In vitro PUVA radiation abolishes fluorescent staining with epidermal cell and basement membrane zone markers.

The purpose of this study was to investigate whether 8-methoxypsoralen (8-MOP) plus long-wave ultraviolet (UV-A) light irradiation (PUVA) had a direct effect on the expression of epidermal cell and basement membrane zone (BMZ) markers without altering intracellular metabolic pathways. Cryostat sections of guinea-pig skin were covered with an 8-MOP solution and irradiated in vitro with UV-A light. Treated sections were stained subsequently with various membrane markers including pemphigus sera, pemphigoid sera (BMZ marker) and a group of biotin-labelled lectins (Concanavalin-A, peanut agglutinin, soybean agglutinin, Ulex europeus agglutinin (UEA) and wheat germ agglutinin). Fluorescent staining with all reagents except for UEA was reduced appreciably in intensity by PUVA radiation at higher energy doses (20 micrograms/ml of 8-MOP plus 20-30 J/cm2 of UV-A). Radiation with lower energy doses did not affect membrane marker staining. Weakened or abolished marker staining was restored to normal when scavengers of oxygen intermediates such as superoxide dismutase (540-5400 units/ml) or sodium azide (10-200 mM) were added to the 8-MOP solution during UV-A irradiation. UEA staining was negative in both PUVA-irradiated and untreated guinea-pig skin. PUVA at higher energy doses appeared to cause tissue damage by photodynamic reactions, resulting in decrease in membrane marker staining.