Chronic sun exposure is associated with distinct histone acetylation changes in human skin

Photoaging is premature aging of the skin caused by sunlight or artificial UV exposure (e.g. tanning beds). It affects almost everyone in the world. Histones are proteins which are positively charged, allowing them to associate with DNA, which is negatively charged. Some histones are like spools for the thread‐like DNA to wrap around. This study, from China, aimed to analyse patterns of changes (modification) to histones, which can regulate gene expression in sun‐exposed and non‐exposed skin, and identify photoaging‐related genes modified by abnormal histones. We tested the histone modification profile in sun‐exposed and non‐exposed skin samples with ELISA (a test that uses antibodies and color change to identify a substance), and found that the level of histone H3 acetylation (a kind of histone modification) increased significantly in sun‐exposed skin samples compared with non‐exposed ones. The increased P300 and decreased HDAC1 and SIRT1 expression in sun‐exposed skin might be the main cause (P300, HDAC1 and SIRT1 are enzymes related to histone modification). Further, tests were performed to screen the genes whose histone H3 acetylation changed in sun‐exposed skin samples and non‐exposed ones. We found that 227 genes displayed significant hyperacetylation (simply put, over‐modification) of histone H3, and 81 genes displayed significant hypoacetylation (under‐modification) of histone H3 in sun‐exposed skin samples compared with non‐exposed ones. In summary, histone H3 hyperacetylation caused by chronic sun exposure may play a critical role in the development of skin photoaging.     

Product application technique alters the sun protection factor.

A number of factors may alter the efficacy of a sunscreen product being tested. Notably among these are (1) the source of ultraviolet (UV) radiation, (2) the filtration of the UV radiation source, (3) such environmental factors as swimming or sweating (4) and/or the amount of product applied. This is the first report in which the technique of product application itself is examined. We find that the act of rubbing the product into the skin appears also to remove product from the skin. In our study, different techniques of product application produced a 25% deviation in product sun protection factor. The variables associated with the application of sunscreening products are discussed.     

Children and sun exposure in the northeast of Italy

Excessive, incorrect exposure to the sun at a young age can be a risk factor for skin cancer at a later age. In this study we have investigated the exposure and protection habits of a group of children to see whether there are behavioral errors that should and possibly could be corrected. We handed out a multiple-choice questionnaire to 310 subjects, 212 boys and 98 girls between the ages of 6 and 14, all residents in the province of Udine in the northeastern part of Italy. Of these children, 24% had sunburn on several occasions; boys were four times more at risk than girls (OR = 0.4) and the frequency reduced by 30% for each skin phototype class higher. In children between 11 and 14 years of age, exposure was prolonged (43% for 2-4 hours, 38% for 4-8 hours) and 30% preferred peak hours. Eighty percent of the children, mostly girls, younger children (6-10), and the lower skin phototypes used sunscreens, but only 38% used them on a regular basis, whereas 20% applied them after sunbathing and 42% used a single daily application. Two percent of the children used sunglasses and 5% wore a T-shirt regularly. The dermatologist and pediatrician play an important role in advising parents that the sun is good for children, but appropriate measures must be taken to reduce any risks, both immediately and in the long term.     

Melanoma awareness and sun exposure in Leicester

The city of Leicester, in conjunction with other centres throughout the U.K., was targeted for publicity about melanoma over a 3-year period from 1987 to 1989. We report the results of a survey to assess the level of awareness of melanoma, and to document current sunbathing practices subsequent to that period. The general level of awareness of melanoma in the community was good (74%). People who knew about melanoma were more likely to use a sunscreen at home and abroad (odds ratios 1·63, 95% CI 1·19-2·24 and 1·39. 95% CI 1·03-1·86). but paradoxically more likely to sunbathe than those who had never heard of melanoma (odds ratio 1·33. 95% CI 1·03-1·72). Females were more knowledgeable than males (odds ratio 1·74, 95% CI 1·26-2·22), but continued to sunbathe. Teenagers and young adults tended to be relatively ignorant of melanoma, and were less likely to protect themselves against sunburn while sunbathing than other age groups. Teenagers, young adults, and males need to be targeted more effectively in future publicity campaigns. Furthermore, many people who know about melanoma continue to put themselves at risk by sunbathing. New strategies need to be developed to influence behaviour as well as increasing awareness.     

银屑病与日光照射相关性的机制

银屑病是一种常见的慢性炎症性皮肤病,其发病原因尚未完全清楚,现多归因于遗传与环境因素的交互作用,其中日光作为环境因素的一个方面与银屑病的发病和转归有着明显的相关性。日光中的紫外线可致角质形成细胞凋亡、并能调节机体异常的免疫应答反应从而减轻银屑病的临床症状。日光照射还可促进皮肤合成维生素D,促进角质形成细胞再生。然而,紫外线也是产生活性氧最常见的污染物,如果体内活性氧生成量增加超出机体的抗氧化能力则可能诱发银屑病,部分解释了光敏性银屑病的发生原因。     

Modelling the seasonal variation of vitamin D due to sun exposure

Background The current interest in vitamin D as a preventive agent in many chronic diseases has led to a reappraisal of adequate sun exposure. Yet just what constitutes adequacy remains to be clearly defined and validated. To do this requires an understanding of how behaviour outdoors during the year translates into seasonal changes in vitamin D status. Objectives To develop a model for estimating the changes in serum 25‐hydroxyvitamin D [25(OH)D] levels as a consequence of sun exposure throughout the year. Methods A novel mathematical model is described that incorporates the changes in serum 25(OH)D following a single, whole‐body exposure to solar ultraviolet radiation with daily sun exposure in order to estimate the annual variation in serum 25(OH)D. Results The model yields results that agree closely with measured data from a large population‐based study. Application of the model showed that current advice about 10–20 min of daily sun exposure during the summer months does little in the way of boosting overall 25(OH)D levels, while sufficient sun exposure that could achieve a worthwhile benefit would compromise skin health. Conclusions There is little in the way of public health advice concerning the benefits of sun exposure that can be given as an effective means of maintaining adequate vitamin D levels throughout the year. Instead it would seem safer and more effective to fortify more foods with vitamin D and/or to consider the use of supplements during the winter months. Messages concerning sun exposure should remain focused on the detrimental effects of excessive sun exposure and should avoid giving specific advice on what might be ‘optimal’ sun exposure.     

Regional distribution of melanocytic naevi in relation to sun exposure, and site-specific counts predicting total number of naevi.

The role of exposure to ultraviolet light in the formation of melanocytic naevi was analysed by investigating the regional naevus distribution in 310 subjects (30-50 years) from a Swedish census file. The lateral aspect of the arms and the back had the largest concentration of naevi. The mean naevus count per unit surface area was higher in intermittently exposed than in rarely exposed skin (p less than 0.001), while the lowest mean count was found in chronically exposed skin. These results support the idea that intermittent exposure to ultraviolet light has a "naevogenic" effect while chronic exposure might be protective. Dysplastic naevi had a distribution pattern quite different from common naevi. Considering the distribution pattern solely, dysplastic naevi seem to develop independently of exposure to ultraviolet light. The numbers of naevi in different skin areas were tested for their power in predicting the total body naevus count. The strongest correlations were found between total counts and counts on the anterior surface of the thighs and the lateral aspect of the arms. Counts from any of these areas will provide a practical and satisfactory estimate of the total number of naevi.     

Malignant melanoma: aetiological importance of individual pigmentation and sun exposure

A case-control study of cutaneous malignant melanoma (CMM) was based on 523 incident cases and 505 age- and sex-matched controls selected from the general population. The purpose was to investigate the relative risk of developing CMM associated with different sun habits and indicators of pigmentation, such as skin type, eye colour and hair colour. Compared to people with black hair, blonde subjects had a relative risk of 744 (95% confidence interval, 45.8–120.8). Associations with skin type and eye colour were considerably weaker. Relative risks of about 1.5–2.5 were found for certain sun habits. The results suggest that in a population of Caucasian origin with a predominantly fair complexion, pigmentary status characterized by hair colour is a far more important aetiological factor than sun habits.