PM2.5 affected ciliary beat frequency of axonemes via the cyclic AMP-dependent protein kinase a pathway

Long-term inhalation of fine particulate matter (PM_2.5) has been linked to the onset of various lung diseases. The mucociliary clearance system, acts as the primary host defense mechanism in the airways, with ciliary beat frequency (CBF) being a key parameter for assessing its functionality. The primary aim of this study was to demonstrate the impact of PM_2.5 on CBF and to investigate the potential mechanisms by which PM_2.5 induced changes in CBF through airway axonemes. Airway axonemes were extracted from bovine ciliated epithelium and treated with different concentrations of PM_2.5 <i>in vitro</i> for 10 min and 1 h to simulate short-term and prolonged exposures. Additionally, the pathway was examined using PKA activator (cAMP) and PKA inhibitor (PKI) on ciliary axonemes. The results revealed that PM_2.5 stimulated CBF in airway axonemes via the cAMP-PKA pathway. Low concentrations and short-term exposure to PM_2.5 stimulated CBF elevation, however, high concentration and prolonged exposure to PM_2.5 might damage respiratory cilia, thereby increasing the risk of respiratory diseases.