Toxicological appraisal of the chemical fractions of ambient fine (PM) and quasi-ultrafine (PM) particles in human bronchial epithelial BEAS-2B cells.

New toxicological research is still urgently needed to improve the current knowledge about the induction of some underlying mechanisms of toxicity by the different chemical fractions of ambient particulate matter (PM). This in vitro study sought also to better evaluate and compare the respective toxicities of fine particles (PM) and their inorganic and organic chemical fractions, and the respective toxicities of the organic chemical fractions of PM and quasi-ultrafine particles (PM). Human bronchial epithelial BEAS-2B cells were also exposed for 6-48 h to relatively low doses of PM and their organic extractable (OEM) and non-extractable (NEM) fractions, and the organic extractable fraction (OEM) of PM. We reported that not only PM, but also, to a lesser extent, its inorganic chemical fraction, NEM, and organic chemical fraction, OEM, were able to significantly induce ROS overproduction and oxidative damage notwithstanding the early activation of NRF2 signaling pathway. Moreover, for any exposure, inflammatory and apoptotic events were noticed. Similar results were observed in BEAS-2B cells exposed to OEM, rich of polycyclic aromatic hydrocarbons and their nitrated and oxygenated derivatives. In BEAS-2B cells exposed for 24 and 48 h to OEM and OEM, to a higher extent, there was an alteration of the levels of some critical proteins even though crucial for the autophagy rather than a real reduction of autophagy. It is noteworthy that the toxicological effects were equal or mostly higher in BEAS-2B cells exposed for 6 and/or 24 h to PM from those exposed to NEM or OEM, and in BEAS-2B cells exposed for 6 and/or mostly 24 h to OEM from those exposed to OEM. Taken together, these results revealed the higher potentials for toxicity, closely linked to their respective physical and chemical characteristics, of PM vs NEM and/or OEM, and OEM vs OEM.