Metabolic effects of dental resin components in vitro detected by NMR spectroscopy

Earlier studies have shown that the comonomer triethyleneglycol-dimethacryl ate (TEGDMA) and the photostabilizer 2-hydroxy-4-methoxybenzophenone (HMBP) are cytotoxic and inhibit cell growth. It was the aim of this study to elu cidate the underlying metabolic effects of TEGDMA and HMBP on immortal cont act-inhibited Swiss albino mouse embryo cells (3T3 fibroblasts) by nuclear magnetic resonance (NMR) spectroscopy. Cell extracts and culture media were analyzed by NMR spectroscopy for metabolic changes after incubation for 24 hours with ED20-concentrations of TEGDMA and HMBP. TEGDMA could be detecte d in all fractions (cytosol, lipid fractions, and culture media) of 3T3 cel ls, while HMBP was found only in the lipid fraction accumulated at a maximu m rate (51 nmol/mg DNA) compared with TEGDMA (27 nmol/mg DNA). TEGDMA incre ased the concentration of phosphomonoesters to 180 +/- 36% and decreased th e phosphodiesters to 65 +/- 5% of controls (control = 100%). Thus, the turn over of phospholipids was enhanced, whereas content and composition of phos pholipids of membranes did not alter markedly. Additionally, TEGDMA changed the metabolic state of cells, indicated by slight decreases of nucleoside triphosphates and an increase in the ratio of nucleoside diphosphates to nu cleoside triphosphates, while HMBP had no effect. The most remarkable effec t of TEGDMA was a nearly complete decline of the intracellular glutathione levels. Analysis of our data shows that NMR spectroscopy of cell-material i nteractions may reveal metabolic effects of organic test substances which a re not detectable by standard in vitro assays. The comonomer TEGDMA affecte d the metabolism of the cells on different levels, while HMBP accumulated i n the lipid fraction and induced significantly fewer effects on cell metabo lism.