2-Hydroxyethyl methacrylate (HEMA) is a major component of many resin-based dental materials. During and after treatment with these materials, both dental personnel and patients are exposed to HEMA. In vitro studies have demonstrated a cytotoxic potential of HEMA, and reactivity towards cysteine (a nucleophilic amino acid (AA)) in glutathione (GSH) is assumed to contribute to the toxic response. This event alone, however, seem insufficient to reduce cell viability. The objective of this study was to elucidate other molecular interactions that could explain HEMA toxicity. Here we explore how exposure to HEMA affects cellular protein S–glutathionylation (PSSG), a post-translational modification of cysteine residues in proteins.
A bronchial epithelial cell line (BEAS-2B) was used as a model. Cells grown in LHC-9 medium were exposed to HEMA. GSH-levels were measured by flow cytometry of monobromobimane stained cells. Western blotting with specific antibodies was used to quantify β-actin and S-glutathionylated proteins. To explore spontaneous HEMA reactivity towards PSSG-sites, four synthetic peptides based on an AA-sequence containing the major PSSG-site of actin were used. The peptides were analysed on UHPLC-MS with or without pre-incubation with HEMA.
Exposure to HEMA caused GSH-depletion and reduced PSSG of at least one protein (MW approximately 42 kDa) in BEAS-2B cells. Further results implied that the observed protein was β-actin. LC-MS analyses showed a binding of HEMA to the synthetic peptides containing cysteine.
This study show that HEMA exposure alters S–glutathionylation of β-actin. Both cellular GSH-depletion and competitive binding of HEMA to the S–glutathionylation site may explain this effect.
Solveig Uvsløkk (Presenter), NIOM – Nordic Institute of Dental Materials
Ida Sofia Stenhagen, NIOM – Nordic Institute of Dental Materials
Jan Tore Samuelsen, NIOM – Nordic Institute of Dental Materials
This poster was presented at the 2018 IADR conference in London, UK.