Gancao Fuzi decoction regulates the Th17/Treg cell imbalance in rheumatoid arthritis by targeting Foxp3 via miR-34a

During the Eastern Han Dynasty, Zhang Zhongjing first recorded the Gancao Fuzi decoction (GCFZD) formula in the “Synopsis of the Golden Chamber”, which is reportedly an effective and safe treatment for rheumatoid arthritis (RA). However, the mechanism underlying the observed improvement in the T helper 17 (Th17)/regulatory T (Treg) cell imbalance in RA obtained with GCFZD has not been reported. This study aimed to demonstrate whether GCFZD ameliorated RA by modulating the Th17/Treg imbalance in RA mice. Collagen was used to induce a model of collagen-induced arthritis (CIA) in mice. GCFZD was administered by gavage, and the arthritis index score, imaging and histopathological changes of the ankle joints, and the levels of the immunoglobulin G (IgG) class antibodies and proinflammatory factors in serum were determined. In addition, the frequencies of Th17 and Treg cells, the levels of relevant transcription factors and functional factors and the miR-34a gene in the spleen and the levels of interleukin-17A (IL-17A) and IL-10 in serum were determined. GCFZD significantly reduced the arthritis score, improved joint swelling and bone damage, reduced the pathological score, and decreased the serum levels of IgG class antibody (IgG and IgG2a) and proinflammatory factor [tumour necrosis factor-alpha (TNF-α), IL-1β and IL-6]. Moreover, the Th17-cell proportion, the expression level of the Th17-specific transcription factor retinoic acid-related orphan receptor γt (RORγt) and functional factor IL-17A in the spleen, and the serum IL-17A level were decreased, whereas the Treg cell proportion, expression levels of the Treg-specific transcription factor forkhead box P3 (Foxp3) and functional factor IL-10 in the spleen, and the serum IL-10 level were increased. Furthermore, GCFZD inhibited miR-34a gene expression while promoting Foxp3 protein expression. The findings of this study demonstrate the therapeutic effect of GCFZD on mice with CIA, and the mechanism is related to an improvement in the Th17/Treg cell imbalance by targeting Foxp3 via miR-34a.