The impact of hUC MSC-derived exosome-nanoliposome hybrids on α-synuclein fibrillation and neurotoxicity

Amyloid aggregation of α-synuclein (αSN) protein amplifies the pathogenesis of neurodegenerative diseases (NDs) such as Parkinson's disease (PD). Consequently, blocking aggregation or redirecting self-assembly to less toxic aggregates could be therapeutic. Here, we improve brain-specific nanocarriers using a hybrid of exosomes (Ex) from human umbilical cord mesenchymal stem cells (hUC MSCs) and nanoliposomes containing baicalein (Ex-NLP-Ba) and oleuropein (Ex-NLP-Ole). The hybrids contained both lipid membranes, Ex proteins, and baicalein or oleuropein. Fluorescence resonance energy transfer analysis confirmed their proper integration. The hybrids reduced the extent of αSN fibrillation and interfered with secondary nucleation and disaggregation. They not only reduced αSN pathogenicity but also enhanced drug internalization into cells, surpassing the efficacy of NLP alone, and also crossed the blood-brain barrier in a cellular model. We conclude that Ex can be successfully extracted and efficiently merged with NLPs while retaining its original properties, demonstrating great potential as a theranostic drug delivery vehicle against NDs like PD.

RGD-decorated nanoliposomes for combined delivery of arsenic trioxide and curcumin to prostate cancer cells

Nanotechnology and drug co-delivery offer a novel avenue in drug delivery research liposome-based co-delivery of anticancer drugs targeting the apoptosis pathway as a promising new approach to treat cancer. In this study, a co-delivery system of liposomes (arsenic trioxide/curcumin) modified with RGD peptide was designed to aim for enhancing the treatment of prostate cancer cells (PC3 cell line). Liposomal co-loaded curcumin and arsenic trioxide modified by RGD peptide (NLPs-RGD-Cur-ATO) were prepared by thin-layer lipid hydration techniques for the treatment of prostate cancer. The stability of the NLPs-RGD-Cur-ATO was evaluated by particle size analysis through dynamic light scattering (DLS) analysis and transmission electron microscopy (TEM). The percentage of cytotoxicity and apoptotic effect in PC3 cells treated with NLPs-RGD-Cur-ATO were detected by MTT and Annexin V-FITC (fluorescein isothiocyanate)/PI affinity assay, respectively. The particle size of NLPs-RGD-Cur-ATO was approximately 100 nm, with an encapsulation efficiency of about 99.52% and 70.61%, for ATO and Cur, respectively. Besides, NLPs-RGD-Cur-ATO displayed an enhanced anti-proliferative effect, increased the percentage of apoptotic cells 98 ± 1.85% (p < 0.0001), and significantly reduced EGFR gene expression level (p < 0.001) in the cell line tested. These results indicated that our NLPs-RGD-Cur-ATO co-delivery system was a promising strategy for prostate cancer therapy.

A methodological primer of extracellular vesicles isolation and characterization via different techniques

We present four different protocols of varying complexity for the isolation of cell culture-derived extracellular vesicles (EVs)/exosome-enriched fractions with the objective of providing researchers with easily conducted methods that can be adapted for many different uses in various laboratory settings and locations. These protocols are primarily based on polymer precipitation, filtration and/or ultracentrifugation, as well as size-exclusion chromatography (SEC) and include: (i) polyethylene glycol and sodium chloride supplementation of the conditioned medium followed by low-speed centrifugation; (ii) ultracentrifugation of conditioned medium; (iii) filtration of conditioned media through a 100-kDa exclusion filter; and (iv) isolation using a standard commercial kit. These techniques can be followed by further purification by ultracentrifugation, sucrose density gradient centrifugation, or SEC if needed and the equipment is available. HEK293 and SH-SY5Y cell cultures were used to generate conditioned medium containing exosomes. This medium was then depleted of cells and debris, filtered through a 0.2-µM filter, and supplemented with protease and RNAse inhibitors prior to exosomal isolation. The purified EVs can be used immediately or stably stored at 4°C (up to a week for imaging or using intact EVS downstream) or at -80°C for extended periods and then used for biochemical study. Our aim is not to compare these methodologies but to present them with descriptors so that researchers can choose the "best method" for their work under their individual conditions.

A comparison between the effects of two liposome-encapsulated bevacizumab formulations on ocular neovascularization inhibition

Bevacizumab (BVZ), an anti-VEGF antibody, has demonstrated reliable outcomes in the treatment of irritating ocular neovascularization. Frequent intravitreal injections are necessitated due to rapid clearance and short local accessibility. We recruited liposome as a highly prevailing drug delivery system to enhance drug availability. Two liposome formulations were characterized and their in vitro stability was analyzed. The toxicity of the formulations on some ocular cell lines was also evaluated. In addition, the anti-angiogenic effects of formulations were examined. Drug permeation was measured across ARPE-19 and HCE cell lines as in vitro cellular barrier models. Results revealed that NLP-DOPE-BVZ acquired high stability at 4 °C, 24 °C, and 37 °C for 45 days. It also showed more capacity to entrap BVZ in NLP-DOPE-BVZ (DEE% 69.1 ± 1.4 and DLE% 55.66 ± 1.15) as compared to NLP-BVZ (DEE% 43.57 ± 14.64, and DLE% 37.72 ± 12.01). Although both formulations inhibited the migration and proliferation of HUVECs, NLP-DOPE-BVZ was more effective at inhibiting angiogenesis. Furthermore, NLP-DOPE-BVZ better crossed our established barrier cellular models. Based on the findings, the inclusion of DOPE in NLPs has significantly enhanced the features of drug carriers. This makes them a potential candidate for treating ocular neovascularization and other related ailments.

A curcumin-nicotinoyl derivative and its transition metal complexes: synthesis, characterization, and in silico and in vitro biological behaviors

Curcumin-nicotinoyl (Cur-Nic) was synthesized by the chemical modification of the curcumin structure, characterized, and used as a ligand for the synthesis of copper(II) and zinc(II) complexes. The biological activities of Cur-Nic and its metal complexes were predicted using the PASS and Swiss Target Prediction online software, respectively, and docking studies with tyrosine-protein kinase SRC were performed using the PyRx software to predict their anticancer activities. The toxicity effects of the complexes on a human breast cancer cell line (MCF-7) compared to a healthy breast cell line (MCF-10A) were investigated by the MTS assay. Although the metal complexes maintained the least toxicity against normal cells, the results indicated that compared to curcumin and Cur-Nic, the cytotoxicity toward cancer cells increased due to the complexation process. Moreover, the antibacterial evaluation of the compounds against a Gram-positive bacterium (MRSA) and a Gram-negative bacterium (E. coli) indicated that the Cu(II) complex and Cur-Nic were the best, respectively. Also, the Zn(II) complex was the most stable compound, and the Cu(II) complex was the best ROS scavenger based on the in vitro evaluation.

Inhibitory effect of plain and functionalized graphene nanoplateles on hen egg white lysozyme fibrillation

Protein fibrillation is a phenomenon associated with misfolding and the production of highly ordered nanofibrils, which may cause serious degenerative diseases such as Parkinson's disease, Alzheimer's disease, and type 2 diabetes. Upon contact with biological fluids, the nanomaterials are immediately covered by proteins and interact with them. In this study, the effects of Graphene NanoPlateles (Plain-GNPs) and their modified forms with a carboxyl group (GNPs -COOH) and an amine group (GNPs -NH2) are evaluated on the fibrillation process of Hen Egg White Lysozyme (HEWL). The fibrillation process of HEWL was studied using thioflavin-T, Circular Dichroism spectrometry, and Atomic Force Microscopy. Plain-GNPs significantly decreased the fibrillation process at different stages, including nucleation, exponential fibrillation phases, and end-mature fibril products. However, GNPs-COOH and GNPs-NH2 affected the final fluorescence of ThT. The species formed in the presence of Plain-GNPs showed less toxicity in SH-SY5Y cells, which could be applicable for therapeutic purposes.

A fabricated hydrogel of hyaluronic acid/curcumin shows super-activity to heal the bacterial infected wound

High risk of acute morbidities and even mortality from expanding the antibiotics resistant infectious wounds force indefinite efforts for development of high performance wound-healing materials. Herein, we design a procedure to fabricate a hyaluronic acid (HA)-based hydrogel to conjugate curcumin (Gel-H.P.Cur). The highlight of this work is to provide a favorite condition for capturing curcumin while protecting its structure and intensifying its activities because of the synchronization with HA. Accordingly, HA as a major component of dermis with a critical role in establishing skin health, could fortify the wound healing property as well as antibacterial activity of the hydrogel. Gel-H.P.Cur showed antibacterial properties against Pseudomonas aeruginosa (P. aeruginosa), which were examined by bactericidal efficiency, disk diffusion, anti-biofilm, and pyocyanin production assays. The effects of Gel-H.P.Cur on the inhibition of quorum sensing (QS) regulatory genes that contribute to expanding bacteria in the injured place was also significant. In addition, Gel-H.P.Cur showed high potential to heal the cutaneous wounds on the mouse excisional wound model with repairing histopathological damages rapidly and without scar. Taken together, the results strongly support Gel-H.P.Cur as a multipotent biomaterial for medical applications regarding the treatment of chronic, infected, and dehiscent wounds.

The anti-platelet drug ticlopidine inhibits FapC fibrillation and biofilm production: Highlighting its antibiotic activity

Multidrug resistance of bacteria and persistent infections related to biofilms, as well as the low availability of new antibacterial drugs, make it urgent to develop new antibiotics. Here, we evaluate the antibacterial and anti-biofilm properties of ticlopidine (TP), an anti-platelet aggregation drug, TP showed antibacterial activity against both gram-positive (MRSA) and gram-negative (E. coli, and P. aeruginosa) bacteria over a long treatment period. TP significantly reduced the survival of gram-negative bacteria in human blood though impact on gram-positives was more limited. TP may cause death in MRSA by inhibiting staphyloxanthin pigment synthesis, leading to oxidative stress, while scanning electron microscopy imaging indicate a loss of membrane integrity, damage, and consequent death due to lysis in gram-negative bacteria. TP showed good anti-biofilm activity against P. aeruginosa and MRSA, and a stronger biofilm degradation activity on P. aeruginosa compared to MRSA. Measuring fluorescence of the amyloid-reporter Thioflavin T (ThT) in biofilm implicated inhibition of amyloid formation as part of TP activity. This was confirmed by assays on the purified protein in P. aeruginosa, FapC, whose fibrillation kinetics was inhibited by TP. TP prolonged the lag phase of aggregation and reduced the subsequent growth rate and prolonging the lag phase to very long times provides ample opportunity to exert TP's antibacterial effect. We conclude that TP shows activity as an antibiotic against both gram-positive and gram-negative bacteria thanks to a broad range of activities, targeting bacterial metabolic processes, cellular structures and the biofilm matrix.

Characterization of exogenous αSN response genes and their relation to Parkinson’s disease using network analyses

Despite extensive research, the molecular mechanisms underlying the toxicity of αSN in Parkinson’s disease (PD) pathology are still poorly understood. To address this, we used a microarray dataset to identify genes that are induced and differentially expressed after exposure to toxic αSN aggregates, which we call exogenous αSN response (EASR) genes. Using systems biology approaches, we then determined, at multiple levels of analysis, how these EASR genes could be related to PD pathology. A key result was the identification of functional connections between EASR genes and previously identified PD-related genes by employing the proteins’ interactions networks and 9 brain region-specific co-expression networks. In each brain region, co-expression modules of EASR genes were enriched for gene sets whose expression are altered by SARS-CoV-2 infection, leading to the hypothesis that EASR co-expression genes may explain the observed links between COVID-19 and PD. An examination of the expression pattern of EASR genes in different non-neurological healthy brain regions revealed that regions with lower mean expression of the upregulated EASR genes, such as substantia nigra, are more vulnerable to αSN aggregates and lose their neurological functions during PD progression. Gene Set Enrichment Analysis of healthy and PD samples from substantia nigra revealed that a specific co-expression network, “TNF-α signaling via NF-κB”, is an upregulated pathway associated with the PD phenotype. Inhibitors of the “TNF-α signaling via NF-κB” pathway may, therefore, decrease the activity level of this pathway and thereby provide therapeutic benefits for PD patients. We virtually screened FDA-approved drugs against these upregulated genes (NR4A1, DUSP1, and FOS) using docking-based drug discovery and identified several promising drugs. Altogether, our study provides a better understanding of αSN toxicity mechanisms in PD and identifies potential therapeutic targets and small molecules for treatment of PD.

Adsorption of azo dyes by a novel bio-nanocomposite based on whey protein nanofibrils and nano-clay: Equilibrium isotherm and kinetic modeling

Excessive discharge of synthetic azo dyes into the aquatic ecosystem is a global concern. Here, we develop a green approach to remediate dye pollutants by fabricating an easily separable bio-nanocomposite, based on nanofibrils from whey protein concentrate together with montmorillonite. The nanocomposite was characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and surface area analysis. Nanofibrils lead to a uniform dispersion of montmorillonite in the matrix and also reinforce the nanocomposite. The adsorption efficacy was monitored using cationic (Chrysoidine-G, Bismarck brown-R), reactive (reactive black-5, reactive orange-16), acidic (acid red-88, acid red-114) and direct (direct violet-51, Congo red) dyes. The nanocomposite adsorbed different dyes with different kinetics, cationic dyes quicker and reactive dyes slower. Greater than 93% of Chrysoidine-G was adsorbed over a wide range of dye concentration and pH. Acidic pH and higher temperature are more favorable for the process. Equilibrium adsorption data were reasonably fitted with a linear (Nernst) isotherm model indicating the existence of an unlimited number of adsorption sites which is consistent with the high experimental uptake of 731 mg/g. Kinetic data were well-described by pseudo-second-order and intra-particle diffusion models. We conclude that this environmentally friendly nanocomposite has good potential for use in wastewater treatment and related purposes.

A Triple Role for a Bilayer: Using Nanoliposomes to Cross and Protect Cellular Membranes

Thanks in large part to the seminal work of Steve White and his colleagues, we appreciate the "ordered complexity" of the lipid bilayer and how it impacts the incorporation of integral membrane proteins as well as more peripherally associated proteins. Steve's work also provides a vital foundation to tackle another challenge: cytotoxic oligomeric complexes which accumulate in various neurodegenerative diseases. These oligomers have a relatively fluid structure and interact with many different proteins in the cell, but their main target is thought to be the phospholipid membrane, either the plasma membrane or internal organelles such as the mitochondria. This fascinating encounter between two essentially fluid phases generates a more disordered membrane, and presumably promotes uncontrolled transport of small metal ions across the membrane barrier. Happily, this unwanted interaction may be suppressed by mobilizing the phospholipid bilayer into its own defense. Extruded nanolipoparticles (NLPs) consisting of DPPC lipids, cholesterol and PEG2000 are excellent vehicles to take up small "oligomer-bashing" hydrophobic molecules such as baicalein and transport them with increased half-life in the plasma and with markedly more efficient crossing of the blood-brain barrier. Thus the bilayer has a triple role in this account: a safe space for a reactive hydrophobic small molecule, a barrier to cross to deliver a drug payload and a target to protect against oligomer attacks. NLPs containing small hydrophobic molecules show great promise in combating neurodegenerative diseases in animal models and may serve as an example of the White approach: applying robust physical-chemical principles to deal with biological problems involving phospholipid membranes.

Preparation, purification, and characterization of low-molecular-weight hyaluronic acid

OBJECTIVE

The use and commercial value of hyaluronic acid (HA) as an important element in the pharmaceutical, biomedical, and cosmetics industry is because of its purity. Four recombinant strains of Corynebacterium glutamicum containing different genes were used to produce HA.

RESULTS

The production parameters were measured and strain 183.2, with the highest amount of HA (2.15 mg/ml), was selected for further experiments. HA was precipitated by different ratios of ethanol-isopropanol at 4 °C and - 20 °C. Active charcoal (1%) was added to the solvent precipitation mixture at pH 5 and 10. Finally, to achieve more purity and separation, gel filtration chromatography was used. The best result was obtained using an ethanol-isopropanol ratio of 1:1 of at - 20 °C, followed by active charcoal treatment at the acidic pH, and three fractions of the chromatography with molecular weights of 27, 27-110, and < 27 KDa were more analyzed with electrophoresis and FTIR.

CONCLUSIONS

The present study described a simple, economical, and reproducible method resulting in a high yield for low-MW HA from C. glutamicum.

Formulation of nanoliposome-encapsulated bevacizumab (Avastin): Statistical optimization for enhanced drug encapsulation and properties evaluation

Bevacizumab (Avastin®), an anti-vascular endothelial growth factor, is one of the most effective drugs widely used to inhibit ocular angiogenesis. Nanoliposomes were recruited to improve the accessibility of bevacizumab (BVZ) during treatment. To optimize drug entrapment efficiency (DEE %), the effect of some independent variables was evaluated utilizing response surface methodology. The optimized formulation containing BVZ (NLP-BVZ) was characterized, and its safety was assessed. Employingarising retinalpigment epithelial (ARPE) cells, the permeability of the nanoliposome was analyzed. Structural stability and integrity of NLP-BVZ were also estimated with different methods. Optimal condition for the maximum DEE (39.9%) was obtained with cholesterol/DPPC (1,2-Dipalimitoyl-Sn-glycero-3-phosphocholine) (%w/w) 13.64, BVZ/DPPC (%w/w) 83.78 and 9 freeze-thaw cycles. Neutral fabricated NLP-BVZ with an average size of 141.5 ± 45.8 nm showed a smooth spherical structure and released the drug in a slow and sustained fashion. The formulation exhibited no obvious effect against human umbilical vein endothelial cells (HUVECs) and ARPEs. Additionally, the pattern of the circular dichroism (CD) and intrinsic fluorescence spectra confirmed the structural integrity of protein remained conserved after encapsulation. Taken together, the analysis indicated that the process of entrapment into nanoliposome meaningfully made the drug safer, more stable, and, therefore, appropriate for treating ocular disorders.

Multiple neuroprotective features of Scutellaria pinnatifida-derived small molecule

Parkinson's disease (PD) is one of the most prevalent neurodegenerative disorders with no precise etiology. Multiple lines of evidence support that environmental factors, either neurotoxins or neuroinflammation, can induce Parkinsonism. In this study, we purified an active compound, neobaicalein (Skullcapflavone II), from the roots of Scutellaria pinnatifida (S. pinnatifida). Neobaicalein not only had protective impacts on rotenone-induced neurotoxicity but in glial cultures, it dampened the inflammatory response when stimulated with lipopolysaccharide (LPS). Neobaicalein had high antioxidant activity without any obvious toxicity. In addition, it could raise the cell viability, decrease early apoptosis, reduce the generation of reactive oxygen species (ROS), and keep the neurite's length normal in the treated SH-SY5Y cells. Pathway enrichment analysis (PEA) and target prediction provided insights into the PD related genes, protein-protein interaction (PPI) network, and the key proteins enriched in the signaling pathways. Furthermore, docking simulation (DS) on the proteins of the PD-PPI network revealed that neobaicalein might interact with the key proteins involved in PD pathology, including MAPK14, MAPK8, and CASP3. It also blocks the destructive processes, such as cell death, inflammation, and oxidative stress pathways. Our results demonstrate that neobaicalein alleviates pathological effects of factors related to PD, and may provide new insight into PD therapy.

The status of the terminal regions of α-synuclein in different forms of aggregates during fibrillization

The α-synuclein (αSN) amyloid fibrillization process is known to be a crucial phenomenon associated with neuronal loss in various neurodegenerative diseases, most famously Parkinson's disease. The process involves different aggregated species and ultimately leads to formation of β-sheet rich fibrillar structures. Despite the essential role of αSN aggregation in the pathoetiology of various neurological disorders, the characteristics of various assemblies are not fully understood. Here, we established a fluorescence-based model for studying the end-parts of αSN to decipher the structural aspects of aggregates during the fibrillization. Our model proved highly sensitive to the events at the early stage of the fibrillization process, which are hardly detectable with routine techniques. Combining fluorescent and PAGE analysis, we found different oligomeric aggregates in the nucleation phase of fibrillization with different sensitivity to SDS and different structures based on αSN termini. Moreover, we found that these oligomers are highly dynamic: after reaching peak levels during fibrillization, they decline and eventually disappear, suggesting their transformation into other αSN aggregated species. These findings shed light on the structural features of various αSN aggregates and their dynamics in synucleinopathies.

Temperature-dependent formulation of a hydrogel based on Hyaluronic acid-polydimethylsiloxane for biomedical applications

Hyaluronic acid (HA), as a safe biomaterial with minimal immunogenicity, is being employed in a broad range of medical applications. Since unmodified HA has a high potential for biodegradation in the physiological condition, herein, an HA-based cross-linked hydrogel was formulated using polydimethylsiloxane-diglycidyl ether terminated (PDMS-DG) via epoxide-OH reaction. The formation of HA-PDMS hydrogel was confirmed using FTIR, NMR, and FESEM. Temperature demonstrated a critical role in the physicochemical properties of the final products. Gel-37, which formed at 37 °C, had a higher modification degree (MD) and more stability against hyaluronidase and oxidative stress than the hydrogel formulated at 25 °C (Gel-25). In addition, the swelling ratio, roughness, and porous network topology of Gel-25 and Gel-37 were different. The rheology measurement indicated that HA-PDMS hydrogel had a stable viscoelastic character. The hydrogel was also biocompatible, non-cytotoxic, and considerably stable during 7-months storage. Overall, various determined parameters confirmed that HA-PDMS hydrogel is worth using in different medical applications. Keywords: Hyaluronic acid; Polydimethylsiloxane-diglycidyl ether terminated; Hydrogels; Long-term stability; Viscoelastic behavior; Biocompatibility.

Plant Polyphenols Inhibit Functional Amyloid and Biofilm Formation in Pseudomonas Strains by Directing Monomers to Off-Pathway Oligomers

Self-assembly of proteins to β-sheet rich amyloid fibrils is commonly observed in various neurodegenerative diseases. However, amyloid also occurs in the extracellular matrix of bacterial biofilm, which protects bacteria from environmental stress and antibiotics. Many Pseudomonas strains produce functional amyloid where the main component is the highly fibrillation-prone protein FapC. FapC fibrillation may be inhibited by small molecules such as plant polyphenols, which are already known to inhibit formation of pathogenic amyloid, but the mechanism and biological impact of inhibition is unclear. Here, we elucidate how polyphenols modify the self-assembly of functional amyloid, with particular focus on epigallocatechin gallate (EGCG), penta-O-galloyl-β-d-glucose (PGG), baicalein, oleuropein, and procyanidin B2. We find EGCG and PGG to be the best inhibitors. These compounds inhibit amyloid formation by redirecting the aggregation of FapC monomers into oligomeric species, which according to small-angle X-ray scattering (SAXS) measurements organize into core-shell complexes of short axis diameters 25-26 nm consisting of ~7 monomers. Using peptide arrays, we identify EGCG-binding sites in FapC's linker regions, C and N-terminal parts, and high amyloidogenic sequences located in the R2 and R3 repeats. We correlate our biophysical observations to biological impact by demonstrating that the extent of amyloid inhibition by the different inhibitors correlated with their ability to reduce biofilm, highlighting the potential of anti-amyloid polyphenols as therapeutic agents against biofilm infections.

Antibiotic hypersensitivity in MRSA induced by special protein aggregates

Emergence of multidrug-resistant bacteria is a major global concern. According to WHO, methicillin-resistant Staphylococcus aureus (MRSA) is a threatening pathogen resistant to a wide spectrum of antibiotics. Herein, to overcome drug resistance in MRSA, we successfully integrated traditional antibacterial methods but with a novel trick that included use of hen egg-white lysozyme's special aggregates generated by fibrillization. The minimum inhibitory concentration of oxacillin (Ox) for MRSA declined from 600 μM to <20 μM when using aggregates. Scanning and transition electron micrographs showed completely disrupted cells when treated with aggregated protein/Ox (20 μM). The assisting role of aggregates to induce antibiotic hypersensitivity was continuous and stable, but sub-inhibitory antibiotic concentration (20 μM) was required again after 8 h. Investigations regarding mechanism of antibiotic hypersensitivity revealed that aggregates were oligomers but not mature fibrils. Furthermore, reactive oxygen species levels rose significantly after treating bacteria with aggregated protein/Ox. Study of resistance mechanisms indicated that in response to wall structure alterations, mecA expression dropped significantly in the presence of aggregated protein/Ox (20 μM) relative to Ox (20 μM). This observation can be a breakthrough in finding alternatives where antibiotic dosage can be significantly reduced, thereby preventing emergence of new multidrug-resistant bacteria.

In vitro models of synucleinopathies: informing on molecular mechanisms and protective strategies

Alpha-synuclein (α-Syn) is a central player in Parkinson's disease (PD) and in a spectrum of neurodegenerative diseases collectively known as synucleinopathies. The protein was first associated with PD just over 20 years ago, when it was found to (i) be a major component of Lewy bodies and (ii) to be also associated with familial forms of PD. The characterization of α-Syn pathology has been achieved through postmortem studies of human brains. However, the identification of toxic mechanisms associated with α-Syn was only achieved through the use of experimental models. In vitro models are highly accessible, enable relatively rapid studies, and have been extensively employed to address α-Syn-associated neurodegeneration. Given the diversity of models used and the outcomes of the studies, a cumulative and comprehensive perspective emerges as indispensable to pave the way for further investigations. Here, we subdivided in vitro models of α-Syn pathology into three major types: (i) models simulating α-Syn fibrillization and the formation of different aggregated structures in vitro, (ii) models based on the intracellular expression of α-Syn, reporting on pathogenic conditions and cellular dysfunctions induced, and (iii) models using extracellular treatment with α-Syn aggregated species, reporting on sites of interaction and their downstream consequences. In summary, we review the underlying molecular mechanisms discovered and categorize protective strategies, in order to pave the way for future studies and the identification of effective therapeutic strategies. This article is part of the Special Issue "Synuclein".

RGD-Modified Nano-Liposomes Encapsulated Eptifibatide with Proper Hemocompatibility and Cytotoxicity Effect

Background

Eptifibatide (Integrilin®) is a hepta-peptide drug which specifically prevents the aggregation of activated platelets. The peptide drugs are encapsulated into nanolipisomes in order to decreasing their side effects and improving their half-life and bioavailability.

Objectives

In this study, the in vitro cytotoxicity and hemocompatibility of RGD-modified nano-liposomes (RGD-MNL) encapsulated a highly potent antiplatelet drug (eptifibatide) was investigated.

Material and Methods

RGD-MNL encapsulated eptifibatide was prepared using lipid film hydration and freeze/thawing method. The morphology and size distribution (about 90 nm) of RGD-MNL were characterized using transmission electron microscopy (TEM). The in-vitro cytotoxicity of nano-liposomes was examined using the MTT, LDH release and reactive oxygen species (ROS) generation assays. The effect of RGD-MNL on red blood cells (RBC) was investigated using hemolysis and LDH release assays.

Results

The results revealed that RGD-MNL had no significant cytotoxic effect on HeLa and HUVEC cell lines, and also no ROS generation increase in the cells. In addition, the adverse effect of RGD-MNL on LDH release and membrane integrity of RBC was not observed.

Conclusions

In conclusion, the recommended RGD-MNL formulations have not any significant cytotoxicity on normal cells or RBC and have potential for protecting and enhancing the activity of antiplatelet drugs.

The primary neuronal cells are more resistant than PC12 cells to α-synuclein toxic aggregates

BACKGROUND

Alpha-synuclein (αSN) is an abundant presynaptic brain protein that its aggregated species believed to play pivotal roles in the development of neurodegenerative diseases, especially Parkinson's disease (PD). In this study, we compared the response of primary neuronal cells with a well-known cell line model, PC12, against the toxic aggregates of αSN.

METHODS

Primary hippocampal neurons (PHNs) were isolated from 17 to 18 days old rat embryos. Fibrillization was induced in recombinant αSN and monitored by standard methods. The toxicity of different aggregates of αSN on the treated cells was then studied. Furthermore, changes in the intracellular reactive oxygen species (ROS) and Ca²⁺ levels were also compared in two kinds of treated cells. We also studied the gene expression profile of certain Ca²⁺ channels and carriers using the GEO2 database.

RESULTS

The viability rate was significantly lower in PC12 versus PHNs, in response to αSN. This is while the intracellular ROS and Ca²⁺ levels were significantly increased in both cell types. Analysis of microarray data indicated that some factors involved in Ca²⁺ hemostasis may face significant changes in the PD condition.

CONCLUSION

By putting these data together, it is clear that PHN is more resistant than PC12 toward αSN cytotoxicity even in the presence of rising cytoplasmic ROS and Ca²⁺ levels. Exploring the supporting mechanisms which PHN uses to be more resistant to αSN cytotoxicity can help to open a roadmap toward therapeutic plans in PD and other synucleinopathy disorders.

Oleuropein derivatives from olive fruit extracts reduce α-synuclein fibrillation and oligomer toxicity

Aggregation of α-synuclein (αSN) is implicated in neuronal degeneration in Parkinson's disease and has prompted searches for natural compounds inhibiting αSN aggregation and reducing its tendency to form toxic oligomers. Oil from the olive tree (Olea europaea L.) represents the main source of fat in the Mediterranean diet and contains variable levels of phenolic compounds, many structurally related to the compound oleuropein. Here, using αSN aggregation, fibrillation, size-exclusion chromatography-multiangle light scattering (SEC-MALS)-based assays, and toxicity assays, we systematically screened the fruit extracts of 15 different olive varieties to identify compounds that can inhibit αSN aggregation and oligomer toxicity and also have antioxidant activity. Polyphenol composition differed markedly among varieties. The variety with the most effective antioxidant and aggregation activities, Koroneiki, combined strong inhibition of αSN fibril nucleation and elongation with strong disaggregation activity on preformed fibrils and prevented the formation of toxic αSN oligomers. Fractionation of the Koroneiki extract identified oleuropein aglycone, hydroxyl oleuropein aglycone, and oleuropein as key compounds responsible for the differences in inhibition across the extracts. These phenolic compounds inhibited αSN amyloidogenesis by directing αSN monomers into small αSN oligomers with lower toxicity, thereby suppressing the subsequent fibril growth phase. Our results highlight the molecular consequences of differences in the level of effective phenolic compounds in different olive varieties, insights that have implications for long-term human health.

The potential of zwitterionic nanoliposomes against neurotoxic alpha-synuclein aggregates in Parkinson's Disease

The protein α-synuclein (αSN) aggregates to form fibrils in neuronal cells of Parkinson's patients. Here we report on the effect of neutral (zwitterionic) nanoliposomes (NLPs), supplemented with cholesterol (NLP-Chol) and decorated with PEG (NLP-Chol-PEG), on αSN aggregation and neurotoxicity. Both NLPs retard αSN fibrillization in a concentration-independent fashion. They do so largely by increasing lag time (formation of fibrillization nuclei) rather than elongation (extension of existing nuclei). Interactions between neutral NLPs and αSN may locate to the N-terminus of the protein. This interaction can even perturb the interaction of αSN with negatively charged NLPs which induces an α-helical structure in αSN. This interaction was found to occur throughout the fibrillization process. Both NLP-Chol and NLP-Chol-PEG were shown to be biocompatible in vitro, and to reduce αSN neurotoxicity and reactive oxygen species (ROS) levels with no influence on intracellular calcium in neuronal cells, emphasizing a prospective role for NLPs in reducing αSN pathogenicity in vivo as well as utility as a vehicle for drug delivery.

A study on the modulation of alpha-synuclein fibrillation by Scutellaria pinnatifida extracts and its neuroprotective properties

Aggregation of alpha-synuclein (α-SN) is a key pathogenic event in Parkinson's disease (PD) leading to dopaminergic degeneration. The identification of natural compounds inhibiting α-SN aggregation may have a major role in treating PD. Different Scutellaria species are known as valuable medicinal plants, primarily due to their high flavonoid levels. Scutellaria pinnatifida (S. pinnatifida) is endemic to Iran; however, the knowledge of its pharmaceutical properties is limited. Here we report that S. pinnatifida extracts have an anti-fibrillation effect on α-SN aggregation and neuroprotective properties on PC12 and primary dopaminergic neurons. Treatment during α-SN fibril formation with S. pinnatifida extracts showed that the extractions performed with dichloromethane (DCMEx) and n-butanol (BuOHEx) strongly inhibited α-SN fibrillation. TLC-based analysis revealed that S. pinnatifida contains a great amount of flavonoids with high antioxidant properties as shown using a radical scavenging assay. Further analysis using HPLC and Mass spectroscopy on the DCMEx revealed the presence of baicalein in this extract. We then selected the more efficient extracts based on cell viability and ROS scavenging on PC12 cells and tested their neuroprotective properties on primary dopaminergic neurons. Our results showed the extracts strongly protected against α-SN oligomers. Surprisingly, they also neutralized the severe toxicity of paraquat. Therefore, S. pinnatifida may be a potential valuable medicinal herb for further studies related to the treatment of PD.

Curcumin-Loaded Amine-Functionalized Mesoporous Silica Nanoparticles Inhibit α-Synuclein Fibrillation and Reduce Its Cytotoxicity-Associated Effects

This study aimed to develop a drug carrier based on amine-functionalized mesoporous silica nanoparticles (AAS-MSNPs) for a poorly water-soluble drug, curcumin (CUR), and to study its effects on α-synuclein (α-Syn) fibrillation and cytotoxicity. Here, we show that AAS-MSNPs possess high values of loading efficiency and capacity (33.5% and 0.45 mg drug/mg MSNPs, respectively) for CUR. It is also revealed that α-Syn species interact strongly with the CUR-loaded AAS-MSNPs, leading to a significant inhibition of the fibrillation process. Furthermore, these samples reduce the toxic effects of CUR. However, drug-loaded AAS-MSNPs do not affect the cytotoxic properties of the formed fibrils considerably. In addition, CUR loaded onto AAS-MSNPs shows enhanced stability in comparison with that of the free drug. These remarkable properties introduce AAS-MSNPs as a promising tool for the formulation of poorly water-soluble drugs such as CUR.

The Effects of Organic Solvents on the Physicochemical Properties of Human Serum Albumin Nanoparticles

BACKGROUND

Recently, applications of albumin nanoparticles as drug delivery carriers have increased. Most toxicology studies have shown that surface chemistry and size of nanoparticles play an important role in biocompatibility and toxicity.

OBJECTIVE

The effect of desolvating agents with different chemical properties on the size of synthesized HSA NPs was investigated.

MATERIALS AND METHODS

Acetone, ethanol, methanol, and acetonitrile were used to synthesize HSA NPs with controllable size by desolvation method. Scanning electron microscopy (SEM), dynamic light scattering (DLS), and circular dichroism (CD) were employed to characterize produced particles. Finally, the toxicity of HSA NPs synthesized under different conditions was evaluated on PC-12 cells.

RESULTS

The sizes of synthesized particles differed according to the different solvents used. The sizes were 275.3 nm, 155.3 nm, 100.11 nm, and 66.2 nm for acetonitrile, ethanol, acetone, and methanol, respectively. CD showed that larger NPs had more changes in the secondary structures. Finally, the toxicity monitored on the cultured PC-12 cells showed no significant toxic effect through treating with these NPs at different concentrations (0-500 μg.mL^-1).

CONCLUSIONS

The size of HSA NPs has a strong dependency on the desolvating agent. The mechanism in which the desolvating agent affects the size of HSA NPs is complex. Various factors such as dielectric constant, polarity, functional groups, and hydrogen bonding of the solvents have the potential to affect the size and structure of HSA NPs. CD analysis suggested that the solvent denaturing capability had a critical effect on the HSA particle size. The stronger denaturing capability of the solvent resulted in the larger HSA particle size.

Gallic acid loaded onto polyethylenimine-coated human serum albumin nanoparticles (PEI-HSA-GA NPs) stabilizes α-synuclein in the unfolded conformation and inhibits aggregation

The aggregation of the 140-residue protein α-synuclein (αSN) plays a major role in the pathogenesis of different neurodegenerative disorders such as Parkinson's Disease (PD).

Strong interactions with polyethylenimine-coated human serum albumin nanoparticles (PEI-HSA NPs) alter α-synuclein conformation and aggregation kinetics

The interaction between nanoparticles (NPs) and the small intrinsically disordered protein α-synuclein (αSN), whose aggregation is central in the development of Parkinson's disease, is of great relevance in biomedical applications of NPs as drug carriers. Here we showed using a combination of different techniques that αSN interacts strongly with positively charged polyethylenimine-coated human serum albumin (PEI-HSA) NPs, leading to a significant alteration in the αSN secondary structure. In contrast, the weak interactions of αSN with HSA NPs allowed αSN to remain unfolded. These different levels of interactions had different effects on αSN aggregation. While the weakly interacting HSA NPs did not alter the aggregation kinetic parameters of αSN, the rate of primary nucleation increased in the presence of PEI-HSA NPs. The aggregation rate changed in a PEI-HSA NP-concentration dependent and size independent manner and led to fibrils which were covered with small aggregates. Furthermore, PEI-HSA NPs reduced the level of membrane-perturbing oligomers and reduced oligomer toxicity in cell assays, highlighting a potential role for NPs in reducing αSN pathogenicity in vivo. Collectively, our results highlight the fact that a simple modification of NPs can strongly modulate interactions with target proteins, which may have important and positive implications in NP safety.

Cuminaldehyde as the Major Component of Cuminum cyminum, a Natural Aldehyde with Inhibitory Effect on Alpha-Synuclein Fibrillation and Cytotoxicity

Fibrillation of alpha-synuclein (α-SN) is a critical process in the pathophysiology of several neurodegenerative diseases, especially Parkinson's disease. Application of bioactive inhibitory compounds from herbal extracts is a potential therapeutic approach for this cytotoxic process. Here, we investigated the inhibitory effects of the Iranian Cuminum cyminum essential oil on the fibrillation of α-SN. Analysis of different fractions from the total extract identified cuminaldehyde as the active compound involved in the antifibrillation activity. In comparison with baicalein, a well-known inhibitor of α-SN fibrillation, cuminaldehyde showed the same activity in some aspects and a different activity on other parameters influencing α-SN fibrillation. The presence of spermidine, an α-SN fibrillation inducer, dominantly enforced the inhibitory effects of cuminaldehyde even more intensively than baicalein. Furthermore, the results from experiments using preformed fibrils and monobromobimane-labeled monomeric protein also suggest that cuminaldehyde prevents α-SN fibrillation even in the presence of seeds, having no disaggregating impact on the preformed fibrils. Structural studies showed that cuminaldehyde stalls protein assembly into β-structural fibrils, which might be achieved by the interaction with amine groups through its aldehyde group as a Schiff base reaction. This assumption was supported by FITC labeling efficiency assay. In addition, cytotoxicity assays on PC12 cells showed that cuminaldehyde is a nontoxic compound, treatment with cuminaldehyde throughout α-SN fibrillation showed no toxic effects on the cells. Taken together, these results show for the first time that the small abundant natural compound, cuminaldehyde, can modulate α-SN fibrillation. Hence, suggesting that such natural active aldehyde could have potential therapeutic applications.

The effect of mesoporous silica nanoparticle surface chemistry and concentration on the α-synuclein fibrillation

Surface chemistry/charge and concentration of mesoporous silica nanoparticles have a great impact on the fibrillation process of α-Syn protein.

Using small molecules as a new challenge to redirect metabolic pathway

The presence of acetate in the bacterial medium leads to a reduction in the growth rate of cells and recombinant protein production. In this study, three compounds including propionic acid, lithium chloride and butyric acid were added to the medium which decreased acetate levels and enhanced recombinant protein production (alpha-synuclein). In fact, propionic acid and lithium chloride are both known as acetate kinase inhibitors. The results obtained in the case of butyric acid were similar to those of the two other compounds indicating that butyric acid may act through a mechanism similar to propionic acid and lithium chloride. Consequently, it was shown that the presence of each of these supplements (5–200 μM) increased recombinant alpha-synuclein production and cell density by approximately 10–15 %. HPLC analysis showed that the levels of acetate in the media containing the supplements were considerably less than those of the control. Furthermore, pH values remained almost constant in the supplemented cultures. Growing the bacteria at lower temperatures (25 °C) indicated that the positive effects of these supplements were not as effective as at higher temperatures (37 °C), presumably due to the adequate balance between oxygen and carbon consumption. This study can confirm the viewpoint regarding the harmful effects of acetate on the recombinant protein production and cell density. Besides, such methods represent easy and complementary ways to increase target recombinant protein production without negatively affecting host cell density, and requiring complex genetic manipulation.

Identification and characterization of a compound from Cuminum cyminum essential oil with antifibrilation and cytotoxic effect

Amyloid pathology is associated with fibril aggregation of different proteins which results in the progressive damage of affected organs. It is strongly believed that specific small molecules interfere with fibrillation by interacting with the amyloidogenic proteins. We had previously reported the strong and long-term inhibition of fibrillation of hen egg white lysozyme (HEWL) by Cuminum cyminum oil. Herein, it was intended to rationally identify the active anti-amyloidogenic compounds of the oil. After fractionation, the highest inhibitory effect was observed in the toluene-ethyl acetate part of the oil. Gas chromatography-mass spectrometry (GC-MS) analysis of this fraction indicated that eight compounds were predominantly present in the fraction. Unexpectedly, two compounds including terpinolene and limonene, having very similar chemical structures, inhibited and induced fibrillation, respectively. PC12 cells (derived from a transplantable rat pheochromocytoma) were affected by HEWL fibrils, whereas the inhibited forms of fibrils in the presence of terpinolene led to higher levels of viability, as shown by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), lactate dehydrogenase (LDH) and flow cytometry assays. Molecular local docking analysis suggested a site of interaction for terpinolene in the flexible cleft of the protein. This interaction site is close to tryptophan -62 and -63 and two other hydrophobic residues in the hot spot regions of the protein. Seemingly, these interactions interrupt protein self-assembly and therefore, fibril formation. Despite previously reported small anti-amyloid molecules which have aromatic flat rings, terpinolene ring is not flat. This functionally durable small molecule may aid us toward developing new anti-amyloidogenic compounds with extended activity.

Benzofuranone derivatives as effective small molecules related to insulin amyloid fibrillation: a structure-function study

Amyloids are protein fibrils of nanometer size resulting from protein self-assembly. They have been shown to be associated with a wide variety of diseases such as Alzheimer's and Parkinson's and may contribute to various other pathological conditions, known as amyloidoses. Insulin is prone to form amyloid fibrils under slightly destabilizing conditions in vitro and may form amyloid structures when subcutaneously injected into patients with diabetes. There is a great deal of interest in developing novel small molecule inhibitors of amyloidogenic processes, as potential therapeutic compounds. In this study, the effects of five new synthetic benzofuranone derivatives were investigated on the insulin amyloid formation process. Protein fibrillation was analyzed by thioflavin-T fluorescence, Congo red binding, circular dichroism, and electron microscopy. Despite high structural similarity, one of the five tested compounds was observed to enhance amyloid fibrillation, while the others inhibited the process when used at micromolar concentrations, which could make them interesting potential lead compounds for the design of therapeutic antiamyloidogenic compounds.

Amyloidogenic potential of alpha-chymotrypsin in different conformational states

Amyloid fibril formation is widely believed to be a generic property of polypeptide chains. In the present study, alpha-chymotrypsin, a well-known serine protease has been driven toward these structures by the use of two different conditions involving (I) high temperature, pH 2.5, and (II) low concentration of trifluoroethanol (TFE), pH 2.5. A variety of experimental methods, including fluorescence emission, dynamic quenching, steady-state fluorescence anisotropy, far-UV circular dichroism, nuclear magnetic resonance spectroscopy, and dynamic light scattering were employed to characterize the conformational states of alpha-chymotrypsin that precede formation of amyloid fibrils. The structure formed under Condition I was an unfolded monomer, whereas an alpha-helical rich oligomer was induced in Condition II. Both the amyloid aggregation-prone species manifested a higher solvent exposure of hydrophobic and aromatic residues compared with the native state. Upon incubation of the protein in these conditions for 48 h, amyloid-like fibrils were formed with diameters of about 10-12 nm. In contrast, at neutral pH and low concentration of TFE, a significant degree of amorphous aggregation was observed, suggesting that charge neutralization of acidic residues in the amyloid core region has a positive influence on amyloid fibril formation. In summary, results presented in this communication suggest that amyloid fibrils of alpha-chymotrypsin may be obtained from a variety of structurally distinct conformational ensembles highlighting the critical importance of protein evolution mechanisms related to prevention of protein misfolding.