LOW-DOSES OF REPETITIVE ULTRAVIOLET A INDUCE MORPHOLOGIC CHANGES IN HUMAN SKIN

Repetitive exposure of skin to sunlight is known to result in dermatoh eliosis, characterized by photoaging and carcinogenesis, It has been d emonstrated previously that relatively large amounts of ultraviolet (U V) A can produce photodamage and it is believed that UVB plays a major role in the induction of photodamage and photocarcinogenesis. The stu dy reported here determines the cutaneous effects of minimal erythemal amounts of solar-simulated UV radiation as well as suberythemal and m inimal erythemal doses of UVA, Previously non-sunexposed human skin wa s irradiated twice weekly for 24 weeks, Biopsies were obtained 12, 24 and 36 weeks after the initial irradiation and assessed for both epide rmal and dermal alterations, Dermal elastic tissue content was measure d via computerized image analysis, All UV treatment regimens produced observable epidermal and dermal changes, These alterations were observ ed after only 12 weeks of twice-weekly irradiation and were still evid ent 12 weeks after the final irradiation. Interestingly, UVA irradiati on produced a decrease in elastic tissue content whereas solar-simulat ed UV produced a slight increase, Most notable were the changes produc ed by the suberythemal dose of UVA, Surprisingly, this relatively low UVA dose produced a reduction in elastic tissue content, The results o f this investigation demonstrate that small amounts of UVA or solar-si mulated UV are capable of producing cutaneous photodamage. These findi ngs suggest that even suberythemal doses of repetitive UVA may lead to photoaging of the skin and that there is a need for daily broad spect rum UV protection.