Papain-based gel is used for chemical-mechanical caries removal and present antimicrobial and anti-inflammatory activities. However, its effects on dental pulp cells and on macrophages remains largely unknown. Therefore, the aim of this study was to investigate whether the papain-based gel Papacárie Duo® acts as an immunomodulator in lipopolysaccharide (LPS)-activated macrophages and its effects on dental pulp cells . J774.1 macrophage and OD-21 dental pulp cells were stimulated with 0.5% and 5% of Papacárie Duo®, following pre-treatment or not with LPS. After 24 h, a lactate dehydrogenase assay was used to measure cytotoxicity, a tetrazolium-based colorimetric assay (MTT) was used to measure cell viability, and qRT-PCR was used to analyze relative gene expression of Ptgs2, Il10, Tnf, Mmp9, Runx2, Ibsp and Spp1. Papacárie Duo® was cytotoxic and reduced cell viability at 5% but not at 0.5% in both cultures. In macrophages, Papacárie Duo® increased the expression Il10 and LPS-induced Ptgs2, but it did not affect Tnf or Mmp9. In OD-21 cells, Papacárie Duo® inhibited Runx2 and Ibsp expression, but stimulated Spp1 expression. Papain-based gel presented a concentration dependent cytotoxicity, without affecting cell viability, for dental pulp cells and macrophages. Interestingly, the gel presented an inhibitory effect on pulp cell differentiation but modulated the activation of macrophages stimulated with LPS. We speculate that in dental pulp tissue, Papacárie Duo® would impair reparative dentinogenesis but could activate macrophages to perform their role in defense and inflammation.

Aim: Leukotriene B 4 (LTB 4 ) is a labile inflammatory lipid mediator important for host defense. We hypothesised that sustained delivery of LTB 4 would be a therapeutic strategy to prevent osteoclast cell differentiation in bone resorption in inflammatory diseases. Therefore, the aim of this study was to investigate the role of LTB 4 in differentiation of monocytic lineage cells into osteoclasts after stimulation with LTB 4 loaded in microspheres (MS). Design: LTB 4 -MS were prepared using an oilin-water emulsion solvent extraction-evaporation process. Sterility, LPS contamination, characterization and efficiency of LTB 4 encapsulation were investigated. J774A.1 cells were cultured in the presence of monocyte colony stimulating factor (M-CSF) and ligand for receptor activator of nuclear factor kappa B (RANKL) and then stimulated with LTB 4 -MS. Cytotoxicity was determined by lactate dehydrogenase assay, osteoclast formation by means of the activity of tartrate-resistant acid phosphatase enzyme and gene expression was measured by quantitative reverse transcription polymerase chain reaction to investigate regulation of Alox5, Alox5ap, Acp5, Mmp9, Calcr and Ctsk. Results: We found that 5-lipoxygenase pathway is involved in the osteoclastic differentiation hematopoietic lineage cells and that exogenous addition of LTB 4 -MS inhibited osteoclastogenesis induced by M-CSF and RANKL. The mechanism of LTB 4 -MS involved induction of Mmp9 gene expression and inhibition of Calcr and Ctsk, without changing Acp5. Conclusion: LTB 4 -MS inhibited differentiation of macrophages into an osteoclastic phenotype and cell activation under M-CSF and RANKL stimulus shedding light on a potential therapeutic strategy to prevent osteoclast differentiation.

To investigate osteoclast formation in vivo and if leukotriene B4 (LTB4) loaded in microspheres (MS) could be used as a therapeutical strategy to promote a sustained delivery of the mediator and prevent osteoclast differentiation. Methods: In vivo, apical periodontitis was induced in mice to investigate osteoclast differentiation and signaling in absence of 5-lipoxygenase (5-LO). In vitro, LTB4-MS were prepared using an oil-in-water emulsion solvent extraction-evaporation process. Characterization and efficiency of LTB4 encapsulation were investigated. J774A.1 macrophages were cultured in the presence of monocyte colony-stimulating factor (M-CSF) and ligand for receptor activator of nuclear factor kappa B (RANKL) and then stimulated with LTB4-MS. Cytotoxicity, in vitro MS-LTB4 uptake, osteoclast formation and gene expression were measured. Results: We found that 5-LO negatively regulates osteoclastic formation in vivo during apical periodontitis development. In vitro, LTB4-MS were up-taken by macrophages and were not cytotoxic to the cells. LTB4-MS inhibited osteoclast formation and the synthesis of osteoclastogenic genes Acp5, Mmp9, Calcr and Ctsk. LTB4-MS inhibited differentiation of macrophages into an osteoclastic phenotype and cell activation under M-CSF and RANKL stimulus.