Department of Emergency Medicine, Emory University, Atlanta, GA 30322, USA.
Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, VA 23298, USA.
Int J Mol Sci. 2020 May 26;21(11):3740. doi: 10.3390/ijms21113740.
NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome inhibition and autophagy induction attenuate inflammation and improve outcome in rodent models of cerebral ischemia. However, the impact of chronic stress on NLRP3 inflammasome and autophagic response to ischemia remains unknown. Progesterone (PROG), a neuroprotective steroid, shows promise in reducing excessive inflammation associated with poor outcome in ischemic brain injury patients with comorbid conditions, including elevated stress. Stress primes microglia, mainly by the release of alarmins such as high-mobility group box-1 (HMGB1). HMGB1 activates the NLRP3 inflammasome, resulting in pro-inflammatory interleukin (IL)-1β production. In experiment 1, adult male Sprague-Dawley rats were exposed to social defeat stress for 8 days and then subjected to global ischemia by the 4-vessel occlusion model, a clinically relevant brain injury associated with cardiac arrest. PROG was administered 2 and 6 h after occlusion and then daily for 7 days. Animals were killed at 7 or 14 days post-ischemia. Here, we show that stress and global ischemia exert a synergistic effect in HMGB1 release, resulting in exacerbation of NLRP3 inflammasome activation and autophagy impairment in the hippocampus of ischemic animals. In experiment 2, an inflammasome assay, primary microglia isolated from neonatal brain tissue, were primed with lipopolysaccharide (LPS) and stimulated with adenosine triphosphate (ATP), displaying impaired autophagy and increased IL-1β production. In experiment 3, hippocampal microglia isolated from stressed and unstressed animals, were stimulated with LPS, exhibiting similar changes than primary microglia. Treatment with PROG reduced HMGB1 release and NLRP3 inflammasome activation, and enhanced autophagy in stressed and unstressed ischemic animals. Pre-treatment with an autophagy inhibitor blocked Progesterone's (PROG's) beneficial effects in microglia. Our data suggest that modulation of microglial priming is one of the molecular mechanisms by which PROG ameliorates ischemic brain injury under stressful conditions.
NOD 样受体含 pyrin 结构域蛋白 3（NLRP3）炎症小体抑制和自噬诱导可减轻炎症并改善脑缺血啮齿动物模型的预后。然而，慢性应激对 NLRP3 炎症小体和自噬对缺血的反应的影响尚不清楚。孕酮（PROG）是一种神经保护类固醇，在降低与合并症相关的缺血性脑损伤患者过度炎症方面显示出希望，包括应激升高。应激使小胶质细胞成熟，主要通过高迁移率族蛋白 B1（HMGB1）等警报素的释放。HMGB1 激活 NLRP3 炎症小体，导致促炎白细胞介素（IL）-1β的产生。在实验 1 中，成年雄性 Sprague-Dawley 大鼠接受社交挫败应激 8 天，然后通过 4 血管闭塞模型进行全脑缺血，这是一种与心脏骤停相关的临床相关脑损伤。PROG 在闭塞后 2 和 6 小时给予，并随后每天给予 7 天。动物在缺血后 7 或 14 天被处死。在这里，我们表明应激和全脑缺血在 HMGB1 释放中发挥协同作用，导致缺血动物海马中 NLRP3 炎症小体激活和自噬受损加重。在实验 2 中，对来自新生脑组织的原代小胶质细胞进行炎症小体测定，用脂多糖（LPS）诱导并刺激三磷酸腺苷（ATP），显示自噬受损和 IL-1β 产生增加。在实验 3 中，应激和未应激动物的海马小胶质细胞分离出来，用 LPS 刺激，表现出与原代小胶质细胞相似的变化。用 PROG 处理可减少 HMGB1 释放和 NLRP3 炎症小体激活，并增强应激和未应激缺血动物的自噬。自噬抑制剂的预处理阻断了 PROG 在小胶质细胞中的有益作用。我们的数据表明，调节小胶质细胞成熟是 PROG 在应激条件下改善缺血性脑损伤的分子机制之一。
