Alzheimer's Disease Senile Plaques Research Articles

Altered Micro-RNA Regulation and Neuroprotection Activity of Eremostachys labiosiformis in Alzheimer’s Disease Model

Background: Amyloid-β peptide (Aβ) is involved in the formation of senile plaques in Alzheimer’s disease (AD), and causes neuronal cell death by inducing oxidative stress. Objective: We investigated the protective effect of Eremostachys labiosiformis extract against the Aβ-induced toxicity in SH-SY5Y cells. Methods: Methanolic extract from the aerial parts of E. labiosiformis was prepared by percolation method at room temperature. SH-SY5Y cells were treated and incubated with different concentrations of the extract for 1 h, before addition of Aβ. Cytotoxicity was measured 24 h after the addition of Aβ to the medium using MTT and reactive oxygen species (ROS) assays. Effective doses were evaluated using real-time polymerase chain reaction to evaluate expression of miR-212 and miR-132. The results were analyzed using SPSS software (16). Results: Exposure of ­SH-SY5Y cells to Aβ significantly affected the viability of cells and increased ROS levels. The results revealed that 1.2 and 2.5 μg/mL of the E. labiosiformis extract reduced Aβ-induced deterioration. Only 2.5 μg/mL of the extract could reduce ROS levels. In addition, 5 μg/mL of the extract increased the expression of the miRNAs, which was reduced after exposure to Aβ. Conclusion: Based on the antioxidant and protective effects of the E. labiosiformis extract on expression of miR-132 and miR-212 and ROS level, this herb could be used as a suitable candidate for future studies on neurodegenerative diseases including AD.

Id1 and Sonic Hedgehog Mediate Cell Cycle Reentry and Apoptosis Induced by Amyloid Beta-Peptide in Post-mitotic Cortical Neurons.

Amyloid beta-peptide (Aβ), the neurotoxic component of senile plaques in Alzheimer's disease (AD) brains, is known to trigger cell cycle reentry in post-mitotic neurons followed by apoptosis. However, the underlying mechanisms remain unclear. Recently, we have reported that Aβs stimulate the expression of inhibitor of differentiation-1 (Id1) to induce sonic hedgehog (SHH) (Hung et al., Mol Neurobiol 53(2):793-809, 2016), and both are mitogens capable of triggering cell cycle progression. In this work, we tested the hypothesis that Aβ-induced Id1 and SHH contribute to cell cycle reentry leading to apoptosis in neurons. We found that Aβ triggered cell cycle progression in the post-mitotic neurons, as indicated by the increased expression of two G1-phase markers including cyclin D1 and phosphorylated retinoblastoma protein (pRb), two G2-phase markers such as proliferating cell nuclear antigen (PCNA) and incorporation of 5-bromo-2'-deoxyuridine (BrdU) into newly synthesized DNA, as well as the mitotic marker histone H3 phosphorylated at Ser-10. As expected, Aβ also enhanced caspase-3 cleavage in the cortical neurons. Id1 siRNA, the neutralization antibody against SHH (SHH-Ab), and the cyclin-dependent kinase (CDK)-4/6 inhibitor PD0332991 all attenuated, in part or in full, the Aβ-induced expression of these cell cycle markers. Indeed, exogenous recombinant Id1 protein and the biologically active N-terminal fragment of SHH (SHH-N) were both sufficient to enhance the expression of cell cycle markers independent of Aβ. Taken together, our results revealed the critical roles of Id1 and SHH mediating Aβ-dependent cell cycle reentry and subsequently caspase-dependent apoptosis in the fully differentiated post-mitotic neurons, at least in vitro.

Construction of Quenchbodies to detect and image amyloid β oligomers

A quenchbody (Q-body) is an antibody-based biosensor that employs fluorescence quenching of the dye(s) attached to the antibody fragment, which are de-quenched upon antigen binding. In this study, we aimed to develop Fab type Q-bodies (UQ-bodies) to aid the diagnosis of Alzheimer's disease (AD). Characteristic senile plaques in AD consist of amyloid-β peptide (Aβ) generated from the amyloid precursor protein. Aβ42, one of the major peptide forms, aggregates fast and manifests higher neurotoxicity. Recent studies showed that Aβ oligomers, such as Aβ-derived diffusible ligand (ADDL), are more toxic than fibrils. Thus, detection of Aβ and its oligomers in body fluid might help detect deterioration caused by the disease. To this end, the Fab fragment of the anti-Aβ antibody h12A11, which binds preferentially to ADDL, was expressed in Escherichia coli, and labeled with a fluorescent dye at the N terminus of either the heavy chain, or the heavy and light chains, via Cys-containing tag(s) to prepare UQ-bodies. As a result, the double-labeled UQ-bodies detected ADDL with higher sensitivity than that for the Aβ peptide. In addition, the UQ-body could be used to image aggregated Aβ with a low background, which suggested the potential of UQ-bodies as a fast bioimaging tool.

Inkjet printing-based β-secretase fluorescence resonance energy transfer (FRET) assay for screening of potential β-secretase inhibitors of Alzheimer's disease

Amyloid-β (Aβ) is generated by proteolytic processing of amyloid precursor protein (APP) by beta-secretase (BACE-1) and gamma-secretase. Amyloid-β is responsible for the formation of senile plaques in Alzheimer's disease (AD). Consequently, inhibition of β-secretase (BACE-1), a rate-limiting enzyme in the production of Aβ, constitutes an attractive therapeutic approach to the treatment of AD. This paper reports an inkjet printing-based fluorescence assay for high throughput screening of β-secretase inhibitors achieved by employing a BACE-1 FRET substrate (Rh-Glu-Val-Asn-Leu-Asp-Ala-Glu-Phe-Lys-Quencher). This peptide substrate is known to be a readily available and suitable substrate for proteolytic activity, and it has high affinity to BACE-1. The BACE-1 peptide substrate printed on parchment paper was effectively cleaved by BACE-1, which was printed on the same spot. The amount of enzyme and substrate required for this inkjet printing-based BACE-1 assay can be less than 1.4ⅹ103, permitting the evaluation of inhibitor activity with femtomolar potency. The inkjet-printing-based BACE-1 inhibitory assay revealed inhibitory effects of inhibitor IV and STA on BACE-1 with an IM50 of 1.00 × 10−15 mol and 1.01 × 10−14 mol, respectively. These data confirm that both BACE-1 inhibitors (inhibitor IV and STA) actively inhibited the BACE-1 proteolysis of BACE-1 substrate on parchment paper. It important to note that the number of mole of BACE-1-substrate and enzyme utilized in the printing-based enzymatic assay are 1.4ⅹ103 smaller than the amount used in the conventional well-plate assay. The inkjet printing-based inhibitory assay constitutes a versatile high throughput technique and the IM50 values of the inhibitors were obtained with satisfactory reproducibility, suggesting that this inkjet-printing BACE-1 inhibitory assay could be quite suitable for the screening of new potential BACE-1 inhibitors for AD.

In Vitro Effects of Serotonin, Melatonin, and Other Related Indole Compounds on Amyloid-β Kinetics and Neuroprotection.

Amyloid-β peptide is the main component of senile plaques in Alzheimer's disease. The inhibition of amyloid-β peptide assembly, the destabilization of amyloid-β peptide aggregates, and the decrease of its cytotoxicity for the prevention of neuronal death are considered neuroprotective effects. In this work, the protective effects against amyloid-β peptide aggregation and cytotoxicity of eight indolic compounds are evaluated: tryptophan, tryptamine, serotonin, tryptophol, N-acetylserotonin, 3-indoleacetic acid, tryptophan ethyl ester, and melatonin. Thioflavin T spectroscopic assay, transmission electron microscopy, western blotting, circular dichroism, NMR, cell viability (thiazolyl blue tetrazolium bromide assay), quantitative PCR, and heme oxygenase activity are used. Serotonin is the most effective compound for inhibiting amyloid-β peptide aggregation. Almost all the indolic compounds tested prevent amyloid-β peptide-induced and increase cell viability, being between 9 and 25%. Melatonin and serotonin are the most active. Moreover, serotonin increased the expression of SIRT-1 and 2, heat shock protein 70, and heme oxygenase activity, this being a possible mechanism underlying the observed neuroprotective effect. Melatonin and other related indolic compounds, mainly serotonin, show an inhibitory and destabilizing effect on amyloid-β peptide fibril formation and they possess neuroprotective properties related to the vitagenes system.

Effects of NADPH Oxidase Inhibitors and Mitochondria-Targeted Antioxidants on Amyloid β1-42-Induced Neuronal Deaths in Mouse Mixed Cortical Cultures.

The Amyloid β peptide (Aβ) is a main component of senile plaques in Alzheimer's disease. Currently, NADPH oxidase (NOX) and mitochondria are considered as primary sources of ROS induced by Aβ. However, the contribution of NOX and mitochondria to Aβ-induced ROS generation has not been well defined. To delineate the relative involvement of NOX and mitochondria in Aβ-induced ROS generation and neuronal death in mouse cortical cultures, we examined the effect of NOX inhibitors, apocynin and AEBSF, and the mitochondria-targeted antioxidants (MTAs), mitotempol and mitoquinone, on Aβ-induced ROS generation and neuronal deaths. Cell death was assessed by measuring lactate dehydrogenase efflux in bathing media at 24 and 48 hrs after exposure to Aβ1-42. Aβ1-42 induced dose- and time-dependent neuronal deaths in cortical cultures. Treatment with 20 µM Aβ1-42 markedly and continuously increased not only the DHE fluorescence (intracellular ROS signal), but also the DHR123 fluorescence (mitochondrial ROS signal) up to 8 hrs. Treatment with apocynin or AEBSF selectively suppressed the increase in DHE fluorescence, while treatment with mitotempol selectively suppressed the increase in DHR123 fluorescence. Each treatment with apocynin, AEBSF, mitotempol or mitoquinone significantly attenuated the Aβ1-42-induced neuronal deaths. However, any combined treatment with apocynin/AEBSF and mitotempol/mitoquinone failed to show additive effects. These findings indicate that 20 µM Aβ1-42 induces oxidative neuronal death via inducing mitochondrial ROS as well as NOX activation in mixed cortical cultures, but combined suppression of intracellular and mitochondrial ROS generation fail to show any additive neuroprotective effects against Aβ neurotoxicity.

The inhibitory effect of chitosan oligosaccharides on β-site amyloid precursor protein cleaving enzyme 1 (BACE1) in HEK293 APPswe cells.

Amyloid precursor protein (APP) proteolysis is essential for the production of β-amyloid peptides (Aβ) that form senile plaques in Alzheimer's disease (AD) brains. The β-site amyloid protein precursor cleaving enzyme 1 (BACE1) is the rate limiting enzyme in the generation of Aβ from APP, inhibition of BACE1 is thereby considered as an attractive strategy for anti-AD drug discovery. Chitosan oligosaccharides (COS) has been shown to possess various biological activities. Here we investigated the potential inhibitory effect of COS on both BACE1 expression in HEK293 APPswe cells and BACE1 enzymatic activity in vitro. The results showed that COS (100-500μg/ml) dose-dependently decreased the cell apoptosis, and potently repressed the secretion of both Aβ40 and Aβ42 as determined by ELISA. Moreover, treatment with COS resulted in a dramatic reduction in BACE1 mRNA and protein expression level, eIF2α phosphorylation as well as BACE1 enzymatic activity. Taken together, our findings indicate that COS can ameliorate Aβ-associated neurotoxicity, which may be, at least in part, attributable to reductions in BACE1 enzymatic activity and expression.

A peptide-based near-infrared fluorescence probe for dynamic monitoring senile plaques in Alzheimer’s disease mouse model

In vivo monitoring neuropathological changes in Alzheimer’s disease (AD) animal model is critical for drug development. Here, by integrating blood-brain barrier penetrable peptide, we have developed a peptide probe which based on angiopep-2. Angiopep-based probe exhibited high binding affinity to Aβ aggregates and labeled senile plaques in vivo. Remarkably, the in vivo near-infrared imaging data revealed that fluorescence signals of this probe were nearly 3-fold higher in the brains of 16-month-old APP/PS1 transgenic mice compared to C57 mice and exhibited linear correlation with the senile plaques load process in 4-, 8-, 16-month-old APP/PS1 transgenic mice. Moreover, senile plaques load was detected in vivo as early as 4 months of age that even at the very beginning of plaques developed in APP/PS1 transgenic mice. Taken together, this novel peptide-based probe achieved dynamic monitoring senile plaques in APP/PS1 transgenic mice and have been ready to use in drug development in AD mouse model.

Non-aggregated Aβ25-35 Upregulates Primary Astrocyte Proliferation In Vitro.

Amyloid beta (Aβ) is a peptide cleaved from amyloid precursor protein that contributes to the formation of senile plaques in Alzheimer’s disease (AD). The relationship between Aβ and astrocyte proliferation in AD remains controversial. Despite pathological findings of increased astrocytic mitosis in AD brains, in vitro studies show an inhibitory effect of Aβ on astrocyte proliferation. In this study, we determined the effect of an active fragment of Aβ (Aβ25-35) on the cell cycle progression of primary rat astrocytes. We found that Aβ25-35 (0.3–1.0 μg/ml) enhanced astrocyte proliferation in vitro in a time- and concentration-dependent manner. Increased DNA synthesis by Aβ25-35 was observed during the S phase of the astrocyte cell cycle, as indicated by proliferation kinetics and bromodeoxyuridine immunocytochemical staining. Aggregation of Aβ25-35 abolished the upregulatory effect of Aβ on astrocyte proliferation. Further examination indicated that Aβ25-35 affected astrocyte proliferation during early or mid-G1 phase but had no effect on DNA synthesis at the peak of S phase. These results provide insight into the relationship between Aβ25-35 and astrocyte cell cycling in AD.

Synthesis and biological evaluation of curcumin analogs as β-amyloid imaging agents.

Detection of β-amyloid (Aβ) plaques in the brain is a very promising biomarker approach for early diagnosis of Alzheimer's disease (AD). A series of curcumin analogs (1,5-diphenyl-1,4-pentadien-3-one derivatives) were synthesized and evaluated. Specific binding to Aβ plaques was demonstrated in vitro using postmortem AD homogenates, and the fluorescent staining and autoradiography in vitro of postmortem AD brain sections were performed. Some compounds showed high binding affinities with Aβ plaques. Fluorescent staining indicated that compound 4e clearly stained Aβ plaques within AD brain sections. In biodistribution, radioiodinated ligand [125I]4e exhibited high brain uptake and favorable clearance from the brain. Autoradiography in vitro further confirmed the high affinities of [125I]4e. The results strongly suggested that [125I]4e might be developed into potential amyloid imaging agent for the detection of senile plaques in AD. [Formula: see text].

RTN1 and RTN3 protein are differentially associated with senile plaques in Alzheimer\u2019s brains

Reticulon proteins (RTNs), consisting of RTN1 to RTN4, were previously shown to interact with BACE1 by negatively modulating its secretase activity. In RTN3-null mice, RTN1 expression was slightly elevated. To understand the in vivo role of RTN1, we generated RTN1-null mice and compared the effects of RTN1 and RTN3 on BACE1 modulation. We show that RTN1 is mostly expressed by neurons and not by glial cells under normal conditions, similar to the expression of RTN3. However, RTN1 is more localized in dendrites and is an excellent marker for dendrites of Purkinje cells, while RTN3 expression is less evident in dendrites. This differential localization also correlates with their associations with amyloid plaques in Alzheimer’s brains: RTN3, but not RTN1, is abundantly enriched in dystrophic neurites. RTN3 deficiency causes elevation of BACE1 protein levels, while RTN1 deficiency shows no obvious effects on BACE1 activity due to compensation by RTN3, as RTN1 deficiency causes elevation of RTN3 expression. Hence, expression of RTN1 and RTN3 is tightly regulated in mouse brains. Together, our data show that RTN1 and RTN3 have differential effects on the formation of senile plaques in Alzheimer’s brains and that RTN3 has a more prominent role in Alzheimer’s pathogenesis.

Molecular characterization of Netrin-1 and APP receptor binding: New leads to block the progression of senile plaques in Alzheimer's disease

Alzheimer's disease is a growing concern in the context of the increasing lifespan of the populations. The work presented here is part of the fight against this threat. It supports a therapeutic approach to reduce the incidence of Alzheimer's disease, taking advantage of the specific binding of several domains of Netrin-1 to the β-amyloid precursor protein. This basic knowledge shall then be used to predict, design or characterize lead compounds that may in turn inhibit/delay Alzheimer's disease’s progression, extending the therapeutic offer of the other leads already being investigated in this line. The present work is focused on the interaction of the various portions of APP with the three domains of Netrin-1, the so-called LamNT, EGF-like and NTR domains respectively. It reveals in detail which portions of APP and Netrin-1 are specifically involved in these interactions, using ELISA technique in combination with protein-protein binding simulations. So far unsuspected interaction sites located in Netrin-1 EGF-like and NTR domains open possibilities for new therapeutic approaches in which these sites will be specifically targeted.

Monocular denervation of visual nuclei modulates APP processing and sAPPα production: A possible role on neural plasticity

Amyloid precursor protein (APP) is essential to physiological processes such as synapse formation and neural plasticity. Sequential proteolysis of APP by beta- and gamma-secretases generates amyloid-beta peptide (Aβ), the main component of senile plaques in Alzheimer Disease. Alternative APP cleavage by alpha-secretase occurs within Aβ domain, releasing soluble α-APP (sAPPα), a neurotrophic fragment. Among other functions, sAPPα is important to synaptogenesis, neural survival and axonal growth. APP and sAPPα levels are increased in models of neuroplasticity, which suggests an important role for APP and its metabolites, especially sAPPα, in the rearranging brain. In this work we analyzed the effects of monocular enucleation (ME), a classical model of lesion-induced plasticity, upon APP content, processing and also in secretases levels. Besides, we addressed whether α-secretase activity is crucial for retinotectal remodeling after ME. Our results showed that ME induced a transient reduction in total APP content. We also detected an increase in α-secretase expression and in sAPP production concomitant with a reduction in Aβ and β-secretase contents. These data suggest that ME facilitates APP processing by the non-amyloidogenic pathway, increasing sAPPα levels. Indeed, the pharmacological inhibition of α-secretase activity reduced the axonal sprouting of ipsilateral retinocollicular projections from the intact eye after ME, suggesting that sAPPα is necessary for synaptic structural rearrangement. Understanding how APP processing is regulated under lesion conditions may provide new insights into APP physiological role on neural plasticity.

Bacterial Amyloid and DNA are Important Constituents of Senile Plaques: Further Evidence of the Spirochetal and Biofilm Nature of Senile Plaques.

It has long been known that spirochetes form clumps or micro colonies in vitro and in vivo. Cortical spirochetal colonies in syphilitic dementia were considered as reproductive centers for spirochetes. Historic and recent data demonstrate that senile plaques in Alzheimer’s disease (AD) are made up by spirochetes. Spirochetes, are able to form biofilm in vitro. Senile plaques are also reported to contain elements of biofilm constituents. We expected that AβPP and Aβ (the main components of senile plaques) also occur in pure spirochetal biofilms, and bacterial DNA (an important component of biofilm) is also present in senile plaques. Histochemical, immunohistochemical, and in situ hybridization techniques and the TUNEL assay were used to answer these questions. The results obtained demonstrate that Aβ and DNA, including spirochete-specific DNA, are key components of both pure spirochetal biofilms and senile plaques in AD and confirm the biofilm nature of senile plaques. These results validate validate previous observations that AβPP and/or an AβPP-like amyloidogenic protein are an integral part of spirochetes, and indicate that bacterial and host derived Aβ are both constituents of senile plaques. DNA fragmentation in senile plaques further confirms their bacterial nature and provides biochemical evidence for spirochetal cell death. Spirochetes evade host defenses, locate intracellularly, form more resistant atypical forms and notably biofilms, which contribute to sustain chronic infection and inflammation and explain the slowly progressive course of dementia in AD. To consider co-infecting microorganisms is equally important, as multi-species biofilms result in a higher resistance to treatments and a more severe dementia.

Aβ40 has a subtle effect on Aβ42 protofibril formation, but to a lesser degree than Aβ42 concentration, in Aβ42/Aβ40 mixtures

Recent findings suggest that the senile plaques in Alzheimer's disease may contain soluble amyloid-β peptide (Aβ) fibril precursors along with insoluble fibrils. These soluble Aβ species, including oligomers and protofibrils, have been well-studied in vitro and are formed via non-covalent self-assembly of Aβ monomers. While both 40- and 42-residue forms of Aβ are observed in the human body, the majority of the Aβ aggregation work has been conducted on Aβ42 or Aβ40 separately, with relatively few investigations of mixtures. In order to study the effect of different combinations of Aβ40 and Aβ42 on protofibril formation, mixtures of either dry solid peptide, or purified Aβ40 and Aβ42 monomer solutions were mixed together and protofibril/monomer distributions were quantified. Increases in the Aβ42/Aβ40 ratio increased protofibril formation but the presence of Aβ40 in the mixed Aβ solutions had a significant negative impact on protofibril formation compared to equivalent solutions of pure Aβ42. Protofibril size was less affected, but β-sheet structure increased with protofibrils formed from higher Aβ42/Aβ40 ratio solutions. Direct measurement of Aβ42/Aβ40 ratios by C-terminal-selective ELISA found very little Aβ40 incorporated into protofibrils. The cumulative data emphasizes the critical importance of Aβ42, yet establishes Aβ40 as a regulator of Aβ42 aggregation.

Bone marrow amyloid spherulites in a case of AL amyloidosis

Parallel arrangement of β-pleated sheets by amyloidogenic proteins is a well known phenomenon. Rarely, amyloid fibrils undergo radial orientation to form globular structures called spherulites. These amyloid spherulites show Maltese cross pattern under polarized microscopy. The clinical significance of amyloid spherulites is undetermined. Amyloidogenic proteins like insulin and β-lactoglobulin form spherulites in vitro. The senile plaques of Alzheimer's disease rarely form in vivo spherulites. Amyloid spherulites have been described in the liver and small intestine. For the first time, we document amyloid spherulite formation in the bone marrow biopsy of an AL amyloidosis patient.

Role of Hydrophobic Patch in LRP6: A Promising Drug Target for Alzheimer's disease

Alzheimer’s disease is one of the most fatal dementia occurring in elderly persons. LRP6 and DKK1 proteins are found in the senile plaques of Alzheimer’s disease patients. Inducing the disassociation/inhibition of the LRP6–DKK1 complex is a vital mechanism for the treatment of Alzheimer’s disease. This study accomplished its goal of targeting potent inhibitors against LRP6 by molecular modeling techniques such as high throughput virtual screening and molecular dynamics simulations. Zinc database compounds were docked in the hydrophobic patch of LRP6 and in the active site of DKK1 using the GLIDE module. The initial docking results were well exemplified to amino acid residues interacting on the hydrophobic patch of LRP6 and active sites of DKK1. Further, the best hit compounds (866) were again redocked with Glide XP and finally six lead compounds were identified as the best inhibitors against LRP6 which was later confirmed by molecular dynamics simulation studies.

Association Study of IL-4 -590 C/T and DDX39B -22 G/C Polymorphisms with the Risk of Late-Onset Alzheimer's Disease in Iranian Population.

Interleukin-4 (IL-4), an important anti-inflammatory cytokine, is elucidated to regulate amyloid β-induced production of the inflammatory cytokines such as IL-1 and IL-6. It is assumed that IL-4 may involve in the inflammation pathology of surrounding senile plaques in Alzheimer's disease (AD) patients. DEAD (Asp-Glu-Ala-Asp) box polypeptide 39B (DDX39B), appears to be involved in regulation of the inflammatory cytokines which are in correlation with AD pathology. This study was conducted to investigate the two single nucleotide polymorphisms (SNPs), IL-4 -590 C/T and DDX39B -22 G/C, association with the risk of late-onset AD (LOAD) in Iranian population. In the present study, therefore, a cohort of 153 LOAD cases and 153 age-matched unrelated, non-dementia control subjects were analyzed for the two polymorphisms by polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP). Our results successfully demonstrate a protective association between the IL-4 -590 T allele, IL-4 -590 C/T heterozygous genotype (P= 0.01, OR= 0.53 and P= 0.041; OR= 0.56, respectively) and LOAD in Iranian population. A resemblance significant association was detected in female population when subjects were stratified by sex: the IL-4 -590 T allele (P= 0.02, OR= 0, 40) and the heterozygous genotype (P= 0.009, OR= 0.29). However, no significant association was observed between the DDX39B -22 G/C polymorphism in the cases and controls. Furthermore, it is clarified that the protective effect of IL-4 -590 is independent from APOE protective genotypes. Accordingly, the IL-4 -590 T allele may be applied as a protective marker in the development of LOAD in Iranian population.

Cerebral amyloid angiopathy and dementia

Cerebral amyloid angiopathy (CAA) is one of the most frequent causes of intracerebral hemorrhage (ICH). The deposition of beta amyloid leads to vascular fragility due to degeneration of vessel walls, formation of microaneurysms particularly in cortical blood vessels and fibrinoid vessel wall necrosis. The Congo red positive amyloid deposits are biochemically similar to the material comprising senile plaques in Alzheimer's disease. Recurrent or multiple simultaneous hemorrhages particularly in older patients should raise the suspicion of CAA. Gradient echo magnetic resonance imaging (MRI) is a sensitive, non-invasive technique for identifying even very small hemorrhages and superficial siderosis, which may cause transient symptoms in CAA. There is also a correlation between CAA, microbleeding and cognitive decline. Inflammatory variants of CAA must be suspected whenever patients present with progressive dementia, headache and multifocal symptoms in association with CAA findings in MRI. Histopathologically, a distinction is made between CAA-related inflammation (CAA-ri) with perivascular inflammatory infiltrates and amyloid beta-related angiitis (ABRA) with histological detection of transmural vasculitis. Inflammatory variants should be treated with corticosteroids and immunosuppressants.

The Golgi-Localized γ-Ear-Containing ARF-Binding (GGA) Proteins Alter Amyloid-β Precursor Protein (APP) Processing through Interaction of Their GAE Domain with the Beta-Site APP Cleaving Enzyme 1 (BACE1).

Proteolytic processing of amyloid-β precursor protein (APP) by beta-site APP cleaving enzyme 1 (BACE1) is the initial step in the production of amyloid beta (Aβ), which accumulates in senile plaques in Alzheimer’s disease (AD). Essential for this cleavage is the transport and sorting of both proteins through endosomal/Golgi compartments. Golgi-localized γ-ear-containing ARF-binding (GGA) proteins have striking cargo-sorting functions in these pathways. Recently, GGA1 and GGA3 were shown to interact with BACE1, to be expressed in neurons, and to be decreased in AD brain, whereas little is known about GGA2. Since GGA1 impacts Aβ generation by confining APP to the Golgi and perinuclear compartments, we tested whether all GGAs modulate BACE1 and APP transport and processing. We observed decreased levels of secreted APP alpha (sAPPα), sAPPβ, and Aβ upon GGA overexpression, which could be reverted by knockdown. GGA-BACE1 co-immunoprecipitation was impaired upon GGA-GAE but not VHS domain deletion. Autoinhibition of the GGA1-VHS domain was irrelevant for BACE1 interaction. Our data suggest that all three GGAs affect APP processing via the GGA-GAE domain.