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.

Abstract:Background: Health behavioral patterns, especially eating patterns, established in childhood often carry over into adulthood, and some of the unhealthy ones are later associated with adult morbidity and mortality. Recently, a few nutrition and food safety education programs have been implemented in primary and junior high schools in China. Purpose: This study aims to examine the effectiveness of a school-based nutrition and food safety education program among primary and junior high school students in China. Methods: A mixed study design incorporating an intervention study and a quantitative survey was conducted for this research. With stratified cluster sampling, students from the 5 th and 6 th grade in one primary school and the 7 th and 8 th grade in one junior high school in Chongqing, China, were all selected and separated randomly into an intervention group (n = 501) and a control group (n = 522). Effectiveness evaluation investigations were performed at the initial time and nine-month follow-up (n = 472), respectively. Effectiveness of pre-/post-intervention and nine-month follow-up changes in scores of nutrition knowledge and food safety was assessed using a two-tailed t-test and analysis of variance. Results: Nutrition knowledge scores for the intervention group were mean 9.03, SD±2.75 at the baseline, and 14.70±3.28 after intervention. There was a significant improvement (t = 29.78, p < 0.01). The nine-month follow-up knowledge scores of the intervention group were 12.35±2.89, which were lower than the immediately after the intervention group (t = 12.40, p<0.01), but higher than those of the baseline level (t = 18.04, p < 0.01). Food safety scores of the postintervention were higher (p < 0.01) than that of the control group in both pre-intervention and nine-month follow-up. The control group had no significant change in the pre-post intervention. Conclusions: It is feasible and effective to improve nutrition and food safety knowledge among primary and junior high school students through school-based nutrition and food safety education programs. (Global Health Promotion, 2016; 23(1): 37-49)

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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.