Abstract
Carbonyl protein (CP), which is produced in the stratum corneum (SC), the outermost layer of the skin, deteriorates SC functions such as water-holding capacity. In the SC, CP is formed by various oxidative stimuli including ultraviolet (UV) radiation. Carbonyl groups can be introduced into proteins via reactions with aldehydes, which could be decomposed from lipid peroxides. We previously established a novel experimental system mimicking stratum corneum carbonyl protein (SCCP) generation via UV-induced lipid oxidation occurring at the skin surface, which involves the induction of SCCP by UV irradiation in the presence of squalene (SQ) as an unsaturated lipid component in sebum. However, to date, no studies have focused on the suppression of SCCP generation by UV absorbers. Therefore, we here evaluated the protective efficacy of various UV absorbers against UV-induced SCCP generation with SQ considering their absorption properties. We found that either a UVB or a UVA absorber could suppress the induction of SCCP by UV in the presence of SQ. In addition, either a UVB or a UVA absorber suppressed the increase of the peroxide value of SQ by UV irradiation. This strongly suggests that UV absorbers can suppress SCCP induction at least in part via the reduced generation of peroxide. Interestingly, a combination of UVB and UVA absorbers, as well as a broad-spectrum UV absorber, exhibited remarkable efficacy in suppressing the increase of peroxide value of SQ by UV irradiation. These results suggest that a wide range of UV protection from UVB to UVA is essential to suppress SCCP induction. We evaluated the protective efficacy of various UV absorbers against SCCP induction by UV irradiation in the presence of SQ and found that both UVB protection and UVA protection are essential to prevent the generation of SCCP and to maintain healthy skin.
