Nan-Hyung Kim

H19 RNA downregulation stimulated melanogenesis in melasma

A variety of factors, including ultraviolet (UV) exposure, have been implicated in the pathogenesis of melasma. However, UV‐induced hyperpigmentation usually recovers spontaneously, whereas melasma does not. Recently, we detected downregulation of the H19 gene on microarray analysis of hyperpigmented and normally pigmented skin from patients with melasma, and identified significant clinical correlations. The H19 downregulation was not accompanied by a reciprocal change of the imprinted gene, insulin‐like growth factor II. Moreover, methylation pattern of the H19 promoter region in maternal ICR was variable. The H19 knockdown in melanocyte monoculture did not result in obvious tyrosinase overexpression, whereas the knockdown in a mixed cell culture system, composed of H19 siRNA transfected normal human keratinocytes and non‐transfected normal human melanocytes, did induce not only a tyrosinase overexpression but also an increase of melanosome transfer. Estrogen treatment of the H19 RNA knockdown in the mixed cell culture was more than an additive effect on the tyrosinase overexpression, whereas UV irradiation was not. These findings suggest that downregulation of H19 and a sufficient dose of estrogen might be involved in the development of melasma.

PDZK1 Upregulation in Estrogen-Related Hyperpigmentation in Melasma

The pathogenesis of melasma is unknown, although the potential role of estrogen has been considered. Microarray and real-time PCR analyses revealed that upregulation of PDZ domain protein kidney 1 (PDZK1) is clinically correlated with melasma. Although there has been no report that PDZK1 is involved in pigmentation and/or melanogenesis, PDZK1 expression can be induced by estrogen. In this study, the role of PDZK1 upregulation in melasma was examined, particularly in connection with estrogen, using biopsied skin specimens from 15 patients and monocultures and cocultures of melanocytes and keratinocytes with or without overexpression or knockdown of PDZK1. Estrogen upregulated PDZK1. Overexpression of PDZK1 increased tyrosinase expression and melanosome transfer to keratinocytes, whereas PDZK1 knockdown reduced estrogen-induced tyrosinase expression, through regulation of expression of estrogen receptors (ERs) ER-α and ER-β. The PDZK1-induced tyrosinase expression and melanosome transfer was regulated by ion transporters such as sodium-hydrogen exchanger (NHE), cystic fibrosis transmembrane conductance regulator (CFTR), and SLC26A3, which showed a specific association with each ER subtype. In the melanosome transfer, PDZK1 also increased phosphorylation of ezrin/radixin/moesin (ERM) and ras-related C3 botulinum toxin substrate 1, but not the expression of proteinase-activated receptor-2. Collectively, upregulation of PDZK1 could have an important role in the development of melasma in connection with estrogen through NHE, CFTR, and SLC26A3.

Reduced aquaporin3 expression and survival of keratinocytes in the depigmented epidermis of vitiligo.

Activation of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway is critical for the survival of differentiating cells and depends on the E-cadherin-catenin complex. In an earlier study we showed impaired PI3K/AKT activation in vitiliginous keratinocytes (KCs). Recently, aquaporin3 (AQP3) has been reported to co-accumulate with E-cadherin in forming cell-to-cell contacts. Therefore, we examined the expression of AQP3 in vitiliginous KCs and the role of AQP3 in KC survival and differentiation by comparing downstream signaling molecules. AQP3 protein expression was significantly decreased in the depigmented epidermis compared with the normally pigmented epidermis of patients with vitiligo. Transfection of cultured normal human KCs with AQP3 small interfering RNA (siRNA) reduced the expression levels of phosphorylated PI3K, E-cadherin, beta-catenin, and gamma-catenin, regardless of the calcium concentration. These downstream signaling molecules were also decreased in the depigmented epidermis. The results of immunoprecipitation and double staining confirmed colocalization of AQP3 with E-cadherin, as well as an active role of AQP3 in E-cadherin expression of cell-to-cell contacts. Moreover, AQP3 knockdown induced no increase in differentiating markers at high calcium concentrations and reduced survival of KCs, suggesting that reduced AQP3 in vitiliginous KCs might be responsible for their reduced survival.

Stem cell factor induces ERM proteins phosphorylation through PI3K activation to mediate melanocyte proliferation and migration.

Stem cell factor (SCF) activates a variety of signals associated with stimulation of proliferation, differentiation, migration, and survival in melanocytes. However, the molecular mechanisms by which SCF and its receptor Kit activates these signaling pathways simultaneously and independently are still poorly defined. Here, we examined whether SCF induces ezrin/radixin/moesin (ERM) proteins phosphorylation as a downstream target of PI3K in melanocytes. ERM proteins are cross‐linkers between the plasma membrane and the actin cytoskeleton and are activated by phosphorylation of a C‐terminal threonine residue. Our results demonstrated that SCF‐induced ERM proteins phosphorylation on threonine residue and Rac1 activation in cultured normal human melanocytes through the activation of PI3K. The functional role of phosphorylated‐ERM proteins was examined using melanocytes infected with adenovirus carrying a dominant negative mutant (Ala‐558, TA) or wild type of moesin. In the TA moesin‐overexpressing melanocytes, SCF‐induced cell proliferation and migration were inhibited. Thus, our results indicate that phosphorylation of ERM proteins plays an important role in the regulation of SCF‐induced melanocyte proliferation and migration.

Cadherin 11, a miR-675 target, induces N-cadherin expression and epithelial-mesenchymal transition in melasma.

Cadherin 11 (CDH11) was identified as a target of miR-675 by using a luciferase reporter assay. CDH11 expression and miR-675 expression were inversely correlated. CDH11 expression was not detected in melanocytes, but CDH11 expression in fibroblasts and keratinocytes positively influenced melanogenesis via the canonical Wnt and AKT activation pathways in cocultured melanocytes. CDH11 in fibroblasts or keratinocytes induced N-cadherin and Twist1 expression, while decreasing E-cadherin expression. This suggests a role for CDH11 in epithelial-mesenchymal transition. CDH11 in fibroblasts also induced the migration of cocultured melanocytes. N-cadherin knockdown abolished the tyrosinase expression that was induced in CDH11-overexpressing fibroblasts. Collectively, our data indicate that CDH11 in fibroblasts and keratinocytes is a target of miR-675, and could be involved in melanogenesis through the induction of N-cadherin during epithelial-mesenchymal transition.

Ferroelectric and magnetic properties of CdMnS films prepared by coevaporation

We report on impurity ferroelectricity and ferromagnetic properties in semiconductor-structured CdMnS films. We observed ferroelectric hysteresis in CdMnS. A remnant polarization of 1.72 μC/cm2 and a coercive field of 14.3 kV/cm were obtained in samples with Mn concentration below 2%. The coevaporated CdMnS samples become ferromagnetic when doped with Au, with a spontaneous magnetization of 1.39×10−6 emu and a coercive magnetic field of 75.4 gauss at 10 K, and the Curie point was found to be higher than room temperature. Through magnetic force microscopy, we observed clear magnetic clusters with sizes ranging from a few nanometers to 102 nm, and found the magnetization to be highly dependent on Au concentration. A combination of this ferroelectricity in CdMnS and ferromagnetism in Au-doped CdMnS may find use in ternary bit nonvolatile memory devices.

Lotus (Nelumbo nuficera) flower essential oil increased melanogenesis in normal human melanocytes

In this study, the essential oil from lotus flower extract, including petals and stamens, was assessed with regard to its effects on melanogenesis in human melanocytes. The lotus flower essential oil was shown to stimulate melanin synthesis and tyrosinase activity in a dose-dependent manner. The lotus flower essential oil induced the expression of tyrosinase, microphthalmia-associated transcription factor M (MITF-M), and tyrosinase-related proten-2 (TRP-2) proteins, but not tyrosinase mRNA. Moreover, it increased the phosphorylation of ERK and cAMP response element binding protein (CREB). In order to verify the effective components of the lotus flower oil, its lipid composition was assessed. It was found to be comprised of palmitic acid methyl ester (22.66%), linoleic acid methyl ester (11.16%), palmitoleic acid methyl ester (7.55%) and linolenic acid methyl ester (5.16%). Among these components, palmitic acid methyl ester clearly induced melanogenesis as the result of increased tyrosinase expression, thereby indicating that it may play a role in the regulation of melanin content. Thus, our results indicate that lotus flower oil may prove useful in the development of gray hair prevention agents or tanning reagents.

Histamine effect on melanocyte proliferation and vitiliginous keratinocyte survival

Please cite this paper as: Histamine effect on melanocyte proliferation and vitiliginous keratinocyte survival. Experimental Dermatology 2010; 19: 1073–1079.

Three New Single Nucleotide Polymorphisms Identified by a Genome-Wide Association Study in Korean Patients with Vitiligo

Genetic susceptibility is involved in the pathogenesis of vitiligo. Association studies with a whole genome-based approach instead of a single or a few candidate genes may be useful for discovering new susceptible genes. Although the etiology of non-segmental and segmental types is different, the association between gene polymorphisms and vitiligo has been reported, without defining types or in non-segmental type. Whole genome-based single nucleotide polymorphisms (SNPs) were examined in patients with non-segmental and segmental types of vitiligo using the Affymetrix GeneChip 500K mapping array, and 10 functional classes of significant SNPs were selected. Genotyping and data analysis of selected 10 SNPs was performed using real-time PCR. Genotype and allele frequencies were significantly different between both types of vitiligo and three of the target SNPs, DNAH5 (rs2277046), STRN3 (rs2273171), and KIAA1005 (rs3213758). A stronger association was suggested between the mutation in KIAA1005 (rs3213758) and the segmental type compared to the non-segmental type of vitiligo. DNAH5 (rs2277046), STRN3 (rs2273171), and KIAA1005 (rs3213758) may be new vitiligo-related SNPs in Korean patients, either non-segmental or segmental type.

Spin currents modulated by magnetic barriers in semiconductor nanowires

We present the properties of ballistic spin transport through magnetic barrier structures in semiconductor nanowires. Landauers approach is adopted for the calculation of spin transport properties for various host material nanowires which are remarkably different from each other in the effective g-factor, g*. The spin polarization effect on the conductance of a nanowire is more efficient than that of a purely two-dimensional electron gas. Especially, when the bias increases the conductance of a nanowire with small g* is quantized as a step function and its spin dependence disappears. However, these behaviours are broken for a host material with large g* and the spin-dependent splitting appears in this case. We achieve the enhancement of the spin polarization effect on currents by increasing the number of magnetic barriers and we can finally obtain the perfect spin-polarized effect on the conductance.