Cytoplasmic aggregation of uranium in human dopaminergic cells after continuous exposure to soluble uranyl at non-cytotoxic concentrations
Cytoplasmic aggregation of uranium in human dopaminergic cells after continuous exposure to soluble uranyl at non-cytotoxic concentrations
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DOI：
10.1016/j.neuro.2020.10.015
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发表时间：
2021-01-01
期刊：
影响因子：
3.4
通讯作者：
Ortega, Richard
中科院分区：
文献类型：
--
作者：
Carmona, Asuncion;Porcaro, Francesco;Ortega, Richard
铀暴露可导致神经行为改变，特别是单胺能系统，即使在非细胞毒性浓度。然而，非细胞毒性暴露后铀神经毒性的机制仍然知之甚少。特别是，在低细胞内浓度下对神经元中的铀进行成像仍然非常具有挑战性。我们利用同步辐射X射线荧光成像技术研究了铀的细胞内定位，该技术具有高空间分辨率（< 300 nm）和高分析灵敏度（< 1 μ g.g（-1）/300 nm像素）。将分化成多巴胺能表型的神经元样SH-SY 5 Y人细胞连续暴露于非细胞毒性浓度（10 μ M）的可溶性天然铀酰7天。细胞质亚微米铀聚集体平均占细胞内铀含量的62%。在某些聚集体中，铀和铁共定位，表明铀和铁储存之间的共同代谢途径。铀聚集体不含钙或磷，表明神经元样细胞的解毒机制与骨或肾细胞中所描述的不同。将铀的细胞内分布与荧光标记的细胞器（溶酶体、早期和晚期内体）以及胎球蛋白A（一种高亲和力铀结合蛋白）进行比较。一个严格的相关性不能证明铀和标记的细胞器，或囊泡含有胎球蛋白A。我们的研究结果表明，一种新的机制，铀细胞质聚集后，非细胞毒性的铀酰暴露，可能参与神经元的防御，通过铀螯合成反应性较低的物种。铀的剩余可溶部分将负责蛋白质结合和由此产生的神经毒性作用。
Uranium exposure can lead to neurobehavioral alterations in particular of the monoaminergic system, even at non-cytotoxic concentrations. However, the mechanisms of uranium neurotoxicity after non-cytotoxic exposure are still poorly understood. In particular, imaging uranium in neurons at low intracellular concentration is still very challenging. We investigated uranium intracellular localization by means of synchrotron X-ray fluorescence imaging with high spatial resolution (< 300 nm) and high analytical sensitivity (< 1 mu g.g(-1) per 300 nm pixel). Neuron-like SH-SY5Y human cells differentiated into a dopaminergic phenotype were continuously exposed, for seven days, to a non-cytotoxic concentration (10 mu M) of soluble natural uranyl. Cytoplasmic submicron uranium aggregates were observed accounting on average for 62 % of the intracellular uranium content. In some aggregates, uranium and iron were co-localized suggesting common metabolic pathways between uranium and iron storage. Uranium aggregates contained no calcium or phosphorous indicating that detoxification mechanisms in neuron-like cells are different from those described in bone or kidney cells. Uranium intracellular distribution was compared to fluorescently labeled organelles (lysosomes, early and late endosomes) and to fetuin-A, a high affinity uranium-binding protein. A strict correlation could not be evidenced between uranium and the labeled organelles, or with vesicles containing fetuin-A. Our results indicate a new mechanism of uranium cytoplasmic aggregation after non-cytotoxic uranyl exposure that could be involved in neuronal defense through uranium sequestration into less reactive species. The remaining soluble fraction of uranium would be responsible for protein binding and for the resulting neurotoxic effects.