Photoaging of human skin

Photoaging is a process of premature aging of the skin due to long-term chronic exposure to solar radiation. Solar radiation may have particularly unfavourable effects on the skin connective tissue resulting in the accumulation of abnormal elastic fibres and simultaneous degradation of collagen fibres as well as other components of the intercellular matrix. Skin exposure to intense thermal radiation (thermal aging) may have similar effects to those observed in the case of photoaging. The paper discusses the mechanism of elastin level regulation in the photoaging process in which human leukocyte elastase and lysozyme are involved. The mechanism of collagen fibre degradation and the role of AP-1 factor in this process are also addressed. The characteristics of individual ultraviolet radiation spectra are provided and the influence of ultraviolet radiation on the skin immune system is discussed, with particular focus on the type B ultraviolet radiation stimulation of anti-bacterial peptides production, as well as the role of Treg lymphocytes in contact immunosuppression and immunotolerance induced by ultraviolet radiation.