Toxicity of acute or repeated exposures to particles from pyrotechnic smokes in normal human bronchial epithelial (NHBE) cells 3D culture

Abstract Background Hexachloroethane (HC) based smokes and colored pyrotechnic smokes are widely used in the military field, as screening and signaling smokes, that are reported to cause pulmonary toxic effects in humans and in animal studies. Toxicity of pyrotechnic smokes might be caused by the inhalation of particles that composed the smoke and gives the desired pyrotechnic effect. In a previous study, we showed that smoke particles from a red signaling smoke (RSS) and from an HC obscuring smoke (HC-OS) have an intrinsic oxidative potential and induce an adaptive response in human small airway epithelial cells after an acute exposure. Thus, the aim of this study was to further explore the underlying mechanisms of toxicity linked to oxidative stress response of RSS and HC-OS particles, by using a 3D model of normal human bronchial epithelial cells (NHBE) cultured at the air-liquid interface (ALI). Results Acute exposure (24 h) to HC-OS particles induced a weak antioxidant response, characterized by increases of glutathione level and weak increase of one enzymatic antioxidant mRNA expression ( NQO-1 ). Acute exposure to RSS particles induced oxidative stress characterized by production of reactive oxygen species (ROS), increases of glutathione level, increases mRNA expression of several enzymatic antioxidants ( SOD-1 , SOD-2 , HO-1 , NQO-1 ) and expression of NQO-1 protein as well as increase expression of IL-8 mRNA. We noticed that 24 h post-exposure to RSS particles, antioxidant response was still induced. Additionally, 24 h post-exposure to RSS particles revealed internalization of particles and morphological changes in 3D NHBE cells like loss of cilia and a cubic epithelium. Repeated exposures to RSS particles on 3D NHBE cells did not induce oxidative stress while cubic changing aspects of 3D NHBE cells were observed. Conclusions Thus, although further studies are needed to understand the mechanisms underlying these cubic changes, these results revealed differences in toxicity responses between the two types of particles, characterized by an RSS particles-induced oxidative stress as well as morphologic changes. Overall, this study provides a better overview of the toxic effects of pyrotechnic smoke particles whose toxic risks were very little studied.