Synaptic Disruption by Soluble Oligomers in Neurodegenerative Diseases: History
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Contributor:
Berenice A. Gutierrez
,
Agenor Limon

Neurodegenerative diseases are the result of progressive dysfunction of the neuronal activity and subsequent neuronal death. Currently, the most prevalent neurodegenerative diseases are by far Alzheimer’s (AD) and Parkinson’s (PD) disease, affecting millions of people worldwide. Although amyloid plaques and neurofibrillary tangles are the neuropathological hallmarks for AD and Lewy bodies (LB) are the hallmark for PD, current evidence strongly suggests that oligomers seeding the neuropathological hallmarks are more toxic and disease-relevant in both pathologies. The presence of small soluble oligomers is the common bond between AD and PD: amyloid β oligomers (AβOs) and Tau oligomers (TauOs) in AD and α-synuclein oligomers (αSynOs) in PD. Such oligomers appear to be particularly increased during the early pathological stages, targeting synapses at vulnerable brain regions leading to synaptic plasticity disruption, synapse loss, inflammation, excitation to inhibition imbalance and cognitive impairment. Absence of TauOs at synapses in individuals with strong AD disease pathology but preserved cognition suggests that mechanisms of resilience may be dependent on the interactions between soluble oligomers and their synaptic targets.

  • oligomers
  • E/I balance
  • neurodegenerative diseases

1. Introduction

Alzheimer’s disease (AD) and Parkinson’s disease (PD) are among the most prevalent neurodegenerative diseases that shares the misfolding of proteins and synaptic dysfunction as part of their neuropathology. The World Health Organization estimates that 55 million people worldwide live with dementia, of which two-thirds are due to AD [1]. PD is the second most common age-related neurodegenerative disorder after AD with an estimated of up to 10 million people worldwide [2]. Due to the large prevalence of these disorders, the economical and psychological costs on society, caregivers and individuals affected is extremely high. Although large advances in understanding the potential causes of the clinical symptoms at different levels of analysis has been made, there is still the need of effective disease-modifying treatments that can help people with a diagnosis and those at high risk.

2. Neurodegeneration Driven by Small Soluble Oligomers

Oligomers are small, soluble protein aggregates which possess unique structural and functional properties. They are intermediary between soluble monomeric proteins and insoluble mature fibrils [3]. For several years, therapeutic research in AD and PD was centered in targeting insoluble fibrillar aggregates of Aβ, tau and αSyn, but recent studies have shown that soluble oligomers are the most toxic species that induce neuronal damage and dysfunction in neurodegenerative disorders [4][5][6][7][8][9][10][11][12][13], suggesting that anti-oligomeric therapeutic strategies would be a better approach to antagonize cognitive deficit symptoms.
Neurodegeneration driven by AβOs has been experimentally proven using human postmortem brain tissue from subjects clinically diagnosed with AD. AβOs extracted from these subjects have shown to alter long-term potentiation, enhance long term depression, and reduce the dendritic spine density of pyramidal neurons in the hippocampus of control mice [14]. The reduction of spine density is consequence of the loss of spine cytoskeletal proteins, a phenomenon that implicates impairment of memory-related receptors such as NMDA receptors [14][15] (See below for effects of oligomers on synaptic receptors). AβOs also contribute to loss of synaptic markers such as synaptic vesicle-associated membrane protein 2 and post-synaptic density protein 95 [16] indicating reduction of synapses and loss of communication between neurons. The synaptic deterioration manifests with memory and learning impairment as observed in control rats after injection of AβOs from human AD brains [14]. Further, levels of AβOs in fractionated brain homogenates from patients with AD correlate with the severity of cognitive impairment (assessed by Blessed Information-Memory-Concentration and the Mini-Mental State Examination scores) [16]. Nevertheless, AβOs are found in subjects without cognitive impairment; they increase physiologically in old age [17]. The fact that both demented and non-demented patients have increased levels of oligomers does not necessarily mean they have the same oligomeric structure. AβOs organize into dimers, trimers, tetramers, and higher order structures.  [17][18].
The relation between oligomer formation and disease state remains controversial. Most studies support the pathogenic role of oligomers in neurodegeneration as mentioned above. For example, elevated levels of plasma AβOs have shown a strong correlation with the cognitive performance in patients with AD (assessed by Mini-Mental State Examination, Cognitive Abilities Screening Instrument, Alzheimer’s Disease Assessment Scale–cognitive portion, and common objects memory test) [19]. Other studies have shown correlation with severity [20][21].
TauOs are present in neurons and astrocytes at early stages of neurodegeneration, they are increased even before the formation of neurofibrillary tangles and clinical manifestations of AD [22][23][24]. As with AβOs, human brain derived TauOs injected in mice impair synaptic plasticity in the hippocampus, and clinically manifest with anterograde memory storage dysfunction [25]. TauOs are not only increased in senile and AD brains, but also, they have been detected in high levels in animal models and brains of individuals with PD, suggesting that TauOs are neurotoxic mediators in synucleinopathies [26][27].
Neurodegeneration driven by αSynOs depends on their interaction with cell membranes. Similar to AβOs and TauOs, αSynOs can perforate the membrane and hence alter the membrane conductance; therefore, formation of ion-permeating pores seems to be a general mechanism to destabilize the cell membrane shared by some oligomeric forms of misfolded proteins. Moreover, perfusion of αSynOs onto hippocampal neurons induce an increase of intracellular calcium level, which supports the idea of strong membrane interactions [28][29]. The elevation of calcium levels is in accordance with the calcium homeostasis dysregulation observed in PD subjects [30][31][32][33].

3. Synaptic Dysfunction Leading to Cognitive Impairment

3.1. Synapse Loss

It has been well established that synaptic dysfunction occurs in AD and PD. Less synapses are found in postmortem brains of patients with AD and PD in brain regions underlying clinical manifestations of both diseases [34][35]. However, only recently it became possible to evaluate synaptic alterations in alive people by using synaptic positron emission tomography (PET) imaging. Specifically, the PET tracer [11C]UCB-J for the synaptic vesicle glycoprotein (SV2A), expressed in all synapses and located in synaptic vesicles at presynaptic terminals, was recently used to detect synaptic alterations in vivo of patients with early AD and PD. In AD, PET imaging of SV2A showed prominent reduction synapses in the hippocampus, followed by the entorhinal cortex, parahippocampal cortex, amygdala, lateral temporal cortex, PCC/precuneus, and lateral parietal cortex, but not in the prefrontal cortex, lateral occipital cortex, medial occipital cortex, or pericentral cortex [36]. The synaptic density reductions were maintained after partial volume correction of the PET images, meaning that the effect is not entirely attributed to loss of gray matter tissue. Importantly, there was a correlation between the reduction of SV2A and cognitive impairment. PET studies correlate with accumulated literature that has consistently shown evidence of synaptic loss across brain regions in AD and other neurodegenerative disorders [37]. In PD, PET imaging showed lower SV2A in the substantia nigra, followed by red nucleus and locus coeruleus as well as other clinically relevant areas [38].

3.2. Inflammatory Response Effects on Synapses

Although AD and PD were not originally considered inflammatory disorders, neuroinflammation is a critical component in the pathogenesis and progression of cognitive impairment. Neuroinflammation involves activation of microglia and astrocytes, and the subsequent release of cytokine radicals which lead to synaptic loss and damage [39][40]. Particularly, microglia are pivotal in the control of synapse activity by establishing direct contact with neurons, meaning that an inflammatory process at this level has a negative impact on synaptic surveillance and thus, cognitive function. However, whether neuroinflammation is caused by soluble oligomers, the most toxic components in the pathology of AD and PD, is not clear yet.
Distinct Aβ conformations seem to trigger different magnitudes of microglial activation. As mentioned before, oligomeric (rather than fibrillary) forms of Aβ, are the most neurotoxic aggregates in AD [14][15][41][42][43]. Thus, it has been investigated in vitro and in vivo whether AβOs are also stronger promoters of glial activation. An in vitro glial cell culture exposed to AβOs and fibrillar-Aβ, demonstrated not only that the pro-inflammatory response of the oligomeric form of Aβ was stronger than its fibrillary counterpart, but also that the response was an M1-like phenotype [44]. Complementarily, a murine study, where brain inflammation was induced by different Aβ42 conformers, showed that the lightest AβOs can activate microglial cells and promote a violent inflammatory response, whereas heavier oligomeric and fibrillary Aβ conformations induced less glial activation and poorer inflammatory responses [45]. Another in vivo model demonstrated AβOs promoted stronger neurotoxicity and inflammatory response mediated by NF-κB, when compared to fibrillar-Aβ [46]. All these studies reinforce the idea that AβOs are the most potent activators of microglial cells, and following studies display how this inflammatory response leads to synaptic disruption and sequential neuronal dysfunction. The inflammatory response followed by synaptic disruption and neuronal loss can be clinically translated as memory, language, and visual perception decline, among other forms of cognitive impairment [47]. In animal models AβOs induce inflammatory signaling leading to this cognitive decline manifestations [48][49][50]. For instance, in an acute experimental model in C57BL/6 mice, memory impairment and inflammation were observed after an intracerebroventricular injection of AβOs, suggesting that oligomers interfere with synaptic transmission necessary to establish new memories; again, the fibrillar-Aβ did not produce this effect [9]. The molecular link between cognitive deficit and neuroinflammation lies in the release of cytokines by microglial cells. In one study, purified AβOs from human AD brain tissue were injected in wild type mice to induce microglial inflammation. The inflammatory response of this model was demonstrated when several cytokines at mRNA and protein levels were identified, including Ccl3, CCl4, and Tnf [51]. Other mechanism underlying AβO-induced microglial activation is explained by TLR-4, which likely induces aberrant TNF-α signaling [52][53]. In support of this deleterious role of the inflammatory response, the cognitive decline, induced by the intracerebral injection of AβOs, was reversed by the administration of anti-inflammatory drugs, doxycycline, and TLR-4 antagonists [54]. In another study of intracerebroventricular injection of AβOs in wild type mice, the complement factors C1q, which initiates the classic complement pathway, and C3, were found elevated at the synapse level, which would explain the synapse loss through microglial activation [55]. In addition to inflammation induced by microglia, astrocytosis is another early phenomenon in AD development, but whether AβOs induce astrocytosis remains to be determined.
TauOs are the most neurotoxic tau species involved in the development of cognitive impairment [56][57]. They induce neuroinflammation in AD and frontotemporal lobar dementia through interaction with astrocytes and microglia [58]. A model for the toxic relationship between TauOs and inflammation has been proposed, where TauOs through astrocytes and microglia trigger the release of cytokines, RAGE receptors and their ligand HMGB1. Activation of RAGE signals NF-κB and p38-MAPK pathways, which in turn promote hyperphosphorylation of Tau and subsequent aggregation of more oligomers, and thus, neuronal damage or death and a vicious cycle of chronic neuroinflammation [23][58].

3.3. Receptors Involved in Synaptic Dysfunction

Accumulated evidence indicates that AβOs directly activates AMPA receptors [59]. AMPA receptors are complex proteins made by the combination of four principal subunits (GluA1-GluA4) [59][60], and co-assembled auxiliary proteins [61][62], that modulate the gating, permeability, and pharmacology of the channel [62][63][64][65][66]. GluA2-lacking AMPA receptors are permeable to Ca2+ and its excessive activation leads to Ca2+ overload, excitotoxicity, and neurodegeneration [67][68][69][70][71]. Recent evidence from Reinders et al., demonstrated that AβOs cause synaptic failure only in neurons expressing GluA3 subunits [72], and mice with severe AD neuropathology but deficient in GluA3 were cognitively resilient [72], strongly indicating that synaptic vulnerability to AβOs may depend on the stoichiometry of synaptic receptors. This is consistent with human postmortem studies where lower gene expression levels for GluA3 correlated with better cognitive performance in prodromal AD [73]. Similarly, it is increasingly acknowledged that AβOs directly activate heterologously-expressed receptors composed by GRIN1/GluN2A and GRIN1/GluN2B subunits [59][74], which are the most abundant NMDA receptors in mammals’ cortical synapses; however, only the activation of receptors containing GluN2B subunits (GluN2B-NMDA receptors) leads to acute activity-dependent postsynaptic failure [75], Ca2+ dysregulation [76], synaptic depression [77][78], and neurotoxicity in in vitro systems [79][80]. Most likely due to the high Ca2+ permeability of GluN2B-NMDA receptors [81] and their downstream signaling [82]. The clinical significance of GluN2B is reinforced by a multisite postmortem study showing that lower cortical gene expression of GluN2B correlates with better cognitive performance in people diagnosed with prodromal AD [73].

3.4. Impaired Excitatory/Inhibitory Ratio

Hyperexcitability of cortical and hippocampal circuits and 87-fold increase in seizures incidence in the AD population is well documented [83], particularly in early-onset familial AD [84]. Convulsive seizures occur in approximately 7–21% of sporadic AD patients [85][86], 31% of patients with PS2 mutations [87] and 56% of patients with APP duplications [88]. These data do not account for hidden hyperexcitability status that occurs early in AD pathogenesis [89]. Since oligomers act mostly on excitatory synapses leading to dysfunction first and synaptic loss later, a large question in the field is how, overall reduction of excitatory inputs leads to hyperexcitability in the AD brain. Although the causes of network hyperactivity are still under investigation by many labs; early studies in animal models suggest that impaired inhibition is a potential mechanism for network hyperactivity [90][91]. Impairment of interneuron activity with changes in their intrinsic properties have been reported in the mice models of amyloidosis [92]. Interneuron deficits reduces neurogenesis and neuronal maturation in the hilus of the hippocampus [93] and leads to age and tau-dependent learning and memory deficits [94]. Potentiation of GABA receptors by pentobarbital restores some of the deficits observed by GABAergic impairment [93]. Some initial studies transplanting human receptors and recording their electrical activity observed a dramatic reduction of GABAA receptors in AD [95]. This severe reduction of gene expression was later confirmed by other groups using high throughput microarray technology [96] and provided evidence that in addition to excitatory synaptic loss, inhibitory synapses were also affected in AD.

4. Conclusions

Oligomeric forms of Aβ, tau and aSyn are the most toxic species affecting synapses leading to synaptic dysfunction and altered neuronal communication in brain regions vulnerable to the neuropathology. The effects of oligomers precede the presence of deposits and seem to be associated to early changes in excitatory and inhibitory synapses. Therefore, oligomers seem to produce a “double hit” on synapses (Figure 1). First, they lead to calcium dys-homeostasis by binding directly to excitatory receptors and leading to a first wave of hyperexcitability, then producing GABAergic dysfunction by a mechanism that is still not understood, which leads to a second chronic wave of hyperexcitablity that ultimately leads to neuronal loss and hypoactivity. Understanding the regional and temporal relationships between oligomers, synaptic targets and E/I balance is a critical need in the field.
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Figure 1. Overview of major effects of toxic oligomers in synapses. Left. Neuroinflammatory and Reactive Oxygen Species (ROS) participate in the production and the effects of toxic oligomers on synapses. Right, Major synaptic effects on synapses. It is still not clear what is the chronological order of events, but each one influence the others and some of them are happening simultaneously at brain regions vulnerable to AD pathology.

This entry is adapted from the peer-reviewed paper 10.3390/biomedicines10071743

References

  1. World Health Organization. Available online: https://www.who.int/news-room/fact-sheets/detail/dementia (accessed on 21 June 2022).
  2. Parkinson’s Disease Statistics. Available online: https://parkinsonsnewstoday.com/parkinsons-disease-statistics/ (accessed on 5 June 2022).
  3. Verma, M.; Vats, A.; Taneja, V. Toxic Species in Amyloid Disorders: Oligomers or Mature Fibrils. Ann. Indian Acad. Neurol. 2015, 18, 138–145.
  4. Forloni, G.; Artuso, V.; la Vitola, P.; Balducci, C. Oligomeropathies and Pathogenesis of Alzheimer and Parkinson’s Diseases. Mov. Disord. 2016, 31, 771–781.
  5. Ono, K. The Oligomer Hypothesis in α-Synucleinopathy. Neurochem. Res. 2017, 42, 3362–3371.
  6. Kuo, Y.M.; Emmerling, M.R.; Vigo-Pelfrey, C.; Kasunic, T.C.; Kirkpatrick, J.B.; Murdoch, G.H.; Ball, M.J.; Roher, A.E. Water-Soluble Aβ (N-40, N-42) Oligomers in Normal and Alzheimer Disease Brains. J. Biol. Chem. 1996, 271, 4077–4081.
  7. Mucke, L.; Selkoe, D.J. Neurotoxicity of Amyloid β-Protein: Synaptic and Network Dysfunction. Cold Spring Harb. Perspect. Med. 2012, 2, a006338.
  8. Walsh, D.M.; Klyubin, I.; Fadeeva, J.V.; Cullen, W.K.; Anwyl, R.; Wolfe, M.S.; Rowan, M.J.; Selkoe, D.J. Naturally Secreted Oligomers of Amyloid β Protein Potently Inhibit Hippocampal Long-Term Potentiation in Vivo. Nature 2002, 416, 535–539.
  9. Balducci, C.; Beeg, M.; Stravalaci, M.; Bastone, A.; Sclip, A.; Biasini, E.; Tapella, L.; Colombo, L.; Manzoni, C.; Borsello, T.; et al. Synthetic Amyloid-β Oligomers Impair Long-Term Memory Independently of Cellular Prion Protein. Proc. Natl. Acad. Sci. USA 2010, 107, 2295–2300.
  10. Haass, C.; Selkoe, D.J. Soluble Protein Oligomers in Neurodegeneration: Lessons from the Alzheimer’s Amyloid β-Peptide. Nat. Rev. Mol. Cell Biol. 2007, 8, 101–112.
  11. Wilcox, K.C.; Lacor, P.N.; Pitt, J.; Klein, W.L. Aβ Oligomer-Induced Synapse Degeneration in Alzheimer’s Disease. Cell. Mol. Neurobiol. 2011, 31, 939–948.
  12. Ward, S.M.; Himmelstein, D.S.; Lancia, J.K.; Binder, L.I. Tau Oligomers and Tau Toxicity in Neurodegenerative Disease. Biochem. Soc. Trans. 2012, 40, 667–671.
  13. Kayed, R.; Lasagna-Reeves, C.A. Molecular Mechanisms of Amyloid Oligomers Toxicity. J. Alzheimer’s Dis. 2013, 33 (Suppl. 1), S67–S78.
  14. Shankar, G.M.; Li, S.; Mehta, T.H.; Garcia-Munoz, A.; Shepardson, N.E.; Smith, I.; Brett, F.M.; Farrell, M.A.; Rowan, M.J.; Lemere, C.A.; et al. Amyloid-β Protein Dimers Isolated Directly from Alzheimer’s Brains Impair Synaptic Plasticity and Memory. Nat. Med. 2008, 14, 837–842.
  15. Lacor, P.N.; Buniel, M.C.; Furlow, P.W.; Clemente, A.S.; Velasco, P.T.; Wood, M.; Viola, K.L.; Klein, W.L. Aβ Oligomer-Induced Aberrations in Synapse Composition, Shape, and Density Provide a Molecular Basis for Loss of Connectivity in Alzheimer’s Disease. J. Neurosci. 2007, 27, 796–807.
  16. Pham, E.; Crews, L.; Ubhi, K.; Hansen, L.; Adame, A.; Cartier, A.; Salmon, D.; Galasko, D.; Michael, S.; Savas, J.N.; et al. Progressive Accumulation of Amyloid-β Oligomers in Alzheimer’s Disease and in Amyloid Precursor Protein Transgenic Mice Is Accompanied by Selective Alterations in Synaptic Scaffold Proteins. FEBS J. 2010, 277, 3051–3067.
  17. Lesné, S.E.; Sherman, M.A.; Grant, M.; Kuskowski, M.; Schneider, J.A.; Bennett, D.A.; Ashe, K.H. Brain Amyloid-β Oligomers in Ageing and Alzheimer’s Disease. Brain 2013, 136, 1383–1398.
  18. Lesné, S.; Koh, M.T.; Kotilinek, L.; Kayed, R.; Glabe, C.G.; Yang, A.; Gallagher, M.; Ashe, K.H. A Specific Amyloid-β Protein Assembly in the Brain Impairs Memory. Nature 2006, 440, 352–357.
  19. Meng, X.; Li, T.; Wang, X.; Lv, X.; Sun, Z.; Zhang, J.; Su, F.; Kang, S.; Kim, S.; An, S.S.A.; et al. Association between Increased Levels of Amyloid-β Oligomers in Plasma and Episodic Memory Loss in Alzheimer’s Disease. Alzheimer’s Res. Ther. 2019, 11, 89.
  20. McLean, C.A.; Cherny, R.A.; Fraser, F.W.; Fuller, S.J.; Smith, M.J.; Beyreuther, K.; Bush, A.I.; Masters, C.L. Soluble Pool of Aβ Amyloid as a Determinant of Severity of Neurodegeneration in Alzheimer’s Disease. Ann. Neurol. 1999, 46, 860–866.
  21. Mc Donald, J.M.; Savva, G.M.; Brayne, C.; Welzel, A.T.; Forster, G.; Shankar, G.M.; Selkoe, D.J.; Ince, P.G.; Walsh, D.M. The Presence of Sodium Dodecyl Sulphate-Stable Aβ Dimers Is Strongly Associated with Alzheimer-Type Dementia. Brain 2010, 133, 1328–1341.
  22. Maeda, S.; Sahara, N.; Saito, Y.; Murayama, S.; Ikai, A.; Takashima, A. Increased Levels of Granular Tau Oligomers: An Early Sign of Brain Aging and Alzheimer’s Disease. Neurosci. Res. 2006, 54, 197–201.
  23. Gaikwad, S.; Puangmalai, N.; Bittar, A.; Montalbano, M.; Garcia, S.; McAllen, S.; Bhatt, N.; Sonawane, M.; Sengupta, U.; Kayed, R. Tau Oligomer Induced HMGB1 Release Contributes to Cellular Senescence and Neuropathology Linked to Alzheimer’s Disease and Frontotemporal Dementia. Cell Rep. 2021, 36, 109419.
  24. Patterson, K.R.; Remmers, C.; Fu, Y.; Brooker, S.; Kanaan, N.M.; Vana, L.; Ward, S.; Reyes, J.F.; Philibert, K.; Glucksman, M.J.; et al. Characterization of Prefibrillar Tau Oligomers in Vitro and in Alzheimer Disease. J. Biol. Chem. 2011, 286, 23063–23076.
  25. Lasagna-Reeves, C.A.; Castillo-Carranza, D.L.; Sengupta, U.; Guerrero-Munoz, M.J.; Kiritoshi, T.; Neugebauer, V.; Jackson, G.R.; Kayed, R. Alzheimer Brain-Derived Tau Oligomers Propagate Pathology from Endogenous Tau. Sci. Rep. 2012, 2, 700.
  26. Paleologou, K.E.; Kragh, C.L.; Mann, D.M.A.; Salem, S.A.; Al-Shami, R.; Allsop, D.; Hassan, A.H.; Jensen, P.H.; El-Agnaf, O.M.A. Detection of Elevated Levels of Soluble α-Synuclein Oligomers in Post-Mortem Brain Extracts from Patients with Dementia with Lewy Bodies. Brain 2009, 132, 1093–1101.
  27. Gerson, J.E.; Farmer, K.M.; Henson, N.; Castillo-Carranza, D.L.; Carretero Murillo, M.; Sengupta, U.; Barrett, A.; Kayed, R. Tau Oligomers Mediate α-Synuclein Toxicity and Can Be Targeted by Immunotherapy. Mol. Neurodegener. 2018, 13, 13.
  28. Surguchev, A.; Surguchov, A. Effect of α-Synuclein on Membrane Permeability and Synaptic Transmission: A Clue to Neurodegeneration? J. Neurochem. 2015, 132, 619–621.
  29. Winner, B.; Jappelli, R.; Maji, S.K.; Desplats, P.A.; Boyer, L.; Aigner, S.; Hetzer, C.; Loher, T.; Vilar, M.; Campioni, S.; et al. In Vivo Demonstration That α-Synuclein Oligomers Are Toxic. Proc. Natl. Acad. Sci. USA 2011, 108, 4194–4199.
  30. Surmeier, D.J.; Schumacker, P.T.; Guzman, J.D.; Ilijic, E.; Yang, B.; Zampese, E. Calcium and Parkinson’s Disease. Biochem. Biophys. Res. Commun. 2017, 483, 1013–1019.
  31. Subramaniam, S.R.; Chesselet, M.-F. Mitochondrial Dysfunction and Oxidative Stress in Parkinson’s Disease. Prog. Neurobiol. 2013, 106–107, 17–32.
  32. Zampese, E.; Surmeier, D.J. Calcium, Bioenergetics, and Parkinson’s Disease. Cells 2020, 9, 2045.
  33. Poewe, W.; Seppi, K.; Tanner, C.M.; Halliday, G.M.; Brundin, P.; Volkmann, J.; Schrag, A.-E.; Lang, A.E. Parkinson Disease. Nat. Rev. Dis. Primers 2017, 3, 17013.
  34. Terry, R.D.; Masliah, E.; Salmon, D.P.; Butters, N.; DeTeresa, R.; Hill, R.; Hansen, L.A.; Katzman, R. Physical Basis of Cognitive Alterations in Alzheimer’s Disease: Synapse Loss Is the Major Correlate of Cognitive Impairment. Ann. Neurol. 1991, 30, 572–580.
  35. Schulz-Schaeffer, W.J. The Synaptic Pathology of α-Synuclein Aggregation in Dementia with Lewy Bodies, Parkinson’s Disease and Parkinson’s Disease Dementia. Acta Neuropathol. 2010, 120, 131–143.
  36. Mecca, A.P.; Chen, M.K.; O’Dell, R.S.; Naganawa, M.; Toyonaga, T.; Godek, T.A.; Harris, J.E.; Bartlett, H.H.; Zhao, W.; Nabulsi, N.B.; et al. In Vivo Measurement of Widespread Synaptic Loss in Alzheimer’s Disease with SV2A PET. Alzheimer’s Dement. 2020, 16, 974–982.
  37. Wilde, M.C.; Overk, C.R.; Sijben, J.W.; Masliah, E. Meta-analysis of Synaptic Pathology in Alzheimer’s Disease Reveals Selective Molecular Vesicular Machinery Vulnerability. Alzheimer’s Dement. 2016, 12, 633–644.
  38. Matuskey, D.; Tinaz, S.; Wilcox, K.C.; Naganawa, M.; Toyonaga, T.; Dias, M.; Henry, S.; Pittman, B.; Ropchan, J.; Nabulsi, N.; et al. Synaptic Changes in Parkinson Disease Assessed with in Vivo Imaging. Ann. Neurol. 2020, 87, 329–338.
  39. Forloni, G.; Balducci, C. Alzheimer’s Disease, Oligomers, and Inflammation. J. Alzheimer’s Dis. 2018, 62, 1261–1276.
  40. Heneka, M.T.; Carson, M.J.; El Khoury, J.; Landreth, G.E.; Brosseron, F.; Feinstein, D.L.; Jacobs, A.H.; Wyss-Coray, T.; Vitorica, J.; Ransohoff, R.M.; et al. Neuroinflammation in Alzheimer’s Disease. Lancet Neurol. 2015, 14, 388–405.
  41. Dahlgren, K.N.; Manelli, A.M.; Stine, W.B.; Baker, L.K.; Krafft, G.A.; LaDu, M.J. Oligomeric and Fibrillar Species of Amyloid-β Peptides Differentially Affect Neuronal Viability. J. Biol. Chem. 2002, 277, 32046–32053.
  42. Ahmed, M.; Davis, J.; Aucoin, D.; Sato, T.; Ahuja, S.; Aimoto, S.; Elliott, J.I.; van Nostrand, W.E.; Smith, S.O. Structural Conversion of Neurotoxic Amyloid-β1–42 Oligomers to Fibrils. Nat. Struct. Mol. Biol. 2010, 17, 561–567.
  43. Walsh, D.M.; Selkoe, D.J. Aβ Oligomers—A Decade of Discovery. J. Neurochem. 2007, 101, 1172–1184.
  44. Michelucci, A.; Heurtaux, T.; Grandbarbe, L.; Morga, E.; Heuschling, P. Characterization of the Microglial Phenotype under Specific Pro-Inflammatory and Anti-Inflammatory Conditions: Effects of Oligomeric and Fibrillar Amyloid-β. J. Neuroimmunol. 2009, 210, 3–12.
  45. Heurtaux, T.; Michelucci, A.; Losciuto, S.; Gallotti, C.; Felten, P.; Dorban, G.; Grandbarbe, L.; Morga, E.; Heuschling, P. Microglial Activation Depends on β-Amyloid Conformation: Role of the Formylpeptide Receptor 2. J. Neurochem. 2010, 114, 576–586.
  46. He, Y.; Zheng, M.-M.; Ma, Y.; Han, X.-J.; Ma, X.-Q.; Qu, C.-Q.; Du, Y.-F. Soluble Oligomers and Fibrillar Species of Amyloid β-Peptide Differentially Affect Cognitive Functions and Hippocampal Inflammatory Response. Biochem. Biophys. Res. Commun. 2012, 429, 125–130.
  47. Rao, J.S.; Kellom, M.; Kim, H.-W.; Rapoport, S.I.; Reese, E.A. Neuroinflammation and Synaptic Loss. Neurochem. Res. 2012, 37, 903–910.
  48. Lourenco, M.V.; Clarke, J.R.; Frozza, R.L.; Bomfim, T.R.; Forny-Germano, L.; Batista, A.F.; Sathler, L.B.; Brito-Moreira, J.; Amaral, O.B.; Silva, C.A.; et al. TNF-α Mediates PKR-Dependent Memory Impairment and Brain IRS-1 Inhibition Induced by Alzheimer’s β-Amyloid Oligomers in Mice and Monkeys. Cell Metab. 2013, 18, 831–843.
  49. Forny-Germano, L.; e Silva, N.L.M.; Batista, A.F.; Brito-Moreira, J.; Gralle, M.; Boehnke, S.E.; Coe, B.C.; Lablans, A.; Marques, S.A.; Martinez, A.M.B.; et al. Alzheimer’s Disease-like Pathology Induced by Amyloid-β Oligomers in Nonhuman Primates. J. Neurosci. 2014, 34, 13629–13643.
  50. Ledo, J.H.; Azevedo, E.P.; Clarke, J.R.; Ribeiro, F.C.; Figueiredo, C.P.; Foguel, D.; de Felice, F.G.; Ferreira, S.T. Amyloid-β Oligomers Link Depressive-like Behavior and Cognitive Deficits in Mice. Mol. Psychiatry 2013, 18, 1053–1054.
  51. Xu, H.; Gelyana, E.; Rajsombath, M.; Yang, T.; Li, S.; Selkoe, D. Environmental Enrichment Potently Prevents Microglia-Mediated Neuroinflammation by Human Amyloid β-Protein Oligomers. J. Neurosci. 2016, 36, 9041–9056.
  52. Ledo, J.H.; Azevedo, E.P.; Beckman, D.; Ribeiro, F.C.; Santos, L.E.; Razolli, D.S.; Kincheski, G.C.; Melo, H.M.; Bellio, M.; Teixeira, A.L.; et al. Cross Talk Between Brain Innate Immunity and Serotonin Signaling Underlies Depressive-Like Behavior Induced by Alzheimer’s Amyloid-β Oligomers in Mice. J. Neurosci. 2016, 36, 12106–12116.
  53. Balducci, C.; Frasca, A.; Zotti, M.; la Vitola, P.; Mhillaj, E.; Grigoli, E.; Iacobellis, M.; Grandi, F.; Messa, M.; Colombo, L.; et al. Toll-like Receptor 4-Dependent Glial Cell Activation Mediates the Impairment in Memory Establishment Induced by β-Amyloid Oligomers in an Acute Mouse Model of Alzheimer’s Disease. Brain Behav. Immun. 2017, 60, 188–197.
  54. Balducci, C.; Forloni, G. Doxycycline for Alzheimer’s Disease: Fighting β-Amyloid Oligomers and Neuroinflammation. Front. Pharmacol. 2019, 10, 738.
  55. Hong, S.; Beja-Glasser, V.F.; Nfonoyim, B.M.; Frouin, A.; Li, S.; Ramakrishnan, S.; Merry, K.M.; Shi, Q.; Rosenthal, A.; Barres, B.A.; et al. Complement and Microglia Mediate Early Synapse Loss in Alzheimer Mouse Models. Science 2016, 352, 712–716.
  56. Lasagna-Reeves, C.A.; Castillo-Carranza, D.L.; Sengupta, U.; Sarmiento, J.; Troncoso, J.; Jackson, G.R.; Kayed, R. Identification of Oligomers at Early Stages of Tau Aggregation in Alzheimer’s Disease. FASEB J. 2012, 26, 1946–1959.
  57. Shafiei, S.S.; Guerrero-Muñoz, M.J.; Castillo-Carranza, D.L. Tau Oligomers: Cytotoxicity, Propagation, and Mitochondrial Damage. Front. Aging Neurosci. 2017, 9, 83.
  58. Nilson, A.N.; English, K.C.; Gerson, J.E.; Barton Whittle, T.; Nicolas Crain, C.; Xue, J.; Sengupta, U.; Castillo-Carranza, D.L.; Zhang, W.; Gupta, P.; et al. Tau Oligomers Associate with Inflammation in the Brain and Retina of Tauopathy Mice and in Neurodegenerative Diseases. J. Alzheimer’s Dis. 2017, 55, 1083–1099.
  59. Alberdi, E.; Sánchez-Gómez, M.V.; Cavaliere, F.; Pérez-Samartín, A.; Zugaza, J.L.; Trullas, R.; Domercq, M.; Matute, C. Amyloid β Oligomers Induce Ca2+ Dysregulation and Neuronal Death through Activation of Ionotropic Glutamate Receptors. Cell Calcium 2010, 47, 264–272.
  60. Traynelis, S.F.; Wollmuth, L.P.; McBain, C.J.; Menniti, F.S.; Vance, K.M.; Ogden, K.K.; Hansen, K.B.; Yuan, H.; Myers, S.J.; Dingledine, R. Glutamate Receptor Ion Channels: Structure, Regulation, and Function. Pharmacol. Rev. 2010, 62, 405–496.
  61. Schwenk, J.; Harmel, N.; Zolles, G.; Bildl, W.; Kulik, A.; Heimrich, B.; Chisaka, O.; Jonas, P.; Schulte, U.; Fakler, B.; et al. Functional Proteomics Identify Cornichon Proteins as Auxiliary Subunits of AMPA Receptors. Science 2009, 323, 1313–1319.
  62. De Boer, H.; Blok, G.J.; Voerman, H.J.; van der Veen, E.A. Is Growth Hormone Supplementation in Growth Hormone Deficiency in Adults Indicated? Ned. Tijdschr. Geneeskd. 1990, 134, 2428–2431.
  63. Herring, B.E.; Shi, Y.; Suh, Y.H.; Zheng, C.-Y.; Blankenship, S.M.; Roche, K.W.; Nicoll, R.A. Cornichon Proteins Determine the Subunit Composition of Synaptic AMPA Receptors. Neuron 2013, 77, 1083–1096.
  64. Kato, A.S.; Gill, M.B.; Yu, H.; Nisenbaum, E.S.; Bredt, D.S. TARPs Differentially Decorate AMPA Receptors to Specify Neuropharmacology. Trends Neurosci. 2010, 33, 241–248.
  65. Cho, C.-H.; St-Gelais, F.; Zhang, W.; Tomita, S.; Howe, J.R. Two Families of TARP Isoforms That Have Distinct Effects on the Kinetic Properties of AMPA Receptors and Synaptic Currents. Neuron 2007, 55, 890–904.
  66. Milstein, A.D.; Zhou, W.; Karimzadegan, S.; Bredt, D.S.; Nicoll, R.A. TARP Subtypes Differentially and Dose-Dependently Control Synaptic AMPA Receptor Gating. Neuron 2007, 55, 905–918.
  67. Noh, K.-M.; Yokota, H.; Mashiko, T.; Castillo, P.E.; Zukin, R.S.; Bennett, M.V.L. Blockade of Calcium-Permeable AMPA Receptors Protects Hippocampal Neurons against Global Ischemia-Induced Death. Proc. Natl. Acad. Sci. USA 2005, 102, 12230–12235.
  68. Liu, S.; Lau, L.; Wei, J.; Zhu, D.; Zou, S.; Sun, H.-S.; Fu, Y.; Liu, F.; Lu, Y. Expression of Ca2+-Permeable AMPA Receptor Channels Primes Cell Death in Transient Forebrain Ischemia. Neuron 2004, 43, 43–55.
  69. Spaethling, J.M.; Klein, D.M.; Singh, P.; Meaney, D.F. Calcium-Permeable AMPA Receptors Appear in Cortical Neurons after Traumatic Mechanical Injury and Contribute to Neuronal Fate. J. Neurotrauma 2008, 25, 1207–1216.
  70. Corona, J.C.; Tapia, R. Ca2+-Permeable AMPA Receptors and Intracellular Ca2+ Determine Motoneuron Vulnerability in Rat Spinal Cord in Vivo. Neuropharmacology 2007, 52, 1219–1228.
  71. Vieira, M.; Fernandes, J.; Burgeiro, A.; Thomas, G.M.; Huganir, R.L.; Duarte, C.B.; Carvalho, A.L.; Santos, A.E. Excitotoxicity through Ca2+-Permeable AMPA Receptors Requires Ca2+-Dependent JNK Activation. Neurobiol. Dis. 2010, 40, 645–655.
  72. Reinders, N.R.; Pao, Y.; Renner, M.C.; da Silva-Matos, C.M.; Lodder, T.R.; Malinow, R.; Kessels, H.W. Amyloid-β Effects on Synapses and Memory Require AMPA Receptor Subunit GluA3. Proc. Natl. Acad. Sci. USA 2016, 113, E6526–E6534.
  73. Berchtold, N.C.; Sabbagh, M.N.; Beach, T.G.; Kim, R.C.; Cribbs, D.H.; Cotman, C.W. Brain Gene Expression Patterns Differentiate Mild Cognitive Impairment from Normal Aged and Alzheimer’s Disease. Neurobiol. Aging 2014, 35, 1961–1972.
  74. Texidó, L.; Martín-Satué, M.; Alberdi, E.; Solsona, C.; Matute, C. Amyloid β Peptide Oligomers Directly Activate NMDA Receptors. Cell Calcium 2011, 49, 184–190.
  75. Sinnen, B.L.; Bowen, A.B.; Gibson, E.S.; Kennedy, M.J. Local and Use-Dependent Effects of β-Amyloid Oligomers on NMDA Receptor Function Revealed by Optical Quantal Analysis. J. Neurosci. 2016, 36, 11532–11543.
  76. Ferreira, I.L.; Bajouco, L.M.; Mota, S.I.; Auberson, Y.P.; Oliveira, C.R.; Rego, A.C. Amyloid β Peptide 1–42 Disturbs Intracellular Calcium Homeostasis through Activation of GluN2B-Containing N-Methyl-d-Aspartate Receptors in Cortical Cultures. Cell Calcium 2012, 51, 95–106.
  77. Kessels, H.W.; Nabavi, S.; Malinow, R. Metabotropic NMDA Receptor Function Is Required for β-Amyloid-Induced Synaptic Depression. Proc. Natl. Acad. Sci. USA 2013, 110, 4033–4038.
  78. Snyder, E.M.; Nong, Y.; Almeida, C.G.; Paul, S.; Moran, T.; Choi, E.Y.; Nairn, A.C.; Salter, M.W.; Lombroso, P.J.; Gouras, G.K.; et al. Regulation of NMDA Receptor Trafficking by Amyloid-β. Nat. Neurosci. 2005, 8, 1051–1058.
  79. Ferreira, I.L.; Ferreiro, E.; Schmidt, J.; Cardoso, J.M.; Pereira, C.M.F.; Carvalho, A.L.; Oliveira, C.R.; Rego, A.C. Aβ and NMDAR Activation Cause Mitochondrial Dysfunction Involving ER Calcium Release. Neurobiol. Aging 2015, 36, 680–692.
  80. Costa, R.O.; Lacor, P.N.; Ferreira, I.L.; Resende, R.; Auberson, Y.P.; Klein, W.L.; Oliveira, C.R.; Rego, A.C.; Pereira, C.M.F. Endoplasmic Reticulum Stress Occurs Downstream of GluN2B Subunit of N-Methyl-d-Aspartate Receptor in Mature Hippocampal Cultures Treated with Amyloid-β Oligomers. Aging Cell 2012, 11, 823–833.
  81. Evans, R.C.; Morera-Herreras, T.; Cui, Y.; Du, K.; Sheehan, T.; Kotaleski, J.H.; Venance, L.; Blackwell, K.T. The Effects of NMDA Subunit Composition on Calcium Influx and Spike Timing-Dependent Plasticity in Striatal Medium Spiny Neurons. PLoS Comput. Biol. 2012, 8, e1002493.
  82. Skeberdis, V.A.; Chevaleyre, V.; Lau, C.G.; Goldberg, J.H.; Pettit, D.L.; Suadicani, S.O.; Lin, Y.; Bennett, M.V.L.; Yuste, R.; Castillo, P.E.; et al. Protein Kinase A Regulates Calcium Permeability of NMDA Receptors. Nat. Neurosci. 2006, 9, 501–510.
  83. Amatniek, J.C.; Hauser, W.A.; DelCastillo-Castaneda, C.; Jacobs, D.M.; Marder, K.; Bell, K.; Albert, M.; Brandt, J.; Stern, Y. Incidence and Predictors of Seizures in Patients with Alzheimer’s Disease. Epilepsia 2006, 47, 867–872.
  84. Palop, J.J.; Mucke, L. Epilepsy and Cognitive Impairments in Alzheimer Disease. Arch. Neurol. 2009, 66, 435–440.
  85. Hauser, W.A.; Morris, M.L.; Heston, L.L.; Anderson, V.E. Seizures and Myoclonus in Patients with Alzheimer’s Disease. Neurology 1986, 36, 1226–1230.
  86. Mendez, M.; Lim, G. Seizures in Elderly Patients with Dementia: Epidemiology and Management. Drugs Aging 2003, 20, 791–803.
  87. Jayadev, S.; Leverenz, J.B.; Steinbart, E.; Stahl, J.; Klunk, W.; Yu, C.-E.; Bird, T.D. Alzheimer’s Disease Phenotypes and Genotypes Associated with Mutations in Presenilin 2. Brain 2010, 133, 1143–1154.
  88. Cabrejo, L.; Guyant-Maréchal, L.; Laquerrière, A.; Vercelletto, M.; de la Fournière, F.; Thomas-Antérion, C.; Verny, C.; Letournel, F.; Pasquier, F.; Vital, A.; et al. Phenotype Associated with APP Duplication in Five Families. Brain 2006, 129, 2966–2976.
  89. Sperling, R.A.; Laviolette, P.S.; O’Keefe, K.; O’Brien, J.; Rentz, D.M.; Pihlajamaki, M.; Marshall, G.; Hyman, B.T.; Selkoe, D.J.; Hedden, T.; et al. Amyloid Deposition Is Associated with Impaired Default Network Function in Older Persons without Dementia. Neuron 2009, 63, 178–188.
  90. Palop, J.J.; Chin, J.; Roberson, E.D.; Wang, J.; Thwin, M.T.; Bien-Ly, N.; Yoo, J.; Ho, K.O.; Yu, G.-Q.; Kreitzer, A.; et al. Aberrant Excitatory Neuronal Activity and Compensatory Remodeling of Inhibitory Hippocampal Circuits in Mouse Models of Alzheimer’s Disease. Neuron 2007, 55, 697–711.
  91. Verret, L.; Mann, E.O.; Hang, G.B.; Barth, A.M.I.; Cobos, I.; Ho, K.; Devidze, N.; Masliah, E.; Kreitzer, A.C.; Mody, I.; et al. Inhibitory Interneuron Deficit Links Altered Network Activity and Cognitive Dysfunction in Alzheimer Model. Cell 2012, 149, 708–721.
  92. Sos, K.E.; Mayer, M.I.; Takács, V.T.; Major, A.; Bardóczi, Z.; Beres, B.M.; Szeles, T.; Saito, T.; Saido, T.C.; Mody, I.; et al. Amyloid β Induces Interneuron-Specific Changes in the Hippocampus of APPNL-F Mice. PLoS ONE 2020, 15, e0233700.
  93. Li, G.; Bien-Ly, N.; Andrews-Zwilling, Y.; Xu, Q.; Bernardo, A.; Ring, K.; Halabisky, B.; Deng, C.; Mahley, R.W.; Huang, Y. GABAergic Interneuron Dysfunction Impairs Hippocampal Neurogenesis in Adult Apolipoprotein E4 Knockin Mice. Cell Stem Cell 2009, 5, 634–645.
  94. Andrews-Zwilling, Y.; Bien-Ly, N.; Xu, Q.; Li, G.; Bernardo, A.; Yoon, S.Y.; Zwilling, D.; Yan, T.X.; Chen, L.; Huang, Y. Apolipoprotein E4 Causes Age- and Tau-Dependent Impairment of GABAergic Interneurons, Leading to Learning and Memory Deficits in Mice. J. Neurosci. 2010, 30, 13707–13717.
  95. Limon, A.; Reyes-Ruiz, J.M.; Miledi, R. Loss of Functional GABAA Receptors in the Alzheimer Diseased Brain. Proc. Natl. Acad. Sci. USA 2012, 109, 10071–10076.
  96. Berchtold, N.C.; Coleman, P.D.; Cribbs, D.H.; Rogers, J.; Gillen, D.L.; Cotman, C.W. Synaptic Genes Are Extensively Downregulated across Multiple Brain Regions in Normal Human Aging and Alzheimer’s Disease. Neurobiol. Aging 2013, 34, 1653–1661.
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