Mechanism of Xiaoying Daotan decoction in treating Hashimoto's thyroiditis based on the Notch/Treg/Th17 pathway

The study created mice model of Hashimoto's thyroiditis (HT) and induced thyroid inflammatory cell lines, exploring the mechanism of Xiaoying Daotan decoction on HT.

Divided HT mice models into model group (0.2 mL saline), Western medicine group (0.2 mL levothyroxine sodium tablets), traditional Chinese medicine group (0.2 mL Xiaoyin Daotan prescription), and Notch protein inhibition group (0.2 mL Xiaoyin Daotan prescription). After treatment, serum Notch protein expression and T cell (Treg)/T helper cell 17 (Th17) cytokines levels were detected through Enzyme linked immunosorbent assay (ELISA). Use real-time qualitative polymerase chain reaction detected Notch protein expression. Thyroid inflammatory cell lines were induced and divided into 5 groups: blank group, iNotch group (knocking down the Notch protein gene of thyroid inflammatory cells), NC group (Notch protein carrier negative control group), iNotch + DS group and DS group (knocking down the Notch protein gene of thyroid inflammatory cells). The cells were treated with serum containing Xiaoying Daotan decoction. After culture, detected Notch protein expression level and Treg/Th17 cytokine level in each group.

For the animal experiment, the serum Notch protein expression, the serum levels of key activating proteins Signal Transducer and Activator of Transcription 3 (STAT3), RAR-related orphan receptor gamma T (RORγt), and interleukin (IL)-22 of Th17 cells of mice in the model group was significantly higher than that of the other groups. Compared with the model group and Western medicine group, the serum transforming growth factor-β (TGF-β) level of the mice in the traditional Chinese medicine group and the Notch protein inhibition group was significantly higher. All the differences were statistically significant (P<0.05). For the cell experiment, the β-actin value of Notch protein in thyroid inflammatory cell genes was significantly downregulated and the key activation protein of Treg was significantly upregulated in iNotch + DS group and DS group compared with the other 3 groups. Levels of Th17 key activating proteins STAT3, IL-17, and IL-22 in the iNotch group, iNotch + DS group, and DS group were lower than those of the blank group and NC group, both with statistically significant difference (P<0.001).

The mechanism of Xiaoying Daotan decoction on HT could be related to the immune inflammatory response of the Treg/Th17 cell axis mediated by the Notch protein pathway.