1.
Fluorinated and iodinated (Z)-2-(4-(2-fluoroethoxy)benzylidene)-5-iodobenzofuran-3(2H)-one.
Authors
Source
Molecular Imaging and Contrast Agent Database (MICAD) [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2004-2011.
2011 Nov 30 [updated 2011 Dec 28].
Excerpt
Fluorinated and iodinated (Z)-2-(4-(2-fluoroethoxy)benzylidene)-5-iodobenzofuran-3(2H)-one (compound 3), abbreviated as [18F]3 and [125I]3, respectively, is an aurone derivative synthesized by Watanabe et al. for single-photon emission computed tomography (SPECT) and positron emission tomography (PET) of Alzheimer’s disease (AD) by targeting β-amyloid (Aβ) plaques (1). AD is characterized in pathology by the presence of extracellular Aβ plaques, intraneuronal neurofibrillary tangles, and neuronal loss in the cerebral cortex (2, 3). Of them, Aβ deposit is the earliest neuropathological marker and is relatively specific to AD and closely related disorders. Aβ plaques are composed of abnormal paired helical filaments 5–10 nm in size. These filaments are largely made of insoluble Aβ peptides that are 40 or 42 amino acids in length (4). In recent years, molecular imaging by targeting the extracellular Aβ has been intensively investigated in attempts to detect early AD, assess Aβ content in vivo, determine the timing of anti-plaque therapy, and evaluate the therapeutic efficacy (4). Radiolabeled Aβ40 peptides were tested first, but they showed poor penetration ability to cross the blood–brain barrier (BBB) (4). Based on the fact that Aβ can be specifically stained in vitro with dyes of Congo red, chrysamine G, and thioflavin-T, an effort was made to develop imaging agents with these dyes. This effort, however, was in general unsuccessful because the bulky ionic groups of heteroatoms in these dyes prevent them from crossing the BBB (2). Importantly, a large class of derivatives (e.g., aminonaphthalenes, benzothiazoles, stilbenes, and imidazopyridines) was synthesized with these dyes as templates (4). Clinical and preclinical studies have shown that these derivatives not only possess a high binding affinity with Aβ plaques as their parent compounds, but also exhibit good penetration ability through the BBB and rapid washout from brain. Ono et al. first synthesized a class of radioiodinated flavone derivatives that present a high binding affinity with Aβ plaques and good penetration ability through the BBB (5). However, these flavone derivatives display poor clearance from the brain, which leads to a high brain background. The investigators then explored another class of flavonoids with aurone as the core structure (6, 7). Aurone is a heterocyclic chemical compound that contains a benzofuran element associated with a benzylidene linked in position 2 and a chalcone-like group being closed into a five-member ring. The aurone derivatives possess a nucleophilic group (NH2, NHMe, or NMe2) at the 4' position and a radioiodine at the 5 position. Although these aurone derivatives exhibit a strong binding affinity with Aβ (inhibition constant (K i) = 1.2–6.8 nM), high penetration ability through the BBB (1.9%−4.6% injected dose per gram tissue (ID/g) at 2 min), and a fast washout from the brain (0.3%−0.5% ID/g at 30 min), the pharmacokinetics of these compounds are less favorable for brain imaging than the pharmacokinetics of the agent [123I]IMPY (6-iodo-2-(4'-dimethylamino)phenyl-imidazo[1,2]pyridine), which is the only SPECT agent to be tested in humans to date (1, 8, 9). The investigators also modified the flavone and aurone derivatives by pegylating them with 1–3 units of ethylene glycol at the 4' position or by conjugating them with the chelating agent bis-amino-bis-thiol (BAT) (7). Favorable pharmacokinetics for brain imaging was observed for the pegylated derivatives ([18F]8(a–c)) but not for the BAT-chelated derivatives ([99mTc]BAT-FL and [99mTc]BAT-AR) (6, 7). This series of chapters summarizes the data obtained with flavone and aurone derivatives, including [125I]15, [125I]9, [125I]14, [125I]16, [125I]17, [99mTc]BAT-FL, [99mTc]BAT-AR, [18F]8(a-c), [125I]3, and [18F]3 (1, 6-8). This chapter presents the data obtained with [125I]3 and [18F]3 (1).
Sections
Radioiodinated (Z)-2-(4-(2-hydroxyethoxy)benzylidene)-5-iodobenzofuran-3(2H)-one.
Authors
Source
Molecular Imaging and Contrast Agent Database (MICAD) [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2004-2011.
2011 Nov 30 [updated 2011 Dec 28].
Excerpt
Radioiodinated (Z)-2-(4-(2-hydroxyethoxy)benzylidene)-5-iodobenzofuran-3(2H)-one (compound 15), abbreviated as [125I]15, is an aurone derivative synthesized by Maya et al. for single-photon emission computed tomography(SPECT) of Alzheimer’s disease (AD) by targeting β-amyloid (Aβ) (1). The other four aurone derivatives include radioiodinated (Z)-2-(4-methoxybenzylidene)-5-iodobenzofuran-3(2H)-one (compound 9), (Z)-2-(4-hydroxybenzylidene)-5-iodobenzofuran-3(2H)-one (compound 14), (Z)-2-(4-(2-(2-hydroxyethoxy)ethoxy)benzylidene)-5-iodobenzofuran-3(2H)-one (compound 16), and (Z)-2-(4-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)benzylidene)-5-iodobenzofuran-3(2H)-one (compound 17), which are abbreviated as [125I]9, [125I]14, [125I]16, and [125I]17, respectively. AD is characterized in pathology by the presence of extracellular Aβ plaques, intraneuronal neurofibrillary tangles, and neuronal loss in the cerebral cortex (2, 3). Of them, Aβ deposit is the earliest neuropathological marker and is relatively specific to AD and closely related disorders. Aβ plaques are composed of abnormal paired helical filaments 5–10 nm in size. These filaments are largely made of insoluble Aβ peptides that are 40 or 42 amino acids in length (4). In recent years, molecular imaging by targeting the extracellular Aβ has been intensively investigated in attempts to detect early AD, assess Aβ content in vivo, determine the timing of anti-plaque therapy, and evaluate the therapeutic efficacy (4). Radiolabeled Aβ40 peptides were tested first, but they showed poor penetration ability to cross the blood–brain barrier (BBB) (4). Based on the fact that Aβ can be specifically stained in vitro with dyes of Congo red, chrysamine G, and thioflavin-T, an effort was made to develop imaging agents with these dyes. This effort, however, was in general unsuccessful because the bulky ionic groups of heteroatoms in these dyes prevent them from crossing the BBB (2). Importantly, a large class of derivatives (e.g., aminonaphthalenes, benzothiazoles, stilbenes, and imidazopyridines) was synthesized with these dyes as templates (4). Clinical and preclinical studies have shown that these derivatives not only possess a high binding affinity with Aβ plaques as their parent compounds, but also exhibit good penetration ability through the BBB and rapid washout from brain with low to no plaque deposits. Ono et al. first synthesized a class of radioiodinated flavone derivatives that present a high binding affinity with Aβ plaques and good penetration ability through the BBB (5). However, these flavone derivatives display poor clearance from the brain, which leads to a high brain background. The investigators then explored another class of flavonoids with aurone as the core structure (6, 7). Aurone is a heterocyclic chemical compound that contains a benzofuran element associated with a benzylidene linked in position 2 and a chalcone-like group being closed into a five-member ring. The aurone derivatives possess a nucleophilic group (NH2, NHMe, or NMe2) at the 4' position and a radioiodine at the 5 position. Although these aurone derivatives exhibit a strong binding affinity with Aβ (inhibition constant (K i) = 1.2–6.8 nM), high penetration ability through the BBB (1.9%−4.6% injected dose per gram tissue (ID/g) at 2 min), and a fast washout from the brain (0.3%−0.5% ID/g at 30 min), the pharmacokinetics of these compounds are less favorable for brain imaging than the pharmacokinetics of the agent [123I]IMPY (6-iodo-2-(4'-dimethylamino)phenyl-imidazo[1,2]pyridine), which is the only SPECT agent to be tested in humans to date (1, 8, 9). The investigators also modified the flavone and aurone derivatives by pegylating them with 1–3 units of ethylene glycol at the 4' position or by conjugating them with the chelating agent bis-amino-bis-thiol (BAT) (7). Favorable pharmacokinetics for brain imaging was observed for the pegylated derivatives ([18F]8(a–c)) but not for the BAT-chelated derivatives ([99mTc]BAT-FL and [99mTc]BAT-AR) (6, 7). This series of chapters summarizes the data obtained with flavone and aurone derivatives, including [125I]15, [125I]9, [125I]14, [125I]16, [125I]17, [99mTc]BAT-FL, [99mTc]BAT-AR, [18F]8(a–c), [125I]3, and [18F]3 (1, 6-8). This chapter presents the data obtained with [125I]15, [125I]9, [125I]14, [125I]16, and [125I]17 (1).
Sections
99mTc-Bis-amino-bis-thiol-conjugated 6-(3-bromopropoxy)-2-(4-(dimethylamino)phenyl)-4H-chromen-4-one and (Z)-5-(3-bromopropoxy)-2-(4-(dimethylamino)benzylidene)benzofuran-3(2H)-one.
Authors
Source
Molecular Imaging and Contrast Agent Database (MICAD) [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2004-2011.
2011 Nov 30 [updated 2011 Dec 28].
Excerpt
99mTc-Bis-amino-bis-thiol (BAT)-conjugated 6-(3-bromopropoxy)-2-(4-(dimethylamino)phenyl)-4H-chromen-4-one and (Z)-5-(3-bromopropoxy)-2-(4-(dimethylamino)benzylidene)benzofuran-3(2H)-one, abbreviated as [99mTc]BAT-FL and [99mTc]BAT-AR, respectively, are flavone and aurone derivatives synthesized by Ono et al. for single-photon emission computed tomography (SPECT) of Alzheimer’s disease (AD) by targeting β-amyloid (Aβ) (1). AD is characterized in pathology by the presence of extracellular Aβ plaques, intraneuronal neurofibrillary tangles, and neuronal loss in the cerebral cortex (2, 3). Of them, Aβ deposit is the earliest neuropathological marker and is relatively specific to AD and closely related disorders. Aβ plaques are composed of abnormal paired helical filaments 5–10 nm in size. These filaments are largely made of insoluble Aβ peptides that are 40 or 42 amino acids in length (4). In recent years, molecular imaging by targeting the extracellular Aβ has been intensively investigated in attempts to detect early AD, assess Aβ content in vivo, determine the timing of anti-plaque therapy, and evaluate the therapeutic efficacy (4). Radiolabeled Aβ40 peptides were tested first, but they showed poor penetration ability to cross the blood–brain barrier (BBB) (4). Based on the fact that Aβ can be specifically stained in vitro with dyes of Congo red, chrysamine G, and thioflavin-T, an effort was made to develop imaging agents with these dyes. This effort, however, was in general unsuccessful because the bulky ionic groups of heteroatoms in these dyes prevent them from crossing the BBB (2). Importantly, a large class of derivatives (e.g., aminonaphthalenes, benzothiazoles, stilbenes, and imidazopyridines) was synthesized with these dyes as templates (4). Clinical and preclinical studies have shown that these derivatives not only possess a high binding affinity with Aβ plaques as their parent compounds, but also exhibit good penetration ability through the BBB and rapid washout from brain with low to no plaque deposits. Ono et al. first synthesized a class of radioiodinated flavone derivatives that present a high binding affinity with Aβ plaques and good penetration ability through the BBB (5). However, these flavone derivatives display poor clearance from the brain, which leads to a high brain background. The investigators then explored another class of flavonoids with aurone as the core structure (1, 6). Aurone is a heterocyclic chemical compound that contains a benzofuran element associated with a benzylidene linked in position 2 and a chalcone-like group closed into a five-member ring. The aurone derivatives possess a nucleophilic group (NH2, NHMe, or NMe2) at the 4' position and a radioiodine at the 5 position. Although these aurone derivatives exhibit a strong binding affinity with Aβ (inhibition constant (K i) = 1.2–6.8 nM), high penetration ability through the BBB (1.9%−4.6% injected dose per gram tissue (ID/g) at 2 min), and a fast washout from the brain (0.3%−0.5% ID/g at 30 min), the pharmacokinetics of these compounds are less favorable for brain imaging than the pharmacokinetics of the agent [123I]IMPY (6-iodo-2-(4'-dimethylamino)phenyl-imidazo[1,2]pyridine), which is the only SPECT agent to be tested in humans to date (7-9). The investigators also modified the flavone and aurone derivatives by pegylating them with 1–3 units of ethylene glycol at the 4' position or by conjugating them with the chelating agent bis-amino-bis-thiol (BAT). Favorable pharmacokinetics for brain imaging was observed for the pegylated derivatives ([18F]8(a–c)) but not for the BAT-chelated derivatives ([99mTc]BAT-FL and [99mTc]BAT-AR) (1, 6). This series of chapters summarizes the data obtained with flavone and aurone derivatives, including [125I]15, [125I]9, [125I]14, [125I]16, [125I]17, [99mTc]BAT-FL, [99mTc]BAT-AR, [18F]8(a–c), [125I]3, and [18F]3 (1, 6-8). This chapter presents the data obtained with [99mTc]BAT-FL and [99mTc]BAT-AR (1).
Sections
18F-Labeled fluoropegylated 6-fluoroethoxy-4'-dimethylaminoflavone, 6-(2-(2-fluoro-ethoxy)-ethoxy)-4'-dimethylaminoflavone, and 6-(2-(2-(2-fluoro-ethoxy)-ethoxy)ethoxy)-4'-dimethylaminoflavone.
Authors
Source
Molecular Imaging and Contrast Agent Database (MICAD) [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2004-2011.
2011 Nov 30 [updated 2011 Dec 28].
Excerpt
18F-Labeled fluoropegylated 6-fluoroethoxy-4'-dimethylaminoflavone (compound 8a), 6-(2-(2-fluoro-ethoxy)-ethoxy)-4'-dimethylaminoflavone (compound 8b), and 6-(2-(2-(2-fluoro-ethoxy)-ethoxy)ethoxy)-4'-dimethylaminoflavone (compound 8c), abbreviated as [18F]8a, [18F]8b, and [18F]8c, respectively, are flavone derivatives synthesized by Ono et al. for positron emission tomography (PET) of Alzheimer’s disease (AD) by targeting β-amyloid (Aβ) (1). AD is characterized in pathology by the presence of extracellular Aβ plaques, intraneuronal neurofibrillary tangles, and neuronal loss in the cerebral cortex (2, 3). Of them, Aβ deposit is the earliest neuropathological marker and is relatively specific to AD and closely related disorders. Aβ plaques are composed of abnormal paired helical filaments 5–10 nm in size. These filaments are largely made of insoluble Aβ peptides that are 40 or 42 amino acids in length (4). In recent years, molecular imaging by targeting the extracellular Aβ has been intensively investigated in attempts to detect early AD, assess Aβ content in vivo, determine the timing of anti-plaque therapy, and evaluate the therapeutic efficacy (4). Radiolabeled Aβ40 peptides were tested first, but they showed poor penetration ability to cross the blood–brain barrier (BBB) (4). Based on the fact that Aβ can be specifically stained in vitro with dyes of Congo red, chrysamine G, and thioflavin-T, an effort was made to develop imaging agents with these dyes. This effort, however, was in general unsuccessful because the bulky ionic groups of heteroatoms in these dyes prevent them from crossing the BBB (2). Importantly, a large class of derivatives (e.g., aminonaphthalenes, benzothiazoles, stilbenes, and imidazopyridines) was synthesized with these dyes as templates (4). Clinical and preclinical studies have shown that these derivatives not only possess a high binding affinity with Aβ plaques as their parent compounds, but also exhibit good penetration ability through the BBB and rapid washout from brain with low to no plaque deposits. Ono et al. first synthesized a class of radioiodinated flavone derivatives that present a high binding affinity with Aβ plaques and good penetration ability through the BBB (5). However, these flavone derivatives display poor clearance from the brain, which leads to a high brain background. The investigators then explored another class of flavonoids with aurone as the core structure (1, 6). Aurone is a heterocyclic chemical compound that contains a benzofuran element associated with a benzylidene linked in position 2 and a chalcone-like group being closed into a five-member ring. The aurone derivatives possess a nucleophilic group (NH2, NHMe, or NMe2) at the 4' position and a radioiodine at the 5 position. Although these aurone derivatives exhibit a strong binding affinity with Aβ (inhibition constant (K i) = 1.2–6.8 nM), high penetration ability through the BBB (1.9%−4.6% injected dose per gram tissue (ID/g) at 2 min), and a fast washout from the brain (0.3%−0.5% ID/g at 30 min), the pharmacokinetics of these compounds are less favorable for brain imaging than the pharmacokinetics of the agent [123I]IMPY (6-iodo-2-(4'-dimethylamino)phenyl-imidazo[1,2]pyridine), which is the only SPECT agent to be tested in humans to date (7-9). The investigators also modified the flavone and aurone derivatives by pegylating them with 1–3 units of ethylene glycol at the 4' position or by conjugating them with the chelating agent bis-amino-bis-thiol (BAT). Favorable pharmacokinetics for brain imaging was observed for the pegylated derivatives ([18F]8(a–c)) but not for the BAT-chelated derivatives ([99mTc]BAT-FL and [99mTc]BAT-AR) (1, 6). This series of chapters summarizes the data obtained with flavone and aurone derivatives, including [125I]15, [125I]9, [125I]14, [125I]16, [125I]17, [99mTc]BAT-FL, [99mTc]BAT-AR, [18F]8(a–c), [125I]3, and [18F]3 (1, 6-8). This chapter presents the data obtained with [18F]8(a–c) (1).
Sections
Resveratrol Protects Rats from Aβ-induced Neurotoxicity by the Reduction of iNOS Expression and Lipid Peroxidation.
Source
Department of Biochemical Science and Biotechnology, National Chia-Yi University, Chia-Yi, Taiwan.
Abstract
Alzheimer disease (AD) is an age-dependent neurodegenerative disease characterized by the formation of β-amyloid (Aβ)-containing senile plaque. The disease could be induced by the administration of Aβ peptide, which was also known to upregulate inducible nitric oxide synthase (iNOS) and stimulate neuronal apoptosis. The present study is aimed to elucidate the cellular effect of resveratrol, a natural phytoestrogen with neuroprotective activities, on Aβ-induced hippocampal neuron loss and memory impairment. On adult Sprague-Dawley rats, we found the injection of Aβ could result in a significant impairment in spatial memory, a marked increase in the cellular level of iNOS and lipid peroxidation, and an apparent decrease in the expression of heme oxygenase-1 (HO-1). By combining the treatment with Aβ, resveratrol was able to confer a significant improvement in spatial memory, and protect animals from Aβ-induced neurotoxicity. These neurological protection effects of resveratrol were associated with a reduction in the cellular levels of iNOS and lipid peroxidation and an increase in the production of HO-1. Moreover, the similar neurological and cellular response were also observed when Aβ treatment was combined with the administration of a NOS inhibitor, N(G)-nitro-L-arginine methyl ester hydrochloride (L-NAME). These findings strongly implicate that iNOS is involved in the Aβ-induced lipid peroxidation and HO-1 downregulation, and resveratrol protects animals from Aβ-induced neurotoxicity by suppressing iNOS production.
- PMID:
- 22220203
- [PubMed - in process]
Tannic Acid is a Natural β-secretase Inhibitor that Prevents Cognitive Impairment and Mitigates Alzheimer-like Pathology in Transgenic Mice.
Source
Saitama Medical Center and University, Japan;
Abstract
Amyloid precursor protein (APP) proteolysis is essential for production of amyloid-β (Aβ) peptides that form β-amyloid plaques in brains of Alzheimer disease (AD) patients. Recent focus has been directed toward a group of naturally-occurring anti-amyloidogenic polyphenols known as flavonoids. We orally administered the flavonoid tannic acid (TA) to the transgenic PSAPP mouse model of cerebral amyloidosis (bearing mutant human APP and presenilin-1 transgenes) and evaluated cognitive function and AD-like pathology. Consumption of TA for 6 months prevented transgene-associated behavioral impairment including hyperactivity, decreased object recognition, and defective spatial reference memory, but did not alter non-transgenic mouse behavior. Accordingly, brain parenchymal and cerebral vascular β-amyloid deposits and abundance of various Aβ species including oligomers were mitigated in TA-treated PSAPP mice. These effects occurred with decreased cleavage of the β-carboxyl-terminal APP fragment, lowered soluble APP-β production, reduced β-site APP cleaving enzyme 1 protein stability and activity, and attenuated neuroinflammation. As in vitro validation, we treated well-characterized mutant human APP-overexpressing murine neuron-like cells with TA and found significantly reduced Aβ production associated with less amyloidogenic APP proteolysis. Taken together, these results raise the possibility that dietary supplementation with TA may be prophylactic for AD by inhibiting β-secretase activity and neuroinflammation and thereby mitigating AD pathology.
- PMID:
- 22219198
- [PubMed - as supplied by publisher]
Low expression and secretion of circulating soluble CTLA-4 in peripheral blood mononuclear cells and sera from type 1 diabetic children.
Source
Division of Paediatrics & Diabetes Research Centre, Department of Molecular & Clinical Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden. anna.ryden@liu.se.
Abstract
BACKGROUND:
High levels of soluble cytotoxic T-lymphocyte antigen 4 (soluble CTLA-4), an alternative splice form of the regulatory T-cell (Treg) associated CTLA-4 gene, have been associated with type 1 diabetes (T1D) and other autoimmune diseases, such as Grave's disease and myasthenia gravis. At the same time, studies have shown soluble CTLA-4 to inhibit T-cell activation through B7 binding. This study aimed to investigate the role of soluble CTLA-4 in relation to full-length CTLA-4 and other Treg-associated markers in T1D children and in individuals with high or low risk of developing the disease.
METHODS:
T1D children were studied at 4 days, 1 and 2 years after diagnosis in comparison to individuals with high or low risk of developing the disease. Isolated peripheral blood mononuclear cells were stimulated with the T1D-associated glutamic acid decarboxylase 65 and phytohaemagglutinin. Subsequently, soluble CTLA-4, full-length CTLA-4, FOXP3 and TGF-β mRNA transcription were quantified and protein concentrations of soluble CTLA-4 were measured in culture supernatant and sera.
RESULTS AND CONCLUSIONS:
Low protein concentrations of circulating soluble CTLA-4 and a positive correlation between soluble CTLA-4 mRNA and protein were seen in T1D, in parallel with a negative correlation in healthy subjects. Further, low levels of mitogen-induced soluble CTLA-4 were accompanied by low C-peptide levels. Interestingly, low mitogen-induced soluble CTLA-4 mRNA and low TGF-β mRNA expression were seen in high risk individuals, suggesting an alteration in activation and down-regulating immune mechanisms during the pre-diabetic phase. Copyright © 2011 John Wiley & Sons, Ltd.
Copyright © 2011 John Wiley & Sons, Ltd.
- PMID:
- 22218756
- [PubMed - in process]
Role(s) of formyl-peptide receptors expressed in nasal epithelial cells.
Source
Department of Clinical Immunology and Allergy, University of Naples Federico II, Naples, Italy.
Abstract
Chronic rhinosinusitis is one of the most frequent chronic diseases in humans. Little is known about stimuli initiating tissue remodeling process that determines the morphological expression of the disease. N-formyl peptide receptors (FPRs) are innate immunity receptors important in tissue remodeling of gastric and intestinal epithelium. The expression and functions of FPRs in nasal epithelial cells were examined to evaluate whether they could be important in the remodeling of nasal mucosa. The aim of this study is to examine FPR expression in a nasal epithelial cell line (RPMI-2650) at mRNA and protein levels. To determine whether FPRs were functional, chemotaxis experiments were carried out. In addition the effects of FPRs agonists on the expression (PCR and ELISA) of VEGF-A and TGF-beta, two key mediators of tissue remodelling, were examined. Here we demonstrate that RPMI-2650 express FPR and FPRL2, but not FPRL1. fMLP, a bacterial product active on FPR, and uPAR84-95, an inflammatory mediator agonist for FPRL2, stimulated migration of nasal epithelial cells. fMLP and uPAR84-95 induce expression and secretion of VEGF-A and TGF-beta. Our results suggest a possible mechanisms initiating tissue remodeling observed during chronic rhinosinusitis. This study provides further evidence that FPRs play a more complex role in human pathophysiology than bacterial recognition.
- PMID:
- 22217988
- [PubMed - in process]
Atomic Force Microscopy and MD Simulations Reveal Pore-Like Structures of All-D-Enantiomer of Alzheimer's β-Amyloid Peptide: Relevance to the Ion Channel Mechanism of AD Pathology.
Abstract
Alzheimer's disease (AD) is a protein misfolding disease characterized by a build-up of β-amyloid (Aβ) peptide as senile plaques, uncontrolled neurodegeneration, and memory loss. AD pathology is linked to the destabilization of cellular ionic homeostasis and involves Aβ peptide-plasma membrane interactions. In principle, there are two possible ways through which disturbance of the ionic homeostasis can take place: directly, where the Aβ peptide either inserts into the membrane and creates ion-conductive pores or destabilizes the membrane organization; or, indirectly, where the Aβpeptide interacts with existing cell membrane receptors. To distinguish between these two possible types of Aβ-membrane interactions, we took advantage of the biochemical tenet that ligand-receptor interactions are stereospecific; L amino acid peptides, but not their D counterparts, bind to cell membrane receptors. However, with respect to the ion channel-mediated mechanism, like L-amino acids, D-amino acid peptides will also form ion channel-like structures. Using atomic force microscopy (AFM) we imaged the structures of both D- and L enantiomers of the full length Aβ1-42 when reconstituted in lipid bilayers. AFM imaging shows that both L- and D-Aβ isomers form similar channel-like structures. Molecular dynamics (MD) simulations support the AFM imaged 3D structures. Earlier we have shown that D-Aβ1-42 channels conduct ions similarly to their L-counter parts. Taken together, our results support the direct mechanism of Aβ ion channel-mediated destabilization of ionic homeostasis rather than the indirect mechanism through Aβ interaction with membrane receptors.
- PMID:
- 22217000
- [PubMed - as supplied by publisher]
A Carrier for Non-Covalent Delivery of Functional Beta-Galactosidase and Antibodies against Amyloid Plaques and IgM to the Brain.
Source
Department of Experimental Pathology, Mayo Clinic, Rochester, Minnesota, United States of America.
Abstract
BACKGROUND:
Therapeutic intervention of numerous brain-associated disorders currently remains unrealized due to serious limitations imposed by the blood-brain-barrier (BBB). The BBB generally allows transport of small molecules, typically <600 daltons with high octanol/water partition coefficients, but denies passage to most larger molecules. However, some receptors present on the BBB allow passage of cognate proteins to the brain. Utilizing such receptor-ligand systems, several investigators have developed methods for delivering proteins to the brain, a critical requirement of which involves covalent linking of the target protein to a carrier entity. Such covalent modifications involve extensive preparative and post-preparative chemistry that poses daunting limitations in the context of delivery to any organ. Here, we report creation of a 36-amino acid peptide transporter, which can transport a protein to the brain after routine intravenous injection of the transporter-protein mixture. No covalent linkage of the protein with the transporter is necessary.
APPROACH:
A peptide transporter comprising sixteen lysine residues and 20 amino acids corresponding to the LDLR-binding domain of apolipoprotein E (ApoE) was synthesized. Transport of beta-galactosidase, IgG, IgM, and antibodies against amyloid plques to the brain upon iv injection of the protein-transporter mixture was evaluated through staining for enzyme activity or micro single photon emission tomography (micro-SPECT) or immunostaining. Effect of the transporter on the integrity of the BBB was also investigated.
PRINCIPAL FINDINGS:
The transporter enabled delivery to the mouse brain of functional beta-galactosidase, human IgG and IgM, and two antibodies that labeled brain-associated amyloid beta plaques in a mouse model of Alzheimer's disease.
SIGNIFICANCE:
The results suggest the transporter is able to transport most or all proteins to the brain without the need for chemically linking the transporter to a protein. Thus, the approach offers an avenue for rapid clinical evaluation of numerous candidate drugs against neurological diseases including cancer. (299 words).
- PMID:
- 22216132
- [PubMed - in process]
Helicobacter pylori versus the Host: Remodeling of the Bacterial Outer Membrane Is Required for Survival in the Gastric Mucosa.
Source
Section of Molecular Genetics and Microbiology, The University of Texas at Austin, Austin, Texas, United States of America.
Abstract
Modification of bacterial surface structures, such as the lipid A portion of lipopolysaccharide (LPS), is used by many pathogenic bacteria to help evade the host innate immune response. Helicobacter pylori, a gram-negative bacterium capable of chronic colonization of the human stomach, modifies its lipid A by removal of phosphate groups from the 1- and 4'-positions of the lipid A backbone. In this study, we identify the enzyme responsible for dephosphorylation of the lipid A 4'-phosphate group in H. pylori, Jhp1487 (LpxF). To ascertain the role these modifications play in the pathogenesis of H. pylori, we created mutants in lpxE (1-phosphatase), lpxF (4'-phosphatase) and a double lpxE/F mutant. Analysis of lipid A isolated from lpxE and lpxF mutants revealed lipid A species with a 1 or 4'-phosphate group, respectively while the double lpxE/F mutant revealed a bis-phosphorylated lipid A. Mutants lacking lpxE, lpxF, or lpxE/F show a 16, 360 and 1020 fold increase in sensitivity to the cationic antimicrobial peptide polymyxin B, respectively. Moreover, a similar loss of resistance is seen against a variety of CAMPs found in the human body including LL37, β-defensin 2, and P-113. Using a fluorescent derivative of polymyxin we demonstrate that, unlike wild type bacteria, polymyxin readily associates with the lpxE/F mutant. Presumably, the increase in the negative charge of H. pylori LPS allows for binding of the peptide to the bacterial surface. Interestingly, the action of LpxE and LpxF was shown to decrease recognition of Helicobacter LPS by the innate immune receptor, Toll-like Receptor 4. Furthermore, lpxE/F mutants were unable to colonize the gastric mucosa of C57BL/6J and C57BL/6J tlr4 -/- mice when compared to wild type H. pylori. Our results demonstrate that dephosphorylation of the lipid A domain of H. pylori LPS by LpxE and LpxF is key to its ability to colonize a mammalian host.
- PMID:
- 22216004
- [PubMed - in process]
Functional Conservation of Clock Output Signaling between Flies and Intertidal Crabs.
Source
*Laboratorio de Genética del Comportamiento,Fundación Instituto Leloir, IIB-BA CONICET, Buenos Aires, Argentina.
Abstract
Intertidal species have both circadian and circatidal clocks. Although the behavioral evidence for these oscillators is more than 5 decades old, virtually nothing is known about their molecular clockwork. Pigment-dispersing hormones (PDHs) were originally described in crustaceans. Their insect homologs, pigment-dispersing factors (PDFs), have a prominent role as clock output and synchronizing signals released from clock neurons. We show that gene duplication in crabs has led to two PDH genes (β-pdh-I and β-pdh-II). Phylogenetically, β-pdh-I is more closely related to insect pdf than to β-pdh-II, and we hypothesized that β-PDH-I may represent a canonical clock output signal. Accordingly, β-PDH-I expression in the brain of the intertidal crab Cancer productus is similar to that of PDF in Drosophila melanogaster, and neurons that express PDH-I also show CYCLE-like immunoreactivity. Using D. melanogaster pdf-null mutants (pdf(01) ) as a heterologous system, we show that β-pdh-I is indistinguishable from pdf in its ability to rescue the mutant arrhythmic phenotype, but β-pdh-II fails to restore the wild-type phenotype. Application of the three peptides to explanted brains shows that PDF and β-PDH-I are equally effective in inducing the signal transduction cascade of the PDF receptor, but β-PDH-II fails to induce a normal cascade. Our results represent the first functional characterization of a putative molecular clock output in an intertidal species and may provide a critical step towards the characterization of molecular components of biological clocks in intertidal organisms.
- PMID:
- 22215610
- [PubMed - in process]
Stress regulation of the PAN-proteasome system in the extreme halophilic archaeon Halobacterium.
Source
Extremophiles and Large Molecular Assemblies Group, UMR5075, CNRS, Institut de Biologie Structurale, 41 rue J. Horowitz, 38027, Grenoble Cedex 1, France.
Abstract
In Archaea, the importance of the proteasome system for basic biological processes is only poorly understood. Proteasomes were partially purified from Halobacterium by native gradient density ultracentrifugation. The peptidase activity profiles showed that the 20S proteasome accumulation is altered depending on the physiological state of the cells. The amount of active 20S particles increases in Halobacterium cells as a response to thermal and low salt stresses. In the same conditions, Northern experiments showed a positive transcriptional regulation of the alpha andbeta proteasome subunits as well as of the two proteasome regulatory ATPases, PANA and PANB. Co-immunoprecipitation experiments demonstrated the existence of a physical interaction between the two Proteasome Activating Nucleotidase (PAN) proteins in cell extracts. Thus, a direct regulation occurs on the PAN-proteasome components to adjust the protein degradation activity to growth and environmental constraints. These results also indicate that, in extreme halophiles, proteasome mediated proteolysis is an important aspect of low salt stress response. The tri-peptide vinyl sulfone inhibitor NLVS was used in cell cultures to study the in vivo function of proteasome in Halobacterium. The chemical inhibition of proteasomes was measured in the cellular extracts. It has no effect on cell growth and mortality under normal growth conditions as well as under heat shock conditions. These results suggest that the PAN activators or other proteases compensate for loss of proteasome activity in stress conditions.
- PMID:
- 22215023
- [PubMed - as supplied by publisher]
Amyloid-β Oligomers in Cerebrospinal Fluid are Associated with Cognitive Decline in Patients with Alzheimer's Disease.
Source
Department of Cardiothoracic Surgery of the Martin-Luther-University Halle-Wittenberg, Halle, Germany.
Abstract
Oligomers of the amyloid-β peptide (Aβ) are thought to be the most toxic form of Aβ and are linked to the development of Alzheimer's disease (AD). Here, we used a flow cytometric approach for the detection and assessment of oligomers in cerebrospinal fluid (CSF) from AD patients and other neurological disorders. 30 CSF samples from patients suffering from AD (n = 14), non-demented controls (n = 12), and other neurological disorders (dementia with Lewy bodies, n = 2; vascular dementia, n = 1; primary progressive aphasia, n = 1) were analyzed for the presence of Aβ-oligomers by flow cytometry. The CSF levels of total tau (t-tau), phosphorylated tau (p-tau), and amyloid-β (Aβ)42 were determined using ELISA. CSF Aβ-oligomer levels in AD patients were elevated in comparison to the non-AD group (p = 0.073). The ratio Aβ-oligomers/Aβ42 was significantly elevated in AD subjects compared to non-AD subjects (p = 0.001). Most important, there was a negative correlation between the amount of Aβ-oligomers and the Mini-Mental Status Exam score (r = -0.65; p = 0.013) in AD patients. The detection of Aβ-oligomers using flow cytometry analysis seems to be useful in assessing the stage of AD. This is a novel and important finding as none of the currently used CSF biomarkers are clearly associated with dementia severity.
- PMID:
- 22214781
- [PubMed - as supplied by publisher]
Comparison between 68Ga-bombesin (68Ga-BZH3) and the cRGD tetramer 68Ga-RGD4 studies in an experimental nude rat model with a neuroendocrine pancreatic tumor cell line.
Abstract
ABSTRACT: Objectives: Receptor scintigraphy gains more interest for diagnosis and treatment of tumors, in particular for neuroendocrine tumors (NET). We used a pan-Bombesin analog, the peptide DOTA-PEG2-[D-tyr6, beta-Ala11, Thi13, Nle14] BN(6-14) amide (BZH3). BZH3 binds to at least three receptor subtypes: the BB1 (Neuromedin B), BB2 (Gastrin-releasing peptide, GRP), and BB3. Imaging of alphanubeta3 integrin expression playing an important role in angiogenesis and metastasis was accomplished with a 68Ga-RGD tetramer. The purpose of this study was to investigate the kinetics and to compare both tracers in an experimental NET cell line.
METHODS:
This study comprised nine nude rats inoculated with the pancreatic tumor cell line AR42J. Dynamic positron emission tomography (PET) scans using 68Ga-BZH3 and 68Ga-RGD tetramer were performed (68Ga-RGD tetramer: n = 4, 68Ga-BZH3: n = 5). Standardized uptake values (SUVs) were calculated, and a two-tissue compartmental learning-machine model (calculation of K1 k4 vessel density (VB) and receptor binding potential (RBP)) as well as a non-compartmental model based on the fractal dimension was used for quantitative analysis of both tracers. Multivariate analysis was used to evaluate the kinetic data.
RESULTS:
The PET kinetic parameters showed significant differences when individual parameters were compared between groups. Significant differences were found in FD, VB, K1, and RBP (p = 0.0275, 0.05, 0.05, and 0.0275 respectively). The 56- to 60-min SUV for 68Ga-BZH3, with a range of 0.86 to 1.29 (median, 1.19) was higher than the corresponding value for the 68Ga-RGD tetramer, with a range of 0.78 to 1.31 (median, 0.99). Furthermore, FD, VB, K1, and RBP for 68Ga-BZH3 were generally higher than the corresponding values for the 68Ga-RGD tetramer, whereas k3 was slightly higher for 68Ga-RGD tetramer.
CONCLUSIONS:
As a parameter that reflects receptor binding, the increase of K1 for 68Ga-BZH3 indicated higher expression of bombesin receptors than that of the alphanubeta3 integrin in neuroendocrine tumors. 68Ga-BZH3 seems better suited for diagnosis of NETs owing to higher global tracer uptake.
- PMID:
- 22214362
- [PubMed - as supplied by publisher]
Isolation of synaptic terminals from Alzheimer's disease cortex.
Source
UCLA School of Nursing, Los Angeles, California 90095; UCLA Center for the Advancement of Gerontological Nursing Sciences, Los Angeles, California 90095; UCLA Brain Research Institute, Los Angeles, California 90095. ssokolow@sonnet.ucla.edu.
Abstract
Amyloid beta (Aβ) oligomers and phosphorylated tau (p-tau) aggregates are increasingly identified as potential toxic intermediates in Alzheimer's disease (AD). In cortical AD synapses, p-tau co-localizes with Aβ, but the Aβ and p-taupeptide species responsible for synaptic dysfunction and demise remains unclear. The present experiments were designed to use high-speed cell sorting techniques to purify synaptosome population based on size, and then extend the method to physically isolate Aβ-positive synaptosomes with the goal of understanding the nature of Aβ and tau pathology in AD synapses. To examine the purity of size-gated synaptosomes, samples were first gated on size; particles with sizes between 0.5 and 1.5 microns were collected. Electron microscopy documented a homogenous population of spherical particles with internal vesicles and synaptic densities. Next, size-gated synaptosomes positive for Aβ were collected by fluorescence activated sorting and then analyzed by immunoblotting techniques. Sorted Aβ-positive synaptosomes were enriched for amyloid precursor protein (APP) and for Aβ oligomers and aggregates; immunolabeling for p-tau showed a striking accumulation of p-tau aggregates compared to the original homogenate and purified synaptosomes. These results confirm co-localization of Aβ and p-tau within individual synaptic terminals and provide proof of concept for the utility of flow sorting synaptosomes. © 2011 International Society for Advancement of Cytometry.
Copyright © 2011 International Society for Advancement of Cytometry.
MALDI based identification of soybean protein markers - Possible analytical targets for allergen detection in processed foods.
Source
Department of Food Safety and Food Quality, Research group Food Chemistry and Human Nutrition, Ghent University, Coupure Links 653, B-9000 Gent, Belgium; Laboratory for Protein Biochemistry and Biomolecular Engineering, Ghent University, KL Ledeganckstraat 35, B-9000 Gent, Belgium.
Abstract
Soybean (Glycine max) is extensively used all over the world due to its nutritional qualities. However, soybean is included in the "big eight" list of food allergens. According to the EU directive 2007/68/EC, food products containing soybeans have to be labeled in order to protect the allergic consumers. Nevertheless, soybeans can still inadvertently be present in food products. The development of analytical methods for the detection of traces of allergens is important for the protection of allergic consumers. Mass spectrometry of marker proteolytical fragments of protein allergens is growingly recognized as a detection method in food control. However, quantification of soybean at the peptide level is hindered due to limited information regarding specific stable markers derived after proteolytic digestion. The aim of this study was to use MALDI-TOF/MS and MS/MS as a fast screening tool for the identification of stable soybean derived tryptic markers which were still identifiable even if the proteins were subjected to various changes at the molecular level through a number of reactions typically occurring during food processing (denaturation, the Maillard reaction and oxidation). The peptides (401)Val-Arg(410) from the G1 glycinin (Gly m 6) and the (518)Gln-Arg(528) from the α' chain of the β-conglycinin (Gly m 5) proved to be the most stable. These peptides hold potential to be used as targets for the development of new analytical methods for the detection of soybean protein traces in processed foods.
Copyright © 2011. Published by Elsevier Inc.
Immunodistribution of amyloid beta protein (Aβ) and advanced glycation end-product receptors (RAGE) in choroid plexus and ependyma of resuscitated patients.
Source
Prof. Danuta Maślińska, Department of Experimental and Clinical Neuropathology, Mossakowski Medical Research Centre, Polish Academy of Sciences, 5 Pawińskiego St, 02-106 Warsaw, Poland, phone +48 22 608 65 02, fax +48 22 608 65 02, e-mail: maslinskad@cmdik.pan.pl.
Abstract
RAGE (receptor for advanced glycation end-products) participates in the influx transport of glycated Aβ (amyloid beta) from the blood to the brain. Because little is known of the RAGE operating in brain barriers such as those in the choroid plexus and ependyma, the aim of the present study was to examine the immunodistributions of RAGE and Aβ peptidesin the choroid plexus where the blood-cerebrospinal fluid barrier (B-CSF) is located, and in ependyma of the brain ventricles associated with functions of the cerebrospinal fluid-brain barrier (CSF-B). The study was performed on patients over 65 years successfully resuscitated after cardiac arrest with survival a few weeks. The control group consisted of age-matched individuals who were not resuscitated and died immediately after cardiac arrest. In resuscitated patients, but not in controls, RAGE receptors were localized in choroid plexus (CP) epithelial cells and in ependymal cells bordering the brain ventricles. These cells form the B-CSF and CSF-B barriers. The presence of Aβ was detected within the CP blood vessels and in the basement membrane of the CP epithelium. In numerous cytoplasmic vacuoles of CP epithelial and ependymal cells Aβ protein was found and our observations suggest that the contents of those vacuoles were undergoing progressive digestion. The results demonstrated that CP epithelium and ependymal cells, equipped with RAGE receptors, not only play an important role in the creation of amyloid deposits in the brain but are also places where Aβ may be utilized. The RAGE transportation system should be a main target in the therapy of brain amyloidosis, a well-known risk factor of Alzheimer disease.
N-linked glycosylation influences on the catalytic and biochemical properties of Penicillium purpurogenum β-d-glucuronidase.
Source
Institute of Bioengineering, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China.
Abstract
To study the influence of N-linked carbohydrate moiety on the catalytic and biochemical properties of glycosylated enzyme, a recombinant β-d-glucuronidase (PGUS-P) from Penicillium purpurogenum as a model glycoprotein, was deglycosylated with peptide-N-glycosidase F (PNGase-F) under native conditions. The enzymatic deglycosylation procedure resulted in the complete removal of carbohydrate moiety. Compared with the glycosylated PGUS-P, the deglycosylated PGUS-P exhibited 20-70% higher activity (p<0.05) within pH 6-9, but 15-45% lower activity (p<0.05) at 45-70°C. The apparent decrease in the thermal stability of the deglycosylated enzyme was reflected by a decrease in the denaturation temperature (T(d)) values determined by differential scanning calorimetry (DSC). The removal of N-linked glycans also reduced enzyme's sensitivity to certain metal ions. The deglycosylated PGUS-P displayed lower K(m) vaules, but higher k(cat)/K(m) ratios than the glycosylated isoform towards glycyrrhizin. The consequent conformational changes were also determined by circular dichroism (CD) and fluorescence spectroscopy which revealed no significant difference in the secondary but a slight dissimilarity between the tertiary structures of both isoforms of PGUS-P.
Copyright © 2011. Published by Elsevier B.V.
Mapping out the multi-stage fibrillation of glucagon.
Source
Interdisciplinary Nanoscience Center, Center for Insoluble Protein Structures, Department of Molecular Biology and Genetics, University of Aarhus, Gustav Wieds Vej 10C, DK-8000 Aarhus C, DENMARK Department of Biomedicine, Aarhus University, Wilhelm Meyers Alle, DK-8000 Aarhus C, DENMARK Novo Nordisk A/S, Hagedornsvej 1, DK-2820 Gentofte, DENMARK Danish Power Systems Ltd., Technical University of Denmark, Kemitorvet, DK-2800 Lyngby, DENMARK. SciAssist ApS, Wildersgade 26A, DK-1408 Copenhagen K, DENMARK.
Abstract
The 29-residue peptide hormone glucagon forms many different morphological types of amyloid-like fibrils, depending on solvent conditions. Here, we combine time-series far-UV circular dichroism with singular value decomposition (SVD) analysis to reveal six different conformational states populated during fibrillation at 25°C and pH 2.5. The existence of these states is supported by complementary fluorescence and electron microscopy data. This highlights a multitude of structural transitions of glucagon from unordered structure to β-sheets, β-turns and further tertiary level changes. We attribute the observed unusual far-UV CD spectra to tertiary level structural changes during the formation and maturation of fibrils. The fibrillation model for the whole process involves formation of three oligomeric species and two different morphologies of fibrils in the same solution. The visualization of annular pore-like species in the early stages of glucagon fibrillation and the prevalence of such species in the amyloidogenesis of several proteins indicates that they may be a common feature of the fibrillation process. This study gives significant insights on the stepwise conversion of soluble glucagon to its fibrillar state and identifies the importance of fibril twisting for its thermodynamic stabilization. STRUCTUREDDIGITALABSTRACT: Glucagon and Glucagon bind by circular dichroism (View interaction) Glucagon and Glucagon bind by transmission electron microscopy (View interaction) Glucagon and Glucagon bind by fluorescence technology (View interaction).
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