Therapeutic and prophylactic effects of PUVA photochemotherapy on atopic dermatitis-like lesions in NC/Nga mice

Background: Psoralens and ultraviolet A radiation (PUVA) photochemotherapy has been used for severe cases of atopic dermatitis (AD). To understand the mechanisms of action is important for the choice of treatments. AD-like lesions can be induced experimentally in NC/Nga mice.

Objectives: To evaluate clinically and histologically the therapeutic and prophylactic effects of PUVA on AD-like dermatitis using NC/Nga mice.

Methods: PUVA therapy was performed with intraperitoneal injection of 4 mg/kg of 8-methoxypsoralen (8-MOP) and 4 J/cm²-UVA irradiation before and after development of AD-like lesions in NC/Nga mice which had been maintained in a conventional room (Conv-NC/Nga mice). Clinical skin conditions were evaluated periodically by a clinical severity score defined. Lesions were histologically examined in haematoxylin–eosin or toluidine blue-stained sections. Plasma levels of total IgE were measured at various time points.

Results: In Conv-NC/Nga mice infested with mite, AD-like lesions started to develop at 8 week of age and thereafter increased in severity score. PUVA therapy at lower does than minimal phototoxic dose suppressed the development of dermatitis and was also therapeutically effective against established lesions. Proliferation of dermal mast cells in AD-like lesions was suppressed, but IgE hyperproduction was not changed after PUVA.

Conclusions: These observations suggest that PUVA photochemotherapy reveals not only therapeutic but also prophylactic effects on human AD.