Neuroinflammation-induced acceleration of amyloid deposition in the APPV717F transgenic mouse.

It has been postulated that neuroinflammation plays a critical role in the pathogenesis of Alzheimer's disease (AD). To directly test whether an inflammatory stimulus can accelerate amyloid deposition in vivo, we chronically administered the bacterial endotoxin, lipopolysaccharide (LPS), intracerebroventricularly (i.c.v.) to 2-month-old APPV717F+/+ transgenic (TG) mice, which overexpress a mutant human amyloid precursor protein (APP 717V-F) with or without apolipoprotein E (apoE) for 2 weeks. Two weeks following central LPS administration a striking global reactive astrocytosis with increased GFAP immunoreactivity was found throughout the brains of all LPS-treated wild-type and transgenic mice including the contralateral brain hemisphere. Localized microglial activation was also evident from lectin immunostaining adjacent to the cannula track of LPS-treated mice. Quantification of thioflavine-S-positive Abeta deposits revealed a marked acceleration of amyloid deposition in LPS-treated APPV717F+/+-apoE+/+ mice compared to nontreated or vehicle-treated APPV717F+/+-apoE+/+ mice (P = 0.005). By contrast, no amyloid deposits were detected by thioflavine-S staining in LPS or vehicle-treated apoE-deficient APPV717F TG mice. Our data suggest that neuroinflammation can accelerate amyloid deposition in the APPV717F+/+ mouse model of AD and that this process requires the expression of apoE.

Statistical aspects of quantitative image analysis of beta-amyloid in the APP(V717F) transgenic mouse model of Alzheimer's disease.

Cerebral beta-amyloidosis is a central part of the neuropathology of Alzheimer's disease (AD). Quantitation of beta-amyloid plaques in the human AD brain, and in animal models of AD, is an important study endpoint in AD research. Methodologic approaches to the measurement of beta-amyloid in the brain vary between investigators, and these differences affect outcome measures. Here, one quantitative approach to the measurement of beta-amyloid plaques in brain sections was analyzed for sources of variability due to sampling. Brain tissue was from homozygous APP(V717F) transgenic male mice. Sampling variables were at the mouse and microscopic slide and field levels. Results indicated that phenotypic variability in the mouse sample population was the largest contributor to the standard error of the analyses. Within each mouse, variability between slides or between fields within slides had smaller effects on the error of the analyses. Therefore, when designing studies of adequate power, in this and in other similar models of cerebral beta-amyloidosis, sufficient numbers of mice per group must be included in order for change in mean plaque burden attributable to an experimental variable to outweigh phenotypic variability.

Peripheral anti-A beta antibody alters CNS and plasma A beta clearance and decreases brain A beta burden in a mouse model of Alzheimer's disease.

Active immunization with the amyloid beta (A beta) peptide has been shown to decrease brain A beta deposition in transgenic mouse models of Alzheimer's disease and certain peripherally administered anti-A beta antibodies were shown to mimic this effect. In exploring factors that alter A beta metabolism and clearance, we found that a monoclonal antibody (m266) directed against the central domain of A beta was able to bind and completely sequester plasma A beta. Peripheral administration of m266 to PDAPP transgenic mice, in which A beta is generated specifically within the central nervous system (CNS), results in a rapid 1,000-fold increase in plasma A beta, due, in part, to a change in A beta equilibrium between the CNS and plasma. Although peripheral administration of m266 to PDAPP mice markedly reduces A beta deposition, m266 did not bind to A beta deposits in the brain. Thus, m266 appears to reduce brain A beta burden by altering CNS and plasma A beta clearance.

DoMCoSAR: a novel approach for establishing the docking mode that is consistent with the structure-activity relationship. Application to HIV-1 protease inhibitors and VEGF receptor tyrosine kinase inhibitors.

DoMCoSAR is a novel approach for statistically determining the docking mode that is consistent with a structure-activity relationship. The approach establishes the binding mode for the compounds in a chemical series with the assumption that all molecules exhibit the same binding mode. It involves three stages. In the first stage all molecules that belong to a given chemical series are docked to the active site of the protein target. The only bias used in the docking at this stage involves the location of the protein binding site. Coordinates of the common substructure (CS) that results from the unbiased docking are then clustered to establish the major substructure docking modes. In the second stage all molecules are docked to the major docking modes (MDMs) with constraints based on the common substructure. The third stage generates, for the major docking modes, interaction-based descriptors that include electrostatic, VDW, strain, and solvation contributions. The problem of docking mode evaluation is now reduced to the question of which descriptor set is more predictive. To establish a quantitative comparison of the descriptor sets associated with the major docking modes, we use 50 instances of random 4-fold cross-validation. For each 4-fold cross-validation the predictive squared correlation coefficient (R(2)) is computed. t-Tests are applied to establish significance of the differences in mean R(2) for one docking mode versus another. We test the methodology on two test cases: HIV-1 protease inhibitors (Holloway et al. J. Med. Chem. 1995, 38, 305-317) and vascular endothelial growth factor (VEGF) receptor tyrosine kinase oxoindoles (Sun et al. J. Med. Chem. 1998, 41, 2588-2603). For both test cases there is statistically significant preference for the binding mode consistent with the X-ray structure. The appeal of this methodology is that researchers gain the objectivity of statistical justification for the selected docking mode. The methodology is relatively insensitive to subtle variations of the protein structure that include, but are not limited to, side chain and small backbone rearrangement during binding. In addition, predictive models that result from the approach can be used to further optimize chemical series.

Apolipoprotein E is essential for amyloid deposition in the APP(V717F) transgenic mouse model of Alzheimer's disease.

We quantified the amount of amyloid beta-peptide (Abeta) immunoreactivity as well as amyloid deposits in a large cohort of transgenic mice overexpressing the V717F human amyloid precursor protein (APP(V717F+/-) TG mice) with no, one, or two mouse apolipoprotein E (Apoe) alleles at various ages. Remarkably, no amyloid deposits were found in any brain region of APP(V717F+/-) Apoe(-/-) TG mice as old as 22 mo of age, whereas age-matched APP(V717F +/-) Apoe(+/-) and Apoe(+/+) TG mice display abundant amyloid deposition. The amount of Abeta immunoreactivity in the hippocampus was also markedly reduced in an Apoe gene dose-dependent manner (Apoe(+/+) > Apoe(+/-) >> Apoe(-/-)), and no Abeta immunoreactivity was detected in the cerebral cortex of APP(V717F+/-) Apoe(-/-) TG mice at any of the time points examined. The absence of apolipoprotein E protein (apoE) dramatically reduced the amount of both Abeta(1-40) and Abeta(1-42) immunoreactive deposits as well as the resulting astrogliosis and microgliosis normally observed in APP(V717F) TG mice. ApoE immunoreactivity was detected in a subset of Abeta immunoreactive deposits and in virtually all thioflavine-S-fluorescent amyloid deposits. Because the absence of apoE alters neither the transcription or translation of the APP(V717F) transgene nor its processing to Abeta peptide(s), we postulate that apoE promotes both the deposition and fibrillization of Abeta, ultimately affecting clearance of protease-resistant Abeta/apoE aggregates. ApoE appears to play an essential role in amyloid deposition in brain, one of the neuropathological hallmarks of Alzheimer's disease.

Long-term effects of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate and 6-nitro-7-sulphamoylbenzo(f)quinoxaline-2,3-dione in the rat basal ganglia: calcification, changes in glutamate receptors and glial reactions.

Previous data from our laboratory indicate that 25 mM ibotenic acid induces intracellular calcifications in the rat basal forebrain. Because of the lack of specificity of ibotenic acid for a glutamate receptor subtype, a dose-response study with alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate was undertaken and calcified areas (identified with Alizarin Red staining) as well as astro- and microglial reactions (by autoradiography with [3H]lazabemide and [3H]Ro 5-4864) were quantified at one month post-lesion. alpha-Amino-3-hydroxy-5-methyl-4-isoxazole propionate administered into the globus pallidus induced, in a dose-dependent manner, the formation of calcium deposits and the activation of both glial cells, the microglial reaction being particularly robust. From this study, a dose of 5.4 mM alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate was selected for further experiments. [3H]alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate, [3H]dizocilpine maleate and [3H]PN 200-110 binding in vitro were performed to assess autoradiographically whether the tissue damage was associated with changes in glutamate receptors and calcium channel binding sites. In the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate-treated animals, the specific binding of [3H]alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate was significantly reduced by 28% in the lesioned ventral pallidum, whereas it was unchanged in the globus pallidus and substantia innominata. In these three nuclei, calcifications developed and an increase in both glial markers was measured. In contrast, the binding of [3H]PN 200-110 and [3H]dizocilpine maleate were unaffected. Co-injection of 15 mM 6-nitro-7-sulphamoylbenzo(f)quinoxaline-2,3-dione, a selective alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate/kainate receptor antagonist, prevented the formation of calcium concretions, the microglial reaction and the decrease in [3H]alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate binding but it failed to inhibit totally the astroglial reaction induced by alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate. This may suggest that the microglial reaction and calcification take place through different mechanisms from the astrogliosis associated with the neuronal loss. In conclusion, acute administration of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate in the rat globus pallidus elicits a dose-dependent calcification process associated with a chronic reaction of astrocytes and microglia. alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate-induced injury is accompanied by a slight reduction of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptors in the ventral pallidum, whereas the binding of N-methyl-D-aspartate and L-type calcium channels receptors remains unchanged in any lesioned nucleus.

Molecular diversity in chemical databases: comparison of medicinal chemistry knowledge bases and databases of commercially available compounds.

A molecular descriptor space has been developed which describes structural diversity. Large databases of molecules have been mapped into it and compared. This analysis used five chemical databases, CMC and MDDR, which represent knowledge bases containing active medicinal agents, ACD and SPECS, two databases of commercially available compounds, and finally the Wellcome Registry. Together these databases contained more than 300,000 structures. Topological indices and the free energy of solvation were computed for each compound in the databases. Factor analysis was used to reduce the dimensionality of the descriptor space. Low density observations were deleted as a way of removing outliers, which allowed a further reduction in the descriptor space of interest. The five databases could then be compared on an efficient basis using a metric developed for this purpose. A Riemann gridding scheme was used to subdivide the factor space into subhypercubes to obtain accurate comparisons. Most of the 300,000 structures were highly clustered, but unique structures were found. An analysis of overlap between the biological and commercial databases was carried out. The metric provides a useful algorithm for choosing screening sets of diverse compounds from large databases.