The blood-brain barrier is disrupted in Machado-Joseph disease/spinocerebellar ataxia type 3: evidence from transgenic mice and humanpost-mortemsamples
The blood-brain barrier is disrupted in Machado-Joseph disease/spinocerebellar ataxia type 3: evidence from transgenic mice and humanpost-mortemsamples
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DOI：
10.1186/s40478-020-00955-0
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发表时间：
2020-08-31
影响因子：
7.1
通讯作者：
Pereira de Almeida, Luis
中科院分区：
文献类型：
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作者：
Duarte Lobo, Diana;Nobre, Rui Jorge;Pereira de Almeida, Luis
血脑屏障(BBB)破坏是神经退行性疾病的常见特征。然而，脊髓小脑性共济失调(SCA)如Machado-Joseph病/SCA 3型(MJD/SCA3)，这是一种由多谷氨酰胺扩张的ataxin-3引发的遗传性疾病，尚未对BBB完整性进行评估。为了研究这一点，我们在MJD转基因小鼠模型和人死后脑组织中评估了血脑屏障的完整性。首先，我们研究了MJD小鼠的血脑屏障通透性：i)免疫荧光法检测小脑中Evans蓝(EB)染料和血源性蛋白(如纤维蛋白原)的渗出；ii)体内动态增强磁共振成像(DCE-MRI)。免疫荧光法和免疫印迹法检测脑血管中ataxin-3聚集体的存在和紧密连接(TJ)相关蛋白水平。人脑样本被用来通过评估纤维蛋白原外渗、ataxin-3聚集体与脑血管的共存和神经炎症来确认血脑屏障的通透性。在MJD小鼠模型的小脑中，与年龄匹配的对照组相比，EB积累增加了5倍。此外，DCE-MRI显示血管通透性增加了13倍。与对照组相比，转基因动物的纤维蛋白原渗出量增加了2倍，证实了这些结果。有趣的是，在转基因小鼠的小脑血管中检测到突变的ataxin-3聚集体，伴随着小脑内皮细胞中TJ相关蛋白的变化，即claudin-5寡聚体减少29%，封闭蛋白切割片段增加10倍。这些结果在MJD患者的尸检样本中得到了验证，因为我们检测到纤维蛋白原通过血脑屏障渗出，血管中存在ataxin-3聚集体，以及相关的小胶质细胞增生。总之，我们的结果证明了MJD/SCA3的血脑屏障受损。这些发现有助于更好地了解疾病机制，并为使用在正常情况下不会越过血脑屏障的药物治疗MJD打开了机会。
Blood-brain barrier (BBB) disruption is a common feature in neurodegenerative diseases. However, BBB integrity has not been assessed in spinocerebellar ataxias (SCAs) such as Machado-Joseph disease/SCA type 3 (MJD/SCA3), a genetic disorder, triggered by polyglutamine-expanded ataxin-3. To investigate that, BBB integrity was evaluated in a transgenic mouse model of MJD and in humanpost-mortembrain tissues. Firstly, we investigated the BBB permeability in MJD mice by: i) assessing the extravasation of the Evans blue (EB) dye and blood-borne proteins (e.g fibrinogen) in the cerebellum by immunofluorescence, and ii) in vivo Dynamic Contrast Enhanced-Magnetic Resonance Imaging (DCE-MRI). The presence of ataxin-3 aggregates in brain blood vessels and the levels of tight junction (TJ)-associated proteins were also explored by immunofluorescence and western blotting. Human brain samples were used to confirm BBB permeability by evaluating fibrinogen extravasation, co-localization of ataxin-3 aggregates with brain blood vessels and neuroinflammation. In the cerebellum of the mouse model of MJD, there was a 5-fold increase in EB accumulation when compared to age-matched controls. Moreover, vascular permeability displayed a 13-fold increase demonstrated by DCE-MRI. These results were validated by the 2-fold increase in fibrinogen extravasation in transgenic animals comparing to controls. Interestingly, mutant ataxin-3 aggregates were detected in cerebellar blood vessels of transgenic mice, accompanied by alterations of TJ-associated proteins in cerebellar endothelial cells, namely a 29% decrease in claudin-5 oligomers and a 10-fold increase in an occludin cleavage fragment. These results were validated inpost-mortembrain samples from MJD patients as we detected fibrinogen extravasation across BBB, the presence of ataxin-3 aggregates in blood vessels and associated microgliosis. Altogether, our results prove BBB impairment in MJD/SCA3. These findings contribute for a better understanding of the disease mechanisms and opens the opportunity to treat MJD with medicinal products that in normal conditions would not cross the BBB.