Parenchymal and Inflammatory Responses to Ozone Exposure in the Aging Healthy and Surfactant Protein C Mutant Lung.

Abstract

Ozone (O₃) is a ubiquitous pollutant known to produce acute, transient inflammation through oxidative injury and inflammation. These effects are exacerbated in susceptible populations, such as the elderly and those exhibiting genetic mutations in central nodes of pulmonary function. To comprehend the impact of these predisposing factors, the present study examines structural, mechanical, and immunological responses to single acute O₃ exposure (0.8 ppm, 3h) in young (8-14 week old), middle-aged (44-52 week old), and old (>80 week old) mice. Furthermore, this work compares the impact of a clinically relevant mutation in the gene encoding for the alveolar epithelial type 2 specific surfactant protein C. Aging was associated with reduced lung resistance and increases in respiratory elastic properties, the latter of which was exacerbated in SP-C mutant mice. Ozone exposure produced focal injury localized at the terminal bronchiole-to-alveolar junctions and enlarged alveoli in aged SP-C mutant lungs. Flow cytometric analysis revealed increases in mononuclear myeloid abundance in aged SP-C mutant lungs, paired with a contraction in CD8⁺ expressing cells. Expansion of tertiary lymphoid tissues was also noted in aged groups, more evident in the mutant mice. Spatial transcriptomics of CD68⁺ macrophages and CD45^- non-immune parenchymal cells highlighted age-dependent shifts in inflammatory and extracellular matrix organization signaling, and enrichment in senescence and chromatin remodeling pathways. These results illustrate the structural and immunological impact of O₃ in the aging wild type and mutant lung and emphasize the significance of modeling environmental exposure in at-risk populations.