Stimulatory effect of topical application of caffeine on UVB-induced apoptosis in the epidermis of p53 and Bax knockout mice.
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Shaved male or female p53(-/-) C57BL/6J mice and their wild-type littermates were irradiated once with UVB (60 mJ/cm(2)). The UVB-induced increase in apoptotic sunburn cells in p53(-/-) mice at 6-10 h after exposure to UVB was only 10-30% of that observed after treatment of p53(+/+) mice with UVB. Topical applications of caffeine immediately after UVB irradiation in female p53(+/+) or p53(-/-) mice enhanced the UVB-induced increase in apoptotic sunburn cells 6 h later by 127% and 563%, respectively. In another study, shaved female Bax(-/-) C57BL/6J mice and their wild-type littermates were irradiated once with UVB (60 mJ/cm(2)). The UVB-induced increase in apoptotic sunburn cells in Bax(-/-) mice at 6 h after exposure to UVB was only 14% of that observed after treatment of Bax(+/+) mice with UVB. Topical application of caffeine immediately after irradiation of Bax(+/+) or Bax(-/-) mice with UVB enhanced the UVB-induced increases in apoptotic sunburn cells at 6 h by 214% and 467%, respectively, and topical application of caffeine immediately after irradiation of Bax(+/+) or Bax(-/-) mice with UVB enhanced the UVB-induced increase in caspase 3 (active form) positive cells at 6 h by 253% and 750%, respectively. The results indicate that UVB-induced increases in apoptosis in the epidermis of wild-type mice are predominantly (but not entirely) by p53- and Bax-dependent pathways and that topical application of caffeine can enhance UVB-induced increases in apoptosis by p53- and Bax-independent pathways. (+info)
Sunburn cell formation, dendritic cell migration, and immunomodulatory factor production after solar-simulated irradiation of sunscreen-treated human skin explants in vitro.
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Using human skin explants, we investigated the effects of two different sunscreen preparations containing a chemical UVB filter alone [sun protection factor (SPF) 5.2] or UVA+UVB filter [SPF 6.2] on sunburn cell formation, dendritic cell (DC) migration, CD86- and CD1a-positive cell number, and tumor necrosis factor alpha (TNFalpha) and interleukin (IL)-1, IL-10, and IL-12 production in the skin after irradiation with different doses of solar-simulated UV radiation. Sunscreen- or placebo-treated skin explants were irradiated with solar-simulated UV radiation at 0.5, 1, and 2 minimal erythematous dose equivalents (MEDE) (as determined in an in vivo human study) multiplied by the SPF of the placebo or sunscreens. After irradiation, skin explants were floated on RMPI medium for 48 h. Cells that had emigrated and the skin explants were histologically analyzed, and the soluble mediators were measured in the supernatants by ELISA. Exposure to UV radiation led to concentration-dependent increases in sunburn cell formation and TNFalpha production but a concentration-dependent decrease in DC migration and CD86- and CD1a-positive cell number in the epidermis. Both chemical sunscreens protected against those alterations. The immunoprotective capacity of the sunscreens correlated with their SPF but was independent of the sunscreens' UVA protection capacity, suggesting that UVA is not a major factor for immunosuppression under the conditions used in the model. UV irradiation did not significantly affect the vitality of emigrated DC; the expression of HLA, CD80, and lag on emigrated cells; the number of CD1a-positive cells in the dermis; or the production of IL-1, IL-10, and IL-12. We conclude that our model may be useful in determining the immunoprotective capacity of sunscreens. (+info)
Genetic variation in XRCC1, sun exposure, and risk of skin cancer.
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The XRCC1 gene is involved in the base excision repair pathway. We assessed the associations of polymorphisms and haplotypes in XRCC1 with skin cancer risk in a nested case-control study within the Nurses' Health Study (219 melanoma, 286 squamous cell carcinoma (SCC) and 300 basal cell carcinoma (BCC), and 873 controls). We genotyped four haplotype-tagging single-nucleotide polymorphisms (Arg194Trp, C26602T, Arg399Gln, and Gln632Gln). There was no significant difference in frequency distribution between cases and controls for any of the five inferred common haplotypes. We observed that the 399Gln allele was inversely associated with SCC risk. This inverse association was only seen among those who had five or more lifetime sunburns, those with a family history of skin cancer, and those in the highest tertile of cumulative sun exposure in a bathing suit, but not among those with low risk defined by these risk factors. We also observed a significant association of the carriage of 194Trp allele with increased SCC risk, which was modified by family history of skin cancer. These two polymorphisms were not associated with BCC or melanoma risk. Our data suggest that the Arg194Trp and Arg399Gln polymorphisms may be differently associated with skin cancer risk according to exposure dose and skin cancer type. (+info)
Melanin acts as a potent UVB photosensitizer to cause an atypical mode of cell death in murine skin.
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Melanin protects the skin against DNA damage induced by direct absorption of sunlight's UV radiation. Yet, irradiating melanin in vitro or in cultured cells also generates active oxygen species such as superoxide, which can indirectly induce oxidative base lesions and DNA strand breaks. This photosensitization is greater for pheomelanin (yellow and red melanin) than for eumelanin (brown and black). The in vivo photosensitizing ability of melanin is unknown. We used congenic mice of black, yellow, and albino coat colors to investigate the induction of DNA lesions and apoptosis after exposure to predominantly UVB (280-320 nm) or UVA (320-400 nm) radiation. Cyclobutane pyrimidine dimers induced by direct UVB absorption were equal in all three strains, as was apoptosis measured as sunburn cells or as keratinocytes containing active caspase-3. However, terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling (TUNEL)-positive cells were approximately 3-fold more frequent in black and yellow mice after UVB or UVA irradiation than in albino. In epidermal sheets, TUNEL-positive cells lined the upper portion of the hair follicle, consistent with UV-induced photosensitization by melanin in the hair shaft. Because the concentration of eumelanin in black mice was three times that of pheomelanin in yellow mice, pheomelanin had 3-fold greater specific activity. We conclude that UV-irradiated melanin, particularly pheomelanin, photosensitizes adjacent cells to caspase-3 independent apoptosis, and this occurs at a frequency greater than the apoptosis induced by direct DNA absorption of UV. Melanin-induced apoptosis may contribute to the increased sensitivity of individuals with blonde and red hair to sunburn and skin cancer. (+info)
An evaluation of UV protection imparted by cotton fabrics dyed with natural colorants.
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BACKGROUND: The ultraviolet properties of textiles dyed with synthetic dyes have been widely reported in literature. However, no study has investigated the ultraviolet properties of natural fabrics dyed with natural colorants. This study reports the Ultraviolet Protection Factor (UPF) of cotton fabrics dyed with colorants of plant and insect origins. METHODS: Three cotton fabrics were dyed with three natural colorants. Fabrics were characterized with respect to fabric construction, weight, thickness and thread count. Influence of fabric characteristics on Ultraviolet Protection Factor was studied. Role of colorant concentration on the ultraviolet protection factor was examined via color strength analysis. RESULTS: A positive correlation was observed between the weight of the fabric and their UPF values. Similarly, thicker fabrics offered more protection from ultraviolet rays. Thread count appears to negatively correlate with UPF. Dyeing with natural colorants dramatically increased the protective abilities of all three fabric constructions. Additionally, within the same fabric type UPF values increased with higher depths of shade. CONCLUSION: Dyeing cotton fabrics with natural colorants increases the ultraviolet protective abilities of the fabrics and can be considered as an effective protection against ultraviolet rays. The UPF is further enhanced with colorant of dark hues and with high concentration of the colorant in the fabric. (+info)
Knowledge of the effects of sun exposure of Turkish high school students and their sun bathing habits.
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Cancer, long a serious problem in developed countries, is now becoming a serious health concern throughout the world. There has been an alarming increase in the number of new cases of melanoma each year, this cancer increasing at a faster rate than any other neoplasm in some regions. This may be a result of depletion of the ozone layer. An association between non-melanocytic skin cancer and exposure to the sun appears to have first been suggested in 1894; it was not until about 1952 that it was argued that exposure to the sun also causes melanoma. It is commonly believed that skin cancers develop only after long-term exposure to UVR. At the individual level, people who live in sunnier climates comparatively have a higher risk for skin cancer than do people who live in colder climates. This is particularly the case for migrant populations with a fair skin. The present study was conducted to evaluate the knowledge of the young generation in Turkey related to the side effects of sun exposure, and their sun bathing habits. Sun sensitivity, use of sunscreens, sunbathing habits and protective behaviours were determined for a total of 1244 high school students from the answers to a questionnaire completed by them. Data from 627 (50.4 %) females and 617 (49.6 %) males were evaluated. All were aged between 15 and 18 years. Sunscreen use was found to be higher in female students (59 %) than in their male counterparts (45.8 %). The wearing of sunglasses was reported by 36.7 %, whereas the incidence of hat wear was found to be 55.1% overall. The results of this study indicate that, although most high school students are aware of the side effects of sun exposure, they do not pay sufficient attention to protective behaviour. A further study should now be conducted to evaluate the use of sunscreens in a large group. (+info)
SunSmart? Skin cancer knowledge and preventive behaviour in a British population representative sample.
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The incidence of skin cancer has risen rapidly in the UK over the last 20 years, prompting public health organizations to try and raise awareness of the dangers of sun exposure and the need to practice sun-safe behaviour. This study aimed to assess baseline levels of sun-safe knowledge and behaviour in a British population-representative sample, prior to the launch of Cancer Research UK's 'SunSmart' campaign. A face-to-face survey was conducted through the Office for National Statistics as part of their Omnibus survey. In total, 1848 men and women aged 18 and over were interviewed. Knowledge of what to do to reduce skin cancer risk was modest. Two-thirds mentioned avoiding the sun by seeking shade, 50% mentioned covering up and only 43% said to use high factor sunscreen. Practice of sun-safe behaviours was also poor, with only one-third saying they sought shade, covered up or used high factor sunscreen to protect themselves from the sun. Men and those from lower socioeconomic groups were least informed and least likely to report using sun-protective behaviours. Increases in both knowledge and use of appropriate sun-protective behaviours are needed if skin cancer incidence rates are to decrease. (+info)
Knowledge, attitudes and behaviour in the sun: the barriers to behavioural change in Northern Ireland.
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To inform future health promotion programmes, we studied the knowledge, attitudes and behaviour of the Northern Ireland population to sun care. An interviewer-administered questionnaire was applied to one adult per household from a random sample of 1242 addresses. Lower levels of knowledge were found among respondents who were male, aged under 25 years or over 65 years, in a manual occupation or living in the west where health promotion activity on this topic was less active than in the east. Younger adults, females and professional groups were more likely to indicate that a suntan was important, healthy or attractive. Use of high factor sunscreen was inversely proportional to perceived importance of a suntan. Sunburn was more common in younger adults but more men reported multiple episodes of burning. Regular skin checks were uncommon and self-assessment of skin type was unrealistic indicating that sun care advice based on self assessment should be avoided in this population. Future campaigns should target appropriate messages at specific population subgroups. The study highlights the importance of collecting baseline information before implementing health promotion programmes and suggests that repeat monitoring is essential to ensure that key messages remain relevant. This study also indicates that Care in the Sun campaigns here impacted on general awareness in the population even with limited resources. There is, therefore, potential for greater impact with high funding levels. (+info)