Catalpol enhances mTORC1/HIF-1α/PDHK1-mediated oxidative metabolism that leads to promote the differentiation of Treg cells in RA

Rheumatoid arthritis (RA) is a chronic autoimmune disease in which regulatory T (Treg) cell dysfunction contributes to its pathogenesis, although the mechanisms regulating Treg differentiation remain unclear. In this study, the effects of Catalpol (CAT) on Treg differentiation and its underlying mechanisms were investigated using a CIA mouse model, with Animals randomly allocated to CIA, CIA+CAT, and No CIA groups. Synovial pathology was assessed by HE staining, while naive CD4⁺ T cells were differentiated into Tregs in vitro, and treated with CAT. Molecular docking predicted CAT-target interactions, and the mTORC1 Activator NV5138 was used alongside CAT for intervention. Treg proportions and mitochondrial membrane potential were analyzed by flow cytometry, IL-10 levels were measured by ELISA, NAD⁺/NADH was detected by assay kit, and mRNA expression of FOXP3, mTOR, Raptor, HIF-1α, and PDHK1 were determined by RT-qPCR, while protein expression was assessed by Western blotting. The results demonstrated that CAT alleviated joint symptoms in CIA mice, promoted Treg differentiation both in vivo and in vitro, and increased mitochondrial membrane potential, NAD⁺/NADH and acetyl-CoA levels in Tregs. CAT also downregulated HIF-1α and PDHK1 mRNA and inhibited p-P70S6K/p70S6K, p-4EBP1/4EBP1, HIF-1α, and PDHK1 protein expression. Treatment with NV5138 was observed to reduce Treg differentiation and oxidative metabolism, effects which were reversed by CAT. These findings demonstrate that CAT promotes Treg differentiation and exerts anti-RA effects through inhibition of the mTORC1/HIF-1α/PDHK1 signaling pathway and enhancement of pyruvate aerobic oxidation.

Aerobic oxidation; CIA mouse model; Catalpol; Regulatory T cells.