Nuclear β-catenin accumulation associates with epithelial morphogenesis in craniopharyngiomas

Activation of the Wnt/wingless signalling cascade is a key mechanism in developmental morphogenesis, whereas aberrant nuclear accumulation of β-catenin in adult tissues seems to be associated with neoplastic transformation and tumour progression. Adamantinomatous craniopharyngiomas carry activating mutations in exon 3 of the β-catenin gene, which results in a distinct pattern of nuclear β-catenin accumulation in up to 95% of respective tumour specimens. To better characterise the impact of nuclear β-catenin aggregation in these neoplasms, we systematically examined epithelial differentiation and cell cycle-associated molecules in accumulating compared to non-accumulating tumour cell clusters using a cohort of 65 adamantinomatous craniopharyngiomas. Monoclonal antibodies directed against cytokeratins 5/6 (CK5/6) were utilised to differentiate squamous from simple epithelium, the latter being identified by immunoreactivity for cytokeratins 8 and 18 (CK8/CK18). Intriguingly, nuclear β-catenin accumulation in whorl-like tumour cell clusters was always associated with a distinct CK8 and CK18 immunoreactivity, whereas surrounding non-accumulating tumour cells showed exclusively squamous differentiation indicated by CK5/6 expression. In addition, a low proliferation activity combined with an increased expression of p21^WAF1/CIP1, a key control protein of the cell cycle, was observed in β-catenin accumulating cells. Our data support an impact of nuclear β-catenin on different cytoarchitectural and epithelial differentiation patterns in adamantinomatous craniopharyngiomas. This work is supported by the Johannes and Frieda Marohn Foundation (to RB and BH).     

Increase expression of α-synuclein in aged human brain associated with neuromelanin accumulation

Although the increased prevalence of Parkinson’s disease (PD) with aging suggests that aging processes predispose dopamine neurons to degeneration, the mechanism involved remains unknown. Dopamine neurons contain significant amounts of neuromelanin, and the amount of neuromelanin increases with aging. In the present study, age-related changes in the number of nigral neurons expressing neuromelanin (NM), α-synuclein, and tyrosine hydroxylase (TH) were stereologically analyzed in the postmortem brains of 28 healthy humans with an age range of 17–84 years. Stereological counting of NM content, α-synuclein content, and TH immunoreactivity revealed significant accumulation of NM and α-synuclein in neurons during the aging process. In cells containing a large amount of NM, α-synuclein-immunoreactive cells in aged individuals outnumbered those of younger individuals. In non-NM cells, the α-synuclein expression profile was similar across age groups. Furthermore, TH-immunoreactive neurons decreased significantly with aging, which was associated with accumulation of NM and α-synuclein. Our results suggest that age related accumulation of NM might induce α-synuclein over-expression and thereby make dopamine neurons more vulnerable to injuries.     

Caspase-cleaved tau accumulation in neurodegenerative diseases associated with tau and α-synuclein pathology

Alzheimers disease (AD), Picks disease (PiD), progressive supranuclear palsy (PSP), corticobasal degeneration (CBD) and dementia with Lewy bodies (DLB) are diseases associated with the accumulation of tau or -synuclein. In AD, -amyloid (A)-associated caspase activation and cleavage of tau at Asp⁴²¹ (Tau) may be an early step in neurofibrillary tangle (NFT) formation. To examine whether Tau accumulates in other diseases not characterized by extracellular A accumulation, we examined PiD, PSP, and CBD cases in comparison to those without extensive tau accumulation including frontotemporal lobar degeneration without Pick bodies (FTLD) and control cases. Additionally, we studied Tau accumulation in DLB cases associated with intracellular -synuclein. Tau was observed in all disease cases except non-PiD FTLD and controls. These results demonstrate that the accumulation of Tau may represent a common pathway associated with abnormal accumulation of intracellular tau or -synuclein and may be relatively less dependent on the extracellular accumulation of A in non-AD dementias.     

Concomitant accumulation of α-synuclein and TDP-43 in a patient with corticobasal degeneration

Pathological changes in corticobasal degeneration (CBD) consist of abnormal deposition of the microtubule-associated protein tau. However, the simultaneous accumulation of different misfolded proteins in the brain can be observed in many neurodegenerative diseases with significantly longer disease durations. We encountered a patient with CBD who survived for an extremely long period (18 years) after the diagnosis. We performed an autopsy to elucidate the effect of the longer survival on the pathology of CBD. We observed abnormal aggregation of trans-activating response region DNA-binding protein of 43 kDa (TDP-43) and α-synuclein, as well as phosphorylated tau, in neurons of broader regions of the brain, beyond the amygdala and other limbic areas. We found that phosphorylated tau, α-synuclein, and TDP-43 partially co-existed in the same cellular aggregates. The triple pathologic changes might be related to the longer survival of the patient compared with the typical clinical course of patients with CBD. Further investigations are required to support the hypothesis that tauopathy, synucleinopathy, and TDP-43 proteinopathy might share common pathogenic mechanisms in terms of cross-seeding of the pathologic proteins.     

Gas1 interferes with AβPP trafficking by facilitating the accumulation of immature AβPP in endoplasmic reticulum-associated raft subdomains

The amyloid-β protein precursor (AβPP) is a type I transmembrane protein that undergoes maturation during trafficking in the secretory pathway. Proper maturation and trafficking of AβPP are necessary prerequisites for AβPP processing to generate amyloid-β (Aβ), the core component of Alzheimer's disease senile plaques. Recently, we reported that the glycosylphosphatidylinositol (GPI)-anchored protein growth arrest-specific 1 (Gas1) binds to and interferes with the maturation and processing of AβPP. Gas1 expression led to a trafficking blockade of AβPP between the endoplasmic reticulum (ER) and the Golgi. GPI-anchored proteins can exit the ER by transiting through raft subdomains acting as specialized sorting platforms. Here, we show that Gas1 co-partitioned and formed a complex with AβPP in raft fractions, wherein Gas1 overexpression triggered immature AβPP accumulation. Pharmacological interference of ER to Golgi transport increased immature AβPP accumulation upon Gas1 expression in these raft fractions, which were found to be positive for the COPII protein complex component Sec31A, a specific marker for ER exit sites. Furthermore, a Gas1 mutant lacking the GPI anchor that could not transit through rafts was still able to form a complex with AβPP but did not lead to immature AβPP accumulation in rafts. Together these data show that Gas1 interfered with AβPP trafficking by interacting with AβPP to facilitate its translocation into specialized ER-associated rafts where immature AβPP accumulated.     

Narcolepsy with cataplexy associated with H1N1 vaccination

IntroductionIt has been suggested that the H1N1 vaccine may be a trigger for the onset of narcolepsy-cataplexy, a rare disease whose autoimmune origin is suspected.ObservationsWe report two patients (a 9-year-old boy and an 18-year-old man) with severe narcolepsy-cataplexy, in whom the illness appeared within 3–4 weeks after H1N1 vaccination. In both cases, symptoms developed unusually abruptly and they presented with severe daytime sleepiness and multiple daily cataplexy attacks. Other similar cases have been recently reported associated with H1N1 vaccine.ConclusionAlthough no formal link can be established, the unusual characteristics of the reported cases and the striking temporal relationship suggests that narcolepsy may be the result of an autoimmune reaction triggered by H1N1 vaccination in susceptible individuals.     

Rate of β-amyloid accumulation varies with baseline amyloid burden: Implications for anti-amyloid drug trials

Introduction

This study examined a longitudinal trajectory of β-amyloid (Aβ) accumulation at the predementia stage of Alzheimer's disease in the context of clinical trials.

Decreased accumulation of subcellular amyloid-β with improved mitochondrial function mediates the neuroprotective effect of huperzine A

A number of recent discoveries indicate that huperzine A, an active herbal medicine employed for the treatment of Alzheimer's disease (AD) in China, can afford neuroprotection on in vitro and in vivo models related to mitochondrial dysfunction. However, it is an intricate and highly debated research topic about whether another pharmacological mechanism is involved in the beneficial profiles of huperzine A, independent of its well-recognized potent acetycholinesterase (AChE) inhibitory effect. As an extension, this study for the first time verified the co-occurrence of the beneficial effects of huperzine A on mitochondrial dysfunction and memory deficits in AβPP/PS1 double transgenic mice, at a time point that AChE was not inhibited. Moreover, using isolated brain cortical mitochondria, we confirmed the ameliorating effect of huperzine A on oligomeric Aβ1-42-induced ATP reduction and mitochondrial swelling, as well as a decrease in the enzymatic activities of respiratory chain complexes, especially complex II-III and complex IV, which may be attributed to the blockage of oligomeric Aβ1-42 from penetrating into mitochondria. These results shed more light on a potential direct target of huperzine A on isolated mitochondria, which may be largely different from its specific inhibition on AChE. This work describes a novel mechanism of neuroprotection by huperzine A and provides important clues for discovering novel therapeutic strategy for AD.     

Abnormal accumulation of autophagic vesicles correlates with axonal and synaptic pathology in young Alzheimer’s mice hippocampus

Dystrophic neurites associated with amyloid plaques precede neuronal death and manifest early in Alzheimer's disease (AD). In this work we have characterized the plaque-associated neuritic pathology in the hippocampus of young (4- to 6-month-old) PS1(M146L)/APP(751SL) mice model, as the initial degenerative process underlying functional disturbance prior to neuronal loss. Neuritic plaques accounted for almost all fibrillar deposits and an axonal origin of the dystrophies was demonstrated. The early induction of autophagy pathology was evidenced by increased protein levels of the autophagosome marker LC3 that was localized in the axonal dystrophies, and by electron microscopic identification of numerous autophagic vesicles filling and causing the axonal swellings. Early neuritic cytoskeletal defects determined by the presence of phosphorylated tau (AT8-positive) and actin-cofilin rods along with decreased levels of kinesin-1 and dynein motor proteins could be responsible for this extensive vesicle accumulation within dystrophic neurites. Although microsomal Aβ oligomers were identified, the presence of A11-immunopositive Aβ plaques also suggested a direct role of plaque-associated Aβ oligomers in defective axonal transport and disease progression. Most importantly, presynaptic terminals morphologically disrupted by abnormal autophagic vesicle buildup were identified ultrastructurally and further supported by synaptosome isolation. Finally, these early abnormalities in axonal and presynaptic structures might represent the morphological substrate of hippocampal dysfunction preceding synaptic and neuronal loss and could significantly contribute to AD pathology in the preclinical stages.     

Pathological methamphetamine exposure triggers the accumulation of neuropathic protein amyloid-β by inhibiting UCHL1

Methamphetamine (METH), a powerful psychoactive drug, causes damage to the nervous system and leads to degenerative changes similar to Alzheimer's disease (AD), however, the molecular mechanism between the toxicity of METH and AD-related symptoms remains poorly understood. In this study, we investigated the effect of METH exposure on the accumulation of amyloid-β by establishing the animal and cell models. The results showed that METH exposure increased amyloid precursor protein (APP) and β-secretase (BACE1), contributed to the accumulation of amyloid-β, and which was alleviated with the pretreatment of BACE1 inhibitor. In addition, METH exposure decreased ubiquitin carboxy-terminal hydrolases L1 (UCHL1) which was related to the degradation of BACE1, and therefore led to the up-regulation of BACE1. In summary, the study could provide a new insight into the molecular mechanisms of METH toxicity and new evidence for the link between METH abuse and AD.     

Brain pericytes ABCA1 expression mediates cholesterol efflux but not cellular amyloid-β peptide accumulation

In brain, excess cholesterol is metabolized into 24S-hydroxycholesterol (24S-OH-chol) and eliminated into the circulation across the blood-brain barrier. 24S-OH-chol is a natural agonist of the nuclear liver X receptors (LXRs) involved in peripheral cholesterol homeostasis. The effects of this oxysterol on the pericytes embedded in the basal lamina of this barrier (close to the brain compartment) have not been previously studied. We used primary cultures of brain pericytes to demonstrate that the latter express LXR nuclear receptors and their target gene ATP-binding cassette, sub-family A, member 1 (ABCA1), known to be one of the major transporters involved in peripheral lipid homeostasis. Treatment with 24S-OH-chol caused an increase in ABCA1 expression that correlated with a reverse cholesterol transfer to apolipoprotein E, apolipoprotein A-I, and high density lipoprotein particles. Inhibition of ABCA1 decreased this efflux. As pericytes are able to internalize the amyloid-β peptides which accumulate in brain of Alzheimer's disease patients, we then investigated the effects of 24S-OH-chol on this process. We found that the cellular accumulation process was not modified by 24S-OH-chol treatment. Overall, our results highlight the importance of the LXR/ABCA1 system in brain pericytes and suggest a new role for these cells in brain cholesterol homeostasis.     

AβPP accumulation and/or intraneuronal amyloid-β accumulation? The 3xTg-AD mouse model revisited

The triple-transgenic Alzheimer's disease (AD) mouse model, 3xTg-AD, played an important role in supporting the intraneuronal amyloid-β (Aβ) hypothesis in AD. However, recent evidence claims that the 3xTg-AD mice accumulate amyloid-β protein precursor (AβPP) instead of Aβ within neurons. In the present report, we re-investigated the 3xTg-AD mouse model and confirmed recent findings of age-dependent AβPP accumulations. In addition, intraneuronal Aβ was detected mainly in the neocortex using conformation-specific as well as antibodies directed against Aβ neo-epitopes. In contrast to previous work, however, only minor levels of intraneuronal Aβ were detected in the CA1 region of the hippocampus in aged 3xTg-AD mice.     

Both NKCC1 and anion exchangers contribute to Cl⁻ accumulation in postnatal forebrain neuronal progenitors

Neuronal progenitors are continuously generated in the postnatal rodent subventricular zone and migrate along the rostral migratory stream to supply interneurons in the olfactory bulb. Nonsynaptic GABAergic signaling affects the postnatal neurogenesis by depolarizing neuronal progenitors, which depends on an elevated intracellular Cl^? concentration. However, the molecular mechanism responsible for Cl^? accumulation in these cells still remains elusive. Using confocal Ca²⁺ imaging, we found that GABA depolarization‐induced Ca²⁺ increase was either abolished by bumetanide, a specific inhibitor of the Na⁺–K⁺–2Cl^? cotransporter, or reduced by partial replacement of extracellular Na⁺ with Li⁺, in the HEPES buffer but not in the CO₂/ buffer. GABA depolarization‐induced Ca²⁺ increase in CO₂/ buffer was abolished by a combination of bumetanide with the anion exchanger inhibitor DIDS or with the carbonic anhydrase inhibitor acetozalimide. Using gramicidin‐perforated patch‐clamp recording, we further confirmed that bumetanide, together with DIDS or acetozalimide, reduced the intracellular chloride concentration in the neuronal progenitors. In addition, with BrdU labeling, we demonstrated that blocking of the Na⁺–K⁺–2Cl^? cotransporter, but not anion exchangers, reduced the proliferation of neuronal progenitors. Our results indicate that both the Na⁺–K⁺–2Cl^? cotransporter and anion exchangers contribute to the elevated intracellular chloride responsible for the depolarizing action of GABA in the postnatal forebrain neuronal progenitors. However, the Na⁺–K⁺–2Cl^? cotransporter displays an additional effect on neuronal progenitor proliferation.     

Dystonic opisthotonus: A “red flag” for neurodegeneration with brain iron accumulation syndromes?

Back arching was reported in one of the very first patients with neurodegeneration with brain iron accumulation syndrome (NBIAs) published in 1936. However, recent reports have mainly focused on the genetic and imaging aspects of these disorders, and the phenotypic characterization of the dystonia has been lost. In evaluating patients with NBIAs in our centers, we have observed that action‐induced dystonic opisthotonus is a common and characteristic feature of NBIAs. Here, we present a case series of patients with NBIAs presenting this feature demonstrated by videos. We suggest that dystonic opisthotonus could be a useful “red flag” for clinicians to suspect NBIAs, and we discuss the differential diagnosis of this feature. This would be particularly useful in identifying patients with NBIAs and no iron accumulation as yet on brain imaging (for example, as in phospholipase A2, group IV (cytosolic, calcium‐independent) [PLA2G6]‐related disorders), and it has management implications. © 2013 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.     

Changes in brain amyloid-β accumulation after donepezil administration

Recent studies using the mouse model of Alzheimer’s disease (AD) have shown that donepezil administration reduces brain amyloid-β (Aβ) accumulation. This study investigated whether donepezil administration can reduce brain Aβ accumulation in human patients with AD. Ten patients with AD underwent two ¹¹C-Pittsburgh Compound B positron emission tomography sessions approximately one year apart to measure brain Aβ accumulation before and after donepezil treatment. Volumes-of-interest were placed on Aβ-preferred regions, and the standardized uptake value ratio (SUVR) was calculated considering the cerebellum as a reference region. Three and seven patients received 10 mg and 5 mg of donepezil, respectively. SUVR was significantly higher in the second than in the first session (P = 0.026). This study showed that one year of donepezil administration does not reduce brain Aβ accumulation in human patients with AD.     

Relative paucity of tau accumulation in the small areas with abundant Aβ42-positive capillary amyloid angiopathy within a given cortical region in the brain of patients with Alzheimer pathology

Cerebral amyloid angiopathy (CAA) is a manifestation of amyloid β-protein (Aβ) accumulation in the elderly as well as in patients with Alzheimer’s disease (AD). Two types of CAA have been noted, based on the type of vasculature in which Aβ is deposited: cerebral capillary amyloid angiopathy (capCAA) and non-capCAA. Non-capCAA is a common form of CAA that consists of Aβ deposited in arteries and arterioles. Recent information on Aβ metabolism in the brain suggests that non-capCAA is associated with Aβ secretion into the cerebrospinal fluid via the perivascular space, whereas capCAA is associated with Aβ removal to blood plasma via the capillary endothelium. Aβ40, a major and relatively soluble Aβ isoform, is deposited predominantly in non-capCAA, and Aβ42, which is insoluble and associated more closely than Aβ40 with AD, is deposited predominantly in capCAA. Studying small areas of microscopic size within a given cortical region, we found an inverse association of capCAA and senile plaques. We also found a relative paucity of tau pathology in the small areas with abundant capCAA compared with the small areas with abundant senile plaques within a cortical region with the same cytoarchitecture. We suppose that both capCAA and senile plaques indicate high Aβ42 in the neuropil but that only Aβ42 in the form of insoluble deposits in senile plaques promotes tau abnormality.