| Summary: | 碩士 === 國立臺灣大學 === 環境衛生研究所 === 102 === Ionizing radiation is one type of radiations that can liberate an electron from an atom or molecule. In other words, ionizing radiation is highly reactive and able to cause cancer or other serious problems to living organisms. Though we already know the radiation damage in the body, the mechanisms of those biological effects are still unclear. Recent “omics” technologies such as genomics, transcrptomics and metabolomics have been flourished which can prvide high through-put molecular measurement to examine effects of genetic modulation or environmental effects in biological samples.
p53 gene is the most often discussed genes which involved in radiation exposure studies. Radiated cells will increase mutation frequency when p53 gene is dysfunction and may not process apoptosis as protect mechanism. Lipidomics can assist comprehensive understanding of lipids which are the end products of cellular processes and able to directly reflect changes of biological function. Glycerophosphocholines (GPCs) and sphingomyelins (SMs), which were the most abundant lipids on cell membrane, also have various biological functions. The profiling of those lipids may be changes after radiation exposure. Since that, we use an established liquid chromatography-tandem MS method to analyze them.
In this study, we use human lymphoblastic cell lines WTK1 (mutant p53) to examine lipidomic effects of ionizing radiation. Dose-response experiments were conducted in cells treated with gamma-ray (iso-survival dose, D0 (TK6: 0.8 Gy; WTK1: 1.5 Gy) or 10 Gy) for 3 or 24 hours. At the same time we compare the GPC and SM profiling of WTK1 and TK6 (wild-type p53) cell lines when not exposed to ionizing radiation. GPCs and SMs are analyzed by ultra performance liquid chromatography coupled with tandem mass spectrometer (UPLC-MS/MS) following multivariate statistical anlayis.
Results show that in WTK1 cell lines dose-response group, the increased alkenyl-acyl PCs can act as antioxidant to protect cell from reactive oxygen species (ROS). The increase of GPCs in cell can modulate membrane tension, reduce membrane oxidation by change the degree of unsaturation, and lower membrane permeability to process cell membrane repair after the attack of oxidative stress from radiation exposure. Though we did not observe cell apoptosis, our results show the decrease of SMs after radiation exposure may be related to apoptosis since SMs may be hydrolyzed to ceramide as a signal messenger, while the decrease of saturated GPCs might also cause further apoptosis. There’s also shown lipid abundance variation between two cell lines.
This study suggest the GPCs level within the cell may be alterd due to the difference of p53. Not only the cell cycle was alterd but also the changes of GPCs were performed to protect cell after radiation exposure. This made GPCs and SMs may serve as potential markers for irradiation-induce toxicity.
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