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The fibrinolytic system is composed of the protease plasmin, its precursor plasminogen and their respective activators, tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA), counteracted by their inhibitors, plasminogen activator inhibitor type 1 (PAI-1), plasminogen activator inhibitor type 2 (PAI-2), protein C inhibitor (PCI), thrombin activable fibrinolysis inhibitor (TAFI), protease nexin 1 (PN-1) and neuroserpin. The action of plasmin is counteracted by α2-antiplasmin, α2-macroglobulin, TAFI, and other serine protease inhibitors (antithrombin and α2-antitrypsin) and PN-1 (protease nexin 1). These components are essential regulators of many physiologic processes. They are also involved in the pathogenesis of many disorders. Recent advancements in our understanding of these processes enable the opportunity of drug development in treating many of these disorders.

Extracellular signal-regulated kinase (ERK), also known as classical mitogen-activated protein kinase, plays critical roles in cell regulation. ERK is activated through phosphorylation by a cascade of protein kinases including MEK. Various ligands activate the MEK/ERK pathway through receptor-dependent cell signaling. In cultured cells, many ligands such as growth factors, hormones, cytokines and vasoactive peptides elicit transient activation of MEK/ERK, often peaking at ~10 min after the cell treatment. Here, we describe a novel biological event, in which ligand-mediated cell signaling results in the dephosphorylation of MEK/ERK. Neuromedin N and neurotensin, peptides derived from the same precursor polypeptide, elicit cell signaling through the neurotensin receptors. In cultured human pulmonary artery smooth muscle cells (PASMCs), but not in human pulmonary artery endothelial cells (PAECs), we found that both neuromedin N and neurotensin promoted the dephosphorylation of ERK and MEK. Human PASMCs were found to express neurotensin receptor (NTR)-1, −2 and −3, while human PAECs only express NTR3. Neuromedin N-mediated dephosphorylation was suppressed by small chemical inhibitors of protein phosphatase 1/2A and peptidyl-prolyl isomerase. Transmission electron microscopy showed the formation of endocytic vesicles in response to neuromedin N treatment, and dephosphorylation did not occur when sorting nexin 9, a critical regulator of the endocytic vesicle formation, was knocked down. We conclude that neuromedin N and neurotensin elicit a unique dephosphorylation signaling in the MEK/ERK pathway that is regulated by endocytosis. Considering the pathophysiological importance of the MEK/ERK pathway, this discovery of the dephosphorylation mechanism should advance the field of cell signaling.

Cultures of glial cells and fibroblasts allowed and lead to the identification SERPINE2/Protease Nexin-1 (SERPINE2/PN-1). Cellular, biochemical, immunological and molecular characterization substantiated its variable expression in many organs as a function of development, adult stages, pathological situations or following injury. It is not a circulating serpin, but as other members of the family, its target specificity is influenced by components of the extracellular matrix. The challenges are to identify where and when SERPINE2/PN-1 modulatory action becomes crucial or even possibly specific in a mosaic of feasible in vivo impacts. Data providing correlations are not sufficient to satisfy this aim. Genetically modified mice, or tissue derived thereof, provide interesting in vivo models to identify and study the relevance of this serpin. This review will highlight sometimes-intriguing results indicating a crucial impact of SERPINE2/PN-1, especially in the vasculature, the nervous system or the behavior of cancer cells in vivo. Data presently available will be discussed in an attempt to define general trends in the diversity of SERPINE2/PN-1 modes of action in vivo.

The MIA complex, composed of FAP100 and FAP73, interacts with I1 dynein components and is required for normal ciliary beat frequency., Axonemal dyneins must be precisely regulated and coordinated to produce ordered ciliary/flagellar motility, but how this is achieved is not understood. We analyzed two Chlamydomonas reinhardtii mutants, mia1 and mia2, which display slow swimming and low flagellar beat frequency. We found that the MIA1 and MIA2 genes encode conserved coiled-coil proteins, FAP100 and FAP73, respectively, which form the modifier of inner arms (MIA) complex in flagella. Cryo–electron tomography of mia mutant axonemes revealed that the MIA complex was located immediately distal to the intermediate/light chain complex of I1 dynein and structurally appeared to connect with the nexin–dynein regulatory complex. In axonemes from mutants that lack both the outer dynein arms and the MIA complex, I1 dynein failed to assemble, suggesting physical interactions between these three axonemal complexes and a role for the MIA complex in the stable assembly of I1 dynein. The MIA complex appears to regulate I1 dynein and possibly outer arm dyneins, which are both essential for normal motility.

Matrix metalloproteinase-9 (MMP-9) expression is known to enhance the invasion and metastasis of tumor cells. In previous work based on a proteomic screen, we identified the serpin protease nexin-1 (PN-1) as a potential target of MMP-9. Here, we show that PN-1 is a substrate for MMP-9 and establish a link between PN-1 degradation by MMP-9 and regulation of invasion. PN-1 levels increased in prostate carcinoma cells after downregulation of MMP-9 and in tissues of MMP-9–deficient mice, consistent with PN-1 degradation by MMP-9. We identified three MMP-9 cleavage sites in PN-1 and showed that mutations in those sites made PN-1 more resistant to MMP-9. Urokinase plasminogen activator (uPA) is inhibited by PN-1. MMP-9 augmented uPA activity in the medium of PC3-ML cells by degrading PN-1. Prostate cancer cells, overexpressing PN-1 or treated with MMP-9 shRNA, had reduced cell invasion in Matrigel. PN-1 siRNA restored uPA activity and the invasive capacity. PN-1 mutated in the serpin inhibitory domain, the reactive center loop, failed to inhibit uPA and to reduce Matrigel invasion. This study shows a novel molecular pathway in which MMP-9 regulates uPA activity and tumor cell invasion through cleavage of PN-1. Cancer Res; 70(17); 6988–98. ©2010 AACR.

Phosphoinositides are a type of cellular phospholipid that regulate signaling in a wide range of cellular and physiological processes through the interaction between their phosphorylated inositol head group and specific domains in various cytosolic proteins. These lipids also influence the activity of transmembrane proteins. Aberrant phosphoinositide signaling is associated with numerous diseases, including cancer, obesity, and diabetes. Thus, identifying phosphoinositide-binding partners and the aspects that define their specificity can direct drug development. However, current methods are costly, time-consuming, or technically challenging and inaccessible to many laboratories. We developed a method called PLIF (for "protein-lipid interaction by fluorescence") that uses fluorescently labeled liposomes and tethered, tagged proteins or peptides to enable fast and reliable determination of protein domain specificity for given phosphoinositides in a membrane environment. We validated PLIF against previously known phosphoinositide-binding partners for various proteins and obtained relative affinity profiles. Moreover, PLIF analysis of the sorting nexin (SNX) family revealed not only that SNXs bound most strongly to phosphatidylinositol 3-phosphate (PtdIns3P or PI3P), which is known from analysis with other methods, but also that they interacted with other phosphoinositides, which had not previously been detected using other techniques. Different phosphoinositide partners, even those with relatively weak binding affinity, could account for the diverse functions of SNXs in vesicular trafficking and protein sorting. Because PLIF is sensitive, semiquantitative, and performed in a high-throughput manner, it may be used to screen for highly specific protein-lipid interaction inhibitors.

Proteolytic processing of the amyloid precursor protein (APP) generates large soluble APP derivatives, β-amyloid (Aβ) peptides, and APP intracellular domain. Expression of the extracellular sequences of APP or its Caenorhabditis elegans counterpart has been shown to be sufficient in partially rescuing the CNS phenotypes of the APP-deficient mice and the lethality of the apl-1 null C. elegans, respectively, leaving open the question as what is the role of the highly conserved APP intracellular domain? To address this question, we created an APP knock-in allele in which the mouse Aβ sequence was replaced by the human Aβ. A frameshift mutation was introduced that replaced the last 39 residues of the APP sequence. We demonstrate that the C-terminal mutation does not overtly affect APP processing and amyloid pathology. In contrast, crossing the mutant allele with APP-like protein 2 (APLP2)-null mice results in similar neuromuscular synapse defects and early postnatal lethality as compared with mice doubly deficient in APP and APLP2, demonstrating an indispensable role of the APP C-terminal domain in these development activities. Our results establish an essential function of the conserved APP intracellular domain in developmental regulation, and this activity can be genetically uncoupled from APP processing and Aβ pathogenesis.

This study aimed to find the most sensitive brain region of APP-PS1 mice in early-stage Alzheimer's disease (AD) and to compare the findings with wild-type mouse brain using (1)H high resolution magic angle spectroscopy (HR-MAS). At 18 and 35 weeks of age, the object recognition test was performed with both APP-PS1 and wild-type mice, and the metabolite concentrations were measured in six brain regions at 38-42 weeks using (1)H HR-MAS. Compared to that of wild-type mice, the memory index of the APP-PS1 mice at 18 weeks was not significantly different; however, the memory index of the APP-PS1 mice at 35 weeks was significantly lower. Similar to the results of the (1)H HR-MAS, the [N-acetyl aspartate (NAA)+acetate (Acet)] level in APP-PS1 mice was decreased in the hippocampus and temporal cortex, and the myo-inositol (mIns) level was increased in the entire brain. In addition, scyllo-inositol (sIns) was also elevated in the frontal, occipital, and parietal cortices, hippocampus and thalamus. These findings demonstrated that the behavioral abnormalities of the APP-PS1 mice started at about 30 weeks of age and that the hippocampus and temporal cortex were the most sensitive regions during early-stage AD. In addition, the results of this study confirmed that an increase of mIns and sIns precedes the reduction of the NAA level. These findings demonstrated that the metabolism of the APP-PS1 mouse was associated with early-stage AD. Furthermore, the regional neurochemical profile of APP-PS1 mouse can be used to investigate the pathophysiological mechanisms associated with AD.

Renal pathologists identify the protein component of renal amyloid deposits by immunohistochemistry using antibodies against known amyloidogenic proteins. The majority of amyloid cases can be categorized by a simple antibody panel that includes immunoglobulin light chains lambda and kappa, and serum amyloid A. In some instances, however, these reagents do not recognize materials that stain with Congo red or yield ambiguous staining results, thus creating a diagnostic dilemma. Chemical analysis of fibrils extracted from such a nonreactive renal biopsy led to the discovery of a previously unknown amyloid formed from leukocyte chemotactic factor 2 (LECT2). Over the past 8 years, we received 285 renal amyloid samples, of which 31 remained unclassified. In an effort to determine whether any of the latter samples were LECT2 related, tandem mass spectrometry was performed. In all, 7 of the 31 cases were identified as an amyloid LECT2 (ALECT2), a finding confirmed immunohistochemically using a LECT2-specific antibody. The deposits strongly stained for Congo red and, in most cases, had distinctive morphological features with diffuse involvement of the interstitium, arteries, and glomeruli. Hence, we believe that ALECT2 represents the third common form of renal amyloidosis.

The amphipathicity of the natively unstructured amyloid-beta (Abeta40) peptide may play an important role in its aggregation into beta-sheet rich fibrils, which is linked to the pathogenesis of Alzheimer's disease. Using the air/subphase interface as a model interface, we characterized Abeta's surface activity and its conformation, assembly, and morphology at the interface. Abeta readily adsorbed to the air/subphase interface to form a 20 A thick film and showed a critical micelle concentration of approximately 120 nM. Abeta adsorbed at the air/subphase exhibited in-plane ordering that gave rise to Bragg peaks in grazing-incidence x-ray diffraction measurements. Analysis of the peaks showed that the air/subphase interface induced Abeta to fold into a beta-sheet conformation and to self-assemble into approximately 100 A-sized ordered clusters. The formation of these clusters at the air/subphase interface was not affected by pH, salts, or the presence of sucrose or urea, which are known to stabilize or denature native proteins, suggesting that interface-driven Abeta misfolding and assembly are strongly favored. Furthermore, Abeta at the interface seeded the growth of fibrils in the bulk with a distinct morphology compared to those formed by homogeneous nucleation. Our results indicate that interface-induced Abeta misfolding may serve as a heterogeneous, nucleation-controlled aggregation mechanism for Abeta fibrillogenesis in vivo.

Increasing evidence suggests that depression may be both a cause and consequence of neurological disorders such as Alzheimer's disease (AD), and that anti-depressants could provide an alternative strategy to current AD therapies. Association of side effect and herbal-drug interaction with conventional anti-depressant and St. John's wort warrant investigating new anti-depressant drugs. Anti-depressant effects of ginkgo biloba extract (EGb 761) have been demonstrated in animal models of depression and in human volunteers. We report here that ginkgo flavonols quercetin and kaempferol stimulates depression-related signaling pathways involving brain-derived neurotrophic factor BDNF/phosphorylation of cyclic AMP response element binding protein CREB/postsynaptic density proteins PSD95, and reduces amyloid-beta peptide (Abeta) in neurons isolated from double transgenic AD mouse (TgAPPswe/PS1e9). In addition, enhanced BDNF expression and reduction of Abeta oligomers was confirmed in hippocampus of the double transgenic mice administered with flavonol, which correlates with cognitive improvement behaviors in these mice. The present results suggest that stimulating BDNF and reducing Abeta toxicity by natural flavonols provide a therapeutic implication for treatment of AD.

Formation of new neurons in the adult brain takes place in the subventricular zone and in the subgranule layer of the dentate gyrus throughout life. Neurogenesis is thought to play a role in hippocampus- and olfaction-dependent learning and memory. However, whether impairments in neurogenesis take place in learning and memory disorders, such as Alzheimer's disease, is yet to be established. Importantly, it remains to be elucidated whether neurogenic impairments play a role in the course of the disease or are the result of extensive neuropathology. We now report that transgenic mice harboring familial Alzheimer's disease-linked mutant APPswe/PS1DeltaE9 exhibit severe impairments in neurogenesis that are evident as early as 2 months of age. These mice exhibit a significant reduction in the proliferation of neural progenitor cells and their neuronal differentiation. Interestingly, levels of hyperphosphorylated tau, the cytotoxic precursor of the Alzheimer's disease hallmark neurofibrillary tangles, are particularly high in the neurogenic niches. Isolation of neural progenitor cells in culture reveals that APPswe/PS1DeltaE9-expressing neurospheres exhibit impaired proliferation and tau hyperphosphorylation compared with wildtype neurospheres isolated from nontransgenic littermates. This study suggests that impaired neurogenesis is an early critical event in the course of Alzheimer's disease that may underlie memory impairments, at least in part, and exacerbate neuronal vulnerability in the hippocampal formation and olfaction circuits. Furthermore, impaired neurogenesis is the result of both intrinsic pathology in neural progenitor cells and extrinsic neuropathology in the neurogenic niches. Finally, hyperphosphorylation of the microtubule-associated protein tau, a critical player in cell proliferation, neuronal maturation, and axonal transport, is a major contributor to impaired neurogenesis in Alzheimer's disease.

Despite general capacity of peripheral nervous system to regenerate, peripheral nerve injury is often followed by incomplete recovery of function and sometimes burdened by neuropathic pain. Amyloid precursor protein (APP) was suggested to play a role in neuronal growth, however, its role in peripheral nerve repair was not studied. The aim of this study was to examine the role of APP overexpression in peripheral nerve regeneration and neuropathic pain-related behavior in mice. Sciatic nerves of APP overexpressing and FVB/N wild-type mice were transected and immediately resutured. Evaluation of motor and sensory function and autotomy was carried out during 4-week follow up. We found no autotomy behavior as well as less significant atrophy of denervated muscles in APP overexpressing animals when compared to wild-type ones. Sciatic nerve function index outcome did not differ between groups. Histological evaluation revealed that the intensity of regeneration features, including GAP-43-positive growth cones and Schwann cells number in the distal stump of the transected nerve, was also similar in both groups. However, the regenerating fibers were organized more chaotically in wild-type mice and neuromas were much more often seen in this group. The number of macrophages infiltrating the injury site was significantly higher in control group. The number of surviving motoneurons was higher in transgenic mice than in control animals. Taken together, our findings suggest that APP overexpression is beneficial for nerve regeneration processes due to better organization of regenerating fibers, increased survival of motoneurons after autotomy and prevention of neuropathic pain.

Various immunotherapy strategies for APP transgenic mice have emerged in recent years. Specifically, active immunization with beta-amyloid (A beta) or passive immunization with anti-A beta-antibodies in APP transgenic mice has appeared most promising. Recent studies have shown that treatment of APP transgenic mice either with A beta(40/42) or A beta-specific antibodies can have beneficial effects in cognitive tasks. Active as well as passive immunization have been shown to affect spatial, non-spatial, emotional and object-related learning and memory. Such effects can be observed when treatments are applied prophylactically (before apparent A beta pathology) or therapeutically (after the development of A beta pathology) in APP transgenic mice. This review focuses on such cognitive outcomes of different active and passive immunization strategies in APP transgenic mice.

Previous studies have shown that amyloid beta protein (Abeta ), the essential molecule for the formation of toxic oligomers and, subsequently, Alzheimer plaques, has been associated in vivo with the immune modulator, macrophage migration inhibitory factor (MIF) (17). To further investigate this association in vivo we used the APP transgenic mouse model. Serial brain sections of transgenic APP mice were stained for Abeta plaques and MIF and we observed MIF immunolabeling in microglial cells in association with Abeta plaques in the transgenic mouse brain sections. In addition, functional studies in murine and human neuronal cell lines revealed that Abeta-induced toxicity could be reversed significantly by a small molecule inhibitor of MIF (ISO-1). Finally, to elucidate the role of MIF in Alzheimer's Disease (AD) we measured MIF levels in the brain cytosol and cerebrospinal fluid (CSF) of AD patients and age-matched controls. Our results demonstrate a marked increase of MIF levels within the CSF of AD patients compared with controls. Combined, our results indicate a strong role for MIF in the pathogenesis of AD and furthermore suggest that inhibition of MIF may provide a valuable avenue of investigation for the prevention of disease onset, progression and/or severity.

The formation of amyloid, a cross-β-sheet fibrillar aggregate, is associated with a variety of aging-associated degenerative diseases. Herein, we report the existence of a mammalian amyloid disaggregase activity that is present in all tissues and cell types tested. Homogenates from mammalian tissues and cell lines are able to disaggregate amyloid fibrils composed of amyloid β (Aβ)1–40 or the 8 kDa plasma gelsolin fragment. The mammalian disaggregase activity is sensitive to proteinase K digestion and can be uncoupled from proteolysis activity using a protease inhibitor cocktail. Amyloid disaggregation and proteolysis activities are remarkably resistant to changes in temperature and pH. Identification and manipulation of the proteins responsible for the amyloid disaggregation/degradation activities offers the possibility of ameliorating aggregation-associated diseases.

Mutant Tg2576 mice which possess the human "Swedish" APP mutation have been shown to demonstrate both Abeta plaque pathology and memory deficits in behavioral tasks. These mice are routinely maintained on a mixed C57BL/6xSJL genetic background which exhibits a high frequency of retinal degeneration allele and high variability in many behavioral assays. The same APP mutation is also available maintained on a 129 genetic background, providing more genetic homogeneity, but little data are published regarding the effects of the mutation on this background. We investigated whether transgenic mice expressing the Swedish mutation on the 129 background show similar behavioral deficits and Abeta pathology as those on the mixed background. Mice on the 129 background were tested at 6-7, 11-12, or 18-19 months of age in locomotor activity, Y-maze spontaneous alternation, and contextual fear conditioning. Differences were detected between WT and Tg mice in locomotor activity at 6-7 and 18-19 months, Y-maze at 6-7 and 11-12 months, and fear conditioning at 6-7, 11-12, and 18-19 months. In contrast, Tg mice on the mixed B6/SJL background tested at 6-7 months only demonstrated significant impairment in the contextual fear conditioning assay and in the Y-maze in one of 2 cohorts tested. Despite the behavioral differences observed, similar Abeta pathology was observed between Tg mice on the two genetic backgrounds. These results indicate that mice on the 129 genetic background may generate more consistent and robust behavioral differences, providing a useful model for testing therapeutic agents for Alzheimer's disease.

Amyloid precursor protein (APP) is strongly related to the onset of Alzheimer's disease. It possesses cleavage sites for beta- and gamma-secretases, and the resulting cleaved products (amyloid-beta peptides) are capable of causing neurotoxicity. Such cleavage is promoted by the Swedish and London mutations (APPSwe/Lon) inside the APP gene. Here, we characterized APPSL transgenic mice (APPSL-Tg) to determine the effects of this mutation. We observed that both the amount of insoluble amyloid-beta and the ratio of amyloid-beta 42/40 increased promptly in the brain during 6-16 months of age. Amyloid-beta plaques were observed in whole brain sections at 12 months. In contrast, the spatial memory assessed by the Morris water maze task was already impaired at 3 months, which suggested that the APPSL-Tg mice may represent an early-onset model of familial Alzheimer's disease. Furthermore, the levels of LAMP-1, a marker protein of lysosome, increased in the brain at 28 months. Such LAMP-1 protein was detected around the amyloid-beta plaques at the hippocampal regions of the APPSL-Tg mice. Our results suggested that the increase in LAMP-1 was enhanced by the accumulation of amyloid-beta occurring during aging. Our findings coincided with the pathological hallmarks of Alzheimer's disease.

Although transgenic mouse models of Alzheimer's disease (AD) recapitulate amyloid-beta (Abeta)-related pathologies and cognitive impairments, previous studies have mainly evaluated their hippocampus-dependent memory dysfunctions using behavioral tasks such as the water maze and fear conditioning. However, multiple memory systems become impaired in AD as the disease progresses and it is important to test whether other forms of memory are affected in AD models. This study was designed to use conditioned taste aversion (CTA) and contextual fear conditioning paradigms to compare the phenotypes of hippocampus-independent and -dependent memory functions, respectively, in 5XFAD amyloid precursor protein/presenilin-1 transgenic mice that harbor five familial AD mutations. Although both types of memory were significantly impaired in 5XFAD mice, the onset of CTA memory deficits ( approximately 9 months of age) was delayed compared with that of contextual memory deficits ( approximately 6 months of age). Furthermore, 5XFAD mice that were genetically engineered to have reduced levels of beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1) (BACE1(+/-).5XFAD) exhibited improved CTA memory, which was equivalent to the performance of wild-type controls. Importantly, elevated levels of cerebral beta-secretase-cleaved C-terminal fragment (C99) and Abeta peptides in 5XFAD mice were significantly reduced in BACE1(+/-).5XFAD mice. Furthermore, Abeta deposition in the insular cortex and basolateral amygdala, two brain regions that are critically involved in CTA performance, was also reduced in BACE1(+/-).5XFAD compared with 5XFAD mice. Our findings indicate that the CTA paradigm is useful for evaluating a hippocampus-independent form of memory defect in AD model mice, which is sensitive to rescue by partial reductions of the beta-secretase BACE1 and consequently of cerebral Abeta.

The presence of A beta(pE3) (N-terminal truncated A beta starting with pyroglutamate) in Alzheimer's disease (AD) has received considerable attention since the discovery that this peptide represents a dominant fraction of A beta peptides in senile plaques of AD brains. This was later confirmed by other reports investigating AD and Down's syndrome postmortem brain tissue. Importantly, A beta(pE3) has a higher aggregation propensity, and stability, and shows an increased toxicity compared to full-length A beta. We have recently shown that intraneuronal accumulation of A beta(pE3) peptides induces a severe neuron loss and an associated neurological phenotype in the TBA2 mouse model for AD. Given the increasing interest in A beta(pE3), we have generated two novel monoclonal antibodies which were characterized as highly specific for A beta(pE3) peptides and herein used to analyze plaque deposition in APP/PS1KI mice, an AD model with severe neuron loss and learning deficits. This was compared with the plaque pattern present in brain tissue from sporadic and familial AD cases. Abundant plaques positive for A beta(pE3) were present in patients with sporadic AD and familial AD including those carrying mutations in APP (arctic and Swedish) and PS1. Interestingly, in APP/PS1KI mice we observed a continuous increase in A beta(pE3) plaque load with increasing age, while the density for A beta(1-x) plaques declined with aging. We therefore assume that, in particular, the peptides starting with position 1 of A beta are N-truncated as disease progresses, and that, A beta(pE3) positive plaques are resistant to age-dependent degradation likely due to their high stability and propensity to aggregate.

Testicular germ cell tumors (TGCTs) commonly metastasize to the lymph node or lung. However, it remains unclear which genes are associated with TGCT metastasis. The aim of this study was to identify gene(s) that promoted human TGCT metastasis. We intraperitoneally administered conditioned medium (CM) from JKT-1, a cell-line from a human testicular seminoma, or JKT-HM, a JKT-1 cell sub-line with high metastatic potential, into mice with JKT-1 xenografts. Administration of CM from JKT-HM significantly promoted lymph node metastasis. A cDNA microarray analysis showed that JKT-HM cells highly expressed the Serpine peptidase inhibitor, clade E, member 2 (SERPINE2), which encodes a secreted protein. Administration of CM from SERPINE2-silenced JKT-HM cells inhibited lymph node metastasis in the xenograft model, compared with administration of CM from JKT-HM cells. There was no significant difference in xenograft volume. Moreover, administration of CM from SERPINE2-over-expressing JKT-1 was likely to promote lymph node metastasis in the xenograft model. There was no difference in the in vitro proliferation or migration of JKT-1 cells cultured with CM from JKT-HM cells, compared to that with CM from JKT-1. There was no promotion of proliferation or lymphangiogenesis in the xenografts, as measured by Ki-67 and LYVE-1 immunohistochemistry, respectively. Although we could not clarify how SERPINE2 promoted lymph node metastasis, it may be a promoter in the development of lymph node metastasis in the human seminoma cells in a mouse xenograft model.

The generation of amyloid-beta peptide (A) and its accumulation in amyloid plaques are generally recognized as key characteristics of Alzheimer’s disease. A number of reports have indicated that A can regulate the proliferation of neural precursor cells and adult neurogenesis, suggesting that this may underpin the cognitive decline and compromised olfaction also associated with the condition. Here we report that A1–42 treatment both in vitro and in vivo, as well as endogenous generation of A in C100 and APP/PS1 transgenic models of Alzheimer’s disease, stimulate neurogenesis of young adult subventricular zone precursors. The neurogenic effect of A1–42 was found to require expression of the p75 neurotrophin receptor (p75 NTR ) by the precursor cells, and activation of p75 NTR by metalloprotease cleavage. However, precursors from 12-month-old APP/PS1 mice failed to respond to A1–42. Our results suggest that overstimulation of p75 NTR -positive progenitors during early life might result in depletion of the stem cell pool and thus a more rapid decline in basal neurogenesis. This, in turn, could lead to impaired neurogenic function in later life. © 2008 Elsevier Inc. All rights reserved.

To gain insight into the relationship between pathological alterations and memory deficits observed in Alzheimer's disease (AD), a number of amyloid precursor protein (APP) transgenic animal models have been generated containing familial AD mutations. The most commonly utilized method involves a cDNA-based approach, utilizing heterologous promoters to drive expression of specific APP isoforms. As a result of the assumptions inherent in the design of each model, the different cDNA-based transgenic mouse models have revealed different relationships between the biochemical, pathological and behavioral alterations observed in these models. Here we provide further characterization of a genomic-based, amyloid precursor protein yeast artificial chromosome transgenic mouse model of AD, R1.40, that makes few assumptions regarding disease pathogenesis to study the relationship between brain pathology and altered behavior. Aged R1.40 transgenic and control mice were tested for learning and memory in the Morris water maze and for working memory in the Y maze. Results from the water maze demonstrated intact learning in the both control and R1.40 mice, but impairments in the long-term retention of this information in the transgenic mice, but not controls. Interestingly, however, long-term memory deficits did not correlate with the presence of Abeta deposits within the group of animals examined. By contrast, age-related working memory impairments were also observed in the Y maze in the R1.40 mice, and these deficits correlated with the presence of Abeta deposits. Our results demonstrate unique behavioral alterations in the R1.40 mouse model of AD that are likely both dependent and independent of Abeta deposition.

Deficiency of caytaxin results in hereditary ataxia or dystonia in humans, mice and rats. Our yeast two-hybrid screen identified kinesin light chains (KLCs) as caytaxin-binding proteins. The tetratricopeptide-repeat region of KLC1 recognizes the ELEWED sequence (amino acids 115-120) of caytaxin. This motif is conserved among BNIP-2 family members and other KLC-interacting kinesin cargo proteins such as calsyntenins. Caytaxin associates with kinesin heavy chains (KHCs) indirectly by binding to KLCs, suggesting that caytaxin binds to the tetrameric kinesin molecule. In cultured hippocampal neurons, we found that caytaxin is distributed in both axons and dendrites in punctate patterns, and it colocalizes with microtubules and KHC. GFP-caytaxin expressed in hippocampal neurons is transported at a speed (∼1 μm/second) compatible with kinesin movement. Inhibition of kinesin-1 by dominant-negative KHC decreases the accumulation of caytaxin in the growth cone. Caytaxin puncta do not coincide with vesicles containing known kinesin cargos such as APP or JIP-1. A part of caytaxin, however, colocalizes with mitochondria and suppression of caytaxin expression by RNAi redistributes mitochondria away from the distal ends of neurites. These data indicate that caytaxin binds to kinesin-1 and functions as an adaptor that mediates intracellular transport of specific cargos, one of which is the mitochondrion.

Converging lines of evidence suggest that soluble A beta-amyloid oligomers play a pivotal role in the pathogenesis of Alzheimer's disease, and present direct effectors of synaptic and cognitive dysfunction. Three pathological E22-A beta-amyloid point mutants (E22G, E22K, E22Q) and the deletion mutant E22 Delta exhibit an enhanced tendency to form prefibrillar aggregates. The present study assessed the effect of these four mutations using molecular dynamics simulations and subsequent structural and energetic analyses. Our data shows that E22 plays a unique role in wild type A beta, since it has a destabilising effect on the oligomer structure due to electrostatic repulsion between adjacent E22 side chains. Mutations in which E22 is replaced by an uncharged residue result in higher oligomer stability. This effect is also observed to a lesser extent for the E22K mutation and is consistent with its lower pathogenicity compared to other mutants. Interestingly, deletion of E22 does not destroy the amyloid fold but is compensated by local changes in the backbone geometry that allow the preservation of a structurally important salt bridge. The finding that all mutant oligomers investigated exhibit higher internal stability than the wild type offers an explanation for the experimentally observed enhanced oligomer formation and stability.

An active lifestyle is to some degree protective against Alzheimer's disease (AD), but the biological basis for this benefit is still far from clear. We hypothesize that physical and cognitive activity increase a reserve for plasticity by increasing adult neurogenesis in the hippocampal dentate gyrus (DG). We thus assessed how age affects the response to activity in the murine APP23 model of AD compared with wild type (WT) controls and studied the effects of physical exercise (RUN) and environmental enrichment (ENR) in comparison with standard housing (CTR) at two different ages (6 months and 18 months) and in both genotypes. At 18 months, both activity paradigms reduced the hippocampal human Abeta1-42/Abeta1-40 ratio when compared with CTR, despite a stable plaque load in the hippocampus. At this age, both RUN and ENR increased the number of newborn granule cells in the DG of APP23 mice when compared with CTR, whereas the levels of regulation were equivalent to those in WT mice under the same housing conditions. At 6 months, however, neurogenesis in ENR but not RUN mice responded like the WT. Quantifying the number of cells at the doublecortin-positive stage in relation to the number of cells on postmitotic stages we found that ENR overproportionally increased the number of the DCX-positive "late" progenitor cells, indicative of an increased potential to recruit even more new neurons. In summary, the biological substrates for activity-dependent regulation of adult hippocampal neurogenesis were preserved in the APP23 mice. We thus propose that in this model, ENR even more than RUN might contribute to a "neurogenic reserve" despite a stable plaque load and that age affects the outcome of an interaction based on "activity."

ADAM10 (a disintegrin and metalloproteinase 10) is the principal alpha-secretase responsible for the non-amyloidogenic processing of the Alzheimer's disease (AD)-associated amyloid precursor protein (APP). A reciprocal relationship exists between non-amyloidogenic and amyloidogenic APP processing such that impaired ADAM10-mediated proteolysis of the protein serves to enhance amyloidogenic processing (by beta- and gamma-secretases) thereby elevating levels of the amyloid beta (A beta)-peptides responsible for the neuronal death observed in the AD-afflicted brain. It has previously been demonstrated that the amyloidogenic processing of APP occurs within specialized regions of the cell membrane known as lipid rafts. Conversely, ADAM10-mediated non-amyloidogenic processing is thought to occur in the non-raft region of the membrane with the majority of ADAM10 being excluded from rafts. In the current study, we hypothesized that the exclusion of ADAM10 from rafts may leave the APP substrate particularly susceptible to alternative beta-secretase cleavage within these microdomains. In order to test this hypothesis, we targeted ADAM10 to rafts by replacing its transmembrane and cytosolic regions with a glycosylphosphatidylinositol (GPI) anchor and examined the associated effects on APP proteolysis. We found that whereas wild-type ADAM10 was exclusively present in the non-raft region of the membrane where it enhanced non-amyloidogenic APP proteolysis, GPI-anchored ADAM10 was effectively targeted to rafts where it competed with beta-secretase thereby reducing amyloidogenic APP processing. These results indicate that it is the exclusion of ADAM10 from rafts rather than simply the raft localization of beta- and gamma-secretases that underlies A beta-peptide generation within these cellular structures.

Chronic cerebral ischemia may accelerate clinicopathological changes in Alzheimer's disease. We have examined whether chronic cerebral hypoperfusion accelerates amyloid beta deposition in amyloid protein precursor transgenic (APP-Tg) mouse. At 5, 8, and 11 months of age, C57Bl/6J male mice overexpressing a mutant form of the human APP bearing the both Swedish (K670N/M671L) and the Indiana (V717F) mutations (APPSwInd) and their litterrmates were subjected to either sham operation or bilateral carotid artery stenosis (BCAS) using microcoils with an internal diameter of 0.18 mm (short-period group). One month after the sham operation or BCAS, these animals were examined by immunohistochemistry for glial fibrillary acidic protein, amyloid beta(1-40) (Abeta(1-40)), amyloid beta(1-42) (Abeta(1-42)), as well as Western blotting and filter assay for Abeta. Another batch of the littermates of APPSwInd mice were subjected to either sham operation or BCAS at 3 months and were examined in the same manner after survival for 9 months (long-period group). In the BCAS-treated group, the white matter was rarefied and astroglia was proliferated. Amyloid beta(1-40) immunoreactivity was found in a few axons in the white matter after BCAS, whereas Abeta(1-42) was accumulated in the scattered cortical neurons and the axons at ages of 6 months and thereafter in the short- and long-period groups. In the neuropil, both Abeta(1-40) and Abeta(1-42) were deposited in the sham-operated and BCAS-treated mice at ages of 9 and 12 months. There were no differences between the short-period group at ages of 12 months and the long-period group. Filter assay showed an increase of Abeta fibrils in the extracellular enriched fraction. Taken together, chronic cerebral hypoperfusion increased Abeta fibrils and induced Abeta deposition in the intracellular compartment and, therefore, may accelerate the pathological changes of Alzheimer's disease.

A large series of 3-, 6-, 9-, and 12-month-old bigenic mice (N=240) with Swedish APP and A246E PS1 mutations was investigated in nest-building, spontaneous alternation, and two learning tasks. Progressive cognitive impairment was observed in APPswe/PS1 mice relative to controls for nest-building, spontaneous alternation, the reversal phase of left-right discrimination learning in a water-filled T-maze, and in retention of passive avoidance learning. The behavioral deficits in transgenic mice start at 6 months, appearing to offer an opportunity for assessing potential therapeutic agents in attenuating or preventing Alzheimer's disease.

The triple transgenic mouse (3xTgAD), harboring human APP(Swe), PS1(M146V) and Tau(P301L) genes, develops age-dependent forebrain intraneuronal Abeta and tau as well as extraneuronal plaques. We evaluated brainstem AD-like pathology using 6E10, AT8, and Alz50 antibodies and unbiased stereology in young and old 3xTgAD mice. Intraneuronal Abeta occurred in the tectum, periaqueductal gray, substantia nigra, red nucleus, tegmentum and mesencephalic V nucleus at all ages. Abeta-positive neuron numbers significantly decreased in the superior colliculus and substantia nigra while AT8-positive superior colliculus, red nucleus, principal sensory V, vestibular nuclei, and tegmental neurons significantly increased between 2 and 12 months. Alz50-positive neuron numbers increased only in the inferior colliculus between these ages. Dual labeling revealed a few Abeta- and tau-positive neurons. Plaques occurred only in the pons of female 3xTgAD mice starting at 9 months. 3xTgAD mice provide a platform to define in vivo mechanisms of Abeta and tau brainstem pathology.

A central question in Alzheimer's disease research is what role synaptic activity plays in the disease process. Synaptic activity has been shown to induce beta-amyloid peptide release into the extracellular space, and extracellular beta-amyloid has been shown to be toxic to synapses. We now provide evidence that the well established synaptotoxicity of extracellular beta-amyloid requires gamma-secretase processing of amyloid precursor protein. Recent evidence supports an important role for intraneuronal beta-amyloid in the pathogenesis of Alzheimer's disease. We show that synaptic activity reduces intraneuronal beta-amyloid and protects against beta-amyloid-related synaptic alterations. We demonstrate that synaptic activity promotes the transport of the amyloid precursor protein to synapses using live cell imaging, and that the protease neprilysin is involved in reduction of intraneuronal beta-amyloid with synaptic activity.

An association between major surgery in the elderly and precipitation of Alzheimer's disease has been reported. As 100% oxygen (hyperoxia) is commonly administered after surgery, we exposed cognitively unimpaired Alzheimer's transgenic mice to hyperoxia typical of human exposure in a hospital setting. Three-hour hyperoxia treatments to young adult Alzheimer's transgenic mice: (i) triggered cognitive impairment that was not otherwise present at that age, (ii) increased aberrant brain synaptophysin staining, and (iii) increased brain levels of isofurans (products of lipid peroxidation sensitive to hyperoxia). Thus, hyperoxia-induced synaptic dysfunction and brain oxidative stress are likely the triggering mechanisms of cognitive dysfunction in Alzheimer's mice. These results may suggest that exposure of elderly patients to excessive amounts of oxygen perioperatively hastens the development of Alzheimer's disease.

Although a battery of neuropsychological tests are often used in making a clinical diagnosis of Alzheimer’s disease (AD), definitive diagnosis still relies on pathological evaluation at autopsy. The identification of AD biomarkers may allow for a less invasive and more accurate diagnosis as well as serve as a predictor of future disease progression and treatment response. Importantly, biomarkers may also allow for the identification of individuals who are already developing the underlying pathology of AD such as plaques and tangles yet who are not yet demented, i.e. “preclinical” AD. Attempts to identify biomarkers have included fluid and imaging studies, with a number of candidate markers showing significant potential. More recently, better reagent availability and novel methods of assessment have further spurred the search for biomarkers of AD. This review will discuss promising fluid and imaging markers to date.

Alzheimer's disease (AD) is a chronic neurodegenerative disorder associated with extracellular accumulation of Aβ peptide that derives from the amyloid precursor protein (APP). While amyloidogenic processing of APP has received most attention, the physiological function of APP and the sequelae of potentially impaired APP function are less understood. APP is a transmembrane glycoprotein being widely expressed in neurons in both central and peripheral nervous system. Its physiological function has been associated with neuronal survival, neurite outgrowth and neuronal plasticity. The aim of the present study was to determine whether FAD-linked mutations of APP, known to be associated with early onset of the disease, might impair its synaptotrophic function, potentially contributing to synaptic deficiencies seen in AD. We performed a quantitative electron microscopy study on synapses in well characterized expression-matched transgenic mice lines expressing either wildtype or FAD-mutated hAPP. Using serial electron microscopic sections, we comparatively analyzed by stereological methods the number and sizes of synaptic contacts and the number of synaptic vesicles in the neocortex. We could clearly show a synaptotrophic effect in mice overexpressing wildtype hAPP evidenced by a significant increase in the number of synapses and the number of vesicles per synapse. This effect was abolished when FAD-mutated APPSw,Ind was expressed instead of wildtype APP. The present study demonstrates a synaptotrophic effect of APP which is lost in the presence of a FAD-mutation. This failure could either be due to a synaptotoxic effect of Aβ potentially counteracting the synaptotrophic effect of APP. Alternatively, the FAD-mutation might impair the physiological function of the extracellular domain of APP and its fragments which might be required for the synaptotrophic effect. This suggests that not only “too much Aβ” but also “too less functional intact APP” might be relevant for synaptic pathology and degeneration in AD.

Downregulation of brain-derived neurotrophic factor (BDNF) in the cortex occurs early in the progression of Alzheimer's disease (AD). Since BDNF plays a critical role in neuronal survival, synaptic plasticity, and memory, BDNF reduction may contribute to synaptic and cellular loss and memory deficits characteristic of AD.In vitroevidence suggests that amyloid-β (Aβ) contributes to BDNF downregulation in AD, but the specific Aβ aggregation state responsible for this downregulationin vivois unknown. In the present study, we examined cortical levels of BDNF mRNA in three different transgenic AD mouse models harboring mutations inAPPresulting in Aβ overproduction, and in a genetic mouse model of Down syndrome. Two of the three Aβ transgenic strains (APPNLhand TgCRND8) exhibited significantly decreased cortical BDNF mRNA levels compared with wild-type mice, whereas neither the other strain (APPswe/PS-1) nor the Down syndrome mouse model (Ts65Dn) was affected. OnlyAPPNLhand TgCRND8 mice expressed high Aβ42/Aβ40ratios and larger SDS-stable Aβ oligomers (∼115 kDa). TgCRND8 mice exhibited downregulation of BDNF transcripts III and IV; transcript IV is also downregulated in AD. Furthermore, in all transgenic mouse strains, there was a correlation between levels of large oligomers, Aβ42/Aβ40, and severity of BDNF decrease. These data show that the amount and species of Aβ vary among transgenic mouse models of AD and are negatively correlated with BDNF levels. These findings also suggest that the effect of Aβ on decreased BDNF expression is specific to the aggregation state of Aβ and is dependent on large oligomers.

Reticulon 3 (RTN3) was initially identified as a negative modulator of BACE1, an enzyme that cleaves amyloid precursor protein (APP) to release β-amyloid peptide. Interestingly, RTN3 can also form aggregates after accumulation, and increased RTN3 aggregation correlates with the formation of RTN3 immunoreactive dystrophic neurites (RIDNs) in brains of Alzheimer's cases. Transgenic mice expressing RTN3 alone develop RIDNs in their hippocampus but not in their cortex. To determine thein vivoeffects of RTN3 and preformed RIDNs on amyloid deposition, we crossed bitransgenic mice expressing APP and presenilin 1 (PS1) mutations with mice overexpressing RTN3. We found that amyloid deposition in cortex, the hippocampal CA3 region, and dentate gyrus was significantly reduced in triple transgenic mice compared with bitransgenic controls. However, reduction of amyloid deposition in the hippocampal CA1 region, where RIDNs predominantly formed before amyloid deposition, was less significant. Hence, preformed RTN3 aggregates in RIDNs clearly offset the negative modulation of BACE1 activity by RTN3. Furthermore, our study indicates that the increased expression of RTN3 could result in an alteration of BACE1 intracellular trafficking by retaining more BACE1 in the endoplasmic reticulum compartment where cleavage of APP by BACE1 is less favored. Our results suggest that inhibition of RTN3 aggregation is likely to be beneficial by reducing both amyloid deposition and the formation RIDNs.

Alzheimer's disease (AD) is a neurodegenerative disorder that impairs memory and cognition. One of the major neuropathological hallmarks is the accumulation of the extracellular senile plaques that are mainly composed of amyloid beta (Abeta) protein. Plaques are associated with synapse loss, dystrophic neurites and altered neurite trajectories. A reversal of such morphological changes has been observed days after single dose anti-Abeta immunotherapy. In this study we investigated the extended effects of a single dose of passive anti-Abeta immunotherapy on morphological changes associated with senile plaques. We found that although plaque burden was not reduced 30 days after immunotherapy, there were fewer dystrophic neurites around each plaque, a recovery of synapse density, and normalization of neurite curvature near plaques. Taken together these results suggest that a single dose of immunotherapy is sufficient to cause lasting benefits to the morphology of cortical neurons, implying substantial plasticity of neural circuits despite the continued presence of plaques.

APP intracellular domain (AICD) has been proposed as a transcriptional inductor that moves to the nucleus with the adaptor protein Fe65 and regulates transcription. The two proteins, APP and Fe65, can be phosphorylated by c-Abl kinase. Neprilysin has been proposed as a target gene for AICD. We found that AICD expression is decreased by treatment with STI-571, a c-Abl inhibitor, suggesting a modulation of AICD transcription by c-Abl kinase. We observed interaction between c-Abl kinase, the AICD fragment and the Fe65 adaptor protein. In addition, STI-571 reduces apoptosis in APPSw, and the apoptotic response induced by Fe65 over-expression was inhibited by with the expression of a kinase dead (KD) c-Abl and enhanced by over-expression of WT-c-Abl. However, in the APPSw cells, the ability of the KD-c-Abl to protect against Fe65 was reduced. Finally, in APPSw clone, we detected higher trans-activation of the pro-apoptotic p73 isoform, TAp73 promoter. Our results show that c-Abl modulates AICD dependent cellular responses, transcriptional induction as well as the apoptotic response, which could participate in the onset and progression of the neurodegenerative pathology, observed in Alzheimer's disease (AD).

The processing of amyloid precursor protein (APP) to Aβ is an important event in the pathogenesis of Alzheimer’s disease (AD), but the physiological function of APP is not well understood. Our previous work has shown that APP processing and Aβ production are regulated by the extracellular matrix protein Reelin. In the present study, we examined whether Reelin interacts with APP, and the functional consequences of that interaction in vitro. Using co-immunoprecipitation and fluorescent lifetime imaging techniques, we found that Reelin interacted with APP through the central domain of Reelin (repeats 3–6) and the E1 extracellular domain of APP. Reelin increased cell surface levels of APP and decreased endocytosis of APP in hippocampal neurons in vitro. In vivo, Reelin levels were increased in brains of APP knock-out mice and decreased in APP over-expressing mice. RNAi knockdown of APP decreased neurite outgrowth in vitro, and prevented Reelin from increasing neurite outgrowth. Knock-out of APP or Reelin decreased dendritic arborization in cortical neurons in vivo, and APP overexpression increased dendritic arborization. APP and Reelin have previously been shown to promote neurite outgrowth through interactions with integrins. We confirmed that APP interacted with α3β1 integrin, and α3β1 integrin altered APP trafficking and processing. Addition of an α3β1 integrin antibody prevented APP and Reelin-induced neurite outgrowth. These findings demonstrate that Reelin interacts with APP, potentially having important effects on neurite development.

Inclusion body myositis (IBM), the most common muscle disease to afflict the elderly, causes slow but progressive degeneration of skeletal muscle and ultimately paralysis. Hallmark pathological features include T-cell mediated inflammatory infiltrates and aberrant accumulations of proteins, including amyloid-β (Aβ), tau, ubiquitinated-proteins, apolipoprotein E, and α-synuclein in skeletal muscle. A large body of work indicates that aberrant Aβ accumulation contributes to the myodegeneration. Here, we investigated whether active immunization to promote clearance of Aβ from affected skeletal muscle fibers mitigates the IBM-like myopathological features as well as motor impairment in a transgenic mouse model. We report that active immunization markedly reduces intracellular Aβ deposits and attenuates the motor impairment compared with untreated mice. Results from our current study indicate that Aβ oligomers contribute to the myopathy process as they were significantly reduced in the affected skeletal muscle from immunized mice. In addition, the anti-Aβ antibodies produced in the immunized mice blocked the toxicity of the Aβ oligomersin vitro, providing a possible key mechanism for the functional recovery. These findings provide support for the hypothesis that Aβ is one of the key pathogenic components in IBM pathology and subsequent skeletal muscle degeneration.

To investigate the relationship between MR image contrast associated with beta-amyloid (Abeta) plaques and their histology and compare the histopathological basis of image contrast and the relaxation mechanism associated with Abeta plaques in human Alzheimer's disease (AD) and transgenic APP/PS1 mouse tissues.With the aid of the previously developed histological coil, T(2) (*)-weighted images and R(2) (*) parametric maps were directly compared with histology stains acquired from the same set of Alzheimer's and APP/PS1 tissue slices.The electron microscopy and histology images revealed significant differences in plaque morphology and associated iron concentration between AD and transgenic APP/PS1 mice tissue samples. For AD tissues, T(2) (*) contrast of Abeta-plaques was directly associated with the gradation of iron concentration. Plaques with significantly less iron load in the APP/PS1 animal tissues are equally conspicuous as the human plaques in the MR images.These data suggest a duality in the relaxation mechanism where both high focal iron concentration and highly compact fibrillar beta-amyloid masses cause rapid proton transverse magnetization decay. For human tissues, the former mechanism is likely the dominant source of R(2) (*) relaxation; for APP/PS1 animals, the latter is likely the major cause of increased transverse proton relaxation rate in Abeta plaques. The data presented are essential for understanding the histopathological underpinning of MRI measurement associated with Abeta plaques in humans and animals.

article i nfo Alzheimer disease (AD) is a progressive neurodegenerative disorder whose clinical manifestations appear in old age. The sporadic nature of 90% of AD cases, the differential susceptibility to and course of the illness, as well as the late age onset of the disease suggest that epigenetic and environmental components play a role in the etiology of late-onset AD. Animal exposure studies demonstrated that AD may begin early in life and may involve an interplay between the environment, epigenetics, and oxidative stress. Early life exposure of rodents and primates to the xenobiotic metal lead (Pb) enhanced the expression of genes associated with AD, repressed the expression of others, and increased the burden of oxidative DNA damage in the aged brain. Epigenetic mechanisms that control gene expression and promote the accumulation of oxidative DNA damage are mediated through alterations in the methylation or oxidation of CpG dinucleotides. We found that environmental influences occurring during brain development inhibit DNA-methyltransferases, thus hypomethylating promoters of genes associated with AD such as the β-amyloid precursor protein (APP). This early life imprint was sustained and triggered later in life to increase the levels of APP and amyloid-β (Aβ). Increased Aβ levels promoted the production of reactive oxygen species, which damage DNA and accelerate neurodegenerative events. Whereas AD-associated genes were overexpressed late in life, others were repressed, suggesting that these early life perturbations result in hypomethylation as well as hypermethyla- tion of genes. The hypermethylated genes are rendered susceptible to Aβ-enhanced oxidative DNA damage because methylcytosines restrict repair of adjacent hydroxyguanosines. Although the conditions leading to early life hypo- or hypermethylation of specific genes are not known, these changes can have an impact on gene expression and imprint susceptibility to oxidative DNA damage in the aged brain.

gamma-Secretase is a multisubunit membrane protein complex consisting of presenilin (PS1), nicastrin (NCT), anterior pharynx-1, and presenilin enhancer 2. To analyze the activity of familial Alzheimer disease mutants and to understand the roles of the subunits, we established a yeast transcriptional activator Gal4p system with artificial gamma-secretase substrates containing amyloid precursor protein or Notch fragments. The gamma-secretase activities were evaluated by transcriptional activation of reporter genes upon Gal4p release from the membrane-bound substrates, i.e. growth of yeast on histidine and adenine, or beta-galactosidase assay. We screened and evaluated gamma-secretase mutants using this reconstitution system in yeast, which does not possess endogenous gamma-secretase activity. When we introduced familial Alzheimer mutants of PS1 in this system, their activities were shown to be loss of function. Although the protease activity of wild type PS1 depends on the other three subunits introduced, we obtained 15 new PS1 mutants, which are active in the absence of NCT. They possessed a S438P mutation at the ninth transmembrane domain (TM9) together with one missense mutation distributed through transmembrane and loop regions. These mutations were not related to familial Alzheimer mutations of PS1 as identified so far. The S438P mutant was partially active but required other mutations for full activation. Results of the beta-galactosidase assay suggested that they have wild type protease activities, which were further confirmed by the endoproteolysis of PS1, amyloid beta peptides, and Notch intracellular domain production in mammalian cells. These results suggest that NCT is dispensable for the protease activity of gamma-secretase.

Abeta accumulation has an important function in the etiology of Alzheimer’s disease (AD) with its typical clinical symptoms, like memory impairment and changes in personality. However, the mode of this toxic activity is still a matter of scientific debate. We used the APP/PS1KI mouse model for AD, because it is the only model so far which develops 50% hippocampal CA1 neuron loss at the age of 1 year. Previously, we have shown that this model develops severe learning deficits occurring much earlier at the age of 6 months. This observation prompted us to study the anatomical and cellular basis at this time point in more detail. In the current report, we observed that at 6 months of age there is already a 33% CA1 neuron loss and an 18% atrophy of the hippocampus, together with a drastic reduction of long-term potentiation and disrupted paired pulse facilitation. Interestingly, at 4 months of age, there was no long-term potentiation deficit in CA1. This was accompanied by reduced levels of pre- and post-synaptic markers. We also observed that intraneuronal and total amount of different Abeta peptides including N-modified, fibrillar and oligomeric Abeta species increased and coincided well with CA1 neuron loss. Overall, these data provide the basis for the observed robust working memory deficits in this mouse model for AD at 6 months of age. peerReviewed

Previously it has been reported that neural stem cells undergoing apoptotic stress have increased levels of Amyloid precursor protein (APP) and increased APP expression results in glial differentiation. APP activity was also shown to be required for staurosporine induced glial differentiation of neuroprogenitor cells. Monocyte chemoattractant protein-1 (MCP-1) is a chemokine that is expressed early during inflammation. The binding of MCP-1 to its chemokine receptor induces expression of novel transcription factor MCP-1 induced protein (MCPIP). MCPIP expression subsequently leads to cell death. Previous studies have shown that pro apoptotic factors have the ability to induce neural differentiation. Therefore, we investigated if MCPIP expression leads to differentiation of NT2 neuroprogenitor cells. Results showed that MCPIP expression increased glial fibrillary acid protein (GFAP) expression and also caused distinct morphological changes, both indicative of glial differentiation. Similar results were observed with MCP-1 treatment. Interestingly, APP expression decreased in response to MCPIP. Instead, we found APP activity regulates expression of both MCP-1 and MCPIP. Furthermore, inhibition of either p38 MAPK or JAK signaling pathways significantly reduced APP’s effect on MCP-1 and MCPIP. These data demonstrates the role APP has in glial differentiation of NT2 cells through MCP-1/MCPIP signaling. It is possible that increased APP expression after CNS injury could play a role in MCP-1 production, possibly promoting astrocyte activation at injured site.

Gene dosage effects of Amyloid precursor protein (APP) can cause familial AD. Recent evidence suggest that microRNA (miRNA) pathways, implicated in gene transcriptional control, could be involved in the development of sporadic Alzheimer's disease (AD). We therefore investigated whether miRNAs could participate in the regulation of APP gene expression. We show that miRNAs belonging to the miR-20a family (that is, miR-20a, miR-17-5p and miR-106b) could regulate APP expression in vitro and at the endogenous level in neuronal cell lines. A tight correlation between these miRNAs and APP was found during brain development and in differentiating neurons. We thus identify miRNAs as novel endogenous regulators of APP expression, suggesting that variations in miRNA expression could contribute to changes in APP expression in the brain during development and disease. This possibility is further corroborated by the observation that a statistically significant decrease in miR-106b expression was found in sporadic AD patients.

Transgenic mice expressing mutant human amyloid precursor protein (APP) develop an age-dependent amyloid pathology and memory deficits, but no overt neuronal loss. Here, in mice overexpressing wild-type human APP (hAPP(wt)) we found an early memory impairment, particularly in the water maze and to a lesser extent in the object recognition task, but beta-amyloid peptide (Abeta(42)) was barely detectable in the hippocampus. In these mice, hAPP processing was basically non-amyloidogenic, with high levels of APP carboxy-terminal fragments, C83 and APP intracellular domain. A tau pathology with an early increase in the levels of phosphorylated tau in the hippocampus, a likely consequence of enhanced ERK1/2 activation, was also observed. Furthermore, these mice presented a loss of synapse-associated proteins: PSD95, AMPA and NMDA receptor subunits and phosphorylated CaMKII. Importantly, signs of neurodegeneration were found in the hippocampal CA1 subfield and in the entorhinal cortex that were associated to a marked loss of MAP2 immunoreactivity. Conversely, in mice expressing mutant hAPP, high levels of Abeta(42) were found in the hippocampus, but no signs of neurodegeneration were apparent. The results support the notion of Abeta-independent pathogenic pathways in Alzheimer's disease.

Secretion of Amyloid-beta peptide (Abeta) circulating oligomers and their aggregate forms derived by processing of beta-amyloid precursor protein (APP) are a key event in Alzheimer's disease (AD). We show that phosphorylation of APP on threonine 668 may play a role in APP metabolism in H4-APP(sw) cell line, a degenerative AD model. We proved that JNK plays a fundamental role in this phosphorylation since its specific inhibition, with the JNK inhibitor peptide (D-JNKI1), induced APP degradation and prevented APP phosphorylation at T668. This results in a significant drop of betaAPPs, Abeta fragments and Abeta circulating oligomers. Moreover the D-JNKI1 treatment produced a switch in the APP metabolism, since the peptide reduced the rate of the amyloidogenic processing in favour of the non-amyloidogenic one. All together our results suggest an important link between APP metabolism and the JNK pathway and contribute to shed light on the molecular signalling pathway of this disease indicating JNK as an innovative target for AD therapy.