Department of Neuroscience, University of Connecticut Health Center, Farmington, CT 06032, USA; Calhoun Cardiology Center, University of Connecticut Health Center, Farmington, CT 06032, USA.
Calhoun Cardiology Center, University of Connecticut Health Center, Farmington, CT 06032, USA.
Brain Behav Immun. 2017 Nov;66:302-312. doi: 10.1016/j.bbi.2017.07.155. Epub 2017 Jul 24.
Acute ischemic injury leads to severe neuronal loss. One of the key mechanisms responsible for this effect is inflammation, which is characterized by the activation of myeloid cells, including resident microglia and infiltrating monocytes/macrophages. P2X4 receptors (P2X4Rs) present on these immune cells modulate the inflammatory response. For example, excessive release of adenosine triphosphate during acute ischemic stroke triggers stimulation of P2X4Rs, leading to myeloid cell activation and proliferation and further exacerbating post-ischemic inflammation. In contrast, during recovery P2X4Rs activation on microglia leads to the release of brain-derived neurotrophic factor (BDNF), which alleviate depression, maintain synaptic plasticity and hasten post-stroke behavioral recovery. Therefore, we hypothesized that deletion of the P2X4R specifically from myeloid cells would have differential effects on acute versus chronic recovery following stroke.
We subjected global or myeloid-specific (MS) P2X4R knock-out (KO) mice and wild-type littermates of both sexes to right middle cerebral artery occlusion (60min). We performed histological, behavioral (sensorimotor and depressive), and biochemical (quantitative PCR and flow cytometry) analyses to determine the acute (three days after occlusion) and chronic (30days after occlusion) effects of receptor deletion.
Global P2X4R deletion led to reduced infarct size in both sexes. In MS P2X4R KO mice, only females showed reduced infarct size, an effect that did not change with ovariectomy. MS P2X4R KO mice of both sexes showed swift recovery from sensorimotor deficits during acute recovery but exhibited a more pronounced post-stroke depressive behavior phenotype that was independent of infarct size. Quantitative PCR analysis of whole cell lysate as well as flow-sorted myeloid cells from the perilesional cortex showed increased cellular interleukin 1 beta (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor alpha (TNF-α) mRNA levels but reduced plasma levels of these cytokines in MS P2X4R KO mice after stroke. The expression levels of BDNF and other depression-associated genes were reduced in MS P2X4R KO mice after stroke.
P2X4R deletion protects against stroke acutely but predisposes to depression-like behavior chronically after stroke. Thus, a time-sensitive approach should be considered when targeting P2X4Rs after stroke.
急性缺血性损伤可导致严重的神经元丧失。导致这种效应的关键机制之一是炎症，其特征为髓样细胞（包括常驻小胶质细胞和浸润的单核细胞/巨噬细胞）的激活。这些免疫细胞上的 P2X4 受体（P2X4Rs）调节炎症反应。例如，急性缺血性脑卒中期间三磷酸腺苷的过度释放会触发 P2X4Rs 的刺激，导致髓样细胞的激活和增殖，并进一步加重缺血后炎症。相比之下，在恢复过程中，小胶质细胞上 P2X4Rs 的激活会导致脑源性神经营养因子（BDNF）的释放，从而缓解抑郁、维持突触可塑性并加速卒中后行为恢复。因此，我们假设 P2X4R 在髓样细胞中的特异性缺失将对卒中后急性和慢性恢复产生不同的影响。
我们使全球或髓样特异性（MS）P2X4R 敲除（KO）小鼠及其同性别野生型对照经历右侧大脑中动脉闭塞（60 分钟）。我们进行了组织学、行为（感觉运动和抑郁）和生化（定量 PCR 和流式细胞术）分析，以确定受体缺失的急性（闭塞后 3 天）和慢性（闭塞后 30 天）效应。
全球 P2X4R 缺失导致两性的梗死体积减小。在 MS P2X4R KO 小鼠中，只有雌性的梗死体积减小，这种效应不因卵巢切除术而改变。MS P2X4R KO 小鼠在急性恢复期间从感觉运动缺陷中迅速恢复，但表现出更明显的卒中后抑郁行为表型，该表型与梗死体积无关。对损伤皮层周围小胶质细胞进行全细胞裂解物的定量 PCR 分析以及流式细胞分选显示，MS P2X4R KO 小鼠卒中后细胞白细胞介素 1β（IL-1β）、白细胞介素 6（IL-6）和肿瘤坏死因子-α（TNF-α）mRNA 水平升高，但血浆中这些细胞因子的水平降低。卒中后 MS P2X4R KO 小鼠的脑源性神经营养因子（BDNF）和其他与抑郁相关基因的表达水平降低。
P2X4R 缺失在急性卒中时起保护作用，但在卒中后慢性期易发生抑郁样行为。因此，在卒中后靶向 P2X4Rs 时应考虑采用时间敏感的方法。
