433 Opsin photoreceptor expression in normal human keratinocytes and melanocytes

The skin is a complex sensory system, reacting to the surrounding environment through an integrated network of cell receptors. Among them, G Protein-Coupled Receptors (GPCRs) represent a major way for cells to sense a large variety of environmental signals. Recent studies identified several extra-retinal opsins localized in human epidermal cells, three of them being sensitive to blue light (400-495 nm). As Light-Emitting Diode (LED)-based devices are increasingly part of our daily life, excessive exposure to artificial blue light can be considered as a source of indoor pollution, which has been shown to impact the circadian rhythm. The aim of the present study was to evaluate opsin expression in human skin. The localization of blue light-sensitive opsins was investigated in cultures of human keratinocytes and melanocytes and in human skin biopsies. Our results showed the expression and distribution of opsin 1 short-wavelength-sensitive, opsin 2 (Rhodopsin) and opsin 3 (Encephalopsin) within the epidermis, and their variation following exposure to blue light emitted from LEDs. In addition, our observations revealed a specific cellular localization of opsin 3 during mitosis. Taken together, these results emphasize the role of opsin photoreceptors in maintaining physiological conditions within the epidermis, and their implication in the skin’s response to stressful conditions induced by blue light.