Highly sensitive visualization of inorganic mercury in mouse neurons using a fluorescent probe

In the present study, we used the previously developed fluorescence probe, EPNP, to generate the first image of the distribution of mercuric ion in primary mouse neuron cultures. At postnatal day 1 (P1), the mice were intraperitoneally (IP) injected with mercuric chloride in doses ranging from 0.05 to 0.6 μg/g body weight. After 1, 2, 3, and 4 days exposure, primary nervous cell cultures and frozen brain and spinal tissue sections were prepared and dyed using EPNP. On the third day of repeated injections, Hg(2+) was visualized in primary cerebral neuron cultures as an increase of Hg(2+)-induced fluorescence at the doses ≥ 0.1 μg/g. A similar accumulation of Hg(2+) was observed in frozen hippocampus tissue sections. In contrast, no Hg(2+) was observed in spinal cord neurons and spinal tissue sections. The detection of a low dose of IP injected mercury in mouse cerebral neurons facilitated the evaluation of the exposure risk to low-dose Hg(2+) in immature organisms. Moreover, the highly sensitive EPNP revealed Hg(2+) in the cerebral neurons of mice younger than P4, while the presence of Hg(2+) was not detected until ≥ P11 in previous reports. Thus, this technology and the results obtained herein are of interest for neurotoxicology.