ABSTRACT
BACKGROUND: The accumulation of excess glutamate in the synapse leads to excitotoxicity, which is the underlying reason of neuronal death in intracranial tumors. METHODS AND RESULTS: We identified the expression levels of glutamate dehydrogenase, glutamine synthetase and sirtuin 4 in U87 cell line and various intracranial tumors. mRNA expressions of glutamate dehydrogenase (GDH), glutamine synthetase (GS) and sirtuin 4 (SIRT4) were analyzed in various intracranial tumors using qPCR. GDH, GS and SIRT4 protein expressions were analyzed in glioblastoma (U87) and glial (IHA-immortalized human astrocytes) cell lines via western blotting. The protein expressions of SIRT4 and GS were shown to be elevated and GDH protein expression was reduced in U87 cells in comparison to IHA cells. All types of intracranial tumors displayed lower GS mRNA expressions compared to controls. SIRT4 mRNA expressions were also shown to be lower in all the tumors and grades, although not significantly. GDH mRNA expression was found to be similar in all groups. CONCLUSION: The molecular mechanisms of glutamate metabolism and excitotoxicity should be discovered to develop therapies against intracranial tumors.
Subject(s)
Brain Neoplasms/genetics , Glioblastoma/genetics , Adolescent , Adult , Aged , Astrocytes/metabolism , Brain Neoplasms/metabolism , Cell Line , Child , Child, Preschool , Female , Gene Expression/genetics , Gene Expression Regulation, Neoplastic/genetics , Glioblastoma/metabolism , Glutamate Dehydrogenase/genetics , Glutamate-Ammonia Ligase/genetics , Glutamic Acid/metabolism , Humans , Male , Middle Aged , Mitochondrial Proteins/genetics , Neuroglia/metabolism , Retrospective Studies , Sirtuins/geneticsABSTRACT
Glioblastoma multiform is a primary brain tumor derived from glial cells. The aim of this study is to investigate how glutamate metabolism is regulated by glutamate transporter 1 (GLT-1) degradation pathway in glioblastoma and glial cell lines. The protein expression levels of GLT-1, total ubiquitin, protein kinase C (PKC) proteins involved in the GLT-1 degradation pathway were measured by the western blot technique. Additionally, in glial and glioblastoma cells, the level of glutamate accumulated in the medium and the lysates was measured with the glutamate assay. GLT-1 protein expression was increased significantly in glioblastoma cells. The expression levels of the PKC protein and total ubiquitin were found to be decreased in glioblastoma cells although not significantly. The glutamate accumulated in the medium and lysates of glioblastoma cells is reduced compared to glial cells. Further research regarding excitotoxicity in glioblastoma focusing on GLT-1 degradation or activation pathway may create new opportunities of drug and treatment development.
