Sublethal, 2-week exposures of dental material components alter TNF-α secretion of THP-1 monocytes

Objectives. The aim of this study was to investigate the hypothesis that dental material components alter cytokine secretion from monocytes if applied for several weeks at sublethal doses. The current study significantly extended exposure times of monocytes to the components over times published in previous studies. These exposure times approached the estimated average life span of monocytes in the bloodstream. Methods. Human THP-1 monocytes were exposed to 2-hydroxyethylmethacrylate (HEMA, 0–1.2 mmol/l), triethyleneglycoldimethacrylate (TEGDMA, 0–0.75 mmol/l), Hg2+ (0–2 μmol/l), or Ni2+ (0–20 μmol/l) for 2 weeks. The cells were then collected and additionally incubated for 24 h, with or without bacterial lipopolysaccharide (LPS), a common component of dental plaque. TNF-α secretion from THP-1 was determined using by enzyme-linked immunosorbent assay. Results. None of the dental material components induced TNF-α from THP-1 by themselves, but LPS alone strongly induced TNF-α secretion as expected. HEMA and TEGDMA significantly suppressed (40–70%) TNF-α secretion from cells stimulated with LPS. Hg2+ at 2.0 μmol/l doubled TNF-α secretion from THP-1s stimulated with LPS over LPS alone. Ni2+ did not significantly affect TNF-α secretion, with or without LPS exposure. Significance. The results in this study suggest that sublethal, 2-week exposures of some dental material components may alter TNF-α secretion from THP-1 monocytes when the cells are challenged. These alterations may influence the biological response of tissues to materials in an inflammatory intraoral environment.