Evaluation of TNF-α, IL-17A and YKL-40 levels in Saliva and serum of patients with psoriasis

Objective: Periodontitis is a chronic inflammatory disease triggered by microbial infections that lead to the destruction of tissues supporting the teeth. Psoriasis, on the other hand, is a chronic skin disease characterized by the excessive proliferation and abnormal differentiation of keratinocytes. Due to the presence of similar inflammatory mechanisms, this study aimed to investigate the immunological relationship between psoriasis and periodontal disease by examining TNF-α, IL-17A, and YKL-40 levels in the saliva and serum of systemically healthy individuals and individuals with psoriasis. Methods: Our study was divided into three main groups: systemically and periodontally healthy (S), a systemically healthy control group, and a psoriasis group. The systemically healthy control group was further subdivided into control gingivitis (KG) and control periodontitis (KP) groups, while the psoriasis group was divided into psoriasis gingivitis (PG) and psoriasis periodontitis (PP) groups. TNF-α, IL-17A, and YKL-40 levels in saliva and serum were measured, and correlations of these cytokines with each other and with clinical periodontal parameters (PI, BOP, PPD, CAL) were evaluated. Results: In intergroup comparisons, the lowest salivary TNF-α level was found in the S group, while the highest was in the PP group; TNF-α levels in the KP and PP groups were significantly higher than in the S group. Serum TNF-α levels were lowest in the S group and highest in the PP group, with significantly higher levels in the PG and PP groups compared to the S, KG, and KP groups. Salivary IL-17A levels were lowest in the S group and highest in the PP group; KP and PP groups showed significantly higher levels than the S group, and the PP group was significantly higher than the KG, PG, and KP groups. Serum IL-17A levels were lowest in the S group and highest in the PP group; KP, PG, and PP groups had significantly higher levels than the S group, and the PP group was significantly higher than the KG and KP groups. Salivary YKL-40 levels were lowest in the S group and highest in the PP group; significant differences were found between the S group and KP, PG, and PP groups, while no difference was observed between the PP and KP groups. Serum YKL-40 levels were lowest in the S group and highest in the PP group, with significant differences between the S group and KP, PG, and PP groups, and between KP and PP groups (p <0.05). Additionally, in the systemically healthy groups, positive correlations were found between salivary TNF-α and BOP; serum TNF-α and PI, BOP, PPD, CAL; salivary IL-17A and PI, BOP, PPD, CAL; serum IL-17A and PI, BOP; salivary YKL-40 and PI, BOP, PPD, CAL; and serum YKL-40 and PI, BOP (p <0.01). Conclusion: The findings of our study suggest that the changes in salivary and serum TNF-α, IL-17A, and YKL-40 levels in individuals with psoriasis and healthy individuals may indicate an immunological relationship between psoriasis and periodontitis. Keywords: periodontitis, psoriasis, TNF-α, IL-17A, YKL-40