AB1518 Sigma-AldrichAnti-Neurofibrillary Tangles Antibody

Tauopathy in the hippocampus is one of the earliest cardinal features of Alzheimer's disease (AD), a condition characterized by progressive memory impairments. In fact, density of tau neurofibrillary tangles (NFTs) in the hippocampus strongly correlates with severity of cognitive impairments in AD. In the present study, we employed a somatic cell gene transfer technique to create a rodent model of tauopathy by injecting a recombinant adeno-associated viral vector with a mutated human tau gene (P301L) into the hippocampus of adult rats. The P301L mutation is causal for frontotemporal dementia with parkinsonism-17 (FTDP-17), but it has been used for studying memory effects characteristic of AD in transgenic mice. To ascertain if P301L-induced mnemonic deficits are persistent, animals were tested for 6 months. It was hypothesized that adult-onset, spatially restricted tau expression in the hippocampus would produce progressive spatial working memory deficits on a learned alternation task. Rats injected with the tau vector exhibited persistent impairments on the hippocampal-dependent task beginning at about 6 weeks post-transduction compared to rats injected with a green fluorescent protein vector. Histological analysis of brains for expression of human tau revealed hyperphosphorylated human tau and NFTs in the hippocampus in experimental animals only. Thus, adult-onset, vector-induced tauopathy spatially restricted to the hippocampus progressively impaired spatial working memory in rats. We conclude that the model faithfully reproduces histological and behavioral findings characteristic of dementing tauopathies. The rapid onset of sustained memory impairment establishes a preclinical model particularly suited to the development of potential tauopathy therapeutics.

PTI-125 is a novel compound demonstrating a promising new approach to treating Alzheimer's disease (AD), characterized by neurodegeneration and amyloid plaque and neurofibrillary pathologies. We show that the toxic signaling of amyloid-β(42) (Aβ(42)) by the α7-nicotinic acetylcholine receptor (α7nAChR), which results in tau phosphorylation and formation of neurofibrillary tangles, requires the recruitment of the scaffolding protein filamin A (FLNA). By binding FLNA with high affinity, PTI-125 prevents Aβ(42)'s toxic cascade, decreasing phospho-tau and Aβ aggregates and reducing the dysfunction of α7nAChRs, NMDARs, and insulin receptors. PTI-125 prevents Aβ(42) signaling by drastically reducing its affinity for α7nAChRs and can even dissociate existing Aβ(42)-α7nAChR complexes. Additionally, PTI-125 prevents Aβ-induced inflammatory cytokine release by blocking FLNA recruitment to toll-like receptor 4, illustrating an anti-inflammatory effect. PTI-125's broad spectrum of beneficial effects is demonstrated here in an intracerebroventricular Aβ(42) infusion mouse model of AD and in human postmortem AD brain tissue.

Entorhinal cortex neuropathology begins very early in Alzheimer's disease (AD), a disorder characterized by severe memory disruption. Indeed, loss of entorhinal volume is predictive of AD and two of the hallmark neuroanatomical markers of AD, amyloid plaques and neurofibrillary tangles (NFTs), are particularly prevalent in the entorhinal area of AD-afflicted brains. Gene transfer techniques were used to create a model neurofibrillary tauopathy by injecting a recombinant adeno-associated viral vector with a mutated human tau gene (P301L) into the entorhinal cortex of adult rats. The objective of the present investigation was to determine whether adult onset, spatially restricted tauopathy could be sufficient to reproduce progressive deficits in mnemonic function. Spatial memory on a Y-maze was tested for approximately 3 months post-surgery. Upon completion of behavioral testing the brains were assessed for expression of human tau and evidence of tauopathy. Rats injected with the tau vector became persistently impaired on the task after about 6 weeks of postoperative testing, whereas the control rats injected with a green fluorescent protein vector performed at criterion levels during that period. Histological analysis confirmed the presence of hyperphosphorylated tau and NFTs in the entorhinal cortex and neighboring retrohippocampal areas as well as limited synaptic degeneration of the perforant path. Thus, highly restricted vector-induced tauopathy in retrohippocampal areas is sufficient for producing progressive impairment in mnemonic ability in rats, successfully mimicking a key aspect of tauopathies such as AD.

G-protein coupled receptor kinase-5 (GRK5) deficiency has been linked to early Alzheimer's disease in humans and mouse models of the disease. To determine potential roles of GRK5 in the disease pathogenesis, the GRK5 knockout mouse was evaluated at pathological and behavioral levels. We found that these mice displayed an age-dependent increase in hippocampal axonal defects characterized by clusters of axonal swellings that accumulated abnormal amounts of molecular motor proteins, microtubule-associated proteins, intracellular beta-amyloid, and subcellular organelles. In severe cases, extracellular beta-amyloid fibrillar deposits were occasionally observed, along with degenerating axonal components, and were tightly surrounded by reactive astrocytes. Moreover, significant loss of synaptic proteins and early signs of cholinoceptive neurodegeneration were evident in the hippocampus as well. Consistent with the moderate level of pathologic change, aged GRK5 knockout mice displayed selective working memory impairment, with other cognitive domains unaffected. Taken together, these findings not only strongly support an important role of GRK5 deficiency in early Alzheimer's pathogenesis, but also promote the GRK5 knockout mouse as an additional model for early Alzheimer-related studies.

Tau hyperphosphorylation, leading to self-aggregation, is widely held to underlie the neurofibrillary degeneration found in Alzheimer's disease (AD) and other tauopathies. However, it is unclear exactly what environmental factors may trigger this pathogenetic tau hyperphosphorylation. From several perspectives, the coagulation serine protease, thrombin, has been implicated in AD and activates several different protein kinase pathways but has not previously been shown how it may contribute to AD pathogenesis. Here we report that nanomolar thrombin induced rapid tau hyperphosphorylation and aggregation in murine hippocampal neurons via protease-activated receptors, which was followed by delayed synaptophysin reduction and apoptotic neuronal death. Mechanistic study revealed that a persistent thrombin signaling via protease-activated receptor 4 and prolonged downstream p44/42 mitogenactivated protein kinase activation are at least in part responsible. These results pathogenetically linked thrombin to subpopulations of AD and other tauopathies associated with cerebrovascular damage. Such knowledge may be instrumental in transforming therapeutic paradigms.

An improved thioflavin-S stain, Gallyas silver stain, and two immunostainings were quantitatively compared for demonstration of neurofibrillary tangles (NFTs) on the same sections. Sections of hippocampal formation from seven cases of Alzheimer's disease (AD) were immunofluorescently stained with a commercially available polyclonal NFT antibody or a PHF-1 monoclonal antibody, followed by an improved thioflavin-S stain, and finally by Gallyas silver staining. The thioflavin-S method was improved by using a combination quenching method that removes background autofluorescence without remarkable tissue damage and by post-treatment with concentrated phosphate buffer, which minimizes photobleaching. PHF-1 or NFT immunostaining is much less sensitive than the improved thioflavin-S staining and Gallyas silver staining, particularly in the transentorhinal region. Moreover PHF-1 immunoreactivity varied greatly among AD individuals. Thioflavin-S staining and Gallyas silver staining show almost the same sensitivity in NFT demonstration, but only the former depends on the secondary protein structure of NFTs. This study suggests that the improved thioflavin-S staining is a simple, sensitive, and consistent method for demonstration of neurofibrillary pathology.

Fractions enriched in neurofibrillary tangles (NFT) and amyloid fibrils were isolated from the cerebral cortex of three cases of senile dementia of the Alzheimer type. Distilled water suspensions of these fractions were excluded from all pore size gels and resisted digestion with various proteolytic enzymes. Formic acid/chloroform treatment of each fraction resulted in the appearance of 4,000-6,000, 15,000-17,000 and 24,000 molecular weight proteins, with concomitant diminution in the amount of excluded material at the top of each gel. The 4,000-6,000 dalton band was best seen in fractions containing randomly arranged amyloid fibrils, and its amino acid composition resembled that of the recently reported "beta" protein. A polyclonal antiserum to purified NFT reacted with tangles in neurons and in dystrophic neurites around plaques by immunoperoxidase staining. No reaction was obtained with cerebrovascular or plaque core amyloid immunohistologically, or with the 4-6 kD protein on immunoblots. Cross-reactivity with the neurofibrillary lesions occurring in Pick's disease, progressive supranuclear palsy, postencephalitic Parkinsonism and dementia pugilistica was also seen. Specific binding of this antiserum to the double filamentous structure was confirmed by immunoelectron microscopy. Although the presence of "beta" protein in both NFT and amyloid-containing fractions suggests that it may be an important constituent of both, cross-contamination cannot be excluded.

An immune serum raised against paired helical filaments (PHF) was able to stain senils plaques (SP) and neurofibrillary tangles (NFT) specifically, the two characteristic lesions of the dementia of Alzheimer-type. This polyclonal antibody against PHF was characterized by immunochemistry and also compared with the classical Bodian silver staining. NFT and SP were observed where they were expected: in the fronto-temporal neo-cortex and hippocampus of Alzheimer-type patients, and also in hippocampus of non-demented elderly subjects. The pattern of SP visualized by the two methods was identical whereas NFT were not detected specifically by silver salts, specially in the nervous tissue where NFT were in discrete quantities. Since the preparation of the antigen is very easy and the resulting antibodies are specific, we conclude that this technique will be of considerable interest for routine neuropathological diagnosis. Finally, the properties of our anti-PHF antibody are compared with those reported in the literature. This antibody will probably be a good tool for the identification of the chemical nature of PHF components.

The reactivity of neurofibrillary tangles (NFT) of Alzheimer's disease with several antisera has been studied by immunocytochemistry. They were heavily labelled by an antiserum prepared against isolated NFT; the latter also remained stainable by Bodian-silver method. Some NFT were labelled on vibratome sections by an antimicrotubular protein but remained able to be counterstained by Congo Red, suggesting this labelling could demonstrate material trapped in NFT. The immunoelectron labelling shows that the abnormal filaments, straight as well as 'twisted', are the only structures recognised by the anti-NFT serum. This labelling was prevented only by pre-incubation with fractions enriched in NFT, confirming the presence of unique antigenic determinants in the latter.