2,3,4-Trihydroxybenzophenone Disassembles Amyloid β Aggregates and Ameliorates Synaptic Deficits.

It is widely known that the degeneration of neural circuits is prominent in the brains of Alzheimer’s disease (AD) patients. The reciprocal connectivity of the medial septum (MS) and hippocampus, which constitutes the septo-hippocampo-septal (SHS) loop, is known to be associated with learning and memory. Despite the importance of the reciprocal projections between the MS and hippocampus in AD, the alteration of bidirectional connectivity between two structures has not yet been investigated at the mesoscale level. In this study, we adopted AD animal model, five familial AD mutations (5XFAD) mice, and anterograde and retrograde tracers, BDA and DiI, respectively, to visualize the pathology-related changes in topographical connectivity of the SHS loop in the 5XFAD brain. By comparing 4.5-month-old and 14-month-old 5XFAD mice, we successfully identified key circuit components of the SHS loop altered in 5XFAD brains. Remarkably, the SHS loop began to degenerate in 4.5-month-old 5XFAD mice before the onset of neuronal loss. The impairment of connectivity between the MS and hippocampus was accelerated in 14-month-old 5XFAD mice. These results demonstrate, for the first time, topographical evidence for the degradation of the interconnection between the MS and hippocampus at the mesoscale level in a mouse model of AD. Our results provide structural and functional insights into the interconnectivity of the MS and hippocampus, which will inform the use and development of various therapeutic approaches that target neural circuits for the treatment of AD.

The ethanol extract of Zizyphus jujuba var. spinosa seeds ameliorates the memory deficits in Alzheimer's disease model mice

BackgroundWorking memory capacity impairment is an early sign of Alzheimer's disease, but the underlying mechanisms remain unclear. Clarifying how working memory capacity is affected will help us better understand the pathological mechanism of Alzheimer's disease. We used the olfactory working memory capacity paradigm to evaluate memory capacity in 3-month-old 5XFAD (an animal model of Alzheimer's disease) mice. Immunofluorescence staining of the prefrontal cortex was performed to detect the number of FOS-positive neurons, calmodulin-dependent protein kinase II-positive neurons, and glutamate decarboxylase-positive neurons in the prelimbic cortex and infralimbic cortex. A chemogenetic method was then used to modulate the inhibition and activation of excitatory neurons in the prelimbic cortex of wild-type and 5XFAD mice and to measure the memory capacity of mice.ResultsWorking memory capacity was significantly diminished in 5XFAD mice compared to littermate wild-type mice. Neuronal activation of the prelimbic cortex, but not the infralimbic cortex, was attenuated in 5XFAD mice performing the olfactory working memory capacity task. Subsequently, the FOS-positive neurons were co-localized with both calmodulin-dependent protein kinase II-positive neurons and glutamate decarboxylase-positive neurons. The results showed that the activation of excitatory neurons in the prelimbic cortex was correlated with working memory capacity in mice. Our results further demonstrate that the chemogenetic inhibition of prelimbic cortex excitatory neurons resulted in reduced working memory capacity in wild-type mice, while the chemogenetic activation of prelimbic cortex excitatory neurons improved the working memory capacity of 5XFAD mice.ConclusionThe diminished activation of prelimbic cortex excitatory neurons in 5XFAD mice during task performance is associated with reduced working memory capacity, and activation modulation of excitatory neurons by chemogenetic methods can improve memory capacity impairment in 5XFAD mice. These findings may provide a new direction for exploring Alzheimer's disease therapeutic approaches.

Peripheral administration of the soluble TNF inhibitor XPro1595 modifies brain immune cell profiles, decreases beta-amyloid plaque load, and rescues impaired long-term potentiation in 5xFAD mice

Introduction Prior studies have shown that the gut microbiomes of Alzheimer’s Disease (AD) patients differ from unaffected individuals. Sleep and circadian rhythm disturbances are common in AD and often precede dementia symptoms. Gut microbiome alterations have also been observed in models of circadian disruption. Therefore, we hypothesized that altering the gut microbiome could improve sleep/circadian rhythms and cognition in an AD mouse model. Methods Mice were given a dietary polysaccharide, Modified Resistant Maltodextrin (MRM), as a 1% solution in the drinking water beginning at 2 months of age. 5xFAD and wild-type (WT) littermates were tested. Sleep-wake was recorded by EEG/EMG, memory consolidation was tested by the Object-Location Memory test, and beta amyloid deposition in the brain was assayed (dot blot). Composition of the gut microbiota was determined from amplicon sequencing of the 16s ribosomal RNA gene from fecal DNA. Results MRM treatment reduced dark (active)-phase sleep and the phase scattering of REM sleep in 5xFAD mice, indices of circadian consolidation. 6-month-old 5xFAD mice given plain water exhibited no 24hr retention of object location memory. However, MRM-treated 5xFAD mice demonstrated 24-hour memory, even at 12 months of age. Both improved memory and increased consolidation of sleep were also observed in WT mice. Two unclassified species of bacteria from the family Tannerellaceae were significantly increased in MRM-treated 5xFAD and WT mice. At 12 months of age, synaptic and neuronal loss become prominent in this AD model. However, the level of beta amyloid deposition in the brain was not significantly different between MRM and water control groups. Conclusion MRM treatment altered the gut microbiome, improved circadian timing of sleep and memory retention, but did not impact beta amyloid deposition in 5xFAD mice. Because these effects were also present in WT mice, MRM-induced microbiome changes may affect sleep and cognition independently from beta amyloid. Support Northwestern University Feinberg School of Medicine Center for Circadian and Sleep Medicine

BackgroundAmyloid‐beta precursor protein (APP) is the source of all amyloid‐beta (Aβ), the amyloidogenic peptide that aggregates in Alzheimer’s disease (AD). Lowering APP mRNA expression with RNA interference (RNAi) is a novel treatment strategy under investigation for AD. The 5xFAD mouse model of AD overexpresses APP and PSEN1 with five familial AD mutations, resulting in robust pathology, including amyloid plaques, microgliosis, inflammation, synaptic loss, neuronal loss, and behavioral changes. This work evaluates the effects of early and late intervention with an APP‐lowering small interfering RNA (siRNA) in this established AD model.MethodAPP‐targeting siRNAor artificial CSF (aCSF; control) was administered by intracerebroventricular injection in 5xFAD mice at late (8‐months‐old) and early (12‐weeks‐old) disease stages, and in age‐matched wild‐type mice. Late intervention mice received either aCSF or 300µg single dose. Early intervention mice received one of four dose regimens: control (aCSF:aCSF), transient lowering (75µg APP siRNA:aCSF), moderate sustained lowering (75µg APP siRNA:75µg APP siRNA), or robust sustained lowering (300µg APP siRNA:300µg APP siRNA). The impact of late and early siRNA intervention on molecular, biochemical, histological, and disease‐related behavioral outcomes (assessed using the elevated plus‐maze and open‐field assay) were assessed in 12‐month‐old mice (Figure 1).ResultTreatment in the late intervention group lowered amyloid burden to levels below the 8‐month baseline (Figure 2A, 2B). Compared with age‐matched aCSF mice, late treatment decreased pathogenic amyloid species, Aβ40 and Aβ42, in CSF and tissue, reduced markers of glial inflammation, and reduced plasma neurofilament light chain (NfL). No significant behavioral changes were noted (Figure 3A).Treatment in early intervention groups lowered amyloid burden in tissue (Figure 2C, 2D), reduced markers of glial inflammation, reduced plasma NfL, and decreased anxiety‐like behavior, all in a dose‐dependent manner. Notably, robust, sustained lowering of APP completely prevented the emergence of disease‐associated anxiety‐like behavior (Figure 3B).ConclusionTreatment with APP‐lowering siRNA reduced AD pathology in the 5xFAD mouse model. Early intervention with the highest dose regimen prevented the emergence of behavioral deficits and substantially improved many aspects of disease phenotype. These results support the continued development of mivelsiran, an investigational, first‐in‐class APP‐lowering RNAi therapeutic, in patients with AD (NCT05231785).

Alzheimer’s disease (AD) is a degenerative neurological disease that primarily affects the elderly. Drug therapy is the main strategy for AD treatment, but current treatments suffer from poor efficacy and a number of side effects. Non-drug therapy is attracting more attention and may be a better strategy for treatment of AD. Hypoxia is one of the important factors that contribute to the pathogenesis of AD. Multiple cellular processes synergistically promote hypoxia, including aging, hypertension, diabetes, hypoxia/obstructive sleep apnea, obesity, and traumatic brain injury. Increasing evidence has shown that hypoxia may affect multiple pathological aspects of AD, such as amyloid-beta metabolism, tau phosphorylation, autophagy, neuroinflammation, oxidative stress, endoplasmic reticulum stress, and mitochondrial and synaptic dysfunction. Treatments targeting hypoxia may delay or mitigate the progression of AD. Numerous studies have shown that oxygen therapy could improve the risk factors and clinical symptoms of AD. Increasing evidence also suggests that oxygen therapy may improve many pathological aspects of AD including amyloid-beta metabolism, tau phosphorylation, neuroinflammation, neuronal apoptosis, oxidative stress, neurotrophic factors, mitochondrial function, cerebral blood volume, and protein synthesis. In this review, we summarized the effects of oxygen therapy on AD pathogenesis and the mechanisms underlying these alterations. We expect that this review can benefit future clinical applications and therapy strategies on oxygen therapy for AD.

Dual specificity protein phosphatase 6 (DUSP6) was recently identified as a key hub gene in a causal VGF gene network that regulates late-onset Alzheimer's disease (AD). Importantly, decreased DUSP6 levels are correlated with an increased clinical dementia rating (CDR) in human subjects, and DUSP6 levels are additionally decreased in the 5xFAD amyloidopathy mouse model. To investigate the role of DUSP6 in AD, we stereotactically injected AAV5-DUSP6 or AAV5-GFP (control) into the dorsal hippocampus (dHc) of both female and male 5xFAD or wild type mice, to induce overexpression of DUSP6 or GFP. Barnes maze testing indicated that DUSP6 overexpression in the dHc of 5xFAD mice improved memory deficits and was associated with reduced amyloid plaque load, Aß1-40 and Aß1-42 levels, and amyloid precursor protein processing enzyme BACE1, in male but not in female mice. Microglial activation, which was increased in 5xFAD mice, was significantly reduced by dHc DUSP6 overexpression in both males and females, as was the number of "microglial clusters," which correlated with reduced amyloid plaque size. Transcriptomic profiling of female 5xFAD hippocampus revealed upregulation of inflammatory and extracellular signal-regulated kinase pathways, while dHc DUSP6 overexpression in female 5xFAD mice downregulated a subset of genes in these pathways. Gene ontology analysis of DEGs (p < 0.05) identified a greater number of synaptic pathways that were regulated by DUSP6 overexpression in male compared to female 5xFAD. In summary, DUSP6 overexpression in dHc reduced amyloid deposition and memory deficits in male but not female 5xFAD mice, whereas reduced neuroinflammation and microglial activation were observed in both males and females, suggesting that DUSP6-induced reduction of microglial activation did not contribute to sex-dependent improvement in memory deficits. The sex-dependent regulation of synaptic pathways by DUSP6 overexpression, however, correlated with the improvement of spatial memory deficits in male but not female 5xFAD.

BackgroundThe gut microbiota has recently attracted attention as a pathogenic factor in Alzheimer’s disease (AD). Microfold (M) cells, which play a crucial role in the gut immune response against external antigens, are also exploited for the entry of pathogenic bacteria and proteins into the body. However, whether changes in M cells can affect the gut environments and consequently change brain pathologies in AD remains unknown.MethodsFive familial AD (5xFAD) and 5xFAD-derived fecal microbiota transplanted (5xFAD-FMT) naïve mice were used to investigate the changes of M cells in the AD environment. Next, to establish the effect of M cell depletion on AD environments, 5xFAD mice and Spib knockout mice were bred, and behavioral and histological analyses were performed when M cell-depleted 5xFAD mice were six or nine months of age.ResultsIn this study, we found that M cell numbers were increased in the colons of 5xFAD and 5xFAD-FMT mice compared to those of wild-type (WT) and WT-FMT mice. Moreover, the level of total bacteria infiltrating the colons increased in the AD-mimicked mice. The levels of M cell-related genes and that of infiltrating bacteria showed a significant correlation. The genetic inhibition of M cells (Spib knockout) in 5xFAD mice changed the composition of the gut microbiota, along with decreasing proinflammatory cytokine levels in the colons. M cell depletion ameliorated AD symptoms including amyloid-β accumulation, microglial dysfunction, neuroinflammation, and memory impairment. Similarly, 5xFAD-FMT did not induce AD-like pathologies, such as memory impairment and excessive neuroinflammation in Spib−/− mice.ConclusionTherefore, our findings provide evidence that the inhibiting M cells can prevent AD progression, with therapeutic implications.

BackgroundAccumulating evidence indicates that partial inhibition of β-site APP-cleaving enzyme 1 (BACE1), which initiates amyloid-β (Aβ) production, mitigates Alzheimer’s disease (AD)-like pathologies and memory deficits in a battery of transgenic mouse models. However, our previous investigations suggest that therapeutic BACE1 suppression may be beneficial only if targeted on earlier stages of AD and encounter dramatic reductions in efficacy during disease progression. This study was designed to test the possibility that a combination approach, aimed at inhibiting BACE1 and boosting neprilysin (a major Aβ-degrading enzyme) activities, may be able to mechanistically overcome the limited efficacy of anti-Aβ therapy in advanced AD.ResultsAfter crossbreeding between BACE1 heterozygous knockout (BACE1+/−), neprilysin transgenic (NEP) and 5XFAD mice, we analyzed the resultant mice at 12 months of age when 5XFAD controls showed robust amyloid-β (Aβ) accumulation and elevation of BACE1 expression (~2 folds). Although haploinsufficiency lowered BACE1 expression by ~50% in concordance with reduction in gene copy number, profound β-amyloidosis, memory deficits and cholinergic neuron death were no longer rescued in BACE1+/− · 5XFAD mice concomitant with their persistently upregulated BACE1 (i.e., equivalent to wild-type control levels). Notably, neprilysin overexpression not only prevented Aβ accumulation but also suppressed the translation initiation factor eIF2α-associated elevation of BACE1 and lowered levels of the β-secretase-cleaved C-terminal fragment of APP (C99) in NEP · 5XFAD mice. Interestingly, these markers for β-amyloidogenesis in BACE1+/− · NEP · 5XFAD mice were further reduced to the levels reflecting a combination of single BACE1 allele ablation and the abolishment of translational BACE1 upregulation. However, since neprilysin overexpression was striking (~8-fold relative to wild-type controls), memory impairments, cholinergic neuronal loss and β-amyloidosis were similarly prevented in NEP · 5XFAD and BACE1+/− · NEP · 5XFAD mice.ConclusionsOur findings indicate that robust overexpression of neprilysin is sufficient to ameliorate AD-like phenotypes in aged 5XFAD mice. We also found that Aβ-degrading effects of overexpressed neprilysin can block deleterious BACE1-elevating mechanisms that accelerate Aβ production, warranting further study to test whether interventions moderately activating neprilysin may be useful for boosting the limited efficacy of therapeutic BACE1 inhibition in treating AD with established Aβ pathology.

Transcranial alternating current stimulation (tACS) is a neuromodulation procedure that is currently studied for the purpose of improving cognitive function in various diseases. A few studies have shown positive effects of tACS in Alzheimer’s disease (AD). However, the mechanism underlying tACS has not been established. The purpose of this study was to investigate the mechanism of tACS in five familial AD mutation (5xFAD) mouse models. We prepared twenty 4-month-old mice and divided them into four groups: wild-type mice without stimulation (WT-NT group), wild-type mice with tACS (WT-T group), 5xFAD mice without stimulation (AD-NT group), and 5xFAD mice with tACS (AD-T group). The protocol implemented was as follows: gamma frequency 200 μA over the bilateral frontal lobe for 20 min over 2 weeks. The following tests were conducted: excitatory postsynaptic potential (EPSP) recording, Western blot analysis (cyclic AMP response element-binding (CREB) proteins, phosphorylated CREB proteins, brain-derived neurotrophic factor, and parvalbumin) to examine the synaptic plasticity. The EPSP was remarkably increased in the AD-T group compared with in the AD-NT group. In the Western blot analysis, the differences among the groups were not significant. Hence, tACS can affect the long-lasting enhancement of synaptic transmission in mice models of AD.

BackgroundEpidemiological studies have identified an association between the exposure to neurotoxic heavy metals such as cadmium (Cd) and an increased risk for Alzheimer's disease (AD). However, the cellular and molecular mechanisms by which Cd or lead (Pb) exposure affects AD pathogenesis and progression are largely unknown. The goal of this study was to determine how Cd and Pb exposure impact cognitive function and AD progression using the 5xFAD transgenic mouse model of AD.MethodsJuvenile (5‐weeks old) 5xFAD mice were challenged with 0.2% Pb or 0.002% Cd in drinking water for 6 weeks to model chronic environmental exposures. Y‐maze tests were performed to assess spatial memory and learning ability. The Open Field Maze test was employed to examine anxiety‐like behaviors. Senescent cells were determined using senescence‐associated β‐galactosidase staining. Quantitative RT‐PCR assays were performed to measure expression levels of senescence markers and senescence‐associated secretory phenotype (SASP) related cytokines. Immunofluorescence and confocal microscopy were used to analyze senescent cells and neuroinflammation markers in brain tissues.ResultsCd and Pb both can accelerate the pace of amyloid beta (Aβ) plaque formation and the decline of cognitive functions in 5xFAD mice. Even at a 100‐fold lower dose, chronic Cd exposure causes a greater level of Aβ deposition and cognitive deficits than Pb does, indicating that Cd is more potent than Pb in exacerbating AD progression. Mechanistically, we found that the increased expression of the p16Ink4a senescence marker was more pronounced in the hippocampus of Cd‐exposed mice compared to those treated with Pb. Notably, Cd upregulates the expression of the SASP marker IL‐6 preferentially in the hippocampus over the cortex, suggesting a spatial difference in Cd‐induced increase in neuroinflammation. Furthermore, in vitro mechanistic studies reveal that Cd exposure induces premature senescence in human microglial cells, and senescent microglia release high levels of IL‐6, a major modulator of neuroinflammation.ConclusionOur studies demonstrate that chronic exposure to Cd or Pb can exacerbate cognitive deficits and AD progression in 5xFAD mice. Mechanistically, we discovered that Cd exposure‐induced acceleration of AD progression was associated with increased levels of senescent cell burden and neuroinflammation in the hippocampus.

The reduced clearance of amyloid-β peptide (Aβ) from the brain partly accounts for the neurotoxic accumulation of Aβ in Alzheimer's disease (AD). Recently, it has been suggested that P-glycoprotein (P-gp), which is an efflux transporter expressed on the luminal membrane of the brain capillary endothelium, is capable of transporting Aβ out of the brain. Although evidence has shown that restoring P-gp reduces brain Aβ in a mouse model of AD, the molecular mechanisms underlying the decrease in P-gp expression in AD is largely unknown. We found that Aβ1–42 reduced P-gp expression in the murine brain endothelial cell line bEnd.3, which was consistent with our in vivo data that P-gp expression was significantly reduced, especially near amyloid plaques in the brains of five familial AD mutations (5XFAD) mice that are used as an animal model for AD. A neutralizing antibody against the receptor for advanced glycation end products (RAGE) and an inhibitor of nuclear factor-kappa B (NF-κB) signaling prevented the decrease in Aβ1–42-induced P-gp expression, suggesting that Aβ reduced P-gp expression through NF-κB signaling by interacting with RAGE. In addition, we observed that the P-gp reduction by Aβ was rescued in bEnd.3 cells receiving inductive signals or factors from astrocytes making contacts with endothelial cells (ECs). These results support that alterations of astrocyte–EC contacts were closely associated with P-gp expression. This suggestion was further supported by the observation of a loss of astrocyte polarity in the brains of 5XFAD mice. Taken together, we found that P-gp downregulation by Aβ was mediated through RAGE–NF-κB signaling pathway in ECs and that the contact between astrocytes and ECs was an important factor in the regulation of P-gp expression.

Olfactory impairments, including deficits in odor detection, discrimination, recognition, and changes in odor hedonics, are reported in the early stages of Alzheimer's disease (AD). Rodent models of AD display deficits in odor learning, detection, and discrimination-recapitulating the clinical condition. However, the impact of familial AD genetic mutations on odor hedonics is unknown. We tested 2-, 4-, and 6-month-old 5XFAD (Tg6799) mice in the 5-port odor multiple-choice task designed to assay a variety of odor-guided behaviors, including odor preferences/hedonics. We found that 5XFAD mice investigated odors longer than controls, an effect that was driven by 6-month-old mice. Interestingly, this effect was carried by females in the 5XFAD group, who investigated odors longer than age-matched males. Upon examining behavior directed toward individual odors to test for aberrant odor preferences, we uncovered that 5XFAD females at several ages displayed heightened preferences toward some of the odors, indicating aberrant hedonics. We observed no impairments in the ability to engage in the task in 5XFAD mice. Taken together, 5XFAD mice, particularly 5XFAD females, displayed prolonged odor investigation behavior and enhanced preferences to certain odors. The data provide insight into hedonic alterations that may occur in AD mouse models and how these are influenced by biological sex. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Traumatic brain injury (TBI) afflicts 70 million people worldwide annually and is the 3rd overall risk factor for developing Alzheimer's disease (AD), behind genetics and aging. In patients with AD, a history of TBI is associated with a 3-4 year earlier onset of cognitive impairment. TBI and AD share many pathologies, including blood brain barrier dysfunction, neuroinflammation, and protein aggregation. Yet, the underlying mechanism of this relationship is not understood, and there are no treatments that protect patients from accelerated AD after TBI. We recently reported that tau, a microtubule binding protein essential for neuronal health, is acetylated after TBI. Acetylation impairs tau binding to microtubules, leading to its mis-localization into the cell soma and pathological aggregation. Acetylated tau is also elevated early in AD, and acetylated tau was significantly more elevated in the brains of human AD subjects with a history of TBI, compared to AD alone and healthy controls. Therefore, we hypothesize that TBI-induced tau acetylation drives the acceleration of AD. To study this phenomenon, we developed a mouse model of TBI that accelerates AD-like pathology and cognitive impairment in 5xFAD mice, and amyloid-driven AD model. Our unique model of multimodal TBI produces a complex and reproducible brain injury with neurodegeneration and neurobehavioral impairment, beginning with acute axonal degeneration and persisting chronically with blood-brain barrier degradation and nerve cell death. This model of TBI also produces the same systemic metabolic alterations that are reported in TBI patients. TBI causes learning deficits in young 5xFAD mice that are not seen in either sham-injured 5xFAD mice or in wild type littermates subjected to TBI. TBI also accelerates amyloid deposition in 5xFAD mice. We hypothesize that TBI will also worsen blood brain barrier function in 5xFAD mice. Importantly, 5xFAD mice show greater elevation of acetylated tau after TBI, compared to WT mice. Preliminary data suggests that treatment with the FDA-approved non-steroidal inflammatory drug diflunisal, which inhibits the enzyme that acetylates tau, reduces acetylated tau and rescues behavior deficits after TBI in 5xFAD mice.