Aquino Grace V, Dabi Amjad, Odom Gabriel J, Zhang Fan, Bruce Erica D
Department of Environmental Science, Baylor University, 101 Bagby Ave., Waco, TX, 76706, USA.
Department of Biostatistics Stempel College of Public Health, Florida International University, 11200 SW 8(th)Street, AHC4-470, Miami, FL, 33199, USA; Department of Public Health Sciences, University of Miami Miller School of Medicine, The University of Miami, 1600 NW 10th Ave. 1140, Miami, FL, 33136, USA.
Toxicology. 2021 Apr 30;454:152748. doi: 10.1016/j.tox.2021.152748. Epub 2021 Mar 13.
Exposure to combustion-derived particulate matter (PM) such as diesel exhaust particles (DEP) is a public health concern because people in urban areas are continuously exposed, and once inhaled, fine and ultrafine DEP may reach the brain. The blood-brain barrier (BBB) endothelial cells (EC) and the perivascular microglia protect the brain from circulating pathogens and neurotoxic molecules like DEP. While the BBB-microglial interaction is critical for maintaining homeostasis, no study has previously evaluated the endothelial-microglial interaction nor comprehensively characterized these cells' inflammatory marker profiles under ultrafine DEP exposures in vitro. Therefore, the goal of this study was to investigate the in vitro rat EC-microglial co-culture under acute (24 h.) exposure to ultrafine DEP (0.002-20 μg/mL), by evaluating key mechanisms associated with PM toxicity: lactate dehydrogenase (LDH) leakage, reactive oxygen species (ROS) generation, cell metabolic activity (CMA) changes, and production of 27 inflammatory markers. These parameters were also evaluated in rat microglial and endothelial monocultures to determine whether the EC-microglial co-culture responded differently than the cerebrovasculature and microglia alone. While results indicated that ultrafine DEP exposure caused concentration-dependent increases in LDH leakage and ROS production in all groups, as expected, exposure also caused mixed responses in CMA and atypical cytokine/chemokine profiles in all groups, which was not expected. The inflammation assay results further suggested that the microglia were not classically activated under this exposure scenario, despite previous in vitro studies showing microglial activation (priming) at similar concentrations of ultrafine DEP. Additionally, compared to the cerebrovasculature alone, the EC-microglia interaction in the co-culture did not appear to cause changes in any parameter save in pro-inflammatory marker production, where the interaction appeared to cause an overall downregulation in cytokine/chemokine levels after ultrafine DEP exposure. Finally, to our knowledge, this is the first study to evaluate the influence of microglia on the BBB's ultrafine DEP-induced cytotoxic and inflammatory responses, which are heavily implicated in the pathogenesis of PM-related cerebrovascular dysfunction and neurodegeneration.
接触燃烧产生的颗粒物（PM），如柴油尾气颗粒（DEP），是一个公共卫生问题，因为城市地区的人们持续暴露于其中，并且一旦吸入，细颗粒和超细颗粒DEP可能会进入大脑。血脑屏障（BBB）内皮细胞（EC）和血管周围的小胶质细胞可保护大脑免受循环病原体和诸如DEP等神经毒性分子的侵害。虽然血脑屏障-小胶质细胞的相互作用对于维持体内平衡至关重要，但此前尚无研究评估内皮细胞-小胶质细胞的相互作用，也没有全面表征这些细胞在体外超细DEP暴露下的炎症标志物谱。因此，本研究的目的是通过评估与PM毒性相关的关键机制：乳酸脱氢酶（LDH）泄漏、活性氧（ROS）生成、细胞代谢活性（CMA）变化以及27种炎症标志物的产生，来研究在急性（24小时）暴露于超细DEP（0.002 - 20μg/mL）下的体外大鼠EC-小胶质细胞共培养情况。这些参数也在大鼠小胶质细胞和内皮细胞单培养中进行了评估，以确定EC-小胶质细胞共培养的反应是否与单独的脑血管系统和小胶质细胞不同。虽然结果表明，超细DEP暴露导致所有组中LDH泄漏和ROS产生呈浓度依赖性增加，但正如预期的那样，暴露还导致所有组中CMA出现混合反应以及细胞因子/趋化因子谱不典型，这是出乎意料的。炎症检测结果进一步表明，尽管之前的体外研究显示在类似浓度的超细DEP下小胶质细胞被激活（启动），但在这种暴露情况下小胶质细胞并未被经典激活。此外，与单独的脑血管系统相比，共培养中的EC-小胶质细胞相互作用似乎除了促炎标志物产生外，并未引起任何参数的变化，在超细DEP暴露后，这种相互作用似乎导致细胞因子/趋化因子水平总体下调。最后，据我们所知，这是第一项评估小胶质细胞对血脑屏障超细DEP诱导的细胞毒性和炎症反应影响的研究，这些反应与PM相关的脑血管功能障碍和神经退行性变的发病机制密切相关。
