Hypoxia (Hx) is a component of multiple disorders, including stroke and sleep-disordered breathing, which often precede or are comorbid with neurodegenerative diseases. However, little is known about how hypoxia affects the ability of microglia, resident CNS macrophages, to respond to subsequent inflammatory challenges that are often present during neurodegenerative processes. We, therefore, tested the hypothesis that hypoxia would enhance or “prime” microglial pro-inflammatory gene expression in response to a later inflammatory challenge without programmatically increasing basal levels of pro-inflammatory cytokine expression. To test this, we pre-exposed immortalized N9 and primary microglia to hypoxia (1% O₂) for 16 h and then challenged them with pro-inflammatory lipopolysaccharide (LPS) either immediately or 3–6 days following hypoxic exposure. We used RNA sequencing coupled with chromatin immunoprecipitation sequencing to analyze primed microglial inflammatory gene expression and modifications to histone H3 lysine 4 trimethylation (H3K4me3) at the promoters of primed genes. We found that microglia exhibited enhanced responses to LPS 3 days and 6 days post-hypoxia. Surprisingly, however, the majority of primed genes were not enriched for H3K4me3 acutely following hypoxia exposure. Using the bioinformatics tool MAGICTRICKS and reversible pharmacological inhibition, we found that primed genes required the transcriptional activities of NF-κB. These findings provide evidence that hypoxia pre-exposure could lead to persistent and aberrant inflammatory responses in the context of CNS disorders.

缺氧 (Hx) 是多种疾病的一个组成部分，包括中风和睡眠呼吸障碍，这些疾病通常先于神经退行性疾病或与神经退行性疾病同时发生。然而，人们对缺氧如何影响小胶质细胞（常驻中枢神经系统巨噬细胞）对神经退行性过程中经常出现的后续炎症挑战的反应能力知之甚少。因此，我们测试了这样的假设：缺氧会增强或“引发”小胶质细胞促炎基因表达，以应对随后的炎症挑战，而不会有计划地增加促炎细胞因子表达的基础水平。为了测试这一点，我们将永生化 N9 和原代小胶质细胞预先暴露于缺氧 (1% O ₂ ) 中 16 小时，然后立即或在缺氧暴露后 3-6 天用促炎脂多糖 (LPS) 挑战它们。我们使用 RNA 测序结合染色质免疫沉淀测序来分析引发的小胶质细胞炎症基因表达以及引发基因启动子处的组蛋白 H3 赖氨酸 4 三甲基化 (H3K4me3) 的修饰。我们发现缺氧后 3 天和 6 天小胶质细胞对 LPS 的反应增强。然而，令人惊讶的是，大多数引发的基因在缺氧暴露后并未急剧富集 H3K4me3。使用生物信息学工具 MAGICTRICKS 和可逆药理抑制，我们发现引发基因需要 NF-κB 的转录活性。这些发现提供的证据表明，在中枢神经系统疾病的情况下，暴露前缺氧可能导致持续且异常的炎症反应。