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Early restoration of parvalbumin interneuron activity prevents memory loss and network hyperexcitability in a mouse model of Alzheimer's disease.

ABSTRACT: Neuronal network dysfunction is increasingly recognized as an early symptom in Alzheimer's disease (AD) and may provide new entry points for diagnosis and intervention. Here, we show that amyloid-beta-induced hyperexcitability of hippocampal inhibitory parvalbumin (PV) interneurons importantly contributes to neuronal network dysfunction and memory impairment in APP/PS1 mice, a mouse model of increased amyloidosis. We demonstrate that hippocampal PV interneurons become hyperexcitable at ~16 weeks of age, when no changes are observed yet in the intrinsic properties of pyramidal cells. This hyperexcitable state of PV interneurons coincides with increased inhibitory transmission onto hippocampal pyramidal neurons and deficits in spatial learning and memory. We show that treatment aimed at preventing PV interneurons from becoming hyperexcitable is sufficient to restore PV interneuron properties to wild-type levels, reduce inhibitory input onto pyramidal cells, and rescue memory deficits in APP/PS1 mice. Importantly, we demonstrate that early intervention aimed at restoring PV interneuron activity has long-term beneficial effects on memory and hippocampal network activity, and reduces amyloid plaque deposition, a hallmark of AD pathology. Taken together, these findings suggest that early treatment of PV interneuron hyperactivity might be clinically relevant in preventing memory decline and delaying AD progression.

SUBMITTER: Hijazi S

PROVIDER: S-EPMC7714697 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature

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Early restoration of parvalbumin interneuron activity prevents memory loss and network hyperexcitability in a mouse model of Alzheimer's disease.

Hijazi Sara S Heistek Tim S TS Scheltens Philip P Neumann Ulf U Shimshek Derya R DR Mansvelder Huibert D HD Smit August B AB van Kesteren Ronald E RE

Molecular psychiatry 20190820 12

Neuronal network dysfunction is increasingly recognized as an early symptom in Alzheimer's disease (AD) and may provide new entry points for diagnosis and intervention. Here, we show that amyloid-beta-induced hyperexcitability of hippocampal inhibitory parvalbumin (PV) interneurons importantly contributes to neuronal network dysfunction and memory impairment in APP/PS1 mice, a mouse model of increased amyloidosis. We demonstrate that hippocampal PV interneurons become hyperexcitable at ~16 weeks ...[more]

PMID: 31431685

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Project description:BackgroundA reduction of the number of parvalbumin (PV)-immunoreactive (PV(+)) GABAergic interneurons or a decrease in PV immunoreactivity was reported in several mouse models of autism spectrum disorders (ASD). This includes Shank mutant mice, with SHANK being one of the most important gene families mutated in human ASD. Similar findings were obtained in heterozygous (PV+/-) mice for the Pvalb gene, which display a robust ASD-like phenotype. Here, we addressed the question whether the observed reduction in PV immunoreactivity was the result of a decrease in PV expression levels and/or loss of the PV-expressing GABA interneuron subpopulation hereafter called "Pvalb neurons". The two alternatives have important implications as they likely result in opposing effects on the excitation/inhibition balance, with decreased PV expression resulting in enhanced inhibition, but loss of the Pvalb neuron subpopulation in reduced inhibition.MethodsStereology was used to determine the number of Pvalb neurons in ASD-associated brain regions including the medial prefrontal cortex, somatosensory cortex and striatum of PV-/-, PV+/-, Shank1-/- and Shank3B-/- mice. As a second marker for the identification of Pvalb neurons, we used Vicia Villosa Agglutinin (VVA), a lectin recognizing the specific extracellular matrix enwrapping Pvalb neurons. PV protein and Pvalb mRNA levels were determined quantitatively by Western blot analyses and qRT-PCR, respectively.ResultsOur analyses of total cell numbers in different brain regions indicated that the observed "reduction of PV(+) neurons" was in all cases, i.e., in PV+/-, Shank1-/- and Shank3B-/- mice, due to a reduction in Pvalb mRNA and PV protein, without any indication of neuronal cell decrease/loss of Pvalb neurons evidenced by the unaltered numbers of VVA(+) neurons.ConclusionsOur findings suggest that the PV system might represent a convergent downstream endpoint for some forms of ASD, with the excitation/inhibition balance shifted towards enhanced inhibition due to the down-regulation of PV being a promising target for future pharmacological interventions. Testing whether approaches aimed at restoring normal PV protein expression levels and/or Pvalb neuron function might reverse ASD-relevant phenotypes in mice appears therefore warranted and may pave the way for novel therapeutic treatment strategies.

Project description:Impaired mitochondrial function and aberrant neuronal network activity are believed to be early events in the pathogenesis of Alzheimer's disease (AD), but how mitochondrial alterations contribute to aberrant activity in neuronal circuits is unknown. In this study, we examined the function of mitochondrial protein deacetylase sirtuin 3 (SIRT3) in the pathogenesis of AD. Compared with AppPs1 mice, Sirt3-haploinsufficient AppPs1 mice (Sirt3+/-AppPs1) exhibit early epileptiform EEG activity and seizure. Both male and female Sirt3+/-AppPs1 mice were observed to die prematurely before 5 months of age. When comparing male mice among different genotypes, Sirt3 haploinsufficiency renders GABAergic interneurons in the cerebral cortex vulnerable to degeneration and associated neuronal network hyperexcitability. Feeding Sirt3+/-AppPs1 AD mice with a ketone ester-rich diet increases SIRT3 expression and prevents seizure-related death and the degeneration of GABAergic neurons, indicating that the aggravated GABAergic neuron loss and neuronal network hyperexcitability in Sirt3+/-AppPs1 mice are caused by SIRT3 reduction and can be rescued by increase of SIRT3 expression. Consistent with a protective role in AD, SIRT3 levels are reduced in association with cerebral cortical A? pathology in AD patients. In summary, SIRT3 preserves GABAergic interneurons and protects cerebral circuits against hyperexcitability, and this neuroprotective mechanism can be bolstered by dietary ketone esters.SIGNIFICANCE STATEMENT GABAergic neurons provide the main inhibitory control of neuronal activity in the brain. By preserving mitochondrial function, SIRT3 protects parvalbumin and calretinin interneurons against A?-associated dysfunction and degeneration in AppPs1 Alzheimer's disease mice, thus restraining neuronal network hyperactivity. The neuronal network dysfunction that occurs in Alzheimer's disease can be partially reversed by physiological, dietary, and pharmacological interventions to increase SIRT3 expression and enhance the functionality of GABAergic interneurons.

Project description:Introduction and methodsIn order to verify whether parvalbumin (PVALB), a protein specifically expressed by GABAergic interneurons, could be a MS-specific marker of grey matter neurodegeneration, we performed neuropathology/molecular analysis of PVALB expression in motor cortex of 40 post-mortem progressive MS cases, with/without meningeal inflammation, and 10 control cases, in combination with cerebrospinal fluid (CSF) assessment. Analysis of CSF PVALB and neurofilaments (Nf-L) levels combined with physical/cognitive/3TMRI assessment was performed in 110 naïve MS patients and in 32 controls at time of diagnosis.ResultsPVALB gene expression was downregulated in MS (fold change = 3.7 ± 1.2, P < 0.001 compared to controls) reflecting the significant reduction of PVALB+ cell density in cortical lesions, to a greater extent in MS patients with high meningeal inflammation (51.8, P < 0.001). Likewise, post-mortem CSF-PVALB levels were higher in MS compared to controls (fold change = 196 ± 36, P < 0.001) and correlated with decreased PVALB+ cell density (r = -0.64, P < 0.001) and increased MHC-II+ microglia density (r = 0.74, P < 0.01), as well as with early age of onset (r = -0.69, P < 0.05), shorter time to wheelchair (r = -0.49, P < 0.05) and early age of death (r = -0.65, P < 0.01). Increased CSF-PVALB levels were detected in MS patients at diagnosis compared to controls (P = 0.002). Significant correlation was found between CSF-PVALB levels and cortical lesion number on MRI (R = 0.28, P = 0.006) and global cortical thickness (R = -0.46, P < 0.001), better than Nf-L levels. CSF-PVALB levels increased in MS patients with severe cognitive impairment (mean ± SEM:25.2 ± 7.5 ng/mL) compared to both cognitively normal (10.9 ± 2.4, P = 0.049) and mild cognitive impaired (10.1 ± 2.9, P = 0.024) patients.ConclusionsCSF-PVALB levels reflect loss of cortical interneurons in MS patients with more severe disease course and might represent an early, new MS-specific biomarker of cortical neurodegeneration, atrophy, and cognitive decline.

Dataset Information

Early restoration of parvalbumin interneuron activity prevents memory loss and network hyperexcitability in a mouse model of Alzheimer's disease.

Publications

Early restoration of parvalbumin interneuron activity prevents memory loss and network hyperexcitability in a mouse model of Alzheimer's disease.

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