DIFFERENTIAL-EFFECTS OF UV-B AND UV-C COMPONENTS OF SOLAR-RADIATION ON MAP KINASE SIGNAL-TRANSDUCTION PATHWAYS IN EPIDERMAL-KERATINOCYTES

Exposure to solar ultraviolet (UV) light is a major cause of skin canc er, the most common human neoplasm. The earth's upper atmosphere absor bs the high energy UV-C wavelengths (100-280 mm), while allowing trans mission of UV-B (280-320 nm) and UV-A (320-400 nm). It is therefore UV -B and to some extent UV-A, that contributes to most human skin malign ancies. We report that the exposure of cultured keratinocytes or skin to UV-C radiation causes activation of MAP kinases (ERK and JNK). In c ontrast, the solar radiation associated with skin cancer (UV-B) was an ineffective activator of the ERK and JNK signal transduction pathways . Therefore, while exposure of epidermal cells to UV-C radiation under laboratory conditions causes marked activation of MAP kinase signal t ransduction pathways, only a low level of MAP kinase signaling is invo lved in the response of skin to biologically relevant solar radiation.