Programmed death 1 ligand 1 (PD-L1) is a negative co-stimulatory molecule in immune responses. Previous reports have indicated that inflammatory cytokines can upregulate the expression of PD-L1 in tumor cells, which in turn suppresses host immune responses. Periodontitis is characterized by persistent inflammation of the periodontium, which is initiated by infection with oral bacteria and results in damage to cells and the matrices of the periodontal connective tissues. In the present study, the expression and function of PD-L1 in periodontal tissue destruction were examined. Periodontal ligament cells (PDLCs) were stimulated by inflammatory cytokines and periodontal pathogens. The expression and function of PD-L1 on the surface of PDLCs was investigated using flow cytometry in vitro. Periodontal disease was induced by the injection of Porphyromonas gingivalis in mouse models. The expression levels of PD-L1 in the periodontal tissues of the mice were analyzed using flow cytometry and immunohistochemistry. PD-L1 was inducibly expressed on the PDLCs by the inflammatory cytokines and periodontal pathogens. The inflammation-induced expression of PD-L1 was shown to cause the apoptosis of activated T lymphocytes and improve the survival of PDLCs. Furthermore, in the mouse model of experimental periodontitis, the expression of PD-L1 in severe cases of periodontitis was significantly lower, compared with that in mild cases. By contrast, no significant differences were observed between the healthy control and severe periodontitis groups. The results of the present study showed that the expression of PD-L1 may inhibit the destruction of periodontal tissues, indicating the involvement of a possible protective feedback mechanism against periodontal infection.

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Background:Occlusal trauma is an important factor promoting bone loss caused by periodontal diseases. Although there are reports of traumatic force promoting bone resorption in periodontal diseases, no studies examining the inhibition of bone formation by traumatic force and the underlying mechanism have been reported. The aim of this study was to investigate the mechanism whereby traumatic force inhibits bone formation.Methods: MC3T3-E1 cells were induced to undergo osteogenic differentiation and subjected to cyclic uniaxial compressive stress with or without stimulation with Pg. LPS. The expression of osteoblast markers and the activation of IKK-NF-B signaling were evaluated in vitro. Then, MC3T3-E1 cells were induced to undergo osteogenic differentiation and subjected to cyclic uniaxial compressive stress with or without IKK-2 Inhibitor VI. The expression of osteoblast markers was determined. Then, the classic Wnt signaling pathway ( -catenin, Gsk3 , p-Gsk3 , and Dkk1) was further evaluated in vitro. Finally, occlusal trauma was induced in Wistar rats with or without the injection of IKK-2 Inhibitor VI, to evaluate changes in bone mass and IKK-NF-B and Wnt/ -catenin signaling in vivo. Results:After stimulation with Pg. LPS and traumatic force, IKK-NF-B signaling was significantly activated in vitro. The expression of osteoblast markers and the activity of alkaline phosphatase in MC3T3-E1 cells declined after traumatic force loading and were rescued when IKK-NF-B signaling was blocked. Wnt/ -catenin signaling was accordingly inhibited upon force loading, but this inhibition was reversed when IKK-NF-B was antagonized in vitro. X-ray and Micro-CT analysis of the mandibles of the rats as well as HE and TRAP staining showed that bone loss induced by occlusal trauma declined after IKK-NF-B was inhibited. The expression of p65 and I B was increased when occlusal trauma was induced in Wistar rats, whereas -catenin, OCN, and Runx2 levels were decreased. After J Periodontol. 2020;91:683-692.

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The association between inflammation and cancer provides a new target for tumor biotherapy. The inflammatory cells and molecules within the tumor microenvironment have decisive dual roles in antitumor immunity and immune evasion. In the present study, phytohemagglutinin (PHA) was used to stimulate peripheral blood mononuclear cells (PBMCs) to simulate the tumor inflammatory microenvironment. The effect of immune cells and inflammatory cytokines on the surface expression of programmed cell death-1 ligand 1 (PD-L1) and tumor immune evasion was investigated using flow cytometry (FCM) and an in vivo xenotransplantation model. Based on the data, PHA-activated, but not resting, immune cells were able to promote the surface expression of PD-L1 in Tca8113 oral squamous carcinoma cells via the secretion of inflammatory cytokines, but not by cell-cell contact. The majority of the inflammatory cytokines had no significant effect on the proliferation, cell cycle progression and apoptosis of the Tca8113 cells, although they each induced the expression of PD-L1 in a dose-dependent manner. In total, 99% of the Tca8113 cells expressed PD-L1 following treatment with the supernatant of PHA-stimulated PBMCs. The PHA-supernatant pretreated Tca8113 cells unusually induced Tca8113 antigen-specific CD8+ T cell apoptosis in vitro and the evasion of antigen-specific T cell attraction in a nude mouse tumor-bearing model. These results indicate a new mechanism for the promotion of tumor immune evasion by the tumor inflammatory microenvironment

Salivary analysis can be used to assess the severity of caries. Of the known salivary proteins, a paucity of information exists concerning the role of proteinase 3 (PR3), a serine protease of the chymotrypsin family, in dental caries. Whole, unstimulated saliva was collected from children with varying degrees of active caries and tested using a Human Protease Array Kit and an enzyme-linked immunosorbent assay. A significantly decreased concentration of salivary PR3 was noted with increasing severity of dental caries (P<0.01); a positive correlation (r=0.87; P<0.01; Pearson's correlation analysis) was also observed between salivary pH and PR3 concentration. In an antibacterial test, a PR3 concentration of 250 ng·mL−1 or higher significantly inhibited Streptococcus mutans UA159 growth after 12 h of incubation (P<0.05). These studies indicate that PR3 is a salivary factor associated with the severity of dental caries, as suggested by the negative relationship between salivary PR3 concentration and the severity of caries as well as the susceptibility of S. mutans to PR3.

Background and Objective Diabetes influences the frequency and development of periodontitis. Inflammation of human periodontal ligament cells (HPDLCs) participates in this pathologic process. Hence, this study aims to explore whether advanced glycation end products (AGEs), by‐products of diabetes, could exaggerate inflammation induced by muramyl dipeptide (MDP) in HPDLCs, and whether nucleotide‐binding oligomerization domain‐like receptors (NLRs) signaling pathway was involved. Material and Methods Human periodontal ligament cells were pre‐treated with 100 μg/mL AGEs for 24 hours and stimulated with 10 μg/mL MDP for 24 hours. IL‐6, IL‐1β, and RAGE were detected, and the activation of NF‐κB signaling pathway was observed. The expression of NLRs was evaluated with or without silencing RAGE or blocking NF‐κB pathway under AGEs stimulation. Statistical analyses were performed by using independent sample t test. Results Advanced glycation end products induced significant increase of inflammatory cytokines in HPDLCs (P < 0.05). Results of western blot (WB) showed that after 45 minutes stimulation of AGEs, p‐p65/p65 ratio peaked; AGEs promoted the expression of NLRP1, NLRP3, and apoptosis‐associated speck‐like protein containing a CARD (ASC). After silencing RAGE or blocking NF‐κB pathway, the up‐regulation of NLRs protein caused by AGEs was attenuated. Additionally, AGEs pre‐treatment could enhance the inflammatory response of MDP and the expression of NLRs, which were demonstrated by more expression of IL‐6, IL‐1β, NOD2, NLRP1, NLRP3, and ASC. Conclusion Advanced glycation end products induced inflammatory response in HPDLCs via NLRP1‐inflammasome and NLRP3‐inflammasome activation in which NF‐κB signal pathway was involved. Besides, AGEs promoted the inflammatory response of MDP via NOD2, NLRP1‐inflammasome, and NLRP3‐inflammasome.

IKK-NF-κB signaling in MC3T3-E1 cells may be activated by proinflammatory cytokines that are produced as a consequence of mechanical stress loading and not by direct compressive mechanical stress.