Ultrastructural neuronal pathology in transgenic mice expressing mutant (P301L) human tau

Transgenic mice expressing mutant (P301L) human tau develop neurofibrillary tangles, amyotrophy and progressive motor disturbance. We present ultrastructural features of neuronal degeneration in this model that suggests involvement of both neurofibrillary and autophagic processes in neurodegeneration. Neurons undergoing neurofibrillary degeneration contain tau-immunoreactive, 15-20 nm-wide straight or wavy filaments with no periodic twists. Tau filaments were found in two types of affected neurons. One type resembled neurons with neurofibrillary tangles (NFT) that were filled with numerous filaments that displaced sparse cytoplasmic organelles to the periphery. Microtubules were almost completely absent. The nucleus remained centrally located, but showed lobulations due to deep infoldings. The other type resembled ballooned neurons seen in some human tauopathies. The nucleus was peripherally placed, but normal appearing. The cytoplasmic organelles were dispersed throughout the swollen perikarya, the Golgi complex was fragmented and duplicated, while mitochondria and other organelles appeared normal. Tau filaments similar to those in NFT were sparse and not tightly packed. Microtubules were also sparse. Many autophagic vacuoles were present in these cells. Heterogeneous appearing axonal swellings resembling spheroids in human tauopathies were present in gray and white matter. Unlike normal appearing axons, axonal spheroids were filled with tau-immunoreactive filaments and autophagic vacuoles, in addition to normal appearing neurofilaments and microtubules. These P301L transgenic mice exhibit many features common to human tauopathies, making them a valuable model to study the pathogenesis of these uncommon disorders.

Transgenic mice overexpressing amyloid beta protein are an incomplete model of Alzheimer disease

We compared lesions in elderly transgenic (tg) mice carrying the Swedish double mutation KM670/671NL with lesions in Alzheimer disease (AD) by histochemical and immunohistochemical techniques. Highly similar staining for beta-amyloid protein (Abeta) was observed in AD and the mouse models. The abundant amyloid deposits in tg mice were in a consolidated state as revealed by strong Congo red birefringence. In both tg mice and AD, amyloid deposits were ApoE-positive and were surrounded by activated astrocytes. However, Bielschowsky silver staining and immunostaining with tau antibodies revealed no neurofibrillary tangles (NFTs) in the mice as opposed to abundant NFTs in AD. The microglial pattern was also distinctly different. Tg mice had only weakly activated microglia, which expressed low levels of the complement receptor CD11b. They were gathered around the periphery of the deposits. In contrast, AD lesions had strongly activated microglia, which expressed high levels of CD11b. They were associated with the plaque core. Immunostaining for complement proteins was weak in tg mice but very strong in AD deposits. We conclude that the weak inflammatory response and absence of NFTs indicate that tg mice are only a limited model of AD. Therapeutic strategies for the treatment of AD based on tg mouse models that overexpress Abeta may be limited in their application.

Quinones facilitate the self-assembly of the phosphorylated tubulin binding region of tau into fibrillar polymers

The fragment of tau containing the first and third tubulin-binding motifs, involved in self-assembly of tau, was phosphorylated by protein kinase A (PKA). In the presence of hydroxynonenal (HNE) or in the presence of quinones such as juglone, 2,3-dimethoxy-5-methyl-1,4-benzoquinone (coenzyme Q(0) or DMM), or menadione, the polymerization of this phosphorylated tau fragment is catalyzed, whereas polymerization of the unmodified fragment takes place in a lesser extent. The quinones coenzyme Q(0) and menadione are found in every cell, including neural cells, and may interact with tau protein to facilitate its assembly into filamentous structures. These tau filaments, assembled in the presence of quinones, have a fibrillar morphology very similar to that of paired helical filaments present in the brains of patients with Alzheimer's disease.

Cholinergic nucleus basalis tauopathy emerges early in the aging-MCI-AD continuum

The cholinergic denervation in Alzheimer's disease (AD) provides the rationale for treatments with anticholinesterases. The presence of this cholinergic lesion is solidly established in advanced AD. Whether it also exists in early disease remains unsettled. This question was addressed with thioflavin-S histofluorescence to identify neurofibrillary tangles (NFT) and two tau antibodies (AT8, Alz-50) to identify pre-tangle cytopathology in the nucleus basalis, the source of cortical cholinergic innervation. Methods for the concurrent visualization of tauopathy and choline acetyltransferase were used to determine if the cytopathology was selectively located within cholinergic neurons. Five elderly index cases who had died at the stage of mild cognitive impairment (MCI) or early AD were identified by longitudinal neuropsychological and behavioral assessments. They were compared to 7 age-matched cognitively normal subjects. NFT and AT8 (or Alz-50) immunostaining in cholinergic nucleus basalis neurons existed even in the cognitively normal subjects. The percentage of tauopathy-containing nucleus basalis neurons was greater in the cognitively impaired and showed a significant correlation with memory scores obtained 1-18 months prior to death. These results show that cytopathology in cortical cholinergic pathways is a very early event in the course of the continuum that leads from advanced age to MCI and AD.

Ballooned neurones in the limbic lobe are associated with Alzheimer type pathology and lack diagnostic specificity

Ballooned neurones (BNs) are one of the pathological hallmarks of several neurodegenerative diseases, including Pick's disease, corticobasal degeneration and argyrophilic grain disease (AGD). They have also been described in Alzheimer disease (AD), but the frequency of BNs in AD has not been systematically addressed. In the present study, immunohistochemistry for alphaB-crystallin was used as a sensitive method to detect BNs to determine the frequency of BNs in the limbic lobe in AD. At least a few BNs were detected in the limbic lobe of virtually all AD cases, and their density correlated with Braak stage, as well as the density of neurofibrillary tangles and senile plaques in the limbic lobe. The density of BN tended to be greater in AD cases with concurrent AGD than in pure AD. Given the high prevalence of AD in brain banks for neurodegenerative disease and the frequent presence of BNs in these areas with alphaB-crystallin immunohistochemistry, the present findings further indicate that BNs confined to the limbic lobe lack specificity in diagnostic neuropathology.

The retinoic acid and brain-derived neurotrophic factor differentiated SH-SY5Y cell line as a model for Alzheimer’s disease-like tau phosphorylation

The paired helical filaments of highly phosphorylated tau protein are the main components of neurofibrillary tangles (NFT) in Alzheimer's disease (AD). Protein kinases including glycogen synthase kinase 3 beta (GSK3beta), cyclin-dependent kinase 5 (Cdk5), and c-Jun N-terminal kinase (JNK) have been implicated in NFT formation making the use of selective kinase inhibitors an attractive treatment possibility in AD. When sequentially treated with retinoic acid (RA) and brain-derived neurotrophic factor (BDNF), the human neuroblastoma SH-SY5Y differentiates to neuron-like cells. We found that coincident with morphologically evident neurite outgrowth, both the content and phosphorylation state of tau increased in RA-BDNF differentiated SH-SY5Y cells. Tau phosphorylation increased at all the examined sites ser-199, ser-202, thr-205, ser-396, and ser-404, all of which are hyperphosphorylated in AD brain. We also investigated whether GSK3beta, Cdk5 or JNK was involved in tau phosphorylation in the differentiated SH-SY5Y cells. We found that GSK3beta contributed most and that Cdk5 made a minor contribution. JNK was not involved in tau phosphorylation in this system. The GSK3beta-inhibitor, lithium, inhibited tau phosphorylation in a concentration-dependent manner and with good reproducibility, which enables ranking of substances in this cell model. RA-BDNF differentiated SH-SY5Y cells could serve as a suitable model for studying the mechanisms of tau phosphorylation and for screening potential GSK3beta inhibitors.

Fibrillization of alpha-synuclein and tau in familial Parkinson's disease caused by the A53T alpha-synuclein mutation

Mutations in the alpha-synuclein (alpha-syn) gene are responsible for a rare familial parkinsonism syndrome, a finding that has led to extensive characterization of altered alpha-syn structure in sporadic Parkinson's disease (PD) and other neurodegenerative disorders. We report here the immunohistochemical, biochemical and ultrastructural characterization of alpha-syn neuropathology in a case of familial PD with the A53T alpha-syn gene mutation. Insoluble filamentous alpha-syn lesions were detected in almost all brain regions examined and as in sporadic PD, we observed the accumulation of insoluble nitrated alpha-syn in this familial disorder. Significant accumulations of filamentous insoluble tau protein also were detected in some brain regions of this patient, suggesting a role for A53T mutant alpha-syn in tau fibrillization. Indeed, in vitro studies of tau and alpha-syn fibrillization showed that the A53T mutation accelerated alpha-syn fibril formation, initiated tau assembly into filaments and synergistically enhanced fibrillization of both tau and alpha-syn. Our data implicate fibrillization of alpha-syn and tau in the pathogenesis of PD, and suggest that distinct amyloidogenic proteins may cross-seed each other in neurodegenerative diseases.

Induction of Dickkopf-1, a negative modulator of the Wnt pathway, is associated with neuronal degeneration in Alzheimer's brain

We used primary cultures of cortical neurons to examine the relationship between beta-amyloid toxicity and hyperphosphorylation of the tau protein, the biochemical substrate for neurofibrillary tangles of Alzheimer's brain. Exposure of the cultures to beta-amyloid peptide (betaAP) induced the expression of the secreted glycoprotein Dickkopf-1 (DKK1). DKK1 negatively modulates the canonical Wnt signaling pathway, thus activating the tau-phosphorylating enzyme glycogen synthase kinase-3beta. DKK1 was induced at late times after betaAP exposure, and its expression was dependent on the tumor suppressing protein p53. The antisense induced knock-down of DKK1 attenuated neuronal apoptosis but nearly abolished the increase in tau phosphorylation in betaAP-treated neurons. DKK1 was also expressed by degenerating neurons in the brain from Alzheimer's patients, where it colocalized with neurofibrillary tangles and distrophic neurites. We conclude that induction of DKK1 contributes to the pathological cascade triggered by beta-amyloid and is critically involved in the process of tau phosphorylation.

Evidence for an intermediate in tau filament formation

Alzheimer's disease is defined in part by the intraneuronal accumulation of filaments comprised of the microtubule-associated protein tau. In vitro, fibrillization of full-length, unphosphorylated recombinant tau can be induced under near-physiological conditions by treatment with various agents, including anionic surfactants. Here we examine the pathway through which anionic surfactants promote tau fibrillization using a combination of electron microscopy and fluorescence spectroscopy. Protein and surfactant first interacted in solution to form micelles, which then provided negatively charged surfaces that accumulated tau aggregates. Surface aggregation of tau protein was followed by the time-dependent appearance of a thioflavin S reactive intermediate that accumulated over a period of hours. The intermediate was unstable in the absence of anionic surfaces, suggesting it was not filamentous. Fibrillization proceeded after intermediate formation with classic nucleation-dependent kinetics, consisting of lag phase followed by the exponential increase in filament lengths, followed by an equilibrium phase reached in approximately 24 h. The pathway did not require protein insertion into the micelle hydrophobic core or conformational change arising from mixed micelle formation, because anionic microspheres constructed from impermeable polystyrene were capable of qualitatively reproducing all aspects of the fibrillization reaction. It is proposed that the progression from amorphous aggregation through intermediate formation and fibrillization may underlie the activity of other inducers such as hyperphosphorylation and may be operative in vivo.

Immunohistochemical study of tau accumulation in early stages of Alzheimer-type neurofibrillary lesions

Accumulation of abnormally phosphorylated tau results in the formation of neurofibrillary tangles (NFTs) in the neuronal cell soma and neuropil threads (NTs) in the cell processes. In the present study, we used immunohistochemistry to investigate serially cut thick tissue sections from the brains of patients with Alzheimer's disease (AD) and non-demented elderly subjects. In the early stages of neurofibrillary pathology, clusters of NTs occurred occasionally in the cerebral cortex. Each NTs cluster, the entire extent of which was observed in the serial sections, corresponded to a dendritic tree that was arborized from a tau-positive neuron. Adult human brain contains six tau isoforms with three having three carboxyl-terminal tandem repeat sequences that are encoded by exon 10 (3R-tau) and the other three having four repeat sequences (4R-tau). Three isoform patterns, 3R-tau(+)/4R-tau(-), 3R-tau(-)/4R-tau(+) and 3R-tau(+)/4R-tau(+), were seen in NFTs in early stage AD lesions. In an individual neuron, the isoform pattern was consistent between the NFTs in the cell soma and the NTs in the cell processes. The results of this study indicate that, in early stages of AD and age-associated neurofibrillary changes, tau accumulates simultaneously in the cell soma and cell processes of affected neurons. The process of AD and age-associated tau pathology is not tau-isoform-specific, but the ratio of 3R-tau and 4R-tau isoforms involved in the neurofibrillary changes varies and is specific to individual neurons.

Histochemical accumulation of oxidative damage products is associated with Alzheimer-like pathology in the canine

An important lesion in Alzheimer's disease (AD) patient brains is the neurofibrillary tangle (NFT). Hyperphosphorylated tau is its major component. In a former paper we described some NFT in the canine brain. During aging, moreover, advanced glycation end products (AGE) might accumulate. Glycated tau induces lipid peroxidation in vivo and tau and AGE antigens have been mentioned to co-localize in NFT. This indicates that AGE may play an important role in Alzheimer disease (AD) by oxidation of tau. The aim of the present study was to investigate amyloid, neurofibrillary tangles, Abeta precursor protein, Abeta, tau, ubiquitin, advanced glycation end products, 4-hyroxynonenal protein and lipofuscin in a series of dogs of varying ages. The results showed a significant positive correlation between age and amyloid quantity (Congo red staining), HNE staining and lipofuscin (LF), and between amyloid quantity and HNE staining and LF. Staining for AbetaPP seemed to have a tendency to increase with age, whereas staining for tau, ubiquitin and AGE each only gave limited positive results in a proportion of the older dogs. Preliminary studies including loss of cognitive capabilities in the older dogs and chemical measurement of lipofuscin-like pigment (LFP) accumulation in brain extracts revealed an increase with old age and dementia. The Congo red, HNE and LF results suggest that deposition of amyloid with aging might be associated with formation of end products of lipid peroxidation. The finding of the limited positive signals for tau, ubiquitin and AGE in some old cases might indicate that the spontaneous brain pathology of the aged dog reveals similarities to early stages observed in AD in humans especially those with Down syndrome.

N epsilon-carboxymethyllysine in brain aging, diabetes mellitus, and Alzheimer's disease

Oxidative stress has been implicated in the pathophysiology of Alzheimer's disease (AD) and diabetes mellitus (DM). N epsilon-carboxymethyllysine (CML) is an advanced glycation end product (AGE) recently found to be associated with oxidative stress mechanisms. Using immunocytochemical methods we examined the distribution of CML in brain tissue from AD and DM subjects and aging controls. CML reactivity was present in the cytoplasm of neurons, but there were marked differences in the intensity of expression, number of cells, and topographical distribution. CML expression was higher in hippocampus than in frontal and temporal cortex. In the hippocampus, neuronal and, to an extent, glial expression was more marked in CA3 and CA4 than in CA1 and CA2. In AD, CML was found to be coexpressed with tau protein, showing the similar neurofibrillary tangle shape, as well as in neuritic plaques but not in the core of amyloid plaques. We noted an increasing degree of CML expression such that the highest reactivity was evident in those with both AD and DM, followed by AD, DM, and aging controls. There was an inverse relationship between Braak staging and topography of CML expression. Although DM cases did not show Abeta deposition or neurofibrillary tangles, these findings suggest increased CML expression is not limited to AD. Nonetheless, high CML expression in AD with coexistent DM suggests there are additive effects compared with AD alone. It is plausible that the microangiopathy also associated with DM could worsen AD pathogenesis.

Regional analysis of differently phosphorylated tau proteins in brains from patients with Alzheimer's disease

Neurofibrillary tangles (NFT) in Alzheimer's disease (AD) are composed of abnormally phosphorylated tau proteins. Many phosphorylation sites have been reported in the AD brain, and NFT distribution was now roughly classified into 3 stages by Braak stage; this classification is based on pathological studies using the specific silver impregnation technique. The aim of our study was to examine the regional distribution of differently phosphorylated tau proteins with 5 site-specific monoclonal antibodies against the tau proteins, AT8, AT180, HT7, Tau2 and Tau5. We then compared our findings with those obtained from silver-stained NFT in an attempt to clarify the relationship between abnormal phosphorylation sites of the tau protein and NFT development. AT180 and AT8 labeled the highest and Tau2 the lowest density of NFT in any regions, while Tau5 and HT7 showed inconsistent distribution. In the limbic cortex, cornu ammonis, entorhinal cortex and cingulate cortex, silver-stained NFT density significantly correlated with density of NFT labeled with the 5 anti-tau antibodies, but cerebral isocortices showed heterogenous patterns of tau-positive NFT. Quantification of tau-positive regional NFT density showed that the AD-associated phosphorylation process progresses from the C-terminal to the N-terminal of the amino acid sequence, and correlation of Gallyas-stained NFT density with tau-labeled NFT density was more significant in the limbic cortices than the cerebral isocortices, which implies that stereotypical phosphorylation occurs in the limbic structures.

Imaging β-Amyloid Plaques and Neurofibrillary Tangles in the Aging Human Brain

The development of radioligands to image beta-amyloid (A beta) plaques and neurofibrillary tangles (NFTs) in vivo in the aging human brain is an important and active area of radiopharmaceutical design. When used in combination with positron emission tomography (Pet) or single photon emission computed tomography (spect), amyloid-imaging tracers could facilitate the evaluation of the efficacy of anti-amyloid therapies currently under intense development by many major pharmaceutical companies throughout the world. Amyloid-imaging agents could also serve as surrogate markers in early diagnosis and neuropathogenesis studies of Alzheimer's disease and other aging-related neurodegenerative disorders. In this review article, the design and biological evaluation of amyloid-imaging agents are discussed. The structures of these agents vary from large proteins and peptides such as radiolabeled A beta peptides and monoclonal antibodies to small molecules derived from Congo red, Chrysamine-G, thioflavin-T, and Acridine Orange. In vitro studies indicate that amyloid plaques contain multiple binding sites that can accommodate structurally diverse compounds, providing flexibility for radiopharmaceutical design of amyloid imaging agents. Compared to large biomolecules, small molecule radiotracers are often readily accessible through chemical synthesis and can display superior brain permeability. Several small molecule amyloid-imaging radioligands display high binding affinities to A beta and sufficient brain penetration for imaging studies. Recent studies demonstrate the feasibility of imaging amyloid plaques in vivo in human subjects with PET. Imaging NFTs, separately or in concert with A beta plaques, is not as far advanced as imaging A beta plaques and remains to be fully characterized and demonstrated.

Cerebral amyloid angiopathy plays a direct role in the pathogenesis of Alzheimer’s disease

For the purposes of this debate here we argue the case that cerebral amyloid angiopathy (CAA) has a direct role in the pathogenesis of Alzheimer's disease (AD). Firstly, there is a very close relationship between CAA and AD and they share genetic risk factors. Secondly, we propose a specific mechanism which puts age-related cerebrovascular degeneration at a crucial point in the pathogenesis of AD as follows. Amyloid beta-protein (Abeta) is normally eliminated from the brain along with extracellular fluid by bulk flow along the perivascular pathway. Age-related fibrosis of cerebral cortical and meningeal arteries leads to impaired drainage of Abeta along the perivascular pathway and, together with the production of Abeta by smooth muscle cells and perivascular cells, is responsible for accumulation of Abeta as CAA. Reduced elimination leads to increased concentration of soluble Abeta in the extracellular fluid of the brain parenchyma. Increased concentration of soluble Abeta leads to the formation of insoluble Abeta plaques, other features of AD pathology, and dementia.

Microglial tau undergoes phosphorylation-independent modification after ischemia

Tau2 is a phosphorylation-independent antibody that immunolabels neurofibrillary tangles (NFTs) of Alzheimer type and microglia around ischemic foci on formalin-fixed, paraffin-embedded sections. We found that copresence of polyethyleneglycol-p-isooctylphenyl ether (Triton X-100; TX) with tau2 abolished its immunoreactivity (IR) in these microglia but not its IR on NFTs. Tau2-immunoreactive bands, exclusively retrieved in Tris-soluble fraction of brain homogenates from ischemic foci, normal human and bovine brains, were of similar electrophoretic mobility, indicating that tau2 IR in these microglia is unrelated to hyperphosphorylation of tau. These tau2-immunoreactive bands except those from bovine brain were abolished in the copresence of TX. This was not due to washing out of tau, because similar immunoreactive bands were detectable with another antitau antibody even under a higher concentration of TX and because washing after TX exposure restored similar tau2 IR both on immunohistochemistry and immunoblot. These findings are explained if tau, modified after ischemia, undergoes a reversible conformational change on TX exposure. Because conformation at Ser101 of bovine tau is crucial for its affinity to tau2, this Ser-like conformation mimicked by its human counterpart Pro may represent pathological modification of tau shared by microglia around ischemic foci and NFTs. Relative resistance of tau2 epitope in NFTs to TX exposure suggests that tau woven into NFTs confers additional stability to this pathological modification on tau2 epitope. Susceptibility of tau2 epitope to TX, seen in these microglia, is shared with glial cytoplasmic inclusions and will show its conformational state to be different from that in NFTs.

Neurofibrillary tangles mediate the association of amyloid load with clinical Alzheimer disease and level of cognitive function

OBJECTIVE

To test the hypothesis that the association of amyloid load with clinical Alzheimer disease (AD) and cognitive impairment is mediated through neurofibrillary tangles.

DESIGN

Longitudinal clinicopathologic cohort study.

PARTICIPANTS AND SETTING

Forty-four individuals with clinically diagnosed AD and 53 without dementia who participated in the Religious Orders Study underwent a uniform structured clinical evaluation for AD and cognitive testing about 8 months prior to death, and brain autopsy at death.

METHODS

The percent area occupied by amyloid-beta and the density of neurofibrillary tangles were quantified from 6 brain regions and averaged to yield summary measures of amyloid load and neurofibrillary tangles. Multivariate regression analyses were used to simultaneously examine the effects of amyloid load and neurofibrillary tangles on clinically diagnosed AD and level of cognition.

MAIN OUTCOME MEASURES

Clinically diagnosed AD and level of global cognitive function proximate to death.

RESULTS

In separate logistic regression analyses, each 1% increase in amyloid load was associated with about a 50% increase in the odds of clinical AD (P =.002), and each neurofibrillary tangle was associated with a greater than 20% increase in the odds of clinical AD (P<.001). When a term for tangles was added to the regression model with amyloid, the association of amyloid load with clinical disease was reduced by more than 60% and was no longer significant, whereas the association of tangles with clinical disease was essentially unchanged. Similar results were found in analyses of global cognitive function.

CONCLUSION

These findings are consistent with a sequence of pathologic events whereby the effect of amyloid deposition on clinical disease is mediated by neurofibrillary tangles.

Characterisation of cytoskeletal abnormalities in mice transgenic for wild-type human tau and familial Alzheimer's disease mutants of APP and presenilin-1

To study the role of Abeta amyloid deposits in the generation of cytoskeletal lesions, we have generated a transgenic mouse line coexpressing in the same neurons a wild-type human tau isoform (0N3R), a mutant form of APP (751SL) and a mutant form of PS1 (M146L). These mice developed early cerebral extracellular deposits of Abeta, starting at 2.5 months. A somatodendritic neuronal accumulation of transgenic tau protein was observed in tau only and in tau/PS1/APP transgenic mice, including in neurons adjacent to Abeta deposits. The phosphorylation status of this somatodendritic tau was similar in the two transgenic lines. The Abeta deposits were surrounded by a neuritic reaction composed of axonal dystrophic processes, immunoreactive for many phosphotau epitopes and for the human tau transgenic protein. Ultrastructural observation showed in these dystrophic neurites a disorganisation of the microtubule and the neurofilament network but animals that were observed up to 18 months of age did not develop neurofibrillary tangles. These results indicate that overexpression of mutant PS1, mutant APP and of wild-type human tau were not sufficient per se to drive the formation of neurofibrillary tangles in a transgenic model. The Abeta deposits, however, were associated to marked changes in cytoskeletal organisation and in tau phosphorylation in adjacent dystrophic neurites.

Amyloid beta peptide 1-42 highly correlates with capillary cerebral amyloid angiopathy and Alzheimer disease pathology

Recent studies reported both positive [Thal et al. (2003) J Neuropathol Exp Neurol 62:1287-1301] and negative [Tian et al. (2003) Neurosci Lett 352:137-140] correlations between cerebral amyloid angiopathy (CAA) and Alzheimer's disease (AD) pathology. We have recently shown high correlations between neuritic AD pathology and amyloid beta peptide (Abeta) deposits in the capillary/pericapillary compartment (CapCAA) with only low correlations to general CAA (non-capillary). We have now studied the relationship between CapCAA and AD pathology with respect to the distribution of Abeta40 and 42 in the frontal cortex of 100 human postmortem brains from both male and female, demented and non-demented patients (mean age +/- SD 84.3 +/- 9.3 years). Using polyclonal antibodies to Abeta40 and 42, capillary and plaques positivity were assessed semiquantiatively on a four-point scale. Abeta42 deposits in capillaries correlated highly with both Abeta42 deposits in plaques and morphological AD criteria (CERAD, Braak stages, and NIA-Reagan-Institute criteria), while only a low correlation with CAA was observed. Abeta40 deposits in capillaries differed morphologically from Abeta42 ones: they were limited to capillary walls, were significantly less frequent in both capillaries and plaques compared to Abeta42 ( P < 0.01), and showed a low correlation with morphological AD criteria ( P < 0.05) and general CAA ( P < 0.01). By contrast, Abeta42 deposits were seen in the glia limitans rather than in capillary walls themselves, and showed high correlation with morphological AD criteria ( P < 0.01). These data indicate that CapCAA is characterized by Abeta42 deposits in pericapillary spaces or in the glia limitans. A low correlation between CAA and CapCAA, but high correlations between morphological AD criteria and CapCAA suggest different pathomechanisms for both types of CAA, and a close relation between CapCAA and AD pathology (both neuritic and plaque type). These data support the concept of a neuronal origin of Abeta via drainage from interstitial fluid from the central nervous system along basement membranes to capillaries.

Curcumin has potent anti-amyloidogenic effects for Alzheimer's beta-amyloid fibrils in vitro

Inhibition of the accumulation of amyloid beta-peptide (Abeta) and the formation of beta-amyloid fibrils (fAbeta) from Abeta, as well as the destabilization of preformed fAbeta in the central nervous system, would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). We reported previously that nordihydroguaiaretic acid (NDGA) and wine-related polyphenols inhibit fAbeta formation from Abeta(1-40) and Abeta(1-42) and destabilize preformed fAbeta(1-40) and fAbeta(1-42) dose-dependently in vitro. Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of curcumin (Cur) and rosmarinic acid (RA) on the formation, extension, and destabilization of fAbeta(1-40) and fAbeta(1-42) at pH 7.5 at 37 degrees C in vitro. We next compared the anti-amyloidogenic activities of Cur and RA with NDGA. Cur and RA dose-dependently inhibited fAbeta formation from Abeta(1-40) and Abeta(1-42), as well as their extension. In addition, they dose-dependently destabilized preformed fAbetas. The overall activities of Cur, RA, and NDGA were similar. The effective concentrations (EC(50)) of Cur, RA, and NDGA for the formation, extension, and destabilization of fAbetas were in the order of 0.1-1 microM. Although the mechanism by which Cur and RA inhibit fAbeta formation from Abeta and destabilize preformed fAbeta in vitro remains unclear, they could be a key molecule for the development of therapeutics for AD.