Calycosin alleviates H 2 O 2 ‐induced astrocyte injury by restricting oxidative stress through the Akt/Nrf2/ HO ‐1 signaling pathway

Oxidative stress-induced brain cell damage is a crucial factor in the pathogenesis of reactive oxygen species (ROS)-associated neurological diseases. Further, studies show that astrocytes are an important immunocompetent cell in the brain and play a potentially significant role in various neurological diseases. Therefore, elimination of ROS overproduction might be a potential strategy for preventing and treating neurological diseases. Accumulating evidence indicates that calycosin, a main active ingredient in the Chinese herbal medicine Huangqi (Radix Astragali Mongolici), is a potential therapeutic candidate with anti-inflammation and/or anticancer effects. Here, we investigated the protective effect of calycosin in brain astrocytes by mimicking in vitro oxidative stress using H2O2. The results revealed that H2O2 significantly induced ROS and inflammatory factor (tumor necrosis factor [TNF]-α and interleukin [IL]-1β) production, whereas post-treatment with calycosin dramatically and concentration-dependently suppressed H2O2-induced damage by enhancing cell viability, repressing ROS and inflammatory factor production, and increasing superoxide dismutase (SOD) expression. Additionally, we found that calycosin facilitated nuclear factor erythroid 2-related factor 2 (Nrf2) expression and promoted its nuclear translocation, thereby inducing the expression of antioxidant molecules (heme oxygenase [HO]-1 and SOD) following H2O2 treatment. Moreover, calycosin did not attenuated H2O2-induced astrocyte damage and ROS production in the presence of the ML385 (a Nrf2-specific inhibitor) and following Nrf2 silencing. Furthermore, calycosin failed to increase Akt phosphorylation and mitigate H2O2-induced astrocyte damage in the presence of the LY294002 (a selective phosphatidylinositol 3-kinase inhibitor), indicating that calycosin-mediated regulation of oxidative-stress homeostasis involved Akt/Nrf2/HO-1 signaling. These findings demonstrated that calycosin protects against oxidative injury in brain astrocytes by regulating oxidative stress through the AKT/Nrf2/HO-1 signaling pathway.