Topical and systemic approaches for protection against solar radiation-induced skin damage

The efficacy of topical sunscreens is currently assessed by crude, costly and time consuming in vivo assays. We have previously demonstrated that components of the dermal extracellular matrix (ECM), rich in UV-absorbing amino acids, are susceptible to damage by solar simulated radiation (SSR) in vitro. Here we developed an in vitro method to test the ability of sunscreens to protect fibrillin-rich microfibrils (FRM) and fibronectin, key components of the dermal ECM from UV-induced damage. Solutions of FRM or fibronectin were irradiated without protection, in the presence of a vehicle or a commercially-available flat-spectrum sunscreen. The effect of SSR on molecular structure was determined by atomic force microscopy (FRM) and SDS-PAGE (fibronectin). Following irradiation, FRM periodicity became bi-modally distributed (peaks: 40 nm & 59 nm) compared to the unimodal distribution in unexposed controls (peak: 50 nm). Irradiation in the presence of flat-spectrum sunscreen protected against this change, maintaining the unimodal distribution. SSR induced significant aggregation of fibronectin (p = 0.005), which was abrogated by sunscreen. These results demonstrate that this in vitro assay system is sufficiently sensitive to act as an initial/additional screen of sunscreen efficacy. We conclude that sunscreen can reduce UV-mediated damage of key dermal ECM in vitro and thereby prevent remodelling associated with photoageing.

Many dermatologic diseases are chronic with no definitive cure. For some diseases, the etiology is not completely understood, with treatment being difficult and associated with side effects. In such cases, patients may try alternative treatments to prevent onset, reduce symptom severity, or prevent reoccurrence of a disease. Dietary modification, through supplementation and exclusion, is an extremely popular treatment modality for patients with dermatologic conditions. It is, therefore, important for dermatologists to be aware of the growing body of literature pertaining to nutrition and skin disease to appropriately inform patients on benefits and harms of specific dietary interventions. We address the role of nutrition in psoriasis, atopic dermatitis, urticaria, and bullous diseases and specific dietary modifications as an adjunct or alternative to conventional therapy.

Autoimmune and nonautoimmune bullous diseases can both be associated with significant morbidity and mortality. Although our understanding of the pathogenic mechanisms of these diseases has increased tremendously, there is still much to learn about the various factors affecting their onset, course, and therapy. In recent years, increasing information has been published about the effect of vitamins, minerals, and other nutrients on bullous skin diseases. Some factors are believed to be inducers (thiol and phenol-containing foods in pemphigus), whereas others are believed to be protective (antioxidants in cutaneous porphyrias). This contribution reviews the evidence in the literature of the role of various dietary factors in bullous diseases, including the nonautoimmune and the deficiency dermatoses. Additional studies and new investigations are needed to provide a better understanding of the specific associations of dietary factors with bullous diseases and better management for patients affected by these conditions.

Ultraviolet radiation (UVR) promotes skin cancer development by mutagenic, immunosuppressive, and oxidative-stress-inducing mechanisms; however, certain antioxidants may counteract and prevent UVR-induced photodamage. Lutein is a xanthophyll carotenoid with potent antioxidant activity. Because reactive oxygen species (ROS) are believed to have a role in UVR-induced skin damage, we investigated whether lutein can modify UVR effects including the tissue swelling response to midrange UVR (280–320 nm, ultraviolet B (UVB) radiation) and UVB suppression of contact hypersensitivity (CHS) in both the local and the systemic models of UV-induced immunosuppression. We found that compared to mice fed the standard laboratory diet, mice fed dietary lutein demonstrated significant inhibition of ear swelling owing to UVB radiation. Mice exposed to 1700 J per m² UVB radiation four times at daily intervals and then sensitized to dinitrofluorobenzene at the site of irradiation showed a decreased CHS response upon challenge. This suppression by UVB radiation was significantly inhibited by lutein feeding. When UVB radiation was given at a single dose of 10,000 J per m² to inhibit the induction of CHS at a distant, nonirradiated site, no effect of lutein was seen. Finally, lutein accumulated in the skin of mice following diet supplementation and was shown to decrease ROS generation following UVR exposure. Thus, lutein modulates the skin's response to UVR and may contribute to the defense against some of the deleterious effects of solar radiation.

—La fotoprotección tiene como objeto prevenir el daño que ocurre en nuestra piel como resultado de su exposición a la radiación ultravioleta. La piel posee unos mecanismos de adaptación y defensa para protegerse de esta agresión, cuya eficacia es variable según los individuos, y francamente insuficiente en aquellos con fototipos claros. Por ello se han desarrollado unas estrategias de fotoprotección basadas en reducir el tiempo de exposición solar, sobre todo durante las horas del mediodía, así como cubrirse con ropas y sombreros adecuados, llevar gafas y complementar lo anterior aplicando apropiadamente un fotoprotector de amplio espectro, con factor de protección solar (FPS) 15 o superior. De todos estos métodos, los fotoprotectores son los más utilizados por la población y, por otra parte, sobre los que existe más controversia.

Esta revisión profundiza en los distintos métodos de fotoprotección, especialmente en los fotoprotectores, tópicos y orales, sus tipos, características, efectos colaterales y controversias, así como en los mecanismos de disminución de su efectividad. Asimismo, se facilitan las guías y recomendaciones actuales de fotoprotección para la población en general, si bien, para que se cumplan, es necesario educar a la población. Estas intervenciones educativas deben iniciarse en la infancia, ya que es en esta etapa de la vida en la que la fotoprotección parece ser crucial.

—Sun protection is aimed at preventing damage to our skin as the result of its exposure to solar ultraviolet radiation. The skin has some mechanisms to protect itself from this harm, whose efficacy varies from one person to the next and is clearly insufficient in fair-skinned people.

Current approaches to photoprotection focus on reducing overall exposure to sunlight, especially during peak sun hours; this includes wearing protective clothing, hats and sunglasses and regular use of broad-spectrum high SPF sunscreen (SPF 15 or higher). Using sunscreen is the most common practice for protecting the skin from the sun, although it is the most controversial.

This review summarizes the different approaches to sun protection, with special reference to sunscreens, either oral or topical: their types, main characteristics, side effects, controversies and mechanisms of failure.

Moreover, Public Health Guidelines and Recommendations from the International Agency for Research on Cancer are presented. Public education on sun protection must be aimed at multiple and diverse target populations and activities. Childhood interventions are very important, not only because behavioural changes are easier in children than adults, but also because ultraviolet damage is cumulative and sun protection strategies should start early in life.

The quest to find or develop a systemic photoprotectant that would avoid the limitations associated with topical application of photoprotective agents has been a compelling endeavour. Such an agent would be expected to act by one or more of the following mechanisms, i.e.: (1) attenuation of the level of actinic insult by acting as a barrier to UV rays; (2) competing with the target molecules for the damaging products of the offending agent, e.g., the action of antioxidants; (3) restorative action; and (4) suppression of various stages of the inflammatory response. Several agents whose protective properties were presumed to result from one or more of these mechanisms have been examined in clinical trials. These include the antimalarials, psoralens, carotenoids, retinoids, vitamins C and E, and selenium. Whereas some agents show promise, others have limitations that preclude their consideration as an universal photoprotectant. However, recent attempts at dietary manipulation show some promise for protection against certain solar-induced effects. Specific strategies, namely reduction in total dietary fat and omega-3 fatty acid supplementation, have resulted in protection against non-melanoma skin cancer and other markers of UV-induced tissue damage, respectively. It is in these directions that future research is likely to be most beneficial with regard to systemic protection against UV-insult.