Neuroprotective effect of (-)-epigallocatechin-3-gallate on autoimmune thyroiditis in a rat model by an anti-inflammation effect, anti-apoptosis and inhibition of TRAIL signaling pathway

(-)-Epigallocatechin-3-gallate (EGCG) is a polyphenol monomer compound extracted and separated from green tea, and is a key catechin in green tea. Recent research has identified that EGCG is equipped with important biological activities, including antitumor, antioxidant, anti-inflammation, blood fat reduction and radiation protection abilities. In the current study, it was investigated whether EGCG exerts a neuroprotective effect on AIT and examined the possible underlying mechanism. The present study sought to establish an experimental autoimmune thyroiditis (AIT) rat model and to investigate the neuroprotective effect of EGCG in this model. EGCG was demonstrated to inhibit urinary iodine values and thyroid pathological features in AIT model rats. Treatment with EGCG significantly reduced interleukin-1 beta, interferon-gamma (INF-gamma) and tumor necrosis factor-alpha (TNF-alpha) levels in the AIT rats through suppression of nuclear factor-kappa B (NF-kappa B) pathway. In addition, pretreatment with EGCG significantly increased B-cell lymphoma-2 protein expression, and suppressed caspase-3 activity and TNF-alpha-related apoptosis-inducing ligand (TRAIL) protein expression levels in the AIT model rats. In conclusion, these results suggested that the neuroprotective effect of EGCG protects against AIT through its anti-inflammatory ability, anti-apoptosis and TRAIL signaling pathway in model rats, and it may be used as a therapeutic agent against AIT caused by inflammation.