depigmented skin disorders.

A Potential Tumor Suppressor Gene Named miR-508-5p Inhibited the Proliferation and Invasion of Human Melanoma Cells by Targeting KIT

Melanoma is the main death cause of human skin cancer. Increasing evidences demonstrate that microRNAs act as key roles in mediating tumor occurrence and progression. MiR-508-5p has proved to participate in the development of various types of human malignancies. However, the role of miR-508-5p in melanoma remained unclear. In in vitro study, miR-508-5p level in peripheral blood samples of patients with melanoma and human melanoma A375 cells was downregulated compared to that in normal peripheral blood samples or normal human epidermal melanocytes (MHEM). MiR-508-5p overexpression significantly inhibited the cell proliferation, migration and invasion in A375 cells, and thus inhibiting KIT expression at both gene and protein levels. Furthermore, western blot analysis showed miR-508-5p reduced cell proliferation by targeting KIT to modulate RAS/RAF/MEK/ERK pathway. Taken together, we speculated that miR-508-5p functioned as an important suppressor in human melanoma by targeting KIT, suggesting miR-508-5p might be a promising tumor suppressor gene for further target therapies from bench to clinic.

Suppression of FADS1 induces ROS generation, cell cycle arrest, and apoptosis in melanocytes: implications for vitiligo.

Vitiligo is a potentially serious condition characterized by loss of melanin and death of melanocytes. To identify potential therapeutic targets for vitiligo, we conducted a microarray analysis of three human vitiligo specimens and paired adjacent normal tissues. Because we found that the fatty acid desaturase 1 (FADS1) gene was downregulated in vitiligo specimens, we carried out experiments to assess its role in melanocyte replication and survival. RT-qPCR was used to verify that FADS1 expression was lower in vitiligo-affected tissues and vitiligo melanocyte PIG3V cells than in matched controls or normal human epidermal PIG1 melanocytes. In addition, CCK-8, immunofluorescence, western blot and flow cytometry assay were used to detect the proliferation and apoptosis in PIG1 cells respectively. Overexpression of FADS1 promoted proliferation of PIG3V melanocytes, while FADS1 silencing inhibited proliferation and induced cell death in PIG1 melanocytes. Increased ROS generation; induction of mitochondrial-mediated apoptosis via upregulation of Bax and active caspases 3 and 9 and downregulation of Bcl-2; and cell cycle arrest via downregulation of c-Myc and Cyclin D1 and upregulation of p21 were all enhanced after FADS1 silencing in PIG1 melanocytes. These findings implicate FADS1 downregulation in the pathogenesis of vitiligo and may open new avenues for its treatment.

Effect of sulfur mustard on melanogenesis in vitro

The chemical warfare agent sulfur mustard (SM) affects all cells in the epidermis including melanocytes which are responsible for melanin synthesis. After exposure to SM, pigment abnormalities like hypo- and hyperpigmentation can occur. The underlying molecular pathomechanisms of SM exposure on human melanogenesis have not been elucidated so far. In our study, we investigated the effect of SM on human melanocytes and melanogenesis. Normal human epidermal melanocytes (NHEM) were used as in vitro model and they were exposed to different concentrations of SM (4.5 μM–100 μM). Melanin production was analyzed by absorption measurements at 405 nm. In addition, quantitative real-time PCR (qPCR) and Western blot experiments were performed to determine the expression of essential melanogenesis-related proteins including tyrosinase (TYR), tyrosinase-related protein (TRP) 1 and 2 and microphthalmia transcription factor (MITF). Our findings demonstrated that exposure to low SM concentrations increased melanin synthesis accompanied with an increase in protein expression. In contrast, high SM concentrations led to decreased melanin content and a downregulation in expression of all investigated melanogenesis-associated proteins. We concluded that low SM concentrations may cause hyperpigmentation while high SM concentrations decreased melanin content which may explain hypopigmented skin areas in SM exposed patients.

564 Melasolv, a skin lightening compound with different mechanisms to regulate skin pigmentation

The pigmentation of human skin (nevi, senile lentigines, melasma, etc) is regulated by a complex process involving the synthesis and distribution of melanin. Overexpression of melanin is induced by the off-balance between the signals which regulates melanin synthesis, this can be caused due to a response to external or internal stimulus that often affects the genes related to melanogenesis. To date, many studies have focused on developing direct enzymatic inhibitors of tyrosinase in order to achieve a skin-lightening effect. However, it was also reported that these direct inhibitors could be converted to quinone derivatives by tyrosinase-catalyzed oxidation, which lead to undesirable outcomes. Therefore, we have studied intrinsic inhibitory factors of melanogenesis in skin with the objective to achieve a lightening effect without the undesirable potential side effects. It was reported that non-coding RNAs including H19, miR125b and WIF1 were decreased in hyper-pigmented skin such as melasma and nevi. And it was found out that melanogenesis could be inhibited by increasing these lightening genes expression in normal human epidermal melanocytes and keratinocytes. Our group showed that the 3, 4, 5-trimethoxy cinnamate thymol ester (TCTE, Melasolv®), synthesized from gallic acid, is a lightening active which decreases tyrosinase protein formation by regulating the MITF. Likewise, we have also observed that Melasolv significantly decreased melanogenesis by increasing expression of the lightening genes H19, miR125b and WIF1 in the skin cells. Finally, we have confirmed the lightening effect of Melasolv in 3D human skin equivalent. Nonetheless, since Melasolv is not a direct inhibitor of tyrosinase enzymatic activity, it is extremely unlikely that nocive quinone derivatives conversions occur. From these results, we have proposed Melasolv as an active for lightening effects with a safer profile, when considering undesirable effects, to treat pigmentary disorder and uneven skin color.

Propofol suppresses proliferation, invasion, and migration of human melanoma cells via regulating microRNA-137 and fibroblast growth factor 9.

Propofol is an intravenous anesthetic widely used in clinical surgeries, such as tumor resection. Propofol affects the growth of many cancers, though its effect on melanoma is unknown. Our study aimed to explore how propofol affects melanoma cells. Melanoma cells A2058 and WM793B were cultured with propofol for 24 hr. Propofol significantly suppressed proliferation, migration, and invasion of A2058 and WM793B cells. Lower miR-137 level was observed in A2058 and WM793B cells, compared with normal human epidermal melanocyte HEMa-LP cells. Propofol-induced miR-137 upregulation and decreased proliferation, invasive ability, and migrated ability of A2058 and WM793B cells. Transfection with the miR-137 inhibitor reversed these effects. Additionally, miR-137 was verified to target and negatively regulate fibroblast growth factor 9 (FGF9) expression. Propofol efficiently downregulated FGF9 protein expression by upregulating miR-137. Furthermore, FGF9 overexpression abrogated propofol's repressive effects on the malignant potential of A2058 and WM793B cells. These findings indicate that propofol suppressed melanoma cell proliferation, invasion, and migration by regulating miR-137 and FGF9.