Evaluation of fluorescent dyes to measure protein aggregation within mammalian cell culture supernatants

The detection methods currently available for protein aggregation in neurological diseases

Protein aggregation is a pathological feature in various neurodegenerative diseases and is thought to play a crucial role in the onset and progression of neurological disorders. This pathological phenomenon has attracted increasing attention from researchers, but the underlying mechanism has not been fully elucidated yet. Researchers are increasingly interested in identifying chemicals or methods that can effectively detect protein aggregation or maintain protein stability to prevent aggregation formation. To date, several methods are available for detecting protein aggregates, including fluorescence correlation spectroscopy, electron microscopy, and molecular detection methods. Unfortunately, there is still a lack of methods to observe protein aggregation in situ under a microscope. This article reviews the two main aspects of protein aggregation: the mechanisms and detection methods of protein aggregation. The aim is to provide clues for the development of new methods to study this pathological phenomenon.

Biosensing-based quality control monitoring of the higher-order structures of therapeutic antibody domains

Advanced biopharmaceutical manufacturing requires novel process analytical technologies for the rapid and sensitive assessment of the higher-order structures of therapeutic proteins. However, conventional physicochemical analyses of denatured proteins have limitations in terms of sensitivity, throughput, analytical resolution, and real-time monitoring capacity. Although probe-based sensing can overcome these limitations, typical non-specific probes lack analytical resolution and provide little to no information regarding which parts of the protein structure have been collapsed. To meet these analytical demands, we generated biosensing probes derived from artificial proteins that could specifically recognize the higher-order structural changes in antibodies at the protein domain level. Biopanning of phage-displayed protein libraries generated artificial proteins that bound to a denatured antibody domain, but not its natively folded structure, with nanomolar affinity. The protein probes not only recognized the higher-order structural changes in intact IgGs but also distinguished between the denatured antibody domains. These domain-specific probes were used to generate response contour plots to visualize the antibody denaturation caused by various process parameters, such as pH, temperature, and holding time for acid elution and virus inactivation. These protein probes can be combined with established analytical techniques, such as surface plasmon resonance for real-time monitoring or plate-based assays for high-throughput analysis, to aid in the development of new analytical technologies for the process optimization and monitoring of antibody manufacturing.

Investigating Protein Binding with the Isothermal Ligand-induced Resolubilization Assay

Target engagement assays typically detect and quantify the direct physical interaction of a protein of interest and its ligand through stability changes upon ligand binding. Commonly used target engagement methods detect ligand-induced stability by subjecting samples to thermal or proteolytic stress. Here we describe a new variation to these approaches called Isothermal Ligand-induced Resolubilization Assay (ILIRA), which utilizes lyotropic solubility stress to measure ligand binding through changes in target protein solubility. We identified distinct buffer systems and salt concentrations that compromised protein solubility for four diverse proteins: dihydrofolate reductase (DHFR), nucleoside diphosphate-linked moiety X motif 5 (NUDT5), poly [ADP-ribose] polymerase 1 (PARP1), and protein arginine N-methyltransferase 1 (PRMT1). Ligand-induced solubility rescue was demonstrated for these proteins, suggesting that ILIRA can be used as an additional target engagement technique. Differences in ligand-induced protein solubility were assessed by Coomassie blue staining for SDS-PAGE and dot blot, as well as by NanoOrange, Thioflavin T, and Proteostat fluorescence, thus offering flexibility for readout and assay throughput.

Molecular Rotors: Fluorescent Sensors for Microviscosity and Conformation of Biomolecules

The viscosity and crowding of biological environment are considered vital for the correct cellular function, and alterations in these parameters are known to underly a number of pathologies including diabetes, malaria, cancer and neurodegenerative diseases, to name a few. Over the last decades, fluorescent molecular probes termed molecular rotors proved extremely useful for exploring viscosity, crowding, and underlying molecular interactions in biologically relevant settings. In this review, we will discuss the basic principles underpinning the functionality of these probes and will review advances in their use as sensors for lipid order, protein crowding and conformation, temperature and non-canonical nucleic acid structures in live cells and other relevant biological settings.

Small molecule fluorescent probes for the study of protein phase separation

Liquid-liquid phase separation (LLPS) and liquid-solid phase transitions (LSPT) play crucial roles in biological systems, including sorting biomolecules, facilitate the transport of substrates for assembly, and accelerate the formation of metabolic and signaling complexes. Efforts towards improved characterization and quantification of phase separated species remain of outstanding interest and priority. In this review, we cover recent advances and the strategies used with small molecule fluorescent probes for the study of phase separation.

Real-time detection of mAb aggregates in an integrated downstream process

The implementation of continuous processing in the biopharmaceutical industry is hindered by the scarcity of process analytical technologies (PAT). To monitor and control a continuous process, PAT tools will be crucial to measure real-time product quality attributes such as protein aggregation. Miniaturizing these analytical techniques can increase measurement speed and enable faster decision-making. A fluorescent dye (FD)-based miniaturized sensor has previously been developed: a zigzag microchannel which mixes two streams under 30 s. Bis-ANS and CCVJ, two established FDs, were employed in this micromixer to detect aggregation of the biopharmaceutical monoclonal antibody (mAb). Both FDs were able to robustly detect aggregation levels starting at 2.5%. However, the real-time measurement provided by the microfluidic sensor still needs to be implemented and assessed in an integrated continuous downstream process. In this work, the micromixer is implemented in a lab-scale integrated system for the purification of mAbs, established in an ÄKTA™ unit. A viral inactivation and two polishing steps were reproduced, sending a sample of the product pool after each phase directly to the microfluidic sensor for aggregate detection. An additional UV sensor was connected after the micromixer and an increase in its signal would indicate that aggregates were present in the sample. The at-line miniaturized PAT tool provides a fast aggregation measurement, under 10 min, enabling better process understanding and control.

Protein reservoirs of seeds are amyloid composites employed differentially for germination and seedling emergence

Seed protein localization in seed storage protein bodies (SSPB) and their significance in germination are well recognized. SSPB are spherical and contain an assembly of water-soluble and salt-soluble proteins. Although the native structures of some SSPB proteins are explored, their structural arrangement to the functional correlation in SSPB remains unknown. SSPB are morphologically analogous to electron-dense amyloid-containing structures reported in other organisms. Here, we show that wheat, mungbean, barley, and chickpea SSPB exhibit a speckled pattern of amyloids interspersed in an amyloid-like matrix along with native structures, suggesting the composite nature of SSPB. This is confirmed by multispectral imaging methods, electron microscopy, infrared, and X-ray diffraction analysis, using in situ tissue sections, ex vivo protoplasts, and in vitro SSPB. Laser capture microdissection coupled with peptide fingerprinting has shown that globulin 1 and 3 in wheat, and 8S globulin and conglycinin in mungbean are the major amyloidogenic proteins. The amyloid composites undergo a sustained degradation during germination and seedling growth, facilitated by an intricate interplay of plant hormones and proteases. These results would lay down the foundation for understanding the amyloid composite structure during SSPB biogenesis and its evolution across the plant kingdom and have implications in both basic and applied plant biology.

Controlling monoclonal antibody aggregation during cell culture using medium additives facilitated by the monitoring of aggregation in cell culture matrix using size exclusion chromatography

Controlling monoclonal antibody aggregation at the upstream stage itself can significantly reduce the burden on downstream processing and can improve the process yield. Hence, we have investigated the use of sugar osmolytes (glucose, mannose, sucrose and maltose) and formulation excipients (mannitol, polysorbate 20 and polysorbate 80) as medium additives to reduce protein aggregation during cell culture. Aggregate content in cell culture samples was estimated using a high-resolution size-exclusion chromatography technique, which efficiently resolved the antibody monomer and aggregates in the cell culture matrix i.e., without purification. Glucose, mannose, maltose and the polysorbates effectively reduced the mean aggregate content over the course of the culture. Sugar-based additives exhibited a higher degree of variation during aggregate quantitation as compared to polysorbate additives, rendering the latter a preferred additive. Therefore, this study demonstrated the potential of sugar osmolytes and formulation excipients as media additives during cell culture to reduce aggregate formation, without negatively impacting cell growth and antibody production, facilitated by the monitoring of aggregate content in cell culture samples without purification.

Amyloid-like RIP1/RIP3 RHIM Fragments' Characterization and Application as a Drug Depot

Amyloid aggregates play a major role in diseases as well as in normal physiological function. Receptor-interacting protein kinases 1 and 3 (RIP1/RIP3) aggregates complexes in cellular necroptosis is one example of protein aggregation in normal cellular function. Although recently there have been several studies on full kinase proteins aggregation, the aggregation potential of small peptide sequences of RIP1/RIP3, the physicochemical properties, and the potential in biomedical applications have not been explored. Hence, in this paper, we study the aggregation propensity of peptides consisting of four and twelve amino acid sequences in the RHIM region of RIP1/RIP3 proteins that are known to drive the beta-sheet formation and the subsequent aggregation. The aggregation kinetics, physicochemical characterization, mechanosensitive properties, cellular effects, and potential as a cancer drug depot have been investigated. The results show that the number and concentration of amino acids play a role in amyloid-like aggregates' properties. Further, the aggregates when formulated with cisplatin-induced significant lung cancer cell toxicity compared to an equal amount of cisplatin with and without ultrasound. The study would serve as a platform for further investigation on RIP1/RIP3 peptide and protein aggregates, their role in multiple cellular functions and diseases, and their potential as drug depots.

Protein adduction causes non-mutational inhibition of p53 tumor suppressor

p53 is a key tumor suppressor that is frequently mutated in human tumors. In this study, we investigated how p53 is regulated in precancerous lesions prior to mutations in the p53 gene. Analyzing esophageal cells in conditions of genotoxic stress that promotes development of esophageal adenocarcinoma, we find that p53 protein is adducted with reactive isolevuglandins (isoLGs), products of lipid peroxidation. Modification of p53 protein with isoLGs diminishes its acetylation and binding to the promoters of p53 target genes causing modulation of p53-dependent transcription. It also leads to accumulation of adducted p53 protein in intracellular amyloid-like aggregates that can be inhibited by isoLG scavenger 2-HOBA in vitro and in vivo. Taken together, our studies reveal a posttranslational modification of p53 protein that causes molecular aggregation of p53 protein and its non-mutational inactivation in conditions of DNA damage that may play an important role in human tumorigenesis.

Excess Absorbance as a Novel Approach for Studying the Self-Aggregation of Vital Dyes in Liquid Solution

In the present paper, a simple method for analyzing the self-aggregation of dyes in a solution by a UV-visible absorption measurements is proposed. The concept of excess absorbance is introduced to determine an equation whose coefficients determine the parameters of the aggregation equilibrium. The computational peculiarities of the model are first discussed theoretically and then applied to sodium fluorescein in polar protic and aprotic solvents, as well as in aqueous solutions of methylene blue, which is a cationic dye. Although the experimental responses are very different, the model appears to work equally well in both cases. The model reveals that the trimer is the most likely configuration in both solvents. Furthermore, aggregation is strongly favored for the protic solvent. Interestingly, the model establishes that in aqueous solutions of methylene blue, the tetramer is the predominant form, which has long been assumed and recently demonstrated with sophisticated computational techniques.

Design of a microfluidic mixer channel: First steps into creating a fluorescent dye-based biosensor for mAb aggregate detection

A major challenge in the transition to continuous biomanufacturing is the lack of process analytical technology (PAT) tools which are able to collect real-time information on the process and elicit a response to facilitate control. One of the critical quality attributes (CQAs) of interest during monoclonal antibodies production is aggregate formation. The development of a real-time PAT tool to monitor aggregate formation is then crucial to have immediate feedback and process control. Miniaturized sensors placed after each unit operation can be a powerful solution to speed up an analytical measurement due to their characteristic short reaction time. In this work, a micromixer structure capable of mixing two streams is presented, to be employed in the detection of mAb aggregates using fluorescent dyes. Computational fluid dynamics (CFD) simulations were used to compare the mixing performance of a series of the proposed designs. A final design of a zigzag microchannel with 45° angle was reached and this structure was subsequently fabricated and experimentally validated with colour dyes and, later, with a FITC-IgG molecule. The designed zigzag micromixer presents a mixing index of around 90%, obtained in less than 30 seconds. Therefore, a micromixer channel capable of a fast and efficient mixing is hereby demonstrated, to be used as a real-time PAT tool for a fluorescence based detection of protein aggregation.

Analysis of Biologics Molecular Descriptors towards Predictive Modelling for Protein Drug Development Using Time-Gated Raman Spectroscopy

Pharmaceutical proteins, compared to small molecular weight drugs, are relatively fragile molecules, thus necessitating monitoring protein unfolding and aggregation during production and post-marketing. Currently, many analytical techniques take offline measurements, which cannot directly assess protein folding during production and unfolding during processing and storage. In addition, several orthogonal techniques are needed during production and market surveillance. In this study, we introduce the use of time-gated Raman spectroscopy to identify molecular descriptors of protein unfolding. Raman spectroscopy can measure the unfolding of proteins in-line and in real-time without labels. Using K-means clustering and PCA analysis, we could correlate local unfolding events with traditional analytical methods. This is the first step toward predictive modeling of unfolding events of proteins during production and storage.

Surface cysteine to serine substitutions in IL-18 reduce aggregation and enhance activity

Background

Interleukin-18 (IL-18) is prone to form multimers resulting in inactive aggregates, making this cytokine unstable for clinical use. Therefore, mutations have been introduced into recombinant IL-18 to overcome this issue.

Methods

To prevent the formation of disulfide bonds between the IL-18 molecules, multiple mutations targeting surface cysteines (C38, C68, C76, and C127) were introduced into our previously modified human IL-18 double mutant E6K+T63A (IL-18 DM) by direct gene synthesis. The open reading frames of IL-18 wild-type (WT), IL-18 DM, and IL-18 multiple mutant E6K+T63A+C38S+C68S+C76S+C127S (IL-18 DM1234) were inserted in the pET28a expression vector and transformed into Escherichia coli Rosetta2 (DE3) pLysS cells for protein production. The inclusion bodies of WT and mutated IL-18 were extracted by sonication and refolded by stepwise dialysis using 8 M urea as the starting concentration. The refolded IL-18 proteins were tested for aggregation using the ProteoStat protein aggregation assay. Their activity was also investigated by treating NK-92MI cells with each IL-18 at concentrations of 75, 150, and 300 ng/ml with 0.5 ng/ml of human IL-12 and interferon-gamma (IFN-γ) levels in the supernatant were evaluated using ELISA. The structure of modified IL-18 was visualized using molecular dynamics (MD) simulations.

Results

IL-18 DM1234 exhibited the lowest aggregation signal, approximately 1.79- and 1.63-fold less than that of the WT and IL-18 DM proteins. Additionally, the IFN-γ inducing activity of IL-18 DM1234 was about 10 and 2.8 times higher than that of the WT and IL-18 DM, respectively. MD simulations revealed that binding site I of IL-18 DM1234 was altered mainly due to surface cysteine replacement with serine (C-to-S substitution). This is the first report showing that C-to-S substitutions in IL-18 improved its activity and stability, suggesting the use of this modified IL-18 for medical purposes in the future.

Thermal Shift Assay for Small GTPase Stability Screening: Evaluation and Suitability

Thermal unfolding methods are commonly used as a predictive technique by tracking the protein's physical properties. Inherent protein thermal stability and unfolding profiles of biotherapeutics can help to screen or study potential drugs and to find stabilizing or destabilizing conditions. Differential scanning calorimetry (DSC) is a 'Gold Standard' for thermal stability assays (TSA), but there are also a multitude of other methodologies, such as differential scanning fluorimetry (DSF). The use of an external probe increases the assay throughput, making it more suitable for screening studies, but the current methodologies suffer from relatively low sensitivity. While DSF is an effective tool for screening, interpretation and comparison of the results is often complicated. To overcome these challenges, we compared three thermal stability probes in small GTPase stability studies: SYPRO Orange, 8-anilino-1-naphthalenesulfonic acid (ANS), and the Protein-Probe. We studied mainly KRAS, as a proof of principle to obtain biochemical knowledge through TSA profiles. We showed that the Protein-Probe can work at lower concentration than the other dyes, and its sensitivity enables effective studies with non-covalent and covalent drugs at the nanomolar level. Using examples, we describe the parameters, which must be taken into account when characterizing the effect of drug candidates, of both small molecules and Designed Ankyrin Repeat Proteins.

The Number and Distinct Clustering Patterns of Voltage-Gated Calcium Channels in Nerve Terminals

Upon the arrival of action potentials at nerve terminals, neurotransmitters are released from synaptic vesicles (SVs) by exocytosis. Ca V 2.1, 2.2, and 2.3 are the major subunits of the voltage-gated calcium channel (VGCC) responsible for increasing intraterminal calcium levels and triggering SV exocytosis in the central nervous system (CNS) synapses. The two-dimensional analysis of Ca V 2 distributions using sodium dodecyl sulfate (SDS)-digested freeze-fracture replica labeling (SDS-FRL) has revealed their numbers, densities, and nanoscale clustering patterns in individual presynaptic active zones. The variation in these properties affects the coupling of VGCCs with calcium sensors on SVs, synaptic efficacy, and temporal precision of transmission. In this study, we summarize how the morphological parameters of Ca V 2 distribution obtained using SDS-FRL differ depending on the different types of synapses and could correspond to functional properties in synaptic transmission.

Functionalized resorcinarenes effectively disrupt the aggregation of αA66-80 crystallin peptide related to cataracts

Cataracts, an eye lens clouding disease, are debilitating and while operable, remain without a cure. αA66-80 crystallin peptide abundant in cataracted eye lenses contributes to aggregation of αA-crystallin protein leading to cataracts. Inspired by the versatility of macrocycles and programmable guest selectivity through discrete functionalizations, we report on three water-soluble ionic resorcinarene receptors (A, B, and C) that disrupt the aggregation of αA66-80 crystallin peptide. A and B each possess four anionic sulfonate groups, while C includes four cationic ammonium groups with four flexible extended benzyl groups. Through multiple non-covalent attractions, these receptors successfully disrupt and reverse the aggregation of αA66-80 crystallin peptide, which was studied through spectroscopic, spectrometric, calorimetric, and imaging techniques. The αA66-80·receptor complexes were also explored using molecular dynamics simulation, and binding energies were calculated. Even though each of the three receptors can bind with the peptide, receptor C was characterized by the highest binding energy and affinity for three different domains of the peptide. In effect, the most efficient inhibitor was a cationic receptor C via extended aromatic interactions. These results highlight the potential of versatile and tunable functionalized resorcinarenes as potential therapeutics to reverse the aggregation of α-crystallin dominant in eye cataracts.

Exploring the limits of conventional small-scale CHO fed-batch for accelerated on demand monoclonal antibody production

In the field of therapeutic antibody production, diversification of fed-batch strategies is flourishing in response to the market demand. All manufacturing approaches tend to follow the generally accepted dogma of increasing titer since it directly increases manufacturing output. While titer is influenced by the biomass (expressed as IVCD), the culture time and the cell-specific productivity (q_P), we changed independently each of these parameters to tune our process strategy towards adapted solutions to individual manufacturing needs. To do so, we worked separately on the increase of the IVCD as high seeding fed-batch capacity. Yet, as intensified fed-batch may not always be possible due to limited facility operational mode, we also separately increased the q_P with the addition of specific media additives. Both strategies improved titer by 100% in 14 days relative to the standard fed-batch process with moderate and acceptable changes in product quality attributes. Since intensified fed-batch could rival the cell-specific productivity of a conventional fed-batch, we developed novel hybrid strategies to either allow for acceptable seeding densities without compromising productivity, or alternatively, to push the productivity the furthest in order to reduce timelines.

Aggregation and Size Attributes Analysis of Unadsorbed and Adjuvant-adsorbed Antigens using a Multispectral Imaging Flow Cytometer Platform

Various vaccine quality attributes should be monitored to ensure consistency, potency, purity, and safety of vaccine products prior to lot release. Vaccine particle size and protein antigen aggregation are two important considerations for particle-adsorbed vaccines. In this study, we evaluated the use of imaging flow cytometry as a potential all-in-one platform to measure adjuvant particle size and to detect protein aggregates through a combination of brightfield microscopy, side scatter detection, and fluorescence microscopy. An aluminum phosphate adjuvant was analyzed for size using the brightfield function, and the size measurement was compared against laser diffraction. Heat-induced protein aggregates of either unadsorbed antigens or aluminum phosphate adjuvant-adsorbed antigens were stained with the fluorescent ProteoStat aggregation dye, followed by detection and analysis using a combination of the brightfield and fluorescence microscopy functions. The change in aggregation of unadsorbed antigens was confirmed using dynamic light scattering. These results demonstrate the versatility of the imaging flow cytometry platform for the evaluation of multiple vaccine quality characteristics.

Sensitive, homogeneous, and label-free protein-probe assay for antibody aggregation and thermal stability studies

Protein aggregation is a spontaneous process affected by multiple external and internal properties, such as buffer composition and storage temperature. Aggregation of protein-based drugs can endanger patient safety due, for example, to increased immunogenicity. Aggregation can also inactivate protein drugs and prevent target engagement, and thus regulatory requirements are strict regarding drug stability monitoring during manufacturing and storage. Many of the current technologies for aggregation monitoring are time- and material-consuming and require specific instruments and expertise. These types of assays are not only expensive, but also unsuitable for larger sample panels. Here we report a label-free time-resolved luminescence-based method using an external Eu³⁺-conjugated probe for the simple and fast detection of protein stability and aggregation. We focused on monitoring the properties of IgG, which is a common format for biological drugs. The Protein-Probe assay enables IgG aggregation detection with a simple single-well mix-and-measure assay performed at room temperature. Further information can be obtained in a thermal ramping, where IgG thermal stability is monitored. We showed that with the Protein-Probe, trastuzumab aggregation was detected already after 18 hours of storage at 60°C, 4 to 8 days earlier compared to SYPRO Orange- and UV250-based assays, respectively. The ultra-high sensitivity of less than 0.1% IgG aggregates enables the Protein-Probe to reduce assay time and material consumption compared to existing techniques.

Chemical Chaperones Modulate the Formation of Metabolite Assemblies

The formation of amyloid-like structures by metabolites is associated with several inborn errors of metabolism (IEMs). These structures display most of the biological, chemical and physical properties of protein amyloids. However, the molecular interactions underlying the assembly remain elusive, and so far, no modulating therapeutic agents are available for clinical use. Chemical chaperones are known to inhibit protein and peptide amyloid formation and stabilize misfolded enzymes. Here, we provide an in-depth characterization of the inhibitory effect of osmolytes and hydrophobic chemical chaperones on metabolite assemblies, thus extending their functional repertoire. We applied a combined in vivo-in vitro-in silico approach and show their ability to inhibit metabolite amyloid-induced toxicity and reduce cellular amyloid content in yeast. We further used various biophysical techniques demonstrating direct inhibition of adenine self-assembly and alteration of fibril morphology by chemical chaperones. Using a scaffold-based approach, we analyzed the physiochemical properties of various dimethyl sulfoxide derivatives and their role in inhibiting metabolite self-assembly. Lastly, we employed whole-atom molecular dynamics simulations to elucidate the role of hydrogen bonds in osmolyte inhibition. Our results imply a dual mode of action of chemical chaperones as IEMs therapeutics, that could be implemented in the rational design of novel lead-like molecules.

Pathomechanism Characterization and Potential Therapeutics Identification for Parkinson's Disease Targeting Neuroinflammation

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by the loss of dopaminergic (DAergic) neurons and the presence of α-synuclein-containing Lewy bodies. The unstructured α-synuclein forms insoluble fibrils and aggregates that result in increased reactive oxygen species (ROS) and cellular toxicity in PD. Neuroinflammation engaged by microglia actively contributes to the pathogenesis of PD. In this study, we showed that VB-037 (a quinoline compound), glycyrrhetic acid (a pentacyclic triterpenoid), Glycyrrhiza inflata (G. inflata, a Chinese herbal medicine), and Shaoyao Gancao Tang (SG-Tang, a formulated Chinese medicine) suppressed the nitric oxide (NO) production and interleukin (IL)-1β maturation in α-synuclein-stimulated BV-2 cells. Mouse inflammation antibody array further revealed increased IL-1α, IL-1β, tumor necrosis factor (TNF)-α, interferon (IFN)-γ, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) expression in α-synuclein-inflamed BV-2 cells and compound pretreatment effectively reduced the expression and release of these pro-inflammatory mediators. The test compounds and herbal medicines further reduced α-synuclein aggregation and associated oxidative stress, and protected cells against α-synuclein-induced neurotoxicity by downregulating NLR family pyrin domain containing 1 (NLRP1) and 3 (NLRP3), caspase 1, IL-1β, IL-6, and associated nuclear factor (NF)-κB inhibitor alpha (IκBα)/NF-κB P65 subunit (P65), c-Jun N-terminal kinase (JNK)/proto-oncogene c-Jun (JUN), mitogen-activated protein kinase 14 (P38)/signal transducer and activator of transcription 1 (STAT1) and Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathways in dopaminergic neurons derived from α-synuclein-expressing SH-SY5Y cells. Our findings indicate the potential of VB-037, glycyrrhetic acid, G. inflata, and SG-Tang through mitigating α-synuclein-stimulated neuroinflammation in PD, as new drug candidates for PD treatment.

The possible effect of silver nanoparticles on glyceraldehyde-3-phosphate dehydrogenase activity and formation of amyloid-like aggregates in MCF-7 cell line

Silver nanoparticles (AgNPs) are widely used in medicine, however, the underlying mechanisms of their action on cellular signaling have not been completely determined, and fundamental studies are required to clarify them. We aimed to investigate AgNPs effects on glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as both the internal control gene and the redox-sensitive enzyme involved in apoptosis-related pathways and the formation of amyloid aggregates. To achieve this purpose, MCF-7 cells were treated with different concentrations (0, 3, 22, and 200 μg/ml) of AgNPs and then cell viability, generation of reactive oxygen species (ROS), induction of apoptosis, expression of GAPDH gene, the formation of amyloid aggregates, and GAPDH activity were assessed. The results indicated that treatment with AgNPs significantly reduced cell viability and increased apoptosis in a dose-dependent manner. The ROS levels increased at lower concentrations of AgNPs (up to 22 μg/ml) and during short-term exposure (30 min). The level of GAPDH gene expression was significantly upregulated by 1.22, 1.47, and 1.56 fold, in the concentrations of 3, 22, and 200 μg/ml, respectively. The amount of amyloid aggregates was significantly increased in a dose-dependent manner. The results of enzyme activity showed that AgNPs were affected on the activity of GAPDH protein, however, it has fluctuated that could not be interpreted by our limited data. In conclusion, our results suggested that AgNPs could affect the GAPDH gene expression and enzyme activity, therefore the selection of GAPDH as a gene and protein internal control in the (AgNPs)-related studies requires careful consideration. Additionally, AgNPs may cause apoptosis due to the increase in the production of amyloid aggregates.

78 kDa Glucose-Regulated Protein Attenuates Protein Aggregation and Monocyte Adhesion Induced by Angiotensin II in Vascular Cells

Investigations of vascular smooth muscle cell (VSMC) phenotypic modulation due to angiotensin II (AngII) stimulation are important for understanding molecular mechanisms contributing to hypertension and associated vascular pathology. AngII induces endoplasmic reticulum (ER) stress in VSMCs, which has been implicated in hypertensive vascular remodeling. Under ER stress, 78 kDa glucose-regulated protein (GRP78) acts as an endogenous chaperone, as well as a master controller of unfolded protein response (UPR) to maintain protein quality control. However, the potential downstream consequences of ER stress induced by AngII on protein quality control and pro-inflammatory phenotype in VSMCs remain elusive. This study aims to identify protein aggregation as evidence of the disruption of protein quality control in VSMCs, and to test the hypothesis that preservation of proteostasis by overexpression of GRP78 can attenuate the AngII-induced pro-inflammatory phenotype in VSMCs. Increases in protein aggregation and enhanced UPR were observed in VSMCs exposed to AngII, which were mitigated by overexpression of GRP78. Moreover, GRP78 overexpression attenuated enhanced monocyte adhesion to VSMCs induced by AngII. Our results thus indicate that the prevention of protein aggregation can potentially mitigate an inflammatory phenotype in VSMCs, which may suggest an alternative therapy for the treatment of AngII-associated vascular disorders.

Effective Gold Nanoparticle-Antibody-Mediated Drug Delivery for Photodynamic Therapy of Lung Cancer Stem Cells

Cancer stem cells (CSCs) are a leading contributor to lung cancer mortality rates. CSCs are responsible for tumor growth and recurrence through inhibition of drug-induced cell death, decreasing the effect of traditional cancer therapy and photodynamic therapy (PDT). PDT can be improved to successfully treat lung cancer by using gold nanoparticles (AuNPs), due to their size and shape, which have been shown to facilitate drug delivery and retention, along with the targeted antibody (Ab) mediated selection of CSCs. In this study, a nanobioconjugate (NBC) was constructed, using a photosensitizer (PS) (AlPcS₄Cl), AuNPs and Abs. The NBC was characterized, using spectroscopy techniques. Photodynamic effects of the NBC on lung CSCs was evaluated, using biochemical assays 24 h post-irradiation, in order to establish its anticancer effect. Results showed successful conjugation of the nanocomposite. Localization of the NBC was seen to be in integral organelles involved in cell homeostasis. Biochemical responses of lung CSCs treated using AlPcS₄Cl-AuNP and AlPcS₄Cl-AuNP-Ab showed significant cell toxicity and cell death, compared to free AlPcS₄Cl. The PDT effects were enhanced when using the NBC, showing significant lung CSC destruction to the point of eradication.

Lactulose and Melibiose Inhibit α-Synuclein Aggregation and Up-Regulate Autophagy to Reduce Neuronal Vulnerability

Parkinson's disease (PD) is a neurodegenerative disease characterized by selective dopaminergic (DAergic) neuronal degeneration in the substantia nigra (SN) and proteinaceous α-synuclein-positive Lewy bodies and Lewy neuritis. As a chemical chaperone to promote protein stability and an autophagy inducer to clear aggregate-prone proteins, a disaccharide trehalose has been reported to alleviate neurodegeneration in PD cells and mouse models. Its trehalase-indigestible analogs, lactulose and melibiose, also demonstrated potentials to reduce abnormal protein aggregation in spinocerebellar ataxia cell models. In this study, we showed the potential of lactulose and melibiose to inhibit α-synuclein aggregation using biochemical thioflavin T fluorescence, cryogenic transmission electron microscopy (cryo-TEM) and prokaryotic split Venus complementation assays. Lactulose and melibiose further reduced α-synuclein aggregation and associated oxidative stress, as well as protected cells against α-synuclein-induced neurotoxicity by up-regulating autophagy and nuclear factor, erythroid 2 like 2 (NRF2) pathway in DAergic neurons derived from SH-SY5Y cells over-expressing α-synuclein. Our findings strongly indicate the potential of lactulose and melibiose for mitigating PD neurodegeneration, offering new drug candidates for PD treatment.

Low pH Exposure During Immunoglobulin G Purification Methods Results in Aggregates That Avidly Bind Fcγ Receptors: Implications for Measuring Fc Dependent Antibody Functions

Evaluating the biophysical and functional nature of IgG is key to defining correlates of protection in infectious disease, and autoimmunity research cohorts, as well as vaccine efficacy trials. These studies often require small quantities of IgG to be purified from plasma for downstream analysis with high throughput immunoaffinity formats which elute IgG at low-pH, such as Protein G and Protein A. Herein we sought to compare Protein G purification of IgG with an immunoaffinity method which elutes at physiological pH (Melon Gel). Critical factors impacting Fc functionality with the potential to significantly influence FcγR binding, such as IgG subclass distribution, N-glycosylation, aggregation, and IgG conformational changes were investigated and compared. We observed that transient exposure of IgG to the low-pH elution buffer, used during the Protein G purification process, artificially enhanced recognition of Fcγ Receptors (FcγRs) as demonstrated by Surface Plasmon Resonance (SPR), FcγR dimer ELISA, and a functional cell-based assay. Furthermore, low-pH exposed IgG caused conformational changes resulting in increased aggregation and hydrophobicity; factors likely to contribute to the observed enhanced interaction with FcγRs. These results highlight that methods employed to purify IgG can significantly alter FcγR-binding behavior and biological activity and suggest that the IgG purification approach selected may be a previously overlooked factor contributing to the poor reproducibility across current assays employed to evaluate Fc-mediated antibody effector functions.