The role of IL-18 and related mediators in periodontal health and disease

ABSTRACT THE ROLE OF IL-18 AND RELATED MEDIATORS IN PERIODONTAL HEALTH AND DISEASE Interleukin-18 (IL-18) is one of the key regulators of the pro-inflammatory response and exerts its effects through the α (IL-18Rα) and β (IL-18Rβ) subunits of the IL-18 receptor, as well as via signaling pathway components such as Myeloid Differentiation Primary Response 88 (MYD88), Tumor Necrosis Factor Receptor-Associated Factor 6 (TRAF6), Nuclear Factor kappa-B (NF-κB), and the Toll/IL-1 receptor (TIR) domain. The IL-18 signaling pathway is known to play a role in cytokine production, immune cell activation, and tissue destruction processes in the pathogenesis of periodontal diseases. The study included periodontally healthy controls, periodontitis grade B, and periodontitis grade C groups, with 18 individuals in each group, for a total of 54 participants. Gingival crevicular fluid (GCF) samples were analyzed for biomarker levels using the enzyme-linked immunosorbent assay (ELISA) method. According to the results, IL-18Rα levels were higher in the healthy group compared with grade B (p = 0.008), but lower compared with grade C (p = 0.018); in addition, grade B levels were lower than grade C (p = 0.026). No significant differences were observed among the groups in terms of IL-18Rβ and TIR levels (p > 0.05). MYD88 levels were significantly higher in the healthy group compared with grade C (p = 0.012), whereas no significant differences were found between grade B and the other groups (p > 0.05). TRAF6 levels in the healthy group were significantly lower than those in the periodontitis grade B (p = 0.016) and grade C (p = 0.027) groups, with no statistically significant difference between grade B and grade C (p > 0.05). A positive, moderate correlation was detected only between TRAF6 and clinical attachment loss (CAL) (p = 0.003). No significant differences were observed among the groups regarding NF-κB levels (p > 0.05). Keywords: Periodontitis, IL-18, IL-18Rα, IL-18Rβ, MYD88, TRAF6, NF-κB, TIR, Clinical Attachment Level