KangJiaFang granules ameliorates experimental autoimmune thyroiditis by regulating CD4+ T cells and altering gut microbiota.

BACKGROUND

KangJiaFang (KJF) is a classical prescription of traditional Chinese medicine for treating Hashimoto's thyroiditis (HT) in clinic, yet the potential mechanisms of its effects remain unclear.

PURPOSE: We established an experimental autoimmune thyroiditis (EAT) model to explore the effects of KJF on HT and to clarify the possible mechanisms.

METHODS

An EAT model was established and rats were administrated with KJF for eight weeks. Thyroid tissues were stained and assayed to assess KJF's impact on HT. CD4+ T cell levels were measured by flow cytometry (FCM) and quantitative real-time PCR (RT-qPCR). Gut flora alterations were analyzed by 16S rRNA sequencing post-KJF intervention.

RESULTS

KJF significantly reduced serum TPOAb and TgAb levels, reversed the levels of T3, T4, FT3, and FT4, and improved the degree of thyroid lymphocytic infiltration, restoring thyroid function. Mechanistically, KJF modulated the balance of CD4+ T cell subsets, primarily by reducing the number of Th1 cells and increasing Treg cells. ELISA results demonstrated that KJF further regulated CD4+ T cell-related cytokines by lowering TNF-α, IFN-γ, and IL-17 levels while elevating TGF-β and IL-4. Additionally, KJF altered the gut microbiota composition, specifically increasing the abundance of beneficial genera Faecalibaculum and Bifidobacterium while decreasing the harmful genus Escherichia-Shigella.

CONCLUSION

The results demonstrated that KJF alleviated the severity of EAT in rats by modulating the proportions of Th1, Th2, Th17, and Treg cells, improving intestinal flora dysbiosis, and reshaping overall structure of gut microbiota. This study has preliminarily confirmed that KJF may have certain therapeutic potential for early-stage thyroiditis.