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Updated: Jun 23, 2025
Lung microRNA Profiling Across the Estrous Cycle in Ozone-exposed Mice
Published on: January 7, 2019
Transcriptional profiling of lung macrophages following ozone exposure in mice identifies signaling pathways
Ley Cody Smith1,2, Elena Abramova2, Kinal Vayas2
1Department of Pharmaceutical Sciences, University of Connecticut School of Pharmacy, Storrs, CT 06269, United States.
Abstract:
Macrophages play a key role in ozone-induced lung injury by regulating both the initiation and resolution of inflammation. These distinct activities are mediated by pro-inflammatory and anti-inflammatory/proresolution macrophages which sequentially accumulate in injured tissues. Macrophage activation is dependent, in part, on intracellular metabolism. Herein, we used RNA-sequencing (seq) to identify signaling pathways regulating macrophage immunometabolic activity following exposure of mice to ozone (0.8 ppm, 3 h) or air control. Analysis of lung macrophages using an Agilent Seahorse showed that inhalation of ozone increased macrophage glycolytic activity and oxidative phosphorylation at 24 and 72 h post-exposure. An increase in the percentage of macrophages in S phase of the cell cycle was observed 24 h post ozone. RNA-seq revealed significant enrichment of pathways involved in innate immune signaling and cytokine production among differentially expressed genes at both 24 and 72 h after ozone, whereas pathways involved in cell cycle regulation were upregulated at 24 h and intracellular metabolism at 72 h. An interaction network analysis identified tumor suppressor 53 (TP53), E2F family of transcription factors (E2Fs), cyclin-dependent kinase inhibitor 1A (CDKN1a/p21), and cyclin D1 (CCND1) as upstream regulators of cell cycle pathways at 24 h and TP53, nuclear receptor subfamily 4 group a member 1 (NR4A1/Nur77), and estrogen receptor alpha (ESR1/ERα) as central upstream regulators of mitochondrial respiration pathways at 72 h. To assess whether ERα regulates metabolic activity, we used ERα-/- mice. In both air and ozone-exposed mice, loss of ERα resulted in increases in glycolytic capacity and glycolytic reserve in lung macrophages with no effect on mitochondrial oxidative phosphorylation. Taken together, these results highlight the complex interaction between cell cycle, intracellular metabolism, and macrophage activation which may be important in the initiation and resolution of inflammation following ozone exposure.
Insights
Ozone exposure alters lung macrophage metabolism and cell cycle, impacting inflammation. Estrogen receptor alpha influences glycolytic activity in macrophages following ozone exposure.
Area of Science:
- Immunology
- Cell Biology
- Environmental Health
Background:
- Macrophages are crucial for ozone-induced lung injury, mediating inflammation initiation and resolution.
- Macrophage function is partly regulated by intracellular metabolism.
- Distinct pro-inflammatory and anti-inflammatory macrophage populations sequentially infiltrate injured tissues.
Purpose of the Study:
- To identify signaling pathways regulating macrophage immunometabolic activity after ozone exposure.
- To investigate the role of intracellular metabolism in macrophage responses to ozone.
Main Methods:
- Mice were exposed to ozone (0.8 ppm, 3 h) or control air.
- Lung macrophages were analyzed using Agilent Seahorse for metabolic activity.
- RNA-sequencing (RNA-seq) was employed to identify differentially expressed genes and signaling pathways.
- Estrogen receptor alpha knockout (ERα-/-) mice were used to assess ERα's role in metabolic regulation.
Main Results:
- Ozone exposure increased macrophage glycolytic activity and oxidative phosphorylation at 24 and 72 hours post-exposure.
- RNA-seq revealed upregulated pathways in innate immune signaling, cytokine production, cell cycle regulation, and intracellular metabolism.
- Key regulators identified include TP53, E2Fs, CDKN1a/p21, CCND1, NR4A1/Nur77, and ESR1/ERα.
- Loss of ERα increased glycolytic capacity and reserve in lung macrophages without affecting mitochondrial oxidative phosphorylation.
Conclusions:
- Ozone exposure significantly alters lung macrophage immunometabolism and cell cycle progression.
- Estrogen receptor alpha plays a role in regulating macrophage glycolytic activity post-ozone exposure.
- The interplay between cell cycle, metabolism, and macrophage activation is critical for ozone-induced lung inflammation and resolution.
