earticle

영어

The skin serves as a protective barrier to various environmental factors, such as ultraviolet (UV) radiation, air pollution, and environmental hormones. These environmental factors enhance the aging of the skin. Skin aging is divided into intrinsic (chronological) and extrinsic processes that involve increased wrinkling, sagging and laxity. Extrinsic aging is generally caused by exposure to UV, which increases the production of reactive oxygen species in skin cells and may cause hyperpigmentation, skin cancer, and photoaging. Upon exposure of the epidermis to UV radiation, melanogenesis is enhanced by activation of melanogenesis enzymes, such as tyrosinase- related proteins (TRP) TRP-1 and TRP-2. These melanogenesis enzymes are located in the melanosomal membrane and catalyze the conversion of melanin to L-tyrosine. Upon exposure of the dermis to UV radiation, photoaging is induced by alterations in expression of collagen and matrix metalloproteinases (MMPs). Expression of MMP- 1 is regulated by the nuclear transcription factor activator protein 1 and nuclear factor-κB in UV-exposed dermal fibroblasts. Thus, collagen production is reduced in UV-exposed skin due to the constant degradation of collagen by increased levels of MMPs. Together, these events affect the regulation of cell signaling pathways in skin cells. In this review, we present an overview of the cellular mechanisms in UV-exposed skin.