Stan Pavel - Academia.edu (original) (raw)
Papers by Stan Pavel
Journal of Cell Science, 2001
The cornified cell envelope (CE), a structure formed in the outermost layers of stratified squamo... more The cornified cell envelope (CE), a structure formed in the outermost layers of stratified squamous epithelia, provides a physical barrier against environmental insults. It is composed of several structural proteins, which are irreversibly crosslinked by calcium-activated transglutaminases. The small proline rich proteins (SPRRs) are one set of CE precursors. SPRR4, a novel member of this gene family, displayed very low or undetectable expression levels in normal human skin or other stratified squamous epithelia, but was clearly induced by UV light both in vivo and in vitro. High epidermal expression of SPRR4 was monitored only after chronic UV exposure and was concomitant with a thickening of the stratum corneum, which is believed to provide protection against subsequent damage. The calcium-dependent translocation of an SPRR4-GFP fusion protein to the cell periphery in living keratinocytes and its integration into both rigid and fragile cornified envelopes proved that SPRR4 is a no...
Vademecum permanente nascholing huisartsen, 2006
Ultraviolette (UV) straling als therapie voor dermatologische aandoeningen wordt sinds lange tijd... more Ultraviolette (UV) straling als therapie voor dermatologische aandoeningen wordt sinds lange tijd met succes toegepast. Op basis van golflengte wordt UV-straling ingedeeld in UVC (100-280 nm), UVB (280-320 nm) en UVA (320-400 nm). Het UVA-gedeelte wordt weer onderverdeeld in UVA-2 (320-340 nm) en UVA-1 (340-400 nm). In de dermatologie maakt men als therapeutische toepassing vrijwel uitsluitend gebruik van UVB en UVA.
Pigment Cell Research, 2006
SummaryThe influence of side‐chain structure on the mode of reaction of ortho‐quinone amines has ... more SummaryThe influence of side‐chain structure on the mode of reaction of ortho‐quinone amines has been investigated with a view, ultimately, to developing potential methods of therapeutic intervention by manipulating the early stages of melanogenesis. Four N‐substituted dopamine derivatives have been prepared and quinone formation studied using pulse radiolysis and tyrosinase‐oximetry. Ortho‐quinones with an amide or urea side chain were relatively stable, although evidence for slow formation of isomeric para‐quinomethanes was observed. A thiourea derivative cyclized fairly rapidly (k = 1.7/s) to a product containing a seven‐membered ring, whereas a related amidine gave more rapidly (k ∼ 2.5 × 102/s) a stable spirocyclic product. The results suggest that cyclization of amides, ureas and carbamates (NHCO‐X; X = R, NHR or OR) does not occur and is not, therefore, a viable approach to the formation of tyrosinase‐activated antimelanoma prodrugs. It is also concluded that for N‐acetyldopa...
Melanoma Research, 2003
CDKN2A is regarded as a major melanoma susceptibility gene. A 19 bp deletion has been detected wi... more CDKN2A is regarded as a major melanoma susceptibility gene. A 19 bp deletion has been detected within Dutch families with familial atypical multiple mole-melanoma syndrome. Genetic analysis revealed two individuals with germline deletions in both copies of CDKN2A. One of them did not develop atypical naevi or melanoma, but died of adenocarcinoma at the age of 54 years. This report describes the results of the investigation of the second p16-null individual, who was also found to have glucose-6phosphate dehydrogenase (G-6-PD) deficiency and who has developed many atypical naevi and seven melanomas. Using electron microscopic techniques, striking alterations in melanosomal structures and deviations in their sulphur, iron and calcium composition indicating a strong preference for phaeomelanogenesis and increased oxidative stress were found in the naevus cells of the patient. Using an in vitro model, we demonstrated that leaking melanin precursors may strongly enhance oxidative DNA damage through iron release from ferritin. We conclude that the homozygous p16 deletion is not sufficient for the development of a dysplastic naevus phenotype and melanoma. However, when an additional modifying factor, such as G-6-PD deficiency, increases the level of oxidative DNA damage in melanin-producing cells, the risk of developing atypical naevi and their malignant transformation may increase significantly. Melanoma Res 13:171-178 & 2003 Lippincott Williams & Wilkins.
Pigment Cell Research, 2003
Pigment Cell Research, 1995
Melanocytes cultured on collagen-coated Cytodex 3 microcarrier Sephadex beads caused remarkable p... more Melanocytes cultured on collagen-coated Cytodex 3 microcarrier Sephadex beads caused remarkable pigmentation of the beads during the period of culture when optimal density was reached. Electron microscopy of melanocytes on the microcarriers revealed that the cells and their dendrites invaginate into the microcarrier surface layer. Removal of the cells by trypsinization showed that some pigment granules were left on the carrier surface and within the cavities present on the microcarrier surface. In order to investigate whether the pigmentation of the microcarriers could be a result of indole intermediates of melanogenesis present in the culture medium, extracts were studied by gas chromatography/mass spectrometry for the presence of these compounds. Two compounds (5,6-dihydroxyindole-2-carboxylic acid and 6-hydroxy-5-methoxyindole-2-carboxylic acid) so far have been identified in the medium extracts. Results indicate that microcarrier culture of melanocytes can serve as an interesting model for electron microscopy studies of melanocytes with regard to pigmentation and cell attachment.
Pigment Cell Research, 1994
Photochemistry and Photobiology, 2008
Melanin synthesis is an oxygen‐dependent process that acts as a potential source of reactive oxyg... more Melanin synthesis is an oxygen‐dependent process that acts as a potential source of reactive oxygen species (ROS) inside pigment‐forming cells. The synthesis of the lighter variant of melanin, pheomelanin, consumes cysteine and this may limit the capacity of the cellular antioxidative defense. We show that tyrosine‐induced melanogenesis in cultured normal human melanocytes (NHM) is accompanied by increased production of ROS and decreased concentration of intracellular glutathione. Clinical atypical (dysplastic) nevi (DN) regularly contain more melanin than do normal melanocytes (MC). We also show that in these cultured DN cells three out of four exhibit elevated synthesis of pheomelanin and this is accompanied by their early senescence. By using various redox‐sensitive molecular probes, we demonstrate that cultured DN cells produce significantly more ROS than do normal MC from the same donor. Our experiments employing single‐cell gel electrophoresis (comet assay) usually reveal high...
![Research paper thumbnail of Preclinical Studies with 5,10,15‐Tris(4‐Methylpyridinium)‐20‐Phenyl‐[21H,23H]‐Porphine Trichloride for the Photodynamic Treatment of Superficial Mycoses Caused by Trichophyton rubrum](https://attachments.academia-assets.com/120144229/thumbnails/1.jpg)
](Photochemistry and Photobiology, 2009
Dermatophytes are fungi that cause infections of keratinized tissues. We have recently demonstrat... more Dermatophytes are fungi that cause infections of keratinized tissues. We have recently demonstrated the susceptibility of the dermatophyte Trichophyton rubrum to photodynamic treatment (PDT) with 5,10,15‐Tris(4‐methylpyridinium)‐20‐phenyl‐[21H,23H]‐porphine trichloride (Sylsens B) in 5 mm citric acid/sodium citrate buffer (pH 5.2, formulation I). In this work, we examined the penetration of Sylsens B in healthy and with T. rubrum infected skin and we investigated the susceptibility of T. rubrum to PDT using formulation I and UVA‐1 radiation (340–550 nm). Skin penetration studies were performed with formulations I and II (Sylsens B in PBS, pH 7.4) applied on dermatomed skin, human stratum corneum (SC), disrupted SC by T. rubrum growth and SC pretreated with a detergent. No penetration was observed in healthy skin. Disruption of SC by preceding fungal growth caused Sylsens B penetration at pH 7.4, but not at pH 5.2. However, chemically damaged SC allowed Sylsens B to penetrate also at...
Medical Mycology, 2008
Treatment strategies for superficial mycosis caused by the dermatophyte Trichophyton rubrum consi... more Treatment strategies for superficial mycosis caused by the dermatophyte Trichophyton rubrum consist of the use of topical or oral antifungal preparations. We have recently discovered that T. rubrum is susceptible to photodynamic treatment (PDT), with 5,10,15-tris(4-methylpyridinium)-20-phenyl-[21H,23H]-porphine trichloride (Sylsens B) as a photosensitizer. The susceptibility appeared to depend on the fungal growth stage, with PDT efficacy higher with microconidia when compared to mycelia. The aim of this study was to investigate, with the use of scanning electron microscopy, the morphological changes caused by a lethal PDT dose to T. rubrum when grown on isolated human stratum corneum. Corresponding dark treatment and light treatment without photosensitizer were used as controls. A sub-lethal PDT dose was also included in this investigation The morphologic changes were followed at various time points after the treatment of different fungal growth stages. Normal fungal growth was characterized by a fiberlike appearance of the surface of the hyphae and microconidia with the exception of the hyphal tips in full mycelia and the microconidia shortly after attachment to the stratum corneum. Here, densely packed globular structures were observed. The light dose (108 J/cm 2) in the absence of Sylsens B, or the application of the photosensitizer in the absence of light, caused reversible fungal wall deformations and bulge formation. However, after a lethal PDT, a sequence of severe disruptions and deformations of both microconidia and the mycelium were observed leading to extrusion of cell material and emptied fungal elements. In case of a non-lethal PDT, fungal re-growth started on the remnants of the treated mycelium.
Journal of the American Academy of Dermatology, 2004
Fig 1. Erythematous crusted erosions and shallow depressed scars on the dorsum of the hands.
Journal of Photochemistry and Photobiology B: Biology, 2001
Cultured melanocytes originating from persons with different skin phototypes were utilized for me... more Cultured melanocytes originating from persons with different skin phototypes were utilized for measurement of endonuclease sensitive sites induced by UVB and the determination of cell survival after UVA or UVB irradiation. During culture, the melanocytes largely maintained their phenotypic characteristics according to their original skin phototype. Total melanin concentrations were 4.9 times higher in the darker skin phototype (IV-VI) melanocytes when compared to the cells from lighter skin phototypes (I-III). Also phaeomelanin contents were higher (2.5 times) in the skin phototype (IV-VI) melanocytes which implies that the cells from light skin types contain less melanin, but a relatively high proportion of phaeomelanin. After UVB irradiation a stronger induction of endonuclease sensitive sites was found for melanocytes with a lower level of total melanin and a high content of pheomelanin. By measuring the clone forming ability in different melanocyte cultures after UVB irradiation, significant better survival was found in case of the cells with the higher melanin content. Despite the large variations in melanin content, no significant difference in survival after UVA irradiation could be demonstrated in this way. Our results suggest a protective effect of melanin for UVB and indicate the importance of the measurements of melanin content and composition when different parameters of UV-induced damage are studied in melanin producing cells.
Journal of Investigative Dermatology, 1987
Three different groups of chemical intermediates are known to be formed durin g the synthesis of ... more Three different groups of chemical intermediates are known to be formed durin g the synthesis of melanin in mel anocytes: (1) phenolic compounds, (2) phenolic thio-conjuga tes, and (3) indolic compounds. All these substances and th eir metabolites can be detected in urine. We measured the urinary excretion of 3,4-dihydroxyphenylalanine (dopa), 5-S-cysteinyldopa (5-S-CD), and 2 inclolic compounds, namely 5-hydroxy-6-methoxyindole (5H6MI) and 5-hydroxy-6-methoxyindole-2-carboxylic acid (5H6MI2C) in urine sampl es of 4 groups of people with different contents of cutaneous mel anin: (a) Asian group, (b) white group, M elanogenesis, the formation of m elanin pigment, is one .o f the characteristi c fea tures of mel anocytes. Tyrosine is known to be a basic substrate fo r the chai n of biochemical reacti ons leadin g to m elanin formation. During this process, 3 different g roups of chemical intermediates are form ed : (1) phenolic com pounds, e.g., 3,4-dihydroxyphenylalanine (dopa), (2) phenolic thio-conjugates, e.g., 5-S-cysteinyldopa (5-S-CD), and (3) indo lic substances, e.g., 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid. All these co mpounds and their metabolites can be detected in urine [1-5). In o rder to find out which of the mentioned groups of metabo lites correlates with the degree of skin pigmentation , w e studied the excretion of the 4 melanin-related substances (Fig 1) in th e urine of 4 groups of people: (a) Asian group, (b) people of European origin (white g roup) .. (c) patients with vitiligo, and (d) patients with tyrosinase-negative oculocutaneous albinism. The excretion of do pa and 5-S-CD was measured with the use of hi gh-performance liquid chro m atogra phy. Mass fragmentography was used for the determin ation of 2 indolic compounds, namely 5-hyd roxy-6-methoxyindole (5H6MI) and 5-hydroxy-6methoxyindole-2-carboxylic acid (5H6MI2C). MA TERIALS AND METHODS Chemicals DL-Dopa and L-isoproterenol were purchased from Sigma C hemi ca l Co., St. Louis, Missouri ; aluminium oxide was Manuscript
Journal of Investigative Dermatology, 2004
The quality, quantity and distribution of melanosomes in epidermis play a crucial role in the det... more The quality, quantity and distribution of melanosomes in epidermis play a crucial role in the determination of skin color and its sensitivity to UV radiation. Melanocyte cultures originating from individuals with light and dark skin types were grown in media with varying concentration of L-tyrosine. Melanosomal melanin content and the size of the organelles were measured after subcellular fractionation. In light-skin type cells, increased melanin production resulted in a more elliptical shape of melanosomes. In melanosomes that constitutively produce more melanin, the tyrosine-induced melanogenesis caused enlargement in all dimensions. X-ray microanalysis provided evidence that the increase in sulfur content induced by high tyrosine concentration was more prominent in the melanosomes from light skin types. A ratio between pheomelanin and eumelanin found in light-skin type melanosomes by HPLC was increased more markedly than that in melanosomes from dark skin melanocytes. These findings suggest that the melanocytes of lightskinned individuals exhibit a preference for pheomelanogenesis. Pheomelanin production is a thiol-consuming process and that might increase the risk of oxidation stress in these cells. This fact, together with the limited ability of pheomelanin to absorb UV radiation may lead to an elevated skin cancer risk among light-skinned individuals.
Journal of Dermatological Science, 1998
European Journal of Cancer, 2004
Dysplastic naevi (DN) are a known risk factor for malignant melanoma. Their occurrence is closely... more Dysplastic naevi (DN) are a known risk factor for malignant melanoma. Their occurrence is closely connected with the degree of skin pigmentation. People with a light complexion are more likely to develop DN than dark-skinned individuals. We examined the proposition that DN exhibit altered melanin formation, which may be involved in their malignant transformation. X-ray microanalysis was used to study the composition of melanosomes from DN and to compare the results with those obtained from melanomas, banal (dermal) naevi and normal cutaneous melanocytes. We analysed sulphur (an indicator of phaeomelanin) and two metals, iron and calcium, involved in oxidative stress. FACS analysis of dihydrorhodamine-123-labelled cells was employed to quantify differences in the production of radical oxygen species in DN cells and normal skin melanocytes. A significantly higher sulphur content was found in melanosomes from DN cells and melanoma cells when compared with normal melanocytes and naevus cells from banal naevi. In addition, melanosomes of DN cells and melanoma cells contained higher amounts of iron and calcium. In the case of calcium, this was associated with a significantly elevated cytoplasmic concentration. FACS analysis showed that DN cells exhibited higher concentrations of radical oxygen species than normal skin melanocytes from the same individuals. We propose that increased phaeomelanogenesis in DN cells is connected with oxidative imbalance, which is reflected by increased intracellular concentrations of reactive oxygen species and raised calcium and iron concentrations. We show that the metabolic alterations in DN cells resemble those found in melanoma cells. Our findings provide support for the idea that DN cells are true precursor lesions of melanoma.
Archives of Dermatological Research, 1994
Catechol-O-methyltransferase (COMT) is involved in the metabolism of neurotransmitters such as ep... more Catechol-O-methyltransferase (COMT) is involved in the metabolism of neurotransmitters such as epinephrine, norepinephrine and dopamine. For melanocytes, the enzyme is of particular importance in preventing the formation of toxic o~uinones during melanin synthesis.It has been suggested that COMT plays a regulatory role in melanin synthesis. Indeed, when the melanin precursor molecule DHI(2C) is methylated by COMT it is no longer available for incorporation into melanin. Autodestruction by intermediates of melanin metabolism has been implicated in the aetiology of vitiligo. Therefore enzyme activities in vitiligo patients and in healthy controls were compared. Systemic COMT activities were measured using red blood cells (RBC) as starting material. However, as local alterations in COMT activity may be specifically involved in vitiligo, the enzyme activity was also measured in epidermal homogenates. Finally, to ascribe epidermal COMT activity to the responsible cell type(s), enzyme activity was measured in cultured vitiligo non-lesional melanocytes and melanocytes from healthy controls as well as in cultured keratinocytes from lesional skin and in purified keratinocytes from control skin. It was found that epidermal homogenates from vitiligo patients expressed higher levels of COMT activity than homogenates from healthy controls. Such differences were not found at the systemic level (i.e. in RBC) nor could they be explained by measurements on separately cultured epidermal cell types, indicating that the COMT activity was induced at the tissue level by extracellular factors. It is possible that elevated levels of catecholamines secreted by keratinocytes or by nerve endings in vitiliginous skin in close proximity to the epidermis cause damage to all epidermal cells, an effect which is insufficiently neutralized by elevated levels of COMT activity. Catecholamines may well be more damaging to the melanocytes than to the keratinocytes because of their slower turnover rate.
Journal of the American Academy of Dermatology, 2004
Fig 1. Erythematous crusted erosions and shallow depressed scars on the dorsum of the hands.
Journal of the American Academy of Dermatology, 2007
Journal of Investigative Dermatology, 2010
Betacellulin regulates hair follicle development and hair cycle induction and enhances angiogenes... more Betacellulin regulates hair follicle development and hair cycle induction and enhances angiogenesis in wounded skin.
Journal of Cell Science, 2001
The cornified cell envelope (CE), a structure formed in the outermost layers of stratified squamo... more The cornified cell envelope (CE), a structure formed in the outermost layers of stratified squamous epithelia, provides a physical barrier against environmental insults. It is composed of several structural proteins, which are irreversibly crosslinked by calcium-activated transglutaminases. The small proline rich proteins (SPRRs) are one set of CE precursors. SPRR4, a novel member of this gene family, displayed very low or undetectable expression levels in normal human skin or other stratified squamous epithelia, but was clearly induced by UV light both in vivo and in vitro. High epidermal expression of SPRR4 was monitored only after chronic UV exposure and was concomitant with a thickening of the stratum corneum, which is believed to provide protection against subsequent damage. The calcium-dependent translocation of an SPRR4-GFP fusion protein to the cell periphery in living keratinocytes and its integration into both rigid and fragile cornified envelopes proved that SPRR4 is a no...
Vademecum permanente nascholing huisartsen, 2006
Ultraviolette (UV) straling als therapie voor dermatologische aandoeningen wordt sinds lange tijd... more Ultraviolette (UV) straling als therapie voor dermatologische aandoeningen wordt sinds lange tijd met succes toegepast. Op basis van golflengte wordt UV-straling ingedeeld in UVC (100-280 nm), UVB (280-320 nm) en UVA (320-400 nm). Het UVA-gedeelte wordt weer onderverdeeld in UVA-2 (320-340 nm) en UVA-1 (340-400 nm). In de dermatologie maakt men als therapeutische toepassing vrijwel uitsluitend gebruik van UVB en UVA.
Pigment Cell Research, 2006
SummaryThe influence of side‐chain structure on the mode of reaction of ortho‐quinone amines has ... more SummaryThe influence of side‐chain structure on the mode of reaction of ortho‐quinone amines has been investigated with a view, ultimately, to developing potential methods of therapeutic intervention by manipulating the early stages of melanogenesis. Four N‐substituted dopamine derivatives have been prepared and quinone formation studied using pulse radiolysis and tyrosinase‐oximetry. Ortho‐quinones with an amide or urea side chain were relatively stable, although evidence for slow formation of isomeric para‐quinomethanes was observed. A thiourea derivative cyclized fairly rapidly (k = 1.7/s) to a product containing a seven‐membered ring, whereas a related amidine gave more rapidly (k ∼ 2.5 × 102/s) a stable spirocyclic product. The results suggest that cyclization of amides, ureas and carbamates (NHCO‐X; X = R, NHR or OR) does not occur and is not, therefore, a viable approach to the formation of tyrosinase‐activated antimelanoma prodrugs. It is also concluded that for N‐acetyldopa...
Melanoma Research, 2003
CDKN2A is regarded as a major melanoma susceptibility gene. A 19 bp deletion has been detected wi... more CDKN2A is regarded as a major melanoma susceptibility gene. A 19 bp deletion has been detected within Dutch families with familial atypical multiple mole-melanoma syndrome. Genetic analysis revealed two individuals with germline deletions in both copies of CDKN2A. One of them did not develop atypical naevi or melanoma, but died of adenocarcinoma at the age of 54 years. This report describes the results of the investigation of the second p16-null individual, who was also found to have glucose-6phosphate dehydrogenase (G-6-PD) deficiency and who has developed many atypical naevi and seven melanomas. Using electron microscopic techniques, striking alterations in melanosomal structures and deviations in their sulphur, iron and calcium composition indicating a strong preference for phaeomelanogenesis and increased oxidative stress were found in the naevus cells of the patient. Using an in vitro model, we demonstrated that leaking melanin precursors may strongly enhance oxidative DNA damage through iron release from ferritin. We conclude that the homozygous p16 deletion is not sufficient for the development of a dysplastic naevus phenotype and melanoma. However, when an additional modifying factor, such as G-6-PD deficiency, increases the level of oxidative DNA damage in melanin-producing cells, the risk of developing atypical naevi and their malignant transformation may increase significantly. Melanoma Res 13:171-178 & 2003 Lippincott Williams & Wilkins.
Pigment Cell Research, 2003
Pigment Cell Research, 1995
Melanocytes cultured on collagen-coated Cytodex 3 microcarrier Sephadex beads caused remarkable p... more Melanocytes cultured on collagen-coated Cytodex 3 microcarrier Sephadex beads caused remarkable pigmentation of the beads during the period of culture when optimal density was reached. Electron microscopy of melanocytes on the microcarriers revealed that the cells and their dendrites invaginate into the microcarrier surface layer. Removal of the cells by trypsinization showed that some pigment granules were left on the carrier surface and within the cavities present on the microcarrier surface. In order to investigate whether the pigmentation of the microcarriers could be a result of indole intermediates of melanogenesis present in the culture medium, extracts were studied by gas chromatography/mass spectrometry for the presence of these compounds. Two compounds (5,6-dihydroxyindole-2-carboxylic acid and 6-hydroxy-5-methoxyindole-2-carboxylic acid) so far have been identified in the medium extracts. Results indicate that microcarrier culture of melanocytes can serve as an interesting model for electron microscopy studies of melanocytes with regard to pigmentation and cell attachment.
Pigment Cell Research, 1994
Photochemistry and Photobiology, 2008
Melanin synthesis is an oxygen‐dependent process that acts as a potential source of reactive oxyg... more Melanin synthesis is an oxygen‐dependent process that acts as a potential source of reactive oxygen species (ROS) inside pigment‐forming cells. The synthesis of the lighter variant of melanin, pheomelanin, consumes cysteine and this may limit the capacity of the cellular antioxidative defense. We show that tyrosine‐induced melanogenesis in cultured normal human melanocytes (NHM) is accompanied by increased production of ROS and decreased concentration of intracellular glutathione. Clinical atypical (dysplastic) nevi (DN) regularly contain more melanin than do normal melanocytes (MC). We also show that in these cultured DN cells three out of four exhibit elevated synthesis of pheomelanin and this is accompanied by their early senescence. By using various redox‐sensitive molecular probes, we demonstrate that cultured DN cells produce significantly more ROS than do normal MC from the same donor. Our experiments employing single‐cell gel electrophoresis (comet assay) usually reveal high...
Photochemistry and Photobiology, 2009
Dermatophytes are fungi that cause infections of keratinized tissues. We have recently demonstrat... more Dermatophytes are fungi that cause infections of keratinized tissues. We have recently demonstrated the susceptibility of the dermatophyte Trichophyton rubrum to photodynamic treatment (PDT) with 5,10,15‐Tris(4‐methylpyridinium)‐20‐phenyl‐[21H,23H]‐porphine trichloride (Sylsens B) in 5 mm citric acid/sodium citrate buffer (pH 5.2, formulation I). In this work, we examined the penetration of Sylsens B in healthy and with T. rubrum infected skin and we investigated the susceptibility of T. rubrum to PDT using formulation I and UVA‐1 radiation (340–550 nm). Skin penetration studies were performed with formulations I and II (Sylsens B in PBS, pH 7.4) applied on dermatomed skin, human stratum corneum (SC), disrupted SC by T. rubrum growth and SC pretreated with a detergent. No penetration was observed in healthy skin. Disruption of SC by preceding fungal growth caused Sylsens B penetration at pH 7.4, but not at pH 5.2. However, chemically damaged SC allowed Sylsens B to penetrate also at...
Medical Mycology, 2008
Treatment strategies for superficial mycosis caused by the dermatophyte Trichophyton rubrum consi... more Treatment strategies for superficial mycosis caused by the dermatophyte Trichophyton rubrum consist of the use of topical or oral antifungal preparations. We have recently discovered that T. rubrum is susceptible to photodynamic treatment (PDT), with 5,10,15-tris(4-methylpyridinium)-20-phenyl-[21H,23H]-porphine trichloride (Sylsens B) as a photosensitizer. The susceptibility appeared to depend on the fungal growth stage, with PDT efficacy higher with microconidia when compared to mycelia. The aim of this study was to investigate, with the use of scanning electron microscopy, the morphological changes caused by a lethal PDT dose to T. rubrum when grown on isolated human stratum corneum. Corresponding dark treatment and light treatment without photosensitizer were used as controls. A sub-lethal PDT dose was also included in this investigation The morphologic changes were followed at various time points after the treatment of different fungal growth stages. Normal fungal growth was characterized by a fiberlike appearance of the surface of the hyphae and microconidia with the exception of the hyphal tips in full mycelia and the microconidia shortly after attachment to the stratum corneum. Here, densely packed globular structures were observed. The light dose (108 J/cm 2) in the absence of Sylsens B, or the application of the photosensitizer in the absence of light, caused reversible fungal wall deformations and bulge formation. However, after a lethal PDT, a sequence of severe disruptions and deformations of both microconidia and the mycelium were observed leading to extrusion of cell material and emptied fungal elements. In case of a non-lethal PDT, fungal re-growth started on the remnants of the treated mycelium.
Journal of the American Academy of Dermatology, 2004
Fig 1. Erythematous crusted erosions and shallow depressed scars on the dorsum of the hands.
Journal of Photochemistry and Photobiology B: Biology, 2001
Cultured melanocytes originating from persons with different skin phototypes were utilized for me... more Cultured melanocytes originating from persons with different skin phototypes were utilized for measurement of endonuclease sensitive sites induced by UVB and the determination of cell survival after UVA or UVB irradiation. During culture, the melanocytes largely maintained their phenotypic characteristics according to their original skin phototype. Total melanin concentrations were 4.9 times higher in the darker skin phototype (IV-VI) melanocytes when compared to the cells from lighter skin phototypes (I-III). Also phaeomelanin contents were higher (2.5 times) in the skin phototype (IV-VI) melanocytes which implies that the cells from light skin types contain less melanin, but a relatively high proportion of phaeomelanin. After UVB irradiation a stronger induction of endonuclease sensitive sites was found for melanocytes with a lower level of total melanin and a high content of pheomelanin. By measuring the clone forming ability in different melanocyte cultures after UVB irradiation, significant better survival was found in case of the cells with the higher melanin content. Despite the large variations in melanin content, no significant difference in survival after UVA irradiation could be demonstrated in this way. Our results suggest a protective effect of melanin for UVB and indicate the importance of the measurements of melanin content and composition when different parameters of UV-induced damage are studied in melanin producing cells.
Journal of Investigative Dermatology, 1987
Three different groups of chemical intermediates are known to be formed durin g the synthesis of ... more Three different groups of chemical intermediates are known to be formed durin g the synthesis of melanin in mel anocytes: (1) phenolic compounds, (2) phenolic thio-conjuga tes, and (3) indolic compounds. All these substances and th eir metabolites can be detected in urine. We measured the urinary excretion of 3,4-dihydroxyphenylalanine (dopa), 5-S-cysteinyldopa (5-S-CD), and 2 inclolic compounds, namely 5-hydroxy-6-methoxyindole (5H6MI) and 5-hydroxy-6-methoxyindole-2-carboxylic acid (5H6MI2C) in urine sampl es of 4 groups of people with different contents of cutaneous mel anin: (a) Asian group, (b) white group, M elanogenesis, the formation of m elanin pigment, is one .o f the characteristi c fea tures of mel anocytes. Tyrosine is known to be a basic substrate fo r the chai n of biochemical reacti ons leadin g to m elanin formation. During this process, 3 different g roups of chemical intermediates are form ed : (1) phenolic com pounds, e.g., 3,4-dihydroxyphenylalanine (dopa), (2) phenolic thio-conjugates, e.g., 5-S-cysteinyldopa (5-S-CD), and (3) indo lic substances, e.g., 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid. All these co mpounds and their metabolites can be detected in urine [1-5). In o rder to find out which of the mentioned groups of metabo lites correlates with the degree of skin pigmentation , w e studied the excretion of the 4 melanin-related substances (Fig 1) in th e urine of 4 groups of people: (a) Asian group, (b) people of European origin (white g roup) .. (c) patients with vitiligo, and (d) patients with tyrosinase-negative oculocutaneous albinism. The excretion of do pa and 5-S-CD was measured with the use of hi gh-performance liquid chro m atogra phy. Mass fragmentography was used for the determin ation of 2 indolic compounds, namely 5-hyd roxy-6-methoxyindole (5H6MI) and 5-hydroxy-6methoxyindole-2-carboxylic acid (5H6MI2C). MA TERIALS AND METHODS Chemicals DL-Dopa and L-isoproterenol were purchased from Sigma C hemi ca l Co., St. Louis, Missouri ; aluminium oxide was Manuscript
Journal of Investigative Dermatology, 2004
The quality, quantity and distribution of melanosomes in epidermis play a crucial role in the det... more The quality, quantity and distribution of melanosomes in epidermis play a crucial role in the determination of skin color and its sensitivity to UV radiation. Melanocyte cultures originating from individuals with light and dark skin types were grown in media with varying concentration of L-tyrosine. Melanosomal melanin content and the size of the organelles were measured after subcellular fractionation. In light-skin type cells, increased melanin production resulted in a more elliptical shape of melanosomes. In melanosomes that constitutively produce more melanin, the tyrosine-induced melanogenesis caused enlargement in all dimensions. X-ray microanalysis provided evidence that the increase in sulfur content induced by high tyrosine concentration was more prominent in the melanosomes from light skin types. A ratio between pheomelanin and eumelanin found in light-skin type melanosomes by HPLC was increased more markedly than that in melanosomes from dark skin melanocytes. These findings suggest that the melanocytes of lightskinned individuals exhibit a preference for pheomelanogenesis. Pheomelanin production is a thiol-consuming process and that might increase the risk of oxidation stress in these cells. This fact, together with the limited ability of pheomelanin to absorb UV radiation may lead to an elevated skin cancer risk among light-skinned individuals.
Journal of Dermatological Science, 1998
European Journal of Cancer, 2004
Dysplastic naevi (DN) are a known risk factor for malignant melanoma. Their occurrence is closely... more Dysplastic naevi (DN) are a known risk factor for malignant melanoma. Their occurrence is closely connected with the degree of skin pigmentation. People with a light complexion are more likely to develop DN than dark-skinned individuals. We examined the proposition that DN exhibit altered melanin formation, which may be involved in their malignant transformation. X-ray microanalysis was used to study the composition of melanosomes from DN and to compare the results with those obtained from melanomas, banal (dermal) naevi and normal cutaneous melanocytes. We analysed sulphur (an indicator of phaeomelanin) and two metals, iron and calcium, involved in oxidative stress. FACS analysis of dihydrorhodamine-123-labelled cells was employed to quantify differences in the production of radical oxygen species in DN cells and normal skin melanocytes. A significantly higher sulphur content was found in melanosomes from DN cells and melanoma cells when compared with normal melanocytes and naevus cells from banal naevi. In addition, melanosomes of DN cells and melanoma cells contained higher amounts of iron and calcium. In the case of calcium, this was associated with a significantly elevated cytoplasmic concentration. FACS analysis showed that DN cells exhibited higher concentrations of radical oxygen species than normal skin melanocytes from the same individuals. We propose that increased phaeomelanogenesis in DN cells is connected with oxidative imbalance, which is reflected by increased intracellular concentrations of reactive oxygen species and raised calcium and iron concentrations. We show that the metabolic alterations in DN cells resemble those found in melanoma cells. Our findings provide support for the idea that DN cells are true precursor lesions of melanoma.
Archives of Dermatological Research, 1994
Catechol-O-methyltransferase (COMT) is involved in the metabolism of neurotransmitters such as ep... more Catechol-O-methyltransferase (COMT) is involved in the metabolism of neurotransmitters such as epinephrine, norepinephrine and dopamine. For melanocytes, the enzyme is of particular importance in preventing the formation of toxic o~uinones during melanin synthesis.It has been suggested that COMT plays a regulatory role in melanin synthesis. Indeed, when the melanin precursor molecule DHI(2C) is methylated by COMT it is no longer available for incorporation into melanin. Autodestruction by intermediates of melanin metabolism has been implicated in the aetiology of vitiligo. Therefore enzyme activities in vitiligo patients and in healthy controls were compared. Systemic COMT activities were measured using red blood cells (RBC) as starting material. However, as local alterations in COMT activity may be specifically involved in vitiligo, the enzyme activity was also measured in epidermal homogenates. Finally, to ascribe epidermal COMT activity to the responsible cell type(s), enzyme activity was measured in cultured vitiligo non-lesional melanocytes and melanocytes from healthy controls as well as in cultured keratinocytes from lesional skin and in purified keratinocytes from control skin. It was found that epidermal homogenates from vitiligo patients expressed higher levels of COMT activity than homogenates from healthy controls. Such differences were not found at the systemic level (i.e. in RBC) nor could they be explained by measurements on separately cultured epidermal cell types, indicating that the COMT activity was induced at the tissue level by extracellular factors. It is possible that elevated levels of catecholamines secreted by keratinocytes or by nerve endings in vitiliginous skin in close proximity to the epidermis cause damage to all epidermal cells, an effect which is insufficiently neutralized by elevated levels of COMT activity. Catecholamines may well be more damaging to the melanocytes than to the keratinocytes because of their slower turnover rate.
Journal of the American Academy of Dermatology, 2004
Fig 1. Erythematous crusted erosions and shallow depressed scars on the dorsum of the hands.
Journal of the American Academy of Dermatology, 2007
Journal of Investigative Dermatology, 2010
Betacellulin regulates hair follicle development and hair cycle induction and enhances angiogenes... more Betacellulin regulates hair follicle development and hair cycle induction and enhances angiogenesis in wounded skin.