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Abstract
Human skin is constantly directly exposed to the air, solar radiation, other environmental pollutants or other mechanical and chemical insults, which are capable of inducing the generation of free radicals as well as reactive oxygen species (ROS) of our own metabolism. Extrinsic skin damage develops due to several factors: ionizing radiation, severe physical and psychological stress, alcohol intake, poor nutrition, overeating, environmental pollution, and exposure to UV radiation (UVR). It is estimated that among all these environmental factors, UVR contributes up to 80%. UV-induced generation of ROS in the skin develops oxidative stress, when their formation exceeds the antioxidant defence ability of the target cell. The primary mechanism by which UVR initiates molecular responses in human skin is via photochemical generation of ROS mainly formation of superoxide anion (O2-), hydrogen peroxide (H2O2), hydroxyl radical (OH), and singlet oxygen (1O2). Oxidative phosphorylation in the mitochondria is an important energy-producing process for eukaryotic cells, but this process can also result in producing potentially cell-damaging side products, e.g. free radicals and other ROS. The only protection of our skin is its endogenous protection (melanin and enzymatic antioxidants) and antioxidants we consumed with the food (vitamin A, C, E, etc.). Dietary antioxidants thus play a major role in maintaining the homeostasis of the oxidative balance. Vitamin C (ascorbic acid), vitamin E (tocopherol), beta-carotene and other micronutrients such as carotenoids, polyphenols and selenium have been evaluated as antioxidant constituents in the human diet. The most important strategy to reduce the risk of sun UVR damage is to avoid the sun exposure and the use of sunscreens. The next step is the use of exogenous antioxidants orally or by topical application and interventions in preventing oxidative stress and in enhanced DNA repair.
Introduction
Human skin is naked and is constantly directly exposed to the air, solar radiation, other environmental pollutants or other mechanical and chemical insults, which are capable of inducing the generation of free radicals as well as reactive oxygen species (ROS) of our own metabolism. Reactive oxygen species are usually of little harm if intracellular mechanisms that reduce their damaging effects work properly. Most important mechanisms include antioxidative enzymatic and non-enzymatic defences as well as repair processes. But the problem arises with age, when endogenous antioxidative...