title: Involvement of changes in stratum corneum keratin in wrinkle formation by chronic ultraviolet irradiation in hairless mice.
abstract: Chronic exposure to ultraviolet (UV) radiation alters components of the skin. We previously reported that chronic low-dose UV irradiation induced wrinkle formation but did not significantly alter dermal components of hairless mice. In the present study, we examined whether the epidermal changes by UV irradiation could contribute to wrinkle formation. Hairless mice were irradiated with one-third the minimum erythema dose (MED) of UVB (20 mJ/cm2) and UVA (14 J/cm2) for 10 weeks, and followed up for another 24weeks without irradiation. Fine wrinkles were detected following irradiation, which existed even 24 weeks after cessation of irradiation. An increase in the viscoelastic proportion of the total distension (Uv/Ue) was recognized in irradiated mice, which may be related to wrinkle formation. In the epidermis, an increase in the amount of transepidermal water loss and a decrease in the water content of the stratum corneum were seen after 10 weeks of UV irradiation, neither of which recovered during the 24-week observation period. In addition, there was a significant increase in the amount of stratum corneum keratin after 10 weeks of irradiation, which persisted during the 24-week follow-up. The results of our study suggest that chronic low-dose UV irradiation primarily alters the epidermal rather than the dermal components of the skin. In addition, our results indicate that the increased keratin content of the stratum corneum may be involved in the alteration of the physical properties of the skin. This process could be one of the early events of wrinkle formation.
authors.affiliation: Lion Corporation, Life Science Research Center, Odawara, Kanagawa, Japan. khiro@lion.co.jp
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kambayashi
authors.forename: Yuki
authors.initials: Y
authors.lastname: Odake
authors.forename: Koji
authors.initials: K
authors.lastname: Takada
authors.forename: Yoko
authors.initials: Y
authors.lastname: Funasaka
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Ichihashi
mesh_terms: D000818:Animals; D001834:Body Water / Q000378:metabolism; D004817:Epidermis / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology / Q000528:radiation effects*; D007633:Keratins / Q000378:metabolism*; D051379:Mice; D008812:Mice, Hairless; D010539:Permeability; D020033:Protein Isoforms / Q000378:metabolism; D015595:Skin Aging; D013997:Time Factors; D014466:Ultraviolet Rays / Q000009:adverse effects*; D014870:Water Loss, Insensible
chemical_list: D020033:Protein Isoforms; D007633:Keratins