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Introduction
Peter Wolf and Thomas M. Rรผnger Ultraviolet Radiation 86
Key features
ยExposure of the skin to UV light has acute, short-term effects and chronic, long-term effects, both of which are wavelengthdependent and occur even at non-erythemogenic doses
ยUV light is sensed via absorption by chromophores; these include urocanic acid, nucleotide bases, membrane lipids, tryptophan, and 7-dehydrocholesterol (provitamin D)
ยUV light induces several types of DNA damage in a wavelength- dependent manner, including 6-4 photoproducts, pyrimidine dimers, and oxidative guanine base modifications; pyrimidine dimers are the most important pre-mutagenic DNA lesions
ยUV light-induced mutations play a pivotal role in photocarcino- genesis; some base substitution mutations (e.g. CโT, CCโTT) are so typical for UV light that they have been termed signature or fingerprint mutations
ยUV light triggers both pro- and anti-inflammatory responses, primarily via innate immunity and adaptive immunity, respectively
ยUV-induced immunosuppression contributes to skin carcino- genesis by induction of regulatory T cells and immunosuppressive cytokines such as IL-10
ยThe proapoptotic, immunomodulatory, antipruritic, antifibrotic, and propigmentary properties of UV light are employed to treat various inflammatory and neoplastic skin disorders