Qin X, Zhang S, Oda H, Nakatsuru Y, Shimizu S, Yamazaki Y, Nikaido O, Ishikawa T
Department of Pathology, Faculty of Medicine, University of Tokyo.
Jpn J Cancer Res. 1995 Nov;86(11):1041-8. doi: 10.1111/j.1349-7006.1995.tb03018.x.
UVB-induced cyclobutane pyrimidine dimers (CPDs) and pyrimidine-pyrimidone (6-4)photoproducts [(6-4)photoproducts] in mouse skin DNA were quantitatively measured using an immunohistochemical approach with a computer-aided color image analyzer. The skins of the C3H/HeN mice were irradiated with ultraviolet B (UV-B, 280-320 nm), and processed to give conventional formalin-fixed, paraffin-embedded histologic sections. Routine immunohistochemistry clearly demonstrated a dose-dependent induction of both photoproducts. CPDs were detectable at doses > or = 125 J/m2, while for (6-4)photoproducts, the minimal dose at which they were detectable was 250 J/m2 in the present study. A time course study showed that the repair of (6-4)photoproducts was more rapid than that of CPDs, and that epidermal cells had a higher capacity for their removal than dermal cells. About half of the (6-4)photoproducts were excised within the first 24 h after the irradiation, and the process was essentially complete by 72 h. In contrast, there was no apparent removal (less than 10%) of CPDs in the first 24 h and they only completely disappeared from the epidermal cells at 120 h after irradiation. The effect of DNA dilution due to increased turnover of epidermal cells after UV-B irradiation was evaluated by quantitative immunohistochemical measurement of the time course of bromodeoxy-uridine (BrdUrd) incorporated into nuclei at 2 days post irradiation when the proliferation reaches a peak. The removal of photoproducts was more marked than the decrease in BrdUrd staining. Our results suggest that mouse skin cells can repair both (6-4)photoproducts and CPDs, but with considerably lower efficiency, especially in the latter case, then human or monkey skin cells.
使用计算机辅助彩色图像分析仪的免疫组织化学方法，对小鼠皮肤DNA中紫外线B（UVB）诱导的环丁烷嘧啶二聚体（CPD）和嘧啶 - 嘧啶酮（6 - 4）光产物[（6 - 4）光产物]进行了定量测量。用紫外线B（UV - B，280 - 320nm）照射C3H/HeN小鼠的皮肤，并制成常规福尔马林固定、石蜡包埋的组织学切片。常规免疫组织化学清楚地显示了两种光产物的剂量依赖性诱导。在剂量≥125J/m²时可检测到CPD，而对于（6 - 4）光产物，本研究中可检测到它们的最小剂量为250J/m²。一项时间进程研究表明，（6 - 4）光产物的修复比CPD更快，并且表皮细胞去除它们的能力比真皮细胞更高。大约一半的（6 - 4）光产物在照射后的头24小时内被切除，并且该过程在72小时时基本完成。相比之下，CPD在头24小时内没有明显去除（小于10%），并且它们仅在照射后120小时从表皮细胞中完全消失。通过在照射后2天（此时增殖达到峰值）对掺入细胞核的溴脱氧尿苷（BrdUrd）时间进程进行定量免疫组织化学测量，评估了UV - B照射后表皮细胞更新增加导致的DNA稀释效应。光产物的去除比BrdUrd染色的减少更明显。我们的结果表明，小鼠皮肤细胞可以修复（6 - 4）光产物和CPD，但效率相当低，尤其是在后一种情况下，比人类或猴皮肤细胞低。
