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Minimal Erythema Dose (minimal + erythema_dose)

Distribution by Scientific Domains

Medical Sciences	94%

Selected Abstracts

Determination of the Minimal Erythema Dose and Colorimetric Measurements as Indicators of Skin Sensitivity to UV-B Radiation,

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2004
Sérgio Dornelles
ABSTRACT There is a strong relation between chronic UV-B-induced sunburns and the development of skin cancer. Therefore, it is important to obtain a method that can be reproduced easily to detect individuals with similar skin color but different sensitiveness to sun exposure. The study evaluated 193 healthy volunteers (68% women; the average age was 38 years). They were divided into six groups of at least 30 subjects, according to skin type. The minimal erythema dose (MED) was assessed in two non-sun-exposed areas (thorax-infra-axillary area and on the buttocks), using a UV-B source (0.5 mW/cm2), with openings of 1 cm2, in increasing doses. The same areas were evaluated with a Minolta CR 300 Chromameter (L*a*b* system). The MED values ranged from 13 to 156 mJ/cm2; the coordinate L* (brightness) ranged from 75.96 to 30.15. The correlation between the MED and the brightness was negative in both areas (Pearson's correlation r =,0.91, P < 0.05). Color measurements, especially brightness, can be used to quickly assess skin sensibility. Considering the MED, there is a substantial overlapping of adjacent phototypes, but they could be separated into two groups: more sensitive individuals (Types I, II, III and IV) and less sensitive ones (Types V and VI). [source]

Minimal erythema dose after multiple UV exposures depends on pre-exposure skin pigmentation

PHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 4 2004
M. Henriksen
Background/purpose: Phototherapy consists of multiple ultraviolet (UV) exposures. Most previous studies have focused on erythema following a single UV exposure in fair-skinned persons. Although it is well known that phototherapy lowers the daily UV-threshold dose for erythema in clinical practice, this is insufficiently documented under controlled experimental conditions. The purpose of this study was to quantify the change in the daily threshold for a dose specific erythema grade after 1,4 consecutive daily UV exposures. Methods: Forty-nine healthy volunteers (skin type II,V) with varying pigmentation quantified by skin reflectance. Two UV sources were used: a narrowband UVB (Philips TL01) and a Solar Simulator (Solar Light Co.). Just perceptible erythema after 24 h was chosen as the minimal erythema dose (+); besides + and ++ were assessed. Results: We found a positive and significant exponential relationship between skin pigmentation and UV dose to elicit a specific erythema grade on the back after 1,4 UV exposures. After repetitive UV exposures the UV dose had to be lowered more in dark-skinned persons compared with fair-skinned persons to elicit a certain erythema grade. This applied to both UV sources and all erythema grades. Conclusion: In the dark-skinned persons the daily UV dose after the 4 days UV exposure should be lowered by 40,50% to avoid burns compared with the single UV exposure. For the most fair-skinned persons essentially no reduction in the daily UV dose was needed. Our results indicate that the pre-exposure pigmentation level can guide the UV dosage in phototherapy. [source]

A clinical trial and molecular study of photoadaptation in vitiligo

BRITISH JOURNAL OF DERMATOLOGY, Issue 3 2009
C.L. Hexsel
Summary Background, Photoadaptation to ultraviolet (UV) B phototherapy is due to both pigmentary and nonpigmentary influences. Objectives, To measure photoadaptation in vitiliginous skin and to compare it with normal pigmented skin. Methods, Seventeen patients with Fitzpatrick skin phototypes III,VI with vitiligo received six to nine UVB treatments, two to three times weekly. Minimal erythema dose (MED) testing was done at baseline and after all treatments; the percentage change in MED was analysed as a measure of photoadaptation. The percentage decrease in cyclobutane pyrimidine dimers (CPDs) over 24 h after a single exposure of 1 MED was analysed on vitiliginous and normal skin. Results, The mean ± SD percentage change in MED from before to after treatments was: treated vitiliginous skin 28·5 ± 39·9% (P = 0·015), treated normal skin 35·9 ± 49·9% (P = 0·015), untreated vitiliginous skin 11·9 ± 22·6% (P =0·070), untreated normal skin 25·1 ± 41·3% (P = 0·041). Of these patients, two-thirds had a positive percentage change in MED (photoadaptation). The mean amount of CPDs induced per megabase of DNA immediately after exposure was significantly higher in vitiliginous skin. The mean ± SD percentage decrease in CPDs (rate of repair) in 24 h was 35·7 ± 26·8% in vitiliginous skin (P = 0·027) and 46·2 ± 19·5% in normally pigmented skin (P = 0·001); no difference was noted in the repair in vitiliginous skin compared with normal skin (P = 0·4). Conclusions, Photoadaptation in vitiliginous and normal skin was observed in two-thirds of patients. Vitiliginous skin had significantly more CPDs following UVB exposure; the rate of repair of UVB-induced DNA damage was equivalent to that in normal skin. [source]

Evaluation of a sunscreen photoprotective effect by ascorbic acid assessment in human dermis using microdialysis and gas chromatography mass spectrometry

EXPERIMENTAL DERMATOLOGY, Issue 3 2005
Nathalie Lévêque
Abstract:, Ultraviolet irradiation causes adverse effects like sunburn, photosensitivity reactions or immunologic suppression. The aim of this study was to evaluate the photo-protective outcome of a sunscreen cream (SPF8) by the determination of erythema indexes and the assessment of ascorbic acid and its metabolites in human dermis. These substances were used as markers of oxidative effect. Eight healthy female subjects were enrolled in this study. Two abdominal areas were exposed to solar simulated irradiation with three minimal erythema dose, one with SPF8 application and the other site without SPF8 application. Two other areas were used as control, one without SPF8 application and the other site after SPF8 application. Ascorbic acid and its metabolites (dehydroascorbic acid, threonic acid, oxalic acid and xylose) were collected from human dermis by microdialysis and assessed by gas chromatography mass spectrometry. Irradiated site without sunscreen application had significantly demonstrated lower dermis ascorbic acid concentrations and a higher erythema index than the three other sites (P < 0.05). Threonic acid, oxalic acid and xylose dermis concentrations were significantly higher in site III than in the control site I (P < 0.05). The protected-irradiated site did not show erythema formation and there was stability of ascorbic acid dermis concentrations with non-variation in its metabolites. The assessment of ascorbic acid and its metabolites in human dermis could be an efficient tool to demonstrate the oxidative process and consequently to control the efficiency of sunscreen creams against undesirable UV effects. [source]

Protective effects of a topical antioxidant mixture containing vitamin C, ferulic acid, and phloretin against ultraviolet-induced photodamage in human skin

JOURNAL OF COSMETIC DERMATOLOGY, Issue 4 2008
Christian Oresajo PhD
Summary Background, Ultraviolet (UV) irradiation of the skin leads to acute inflammatory reactions, such as erythema, sunburn, and chronic reactions, including premature skin aging and skin cancer. Aim, In this study, the effects of a topical antioxidant mixture consisting of vitamin C, ferulic acid, and phloretin on attenuating the harmful effects of UV irradiation on normal healthy volunteers were studied using biomarkers of skin damage. Subjects/methods, Ten subjects (age, 18,60 years; Fitzpatrick skin types II and III) were randomized and treated with antioxidant product or vehicle control on the lower back for four consecutive days. On day 3, the minimal erythema dose (MED) was determined for each subject at a different site on the back. On day 4, the two test sites received solar-simulated UV irradiation 1,5× MED at 1× MED intervals. On day 5, digital images were taken, and 4-mm punch biopsies were collected from the two 5× MED test sites and a control site from each subject for morphology and immunohistochemical studies. Results, UV irradiation significantly increased the erythema of human skin in a linear manner from 1× to 5× MED. As early as 24 h after exposure to 5× MEDs of UV irradiation, there were significant increases in sunburn cell formation, thymine dimer formation, matrix metalloproteinase-9 expression, and p53 protein expression. All these changes were attenuated by the antioxidant composition. UV irradiation also suppressed the amount of CD1a-expressing Langerhans cells, indicating immunosuppressive effects of a single 5× MED dose of UV irradiation. Pretreatment of skin with the antioxidant composition blocked this effect. Conclusion, This study confirms the protective role of a unique mixture of antioxidants containing vitamin C, ferulic acid, and phloretin on human skin from the harmful effects of UV irradiation. Phloretin, in addition to being a potent antioxidant, may stabilize and increase the skin availability of topically applied vitamin C and ferulic acid. We propose that antioxidant mixture will complement and synergize with sunscreens in providing photoprotection for human skin. [source]

Variables in full-body ultraviolet B treatment of skin diseases

PHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 3 2010
Hans Christian Wulf
Ultraviolet B (UVB) treatment is most often performed according to a fixed schedule, not necessarily considering important variables such as UV intensity, type of UVB source and skin pigmentation. These variables can rather easily be taken into consideration by the right choice of dosing unit. The advantage of going from dosing in time to Joule to standard erythema dose or to minimal erythema dose is considered. The size of most variables may be diminished considerably. Following these guidelines, it is possible to increase the efficacy of UVB phototherapy without increasing the risk of unintentional burning. [source]

Minimal erythema dose after multiple UV exposures depends on pre-exposure skin pigmentation

UV-induced skin changes due to regular use of commercial sunbeds

PHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 5 2002
J. Ruegemer
Background/aim: Increased pigmentation and thickening of the epidermis are the most important photoprotective skin reactions induced by ultraviolet (UV) radiation. The present study was designed to find out what changes are induced by regular use of commercial sunbeds twice weekly over a period of 6 weeks. Methods: The parameters analysed were skin pigmentation measured by chromametry, minimal erythema dose (MED) as a parameter of light sensitivity, epidermal thickening as determined by histology, induction of keratinocyte apoptosis as determined by TUNEL staining and antioxidant metabolism as measured by changes of cis - and trans -urocanic acid (UCA) content of the skin. Results: As expected, chromametry confirmed the clinically obvious increased skin pigmentation. However, no increase in MED was observed. In addition, neither epidermal thickening nor sunburn cells were seen. Significant detectable changes in proportion of the UCA isomer content of the UV-exposed skin were seen. The total UCA and cis -UCA content increased significantly between nearly all points of measurement. The amount of trans -UCA first decreased, then increased significantly between the different time points. Conclusion: Our data indicate that sunbed-induced tanning is non-protective, which has to be addressed for persons looking for this effect before planning a stay in a sunny climate. However, sunbed-induced tanning may influence immunological reactions. [source]

A full-UV spectrum absorbing daily use cream protects human skin against biological changes occurring in photoaging

PHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 4 2000
S. Seité
Background: There is overwhelming evidence that exposure of human skin to ultraviolet radiations (UVR) leads to the development of cutaneous photoaging and eventually to neoplasia. This study was designed to evaluate in humans the protection afforded by a daily use cream containing a photostable combination of UVB and UVA absorbers (Uvinul® N539, Parsol® 1789 and Mexoryl® SX) providing a continuous absorption through the entire UV spectrum, against damages induced by repeated daily exposure to solar simulated radiation (SSR). Methods: Buttock skin of 12 healthy volunteers was exposed 5 days per week for 6 weeks to one minimal erythema dose of solar simulated radiation per exposure. The following parameters in treated and untreated skin were evaluated: erythema, pigmentation, skin hydration, skin microtopography, histology and immunochemistry, and collagen and metalloproteinase (MMP) mRNA levels. Results: In SSR exposed unprotected skin sites, we observed melanization and changes in the skin hydration and microtopography. The epidermis revealed a significant increase in stratum corneum and stratum granulosum thickness. In the dermis, an enhanced expression of tenascin and a reduced expression of type I pro-collagen were evidenced just below the dermal epidermal junction. Although we were unable to visualize any change in elastic fibers in exposed buttock skin, a slightly increased deposition of lysozyme and alpha 1 antitrypsin on these fibers was observed using immunofluorescence techniques. Furthermore, types I and III collagen mRNA were slightly increased and a significant enhancement (up to 2.8-fold) of MMP-2 mRNA level was observed. The daily use cream was shown to prevent all these biological changes. Conclusion: Our results show in vivo that an appropriate full-UV spectrum product significantly reduces the solar-UV-induced skin damage, demonstrating the benefit of daily photoprotection. [source]

Itch and scratching as predictors of time to clearance of psoriasis with narrow-band ultraviolet B therapy

BRITISH JOURNAL OF DERMATOLOGY, Issue 3 2009
A.W.M. Evers
Summary Background, Narrow-band ultraviolet (UV) B phototherapy is an effective treatment for psoriasis. However, there is considerable variability in the number of treatment sessions needed to achieve psoriasis clearance. While several clinical and treatment-related factors predict time to clearance, the effect of itching and scratching on the number of irradiation sessions is insufficiently understood. Objective, Predictors of the time to clearance were assessed in patients with psoriasis who were referred for UVB treatment in a randomized double-blind comparison of irradiation regimens for UVB phototherapy. Methods, After randomization to either UVB irradiation with a suberythematogenic or an erythematogenic regimen, patients were irradiated with 20% and 40% incremental doses, respectively, three times weekly. The Psoriasis Area and Severity Index (PASI) score was measured at baseline and every 4 weeks, and itching and habitual scratching were measured at baseline. Results, Among the 77 patients who achieved psoriasis clearance (90% reduction of PASI), itching and scratching were correlated with the number of irradiation sessions needed to achieve clearance, with higher levels of itch and scratching predicting more sessions. These effects remained significant after controlling for the initial PASI score, irradiation schemes, minimal erythema dose (MED), skin type, cumulative dose, protocol adjustments and lifestyle factors (smoking habits and alcohol consumption). Conclusions, Patients with higher levels of itch and scratching need more irradiation sessions to achieve clearance of psoriasis with UVB phototherapy. Systematic assessment of the severity of itch and scratching, followed by short-term itch-coping programmes for patients at risk, might be a cost-effective, adjunct to UVB therapy. [source]

Chronic actinic dermatitis treated with mycophenolate mofetil

BRITISH JOURNAL OF DERMATOLOGY, Issue 4 2005
M.A. Thomson
Summary Chronic actinic dermatitis (CAD) is a persistent photodermatosis that usually affects elderly men. We report two male patients, aged 55 years (patient A) and 49 years (patient B), who presented with an eczematous eruption on sun-exposed skin. Phototesting revealed a markedly reduced 24-h minimal erythema dose (MED). Both patients had refractory disease and developed significant side-effects to conventional therapies, including topical steroids, prednisolone, psoralen with ultraviolet A, azathioprine and ciclosporin. They had each received at least 6 years of treatment prior to commencing mycophenolate mofetil (MMF). Each noted a significant improvement in symptoms within 6 weeks and subsequent clearing of the eczematous lesions. Patient A still requires continuous treatment with MMF 500 mg twice daily to prevent relapses. Patient B maintains remission by using MMF 1 g twice daily only during the spring and summer months. Both patients have tolerated the treatment well with no abnormalities in blood cell counts or liver biochemistry. Since commencing MMF, their quality of life has significantly improved. These observations suggests that MMF should be considered as an alternative treatment to conventional therapies for refractory CAD. [source]

Photosensitivity in patients with lupus erythematosus: a clinical and photobiological study of 100 patients using a prolonged phototest protocol

BRITISH JOURNAL OF DERMATOLOGY, Issue 1 2003
C.J.G. Sanders
SummaryBackground There is a clear relationship between ultraviolet (UV) radiation (UVR) and the clinical manifestations of patients with lupus erythematosus (LE). Cutaneous lesions are induced or exacerbated by exposure to UVR. Of patients with LE, 24,83% are reported to be photosensitive to UVR. LE tumidus appears to be the most photosensitive subtype of LE, followed by subacute cutaneous LE (SCLE). In general, the history of patients with LE correlates poorly with the presence or absence of photosensitivity, due to a delayed time interval between UV exposure and exacerbation of skin lesions. Phototesting using artificial UVR and visible light is a reliable way of diagnosing photosensitivity. Objectives To investigate the photoreactivity of patients with various subtypes of LE using an individualized phototest protocol. The results of phototests were correlated with the history of photosensitivity, the subtype of LE, the presence of autoantibodies and the use of anti-inflammatory medication by these patients. Methods Phototesting with UVA, UVB and visible light was performed in 100 patients with LE. The diagnosis of LE was established both on clinical examination and skin histology. Serological studies were also performed in all patients. The phototests were performed on large skin areas of the forearm or trunk; the first dose was twice the minimal erythema dose and the dosage was increased according to the individual reactions of the patients at the test sites. Follow-up of skin reactions at the test sites was performed for up to 2 months. Histological examination of the photoprovoked skin lesions was carried out in 57 patients. Results Of the 100 patients included (81 women and 19 men; mean age 41 years, range 17,79), 46 had chronic discoid LE, 30 SCLE and 24 systemic LE. An abnormal reaction to UVR and visible light was found in 93% of our patients with LE. No clinical or histological evidence at the phototest sites of polymorphic light eruption was found. There was no correlation between photosensitivity and LE subtype, presence of autoantibodies or medical history. Concomitant use of anti-inflammatory medication seemed to exert only minimal influence on the results of phototesting. Conclusions When using an extended phototesting protocol, almost all patients with LE in this study showed clinical and histological evidence of aberrant photosensitivity. Therefore, patients with LE should receive thorough advice and instruction on photoprotective measures, regardless of their history, LE subtype or presence of autoantibodies. [source]

High-dose squalene ingestion increases type I procollagen and decreases ultraviolet-induced DNA damage in human skin in vivo but is associated with transient adverse effects

CLINICAL & EXPERIMENTAL DERMATOLOGY, Issue 4 2009
S. Cho
Summary Background., Evidence for beneficial effects of squalene on ultraviolet (UV)-induced photoageing of the skin is lacking. Aim., To investigate whether squalene supplementation improves signs and molecular markers of photoageing in human skin in vivo. Methods., In total, 40 female volunteers aged > 50 years received two different doses [13.5 g/day (low-dose group) and 27 g/day (high-dose group)] of squalene for 90 days. At baseline and at the completion of the study, facial wrinkles were measured using skin replicas. Skin samples were taken to compare type I procollagen and matrix metalloproteinase 1 mRNA levels by real-time reverse-transcriptase PCR, and for type I procollagen immunostaining. Skin samples were also taken 24 h after 2 × minimal erythema dose (MED) of UV irradiation before and after squalene intake to assess UV-induced thymine dimer formation and keratinocytic apoptosis. Results., In total, 37 subjects completed the trial. Transient loose stool was experienced by 35% of volunteers in the low-dose group and 55% in the high-dose group. Facial wrinkles decreased significantly (P < 0.05) in the high-dose group, while procollagen type I mRNA levels and MED increased significantly in the low-dose group. Procollagen immunostaining tended to increase in both groups. Facial erythema decreased and pigmentation increased significantly in both groups. UV-induced keratinocytic apoptosis and thymine dimer staining were substantially reduced in both groups. Conclusions., Daily ingestion of 13.5 or 27 g of squalene per day resulted in antiageing effects in photoaged skin. However, in view of the frequent incidence of loose stool experienced by the subjects, the risk,benefit ratio of high-dose squalene supplementation is too high to recommend it for treating skin ageing. [source]

Sensitivity to ultraviolet B is a risk factor for cutaneous melanoma in a Mediterranean population: results from an Italian case,control study

CLINICAL & EXPERIMENTAL DERMATOLOGY, Issue 1 2009
A. Chiarugi
Summary Background., Sun sensitivity is one of the predictors of melanoma risk, together with other individual characteristics such as skin and eye colour and number of naevi. However, it is unclear how best to measure sun sensitivity in order to quantify the individual risk of melanoma. Objectives., In this case,control study, the relationship between minimal erythema dose (MED) and skin colour (both instrumentally assessed) was investigated, and their possible role as independent risk factors for melanoma in a Mediterranean population evaluated. Methods., In total, 143 patients with cutaneous melanoma and 102 controls were enrolled in the study. Skin colour was assessed using a Minolta CR-200 chromameter. For MED calculation, a fluorescent lamp (Philips TL 4W/12) was used as a source of ultraviolet B light. MED was defined as the lowest dose that produced an increase of 2.5 in the redness value, expressed by the parameter a* of the Commission Internationale d'Eclairage (CIE) L*a*b* colour space (,a* = 2.5). Results., A significant excess of risk was associated with increasing L* values of skin colour (P < 0.05; OR = 1.12; 95% CI 1.01,1.24) for each unit of change. Low MED values were also associated with an increasing risk of melanoma, with an excess of risk of 18% (OR = 1.18, 95% CI 1.04,1.35) for every 10 mJ/cm2 of MED reduction. Compared with the highest MED values (> 97.7 mJ/cm2), subjects with MED values , ,50 mJ/cm2 or lower had a > 2-fold increased risk of melanoma (OR = 2.37, 95% CI 1.05,5.38). The effect of decreasing MED value as a melanoma risk factor persisted after adjustment for skin colour and atypical naevi in a multivariate model. Conclusions., In conclusion, both instrumentally assessed skin colour and MED are significant risk factors for malignant melanoma in a Mediterranean population. MED seems be an independent variable in establishing the subject's risk profile. [source]

Production and clearance of cyclobutane dipyrimidine dimers in UV-irradiated skin pretreated with 1% pimecrolimus or 0.1% triamcinolone acetonide creams in normal and atopic patients

EXPERIMENTAL DERMATOLOGY, Issue 5 2006
Laurence Doelker
Background:, Ultraviolet (UV)-induced pyrimidine dimers are an early step in skin carcinogenesis, which is accelerated in the setting of long-term immunosuppression with systemic calcineurin inhibitors. It is not known whether topical application of calcineurin inhibitors exposes to a similar risk. Objective:, To assess the formation and clearance of UV-induced dipyrimidine dimers in human epidermis treated with topical pimecrolimus as compared to topical steroid, vehicle and untreated control. Methods:, Pretreated buttock skin of 20 human volunteers with (10) or without (10) atopic dermatitis was exposed to two minimal erythema doses (MED) of simulated solar radiation. DNA was extracted from epidermis 1 and 24 h postirradiation. Pyrimidine dimers were visualized by immuno slot blots and quantified by chemoluminescence image analysis. Results:, One-hour postirradiation, pimecrolimus-treated epidermis contains less DNA damage as compared to untreated control, but there were no statistically significant differences between pimecrolimus, triamcinolone acetonide and vehicle. Dimer levels at 24 h postirradiation showed no significant differences between different treatments. Conclusion:, Treatment with pimecrolimus cream, triamcinolone acetonide cream and vehicle is not associated with increased epidermal DNA damage at 1 and 24 h post-UV exposure. [source]

In vivo UVB irradiation induces clustering of Fas (CD95) on human epidermal cells

EXPERIMENTAL DERMATOLOGY, Issue 6 2003
Bo Bang
Abstract:,In vitro studies with human cell lines have demonstrated that the death receptor Fas plays a role in ultraviolet (UV)-induced apoptosis. The purpose of the present study was to investigate the relation between Fas expression and apoptosis as well as clustering of Fas in human epidermis after a single dose of UVB irradiation. Normal healthy individuals were irradiated with three minimal erythema doses (MED) of UVB on forearm or buttock skin. Suction blisters from unirradiated and irradiated skin were raised, and Fas, FasL, and apoptosis of epidermal cells were quantified by flow cytometry. Clustering of Fas was demonstrated by confocal laser scanning microscopy on cryostat sections from skin biopsies. Soluble FasL in suction blister fluid was quantified by ELISA. Flow cytometric analysis demonstrated increased expression intensity of Fas after irradiation, with 1.6-, 2.2- and 2.7-fold increased median expression at 24, 48 and 72 h after irradiation, respectively (n = 4). Apoptosis was demonstrated by the TUNEL reaction, and the maximum of apoptotic cells was detected at 48 h after irradiation. Double-staining for Fas and TUNEL showed that apoptosis was restricted to the Fas-positive epidermal subpopulation, but there was no correlation between the intensities of Fas expression and TUNEL reaction. Median expression intensity of FasL-positive cells transiently decreased to 0.9- and 0.8-fold of the preirradiation respective level after 24 h and 48 h, respectively, and returned to the respective preirradiation level at 72 h after irradiation (n = 4). Concentrations of soluble FasL in suction blister fluid from UVB-irradiated skin did not differ from those in unirradiated skin (n = 5). Confocal laser scanning microscopy showed a rapid clustering of Fas within 30 min after irradiation. A simultaneous clustering of the adapter signalling protein FADD suggested that Fas clustering has a functional significance. Our results are in accordance with previous findings from in vitro studies, and suggest that Fas is activated in vivo in human epidermis after UVB exposure. [source]

Modulations of nerve growth factor and Bcl-2 in ultraviolet-irradiated human epidermis

JOURNAL OF CUTANEOUS PATHOLOGY, Issue 6 2003
Catherine M. Stefanato
Background:, Ultraviolet (UV) irradiation to the skin causes apoptosis of keratinocytes. Melanocytes are more resistant to UV-induced apoptosis, due, in part, to high levels of antiapoptotic proteins such as Bcl-2. In vitro studies have shown that nerve growth factor (NGF), a neurotrophic polypeptide, is produced by keratinocytes and exerts a protective role for melanocytes by upregulating Bcl-2. The purpose of this study was to determine NGF and Bcl-2 modulations in UV-irradiated human skin. Methods:, Nine volunteers were irradiated with two minimal erythema doses using solar-simulated UV irradiation. Seventy-two hours post irradiation, skin biopsies were obtained from irradiated and sun-protected skin. The skin specimens were stained with anti-tyrosinase-related protein-1 monoclonal antibody IgG2a (Mel-5), anti-Bcl-2 (monoclonal antibody IgG-kappa), and with anti-NGF (polyclonal antibody IgG). Results:, NGF staining was identified within the cytoplasm of epidermal melanocytes, similar to the staining observed for TRP-1 and Bcl-2. While no significant difference in the number of TRP-1- and Bcl-2-positive melanocytes was observed between irradiated and non-irradiated skin within 72 h, the number of NGF-positive melanocytes decreased significantly, 72 h after UV irradiation (p < 0.024). NGF was also identified within keratinocytes, and while non-irradiated skin exhibited cytoplasmic NGF staining throughout the epidermis, NGF staining was reduced in the lower epidermal layers after UV irradiation. Conclusions:, This is the first in vivo study showing NGF to be present in melanocytes, as well as showing modulations of NGF and Bcl-2 in melanocytes, following solar-simulated UV irradiation. [source]

Effect of photoreactivating light on UV radiation-induced alterations in human skin

PHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 5 2001
S. E. Whitmore
Background/Aims: Photoreactivating light (PRL) after ultraviolet radiation (UVR) exposure causes photoreversal of cyclobutane pyrimidine dimers through the activation of photolyase. Although photoreversal has been demonstrated in the ,three kingdoms of life,' its existence in man remains controversial. We sought evidence for photoreversal in man. Methods and Results: Seven subjects were spot-irradiated at two sites with 4 minimal erythema doses (MED) of solar-simulating UVR. Of the two sites, one was then immediately exposed to a PRL source. Epidermal biopsies were taken immediately after exposure. No significant difference in the quantity of pyrimidine dimers was detected comparing the ,UVR only' site to the ,UVR, PRL-exposed' site. Biopsies were repeated 24 h later and no significant difference in p53 protein expression or dendritic cell number was detected. However, the ,UVR, PRL-exposed' site showed a greater reduction in pyrimidine dimer quantity. Conclusions: We found no evidence for a direct effect of PRL causing photoreversal of UVR-induced pyrimidine dimers in man. Our results do, however, suggest that some indirect effect of PRL may enhance pyrimidine dimer repair in the 24-h period following UVR exposure. [source]