Objective To investigate the effects of acute ozone exposure at different concentrations on pulmonary function and inflammation in mice.

Methods Sixty-three male C57BL/6 mice were randomly divided into 9 groups and exposed daily to filtered air or ozone (1.6 mg/m³, 2.4 mg/m³) for 3 hours. After 1, 3, and 5 days of exposure, pulmonary function of the mice was assessed by whole-body plethysmography. Inflammatory cells were counted in bronchoalveolar lavage fluid (BALF). The degree of pulmonary inflammatory infiltration was evaluated via hematoxylin-eosin (HE) staining. The expression level of calcitonin gene-related peptide (CGRP) in lung tissue was analyzed by immunohistochemistry. The mRNA expression levels of inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-13 (IL-13), and CXC chemokine ligand-15 (CXCL15) in mouse lung tissues and their protein concentrations in BALF, were detected by reverse transcriptionquantitative polymerase chain reaction (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA), respectively.

Results Ozone exposure induced changes in the pulmonary function indices of mice, characterized by a decrease in respiratory frequency (F) and minute ventilation (Mv), and an increase in enhanced pause (Penh) (P < 0.05). From the perspective of time-response, compared with the 2.4 mg/m³ exposure group exposed to the same concentration for 1 day, Penh and peak expiratory flow (PEF) were significantly decreased after 5 consecutive days of exposure (P < 0.05). HE staining showed acute ozone exposure could lead to pulmonary inflammatory cell infiltration and airway stenosis in mice. Immunohistochemistry revealed that compared with the the filtered air control group, the mean optical density value of CGRP protein and the proportion of CGRP-positive cells in lung tissues were increased after 3 consecutive days of 1.6 mg/m³ ozone exposure. The BALF inflammatory cell counts indicated that the total number of inflammatory cells in mice of the ozone groups was increased (all P < 0.05). RT-qPCR and ELISA analyses showed that continuous exposure to 2.4 mg/m³ ozone for 3 days could significantly increase the levels of pro-inflammatory factors TNF-α, IL-6, CXCL15 and decrease the level of antiinflammatory factor IL-13 (all P < 0.05).

Conclusion Acute ozone exposure can reduce pulmonary function and increase respiratory inflammation, with dose- and time-response relationships.