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KMID : 0984920130150020111
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Journal of Skin Barrier Research
2013 Volume.15 No. 2 p.111 ~ p.111
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Urocanic Acid Isomer Ratio (cis/trans) in the Stratum Corneum (SC) Showed Good Correlation to the Transient Seasonal Changes of Solar UV Index
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Sakamoto Kazutami
Yamashita Yuji
Ohtaka Hiroyasu
Hashimoto Yosuke
Uchida Yoshikazu
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Abstract
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Trans-Urocanic acid (t-UCA) is recognized as an end metabolite of filaggrin via histidine which is a part of NMF amino acids in the stratum corneum (SC). As an intrinsic chromophore in SC under UV exposure, t-UCA converts to cis isomer (c-UCA) which initiates UV-induced immunosuppression. There are controversial discussions about c-UCA whether its immunosuppressive function is for the protection of body or rather to trigger carcinogenic reactions. Even though, existence of t-UCA in SC and conversion to c-UCA by UV radiation is real events evolved in Nature for the mammalian skin especially in human. The objective of this study is to investigate the transient isomerization of t-UCA in SC to c-UCA during the course of seasonal solar UV Index change in order to better understand the role of UCA for the skin physiology. Ten volunteers with age 21 to 34 are recruited and UCA isomer ratio was measured twice a week for six weeks (Sep 14th through Oct 19 in 2012). SC samples were tape stripped from the inner upper arm and UCA isomers are analyzed by HPLC. Average cis/trans ratio decreased gradually from c.a. 2.0 to 0.2. Solar UV Index reported for the area of experiment also decreased by the duration of days during the 6 weeks test period and there are good correlation found between isomer ratio and Solar UV Index. As a result, dynamic photo-isomerization of UCA in response to the solar UV radiation was confirmed. This finding would lead us further investigation of the functional roles of UCA in the skin especially for the Filaggrin mutation and Atopic Dermatitis, which is one of the hot topics in skin science.
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