The blood-brain barrier (BBB) is a complex and dynamic physiological interface between brain parenchyma and cerebral vasculature. It is composed of closely interacting cells and signaling molecules that regulate movement of solutes, ions, nutrients, macromolecules, and immune cells into the brain and removal of products of normal and abnormal brain cell metabolism. Dysfunction of multiple components of the BBB occurs in aging, inflammatory diseases, traumatic brain injury (TBI, severe or mild repetitive), and in chronic degenerative dementing disorders for which aging, inflammation, and TBI are considered risk factors. BBB permeability changes after TBI result in leakage of serum proteins, influx of immune cells, perivascular inflammation, as well as impairment of efflux transporter systems and accumulation of aggregation-prone molecules involved in hallmark pathologies of neurodegenerative diseases with dementia. In addition, cerebral vascular dysfunction with persistent alterations in cerebral blood flow and neurovascular coupling contribute to brain ischemia, neuronal degeneration, and synaptic dysfunction. While the idea of TBI as a risk factor for dementia is supported by many shared pathological features, it remains a hypothesis that needs further testing in experimental models and in human studies. The current review focusses on pathological mechanisms shared between TBI and neurodegenerative disorders characterized by accumulation of pathological protein aggregates, such as Alzheimer's disease and chronic traumatic encephalopathy. We discuss critical knowledge gaps in the field that need to be explored to clarify the relationship between TBI and risk for dementia and emphasize the need for longitudinal in vivo studies using imaging and biomarkers of BBB dysfunction in people with single or multiple TBI.

中文翻译：

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脑损伤引起的血脑屏障功能障碍是痴呆症的风险。

血脑屏障（BBB）是脑实质和脑血管之间的复杂而动态的生理界面。它由紧密相互作用的细胞和信号分子组成，这些分子和细胞调节溶质，离子，营养素，大分子和免疫细胞进入大脑的活动，并清除正常和异常的脑细胞代谢产物。在衰老，炎症性疾病，脑外伤（TBI，严重或轻度重复）和慢性退行性痴呆疾病中，BBB的多种成分功能异常，这些疾病被认为是危险因素。TBI后BBB通透性变化导致血清蛋白泄漏，免疫细胞大量涌入，血管周围炎症，以及外排转运蛋白系统的损害和易聚集性分子的积累，这些分子参与了痴呆性神经退行性疾病的典型病理。另外，脑血管功能障碍与脑血流和神经血管耦合的持续改变导致脑缺血，神经元变性和突触功能障碍。虽然TBI作为痴呆症的危险因素的想法得到了许多共同病理特征的支持，但它仍然是一个假设，需要在实验模型和人体研究中进行进一步测试。目前的审查集中在TBI和神经退行性疾病之间共享的病理机制，这些疾病的特征在于病理性蛋白质聚集体的积累，例如阿尔茨海默氏病和慢性创伤性脑病。