Clémence Méausoone1, Yann Landkocz1, Fabrice Cazier2, Marianne Seigneur1 Dominique Courcot1, Sylvain Billet1
1Unité de Chimie Environnementale et Interactions sur le Vivant, SFR Condorcet FR CNRS 3417, Université du Littoral Côte d'Opale, Dunkirk, France
2Centre Commun de Mesures, Université du Littoral Côte d'Opale, Dunkirk, France
Benzene and toluene are solvents largely used in industries and emitted into the atmosphere, despite major and direct impacts on human health. This study shows the feasibility of observing mechanisms of toxic action during repeated exposure at ALI to doses close to human exposure. The second strength of this study was the measure of XME induction level with the initiation of several xenobiotic metabolism pathways over time. BEAS-2B cells were exposed to benzene, toluene, m-xylene, or mesitylene gaseous stream diluted in air using the Vitrocell ALI system.
In order to reduce exposure to toxic chemicals, the European REACH regulation (1907/2006) recommends substituting toxic molecules with compounds that are less harmful to human health and the environment. Toluene is one of the most frequently used solvents in industries despite its toxicity. The objective of this study is to better understand and compare the toxicity of toluene and its homologues in a bronchial cell model. Thus, human bronchial BEAS-2B cells were exposed to steams of toluene, m-xylene, mesitylene (1,3,5-trimethylbenzene), and benzene (20 and 100 ppm). Exposure was carried out using an air–liquid interface (ALI) system (Vitrocell) during 1 h/ day for 1, 3, or 5 days. Cytotoxicity, xenobiotic metabolism enzyme gene expression, and inflammatory response were evaluated following cell exposures. BEAS-2B cell exposure to toluene and its homologues revealed the involvement of major (CYP2E1) and minor metabolic pathways (CYP1A1). A late induction of genes (EPHX1, DHDH, ALDH2, and ALDH3B1) was measured from Day 3 and can be linked to the formation of metabolites. An increase in the secretion level of inflammatory markers (TNF-α, IL-6, IL-8, MCP-1, and GM-CSF) was also observed. In parallel, regulation between inflammatory mediators and the expression of transmembrane glycoprotein mucin MUC1 was also studied. This in vitro approach with ALI system points out the relevance of conducting repeated exposures to detect potential late effects. The difference recorded after cell exposure to toluene and its homologues highlights the importance of substitution principle.