Mechanisms of amyloid proteins aggregation and their inhibition by antibodies, small molecule inhibitors, nano-particles and nano-bodies

Multifunctional porphyrin-substituted phenylalanine-phenylalanine nanoparticles for diagnostic and therapeutic applications in Alzheimer's disease

β-Amyloid (Aβ) peptides are believed as the diagnostic biomarkers and therapeutic targets of Alzheimer's disease (AD). Their complexes with copper ions can catalyze the generation of reactive oxygen species (ROS) to further promote neuronal death. Herein, we suggested that porphyrin-substituted phenylalanine-phenylalanine nanoparticles (TPP-FF NPs) could inhibit the aggregation of Aβ monomers, disassemble the fibrillar Aβ aggregates under light illumination, and depressing the Cu2+-induced generation of ROS. Meanwhile, the TPP-FF NPs could be used as the nanocarriers and quenchers of fluorescently-labeled probes for the detection of Aβ oligomer (AβO). Inhibition of Aβ assembly and dissolution of Aβ aggregates were monitored by Thioflavin T (ThT)-based fluorescent assay and characterized by atomic force microscopy. The Aβ/Cu2+-induced generation of ROS was limited by TPP-FF NPs. The fluorescein-labeled probe aptamers attached on the surface of TPP-FF NPs emitted low fluorescence. The interaction between AβO and aptamers induced the release of the probes from the surface of TPP-FF NPs, driving the fluorophore far away from the quenchers and turning on the fluorescence. The signal-on strategy can be used for the detection of AβO with a low detection limit. This work should be evaluable for the development of multifunctional candidates for the diagnosis and treatment of AD.

From experimental studies to computational approaches: recent trends in designing novel therapeutics for amyloidogenesis

Amyloidosis is a condition marked by misfolded proteins that build up in tissues and eventually destroy organs. It has been connected to a number of fatal illnesses, including non-neuropathic and neurodegenerative conditions, which in turn have a significant influence on the worldwide health sector. The inability to identify the underlying etiology of amyloidosis has hampered efforts to find a treatment for the condition. Despite the identification of a multitude of putative pathogenic variables that may operate independently or in combination, the molecular mechanisms responsible for the development and progression of the disease remain unclear. A thorough investigation into protein aggregation and the impacts of toxic aggregated species will help to clarify the cytotoxicity of aggregation-mediated cellular apoptosis and lay the groundwork for future studies aimed at creating effective treatments and medications. This review article provides a thorough summary of the combination of various experimental and computational approaches to modulate amyloid aggregation. Further, an overview of the latest developments of novel therapeutic agents is given, along with a discussion of the possible obstacles and viewpoints on this developing field. We believe that the information provided by this review will help scientists create innovative treatment strategies that affect the way proteins aggregate.

Immune Response in Traumatic Brain Injury

PURPOSE OF REVIEW

This review aims to comprehensively examine the immune response following traumatic brain injury (TBI) and how its disruption can impact healing and recovery.

RECENT FINDINGS

The immune response is now considered a key element in the pathophysiology of TBI, with consequences far beyond the acute phase after injury. A delicate equilibrium is crucial for a healthy recovery. When this equilibrium is disrupted, chronic inflammation and immune imbalance can lead to detrimental effects on survival and disability. Globally, traumatic brain injury (TBI) imposes a substantial burden in terms of both years of life lost and years lived with disability. Although its epidemiology exhibits dynamic trends over time and across regions, TBI disproportionally affects the younger populations, posing psychosocial and financial challenge for communities and families. Following the initial trauma, the primary injury is succeeded by an inflammatory response, primarily orchestrated by the innate immune system. The inflammasome plays a pivotal role during this stage, catalyzing both programmed cell death pathways and the up-regulation of inflammatory cytokines and transcription factors. These events trigger the activation and differentiation of microglia, thereby intensifying the inflammatory response to a systemic level and facilitating the migration of immune cells and edema. This inflammatory response, initially originated in the brain, is monitored by our autonomic nervous system. Through the vagus nerve and adrenergic and cholinergic receptors in various peripheral lymphoid organs and immune cells, bidirectional communication and regulation between the immune and nervous systems is established.

Unraveling the Molecular Jam: How Crowding Shapes Protein Aggregation in Neurodegenerative Disorders

Protein misfolding and aggregation are the hallmarks of neurodegenerative diseases including Huntington's disease, Parkinson's disease, Alzheimer's disease, and prion diseases. A crowded cellular environment plays a crucial role in modulating protein aggregation processes in vivo and the pathological aggregation of proteins linked to different neurodegenerative disorders. Here, we review recent studies examining the effects of various crowding agents, such as polysaccharides, polyethylene glycol, and proteins like BSA and lysozyme on the behaviors of aggregation of several amyloidogenic peptides and proteins, including amylin, huntingtin, tau, α-synuclein, prion, and amyloid-β. We also summarize how the aggregation kinetics, thermodynamic stability, and morphology of amyloid fibrils are altered significantly in the presence of crowding agents. In addition, we also discuss the molecular basis underlying the modulation of amyloidogenic aggregation, focusing on changes in the protein conformation, and the nucleation mechanism. The molecular understanding of the effects of macromolecular crowding on amyloid aggregation is essential for revealing disease pathologies and identifying possible therapeutic targets. Thus, this review offers a perspective on the complex interplay between protein aggregation and the crowded cellular environment in vivo and explains the relevance of crowding in the context of neurodegenerative disorders.

Fibrillation of soy protein isolate in the presence of metal ions: Structure and gelation behavior

The structure and functional properties of protein fibrils are closely related to environmental factors in fibrillation. Herein, soy protein isolate fibrils (SPIFs, 22 mg/mL) were prepared under acid-heating conditions in the presence of 100 mM metal ions (K+, Na+, Ca2+, Mg2+, and Fe3+). Except for Fe3+, fibrillation and subsequent larger fibril aggregates were promoted, ultimately leading to gel formation. Compared with K+ or Na+, the addition of Ca2+ or Mg2+ resulted in more organized SPIF structures with increased β-sheet contents and higher ThT fluorescence intensities. Furthermore, both of them resulted in longer fibrils with an average contour length of 700-800 nm, which significantly enhanced the storage modulus. However, the presence of Fe3+ accelerated protein hydrolysis and inhibited SPIF formation, resulting in samples consistently exhibited liquid behavior. These findings provide a foundation for understanding the influence of metal ions on regulating the fibrillation and gelling properties of SPIFs.

Insulin fibrillation under physicochemical parameters of bioprocessing and intervention by peptides and surface-active agents

Even after the centenary celebration of insulin discovery, there prevail challenges concerning insulin aggregation, not only after repeated administration but also during industrial production, storage, transport, and delivery, significantly impacting protein quality, efficacy, and effectiveness. The aggregation reduces insulin bioavailability, increasing the risk of heightened immunogenicity, posing a threat to patient health, and creating a dent in the golden success story of insulin therapy. Insulin experiences various physicochemical and mechanical stresses due to modulations in pH, temperature, ionic strength, agitation, shear, and surface chemistry, during the upstream and downstream bioprocessing, resulting in insulin unfolding and subsequent fibrillation. This has fueled research in the pharmaceutical industry and academia to unveil the mechanistic insights of insulin aggregation in an attempt to devise rational strategies to regulate this unwanted phenomenon. The present review briefly describes the impacts of environmental factors of bioprocessing on the stability of insulin and correlates with various intermolecular interactions, particularly hydrophobic and electrostatic forces. The aggregation-prone regions of insulin are identified and interrelated with biophysical changes during stress conditions. The quest for novel additives, surface-active agents, and bioderived peptides in decelerating insulin aggregation, which results in overall structural stability, is described. We hope this review will help tackle the real-world challenges of insulin aggregation encountered during bioprocessing, ensuring safer, stable, and globally accessible insulin for efficient management of diabetes.

Dietary phenolic compounds as promising therapeutic agents for diabetes and its complications: A comprehensive review

In the middle of an ever-changing landscape of diabetes care, precision medicine, and lifestyle therapies are becoming increasingly important. Dietary polyphenols are like hidden allies found in our everyday meals. These biomolecules, found commonly in fruits, vegetables, and various plant-based sources, hold revolutionary potential within their molecular structure in the way we approach diabetes and its intimidating consequences. There are currently numerous types of diabetes medications, but they are not appropriate for all patients due to limitations in dosages, side effects, drug resistance, a lack of efficacy, and ethnicity. Currently, there has been increased interest in practicing herbal remedies to manage diabetes and its related complications. This article aims to summarize the potential of dietary polyphenols as a foundation in the treatment of diabetes and its associated consequences. We found that most polyphenols inhibit enzymes linked to diabetes. This review outlines the potential benefits of selected molecules, including kaempferol, catechins, rosmarinic acid, apigenin, chlorogenic acid, and caffeic acid, in managing diabetes mellitus as these compounds have exhibited promising results in in vitro, in vivo, in silico, and some preclinical trials study. This encompassing exploration reveals the multifaceted impact of polyphenols not only in mitigating diabetes but also in addressing associated conditions like inflammation, obesity, and even cancer. Their mechanisms involve antioxidant functions, immune modulation, and proinflammatory enzyme regulation. Furthermore, these molecules exhibit anti-tumor activities, influence cellular pathways, and activate AMPK pathways, offering a less toxic, cost-effective, and sustainable approach to addressing diabetes and its complications.

Therapeutic approaches in proteinopathies

A family of maladies known as amyloid disorders, proteinopathy, or amyloidosis, are characterized by the accumulation of abnormal protein aggregates containing cross-β-sheet amyloid fibrils in many organs and tissues. Often, proteins that have been improperly formed or folded make up these fibrils. Nowadays, most treatments for amyloid illness focus on managing symptoms rather than curing or preventing the underlying disease process. However, recent advances in our understanding of the biology of amyloid diseases have led to the development of innovative therapies that target the emergence and accumulation of amyloid fibrils. Examples of these treatments include the use of small compounds, monoclonal antibodies, gene therapy, and others. In the end, even if the majority of therapies for amyloid diseases are symptomatic, greater research into the biology behind these disorders is identifying new targets for potential therapy and paving the way for the development of more effective treatments in the future.

Enhancing anti-amyloidogenic properties and antioxidant effects of Scutellaria baicalensis polyphenols through novel nanoparticle formation

Protein aggregation and oxidative stress have gained significant research attention due to their association with a group of diseases known as amyloidosis. Among the strategies developed to prevent amyloidosis, utilization of polyphenols stands out as one of the most commonly employed approaches. Scutellaria baicalensis is renowned as one of the foremost herbal sources of polyphenols. In this study, we employed a direct oxidative pyrolysis method for polymerizing S. baicalensis's polyphenols (SBPPs) after their extraction, resulting in the formation of novel SBPPs nanoparticles. Upon polymerization, SBPPs nanoparticles showed remarkable properties including heightened water solubility, increased surface area, modified surface functional groups, and enhanced stability. As a result of these diverse factors, there was a considerable enhancement in the anti-amyloidogenic properties and antioxidant effects of SBPPs nanoparticles compared to its bulk form. The fibrillation kinetics, AFM images, and cytotoxicity assays strongly indicate that SBPPs nanoparticles are more effective than SBPPs at preventing amyloid fibril formation and associated cell toxicity. Additionally, SBPPs nanoparticles demonstrated more effective prevention of reactive oxygen species (ROS) production. In conclusion, the use of SBPPs in nanoparticle form presents a promising strategy to enhance anti-amyloidogenic properties, mitigate oxidative stress, and offer potential therapeutic benefits for amyloidosis-related diseases.

Disaggregation of amyloid-beta fibrils via natural metabolites using long timescale replica exchange molecular dynamics simulation studies

CONTEXT

Amyloid fibrils are self-assembled fibrous protein aggregates that are associated with several presently incurable diseases such as Alzheimer's. disease that is characterized by the accumulation of amyloid fibrils in the brain, which leads to the formation of plaques and the death of brain cells. Disaggregation of amyloid fibrils is considered a promising approach to cure Alzheimer's disease. The mechanism of amyloid fibril formation is complex and not fully understood, making it difficult to develop drugs that can target the process. Diacetonamine and cystathionine are potential lead compounds to induce disaggregation of amyloid fibrils.

METHODS

In the current research, we have used long timescale molecular simulation studies and replica exchange molecular dynamics (REMD) for 1000 ns (1 μs) to examine the mechanisms by which natural metabolites can disaggregate amyloid-beta fibrils. Molecular docking was carried out using Glide and with prior protein minimization and ligand preparation. We focused on a screening a database of natural metabolites, as potential candidates for disaggregating amyloid fibrils. We used Desmond with OPLS 3e as a force field. MM-GBSA calculations were performed. Blood-brain barrier permeability, SASA, and radius of gyration parameters were calculated.

A Diruthenium Metallodrug as a Potent Inhibitor of Amyloid-β Aggregation: Synergism of Mechanisms of Action

The physical and chemical properties of paddlewheel diruthenium compounds are highly dependent on the nature of the ligands surrounding the bimetallic core. Herein, we compare the ability of two diruthenium compounds, [Ru2Cl(D-p-FPhF)(O2CCH3)3]·H2O (1) (D-p-FPhF- = N,N'-bis(4-fluorophenyl)formamidinate) and K3[Ru2(O2CO)4]·3H2O (2), to act as inhibitors of amyloid aggregation of the Aβ1-42 peptide and its peculiar fragments, Aβ1-16 and Aβ21-40. A wide range of biophysical techniques has been used to determine the inhibition capacity against aggregation and the possible mechanism of action of these compounds (Thioflavin T fluorescence and autofluorescence assays, UV-vis absorption spectroscopy, circular dichroism, nuclear magnetic resonance, mass spectrometry, and electron scanning microscopy). Data show that the most effective inhibitory effect is shown for compound 1. This compound inhibits fiber formation and completely abolishes the cytotoxicity of Aβ1-42. The antiaggregatory capacity of this complex can be explained by a binding mechanism of the dimetallic units to the peptide chain along with π-π interactions between the formamidinate ligand and the aromatic side chains. The results suggest the potential use of paddlewheel diruthenium complexes as neurodrugs and confirm the importance of the steric and charge effects on the properties of diruthenium compounds.

Structural, kinetic, and thermodynamic aspects of insulin aggregation

Given the significance of protein aggregation in proteinopathies and the development of therapeutic protein pharmaceuticals, revamped interest in assessing and modelling the aggregation kinetics has been observed. Quantitative analysis of aggregation includes data of gradual monomeric depletion followed by the formation of subvisible particles. Kinetic and thermodynamic studies are essential to gain key insights into the aggregation process. Despite being the medical marvel in the world of diabetes, insulin suffers from the challenge of aggregation. Physicochemical stresses are experienced by insulin during industrial formulation, storage, delivery, and transport, considerably impacting product quality, efficacy, and effectiveness. The present review briefly describes the pathways, mathematical kinetic models, and thermodynamics of protein misfolding and aggregation. With a specific focus on insulin, further discussions include the structural heterogeneity and modifications of the intermediates incurred during insulin fibrillation. Finally, different model equations to fit the kinetic data of insulin fibrillation are discussed. We believe that this review will shed light on the conditions that induce structural changes in insulin during the lag phase of fibrillation and will motivate scientists to devise strategies to block the initialization of the aggregation cascade. Subsequent abrogation of insulin fibrillation during bioprocessing will ensure stable and globally accessible insulin for efficient management of diabetes.

Effect of plasmonic excitation on mature insulin amyloid fibrils

Interactions between amyloid protein structures and nanomaterials have been extensively studied to develop effective inhibitors of amyloid aggregation. Limited investigations are reported on the impact of nanoparticles on mature fibrils. In this work, gold nanoparticles are used as photothermal agents to alter insulin fibrils. To this end, gold colloids bearing a negatively charged capping shell, with an average diameter of 14 nm and a plasmon resonance maximum at 520 nm are synthesized. The effects on mature insulin fibril morphology and structure upon plasmonic excitation of the nanoparticles-fibril samples have been monitored by spectroscopic and microscopic methods. The obtained data indicate that an effective destruction of the amyloid aggregates occur upon irradiation of the plasmonic nanoparticles, allowing the development of emerging strategies to alter the structure of amyloid fibrils.

Modulatory role of copper on hIAPP aggregation and toxicity in presence of insulin

Aggregation of the human islets amyloid polypeptide, or hIAPP, is linked to β-cell death in type II diabetes mellitus (T2DM). Different pancreatic β-cell environmental variables such as pH, insulin and metal ions play a key role in controlling the hIAPP aggregation. Since insulin and hIAPP are co-secreted, it is known from numerous studies that insulin suppresses hIAPP fibrillation by preventing the initial dimerization process. On the other hand, zinc and copper each have an inhibitory impact on hIAPP fibrillation, but copper promotes the production of toxic oligomers. Interestingly, the insulin oligomeric equilibrium is controlled by the concentration of zinc ions when the effect of insulin and zinc has been tested together. Lower zinc concentrations cause the equilibrium to shift towards the monomer and dimer states of insulin, which bind to monomeric hIAPP and stop it from developing into a fibril. On the other hand, the combined effects of copper and insulin have not yet been done. In this study, we have demonstrated how the presence of copper affects hIAPP aggregation and the toxicity of the resultant conformers with or without insulin. For this purpose, we have used a set of biophysical techniques, including NMR, fluorescence, CD etc., in combination with AFM and cell cytotoxicity assay. In the presence and/or absence of insulin, copper induces hIAPP to form structurally distinct stable toxic oligomers, deterring the fibrillation process. More specifically, the oligomers generated in the presence of insulin have slightly higher toxicity than those formed in the absence of insulin. This research will increase our understanding of the combined modulatory effect of two β-cell environmental factors on hIAPP aggregation.

Effect of artificial sweetener saccharin on lysozyme aggregation: A combined spectroscopic and in silico approach

The use of saccharin in food products attracts much attention as it involves the risk of lethal allergies and many protein aggregation diseases. However, its role in protein aggregation has not been explored to date. This study embodies the effect of artificial sweeteners on HEWL in the absence and presence of commonly available natural products such as curcumin and EGCG. Various techniques have been used to characterize the protein interaction, such as steady-state emission and time-resolved fluorescence, FTIR, gel electrophoresis, TEM, and molecular docking. Steady-state and time-resolved studies revealed the binding strength and concomitant effect of saccharin on HEWL protein. Kinetic measurements revealed that saccharin causes significant enhancement of HEWL aggregation with a considerable reduction in lag phase time i.e. from 37 hr to 08 hr. Whereas in the presence of natural products, the effect of saccharin on HEWL aggregation was significantly reduced specifically in the case of curcumin. The result obtained in the fluorescence experiment were also supported by the gel electrophoresis technique and morphological images taken by TEM. The rapid change in the secondary structure of the protein in the presence of saccharin was confirmed by the FTIR spectroscopy technique. This study is instrumental in understanding the effect of saccharin on protein aggregation and the role of commonly available natural products in curbing its effect.

New Pathways Identify Novel Drug Targets for the Prevention and Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is an incurable, progressive neurodegenerative disorder. AD is a complex and multifactorial disease that is responsible for 60-80% of dementia cases. Aging, genetic factors, and epigenetic changes are the main risk factors for AD. Two aggregation-prone proteins play a decisive role in AD pathogenesis: β-amyloid (Aβ) and hyperphosphorylated tau (pTau). Both of them form deposits and diffusible toxic aggregates in the brain. These proteins are the biomarkers of AD. Different hypotheses have tried to explain AD pathogenesis and served as platforms for AD drug research. Experiments demonstrated that both Aβ and pTau might start neurodegenerative processes and are necessary for cognitive decline. The two pathologies act in synergy. Inhibition of the formation of toxic Aβ and pTau aggregates has been an old drug target. Recently, successful Aβ clearance by monoclonal antibodies has raised new hopes for AD treatments if the disease is detected at early stages. More recently, novel targets, e.g., improvements in amyloid clearance from the brain, application of small heat shock proteins (Hsps), modulation of chronic neuroinflammation by different receptor ligands, modulation of microglial phagocytosis, and increase in myelination have been revealed in AD research.

Effect of silibinin and trans-chalcone in an Alzheimer's disease-like model generated by insulin amyloids

Amyloid fibrils are characteristic of several disorders including Alzheimer's disease (AD), with no cure or preventive therapy. Diminishing amyloid deposits using aromatic compounds is an interesting approach toward AD treatment. The present study examined the anti-fibrillogenic effects of silibinin and trans-chalcone in vitro, in vivo, and in silico on insulin amyloids. In vitro incubation of insulin at 37°C for 24 h induced amyloid formation. Addition of trans-chalcone and silibinin to insulin led to reduced amounts of fibrils as shown by thioflavin S fluorescence and Congo red absorption spectroscopy, with a better effect observed for silibinin. In vivo bilateral injection of fibrils formed by incubation of insulin in the presence or absence of silibinin and trans-chalcone or insulin fibrils plus the compounds in rats' hippocampus was performed to obtain AD characteristics. Passive avoidance (PA) test showed that treatment with both compounds efficiently increased latency compared with the model group. Histological investigation of the hippocampus in the cornu ammonis (CA1) and dentate gyrus (DG) regions of the rat's brain stained with hematoxylin-eosin and thioflavin S showed an inhibitory effect on amyloid aggregation and markedly reduced amyloid plaques. In silico, a docking experiment on native and fibrillar forms of insulin provided an insight onto the possible binding site of the compounds. In conclusion, these small aromatic compounds are suggested to have a protective effect on AD.

Probing the interactions between amyloidogenic proteins and bio-membranes

Protein misfolding diseases (PMDs) in humans are characterized by the deposition of protein aggregates in tissues, including Alzheimer's disease, Parkinson's disease, type 2 diabetes, and amyotrophic lateral sclerosis. Misfolding and aggregation of amyloidogenic proteins play a central role in the onset and progression of PMDs, and these processes are regulated by multiple factors, especially the interaction between proteins and bio-membranes. Bio-membranes induce conformational changes in amyloidogenic proteins and affect their aggregation; on the other hand, the aggregates of amyloidogenic proteins may cause membrane damage or dysfunction leading to cytotoxicity. In this review, we summarize the factors that affect the binding of amyloidogenic proteins and membranes, the effects of bio-membranes on the aggregation of amyloidogenic proteins, mechanisms of membrane disruption by amyloidogenic aggregates, technical approaches for detecting these interactions, and finally therapeutic strategies targeting membrane damage caused by amyloidogenic proteins.

FapA is an Intrinsically Disordered Chaperone for Pseudomonas Functional Amyloid FapC

Bacterial functional amyloids contribute to biofilm development by bacteria and provide protection from the immune system and prevent antibiotic treatment. Strategies to target amyloid formation and interrupt biofilm formation have attracted recent interest due to their antimicrobial potential. Functional amyloid in Pseudomonas (Fap) includes FapC as the major component of the fibril while FapB is a minor component suggested to function as a nucleator of FapC. The system also includes the small periplasmic protein FapA, which has been shown to regulate fibril composition and morphology. The interplay between these three components is central in Fap fibril biogenesis. Here we present a comprehensive biophysical and spectroscopy analysis of FapA, FapB and FapC and provide insight into their molecular interactions. We show that all three proteins are primarily disordered with some regions with structural propensities for α-helix and β-sheet. FapA inhibits FapC fibrillation by targeting the nucleation step, whereas for FapB the elongation step is modulated. Furthermore, FapA alters the morphology of FapC (more than FapB) fibrils. Complex formation is observed between FapA and FapC, but not between FapA and FapB, and likely involves the N-terminus of FapA. We conclude that FapA is an intrinsically disordered chaperone for FapC that guards against fibrillation within the periplasm. This new understanding of a natural protective mechanism of Pseudomonas against amyloid formations can serve as inspiration for strategies blocking biofilm formation in infections.

The role of dietary antioxidants in type 2 diabetes and neurodegenerative disorders: An assessment of the benefit profile

Healthy diet is vital to cellular health. The human body succumbs to numerous diseases which afflict severe economic and psychological burdens on the patient and family. Oxidative stress is a possible crucial regulator of various pathologies, including type 2 diabetes and neurodegenerative diseases. It generates reactive oxygen species (ROS) that trigger the dysregulation of essential cellular functions, ultimately affecting cellular health and homeostasis. However, lower levels of ROS can be advantageous and are implicated in a variety of signaling pathways. Due to this dichotomy, the terms oxidative "eustress," which refers to a good oxidative event, and "distress," which can be hazardous, have developed. ROS affects multiple signaling pathways, leading to compromised insulin secretion, insulin resistance, and β-cell dysfunction in diabetes. ROS is also associated with increased mitochondrial dysfunction and neuroinflammation, aggravating neurodegenerative conditions in the body, particularly with age. Treatment includes drugs/therapies often associated with dependence, side effects including non-selectivity, and possible toxicity, particularly in the long run. It is imperative to explore alternative medicines as an adjunct therapy, utilizing natural remedies/resources to avoid all the possible harms. Antioxidants are vital components of our body that fight disease by reducing oxidative stress or nullifying the excess toxic free radicals produced under various pathological conditions. In this review, we focus on the antioxidant effects of components of dietary foods such as tea, coffee, wine, oils, and honey and the role and mechanism of action of these antioxidants in alleviating type 2 diabetes and neurodegenerative disorders. We aim to provide information about possible alternatives to drug treatments used alone or combined to reduce drug intake and encourage the consumption of natural ingredients at doses adequate to promote health and combat pathologies while reducing unwanted risks and side effects.

Polyisobutylene-based glycopolymers as potent inhibitors for in vitro insulin aggregation

A family of amphiphilic diblock copolymers containing a hydrophobic polyisobutylene (PIB, M_n = 1000 g mol^-1) segment and a hydrophilic block with sugar pendants has been synthesized by combining living cationic and reversible addition-fragmentation chain transfer (RAFT) polymerization techniques; to explore their potential in insulin fibrillation inhibition. The glucose content in the hydrophilic segment has been tailor-made from 20 to 57 units to prepare block copolymers. The removal of the acetates from the pendent glucose units resulted in amphiphilic block copolymers that generated micellar aggregates in aqueous media. The treatment of insulin with these block copolymers affected the fibril formation process which was demonstrated using an array of biophysical techniques, namely, thioflavin T (ThT) fluorescence, tyrosine (Tyr) fluorescence, Nile red (NR) fluorescence, isothermal titration calorimetry (ITC), etc. The Tyr fluorescence assay and NR fluorescence study revealed the crucial role of hydrophobic interaction in the inhibition process, whereas ITC measurements confirmed the importance of polar interaction. Thus, the block copolymers exhibit potent inhibition of insulin fibrillation owing to hydrophobic (from PIB segment) and glycosidic cluster effect (from sugar pendant block).

Cirsiliol mitigates Aβ fibrillation and underlying membrane-leakage associated neurotoxicity: A possible implication in the treatment of neurodegenerative disease

Protein aggregating is known as a leading pathogenic characteristic of a wide range of neurodegenerative diseases (NDs). Preventing amyloid-β (Aβ) aggregation and uncovering the associated mechanism through the application of small bioactive compounds can be considered as a useful strategy in hampering the onset of ND. In this study, we analyzed the inhibitory effects of cirsiliol, a trihydroxy-dimethoxyflavone, against human Αβ₄₂ fibrillization. Also, we explored the probable neurotoxicity of Αβ₄₂ oligomers grown with cirsiliol at different molar ratios on PC-12 cells after 24 h. The results showed that significant changes in ThT and ANS fluorescence intensities, Congo red absorbance, and ellipticity changes were modulated by co-incubation of cirsiliol with Αβ₄₂, in a concentration-dependent manner. The spectroscopy outcomes were also supported by imaging analysis, where a few Αβ₄₂ fibrillar conformations were detected with cirsiliol. In addition, cellular assays demonstrated that co-incubated Αβ₄₂ samples with cirsiliol regulated the cell mortality, LDH release, and caspase-3 activation relative to the PC-12 exposed to Aβ₄₂ oligomers alone. In conclusion, it can suggest that cirsiliol can be used as a potential candidate in the development of small molecules-based drugs for the advancement of therapeutic platforms against ND.

Glucosyl Platinum(II) Complexes Inhibit Aggregation of the C-Terminal Region of the Aβ Peptide

Neurodegenerative diseases are often caused by uncontrolled amyloid aggregation. Hence, many drug discovery processes are oriented to evaluate new compounds that are able to modulate self-recognition mechanisms. Herein, two related glycoconjugate pentacoordinate Pt(II) complexes were analyzed in their capacity to affect the self-aggregation processes of two amyloidogenic fragments, Aβ21-40 and Aβ25-35, of the C-terminal region of the β-amyloid (Aβ) peptide, the major component of Alzheimer's disease (AD) neuronal plaques. The most water-soluble complex, 1Ptdep, is able to bind both fragments and to deeply influence the morphology of peptide aggregates. Thioflavin T (ThT) binding assays, electrospray ionization mass spectrometry (ESI-MS), and ultraviolet-visible (UV-vis) absorption spectroscopy indicated that 1Ptdep shows different kinetics and mechanisms of inhibition toward the two sequences and demonstrated that the peptide aggregation inhibition is associated with a direct coordinative bond of the compound metal center to the peptides. These data support the in vitro ability of pentacoordinate Pt(II) complexes to inhibit the formation of amyloid aggregates and pave the way for the application of this class of compounds as potential neurotherapeutics.

Nanobody as solubilization chaperone for the expression and purification of inclusion-body prone proteins

Here we report a new protocol for enhancing the soluble expression of inclusion body (IB)-prone proteins in E. coli using nanobody (Nb) as a molecular-specific chaperone. The specific intracellular binding...

Hydroxylated single-walled carbon nanotube inhibits β2m21-31 fibrillization and disrupts pre-formed proto-fibrils

Pathological aggregation of amyloid polypeptides is associated with numerous degenerative diseases. Preventing aggregation and clearing amyloid deposits are considered as promising strategies against amyloidosis. With the capacity of crossing the blood-brain barrier and good biocompatibility, the hydroxylated single-walled carbon nanotube (SWCNT-OH) has been shown with excellent anti-amyloid properties. Here, we systematically studied the SWCNT-OH effects on the fibrillization of the β2m_21-31 peptides utilizing all-atom discrete molecular dynamics (DMD) simulation. Our results demonstrated the isolated β2m_21-31 peptides first nucleated into unstructured oligomers followed by coil-to-sheet conformational conversions in oligomers with at least six peptides. The elongation and lateral surfaces of the preformed β-sheet could catalyze the other unstructured monomers and small oligomers converted into β-sheet formations via dock-lock fibril growth and secondary nucleation processes. Eventually, the β2m_21-31 peptides would self-assemble into well-ordered cross-β structures. Regardless of isolated monomers or well-defined cross-β assemblies, the β2m_21-31 would attach on the surfaces of SWCNT-OH adopting unstructured formations indicating the SWCNT-OH not only inhibited the fibrillization of β2m_21-31 but also destroyed pre-formed proto-fibrils. Overall, our study displays a complete picture of the fibrillization mechanism of β2m_21-31 and the amyloid inhibitory mechanism of SWCNT-OH, offering new insight into the de-novo design of anti-amyloid inhibitors.

Effects of the Toxic Metals Arsenite and Cadmium on α-Synuclein Aggregation In Vitro and in Cells

Exposure to heavy metals, including arsenic and cadmium, is associated with neurodegenerative disorders such as Parkinson’s disease. However, the mechanistic details of how these metals contribute to pathogenesis are not well understood. To search for underlying mechanisms involving α-synuclein, the protein that forms amyloids in Parkinson’s disease, we here assessed the effects of arsenic and cadmium on α-synuclein amyloid formation in vitro and in Saccharomyces cerevisiae (budding yeast) cells. Atomic force microscopy experiments with acetylated human α-synuclein demonstrated that amyloid fibers formed in the presence of the metals have a different fiber pitch compared to those formed without metals. Both metal ions become incorporated into the amyloid fibers, and cadmium also accelerated the nucleation step in the amyloid formation process, likely via binding to intermediate species. Fluorescence microscopy analyses of yeast cells expressing fluorescently tagged α-synuclein demonstrated that arsenic and cadmium affected the distribution of α-synuclein aggregates within the cells, reduced aggregate clearance, and aggravated α-synuclein toxicity. Taken together, our in vitro data demonstrate that interactions between these two metals and α-synuclein modulate the resulting amyloid fiber structures, which, in turn, might relate to the observed effects in the yeast cells. Whilst our study advances our understanding of how these metals affect α-synuclein biophysics, further in vitro characterization as well as human cell studies are desired to fully appreciate their role in the progression of Parkinson’s disease.

Protein clearance strategies for disease intervention

Protein homeostasis, or proteostasis, is essential for cell function and viability. Unwanted, damaged, misfolded and aggregated proteins are degraded by the ubiquitin–proteasome system (UPS) and the autophagy-lysosome pathway. Growing evidence indicates that alterations in these major proteolytic mechanisms lead to a demise in proteostasis, contributing to the onset and development of distinct diseases. Indeed, dysregulation of the UPS or autophagy is linked to several neurodegenerative, infectious and inflammatory disorders as well as cancer. Thus, modulation of protein clearance pathways is a promising approach for therapeutics. In this review, we discuss recent findings and open questions on how targeting proteolytic mechanisms could be applied for disease intervention.