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 proteins (HSP) or stress proteins, are considered to play a general role in protection from cellular injury. Exposure to UVA (320-400 nm) following application of 8-methoxypsoralen (8-MOP), termed PUVA is commonly used in the field of dermatology. In order to understand the induction of HSP in PUVA-treated human skin, indirect immunofluorescence using a monoclonal antibody specific for the 72 kDa HSP (HSP 72) was carried out in organ-cultured normal human skin that was treated with PUVA. When the organ-cultured skin was treated at 37 degrees for 1 h with 8-MOP at a final concentration of 10 or 100 micrograms/mL and exposed to UVA (51.3 kJ/m2), nuclear immunofluorescence of HSP 72 was detected in the epidermal cells 12 h after UVA irradiation. In contrast, the induction of HSP 72 was not detected either by UVA irradiation or 8-MOP treatment. These results suggest that PUVA treatment is one of the stressors for human skin, and DNA damage caused by PUVA induces HSP 72.