Anethole reduces inflammation and joint damage in rats with adjuvant-induced arthritis.

Aim: This study evaluated whether anethole attenuates the inflammatory response and joint damage in a model of adjuvant-induced arthritis (AIA) in rats.

Methods: The animals were treated with 62.5-, 125-, or 250-mg/kg anethole daily for 21 days after AIA and necropsied on days 14 and 21 to evaluate the number of serum and synovial leukocytes (total and differential), serum cytokines (IL-2, IL-6, IL-12, IL-17, and TNF-α), and nitric oxide concentrations. Morphologic changes in the cartilage and bone of the femorotibial articulation in both left paw and right paw were studied in hematoxylin/eosin and Sirius Red-hematoxylin sections.

Results: Different doses of anethole suppressed paw swelling and the number of serum and synovial leukocytes. However, 250 mg/kg of anethole more effectively controlled local and systemic inflammation. Histological evaluation revealed significant prevention of cartilage damage and inflammatory infiltrate scores. Morphometric analysis showed pannus formation, the thickness of the articular cartilage, and bone resorption lower in the anethole-treated AIA group compared to untreated AIA group on both days 14 and 21. These significant anti-inflammatory effects in the anethole-treated AIA group were associated with downregulation of cytokines and nitric oxide levels.

Conclusion: Therefore, anethole may be a useful intervention to treat inflammatory arthritis.