Long-term neprilysin gene transfer is associated with reduced levels of intracellular Abeta and behavioral improvement in APP transgenic mice

Background  

Proteolytic degradation has emerged as a key pathway involved in controlling levels of the Alzheimer's disease (AD)-associated amyloid-β (Aβ) peptide in the brain. The endopeptidase, neprilysin, has been implicated as a major Aβ degrading enzyme in mice and humans. Previous short and intermediate term studies have shown the potential therapeutic application of neprilysin by delivering this enzyme into the brain of APP transgenic mice using gene transfer with viral vectors. However the effects of long-term neprilysin gene transfer on other aspects of Aβ associated pathology have not been explored yet in APP transgenic mice.     

Overcoming antigen masking of anti-amyloidbeta antibodies reveals breaking of B cell tolerance by virus-like particles in amyloidbeta immunized amyloid precursor protein transgenic mice

Background  

In prior work we detected reduced anti-Aβ antibody titers in Aβ-vaccinated transgenic mice expressing the human amyloid precursor protein (APP) compared to nontransgenic littermates. We investigated this observation further by vaccinating APP and nontransgenic mice with either the wild-type human Aβ peptide, an Aβ peptide containing the "Dutch Mutation", E22Q, or a wild-type Aβ peptide conjugated to papillomavirus virus-like particles (VLPs).     

Improvement of a low pH antigen-antibody dissociation procedure for ELISA measurement of circulating anti-Aβ antibodies

Background  

Prior work from our group found that acid dissociation (pH 2.5 incubation) of serum from APP transgenic mice vaccinated against Aβ increased the apparent anti-Aβ titers, suggesting antibody masking by antigen in the ELISA assay. Subsequently, we found that pH 2.5 incubation of serum from unvaccinated non-transgenic mice showed antibody binding to Aβ1–42, but no increase when other proteins, including shorter Aβ peptides, coated the ELISA plate. To investigate further the effects of low pH incubation on apparent anti-Aβ1–42 signals, we examined normal sera from nonTg unvaccinated mice, nonTg mice vaccinated with Aβ peptide (to produce authentic anti-Aβ antibodies) or a monoclonal antibody against Aβ (6E10) using competitive-inhibition ELISA and Aβ epitope mapping assays. In addition, we examined use of a less stringent low pH procedure at pH 3.5, to ascertain if it had the same effects as the pH 2.5 procedure.     

Chronic administration of R-flurbiprofen attenuates learning impairments in transgenic amyloid precursor protein mice

Background  

Long-term use of non-steroidal anti-inflammatory drugs (NSAIDs) is associated with a reduced incidence of Alzheimer's disease (AD). We and others have shown that certain NSAIDs reduce secretion of Aβ42 in cell culture and animal models, and that the effect of NSAIDs on Aβ42 is independent of the inhibition of cyclooxygenase by these compounds. Since Aβ42 is hypothesized to be the initiating pathologic molecule in AD, the ability of these compounds to lower Aβ42 selectively may be associated with their protective effect. We have previously identified R-flurbiprofen (tarenflurbil) as a selective Aβ42 lowering agent with greatly reduced cyclooxygenase activity that shows promise for testing this hypothesis. In this study we report the effect of chronic R-flurbiprofen treatment on cognition and Aβ loads in Tg2576 APP mice.     

Dysregulation of Na+/K+ ATPase by amyloid in APP+PS1 transgenic mice

Background  

The pathology of Alzheimer's disease (AD) is comprised of extracellular amyloid plaques, intracellular tau tangles, dystrophic neurites and neurodegeneration. The mechanisms by which these various pathological features arise are under intense investigation. Here, expanding upon pilot gene expression studies, we have further analyzed the relationship between Na+/K+ ATPase and amyloid using APP+PS1 transgenic mice, a model that develops amyloid plaques and memory deficits in the absence of tangle formation and neuronal or synaptic loss.     

In vivo1H-magnetic resonance spectroscopy can detect metabolic changes in APP/PS1 mice after donepezil treatment

Background  

Donepezil improves cognitive functions in AD patients. Effects on the brain metabolites N-acetyl-L-aspartate, choline and myo-inositol levels have been reported in clinical studies using this drug. The APP/PS1 mouse coexpresses the mutated forms of human β-amyloid precursor protein (APP) and mutated human presenilin 1 (PS1). Consequently, the APP/PS1 mouse model reflects important features of the neurochemical profile in humans. In vivo magnetic resonance spectroscopy (¹H-MRS) was performed in fronto-parietal cortex and hippocampus (ctx/hipp) and in striatum (str). Metabolites were quantified using the LCModel and the final analysis was done using multivariate data analysis. The aim of this study was to investigate if multivariate data analysis could detect changes in the pattern of the metabolic profile after donepezil treatment.     

Dimerization of the transmembrane domain of amyloid precursor proteins and familial Alzheimer's disease mutants

Background  

Amyloid precursor protein (APP) is enzymatically cleaved by γ-secretase to form two peptide products, either Aβ40 or the more neurotoxic Aβ42. The Aβ42/40 ratio is increased in many cases of familial Alzheimer's disease (FAD). The transmembrane domain (TM) of APP contains the known dimerization motif GXXXA. We have investigated the dimerization of both wild type and FAD mutant APP transmembrane domains.     

Resonance assignment of<Superscript>13</Superscript>C−<Superscript>15</Superscript>N-labeled snake neurotoxin II from<Emphasis Type="Italic">Naja oxiana</Emphasis>

Neurotoxin II fromNaja oxiana venom is a short-chain snake curaremimetic neurotoxin containing four disulfide bonds. We obtained¹³C-¹⁵N-labeled neurotoxin II to study its internal dynamics and surface properties with atomic resolution. The recombinant protein has the native spatial structure and is biologically active. The nearly complete assignment of¹H,¹³C and¹⁵N resonances for neurotoxin II was obtained by heteronuclear triple-resonance nuclear magnetic resonance spectroscopy. Analysis of the secondary chemical shifts of the¹H^α,¹³C^α,¹³C^β and¹³CO nuclei reveal their strong correlation with the protein secondary structure.     

Three-body analysis of<Superscript>11</Superscript>Li and its<Emphasis Type="Italic">β</Emphasis>-decay to deuteron channel and to halo analog state<Superscript>11</Superscript>Be* (18.3 MeV)

The ground state wave function of¹¹Li obtained in a three-body model proposed earlier (S Kumar and V S Bhasin,Phys. Rev. C65, 034007 (2002)) has been employed to study the probability distributions, momentum distributions and n−n correlation. Complex scaling method has been used to find the energy positions and widths of the three resonant states of¹¹Li above the breakup threshold. The formalism is extended further to study the β-decay of¹¹Li to two channels. One is the β-transition of¹¹Li into a high lying excited state of¹¹Be at 18.3 MeV, i.e.,¹¹Be* and the second is the decay to deuteron +⁹Li channel. The¹¹Be* state has been considered as a halo analog state identified as a bound three-body (⁹Li + n + p) system. The n-⁹Li interaction incorporates both the virtual state and the p-wave resonance observed experimentally. For p-⁹Li interaction, a Coulomb corrected separable interaction is constructed using charge indepedendence for strong interaction part. The n-p interaction is operative only in³S₁ state corresponding to the isotopic spin T^h =0. As a result the¹¹Be* state has the same isotopic spin as that of⁹Li core, i.e.,T = 3/2. Using these realistic parameters as input and without invoking any other free parameter, the model has been used to predict the strength of the Gamow-Teller β-decay of¹¹Li to¹¹Be*, i.e.,Bgt = 1.5 and the value of the branching ratio to⁹Li + deuteron channel to be 1.3 × 10^-4. These results are found to be in rather good agreement with the recent experimental findings.     

Requirement of aggregation propensity of Alzheimer amyloid peptides for neuronal cell surface binding

Background  

Aggregation of the amyloid peptides, Aβ40 and Aβ42, is known to be involved in the pathology of Alzheimer's disease (AD). Here we investigate the relationship between peptide aggregation and cell surface binding of three forms of Aβ (Aβ40, Aβ42, and an Aβ mutant).     

Nuclear deformation and the two-neutrino double- β decay in <Superscript>124, 126</Superscript>Xe , <Superscript>128, 130</Superscript>Te , <Superscript>130, 132</Superscript>Ba and <Superscript>150</Superscript>Nd isotopes

The two-neutrino double-beta decay of ^{124, 126}Xe , ^{128, 130}Te , ^{130, 132}Ba and ¹⁵⁰Nd isotopes is studied in the Projected Hartree-Fock-Bogoliubov (PHFB) model. Theoretical 2ν β^-β^- half-lives of ^{128, 130}Te , and ¹⁵⁰Nd isotopes, and 2ν β⁺β⁺ , 2ν β⁺ EC and 2ν ECEC for ^{124, 126}Xe and ^{130, 132}Ba nuclei are presented. Calculated quadrupolar transition probabilities B(E2 : 0⁺ → 2⁺) , static quadrupole moments and g -factors in the parent and daughter nuclei reproduce the experimental information, validating the reliability of the model wave functions. The anticorrelation between nuclear deformation and the nuclear transition matrix element M _2ν is confirmed.     

Isolation of mineralizing Nestin+ Nkx6.1+ vascular muscular cells from the adult human spinal cord

Background

Evidence suggests that rheumatoid arthritis (RA) may enhance or reduce the progression of Alzheimer's disease (AD). The present study was performed to directly explore the effects of collagen-induced rheumatoid arthritis (CIA) on amyloid plaque formation, microglial activation, and microvascular pathology in the cortex and hippocampus of the double transgenic APP/PS1 mouse model for AD. Wild-type or APP/PS1 mice that received type II collagen (CII) in complete Freund's adjuvant (CFA) at 2 months of age revealed characteristics of RA, such as joint swelling, synovitis, and cartilage and bone degradation 4 months later. Joint pathology was accompanied by sustained induction of IL-1β and TNF-α in plasma over 4 weeks after administration of CII in CFA.

Results

CIA reduced levels of soluble and insoluble amyloid beta (Aβ) peptides and amyloid plaque formation in the cortex and hippocampus of APP/PS1 mice, which correlated with increased blood brain barrier disruption, Iba-1-positive microglia, and CD45-positive microglia/macrophages. In contrast, CIA reduced vessel density and length with features of microvascular pathology, including vascular segments, thinner vessels, and atrophic string vessels.

Conclusions

The present findings suggest that RA may exert beneficial effects against Aβ burden and harmful effects on microvascular pathology in AD.     

Influence of pairing in double beta decay of <Superscript>48</Superscript>Ca

Two-neutrino ββ decay matrix elements and half-life of ⁴⁸Ca are calculated after including neutron-proton pairing correlations in projected Hartree-Fock-Bogoliubov (PHFB) formalism. The GT matrix elements in 2νββ decay are reduced due to broader smearing of Fermi surfaces. Half-life results for 2νββ decay of 48Ca with np pairing are better than without pairing.     

Beta decay of <Superscript>115</Superscript>In to the first excited level of <Superscript>115</Superscript>Sn: Potential outcome for neutrino mass

Recent observation of β decay of ¹¹⁵In to the first excited level of ¹¹⁵Sn with an extremely low Q _β value (Q _β ≤ O(1) [keV]) could be used to set a limit on neutrino mass. To give a restriction potentially competitive with those extracted from experiments with ³H (≃2 eV) and ¹⁸⁷Re (≃15 eV), the atomic mass difference between ¹¹⁵In and ¹¹⁵Sn and energy of the first ¹¹⁵Sn level should be remeasured with higher accuracy (possibly of the order of ∼1 eV). The text was submitted by the authors in English.     

Investigation of <Superscript>235</Superscript>U and <Superscript>239</Superscript>Pu photofission

Average angular momenta of fission fragments ⁹⁰Rb, ^129,130,132Sb, ^131,133Te, ^134,136I, and ¹³⁵Xe produced in photofission of ²³⁵U and ²³⁹Pu by bremsstrahlung γ rays with a threshold energy of 9.6 and 9.8 MeV, respectively, were determined by measuring the isomeric yield ratios. The experimental values of the isomeric ratios were calculated with account of the contribution from β decay of isobaric nuclei in the yields of the studied isotopes.     

Investigations of EPR parameters and impurity structure for Co<Superscript>2+</Superscript> in Ca(OH)<Subscript>2</Subscript> crystal

The electron paramagnetic resonance (EPR) parameters (g _‖ andg _⊥ factors and hyperfine structure constantsA _‖,A _⊥) for Co²⁺ in Ca(OH)₂ are studied from the second-order perturbation formulas on the basis of the cluster approach. In these formulas, the contributions to EPR parameters from the state interactions and covalency effects are considered and the parameters related to both effects are obtained from the optical spectra and impurity structure of the studied system. From the study, it is found that the β angle between the metal-ligand bond and the C₃ axis changes from 61° in a pure crystal to 53.68(26)° in the impurity center of a Co²⁺-doped Ca(OH)₂ crystal because of the impurity-induced local lattice relaxation. The reduction of the angle β in the impurity center is also supported by the result obtained by analyzing the EPR zero-field splitting for Mn²⁺ in the same Ca(OH)₂ crystal. The EPR parameters of Ca(OH)₂:Co²⁺ are also reasonably explained by considering the suitable local lattice relaxation.     

Low-spin states in <Superscript>182</Superscript>Os and K<Superscript>π</Superscript> = 0<Superscript>+</Superscript>, 2<Superscript>+</Superscript> excited bands

Excited states in ¹⁸²Os were populated by the β⁺/EC decay of ¹⁸²Ir following mass separation. Gamma-ray and conversion electron spectroscopy techniques were employed. Monopole (E0) contributions were determined in transitions populating the ground-state band. A systematic study of the low-spin structures in the Os isotopes is presented and a detailed analysis in the framework of a microscopic configuration mixing approach is performed.     

Structure of excited states of <Superscript>123</Superscript>Te

The β decay of ¹²³I has been calculated within the dynamic collective model developed by the authors earlier. The expression for the reduced matrix element of the weak-interaction Hamiltonian has been used for the partial β decay. The influence of the vacuum fluctuations and creation or annihilation of one or two phonons on the reduced β-decay probabilities is taken into account.     

Diffusion and aggregation of Alzheimer’s Aβ1–40 peptide in aqueous trifluoroethanol solutions as studied by pulsed field gradient NMR

Pulsed field gradient nuclear magnetic resonance technique was applied to measure the self-diffusion coefficient of Aβ_1–40 peptide in trifluoroethanol (TFE) and mixed solvent TFE-water (D₂O) buffer (pD 7.8) at 293 K. The data were analyzed on the basis of the Stokes model and the hardsphere approach was used to estimate self-diffusion coefficients. It was found that the extent of the Aβ_1–40 aggregation in TFE solutions depends on the concentration of the peptide and the sample preparation protocol. After soft mixing, i.e., without any additional mechanical pretreatment of the peptide, the peptide is present in the monomeric form in TFE solutions. However, the additional water-bath sonication of the sample during the dissolution of Aβ_1–40 in TFE enforces oligomerization of the peptide with the size of aggregates ranging from tetra- to hexamers. An increase of D₂O in the mixed TFE-D₂O solvent of up to 75% leads to the aggregation of the larger part of the peptide. However, the components of self-diffusion coefficients related to low-mass Aβ_1–40 oligomers (dimers and trimers) were not observed in the diffusion decay curves. The most probable explanation is that dimers and trimers are not the principal intermediate species in the aggregation of Aβ_1–40 peptide.     

Detailed immunohistochemical characterization of temporal and spatial progression of Alzheimer's disease-related pathologies in male triple-transgenic mice

Background

Several transgenic animal models genetically predisposed to develop Alzheimer's disease (AD)-like pathology have been engineered to facilitate the study of disease pathophysiology and the vetting of potential disease-modifying therapeutics. The triple transgenic mouse model of AD (3xTg-AD) harbors three AD-related genetic loci: human PS1^M146V, human APP^swe, and human tau^P301L. These mice develop both amyloid plaques and neurofibrillary tangle-like pathology in a progressive and age-dependent manner, while these pathological hallmarks are predominantly restricted to the hippocampus, amygdala, and the cerebral cortex the main foci of AD neuropathology in humans. This model represents, at present, one of the most advanced preclinical tools available and is being employed ever increasingly in the study of mechanisms underlying AD, yet a detailed regional and temporal assessment of the subtleties of disease-related pathologies has not been reported.

Methods and results

In this study, we immunohistochemically documented the evolution of AD-related transgene expression, amyloid deposition, tau phosphorylation, astrogliosis, and microglial activation throughout the hippocampus, entorhinal cortex, primary motor cortex, and amygdala over a 26-month period in male 3xTg-AD mice. Intracellular amyloid-beta accumulation is detectable the earliest of AD-related pathologies, followed temporally by phospho-tau, extracellular amyloid-beta, and finally paired helical filament pathology. Pathology appears to be most severe in medial and caudal hippocampus. While astrocytic staining remains relatively constant at all ages and regions assessed, microglial activation appears to progressively increase temporally, especially within the hippocampal formation.

Conclusion

These data fulfill an unmet need in the ever-widening community of investigators studying 3xTg-AD mice and provide a foundation upon which to design future experiments that seek to examine stage-specific disease mechanisms and/or novel therapeutic interventions for AD.