Etsuro Matsubara

Dimeric Amyloid β Protein Rapidly Accumulates in Lipid Rafts followed by Apolipoprotein E and Phosphorylated Tau Accumulation in the Tg2576 Mouse Model of Alzheimer's Disease

To investigate lipid rafts as a site where amyloid β protein (Aβ) oligomers might accumulate and cause toxicity in Alzheimers disease (AD), we analyzed Aβ in the Tg2576 transgenic mouse model of AD. Aβ was highly concentrated in lipid rafts, which comprise a small fraction of brain volume but contain 27% of brain Aβ42 and 24% of Aβ40 in young mice. In the Tg2576 model, memory impairment begins at 6 months before amyloid plaques are visible. Here we show that Aβ dimers appear in lipid rafts at 6 months and that raft Aβ, which is primarily dimeric, rapidly accumulates reaching levels >500× those in young mice by 24–28 months. A similar large accumulation of dimeric Aβ was observed in lipid rafts from AD brain. In contrast to extracellular amyloid fibrils, which are SDS-insoluble, virtually all Aβ in lipid rafts is SDS soluble. Coupled with recent studies showing that synthetic and naturally occurring Aβ oligomers can inhibit hippocampal long-term potentiation, the in vivo age-dependent accumulation of SDS-soluble Aβ dimers in lipid rafts at the time when memory impairment begins in Tg2576 mice provides strong evidence linking Aβ oligomers to memory impairment. After dimeric Aβ began to accumulate in lipid rafts of the Tg2576 brain, apolipoprotein E (ApoE) and then phosphorylated tau accumulated. A similar increase in ApoE and a large increase in phosphorylated tau was observed in lipid rafts from AD brain. These findings suggest that lipid rafts may be an important site for interaction between dimeric Aβ, ApoE, and tau.

Mild hypercholesterolemia is an early risk factor for the development of Alzheimer amyloid pathology.

Background: Epidemiologic and experimental data suggest that cholesterol may play a role in the pathogenesis of AD. Modulation of cholesterolemia in transgenic animal models of AD strongly alters amyloid pathology. Objective: To determine whether a relationship exists between amyloid deposition and total cholesterolemia (TC) in the human brain. Methods: The authors reviewed autopsy cases of patients older than 40 years and correlated cholesterolemia and presence or absence of amyloid deposition (amyloid positive vs amyloid negative subjects) and cholesterolemia and amyloid load. Amyloid load in human brains was measured by immunohistochemistry and image analysis. To remove the effect of apoE isoforms on cholesterol levels, cases were genotyped and duplicate analyses were performed on apoE3/3 subjects. Results: Cholesterolemia correlates with presence of amyloid deposition in the youngest subjects (40 to 55 years) with early amyloid deposition (diffuse type of senile plaques) (p = 0.000 for all apoE isoforms; p = 0.009 for apoE3/3 subjects). In this group, increases in cholesterolemia from 181 to 200 almost tripled the odds for developing amyloid, independent of apoE isoform. A logistic regression model showed consistent results (McFadden ρ2 = 0.445). The difference in mean TC between subjects with and without amyloid disappeared as the age of the sample increased (>55 years: p = 0.491), possibly reflecting the effect of cardiovascular deaths among other possibilities. TC and amyloid load were not linearly correlated, indicating that there are additional factors involved in amyloid accumulation. Conclusions: Serum hypercholesterolemia may be an early risk factor for the development of AD amyloid pathology.

Melatonin increases survival and inhibits oxidative and amyloid pathology in a transgenic model of Alzheimer's disease

Increased levels of a 40–42 amino‐acid peptide called the amyloid β protein (Aβ) and evidence of oxidative damage are early neuropathological markers of Alzheimers disease (AD). Previous investigations have demonstrated that melatonin is decreased during the aging process and that patients with AD have more profound reductions of this hormone. It has also been recently shown that melatonin protects neuronal cells from Aβ‐mediated oxidative damage and inhibits the formation of amyloid fibrils in vitro. However, a direct relationship between melatonin and the biochemical pathology of AD had not been demonstrated. We used a transgenic mouse model of Alzheimers amyloidosis and monitored over time the effects of administering melatonin on brain levels of Aβ, abnormal protein nitration, and survival of the mice. We report here that administration of melatonin partially inhibited the expected time‐dependent elevation of β‐amyloid, reduced abnormal nitration of proteins, and increased survival in the treated transgenic mice. These findings may bear relevance to the pathogenesis and therapy of AD.

Apolipoprotein J (clusterin) and Alzheimer's disease.

Apolipoprotein J (clusterin) is a ubiquitous multifunctional glycoprotein capable of interacting with a broad spectrum of molecules. In pathological conditions, it is an amyloid associated protein, co‐localizing with fibrillar deposits in systemic and localized amyloid disorders. In Alzheimers disease, the most frequent form of amyloidosis in humans and the major cause of dementia in the elderly, apoJ is present in amyloid plaques and cerebrovascular deposits but is rarely seen in NFT‐containing neurons. ApoJ expression is up‐regulated in a wide variety of insults and may represent a defense response against local damage to neurons. Four different mechanisms of action could be postulated to explain the role of apoJ as a neuroprotectant during cellular stress: (1) function as an anti‐apoptotic signal, (2) protection against oxidative stress, (3) inhibition of the membrane attack complex of complement proteins locally activated as a result of inflammation, and (4) binding to hydrophobic regions of partially unfolded, stressed proteins, and therefore avoiding aggregation in a chaperone‐like manner. This review focuses on the association of apoJ in biological fluids with Alzheimers soluble Aβ. This interaction prevents Aβ aggregation and fibrillization and modulates its blood‐brain barrier transport at the cerebrovascular endothelium. Microsc. Res. Tech. 50:305–315, 2000.

Combination assay of CSF Tau, Aβ1-40 and Aβ1-42(43) as a biochemical marker of Alzheimer's disease

Cerebrospinal fluid samples from a total of 157 subjects consisting of 55 patients with sporadic Alzheimers disease (AD), 34 normal controls, 23 patients with non-AD dementia, and 45 with other neurological diseases were examined by ELISA of tau, Aβ1-40, and Aβ1-42(43). The AD group had a significantly higher level of tau than the normal control group (P<0.001), and the diagnostic sensitivity was 31% and specificity was 94%. CSF Aβ1-40 levels did not show any significant differences. Although the level of Aβ1-42(43) was decreased significantly in the AD group compared to the control group (P<0.005), the overlap of Aβ1-42(43) levels among all groups meant that none of the AD samples exceeded the cut-off value, the mean 2SD of normal control subjects. Reduction of Aβ1-42(43) levels in AD resulted in a significant increase in the ratio of Aβ1-40 to Aβ1-42(43) (Aβ ratio) as an improved marker. The diagnostic sensitivity and specificity of Aβ ratio were 51% and 82% respectively. The three indexes, using the tau level and Aβ ratio (tau or Aβ ratio, deviation score and tau×Aβ ratio), showed better sensitivity (58%, 67%, 69%) and specificity (82%, 86%, 88%) than previously reported methods. Combination assay for CSF tau, Aβ1-40 and Aβ1-42(43) in CSF is a biological marker of AD and may be useful to biochemically monitor subjects under treatment.

Amyloid β protein 42(43) in cerebrospinal fluid of patients with Alzheimer's disease

To investigate the pathomechanism of amyloid β protein (Aβ) deposition in brains with Alzheimers disease (AD), cerebrospinal fluid (CSF) levels of Aβ species (CSF-Aβ) with different carboxy termini, i.e. AβX-40 and AβX-42(43) as well as Aβ1-40 and Aβ1-42(43), were measured in patients with AD and age-matched controls without dementia (CTR) using sandwich enzyme-linked immunosorbent assays (ELISAs). The present study revealed that both CSF-AβX-42(43) and Aβ1-42(43) levels were significantly lower in the AD patients (P<0.005) than in the CTR group, whereas neither CSF-AβX-40 nor CSF-Aβ1-40 levels showed any differences between the two groups. In addition, although there was no difference between the ratios of AβX-40 to Aβ1-40 in the AD and CTR groups, the ratios of AβX-42(43) to Aβ1-42(43) were increased in the AD group compared with those in the CTR group (P<0.05). Therefore, it can be assumed that amino the ratios of terminal truncations and/or modifications of CSF-Aβ42(43) with carboxy termini ending at residue 42(43) were more increased in the AD group than in the CTR group. Increased adsorption of Aβ42(43) to Aβ deposition in AD brains, decreased secretion of Aβ42(43) to CSF and/or increased clearance of Aβ42(43) from CSF might explain the diminished levels of Aβ42(43) in the CSF of AD patients. In addition, CSF-Aβ42(43) could reflect increased amino terminal truncations and/or modifications of Aβ42(43) in AD brains.

Ubiquitin-positive intraneuronal inclusions in the extramotor cortices of presenile dementia patients with motor neuron disease

SummaryUbiquitin-positive intraneuronal inclusions were found in the extramotor cortices of ten presenile dementia patients with motor neuron disease. There were inclusions in the hippocampal granular cells and in the small neurons of the superficial layers of the temporal and frontal cortices. Bunina bodies were present in the anterior horn cells in all cases. These results suggest that ubiquitin-related cytoskeletal abnormalities are common in cerebral non-motor small neurons in these patients.

Tau in cerebrospinal fluids: establishment of the sandwich ELISA with antibody specific to the repeat sequence in tau

Clinical diagnosis for Alzheimers disease (AD) is provided by the criteria of DSMIV and clinical progress in addition to imaging analysis with MRI after negative screening. The final exclusive diagnosis is confirmed by the neuropathological findings of neurofibrillary tangles and senile plaques in autopsy brains. We developed a new ELISA system to measure the amount of tau in cerebrospinal fluids (CSF) using phosphorylation-independent and sequence-specific antibodies. The present ELISA was sensitive enough to detect tau in CSF of normal subjects. The amount of tau was significantly elevated in CSF of AD subjects compared with those of normal subjects and subjects with dementia of cerebrovascular disease, suggesting that tau in CSF reflects the massive and continuous neuronal cell death in the AD brain. In conclusion, we established an ELISA system which enabled us to detect tau in CSF and demonstrated that tau was significantly and specifically elevated in CSF of AD subjects. This assay system can provide us with a potent diagnostic tool for clinical AD.

Pael-R is accumulated in Lewy bodies of Parkinson's disease.

We examined the distribution of Pael‐R, a newly identified substrate for Parkin, in Parkinsons disease (PD) and multiple system atrophy (MSA). Pael‐R, Parkin, α‐synuclein, and ubiquitin accumulated in Lewy bodies (LBs) and neurites. Pael‐R was localized in the core of LBs. Parkin and α‐synuclein accumulated in the halo, neuronal cell bodies, and processes. These findings potentially suggest the involvement of Pael‐R in LB formation, and protection role of Parkin in Pael‐R‐mediated neurotoxicity in PD. The absence of Pael‐R and Parkin in glial cytoplasmic inclusions (GCIs) in MSA implies a distinct pathway involved in the formation of LBs and GCIs. Ann Neurol 2004

Aβ amyloidosis induces the initial stage of tau accumulation in APPSW mice

Abstract To clarify how Aβ deposits induce secondary tauopathy, the presence of phosphorylated tau, glycogen synthase kinase 3α (GSK3α), GSK3β, cyclin-dependent kinase 5 (CDK5), mitogen-activated protein kinase (MAPK) and fyn were examined in the Tg2576 brain showing substantial brain Aβ amyloidosis and behavioral abnormalities. Phosphorylated tau at Ser199, Thr231/Ser235, Ser396 and Ser413 accumulated in the dystrophic neurites of senile plaques. The major kinase for tau phosphorylation was GSK3β. Smaller contributions of GSK3α, CDK5 and MAPK were suggested. Thus, brain Aβ amyloidosis has a potential role in the induction of tauopathy leading to the mental disturbances of Alzheimers disease.