print

This month we address how monomers from composite llings may impair the immune response of macrophages. When activated macrophages were exposed to HEMA and TEGDMA, the release of mediators (cytokines) was reduced. The cytokines are involved in the in ammation prosess which is regarded as a defence mechanism against for example bacteria. Insuf cient release of in ammatory cytokines has been reported to cause impaired bacterial clearance.

 

Photo: Gunnar Svendsen, DDS

Monomers from composite fillings
may impair the immune response of macrophages.

 

Dental biofilms may contain gram-negative bacteria that release the endotoxin lipopolysaccharide (LPS). This virulence factor plays an essential role in triggering periodontal inflammation. Macrophages are immune cells that remove pathogens and foreign substances. When exposed to LPS they may release pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) as a part of the innate immune response.

In this study, we report that relatively low concentrations of the methacrylate monomers TEGDMA (triethylene glycol dimethacrylate) and HEMA (2-hydroxyethyl methacrylate) reduced the LPS-induced cytokine release from the macrophage cell line RAW264.7. In the literature, insufficient release of inflammatory mediators has been reported to cause impaired bacterial clearance, which could have implications for the innate immune response. Our experiments suggested that co-exposure to dental monomers caused an additive effect, which means that the response to combined exposure was similar to the sum of the responses induced by the individual monomers. Also, the reduced cytokine release persisted for 24 hours after termination of the monomer exposure, suggesting that the monomers could affect the macrophage function up to 24 hours after exposure. Studies of the mechanisms involved in the observed effects indicated disturbed regulation of synthesis and release of the cytokines, but further studies are necessary to clarify this.

The concentrations of TEGDMA and HEMA used in this study were based on laboratory studies of leakage from dental fillings investigating the 24 hour cumulative release of monomers (from a meta-analysis by Van Landuyt et al. (2011)). These concentrations can therefore be considered to be relevant for oral exposure after placement of a composite filling. The applied concentrations were lower than those previously used in similar studies.

In conclusion, the observed reduction in the LPS-induced cytokine release after monomer exposure could have implications for the macrophage immune response. However, further studies are necessary to confirm these findings in other model systems.


From
Bølling AK, Samuelsen JT, Morisbak E, Ansteinsson V, Becker R, Dahl JE, Mathisen GH.
Dental monomers inhibit LPS-induced cytokine release from the macrophage cell line RAW264.7.
Toxicology Letters 216, 2013, pp. 130–138.

Download
NOIM Newsletter April 2013