Meta-analysis of synaptic pathology in Alzheimer's disease reveals selective molecular vesicular machinery vulnerability

AbstractIntroductionLoss of synapses best correlates to cognitive deficits in Alzheimer's disease (AD) in which oligomeric neurotoxic species of amyloid-β appears to contribute synaptic pathology. Although a number of clinical pathologic studies have been performed with limited sample size, there are no systematic studies encompassing large samples. Therefore, we performed a meta-analysis study.MethodsWe identified 417 publications reporting postmortem synapse and synaptic marker loss from AD patients. Two meta-analyses were performed using a single database of subselected publications and calculating the standard mean differences.ResultsMeta-analysis confirmed synaptic loss in selected brain regions is an early event in AD pathogenesis. The second meta-analysis of 57 synaptic markers revealed that presynaptic makers were affected more than postsynaptic markers.DiscussionThe present meta-analysis study showed a consistent synaptic loss across brain regions and that molecular machinery including endosomal pathways, vesicular assembly mechanisms, glutamate receptors, and axonal transport are often affected

Hippocampal neuronal cells that accumulate α-synuclein fragments are more vulnerable to Aβ oligomer toxicity via mGluR5--implications for dementia with Lewy bodies.

BackgroundIn dementia with Lewy bodies (DLB) abnormal interactions between α-synuclein (α-syn) and beta amyloid (Aβ) result in selective degeneration of neurons in the neocortex, limbic system and striatum. However, factors rendering these neurons selectively vulnerable have not been fully investigated. The metabotropic glutamate receptor 5 (mGluR5) has been shown to be up regulated in DLB and might play a role as a mediator of the neurotoxic effects of Aβ and α-syn in vulnerable neuronal populations. In this context, the main objective of the present study was to investigate the role of mGluR5 as a mediator of the neurotoxic effects of α-syn and Aβ in the hippocampus.ResultsWe generated double transgenic mice over-expressing amyloid precursor protein (APP) and α-syn under the mThy1 cassette and investigated the relationship between α-syn cleavage, Aβ, mGluR5 and neurodegeneration in the hippocampus. We found that compared to the single tg mice, the α-syn/APP tg mice displayed greater accumulation of α-syn and mGluR5 in the CA3 region of the hippocampus compared to the CA1 and other regions. This was accompanied by loss of CA3 (but not CA1) neurons in the single and α-syn/APP tg mice and greater loss of MAP 2 and synaptophysin in the CA3 in the α-syn/APP tg. mGluR5 gene transfer using a lentiviral vector into the hippocampus CA1 region resulted in greater α-syn accumulation and neurodegeneration in the single and α-syn/APP tg mice. In contrast, silencing mGluR5 with a lenti-shRNA protected neurons in the CA3 region of tg mice. In vitro, greater toxicity was observed in primary hippocampal neuronal cultures treated with Aβ oligomers and over-expressing α-syn; this effect was attenuated by down-regulating mGluR5 with an shRNA lentiviral vector. In α-syn-expressing neuronal cells lines, Aβ oligomers promoted increased intracellular calcium levels, calpain activation and α-syn cleavage resulting in caspase-3-dependent cell death. Treatment with pharmacological mGluR5 inhibitors such as 2-Methyl-6-(phenylethynyl)pyridine (MPEP) and 3-((2-Methyl-4-thiazolyl)ethynyl)pyridine (MTEP) attenuated the toxic effects of Aβ in α-syn-expressing neuronal cells.ConclusionsTogether, these results support the possibility that vulnerability of hippocampal neurons to α-syn and Aβ might be mediated via mGluR5. Moreover, therapeutical interventions targeting mGluR5 might have a role in DLB

The many faces of α-synuclein: from structure and toxicity to therapeutic target

Disorders characterized by α-synuclein (α-syn) accumulation, Lewy body formation and parkinsonism (and in some cases dementia) are collectively known as Lewy body diseases. The molecular mechanism (or mechanisms) through which α-syn abnormally accumulates and contributes to neurodegeneration in these disorders remains unknown. Here, we provide an overview of current knowledge and prevailing hypotheses regarding the conformational, oligomerization and aggregation states of α-syn and their role in regulating α-syn function in health and disease. Understanding the nature of the various α-syn structures, how they are formed and their relative contributions to α-syn-mediated toxicity may inform future studies aiming to develop therapeutic prevention and intervention

Combined Active Humoral and Cellular Immunization Approaches for the Treatment of Synucleonopathies

Objectives: Parkinson’s Disease (PD), Dementia with Lewy bodies (DLB), and Multiple System Atrophy (MSA) are neurodegenerative disorders of the aging population characterized by the progressive accumulation of alpha-synuclein. Jointly these disorders have been denominated synucleinopathies and currently no disease modifying treatments are available. Previous in vivo studies in transgenic (tg) mice have shown that active and passive immunization targeting alpha-synuclein ameliorates to some extent deficits and synuclein accumulation, however it’s unknown if combining humoral and cellular immunization might synergize and also reduce inflammation and improve microglial cell mediated synuclein clearance. Methods: PDGF- alpha-synuclein tg mice and control non-tg mice were immunized with: 1) Glucan Particle (GP) adjuvant alone, 2) GP human (hu)- alpha-synuclein (active immunization), 3) GP plus rapamycin and 4) GP plus rapamycin and hu-alpha-synuclein (combined active and humoral) and analyzed by neuropathological and biochemical markers. Results: Compared to tg mice treated with adjuvant alone, mice immunized with GP hu-alpha-synuclein displayed a 30% reduction in alpha-synuclein accumulation. Combined immunotherapy with GP plus rapamycin and hu-alpha-synuclein resulted in 50% reduction in alpha-synuclein accumulation which was accompanied by reduced neuro-inflammation (Iba-1, GFAP, IL6, TNFalpha), phospho and insoluble alpha-synuclein, microglia and astroglia cell numbers, and retention of CD25, FoxP3 and CD4 positive cells. Levels of TGFb1 were also increased. Serological studies showed that active immunization resulted in higher levels of total IgG, IgG1 and IgG2 titers, levels were slightly higher in the combined group. Conclusions: In vivo studies targeting alpha-synuclein support the hypothesis that cellular immunization might enhance the effects of active immunotherapy for the treatment of synucleionopathies

Accumulation of oligomer-prone α-synuclein exacerbates synaptic and neuronal degeneration in vivo

The toxicity of α-synuclein invivo is not well understood. Rockenstein etal. describe an α-synuclein transgenic model expressing the E57K mutant that forms stable oligomers. They show that oligomers accumulate at synapses and that the mutation interferes with synaptic vesicles and is associated with behavioural deficits and neurodegeneratio

Brainstem Alzheimer\u27s-like pathology in the triple transgenic mouse model of Alzheimer\u27s disease

The triple transgenic mouse (3xTgAD), harboring human APPSwe, PS1M146V and TauP301L genes, develops age-dependent forebrain intraneuronal Aβ and tau as well as extraneuronal plaques. We evaluated brainstem AD-like pathology using 6E10, AT8, and Alz50 antibodies and unbiased stereology in young and old 3xTgAD mice. Intraneuronal Aβ occurred in the tectum, periaqueductal gray, substantia nigra, red nucleus, tegmentum and mesencephalic V nucleus at all ages. Aβ-positive neuron numbers significantly decreased in the superior colliculus and substantia nigra while AT8-positive superior colliculus, red nucleus, principal sensory V, vestibular nuclei, and tegmental neurons significantly increased between 2 and 12 months. Alz50-positive neuron numbers increased only in the inferior colliculus between these ages. Dual labeling revealed a few Aβ- and tau-positive neurons. Plaques occurred only in the pons of female 3xTgAD mice starting at 9 months. 3xTgAD mice provide a platform to define in vivo mechanisms of Aβ and tau brainstem pathology. © 2009 Elsevier Inc. All rights reserved

A novel approach for long-term oral drug administration in animal research

In the field of pharmacological research, the oral consumption of anastrozole, an aromatase inhibitor, when added to an animal\u27s drinking water is hindered by poor drug palatability and environmental loss of drug solution. To overcome these caveats, we developed a novel approach for the oral delivery of anastrozole mixed in a solid hydration gel matrix that functions as a replacement for water. Heated hydration gel was mixed with anastrozole and distributed into a gel delivery device consisting of a 50. mL plastic conical tube containing four stacked 200μL pipette tips to allow for air pressure induced gel disbursement. Transgenic female 3xTgAD mice were randomized to receive either anastrozole-treated or untreated hydration gel at 3 months of age. Body weights were recorded weekly, and gel consumption was measured every 1-3 days. Six months post treatment mice were killed and serum anastrozole levels were determined using liquid chromatography-mass spectrometry (LC-MS). Anastrozole-treated mice gained significantly more weight despite consuming significantly less hydration gel compared to vehicle treated mice. LC-MS analysis, using a low serum volume (10μL), revealed average anastrozole serum levels of 2.91. ng/mL. Anastrozole-treated ovarian tissue displayed ovarian cysts, massive edema-like stroma, and also lacked corpa lutea compared to control mice. These findings demonstrate that hydration gel delivered using the newly developed oral delivery method is a viable approach for pharmacological research involving compounds with poor palatability, low water solubility, and cost prohibitive compounds where environmental loss needs to be minimized. © 2010 Elsevier B.V