[Photo oxidative reactions of psoralens and their role in therapy of dermatoses]

Abstract

Psoralenes (furocoumarins) in combination with ultraviolet (UV) A radiation (320-400 nm) are used in the treatment of vitiligo, psoriasis, cutaneous T-cell lymphoma and other skin and autoimmune diseases (PUFA therapy). The mechanism of psoralene-photosensitive modification of biologically significant molecules, such as DNA, protein unsaturated lipids, antioxidants, etc. is considered in the paper. Particular emphasis is laid on the mechanism and biomedical significance of photo reactions proceeding via the stage of formation of psoralene photo oxidation products (POP). POP causes oxidative damage to many molecules in in vitro experiments and mediates the T-cell immunity cell in vivo, as appeared as suppression of delayed hypersensitivity and contact sensitivity in mice. The use of randomized double blind control has indicated that POP has therapeutical effects on eczema. A new modality of psoralene photo chemotherapy that consists in the UV-A radiation of psoralene solution followed by its administration (POP therapy) to patients. Unlike conventional PUFA therapy, POP therapy does not require the patients' skin to be exposed to UF-A radiation, which allows adverse effects, such erythema, skin hyperpigmentation, etc. to be avoided.