Metabolomic Profiling of Urine Samples from Mice Exposed to Protons Reveals Radiation Quality and Dose Specific Differences

Abstract

As space travel is expanding to include private tourism and travel beyond low-Earth orbit, so is the risk of exposure to space radiation. Galactic cosmic rays and solar particle events have the potential to expose space travelers to significant doses of radiation that can lead to increased cancer risk and other adverse health consequences. Metabolomics has the potential to assess an individual’s risk by exploring the metabolic perturbations in a biofluid or tissue. In this study, C57BL/6 mice were exposed to 0.5 and 2 Gy of 1 GeV/nucleon of protons and the levels of metabolites were evaluated in urine at 4 h after radiation exposure through liquid chromatography coupled to time-of-flight mass spectrometry. Significant differences were identified in metabolites that map to the tricarboxylic acid (TCA) cycle and fatty acid metabolism, suggesting that energy metabolism is severely impacted after exposure to protons. Additionally, various pathways of amino acid metabolism (tryptophan, tyrosine, arginine and proline and phenylalanine) were affected with potential implications for DNA damage repair and cognitive impairment. Finally, presence of products of purine and pyrimidine metabolism points to direct DNA damage or increased apoptosis. Comparison of these metabolomic data to previously published data from our laboratory with gamma radiation strongly suggests a more pronounced effect on metabolism with protons. This is the first metabolomics study with space radiation in an easily accessible biofluid such as urine that further investigates and exemplifies the biological differences at early time points after exposure to different radiation qualities.

Metabolic Dysregulation after Neutron Exposures Expected from an Improvised Nuclear Device

“…From the analysis obtained, it was evident that the overall potential metabolic pathways affected exhibited similarities with previously published analyses (9, 13, 29) between the two radiation types, with amino acids and fatty acid β -oxidation among the more prominent ones. Although DNA damage and repair products have been identified as significantly increased with neutrons, whether that is assessed with micronuclei (22), comet assay (39) or chromosomal changes (40, 41), small molecules associated with such a process or DNA repair were not identified in the biofluids through a global LC-MS approach.…”

“…Serum metabolomic and lipidomic preprocessing was performed with Progenesis QI (Nonlinear Dynamics, Newcastle, UK). Normalization was performed with the option, “normalize to all compounds”, utilized in previously published studies (15, 28, 29) to minimize the influence of outliers and create a normal distribution of the data. Deconvoluted data consisted of a matrix with normalized abundance levels for each ion of each sample, where each ion was identified by a unique set of mass over charge ratios ( m / z ) and retention time.…”

Implications of genotypic differences in the generation of a urinary metabolomics radiation signature

“…2), specifically within the irradiated groups, indicating possible radiation injury to the kidney. Normalization to all compounds, a method that has been previously used to account for creatinine differences and minimize the variance [7], was applied to the D3 data. To explain this normalization method briefly, one run was chosen automatically from the software that exhibited the lowest pooled variance.…”

“…Urine samples were analyzed as previously described [5,7]. Briefly, urine was deproteinized with 50% acetonitrile: 50% water and 2 μL were injected into an Acquity UPLC H-Class (Waters Corporation, MA) equipped with a BEH C18 column, 130 Å, 2.1 × 50 mm coupled to a Xevo G2 Time-of-Flight mass spectrometer (Waters Corporation, UK) (LC–MS).…”

Plasma Biomarkers of Poor Muscle Quality in Older Men and Women from the Baltimore Longitudinal Study of Aging

“…Metabolomics, unlike the other -omics, provides a direct signature of the metabolic state of the organism (12)(13)(14). Recent advances in mass spectrometry allow the simultaneous analysis of hundreds of metabolites from small amounts of biological material (15,16).…”