Natural Compound from Olive Oil Inhibits S100A9 Amyloid Formation and Cytotoxicity: Implications for Preventing Alzheimer's Disease

Luteoloside inhibits Aβ1-42 fibrillogenesis, disintegrates preformed fibrils, and alleviates amyloid-induced cytotoxicity

Abnormal aggregation and fibrillogenesis of amyloid-β protein (Aβ) can cause Alzheimer's disease (AD). Thus, the discovery of effective drugs that inhibit Aβ fibrillogenesis in the brain is crucial for the treatment of AD. Luteoloside, as one of the polyphenolic compounds, is found to have a certain therapeutic effect on nervous system diseases. However, it remains unknown whether luteoloside is a potential drug for treating AD by modulating Aβ aggregation pathway. In this study, we performed diverse biophysical and biochemical methods to explore the inhibition of luteoloside on Aβ1-42 which is linked to AD. The results demonstrated that luteoloside efficiently prevented amyloid oligomerization and cross-β-sheet formation, reduced the rate of amyloid growth and the length of amyloid fibrils in a dose-dependent manner. Moreover, luteoloside was able to influence aggregation and conformation of Aβ1-42 during different fiber-forming phases, and it could disintegrate already preformed fibrils of Aβ1-42 and convert them into nontoxic aggregates. Furthermore, luteoloside protected cells from amyloid-induced cytotoxicity and hemolysis, and attenuated the level of reactive oxygen species (ROS). The molecular docking study showed that luteoloside interacted with Aβ1-42 mainly via Conventional Hydrogen Bond, Carbon Hydrogen Bond, Pi-Pi T-shaped, Pi-Alkyl and Pi-Anion, thereby possibly preventing it from forming the aggregates. These observations indicate that luteoloside, a natural anti-oxidant molecule, may be applicable as an effective inhibitor of Aβ, and promote further exploration of the therapeutic strategy against AD.

The Surprising Nonlinear Effects of S100A9 Proteins in the Retina

Age-related macular degeneration (AMD) is a complex disease in which inflammation is implicated as a key factor but the precise molecular mechanisms are poorly understood. AMD lesions contain an excess of the pro-inflammatory S100A9 protein, but its retinal significance was yet unexplored. S100A9 was shown to be intrinsically amyloidogenic in vitro and in vivo. Here, we hypothesized that the retinal effects of S100A9 are related to its supramolecular conformation. ARPE-19 cultures were treated with native dimeric and fibrillar S100A9 preparations, and cell viability was determined. Wild-type rats were treated intravitreally with the S100A9 solutions in the right eye and with the vehicle in the left. Retinal function was assessed longitudinally by electroretinography (ERG), comparing the amplitudes and configurations for each intervention. Native S100A9 had no impact on cellular viability in vitro or on the retinal function in vivo. Despite dispersed intracellular uptake, fibrillar S100A9 did not decrease ARPE-19 cell viability. In contrast, S100A9 fibrils impaired retinal function in vivo following intravitreal injection in rats. Intriguingly, low-dose fibrillar S100A9 induced contrasting in vivo effects, significantly increasing the ERG responses, particularly over 14 days postinjection. The retinal effects of S100A9 were further characterized by glial and microglial cell activation. We provide the first indication for the retinal effects of S100A9, showing that its fibrils inflicted retinal dysfunction and glial activation in vivo, while low dose of the same assemblies resulted in an unpredicted enhancement of the ERG amplitudes. These nonlinear responses highlight the consequences of self-assembly of S100A9 and provide insight into its pathophysiological and possibly physiological roles in the retina.

Olea europaea L-derived secoiridoids: Beneficial health effects and potential therapeutic approaches

Over the years, health challenges have become increasingly complex and global and, at the beginning of the 21st century, chronic diseases, including cardiovascular, neurological, and chronic respiratory diseases, as well as cancer and diabetes, have been identified by World Health Organization as one of the biggest threats to human health. Recently, antimicrobial resistance has also emerged as a growing problem of public health for the management of infectious diseases. In this scenario, the exploration of natural products as supplementation or alternative therapeutic options is acquiring great importance, and, among them, the olive tree, Olea europaea L, specifically leaves, fruits, and oil, has been increasingly investigated for its health promoting properties. Traditionally, these properties have been largely attributed to the high concentration of monounsaturated fatty acids, although, in recent years, beneficial effects have also been associated to other components, particularly polyphenols. Among them, the most interesting group is represented by Olea europaea L secoiridoids, comprising oleuropein, oleocanthal, oleacein, and ligstroside, which display anti-inflammatory, antioxidant, cardioprotective, neuroprotective and anticancer activities. This review provides an overview of the multiple health beneficial effects, the molecular mechanisms, and the potential applications of secoiridoids from Olea europaea L.

Screening Method for the Visual Discrimination of Olive Oil from Other Vegetable Oils by a Multispecies DNA Sensor

Olive oil is a prominent agricultural product which, in addition to its nutritional value and unique organoleptic characteristics, offers a variety of health benefits protecting against cardiovascular disease, cancer, and neurodegenerative diseases. The assessment of olive oil authenticity is an extremely important and challenging process aimed at protecting consumers and producers. The most frequent adulteration involves blending with less expensive and readily available vegetable/seed oils. The methods for adulteration detection, whether based on changes in metabolite profiles or based on DNA markers, require advanced and expensive instrumentation combined with powerful chemometric and statistical tools. To this end, we present a simple, multiplex, and inexpensive screening method based on the development of a multispecies DNA sensor for sample interrogation with the naked eye. It is the first report of a DNA sensor for olive oil adulteration detection with other plant oils. The sensor meets the 2-fold challenge of adulteration detection, i.e., determining whether the olive oil sample is adulterated and identifying the added vegetable oil. We have identified unique, nucleotide variations, which enable the discrimination of seven plant species (olive, corn, sesame, soy, sunflower, almond, and hazelnut). Following a single PCR step, a 20 min multiplex plant-discrimination reaction is performed, and the products are applied directly to the sensing device. The plant species are visualized as red spots using functionalized gold nanoparticles as reporters. The spot position reveals the identity of the plant species. As low as <5-10% of adulterant was detected with particularly good reproducibility and specificity.

Nanoscopic Elucidation of Spontaneous Self-Assembly of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Open Reading Frame 6 (ORF6) Protein

Open reading frame 6 (ORF6), the accessory protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that suppresses host type-I interferon signaling, possesses amyloidogenic sequences. ORF6 amyloidogenic peptides self-assemble to produce cytotoxic amyloid fibrils. Currently, the molecular properties of the ORF6 remain elusive. Here, we investigate the structural dynamics of the full-length ORF6 protein in a near-physiological environment using high-speed atomic force microscopy. ORF6 oligomers were ellipsoidal and readily assembled into ORF6 protofilaments in either a circular or a linear pattern. The formation of ORF6 protofilaments was enhanced at higher temperatures or on a lipid substrate. ORF6 filaments were sensitive to aliphatic alcohols, urea, and SDS, indicating that the filaments were predominantly maintained by hydrophobic interactions. In summary, ORF6 self-assembly could be necessary to sequester host factors and causes collateral damage to cells via amyloid aggregates. Nanoscopic imaging unveiled the innate molecular behavior of ORF6 and provides insight into drug repurposing to treat amyloid-related coronavirus disease 2019 complications.

An insight into structure-activity relationship of naturally derived biological macromolecules for the treatment of Alzheimer's disease: a review

Alzheimer's disease (AD) is a neurological disorder that affects millions of people worldwide. There are currently no cures for AD, although various drugs are used to manage the symptoms and reduce the disease's progression. AChE inhibitors such as rivastigmine, donepezil, galantamine, and the NMDA glutamate receptor antagonist memantine are currently FDA-approved drugs used in the treatment of AD. Recently, naturally derived biological macromolecules have shown promising results in the treatment of AD. Several biological macromolecules derived from natural sources are in various stages of preclinical and clinical trials. During the literature search, it was observed that there is a lack of a comprehensive review that particularly focuses on the role of naturally derived biological macromolecules (protein, carbohydrates, lipids, and nucleic acids) in the treatment of AD and the structure-activity relationship (SAR) approach for understanding the medicinal chemistry perspective. This review focuses on the SAR and probable mechanisms of action of biological macromolecules derived from natural sources for the treatment of AD, including peptides, proteins, enzymes, and polysaccharides. The paper further addresses the therapeutic possibilities of monoclonal antibodies, enzymes, and vaccines for the treatment of AD. Overall, the review provides insight into the SAR of naturally derived biological macromolecules in the treatment of AD. The ongoing research in this field holds great promise for the future development of AD treatment and provides hope for individuals affected by this devastating disease.Communicated by Ramaswamy H. Sarma.

Pro-inflammatory protein S100A9 alters membrane organization by dispersing ordered domains

Pro-inflammatory, calcium-binding protein S100A9 is localized in the cytoplasm of many cells and regulates several intracellular and extracellular processes. S100A9 is involved in neuroinflammation associated with the pathogenesis of Alzheimer's disease (AD). The number of studies on the impact of S100A9 in co-aggregation processes with amyloid-like proteins is increasing. However, there is still a lack of data on how this protein interacts with lipid membranes. We employed atomic force microscopy (AFM), dynamic light scattering (DLS), and fluorescence measurements (Laurdan and Thioflavin-T) to study the interaction between protein and the membrane surface. We used lipid vesicles in bulk and planar tethered lipid bilayers as biomimetic membrane models. We demonstrated that the protein accumulates on negatively charged lipid bilayers but with no further loss of the bilayer's integrity. The most important result is that the initial adsorption and accumulation of apo-form of S100A9 on the lipid membrane surface is lipid phase-sensitive. The breaking down of raft-like and disappearance of gel-like domains indicate that protein incorporates into the hydrophobic part of the lipid bilayer. We observed the most noticeable loss of integrity in lipid bilayers constructed from a lipid mixture (brain total lipid extract). Understanding the function and interactions of these proteins in cellular environments might expand the development of new diagnostic and therapeutic approaches for AD or other related diseases.

Gut microbiota, pathogenic proteins and neurodegenerative diseases

As the world's population ages, neurodegenerative diseases (NDs) have brought a great burden to the world. However, effective treatment measures have not been found to alleviate the occurrence and development of NDs. Abnormal accumulation of pathogenic proteins is an important cause of NDs. Therefore, effective inhibition of the accumulation of pathogenic proteins has become a priority. As the second brain of human, the gut plays an important role in regulate emotion and cognition functions. Recent studies have reported that the disturbance of gut microbiota (GM) is closely related to accumulation of pathogenic proteins in NDs. On the one hand, pathogenic proteins directly produced by GM are transmitted from the gut to the central center via vagus nerve. On the other hand, The harmful substances produced by GM enter the peripheral circulation through intestinal barrier and cause inflammation, or cross the blood-brain barrier into the central center to cause inflammation, and cytokines produced by the central center cause the production of pathogenic proteins. These pathogenic proteins can produced by the above two aspects can cause the activation of central microglia and further lead to NDs development. In addition, certain GM and metabolites have been shown to have neuroprotective effects. Therefore, modulating GM may be a potential clinical therapeutic approach for NDs. In this review, we summarized the possible mechanism of NDs caused by abnormal accumulation of pathogenic proteins mediated by GM to induce the activation of central microglia, cause central inflammation and explore the therapeutic potential of dietary therapy and fecal microbiota transplantation (FMT) in NDs.

Human microRNA-4433 (hsa-miR-4443) Targets 18 Genes to be a Risk Factor of Neurodegenerative Diseases

BACKGROUND

Neurodegenerative diseases, such as Alzheimer's disease patients (AD), Huntington's disease (HD) and Parkinson's disease (PD), are common causes of morbidity, mortality, and cognitive impairment in older adults.

OBJECTIVE

We aimed to understand the transcriptome characteristics of the cortex of neurodegenerative diseases and to provide an insight into the target genes of differently expressed microRNAs in the occurrence and development of neurodegenerative diseases.

METHODS

The Limma package of R software was used to analyze GSE33000, GSE157239, GSE64977 and GSE72962 datasets to identify the differentially expressed genes (DEGs) and microRNAs in the cortex of neurodegenerative diseases. Bioinformatics methods, such as GO enrichment analysis, KEGG enrichment analysis and gene interaction network analysis, were used to explore the biological functions of DEGs. Weighted gene co-expression network analysis (WGCNA) was used to cluster DEGs into modules. RNA22, miRDB, miRNet 2.0 and TargetScan7 databases were performed to predict the target genes of microRNAs.

RESULTS

Among 310 Alzheimer's disease (AD) patients, 157 Huntington's disease (HD) patients and 157 non-demented control (Con) individuals, 214 co-DEGs were identified. Those co-DEGs were filtered into 2 different interaction network complexes, representing immune-related genes and synapserelated genes. The WGCNA results identified five modules: yellow, blue, green, turquoise, and brown. Most of the co-DEGs were clustered into the turquoise module and blue module, which respectively regulated synapse-related function and immune-related function. In addition, human microRNA-4433 (hsa-miR-4443), which targets 18 co-DEGs, was the only 1 co-up-regulated microRNA identified in the cortex of neurodegenerative diseases.

CONCLUSION

214 DEGs and 5 modules regulate the immune-related and synapse-related function of the cortex in neurodegenerative diseases. Hsa-miR-4443 targets 18 co-DEGs and may be a potential molecular mechanism in neurodegenerative diseases' occurrence and development.

Repurposing of intestinal defensins as multi-target, dual-function amyloid inhibitors via cross-seeding

Amyloid formation and microbial infection are the two common pathological causes of neurogenerative diseases, including Alzheimer's disease (AD), type II diabetes (T2D), and medullary thyroid carcinoma (MTC). While significant efforts have been made to develop different prevention strategies and preclinical hits for these diseases, conventional design strategies of amyloid inhibitors are mostly limited to either a single prevention mechanism (amyloid cascade vs. microbial infection) or a single amyloid protein (Aβ, hIAPP, or hCT), which has prevented the launch of any successful drug on the market. Here, we propose and demonstrate a new “anti-amyloid and anti-bacteria” strategy to repurpose two intestinal defensins, human α-defensin 6 (HD-6) and human β-defensin 1 (HBD-1), as multiple-target, dual-function, amyloid inhibitors. Both HD-6 and HBD-1 can cross-seed with three amyloid peptides, Aβ (associated with AD), hIAPP (associated with T2D), and hCT (associated with MTC), to prevent their aggregation towards amyloid fibrils from monomers and oligomers, rescue SH-SY5Y and RIN-m5F cells from amyloid-induced cytotoxicity, and retain their original antimicrobial activity against four common bacterial strains at sub-stoichiometric concentrations. Such sequence-independent anti-amyloid and anti-bacterial functions of intestinal defensins mainly stem from their cross-interactions with amyloid proteins through amyloid-like mimicry of β-sheet associations. In a broader view, this work provides a new out-of-the-box thinking to search and repurpose a huge source of antimicrobial peptides as amyloid inhibitors, allowing the blocking of the two interlinked pathological pathways and bidirectional communication between the central nervous system and intestines via the gut–brain axis associated with neurodegenerative diseases.

Amyloid formation and microbial infection are the two common pathological causes of neurogenerative diseases. Here, we proposed a new “anti-amyloid and anti-bacteria” strategy to repurpose two intestinal defensins as multiple-target, dual-function amyloid inhibitors.

Neuroprotective effects of oleuropein: Recent developments and contemporary research

Neurological disorders are increasing at a faster pace due to oxidative stress, protein aggregation, excitotoxicity, and neuroinflammation. It is reported that the Mediterranean diet including olives as a major dietary component prevents and ameliorates neurological anomalies. Oleuropein is the major bioactive component in different parts of the Olive (Olea europaea L.) tree. Several mechanisms have been reported for the neuroprotective role of oleuropein including induction of apoptosis and autophagy, enhancing the antioxidant pool of the cerebral region, decreasing the unnecessary release of proinflammatory cytokines and chemokines by deactivating the microglia cells and astrocytes thus preventing the occurrence of neuroinflammation. Regular intake of oleuropein seems to be correlated with decreased risks of neural disorders including Alzheimer's, Parkinson's, strokes, depression, anxiety, epilepsy, and others. This review majorly discusses the chemistry, biosynthesis, and metabolism of oleuropein along with an updated vision of its neuroprotective role in counteracting the acute and chronic neurodegenerative and neuropsychiatric disorders. Moreover, mechanisms by which oleuropein may prevent neurodegeneration are reviewed. PRACTICAL APPLICATION: Neurological disorders are negatively affecting the health and life quality of individuals around the globe. Although various medicinal solutions are available to tackle such ailments, none has proven to fully cure and being deprived of side effects. In this respect, the prevention of such disorders using natural remedies may be an effective strategy to overcome the incidence of the increasing cases. Furthermore, the natural compounds provide a safer alternative to pharmaceutical drugs. Hence, oleuropein from olive tree products is found to be efficacious against neurological disorders. This review provides an updated insight on the positive effects of oleuropein against neurodegenerative and neuropsychiatric disorders. The diet practitioners and nutraceutical companies may benefit from the provided information to design and develop strategies to improve the mental health of suffering individuals.

Ellagic Acid Modulates Uninduced as well as Mutation and Metal-Induced Aggregation of α-Synuclein: Implications for Parkinson's Disease

α-Synuclein (αS) is an intrinsically disordered protein whose aggregation and deposition in Lewy bodies is involved in the progression of Parkinson's disease (PD) and other related disorders. The aggregation process of αS is also triggered by mutations like A53T and E46K in the SNCA gene and disruption in metal-ion homeostasis. Currently, there is no obviating therapy available in the market that could effectively prevent the progression of the disease. In this backdrop, there exists an emerging need to consider naturally occurring polyphenols and flavonoids as potential therapeutic agents against PD. In this study, we demonstrate the modulatory effect of ellagic acid (EA) against wild-type as well as mutation and metal-induced aggregation of αS. Thioflavin T (ThT) fluorescence assay suggests that EA acts on the nucleation phase of αS fibrillization, thereby increasing the lag phase from 21.33 ± 3.01 to 48.20 ± 5.05 h and reducing the fibrils growth rate from 4.60 ± 2.06 to 0.890 ± 0.36 h^-1. 8-Anilino-1-naphthalene sulfonic acid (ANS), Congo red (CR), and intrinsic fluorescence studies indicate that the interaction of EA with αS facilitates the structural changes in the protein that lead to inhibition of fibril formation. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) images illustrate that the size of fibrils diminishes up to 100 nm in the presence of EA. Dot blot and seeding experiments put forward that EA directs the αS aggregation toward off-pathway fibrillization. Our 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay deciphers the role of EA in minimizing the αS fibril-induced toxicity, thereupon leading to an increase in cell viability. Also, EA attenuates both mutations as well as metal-induced αS fibrillization and disaggregates the preexisting fibrils. Additionally, computational studies elucidate that EA preferentially interacts with the N-terminal and NAC domain of αS. Hence, this work reveals the aggregation inhibition mechanism of EA and provides considerable therapeutic interventions against PD and related disorders.

Synergy of the Inhibitory Action of Polyphenols Plus Vitamin C on Amyloid Fibril Formation: Case Study of Human Stefin B

In order to study how polyphenols and vitamin C (vitC) together affect protein aggregation to amyloid fibrils, we performed similar in vitro studies as before using stefin B as a model and a potentially amyloid-forming protein (it aggregates upon overexpression, under stressful conditions and some progressive myoclonus epilepsy of tape 1-EPM1-missense mutations). In addition to the chosen polyphenol, this time, we added a proven antioxidant concentration of 0.5 mM vitC into the fibrillation mixture and varied concentrations of resveratrol, quercetin, and curcumin. Synergy with vitC was observed with curcumin and quercetin.

Co-Aggregation of S100A9 with DOPA and Cyclen-Based Compounds Manifested in Amyloid Fibril Thickening without Altering Rates of Self-Assembly

The amyloid cascade is central for the neurodegeneration disease pathology, including Alzheimer’s and Parkinson’s, and remains the focus of much current research. S100A9 protein drives the amyloid-neuroinflammatory cascade in these diseases. DOPA and cyclen-based compounds were used as amyloid modifiers and inhibitors previously, and DOPA is also used as a precursor of dopamine in Parkinson’s treatment. Here, by using fluorescence titration experiments we showed that five selected ligands: DOPA-D-H-DOPA, DOPA-H-H-DOPA, DOPA-D-H, DOPA-cyclen, and H-E-cyclen, bind to S100A9 with apparent K_d in the sub-micromolar range. Ligand docking and molecular dynamic simulation showed that all compounds bind to S100A9 in more than one binding site and with different ligand mobility and H-bonds involved in each site, which all together is consistent with the apparent binding determined in fluorescence experiments. By using amyloid kinetic analysis, monitored by thioflavin-T fluorescence, and AFM imaging, we found that S100A9 co-aggregation with these compounds does not hinder amyloid formation but leads to morphological changes in the amyloid fibrils, manifested in fibril thickening. Thicker fibrils were not observed upon fibrillation of S100A9 alone and may influence the amyloid tissue propagation and modulate S100A9 amyloid assembly as part of the amyloid-neuroinflammatory cascade in neurodegenerative diseases.