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Sleep-active hypothalamic MCH-system modulates hippocampal synaptic plasticity and is vulnerable in early Alzheimer’s Disease

ABSTRACT: In Alzheimer’s disease (AD), pathophysiological changes in the hippocampus cause deficits in episodic memory formation, leading to cognitive impairment. Hippocampal hyperactivity and decreased sleep quality are associated with early AD, but their basis is poorly understood. We find that homeostatic mechanisms transiently counteract increased excitatory drive of hippocampal CA1 neurons in AppNL-G-F mice, but fail to stabilize it at control levels. Spatial transcriptomics (ST) analysis identifies the Pmch gene encoding Melanin-Concentrating Hormone (MCH) as part of the adaptive response in AppNL-G-F mice. Hypothalamic MCH peptide is produced in sleep-active lateral hypothalamic neurons that project to CA1 and modulate memory. We show that MCH downregulates synaptic transmission and modulates firing rate homeostasis in hippocampal neurons. Moreover, MCH reverses the increased excitatory drive of CA1 neurons in AppNL-G-F mice. Consistent with our finding that a reduced fraction of MCH-neurons is active in AppNL-G-F mice, these animals spend less time in rapid eye movement (REM) sleep. In addition, MCH-axons projecting to CA1 become progressively impaired in both AppNL-G-F mice and AD patients. Our findings identify the MCH-system as vulnerable in early AD and suggest that impaired MCH-system function contributes to aberrant excitatory drive and sleep defects, which can compromise hippocampal-dependent functions.

ORGANISM(S): Mus musculus

PROVIDER: GSE225181 | GEO | 2023/09/07

REPOSITORIES: GEO

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Project description:Background:Episodic memory loss is a prominent clinical manifestation of Alzheimer's disease(AD), which is closely related to tau pathology and hippocampal impairment. Given the heterogeneity of brain neurons, the precise role of different brain neurons in terms of their sensitivity to tau accumulation and contribution to AD-like social memory loss remains unclear and requires further investigation. Methods: We investigated the effects of AD-like tau pathology by Tandem mass tag proteomic and phosphoproteomic experiments, social behavioral test, hippocampal electrophysiology, immunofluorescent staining and in vivo optical fiber recording of GCaMP6f and iGABASnFR. Additionally, we utilized optogenetics and administered ursolic acid (UA) via oral gavage to examine their effects on social memory in mice. Results: By proteomic and phosphoproteomic analyses, we identified the characteristics of ventral hippocampal CA1 (vCA1) under both physiological conditions and AD-like tau pathology. As tau progressively accumulated, not dorsal CA1 (dCA1), but vCA1, especially its excitatory and PV neurons, were fully filled with mislocated and phosphorylated tau. Overexpression of human Tau (hTau) in excitatory and PV neurons respectively mimicked AD-like tau accumulation, significantly inhibited the neuronal excitability and suppressed distinct discrimination-associated firings of these neurons within vCA1. Photoactivating excitatory and PV neurons in vCA1 at specific rhythm and time-window efficiently ameliorated tau-impaired social memory. Significantly, one-month administration of UA efficiently decreased tau accumulation via autophagy in a TFEB (transcription factor EB)-dependent manner and recovered vCA1 microcircuit to ameliorate tau-impaired social memory.Conclusion: This study elucidated distinct protein and phosphoprotein networks between dCA1 and vCA1, and highlighted the susceptibility of the vCA1 microcircuit to AD-like tau accumulation. Notably, our novel findings regarding the efficacy of UA in reducing tau load and targeting the vCA1 microcircuit may provide a promising strategy for AD treatment in the future.

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Sleep-active hypothalamic MCH-system modulates hippocampal synaptic plasticity and is vulnerable in early Alzheimer’s Disease

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