Initial periodontal treatment affects nucleotide-binding domain leucine-rich repeat-containing protein 3 inflammasome priming in peripheral blood mononuclear cells.

OBJECTIVE: Accumulating evidence suggests an association between periodontitis and several systemic diseases, such as atherosclerosis. In the lesions of these diseases, nucleotide-binding domain leucine-rich repeat-containing protein 3 (NLRP3), apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (ASC) and caspase-1 form inflammasome complex, which leads to the functional maturation of interleukin (IL)-1ß via cleavage of caspase-1 in macrophages. IL-1ß plays a critical role in the etiology of these diseases; however, inflammasome priming-specifically, IL-1ß and NLRP3 upregulation-is necessary for effective IL-1ß production. We investigated the effect of initial periodontal treatment on the inflammasome priming of peripheral blood mononuclear cells (PBMCs). METHODS: Twenty-two patients with chronic periodontitis were enrolled in this study and given initial periodontal treatment. Peripheral blood samples were collected at baseline and re-evaluation (41.1 ± 29.1 d after the treatment), and the relative expression of IL-1ß, and three inflammasome components, ASC, NLRP3 and Caspase-1, mRNA was determined using quantitative reverse transcription PCR. PBMCs were stimulated with silica crystals, and the IL-1ß secretion was measured via enzyme-linked immunosorbent assay. RESULTS: Probing pocket depth and bleeding on probing (BOP) were significantly improved after the treatment. Expression of IL-1ß and ASC in the PBMCs decreased after the treatment. PBMCs stimulated with silica crystals secreted IL-1ß. The treatment attenuated IL-1ß secretion by PBMCs in low BOP percentages group whereas IL-1ß secretion was increased in high BOP percentages group. CONCLUSION: Periodontal treatment altered the inflammasome priming status of the PBMCs, however, the effects on systemic diseases need to be further investigated.

Dental Calculus Stimulates Interleukin-1ß Secretion by Activating NLRP3 Inflammasome in Human and Mouse Phagocytes.

Dental calculus is a mineralized deposit associated with periodontitis. The bacterial components contained in dental calculus can be recognized by host immune sensors, such as Toll-like receptors (TLRs), and induce transcription of proinflammatory cytokines, such as IL-1ß. Studies have shown that cellular uptake of crystalline particles may trigger NLRP3 inflammasome activation, leading to the cleavage of the IL-1ß precursor to its mature form. Phagocytosis of dental calculus in the periodontal pocket may therefore lead to the secretion of IL-1ß, promoting inflammatory responses in periodontal tissues. However, the capacity of dental calculus to induce IL-1ß secretion in human phagocytes has not been explored. To study this, we stimulated human polymorphonuclear leukocytes (PMNs) and peripheral blood mononuclear cells (PBMCs) with dental calculus collected from periodontitis patients, and measured IL-1ß secretion by ELISA. We found that calculus induced IL-1ß secretion in both human PMNs and PBMCs. Calculus also induced IL-1ß in macrophages from wild-type mice, but not in macrophages from NLRP3- and ASC-deficient mice, indicating the involvement of NLRP3 and ASC. IL-1ß induction was inhibited by polymyxin B, suggesting that LPS is one of the components of calculus that induces pro-IL-1ß transcription. To analyze the effect of the inorganic structure, we baked calculus at 250°C for 1 h. This baked calculus failed to induce pro-IL-1ß transcription. However, it did induce IL-1ß secretion in lipid A-primed cells, indicating that the crystalline structure of calculus induces inflammasome activation. Furthermore, hydroxyapatite crystals, a component of dental calculus, induced IL-1ß in mouse macrophages, and baked calculus induced IL-1ß in lipid A-primed human PMNs and PBMCs. These results indicate that dental calculus stimulates IL-1ß secretion via NLRP3 inflammasome in human and mouse phagocytes, and that the crystalline structure has a partial role in the activation of NLRP3 inflammasome.