[Show abstract][Hide abstract] ABSTRACT: 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.
Full-text · Article · Feb 2014 · ZOOLOGICAL SCIENCE
[Show abstract][Hide abstract] ABSTRACT: In our laboratory, a single autosomal recessive mutation in a phenotype similar to ruby-eye (ru/Hps6(ru)) or ruby-eye 2 (ru2/Hps5(ru2)) spontaneously occurred in siblings of C57BL/10JHir (+/+, black) mice in 2006. RT-PCR analysis revealed that this novel mutation, named ru2(d)/Hps5(ru2-d), exhibited frameshift by 997G deletion in the Hps5 gene. To clarify the mechanism of the hypopigmentation, the characteristics of proliferation and differentiation of ru2(d)/ru2(d) epidermal melanoblasts and melanocytes cultured in a serum-free medium were investigated. The proliferation of ru2(d)/ru2(d) melanoblasts and melanocytes did not differ from that of +/+ melanoblasts and melanocytes. However, the differentiation of ru2(d)/ru2(d) melanocytes was greatly inhibited. Tyrosinase (TYR) activity, expression of TYR, TYR-related protein 1 (TRP1) and TRP2 (dopachrome tautomerase, DCT), eumelanin synthesis, and the number of stage IV melanosomes markedly decreased in ru2(d)/ru2(d) melanocytes. However, excess L-tyrosine (Tyr) added to culture media from initiation of the primary culture rescued the reduced differentiation through increase in TYR activity, expression of TYR, TRP1, TRP2 and Kit, eumelanin synthesis, and stage IV melanosomes. L-Tyr injected into ru2(d)/ru2(d) mice also stimulated melanocyte differentiation. These results suggest that the ru2(d) allele inhibits melanocyte differentiation, and that its impaired differentiation is rescued by excess Tyr.
Full-text · Article · Nov 2011 · ZOOLOGICAL SCIENCE
[Show abstract][Hide abstract] ABSTRACT: In congenital or acquired dermal melanocytosis, attachment of melanocyte with elastic fiber was shown in electron microscopy of unknown biological meaning. We hypothesize elastin-derived peptide may play a role in activating dermal melanocyte precursors.
This study was designed to determine: (i) whether melanocyte precursors express elastin binding protein (EBP); (ii) ontogenic expression of EBP and elastin in murine embryonic skin; (iii) the effects of elastin-derived peptide (VGVAPG) on melanocyte precursors.
Using immunohistochemistry or Western blot to identify EBP on murine embryonic sections, neural crest cell (NCC) primary culture explants, or two melanocyte precursor cell lines, NCCmelb4 and NCCmelan5. NCC explants or cells were treated with VGVAPG to compare its effect on proliferation, dendrite formation, melanosome maturation and tyrosinase mRNA expression of melanocyte precursors.
EBP was immunostained on c-kit+ melanocyte precursors. 67kDa EBP protein was immunoblotted on NCCmelb4 and NCCmelan5 cells. EBP was expressed early at embryonic day (E) 9.5, but elastin appeared later at E12.5 skin. VGVAPG increased DOPA-positive cell number and enhanced their dendrite formation in NCC explants. Electron microscopy showed advanced melanosome maturation in NCC explants or cells treated with VGVAPG. VGVAPG enhanced tyrosinase mRNA expression in NCCmelan5 cells.
Melanocyte precursors expressed EBP. VGVAPG stimulated their melanogenesis and dendrite formation. In the developmental journey interaction between elastin and EBP-expressed melanocyte precursors in embryos happened mainly since the stage of tertiary melanoblasts. These findings first provide biological evidences for the interaction between melanocyte and elastic fiber.
No preview · Article · Jun 2008 · Journal of Dermatological Science
[Show abstract][Hide abstract] ABSTRACT: Genes encoding Kit and the Kit ligand (KL) play essential roles in the differentiation of melanoblasts. We previously established three immortal but distinct cell populations of mouse neural crest (NC) cells. NCCmelb4M5 cells do not express Kit and grow independently of KL; they have the potential to differentiate into NCCmelb4 cells, which are Kit-positive melanocyte precursors. NCCmelan5 cells show the characteristics of differentiated melanocytes. All three cell lines demonstrated bone morphogenetic protein (BMP) receptor expression. BMP-4 upregulated Kit protein and mRNA expression in most immature NCCmelb4M5 cells. Noggin, a BMP-4 antagonist, dramatically decreased the Kit expression induced by BMP-4. Western blot analysis revealed that extrinsic BMP-4 leads to the phosphorylation of Smads in NCCmelb4M5 cells. Using transfected Kit-promoter reporter, we showed BMP-4 could activate Kit promoter in transfected NCCmelb4M5 cells. We conclude that BMP-4 is active and is involved in the regulation of Kit expression on most immature melanocyte precursors. We further investigated the influence of BMP-4 in vitro using primary NC cells cultured from wild-type mice. Addition of BMP-4 to the medium increased the number of Kit-positive cells compared to diluent-treated controls. We have identified BMP-4 as an important factor for prenatal Kit-negative melanoblasts just prior to entering the Kit-dependent cycle of melanogenesis.
Full-text · Article · Jun 2008 · Journal of Investigative Dermatology
[Show abstract][Hide abstract] ABSTRACT: We have established two immature melanocyte cell lines from murine neural crest cells. NCC-E3 cells have Stage II melanosomes and express tyrosinase while in NCCmelb4 cells, the melanosomes remain at Stage I and tyrosinase is not expressed. These cell lines may be useful in studying the differentiation of melanocyte precursors.
To perform proteomic analysis of the two cell lines to identify proteins related to and possibly responsible for their different maturation stages.
Western blotting, two-dimensional differential image gel electrophoresis (2D-DIGE), liquid chromatography-tandem mass spectrometry (LC-MS/MS), real-time PCR analysis and RNA interference using siRNA were employed in this study.
Western blotting revealed that the processed form of gp100, which is specific for Stage II melanosomes, is expressed in NCC-E3 cells but not in NCCmelb4 cells. 2D-DIGE identified two protein spots showing 4.06- and 2.22-fold increases in NCC-E3 cells compared to NCCmelb4 cells. Analysis of those proteins by LC-MS/MS revealed that the former was calreticulin and the latter was BiP/GRP78. When calreticulin mRNA expression in NCC-E3 cells was blocked by siRNA, tyrosinase protein was abolished and DOPA-reactivity was decreased, although tyrosinase mRNA was abundantly expressed after the same treatment.
Calreticulin, a lectin chaperone, is an essential molecule for the processing of tyrosinase in murine melanocytes. The role of molecular chaperones such as calreticulin should be considered when analyzing the mechanism(s) of melanocyte differentiation.
No preview · Article · Feb 2008 · Journal of Dermatological Science
[Show abstract][Hide abstract] ABSTRACT: Melanosomes are unique membrane-bound organelles specialized for the synthesis and distribution of melanin. Mechanisms involved in the trafficking of proteins to melanosomes and in the transport of mature pigmented melanosomes to the dendrites of melanocytic cells are being characterized, but details about those processes during early stages of melanosome maturation are not well understood. Early melanosomes must remain in the perinuclear area until critical components are assembled. In this study, we characterized the processing of two distinct melanosomal proteins, tyrosinase (TYR) and Pmel17, to elucidate protein processing in early or late steps of the secretory pathway, respectively, and to determine mechanisms underlying the subcellular localization and transport of early melanosomes. We used immunological, biochemical, and molecular approaches to demonstrate that the movement of early melanosomes in the perinuclear area depends primarily on microtubules but not on actin filaments. In contrast, the trafficking of TYR and Pmel17 depends on cytoplasmic dynein and its interaction with the spectrin/ankyrin system, which is involved with the sorting of cargo from the plasma membrane. These results provide important clues toward understanding the processes involved with early events in melanosome formation and transport.
Full-text · Article · Feb 2008 · Journal of Investigative Dermatology
[Show abstract][Hide abstract] ABSTRACT: The murine recessive yellow (Mc1r(e)) is a loss-of-function mutation in the receptor for alpha-melanocyte-stimulating hormone, melanocortin receptor 1 (Mc1r) and produces yellow coats by inducing pheomelanin synthesis in hair follicular melanocytes. However, it is not known whether the Mc1r(e) mutation affects the proliferation and differentiation of melanocytes. In this study, the proliferation and differentiation of recessive yellow epidermal melanocytes cultured in dibutyryl cyclic AMP-supplemented serum-free medium were investigated in detail. The melanocytes produced mainly eumelanin in this culture system. The proliferation of recessive yellow melanocytes was decreased compared with that of wild-type at the e-locus, black melanocytes. The differentiation of melanocytes was also delayed and inhibited in recessive yellow mice. Tyrosinase (TYR) activity and TYR-related protein 1 (TRP1) and TRP2 (dopachrome tautomerase, DCT) expressions were decreased and, in addition, the maturation of stage IV melanosomes was inhibited. Excess l-tyrosine (l-Tyr) added to the culture media rescued the reduced activity of proliferation of melanocytes. l-Tyr also stimulated TYR activity and TRP1 and TRP2 expressions as well as the maturation of stage IV melanosomes and pigmentation. These results suggest that the Mc1r(e) mutation affects the proliferation and differentiation of melanocytes and l-Tyr rescues the reduced proliferative and differentiative activities by stimulating TYR activity and TRP1 and TRP2 expressions as well as melanosome maturation.
Full-text · Article · Jul 2007 · European Journal of Cell Biology
[Show abstract][Hide abstract] ABSTRACT: The slaty (Dct(slt)) mutation is known to reduce the activity of dopachrome tautomerase (DCT) in melanocytes. However, it is unknown whether the reduced DCT activity leads to a defect in the proliferation and differentiation of mouse melanocytes. To address this point, the proliferation and differentiation of neonatal melanocytes from Dct(slt)/Dct(slt) congenic mice in serum-free primary culture were investigated in detail. The proliferation of slaty epidermal melanoblasts/melanocytes in culture did not differ from that of wild-type mice. However, the differentiation was greatly inhibited. Tyrosinase (TYR) activity detected by dopa reaction as well as staining of DCT in slaty melanocytes was greatly reduced. The content of eumelanin in cultured slaty melanocytes was reduced, whereas the content of pheomelanin in media derived from cultured 7.5-day-old slaty melanocytes was greatly increased. The contents of eumelanin and pheomelanin in the neonatal slaty epidermis and dermis were reduced, except that the pheomelanin content in 3.5-day-old dermis was increased. These results suggest that the slaty mutation affects both eumelanin and pheomelanin synthesis in developmental stage-specific and skin site-specific manners, and, in addition, the gene controls the differentiation of melanocytes via the regulation of activity of TYR in addition to its own DCT.
Full-text · Article · Jul 2006 · European Journal of Cell Biology
[Show abstract][Hide abstract] ABSTRACT: It is known that skin often shows irregular pigmentation during aging, which is frequently associated with hyperpigmentation. Many studies have utilized brownish A1 guinea pigs to investigate the pathogenesis of ultraviolet B (UVB)-induced skin pigmentation, however, responses associated with aging following UVB irradiation have not been elucidated. To characterize those responses, dorsal skin of A1 guinea pigs from 14-weeks to 5-yr old were investigated. The minimal erythema dose was found to increase with aging. Further, in pigmentation induced by UVB radiation, skin brightness (DeltaL*-value) decreased equally in both the 14-week old (young) group and in the 3-yr old (old) group of guinea pigs. The DeltaL*-value recovered in the young group from 21 d after UVB irradiation, whereas no such recovery was seen in the old group. In addition, the amount of melanin and the number of melanocytes returned near pre-irradiation levels in the young group, while they remained high in the old group. Our results therefore demonstrate for the first time that skin responses following UVB irradiation change with aging in A1 guinea pigs.
No preview · Article · Sep 2005 · Pigment Cell Research
[Show abstract][Hide abstract] ABSTRACT: We previously established a mouse neural crest cell line named NCCmelb4, which is positive for Kit and negative for tyrosinase. NCCmelb4 cells were useful to study the effects of extrinsic factors such as retinoic acids and vitamin D(3) on melanocyte differentiation, but in order to study the development of melanocytes from multipotent neural crest cells, cell lines of melanocyte progenitors in earlier developmental stages are needed. In the present study, we established an immortal cell line named NCCmelb4M5 that was derived from NCCmelb4 cells. NCCmelb4M5 cells do not express Kit and are immortal and stable in the absence of Kit ligand. They are positive for melanocyte markers such as tyrosinase-related protein 1 and DOPAchrome tautomerase and they contain stage I melanosomes. Interestingly, glial fibrillary acidic protein, which is a marker for glial cells, is also positive in NCCmelb4M5 cells, while NCCmelb4 cells are negative for this protein. Immunostaining and a cell ELISA assay revealed that 12-O-tetradecanoylphorbol 13-acetate (TPA) and cholera toxin (CT) induce Kit expression in NCCmelb4M5 cells. Real-time polymerase chain reaction analysis also demonstrated the induction of Kit mRNA by TPA and CT. Microphthalmia-associated transcription factor mRNA is simultaneously enhanced by the same treatment. Kit induced by TPA/CT in NCCmelb4M5 cells disappeared after the cells were subcultured and incubated without TPA/CT. These findings show that NCCmelb4M5 cells have the potential to differentiate into Kit-positive melanocyte precursors and may be useful to study mechanisms of development and differentiation of melanocytes in mouse neural crest cells.
No preview · Article · Jul 2005 · Pigment Cell Research
[Show abstract][Hide abstract] ABSTRACT: Stem cell factor (SCF) and its receptor, KIT, are essential to the migration and differentiation of melanocytes during embryogenesis. We previously demonstrated that apoptosis is induced by blocking survival function of the SCF/KIT interaction in a mouse neural crest cell (NCC) primary culture. Using the NCCmelb4 cell line, we investigated the occurrence of apoptosis in the cultured cells when KIT receptors were blocked by the monoclonal anti-KIT antibody (ACK2). Apoptosis following treatment with ACK2 was detected by DNA fragmentation assay, in situ apoptosis detection, and electron microscopy. We noted a decrease in extracellular signal-related kinase (ERK) and ribosomal S6 kinase (RSK) protein expression following ACK2 incubation. Western blot analysis and real-time quantitative RT-PCR revealed an apparent time-dependent reduction in Bcl-2 protein levels with respect to ACK2 within the NCCmelb4 cells. In terms of Bax expression, a difference was not found. Fas and caspase8 proteins increased time-dependently in proportion to ACK2 incubation. We noted apoptotic cell death upon addition of ACK2, with evidence of possible involvement of Bcl-2 and Fas in the induction of apoptosis. In contrast, no significant correlation between Fas ligand (Fas-L) expression and ACK2 was found. Fas activation appears to occur independent of Fas-L during ACK2-induced cell death. Therefore, we propose that Fas-L expression in NCCmelb4 cells does not play a major role in facilitating apoptosis. Furthermore, we hypothesize that these molecules combined with SCF/KIT play an important role in regulating the induction of vertebrate NCC apoptosis during embryogenesis.
Preview · Article · Feb 2005 · Journal of Investigative Dermatology
[Show abstract][Hide abstract] ABSTRACT: We devised a unique new single-cell cloning method which uses microscope cover glasses and established a melanoblast cell line derived from mouse neural crest cells. A microscope cover glass was nicked and broken into small pieces and put on a dish. Culture medium and a suspension of 20-30 cells/ml were dropped in the dish. After 1-3 d, a piece of glass to which only one cell was adhered was picked up and transferred to another dish containing culture medium. The greatest advantage of this method is that the derivation of a colony from a single cell can be directly confirmed by microscopy and there is no risk of migratory cells being contaminated by other colonies. Using this single-cell cloning method, in this study we established a cell line derived from a neural crest cell line (NCC-S4.1) and designated it as NCCmelb4. When the culture medium was supplemented with stem cell factor (SCF) alone, NCCmelb4 cells were KIT-positive and tyrosinase-negative melanocyte precursors; they remained at an immature and undifferentiated stage. When the medium was supplemented with phorbol 12-o-tetradecanoyl-13-acetate (TPA) + cholera toxin (CT), the cell morphology changed and became L-3,4-dihydroxyphenylalanine (DOPA)-positive. This observation indicates that the NCCmelb4 cells are capable of further differentiation with suitable stimulation. NCCmelb4 cells derived from the mouse neural crest has characteristics of melanocyte precursors (melanoblasts), and is a cell line which can be utilized to study differentiation-inducing factors and growth factors without the effects of feeder cells.
No preview · Article · Dec 2004 · Pigment Cell Research
[Show abstract][Hide abstract] ABSTRACT: It is known that skin often shows irregular pigmentation during aging which is frequently associated with hyperpigmentation. Many studies have utilized brownish A1 guinea pigs to investigate the pathogenesis of ultraviolet (UV)-induced skin pigmentation, however, changes associated with intrinsic aging in A1 guinea pig skin have not been documented. To characterize such changes, skin from the dorsal and neck areas of 20-week, 1-, 2-, 3- and 5-yr-old guinea pigs was examined. Skin color was measured using a colorimeter, and biopsy specimens were stained with Masson-Fontana, L-3,4-dihydroxyphenylalanine (DOPA), and antibodies against KIT (ACK-45), gp100 (HMB-45) and S-100 proteins. The L* value of skin color decreased with aging and melanin deposits increased in the epidermis. Further, DOPA+, gp100+ and S-100+ melanocytes increased, indicating that the number of melanocytes had increased with age, whereas KIT+ melanocytes did not increase in dorsal skin and actually decreased in neck skin with aging. Further, rippled pigmented areas appeared in the neck skin of the 3-yr-old animals, and in the dorsal and neck skin of 5-yr-old guinea pigs in the absence of UV irradiation. Melanocytes were distributed uniformly in younger skin, whereas they were clustered in older skin. UV irradiation caused an increase in the number of melanocytes, although they were not clustered. These results are the first to provide evidence that pigmentation is induced in the skin of intrinsically aged A1 guinea pigs in the absence of UV irradiation, a process that differs from that elicited by UV irradiation.
No preview · Article · Dec 2004 · Pigment Cell Research
[Show abstract][Hide abstract] ABSTRACT: Sweet syndrome (SS), an acute inflammatory disease, has clinical and laboratory features similar to those of Behçet disease (BD). Serum levels of granulocyte colony-stimulating factor (G-CSF) are elevated in patients with SS, and exogenous administration of G-CSF has repeatedly been implicated in the causation of SS. Granulocyte colony-stimulating factor is a hematopoietic growth factor that regulates the production and differentiation of neutrophils.
To clarify the role of elevated serum G-CSF levels in patients with active SS and active BD compared with those with inactive SS or BD and healthy controls. To then analyze neutrophil apoptosis in the active state of SS and BD; and to also investigate the influence of autologous serum on neutrophil apoptosis.
Serum G-CSF was examined in 5 patients with active SS, 7 with inactive SS, 7 with active BD, 9 with inactive BD, and 5 healthy controls by means of an enzyme immunoassay kit. We measured apoptotic cells in the neutrophil fraction of peripheral blood collections in patients with active diseases and controls by means of flow cytometry.
Serum G-CSF level was significantly higher in patients with active SS than in those with inactive SS. The difference in serum G-CSF levels among patients with active and inactive BD was also significant. Serum G-CSF level was significantly higher in patients with active SS than in those with active BD. Neutrophil apoptosis was significantly higher in patients with active SS than healthy controls. This increased apoptosis rate was also seen in patients with active BD. The increased rate of neutrophil apoptosis was significantly suppressed when the neutrophils were cultured for 18 hours in the presence of autologous active SS serum. Similarly, neutrophil apoptosis was suppressed in the presence of autologous serum in patients with active BD, but not significantly so.
These findings indicate that increased production of G-CSF in patients with SS and BD may play an important role in the manifestation of these disorders. Given the suppression of neutrophil apoptosis in the active state in the presence of the influence of autologous serum, which includes elevated G-CSF level, we propose that serum G-CSF plays a significant role in the suppression of neutrophil apoptosis. Furthermore, G-CSF-induced suppression of neutrophil apoptosis appears to be deeply involved in the pathogenesis of SS and BD.
Preview · Article · Jun 2004 · Archives of Dermatology
[Show abstract][Hide abstract] ABSTRACT: To evaluate the etiologic role of ultraviolet (UV) radiation in acquired dermal melanocytosis (ADM), we investigated the effects of UVA and UVB irradiation on the development and differentiation of melanocytes in primary cultures of mouse neural crest cells (NCC) by counting the numbers of cells positive for KIT (the receptor for stem cell factor) and for the L-3,4-dihydroxyphenylalanine (DOPA) oxidase reaction. No significant differences were found in the number of KIT- or DOPA-positive cells between the UV-irradiated cultures and the non-irradiated cultures. We then examined the effects of UV light on KIT-positive cell lines derived from mouse NCC cultures. Irradiation with UVA but not with UVB inhibited the tyrosinase activity in a tyrosinase-positive cell line (NCCmelan5). Tyrosinase activity in the cells was markedly enhanced by treatment with alpha-melanocyte-stimulating hormone (alpha-MSH), but that stimulation was inhibited by UVA or by UVB irradiation. Irradiation with UVA or UVB did not induce tyrosinase activity in a tyrosinase-negative cell line (NCCmelb4). Levels of KIT expression in NCCmelan5 cells and in NCCmelb4 cells were significantly decreased after UV irradiation. Phosphorylation levels of extracellular signal-regulated kinase 1/2 in cells stimulated with stem cell factor were also diminished after UV irradiation. These results suggest that UV irradiation does not stimulate but rather suppresses mouse NCC. Thus if UV irradiation is a causative factor for ADM lesions, it would not act directly on dermal melanocytes but may act in indirect manners, for instance, via the overproduction of melanogenic cytokines such as alpha-MSH and/or endothelin-1.
No preview · Article · May 2004 · Pigment Cell Research
[Show abstract][Hide abstract] ABSTRACT: Stem cell factor (SCF) and endothelin-3 (ET3) are both necessary for melanocyte development. In order to obtain immortal cell populations of melanoblasts that can survive without feeder cells, we first obtained an immortal cell population of neural crest cells (NCCs) from Sl/+ and +/+ mice of strain WB by incubating with a culture medium supplemented with SCF and ET3, and then we designated them as NCC-SE3 cells. NCC-SE3 cells were bipolar, polygonal, or round in shape and possessed melanosomes of stages I–III (mainly stage I). They were positive to dihydroxyphenylalanine (DOPA) reaction and expressed KIT (a receptor tyrosine kinase), tyrosinase, tyrosinase-related protein-1 (TRP1), tyrosinase-related protein-2 (TRP2), and endothelin-B receptor (ETRB) as determined by immunostaining. We next cultured NCC-SE3 cells by changing culture medium from the one supplemented with SCF+ET3 to the one supplemented with SCF or ET3. NCC-SE3 cells cultured with ET3 alone, designated as NCC-E3 cells, were bipolar in shape and had mainly stage II melanosomes and expressed the same proteins as did NCC-SE3 cells. However, NCC-SE3 cells cultured with SCF alone, designated as NCC-S4.1 cells, were polygonal in shape and had mainly stage I melanosomes. They are thought to be more immature because they were positive to KIT, TRP1, and TRP2, but not to ETRB, tyrosinase, and DOPA reaction. When 12-O-tetradecanoyl phorbol-13-acetate and cholera toxin were added to the culture medium, NCC-S4.1 cells changed shape from polygonal to bipolar and became DOPA-positive. This suggests that NCC-S4.1 cells are melanoblasts that have the potential to differentiate into melanocytes. These cell populations will be extremely useful to study factors that affect melanocyte development and melanogenesis.
No preview · Article · Dec 2003 · Pigment Cell Research
[Show abstract][Hide abstract] ABSTRACT: Down-regulation of melanin synthesis is required for recovery of pigmentary disorders and it is known that direct inhibitors of tyrosinase, the key enzyme in melanin synthesis, such as hydroquinone with a phenol structure, suppress melanin synthesis. We screened several phenolic derivatives using B16 melanoma cells and found that a biphenyl derivative, 2,2'-dihydroxy-5,5'-dipropyl-biphenyl (DDB), down-regulated melanin synthesis effectively. Although DDB has a phenol structure, it did not inhibit tyrosinase in vitro, thus we examined its mechanism in detail. Western blotting revealed that the amount of tyrosinase was decreased by DDB, and pulse-chase labeling and immunoprecipitation analysis showed a decrease of mature tyrosinase and acceleration of tyrosinase degradation in its presence. These results suggest that DDB down-regulates melanin synthesis by inhibiting the maturation of tyrosinase, leading to acceleration of tyrosinase degradation.
No preview · Article · Nov 2003 · Pigment Cell Research
[Show abstract][Hide abstract] ABSTRACT: The mechanism by which a low dose of methotrexate (MTX) works to treat psoriasis is not clear. The overexpression of cell adhesion molecules on dermal vessels is important in the pathogenesis of psoriasis and is probably induced by upregulation of tumour necrosis factor (TNF)-alpha.
To determine the effects of MTX at concentrations comparable with in vivo levels after the administration of low-dose MTX to human umbilical vein endothelial cells (HUVEC) on the growth and expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1).
Cell proliferation assay, immunostaining, immunoblotting, cell enzyme-linked immunosorbent assay and reverse transcriptase-polymerase chain reaction (RT-PCR) were performed to examine the effects of MTX on HUVEC.
MTX inhibited the proliferation of HUVEC at 10-7 mol L-1 and 10-6 mol L-1 without showing cytotoxic effects. It also inhibited TNF-alpha-induced ICAM-1 and VCAM-1 expression by HUVEC at 10-6 mol L-1. The inhibitory effect of MTX was more pronounced on ICAM-1 expression than on VCAM-1 expression. RT-PCR analysis revealed that TNF-alpha-induced ICAM-1 gene expression was strongly downregulated by MTX.
Low-dose MTX may act on psoriasis by suppressing the TNF-alpha-induced expression of ICAM-1 and VCAM-1 by vascular endothelial cells. Inhibition of neovascularization may be another mechanism of action of MTX.
No preview · Article · Aug 2003 · British Journal of Dermatology