Neuroprotective FK506 does not alter in vivo nitric oxide production during ischemia and early reperfusion in rats.
Neuroprotective FK506 does not alter in vivo nitric oxide production during ischemia and early reperfusion in rats.
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DOI：
10.1161/01.str.30.6.1279
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发表时间：
1999-06
期刊：
影响因子：
8.3
通讯作者：
Thomas J. K. Toung;A. Bhardwaj;V. Dawson;Ted M. Dawson;R. Traystman;P. Hurn
中科院分区：
文献类型：
--
作者：
Thomas J. K. Toung;A. Bhardwaj;V. Dawson;Ted M. Dawson;R. Traystman;P. Hurn
背景和目的以前的研究已经证明，免疫抑制剂FK 506在实验性脑损伤中提供神经保护，并表明这种作用可能是通过抑制缺血去极化后发生的神经元一氧化氮合酶激活来介导的。我们试图确定FK 506是否减少大鼠大脑中动脉闭塞（MCAO）后的组织学损伤，以及神经保护作用是否通过抑制缺血或早期再灌注期间体内一氧化氮（NO）的产生来介导。方法在常氧、常二氧化碳和常温的控制条件下，氟烷麻醉的雄性Wistar大鼠在一个盲法、随机的实验中通过管腔内闭塞技术进行MCAO 2 h。在整个缺血过程中监测同侧顶叶皮质激光多普勒血流仪。将动物随机分配至4个给药前组：静脉注射FK 506 0.3 mg/kg或1. 0 mg/kg、媒介物（cremaphor）或在MCAO前30分钟给予的等体积盐水。在再灌注22小时通过氯化三苯基四氮唑染色评估梗死体积。在单独的实验中，将微透析探针双侧放置到纹状体中。用含3 μ mol/L [14 C]-L-精氨酸的人工脑脊液灌注大鼠3小时，然后进行2小时的右侧MCAO。在右侧MCAO前30分钟静脉给予0.3 mg/kg FK 506或Cremaphor。假设流出物中[14 C]-L-瓜氨酸的左右差异反映了NO产生的差异。结果所有值均为平均值+/-SE。与生理盐水（109+/-15 mm 3）和Cremaphor溶剂（148+/-23 mm 3）相比，0.3 mg/kg FK 506可减少皮质梗死体积：40+/-12 mm 3（P<0.05）。低剂量FK 506也可减少纹状体梗死：生理盐水组和溶剂组分别为16+/-4 mm 3 vs 36+/-4 mm 3和34+/-4 mm 3（P<0.05）。高剂量治疗减少了皮质（61+/-14 mm 3，生理盐水和溶剂组P<0.05）和纹状体（22+/-5 mm 3，生理盐水和溶剂组P<0.05）的梗死体积。与非缺血性纹状体相比，缺血性纹状体中通过微透析的[14 C]-L-瓜氨酸回收率显著提高。然而，与溶剂处理动物相比，FK 506处理大鼠中缺血诱发的[14 C]-L-瓜氨酸恢复无差异。结论：FK 506对大鼠短暂性局灶性脑缺血具有明显的神经保护作用。在体内的保护机制不是通过减少MCAO和再灌注早期缺血诱发的NO产生。
BACKGROUND AND PURPOSE Previous studies have demonstrated that the immunosuppressant FK506 provides neuroprotection in experimental brain injury and suggest that this action may be mediated by suppression of neuronal nitric oxide synthase activation that occurs after ischemic depolarization. We sought to determine whether FK506 reduces histological injury after middle cerebral artery occlusion (MCAO) in the rat and whether the neuroprotective effect is mediated via suppression of in vivo nitric oxide (NO) production during ischemia or early reperfusion. METHODS Under controlled conditions of normoxia, normocarbia, and normothermia, halothane-anesthetized male Wistar rats were subjected to 2 hours of MCAO by the intraluminal occlusion technique in a blinded, randomized experimental trial. Ipsilateral parietal cortical laser-Doppler flowmetry was monitored throughout ischemia. Animals were randomly assigned to 4 pretreatment groups: intravenous FK506 0.3 mg/kg or 1. 0 mg/kg, vehicle (cremaphor), or an equivalent volume of saline administered 30 minutes before MCAO. Infarction volume was assessed by a triphenyltetrazolium chloride staining at 22 hours of reperfusion. In separate experiments, microdialysis probes were placed bilaterally into the striatum. Rats were perfused with artificial cerebrospinal fluid containing 3 micromol/L [14C]- L-arginine for 3 hours and then subjected to 2 hours of right MCAO. Intravenous 0.3 mg/kg FK506 or cremaphor was given 30 minutes before right MCAO. Right-left differences between [14C]-L-citrulline in the effluent were assumed to reflect differences in NO production. RESULTS All values are mean+/-SE. FK506 at 0.3 mg/kg reduced infarction volume in cortex: 40+/-12 mm3 compared with saline (109+/-15 mm3) and cremaphor vehicle (148+/-23) (P<0.05). Striatal infarction was also reduced by low-dose FK506: 16+/-4 mm3 versus 36+/-4 mm3 and 34+/-4 mm3 in saline and vehicle groups, respectively (P<0.05). High-dose treatment reduced infarction volume in cortex (61+/-14 mm3, P<0.05 from saline and vehicle groups) and in striatum (22+/-5 mm3, P<0.05 from saline and vehicle groups). [14C]-L-citrulline recovery via microdialysis was markedly enhanced in ischemic compared with nonischemic striatum. However, ischemia-evoked [14C]-L-citrulline recovery was not different in FK506-treated rats compared with vehicle-treated animals. CONCLUSIONS These data demonstrate that FK506 provides robust neuroprotection against transient focal cerebral ischemia in the rat. The mechanism of protection in vivo is not through attenuation of ischemia-evoked NO production during MCAO and early reperfusion.