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Hippocampal neurons require a large pool of glutathione to sustain dendrite integrity and cognitive function.

ABSTRACT: Loss of brain glutathione has been associated with cognitive decline and neuronal death during aging and neurodegenerative diseases. However, whether decreased glutathione precedes or follows neuronal dysfunction has not been unambiguously elucidated. Previous attempts to address this issue were approached by fully eliminating glutathione, a strategy causing abrupt lethality or premature neuronal death that led to multiple interpretations. To overcome this drawback, here we aimed to moderately decrease glutathione content by genetically knocking down the rate-limiting enzyme of glutathione biosynthesis in mouse neurons in vivo. Biochemical and morphological analyses of the brain revealed a modest glutathione decrease and redox stress throughout the hippocampus, although neuronal dendrite disruption and glial activation was confined to the hippocampal CA1 layer. Furthermore, the behavioral characterization exhibited signs consistent with cognitive impairment. These results indicate that the hippocampal neurons require a large pool of glutathione to sustain dendrite integrity and cognitive function.

SUBMITTER: Fernandez-Fernandez S

PROVIDER: S-EPMC6092450 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

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Hippocampal neurons require a large pool of glutathione to sustain dendrite integrity and cognitive function.

Fernandez-Fernandez Seila S Bobo-Jimenez Veronica V Requejo-Aguilar Raquel R Gonzalez-Fernandez Silvia S Resch Monica M Carabias-Carrasco Monica M Ros Joaquim J Almeida Angeles A Bolaños Juan P JP

Redox biology 20180807

Loss of brain glutathione has been associated with cognitive decline and neuronal death during aging and neurodegenerative diseases. However, whether decreased glutathione precedes or follows neuronal dysfunction has not been unambiguously elucidated. Previous attempts to address this issue were approached by fully eliminating glutathione, a strategy causing abrupt lethality or premature neuronal death that led to multiple interpretations. To overcome this drawback, here we aimed to moderately d ...[more]

PMID: 30107295

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Project description:BACKGROUND:Platelet-activating factor acetylhydrolase 1B1 (LIS1), a critical mediator of neuronal migration in developing brain, is expressed throughout life. However, relatively little is known about LIS1 function in the mature brain. We previously demonstrated that LIS1 involvement in the formation and turnover of synaptic protrusions and synapses of young brain after neuronal migration is complete. Here we examine the requirement for LIS1 to maintain hippocampal circuit function in adulthood. METHODS:Effects of conditional Lis1 inactivation in excitatory pyramidal neurons, starting in juvenile mouse brain, were probed using high-resolution approaches combining mouse genetics, designer receptor exclusively activated by designer drug technology to specifically manipulate CA1 pyramidal neuron excitatory activity, electrophysiology, hippocampus-selective behavioral testing, and magnetic resonance imaging tractography to examine the connectivity of LIS1-deficient neurons. RESULTS:We found progressive excitatory and inhibitory postsynaptic dysfunction as soon as 10 days after conditional inactivation of Lis1 targeting CA1 pyramidal neurons. Surprisingly, by postnatal day 60 it also caused CA1 histological disorganization, with a selective decline in parvalbumin-expressing interneurons and further reduction in inhibitory neurotransmission. Accompanying these changes were behavioral and cognitive deficits that could be rescued by either designer receptor exclusively activated by designer drug-directed specific increases in CA1 excitatory transmission or pharmacological enhancement of gamma-aminobutyric acid transmission. Lagging behind electrophysiological changes was a progressive, selective decline in neural connectivity, affecting hippocampal efferent pathways documented by magnetic resonance imaging tractography. CONCLUSIONS:LIS1 supports synaptic function and plasticity of mature CA1 neurons. Postjuvenile loss of LIS1 disrupts the structure and cellular composition of the hippocampus, its connectivity with other brain regions, and cognition dependent on hippocampal circuits.

Project description:BackgroundFetal-neonatal iron deficiency causes learning/memory deficits that persist after iron repletion. Simplified hippocampal neuron dendrite structure is a key mechanism underlying these long-term impairments. Early life choline supplementation, with postnatal iron repletion, improves learning/memory performance in formerly iron-deficient (ID) rats.ObjectivesTo understand how choline improves iron deficiency-induced hippocampal dysfunction, we hypothesized that direct choline supplementation of ID hippocampal neurons may restore cellular energy production and dendrite structure.MethodsEmbryonic mouse hippocampal neuron cultures were made ID with 9 μM deferoxamine beginning at 3 d in vitro (DIV). At 11 DIV, iron repletion (i.e., deferoxamine removal) was performed on a subset of ID cultures. These neuron cultures and iron-sufficient (IS) control cultures were treated with 30 μM choline (or vehicle) between 11 and 18 DIV. At 18 DIV, the independent and combined effects of iron and choline treatments (2-factor ANOVA) on neuronal dendrite numbers, lengths, and overall complexity and mitochondrial respiration and glycolysis were analyzed.ResultsCholine treatment of ID neurons (ID + Cho) significantly increased overall dendrite complexity (150, 160, 180, and 210 μm from the soma) compared with untreated ID neurons to a level of complexity that was no longer significantly different from IS neurons. The average and total length of primary dendrites in ID + Cho neurons were significantly increased by ∼15% compared with ID neurons, indicating choline stimulation of dendrite growth. Measures of mitochondrial respiration, glycolysis, and ATP production rates were not significantly altered in ID + Cho neurons compared with ID neurons, remaining significantly reduced compared with IS neurons. Iron repletion significantly improved mitochondrial respiration, ATP production rates, overall dendrite complexity (100-180 μm from the soma), and dendrite and branch lengths compared with untreated ID neurons.ConclusionsBecause choline partially restores dendrite structure in ID neurons without iron repletion, it may have therapeutic potential when iron treatment is not possible or advisable. Choline's mechanism in ID neurons requires further investigation.

Dataset Information

Hippocampal neurons require a large pool of glutathione to sustain dendrite integrity and cognitive function.

Publications

Hippocampal neurons require a large pool of glutathione to sustain dendrite integrity and cognitive function.

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