Abstract
Photoaging, which is different from intrinsic or chronological aging, is a skin change induced by chronic and repeated exposure to ultraviolet light (UV). Photoaging skin is characterized by sallowness, mottled pigmentation, solar lentigines, dry and rough skin, telangiectasia, loss of skin tone, leathery texture, laxity, coarse and fine wrinkles, and benign and malignant skin tumors. The dermis of photoaging skin displays solar elastosis and prominent alterations in the collagenous extracellular matrix of the connective tissue. Solar elastosis is the accumulation of massive amounts of abnormal elastic material in the dermis. Some studies using a novel transgenic mouse model expressing a human elastin promoter-reporter gene construct have revealed that an increase in human elastin promoter activity is involved in accelated synthesis of elastin-related proteins. UV irradiation induces an increase in the activity, mRNA, and protein of matrix metalloproteinases via downstream signal transduction through activation of MAP kinase pathways and may contribute to photoaging. Sunscreens are known to be capable of preventing photoaging.
