title: Inhibitory effect of homocysteine on rat neural stem cell growth in vitro is associated with reduced protein levels and enzymatic activities of aconitase and respiratory complex III.
abstract: Increased blood plasma concentration of the sulphur amino acid homocysteine (Hcy) is considered as an independent risk factor of the neurodegenerative diseases. However, the detailed molecular mechanisms by which Hcy leads to neurotoxicity have yet to be clarified. Recent research has suggested that neurotoxicity of Hcy may involve negative regulation of neural stem cell (NSC) proliferation. In the current study, primary NSCs were isolated from neonatal rat brain hippocampus and the inhibition in cell growth was observed after exposure to l50 μM and 500 μM L-Hcy. The changes in protein expression were monitored with densitometric 2D-gel electrophoresis coupled with MALDI-TOF mass spectrometry. Proteomic analysis revealed that the expression levels of two mitochondrial proteins, cytochrome bc1 complex2 (UQCRC2, the major component of electron transport chain complex III) and aconitase (an enzyme involved in the tricarboxylic acid cycle), were decreased in Hcy treatment group, compared to control group. Protein expression was further verified by Western blot, and their enzymatic activities were also down-regulated in NSCs after Hcy treatment. Restoration of aconitase and UQCRC2 protein levels using their expression vectors could partly rescue the cell viability inhibition caused by Hcy. Moreover, Hcy caused the increase in the intracellular levels of reactive oxygen species (ROS) and the decrease in ATP content, which are known to play important roles in the cellular stress response of the cell growth. Altogether, the results suggest that the decreased expression and enzymatic activities of the mitochondrial proteins may be possible causes of the overproduction of ROS and depletion of ATP. The inhibition in cell growth at the end of Hcy treatment was probably due to the changes in protein expression and mitochondrial dysfunction in vitro cultures of NSCs.
authors.affiliation: Department of Nutrition and Food Science, School of Public Health, Tianjin Medical University, Tianjin, 300070, China.
authors.forename: Xu-Mei
authors.initials: XM
authors.lastname: Zhang
authors.affiliation: Department of Nutrition and Food Science, School of Public Health, Tianjin Medical University, Tianjin, 300070, China.
authors.forename: Ya-Qian
authors.initials: YQ
authors.lastname: Zhao
authors.affiliation: Department of Nutrition and Food Science, School of Public Health, Tianjin Medical University, Tianjin, 300070, China.
authors.forename: Hai
authors.initials: H
authors.lastname: Yan
authors.affiliation: Department of Nutrition and Food Science, School of Public Health, Tianjin Medical University, Tianjin, 300070, China.
authors.forename: Huan
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Nutrition and Food Science, School of Public Health, Tianjin Medical University, Tianjin, 300070, China. huangguowei@tmu.edu.cn.
authors.forename: Guo-Wei
authors.initials: GW
authors.lastname: Huang
mesh_terms: D000154:Aconitate Hydratase / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D014450:Electron Transport Complex III / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology; D006710:Homocysteine / Q000097:blood / Q000494:pharmacology*; D058953:Neural Stem Cells / Q000166:cytology*; D040901:Proteomics; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D017382:Reactive Oxygen Species; D006710:Homocysteine; D000255:Adenosine Triphosphate; D000154:Aconitate Hydratase; D014450:Electron Transport Complex III
keywords: ATP; Aconitase; Cytochrome bc1 complex2; Homocysteine; Neural stem cell; ROS