Reeve V E, Ley R D, Reilly W G, Bosnic M
Department of Veterinary Pathology, University of Sydney, Australia.
Int Arch Allergy Immunol. 1996 Mar;109(3):266-71. doi: 10.1159/000237248.
A single specific epidermal photoreceptor for the immunosuppressive action of UV radiation has not been defined, although separate evidence is accruing in favour of each of two candidates, trans-urocanic acid and DNA. In Monodelphis domestica, specific photoreactivation repair of UV radiation-induced pyrimidine dimers has been shown to abrogate the suppression of contact hypersensitivity (CHS), thus suggesting that DNA is the target for this impairment. However, the both haired and hairless mice, immunosuppressive effects of UV radiation have been reproduced by the exogenous administration of the UV photoproduct of urocanic acid, cis-urocanic acid. We show here that the epidermis of M. domestica contains urocanic acid, that UV irradiation of the shaved dorsal skin has resulted in an increase in epidermal cis-urocanic acid and that the topical application of a cis-urocanic acid-containing lotion significantly depressed the capacity of Monodelphis to respond to contact sensitisers, in a manner analogous to these responses in the hairless mouse. Therefore in Monodelphis, suppression of CHS by UV irradiation appears to involve both urocanic acid photo-isomerisation and epidermal DNA damage.
尽管有越来越多的独立证据支持反式尿刊酸和DNA这两种候选物质，但尚未确定单一的特定表皮光感受器介导紫外线辐射的免疫抑制作用。在短尾负鼠中，紫外线辐射诱导的嘧啶二聚体的特异性光复活修复已被证明可消除对接触性超敏反应（CHS）的抑制，因此表明DNA是这种损伤的靶点。然而，在有毛和无毛小鼠中，尿刊酸的紫外线光产物顺式尿刊酸的外源给药重现了紫外线辐射的免疫抑制作用。我们在此表明，短尾负鼠的表皮含有尿刊酸，剃毛背部皮肤的紫外线照射导致表皮顺式尿刊酸增加，并且局部应用含顺式尿刊酸的洗剂以类似于无毛小鼠的反应方式显著降低了短尾负鼠对接触性致敏剂的反应能力。因此，在短尾负鼠中，紫外线照射对CHS的抑制似乎涉及尿刊酸的光异构化和表皮DNA损伤。
