Resin-monomer modified the expression of antioxidant enzymes

Objectives: The intracellular redox homeostasis is tightly controlled by glutathione (GSH), the major non-enzymatic antioxidant, and diverse antioxidant enzymes in order to maintain normal cell function. Adverse effects of dental resin monomers including cell cycle arrest and apoptosis are most likely associated with an increase of intracellular reactive oxygen species (ROS) and the depletion of GSH. Therefore, it was hypothesized that the monomer 2-hydroxyethylmethacrylate (HEMA) influences the intracellular enzymatic antioxidant defense, such as superoxide dismutase (SOD-1), catalase (CAT), glutathione peroxidase 1/2 (GPx1/2), hemeoxyenase (HMOX-1), thioredoxin (TRX1) and hypoxia inducible factor (HIF1-α). In addition the intracellular GSH-level was either reduced by buthionine sulfoximine (BSO) or enhanced by 2-oxothiazolidine-4-carboxylate (OTC) and N-acetyl cysteine (NAC). Methods: RAW246.7 mouse macrophages were exposed to HEMA (0-6-8mM) in absence and presence of 50µM BSO, 5mM OTC and 10mM NAC for 24h. The proteins in the cytoplasmic cell fraction were resolved by SDS-PAGE and then the expression of SOD-1, CAT, GPx1/2, HMOX-1, TRX1 and HIF1-α was analyzed by Western blotting. Results: HEMA reduced the expression of SOD1, TRX1 and HIF1-α, but enhanced the expression of CAT and HMOX-1. The expression of SOD1, GPx1/2 and HMOX-1 was increased by BSO and NAC increased the expression of SOD1 and GPx1/2. HEMA in presence of BSO suppressed the expression of SOD1, GPx1/2 and HIF1-α, whereas the presence of OTC and NAC in HEMA treated cultures increased the expression of antioxidant enzymes, except CAT and HMOX-1. Conclusions: HEMA affected the expression of antioxidant enzymes suggesting a principal role of ROS and accordingly the intracellular antioxidant defense in monomer-induced cellular damage. Supported by the University of Regensburg (S.K.) and the Deutsche Forschungsgemeinschaft (Schw 431/13-1).