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Andrade K, Guieysse T, Medani T, Koechlin E, Pantazis D, Dubois B. The dual-path hypothesis for the emergence of anosognosia in Alzheimer's disease. Front Neurol 2023; 14:1239057. [PMID: 38020610 PMCID: PMC10654627 DOI: 10.3389/fneur.2023.1239057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 10/20/2023] [Indexed: 12/01/2023] Open
Abstract
Although neurocognitive models have been proposed to explain anosognosia in Alzheimer's disease (AD), the neural cascade responsible for its origin in the human brain remains unknown. Here, we build on a mechanistic dual-path hypothesis that brings error-monitoring and emotional processing systems as key elements for self-awareness, with distinct impacts on the emergence of anosognosia in AD. Proceeding from the notion of anosognosia as a dimensional syndrome, varying between a lack of concern about one's own deficits (i.e., anosodiaphoria) and a complete lack of awareness of deficits, our hypothesis states that (i) unawareness of deficits would result from primary damage to the error-monitoring system, whereas (ii) anosodiaphoria would more likely result from an imbalance between emotional processing and error-monitoring. In the first case, a synaptic failure in the error-monitoring system, in which the anterior and posterior cingulate cortices play a major role, would have a negative impact on error (or deficits) awareness, preventing patients from becoming aware of their condition. In the second case, an impairment in the emotional processing system, in which the amygdala and the orbitofrontal cortex play a major role, would prevent patients from monitoring the internal milieu for relevant errors (or deficits) and assigning appropriate value to them, thus biasing their impact on the error-monitoring system. Our hypothesis stems on two scientific premises. One comes from preliminary results in AD patients showing a synaptic failure in the error-monitoring system along with a decline of awareness for cognitive difficulties at the time of diagnosis. Another comes from the somatic marker hypothesis, which proposes that emotional signals are critical to adaptive behavior. Further exploration of these premises will be of great interest to illuminate the foundations of self-awareness and improve our knowledge of the underlying paths of anosognosia in AD and other brain disorders.
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Affiliation(s)
- Katia Andrade
- Institute of Memory and Alzheimer’s Disease (IM2A), Department of Neurology, Assistance Publique-Hôpitaux de Paris (AP-HP), Sorbonne University, Pitié-Salpêtrière Hospital, Paris, France
- Frontlab, Paris Brain Institute (Institut du Cerveau, ICM), AP-HP, Pitié-Salpêtrière Hospital, Paris, France
| | - Thomas Guieysse
- Institute of Memory and Alzheimer’s Disease (IM2A), Department of Neurology, Assistance Publique-Hôpitaux de Paris (AP-HP), Sorbonne University, Pitié-Salpêtrière Hospital, Paris, France
| | - Takfarinas Medani
- Signal and Image Processing Institute, University of Southern California, Los Angeles, CA, United States
| | - Etienne Koechlin
- École Normale Supérieure, Laboratoire de Neurosciences Cognitives et Computationnelles, Paris, France
| | - Dimitrios Pantazis
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Bruno Dubois
- Institute of Memory and Alzheimer’s Disease (IM2A), Department of Neurology, Assistance Publique-Hôpitaux de Paris (AP-HP), Sorbonne University, Pitié-Salpêtrière Hospital, Paris, France
- Frontlab, Paris Brain Institute (Institut du Cerveau, ICM), AP-HP, Pitié-Salpêtrière Hospital, Paris, France
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Shi Y, Lv J, Chen L, Luo G, Tao M, Pan J, Hu X, Sheng J, Zhang S, Zhou M, Fan H. Phosphodiesterase-4D Knockdown in the Prefrontal Cortex Alleviates Memory Deficits and Synaptic Failure in Mouse Model of Alzheimer's Disease. Front Aging Neurosci 2021; 13:722580. [PMID: 34539384 PMCID: PMC8446525 DOI: 10.3389/fnagi.2021.722580] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 06/30/2021] [Indexed: 01/19/2023] Open
Abstract
Phosphodiesterase 4 (PDE4)-dependent cAMP signaling plays a crucial role in cognitive impairment associated with Alzheimer’s disease (AD). However, whether inhibition of PDE4 subtypes or their splice variants in the prefrontal cortex positively regulates synaptic plasticity and antioxidative stress, and reverses β-amyloid 1–42 (Aβ1–42, Aβ42)-induced cognitive impairment still need to be clarified. The present study determined whether and how PDE4D knockdown by microinjection of lenti-PDE4D-miRNA into the prefrontal cortex reversed Aβ1–42-induced cognitive impairment in behavioral, neurochemical, and molecular biology assays. The results suggested that PDE4D knockdown increased time to explore the novel object and decreased latency to leave the platform in novel object recognition and step-down passive avoidance tests. Further study suggested that PDE4D knockdown decreased the number of working memory errors in the eight-arm maze test. These effects were prevented by PKA inhibitor H89. The subsequent experiment suggested that inhibition of PDE4D in the prefrontal cortex rescued the long-term potentiation (LTP) and synaptic proteins’ expression; it also increased antioxidant response by increasing superoxide dismutase (SOD) and decreasing malondialdehyde (MDA) levels. PDE4D knockdown also increased phosphorylated cAMP response element-binding protein (pCREB), brain-derived neurotrophic factor (BNDF), and anti-apoptotic proteins’ expression, i.e., the ratio of Bcl-2/Bax, and decreased caspase-3 level in the prefrontal cortex. These findings extend the previous findings and support the hypothesis that RNA interference-mediated PDE4D knockdown in the prefrontal cortex ameliorated memory loss associated with synaptic failure in an AD mouse model by its antioxidant, anti-apoptotic, and neuroprotective properties.
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Affiliation(s)
- Yongchuan Shi
- Department of Medicine, Jinshan Branch of the Sixth People's Hospital of Shanghai, Shanghai Jiao Tong University, Shanghai, China
| | - Jinpeng Lv
- School of Pharmaceutical Engineering, Changzhou University, Changzhou, China
| | - Ling Chen
- Key Laboratory of Clinical Cancer Pharmacology and Toxicology Research of Zhejiang Province, Department of Clinical Pharmacy, Affiliated Hangzhou First People's Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Guojun Luo
- Department of Medicine, Jinshan Branch of the Sixth People's Hospital of Shanghai, Shanghai Jiao Tong University, Shanghai, China
| | - Mengjia Tao
- School of Pharmacy, Brain Institute, Wenzhou Medical University, Wenzhou, China
| | - Jianchun Pan
- School of Pharmacy, Brain Institute, Wenzhou Medical University, Wenzhou, China
| | - Xiaoxiong Hu
- Department of Gastroenterology, The People's Hospital of Yichun City, Yi Chun University, Yichun, China
| | - Jianwen Sheng
- Department of Gastroenterology, The People's Hospital of Yichun City, Yi Chun University, Yichun, China
| | - Shanjin Zhang
- Department of Gastroenterology, The People's Hospital of Yichun City, Yi Chun University, Yichun, China
| | - Min Zhou
- Department of Medicine, Jinshan Branch of the Sixth People's Hospital of Shanghai, Shanghai Jiao Tong University, Shanghai, China
| | - Huizhen Fan
- Department of Gastroenterology, The People's Hospital of Yichun City, Yi Chun University, Yichun, China
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le Feber J, Erkamp N, van Putten MJAM, Hofmeijer J. Loss and recovery of functional connectivity in cultured cortical networks exposed to hypoxia. J Neurophysiol 2017; 118:394-403. [PMID: 28424292 DOI: 10.1152/jn.00098.2017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 04/18/2017] [Accepted: 04/18/2017] [Indexed: 01/13/2023] Open
Abstract
In the core of a brain infarct, loss of neuronal function is followed by neuronal death within minutes. In an area surrounding the core (penumbra), some perfusion remains. Here, neurons initially remain structurally intact, but massive synaptic failure strongly reduces neural activity. Activity in the penumbra may eventually recover or further deteriorate toward massive cell death. Besides activity recovery, return of brain functioning requires restoration of connectivity. However, low activity has been shown to initiate compensatory mechanisms that affect network connectivity. We investigated the effect of transient hypoxia and compensatory mechanisms on activity and functional connectivity using cultured cortical networks on multielectrode arrays. Networks were exposed to hypoxia of controlled depth (10-90% of normoxia) and duration (6-48 h). First, we determined how hypoxic depth and duration govern activity recovery. Then, we investigated connectivity changes during and after hypoxic incidents, mild enough for activity to recover. Shortly after hypoxia onset, activity and connectivity decreased. Following 4-6 h of ongoing hypoxia, we observed partial recovery. Only if the hypoxic burden was limited did connectivity show further recovery upon return to normoxia. Partial recovery during hypoxia was dominated by restored baseline connections, rather than newly formed ones. Baseline strengths of surviving (persisting or recovered) and lost connections did not differ nor did baseline activity at their "presynaptic" electrodes. However, "postsynaptic" electrodes of surviving connections were significantly more active during baseline than those of lost connections. This implies that recovery during hypoxia reflects an effective mechanism to restore network activity, which does not necessarily conserve prehypoxia connectivity.NEW & NOTEWORTHY Hypoxia reduced the firing rates of cultured neurons. Depending on hypoxic depth and duration, activity recovered during hypoxia and upon return to normoxia. Recovery (partial) during hypoxia was associated with restored baseline connections rather than newly formed ones. Predominantly, baseline connections with most active postsynaptic electrodes recovered, supporting the notion of effective activity homeostasis. This compensatory mechanism remained effective during ~20 h of hypoxia. Beyond 20 h of compensation, loss of activity and connectivity became irreversible.
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Affiliation(s)
- Joost le Feber
- Clinical Neurophysiology, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands;
| | - Niels Erkamp
- Clinical Neurophysiology, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands
| | - Michel J A M van Putten
- Clinical Neurophysiology, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands.,Department of Clinical Neurophysiology, Medisch Spectrum Twente, Enschede, the Netherlands; and
| | - Jeannette Hofmeijer
- Clinical Neurophysiology, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands.,Department of Neurology, Rijnstate Hospital, Arnhem, the Netherlands
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Marshall MS, Bongarzone ER. Beyond Krabbe's disease: The potential contribution of galactosylceramidase deficiency to neuronal vulnerability in late-onset synucleinopathies. J Neurosci Res 2016; 94:1328-32. [PMID: 27638614 PMCID: PMC5027968 DOI: 10.1002/jnr.23751] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Revised: 03/22/2016] [Accepted: 03/30/2016] [Indexed: 12/21/2022]
Abstract
New insights into the pathophysiological mechanisms behind late-onset neurodegenerative diseases have come from unexpected sources in recent years. Specifically, the group of inherited metabolic disorders known as lysosomal storage diseases that most commonly affect infants has been found to have surprising similarities with adult neurodegenerative disorders. Most notable has been the identification of Gaucher's disease as a comorbidity for Parkinson's disease. Prompted by the recent identification of neuronal aggregates of α-synuclein in another lysosomal storage disease, Krabbe's disease, we propose the idea that a similar connection exists between adult synucleinopathies and Krabbe's. Similarities between the two diseases, including the pattern of α-synuclein aggregation in the brain of the twitcher mouse (the authentic murine model of Krabbe's disease), changes to lipid membrane dynamics, and possible dysfunction in synaptic function and macroautophagy, underscore a link between Krabbe's disease and late-onset synucleinopathies. Silent GALC mutations may even constitute a risk factor for the development of Parkinson's in certain patients. More research is required to identify definitively any link and the validity of this hypothesis, but such a connection would prove invaluable for developing novel therapeutic targets for Parkinson's based on our current understanding of Krabbe's disease and for establishing new biomarkers for the identification of at-risk patients. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Michael S Marshall
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, Illinois.
- Graduate Program in Neuroscience, University of Illinois at Chicago, Chicago, Illinois.
- Medical Scientist Training Program, University of Illinois at Chicago, Chicago, Illinois.
| | - Ernesto R Bongarzone
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, Illinois.
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Buskila Y, Crowe SE, Ellis-Davies GCR. Synaptic deficits in layer 5 neurons precede overt structural decay in 5xFAD mice. Neuroscience 2013; 254:152-9. [PMID: 24055684 DOI: 10.1016/j.neuroscience.2013.09.016] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/20/2013] [Accepted: 09/06/2013] [Indexed: 12/15/2022]
Abstract
Synaptic decay and neurodegeneration are hallmarks of Alzheimer's disease that are thought to precede dementia. Recently, we have reported that the first signs of neuritic dystrophy in a new transgenic mouse model of familial Alzheimer's disease (FAD) called the "5xFAD" are axonal dystrophy followed by loss of spines on basal dendrites. The 5xFAD mouse has profound loss of layer 5 neurons by 12months, and these initial structural insults appear between 4 and 6months of age. Here, we test, for the first time, if synaptic failure of layer 5 neurons in the 5xFAD mouse precedes these structural changes. We used longitudinal, in vivo two-photon fluorescence imaging of bigenic 5xFAD/YFP mice to assess the overall structural stability of layer 5 neurons in young mice (age less than 14weeks). We found these neurons to be structurally and morphologically sound. In parallel, we used in vitro, whole-cell patch clamp electrophysiology of layer 5 pyramidal neurons, from mice aged 8-12weeks, to reveal significant pre- and postsynaptic defects in these cells. Thus our data suggest that layer 5 neurons in the 5xFAD mouse model have synaptic deficits at an early time point, before any overt structural dystrophy, and that such synaptic failure, with co-temporal biochemical changes, may be an early step in neuronal loss.
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Affiliation(s)
- Y Buskila
- Department of Neuroscience, Mount Sinai School of Medicine, New York, NY 10029, USA; Bioelectronics and Neuroscience Group, The MARCS Institute, University of Western Sydney, NSW 2560, Australia
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