| 1. |
- Rorsman, Hans
(författare)
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The pigmented life of a redhead.
- 2004
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Ingår i: Pigment Cell Research. - : Wiley. - 0893-5785 .- 1600-0749. ; 17:2, s. 191-202
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Forskningsöversikt (refereegranskat)abstract
- As a redhead I have had a personal interest in red hair, freckles and sunburns since childhood. An observation of a formaldehyde-induced fluorescence in human epidermal melanocytes initiated my scientific interest in these cells. Prota and Nicolaus demonstrated that oxidation products of cysteinyldopas are the main components of pheomelanin. Our identification of 5-S-cysteinyldopa as the source of formaldehyde-induced fluorescence of normal and pathological melanocytes started a series of investigations into this amino acid, enzymatic and non-enzymatic oxidation of catecholic compounds and the metabolism of thiols. All melanocytes with functioning tyrosinase produce cysteinyldopas and the levels of 5-S-cysteinyldopa in serum and urine are related to the size and pigment forming activity of the melanocyte population. The determination of 5-S-cysteinyldopa in serum or urine is a sensitive diagnostic method in the detection of melanoma metastasis. Some non-specific formation of cysteinyldopa is present in the body, as demonstrated by 5-S-cysteinyldopa in individuals with tyrosinase-negative albinism.
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| 2. |
- Johansson, Peter, et al.
(författare)
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Confirmation of a BRAF mutation-associated gene expression signature in melanoma
- 2007
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Ingår i: Pigment Cell Research. - : Wiley. - 0893-5785 .- 1600-0749. ; 20:3, s. 216-221
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Tidskriftsartikel (refereegranskat)abstract
- Mutations in the BRAF oncogene occur in the majority of melanomas, leading to the activation of the mitogen-activated protein kinase pathway and the transcription of downstream effectors. As BRAF and its effectors could be good melanoma therapy targets, defining the repertoire of genes that are differentially regulated because of BRAF mutational activation is an important objective. Towards this goal, we and others have attempted to determine whether a BRAF mutation-associated gene expression profile exists. Results have been mixed, with some groups reporting a BRAF-signature and another group not. Here we resolve this issue and confirm that while gene-by-gene correlations fail to reveal a specific gene(s) whose expression correlates with BRAF status, a BRAF signature can be distinguished by analysis of global expression patterns. Specifically, we have here applied support vector machine (SVM) analysis to Affymetrix microarray data from a panel of 63 melanoma cell lines. SVMs found a BRAF signature in training samples and predicted BRAF mutation status with high accuracy (AUC = 0.840) in the remaining samples. We verified this is a generalized BRAF signature by repeating the analysis in three published microarray datasets, and again found that SVMs predicted BRAF mutation well (Philadelphia: AUC = 0.788; Zurich: AUC = 0.688; Mannheim: AUC = 0.686). An ensemble of 300 SVMs trained on our data also predicted BRAF mutation status in two of the three published datasets (Philadelphia AUC = 0.778; Zurich AUC = 0.719; Mannheim AUC = 0.564). Taken together, these data support the existence of a BRAF mutation-specific expression signature.
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| 3. |
- Andersson, Tony, 1973-, et al.
(författare)
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Regulation of melanosome movement by MAP kinase
- 2003
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Ingår i: Pigment Cell Research. - : Wiley. - 0893-5785 .- 1600-0749. ; 16:3, s. 215-221
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Tidskriftsartikel (refereegranskat)abstract
- Our objectives were to further characterize the signaling pathways in melatonin-induced aggregation in Xenopus melanophores, specifically to investigate a possible role of mitogen-activated protein kinase (MAPK). By Western blotting we found that melatonin activates MAPK, which precedes melanosome aggregation measured in a microplate reader. Activation of MAPK, tyrosine phosphorylation of a previously described 280-kDa protein, and melanosome aggregation are sensitive to PD98059, a selective inhibitor of MAPK kinase. The MAPK activation is also decreased by the adenylate cyclase stimulant forskolin. In summary, we found that MAPK is activated during melatonin-induced melanosome aggregation. Activation was decreased by an inhibitor of MAPK kinase, and by forskolin. In addition to inhibition of cyclic adenosine 3′,5′-monophosphate (cAMP), reduction in protein kinase A activity (PKA), and activation of protein phosphatase 2A, we suggest that melatonin receptors activate the MAPK cascade and tyrosine phosphorylation of the 280-kDa protein. Although the cAMP/PKA signaling pathway is the most prominent, our data suggest that simultaneous activation of the MAPK cascade is of importance to obtain a completely aggregated state. This new regulatory mechanism of organelle transport by the MAPK cascade might be important in other eukaryotic cells.
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| 4. |
- Aspengren, Sara, 1977, et al.
(författare)
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A role for spectrin in dynactin-dependent melanosome transport in Xenopus laevis melanophores
- 2004
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Ingår i: Pigment Cell Research. - : Wiley. - 0893-5785 .- 1600-0749. ; 17:3, s. 295-301
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Tidskriftsartikel (refereegranskat)abstract
- The bi-directional movement of pigment granules in frog melanophores involves the microtubule-based motors cytoplasmic dynein, which is responsible for aggregation, and kinesin II and myosin V, which are required for dispersion of pigment. It was recently shown that dynactin acts as a link between dynein and kinesin II and melanosomes, but it is not fully understood how this is regulated and if more proteins are involved. Here, we suggest that spectrin, which is known to be associated with Golgi vesicles as well as synaptic vesicles in a number of cells, is of importance for melanosome movements in Xenopus laevis melanophores. Large amounts of spectrin were found on melanosomes isolated from both aggregated and dispersed melanophores. Spectrin and two components of the oligomeric dynactin complex, p150(glued) and Arp1/centractin, co-localized with melanosomes during aggregation and dispersion, and the proteins were found to interact as determined by co-immunoprecipitation. Spectrin has been suggested as an important link between cargoes and motor proteins in other cell types, and our new data indicate that spectrin has a role in the specialized melanosome transport processes in frog melanophores, in addition to a more general vesicle transport.
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| 5. |
- Aspengren, Sara, 1977, et al.
(författare)
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Studies of pigment transfer between Xenopus laevis melanophores and fibroblasts in vitro and in vivo
- 2006
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Ingår i: Pigment Cell Research. - : Wiley. - 0893-5785 .- 1600-0749. ; 19:2, s. 136-145
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Tidskriftsartikel (refereegranskat)abstract
- Frog melanophores rapidly change colour by dispersion or aggregation of melanosomes. A long-term colour change exists where melanosomes are released from melanophores and transferred to surrounding skin cells. No in vitro model for pigment transfer exists for lower vertebrates. Frog melanophores of different morphology exist both in epidermis where keratinocytes are present and in dermis where fibroblasts dominate. We have examined whether release and transfer of melanosomes can be studied in a melanophore-fibroblast co-culture, as no frog keratinocyte cell line exists. Xenopus laevis melanophores are normally cultured in conditioned medium from fibroblasts and fibroblast-derived factors may be important for melanophore morphology. Melanin was exocytosed as membrane-enclosed melanosomes in a process that was upregulated by alpha-melanocyte-stimulating hormone (alpha-MSH), and melanosomes where taken up by fibroblasts. Melanosome membrane-proteins seemed to be of importance, as the cluster-like uptake pattern of pigment granules was distinct from that of latex beads. In vivo results confirmed the ability of dermal fibroblasts to engulf melanosomes. Our results show that cultured frog melanophores can not only be used for studies of rapid colour change, but also as a model system for long-term colour changes and for studies of factors that affect pigmentation.
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| 6. |
- Kågedal, Bertil, 1943-, et al.
(författare)
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Pterin-dependent tyrosine hydroxylase mRNA is not expressed in human melanocytes or melanoma cells
- 2004
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Ingår i: Pigment Cell Research. - : Wiley. - 0893-5785 .- 1600-0749. ; 17:4, s. 346-351
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Tidskriftsartikel (refereegranskat)abstract
- Pterin-dependent tyrosine hydroxylase has been described to occur occasionally in melanocytes. It is therefore important to quantify the mRNA of this enzyme in pigment cells to understand whether this enzyme can take an active part in pigment formation. A real-time reverse transcription-polymerase chain reaction method was used to quantify tyrosine hydroxylase mRNA in melanocytes and melanoma cells. The calibrator was obtained by amplification of a segment of cDNA from tyrosine hydroxylase mRNA, which included the target thus allowing enumeration of the number of transcripts per cell. In melanocytes (n = 3), tyrosine hydroxylase mRNA ranged from non-detectable to 0.000492 transcripts/cell and in melanoma cells from non-detectable to 0.005340 transcripts/cell. In neuroblastoma cells, the median tyrosine hydroxylase mRNA number was 0.4 transcripts/cell (range 0.02-25 transcripts/cell). The amount of tyrosine hydroxylase mRNA in the pigment cells was far less than the mRNA concentrations of four melanocyte-specific proteins measured in the same melanocytes and melanoma cells. We conclude that on the average less than 1 of 1000 melanocytes and melanoma cells contains at least one tyrosine hydroxylase mRNA molecule. Consequently, in 999 of 1000 cells translation into the corresponding enzyme protein cannot occur because of the lack of an mRNA template. Thus, in these cells there is no pterin-dependent tyrosine hydroxylase that can contribute to pigment formation by producing priming amounts of L-dopa for proper function of tyrosinase.
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| 7. |
- Nilsson, Harriet M., et al.
(författare)
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L-NAME-induced dispersion of melanosomes in melanophores activates PKC, MEK and ERK1
- 2001
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Ingår i: Pigment Cell Research. - : Wiley. - 0893-5785 .- 1600-0749. ; 14:6, s. 450-455
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Tidskriftsartikel (refereegranskat)abstract
- Melanosome movement represents a good model of cytoskeleton-mediated transport of organelles in eukaryotic cells. We recently observed that inhibiting nitric oxide synthase (NOS) with Nω-nitro-l-arginine methyl ester (l-NAME) induced dispersion in melanophores pre-aggregated with melatonin. Activation of cyclic adenosine 3′,5′-monophosphate (cAMP)-dependent protein kinase (PKA) or calcium-dependent protein kinase (PKC) is known to cause dispersion. Also, PKC and NO have been shown to regulate the mitogen/extracellular signal-regulated kinase (MEK)-ERK pathway. Accordingly, our objective was to further characterize the signaling pathway of l-NAME-induced dispersion. We found that the dispersion was decreased by staurosporine and PD98059, which respectively inhibit PKC and MEK, but not by the PKA inhibitor H89. Furthermore, Western blotting revealed that ERK1 kinase was phosphorylated in l-NAME-dispersed melanophores. l-NAME also caused dispersion in latrunculin-B-treated cells, suggesting that this effect is not due to inhibition of the melatonin signaling pathway. Summarizing, we observed that PKC and MEK inhibitors decreased the l-NAME-induced dispersion, which caused phosphorylation of ERK1. Our results also suggest that NO is a negative regulator of phosphorylations that leads to organelle transport.
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| 8. |
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| 9. |
- Svensson, Samuel, 1962-, et al.
(författare)
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Melanin inhibits cytotoxic effects of doxorubicin and daunorubicin in MOLT 4 cells
- 2003
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Ingår i: Pigment Cell Research. - : Wiley. - 0893-5785 .- 1600-0749. ; 16:4, s. 351-354
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Tidskriftsartikel (refereegranskat)abstract
- In the present study we have developed a simple method to elucidate the melanin binding ability of different chemotherapeutic agents. The anthracyclines, doxorubicin and daunorubicin, or the alkylating agent cisplatin were preincubated with melanin (Sepia). Melanin and free drug was then separated through centrifugation and the cytotoxic effects of corresponding drug were evaluated in a MTT (3-(4,5-dimetyltiazol-2-yl)-2,5-difenyl-tetrazoliumbromide) assay using MOLT-4 cells. Our results show that melanin pretreatment shifted the IC50 value for doxorubicin from 0.06 to 0.97 ╡M and for daunorubicin from 0.04 to 0.80 pM. In contrast, the IC50 values of cisplatin was not influenced by melanin pretreatment indicating that cisplatin does not bind to melanin. By comparing equi-active concentrations from concentration-response curves with or without melanin pretreatment an approximate binding capacity of melanin could be estimated. Our results show that melanin binds about 900 nmol/mg doxorubicin and 760 nmol/mg daunorubicin. Chloroquine, which is known to bind to melanin with high affinity, was found to inhibit melanin binding of both daunorubicin and doxorubicin, thereby leading to an increased sensitivity of the anthracyclines. The clinical implications of melanin binding regarding unwanted accumulation of anthracyclines in the skin as well as chemoprotective effects against chemotherapy are discussed.
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| 10. |
- Takasaki, Akihiko, et al.
(författare)
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HPLC analysis of pheomelanin degradation products in human urine
- 2003
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Ingår i: Pigment Cell Research. - : Wiley. - 0893-5785 .- 1600-0749. ; 16:5, s. 480-486
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Tidskriftsartikel (refereegranskat)abstract
- A sensitive and specific high performance liquid chromatography (HPLC) method was developed to quantify 4-amino-3-hydroxyphenylalanine (4-AHP) and 3-amino-4-hydroxyphenylalanine (3-AHP) in urine. In degradation studies of melanin pigment, 4-AHP and 3-AHP are derived from benzothiazine units of pheomelanin and pheomelanin-related metabolites such as trichochromes. 5-S-Cysteinyldopa-derived benzothiazine products give 4-AHP while 2-S-cysteinyldopa-derived benzothiazine products give 3-AHP. 3-AHP is also derived from nitrotyrosine formed by nitration of tyrosine with reactive nitrogen species. For this reason, the influence of this biological process on the amount of 3-AHP found in biological material have been investigated. The method is based on hydriodic acid hydrolysis of the melanin polymer and reversed-phase HPLC with electrochemical detection of the degradation products 4-AHP and 3-AHP. The mobile phase consists of 25 mM ammonium acetate and sodium octanesulfonate as an ion-pairing reagent. The 4-AHP and 3-AHP peaks were well separated and the detector response was linear within the range 0-2 ng injected for both compounds. With the developed chromatographic system, 4-AHP and 3-AHP showed good separation in the biological samples. There was a strong correlation between 4-AHP and 3-AHP in the urine of 50 malignant melanoma patients and two healthy subjects (R0.977). The two compounds were also strongly correlated with 5-S-cysteinyldopa in urine, the correlation coefficients being 0.862 and 0.907, respectively. The method described is sensitive enough for analysis of pheomelanin in urine and in several other biological samples. The results indicate that 3-AHP in urine is not influenced by excreted 3-nitrotyrosine and the data indicate that pheomelanins are excreted in the urine of melanoma patients.
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| 11. |
- Testorf, Martin, 1972-, et al.
(författare)
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Volume changes of individual melanosomes measured by scanning force microscopy
- 2001
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Ingår i: Pigment Cell Research. - : Wiley. - 0893-5785 .- 1600-0749. ; 14:6, s. 445-449
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Tidskriftsartikel (refereegranskat)abstract
- Black pigment cells, melanophores, e.g. located in the epidermis and dermis of frogs, are large flat cells having intracellular black pigment granules, called melanosomes. Due to a large size, high optical contrast, and quick response to drugs, melanophores are attractive as biosensors as well as for model studies of intracellular processes; e.g. organelle transport and G-protein coupled receptors. The geometry of melanosomes from African clawed toad, Xenopus laevis, has been measured using scanning force microscopy (SFM). Three-dimensional images from SFM were used to measure height, width, and length of the melanosomes (100 from aggregated cells and 100 from dispersed cells). The volumes of melanosomes isolated from aggregated and dispersed melanophores were significantly different (P<0.05, n=200). The average ellipsoidal volume was 0.14±0.01 (aggregated) and 0.17±0.01 μm3 (dispersed), a difference of 18%. The average major diameter was 810±20 and 880±20 nm for aggregated and dispersed melanosomes, respectively. To our knowledge, this is the first time SFM has been used to study melanosomes. This may provide an alternative non-destructive technique that may be particularly suitable for studying morphological aspects of various melanin granules.
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| 12. |
- Wakamatsu, Kazumasa, et al.
(författare)
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Determination of eumelanin in human urine
- 2006
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Ingår i: Pigment Cell Research. - : Wiley. - 0893-5785 .- 1600-0749. ; 19:2, s. 163-169
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Tidskriftsartikel (refereegranskat)abstract
- Normal and malignant melanocytes produce melanins and melanin-related metabolites, most of which are retained in the cells but some are secreted into the blood and then excreted in the urine. In this study, we developed a method to measure levels of eumelanin in urine samples and evaluated its clinical significance in comparison with the melanin-related metabolites 6-hydroxy-5-methoxyindole-2-carboxylic acid (6H5MI2C) and 5-S-cysteinyldopa (5-S-CD), and with pheomelanin, measured after degradation as 4-amino-3-hydroxyphenylalanine (4-AHP). The method is based on the production of pyrrole-2,3,5-tricarboxylic acid (PTCA) on permanganate oxidation of eumelanin, followed by quantification by liquid chromatography. For 118 urine samples from 10 control subjects, mean urinary excretions of PTCA, 6H5MI2C, 5-S-CD and 4-AHP were 19, 67, 37 and 59 μmol/mol creatinine respectively. In melanoma patients (n = 45), the mean urinary excretions of PTCA, 6H5MI2C, 5-S-CD, and 4-AHP were 91, 926, 4070 and 3530 μmol/mol creatinine respectively. Median level of PTCA in melanoma patients was elevated 2.1-fold compared with control subjects. The degrees of elevation for 6H5MI2C, 5-S-CD, and 4-AHP were 1.8-, 22- and 6.2-fold respectively. Thus, although urinary PTCA is of little clinical value in following the progression of melanoma, urinary 4-AHP appears to be of considerable value in this respect. © 2006 Blackwell Munksgaard.
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| 13. |
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| 14. |
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| 15. |
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| 16. |
- Aspengren, Sara, 1977, et al.
(författare)
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Noradrenaline- and melatonin-mediated regulation of pigment aggregation in fish melanophores
- 2003
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Ingår i: Pigment Cell Research. - : Wiley. - 0893-5785. ; 16:1, s. 59-64
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Tidskriftsartikel (refereegranskat)abstract
- The effects of melatonin and noradrenaline (NA) on bi-directional melanosome transport were analysed in primary cultures of melanophores from the Atlantic cod. Both agents mediated rapid melanosome aggregation, and by using receptor antagonists, melatonin was found to bind to a melatonin receptor whereas NA binds to an α2-adrenoceptor. It has previously been stated that melatonin-mediated melanosome aggregation in Xenopus is coupled with tyrosine phosphorylation of a so far unidentified high molecular weight protein and we show that although acting through different receptors and through somewhat different downstream signalling events, tyrosine phosphorylation is of the utmost importance for melanosome aggregation mediated by both NA and melatonin in cod melanophores. Together with cyclic adenosine 3-phosphate-fluctuations, tyrosine phosphorylation functions as a switch signal for melanosome aggregation and dispersion in these cells.
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| 17. |
- Kågedal, B, et al.
(författare)
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The stability of 5-S-cysteinyldopa and 6-hydroxy-5-methoxyindole-2-carboxylic acid in human urine
- 1992
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Ingår i: Pigment Cell Research. - 0893-5785. ; :Suppl 2, s. 304-307
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Tidskriftsartikel (refereegranskat)abstract
- 5-S-cysteinyldopa and 6-hydroxy-5-methoxyindole-2-carboxylic acid are important intermediate metabolites in the formation of cutaneous melanin pigment. Since they both are serious candidates as markers of melanoma progression, their stability in urine has been investigated during storage at various conditions. The results show that storage at -20 degrees C is necessary. Both compounds are nonstable at room temperature, particularly if the urine was not acidified to pH 4-5. Reference levels were obtained from analysis of urine from 31 men and 40 women. The mean (SD) excretion of 5-S-cysteinyldopa was 32 (12.5) mumol/mol creatinine (women). Corresponding figures for 6H5MI2C were 23 (10.3) and 24 (8.1) mumol/mol creatinine for men and women respectively.
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| 18. |
- Nilsson Sköld, Helen, 1970, et al.
(författare)
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Regulatory control of both microtubule- and actin-dependent fish melanosome movement
- 2002
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Ingår i: Pigment Cell Research. - 0893-5785. ; 15:5, s. 357-366
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Tidskriftsartikel (refereegranskat)abstract
- In fish melanophores, melanosomes can either aggregate around the cell centre or disperse uniformly throughout the cell. This organelle transport involves microtubule- and actin-dependent motors and is regulated by extracellular stimuli that modulate levels of intracellular cyclic adenosine 3-phosphate (cAMP). We analysed melanosome dynamics in Atlantic cod melanophores under different experimental conditions in order to increase the understanding of the regulation and relative contribution of the transport systems involved. By inhibiting dynein function via injection of inhibitory antidynein IgGs, and modulating cAMP levels using forskolin, we present cellular evidence that dynein is inactivated by increased cAMP during dispersion and that the kinesin-related motor is inactivated by low cAMP levels during aggregation. Inhibition of dynein further resulted in hyperdispersed melanosomes, which subsequently reversed movement towards a more normal dispersed state, pointing towards a peripheral feedback regulation in maintaining the evenly dispersed state. This reversal was blocked by noradrenaline. Analysis of actin-mediated melanosome movements shows that actin suppresses aggregation and dispersion, and indicates the possibility of down-regulating actin-dependent melanosome movement by noradrenaline. Data from immuno-electron microscopy indicate that myosinV is associated with fish melanosomes. Taken together, our study presents evidence that points towards a model where both microtubule- and actin-mediated melanosome transport are synchronously regulated during aggregation and dispersion, and this provides a cell physiological explanation behind the exceptionally fast rate of background adaptation in fish.
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| 19. |
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| 20. |
- Thorneby-Andersson, K, et al.
(författare)
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Tyrosinase-mediated formation of a reactive quinone from the depigmenting agents, 4-tert-butylphenol and 4-tert-butylcatechol
- 2000
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Ingår i: Pigment Cell Research. - 0893-5785. ; 13:1, s. 33-38
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Tidskriftsartikel (refereegranskat)abstract
- Exposure of the skin to certain phenols or catechols such as 4-tert-butylphenol (TBP) and 4-tert-butylcatechol (TBC) may cause leukoderma. These substances are used in the polymer industry and numerous cases have been reported. Several theories of the mechanism for chemical leukoderma have been suggested. In the present study, TBP and TBC are shown to be oxidised by tyrosinase. The oxidation of TBC yields a quinone that is further investigated on its reactions with cysteine or glutathione (GSH). The products formed are isolated and identified by mass spectrometry and nuclear magnetic resonance as being 4-tert-butyl-6-S-cysteinylcatechol (cys-TBC) and 4-tert-butyl-6-S-glutathionylcatechol (GS-TBC). The reactive quinone is a strongly electrophilic substance that rapidly reacts with GSH. A depletion of the GSH defence system may give conditions where the quinone lives long enough to effect its toxic properties. The influence of the reactive tert-butylquinone on enzymatic activities is demonstrated by the inhibition of glyceraldehyde-3-phosphate dehydrogenase.
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