Cerebral deposition of amyloid b-peptide (Ab) in the brain is an invariant feature of Alzheimer's disease (AD). A consistent protective effect of wine consumption on AD has been documented by epidemiological studies. In the present study, we used fluorescence spectroscopy with thioflavin T and electron microscopy to examine the effects of wine-related polyphenols (myricetin, morin, quercetin, kaempferol (+)-catechin and (-)-epicatechin) on the formation, extension, and destabilization of b-amyloid fibrils (fAb) at pH 7.5 at 37°C in vitro. All examined polyphenols dose-dependently inhibited formation of fAb from fresh Ab(1-40) and Ab(1-42), as well as their extension. Moreover, these polyphenols dose-dependently destabilized preformed fAbs. The overall activity of the molecules examined was in the order of: myricetin ¼ morin ¼The effective concentrations (EC 50 ) of myricetin, morin and quercetin for the formation, extension and destabilization of fAbs were in the order of 0.1-1 lM. In cell culture experiments, myricetin-treated fAb were suggested to be less toxic than intact fAb, as demonstrated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. Although the mechanisms by which these polyphenols inhibit fAb formation from Ab, and destabilize pre-formed fAb in vitro are still unclear, polyphenols could be a key molecule for the development of preventives and therapeutics for AD.

Neurofibrillary tangles (NFTs) are pathological hallmarks of several neurodegenerative disorders, including Alzheimer's disease (AD). NFTs are composed of microtubule-binding protein tau, which assembles to form paired helical filaments (PHFs) and straight filaments. Here we show by atomic force microscopy that AD brain tissue and in vitro tau form granular and fibrillar tau aggregates. CD spectral analysis and immunostaining with conformation-dependent antibodies indicated that tau may undergo conformational changes during fibril formation. Enriched granules generated filaments, suggesting that granular tau aggregates may be an intermediate form of tau fibrils. The amount of granular tau aggregates was elevated in prefrontal cortex of Braak stage I cases compared to that of Braak stage 0 cases, suggesting that granular tau aggregation precedes PHF formation. Thus, granular tau aggregates may be a relevant marker for the early diagnosis of tauopathy. Reducing the level of these aggregates may be a promising therapy for tauopathies and for promoting healthy brain aging.

Amyloid-␤ protein (A␤) aggregates in the brain to form senile plaques. By using thioflavin T, a dye that specifically binds to fibrillar structures, we found that metals such as Zn(II) and Cu(II) normally inhibit amyloid ␤-aggregation. Another method for detecting A␤, which does not distinguish the types of aggregates, showed that these metals induce a non-␤-sheeted aggregation, as reported previously. Secondary structural analysis and microscopic studies revealed that metals induced A␤ to make non-fibrillar aggregates by disrupting ␤-sheet formation. These non-fibrillar A␤ aggregates displayed much weaker Congo Red birefringence, and in separate cell culture experiments, were less toxic than self ␤-aggregates, as demonstrated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. The toxicity of soluble A␤ was enhanced in the presence of Cu(II), which suggests the previously hypothesized role of A␤ in generating oxidative stress. Finally, under an acidic condition, similar to that in the inflammation associated with senile plaques, ␤-aggregation was robustly facilitated at one specific concentration of Zn(II) in the presence of heparin. However, because a higher concentration of Zn(II) virtually abolished this abnormal phenomenon, and at normal pH any concentrations strongly inhibit ␤-aggregation and its associated cytotoxicity, including its anti-oxidative nature we suggest that Zn(II) has an overall protective effect against ␤-amyloid toxicity. Amyloid-␤ protein (A␤)1 is one of the main components of senile plaques, a pathological hallmark of Alzheimer's disease (AD) (1, 2). Although A␤ is undisputedly associated with the pathology of AD, it is still an open question as to what specific aspects of A␤ and its processing are the important variables in the pathophysiology of the disease. For example, fibrillar A␤, but not non-amyloidogenic, amorphous aggregates of A␤, was reported to cause neuronal cell death in primary rat hippocampal cultures (3), and soluble monomeric species of A␤ are relatively nontoxic as compared with fibrillar A␤ (4). Thus, these in vitro studies suggest that the degree of ␤-aggregation is particularly important for neurotoxicity to occur (5-8). However, many controversial results from in vivo studies have been reported concerning the pathological role of plaque formation in AD. Irizarry et al. (9) reported that transgenic (TG) mice expressing human A␤ failed to exhibit neuronal loss despite depositing substantial amounts of A␤. On the other hand, TG mice that express Swedish mutant amyloid precursor protein (APP) formed plaques that were detected by both an anti-APP antibody and a ␤-sheet specific dye (10). Moreover, these APP TG mice also displayed memory deficits. Taken together, these results indicate that, although the plaque assembly process may require further investigation, amyloid ␤-aggregation certainly is an essential event in the pathogenesis of AD.Based on these lines of evidence, the search for a compound that interrupts ␤-aggregation and thus protects agai...