Prestigiacomo C J, Kim S C, Connolly E S, Liao H, Yan S F, Pinsky D J
Columbia University, College of Physicians and Surgeons, New York, NY, USA.
Stroke. 1999 May;30(5):1110-7. doi: 10.1161/01.str.30.5.1110.
Neutrophil (PMN) recruitment mediated by increased expression of intercellular adhesion molecule-1 expression (ICAM-1, CD54) in the cerebral microvasculature contributes to the pathogenesis of tissue injury in stroke. However, studies using blocking antibodies against the common beta2-integrin subunit on the PMN, the counterligand for ICAM-1 (CD18), have demonstrated equivocal efficacy. The current study tested the hypothesis that mice deficient in CD18 would be protected in the setting of reperfused but not nonreperfused stroke.
Two groups of mice were studied, those whose PMNs could express CD18 (CD18 +/+) and those mice hypomorphic for the CD-18 gene (CD18 -/-). PMNs obtained from CD18 -/- or CD18 +/+ mice were fluorescently labeled and tested for binding to murine brain endothelial monolayers. Using a murine model of focal cerebral ischemia in which an occluding suture placed in the middle cerebral artery (MCA) is removed after 45 minutes (transient ischemia, reperfused stroke) or left in place (permanent ischemia, nonreperfused stroke), cerebral infarct volumes (% ipsilateral hemisphere by TTC staining), cerebral blood flow (CBF, % contralateral hemisphere by laser-Doppler flowmetry), and survival (%) were examined 24 hours after the initial ischemic event. Adoptive transfer studies used 111In-labeled PMNs (from either CD18 +/+ or CD18 -/- mice) to examine the relative accumulation of PMNs in the ischemic region.
PMNs obtained from CD18 -/- mice exhibit reduced adhesivity (compared with CD18 +/+ PMNs) for both quiescent and cytokine-activated endothelial monolayers. CD18 -/- mice (n=14) subjected to transient focal cerebral ischemia demonstrated a 53% decrease in infarct volumes versus CD18 +/+ mice (n=26, P<0.05), improved penumbral CBF at 24 hours (1.8-fold, P=0.02), and a 3.7-fold decrease in mortality (P=0.02). However, when CD18 -/- mice (n=12) were subjected to permanent focal cerebral ischemia, no differences were noted in infarct volume, mortality, or CBF versus similarly treated CD18 +/+ mice (n=10). There was a greater accumulation of CD18 +/+ PMNs in the ischemic zone of CD18 +/+ animals than CD18 -/- animals subjected to reperfused stroke (82% increase, P=0.02), although there was no difference between groups when subjected to permanent MCA occlusion.
Deficiency for the CD18 gene confers cerebral protection in a murine model of reperfused stroke, but this benefit does not extend to CD18-deficient animals subjected to permanent MCA occlusion. These data suggest that anti-PMN strategies should be targeted to reperfused stroke and may perhaps be used in conjunction with thrombolytic therapy that establishes reperfusion.
脑微血管中细胞间黏附分子-1（ICAM-1，CD54）表达增加介导的中性粒细胞（PMN）募集，在中风组织损伤的发病机制中起作用。然而，使用针对PMN上共同的β2整合素亚基（ICAM-1的反配体，CD18）的阻断抗体的研究，其疗效并不明确。本研究检验了以下假设：CD18基因缺陷的小鼠在再灌注性而非非再灌注性中风情况下会受到保护。
研究了两组小鼠，一组其PMN可表达CD18（CD18 +/+），另一组为CD-18基因低表达的小鼠（CD18 -/-）。从CD18 -/-或CD18 +/+小鼠获得的PMN进行荧光标记，并检测其与小鼠脑内皮单层的结合。使用局灶性脑缺血小鼠模型，其中在大脑中动脉（MCA）放置的阻塞缝线在45分钟后移除（短暂性缺血，再灌注性中风）或留在原位（永久性缺血，非再灌注性中风），在初始缺血事件后24小时检查脑梗死体积（通过TTC染色计算同侧半球百分比）、脑血流量（CBF，通过激光多普勒血流仪测量对侧半球百分比）和存活率（%）。过继转移研究使用111In标记的PMN（来自CD18 +/+或CD18 -/-小鼠）来检查缺血区域中PMN的相对积聚情况。
从CD18 -/-小鼠获得的PMN对静止和细胞因子激活的内皮单层的黏附性均降低（与CD18 +/+ PMN相比）。经历短暂性局灶性脑缺血的CD18 -/-小鼠（n = 14）与CD18 +/+小鼠（n = 26，P < 0.05）相比，梗死体积减少53%，24小时时半暗带CBF改善（1.8倍，P = 0.02），死亡率降低3.7倍（P = 0.02）。然而，当CD18 -/-小鼠（n = 12）经历永久性局灶性脑缺血时，与同样处理的CD18 +/+小鼠（n = 10）相比，在梗死体积、死亡率或CBF方面未观察到差异。与经历再灌注性中风的CD18 -/-动物相比，CD18 +/+动物缺血区中CD18 +/+ PMN的积聚更多（增加82%，P = 0.02），尽管在永久性MCA闭塞时两组之间没有差异。
CD18基因缺陷在再灌注性中风小鼠模型中赋予脑保护作用，但这种益处并不扩展到经历永久性MCA闭塞的CD18缺陷动物。这些数据表明，抗PMN策略应针对再灌注性中风，并且可能与建立再灌注的溶栓治疗联合使用。
