Study on p-Hydroxybenzoic Acid on Rheumatoid Arthritis Via Inhibiting NF-κB/caspase-1 Signaling Pathway

OBJECTIVE To investigate the therapeutic effect of natural phenolic compound p-hydroxybenzoic acid(HA) on adjuvant arthritis(AA) induced by the complete Freund's adjuvant(CFA), and to clarify the mechanism of HA preliminary. METHODS Apart from the normal group, all rats received 0.1 mL CFA by plantar subcutaneous injection to induce AA rats model. And rats with AA were randomized to the model group, the low-, medium-, and high-dose HA group(2.5, 5, and 10 mg·kg^-1, respectively), the positive control group(indomethacine, 5 mg·kg^-1). The rats in each group were orally treated with the corresponding drugs for therapeutic intervention. The volume and leg thickness of the rats in each group were recorded and an inflated articular score was obtained. Inflammation cytokine expression(TNF-α, IL-1β and IL-6) was determined by ELISA and qPCR. Radiographs and HE staining were used to observe histopathological and pathological changes in the foot. The expressions of caspase-1 and NF-κB were examined in Western blotting. RESULTS HA could significantly alleviate joint swelling in AA rat(P<0.05), inhibited the production of inflammatory factors(TNF-α, IL-1β and IL-6) from protein and mRNA levels(P<0.05), and decreased the expression levels of caspase-1 and NF-κB at protein level(P<0.05). HA alleviated ankle injury in rats by X-ray examination, and HE staining showed that HA could significantly inhibit the infiltration of inflammatory cells and the destruction of cartilage surface(P<0.05), and these results were dose-dependent. CONCLUSION HA may relieve rheumatoid arthritis by inhibiting the NF-κB/casepase-1 signaling pathway.