Cr(VI)/Pb²⁺ are responsible for PM2.5-induced cytotoxicity in A549 cells while pulmonary surfactant alleviates such...

The composition of PM_2.5 is extremely complicated, making the causes of PM_2.5-induced toxicity hard to understand. To identify the major toxic components of PM_2.5 particles, we used reductionism approach, synthesized and investigated a model PM_2.5 library containing 24 carbon nanoparticles with adsorbed pollutants including Cr(VI), Pb²⁺, As(III) and BaP either individually or in combinations. Our data showed that major physicochemical characteristics of model PM_2.5 library members were similar to PM_2.5 particles from Guangzhou city (PM_2.5-GZ). Cytotoxicity of lung cells (A549) was increasing as the member of adsorbed pollutants at environment relevant concentrations. Using these model particles, we identified that co-existence of Cr(VI) and Pb²⁺ components contributed to the PM_2.5-induced cytotoxicity in A549 cells. Besides, pulmonary surfactant reduced the PM_2.5-induced cytotoxicity in A549 cells probably via enhancing cell autophagy. The findings from this study suggest that systematic investigation using model PM_2.5 particle library helps identify key toxic pollutants in otherwise very complex PM_2.5 particles and facilitate our understanding of the underlying biological mechanisms.