Purpose: Reactive oxygen species (ROS) are considered a direct cause of neurodegenerative diseases (NDDs). Drugs developed to target ROS are effective for the treatment of NDDs. Orientin is a pyrone glucoside extracted from Polygonum orientale , and it exhibits many pharmacological activities. In this study, we aimed to determine whether orientin could relieve hydrogen peroxide (H₂O₂)-induced neuronal apoptosis and to investigate the specific target of orientin.
Materials and methods: In this study, the neuroprotective effect and its possible mechanisms of orientin in mouse pheochromocytoma cell line (PC12) cells stimulated by H₂O₂, establishing an oxidative stress model, were investigated. And we further tested the role of ROS in the neuroprotective effects of orientin.
Results: Orientin (5–100 µg/mL) did not cause toxicity in PC12 cells but significantly decreased H₂O₂-induced reduction in PC12 cell viability, cell apoptosis rates, and nuclear condensation. It also inhibited the activation of caspase-3 and degradation of poly(ADP-ribose) polymerase (PARP). Under the stimulation of H₂O₂, MAPKs (ERK, JNK, and p38), AKT, and Src signaling proteins in PC12 cells were activated in a time-dependent manner. The application of inhibitors that were specific for MAPKs, AKT, and Src effectively alleviated H₂O₂-induced cell apoptosis. In addition, the Src inhibitor decreased the activation of MAPKs and AKT signaling. More importantly, orientin effectively decreased H₂O₂-induced phosphorylation of MAPKs, AKT, and Src signaling proteins. Finally, we confirmed that orientin effectively inhibited H₂O₂-induced accumulation of ROS in cells. In addition, ROS inhibitors blocked the Src-MAPKs/AKT signaling pathway-dependent cell apoptosis stimulated by H₂O₂.
Conclusion: These results indicate that alleviation of H₂O₂-induced cell apoptosis by orientin is Src-MAPKs/AKT dependent. Overall, our study confirms that orientin alleviates H₂O₂-induced cell apoptosis by inhibiting the ROS-mediated activation of Src-MAPKs/AKT signaling.
Keywords: oxidative stress, orientin, neuroprotection, apoptosis, Src, MAPKs, AKT