Publicações de Ludger KOLBE (28)

High-energy visible light at ambient doses and intensities induces oxidative stress of skin-Protective effects of the antioxidant and Nrf2 inducer Licochalcone A in vitro and in vivo.

Mar, 2020

Solar radiation causes skin damage through the generation of reactive oxygen species (ROS). While UV filters effectively reduce UV-induced ROS, they cannot prevent VIS-induced (400-760 nm) oxidative stress. Therefore, potent antioxidants are needed as additives to sunscreen products. Ler mais

Photodermatology, photoimmunology & photomedicine

Effective Tyrosinase Inhibition by Thiamidol Results in Significant Improvement of Mild to Moderate Melasma.

08, 2019

Melasma is a pigmentary disorder characterized by hyperpigmented patchy skin in sun-exposed areas, especially the face. Treatment of melasma can be challenging because long-term therapy is required, reoccurrence is common, and existing therapies are insufficient and unsatisfactory. To investigate new treatment options, we performed an exploratory double-blinded, randomized split-face study to assess the efficacy of the tyrosinase inhibitor Thiamidol compared to hydroquinone in women with mild to moderate melasma. After 12 weeks, modified Melasma Area and Severity Index scores significantly impr…

The Journal of investigative dermatology

Anti-inflammatory / anti-oxidant activity of ingredients of sunscreen products? Implications for SPF.

Jun, 2019

The Sun Protection Factor (SPF) of sunscreen products is derived from testing in vivo their ability to prevent erythema ("sunburn"). Recently, certain articles have raised concerns that sunscreen products may actively suppress erythema via anti-inflammatory / anti-oxidant (AI/AO) activity. These articles reason that this may result in a higher labelled SPF value than that provided by the efficacy of the UVR filters alone, giving consumers a "false sense of security". On the other hand, since inflammatory processes are known to play a role in the mechanisms of photodamage / skin cancer induction and propagation, AI/AO acti…

International journal of cosmetic science Carregar mais  

Visible light accelerates the ultraviolet A-induced degradation of eumelanin and pheomelanin.

05, 2019

Exposure to excess ultraviolet (UV) A radiation induces the degradation/modification of both eumelanin and pheomelanin that may be deleterious to pigmented tissues. Although the spectral distribution of solar energy comprises nearly half of visible light (VL), few studies have been conducted to examine the role of VL in the photodegradation of both types of melanin, either VL alone or in combination with UVA. In this study, we examined the effects of physiological doses of VL (150 to 300 J cm ) alone or in combination with a physiological dose of UVA (20 J cm ) in normal human epidermal melanocytes. The degradation/modification of melanin structures was evaluated by our chemical degradation-high performance liquid chromatography methods. The results show that VL accelerates UVA-induced changes in the structural features of both eumelanin and pheomelanin, although VL or UVA alone induced only minor changes in melanin structure. The differential spectral method provides support for the additive effects of VL. Ler mais

Pigment cell & melanoma research

Inhibition of Human Tyrosinase Requires Molecular Motifs Distinctively Different from Mushroom Tyrosinase.

07, 2018

Tyrosinase is the rate-limiting enzyme of melanin production and, accordingly, is the most prominent target for inhibiting hyperpigmentation. Numerous tyrosinase inhibitors have been identified, but most of those lack clinical efficacy because they were identified using mushroom tyrosinase as the target. Therefore, we used recombinant human tyrosinase to screen a library of 50,000 compounds and compared the active screening hits with well-known whitening ingredients. Hydroquinone and its derivative arbutin only weakly inhibited human tyrosinase with a half-maximal inhibitory concentration (IC) in the millimolar range, and kojic acid showed a weak efficacy (IC > 500 μmol/L). The most potent inhibitors of human tyrosinase identified in this screen were resorcinyl-thiazole derivatives, especially the newly identified Thiamidol (Beiersdorf AG, Hamburg, Germany) (isobutylamido thiazolyl resorcinol), which had an IC of 1.1 μmol/L. In contrast, Thiamidol only weakly inhibited mushroom tyrosinase (IC = 108 μmol/L). In melanocyte cultures, Thiamidol strongly but reversibly inhibited melanin production (IC = 0.9 μmol/L), whereas hydroquinone irreversibly inhibited melanogenesis (IC = 16.3 μmol/L). Clinically, Thiamidol visibly reduced the appearance of age spots within 4 weeks, and after 12 weeks some age spots were indistinguishable from the normal adjacent skin. The full potential of Thiamidol to reduce hyperpigmentation of human skin needs to be explored in future studies. Ler mais

The Journal of investigative dermatology

Validation of an in vitro sun protection factor (SPF) method in blinded ring-testing.

Apr, 2018

The objective of this work was to investigate the utility of a new in vitro SPF test method in blinded ring-testing, against new ISO acceptance criteria. Ler mais

International journal of cosmetic science

Structure-Activity Relationships of Thiazolyl Resorcinols, Potent and Selective Inhibitors of Human Tyrosinase.

Feb, 2018

Tyrosinase inhibitors are of great clinical interest as agents for the treatment of hyperpigmentary disorders; however, most compounds described in the literature lack clinical efficiency due to insufficient inhibitory activity against human tyrosinase (hTyr). Recently, we reported that thiazolyl resorcinols (4-resorcinylthiazol-2-amines and -amides) are both selective and efficacious inhibitors of hTyr in vitro and in vivo. Here, we measured dose-activity profiles of a large number of thiazolyl resorcinols and analogous compounds to better understand the molecular basis of their interaction with hTyr. We show that both the resorcinyl moiety and the thiazole ring must be intact to allow efficient inhibition of hTyr, while the substituents at the thiazole 2-amino group confer additional inhibitory activity, depending on their size and polarity. The results of molecular docking simulations were in excellent agreement with the experimental data, affording a rationale for the structural importance of either ring. We further propose that a special type of interaction between the thiazole sulfur and a conserved asparagine residue is partially responsible for the superior inhibitory activity of thiazolyl resorcinols against hTyr. Ler mais

International journal of molecular sciences

Molecular and histological characterization of age spots.

03, 2017

Age spots, also called solar lentigines and lentigo senilis, are light brown to black pigmented lesions of various sizes that typically develop in chronically sun-exposed skin. It is well known that age spots are strongly related to chronic sun exposure and are associated with photodamage and an increased risk for skin cancer; however, the mechanisms underlying their development remain poorly understood. We used immunohistochemical analysis and microarray analysis to investigate the processes involved in their formation, focusing on specific markers associated with the functions and proliferation of melanocytes and keratinocytes. A total of 193 genes were differentially expressed in age spots, but melanocyte pigment genes were not among them. The increased expression of keratins 5 and 10, markers of basal and suprabasal keratinocytes, respectively, in age spots suggests that the increased proliferation of basal keratinocytes combined with the decreased turnover of suprabasal keratinocytes leads to the exaggerated formation of rete ridges in lesional epidermis which in turn disrupts the normal processing of melanin upwards from the basal layer. Based on our results, we propose a model for the development of age spots that explains the accumulation of melanin and the development of extensive rete ridges in those hyperpigmented lesions. Ler mais

Experimental dermatology

Impaired glyoxalase activity is associated with reduced expression of neurotrophic factors and pro-inflammatory processes in diabetic skin cells.

01, 2017

Patients suffering from type II diabetes develop several skin manifestations including cutaneous infections, diabetic dermopathy, diabetic bullae and acanthosis nigricans. Diabetic micro- and macroangiopathy as well as diabetic neuropathy are believed to play a crucial role in the development of diabetic skin disorders. A reduced cutaneous nerve fibre density was reported in diabetic subjects, which subsequently leads to impaired sensory nerve functions. Using an innervated skin model, we investigated the impact of human diabetic dermal fibroblasts and keratinocytes on porcine sensory neurons. Diabetic skin cells showed a reduced capacity to induce neurite outgrowth due to a decreased support with neurotrophic factors, such as NGF. Furthermore, diabetic keratinocytes displayed insulin resistance and increased expression of pro-inflammatory cytokines demonstrating the persistent effect of diabetes mellitus on human skin cells. Dysregulations were related to a significantly reduced glyoxalase enzyme activity in diabetic keratinocytes as experimentally reduced glyoxalase activity mimicked the increase in pro-inflammatory cytokine expression and reduction in NGF. Our results demonstrate an impaired crosstalk of diabetic skin cells and sensory neurons favouring hypo-innervation. We suggest that reduced methylglyoxal detoxification contributes to an impaired neurocutaneous interaction in diabetic skin. Ler mais

Experimental dermatology

Tyrosine peptides provide a color palette upon tyrosinase oxidation: nanosize does matter.

01, 2017

Ler mais

Pigment cell & melanoma research

Identification of Genes Expressed in Hyperpigmented Skin Using Meta-Analysis of Microarray Data Sets.

Oct, 2015

More than 375 genes have been identified that are involved in regulating skin pigmentation and these act during development, survival, differentiation, and/or responses of melanocytes to the environment. Many of these genes have been cloned, and disruptions of their functions are associated with various pigmentary diseases; however, many remain to be identified. We have performed a series of microarray analyses of hyperpigmented compared with less pigmented skin to identify genes responsible for these differences. The rationale and goal for this study was to perform a meta-analysis on these microarray databases to identify genes that may be significantly involved in regulating skin phenotype either directly or indirectly that might not have been identified due to subtle differences by any of these individual studies alone. The meta-analysis demonstrates that 1,271 probes representing 921 genes are differentially expressed at significant levels in the 5 microarray data sets compared, providing new insights into the variety of genes involved in determining skin phenotype. Immunohistochemistry was used to validate two of these markers at the protein level (TRIM63 and QPCT), and we discuss the possible functions of these genes in regulating skin physiology. Ler mais

The Journal of investigative dermatology

Genome-wide expression analysis of wounded skin reveals novel genes involved in angiogenesis.

Jul, 2015

Wound healing is a multistage process involving collaborative efforts of different cell types and distinct cellular functions. Among others, the high metabolic activity at the wound site requires the formation and sprouting of new blood vessels (angiogenesis) to ensure an adequate supply of oxygen and nutrients for a successful healing process. Thus, a cutaneous wound healing model was established to identify new factors that are involved in vascular formation and remodeling in human skin after embryonic development. By analyzing global gene expression of skin biopsies obtained from wounded and unwounded skin, we identified a small set of genes that were highly significant differentially regulated in the course of wound healing. To initially investigate whether these genes might be involved in angiogenesis, we performed siRNA experiments and analyzed the knockdown phenotypes using a scratch wound assay which mimics cell migration and proliferation in vitro. The results revealed that a subset of these genes influence cell migration and proliferation in primary human endothelial cells (EC). Furthermore, histological analyses of skin biopsies showed that two of these genes, ALBIM2 and TMEM121, are colocalized with CD31, a well known EC marker. Taken together, we identified new genes involved in endothelial cell biology, which might be relevant to develop therapeutics not only for impaired wound healing but also for chronic inflammatory disorders and/or cardiovascular diseases. Ler mais

Angiogenesis

UV exposure modulates hemidesmosome plasticity, contributing to long-term pigmentation in human skin.

May, 2015

Human skin colour, ie pigmentation, differs widely among individuals, as do their responses to various types of ultraviolet radiation (UV) and their risks of skin cancer. In some individuals, UV-induced pigmentation persists for months to years in a phenomenon termed long-lasting pigmentation (LLP). It is unclear whether LLP is an indicator of potential risk for skin cancer. LLP seems to have similar features to other forms of hyperpigmentation, eg solar lentigines or age spots, which are clinical markers of photodamage and risk factors for precancerous lesions. To investigate what UV-induced molecular changes may persist in individuals with LLP, clinical specimens from non-sunburn-inducing repeated UV exposures (UVA, UVB or UVA + UVB) at 4 months post-exposure (short-term LLP) were evaluated by microarray analysis and dataset mining. Validated targets were further evaluated in clinical specimens from six healthy individuals (three LLP+ and three LLP-) followed for more than 9 months (long-term LLP) who initially received a single sunburn-inducing UVA + UVB exposure. The results support a UV-induced hyperpigmentation model in which basal keratinocytes have an impaired ability to remove melanin that leads to a compensatory mechanism by neighbouring keratinocytes with increased proliferative capacity to maintain skin homeostasis. The attenuated expression of SOX7 and other hemidesmosomal components (integrin α6β4 and plectin) leads to increased melanosome uptake by keratinocytes and points to a spatial regulation within the epidermis. The reduced density of hemidesmosomes provides supporting evidence for plasticity at the epidermal-dermal junction. Altered hemidesmosome plasticity, and the sustained nature of LLP, may be mediated by the role of SOX7 in basal keratinocytes. The long-term sustained subtle changes detected are modest, but sufficient to create dramatic visual differences in skin colour. These results suggest that the hyperpigmentation phenomenon leading to increased interdigitation develops in order to maintain normal skin homeostasis in individuals with LLP. Ler mais

The Journal of pathology

UV radiation induces CXCL5 expression in human skin.

Apr, 2015

CXCL5 has recently been identified as a mediator of UVB-induced pain in rodents. To compare and to extend previous knowledge of cutaneous CXCL5 regulation, we performed a comprehensive study on the effects of UV radiation on CXCL5 regulation in human skin. Our results show a dose-dependent increase in CXCL5 protein in human skin after UV radiation. CXCL5 can be released by different cell types in the skin. We presumed that, in addition to immune cells, non-immune skin cells also contribute to UV-induced increase in CXCL5 protein. Analysis of monocultured dermal fibroblasts and keratinocytes revealed that only fibroblasts but not keratinocytes displayed up regulated CXCL5 levels after UV stimulation. Whereas UV treatment of human skin equivalents, induced epidermal CXCL5 mRNA and protein expression. Up regulation of epidermal CXCL5 was independent of keratinocyte differentiation and keratinocyte-keratinocyte interactions in epidermal layers. Our findings provide first evidence on the release of CXCL5 in UV-radiated human skin and the essential role of fibroblast-keratinocyte interaction in the regulation of epidermal CXCL5. Ler mais

Experimental dermatology

Photobiological implications of melanin photoprotection after UVB-induced tanning of human skin but not UVA-induced tanning.

Mar, 2015

Repetitive suberythemal UVA and/or UVB exposures were used to generate comparable UV-induced tans in human skin over the course of 2 weeks. To evaluate the potential photoprotective values of those UVA- and/or UVB- induced tans and to avoid the confounding issue of residual UV-induced DNA damage, we waited 1 week before challenging those areas with a 1.5 MED of UVA+UVB after which we measure DNA damage. The results show that the type of UV used to induce skin pigmentation affects the redistribution of melanin in the skin and/or de novo melanin synthesis. The UVA-induced tans failed to even provide a minimal SPF of 1.5, which suggests that producing a tan with UVA-rich sunlamps prior to a holiday or vacation is completely counterproductive. Ler mais

Pigment cell & melanoma research

Licochalcone A activates Nrf2 in vitro and contributes to licorice extract-induced lowered cutaneous oxidative stress in vivo.

Jan, 2015

The retrochalcone licochalcone A (LicA) has previously been shown to possess antimicrobial and anti-inflammatory properties. In this study, we focused on pathways responsible for the antioxidative properties of LicA. In vitro, LicA protected from oxidative stress mediated by reactive oxygen species (ROS) by activating the expression of cytoprotective phase II enzymes. LicA induced nuclear translocation of NF-E2-related factor 2 (Nrf2) in primary human fibroblasts and elevated the expression of the cytoprotective and anti-inflammatory enzymes heme oxygenase 1 and glutamate-cysteine ligase modifier subunit. LicA-treated cells displayed a higher ratio of reduced to oxidized glutathione and decreased concentrations of ROS in UVA-irradiated human dermal fibroblasts, as well as in activated neutrophils. In vivo, ultraweak photon emission analysis of skin treated with LicA-rich licorice extract revealed a significantly lowered UVA-induced luminescence, indicative for a decrease in oxidative processes. We conclude from these data that topical application of licorice extract is a promising approach to induce Nrf2-dependent cytoprotection in human skin. Ler mais

Experimental dermatology

Human tyrosinase is able to oxidize both enantiomers of rhododendrol.

Nov, 2014

Racemic RS-4-(4-hydroxyphenyl)-2-butanol (rhododendrol, RD) was used as a topical skin-whitening agent until it was recently reported to induce leukoderma. We then showed that oxidation of RD with mushroom tyrosinase rapidly produces RD-quinone, which is quickly converted to RD-cyclic quinone and RD-hydroxy-p-quinone. In this study, we examined whether either or both of the enantiomers of RD can be oxidized by human tyrosinase. Using a chiral HPLC column, racemic RD was resolved optically to R(-)-RD and S(+)-RD enantiomers. In the presence of a catalytic amount of l-dopa, human tyrosinase, which can oxidize l-tyrosine but not d-tyrosine, was found to oxidize both R(-)- and S(+)-RD to give RD-catechol and its oxidation products. S(+)-RD was more effectively oxidized than l-tyrosine, while R(-)-RD was less effective. These results support the notion that the melanocyte toxicity of RD depends on its tyrosinase-catalyzed conversion to toxic quinones and the concomitant production of reactive oxygen species. Ler mais

Pigment cell & melanoma research

Epidermal gene expression and ethnic pigmentation variations among individuals of Asian, European and African ancestry.

Oct, 2014

Differences in visible skin pigmentation give rise to the wide variation of skin colours seen in racial/ethnic populations. Skin pigmentation is important not only from cosmetic and psychological points of view, but more importantly because of its implications for the risk of all types of skin cancers, on photoaging, etc. Despite differences in those parameters in Caucasian and Asian skin types, they are remarkably similar in their production and distribution of melanins, and the mechanism(s) underlying their different characteristics have remained obscure. In this study, we used microarray analysis of skin suction blisters to investigate molecular differences underlying the determination of pigmentation in various skin types, and we used immunohistochemistry to validate the expression patterns of several interesting targets that were identified. Intriguingly, Caucasian and Asian skins had highly similar gene expression patterns that differed significantly from the pattern of African skin. The results of this study suggest the dynamic interactions of different types of cells in human skin that regulate its pigmentation, reveal that the known pigmentation genes have a limited contribution and uncover a new array of genes, including NINL and S100A4, that might be involved in that regulation. Ler mais

Experimental dermatology

Photoaging of human retinal pigment epithelium is accompanied by oxidative modifications of its eumelanin.

May, 2013

Although photodegradation of the retinal pigment epithelium (RPE) melanin may contribute to the etiology of age-related macular degeneration, the molecular mechanisms of this phenomenon and the structural changes of the modified melanin remain unknown. Recently, we found that the ratio of pyrrole-2,3,4,5-tetracarboxylic acid (PTeCA) to pyrrole-2,3,5-tricarboxylic acid (PTCA) is a marker for the heat-induced cross-linking of eumelanin. In this study, we examined UVA-induced changes in synthetic eumelanins to confirm the usefulness of the PTeCA/PTCA ratio as an indicator of photo-oxidation and compared changes in various melanin markers and their ratios in human melanocytes exposed to UVA, in isolated bovine RPE melanosomes exposed to strong blue light and in human RPE cells from donors of various ages. The results indicate that the PTeCA/PTCA ratio is a sensitive marker for the oxidation of eumelanin exposed to UVA or blue light and that eumelanin and pheomelanin in human RPE cells undergo extensive structural modifications due to the life-long exposure to blue light. Ler mais

Pigment cell & melanoma research

Expression in non-melanogenic systems and purification of soluble variants of human tyrosinase.

May, 2013

Mammalian tyrosinases are key enzymes of melanin formation. Their native forms undergo complex maturation and sorting processes before being integrated into the melanosomal membrane, which greatly complicates their heterologous expression in other cell types. In the present work, we constructed several differently truncated, soluble variants of human tyrosinase and studied their properties after expression in HEK 293 cells. In addition, we prepared two affinity-tagged forms of the enzyme for expression in the yeast Kluyveromyces lactis and HEK cells, respectively. A Strep-tagged variant was secreted by K. lactis in excellent yields but found to be inactive, whereas a His-tagged variant secreted by HEK 293 cells in an active state could be purified from cell supernatants to near homogeneity. The resulting preparation consisted of an inactive, probably unglycosylated species of about 57 kDa and several glycosylated forms with masses between 63 and 75 kDa, as confirmed by activity staining, Western blotting and mass spectrometry. Ler mais

Biological chemistry

The revised COLIPA in vitro UVA method.

Feb, 2013

A multicentred study derived from the COLIPA in vitro UVA method was performed to assess the influence of test conditions on UVA protection factor (UVAPF) values in terms of amplitude, reproducibility between laboratories and correlation with in vivo UVA results. Eight products with a range of in vivo UVAPF from three to 29 were used. Two different types of plates, namely high-roughness (5 μm) and low-roughness (2 μm) plates, were used with a different application rate for each (1.3 mg cm(-2) and 0.75 mg cm(-2) respectively). The UVR dose applied to both plate types followed the same principle as the original test (1.2 J. cm(-2)  × UVAPF0). Strong, significant correlations between in vitro and in vivo UVAPF values were observed for both plate types (Pearson correlation > 0.9, P ≤ 0.01). The correlation and slope obtained with the low-roughness plates confirmed the previous results obtained by COLIPA. Across all laboratories, higher UVAPF values were obtained on the high-roughness plates (P < 0.01). Reproducibility of UVAPF values between laboratories was comparable between the two plate roughness values (low roughness, COV = 8%; high roughness, COV = 12%). Considering the in vitro/in vivo comparisons, a regression slope of 0.83 was observed for the low-roughness plates, in comparison with a value of 1.05 for the high-roughness plates. The accuracy of the method was improved, therefore, with the use of the high-roughness plates. With a constraint to recommend the use of only one plate type in the COLIPA UVA in vitro Test, the high-roughness plate was selected on an on-going basis to limit variability of results and to provide better accuracy with in vivo data. Ler mais

International journal of cosmetic science

4-n-butylresorcinol, a highly effective tyrosinase inhibitor for the topical treatment of hyperpigmentation.

Jan, 2013

Hyperpigmentary disorders like melasma, actinic and senile lentigines are a major cosmetic concern. Therefore, many topical products are available, containing various active ingredients aiming to reduce melanin production and distribution. The most prominent target for inhibitors of hyperpigmentation is tyrosinase, the key regulator of melanin production. Many inhibitors of tyrosinase are described in the literature; however, most of them lack clinical efficacy. Ler mais

Journal of the European Academy of Dermatology and Venereology : JEADV

How much sun protection is needed?: Are we on the way to full-spectrum protection?

Jul, 2012

The skin-damaging effects of the UV part of solar radiation are well known and therefore are a focus of photobiological research. However, UVR is only a small part of the solar radiation flux that reaches the earth's surface. In this issue, Liebel et al. shed light on the biological effects of visible solar radiation on human skin. Ler mais

The Journal of investigative dermatology

UVA-induced oxidative degradation of melanins: fission of indole moiety in eumelanin and conversion to benzothiazole moiety in pheomelanin.

Jul, 2012

Eumelanin is photoprotective while pheomelanin is phototoxic to pigmented tissues. Ultraviolet A (UVA)-induced tanning seems to result from the photooxidation of pre-existing melanin and contributes no photoprotection. However, data available for melanin biodegradation remain limited. In this study, we first examined photodegradation of eumelanin and pheomelanin in human black hairs and found that the ratio of Free (formed by peroxidation in situ) to Total (after hydrogen peroxide oxidation) pyrrole-2,3,5-tricarboxylic acid (PTCA) increases with hair aging, indicating fission of the dihydroxyindole moiety. In red hair, the ratio of thiazole-2,4,5-tricarboxylic acid (TTCA) to 4-amino-3-hydroxyphenylalanine (4-AHP) increases with aging, indicating the conversion from benzothiazine to benzothiazole moiety. These photodegradation of melanins were confirmed by UVA (not UVB) irradiation of melanins from mice and human hairs and synthetic eumelanin and pheomelanin. These results show that both eumelanin and pheomelanin degrade by UVA and that Free/Total PTCA and TTCA/4-AHP ratios serve as sensitive indicators of photodegradation. Ler mais

Pigment cell & melanoma research

Characterization of the bioactive motif of neuregulin-1, a fibroblast-derived paracrine factor that regulates the constitutive color and the function of melanocytes in human skin.

Jul, 2012

Interactions between melanocytes and neighboring cells in the skin (keratinocytes and fibroblasts) play important roles in regulating human skin color. We recently reported that neuregulin-1 (NRG1) is highly expressed in fibroblasts from Fitzpatrick type VI skin (the darkest) and at least in part determines the constitutive color of human skin. We have now characterized the bioactive motif of NRG1 that is involved in modulating melanin production in human melanocytes. We found that 8-mer motifs (PSRYLCKC and LCKCPNEF) increased melanin production but did not increase the proliferation of melanocytes; the minimum fragment that could elicit that effect was the tetrapeptide LCKC. This smaller bioactive peptide might have an advantage in clinical applications in which it modulates only pigmentation and does not stimulate melanocyte proliferation. Ler mais

Pigment cell & melanoma research

UV radiation induces the release of angiopoietin-2 from dermal microvascular endothelial cells.

Feb, 2012

In human skin, ultraviolet radiation (UVR)-induced erythema is characterized by the inflammatory and angiogenic activation of dermal endothelial cells. Recently, it has been shown that the release of angiopoietin-2 (Ang-2) from cytoplasmic storages of activated endothelial cells is crucial for the induction of inflammation and angiogenesis. Therefore, we hypothesized that UVR exposure induces the release of Ang-2 from endothelial cells controlling the early steps of erythema formation. In an in vivo study, suction blister fluids generated from UV-irradiated skin showed significantly increased concentrations of Ang-2, vascular endothelial growth factor (VEGF) and tumor necrosis factor-α (TNFα). Likewise, in vitro UVR exposure of human dermal microvascular endothelial cells (HDMECs) triggered the release of Ang-2 that enhanced the pro-inflammatory response of these cells and facilitated their detachment from smooth muscle cells as evidenced by employing a three-dimensional co-culture spheroid model. These effects were inhibited by angiopoietin-1 (Ang-1), which competes with Ang-2 for binding the endothelial cell Tie2 receptor. Collectively, these observations suggest that UVR triggers the release of endothelial Ang-2 which may promote the destabilization and pro-inflammatory phenotype of the microvascular endothelium. As Ang-1 counteracts UVR-induced effects, stimulating the Ang-1 activity may represent a strategy to stabilize the dermal microcirculatory system, thus protecting against UVR-induced skin damages. Ler mais

Experimental dermatology

TRP-channel-specific cutaneous eicosanoid release patterns.

Dec, 2011

Analyzing mechanisms and key players in peripheral nociception nonneuronal skin cells are getting more and more into focus. Herein we investigated the functional expression of TRPV1 and TRPA1 in human keratinocytes and fibroblasts and assessed proinflammatory lipid mediator release upon their stimulation as well as sensory effects after topical application, combining in vitro and in vivo approaches. In vitro, the expression of functional TRPV1 and TRPA1 channels on fibroblasts and keratinocytes was confirmed via immunofluorescence, qualitative real time (RT) polymerase chain reaction, and cellular Ca(2+) influx measurements. Additionally, the agonists allyl isothiocyanate (TRPA1) and capsaicin (TRPV1) induce a differential secretion pattern of the eicosanoids PGE(2) and LTB(4) in human dermal fibroblasts and keratinocytes, which was also detectable invivo, analyzing suction blister fluid at various times after short-term topical application. Capsaicin provoked the release of LTB(4) at 2 and 24 hours. In contrast, PGE(2) levels were reduced upon stimulation. Allyl isothiocyanate, however, increased PGE(2) levels only at 24 hours, but did not alter LTB(4) levels. In parallel, heat pain thresholds were reduced by both agents after short-term topical application, but only AITC provoked a long-lasting local erythema. In conclusion, the agonist-induced activation of nociceptors by TRPA1 and TRPV1 elicits painful sensations, whereas nonneuronal tissue cells respond with differential release of inflammatory mediators, thus influencing local vasodilatation and neuronal sensitization. These results have implications for the application of transient receptor potential antagonists to improve inflammatory skin conditions and pain management. Ler mais

Pain

Usefulness of alkaline hydrogen peroxide oxidation to analyze eumelanin and pheomelanin in various tissue samples: application to chemical analysis of human hair melanins.

Aug, 2011

Eumelanin and pheomelanin in tissue samples can be specifically measured as the markers pyrrole-2,3,5-tricarboxylic acid (PTCA) and 4-amino-3-hydroxyphenylalanine after acidic permanganate oxidation and hydroiodic acid hydrolysis, respectively. Those degradation methods, although widely applied, are not easily performed in most laboratories. To overcome this difficulty, we developed alkaline H(2)O(2) oxidation in 1 M K(2)CO(3) that produces, in addition to the eumelanin marker PTCA, thiazole-2,4,5-tricarboxylic acid (TTCA) and thiazole-4,5-dicarboxylic acid (TDCA) as markers for pheomelanin and pyrrole-2,3-dicarboxylic acid (PDCA) as a marker for 5,6-dihydroxyindole-derived eumelanin. Those four degradation products can be easily separated by HPLC and analyzed with ultraviolet detection. The alkaline H(2)O(2) oxidation method is simple, reproducible and applicable to all pigmented tissues. Its application to characterize eumelanin and pheomelanin in human hair shows that PTCA and TTCA serve as specific markers for eumelanin and pheomelanin, respectively, although some caution is needed regarding the artificial production of TTCA from eumelanic tissue proteins. Ler mais

Pigment cell & melanoma research