Department of Pathology and Laboratory Medicine, The Lewis Katz School of Medicine at Temple University, Philadelphia, PA 19140, United States of America; Center for Substance Abuse Research, The Lewis Katz School of Medicine at Temple University, Philadelphia, PA 19140, United States of America.
Department of Biomedical Engineering, Rowan University, Glassboro, NJ 08028, United States of America.
Neurobiol Dis. 2020 Dec;146:105131. doi: 10.1016/j.nbd.2020.105131. Epub 2020 Oct 11.
As researchers across the globe have focused their attention on understanding SARS-CoV-2, the picture that is emerging is that of a virus that has serious effects on the vasculature in multiple organ systems including the cerebral vasculature. Observed effects on the central nervous system include neurological symptoms (headache, nausea, dizziness), fatal microclot formation and in rare cases encephalitis. However, our understanding of how the virus causes these mild to severe neurological symptoms and how the cerebral vasculature is impacted remains unclear. Thus, the results presented in this report explored whether deleterious outcomes from the SARS-CoV-2 viral spike protein on primary human brain microvascular endothelial cells (hBMVECs) could be observed. The spike protein, which plays a key role in receptor recognition, is formed by the S1 subunit containing a receptor binding domain (RBD) and the S2 subunit. First, using postmortem brain tissue, we show that the angiotensin converting enzyme 2 or ACE2 (a known binding target for the SARS-CoV-2 spike protein), is ubiquitously expressed throughout various vessel calibers in the frontal cortex. Moreover, ACE2 expression was upregulated in cases of hypertension and dementia. ACE2 was also detectable in primary hBMVECs maintained under cell culture conditions. Analysis of cell viability revealed that neither the S1, S2 or a truncated form of the S1 containing only the RBD had minimal effects on hBMVEC viability within a 48 h exposure window. Introduction of spike proteins to invitro models of the blood-brain barrier (BBB) showed significant changes to barrier properties. Key to our findings is the demonstration that S1 promotes loss of barrier integrity in an advanced 3D microfluidic model of the human BBB, a platform that more closely resembles the physiological conditions at this CNS interface. Evidence provided suggests that the SARS-CoV-2 spike proteins trigger a pro-inflammatory response on brain endothelial cells that may contribute to an altered state of BBB function. Together, these results are the first to show the direct impact that the SARS-CoV-2 spike protein could have on brain endothelial cells; thereby offering a plausible explanation for the neurological consequences seen in COVID-19 patients.
当全球研究人员将注意力集中在了解 SARS-CoV-2 上时,出现的情况是,这种病毒对包括脑血管在内的多个器官系统的血管有严重影响。观察到对中枢神经系统的影响包括神经系统症状(头痛、恶心、头晕)、致命的微血栓形成,在极少数情况下还会出现脑炎。然而,我们对病毒如何导致这些轻度至重度神经系统症状以及脑血管如何受到影响的理解仍不清楚。因此,本报告中介绍的结果探讨了是否可以观察到 SARS-CoV-2 病毒刺突蛋白对原代人脑微血管内皮细胞(hBMVECs)的有害影响。刺突蛋白在受体识别中起关键作用,由包含受体结合域(RBD)的 S1 亚基和 S2 亚基组成。首先,我们使用尸检脑组织表明,血管紧张素转换酶 2 或 ACE2(SARS-CoV-2 刺突蛋白的已知结合靶标)在额皮质的各种血管直径中均广泛表达。此外,ACE2 的表达在高血压和痴呆病例中上调。ACE2 也可在维持细胞培养条件下的原代 hBMVEC 中检测到。细胞活力分析表明,在 48 小时暴露窗口内,S1、S2 或仅包含 RBD 的 S1 的截断形式对 hBMVEC 活力均没有最小影响。将刺突蛋白引入血脑屏障(BBB)的体外模型中显示出对屏障特性的重大变化。我们研究结果的关键是证明 S1 促进了更接近该中枢神经系统界面生理条件的人 BBB 的高级 3D 微流控模型中屏障完整性的丧失。提供的证据表明,SARS-CoV-2 刺突蛋白在脑内皮细胞上引发促炎反应,这可能导致 BBB 功能改变。总之,这些结果首次表明 SARS-CoV-2 刺突蛋白可能直接对脑内皮细胞产生影响;从而为 COVID-19 患者中出现的神经后果提供了合理的解释。
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