Cross-linking of collagen by singlet oxygen generated with UV-A.
Singlet oxygen (1O2), a highly reactive and toxic intermediate, may play a role in photo-induced aging. We examined singlet oxygen generation from hematoporphyrin (HP) with UV-A, by monitoring the emission at 1,268 nm corresponding to 1O2 --> 3O2. Singlet oxygen was formed HP-dose-dependently in this system. We then investigated the reaction of singlet oxygen generated by UV-A irradiation with collagen, which is related to skin elasticity and softness. Collagen from skin was rapidly and dose-dependently cross-linked by singlet oxygen. The reaction was inhibited by NaN3, a selective quencher of singlet oxygen. In contrast, SOD (superoxide dismutase) and mannitol had no effect. These results suggested that cross-linking of collagen was caused by UV-A-generated singlet oxygen, not by any other reactive oxygen species. Compared with another multisubunit protein, alcohol dehydrogenase, collagen was cross-linked much more efficiently. Further, the finding that semicarbazide inhibited cross-linking of collagen showed that cross-links were formed between photooxidized histidyl residues and amino groups. Singlet oxygen generated by UV-A irradiation may contribute to cross-linking of collagen in the process of skin photoaging.
Ryu
A
A
Research Laboratory, KOSE Corporation, Tokyo, Japan.
Naru
E
E
Arakane
K
K
Masunaga
T
T
Shinmoto
K
K
Nagano
T
T
Hirobe
M
M
Mashiko
S
S
D003094:Collagen / Q000737:chemistry*; D003432:Cross-Linking Reagents; D004591:Electrophoresis, Polyacrylamide Gel; D005609:Free Radicals / Q000737:chemistry; D006415:Hematoporphyrins / Q000737:chemistry* / Q000528:radiation effects; D010100:Oxygen / Q000737:chemistry* / Q000528:radiation effects; D012663:Semicarbazides; D014466:Ultraviolet Rays
D003432:Cross-Linking Reagents; D005609:Free Radicals; D006415:Hematoporphyrins; D012663:Semicarbazides; D003094:Collagen; D010100:Oxygen