Oxidative stress in the pathogenesis of skin disease.

Solar light is the primary source of UV radiation for all living systems. UV photons can mediate damage through two different mechanisms, either by direct absorption of UV via cellular chromophores, resulting in excited states formation and subsequent chemical reaction, or by phosensitization mechanisms, where the UV light is absorbed by endogenous (or exogenous) sensitizers that are excited and their further reactions lead to formation of reactive oxygen species (ROS). These highly reactive species can interact with cellular macromolecules such as DNA, proteins, fatty acids and saccharides causing oxidative damage. Direct and indirect injuries result in a number of harmful effects such as disrupted cell metabolism, morphological and ultrastructural changes, attack on the regulation pathways and, alterations in the differentiation, proliferation and apoptosis of skin cells. Processes like these can lead to erythema, sunburn, inflammation, immunosuppression, photoaging, gene mutation, and development of cutaneous malignancies. The endogenous and exogenous mechanisms of skin photoprotection are discussed.

/pdf/ultraviolet-light-induced-alteration-to-the-skin-iosnna7jdm.pdf

Ultraviolet light induced alteration to the skin.

Exposure to solar radiation, particularly its ultraviolet (UV) B component, has a variety of harmful effects on human health. Some of these effects include sunburn cell formation, basal and squamous cell cancers, melanoma, cataracts, photoaging of the skin, and immune suppression. Amongst these various adverse effects of UV radiation, skin cancer is of the greatest concern. Over the years, changes in lifestyle has led to a significant increase in the amount of UV radiation that people receive, and this consequently has led to a surge in the incidence of skin cancer. The development of skin cancer is a complex multistage phenomenon involving three distinct stages exemplified by initiation, promotion and progression stages. Each of these stages is mediated via alterations in various cellular, biochemical, and molecular changes. Initiation, the first step in the carcinogenesis process is essentially an irreversible step in which genetic alterations occur in genes that ultimately leads to DNA modification and fixation of mutation. Tumor promotion is the essential process in cancer development involving clonal expansion of initiated cells giving rise to pre-malignant and then to malignant lesions, essentially by alterations in signal transduction pathways. Tumor progression involves the conversion of pre-malignant and malignant lesions into an invasive and potentially metastatic malignant tumor. All these processes for skin cancer development involve stimulation of DNA synthesis, DNA damage and proliferation, inflammation, immunosuppression, epidermal hyperplasia, cell cycle dysregulation, depletion of antioxidant defenses, impairment of signal transduction pathways, induction of cyclooxygenase, increase in prostaglandin synthesis, and induction of ornithine decarboxylase. Photochemoprevention has been appreciated as a viable approach to reduce the occurrence of skin cancer and in recent years, the use of agents, especially botanical antioxidants, present in the common diet and beverages consumed by human population have gained considerable attention as photochemopreventive agents for human use. Many such agents have also found a place in skin care products. Although this is more common in oriental countries, its popularity is significantly growing in western countries. In this article, we have summarized the available information of laboratory studies on UVB-mediated signaling that can be exploited as targets for photochemoprevention. We suggest that the use of skin care products supplemented with proven chemopreventive agents in conjunction with the use of sunscreens along with educational efforts may be an effective strategy for reducing UV-induced photodamage and skin cancer in humans. The mechanistic basis for the use of such products is discussed.

Photochemoprevention of ultraviolet B signaling and photocarcinogenesis

The concept of systemic photoprotection by dietary means is gaining momentum. Skin is continuously exposed to ultraviolet (UV) radiation, the major cause of skin disorders such as sunburn, photodamage, and nonmelanoma skin cancer. Most of the erythemal annual UV dose is encountered under nonvacation conditions, when no sunscreen is applied. In the absence of topically added compounds, skin protection depends solely on endogenous defense. Micronutrients can act as UV absorbers, as antioxidants, or can modulate signaling pathways elicited upon UV exposure. UV-induced erythema is a suitable parameter to assess photoprotection. Dietary protection is provided by carotenoids, tocopherols, ascorbate, flavonoids, or n-3 fatty acids, contributing to maintenance resistance as part of lifelong protection.

https://www.dr-baumann-international.co.uk/science/Nutritional%20Protection%20against%20Skin%20Damage%20from%20Sun%20Light.pdf

Nutritional protection against skin damage from sunlight.

Exposure of the skin to ultraviolet (UV) radiation, particularly its UV-B component (280-320 nm), from the sun results in erythema, edema, hyperplasia, hyperpigmentation, sunburn cells, immunosuppression, photoaging, and skin cancer. Amongst these various adverse effects of UV-B radiation, skin cancer and photoaging are of great concern. More recent changes in lifestyle have led to a significant increase in the amount of UV-B radiation people receive leading to a surge in the incidence of skin cancer and photoaging. As these trends are likely to continue in the foreseeable future, the adverse effect of UV-B has become a major human health concern. Therefore, development of novel strategies to reduce the occurrence of skin cancer and delay the process of photoaging are highly desirable goals. One approach to reduce their occurrence is through photochemoprevention, which we define as the use of agents capable of ameliorating the adverse effects of UV-B on the skin. Photochemoprevention via use of botanical antioxidants, present in the common diet of human have gained considerable attention as photochemopreventive agents for human use. Many such agents have also found a place in skin care products. This review will focus on the effects of selected botanical antioxidants in the prevention of photocarcinogenesis and photoaging.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1600-0625.2006.00466.x

Botanical antioxidants in the prevention of photocarcinogenesis and photoaging.

Photochemoprevention has become an important armamentarium in the fight against ultraviolet radiation (UVR)-induced damage to the skin. Among many UVR-induced damages, skin cancer is of the greatest concern as its rates have been steadily increasing in recent years and the same trend is expected to continue in the future. Ultraviolet radiation increases oxidative stress in skin cells by causing excessive generation of reactive oxygen species (ROS), leading to cancer initiation and promotion. Antioxidants have the capability to quench these ROS and much recent work shows that some of these can inhibit many UVR-induced signal transduction pathways. Thus, identifying nontoxic strong antioxidants - capable of preventing UVR-induced skin cancer - has become an important area of research. The use of botanical antioxidants in skin care products is growing in popularity. A wide range of such agents has been shown to prevent skin cancer in animal model systems. New agents are constantly being investigated; however, only a few have been tested for their efficacy in humans. Animal model and cell culture studies have clarified that antioxidants act by several mechanisms at various stages of skin carcinogenesis. This review focuses on skin cancer photochemopreventive effects of selected botanical antioxidants.

Sleem F'guyer

Papers

Photochemoprevention of skin cancer by botanical agents.