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Effects of organic selenium on lead-induced impairments of spatial learning and memory as well as synaptic structural
Xiao-jie Han1, Yong-mei Xiao, Bao-min Ai
1Department of Preventive Medicine, School of Public Health, Sun Yat-Sen University.
Insights
Organic selenium (Se) protects against lead (Pb) induced spatial learning and memory deficits in weaned rats. However, maternal Pb exposure impairs neural development, with Se offering limited recovery.
Area of Science:
- Neuroscience
- Toxicology
- Developmental Biology
Background:
- Lead (Pb) exposure during development can cause significant cognitive deficits and neurotoxicity.
- Synaptic structural plasticity is crucial for learning and memory, and is vulnerable to environmental toxins like Pb.
- Organic selenium (Se) is known for its antioxidant and neuroprotective properties.
Purpose of the Study:
- To investigate the protective effects of organic Se against Pb-induced spatial learning and memory impairments.
- To examine the relationship between Se supplementation and alterations in synaptic structural plasticity following Pb exposure.
- To compare the effects of Pb exposure at different developmental stages (postnatal vs. maternal) and the efficacy of Se intervention.
Main Methods:
- Postnatal rat pups were exposed to Pb and/or organic Se at different developmental stages.
- Spatial learning and memory were assessed using the Morris water maze (MWM).
- Synaptic structural plasticity was evaluated by analyzing neuronal and synaptic parameters, including synapse number, postsynaptic density (PSD) thickness, synaptic active zone length, synaptic curvature, and synaptic cleft width.
Main Results:
- Organic Se supplementation significantly improved spatial learning and memory in rats exposed to Pb after weaning.
- Maternal Pb exposure led to a significant decrease in neuron and synapse numbers, with Se offering limited recovery.
- Se treatment in Pb-exposed rats (post-weaning) reversed synaptic alterations, including increased synapse number, PSD thickness, and synaptic active zone length.
Conclusions:
- Organic Se demonstrates protective effects against Pb-induced spatial learning and memory deficits and synaptic plasticity impairments when administered after weaning.
- Maternal Pb exposure poses a greater risk to early neural development, causing irreversible damage to neuron and synapse numbers.
- Intervention with organic Se is most effective when initiated after weaning, highlighting the critical window for developmental Pb exposure and subsequent Se treatment.
Abstract:
To study the effect of organic Se on spatial learning and memory deficits induced by Pb exposure at different developmental stages, and its relationship with alterations of synaptic structural plasticity, postnatal rat pups were randomly divided into five groups: Control; Pb (Weaned pups were exposed to Pb at postnatal day (PND) 21-42); Pb-Se (Weaned pups were exposed to Se at PND 43-63 after Pb exposure); maternal Pb (mPb) (Parents were exposed to Pb from 3 weeks before mating to the weaning of pups); mPb-Se (Parents were exposed to Pb and weaned pups were exposed to Se at PND 43-63). The spatial learning and memory of rat pups was measured by Morris water maze (MWM) on PND 63. We found that rat pups in Pb-Se group performed significantly better than those in Pb group (p<0.05). However, there was no significant difference in the ability of spatial learning and memory between the groups of mPb and mPb-Se (p>0.05). We also found that, before MWM, the numbers of neurons and synapses significantly decreased in mPb group, but not in Pb group. After MWM, the number of synapses, the thickness of postsynaptic density (PSD), the length of synaptic active zone and the synaptic curvature increased significantly in Pb-Se and mPb-Se group; while the width of synaptic cleft decreased significantly (p<0.05), compared to Pb group and mPb group, respectively. However, the number of synapses in mPb-Se group was still significantly lower than that in the control group (p<0.05). Our data demonstrated that organic Se had protective effects on the impairments of spatial learning and memory as well as synaptic structural plasticity induced by Pb exposure in rats after weaning, but not by the maternal Pb exposure which reduced the numbers of neurons and synapses in the early neural development.
