Protective effects of total flavonoids of Astragalus against adjuvant-induced arthritis in rats by regulating OPG/RANKL/NF-κB pathway

BACKGROUND

Astragalus membranaceus Bunge is one of the oldest and most frequently used crude herbs in traditional Chinese medicine. The total flavonoids of Astragalus (TFA) are the main active components isolated from Astragalus membranaceus Bunge. Our recent study has shown its potential immunomodulatory and anti-inflammatory effects in vivo and in vitro. However, its anti-arthritic effects and mechanisms of action involved have not been elucidated. The aim of this study was to evaluate the protective effects and possible mechanisms of TFA on Freund's complete adjuvant (FCA)-induced arthritis in rats.

METHODS

Wistar rats were intradermally injected FCA into the right hind metatarsal footpads to establish adjuvant-arthritic model. The rats were intragastrically administered daily with TFA at 25, 50 and 100mg/kg for 28days after FCA induction. Body weight, primary paw swelling, arthritis index, thymus and spleen indices were measured. The levels of serum tumor necrosis factor (TNF)-α, interleukin (IL)-1β, prostaglandin (PG)E₂, osteoprotegerin (OPG) and receptor activator of nuclear factor-κB ligand (RANKL) were determined using ELISA. Histopathological changes and scores in joint tissues were examined using hematoxylin and eosin (H&E). The expression of nuclear factor (NF)-κB p65 in synovial tissues was assayed using immunohistochemical method.

RESULTS

TFA significantly increased body weight, attenuated primary paw swelling and arthritis index, decreased thymus and spleen indices of rats induced by FCA. Furthermore, TFA significantly inhibited serum TNF-α, IL-1β, PGE₂ and RANKL production, and promoted serum OPG production and OPG/RANKL ratio of rats induced by FCA. Histopathological examination indicated that TFA significantly attenuated inflammatory cell infiltration, synovial hyperplasia, pannus formation, and bone and cartilage damage. Immunohistochemical assay indicated that TFA inhibited NF-κB p65 expression in synovial tissues of rats induced by FCA.

CONCLUSIONS

These results suggest that TFA exerts potential protective effects against FCA-induced arthritis in rats by regulating OPG/RANKL/NF-κB pathway.

Protective effects of piperlongumine against adjuvant-induced arthritis in rats through modulating OPG/RANKL/NF-κB signaling pathway

OBJECTIVES

We examined the antirheumatoid effects of piperlongumine (PLM) on rat adjuvant-induced arthritis (AIA) and explored the underlying mechanisms involved.

METHODS

PLM (2.5, 5, and 10 mg/kg) was administered intraperitoneally to AIA rats to assess its effectiveness. Blood, thymus, spleen, ankle joint, and synovial tissue samples were gathered for subsequent analyses, like enzyme-linked immunosorbent assay, thymus/spleen index measurement, ankle joint pathological examination, immunohistochemistry assay, polymerase chain reaction, and western blot assay. Moreover, the involvement of osteoprotegerin (OPG)/receptor activators of nuclear factor κB ligand (RANKL)/nuclear factor-κB (NF-κB) signaling was investigated.

KEY FINDINGS

PLM effectively relieved inflammation and joint destruction in AIA rats, as indicated by reductions in hind paw swelling, arthritis index, thymus/spleen index, ankle joint pathological damage, production of TNF-α, IL-1β, and IL-6 in both serum and synovium, and osteoclast formation. Also, PLM treatment raised OPG production, reduced RANKL expression, and elevated the OPG/RANKL ratio in synovial tissues. Furthermore, PLM prevented IκBα degradation and phosphorylation, resulting in a reduced expression of the nuclear NF-κB p65 protein in AIA rat synovial tissues.

CONCLUSIONS

PLM demonstrated strong antiarthritic effects in rats with AIA by influencing the OPG/RANKL/NF-κB signaling pathway, highlighting its potential clinical relevance in treating rheumatoid arthritis.