caa a22 4500 465773680 CHVBK 20180323111936.0 cr unu---uuuuu 170327e19901201xx s 000 0 eng 10.1007/BF00371948 doi (NATIONALLICENCE)springer-10.1007/BF00371948 The effect of UV radiation and sun blockers on free radical defence in human and guinea pig epidermis [Elektronische Daten] [C. Sundaram, W. Köster, K. Schallreuter] Summary: Defence against oxidative damage by UV-generated free radicals in both guinea pig and human skin has been found to be mediated by the ubiquitous thioprotein, thioredoxin reductase. Human keratinocytes contain approximately 5% thioredoxin reductase in their total acidic protein fraction and also express membrane-associated enzyme activity in cells cultured in synthetic medium. The thioredoxin reductase/thioredoxin system has been shown to reduce superoxide anion radicals through hydrogen peroxide to water. However, both UVA and UVB radiation, below the minimal erythemal dose, generate a sufficiently high concentration of oxygen radicals to deactivate thioredoxin reductase considerably. In albino guinea pigs, enzyme deactivation was up to 70% for UVA and 66% for UVB (n=10 animals/protocol). The application of sun blockers SPF4, SPF8 and SPF15 to albino guinea pig skin offered no significant protection for the deactivation of thioredoxin reductase by either UVA or UVB radiation. In the human population (n=15), thioredoxin reductase was deactivated by 54% with UVA and 36% with UVB radiation, although the degree of enzyme inhibition depended on skin phototype (I-VI, Fitzpatrick Classification). SPF24 offered considerable protection for thioredoxin reductase against both UVA and UVB for skin types I and II. However, SPF24 yielded no significant protection with UVA for skin types III-VI, and enhanced the enzyme inhibition with UVB additively. These results indicate that UVB photo-oxidation of oxybenzone (the UVA filter in SPF24) may deactivate thioredoxin reductase in more pigmented members of the population by Michael addition of oxybenzone semiquinone to the thiolate active site of this enzyme. Springer-Verlag, 1990 UV radiation nationallicence Thioredoxin reductase nationallicence Sun blockers nationallicence Free radical defence nationallicence Pigmentation nationallicence Sundaram C. Department of Dermatology, University of Hamburg, Martinistrasse 52, W-2000, Hamburg 20, Germany aut Köster W. Department of Dermatology, University of Hamburg, Martinistrasse 52, W-2000, Hamburg 20, Germany aut Schallreuter K. Department of Dermatology, University of Hamburg, Martinistrasse 52, W-2000, Hamburg 20, Germany aut Archives of Dermatological Research Springer-Verlag 282/8(1990-12-01), 526-531 0340-3696 282:8<526 1990 282 403 https://doi.org/10.1007/BF00371948 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00371948 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Sundaram C. Department of Dermatology, University of Hamburg, Martinistrasse 52, W-2000, Hamburg 20, Germany aut NATIONALLICENCE 700 1- Köster W. Department of Dermatology, University of Hamburg, Martinistrasse 52, W-2000, Hamburg 20, Germany aut NATIONALLICENCE 700 1- Schallreuter K. Department of Dermatology, University of Hamburg, Martinistrasse 52, W-2000, Hamburg 20, Germany aut NATIONALLICENCE 773 0- Archives of Dermatological Research Springer-Verlag 282/8(1990-12-01), 526-531 0340-3696 282:8<526 1990 282 403 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer