Effects of antioxidants on DNA double-strand breaks in human gingival fibroblasts exposed to dental resin co-monomer epoxy metabolites

Abstract

ObjectiveEluted dental resin co-monomers can be metabolized to intermediate methacrylic acid (MA) and, further, to epoxy metabolites. Antioxidants have been studied previously, with the intention of decreasing the DNA double-strand breaks (DNA-DSBs) in human gingival fibroblasts (HGFs). In this study, the effects of the antioxidants, ascorbic acid (Asc) and N-acetylcysteine (NAC), were investigated on co-monomer metabolite-induced DNA-DSBs. MethodsHGFs were incubated with MA, 2,3-epoxy-2-methyl-propionicacid-methylester (EMPME) and 2,3-epoxy-2-methylpropionic acid (EMPA), respectively, in the presence or absence of antioxidants (Asc or NAC). EC50 Values were obtained from an XTT-based viability assay. DNA-DSBs were determined using a γ-H2AX assay. ResultsThe cytotoxicity of the compounds could be ranked in the following order (mean±SEM; n=4): EMPA>EMPME>MA. The average number of DSBs-foci/cell induced by each substance at EC50-concentration could be ranked in the following order (mean±SD; n=4): EMPA>EMPME>MA. EMPA (1.72mM) and EMPME (2.58mM) induced the highest number of DSBs-foci, that is 21-fold and 13-fold, respectively, compared to control (0.48±0.08 foci/cell). The addition of Asc (50; 100; 200μM) or NAC (50; 100; 200; 500μM) to MA (15.64; 5.21mM), EMPME (2.58mM), and EMPA (1.72; 0.57mM) significantly reduced the number of foci/cell in HGFs. The highest reduction could be found in HGFs with 1.72mM EMPA, the addition of NAC (50; 100; 200; 500μM) induced a 15-fold, 17-fold, 14-fold and 14-fold lower number of DSBs-foci/cell, respectively. SignificanceDental co-monomer epoxy metabolites, EMPME and EMPA, can induce DNA-DSBs. The addition of antioxidants (Asc or NAC) leads to reduction of DNA-DSBs, and NAC leads to more prominent reduction of DNA-DSBs compared to Asc.