Evaluation of biological effects of thermally decomposed asbestos

通过热处理将温石棉(CH)转化为镁橄榄石(FO)被认为是一种可接受的温石棉脱毒技术。本研究从氧化损伤和肺损伤两个方面比较了CH1 0 0℃加热合成的CH1和An FO的生物学效应。在气管内单次给药1 mg后，我们观察了肺组织的病理变化，用高效液相-电化学检测法测定了肺组织中8-羟基-2‘-脱氧鸟苷(8-OHdG)的浓度，并用免疫组织化学方法检测了5 40d后8-OHdG的表达。对照组气管内单次注入无菌生理盐水。在气管内注射CH后的早期，8-OHdG在细支气管和肺泡上皮细胞以及炎症细胞和肉芽肿中均有表达，同时肺组织中8-OHdG浓度升高。随着纤维化的发展，8-OHdG在纤维化病变周围的气道上皮细胞和炎性细胞中的表达越来越明显，即使在给药后540天，8-OHdG的表达也明显高于对照组。另一方面，与CH组相比，FO组的急性肺部炎症较轻，且未见进行性纤维化病变。8-OHdG在细支气管炎性细胞和细支气管炎性细胞中表达较弱，与肺组织中8-OHdG的低浓度表达相一致。这项研究表明，合成FO引起的肺部炎症和氧化DNA损伤明显低于CH。

The conversion of chrysotile (CH) to forsterite (FO) by thermal treatment is considered to be an acceptable technique for detoxifying chrysotile. In this study, the biological effects of CH and an FO that is synthesized by heating CH at 1000℃ were compared with respect oxidative DNA damage and lung injury.Following the administration of a single 1-mg intratracheal dose of CH or FO, we evaluated histopathological changes in the lung tissue, the lung concentrations of 8-hydroxy-2'-deoxyguanosine (8-OHdG) by HPLC-electrochemical detection (ECD) method, and the expression of 8-OHdG by immunostaining for 540 days. For the control group, we administered a single intratracheal dose of sterile saline.In the early period following the intratracheal administration of CH, expression of 8-OHdG was observed in the bronchiolar and alveolar epithelial cells as well as in inflammatory cells and granulomas ; at the same time, an increase in the lung concentration of 8-OHdG was observed. As fibrosis progressed, expression of 8-OHdG became more apparent in the airway epithelial and inflammatory cells surrounding the fibrotic lesions ; even at 540 days post-administration, the expression of 8-OHdG was significantly higher than that of the control group. On the other hand, compared with the CH group, the acute lung inflammation observed in the FO group was less apparent and exhibited no progressive fibrosing lesions. The expression of 8-OHdG was transient and weak in the bronchiolar epithelial cells as well as in the inflammatory cells, which was consistent with the low concentration of 8-OHdG in the lungs. This study demonstrates that synthetic FO causes significantly less inflammation and oxidative DNA damage in the lungs than CH.