Differentiation of HT22 neurons induces expression of NMDA receptor that mediates homocysteine cytotoxicity

Abstract

Introduction 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. Materials and 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. Conclusion 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…