Effect of ionizing radiation on liver protein oxidation and metabolic function in C57BL/6J mice

Abstract

Purpose: Protein oxidation in response to radiation results in DNA damage, endoplasmic reticulum stress/unfolded protein response, cell cycle arrest, cell death and senescence. The liver, a relatively radiosensitive organ, undergoes measurable alterations in metabolic functions following irradiation. Accordingly, we investigated radiation-induced changes in liver metabolism and alterations in protein oxidation.

Materials and methods: C57BL/6 mice were sham irradiated or exposed to 8.5 Gy ⁶⁰Co (0.6 Gy/min) total body irradiation. Metabolites and metabolic enzymes in the blood and liver tissue were analyzed. Two-dimensional gel electrophoresis and OxyBlot™ were used to detect carbonylated proteins that were then identified by peptide mass fingerprinting.

Results: Analysis of serum metabolites revealed elevated glucose, bilirubin, lactate dehydrogenase (LDH), high-density lipoprotein, and aspartate aminotransferase within 24–72 h post irradiation. Liver tissue LDH and alkaline phosphatase activities were elevated 24–72 h post irradiation. OxyBlotting revealed that the hepatic proteome contains baseline protein carbonylation. Radiation exposure increased carbonylation of specific liver proteins including carbonic anhydrase 1, α-enolase, and regucalcin.

Conclusions: 8.5 Gy irradiation resulted in distinct metabolic alterations in hepatic functions. Coincident with these changes, radiation induced the carbonylation of specific liver enzymes. The oxidation of liver enzymes may underlie some radiation-induced alterations in hepatic function.

Keywords::

• Protein damage
• radiosensitivity
• protein biochemistry

Acknowledgements

We are thankful to Mrs Laura Lewis from the Pathology Department of Uniformed Services University of the Health Sciences, for conducting the blood metabolic panel experiments in this study. Financial Support: This work was supported by Defense Medical Research and Development Program Grant D61 I 10 J7 62 to Drs R.M. Day and G.P. Mueller. Some of the authors are employees of the U.S. Government, and this manuscript was prepared as part of their official duties. Title 17 U.S.C. §105 provides that ‘Copyright protection under this title is not available for any work of the United States Government.’ Title 17 U.S.C §101 defined a U.S. Government work as a work prepared by a military service member or employees of the U.S. Government as part of that person's official duties. The views in this article are those of the authors and do not necessarily reflect the views, official policy, or position of the Uniformed Services University of the Health Sciences, Department of the Navy, Department of Defense, or the U.S. Federal Government.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.