Fish Oil Mitigates Ozone-Induced Lung Inflammation by Restoring Oxylipin Homeostasis

Abstract Background and Aim: Ground-level ozone threatens respiratory health by inducing pulmonary inflammation. Although fish oil has demonstrated anti-inflammatory properties, its protective mechanisms against ozone-induced lung injury remain unclear. This study investigated fish oil efficacy in modulating oxylipin homeostasis and mitigating pulmonary toxicity induced by ozone exposure in a mouse model. Methods: Six-week-old male C57BL/6j mice (N = 40) were gavaged with fish oil (100 mg/kg, 91.46% EPA+DHA) or saline for 28 days, followed by ozone exposure (800 ppb, 3 h/day, 3 days) or filtered air. Lung function was assessed using whole-body plethysmography. Pulmonary inflammation was evaluated through histological examination, quantitative PCR (qPCR) analysis of inflammatory cytokine expression, and immunofluorescence staining for pro- and anti-inflammatory macrophage polarization markers. Oxylipin profiles were quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS), with pathway analysis conducted via KEGG enrichment analysis. Results: Fish oil supplementation did not significantly improve ozone-induced decrements in lung function parameters. However, we observed that fish oil attenuated ozone-induced lung histopathological changes, including peribronchiolar inflammatory infiltration and bronchial wall thickening. Fish oil significantly reduced BALF neutrophil and macrophage counts, downregulated pro-inflammatory Il-6 and Cxcl15 mRNA expression, and restored Il-13 levels. Additionally, fish oil reversed ozone-induced macrophage polarization imbalance by reducing the pro- to anti-inflammatory macrophage ratio. These anti-inflammatory effects were accompanied by suppression of ozone-induced upregulation of Cox1, Cox2, and 5-lox expression, restoration of altered pro-inflammatory oxylipin profiles (including LTB4, 2,3-dinor-8-iso-PGF2α, and 8-HEPE), and enrichment of pathways associated with inflammation resolution. Conclusions: Fish oil effectively mitigates ozone-induced pulmonary inflammation, an effect that was associated with oxylipin profile remodeling and restoration of macrophage polarization homeostasis, independent of lung function improvement. These findings support further investigation of fish oil as a nutraceutical intervention against ozone-related respiratory burdens.