Quercetin alleviates hyperthyroidism-induced liver damage via Nrf2 Signaling pathway.

Quercetin is a plant flavonoid and has antioxidative properties. In this study, we evaluated the therapeutic effect of quercetin on thyroid dysfunction in L-thyroxin (LT4)-induced hyperthyroidism rats. LT4 was used to prepare the experimental hyperthyroidism model via the intraperitoneal injection. Quercetin was injected at a series doses (5, 50, and 100 mg/kg) to LT4-induced hypothyroidism rats once a day for 14 days. The body weight and food intake were measured once a week. The levels of thyroid hormones, liver function, oxidative stress markers, and antioxidant markers were measured using commercial enzyme-linked immunosorbent assay kits. Hematoxylin-eosin staining was used to observe the thyroid tissue histological changes. The levels of nuclear and total nuclear factor erythroid 2-related factor 2 (Nrf2) were determined by western blot. The liver oxidative stress markers in LT4-induced hyperthyroidism Nrf2 knockout rats were determined to evaluate the role of Nrf2 on quercetin induced protective effects. LT4 administration increased the levels of serum triiodothyronine and thyroxine, activity of oxidative stress markers with a parallel decrease in antioxidant markers and Nrf2. However, the simultaneous administration of quercetin, reversed all these effects indicating its potential in the regulation of hyperthyroidism. Furthermore, the loss function of Nrf2 diminished these effects resulting from the quercetin application, indicating the inhibitory effects caused by the quercetin may be involved in Nrf2 signaling pathway. These results indicate that quercetin could be used to protect against experimental hyperthyroidism-induced liver damage via Nrf2 signaling pathway.