Expression of CYP450-2E1 and formation of 2,3-epoxymethacrylic acid (2,3-EMA) in human oral cells exposed to dental materials.

Objectives: Methacrylate-based (co)monomers released from dental composites can be, metabolized in vivo to methacrylic acid (MA). MA can be further oxidized to the toxic 2,3-epoxymethacrylic acid (2,3-EMA) by cytochrome P450 (CYP450) enzymes. The subform CYP450-2E1, can metabolize xenobiotics with low-molecular weight to epoxides. Oral cells are highly exposed to (co)monomers released from composites. Therefore in this study the, expression of CYP450-2E1 in human oral (and other) cells was investigated as well as the formation of 2,3-EMA in cells exposed to MA.

Methods: Following human oral cells were used: human gingiva fibroblasts (HGF), human pulp fibroblasts (HPF), and human tumor buccal keratinocytes (SqCC/Y1). As negative control V79 cells without CYP450-2E1 expression were used. As positive controls V79 cells with CYP450-2E1 expression (V79-CYP450-2E1) and pooled human liver microsomes were used. The expression of CYP450-2E1 in cells was analyzed with the real-time polymerase chain reaction (RT-PCR). 2,3-EMA was quantified by the use of the method of gas chromatography/mass spectrometry (GC/MS).

Results: The highest expression of CYP450-2E1 was found in human liver microsomes, followed by SqCC/Y1 cells, V79-CYP450-2E1 cells, HGF, and HPF. The highest amount of 2,3-EMA (μmol/L; mean±SEM, n=3) was found in human liver microsomes (5.0±1.0), followed by SqCC/Y1 cells (2.5±0.8), V79-CYP450-2E1 cells (1.5±0.6), HPF (0.3±0.3), and HGF (0.2±0.2).

Significance: It is concluded that the formation of the toxic epoxide 2,3-EMA, as intermediate in the metabolism of dental materials, can occur also in human oral cells which can express the CYP450-2E1 enzyme system.