Integrative phenotypic and genomic analyses reveal strain-dependent responses to acute ozone exposure and their associations with airway macrophage transcriptional activity [RNA-seq]. Integrative phenotypic and genomic analyses reveal strain-dependent responses to acute ozone exposure and their associations with airway macrophage transcriptional activity [RNA-seq]

Acute ozone (O₃) exposure is associated with multiple adverse cardiorespiratory outcomes, the severity of which varies across human populations and rodent models from diverse genetic backgrounds. However, molecular determinants of response, including biomarkers that distinguish which individuals will develop more severe injury and inflammation (i.e., high responders), are poorly characterized. Here, we exposed adult, female and male mice from 6 strains, including 5 Collaborative Cross (CC) strains, to filtered air (FA) or 2 ppm O₃ for 3 hours, and measured several inflammatory and injury parameters 21 hours later. Additionally, we collected airway macrophages and performed RNA-seq analysis to investigate influences of strain, treatment, and strain-by-treatment interactions on gene expression as well as transcriptional correlates of lung phenotypes. Animals exposed to O₃ developed airway neutrophilia and lung injury, with varying degrees of severity. We identified many genes that were altered by O₃ exposure across all strains, and examination of genes whose expression was influenced by strain-by-treatment interactions revealed prominent differences in response between the CC017/Unc and CC003/Unc strains, which were low- and high-responders, respectively (as measured by cellular inflammation and injury). Further investigation of this contrast indicated that baseline gene expression differences likely contribute to their divergent post-O₃ exposure transcriptional responses. We also observed alterations in chromatin accessibility that differed by strain and with strain-by-treatment interactions, lending further plausibility that baseline differences can modulate post-exposure responses. Together, these results suggest that aspects of the respiratory response to O₃ exposure may be mediated through altered airway macrophage transcriptional signatures, and further confirms the importance of gene-by-environment interactions in mediating differential responsiveness to environmental agents. Overall design: We profiled transcriptomes from adult, male and female mice representing 6 different strains (C57BL/6J and 5 CC strains) collected from airway macrophages 21 hours after a 3 hour exposure to filtered air or 2 ppm ozone.

急性臭氧（O₃）暴露可引发多种不良心肺结局，其严重程度在不同遗传背景的人类群体与啮齿类动物模型中存在显著差异。然而，目前针对臭氧暴露应答的分子决定因素——包括可区分个体是否会发生更严重损伤与炎症的生物标志物（即高应答者）——的研究仍较为匮乏。
本研究中，我们将来自6个品系（含5个协作杂交（Collaborative Cross, CC）品系）的成年雌雄小鼠暴露于过滤空气（FA）或2 ppm臭氧中3小时，并于暴露后21小时检测了多项炎症与损伤相关指标。此外，我们收集了气道巨噬细胞并开展RNA测序（RNA-seq）分析，以探究品系、处理方式以及品系-处理交互作用对基因表达的影响，同时分析肺表型的转录关联特征。
暴露于臭氧的小鼠均出现气道中性粒细胞增多与肺损伤，且严重程度存在显著异质性。我们鉴定出了所有品系中均因臭氧暴露发生表达改变的大量基因；对受品系-处理交互作用影响的基因进行分析后发现，CC017/Unc与CC003/Unc两个品系的应答存在显著差异：前者为低应答者，后者为高应答者（以细胞炎症与损伤程度作为评估标准）。针对这一差异的进一步研究表明，基础基因表达差异可能是二者臭氧暴露后转录应答出现分歧的原因。我们还观察到染色质可及性的改变，且该改变因品系及品系-处理交互作用而异，进一步佐证了基础差异可调控暴露后应答这一结论。
综上，本研究结果提示，臭氧暴露引发的呼吸道应答特征可能通过气道巨噬细胞的转录谱改变得以介导，同时进一步证实了基因-环境交互作用在调控机体对环境因子的差异化应答中的重要性。
实验整体设计：我们采集了6个品系（C57BL/6J及5个CC品系）的成年雌雄小鼠的气道巨噬细胞，这些小鼠在暴露于过滤空气或2 ppm臭氧3小时后21小时被采样，并对其转录组进行了分析。