Ozone impairs endogenous compensatory responses in allergic asthma

Area of Science:

• Environmental Health
• Pulmonology
• Immunology

Background:

• Asthma is a chronic airway disease exacerbated by allergens and air pollution.
• Ozone (O3), a key air pollutant, damages lung epithelium, but its role in chronic lung disease, like asthma, is unclear.
• Epidemiological studies link ambient O3 to increased asthma exacerbations.

Purpose of the Study:

• To investigate the mechanisms by which ozone exposure exacerbates asthma.
• To develop and utilize a two-hit mouse model combining allergen sensitization and ozone exposure.

Main Methods:

• A two-hit mouse model was created by sensitizing mice to common allergens (dust mite, ragweed, Aspergillus fumigatus - DRA).
• Mice with allergic inflammation were then exposed to ozone (O3).
• Lung physiology, inflammatory cell counts (BAL eosinophilia, neutrophilia), and immune cell populations (monocytes, ILC2s) were analyzed.

Main Results:

• Ozone exposure after allergen sensitization significantly increased airway hyperreactivity (AHR), independent of TLR4.
• Allergen exposure increased eosinophils, while ozone exposure induced neutrophilia.
• Dual exposure (DRA-O3) blunted anti-inflammatory and antioxidant responses and reduced monocytes and innate lymphoid type 2 cells (ILC2s).

Conclusions:

• The developed mouse model mimics clinical aspects of asthma exacerbations linked to air pollution.
• Ozone exposure in an already inflamed asthmatic lung impairs endogenous anti-inflammatory and antioxidant defenses.
• Reduced monocyte and ILC2 populations may contribute to ozone-induced AHR in allergic inflammation.