Expression of Heat Shock Protein 70 in Human Skin Cells as a Photoprotective Function after UV Exposure.

BACKGROUND Human skin is exposed to various environmental stresses, such as heat, cold, and ultraviolet (UV) radiation. Heat shock proteins (HSPs) induced by temperature elevations, as a physiologic response to mediate repair mechanisms and reduce cellular damage. OBJECTIVE The purpose of this study was to investigate the induction of HSPs in human skin cells after UV exposure. METHODS We performed immunoblotting using a specific monoclonal antibody to the HSP70 family, one of the best-conserved stress proteins in humans, with cultured normal human keratinocytes, A431 cells, human melanocytes, SK30 cells, and human dermal fibroblasts (HDF). RESULTS Our results indicated that high expression of HSP70 in the unstressed state was noted in epidermal cells, including normal human keratinocytes, A431 cells, human melanocytes, and SK30 cells, but epidermal cells showed no additional up-regulation of HSP70 after UV irradiation. On the other hand, HDF expressed very small amounts of HSP70 at baseline, but significantly higher amounts of HSP70 after UV exposure. CONCLUSION These findings suggest that constitutive expression of HSP70 in epidermal cells may be an important mechanism for protection of the human epidermis from environmental stresses, such as sunlight exposure.