Abstract
Benzene, toluene, ethylbenzene, and xylenes (o-, m-, and p-xylenes) constitute a family, named BTEX, of volatile organic compounds (VOCs) known for its toxicity. This study aimed to study the acute in vitro toxicity of ethylbenzene and m-xylene on human bronchial epithelial cells exposed at the air-liquid interface (ALI). The cells were exposed to VOCs alone and in a mixture for 1 h, followed by 5, 23, and 47 h of incubation. The kinetics of the cell response was characterized, including cytotoxicity, xenobiotic biotransformation, antioxidant defense system, inflammatory response, and apoptosis. The gene expression results showed major differences between these two compounds, even though their chemical structure is very similar. Ethylbenzene did not appear to be metabolized in BEAS-2B cells, as it inhibited gene expression of xenobiotic metabolizing enzymes (XME) and did not induce antioxidant defense systems or apoptosis. However, a slight inflammatory response was observed after exposure. m-Xylene was metabolized in BEAS-2B cells, inducing several XMEs and upregulating enzymes involved in the antioxidant defense system, as well as markers of inflammation and apoptosis. Co-exposure to the binary mixture resulted in an inhibition phenomenon, resulting in the inhibition of toxic action mechanisms studied. The results provide new information on the toxicity of ethylbenzene and m-xylene and highlight the importance of conducting ALI exposures to mixtures of toxicants.