title: Differentiation of HT22 neurons induces expression of NMDA receptor that mediates homocysteine cytotoxicity.
abstract: BACKGROUND
  Neurotoxic homocysteine (Hcy) is thought to be an independent risk factor for neurodegenerative diseases, including Alzheimer's disease. This study is to determine whether HT22 cells, a murine hippocampal neuronal model, can be used as an  in vitro model, besides the primary neuronal cultures, to investigate the effects of Hcy.
  
  
  METHODS
  MTS assay and Hoechst 33342/propidium iodide discrimination were used to assess the cell viability and cell death on undifferentiated and differentiated HT22 cells.  Semi-quantitative reverse transcription polymerase chain reaction and western blot were used to determine the expression of N-methyl D-aspartate (NMDA) receptor.
  
  
  RESULTS
  We found that undifferentiated and differentiated HT22 cells responded to Hcy toxicity differentially, with the  undifferentiated cells resistant while the differentiated cells sensitive. The underlying mechanism appeared to be the differential expression levels of NMDA glutamate receptor between the undifferentiated and differentiated cells. Similar to what have been observed in primary neuronal cultures,  the Hcy toxicity in the differentiated HT22 cells was largely attenuated by NMDA receptor antagonists, MK-801 and memantine.
  
  
  CONCLUSIONS
  These results suggest for the first time that the differentiation of HT22 cells could induce the expression of NMDA receptors, which lead to Hcy  mediate concentration-dependent apoptosis-necrotic continuum of HT22 cell death. The differentiation status of the HT22 cells is important for modeling neurons in vitro, with the differentiated HT22 neurons resembling more characteristics of primary hippocampal neurons while the undifferentiated  HT22 cells being proliferating neuronal precursor cells. The differentiated HT22 neurons can be used as a platform to study Hcy toxicity.
authors.affiliation: Department of Neurology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China.
authors.forename: Zhongyan
authors.initials: Z
authors.lastname: Zhao
authors.forename: Ruiyan
authors.initials: R
authors.lastname: Lu
authors.forename: Bei
authors.initials: B
authors.lastname: Zhang
authors.forename: Jun
authors.initials: J
authors.lastname: Shen
authors.forename: Lianhong
authors.initials: L
authors.lastname: Yang
authors.forename: Songhua
authors.initials: S
authors.lastname: Xiao
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: William Z
authors.initials: WZ
authors.lastname: Suo
mesh_terms: D000818:Animals; D016923:Cell Death; D002454:Cell Differentiation / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003603:Cytotoxins / Q000633:toxicity; D016291:Dizocilpine Maleate / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D006710:Homocysteine / Q000633:toxicity*; D008559:Memantine / Q000494:pharmacology; D051379:Mice; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D003603:Cytotoxins; D016194:Receptors, N-Methyl-D-Aspartate; D006710:Homocysteine; D016291:Dizocilpine Maleate; D008559:Memantine