Expression of Pro-inflammatory Protein S100A12 (EN-RAGE) in Behçet's Disease and Its Association with Disease Activity: A Pilot Study

BACKGROUND: S100A12 is a member of the S100 family of calcium-binding proteins and is secreted either in inflamed tissues or in the bloodstream by activated neutrophils. Expression of S100A12 has been reported in various diseases, especially non-infectious inflammatory diseases, such as Kawasaki disease, giant cell arteritis and inflammatory bowel disease. OBJECTIVE: This study was conducted to determine both the tissue expression and the serum levels of S100A12 in Behçet's disease (BD) patients and the correlation of the S100A12 serum level with disease activity of BD. METHODS: We included in this study ten BD patients who fulfilled the criteria for diagnosis, according to the International Study Group for BD. The activity of BD was calculated using the BD Current Activity Form. The serum concentrations of both S100A12 and interleukin-8 were measured by the enzyme-linked immunosorbent assay, before and after treatment. Immunohistochemical studies were also performed to detect S100A12 expression in the skin. RESULTS: The serum S100A12 level was significantly increased in the active BD period (p<0.001), in the inactive BD period (p=0.041) and in patients with active Kawasaki disease (p=0.028), compared with the serum level in the healthy controls. The serum S100A12 level decreased significantly from baseline, compared to post-treatment (p=0.017). The activity score of BD was significantly correlated with the serum level of S100A12 (Spearman's coefficient=0.464, p=0.039). Immunohistochemical studies showed that S100A12 was strongly expressed in the erythema nodosum-like skin lesions of patients. CONCLUSION: S100A12 contributes to the pathogenesis of BD related to neutrophil hyperactivity and reflects the disease activity in BD patients.