Shapiro Aaron M, Chan Hing Man
Community Health Science Program, University of Northern British Columbia, Prince George, British Columbia, Canada.
Chemosphere. 2008 Dec;74(1):112-8. doi: 10.1016/j.chemosphere.2008.09.019. Epub 2008 Oct 23.
Mercury (Hg) is a well-known neurotoxicant but its toxicity depends on the species present. A steady emergence of inorganic Hg in the brain following chronic and accidental exposure to methylmercury (MeHg) has suggested that MeHg can undergo demethylation. The objective of this study is to develop an in vitro model to study factors affecting Hg demethylation in the central nervous system. Astrocytes obtained from neonatal rat pups were cultured for 24h with 1 microM MeHg in the presence of two pro-oxidants, buthionine sulphoximine (BSO) and rotenone. The BSO treatment produced a 21% increase in reactive oxygen species (ROS) content compared to the control (control vs. BSO; 100+/-1.35 vs. 121+/-1.52 relative fluorescence units (RFU)mg(-1) protein, p<0.001) but did not affect total Hg accumulation (control vs. BSO=86.5+/-4.14 ng mg(-1) vs. 95.7+/-9.26 ng mg(-1)). Rotenone increased ROS levels 107% (control vs. rotenone; 100%+/-1.35 vs. 207%+/-6.78RFU mg(-1)protein, p<0.001) and significantly increased the accumulation of total Hg (control vs. rotenone=86.5+/-4.14 ng mg(-1) vs. 124+/-3.80 ng mg(-1), p<0.001). There was no detectable demethylation in the control or BSO treated group, however, the rotenone treatment significantly increased the demethylation (control vs. rotenone=-1.86+/-5.57% vs. 16.3+/-2.68%, p<0.05). For the first time, we have demonstrated in an in vitro primary astrocyte culture model that MeHg can be converted to inorganic Hg and demethylation increases with oxidative stress. Our results provide a useful model to study demethylation of Hg in astrocytes and to explore potential ways to protect against Hg toxicity.
汞（Hg）是一种众所周知的神经毒素，但其毒性取决于其存在的形态。长期或意外接触甲基汞（MeHg）后，大脑中会持续出现无机汞，这表明MeHg可以发生去甲基化。本研究的目的是建立一个体外模型，以研究影响中枢神经系统中汞去甲基化的因素。从新生大鼠幼崽中获取的星形胶质细胞在两种促氧化剂丁硫氨酸亚砜胺（BSO）和鱼藤酮存在的情况下，用1微摩尔的MeHg培养24小时。与对照组相比，BSO处理使活性氧（ROS）含量增加了21%（对照组与BSO组；相对荧光单位（RFU）mg(-1)蛋白质分别为100±1.35和121±1.52，p<0.001），但不影响总汞积累（对照组与BSO组=86.5±4.14纳克毫克(-1)与95.7±9.26纳克毫克(-1)）。鱼藤酮使ROS水平增加了107%（对照组与鱼藤酮组；100%±1.35与207%±6.78RFU毫克(-1)蛋白质，p<0.001），并显著增加了总汞的积累（对照组与鱼藤酮组=86.5±4.14纳克毫克(-1)与124±3.80纳克毫克(-1)）。在对照组或BSO处理组中未检测到去甲基化，然而，鱼藤酮处理显著增加了去甲基化（对照组与鱼藤酮组=-1.86±5.57%与16.3±2.68%，p<0.05）。我们首次在体外原代星形胶质细胞培养模型中证明，MeHg可以转化为无机汞，并且去甲基化随着氧化应激而增加。我们的结果提供了一个有用的模型，用于研究星形胶质细胞中汞的去甲基化，并探索预防汞毒性的潜在方法。
