Ambient ozone primes pulmonary innate immunity in mice

Area of Science:

• Environmental Health
• Immunology
• Toxicology

Background:

• Ozone, a major air pollutant, is linked to increased respiratory hospitalizations and mortality.
• Ozone exposure is known to affect the lung's ability to clear bacterial pathogens.
• The impact of ozone on innate immune responses in the lung remains incompletely understood.

Purpose of the Study:

• To investigate how inhaled ozone exposure modifies innate immune responses in the lung.
• To determine the effect of ozone pre-exposure on the lung's reaction to bacterial lipopolysaccharide (LPS).

Main Methods:

• C57BL/6J mice were exposed to filtered air or ozone.
• Mice were subsequently challenged with an aerosol of Escherichia coli LPS.
• Lung lavage fluid, lung tissue, serum, and immune cell apoptosis were analyzed.

Main Results:

• Ozone pre-exposure elevated protein and pro-inflammatory cytokines in lung lavage fluid and increased serum IL-6 after LPS challenge.
• Ozone pre-exposure led to reduced inflammatory cell accumulation in the lower airways following LPS inhalation.
• Enhanced apoptosis of lung macrophages and circulating monocytes was observed after ozone exposure.
• Ozone altered Toll-like receptor 4 (TLR4) distribution on alveolar macrophages and enhanced their functional response to LPS.

Conclusions:

• Ozone exposure primes the innate immune system, leading to heightened pulmonary and systemic responses to LPS.
• Ozone-induced immune cell apoptosis contributes to reduced inflammatory cell infiltration in the airways.
• These findings highlight a complex interplay between air pollution and immune defense mechanisms in the lung.