Postsynaptic density protein PSD-95 expression in Alzheimer's disease and okadaic acid induced neuritic retraction

Protective effects of 2,4-dinitrophenol in okadaic acid-induced cellular model of Alzheimer's disease

Alzheimer's disease (AD) research started several decades ago and despite the many efforts employed to develop new treatments or approaches to slow and/or revert disease progression, AD treatment remains an unsolved issue. Knowing that mitochondria loss of function is a central hub for many AD-associated pathophysiological processes, there has been renewed interest in exploring mitochondria as targets for intervention. In this perspective, the present study was aimed to investigate the possible beneficial effects of 2,4 dinitrophenol (DNP), a mitochondrial uncoupler agent, in an in vitro model of AD. Retinoic acid-induced differentiated SH-SY5Y cells were incubated with okadaic acid (OA), a neurotoxin often used as an AD experimental model, and/or with DNP. OA caused a decrease in neuronal cells viability, induced multiple mitochondrial anomalies including increased levels of reactive oxygen species, decreased bioenergetics and mitochondria content markers, and an altered mitochondria morphology. OA-treated cells also presented increased lipid peroxidation levels, and overactivation of tau related kinases (GSK3β, ERK1/2 and AMPK) alongside with a significant augment in tau protein phosphorylation levels. Interestingly, DNP co-treatment ameliorated and rescued OA-induced detrimental effects not only on mitochondria but also but also reinstated signaling pathways homeostasis and ameliorated tau pathology. Overall, our results show for the first time that DNP has the potential to preserve mitochondria homeostasis under a toxic insult, like OA exposure, as well as to reestablish cellular signaling homeostasis. These observations foster the idea that DNP, as a mitochondrial modulator, might represent a new avenue for treatment of AD.

Induced expression of rabies glycoprotein in the dorsal hippocampus enhances hippocampal dependent memory in a rat model of Alzheimer's disease

The Rabies virus is a neurotropic virus that manipulates the natural cell death processes of its host to ensure its own survival and replication. Studies have shown that the anti-apoptotic effect of the virus is mediated by one of its protein named, rabies glycoprotein (RVG). Alzheimer's disease (AD) is characterized by the loss of neural cells and memory impairment. We aim to examine whether expression of RVG in the hippocampal cells can shield the detrimental effects induced by Aβ. Oligomeric form of Aβ (oAβ) or vehicle was bilaterally microinjected into the dorsal hippocampus of male Wistar rats. One week later, two μl (108 T.U. /ml) of the lentiviral vector carrying RVG gene was injected into their dorsal hippocampus (post-treatment). In another experiment, the lentiviral vector was microinjected one week before Aβ injection (pre-treatment). One week later, the rat's brain was sliced into cross-sections, and the presence of RVG-expressing neuronal cells was confirmed using fluorescent microscopy. Rats were subjected to assessments of spatial learning and memory as well as passive avoidance using the Morris water maze (MWM) and the Shuttle box apparatuses, respectively. Protein expression of AMPA receptor subunit (GluA1) was determined using western blotting technique. In MWM, Aβ treated rats showed decelerated acquisition of the task and impairment of reference memory. RVG expression in the hippocampus prevented and restored the deficits in both pre- and post- treatment conditions, respectively. It also improved inhibitory memory in the oAβ treated rats. RVG increased the expression level of GluA1 level in the hippocampus. Based on our findings, the expression of RVG in the hippocampus has the potential to enhance both inhibitory and spatial learning abilities, ultimately improving memory performance in an AD rat model. This beneficial effect is likely attributed, at least in part, to the increased expression of GluA1-containing AMPA receptors.

A Comprehensive Review on Potential Molecular Drug Targets for the Management of Alzheimer's Disease

Alzheimer's disease (AD) is an onset and incurable neurodegenerative disorder that has been linked to various genetic, environmental, and lifestyle factors. Recent research has revealed several potential targets for drug development, such as the prevention of Aβ production and removal, prevention of tau hyperphosphorylation, and keeping neurons alive. Drugs that target numerous ADrelated variables have been developed, and early results are encouraging. This review provides a concise map of the different receptor signaling pathways associated with Alzheimer's Disease, as well as insight into drug design based on these pathways. It discusses the molecular mechanisms of AD pathogenesis, such as oxidative stress, aging, Aβ turnover, thiol groups, and mitochondrial activities, and their role in the disease. It also reviews the potential drug targets, in vivo active agents, and docking studies done in AD and provides prospects for future drug development. This review intends to provide more clarity on the molecular processes that occur in Alzheimer's patient's brains, which can be of use in diagnosing and preventing the condition.

Folicitin abrogates scopolamine induced oxidative stress, hyperlipidemia mediated neuronal synapse and memory dysfunction in mice

No effective drug treatment is available for Alzheimer disease, thus the need arise to develop efficient drugs for its treatment. Natural products have pronounced capability in treating Alzheimer disease therefore current study aimed to evaluate the neuro-protective capability of folicitin against scopolamine-induced Alzheimer disease neuropathology in mice. Experimental mice were divided into four groups i.e. control (single dose of 250 μL saline), scopolamine-administered group (1 mg/kg administered for three weeks), scopolamine plus folicitin-administered group (scopolamine 1 mg/kg administration for three weeks followed by folicitin administration for last two weeks) and folicitin-administered group (20 mg/kg administered for 5 alternate days). Results of behavioral tests and Western blot indicated that folicitin has the capability of recovering the memory against scopolamine-induced memory impairment by reducing the oxidative stress through up-regulating the endogenous antioxidant system like nuclear factor erythroid 2-related factor and Heme oxygenase-1 while prohibiting phosphorylated c-Jun N-terminal kinase. Similarly, folicitin also improved the synaptic dysfunction by up-regulating SYP and PSD95. Scopolamine-induced hyperglycemia and hyperlipidemia were abolished by folicitin as evidenced through random blood glucose test, glucose tolerance test and lipid profile test. All these results revealed that folicitin being a potent anti-oxidant is capable of improving synaptic dysfunction and reducing oxidative stress through Nrf-2/HO-1 pathway, thus plays a key role in treating Alzheimer disease as well as possess hyperglycemic and hyperlipidemic effect. Furthermore, a detailed study is suggested.

Translationally controlled tumor protein restores impaired memory and altered synaptic protein expression in animal models of dementia

This study describes the effects of translationally controlled tumor protein (TCTP) on mice with memory impairment caused by scopolamine (SCO) administration. Specifically, memory functions and expression levels of hippocampal synaptic proteins in 7- to 12-month-old SCO-treated wild-type (WT-SCO) mice were compared to those of TCTP-overexpressing (TG) and TCTP knocked-down (KD) mice similarly treated with SCO. Passive-avoidance tasks were performed with WT, TG, and KD mice for four weeks after intraperitoneal injection of SCO or saline followed by an acquisition test. After completing behavioral studies, hippocampi of all mice groups were collected and their synaptic protein contents were subjected to Western blotting or immunohistochemical analyses, and compared with those of 5x familial Alzheimer's disease (5xFAD) mice and postmortem AD patients. Results of passive avoidance tests revealed that SCO-induced memory impairment was repaired in TCTP-TG mice, but not in TCTP-KD mice. Hippocampal expression levels of synaptophysin, synapsin-1, and PSD-95 were increased in TCTP-TG mice treated with SCO (TG-SCO) but decreased in TCTP-KD mice treated with SCO (KD-SCO). Decreased levels of TCTP, synaptophysin, and PSD-95 were also found in hippocampi of 5xFAD mice and AD patients. Expression levels of p-CREB/CREB and brain-derived neurotrophic factor (BDNF) in TCTP-TG and TG-SCO mice were similar to or increased compared to those in WT mice, but decreased in TCTP-KD and KD-SCO mice. BDNF immunoreactivity was restored in CA1 regions of hippocampi of TG-SCO mice, but not in KD-SCO mice. These results suggest that TCTP can restore damaged memory in mice possibly through restored synaptic protein expression.

Alzheimer's Disease: Challenges and a Therapeutic Opportunity to Treat It with a Neurotrophic Compound

Alzheimer’s disease (AD) is a progressive neurodegenerative disease with an insidious onset and multifactorial nature. A deficit in neurogenesis and synaptic plasticity are considered the early pathological features associated with neurofibrillary tau and amyloid β pathologies and neuroinflammation. The imbalance of neurotrophic factors with an increase in FGF-2 level and a decrease in brain derived neurotrophic factor (BDNF) and neurotrophin 4 (NT-4) in the hippocampus, frontal cortex and parietal cortex and disruption of the brain micro-environment are other characteristics of AD. Neurotrophic factors are crucial in neuronal differentiation, maturation, and survival. Several attempts to use neurotrophic factors to treat AD were made, but these trials were halted due to their blood-brain barrier (BBB) impermeability, short-half-life, and severe side effects. In the present review we mainly focus on the major etiopathology features of AD and the use of a small neurotrophic and neurogenic peptide mimetic compound; P021 that was discovered in our laboratory and was found to overcome the difficulties faced in the administration of the whole neurotrophic factor proteins. We describe pre-clinical studies on P021 and its potential as a therapeutic drug for AD and related neurodegenerative disorders. Our study is limited because it focuses only on P021 and the relevant literature; a more thorough investigation is required to review studies on various therapeutic approaches and potential drugs that are emerging in the AD field.

Preferential Involvement of BRCA1/BARD1, Not Tip60/Fe65, in DNA Double-Strand Break Repair in Presenilin-1 P117L Alzheimer Models

Recently, we showed that DNA double-strand breaks (DSBs) are increased by the Aβ₄₂-amyloid peptide and decreased by all-trans retinoic acid (RA) in SH-SY5Y cells and C57BL/6J mice. The present work was aimed at investigating DSBs in cells and murine models of Alzheimer's disease carrying the preseniline-1 (PS1) P117L mutation. We observed that DSBs could hardly decrease following RA treatment in the mutated cells compared to the wild-type cells. The activation of the amyloidogenic pathway is proposed in the former case as Aβ₄₂- and RA-dependent DSBs changes were reproduced by an α-secretase and a γ-secretase inhibitions, respectively. Unexpectedly, the PS1 P117L cells showed lower DSB levels than the controls. As the DSB repair proteins Tip60 and Fe65 were less expressed in the mutated cell nuclei, they do not appear to contribute to this difference. On the contrary, full-length BRCA1 and BARD1 proteins were significantly increased in the chromatin compartment of the mutated cells, suggesting that they decrease DSBs in the pathological situation. These Western blot data were corroborated by in situ proximity ligation assays: the numbers of BRCA1-BARD1, not of Fe65-Tip60 heterodimers, were increased only in the mutated cell nuclei. RA also enhanced the expression of BARD1 and of the 90 kDa BRCA1 isoform. The increased BRCA1 expression in the mutated cells can be related to the enhanced difficulty to inhibit this pathway by BRCA1 siRNA in these cells. Overall, our study suggests that at earlier stages of the disease, similarly to PS1 P117L cells, a compensatory mechanism exists that decreases DSB levels via an activation of the BRCA1/BARD1 pathway. This supports the importance of this pathway in neuroprotection against Alzheimer's disease.

Binaural processing deficit and cognitive impairment in Alzheimer's disease

Speech comprehension in noisy environments depends on central auditory functions, which are vulnerable in Alzheimer's disease (AD). Binaural processing exploits two ear sounds to optimally process degraded sound information; its characteristics are poorly understood in AD. We studied behavioral and electrophysiological alterations in binaural processing among 121 participants (AD = 27; amnestic mild cognitive impairment [aMCI] = 33; subjective cognitive decline [SCD] = 30; cognitively normal [CN] = 31). We observed impairment of binaural processing in AD and aMCI, and detected a U-shaped curve change in phase synchrony (declining from CN to SCD and to aMCI, but increasing from aMCI to AD). This improvement in phase synchrony accompanying more severe cognitive stages could reflect neural adaptation for binaural processing. Moreover, increased phase synchrony is associated with worse memory during the stages when neural adaptation apparently occurs. These findings support a hypothesis that neural adaptation for binaural processing deficit may exacerbate cognitive impairment, which could help identify biomarkers and therapeutic targets in AD.

LMDS-1, a potential TrkB receptor agonist provides a safe and neurotrophic effect for early-phase Alzheimer's disease

RATIONALE

The signaling pathways of tropomyosin-related kinase B (TrkB) receptor play a pivotal role in axonal sprouting, proliferation of dendritic arbor, synaptic plasticity, and neuronal differentiation. The levels of BDNF and TrkB receptor were reduced in patients with Alzheimer's disease (AD).

OBJECTIVES

The activation of TrkB signaling pathways is a potential strategy for AD therapies. We intended to identify potential TrkB agonists to activate the neuroprotective signaling to alleviate the pathological features of AD mice.

RESULTS

Both of the Aβ-deteriorated hippocampal primary neurons and mouse models were generated and showed AD characteristics. We first investigated 12 potential TrkB agonists with primary hippocampal neurons of mice. Both 7,8-DHF and LMDS-1 were identified to have better effect than the other compounds on dendritic arborization of the neurons and were further applied to the Aβ-injected mouse model. The short-term cognitive behavior and pathology in the mice were improved by LMDS-1. Further investigation indicated that LMDS-1 activated the TrkB through phosphorylation at Y516 rather than Y816. In addition, the ERK but not CaMKII or Akt was activated in the mouse hippocampus with LMDS-1 administration. LMDS-1 treatment also upregulated CREB and BDNF while downregulated the GSK3β active form and tau phosphorylation.

CONCLUSIONS

This study suggests that LMDS-1 upregulates the expression of BDNF and ameliorates the early-phase phenotypes of the AD-like mice through the pTrkB (Y516)-ERK-CREB pathway. In addition, LMDS-1 has better effect than 7,8-DHF in ameliorating the behavioral and pathological features of AD-like mice.

Synaptic Loss, ER Stress and Neuro-Inflammation Emerge Late in the Lateral Temporal Cortex and Associate with Progressive Tau Pathology in Alzheimer's Disease

The complex multifactorial nature of AD pathogenesis has been highlighted by evidence implicating additional neurodegenerative mechanisms, beyond that of amyloid-β (Aβ) and tau. To provide insight into cause and effect, we here investigated the temporal profile and associations of pathological changes in synaptic, endoplasmic reticulum (ER) stress and neuro-inflammatory markers. Quantifications were established via immunoblot and immunohistochemistry protocols in post-mortem lateral temporal cortex (n = 46). All measures were assessed according to diagnosis (non-AD vs. AD), neuropathological severity (low (Braak ≤ 2) vs. moderate (3–4) vs. severe (≥ 5)) and individual Braak stage, and were correlated with Aβ and tau pathology and cognitive scores. Postsynaptic PSD-95, but not presynaptic synaptophysin, was decreased in AD cases and demonstrated a progressive decline across disease severity and Braak stage, yet not with cognitive scores. Of all investigated ER stress markers, only phospho-protein kinase RNA-like ER kinase (p-PERK) correlated with Braak stage and was increased in diagnosed AD cases. A similar relationship was observed for the astrocytic glial fibrillary acidic protein (GFAP); however, the associated aquaporin 4 and microglial Iba1 remained unchanged. Pathological alterations in these markers preferentially correlated with measures of tau over those related to Aβ. Notably, GFAP also correlated strongly with Aβ markers and with all assessments of cognition. Lateral temporal cortex-associated synaptic, ER stress and neuro-inflammatory pathologies are here determined as late occurrences in AD progression, largely associated with tau pathology. Moreover, GFAP emerged as the most robust indicator of disease progression, tau/Aβ pathology, and cognitive impairment.

RPS23RG1 Is Required for Synaptic Integrity and Rescues Alzheimer's Disease-Associated Cognitive Deficits

BACKGROUND

Although synaptic impairment is a prerequisite to cognitive deficiencies in Alzheimer's disease (AD), mechanisms underlying the dysregulation of essential synaptic scaffolding components and their integrity remain elusive. RPS23RG1 is a newly identified protein implicated in AD. However, the physiological function of RPS23RG1 has yet to be determined.

METHODS

We investigated the role of RPS23RG1 in maintaining synaptic structure and function in cell cultures and in Rps23rg1 knockout mice and determined whether targeting RPS23RG1-mediated pathways has therapeutic potential in APP/PS1 AD model mice.

RESULTS

Deletion of the Rps23rg1 gene resulted in severe memory deficits and impairment of postsynaptic structure and function, with marked reductions in postsynaptic densities-93 and -95 (PSD-93 and PSD-95) levels. RPS23RG1 interacted with PSD-93/PSD-95 through its intracellular domain, consequently sequestering PSD-93/PSD-95 from murine double minute 2-mediated ubiquitination and degradation, thereby maintaining synaptic function. Restoration of PSD-93/PS-D95 levels reversed synaptic and memory deficits in Rps23rg1 knockout mice. We further observed attenuated RPS23RG1 expression in human AD, which positively correlated with PSD-93/PSD-95 levels. Importantly, an RPS23RG1-derived peptide comprising a unique PSD-93/PSD-95 interaction motif rescued synaptic and cognitive defects in Rps23rg1 knockout and AD mouse models.

CONCLUSIONS

Our results reveal a role for RPS23RG1 in maintaining synaptic integrity and function and provide a new mechanism for synaptic dysfunction in AD pathogenesis. This demonstrates that RPS23RG1-mediated pathways show good therapeutic potential in AD intervention.

A Novel Therapeutic Approach to Treat Alzheimer's Disease by Neurotrophic Support During the Period of Synaptic Compensation

Alzheimer’s disease (AD), at present, is considered an incurable disease and a major dilemma with no drug to stop or slow down its progression. Drugs that are currently available in the market are able to only transiently improve the clinical symptoms. The repeated failures in developing an effective drug has led to the suggestion that the medical intervention was probably too late to be effective since the pathology starts many years before the appearance of the clinical symptoms. Probably, at the time of the appearance of clinical symptoms the brain has undergone major neuronal and synaptic loss. Because of the uncertainty on when to use a prevention therapy, especially targeting amyloid-β (Aβ) and tau pathologies, interventions that rely on the regenerative capacity of the brain such as the modulation of the inherent neurogenesis and neuronal plasticity represent a promising therapeutic strategy. Such an approach can act both at early as well as late stages of the disease and remove the barrier of the time of intervention. In this article, we review studies mainly from our laboratory that show the merit of early intervention during the synaptic and neuronal compensation period where the brain still has the capacity to self-repair by offering neurotrophic support in reversing cognitive impairment, neuronal and synaptic deficits, Aβ, and tau pathologies and decreasing mortality in a transgenic mouse model of AD.

HIV-1 Tat protein promotes neuronal dysregulation by inhibiting E2F transcription factor 3 (E2F3)

Individuals who are infected with HIV-1 accumulate damage to cells and tissues (e.g. neurons) that are not directly infected by the virus. These include changes known as HIV-associated neurodegenerative disorder (HAND), leading to the loss of neuronal functions, including synaptic long-term potentiation (LTP). Several mechanisms have been proposed for HAND, including direct effects of viral proteins such as the Tat protein. Searching for the mechanisms involved, we found here that HIV-1 Tat inhibits E2F transcription factor 3 (E2F3), CAMP-responsive element-binding protein (CREB), and brain-derived neurotropic factor (BDNF) by up-regulating the microRNA miR-34a. These changes rendered murine neurons dysfunctional by promoting neurite retraction, and we also demonstrate that E2F3 is a specific target of miR-34a. Interestingly, bioinformatics analysis revealed the presence of an E2F3-binding site within the CREB promoter, which we validated with ChIP and transient transfection assays. Of note, luciferase reporter assays revealed that E2F3 up-regulates CREB expression and that Tat interferes with this up-regulation. Further, we show that miR-34a inhibition or E2F3 overexpression neutralizes Tat's effects and restores normal distribution of the synaptic protein synaptophysin, confirming that Tat alters these factors, leading to neurite retraction inhibition. Our results suggest that E2F3 is a key player in neuronal functions and may represent a good target for preventing the development of HAND.

Dynamic SAP102 expression in the hippocampal subregions of rats and APP/PS1 mice of various ages

The hippocampus is a structurally and functionally complex brain area that plays important and diverse roles in higher brain functions, such as learning and memory, and mounting evidence indicates that different hippocampal subregions play distinctive roles. The hippocampus is also one of the first regions in the brain to suffer damage in Alzheimer's disease (AD). Synaptic dysfunction in the hippocampus, rather than neuronal loss per se, is paralleled by behavioural and functional deficits in AD. The membrane-associated guanylate kinase (MAGUK) family of proteins, including SAP102, PSD-95, PSD-93 and SAP97, have long been recognized as essential components of the postsynaptic density (PSD) at excitatory synapses. Hippocampal spines are the predominant synaptic transmission sites of excitatory glutamatergic synapses. During postnatal brain development, individual MAGUK members show distinct expression patterns. Although SAP102 has been confirmed as the dominant scaffold protein in neonatal synapses, its expression profiles in adult and ageing rodent hippocampi are discrepant. Furthermore, in AD brains, significantly reduced SAP102 protein levels have been found, suggesting that SAP102 may be related to AD progression; however, the precise mechanism underlying this result remains unclear. Herein, we observed distinct SAP102 expression profiles in the hippocampal CA1, CA3 and DG subregions of rats and APPswe/PS1dE9 (APP/PS1) mice at various ages using immunofluorescence. In Wistar rats, SAP102 was not only highly expressed in the hippocampal subregions of neonatal rats but also maintained relatively high expression levels in adult hippocampi and displayed no obvious decreases in the CA1 and DG subregions of aged rats. Surprisingly, we observed abnormally high SAP102 expression levels in the CA1 stratum moleculare and CA3 stratum polymorphum subregions of 2-month-old APP/PS1 mice, but low SAP102 levels in the DG and CA3 subregions of 7-month-old APP/PS1 mice, reflecting the subregion-specific reactivity and vulnerability of AD mouse models in different disease stages. Our findings provide fundamental data to support the functional differences of SAP102 in different hippocampal subregions during postnatal periods and may serve as the basis for additional functional studies on SAP102 in normal physiological conditions and different stages of AD.

Synaptic Compensation as a Probable Cause of Prolonged Mild Cognitive Impairment in Alzheimer's Disease: Implications from a Transgenic Mouse Model of the Disease

Alzheimer's disease (AD) is a slow, progressive neurodegenerative disease in which cognitive decline takes place over a period of several years with a very variable period of mild cognitive impairment (MCI) and, in some cases, relatively long period before progression to dementia. The cognitive deficit during MCI is probably due to neuronal loss, an intermediate level of amyloid-β (Aβ) plaques and neurofibrillary tangles (NFT) and synaptosis, which is interrupted with a transient compensatory increase. We found impairment in reference memory accompanied by a decrease in the expression of synaptophysin, β-III tubulin, and MAP2 and a trend for GluR1, at 12 weeks of age in 3xTg-AD mice (hAPPSwe, P301L tau, PS1 [M146V] knock-in), a widely used transgenic model of AD. Past 12 weeks, the cross-sectional analysis of different age groups showed a compensatory increase in synaptic markers relative to that in wild type animals in a topographic and time-dependent manner. When studied across time we found that in 3xTg-AD mice, the compensatory phenomenon occurred in parallel in different regions of the brain. However, this attempt of the brain to repair itself was able to only partially rescue cognitive impairment. These findings for the first time raise the intriguing possibility that AD causing mutated transgenes may initially cause an increase in synaptic and dendritic markers as a compensatory mechanism for synaptic deficit, and this phenomenon, though transient, could be the biological basis of the period of MCI seen in AD.

Identification of differentially expressed genes response to TCDD in rat brain after long-term low-dose exposure

Several cohort studies have reported that dioxin and dioxin-like polychlorinated biphenyls might impair the nervous system and lead to neurological or neurodegenerative diseases in the elder people, but there is limited research on the involved mechanism. By using microarray analysis, we figured out the differentially expressed genes between brain samples from SD rats after low-dose (0.1μg/(kg▪bw)) dioxin exposure for six months and controls. To investigate the function changes in the course of dioxin exposure, Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed on the differentially expressed genes. And the changes of several picked genes have been verified by real-time PCR. A total of 145 up-regulated and 64 down-regulated genes were identified. The metabolic processes, interleukin-1 secretion and production were significantly associated with the differentially expressed genes. And the genes regulated by dioxin also clustered to cholinergic synapse and long-term potentiation. Candidate biomarker genes such as egr1, gad2, gabrb3, abca1, ccr5 and pycard may be toxicological targets for dioxin. Furthermore, synaptic plasticity and neuro-immune system may be two principal affected areas by dioxin.

Identification of the Role of miR-142-5p in Alzheimer's Disease by Comparative Bioinformatics and Cellular Analysis

Alzheimer's disease (AD) is the most common neurodegenerative disease characterized by the formation of amyloid beta (Aβ) or tau protein aggregates, the hallmark of cognitive decline. MicroRNAs (miRNAs) have emerged as critical factors in neurogenesis and synaptic functions in the central nervous system (CNS). Recent studies have reported alterations in miRNA expression in patients with AD. However, miRNAs associated with AD varied with patient groups or experimental models, suggesting the need for a comparative study to identify miRNAs commonly dysregulated in diverse AD models. Here, we investigated the miRNAs that show dysregulated expression in two different human AD groups and mouse and cellular AD models. After selection of commonly dysregulated miRNAs in these groups, we investigated the pathophysiological significance of miR-142-5p in SH-SY5Y neuronal cells. We found that miR-142-5p was increased upon treatment with Aβ peptide 1-42 (Aβ₄₂). Inhibition of miR-142-5p rescued the Aβ₄₂-mediated synaptic dysfunctions, as indicated by the expression of postsynaptic density protein 95 (PSD-95). Among genes with decreased expression in Aβ₄₂-treated SH-SY5Y cells, the predicted miR-142-5p target genes were significantly related with neuronal function and synapse plasticity. These findings suggest that dysregulation in miR-142-5p expression contributes the pathogenesis of AD by triggering synaptic dysfunction associated with Aβ₄₂-mediated pathophysiology.

Prevention of dendritic and synaptic deficits and cognitive impairment with a neurotrophic compound

Background

The use of neurotrophic factors to treat Alzheimer’s disease (AD) is hindered by their blood–brain barrier impermeability, short half-life, and severe side effects. Peptide 021 (P021) is a neurotrophic/neurogenic tetra-peptide that was derived from the most active region of the ciliary neurotrophic factor (CNTF) by epitope mapping. Admantylated glycine was added to its C-terminal to increase its blood–brain barrier permeability and decrease its degradation by exopeptidases to make it druggable. Here, we report on the preventive effect of P021 in 3 × Tg-AD, a transgenic mouse model of AD.

Methods

P021 was administered in the diet at 3 months, i.e., 6–9 months before any overt amyloid beta (Aβ) or tau pathology, and during the period of synaptic compensation, and was continued until 21 months in 3 × Tg-AD mice. The 3 × Tg-AD mice and wild-type (WT) mice were treated identically but with a vehicle-only diet serving as controls. The effects of P021 on neurogenesis, dendritic and synaptic markers, and cognitive performance were investigated.

Results

We found that P021 treatment was able to rescue dendritic and synaptic deficits, boost neurogenesis, and reverse cognitive impairment in 3 × Tg-AD mice.

Conclusions

Availability of appropriate neurotrophic support during the period of synaptic compensation can prevent synaptic deficit and cognitive impairment, and P021 is a promising neurotrophic compound for this purpose.

Electronic supplementary material

The online version of this article (doi:10.1186/s13195-017-0273-7) contains supplementary material, which is available to authorized users.

Oleocanthal ameliorates amyloid-β oligomers' toxicity on astrocytes and neuronal cells: In vitro studies

Extra-virgin olive oil (EVOO) has several health promoting effects. Evidence have shown that EVOO attenuates the pathology of amyloid-β (Aβ) and improves cognitive function in experimental animal models, suggesting it's potential to protect and reduce the risk of developing Alzheimer's disease (AD). Available studies have linked this beneficial effect to oleocanthal, one of the active components in EVOO. The effect of oleocanthal against AD pathology has been linked to its ability to attenuate Aβ and tau aggregation in vitro, and enhance Aβ clearance from the brains of wild-type and AD transgenic mice in vivo. However, the ability of oleocanthal to alter the toxic effect of Aβ on brain parenchymal cells is unknown. In the current study, we investigated oleocanthal effect on modulating Aβ oligomers (Aβo) pathological events in neurons and astrocytes. Our findings demonstrated oleocanthal prevented Aβo-induced synaptic proteins, SNAP-25 and PSD-95, down-regulation in neurons, and attenuated Aβo-induced inflammation, glutamine transporter (GLT1) and glucose transporter (GLUT1) down-regulation in astrocytes. Aβo-induced inflammation was characterized by interleukin-6 (IL-6) increase and glial fibrillary acidic protein (GFAP) upregulation that were reduced by oleocanthal. In conclusion, this study provides further evidence to support the protective effect of EVOO-derived phenolic secoiridoid oleocanthal against AD pathology.

Exposure of okadaic acid alters the angiogenesis in developing chick embryos

Okadaic acid (OA) is a common phycotoxin, which concerns diarrheic shellfish poisoning (DSP) in human being. It has been known that OA can induce disorganization in cytoskeletal architecture and cell-cell contact, cause chromosome loss, apoptosis, DNA damage and inhibit phosphatases, suggesting its potential embryotoxicity. In this paper, we found that low concentration of OA (50 nM, 100 nM and 200 nM) significantly reduced the density of vascular plexus in yolk-sac membrane (YSM) of chick embryo, while high concentration of OA (500 nM) distinctly depressed the blood vessel density in chorioallantoic membrane (CAM). After exposed to OA, MDA level and SOD activity increased significantly in CAM tissues. However, addition of vitamin C could rescue OA-suppressed angiogenesis in CAM of chick embryo. After exposure of OA, Ang-2 expression was down-regulated in CAM tissues. Taking together, we proposed that OA interfered with angiogenesis in developing chick embryo, through, at least partly, the induction of excessive ROS generation.

Long non-coding RNAs in brain development, synaptic biology, and Alzheimer's disease

Long non-coding RNAs (lncRNAs), which are long transcripts without apparent protein-coding roles, interfere with gene expression and signaling events at various stages. Increasing evidence has suggested that lncRNAs function in the regulation of tissue homeostasis and under pathophysiologic conditions. In the nervous system, the expression of lncRNAs has been detected and characterized under normal physiologic conditions and in disease states. Some lncRNAs regulate brain development and synaptic plasticity. In Alzheimer's disease (AD), several lncRNAs have been demonstrated to regulate β-amyloid production/generation, synaptic impairment, neurotrophin depletion, inflammation, mitochondrial dysfunction, and stress responses. This review summarizes data on lncRNA expression and focuses on neural lncRNAs that may function in AD. Although our understanding of lncRNAs remains in its infancy, this review provides insight into the contribution of lncRNAs to AD.

Adapting tissue-engineered in vitro CNS models for high-throughput study of neurodegeneration

Neurodegenerative conditions remain difficult to treat, with the continuing failure to see therapeutic research successfully advance to clinical trials. One of the obstacles that must be overcome is to develop enhanced models of disease. Tissue engineering techniques enable us to create organised artificial central nervous system tissue that has the potential to improve the drug development process. This study presents a replicable model of neurodegenerative pathology through the use of engineered neural tissue co-cultures that can incorporate cells from various sources and allow degeneration and protection of neurons to be observed easily and measured, following exposure to neurotoxic compounds – okadaic acid and 1-methyl-4-phenylpyridinium. Furthermore, the technology has been miniaturised through development of a mould with 6 mm length that recreates the advantageous features of engineered neural tissue co-cultures at a scale suitable for commercial research and development. Integration of human-derived induced pluripotent stem cells aids more accurate modelling of human diseases, creating new possibilities for engineered neural tissue co-cultures and their use in drug screening.

Association analysis of genetic variant of rs13331 in PSD95 gene with autism spectrum disorders: A case-control study in a Chinese population

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by high heritability. Recently, autism, the most profound form of ASD, has been increasingly attributed to synaptic abnormalities. Postsynaptic density 95 (PSD95), encoding PSD protein-95, was found essential for synaptic formation, maturation and plasticity at a PSD of excitatory synapse. It is possibly a crucial candidate gene for the pathogenesis of ASD. To identify the relationship between the rs13331 of PSD95 gene and ASD, we performed a case-control study in 212 patients and 636 controls in a Chinese population by using a polymerase chain reaction-restriction fragment length polymerase (PCR-RFLP) assay. The results showed that in genetic analysis of the heterozygous model, an association between the T allele of the rs13331 and ASD was found in the dominant model (OR=1.709, 95% CI 1.227-2.382, P=0.002) and the additive model (OR=1.409, 95% CI=1.104-1.800, P=0.006). Our data indicate that the genetic mutation C>T at the rs13331 in the PSD95 gene is strikingly associated with an increased risk of ASD.

Meta-analysis of synaptic pathology in Alzheimer's disease reveals selective molecular vesicular machinery vulnerability

INTRODUCTION

Loss of synapses best correlates to cognitive deficits in Alzheimer's disease (AD) in which oligomeric neurotoxic species of amyloid-β appears to contribute synaptic pathology. Although a number of clinical pathologic studies have been performed with limited sample size, there are no systematic studies encompassing large samples. Therefore, we performed a meta-analysis study.

METHODS

We identified 417 publications reporting postmortem synapse and synaptic marker loss from AD patients. Two meta-analyses were performed using a single database of subselected publications and calculating the standard mean differences.

RESULTS

Meta-analysis confirmed synaptic loss in selected brain regions is an early event in AD pathogenesis. The second meta-analysis of 57 synaptic markers revealed that presynaptic makers were affected more than postsynaptic markers.

DISCUSSION

The present meta-analysis study showed a consistent synaptic loss across brain regions and that molecular machinery including endosomal pathways, vesicular assembly mechanisms, glutamate receptors, and axonal transport are often affected.

Tau hyperphosphorylation in synaptosomes and neuroinflammation are associated with canine cognitive impairment

Canine cognitive impairment syndrome (CDS) represents a group of symptoms related to the aging of the canine brain. These changes ultimately lead to a decline of memory function and learning abilities, alteration of social interaction, impairment of normal housetraining, and changes in sleep-wake cycle and general activity. We have clinically examined 215 dogs, 28 of which underwent autopsy. With canine brains, we performed extensive analysis of pathological abnormalities characteristic of human Alzheimer's disease and frontotemporal lobar degeneration, including β-amyloid senile plaques, tau neurofibrillary tangles, and fused in sarcoma (FUS) and TAR DNA-binding protein 43 (TDP43) inclusions. Most demented dogs displayed senile plaques, mainly in the frontal and temporal cortex. Tau neurofibrillary inclusions were found in only one dog. They were identified with antibodies used to detect tau neurofibrillary lesions in the human brain. The inclusions were also positive for Gallyas silver staining. As in humans, they were distributed mainly in the entorhinal cortex, hippocampus, and temporal cortex. On the other hand, FUS and TDP43 aggregates were not present in any of the examined brain samples. We also found that CDS was characterized by the presence of reactive and senescent microglial cells in the frontal cortex. Our transcriptomic study revealed a significant dysregulation of genes involved in neuroinflammation. Finally, we analyzed tau phosphoproteome in the synaptosomes. Proteomic studies revealed a significant increase of hyperphosphorylated tau in synaptosomes of demented dogs compared with nondemented dogs. This study suggests that cognitive decline in dogs is related to the tau synaptic impairment and neuroinflammation. J. Comp. Neurol. 524:874-895, 2016. © 2015 Wiley Periodicals, Inc.

p35 and Rac1 underlie the neuroprotection and cognitive improvement induced by CDK5 silencing

CDK5 plays an important role in neurotransmission and synaptic plasticity in the normal function of the adult brain, and dysregulation can lead to Tau hyperphosphorylation and cognitive impairment. In a previous study, we demonstrated that RNAi knock down of CDK5 reduced the formation of neurofibrillary tangles (NFT) and prevented neuronal loss in triple transgenic Alzheimer's mice. Here, we report that CDK5 RNAi protected against glutamate-mediated excitotoxicity using primary hippocampal neurons transduced with adeno-associated virus 2.5 viral vector eGFP-tagged scrambled or CDK5 shRNA-miR during 12 days. Protection was dependent on a concomitant increase in p35 and was reversed using p35 RNAi, which affected the down-stream Rho GTPase activity. Furthermore, p35 over-expression and constitutively active Rac1 mimicked CDK5 silencing-induced neuroprotection. In addition, 3xTg-Alzheimer's disease mice (24 months old) were injected in the hippocampus with scrambled or CDK5 shRNA-miR, and spatial learning and memory were performed 3 weeks post-injection using 'Morris' water maze test. Our data showed that CDK5 knock down induced an increase in p35 protein levels and Rac activity in triple transgenic Alzheimer's mice, which correlated with the recovery of cognitive function; these findings confirm that increased p35 and active Rac are involved in neuroprotection. In summary, our data suggest that p35 acts as a mediator of Rho GTPase activity and contributes to the neuroprotection induced by CDK5 RNAi.

A framework to understand the variations of PSD-95 expression in brain aging and in Alzheimer's disease

The postsynaptic density protein PSD-95 is a major element of synapses. PSD-95 is involved in aging, Alzheimer's disease (AD) and numerous psychiatric disorders. However, contradictory data about PSD-95 expression in aging and AD have been reported. Indeed in AD versus control brains PSD-95 varies according to regions, increasing in the frontal cortex, at least in a primary stage, and decreasing in the temporal cortex. In contrast, in transgenic mouse models of aging and AD PSD-95 expression is decreased, in behaviorally aged impaired versus unimpaired rodents it can decrease or increase and finally, it is increased in rodents grown in enriched environments. Different factors explain these contradictory results in both animals and humans, among others concomitant psychiatric endophenotypes, such as depression. The possible involvement of PSD-95 in reactive and/or compensatory mechanisms during AD progression is underscored, at least before the occurrence of important synaptic elimination. Thus, in AD but not in AD transgenic mice, enhanced expression might precede the diminution commonly observed in advanced aging. A two-compartments cell model, separating events taking place in cell bodies and synapses, is presented. Overall these data suggest that AD research will progress by untangling pathological from protective events, a prerequisite for effective therapeutic strategies.

The structure of an LIM-only protein 4 (LMO4) and Deformed epidermal autoregulatory factor-1 (DEAF1) complex reveals a common mode of binding to LMO4

LIM-domain only protein 4 (LMO4) is a widely expressed protein with important roles in embryonic development and breast cancer. It has been reported to bind many partners, including the transcription factor Deformed epidermal autoregulatory factor-1 (DEAF1), with which LMO4 shares many biological parallels. We used yeast two-hybrid assays to show that DEAF1 binds both LIM domains of LMO4 and that DEAF1 binds the same face on LMO4 as two other LMO4-binding partners, namely LIM domain binding protein 1 (LDB1) and C-terminal binding protein interacting protein (CtIP/RBBP8). Mutagenic screening analysed by the same method, indicates that the key residues in the interaction lie in LMO4_LIM2 and the N-terminal half of the LMO4-binding domain in DEAF1. We generated a stable LMO4_LIM2-DEAF1 complex and determined the solution structure of that complex. Although the LMO4-binding domain from DEAF1 is intrinsically disordered, it becomes structured on binding. The structure confirms that LDB1, CtIP and DEAF1 all bind to the same face on LMO4. LMO4 appears to form a hub in protein-protein interaction networks, linking numerous pathways within cells. Competitive binding for LMO4 therefore most likely provides a level of regulation between those different pathways.

Neurotropic and neuroprotective activities of the earthworm peptide Lumbricusin

We recently isolated a polypeptide from the earthworm Lumbricus terrestris that is structurally similar to defensin, a well-known antibacterial peptide. An 11-mer antibacterial peptide (NH2-RNRRWCIDQQA), designated Lumbricusin, was synthesized based on the amino acid sequence of the isolated polypeptide. Since we previously reported that CopA3, a dung beetle peptide, enhanced neuronal cell proliferation, we here examined whether Lumbricusin exerted neurotropic and/or neuroprotective effects. Lumbricusin treatment induced a time-dependent increase (∼51%) in the proliferation of human neuroblastoma SH-SY5Y cells. Lumbricusin also significantly inhibited the apoptosis and decreased viability induced by treatment with 6-hydroxy dopamine, a Parkinson's disease-mimicking agent. Immunoblot analyses revealed that Lumbricusin treatment increased ubiquitination of p27(Kip1) protein, a negative regulator of cell-cycle progression, in SH-SY5Y cells, and markedly promoted its degradation. Notably, adenoviral-mediated over-expression of p27(Kip1) significantly blocked the antiapoptotic effect of Lumbricusin in 6-hydroxy dopamine-treated SH-SY5Y cells. These results suggest that promotion of p27(Kip1) degradation may be the main mechanism underlying the neuroprotective and neurotropic effects of Lumbricusin.

Early structural and functional defects in synapses and myelinated axons in stratum lacunosum moleculare in two preclinical models for tauopathy

The stratum lacunosum moleculare (SLM) is the connection hub between entorhinal cortex and hippocampus, two brain regions that are most vulnerable in Alzheimer's disease. We recently identified a specific synaptic deficit of Nectin-3 in transgenic models for tauopathy. Here we defined cognitive impairment and electrophysiological problems in the SLM of Tau.P301L mice, which corroborated the structural defects in synapses and dendritic spines. Reduced diffusion of DiI from the ERC to the hippocampus indicated defective myelinated axonal pathways. Ultrastructurally, myelinated axons in the temporoammonic pathway (TA) that connects ERC to CA1 were damaged in Tau.P301L mice at young age. Unexpectedly, the myelin defects were even more severe in bigenic biGT mice that co-express GSK3β with Tau.P301L in neurons. Combined, our data demonstrate that neuronal expression of protein Tau profoundly affected the functional and structural organization of the entorhinal-hippocampal complex, in particular synapses and myelinated axons in the SLM. White matter pathology deserves further attention in patients suffering from tauopathy and Alzheimer's disease.

Physical exercise improves synaptic dysfunction and recovers the loss of survival factors in 3xTg-AD mouse brain

Physical exercise has become a potentially beneficial therapy for reducing neurodegeneration symptoms in Alzheimer's disease. Previous studies have shown that cognitive deterioration, anxiety and the startle response observed in 7-month-old 3xTg-AD mice were ameliorated after 6 months of free access to a running wheel. Also, alterations in synaptic response to paired-pulse stimulation were improved. The present study further investigated some molecular mechanisms underlying the beneficial effects of 6 months of voluntary exercise on synaptic plasticity in 7-month-old 3xTg-AD mice. Changes in binding parameters of [(3)H]-flunitrazepam to GABAA receptor and of [(3)H]-MK-801 to NMDA receptor in cerebral cortex of 3xTgAD mice were restored by voluntary exercise. In addition, reduced expression levels of NMDA receptor NR2B subunit were reestablished. The synaptic proteins synaptophysin and PSD-95 and the neuroprotective proteins GDNF and SIRT1 were downregulated in 3xTgAD mice and were recovered by exercise treatment. Overall, in this paper we highlight the fact that different interrelated mechanisms are involved in the beneficial effects of exercise on synaptic plasticity alterations in the 3xTg-AD mouse model.

Differential Changes in Postsynaptic Density Proteins in Postmortem Huntington's Disease and Parkinson's Disease Human Brains

NMDA and AMPA-type glutamate receptors and their bound membrane-associated guanylate kinases (MAGUKs) are critical for synapse development and plasticity. We hypothesised that these proteins may play a role in the changes in synapse function that occur in Huntington's disease (HD) and Parkinson's disease (PD). We performed immunohistochemical analysis of human postmortem brain tissue to examine changes in the expression of SAP97, PSD-95, GluA2 and GluN1 in human control, and HD- and PD-affected hippocampus and striatum. Significant increases in SAP97 and PSD-95 were observed in the HD and PD hippocampus, and PSD95 was downregulated in HD striatum. We observed a significant increase in GluN1 in the HD hippocampus and a decrease in GluA2 in HD and PD striatum. Parallel immunohistochemistry experiments in the YAC128 mouse model of HD showed no change in the expression levels of these synaptic proteins. Our human data show that major but different changes occur in glutamatergic proteins in HD versus PD human brains. Moreover, the changes in human HD brains differ from those occurring in the YAC128 HD mouse model, suggesting that unique changes occur at a subcellular level in the HD human hippocampus.

Synaptic alterations in the rTg4510 mouse model of tauopathy

Synapse loss, rather than the hallmark amyloid-β (Aβ) plaques or tau-filled neurofibrillary tangles (NFT), is considered the most predictive pathological feature associated with cognitive status in the Alzheimer's disease (AD) brain. The role of Aβ in synapse loss is well established, but despite data linking tau to synaptic function, the role of tau in synapse loss remains largely undetermined. Here we test the hypothesis that human mutant P301L tau overexpression in a mouse model (rTg4510) will lead to age-dependent synaptic loss and dysfunction. Using array tomography and two methods of quantification (automated, threshold-based counting and a manual stereology-based technique) we demonstrate that overall synapse density is maintained in the neuropil, implicating synapse loss commensurate with the cortical atrophy known to occur in this model. Multiphoton in vivo imaging reveals close to 30% loss of apical dendritic spines of individual pyramidal neurons, suggesting these cells may be particularly vulnerable to tau-induced degeneration. Postmortem, we confirm the presence of tau in dendritic spines of rTg4510-YFP mouse brain by array tomography. These data implicate tau-induced loss of a subset of synapses that may be accompanied by compensatory increases in other synaptic subtypes, thereby preserving overall synapse density. Biochemical fractionation of synaptosomes from rTg4510 brain demonstrates a significant decrease in expression of several synaptic proteins, suggesting a functional deficit of remaining synapses in the rTg4510 brain. Together, these data show morphological and biochemical synaptic consequences in response to tau overexpression in the rTg4510 mouse model.

Comparison of frailty of primary neurons, embryonic, and aging mouse cortical layers

Superficial layers I to III of the human cerebral cortex are more vulnerable toward Aβ peptides than deep layers V to VI in aging. Three models of layers were used to investigate this pattern of frailty. First, primary neurons from E14 and E17 embryonic murine cortices, corresponding respectively to future deep and superficial layers, were treated either with Aβ(1-42), okadaic acid, or kainic acid. Second, whole E14 and E17 embryonic cortices, and third, in vitro separated deep and superficial layers of young and old C57BL/6J mice, were treated identically. We observed that E14 and E17 neurons in culture were prone to death after the Aβ and particularly the kainic acid treatment. This was also the case for the superficial layers of the aged cortex, but not for the embryonic, the young cortex, and the deep layers of the aged cortex. Thus, the aged superficial layers appeared to be preferentially vulnerable against Aβ and kainic acid. This pattern of vulnerability corresponds to enhanced accumulation of senile plaques in the superficial cortical layers with aging and Alzheimer's disease.

RETRACTED: Increased neuroinflammatory and arachidonic acid cascade markers, and reduced synaptic proteins, in the postmortem frontal cortex from schizophrenia patients

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editors. The National Institutes of Health has found that Dr. Jagadeesh S. Rao engaged in research misconduct by falsifying data. Data in Figures 1A, 1E, 3E and 3F were falsified. Dr. Rao was solely responsible for the falsification. None of the other authors are implicated in any way.

Increased postsynaptic density protein-95 expression in the frontal cortex of aged cognitively impaired rats

In the present work we studied synaptic protein concentrations in relation to behavioral performance. Long-Evans rats, aged 22-23 months, were classified for individual expression of place memory in the Morris water maze, in reference to young adults. Two main subgroups of aged rats were established: the Aged cognitively Unimpaired (AU) had search accuracy within the range (percent of time in training sector within mean ± 2 SEM) of young rats and the Aged cognitively Impaired (AI) rats had search accuracy below this range. Samples from the hippocampus and frontal cortex of all the AI, AU and young rats were analyzed for the expression of postsynaptic protein PSD-95 by Image J analysis of immunohistochemical data and by Western blots. PSD-95 expression was unchanged in the hippocampus, but, together with synaptophysin, was significantly increased in the frontal cortex of the AI rats. A significant correlation between individual accuracy (time spent in the training zone) and PSD-95 expression was observed in the aged group. No significant effect of age or PSD-95 expression was observed in the learning of a new position. All together, these data suggest that increased expression of PSD-95 in the frontal cortex of aged rats co-occurs with cognitive impairment that might be linked to functional alterations extending over frontal networks.

Induced tauopathy in a novel 3D-culture model mediates neurodegenerative processes: a real-time study on biochips

Tauopathies including Alzheimer's disease represent one of the major health problems of aging population worldwide. Therefore, a better understanding of tau-dependent pathologies and consequently, tau-related intervention strategies is highly demanded. In recent years, several tau-focused therapies have been proposed with the aim to stop disease progression. However, to develop efficient active pharmaceutical ingredients for the broad treatment of Alzheimer's disease patients, further improvements are necessary for understanding the detailed neurodegenerative processes as well as the mechanism and side effects of potential active pharmaceutical ingredients (API) in the neuronal system. In this context, there is a lack of suitable complex in vitro cell culture models recapitulating major aspects of taupathological degenerative processes in sufficient time and reproducible manner.Herewith, we describe a novel 3D SH-SY5Y cell-based, tauopathy model that shows advanced characteristics of matured neurons in comparison to monolayer cultures without the need of artificial differentiation promoting agents. Moreover, the recombinant expression of a novel highly pathologic fourfold mutated human tau variant lead to a fast and emphasized degeneration of neuritic processes. The neurodegenerative effects could be analyzed in real time and with high sensitivity using our unique microcavity array-based impedance spectroscopy measurement system. We were able to quantify a time- and concentration-dependent relative impedance decrease when Alzheimer's disease-like tau pathology was induced in the neuronal 3D cell culture model. In combination with the collected optical information, the degenerative processes within each 3D-culture could be monitored and analyzed. More strikingly, tau-specific regenerative effects caused by tau-focused active pharmaceutical ingredients could be quantitatively monitored by impedance spectroscopy.Bringing together our novel complex 3D cell culture taupathology model and our microcavity array-based impedimetric measurement system, we provide a powerful tool for the label-free investigation of tau-related pathology processes as well as the high content analysis of potential active pharmaceutical ingredient candidates.

Injury and repair in the neurovascular unit

The neurovascular unit provides a conceptual framework for investigating the pathophysiology of how brain cells die after stroke, brain injury, and neurodegeneration. Emerging data now suggest that this concept can be further extended. Cell-cell signaling between neuronal, glial, and vascular elements in the brain not only mediates the mechanisms of acute injury, but integrated responses in these same elements may also be required for recovery as the entire neurovascular unit attempts to reorganize and remodel. Understanding the common signals and substrates of this transition between acute injury and delayed repair in the neurovascular unit may reveal useful paradigms for augmenting neuronal, glial, and vascular plasticity in damaged and diseased brain.

Abcg2 deficiency augments oxidative stress and cognitive deficits in Tg-SwDI transgenic mice

Oxidative stress and neuroinflammation play important roles in Alzheimer's disease (AD). ABCG2 is a transporter protein expressed in the brain and involved in GSH transport. To study the roles of Abcg2 in oxidative stress and AD, we cross-bred Tg-SwDI and Abcg2-KO mice and generated Tg-SwDI/Abcg2-KO (double-tg) mice. Brain tissues from double-tg, Tg-SwDI, wild-type, and Abcg2-KO mice at various ages were analyzed. Aβ40 and Aβ42 were detected in Tg-SwDI and double-tg mice. Total brain GSH was decreased and levels of lipid/DNA oxidation were increased in 3-month double-tg compared to Tg-SwDI mice. Low brain GSH was still detected in 9-month double-tg mice. Increased HMOX-1 and MCP-5 expression was observed in 9-month double-tg mice but not in Tg-SwDI mice compared to WT and Abcg2-KO mice. Increased HMOX-1 and decreased ICAM-1 expression were observed in 12-month double-tg mice compared to Tg-SwDI mice. The levels of Nrf-2 expression and activity were decreased in 6-month double-tg mice. Behavioral tests show impaired cognitive/memory performance of 9-month double-tg compared to Tg-SwDI mice as well as WT and Abcg2-KO mice. These results suggest that Abcg2 deficiency increases oxidative stress and alters inflammatory response in the brain and exacerbates cognitive/memory deficit in double-tg mice at different developmental stages.

Postsynaptic degeneration as revealed by PSD-95 reduction occurs after advanced Aβ and tau pathology in transgenic mouse models of Alzheimer's disease

Impairment of synaptic plasticity underlies memory dysfunction in Alzheimer's disease (AD). Molecules involved in this plasticity such as PSD-95, a major postsynaptic scaffold protein at excitatory synapses, may play an important role in AD pathogenesis. We examined the distribution of PSD-95 in transgenic mice of amyloidopathy (5XFAD) and tauopathy (JNPL3) as well as in AD brains using double-labeling immunofluorescence and confocal microscopy. In wild type control mice, PSD-95 primarily labeled neuropil with distinct distribution in hippocampal apical dendrites. In 3-month-old 5XFAD mice, PSD-95 distribution was similar to that of wild type mice despite significant Aβ deposition. However, in 6-month-old 5XFAD mice, PSD-95 immunoreactivity in apical dendrites markedly decreased and prominent immunoreactivity was noted in neuronal soma in CA1 neurons. Similarly, PSD-95 immunoreactivity disappeared from apical dendrites and accumulated in neuronal soma in 14-month-old, but not in 3-month-old, JNPL3 mice. In AD brains, PSD-95 accumulated in Hirano bodies in hippocampal neurons. Our findings support the notion that either Aβ or tau can induce reduction of PSD-95 in excitatory synapses in hippocampus. Furthermore, this PSD-95 reduction is not an early event but occurs as the pathologies advance. Thus, the time-dependent PSD-95 reduction from synapses and accumulation in neuronal soma in transgenic mice and Hirano bodies in AD may mark postsynaptic degeneration that underlies long-term functional deficits.

Increased phosphorylation of tau and synaptic protein loss in the aged transgenic mice expressing familiar Alzheimer's disease-linked presenilin 1 mutation

Mutations in presenilin 1 (PS-1) are associated with most early-onset familiar Alzheimer's disease (AD). Previous studies have demonstrated that PS-1 mutations enhance the production of beta-amyloid (Aβ). In this study, we further examined the in vivo effects of PS-1 mutation on tau and synapse protein markers. The data showed that the phosphorylation of tau at Ser396, Ser404, Thr231 and Tau-1 (Ser198/199/202) epitopes was significantly increased in hippocampus of the aged (twenty-one and a half-month-old) transgenic mice expressing PS-1 (L235P) compared to that of the age-matched wild-type littermates (WTs). Concurrently, a significant decrease in the phosphorylation of glycogen synthase kinase (GSK)-3β at Ser9 was observed. The above changes were not observed in the young transgenic mice (6-8 months old). No significant changes in the levels of cyclin-dependent kinase (CDK)-5, its co-activator p35, and phosphorylation of protein phosphatase (PP)-2A catalytic subunit at Tyrosine 307 (Y307), a crucial site regulating the activity of PP-2A, were observed both in the young and aged transgenic mice compared to that of WTs. Furthermore, we also observed that the levels of presynaptic synaptophysin were significantly decreased but postsynaptic density protein (PSD)-95 were not significantly altered in hippocampus of the aged transgenic mice. No significant changes of synaptophysin or PSD-95 were observed in the brains of the young transgenic mice. Our data indicate that the L235P PS-1 mutation can induce Alzheimer-like tau hyperphosphorylation and synaptic protein loss, as well as increased production of Aβ.