Nucleotide excision repair pathway assessment in DNA exposed to low-intensity red and infrared lasers

Low-intensity lasers are used for prevention and management of oral mucositis induced by anticancer therapy, but the effectiveness of treatment depends on the genetic characteristics of affected cells. This study evaluated the survival and induction of filamentation of Escherichia coli cells deficient in the nucleotide excision repair pathway, and the action of T4endonuclease V on plasmid DNA exposed to low-intensity red and near-infrared laser light. Cultures of wild-type (strain AB1157) E. coli and strain AB1886 (deficient in uvrA protein) were exposed to red (660 nm) and infrared (808 nm) lasers at various fluences, powers and emission modes to study bacterial survival and filamentation. Also, plasmid DNA was exposed to laser light to study DNA lesions produced in vitro by T4endonuclease V. Low-intensity lasers: i) had no effect on survival of wild-type E. coli but decreased the survival of uvrA protein-deficient cells, ii) induced bacterial filamentation, iii) did not alter the electrophoretic profile of plasmids in agarose gels, and iv) did not alter the electrophoretic profile of plasmids incubated with T4 endonuclease V. These results increase our understanding of the effects of laser light on cells with various genetic characteristics, such as xeroderma pigmentosum cells deficient in nucleotide excision pathway activity in patients with mucositis treated by low-intensity lasers.

低强度激光（low-intensity lasers）被用于抗肿瘤治疗诱导的口腔黏膜炎的预防与管理，但该治疗的有效性取决于受影响细胞的遗传特性。本研究针对核苷酸切除修复通路（nucleotide excision repair pathway）缺陷型大肠杆菌（Escherichia coli）细胞的存活率及丝化现象诱导情况，以及T4核酸内切酶V（T4endonuclease V）对暴露于低强度红光与近红外激光的质粒DNA（plasmid DNA）的作用进行了评估。本研究将野生型（菌株AB1157）大肠杆菌与uvrA蛋白缺陷型AB1886菌株的菌液，分别置于不同辐照剂量、功率及发射模式的红光（660 nm）与红外光（808 nm）激光照射条件下，以探究细菌存活率与丝化现象；同时将质粒DNA暴露于激光下，以研究T4核酸内切酶V在体外诱导的DNA损伤。结果显示，低强度激光具有如下效应：① 对野生型大肠杆菌的存活率无显著影响，但可降低uvrA蛋白缺陷型细胞的存活率；② 诱导细菌丝化现象；③ 未改变琼脂糖凝胶中质粒的电泳图谱；④ 未改变与T4核酸内切酶V共孵育的质粒的电泳图谱。本研究结果有助于加深我们对激光照射对不同遗传特性细胞影响的理解，例如在接受低强度激光治疗的黏膜炎患者体内，存在核苷酸切除通路活性缺陷的着色性干皮病（xeroderma pigmentosum）细胞。