Effects of hydroxyl group variations on a flavonoid backbone toward modulation of metal-free and metal-induced amyloid-?? aggregation

Amyloid-?? (A??) and metal ions are suggested to be involved in the pathogenesis of Alzheimer???s disease(AD). Cu(II) and Zn(II) can interact with A?? and facilitate peptide aggregation producing toxic oligomeric peptide species. Additionally, redox-active metal-bound A?? is shown to generate reactive oxygen species(ROS). Although the interaction of metal ions with A?? and the reactivity of metal-associated A?? (metal-A??) are indicated, the relationship between metal-A?? and AD etiology is still unclear. Some naturally occurring flavonoids capable of redirecting metal-A?? peptides into nontoxic, off-pathway A?? aggregates have been presented as valuable tools for elucidating the role of metal-A?? in AD. The structural moieties of the flavonoids responsible for their reactivity toward metal-A?? are not identified, however. To determine a structure-interaction-reactivity relationship between flavonoids and metal-free A?? or metal-A??, four flavonoids (morin, quercetin, galangin, and luteolin) were rationally selected based on structural variations(i.e., number and position of hydroxyl groups). These four flavonoids could noticeably modulate metal-A?? aggregation over metal-free analogue to different extents. Moreover, nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) studies reveal that the direct interactions of the flavonoids with metal-free and/or metal-bound A?? are distinct. Overall, our studies demonstrate that alternation of the hydroxyl groups on the B and C rings of flavonoids (structure) could differentiate their metal/metal-free A??/metal-A?? interactions (interaction) and subsequently direct their effects on metal-free A?? and metal-A?? aggregation in vitro and A??-/metal-A??-triggered toxicity in living cells (reactivity), suggesting a structure-interaction-reactivity relationship.open

Reactivity of Metal-Free and Metal-Associated Amyloid-?? with Glycosylated Polyphenols and Their Esterified Derivatives

Both amyloid-?? (A??) and transition metal ions are shown to be involved in the pathogenesis of Alzheimer???s disease (AD), though the importance of their interactions remains unclear. Multifunctional molecules, which can target metal-free and metal-bound A?? and modulate their reactivity (e.g., A?? aggregation), have been developed as chemical tools to investigate their function in AD pathology; however, these compounds generally lack specificity or have undesirable chemical and biological properties, reducing their functionality. We have evaluated whether multiple polyphenolic glycosides and their esterified derivatives can serve as specific, multifunctional probes to better understand AD. The ability of these compounds to interact with metal ions and metal-free/-associated A??, and further control both metal-free and metal-induced A?? aggregation was investigated through gel electrophoresis with Western blotting, transmission electron microscopy, UV-Vis spectroscopy, fluorescence spectroscopy, and NMR spectroscopy. We also examined the cytotoxicity of the compounds and their ability to mitigate the toxicity induced by both metal-free and metal-bound A??. Of the polyphenols investigated, the natural product (Verbascoside) and its esterified derivative (VPP) regulate the aggregation and cytotoxicity of metal-free and/or metal-associated A?? to different extents. Our studies indicate Verbascoside represents a promising structure for further multifunctional tool development against both metal-free A?? and metal-A??.open0

Resisting Corporations : Violent and Nonviolent Conflict in the context of Natural Resource Extraction

Corporations in the resource extraction industry are frequently criticized and their operations opposed by local communities demanding more benefits, compensation for negative consecuences or oppose resource extraction altogether. Research has focused extensively on nonviolent and violent resistance campaigns that target state and quasi-state actors attempting regime change or self-determination. However, campaigns targeting corporations have received little attention so far. This thesis addresses this gap. I argue that nonviolent campaigns have a strategic advantage over violent campaigns in building leverage and forcing corporations to fulfill their demands because they are able to mobilize more numerous and diverse support and have a higher tactical diversity. I test the hypothesis that nonviolent campaigns are more likely to succeed in achieving their objectives and the expected causal mechanism in a qualitative comparative case study using the structured focused comparison method and aspects of process tracing. Applying a most- similar case selection, I select nonviolent and violent resistance campaigns targeting (multinational) corporations in Nigeria and Colombia. I find partial support for the hypothesis. However, limited data availability does not allow for a conclusive evaluation of the theorized causal mechanism. Findings indicate the value of studying resistance campaigns targeting corporations. In particular, future research should use a more fine-grained analysis of causal mechanisms linking the type and outcome of campaigns in this context. Additionally, applying large-n research designs allowing for greater generalizability of findings would be a valuable contribution in the future.

Resisting Corporations : Violent and Nonviolent Conflict in the context of Natural Resource Extraction

Corporations in the resource extraction industry are frequently criticized and their operations opposed by local communities demanding more benefits, compensation for negative consecuences or oppose resource extraction altogether. Research has focused extensively on nonviolent and violent resistance campaigns that target state and quasi-state actors attempting regime change or self-determination. However, campaigns targeting corporations have received little attention so far. This thesis addresses this gap. I argue that nonviolent campaigns have a strategic advantage over violent campaigns in building leverage and forcing corporations to fulfill their demands because they are able to mobilize more numerous and diverse support and have a higher tactical diversity. I test the hypothesis that nonviolent campaigns are more likely to succeed in achieving their objectives and the expected causal mechanism in a qualitative comparative case study using the structured focused comparison method and aspects of process tracing. Applying a most- similar case selection, I select nonviolent and violent resistance campaigns targeting (multinational) corporations in Nigeria and Colombia. I find partial support for the hypothesis. However, limited data availability does not allow for a conclusive evaluation of the theorized causal mechanism. Findings indicate the value of studying resistance campaigns targeting corporations. In particular, future research should use a more fine-grained analysis of causal mechanisms linking the type and outcome of campaigns in this context. Additionally, applying large-n research designs allowing for greater generalizability of findings would be a valuable contribution in the future.

Minor Structural Variations of Small Molecules Tune Regulatory Activities Towards Pathological Factors in Alzheimer???s Disease

Chemical tools have been valuable for establishing a better understanding of the relationships between metal ion dyshomeostasis, the abnormal aggregation and accumulation of amyloid-?? (A??), and oxidative stress in Alzheimer's disease (AD). Still, very little information is available to correlate the structures of chemical tools with specific reactivities used to uncover such relationships. Recently, slight structural variations to the framework of a chemical tool were found to drastically determine the tool's reactivities toward multiple pathological facets to various extents. Herein, we report our rational design and characterization of a structural series to illustrate the extent to which the reactivities of small molecules vary toward different targets as a result of minor structural modifications. These compounds were rationally and systematically modified based on consideration of properties, including ionization potentials and metal binding, to afford their desired reactivities with metal-free or metal-bound A??, reactive oxygen species (ROS), and free organic radicals. Our results show that although small molecules are structurally similar, they can interact with multiple factors associated with AD pathogenesis and alleviate their reactivities to different degrees. Together, our studies demonstrate the rational structure-directed design that can be used to develop chemical tools capable of regulating individual or interrelated pathological features in AD

Electrocautery effects on fluorescence lifetime measurements: An in vivo study in the oral cavity.

Tumor removal typically involves electrocautery, but no studies to date have quantified the effect of electrocautery on fluorescence emission. Electrocautery was applied to N=4 locations of the oral cavity and striated leg muscle of a live Yorkshire pig. Autofluorescence of cauterized tissues and surrounding regions was measured at distinct time points up to 120 minutes following cauterization. The fluorescence lifetime was spectrally resolved in four spectral detection channels that maximized the signal emanating from endogenous fluorophores of interest. The autofluorescence emission (355 nm excitation) was temporally resolved using a high-speed digitizer; resulting fluorescence decay characteristics were retrieved using the Laguerre deconvolution technique. Histology was performed and co-registered with the autofluorescence data. Results show that cauterized tissue presents a distinct autofluorescence signature from surrounding regions immediately after cauterization. Differences become less evident with time. The autofluorescence-derived parameters suggest altered metabolism in peripheral regions compared to the region of maximal damage. Within the time-frame of this study, tissues investigated show variable degrees of recovery from the effects of electrocautery that can be monitored by changes in fluorescence lifetime characteristics. Our findings suggest delineation of pathologic conditions could be affected by tissue cauterization and that future studies in this area will be necessary

Myricetin: A Naturally Occurring Regulator of Metal-Induced Amyloid-beta Aggregation and Neurotoxicity

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Copper Induces Protein Aggregation, a Toxic Process Compensated by Molecular Chaperones

International audienceCopper is well known for its antimicrobial and antiviral properties. Under aerobic conditions, copper toxicity relies in part on the production of reactive oxygen species (ROS), especially in the periplasmic compartment. However, copper is significantly more toxic under anaerobic conditions, in which ROS cannot be produced. This toxicity has been proposed to arise from the inactivation of proteins through mismetallations. Here, using the bacterium Escherichia coli, we discovered that copper treatment under anaerobic conditions leads to a significant increase in protein aggregation. In vitro experiments using E. coli lysates and tightly controlled redox conditions confirmed that treatment with Cu+ under anaerobic conditions leads to severe ROS-independent protein aggregation. Proteomic analysis of aggregated proteins revealed an enrichment of cysteine- and histidine-containing proteins in the Cu+-treated samples, suggesting that nonspecific interactions of Cu+ with these residues are likely responsible for the observed protein aggregation. In addition, E. coli strains lacking the cytosolic chaperone DnaK or trigger factor are highly sensitive to copper stress. These results reveal that bacteria rely on these chaperone systems to protect themselves against Cu-mediated protein aggregation and further support our finding that Cu toxicity is related to Cu-induced protein aggregation. Overall, our work provides new insights into the mechanism of Cu toxicity and the defense mechanisms that bacteria employ to survive. IMPORTANCE With the increase of antibiotic drug resistance, alternative antibacterial treatment strategies are needed. Copper is a well-known antimicrobial and antiviral agent; however, the underlying molecular mechanisms by which copper causes cell death are not yet fully understood. Herein, we report the finding that Cu+, the physiologically relevant copper species in bacteria, causes widespread protein aggregation. We demonstrate that the molecular chaperones DnaK and trigger factor protect bacteria against Cu-induced cell death, highlighting, for the first time, the central role of these chaperones under Cu+ stress. Our studies reveal Cu-induced protein aggregation to be a central mechanism of Cu toxicity, a finding that will serve to guide future mechanistic studies and drug development