Navel orange peel ethanolic extract and naringin ameliorate CFA-induced arthritis in Wistar rats through their modulatory effects on Th1/Th2/Th17 cytokines and oxidative stress

Rheumatoid arthritis (RA) is an autoimmune illness affecting joint articulations, leading to a disability state. Currently, there is no satisfying optimal therapy except for immunosuppressants, which have variable and bad effects after long-term use. Hence, researchers have attempted to develop other alternative, safer, and more effective natural treatment agents that are effective and without undesirable effects. The objective of this research is to assess the antiarthritic properties of navel orange peel ethanolic extract (NOPEE) and naringin (NAR) in experimentally induced RA in male Wistar rats. RA was induced via two successive subcutaneous injections of 0.1 mL complete Freund's adjuvant (CFA) into a footpad of the right hind leg. The arthritic rats were orally treated with 100 mg/kg body weight (b.w.)/day of NOPEE or with 25 mg/kg b.w./day of NAR for 14 days. Results showed that treatment with NOPEE or NAR obviously counteracted the increased ankle joint circumference, inflammatory cell infiltration, pannus development, cartilage degradation, and synovial hyperplasia that developed in CFA-induced arthritic rats. Additionally, the elevation of serum rheumatoid factor (RF), prostaglandin E2 (PGE-2), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-17 (IL-17) were significantly declined in parallel to enhanced level of serum interleukin-4 (IL-4). Furthermore, NOPEE and NAR supplementation, reversed the negative oxidative effects of lipid peroxidation (LPO), nitric oxide (NO), as well as improved the antioxidant glutathione level (GSH), glutathione reductase (GR) and superoxide dismutase (SOD) activities. Overall, the anti-arthritic effects of NOPEE and NAR may be mediated through their modulatory effects on T helper (Th)1/Th2/Th17 cytokines, oxidative stress, and the antioxidant defense system.