Roberts L K, Beasley D G
Advanced Product Research, Schering-Plough HealthCare Products, Memphis, TN 38151, USA.
J Photochem Photobiol B. 1997 Jun;39(2):121-9. doi: 10.1016/s1011-1344(97)00003-1.
Ultraviolet (UV) irradiation causes the immunosuppression of contact hypersensitivity (CH) responses in animals and humans. There are conflicting reports regarding the effectiveness of sunscreens in preventing UV-induced suppression of both local-type CH (induced by the application of the contact sensitizer directly to UV-exposed skin) and systemic-type CH (induced by the application of the contact sensitizer to an unirradiated skin site 3 days after UV exposure). The purposes of this study were as follows: 1. to derive solar simulator UV dose-response curves for the induction of local and systemic CH suppression in C3H mice; 2. to establish minimum immune suppression doses (MISDs) for local and systemic CH; 3. to determine the local and systemic immune protection capacity of two commercial sunscreen lotions with labeled sun protection factors (SPFs) of 4 and 8. Dose-response curves for the induction of local and systemic CH suppression were derived by exposing groups of mice to a range of full-spectrum UV doses (0.37-21.4 kJ m-2) on two consecutive days delivered from a filtered 1000 W xenon arc lamp solar simulator. The MISDs, defined as the lowest dose tested to cause approximately 50% suppression of the normal CH response, were obtained from the dose-response curves. Although the local and systemic immunosuppression dose-response curves were not statistically different, the MISD for local suppression of CH (1.35 kJ m-2) was about fivefold lower than that for systemic CH suppression (6.76 kJ m-2). The MISD was used as the endpoint to determine sunscreen immune protection levels. Both sunscreens, applied at 2 mg cm-2, provided immune protection against the induction of local and systemic CH suppression in mice exposed to an effective UV dose of 1 MISD given through the sunscreen, i.e. 4 MISD to SPF 4 sunscreen-protected mice and 8 MISD to SPF 8 sunscreen-protected mice mounted CH responses that were significantly greater than those elicited in unprotected mice exposed to 1 MISD of solar-simulated UV radiation. The calculated immune protection factors for these sunscreens exceeded the level of protection predicted by their labeled SPFs, i.e. the local immune protection factor of both sunscreens was 15 and the systemic immune protection factors were 8 for the SPF 4 sunscreen and 15 for the SPF 8 sunscreen. Our data show that these two sunscreens provide levels of immune protection which exceed the levels predicted by their labeled SPFs in immunoprotection tests conducted in mice exposed to a relevant MISD of UV radiation from a source emitting a UV power spectrum similar to that of sunlight.
紫外线（UV）照射会导致动物和人类接触性超敏反应（CH）的免疫抑制。关于防晒霜在预防紫外线诱导的局部型CH（通过将接触致敏剂直接应用于紫外线照射的皮肤诱导）和全身型CH（在紫外线照射3天后将接触致敏剂应用于未照射的皮肤部位诱导）抑制方面的有效性，存在相互矛盾的报道。本研究的目的如下：1. 得出在C3H小鼠中诱导局部和全身CH抑制的太阳模拟器紫外线剂量反应曲线；2. 确定局部和全身CH的最小免疫抑制剂量（MISD）；3. 测定两种标注防晒系数（SPF）分别为4和8的市售防晒霜乳液的局部和全身免疫保护能力。通过将几组小鼠连续两天暴露于一系列全光谱紫外线剂量（0.37 - 21.4 kJ m-2）下，这些剂量由经过滤的1000 W氙弧灯太阳模拟器提供，从而得出诱导局部和全身CH抑制的剂量反应曲线。MISD定义为导致正常CH反应约50%抑制的最低测试剂量，从剂量反应曲线中获得。虽然局部和全身免疫抑制剂量反应曲线在统计学上没有差异，但局部CH抑制的MISD（1.35 kJ m-2）比全身CH抑制的MISD（6.76 kJ m-2）低约五倍。MISD被用作确定防晒霜免疫保护水平的终点。两种防晒霜均以2 mg cm-2的用量涂抹，为暴露于通过防晒霜给予的1个MISD有效紫外线剂量的小鼠提供了针对局部和全身CH抑制诱导的免疫保护，即对于涂抹SPF 4防晒霜的小鼠，给予4个MISD剂量，对于涂抹SPF 8防晒霜的小鼠，给予8个MISD剂量，其引发的CH反应明显大于暴露于1个MISD太阳模拟紫外线辐射的未受保护小鼠所引发的反应。这些防晒霜计算得出的免疫保护因子超过了其标注SPF所预测的保护水平，即两种防晒霜的局部免疫保护因子均为15，对于SPF 4防晒霜，全身免疫保护因子为8，对于SPF 8防晒霜，全身免疫保护因子为15。我们的数据表明，在暴露于来自发出与太阳光相似紫外线功率谱的光源的相关MISD紫外线辐射的小鼠中进行的免疫保护测试中，这两种防晒霜提供的免疫保护水平超过了其标注SPF所预测的水平。
