Low molecular weight chondroitin sulfate ameliorates pathological changes in 5XFAD mice by improving various functions in the brain.

Our previous study found that low molecular weight chondroitin sulfate (LMWCS) had neuroprotective effects against the toxicity of amyloid-ß (Aß) peptides both in vitro and in vivo, and we speculated that the effects might be related with its anti-oxidative activities. In this study, the anti-Alzheimer's disease (AD) activity of LMWCS was further studied in 5XFAD transgenic mice. After 4-month gavage, the levels of Aß1-42 level, amyloid precursor protein (APP) and presenilin 1 (PS1) were significantly decreased in the brains of 5XFAD mice, indicating the alteration of APP metabolism by LMWCS. Besides, LMWCS inhibited the secretions of pro-inflammatory cytokines, including interleukin-1ß (IL-1ß), tumor necrosis factor-α (TNF-α) and IL-6. Furthermore, the suppression of neuroinflammation by LMWCS was supported by the decreased expressions of glial fibrillary acidic protein (GFAP) and toll-like receptor 2 (TLR2) in the brains. LMWCS also reduced the production of reactive oxygen species (ROS) and the level of phospho-tau (Ser404) in the brains. Nevertheless, the changes in the behavior tests were moderate. In conclusion, LMWCS administration ameliorated APP metabolism, neuroinflammation, ROS production and tau protein abnormality in the brains of 5XFAD mice, displaying the potential to improve the pathological changes of AD mouse brain. LMWCS could be considered as a promising anti-AD drug candidate, nonetheless, the therapy regimen need to be optimized to improve its pharmacotherapy efficacy.

Comparative Effects of Alpha- and Gamma-Tocopherol on Mitochondrial Functions in Alzheimer's Disease In Vitro Model.

Vitamin E acts as an antioxidant and reduces the level of reactive oxygen species (ROS) in Alzheimer's disease (AD). Alpha-tocopherol (ATF) is the most widely studied form of vitamin E besides gamma-tocopherol (GTF) which also shows beneficial effects in AD. The levels of amyloid-beta (Aß) and amyloid precursor protein (APP) increased in the brains of AD patients, and mutations in the APP gene are known to enhance the production of Aß. Mitochondrial function was shown to be affected by the increased level of Aß and may induce cell death. Here, we aimed to compare the effects of ATF and GTF on their ability to reduce Aß level, modulate mitochondrial function and reduce the apoptosis marker in SH-SY5Y cells stably transfected with the wild-type or mutant form of the APP gene. The Aß level was measured by ELISA, the mitochondrial ROS and ATP level were quantified by fluorescence and luciferase assay respectively whereas the complex V enzyme activity was measured by spectrophotometry. The expressions of genes involved in the regulation of mitochondrial membrane permeability such as voltage dependent anion channel (VDAC1), adenine nucleotide translocase (ANT), and cyclophilin D (CYPD) were determined by quantitative real-time polymerase chain reaction (qRT-PCR), while the expressions of cyclophilin D (CypD), cytochrome c, Bcl2 associated X (BAX), B cell lymphoma-2 (Bcl-2), and pro-caspase-3 were determined by western blot. Our results showed that mitochondrial ROS level was elevated accompanied by decreased ATP level and complex V enzyme activity in SH-SY5Y cells expressing the mutant APP gene (p < 0.05). Treatment with both ATF and GTF reduced the mitochondrial ROS level with maximum reduction was observed in the cells treated with high concentrations of ATF and GTF (p < 0.05). However, only GTF at 80 µM significantly increase the ATP level and complex V enzyme activity (p < 0.05). VDAC1 and CYPD were downregulated and CypD protein was significantly overexpressed in cells transfected with the wild-type (WT) and mutant APP gene (p < 0.05). Cytochrome c release, the ratio of BAX/Bcl-2, and pro-caspase-3 expression increased in cells expressing mutated APP gene (p < 0.05). The expression of CypD and pro-caspase 3 protein, and the ratio of BAX/Bcl-2 were increased in the following order; SH-SY5Y-APP-WT < SH-SY5Y-APP Swe

Neuroprotective Effect of ß-secretase Inhibitory Peptide from Pacific Hake (Merluccius productus) Fish Protein Hydrolysate.

BACKGROUND: Various methodologies have been employed for the therapeutic interpolation of the progressive brain disorder Alzheimer's disease. Thus, ß-secretase inhibition is significant to prevent disease progression in the early stages. OBJECTIVE: This study seeks to purify and characterize a novel ß-secretase inhibitory peptide from Pacific hake enzymatic hydrolysate. METHODS: A potent ß-secretase inhibitory peptide was isolated by sequential purifications using Sephadex G-25 column chromatography and octadecylsilane (ODS) C18 reversed-phase HPLC. A total of seven peptides were synthesized using the isolated peptide sequences. SH-SY5Y cells stably transfected with the human ''Swedish'' amyloid precursor protein (APP) mutation APP695 (SH-SY5YAPP695swe) were used as an in-vitro model system to investigate the effect of Leu-Asn peptide on APP processing. RESULTS: The ß-secretase inhibitory activity (IC50) of the purified peptide (Ser-Leu-Ala-Phe-Val-Asp- Asp-Val-Leu-Asn) from fish protein hydrolysate was 18.65 µM and dipeptide Leu-Asn was the most potent ß-secretase inhibitor (IC50 value = 8.82 µM). When comparing all the seven peptides, the inhibition pattern of Leu-Asn dipeptide was found to be competitive by Lineweaver-Burk plot and Dixon plot (Ki value = 4.24 µM). The 24 h treatment with Leu-Asn peptide in SH-SY5Y cells resulted in reducing the ß-amyloid (Aß) production in a dose-dependent manner. CONCLUSION: Therefore, the results of this study suggest that ß-secretase inhibitory peptides derived from marine organisms could be potential candidates to develop nutraceuticals or pharmaceuticals as antidementia agents.

The cyanobacterial neurotoxin ß-N-methylamino-l-alanine prevents addition of heparan sulfate to glypican-1 and increases processing of amyloid precursor protein in dividing neuronal cells.

The neurotoxin ß-N-methylamino-l-alanine replaces l-serine in proteins and produces Alzheimer-like pathology. In proteoglycans, e.g. glypican-1, this should preclude substitution with heparan sulfate chains. Reduced release of heparan sulfate should increase ß-secretase activity and processing of amyloid precursor protein. Cultured cells were treated with ß-N-methylamino-l-alanine during the growth-phase and the effect on heparan sulfate substitution and amyloid precursor protein processing was evaluated using antibodies specific for heparan sulfate, the N- and C-termini of the C-terminal fragment of ß-cleaved amyloid precursor protein, and amyloid beta followed by immunofluorescence microscopy, flow cytometry or SDS-PAGE. Mouse fibroblasts, N2a neuroblastoma cells and human neural stem cells released less heparan sulfate when grown in the presence of ß-N-methylamino-l-alanine. Cells expressing a recombinant, anchor-less glypican-1 secreted heparan sulfate-deficient glypican-1. There was increased processing of amyloid precursor protein in N2a cells when grown in the presence of the neurotoxin. The degradation products accumulated in cytoplasmic clusters. Secretion of amyloid beta increased approx. 3-fold. Human neural stem cells also developed cytoplasmic clusters containing degradation products of amyloid precursor protein. When non-dividing mouse N2a cells or cortical neurons were exposed to ß-N-methylamino-l-alanine there was no effect on heparan sulfate substitution in glypican-1 or on amyloid precursor protein processing.

Small Molecule Amyloid-ß Protein Precursor Processing Modulators Lower Amyloid-ß Peptide Levels via cKit Signaling.

Alzheimer's disease (AD) is characterized by the accumulation of neurotoxic amyloid-ß (Aß) peptides consisting of 39-43 amino acids, proteolytically derived fragments of the amyloid-ß protein precursor (AßPP), and the accumulation of the hyperphosphorylated microtubule-associated protein tau. Inhibiting Aß production may reduce neurodegeneration and cognitive dysfunction associated with AD. We have previously used an AßPP-firefly luciferase enzyme complementation assay to conduct a high throughput screen of a compound library for inhibitors of AßPP dimerization, and identified a compound that reduces Aß levels. In the present study, we have identified an analog, compound Y10, which also reduced Aß. Initial kinase profiling assays identified the receptor tyrosine kinase cKit as a putative Y10 target. To elucidate the precise mechanism involved, AßPP phosphorylation was examined by IP-western blotting. We found that Y10 inhibits cKit phosphorylation and increases AßPP phosphorylation mainly on tyrosine residue Y743, according to AßPP751 numbering. A known cKit inhibitor and siRNA specific to cKit were also found to increase AßPP phosphorylation and lower Aß levels. We also investigated a cKit downstream signaling molecule, the Shp2 phosphatase, and found that known Shp2 inhibitors and siRNA specific to Shp2 also increase AßPP phosphorylation, suggesting that the cKit signaling pathway is also involved in AßPP phosphorylation and Aß production. We further found that inhibitors of both cKit and Shp2 enhance AßPP surface localization. Thus, regulation of AßPP phosphorylation by small molecules should be considered as a novel therapeutic intervention for AD.

[Effect of ßsheet blocking peptide H102 on APP metabolic enzymes in hippocampal brain of double transgenic AD mice].

OBJECTIVE: To investigate the effect of ß-sheet breaker peptide H102 on APP associated secretase in the hippocampus brain regions of APP/PS1 double transgenic mice(AD mice). METHODS: Thirty 6-month-old APP/PS1 double transgenic mice were randomly divided into AD group and H102 group, a group of C57BL/6J mice with the same age, number and background was set as controls(n=15). H102 (5.8 mg/kg) 5 µl was infused by intranasal administration to mice in H102 treatment group, and equal volume of blank solution of H102 was given to mice in control group and AD group. The ability of spatial reference memory was tested by Morris water maze after 30 days of treatment. And then immunohistochemistry tests and Western blot were used to detect the content of α-secretase (ADAM10, ADAM17), ß-secretase (BACE1), γ-secretase (PS1, APH1a, PEN2) in the hippocampus brain regions. RESULTS: Compared with the control group, the expression of BACE1, PS1, PEN-2 and APH1-a protein in the hippocampus of AD group were significantly increased, ADAM10, ADAM17 protein expression were significantly reduced (P<0.05); Compared with the model group, H102 could significantly improve the spatial learning and memory ability of AD mice, significantly decreased the expression of BACE1, PS1, PEN-2 and APH1-a protein in the hippocampus, significantly increased the expression of ADAM10 and ADAM17 protein(P<0.05). CONCLUSIONS: ß sheet peptides blocked H102 can reduce the formation of Aß in the hippocampus brain area, improve the activity of α-secretase in the hippocampus brain region, decrease the activity of ß-and γ-secretase, improve the learning and memory ability of AD mice.

Axonal protection via modulation of the amyloidogenic pathway in tumor necrosis factor-induced optic neuropathy.

PURPOSE: To examine the changes in and localization of phosphorylated presenilin1 (p-PS1) and amyloid precursor protein (APP) in the optic nerve after intravitreal injection of TNF and to investigate the role of γ-secretase in the cleavage of APP in optic nerve degeneration. METHODS: Groups of rats were euthanatized at 1 or 2 weeks after intravitreal injection of TNF. Levels of p-PS1 protein in the optic nerve were determined by immunoblotting and immunohistochemistry. The localization of APP was determined by immunohistochemistry, and its downstream cleavage was determined by immunoprecipitation using 6E10 antibody followed by immunoblotting with an APP intracellular domain (AICD) antibody. The effect of a γ-secretase inhibitor on TNF-induced optic nerve degeneration was determined by counting the number of axons. RESULTS: p-PS1 was increased in the optic nerve after TNF injection and was found to colocalize with vimentin and glial fibrillary acidic protein, markers of astrocytes. Immunoprecipitation using 6E10 antibody followed by immunoblotting with AICD antibody revealed an increase in γ-secretase activation in the optic nerve after TNF injection, which was inhibited by treatment with the γ-secretase inhibitor. Moreover, γ-secretase inhibition significantly prevented the loss of axons in the optic nerve after TNF injection. CONCLUSIONS: The increase in p-PS1 and activation of γ-secretase in the optic nerve may be associated with TNF-induced axonal degeneration. Modulation of γ-secretase activity may be useful for the treatment of TNF-related optic neuropathy.

Resveratrol, a neuroprotective supplement for Alzheimer's disease.

The polyphenolic compound resveratrol (3,4',5-trihydroxystilbene) is a naturally occurring phytochemical which has been found in more than 70 plant species, including herbs and human food products such as grapes, berries, and peanuts. Resveratrol was first isolated in 1940; however, little attention was paid to it until its benefits in coronary heart disease were studied in 1992. Since then, increasing evidence has indicated that resveratrol may be useful in treating cardiovascular diseases, cancers, pain, inflammation, tissue injury, and in reducing the risk of neurodegenerative disorders, especially Alzheimer's disease (AD). AD is characterized by a progressive dementia, and is one of the most common neurodegenerative disorders in the elderly. It has been reported that resveratrol exhibits neuroprotective benefits in animal models of AD. Resveratrol promotes the non-amyloidogenic cleavage of the amyloid precursor protein, enhances clearance of amyloid beta-peptides, and reduces neuronal damage. Despite the effort spent trying to understand the mechanisms by which resveratrol functions, the research work in this field is still incomplete. Many concerns such as bioavailability, biotransformation, synergism with other dietary factors, and risks inherent to its possible pro-oxidant activities still need to be addressed. This review summarizes and discusses the neuroprotective effects of resveratrol on AD, and their potential mechanisms.

A novel pathway for amyloid precursor protein processing.

Amyloid precursor protein (APP) can be proteolytically processed along two pathways, the amyloidogenic that leads to the formation of the 40-42 amino acid long Alzheimer-associated amyloid ß (Aß) peptide and the non-amyloidogenic in which APP is cut in the middle of the Aß domain thus precluding Aß formation. Using immunoprecipitation and mass spectrometry we have shown that Aß is present in cerebrospinal fluid (CSF) as several shorter isoforms in addition to Aß1-40 and Aß1-42. To address the question by which processing pathways these shorter isoforms arise, we have developed a cell model that accurately reflects the Aß isoform pattern in CSF. Using this model, we determined changes in the Aß isoform pattern induced by α-, ß-, and γ-secretase inhibitor treatment. All isoforms longer than and including Aß1-17 were γ-secretase dependent whereas shorter isoforms were γ-secretase independent. These shorter isoforms, including Aß1-14 and Aß1-15, were reduced by treatment with α- and ß-secretase inhibitors, which suggests the existence of a third and previously unknown APP processing pathway involving concerted cleavages of APP by α- and ß-secretase.

Oleic acid ameliorates amyloidosis in cellular and mouse models of Alzheimer's disease.

Several lines of evidence support protective as well as deleterious effects of oleic acid (OA) on Alzheimer's disease (AD) and other neurological disorders; however, the bases of these effects are unclear. Our investigation demonstrates that amyloid precursor protein (APP) 695 transfected Cos-7 cells supplemented with OA have reduced secreted amyloid-beta (Aß) levels. An early-onset AD transgenic mouse model expressing the double-mutant form of human APP, Swedish (K670N/M671L) and Indiana (V717F), corroborated our in vitro findings when they were fed a high-protein, low-fat (18% reduction), cholesterol-free diet enriched with OA. These mice exhibited an increase in Aß40/Aß42 ratio, reduced levels of beta-site APP cleaving enzyme (BACE) and reduced presenilin levels along with reduced amyloid plaques in the brain. The decrease in BACE levels was accompanied by increased levels of a non-amyloidogenic soluble form of APP (sAPPα). Furthermore, the low-fat/+OA diet resulted in an augmentation of insulin-degrading enzyme and insulin-like growth factor-II. These results suggest that OA supplementation and cholesterol intake restriction in a mouse model of AD reduce AD-type neuropathology.

miR-20a promotes proliferation and invasion by targeting APP in human ovarian cancer cells.

MicroRNAs (miRNAs) are emerging as a class of small regulated RNAs, and the alterations of miRNAs are implicated in the initiation and progression of human cancers. Our study shows that inhibition of miR-20a in OVCAR3 ovarian cancer cell line could suppress, whereas overexpression of miR-20a could enhance cell long-term proliferation and invasion. We also confirmed amyloid precursor protein (APP) as a direct target gene of miR- 20a. Furthermore, suppression of APP expression could also promote ovarian cancer cell proliferation and invasion, which is consistent with the results of miR-20a overexpression. Therefore, we concluded that the regulation of APP is an important mechanism for miR-20a to promote proliferation and invasion in ovarian cancer cells.

Vascular endothelial growth factor (VEGF) affects processing of amyloid precursor protein and beta-amyloidogenesis in brain slice cultures derived from transgenic Tg2576 mouse brain.

The up-regulation of the angiogenic vascular endothelial growth factor (VEGF) in brains of Alzheimer patients in close relationship to beta-amyloid (Abeta) plaques, suggests a link of VEGF action and processing of the amyloid precursor protein (APP). To reveal whether VEGF may affect APP processing, brain slices derived from 17-month-old transgenic Tg2576 mice were exposed with 1ng/ml VEGF for 6, 24, and 72h, followed by assessing cytosolic and membrane-bound APP expression, level of both soluble and fibrillar Abeta-peptides, as well as activities of alpha- and beta-secretases in brain slice tissue preparations. Treatment of brain slices with VEGF did not significantly affect the expression level of APP, regardless of the exposure time studied. In contrast, VEGF exposure of brain slices for 6h reduced the formation of soluble, SDS extractable Abeta(1-40) and Abeta(1-42) as compared to brain slice cultures incubated in the absence of any drug, while the fibrillar Abeta peptides did not change significantly. This effect was less pronounced 24h after VEGF exposure, but was no longer detectable when brain slices were exposed by VEGF for 72h, which indicates an adaptive response to chronic VEGF exposure. The VEGF-mediated reduction in Abeta formation was accompanied by a transient decrease in beta-secretase activity peaking 6h after VEGF exposure. To reveal whether the VEGF-induced changes in soluble Abeta-level may be due to actions of VEGF on Abeta fibrillogenesis, the fibrillar status of Abeta was examined using the thioflavin-T binding assay. Incubation of Abeta preparations obtained from Tg2576 mouse brain cortex, in the presence of VEGF slightly decreased the fibrillar content with increasing incubation time up to 72h. The data demonstrate that VEGF may affect APP processing, at least in vitro, suggesting a role of VEGF in the pathogenesis of Alzheimer's disease.

Protective effects of progesterone administration on axonal pathology in mice with experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE), an induced model of Multiple Sclerosis presents spinal cord demyelination, axonal pathology and neuronal dysfunction. Previous work has shown that progesterone attenuated the clinical severity, demyelination and neuronal dysfunction of EAE mice (Garay et al., J. Steroid Biochem. Mol. Biol., 2008). Here we studied if progesterone also prevented axonal damage, a main cause of neurological disability. To this end, some axonal parameters were compared in EAE mice pretreated with progesterone a week before immunization with MOG(40-54) and in a group of steroid-free EAE mice. On day 16th after EAE induction, we determined in both groups and in control mice: a) axonal density in semithin sections of the spinal cord ventral funiculus; b) appearance of amyloid precursor protein (APP) immunopositive spheroids as an index of damaged axons; c) levels of the growth associated protein GAP43 mRNA and immunopositive cell bodies, as an index of aberrant axonal sprouting. Steroid-naive EAE mice showed decreased axonal density, shrunken axons, abundance of irregular vesicular structures, degenerating APP+ axons, increased expression of GAP43 mRNA and immunoreactive protein in motoneurons. Instead, EAE mice receiving progesterone treatment showed increased axonal counts, high proportion of small diameter axons, reduced APP+ profiles, and decreased GAP43 expression. In conclusion, progesterone enhanced axonal density, decreased axonal damage and prevented GAP43 hyperexpression in the spinal cord of EAE mice. Thus, progesterone also exerts protective effects on the axonal pathology developing in EAE mice.

Nonsteroidal anti-inflammatory drugs and ectodomain shedding of the amyloid precursor protein.

BACKGROUND: Epidemiological studies have suggested that long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with a reduced incidence of Alzheimer's disease (AD). Several mechanisms have been proposed to explain these findings including increased shedding of the soluble ectodomain of the amyloid precursor protein (sAPP), which functions as a neurotrophic and neuroprotective factor in vitroand in vivo. OBJECTIVE: To clarify whether NSAIDs consistently stimulate sAPP secretion. METHODS: 293-EBNA cells with stable overexpression of an APP-alkaline phosphatase fusion protein (APP-AP), SH-SY5Y and PC12 cells or primary telencephalic chicken neurons were treated with ibuprofen or indomethacin. APP shedding was then determined by measuring AP activity in conditioned media, Western blot analysis with antibodies against total sAPP or specific for sAPP-alpha, or in a pulse-chase paradigm. RESULTS: AP activity in conditioned media was not increased after NSAID treatment of 293-EBNA cells whereas it was elevated by phorbol ester. Surprisingly, ibuprofen or indomethacin treatment of SH-SY5Y and PC12 cells expressing endogenous APP did not cause changes in sAPP or sAPP-alpha secretion or downregulation of cellular APP. These findings were further corroborated in primary chicken neuronal cultures. CONCLUSIONS: Using various experimental settings, we were unable to confirm sAPP or sAPP-alpha stimulation with the NSAIDs ibuprofen and indomethacin in transfected and nontransfected cells of neuronal and nonneuronal origin. Importantly, these findings seem to rule out chronic sAPP stimulation as an alternative mechanism of NSAID action in AD.

Huperzine A regulates amyloid precursor protein processing via protein kinase C and mitogen-activated protein kinase pathways in neuroblastoma SK-N-SH cells over-expressing wild type human amyloid precursor protein 695.

Alpha-secretase (alpha-secretase), cleaves the amyloid precursor protein (APP) within the amyloid-beta (Abeta) sequence, resulting in the release of a secreted fragment of APP (alphaAPPs) and precluding Abeta generation. We investigated the effects of the acetylcholinesterase inhibitor, huperzine A (Hup A), on APP processing and Abeta generation in human neuroblastoma SK-N-SH cells overexpressing wild-type human APP695. Hup A dose-dependently (0-10 microM) increased alphaAPPs release. Therefore, we evaluated two alpha-secretase candidates, a disintegrin and metalloprotease (ADAM) 10 and ADAM17 in Hup A-induced non-amyloidogenic APP metabolism. Hup A enhanced the level of ADAM10, and the inhibitor of tumor necrosis factor-alpha converting enzyme (TACE)/ADAM17 inhibited the Hup A-induced rise in alphaAPPs levels, further suggesting Hup A directed APP metabolism toward the non-amyloidogenic alpha-secretase pathway. Hup A had no effect on Abeta generation in this cell line. The steady-state levels of full-length APP and cell viability were unaffected by Hup A. Alpha-APPs release induced by Hup A treatment was significantly reduced by muscarinic acetylcholine receptor antagonists (particularly by an M1 antagonist), protein kinase C (PKC) inhibitors, GF109203X and calphostin C, and the mitogen-activated kinase kinase (MEK) inhibitors, U0126 and PD98059. Furthermore, Hup A markedly increased the phosphorylation of p44/p42 mitogen-activated protein (MAP) kinase, which was blocked by treatment with U0126 and PD98059. In addition, Hup A inhibited acetylcholinesterase activity by 20% in neuroblastoma cells. Our results indicate that the activation of muscarinic acetylcholine receptors, PKC and MAP kinase may be involved in Hup A-induced alphaAPPs secretion in neuroblastoma cells and suggest multiple pharmacological mechanisms of Hup A regarding the treatment of Alzheimer's disease (AD).

Receptor- and non-receptor tyrosine kinases induce processing of the amyloid precursor protein: role of the low-density lipoprotein receptor-related protein.

The Alzheimer's beta-amyloid peptides derive from the proteolytic processing of the beta-amyloid precursor protein, APP, by beta- and gamma-secretases. The regulation of this processing is not fully understood. Experimental evidence suggests that the activation of pathways involving protein tyrosine kinases, such as PDGFR and Src, could induce the cleavage of APP and in turn the generation of amyloid peptides. In this paper we addressed the effect of receptor and nonreceptor protein tyrosine kinases on the cleavage of APP and the mechanisms of their action. To this aim, we developed an in vitro system based on the APP-Gal4 fusion protein stably transfected in SHSY5Y neuroblastoma cell line. The cleavage of this molecule, induced by various stimuli, results in the activation of the transcription of the luciferase gene under the control of Gal4 cis-elements. By using this experimental system we demonstrated that, similarly to Src, three tyrosine kinases, TrkA, Ret and EGFR, induced the cleavage of APP-Gal4. We excluded that this effect was mediated by the activation of Ras-MAPK, PI3K-Akt and PLC-gamma pathways. Furthermore, the direct phosphorylation of the APP cytosolic domain does not affect Abeta peptide generation. On the contrary, experiments in cells lacking the LDL-receptor related protein LRP support the hypothesis that the interaction of APP with LRP is required for the induction of APP cleavage by tyrosine kinases.

Mechanisms of aluminum-induced neurodegeneration in animals: Implications for Alzheimer's disease.

For four decades the controversial question concerning a possible role for aluminum neurotoxicity in contributing to the pathogenesis of Alzheimer's disease has been debated, and studies by different investigators have yielded contradictory results. The lack of sensitivity to aluminum neurotoxicity in transgenic mouse models of Alzheimer's disease has not allowed the system to be used to explore important aspects of this toxicity. Rabbits are particularly sensitive to aluminum neurotoxicity and they develop severe neurological changes that are dependent on dose, age and route of administration. The most prominent feature induced by aluminum in rabbit brain is a neurofibrillary degeneration that shares some similarity with the neurofibrillary tangles found in Alzheimer's disease patients. In the present review we discuss data from our laboratory and others, on the effects of aluminum on behaviour, neurologic function and morphology, using aluminum administered to rabbits via different routes. Finally, we will examine data on the possible cellular mechanisms underlying aluminum neurotoxicity, and potential neuroprotective strategies against aluminum toxicity.

Pomegranate juice decreases amyloid load and improves behavior in a mouse model of Alzheimer's disease.

Although there are no proven ways to delay onset or slow progression of Alzheimer's disease (AD), studies suggest that diet can affect risk. Pomegranates contain very high levels of antioxidant polyphenolic substances as compared to other fruits and vegetables. Polyphenols have been shown to be neuroprotective in different model systems. We asked whether dietary supplementation with pomegranate juice (PJ) would influence behavior and AD-like pathology in a transgenic mouse model. Transgenic mice (APP(sw)/Tg2576) received either PJ or sugar water control from 6 to 12.5 months of age. PJ-treated mice learned water maze tasks more quickly and swam faster than controls. Mice treated with PJ had significantly less (approximately 50%) accumulation of soluble Abeta42 and amyloid deposition in the hippocampus as compared to control mice. These results suggest that further studies to validate and determine the mechanism of these effects, as well as whether substances in PJ may be useful in AD, should be considered.

The effect of S-adenosylmethionine on CNS gene expression studied by cDNA microarray analysis.

High homocysteine (Hcy) together with low S-adenosylmethionine (SAM) levels are often observed in Alzheimer disease (AD), and this could be a sign of alteration of SAM/Hcy metabolism. It has already been shown that DNA methylation is involved in amyloid-beta-protein precursor (AbetaPP) processing and amyloid-beta(Abeta) production through the regulation of Presenilin 1 (PS1) expression and that exogenous SAM can silence the gene reducing Abeta. To investigate whether SAM administration globally influenced gene expression in the brain, we analysed 588 genes of the central nervous system in SK-N-BE neuroblastoma cells, with cDNA probes derived from untreated (DM; Differentiation Medium) or SAM treated (DM+SAM) cultures. In these conditions only seven genes were modulated by SAM treatment (and therefore by DNA methylation); three were up-regulated and four down-regulated, showing low levels of modulation.

RNA therapeutics directed to the non coding regions of APP mRNA, in vivo anti-amyloid efficacy of paroxetine, erythromycin, and N-acetyl cysteine.

Lead compounds directed to the 5' leader of the Amyloid Precursor Protein transcript (i.e., paroxetine (SSRI), N-acetyl cysteine (antioxidant), and erythromycin (macrolide antibiotic)) were employed in a pilot study to evaluate their anti-amyloid efficacy in the TgCRND8 transgenic mouse model for Alzheimer's Disease (AD). The relative levels of Abeta peptide were reduced after exposure of mice to paroxetine (N=5), NAC (N=7), and erythromycin (N=7) relative to matched placebo counterparts. Paroxetine limited the levels of APP holoprotein and total Abeta peptide levels (measurements of Abeta were performed at two separate sites by quantitative western blotting and ELISA assay). The paroxetine data provided proof-of-concept for our strategy for further screening the APP 5'UTR target to identify novel drugs that exhibit anti-amyloid efficacy in vivo. Erythromycin and azithromycin were macrolide antibiotics that markedly changed the cleavage of the APP C-Terminal Fragment (CTF) in SH-SY5Y cells. Erythromycin provided orally to TgCRND8 mice consistently (100%) reduced brain Abeta(1-42) levels. These data demonstrated a highly statistically significant anti-amyloid trend for paroxetine, NAC and erythromycin. The potential for conducting further studies with these compounds using larger cohorts of TgCRND8 mice is discussed, particularly since erythromycin has recently been exposed to mice for a further 6 months (N=6). It will be possible to employ the chemical structures of paroxetine and erythromycin as starting points for drug design and development for AD therapeutics.