Sturmey R G, Wild C P, Hardie L J
Molecular Epidemiology Unit, Centre for Epidemiology and Biostatistics, Leeds Institute of Genetics, Health and Therapeutics, LIGHT Laboratories, University of Leeds, Leeds, UK.
Mutagenesis. 2009 May;24(3):253-8. doi: 10.1093/mutage/gep004. Epub 2009 Feb 13.
Barrett's oesophagus (BO) carries an increased risk of progression to oesophageal adenocarcinoma. Chromoendoscopy with methylene blue (MB) can be used to facilitate identification of BO and target areas for biopsy. If photoexcited, MB can generate reactive oxygen species and genotoxic photodegradation products leading to DNA damage. We have previously demonstrated that levels of DNA damage are increased in BO following MB chromoendoscopy. The aim of this study was to investigate whether DNA damage, as measured by the comet assay, can be minimized during chromoendoscopy by varying MB concentration and light wavelength using an in vitro model. OE33 cells were treated with MB (0.015-15 mM) and exposed to white light (WL). Cells were also illuminated with WL fractions (580-700, 480-580, 350-480, <575, <610 and <688 nm) in the presence of MB. At clinically relevant concentrations, WL illumination of MB (15 mM) caused significant DNA damage in vitro (P < 0.001). Illumination of MB with red light (580-700 nm) also stimulated high levels of DNA damage in OE33 cells (P < 0.001). This effect was not observed with green or blue light. Filtering WL to remove red light wavelengths (>575 nm) reduced DNA damage and apoptosis to control levels in MB-treated cells. In addition, reducing the concentration of MB 10-fold markedly reduced the DNA-damaging effect of MB in vitro. The results show that photoactivation of MB by red light is responsible for the majority of DNA damage. Simple modifications to MB chromoendoscopy, such as filtering out red light from endoscopic WL or reducing MB concentration, are likely to limit DNA damage induced by the procedure.
巴雷特食管（BO）进展为食管腺癌的风险增加。亚甲蓝（MB）染色内镜可用于辅助识别BO及活检的靶区域。若受到光激发，MB可产生活性氧和基因毒性光降解产物，导致DNA损伤。我们之前已证明，MB染色内镜检查后BO中的DNA损伤水平会升高。本研究的目的是使用体外模型，通过改变MB浓度和光波长，研究在染色内镜检查期间，能否将彗星试验所测定的DNA损伤降至最低。用MB（0.015 - 15 mM）处理OE33细胞并暴露于白光（WL）下。在存在MB的情况下，细胞还用WL波段（580 - 700、480 - 580、350 - 480、<575、<610和<688 nm）进行照射。在临床相关浓度下，MB（15 mM）的WL照射在体外引起了显著的DNA损伤（P < 0.001）。用红光（580 - 700 nm）照射MB也在OE33细胞中刺激了高水平的DNA损伤（P < 0.001）。绿光或蓝光照射未观察到这种效应。过滤WL以去除红光波长（>575 nm）可将MB处理细胞中的DNA损伤和凋亡降低至对照水平。此外，将MB浓度降低10倍可显著降低MB在体外的DNA损伤作用。结果表明，红光对MB的光激活是造成大部分DNA损伤的原因。对MB染色内镜进行简单修改，如从内镜WL中滤除红光或降低MB浓度，可能会限制该操作引起的DNA损伤。
