The effect of enalapril on inflammation and IL-1β and IL-8 production in chronic arthritis

Background and the purpose of the study: Angiotensin II (Ang II) other than acting as a vasopressor hormone has pro-inflammatory proper-ties. Since angiotensin-converting enzyme (ACE), is present in inflamed synovial membrane, in this study the effect of enalapril in modulation of inflammation and cytokine production in experimental induced chronic arthritis was investigated. Methods: Chronic joint inflammation was induced by antigen-induced arthritis method in rabbits and enalapril was given orally (7.5mg/kg/day) two weeks before (prophylaxis group) or two weeks after (treatment group) induction. Serum of arthritis's ACE activity was measured by HPLC, pro-inflammatory cytokines, IL-1 beta & IL-8 were measured in synovial fluid, and histology of knee joints was assessed in both groups. Results: Results revealed that enalapril reduced ACE activity in serum significantly (P=0.004), had no effect on IL-8 of synovial fluid and reduced the IL-1 beta production (P<0.05). Histological results revealed a significant reduction in villous hyperplasia and pannus formation (P<0.05 in both groups). While in prophylaxis group no bone erosion was observed and the cartilage was either intact or slightly invaded by synoviocytes, in non-treated group the cartilage was mostly invaded. Conclusion: Enalapril reduces production of pro-inflammatory cytokine IL-1 beta and severity of joint damage in chronic arthritis and may have therapeutics benefits in inflammatory joint diseases.