Icaritin activates Nrf2/Keap1 signaling to protect neuronal cells from oxidative stress

Our earlier study indicated that icaritin (ICT) protected mice from cerebral ischemic injury by inhibiting oxidative stress, and this study aimed to investigate its mechanism using a H2 O2 -treated SH-SY5Y cells model. Cell viability was assessed by cell counting kit 8 (CCK-8). Oxidative stress parameters were detected by flow cytometry, and signaling pathways were analyzed by immunoblotting. We found that ICT alleviated apoptosis and intracellular and mitochondrial reactive oxygen species (ROS) levels, decreased the expressions of Bax and cleaved caspase-3, and increased the expressions of Bcl-2 compared to H2 O2 group. ICT increased mitochondrial membrane potential (ΔΨm) and blocked the opening of mitochondrial membrane permeability transporter (MPT), and increased the activity of glutathione peroxidase (GSH-px), catalase (CAT) and superoxide dismutase (SOD), meanwhile, decreased the activity of malondialdehyde (MDA) compared to H2 O2 group. Futher investigation revealed that ICT significantly up-regulated the expressions of nuclear factor erythroid 2-related factor 2 (Nrf2), hemeoxygenase 1 (HO-1) and NAD(P)H-quinone oxidoreductase 1 (NQO-1). The anti-apoptosis and anti-oxidative effects of ICT were blocked by ML385, a Nrf2/Keap1 signaling pathway inhibitor. These results indicate that ICT can play a neuroprotective role against oxidative stress injury by activating Nrf2/Keap1 signaling pathway.