Resin-based dental materials are a common first choice when restoring dental function. Both dental personnel and patients are exposed to methacrylate monomers, one main component in these materials. A concern regarding possible side effects these materials may induce has been the motivation of several in vitro studies. A cytotoxic potential have been described in vitro, but detailed knowledge regarding molecular interactions of monomers in living cells remain scarce. A suggested mechanism, however, involves thiol-reactivity and increased levels of oxidative stress. 2-Hydroxyethylmethacrylate (HEMA) is shown to form spontaneous adduct formation towards the thiol-group in glutathione (GSH), and it is speculated if similar reactions between proteins and HEMA occurs. The aim of this study was to investigate if the commonly used methacrylate HEMA affects protein cysteines. For this in vitro study, a bronchial epithelial cell line (BEAS-2B) was used as a model. Results showed that exposure to HEMA (4-10 mM) reduced the cell viability. In addition, HEMA reduced the level of GSH and S-glutathionylation of at least one protein (MW approx. 42 kDa). These changes were also observed for concentrations lower than those affecting the cell viability. The results further imply that the observed protein is β-actin. Although, S-glutathionylation of β-actin is suggested to affect the cytoskeleton by inhibiting polymerisation of actin, this study could not detect any changes in actin structure after HEMAexposure. LC-MS analysis of binding between synthetic peptides and HEMA implies that HEMA can bind to S–glutathionylation site in β-actin. In addition to this possible competitive binding, results obtained by inhibiting the GSH-synthesis imply that cellular GSH-level also influence the level of β-actin Sglutathionylation

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