Effect of 2-hydroxyethyl-methacrylate (HEMA) on the phagocytic and respiratory burst activity of human neutrophils and monocytes

The effects of the dental methacrylates TEGDMA, Bis-GMA, and UDMA on neutrophils in vitro

Objectives

The prevalent usage of methacrylates in modern dentistry demands good knowledge of their biological impacts. While there have been several studies demonstrating the effects of different methacrylic monomers on mononuclear white blood cells, very little is known about the effects caused by these monomers on neutrophilic granulocytes. The objective of this study was to add novel knowledge about how neutrophils are affected by exposure to triethylene glycol dimethacrylate (TEGDMA), urethane dimethacrylate (UDMA), and bisphenol A glycol dimethacrylate (Bis‐GMA) alone or in combinations.

Materials and Methods

Isolated neutrophils were cultured in the presence or absence of methacrylates. The IL‐8 release was measured using a DuoSet ELISA development kit. Apoptosis and necrosis were analyzed using flow cytometry. The formation of neutrophil extracellular traps (NETs) was investigated using Sytox green DNA staining combined with microscopically examination of released DNA and myeloperoxidase (MPO).

Results

The release of IL‐8 was significantly increased after exposure to TEGDMA, Bis‐GMA, UDMA, or TEGDMA in combination with Bis‐GMA or UDMA compared to the unstimulated controls. Exposure to TEGDMA, UDMA, and Bis‐GMA for 24 hr separately or in combination did not affect apoptosis or necrosis of the exposed neutrophils. NET structures were formed by neutrophils after exposure to the different combinations of the methacrylates.

Conclusion

The combination of TEGDMA and Bis‐GMA had a synergistic proinflammatory effect on neutrophils by increasing the release of IL‐8 and the formation of NET structures. The changes in the normal functions of neutrophils caused by methacrylate exposure may lead to altered inflammatory response and relate to previously reported adverse immune reactions caused by these substances.

Establishing a macrophage model with relevance for oral methacrylate monomer exposures: Attenuated Staphylococcus aureus-induced cytokine release from human macrophages

BACKGROUND

Leakage of unpolymerized methacrylate monomers after placement of methacrylate-containing polymeric dental materials leads to human exposure. Based on studies using murine macrophages and LPS from Escherichia coli (E. coli), dental monomers like 2-hydroxyethyl methacrylate (HEMA) are known to inhibit lipopolysaccharide (LPS) induced cytokine release. The aim of this study was to establish a model system with relevance for human oral monomer exposure using exposure to live gram-positive bacteria, and to confirm the HEMA-induced effects on cytokine release in this model.

METHODS

The human THP-1 monocyte cell line was differentiated to macrophages using phorbol 12-myristate 13-acetate (PMA), before exposure to 0.5-2mM HEMA and live Staphylococcus aureus (S. aureus) in various multiplicity of infections (MOI). Cytokine release and cytotoxicity were determined after (i) 2-24h pre-exposure to HEMA followed by 2-4h S. aureus exposure and (ii) 2-4h simultaneous exposure. The 24h pre-exposure regime was also tested in primary human airway macrophages and for phagocytosis of S. aureus in THP-1 macrophages.

RESULTS

HEMA attenuated the cytokine release more strongly in the pre-exposure than combined exposure regime, with a maximal reduction of 95% in the S. aureus-induced cytokine release. A MOI of 0.1 (corresponding to a bacteria-macrophage ratio of 1:10) was determined to be optimal in the THP-1 macrophages as it induced sufficient cytokine release and negligible cytotoxicity. Attenuated release of S. aureus-induced interleukin (IL)-1β after HEMA exposure was confirmed in primary airway macrophages, while HEMA increased the phagocytosis of S. aureus in THP-1 cells.

CONCLUSION

The model was successfully established and attenuated bacteria-induced cytokine release after HEMA exposure confirmed.

Influence of sirolimus-loaded nanoparticles on physiological functions of native human polymorphonuclear neutrophils

Sirolimus (SRL) is an immunosuppressive agent of high clinical relevance that has been associated with serious side effects. Biodegradable, SRL-loaded poly(d,l-lactide) nanoparticles (SRL-PLA-NPs) are being investigated as a drug delivery system to improve drug targeting. Polymorphonuclear neutrophils (PMNs) are phagocytes for particulate xenobiotics and also important trigger cells of the primary immune response. Therefore, the effects of SRL, SRL-PLA-NPs, and plain PLA-NPs on the viability of human PMNs, their essential functions, and the secretion of relevant cytokines were determined and evaluated with respect to the intracellular concentrations assessed by liquid chromatography-mass spectrometry ultra-trace analysis. For the first time to our knowledge, incorporation of NPs into PMNs was monitored by flow cytometry using fluorescence-labeled NPs. SRL accumulated intracellularly, exceeding therapeutic blood levels by a factor of two to four. Phagocytic activity was promptly reduced but recovered within 3 hours. No other parameters of the PMNs were affected. Hence, PLA-NPs appear suitable as drug carriers for SRL, allowing for better control of drug release.

FROM THE CLINICAL EDITOR

This team of authors describe the incorporation of sirolimus loaded florescent NPs into polymorphonuclear neutrophils, a process that has been monitored by flow cytometry utilizing the fluorescent properties of the polymeric NPs. SRL accumulated intracellularly, exceeding therapeutic blood levels by a factor of two to four, resulting in reduced phagocytic activity that recovered within 3 hours.

Exogenous factors in the immunotoxicity of oral PMN

Current evidence indicates that periodontal disease is frequently due to inappropriate levels of gingival granulocyte functions. Reason of this failure may be the toxic effects of a number of local or systemic exogenous factors, capable of spreading through the gingival crevice environment, and strongly conditioning the granulocyte activities. The wide list includes bacteria and granulotoxic products, hedonistic drugs (mainly tobacco), and chemotherapeutic agents (especially antimicrobials used for preventing or reducing the accumulation of dental plaque). Almost always, their presence induces a time- and/or dose-dependent toxicity.