The Biological Effects and Global Gene Expression Profiles of Post-irradiation Hypertonic Saline Treated U87MG Glioma Cells

• Main Authors: Hsin-Ju Ding, 丁欣茹
• Other Authors: Frank QH Ngo
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/49799500994485354041

碩士 === 國立陽明大學 === 放射醫學科學研究所 === 92 === The molecular mechanism(s) underlying fixation of radiation potentially lethal damage (PLD) has been of great interest in radiation biology for more that 30 years. However, to date our knowledge accumulated relevant to this important question remains elusive. In this study, we have attempted to employ high-density oligonucleotide microarray and bioinformatics to elucidate the effect on PLD of post-irradiation (PI) 0.5M hypertonicity in U87MG glioma cells at the transcription level. Analysis of the microarray data using appropriately stringent filtering and selection procedure showed that among nearly 20,000 genes, the expression levels of 96 genes were altered. Classification of these affected genes according to biological functions indicated that they are involved in metabolism/energy, transcriptional and translational regulation, cell communication/signaling, cell proliferation/transformation, transport, DNA/RNA modification, protein metabolism, cell structure, stress response and chromatin remodeling, were altered. Among them, a unique set of mitochondrial DNA encoded genes including MTND1, MTND3, MTND6, MTCO1, MTCO2 and MTATP8 were down-regulated. Down-regulation of these 6 genes together with ATP6V1B1 of nuclear DNA orientation effectively causes dysfunction of ATP production in the mitochondria. Inhibition of mitochondria transcription machinery and ATP energy exhaustion can by itself lead to apoptosis via release of cytochrome c. Such catastrophe action due to energy depletion not only explains enhanced cell killing, but also explains inhibited repair protein mobility (reported by others), following hypertonic salt treatment. In addition, by measuring phosphorylated H2AX after hypertonic treatment PI, we detected an increase of DNA double strand breaks (DSBs), a result that is consistent with the increased α value in the survival response curve. DNA content analysis revealed that the enhanced cell killing due to hypertonic treatment operates with mechanism(s) that is(are) independent of cell-cycle checkpoints. In summary, our microarray data help in explaining molecular mechanism(s) underlying fixation of PLD at the gene expression level and, to our knowledge, this is a novel finding via a systems biology high-throughput microarray approach.