Fluoride induces endoplasmic reticulum stress in ameloblasts responsible for dental enamel formation
Fluoride induces endoplasmic reticulum stress in ameloblasts responsible for dental enamel formation
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DOI：
10.1074/jbc.m503288200
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发表时间：
2005-06-17
影响因子：
4.8
通讯作者：
Bartlett, JD
中科院分区：
文献类型：
--
作者：
Kubota, K;Lee, DH;Bartlett, JD
氟是如何引起氟中毒的机制仍不清楚。暴露于氟化物可以抑制蛋白质合成，这也可能发生的代理，导致内质网（ER）的压力。当翻译的蛋白质不能正确折叠或错误折叠时，ER应激反应基因被诱导，它们共同构成未折叠的蛋白质反应。由于成釉细胞负责牙釉质形成，我们使用成釉细胞衍生的细胞系（LS 8）来表征对氟化物处理的特异性反应。低至1.9-3.8 ppm的氟化物可抑制LS 8细胞的生长，而高剂量则可诱导ER应激和半胱天冬酶介导的DNA断裂。生长停滞和DNA损伤诱导蛋白（GADD 153/CHOP，GADD 45 α），结合蛋白（BiP/葡萄糖反应蛋白78（GRP 78），碳酸酐酶VI（CA-VI）的非分泌形式，和活性X-box结合蛋白-1（Xbp-1）都显着诱导暴露于38 ppm氟化物后。出乎意料的是，当GADD 153表达被短干扰RNA处理抑制时，DNA片段化增加，但不受瞬时GADD 153过表达的影响。对照和GADD 153（-/-）胚胎成纤维细胞的分析表明，胱天蛋白酶-3介导了在GADD 153缺失细胞中观察到的增加的DNA片段化。我们还证明，小鼠切牙成釉细胞是敏感的高剂量氟的饮用水中的毒性作用。激活的Ire 1启动ER应激反应途径，小鼠成釉细胞表达激活的Ire 1。Ire 1水平出现诱导氟治疗，表明ER应激可能在氟斑牙中发挥作用。低剂量的氟，如含氟饮用水中的氟，不会引起内质网应激。
mechanism of how fluoride causes fluorosis remains unknown. Exposure to fluoride can inhibit protein synthesis, and this may also occur by agents that cause endoplasmic reticulum (ER) stress. When translated proteins fail to fold properly or become misfolded, ER stress response genes are induced that together comprise the unfolded protein response. Because ameloblasts are responsible for dental enamel formation, we used an ameloblast-derived cell line (LS8) to characterize specific responses to fluoride treatment. LS8 cells were growth-inhibited by as little as 1.9-3.8 ppm fluoride, whereas higher doses induced ER stress and caspase-mediated DNA fragmentation. Growth arrest and DNA damage-inducible proteins (GADD153/CHOP, GADD45 alpha), binding protein (BiP/glucose-responsive protein 78 (GRP78), the non-secreted form of carbonic anhydrase VI (CA-VI), and active X-box-binding protein-1 (Xbp-1) were all induced significantly after exposure to 38 ppm fluoride. Unexpectedly, DNA fragmentation increased when GADD153 expression was inhibited by short interfering RNA treatment but remained unaffected by transient GADD153 overexpression. Analysis of control and GADD153(-/-) embryonic fibroblasts demonstrated that caspase-3 mediated the increased DNA fragmentation observed in the GADD153 null cells. We also demonstrate that mouse incisor ameloblasts are sensitive to the toxic effects of high dose fluoride in drinking water. Activated Ire1 initiates an ER stress response pathway, and mouse ameloblasts were shown to express activated Ire1. Ire1 levels appeared induced by fluoride treatment, indicating that ER stress may play a role in dental fluorosis. Low dose fluoride, such as that present in fluoridated drinking water, did not induce ER stress.