Gibbs N K, Norval M, Traynor N J, Wolf M, Johnson B E, Crosby J
Photobiology Unit, Ninewells Hospital, University of Dundee, Scotland.
Photochem Photobiol. 1993 Mar;57(3):584-90. doi: 10.1111/j.1751-1097.1993.tb02338.x.
Urocanic acid (UCA) is a major UV chromophore in the upper layers of the skin where it is found predominantly as the trans isomer. UV irradiation induces photoisomerisation of trans-UCA to cis-UCA which has been shown to mimic some of the immunosuppressive properties of UV exposure. We examined the wavelength dependence for trans-UCA to cis-UCA photoisomerisation in vitro and in mouse skin in vivo over the spectral range 270-340 nm. The resulting action spectra were very similar with maximal effectiveness at 300-315 nm and equal activity at 270 nm and 325-330 nm, demonstrating that UVA-II radiation (320-340 nm) is efficient at UCA photoisomerisation. These action spectra differed markedly from the trans-UCA absorption spectrum in vitro and also the reported action spectrum for UV suppression of contact hypersensitivity in mice. These findings suggest that the relationship between cis-UCA formation in skin and UV-induced immunosuppression may be complex.
尿刊酸（UCA）是皮肤上层的一种主要紫外线发色团，在那里它主要以反式异构体的形式存在。紫外线照射会诱导反式UCA光异构化为顺式UCA，已证明顺式UCA可模拟紫外线暴露的一些免疫抑制特性。我们在体外以及在270 - 340 nm光谱范围内的小鼠体内皮肤中研究了反式UCA到顺式UCA光异构化的波长依赖性。所得的作用光谱非常相似，在300 - 315 nm处效果最佳，在270 nm以及325 - 330 nm处活性相同，这表明UVA-II辐射（320 - 340 nm）在UCA光异构化方面效率很高。这些作用光谱与体外反式UCA吸收光谱以及报道的小鼠紫外线抑制接触性超敏反应的作用光谱明显不同。这些发现表明皮肤中顺式UCA的形成与紫外线诱导的免疫抑制之间的关系可能很复杂。
