Withania somnifera extract attenuates stem cell factor-stimulated pigmentation in human epidermal equivalents through interruption of ERK phosphorylation within melanocytes

The interleukin-1α stimulated expression of the wrinkle-inducing elastase neprilysin in adult human dermal fibroblasts is mediated via the intracellular signaling axis of ERK/JNK/c-Jun/c-Fos/AP-1

Neprilysin is a skin wrinkle-inducing membrane bound elastase that is expressed abundantly in UV-exposed and in aged dermal fibroblasts. The overexpression of neprilysin is closely associated with enhanced epithelial-mesenchymal cytokine interactions mainly via interleukin (IL)-1α, which has the distinct potential to stimulate the expression of neprilysin by human dermal fibroblasts (HDFs). The over-expression of neprilysin also accelerates the formation of wrinkles, accompanied by disruptions of the three-dimensional architecture of dermal elastic fibers that are responsible for the loss of skin elasticity. Because the signaling pathway(s) that lead to the IL-1α-stimulated expression of neprilysin in HDFs remain unclear, we characterized the signaling pathway involved, including their related transcription factors, in IL-1α-treated HDFs. Since qRT-PCR analysis revealed that the mRNA expression level of neprilysin is stimulated to a stronger extent in adult HDFs (aHDFs) by IL-1α than in neonatal HDFs, we used aHDFs for the signaling analysis. Western blotting analysis of the phosphorylation of signaling factors revealed that IL-1α significantly stimulated the phosphorylation of ERK1/2, RSK, JNK, p38, MSK1, NFkB, c-Jun, ATF-2, CREB, and STAT3. Analysis using various signaling inhibitors demonstrated that inhibiting ERK and JNK but not p38, MSK1, NFkB, or STAT3 significantly abrogated the IL-1α stimulated expression of neprilysin at the mRNA, protein, and enzyme activity levels. Furthermore, silencing c-Fos significantly down-regulated the IL-1α-increased expression of neprilysin at the protein and enzyme activity levels. These findings strongly suggest that the IL-1α-stimulated expression of neprilysin in aHDFs is mediated via the intracellular signaling axis of ERK/JNK/c-Jun/c-Fos/AP-1.

Daturataturin A, a withanolide in Datura metel L., induces HaCaT autophagy through the PI3K-Akt-mTOR signaling pathway

Daturataturin A (DTA), a withanolide compound in Datura metel L., exhibits excellent anti-inflammatory and anti-proliferative activities. Here, we report the study of DTA-induced proliferation and inflammation in human immortalized keratinocytes (HaCaTs) and the associated molecular mechanisms. HaCaTs are a model of the epidermal proliferative state of cells. The pharmacodynamics and mechanism of DTA were studied by western blot, immunofluorescence, apoptosis and proliferation detection, and real-time quantitative polymerase chain reaction. We confirmed that DTA induced HaCaT autophagy, which, in turn, induced HaCaT senescence and, ultimately, led to cell cycle arrest. DTA also negatively regulated inflammation through the activation of autophagy. This may be one of the mechanisms underlying the action of Datura metel L. preparation used for the treatment of psoriasis.

Effect of serum from healthy individuals on the growth of melanocytes in vitro following moxibustion at the "Jiudianfeng" point

Objective

To investigate the effects of serum from healthy individuals obtained following moxibustion at the “Jiudianfeng” point on melanocytes in vitro .

Methods

Ten healthy adults (five male and five female) were treated by moxibustion at the “Jiudianfeng” point for 30 minutes once daily for 3 months. The effects of treatment with serum obtained following moxibustion on melanocyte proliferation, melanin content, tyrosinase activity, cell cycle progression, and c-kit mRNA and protein expression were assessed in vitro before and after moxibustion for 1, 2, and 3 months.

Results

Exposure to sera from healthy adults following moxibustion therapy promoted melanocyte proliferation, melanin synthesis, tyrosinase activity, and c-kit mRNA and protein expression in vitro . Melanin synthesis and tyrosinase activity increased in the first 2 months following moxibustion and a synchronous decline was observed during the third month. Serum also promoted melanocyte entry into the G1 phase of the cell cycle.

Conclusions

Serum treatment following moxibustion at the “Jiudianfeng” point promoted melanocyte proliferation and melanin synthesis. Further exploration of this intriguing phenomenon is essential.

Stem Cell Factor-Inducible MITF-M Expression in Therapeutics for Acquired Skin Hyperpigmentation

Rationale: Microphthalmia-associated transcription factor M (MITF-M) plays important roles in the pigment production, differentiation and survival of melanocytes. Stem cell factor (SCF) and its receptor KIT stimulate MITF-M activity via phosphorylation at the post-translation level. However, the phosphorylation shortens half-life of MITF-M protein over the course of minutes. Here, we investigated novel hypotheses of (i) whether SCF/KIT can regulate MITF-M activity through gene expression as the alternative process, and (ii) whether chemical inhibition of KIT activity can mitigate the acquired pigmentation in skin by targeting the expression of MITF-M. Methods: We employed melanocyte cultures in vitro and pigmented skin samples in vivo, and applied immunoblotting, RT-PCR, siRNA-based gene knockdown and confocal microscopy. Results: The protein and mRNA levels of MITF-M in epidermal melanocytes and the promoter activity of MITF-M in B16-F0 melanoma cells demonstrated that SCF/KIT could trigger the expression of MITF-M de novo, following the phosphorylation-dependent proteolysis of pre-existing MITF-M protein. SCF/KIT regulated the transcription abilities of cAMP-responsive element-binding protein (CREB), CREB-regulated co-activator 1 (CRTC1) and SRY-related HMG-box 10 (SOX10) but not β-catenin at the MITF-M promoter. Meanwhile, chemical inhibition of KIT activity abolished SCF-induced melanin production in epidermal melanocyte cultures, as well as protected the skin from UV-B-induced hyperpigmentation in HRM2 mice or brownish guinea pigs, in which it down-regulated the expression of MITF-M de novo at the promoter level. Conclusion: We propose the targeting of SCF/KIT-inducible MITF-M expression as a strategy in the therapeutics for acquired pigmentary disorders.

The role and mechanism of Asian medicinal plants in treating skin pigmentary disorders

ETHNOPHARMACOLOGICAL RELEVANCE

Chloasma, senile plaques, vitiligo and other pigmentary disorders seriously affect patients' appearance and life quality. Medicinal plant is the product of long-term medical practice worldwide, with the advantages of outstanding curative properties and less side effects. Recently, research were made to explore the value of medicinal plants in the treatment of pigmentary disorders, and remarkable results were achieved.

AIM OF THE REVIEW

This review outlines the current understanding of the role and potential mechanisms of medicinal plants (including active ingredients, extracts and prescriptions) in pigmentary disorders, especially Chinese medicinal plants, provides the preclinical evidence for the clinical benefits. This study hopes to provide comprehensive information and reliable basis for exploring new therapeutic strategies of plant drugs in the treatment of skin pigmented diseases.

METHODS

The literature information was obtained from the scientific databases (up to Oct, 2017), mainly from the PubMed, Web of Science and CNKI databases, and was to identify the experimental studies on the regulating melanogenesis role of the active agents from herbal medicine and the involved mechanisms. The search keywords for such work included: "pigmentary" or "pigmentation", "melanogenesis", and "traditional Chinese medicine" or "Chinese herbal medicine", "herb", "medicinal plant".

RESULTS

We summarized the function of medicinal plants involved in melanogenesis, especially Chinese medicine. It was reported that the active ingredients, extracts, or prescriptions of medicinal plants can regulate the expression of genes related to melanogenesis by affecting the signaling pathways such as MAPK and PKA, thereby regulating pigment synthesis. Some of them can promote melanogenesis (such as isoliquiritigenin, geniposide; Cornus officinalis Siebold & Zucc., Eclipta prostrata (L.) L.; the Bairesi complex prescription, etc.). While others have the opposite effect (such as biochanin A, Gomisin N; Panax ginseng C.A. Meyer, Nardostachys chinensis Bat.; Sanbaitang, etc.).

CONCLUSION

Asian medicinal plants, especially their active ingredients, have multilevel effects on melanogenesis by regulating melanogenesis-related genes or signaling pathways. They are of great clinical value for the treatment of skin pigmentary disorders. However, the experimental effect, safety, and functional mechanism of the medicinal plants require further determination before studying their clinical efficacy.

Discovery of new depigmenting compounds and their efficacy to treat hyperpigmentation: Evidence from in vitro study

Human skin pigmentation is a result of constitutive and facultative pigmentation. Facultative pigmentation is frequently stimulated by UV radiation, pharmacologic drugs, and hormones whereby leads to the development of abnormal skin hyperpigmentation. To date, many state-of-art depigmenting compounds have been studied using in vitro model to treat hyperpigmentation problems for cosmetic dermatological applications; little attention has been made to compare the effectiveness of these depigmenting compounds and their mode of actions. In this present article, new and recent depigmenting compounds, their melanogenic pathway targets, and modes of action are reviewed. This article compares the effectiveness of these new depigmenting compounds to modulate several melanogenesis-regulatory enzymes and proteins such as tyrosinase (TYR), TYR-related protein-1 (TRP1), TYR-related protein-2 (TRP2), microphthalmia-associated transcription factor (MITF), extracellular signal-regulated kinase (ERK) and N-terminal kinases (JNK) and mitogen-activated protein kinase p38 (p38 MAPK). Other evidences from in vitro assays such as inhibition on melanosomal transfer, proteasomes, nitric oxide, and inflammation-induced melanogenesis are also highlighted. This article also reviews analytical techniques in different assays performed using in vitro model as well as their advantages and limitations. This article also provides an insight on recent finding and re-examination of some protocols as well as their effectiveness and reliability in the evaluation of depigmenting compounds. Evidence and support from related patents are also incorporated in this present article to give an overview on current patented technology, latest trends, and intellectual values of some depigmenting compounds and protocols, which are rarely highlighted in the literatures.

Glucosamine abrogates the stem cell factor + endothelin-1-induced stimulation of melanogenesis via a deficiency in MITF expression due to the proteolytic degradation of CREB in human melanocytes

We have already reported that glucosamine (GlcN) distinctly abrogates the pigmentation of human epidermal equivalents stimulated by stem cell factor + endothelin-1 (SE). In this study, we characterized the molecular mechanism involved in the anti-melanogenic effects of GlcN using normal human melanocytes (NHMs) in culture. The SE-stimulated gene (12 h) and protein (24 h) expression levels of melanocyte-specific proteins (at the indicated times post-stimulation) were significantly abrogated by pretreatment with GlcN for 72 h. Western blotting analysis of the phosphorylation of intracellular signaling molecules in the MAPK pathway revealed that despite the significantly decreased level of total CREB protein at all times post-stimulation, the SE-stimulated phosphorylation of ERK, CREB and MITF is not attenuated at 15 min post-stimulation in GlcN-treated NHMs. However, the SE-stimulated protein expression level of total MITF at 2 and 6 h post-stimulation was significantly abrogated by 72 h pretreatment with GlcN. Consistently, pretreatment with GlcN for 72 h abrogated the stimulated gene and protein expression levels of MITF at 1 h and 2 h post-stimulation, respectively. Analysis of gene and protein expression levels also demonstrated that pretreatment with GlcN for 72 h significantly reduced the protein levels of CREB and MITF without affecting their gene expression levels prior to the SE stimulation. Silencing with a CREB siRNA distinctly abrogated the SE-stimulated expression of MITF (at 2 h post-stimulation) and melanocyte-specific proteins (at 24 h post-stimulation). Similarly, transfection of MITF siRNA markedly abrogated the SE-stimulated expression of MITF protein and melanocyte-specific proteins at 2 and 24 h post-stimulation, respectively. Finally, the decreased levels of CREB and MITF proteins induced by 72 h pretreatment with GlcN were abrogated by the co-addition of the proteosomal degradation inhibitor MG132. These findings suggest that the anti-melanogenic effect elicited by GlcN is mediated via the decreased expression of MITF which results from the attenuated transcriptional activity of CREB due to proteolytic degradation.

Dioscin Derived from Solanum melongena L. "Usukawamarunasu" Attenuates α-MSH-Induced Melanogenesis in B16 Murine Melanoma Cells via Downregulation of Phospho-CREB and MITF

This study aimed to chemically isolate and explore an antimelanogenesis inducer in extracts of Solanum melongena L. "Usukawamarunasu" eggplant. We successfully identified dioscin ([25R]-Spirost-5-en-3β-yl) 2-O-(6-deoxy-α-L-mannopyranosyl) - 4-O-(6-deoxy-α-L-mannopyranosyl)-β-D-glucopyranoside] in the plant, and examined the effects of α-melanocyte-stimulating hormone (MSH)-induced melanogenesis in B16 murine melanoma cells by this plant-derived dioscin. Immunoblot analysis suggested that dioscin reduced the expression of tyrosinase, tyrosinase-related protein-1 (TRP-1), and TRP-2, resulting in inhibition of intracellular production of melanin. In addition, dioscin caused reduction of phosphorylated cAMP-responsive element binding protein 1 transcription factors (CREB), which led to a reduction of microphthalmia-related transcription factor (MITF) in α-MSH-stimulated cells, but did not affect phosphorylation of extracellular signal-regulated kinase. Furthermore, dioscin significantly downregulated the expression of tyrosinase, TRP-1, and TRP-2, which led to the reduction of α-MSH-induced melanogenesis in B16 cells. These results suggest that dioscin may decrease the level of MITF via inhibition of phosphorylation of CREB in α-MSH-induced melanogenesis in B16 cells.

Homology modelling and virtual screening of P-protein in a quest for novel antimelanogenic agent and in vitro assessments

An adequate knowledge on molecular mechanism of melanogenesis provides an opportunity to find the novel molecular targets for the discovery and development of new cosmetics. Among various genes, the OCA2 is being essential for proper melanin synthesis, and mutation or deletion of this gene leads to oculocutaneous albinism type 2. Thus, for this study, the product of this gene, that is P-protein, was targeted in quest for novel inhibitors as antimelanogenic agents. Based on pattern search of amino acid sequence and homology analysis, the protein structure was modelled. The role of this protein has been predicted as a tyrosine transporter of melanosomes. Thus, the molecular library was generated on the basis of tyrosine transporter inhibitor. Based on the dock score, 20 molecules have been considered as putative inhibitors for P-protein. Among these compounds, five molecules (compound #1, #4, #8, #13 and #17) were found to be quite effective as antimelanogenic without having any toxicity. Further investigations to establish the mechanism of action, the indirect methods such as tyrosinase assay, analysis for eumelanin and pheomelanins and investigation of mRNA levels were being carried out. The results from the studies offered a new lead in antimelanogenic therapy and may be very useful for further optimization work in developing them as novel depigmenting agents.

Astaxanthin and withaferin A block paracrine cytokine interactions between UVB-exposed human keratinocytes and human melanocytes via the attenuation of endothelin-1 secretion and its downstream intracellular signaling

BACKGROUND

Paracrine interactions between keratinocytes and melanocytes via cytokines play an essential role in regulating pigmentation in epidermal hyperpigmentary disorders. There is an urgent need for a human epidermal model in which melanogenic paracrine interactions between UVB-exposed keratinocytes and melanocytes can be precisely evaluated because human epidermal equivalents consisting of multilayered keratinocytes and melanocytes have significant limitations in this respect.

OBJECTIVE

To resolve this challenge, we established a co-culture system with cell inserts using human keratinocytes and human melanocytes that serves as an appropriate new model for UVB-induced hyperpigmentation. Using that new model, we examined the blocking effects of two natural chemicals, astaxanthin and withaferin A, on paracrine cytokine interactions between UVB-exposed keratinocytes and melanocytes and characterized their mechanisms of action.

METHODS AND RESULTS

RT-PCR analysis showed that co-culture of human keratinocytes that had been exposed to UVB significantly stimulated human melanocytes to increase their expression of genes encoding microphthalmia-associated transcription factor, tyrosinase and tyrosinase-related protein 1. The catalytic activity of tyrosinase was also increased. ELISA assays revealed that UVB significantly increased the secretion of interleukin-1α, interleukin-6/8, granulocyte macrophage stimulatory factor and endothelin-1 but not α-melanocyte stimulating hormone. The addition of an endothelin-1 neutralizing antibody significantly abrogated the increase of tyrosinase activity. Post-irradiation treatment with astaxanthin or withaferin A significantly abolished the up-regulation of tyrosinase activity induced by UVB. Treatment with astaxanthin or withaferin A significantly reduced the increased levels of interleukin-1α, interleukin-6/8, granulocyte macrophage stimulatory factor and endothelin-1. Withaferin A but not astaxanthin also significantly abrogated the endothelin-1-stimulated activity of tyrosinase in melanocytes. Western blot analysis of intracellular signaling factors revealed that withaferin A but not astaxanthin significantly abolished the endothelin-1-stimulated phosphorylation of Raf-1, MEK, ERK, MITF and CREB in human melanocytes.

CONCLUSIONS

These results demonstrate that this co-culture system is an appropriate model to characterize melanogenic paracrine interactions and that astaxanthin and withaferin A serve as potent inhibitors of those interactions. Their effects are caused not only by down-regulating the increased secretion of an intrinsic melanogenic cytokine, endothelin-1, by UVB-exposed human keratinocytes, but also by interrupting the endothelin-1-triggered downstream intracellular signaling between protein kinase C and Raf-1 in human melanocytes (only for withaferin A).

Withaferin A abolishes the stem cell factor-stimulated pigmentation of human epidermal equivalents by interrupting the auto-phosphorylation of c-KIT in human melanocytes

We characterized the mechanism(s) underlying the abrogating effect of withaferin A (WFA) on the stem cell factor (SCF)-stimulated pigmentation of human epidermal equivalents (HEEs). Increased gene and protein expression levels of tyrosinase, tyrosinase-related protein1, dopachrome tautomerase, PMEL17, c-KIT and their targeted transcription factor, microphthalmia-associated transcription factor (MITF) were significantly reversed at days 7 and 10, respectively, by treatment with WFA. In WFA-treated normal human melanocytes (NHMs), there was a marked deficiency in the SCF-stimulated series of phosphorylations of c-KIT, Shc, Raf-1, MEK, ERK, MITF and CREB. Treatment with dithiothreitol (DTT) distinctly abolished the suppressive effect of WFA on the SCF-stimulated phosphorylation of c-KIT in NHMs. On the other hand, even after incubation at 4 °C for 2 h with 5 nM SCF, followed by the removal of unbound SCF by washing and then raising the temperature to 37 °C to start the signaling reaction, c-KIT was distinctly phosphorylated to a similar extent by incubation for 15 min with SCF only or with SCF + WFA. These findings indicate that WFA attenuates the SCF-induced activation of c-KIT in NHMs by interrupting the auto-phosphorylation of c-KIT through DTT-suppressible Michael addition thioalkylation reactions without interrupting the binding of SCF to the c-KIT receptor.

Inhibitors of intracellular signaling pathways that lead to stimulated epidermal pigmentation: perspective of anti-pigmenting agents

Few anti-pigmenting agents have been designed and developed according to their known hyperpigmentation mechanisms and corresponding intracellular signaling cascades. Most anti-pigmenting agents developed so far are mechanistically involved in the interruption of constitutional melanogenic mechanisms by which skin color is maintained at a normal and unstimulated level. Thus, owing to the difficulty of confining topical application to a specific hyperpigmented skin area, potent anti-pigmenting agents capable of attenuating the natural unstimulated pigmentation process have the risk of leading to hypopigmentation. Since intracellular signaling pathways within melanocytes do not function substantially in maintaining normal skin color and are activated only by environmental stimuli such as UV radiation, specifically down-regulating the activation of melanogenesis to the constitutive level would be an appropriate strategy to develop new potent anti-pigmenting agents with a low risk of hypopigmentation. In this article, we review the hyperpigmentation mechanisms and intracellular signaling pathways that lead to the stimulation of melanogenesis. We also discuss a screening and evaluation system to select candidates for new anti-melanogenic substances by focusing on inhibitors of endothelin-1 or stem cell factor-triggered intracellular signaling cascades. From this viewpoint, we show that extracts of the herbs Withania somnifera and Melia toosendan and the natural chemicals Withaferin A and Astaxanthin are new candidates for potent anti-pigmenting substances that avoid the risk of hypopigmentation.

The regulation of epidermal melanogenesis via cAMP and/or PKC signaling pathways: insights for the development of hypopigmenting agents

Abnormal pigmentation, particularly hyperpigmentation, is major issue of concern for people with colored skin. Several hypopigmenting agents, which exert their action by inhibiting tyrosinase activity and/or transcription, have been used for treatment. However, results have been discouraging. To manage abnormal pigmentation properly, the mechanisms of melanogenesis should be understood. Endogenous and exogenous factors affect melanogenesis via intracellular machineries. cAMP and PKC are critical factors of important transduction pathways and cross-talk between them could amplify the melanogenic effect. Here, factors involved in melanogenesis regulation via cAMP and/or PKC pathways are reviewed with their action mechanisms.

Glyceollins, a novel class of soybean phytoalexins, inhibit SCF-induced melanogenesis through attenuation of SCF/c-kit downstream signaling pathways

The anti-melanogenesis effect of glyceollins was examined by melanin synthesis, tyrosinase activity assay in zebrafish embryos and in B16F10 melanoma cells. When developing zebrafish embryos were treated with glyceollins, pigmentation of the embryos, melanin synthesis and tyrosinase activity were all decreased compared with control zebrafish embryos. In situ expression of a pigment cell-specific gene, Sox10, was dramatically decreased by glyceollin treatment in the neural tubes of the trunk region of the embryos. Stem cell factor (SCF)/c-kit signaling pathways as well as expression of microphthalmia-associated transcription factor (MITF) were determined by western blot analysis. Glyceollins inhibited melanin synthesis, as well as the expression and activity of tyrosinase induced by SCF, in a dose-dependent manner in B16F10 melanoma cells. Pretreatment of B16F10 cells with glyceollins dose-dependently inhibited SCF-induced c-kit and Akt phosphorylation. Glyceollins significantly impaired the expression and activity of MITF. An additional inhibitory function of glyceollins was to effectively downregulate intracellular cyclic AMP levels stimulated by SCF in B16F10 cells. Glyceollins have a depigmentation/whitening activity in vitro and in vivo, and that this effect may be due to the inhibition of SCF-induced c-kit and tyrosinase activity through the blockade of downstream signaling pathway.

Topobiology of human pigmentation: P-cadherin selectively stimulates hair follicle melanogenesis

P-cadherin serves as a major topobiological cue in mammalian epithelium. In human hair follicles (HFs), it is prominently expressed in the inner hair matrix that harbors the HF pigmentary unit. However, the role of P-cadherin in normal human pigmentation remains unknown. As patients with mutations in the gene that encodes P-cadherin show hypotrichosis and fair hair, we explored the hypothesis that P-cadherin may control HF pigmentation. When P-cadherin was silenced in melanogenically active organ-cultured human scalp HFs, this significantly reduced HF melanogenesis and tyrosinase activity as well as gene and/or protein expression of gp100, stem cell factor, c-Kit, and microphthalmia-associated transcription factor (MITF), both in situ and in isolated human HF melanocytes. Instead, epidermal pigmentation was unaffected by P-cadherin knockdown in organ-cultured human skin. In hair matrix keratinocytes, P-cadherin silencing reduced plasma membrane β-catenin, whereas glycogen synthase kinase 3 beta (GSK3β) and phospho-β-catenin expression were significantly upregulated. This suggests that P-cadherin-GSK3β/Wnt signaling is required for maintaining the expression of MITF to sustain intrafollicular melanogenesis. Thus, P-cadherin-mediated signaling is a melanocyte subtype-specific topobiological regulator of normal human pigmentation, possibly via GSK3β-mediated canonical Wnt signaling.

Abrogating effect of N-linked carbohydrate modifiers on the stem cell factor and endothelin-1-stimulated epidermal pigmentation in human epidermal equivalents

BACKGROUND

We previously demonstrated that the hyperpigmentation that occurs in UVB-melanosis as well as in solar lentigos is associated with the increased production of melanogenic cytokines, such as endothelin (EDN)-1 and stem cell factor (SCF), by keratinocytes in those areas of the skin.

OBJECTIVE

We developed a model for these hyperpigmentary disorders in EDN1+SCF stimulated human epidermal equivalents (HEEs) and characterized the effects of the N-linked carbohydrate core synthesis inhibitor glucosamine or N-linked carbohydrate processing inhibitors deoxynojirimycin or monensin on the stimulated HEE pigmentation.

METHODS

Those effects were assessed by melanin analysis, real-time RT-PCR and Western blotting.

RESULTS

The addition of these N-linked carbohydrate modifiers (NCMs) markedly abolished the EDN1+SCF-elicited increase in HEE pigmentation over 14 days. Real-time RT-PCR and Western blotting of these NCM-treated HEEs unexpectedly revealed that the EDN1+SCF-stimulated steady-state levels of tyrosinase (TYR), TYR-related protein-1, dopachrome tautomerase and PMEL17 as well as microphthalmia-associated transcription factor (MITF) were significantly attenuated at the transcriptional and translational levels without any cytotoxic effects on keratinocytes and melanocytes in the HEEs. Pre-treatment of cultured normal human melanocytes with the NCMs interrupted the EDN1+SCF-induced stimulation of steady-state levels of MITF at the transcriptional and translational levels and TYR activity without any direct inhibitory effect on the catalytic activity of TYR in vitro.

CONCLUSION

This study provides evidence that NCMs have a potential to attenuate the EDN1+SCF-stimulated pigmentation of HEEs by abrogating the increased steady-state levels of MITF mRNA, which results in the attenuation of the increased steady-state levels of these melanocyte-specific proteins.

Emerging stem cell therapies: treatment, safety, and biology

Stem cells are the fundamental building blocks of life and contribute to the genesis and development of all higher organisms. The discovery of adult stem cells has led to an ongoing revolution of therapeutic and regenerative medicine and the proposal of novel therapies for previously terminal conditions. Hematopoietic stem cell transplantation was the first example of a successful stem cell therapy and is widely utilized for treating various diseases including adult T-cell leukemia-lymphoma and multiple myeloma. The autologous transplantation of mesenchymal stem cells is increasingly employed to catalyze the repair of mesenchymal tissue and others, including the lung and heart, and utilized in treating various conditions such as stroke, multiple sclerosis, and diabetes. There is also increasing interest in the therapeutic potential of other adult stem cells such as neural, mammary, intestinal, inner ear, and testicular stem cells. The discovery of induced pluripotent stem cells has led to an improved understanding of the underlying epigenetic keys of pluripotency and carcinogenesis. More in-depth studies of these epigenetic differences and the physiological changes that they effect will lead to the design of safer and more targeted therapies.