Tg Mouse Model Research Articles

Seizing the opportunity to therapeutically address neuronal hyperexcitability in Alzheimer's disease.

Seizures in people with Alzheimer's disease are increasingly recognized to worsen disease burden and accelerate functional decline. Harnessing established antiseizure medicine discovery strategies in rodents with Alzheimer's disease associated risk genes represents a novel way to uncover disease modifying treatments that may benefit these Alzheimer's disease patients. This commentary discusses the recent evaluation by Dejakaisaya and colleagues to assess the antiseizure and disease-modifying potential of the repurposed cephalosporin antibiotic, ceftriaxone, in the Tg2576 mouse model. The use of established epilepsy models in Alzheimer's disease research carries the potential to advance novel disease-modifying treatments.

A systematic review with meta‐analysis of the GABAergic system in transgenic rodent models of amyloidosis and tauopathy

AbstractBackgroundAlzheimer’s disease (AD) is characterized by the accumulation of amyloid‐β (Aβ) plaques and tau tangles in the brain, and neurotransmission dysfunctions. Indeed, our group recently demonstrated that the γ‐aminobutyric acid (GABA)ergic system is vulnerable to AD pathology in humans. However, whether this vulnerability is also present in AD rodent models is still unknown. Thus, we aimed to examine the GABAergic system in rodent models of amyloidosis and tauopathy.MethodWe systematically reviewed the literature following the PRISMA 2020 Statement. We searched PubMed and Web of Science from database inception to March 2023 for studies reporting GABA, glutamate decarboxylase (GAD) 65/67, GABA transporters (GAT), and GABAA and GABAB receptors in the brain of 3xTg‐AD, 5xFAD, APP/PSEN1, McGill‐R‐Thy1‐APP, Tg2576, TauPS2APP, TgCRND8, APP SweDI, and hAPP‐J20 AD rodent models. Then, we performed a random‐effects meta‐analysis of standardized mean differences (SMD) using the metafor and metaviz packages in R (FDR‐adjusted p‐value < 0.05).ResultThe search identified 3,631 articles and 27 met the inclusion criteria (Table 1 and Figure 1A). The systematic review showed decreased levels of GAD65/67 in the hippocampus, dentate gyrus, and hilus of TauPS2APP, hippocampus of TgCRND8, hippocampus and cortex of APP SweDI, and suprachiasmatic nucleus of Tg2576 mouse models. However, no differences in the cortex and cerebellum of APP/PSEN1 and hippocampus of hAPP‐J20 mice were found (Figure 1B). APP/PSEN1 had decreased vGAT in the hippocampus and increased in cortex (Figure 1B). GABAA receptors (Figure 1B) were decreased in APP/PSEN1 mice, while GABAB receptors (Figure 1B) remained unchanged. Due to insufficient number of studies, we meta‐analyzed only GABA. There were no differences in GABA levels in the cortex of APP/PSEN1 and Tg2576 mouse models (Figures 2A and 2B, p = 0.226 and 0.968, respectively), and in the hippocampal GABA levels in 5xFAD mice (Figure 2C, p = 0.924).ConclusionHere, we show decreased levels of GABAergic synthesis enzymes and GABAA receptors, and alterations in GABA transporters in AD rodent models. By contrast, there were no changes in GABA levels and GABAB receptors. Our results suggest that the AD rodent models recapitulate the GABAergic system vulnerability seen in human AD.

AssociatIion of metabotropic glutamate receptor 5 with amyloid deposition in Alzheimer's disease's patient and mouse models

AbstractBackgroundMetabotropic glutamate receptor 5 (mGluR5) modulates excitatory glutamatergic synaptic transmission and plays an important role in learning and memory, and in the pathphysiology of Alzheimer’s disease (AD). Here, we aimed to assess the alterations of mGluR5 in the hippocampus of AD patients and mouse model, and the association with amyloid pathology.MethodImmunofluorescence staining was performed on postmortem brain tissue from 35 AD patients and 36 control patients, as well as on the brain tissue slices from 15 months‐old 3×Tg and arcAβ mouse models of AD amyloidosis. Autoradiography was performed on brain tissue slices from arcAβ mice using mGluR5 tracer [18F]PSS232. Proteomic profiling and pathway analysis were performed on hippocampal tissue from six 15 months‐old 3xTg mice and six age‐matched wildtype mice.ResultReduced levels of mGluR5 were observed in the hippocampus of AD patients compared to non‐demented control. Ex vivo autoradiography revealed a reduced level of [18F]PSS232 in the hippocampus and striatum of arcAβ mice compared to nontransgenic littermate mice. Reduced mGluR5 immunoreactivity was observed near 6E10‐positive Aβ plaques in the hippocampus. In contrast, upregulated levels of Shank3, Grin2a, Grin2b, and Grm5; and upregulation of glutamatergic pathway (GO and KEGG pathway enrichment analyses) were detected in hippocampal tissue from 3xTg mice compared to wildtype mice.ConclusionThis study revealed a reduction in the level of mGluR5 in the hippocampus of AD patients, and a strain‐dependent alteration of mGluR5 in mouse models of AD.

Dysregulated acetylcholine-mediated dopamine neurotransmission in the eIF4E Tg mouse model of autism spectrum disorders

Autism spectrum disorder (ASD) consists of diverse neurodevelopmental conditions where core behavioral symptoms are critical for diagnosis. Altered dopamine (DA) neurotransmission in the striatum has been suggested to contribute to the behavioral features of ASD. Here, we examine DA neurotransmission in a mouse model of ASD characterized by elevated expression of eukaryotic initiation factor 4E (eIF4E), a key regulator of cap-dependent translation, using a comprehensive approach that encompasses genetics, behavior, synaptic physiology, and imaging. The results indicate that increased eIF4E expression leads to behavioral inflexibility and impaired striatal DA release. The loss of normal DA neurotransmission is due to a defect in nicotinic receptor signaling that regulates calcium dynamics in dopaminergic axons. These findings provide a mechanistic understanding of ASD symptoms and offer a foundation for targeted therapeutic interventions by revealing the intricate interplay between eIF4E, DA neurotransmission, and behavioral flexibility.

The R436Q missense mutation in WWP1 disrupts autoinhibition of its E3 ubiquitin ligase activity, leading to self-degradation and loss of function.

Muscular dystrophy in the NH-413 chicken is caused by a missense mutation in the WWP1 gene. WWP1 is a HECT-type E3 ubiquitin ligase containing four tandem WW domains that interact with proline-rich peptide motifs of target proteins, and a short region connecting the second and third WW domains is crucial for the E3 ligase to maintain an autoinhibitory state. A mutation of the arginine in the WW2-WW3 linker to glutamine is thought to affect WWP1 function, but there is little information on this mutation to date. In this study, we generated a transgenic (Tg) mouse model expressing the WWP1 transgene with the R436Q mutation, which corresponds to the missense mutation found in the NH-413 chicken. Tg mice showed marked degradation of mutant WWP1 proteins in various tissues, particularly in striated muscle. Immunoprecipitation analysis using a WWP1-specific antibody demonstrated that the mutant WWP1 proteins lacked the C-terminal catalytic cysteine residue that is required for their binding to the E2-substrate complex during their degradation. In vitro analysis using the R436Q mutant of WWP1 lacking this catalytic cysteine residue showed no autodegradation, indicating that the loss-of-function degradation of this protein is caused by self-ubiquitination. Tg mice expressing R436Q WWP1 did not show stunted growth or premature death. Furthermore, histological analysis did not reveal any obvious changes. These observations suggested that the R436Q mutant WWP1 protein, which is released from autoinhibitory mode by its missense mutation, does not have abnormally activated enzyme function to substrates before its self-degradation and loss of enzyme function.

Genotype- and sex-specific changes in vital parameters during isoflurane anesthesia in a mouse model of Alzheimer's disease.

The prevalence of neurodegenerative diseases is increasing as is life expectancy with Alzheimer's disease accounting for two-thirds of dementia cases globally. Whether general anesthesia and surgery worsen cognitive decline is still a matter of debate and most likely depending on the interplay of various influencing factors. In order to account for this complexity, Alzheimer's disease animal models have been developed. The Tg2576 model of Alzheimer's disease is a well-established mouse model exhibiting amyloidopathy and age-dependent sex-specific differences in Alzheimer's disease symptomology. Yet, data on anesthesia in this mouse model is scarce and a systematic comparison of vital parameters during anesthesia with wild-type animals is missing. In order to investigate the safety of general anesthesia and changes in vital parameters during general anesthesia in Tg2576 mice, we did a secondary analysis of vital parameters collected during general anesthesia in aged Tg2576 mice. After governmental approval (General Administration of the Free State of Bavaria, file number: 55.2-1-54-2532-149-11) 60 mice at 10-12 months of age were exposed to isoflurane (1.6 Vol%) for 120 min, data of 58 mice was analyzed. During general anesthesia, heart rate, respiratory rate, temperature, isoflurane concentration and fraction of inspired oxygen were monitored and collected. Data were analyzed using univariate and multivariate linear mixed regression models. During general anesthesia, heart rate decreased in a sex-specific manner. Respiratory rate decreased and body temperature increased dependent on genotype. However, the changes were limited and all vital parameters stayed within physiological limits. Isoflurane anesthesia in the Tg2576 mouse model is safe and does not seem to influence experimental results by interacting with vital parameters. The present study provides information on appropriate anesthesia in order to advance research on anesthesia and AD and could contribute to improving laboratory animal welfare.

No major effect of dopamine receptor 1/5 antagonist SCH-23390 on epileptic activity in the Tg2576 mouse model of amyloidosis.

The excitation-inhibition imbalance manifesting as epileptic activities in Alzheimer's disease is gaining more and more attention, and several potentially involved cellular and molecular pathways are currently under investigation. Based on in vitro studies, dopamine D1-type receptors in the anterior cingulate cortex and the hippocampus have been proposed to participate in this peculiar co-morbidity in mouse models of amyloidosis. Here, we tested the implication of dopaminergic transmission in vivo in the Tg2576 mouse model of Alzheimer's disease by monitoring epileptic activities via intracranial EEG before and after treatment with dopamine antagonists. Our results show that neither the D1-like dopamine receptor antagonist SCH23390 nor the D2-like dopamine receptor antagonist haloperidol reduces the frequency of epileptic activities. While requiring further investigation, our results indicate that on a systemic level, dopamine receptors are not significantly contributing to epilepsy observed in vivo in this mouse model of Alzheimer's disease.

Aberrant Cortical Activity in 5xFAD Mice in Response to Social and Non-Social Olfactory Stimuli.

Neuroimaging studies investigating the behavioral and psychological symptoms of dementia (BPSD)- such as apathy, anxiety, and depression- have linked some of these symptoms with altered neural activity. However, inconsistencies in operational definitions and rating scales, limited scope of assessments, and poor temporal resolution of imaging techniques have hampered human studies. Many transgenic (Tg) mouse models of Alzheimer's disease (AD) exhibit BPSD-like behaviors concomitant with AD-related neuropathology, allowing examination of how neural activity may relate to BPSD-like behaviors with high temporal and spatial resolution. To examine task-dependent neural activity in the medial prefrontal cortex (mPFC) of AD-model mice in response to social and non-social olfactory stimuli. We previously demonstrated age-related decreases in social investigation in Tg 5xFAD females, and this reduced social investigation is evident in Tg 5xFAD females and males by 6 months of age. In the present study, we examine local field potential (LFP) in the mPFC of awake, behaving 5xFAD females and males at 6 months of age during exposure to social and non-social odor stimuli in a novel olfactometer. Our results indicate that Tg 5xFAD mice exhibit aberrant baseline and task-dependent LFP activity in the mPFC- including higher relative delta (1-4 Hz) band power and lower relative power in higher bands, and overall stronger phase-amplitude coupling- compared to wild-type controls. These results are consistent with previous human and animal studies examining emotional processing, anxiety, fear behaviors, and stress responses, and suggest that Tg 5xFAD mice may exhibit altered arousal or anxiety.

Dopamine neuron degeneration in the Ventral Tegmental Area causes hippocampal hyperexcitability in experimental Alzheimer’s Disease

Early and progressive dysfunctions of the dopaminergic system from the Ventral Tegmental Area (VTA) have been described in Alzheimer’s Disease (AD). During the long pre-symptomatic phase, alterations in the function of Parvalbumin interneurons (PV-INs) are also observed, resulting in cortical hyperexcitability represented by subclinical epilepsy and aberrant gamma-oscillations. However, it is unknown whether the dopaminergic deficits contribute to brain hyperexcitability in AD. Here, using the Tg2576 mouse model of AD, we prove that reduced hippocampal dopaminergic innervation, due to VTA dopamine neuron degeneration, impairs PV-IN firing and gamma-waves, weakens the inhibition of pyramidal neurons and induces hippocampal hyperexcitability via lower D2-receptor-mediated activation of the CREB-pathway. These alterations coincide with reduced PV-IN numbers and Perineuronal Net density. Importantly, L-DOPA and the selective D2-receptor agonist quinpirole rescue p-CREB levels and improve the PV-IN-mediated inhibition, thus reducing hyperexcitability. Moreover, similarly to quinpirole, sumanirole – another D2-receptor agonist and a known anticonvulsant – not only increases p-CREB levels in PV-INs but also restores gamma-oscillations in Tg2576 mice. Conversely, blocking the dopaminergic transmission with sulpiride (a D2-like receptor antagonist) in WT mice reduces p-CREB levels in PV-INs, mimicking what occurs in Tg2576. Overall, these findings support the hypothesis that the VTA dopaminergic system integrity plays a key role in hippocampal PV-IN function and survival, disclosing a relevant contribution of the reduced dopaminergic tone to aberrant gamma-waves, hippocampal hyperexcitability and epileptiform activity in early AD.

Treatment with 1, 10 Phenanthroline-5-Amine Reduced Amyloid Burden in a Mouse Model of Alzheimer's Disease.

Alzheimer's disease (AD) is the most prevalent age-related dementia, and, despite numerous attempts to halt or reverse its devastating progression, no effective therapeutics have yet been confirmed clinically. However, one class of agents that has shown promise is certain metal chelators. For the novel assessment of the effect of oral administration of 1,10-phenanthroline-5-amine (PAA) on the severity of amyloid plaque load, we used a transgenic (Tg) mouse model with inserted human autosomally dominant (familial) AD genes: amyloid-β protein precursor (AβPP) and tau. AβPP/Tau transgenic mice that model AD were allotted into one of two groups. The control group received no treatment while the experimental group received PAA in their drinking water starting at 4 months of age. All animals were sacrificed at 1 year of age and their brains were stained with two different markers of amyloid plaques, Amylo-Glo+ and HQ-O. The control animals exhibited numerous dense core plaques throughout the neo- and allo- cortical brain regions. The experimental group treated with PAA, however, showed 62% of the amyloid plaque burden seen in the control group. Oral daily dosing with PAA will significantly reduce the amyloid plaque burden in transgenic mice that model AD. The underlying mechanism for this protection is not fully known; however, one proposed mechanism involves inhibiting the "metal-seeding" of Aβ.

Dentate Gyrus Granule Cells Show Stability of BDNF Protein Expression in Mossy Fiber Axons with Age, and Resistance to Alzheimer's Disease Neuropathology in a Mouse Model.

Brain-derived neurotrophic factor (BDNF) is important in the development and maintenance of neurons and their plasticity. Hippocampal BDNF has been implicated in Alzheimer's disease (AD) because hippocampal levels in AD patients and AD animal models are often downregulated, suggesting that reduced BDNF contributes to AD. However, the location where hippocampal BDNF protein is most highly expressed, the mossy fiber (MF) axons of dentate gyrus granule cells (GCs), has been understudied, and not in controlled conditions. Therefore, we evaluated MF BDNF protein in the Tg2576 mouse model of AD. Tg2576 and wild-type (WT) mice of both sexes were examined at 2-3 months of age, when amyloid-β (Aβ) is present in neurons but plaques are absent, and 11-20 months of age, after plaque accumulation. As shown previously, WT mice exhibited high levels of MF BDNF protein. Interestingly, there was no significant decline with age in either the genotype or sex. Notably, MF BDNF protein was correlated with GC ΔFosB, a transcription factor that increases after 1-2 weeks of elevated neuronal activity. We also report the novel finding that Aβ in GCs or the GC layer was minimal even at old ages. The results indicate that MF BDNF is stable in the Tg2576 mouse, and MF BDNF may remain unchanged due to increased GC neuronal activity, since BDNF expression is well known to be activity dependent. The resistance of GCs to long-term Aβ accumulation provides an opportunity to understand how to protect vulnerable neurons from increased Aβ levels and therefore has translational implications.

A systematic evaluation of cortical GABA levels in transgenic mouse models of amyloid

AbstractBackgroundRodent models that overexpress mutations in the amyloid precursor protein (APP) and presenilin 1 (PSEN1) genes have been widely applied in Alzheimer’s disease (AD) research. These models classically present amyloid plaque deposition in cortical and hippocampal areas and neurotransmission changes. Although amyloid‐related glutamatergic abnormalities have been extensively described, little is known about its effects on the GABAergic system. Thus, we aimed to examine GABA levels in the cortex of two transgenic amyloid mouse models.MethodWe systematically reviewed the literature following the PRISMA 2020 guidelines. PubMed and Web of Science databases were searched for studies reporting GABA levels in the cortex of APPswe/PSEN1dE9 and Tg2576 mice. We opted to evaluate only animals with mature amyloid plaques in their cortices, according to each mouse model previous characterization.ResultThe search identified 3576 papers. Seven records met the inclusion criteria (Tg2576: n = 21, mean age ± standard deviation (SD) = 14.7 ± 3.7 months; controls: n = 21; APPswe/PSEN1dE9: n = 25, mean age ± SD = 8.5 ± 4.1 months; controls: n = 25). Five out of seven results reported non‐significant differences in the GABA levels in multiple cortical regions, such as the frontal, pre‐frontal, and rhinal cortices of the Tg2576 mouse model, but two studies described that GABA is significantly decreased. Furthermore, all studies with the APP/PSEN1 model consistently reported decreased cortical GABA levels. Figure 1 provides a summary of our findings.ConclusionOur results suggest that APP and PSEN1 mutations may contribute to the decrease in the levels of GABA in cortical regions of amyloid models. Future meta‐analyses and clinical studies are needed to ascertain the consistency of the reported results.

The Effect of Fat Intake with Increased Omega-6-to-Omega-3 Polyunsaturated Fatty Acid Ratio in Animal Models of Early and Late Alzheimer’s Disease-like Pathogenesis

This work aims to clarify the effect of dietary polyunsaturated fatty acid (PUFA) intake on the adult brain affected by amyloid pathology. McGill-R-Thy1-APP transgenic (Tg) rat and 5xFAD Tg mouse models that represent earlier or later disease stages were employed. The animals were exposed to a control diet (CD) or an HFD based on corn oil, from young (rats) or adult (mice) ages for 24 or 10 weeks, respectively. In rats and mice, the HFD impaired reference memory in wild-type (WT) animals but did not worsen it in Tg, did not cause obesity, and did not increase triglycerides or glucose levels. Conversely, the HFD promoted stronger microglial activation in Tg vs. WT rats but had no effect on cerebral amyloid deposition. IFN-γ, IL-1β, and IL-6 plasma levels were increased in Tg rats, regardless of diet, while CXCL1 chemokine levels were increased in HFD-fed mice, regardless of genotype. Hippocampal 3-nitrotyrosine levels tended to increase in HFD-fed Tg rats but not in mice. Overall, an HFD with an elevated omega-6-to-omega-3 ratio as compared to the CD (25:1 vs. 8.4:1) did not aggravate the outcome of AD regardless of the stage of amyloid pathology, suggesting that many neurobiological processes relevant to AD are not directly dependent on PUFA intake.

Effects of B Cell Depletion by CD19-Targeted Chimeric Antigen Receptor T Cells in a Murine Model of Systemic Sclerosis.

Our goal was to study the tolerance and efficacy of two B cell depletion strategies, including one with CD19-targeted chimeric antigen receptor (CAR) T cells, in a preclinical model mimicking the severe lung damages observed in systemic sclerosis. B cell depletion strategies were evaluated in the Fra-2 transgenic (Tg) mouse model. We considered a first group of 16 untreated mice, a second group of 15 mice receiving a single dose of anti-CD20 monoclonal antibody (mAb), and a third group of 8 mice receiving CD19-targeted CAR-T cells in combination with anti-CD20 monoclonal antibody. After six weeks of clinical evaluation, different validated markers of inflammation, lung fibrosis, and pulmonary vascular remodeling were assessed. CD19-targeted CAR-T cells infusion in combination with anti-CD20 mAb resulted in a deeper B cell depletion than anti-CD20 mAb alone in the peripheral blood and lesional lungs of Fra-2 Tg mice. CAR-T cell infusion worsened the clinical score and increased mortality in Fra-2 Tg mice. In line with the above findings, CAR-T cell infusion significantly increased lung collagen content, the histological fibrosis score, and right ventricular systolic pressure. CAR-T cells accumulated in lesional lungs and promoted T activation and inflammatory cytokine production. Treatment with anti-CD20 mAb in monotherapy had no impact on lung inflammation-driven fibrosis and pulmonary hypertension. B cell therapies failed to show efficacy in the Fra2 Tg mice. The exacerbated Fra-2 lung inflammatory burden stimulated accumulation and expansion of activated CD19-targeted CAR-T cells, secondarily inducing T cell activation and systemic inflammation, finally leading to disease worsening.

Exploratory Study of Gastrointestinal Redox Biomarkers in the Presymptomatic and Symptomatic Tg2576 Mouse Model of Familial Alzheimer's Disease: Phenotypic Correlates and Effects of Chronic Oral d-Galactose.

The gut might play an important role in the etiopathogenesis of Alzheimer's disease (AD) as gastrointestinal alterations often precede the development of neuropathological changes in the brain and correlate with disease progression in animal models. The gut has an immense capacity to generate free radicals whose role in the etiopathogenesis of AD is well-known; however, it remains to be clarified whether gastrointestinal redox homeostasis is associated with the development of AD. The aim was to (i) examine gastrointestinal redox homeostasis in the presymptomatic and symptomatic Tg2576 mouse model of AD; (ii) investigate the effects of oral d-galactose previously shown to alleviate cognitive deficits and metabolic changes in animal models of AD and reduce gastrointestinal oxidative stress; and (iii) investigate the association between gastrointestinal redox biomarkers and behavioral alterations in Tg2576 mice. In the presymptomatic stage, Tg2576 mice displayed an increased gastrointestinal electrophilic tone, characterized by higher lipid peroxidation and elevated Mn/Fe-SOD activity. In the symptomatic stage, these alterations are rectified, but the total antioxidant capacity is decreased. Chronic oral d-galactose increased the antioxidant capacity and reduced lipid peroxidation in the Tg2576 but had the opposite effects in the wild-type animals. The total antioxidant capacity of the gastrointestinal tract was associated with greater spatial memory. Gut redox homeostasis might be involved in the development and progression of AD pathophysiology and should be further explored in this context.

GP120 and tenofovir alafenamide alter cannabinoid receptor 1 expression in hippocampus of mice

Central nervous system (CNS) dysfunction remains prevalent in people with HIV (PWH) despite effective antiretroviral therapy (ART). There is evidence that low-level HIV infection and ART drugs may contribute to CNS damage in the brain of PWH with suppressed viral loads. As cannabis is used at a higher rate in PWH compared to the general population, there is interest in understanding how HIV proteins and ART drugs interact with the endocannabinoid system (ECS) and inflammation in the CNS. Therefore, we investigated the effects of the HIV envelope protein gp120 and tenofovir alafenamide (TAF) on cannabinoid receptor 1 (CB1R), glial fibrillary acidic protein (GFAP), and IBA1 in the brain and on locomotor activity in mice. The gp120 transgenic (tg) mouse model was administered TAF daily for 30 days and then analyzed using the open field test before being euthanized, and their brains were analyzed for CB1R, GFAP, and IBA1 expression using immunohistochemical approaches. CB1R expression levels were significantly increased in CA1, CA2/3, and dentate gyrus of gp120tg mice compared to wt littermates; TAF reversed these effects. As expected, TAF showed a medium effect of enhancing GFAP in the frontal cortex of gp120tg mice in the frontal cortex. TAF had minimal effect on IBA1 signal. TAF showed medium to large effects on fine movements, rearing, total activity, total distance, and lateral activity in the open-field test. These findings suggest that TAF may reverse gp120-induced effects on CB1R expression and, unlike tenofovir disoproxil fumarate (TDF), may not affect gliosis in the brain.

Influence of complement protein C1q or complement receptor C5aR1 on gut microbiota composition in wildtype and Alzheimer’s mouse models

The contribution of the gut microbiome to neuroinflammation, cognition, and Alzheimer’s disease progression has been highlighted over the past few years. Additionally, inhibition of various components of the complement system has repeatedly been demonstrated to reduce neuroinflammation and improve cognitive performance in AD mouse models. Whether the deletion of these complement components is associated with distinct microbiome composition, which could impact neuroinflammation and cognitive performance in mouse models has not yet been examined. Here, we provide a comprehensive analysis of conditional and constitutive knockouts, pharmacological inhibitors, and various housing paradigms for the animal models and wild-type controls at various ages. We aimed to determine the impact of C1q or C5aR1 inhibition on the microbiome in the Arctic and Tg2576 mouse models of AD, which develop amyloid plaques at different ages and locations. Analysis of fecal samples from WT and Arctic mice following global deletion of C1q demonstrated significant alterations to the microbiomes of Arctic but not WT mice, with substantial differences in abundances of Erysipelotrichales, Clostridiales and Alistipes. While no differences in microbiome diversity were detected between cohoused wildtype and Arctic mice with or without the constitutive deletion of the downstream complement receptor, C5aR1, a difference was detected between the C5aR1 sufficient (WT and Arctic) and deficient (C5ar1KO and ArcticC5aR1KO) mice, when the mice were housed segregated by C5aR1 genotype. However, cohousing of C5aR1 sufficient and deficient wildtype and Arctic mice resulted in a convergence of the microbiomes and equalized abundances of each identified order and genus across all genotypes. Similarly, pharmacologic treatment with the C5aR1 antagonist, PMX205, beginning at the onset of beta-amyloid plaque deposition in the Arctic and Tg2576 mice, demonstrated no impact of C5aR1 inhibition on the microbiome. This study demonstrates the importance of C1q in microbiota homeostasis in neurodegenerative disease. In addition, while demonstrating that constitutive deletion of C5aR1 can significantly alter the composition of the fecal microbiome, these differences are not present when C5aR1-deficient mice are cohoused with C5aR1-sufficient animals with or without the AD phenotype and suggests limited if any contribution of the microbiome to the previously observed prevention of cognitive and neuronal loss in the C5aR1-deficient AD models.

The Cleavage-Specific Tau 12A12mAb Exerts an Anti-Amyloidogenic Action by Modulating the Endocytic and Bioenergetic Pathways in Alzheimer's Disease Mouse Model.

Beyond deficits in hippocampal-dependent episodic memory, Alzheimer's Disease (AD) features sensory impairment in visual cognition consistent with extensive neuropathology in the retina. 12A12 is a monoclonal cleavage specific antibody (mAb) that in vivo selectively neutralizes the AD-relevant, harmful N-terminal 20-22 kDa tau fragment(s) (i.e., NH2htau) without affecting the full-length normal protein. When systemically injected into the Tg2576 mouse model overexpressing a mutant form of Amyloid Precursor Protein (APP), APPK670/671L linked to early onset familial AD, this conformation-specific tau mAb successfully reduces the NH2htau accumulating both in their brain and retina and, thus, markedly alleviates the phenotype-associated signs. By means of a combined biochemical and metabolic experimental approach, we report that 12A12mAb downregulates the steady state expression levels of APP and Beta-Secretase 1 (BACE-1) and, thus, limits the Amyloid beta (Aβ) production both in the hippocampus and retina from this AD animal model. The local, antibody-mediated anti-amyloidogenic action is paralleled in vivo by coordinated modulation of the endocytic (BIN1, RIN3) and bioenergetic (glycolysis and L-Lactate) pathways. These findings indicate for the first time that similar molecular and metabolic retino-cerebral pathways are modulated in a coordinated fashion in response to 12A12mAb treatment to tackle the neurosensorial Aβ accumulation in AD neurodegeneration.

Inhibition of ACAT as a Therapeutic Target for Alzheimer’s Disease is Independent of ApoE4-lipidation

<b>Abstract ID 24886</b> <b>Poster Board 10</b> <b>Background:</b> While the mechanism(s) underlying <i>APOE4</i>-induced AD risk remains unclear, apoE4 levels in the brains of humans and transgenic mice (Tg) expressing human <i>APOE4</i> are lower than those expressing <i>APOE3</i>, and apoE4-lipoproteins are poorly lipidated compared to apoE3-lipoproteins. Increasing the lipidation of apoE4 can stabilize apoE4-lipoproteins, thus making this process an attractive therapeutic target. Several enzymes affect CNS cholesterol levels including ACAT (acyl-CoA:cholesterol-acyltransferase), which catalyzes the formation of intracellular cholesteryl-ester droplets, reducing the intracellular free cholesterol (FC) pool. Inhibition of ACAT increases the FC pool, making the lipids available for secretion to extracellular apoE-containing lipoproteins. Previous studies using commercially available ACAT inhibitors, including Avasimibe (AVAS), as well as <i>ACAT</i>-knock out (KO) mice, demonstrate reduced plaque burden, gliosis, amyloid-beta peptide (Ab), and altered amyloid precursor protein (APP) processing in familial AD (FAD)-Tg mouse models. However, the effects of AVAS in the presence of human apoE4 remain unknown. Our hypothesis is that AVAS, via inhibition of ACAT, will increase the FC pool, promoting ABCA1-mediated efflux of cholesterol to nascent apoE4-lipoproteins. This correction of apoE4 structure via lipidation will restore its function in the CNS, including clearance of oAβ and reducing neuroinflammation. <b>Methods:</b> Male E4FAD-Tg mice (5xFAD^+/-/<i>APOE4</i>^+/+) were treated by oral gavage with AVAS from 6-8 months. Synaptic proteins were measured by Western blot and learning and memory by Morris Water Maze (MWM). Lipid droplets/cell were analyzed by staining with LipidSpot. Ab pathology was evaluated by measuring Ab solubility (3-step sequential extraction followed by ELISA) and Ab/amyloid deposition (immunostaining). Neuroinflammation (astrogliosis and microgliosis) were evaluated by immuhistochemistry. ApoE levels and lipidation were analyzed by apoE-ELISA and native gels. <b>Results:</b> AVAS treatment significantly reduced intracellular lipid droplets, demonstrating indirect target engagement, increased MWM measures of memory and postsynaptic protein levels, indicating surrogate efficacy, and reduced pathological changes in Aβ solubility/deposition, and neuroinflammation, all critical components of <i>APOE4</i>-modulated AD pathology. However, there was no increase in apoE4 levels or lipidation, while amyloidogenic processing of APP was significantly reduced. <b>Conclusion:</b> This study suggests that the AVAS-induced reduction in Aβ via reduced APP processing was sufficient to reduce AD pathology, while apoE4-lipoproteins remained poorly lipidated. This study was partially sponsored by AbbVie, Inc. AbbVie contributed to the study design, research, and interpretation of data, reviewing, and approving the manuscript.

Upregulation of extracellular proteins in a mouse model of Alzheimer’s disease

Various risk factors of Alzheimer’s disease (AD) are known, such as advanced age, possession of certain genetic variants, accumulation of toxic amyloid-β (Aβ) peptides, and unhealthy lifestyle. An estimate of heritability of AD ranges from 0.13 to 0.25, indicating that its phenotypic variation is accounted for mostly by non-genetic factors. DNA methylation is regarded as an epigenetic mechanism that interfaces the genome with non-genetic factors. The Tg2576 mouse model has been insightful in AD research. These transgenic mice express a mutant form of human amyloid precursor protein linked to familial AD. At 9–13 months of age, these mice show elevated levels of Aβ peptides and cognitive impairment. The current literature lacks integrative multiomics of the animal model. We applied transcriptomics and DNA methylomics to the same brain samples from ~ 11-month-old transgenic mice. We found that genes involved in extracellular matrix structures and functions are transcriptionally upregulated, and genes involved in extracellular protein secretion and localization are differentially methylated in the transgenic mice. Integrative analysis found enrichment of GO terms related to memory and synaptic functionability. Our results indicate a possibility of transcriptional modulation by DNA methylation underlying AD neuropathology.