Protective effects of 6,7,4'-trihydroxyisoflavone, a major metabolite of daidzein, on 6-hydroxydopamine-induced neuronal cell death in SH-SY5Y human neuroblastoma cells.

Daidzein, one of the important isoflavones, is extensively metabolized in the human body following consumption. In particular, 6,7,4'-trihydroxyisoflavone (THIF), a major metabolite of daidzein, has been the focus of recent investigations due to its various health benefits, such as anti-cancer and anti-obesity effects. However, the protective effects of 6,7,4'-THIF have not yet been studied in models of Parkinson's disease (PD). Therefore, the present study aimed to investigate the protective activity of 6,7,4'-THIF on 6-hydroxydopamine (OHDA)-induced neurotoxicity in SH-SY5Y human neuroblastoma cells. Pretreatment of SH-SY5Y cells with 6,7,4'-THIF significantly inhibited 6-OHDA-induced neuronal cell death, lactate dehydrogenase release, and reactive oxygen species production. In addition, 6,7,4'-THIF significantly attenuated reductions in 6-OHDA-induced superoxide dismutase activity and glutathione content. Moreover, 6,7,4'-THIF attenuated alterations in Bax and Bcl-2 expression and caspase-3 activity in 6-OHDA-induced SH-SY5Y cells. Furthermore, 6,7,4'-THIF significantly reduced 6-OHDA-induced phosphorylation of c-Jun N-terminal kinase, p38 mitogen-activated protein kinase, and extracellular signal-regulated kinase 1/2. Additionally, 6,7,4'-THIF effectively prevented 6-OHDA-induced loss of tyrosine hydroxylase. Taken together, these results suggest that 6,7,4'-THIF, a major metabolite of daidzein, may be an attractive option for treating and/or preventing neurodegenerative disorders such as PD.