An Integrated Omics Approach to Define the Molecular Mechanisms of Low Dose, High Charge, High Energy Irradiation (HZE) in Liver

Galactic Cosmic Rays are primarily composed of protons (85%), helium (14%), and high charge-high energy ions (HZE) such as 56Fe, 28Si, and 16O. Humans are normally not exposed to HZE ions but will be exposed during deep space travel such as upcoming missions to Mars and the dark side of the moon. Exposure to HZE is a major risk factor for astronauts due to the possibility of HZE induced cancer as well as other potential health risks. In order to access the risks of HZE irradiation, our approach utilized a multi-omics, systems biology platform encompassing lipidomics, metabolomics, proteomics and deep RNA sequencing as well as molecular techniques to define these changes induced by HZE exposure. C3H/HeNCrL mice (more susceptible to HCC) along with C57BL16 (more of a wild type) were placed into 6 treatment groups and received the following irradiation treatments: 600 Me V/n 56Fe (0.2 Gy), 1 GeV/n 16O (0.2 Gy), 350 MeV/n 28Si (0.2 Gy), 137Cs (1.0 Gy) gamma rays, 137Cs (3.0 Gy) gamma rays, and sham irradiation. Left liver lobes were collected at 30, 60, 120, 270 & 360 days post-irradiation. Radiation exposure is known to produce excess reactive oxygen species (ROS) that can result in functional changes in target cells by interacting with and modifying molecules such as lipids, cellular proteins, and DNA. When comparing data from transcriptomics and proteomics utilizing ingenuity pathway analysis (IPA), several pathways involved in mitochondrial function were altered after HZE irradiation. Lipids and metabolites also exhibited changes that are connected to mitochondrial function. Molecular assays for determining Complex I activity, mitochondria count and cardiolipin levels were also used as validation of these findings. Significant decreases were seen in Complex I activity and while not significant, changes were also seen in the mitochondria number and cardiolipin levels that also support mitochondria dysfunction. These altered pathways indicate an increased risk for astronauts during deep space travel and could potentially lead to possible targets for countermeasures to mitigate the risk.