铝对大鼠脑内miR29及BACE1的影响

Influence of aluminum on microRNA29 and β-site amyloid precursor protein cleaving enzyme 1 in the brain of rats

目的 研究铝对大鼠脑内微小核糖核酸29（miR29）各亚型（miR29a、miR29a^＊、miR29b1、miR29b2、miR29c1、miR29c2）及β淀粉样前体蛋白裂解酶1（BACE1）的影响情况.方法 40只普通级SD大鼠按体重随机分为对照组和15、30、45μmol/kg组,每组10只.采用腹腔注射的方式染毒（注射量为0.1 ml/100 g体重）8周,对照组给予0.9%生理盐水,染毒组给予不同浓度的麦芽酚铝（染毒前将麦芽酚和铝溶液等体积混合）.染毒结束后,分离大鼠脑皮质和海马,采用蛋白免疫印迹（Western blotting）法检测BACE1蛋白的变化;实时荧光定量反转录聚合酶链反应（RT-PCR）检测大鼠脑皮质和海马miR29各亚型基因的表达水平.结果 与对照组比较,45μmol/kg组大鼠脑皮质BACE1蛋白表达明显升高,30、45μmol/kg组大鼠海马BACE1蛋白表达明显升高,差异均有统计学意义（均P〈0.05）;与对照组比较,15、30、45μmol/kg组大鼠脑皮质和海马中miR29a^＊、miR29b2、miR29c1、miR29c2基因表达明显降低,差异均有统计学意义（均P〈0.01）;与对照组比较,45μmol/kg组大鼠脑皮质和海马miR29a和miR29b1基因表达明显降低,差异均有统计学意义（均P〈0.05）.相关分析结果显示,皮质和海马miR29a^＊、miR29b2、miR29c1、miR29c2基因与BACE1蛋白表达均无相关性（均P〉0.05）,而miR29a、miR29b1基因与BACE1蛋白表达均呈负相关（皮质：r=-0.987、-0.981;海马：r=-0.992、-0.991;均P〈0.05）.结论 铝可以引起脑内miR29各亚型表达降低,BACE1表达升高,且miR29a、miR29b1与BACE1表达呈负相关.

Objective To investigate the influence of aluminum on microRNA29 （miR29） subtypes miR29a, miR29a^＊, miR29b1, miR29b2, miR29c1, and miR29c2 andβ-site amyloid precursor protein cleaving enzyme 1 （BACE1） in the brain of rats. Methods A total of 40 Sprague-Dawley rats were randomly divided into control group and 15, 30, and 45μmol/kg groups according to the body weight, with 10 rats in each group. The rats were exposed to aluminum （at a dose of 0.1 ml/100 g body weight） by intraperitoneal injection for 8 weeks. The rats in control group were given 0.9% normal saline, and those in exposure groups were given aluminum-maltolate （equivalent volumesof maltolate and aluminum solution were mixed before exposure）. The cerebral cortex and hippocampus were isolated after exposure ended;Western blotting was used to measure the change in BACE1 expression, and real-time reverse transcription polymerase chain reaction was used to measure the mRNA expression of miR29 subtypes in the cerebral cortex and hippocampus. Results Compared with the control group, the 45μmol/kg group had a significant increase in BACE1 expression in the cerebral cortex, and the 30 and 45μmol/kg groups had significant increases in BACE1 expression in the hippocampus （all P〈0.05）. Compared with the control group, the 15, 30, and 45 μmol/kg groups had significant reductions in the mRNA expression of miR29a^＊, miR29b2, miR29c1, and miR29c2 in the cerebral cortex and hippocampus （all P〈0.01）, and the 45μmol/kg group had significant reductions in the mRNA expression of miR29a and miR29b1 in the cerebral cortex and hippocampus（all P〈0.05）. The results of correlation analysis showed that there was no correlation between the mRNA expression of miR29a^＊, miR29b2, miR29c1, and miR29c2 and BACE1 expression in the cerebral cortex and hippocampus （all P〉0.05）, while the mRNA expression of miR29a and miR29b1 was negatively correlated with BACE1 expression （cerebral cortex：r=-0.987 and-0.981, P〈0.05;hippocampus：r=-0.992 and-0.991, P〈0.05）. Conclusion Aluminum can reduce the expression of miR29 subtypes and increase BACE1 expression in the brain, and the expression of miR29a and miR29b1 is negatively correlated with BACE1 expression.