Effect of sub-lethal concentrations of HEMA (2-hydroxyethyl methacrylate) on THP-1 human monocyte-macrophages, in vitro.
OBJECTIVE
Resin monomers such as HEMA (2-hydroxyethyl methacrylate) can be released from restorative materials and diffuse into the tooth pulp over long periods of time. Although the short-term toxicity of resin monomers has been well documented, little is known about the risk for chronic toxicity resulting from low concentrations of resins. Thus, the hypothesis tested in this study was that sub-lethal concentrations of HEMA alter the functions of macrophages after long-term exposure.


METHODS
Human THP-1 monocyte-macrophages were exposed to concentrations of HEMA between 0 and 1.5 mmol/l for up to 6 weeks. Cellular proliferation was measured by a hemocytometer with trypan-blue dye exclusion. Mitochondrial activity was measured by the MTT assay, and total cellular protein was measured using the bicinchoninic acid assay.


RESULTS
Macrophage proliferation was inhibited 40-50% (significant, p < 0.05) by as little as 0.75 mmol/l after 1 week of exposure. Inhibition of proliferation remained constant after 1 week. The total protein per cell increased by as much as 80% (significant, p < 0.05) after 2 weeks and remained elevated through 6 weeks. Mitochondrial activity per cell increased 60-80% (significant, p < 0.05) after 2 weeks, then decreased. However, mitochondrial activity remained significantly elevated above controls through 6 weeks.


CONCLUSIONS
Findings from the current study indicate that 6-week exposures of monocytes to HEMA alter their proliferation and other activities at concentrations substantially lower than previously reported. This is particularly relevant in light of evidence that such concentrations have been previously shown to come through dentin by diffusion.
Bouillaguet
S
S
Department of Operative Dentistry and Endodontics, School of Dentistry, Geneva, Switzerland. watahaj@mail.mcg.edu
Wataha
J C
JC
Virgillito
M
M
Gonzalez
L
L
Rakich
D R
DR
Meyer
J M
JM
D000704:Analysis of Variance; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004396:Coloring Agents; D006801:Humans; D007202:Indicators and Reagents; D008264:Macrophages / Q000187:drug effects*; D008689:Methacrylates / Q000633:toxicity*; D008928:Mitochondria / Q000187:drug effects; D009000:Monocytes / Q000187:drug effects*; D010865:Pilot Projects; D011506:Proteins / Q000187:drug effects; D011804:Quinolines; D013223:Statistics as Topic; D013385:Succinate Dehydrogenase / Q000187:drug effects; D013778:Tetrazolium Salts; D013844:Thiazoles; D013997:Time Factors; D014343:Trypan Blue
D004396:Coloring Agents; D007202:Indicators and Reagents; D008689:Methacrylates; D011506:Proteins; D011804:Quinolines; D013778:Tetrazolium Salts; D013844:Thiazoles; C005044:hydroxyethyl methacrylate; C047117:bicinchoninic acid; D013385:Succinate Dehydrogenase; C022616:thiazolyl blue; D014343:Trypan Blue