APP23 Mice Research Articles

Relationship between uric acid and cerebral amyloid angiopathy

Purpose: To explored Relationship between uric acid and cerebral amyloid angiopathy; Materials and methods: ZO-1 and RAGE in HBMECs were detected by western blotting, and then, we analyzed ZO-1, occludin, and RAGE mRNA expression levels in different treatment groups using RTPCR. Cell counts and the relative αSMA fluorescence intensity were measured in order to evaluate the protective effect of uric acid against injury to HBVSMCs. Analysis of variance showed that LDH leakage rate was used to verify the uric acid protective effect on the injury induced by Aβ1–40. After that, the level of uric acid in serum and Aβ1–40 in brain tissue was analyzed by western blotting and immunohistochemistry to evaluate the protective effect of uric acid in the brain of APP23 mice. Meanwhile, Occludin, ZO-1, and RAGE protein levels were measured by western blotting; Results: Uric acid reduced the negative effects of Aβ on the vascular endothelium and smooth muscle cells and protected the vascular wall in vitro. In APP23 mice, Aβ1–40 and Aβ1–42 levels were significantly elevated in brain tissues and further increased after uric acid concentration was decreased. In APP23 mice, ZO-1 and occludin expression levels were both significantly lower than those in wild-type animals. After uric acid concentration was lowered in APP23 mice, ZO-1 and occludin expression levels were significantly lower than those in untreated animals; Conclusions: Uric acid in the blood protects the blood vessels from CAA damage to the blood vessel wall, and reduces the occurrence of cerebral hemorrhage.

Upregulated expression of a subset of genes in APP;ob/ob mice: Evidence of an interaction between diabetes-linked obesity and Alzheimer's disease.

Clinical studies have indicated that obesity and diabetes are associated with Alzheimer's disease (AD) and neurodegeneration. However, the mechanism by which obesity/diabetes and AD interact with each other and contribute to dementia remains elusive. To obtain insights into their interaction at molecular levels, we performed gene expression analysis of APP;ob/ob mice, which were generated by crossing transgenic AD model mice (APP23 mice) with ob/ob mice, which are obese and mildly diabetic. The Aβ level in these mice was reduced compared with that in pure APP mice. However, we identified a cluster of genes (cluster 10) upregulated in APP;ob/ob mice but not in either APP or ob/ob mice. Interestingly, genes upregulated in the human AD brain were enriched in cluster 10. Moreover, genes in cluster 10 formed a network and shared upregulated genes with a cell model of neurodegeneration and other models of neurological disorders such as ischemia and epilepsy. In silico analyses showed that serum response factor (SRF), recently identified in a single‐cell analysis of human brains as a transcription factor that can control the conversion from healthy cells to AD cells, might be a common transcriptional regulator for a subset of cluster 10 genes. These data suggest that upregulation of genes uniquely associated with APP;ob/ob mice is an evidence of the interaction between obesity/diabetes and AD.

Cover Image, Volume 69, Issue 4

Cover Illustration: Triple confocal immunofluorescence image of a primary astrocyte (green; GFAP) which has engulfed Abeta-containing synaptoneurosomes (red; Abeta42) derived from APP mice. Lysosomes (blue; Lamp1) surround the internalized synaptic elements but there is no overlap between both compartments indicating an inefficient degradation capacity. (See Sanchez-Mico, MV et al, https://doi.org/10.1002/glia.23943.)

Decreased pH in the aging brain and Alzheimer's disease

Using publicly available data sets, we compared pH in the human brain and the cerebrospinal fluid (CSF) of postmortem control and Alzheimer's disease cases. We further investigated the effects of long-term acidosis in vivo in the APP-PS1 mouse model of Alzheimer's disease. We finally examined in vitro whether low pH exposure could modulate the release of proinflammatory cytokines and the uptake of amyloid beta by microglia. In the human brain, pH decreased with aging. Similarly, we observed a reduction of pH in the brain of C57BL/6 mice with age. In addition, independent database analyses revealed that postmortem brain and CSF pH is further reduced in Alzheimer's disease cases compared with controls. Moreover, in vivo experiments showed that low pH CSF infusion increased amyloid beta plaque load in APP-PS1 mice. We further observed that mild acidosis reduced the amyloid beta 42–induced release of tumor necrosis factor–alpha by microglia and their capacity to uptake this peptide. Brain acidosis is associated with aging and might affect pathophysiological processes such as amyloid beta aggregation or inflammation in Alzheimer's disease.

Covert strokes prior to Alzheimer’s disease onset accelerate peri-lesional pathology but not cognitive deficits in an inducible APP mouse model

It is estimated that up to 1 in 3 healthy middle-aged adults will have had a covert stroke during their lifetime. Furthermore, post-stroke, survivors are more than twice as likely to develop dementia. In the present study, we aimed to model the impact of focal subclinical ischemia prior to the onset of AD pathogenesis in a preclinical model. We utilized endothelin-1 to induce ischemia in an iducible transgenic mouse model of Alzheimer’s disease, APPsi:tTA, allowing for temporal control of APP gene expression. We induced the focal subclinical ischemic events in the absence of APP expression, thus prior to AD onset. T2 structural magnetic resonance imaging confirmed the volume and location of focal subclinical ischemic lesions to the medial prefrontal cortex. Following recovery from surgery and 7 weeks of APP expression, we found that two subclinical ischemic lesions resulted in a significant localized increase in amyloid load and in microglial activation proximal to the lesion. However, no differences were found in astrogliosis. A battery of behaviour tests was conducted, in which no significant differences were detected in activities of daily living and cognitive function between stroked and sham cohorts. Overall, our results demonstrated that APP expression was the sole driving force behind behavioural deficits. In conclusion, our results suggest that a history of two subclinical strokes prior to AD onset does not worsen early disease trajectory in a mouse model.

Different Age Related Neurological and Cardiac Effects of Verapamil on a Transgenic Mouse Model of Alzheimer's Disease.

Dementias are the third cause of the disability-adjusted life-years (DALYs) worldwide with Alzheimer’s (AD) having the highest prevalence. Despite ample research in the field, therapeutic options are limited. However, with the increase in lifespan, a larger number of AD patients will receive other medication for the evermore-increased number of comorbidities that such patients face. The purpose of this study was to evaluate the neurological and cardiac effects of verapamil, on C57BL/6J-TgN (Thy1-APPKM670/671NL; Thy1-PS1L166P (APP) mice. The daily administration of 3.5mg/kg of verapamil for 28 days revealed different effects on young and aged APP mice. While young animals showed less anxiety and improved short-term memory with minimal cardiac effects (an increase in the duration of ventricular depolarization), aged ones did not present behavioral improvements, but with a decrease in the duration of ventricular depolarizing. Repolarization effects of verapamil were similar in young and aged animals, except for the duration of the ST segment that was longer in aged animals. Considering our results, the use of calcium blockers in AD patients should take into consideration the stage of the disease, as different effects could be seen at different stages of AD, in our model.

Pharmacological suppression of seizure‐like activity in the PS2APP model of amyloidosis

AbstractBackgroundSeizure activity is significantly increased in patients with Alzheimer Disease relative to healthy controls. Concurrently, the J20 mouse model of amyloidosis has increased seizure‐like activity, and compounds that lower this activity can lead to cognitive benefits in this model. Here we aim to extend these studies to the PS2APP mouse model of amyloidosis.MethodLocomotor activity was measured for 60 min in C57BL/6J mice with a beam‐break based monitoring system (PAS Open Field, San Diego Instruments) using a between‐subjects design with 9‐10 mice/dose group. EEG/EMG headmounts were implanted into PS2APP mice with amyloid‐beta pathology. Data was recorded for 6h using a Pinnacle Technologies recording system and processed with MATLAB (Mathworks) routines. EEG spikes were detected using a thresholded line‐length algorithm.A within subject crossover‐design was used for vehicle vs. Levetiracetam treatment and data from 13 PS2APP mice was analyzed.ResultLocomotor activity measures showed that an acute dose of 200 mg/kg of the anti‐seizure medication Levetiracetam did not affect activity levels. EEG recordings demonstrated that the frequency of seizure‐like spikes during sleep was increased from 38 spikes/h in 4 months old PS2APP mice to 75 spikes/h in 13 months old PS2APP mice. This measure was reduced by ∼60% in 13 months old PS2APP mice in response to acute treatment with 200 mg/kg of Levetiracetam.ConclusionSeizure‐like activity is increased in patients with Alzheimer’s disease and in mouse models of amyloidosis. Our Levetiracetam studies confirm that pharmacological intervention can normalize seizure‐like activity in PS2APP mice. Medications with different mechanism of action need to be tested for their ability to reduce spike activity and improve cognition in this animal model.Ultimately, it will be important to see if such pharmacological effects translate to humans and if reductions in seizure activity are linked to functional improvements.

A preclinical model for modulation and characterisation of neuropsychiatric disturbances in Alzheimer’s disease

AbstractBackgroundThe events that direct the shift from asymptomatic to symptomatic Alzheimer’s disease (AD) have yet to be fully characterized, however the consensus is that neuropsychiatric disturbances (NPDs) play a significant role in this. Most AD patients (80‐97%) experience at least one NPD at least once during their disease, nevertheless recognizing and treating NPDs remain a major challenge due to the poor understanding of the underlying pathology. Inflammation is thought to contribute to NPD development and ultimately exacerbate AD pathology. In AD, sleep disturbances drive neuroinflammation processes, precede clinical symptoms, and increase the risk of developing AD. Neuroinflammation can also be associated with more server NPDs and is linked to faster cognitive decline and worse prognosis. Contrary to memory and learning, which is reasonably well modelled in transgenic animals, robust preclinical models for NPDs are still lacking. We hypothesis that circadian disruption combined with chronic mild stress can introduce sleep disturbances, alter phenotypic behavior, and exacerbate AD‐related neuropathology in a common mouse model of AD.MethodWe introduced socio‐environmental stress and circadian disruption to APPPS1 and wildtype (WT) littermates, to investigate NPD‐like behavior and changes in the proteome and transcriptome.ResultThis approach altered normal circadian rhythm activity patterns and induced subtle NPD‐like behavior in both WT and APPPS1 mice. Furthermore, these conditions changed normal transcription of clock genes, particularly transcription levels of Cry1, Per1 and Per2 were changed in WT and APPPS1 mice. β‐amyloid plaque load was elevated in prefrontal cortex of APPPS1 mice and we observed changes in the hippocampal proteome of APPPS1 and WT compared to WT and APPPS1 mice under normal conditions.ConclusionAlthough further characterization of the model is needed, we believe the model presented here can increase our understanding of the circuits responsible for NPD development in AD. This may hold the key to developing better treatments for NPDs and thus improving the quality of life for both AD patients and caregivers.

Gut microbiome perturbations influence brain amyloidosis only in the presence of microglia in APPPS1‐21 mice

AbstractBackgroundIn prior efforts, we demonstrated reduced amyloidosis and altered microgliosis in long‐term antibiotics (abx)‐treated APPPS1‐21 male mice. Restoration of the gut microbiome into abx‐treated male mice by fecal microbiota transfer (FMT) established a causality between the gut microbiome and amyloidosis. We have used FMT studies using our current short‐term abx APPPS1‐21 mice to evaluate the microbiome‐microglia‐amyloidosis axis.MethodShort‐term, postnatal abx (4mg/ml Kanamycin, 0.35mg/ml Gentamicin, 8500U/ml Colistin, 2.15mg/ml Metronidazole, 0.45mg/ml Vancomycin: post‐natal day 14 to day 21) was performed. To establish causality, we performed FMT (200µl of 5mg/ml fecal slurry daily gavage) into abx‐treated APPPS1‐21 male mice. Pathogenicity of the gut microbiome in WT or Tg mice were confirmed using age‐matched FMT from WT and Tg controls into abx‐treated male mice. We performed total RNAseq transcriptome analysis to evaluate potential mechanism(s). The role of microglial cells were evaluated in PLX6522 (CSF‐1 receptor inhibitor)‐treated FMT‐transplanted abx‐treated APPPS1‐21 male mice. Nine weeks old GF APPPS1‐21 were used to characterize the amyloidosis and glial cells in both genders.ResultAn early life abx treatment resulted in gut microbiota changes in a sex‐dependent manner. Only male mice showed reduced amyloidosis and altered microglial phenotypes. Age matched Tg FMT or WT FMT resulted in higher amyloidosis in abx‐treated male mice. RNAseq analysis of total cortical RNA showed significantly different mRNA levels that occurred in a sex‐specific manner and changes in abx‐treated male mice were restored with FMT. GO term analysis showed gliogenesis and microglia development as significantly altered pathways in abx‐treated male group only. To confirm the exact role of the microglia in this model, we employed PLX6522 in FMT‐treated ABX‐male mice. Microglia depletion did not result in an FMT‐dependent increase in amyloidosis in abx‐treated male mice. Finally, germ‐free APPPS1‐21 mice showed reduced amyloidosis that occurs in a sex‐specific manner.ConclusionFrom GF APPPS1‐21 and FMT‐treated abx‐male APPPS1‐21 studies, we conclude that gut microbiome plays a critical role in modulating amyloidosis in APPPS1‐21 mice. Furthermore, microglia mediates the effects of early life gut microbiota perturbations, which results in altered amyloidosis in APPPS1‐21 male mice.

The pathological role of Pb in AD through impairing functions of blood‐brain barrier system

AbstractBackgroundLead (Pb) is an environmental factor has been suspected of contributing to Alzheimer’s disease (AD) and other dementia. Our previous study has shown that chronic Pb exposure increased brain levels of beta‐amyloid (Aβ) and amyloid plaques, a pathological hallmark for AD, in APP transgenic mice possibly by inhibiting Aβ clearance. However, it remains unclear how different levels of Pb affect Aβ clearance and the blood‐brain system (BBBS) in the blood‐brain barrier system.MethodTg‐APP mice were administrated with Pb‐acetate at three different doses by oral gavage for 4 weeks. Dynamic contrast‐enhanced CT (DCE‐CT) imaging method was used to quantify the real‐time brain regional blood flow, blood volume, and BBBS permeability.ResultChronic Pb exposures significantly increased permeability surface area product (PS) and brain perfusion, indicating that Pb disrupted the mouse blood‐brain barrier system was possibly mediated by inflammation.ConclusionChronic Pb exposure at toxic and even subtoxic levels would damage the BBBS and induce dementia by allowing blood contents to escape into the brain parenchyma.

Impact of the presence of AβN3pE and AβpSer8 in Aβ aggregates on the induction of Aβ seeding and spreading in the brains of APP23 mice

AbstractBackgroundAmyloid β‐plaques are a hallmark lesion of Alzheimer’s disease (AD) and consist of aggregates of the amyloid β‐peptide (Aβ). Aβ peptides can undergo posttranslational modifications, including N‐terminal truncation with subsequent pyroglutamate formation at glutamate 3, and phosphorylation at serine 8, leading to the formation of AβN3pE and AβpSer8, respectively. These posttranslationally modified forms are present in the brain in addition to non‐modified Aβ. During disease development the composition of the Aβ aggregates changes from aggregates without detectable modified Aβ, in non‐demented individuals, into aggregates containing AβN3pE and AβSer8 in symptomatic AD cases. Brain‐derived Aβ aggregates are capable of inducing deposition and spreading of Aβ pathology when injected into the brain of APP‐transgenic mice. Therefore, the question arises whether the composition of Aβ aggregates has impact on its seeding capabilities as well as on the composition of the seeded Aβ plaques.MethodAPP23 mice were injected into the left hippocampus at two months of age. They received injections from three different brain homogenates. The first one lacked detectable Aβ (control), in a second homogenate only Aβ without detectable modifications was found (p‐preAD), and in the third homogenate both Aβ and AβN3pE were detected. Mice were sacrificed at six months and their brains were immunohistochemically analyzed for the presence and composition of the induced plaque pathology.ResultAPP23 mice injected with the AD or p‐preAD brain homogenates developed similar Aβ plaque loads and the plaques exhibited AβN3pE and AβpSer8 immunoreactivity. Mice receiving control brain homogenates developed very few plaques in the injected hemisphere, which were detectable with antibodies against Aβ and AβN3pE, but not with anti‐AβpSer8.ConclusionThe presence of Aβ seeds accelerates the accumulation of detectable amounts of AβN3pE and AβpSer8 and, thereby, promote the formation of fully mature Aβ aggregates similar to that seen in symptomatic AD patients. The acceleration of Aβ aggregate maturation, however, does not depend on the presence of posttranslationally modified Aβ forms in the seeds. Support: FWO.

Chia seeds as a potential cognitive booster in the APP23 Alzheimer\u2019s disease model

Glucose hypometabolism potentially contributes to Alzheimer’s disease (AD) and might even represent an underlying mechanism. Here, we investigate the relationship of diet-induced metabolic stress and AD as well as the therapeutic potential of chia seeds as a modulator of glucose metabolism in the APP23 mouse model. 4–6 (pre-plaque stage, PRE) and 28–32 (advanced-plaque stage, ADV) weeks old APP23 and wild type mice received pretreatment for 12 weeks with either sucrose-rich (SRD) or control diet, followed by 8 weeks of chia seed supplementation. Although ADV APP23 mice generally showed functioning glucose homeostasis, they were more prone to SRD-induced glucose intolerance. This was accompanied by elevated corticosterone levels and mild insulin insensitivity. Chia seeds improved spatial learning deficits but not impaired cognitive flexibility, potentially mediated by amelioration of glucose tolerance, attenuation of corticosterone levels and reversal of SRD-induced elevation of pro-inflammatory cytokine levels. Since cognitive symptoms and plaque load were not aggravated by SRD-induced metabolic stress, despite enhanced neuroinflammation in the PRE group, we conclude that impairments of glucose metabolism do not represent an underlying mechanism of AD in this mouse model. Nevertheless, chia seeds might provide therapeutic potential in AD as shown by the amelioration of cognitive symptoms.

Protective effects of edaravone on white matter pathology in a novel mouse model of Alzheimer’s disease with chronic cerebral hypoperfusion

White matter lesions (WMLs) caused by cerebral chronic hypoperfusion (CCH) may contribute to the pathophysiology of Alzheimer’s disease (AD). However, the underlying mechanisms and therapeutic approaches have yet to be totally identified. In the present study, we investigated a potential therapeutic effect of the free radical scavenger edaravone (EDA) on WMLs in our previously reported novel mouse model of AD (APP23) plus CCH with motor and cognitive deficits. Relative to AD with CCH mice at 12 months (M) of age, EDA strongly improved CCH-induced WMLs in the corpus callosum of APP23 mice at 12 M by improving the disruption of white matter integrity, enhancing the proliferation of oligodendrocyte progenitor cells, attenuating endothelium/astrocyte unit dysfunction, and reducing neuroinflammation and oxidative stress. The present study demonstrates that the long-term administration of EDA may provide a promising therapeutic approach for WMLs in AD plus CCH disease with cognitive deficits.

Identification of truncated C-terminal fragments of the Alzheimer's disease amyloid protein precursor derived from sequential proteolytic pathways.

Recent evidence supports the emerging hypothesis that the amyloid-β precursor protein C-terminal fragments (APP-CTFs) and dysregulations in both their qualitative and quantitative productions may actively and directly contribute to the neuronal toxicity in early phases of Alzheimer's disease (AD). These new findings revealed the urgent needs and gaps in better understanding the metabolism and full spectrum of APP-CTFs. In this study, we characterized by mass spectrometry the full patterns of APP-CTFs in different cell types and in the brain of an AD APPPS1 mouse model. In these systems, we first discovered a series of 71-80 amino acids long N-terminally truncated APP-CTFs of unknown functions. We next demonstrated that these N-terminally truncated APP-CTFs are sequentially produced by the proteolytic processing of APP-C80, by an as yet unidentified protease. Finally, these N-terminally truncated APP-CTFs are likely protein substrates recognized and processed by the γ-secretase complex, leading to the production of N-terminally truncated Aβ peptides. Together, our findings provide new insights into the metabolism of APP and offer potential new strategies to modulate the production of toxic Aβ peptides in AD.

Microglia depletion diminishes key elements of the leukotriene pathway in the brain of Alzheimer\u2019s Disease mice

Leukotrienes (LTs) contribute to the neuropathology of chronic neurodegenerative disorders including Alzheimer’s Disease (AD), where they mediate neuroinflammation and neuronal cell-death. In consequence, blocking the action of Leukotrienes (LTs) ameliorates pathologies and improves cognitive function in animal models of neurodegeneration. Surprisingly, the source of Leukotrienes (LTs) in the brain is largely unknown. Here, we identified the Leukotriene (LT) synthesis rate-limiting enzyme 5-Lipoxygenase (5-Lox) primarily in neurons and to a lesser extent in a subpopulation of microglia in human Alzheimer´s Disease (AD) hippocampus brain sections and in brains of APP Swedish PS1 dE9 (APP-PS1) mice, a transgenic model for Alzheimer´s Disease (AD) pathology. The 5-Lipoxygenase (5-Lox) activating protein (FLAP), which anchors 5-Lipoxygenase (5-Lox) to the membrane and mediates the contact to the substrate arachidonic acid, was confined exclusively to microglia with the entire microglia population expressing 5-Lipoxygenase activating protein (FLAP). To define the contribution of microglia in the Leukotriene (LT) biosynthesis pathway, we ablated microglia using the colony stimulating factor 1 receptor (CSF1R) inhibitor PLX5622 in wildtype (WT) and APP-PS1 mice. Microglia ablation not only diminished the expression of FLAP and of the Leukotriene (LT) receptor Cysteinylleukotriene receptor 1 (CysLTR1), as expected based on their microglia cell type-specific expression, but also drastically reduced 5-Lipoxygenase (5-Lox) mRNA expression in the brain and its protein expression in neurons, in particular in wildtype (WT) mice. In conclusion i) microglia are key in Leukotriene (LT) biosynthesis, and ii) they regulate neuronal 5-Lipoxygenase (5-Lox) expression implying a yet unknown signaling mechanism between neurons and microglia.

Chemokines and chemokinesâs receptors in APPPS1 mice

The amyloid precursor protein plus presenilin-1 (APP/PS1) mice are a frequently-used model for Alzheimer’s disease studies (AD). Using behavioral studies, quantitative RT-PCR and Western-blot techniques, significant findings were determined by the expression of proteins involved in inflammation comparing APP/PS1 and Wild type mice. Increased GFAP expression could be associated with the elevation in number of reactive astrocytes. IL-3 is involved in inflammation and ABDF1 intervenes normally in the transport across cell membranes and both were found up-regulated in APP/PS1 mice compared to Wild type mice. We noted for the first time, a CCR8 increase expression with diminution of its CCL1 chemokine, both normally involved in protection from bacterial infection and demyelination. Furthermore, CCR5 expression was decreased and both CCL3 and CCL4 chemokines were highly expressed indicating a possible gliosis and probably an increase in chemotaxis from lymphocytes and T cell generation. Inflammation in AD will be the next step in the therapeutic approach.

The role of APOE in Microglia regulation in Neurogeneration

Alzheimer’s disease (AD) is the most prevalent senile dementia affecting 4.5 million Americans. Neuroinflammatory changes are prominent and may significantly contribute to the pathologic process. Mononuclear phagocytes (brain resident microglia and recruited peripheral monocytes) accumulate around amyloid plaque in AD brains. However, their exact cellular identity, molecular and functional phenotypes, and their protective or destructive roles in AD are not well understood. This stems in part from the lack of a specific molecular signatures for mononuclear phagocytes, cell type-specific antibodies, and analytic tools for in situ characterization. We recently identified a unique TGFβ-dependent molecular signature of homeostatic (M0)- and APOE-dependent (MGnD)- microglia in mouse models including APP-PS1 mice and human AD. Mechanistically, the TREM2-APOE pathway mediates a switch from M0- to MGnD-microglia phenotype after phagocytosis of apoptotic neurons in a cell-autonomous manner. TREM2 induces APOE signaling which is a negative regulator of the transcription program in M0-microglia.Transcription regulatory network analysis identified direct effect of APOE on suppression of major microglial homeostatic regulators including TGFβ signaling and induction of disease-associated molecules which are essential for pathogenicity in neuroinflammation. Specific genetic ablation of Apoe and/orTrem2 in microglia restored their homeostatic phenotype and genetic ablation of Apoe or Trem2 in TAU (P301S) mice arrested neurodegeneration and brain atrophy. Therefore, APOE plays an important role in microglia phenotype regulation in conditions, and restoration of the homeostatic microglia by targeting the APOE-signaling in microglia represents a novel immunotherapeutic approach. Taken together, our work identifies the TREM2-APOE pathway as a major regulator of microglial functional phenotype in diseases and serves as a novel target to restore homeostatic microglia. These advances have major implications not only for understanding normal CNS function, but have opened up new avenues to understand the role of microglia in disease and most importantly have created the opportunity for consideration of ways in which microglial may be imaged and targeted for the treatment of disease. Since APOE e4 is the major risk factor of the disease, we study the role of APOE e4 in microglia regulation by employing novel tools including new mouse models and techniques to specifically target APOE in order to restore microglia-mediated protein clearance and brain function in animal models of tauopathies and AD. I will present recent advances in understanding the new molecular signature of homeostatic microglia, disease associated microglia and how microglia are regulated in health and disease. This impairment triggers a progressive loss of cognitive skills such as memory and decision making. Neurodegeneration is a key aspect of a large number of diseases that come under the umbrella of neurodegenerative diseases. Of these hundreds of different disorders, attention has so far focused mainly on just a handful, with Parkinson's disease, Huntington disease, being the most notable and Alzheimer's disease. A large proportion of the lesser-advertised diseases were essentially ignored. Such disorders can lead to irreversible damage to the brain and neurodegeneration. While all three of the diseases manifest with different clinical characteristics, the mechanisms of disease tend to be identical at the cellular level. Parkinson's disease, for example , affects the basal ganglia in the Mind, it depletes dopamine. It results in swelling, swelling and tremors in the body's main muscles, which are common features of the disease. There are deposits of tiny protein plaques in Alzheimer's disease which damage various parts of the brain and lead to progressive memory loss. Huntington's disease is a progressive genetic disorder which affects the body’s major muscles Severe restriction on the engine, and ultimately death.

Trem2 deficiency differentially affects phenotype and transcriptome of human APOE3 and APOE4 mice

BackgroundAlzheimer’s Disease (AD) is a neurodegenerative disorder influenced by aging and genetic risk factors. The inheritance of APOEε4 and variants of Triggering Receptor Expressed on Myeloid cells 2 (TREM2) are major genetic risk factors for AD. Recent studies showed that APOE binds to TREM2, thus raising the possibility of an APOE-TREM2 interaction that can modulate AD pathology.MethodsThe aim of this study was to investigate this interaction using complex AD model mice - a crossbreed of Trem2ko and APP/PSEN1dE9 mice expressing human APOE3 or APOE4 isoforms (APP/E3 and APP/E4 respectively), and their WT littermates (E3 and E4), and evaluate cognition, steady-state amyloid load, plaque compaction, plaque growth rate, glial response, and brain transcriptome.ResultsIn both, APP/E3 and APP/E4 mice, Trem2 deletion reduced plaque compaction but did not significantly affect steady-state plaque load. Importantly, the lack of TREM2 increased plaque growth that negatively correlated to the diminished microglia barrier, an effect most pronounced at earlier stages of amyloid deposition. We also found that Trem2 deficiency significantly decreased plaque-associated APOE protein in APP/E4 but not in APP/E3 mice in agreement with RNA-seq data. Interestingly, we observed a significant decrease of Apoe mRNA expression in plaque-associated microglia of APP/E4/Trem2ko vs APP/E4 mice. The absence of TREM2, worsened cognitive performance in APP transgenic mice but not their WT littermates.Gene expression analysis identified Trem2 signature - a cluster of highly connected immune response genes, commonly downregulated as a result of Trem2 deletion in all genotypes including APP and WT littermates. Furthermore, we identified sets of genes that were affected in TREM2- and APOE isoform-dependent manner. Among them were Clec7a and Csf1r upregulated in APP/E4 vs APP/E3 mice, a result further validated by in situ hybridization analysis. In contrast, Tyrobp and several genes involved in the C1Q complement cascade had a higher expression level in APP/E3 versus their APP/E4 counterparts.ConclusionsOur data demonstrate that lack of Trem2 differentially impacts the phenotype and brain transcriptome of APP mice expressing human APOE isoforms. The changes probably reflect the different effect of APOE isoforms on amyloid deposition.

Increase of BACE1, Brain-Renal Risk Factor, Contributes to Kidney Damage in an Alzheimer's Disease Mouse Model.

It is believed that there is a certain correlation between the brain and kidneys, but it is poorly understood. Many findings suggested that there were previously unknown signaling pathways involving AβPP and BACE1 in the kidney. Exploring the changes of BACE1 activity in APP23 mouse kidneys, providing evidence for the function of AβPP and BACE1 activity in the kidney. The activity and expression of BACE1 were detected in the kidney of APP23 mice by enzymatic assay and western blotting. The protein expression levels of AβPP, claudin1, occludin, VE-cadherin, and Klotho (membrane-form klotho) were examined by using western blotting. The renal pathological changes of APP23 mice were examined by the routine renal pathological procedures. In this study, we found that the AβPP protein level was increased in kidneys of APP23 mice compared with wild-type (WT) mice. Additionally, the activity and expression of BACE1 were increased in kidneys of APP23 mice compared to that of WT. BACE1 was predominantly distributed on the lumen side of renal tubular epithelial cells. The protein levels of Klotho and VE-cadherin were decreased, occludin expression was also decreased, and claudin-1 expression was increased. Renal pathological damage which observed in kidneys of APP23 mice was more serious than that in kidneys of WT mice. Our findings suggest that the increase of AβPP protein levels under Thy-1 neuron promoter in the APP23 mice promoted the increase of renal BACE1 expression and enzymatic activity in the kidneys. Moreover, certain pathological damage in the kidneys of APP23 mice were observed. APP23 mice are easily affected by external risk factors compared with WT mice.

Fibrillar Aβ triggers microglial proteome alterations and dysfunction in Alzheimer mouse models.

Microglial dysfunction is a key pathological feature of Alzheimer's disease (AD), but little is known about proteome-wide changes in microglia during the course of AD and their functional consequences. Here, we performed an in-depth and time-resolved proteomic characterization of microglia in two mouse models of amyloid β (Aβ) pathology, the overexpression APPPS1 and the knock-in APP-NL-G-F (APP-KI) model. We identified a large panel of Microglial Aβ Response Proteins (MARPs) that reflect heterogeneity of microglial alterations during early, middle and advanced stages of Aβ deposition and occur earlier in the APPPS1 mice. Strikingly, the kinetic differences in proteomic profiles correlated with the presence of fibrillar Aβ, rather than dystrophic neurites, suggesting that fibrillar Aβ may trigger the AD-associated microglial phenotype and the observed functional decline. The identified microglial proteomic fingerprints of AD provide a valuable resource for functional studies of novel molecular targets and potential biomarkers for monitoring AD progression or therapeutic efficacy.