CSF Aβ42 and tau in Parkinson's disease with cognitive impairment

We tested the hypothesis that the CSF biomarker signature associated with Alzheimer's disease (AD) is present in a subset of individuals with Parkinson's disease and Dementia (PD‐D) or with PD and Cognitive Impairment, Not Dementia (PD‐CIND). We quantified CSF Aβ₄₂, total tau (T‐tau), and phospho‐tau (P181‐tau) using commercially available kits. Samples were from 345 individuals in seven groups (n): Controls ≤50 years (35), Controls >50 years (115), amnestic Mild Cognitive Impairment (aMCI) (24), AD (49), PD (49), PD‐CIND (62), and PD‐D (11). We observed expected changes in AD or aMCI compared with age‐matched or younger controls. CSF Aβ₄₂ was reduced in PD‐CIND (P < 0.05) and PD‐D (P < 0.01), whereas average CSF T‐tau and P181‐tau were unchanged or decreased. One‐third of PD‐CIND and one‐half of PD‐D patients had the biomarker signature of AD. Abnormal metabolism of Aβ₄₂ may be a common feature of PD‐CIND and PD‐D. © 2010 Movement Disorder Society     

A critical role of TRPM2 channel in Aβ42‐induced microglial activation and generation of tumor necrosis factor‐α

Amyloid β (Aβ)‐induced neuroinflammation plays an important part in Alzheimer's disease (AD). Emerging evidence supports a role for the transient receptor potential melastatin‐related 2 (TRPM2) channel in Aβ‐induced neuroinflammation, but how Aβ induces TRPM2 channel activation and this relates to neuroinflammation remained poorly understood. We investigated the mechanisms by which Aβ₄₂ activates the TRPM2 channel in microglial cells and the relationships to microglial activation and generation of tumor necrosis factor‐α (TNF‐α), a key cytokine implicated in AD. Exposure to 10–300 nM Aβ₄₂ induced concentration‐dependent microglial activation and generation of TNF‐α that were ablated by genetically deleting (TRPM2 knockout ;TRPM2‐KO) or pharmacologically inhibiting the TRPM2 channel, revealing a critical role of this channel in Aβ₄₂‐induced microglial activation and generation of TNF‐α. Mechanistically, Aβ₄₂ activated the TRPM2 channel via stimulating generation of reactive oxygen species (ROS) and activation of poly(ADPR) polymerase‐1 (PARP‐1). Aβ₄₂‐induced generation of ROS and activation of PARP‐1 and TRPM2 channel were suppressed by inhibiting protein kinase C (PKC) and NADPH oxidases (NOX). Aβ₄₂‐induced activation of PARP‐1 and TRPM2 channel was also reduced by inhibiting PYK2 and MEK/ERK. Aβ₄₂‐induced activation of PARP‐1 was attenuated by TRPM2‐KO and moreover, the remaining PARP‐1 activity was eliminated by inhibiting PKC and NOX, but not PYK2 and MEK/ERK. Collectively, our results suggest that PKC/NOX‐mediated generation of ROS and subsequent activation of PARP‐1 play a role in Aβ₄₂‐induced TRPM2 channel activation and TRPM2‐dependent activation of the PYK2/MEK/ERK signalling pathway acts as a positive feedback to further facilitate activation of PARP‐1 and TRPM2 channel. These findings provide novel insights into the mechanisms underlying Aβ‐induced AD‐related neuroinflammation.     

Co‐localization of β‐peptide and phosphorylated tau in astrocytes in a patient with corticobasal degeneration

The co‐localization of amyloid β (Aβ) and phosphorylated tau in astrocytes in a patient with corticobasal degeneration is described. At autopsy, the present case exhibited neuropathological findings compatible with those of corticobasal degeneration, including atrophy of the frontal and temporal lobes, neuronal loss and gliosis in the cortical and subcortical regions, and presence of cortical ballooned neurons and astrocytic plaques. Moreover, many senile plaques were found in the cerebral cortex. There were also clusters of Aβ‐positive granules associated with astrocytic cytoplasm and processes in the subiculum and entorhinal cortex. In the entorhinal cortex, the Aβ‐positive granules were occasionally co‐localized with phosphorylated tau‐positive fibrillary structures in the astrocytic cytoplasm. To our knowledge, this is the first demonstration of co‐localization of Aβ and phosphorylated tau in astrocytes. This phenomenon implies that phagocytosis of Aβ coincides with production of phosphorylated tau in the same reactive astrocytes.     

CSF total and phosphorylated tau protein,regional glucose metabolism and dementia severity in Alzheimer’s disease

Background and purpose: We investigated associations between severity of cognitive impairment, cerebrospinal fluid (CSF) concentrations of total‐tau (t‐tau) protein and tau phosphorylated at threonin 181 (p‐tau₁₈₁) and regional glucose metabolism measured with 18F‐fluorodeoxyglucose‐positron emission tomography (18F‐FDG‐PET) in patients with probable Alzheimer’s disease (AD). Methods: In 38 patients (mean age 66.5 ± 8.0 years) with AD, Mini‐Mental State Examination (MMSE) scores were evaluated and CSF levels of t‐tau and p‐tau₁₈₁ measured. All patients underwent an 18F‐FDG‐PET scan. Image analysis including correlation analysis and principal component analysis (PCA) were performed using SPM5 and VINCI. Results: Dementia severity (MMSE 21.2 ± 4.9) correlated well with metabolic impairment especially in left hemisphere association areas that are typically affected in patients with AD (e.g. inferior parietal lobule, r = 0.512; medial temporal gyrus, r = 0.478; inferior temporal gyrus, r = 0.488; precuneus, r = 0.468; PCA: r = 0.639, F = 7.751; all P < 0.001). There were no associations between t‐tau and p‐tau₁₈₁ with dementia severity and only weak correlations between t‐tau and cerebral glucose metabolism (superior parietal gyrus, r = ?0.325, P < 0.05; precentral gyrus r = ?0.418, P < 0.01; amygdala r = ?0.362, P < 0.05). No correlations were found between p‐tau₁₈₁ and regional hypometabolism in FDG‐PET. Conclusion: MMSE and CSF t‐tau represent different aspects of disease severity. Whilst MMSE is closely related to impaired cerebral glucose metabolism, CSF t‐tau is less closely related and appears to be less well suited for assessment of disease progression.     

Serum amyloid β protein in young and elderly depression: a pilot study

Background: Depression may increase the risk of developing Alzheimer's disease (AD). Recent large cohort studies have also shown that a low plasma amyloid β (Aβ)‐42 level combined with a high Aβ40 level increases the risk of developing AD, suggesting plasma Aβ42/40 ratio as useful for identifying risk of developing mild cognitive impairment and AD. Although several studies have examined Aβ levels in the peripheral blood of elderly individuals with depression, results have been inconsistent. Furthermore, no results have been described for younger depression. Methods: Serum Aβ40, Aβ42 level and Aβ40/42 ratio were evaluated using enzyme‐linked immunosorbent assay in 60 patients with major depressive disorder (MDD) and 60 healthy controls. The results were analyzed in two age groups (young, <60 years; elderly, ≥60 years). Results: Serum Aβ40 level was significantly higher in young MDD patients compared to young controls (P < 0.001), but it was not significantly deferent in the elderly group. Serum Aβ42 level did not differ significantly in both young and elderly groups. Aβ40/42 ratio was significantly higher in both young (P < 0.001) and elderly (P < 0.001) patients with MDD compared to controls. Conclusions: Serum Aβ40/42 ratio was significantly higher in MDD patients than in controls, and this difference was seen for both elderly and young subjects. This may suggest that even young subjects with MDD undergo pathological changes in the very early stage of amyloid deposition.     

Attenuation of β‐amyloid‐induced tauopathy via activation of CK2α/SIRT1: Targeting for cilostazol

β‐Amyloid (Aβ) deposits and hyperphosphorylated tau aggregates are the chief hallmarks in the Alzheimer's disease (AD) brains, but the strategies for controlling these pathological events remain elusive. We hypothesized that CK2‐coupled SIRT1 activation stimulated by cilostazol suppresses tau acetylation (Ac‐tau) and tau phosphorylation (P‐tau) by inhibiting activation of P300 and GSK3β. Aβ was endogenously overproduced in N2a cells expressing human APP Swedish mutation (N2aSwe) by exposure to medium containing 1% fetal bovine serum for 24 hr. Increased Aβ accumulation was accompanied by increased Ac‐tau and P‐tau levels. Concomitantly, these cells showed increased P300 and GSK3β P‐Tyr216 expression; their expressions were significantly reduced by treatment with cilostazol (3–30 μM) and resveratrol (20 μM). Moreover, decreased expression of SIRT1 and its activity by Aβ were significantly reversed by cilostazol as by resveratrol. In addition, cilostazol strongly stimulated CK2α phosphorylation and its activity, and then stimulated SIRT1 phosphorylation. These effects were confirmed by using the pharmacological inhibitors KT5720 (1 μM, PKA inhibitor), TBCA (20 μM, inhibitor of CK2), and sirtinol (20 μM, SIRT1 inhibitor) as well as by SIRT1 gene silencing and overexpression techniques. In conclusion, increased cAMP‐dependent protein kinase‐linked CK2/SIRT1 expression by cilostazol can be a therapeutic strategy to suppress the tau‐related neurodegeneration in the AD brain. © 2013 Wiley Periodicals, Inc.     

Soybean isoflavone ameliorates β‐amyloid 1‐42‐induced learning and memory deficit in rats by protecting synaptic structure and function

This research aims to investigate whether soybean isoflavone (SIF) could alleviate the learning and memory deficit induced by β‐amyloid peptides 1‐42 (Aβ1‐42) by protecting the synapses of rats. Adult male Wistar rats were randomly allocated to the following groups: (1) control group; (2) Aβ1‐42 group; (3) SIF group; (4) SIF + Aβ1‐42 group (SIF pretreatment group) according to body weight. The 80 mg/kg/day of SIF was administered orally by gavage to the rats in SIF and SIF+Aβ1‐42 groups. Aβ1‐42 was injected into the lateral cerebral ventricle of rats in Aβ1‐42 and SIF+Aβ1‐42 groups. The ability of learning and memory, ultramicrostructure of hippocampal synapses, and expression of synaptic related proteins were investigated. The Morris water maze results showed the escape latency and total distance were decreased in the rats of SIF pretreatment group compared to the rats in Aβ1‐42 group. Furthermore, SIF pretreatment could alleviate the synaptic structural damage and antagonize the down‐regulation expressions of below proteins induced by Aβ1‐42: (1) mRNA and protein of the synaptophysin and postsynaptic density protein 95 (PSD‐95); (2) protein of calmodulin (CaM), Ca²⁺/calmodulin‐dependent protein kinase II (CaMK II), and cAMP response element binding protein (CREB); (3) phosphorylation levels of CaMK II and CREB (pCAMK II, pCREB). These results suggested that SIF pretreatment could ameliorate the impairment of learning and memory ability in rats induced by Aβ1‐42, and its mechanism might be associated with the protection of synaptic plasticity by improving the synaptic structure and regulating the synaptic related proteins. Synapse 67:856–864, 2013 . © 2013 Wiley Periodicals, Inc.     

Long‐term oral intake of aluminium or zinc does not accelerate Alzheimer pathology in AβPP and AβPP/tau transgenic mice

Whether or not the oral intake of metals such as aluminium (Al) and zinc (Zn) is a risk for Alzheimer's disease (AD) has been a matter of controversy. Lack of AD pathology in patients with Al encephalopathy indicates Al does not cause AD. On the other hand, some epidemiological studies have suggested high Al increases the occurrence of AD. Our purpose is to test if high Al in drinking water is a risk factor for AD. We administered Al and Zn in drinking water to Tg2576, a transgenic mouse model for amyloid β‐protein (Aβ) deposition with the Aβ precursor protein (AβPP) mutations (K670N/M671L), and Tg2576/tau(P301L), a model for Aβ and tau deposition. Deionized water was given to the control Tg2576 and Tg2576/tau. After administration for 4–10 months of approximately 100 mg/kg body weight Al or Zn per day, we were not able to find by quantitative immunohistochemical analyses differences in the deposition of Aβ and tau between the treated and untreated groups. Nor did the Al or Zn treatment affect the amount of soluble Aβ and Aβ*56, an Aβ oligomer, measured by ELISA or immunoblot. The oral intake of excess Al or Zn does not accelerate AD pathology in the transgenic mouse models for Aβ and tau accumulation. Such results do not seem to support the notion that excessive oral intake of Al or Zn is a risk factor for AD.     

γ‐Secretase binding sites in aged and Alzheimer's disease human cerebrum: the choroid plexus as a putative origin of CSF Aβ

Deposition of β ‐amyloid (Aβ) peptides, cleavage products of β‐amyloid precursor protein (APP) by β‐secretase‐1 (BACE1) and γ‐secretase, is a neuropathological hallmark of Alzheimer's disease (AD). γ‐Secretase inhibition is a therapeutical anti‐Aβ approach, although changes in the enzyme's activity in AD brain are unclear. Cerebrospinal fluid (CSF) Aβ peptides are thought to derive from brain parenchyma and thus may serve as biomarkers for assessing cerebral amyloidosis and anti‐Aβ efficacy. The present study compared active γ‐secretase binding sites with Aβ deposition in aged and AD human cerebrum, and explored the possibility of Aβ production and secretion by the choroid plexus (CP). The specific binding density of [³H]‐L‐685,458, a radiolabeled high‐affinity γ‐secretase inhibitor, in the temporal neocortex and hippocampal formation was similar for AD and control cases with similar ages and post‐mortem delays. The CP in post‐mortem samples exhibited exceptionally high [³H]‐L‐685,458 binding density, with the estimated maximal binding sites (Bmax) reduced in the AD relative to control groups. Surgically resected human CP exhibited APP, BACE1 and presenilin‐1 immunoreactivity, and β‐site APP cleavage enzymatic activity. In primary culture, human CP cells also expressed these amyloidogenic proteins and released Aβ40 and Aβ42 into the medium. Overall, our results suggest that γ‐secretase activity appears unaltered in the cerebrum in AD and is not correlated with regional amyloid plaque pathology. The CP appears to be a previously unrecognised non‐neuronal contributor to CSF Aβ, probably at reduced levels in AD.     

Scavenging of Alzheimer's amyloid β-protein by microglia in culture

Deposits of amyloid β-protein (Aβ) form the cores of the pathological plaques which characterize Alzheimer's disease. The mechanism of formation of the deposits is unknown; one possibility is failure of a clearance mechanism that would normally remove the protein from brain parenchyma. This study has investigated the capacity of the central nervous system (CNS) phagocytes, microglia cells, to clear exogenous Aβ_1–42 from their environment. Cultured microglia from adult rat CNS have a high capacity to remove Aβ from serum-free medium, shown by immunoblotting experiments. Aβ from incubation medium was attached to the cell surface and could be identified by immunocytochemistry at the light or electron microscopic (EM) level; by EM, Aβ also appeared in phagosome-like intracellular vesicles. Light microscopic immunocytochemistry combined with computer-assisted image analysis showed that cells accumulated Aβ within 24 hr. from culture medium containing from 1 to 20 μg/ml Aβ. Microglial accumulation of Aβ was substantially reduced in the presence of fetal bovine serum. Addition of the protease inhibitor leupeptin to incubation medium with serum resulted in accumulation of Aβ in a membrane-bound intracellular compartment, but not at the cell surface. The increase in intracellular accumulation in the presence of the protease inhibitor indicates a microglial capacity for intracellular degradation of Aβ in the absence of inhibition. The change from predominantly cell-surface accumulation in serum-free medium to predominantly intracellular accumulation with serum may be explained by the presence in serum of carrier proteins that complex with Aβ and target it to cell surface receptors capable of stimulating endocytosis. Microglia were also cultured on unfixed cryostat sections of human brain tissue containing Alzheimer's plaques. Very little Aβ from the tissue was accumulated by the cells, although cultured microglia were found in direct contact with anti-Aβ immunopositive plaques. Possibly Aβ in tissue sections was complexed with other proteins which either inhibited its uptake by microglia or enhanced its proteolysis, preventing cellular accumulation of immunostainable Aβ. The results indicate that cultured microglia effectively remove Aβ from tissue culture medium and from the surface of the dish and concentrate monomer and aggregates of Aβ either on the cell surface or intracellularly. This process may be modified by proteins present in Alzheimer's brain sections. © 1996 Wiley-Liss, Inc.     

Effects of antiparkinsonian agents on β‐amyloid and α‐synuclein oligomer formation in vitro

The aggregation of β‐amyloid protein (Aβ) and α‐synuclein (αS) are hypothesized to be the key pathogenic event in Alzheimer's disease (AD) and Lewy body diseases (LBD), with oligomeric assemblies thought to be the most neurotoxic. Inhibitors of oligomer formation, therefore, could be valuable therapeutics for patients with AD and LBD. Here, we examined the effects of antiparkinsonian agents (dopamine, levodopa, trihexyphenidyl, selegiline, zonisamide, bromocriptine, peroxide, ropinirole, pramipexole, and entacapone) on the in vitro oligomer formation of Aβ40, Aβ42, and αS using a method of photo‐induced cross‐linking of unmodified proteins (PICUP), electron microscopy, and atomic force microscopy. The antiparkinsonian agents except for trihexyphenidyl inhibited both Aβ and αS oligomer formations, and, among them, dopamine, levodopa, pramipexole, and entacapone had the stronger in vitro activity. Circular dichroism and thioflavin T(S) assays showed that secondary structures of Aβ and αS assemblies inhibited by antiparkinsonian agents were statistical coil state and that their seeding activities had disappeared. The antiparkinsonian agents could be potential therapeutic agents to prevent or delay AD and LBD progression. © 2013 Wiley Periodicals, Inc.     

Distribution of tau protein kinase I/glycogen synthase kinase-3β, phosphatases 2A and 2B, and phosphorylated tau in the developing rat brain

When trying to elucidate the role played by tau protein kinase I/glycogen synthase kinase-3β (TPKI/GSK-3β) in tau phosphorylation, it is important to consider the balance that exists between the various kinases and phosphatases that are involved in vivo. We studied developmental changes in the expressions of TPKI/GSK-3β and phosphatases 2A and 2B in rat brains using immunoblot analysis. The expression of the kinase peaked postnatally at days 8–11 and returned then to low level after 5 weeks. Phosphatase 2A showed a similar pattern, increasing postnatally until day 14 and decreasing thereafter. On the other hand, phosphatase 2B was undetectable at the juvenile stage, but later its presence increased rapidly to peak at 5 weeks after birth, after which it was maintained at high levels throughout the adult stage. Immunohistochemical studies using the PAP method revealed details of the distribution of TPKI/GSK-3β. At postnatal days 3–21 both gray and white matter were immunoreactive. Later, after 5 weeks, the immunoreactivity became more restricted to the gray matter. The staining of tau phosphorylated at Ser 199, Ser 396, and Ser 413 followed mostly the pattern of the kinase distribution throughout all stages of development. These data, therefore, confirm that TPKI/GSK-3β is expressed primarily in neurons and especially in neurites until postnatal day 21, whereafter the distribution is concentrated mostly in the cell soma and the proximal neurite region.     

Cerebrospinal fluid Tau/α‐synuclein ratio in Parkinson's disease and degenerative dementias

Although alpha‐synuclein is the main constituent of Lewy bodies, cerebrospinal fluid determination on its own does not seem fundamental for the diagnosis of synucleinopathies. We evaluated whether the combination of classical biomarkers, Aβ_1–42, total tau, phosphorylated tau, and α‐synuclein can improve discrimination of Parkinson's disease, dementia with Lewy bodies, Alzheimer's disease, and frontotemporal dementia. Aβ_1–42, total tau, phosphorylated tau, and α‐synuclein were measured in a series of patients with Parkinson's disease (n = 38), dementia with Lewy bodies (n = 32), Alzheimer's disease (n = 48), frontotemporal dementia (n = 31), and age‐matched control patients with other neurological diseases (n = 32). Mean α‐synuclein levels in cerebrospinal fluid were significantly lower in the pathological groups than in cognitively healthy subjects. An inverse correlation of α‐synuclein with total tau (r = ?0.196, P < .01) was observed. In the group of patients with Parkinson's disease, Aβ_1–42, total tau, and phosphorylated tau values were similar to controls, whereas total tau/α‐synuclein and phosphorylated tau/α‐synuclein ratios showed the lowest values. Cerebrospinal fluid α‐synuclein alone did not provide relevant information for Parkinson's disease diagnosis, showing low specificity (area under the curve, 0.662; sensitivity, 94%; specificity, 25%). Instead, a better performance was obtained with the total tau/α‐syn ratio (area under the curve, 0.765; sensitivity, 89%; specificity, 61%). Combined determination of α‐synuclein and classical biomarkers in cerebrospinal fluid shows differential patterns in neurodegenerative disorders. In particular, total tau/α‐synuclein and phosphorylated tau/α‐synuclein ratios can contribute to the discrimination of Parkinson's disease. © 2011 Movement Disorder Society     

NMDA receptor–dependent signaling pathways that underlie amyloid β‐protein disruption of LTP in the hippocampus

Alzheimer's disease (AD), the most common neurodegenerative disease in the elderly population, is characterized by the hippocampal deposition of fibrils formed by amyloid β‐protein (Aβ), a 40‐ to 42‐amino‐acid peptide. The folding of Aβ into neurotoxic oligomeric, protofibrillar, and fibrillar assemblies is believed to mediate the key pathologic event in AD. The hippocampus is especially susceptible in AD and early degenerative symptoms include significant deficits in the performance of hippocampal‐dependent cognitive abilities such as spatial learning and memory. Transgenic mouse models of AD that express C‐terminal segments or mutant variants of amyloid precursor protein, the protein from which Aβ is derived, exhibit age‐dependent spatial memory impairment and attenuated long‐term potentiation (LTP) in the hippocampal CA1 and dentate gyrus (DG) regions. Recent experimental evidence suggests that Aβ disturbs N‐methyl‐D ‐aspartic acid (NMDA) receptor–dependent LTP induction in the CA1 and DG both in vivo and in vitro. Furthermore, these studies suggest that Aβ specifically interferes with several major signaling pathways downstream of the NMDA receptor, including the Ca²⁺‐dependent protein phosphatase calcineurin, Ca²⁺/calmodulin‐dependent protein kinase II (CaMKII), protein phosphatase 1, and cAMP response element–binding protein (CREB). The influence of Aβ on each of these downstream effectors of the NMDA receptor is reviewed in this article. Additionally, other mechanisms of LTP modulation, such as Aβ attenuation of α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) receptor currents, are briefly discussed. © 2009 Wiley‐Liss, Inc.     

A novel antibody targeting sequence 31–35 in amyloid β protein attenuates Alzheimer's disease‐related neuronal damage

Amyloid β protein (Aβ) plays a critical role in pathogenesis of Alzheimer's disease (AD). Our previous studies indicated that the sequence 31–35 in Aβ molecule is an effective active center responsible for Aβ neurotoxicity in vivo and in vitro. In the present study, we prepared a novel antibody specifically targeting the sequence 31–35 of amyloid β protein, and investigated the neuroprotection of the anti‐Aβ_31–35 antibody against Aβ_1–42‐induced impairments in neuronal viability, spatial memory, and hippocampal synaptic plasticity in rats. The results showed that the anti‐Aβ_31–35 antibody almost equally bound to both Aβ_31–35 and Aβ_1–42, and pretreatment with the antibody dose‐dependently prevented Aβ_1–42‐induced cytotoxicity on cultured primary cortical neurons. In behavioral study, intracerebroventricular (i.c.v.) injection of anti‐Aβ_31–35 antibody efficiently attenuated Aβ_1–42‐induced impairments in spatial learning and memory of rats. In vivo electrophysiological experiments further indicated that Aβ_1–42‐induced suppression of hippocampal synaptic plasticity was effectively reversed by the antibody. These results demonstrated that the sequence 31–35 of Aβ may be a new therapeutic target, and the anti‐Aβ_31–35 antibody could be a novel immunotheraputic approach for the treatment of AD. © 2016 Wiley Periodicals, Inc.     

Costimulatory Effects of Interferon-γ and Interleukin-1β or Tumor Necrosis Factor α on the Synthesis of Aβ1-40 and Aβ1-42 by Human Astrocytes

Chronic inflammation and astrocytosis are characteristic histopathological features of Alzheimer's Disease (AD). Astrocytes are one of the predominant cell types in the brain. In AD they are activated and produce inflammatory components such as complement components, acute phase proteins, and cytokines. In this study we analyzed the effect of cytokines on the production of amyloid β (Aβ) in the astrocytoma cell line U373 and in primary human astrocytes isolated postmortem from healthy aged persons as well as from patients with AD. Astrocytes did not produce Aβ in the absence of stimuli or following stimulation with IL-1β, TNFα, IL-6, and TGF-β1. Neither did combinations of TNFα and IL-1β, IL-6 or TGF-β1, or the coadministration of IFNγ and IL-6 or TGF-β1 induce Aβ production. In contrast, pronounced production of Aβ1-40 and Aβ1-42 was observed when primary astrocytes or astrocytoma cells were stimulated with combinations of IFNγ and TNFα or IFNγ and IL-1β. Induction of Aβ production was accompanied by decreased glycosylation of APP as well as by increased secretion of APPsβ. Our results suggest that astrocytes may be an important source of Aβ in the presence of certain combinations of inflammatory cytokines. IFNγ in combination with TNFα or IL-1β seems to trigger Aβ production by supporting β-secretase cleavage of the immature APP molecule.     

Fustin flavonoid attenuates β‐amyloid (1–42)‐induced learning impairment

Natural flavonoids ameliorate amyloid‐β peptide (Aβ)‐induced neurotoxicity. We examined whether the fustin flavonoid affects Aβ‐induced learning impairment in mice. Repeated treatment with fustin significantly attenuated Aβ (1–42)‐induced conditioned fear and passive avoidance behaviors. This effect was comparable to that of EGb761, a standard extract of ginkgo. Fustin treatment significantly prevented decreases in acetylcholine (ACh) levels, choline acetyltransferase (ChAT) activity, and ChAT gene expression induced by Aβ (1–42). Fustin also consistently suppressed increases in acetyl cholinesterase (AChE) activity and AChE gene expression induced by Aβ (1–42). In addition, fustin significantly attenuated Aβ (1–42)‐induced selective decreases in muscarinic M1 receptor gene expression and muscarinic M1 receptor binding activity (as determined by [³H]pirenzepine binding) by modulating extracellular signal‐regulated kinase 1/2 (ERK 1/2) and cAMP response‐element binding protein (CREB) phosphorylation and brain‐derived neurotrophic factor (BDNF) expression. These effects of fustin were reversed by treatment with dicyclomine, a muscarinic M1 receptor antagonist, and SL327, a selective ERK inhibitor, but not by chelerythrine, a pan‐protein kinase C (PKC) inhibitor. Taken together, our results suggest that fustin attenuates Aβ (1–42)‐impaired learning, and that the ERK/CREB/BDNF pathway is important for the M1 receptor‐mediated cognition‐enhancing effects of fustin. © 2009 Wiley‐Liss, Inc.