*** Welcome to piglix ***

Photoaging


Photoaging or photoageing (also known as "dermatoheliosis") is a term used for the characteristic changes to skin induced by chronic UVA and UVB exposure.Tretinoin is the best studied retinoid in the treatment of photoaging

The deterioration of biological functions and ability to manage metabolic stress is one of the major consequences of the aging process. Aging is a complex, progressive process that leads to functional and esthetic changes in the skin. This process can result from both intrinsic (i.e., genetically determined) as well as extrinsic processes (i.e., environmental factors). Photoaging is attributed to continuous, long-term exposure to ultraviolet (UV) radiation of approximately 300–400 nm, either natural or synthetic, on an intrinsically aged skin.

UVB rays are a primary mutagen that can only penetrate through the epidermal (outermost) layer of the skin, resulting in DNA mutations. These mutations arise due to chemical changes, the formation of cyclobutane pyrimidine dimers and photoproducts formed between adjacent pyrimidine bases. These mutations may be clinically related to specific signs of photoaging such as wrinkling, increasing in elastin and collagen damage.

The epidermal layer does not contain any blood vessels or nerve endings but melanocytes and basal cells are embedded in this layer. Upon exposure to UVB rays, melanocytes will produce melanin, a pigment that gives the skin its color tone. However, UVB will cause the formation of freckles and dark spots, both of which are symptoms of photoaging. With constant exposure to UVB rays, signs of photoaging might appear and precancerous lesions or skin cancer may develop.

UVA rays are able to penetrate deeper into the skin as compared to UVB rays. Hence, in addition to the epidermal layer, the dermal layer will also be damaged. The dermis is the second major layer of the skin and it comprises collagen, elastin, and extrafibrillar matrix which provides structural support to the skin. However, with constant UVA exposure, the size of the dermis layer will be reduced, thereby causing the epidermis to start drooping off the body. Due to the presence of blood vessels in the dermis, UVA rays can lead to dilated or broken blood vessels which are most commonly visible on the nose and cheeks. UVA can also damage DNA indirectly through the generation of reactive oxygen species (ROS), which include superoxide anion, peroxide and singlet oxygen. These ROS damage cellular DNA as well as lipids and proteins.


...
Wikipedia

...