Oxidative stress-mediated epidermal growth factor receptor activation regulates PM_2.5-induced over-secretion of pro-inflammatory mediators from human bronchial epithelial cells

Background: Exposure to PM_2.5 has been associated with increased morbidity and mortality of lung diseases although the underlying mechanisms have not been fully uncovered. Airway inflammation is a critical event in the pathogenesis of lung diseases. This study aimed to examine the role of oxidative stress and epidermal growth factor receptor (EGFR) in PM_2.5-induced pro-inflammatory response in a human bronchial epithelial cell line, BEAS-2B.

Methods: BEAS-2B cells were exposed to 0, 20, 50, 100 and 150 μg/ml of PM_2.5. Secretion of pro-inflammatory mediators including interleukin-6 (IL-6), IL-8 and IL-1β was determined using enzyme linked immunosorbent assay. Levels of intracellular reactive oxygen species (ROS) were determined using flow cytometry. Phosphorylation of the EGFR was examined with immunoblotting.

Results: PM_2.5 exposure increased the secretion of IL-6, IL-8, and IL-1β in a concentration-dependent fashion. Moreover, exposure to PM_2.5 elevated intracellular levels of ROS, and phosphorylation of the EGFR (Y1068). Pretreatment of BEAS-2B cells with either an antioxidant or a specific EGFR inhibitor significantly reduced PM_2.5-induced IL-6, IL-8 and IL-1β secretion, implying that both oxidative stress and EGFR activation were involved in PM_2.5-induced pro-inflammatory response. Furthermore, pre-treatment of BEAS-2B cells with an antioxidant significantly blunted PM_2.5-induced EGFR activation, suggesting that oxidative stress was required for PM_2.5-induced EGFR activation.

Conclusion: PM_2.5 exposure induces pro-inflammatory response in human bronchial epithelial cells through oxidative stress-mediated EGFR activation.