Brain Health Research Centre, University of Otago, PO Box 56, Dunedin New Zealand.
BMC Genomics. 2013 Jun 6;14:376. doi: 10.1186/1471-2164-14-376.
Differential processing of the amyloid precursor protein liberates either amyloid-ß, a causative agent of Alzheimer's disease, or secreted amyloid precursor protein-alpha (sAPPα), which promotes neuroprotection, neurotrophism, neurogenesis and synaptic plasticity. The underlying molecular mechanisms recruited by sAPPα that underpin these considerable cellular effects are not well elucidated. As these effects are enduring, we hypothesised that regulation of gene expression may be of importance and examined temporally specific gene networks and pathways induced by sAPPα in rat hippocampal organotypic slice cultures. Slices were exposed to 1 nM sAPPα or phosphate buffered saline for 15 min, 2 h or 24 h and sAPPα-associated gene expression profiles were produced for each time-point using Affymetrix Rat Gene 1.0 ST arrays (moderated t-test using Limma: p < 0.05, and fold change ± 1.15).
Treatment of organotypic hippocampal slice cultures with 1 nM sAPPα induced temporally distinct gene expression profiles, including mRNA and microRNA associated with Alzheimer's disease. Having demonstrated that treatment with human recombinant sAPPα was protective against N-methyl d-aspartate-induced toxicity, we next explored the sAPPα-induced gene expression profiles. Ingenuity Pathway Analysis predicted that short-term exposure to sAPPα elicited a multi-level transcriptional response, including upregulation of immediate early gene transcription factors (AP-1, Egr1), modulation of the chromatin environment, and apparent activation of the constitutive transcription factors CREB and NF-κB. Importantly, dynamic regulation of NF-κB appears to be integral to the transcriptional response across all time-points. In contrast, medium and long exposure to sAPPα resulted in an overall downregulation of gene expression. While these results suggest commonality between sAPPα and our previously reported analysis of plasticity-related gene expression, we found little crossover between these datasets. The gene networks formed following medium and long exposure to sAPPα were associated with inflammatory response, apoptosis, neurogenesis and cell survival; functions likely to be the basis of the neuroprotective effects of sAPPα.
Our results demonstrate that sAPPα rapidly and persistently regulates gene expression in rat hippocampus. This regulation is multi-level, temporally specific and is likely to underpin the neuroprotective effects of sAPPα.
淀粉样前体蛋白的差异处理释放出淀粉样β，这是阿尔茨海默病的致病因子，或分泌的淀粉样前体蛋白-α（sAPPα），它促进神经保护、神经营养、神经发生和突触可塑性。sAPPα 所依赖的、支撑这些显著细胞效应的潜在分子机制尚未得到很好的阐明。由于这些效应是持久的，我们假设基因表达的调节可能很重要，并在大鼠海马器官型切片培养物中检查了 sAPPα 诱导的特定时间的基因网络和途径。将切片暴露于 1 nM sAPPα 或磷酸盐缓冲盐水 15 分钟、2 小时或 24 小时，然后使用 Affymetrix Rat Gene 1.0 ST 阵列产生每个时间点的 sAPPα 相关基因表达谱（使用 Limma 进行的适度 t 检验：p<0.05，变化倍数±1.15）。
用 1 nM sAPPα 处理器官型海马切片培养物诱导了具有时间差异的基因表达谱，包括与阿尔茨海默病相关的 mRNA 和 microRNA。已经证明用重组人 sAPPα 治疗可防止 N-甲基-D-天冬氨酸诱导的毒性，我们接下来探索了 sAPPα 诱导的基因表达谱。Ingenuity Pathway Analysis 预测，短期暴露于 sAPPα 会引发多层次的转录反应，包括立即早期基因转录因子（AP-1、Egr1）的上调、染色质环境的调节以及组成型转录因子 CREB 和 NF-κB 的明显激活。重要的是，NF-κB 的动态调节似乎是所有时间点转录反应的重要组成部分。相比之下，中、长期暴露于 sAPPα 会导致基因表达总体下调。虽然这些结果表明 sAPPα 与我们之前报告的与可塑性相关的基因表达分析之间存在共性，但我们发现这些数据集之间几乎没有交叉。中、长期暴露于 sAPPα 后形成的基因网络与炎症反应、细胞凋亡、神经发生和细胞存活有关；这些功能可能是 sAPPα 神经保护作用的基础。
我们的结果表明，sAPPα 可快速且持续地调节大鼠海马中的基因表达。这种调节是多层次的、特定时间的，可能是 sAPPα 神经保护作用的基础。
