亚低温对急性脑缺血再灌注大鼠TNF-α表达的影响

目的：探讨亚低温对大鼠急性脑缺血／再灌注损伤后神经功能及缺血脑组织中TNF—α表达的影响。方法：取健康成年雄性SD大鼠150只。随机均分为假手术组、脑缺血再灌注常温组、脑缺血再灌注亚低温组；根据再灌注时间不同，每组分别于再灌注8h，24h，3d，7d，30d各处死10只大鼠，并取其缺血脑组织，其中5只用于免疫组化染色，另外5只用于RT—PCR检测TNF—αmRNA。结果：脑缺血再灌注后，TNF—α阳性细胞数在再灌注1d时即达高峰，3d后迅速下降，再灌注7d时即降到较低水平，组间比较差异有统计学意义（P〈0．05）。TNF—α及其mRNA表达假手术组很弱，缺血再灌注后TNF—α及其mRNA在8h表达为顶峰，随后有所下降，但直到再灌注7d仍然保持相对高的表达水平，一个月基本恢复正常；其表达在亚低温组较常温脑缺血组有显著地下降（P〈0．05），但仍较假手术组高（P〈0．05）。结论：脑缺血再灌注损伤后TNF—α明显升高，应用亚低温可以降低TNF—α升高的程度；亚低温可以明显减少缺血再灌注后脑梗死的区域，并能明显改善缺血再灌注大鼠的神经功能。提示亚低温治疗对脑的保护作用有可能通过降低TNF—α水平来实现的。

The Influence of Mild Hypothermia on the Expression of TNF-α after Acute Cerebral Ischemia Reperfusion in Adult Rats

Objective ：To investigate the effects of mild hypothermia on nerval function after injuries of acute cerebral ischemia/ reperfusion and the expression of TNF-α in the ischemic brain tissue in rats, Methods： 150 adult male SD rats with weight of 280 to 320 g, were randomly divided into three groups, including sham-operated, cerebral ischemia/reperfusion in ordinary temperature, and cerebral ischemla/reperfusion in mild hypothermia, each group was consisted of 50 rats, At the points of eighth hour, twenty-forth hour, third day, seventh day and first month after reperfusion, ten rats from each group were killed, and their ischemic brain tissues were taken out. These tissues were applied for research on immunohistochemistry expression of TNF-α mRNA. Each subgroup included five brain tissue specimen from same group at the same time after reperfusion, Results ： The TNF-α positive cell population reached its peak on the first day after reperfusion, then decreased rapidly on third day, and maintained at the lowest level after seventh day. The intensity of TNF-α immunoreactivity was increased in ordinary temperature group compared to that in sham-operated group （P 〈 0. 05 ）, but were lower than that in mild hypothermia group（ P 〈 0. 05 ）, The expressions of TNF-α and its mRNA were weak in the sham-operated group, their expression reached peak at 8th hour after cerebral ischemia reperfusion ,whereafter decreased to some extent, but remained at a higher level until 7th day, and recovered to normal level at 1 month later, The expressions of TNF-α and its mRNA in ordinary temperature group were highest in three groups, those in mild hypothermia group were second, Conclusions： The expression of TNF-α increases rapidly after cerebral ischemia reperfusion, Mild hypothermia treatment could depress the expressions of TNF-α and its mRNA, indicating that mild hypothermia would protect cerebral tissues from injuries induced by cerebral ischemia reperfusion via depressing the production and expression of TN