SISTER CHROMATID EXCHANGES IN PHOTOCHEMOTHERAPY

[摘要] Sister chromatid exchanges (SCE), presently considered highly sensitive indicators for chromosomal effects of potential mutagens and carcinogens in mammalian cells, were studied in circulating white blood cells from patients with widespread psoriasis who were being treated with 8-methoxy-psoralen and long-wavelength UV light (UVA) photochemotherapy (PUVA). SCE counts of patients with psoriasis treated with PUVA neither differed from SCE counts of those treated with topical dithranol and corticosteroids, nor from SCE of nonpsoriatic, clinically healthy individuals. The duration of PUVA treatment (up to 2 yr) and the total cumulative dose of UVA energy given to the patients also had no effect on the number of SCE of circulating lymphocytes. However, the SCE counts of patients with psoriatic arthropathy were higher than those of patients with psoriasis without joint involvement or normal controls, irrespective of the type of treatment given. There was no difference between SCE counts obtained before and after PUVA treatment sessions, but when white blood cells removed from patients after treatment were reirradiated with UVA in vitro there was a significant increase of SCE. Whereas the principle of PUVA does induce an increased number of SCE in human lymphocytes in vitro, the same principle, employed as a clinical form of therapy, does not result in similar alterations in circulating lymphocytes in vivo. Harmful effects of PUVA on the genome of circulating lymphocytes were not detected in patients subjected to this treatment.