Postmortem Alzheimer's Disease Research Articles

A Copper Complex of a Thiosemicarbazone-Pyridylhydrazone Ligand Containing a Vinylpyridine Functional Group as a Potential Imaging Agent for Amyloid-β Plaques

Complexes containing positron-emitting radionuclides of copper have the potential to be of use for diagnostic imaging with positron emission tomography. Alzheimer’s disease is characterised by the presence of amyloid-β plaques in the brain. A new thiosemicarbazone-pyridyl hydrazone tetradentate ligand with a pyridyl-4-vinylpyridine functional group was prepared with the aim of making a copper complex that binds to amyloid-β plaques to assist in the diagnosis of Alzheimer’s disease. The ligand forms a charge neutral complex with copper(ii) that was characterised by X-ray crystallography and the electrochemical behaviour of the complex was investigated by cyclic voltammetry. The new ligand can be radiolabelled with positron-emitting copper-64 at room temperature in excellent radiochemical yields. The new complex interacts with synthetic amyloid-β fibrils and binds amyloid-β plaques present in post-mortem Alzheimer’s disease brain tissue.

GABAergic signaling in Alzheimer's disease

GABAergic signaling in Alzheimer's disease

Estrogen activates Alzheimer's disease genes

IntroductionWomen are at increased risk for Alzheimer's disease (AD), but the reason why remains unknown. One hypothesis is that low estrogen levels at menopause increases vulnerability to AD, but this remains unproven. MethodsWe compared neuronal genes upregulated by estrogen in ovariectomized female rhesus macaques with a database of >17,000 diverse gene sets and applied a rare variant burden test to exome sequencing data from 1208 female AD patients with the age of onset < 75 years and 2162 female AD controls. ResultsWe found a striking overlap between genes upregulated by estrogen in macaques and genes downregulated in the human postmortem AD brain, and we found that estrogen upregulates the APOE gene and that progesterone acts antagonistically to estrogen genome-wide. We also found that female patients with AD have excess rare mutations in the early menopause gene MCM8. DiscussionWe show with genomic data that the menopausal loss of estrogen could underlie the increased risk for AD in women.

Antemortem CSF Aβ42/Aβ40 ratio predicts Alzheimer's disease pathology better than Aβ42 in rapidly progressive dementias.

ObjectiveDespite the critical importance of pathologically confirmed samples for biomarker validation, only a few studies have correlated CSF Aβ42 values in vivo with postmortem Alzheimer's disease (AD) pathology, while none evaluated the CSF Aβ42/Aβ40 ratio. We compared CSF Aβ42 and Aβ42/Aβ40 ratio as biomarkers predicting AD neuropathological changes in patients with a short interval between lumbar puncture and death.MethodsWe measured CSF Aβ40 and Aβ42 and assessed AD pathology in 211 subjects with rapidly progressive dementia (RPD) and a definite postmortem diagnosis of Creutzfeldt‐Jakob disease (n = 159), AD (n = 12), dementia with Lewy bodies (DLB, n = 4), AD/DLB mixed pathologies (n = 5), and various other pathologies (n = 31).ResultsThe score reflecting the severity of Aβ pathology showed a better correlation with ln(Aβ42/Aβ40) (R 2 = 0.506, β = −0.713, P < 0.001) than with ln(Aβ42) (R 2 = 0.206, β = −0.458, P < 0.001), which was confirmed after adjusting for covariates. Aβ42/Aβ40 ratio showed significantly higher accuracy than Aβ42 in the distinction between cases with or without AD pathology (AUC 0.818 ± 0.028 vs. 0.643 ± 0.039), especially in patients with Aβ42 levels ≤495 pg/mL (AUC 0.888 ± 0.032 vs. 0.518 ± 0.064). Using a cut‐off value of 0.810, the analysis of Aβ42/Aβ40 ratio yielded 87.0% sensitivity, 88.2% specificity in the distinction between cases with an intermediate‐high level of AD pathology and those with low level or no AD pathology.InterpretationThe present data support the use of CSF Aβ42/Aβ40 ratio as a biomarker of AD pathophysiology and noninvasive screener for Aβ pathology burden, and its introduction in the research diagnostic criteria for AD.

Nurr1 (NR4A2) regulates Alzheimer's disease-related pathogenesis and cognitive function in the 5XFAD mouse model.

The orphan nuclear receptor Nurr1 (also known as NR4A2) is critical for the development and maintenance of midbrain dopaminergic neurons, and is associated with Parkinson's disease. However, an association between Nurr1 and Alzheimer's disease (AD)‐related pathology has not previously been reported. Here, we provide evidence that Nurr1 is expressed in a neuron‐specific manner in AD‐related brain regions; specifically, it is selectively expressed in glutamatergic neurons in the subiculum and the cortex of both normal and AD brains. Based on Nurr1’s expression patterns, we investigated potential functional roles of Nurr1 in AD pathology. Nurr1 expression was examined in the hippocampus and cortex of AD mouse model and postmortem human AD subjects. In addition, we performed both gain‐of‐function and loss‐of‐function studies of Nurr1 and its pharmacological activation in 5XFAD mice. We found that knockdown of Nurr1 significantly aggravated AD pathology while its overexpression alleviated it, including effects on Aβ accumulation, neuroinflammation, and neurodegeneration. Importantly, 5XFAD mice treated with amodiaquine, a highly selective synthetic Nurr1 agonist, showed robust reduction in typical AD features including deposition of Aβ plaques, neuronal loss, microgliosis, and impairment of adult hippocampal neurogenesis, leading to significant improvement of cognitive impairment. These in vivo and in vitro findings suggest that Nurr1 critically regulates AD‐related pathophysiology and identify Nurr1 as a novel AD therapeutic target.

Amyloid-beta and phosphorylated tau in post-mortem Alzheimer\u2019s disease retinas

In-vivo labeling of retinal amyloid-beta(Aβ) and tau has potential as non-invasive biomarker for Alzheimer’s disease (AD). However, literature on the presence of Aβ and phosphorylated tau (pTau) in AD retinas is inconclusive. We therefore assessed the presence of Aβ and pTau in post-mortem retinas in 6 AD and 6 control cases who donated brains and eyes to the Netherlands Brain Bank. Neuropathological diagnosis of AD was made according to NIA-AA criteria. Formalin fixed retinas were dissected in quadrants and cross-sections of medial and superior retinas were made. Immuno-histochemical stainings were performed for Aβ, amyloid precursor protein (APP) and pTau. To assess translation to an in-vivo set up using curcumin as labelling fluorophore, co-stainings with curcumin were performed. No typical Aβ-plaques and neurofibrillary tangles, like in the cerebral cortex, were observed in AD retinas. A diffuse immunoreactive signal for pTau was increased in the inner and outer plexiform layers of the retina in AD cases compared to control cases with absence of cerebral amyloid pathology. Immunostaining with anti-Aβ and anti-APP antibodies yielded signal in ganglion cells, amacrine cells, horizontal cells and Müller cells in both control and AD cases. We observed small extracellular deposits positive for anti-Aβ antibodies 12F4 and 6E10 and negative for 4G8 and curcumin. A subset of these deposits could be characterized as corpora amylacea. In conclusion we found that retinal manifestations of AD pathology appear to be different compared to cerebral AD pathology. Using a qualitative cross-sectional approach, we did not find Aβ/APP related differences in the retina between AD and control subjects. In contrast, tau related changes were found to be present in cases with cerebral AD pathology, suggesting retinal tau as a potential biomarker for AD.

Lipocalin 2 contributes to brain iron dysregulation but does not affect cognition, plaque load, and glial activation in the J20 Alzheimer mouse model

BackgroundLipocalin 2 (Lcn2) is an acute-phase protein implicated in multiple neurodegenerative conditions. Interestingly, both neuroprotective and neurodegenerative effects have been described for Lcn2. Increased Lcn2 levels were found in human post-mortem Alzheimer (AD) brain tissue, and in vitro studies indicated that Lcn2 aggravates amyloid-β-induced toxicity. However, the role of Lcn2 has not been studied in an in vivo AD model. Therefore, in the current study, the effects of Lcn2 were studied in the J20 mouse model of AD.MethodsJ20 mice and Lcn2-deficient J20 (J20xLcn2 KO) mice were compared at the behavioral and neuropathological level.ResultsJ20xLcn2 KO and J20 mice presented equally strong AD-like behavioral changes, cognitive impairment, plaque load, and glial activation. Interestingly, hippocampal iron accumulation was significantly decreased in J20xLcn2 KO mice as compared to J20 mice.ConclusionsLcn2 contributes to AD-like brain iron dysregulation, and future research should further explore the importance of Lcn2 in AD.

Loss of Ca2+/Calmodulin Dependent Protein Kinase Kinase 2 Leads to Aberrant Transferrin Phosphorylation and Trafficking: A Potential Biomarker for Alzheimer's Disease.

Ca2+/calmodulin-dependent protein kinase kinase 2 (CaMKK2) is a serine/threonine kinase that is activated following an increase in the intracellular Ca2+ concentration and activates multiple signaling cascades that control physiologically important neuronal processes. CaMKK2 has been implicated in schizophrenia, bipolar disease, neurodegeneration, and cancer. Using isoelectric focusing (IEF) and mass spectrometry-based proteomic analysis, it was found that knockdown (KD) of CaMKK2 in cultured adult primary dorsal root ganglion (DRG) neurons resulted in the reduction of transferrin (TF) phosphorylation at multiple functionally relevant residues which corresponded to loss of an acidic fraction (pH~3-4) of TF. In vitro studies using CRISPR/Cas9 based CaMKK2 knockout (KO) HEK293 and HepG2 cells lines validated previous findings and revealed that loss of CaMKK2 interfered with TF trafficking and turnover. TF is an iron transporter glycoprotein. Abnormal accumulation of iron and/or deregulated Ca2+ homeostasis leads to neurodegeneration in Alzheimer's disease (AD). Therefore, it was hypothesized that aberrant CaMKK2 in AD may lead to aberrant phosphorylated transferrin (P-TF: pH~3-4 fraction) which may serve as a hallmark biomarker for AD. A significant reduction of P-TF in the brain and serum of CaMKK2 KO mice and a triple-transgenic mouse model of AD (3xTg-AD) supported this hypothesis. In addition, analysis of early (< 65 years) and late-stage (>65 years) postmortem human AD cerebrospinal fluid (CSF) and serum samples revealed that aberrant P-TF (pH~3-4 fraction) profile was associated with both early and late-stage AD compared to age-matched controls. This indicates P-TF (pH~3-4 fraction) profile may be useful as a minimally invasive biomarker for AD. In addition, this study provides a link between aberrant CaMKK2 with TF trafficking and turnover which provides a novel insight into the neurodegeneration process.

Dissecting the genetic relationship between cardiovascular risk factors and Alzheimer's disease.

Cardiovascular (CV)- and lifestyle-associated risk factors (RFs) are increasingly recognized as important for Alzheimer's disease (AD) pathogenesis. Beyond the ε4 allele of apolipoprotein E (APOE), comparatively little is known about whether CV-associated genes also increase risk for AD. Using large genome-wide association studies and validatedtools to quantify genetic overlap, we systematically identified single nucleotide polymorphisms (SNPs) jointly associated with AD and one or more CV-associated RFs, namely body mass index (BMI), type 2 diabetes (T2D), coronary artery disease (CAD), waist hip ratio (WHR), total cholesterol (TC), triglycerides (TG), low-density (LDL) and high-density lipoprotein (HDL). In fold enrichment plots, we observed robust genetic enrichment in AD as a function of plasma lipids (TG, TC, LDL, and HDL); we found minimal AD genetic enrichment conditional on BMI, T2D, CAD, and WHR. Beyond APOE, at conjunction FDR < 0.05 we identified 90 SNPs on 19 different chromosomes that were jointly associated with AD and CV-associated outcomes. In meta-analyses across three independent cohorts, we found four novel loci within MBLAC1 (chromosome 7, meta-p = 1.44 × 10-9), MINK1 (chromosome 17, meta-p = 1.98 × 10-7) and two chromosome 11 SNPs within the MTCH2/SPI1 region (closest gene = DDB2, meta-p = 7.01 × 10-7 and closest gene = MYBPC3, meta-p = 5.62 × 10-8). In a large 'AD-by-proxy' cohort from the UK Biobank, we replicated three of the four novel AD/CV pleiotropic SNPs, namely variants within MINK1, MBLAC1, and DDB2. Expression of MBLAC1, SPI1, MINK1 and DDB2 was differentially altered within postmortem AD brains. Beyond APOE, we show that the polygenic component of AD is enriched for lipid-associated RFs. We pinpoint a subset of cardiovascular-associated genes that strongly increase the risk for AD. Our collective findings support a disease model in which cardiovascular biology is integral to the development of clinical AD in a subset of individuals.

Evidence of intraneuronal Aβ accumulation preceding tau pathology in the entorhinal cortex.

Growing evidence gathered from transgenic animal models of Alzheimer's disease (AD) indicates that the intraneuronal accumulation of amyloid-β (Aβ) peptides is an early event in the AD pathogenesis, producing cognitive deficits before the deposition of insoluble plaques. Levels of soluble Aβ are also a strong indicator of synaptic deficits and concurrent AD neuropathologies in post-mortem AD brain; however, it remains poorly understood how this soluble amyloid pool builds within the brain in the decades leading up to diagnosis, when a patient is likely most amenable to early therapeutic interventions. Indeed, characterizing early intracellular Aβ accumulation in humans has been hampered by the lack of Aβ-specific antibodies, variability in the quality of available human brain tissue and the limitations of conventional microscopy. We therefore sought to investigate the development of the intraneuronal Aβ pathology using extremely high-quality post-mortem brain material obtained from a cohort of non-demented subjects with short post-mortem intervals and processed by perfusion-fixation. Using well-characterized monoclonal antibodies, we demonstrate that the age-dependent intraneuronal accumulation of soluble Aβ is pervasive throughout the entorhinal cortex and hippocampus, and that this phase of the amyloid pathology becomes established within AD-vulnerable regions before the deposition of Aβ plaques and the formation of tau neurofibrillary tangles. We also show for the first time in post-mortem human brain that Aβ oligomers do in fact accumulate intraneuronally, before the formation of extracellular plaques. Finally, we validated the origin of the Aβ-immunopositive pool by resolving Aβ- and APP/CTF-immunoreactive sites using super resolution structured illumination microscopy. Together, these findings indicate that the lifelong accrual of intraneuronal Aβ may be a potential trigger for downstream AD-related pathogenic events in early disease stages.

Tau protein aggregation is associated with cellular senescence in the brain.

Tau protein accumulation is the most common pathology among degenerative brain diseases, including Alzheimer's disease (AD), progressive supranuclear palsy (PSP), traumatic brain injury (TBI), and over twenty others. Tau‐containing neurofibrillary tangle (NFT) accumulation is the closest correlate with cognitive decline and cell loss (Arriagada, Growdon, Hedley‐Whyte, & Hyman, 1992), yet mechanisms mediating tau toxicity are poorly understood. NFT formation does not induce apoptosis (de Calignon, Spires‐Jones, Pitstick, Carlson, & Hyman, 2009), which suggests that secondary mechanisms are driving toxicity. Transcriptomic analyses of NFT‐containing neurons microdissected from postmortem AD brain revealed an expression profile consistent with cellular senescence. This complex stress response induces aberrant cell cycle activity, adaptations to maintain survival, cellular remodeling, and metabolic dysfunction. Using four AD transgenic mouse models, we found that NFTs, but not Aβ plaques, display a senescence‐like phenotype. Cdkn2a transcript level, a hallmark measure of senescence, directly correlated with brain atrophy and NFT burden in mice. This relationship extended to postmortem brain tissue from humans with PSP to indicate a phenomenon common to tau toxicity. Tau transgenic mice with late‐stage pathology were treated with senolytics to remove senescent cells. Despite the advanced age and disease progression, MRI brain imaging and histopathological analyses indicated a reduction in total NFT density, neuron loss, and ventricular enlargement. Collectively, these findings indicate a strong association between the presence of NFTs and cellular senescence in the brain, which contributes to neurodegeneration. Given the prevalence of tau protein deposition among neurodegenerative diseases, these findings have broad implications for understanding, and potentially treating, dozens of brain diseases.

Integrative approach to sporadic Alzheimer\u2019s disease: deficiency of TYROBP in a tauopathy mouse model reduces C1q and normalizes clinical phenotype while increasing spread and state of phosphorylation of tau

TYROBP/DAP12 forms complexes with ectodomains of immune receptors (TREM2, SIRPβ1, CR3) associated with Alzheimer’s disease (AD) and is a network hub and driver in the complement subnetwork identified by multi-scale gene network studies of postmortem human AD brain. Using transgenic or viral approaches, we characterized in mice the effects of TYROBP deficiency on the phenotypic and pathological evolution of tauopathy. Biomarkers usually associated with worsening clinical phenotype (i.e., hyperphosphorylation and increased tauopathy spreading) were unexpectedly increased in MAPTP301S;Tyrobp-/- mice despite the improved learning behavior and synaptic function relative to controls with normal levels of TYROBP. Notably, levels of complement cascade initiator C1q were reduced in MAPTP301S;Tyrobp-/- mice, consistent with the prediction that C1q reduction exerts a neuroprotective effect. These observations suggest a model wherein TYROBP-KO-(knock-out)-associated reduction in C1q is associated with normalized learning behavior and electrophysiological properties in tauopathy model mice despite a paradoxical evolution of biomarker signatures usually associated with neurological decline.

The intellectual disability gene PQBP1 rescues Alzheimer\u2019s disease pathology

Early-phase pathologies of Alzheimer’s disease (AD) are attracting much attention after clinical trials of drugs designed to remove beta-amyloid (Aβ) aggregates failed to recover memory and cognitive function in symptomatic AD patients. Here, we show that phosphorylation of serine/arginine repetitive matrix 2 (SRRM2) at Ser1068, which is observed in the brains of early phase AD mouse models and postmortem end-stage AD patients, prevents its nuclear translocation by inhibiting interaction with T-complex protein subunit α. SRRM2 deficiency in neurons destabilized polyglutamine binding protein 1 (PQBP1), a causative gene for intellectual disability (ID), greatly affecting the splicing patterns of synapse-related genes, as demonstrated in a newly generated PQBP1-conditional knockout model. PQBP1 and SRRM2 were downregulated in cortical neurons of human AD patients and mouse AD models, and the AAV-PQBP1 vector recovered RNA splicing, the synapse phenotype, and the cognitive decline in the two mouse models. Finally, the kinases responsible for the phosphorylation of SRRM2 at Ser1068 were identified as ERK1/2 (MAPK3/1). These results collectively reveal a new aspect of AD pathology in which a phosphorylation signal affecting RNA splicing and synapse integrity precedes the formation of extracellular Aβ aggregates and may progress in parallel with tau phosphorylation.

Anti-neuroinflammatory effects of SLOH in Aβ-induced BV-2 microglial cells and 3xTg-AD mice involve the inhibition of GSK-3β

Neuroinflammation has been observed in post-mortem Alzheimer’s disease (AD) brains which could be due to Aβ interacting with microglia and astrocytes. SLOH, a carbazole-based fluorophore, was shown to bind to Aβ peptides. Herein, we investigated the anti-neuroinflammatory effects of SLOH using a BV-2 microglial cell model and a triple transgenic AD (3xTg-AD) mouse model. BV-2 cells were incubated with Aβ in the presence of SLOH for 24 h. The levels of pro-inflammatory and anti-inflammatory cytokines were determined. Moreover, 3xTg-AD mice were administrated with SLOH (2 mg kg−1) for one month. The mice were then sacrificed and the brains were used to assess the levels of pro-inflammatory, anti-inflammatory cytokines and the activation of ionized calcium-binding adapter molecule 1 (Iba1). BV-2 cell studies suggested that SLOH reduced the production and mRNA levels of pro-inflammatory cytokines TNF-α, IL-1β, COX-2, iNOS, and increased IL-10. Animal study confirmed that SLOH reduced the production of pro-inflammatory cytokines and increased the level of anti-inflammatory cytokine. Moreover, SLOH inhibited the activity of GSK-3β. In 3xTg-AD mouse model, SLOH treatment significantly decreased the number of Iba1-positive cells in mouse brains. Our results demonstrated that SLOH significantly attenuated the neuroinflammation through down-regulating the activity of GSK-3β.

Role of Rab GTPases in Alzheimer's Disease.

Alzheimer's disease (AD) comprises two major pathological hallmarks: extraneuronal deposition of β-amyloid (Aβ) peptides ("senile plaques") and intraneuronal aggregation of the microtubule-associated protein tau ("neurofibrillary tangles"). Aβ is derived from sequential cleavage of the β-amyloid precursor protein by β- and γ-secretases, while aggregated tau is hyperphosphorylated in AD. Mounting evidence suggests that dysregulated trafficking of these AD-related proteins contributes to AD pathogenesis. Rab proteins are small GTPases that function as master regulators of vesicular transport and membrane trafficking. Multiple Rab GTPases have been implicated in AD-related protein trafficking, and their expression has been observed to be altered in postmortem AD brain. Here we review current implicated roles of Rab GTPase dysregulation in AD pathogenesis. Further elucidation of the pathophysiological role of Rab GTPases will likely reveal novel targets for AD therapeutics.

Metabolomic Assays of Postmortem Brain Extracts: Pitfalls in Extrapolation of Concentrations of Glucose and Amino Acids to Metabolic Dysregulation In Vivo in Neurological Diseases.

Glucose utilization is reduced in vulnerable brain regions affected by neurological disorders, especially Alzheimer's disease (AD), but the basis for abnormal glucose homeostasis is unknown. Studies of brain-bank human tissue have made major contributions to understanding complex aspects of neurological, psychiatric, and neurodegenerative diseases, but they are not appropriate for metabolomic analysis of labile metabolites because postmortem intervals between death and tissue freezing are much too long. Recent reports of postmortem brain glucose levels led to suggestions that AD patients may be hyperglycemic and that elevated brain glucose levels along with reduced glycolytic activity reveal abnormal glucose homeostasis before clinical symptoms become manifest. These conclusions are, however, questioned because virtually all brain glucose is consumed within minutes after death, followed by progressive increases in glucose and amino acid levels, presumably due to autolytic changes. To illustrate pitfalls in use of autopsy material for metabolomic assays of labile metabolites, data from living human brain are compared with those from autopsy samples, and metabolism at the onset of postmortem ischemia is compared with calculated glycolytic enzyme activities. Postmortem glucose levels range from extremely low to unrealistically high, precluding their extrapolation to living brain. Indirect evaluation of glycolytic enzyme activities in postmortem AD brain is not valid because the glucose and amino acid concentrations used in the calculations are not stable after death, and reported values are unrealistically high. Specific recommendations are provided for non-invasive longitudinal monitoring of brain metabolism and metabolite levels in patients with neurological diseases.

Anti-Tau Monoclonal Antibodies Derived from Soluble and Filamentous Tau Show Diverse Functional Properties in vitro and in vivo.

The tau spreading hypothesis provides rationale for passive immunization with an anti-tau monoclonal antibody to block seeding by extracellular tau aggregates as a disease-modifying strategy for the treatment of Alzheimer's disease (AD) and potentially other tauopathies. As the biochemical and biophysical properties of the tau species responsible for the spatio-temporal sequences of seeding events are poorly defined, it is not yet clear which epitope is preferred for obtaining optimal therapeutic efficacy. Our internal tau antibody collection has been generated by immunizations with different tau species: aggregated- and non-aggregated tau and human postmortem AD brain-derived tau fibrils. In this communication, we describe and characterize a set of these anti-tau antibodies for their biochemical and biophysical properties, including binding, tissue staining by immunohistochemistry, and epitope. The antibodies bound to different domains of the tau protein and some were demonstrated to be isoform-selective (PT18 and hTau56) or phospho-selective (PT84). Evaluation of the antibodies in cellular- and in vivo seeding assays revealed clear differences in maximal efficacy. Limited proteolysis experiments support the hypothesis that some epitopes are more exposed than others in the tau seeds. Moreover, antibody efficacy seems to depend on the structural properties of fibrils purified from tau Tg mice- and postmortem human AD brain.

3D Culture Method for Alzheimer's Disease Modeling Reveals Interleukin-4 Rescues Aβ42-Induced Loss of Human Neural Stem Cell Plasticity

Neural stem cells (NSCs) constitute an endogenous reservoir for neurons that could potentially be harnessed for regenerative therapies in disease contexts such as neurodegeneration. However, in Alzheimer's disease (AD), NSCs lose plasticity and thus possible regenerative capacity. We investigate how NSCs lose their plasticity in AD by using starPEG-heparin-based hydrogels to establish a reductionist 3D cell-instructive neuro-microenvironment that promotes the proliferative and neurogenic ability of primary and induced human NSCs. We find that administration of AD-associated Amyloid-β42 causes classicalneuropathology and hampers NSC plasticity by inducing kynurenic acid (KYNA) production. Interleukin-4 restores NSC proliferative and neurogenic ability by suppressing the KYNA-producing enzyme Kynurenine aminotransferase (KAT2), which is upregulated in APP/PS1dE9 mouse model of AD and in postmortem human AD brains. Thus, our culture system enables a reductionist investigation of regulation of human NSC plasticity for the identification of potential therapeutic targets for intervention in AD.

RELEVANCE OF PHOSPHORYLATION AND TRUNCATION OF TAU TO THE ETIOPATHOGENESIS OF ALZHEIMER’S DISEASE

Alzheimer's disease (AD), the major neurodegenerative disease and cause of dementia, is a slow progressive disorder pathologically characterized by extracellular amyloid-b plaques and intracellular neurofibrillary tangles (NFTs) of abnormally hyperphosphorylated tau. Hyperphosphorylation and truncation of tau have been linked to the progression of the disease. However, the nature of phosphorylation and truncation of tau in AD brain is not very clear. In the present study we investigated the association of truncation with high-molecular weight oligomers of tau (HMW-tau) in post-mortem AD brain by Western blots. We found that tau from AD brain appears as a smear from low molecular weight (LMW) to HMW tau species in Western blots developed with pan-tau antibodies. Similar level of LMW-tau was found in AD and control brains, whereas HMW-tau was found in AD brain only. HMW-tau was hyperphosphorylated at multiple sites and not unphosphorylated at Ser46 or Ser198/199/202. HMW-tau was weakly labeled by tau antibodies 43D against a.a. 6-18 and HT7 against a.a. 159-163 of tau, whereas, the C-terminal antibodies, tau46 and tau46.1, strongly labeled HMW-tau. The ratio of HMW-tau/LMW-tau detected by tau antibodies increased as the epitope of tau antibodies ranges from the N- to the C-termini of tau. The level of tau truncated at Asp421 was increased in AD brain, but was poorly associated with the HMW-tau. HMW-tau is hyperphosphorylated at multiple sites, and unphosphorylated tau, such as at Ser46 and at Ser198/199/202, is absent in these aggregates. The N-terminally truncated tau is associated with HMW-tau more than the C-terminal truncated tau. These findings provide a novel insight into the association of the hyperphosphorylation and predominantly N-terminal truncation of tau with tau aggregation into oligomers in AD.

Scallop-derived plasmalogens attenuate the activation of PKCδ associated with the brain inflammation

Activation of protein kinase C delta (PKCδ) has been linked to the neuroinflammation but the relationship with the various neurodegenerative diseases including the Alzheimer's disease (AD) was mostly elusive. In the AD brains, the special phospholipids, ethanolamine plasmalogens (Pls), were found to be reduced and our previous study showed that these lipids possess neuroprotective and anti-inflammatory functions. In the present study, we could find that these lipids can significantly attenuate the microglial expression of PKCδ in the neuroinflammation model and in the AD model mice brains. We also show an increase of PKCδ in the human postmortem AD brains. In addition, we also report that scallop derived Pls (sPls) inhibited the p38MAPK and JNK protein expression which are involved in the expressional regulation of PKCδ in the microglial cells. In addition, the lentiviral shRNA-mediated knockdown of PKCδ attenuated the LPS-induced p65 (NF-kB) activation and inflammatory cytokine expression, suggesting that the PKCδ can induce the inflammatory response which can be inhibited by the sPls. Taken together, our recent findings suggest that the sPls can attenuate the increased expression of PKCδ associated with the neuro-inflammation in the murine brain.