Phenotypic and lipidomic alterations in lung cells induced by organophosphate flame retardants

Organophosphate flame retardants (OPFRs) are widely used as additives in plastics, electronics, and construction materials due to their flame-retardant properties. However, previous evidence suggests that OPFRs may pose potential respiratory health risks, including airway hyperresponsiveness, impaired lung function, and potential carcinogenic effects. This study evaluated the effects of seven OPFRs-TBOEP, TPhP, EHDPhP, TDCPP, TEHP, TCP, and TCEP-on the phenotype and lipidomic profile of A549 lung cancer cells, using both 2D and 3D culture models. TDCPP and TPhP significantly reduced cell viability, while TBOEP caused the highest increase in reactive oxygen species (ROS), followed by TPhP, TDCPP, and TCP. Moreover, TPhP, TDCPP, EHDPhP, and TBOEP also elevated the levels of pro-inflammatory cytokine interleukin-8 (IL-8). The lipidomic analysis of 3D cell spheroids exposed to OPFRs for 72 h revealed distinct lipid profiles for each compound at low (25 μM) and high (100 μM) doses. Common features were observed, particularly at high doses, including significant increases in triacylglycerol, diacylglycerol, ceramide, ether-linked phosphatidylethanolamine, and phosphatidylinositol species. These effects were generally more pronounced for TPhP, TDCPP, EHDPhP, TCP, and TBOEP. The accumulation of triglycerides, indicative of augmented energy storage, was confirmed by the visualization of lipid droplets formation. Results suggest disruptions in key toxicological pathways, including oxidative stress, inflammatory signaling (IL-8 upregulation), and apoptosis (ceramide accumulation), all implicated in lung diseases, such as COPD and fibrosis. These results provide a basis for assessing the health risks associated with OPFRs, highlighting the need for further research on chronic low-dose exposure levels.