Distinct spatiotemporal accumulation of N-truncated and full-length amyloid-β42 in Alzheimer’s disease

Abstract

Accumulation of amyloid-β peptides is a dominant feature in the pathogenesis of Alzheimer's disease; however, it is not clear how individual amyloid-β species accumulate and affect other neuropathological and clinical features in the disease. Thus, we compared the accumulation of N-terminally truncated amyloid-β and full-length amyloid-β, depending on disease stage as well as brain area, and determined how these amyloid-β species respectively correlate with clinicopathological features of Alzheimer's disease. To this end, the amounts of amyloid-β species and other proteins related to amyloid-β metabolism or Alzheimer's disease were quantified by enzyme-linked immunosorbent assays (ELISA) or theoretically calculated in 12 brain regions, including neocortical, limbic and subcortical areas from Alzheimer's disease cases (n = 19), neurologically normal elderly without amyloid-β accumulation (normal ageing, n = 13), and neurologically normal elderly with cortical amyloid-β accumulation (pathological ageing, n = 15). We observed that N-terminally truncated amyloid-β42 and full-length amyloid-β42 accumulations distributed differently across disease stages and brain areas, while N-terminally truncated amyloid-β40 and full-length amyloid-β40 accumulation showed an almost identical distribution pattern. Cortical N-terminally truncated amyloid-β42 accumulation was increased in Alzheimer's disease compared to pathological ageing, whereas cortical full-length amyloid-β42 accumulation was comparable between Alzheimer's disease and pathological ageing. Moreover, N-terminally truncated amyloid-β42 were more likely to accumulate more in specific brain areas, especially some limbic areas, while full-length amyloid-β42 tended to accumulate more in several neocortical areas, including frontal cortices. Immunoprecipitation followed by mass spectrometry analysis showed that several N-terminally truncated amyloid-β42 species, represented by pyroglutamylated amyloid-β11-42, were enriched in these areas, consistent with ELISA results. N-terminally truncated amyloid-β42 accumulation showed significant regional association with BACE1 and neprilysin, but not PSD95 that regionally associated with full-length amyloid-β42 accumulation. Interestingly, accumulations of tau and to a greater extent apolipoprotein E (apoE, encoded by APOE) were more strongly correlated with N-terminally truncated amyloid-β42 accumulation than those of other amyloid-β species across brain areas and disease stages. Consistently, immunohistochemical staining and in vitro binding assays showed that apoE co-localized and bound more strongly with pyroglutamylated amyloid-β11-x fibrils than full-length amyloid-β fibrils. Retrospective review of clinical records showed that accumulation of N-terminally truncated amyloid-β42 in cortical areas was associated with disease onset, duration and cognitive scores. Collectively, N-terminally truncated amyloid-β42 species have spatiotemporal accumulation patterns distinct from full-length amyloid-β42, likely due to different mechani...

Selective loss of cortical endothelial tight junction proteins during Alzheimer’s disease progression

“…A modified Bielschowsky stain was used to determine the Braak neurofibrillary tangle stages (Braak and Braak, 1991). The cohort and enzyme-linked immunosorbent assay (ELISA) measurements of Alzheimer's disease-related molecules other than tight junction proteins overlapped with that of our previous studies (Shinohara et al, 2013(Shinohara et al, , 2014(Shinohara et al, , 2017.…”

“…Samples were prepared as described previously (Shinohara et al, 2013(Shinohara et al, , 2014(Shinohara et al, , 2017. In brief, grey matter from seven cortical areas (dorsolateral prefrontal, orbitofrontal, inferior temporal, inferior parietal, primary visual cortex, posterior cingulate, entorhinal) and five subcortical areas (amygdala, striatum, thalamus, hypothalamus, cerebellum) was dissected and kept frozen until protein extraction.…”

“…The amounts of total amyloid-b 40 (Abx-40), total amyloidb 42 (Abx-42), full-length amyloid-b 40 (Ab1-40), full-length amyloid-b 42 (Ab1-42), tau, postsynaptic density protein 95 (PSD-95, also known as DLG4), synaptophysin (SYP), and glial fibrillary acidic protein (GFAP) were determined by ELISAs as described previously (Shinohara et al, 2013(Shinohara et al, , 2014(Shinohara et al, , 2017. The amounts of N-terminally truncated amyloid-b 40 (Abt-40) and amyloid-b 42 (Abt-42) were calculated by subtracting values of Ab1-40 and Ab1-42 from Abx-40 and Abx-42 values, respectively (Shinohara et al, 2017). The TBS fraction was used to measure the amounts of cytosolic or secreted proteins, and molecules (GFAP, and PSD-95), while the TX fraction was used to measure the amounts of membrane proteins (i.e.…”

“…Region-specific appearances of Alzheimer's disease pathologies, including amyloid-b accumulation and neurofibrillary tangles, have provided important insights into disease pathogenesis (Klunk et al, 2004;Buckner et al, 2005;Jack et al, 2008;Vlassenko et al, 2010;Wang et al, 2016). Indeed, by analysing biochemical markers in multiple brain regions dissected from post-mortem brains of normal ageing, pathological ageing and Alzheimer's disease, we have found novel evidence regarding pathomechanisms of amyloid-b accumulation and disease development (Shinohara et al, 2013(Shinohara et al, , 2014(Shinohara et al, , 2017. In this study, we quantified the amounts of tight junction proteins, which uniquely constitute the para-cellular barrier in the blood-brain barrier, in 12 brain areas, compared these among three disease groups, and assessed their associations with the Braak neurofibrillary tangle stage, CAA severity, vascular pathology severity, and other Alzheimer's diseaserelated features.…”

Apolipoprotein E Epsilon 4 Genotype, Mild Traumatic Brain Injury, and the Development of Chronic Traumatic Encephalopathy

“…Transgenic mice with APOE-ε4 experience greater excitotoxicity, edema, and ischemia with head trauma [ 19 , 21 , 22 ]. APOE-ε4 has been shown to be a strong genetic risk factor for amyloid pathology (e.g., β-amyloid deposition, subsequent neuroinflammation and microglia activation) in Alzheimer’s disease [ 23 , 24 , 25 , 26 ]; however its association with tauopathies—the typical pathological hallmark of CTE—is less clear. Recent studies show that APOE-ε4 may associate with cerebrospinal fluid (CSF) levels of tau and p-tau [ 23 , 27 , 28 ], as well as possible associations and/or interactions between APOE and tauopathies in the setting of β-amyloid deposition.…”