Adhesins, Bacterial ; Biomedical Research ; Fusobacterium nucleatum

Increasing scientific evidence supports the positive relationship between inflammation and cancer development. The immune response initiated by pattern recognition receptors is critical to triggering of tumor-associated inflammation. Triggering receptor expressed on myeloid cells (TREM) is an immunoglobulin of the super transmembrane glycoprotein family, which is mainly expressed on select groups of myeloid cells. The most important members of TREM comprise TREM-1 and TREM-2. Activation of TREM-1 and TREM-2 signaling is initiated upon binding of their ligands. Subsequently, cross-linking reactions of downstream effectors occur, resulting in inflammation regulation. Recently, the connection between TREM and malignant tumors has been widely noticed and studied. This review summarizes studies of association between TREM-1, TREM-2, and malignant tumors in the medical field to provide new ideas for study on the correlation between periodontitis and oral cavity cancer.

Objective: To illuminate the temporal expression of the triggering receptor expressed on myeloid cells-1 (TREM-1) in the experimental periodontitis in rat and to investigate the function of TREM-1 in the pathogenesis of experimental periodontitis in rat. Methods: The experimental periodontitis model was established in the maxillary first molar by means of 'wire ligation + vaccination periodontal pathogen Porphyromanus gingivalis (Pg) + high-sugar diet' in Sprague-Dawley (SD) rats. The experimental animals were divided into six groups: the control group and each of the time points of establishing the models for one week and two to five weeks. There were six rats for each of the six groups. The bone loss of the palatal site was calculated to estimate whether the periodontitis model was successfully established. The expression of TREM-1, proinflammatory cytokines: tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6, anti-inflammatory cytokines: IL-4, IL-10 and transforming growth factor-β (TGF-β) were examined by using quantitative real-time PCR. The expression level of TREM-1 protein was analyzed by the method of immunohistochemistry. Results: The average bone loss area of the palatal site was (0.17±0.04) mm² in the group of three weeks and was statistically significant (P<0.05) compared to the control group [(0.10±0.01) mm²]. The experimental periodontitis model was successfully established in the group of three weeks. The expression of TREM-1 increased significantly in the inflamed periodontal tissues and reached to its maximum expression in the three weeks group accounting for 159.50±38.26 in protein expression and 4.35±0.60 in mRNA expression, respectively. TREM-1 expression difference between the three weeks group and control group was statistically significant (P<0.01). The expression of IL-6 by gingival tissues was correlated with the mRNA level of TREM-1 (r=0.813 P=0.049). Conclusions TREM-1, as a proinflammatory receptor, could facilitate the periodontal inflammatory response. The possible way of TREM-1 to promote inflammation may be through controling the expression of IL-6.