The aim was to investigate if hydrogen sulfide (H2S) induces the formation of the NLRP3 inflammasome and subsequent IL‐1β and IL‐18 secretion in human peripheral blood mononuclear cells (PBMCs) and in the human monocyte cell line THP1. Bacterial production of H2S has been suggested to participate in the inflammatory host response in periodontitis pathogenesis. H2S is a toxic gas with pro‐inflammatory properties. It is produced by bacterial degradation of sulfur‐containing amino acids, for example, cysteine. We hypothesize that H2S affects the inflammatory host response by inducing formation of the NLRP3 inflammasome and thereby causes the secretion of IL‐1ß and IL‐18. PBMCs from eight healthy blood donors, the human monocyte cell line THP1 Null, and two variants of the THP1 cell line unable to form the NLRP3 inflammasome were cultured in the presence or absence of 1 mM sodium hydrosulfide (NaHS) in 24‐well plates at 37°C for 24 hr. Supernatants were collected and the IL‐1β and IL‐18 concentrations were measured with DuoSet ELISA Development kit. PBMCs exposed to NaHS produced more IL‐1ß and IL‐18 than unexposed control cells (p = .023 and p = .008, respectively). An increase of extracellular potassium ions (K+) inhibited the secretion of IL‐1ß and IL‐18 (p = .008). Further, NaHS triggered the secretion of IL‐1ß and IL‐18 in human THP1‐Null monocytes (p = .0006 and p = .002, respectively), while the NaHS‐dependent secretion was reduced in the monocyte cell lines unable to form the NLRP3 inflammasome. Hence, the results suggest that NaHS induces the formation of the NLRP3 inflammasome and thus the secretion of IL‐1ß and IL‐18. Enhanced NLRP3 inflammasome‐dependent secretion of IL‐1β and IL‐18 in human mononuclear leukocytes exposed to NaHS in vitro is reported. This may be a mode for H2S to contribute to the inflammatory host response and pathogenesis of periodontal disease.

Incomplete curing of dental fillings may lead to leakage of methacrylate/acrylate monomers, which may come in contact with different cells of the immune system in oral tissues. Very little is known about the different immunologic effects caused by these methacrylates/acrylates. The objective of the present study was to study if and how the methacrylate/acrylate monomers ethyl methacrylate (EMA) and diethylene glycol diacrylate (DEGDA) affect the immune system in vivo and in vitro in comparison to 2‐hydroxyethyl methacrylate (HEMA) and triethylene glycol dimethacrylate (TEGDMA). Human peripheral blood mononuclear cells were exposed to the different monomers (500 and 1000 μM) for 24 hr in vitro. BioPlex Pro™ assays were used for cytokine analysis. In vivo, BALB/c mice were immunized subcutaneously at the base of the tail with HEMA, TEGDMA, EMA, or DEGDA in combination with ovalbumin (OVA) in order to study adjuvant properties of the 4 monomers. Peripheral blood mononuclear cells exposed to DEGDA had viability less than 50% of the cells. A pattern was observed where the levels of most cytokines were elevated after exposure to HEMA or TEGDMA. Since that, many cells died after DEGDA‐exposure, the only observed cytokine secretion was a significantly increased production of interleukin‐18. In the in vivo experiments, all mice immunized with DEGDA died after the booster injection. Mice receiving OVA in combination with HEMA, TEGDMA, or EMA developed a higher immunoglobulin G anti‐OVA antibody levels compared to the group immunized with OVA alone. We could not demonstrate any significant difference in antibody levels among the mice receiving the various methacrylate/acrylate monomers. The different monomers affected the production, increase and decrease, of different cytokines in vitro but resulted also in vivo in increased antibody production and T‐cell activity.

Objective: Leakage of monomers from dental fillings due to incomplete curing is very common. The objective of the present study was to examine the cytokine profile in cells exposed to triethyleneglycol dimethacrylate (TEGDMA) and the adjuvant properties of TEGDMA. Materials and methods: Human peripheral blood mononuclear cells were exposed to TEGDMA (500 and 1000 μM) for 24 h in vitro. Bio-Plex Pro™ assays were used for analysis and detection of cytokines. In vivo, BALB/c mice were immunized subcutaneously in the base of the tail with TEGDMA in combination with ovalbumin (OVA). Results: The cytokine levels of IL-8, IL-18, GRO-α and MCP-1 were significantly increased for both concentrations. IL-1β, IL-6 and TNF-α was only significantly increased in cultures exposed to 500 μM TEGDMA. The concentration of TNF-α was significantly decreased in cultures exposed to 1000 μM TEGDMA. Animals immunized with OVA co-administrated with TEGDMA had a significantly higher IgE and IgG anti-OVA antibody levels in blood than animals immunized with OVA only. Conclusions: TEGDMA affects production of proinflammatory cytokines IL-1β, IL-6, IL-8, IL-18 and TNF-α. This inflammatogenic capacity renders TEGDMAs adjuvant properties, which may interfere with the homeostasis between the immune system and the indigenous microflora in the oral cavity.

Oral mucosal lesions are commonly found in Swedish smokeless tobacco (snus) users where the pouch is placed. These lesions are reversible, that is, clinical and histological tissue changes return to normal following cessation. However, the exact mechanisms behind these changes are unknown. The main aim of this study was to investigate how snus‐like non‐tobacco‐based nicotine pouches affect the oral mucosa and the severity of pre‐existing lesions. Sixty regular users of Swedish smokeless tobacco were encouraged to substitute their snus with non‐tobacco‐based nicotine pouch products during a 6‐week period. Meanwhile, oral mucosal lesions were assessed using a four‐degree scale. Over time, a reduction of pre‐existing mucosal lesions was observed between baseline and the final visit. In a second part, the effect of exposure to regular snus on the production of 48 different cytokines in peripheral blood mononuclear cells was compared in vitro with that resulting from exposure to the non‐tobacco‐based nicotine products. Results showed significantly increased production of proinflammatory cytokines in cells exposed to regular snus compared to untreated or cells exposed to the non‐tobacco‐based nicotine products. This may be related to the improved clinical appearance of the oral mucosa in the participants that used the non‐tobacco‐based nicotine test pouches.

Porphyromonas gingivalis (P. gingivalis) is a gram-negative bacterium and an important etiologic agent of periodontitis. P. gingivalis releases outer membrane vesicles containing lipopolysaccharides (LPS), which can penetrate periodontal tissues. Once in the periodontal tissues and in contact with immune cells, it may participate in the destructive innate host response associated with the disease. The exact mechanism of P. gingivalis LPS in the disease process is not clear, but it is known to affect a variety of immune responses.Objectives: To investigate how LPS from P. gingivalis affect neutrophil extracellular trap (NET) formation, cell death and production of cytokines from human neutrophils and peripheral mononuclear blood mononuclear cells (PBMCs).Materials and methods: Isolated neutrophils and PBMCs were cultured with LPS from P. gingivalis or Escherichia coli (E. coli) (control). The NET formation was measured using Sytox green stain. Cell death of neutrophils and PBMCs was analyzed using flow cytometry or Sytox green stain. Cytokine production was measured using enzyme-linked immunosorbent assay (ELISA) kit or Bio-Plex assay.Results: Exposure to LPS from P. gingivalis and E. coli caused significantly lower cell death in neutrophils. NETs were formed after exposure to the two different LPS. In PBMCs, exposure to P. gingivalis and E. coli LPS caused increased levels of IL-1β and IL-6 compared to unstimulated controls. Increased cell death in PBMCs after exposure to LPS from E. coli in comparison to LPS from P. gingivalis and unstimulated controls was also observed.Conclusions: LPS from P. gingivalis has the ability to affect both human neutrophils and PBMCs with regard to cytokine production, cell death and production of NETs.LPS from P. gingivalis could be involved in the pathogenesis of periodontitis, and our results may contribute information regarding possible markers for diagnosis and targets for treatment of periodontal disease.