Intraneuronal Neurofibrillary Tangles Research Articles

Novel Insights on Systemic and Brain Aging, Stroke, Amyotrophic Lateral Sclerosis, and Alzheimer's Disease.

The mechanisms that underlie the pathophysiology of aging, amyotrophic lateral sclerosis (ALS), Alzheimer’s disease (AD) and stroke are not fully understood and have been the focus of intense and constant investigation worldwide. Studies that provide insights on aging and age-related disease mechanisms are critical for advancing novel therapies that promote successful aging and prevent or cure multiple age-related diseases. The April 2019 issue of the journal, "Aging & Disease" published a series of articles that confer fresh insights on numerous age-related conditions and diseases. The age-related topics include the detrimental effect of overweight on energy metabolism and muscle integrity, senoinflammation as the cause of neuroinflammation, the link between systemic C-reactive protein and brain white matter loss, the role of miR-34a in promoting healthy heart and brain, the potential of sirtuin 3 for reducing cardiac and pulmonary fibrosis, and the promise of statin therapy for ameliorating asymptomatic intracranial atherosclerotic stenosis. Additional aging-related articles highlighted the involvement of miR-181b-5p and high mobility group box-1 in hypertension, Yes-associated protein in cataract formation, multiple miRs and long noncoding RNAs in coronary artery disease development, the role of higher meat consumption on sleep problems, and the link between glycated hemoglobin and depression. The topics related to ALS suggested that individuals with higher education and living in a rural environment have a higher risk for developing ALS, and collagen XIX alpha 1 is a prognostic biomarker of ALS. The topics discussed on AD implied that extracellular amyloid β42 is likely the cause of intraneuronal neurofibrillary tangle accumulation in familial AD and traditional oriental concoctions may be useful for slowing down the progression of AD. The article on stroke suggested that inhibition of the complement system is likely helpful in promoting brain repair after ischemic stroke. The significance of the above findings for understanding the pathogenesis in aging, ALS, AD, and stroke, slowing down the progression of aging, ALS and AD, and promoting brain repair after stroke are discussed.

PL - 028 Aerobic exercise inhibits tau hyperphosphorylation through activation of the PI3K/Akt pathway in the hippocampus of APP/PS1 mice

Objective Many studies suggest that regular physical exercise can reduce the risk of Alzheimer’s disease and slow its onset and progression. However, the exact mechanism is still unclear. Clinically, Alzheimer’s disease is characterized by the presence of extracellular amyloid plaques and intraneuronal neurofibrillary tangles, which are associated with amyloid-β and tau hyperphosphorylation respectively. The PI3K/Akt signaling pathway regulates tau phosphorylation and plays a pivotal role in the development of pathology in Alzheimer’s disease. Here we investigated the effects of aerobic exercise on tau phosphorylation and examined whether these effects were mediated by the PI3K/Akt pathway in the hippocampus of APP/PS1 transgenic mice.
 Methods 40 male APP/PS1 transgenic mice were randomly divided into four groups: sedentary group (T-SE; n=10), exercise group (T-EX; n=10), sedentary with GNE-317 treatment group (T-SEG; n=10) and exercise with GNE-317 treatment group (T-EXG; n=10). GNE-317 is a potent and selective PI3K/Akt pathway inhibitor that can cross the blood-brain barrier and show effective suppression of Akt phosphorylation in the mice brain. The mice in the T-EX and T-EXG groups were given exercise training on a treadmill for 5 days/week for 8 weeks with 0% grade, and progressively ran from 30 min/day at 12 m/min, up to 60 min/day at 15 m/min. The mice in the T-SE and T-SEG groups were placed individually on another treadmill at 0 m/min for the same duration. 48 hours after the last exercise bout, all mice were intraperitoneally injected an anesthetic for inducing anesthesia, and the hippocampus were rapidly extracted. The protein and phosphorylation levels of tau, PI3K, Akt and GSK3β were assayed by Western blot and immunohistochemistry. The cognitive function were tested by morris water maze.
 Results We found out that 8 weeks of aerobic exercise reduced tau phosphorylation at multiple sites including Ser202, Thr231 and Ser396, and increased phosphorylation of Akt at Thr308 and Ser473 and of GSK3β at Ser9. Furthermore, in the morris water maze test, the exercise group showed a reduced escape time and distance compared with those of the sedentary group, suggesting that aerobic exercise improved learning and cognitive ability. While the above-mentioned results were attenuated in the PI3K/Akt inhibitor GNE-317 treatment groups.
 Conclusions Our study demonstrated that aerobic exercise could inhibit tau hyperphosphorylation and improve cognitive funtion through activation of the PI3K/Akt pathway in the hippocampus of APP/PS1 mice.

TAU AND AMYLOID CAUSE DISRUPTION IN WHITE MATTER CONNECTIVITY DIFFERENTLY FOR EARLY- AND LATE-ONSET ALZHEIMER'S DISEASE

Early-onset (EOAD) and late-onset Alzheimer's disease (LOAD) are known to have heterogeneous pathogenesis. The detection of the extracellular amyloid plaques and intraneuronal neurofibrillary tangles, important component of AD brain, is available owing to development of tracers for positron emission tomography (PET). The white matter (WM) connectivity can be acquired by diffusion-weighted magnetic resonance imaging (MRI) and is recently commonly used for classification of AD. In this study, we recruited 33 young controls (YC), 32 old controls (OC), 50 EOAD patients, and 38 LOAD patients with T1- and diffusion-weighted MRI, amyloid PET and tau PET. The PET images were acquired by using [18F]THK5351 and [18F]Flutemetamol as tracers of tau and amyloid pathology and global standardized uptake value ratios (SUVRs) were calculated for them. We constructed FA-weighted WM networks from MR images and computed w-scores of EOAD and LOAD using YC and OC networks respectively with covariates. We performed permutation-based cluster-based statistics for correlation analysis between disruption of WM connectivity and global SUVRs and for group comparison of disruption of WM connectivity between ADs. In the global association study, EOAD patients showed significantly decreased WM connectivity with increased tau SUVRs and LOAD patients showed same trends with amyloid SUVRs at the threshold of -0.5. In the former analysis, the hub regions are the right gyrus rectus, the left superior parietal lobule, and the left precuneus. In the later analysis, the hub region is the left middle occipital gyrus. For the group comparison study, EOAD patients showed significantly greater WM connectivity than LOAD patients at the threshold of 10, and the hub region is the left inferior parietal lobule. A. WM connectivity of EOAD in association with Global Tau

Alzheimer’s disease as a metabolic disorder

Alzheimer’s disease (AD) is defined by memory loss and cognitive impairment, along with the accumulation in brain of two types of abnormal structures, extracellular amyloid plaques and intraneuronal neurofibrillary tangles. Both plaques and tangles are composed predominantly of poorly soluble filaments that respectively assemble from amyloid-β (Aβ) peptides and the neuron-specific, microtubule-associated protein, tau. It is now widely acknowledged that soluble oligomers of Aβ and tau, the building blocks of plaques and tangles, are principal drivers of AD pathogenesis by acting coordinately to impair and destroy synapses, and kill neurons. The behavioral features of AD are a direct consequence of these attacks on synapses and neuronal viability, which in turn reflect a reduced capacity of AD neurons to utilize energy sources needed to maintain neuronal function and vitality. In other words, AD neurons are starving, even when they may be surrounded by abundant nutrients. Here, we review some of the evidence for the metabolic deficiencies of neurons in AD and how they impact neuronal health.

Toward a New Concept of Alzheimer's Disease Models: A Perspective from Neuroinflammation.

The continuing failure to develop an effective treatment for Alzheimer's disease urges a better understanding of the pathogenic mechanisms and the improvement of current animal models to facilitate success for clinical interventions. The transgenic models have been so far designed to recapitulate one, or both, protein lesions found in the brain of patients, the extracellular amyloid plaques and the intraneuronal neurofibrillary tangles. However, in recent years, a third pathogenic component is gaining strength in the onset and progression of this disease, the neuroinflammatory response mediated primarily by the brain's resident immune cells, microglia. This has been highlighted by the identification of genes involved in innate immunity as risk factors to develop this neurodegenerative disease. Our current concept, mostly derived from amyloid-β producing models which show a robust microglial activation, supports an initial beneficial role of these glial cells followed by a pro-inflammatory cytotoxic function later on. This view is now challenged by emerging data in human postmortem samples. We have recently demonstrated that in the hippocampus of Braak V-VI individuals there is a prominent degenerative process of the microglial population, driven by phospho-tau, that might compromise neuronal homeostasis. This scenario of microglial dysfunction/degeneration should be taken into account for developing more reliable animal models of this disease and improve their predictive value for human drug efficacy testing. Finally, correcting dysregulated brain inflammatory responses might be a promising avenue to restore cognitive function.

Synaptic Tau Seeding Precedes Tau Pathology in Human Alzheimer's Disease Brain.

Alzheimer's disease (AD) is defined by the presence of intraneuronal neurofibrillary tangles (NFTs) composed of hyperphosphorylated tau aggregates as well as extracellular amyloid-beta plaques. The presence and spread of tau pathology through the brain is classified by Braak stages and thought to correlate with the progression of AD. Several in vitro and in vivo studies have examined the ability of tau pathology to move from one neuron to the next, suggesting a “prion-like” spread of tau aggregates may be an underlying cause of Braak tau staging in AD. Using the HEK293 TauRD-P301S-CFP/YFP expressing biosensor cells as a highly sensitive and specific tool to identify the presence of seed competent aggregated tau in brain lysate—i.e., tau aggregates that are capable of recruiting and misfolding monomeric tau—, we detected substantial tau seeding levels in the entorhinal cortex from human cases with only very rare NFTs, suggesting that soluble tau aggregates can exist prior to the development of overt tau pathology. We next looked at tau seeding levels in human brains of varying Braak stages along six regions of the Braak Tau Pathway. Tau seeding levels were detected not only in the brain regions impacted by pathology, but also in the subsequent non-pathology containing region along the Braak pathway. These data imply that pathogenic tau aggregates precede overt tau pathology in a manner that is consistent with transneuronal spread of tau aggregates. We then detected tau seeding in frontal white matter tracts and the optic nerve, two brain regions comprised of axons that contain little to no neuronal cell bodies, implying that tau aggregates can indeed traverse along axons. Finally, we isolated cytosolic and synaptosome fractions along the Braak Tau Pathway from brains of varying Braak stages. Phosphorylated and seed competent tau was significantly enriched in the synaptic fraction of brain regions that did not have extensive cellular tau pathology, further suggesting that aggregated tau seeds move through the human brain along synaptically connected neurons. Together, these data provide further evidence that the spread of tau aggregates through the human brain along synaptically connected networks results in the pathogenesis of human Alzheimer's disease.

Differential Hyperphosphorylation of Tau-S199, -T231 and -S396 in Organotypic Brain Slices of Alzheimer Mice. A Model to Study Early Tau Hyperphosphorylation Using Okadaic Acid.

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder of the brain, characterized by extracellular aggregation of beta-amyloid (Aβ) and hyperphosphorylation of tau causing intraneuronal neurofibrillary tangles (NFTs). There is urgent need to study the interactions between Aβ and tau, especially to solve the question of the pathological cascade. In the present study, we aim to develop a model of organotypic brain slices in which both plaque and tau pathology can be examined. Organotypic brain slices (150 μm thick, coronal, at the hippocampal level) from adult (9 month) wildtype (WT, C57BL/6N) and transgenic AD mice (TG, APP_SweDI) were cultured for 2 weeks. To induce tau hyperphosphorylation 100 nM okadaic acid (OA), 10 μM wortmannin (WM) or both were added to the slices. Hyperphosphorylation of tau was tested at tau-S199, tau-T231 and tau-S396 using Western blot. Our data show that in TG mice with plaques a 50 kDa fragment of tau-S396 was hyperphosphorylated and that OA induced hyperphosphorylation of tau-S199. In WT mice (without plaques) OA caused hyperphosphorylation of a 50 kDa and a 38 kDa tau-T231 form and a 25 kDa sdftau-S396 fragment. The N-methyl-D-aspartate (NMDA) antagonist MK801 (1 μM) did not block these effects. Immunohistochemistry showed diffuse increased tau-S396 and tau-T231-like immunoreactivities at the hippocampal level but no formation of NFTs. Confocal microscopy indicated, that pTau-T231 was preferentially located in cytoplasma surrounding nuclei whereas pTau-S396 was found mainly in nerve fibers and strongly associated with plaques. In conclusion we provide a novel in vitro model to study both plaque and tau hyperphosphorylation but not NFTs, which could be useful to study pathological processes in AD and to screen for drugs.

Amyloid-\u03b2 with isomerized Asp7 cytotoxicity is coupled to protein phosphorylation

Neuronal dysfunction and loss associated with the accumulation of amyloid-β (Aβ) in the form of extracellular amyloid plaques and hyperphosphorylated tau in the form of intraneuronal neurofibrillary tangles represent key features of Alzheimer’s disease (AD). Amyloid plaques found in the brains of AD patients are predominantly composed of Aβ42 and its multiple chemically or structurally modified isoforms. Recently, we demonstrated that Aβ42 with isomerised Asp7 (isoAβ42) which is one of the most abundant Aβ isoform in plaques, exhibited high neurotoxicity in human neuronal cells. Here, we show that, in SH-SY5Y neuroblastoma cells, the administration of synthetic isoAβ42 rather than intact Aβ42 resulted in a significantly higher level of protein phosphorylation, especially the phosphorylation of tau, tubulins, and matrin 3. IsoAβ42 induced a drastic reduction of tau protein levels. Our data demonstrate, for the first time, that isoAβ42, being to date the only known synthetic Aβ species to cause AD-like amyloidogenesis in an animal AD model, induced cell death by disabling structural proteins in a manner characteristic of that observed in the neurons of AD patients. The data emphasize an important role of isoAβ42 in AD progression and provide possible neurotoxicity paths for this particular isoform.

A Novel Antibody Targeting Tau Phosphorylated at Serine 235 Detects Neurofibrillary Tangles.

Alzheimer's disease is characterized by two main pathological hallmarks in the human brain: the extracellular deposition of amyloid-β as plaques and the intracellular accumulation of the hyperphosphorylated protein tau as neurofibrillary tangles (NFTs). Phosphorylated tau (p-tau) specific-antibodies and silver staining have been used to reveal three morphological stages of NFT formation: pre-NFTs, intraneuronal NFTs (iNFTs), and extraneuronal NFTs (eNFTs). Here we characterize a novel monoclonal antibody, RN235, which is specific for tau phosphorylated at serine 235, and detects iNFTs and eNFTs in brain tissue, suggesting that phosphorylation at this site is indicative of late stage changes in tau.

Current Concepts of Neurodegenerative Mechanisms in Alzheimer's Disease.

Neurodegenerative diseases are hereditary or sporadic conditions that result in the progressive loss of the structure and function of neurons as well as neuronal death. Although a range of diseases lie under this umbrella term, Alzheimer's disease (AD) and Parkinson's disease (PD) are the most common neurodegenerative diseases that affect a large population around the globe. Alzheimer's disease is characterized by the abnormal accumulation of extracellular amyloid-β plaques and intraneuronal neurofibrillary tangles in brain regions and manifests as a type of dementia in aged individuals that results in memory loss, multiple cognitive abnormalities, and intellectual disabilities that interfere with quality of life. Since the discovery of AD, a wealth of new information has emerged that delineates the causes, mechanisms of disease, and potential therapeutic agents, but an effective remedy to cure the diseases has not been identified yet. This could be because of the complexity of the disease process, as it involves various contributing factors that include environmental factors and genetic predispositions. This review summarizes the current understanding on neurodegenerative mechanisms that lead to the emergence of the pathology of AD.

Exposure to Aluminum in Daily Life and Alzheimer's Disease.

Aluminum is the third most abundant element on the earth's crust and has been considered a constituent of rather inert minerals. Therefore, it has often been regarded as not having a significant health hazard. Consequently, aluminum-containing agents have been used in processing, packaging, and storage of food products and also in the treatment of drinking water as flocculants. Recently, acid rain due to environmental pollution has transported more aluminum-containing minerals into residential drinking water resources. It is therefore not surprising that aluminum burden in the human body has increased. Research data showed that aluminum is not as safe as was previously thought and that aluminum may contribute to the initial advancement of Alzheimer's disease. Aluminum-mediated neurodegeneration resulting in cognitive dysfunction has been associated with amyloidβ (Aβ) deposition, formation of intraneuronal neurofibrillary tangles (NFTs), and apoptotic neuronal death characterized histopathologically in AD. The origin of Alzheimer's disease is generally not known; its development is likely triggered by unknown environmental factors. Although it is inconsistent with the link between human exposure to aluminum in everyday life and its contribution to Alzheimer's disease, a growing body of evidence points to aluminum as being one such significant influence.

Oligomeric amyloid-beta induces MAPK-mediated activation of brain cytosolic and calcium-independent phospholipase A2 in a spatial-specific manner

Alzheimer’s disease (AD) is histopathologically characterized by the build-up of fibrillar amyloid beta (Aβ) in the form of amyloid plaques and the development of intraneuronal neurofibrillary tangles consisting of aggregated hyperphosphorylated Tau. Although amyloid fibrils were originally considered responsible for AD pathogenesis, recent convincing evidence strongly implicates soluble oligomeric Aβ as the primary neurotoxic species driving disease progression. A third largely ignored pathological hallmark, originally described by Alois Alzheimer, is the presence of “adipose inclusions”, suggestive of aberrant lipid metabolism. The molecular mechanisms underlying these “lipoid granules”, as well as their potential link to soluble and/or fibrillar Aβ remain largely unknown. Seeking to better-understand these conundrums, we took advantage of the powerful technology of multidimensional mass spectrometry-based shotgun lipidomics and an AD transgenic mouse model overexpressing mutant amyloid precursor protein (APP E693Δ-Osaka-), where AD-like pathology and neurodegeneration occur as a consequence of oligomeric Aβ accumulation in the absence of amyloid plaques. Our results revealed for the first time that APP overexpression and oligomeric Aβ accumulation lead to an additive global accumulation of nonesterified polyunsaturated fatty acids (PUFAs) independently of amyloid plaques. Furthermore, we revealed that this accumulation is mediated by an increase in phospholipase A2 (PLA2) activity, evidenced by an accumulation of sn-1 lysophosphatidylcholine and by MAPK-mediated phosphorylation/activation of group IV Ca2+-dependent cytosolic (cPLA2) and the group VI Ca2+-independent PLA2 (iPLA2) independently of PKC. We further revealed that Aβ-induced oxidative stress also disrupts lipid metabolism via reactive oxygen species-mediated phospholipid cleavage leading to increased sn-2 lysophosphatidylcholine as well as lipid peroxidation and the subsequent accumulation of 4-hydroxynonenal. Brain histological studies implicated cPLA2 activity with arachidonic acid accumulation within myelin-rich regions, and iPLA2 activity with docosahexaenoic acid accumulation within pyramidal neuron-rich regions. Taken together, our results suggest that PLA2-mediated accumulation of free PUFAs drives AD-related disruption of brain lipid metabolism.

IDENTIFICATION OF SERUM MICRORNA AS A POTENTIAL BIOMARKER RELATED TO THE PROGRESSION OF ALZHEIMER’S DISEASE

Alzheimer's disease (AD) is characterized by two neuropathological hallmarks: extracellular senile plaques (SPs) and intraneuronal neurofibrillary tangles (NFTs). These two lesions are thought to eventually lead to progressive synaptic dysfunction followed by neuronal cell death in the brain. The spreading of NFTs across the human brain is well correlated with the cognitive severity of AD. As the genetic background contributes to a course of the development of AD, genome-wide association studies have been performed to identify genetic risk factor. A number of genetic risk variants have been identified and almost all variants are located in introns or intergenic regions. Consequently, non-coding RNAs including microRNA (miRNA) are attractive molecules involved in post-transcriptional regulation on AD pathology. We attempted to identify the serum miRNA accompanied with pathological changes in the brain because miRNAs are relatively stable in serum or plasma. To determine serum miRNA by next-generation sequencing, we first surveyed 45 serum samples (discovery set) consist of 27 AD patients (SP stage: C, NFT stage: IV through VI) and 18 controls (SP stage: 0 and A, NFT stage: 0 through II) that were obtained within two weeks before neuropathological diagnosis. Significant miRNAs were validated with clinical sample set composed of 36 AD patients and 22 age-matched cognitively normal controls. Three miRNAs, hsa-miR-501–3p, hsa-let-7f-5p, and hsa-miR-26b-5p, were significantly deregulated in AD patients compared with controls. Among them the most significant serum hsa-miR-501–3p levels were downregulated in AD patients, and its lower levels significantly correlated with lower MMSE scores. Contrary to the serum levels, hsa-miR-501–3p was remarkably upregulated in AD autopsy brains as the lesion advanced. The hsa-miR-501–3p overexpression in cultured cells, which mimicked the hsa-miR-501–3p upregulation in the AD brains, induced significant downregulation of 128 genes that overrepresented the Gene Ontology terms such as DNA replication and the mitotic cell cycle. Our results suggest that hsa-miR-501–3p is a novel serum biomarker that presumably corresponds to pathological events occurring in AD brains.

Neurofibrillary Tangles of Aβx-40 in Alzheimer's Disease Brains.

The two pathognomonic lesions in the brain of AD patients are senile plaques and intraneuronal neurofibrillary tangles (NFT). Previous studies have demonstrated that amyloid-β (Aβ) is a component of both senile plaques and NFTs, and have showed that intracellular accumulation of Aβ is toxic for cells and precedes the appearance of extracellular amyloid deposits. Here we report that there are numerous intraneuronal NFT and extraneuronal NFT immunoreactive for Aβx-40 in which there is no co-localization with tau staining suggesting the existence of two different neurodegenerating populations associated with the intracellular accumulation of either tau protein or Aβx-40 in AD.

Insulin deprivation induces PP2A inhibition and tau hyperphosphorylation in hTau mice, a model of Alzheimer\u2019s disease-like tau pathology

Abnormally hyperphosphorylated tau aggregated as intraneuronal neurofibrillary tangles is one of the two neuropathological hallmarks of Alzheimer’s disease (AD). The majority of AD cases are sporadic with numerous environmental, biological and genetic risks factors. Interestingly, insulin dysfunction and hyperglycaemia are both risk factors for sporadic AD. However, how hyperglycaemia and insulin dysfunction affect tau pathology, is not well understood. In this study, we examined the effects of insulin deficiency on tau pathology in transgenic hTau mice by injecting different doses of streptozotocin (STZ), a toxin that destroys insulin-producing cells in the pancreas. One high dose of STZ resulted in marked diabetes, and five low doses led to a milder diabetes. Both groups exhibited brain tau hyperphosphorylation but no increased aggregation. Tau hyperphosphorylation correlated with inhibition of Protein Phosphatase 2A (PP2A), the main tau phosphatase. Interestingly, insulin injection 30 minutes before sacrifice partially restored tau phosphorylation to control levels in both STZ-injected groups. Our results confirm a link between insulin homeostasis and tau phosphorylation, which could explain, at least in part, a higher incidence of AD in diabetic patients.

Personalized Medicine and Resurrected Hopes for the Management of Alzheimer's Disease: A Modular Approach Based on GSK-3β Inhibitors.

Alzheimer's disease (AD) is one of the most common neurological disorders with vast reaching worldwide prevalence. Research attempts to decipher what's happening to the human mind have shown that pathogenesis of AD is associated with misfolded protein intermediates displaying tertiary structure conformational changes eventually leading to forming large polymers of unwanted aggregates. The two hallmarks of AD pathological protein aggregates are extraneuronal β-amyloid (Aβ) based senile plaques and intraneuronal neurofibrillary tangles (NFTs). As such, AD is categorized as a protein misfolding neurodegenerative disease (PMND) . Therapeutic interventions interfering with the formation of these protein aggregates have been widely explored as potential pathways for thwarting AD progression. One such tactic is modulating the function of enzymes involved in the metabolic pathways leading to formation of these misfolded protein aggregates. Much evidence has shown that glycogen synthase kinase-3β (GSK-3β) plays a key role in hyperphosphorylation of tau protein leading eventually to its aggregation to form NFTs. Data presented hereby will display a plethora of information as to how to interfere with progression of AD through the route of GSK-3β activity control.

Copper and Alzheimer's Disease.

Alzheimer's disease (AD) is the most common form of adult neurode-generation and is characterised by progressive loss of cognitive function leading to death. The neuropathological hallmarks include extracellular amyloid plaque accumulation in affected regions of the brain, formation of intraneuronal neurofibrillary tangles, chronic neuroinflammation, oxidative stress, and abnormal biometal homeostasis. Of the latter, major changes in copper (Cu) levels and localisation have been identified in AD brain, with accumulation of Cu in amyloid deposits, together with deficiency of Cu in some brain regions. The amyloid precursor protein (APP) and the amyloid beta (Aβ) peptide both have Cu binding sites, and interaction with Cu can lead to potentially neurotoxic outcomes through generation of reactive oxygen species. In addition, AD patients have systemic changes to Cu metabolism, and altered Cu may also affect neuroinflammatory outcomes in AD. Although we still have much to learn about Cu homeostasis in AD patients and its role in disease aetiopathology, therapeutic approaches for regulating Cu levels and interactions with Cu-binding proteins in the brain are currently being developed. This review will examine how Cu is associated with pathological changes in the AD brain and how these may be targeted for therapeutic intervention.

N-Acetylcysteine: A Natural Antidote for Alzheimer's Disease

Alzheimer's disease (AD) is the most devastating age-related dementia, which has no effective treatment. Since the pathological hallmarks of AD brains are Aβ plaques and intra-neuronal tau-containing neurofibrillary tangles, most therapeutic approaches, including immunotherapy, are based on the concept that the accumulation of these proteins produces neuronal damage and death. Alternatively, it has been proposed that reactive species can cause oxidative damage including mitochondrial disruption, contributing to AD initiation and progression. Can these cellular dysfunctions be linked by a common pathogenic mechanism susceptible to therapy with the natural compound N-acetylcysteine? A cellular cysteine network (CYSTEINET) has been proposed as a functional and structural matrix of interconnected sensitive cysteine-containing proteins (SCCPs) that in conjunction with reactive species and the cysteine/glutathione cycles can regulate the bioenergetic metabolism, the redox homeostasis, and the cellular survival through different pathways that bear the same regulatory thiol radical. The present paper proposes that cysteinet is impaired in Alzheimer's disease resulting in a functional and structural deregulation of the matrix of interconnected cysteine-containing proteins that result in misfolding, aggregation and accumulation of specific toxic proteins. In this context, the role of N-acetylcysteine to prevent and restore cysteinet deregulation in AD development and progression is discussed.

384 - Okadaic Acid and Hypoxia Induced Dementia Model of Alzheimer’s Type in Rats

Alzheimer's disease (AD) is the most common cause of progressive decline of memory function in aged humans. To study about a disease mechanism, animal models for the specific disease are needed. Various animal models are developed which produce one or the other AD feature but none has been known which produces full AD symptomatology. Okadaic acid (OKA) is a protein phosphatse 2A (PP2A) inhibitor which leads to hyperphosphorylation of tau protein. Hyperphosphorylated tau protein is present in intraneuronal neurofibrillary tangles, a characteristic feature of AD pathology. Intracerebroventricular (ICV) injection of OKA in rats causes neurotoxicity associated with oxidative damage and mitochondrial dysfunction. However, this model lacks amyloid pathology as observed in AD. There are compelling evidences suggesting that patients with history of stroke in which hypoxic conditions occur are more susceptible in developing AD. In this study we developed a rat model of AD by combining two different treatments, OKA and hypoxia which mimics most of the neuropathological, neurobehavioural and neurochemical changes observed in AD. In an attempt to do so, OKA, (200ng, ICV) was microinjected bilaterally into the hippocampus of male wistar rats followed by exposure of same rats to hypoxic conditions (10%) for 3 days. The combination model exhibited induction tau hyperphosphorylation along with Aβ upregulation. This induced animal model showed dysfunction in neurotransmitter system (acetylcholine activity and expression); memory impairment as assessed by morris water maze and avoidance tests along with enhanced oxidative damage. These data suggest that the OKA injection into the hippocampus of rats followed by hypoxia exposure causes amyloid beta (Aβ) upregulation, neurofibrillary tangles (NFTs) like changes, cognitive deficiency, loss of acetylcholinesterase (AChE) neurons, and oxidative stress in rats similar to that seen in AD.

Phospho-Tau and Cognitive Decline in Alzheimer's Disease. Commentary: Tau in physiology and pathology.

In the brain, abnormal phosphorylation of tau leads to the formation of paired helical filaments, which are the main components of intraneuronal neurofibrillary tangles (NFT) (Grundke-Iqbal et al., 1986) that are characteristic of Alzheimer's disease (AD) and other tauopathies (Lee et al., 2001). There is an intense debate about the relationship of phospho-tau and the typical cognitive deficits in AD (Castellani et al., 2008) but, owing to the limited data that is available about synaptic circuits in the normal human brain and in that of the AD patient, the basic mechanism/s of cognitive deterioration are still a mystery. The article by Wang and Mandelkow (2016) presents a timely review of the roles of tau in physiology and disease. However, the role of hyperphosphorylation of tau in dendritic pathology is not fully addressed. Wang and Mandelkow concluded that NFT are probably unrelated to cognitive impairment, mainly based on studies using several lines of mice transgenic for wild-type or mutant human tau. However, in a previous study assessing the possible alterations to dendritic spines in pyramidal cells from AD patients (Merino-Serrais et al., 2013), we found a remarkable loss of dendritic spines from pyramidal cells containing NFT. Since pyramidal neurons represent the principal building blocks of the cerebral cortex and dendritic spines are the main postsynaptic elements of cortical excitatory synapses and are fundamental structures in memory, learning, and cognition (DeFelipe, 2015), these alterations constitute what we think is an important early event in the pathogenesis of AD. We used intracellular injections of Lucifer yellow (LY) in fixed brain tissue from AD patients to visualize and reconstruct dendritic arbors of pyramidal neurons—using high-resolution tile scan stacks of confocal microscopy images—to compare neurons that were free of signs of any neurofibrillary pathology with those showing either diffuse phospho-tau (putative pre-tangle state) or aggregated tau NFT. Following injection in the parahippocampal cortex and CA1, the sections were immunostained for LY and phospho-tau. In the so-called putative “pre-tangle” stage, the dendritic trees of pyramidal neurons were unchanged (pattern I; Figure 1, Panel 1). In the presence of well-developed NFT, however, dendritic spine loss was obvious (pattern IIb; Figure 1, Panel 2). In cases with an intermediate state of neurofibrillary pathology (pattern IIa), the loss of dendritic spines was more variable. Importantly, we compared neighboring cells with and without neurofibrillary pathology (see A, B in Figure 1, Panel 1) to avoid confounding factors such as: (1) morphological differences in the structure of pyramidal cells due to regional specializations (i.e., pyramidal cells in different cortical regions and layers may show morphological differences); (2) high inter-individual variability (sex, age, medical treatment, etc.,) factors that could affect brain structure; and (3) the highly variable course of AD, as the neuropathological changes are not homogenous among patients or in different regions of the brain of the same patient, giving rise to variation in the alterations to cortical circuits. Figure 1 Panel 1. Neurons and dendrites in the parahippocampal cortex of patient P9 injected with LY whose soma is free of phospho-tau PHF-tauAT8-ir (PHF-tauAT8-; A–D) or contains phospho-tau (PHF-tauAT8+ in the putative pre-tangle state (Pattern I; E–H) ... We concluded that the presence of phospho-tau in neurons does not necessarily mean that they suffer severe and irreversible effects as thought previously, but rather the characteristic cognitive impairment in AD is likely to depend on the relative number of neurons that have well-developed tangles. Certainly, these observations differ from those of studies on transgenic mouse brains, where human mutant tau was overexpressed. However, this discrepancy could be explained by the fact that transgenic mouse brains do not reproduce all features of AD found in humans. Furthermore, there are many molecular and structural differences between mouse and human brain. Thus, extrapolation of data obtained in mice and humans is rather difficult and possible mismatches between the two species should be taken into consideration when dealing with animal models of AD.