Psoriasis and Periodontitis Are Chronic Inflammatory Diseases That May Share Common Immunopathogenic Pathways. TNF-α, IL-17A, and YKL-40 Are Inflammatory Biomarkers Associated With Both Conditions. This Study Aims to Evaluate the Levels of These Markers in Saliva and Serum of Individuals With Psoriasis, Considering Their Periodontal Status, to Investigate a Potential Link Between the Two Diseases

Periodontitis is a chronic inflammatory disease affecting the supporting structures of the teeth, characterized by gingival inflammation, destruction of periodontal tissues, and alveolar bone loss. The disease primarily develops due to bacterial colonization at the tooth-gingival interface. Inflammatory mediators released in response to the interaction between a dysbiotic microbial biofilm and the host immune system play a critical role in tissue destruction and disease progression. Systemic conditions that affect the host immune system may exacerbate periodontal destruction in this multifactorial disease.

Psoriasis is a chronic inflammatory skin condition characterized by erythematous plaques or papules covered with silvery-white scales. The prevalence ranges between 1% and 3%, depending on the ethnic population, and it affects both genders equally. Although the exact etiopathogenesis of psoriasis remains unclear, several environmental and systemic factors-such as trauma, ultraviolet radiation, infections, medications, endocrine influences, psychological stress, alcohol consumption, and smoking-have been identified as potential triggers.

A possible association between psoriasis and periodontitis has been reported in multiple clinical studies and meta-analyses. Interleukin-17 (IL-17) is a pro-inflammatory cytokine that induces the expression of various inflammation-related mediators. It plays a central role in immune regulation and is implicated in inflammatory diseases, autoimmune disorders, and cancer. Elevated IL-17A levels have been detected in both psoriatic skin and serum samples of individuals with psoriasis when compared to healthy controls.

Tumor necrosis factor-alpha (TNF-α) is a polypeptide cytokine produced primarily by macrophages and monocytes. It functions as a multipotent regulator in immune responses by stimulating fibroblasts to release collagenase, increasing vascular permeability, promoting the release of other cytokines (such as IL-1α, IL-1β, IL-6, and IL-8), and enhancing the production of matrix metalloproteinases and adhesion molecules. TNF-α also synergizes with IL-1 to promote bone resorption. Elevated TNF-α levels in both serum and psoriatic lesions have been shown to decrease following effective treatment.

YKL-40 is a 40-kDa glycoprotein composed of tyrosine (Y), lysine (K), and leucine (L) at its N-terminal. It is secreted by neutrophils, macrophages, chondrocytes, synovial cells, osteoblasts, endothelial cells, and cancer cells. YKL-40 is associated with immune responses involving inflammation, tissue remodeling, and angiogenesis, and is considered an acute-phase protein.