Monomers like triethylene glycol dimethacrylate (TEGDMA) leach from dental composites and adhesives. The release of these monomers causes a variety of reactions that can lead to cell death. This cell death can be either necrotic that is characterized mainly by inflammation and injury to the surrounding tissues, or apoptotic that elicits little inflammatory responses, if any at all. TEGDMA-induced apoptosis in human pulp has been reported. However, the molecular mechanisms and the apoptotic (pro and anti) proteins involved in this process remain unclear. Therefore, the purpose of this study was to determine the apoptotic proteins enhanced or suppressed during TEGDMA-induced apoptosis.
Human pulp fibroblasts (HPFs) were incubated for 24 hours with different TEGDMA concentrations (0.125-1.0 mM) and cytotoxicity determined using a cytotoxicity detection kit. TEGDMA was shown to cause cell cytotoxicity at concentrations of 0.50 mM and up. The highest TEGDMA concentration with no significant cytotoxicity was used (0.25 mM) to examine TEGDMA induced apoptosis. Cells were incubated with or without TEGDMA for 6 and 24 hours. Cell lysates were then prepared and the protein concentrations determined using the Bradford protein assay. Human apoptosis arrays were utilized to detect the relative levels of 43 apoptotic proteins.
HPFs exposed to TEGDMA showed statistically significant increases in multiple pro-apoptotic proteins such as BH3-interacting domain death agonist (BID), BCL2 interacting protein (BIM), caspase 3, caspase 8, TNF-related apoptosis-inducing ligand receptor 1 (TRAILR 1), TRAILR 2, Bcl-2–associated X protein (BAX), and cytochrome c at 24 hours. Some anti-apoptotic proteins were also altered.
Conclusions: Pro-apoptotic proteins involved in both the intrinsic and extrinsic apoptotic pathways were increased significantly by TEGDMA.
Keywords: Apoptosis, Composites, Fibroblasts, Pulp and TEGDMA
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