Total triterpenes of Euphorbium alleviates rheumatoid arthritis via Nrf2/HO-1/GPX4 pathway

Abstract

This study aims to investigate the effect and mechanism of total triterpenes of Euphorbium in treating rheumatoid arthritis(RA). The rat model of RA was established with Freund's complete adjuvant(FCA). Male rats were randomly assigned into control, model, Tripterygium glycosides(7.5 mg·kg~(-1)), and low-, medium-, and high-dose total triterpenes of Euphorbium(32, 64, and 128 mg·kg~(-1), respectively) groups, with 10 rats in each group. In other groups except the control group, 0.2 mL FCA was injected into the right hind toe. Rats in the intervention groups were administrated with corresponding drugs by gavage, and the control group and the model group with the same volume of 0.5% CMC-Na solution once a day. During the treatment period, the swelling degree of the hind paw was measured and the arthritis was scored until day 30. At the end of drug administration, the pathological changes of the joint tissue were observed by hematoxylin-eosin staining. The content of malondialdehyde(MDA), glutathione(GSH), and Fe~(2+) and the activity of superoxide dismutase(SOD) in the joint tissue were measured by biochemical colorimetry. RT-PCR was performed to determine the mRNA levels of nuclear factor erythroid 2-related factor 2(Nrf2), glutathione peroxidase 4(GPX4), and acyl-CoA synthetase long chain family member 4(ACSL4) in the joint tissue. Western blot was employed to determine the protein levels of Nrf2, Kelch-like ECH-associated protein 1(Keap1), heme oxygenase-1(HO-1), NAD(P)H quinone oxidoreductase 1(NQO1), SOD2, GPX4, and ACSL4 in the joint tissue. The results showed that the treatment with Tripterygium glycosides(7.5 mg·kg~(-1)) and total triterpenes of Euphorbium(32, 64, and 128 mg·kg~(-1)) alleviated the swelling degree of bilateral hind limbs, decreased the arthritis score, reduced joint tissue lesions and the content of MDA and Fe~(2+) in the joint tissue, and increased GSH content and SOD activity. Furthermore, the interventions up-regulated the protein and mRNA levels of Nrf2 and GPX4, down-regulated the protein and mRNA levels of ACSL4, and up-regulated the protein levels of Keap1, NQO1, HO-1, and SOD2 in the Nrf2/HO-1/GPX4. In summary, the total triterpenes of Euphorbium can treat RA by inhibiting lipid peroxidation and abnormal ferroptosis, which may involve the Nrf2/HO-1/GPX4 signaling pathway.