title: Inhibition of cPLA2 activation by Ginkgo biloba extract protects spinal cord neurons from glutamate excitotoxicity and oxidative stress-induced cell death.
abstract: Ginkgo biloba extract (EGb761) has been shown to be neuroprotective; however, the mechanism by which EGb761 mediates neuroprotection remains unclear. We hypothesized that the neuroprotective effect of EGb761 is mediated by inhibition of cytosolic phospholipase A(2) (cPLA(2)), an enzyme that is known to play a key role in mediating secondary pathogenesis after acute spinal cord injury (SCI). To determine whether EGb761 neuroprotection involves the cPLA(2) pathway, we first investigated the effect of glutamate and hydrogen peroxide on cPLA(2) activation. Results showed that both insults induced an increase in the expression of phosphorylated cPLA(2) (p-cPLA(2)), a marker of cPLA(2) activation, and neuronal death in vitro. Such effects were significantly reversed by EGb761 administration. Additionally, EGb761 significantly decreased prostaglandin E(2) (PGE(2)) release, a downstream metabolite of cPLA(2). Moreover, inhibition of cPLA(2) activity with arachidonyl trifluromethyl ketone improved neuroprotection against glutamate and hydrogen peroxide-induced neuronal death, and reversed Bcl-2/Bax ratio; notably, EGb761 produced greater effects than arachidonyl trifluromethyl ketone. Finally, we showed that the extracellular signal-regulated kinase 1/2 signaling pathway is involved in EGb761's modulation of cPLA(2) phosphorylation. These results collectively suggest that the protective effect of EGb761 is mediated, at least in part, through inhibition of cPLA(2) activation, and that the extracellular signal-regulated kinase 1/2 signaling pathway may play an important role in mediating the EGb761's effect.
authors.affiliation: Department of Neurobiology, Shanghai Jiaotong University School of Medicine, Shanghai, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Zhao
authors.forename: Naikui
authors.initials: N
authors.lastname: Liu
authors.forename: Jingya
authors.initials: J
authors.lastname: Huang
authors.forename: Pei-Hua
authors.initials: PH
authors.lastname: Lu
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Xu
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D016923:Cell Death / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D020441:Ginkgo biloba; D018698:Glutamic Acid / Q000633:toxicity*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009474:Neurons / Q000187:drug effects*; D009498:Neurotoxins / Q000633:toxicity*; D018384:Oxidative Stress / Q000187:drug effects*; D054510:Phospholipases A2, Cytosolic / Q000378:metabolism*; D010936:Plant Extracts / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000166:cytology*; D013997:Time Factors; D000096983:Ginkgo Extract
chemical_list: D018698:Glutamic Acid; D006861:Hydrogen Peroxide; D048052:Mitogen-Activated Protein Kinase 3; D009498:Neurotoxins; D054510:Phospholipases A2, Cytosolic; D010936:Plant Extracts; C063170:Ginkgo biloba extract; D000096983:Ginkgo Extract