Herz Josephine, Sabellek Pascal, Lane Thomas E, Gunzer Matthias, Hermann Dirk M, Doeppner Thorsten R
From the Department of Neurology (J.H., P.S., D.M.H., T.R.D.), Department of Pediatrics I (J.H.), and Institute of Experimental Immunology and Imaging, University Duisburg-Essen (M.G.), University Hospital Essen, Essen, Germany; and Division of Microbiology and Immunology, Department of Pathology, University of Utah School of Medicine, Salt Lake City (T.E.L.).
Stroke. 2015 Oct;46(10):2916-25. doi: 10.1161/STROKEAHA.115.010620. Epub 2015 Sep 3.
Inflammation-related comorbidities contribute to stroke-induced immune responses and brain damage. We previously showed that hyperlipidemia exacerbates ischemic brain injury, which is associated with elevated peripheral and cerebral granulocyte numbers. Herein, we evaluate the contribution of neutrophils to the exacerbation of ischemic brain injury.
Wild-type mice fed with a normal chow and ApoE knockout mice fed with a high cholesterol diet were exposed to middle cerebral artery occlusion. CXCR2 was blocked using the selective antagonist SB225002 (2 mg/kg) or neutralizing CXCR2 antiserum. Neutrophils were depleted using an anti-Ly6G antibody. At 72 hours post ischemia, immunohistochemistry, flow cytometry, and real-time polymerase chain reaction were performed to determine cerebral tissue injury and immunologic changes in the blood, bone marrow, and brain. Functional outcome was assessed by accelerated rota rod and tight rope tests at 4, 7, and 14 days post ischemia.
CXCR2 antagonization reduced neurological deficits and infarct volumes that were exacerbated in hyperlipidemic ApoE-/- mice. This effect was mimicked by neutrophil depletion. Cerebral neutrophil infiltration and peripheral neutrophilia, which were increased on ischemia in hyperlipidemia, were attenuated by CXCR2 antagonization. This downscaling of neutrophil responses was associated with increased neutrophil apoptosis and reduced levels of CXCR2, inducible nitric oxide synthase, and NADPH oxidase 2 expression on bone marrow neutrophils.
Our data demonstrate a role of neutrophils in the exacerbation of ischemic brain injury induced by hyperlipidemia. Accordingly, CXCR2 blockade, which prevents neutrophil recruitment into the brain, might be an effective option for stroke treatment in patients with hyperlipidemia.
炎症相关的合并症会导致中风诱导的免疫反应和脑损伤。我们之前表明，高脂血症会加剧缺血性脑损伤，这与外周和脑内粒细胞数量增加有关。在此，我们评估中性粒细胞在缺血性脑损伤加剧过程中的作用。
喂食普通饲料的野生型小鼠和喂食高胆固醇饮食的载脂蛋白E基因敲除小鼠接受大脑中动脉闭塞手术。使用选择性拮抗剂SB225002（2毫克/千克）或中和性CXCR2抗血清阻断CXCR2。使用抗Ly6G抗体清除中性粒细胞。在缺血后72小时，进行免疫组织化学、流式细胞术和实时聚合酶链反应，以确定脑组织损伤以及血液、骨髓和脑中的免疫变化。在缺血后4天、7天和14天，通过加速转棒试验和紧绳试验评估功能结果。
CXCR2拮抗作用减少了高脂血症的载脂蛋白E基因敲除小鼠中加剧的神经功能缺损和梗死体积。中性粒细胞清除可模拟这种效果。高脂血症中缺血时增加的脑内中性粒细胞浸润和外周中性粒细胞增多，通过CXCR2拮抗作用而减弱。中性粒细胞反应的这种下调与中性粒细胞凋亡增加以及骨髓中性粒细胞上CXCR2、诱导型一氧化氮合酶和NADPH氧化酶2表达水平降低有关。
我们的数据证明中性粒细胞在高脂血症诱导的缺血性脑损伤加剧过程中起作用。因此，阻止中性粒细胞募集到脑内的CXCR2阻断可能是高脂血症患者中风治疗的有效选择。
