Mineral trioxide aggregate suppresses pro-inflammatory cytokine expression via the calcineurin/nuclear factor of activated T cells/early growth response 2 pathway in lipopolysaccharide-stimulated macrophages

Evaluation of Cytotoxicity, Cell Attachment, and Elemental Characterization of Three Calcium Silicate-Based Sealers

We investigated three calcium silicate-based sealers with respect to their chemical characterization, cytotoxicity, and attachment to RAW264.7 cells. BioRoot RCS (BR), Bio-C Sealer (BC), and Sealer Plus BC (SPBC) were assessed using Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence spectroscopy (XRF), and energy-dispersive X-ray spectroscopy (EDX) (n = 4) for elemental characterization, and using scanning electron microscopy (SEM) to evaluate cell morphology and adhesion. Cytotoxicity was determined at different dilutions (1:1, 1:2, and 1:5) using the succinate dehydrogenase activity (MTT assay). Statistical analysis was performed for normal distribution using the Shapiro-Wilk test and for homoscedasticity using Levene's test, and one-way ANOVA, Tukey's/Dunnett's post hoc tests for cell viability and XRF (α = 0.05). Calcium silicate hydrate and calcium hydroxide were detected by FTIR in all groups. EDX detected a higher calcium content for BR and SPBC and aluminum only in the premixed sealers. XRF detected the highest calcium release in BR (p < 0.05). The surface morphology showed irregular precipitates for all the sealers. SPBC at a 1:2 dilution resulted in the lowest cell viability compared to BR (p < 0.05) and BC (p < 0.05). The calcium silicate-based sealers produced a statistically significant reduction in cellular viability at a 1:1 dilution compared to the control group (p < 0.0001). All the sealers maintained viability above 70%.

Hydraulic calcium silicate-based root canal sealers mitigate proinflammatory cytokine synthesis and promote osteogenesis in vitro

Background/purpose

The mineralized tissue-inductive ability and anti-inflammatory properties of hydraulic calcium silicate-based (HCSB) sealers have not been fully elucidated. This study aimed to evaluate the effects of the HCSB sealers Bio-C sealer (BioC), Well-Root ST (WST), and EndoSequence BC sealer (BC), on osteoblastic differentiation/mineralization and proinflammatory cytokine synthesis by macrophages.

Materials and methods

Diluted extracts of set sealers or calcium chloride solutions of approximately equivalent Ca2+ concentrations were applied to a mouse osteoblastic cell line (Kusa-A1 cells) and lipopolysaccharide-stimulated mouse macrophage cell line (RAW264.7 cells). Expressions of osteoblastic markers in Kusa-A1 cells and proinflammatory cytokines in RAW264.7 cells were evaluated by reverse transcription-quantitative polymerase chain reaction and enzyme-linked immunosorbent assays. Mineralized nodules were detected by Alizarin red S staining. Cell proliferation was assessed by WST-8 assay and cell attachment on set sealers was examined by scanning electron microscopy.

Results

The three sealer extracts significantly upregulated osteocalcin and osteopontin mRNA, and promoted significant mineralized nodule formation in Kusa-A1 cells. The three sealer extracts significantly downregulated the mRNA expressions of interleukin (IL)-1α, IL-1β, IL-6, and tumor necrosis factor (TNF)-α and protein levels of IL-6 and TNF-α in RAW264.7 cells. Calcium chloride solutions induced osteoblastic differentiation/mineralization. AH Plus Jet (a control sealer) extract did not. The three HCSB sealers did not interfere with the growth and attachment of Kusa-A1 cells.

Conclusion

BioC, WST, and BC were biocompatible, upregulated osteoblastic differentiation/mineralization, and downregulated proinflammatory cytokine expression. Ca2+ released from HCSB sealers might be involved, at least in part, in the induction of osteoblastic differentiation/mineralization.

Modulation of fibroblast growth factor-23 expression and transepithelial calcium absorption in Caco-2 monolayer by calcium-sensing receptor and calcineurin under calcium hyperabsorptive state

Fibroblast growth factor (FGF)-23 and calcium-sensing receptor (CaSR) have previously been postulated to be parts of a negative feedback regulation of the intestinal calcium absorption to prevent excessive calcium uptake and its toxicity. However, the underlying mechanism of this feedback regulation remained elusive, especially whether it required transcription of FGF-23. Herein, we induced calcium hyperabsorptive state (CHS) by exposing intestinal epithelium-like Caco-2 monolayer to 30 mM CaCl₂ and 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃] after which FGF-23 mRNA levels and transepithelial calcium flux were determined. We found that CHS upregulated FGF-23 transcription, which was reverted by CaSR inhibitors (Calhex-231 and NPS2143) but without effect on CaSR transcription. Although 10 nM 1,25(OH)₂D₃ was capable of enhancing transepithelial calcium flux, the higher-than-normal calcium inundation as in CHS led to a decrease in calcium flux, consistent with an increase in FGF-23 protein expression. Administration of inhibitors (≤10 μM CN585 and cyclosporin A) of calcineurin, a mediator of CaSR action to control transcription and production of its target proteins, was found to partially prevent FGF-23 protein production and the negative effect of CHS on calcium transport, while having no effect on FGF-23 mRNA expression. Direct exposure to FGF-23, but not FGF-23 + PD173074 (FGFR1/3 inhibitor), also completely abolished the 1,25(OH)₂D₃-enhanced calcium transport in Caco-2 monolayer. Nevertheless, CHS and CaSR inhibitors had no effect on the mRNA levels of calcineurin (PPP3CB) or its targets (i.e., NFATc1-4). In conclusion, exposure to CHS induced by high apical calcium and 1,25(OH)₂D₃ triggered a negative feedback mechanism to prevent further calcium uptake. CaSR and its downstream mediator, calcineurin, possibly contributed to the regulatory process, in part by enhancing FGF-23 production to inhibit calcium transport. Our study, therefore, corroborated the physiological significance of CaSR-autocrine FGF-23 axis as a local feedback loop for prevention of excessive calcium uptake.

Evaluation of the anti-inflammatory effects of surface-reaction-type pre-reacted glass-ionomer filler containing root canal sealer in lipopolysaccharide-stimulated RAW264.7 macrophages

A prototype surface-reaction-type pre-reacted glass-ionomer (S-PRG) filler containing root canal sealer (S-PRG sealer) exhibits bioactive potential by releasing multiple ions. This study explored the suppressive effects and modes of action of S-PRG sealer extracts on proinflammatory cytokine expression in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Expression of proinflammatory cytokines was evaluated by RT-qPCR and ELISA. Expression of phosphorylated nuclear factor-kappa B (p-NF-kB) p65 was evaluated by western blotting. S-PRG sealer extracts significantly downregulated mRNA expression levels of interleukin (IL)-1α, IL-6, and TNF-α in LPS-stimulated RAW264.7 cells; the extracts also reduced the levels of IL-6 protein and p-NF-kB. In order to verify that Zn²⁺ was responsible for downregulation of proinflammatory cytokine expression, N,N,N',N'-tetrakis(2-pyridylmethyl) ethylenediamine (TPEN) was used as a heavy metal chelator with strong affinity for Zn²⁺. These effects were mitigated by TPEN. The application of ZnCl₂ reproduced the actions of S-PRG sealer extracts. These data suggest that S-PRG sealer has anti-inflammatory potential involving heavy metal ions such as Zn²⁺.