Exposure to indoor air pollution from solid fuels combustion is associated with lung diseases and cancer. This study aimed to explore the cytotoxicity and molecular mechanisms of biomass combustion-derived particles in human pulmonary alveolar epithelial cells (HPAEpiC) using a platform that combines air-liquid-interface (ALI) and dynamic culture (DC) systems.
HPAEpiC were cultured on the surface of polycarbonate (PC) membranes in ALI-DC platform. The top surface of cells was sprayed with a solution of biomass combustion soluble constituents (BCSCs) and simultaneously nourished with medium flowing from below PC membranes. BCSC particles' morphology and dosages deposited on the chip was determined for particle characterization. A flow cytometer, laser scanning confocal microscopy (LSCM), and transmission electron microscope (TEM) were used to investigate the apoptosis of HPAEpiC and the changes in the ultrastructure of HPAEpiC induced by BCSCs. Additionally, the underlying apoptotic pathway was studied through the determination of the protein expression levels by western blotting.
Scanning electron microscope (SEM) results demonstrated that the sample processing and delivering approach were very suitable for pollutant exposure of the platform. The decline in cell viability and increase in apoptosis rate after exposure to similar doses of BCSCs were more under ALI-DC conditions than under submerged conditions. This indicated that the ALI-DC platform is a superior system for investigating cytotoxicity of indoor air pollutants in lung cells. The morphology and ultrastructure of the cells were damaged after exposure to BCSCs. Our results demonstrated that the p53 pathway was activated after exposure of cells cultured using this platform to BCSCs. This further decreased the Bcl-2/Bax ratio thereby activating the expression of caspase-9 and caspase-3, which in turn induced apoptosis in HPAEpiC. Additionally, antioxidants (N-acetyl-cysteine; NAC) could significantly alleviate the cytotoxicity induced by BCSCs.
A novel ALI-DC platform was successfully presented to study cytotoxicity of air pollution on lung cells. Based on the platform, the BCSCs was demonstrated that it could damage mitochondria, produce ROS, and activate p53 in HPAEpiC. Furthermore, BCSCs decreased the Bcl-2/Bax ratio and efficiently upregulated the expression of cleaved caspases-9 and − 3, ultimately inducing apoptosis.