No one would underestimate the importance of sunlight to the evolution of life on the earth and its role in human development. However, all humans - especially individuals who are lightly pigmented or whose occupation or lifestyle exposes them to excessive amounts of sunlight - are potentially susceptible to its deleterious effects. These effects can range from acute biological responses, such as sunburn and skin tanning, to conditions resulting from chronic exposure such as photoaged skin and potentially life-threatening conditions such as skin cancer. The objective of this review is to present a concise and up-to-date perspective on the effects of UVB, UVA, visible, and infrared radiation on cutaneous biochemistry and physiology.

The presence of ozone (O(3)) in photochemical smog is an important health concern. We hypothesized that the stratum corneum (SC), as the outermost skin layer and the permeability barrier of the skin, represents a sensitive target for O(3)-induced oxidative stress. To test this hypothesis, SKH-1 hairless mice were anesthetized and exposed for 2 h to O(3) by using two strategies: (i) single exposures to 0 (n = 12), 1 (n = 4), 5 (n = 4), and 10 (n = 4) ppm; and (ii) repeated daily exposures to 0 ppm (controls; n = 4) and 1 ppm (n = 4) for six consecutive days. New techniques based on the removal of SC by tape stripping were used to analyze the biologic effects of O(3) with respect to vitamin E depletion and lipid peroxidation. SC tissue was extracted from the tape and immediately analyzed by HPLC for vitamin E and malondialdehyde (MDA) concentrations. After in vivo exposure to increasing O(3) doses, vitamin E was depleted and MDA formation was increased, both in a dose-dependent manner. Remarkably, repeated low-level O(3) exposures resulted in cumulative oxidative effects in the SC: As compared with O(3) exposures of 0 ppm (alpha-tocopherol, 8.95 +/- 1.3 pmol per mg; gamma-tocopherol, 3.00 +/- 0.3 pmol per mg; MDA, 3.69 +/- 0.3 pmol per mg), vitamin E was depleted (alpha-tocopherol, 2.90 +/- 0.6 pmol per mg, p < 0.001; gamma-tocopherol, 0.5 +/- 0.1 pmol per mg, p < 0.001) and MDA levels were increased (4.5 +/- 0.2; p < 0.01). This report demonstrates the unique susceptibility of the SC to oxidative damage upon exposure to O(3).

The impact of troposphere ozone (O(3)), the major oxidant in photochemical smog, on the overall wellbeing of skin is of considerable interest. To date, limited information is available on the impact of O(3) on human skin. Using a specially designed O(3) exposure chamber, we provide the first evidence that exposure of human skin to O(3) (0.8 ppm, 2-h time-weighted average) significantly reduced vitamin E by 70% and concomitantly increased lipid hydroperoxides by 2.3 fold in the superficial stratum corneum (SC). Although the dose of O(3) used here reduced the resident microflora population by 50% and created a state of oxidative stress within the SC, it did not affect several key enzymes involved in SC homeostasis including the redox-sensitive transglutaminase and the SC tryptic (KLK5) and chymotryptic (KLK7) proteases. Importantly, no signs of skin dryness or erythema were observed. We hypothesize that the limited effects of low doses of O(3) on SC function is attributable to several factors including: (i) protection provided by the anti-oxidant defence system; (ii) inability of O(3) to penetrate the SC; and (iii) limited water available to catalyse the Criegee reaction. Although chronic exposure to O(3) may produce a different outcome than that reported here, our data suggest that exposure to environmentally relevant doses of O(3), at best, induces a moderate state of oxidative stress, without producing a visible clinical response. In our opinion, exposure of skin to UV radiation is a much more significant threat than exposure to ground-level O(3).

SynopsisThere is growing scientific evidence that the health, well-being and the attractiveness of the skin are strongly influenced by nutrition. Consumers recognize this and have supported the creation of a global cosmeceuticals market estimated in 2010 at $27.2 billion. Early in 2011, the US Department of Health and Human Services and Department of Agriculture issued the Dietary Guidelines for Americans, 2010. Twelve vitamins and nine minerals were recognized as essential. The minerals include calcium, copper, iron, magnesium, phosphorus, selenium, zinc, potassium and sodium. Although the topical benefits of several minerals such as zinc, magnesium and iron are recognized and, in some cases, approved by the FDA, the topical benefits of the others to the skin are largely unexplored and unexploited. This review attempts to summarize what has been published in the literature on the interactions of the eight of the nine essential elements with the skin. Ré suméLes preuves s'accumulent pour indiquer que la nutrition influence fortement la santé, le bien-être et l'attractivité de la peau. Les consommateurs en sont conscients et ont permis d'établir un marché mondial de compléments alimentaires "nutracosmétiques" estimé en 2010 à 27,2 milliards de dollars. Début 2011, les Ministères de la Santé et de l'Agriculture des USA ont édité un guide diététique adressé à la population américaine. Ce guide reconnaît douze vitamines et neuf minéraux en tant qu'éléments essentiels. Les minér-aux incluent le calcium, le cuivre, le fer, le magnésium, le phosphore, le sélénium, le zinc, le potassium et le sodium. Bien que les bienfaits cutanés des minéraux tels que le zinc, le magnésium et le fer sont reconnus et parfois approuvés par la FDA, les bénéfices au niveau de la peau des autres sont, à ce jour, largement sousexplorés et sous-exploités. La présente revue se propose de résumer ce qui a été publié dans la littérature sur les interactions entre les huit (sur neuf) éléments minéraux essentiels avec la peau.

The earliest known microfossil records suggest that microorganisms existed on the earth approximately 3.8 billion years ago. Not only did sunlight drive this evolutionary process, but it also allowed photosynthetic organisms to elaborate oxygen and fundamentally change the earth's atmosphere and subsequent evolution. Paradoxically, however, an atmosphere of 20% oxygen offers aerobic organisms both benefits and some key challenges, particularly, to the external integument. This mini-review summarizes almost 40 years of research and provides a "60 000-foot" perspective on cutaneous oxidative stress. Topics reviewed include the following: What are free radicals and reactive oxygen species? Where do they come from? What is their chemistry? What are their roles and/or impact on the skin? What antioxidant defenses are available to mitigate oxidative stress.