392 research outputs found
Recommended from our members
In Vivo Characterization of CLR01, an Aggregation and Toxicity Inhibitor, with an Alzheimer's Disease Focus
No full textAberrant protein self-assembly underlies over 30 human diseases called amyloidoses, for which there are no cures. In these diseases, particular proteins misfold and self-assemble into toxic oligomers that disrupt cellular function, and proceed to form insoluble amyloid fibrils that deposit in specific tissues. A promising strategy for preventing and treating amyloidoses is inhibition or modulation of the self-assembly process to disrupt the formation of the toxic oligomers. In practice, this has proven immensely difficult because the oligomer structures are unknown, are metastable, and do not have distinct binding sites. In this dissertation, three primary studies are presented that evaluate and characterize a small molecule, CLR01, which utilizes a novel strategy circumventing these challenges and has been found to be efficacious as an aggregation and toxicity inhibitor in vitro and in vivo. In the first study, CLR01 was evaluated for its ability to rescue synaptic toxicity in cell culture and brain slices. Additionally, it was tested in a transgenic mouse model of AD for its ability to reduce the pathological hallmarks of AD: amyloid plaques and neurofibrillary tangles. This study found positive results in all domains tested; a rescue from amyloid β-protein (Aβ)-induced depletion of synaptic spine density, a rescue of Aβ-induced disruption of basal synaptic transmission and long-term potentiation, and reduction of brain Aβ, hyperphosphorylated tau, and microglia burden. CLR01 also showed low propensity for causing metabolic toxicity or drug-drug interaction, indicating favorable drug-like characteristics. In the second study, CLR01's safety and pharmacological profile were characterized in mice. CLR01 was found not to disrupt normal protein assembly, to have a high safety margin in mice, and to penetrate the blood-brain barrier (BBB) at 1-3%. Interestingly, brain levels of CLR01 remained stable for 72 hours following administration despite rapid clearance from the plasma. These results suggest a large safety margin for CLR01 and a pharmacokinetic profile that allows reaching high levels in the brain by administering relatively low doses. The third study delineates a detailed optimization of behavioral testing of mice for detection of memory deficits using the Barnes maze, and validates for the first time memory deficits in a triple-transgenic mouse model of AD at the youngest age described in the literature. The study provides a framework for analysis of CLR01's influence on learning and memory deficits in this triple transgenic model. Additionally, the study provides specific and detailed guidelines for optimizing both the performance and the analysis of the Barnes maze in a manner that increases the likelihood of detecting subtle changes in future studies using mouse models of AD. The work described in this dissertation provides a strong foundation supporting formal pre-clinical development of CLR01 as a promising disease-modifying therapeutic drug for AD
Chapter Fifteen Disease-modifying therapy for proteinopathies: Can the exception become the rule?
No full textDisease-modifying therapies for proteinopathies are urgently needed yet clinical trials for the major neurodegenerative diseases, Alzheimer's and Parkinson's, have been failing at an alarming rate leaving patients and caregivers scrambling for any sign of hope. At the same time, for one family of proteinopathies, the rare TTR amyloidoses, disease-modifying therapy has existed for almost 3 decades and two new types of disease-modifying therapy have become available more recently. In this chapter, I discuss those therapies, examine to what extent they can be generalized for other diseases, and consider what we may learn from their relative success
Structural Studies of Prion Proteins and Prions
No full textPrion diseases are a group of fatal and incurable neurodegenerative disorders of mammals. They uniquely manifest as sporadic, genetic, and infectious maladies. The agent responsible for prion diseases is the prion. A prion is defined as a proteinaceous infectious particle, which is solely constituted by an alternately folded form of the prion protein (PrP) (Prusiner 1982).
In diseased animals and humans, PrP exists in two forms, the physiological, cel- lular form of PrP, PrPC, and the pathological prion form denoted as PrPSc. The mech- anism whereby nascent PrPSc is generated is currently unknown. Structural studies of either isoform are of great importance for understanding the biology of prion diseases since they may clarify the molecular mechanisms responsible for these pathologies. In this chapter, we present an overview of the studies into PrPC as well as structures of prions
The recent failure of the PROMESA clinical trial for multiple system atrophy raises the question—are polyphenols a viable therapeutic option against proteinopathies?
No full textRadical research as research at the roots: Practitioner self-image, public relations and ethics
No full textSemantically, radical derives from ‘radix’, the Latin for root. This paper argues that little public relations research goes back to the roots of actual practice and addresses this neglect through a project focusing on practitioner accounts of their work. When considering public relations ethics, practitioner self-images and cultural values become an essential research component. In addressing this neglected area of research, this paper examines the subjective perceptions of public relations practitioners regarding their role, commitments, and responsibilities within the framework of their specific culture and national history. In considering practitioner testimonials about professional integrity, briefs, and goals, especially as members of the society and nation to which they belong, the paper engages with ethical aspects of the practice from a cultural perspective that assumes different cultures can have different ethical expectations. In revealing the impact of features that are often ‘taken for granted’ in one country, the paper uses the example of four generations of practitioners who served one major institution in Israel to suggest how similar research at the professional roots in other nations might enable knowledge of international similarities and difference in relation to ethics in action
Structural Study of Metastable Amyloidogenic Protein Oligomers by Photo‐Induced Cross‐Linking of Unmodified Proteins
No full textEffects of different forms of amyloid β-peptide on synaptic function.
No full textIntroduction: In early stages of Alzheimer’s disease, that precede plaque formation and neuronal death, cognitive deficits are likely the result of synaptic function impairment. The key initiating pathogenic event is the accumulation of neurotoxic aggregates of amyloid β-peptide (Aβ) in hippocampus and cortex. We previously demonstrated that the redox state of methionine in position 35 (Met35) plays a critical role in Aβ toxicity.
Objective: To determine whether oxidation of Met35 also influences Aβ synaptotoxicity we investigated the effects of 20-min lasting perfusion with 200 nM AβWT and its oxidized analogues (AβMet35(O), AβMet35(O2)) on synaptic transmission and plasticity, and on synaptophysin (Syn) expression.
Methods: We performed electrophysiological experiment on hippocampal brain slices and autaptic neurons to study the long-term potentiation (LTP) and synaptic transmission. We also studied Syn density as the ratio between Syn fluorescence intensity and MAP2 labeled area by confocal microscopy.
Results: In control slices, 60 min after tetanus fEPSP amplitude (A) and slope (S) were increased by 138% and 132% of baseline, respectively. This potentiation was significantly lower after AβWT treatment (A: +72%; S: +68%; P<0.001) whereas no changes in LTP were observed in slices exposed to AβMet35(O). Surprisingly, AβMet35(O2) reduced the synaptic plasticity to the same level as AβWT. In autaptic microcultures, AβWT and AβMet35(O2) significantly reduced the amplitude of EPSCs evoked by action potentials and mEPSC frequency (P<0.05) whereas AβMet35(O) had no effects on basal synaptic transmission. Finally, AβWT and AβMet35(O2) significantly reduced Syn density while AβMet35(O) did not affect presynaptic terminals.
Conclusion: Our results indicate that the chemical state of Met35 plays a key role in Aβ- induced: (i) synaptic depression, (ii) inhibition of synaptic plasticity and (iii) alterations in the expression of proteins relevant for the synaptic function
Surprising toxicity and assembly behavior of amyloid beta-protein oxidized to sulfone.
No full textA beta (amyloid beta-peptide) is believed to cause AD (Alzheimer's disease). A beta 42 (A beta comprising 42 amino acids) is substantially more neurotoxic than A beta 40 (A beta comprising 40 amino acids), and this increased toxicity correlates with the existence of unique A beta 42 oligomers. Met(35) oxidation to sulfoxide or sulfone eliminates the differences in early oligomerization between A beta 40 and A beta 42. Met(35) oxidation to sulfoxide has been reported to decrease A beta assembly kinetics and neurotoxicity, whereas oxidation to sulfone has rarely been studied. Based on these data, we expected that oxidation of A beta to sulfone would also decrease its toxicity and assembly kinetics. To test this hypothesis, we compared systematically the effect of the wild-type, sulfoxide and sulfone forms of A beta 40 and A beta 42 on neuronal viability, dendritic spine morphology and macroscopic Ca2+ currents in primary neurons, and correlated the data with assembly kinetics. Surprisingly, we found that, in contrast with A beta-sulfoxide, A beta-sulfone was as toxic and aggregated as fast, as wild-type A beta. Thus, although A beta-sulfone is similar to A beta-sulfoxide in its dipole moment and oligomer size distribution, it behaves similarly to wild-type A beta in its aggregation kinetics and neurotoxicity. These surprising data decouple the toxicity of oxidized A beta from its initial oligomerization, and suggest that our current understanding of the effect of methionine oxidation in A beta is limited
Rapid Photochemical Cross‐Linking — A New Tool for Studies of Metastable, Amyloidogenic Protein Assemblies
No full textAmyloidoses comprise a class of diseases characterized pathologically by the presence of deposits of fibrillar, aberrantly folded proteins, known as amyloids. Historically, these deposits were considered the key factors causing disease. However, recent evidence suggests that soluble protein oligomers, which are precursors for amyloid fibrils, are the primary toxic effectors responsible for the disease process. Understanding the mechanism by which these oligomers exert their toxicity requires knowledge of the structure, kinetics, and thermodynamics of their formation and conversion into larger assemblies. Such studies have been difficult due to the metastable nature of the oligomers. For the amyloid beta-protein (Abeta), a consensus about the size and relative abundance of small oligomers has not been achieved. We describe here the application of the method Photoinduced Cross-Linking of Unmodified Proteins (PICUP) to the study of Abeta oligomerization. This approach distinguishes oligomerization patterns of amyloidogenic and nonamyloidogenic proteins, allows quantification of each component in oligomer mixtures, and provides a means of correlating primary structure modifications with assembly characteristics. PICUP thus is a powerful tool for the investigation of small, metastable protein oligomers. The method provides essential insights into the factors that control the assembly of pathogenic protein oligomers, facilitating efforts toward the development of therapeutic agents
- …
