Tyrosinase Expression In Melanocytes Research Articles

DCUN1D1, a new molecule involved in depigmentation via upregulating CXCL10.

CD8+ T cells in the lesioned site play a crucial role in the pathogenesis of vitiligo. The chemokine CXCL10 secreted by keratinocytes regulates the migration of CD8+ T cells into the skin. In our previous study, we found that DCUN1D1 expression in vitiligo lesions positively correlates with Cxcl10 expression. In this study, the regulatory effect of DCUN1D1 on CXCL10 and cell function was investigated. DCUN1D1 protein expression was significantly higher in the skin tissue from vitiligo lesions compared with samples from healthy controls. High expression of DCUN1D1 in keratinocytes caused local hair depigmentation in mice, reduced melanin content, high infiltration of CD8+ T cells and increased CXCL10 expression. This suggested that DCUN1D1 may regulate CD8+ T-cell infiltration and depigmentation through CXCL10. Inhibition of DCUN1D1 expression in HaCaT cells abolished the IFN-γ-induced upregulation of p-JAK1, p-STAT1 and CXCL10, suppressed the H2 O2 -induced ROS generation and apoptosis, and upregulated tyrosinase expression in melanocytes. Collectively, these results show that DCUN1D1 is an important regulator of CXCL10 and may be a new target for the treatment of vitiligo.

Oxidative stress in the skin: Impact and related protection.

Skin, our first interface to the external environment, is subjected to oxidative stress caused by a variety of factors such as solar ultraviolet, infrared and visible light, environmental pollution, including ozone and particulate matters, and psychological stress. Excessive reactive species, including reactive oxygen species and reactive nitrogen species, exacerbate skin pigmentation and aging, which further lead to skin tone unevenness, pigmentary disorder, skin roughness and wrinkles. Besides these, skin microbiota are also a very important factor ensuring the proper functions of skin. While environmental factors such as UV and pollutants impact skin microbiota compositions, skin dysbiosis results in various skin conditions. In this review, we summarize the generation of oxidative stress from exogenous and endogenous sources. We further introduce current knowledge on the possible roles of oxidative stress in skin pigmentation and aging, specifically with emphasis on oxidative stress and skin pigmentation. Meanwhile, we summarize the science and rationale of using three well-known antioxidants, namely vitamin C, resveratrol and ferulic acid, in the treatment of hyperpigmentation. Finally, we discuss the strategy for preventing oxidative stress-induced skin pigmentation and aging.

PAR‐2 is involved in melanogenesis by mediating stem cell factor production in keratinocytes

<scp>PAR</scp>‐2 is involved in melanogenesis by mediating stem cell factor production in keratinocytes

In vitro evaluation of the effects of human umbilical cord extracts on human fibroblasts, keratinocytes, and melanocytes

Skin aging is the result of internal and external factors. So-called photoaging has been identified as the major factor in skin aging. Effects of photoaging include inhibition of fibroblast and keratinocyte proliferation as well as collagen and fibronectin expression, while activating expression of collagenases such as matrix metalloproteinase-1. Previous studies have shown that extracts or products from human placenta significantly improve skin aging and chronic wound healing. However, there are few studies of umbilical cord extracts. Therefore, this study aimed to evaluate the effects of umbilical cord extract-derived formulae on three kinds of skin cells including fibroblasts, keratinocytes, and melanocytes. We prepared 20 formulae from intracellular umbilical cord extracts, extracellular umbilical cord extracts, and umbilical cord-derived stem cell extracts, as well as five control formulae. We evaluated the effects of the 25 formulae on fibroblast and keratinocyte proliferation, and expression of collagen I, fibronectin, and matrix metalloproteinase-1 in fibroblasts and tyrosinase in melanocytes. The results showed that 7.5% formula 35 was the most effective formula for promotion of fibroblast and keratinocyte proliferation. At this concentration, formula 35 also induced collagen expression and inhibited matrix metalloproteinase-1 expression at the transcriptional level. However, this formula had no effect on tyrosinase expression in melanocytes. These results demonstrate that umbilical cord extracts can serve as an attractive source of proteins for skincare and chronic wound healing products.

Diacylglycerol Kinase Regulates Tyrosinase Expression and Function in Human Melanocytes

Diacylglycerol increases the melanin content of human melanocytes in vitro and increases the pigmentation of guinea pig skin in vivo, but the mechanism(s) underlying those effects remain unknown. In this study, we characterized the role of diacylglycerol kinase (DGK), which phosphorylates diacylglycerol to generate phosphatidic acid, in the regulation of pigmentation. Ten isoforms of DGK have been identified, and we show that DGKζ is the most abundant isoform expressed by human melanocytic cells. Melanin content, tyrosinase activity and tyrosinase protein levels were significantly reduced by a DGK inhibitor, but tyrosinase and MITF mRNA levels were not changed by that inhibition, and there were no effects on the expression of other melanogenesis-related proteins. Isoform-specific siRNAs showed that knockdown of DGKζ decreased melanin content and tyrosinase expression in melanocytic cells. Over-expression of DGKζ increased tyrosinase protein levels, but did not increase tyrosinase mRNA levels. Glycosidase digestion revealed that inhibition of DGK reduced only the mature form of tyrosinase and the decrease of tyrosinase resulting from DGK inhibition could be blocked partially by protease inhibitors. These results suggest that DGK regulates melanogenesis via modulation of the post-translational processing of tyrosinase, which may be related with the protein degradation machinery.

The tyrosinase enhancer is activated by Sox10 and Mitf in mouse melanocytes

The terminal differentiation of melanocytes is associated with the transcriptional activation of genes responsible for pigment production such as tyrosinase. Pigment cell-specific transcription factors, such as Mitf, as well as specific proximal and distal regulatory elements (DRE) are implicated in the tight control of tyrosinase expression during development and adulthood. Proper tyrosinase expression in melanocytes depends upon the presence of a DRE that is located at -15 kb and provides enhancer activity via a central element termed core-enhancer. In this report, we show that the transcription factors Sox10, Mitf and USF-1 are able to activate the core-enhancer in luciferase reporter assays. Comparative sequence analysis identified evolutionarily motifs resembling Sox10 binding sites that were required for full enhancer activity in melanoma cells and in tyrosinase::lacZ transgenic mice. Sox10 was able to bind the DRE in vitro and mutation of the conserved motifs abolished the enhancer transactivation mediated by Sox10. In addition, two highly conserved CAGCTG E-box motifs were identified that were also required for enhancer activity and for transactivation by Mitf. The results suggest that Sox10 directly, and Mitf, most likely indirectly, activate the tyrosinase enhancer, underlining the contribution of Sox10 to tyrosinase gene regulation in melanocytes.

Distinct distal regulatory elements control tyrosinase expression in melanocytes and the retinal pigment epithelium

Pigment cells of mammals are characterized by two different developmental origins: cells of the retinal pigment epithelium (RPE) originate from the optic cup of the developing forebrain, whereas melanocytes arise from the neural crest. The pigmentation gene tyrosinase is expressed in all pigment cells but differentially regulated in melanocytes and RPE. The tyrosinase promoter does not confer strong expression in pigment cells in vivo, while inclusion of a distal regulatory element at position − 15 kb is necessary and sufficient to provide strong expression in melanocytes. Nevertheless, the regulatory elements responsible for correct spatial and temporal tyrosinase expression in the RPE remained unidentified so far. In this report, we show that a 186 kb BAC containing the tyrosinase gene provides transgene expression in both RPE and melanocytes indicating the presence of regulatory sequences required for expression in the RPE. A deletion analysis of the BAC was performed demonstrating that a RPE-regulatory element resides between − 17 and − 75 kb. Using multi-species comparative genomic analysis we identified three conserved sequences within this region. When tested in transgenic mice one of these sequences located at − 47 kb targeted expression to the RPE. In addition, deletion of this regulatory element within a tyrosinase∷lacZ BAC provided evidence that this sequence is not only sufficient but also required for correct spatial and temporal expression in the RPE. The identification of this novel element demonstrates that tyrosinase gene expression is controlled by separate distal regulatory sequences in melanocytes and RPE.

New EIA technique for tyrosinase in human melanocytes and its application

The expression of tyrosinase in melanocytes relates to skin pigmentation or depigmentation. Although many types of drugs with whitening effects are well known, neither the definite effect nor the mechanism underlying the effect has been elucidated. In this study, we attempted to develop the rapid and simple EIA technique for tyrosinase protein, then this technique was applied to normal human cultured melanocytes. When primary antibody and tyrosinase were incubated in non-coated 96-well microtitre plates for 48 hours at 4 °C, then the solution in tyrosinase-coated plate was further incubated for another 1 hour at 37 °C Thus the best results were obtained. The developed EIA system could detect authentic tyrosinase until 0.1–1.0 ng mL . This EIA technique could also be applied to human cultured melanocytes. The melanocytes cultured with endothelin-1 induced tyrosinase like immune reactive protein. The protein induction with endothelin-1 was suppressed by BQ 123, ETa receptor antagonists. The simple EIA technique developed for tyrosinase may give a clue to determination of the onset mechanisms underlying pigmental diseases of the skin as well as the mechanisms underlying the effects of various whitening drugs.

Indication of a common ancestry for copper tyrosinases and heme catalases revealed by hydrophobic cluster analysis of the brown locus protein sequence.

In mammalian melanocytes, a membrane-anchored high molecular weight protein complex consisting of tyrosinase (monophenol monooxygenase, EC 1.14.18.1) and two tyrosinase-related proteins (TRP-1 and TRP-2, respectively), catalyzes the conversion of tyrosine into the pigment eumelanin. These three proteins are members of a large gene family of binuclear copper proteins (Halaban and Moellmann, 1990). TRP-2 has recently been shown (Tsukamoto et al., 1992; Solano et al., 1996) to possess DOPAchrome tautomerase activity (EC 5.3.2.3). On the other hand, the function of TRP-1, the most abundant glycoprotein expressed in human melanocytes remains controversial. This protein, encoded by the brown locus, exhibits more than 50% sequence identity with tyrosinase (Cohen et al., 1990) and shows some tyrosine hydroxylase activity, but may specifically act as 5,6-dihydroxyindole-2-carboxylic acid (DHICA) oxidase (Jimenez-Cervantes et al., 1994; Kobayashi et al., 1994). However, this protein has also been suggested to act as a melanocyte-specific catalase entitled TRP-1 or catalase B (Halaban and Moellmann, 1990). Several observations support this: the oxidation of 5,6dihydroxyindole and DHICA is associated with the generation of hydrogen peroxide, which is in turn known to destroy melanin and some of its precursors. H2O2 may thus regulate the expression of tyrosinase in melanocytes (Karg et al., 1993), and obviously the course of melanogenesis is strongly affected by factors modulating the level of intracellular peroxides (Nappi and Vass, 1996). Furthermore, H2O2 is a rather potent reversible inhibitor of tyrosinase (Schallreuther et al., 1991), and the oxy-form of this enzyme even shows a limited catalatic potential (Wood and Schallreuther, 1991). The evolutionary relationships among different members of the tyrosinase family have been studied (Morrison et al., 1994), but so far there was no indication of any structural as well as evolutionary relatedness between TRP-1 (catalase B) and the family of heme containing catalases (EC 1.11.1.6). This is caused mainly by the fact that the sequences of brown locus proteins (which obviously bind copper) and those of heme catalases exhibit no easily detectable sequence similarities. For instance, the sequence identity between human TRP-1 (Cohen et al., 1990) and Saccharomyces cerevisiae catalase A (Cohen et al., 1988) is only about 16% in the 400 amino acid overlap (alignment not shown). The presumably related function of these two supposedly structurally unrelated enzymes has evoked the idea on their eventual very distant evolutionary relationship. We have recently shown that one of the most strictly conserved structural parts among heme catalases is formed by the major substrate channel allowing the diffusion