Alzheimer's Plaques Research Articles

Cystatin C Shifts APP Processing from Amyloid-β Production towards Non-Amyloidgenic Pathway in Brain Endothelial Cells.

Amyloid-β (Aβ), the major component of neuritic plaques in Alzheimer’s disease (AD), is derived from sequential proteolytic cleavage of amyloid protein precursor (APP) by secretases. In this study, we found that cystatin C (CysC), a natural cysteine protease inhibitor, is able to reduce Aβ40 secretion in human brain microvascular endothelial cells (HBMEC). The CysC-induced Aβ40 reduction was caused by degradation of β-secretase BACE1 through the ubiquitin/proteasome pathway. In contrast, we found that CysC promoted secretion of soluble APPα indicating the activated non-amyloidogenic processing of APP in HBMEC. Further results revealed that α-secretase ADAM10, which was transcriptionally upregulated in response to CysC, was required for the CysC-induced sAPPα secretion. Knockdown of SIRT1 abolished CysC-triggered ADAM10 upregulation and sAPPα production. Taken together, our results demonstrated that exogenously applied CysC can direct amyloidogenic APP processing to non-amyloidgenic pathway in brain endothelial cells, mediated by proteasomal degradation of BACE1 and SIRT1-mediated ADAM10 upregulation. Our study unveils previously unrecognized protective role of CysC in APP processing.

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.

6-Methoxy-indanone derivatives as potential probes for β-amyloid plaques in Alzheimer's disease

A series of 6-methoxy indanone derivatives was synthesized and evaluated as potential probes for β-amyloid plaque imaging in Alzheimer's disease (AD). Two derivatives (5d and 5k) displayed significant binding abilities in fluorescent staining experiments using the brain sections of AD patients. Two derivatives showed high binding affinities to β-amyloid aggregates (5j, Ki = 5.82 ± 0.19 nM) and brain homogenates of AD patients (5j, Ki = 18.96 ± 0.28 nM) in in vitro binding assay. With a log P value of 3.45, [125I]5k exhibited an excellent initial brain uptake (5.29%ID g−1, 2 min after i.v.) and a fast clearance from the brain in biodistribution experiments in normal mice. In autoradiography, [125I]5k exhibited an obvious binding ability to β-amyloid plaques and a relatively low nonspecific binding in the brain sections of AD patients (in vitro) and APP/PS1 transgenic mice (in vitro and ex vivo). Results suggest that 5k is a potential probe for detecting β-amyloid plaques in vivo.

Tenascin-C Is Associated with Cored Amyloid-β Plaques in Alzheimer Disease and Pathology Burdened Cognitively Normal Elderly.

Tenascin-C (TN-C) is an extracellular matrix glycoprotein linked to inflammatory processes in pathological conditions including Alzheimer disease (AD). We examined the distribution of TN-C immunoreactivity (ir) in relation to amyloid-β (Aβ) plaques and vascular Aβ deposits in autopsy brain tissues from 14 patients with clinical and neuropathological AD and 10 aged-matched controls with no cognitive impairment; 5 of the controls had Aβ plaques and 5 did not. TN-C ir was abundant in cortical white matter and subpial cerebral gray matter in all cases, whereas TN-C ir was weak in blood vessels. In all cases with Aβ plaques but not in plaque-free controls, TN-C ir was detected as large (>100 µm in diameter) diffuse extracellular deposits in cortical grey matter. TN-C plaques completely overlapped and surrounded cored Aβ plaques labeled with X-34, a fluorescent derivative of Congo red, and they were associated with reactive astrocytes astrocytes, microglia and phosphorylated tau-containing dystrophic neurites. Diffuse Aβ plaques lacking amyloid cores, reactive glia or dystrophic neurites showed no TN-C ir. In cases with cerebral amyloid angiopathy, TN-C ir in vessel walls did not spread into the surrounding neuropil. These results suggest a role for TN-C in Aβ plaque pathogenesis and its potential as a biomarker and therapy target.

Transcriptional profiling of CD11c-positive microglia accumulating around amyloid plaques in a mouse model for Alzheimer's disease

Amyloid plaques in Alzheimer's disease (AD) mice are surrounded by activated microglia. The functional role of microglia activation in AD is not well understood; both detrimental and beneficial effects on AD progression have been reported. Here we show that the population of activated microglia in the cortex of the APPswe/PS1dE9 mouse AD model is divided into a CD11c-positive and a CD11c-negative subpopulation.Cd11c transcript levels and number of CD11c-positive microglia increase sharply when plaques start to occur and both parameters continue to rise in parallel with the age-related increasing plaque load. CD11c cells are localized near plaques at all stages of the disease development and constitute 23% of all activated microglia. No differences between these two populations were found in terms of proliferation, immunostaining intensity of Iba1, MHC class II, CD45, or immunoproteasome subunit LMP7/β5i. Comparison of the transcriptome of isolated CD11c-positive and CD11c-negative microglia from the cortex of aged APPswe/PS1dE9 with WT microglia showed that gene expression changes had a similar general pattern. However, a differential expression was found for genes involved in immune signaling (Il6, S100a8/Mrp8, S100a9/Mrp14, Spp1, Igf1), lysosome activation, and carbohydrate- and cholesterol/lipid-metabolism (Apoe). In addition, the increased expression of Gpnmb/DC-HIL, Tm7sf4/DC-STAMP, and Gp49a/Lilrb4, suggests a suppressive/tolerizing influence of CD11c cells.We show that amyloid plaques in the APP/PS1 model are associated with two distinct populations of activated microglia: CD11c-positive and CD11c-negative cells. Our findings imply that CD11c-positive microglia can potentially counteract amyloid deposition via increased Aβ-uptake and degradation, and by containing the inflammatory response.

Inhibiting TLR2 activation attenuates amyloid accumulation and glial activation in a mouse model of Alzheimer’s disease

The effects of Toll-like receptor (TLR) activation in peripheral cells are well characterized but, although several TLRs are expressed on cells of the brain, the consequences of their activation on neuronal function remain to be fully investigated, particularly in the context of assessing their potential as therapeutic targets in neurodegenerative diseases. Several endogenous TLR ligands have been identified, many of which are soluble factors released from cells exposed to stressors. In addition, amyloid-β (Aβ) the main constituent of the amyloid plaques in Alzheimer’s disease (AD), activates TLR2, although it has also been shown to bind to several other receptors. The objective of this study was to determine whether activation of TLR2 played a role in the developing inflammatory changes and Aβ accumulation in a mouse model of AD. Wild type and transgenic mice that overexpress amyloid precursor protein and presenilin 1 (APP/PS1 mice) were treated with anti-TLR2 antibody for 7months from the age of 7–14months. We demonstrate that microglial and astroglial activation, as assessed by MHCII, CD68 and GFAP immunoreactivity was decreased in anti-TLR2 antibody-treated compared with control (IgG)-treated mice. This was associated with reduced Aβ plaque burden and improved performance in spatial learning. The data suggest that continued TLR2 activation contributes to the developing neuroinflammation and pathology and may be provide a strategy for limiting the progression of AD.

Proteolytic processing of Neuregulin-1.

Neuregulin-1 (NRG1), known also as heregulin, acetylcholine receptor inducing activity (ARIA), glial growth factor (GGF), or sensory and motor neuron derived factor (SMDF), is a key factor for many developmental processes and in adult brain. All known splice variants contain an epidermal growth factor (EGF)-like domain, which is mediating signaling via receptors of the ErbB family. In particular, NRG1 acts as an essential signaling molecule expressed on the axonal surface, where it signals to Schwann cells throughout development and regulates the thickness of the myelin sheath. NRG1 is required also by other cell types in the nervous system, for instance as an axonal signal released by proprioceptive afferents to induce development of the muscle spindle, and it controls aspects of cortical interneuron development as well as the formation of thalamo-cortical projections. The precursor protein of NRG1 can be activated and released from the membrane through limited proteolysis by the β-Secretase (β-site amyloid precursor protein cleaving enzyme 1, BACE1) which was first identified through its function as the rate limiting enzyme of amyloid-β-peptide (Aβ) production. Aβ is the major component of amyloid plaques in Alzheimer's disease (AD). Due to the hairpin nature of NRG1 type III two membrane-bound stubs with a type 1 and a type 2 orientation are generated by an initial proteolytic cleavage and successive release of the EGF-like domain either by dual cleavage by BACE1 or by ADAM17 (a disintegrin and metalloprotease) which is also called TACE (Tumor Necrosis Factor-α-converting enzyme). The cleavages activate NRG1 to allow juxtacrine or paracrine signaling. The type 1 oriented stub is further cleaved by γ-secretase in the transmembrane domain with a putative role in intracellular domain (ICD) signaling, while the type II oriented stub is cleaved by signal peptidase like proteases (SPPLs). Neuregulin-1 was identified as a major physiological substrate of BACE1 during early postnatal development when similarities in BACE1 KO mice and NRG1 heterozygous mice were discovered. Both display severe hypomyelination of peripheral nerves. Later it was shown with genetic and pharmacological evidence that the developmental effect of type I NRG1 on the formation and the maintenance of muscle spindles is BACE1 dependent. Thus, NRG1 functions in PNS and CNS are likely to set limits to an Alzheimer disease therapy with relatively strong BACE1 inhibition.

Atomic Details of the Interactions of Glycosaminoglycans with Amyloid-β Fibrils.

The amyloid plaques associated with Alzheimer's disease (AD) comprise fibrillar amyloid-β (Aβ) peptides as well as non-protein factors including glycosaminoglycan (GAG) polysaccharides. GAGs affect the kinetics and pathway of Aβ self-assembly and can impede fibril clearance; thus, they may be accessory molecules in AD. Here we report the first high-resolution details of GAG-Aβ fibril interactions from the perspective of the saccharide. Binding analysis indicated that the GAG proxy heparin has a remarkably high affinity for Aβ fibrils with 3-fold cross-sectional symmetry (3Q). Chemical synthesis of a uniformly (13)C-labeled octasaccharide heparin analogue enabled magic-angle spinning solid-state NMR of the GAG bound to 3Q fibrils, and measurements of dynamics revealed a tight complex in which all saccharide residues are restrained without undergoing substantial conformational changes. Intramolecular (13)C-(15)N dipolar dephasing is consistent with close (<5 Å) contact between GAG anomeric position(s) and one or more histidine residues in the fibrils. These data provide a detailed model for the interaction between 3Q-seeded Aβ40 fibrils and a major non-protein component of AD plaques, and they reveal that GAG-amyloid interactions display a range of affinities that critically depend on the precise details of the fibril architecture.

LIPOPOLYSACCHARIDE AND E. COLI PROTEINS AND DNA IN ALZHEIMER’S DISEASE BRAINS COMPARED TO CONTROLS

Amyloid plaques in Alzheimer's disease (AD) are believed to be derived in part from clevage products of amyloid precursor protein (APP). However, Gram-negative Escherichia coli (E. coli) bacteria and other microorganisms can form extracellular amyloid. Moreover, administration of Gram-negative bacterial derived Lipopolysaccharide (LPS) followed by ischemia and hypoxia produce plaque-like aggregates of myelin and amyloid ß in adult rat brains. These findings led us to examine human brain for LPS and E. coli proteins and DNA. Brain samples from superior temporal gyrus gray matter and frontal lobe white matter were studied from AD patients (n=24) and age-matched controls (n=18). LPS and E. coli proteins including K99 pili protein were evaluated by Western blots and immunocytochemistry. DNA from human brains was assessed for E. coli DNA. LPS and E. coli K99 were detected immunocytochemically in brain parenchyma and vessels in all AD and control brains. K99 levels by Western blots were greater in AD compared to control brains (p < 0.01) and K99 was localized to neurons in AD but not control brains. LPS co-localized with Aß1-40/42 in amyloid plaques and with Aß1-40/42 around vessels in AD brains. E. coli DNA or the E. coli K99 pili protein were detected in 9/10 control and 13/13 AD brains. LPS and E. coli bacterial proteins and DNA are found in control and AD brains. LPS co-localization with Aß1-40/42 in amyloid plaques and around vessels in AD brain suggest that LPS and/or other bacterial components could play a role in AD pathogenesis.

Methionine oxidation reduces lag-times for amyloid-β(1–40) fiber formation but generates highly fragmented fibers

Oxidative stress and the formation of amyloid plaques containing amyloid-β (Aβ) peptides are two key hallmarks of Alzheimer's disease. A proportion of methionine (Met) at position 35 within Aβ is oxidized to methionine sulphoxide (MetOX) within the Alzheimer's plaques. These oxidative processes may be the key to understanding the early stages of Alzheimer's disease. In vitro oxidation of Aβ, by the physiological oxidant H2O2, was monitored using 1H NMR and mass spectrometry. Here we investigate the effect of Aβ methionine oxidation on fiber formation kinetics and morphology using the amyloid specific fluorescence dye Thioflavin T (ThT) and Transmission Electron Microscopy (TEM). Methionine oxidation reduces the total amount of fibers generated for both dominant forms of Aβ, however there are marked differences in the effect of MetOX between Aβ(1–40) and Aβ(1–42). Surprisingly the presence of MetOX reduces lag-times for Aβ(1–40) fiber formation but extends lag-times for Aβ(1–42). TEM indicates a change in fiber morphology with a pronounced reduction in fiber length for both methionine oxidized Aβ(1–40) and Aβ(1–42). In contrast, the morphology of preformed amyloid fibers is largely unaffected by the presence of H2O2. Our studies suggest that methionine oxidation promotes highly fragmented fiber assemblies of Aβ. Oxidative stress associated with Alzheimer's disease can cause oxidation of methionine within Aβ and this in turn will influence the complex assembly of Aβ monomer into amyloid fibers, which is likely to impact Aβ toxicity.

(68)Ga-Bivalent Polypegylated Styrylpyridine Conjugates for Imaging Aβ Plaques in Cerebral Amyloid Angiopathy.

Aβ plaques deposited on blood vessels are associated with cerebral amyloid angiopathy (CAA). In an effort to selectively map these Aβ plaques, we are reporting a new series of (68)Ga labeled styrylpyridine derivatives with high molecular weights. In vitro binding to Aβ plaques in post-mortem Alzheimer's disease (AD) brain tissue showed that these (68)Ga labeled bivalent styrylpyridines displayed good affinities and specificity (Ki < 30 nM). In vitro autoradiography using post-mortem AD brain sections showed specific binding of these (68)Ga complexes to Aβ plaques. Biodistribution studies in normal mice showed very low initial brain uptakes (<0.3% dose/g) indicating a low blood-brain barrier (BBB) penetration. The preliminary results suggest that (68)Ga labeled bivalent styrylpyridines may be promising candidates as PET imaging radiotracers for detecting CAA.

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.

Tau and Alzheimer pathobiology

The neurotoxicity of amyloid beta (Aβ), a major cleavage product of the amyloid precursor protein (APP), is enhanced by iron, as found in the amyloid plaques of Alzheimer's disease (AD) patients. By contrast, the long-known neuroprotective activity of APP is evident after α-secretase cleavage of the precursor to release sAPPα, and depends on the iron export actions of APP itself. The latter underlie its neurotrophic and protective effects in facilitating the homeostatic actions of ferroportin mediated-iron export. Thus APP-dependent iron export may alleviate oxidative stress by minimizing labile iron thus protecting neurons from iron overload during stroke and hemorrhage. Consistent with this, altered phosphorylation of iron-regulatory protein-1 (IRP1) and its signaling processes play a critical role in modulating APP translation via the 5′ untranslated region (5′UTR) of its transcript. The APP 5′UTR region encodes a functional iron-responsive element (IRE) RNA stem loop that represents a potential target for modulating APP production. Targeted regulation of APP gene expression via the modulation of 5′UTR sequence function represents a novel approach for the potential treatment of AD since altering APP translation can be used to improve both the protective brain iron balance and provide anti-amyloid efficacy. Approved drugs including paroxetine and desferrioxamine and several novel compounds have been identified that suppress abnormal metal-promoted Aβ accumulation with a subset of these acting via APP 5′UTR-dependent mechanisms to modulate APP translation and cleavage to generate the non-toxic sAPPα.

Abstract 135: Complementary-Medicine Prevention of Alzheimer’s Disease by Blackcurrant Extract

Background: Every 3.2 s, an individual falls ill with dementia, the number of persons concerned will almost be trebled by 2050, scientists communicated in London at the World Alzheimer Report 2015. They called upon government and employers to invest more in prevention. At present, 46.8 million people live with a demential disease worldwide. From a public health point of view, this high prevalence should motivate to greater efforts regarding prevention and treatment of the vascular component of the disease, because this has the potential to markedly reduce the occurrence of dementia. Methods: Flow-dependent isometric tension was measured in segments of isolated human intracerebral arteries from consciousness areas (brain surgery). Flow variations of the Krebs solution were 3, 5, 20, 40 and 100 mL/min. Krebs without and with addition of either 0.01% membrane filtered blackcurrant extract (BCE, Code 70140015, BerryPharma®) or ethanol extracted BCE was used as superfusate. Biosensor ellipsometry and EIAs were applied. VLDLapoE4/E4 (10 mg/dL) from genotypized patients and human β-amyloid Aβ42 were used in ellipsometry. Results: In controls (n = 14), brain arteries relaxed from 1.416 g (T3) to 1.011 g (T100), i.e. by 28.6% of their initial tone. Under BCE 70140015 (n = 5), vascular tone decreased from 1.390 g to 0.803 g (against control p &lt; 0.0354). This is a 42.2% reduction in tension, a 45.2% increase in flow relaxation, and a 50.7% rise in blood perfusion. Ethanol extracted BCE, however, showed against controls an even slightly impaired relaxation (contraction by 3.6%). - BCE is bound to membrane proteoheparan sulfate (HS-PG), the natural flow sensor and peripheral lipoprotein receptor. Addition of VLDLapoE4/E4, Aβ42, and Ca2+ ions to HS-PG adsorbed to a silica surface led to quaternary Alzheimer plaque formation. Preincubation of HS-PG with BCE reduced VLDL docking by 5.9%, ternary plaques with Aβ42 by 11.6%, and quaternary calcified Alzheimer nanoplaques by 17.3%. Conclusion: The flow experiments show that membrane filtered BCE clearly improved endothelial function by an additional NO release, while ethanol extracted did not. This vasodilatation together with the reduction of Alzheimer nanoplaques may have a beneficial effect on cognitive functions in dementiae of the Alzheimer type, in prevention of TIA and stroke.

Amyloid Plaque in the Human Brain Can Decompose from Aβ(1-40/1-42) by Spontaneous Nonenzymatic Processes.

The degradation of long-lived proteins in the body is an important aspect of aging, and much of the breakdown is due to the intrinsic instability of particular amino acids. In this study, peptides were examined to discover if spontaneous nonenzymatic reactions could be responsible for the composition of Alzheimer's (AD) plaque in the human brain. The great majority of AD plaque consists of N-terminally truncated versions of Aβ(1-40/1-42), with the most abundant peptide commencing with Glu (residue 3 in Aβ1-40/1-42) that is present as pyroGlu. Several Asp residues are racemized in Aβ plaque, with residue 1 being predominantly l-isoAsp and peptide bond cleavage next to Ser 8 is also evident. In peptides, loss of the two N-terminal amino acids as a diketopiperazine was demonstrated at pH 7. For the Aβ N-terminal hexapeptide, AspAlaGluPheArgHis, this resulted in the removal of AspAla diketopiperazine and the generation of Glu as the new N-terminal residue. The Glu cyclized readily to pyroGlu. This pathway was altered significantly by zinc, which promoted pyroGlu formation but decreased AspAla diketopiperazine release. Zinc also facilitated cleavage on the N-terminal side of Ser 8. Racemization of the original N-terminal Asp to l-isoAsp was also detected and loss of one amino acid from the N-terminus. These data are therefore entirely consistent with plaque in the human brain forming from deposition of Aβ(1-40/1-42) and, over time, decomposing spontaneously. Since amyloid plaque is present in the human brain for years prior to the onset of AD, gradual spontaneous changes to the polypeptides within it will alter its properties and those of the oligomers that can diffuse from it. Such incremental changes in composition may therefore contribute to the origin of AD-associated cytotoxicity.

Discovery of boronic acid-based fluorescent probes targeting amyloid-beta plaques in Alzheimer’s disease

A boronic acid-based fluorescent probe was developed for diagnosis of amyloid-β (Aβ) plaques from Alzheimer’s disease (AD). Probe 4c, which included boronic acid as a functional group, exhibited a significant increase (64.37-fold, FAβ/F0) in fluorescence intensity as a response to Aβ aggregates, with a blue shift (105nm) in the maximum emission wavelength. We found that boronic acid as a functional group improved the binding affinity (KD value=0.79±0.05μM for 4c) for Aβ aggregates and confirmed that 4c selectively stained Aβ plaques in brain sections from APP/PS1 mice. Ex vivo fluorescence imaging using mice (normal and APP/PS1) also revealed that 4c was able to penetrate the blood–brain barrier (BBB) and to stain Aβ plaques in the brain. From these results, we believe that 4c will be useful as a fluorescent probe in preclinical research related to AD. Furthermore, we believe that our results with boronic acid also provide valuable information for the development of a probe for Aβ plaques.

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.

Specific Binding of Cu(II) Ions to Amyloid-Beta Peptides Bound to Aggregation-Inhibiting Molecules or SDS Micelles Creates Complexes that Generate Radical Oxygen Species.

Aggregation of the amyloid-beta (Aβ) peptide into insoluble plaques is a major factor in Alzheimer's disease (AD) pathology. Another major factor in AD is arguably metal ions, as metal dyshomeostasis is observed in AD patients, metal ions modulate Aβ aggregation, and AD plaques contain numerous metals including redox-active Cu and Fe ions. In vivo, Aβ is found in various cellular locations including membranes. So far, Cu(II)/Aβ interactions and ROS generation have not been investigated in a membrane environment. Here, we study Cu(II) and Zn(II) interactions with Aβ bound to SDS micelles or to engineered aggregation-inhibiting molecules (the cyclic peptide CP-2 and the ZAβ3(12-58)Y18L Affibody molecule). In all studied systems the Aβ N-terminal segment was found to be unbound, unstructured, and free to bind metal ions. In SDS micelles, Aβ was found to bind Cu(II) and Zn(II) with the same ligands and the same KD as in aqueous solution. ROS was generated in all Cu(II)/Aβ complexes. These results indicate that binding of Aβ to membranes, drugs, and other entities that do not interact with the Aβ N-terminal part, appears not to compromise the N-terminal segment's ability to bind metal ions, nor impede the capacity of N-terminally bound Cu(II) to generate ROS.

Understanding the structural requirements of cyclic sulfone hydroxyethylamines as hBACE1 inhibitors against Aβ plaques in Alzheimer's disease: a predictive QSAR approach

Beta (β)-site amyloid precursor protein cleaving enzyme 1 (BACE1) is one of the most important targets in Alzheimer's disease (AD), which is responsible for production and accumulation of beta amyloid (Aβ).

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.