Protective effect of Cordyceps militaris against hydrogen peroxide-induced oxidative stress in vitro

Excessive production of reactive oxygen species (ROS) such as hydroxyl (·OH), nitric oxide (NO), and hydrogen peroxide (H₂O₂) is reported to induce oxidative stress. ROS generated by oxidative stress can potentially damage glial cells in the nervous system. Cordyceps militaris (CM), a kind of natural herb widely found in East Asia. In this study, we investigated the free radical scavenging activity of the CM extract and its neuroprotective effects in H₂O₂-induced C6 glial cells.

The ethanol extract of CM (100-1,000 µg/mL) was used to measure DPPH, ·OH, and NO radical scavenging activities. In addition, hydrogen peroxide (H₂O₂)-induced C6 glial cells were treated with CM at 0.5-2.5 µg/mL for measurement of cell viability, ROS production, and protein expression resulting from oxidative stress.

The CM extract showed high scavenging activities against DPPH, ·OH, and NO radicals at concentration of 1,000 µg/mL. Treatment of CM with H₂O₂-induced oxidative stress in C6 glial cells significantly increased cell viability, and decreased ROS production. Cyclooxygenase-2 and inducible nitric oxide synthase protein expression was down-regulated in CM-treated groups. In addition, the protein expression level of phospho-p38 mitogen-activated protein kinase (p-p38 MAPK), phospho-c-Jun N-terminal kinase (p-JNK), and phospho-extracellular regulated protein kinases (p-ERK) in H₂O₂-induced C6 glial cells was down-regulated upon CM administration.

CM exhibited radical scavenging activity and protective effect against H₂O₂ as indicated by the increased cell viability, decreased ROS production, down-regulation of inflammation-related proteins as well as p-p38, p-JNK, and p-ERK protein levels. Therefore, we suggest that CM could play the protective role from oxidative stress in glial cells.