STAT3 activation in astrocytes as a driver of neurovascular dysfunction in Alzheimer's disease and related dementias

项目总结 阿尔茨海默病(AD)和相关痴呆(ADRD)会因神经血管功能障碍而加重。 星形胶质细胞是神经血管健康和血脑屏障(BBB)功能的关键贡献者。作为对.的回应 在致病刺激下，星形胶质细胞采用一种“反应性”表型，通常以形态变化为特征。 最近的研究表明，反应性星形胶质细胞可以采用不同的分子特性，但 这些不同亚型的反应性星形胶质细胞与脑血管系统之间的相互作用尚不清楚。 事实上，一些研究表明，反应性星形胶质细胞对血脑屏障功能有负面影响，而其他研究则有。 研究表明，反应性星形胶质细胞对损伤后的神经血管修复至关重要。这些研究中的大多数是 在中风或身体创伤的背景下进行的，虽然在单细胞研究中有一些新兴的研究 关于ADRD中反应性星形胶质细胞状态的解析，几乎没有关于这些不同状态如何的信息 可能直接导致神经血管功能障碍。在这里，我们建议研究STAT3激活是如何 在ADRDS中，星形胶质细胞的存在会导致神经血管功能障碍。在前期工作中，使用来自 死后的人脑组织，我们已经表明AD患者显著增加了 STAT3激活星形胶质细胞和发炎的血管。在与星形胶质细胞共培养的人体外模型中 脑内皮细胞，我们已经证明炎症刺激激活星形胶质细胞中的STAT3信号，这是 导致血脑屏障破坏，抑制星形胶质细胞中STAT3的激活可以减轻这些结果。此外， 使用人类体外模型、体外小鼠皮质切片培养和体内操作的组合， 我们已经证明，α1-抗糜蛋白酶(ACT)--一种由STAT3调节的丝氨酸蛋白酶抑制物--有助于 直接导致神经血管功能障碍。展望未来，我们将在这些有希望的成果的基础上，在以下方面再接再厉 举止。在目标1中，我们将把我们的人体组织研究扩展到更大的ADRD队列，并采用先进的 量化STAT3激活的星形胶质细胞和星形胶质细胞之间三维空间关系的成像技术 血管损伤的部位。在目标2中，我们将在转基因小鼠模型中抑制星形胶质细胞中的STAT3信号 并评估神经血管功能障碍的纵向变化；这些评估将包括 单细胞RNA测序，以表征整个血管树上内皮细胞的分子变化。 在目标3中，我们将在转基因小鼠模型中将星形胶质细胞来源的ACT与神经血管功能障碍联系起来 以及前瞻性地描述了ACT和APOE之间的协同作用，这两个机构已经知道 阿尔茨海默病与痴呆风险之间的联系。总体而言，这项工作的结果将定义 STAT3激活的星形胶质细胞在ADRD相关神经血管功能障碍中的作用及潜在途径 将星形胶质细胞作为ADRD的治疗策略。

Project summary Alzheimer’s disease (AD) and related dementias (ADRD) are exacerbated by neurovascular dysfunction. Astrocytes are key contributors to neurovascular health and blood-brain barrier (BBB) function. In response to pathogenic stimuli, astrocytes adopt a “reactive” phenotype generally characterized by morphological changes. Recent research has shown that reactive astrocytes can adopt a diverse spectrum of molecular identities, but the interplay between these different subtypes of reactive astrocytes and the brain vasculature remains unclear. Indeed, some studies have shown that reactive astrocytes negatively influence BBB function, while others have shown that reactive astrocytes are vital to neurovascular repair after injury. Most of these studies have been performed in the context of stroke or physical trauma, and while there are some emerging studies at single-cell resolution on reactive astrocyte states in ADRDs, there is little to no information on how these different states may directly contribute to neurovascular dysfunction. Herein, we propose to investigate how STAT3 activation in astrocytes drives neurovascular dysfunction in ADRDs. In preliminary work, using thin sections from postmortem human brain tissue, we have shown that AD patients have significantly increased numbers of STAT3-activated astrocytes and inflamed blood vessels. In a human in vitro model of astrocytes cocultured with brain endothelial cells, we have shown that inflammatory stimuli activate STAT3 signaling in astrocytes, which leads to BBB disruption, and inhibition of STAT3 activation in astrocytes mitigates these outcomes. Further, using combinations of the human in vitro model, ex vivo mouse cortical slice cultures, and in vivo manipulations, we have shown that alpha 1-antichymotrypsin (ACT)—a STAT3-regulated serine protease inhibitor—contributes directly to neurovascular dysfunction. Moving forward, we will build on these promising results in the following manner. In Aim 1, we will expand our human tissue studies into larger ADRD cohorts and employ advanced imaging techniques to quantify three-dimensional spatial relationships between STAT3-activated astrocytes and sites of vascular damage. In Aim 2, we will inhibit STAT3 signaling in astrocytes within transgenic mouse models of ADRD and evaluate longitudinal alterations to neurovascular dysfunction; these assessments will include single-cell RNA sequencing to characterize molecular changes to endothelial cells along the entire vascular tree. In Aim 3, we will causally link astrocyte-derived ACT to neurovascular dysfunction in transgenic mouse models of ADRD, as well as characterize prospectively synergy between ACT and APOE, which have known connections in AD and dementia risk. Collectively, outcomes from this work will define the mechanistic roles of STAT3-activated astrocytes in neurovascular dysfunction associated with ADRD and identify potential avenues for targeting astrocytes as an ADRD treatment strategy.