Expression of Nrf2 target genes in human embryonic kidney (HEK) cells after exposure to different qualities of ionizing radiation

Abstract

Space agencies around the world are currently aiming to extend human spaceflight further from Earth than ever before attempted, to Mars. This involves an increased risk to an astronaut’s health due to an increase in exposure to radiation of a type not normally encountered on Earth. One particular protein in human cells, Nrf2, seems to be central to how cells respond to radiation. This protein has previously been shown to cause an increase in the expression of a number of enzymes responsible for detoxifying cells after radiation exposure. In this study to mimic an aspect of space radiation, we exposed human cells to highly charged carbon particles and compared it with human cells exposed to X-rays. Comparisons were made of cell survival after exposure and the amount of Nrf2 activation by measuring how much it binds to its target DNA. Finally measurements were made of how much Nrf2, and its targets, were being made by the cells. The results show that the carbon particles were 25% more effective in reducing cell survival than the X-rays. However Nrf2 was not activat ed 18 and 48 hours after exposure to radiation. Contrary to this, the amount of Nrf2 being produced appears to increase 8 hours after exposure to X-rays. It was also found that one of the enzymes controlled by Nrf2, called NQO1, had increased production after exposure to both types of radiation. Additionally, another enzyme called GST was found to have less production after exposure to both types of radiation. Overall , despitet he space-like radiation being more effective at reducing cell survival than X-rays, it is thought that the changes in enzymes was not due to Nrf2 as its activation and production was generally unchanged.