The application of antioxidants in investigations and optimization of photochemotherapy

Psoralens (furocoumarins) are photosensitizers of plant origin. They are used in combination with near-ultraviolet (320-400 nm) light for the treatment of vitiligo, psoriasis, cutaneous T-cell lymphoma (CTCL), alopecia areata, eczema, and other skin diseases. Photobiological effects of psoralens in humans are numerous. They photosensitize erythema, hyperpigmentation, and skin aging, affect immune system, etc. Molecular mechanisms of photochemical reactions of psoralens with substrates are also numerous. The molecular basis and the relationships between different photobiological effects of psoralens remain the subject of discussion. The use of antioxidants is an essential instrument for clearing up these problems as well as for the progress of photochemotherapy. It was found that antioxidants (alpha-tocopherol, butylated hydroxytoluene, etc.) selectively inhibited the photochemical stage of erythema and hyperpigmentation but had no impact on the post-irradiation stages of these processes. Evidently, the basis of these processes is the reaction of psoralen-photosensitized oxidation of unsaturated lipids and the impairment of barrier functions of biomembranes, since the photochemical stage of these reactions is inhibited by the antioxidant. At the same time, antioxidants did not inhibit the therapeutic effect in the cases of psoriasis and CTCL. Thus, antioxidants can be used as a tool for improvement of psoralen photochemotherapy.