Hypomagnetic Field Induces the Production of Reactive Oxygen Species and Cognitive Deficits in Mice Hippocampus

Abstract

Previous studies have found that hypomagnetic field (HMF) exposure impairs cognition behaviors in animals; however, the underlying neural mechanisms of cognitive dysfunction are unclear. The hippocampus plays important roles in magnetoreception, memory, and spatial navigation in mammals. Therefore, the hippocampus may be the key region in the brain to reveal its neural mechanisms. We recently reported that long-term HMF exposure impairs adult hippocampal neurogenesis and cognition through reducing endogenous reactive oxygen species (ROS) levels in adult neural stem cells that are confined in the subgranular zone (SGZ) of the hippocampus. In addition to adult neural stem cells, the redox state of other cells in the hippocampus is also an important factor affecting the functions of the hippocampus. However, it is unclear whether and how long-term HMF exposure affects ROS levels in the entire hippocampus (i.e., the dentate gyrus (DG) and ammonia horn (CA) regions). Here, we demonstrate that male C57BL/6J mice exposed to 8-week HMF exhibit cognitive impairments. We then found that the ROS levels of the hippocampus were significantly higher in these HMF-exposed mice than in the geomagnetic field (GMF) group. PCR array analysis revealed that the elevated ROS levels were due to HMF-regulating genes that maintain the redox balance in vivo, such as Nox4, Gpx3. Since high levels of ROS may cause hippocampal oxidative stress, we suggest that this is another reason why HMF exposure induces cognitive impairment, besides the hippocampal neurogenesis impairments. Our study further demonstrates that GMF plays an important role in maintaining hippocampal function by regulating the appropriate endogenous ROS levels.

Homo sapiens—A Species Not Designed for Space Flight: Health Risks in Low Earth Orbit and Beyond, Including Potential Risks When Traveling beyond the Geomagnetic Field of Earth

“…If the development of such magnetic-field-sensitive systems occurred early in evolution, then they should also be evident in less complex organisms and other mammals, but such studies may miss insights into human cognition aspects that could be unique to Homo sapiens . The exposure of mammals to hypomagnetic fields (prolonged weakening of the GMF) ( Table 2 ) led to altered immune systems in rats [ 152 ], cognitive deficits in the mouse hippocampus [ 153 ], and altered noradrenergic activities in the brainstems of hamsters [ 154 ]. In Drosophila, exposure to hypomagnetic fields for 10 generations led to amnesia, but this effect was reversible after 6 generations in normal GMF [ 155 ].…”

Radical triads, not pairs, may explain effects of hypomagnetic fields on neurogenesis

“…The artificial absence of magnetic fields, i.e., exposure to hypomagnetic field, has likewise been linked to biological effects in cells, animals and plants [ 1 ]. A recent study by Zhang et al suggests that male mice exposed to hypomagnetic fields (HMF; by means of near elimination of the geomagnetic field; 0.29 μ T) suffer a significant impairment of adult hippocampal neurogenesis and hippocampus-dependent learning [ 2 , 3 ]. Specifically, decreased adult neuronal stem cell proliferation, altered cell lineages in critical development stages of neurogenesis and impeded dendritic development in new-born neurons have been implicated.…”