Department of Ophthalmology, Louisiana State University Health Science Center, New Orleans, Louisiana 70112, USA.
J Biol Chem. 2010 Dec 10;285(50):38951-60. doi: 10.1074/jbc.M110.178848. Epub 2010 Oct 11.
Specific microRNAs (miRNAs), small non-coding RNAs that support homeostatic gene expression, are significantly altered in abundance in human neurological disorders. In monocytes, increased expression of an NF-κB-regulated miRNA-146a down-regulates expression of the interleukin-1 receptor-associated kinase-1 (IRAK-1), an essential component of Toll-like/IL-1 receptor signaling. Here we extend those observations to the hippocampus and neocortex of Alzheimer disease (AD) brain and to stressed human astroglial (HAG) cells in primary culture. In 66 control and AD samples we note a significant up-regulation of miRNA-146a coupled to down-regulation of IRAK-1 and a compensatory up-regulation of IRAK-2. Using miRNA-146a-, IRAK-1-, or IRAK-2 promoter-luciferase reporter constructs, we observe decreases in IRAK-1 and increases in miRNA-146a and IRAK-2 expression in interleukin-1β (IL-1β) and amyloid-β-42 (Aβ42) peptide-stressed HAG cells. NF-κB-mediated transcriptional control of human IRAK-2 was localized to between -119 and +12 bp of the immediate IRAK-2 promoter. The NF-κB inhibitors curcumin, pyrrolidine dithiocarbamate or CAY10512 abrogated both IRAK-2 and miRNA-146a expression, whereas IRAK-1 was up-regulated. Incubation of a protected antisense miRNA-146a was found to inhibit miRNA-146a and restore IRAK-1, whereas IRAK-2 remained unaffected. These data suggest a significantly independent regulation of IRAK-1 and IRAK-2 in AD and in IL-1β+Aβ42 peptide-stressed HAG cells and that an inducible, NF-κB-sensitive, miRNA-146a-mediated down-regulation of IRAK-1 coupled to an NF-κB-induced up-regulation of IRAK-2 expression drives an extensively sustained inflammatory response. The interactive signaling of NF-κB and miRNA-146a further illustrate interplay between inducible transcription factors and pro-inflammatory miRNAs that regulate brain IRAK expression. The combinatorial use of NF-κB inhibitors with miRNA-146a or antisense miRNA-146a may have potential as a bi-pronged therapeutic strategy directed against IRAK-2-driven pathogenic signaling.
特定的 microRNAs（miRNAs）是支持基因表达稳态的小型非编码 RNA，在人类神经紊乱疾病中其丰度显著改变。在单核细胞中，NF-κB 调节的 miRNA-146a 的表达增加会下调白细胞介素-1 受体相关激酶-1（IRAK-1）的表达，后者是 Toll 样受体/IL-1 受体信号的重要组成部分。在这里，我们将这些观察结果扩展到阿尔茨海默病（AD）大脑的海马体和新皮层以及原代培养的应激人星形胶质细胞（HAG）中。在 66 个对照和 AD 样本中，我们注意到 miRNA-146a 的显著上调与 IRAK-1 的下调以及 IRAK-2 的代偿性上调相关。使用 miRNA-146a、IRAK-1 或 IRAK-2 启动子荧光素酶报告基因构建体，我们观察到在白细胞介素-1β（IL-1β）和淀粉样蛋白-β-42（Aβ42）肽应激 HAG 细胞中 IRAK-1 的表达降低和 miRNA-146a 和 IRAK-2 的表达增加。NF-κB 介导的人类 IRAK-2 的转录控制定位于 IRAK-2 启动子的-119 至+12 bp 之间。NF-κB 抑制剂姜黄素、吡咯烷二硫代氨基甲酸盐或 CAY10512 消除了 IRAK-2 和 miRNA-146a 的表达，而 IRAK-1 则被上调。发现孵育保护性反义 miRNA-146a 可抑制 miRNA-146a 并恢复 IRAK-1，而 IRAK-2 不受影响。这些数据表明，在 AD 和 IL-1β+Aβ42 肽应激 HAG 细胞中 IRAK-1 和 IRAK-2 的表达受到显著独立调节，并且诱导型、NF-κB 敏感的 miRNA-146a 介导的 IRAK-1 下调与 NF-κB 诱导的 IRAK-2 表达上调偶联，驱动广泛持续的炎症反应。NF-κB 和 miRNA-146a 的相互信号进一步说明了可诱导转录因子和促炎 miRNA 之间的相互作用，这些 miRNA 调节大脑 IRAK 的表达。NF-κB 抑制剂与 miRNA-146a 或反义 miRNA-146a 的联合使用可能具有作为针对 IRAK-2 驱动的致病信号的双管齐下的治疗策略的潜力。
