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Effects of inhaled ozone on gene expression profiles in mouse lung macrophages

ABSTRACT: Acute exposure to inhaled ozone causes oxidative stress, lung injury, and inflammation. Activated macrophages play a key role in both the initiation and resolution of the inflammatory response to inhaled ozone; this activity is mediated by distinct subsets, broadly classified as proinflammatory (M1) and anti-inflammatory/pro-resolution (M2) macrophages. Successful resolution of inflammation and tissue repair require balanced activity of M1 and M2 macrophages. In this context, overactivation of M1 macrophages or inadequate activation of M2 macrophages results in a failure to resolve inflammation and prolonged injury. Thus, identifying signaling mechanisms contributing to aberrant activation of lung macrophages is critical to mitigating lung injury and decrements in pulmonary function caused by this ubiquitous air pollutant. The purpose of the present study was to identify mechanisms regulating macrophage activation in response to acute exposure to ozone by characterizing global transcriptional profiles using RNA-seq. We hypothesized that gene expression patterns would be distinctly regulated at 24 and 72 hr post exposure to ozone as these time points reflect different phases of the inflammatory response, namely initiation and resolution, when macrophage subpopulations derived from different origins would predominate. We identified significant enrichment of pathways involved in innate immune signaling and cytokine production among differentially expressed genes at 24 and 72 hr post exposure. In addition, we observed a preponderance of pathways involved in cell cycle regulation at 24 hr and intracellular metabolism at 72 hr post exposure. These studies are significant as they permit the identification of signaling pathways representing prospective therapeutic targets to fine tune macrophage responses and limit ozone-induced lung injury.

ORGANISM(S): Mus musculus

PROVIDER: GSE237594 | GEO | 2024/09/13

REPOSITORIES: GEO

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Project description:Background: Ozone (O3) is the predominant oxidant air pollutant associated with respiratory inflammation, lung dysfunction, and worsening preexisting airway diseases. We determined that TNFR signlaing pathway plays a key role in lung injury and inflammation caused by O3 in mice. However, downstream molecular mechanisms underlying TNFR pathway have not been investigated. Methods: To investigate the role of TNFR pathway in gene expression changes, Tnfr1/2-deficient (Tnfr-/-) and wild-type (Tnfr+/+, C57BL/6J) 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 TNFR-directed transcriptomics in basal lungs (air-exposed) as well as in the lung exposed to time course of O3 (24, 48, and 72 hr). Results: O3 caused time-dependent changes in lung gene expressions with the greatest transcriptome changes at 48-72 hr of exposure in Tnfr+/+ mice. At early time of exposure (24 hr), acute phase and inflammatory responses gene as well as redox and lipid metabolism genes were increased by O3 while cell cycle and DNA damage repair genes were markedly increased by O3 at later time points (48-72 hr). Compared to Tnfr+/+ mice, Tnfr-/- mice had lowered expression of inflammatory response and vascular disorder-related genes at baseline (air). After O3 exposure, Tnfr-/- had enhanced expression of immune and inflammatory genes at 24 hr, indicating compensatory or adpative poentiation of immunity in Tnfr-/- mice. At 48 hr of O3 exposure, Tnfr-/- mice showed suppressed expression of genes involved in epithelial proliferation, inflammatory cell influxes and epithelial injury, compared to Tnfr+/+ mice. At 72 hr of O3 exposure, neurodegeneration and neurotransmitter transport genes were suppressed in Tnfr-/- than in Tnfr+/+. Conclusion: Overall, deficiency of TNFR-mediated signaling in mouse lungs altered transcriptomes to protect lungs from O3-induced inflammation, cell proliferation, oxidative stress, and neuronal disorders.

Project description:Background: When exposed to specific stimuli, macrophages exhibit distinct activation programs, M1 and M2 polarization, that define macrophage function as inflammatory/immune effectors or anti-inflammatory/tissue remodeling cells, respectively. Due to their position on the lung epithelial surface, alveolar macrophages (AM) directly interact with environmental stimuli such as cigarette smoke, the major risk factor for the development of chronic obstructive pulmonary disease (COPD). Based on the current paradigm that, in response to smoking, AM contribute to both inflammatory and tissue remodeling processes in the lung relevant to the pathogenesis of COPD, we hypothesized that chronic exposure to cigarette smoking activates both the M1 and M2 polarization programs in AM. Methods and Findings: To assess this hypothesis, global transcriptional profiling with TaqMan confirmation and flow cytometry analysis was carried out on AM obtained by bronchoalveolar lavage of 24 healthy nonsmokers, 34 healthy smokers and 12 smokers with COPD to assess the expression of 41 M1 genes and 32 M2 genes in each group. Contrary to our expectations, while there was up-regulation of some genes typical for M2-related phenotypes, AM of healthy smokers exhibited substantial suppression of M1-related inflammatory/immune genes. These M1- and M2-related changes progressed with the development of smoking-induced lung disease, with AM of smokers with COPD exhibiting further down-regulation of M1-related genes accompanied with further up-regulation of some M2-related genes. Conclusion: The data demonstrates that the modifications of the AM transcriptome associated with smoking result in a unique phenotype characterized by reprogramming of AM towards M1-deactivated partially M2-polarized macrophages and suggests that, while AM likely contribute to smoking-induced tissue remodeling, the role of AM in the early pathogenesis of smoking-induced COPD in humans is not inflammatory. This concept is a departure from the conventional concept that AM-mediated inflammation participates in the early derangements of the lung induced by smoking, and suggests a novel paradigm for conceptualizing COPD and developing new approaches to prevent the development of smoking-induced lung disease. Comparison of gene expression in alveolar macrophages of normal non-smokers and normal smokers and smokers with COPD

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Project description:Inflammation is the natural defensive response of the immune system to an injury or infection and is regulated by small molecule mediators triggering different phases of the inflammatory process. In particular, lipid mediators (LM) and cytokines exhibit crucial regulatory functions in the progression and resolution of inflammation. Macrophages play a central role in this process and can adopt distinct phenotypes with specialized functions depending on their microenvironment: inflammatory M1 macrophages drive inflammation by the release of pro-inflammatory cytokines and LMs, like prostaglandins (PG) and leukotrienes (LT), while resolving M2 macrophages promote inflammation resolution and tissue regeneration by production of anti-inflammatory cytokines and specialized pro resolving mediators (SPM). Aging is associated with chronic and unresolved, low-grade inflammation (“inflammaging”) and aging-related dysfunction of macrophages in the resolution of inflammation and tissue maintenance has been reported. Yet, the underlying molecular mechanisms and functional consequences of latter processes remain poorly understood. Here, we show that polarization of peritoneal macrophages (PM) from geriatric mice towards an M2-like phenotype is impaired versus adult mice, resulting in aberrant LM formation and cytokine release. In PMs isolated from adult mice (PM-A) we observed a shift in LM formation from PGs and LTs to SPMs already after 4 h of polarization towards M2 with interleukin (IL) 4. In contrast, PMs from geriatric mice (PM-G) produced mainly LTs and PGs upon polarization. This pattern persists over the course of 48 h of polarization. Proteomic profiling revealed that polarization of PM A towards M2 yields a more distinct phenotype, clearly separated from M1, when compared to PM-G. We observed similar aging-related changes in the lipidome and cytokine profile of spleen, lung and liver tissue from mice. Hence, we hypothesize that during aging macrophage polarization towards M2 is impaired, which in turn drives chronic inflammation and disturbs tissue maintenance. By combining state-of-the art lipidomic and proteomic profiling we aim to uncover new molecular targets for pharmaceutical interventions to improve therapeutic strategies for elderly patients with chronic inflammatory diseases.

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Effects of inhaled ozone on gene expression profiles in mouse lung macrophages

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