The Impact of Microgravity on the Accumulation of DNA Damage in Human Cells

For over three decades, the National Aeronautics and Space Administration (NASA) has been collecting data on the radiation levels of NASA astronauts as a way to monitor changes in biological function (National Aeronautics and Space Administration, 2008). In outer space, astronauts undergo direct exposure to oxidative stress and ultra-violet (UV) radiation due to a low-oxygen environment and the absence of an ozone layer. Although prolonged oxidative stress and UV radiation damages genomic deoxyribonucleic acid (DNA) and requires repair mechanisms, the long-term effects of microgravity on these cellular repair mechanisms are not fully understood. The purpose of this study is to determine how microgravity impacts the proliferation and DNA repair pathways of human cells. We measured the effects of hydrogen peroxide, bleomycin, and camptothecin on human cells under normal gravitational conditions and microgravity simulation. Hydrogen peroxide (oxidative stress) elicits damage that mimics the conditions of outer space, while bleomycin and camptothecin caused double-stranded and single-stranded breaks respectively. Treatment occurred at timed increments while the cell viability, physical morphology, and nucleic DNA damage were monitored using a variety of biochemical assays. We found that all reagents induced concentration-dependent DNA damage in normal gravitational conditions while damage was variable under microgravity simulation. Furthermore, DNA damage increased under microgravity simulation alone. The experimental outcomes seek to increase the safety of space travel by understanding how microgravitational environments could impact DNA repair mechanisms.