Chronic bronchiolitis in nonhuman primates after prolonged ozone exposure

Area of Science:

• Environmental toxicology
• Pulmonary pathology
• Primate research

Background:

• Ozone is a major air pollutant with known respiratory effects.
• Understanding the long-term pulmonary response to ozone is crucial for public health.

Purpose of the Study:

• To investigate the chronic pulmonary effects of ozone exposure in bonnet monkeys (Macaca radiata).
• To evaluate morphological and functional changes in the lungs following prolonged ozone insult.

Main Methods:

• Bonnet monkeys were exposed to varying concentrations of ozone (0.0, 0.5, 0.8 ppm) for extended periods (7, 28, 90 days).
• Pulmonary function testing, light and electron microscopy, autoradiography, and morphometry were employed.
• Inflammatory cell counts and epithelial cell proliferation were quantified.

Main Results:

• Pulmonary function tests showed no significant pre- vs. post-exposure differences, though quasistatic compliance trended higher.
• Morphological changes included chronic respiratory bronchiolitis with macrophage accumulation and cuboidal epithelial cell hyperplasia.
• Inflammation intensity peaked early and decreased by 90 days, despite continued ozone exposure.
• Epithelial cell proliferation (labeling index) and the proportion of cuboidal cells increased significantly, with evidence of secretory activity.

Conclusions:

• Bonnet monkeys exhibit adaptive responses to chronic ozone exposure, characterized by reduced inflammation over time.
• Persistent ozone exposure leads to significant cellular changes in the respiratory bronchioles, including hyperplasia and altered cell differentiation.
• While lung function did not drastically decline, the observed morphological changes suggest ongoing subclinical pulmonary remodeling.