APOE4-specific Changes in Aβ Accumulation in a New Transgenic Mouse Model of Alzheimer Disease

In the paper

“Introduction of human APOE to existing FAD-Tg mice significantly delays plaque deposition, although once detected, plaque levels are generally greater with APOE4 than APOE3 (3, 6 -8).”

What the sources say

• ?Not checked — no full text of the sourcecites [3] Bales, 2009, Human APOE isoform-dependent effects on brain β-amyloid levels in PDAPP transgenic mice, J. Neurosci. source
• Partly supported

  In the Results section on plaque formation (page unavailable), plaques were absent at 6–15 months in mice with or without human apoE, while 19–24-month-old hAPP/apoE4 mice had more plaques than hAPP/apoE3 mice. The paper supports the APOE4-versus-APOE3 comparison, but it does not show that introducing human APOE significantly delayed plaque deposition relative to hAPP mice lacking apoE. (LLM, conf=0.88)

  cites [6] Buttini, 2002, Modulation of Alzheimer-like synaptic and cholinergic deficits in transgenic mice by human apolipoprotein E depends on isoform, aging, and overexpression of amyloid β peptides but not on plaque formation, J. Neurosci. sourceExperimental — accuracy not yet measured
• Supported

  The Discussion (page not specified) states that both human apoE3 and apoE4 delay Aβ deposition relative to mouse apoE or no apoE. The Results (page not specified) report significantly greater deposition in apoE4- than apoE3-expressing mice once deposits develop. (LLM, conf=0.92)

  cites [7] Holtzman, 2000, Apolipoprotein E isoform-dependent amyloid deposition and neuritic degeneration in a mouse model of Alzheimer's disease, Proc. Natl. Acad. Sci. U.S.A. source

In the paper

“This APOE2induced deposition of diffuse plaques is novel in a mouse model and consistent with the previous work by Dr. C. Kawas and co-workers (54,55) who report that increased diffuse plaques are associated with APOE2 in cognitively normal subjects compared with compact plaques in APOE4 AD patients from the oldest of the old study.”

What the sources say

• Partly supported

  The Results (page unavailable) report a trend toward more diffuse plaques in oldest-old APOE2 carriers versus APOE3/3 carriers, and greater plaque pathology in non-demented APOE2 carriers. They do not establish increased diffuse plaques specifically in cognitively normal APOE2 subjects or the claimed contrast with compact plaques in APOE4 Alzheimer’s patients. The mouse-model novelty is the citing authors’ own finding, not a claim attributed to this source. (LLM, conf=0.86)

  cites [54] Berlau, 2009, APOE ϵ2 is associated with intact cognition but increased Alzheimer pathology in the oldest old, Neurology sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [55] Berlau, 2007, Dissociation of neuropathologic findings and cognition: case report of an apolipoprotein E ϵ2/ϵ2 genotype, Arch. Neurol. source

In the paper

“In addition, the MOAB-2-based oA␤42 ELISA detects oligomeric but not monomeric A␤42 using synthetic preparations characterized previously by our laboratory (data not shown) (47,48).”

What the sources say

• ?Not checked — no full text of the sourcecites [47] Dahlgren, 2002, Oligomeric and fibrillar species of amyloid-β peptides differentially affect neuronal viability, J. Biol. Chem. source
• Supported

  The citation follows “synthetic preparations characterized previously,” and the paper characterizes preparations of unaggregated and oligomeric Aβ1-42 (Results, “Detection of Aβ1-42 Fibrils…,” page not available). The citing sentence labels the MOAB-2 ELISA result “data not shown”; it does not attribute that assay result to this source. (LLM, conf=0.88)

  cites [48] Stine, 2003, In vitro characterization of conditions for amyloid-β peptide oligomerization and fibrillogenesis, J. Biol. Chem. source

In the paper

“Female mice were excluded from this initial study for consistency, as apoE isoform-specific interaction with A␤ are known to be influenced by gender (for review (44)).”

What the sources say

• Partly supported

  Sections 2.3 and 2.4 report that apoE isoform-related cognitive effects differ between female and male mice, supporting the general concern about sex differences. Sections 3.3 and 3.5 discuss isoform-specific Aβ pathology but do not establish that the apoE–Aβ interaction itself differs by sex. The paper also does not address the citing study’s decision to exclude female mice. (LLM, conf=0.82)

  cites [44] Tai, 2011, Introducing human APOE into Aβ transgenic mouse models, Int. J. Alzheimers Dis. sourceExperimental — accuracy not yet measured

In the paper

“bexarotene (an RXR agonist) increases apoE levels”

What the sources say

• Partly supported

  The apoE-expression passage (indexed under Abstract; page not provided) reports increased apoE expression in bexarotene-treated mice after treatment measured in days. The six-hour passage reports a decrease in Aβ, not an increase in apoE, so the added 'within hours' timing is not supported. (LLM, conf=0.88)

  cites [76] Cramer, 2012, ApoE-directed therapeutics rapidly clear β-amyloid and reverse deficits in AD mouse models, Science sourceExperimental — accuracy not yet measured

In the paper

“A renewed interest in the pathological role of plaques has suggested that oA␤ species accumulate at the periphery of densecored plaques (60,61) and that compact plaques enhance A␤ toxicity indirectly by creating a platform on which toxic oA␤ species can accumulate or stabilize.”

What the sources say

• Supported

  The section “Senile Plaques Contain, and Are Surrounded by, a Halo of Aβ Oligomers” reports oligomeric Aβ in and around dense plaque cores. The Discussion proposes that plaques act as a local reservoir of soluble oligomeric Aβ that is toxic to synapses, supporting the citing sentence’s suggested indirect role for plaques. (LLM, conf=0.91)

  cites [60] Koffie, 2009, Oligomeric amyloid β associates with postsynaptic densities and correlates with excitatory synapse loss near senile plaques, Proc. Natl. Acad. Sci. U.S.A. source
• ?Could not verify

  The Discussion (page unavailable) links plaques to nearby neuronal damage and identifies soluble Aβ as a possible mediator. It does not say that oligomeric Aβ accumulates at the periphery of dense-cored plaques or that compact plaques provide a platform that stabilizes it. Searches for oligomers at plaque edges and for the proposed platform mechanism found no passage addressing those points. (LLM, conf=0.70)

  cites [61] Spires-Jones, 2011, Monitoring protein aggregation and toxicity in Alzheimer's disease mouse models using in vivo imaging, Methods sourceExperimental — accuracy not yet measured

In the paper

“significantly reduces insoluble A␤ after 3 days”

What the sources say

• Supported

  The passage on acute treatment (section labeled Abstract; page unavailable) reports that insoluble Aβ levels in six-month-old APP/PS1 mice fell by 40% after 72 hours of bexarotene treatment. That supports the claimed reduction after three days, although the passage does not explicitly call the 72-hour result statistically significant. (LLM, conf=0.89)

  cites [76] Cramer, 2012, ApoE-directed therapeutics rapidly clear β-amyloid and reverse deficits in AD mouse models, Science source

In the paper

“These data are in apparent contrast with data from a single study in humans that reports an increase in intraneuronal A␤ with one or two alleles of APOE4 (63).”

What the sources say

• Supported

  The Introduction states that this human study found a significant correlation between intraneuronal Aβ accumulation and the presence of at least one ApoE4 allele. The Results likewise report increased intraneuronal Aβ staining in ApoE4 carriers; the claim describes an association, not a causal effect. (LLM, conf=0.92)

  cites [63] Christensen, 2010, Accumulation of intraneuronal Aβ correlates with ApoE4 genotype, Acta Neuropathol. source

In the paper

“soluble oligomers correlate with cognitive decline (Mini Mental State Examination (MMSE) scores) and tangle stage (20).”

What the sources say

• Supported

  The Results section reports significant correlations between soluble fibrillar oligomer levels and MMSE scores in several brain regions, as well as significant correlations with tangle stage in all regions examined except the olfactory bulb. The Discussion describes the MMSE relationship as an inverse correlation, consistent with greater cognitive decline at higher oligomer levels. (LLM, conf=0.94)

  cites [20] Tomic, 2009, Soluble fibrillar oligomer levels are elevated in Alzheimer's disease brain and correlate with cognitive dysfunction, Neurobiol. Dis. source

In the paper

“APOE4 carriers can exhibit a differential response to certain therapeutic interventions, complicating the interpretation of drug trials”

What the sources say

• Supported

  The “Effects of APOE genotype on AD therapeutic response” section reports differences in efficacy or adverse effects between APOE ε4 carriers and non-carriers for some treatments, while noting that other trials found no genotype effect. It concludes that genotype-related differences in efficacy and outcome are important to consider in trial design, supporting the claim’s qualified wording. Page numbers were not provided in our copy. (LLM, conf=0.94)

  cites [53] Verghese, 2011, Apolipoprotein E in Alzheimer's disease and other neurological disorders, Lancet Neurol. source

In the paper

“decreases soluble A␤ in mice within hours”

What the sources say

• Supported

  The passage describing hippocampal microdialysis in 2-month-old APP/PS1 mice reports that bexarotene lowered interstitial-fluid Aβ40 and Aβ42 within 6 hours. This directly supports the claim about soluble Aβ decreasing in mice within hours. (LLM, conf=0.95)

  cites [76] Cramer, 2012, ApoE-directed therapeutics rapidly clear β-amyloid and reverse deficits in AD mouse models, Science source

In the paper

“In FAD-Tg mice, soluble oA␤ suppresses synaptic function”

What the sources say

• Partly supported

  In ‘II. Toxicity of Oligomeric Aβ Assemblies’ (page unavailable), the review reports that soluble Aβ oligomers inhibit LTP, a measure of synaptic plasticity. It also describes Aβ-induced neuronal and cognitive deficits in APP-transgenic mice, but does not clearly establish that soluble oligomers suppress synaptic function specifically in those mice. (LLM, conf=0.80)

  cites [52] Larson, 2012, Soluble Aβ oligomer production and toxicity, J. Neurochem. sourceExperimental — accuracy not yet measured

In the paper

“impairs learning and memory (52).”

What the sources say

• Supported

  The Toxicity of Oligomeric Aβ Assemblies section reports that Aβ*56 impairs cognition in Tg2576 mice and is associated with memory decline in other APP-transgenic mouse models of Alzheimer’s disease. It also describes poorer Morris water-maze performance in Tg2576 mice, supporting the claim about learning and memory. (LLM, conf=0.89)

  cites [52] Larson, 2012, Soluble Aβ oligomer production and toxicity, J. Neurochem. source

In the paper

“recent evidence indicates that intraneuronal A␤ accumulation may be an important proximal neurotoxic event in AD pathogenesis (for review see Ref. 56,57).”

What the sources say

• Supported

  The “Implications of intraneuronal Aβ for Alzheimer’s disease” section says evidence is mounting that intraneuronal Aβ42 is a driving force in Aβ-related AD pathogenesis. The “Pathology” section describes its accumulation in neurites and synapses as leading to their destruction from within. Page numbers were not provided in our copy. (LLM, conf=0.93)

  cites [56] Gouras, 2010, Intraneuronal β-amyloid accumulation and synapse pathology in Alzheimer's disease, Acta Neuropathol. source
• Supported

  The Introduction describes intraneuronal Aβ accumulation as a hypothesized early pathological event that triggers a cascade leading to neurodegeneration. The Conclusion reports accumulating evidence that intraneuronal Aβ triggers early synaptic deficits and neuron loss, supporting the citing sentence’s qualified claim. (LLM, conf=0.93)

  cites [57] Bayer, 2010, Intracellular accumulation of amyloid-β: a predictor for synaptic dysfunction and neuron loss in Alzheimer's disease, Front. Aging Neurosci. source

In the paper

“reduces synaptic plasticity”

What the sources say

• Partly supported

  The Toxicity of Oligomeric Aβ Assemblies section (page unavailable) says oligomeric Aβ can impair synaptic plasticity. It also discusses Aβ oligomers and deficits in transgenic mouse models, but the passages do not establish that soluble oligomers reduced synaptic plasticity specifically in those mice; the mouse-model findings described concern cognition or neuronal function. (LLM, conf=0.82)

  cites [52] Larson, 2012, Soluble Aβ oligomer production and toxicity, J. Neurochem. sourceExperimental — accuracy not yet measured

In the paper

“although plaque levels at 3 months remained unchanged (76).”

What the sources say

• Supported

  The passage on chronic treatment reports that APP/PS1 mice given bexarotene daily for three months had unchanged amyloid plaque burden. The three months refers to treatment duration, not the mice’s age. (LLM, conf=0.95)

  cites [76] Cramer, 2012, ApoE-directed therapeutics rapidly clear β-amyloid and reverse deficits in AD mouse models, Science source

In the paper

“MOAB-2 was developed in the LaDu laboratory and is a high-affinity antibody specific for A␤ that does not detect APP.”

What the sources say

• Supported

  The Background identifies MOAB-2 as an antibody specific for Aβ that does not detect APP. The Results report Aβ detection at low antigen and antibody concentrations and show that MOAB-2 did not recognize APP in the tested cell lysates and mouse brain extracts; these findings support the high-affinity description. (LLM, conf=0.88)

  cites [25] Youmans, 2012, Intraneuronal Aβ detection in 5xFAD mice by a new Aβ-specific antibody, Mol. Neurodegener. source

In the paper

“In E4FAD mice, oA␤ levels were ϳ2-fold higher in the cortex and 3-fold higher in the hippocampus compared with those in E2FAD and E3FAD mice.”

In the paper

“As observed for apoE, A␤42 levels were lowest in the cerebellum, higher in the cortex, and highest in the hippocampus (Fig. 4B, p Ͻ 0.001; note the y axis values change for the cerebellum and cortex versus the hippocampus).”

In the paper

“A␤ accumulation appeared earlier and was greater in the subiculum compared with the frontal cortex, allowing for regional, as well as temporal, comparisons of the effects of the APOE genotype on the progression of A␤ accumulation.”

In the paper

“Specifically, apoE4 levels are significantly lower than apoE2 and apoE3 in the cerebellum at 4 months, in the cortex at 2, 4, and 6 months, and in the hippocampus at 2 and 4 months of age (for specific comparisons, see Fig. 4A).”

In the paper

“Interestingly, total apoE levels in the EFAD mice were lowest in the cerebellum, significantly higher in the cortex, and highest in the hippocampus (Fig. 4A, dashed lines mean the data are collapsed by genotype and age within a region; p Ͻ 0.001).”

In the paper

“The majority of the plaques in EFAD mice were either diffuse or compact, and this distribution in plaque morphology did not change with age (Fig. 2E).”

In the paper

“In addition, apoE levels did not change in response to age, and thus there was no APOE genotype-specific response to increasing A␤ accumulation (Fig. 4B).”

In the paper

“FA-extracted A␤42 levels increased with age for all APOE genotypes and were significantly higher in E4FAD mice at 4 and 6 months compared with E2FAD and E3FAD mice (Fig. 5B).”

In the paper

“The reverse pattern was observed with compact plaques; ϳ20% of the plaques in E2FAD and E3FAD mice were compact, whereas 40 -50% of plaques in E4FAD mice were compact.”

In the paper

“In the cortex, A␤42 levels were generally low at 2 months but increased significantly by 4 months such that E4FAD Ͼ E3FAD ϭ E2FAD.”

In the paper

“In the hippocampus, A␤42 levels were low at 2 months but increased significantly by 4 and 6 months such that E4FAD Ͼ E3FAD ϭ E2FAD.”

In the paper

“ApoE2 and apoE3 were extracted primarily to the TBSX fraction, whereas apoE4 levels were significantly lower in this fraction at 2, 4, and 6 months.”

In the paper

“Soluble apoE levels were comparable in the cortex (Fig. 6A) and hippocampus (Fig. 6B) and did not vary significantly by APOE genotype.”

In the paper

“Compared with 5xFAD mice, A␤ deposition was delayed ϳ4 months in the EFAD mice, with accumulation earliest in E4FAD Ͼ E3FAD ϭ E2FAD.”

In the paper

“In E2FAD and E3FAD mice the majority of plaques were diffuse, accounting for more than 50% of total plaques, whereas diffuse plaques were significantly lower in E4FAD mice (e.g.30% at 6 months).”

In the paper

“In addition, from 4 to 6 months, the proportion of diffuse plaques decreased and that of compact plaques increased only in the E4FAD mice (Fig. 2E).”

In the paper

“Further, in both the cortex and the hippocampus, soluble A␤42 levels were 2-fold and 3-fold higher, respectively, in E4FAD mice compared with E2FAD and E3FAD mice.”

In the paper

“However, analysis of plaque morphology revealed that whereas the majority of the APOE4 plaques are compact, the majority of the APOE2 plaques are diffuse.”

In the paper

“whereas the EFAD mice express almost exclusively A␤42”

In the paper

“Further, this apoE4-specific distribution appears to occur in the hippocampus and cortex, which are AD-susceptible brain regions, and not the cerebellum, a disease-resistant region.”

In the paper

“Compared with 5xFAD mice, A␤ deposition was delayed by ϳ4 months in the EFAD mice, allowing detection of early changes in A␤ accumulation from 2-6 months.”

In the paper

“In EFAD mice, A␤ deposition is delayed ϳ4 months compared with 5xFAD mice, creating a window from 2 to 6 months during which comparisons of multiple forms of A␤ accumulation can be measured, although this is still early in the overall process of A␤ accumulation in either the hippocampus or the cortex.”

In the paper

“For example, crossing apoE-targeted replacement mice (apoE-TR) (9) with PDAPP mice (10) delays plaque deposition from ϳ10 to 18 months, although once detected, plaque levels are greater with APOE4 than APOE3 (3).”

What the sources say

• ?Not checked — no full text of the sourcecites [3] Bales, 2009, Human APOE isoform-dependent effects on brain β-amyloid levels in PDAPP transgenic mice, J. Neurosci. source

In the paper

“The primary genetic risk factor for Alzheimer disease (AD) 4 is APOE4, increasing the risk by ϳ4and 15-fold with a single or double allele, whereas APOE2 reduces the risk compared with APOE3.”

What the sources say

• ?Not checked — no full text of the sourcecites [4] Drzezga, 2009, Effect of APOE genotype on amyloid plaque load and gray matter volume in Alzheimer disease, Neurology source

In the paper

“Overall, these data demonstrate that APOE genotype modulates A␤ speciation, an effect likely mediated by functional differences among the apoE isoforms.”

In the paper

“The number of neurons containing intraneuronal A␤ was determined using unbiased stereology (51) and counted by an investigator blinded to APOE genotype using sections immunostained with MOAB-2 (for A␤) and NeuN.”

In the paper

“This ELISA pairing detects synthetic oA␤ preparations but not monomeric A␤ using preparations of oA␤ optimized for the original protocol (data not shown) (46).”

What the sources say

• ?Not checked — no full text of the sourcecites [46] Moore, 2009, Biophysical analyses of synthetic amyloid-β(1–42) aggregates before and after covalent cross-linking. Implications for deducing the structure of endogenous amyloid-β oligomers, Biochemistry source

In the paper

“which is one possible explanation for the discrepancy.”

In the paper

“Thio-S plaque staining and quantification was conducted by an investigator blinded to the APOE genotype using every ninth tissue section for six consecutive sections, beginning with the lateral-most section in the region of interest (ROI).”

In the paper

“The number of neurons containing intraneuronal A␤ was determined using unbiased stereology (51) and counted by an investigator blinded to APOE genotype using sections immunostained with MOAB-2 (for A␤) and NeuN.”

What the sources say

• ?Not checked — no full text of the sourcecites [51] West, 1991, Unbiased stereological estimation of the total number of neurons in thesubdivisions of the rat hippocampus using the optical fractionator, Anat. Rec. source

In the paper

“This effect would be enhanced with APOE4, as it is associated with a larger proportion of compact plaques.”

In the paper

“Experiments follow the University of Illinois at Chicago Institutional Animal Care and Use Committee protocols.”