局部亚低温对大鼠脑出血后基质金属蛋白酶-9及血脑屏障通透性的影响

Effect of local mild hypothermia on expression of matrix metalloproteinase-9 following intracerebral hemorrhage in rats

目的探讨局部亚低温对大鼠自体血注入法脑出血模型基质金属蛋白酶-9(matrix metalloproteinase-9,MMP-9)mRNA及蛋白表达的影响以及局部亚低温减轻脑出血后水肿的可能机制。方法雄性Wistar大鼠240只,随机分为脑出血(ICH)组和脑出血加局部亚低温(ICH+H)组。每组分为对照、脑出血后6h、24h、72h、5d、7d共6个亚组,ICH+H组于注血后立即给以4h的局部亚低温治疗,各亚组分别进行血脑屏障(BBB)通透性、脑水含量的检测以及应用RT-PCR及Western印记对MMP-9进行测定。结果ICH组大鼠脑内注血后6h开始出现脑组织水含量(P<0.01)及BBB通透性(P<0.05)的显著增加,二者在72h达到高峰,然后逐渐消退,ICH组MMP-9蛋白表达量与脑含水量和血脑屏障通透性呈正相关(r=0.88和r=0.96),ICH组MMP-9 mRNA表达量也与脑含水量和血脑屏障通透性呈正相关(r=0.78和r=0.85)。ICH+H组大鼠脑组织水含量、BBB通透性以及MMP-9蛋白的表达与ICH组各时间点相比较,明显降低,而MMP-9 mRNA的表达与ICH组相比仅有轻度下降。结论脑出血后MMP-9的变化与BBB通透性和脑水肿密切相关,局部亚低温可以抑制脑出血后MMP-9蛋白表达的增加以及脑水肿的形成。提示局部亚低温可能通过影响MMP-9的变化来抑制脑出血后的水肿形成。

Objective To explore the effect of local mild hypothermia on the expression of matrix metalloproteinase- 9（MMP-9） following intracerebral hemorrhage in rats. Methods 240 male Wistar rats were randomly divided into two groups：the intracerebral hemorrhage（ICH） group,in which autologous arterial blood were stereotaxically injected into right caudate nucleus ;the local mild hypothermia（ ICH ＋ H） group,in which the rats were given 4h local mild hypothermia right after the injection of blood. Each group was divided into 6 subgroups：control,6h,24h,72h,5d and 7d after operation;Brain water content（BWC） was determined by dry-wet weight method and the permeability of BBB was measured by Evans-Blue extravasation. RT-PCR and Western blot were respectively used to evaluate MMP-9 mRNA and protein expression. Results In ICH group, compared with control,autologous arterial blood injection significantly increased BWC（ P 〈 0.01 ） and the permeability of BBB（P 〈 0.05） , both began at 6h and peaked at 72h, and thereafter decreased. Both the mRNA and the protein expression of MMP-9 were positively correlated with both the permeability of BBB （ r = 0.96 and r = 0.85 respectively） and BWC（ r = 0.88 and r = 0.78 respectively）. In ICH ＋ H group, compared with ICH group, the elevation of BWC and BBB permeability and MMP-9 protein expression were strongly attenuated at all time points by hypothermia treatment（ P 〈 0.01 ） ,while MMP-9 mRNA levels demonstrated a modest attenuation. Conclusions These findings suggest that MMP- 9 should be positively correlated with both the permeability of BBB and brain edema formation,and local mild hypothermia can reduce the brain edema formation following ICH by suppressing the elevation of MMP-9 protein expression.