Abstract
With the advent of long-duration space explorations, ionizing radiation (IR) may pose a constant threat to astronauts without the protection of Earth’s magnetic field, or hypomagnetic field (HMF). However, the potential biological effects of a HMF on the cellular response to IR have not been well characterized so far. In this study, immortalized human bronchial epithelial cells were exposed to X-rays under either a geomagnetic field (GMF, ~50 uT) or HMF (<50 nT) culture condition. A significant increase of the cell survival rate in HMF after radiation was observed by colony formation analysis. The kinetics of DNA double-strand breaks (DSBs), determined by γH2AX foci formation and disappearance, presented a faster decrease of foci-positive cells and a significantly lower mean number of γH2AX foci per nucleus in HMF-cultured cells than in GMF-cultured cells after radiation. In addition, a γH2AX/53BP1 colocalization assay showed an upregulated DSB recovery rate in HMF cultured cells. These findings provided the first evidence that HMF exposure may enhance the cellular DSB repair efficiency upon radiation, and consequently modulate the genotoxic effects of IR.
Highlights
From the 1980s to the 2010s, all manned spaceflights have been taken place in low-Earth orbit with the protection of our planet’s geomagnetic field (GMF, about 50 μT)
To counteract DNA damage, cells have developed specific mechanisms that locate and repair DNA lesions. These mechanisms consist of a network of cellular proteins involved in DNA damage response pathways, such as cell cycle regulation, DNA repair, and apoptosis [5]
The present study was designed to explore the biological effect of hypomagnetic field (HMF) on DNA damage response in human bronchial epithelial cells upon exposure to ionizing radiation
Summary
From the 1980s to the 2010s, all manned spaceflights have been taken place in low-Earth orbit with the protection of our planet’s geomagnetic field (GMF, about 50 μT). The environmental magnetic field in outer space decreases geometrically with the distance from the ground, which exposes the astronauts to space radiation during lengthy voyages outside the Earth’s magnetosphere This GMF-eliminated environment is defined as a hypomagnetic field (HMF), to represent radiation situations in interplanetary space (6.6 nT) [1], Moon surface (
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