Cleavage site-directed antibodies reveal the prion protein in humans is shed by ADAM10 at Y226 and associates with misfolded protein deposits in neurodegenerative diseases.

Proteolytic cell surface release ('shedding') of the prion protein (PrP), a broadly expressed GPI-anchored glycoprotein, by the metalloprotease ADAM10 impacts on neurodegenerative and other diseases in animal and in vitro models. Recent studies employing the latter also suggest shed PrP (sPrP) to be a ligand in intercellular communication and critically involved in PrP-associated physiological tasks. Although expectedly an evolutionary conserved event, and while soluble forms of PrP are present in human tissues and body fluids, for the human body neither proteolytic PrP shedding and its cleavage site nor involvement of ADAM10 or the biological relevance of this process have been demonstrated thus far. In this study, cleavage site prediction and generation (plus detailed characterization) of sPrP-specific antibodies enabled us to identify PrP cleaved at tyrosin 226 as the physiological and apparently strictly ADAM10-dependent shed form in humans. Using cell lines, neural stem cells and brain organoids, we show that shedding of human PrP can be stimulated by PrP-binding ligands without targeting the protease, which may open novel therapeutic perspectives. Site-specific antibodies directed against human sPrP also detect the shed form in brains of cattle, sheep and deer, hence in all most relevant species naturally affected by fatal and transmissible prion diseases. In human and animal prion diseases, but also in patients with Alzheimer`s disease, sPrP relocalizes from a physiological diffuse tissue pattern to intimately associate with extracellular aggregated deposits of misfolded proteins characteristic for the respective pathological condition. Findings and research tools presented here will accelerate novel insight into the roles of PrP shedding (as a process) and sPrP (as a released factor) in neurodegeneration and beyond.

Probing Alzheimer's pathology: Exploring the next generation of FDDNP analogues for amyloid ß detection.

Fluorescent probes are a powerful tool for imaging amyloid ß (Aß) plaques, the hallmark of Alzheimer's disease (AD). Herein, we report the synthesis and comprehensive characterization of 21 novel probes as well as their optical properties and binding affinities to Aß fibrils. One of these dyes, 1Ae, exhibited several improvements over FDDNP, an established biomarker for Aß- and Tau-aggregates. First, 1Ae had large Stokes shifts (138-213 nm) in various solvents, thereby reducing self-absorption. With a high quantum yield ratio (φ(dichloromethane/methanol) = 104), 1Ae also ensures minimal background emission in aqueous environments and high sensitivity. In addition, compound 1Ae exhibited low micromolar binding affinity to Aß fibrils in vitro (Kd = 1.603 µM), while increasing fluorescence emission (106-fold) compared to emission in buffer alone. Importantly, the selective binding of 1Ae to Aß1-42 fibrils was confirmed by an in cellulo assay, supported by ex vivo fluorescence microscopy of 1Ae on postmortem AD brain sections, allowing unequivocal identification of Aß plaques. The intermolecular interactions of fluorophores with Aß were elucidated by docking studies and molecular dynamics simulations. Density functional theory calculations revealed the unique photophysics of these rod-shaped fluorophores, with a twisted intramolecular charge transfer (TICT) excited state. These results provide valuable insights into the future application of such probes as potential diagnostic tools for AD in vitro and ex vivo such as determination of Aß1-42 in cerebrospinal fluid or blood.

Ibogaine-Mediated ROS/Antioxidant Elevation in Isolated Rat Uterus Is ß-Adrenergic Receptors and KATP Channels Mediated.

Ibogaine effects are mediated by cellular receptors, ATP depletion followed by ROS production and antioxidant enzyme activity elevation in a dose and time dependent manner. Since the role of KATP channels and ß-adrenoceptors in ROS cellular circuit was established here we explored their role in ibogaine pro-antioxidant effectiveness. Single dose of ibogaine (10 mg/L i.e., 28.8 µmol/L) was applied to isolated rat uterus (spontaneous and Ca2+-stimulated) and contractility and antioxidant enzymes activity were monitored during 4 h. Ibogaine increased amplitude and frequency of spontaneous active uteri immediately after addition that was prevented by propranolol (ß1 and ß2 adrenoceptors selective antagonists) and glibenclamide (KATP sensitive channels inhibitor; only frequency) pre-treatment. In Ca2+-stimulated uteri, ibogaine decreased both amplitude and frequency after 4 h. Pre-treatment with propranolol abolished ibogaine induced amplitude lowering, while glibenclamide had no effect. In both types of active uterus, ibogaine induced a decrease in SOD1 and an increase in CAT activity after 2 h. In Ca2+-stimulated uterus, there was also a decrease of SOD2 activity after 2 h. After 4 h, SOD1 activity returned to the baseline level, but GSH-Px activity increased. Pre-treatment with both propranolol and glibenclamide abolished observed changes of antioxidant enzymes activity suggesting that ibogaine pro-antioxidative effectiveness is ß-adrenergic receptors and KATP channels mediated.

Lay Public View of Neuroscience and Science-Based Brain Health Recommendations in Slovenia.

Background: Brain health is one of the cornerstones of a long and full life. Active care for brain health and reduction of lifestyle-related risks for brain disorders may be a key strategy in tackling the growing prevalence of mental and neurological illnesses. Public knowledge, perception, and preventive behavior need to be considered in the planning of effective strategies for brain health promotion. Our research is the first effort aimed at assessing Slovenian lay public knowledge, search and use of scientific information about the brain, and care for brain health. Methods: An online survey was used to gather data for descriptive and associative statistical analyses of a sample of the Slovenian public (n = 2568) in August 2017. Participants with formal brain-related education were excluded, leaving the remaining sample of the lay public (n = 1012). Demographic characteristics and information regarding the perceived importance and knowledge of brain health and engagement in preventive behaviors of participants were collected, and key associative analyses were carried out. Results: The majority of respondents (89%) considered brain health to be important. Over one-third (39%) considered their knowledge of the brain as sufficient relative to their needs. Most of the respondents identified science-recommended practices to be important for brain health. No recommendation was followed daily by the majority of the respondents, primarily due to declared lack of time (59%), and lack of information (32%). Information was obtained primarily from television (38%), followed by newspapers and magazines (31%), the Internet (31%), and direct conversations (27%). However, the highest-rated, preferred source of information was lectured by experts. One-third of our sample struggled with the trustworthiness of information sources. Female gender and older age were associated with a higher frequency of healthy practices. Personal or familial diagnoses of brain disorders were not associated with a higher frequency of the behavior in favor of brain health, but did affect available time and perceived value of preventive practices. Conclusions: Our research provides an initial insight into the perceptions, knowledge, and brain health-promoting behavior of the Slovenian lay public. Our findings can inform future strategies for science communication, public education and engagement, and policy-making to improve lifelong active care for brain health.

Ibogaine Has Sex-Specific Plasma Bioavailability, Histopathological and Redox/Antioxidant Effects in Rat Liver and Kidneys: A Study on Females.

Ibogaine induces rapid changes in cellular energetics followed by the elevation of antioxidant activities. As shown earlier in male rats, ibogaine treatment with both 1 and 20 mg/kg b.w. per os led to significant glycogenolytic activity in the liver. In this work, female rats treated with the same doses of ibogaine per os displayed lower liver glycogenolytic activity relative to males, dilatation of the central vein and branches of the portal vein, and increased concentration of thiols 6 h after treatment. These changes were followed by increased catalase activity and lipid peroxidation, and decreased xanthine oxidase activity after 24 h. In kidneys, mild histopathological changes were found in all treated animals, accompanied by a decrease of glutathione reductase (after 6 and 24 h at both doses) and an increase of catalase (6 h) and xanthine oxidase activity (6 and 24 h). Ibogaine did not affect antioxidant enzymes activity in erythrocytes. Bioavailability of ibogaine was two to three times higher in females than males, with similar kinetic profiles. Compared to previous results in males, ibogaine showed sex specific effect at the level of antioxidant cellular system. Effects of ibogaine in rats are sex- and tissue-specific, and also dose- and time-dependent.

The Effects of Ibogaine on Uterine Smooth Muscle Contractions: Relation to the Activity of Antioxidant Enzymes.

Ibogaine is an indole alkaloid originally extracted from the root bark of the African rainforest shrub Tabernanthe iboga. It has been explored as a treatment for substance abuse because it interrupts drug addiction and relieves withdrawal symptoms. However, it has been shown that ibogaine treatment leads to a sharp and transient fall in cellular ATP level followed by an increase of cellular respiration and ROS production. Since contractile tissues are sensitive to changes in the levels of ATP and ROS, here we investigated an ibogaine-mediated link between altered redox homeostasis and uterine contractile activity. We found that low concentrations of ibogaine stimulated contractile activity in spontaneously active uteri, but incremental increase of doses inhibited it. Inhibitory concentrations of ibogaine led to decreased SOD1 and elevated GSH-Px activity, but doses that completely inhibited contractions increased CAT activity. Western blot analyses showed that changes in enzyme activities were not due to elevated enzyme protein concentrations but posttranslational modifications. Changes in antioxidant enzyme activities point to a vast concentration-dependent increase in H2O2 level. Knowing that extracellular ATP stimulates isolated uterus contractility, while H2O2 has an inhibitory effect, this concentration-dependent stimulation/inhibition could be linked to ibogaine-related alterations in ATP level and redox homeostasis.

Design, Syntheses, and in Vitro Evaluation of New Fluorine-18 Radiolabeled Tau-Labeling Molecular Probes.

Deposition of aggregates of hyperphosphorylated tau protein is a hallmark of tauopathies like Alzheimer and many other neurodegenerative diseases. A sensitive and selective method of in vivo detection of tau-aggregate presence and distribution could provide the means of an early diagnosis of tau-associated diseases. Furthermore, the use of selective molecular probes that enable histochemical differentiation of protein aggregates post-mortem would be advantageous for the insight into the properties of tau protein aggregates. We chose to design new molecular probes based on the structure of 2-(1-(6-((2-[18F]fluoroethyl)(methyl)amino)-2-naphthyl)ethylidene)malononitrile to investigate their likelihood of fitting into VQIVYK tau protein binding channel model. In a modular approach, using cross-coupling reactions, we synthesized a series of candidates, radiolabeled them with fluorine-18 radioisotope, and determined their physicochemical and in vitro binding properties. Herein we report the synthesis of a series of molecular probes capable of detection of tau protein deposits in vitro.

Postmortem 3-D brain hemisphere cortical tau and amyloid-ß pathology mapping and quantification as a validation method of neuropathology imaging.

This work is aimed at correlating pre-mortem [18F]FDDNP positron emission tomography (PET) scan results in a patient with dementia with Lewy bodies (DLB), with cortical neuropathology distribution determined postmortem in three physical dimensions in whole brain coronal sections. Analysis of total amyloid-ß (Aß) distribution in frontal cortex and posterior cingulate gyrus confirmed its statistically significant correlation with cortical [18F]FDDNP PET binding values (distribution volume ratios, DVR) (p < 0.001, R = 0.97, R2 = 0.94). Neurofibrillary tangle (NFT) distribution correlated significantly with cortical [18F]FDDNP PET DVR in the temporal lobe (p < 0.001, R = 0.87, R2 = 0.76). Linear combination of Aß and NFT densities was highly predictive of [18F]FDDNP PET DVR through all analyzed regions of interest (p < 0.0001, R = 0.92, R2 = 0.85), and both densities contributed significantly to the model. Lewy bodies were present at a much lower level than either Aß or NFTs and did not significantly contribute to the in vivo signal. [18F]FDG PET scan results in this patient were consistent with the distinctive DLB pattern of hypometabolism. This work offers a mapping brain model applicable to all imaging probes for verification of imaging results with Aß and/or tau neuropathology brain distribution using immunohistochemistry, fluorescence microscopy, and autoradiography.

Metabolic aspects of prion diseases: an overview.

Prion diseases are fatal neurodegenerative disorders that affect humans and other mammals. The hallmark of these diseases is the conformational change of the cellular prion protein (PrP(C)) to the misfolded protein capable of propagation and associated with neurodegenration, named prion (PrP(Sc)). In a strict sense, prion diseases are a consequence of aberrations in the metabolism of the cellular prion protein (PrP(C)). This brief review addresses current understanding of metabolic disturbances in prion disorders at the cellular, organ and organism level, selectively pointing out some relevant diagnostic and treatment options.

Curcumin labeling of neuronal fibrillar tau inclusions in human brain samples.

The study aimed to characterize curcumin (CCM) (fluorescent yellow curry pigment) labeling of neuronal fibrillar tau inclusions (FTIs) in representative cases of 3 main tauopathies: Alzheimer disease (AD), progressive supranuclear palsy, and Pick disease. After identification of FTIs in hematoxylin and eosin-stained brain sections, sequential labeling and signal colocalization image analysis were used to compare CCM with thioflavine S (ThS), monoclonal antibody AT8 immunofluorescence, and Gallyas silver staining by visualizing the same FTIs. Curcumin preference for specific tau isoforms was tested with 3-repeat tau and 4-repeat tau isoform-specific immunofluorescence. Curcumin proved highly comparable to ThS and Gallyas staining in its detection of FTIs. When comparing CCM with AT8, ThS, and Gallyas staining in AD and progressive supranuclear palsy, 3 types of neuronal tau deposits were observed: nonfibrillar intracellular material labeled only with AT8, fibrillar intracellular inclusions labeled by all the methods, and fibrillar extracellular FTIs labeled with CCM, ThS, and Gallyas staining but not with AT8. Although CCM labeling overlapped with both 3-repeat tau and 4-repeat tau in AD, it did not label 3-repeat tau FTIs in Pick disease probably because of their different ultrastructural characteristics. In summary, CCM fluorescence reliably detected neuronal FTIs in AD and progressive supranuclear palsy and surpassed AT8 immunolabeling in visualizing later stages of FTIs, including ghost tangles. These results provide the basis for potential future applications of CCM binding of tau aggregates in diagnostic pathology and in vivo.

PET of brain prion protein amyloid in Gerstmann-Sträussler-Scheinker disease.

In vivo amyloid PET imaging was carried out on six symptomatic and asymptomatic carriers of PRNP mutations associated with the Gerstmann-Sträussler-Scheinker (GSS) disease, a rare familial neurodegenerative brain disorder demonstrating prion amyloid neuropathology, using 2-(1-{6-[(2-[F-18]fluoroethyl)(methyl)amino]-2-naphthyl}ethylidene)malononitrile ([F-18]FDDNP). 2-Deoxy-2-[F-18]fluoro-d-glucose PET ([F-18]FDG) and magnetic resonance imaging (MRI) scans were also performed in each subject. Increased [F-18]FDDNP binding was detectable in cerebellum, neocortex and subcortical areas of all symptomatic gene carriers in close association with the experienced clinical symptoms. Parallel glucose metabolism ([F-18]FDG) reduction was observed in neocortex, basal ganglia and/or thalamus, which supports the close relationship between [F-18]FDDNP binding and neuronal dysfunction. Two asymptomatic gene carriers displayed no cortical [F-18]FDDNP binding, yet progressive [F-18]FDDNP retention in caudate nucleus and thalamus was seen at 1- and 2-year follow-up in the older asymptomatic subject. In vitro FDDNP labeling experiments on brain tissue specimens from deceased GSS subjects not participating in the in vivo studies indicated that in vivo accumulation of [F-18]FDDNP in subcortical structures, neocortices and cerebellum closely related to the distribution of prion protein pathology. These results demonstrate the feasibility of detecting prion protein accumulation in living patients with [F-18]FDDNP PET, and suggest an opportunity for its application to follow disease progression and monitor therapeutic interventions.

Curcumin binds to the alpha-helical intermediate and to the amyloid form of prion protein - a new mechanism for the inhibition of PrP(Sc) accumulation.

Conversion of the native, predominantly alpha-helical conformation of prion protein (PrP) into the beta-stranded conformation is characteristic for the transmissible spongiform encephalopathies such as Creutzfeld-Jakob disease. Curcumin, an extended planar molecule and a dietary polyphenol, inhibits in vitro conversion of PrP and formation of protease resistant PrP in neuroblastoma cell lines. Curcumin recognizes the converted beta-form of the PrP both as oligomers and fibrils but not the native form. Curcumin binds to the prion fibrils in the left-handed chiral arrangement as determined by circular dichroism. We show that curcumin labels the plaques of the brain sections of variant Creutzfeld-Jakob disease cases and stains the same structures as antibodies against the PrP. In contrast to thioflavin T, curcumin also binds to the alpha-helical intermediate of PrP present at acidic pH at stoichiometry of 1 : 1. Congo red competes with curcumin for binding to the alpha-intermediate as well as to the beta-form of PrP but is toxic and binds also to the native form of PrP. We therefore show that the partially unfolded structural intermediate of the PrP can be targeted by non-toxic compound of natural origin.

The 2,6-disubstituted naphthalene derivative FDDNP labeling reliably predicts Congo red birefringence of protein deposits in brain sections of selected human neurodegenerative diseases.

Deposition of conformationally altered proteins prominently characterizes pathogenesis and pathomorphology of a number of neurodegenerative disorders. 2-(1-{6-[(2-[F-18]fluoroethyl) (methyl)amino]-2-naphthyl} ethylidene) malononitrile ([F-18]FDDNP), a hydrophobic, viscosity-sensitive, solvent-sensitive, fluorescent imaging probe has been used with positron emission tomography to visualize brain pathology in the living brain of Alzheimer disease (AD) patients. Its non-radiofluorinated analog FDDNP was shown to label senile plaques and neurofibrillary tangles (NFTs) in brain tissue sections. This work aimed at evaluating FDDNP labeling of various protein deposits in fixed, paraffin-embedded brain tissue sections of selected neurodegenerative disorders: AD, cerebral amyloid angiopathy (CAA), transmissible spongiform encephalopathies, progressive supranuclear palsy (PSP), Pick disease (PiD), Parkinson disease, dementia with Lewy bodies, multiple system atrophy (MSA). Cerebral hypertensive vascular hyalinosis (HVH) was used as negative control. Significant agreement between amyloid histochemical properties and FDDNP labeling of the deposits was established. FDDNP labeling showed high positive predictive value for birefringence in senile plaques and NFTs in AD, prion plaques and amyloid deposits in CAA. No FDDNP labeled structures were observed in HVH, PSP, PiD or MSA tissue sections. Our findings may be of significant value for the detection of neuropathological aggregates with [F-18]FDDNP in some of these disorders in the living brain of human subjects.

Monoclonal antibody against a peptide of human prion protein discriminates between Creutzfeldt-Jacob's disease-affected and normal brain tissue.

Current methods for diagnosing transmissible spongiform encephalopathies rely on the degradation of the cellular prion protein (PrP(C)) and the subsequent detection of the protease-resistant remnant of the pathological prion isoform PrP(Sc) by antibodies that react with all forms of PrP. We report on a monoclonal antibody, V5B2, raised against a peptide from the C-terminal part of PrP, which recognizes an epitope specific to PrP(Sc). In cryostat sections from Creutzfeldt-Jacob's disease (CJD) patients' brains, V5B2 selectively labels various deposits of PrP(Sc) without any pretreatment for removal of PrP(C). V5B2 does not bind to non-CJD brain samples or to recombinant PrP, either in its native or denatured form. Specificity for PrP is confirmed by a sandwich enzyme-linked immunosorbent assay utilizing V5B2, which discriminates between CJD and normal samples without proteinase K treatment, and by immunoprecipitation from CJD brain homogenate. The PrP(Sc)-specific epitope is disrupted by denaturation. We conclude that the C-terminal part of PrP in disease-associated PrP(Sc) aggregates forms a structural epitope whose conformation is distinct from that of PrP(C).

Molecular-imaging probe 2-(1-[6-[(2-fluoroethyl)(methyl) amino]-2-naphthyl]ethylidene) malononitrile labels prion plaques in vitro.

The study aimed to evaluate the fluorescent molecular-imaging probe 2-(1-[6-[(2-fluoroethyl)(methyl)amino]-2-naphthyl]ethylidene)malononitrile (FDDNP) for its ability to selectively and reproducibly label prion plaques in fixed, paraffin-embedded cerebellar sections from patients of confirmed Gerstmann-Sträussler-Scheinker disease, sporadic Creutzfeldt-Jacob disease (CJD) with kuru plaques, and variant CJD (vCJD). FDDNP is a highly hydrophobic, viscosity-sensitive, solvent-sensitive, fluorescent substance, whose radiofluorinated analog [18F]FDDNP has recently been successfully used to label senile plaques and neurofibrillary tangles in the living brain of Alzheimer's disease patients with positron emission tomography. Our results show that FDDNP reliably identifies all prion plaques, including small cluster-plaques in vCJD. This finding may open new in vivo diagnostic possibilities for vCJD.

Neurotransplantation-induced plasticity in the recipient CNS: focusing on the recipient response.

In the last two decades, neurotransplantation has gained the status of a potentially valuable treatment option in various central nervous system (CNS) disorders. This technique has provided considerable functional improvement in animal models of neurodegenerative diseases, stroke and trauma. In order to make the best therapeutic use of this treatment option, mechanisms of neurotransplantation-induced recovery need to be better understood.Specific interactions of transplants with the recipient brain, which are prominent in embryonic neural cell grafts, include formation of synapses between grafted neurons and recipient neuronal population with controled release of neurotransmitters. Production and release of specific trophic substances for the recipient neurons by the grafted cells also play a considerable role in some transplants. In the above cases, the functional recovery seems to correlate well with the number of surviving cells in the transplant.There is, however, another component to the graft-induced recovery, best revealed in those graft recipients who display functional improvement although only few or no grafted cells can be found at the post mortem analysis. While psychological factors (placebo effect) have been proposed to play a central role in human graft recipients with functional recovery in the absence of surviving grafts, animal models of neurodegenerative disease have consistently shown the same phenomenon.Our recent results point to the local inflammatory and immune response to transplantation as a key element which induces a trophic response in the CNS parenchyma and stimulates plastic changes of the recipient neural connections. Findings by other investigators, who studied the connections between the inflammatory and neurotrophic responses in vitro 1 and in vivo 2, and glial reaction to CNS trauma and trophic factor synthesis in vivo 3, support such conclusions.Accumulated evidence point to the need for further studies that would elucidate the role of the immune response in connection with CNS transplantation outcome.