Abstract

Purpose

Depleted uranium (DU) has several civilian and military applications. The effects of this emerging environmental pollutant on human health raise some concerns. Previous experimental studies have shown that uranium (U) exposure can disturb the central nervous system. A small quantity of U reaches the brain via the blood, but the effects on the blood-brain barrier (BBB) remain unclear.

Materials and methods

In the present work, two cell culture models were exposed to DU for different times to study its cytotoxicity, paracellular permeability and extracellular concentration of U. The well-known immortalized human cerebral microvascular endothelial cells, hCMEC/D3, were cultured on the filter in the first model. In the second model, human primary cells of pericytes were cultured under the filter to understand the influence of cell environment after U exposure.

Results

The results show that U is not cytotoxic to hCMEC/D3 cells or pericytes until 500 µM (1.6 Bq.L⁻¹). In addition, acute or chronic low-dose exposure of U did not disturb permeability and was conserved in both cell culture models. However, U is able to reach the brain compartment. During the first hours of exposure, the passage of U to the abluminal compartment was significantly reduced in the presence of pericytes. Electronic microscopy studies evidenced the formation of needlelike structures, like urchin-shaped precipitates, from 1 h of exposure. Analytical microscopy confirmed the U composition of these precipitates. Interestingly, precipitated U was detected only in endothelial cells and not in pericytes. U was localized in multilamellar or multivesicular bodies along the endo-lysosomal pathway, suggesting the involvement of these traffic vesicles in U sequestration and/or elimination.

Conclusions

We show for the first time the in vitro passage of U across a human cerebral microvascular endothelial cells, and the intracellular localization of U precipitates without any cytotoxicity or modification of paracellular permeability. The difference between the results obtained with monolayers and co-culture models with pericytes illustrates the need to use complex in vitro models in order to mimic the neurovascular unit. Further in vivo studies should be performed to better understand the passage of U across the blood-brain barrier potentially involved in behavioral consequences.

摘要：

目的：贫铀（DU）具有多种民用和军事用途。这种新兴的环境污染物对人类健康的影响引起了一些关注。先前的实验研究表明，暴露于铀（U）会干扰中枢神经系统。少量的U通过血液到达大脑，但对血脑屏障（BBB）的影响仍不清楚。

材料与方法：在目前的工作中，将两种细胞培养模型在不同时间暴露于DU，以研究其细胞毒性，细胞旁通透性和U的细胞外浓度。在第一个模型的过滤器上 在第二种模型中，在过滤器下培养人周细胞的原代细胞，以了解暴露于U后细胞环境的影响。

结果：结果表明，U对hCMEC / D3细胞或周细胞无细胞毒性，直到500 µM（1.6Bq.L ^-1）。此外，急性或慢性低剂量暴露于U不会干扰通透性，并且在两种细胞培养模型中均保持不变。但是，U可以到达脑室。在暴露的最初几个小时内，在有周细胞的情况下，U进入房室的通道显着减少。电子显微镜研究证明，从暴露1小时起就形成了针状结构，如海胆形沉淀物。分析显微镜证实了这些沉淀物的U组成。有趣的是，仅在内皮细胞中检测到沉淀的U，而在周细胞中未检测到。U位于沿溶酶体途径的多层或多囊体中，表明这些交通囊泡参与了U的螯合和/或消除。

结论：我们示出了用于第一次体外U形跨人通道脑微血管内皮细胞，和U析出物的细胞内定位，而不旁渗透性的任何细胞毒性或修改。用单层细胞和带有周细胞的共培养模型获得的结果之间的差异说明，需要使用复杂的体外模型来模拟神经血管单元。应该进行进一步的体内研究，以更好地了解U跨过可能涉及行为后果的血脑屏障的通道。