AT1受体阻断剂对小鼠海马脑源性神经营养因子信号的影响

Influence of AT1 receptor blockade on brain-derived neurotrophic factor signaling in hippocampus of mice

目的：探讨血管紧张素转换酶2（ACE2）基因敲除（KO）小鼠脑海马组织中脑源性神经营养因子（BDNF）信号的改变以及厄贝沙坦干预对该信号通路的影响。方法：采用10～11周龄ACE2KO （Ace2／y ）小鼠每天分别给予血管紧张素II （Ang II）1型（AT1）受体阻断剂厄贝沙坦（50 mg／kg）或安慰剂治疗，为期2周。正常野生型（WT ；Ace2＋／y ）小鼠作为正常对照。用 Western 印迹检测小鼠海马组织中 BDNF 与细胞外信号调节激酶1／2（ERK1／2）水平。采用放射免疫法测定小鼠血浆血管紧张素水平。结果：与正常WT对照小鼠相比， ACE2 KO小鼠海马组织中BDNF蛋白表达[（1±0.16）比（0.54±0.16）]及血浆Ang‐（1‐7）水平[（55.6±7.5） pg／ml比（42.8±5.8） pg／ml]明显下调，伴有ERK1／2磷酸化[（1±0.28）比（1.79±0.29）]明显增加（P均＜0.01），而经厄贝沙坦治疗后， ACE2 KO小鼠海马组织BDNF蛋白表达（0.88±0.13）及血浆Ang‐（1‐7）水平[（59.4±8.4） pg／ml]明显增加，伴有ERK1／2磷酸化水平（1.33±0.19）明显降低（P＜0.05或＜0.01）。结论：ACE2基因缺失小鼠存在海马组织中BDNF蛋白表达下调及ERK1／2磷酸化增强，而AT1受体阻断剂厄贝沙坦干预在改善ACE2基因缺失小鼠Ang‐（1‐7）水平与海马BDNF表达的同时，可降低海马ERK磷酸化信号，提示AT1受体阻断具有一定的脑保护效应。

Objective：To explore the alteration of brain‐derived neurotrophic factor （BDNF） signaling and the influ‐ence of irbesartan on it in hippocampus of angiotensin‐converting enzyme 2 （ACE2） knock‐out （KO） mice . Meth‐ods：The 10~11‐week ACE2 KO （Ace2/y ） mice received daily treatment with angiotensin II （Ang II） type 1 （AT1） receptor blocker irbesartan （50 mg/kg） or placebo for two weeks. The wild‐type mice （WT ,Ace2＋ /y ） were regarded as normal control. Western blotting method was used to measure levels of BDNF and extracellular signal regulated kinase 1/2 （ERK1/2） in the mice hippocampus. Radioimmunoassay was used to measure plasma Ang level in mice . Results ：Compared with normal WT control mice ,there were significant down‐regulations of BDNF protein expres‐sion [ （1 ± 0.16） vs .（0.54 ± 0.16）] in hippocampus and plasma Ang‐ （1‐7） level [ （55.6 ± 7.5） pg/ml vs .（42.8 ± 5.8） pg/ml] ,and significant rise in ERK1/2 phosphorylation [ （1 ± 0.28） vs .（1.79 ± 0.29）] in ACE2 KO mice （P〈0.01 all）. After irbesartan treatment ,there were significant rise in BDNF protein expression （0.88 ± 0.13） in hippocampus and plasma Ang‐ （1‐7） level [（59.4 ± 8.4） pg/ml] ,and significant reduction in ERK1/2 phosphoryla‐tion level （1.33 ± 0.19） in ACE2 KO mice （P〈0.05 or 〈0.01） .Conclusion：There are BDNF protein expression down‐regulation and enhanced ERK1/2 phosphorylation in hippocampus of ACE2 KO mice. AT1 receptor blockade irbesartan can improve Ang‐ （1‐7 ） level and hippocampus BDNF expression , while reducing hippocampus ERK phosphorylation signal in ACE2 KO mice ,suggesting that AT1 receptor blockade possesses certain brain protective effect.