Effect of NF-kappa B (NF-kB) p50 (Nfkb1) deletion on ozone-induced pulmonary transcriptome changes in mice

Background: Ozone (O3) is the predominant oxidant air pollutant associated with respiratory inflammation, lung dysfunction, and worsening preexisting airway diseases. We previously determined that lack of NF-kB signlaing pathway suppressed lung injury and inflammation caused by O3 in mice. The current study was to determine transcriptome mechanisms orchestrated by NF-kB during the development of pulmonary O3 injury. Methods: To investigate the role of NF-kB1 pathway in lung gene expression changes, Nfkb1-deficient (Nfkb1-/-) and wild-type (Nfkb1+/+) mice were exposed to air or 0.3-ppm O3. Total RNAs were isolated from lung homogenates and cDNA microarray analyses were performed to elucidate NF-kB1-directed transcriptomics in basal lungs (air-exposed) as well as in the lung exposed to O3 (48 hr). Results: In air-exposed Nfkb1-/- lungs, leukocyte extravasation/adhesion and antigen presentation genes were overexpressed while immunity genes were suppressed, supporting the dual role of Nf-kB1 homodimer as a transcriptional repressor as well as transcriptional activator and the phenotype of Nfkb1-/- mice (defective response to infection and specific antibody production). After O3 exposure. Nfkb1-/- mice showed suppressed expression of lung cell cycle genes and enhanced expression of DNA damage checkpoint regulation pathway genes, compared to Nfkb1+/+ mice. Conclusion: Overall, deficiency of NF-kB1 in mouse lungs altered transcriptomes to protect lungs from O3-induced inflammation, cell proliferation, and DNA damages. PARALLEL study design with 12 samples comparing 4 groups of gene and exposure: (2 groups Nfkb1+/+ wild type; air-48 hr O3 exposure) (2 groups Nfkb1-/- knockout; air-48 hr O3 exposure). Biological replicates: 3 per group.背景：臭氧（O3）是一类主要的氧化性空气污染物，与呼吸道炎症、肺功能障碍以及已存在的气道疾病恶化密切相关。我们此前的研究证实，核因子κB（NF-kB）信号通路缺失可减轻小鼠臭氧诱导的肺损伤与炎症。本研究旨在探究NF-kB在肺臭氧损伤发生过程中调控的转录组学机制。 方法：为探究NF-kB1通路对肺基因表达变化的调控作用，我们将Nfkb1缺陷型（Nfkb1-/-）与野生型（Nfkb1+/+）小鼠分别暴露于空气或0.3ppm的臭氧中。从肺组织匀浆中提取总RNA，通过cDNA微阵列分析，阐明基础状态（空气暴露）及臭氧暴露48小时后肺组织中NF-kB1介导的转录组特征。 结果：在空气暴露的Nfkb1-/-小鼠肺组织中，白细胞渗出/黏附及抗原呈递相关基因表达上调，而免疫相关基因表达受抑，这佐证了Nf-kB1同源二聚体兼具转录抑制与转录激活的双重功能，以及Nfkb1-/-小鼠的表型特征（对感染的应答缺陷与特异性抗体生成受损）。臭氧暴露后，与Nfkb1+/+小鼠相比，Nfkb1-/-小鼠的肺细胞周期基因表达受抑，而DNA损伤检查点调控通路相关基因表达上调。 结论：总体而言，小鼠肺组织中NF-kB1的缺失会改变转录组谱，从而保护肺脏免受臭氧诱导的炎症、细胞增殖与DNA损伤。本研究采用平行实验设计，共纳入12个样本，对比4组基因类型与暴露条件：（2组为Nfkb1+/+野生型，分别接受空气暴露、48小时臭氧暴露）；（2组为Nfkb1-/-基因敲除型，分别接受空气暴露、48小时臭氧暴露）。每组设置3个生物学重复。