Elevated serum levels of TNF-α and IL-17 in psoriatic and rheumatoid arthritis

Psoriatic arthritis (PsA) and rheumatoid arthritis (RA) are chronic inflammatory immune-mediated rheumatic diseases, in which cytokine dysregulation is key for pathogenesis. In terms of the specific processes involved in predominantly enthesopathic inflammation and predominantly synovial inflammation, PsA and RA are distinct disease entities. The aim of the present study was to investigate the serum cytokine expression profiles of TNF-α and IL-17 in the two inflammatory arthropathies, discussing their role in the context of disease activity assessed by means of DAS28-CRP, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). The study included 32 patients with PsA, 30 with RA and 20 healthy subjects. In patients with RA and PsA, higher serum levels of both cytokines were measured compared to healthy controls, with the difference being significant, except for TNF-α for patients with PsA, whose concentration was numerically but not significantly higher compared to healthy individuals. We also recorded a significant increase in circulating TNF-α in RA versus PsA, with no difference for IL-17 in the two inflammatory joint diseases. The two studied cytokines did not show a significant difference in serum concentrations according to the state of the disease activity (DAS28- CRP < 3.2 vs. DAS28- CRP ≥ 3.2) in both PsA and RA, as well as association with clinical and laboratory parameters of activity from correlation analyses, supporting the claim that they are not useful markers for its assessment. In conclusion, both cytokines are clearly abundant in the circulation in conditions of both inflammatory arthropathies. The TNF-α and IL-17 pathways are important links and an active participant in these types of rheumatic inflammation.