亚低温对脑缺血再灌注后缺血核心区皮质内IL-1β和MCP-1含量的影响

Effect of intraischemic mild hypothermia on interleukin-1β and monocyte chemoattractant protein-1 contents in ischemic core of rat cortex after transient focalcerebral ischemia

目的 探讨缺血过程中亚低温对大鼠脑缺血再灌注后缺血核心区皮质内白细胞介素1β(IL 1β)及单核细胞趋化蛋白 (MCP) 1含量的影响。 方法 选用 80只雄性Wistar大鼠 ,随机分为常温组 (37℃ )和亚低温组 (32～ 33℃ ) ,用ELISA法测定缺血 2h再灌不同时间缺血核心区脑皮质内IL 1β和MCP 1含量变化 ;用 2 ,3,5三苯基四氮唑 (TTC)染色法观察脑皮质梗死灶的变化。 结果 常温组再灌注后各时间点缺血核心区皮质内IL 1β含量无明显变化 ;MCP 1含量于再灌注 6h后开始升高 (2 2 5± 8 7)ng/g ,是假手术组的 17 0倍 (P <0 0 5 ) ,4 8h逐渐达到高峰 (110 9± 4 7 0 )ng/g ,是假手术组的 83 7倍 (P <0 0 0 1)。与常温组相比 ,亚低温组再灌注后缺血核心区皮质内IL 1β含量没有明显变化 ,但MCP 1的含量于再灌注后 6h为 (8 7± 7 6 )ng/g(P <0 0 0 5 ) ,再灌注后 4 8h为 (5 6 0± 4 0 3)ng/g(P <0 0 5 ) ,明显低于常温组 ,皮质梗死灶也显著小于常温组。 结论 降低缺血再灌注后脑皮质内MCP 1的含量 ,可能是亚低温发挥脑保护作用的重要途径之一。

Objective To investigate the effect of intraischemic mild hypothermia on the protein levels of interleukin (IL)-1β and monocyte chemoattractant protein (MCP)-1 in the ischemic core of rat cortex after transient focal cerebral ischemia. Methods Eighty male Wistar rats were randomly divided into normothermic (37℃) and mild hypothermic (32～33℃) groups. The normothermic group was redivided into six subgroups of 8 rats: sham operation, ischemia for 2 hours without reperfusion, and reperfusion for 6 hours, 16 hours, 24 hours, and 48 hours respectively after ischemia; and the mild hypothermic group was redivided into 4 group with 8 rats: reperfusion for 6, 16, 24, and 48 hours. The rats except those in the sham operation subgroup were subjected to right middle cerebral artery occlusion by insertion a speciully prepared nylon filament for two hours. Ice bag was used to lower the brain temperature and anal temperature soon after ischemia to 32.0～33.0℃ within 10 minutes in the mild hypothermic subgroups. The brain and anal temperature remained at 37.0～37.5℃ in all normothermic subgroups. Then the rats were killed 0, 6, 16, 24 and 48 hours after reperfusion respectively and their brains were taken out to examine the size of brain infarct by 2,3,5-triphenyltetrazolium chloride (TTC) staini ng reaction. The protein levels of IL-1β and MCP-1 in the cortical ischemic core were measured by ELISA. Results No significant cha nge of IL-1β protein level was found in the cortical ischemic cores at any time point after reperfusion amo ng the normothermic subgroups. The IL-1β protein levels at different time points were not significantly different between the intraischemic mild hypothermia subgroups and the normothermic subgroups (all P >0.05). The MCP-1 protein level in the cortical ischemic cores of the normothermic subgroups began to increase since the 6th hour afer reperfusion (22.5±8.7 ng·g tissue -1 , 17 times that in the sham operation samples, P <0.05), peaked in 48 hours (110.9±47.0 ng·g tissue -1 , 83.7 times that in the sham operation sample, P <0.001). The protein level of MCP-1 in the mild hypothermic subgroups was 8.7±7.6 ng·g tissue -1 6 h after reperfusion ( P <0.005 in comparison with those in sham operation subgriup and ischemia subgroup) and was 56.0±40.3 ng·g tissue -1 , 48 hours after reperfusion ( P <0.05) incomparison with thosein the normothermic subgroups). The sizes of cortical infarct at different time points in the mild hypothermic subgroups were significantly smaller than those in the normothermic subgroups ( P <0.05). Conclusion Mild hypothermia reduces the level of MCP-1 in the cortex after cerebral ischemia/reperfusion which may be one of the important mechanisms of the neuroprotective effects of mild hypothermia.