Role of Tau Conformations in Vascular Contribution to Cognitive Impairment and Dementia

科学证据继续支持血管对认知障碍和痴呆（VCID）的贡献 如阿尔茨海默病（AD）。事实上，约50%的痴呆患者具有混合的血管和AD病理 在他们的大脑中。在许多潜在的临床触发因素中，多栓塞性梗死和脑灌注不足， 特别是在存在衰老和高血压的情况下，是VCID中的主要血管因素，称为血管性 痴呆症（VaD），但潜在的机制仍然难以捉摸。值得注意的是，神经元缠结由 过度磷酸化tau蛋白是AD的神经病理学标志，但纯VaD人脑不具有 明显的tau缠结病理，因此关于tau病理在VaD发展中的作用知之甚少。 最近，我们发现了一种独特的脯氨酰异构酶Pin 1，它可以防止脯氨酰的积累。 在致病性顺式构象中，tau中的磷酸化Thr 231-Pro基序（P-tau），但在AD中被 老化、氧化等。顺式P-tau是一种以前未知的tau病理学前体， 传播与AD和创伤性脑损伤（TBI）相关的神经变性和痴呆，但也可能 被cis mAb阻断。在我们的初步研究中，我们在没有tau缠结的神经血管单位细胞中发现了强大的顺式P-tau 在多栓塞性梗塞或脑灌注不足后的纯VaD人脑和小鼠模型中的病理学。 此外，纯化的cis P-tau对神经元和脑微血管内皮细胞都有毒性， 引起小鼠脑功能障碍，这两种作用均被cis mAb有效地阻断。此外，顺式mAb 阻断缺氧或血清耗竭诱导血管内皮细胞中的顺式P-tau和细胞死亡， 神经元的体外培养，并在小鼠中反复TBI后恢复白色和灰质病变以及神经功能缺损。 在这个提议中，我们组建了一个拥有所有必要专业知识的团队来测试我们的新假设 在衰老过程中，血管损伤导致氧化应激，使Pin 1失活，导致顺式 P-tau蛋白损伤神经血管单位，从而作为VaD的早期和可药物驱动。我们将 首先评估不同神经血管单位细胞中Pin 1抑制和顺式P-tau诱导，以及它们之间的关系 VaD人脑中血管病理学和白色病变以及多栓塞性梗死后，或 有或无高血压或Pin 1基因敲除的年轻和老年小鼠的脑灌注不足。然后我们将 从VaD人脑和VaD小鼠脑中纯化顺式P-tau蛋白，以表征其生物化学性质， 在体外和体内损伤神经血管单位细胞以诱导白色病变的性质和能力， 与VaD相关的神经功能缺损。最后，我们将评估cis mAb在抑制神经血管生成方面的功效。 体外单位损伤和恢复白色病变、迟发性神经变性和神经功能缺损 在老年高血压或Pin 1基因敲除小鼠的多栓塞性梗死或脑灌注不足后。这些 研究应该帮助我们确定顺式P-tau作为VCID的早期疾病驱动因素，揭示一个共同的分子 研究血管和AD病理的潜在机制，并寻求这些主要疾病的靶向治疗。

Scientific evidence continues to support vascular contributions to cognitive impairment and dementia (VCID) such as Alzheimer's disease (AD). In fact, ~50% of dementia patients have mixed vascular and AD pathologies in their brains. Among many potential clinical triggers, multi-embolic infarcts and cerebral hypoperfusion, especially in the presence of aging and hypertension, are major vascular factors in VCID, referred as vascular dementia (VaD), but underlying mechanisms remain elusive. Notably, neurofibrillary tangles composed of hyperphosphorylated tau are a neuropathological hallmark of AD, but pure VaD human brains do not have obvious tau tangle pathology so that little is known about the role of tau pathology in the development of VaD. Recently, we have identified a unique prolyl isomerase, Pin1 that prevents accumulation of the phosphorylated Thr231-Pro motif in tau (P-tau) in the pathogenic cis conformation, but is inactivated in AD by aging, oxidation and others. Cis P-tau is a previously unknown precursor of tau pathology that instigates and propagates neurodegeneration and dementia associated with AD and traumatic brain injury (TBI), but can be blocked by cis mAb. In our pilot studies, we found robust cis P-tau in neurovascular unit cells without tau tangle pathology in pure VaD human brains and mouse models after multi-embolic infarcts or cerebral hypoperfusion. Furthermore, purified cis P-tau was toxic both to neurons and brain microvascular endothelial cells and also caused brain dysfunction in mice, both of which were effectively blocked by cis mAb. Moreover, cis mAb blocked hypoxia or serum depletion from inducing cis P-tau and cell death in vascular endothelial cells and neurons in vitro and restored white and gray matter lesions and neurologic deficits after repetitive TBI in mice. In this proposal, we have assembled a team with all the requisite expertise to test our novel hypothesis that during aging, vascular insults lead to oxidative stress that inactivates Pin1, resulting in accumulation of cis P-tau that damages the neurovascular unit, thereby serving as an early and druggable driver of VaD. We will first assess Pin1 inhibition and cis P-tau induction in different neurovascular unit cells, and their relationships with vascular pathology and white matter lesions in VaD human brains and after multi-embolic infarcts or cerebral hypoperfusion in young and old mice with or without hypertension or Pin1 knockout. We will then purify cis P-tau proteins from VaD human brains and VaD mouse brains to characterize their biochemical property and ability to damage neurovascular unit cells in vitro and in vivo to induce white matter lesions and neurologic deficits relevant to VaD. Finally, we will evaluate the efficacy of cis mAb in inhibiting neurovascular unit damage in vitro and restoring white matter lesions, delayed neurodegeneration and neurologic deficits after multi-embolic infarcts or cerebral hypoperfusion in aged hypertensive or Pin1 knockout mice. These studies should help us identify cis P-tau as an early disease driver of VCID, uncover a common molecular mechanism underlying vascular and AD pathologies, and pursue targeted therapy for these major diseases.