Hydramethylnon induces mitochondria-mediated apoptosis in BEAS-2B human bronchial epithelial cells

Typically used household chemicals comprise numerous compounds. Determining mixture toxicity, as observed when using household chemicals containing multiple substances, is of considerable importance from a regulatory perspective. Upon examining the toxic effects of household chemical mixtures, we observed that hydramethylnon combined with tetramethrin resulted in synergistic toxicity. To determine the unknown toxicity mechanism of hydramethylnon, which carries the risk of inhalation exposure when using household chemicals, we conducted a further investigation using BEAS-2B cells, a human bronchial epithelial cell line. Hydramethylnon-induced cytotoxicity was determined following 24 and 48 h of exposure using the water-soluble tetrazolium 1 and lactate dehydrogenase assays. To elucidate the toxicity mechanism, we utilized flow cytometry and measured the levels of apoptosis-related proteins and caspase activities. Given that hydramethylnon, as an insecticide, disrupts the mitochondrial electron transfer chain, we analyzed the relevant mechanisms, including mitochondrial superoxide levels as well as the mitochondrial membrane potential (MMP). Hydramethylnon dose-dependently induced BEAS-2B cell apoptosis via the intrinsic pathway. Furthermore, it significantly increased mitochondrial superoxide levels and disrupted the MMP. Pre-treatment with a caspase inhibitor (Z-DEVD-FMK) confirmed that hydramethylnon induced caspase-dependent apoptosis. Apoptosis, a key event in the toxicological process of chemicals, can lead to lung diseases, including fibrosis and cancer. The results of the present study suggest a mechanism of toxicity of hydramethrylnon, an organofluorine biocide whose toxicity has been little studied, to the lung epithelium. Considering the potential risks associated with inhalation exposure, these results highlight the need for careful management and regulation of hydramethylnon.