Metabolomic changes in gastrointestinal tissues after whole body radiation in a murine model

Abstract

Exposure to ionizing radiation (IR) elicits a set of complex biological responses involving gene expression and protein turnover that ultimately manifest as dysregulation of metabolic processes representing the cellular phenotype. Although radiation biomarkers have been reported in urine and serum, they are not informative about IR mediated tissue or organ specific injury. In the present study we report IR induced metabolic changes in gastrointestinal (GI) tissue of CD2F1 mice using ultra-performance liquid chromatography (UPLC) coupled with electrospray time-of-flight mass spectrometry. Post-radiation GI injury is a critical determinant of survival after exposure to IR. Our results show a distinct dose and time dependent response to GI tissue injury.

Figure 1

Schema for GI metabolomics

Figure 2. UPLC-ESI-TOFMS profiling of GI tissue in CD2F1 mice

Animals were either sham irradiated or exposed to 4Gy of γ radiation. The mice were euthanized 1 day, post-IR exposure for blood and organ collection. Comparative metabolomics analyses were performed as described in methods. Panel A. OPLS loadings S-plot displaying dysregulated features in irradiated tissue samples as compared to those from sham exposed group. Panel B. Two dimensional accuracy plot for top 50 features interrogated using Random Forests. The X-axis (dimension 1) denotes the interclass separation while Y-axis (dimension 2) displays the intra-class variability. Panel C. Heat map visualization of the feature rankings comparing relative levels of metabolites in control and irradiated GI tissue samples. Each row represents a unique feature with a characteristic mass to charge and retention time value.

Figure 3. Gamma radiation exposure in CD2F1 mice induces dose dependent alterations in metabolite levels in the GI tissue

Mean normalized ion abundance for each metabolite is plotted for groups of CD2F1 mice that were exposed to sham, 4 Gy or 8 Gy of IR at days 1 and 4.

Figure 4. GI metabolomics shows a distinct metabolic response, 4 days post-IR exposure

Panel A. OPLS loadings S-plot displaying significantly altered features in GI tissue samples obtained from irradiated mice as compared to sham exposed mice. Panel B. Two dimensional accuracy plot for top 50 features interrogated using Random Forests. Panel C. Heat map visualization of the feature rankings comparing relative levels in GI tissue samples obtained from sham and irradiated mice.

Figure 5. Canonical pathways associated with response of gamma radiation in GI tissue of CD2F1 mice

The four groups were compared viz. Day1_4 Gy, Day1_8 Gy, Day4_4 Gy & Day4_8 Gy. Each bar represents type of metabolism in particular pathway dys-regulated after radiation exposure.