腺病毒介导kallikrein基因过度表达对脑梗死周边区细胞凋亡的作用

Adenovirus-mediated kallikrein gene over-expression inhibits neuronal apoptosis around the cerebral infarction in rats

目的 探讨激肽释放酶（kallikrein）对脑梗死周边区域缺血神经细胞凋亡的作用。方法建立大鼠大脑中动脉闭塞（MCAO）模型，将造模成功的30只大鼠采用随机数字表法分为以下几组：A组。空白对照组；B组，注射生理盐水；C组，注射pAdCMV-人类组织激肽释放酶（HTK）；每组10只。观察每组大鼠处理前后神经功能损害评分（NSS），用免疫组化技术检测外源性HTK的表达．并通过TUNEL染色、RT—PCR检测细胞凋亡及凋亡因子bcl-2、bax、caspase．3mRNA水平。结果治疗后24h在C组中可见HTK表达阳性细胞并逐渐增多，72h后达高峰，与B组以及A组相比差异有统计学意义（112±6．1、68±4．2、59±3．9，P〈0．05）。治疗后72h，C组大鼠NSS神经功能评分明显低于B组以及A组（6．70±0，16、8．13±0．16、7．93±0．20，P〈0．05）；治疗后7d差异更明显（5．14±0．18、7．82±0．14、7．91±0．10，（p〈0．01）。凋亡神经细胞集中于梗死周边区，治疗后72h及7d时，C组平均TUNEL阳性细胞数较B组与A组明显减少（72h：10．1±0．9、16．7±1．1、20．4±0．8；7d：15．2±1．2、33．6±1．3、28．8±1．7。P〈0．05）。与B、A组比较，C组中bcl-2mRNA水平增高不明显（P〉0．05）；治疗后72h及7d，bax与caspase．3mRNA水平则明显降低（p〈0.05）。结论Kallikrein可能通过减少凋亡因子bax、caspase-3的表达。抑制脑梗死周边区域的神经细胞凋亡，从而达到保护缺血神经细胞，改善神经功能的作用。

Objective To investigate the effect of exogenous kallikrein on apoptosis of the neurons around the cerebral infarct area in rats. Methods Thirty rats with cerebral infarction induced by middle cerebral artery occlusion （MCAO） were assigned randomly into 3 groups （n=10）, namely the blank control group, saline group, and pAdCMV-HTK group. In the pAdCMV-HTK group, kallikrein gene was delivered into the cerebral ischemic lesion via a replication-defective adenovirus using stereotactic injection technique, and the expression of exogenous kallikrein was detected immunohistochemically. TUNEL staining was performed to evaluate the neuronal apoptosis around the infarct area, and RT-PCR used to detect the mRNA expressions of bcl-2, bax and caspase-3 in the brain tissues. Results At 24 h after treatment there were some HTK expressed cells found in group C and peak at 72 h after treatment. While compare with group B and group C, there existed significant difference （112±6.1, 68±4.2, 59±3.9, P〈0.05）. At 72 h after treatment, the NSS of group C was significantly lower than that of gruop B and A（6.70±0.16, 8.13±0.16, 7.93±0.20, P〈0.05） ; 7 days after the treatment, the difference was more significant（5.14±0.18, 7.82±0.14, 7.91±0.10, P〈0.01）. Apoptotic cells were mostly seen around the infarct area. The rats in pAdCMV-HTK group showed significantly reduced number of cells positive for TUNEL staining as compared to those in the saline and blank control groups at 3 days （10.1±0.9, 16.7±1.1, and 20.4±0.8, respectively） and 7 days after the treatment （15.2±1.2, 33.6±1.3, and 28.8±1.7, respectively） （P〈0.05）. The mRNA levels ofbcl-2, bax and caspase-3 were elevated in all the groups at 24 h, peaked at 72 h, and decreased gradually till 7 days after the treatment. Compared with those in the other two groups, bcl-2 mRNA level in the pAdCMV-HTK group increased slightly （P〉0.05） while bax and caspase-3 mRNA levels decreased markedly （P〈0.05） 72 h and 7 days after the treatment. Conclusion Kallikrein can inhibit neuronal apoptosis around the cerebral infarct and improve the neurological function of rats following cerebral infarction probably by reducing the expressions of such apoptotic factors as bax and caspase-3.