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Alterations in CA1 pyramidal neuronal intrinsic excitability mediated by Ih channel currents in a rat model of amyloid beta pathology. Neuroscience 2015; 305:279-92. [PMID: 26254243 DOI: 10.1016/j.neuroscience.2015.07.087] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 07/28/2015] [Accepted: 07/31/2015] [Indexed: 01/05/2023]
Abstract
Amyloid beta (Aβ) accumulation plays an important role in the pathogenesis of Alzheimer's disease (AD) by changing the neuronal excitability. However, the cellular mechanisms by which accumulation of Aβ affects intrinsic neuronal properties are not well understood. The effect of bilateral intra-frontal cortex Aβ (1-42) peptide injection on the intrinsic excitability of hippocampal CA1 pyramidal neurons with particular focus on the contribution of hyperpolarization-activated (Ih) channel currents was examined using whole-cell patch-clamp recording. Passive avoidance memory impairment and morphological changes in rats receiving intra-frontal Aβ treatment were observed, which was associated with significant changes both in passive and active intrinsic electrical membrane properties of CA1 pyramidal neurons. Electrophysiological recording showed a significant decrease in neuronal excitability associated with an augmentation in the first spike after-hyperpolarization (AHP) amplitude. In addition, the depolarizing sag voltage was altered in neurons recorded from Aβ-treated group. In voltage-clamp condition, a hyperpolarizing activated inward current sensitive to ZD7288 and capsaicin was significantly increased in neurons from Aβ-treated rats. The Ih current density was increased and the activation curve was shifted toward less negative potential in the Aβ-treated group as compared to control group. The enhancing effect of Aβ treatment on Ih current was confirmed by showing upregulation of the mRNA of HCN1 channel in the CA1 pyramidal layer of hippocampi. These findings suggest the contribution of Ih and possibly TRPV1 channel currents to the changes induced by Aβ treatment in the intrinsic membrane properties, which, in turn, may provide therapeutic targets for treatment of AD.
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152
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Glucagon-like peptide-1 regulates mitochondrial biogenesis and tau phosphorylation against advanced glycation end product-induced neuronal insult: Studies in vivo and in vitro. Neuroscience 2015; 300:75-84. [DOI: 10.1016/j.neuroscience.2015.05.023] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 05/07/2015] [Accepted: 05/08/2015] [Indexed: 01/21/2023]
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153
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Mitochondrial Dysfunction Contributes to the Pathogenesis of Alzheimer's Disease. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2015. [PMID: 26221414 PMCID: PMC4499633 DOI: 10.1155/2015/509654] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Alzheimer's disease (AD) is a neurodegenerative disease that affects millions of people worldwide. Currently, there is no effective treatment for AD, which indicates the necessity to understand the pathogenic mechanism of this disorder. Extracellular aggregates of amyloid precursor protein (APP), called Aβ peptide and neurofibrillary tangles (NFTs), formed by tau protein in the hyperphosphorylated form are considered the hallmarks of AD. Accumulative evidence suggests that tau pathology and Aβ affect neuronal cells compromising energy supply, antioxidant response, and synaptic activity. In this context, it has been showed that mitochondrial function could be affected by the presence of tau pathology and Aβ in AD. Mitochondria are essential for brain cells function and the improvement of mitochondrial activity contributes to preventing neurodegeneration. Several reports have suggested that mitochondria could be affected in terms of morphology, bioenergetics, and transport in AD. These defects affect mitochondrial health, which later will contribute to the pathogenesis of AD. In this review, we will discuss evidence that supports the importance of mitochondrial injury in the pathogenesis of AD and how studying these mechanisms could lead us to suggest new targets for diagnostic and therapeutic intervention against neurodegeneration.
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154
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Liu G, Liu C, Zhang XN. Comparison of the neuropsychological mechanisms of 2,6-diisopropylphenol and N-methyl-D-aspartate receptor antagonist against electroconvulsive therapy-induced learning and memory impairment in depressed rats. Mol Med Rep 2015; 12:3297-3308. [PMID: 25998151 PMCID: PMC4526078 DOI: 10.3892/mmr.2015.3803] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2014] [Accepted: 04/14/2015] [Indexed: 11/06/2022] Open
Abstract
The present study aimed to examine the neurophysiological mechanisms of the 2,6-diisopropylphenol and N-methyl-D-aspartate (NMDA) receptor antagonist against learning and memory impairment, induced by electroconvulsive therapy (ECT). A total of 48 adult depressed rats without olfactory bulbs were randomly divided into six experimental groups: i) saline; ii) 10 mg/kg MK‑801; iii) 10 mg/kg MK‑801 and a course of ECT; iv) 200 mg/kg 2,6‑diisopropylphenol; v) 200 mg/kg 2,6‑diisopropylphenol and a course of ECT; and vi) saline and a course of ECT. The learning and memory abilities of the rats were assessed using a Morris water maze 1 day after a course of ECT. The hippocampus was removed 1 day after assessment using the Morris water maze assessment. The content of glutamate in the hippocampus was detected using high‑performance liquid chromatography. The expression levels of p‑AT8Ser202 and GSK‑3β1H8 in the hippocampus were determined using immunohistochemical staining and western blot analysis. The results demonstrated that the 2,6‑diisopropylphenol NMDA receptor antagonist, MK‑801 and ECT induced learning and memory impairment in the depressed rats. The glutamate content was significantly upregulated by ECT, reduced by 2,6‑diisopropylphenol, and was unaffected by the NMDA receptor antagonist in the hippocampus of the depressed rats. Tau protein hyperphosphorylation in the hippocampus was upregulated by ECT, but was reduced by 2,6‑diisopropylphenol and the MK‑801 NMDA receptor antagonist. It was also demonstrated that 2,6‑diisopropylphenol prevented learning and memory impairment and reduced the hyperphosphorylation of the Tau protein, which was induced by eECT. GSK‑3β was found to be the key protein involved in this signaling pathway. The ECT reduced the learning and memory impairment, caused by hyperphosphorylation of the Tau protein, in the depressed rats by upregulating the glutamate content.
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Affiliation(s)
- Gang Liu
- Department of Anesthesiology, General Hospital of Beijing Military Area of PLA, Beijing 100700, P.R. China
| | - Chao Liu
- Department of Anesthesiology, Tianjin Chest Hospital, Tianjin 300222, P.R. China
| | - Xue-Ning Zhang
- Department of Radiology, The Second Hospital of Tianjin Medical University, Tianjin 300211, P.R. China
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155
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Alzheimer's pathogenesis and its link to the mitochondrion. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2015; 2015:803942. [PMID: 25973139 PMCID: PMC4417983 DOI: 10.1155/2015/803942] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Revised: 03/16/2015] [Accepted: 04/02/2015] [Indexed: 01/02/2023]
Abstract
Alzheimer's disease (AD) is the most common form of dementia in the elderly. This neurodegenerative disorder is clinically characterized by impairment of cognitive functions and changes in behaviour and personality. The pathogenesis of AD is still unclear. Recent evidence supports some role of mitochondria dysfunction and oxidative stress in the development of the neurodegenerative process. In this review, we discuss the role of mitochondrial dysfunction in AD, focusing on the mechanisms that lead to mitochondrial impairment, oxidative stress, and neurodegeneration, a “vicious circle” that ends in dementia.
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156
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Bennett RE, Brody DL. Array tomography for the detection of non-dilated, injured axons in traumatic brain injury. J Neurosci Methods 2015; 245:25-36. [PMID: 25687633 DOI: 10.1016/j.jneumeth.2015.02.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Revised: 02/05/2015] [Accepted: 02/06/2015] [Indexed: 10/24/2022]
Abstract
BACKGROUND Axonal injury is a key feature of several types of brain trauma and neurological disease. However, in mice and humans, many axons are less than 500 nm in diameter which is at or below the resolution of most conventional light microscopic imaging methods. In moderate to severe forms of axon injury, damaged axons become dilated and therefore readily detectible by light microscopy. However, in more subtle forms of injury, the damaged axons may remain undilated and therefore difficult to detect. NEW METHOD Here we present a method for adapting array tomography for the identification and quantification of injured axons. In this technique, ultrathin (∼70 nm) plastic sections of tissue are prepared, labeled with axon injury-relevant antibodies and imaged using conventional epifluorescence. RESULTS To demonstrate the use of array-tomography-based methods, we determined that mice that received two closed-skull concussive traumatic brain injury impacts had significantly increased numbers of non-dilated axons that were immunoreactive for non-phosphorylated neurofilament (SMI-32; a marker of axonal injury), compared to sham mice (1682±628 versus 339±52 per mm(2), p=0.004, one-tailed Mann-Whitney U test). Tubulin loss was not evident (p=0.2063, one-tailed Mann-Whitney U test). Furthermore, mice that were subjected to more severe injury had a loss of tubulin in addition to both dilated and non-dilated SMI-32 immunoreactive axons indicating that this technique is suitable for the analysis of various injury conditions. COMPARISON WITH EXISTING METHOD With array tomography we could detect similar overall numbers of axons as electron microscopy, but accurate diameter measurements were limited to those with diameters >200 nm. Importantly, array tomography had greater sensitivity for detecting small non-dilated injured axons compared with conventional immunohistochemistry. CONCLUSION Imaging of individual axons and quantification of subtle axonal injury is possible using this array tomography method. This method may be most useful for the assessment of concussive injuries and other pathologies in which injured axons are not typically dilated. The ability to process moderately large volumes of tissue, label multiple proteins of interest, and automate analysis support array tomography as a useful alternative to electron microscopy.
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Affiliation(s)
- Rachel E Bennett
- Department of Neurology, Washington University in St. Louis, 660 S. Euclid Avenue, Saint Louis, MO 63110, USA
| | - David L Brody
- Department of Neurology, Washington University in St. Louis, 660 S. Euclid Avenue, Saint Louis, MO 63110, USA.
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157
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Tu S, Okamoto SI, Lipton SA, Xu H. Oligomeric Aβ-induced synaptic dysfunction in Alzheimer's disease. Mol Neurodegener 2014; 9:48. [PMID: 25394486 PMCID: PMC4237769 DOI: 10.1186/1750-1326-9-48] [Citation(s) in RCA: 377] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 10/08/2014] [Indexed: 11/30/2022] Open
Abstract
Alzheimer’s disease (AD) is a devastating disease characterized by synaptic and neuronal loss in the elderly. Compelling evidence suggests that soluble amyloid-β peptide (Aβ) oligomers induce synaptic loss in AD. Aβ-induced synaptic dysfunction is dependent on overstimulation of N-methyl-D-aspartate receptors (NMDARs) resulting in aberrant activation of redox-mediated events as well as elevation of cytoplasmic Ca2+, which in turn triggers downstream pathways involving phospho-tau (p-tau), caspases, Cdk5/dynamin-related protein 1 (Drp1), calcineurin/PP2B, PP2A, Gsk-3β, Fyn, cofilin, and CaMKII and causes endocytosis of AMPA receptors (AMPARs) as well as NMDARs. Dysfunction in these pathways leads to mitochondrial dysfunction, bioenergetic compromise and consequent synaptic dysfunction and loss, impaired long-term potentiation (LTP), and cognitive decline. Evidence also suggests that Aβ may, at least in part, mediate these events by causing an aberrant rise in extrasynaptic glutamate levels by inhibiting glutamate uptake or triggering glutamate release from glial cells. Consequent extrasynaptic NMDAR (eNMDAR) overstimulation then results in synaptic dysfunction via the aforementioned pathways. Consistent with this model of Aβ-induced synaptic loss, Aβ synaptic toxicity can be partially ameliorated by the NMDAR antagonists (such as memantine and NitroMemantine). PSD-95, an important scaffolding protein that regulates synaptic distribution and activity of both NMDA and AMPA receptors, is also functionally disrupted by Aβ. PSD-95 dysregulation is likely an important intermediate step in the pathological cascade of events caused by Aβ. In summary, Aβ-induced synaptic dysfunction is a complicated process involving multiple pathways, components and biological events, and their underlying mechanisms, albeit as yet incompletely understood, may offer hope for new therapeutic avenues.
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Affiliation(s)
- Shichun Tu
- Neuroscience and Aging Research Center, Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA.
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158
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Du X, Zheng Y, Wang Z, Chen Y, Zhou R, Song G, Ni J, Liu Q. Inhibitory Act of Selenoprotein P on Cu+/Cu2+-Induced Tau Aggregation and Neurotoxicity. Inorg Chem 2014; 53:11221-30. [DOI: 10.1021/ic501788v] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Xiubo Du
- Department
of Marine Biology, Shenzhen Key Laboratory of Marine Biotechnology
and Ecology and ‡College of Life Sciences, Shenzhen Key Laboratory of Microbial Genetic
Engineering, Shenzhen University, Shenzhen 518060, China
| | - Youbiao Zheng
- Department
of Marine Biology, Shenzhen Key Laboratory of Marine Biotechnology
and Ecology and ‡College of Life Sciences, Shenzhen Key Laboratory of Microbial Genetic
Engineering, Shenzhen University, Shenzhen 518060, China
| | - Zhi Wang
- Department
of Marine Biology, Shenzhen Key Laboratory of Marine Biotechnology
and Ecology and ‡College of Life Sciences, Shenzhen Key Laboratory of Microbial Genetic
Engineering, Shenzhen University, Shenzhen 518060, China
| | - Yijing Chen
- Department
of Marine Biology, Shenzhen Key Laboratory of Marine Biotechnology
and Ecology and ‡College of Life Sciences, Shenzhen Key Laboratory of Microbial Genetic
Engineering, Shenzhen University, Shenzhen 518060, China
| | - Rui Zhou
- Department
of Marine Biology, Shenzhen Key Laboratory of Marine Biotechnology
and Ecology and ‡College of Life Sciences, Shenzhen Key Laboratory of Microbial Genetic
Engineering, Shenzhen University, Shenzhen 518060, China
| | - Guoli Song
- Department
of Marine Biology, Shenzhen Key Laboratory of Marine Biotechnology
and Ecology and ‡College of Life Sciences, Shenzhen Key Laboratory of Microbial Genetic
Engineering, Shenzhen University, Shenzhen 518060, China
| | - Jiazuan Ni
- Department
of Marine Biology, Shenzhen Key Laboratory of Marine Biotechnology
and Ecology and ‡College of Life Sciences, Shenzhen Key Laboratory of Microbial Genetic
Engineering, Shenzhen University, Shenzhen 518060, China
| | - Qiong Liu
- Department
of Marine Biology, Shenzhen Key Laboratory of Marine Biotechnology
and Ecology and ‡College of Life Sciences, Shenzhen Key Laboratory of Microbial Genetic
Engineering, Shenzhen University, Shenzhen 518060, China
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159
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Grishchuk Y, Sri S, Rudinskiy N, Ma W, Stember KG, Cottle MW, Sapp E, Difiglia M, Muzikansky A, Betensky RA, Wong AMS, Bacskai BJ, Hyman BT, Kelleher RJ, Cooper JD, Slaugenhaupt SA. Behavioral deficits, early gliosis, dysmyelination and synaptic dysfunction in a mouse model of mucolipidosis IV. Acta Neuropathol Commun 2014; 2:133. [PMID: 25200117 PMCID: PMC4173007 DOI: 10.1186/s40478-014-0133-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 08/26/2014] [Indexed: 12/04/2022] Open
Abstract
Mucolipidosis IV (MLIV) is caused by mutations in the gene MCOLN1. Patients with MLIV have severe neurologic deficits and very little is known about the brain pathology in this lysosomal disease. Using an accurate mouse model of mucolipidosis IV, we observed early behavioral deficits which were accompanied by activation of microglia and astrocytes. The glial activation that persisted during the course of disease was not accompanied by neuronal loss even at the late stage. In vivo [Ca2+]-imaging revealed no changes in resting [Ca2+] levels in Mcoln1−/− cortical neurons, implying their physiological health. Despite the absence of neuron loss, we observed alterations in synaptic plasticity, as indicated by elevated paired-pulse facilitation and enhanced long-term potentiation. Myelination deficits and severely dysmorphic corpus callosum were present early and resembled white matter pathology in mucolipidosis IV patients. These results indicate the early involvement of glia, and challenge the traditional view of mucolipidosis IV as an overtly neurodegenerative condition.
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160
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Purnell PR, Fox HS. Efavirenz induces neuronal autophagy and mitochondrial alterations. J Pharmacol Exp Ther 2014; 351:250-8. [PMID: 25161171 DOI: 10.1124/jpet.114.217869] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Efavirenz (EFV) is a non-nucleoside reverse-transcriptase inhibitor in wide use for the treatment of human immunodeficiency virus infection. Although EFV is generally well tolerated, neuropsychiatric toxicity has been well documented. The toxic effects of EFV in hepatocytes and keratinocytes have been linked to mitochondrial perturbations and changes in autophagy. Here, we studied the effect of EFV on mitochondria and autophagy in neuronal cell lines and primary neurons. In SH-SY5Y cells, EFV induced a drop in ATP production, which coincided with increased autophagy, mitochondrial fragmentation, and mitochondrial depolarization. EFV-induced mitophagy was also detected by colocalization of mitochondria and autophagosomes and use of an outer mitochondrial membrane tandem fluorescent vector. Pharmacologic inhibition of autophagy with 3-methyladenine increased the cytotoxic effect of EFV, suggesting that autophagy promotes cell survival. EFV also reduces ATP production in primary neurons, induces autophagy, and changes mitochondrial morphology. Overall, EFV is able to acutely induce autophagy and mitochondrial changes in neurons. These changes may be involved in the mechanism leading to central nervous system toxicity observed in clinical EFV use.
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Affiliation(s)
- Phillip R Purnell
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, Nebraska
| | - Howard S Fox
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, Nebraska
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161
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Synapse Density and Dendritic Complexity Are Reduced in the Prefrontal Cortex following Seven Days of Forced Abstinence from Cocaine Self-Administration. PLoS One 2014; 9:e102524. [PMID: 25072653 PMCID: PMC4114454 DOI: 10.1371/journal.pone.0102524] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 06/19/2014] [Indexed: 12/03/2022] Open
Abstract
Chronic cocaine exposure in both human addicts and in rodent models of addiction reduces prefrontal cortical activity, which subsequently dysregulates reward processing and higher order executive function. The net effect of this impaired gating of behavior is enhanced vulnerability to relapse. Previously we have shown that cocaine-induced increases in brain-derived neurotrophic factor (BDNF) expression in the medial prefrontal cortex (PFC) is a neuroadaptive mechanism that blunts the reinforcing efficacy of cocaine. As BDNF is known to affect neuronal survival and synaptic plasticity, we tested the hypothesis that abstinence from cocaine self-administration would lead to alterations in neuronal morphology and synaptic density in the PFC. Using a novel technique, array tomography and Golgi staining, morphological changes in the rat PFC were analyzed following 14 days of cocaine self-administration and 7 days of forced abstinence. Our results indicate that overall dendritic branching and total synaptic density are significantly reduced in the rat PFC. In contrast, the density of thin dendritic spines are significantly increased on layer V pyramidal neurons of the PFC. These findings indicate that dynamic structural changes occur during cocaine abstinence that may contribute to the observed hypo-activity of the PFC in cocaine-addicted individuals.
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162
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Gerson JE, Sengupta U, Lasagna-Reeves CA, Guerrero-Muñoz MJ, Troncoso J, Kayed R. Characterization of tau oligomeric seeds in progressive supranuclear palsy. Acta Neuropathol Commun 2014; 2:73. [PMID: 24927818 PMCID: PMC4229782 DOI: 10.1186/2051-5960-2-73] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 06/10/2014] [Indexed: 02/01/2023] Open
Abstract
Background Progressive supranuclear palsy (PSP) is a neurodegenerative tauopathy which is primarily defined by the deposition of tau into globose-type neurofibrillary tangles (NFT). Tau in its native form has important functions for microtubule dynamics. Tau undergoes alternative splicing in exons 2, 3, and 10 which results in six different isoforms. Products of splicing on exon 10 are the most prone to mutations. Three repeat (3R) and four repeat (4R) tau, like other disease-associated amyloids, can form oligomers which may then go on to further aggregate and form fibrils. Recent studies from our laboratory and others have provided evidence that tau oligomers, not NFTs, are the most toxic species in neurodegenerative tauopathies and seed the pathological spread of tau. Results Analysis of PSP brain sections revealed globose-type NFTs, as well as both phosphorylated and unphosphorylated tau oligomers. Analysis of PSP brains via Western blot and ELISA revealed the presence of increased levels of tau oligomers compared to age-matched control brains. Oligomers were immunoprecipitated from PSP brain and were capable of seeding the oligomerization of both 3R and 4R tau isoforms. Conclusions This is the first time tau oligomers have been characterized in PSP. These results indicate that tau oligomers are an important component of PSP pathology, along with NFTs. The ability of PSP brain-derived tau oligomers to seed 3R and 4R tau suggests that these oligomers represent the pathological species responsible for disease propagation and the presence of oligomers in a pure neurodegenerative tauopathy implies a common neuropathological process for tau seen in diseases with other amyloid proteins.
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163
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Spires-Jones TL, Hyman BT. The intersection of amyloid beta and tau at synapses in Alzheimer's disease. Neuron 2014; 82:756-71. [PMID: 24853936 PMCID: PMC4135182 DOI: 10.1016/j.neuron.2014.05.004] [Citation(s) in RCA: 748] [Impact Index Per Article: 74.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/02/2014] [Indexed: 02/07/2023]
Abstract
The collapse of neural networks important for memory and cognition, including death of neurons and degeneration of synapses, causes the debilitating dementia associated with Alzheimer's disease (AD). We suggest that synaptic changes are central to the disease process. Amyloid beta and tau form fibrillar lesions that are the classical hallmarks of AD. Recent data indicate that both molecules may have normal roles at the synapse, and that the accumulation of soluble toxic forms of the proteins at the synapse may be on the critical path to neurodegeneration. Further, the march of neurofibrillary tangles through brain circuits appears to take advantage of recently described mechanisms of transsynaptic spread of pathological forms of tau. These two key phenomena, synapse loss and the spread of pathology through the brain via synapses, make it critical to understand the physiological and pathological roles of amyloid beta and tau at the synapse.
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Affiliation(s)
- Tara L Spires-Jones
- Centre for Cognitive and Neural Systems, The University of Edinburgh, 1 George Square, Edinburgh, EH8 9JZ, UK; The Euan MacDonald Centre, The University of Edinburgh, 1 George Square, Edinburgh, EH8 9JZ, UK.
| | - Bradley T Hyman
- Massachusetts General Hospital, Harvard Medical School, Neurology, 114 16(th) Street, Charlestown, MA 02129, USA.
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164
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Insulin therapy modulates mitochondrial dynamics and biogenesis, autophagy and tau protein phosphorylation in the brain of type 1 diabetic rats. Biochim Biophys Acta Mol Basis Dis 2014; 1842:1154-66. [PMID: 24747740 DOI: 10.1016/j.bbadis.2014.04.011] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 04/08/2014] [Accepted: 04/10/2014] [Indexed: 01/22/2023]
Abstract
The main purpose of this study was to examine whether streptozotocin (STZ)-induced type 1 diabetes (T1D) and insulin (INS) treatment affect mitochondrial function, fission/fusion and biogenesis, autophagy and tau protein phosphorylation in cerebral cortex from diabetic rats treated or not with INS. No significant alterations were observed in mitochondrial function as well as pyruvate levels, despite the significant increase in glucose levels observed in INS-treated diabetic rats. A significant increase in DRP1 protein phosphorylated at Ser616 residue was observed in the brain cortex of STZ rats. Also an increase in NRF2 protein levels and in the number of copies of mtDNA were observed in STZ diabetic rats, these alterations being normalized by INS. A slight decrease in LC3-II levels was observed in INS-treated rats when compared to STZ diabetic animals. An increase in tau protein phosphorylation at Ser396 residue was observed in STZ diabetic rats while INS treatment partially reversed that effect. Accordingly, a modest reduction in the activation of GSK3β and a significant increase in the activity of phosphatase 2A were found in INS-treated rats when compared to STZ diabetic animals. No significant alterations were observed in caspases 9 and 3 activity and synaptophysin and PSD95 levels. Altogether our results show that mitochondrial alterations induced by T1D seem to involve compensation mechanisms since no significant changes in mitochondrial function and synaptic integrity were observed in diabetic animals. In addition, INS treatment is able to normalize the alterations induced by T1D supporting the importance of INS signaling in the brain.
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165
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Beharry C, Cohen LS, Di J, Ibrahim K, Briffa-Mirabella S, Alonso ADC. Tau-induced neurodegeneration: mechanisms and targets. Neurosci Bull 2014; 30:346-58. [PMID: 24733656 DOI: 10.1007/s12264-013-1414-z] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Accepted: 01/03/2014] [Indexed: 11/28/2022] Open
Abstract
The accumulation of hyperphosphorylated tau is a common feature of several dementias. Tau is one of the brain microtubule-associated proteins. Here we discuss tau's functions in microtubule assembly and stabilization and with regard to its interactions with other proteins. We describe and analyze important post-translational modifications: hyperphosphorylation, ubiquitination, glycation, glycosylation, nitration, polyamination, proteolysis, acetylation, and methylation. We discuss how these post-translational modifications can alter tau's biological function. We analyze the role of mitochondrial health in neurodegeneration. We propose that microtubules could be a therapeutic target and review different approaches. Finally, we consider whether tau accumulation or its conformational change is related to tau-induced neurodegeneration, and propose a mechanism of neurodegeneration.
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Affiliation(s)
- Cindy Beharry
- Department of Biology and Center for Developmental Neuroscience, College of Staten Island, Graduate Center, The City University of New York, Staten Island, NY, 10314, USA
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166
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Majid T, Ali YO, Venkitaramani DV, Jang MK, Lu HC, Pautler RG. In vivo axonal transport deficits in a mouse model of fronto-temporal dementia. NEUROIMAGE-CLINICAL 2014; 4:711-7. [PMID: 24936422 PMCID: PMC4053640 DOI: 10.1016/j.nicl.2014.02.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/12/2013] [Revised: 02/12/2014] [Accepted: 02/14/2014] [Indexed: 11/16/2022]
Abstract
Background Axonal transport is vital for neurons and deficits in this process have been previously reported in a few mouse models of Alzheimer's disease prior to the appearance of plaques and tangles. However, it remains to be determined whether axonal transport is defective prior to the onset of neurodegeneration. The rTg4510 mouse, a fronto-temporal dementia and parkinsonism-17 (FTDP-17) tauopathy model, over-express tau-P301L mutation found in familial forms of FTDP-17, in the forebrain driven by the calcium–calmodulin kinase II promoter. This mouse model exhibits tau pathology, neurodegeneration in the forebrain, and associated behavioral deficits beginning at 4–5 months of age. Animal model rTg4510 transgenic mice were used in these studies. Mice were given 2 μL of MnCl2 in each nostril 1 h prior to Magnetic Resonance Imaging (MRI). Following MnCl2 nasal lavage, mice were imaged using Manganese enhanced Magnetic Resonance Imaging (MEMRI) Protocol with TE = 8.5 ms, TR = 504 ms, FOV = 3.0 cm, matrix size = 128 × 128 × 128, number of cycles = 15 with each cycle taking approximately 2 min, 9 s, and 24 ms using Paravision software (BrukerBioSpin, Billerica, MA). During imaging, body temperature was maintained at 37.0 °C using an animal heating system (SA Instruments, Stony Brook, NY). Data analysis Resulting images were analyzed using Paravision software. Regions of interest (ROI) within the olfactory neuronal layer (ONL) and the water phantom consisting of one pixel (ONL) and 9 pixels (water) were selected and copied across each of the 15 cycles. Signal intensities (SI) of ONL and water phantom ROIs were measured. SI values obtained for ONL were then normalized the water phantom SI values. The correlation between normalized signal intensity in the ONL and time were assessed using Prism (GraphPad Software, San Diego, CA). Results Using the MEMRI technique on 1.5, 3, 5, and 10-month old rTg4510 mice and littermate controls, we found significant axonal transport deficits present in the rTg4510 mice beginning at 3 months of age in an age-dependent manner. Using linear regression analysis, we measured rates of axonal transport at 1.5, 3, 5, and 10 months of age in rTg4510 and WT mice. Axonal transport rates were observed in rTg4510 mice at 48% of WT levels at 3 months, 40% of WT levels at 5 months, and 30% of WT levels at 10 months of age. In order to determine the point at which tau appears in the cortex, we probed for phosphorylated tau levels, and found that pSer262 is present at 3 months of age, not earlier at 1.5 months of age, but observed no pathological tau species until 6 months of age, months after the onset of the transport deficits. In addition, we saw localization of tau in the ONL at 6 months of age. Discussion In our study, we identified the presence of age-dependent axonal transport deficits beginning at 3 months of age in rTg4510 mice. We correlated these deficits at 3 months to the presence of hyperphosphorylated tau in the brain and the presence within the olfactory epithelium. We observed tau pathology not only in the soma of these neurons but also within the axons and processes of these neurons. Our characterization of axonal transport in this tauopathy model provides a functional time point that can be used for future therapeutic interventions. We used MEMRI to define axonal transport rate changes in the rTg4510 mouse. We observed significant hyperphosphorylated tau starting at 3 months of age. We found an age-dependent decline in axonal transport rates. Declines in axonal transport correlated with increases in hyperphosphorylated tau.
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Affiliation(s)
- Tabassum Majid
- Interdepartmental Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, TX, USA ; Department of Molecular Physiology and Biophysics, Baylor College of Medicine, USA
| | - Yousuf O Ali
- Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA ; The Cain Foundation Laboratories, Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, TX, USA
| | - Deepa V Venkitaramani
- Institute for Applied Cancer Science, The University of Texas M.D. Anderson Cancer Center, Houston, TX, USA
| | - Ming-Kuei Jang
- Institute for Applied Cancer Science, The University of Texas M.D. Anderson Cancer Center, Houston, TX, USA
| | - Hui-Chen Lu
- Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA ; The Cain Foundation Laboratories, Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, TX, USA ; Developmental Biology Program, Baylor College of Medicine, Houston, TX, USA ; Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Robia G Pautler
- Interdepartmental Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, TX, USA ; Department of Molecular Physiology and Biophysics, Baylor College of Medicine, USA ; Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
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Barbosa DJ, Serrat R, Mirra S, Quevedo M, de Barreda EG, Àvila J, Ferreira LM, Branco PS, Fernandes E, Lourdes Bastos MD, Capela JP, Soriano E, Carvalho F. The mixture of "ecstasy" and its metabolites impairs mitochondrial fusion/fission equilibrium and trafficking in hippocampal neurons, at in vivo relevant concentrations. Toxicol Sci 2014; 139:407-20. [PMID: 24595818 DOI: 10.1093/toxsci/kfu042] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
3,4-Methylenedioxymethamphetamine (MDMA; "ecstasy") is a potentially neurotoxic recreational drug of abuse. Though the mechanisms involved are still not completely understood, formation of reactive metabolites and mitochondrial dysfunction contribute to MDMA-related neurotoxicity. Neuronal mitochondrial trafficking, and their targeting to synapses, is essential for proper neuronal function and survival, rendering neurons particularly vulnerable to mitochondrial dysfunction. Indeed, MDMA-associated disruption of Ca(2+) homeostasis and ATP depletion have been described in neurons, thus suggesting possible MDMA interference on mitochondrial dynamics. In this study, we performed real-time functional experiments of mitochondrial trafficking to explore the role of in situ mitochondrial dysfunction in MDMA's neurotoxic actions. We show that the mixture of MDMA and six of its major in vivo metabolites, each compound at 10μM, impaired mitochondrial trafficking and increased the fragmentation of axonal mitochondria in cultured hippocampal neurons. Furthermore, the overexpression of mitofusin 2 (Mfn2) or dynamin-related protein 1 (Drp1) K38A constructs almost completely rescued the trafficking deficits caused by this mixture. Finally, in hippocampal neurons overexpressing a Mfn2 mutant, Mfn2 R94Q, with impaired fusion and transport properties, it was confirmed that a dysregulation of mitochondrial fission/fusion events greatly contributed to the reported trafficking phenotype. In conclusion, our study demonstrated, for the first time, that the mixture of MDMA and its metabolites, at concentrations relevant to the in vivo scenario, impaired mitochondrial trafficking and increased mitochondrial fragmentation in hippocampal neurons, thus providing a new insight in the context of "ecstasy"-induced neuronal injury.
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Affiliation(s)
- Daniel José Barbosa
- REQUIMTE (Rede de Química e Tecnologia), Toxicology Laboratory, Department of Biological Sciences, Faculty of Pharmacy, University of Porto, Rua Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
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168
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MDMA impairs mitochondrial neuronal trafficking in a Tau- and Mitofusin2/Drp1-dependent manner. Arch Toxicol 2014; 88:1561-72. [PMID: 24522274 DOI: 10.1007/s00204-014-1209-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Accepted: 01/29/2014] [Indexed: 01/11/2023]
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169
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Soluble pathological tau in the entorhinal cortex leads to presynaptic deficits in an early Alzheimer's disease model. Acta Neuropathol 2014; 127:257-70. [PMID: 24271788 DOI: 10.1007/s00401-013-1215-5] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Revised: 10/28/2013] [Accepted: 11/09/2013] [Indexed: 10/26/2022]
Abstract
Neurofibrillary tangles (NFTs), a hallmark of Alzheimer's disease, are intracellular silver and thioflavin S-staining aggregates that emerge from earlier accumulation of phospho-tau in the soma. Whether soluble misfolded but nonfibrillar tau disrupts neuronal function is unclear. Here we investigate if soluble pathological tau, specifically directed to the entorhinal cortex (EC), can cause behavioral or synaptic deficits. We studied rTgTauEC transgenic mice, in which P301L mutant human tau overexpressed primarily in the EC leads to the development of tau pathology, but only rare NFT at 16 months of age. We show that the early tau lesions are associated with nearly normal performance in contextual fear conditioning, a hippocampal-related behavior task, but more robust changes in neuronal system activation as marked by Arc induction and clear electrophysiological defects in perforant pathway synaptic plasticity. Electrophysiological changes were likely due to a presynaptic deficit and changes in probability of neurotransmitter release. The data presented here support the hypothesis that misfolded and hyperphosphorylated tau can impair neuronal function within the entorhinal-hippocampal network, even prior to frank NFT formation and overt neurodegeneration.
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170
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Barbosa DJ, Serrat R, Ferreira LM, Branco PS, Bastos MDL, Capela JP, Soriano E, Carvalho F. Neuronal Mitochondrial Trafficking Impairment: The Cause or a Consequence of Neuronal Dysfunction Caused by Amphetamine-Like Drugs. ACTA ACUST UNITED AC 2014. [DOI: 10.4303/jdar/235868] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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171
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Kopeikina KJ, Polydoro M, Tai HC, Yaeger E, Carlson GA, Pitstick R, Hyman BT, Spires-Jones TL. Synaptic alterations in the rTg4510 mouse model of tauopathy. J Comp Neurol 2013; 521:1334-53. [PMID: 23047530 DOI: 10.1002/cne.23234] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Revised: 09/07/2012] [Accepted: 10/02/2012] [Indexed: 01/01/2023]
Abstract
Synapse loss, rather than the hallmark amyloid-β (Aβ) plaques or tau-filled neurofibrillary tangles (NFT), is considered the most predictive pathological feature associated with cognitive status in the Alzheimer's disease (AD) brain. The role of Aβ in synapse loss is well established, but despite data linking tau to synaptic function, the role of tau in synapse loss remains largely undetermined. Here we test the hypothesis that human mutant P301L tau overexpression in a mouse model (rTg4510) will lead to age-dependent synaptic loss and dysfunction. Using array tomography and two methods of quantification (automated, threshold-based counting and a manual stereology-based technique) we demonstrate that overall synapse density is maintained in the neuropil, implicating synapse loss commensurate with the cortical atrophy known to occur in this model. Multiphoton in vivo imaging reveals close to 30% loss of apical dendritic spines of individual pyramidal neurons, suggesting these cells may be particularly vulnerable to tau-induced degeneration. Postmortem, we confirm the presence of tau in dendritic spines of rTg4510-YFP mouse brain by array tomography. These data implicate tau-induced loss of a subset of synapses that may be accompanied by compensatory increases in other synaptic subtypes, thereby preserving overall synapse density. Biochemical fractionation of synaptosomes from rTg4510 brain demonstrates a significant decrease in expression of several synaptic proteins, suggesting a functional deficit of remaining synapses in the rTg4510 brain. Together, these data show morphological and biochemical synaptic consequences in response to tau overexpression in the rTg4510 mouse model.
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Affiliation(s)
- Katherine J Kopeikina
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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172
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Synaptic protein α1-takusan mitigates amyloid-β-induced synaptic loss via interaction with tau and postsynaptic density-95 at postsynaptic sites. J Neurosci 2013; 33:14170-83. [PMID: 23986251 DOI: 10.1523/jneurosci.4646-10.2013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The synaptic toxicity of soluble amyloid-β (Aβ) oligomers plays a critical role in the pathophysiology of Alzheimer's disease (AD). Here we report that overexpressed α1-takusan, which we previously identified as a protein that enhances synaptic activity via interaction with PSD-95, mitigates oligomeric Aβ-induced synaptic loss. In contrast, takusan knockdown results in enhanced synaptic damage. α1-Takusan interacts with tau either directly or indirectly, and prevents Aβ-induced tau hyperphosphorylation and mitochondrial fragmentation. Deletion analysis identified the second domain (D2) within the takusan protein that is required for PSD-95 clustering and synaptic protection from Aβ. A 51 aa sequence linking D2 to the PDZ-binding C terminus was found to be as effective as full-length takusan in protecting synapses from Aβ-induced damage. Moreover, a sequence containing the D2 from the human protein discs large homolog 5, when linked to a C-terminal PDZ-binding motif, can also increase the clustering of PSD-95 in cortical dendrites. In summary, α1-takusan protects synapses from Aβ-induced insult via interaction with PSD-95 and tau. Thus, takusan-based protein sequences from either mouse or human may be of potential therapeutic benefit in AD.
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173
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Amadoro G, Corsetti V, Florenzano F, Atlante A, Ciotti MT, Mongiardi MP, Bussani R, Nicolin V, Nori SL, Campanella M, Calissano P. AD-linked, toxic NH2 human tau affects the quality control of mitochondria in neurons. Neurobiol Dis 2013; 62:489-507. [PMID: 24411077 DOI: 10.1016/j.nbd.2013.10.018] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 09/10/2013] [Accepted: 10/16/2013] [Indexed: 12/01/2022] Open
Abstract
Functional as well as structural alterations in mitochondria size, shape and distribution are precipitating, early events in progression of Alzheimer's Disease (AD). We reported that a 20-22kDa NH2-tau fragment (aka NH2htau), mapping between 26 and 230 amino acids of the longest human tau isoform, is detected in cellular and animal AD models and is neurotoxic in hippocampal neurons. The NH2htau -but not the physiological full-length protein- interacts with Aβ at human AD synapses and cooperates with it in inhibiting the mitochondrial ANT-1-dependent ADP/ATP exchange. Here we show that the NH2htau also adversely affects the interplay between the mitochondria dynamics and their selective autophagic clearance. Fragmentation and perinuclear mislocalization of mitochondria with smaller size and density are early found in dying NH2htau-expressing neurons. The specific effect of NH2htau on quality control of mitochondria is accompanied by (i) net reduction in their mass in correlation with a general Parkin-mediated remodeling of membrane proteome; (ii) their extensive association with LC3 and LAMP1 autophagic markers; (iii) bioenergetic deficits and (iv) in vitro synaptic pathology. These results suggest that NH2htau can compromise the mitochondrial biology thereby contributing to AD synaptic deficits not only by ANT-1 inactivation but also, indirectly, by impairing the quality control mechanism of these organelles.
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Affiliation(s)
- G Amadoro
- Institute of Translational Pharmacology (IFT), CNR, Via Fosso del Cavaliere 100-00133, Rome, Italy; European Brain Research Institute (EBRI), Via del Fosso di Fiorano 64-65-00143, Rome, Italy.
| | - V Corsetti
- European Brain Research Institute (EBRI), Via del Fosso di Fiorano 64-65-00143, Rome, Italy
| | - F Florenzano
- European Brain Research Institute (EBRI), Via del Fosso di Fiorano 64-65-00143, Rome, Italy; Institute of Cellular Biology and Neurobiology (IBCN), CNR, IRCSS Fondazione Santa Lucia, Via del Fosso di Fiorano 64-65-00143, Rome, Italy
| | - A Atlante
- Insitute of Biomembrane and Bioenergetic (IBBE), CNR, Via Amendola 165/A-70126, Bari, Italy
| | - M T Ciotti
- Institute of Cellular Biology and Neurobiology (IBCN), CNR, IRCSS Fondazione Santa Lucia, Via del Fosso di Fiorano 64-65-00143, Rome, Italy
| | - M P Mongiardi
- Institute of Cellular Biology and Neurobiology (IBCN), CNR, IRCSS Fondazione Santa Lucia, Via del Fosso di Fiorano 64-65-00143, Rome, Italy
| | - R Bussani
- UCO Anatomy and Pathological Histology, Hospital of Cattinara, Strada di Fiume 447-34149, Trieste Italy
| | - V Nicolin
- University of Trieste, Clinical Department of Medical, Surgical and Health Science-section of Human Morphology, Via Manzoni 16-34138, Trieste, Italy
| | - S L Nori
- University of Salerno, Department of Pharmaceutical and Biomedical Sciences (FARMABIOMED), NANOMATES, Via Ponte don Melillo 1-85084, Fisciano (SA), Italy
| | - M Campanella
- European Brain Research Institute (EBRI), Via del Fosso di Fiorano 64-65-00143, Rome, Italy; Department of Comparative Biomedical Sciences, The Royal Veterinary College, and Consortium for Mitochondrial Research, University College London, Royal College Street, NW1 0TU, United Kingdom
| | - P Calissano
- European Brain Research Institute (EBRI), Via del Fosso di Fiorano 64-65-00143, Rome, Italy
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174
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Reversal of neurofibrillary tangles and tau-associated phenotype in the rTgTauEC model of early Alzheimer's disease. J Neurosci 2013; 33:13300-11. [PMID: 23946388 DOI: 10.1523/jneurosci.0881-13.2013] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neurofibrillary tangles (NFTs), a marker of neuronal alterations in Alzheimer's disease (AD) and other tauopathies, are comprised of aggregates of hyperphosphorylated tau protein. We recently studied the formation of NFTs in the entorhinal cortex (EC) and their subsequent propagation through neural circuits in the rTgTauEC mouse model (de Calignon et al., 2012). We now examine the consequences of suppressing transgene expression with doxycycline on the NFT-associated pathological features of neuronal system deafferentation, NFT progression and propagation, and neuronal loss. At 21 months of age we observe that EC axonal lesions are associated with an abnormal sprouting response of acetylcholinesterase (AChE)-positive fibers, a phenotype reminiscent of human AD. At 24 months, NFTs progress, tau inclusions propagate to the dentate gyrus, and neuronal loss is evident. Suppression of the transgene expression from 18 to 24 months led to reversal of AChE sprouting, resolution of Gallyas-positive and Alz50-positive NFTs, and abrogation of progressive neuronal loss. These data suggest that propagation of NFTs, as well as some of the neural system consequences of NFTs, can be reversed in an animal model of NFT-associated toxicity, providing proof in principle that these lesions can be halted, even in established disease.
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175
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Gendreau KL, Hall GF. Tangles, Toxicity, and Tau Secretion in AD - New Approaches to a Vexing Problem. Front Neurol 2013; 4:160. [PMID: 24151487 PMCID: PMC3801151 DOI: 10.3389/fneur.2013.00160] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 09/26/2013] [Indexed: 12/14/2022] Open
Abstract
When the microtubule (MT)-associated protein tau is not bound to axonal MTs, it becomes hyperphosphorylated and vulnerable to proteolytic cleavage and other changes typically seen in the hallmark tau deposits (neurofibrillary tangles) of tau-associated neurodegenerative diseases (tauopathies). Neurofibrillary tangle formation is preceded by tau oligomerization and accompanied by covalent crosslinking and cytotoxicity, making tangle cytopathogenesis a natural central focus of studies directed at understanding the role of tau in neurodegenerative disease. Recent studies suggest that the formation of tau oligomers may be more closely related to tau neurotoxicity than the presence of the tangles themselves. It has also become increasingly clear that tau pathobiology involves a wide variety of other cellular abnormalities including a disruption of autophagy, vesicle trafficking mechanisms, axoplasmic transport, neuronal polarity, and even the secretion of tau, which is normally a cytosolic protein, to the extracellular space. In this review, we discuss tau misprocessing, toxicity and secretion in the context of normal tau functions in developing and mature neurons. We also compare tau cytopathology to that of other aggregation-prone proteins involved in neurodegeneration (alpha synuclein, prion protein, and APP). Finally, we consider potential mechanisms of intra- and interneuronal tau lesion spreading, an area of particular recent interest.
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Affiliation(s)
- Kerry L Gendreau
- Department of Biological Sciences, University of Massachusetts Lowell , Lowell, MA , USA
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176
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Eckert A, Nisbet R, Grimm A, Götz J. March separate, strike together--role of phosphorylated TAU in mitochondrial dysfunction in Alzheimer's disease. Biochim Biophys Acta Mol Basis Dis 2013; 1842:1258-66. [PMID: 24051203 DOI: 10.1016/j.bbadis.2013.08.013] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 08/08/2013] [Accepted: 08/12/2013] [Indexed: 12/17/2022]
Abstract
The energy demand and calcium buffering requirements of the brain are met by the high number of mitochondria in neurons and in these, especially at the synapses. Mitochondria are the major producer of reactive oxygen species (ROS); at the same time, they are damaged by ROS that are induced by abnormal protein aggregates that characterize human neurodegenerative diseases such as Alzheimer's disease (AD). Because synaptic mitochondria are long-lived, any damage exerted by these aggregates impacts severely on neuronal function. Here we review how increased TAU, a defining feature of AD and related tauopathies, impairs mitochondrial function by following the principle: 'March separate, strike together!' In the presence of amyloid-β, TAU's toxicity is augmented suggesting synergistic pathomechanisms. In order to restore mitochondrial functions in neurodegeneration as a means of therapeutic intervention it will be important to integrate the various aspects of dysfunction and get a handle on targeting distinct cell types and subcellular compartments.
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Affiliation(s)
- Anne Eckert
- Neurobiology Laboratory, Psychiatric University Clinics Basel, University of Basel, Switzerland
| | - Rebecca Nisbet
- Centre for Ageing Dementia Research (CADR), Queensland Brain Institute (QBI), The University of Queensland, Australia
| | - Amandine Grimm
- Neurobiology Laboratory, Psychiatric University Clinics Basel, University of Basel, Switzerland
| | - Jürgen Götz
- Centre for Ageing Dementia Research (CADR), Queensland Brain Institute (QBI), The University of Queensland, Australia.
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177
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Cowan CM, Mudher A. Are tau aggregates toxic or protective in tauopathies? Front Neurol 2013; 4:114. [PMID: 23964266 PMCID: PMC3741634 DOI: 10.3389/fneur.2013.00114] [Citation(s) in RCA: 130] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 07/29/2013] [Indexed: 11/13/2022] Open
Abstract
Aggregation of highly phosphorylated tau into aggregated forms such as filaments and neurofibrillary tangles is one of the defining pathological hallmarks of Alzheimer's disease and other tauopathies. Hence therapeutic strategies have focused on inhibition of tau phosphorylation or disruption of aggregation. However, animal models imply that tau-mediated dysfunction and toxicity do not require aggregation but instead are caused by soluble hyper-phosphorylated tau. Over the years, our findings from a Drosophila model of tauopathy have reinforced this. We have shown that highly phosphorylated wild-type human tau causes behavioral deficits resulting from synaptic dysfunction, axonal transport disruption, and cytoskeletal destabilization in vivo. These deficits are evident in the absence of neuronal death or filament/tangle formation. Unsurprisingly, both pharmacological and genetic inhibition of GSK-3β rescue these tau phenotypes. However, GSK-3β inhibition also unexpectedly increases tau protein levels, and produces insoluble granular tau oligomers. As well as underlining the growing consensus that tau toxicity is mediated by a highly phosphorylated soluble tau species, our findings further show that not all insoluble tau aggregates are toxic. Some tau aggregates, in particular tau oligomers, are non-toxic, and may even be protective against tau toxicity in vivo. This has serious implications for emerging therapeutic strategies to dissolve tau aggregates, which might be ineffective or even counter-productive. In light of this, it is imperative to identify the key toxic tau species and to understand how it mediates dysfunction and degeneration so that the effective disease-modifying therapies can be developed.
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Affiliation(s)
- Catherine M Cowan
- Centre for Biological Sciences, University of Southampton , Southampton , UK
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178
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Gerson JE, Kayed R. Formation and propagation of tau oligomeric seeds. Front Neurol 2013; 4:93. [PMID: 23882255 PMCID: PMC3713404 DOI: 10.3389/fneur.2013.00093] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Accepted: 07/01/2013] [Indexed: 12/14/2022] Open
Abstract
Tau misfolding and aggregation leads to the formation of neurofibrillary tangles (NFTs), which have long been considered one of the main pathological hallmarks for numerous neurodegenerative diseases known as tauopathies, including Alzheimer’s Disease (AD) and Parkinson’s Disease (PD). However, recent studies completed both in vitro and in vivo suggest that intermediate forms of tau, known as tau oligomers, between the monomeric form and NFTs are the true toxic species in disease and the best targets for anti-tau therapies. However, the exact mechanism by which the spread of pathology occurs is unknown. Evidence suggests that tau oligomers may act as templates for the misfolding of native tau, thereby seeding the spread of the toxic forms of the protein. Recently, researchers have reported the ability of tau oligomers to enter and exit cells, propagating from disease-affected regions to unaffected areas. While the mechanism by which the spreading of misfolded tau occurs has yet to be elucidated, there are a few different models which have been proposed, including cell membrane stress and pore-formation, endocytosis and exocytosis, and non-traditional secretion of protein not enclosed by a membrane. Coming to an understanding of how toxic tau species seed and spread through the brain will be crucial to finding effective treatments for neurodegenerative tauopathies.
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Affiliation(s)
- Julia E Gerson
- George P. and Cynthia Woods Mitchell Center for Neurodegenerative Diseases, University of Texas Medical Branch , Galveston, TX , USA ; Department of Neurology, University of Texas Medical Branch , Galveston, TX , USA ; Department of Neuroscience and Cell Biology, University of Texas Medical Branch , Galveston, TX , USA
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179
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Phosphorylation of tau protein as the link between oxidative stress, mitochondrial dysfunction, and connectivity failure: implications for Alzheimer's disease. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2013; 2013:940603. [PMID: 23936615 PMCID: PMC3723250 DOI: 10.1155/2013/940603] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Accepted: 06/06/2013] [Indexed: 11/28/2022]
Abstract
Alzheimer's disease (AD) is defined by the concurrence of abnormal aggregates composed of phosphorylated tau protein and of abnormal cellular changes including neurite degeneration, loss of neurons, and loss of cognitive functions. While a number of mechanisms have been implicated in this complex disease, oxidative stress remains one of the earliest and strongest events related to disease progression. However, the mechanism that links oxidative stress and cognitive decline remains elusive. Here, we propose that phosphorylated tau protein could be playing the role of potential connector and, therefore, that a combined therapy involving antioxidants and check points for synaptic plasticity during early stages of the disease could become a viable therapeutic option for AD treatment.
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180
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Noble W, Hanger DP, Miller CCJ, Lovestone S. The importance of tau phosphorylation for neurodegenerative diseases. Front Neurol 2013; 4:83. [PMID: 23847585 PMCID: PMC3696910 DOI: 10.3389/fneur.2013.00083] [Citation(s) in RCA: 263] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 06/14/2013] [Indexed: 01/20/2023] Open
Abstract
Fibrillar deposits of highly phosphorylated tau are a key pathological feature of several neurodegenerative tauopathies including Alzheimer's disease (AD) and some frontotemporal dementias. Increasing evidence suggests that the presence of these end-stage neurofibrillary lesions do not cause neuronal loss, but rather that alterations to soluble tau proteins induce neurodegeneration. In particular, aberrant tau phosphorylation is acknowledged to be a key disease process, influencing tau structure, distribution, and function in neurons. Although typically described as a cytosolic protein that associates with microtubules and regulates axonal transport, several additional functions of tau have recently been demonstrated, including roles in DNA stabilization, and synaptic function. Most recently, studies examining the trans-synaptic spread of tau pathology in disease models have suggested a potential role for extracellular tau in cell signaling pathways intrinsic to neurodegeneration. Here we review the evidence showing that tau phosphorylation plays a key role in neurodegenerative tauopathies. We also comment on the tractability of altering phosphorylation-dependent tau functions for therapeutic intervention in AD and related disorders.
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Affiliation(s)
- Wendy Noble
- Department of Neuroscience, King's College London, Institute of Psychiatry , London , UK
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181
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Kay KR, Smith C, Wright AK, Serrano-Pozo A, Pooler AM, Koffie R, Bastin ME, Bak TH, Abrahams S, Kopeikina KJ, McGuone D, Frosch MP, Gillingwater TH, Hyman BT, Spires-Jones TL. Studying synapses in human brain with array tomography and electron microscopy. Nat Protoc 2013; 8:1366-80. [PMID: 23787894 DOI: 10.1038/nprot.2013.078] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Postmortem studies of synapses in human brain are problematic because of the axial resolution limit of light microscopy and the difficulty in preserving and analyzing ultrastructure with electron microscopy (EM). Array tomography (AT) overcomes these problems by embedding autopsy tissue in resin and cutting ribbons of ultrathin serial sections. Ribbons are imaged with immunofluorescence, allowing high-throughput imaging of tens of thousands of synapses to assess synapse density and protein composition. The protocol takes ~3 d per case, excluding image analysis, which is done at the end of the study. Parallel processing for transmission electron microscopy (TEM) using a protocol modified to preserve the structure in human samples allows complementary ultrastructural studies. Incorporation of AT and TEM into brain banking is a potent way of phenotyping synapses in well-characterized clinical cohorts in order to develop clinicopathological correlations at the synapse level. This will be important for research in neurodegenerative disease, developmental disease and psychiatric illness.
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Affiliation(s)
- Kevin R Kay
- Massachusetts General Hospital and Harvard Medical School, MassGeneral Institute for Neurodegenerative Disease, Charlestown, MA, USA
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182
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García-Escudero V, Martín-Maestro P, Perry G, Avila J. Deconstructing mitochondrial dysfunction in Alzheimer disease. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2013; 2013:162152. [PMID: 23840916 PMCID: PMC3693159 DOI: 10.1155/2013/162152] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Accepted: 05/23/2013] [Indexed: 11/17/2022]
Abstract
There is mounting evidence showing that mitochondrial damage plays an important role in Alzheimer disease. Increased oxygen species generation and deficient mitochondrial dynamic balance have been suggested to be the reason as well as the consequence of Alzheimer-related pathology. Mitochondrial damage has been related to amyloid-beta or tau pathology or to the presence of specific presenilin-1 mutations. The contribution of these factors to mitochondrial dysfunction is reviewed in this paper. Due to the relevance of mitochondrial alterations in Alzheimer disease, recent works have suggested the therapeutic potential of mitochondrial-targeted antioxidant. On the other hand, autophagy has been demonstrated to play a fundamental role in Alzheimer-related protein stress, and increasing data shows that this pathway is altered in the disease. Moreover, mitochondrial alterations have been related to an insufficient clearance of dysfunctional mitochondria by autophagy. Consequently, different approaches for the removal of damaged mitochondria or to decrease the related oxidative stress in Alzheimer disease have been described. To understand the role of mitochondrial function in Alzheimer disease it is necessary to generate human cellular models which involve living neurons. We have summarized the novel protocols for the generation of neurons by reprogramming or direct transdifferentiation, which offer useful tools to achieve this result.
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Affiliation(s)
- Vega García-Escudero
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), 28049 Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), 28031 Madrid, Spain
| | - Patricia Martín-Maestro
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), 28049 Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), 28031 Madrid, Spain
| | - George Perry
- University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - Jesús Avila
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), 28049 Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), 28031 Madrid, Spain
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183
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Crimins JL, Pooler A, Polydoro M, Luebke JI, Spires-Jones TL. The intersection of amyloid β and tau in glutamatergic synaptic dysfunction and collapse in Alzheimer's disease. Ageing Res Rev 2013; 12:757-63. [PMID: 23528367 PMCID: PMC3735866 DOI: 10.1016/j.arr.2013.03.002] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Revised: 03/06/2013] [Accepted: 03/13/2013] [Indexed: 12/23/2022]
Abstract
The synaptic connections that form between neurons during development remain plastic and able to adapt throughout the lifespan, enabling learning and memory. However, during aging and in particular in neurodegenerative diseases, synapses become dysfunctional and degenerate, contributing to dementia. In the case of Alzheimer's disease (AD), synapse loss is the strongest pathological correlate of cognitive decline, indicating that synaptic degeneration plays a central role in dementia. Over the past decade, strong evidence has emerged that oligomeric forms of amyloid beta, the protein that accumulates in senile plaques in the AD brain, contribute to degeneration of synaptic structure and function. More recent data indicate that pathological forms of tau protein, which accumulate in neurofibrillary tangles in the AD brain, also cause synaptic dysfunction and loss. In this review, we will present the case that soluble forms of both amyloid beta and tau protein act at the synapse to cause neural network dysfunction, and further that these two pathological proteins may act in concert to cause synaptic pathology. These data may have wide-ranging implications for the targeting of soluble pathological proteins in neurodegenerative diseases to prevent or reverse cognitive decline.
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184
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Vazquez A. Metabolic states following accumulation of intracellular aggregates: implications for neurodegenerative diseases. PLoS One 2013; 8:e63822. [PMID: 23667676 PMCID: PMC3646825 DOI: 10.1371/journal.pone.0063822] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Accepted: 04/09/2013] [Indexed: 11/18/2022] Open
Abstract
The formation of intracellular aggregates is a common etiology of several neurodegenerative diseases. Mitochondrial defects and oxidative stress has been pointed as the major mechanistic links between the accumulation of intracellular aggregates and cell death. In this work we propose a “metabolic cell death by overcrowding” as an alternative hypothesis. Using a model of neuron metabolism, we predict that as the concentration of protein aggregates increases the neurons transit through three different metabolic phases. The first phase (0–6 mM) corresponds with the normal neuron state, where the neuronal activity is sustained by the oxidative phosphorylation of lactate. The second phase (6–8.6 mM) is characterized by a mixed utilization of lactate and glucose as energy substrates and a switch from ammonia uptake to ammonia release by neurons. In the third phase (8.6–9.3 mM) neurons are predicted to support their energy demands from glycolysis and an alternative pathway for energy generation, involving reactions from serine synthesis, one carbon metabolism and the glycine cleavage system. The model also predicts a decrease in the maximum neuronal capacity for energy generation with increasing the concentration of protein aggregates. Ultimately this maximum capacity becomes zero when the protein aggregates reach a concentration of about 9.3 mM, predicting the cessation of neuronal activity.
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Affiliation(s)
- Alexei Vazquez
- Department of Radiation Oncology and Center for Systems Biology, The Cancer Institute of New Jersey, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, New Brunswick, New Jersey, United States of America.
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185
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Oshima E, Ishihara T, Yokota O, Nakashima-Yasuda H, Nagao S, Ikeda C, Naohara J, Terada S, Uchitomi Y. Accelerated tau aggregation, apoptosis and neurological dysfunction caused by chronic oral administration of aluminum in a mouse model of tauopathies. Brain Pathol 2013; 23:633-44. [PMID: 23574527 DOI: 10.1111/bpa.12059] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Accepted: 03/28/2013] [Indexed: 11/30/2022] Open
Abstract
To clarify whether long-term oral ingestion of aluminum (Al) can increase tau aggregation in mammals, we examined the effects of oral Al administration on tau accumulation, apoptosis in the central nervous system (CNS) and motor function using tau transgenic (Tg) mice that show very slowly progressive tau accumulation. Al-treated tau Tg mice had almost twice as many tau-positive inclusions in the spinal cord as tau Tg mice without Al treatment at 12 months of age, a difference that reached statistical significance, and the development of pretangle-like tau aggregates in the brain was also significantly advanced from 9 months. Al exposure did not induce any tau pathology in wild-type (WT) mice. Apoptosis was observed in the hippocampus in Al-treated tau Tg mice, but was virtually absent in the other experimental groups. Motor function as assessed by the tail suspension test was most severely impaired in Al-treated tau Tg mice. Given our results, chronic oral ingestion of Al may more strongly promote tau aggregation, apoptosis and neurological dysfunction if individuals already had a pathological process causing tau aggregation. These findings may also implicate chronic Al neurotoxicity in humans, who frequently have had mild tau pathology from a young age.
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Affiliation(s)
- Etsuko Oshima
- Department of Neuropsychiatry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
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186
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Leung LC, Wang GX, Mourrain P. Imaging zebrafish neural circuitry from whole brain to synapse. Front Neural Circuits 2013; 7:76. [PMID: 23630470 PMCID: PMC3634052 DOI: 10.3389/fncir.2013.00076] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Accepted: 04/03/2013] [Indexed: 12/20/2022] Open
Abstract
Recent advances in imaging tools are inspiring zebrafish researchers to tackle ever more ambitious questions in the neurosciences. Behaviorally fundamental conserved neural networks can now be potentially studied using zebrafish from a brain-wide scale to molecular resolution. In this perspective, we offer a roadmap by which a zebrafish researcher can navigate the course from collecting neural activities across the brain associated with a behavior, to unraveling molecular identities and testing the functional relevance of active neurons. In doing so, important insights will be gained as to how neural networks generate behaviors and assimilate changes in synaptic connectivity.
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Affiliation(s)
- Louis C Leung
- Department of Psychiatry and Behavioral Sciences, Center for Sleep Sciences, Beckman Center, Stanford University Palo Alto, CA, USA
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187
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DuBoff B, Feany M, Götz J. Why size matters - balancing mitochondrial dynamics in Alzheimer's disease. Trends Neurosci 2013; 36:325-35. [PMID: 23582339 DOI: 10.1016/j.tins.2013.03.002] [Citation(s) in RCA: 126] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 03/07/2013] [Accepted: 03/11/2013] [Indexed: 12/31/2022]
Abstract
Once perceived as solitary structures, mitochondria are now recognized as highly dynamic, interconnected organelles. The tight control of their fusion and fission, a process termed 'mitochondrial dynamics', is crucial for neurons, given their unique architecture and special energy and calcium-buffering requirements at the synapse. Interestingly, in Alzheimer's disease (AD), a condition initiated at the synapse, mitochondrial dynamics are severely impaired. Of the two proteins implicated in AD pathogenesis, amyloid-β (Aβ) and TAU, only the impact of Aβ on mitochondrial dynamics has been studied in detail. We highlight recent findings that TAU exerts a determinative effect in the regulation of mitochondrial dynamics, and therefore neuronal function. In this process, the GTPase DRP1 has emerged as a key target of both Aβ and TAU.
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Affiliation(s)
- Brian DuBoff
- Brigham and Women's Hospital and Harvard Medical School, Department of Pathology, Brigham and Women's Hospital, Harvard New Research Building, Room 630, 77 Avenue Louis Pasteur, Boston, MA 02115, USA
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188
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Capurro V, Busquet P, Lopes JP, Bertorelli R, Tarozzo G, Bolognesi ML, Piomelli D, Reggiani A, Cavalli A. Pharmacological characterization of memoquin, a multi-target compound for the treatment of Alzheimer's disease. PLoS One 2013; 8:e56870. [PMID: 23441223 PMCID: PMC3575497 DOI: 10.1371/journal.pone.0056870] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 01/15/2013] [Indexed: 11/18/2022] Open
Abstract
Alzheimer's disease (AD) is characterized by progressive loss of cognitive function, dementia and altered behavior. Over 30 million people worldwide suffer from AD and available therapies are still palliative rather than curative. Recently, Memoquin (MQ), a quinone-bearing polyamine compound, has emerged as a promising anti-AD lead candidate, mainly thanks to its multi-target profile. MQ acts as an acetylcholinesterase and β-secretase-1 inhibitor, and also possesses anti-amyloid and anti-oxidant properties. Despite this potential interest, in vivo behavioral studies with MQ have been limited. Here, we report on in vivo studies with MQ (acute and sub-chronic treatments; 7–15 mg/kg per os) carried out using two different mouse models: i) scopolamine- and ii) beta-amyloid peptide- (Aβ-) induced amnesia. Several aspects related to memory were examined using the T-maze, the Morris water maze, the novel object recognition, and the passive avoidance tasks. At the dose of 15 mg/kg, MQ was able to rescue all tested aspects of cognitive impairment including spatial, episodic, aversive, short and long-term memory in both scopolamine- and Aβ-induced amnesia models. Furthermore, when tested in primary cortical neurons, MQ was able to fully prevent the Aβ-induced neurotoxicity mediated by oxidative stress. The results support the effectiveness of MQ as a cognitive enhancer, and highlight the value of a multi-target strategy to address the complex nature of cognitive dysfunction in AD.
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Affiliation(s)
- Valeria Capurro
- Drug Discovery and Development, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Perrine Busquet
- Drug Discovery and Development, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Joao Pedro Lopes
- Drug Discovery and Development, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Rosalia Bertorelli
- Drug Discovery and Development, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Glauco Tarozzo
- Drug Discovery and Development, Istituto Italiano di Tecnologia, Genoa, Italy
| | | | - Daniele Piomelli
- Drug Discovery and Development, Istituto Italiano di Tecnologia, Genoa, Italy
- Departments of Anatomy and Neurobiology, Pharmacology and Biological Chemistry, University of California Irvine, Irvine, United States of America
| | - Angelo Reggiani
- Drug Discovery and Development, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Andrea Cavalli
- Drug Discovery and Development, Istituto Italiano di Tecnologia, Genoa, Italy
- Department of Pharmacy and Biotechnology, Bologna University, Bologna, Italy
- * E-mail:
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189
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Goncalves MB, Clarke E, Hobbs C, Malmqvist T, Deacon R, Jack J, Corcoran JPT. Amyloid β inhibits retinoic acid synthesis exacerbating Alzheimer disease pathology which can be attenuated by an retinoic acid receptor α agonist. Eur J Neurosci 2013; 37:1182-92. [PMID: 23379615 PMCID: PMC3655538 DOI: 10.1111/ejn.12142] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Accepted: 12/23/2012] [Indexed: 12/03/2022]
Abstract
The retinoic acid receptor (RAR) α system plays a key role in the adult brain, participating in the homeostatic control of synaptic plasticity, essential for memory function. Here we show that RARα signalling is down-regulated by amyloid beta (Aβ), which inhibits the synthesis of the endogenous ligand, retinoic acid (RA). This results in the counteraction of a variety of RARα-activated pathways that are key in the aetiopathology of Alzheimer's disease (AD) but which can be reversed by an RARα agonist. RARα signalling improves cognition in the Tg2576 mice, it has an anti-inflammatory effect and promotes Aβ clearance by increasing insulin degrading enzyme and neprilysin activity in both microglia and neurons. In addition, RARα signalling prevents tau phosphorylation. Therefore, stimulation of the RARα signalling pathway using a synthetic agonist, by both clearing Aβ and counteracting some of its toxic effects, offers therapeutic potential for the treatment of AD.
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Affiliation(s)
- Maria B Goncalves
- The Wolfson Centre For Age-Related Diseases, King's College London, Guy's Campus, London, SE11UL, UK
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190
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Crimins JL, Rocher AB, Luebke JI. Electrophysiological changes precede morphological changes to frontal cortical pyramidal neurons in the rTg4510 mouse model of progressive tauopathy. Acta Neuropathol 2012; 124:777-95. [PMID: 22976049 DOI: 10.1007/s00401-012-1038-9] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Revised: 08/20/2012] [Accepted: 08/21/2012] [Indexed: 12/14/2022]
Abstract
Whole-cell patch-clamp recordings and high-resolution morphometry were used to assess functional and structural properties of layer 3 pyramidal neurons in early (<4 months) and advanced (>8 months) stages of tauopathy in frontal cortical slices prepared from rTg4510 tau mutant (P301L) mice. In early tauopathy, dendritic architecture is preserved. In advanced tauopathy, neurons can be categorized as either "atrophic" (58 %)-exhibiting marked atrophy of the apical tuft, or "intact" (42 %)-with normal apical tufts and, in some instances, proliferative sprouting of oblique branches of the apical trunk. Approximately equal numbers of atrophic and intact neurons contain neurofibrillary tangles (NFTs) or are tangle-free, lending further support to the idea that NFTs per se are not toxic. Spine density is decreased due to a specific reduction in mushroom spines, but filopodia are increased in both atrophic and intact neurons. By contrast to these morphological changes, which are robust only in the advanced stage, significant electrophysiological changes are present in the early stage and persist in the advanced stage in both atrophic and intact neurons. The most marked of these changes are: a depolarized resting membrane potential, an increased depolarizing sag potential and increased action potential firing rates-all indicative of hyperexcitability. Spontaneous excitatory postsynaptic currents are not reduced in frequency or amplitude in either stage. The difference in the time course of functionally important electrophysiological changes versus regressive morphological changes implies differences in pathogenic mechanisms underlying functional and structural changes to neurons during progressive tauopathy.
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Affiliation(s)
- Johanna L Crimins
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118, USA
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191
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DuBoff B, Götz J, Feany MB. Tau promotes neurodegeneration via DRP1 mislocalization in vivo. Neuron 2012; 75:618-32. [PMID: 22920254 DOI: 10.1016/j.neuron.2012.06.026] [Citation(s) in RCA: 280] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/01/2012] [Indexed: 01/02/2023]
Abstract
Mitochondrial abnormalities have been documented in Alzheimer's disease and related neurodegenerative disorders, but the causal relationship between mitochondrial changes and neurodegeneration, and the specific mechanisms promoting mitochondrial dysfunction, are unclear. Here, we find that expression of human tau results in elongation of mitochondria in both Drosophila and mouse neurons. Elongation is accompanied by mitochondrial dysfunction and cell cycle-mediated cell death, which can be rescued in vivo by genetically restoring the proper balance of mitochondrial fission and fusion. We have previously demonstrated that stabilization of actin by tau is critical for neurotoxicity of the protein. Here, we demonstrate a conserved role for actin and myosin in regulating mitochondrial fission and show that excess actin stabilization inhibits association of the fission protein DRP1 with mitochondria, leading to mitochondrial elongation and subsequent neurotoxicity. Our results thus identify actin-mediated disruption of mitochondrial dynamics as a direct mechanism of tau toxicity in neurons in vivo.
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Affiliation(s)
- Brian DuBoff
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
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192
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Mitochondrial dynamics in cancer and neurodegenerative and neuroinflammatory diseases. Int J Cell Biol 2012; 2012:729290. [PMID: 22792111 PMCID: PMC3391904 DOI: 10.1155/2012/729290] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 04/12/2012] [Indexed: 11/18/2022] Open
Abstract
Mitochondria are key organelles in the cell, hosting essential functions, from biosynthetic and metabolic pathways, to oxidative phosphorylation and ATP production, from calcium buffering to red-ox homeostasis and apoptotic signalling pathways. Mitochondria are also dynamic organelles, continuously fusing and dividing, and their localization, size and trafficking are finely regulated. Moreover, in recent decades, alterations in mitochondrial function and dynamics have been implicated in an increasing number of diseases. In this review, we focus on the relationship clarified hitherto between mitochondrial dynamics and cancer, neurodegenerative and neuroinflammatory diseases.
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193
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Jellinger KA. Interaction between pathogenic proteins in neurodegenerative disorders. J Cell Mol Med 2012; 16:1166-83. [PMID: 22176890 PMCID: PMC3823071 DOI: 10.1111/j.1582-4934.2011.01507.x] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 12/16/2011] [Indexed: 12/21/2022] Open
Abstract
The misfolding and progressive aggregation of specific proteins in selective regions of the nervous system is a seminal occurrence in many neurodegenerative disorders, and the interaction between pathological/toxic proteins to cause neurodegeneration is a hot topic of current neuroscience research. Despite clinical, genetic and experimental differences, increasing evidence indicates considerable overlap between synucleinopathies, tauopathies and other protein-misfolding diseases. Inclusions, often characteristic hallmarks of these disorders, suggest interactions of pathological proteins enganging common downstream pathways. Novel findings that have shifted our understanding in the role of pathologic proteins in the pathogenesis of Alzheimer, Parkinson, Huntington and prion diseases, have confirmed correlations/overlaps between these and other neurodegenerative disorders. Emerging evidence, in addition to synergistic effects of tau protein, amyloid-β, α-synuclein and other pathologic proteins, suggests that prion-like induction and spreading, involving secreted proteins, are major pathogenic mechanisms in various neurodegenerative diseases, depending on genetic backgrounds and environmental factors. The elucidation of the basic molecular mechanisms underlying the interaction and spreading of pathogenic proteins, suggesting a dualism or triad of neurodegeneration in protein-misfolding disorders, is a major challenge for modern neuroscience, to provide a deeper insight into their pathogenesis as a basis of effective diagnosis and treatment.
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194
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Modeling the encephalopathy of prematurity in animals: the important role of translational research. Neurol Res Int 2012; 2012:295389. [PMID: 22685653 PMCID: PMC3366246 DOI: 10.1155/2012/295389] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 01/18/2012] [Indexed: 12/23/2022] Open
Abstract
Translational research in preterm brain injury depends upon the delineation of the human neuropathology in order that animal models faithfully reiterate it, thereby ensuring direct relevance to the human condition. The major substrate of human preterm brain injury is the encephalopathy of prematurity that is characterized by gray and white matter lesions reflecting combined acquired insults, altered developmental trajectories, and reparative phenomena. Here we highlight the key features of human preterm brain development and the encephalopathy of prematurity that are critical for modeling in animals. The complete mimicry of the complex human neuropathology is difficult in animal models. Many models focus upon mechanisms related to a specific feature, for example, loss of premyelinating oligodendrocytes in the cerebral white matter. Nevertheless, animal models that simultaneously address oligodendrocyte, neuronal, and axonal injury carry the potential to decipher shared mechanisms and synergistic treatments to ameliorate the global consequences of the encephalopathy of prematurity.
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195
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Hyman BT, Yuan J. Apoptotic and non-apoptotic roles of caspases in neuronal physiology and pathophysiology. Nat Rev Neurosci 2012; 13:395-406. [PMID: 22595785 DOI: 10.1038/nrn3228] [Citation(s) in RCA: 189] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Caspases are cysteine proteases that mediate apoptosis, which is a form of regulated cell death that effectively and efficiently removes extra and unnecessary cells during development. In the mature nervous system, caspases are not only involved in mediating cell death but also regulatory events that are important for neural functions, such as axon pruning and synapse elimination, which are necessary to refine mature neuronal circuits. Furthermore, caspases can be reactivated to cause cell death as well as non-lethal changes in neurons during numerous pathological processes. Thus, although a global activation of caspases leads to apoptosis, restricted and localized activation may control normal physiology and pathophysiology in living neurons. This Review explores the multiple roles of caspase activity in neurons.
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Affiliation(s)
- Bradley T Hyman
- Neurology Service, Massachusetts General Hospital, 114 16th Street Charlestown, Massachusetts 01029, USA.
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196
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Manczak M, Reddy PH. Abnormal interaction between the mitochondrial fission protein Drp1 and hyperphosphorylated tau in Alzheimer's disease neurons: implications for mitochondrial dysfunction and neuronal damage. Hum Mol Genet 2012; 21:2538-47. [PMID: 22367970 DOI: 10.1093/hmg/dds072] [Citation(s) in RCA: 318] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
We recently reported increased mitochondrial fission and decreased fusion, increased amyloid beta (Aβ) interaction with the mitochondrial fission protein Drp1, increased mitochondrial fragmentation, impaired axonal transport of mitochondria and synaptic degeneration in neurons affected by AD. In the present study, we extended our previous investigations to determine whether phosphorylated tau interacts with Drp1 and to elucidate mitochondrial damage in the progression of AD. We also investigated GTPase activity, which is critical for mitochondrial fragmentation, in postmortem brain tissues from patients with AD and brain tissues from APP, APP/PS1 and 3XTg.AD mice. Using co-immunoprecipitation and immunofluorescence analyses, for the first time, we demonstrated the physical interaction between phosphorylated tau and Drp1. Mitochondrial fission-linked GTPase activity was significantly elevated in the postmortem frontal cortex tissues from AD patients and cortical tissues from APP, APP/PS1 and 3XTg.AD mice. On the basis of these findings, we conclude that Drp1 interacts with Aβ and phosphorylated tau, likely leading to excessive mitochondrial fragmentation, and mitochondrial and synaptic deficiencies, ultimately possibly leading to neuronal damage and cognitive decline. Treatment designed to reduce the expression of Drp1, Aβ and/or phosphorylated tau may decrease the interaction between Drp1 and phosphorylated tau and the interaction between Drp1 and Aβ, conferring protection to neurons from toxic insults of excessive Drp1, Aβ and/or phosphorylated tau.
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Affiliation(s)
- Maria Manczak
- Neurogenetics Laboratory, Neuroscience Division, Oregon National Primate Research Center, West Campus, Oregon Health and Science University, Beaverton, OR 97006, USA
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197
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Oettinghaus B, Licci M, Scorrano L, Frank S. Less than perfect divorces: dysregulated mitochondrial fission and neurodegeneration. Acta Neuropathol 2012; 123:189-203. [PMID: 22179580 DOI: 10.1007/s00401-011-0930-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Revised: 12/06/2011] [Accepted: 12/07/2011] [Indexed: 12/29/2022]
Abstract
Research efforts during the last decade have deciphered the basic molecular mechanisms governing mitochondrial fusion and fission. We now know that in mammalian cells mitochondrial fission is mediated by the large GTPase dynamin-related protein 1 (Drp1) acting in concert with outer mitochondrial membrane (OMM) proteins such as Fis1, Mff, and Mief1. It is also generally accepted that organelle fusion depends on the action of three large GTPases: mitofusins (Mfn1, Mfn2) mediating membrane fusion on the OMM level, and Opa1 which is essential for inner mitochondrial membrane fusion. Significantly, mutations in Drp1, Mfn2, and Opa1 have causally been linked to neurodegenerative conditions. Despite this knowledge, crucial questions such as to how fission of the inner and outer mitochondrial membranes are coordinated and how these processes are integrated into basic physiological processes such as apoptosis and autophagy remain to be answered in detail. In this review, we will focus on what is currently known about the mechanism of mitochondrial fission and explore the pathophysiological consequences of dysregulated organelle fission with a special focus on neurodegenerative conditions, including Alzheimer's, Huntington's and Parkinson's disease, as well as ischemic brain damage.
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Affiliation(s)
- Björn Oettinghaus
- Department of Cell Physiology and Metabolism, University of Geneva Medical School, Switzerland
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Colca JR, Feinstein DL. Altering Mitochondrial Dysfunction as an Approach to Treating Alzheimer’s Disease. CURRENT STATE OF ALZHEIMER'S DISEASE RESEARCH AND THERAPEUTICS 2012; 64:155-76. [DOI: 10.1016/b978-0-12-394816-8.00005-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Abstract
Accumulation of neurofibrillary tangles (NFT), intracellular inclusions of fibrillar forms of tau, is a hallmark of Alzheimer Disease. NFT have been considered causative of neuronal death, however, recent evidence challenges this idea. Other species of tau, such as soluble misfolded, hyperphosphorylated, and mislocalized forms, are now being implicated as toxic. Here we review the data supporting soluble tau as toxic to neurons and synapses in the brain and the implications of these data for development of therapeutic strategies for Alzheimer's disease and other tauopathies.
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Spines, plasticity, and cognition in Alzheimer's model mice. Neural Plast 2011; 2012:319836. [PMID: 22203915 PMCID: PMC3238410 DOI: 10.1155/2012/319836] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Accepted: 10/27/2011] [Indexed: 01/03/2023] Open
Abstract
The pathological hallmarks of Alzheimer's disease (AD)--widespread synaptic and neuronal loss and the pathological accumulation of amyloid-beta peptide (Aβ) in senile plaques, as well as hyperphosphorylated tau in neurofibrillary tangles--have been known for many decades, but the links between AD pathology and dementia and effective therapeutic strategies remain elusive. Transgenic mice have been developed based on rare familial forms of AD and frontotemporal dementia, allowing investigators to test in detail the structural, functional, and behavioral consequences of AD-associated pathology. Here, we review work on transgenic AD models that investigate the degeneration of dendritic spine structure, synaptic function, and cognition. Together, these data support a model of AD pathogenesis in which soluble Aβ initiates synaptic dysfunction and loss, as well as pathological changes in tau, which contribute to both synaptic and neuronal loss. These changes in synapse structure and function as well as frank synapse and neuronal loss contribute to the neural system dysfunction which causes cognitive deficits. Understanding the underpinnings of dementia in AD will be essential to develop and evaluate therapeutic approaches for this widespread and devastating disease.
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