Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China.
Brain Res. 2012 Jan 6;1429:116-23. doi: 10.1016/j.brainres.2011.10.007. Epub 2011 Oct 6.
MicroRNAs (miR) are single-stranded short RNA molecules that regulate gene expression by degradation or translational repression of mRNA. It has been reported that the downregulation of miR-199a plays an important role in cardiac ischemic tolerance. We examined the expression of miR-199a after 3-nitropropionic acid (3-NPA) preconditioning in rat brain. 3-NPA (20mg/kg), an irreversible inhibitor of succinate dehydrogenase, was injected intraperitoneally to induce ischemic tolerance in rats. For comparison, the control group received intraperitoneal injections of vehicle (0.9% sodium chloride). Quantitative RT-PCR assay was applied to detect the expression of miR-199a. Luciferase reporter assays and Western blotting were used to verify the target genes of miR-199a. In cortex and striatum, miR-199a was downregulated at two separate time intervals (the 2nd and 4th day), while in the hippocampus, it was downregulated on the 2nd day after 3-NPA preconditioning. The maximum reduction of miR-199a was 66.3% in striatum (4th day), 54.9% in hippocampus (2nd day), and 27.6% in cortex (2nd day). The level of sirt1 protein, a putative target of miR-199a and a known mediator of neuroprotective effect in brain ischemic tolerance, decreased significantly in hippocampal neurons by overexpression of miR-199a, while it increased with knockdown of miR-199a. Taking these results together, we hypothesize miR-199a may have a role in the formation of cerebral ischemic tolerance.
微小 RNA（miR）是单链短 RNA 分子，通过降解或翻译抑制 mRNA 来调节基因表达。已有报道称 miR-199a 的下调在心脏缺血耐受中发挥重要作用。我们检测了 3-硝基丙酸（3-NPA）预处理后大鼠脑内 miR-199a 的表达。3-NPA（20mg/kg）是琥珀酸脱氢酶的不可逆抑制剂，腹腔内注射可诱导大鼠产生缺血耐受。为了比较，对照组接受腹腔内注射载体（0.9%氯化钠）。应用定量 RT-PCR 检测 miR-199a 的表达。荧光素酶报告基因检测和 Western blot 用于验证 miR-199a 的靶基因。在皮质和纹状体中，miR-199a 在两个不同的时间间隔（第 2 天和第 4 天）下调，而在海马体中，在 3-NPA 预处理后第 2 天下调。miR-199a 的最大下调幅度为皮质 66.3%（第 4 天）、海马体 54.9%（第 2 天）和纹状体 27.6%（第 2 天）。sirt1 蛋白水平显著降低，sirt1 蛋白是 miR-199a 的一个假定靶标，也是脑缺血耐受中神经保护作用的已知介导物。miR-199a 的过表达显著降低了海马神经元中 sirt1 蛋白的水平，而 miR-199a 的敲低则增加了 sirt1 蛋白的水平。综上所述，我们假设 miR-199a 可能在脑缺血耐受的形成中发挥作用。
