Zak-Prelich M, Norval M, Venner T J, Bisset Y, Walker C, Rafferty T S, Sauder D N, McKenzie R C
Department of Dermatology, Medical University of Lodz, Poland.
Photochem Photobiol. 2001 Mar;73(3):238-44. doi: 10.1562/0031-8655(2001)073<0238:cuadni>2.0.co;2.
trans-Urocanic acid (UCA) acts as a chromophore for UV radiation in the epidermis and isomerizes to cis-UCA which then initiates some of the changes leading to UV-induced immunosuppression. The mechanism of the immunomodulation by cis-UCA is unknown at present, but one possibility is that the interaction between cis-UCA and keratinocytes causes the release of immunosuppressive cytokines locally. To test this hypothesis, PAM-212 cells, a murine keratinocyte cell line, were incubated with 0.10-100 micrograms/mL trans- and cis-UCA for 6 or 24 h, respectively. The expression of interleukin (IL)-10, transforming growth factor (TGF)-beta and tumor necrosis factor (TNF)-alpha messenger RNA (mRNA) was then measured by reverse transcription-polymerase chain reaction in comparison with the mRNA for the house-keeping gene, beta-actin. No change or significant induction of any of the cytokine messages occurred. However, the expression of IL-10 messenger RNA (mRNA) was induced 24 h after UVB irradiation (300 J/m2) and that of TNF-alpha mRNA occurred 6 h after treatment with phorbol myristate acetate. The expression of IL-10 protein was also examined by immunostaining in both PAM-212 cells and B16-F10 murine melanoma cells between 3 and 48 h after incubation with 10 and 100 micrograms/mL cis- and trans-UCA. No alteration was seen with either isomer at either concentration. In contrast, UVB irradiation of both cell lines resulted in a marked increase in intracellular IL-10 protein at 24 and 48 h. Therefore the upregulation of the immunosuppressive cytokines, IL-10, TNF-alpha and TGF-beta, in keratinocytes is unlikely to be the mechanism by which cis-UCA induces immunosuppression in mice.
反式尿刊酸（UCA）作为表皮中紫外线辐射的发色团，异构化为顺式UCA，然后引发一些导致紫外线诱导免疫抑制的变化。目前尚不清楚顺式UCA免疫调节的机制，但一种可能性是顺式UCA与角质形成细胞之间的相互作用导致局部免疫抑制细胞因子的释放。为了验证这一假设，将鼠角质形成细胞系PAM-212细胞分别与0.10 - 100微克/毫升的反式和顺式UCA孵育6小时或24小时。然后通过逆转录 - 聚合酶链反应测量白细胞介素（IL）-10、转化生长因子（TGF）-β和肿瘤坏死因子（TNF）-α信使核糖核酸（mRNA）的表达，并与管家基因β-肌动蛋白的mRNA进行比较。未发生任何细胞因子信息的变化或显著诱导。然而，紫外线B照射（300 J/m2）24小时后诱导了IL-10信使核糖核酸（mRNA）的表达，佛波醇肉豆蔻酸酯处理6小时后诱导了TNF-α mRNA的表达。在用10和100微克/毫升的顺式和反式UCA孵育3至48小时后，还通过免疫染色检测了PAM-212细胞和B16-F10鼠黑色素瘤细胞中IL-10蛋白的表达。在任何一种浓度下，两种异构体均未观察到改变。相比之下，两种细胞系的紫外线B照射在24和48小时导致细胞内IL-10蛋白显著增加。因此，角质形成细胞中免疫抑制细胞因子IL-10、TNF-α和TGF-β的上调不太可能是顺式UCA诱导小鼠免疫抑制的机制。
