空氣汙染與肺部疾病:從流行病學到毒理學的跨領域研究
Air Pollution and Respiratory Disease: From Epidemiology to Toxicology
Chronic obstructive pulmonary disease (COPD) is a significant global public health concern, currently the fourth-leading cause of death worldwide, and projected to become the third-leading cause by 2020. While smoking is a well-known risk factor for COPD, a notable proportion of COPD patients are non-smokers, suggesting other contributing factors. Epidemiological evidence indicates that acute exacerbations (AEs) of COPD are associated with typical urban levels of particulate matter (PM). PM exposure has been shown to reduce lung function, contributing to the development and progression of COPD. In one cohort study, a unit increase in PM2.5 (particulate matter less than 2.5 um in aerodynamic diameter) concentration was associated with a 2.3% rise in COPD AEs. Furthermore, participants exposed to PM2.5 levels above 15.4 μg/m³ exhibited a 54% higher risk of COPD AEs compared to those in a reference group.
Recent U.S. cohort studies have correlated chronic air pollution exposure with emphysema progression, using CT imaging and lung function measurements. Findings show that prolonged exposure to ambient pollutants, particularly PM2.5 and NOx, is associated with increased emphysema, a hallmark of COPD. Cellular senescence, a state where cells permanently cease to divide, has been implicated in aging and age-related diseases like COPD. Alveolar type II epithelial cells (AECII), which produce surfactant and regenerate type I alveolar cells (AECI) after injury, act as alveolar progenitor cells essential for maintaining alveolar integrity.
Increased apoptosis of alveolar epithelial cells contributes to the development of emphysematous changes in COPD by disrupting the natural regenerative process, in which cells lost to apoptosis are typically replaced through cell proliferation. Research indicates that emphysema is associated with abnormal alveolar cell turnover, marked by both heightened proliferation and apoptosis, which progressively destroys alveolar structures and reduces lung surface area—a defining characteristic of emphysema. In COPD patients, accelerated senescence of alveolar cells is commonly observed, contributing to abnormal cell turnover and substantial cell loss in emphysematous lungs. Understanding the phenotypes of COPD in response to air pollution exposure is therefore crucial to addressing these pathological changes.