INTRODUCTION:Dysfunctional microRNAs and GABAergic interneurons are features of Alzheimer's disease (AD). The role of neuronal microRNA155 (miR155), elevated in both AD and Down syndrome (DS), remains unknown. METHODS:We utilized in silico analyses of published databases, MIR155-deleted and -overexpressing human induced pluripotent stem cell (hiPSC)-derived cells, cortical organoids, and amyloid beta precursor protein (APP)/PS1-miR155 knockout mouse. RESULTS:MIR155HG (miR155 host gene) colocalizes with APP in a neuron-specific, topologically associated domain (TAD) in chromosome 21. In human neural stem cells (NSCs), neurons, and cortical organoids, MIR155 deletion enhanced NSC proliferation and GABAergic interneuron generation. MIR155 overexpression inhibited NSC marker expression and GABAergic interneuron generation. In APP/PS1 mice, miR155 deletion induced the expansion of hippocampal NSCs and increased hippocampal GABAergic interneurons. DISCUSSION:Our findings, alongside the extensive studies of the role of microglial miR155 in neuroinflammation, reveal previously unrecognized miR155 roles in hippocampal NSC dynamics and GABAergic interneuron development, highlighting miR155 as a therapeutic target.

BackgroundCerebrospinal fluid (CSF) pTau181 is used to support Alzheimer's disease (AD) diagnosis but can also rise in amyloid-negative individuals. This CSF profile (Aβ-/pTau181+) lies outside the AD continuum and complicates real-world etiologic diagnosis of neurocognitive disorders.ObjectiveTo determine the prevalence and clinical phenotype associated with the Aβ-/pTau181+ CSF biomarker profile in a real-world memory clinic population.MethodsWe screened the Mount Sinai Hospital database (2015-2024) for patients who underwent ADmark CSF biomarker testing. An Aβ-/pTau181+ group was classified using assay cutoffs (Amyloid-Total-Tau Index>1.2, pTau181 > 54 pg/mL) and compared to an Aβ+ group (Amyloid-Total-Tau Index<0.8) matched for pTau181 and total-Tau. Clinical variables were extracted via chart review, limited to notes preceding CSF and blinded to CSF results.ResultsThe Aβ-/pTau181+ group included 25 individuals (10.1% of the cohort) and had equally impaired cognition but fewer episodic memory complaints. Diagnosis was more often Lewy body or frontotemporal dementia. On neuroimaging, Aβ-/pTau181+ exhibited less white matter hyperintensity burden and temporoparietal atrophy.ConclusionsCSF Aβ-/pTau181+ is frequent in real-world evaluations of cognitive impairment and presents with fewer AD phenotypic features. Further research is required to clarify Aβ-/pTau181+ underlying biology and clinical trajectory.

Alzheimer’s disease (AD) is an aging-related neurodegenerative disease characterized by an initial memory impairment that progresses to a widespread cerebrocortical failure, culminating in death. Understanding the molecular mechanisms that protect brain function during aging may help reveal novel targets for the development of effective treatments for the memory and cognitive deficits associated with AD. In this study, we analyzed a gene expression dataset generated from the prefrontal cortices of individuals showing no neurological or cognitive abnormalities. The gene expression profiles were used to identify candidate protective genes. We then compared the expression patterns of these genes in aging with their expression patterns in AD, thereby enabling us to pinpoint the genes that potentially contribute to brain resilience that delays or prevents aging-related dementia. We selected seven genes that are potentially protective for aging and AD, and have known homologues in Caenorhabditis elegans (C. elegans). Among these genes, SRPK2, AAK1, EFR3A and MAPK10 were previously implicated in attenuating AD-related cognitive decline. Our experiments demonstrated that all seven genes prioritized by our resilience model significantly extended the lifespan of C. elegans. Given the important relationship between neuronal functional integrity and lifespan (i.e., lifespan vs. brain health span), this work suggests the predicted AD resilience genes could serve as important candidate targets for therapeutic intervention.

BACKGROUND:APPE693Q ("Dutch") transgenic mice develop aging-related learning deficits and accumulate endogenously generated non-fibrillar aggregates (NFAs) of amyloid beta (Aβ) and amyloid precursor protein α-carboxy terminal fragments. NFA-Aβ correlates with synaptic loss and memory deficits more closely than does fibrillar Aβ. METHODS:We assessed the physiological, transcriptomic, ultrastructural, histological, and metabolic changes associated with the accumulation of NFA of Dutch Aβ in brains of APPE693Q mice. RESULTS:Aging-related accumulation of NFA-Aβ in APPE693Q mice was revealed by A11 immunohistochemistry and cyclic D,L-α-peptide-fluorescein-5-isothiocyanate microscopy. Presynaptic termini of APPE693Q mice developed physiological abnormalities in post-tetanic potentiation, synaptic fatigue, synaptic vesicle replenishment, and an aging-related reduction in mitochondrial complex I activity. Single-cell RNA sequencing showed that excitatory neurons exhibited an altered transcriptomic profile involving "protein translation" and "oxidative phosphorylation." DISCUSSION:Accumulation of NFA-Aβ alters neuronal metabolism but does not activate inflammation. Depletion of all forms of Aβ may be required to eliminate Aβ toxicity with anti-amyloid antibodies.

To assess the possibility that individualized duration of donanemab treatment might enable early pausing of therapy, and to explore the possible utility of plasma P-tau217 as a biomarker for treatment response monitoring in real-time, two unrelated patients with early-stage Alzheimer's disease were treated with donanemab at the Icahn School of Medicine at Mount Sinai. Clinical progress was monitored via medical chart review, including serial brain MRI, amyloid PET scans, and blood-based biomarker assays (Quanterix Simoa® and Fujirebio Lumipulse®). Both patients achieved complete amyloid clearance as judged by amyloid PET prior to their 6th and 9th infusions, which were significantly earlier than the 12-month mark typically recommended for follow-up amyloid assessment. In agreement with the amyloid PET, concurrently measured plasma P-tau217 levels fell within a low range. Treatment was discontinued for both patients. These patients highlight the possibility of individualized treatment durations for anti-amyloid therapy with donanemab, guided by biomarker response. Early cessation following rapid plaque clearance could reduce healthcare costs and minimize exposure to the risk of amyloid-related imaging abnormalities and the generation of neutralizing antibodies. Plasma P-tau217 warrants further investigation as a reliable, cost-effective surrogate for PET scans to monitor real-time treatment response and guide the timing of discontinuation.

Human cytomegalovirus (HCMV) is a β-herpesvirus that establishes asymptomatic infections in immunocompetent individuals but can cause severe or even life-threatening symptoms in immunocompromised patients. HCMV can replicate in a wide variety of cells through the engagement of diverse cell factors with the viral envelope protein gH/gL/gO (trimer) or gH/gL/UL128/UL130/UL131a (pentamer), allowing for systemic spread within the human host. This study explores HCMV infection tropism and dynamics in human microglia, demonstrating the susceptibility of microglia to both clinical and laboratory HCMV strains, albeit with lower efficacy for the laboratory strain, implying that both the gH/gL-trimer and -pentamer can mediate virus entry in microglia. The importance of the gH/gL pentamer for virus entry was demonstrated by the inhibition of virus infection upon pre-incubation with a soluble neuropilin-2 (NRP-2) entry factor. Further, we demonstrated that HCMV infection can be effectively inhibited by monoclonal antibodies specific for the gH/gL complexes and HCMV hyperimmunoglobulin. Lastly, we report that microglia infection can be prevented by newly characterized chemical entry inhibitors. Altogether, these findings underscore the potential of microglia as valuable models for studying HCMV neurotropism and strategies to block virus infection in cells that can impact neurological disorders.

Identification of early-stage Alzheimer's disease (AD) remains a challenge due to limited specialist availability, diagnostic access, disease awareness, and cultural factors. Blood-based biomarkers (BBBM) could play a critical role in the identification and referral of patients suspected of AD to specialty care. A multidisciplinary AD Biomarker Task Force was convened to evaluate current biomarker use cases, define an optimal biomarker-enabled AD diagnostic care pathway, and understand factors impacting adoption. The Task Force identified opportunities to support biomarker-enabled AD diagnostic care pathway adoption, including streamlining risk assessment and screening by leveraging digital tools, activating primary care providers through education, generating data to expand applicability to diverse populations, and advocating for aligned policies and quality measures. Adoption of BBBMs in the primary care setting will be critical to improve early AD detection. However, challenges to pathway adoption persist and will require action from clinicians, payers, policy makers, and patients to address. Highlights:Blood-based biomarkers can streamline the identification of AD in primary care.Future biomarker-enabled diagnostic care pathways will leverage digital assessments.Education, data generation, and policy advocacy are vital to encourage BBBM use.Implementation of AD care pathways requires the activation of diverse stakeholders.

BACKGROUND:Amyloid-β proteins, a hallmark of Alzheimer's disease, are believed to play an adaptive role in the cerebral immune response. OBJECTIVE:Amyloid is believed to play a role in cerebral immune response and could play a similar role in response to air pollution exposures. In the present study, we examined whether WTC exposure duration was associated with cerebral amyloidosis in WTC responders. METHODS:WTC responders (aged 44-65 years) who varied in exposure duration but did not use personalized protective equipment were assessed using positron-emission tomography with [18F]-Florbetaben. The outcome was the cortical [18F]-Florbetaben burden, measured using regional standardized uptake value ratios (SUVRs) in 34 Desikan-Killiany regions of interest. Spearman's ρ and generalized linear models were used to estimate correlations between WTC exposure duration and cortical [18F]-Florbetaben SUVR. Cognitive and behavioral symptoms were measured. Magnetic resonance imaging was used to measure cortical thickness and diffusivity. RESULTS:The mean age of imaged responders was 56 years old. WTC exposure duration was associated with olfactory [18F]-Florbetaben SUVR (Spearman's ρ = 0.43, p = 0.011), which was in turn associated with elevated [18F]-Florbetaben SUVR in ventral regions (ρ = 0.41, p = 0.016). Cortical [18F]-Florbetaben in ventral regions was associated with reduced response speed (ρ = -0.72, p < 0.001), was co-located with cortical diffusivity across regions in the parietal and frontal lobes and reduced cortical thickness in the isthmus cingulate (ρ = -0.53, p = 0.001). CONCLUSIONS:Low-grade amyloidosis in the olfactory and frontal lobes was associated with WTC exposure duration. Future work should examine whether low-grade amyloidosis is correlated with the location or distribution of neurofibrillary tangles in WTC responders.

INTRODUCTION:While there may be microbial contributions to Alzheimer's disease (AD), findings have been inconclusive. We recently reported an AD-associated CD83(+) microglia subtype associated with increased immunoglobulin G4 (IgG4) in the transverse colon (TC). METHODS:We used immunohistochemistry (IHC), IgG4 repertoire profiling, and brain organoid experiments to explore this association. RESULTS:CD83(+) microglia in the superior frontal gyrus (SFG) are associated with elevated IgG4 and human cytomegalovirus (HCMV) in the TC, anti-HCMV IgG4 in cerebrospinal fluid, and both HCMV and IgG4 in the SFG and vagal nerve. This association was replicated in an independent AD cohort. HCMV-infected cerebral organoids showed accelerated AD pathophysiological features (Aβ42 and pTau-212) and neuronal death. DISCUSSION:Findings indicate complex, cross-tissue interactions between HCMV and the adaptive immune response associated with CD83(+) microglia in persons with AD. This may indicate an opportunity for antiviral therapy in persons with AD and biomarker evidence of HCMV, IgG4, or CD83(+) microglia. HIGHLIGHTS:Cross-tissue interaction between HCMV and the adaptive immune response in a subset of persons with AD. Presence of CD83(+) microglial associated with IgG4 and HCMV in the gut. CD83(+) microglia are also associated presence of HCMV and IgG4 in the cortex and vagal nerve. Replication of key association in an independent cohort of AD subjects. HCMV infection of cerebral organoids accelerates the production of AD neuropathological features.

BACKGROUND:Insulin-like growth factor-1 (IGF-1) promotes neurogenesis, cell survival, and glial function, making it a promising candidate therapy in Alzheimer's disease (AD). OBJECTIVE:Long arginine 3-IGF-1 (LR3-IGF-1) is a potent IGF-1 analogue. We sought to determine whether intranasal (IN) LR3 treatment would delay cognitive decline and pathology in 5XFAD mice. METHODS:Wildtype and 5XFAD male mice were treated for 7 months (3-10 months of age), with IN LR3-IGF-1 or IN Vehicle (Veh) (n = 19-27 mice/group). Behavior, memory, and brain imaging were assessed at 8-9 months of age and tissues collected at 10 months. A comprehensive amyloid-β (Aβ) profile and other pathologic features were conducted and supportive in vitro stimulation studies in BV-2 microglial cells were also performed. RESULTS:In male 5XFAD mice, IN LR3-IGF-1 treatment improved body composition, but did not significantly alter cognitive symptoms, as assessed by multiple assays. In cortex, LR3 treatment improved some facets of pathology, including a reduction in filamentous plaques, and increase in inert plaques, corresponding with a reduction in low molecular weight Aβ oligomers. In vitro, uptake of Aβ1-42 peptide by BV2 cells was enhanced by LR3-IGF-1, which was also found to promote gene pathways implicated in actin remodeling and endocytosis. CONCLUSIONS:LR3 promotes favorable effects on Aβ plaque remodeling in cortex of male 5XFAD mice but fails to preserve aspects of behavior or memory. While these data do not support LR3 as a monotherapy per se, they do warrant further investigation into its potential for combinatorial formulations aimed at targeting the complexity of AD.

Background:Dual specificity protein phosphatase 6 (DUSP6) was recently identified as a key hub gene in a causal network that regulates late-onset Alzheimer's disease. Importantly, decreased DUSP6 levels are correlated with an increased clinical dementia rating in human subjects, and DUSP6 levels are additionally decreased in the 5xFAD amyloidopathy mouse model. Methods:AAV5-DUSP6 or AAV5-GFP (control) were stereotactically injected into the dorsal hippocampus (dHc) of female and male 5xFAD or wild type mice to overexpress DUSP6 or GFP. Spatial learning memory of these mice was assessed in the Barnes maze, after which hippocampal tissues were isolated for downstream analysis. Results:Barnes maze testing indicated that DUSP6 overexpression in the dHc of 5xFAD mice improved memory deficits and was associated with reduced amyloid plaque load, Aß 1-40 and Aß 1-42 levels, and amyloid precursor protein processing enzyme BACE1, in male but not in female mice. Microglial activation and microgliosis, which are increased in 5xFAD mice, were significantly reduced by dHc DUSP6 overexpression in both males and females. Transcriptomic profiling of female 5xFAD hippocampus revealed upregulated expression of genes involved in inflammatory and extracellular signal-regulated kinase (ERK) pathways, while dHc DUSP6 overexpression in female 5xFAD mice downregulated a subset of genes in these pathways. A limited number of differentially expressed genes (DEGs) (FDR<0.05) were identified in male mice; 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. Notably, the msh homeobox 3 gene, Msx3 , previously shown to regulate microglial M1/M2 polarization and reduce neuroinflammation, was one of the most robustly upregulated genes in female and male wild type and 5xFAD mice overexpressing DUSP6. Conclusions:In summary, our data indicate that 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. 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.

Tauopathies are a heterogeneous group of neurodegenerative disorders that are clinically and pathologically distinct from Alzheimer's disease (AD) having tau inclusions in neurons and/or glia as their most prominent neuropathological feature. BCI-838 (MGS00210) is a group II metabotropic glutamate receptor (mGluR2/3) antagonist pro-drug. Previously, we reported that orally administered BCI-838 improved learning behavior and reduced anxiety in Dutch (APPE693Q) transgenic mice, a model of the pathological accumulation of All oligomers found in AD. Herein, we investigated effects of BCI-838 on PS19 male mice that express the tauopathy mutation MAPTP301S associated with human frontotemporal lobar degeneration (FTLD). These mice develop an agingrelated tauopathy without amyloid accumulation. Mice were divided into three experimental groups: (1) nontransgenic wild type mice treated with vehicle, (2) PS19 mice treated with vehicle and (3) PS19 mice treated with 5 mg/kg BCI-838. Groups of 10-13 mice were utilized. Vehicle or BCI-838 was administered by oral gavage for 4 weeks. Behavioral testing consisting of a novel object recognition task was conducted after drug administration. Two studies were performed beginning treatment of mice at 3 or 7 months of age. One month of BCI838 treatment rescued deficits in recognition memory in PS19 mice whether treatment was begun at 3 or 7 months of age. These studies extend the potential utility of BCI-838 to neurodegenerative conditions that have tauopathy as their underlying basis. They also suggest an mGluR2/3 dependent mechanism as a basis for the behavioral deficits in PS19 mice.

Tauopathies are a heterogeneous group of neurodegenerative disorders that are clinically and pathologically distinct from Alzheimer’s disease (AD) having tau inclusions in neurons and/or glia as their most prominent neuropathological feature. BCI-838 (MGS00210) is a group II metabotropic glutamate receptor (mGluR2/3) antagonist pro-drug. Previously, we reported that orally administered BCI-838 improved learning behavior and reduced anxiety in Dutch (APPE693Q) transgenic mice, a model of the pathological accumulation of Aβ oligomers found in AD. Herein, we investigated effects of BCI-838 on PS19 male mice that express the tauopathy mutation MAPTP301S associated with human frontotemporal lobar degeneration (FTLD). These mice develop an aging-related tauopathy without amyloid accumulation. Mice were divided into three experimental groups: (1) non-transgenic wild type mice treated with vehicle, (2) PS19 mice treated with vehicle and (3) PS19 mice treated with 5 mg/kg BCI-838. Groups of 10–13 mice were utilized. Vehicle or BCI-838 was administered by oral gavage for 4 weeks. Behavioral testing consisting of a novel object recognition task was conducted after drug administration. Two studies were performed beginning treatment of mice at 3 or 7 months of age. One month of BCI-838 treatment rescued deficits in recognition memory in PS19 mice whether treatment was begun at 3 or 7 months of age. These studies extend the potential utility of BCI-838 to neurodegenerative conditions that have tauopathy as their underlying basis. They also suggest an mGluR2/3 dependent mechanism as a basis for the behavioral deficits in PS19 mice.

Background: The apolipoprotein E (APOE, gene; apoE, protein) ε4 allele is the most common identified genetic risk factor for typical late-onset sporadic Alzheimer’s disease (AD). Each APOE ε4 allele roughly triples the relative risk for AD compared to that of the reference allele, APOE ε3. Methods: We have employed hyperspectral fluorescence imaging with an amyloidspecific, conformation-sensing probe, p-FTAA, to elucidate protein aggregate structure and morphology in fresh frozen prefrontal cortex samples from human postmortem AD brain tissue samples from patients homozygous for either APOE ε3 or APOE ε4. Results: As expected APOE ε4/ε4 tissues had significantly larger load of CAA than APOE ε3/ε3. APOE isoform-dependent morphological differences in amyloid plaques were also observed. Amyloid plaques in APOE ε3/ε3 tissue had small spherical cores and large corona while amyloid plaques in APOE ε4/ε4 tissues had large irregular and multilobulated plaques with relatively smaller corona. Despite the different morphologies of their cores, the p-FTAA stained APOE ε3/ε3 amyloid plaque cores had spectral properties identical to those of APOE ε4/ε4 plaque cores. Conclusions: These data support the hypothesis that one mechanism by which the APOE ε4 allele affects AD is by modulating the macrostructure of pathological protein deposits in brain. APOE ε4 is associated with a higher density of amyloid plaques (as compared to APOE ε3). We speculate that multilobulated APOE ε4-associated plaques arise from multiple initiation foci that coalesce as the plaques grow.

Alcadeins are among the 90 known substrates for γ-secretase, the aspartyl proteinase complex that liberates the amyloid β (Aβ) peptide by intramembranous cleavage of the ß-carboxy terminal fragment of the Alzheimer's amyloid precursor protein (APP). A new study by Hata et al. provides some surprising results regarding a potential role for alcadeins and their fragments in the prevention and/or treatment of the dementia of Alzheimer's disease (AD).

Alzheimer’s disease (AD) is the most common cause of dementia and is characterized by the cerebral accumulation of amyloid plaques and tauopathy. The gene inositol polyphosphate-5-phosphatase D (INPP5D), which encodes Src homology 2-containing-inositol-phosphatase-1 (SHIP1), has been highlighted by multiple approaches as a gene that modulates the risk for AD. SHIP1 expression in brain is restricted to inflammatory cells called microglia that have been shown to play significant roles in the induction and spread of tauopathy. Therefore, the goal of the current study was to examine the effect of microglial Inpp5d/SHIP1 knockdown on a mouse model of tauopathy. We generated a mouse model of conditional Inpp5d knockdown in microglia to assess the impact on pathology in the MAPT P301S mouse model of tauopathy, using Inpp5d flox mice crossed with an inducible Cx3cr1 CreER/+ . To induce recombination, 3-month-old (mo) Inpp5d fl/fl /Cx3cr1 CreER/+ mice, with and without the MAPT P301S transgene, were injected for 5 consecutive days with either tamoxifen (TAM) or corn oil (CO). At 8.5 mo, we assessed learning behavior using the Barnes Maze test and Novel Object Recognition test. Finally, we performed immunohistochemistry, immunoblotting, and quantitative real-time PCR to assess neuroinflammation and tau pathology. TAM treatment of Inpp5d fl/fl /Cx3cr1 CreER/+ mice and MAPT P301S /Inpp5d fl/fl /Cx3cr1 CreER/+ mice was used to induce microglial Inpp5d deficiency in both lines. Microglial Inpp5d deficiency in MAPT P301S mice was associated with increased levels of AT8 + hyperphosphorylated tau, yet the numbers of IBA1 + microglia and GFAP + astrocytes were similar to MAPT P301S expressing normal levels of Inpp5d. Our findings suggest that, in our mouse model, Inpp5d deficiency plays an important role in the pathogenesis of tauopathy, but fails to induce an obvious increase in the numbers of either IBA1 + microglia or GFAP + astrocytes. Our results provide evidence for further evaluation of INPP5D/SHIP1 as a potential target for treating and/or preventing AD.

Calcific aortic valve disease (CAVD) and stenosis have a complex pathogenesis, and no therapies are available that can halt or slow their progression. Several studies have shown the presence of apolipoprotein-related amyloid deposits in close proximity to calcified areas in diseased aortic valves. In this Perspective, we explore a possible relationship between amyloid deposits, calcification and the development of aortic valve stenosis. These amyloid deposits might contribute to the amplification of the inflammatory cycle in the aortic valve, including extracellular matrix remodelling and myofibroblast and osteoblast-like cell proliferation. Further investigation in this area is needed to characterize the amyloid deposits associated with CAVD, which could allow the use of antisense oligonucleotides and/or isotype gene therapies for the prevention and/or treatment of CAVD.

BackgroundModulation of physical activity represents an important intervention that may delay, slow, or prevent mild cognitive impairment (MCI) or dementia due to Alzheimer's disease (AD). One mechanism proposed to underlie the beneficial effect of physical exercise (PE) involves the apparent stimulation of adult hippocampal neurogenesis (AHN). BCI-838 is a pro-drug whose active metabolite BCI-632 is a negative allosteric modulator at group II metabotropic glutamate receptors (mGluR2/3). We previously demonstrated that administration of BCI-838 to a mouse model of brain accumulation of oligomeric AβE22Q (APPE693Q = “Dutch APP”) reduced learning behavior impairment and anxiety, both of which are associated with the phenotype of Dutch APP mice.Methods3-month-old mice were administered BCI-838 and/or physical exercise for 1 month and then tested in novel object recognition, neurogenesis, and RNAseq.ResultsHere we show that (i) administration of BCI-838 and a combination of BCI-838 and PE enhanced AHN in a 4-month old mouse model of AD amyloid pathology (APPKM670/671NL/PSEN1Δexon9= APP/PS1), (ii) administration of BCI-838 alone or with PE led to stimulation of AHN and improvement in recognition memory, (iii) the hippocampal dentate gyrus transcriptome of APP/PS1 mice following BCI-838 treatment showed up-regulation of brain-derived neurotrophic factor (BDNF), PIK3C2A of the PI3K-mTOR pathway, and metabotropic glutamate receptors, and down-regulation of EIF5A involved in modulation of mTOR activity by ketamine, and (iv) validation by qPCR of an association between increased BDNF levels and BCI-838 treatment.ConclusionOur study points to BCI-838 as a safe and orally active compound capable of mimicking the beneficial effect of PE on AHN and recognition memory in a mouse model of AD amyloid pathology.

Studies of microglial gene manipulation in mouse models of Alzheimer's disease (AD) amyloidopathy can cause unpredictable effects on various key endpoints, including amyloidosis, inflammation, neuritic dystrophy, neurodegeneration, and learning behavior. In this Correspondence, we discuss three examples, microRNA 155 (miR155), TREM2, and INPP5D, in which observed results have been difficult to reconcile with predicted results based on precedent, because these six key endpoints do not reliably track together. The pathogenesis of AD involves multiple cell types and complex events that may change with disease stage. We propose that cell-type targeting and timing of intervention are responsible for the sometimes impossibility of predicting whether any prospective therapeutic intervention should aim at increasing or decreasing the level or activity of a particular molecular target.