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Slutsky I. Linking activity dyshomeostasis and sleep disturbances in Alzheimer disease. Nat Rev Neurosci 2024; 25:272-284. [PMID: 38374463 DOI: 10.1038/s41583-024-00797-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/30/2024] [Indexed: 02/21/2024]
Abstract
The presymptomatic phase of Alzheimer disease (AD) starts with the deposition of amyloid-β in the cortex and begins a decade or more before the emergence of cognitive decline. The trajectory towards dementia and neurodegeneration is shaped by the pathological load and the resilience of neural circuits to the effects of this pathology. In this Perspective, I focus on recent advances that have uncovered the vulnerability of neural circuits at early stages of AD to hyperexcitability, particularly when the brain is in a low-arousal states (such as sleep and anaesthesia). Notably, this hyperexcitability manifests before overt symptoms such as sleep and memory deficits. Using the principles of control theory, I analyse the bidirectional relationship between homeostasis of neuronal activity and sleep and propose that impaired activity homeostasis during sleep leads to hyperexcitability and subsequent sleep disturbances, whereas sleep disturbances mitigate hyperexcitability via negative feedback. Understanding the interplay among activity homeostasis, neuronal excitability and sleep is crucial for elucidating the mechanisms of vulnerability to and resilience against AD pathology and for identifying new therapeutic avenues.
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Affiliation(s)
- Inna Slutsky
- Department of Physiology and Pharmacology, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.
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2
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Almeida VN. Somatostatin and the pathophysiology of Alzheimer's disease. Ageing Res Rev 2024; 96:102270. [PMID: 38484981 DOI: 10.1016/j.arr.2024.102270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 03/09/2024] [Accepted: 03/09/2024] [Indexed: 03/28/2024]
Abstract
Among the central features of Alzheimer's disease (AD) progression are altered levels of the neuropeptide somatostatin (SST), and the colocalisation of SST-positive interneurons (SST-INs) with amyloid-β plaques, leading to cell death. In this theoretical review, I propose a molecular model for the pathogenesis of AD based on SST-IN hypofunction and hyperactivity. Namely, hypofunctional and hyperactive SST-INs struggle to control hyperactivity in medial regions in early stages, leading to axonal Aβ production through excessive presynaptic GABAB inhibition, GABAB1a/APP complex downregulation and internalisation. Concomitantly, excessive SST-14 release accumulates near SST-INs in the form of amyloids, which bind to Aβ to form toxic mixed oligomers. This leads to differential SST-IN death through excitotoxicity, further disinhibition, SST deficits, and increased Aβ release, fibrillation and plaque formation. Aβ plaques, hyperactive networks and SST-IN distributions thereby tightly overlap in the brain. Conversely, chronic stimulation of postsynaptic SST2/4 on gulutamatergic neurons by hyperactive SST-INs promotes intense Mitogen-Activated Protein Kinase (MAPK) p38 activity, leading to somatodendritic p-tau staining and apoptosis/neurodegeneration - in agreement with a near complete overlap between p38 and neurofibrillary tangles. This model is suitable to explain some of the principal risk factors and markers of AD progression, including mitochondrial dysfunction, APOE4 genotype, sex-dependent vulnerability, overactive glial cells, dystrophic neurites, synaptic/spine losses, inter alia. Finally, the model can also shed light on qualitative aspects of AD neuropsychology, especially within the domains of spatial and declarative (episodic, semantic) memory, under an overlying pattern of contextual indiscrimination, ensemble instability, interference and generalisation.
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Affiliation(s)
- Victor N Almeida
- Institute of Psychiatry, Faculty of Medicine, University of São Paulo (USP), Brazil; Faculty of Languages, Federal University of Minas Gerais (UFMG), Brazil.
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Nir Sade A, Levy G, Schokoroy Trangle S, Elad Sfadia G, Bar E, Ophir O, Fischer I, Rokach M, Atzmon A, Parnas H, Rosenberg T, Marco A, Elroy Stein O, Barak B. Neuronal Gtf2i deletion alters mitochondrial and autophagic properties. Commun Biol 2023; 6:1269. [PMID: 38097729 PMCID: PMC10721858 DOI: 10.1038/s42003-023-05612-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 11/20/2023] [Indexed: 12/17/2023] Open
Abstract
Gtf2i encodes the general transcription factor II-I (TFII-I), with peak expression during pre-natal and early post-natal brain development stages. Because these stages are critical for proper brain development, we studied at the single-cell level the consequences of Gtf2i's deletion from excitatory neurons, specifically on mitochondria. Here we show that Gtf2i's deletion resulted in abnormal morphology, disrupted mRNA related to mitochondrial fission and fusion, and altered autophagy/mitophagy protein expression. These changes align with elevated reactive oxygen species levels, illuminating Gtf2i's importance in neurons mitochondrial function. Similar mitochondrial issues were demonstrated by Gtf2i heterozygous model, mirroring the human condition in Williams syndrome (WS), and by hemizygous neuronal Gtf2i deletion model, indicating Gtf2i's dosage-sensitive role in mitochondrial regulation. Clinically relevant, we observed altered transcript levels related to mitochondria, hypoxia, and autophagy in frontal cortex tissue from WS individuals. Our study reveals mitochondrial and autophagy-related deficits shedding light on WS and other Gtf2i-related disorders.
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Affiliation(s)
- Ariel Nir Sade
- The Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Gilad Levy
- The Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Sari Schokoroy Trangle
- The School of Psychological Sciences, Faculty of Social Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Galit Elad Sfadia
- The School of Psychological Sciences, Faculty of Social Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Ela Bar
- The School of Psychological Sciences, Faculty of Social Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Omer Ophir
- The Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Inbar Fischer
- The Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - May Rokach
- The Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Andrea Atzmon
- The Shmunis School of Biomedicine & Cancer Research, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Hadar Parnas
- Neuro-Epigenetics Laboratory, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Tali Rosenberg
- Neuro-Epigenetics Laboratory, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Asaf Marco
- Neuro-Epigenetics Laboratory, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Orna Elroy Stein
- The Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
- The Shmunis School of Biomedicine & Cancer Research, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Boaz Barak
- The Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.
- The School of Psychological Sciences, Faculty of Social Sciences, Tel Aviv University, Tel Aviv, Israel.
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Zegarra-Valdivia JA, Pignatelli J, Nuñez A, Torres Aleman I. The Role of Insulin-like Growth Factor I in Mechanisms of Resilience and Vulnerability to Sporadic Alzheimer's Disease. Int J Mol Sci 2023; 24:16440. [PMID: 38003628 PMCID: PMC10671249 DOI: 10.3390/ijms242216440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Revised: 11/06/2023] [Accepted: 11/14/2023] [Indexed: 11/26/2023] Open
Abstract
Despite decades of intense research, disease-modifying therapeutic approaches for Alzheimer's disease (AD) are still very much needed. Apart from the extensively analyzed tau and amyloid pathological cascades, two promising avenues of research that may eventually identify new druggable targets for AD are based on a better understanding of the mechanisms of resilience and vulnerability to this condition. We argue that insulin-like growth factor I (IGF-I) activity in the brain provides a common substrate for the mechanisms of resilience and vulnerability to AD. We postulate that preserved brain IGF-I activity contributes to resilience to AD pathology as this growth factor intervenes in all the major pathological cascades considered to be involved in AD, including metabolic impairment, altered proteostasis, and inflammation, to name the three that are considered to be the most important ones. Conversely, disturbed IGF-I activity is found in many AD risk factors, such as old age, type 2 diabetes, imbalanced diet, sedentary life, sociality, stroke, stress, and low education, whereas the Apolipoprotein (Apo) E4 genotype and traumatic brain injury may also be influenced by brain IGF-I activity. Accordingly, IGF-I activity should be taken into consideration when analyzing these processes, while its preservation will predictably help prevent the progress of AD pathology. Thus, we need to define IGF-I activity in all these conditions and develop a means to preserve it. However, defining brain IGF-I activity cannot be solely based on humoral or tissue levels of this neurotrophic factor, and new functionally based assessments need to be developed.
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Affiliation(s)
- Jonathan A. Zegarra-Valdivia
- Achucarro Basque Center for Neuroscience, 48940 Leioa, Spain;
- Biomedical Research Networking Center on Neurodegenerative Diseases (CIBERNED), 28029 Madrid, Spain;
- School of Medicine, Universidad Señor de Sipán, Chiclayo 14000, Peru
| | - Jaime Pignatelli
- Biomedical Research Networking Center on Neurodegenerative Diseases (CIBERNED), 28029 Madrid, Spain;
- Cajal Institute (CSIC), 28002 Madrid, Spain
| | - Angel Nuñez
- Department of Anatomy, Histology and Neuroscience, Universidad Autónoma de Madrid, 28049 Madrid, Spain;
| | - Ignacio Torres Aleman
- Achucarro Basque Center for Neuroscience, 48940 Leioa, Spain;
- Biomedical Research Networking Center on Neurodegenerative Diseases (CIBERNED), 28029 Madrid, Spain;
- Ikerbasque, Basque Foundation for Science, 48009 Bilbao, Spain
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Nuñez A, Zegarra-Valdivia J, Fernandez de Sevilla D, Pignatelli J, Torres Aleman I. The neurobiology of insulin-like growth factor I: From neuroprotection to modulation of brain states. Mol Psychiatry 2023; 28:3220-3230. [PMID: 37353586 DOI: 10.1038/s41380-023-02136-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 05/30/2023] [Accepted: 06/13/2023] [Indexed: 06/25/2023]
Abstract
After decades of research in the neurobiology of IGF-I, its role as a prototypical neurotrophic factor is undisputed. However, many of its actions in the adult brain indicate that this growth factor is not only involved in brain development or in the response to injury. Following a three-layer assessment of its role in the central nervous system, we consider that at the cellular level, IGF-I is indeed a bona fide neurotrophic factor, modulating along ontogeny the generation and function of all the major types of brain cells, contributing to sculpt brain architecture and adaptive responses to damage. At the circuit level, IGF-I modulates neuronal excitability and synaptic plasticity at multiple sites, whereas at the system level, IGF-I intervenes in energy allocation, proteostasis, circadian cycles, mood, and cognition. Local and peripheral sources of brain IGF-I input contribute to a spatially restricted, compartmentalized, and timed modulation of brain activity. To better define these variety of actions, we consider IGF-I a modulator of brain states. This definition aims to reconcile all aspects of IGF-I neurobiology, and may provide a new conceptual framework in the design of future research on the actions of this multitasking neuromodulator in the brain.
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Affiliation(s)
- A Nuñez
- Department of Anatomy, Histology and Neurosciences, Universidad Autónoma de Madrid, Madrid, Spain
| | - J Zegarra-Valdivia
- Achucarro Basque Center for Neuroscience, Leioa, Spain
- CIBERNED, Madrid, Spain
- Universidad Señor de Sipán, Chiclayo, Perú
| | - D Fernandez de Sevilla
- Department of Anatomy, Histology and Neurosciences, Universidad Autónoma de Madrid, Madrid, Spain
| | - J Pignatelli
- CIBERNED, Madrid, Spain
- Cajal Institute (CSIC), Madrid, Spain
| | - I Torres Aleman
- Achucarro Basque Center for Neuroscience, Leioa, Spain.
- CIBERNED, Madrid, Spain.
- Ikerbasque Science Foundation, Bilbao, Spain.
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