The microtubule-dynamin binding inhibitor peptide PHDP5 rescues spatial learning and memory deficits in Alzheimer's disease model mice.

Dynamin is a microtubule (MT) binding protein playing a key role in vesicle endocytosis. In a brain slice model, tau loaded in presynaptic terminals assembles MTs, thereby impairing vesicle endocytosis via depletion of cytosolic dynamin. The peptide PHDP5, derived from the pleckstrin homology domain of dynamin 1, inhibits dynamin-MT interaction and rescues endocytosis and synaptic transmission impaired by tau when co-loaded in presynaptic terminals. We tested whether in vivo administration of PHDP5 could rescue their learning/memory deficits observed in Alzheimer's disease (AD) model mice. A modified PHDP5 incorporating a cell-penetrating peptide (CPP) and a FITC fluorescent marker was delivered intranasally to Tau609 transgenic (Tg) and 3xTg-AD mice. FITC-positive puncta were observed in the hippocampus of mice infused with PHDP5 or scrambled (SPHDP5) peptide, but not in saline-infused controls. In the Morris water maze (MWM) test for spatial learning/memory, AD model mice treated with FITC-PHDP5-CPP showed prominent improvements in learning and memory, performing close to the level of saline-infused WT mice control. In contrast, mice treated with a scrambled construct (FITC-SPHDP5-CPP) showed no significant improvement. We conclude that PHDP5 can be a candidate for human AD therapy.

Investigating the efficacy of nasal administration for delivering magnetic nanoparticles into the brain for magnetic particle imaging.

This study explored the effectiveness of nasal administration in delivering magnetic nanoparticles into the brain for magnetic particle imaging of target regions. Successful delivery of iron oxide nanoparticles, which serve as contrast agents, to specific sites within the brain is crucial for achieving magnetic particle imaging. Nasal administration has gained attention as a method to bypass the blood-brain barrier and directly deliver therapeutics to the brain. In this study, we investigated surface modification techniques for administering magnetic nanoparticles into the nasal cavity, and provided experimental validation through in vivo studies. By compositing magnetic nanoparticles with gold nanoparticles, we enabled additional surface modification via AuS bonds without compromising their magnetic properties. The migration of the designed PEGylated magnetic nanoparticles into the brain following nasal administration was confirmed by magnetization measurements. Furthermore, we demonstrated the accumulation of these nanoparticles at specific target sites using probe molecules immobilized on the PEG terminus. Thus, the efficacy of delivering magnetic nanoparticles to the brain via nasal administration was demonstrated in this study. The findings of this research are expected to contribute significantly to the realization of magnetic particle imaging of target regions within the brain.

Hawaiian native herb Mamaki prevents dementia by ameliorating neuropathology and repairing neurons in four different mouse models of neurodegenerative diseases.

Neurodegenerative diseases including Alzheimer's disease, frontotemporal dementia, and dementia with Lewy bodies are age-related disorders and the main cause of dementia. They are characterized by the cerebral accumulation of Aß, tau, α-synuclein, and TDP-43. Because the accumulation begins decades before disease onset, treatment should be started in the preclinical stage. Such intervention would be long-lasting, and therefore, prophylactic agents should be safe, non-invasively taken by the patients, and inexpensive. In addition, the agents should be broadly effective against etiologic proteins and capable of repairing neurons damaged by toxic oligomers. These requirements are difficult to meet with single-ingredient pharmaceuticals but may be feasible by taking proper diets composed of multiple ingredients. As a source of such diets, we focused on the Hawaiian native herb Mamaki. From its dried leaves and fruits, we made three preparations: hot water extract of the leaves, non-extracted simple crush powder of the leaves, and simple crush powder of the fruits, and examined their effects on the cognitive function and neuropathologies in four different mouse models of neurodegenerative dementia. Hot water extract of the leaves attenuated neuropathologies, restored synaptophysin levels, suppressed microglial activation, and improved memory when orally administered for 1 month. Simply crushed leaf powder showed a higher efficacy, but simply crushed fruit powder displayed the strongest effects. Moreover, the fruit powder significantly enhanced the levels of brain-derived neurotrophic factor expression and neurogenesis, indicating its ability to repair neurons. These results suggest that crushed Mamaki leaves and fruits are promising sources of dementia-preventive diets.

C9orf72 Hexanucleotide Repeat Expansion-Related Neuropathology Is Attenuated by Nasal Rifampicin in Mice.

The non-coding GGGGCC hexanucleotide repeat expansion (HRE) in C9orf72 gene is a dominant cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). This intronic mutation elicits the formation of nuclear and cytoplasmic inclusions containing RNA, RNA-binding proteins, and HRE-derived dipeptide repeat proteins (DPRs), leading to neurodegeneration via the gain-of-toxic function or loss-of-function of relevant proteins. Using C9-500 mice harboring ~500 repeats of the GGGGCC sequence in human C9orf72 gene, we investigated the effects of rifampicin against HRE-related pathological phenotypes. Rifampicin was administered intranasally to 4.5- to 5-month-old mice for 1 month, and their cognitive function and neuropathology were assessed by the Morris water maze test and immunohistochemical staining. Rifampicin treatment reduced the formation of RNA foci and cytoplasmic inclusions containing DPRs or phosphorylated TDP-43, and furthermore, the levels of phosphorylated double-strand RNA-dependent protein kinase (PKR) that regulates repeat-associated non-ATG (RAN) translation. Synapse loss in the hippocampus and neuronal loss and microglial activation in the prefrontal and motor cortices were also attenuated, and mouse memory was significantly improved. Our findings suggest a therapeutic potential of nasal rifampicin in the prevention of C9orf72-linked neurodegenerative disorders.

Peripheral Aß acts as a negative modulator of insulin secretion.

Type 2 diabetes mellitus is known to be a risk factor for Alzheimer's disease (AD), but the underlying mechanisms remain unclear. In AD, the cerebral accumulation of amyloid ß (Aß) triggers a pathological cascade leading to neurodegeneration. Plasma Aß levels are thought to reflect the brain amyloid pathology and currently used as a diagnostic biomarker of AD. However, amyloid precursor protein and Aß-generating enzymes, ß- and γ-secretases, are widely expressed in various peripheral tissues. Previous reports have shown that glucose and insulin loading cause a transient increase of plasma Aß in mice and humans. These findings led us to speculate that plasma Aß is produced from glucose- and insulin-susceptible peripheral tissues to play a role in glucose and insulin metabolism. To test this hypothesis, we investigated the effects of glucose and insulin on Aß secretion and the effect of Aß on insulin secretion in vivo, ex vivo, and in vitro. Aß was found to be secreted from ß-cells of the pancreas along with insulin upon glucose stimulation. Upon insulin stimulation, Aß was secreted from cells of insulin-targeted organs, such as adipose tissues, skeletal muscles, and the liver, along with their organokines. Furthermore, Aß inhibited the glucose-triggered insulin secretion from ß-cells, slowing down glucose clearance from the blood. These results suggest that peripheral Aß acts as a negative modulator of insulin secretion. Our findings provide a possible mechanism linking diabetes to AD and call attention to how plasma Aß levels are used in AD diagnosis.

Nasal Rifampicin Halts the Progression of Tauopathy by Inhibiting Tau Oligomer Propagation in Alzheimer Brain Extract-Injected Mice.

The cell-to-cell transmission of tau aggregates is considered a mechanism underlying the intracerebral spreading of tau pathology in Alzheimer's disease (AD) and other tauopathies. Recent studies suggest that tau oligomers, rather than fibrils, participate in this process. We previously showed that intranasal rifampicin inhibits tau oligomer accumulation and improves cognition in tauopathy mice. In the present study, we examined the effects of nasal rifampicin on tau propagation in a new mouse model of tauopathy. A tau oligomer-rich fraction prepared from the brain of an AD patient was injected into a unilateral hippocampus of tau264 mice that express both 3-repeat and 4-repeat wild-type human tau. Rifampicin administration was started one week after the injection and performed three times a week for 24 weeks. Cognitive function and tau pathology were assessed by the Morris water maze test and brain section staining. Rifampicin treatment inhibited the spreading of tau oligomers from the injection site to other brain regions and neurofibrillary tangle formation in the entorhinal cortex. Synapse and neuronal loss in the hippocampus were also prevented, and cognitive function remained normal. These results suggest that intranasal rifampicin could be a promising remedy that halts the progression of tauopathy by inhibiting tau oligomer propagation.

Oligomer-Targeting Prevention of Neurodegenerative Dementia by Intranasal Rifampicin and Resveratrol Combination - A Preclinical Study in Model Mice.

Amyloidogenic protein oligomers are thought to play an important role in the pathogenesis of neurodegenerative dementia, including Alzheimer's disease, frontotemporal dementia, and dementia with Lewy bodies. Previously we demonstrated that oral or intranasal rifampicin improved the cognition of APP-, tau-, and α-synuclein-transgenic mice by reducing the amount of Aß, tau, and α-synuclein oligomers in the brain. In the present study, to explore more effective and safer medications for dementia, we tested the drug combination of rifampicin and resveratrol, which is a multifunctional natural polyphenol with the potential to antagonize the adverse effects of rifampicin. The mixture was intranasally administered to APP-, tau-, and α-synuclein-transgenic mice, and their memory and oligomer-related pathologies were evaluated. Compared with rifampicin and resveratrol alone, the combinatorial medicine significantly improved mouse cognition, reduced amyloid oligomer accumulation, and recovered synaptophysin levels in the hippocampus. The plasma levels of liver enzymes, which reflect hepatic injury and normally increase by rifampicin treatment, remained normal by the combination treatment. Notably, resveratrol alone and the combinatorial medicine, but not rifampicin alone, enhanced the levels of brain-derived neurotrophic factor (BDNF) and its precursor, pro-BDNF, in the hippocampus. Furthermore, the combination showed a synergistic effect in ameliorating mouse cognition. These results show the advantages of this combinatorial medicine with regards to safety and effectiveness over single-drug rifampicin. Our findings may provide a feasible means for the prevention of neurodegenerative dementia that targets toxic oligomers.

Nasal Rifampicin Improves Cognition in a Mouse Model of Dementia with Lewy Bodies by Reducing α-Synuclein Oligomers.

α-Synuclein oligomers are thought to play an important role in the pathogenesis of dementia with Lewy bodies (DLB). There is no effective cure for DLB at present. Previously, we demonstrated that in APP- and tau-transgenic mice, oral or intranasal rifampicin reduced brain Aß and tau oligomers and improved mouse cognition. In the present study, we expanded our research to DLB. Rifampicin was intranasally administered to 6-month-old A53T-mutant α-synuclein-transgenic mice at 0.1 mg/day for 1 month. The mice displayed memory impairment but no motor deficit at this age, indicating a suitable model of DLB. α-Synuclein pathologies were examined by the immunohistochemical/biochemical analyses of brain tissues. Cognitive function was evaluated by the Morris water maze test. Intranasal rifampicin significantly reduced the levels of [pSer129] α-synuclein in the hippocampus and α-synuclein oligomers in the visual cortex and hippocampus. The level of the presynaptic marker synaptophysin in the hippocampus was recovered to the level in non-transgenic littermates. In the Morris water maze, a significant improvement in spatial reference memory was observed in rifampicin-treated mice. Taken together with our previous findings, these results suggest that intranasal rifampicin is a promising remedy for the prevention of neurodegenerative dementia, including Alzheimer's disease, frontotemporal dementia, and DLB.

Visualizing and Evaluating Finger Movement Using Combined Acceleration and Contact-Force Sensors: A Proof-of-Concept Study.

The 10-s grip and release is a method to evaluate hand dexterity. Current evaluations only visually determine the presence or absence of a disability, but experienced physicians may also make other diagnoses. In this study, we investigated a method for evaluating hand movement function by acquiring and analyzing fingertip data during a 10-s grip and release using a wearable sensor that can measure triaxial acceleration and strain. The subjects were two healthy females. The analysis was performed on the x-, y-, and z-axis data, and absolute acceleration and contact force of all fingertips. We calculated the variability of the data, the number of grip and release, the frequency response, and each finger's correlation. Experiments with some grip-and-release patterns have resulted in different characteristics for each. It was suggested that this could be expressed in radar charts to intuitively know the state of grip and release. Contact-force data of each finger were found to be useful for understanding the characteristics of grip and release and improving the accuracy of calculating the number of times to grip and release. Frequency analysis suggests that knowing the periodicity of grip and release can detect unnatural grip and release and tremor states. The correlations between the fingers allow us to consider the finger's grip-and-release characteristics, considering the hand's anatomy. By taking these factors into account, it is thought that the 10-s grip-and-release test could give us a new value by objectively assessing the motor functions of the hands other than the number of times of grip and release.

Fabrication of novel bone haemostasis sheet by using sugar-containing hydroxyapatite and plant-derived polymer.

The fabrication conditions of bone-haemostasis sheet were examined by using (i) phosphoryl oligosaccharides of calcium (POs-Ca), sugar-containing hydroxyapatite (s-Ca10(PO4)6(OH)2: s-HAp) derived from POs-Ca and (ii) natural plant-derived polymers (locust bean gum (LBG), guar gum (GG) and alginate (AG)). The sol, which had been prepared by dissolving 2 mass% LBG/GG and 2 mass% AG into 200 cm3 deionized water and then by agitating at the speed of 20 000 r.p.m., was immersed into 3 mass% POs-Ca solution at room temperature for 24 h; it was hydrothermally treated at 100°C for 5 h, and then freeze-dried at -50°C for 24 h to form porous composite sheet. The microscopic observation showed that the pore sizes were controlled in the range of 5-100 µm by the optimization of LBG/GG ratio. The composite sheet showed the noted uptake of simulated body fluid (1426%) at 37.0°C and also the human blood. Thus, the porous composite sheet was found to be a promising candidate of the bone haemostasis, on the basis of the data of haemostasis, uptake ability of SBF and solubility in acetic acid-sodium acetate buffer solution.

Intranasal rifampicin for Alzheimer's disease prevention.

INTRODUCTION: Oral rifampicin has been shown to significantly reduce amyloid ß (Aß) and tau pathologies in mice. However, it shows occasional adverse effects such as liver injury in humans, making its use difficult for a long period. METHODS: To explore safer rifampicin treatment, APPOSK mice, a model of Alzheimer's disease, were treated with rifampicin for 1 month via oral, intranasal, and subcutaneous administration, and its therapeutic efficacy and safety were compared. RESULTS: Intranasal or subcutaneous administration of rifampicin improved memory more effectively than oral administration. The improvement of memory was accompanied with the reduction of neuropathologies, including Aß oligomer accumulation, tau abnormal phosphorylation, and synapse loss. Serum levels of a liver enzyme significantly rose only by oral administration. Pharmacokinetic study revealed that the level of rifampicin in the brain was highest with intranasal administration. DISCUSSION: Considering its easiness and noninvasiveness, intranasal administration would be the best way for long-term dosing of rifampicin.

Mutation-induced loss of APP function causes GABAergic depletion in recessive familial Alzheimer's disease: analysis of Osaka mutation-knockin mice.

The E693Δ (Osaka) mutation in APP is linked to familial Alzheimer's disease. While this mutation accelerates amyloid ß (Aß) oligomerization, only patient homozygotes suffer from dementia, implying that this mutation is recessive and causes loss-of-function of amyloid precursor protein (APP). To investigate the recessive trait, we generated a new mouse model by knocking-in the Osaka mutation into endogenous mouse APP. The produced homozygous, heterozygous, and non-knockin littermates were compared for memory, neuropathology, and synaptic plasticity. Homozygotes showed memory impairment at 4 months, whereas heterozygotes did not, even at 8 months. Immunohistochemical and biochemical analyses revealed that only homozygotes displayed intraneuronal accumulation of Aß oligomers at 8 months, followed by abnormal tau phosphorylation, synapse loss, glial activation, and neuron loss. These pathologies were not observed at younger ages, suggesting that a certain mechanism other than Aß accumulation underlies the memory disturbance at 4 months. For the electrophysiology studies at 4 months, high-frequency stimulation evoked long-term potentiation in all mice in the presence of picrotoxin, but in the absence of picrotoxin, such potentiation was observed only in homozygotes, suggesting their GABAergic deficit. In support of this, the levels of GABA-related proteins and the number of dentate GABAergic interneurons were decreased in 4-month-old homozygotes. Since APP has been shown to play a role in dentate GABAergic synapse formation, the observed GABAergic depletion is likely associated with an impairment of the APP function presumably caused by the Osaka mutation. Oral administration of diazepam to homozygotes from 6 months improved memory at 8 months, and furthermore, prevented Aß oligomer accumulation, indicating that GABAergic deficiency is a cause of memory impairment and also a driving force of Aß accumulation. Our findings suggest that the Osaka mutation causes loss of APP function, leading to GABAergic depletion and memory disorder when wild-type APP is absent, providing a mechanism of the recessive heredity.

How Live Performance Moves the Human Heart.

We investigated how the audience member's physiological reactions differ as a function of listening context (i.e., live versus recorded music contexts). Thirty-seven audience members were assigned to one of seven pianists' performances and listened to his/her live performances of six pieces (fast and slow pieces by Bach, Schumann, and Debussy). Approximately 10 weeks after the live performance, each of the audience members returned to the same room and listened to the recorded performances of the same pianists' via speakers. We recorded the audience members' electrocardiograms in listening to the performances in both conditions, and analyzed their heart rates and the spectral features of the heart-rate variability (i.e., HF/TF, LF/HF). Results showed that the audience's heart rate was higher for the faster than the slower piece only in the live condition. As compared with the recorded condition, the audience's sympathovagal balance (LF/HF) was less while their vagal nervous system (HF/TF) was activated more in the live condition, which appears to suggest that sharing the ongoing musical moments with the pianist reduces the audience's physiological stress. The results are discussed in terms of the audience's superior attention and temporal entrainment to live performance.

Rifampicin is a candidate preventive medicine against amyloid-ß and tau oligomers.

Amyloid-ß, tau, and α-synuclein, or more specifically their soluble oligomers, are the aetiologic molecules in Alzheimer's disease, tauopathies, and α-synucleinopathies, respectively. These proteins have been shown to interact to accelerate each other's pathology. Clinical studies of amyloid-ß-targeting therapies in Alzheimer's disease have revealed that the treatments after disease onset have little benefit on patient cognition. These findings prompted us to explore a preventive medicine which is orally available, has few adverse effects, and is effective at reducing neurotoxic oligomers with a broad spectrum. We initially tested five candidate compounds: rifampicin, curcumin, epigallocatechin-3-gallate, myricetin, and scyllo-inositol, in cells expressing amyloid precursor protein (APP) with the Osaka (E693Δ) mutation, which promotes amyloid-ß oligomerization. Among these compounds, rifampicin, a well-known antibiotic, showed the strongest activities against the accumulation and toxicity (i.e. cytochrome c release from mitochondria) of intracellular amyloid-ß oligomers. Under cell-free conditions, rifampicin inhibited oligomer formation of amyloid-ß, tau, and α-synuclein, indicating its broad spectrum. The inhibitory effects of rifampicin against amyloid-ß and tau oligomers were evaluated in APPOSK mice (amyloid-ß oligomer model), Tg2576 mice (Alzheimer's disease model), and tau609 mice (tauopathy model). When orally administered to 17-month-old APPOSK mice at 0.5 and 1 mg/day for 1 month, rifampicin reduced the accumulation of amyloid-ß oligomers as well as tau hyperphosphorylation, synapse loss, and microglial activation in a dose-dependent manner. In the Morris water maze, rifampicin at 1 mg/day improved memory of the mice to a level similar to that in non-transgenic littermates. Rifampicin also inhibited cytochrome c release from the mitochondria and caspase 3 activation in the hippocampus. In 13-month-old Tg2576 mice, oral rifampicin at 0.5 mg/day for 1 month decreased amyloid-ß oligomer accumulation, tau hyperphosphorylation, synapse loss, and microglial activation, but not amyloid deposition. Rifampicin treatment to 14-15-month-old tau609 mice at 0.5 and 1 mg/day for 1 month also reduced tau oligomer accumulation, tau hyperphosphorylation, synapse loss, and microglial activation in a dose-dependent fashion, and improved the memory almost completely at 1 mg/day. In addition, rifampicin decreased the level of p62/sequestosome-1 in the brain without affecting the increased levels of LC3 (microtubule-associated protein light chain 3) conversion, suggesting the restoration of autophagy-lysosomal function. Considering its prescribed dose and safety in humans, these results indicate that rifampicin could be a promising, ready-to-use medicine for the prevention of Alzheimer's disease and other neurodegenerative diseases.

Intracellular amyloid ß oligomers impair organelle transport and induce dendritic spine loss in primary neurons.

INTRODUCTION: Synaptic dysfunction and intracellular transport defects are early events in Alzheimer's disease (AD). Extracellular amyloid ß (Aß) oligomers cause spine alterations and impede the transport of proteins and organelles such as brain-derived neurotrophic factor (BDNF) and mitochondria that are required for synaptic function. Meanwhile, intraneuronal accumulation of Aß precedes its extracellular deposition and is also associated with synaptic dysfunction in AD. However, the links between intracellular Aß, spine alteration, and mechanisms that support synaptic maintenance such as organelle trafficking are poorly understood. RESULTS: We compared the effects of wild-type and Osaka (E693Δ)-mutant amyloid precursor proteins: the former secretes Aß into extracellular space and the latter accumulates Aß oligomers within cells. First we investigated the effects of intracellular Aß oligomers on dendritic spines in primary neurons and their tau-dependency using tau knockout neurons. We found that intracellular Aß oligomers caused a reduction in mushroom, or mature spines, independently of tau. We also found that intracellular Aß oligomers significantly impaired the intracellular transport of BDNF, mitochondria, and recycling endosomes: cargoes essential for synaptic maintenance. A reduction in BDNF transport by intracellular Aß oligomers was also observed in tau knockout neurons. CONCLUSIONS: Our findings indicate that intracellular Aß oligomers likely contribute to early synaptic pathology in AD and argue against the consensus that Aß-induced spine loss and transport defects require tau.

Passive immunotherapy of tauopathy targeting pSer413-tau: a pilot study in mice.

OBJECTIVE: Cellular inclusions of hyperphosphorylated tau are a hallmark of tauopathies, which are neurodegenerative disorders that include Alzheimer's disease (AD). Active and passive immunization against hyperphosphorylated tau has been shown to attenuate phenotypes in model mice. We developed new monoclonal antibodies to hyperphosphorylated tau and sought high therapeutic efficacy for future clinical use. METHODS: Using more than 20 antibodies, we investigated which sites on tau are phosphorylated early and highly in the tauopathy mouse models tau609 and tau784. These mice display tau hyperphosphorylation, synapse loss, memory impairment at 6 months, and tangle formation and neuronal loss at 15 months. We generated mouse monoclonal antibodies to selected epitopes and examined their effects on memory and tau pathology in aged tau609 and tau784 mice by the Morris water maze and by histological and biochemical analyses. RESULTS: Immunohistochemical screening revealed that pSer413 is expressed early and highly. Monoclonal antibodies to pSer413 and to pSer396 (control) were generated. These antibodies specifically recognized pathological tau in AD brains but not normal tau in control brains according to Western blots. Representative anti-pSer413 and anti-pSer396 antibodies were injected intraperitoneally into 10-11- or 14-month-old mice once a week at 0.1 or 1 mg/shot 5 times. The anti-pSer413 antibody significantly improved memory, whereas the anti-pSer396 antibodies showed less effect. The cognitive improvement paralleled a reduction in the levels of tau hyperphosphorylation, tau oligomer accumulation, synapse loss, tangle formation, and neuronal loss. INTERPRETATION: These results indicate that pSer413 is a promising target in the treatment of tauopathy.

Neurofibrillary tangle formation by introducing wild-type human tau into APP transgenic mice.

Senile plaques comprised of Aß aggregates and neurofibrillary tangles (NFTs) composed of hyperphosphorylated tau filaments are the hallmarks of Alzheimer's disease (AD). A number of amyloid precursor protein (APP) transgenic (Tg) mice harboring APP mutations have been generated as animal models of AD. These mice successfully display amyloid plaque formation and subsequent tau hyperphosphorylation, but seldom induce NFT formations. We have demonstrated that the APPOSK-Tg mice, which possess the E693Δ (Osaka) mutation in APP and thereby accumulate Aß oligomers without plaques, exhibit tau hyperphosphorylation at 8 months, but not NFT formation even at 24 months. We assumed that APP-Tg mice, including ours, failed to form NFTs because NFT formation requires human tau. To test this hypothesis, we crossbred APPOSK-Tg mice with tau-Tg mice (tau264), which express low levels of 3-repeat and 4-repeat wild-type human tau without any pathology. The resultant double Tg mice displayed tau hyperphosphorylation at 6 months and NFT formation at 18 months in the absence of tau mutations. Importantly, these NFTs contained both 3-repeat and 4-repeat human tau, similar to those in AD. Furthermore, the double Tg mice exhibited Aß oligomer accumulation, synapse loss, and memory impairment at 6 months and neuronal loss at 18 months, all of which appeared earlier than in the parent APPOSK-Tg mice. These results suggest that Aß and human tau synergistically interact to accelerate each other's pathology, that the presence of human tau is critical for NFT formation, and that Aß oligomers can induce NFTs in the absence of amyloid plaques.

The E693Δ (Osaka) mutation in amyloid precursor protein potentiates cholesterol-mediated intracellular amyloid ß toxicity via its impaired cholesterol efflux.

It has been shown that amyloid ß (Aß) secretion regulates cholesterol efflux from cells and that the E693Δ (Osaka) mutation in amyloid precursor protein (APP) promotes intracellular accumulation of Aß and thus reduces its secretion. These findings led us to speculate that APP with the Osaka mutation (APPOSK ) might have a defect in cholesterol efflux and thus cause cellular malfunction. We therefore examined the effects of this mutation on intracellular cholesterol transport and efflux in cultured cells. Upon cholesterol loading, APPOSK -expressing cells exhibited higher levels of cellular cholesterol than wild-type APP-expressing cells, suggesting impaired cholesterol efflux. It is known that, after its internalization, cholesterol is transported from the endosomes to the endoplasmic reticulum (ER) and Golgi apparatus and then to the plasma membrane. In APPOSK -expressing cells, cholesterol accumulated with Aß in the ER and Golgi apparatus and alone in endosomes/lysosomes. These results imply that the mutation-induced disturbance of Aß trafficking from the ER to the plasma membrane affects cholesterol transport to cause cholesterol accumulation in the ER and Golgi apparatus and, consequently, in endosomes. Furthermore, we detected an enhanced mitochondrial accumulation of Aß and cholesterol in APPOSK -expressing cells, and this was accompanied by an increase in the generation of reactive oxygen species (ROS). The present findings suggest that Aß trafficking is important for intracellular cholesterol transport and efflux and that the Osaka mutation potentiates cholesterol-dependent exacerbation of intracellular Aß toxicity, i.e. Aß-induced ROS generation, by disturbing Aß-mediated cholesterol efflux from the cell.

Neurodegenerative disorder FTDP-17-related tau intron 10 +16C → T mutation increases tau exon 10 splicing and causes tauopathy in transgenic mice.

Frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) is a neurodegenerative disorder caused by mutations in the tau gene. Many mutations identified in FTDP-17 have been shown to affect tau exon 10 splicing in vitro, which presumably causes pathologic imbalances in exon 10(-) [3-repeat (3R)] and exon 10(+) [4-repeat (4R)] tau expression and leads to intracellular inclusions of hyperphosphorylated tau in patient brains. However, no reports have investigated this theory using model mice with a tau intronic mutation. Herein, we generated new transgenic mice harboring the tau intron 10 +16C → T mutation. We prepared a transgene construct containing intronic sequences required for exon 10 splicing in the longest tau isoform cDNA. Although mice bearing the construct without the intronic mutation showed normal developmental changes of the tau isoform from 3R tau to equal amounts of 3R and 4R tau, mice with the mutation showed much higher levels of 4R tau at the adult stage. 4R tau was selectively recovered in insoluble brain fractions in their old age. Furthermore, these mice displayed abnormal tau phosphorylation, synapse loss and dysfunction, memory impairment, glial activation, tangle formation, and neuronal loss in an age-dependent manner. These findings provide the first evidence in a mouse model that a tau intronic mutation-induced imbalance of 3R and 4R tau could be a cause of tauopathy.

Hypercholesterolemia accelerates intraneuronal accumulation of Aß oligomers resulting in memory impairment in Alzheimer's disease model mice.

AIMS: Hypercholesterolemia is known to be a risk factor for Alzheimer's disease (AD), and diet-induced hypercholesterolemia has been shown to accelerate amyloid pathology in animals. While growing evidence has shown that synaptic and cognitive dysfunction in AD is associated with intraneuronal accumulation of Aß, the relationships between hypercholesterolemia, memory impairment, and intraneuronal Aß remains unclear. The present study aims to clarify this association. MAIN METHODS: Transgenic mice expressing amyloid precursor protein (APP) harboring the Osaka (E693∆) mutation (APP(OSK)-Tg mice) were used. These mice exhibit intraneuronal Aß oligomers and memory impairment from 8months of age. Five-month-old male APP(OSK)-Tg mice and non-Tg littermates were fed a high-cholesterol diet for 1 month to induce hypercholesterolemia. At 6 months of age, their cognitive function was evaluated by the Morris water maze. Intraneuronal Aß, synaptic density, and tau phosphorylation were examined by immunohistochemistry. KEY FINDINGS: Serum and brain cholesterol levels were significantly higher in APP(OSK)-Tg mice and non-Tg littermates that were fed a high-cholesterol diet than in control mice that were fed normal chow, indicating that hypercholesterolemia was successfully induced. Hypercholesterolemic APP(OSK)-Tg mice, but not control APP(OSK)-Tg mice or hypercholesterolemic non-Tg littermates, exhibited impaired spatial reference memory, which was accompanied with intraneuronal accumulation of Aß oligomers, reduced synaptophysin immunoreactivity, and abnormal tau phosphorylation in the hippocampus. Hypercholesterolemia-accelerated accumulation of intraneuronal Aß oligomers was also observed in another model mouse, Tg2576. SIGNIFICANCE: Our findings suggest that hypercholesterolemia accelerates intraneuronal accumulation of Aß oligomers and subsequent synapse loss, resulting in memory impairment.