An Intracellular Amyloid-β/AβPP Epitope Correlates with Neurodegeneration in those Neuronal Populations Early Involved in Alzheimer’s Disease

Abstract

The main histopathological hallmarks of Alzheimer's disease (AD) are the extracellular deposition of neuritic amyloid plaques, composed of amyloid-β (Aβ) peptide, and the intracellular accumulation of neurofibrillary tangles, composed of hyperphosphorylated tau. Both traits are emulated in the 3xTg-AD mouse model. Because the relevance of this model in the bibliography and the main role of Aβ in neuronal impairment, here we have detailed the brain Aβ/AβPP distribution to subsequently quantify cellular density and intracellular burden for specific neuronal populations in the early stages of the disease. 6E10 immunoreactivity was evident in the deep layers of the cerebral cortex, in the pyramidal cell layer of the hippocampus, in the basolateral amygdala nucleus, and in the deep cerebellar nuclei macroneurons; whereas the specific neuronal populations with decreased cellular density were the large pyramidal neurons from the layers V-VI in the cerebral cortex, the pyramidal neurons from the CA2-3 region in the hippocampus, and the large neurons from the basolateral nucleus in the amygdala, apart from the already reported deep cerebellar nuclei. Interestingly, we found a strong correlation between intracellular Aβ/AβPP burden and cellular density in all these populations. In addition, behavioral testing showed the functional consequences of such a neuronal depletion. Concretely, anxious-like behavior is manifested in the corner and open-field tests, as well as cognitive functions shown to be impaired in the novel object recognition test and Morris water maze paradigm. To our knowledge, this is the first deep characterization of the specific neuronal populations affected in the 3xTg-AD mouse model.

Progression of Alzheimer's disease and effect of scFv‐h3D6 immunotherapy in the 3xTg‐AD mouse model: An in vivo longitudinal study using Magnetic Resonance Imaging and Spectroscopy

“…This early volume variation might be related with intracellular Aβ accumulation, which is already described at 2–3‐mo in this model . Moreover, we recently described the existence of a direct relationship between the amount of intracellular Aβ peptide and cell death in several affected neuronal populations at 5‐mo and the mechanism by which scFv‐h3D6 protects these neurons from demise . In this study, the volume results are compatible with histological and biochemical analyses, as 3xTg‐AD mice showed an evident development of Aβ pathology.…”

“…Finally, the brains were completely embedded in paraffin. The brain samples ( N = 4) were serially sectioned in the coronal plane (10‐μm sections) and stained either by immunohistochemistry or by immunofluorescence as previously described . The primary antibodies used were 6E10 Mouse anti‐amyloid‐β (1‐16) (bioLegend®, San Diego, California, USA) and rabbit polyclonal anti‐NeuN (Merck‐Millipore, Billerica, MA, USA), both at 1:100, while the secondary antibodies used were goat anti‐mouse IgG Cy3 conjugated (Chemicon, Merck‐Millipore) and goat anti‐rabbit IgG (H + L) Alexa Fluor 488 (Abcam, Cambridge, UK), both at 1:200, for immunofluorescence, and goat anti‐mouse conjugated to biotin (Sigma, Saint Louis, MO, USA) and mouse extravidin peroxidase conjugate (Sigma), both at 1:50, and DAB solution for immunochemistry.…”

Cognitive Impairment in the 3xTg-AD Mouse Model of Alzheimer’s Disease is Affected by Aβ-ImmunoTherapy and Cognitive Stimulation

“…At 9 months of age, diffuse amyloid plaques in the subiculum of 3xTg-AD and intraneuronal Aβ pathology, mainly in the CA1 of the hippocampus, could be clearly seen ( Figure 7 A). As a reference, only intraneuronal Aβ pathology in the hippocampus was reported at 5 months of age [ 53 ]. In addition, total tau staining was also evident in 9-month-old 3xTg-AD mice.…”

Dihydroartemisinin Ameliorates Learning and Memory in Alzheimer’s Disease Through Promoting Autophagosome-Lysosome Fusion and Autolysosomal Degradation for Aβ Clearance

“…Aβ excessive formation and blocked degradation impel SP deposition in the brain that, subsequently, accelerate the occurrence of overactive microglia, excessive apoptotic neurons and cerebral atrophy (Selkoe and Hardy, 2016;Nixon, 2017). In recent years, it has been found that extracellular Aβ is only the result of its toxic effect on cells, and the accumulation of intracellular Aβ is the fundamental factor leading to the cytotoxic effects (Esquerda-Canals et al, 2017). The degradation of extracellular Aβ is mainly completed by the insulin-degrading enzyme (IDE) and enkephalinase (Yamamoto et al, 2013(Yamamoto et al, , 2014, while the degradation of intracellular Aβ is mainly transported to lysosome through endocytosis or autophagy (Thal, 2015).…”

“…With the development of AD, the clearance of Aβ decreased due to the fusion of APs and lysosomes. The accumulation of APs due to the inhibition of degradation led to the further increase of Aβ production (De Strooper and Karran, 2016;Esquerda-Canals et al, 2017). So it has been reported that autophagy acts as a ''double-edged sword'' in the development of AD (Martinet et al, 2009;Choi et al, 2018;Hamano et al, 2018).…”