The role of iNOS and PHOX in periapical bone resorption.

Nitric oxide (NO) and reactive oxygen species (ROS) are key molecules in resistance to pathogens. Little is known about their role in pathogenesis of periapical lesions. To address this issue, we induced periapical lesions in mice lacking nitric oxide synthase (iNOS(-/-)) or phagocyte oxidase (PHOX(-/-)). iNOS(-/-) mice expressed higher levels of IL-1ß, TNF-α, RANK, RANKL, and MCP-1 than C57BL/6 and PHOX(-/-). Apical thickening of the periodontal ligament was also greater in iNOS(-/-) compared with other groups. Interestingly, ROS production did not interfere in periapical lesion progression, but seemed to be essential for the appearance of multinucleated TRAP-positive cells. Thus, periapical lesion progression in iNOS(-/-) was associated with an imbalance of pro-inflammatory cytokines (IL-1ß and TNF-α), bone-resorptive modulators (RANK and RANKL), and MCP-1. We conclude that NO, but not ROS, controls progression of bone resorption in a murine experimental model of apical periodontitis.

The effect of mineral trioxide aggregate on phagocytic activity and production of reactive oxygen, nitrogen species and arginase activity by M1 and M2 macrophages.

AIM: To assess the influence of co-culture with mineral trioxide aggregate (MTA) on phagocytosis and the production of reactive oxygen intermediates (ROI) and nitrogen (NO) species and the arginase activity by M1 and M2 peritoneal macrophages. METHODOLOGY: Cellular viability, adherence and phagocytosis of Saccharomyces boulardii were assayed in the presence of MTA. Macrophages were stimulated with zymosan for ROI assays and with Fusobacterium nucleatum and Peptostreptococcus anaerobius and IFN-gamma for NO production and arginase activity, when in contact with capillaries containing MTA. Data were analysed by T, anova, Kruskall-Wallis and Mann-Whitney tests. RESULTS: M2 macrophages displayed greater cellular viability in polypropylene tubes, greater ability to ingest yeast and smaller production of ROI and higher arginase activity when compared with M1 macrophages. Both macrophages, M1 and M2, presented similar cell adherence and NO production. The addition of bacterial preparations to macrophages interfered with NO and arginase productions. MTA did not interfere with any of the parameters measured. CONCLUSIONS: Phagocytosis and the ability of the two macrophage subtypes to eliminate microbes were not affected by MTA.

Effect of mineral trioxide aggregate on cytokine production by peritoneal macrophages.

AIM: To test the effect of two commercial brands of grey mineral trioxide aggregate (ProRoot and MTA-Angelus) on cytokine production by M1 and M2 inflammatory macrophages. METHODOLOGY: M1 (from C57BL/6 mice) and M2 peritoneal inflammatory macrophages (from C57BL/6 IL12p40-/- mice) were obtained and cultured in vitro in the presence of MTA. The cellular viability and the production of tumour necrosis factor-alpha, interleukin (IL)-12 and IL-10 in response to stimulation with interferon-gamma and Fusobacterium nucleatum or Peptostreptococcus anaerobius were evaluated. Data were analysed by Mann-Whitney, Kruskal-Wallis and anova tests. RESULTS: The cements did not interfere with cellular viability or with cytokine production by either type of macrophage. However, M2 macrophages produced higher levels of IL-10 when stimulated with F. nucleatum than M1 macrophages (P < 0.05). CONCLUSIONS: The brands of MTA evaluated did not interfere in the cytokine response by M1 or M2 macrophages to the two bacteria tested. However, a difference in cytokine production between the two types of macrophages was found.