Abstract：
Neuroinflammation and oxidative stress contribute to the progression of sepsis-associated encephalopathy (SAE). Angiotensin-converting enzyme 2 (ACE2) is considered to be a neuroprotective factor due to its anti-inflammatory and antioxidant properties. However, the role of ACE2 on myeloid cells in regulating SAE and the underlying mechanism warrants further exploration. SAE was induced in ACE2 transgenic (TG), knockout (KO), and bone marrow (BM) chimeric mice by cecal ligation and puncture (CLP). The expression levels of apoptosis-, oxidation- and neuroinflammation-associated mediators and morphological changes were monitored by quantitative real-time PCR analyses and histological examinations in the cortex of septic mice. The contents of angiotensin (Ang) II and Ang-(1-7) along with the activity of ACE2 were examined with commercial kits. The expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and Sestrin2 was detected by immunoblotting analysis. Our results indicated that the expression of cortical ACE2 was significantly reduced in the early phase of CLP-induced sepsis. Moreover, ACE2 overexpression in TG mice conferred neuroprotection against sepsis, as evidenced by alleviated neuronal apoptosis, oxidative stress, and proinflammatory M1-like microglial polarization, accompanied by upregulation of the Ang-(1-7), Nrf2, and Sestrin2 protein levels. Conversely, ACE2 deficiency in KO mice exacerbated SAE. The neuroprotective effects of ACE2 were further confirmed in wild-type mice transplanted with ACE2-TG and KO BM cells. Therefore, our data suggest that myeloid ACE2 exerts a protective role in the pathogenesis of SAE, potentially by activating Ang-(1-7)-Nrf2/sestrin2 signaling pathway, and highlight that upregulating ACE2 expression and activity may represent a promising approach for the treatment of SAE in patients with sepsis.
摘要：
神经炎症和氧化应激有助于脓毒症相关性脑病（SAE）的进展。血管紧张素转换酶2（ACE2）由于其抗炎和抗氧化特性而被认为是神经保护因子。然而,ACE2在髓系细胞中对SAE的调控作用及其潜在机制有待进一步探索。SAE在ACE2转基因（TG）中诱导，淘汰赛(KO),和骨髓（BM）嵌合小鼠通过盲肠结扎和穿刺（CLP）。凋亡的表达水平-，通过定量实时PCR分析和脓毒症小鼠皮质的组织学检查监测氧化和神经炎症相关介质和形态学变化。用商业试剂盒检查血管紧张素（Ang）II和Ang-（1-7）的含量以及ACE2的活性。通过免疫印迹分析检测核因子红细胞2相关因子2（Nrf2）和Sestrin2的表达。我们的结果表明，在CLP诱导的脓毒症早期，皮质ACE2的表达显着降低。此外，ACE2在TG小鼠中的过度表达赋予了对脓毒症的神经保护作用，正如神经元凋亡减轻所证明的那样，氧化应激，和促炎M1样小胶质细胞极化，伴随着Ag-（1-7）的上调，Nrf2和Sestrin2蛋白水平。相反，KO小鼠的ACE2缺乏加剧了SAE。在移植ACE2-TG和KOBM细胞的野生型小鼠中进一步证实了ACE2的神经保护作用。因此,我们的数据表明，髓样ACE2在SAE的发病机制中发挥保护作用，可能通过激活Ang-（1-7）-Nrf2/sestrin2信号通路，并强调上调ACE2的表达和活性可能是治疗脓毒症患者SAE的一种有希望的方法。
