Faux S P, Michelangeli F, Levy L S
Institute of Occupational Health, University of Birmingham, Edgbaston.
Mutat Res. 1994 Dec 1;311(2):209-15. doi: 10.1016/0027-5107(94)90178-3.
Exposure of human white blood cells to UICC crocidolite asbestos in vitro resulted in the formation of DNA strand breakage in a dose-dependent manner up to a fibre concentration of 100 micrograms/ml. Subsequent incubations with the iron chelator desferrioxamine or the intracellular Ca2+ chelator Quin-2 prevented DNA strand break formation above control incubations. Addition of aurintricarboxylic acid, an endonuclease inhibitor, similarly abolished crocidolite-induced DNA strand breaks in these cells. These results suggest that crocidolite-derived hydroxyl radicals do not directly induce DNA strand breakage in mammalian white blood cells. In order to assess Ca2+ mobilisation from intracellular stores in control and crocidolite-treated cells, the fullness of these stores was measured by treating with thapsigargin, a specific inhibitor of the endoplasmic reticulum Ca(2+)-ATPase. On addition of thapsigargin to fura-2AM-loaded cells treated with crocidolite we demonstrated that the endoplasmic reticulum stores had been depleted as no further Ca2+ was released, unlike control cells. We suggest that strand breakage is caused by a complex set of events involving oxygen free radicals that may disturb intracellular Ca2+ homoeostasis and the breaks are produced by secondary reactions, involving Ca(2+)-mediated enzymes.
在体外将人类白细胞暴露于国际抗癌联盟（UICC）标准的青石棉中，在纤维浓度高达100微克/毫升时，会导致DNA链断裂呈剂量依赖性形成。随后用铁螯合剂去铁胺或细胞内Ca2+螯合剂喹啉-2进行孵育，可防止DNA链断裂的形成超过对照孵育水平。添加核酸内切酶抑制剂金精三羧酸同样可消除这些细胞中青石棉诱导的DNA链断裂。这些结果表明，青石棉衍生的羟基自由基不会直接诱导哺乳动物白细胞中的DNA链断裂。为了评估对照细胞和经青石棉处理的细胞中细胞内储存的Ca2+动员情况，通过用内质网Ca(2+)-ATP酶的特异性抑制剂毒胡萝卜素处理来测量这些储存的充盈度。在用青石棉处理的、加载了fura-2AM的细胞中添加毒胡萝卜素后，我们发现内质网储存已被耗尽，因为与对照细胞不同，没有进一步释放Ca2+。我们认为，链断裂是由一系列复杂事件引起的，这些事件涉及可能扰乱细胞内Ca2+稳态的氧自由基，并且断裂是由涉及Ca(2+)介导的酶的二级反应产生的。
