An 11-mer Amyloid Beta Peptide Fragment Provokes Chemical Mutations and Parkinsonian Biomarker Aggregation in Dopaminergic Cells: A Novel Road Map for "Transfected" Parkinson's

Lung endothelium, tau, and amyloids in health and disease

Lung endothelia in the arteries, capillaries, and veins are heterogeneous in structure and function. Lung capillaries in particular represent a unique vascular niche, with a thin yet highly restrictive alveolar-capillary barrier that optimizes gas exchange. Capillary endothelium surveys the blood while simultaneously interpreting cues initiated within the alveolus and communicated via immediately adjacent type I and type II epithelial cells, fibroblasts, and pericytes. This cell-cell communication is necessary to coordinate the immune response to lower respiratory tract infection. Recent discoveries identify an important role for the microtubule-associated protein tau that is expressed in lung capillary endothelia in the host-pathogen interaction. This endothelial tau stabilizes microtubules necessary for barrier integrity, yet infection drives production of cytotoxic tau variants that are released into the airways and circulation, where they contribute to end-organ dysfunction. Similarly, beta-amyloid is produced during infection. Beta-amyloid has antimicrobial activity, but during infection it can acquire cytotoxic activity that is deleterious to the host. The production and function of these cytotoxic tau and amyloid variants are the subject of this review. Lung-derived cytotoxic tau and amyloid variants are a recently discovered mechanism of end-organ dysfunction, including neurocognitive dysfunction, during and in the aftermath of infection.

Effects of latroeggtoxin-VI on dopamine and α-synuclein in PC12 cells and the implications for Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is characterized by death of dopaminergic neurons leading to dopamine deficiency, excessive α-synuclein facilitating Lewy body formation, etc. Latroeggtoxin-VI (LETX-VI), a proteinaceous neurotoxin discovered from the eggs of spider L. tredecimguttatus, was previously found to promote the synthesis and release of PC12 cells, showing a great potential as a drug candidate for PD. However, the relevant mechanisms have not been understood completely. The present study explored the mechanism underlying the effects of LETX-VI on dopamine and α-synuclein of PC12 cells and the implications for PD.

RESULTS

After PC12 cells were treated with LETX-VI, the level of dopamine was significantly increased in a dose-dependent way within a certain range of concentrations. Further mechanism analysis showed that LETX-VI upregulated the expression of tyrosine hydroxylase (TH) and L-dopa decarboxylase to enhance the biosynthesis of dopamine, and downregulated that of monoamine oxidase B to reduce the degradation of dopamine. At the same time, LETX-VI promoted the transport and release of dopamine through modulating the abundance and/or posttranslational modification of vesicular monoamine transporter 2 (VMAT2) and dopamine transporter (DAT). While the level of dopamine was increased by LETX-VI treatment, α-synuclein content was reduced by the spider toxin. α-Synuclein overexpression significantly decreased the dopamine level and LETX-VI efficiently alleviated the inhibitory action of excessive α-synuclein on dopamine. In the MPTP-induced mouse model of PD, application of LETX-VI ameliorated parkinsonian behaviors of the mice, and reduced the magnitude of MPTP-induced α-synuclein upregulation and TH downregulation. In addition, LETX-VI displayed neuroprotective effects by inhibiting MPTP-induced decrease in the numbers of TH-positive and Nissl-stained neurons in mouse brain tissues.

CONCLUSIONS

All the results demonstrate that LETX-VI promotes the synthesis and release of dopamine in PC12 cells via multiple mechanisms including preventing abnormal α-synuclein accumulation, showing implications in the prevention and treatment of PD.

Protective Effects of Heat-Killed Ruminococcus albus against β-Amyloid-Induced Apoptosis on SH-SY5Y Cells

A high level of β-amyloid (Aβ) in the brains of patients with Alzheimer's disease (AD) generates reactive oxygen species that induce neuronal death and DNA damage. The interaction between the gut microbiota and brain health has attracted attention in recent years. Heat-killed Ruminococcus albus (hkRA) reportedly protects neurons against damage induced by oxidative stress. However, whether hkRA can inhibit Aβ-induced apoptosis and thus alleviate AD remains unclear. Hence, we aimed to evaluate the protective effects of hkRA against Aβ-induced apoptosis on the human neuroblastoma SH-SY5Y cell. HkRA treatment (108 cells/ml) significantly decreased the Aβ-induced cytotoxicity and DNA damage in the SH-SY5Y cells. It also showed a significant increase of the bax/bcl-2 ratio in the Aβ-treated SH-SY5Y cells. Moreover, hkRA treatment stimulated the expression of antioxidation-related genes HO-1, Nrf2, and PKC-δ and increased the expression of brain-derived neurotrophic factor (BDNF). Meanwhile, it significantly decreased the activity of caspase-3 and protein expression of cleaved caspase-3 in the Aβ-treated SH-SY5Y cells. Additionally, the protein levels of mitochondrial and cytosolic cytochrome c increased and decreased, respectively, in the cells. These results suggest that hkRA protects human neuroblastoma cells from Aβ-induced apoptosis and oxidative stress. Thus, hkRA may be developed into a health-promoting paraprobiotic (the inactivated microbial cells of probiotics) for patients with AD.

The manifold role of octapeptide repeats in prion protein assembly

Prion protein misfolding is associated with fatal neurodegenerative disorders such as kuru, Creutzfeldt-Jakob disease, and several animal encephalopathies. While the C-terminal 106-126 peptide has been well studied for its role in prion replication and toxicity, the octapeptide repeat (OPR) sequence found within the N-terminal domain has been relatively under explored. Recent findings that the OPR has both local and long-range effects on prion protein folding and assembly, as well as its ability to bind and regulate transition metal homeostasis, highlights the important role this understudied region may have in prion pathologies. This review attempts to collate this knowledge to advance a deeper understanding on the varied physiologic and pathologic roles the prion OPR plays, and connect these findings to potential therapeutic modalities focused on OPR-metal binding. Continued study of the OPR will not only elucidate a more complete mechanistic model of prion pathology, but may enhance knowledge on other neurodegenerative processes underlying Alzheimer's, Parkinson's, and Huntington's diseases.

Preclinical Model to Evaluate Outcomes of Amyloid Cross-Toxicity in the Rodent Brain

The progress of neurodegenerative disorders correlates with the spread of their associated amyloidogenic proteins. Here, we investigated whether amyloid entry into nonconstitutive neurons could drive cross-toxic outcomes. Amyloid β (Aβ) was stereotaxically introduced into the rodent midbrain tegmentum, where it is not endogenously expressed. Postinfusion, rodent motor and sensorimotor capacities were assessed by standard behavioral tests at 3, 6, 9, and 12 months. The longitudinal study revealed no behavioral abnormalities. However, Aβ insult provoked intraneuronal inclusions positive for phosphorylated α-synuclein in dopaminergic neurons and were seen throughout the midbrain, a pathognomonic biomarker suggesting Parkinson's pathogenesis. These findings not only underscore the cross-toxic potential of amyloid proteins but also provide a mechanism by which they disrupt homeostasis in nonconstitutive neurons and cause neuronal corruption, injury, and demise. This study may help reconcile the large incidence of neurodegenerative comorbidity observed clinically.

Citric Acid-Derived Carbon Quantum Dots Attenuate Paraquat-Induced Neuronal Compromise In Vitro and In Vivo

The potent environmental herbicide and weedicide paraquat is linked to neuromotor defects and Parkinson's disease (PD). We have evaluated the neuroprotective role of citric acid-sourced carbon quantum dots (Cit-CQDs) on paraquat-insulted human neuroblastoma-derived SH-SY5Y cell lines and on a paraquat-exposed nematode (Caenorhabditis elegans). Our data reveal that Cit-CQDs are able to scavenge free radicals in test tube assays and mitigate paraquat-elevated reactive oxygen species (ROS) levels in SH-SY5Y cells. Furthermore, Cit-CQDs protect the cell line from paraquat, which otherwise elicits cell death. Cit-CQDs-challenged nematodes demonstrate enhanced survival rates 72 h post-paraquat exposure compared to controls. Paraquat ablates dopamine (DA) neurons, which results in compromised locomotor function in nematodes. However, the neurons remained intact when the nematodes were incubated with Cit-CQDs prior to neurotoxicant exposure. The collective data suggest Cit-CQDs offer neuroprotection for cell lines and organisms from xenotoxicant-associated neuronal injury and death. The study suggests Cit-CQDs as a potentially viable green chemistry-synthesized, biobased nanomaterial for intervention in neurodegenerative disorders.

Gelatin-derived carbon quantum dots mitigate herbicide-induced neurotoxic effects in vitro and in vivo

The herbicide and viologen, N, N'-dimethyl-4,4'-bipyridinium dichloride (Paraquat) is known to be toxic to neuronal cells by a multifactorial process involving an elevation in the levels of reactive oxygen species (ROS), the triggering of amyloid-protein aggregation and their accumulation, collectively leading to neuronal dyshomeostasis. We demonstrate that green-chemistry-synthesized sustainable gelatin-derived carbon quantum dots (CQDs) mitigate paraquat-induced neurotoxic outcomes and resultant compromise in organismal mortality. Gelatin-derived CQDs were found to possess antioxidant properties and ameliorated ROS elevation in paraquat-insulted neuroblastoma-derived SHSY-5Y cells, protecting them from herbicide-induced cell death. These CQDs also increased lifespan in paraquat-compromised Caenorhabditis elegans and herbicide-mediated dopamine neuron ablation. Collectively, the data underscore the ability of this sustainably synthesized, environmentally friendly biocompatible nanomaterial to protect cell lines and organisms against neurotoxic outcomes. The study findings strategically position this relatively novel nanoscopic carbon quantum framework for further testing in vertebrate trials of neurotoxic insult.

Carvedilol inhibits Aβ25-35 fibrillation by intervening the early stage helical intermediate formation: A biophysical investigation

Self-assembly of disordered amyloid-beta (Aβ) peptides results in highly ordered amyloid fibrils. The structural information of the early-stage events and also in the presence of inhibitors is of great significance. It is challenging to acquire due to the nature of the amyloids and experimental constraints. Here, we demonstrate the cascade of aggregation (early to late) of the Aβ_25-35 peptide in the absence and presence of carvedilol, a nonselective β-adrenergic receptor blocker. The aggregation process of Aβ_25-35 peptide is monitored using Thioflavin T (ThT) fluorescence, dynamic light scattering (DLS), circular dichroism (CD), Raman spectroscopic techniques, and imaging experiments. We find that the Aβ_25-35 peptide undergoes an early-stage (3-6 h) helical intermediate formation across the fibrillation pathway using CD and Raman measurements. Carvedilol obstructs the helical intermediate formation of Aβ_25-35 peptide resulting in inhibition. CD spectra and deconvolution of the Raman bands suggest the β-sheet formation (24-100 h) in the absence of carvedilol. Spectroscopic results indicate a disordered structure for the peptide in the presence of carvedilol (24-100 h). Electron microscopy (EM) shows the formation of polymorphic fibrils for the peptide alone and non-amyloidal aggregates in the presence of carvedilol. Molecular docking study suggests that the plausible mode of interaction with carvedilol involves the C-terminal residues of the peptide.

Carbon Quantum Dots for Treatment of Amyloid Disorders

Prion-like amyloids self-template and form toxic oligomers, protofibrils, and fibrils from their soluble monomers; a phenomenon that has been implicated in the onset and progress of neurodegenerative disorders such as Alzheimer's (AD), Parkinson's (PD), Huntington's, and systemic lysozyme amyloidosis. Carbon quantum dots (CQDs), sourced from Na-citrate as a carbon precursor were synthesized and characterized before being tested for their ability to intervene in amyloidogenic (fibril-forming) trajectories. Hen-egg white lysozyme (HEWL) served as a model amyloidogenic protein. A pulse-chase lysozyme fibril-forming assay developed to examine the impact of CQDs on the HEWL amyloid-fibril-forming trajectory used ThT fluorescence as a reporter of mature fibril presence. The results revealed that the Na-citrate-derived CQDs were able to intervene at multiple points along the fibril-forming trajectory by preventing the conversion of both monomeric and oligomeric HEWL intermediates into mature fibrils. In addition, and importantly, the carbon nano material (CNM) was able to dissolve oligomeric HEWL into monomeric HEWL and provoke the disaggregation of mature HEWL fibrils. These results suggest that Na-citrate CQD's intervene in amyloidogenesis by multiple mechanisms. The gathered data, coupled with cell-line results demonstrating the relatively low cytotoxicity of Na-citrate CQDs, suggest that this emerging CNM has the potential to intervene both prophylactically and therapeutically in protein misfolding diseases. The aforementioned findings are likely to enable Na-citrate CQDs to eventually transition to both cell-line and preclinical models of protein-misfolding-related disorders. Importantly, the study outcomes positions Na-citrate CQDs as an important class of chemical, nanotechnological, and biobased interventional tools in neuroscience.

Neuroprotective Effect of Brazilin on Amyloid β (25-35)-Induced Pathology in a Human Neuroblastoma Model

Until the recent past, the sole exemplar of proteins as infectious agents leading to neurodegenerative disorders remained the prion protein. Since then, the self-seeding mechanism characteristic of the prion protein has also been attributed to other neurodegenerative-disease-associated proteins, including amyloid-β (Aβ), tau, and α-synuclein (α-Syn). In model cell line studies, truncated Aβ, viz. amyloid beta (25-35), has been found to influence cellular homeostasis through its interactions with, and via, the disruption of key housekeeping machinery. Here, we demonstrate that the incubation of human neuroblastoma (SH-SY5Y) cell line with Brazilin ((6aS,11bR)-7,11b-dihydro-6H-indeno[2,1-c]chromene-3,6a,9,10-tetrol) prior to Aβ (25-35)-insult protected the cells from oxidative stress and apoptotic cell death. Furthermore, Brazilin mitigated Aβ-induced alterations in protein disulfide isomerase (PDI) and α-synuclein status, both of which are important biomarkers that report on Parkinson's pathogenesis. The results obtained in this study suggest that the tetrol is neuroprotective and helps resist Aβ-induced cross-pathology and amyloidogenic onset.

Chitosan-Ellagic Acid Nanohybrid for Mitigating Rotenone-induced Oxidative Stress

Antioxidants derived from nature, such as ellagic acid (EA), demonstrated high potency to mitigate neuronal oxidative stress and related pathologies, including Parkinson's disease. However, the application of EA is limited due to its toxicity at moderate doses and poor solubility, cellular permeability, and bioavailability. Here, we introduce a sustainably resourced, green nanoencasement strategy to overcome the limitations of EA and derive synergistic effects to prevent oxidative stress in neuronal cells. Chitosan, with its high biocompatibility, potential antioxidant properties, and flexible surface chemistry, was chosen as the primary component of the nanoencasement in which EA is immobilized. Using a rotenone model to mimic intracellular oxidative stress, we examined the effectiveness of EA and chitosan to limit cell death. Our studies indicate a synergistic effect between EA and chitosan in mitigating rotenone-induced reactive oxygen species death. Our analysis suggests that chitosan encapsulation of EA reduces the inherent cytotoxicity of the polyphenol (a known anticancer molecule). Furthermore, its encapsulation permits its delivery via a rapid burst phase and a relatively slow phase making the nanohybrid suitable for drug release over extended time periods.

The Era of Neurodegenerative Metastasis

The incidence of converging end points across neurodegenerative disorders, leading to comorbidity, has spurred the search for common neurometabolic denominators among otherwise distinct pathologies. While recent data have hinted at crossover factors, and genetic risk-factors across the neurodegenerative landscape, we discuss the potential of prion-like amyloid proteins as suspects, if not causals, in seeding cross-pathology. While much work remains to be done on how they spread and "fertilize" seemingly unrelated neuropathies, it is safe to assume that the era of neurodegenerative metastasis is here.

Nanoscopic Portrait of an Amyloidogenic Pathway Visualized through Tip-Enhanced Raman Spectroscopy

Inroads into understanding the process by which amyloid proteins become toxic have been hampered by the lack of experimental techniques that adequately resolve the process. Recently, tip-enhanced Raman spectroscopy, with its unique capability to spectroscopically image and chemically identify reaction mixtures with nanoscale precision, was used to obtain a high-resolution roadmap of the soluble-to-toxic conversion of amyloid beta. This technique opens the door for studying the toxic aggregation pathways of other amyloid proteins and spurs efforts devoted to prophylactic and therapeutic intervention in neurodegenerative and protein-misfolding-related disorders.

Chitosan Nanoparticles Rescue Rotenone-Mediated Cell Death

The aim of the present investigation was to study the anti-oxidant effect of chitosan nanoparticles on a human SH-SY5Y neuroblastoma cell line using a rotenone model to generate reactive oxygen species. Chitosan nanoparticles were synthesized using an ionotropic gelation method. The obtained nanoparticles were characterized using various analytical techniques such as Dynamic Light Scattering, Scanning Electron Microscopy, Transmission Electron Microscopy, Fourier Transmission Infrared spectroscopy and Atomic Force Microscopy. Incubation of SH-SY5Y cells with 50 µM rotenone resulted in 35-50% cell death within 24 h of incubation time. Annexin V/Propidium iodide dual staining verified that the majority of neuronal cell death occurred via the apoptotic pathway. The incubation of cells with chitosan nanoparticles reduced rotenone-initiated cytotoxicity and apoptotic cell death. Given that rotenone insult to cells causes oxidative stress, our results suggest that Chitosan nanoparticles have antioxidant and anti-apoptotic properties. Chitosan can not only serve as a novel therapeutic drug in the near future but also as a carrier for combo-therapy.

The roles of S-nitrosylation and S-glutathionylation in Alzheimer's disease

Alzheimer's disease (AD) is a debilitating dementia with complex pathophysiological alterations including modifications to endogenous cysteine. S-nitrosylation (SNO) is a well-studied posttranslational modification (PTM) in the context of AD while S-glutathionylation (PSSG) remains less studied. Excess reactive oxygen and reactive nitrogen species (ROS/RNS) directly or indirectly generate SNO and PSSG. SNO is dysregulated in AD and plays a pervasive role in processes such as protein function, cell signaling, metabolism, and apoptosis. Despite some studies into the role of SNO in AD, multiple identified SNO proteins lack deep investigation and SNO modifications outside of brain tissues are limited, leaving the full role of SNO in AD to be elucidated. PSSG homeostasis is perturbed in AD and may affect a myriad of cellular processes. Here we overview the role of nitric oxide (NO) in AD, discuss proteomic methodologies to investigate SNO and PSSG, and review SNO and PSSG in AD. A more thorough understanding of SNO, PSSG, and other cysteinyl PTMs in AD will be helpful for the development of novel therapeutics against neurodegenerative diseases.

A new family of fullerene derivatives: Fullerene-curcumin conjugates for biological and photovoltaic applications

The synthesis and characterization of a family of [60]fullerocurcuminoids obtained via Bingel reactions is reported. The new C60 derivatives include curcumin and curcuminoids with a variety of end groups. Preliminary biological experiments show the potential activity of the compound containing a curcumin addend, which exhibits moderate anti-HIV-1 and radical scavenger properties, but no anti-cancer activity. In addition, the new fullerocurcuminoids exhibit HOMO/LUMO energy levels that are reasonably matched with those of perovskites and when they were tested in perovskite solar cells (PSCs) as the electron transporting material (ETM), photoconversion efficiencies ranging from 14.04%-14.95% were obtained, whereas a value of 16.23% was obtained for [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) based devices.

Attenuation of the in vitro neurotoxicity of 316L SS by graphene oxide surface coating

A persistent theme in biomaterials research comprises of surface engineering and modification of bare metallic substrates for improved cellular response and biocompatibility. Graphene Oxide (GO), a derivative of graphene, has outstanding chemical and mechanical properties; its large surface to volume ratio, ease of surface modification and processing make GO an attractive coating material. GO-coatings have been extensively studied as biosensors. Further owing to its surface nano-architecture, GO-coated surfaces promote cell adhesion and growth, making it suitable for tissue engineering applications. The need to improve the long-term durability and therapeutic effectiveness of commercially available bare 316L stainless steel (SS) surfaces led us to adopt a polymer-free approach which is cost-effective and scalable. GO was immobilized on to 316L SS utilizing amide linkage, to generate a strongly adherent uniform coating with surface roughness. GO-coated 316L SS surfaces showed increased hydrophilicity and biocompatibility with SHSY-5Y neuronal cells, which proliferated well and showed decreased reactive oxygen species (ROS) expression. In contrast, cells did not adhere to bare uncoated 316L SS meshes nor maintain viability when cultured in the vicinity of bare meshes. Therefore the combination of the improved surface properties and biocompatibility implies that GO-coating can be utilized to overcome pertinent limitations of bare metallic 316L SS implant surfaces, especially SS neural electrodes. Also, the procedure for making GO-based protective coatings can be applied to numerous other implants where the development of such protective films is necessary.

Protein disulfide isomerases: Redox connections in and out of the endoplasmic reticulum

Protein disulfide isomerases are thiol oxidoreductase chaperones from thioredoxin superfamily. As redox folding catalysts from the endoplasmic reticulum (ER), their roles in ER-related redox homeostasis and signaling are well-studied. PDIA1 exerts thiol oxidation/reduction and isomerization, plus chaperone effects. Also, substantial evidence indicates that PDIs regulate thiol-disulfide switches in other cell locations such as cell surface and possibly cytosol. Subcellular PDI translocation routes remain unclear and seem Golgi-independent. The list of signaling and structural proteins reportedly regulated by PDIs keeps growing, via thiol switches involving oxidation, reduction and isomerization, S-(de)nytrosylation, (de)glutathyonylation and protein oligomerization. PDIA1 is required for agonist-triggered Nox NADPH oxidase activation and cell migration in vascular cells and macrophages, while PDIA1-dependent cytoskeletal regulation appears a converging pathway. Extracellularly, PDIs crucially regulate thiol redox signaling of thrombosis/platelet activation, e.g., integrins, and PDIA1 supports expansive caliber remodeling during injury repair via matrix/cytoskeletal organization. Some proteins display regulatory PDI-like motifs. PDI effects are orchestrated by expression levels or post-translational modifications. PDI is redox-sensitive, although probably not a mass-effect redox sensor due to kinetic constraints. Rather, the "all-in-one" organization of its peculiar redox/chaperone properties likely provide PDIs with precision and versatility in redox signaling, making them promising therapeutic targets.