Aβ Plaque Deposition Research Articles

Greater sensitivity of the hippocampus than the entorhinal cortex in response to western diet, manifested by accelerated neuroinflammation and neurodegeneration in the progression of Alzheimer’s disease

AbstractBackgroundThe western diet (WD), characterized by a combination of simple carbohydrates, saturated fatty acids and cholesterol, is known to induce metabolic syndrome and systemic inflammation. These peripheral disorders induce neuroinflammation and affect brain function, suggesting that WD may have a significant impact on Alzheimer’s disease (AD) progression (Więckowska‐Gacek et al., 2021). In this study we aimed to verify the hypothesis that WD feeding accelerates neuroinflammation, resulting in accelerated deposition of Aβ plaques, accelerated appearance of neurodegeneration markers and destabilization of neuronal cytoskeleton.MethodsTransgenic male mice expressing human APP with the Swedish mutation (APPswe) were divided into three age groups: 4‐ and 8‐month old animals (4M, 8M) represent early pre‐symptomatic stages of AD, while 12‐month old animals (12M) represent later stages of AD with visible amyloid pathology. The APPswe mice were fed standard or western diet from the 3rd month of age. The effect of WD on selected markers was analyzed in the hippocampus and entorhinal cortex by Western blotting and immunohistochemistry.ResultsCompared to control mice fed standard diet, WD feeding induced astrogliosis (GFAP) in the hippocampus as early as in 4M, followed by several changes in 8M such as activation of the pro‐inflammatory microglia (↑Iba1, ↓CD68, ↓P2RY12), a decrease in the level of TLR4, and the fluctuations of levels of pro‐inflammatory cytokines (IL‐1β, IL‐6). These changes in the hippocampus at 8M co‐occurred with enhanced production of Aβ plaques. Moreover, WD accelerated the processes associated with age‐related neurodegeneration (lower levels of PSD95 in 8M, and of NeuN in 12M). In the entorhinal cortex, the examined molecular changes appeared with a delay in time or not at all.ConclusionThese results indicate that the westernized pattern of nourishment is an important modifiable risk factor of AD which can accelerate development of AD pathology. Furthermore, the data demonstrate that, compared to the entorhinal cortex, the hippocampus is a brain structure that is generally more sensitive to the macronutrient composition characteristic of WD, manifested by accelerated neuroinflammation, amyloidopathy and neurodegeneration.Polish National Science Center grants: 2018/29/N/NZ7/01724, 2014/15/D/NZ4/04361

A novel DYRK1a inhibitor, DYR533, reduces tau pathology and TNF alpha in the 3xTg‐AD and PS19 mouse models

AbstractBackgroundDual specificity tyrosine phosphorylation kinase 1a (DYRK1a) directly phosphorylates tau and amyloid precursor protein and is upregulated in postmortem brain tissue of patients with disorders including Alzheimer’s (AD) and Picks disease (a tauopathy). Our lab has shown that treatment with a DYRK1a inhibitor (DYR219) reduced Aβ plaque deposition and decreased phosphorylated tau at Serine 396 (pTauSer396) in the 3xTg‐AD mouse model. Here, we developed and tested a novel DYRK1a inhibitor (DYR533), which has an increased half‐life and bioavailability, in 3xTg‐AD mice that develop both Aβ and pathological tau, and PS19 mice that develop solely pathological tau.MethodWe dosed eight‐month‐old 3xTg‐AD and four‐month‐old PS19 mice daily with either 1.0‐, 2.5‐, or 5.0‐mg/kg DYR533 or a vehicle dose for two or four months respectively per model. Treatment start age occurred at the onset of neuropathology. Mice underwent rotarod testing to assess motor function and water maze testing to assess spatial learning and memory, with testing starting 2 weeks prior to the end of treatment. Blood and brain tissue were collected for neuropathology assessment. We assessed Aβ 40‐42 in the 3xTg‐AD mice, and pTauSer396 and the pro‐inflammatory cytokine tumor necrosis factor (Tnf)α in the hippocampus of both models. Blood plasma was extracted and analyzed for Tnfα levels.ResultIn both 3xTg‐AD and PS19 mice, DYR533 reduced soluble and insoluble fractions of pTau Ser396 in a dose dependent manner. Notably, DYR533 in 3xTg‐AD mice reduced pTau at threonine 217, which was recently identified as an early marker of AD progression. Soluble cortical Aβ42 levels were significantly reduced in the 1.0 mg/kg and 5.0 mg/kg 3xTg‐AD groups. DYR533 significantly reduced the levels of Tnfα in blood plasma and the hippocampus of both 3xTg‐AD and PS19 mice.ConclusionIn conclusion, the DYRK1a inhibitor, DYR533, reduces pTauSer396, as well as blood plasma and hippocampal levels of Tnf α in both 3xTg‐AD and PS19 models. Ongoing efforts include testing the effects of DYR533 in a rodent model of Down syndrome (Ts65Dn), which harbors three copies of DYRK1a, and completion of 3xTg‐AD and PS19 experiments. Thus far, these results support DYR533 as a potential therapeutic for AD and the tauopathies.

Tracking plasma biomarkers in cognitively unimpaired individuals at risk of Alzheimer’s disease

AbstractAlzheimer’s disease (AD) is as a continuum that includes a preclinical phase, where individuals are cognitively unimpaired but there is evidence of amyloid‐β (Aβ) and tau pathology, followed by a clinical phase (including mild cognitive impairment and dementia). This preclinical phase is not a uniform or unvarying phase, but it is a long process during which Aβ and tau gradually accumulates until overt Aβ plaque deposition and neurofibrillary tangles are present. Moreover, this is a heterogeneous phase, there are differences in the rate of progression of those individuals that are Aβ‐positive to cognitive impairment and some of them will not even develop symptoms. It is important to develop biomarkers that accurately detect Preclinical AD, but also biomarkers to stage the disease, and prognostic biomarkers that identify those individuals that will progress to cognitive impairment. Furthermore, amid the new developments of disease modifying treatments, there is an unmet need to develop biomarkers to predict and monitor the response to an intervention.We now have a range of plasma biomarkers that detect symptomatic AD but also increase in Preclinical AD, including several epitopes of p‐tau (pT181, pT217, pT231), Aβ42/40, GFAP and NfL. Yet, there are differences between them. They may differ on which point of the long preclinical stage they start to increase, their discrimination accuracy, their longitudinal changes across the disease continuum or the physiopathological mechanism that they indicate. Moreover, the performance of plasma biomarkers may be influenced by sex and gender, race and ethnicity, or comorbidities. Therefore, the choice of the plasma biomarker may differ depending on its goal.In this presentation, plasma biomarkers in Preclinical AD will be reviewed and their differential roles will be discussed.

Nicotinic acid modulates microglial TREM-2 gene in Phytohaemagglutinin-Induced in vitro model of Alzheimer’s disease like pathology

Alzheimer’s disease (AD) is a multifactorial,neurodegenerative disorder linked withextracellular amyloid beta (Aβ) plaques deposition and formation of intracellular neurofibrillary tangles (NFTs). Currently, no effective therapies are available to cure AD. Neuroinflammation isa well-known hallmark in the onset and advancement of AD and triggering receptor expressed on myeloid cells-2 (TREM-2), a microglial gene, is responsible for regulating inflammatory responses and clearance of cellular debris. Loss of TREM-2functionincreases neuroinflammation associated expression of pro-inflammatory markersthus resultingin reduced clearance of Aβ that further aid in disease progression.Therefore, targeting neuroinflammation is a good therapeutic approach for AD. This study aimed to determine the neuroprotective effect of nicotinic acid (NA) in vitro model of AD-like pathology induced in F-98 cell line using Phytohemagglutinin (PHA). MTT assay was employed for checking the cell viability as well as the proliferation of the cells following treatment with NA. PHA at the concentration of 10 μg/mL produces maximum plaques. The neuroprotective effect of NA was next evaluated against PHA-induced plaques and it was observed that NA reverses the damages induced by PHA i.e., by inhibiting the clustering of the cells and replacing the damaged cells with the new ones. Further, NA also increased the expression of TREM-2/DAP-12 with parallel decreased in the expression of IL-1β, TNF-α and iNOS. It also successfully altered disease associated ADAM-10 and BACE-1 compared to PHA control. These findings suggest that NA might be considered as a good therapeutic candidate for the treatment of neurodegenerative disorders like AD.

Application of Dominant Gut Microbiota Promises to Replace Fecal Microbiota Transplantation as a New Treatment for Alzheimer's Disease.

Several studies have confirmed that the pathophysiological progression of Alzheimer's disease (AD) is closely related to changes in the intestinal microbiota; thus, modifying the intestinal microbiota has emerged as a new way to treat AD. Effective interventions for gut microbiota include the application of probiotics and other measures such as fecal microbiota transplantation (FMT). However, the application of probiotics ignores that the intestine is a complete microecosystem with competition among microorganisms. FMT also has issues when applied to patient treatment. In a previous study, we found that eight species of bacteria that are isolated with high frequency in the normal intestinal microbiota (i.e., intestinal dominant microbiota) have biological activities consistent with the effects of FMT. In this article, we confirmed that the treatment of intestinal dominant microbiota significantly restored intestinal microbiota abundance and composition to normal levels in APP/PS1 mice; downregulated brain tissue pro-inflammatory cytokines (IL-1β and IL-6) and amyloid precursor protein (APP) and β-site APP cleavage enzyme 1 (BACE1) expression levels; and reduced the area of Aβ plaque deposition in the brain hippocampus. Our study provides a new therapeutic concept for the treatment of AD, adjusting the intestinal microecological balance through dominant intestinal microbiota may be an alternative to FMT.

Cytokine enrichment in deep cerebellar nuclei is contributed by multiple glial populations and linked to reduced amyloid plaque pathology

Alzheimer’s disease (AD) pathology and amyloid-beta (Aβ) plaque deposition progress slowly in the cerebellum compared to other brain regions, while the entorhinal cortex (EC) is one of the most vulnerable regions. Using a knock-in AD mouse model (App KI), we show that within the cerebellum, the deep cerebellar nuclei (DCN) has particularly low accumulation of Aβ plaques. To identify factors that might underlie differences in the progression of AD-associated neuropathology across regions, we profiled gene expression in single nuclei (snRNAseq) across all cell types in the DCN and EC of wild-type (WT) and App KI male mice at age 7 months. We found differences in expression of genes associated with inflammatory activation, PI3K–AKT signalling, and neuron support functions between both regions and genotypes. In WT mice, the expression of interferon-response genes in microglia is higher in the DCN than the EC and this enrichment is confirmed by RNA in situ hybridisation, and measurement of inflammatory cytokines by protein array. Our analyses also revealed that multiple glial populations are responsible for establishing this cytokine-enriched niche. Furthermore, homogenates derived from the DCN induced inflammatory gene expression in BV2 microglia. We also assessed the relationship between the DCN microenvironment and Aβ pathology by depleting microglia using a CSF1R inhibitor PLX5622 and saw that, surprisingly, the expression of a subset of inflammatory cytokines was increased while plaque abundance in the DCN was further reduced. Overall, our study revealed the presence of a cytokine-enriched microenvironment unique to the DCN that when modulated, can alter plaque deposition.

Improvement Effect of Mitotherapy on the Cognitive Ability of Alzheimer's Disease through NAD+/SIRT1-Mediated Autophagy.

To date, Alzheimer's disease (AD) has grown to be a predominant health challenge that disturbs the elderly population. Studies have shown that mitochondrial dysfunction is one of the most significant features of AD. Transplantation therapy of healthy mitochondria (mitotherapy), as a novel therapeutic strategy to restore mitochondrial function, is proposed to treat the mitochondria-associated disease. Also, the molecular mechanism of mitotherapy remains unclear. Here, we applied the mitotherapy in AD model mice induced by amyloid-β (Aβ) plaque deposition and suggested that autophagy would be an important mechanism of the mitotherapy. After the healthy mitochondria entered the defective neuronal cells damaged by the misfolded Aβ protein, autophagy was activated through the NAD+-dependent deacetylase sirtuin 1 (SIRT1) signal. The damaged mitochondria and Aβ protein were eliminated by autophagy, which could also decrease the content of radical oxygen species (ROS). Moreover, the levels of brain-derived neurotrophic factor (BDNF) and extracellular-regulated protein kinases (ERK) phosphorylation increased after mitotherapy, which would be beneficial to repair neuronal function. As a result, the cognitive ability of AD animals was ameliorated in a water maze test after the healthy mitochondria were administrated to the mice. The study indicated that mitotherapy would be an effective approach to AD treatment through the mechanism of autophagy activation.

Low-dose IL-2 Treatment Rescues Cognitive Deficits by Repairing the Imbalance Between Treg and Th17 Cells at the Middle Alzheimer's Disease Stage.

Multiple studies highlight the role of effector and regulatory CD4+T cells in the pathophysiology of Alzheimer's disease, and foster low-dose IL-2 treatment which induces regulatory CD4+T (Treg) cells expansion and activation as a promising strategy for its treatment. However, studies demonstrating discrepant Treg functions in AD have been reported. In addition, a compromised immune system associated with aging may substantially impact on these processes. Here, we report that there is an altered balance of activity between Treg cells and IL-17-producing helper T (Th17) cells in periphery and brain of APP/PS1 mice along the disease progression. A dramatic loss of the healthy balance of activity between Treg and Th17 cells was found at the middle disease stage. While peripheral low-dose recombinant human IL-2 administration could selectively modulate the abundance of Treg cells and repair the imbalance between Treg and Th17 subsets at the middle disease stage. We further show that modulation of peripheral immune balance through low-dose IL-2 treatment reduces the neuro-inflammation and increases numbers of plaque-associated microglia, accompanied by marked reduction of Aβ plaque deposition and slower cognitive declines in APP/PS1 mice at the middle disease stage. Our study highlights the therapeutic potential of repurposed IL-2 for innovative immunotherapy based on modulation of the homeostasis of CD4+T cell subsets in Alzheimer's disease at the middle disease stage.

PCSK9 ablation attenuates Aβ pathology, neuroinflammation and cognitive dysfunctions in 5XFAD mice

BackgroundIncreasing evidence highlights the importance of novel players in Alzheimer’s disease (AD) pathophysiology, including alterations of lipid metabolism and neuroinflammation. Indeed, a potential involvement of Proprotein convertase subtilisin/kexin type 9 (PCSK9) in AD has been recently postulated. Here, we first investigated the effects of PCSK9 on neuroinflammation in vitro. Then, we examined the impact of a genetic ablation of PCSK9 on cognitive performance in a severe mouse model of AD. Finally, in the same animals we evaluated the effect of PCSK9 loss on Aβ pathology, neuroinflammation, and brain lipids. MethodsFor in vitro studies, U373 human astrocytoma cells were treated with Aβ fibrils and human recombinant PCSK9. mRNA expression of the proinflammatory cytokines and inflammasome-related genes were evaluated by q-PCR, while MCP-1 secretion was measured by ELISA. For in vivo studies, the cognitive performance of a newly generated mouse line - obtained by crossing 5XFADHet with PCSK9KO mice – was tested by the Morris water maze test. After sacrifice, immunohistochemical analyses were performed to evaluate Aβ plaque deposition, distribution and composition, BACE1 immunoreactivity, as well as microglia and astrocyte reactivity. Cholesterol and hydroxysterols levels in mouse brains were quantified by fluorometric and LC-MS/MS analyses, respectively. Statistical comparisons were performed according to one- or two-way ANOVA, two-way repeated measure ANOVA or Chi-square test. ResultsIn vitro, PCSK9 significantly increased IL6, IL1B and TNFΑ mRNA levels in Aβ fibrils-treated U373 cells, without influencing inflammasome gene expression, except for an increase in NLRC4 mRNA levels. In vivo, PCSK9 ablation in 5XFAD mice significantly improved the performance at the Morris water maze test; these changes were accompanied by a reduced corticohippocampal Aβ burden without affecting plaque spatial/regional distribution and composition or global BACE1 expression. Furthermore, PCSK9 loss in 5XFAD mice induced decreased microgliosis and astrocyte reactivity in several brain regions. Conversely, knocking out PCSK9 had minimal impact on brain cholesterol and hydroxysterol levels. ConclusionsIn vitro studies showed a pro-inflammatory effect of PCSK9. Consistently, in vivo data indicated a protective role of PCSK9 ablation against cognitive impairments, associated with improved Aβ pathology and attenuated neuroinflammation in a severe mouse model of AD. PCSK9 may thus be considered a novel pharmacological target for the treatment of AD.

Omaveloxolone ameliorates cognitive dysfunction in APP/PS1 mice by stabilizing the STAT3 pathway

AimsTo determine the availability and the potential molecular mechanisms underlying the therapeutic effect of omaveloxolone (RTA408) on Alzheimer's Disease (AD). Materials and methodsThis study employed network pharmacology to assess the feasibility of drug treatment of AD. To determine the cognitive status and emotional state of APPswe/PS1dE9 (APP/PS1) mice after the RTA408 treatment, three classical behavioral experiments (water maze, Y-maze, and open field test) were conducted. Immunofluorescence and immunohistochemical staining were utilized to evaluate hippocampal neuronal status and amyloid (Aβ) deposition in mice. RNA-seq and transcription factor prediction analyses were performed to explore the potential molecular mechanisms regulating the therapeutic effects of RTA408. Molecular docking was employed to predict the direct drug targets. To validate these molecular mechanisms, quantitative reverse transcription PCR (qRT-PCR), Western blotting, and immunofluorescence analyses were performed in two instrumental cell lines, i.e., mouse hippocampal neuronal cells (HT22) and microglia (BV2). ResultsRTA408 was revealed with the capability to reduce Aβ plaque deposition and to restore damaged neurons in the hippocampal region of APP/PS1 mice, ultimately leading to an improvement in cognitive function. This beneficial effect was achieved by balancing the STAT3 pathway. Specifically, RTA408 facilitated the activations of both STAT3/OXR1 and NRF2/ARE axes, thereby enhancing the compromised resistance in neurons to oxidative stress. RTA408 inhibited the NFκB/IL6/STAT3 pathway, effectively countering the neuroinflammation triggered by microglial activation. ConclusionRTA408 is revealed with promising potential in the treatment of AD based on preclinical data.

Baicalein promotes the microglia M2 polarization and suppresses apoptosis by targeting HMOX1/PDE4D to alleviate Alzheimer’s disease

Alzheimer's disease (AD) is a neurodegenerative disorder that has quickly becoming one of the most expensive, lethal, and burdening diseases of this century. In the past twenty years, hundreds of drugs have been tested while only several have been authorized by FDA for AD treatment, hence, searching for candidate agent with therapeutic potential for AD is imminent. Controlling polarization direction of microglia is crucial in AD therapy. Recent research suggests that baicalein has potential to reduce neuroinflammation and prevent neurodegenerative diseases by affecting microglia, while the specific molecular mechanism of baicalein in regulating microglia in the treatment of AD is still unclear. In this study, we investigated how baicalein affected microglial polarization in AD and potential biological mechanisms. In cell experiments, it was verified that baicalein significantly shifted the BV-2 microglia phenotype from the pro-inflammatory M1 to the anti-inflammatory M2 phenotype, inhibited the microglial apoptosis and pro-inflammatory factors, promoted the microglial Aβ uptake and anti-inflammatory factors after LPS stimulated. In APP/PS1 mice, it was found that baicalein decreased the Aβ plaque deposition in brain, attenuated NLRP3 inflammasome activation and neuronal apoptosis in APP/PS1 mice. Furthermore, bioinformatics analysis and experiment validated that HMOX1 is a target of baicalein, and we elucidated that baicalein modulated the microglial polarization to inhibit neuroinflammation and neural injury through targeting on the HMOX1/PDE4D axis in AD. In conclusion, our findings indicate the therapeutic effect of baicalein for AD, and baicalein might serve a potential agent for AD treatment.

Intermittent hypoxia therapy ameliorates beta-amyloid pathology via TFEB-mediated autophagy in murine Alzheimer's disease

BackgroundAlzheimer's disease (AD) is the most prevalent neurodegenerative disorder. Impaired autophagy in plaque-associated microglia (PAM) has been reported to accelerate amyloid plaque deposition and cognitive impairment in AD pathogenesis. Recent evidence suggests that the transcription factor EB (TFEB)-mediated activation of the autophagy–lysosomal pathway is a promising treatment approach for AD. Moreover, the complementary therapy of intermittent hypoxia therapy (IHT) has been shown to upregulate autophagy and impart beneficial effects in patients with AD. However, the effect of IHT on PAM remains unknown.Methods8-Month-old APP/PS1 mice were treated with IHT for 28 days. Spatial learning memory capacity and anxiety in mice were investigated. AD pathology was determined by the quantity of nerve fibers and synapses density, numbers of microglia and neurons, Aβ plaque deposition, pro-inflammatory factors, and the content of Aβ in the brain. TFEB-mediated autophagy was determined by western blot and qRT-PCR. Primary microglia were treated with oligomeric Aβ 1–42 (oAβ) combined with IHT for mechanism exploration. Differential genes were screened by RNA-seq. Autophagic degradation process of intracellular oAβ was traced by immunofluorescence.ResultsIn this study, we found that IHT ameliorated cognitive function by attenuating neuronal loss and axonal injury in an AD animal model (APP/PS1 mice) with beta-amyloid (Aβ) pathology. In addition, IHT-mediated neuronal protection was associated with reduced Aβ accumulation and plaque formation. Using an in vitro PAM model, we further confirmed that IHT upregulated autophagy-related proteins, thereby promoting the Aβ autophagic degradation by PAM. Mechanistically, IHT facilitated the nuclear localization of TFEB in PAM, with TFEB activity showing a positive correlation with Aβ degradation by PAM in vivo and in vitro. In addition, IHT-induced TFEB activation was associated with the inhibition of the AKT–MAPK–mTOR pathway.ConclusionsThese results suggest that IHT alleviates neuronal damage and neuroinflammation via the upregulation of TFEB-dependent Aβ clearance by PAM, leading to improved learning and memory in AD mice. Therefore, IHT may be a promising non-pharmacologic therapy in complementary medicine against AD.Graphical

Recent advances in understanding Alzheimer's Disease: diagnosis and management strategies.

As the rates of Alzheimer's Disease (AD) increase in the world due to the aging of the population, research has made tremendous advances to target the two hallmark pathologies of AD: amyloid-β (Aβ) plaque deposition and neurofibrillary tangles of hyperphosphorylated tau. Here, we discuss recent advances in the clinical evaluation and management of AD, with a focus on new hypotheses related to the etiology of AD and new evidence related to AD-mimicking neurodegenerative diseases. Though recent clinical studies suggest anti-amyloid disease modifying agents may slow the progression of AD, there is currently no medication that stops it. Moreover, slowing the progression will result in more individuals in the mild cognitive impairment (MCI) and mild dementia stages of AD. Given this reality, we evaluate the development of non-pharmacological strategies to help sustain cognitive function and quality of life.

Amyloid PET across the cognitive spectrum in former professional and college American football players: findings from the DIAGNOSE CTE Research Project

BackgroundExposure to repetitive head impacts (RHI) in American football players can lead to cognitive impairment and dementia due to neurodegenerative disease, particularly chronic traumatic encephalopathy (CTE). The pathognomonic lesion of CTE consists of perivascular aggregates of hyper-phosphorylated tau in neurons at the depths of cortical sulci. However, it is unclear whether exposure to RHI accelerates amyloid-β (Aβ) plaque formation and increases the risk for Alzheimer’s disease (AD). Although the Aβ neuritic plaques characteristic of AD are observed in a minority of later-stage CTE cases, diffuse plaques are more common. This study examined whether former professional and college American football players, including those with cognitive impairment and dementia, have elevated neuritic Aβ plaque density, as measured by florbetapir PET. Regardless of cognitive and functional status, elevated levels of florbetapir uptake were not expected.MethodsWe examined 237 men ages 45–74, including 119 former professional (PRO) and 60 former college (COL) football players, with and without cognitive impairment and dementia, and 58 same-age men without a history of contact sports or TBI (unexposed; UE) and who denied cognitive or behavioral symptoms at telephone screening. Former players were categorized into four diagnostic groups: normal cognition, subjective memory impairment, mild cognitive impairment, and dementia. Positive florbetapir PET was defined by cortical-cerebellar average SUVR of ≥ 1.10. Multivariable linear regression and analysis of covariance (ANCOVA) compared florbetapir average SUVR across diagnostic and exposure groups. Multivariable logistic regression compared florbetapir positivity. Race, education, age, and APOE4 were covariates.ResultsThere were no diagnostic group differences either in florbetapir average SUVR or the proportion of elevated florbetapir uptake. Average SUVR means also did not differ between exposure groups: PRO-COL (p = 0.94, 95% C.I. = [− 0.033, 0.025]), PRO-UE (p = 0.40, 95% C.I. = [− 0.010, 0.029]), COL-UE (p = 0.36, 95% CI = [0.0004, 0.039]). Florbetapir was not significantly associated with years of football exposure, cognition, or daily functioning.ConclusionsCognitive impairment in former American football players is not associated with PET imaging of neuritic Aβ plaque deposition. These findings are inconsistent with a neuropathological diagnosis of AD in individuals with substantial RHI exposure and have both clinical and medico-legal implications.Trial registrationNCT02798185.

Pharmacological inhibition of plasminogen activator inhibitor-1 prevents memory deficits and reduces neuropathology in APP/PS1 mice.

Extracellular proteolytic activity plays an important role in memory formation and the preservation of cognitive function. Previous studies have shown increased levels of plasminogen activator inhibitor-1 (PAI-1) in the brain of mouse models of Alzheimer's disease (AD) and plasma of AD patients, associated with memory and cognitive decline; however, the exact function of PAI-1 in AD onset and progression is largely unclear. In this study, we evaluated a novel PAI-1 inhibitor, TM5A15, on its ability to prevent or reverse memory deficits and decrease Aβ levels and plaque deposition in APP/PS1 mice. We administered TM5A15 mixed in a chow diet to 3-month and 9-month-old APP/PS1 mice before and after neuropathological changes were distinguishable. We then evaluated the effects of TM5A15 on memory function and neuropathology at 9 months and 18 months of age. In the younger mice, 6 months of TM5A15 treatment protected against recognition and short-term working memory impairment. TM5A15 also decreased oligomer levels and amyloid plaques, and increased mBDNF expression in APP/PS1 mice at 9 months of age. In aged mice, 9 months of TM5A15 treatment did not significantly improve memory function nor decrease amyloid plaques. However, TM5A15 treatment showed a trend in decreasing oligomer levels in APP/PS1 mice at 18 months of age. Our results suggest that PAI-1 inhibition could improve memory function and reduce the accumulation of amyloid levels in APP/PS1 mice. Such effects are more prominent when TM5A15 is administered before advanced AD pathology and memory deficits occur.

Feasibility and therapeutical potential of local intracerebral encapsulated cell biodelivery of BDNF to AppNL-G-F knock-in Alzheimer mice.

Alzheimer's disease (AD) is an age-related disease characterized by altered cognition, neuroinflammation, and neurodegeneration against which there is presently no effective cure. Brain-derived neurotrophic factor (BDNF) is a key neurotrophin involved in the learning and memory process, with a crucial role in synaptic plasticity and neuronal survival. Several findings support that a reduced BDNF expression in the human brain is associated with AD pathogenesis. BDNF has been proposed as a potential therapy for AD, but BDNF has low brain penetration. In this study, we used an innovative encapsulated cell biodelivery (ECB) device, containing genetically modified cells capable of releasing BDNF and characterized its feasibility and therapeutic effects in the novel App knock-in AD mouse model (AppNL-G-F). ECB's containing human ARPE-19 cells genetically modified to release BDNF (ECB-BDNF devices) were stereotactically implanted bilaterally into hippocampus of 3-month-old AppNL-G-F mice. The stability of BDNF release and its effect on AD pathology were evaluated after 1, 2-, and 4-months post-implantation by immunohistochemical and biochemical analyses. Exploratory and memory performance using elevated plus maze (EPM) and Y-maze test were performed in the 4-months treatment group. Immunological reaction towards ECB-BDNF devices were studied under ex vivo and in vivo settings. The surgery and the ECB-BDNF implants were well tolerated without any signs of unwanted side effects or weight loss. ECB-BDNF devices did not induce host-mediated immune response under ex vivo set-up but showed reduced immune cell attachment when explanted 4-months post-implantation. Elevated BDNF staining around ECB-BDNF device proximity was detected after 1, 2, and 4months treatment, but the retrieved devices showed variable BDNF release. A reduction of amyloid-β (Aβ) plaque deposition was observed around ECB-BDNF device proximity after 2-months of BDNF delivery. The result of this study supports the use of ECB device as a promising drug-delivery approach to locally administer BBB-impermeable factors for treating neurodegenerative conditions like AD. Optimization of the mouse-sized devices to reduce variability of BDNF release is needed to employ the ECB platform in future pre-clinical research and therapy development studies.

Antibody binding of amyloid beta peptide epimers/isomers and ramifications for immunotherapies and drug development

Extracellular deposition of amyloid beta (Aβ) peptide is a contributing factor of Alzheimer’s disease (AD). Considerable effort has been expended to create effective antibodies, or immunotherapies, targeting Aβ peptides. A few immunotherapies are thought to provide some benefit. It is possible that a contributing factor to the responses of such therapies may be the presence of modified, or aberrant, Aβ peptides found in AD patients. These aberrations include the isomerization and epimerization of L-Asp and L-Ser residues to form D-Asp, L/D-isoAsp, and D-Ser residues, respectively. An effective methodology is essential to isolate all Aβ peptides and then to quantify and locate the aberrant amino acids. Modifications to Aβ peptides may elevate the deposition of Aβ plaques and/or contribute to the neurodegeneration in AD patients, and may alter the binding affinity to antibodies. Herein, we used immunoprecipitation to examine the binding affinity of four antibodies against 18 epimeric and/or isomeric Aβ peptides compared to wild type (all L) Aβ peptide. Tandem mass spectrometry was used as a detection method, which also was found to produce highly variable results for epimeric and/or isomeric Aβ.

Salvianolic acid B ameliorates retinal deficits in an early-stage Alzheimer's disease mouse model through downregulating BACE1 and Aβ generation.

Alzheimer's disease (AD) is a neurodegenerative disease with subtle onset, early diagnosis remains challenging. Accumulating evidence suggests that the emergence of retinal damage in AD precedes cognitive impairment, and may serve as a critical indicator for early diagnosis and disease progression. Salvianolic acid B (Sal B), a bioactive compound isolated from the traditional Chinese medicinal herb Salvia miltiorrhiza, has been shown promise in treating neurodegenerative diseases, such as AD and Parkinson's disease. In this study we investigated the therapeutic effects of Sal B on retinopathy in early-stage AD. One-month-old transgenic mice carrying five familial AD mutations (5×FAD) were treated with Sal B (20 mg·kg-1·d-1, i.g.) for 3 months. At the end of treatment, retinal function and structure were assessed, cognitive function was evaluated in Morris water maze test. We showed that 4-month-old 5×FAD mice displayed distinct structural and functional deficits in the retinas, which were significantly ameliorated by Sal B treatment. In contrast, untreated, 4-month-old 5×FAD mice did not exhibit cognitive impairment compared to wild-type mice. In SH-SY5Y-APP751 cells, we demonstrated that Sal B (10 μM) significantly decreased BACE1 expression and sorting into the Golgi apparatus, thereby reducing Aβ generation by inhibiting the β-cleavage of APP. Moreover, we found that Sal B effectively attenuated microglial activation and the associated inflammatory cytokine release induced by Aβ plaque deposition in the retinas of 5×FAD mice. Taken together, our results demonstrate that functional impairments in the retina occur before cognitive decline, suggesting that the retina is a valuable reference for early diagnosis of AD. Sal B ameliorates retinal deficits by regulating APP processing and Aβ generation in early AD, which is a potential therapeutic intervention for early AD treatment.

Dauricine alleviates cognitive impairment in Alzheimer's disease mice induced by D-galactose and AlCl3 via the Ca2+/CaM pathway

Alzheimer's disease (AD) is a common neurodegenerative disease in the elderly. Dysregulation of intracellular Ca2+ homeostasis plays a critical role in the pathological development of AD. Dauricine (DAU) is a bisbenzylisoquinoline alkaloid isolated from Menispermum dauricum DC., which can prevent the influx of extracellular Ca2+ and inhibit the release of Ca2+ from the endoplasmic reticulum. DAU has a potential for anti-AD. However, it is unclear whether DAU can exert its anti-AD effect in vivo by regulating the Ca2+ related signaling pathways. Here, we investigated the effect and mechanism of DAU on D-galactose and AlCl3 combined-induced AD mice based on the Ca2+/CaM pathway. The results showed that DAU (1 mg/kg and 10 mg/kg for 30 days) treatment attenuated learning and memory deficits and improved the nesting ability of AD mice. The HE staining assay showed that DAU could inhibit the histopathological alterations and attenuate neuronal damage in the hippocampus and cortex of AD mice. Studies on the mechanism indicated that DAU decreased the phosphorylation of CaMKII and Tau and reduced the formation of NFTs in the hippocampus and cortex. DAU treatment also reduced the abnormally high expression of APP, BACE1, and Aβ1–42, which inhibited the deposition of Aβ plaques. Moreover, DAU could decrease Ca2+ levels and inhibit elevated CaM protein expression in the hippocampus and cortex of AD mice. The molecular docking results showed that DAU may have a high affinity with CaM or BACE1. DAU has a beneficial impact on pathological changes in AD mice induced by D-galactose and AlCl3 and may act by negative regulation of the Ca2+/CaM pathway and its downstream molecules such as CaMKII and BACE1.

APP/PS1 Gene-Environmental Cadmium Interaction Aggravates the Progression of Alzheimer's Disease in Mice via the Blood-Brain Barrier, Amyloid-β, and Inflammation.

There is limited information about gene-environment interaction on the occurrence and the progression of Alzheimer's disease. To explore the effect of environmental low-dose cadmium (Cd) exposure on the progress of Alzheimer's disease and the underlining mechanism. We administered 1 mg/L, 10 mg/L cadmium chloride (treated groups), and water (control group) to C57BL/6J and APP/PS1 mice through drinking water, from one week before mating, until the offspring were sacrificed at 6 months of age. The behaviors, Cd level, blood-brain barrier (BBB) leakage, Aβ1-42 deposition, and inflammation expression were evaluated in these mice. Mice of both genotypes had similar blood Cd levels after exposure to the same dose of Cd. The toxic effects of Cd on the two genotypes differed little in terms of neuronal histomorphology and BBB permeability. Cd caused a series of pathological morphological changes in the mouse brains and more fluorescent dye leakage at higher doses. Furthermore, the APP/PS1 mice had more severe damage than the C57BL/6J mice, based on the following five criteria. They were increasing anxiety-like behavior and chaos movement, spatial reference memory damage, Aβ plaque deposition in mouse brains, increasing microglia expression in the brain, and IL-6 higher expression in the cortex and in the serum. Low-dose Cd exposure for 6 months increases Aβ plaque deposition and BBB permeability, exacerbates inflammatory responses, and activates microglia, in APP/PS1 mice. APP/PS1 gene-environmental Cd interaction aggravates the progression of Alzheimer's disease in mice.