8-METHOXYPSORALEN PLUS UVA INDUCES THE 72 KDA HEAT-SHOCK PROTEIN IN ORGAN-CULTURED NORMAL HUMAN SKIN

The proteins induced by heat and other stressors, called heat shock pr oteins (HSP) or stress proteins, are considered to play a general role in protection from cellular injury. Exposure to UVA (320-400 nm) foll owing application of s-methoxypsoralen (8-MOP), termed PUVA is commonl y used in the field of dermatology. In order to understand the inducti on of HSP in PUVA-treated human skin, indirect immunofluorescence usin g a monoclonal antibody specific for the 72 kDa HSP (HSP 72) was carri ed out in organ-cultured normal human skin that was treated with PUVA. When the organ-cultured skin was treated at 37 degrees C for 1 h with 8-MOP at a final concentration of 10 or 100 mu g/mL and exposed to UV A (51.3 kJ/m(2)), nuclear immunofluorescence of HSP 72 was detected in the epidermal cells 12 h after UVA irradiation. In contrast, the indu ction of HSP 72 was not detected either by UVA irradiation or 8-MOP tr eatment. These results suggest that PUVA treatment is one of the stres sors for human skin, and DNA damage caused by PUVA induces HSP 72.