Among aggressive environmental factors, solar radiation has the most detrimental effect on the skin, according to Pannochka, an online publication for girls and women aged 14 to 35.. net The set of signs of skin aging caused by the action of solar radiation is called photoaging.

There is much in common between the phenomena of photoinduced and chronobiological aging, moreover, these processes are synergistic..

However, they also have some differences in physiological, pathological, histological and clinical signs, and various approaches are used to correct them..

Photoaging.

The processes of photoaging are affected by: skin phototype, wavelength and spectrum of insolation, age of onset of exposure, duration of the solar energy accumulation period.

The sun emits electromagnetic energy in a wide range of wavelengths: 200-400 nm - ultraviolet irradiation (UVR) (200-290 nm - UV-C, 290-320 nm UV-B, 320-400 nm - UV-A), 400-.

UV-C is completely blocked by the ozone layer, however, UV-C rays cause conjunctivitis, they convert the histidine of the skin into histamine and cause inflammation.. In addition, UV-C rays destroy the bactericidal flora of the skin surface, thereby breaking the fatty film and, as a result, contributing to dehydration and dryness of the skin..

Under the action of UV-B rays, the cell nuclei of epidermocytes are destroyed, a histamine-like substance is formed, causing vasodilation, reddening of the skin, inflammation. In order to subsequently protect itself from radiation, the skin forms a “corn”, thickening the stratum corneum and releasing a pigment - melanin, which absorbs the sun's rays..

UV-B - stimulates the production of epidermal growth factor, damaging DNA, which leads to the development of skin cancer, causes a phototoxic reaction in the epidermis, leading to immunosuppression. Histologically manifested by dyskeratosis and a decrease in the number of Langerhans cells, and clinically by burns and hyperpigmentation. UV-C and B contribute to the formation of vitamin D in the skin.

UV-A - causes oxidative stress leading to photoaging and carcinogenesis, and also causes sunburn. Infrared radiation has a thermal effect.

Thus, the most active spectrum is ultraviolet, which promotes immune reactions in the skin, accompanied by the synthesis and release of arachidonic acid derivatives, causes inflammation and the development of photochemical reactions, oxidative stress..

Genetic mutations occur, the nature of gene expression changes. Cell division is stimulated, which leads to a mismatch between proliferation and differentiation and underlies carcinogenesis.

The degree of penetration into the skin of radiation of different wavelengths (Rolf Kawa et al.. , 2000) Glycation products of aging skin (caramelized proteins) are endogenous photosensitizers that contribute to photoaging and carcinogenesis. UV radiation causes direct damage to biological molecules (proteins, nucleic acids) and indirect - mediated by free radicals.

When light quanta are absorbed, the molecules go into unstable excitation, resulting in the formation of stable compounds and free radicals.. Proteins and nucleic acids have a maximum absorption, so they are the first to be exposed to the harmful effects of UV radiation..

Then, as a result of free radical reactions, the lipid layers of the epidermis and cell membranes are damaged.. Lipid oxidation reactions proceed with the release of a large amount of reactive oxygen species, which in turn damages proteins and nucleic acids..

Histologically, during photoaging, actinic elastosis is observed in the dermis: elastic fibers are damaged, disorganized. In the dermis, there are many cellular infiltrates represented by fibroblasts, histiocytes, monocytes and macrophages.

The number of collagen fibers decreases, they swell and fragment. The capillaries of the dermis are dilated, however, subsequently there is a decrease in the number and size of vessels. At the level of the epidermis, there is a thickening of the structure due to hyperkeratosis, acanthosis.

The number and functional activity of melanocytes decreases, their uneven distribution along the thickened basement membrane is recorded. Atypical cells appear. Free radicals cause damage at all cellular levels, up to mutations in the gene apparatus.

In most cells, as a result of mutations, a program for self-destruction (apoptosis) comes into action, but melanocytes do not have such a program, which leads to the accumulation of mutations and is one of the moments leading to melanoma.

medbe. en.