Synovial fractalkine plays important role in cytokines’ related knee edema variation in rat arthritis model

Introduction: The systemic and local content of inflammatory cytokines and chemokines play substantial roles in pathophysiology of arthritis. This study was purposed to verify the roles of synovial TNF-α, IL-6 and fractalkine (Fkn) in edema changes during different stages of Complete Freund’s Adjuvant (CFA)-induced knee arthritis in rats. Methods: 168 male Wistar rats were divided in 7 groups and each group was divided to 4 subgroups. Each subgroup contains 6 male rats. Arthritis was evoked into the right knee joint. Changes in knee edema were evaluated by caliper and synovial TNF-α and IL-6 levels were assayed by rat standard ELISA kit in homogenized synovial tissues on days 0, 7, 14 and 21 of study. Synovial Fkn content was assessed during different stages of study using western blot. For analysis of within-groups differences, ANOVA followed by post hoc Tukeys was used. Unpaired student t-test was used for analysis of differences between groups. Results: CFA injection caused intense knee edema which was reduced by anti-TNF-α and anti-Fkn administration. In anti-IL-6 treated rats, knee edema was reduced in the first two weeks but increased on day 21 of study. Remarkable increase in synovial TNF-α, IL-6 and Fkn levels were observed after CFA treatment. Anti-TNF-α treatment reduced synovial levels of IL-6 and Fkn. Anti-IL-6 administration caused a reduction in synovial IL-6 level and an increase in TNF-α synovial level. Anti-Fkn administration caused a reduction in Fkn and TNF-α level. Conclusion: It seems that Fkn plays an important role in modulating the TNF-α and IL-6 effects on edema changes in CFA-induced inflammation.