[Pterocarya hupehensis Skan total flavones ameliorate rheumatoid arthritis in rats by suppressing formation of neutrophil extracellular traps]

Objective: To investigate the therapeutic mechanism of Pterocarya hupehensis Skan total flavonoids (PHSTF) for rheumatoid arthritis (RA).

Methods: Twenty-five male SD rats were randomly divided into normal control group, RA model group, PHSTF treatment (45 and 90 mg/kg) groups, and Tripterygium glycosides (TPG) tablet (10 mg/kg) group (n=5). Except for those in the normal control group, all the rats were subjected to collagen-induced arthritis (CIA) modeling using a secondary immunization method, after which PHSTF and TPG were administered via gavage once daily for 4 weeks. After the treatments, serum levels of TNF-α and IL-1β were measured using ELISA, and ankle joint pathologies were assessed with HE staining; the expression of citrullinated histone H3 (Cit-H3), a neutrophil extracellular trap (NET) marker, in the ankle joints was evaluated with immunohistochemistry. In primary cultures of rat peripheral blood neutrophils stimulated with phorbol ester (PMA), the effects of PHSTF (100 and 200 μg/mL) on the expressions of Cit-H3, peptidylarginine deiminase 4 (PADI4), neutrophil elastase (NE), and myeloperoxidase (MPO) were examined with Western blotting; immunofluorescence assay was used to observe Cit-H3 expression and NET formation in the cells.

Results: In the CIA rat models, PHSTF significantly alleviated ankle swelling, decreased serum levels of TNF-α and IL-1β, improved histopathological changes in the ankle joints, and reduced Cit-H3 expression in both the serum and ankle joint cartilage. In the isolated rat neutrophils, PHSTF showed no significant effect on cell viability but strongly inhibited PMA-induced NET release.

Conclusion: PHSTF can alleviate RA by inhibiting the formation of NETs.