Ginsenoside Rg-1 Protects Retinal Pigment Epithelium (RPE) Cells from Cobalt Chloride (CoCl(2)) and Hypoxia Assaults

Severe retinal ischemia causes persistent visual impairments in eye diseases. Retinal pigment epithelium (RPE) cells are located near the choroidal capillaries, and are easily affected by ischemic or hypoxia. Ginsenoside Rg-1 has shown significant neuroprotective effects. This study was performed to test the cytoprotective effect of ginsenoside Rg-1 in RPE cells against hypoxia and cobalt chloride (CoCl(2)) assaults, and to understand the underlying mechanisms. We found that Rg-1 pre-administration significantly inhibited CoCl(2)- and hypoxia-induced RPE cell death and apoptosis. Reactive oxygen specisis (ROS)-dependent p38 and c-Jun NH(2)-terminal kinases (JNK) MAPK activation was required for CoCl(2)-induced RPE cell death, and Rg-1 pre-treatment significantly inhibited ROS production and following p38/JNK activation. Further, CoCl(2) suppressed pro-survival mTOR complex 1 (mTORC1) activation in RPE cells through activating of AMP-activated protein kinase (AMPK), while Rg-1 restored mTORC1 activity through inhibiting AMPK activation. CoCl(2)-induced AMPK activation was also dependent on ROS production, and anti-oxidant N-acetylcysteine (NAC) prevented AMPK activation and RPE cell death by CoCl(2). Our results indicated that Rg-1 could be further investigated as a novel cell-protective agent for retinal ischemia.