Reeve Vivienne E, Domanski Diane
Faculty of Veterinary Science, University of Sydney, NSW, Australia.
Photochem Photobiol. 2002 Oct;76(4):401-5. doi: 10.1562/0031-8655(2002)076<0401:rouipf>2.0.co;2.
Single suberythemal exposures of UVA radiation have been shown to block the immunosuppressive effects of UVB radiation in the mouse. The immunoprotection is dependent both on the presence of the cytokine, IFN-gamma, and on the induction of the antioxidant stress enzyme, heme oxygenase (HO), in the skin. Recently, the transcriptional response of the HO-1 gene to UVA radiation in cultured human skin fibroblasts was reported to be refractory to a second UVA irradiation. In this study on the hairless mouse, we demonstrate that the inducibility of HO enzyme activity in the skin similarly became refractory to a second UVA irradiation at 24 h but, like the fibroblast response, was restored when the interval between the UVA exposures was increased to 96 h. Under the conditions of refractory HO enzyme induction, the protective effect of UVA radiation against the suppression of contact hypersensitivity induced by UVB radiation or cis-urocanic acid was strongly attenuated but was restored when the interval between UVA exposures was increased to 96 h. The results thus confirm the strong relationship between HO induction and photoimmunoprotection by UVA radiation, and describe a new phenomenon of immunological refractoriness that develops with rapidly repeated UVA exposures.
已表明，单次低于红斑量的UVA辐射可阻断UVB辐射在小鼠体内的免疫抑制作用。这种免疫保护作用既依赖于细胞因子γ干扰素（IFN-γ）的存在，也依赖于皮肤中抗氧化应激酶血红素加氧酶（HO）的诱导。最近有报道称，在培养的人皮肤成纤维细胞中，HO-1基因对UVA辐射的转录反应对第二次UVA照射具有抗性。在这项针对无毛小鼠的研究中，我们证明，皮肤中HO酶活性的诱导性在24小时时同样对第二次UVA照射变得具有抗性，但与成纤维细胞反应一样，当UVA照射之间的间隔增加到96小时时，这种抗性得以恢复。在HO酶诱导具有抗性的条件下，UVA辐射对UVB辐射或顺式尿刊酸诱导的接触性超敏反应抑制的保护作用大大减弱，但当UVA照射之间的间隔增加到96小时时，这种保护作用得以恢复。因此，这些结果证实了HO诱导与UVA辐射的光免疫保护之间的密切关系，并描述了一种随着UVA快速重复照射而出现的免疫抗性新现象。
