Radical pairs may explain reactive oxygen species-mediated effects of hypomagnetic field on neurogenesis

Abstract

Exposures to a hypomagnetic field can affect biological processes. Recently, it has been observed that hypomagnetic field exposure can adversely affect adult hippocampal neurogenesis and hippocampus-dependent cognition in mice. In the same study, the role of reactive oxygen species (ROS) in hypomagnetic field effects has been demonstrated. However, the mechanistic reasons behind this effect are not clear. This study proposes a radical pair mechanism based on a flavin-superoxide radical pair to explain the modulation of ROS production and the attenuation of adult hippocampal neurogenesis in a hypomagnetic field. The results of our calculations favor a singlet-born radical pair over a triplet-born radical pair. Our model predicts hypomagnetic field effects on the triplet/singlet yield of comparable strength as the effects observed in experimental studies on adult hippocampal neurogenesis. Our predictions are in qualitative agreement with experimental results on superoxide concentration and other observed ROS effects. We also predict the effects of applied magnetic fields and oxygen isotopic substitution on adult hippocampal neurogenesis.

Magnetic field effects in biology from the perspective of the radical pair mechanism

“…Another study suggests that exposure to magnetic fields greater than the geomagnetic field will reduce microtubule assembly [ 60 ]. Further, it is also predicted that hippocampal neurogenesis [ 61 ], the circadian clock [ 59 ] and microtubule reorganization [ 60 ] will be isotope-dependent using different isotopes of oxygen, lithium and zinc, respectively.…”

“…This might involve including multiple nuclei, dipolar, and exchange interactions in the models. It should also be pointed out that including these interactions can reduce the predicted effect size [ 61 , 440 ]. However, this may be balanced by potential amplification effects in the biological systems [ 59 , 594 ].…”

“…Based on these findings, a recent study [ 61 ] suggests that a radical pair model may explain the modulation of ROS production and the attenuation of adult hippocampal neurogenesis in a hypomagnetic field, observed by Zhang and colleagues [ 172 ]. The authors proposed that the reduction of the geomagnetic field influences the spin dynamics of the naturally occurring radical pairs in the form of , similar to other studies [ 58 , 59 , 446 ] (see also §§4.2 and 4.3).…”

“…( a ) false[FADH.⋯O2.−false] radical pair. ( b ) The dependence of the triplet yield of the radical pair model for singlet-born radical pair on external magnetic field [61]. ( c ) Triplet yield ratio (geomagnetic field to hypomagnetic field) for singlet-born radical pair in the plan of reaction rate ( k ) and relaxation rate ( r ).…”

“…Recent studies have proposed roles for radical pairs beyond avian magnetoreception, in particular in xenon-induced anaesthesia [ 57 ], lithium effects on mania [ 58 ], magnetic field and lithium effects on the circadian clock [ 59 ], and hypomagnetic field effects on microtubule reorganization [ 60 ] and neurogenesis [ 61 ] (where hypomagnetic fields are fields much weaker than that of the Earth). Here, we suggest that the radical pair mechanism is in fact quite common in biology, and that it may provide an explanation for many of the weak magnetic field effects on physiological functions that have been observed.…”