Bredberg A, Lambert B, Söderhäll S
Mutat Res. 1982 Mar;93(1):221-34. doi: 10.1016/0027-5107(82)90137-3.
Skin fibroblasts from normal human subjects were exposed in vitro to long-wave ultraviolet radiation (UVA, 320-400 nm) alone, or in combination with 8-methoxypsoralen (8-MOP). DNA damage was analysed with the alkaline elution technique before and after post-treatment incubation of the cells at 37 degrees C for various times. Cells treated with UVA at 1.1 J/cm/ showed an increased DNA elution rate, which returned to the normal level within 30 min of post-treatment incubation. In cells treated with PUVA (8-MOP at 20 microgram/ml plus UVA at 0.04 J/cm2), the alkaline elution rate was not different from untreated control cells, either before or after post-treatment incubation for time up to 7 days. When the PUVA treatment was followed first by a washing, to remove any unbound 8-MOP, and then by UVA (PUVA + UVA) at 1.1 J/cm2, the alkaline elution rate decreased below the control level. During the post-treatment incubation of the PUVA + UVA-treated cells there was a gradual increase of the alkaline elution rate to a level significantly above that in control cells. This increase was observed after 30 min. It reached a maximum after 24 h and remained after 7 days of post-treatment incubation. Cells from a patient with xeroderma pigmentosum of complementation group A, which were given the same PUVA + UVA treatment, did not show any change in the alkaline elution rate during the post-treatment incubation. If, as seems likely, an increased alkaline elution rate indicates as increase of DNA breaks, and a decreased alkaline elution rate indicates the sealing of breaks and/or the formation of cross-links, and results would suggest the following: (1) UVA irradiation in itself is capable of inducing DNA breaks, which are rapidly sealed during post-treatment incubation; (2) PUVA treatment induces mono-adducts, some of which appear to remain in the DNA for at least 7 days of post-treatment incubation and can be activated to form DNA cross-links by a second dose of UVA; (3) DNA cross-links induced by PUVA + UVA can be recognized by a repair process that involves the formation of DNA breaks. This process is not observed in xeroderma pigmentosum cells of group A.
将来自正常人类受试者的皮肤成纤维细胞在体外单独暴露于长波紫外线辐射（UVA，320 - 400纳米），或与8 - 甲氧基补骨脂素（8 - MOP）联合暴露。在细胞于37℃进行不同时间的后处理孵育前后，用碱性洗脱技术分析DNA损伤情况。用1.1焦耳/平方厘米的UVA处理的细胞显示DNA洗脱率增加，在后处理孵育30分钟内恢复到正常水平。在用PUVA（20微克/毫升的8 - MOP加0.04焦耳/平方厘米的UVA）处理的细胞中，无论在后处理孵育长达7天之前还是之后，碱性洗脱率与未处理的对照细胞均无差异。当首先对PUVA处理后的细胞进行洗涤以去除任何未结合的8 - MOP，然后再用1.1焦耳/平方厘米的UVA（PUVA + UVA）处理时，碱性洗脱率降至对照水平以下。在对PUVA + UVA处理的细胞进行后处理孵育期间，碱性洗脱率逐渐增加至显著高于对照细胞的水平。这种增加在30分钟后观察到。在24小时后达到最大值，并在7天的后处理孵育后仍然存在。给予相同PUVA + UVA处理的A组着色性干皮病患者的细胞，在后处理孵育期间碱性洗脱率未显示任何变化。如果碱性洗脱率增加可能表明DNA断裂增加，而碱性洗脱率降低表明断裂的封闭和/或交联的形成，那么结果将提示如下：（1）UVA照射本身能够诱导DNA断裂，这些断裂在后处理孵育期间迅速封闭；（2）PUVA处理诱导单加合物，其中一些似乎在后处理孵育至少7天内保留在DNA中，并且可以通过第二剂量的UVA激活形成DNA交联；（3）PUVA + UVA诱导的DNA交联可以被涉及DNA断裂形成的修复过程识别。在A组着色性干皮病细胞中未观察到这个过程。
