Euphorbium total triterpenes improve Freund's complete adjuvant-induced arthritis through PI3K/AKT/Bax and NF-κB/NLRP3 signaling pathways

Euphorbium is the resinous secretion of Euphorbia resinifera Berg. According to the record, Euphorbium was first used by Roman doctors to treat the emperor's joint pain. In China, it is applied in folk medicine to treat damp-cold or mucous diseases, such as arthralgia and ascites, etc. This herb is used for rheumatoid arthritis and skin tumors in the folklore of northeastern Brazil. Triterpenes are mainly characteristic constituents of Euphorbium, and possibly possess anti-rheumatoid arthritis.To explore the preventive effect of Euphorbium total triterpenes (TTE) on Freund's complete adjuvant (FCA) induced arthritis in rats and its mechanism.TTE was extracted and isolated from Euphorbium, and its components were analyzed by HPLC. The safety of TTE was evaluated by an acute toxicity test in mice. Arthritis was induced in rats by injecting 0.2 mL FCA into the right hind paw toe, except for the control group, which was given the same volume of physiological saline. Tripterygium Glycosides (TG, 7.5 mg/kg) and TTE (32, 64 and 128 mg/kg) were administered by gavage for 30 days. Body weights, paw swelling, and arthritic scores were measured during the experiment process. After 30 days, blood and joints were harvested to determine various indicators of arthritis.The contents of euphol and euphorbol in TTE were 47.03% and 18.77% respectively, and the maximal feasible dose of TTE in mice is 12 g/kg. The experimental results showed that arthritis indicators in rats deteriorated after FCA inducement compared with the control group. After treatment with TTE, the swelling degree and histopathological change of the hind paws in rats were significantly improved as well as arthritic score; the serum TNF-α, CRP, IL-1β, IL-6, IL-18 and RF levels in rats were significantly reduced; The expression of PI3K, AKT, P-AKT, Bcl-2, NF-κB, NLRP3 and Pro-caspase-1 protein in joint tissue were down-regulated, and the expression of Bax protein was up-regulated.The results suggested that TTE possessed anti-arthritis effects, and its mechanism may be related to its anti-inflammatory and immunomodulatory properties, as well as regulation of PI3K/AKT/Bax and NF-κB/NLRP3 signaling pathway.