Baicalin, a flavonoid isolated from Scutellaria baicalensis, has anti-inflammatory, antioxidant, and neuroprotective effects. Glutamate is a major neurotransmitter that plays an important role in brain function, but excessive release of glutamate causes excitotoxicity and damages cells. We investigated the neuroprotective effects of baicalin in glutamate-exposed neurons. The mouse hippocampal neuronal cell line (HT22) was cultured in a general manner, glutamate and/or baicalin were treated on the cells. Baicalin was administered 1 hr before glutamate treatment. Cells were collected 24 hr after glutamate, and cell viability was measured using MTT assay. Reactive oxygen species (ROS) and lipid peroxidation (LPO) assays were performed to measure oxidative stress. Glutamate reduced cell viability in a dose- and time-dependent manner. MTT assay showed that baicalin treatment ameliorated the decrease in cell viability due to glutamate toxicity. The effect of baicalin is dose-dependent. Glutamate caused severe nerve damage, including condensation of the cell shape, loss of dendrites and axons. However, baicalin treatment attenuated these morphological changes, and the effect of baicalin was dose-dependent. ROS and LPO analyses showed that glutamate increases oxidative stress, and baicalin attenuates this change due to glutamate toxicity. The effect of baicalin on these results was dose-dependent. We confirmed that baicalin performs an antioxidant function against glutamate toxicity in neurons. In conclusion, these results suggest that baicalin exerts neuroprotective effects on damaged neurons through antioxidant activity.

Glutamate-mediated oxidative stress causes neuronal cell death by increasing intracellular Ca2+ uptake, reactive oxidative species (ROS) generation, mitogen-activated protein kinase (MAPK) activation, and translocation of apoptosis-inducing factor (AIF) to the nucleus. In the current study, we demonstrated that corydaline exerts potent neuroprotective effects against glutamate-induced neurotoxicity. Treatment with 5 mmol/L glutamate increased cellular Ca2+ influx, ROS generation, MAPK activation, and AIF translocation. In contrast, corydaline treatment decreased cellular Ca2+ influx and ROS generation. Western blot analysis revealed that glutamate-mediated MAPK activation was attenuated by corydaline treatment. We further demonstrated that corydaline treatment inhibited the glutamate-mediated translocation of AIF to the nucleus. We propose that corydaline is a promising lead structure for the development of safe and effective neuroprotectants.

Calbindin-D28k is a calcium-binding protein that mediates intracellular calcium concentrations and exerts a neuroprotective effect against ischemic injury. Ferulic acid provides a neuroprotective effect against focal cerebral ischemia through its anti-oxidative and anti-inflammatory mechanisms. In this study, we investigated whether ferulic acid regulates calbindin-D28k expression during focal cerebral ischemia and glutamate treatment-induced neuronal cell death. Middle cerebral artery occlusion (MCAO) was performed to induce focal cerebral ischemia. Ferulic acid (100 mg/kg, i.v.) or vehicle was immediately administered after MCAO, and brain tissues were isolated 24 h after MCAO. RT-PCR and Western blot analyses showed a decrease in calbindin-D28k in MCAO-operated animals. We found that ferulic acid treatment prevented the MCAO-induced decrease in calbindin-D28k expression. Glutamate exposure elevated the intracellular calcium levels in cultured hippocampal cells, and ferulic acid prevented the glutamate exposure-induced increase in calcium levels. Moreover, ferulic acid also attenuated the glutamate toxicity-induced decrease in calbindin-D28k. Taken together, these in vivo and in vitro results demonstrate that ferulic acid regulates calbindin-D28k expression in neuronal cell injury. Therefore, these findings suggest that ferulic acid exerts a neuroprotective effect by modulating calbindin-D28k expression.