Aldehyde metabolism governs resilience of mucociliary clearance to air pollution exposure.

Air pollution is a serious environmental threat to public health; however, the molecular basis underlying its detrimental effects on respiratory fitness remains poorly understood. Here, we showed that exposure to particulate matter ≤ 2.5 μm (PM2.5), a substantial fraction of air pollutants, induced the generation of reactive aldehyde species in the airway. We identified aldehyde dehydrogenase 1A1 (ALDH1A1), which was selectively expressed in airway epithelium, as an enzyme responsible for detoxifying these reactive aldehyde species. Loss of ALDH1A1 function resulted in the accumulation of aldehyde adducts in the airway, which selectively impaired mucociliary clearance (MCC), a critical defense mechanism against respiratory pathogens. Thus, ALDH1A1-deficient mice pre-exposed to PM2.5 exhibited increased susceptibility to pneumonia. Conversely, pharmacological enhancement of ALDH1A1 activity promoted the restoration of MCC function. These findings elucidate the critical role of aldehyde metabolism in protecting against PM2.5 exposure, offering a potential target to mitigate the negative health consequences of air pollution.