摘要：Just like every other part of the organism, the skin ages as a result of the passage of time. That process is called chronologic or intrinsic aging. However, skin is also exposed to external insults, such as UV radiation, which is the most influential extrinsic factor in skin aging, causing so called photoaging or extrinsic skin aging. Photoaging is a cumulative process which depends on the degree of UV exposure and the skin type. It is much more visible in individuals with skin types I and II and, less prominent in dark-skinned population. Chronic sun exposure can result in numerous changes in human skin, particularly on the face, nape, and arms. Keratinocytes, melanocytes, fibroblasts, and endothelial cells are altered by UV radiation. Therefore, changes in photoaging include wrinkling, elastosis, actinic keratoses, irregular pigmentation, telangiectases, and the development of malignant skin tumours. In the last decades, important progress has been made in understanding molecular mechanisms of photoaging. It is a complex process in which UV radiation has effects on numerous molecular processes that damage the skin, especially connective tissue of the skin. These processes include cell surface receptors, certain signal transduction pathways, transcription factors and, various enzymes involved in the synthesis and degradation of the dermal elements. Initial process in the activation of this process is UV-induced generation of the reactive oxygen species, which can also directly damage cell’s DNA, membrane and proteins. Most of alterations found on the photoaged skin had formerly been considered to be caused by UVB wavelengths. However, a number of recent studies have demonstrated that UVA can also cause burning, elastosis, and skin cancer.
关键词：aging; skin aging; photoaging; UV radiation; elderly population
