title: Protective effects of onion-derived quercetin on glutamate-mediated hippocampal neuronal cell death.
abstract: BACKGROUND
  Neurodegenerative diseases are characterized by progressive neuron degeneration in specific functional systems of the central or peripheral nervous system. This study investigated the protective effects of quercetin isolated from onion on neuronal cells and its protective mechanisms against glutamate-induced apoptosis in HT22 cells.
  
  
  METHODS
  HT22 cells were cultured to study the neuroprotective mechanism of quercetin against glutamate-mediated oxidative stress. The intracellular reactive oxygen species (ROS) level and mitochondrial membrane potential (ΔΨm) were measured. The protein expression of calpain, spectrin, Bcl-2, Bax, Bid, cytochrome c, and mitogen-activated protein kinases (MAPKs) was evaluated by Western blotting.
  
  
  RESULTS
  Quercetin had a protective effect by reducing both intracellular ROS overproduction and glutamate-mediated Ca(2+) influx. These effects were due to the downregulation of several apoptosis-related biochemical markers. Calpain expression was reduced and spectrin cleavage was inhibited by quercetin in glutamate-exposed HT22 cells. Disruption of the mitochondrial membrane potential (ΔΨm), activation of the pro-apoptotic proteins Bid and Bax, and cytochrome c release in response to glutamate-induced oxidative stress were reduced. Quercetin also suppressed phosphorylation of MAPKs.
  
  
  CONCLUSIONS
  This is the first report on the detailed mechanisms of the protective effect of quercetin on HT22 cells. Onion extract and quercetin may be useful for preventing or treating neurodegenerative disorders.
authors.affiliation: BK21 Research Team for Developing Functional Health and Food Materials, College of Agriculture and Life Sciences, Kyungpook National University, Daegu 702-701, Republic of Korea.
authors.forename: Eun-Ju
authors.initials: EJ
authors.lastname: Yang
authors.forename: Geum-Soog
authors.initials: GS
authors.lastname: Kim
authors.forename: Jeong Ah
authors.initials: JA
authors.lastname: Kim
authors.forename: Kyung-Sik
authors.initials: KS
authors.lastname: Song
keywords: Glutamate; neuroprotective effects; onion; oxidative stress; quercetin