Abstract
Photoaging of the skin depends primarily on the degree of ultraviolet radiation (UVR) and on an amount of melanin in the skin (skin phototype). In addition to direct or indirect DNA damage, UVR activates cell surface receptors of keratinocytes and fibroblasts in the skin, which leads to a breakdown of collagen in the extracellular matrix and a shutdown of new collagen synthesis. It is hypothesized that dermal collagen breakdown is followed by imperfect repair that yields a deficit in the structural integrity of the skin, formation of a solar scar, and ultimately clinically visible skin atrophy and wrinkles. Many studies confirmed that acute exposure of human skin to UVR leads to oxidation of cellular biomolecules that could be prevented by prior antioxidant treatment and to depletion of endogenous antioxidants. Skin has a network of all major endogenous enzymatic and nonenzymatic protective antioxidants, but their role in protecting cells against oxidative damage generated by UV radiation has not been elucidated. It seems that skin's antioxidative defence is also influenced by vitamins and nutritive factors and that combination of different antioxidants simultaneously provides synergistic effect.
Highlights
Unlike chronological aging, which is predetermined by individual’s physiological predisposition, photoaging depends primarily on the degree of sun exposure and on an amount of melanin in the skin
Many studies confirmed that acute exposure of human skin to ultraviolet radiation (UVR) leads to oxidation of cellular biomolecules that could be prevented by prior antioxidant treatment and to depletion of endogenous antioxidants
Individuals who have a history of intensive sun exposure, live in sunny geographical areas, and have fair skin will experience the greatest amount of ultraviolet radiation (UVR) skin load and severe photoaging [1, 2]
Summary
Unlike chronological aging, which is predetermined by individual’s physiological predisposition, photoaging depends primarily on the degree of sun exposure and on an amount of melanin in the skin. UVA (320 to 400 nm) was believed to have a minor effect on the skin, but studies showed that they penetrate deeper in the skin (e.g., about 20% at 365 nm), are more abundant in sunlight (95% of UVA and 5% of UVB), and exhibit more severe damage [9, 10]. The exposure of human to environmental and artificial UVR has increased significantly in the last 50 years This is due to an increased solar UVR as a consequence of the stratospheric ozone depletion, use of sunscreens, false believe of being well protected while exposed to sun for longer time, outdoor leisure activities, and prolonged life expectancy in industrialized countries [11]
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