title: Expression of CYP450-2E1 and formation of 2,3-epoxymethacrylic acid (2,3-EMA) in human oral cells exposed to dental materials.
abstract: OBJECTIVE
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Operative Dentistry and Periodontology, Ludwig-Maximilians-University, 80336 Munich, Germany.
authors.forename: Franz-Xaver
authors.initials: FX
authors.lastname: Reichl
authors.forename: Mario
authors.initials: M
authors.lastname: Seiss
authors.forename: Jeroen
authors.initials: J
authors.lastname: Buters
authors.forename: Heidrun
authors.initials: H
authors.lastname: Behrendt
authors.forename: Reinhard
authors.initials: R
authors.lastname: Hickel
authors.forename: Jürgen
authors.initials: J
authors.lastname: Durner
mesh_terms: D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003188:Composite Resins / Q000737:chemistry / Q000633:toxicity*; D019392:Cytochrome P-450 CYP2E1 / Q000096:biosynthesis* / Q000378:metabolism; D003782:Dental Pulp / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D005881:Gingiva / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism; D008689:Methacrylates / Q000378:metabolism* / Q000633:toxicity; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C519317:2,3-epoxymethacrylic acid; D003188:Composite Resins; D008689:Methacrylates; D019392:Cytochrome P-450 CYP2E1