Ultraviolet erythema sensitivity in anamnestic (I-IV) and phototested (1-4) Caucasian skin phototypes: the need for a new classification system

Skin typing: Fitzpatrick grading and others

Skin phototyping refers to a skin classification scheme based on how the skin responds to sun exposure. The Fitzpatrick classification is the most widely accepted method of skin phototyping, based on a person's tendency to sunburn and ability to tan. Apart from estimating the initial therapeutic dose of UV light, skin phototyping is also useful in predicting the risk of photodamage and skin cancer and the outcome of esthetic procedures. Techniques to type the skin objectively have been developed to address the deficiencies associated with the subjective Fitzpatrick classification. Some skin typing systems have been proposed specifically to predict the response of skin to cosmetic procedures such as chemical peeling and laser resurfacing. We discuss the concept of skin type and its relation to skin color, as well as critically appraising the various available methods of skin typing.

UV-induced tolerance to a contact allergen is impaired in polymorphic light eruption

Polymorphic light eruption (PLE) is a common skin disorder provoked by exposure to UVR. Its clinical symptoms resemble those of a contact allergic reaction. PLE is generally considered a T-cell-mediated autoimmune reaction toward a yet unidentified antigen formed in UVR-exposed skin. Predisposition to such an immune reaction may result from aberrant epitope formation, increased immune reactivity to a universal epitope, or diminished propensity to UVR-induced immunosuppression or to the induction of tolerance. In a study comprising a total of 24 PLE patients and 24 healthy sex- and age-matched controls, we found that both groups demonstrated similar immunosuppression of contact sensitization to diphenylcyclopropenone by earlier exposure to solar-simulating UVR. However, only 1 out of 13 PLE patients (8%) versus 6 out of 11 controls (55%) that had been immunosuppressed by UVR exhibited a state of immunotolerance toward the same allergen after 10-24 months (P=0.023). We conclude that the impaired propensity to UVR-induced allergen-specific immunotolerance may promote recurrent PLE.

Adolescent attitudes towards tanning: does age matter?

Adolescents seem to be obsessed with tanning. One third of both adolescents and adults report sunbathing. On average, about 20% of adolescents report ever-using of artificial UV tanning devices with 15% currently using them. Tanning attitudes appear similar for adolescents and adults. The top three reasons for tanning included beliefs that a tan makes them more comfortable socializing with friends, looks better and is attractive. The top reason for using artificial UV tanning devices is also aesthetics, followed by relaxation. Other reasons for using artificial UV tanning devices include vacation preparation and to gain a protective base. Attitudes related to appearance that result in more frequent tanning may be difficult to change.

Home versus outpatient ultraviolet B phototherapy for mild to severe psoriasis: pragmatic multicentre randomised controlled non-inferiority trial (PLUTO study)

OBJECTIVE

To determine whether ultraviolet B phototherapy at home is equally safe and equally effective as ultraviolet B phototherapy in an outpatient setting for patients with psoriasis.

DESIGN

Pragmatic multicentre single blind randomised clinical trial (PLUTO study).

SETTING

Dermatology departments of 14 hospitals in the Netherlands.

PARTICIPANTS

196 patients with psoriasis who were clinically eligible for narrowband (TL-01) ultraviolet B phototherapy. The first 105 consecutive patients were also followed for one year after therapy.

INTERVENTION

Ultraviolet B phototherapy at home using a TL-01 home phototherapy unit compared with standard narrowband ultraviolet B phototherapy in an outpatient setting. Both therapies were done in a setting reflecting routine daily practice in the Netherlands.

MAIN OUTCOME MEASURES

The main outcome measure was effectiveness as measured by the proportion of patients with a 50% or more reduction of the baseline psoriasis area and severity index (PASI) or self administered psoriasis area and severity index (SAPASI), called the PASI 50 and SAPASI 50 (relevant treatment effect). Another outcome of effectiveness was the percentage reduction in median scores on the PASI as well as SAPASI. Also the proportions of patients reaching the PASI 75 and SAPASI 75 (successful treatment effect), and the PASI 90 and SAPASI 90 (almost complete clearance) were calculated. Other secondary outcomes were quality of life (SF-36, psoriasis disability index), burden of treatment (questionnaire), patients' preferences and satisfaction (questionnaire), and dosimetry and short term side effects (diary).

RESULTS

82% of the patients treated at home compared with 79% of the patients treated in an outpatient setting reached the SAPASI 50 (difference 2.8%, 95% confidence interval -8.6% to 14.2%), and 70% compared with 73% reached the PASI 50 (-2.3%, -15.7% to 11.1%). For patients treated at home the median SAPASI score decreased 82% (from 6.7 to 1.2) and the median PASI score decreased 74% (from 8.4 to 2.2), compared with 79% (from 7.0 to 1.4) and 70% (from 7.0 to 2.1) for patients treated in an outpatient setting. Treatment effect as defined by the mean decline in PASI and SAPASI scores was significant (P<0.001) and similar across groups (P>0.3). Total cumulative doses of ultraviolet B light were similar (51.5 v 46.1 J/cm(2), difference 5.4, 95% confidence interval -5.2 to 16.0), and the occurrence of short term side effects did not differ. The burden of undergoing ultraviolet B phototherapy was significantly lower for patients treated at home (differences 1.23 to 3.01, all P

CONCLUSION

Ultraviolet B phototherapy administered at home is equally safe and equally effective, both clinically and for quality of life, as ultraviolet B phototherapy administered in an outpatient setting. Furthermore, ultraviolet B phototherapy at home resulted in a lower burden of treatment and led to greater patients' satisfaction. Trial registration Current Controlled Trials ISRCTN83025173 and Clinicaltrials.gov NCT00150930.

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MESH Headings

• Adult
• Ambulatory Care
• Chemotherapy, Adjuvant
• Female
• Home Care Services
• Humans
• Male
• Middle Aged
• Netherlands
• Psoriasis/radiotherapy
• Treatment Outcome
• Ultraviolet Therapy/methods
• Waiting Lists

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Affiliation(s)

Mayke B G Koek Department of Dermatology/Allergology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, Netherlands.
Erik Buskens
Huib van Weelden
Paul H A Steegmans
Carla A F M Bruijnzeel-Koomen
Vigfús Sigurdsson

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Repair of UV dimers in skin DNA of patients with basal cell carcinoma

Epidemiologic studies suggest that exposure to sunlight is the primary etiologic agent for basal cell carcinoma. Formation of UV-induced DNA damage is believed to be a crucial event in the process leading to skin cancer. In this study, repair of photoproducts in DNA was followed in the skin of patients with basal cell carcinoma and control subjects. The subjects were exposed to 800 J/m(2) Commission Internationale de 1'Eclairag of solar-simulating radiation on buttock skin. Biopsies were taken at 0 hour, 24 hours, and 3 weeks after the exposure. Two cyclobutane pyrimidine dimers, TT=C and TT=T, were measured using a sensitive (32)P-postlabeling assay. Initial levels of both TT=C and TT=T differed between individuals in both groups. The levels of TT=T in patients with basal cell carcinoma and controls were similar (9.9 +/- 4.0 and 9.2 +/- 2.9 products per 10(6) normal nucleotides), whereas the level of TT=C was significantly lower in controls than in patients with basal cell carcinoma (6.2 +/- 3.1 versus 10.9 +/- 4.5 products per 10(6) normal nucleotides). The fractions of TT=T remaining after 24 hours and 3 weeks were significantly higher in patients with basal cell carcinoma (72% and 11%) compared with controls (48% and 5%). A slower removal in patients with basal cell carcinoma than in controls was indicated also for TT=C (52% versus 42% remaining at 24 hours); however, the difference between groups was not significant. When including data from our previously reported small-scale study, the fraction of dimers remaining at 24 hours was significantly higher in patients with basal cell carcinoma for both TT=C and TT=T. The data suggest that patients with basal cell carcinoma have a reduced capacity to repair UV-induced DNA lesions.

Skin phototypes of a Maltese sample population

BACKGROUND AND AIM

Skin phototyping is a clinical classification system based on a patient's historical reporting of the acute skin response to sunlight. We carried out a simple study to estimate the skin phototypes of the Maltese people in order to acquire more information on the relative risk of the general Maltese population to sun burning and to the more chronic effects of sun exposure, including photoaging and skin cancers.

METHOD

A consultant dermatologist and dermatology trainees determined the skin phototype of patients seen with skin infections or skin tags at dermatology outpatients in Malta by carrying out a short interview.

RESULTS

Data were collected on 756 patients. The commonest reported skin phototype in both sexes was type III (48.0% overall; 52.4% in males, 43.8% in females); this was followed by type IV in males (30.4%) and type II in females (32.3%). Only 1.2% of the total was of skin type I.

CONCLUSION

Approximately one half of the Maltese population is at moderate risk of sun damage; about one quarter is at low risk; and the other quarter is at high risk, the latter group needing more thorough sun avoidance and better surveillance for skin tumours. Social desirability can influence responses to such questionnaires and might have contributed to the difference between males and females noted in our study.

Reference Limits for Erythema-effective UV Doses

Diagnostic phototesting, including the determination of the minimal erythema dose (MED), is a useful procedure to detect abnormal sensitivity to UV radiation. We aimed to estimate the reference limits (RLs) of the MED in a reasonably large reference sample of white individuals. Skin phototypes and MED values for broadband UVB and for UVA were determined in 461 white subjects. When appropriate, the 95% reference intervals, including the 0.025 fractile and 0.975 fractile, were computed for the MED-UVB reference values (by means of parametric methods) and the MED-UVA reference values (by means of nonparametric methods). MED data were also converted to standard erythema doses (SEDs). As described elsewhere we observed a considerable overlap of MED values for all skin phototypes and confirmed that age and sex do not substantially influence the MED. The lower RLs observed for MED-UVB were 33 mJ cm(-2) (0.5 SEDs) and for MED-UVA 12.6 mJ cm(-2) (1.2 SEDs). The MED and SED findings from this investigation may serve as reference data for white individuals and give support to the clinician in differentiating between normal and pathologically abnormal photosensitivity. Although the MED data given here are limited to the phototest device used in the present study, the SED results establish comparability between our data and phototest results obtained from laboratories using different UV sources.

Assessing the role of race in quantitative measures of skin pigmentation and clinical assessments of photosensitivity

BACKGROUND

Given the increasing demographic diversity in the United States, clarifying relationships between race, color, ethnicity, and disease processes is critical.

OBJECTIVES

We sought to examine the correlation between objective measures of skin pigmentation, racial identification, and physician-diagnosed and self-reported skin phototypes.

METHODS

A total of 558 participants (76 nonwhite) were evaluated. A subset underwent spectrometric readings and digital photography of the upper aspect of the inner arm. Self-identified race was compared with 7 measures of pigmentation.

RESULTS

Race correlates best with physician-diagnosed skin phototype (r = 0.55, P < .01), whereas self-reported skin phototype, spectrometry, and colorimetry correlate poorly with race (r = 0.28, < 0.40, and r > -0.31, respectively, P < .01). Associations between race and subjective measures strengthen among patients with darker skin.

CONCLUSION

Objective measures of pigmentation fail to correlate well with race, whereas race correlates moderately with physician-diagnosed skin phototype. Including objective methods of analyzing skin color may reduce subjective influences of race in assessing photosensitivity and potential risk for skin cancer.

Design and evaluation of a novel portable erythema-melanin-meter

BACKGROUND AND OBJECTIVES

Objective evaluation of the pigmentation index (PI) and the eythema index (EI) of human skin is a prerequisite for successful optimization of laser- and intense-pulsed-light (IPL)-based treatment modalities in dermatology.

STUDY DESIGN/MATERIALS AND METHODS

We describe a three-wavelength technique for determining PI and EI as well as its particular implementation using LEDs operating at wavelengths of 560, 650, and 710 nm and a large-area photodiode. The instrument has been evaluated both in vitro and in vivo.

RESULTS

In vitro, good correlation between the measured indices and results obtained with commercially available techniques has been observed. In addition, linearity of the PI with melanin concentration in the phantom medium up to 7 x 10(-3) nm(-1) (defined as a slope of the optical density spectrum) has been established. In vivo, feasibility of using the technique for predicting the minimal erythema dose (MED), minimal phototoxic dose (MPD), and the threshold of epidermal damage in a photothermal treatment has been demonstrated.

CONCLUSIONS

The data suggest that the technique has a substantial potential as a method of pre-treatment diagnostics for photochemical and photothermal procedures.

Comparing quantitative measures of erythema, pigmentation and skin response using reflectometry

We measured a number of pigmentation and skin response phenotypes in a sample of volunteers (n=397) living in State College, PA. The majority of this sample was composed of four groups based on stated ancestry: African-American, European-American, Hispanic and East Asian. Several measures of melanin concentration (L*, melanin index and adjusted melanin index) were estimated by diffuse reflectance spectroscopy and compared. The efficacy of these measures for assessing constitutive pigmentation and melanogenic dose-response was evaluated. Similarly, several measures of erythema (a*, erythema index and adjusted erythema index) were compared and evaluated in their efficacy in measuring erythema and erythemal dose-response. We show a high correspondence among all of the measures for the assessment of constitutive pigmentation and baseline erythema. However, our results demonstrate that evaluating melanogenic dose-response is highly dependent on the summary statistic used: while L* is a valid measure of constitutive pigmentation it is not an effective measure of melanogenic dose-response. Our results also confirm the use of a*, as it is shown to be highly correlated with the adjusted erythema index, a more advanced measure of erythema based on the apparent absorbance. Diffuse reflectance spectroscopy can be used to quantify the constitutive pigmentation, melanogenic dose-response at 7 d and erythemal dose-response at both 24 h and 7 d postexposure.

In situ repair of cyclobutane pyrimidine dimers in skin and melanocytic nevi of cutaneous melanoma patients

The development of cutaneous malignant melanoma (CMM) and its precursor lesions, melanocytic nevi, has been linked to sun exposure. Cyclobutane pyrimidine dimers (CPDs) are the majority of DNA lesions induced by sun exposure. In our study, we investigated if CMM patients have impaired ability to repair CPDs in skin as well as in melanocytic nevi. The repair kinetics were followed up to 3 weeks after exposure to 40 mJ/cm(2) of solar simulating radiation. Altogether 12 CMM patients and 10 healthy controls were included in our study. Buttock skin biopsies were taken at 0 hr, 48 hr and 3 weeks after UV exposure, whereas melanocytic nevi and surrounding skin biopsies were taken only at 0 hr and 3 weeks. The CPD levels were measured by a (32)P-postlabeling method. The results showed that the repair rate of CPDs in neither the skin nor the nevi was significantly different between the CMM patients and the control group. For both groups, the repair rate of TT = C was faster than that for TT = T. The important finding is that about 10% of the initial TT = T damage remained unrepaired after 3 weeks, and was detectable in normal epidermis as well as in nevi of all subjects. We also found that the amount of TT = C and TT = T at 0 hr in nevi was significantly lower than that in surrounding skin (Wilcoxon rank sum test, p < 0.05).

Ultraviolet photoproduct levels in melanocytic nevi and surrounding epidermis in human skin in situ

Melanocytic nevi are localized benign proliferations of melanocytes. The number of nevi has been shown to be the major risk marker for the development of cutaneous melanoma. This study compares the induction of photoproducts in nevi and in surrounding skin after exposure to solar-simulating radiation. Cyclobutane pyrimidine dimers (TT=T and TT=C) and 6-4 photoproducts (TT-T and TT-C) were measured in 20 nevi and 20 surrounding skin samples obtained from 14 subjects, using a 32P-postlabeling method. The amount of all four types of photoproducts in nevi was found to be 3-5-fold lower than that in surrounding skin, and the difference was statistically significant (paired t test, p < 0.01). In nevi, the photoproduct level was significantly associated with the color of nevi (the lowest level in the darkest color of nevi; r = -0.86, p < 0.01 for TT=T; r = -0.68, p < 0.01 for TT=C). Our findings suggest that the magnitude of the DNA damage is not a sole risk marker for the development of cutaneous melanoma.

The relation between melanocortin 1 receptor genotype and experimentally assessed ultraviolet radiation sensitivity

Pigmentary phenotype is a key determinant of an individual's response to ultraviolet radiation with the presence of phaeomelanin thought to be of particular importance. Reports of minimal erythema testing, however, have failed to show a consistent difference between skin type I and other skin types. The melanocortin 1 receptor is a key genetic determinant of the cutaneous response to ultraviolet radiation. In this study we investigate the relation between experimentally induced erythemal response to ultraviolet radiation and the melanocortin 1 receptor genotype. Phototesting was performed in 20 redheads and 20 nonredheaded subjects, the majority of whom were also screened for the presence of melanocortin 1 receptor variants. The majority of redheads sequenced (89%) had two melanocortin 1 receptor variants previously found to be associated with red hair compared to none of the controls. There was no significant difference between the groups in minimal erythema dose: the median minimal erythema dose in redheads was 44 mJ per cm2 (interquartile range 34-56) and in the nonredheaded group was 40 mJ per cm2 (interquartile range 40-56). Objective measurements of ultraviolet-B-induced erythema were performed using reflectance instrument measurements of erythema intensity and dose-response curves constructed for each subject. The slope of the dose-response curve in the redheaded group was statistically greater than in the nonredheaded group (median in redheads 4.08 vs 3.56 for controls, 95% confidence interval for the difference between the medians being 0.01-1.23, p = 0.043). In addition the ratio D0.05:D0.025 was significantly lower for the redheaded group (median in redheads 1.22, interquartile range 1.18-1.26; median in nonreds 1.28, interquartile range 1.23-1.32; p < 0.05). Thus, although the minimal erythema dose values were not different, subjects with red hair develop greater intensity of erythema than nonredheaded individuals when doses greater than the minimal erythema dose are given. Importantly, when analyzed by genotype alone rather than phenotype, the slope of the erythema dose-response differed between those persons who were homozygous or heterozygous mutants and wildtype/pseudo-wildtype (p = 0.026).

Evaluation of sunscreen protection in human melanocytes exposed to UVA or UVB irradiation using the alkaline comet assay

The in vivo assessment of sunscreen protection does not include the photogenotoxicity of UVA or UVB solar radiation. Using the comet assay we have developed a simple and rapid technique to quantify sunscreen efficacy against DNA damage induced by UV light. Cutaneous human melanocytes from primary cultures were embedded in low-melting point (LPM) agarose and exposed to UVA (0.8 J/cm2) or to UVB (0.06 J/cm2) through a quartz slide covered with 10 microL volumes of sunscreens. DNA single-strand breaks induced directly by UVA at 4 degrees C and indirectly through nucleotide excision repair by UVB following a 35 min incubation period at 37 degrees C were quantified using the comet assay. Tail moments (TM) (tail length x %tail DNA) of 100 cells/sample were determined by image analysis. DNA damage was evaluated with a nonlinear regression analysis on the normalized distribution frequencies of TM using a chi 2 function. The coefficients of genomic protection (CGP) were defined as the percentage of inhibition of DNA lesions caused by the sunscreens. Twenty-one sunscreens were evaluated, and the calculated CGP were compared with the in vivo sun protective factor (SPF) and with the protection factor UVA (PFA). Nonlinear relationships were found between SPF and CGPUVB and between PFA and CGPUVA.

Synthesis, photophysical properties, tumor uptake, and preliminary in vivo photosensitizing efficacy of a homologous series of 3-(1'-alkyloxy)ethyl-3-devinylpurpurin-18-N-alkylimides with variable lipophilicity

Starting from methylpheophorbide-a, a homologous series of purpurinimides containing alkyl substituents at two different positions [as 3-(1(1)-O-alkyl) and 13(2)-N-alkyl] were synthesized. These compounds with variable lipophilicity (log P 5.32-16.44) exhibit long wavelength absorption near lambda(max)700 nm (epsilon: 45 000 in dichloromethane) with singlet oxygen ((1)O2) production in the range of 57-60%. The shifts in in vivo absorptions and tumor/skin uptake of these compounds were determined in C3H mice bearing RIF tumors by in vivo reflectance spectroscopy. The results obtained from a set of photosensitizers with similar lipophilicity (log P 10.68-10.88) indicate that besides the overall lipophilicity, the presence and position of the alkyl groups (O-alkyl vs N-alkyl) in a molecule play an important role in tumor uptake, tumor selectivity, and in vivo PDT efficacy. At present, all purpurinimide analogues are being evaluated at various doses, and experiments are underway to establish a quantitative structure-activity relationship on a limited set of compounds. The 1D and 2D NMR and mass spectrometry analyses confirmed the structures of the desired purpurinimides and the byproducts formed during various reaction conditions. The mechanisms of the formation of the unexpected 12-formyl- and 12-(hydroxymethyl)purpurinimides under certain reaction conditions are also discussed.

Levels and repair of cyclobutane pyrimidine dimers and 6-4 photoproducts in skin of sporadic basal cell carcinoma patients

The 32P-postlabeling method was applied to measure directly the levels and repair rates of specific cyclobutane pyrimidine dimers and 6-4 photoproducts in 10 basal cell carcinoma patients and 10 controls matched on age, skin type, and gender after exposure to 400 J per m2 of solar simulating radiation on previously unexposed buttock skin. The results showed an identical level of photoproducts at 0 h after solar simulating radiation in the basal cell carcinoma group and the control group. Erythemal response correlated with the repair of cyclobutane pyrimidine dimers within 24 h in both groups, i.e., repair was faster in those with a strong erythemal reaction. The basal cell carcinoma patients showed a somewhat slower repair of photoproducts in skin compared with the controls, but the result was not significant. Photoproducts formed at the TTC sites were repaired faster than those at the TTT sites for both cyclobutane pyrimidine dimers and 6-4 photoproducts in the basal cell carcinoma group and in the controls.

Effect of age on the formation and repair of UV photoproducts in human skin in situ

Ultraviolet radiation (UVR)-induced photoproducts can be measured by a number of methods. The newly developed 32P-postlabelling method is feasible in molecular epidemiological studies due to its sensitivity, specificity and little amount DNA needed. We applied the 32P-postlabelling method to investigate the induction and repair of photoproducts (cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts) after UVR in human skin in situ and studied the effects of age, skin type and gender. The study included 30 subjects aged 32-78 years. The photoproduct induction levels varied 7- to 15-fold between the individuals tested. All four types of photoproducts were induced at a higher frequency in the older population (>/=50 years) than in the younger population (<50 years). Individuals with skin type I and II had a higher CPD induction frequency than individuals with skin type III and IV. In both cases, the differences in thymidylyl (3'-5') thymidylyl (3'-5')-2'-deoxycytidine induction reached statistical significant levels (p<0.05). Photoproduct repair rates 24 h and 48 h after UV irradiation showed a large inter-individual variation. No clear effects of age, skin type or gender on DNA repair could be detected. Our data suggest that UV-induced DNA photoproduct levels increase with age.

Cutaneous melanoma patients have normal repair kinetics of ultraviolet-induced DNA repair in skin in situ

The DNA lesions induced by ultraviolet radiation include cyclobutane pyrimidine dimers and 6-4 photoproducts. We investigated whether cutaneous melanoma patients have an impaired ability to repair their ultraviolet-induced photolesions. Seventeen patients with melanoma and 13 healthy controls took part in this study. Both groups received a dose of 40 mJ per cm2 Commission Internationale de l'Eclairage of solar simulating radiation on previously unexposed buttock skin. Skin biopsies were taken at 0 h, 24 h, and 48 h after ultraviolet exposure. A 32P-postlabeling method was used to measure both cyclobutane pyrimidine dimers and 6-4 photoproducts in skin. Cyclobutane pyrimidine dimers and 6-4 photoproduct levels did not differ in the melanoma patients from those in the control group at any time point post-ultraviolet radiation. The repair rate of cyclobutane dimer TT=C was faster than that for TT=T both at 24 h and 48 h postirradiation in both groups, providing evidence of site-specific repair (p < 0.05). We conclude that patients with melanoma have a normal ultraviolet-induced DNA repair capacity in skin in situ.

Ultraviolet irradiation induces cyclooxygenase-2 expression in keratinocytes

We examined the effect of ultraviolet (UV) irradiation on the expression of cyclooxygenases in cultured HaCaT keratinocytes and in human skin in vivo. UVB irradiation (10 and 50 mJ/cm2) and hydrogen peroxide (200 micromol/L) increased cyclooxygenase-2 mRNA expression in HaCaT keratinocytes. No clear expression of cyclooxygenase-1 mRNA was detected in either control or stimulated HaCaT cells. Genistein, a tyrosine kinase inhibitor, suppressed both the basal and stimulated expression of cyclooxygenase-2 in HaCaT cells. UVB-induced cyclooxygenase-2 mRNA expression was partly inhibited by the antioxidant N-acetylcysteine and by H-7, a non-specific inhibitor of protein kinase C. Solar-simulated irradiation (40 mJ/cm2) was found to induce in vivo both cyclooxygenase-2 mRNA and protein expression in human skin, whereas the expression of cyclooxygenase-1 mRNA remained at the basal level. Our results show that cyclooxygenase-2 expression is induced by UV irradiation and suggest that tyrosine kinases and reactive oxygen intermediates are involved in this induction of cyclooxygenase-2.

Isomerization of urocanic acid after ultraviolet radiation is influenced by skin pigmentation

Exposure to ultraviolet (UV) radiation may induce erythema, DNA damage and suppression of immune responses. Melanin pigmentation offers protection against the first two of these effects, but immunosuppression seems to occur irrespective of the subject's pigmentation. Cis-urocanic acid (cis-UCA), produced by isomerization of trans-UCA in the stratum corneum on UV exposure, initiates some of the immunomodulatory effects of UV radiation. In the present study the relationship between skin pigmentation and UCA isomerization has been examined in 28 healthy individuals of skin types I-IV. Pigmentation is measured in five areas of not recently exposed back skin before irradiation with 0, 0.45, 0.9, 1.8 and 3.6 standard erythema dose (SED) of filtered broadband UV-B (1 SED = 10 mJ cm-2 at 298 nm). The concentration of UCA isomers is measured immediately after the irradiation. With 3.6 SED, the relative production of cis-UCA is close to the maximum obtainable, irrespective of skin type. A significant negative correlation is found between pigmentation and relative production of cis-UCA at 0.45 and 1.8 SED, and between pigmentation and absolute production of cis-UCA at 0.45 SED. At doses of 0.45 and 0.9 SED the relative and absolute production of cis-UCA are higher in the group with skin types I and II when compared with the group with skin types III and IV. The higher isomerization in the lightly pigmented subjects than in the more pigmented ones may indicate that people with fair skin are at a relatively higher risk of immunosuppression when exposed to low doses of UV radiation.

Urocanic acid isomers and photosensitivity in healthy children

Episodes of intense sun exposure, particularly in childhood, seem to carry a risk for the development of malignant melanoma in later life. However, little is known about photosensitivity and natural photoprotection in children. In adult subjects, photoprotection is provided mainly by the epidermal content of melanin and the thickness of the stratum corneum, while the amount of urocanic acid (UCA), a major ultraviolet-absorbing component of the stratum corneum, is not thought to contribute significantly to photoprotection. The minimal erythema dose (MED) was determined in 22 healthy children aged 6-13 years and in 36 healthy adults (mean age 28.1 years). Pigmentation was measured at six body sites by use of reflectance spectroscopy and the concentration of UCA isomers was measured in a sun-exposed area (upper back) and in unexposed buttock skin. No significant differences between children and adults were found, either in pigmentation at exposed and unexposed body sites, or in MED. The concentration of total UCA was significantly higher in the children than in the adults on the buttock (median 22.2 vs. 13.6 nmol/cm2), but not on the back. On exposed back skin, the children had a significantly higher percentage of cis-UCA than the adults (median 60.1 vs. 28.3%), while no difference was found on the buttock. In both groups, a significant correlation was found between pigmentation and MED (children: Spearman correlation coefficient 0. 58, P = 0.006; adults: Spearman correlation coefficient 0.69, P < 0. 0001), indicating that pigmentation is of major importance in determining photosensitivity in children as well as in adults. The concentration of total UCA did not correlate with the MED in either group.

Differential regulation of the AP-1 family members by UV irradiation in vitro and in vivo

We have examined the effect of UVB and solar-simulated irradiation on the expression of the AP-1 family of transcription factors and the cytokine IL-6 both in cell cultures and in human skin in vivo. UVB irradiation potently induced c-jun, junB and c-fos mRNA levels in vitro in HaCaT cells. IL-6 mRNA was induced in response to UVB irradiation 2-3 h later than c-jun, junB and c-fos mRNAs. In human skin in vivo, solar-simulated irradiation induced transiently junB expression. Genistein, a tyrosine kinase inhibitor, augmented the induction of c-jun and junB by UVB irradiation in HaCaT cells. The results of this study provide evidence that in addition to c-jun and c-fos, junB is also an essential component of the human UV-response. This study also suggests that UVB irradiation regulates the AP-1 family by several mechanisms and that the signalling mechanisms of UVB irradiation are considerably different from the ones used by UVC irradiation.

UVB induction of epithelial tumors in human skin using a RAG-1 mouse xenograft model

To examine the effects of chronic ultraviolet light on human epidermal cells, we grafted white human skin onto recombinase activating gene-1 knockout mice. We found previously that the maximal concentration of ultraviolet B radiation (290-320 nm) tolerated by human skin xenografts was 500 J per m2 when given three times weekly. One hundred and fifty-eight grafted mice were randomized and observed for a median of 10 mo in four groups: (i) no treatment; (ii) one treatment with the chemical carcinogen dimethyl-(a)benzanthracene; (iii) ultraviolet B three times weekly; and (iv) a combination of dimethyl-(a)benzanthracene and ultraviolet B. Approximately half of the skin specimens treated with ultraviolet B developed superficial milia and epidermal cysts. Grafts contained up to seven milia lesions between 4 and 8 mo after initiation of treatment, whereas the number of larger epidermal cysts was rarely more than two. Milia and cysts developed in the skin regardless of pigmentation or tanning. Actinic keratoses arose in 9% of grafts treated with ultraviolet B alone and in 19% of grafts treated with the combination of dimethyl-(a)benzanthracene and ultraviolet B. Invasive squamous cell carcinomas developed in 10% of grafts after combined dimethyl-(a)benzanthracene and ultraviolet B treatment and lesions were restricted to skin grafts that did not tan. These findings demonstrate that (i) development of ultraviolet-induced lesions can be experimentally accelerated in human skin, (ii) xenografted recombinase activating gene-1 deficient mice are superior to severe combined immunodeficiency disease mice for chronic ultraviolet B studies, and (iii) benign cystic tumors and squamous cell carcinomas are caused by ultraviolet B.

UV induced erythema evaluated 24 h post-exposure by skin reflectance and laser Doppler flowmetry is identical in healthy persons and patients with cutaneous malignant melanoma and basal cell cancer

Twenty-one patients with invasive cutaneous malignant melanoma and 19 patients with basal cell skin cancer and 29 healthy volunteers were phototested on non-UV exposed buttock skin to examine their 24 h reaction to a series of increasing doses of simulated sunlight with 25% dose increments. Skin pigmentation at the phototest sites was determined by skin reflectance before testing to assure an equal level of constitutive skin pigmentation in the 3 groups. Erythema reactions were scored visually 24 hours post-exposure and objective measurements of erythema were performed by skin reflectance and laser Doppler flowmetry. In adjacent non-irradiated skin the redness was also quantified to determine the increase in redness in irradiated skin compared to non-irradiated skin. Constitutional skin pigmentation correlated well to UV sensitivity (r = 0.75) and skin redness measured by skin reflectance technique correlated to laser Doppler flowmetry (r = 0.86). No significant differences in UV doses to barely perceptible erythema or to the higher erythema grades were found between the two skin tumour groups and the control group, and no significant differences were found in skin reflectance measured redness or in laser Doppler flowmetry of any erythema reactions between the 3 groups. The 24 h erythema reaction to sunlight can therefore not be used to distinguish patients with invasive cutaneous malignant melanoma or basal cell carcinoma from normal persons.

Urocanic acid concentration and photoisomerization in Caucasian skin phototypes

To investigate the relationship between erythemal sensitivity of the skin to UV radiation and epidermal urocanic acid (UCA) concentration, 45 healthy volunteers of anamnestic skin phototypes (ASP) 1-IV were studied. In 16 of the subjects, we analyzed UCA photoisomerization after graded UVB exposures. The median and mean total UCA concentration in unirradiated skin was 22.4 and 35.3 nmol/cm2, and no statistically significant difference in total UCA concentrations was detectable either between ASP I through II and III through IV or between the phototested skin type (PSP) groups 1 through 2 and 3 through 4. The relative amount of the cis-isomer varied between 3 and 35%, with median and mean values of 7 and 12%, respectively. No statistically significant difference in absolute or relative cis-UCA concentrations was detectable between ASP I through II and III through IV, but a significantly lower absolute (P < 0.009) and relative (P < 0.002) cis-UCA concentration in unirradiated skin was recorded in PSP groups 1 through 2, compared to types 3 through 4. In all tested subjects, an erythemally weighted dose of 1 mJ/cm2 sufficed to cause trans- to cis-UCA isomerization. When comparing photosensitive (skin phototype I) and phototolerant (phototypes III and IV) individuals, who were irradiated with a reference 5 mJ/cm2 UV dose or with fractions of 0.1-1.0 of their individual minimal erythema dose values, no skin phototype-dependent difference in ability to photoisomerize was discernible.

Up-regulation of human epidermal Langerhans' cell B7-1 and B7-2 co-stimulatory molecules in vivo by solar-simulating irradiation

Ultraviolet (UV) radiation impairs cutaneous immune functions and induces antigen-specific tolerance both locally at the irradiated skin site, as well as at distant skin sites and systemically. It has been postulated that in the local model, altered Langerhans' cells (LC) provide tolerogenic signals, and studies in vitro have indicated that UV radiation may down-regulate the expression of co-stimulatory molecules on the surface of these cells. To examine the effect of UV radiation on LC co-stimulatory molecules in vivo, we irradiated human volunteers with erythematogenic doses of solar-simulating UV radiation (SSR), and analyzed the expression of cell surface markers in dermatome skin samples obtained 1-72 h post-irradiation. For flow cytometric analysis, epidermal cell (EC) suspensions were prepared and double labeled with monoclonal antibodies against CD1a or HLA-DR, and B7-1 (CD80), B7-2 (CD86), ICAM-1 (CD54), ICAM-3 (CD50), LFA-3 (CD58), E-cadherin, or integrin-beta4 (CD104). In unirradiated control skin samples, keratinocytes (KC) expressed high levels of E-cadherin. LC expressed high levels of both E-cadherin and ICAM-3, and low levels of B7-2, LFA-3, ICAM-1, and integrin-beta4. Following SSR, a triphasic reaction pattern was seen: an immediate, down-regulatory phase prevailing 2-6 h post-irradiation, when the number of DR+ and CD1a+ cells were temporarily reduced; a delayed, up-regulatory phase in which the number of LC was increased and the expression intensities of CD1a, HLA-DR, B7-1, and B7-2 were strongly up-regulated, maximally evident 12-24 h after irradiation, but no more seen at 48 h; and a late phase at 72 h, in which an influx of monocytes and a concomitant rise in DR+ cells was recorded. We conclude that to understand real-life cutaneous UV immunology, studies in vitro need to be complemented with studies in vivo. In the case of LC, the effects of erythematogenic UV radiation in vivo on human LC B7 co-stimulatory molecules include an up-regulatory stage.