Amyloid-Driven Tau Accumulation on Mitochondria Potentially Leads to Cognitive Deterioration in Alzheimer's Disease.

Despite the well-accepted role of the two main neuropathological markers (ß-amyloid and tau) in the progression of Alzheimer's disease, the interaction and specific contribution of each of them is not fully elucidated. To address this question, in the present study, an adeno-associated virus (AAV9) carrying the mutant P301L form of human tau, was injected into the dorsal hippocampi of APP/PS1 transgenic mice or wild type mice (WT). Three months after injections, memory tasks, biochemical and immunohistochemical analysis were performed. We found that the overexpression of hTauP301L accelerates memory deficits in APP/PS1 mice, but it did not affect memory function of WT mice. Likewise, biochemical assays showed that only in the case of APP/PS1-hTauP301L injected mice, an important accumulation of tau was observed in the insoluble urea fraction. Similarly, electron microscopy images revealed that numerous clusters of tau immunoparticles appear at the dendrites of APP/PS1 injected mice and not in WT animals, suggesting that the presence of amyloid is necessary to induce tau aggregation. Interestingly, these tau immunoparticles accumulate in dendritic mitochondria in the APP/PS1 mice, whereas most of mitochondria in WT injected mice remain free of tau immunoparticles. Taken together, it seems that amyloid induces tau aggregation and accumulation in the dendritic mitochondria and subsequently may alter synapse function, thus, contributing to accelerate cognitive decline in APP/PS1 mice.

Liver Bile Acid Changes in Mouse Models of Alzheimer's Disease.

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive cognitive impairment. It is hypothesized to develop due to the dysfunction of two major proteins, amyloid-ß (Aß) and microtubule-associated protein, tau. Evidence supports the involvement of cholesterol changes in both the generation and deposition of Aß. This study was performed to better understand the role of liver cholesterol and bile acid metabolism in the pathophysiology of AD. We used male and female wild-type control (C57BL/6J) mice to compare to two well-characterized amyloidosis models of AD, APP/PS1, and AppNL-G-F. Both conjugated and unconjugated primary and secondary bile acids were quantified using UPLC-MS/MS from livers of control and AD mice. We also measured cholesterol and its metabolites and identified changes in levels of proteins associated with bile acid synthesis and signaling. We observed sex differences in liver cholesterol levels accompanied by differences in levels of synthesis intermediates and conjugated and unconjugated liver primary bile acids in both APP/PS1 and AppNL-G-F mice when compared to controls. Our data revealed fundamental deficiencies in cholesterol metabolism and bile acid synthesis in the livers of two different AD mouse lines. These findings strengthen the involvement of liver metabolism in the pathophysiology of AD.

P38α-MAPK phosphorylates Snapin and reduces Snapin-mediated BACE1 transportation in APP-transgenic mice.

Amyloid ß peptide (Aß) is the major pathogenic molecule in Alzheimer's disease (AD). BACE1 enzyme is essential for the generation of Aß. Deficiency of p38α-MAPK in neurons increases lysosomal degradation of BACE1 and decreases Aß deposition in the brain of APP-transgenic mice. However, the mechanisms mediating effects of p38α-MAPK are largely unknown. In this study, we used APP-transgenic mice and cultured neurons and observed that deletion of p38α-MAPK specifically in neurons decreased phosphorylation of Snapin at serine, increased retrograde transportation of BACE1 in axons and reduced BACE1 at synaptic terminals, which suggests that p38α-MAPK deficiency promotes axonal transportation of BACE1 from its predominant locations, axonal terminals, to lysosomes in the cell body. In vitro kinase assay revealed that p38α-MAPK directly phosphorylates Snapin. By further performing mass spectrometry analysis and site-directed mutagenic experiments in SH-SY5Y cell lines, we identified serine residue 112 as a p38α-MAPK-phosphorylating site on Snapin. Replacement of serine 112 with alanine did abolish p38α-MAPK knockdown-induced reduction of BACE1 activity and protein level, and transportation to lysosomes in SH-SY5Y cells. Taken together, our study suggests that activation of p38α-MAPK phosphorylates Snapin and inhibits the retrograde transportation of BACE1 in axons, which might exaggerate amyloid pathology in AD brain.

Post-transcriptional regulation of α7 nAChR expression by miR-98-5p modulates cognition and neuroinflammation in an animal model of Alzheimer's disease.

Alzheimer's disease (AD) is a complicated neurodegenerative disease and therefore addressing multiple targets simultaneously has been believed as a promising therapeutic strategy against AD. α7 nicotinic acetylcholine receptor (nAChR), which plays an important role in improving cognitive function and alleviating neuroinflammation in central nervous system (CNS), has been regarded as a potential target in the treatment of AD. However, the regulation of α7 nAChR at post-transcriptional level in mammalian brain remains largely speculated. Herein, we uncovered a novel post-transcriptional regulatory mechanism of α7 nAChR expression in AD and further demonstrated that miR-98-5p suppressed α7 nAChR expression through directly binding to the 3'UTR of mRNA. Knockdown of miR-98-5p activated Ca2+ signaling pathway and consequently reversed cognitive deficits and Aß burden in APP/PS1 mice. Furthermore, miR-98-5p downregulation increased α7 nAChR expression, and ameliorated neuroinflammation via inhibiting NF-κB pathway and upregulating Nrf2 target genes. Our findings illustrate a prominent regulatory role of miR-98-5p in targeting inflammation and cognition, and provide an insight into the potential of miR-98-5p/α7 nAChR axis as a novel therapeutic strategy for AD.

TUFM is involved in Alzheimer's disease-like pathologies that are associated with ROS.

Mitochondrial Tu translation elongation factor (TUFM or EF-Tu) is part of the mitochondrial translation machinery. It is reported that TUFM expression is reduced in the brain of Alzheimer's disease (AD), suggesting that TUFM might play a role in the pathophysiology. In this study, we found that TUFM protein level was decreased in the hippocampus and cortex especially in the aged APP/PS1 mice, an animal model of AD. In HEK cells that stably express full-length human amyloid-ß precursor protein (HEK-APP), TUFM knockdown or overexpression increased or reduced the protein levels of ß-amyloid protein (Aß) and ß-amyloid converting enzyme 1 (BACE1), respectively. TUFM-mediated reduction of BACE1 was attenuated by translation inhibitor cycloheximide (CHX) or α-[2-[4-(3,4-Dichlorophenyl)-2-thiazolyl]hydrazinylidene]-2-nitro-benzenepropanoic acid (4EGI1), and in cells overexpressing BACE1 constructs deleting the 5' untranslated region (5'UTR). TUFM silencing increased the half-life of BACE1 mRNA, suggesting that RNA stability was affected by TUFM. In support, transcription inhibitor Actinomycin D (ActD) and silencing of nuclear factor κB (NFκB) failed to abolish TUFM-mediated regulation of BACE1 protein and mRNA. We further found that the mitochondria-targeted antioxidant TEMPO diminished the effects of TUFM on BACE1, suggesting that reactive oxygen species (ROS) played an important role. Indeed, cellular ROS levels were affected by TUFM knockdown or overexpression, and TUFM-mediated regulation of apoptosis and Tau phosphorylation at selective sites was attenuated by TEMPO. Collectively, TUFM protein levels were decreased in APP/PS1 mice. TUFM is involved in AD pathology by regulating BACE1 translation, apoptosis, and Tau phosphorylation, in which ROS plays an important role.

Reactive or transgenic increase in microglial TYROBP reveals a TREM2-independent TYROBP-APOE link in wild-type and Alzheimer's-related mice.

INTRODUCTION: Microglial TYROBP (DAP12) is a network hub and driver in sporadic late-onset Alzheimer's disease (AD). TYROBP is a cytoplasmic adaptor for TREM2 and other receptors, but little is known about its roles and actions in AD. Herein, we demonstrate that endogenous Tyrobp transcription is specifically increased in recruited microglia. METHODS: Using a novel transgenic mouse overexpressing TYROBP in microglia, we observed a decrease of the amyloid burden and an increase of TAU phosphorylation stoichiometry when crossed with APP/PSEN1 or MAPTP301S mice, respectively. Characterization of these mice revealed Tyrobp-related modulation of apolipoprotein E (Apoe) transcription. We also showed that Tyrobp and Apoe mRNAs were increased in Trem2-null microglia recruited around either amyloid beta deposits or a cortical stab injury. Conversely, microglial Apoe transcription was dramatically diminished when Tyrobp was absent. CONCLUSIONS: Our results provide evidence that TYROBP-APOE signaling does not require TREM2 and could be an initiating step in establishment of the disease-associated microglia (DAM) phenotype.

ß2-adrenergic Agonists Rescue Lysosome Acidification and Function in PSEN1 Deficiency by Reversing Defective ER-to-lysosome Delivery of ClC-7.

Lysosomal dysfunction is considered pathogenic in Alzheimer disease (AD). Loss of presenilin-1 (PSEN1) function causing AD impedes acidification via defective vacuolar ATPase (vATPase) V0a1 subunit delivery to lysosomes. We report that isoproterenol (ISO) and related ß2-adrenergic agonists reacidify lysosomes in PSEN1 Knock out (KO) cells and fibroblasts from PSEN1 familial AD patients, which restores lysosomal proteolysis, calcium homeostasis, and normal autophagy flux. We identify a novel rescue mechanism involving Portein Kinase A (PKA)-mediated facilitation of chloride channel-7 (ClC-7) delivery to lysosomes which reverses markedly lowered chloride (Cl-) content in PSEN1 KO lysosomes. Notably, PSEN1 loss of function impedes Endoplasmic Reticulum (ER)-to-lysosome delivery of ClC-7. Transcriptomics of PSEN1-deficient cells reveals strongly downregulated ER-to-lysosome transport pathways and reversibility by ISO, thus accounting for lysosomal Cl- deficits that compound pH elevation due to deficient vATPase and its rescue by ß2-adrenergic agonists. Our findings uncover a broadened PSEN1 role in lysosomal ion homeostasis and novel pH modulation of lysosomes through ß2-adrenergic regulation of ClC-7, which can potentially be modulated therapeutically.

Effects of progesterone on glucose uptake in neurons of Alzheimer's disease animals and cell models.

AIMS: Alzheimer's disease (AD) is closely related to abnormal glucose metabolism in the central nervous system. Progesterone has been shown to have obvious neuroprotective effects in the pathogenesis of AD, but the specific mechanism has not been fully elucidated. Therefore, the purpose of this study was to investigate the effect of progesterone on the glucose metabolism of neurons in amyloid precursor protein (APP)/presenilin 1 (PS1) mice and Aß-induced AD cell model. MATERIALS AND METHODS: APP/PS1 mice were treated with 40 mg/kg progesterone for 40 days and primary cultured cortical neurons were treated with 1 µM progesterone for 48 h.Then behavior tests,2-NBDG glucose uptake tests and the protein levels of glucose transporter 3 (GLUT3), GLUT4, cAMP-response element binding protein (CREB) and proliferator-activated receptor γ (PPARγ) were examined. KEY FINDINGS: Progesterone increased the expression levels of GLUT3 and GLUT4 in the cortex of APP/PS1 mice, accompanied by an improvement in learning and memory. Progesterone increased the levels of CREB and PPARγ in the cerebral cortex of APP/PS1 mice. In vitro, progesterone increased glucose uptake in primary cultured cortical neurons, this effect was blocked by the progesterone receptor membrane component 1 (PGRMC1)-specific blocker AG205 but not by the progesterone receptor (PR)-specific blocker RU486. Meanwhile, progesterone increased the expression of GLUT3, GLUT4, CREB and PPARγ, and AG205 blocked this effect. SIGNIFICANCE: These results confirm that progesterone significantly improves the glucose metabolism of neurons.One of the mechanisms of this effect is that progesterone upregulates protein expression of GLUT3 and GLUT4 through pathways PGRMC1/CREB/GLUT3 and PGRMC1/PPARγ/GLUT4.

Plasmon-Activated Water Reduces Amyloid Burden and Improves Memory in Animals with Alzheimer's Disease.

With the great extension of the human lifespan in recent times, many aging diseases have inevitably followed. Dementia is one of the most-commom neurodegenerative aging diseases, in which inflammation-related Alzheimer's disease (AD) is the most prevalent cause of dementia. Amyloid accumulation in the brain, which occurs before any clinical presentations, might be the first and key step in the development of AD. However, many clinical trials have attempted to remove amyloid from brains of AD patients, but none has so far been successful. Negatively charged plasmon-activated water (PAW) is created by resonantly illuminated gold (Au) nanoparticles (NPs), which reduce the hydrogen-bonded (HB) structure of water. PAW was found to possess anti-oxidative and anti-inflammatory effects. Herein, we report on an innovative strategy to retard the progression of AD by the daily consumption of PAW instead of normal deionized (DI) water. APPswe/PS1dE9 transgenic mice were treated with PAW or DI water from the age of 5 months for the next 9 months. Encouragingly, compared to DI water-treated mice, mice treated with PAW presented better memory performance on a test of novel object recognition and had a significantly lower amyloid burden according to 18F-florbetapir amyloid-PET and phosphorylated (p)-tau burden according to Western blotting and immunohistochemistry measurements. There were no obvious side effects in PAW-treated mice. Collectively, our findings support that PAW was able to reduce the amyloid and p-tau burden and improve memory in an AD mouse model. However, the protein levels of molecules involved in amyloid metabolism and oligomeric amyloid did not change. We propose that the effects of PAW of reducing the amyloid burden and improving memory function cannot be attributed to synthesis/degradation of amyloid-ßprotein but probably in preventing aggregation of amyloid-ß proteins or other mechanisms, including anti-inflammation. Further applications of PAW in clinical trials to prevent the progression of AD are being designed.

Evaluation of Hemisphere Lateralization with Bilateral Local Field Potential Recording in Secondary Motor Cortex of Mice.

This article demonstrates complete, detailed procedures for both in vivo bilateral recording and analysis of local field potential (LFP) in the cortical areas of mice, which are useful for evaluating possible laterality deficits, as well as for assessing brain connectivity and coupling of neural network activities in rodents. The pathological mechanisms underlying Alzheimer's disease (AD), a common neurodegenerative disease, remain largely unknown. Altered brain laterality has been demonstrated in aging people, but whether or not abnormal lateralization is one of the early signs of AD has not been determined. To investigate this, we recorded bilateral LFPs in 3-5-month-old AD model mice, APP/PS1, together with littermate wild type (WT) controls. The LFPs of the left and right secondary motor cortex (M2), specifically in the gamma band, were more synchronized in APP/PS1 mice than in WT controls, suggesting a declined hemispheric asymmetry of bilateral M2 in this AD mouse model. Notably, the recording and data analysis processes are flexible and easy to carry out, and can also be applied to other brain pathways when conducting experiments that focus on neuronal circuits.

Individual and combined presenilin 1 and 2 knockouts reveal that both have highly overlapping functions in HEK293T cells.

Presenilins 1 and 2 (PS1 and 2) are the catalytic subunits of γ-secretase, a multiprotein protease that cleaves amyloid protein precursor and other type I transmembrane proteins. Previous studies with mouse models or cells have indicated differences in PS1 and PS2 functions. We have recently reported that clinical γ-secretase inhibitors (GSIs), initially developed to manage Alzheimer's disease and now being considered for other therapeutic interventions, are both pharmacologically and functionally distinct. Here, using CRISPR/Cas9-based gene editing, we established human HEK 293T cell lines in which endogenous PS1, PS2, or both have been knocked out. Using these knockout lines to examine differences in PS1- and PS2-mediated cleavage events, we confirmed that PS2 generates more intracellular ß-amyloid than does PS1. Moreover, we observed subtle differences in PS1- and PS2-mediated cleavages of select substrates. In exploring the question of whether differences in activity among clinical GSIs could be attributed to differential inhibition of PS1 or PS2, we noted that select GSIs inhibit PS1 and PS2 activities on specific substrates with slightly different potencies. We also found that endoproteolysis of select PS1 FAD-linked variants in human cells is more efficient than what has been previously reported for mouse cell lines. Overall, these results obtained with HEK293T cells suggest that selective PS1 or PS2 inhibition by a given GSI does not explain the previously observed differences in functional and pharmacological properties among various GSIs.

Microglial Trem2 induces synaptic impairment at early stage and prevents amyloidosis at late stage in APP/PS1 mice.

Triggering receptor expressed in myeloid cells (TREM)2 is a genetic high-risk factor for sporadic Alzheimer's disease (AD) and is considered a potential target for AD diagnosis and therapy, although its role in the different stages of AD remains controversial. We generated an embryonic deletion of Trem2 (whole body deletion) and induced hippocampal- and cortical-specific knockdown of microglial Trem2 at different stages of the AD process in amyloid precursor protein/Psen1 mice by adeno-associated virus (AAV) infection. AAV infection induced microglial Trem2 overexpression in the hippocampus of wild-type (WT) and thymus cell antigen 1-enhanced green fluorescent protein mice. Mice were subjected to ethological and pathologic tests. Whole body genetic deletion of Trem2 exerted different electrophysiological outcomes between different AD pathologic stages, which results from a complex integration of synaptic loss and amyloid aggregation. Interestingly, knockdown of Trem2 at the early-middle stage of AD (2-6 mo) prevents synaptic loss through directly inhibiting microglial phagocytosis, whereas knockdown of Trem2 at the middle-late stage of AD (6-10 mo) accelerates synaptic dysfunction because of more severe amyloid deposition caused by the depression of microglial phagocytosis. Additionally, hippocampal overexpression of Trem2 in WT mice results in significant synaptic impairment. Here, with transgenic technology and electrophysiological assay, we revealed that TREM2 up-regulation promotes microglial phagocytosis equally against synapse and amyloid plaques and eventually results in different outcomes. During the early-middle pathologic stage, TREM2 enhancing microglial phagocytosis mainly causes synaptic loss. However, TREM2 up-regulating microglial phagocytosis gradually supports a positive role when amyloid deposition occupies the leading position at the middle-late pathologic stage. In this study, we highlighted that TREM2 triggers synaptic loss during AD pathology development.-Sheng, L., Chen, M., Cai, K., Song, Y., Yu, D., Zhang, H., Xu, G. Microglial Trem2 induces synaptic impairment at early stage and prevents amyloidosis at late stage in APP/PS1 mice.

The Effect of Triggering Receptor Expressed by Myeloid Cells 2 Modified Bone Marrow Mesenchymal Stem Cells on Alzheimer's Disease-Mouse Model.

OBJECTIVE: This study aims to explore the effect of TREM2 modified BMSCs on hippocampus of AD mice. METHODS: Mouse bone marrow mesenchymal stem cells were isolated and identified. APP/PS1 double transgenic mice were confirmed to be AD model and divided into 4 groups: control group, MSCs group, MSCs+vector group and MSCs+pEGFP-TREM2 group. RESULTS: The incubation period and the number of errors in the MSCs+pEGFP-TREM2 group were significantly decreased than that of control group after 3 days. The quantity and area of Aß deposition in MSCs+pEGFP-TREM2 group were significantly smaller than that of control group. Aß40 and Aß42 levels were significantly decreased most in MSCs+pEGFP-TREM2 group. The expression levels of TREM2 and DAP12 significantly increased in the MSCs+pEGFP-TREM2 group. CONCLUSIONS: TREM2 modified bone marrow MSCs affected the ability of learning and memory of AD model mice and this mechanism may be related to the expression of TREM2 and DAP12 genes.

Resveratrol improves cognition and decreases amyloid plaque formation in Tg6799 mice.

Alzheimer's disease (AD) is an irreversible, progressive neurodegenerative disorder of the central nervous system that causes severe cognitive impairment. One of the most significant pathological features of AD is the accumulation of ß­amyloid (Aß) peptide in the brain. Resveratrol (Res) is a polyphenol derived from peanuts, red grapes and other plants, which has received increasing attention due to its neuroprotective features. Tg6799 mice are transgenic mice with five familial AD (FAD) mutations that are also known as 5XFAD mice. The present study aimed to investigate the effects of Res on Tg6799 mice. The transgenic mice were randomly divided into the Res treatment group and the vehicle control group, and were treated with 0.5% Res solution (60 mg/kg) or volume­matched normal saline, respectively. Treatment was administered by oral gavage daily for 60 consecutive days. Res reduced amyloid plaque formation and the levels of Aß42, and ß­secretase 1 levels were also significantly decreased. Furthermore, Res was able to reduce the expression of amyloid precursor protein and its cleavage products. The administration of Res to Tg6799 mice also improved their spatial working memory, as measured by the Y­maze test, and rescued spatial memory deficits, as measured using the Morris water maze test; however, Res did not affect their motor function. In conclusion, this study suggested that Res may reduce Aß­induced neuronal damage, thus preventing memory loss.

Beclin1-driven autophagy modulates the inflammatory response of microglia via NLRP3.

Alzheimer's disease is characterized not only by extracellular amyloid plaques and neurofibrillary tangles, but also by microglia-mediated neuroinflammation. Recently, autophagy has been linked to the regulation of the inflammatory response. Thus, we investigated how an impairment of autophagy mediated by BECN1/Beclin1 reduction, as described in Alzheimer's disease patients, would influence cytokine production of microglia. Acutely stimulated microglia from Becn1+/- mice exhibited increased expression of IL-1beta and IL-18 compared to wild-type microglia. Becn1+/-APPPS1 mice also contained enhanced IL-1beta levels. The investigation of the IL-1beta/IL-18 processing pathway showed an elevated number of cells with inflammasomes and increased levels of NLRP3 and cleaved CASP1/Caspase1 in Becn1+/- microglia. Super-resolation microscopy revealed a very close association of NLRP3 aggregates and LC3-positive vesicles. Interestingly, CALCOCO2 colocalized with NLRP3 and its downregulation increased IL-1beta release. These data support the notion that selective autophagy can impact microglia activation by modulating IL-1beta and IL-18 production via NLRP3 degradation and thus present a mechanism how impaired autophagy could contribute to neuroinflammation in Alzheimer's disease.

Combined treatment with the phenolics (-)-epigallocatechin-3-gallate and ferulic acid improves cognition and reduces Alzheimer-like pathology in mice.

"Nutraceuticals" are well-tolerated natural dietary compounds with drug-like properties that make them attractive as Alzheimer's disease (AD) therapeutics. Combination therapy for AD has garnered attention following a recent National Institute on Aging mandate, but this approach has not yet been fully validated. In this report, we combined the two most promising nutraceuticals with complementary anti-amyloidogenic properties: the plant-derived phenolics (-)-epigallocatechin-3-gallate (EGCG, an α-secretase activator) and ferulic acid (FA, a ß-secretase modulator). We used transgenic mice expressing mutant human amyloid ß-protein precursor and presenilin 1 (APP/PS1) to model cerebral amyloidosis. At 12 months of age, we orally administered EGCG and/or FA (30 mg/kg each) or vehicle once daily for 3 months. At 15 months, combined EGCG-FA treatment reversed cognitive impairment in most tests of learning and memory, including novel object recognition and maze tasks. Moreover, EGCG- and FA-treated APP/PS1 mice exhibited amelioration of brain parenchymal and cerebral vascular ß-amyloid deposits and decreased abundance of amyloid ß-proteins compared with either EGCG or FA single treatment. Combined treatment elevated nonamyloidogenic soluble APP-α and α-secretase candidate and down-regulated amyloidogenic soluble APP-ß, ß-C-terminal APP fragment, and ß-secretase protein expression, providing evidence for a shift toward nonamyloidogenic APP processing. Additional beneficial co-treatment effects included amelioration of neuroinflammation, oxidative stress, and synaptotoxicity. Our findings offer preclinical evidence that combined treatment with EGCG and FA is a promising AD therapeutic approach.

Specific deletion connexin43 in astrocyte ameliorates cognitive dysfunction in APP/PS1 mice.

Emerging data indicate an important role for connexin43 (Cx43) in cognitive function, but there is a lack of direct evidence of the role of astroglial Cx43 in cognitive dysfunction in Alzheimer's disease (AD). Here we evaluated the expression pattern of Cx43 in AD and found progressive upregulation of the mRNA and protein levels of Cx43. Subsequently, we generated an astroglial Cx43 knockout (KO) AD mouse model by crossbreeding Gfap (glial fibrillary acidic protein)-Cx43 KO mice with APP/PS1 mice. Then we assessed the cognitive function of 12-month-old APP (amyloid precursor protein)/PS1 (presenilin 1)/Gfap-Cx43 KO mice, which demonstrated that the deletion of astroglial Cx43 significantly ameliorated cognitive dysfunction. To further investigate the underlying mechanisms, we evaluated amyloid plaque formation, astrogliosis, and synaptic function. The number and area of amyloid plaques were not altered, but GFAP expression was significantly decreased and the number of synapses was markedly upregulated. These results suggest that deletion of astroglial Cx43 in APP/PS1 mice did not affect the formation of amyloid plaques but depressed astrogliosis and upregulated synaptic function. Moreover, levels of critical modulators of astroglial activation were also notably reduced, but those of pro- and anti-inflammatory cytokines were not altered. Furthermore, Cx43 regulation of postsynaptic elements targets mainly NMDAR (N-methyl-d-aspartate). In addition, the prevention of AD pathology was reversed by Cx43 re-expression. In sum, specific deletion of astroglial Cx43 in APP/PS1 mice improved cognitive dysfunction by decreasing astrogliosis and increasing synaptic function without affecting amyloid plaque formation or the inflammatory response.

Inflammation, insulin signaling and cognitive function in aged APP/PS1 mice.

Cognitive dysfunction and neuroinflammation are typical in Alzheimer's disease (AD), but are also associated with normal aging, albeit less severely. Insulin resistance in the brain has been demonstrated in AD patients and is thought to be involved in AD pathophysiology. Using 15-18 month-old APP/PS1 mice, this study measured peripheral and central insulin signaling and sensitivity, inflammatory markers in brain and plasma and oxidative stress and synapse density in the brain. Novel object recognition, Morris water maze and reversal water maze tasks were performed to assess cognitive function in aged APP/PS1 mice and wild type littermates. Glucose tolerance and insulin sensitivity were similar in APP/PS1 mice and wild type controls, however IRS-1 pSer616 was increased in cortex and dentate gyrus of APP/PS1 mice. Recognition and spatial memory was impaired in both APP/PS1 and wild type mice, however learning impairments were apparent in APP/PS1 mice. Expression of GLP-1 receptor, ERK2, IKKß, mTOR, PKCθ, NF-κB1 and TLR4 was similar between aged APP/PS1 mice and age-matched wild types. Compared to age-matched wild type mice, IFNγ and IL-4 were increased in brains of APP/PS1 mice. These results suggest that normal aging may be associated with enhanced neuroinflammation, oxidative stress, and cognitive decline, however distinctions are apparent in the brain of APP/PS1 mice in terms of inflammation and insulin signaling and in certain cognitive domains. Demarcation of pathological events that distinguish AD from normal aging will allow for improvements in diagnostic tools and the development of more effective therapeutics.

Intracellular Ca2+ stores control in vivo neuronal hyperactivity in a mouse model of Alzheimer's disease.

Neuronal hyperactivity is the emerging functional hallmark of Alzheimer's disease (AD) in both humans and different mouse models, mediating an impairment of memory and cognition. The mechanisms underlying neuronal hyperactivity remain, however, elusive. In vivo Ca2+ imaging of somatic, dendritic, and axonal activity patterns of cortical neurons revealed that both healthy aging and AD-related mutations augment neuronal hyperactivity. The AD-related enhancement occurred even without amyloid deposition and neuroinflammation, mainly due to presenilin-mediated dysfunction of intracellular Ca2+ stores in presynaptic boutons, likely causing more frequent activation of synaptic NMDA receptors. In mutant but not wild-type mice, store emptying reduced both the frequency and amplitude of presynaptic Ca2+ transients and, most importantly, normalized neuronal network activity. Postsynaptically, the store dysfunction was minor and largely restricted to hyperactive cells. These findings identify presynaptic Ca2+ stores as a key element controlling AD-related neuronal hyperactivity and as a target for disease-modifying treatments.

The Efficacy and Pharmacological Mechanism of Zn7MT3 to Protect against Alzheimer's Disease.

Alzheimer's disease (AD) is one of the leading causes of death for people over 65 years. Worse still, no completely effective therapeutic agent is available so far. One important pathological hallmark of AD is accumulated amyloid-ß (Aß) plaques with dysregulated metal homeostasis. Human metallothionin 3 (MT3), a regulator of metal homeostasis, is downregulated at least 30% in AD brain. So far, some in vitro studies demonstrated its multiple functions related to AD. However, it is a great pity that systematic in vivo studies of MT3 on AD model animals are still a blank so far. In this study, we treated APP/PS1 mice with sustained drug release of Zn7MT3 directly to the central nervous system, and investigated the role and molecular mechanism of Zn7MT3 to protect against AD mice systematically. The results demonstrated that Zn7MT3 can significantly ameliorate cognitive deficits, regulate metal homeostasis, abolish Aß plaque load, and reduce oxidative stress. Additionally, it has been confirmed that MT3 is penetrable to the blood brain barrier of AD mice. All these results support that Zn7MT3 is an effective AD suppressing agent and has potential for applications in Alzheimer's disease therapy.