Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland.
Cell Death Dis. 2012 Mar 22;3(3):e287. doi: 10.1038/cddis.2012.23.
MicroRNAs (miRNAs) are short, noncoding RNAs that function as posttranscriptional regulators of gene expression by controlling translation of mRNAs. A subset of miRNAs may be critical for the control of cell death, including the p53-regulated miRNA, miR-34a. Because seizures activate p53, and p53-deficient mice are reportedly resistant to damage caused by prolonged seizures, we investigated the role of miR-34a in seizure-induced neuronal death in vivo. Status epilepticus was induced by intra-amygdala microinjection of kainic acid in mice. This led to an early (2 h) multifold upregulation of miR-34a in the CA3 and CA1 hippocampal subfields and lower protein levels of mitogen-activated kinase kinase kinase 9, a validated miR-34a target. Immunoprecipitation of the RNA-induced silencing complex component, Argonaute-2, eluted significantly higher levels of miR-34a after seizures. Injection of mice with pifithrin-α, a putative p53 inhibitor, prevented miR-34a upregulation after seizures. Intracerebroventricular injection of antagomirs targeting miR-34a reduced hippocampal miR-34a levels and had a small modulatory effect on apoptosis-associated signaling, but did not prevent hippocampal neuronal death in models of either severe or moderate severity status epilepticus. Thus, prolonged seizures cause subfield-specific, temporally restricted upregulation of miR-34a, which may be p53 dependent, but miR-34a is probably not important for seizure-induced neuronal death in this model.
微小 RNA（miRNAs）是短的非编码 RNA，通过控制 mRNA 的翻译来作为基因表达的转录后调节剂。一些 miRNA 可能对细胞死亡的控制至关重要，包括 p53 调节的 miRNA，miR-34a。由于癫痫发作激活 p53，并且据报道 p53 缺陷型小鼠对长时间癫痫发作引起的损伤具有抗性，我们研究了 miR-34a 在体内癫痫诱导的神经元死亡中的作用。通过在小鼠内侧杏仁核内微量注射海人酸诱导癫痫持续状态。这导致 CA3 和 CA1 海马亚区中 miR-34a 的早期（2 小时）多倍上调和丝裂原活化蛋白激酶激酶激酶 9 的蛋白质水平降低，这是 miR-34a 的一个已验证的靶标。RNA 诱导沉默复合物成分 Argonaute-2 的免疫沉淀在癫痫发作后明显洗脱更高水平的 miR-34a。用 pifithrin-α（一种假定的 p53 抑制剂）注射小鼠可防止癫痫发作后 miR-34a 的上调。针对 miR-34a 的反义寡核苷酸的脑室内注射降低了海马 miR-34a 水平，并对凋亡相关信号有较小的调节作用，但不能预防严重或中度癫痫持续状态模型中的海马神经元死亡。因此，长时间的癫痫发作导致 CA3 和 CA1 海马亚区特异性、时间限制的 miR-34a 上调，这可能依赖于 p53，但 miR-34a 在该模型中可能对癫痫诱导的神经元死亡不重要。
