Genesis of Neurotoxic Hybrid Nanofibers from the Coassembly of Aromatic Amino Acids.

Considering the relevance of accumulation and self-assembly of metabolites and aftermath of biological consequences, it is important to know whether they undergo coassembly and what properties the resultant hybrid higher-order structures would exhibit. This work reveals the inherent tendency of aromatic amino acids to undergo a spontaneous coassembly process under physiologically mimicked conditions, which yields neurotoxic hybrid nanofibers. Resultant hybrid nanostructures resembled the ß-structured conformers stabilized by H-bonds and π-π stacking interactions, which were highly toxic to human neuroblastoma cells. The hybrid nanofibers also showed strong cross-seeding potential that triggered in vitro aggregation of diverse globular proteins and brain extract components, converting the native structures into cross-ß-rich amyloid aggregates. The heterogenic nature of the hybrid nanofibers seems crucial for their higher toxicity and faster cross-seeding potential as compared to the homogeneous amino acid nanofibers. Our findings reveal the importance of aromaticity-driven optimized intermolecular arrangements for the coassembly of aromatic amino acids, and the results may provide important clues to the fundamental understanding of metabolite accumulation-related complications.

Berberine-Based Heterogeneous Linear Supramolecules Neutralized the Acute Nephrotoxicity of Aristolochic Acid by the Self-Assembly Strategy.

Aristolochic acid (AA) has been reported to cause a series of health problems, including aristolochic acid nephropathy and liver cancer. However, AA-containing herbs are highly safe in combination with berberine (Ber)-containing herbs in traditional medicine, suggesting the possible neutralizing effect of Ber on the toxicity of AA. In the present study, in vivo systematic toxicological experiments performed in zebrafish and mice showed that the supramolecule self-assembly formed by Ber and AA significantly reduced the toxicity of AA and attenuated AA-induced acute kidney injury. Ber and AA can self-assemble into linear heterogenous supramolecules (A-B) via electrostatic attraction and π-π stacking, with the hydrophobic groups outside and the hydrophilic groups inside during the drug combination practice. This self-assembly strategy may block the toxic site of AA and hinder its metabolism. Meanwhile, A-B linear supramolecules did not disrupt the homeostasis of gut microflora as AA did. RNA-sequence analysis, immunostaining, and western blot of the mice kidney also showed that A-B supramolecules almost abolished the acute nephrotoxicity of AA in the activation of the immune system and tumorigenesis-related pathways.

Metabolite amyloid-like fibrils interact with model membranes.

Amyloid-like structure formation by various metabolites represents a significant extension of the amyloidogenic building block family. Similar to protein amyloids, metabolite amyloids induce apoptotic toxicity, a process that was linked to membrane association. Here, we demonstrate that metabolite amyloids interact with model membranes and study the mechanism by molecular dynamics.

Exploring Orthogonal Hydrogen Bonding towards Designing Organic-Salt-Based Supramolecular Gelators: Synthesis, Structures, and Anticancer Properties.

A series of primary ammonium monocarboxylate (PAM) salts derived from ß-alanine derivatives of pyrene and naphthalene acetic acid, along with the parent acids, were explored to probe the plausible role of orthogonal hydrogen bonding resulting from amide⋅⋅⋅amide and PAM synthons on gelation. Single-crystal X-ray diffraction (SXRD) studies were performed on two parent acids and five PAM salts in the series. The data revealed that orthogonal hydrogen bonding played an important role in gelation. Structure-property correlation based on SXRD and powder X-ray diffraction data also supported the working hypothesis upon which these gelators were designed. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and cell migration assay on a highly aggressive human breast cancer cell line, MDA-MB-231, revealed that one of the PAM salts in the series, namely, PAA.B2, displayed anticancer properties, and internalization of the gelator salt in the same cell line was confirmed by cell imaging.

Mediation of inflammatory ascites formation induced by macromolecules in mice.

The first 60-min phase of inflammatory ascites formation was studied by intraperitoneally (i.p.) administered macromolecular inducers: yeast cell wall zymosan binds to specific macrophage receptors, polyethyleneimine (PEI) and concanavalin A (ConA), produces non-covalent cross-links on the surface of various cells, while λ-carrageenan may function as a contact activator. Depletion of peritoneal macrophages was performed by overnight pretreatment with diphtheria toxin in transgenic mice, resulting in a significant (p < 0.01) decrease in the induced formation of ascitic fluid. It was shown that induced ascites is mediated partly (PEI, ConA, and carrageenan) or completely (zymosan) by peritoneal macrophages. Inhibition of prostanoid synthesis with indomethacine or of the kallikrein/bradykinin system with aprotinin also produced a significant (p < 0.01) but incomplete inhibition. A slight additivity occurred between the different inhibitory effects. In another series of experiments, the i.p. administration of bradykinin (without a macromolecular inducer) also produced marked ascites, which was not affected by macrophage depletion. The origin of the macrophage-independent part of the induced ascites is best explained by the deformation of the mesothelial cell surface, resulting in signal transfer to the underlying endothelium and the passage of ascitic fluid in the opposite direction. The soluble mediators are represented by prostanoids, bradykinin and other, unidentified agonists.

Water-Soluble Pd8L4 Self-assembled Molecular Barrel as an Aqueous Carrier for Hydrophobic Curcumin.

A tetrafacial water-soluble molecular barrel (1) was synthesized by coordination driven self-assembly of a symmetrical tetrapyridyl donor (L) with a cis-blocked 90° acceptor [cis-(en)Pd(NO3)2] (en = ethane-1,2-diamine). The open barrel structure of (1) was confirmed by single crystal X-ray diffraction. The presence of a hydrophobic cavity with large windows makes it an ideal candidate for encapsulation and carrying hydrophobic drug like curcumin in an aqueous medium. The barrel (1) encapsulates curcumin inside its molecular cavity and protects highly photosensitive curcumin from photodegradation. The photostability of encapsulated curcumin is due to the absorption of a high proportion of the incident photons by the aromatic walls of 1 with a high absorption cross-sectional area, which helps the walls to shield the guest even against sunlight/UV radiations. As compared to free curcumin in water, we noticed a significant increase in solubility as well as cellular uptake of curcumin upon encapsulation inside the water-soluble molecular barrel (1) in aqueous medium. Fluorescence imaging confirmed that curcumin was delivered into HeLa cancer cells by the aqueous barrel (1) with the retention of its potential anticancer activity. While free curcumin is inactive toward cancer cells in aqueous medium at room temperature due to negligible solubility, the determined IC50 value of ∼14 µM for curcumin in aqueous medium in the presence of the barrel (1) reflects the efficiency of the barrel as a potential curcumin carrier in aqueous medium without any other additives. Thus, two major challenges of increasing the bioavailability and stability of curcumin in aqueous medium even in the presence of UV light have been addressed by using a new supramolecular water-soluble barrel (1) as a drug carrier.

Structural and functional properties of prefibrillar α-synuclein oligomers.

The deposition of fibrillar alpha-synuclein (α-syn) within inclusions (Lewy bodies and Lewy neurites) in neurons and glial cells is a hallmark of synucleinopathies. α-syn populates a variety of assemblies ranging from prefibrillar oligomeric species to fibrils whose specific contribution to neurodegeneration is still unclear. Here, we compare the specific structural and biological properties of distinct soluble prefibrillar α-syn oligomers formed either spontaneously or in the presence of dopamine and glutaraldehyde. We show that both on-fibrillar assembly pathway and distinct dopamine-mediated and glutaraldehyde-cross-linked α-syn oligomers are only slightly effective in perturbing cell membrane integrity and inducing cytotoxicity, while mature fibrils exhibit the highest toxicity. In contrast to low-molecular weight and unstable oligomers, large stable α-syn oligomers seed the aggregation of soluble α-syn within reporter cells although to a lesser extent than mature α-syn fibrils. These oligomers appear elongated in shape. Our findings suggest that α-syn oligomers represent a continuum of species ranging from unstable low molecular weight particles to mature fibrils via stable elongated oligomers composed of more than 15 α-syn monomers that possess seeding capacity.

Value of monitoring Nrf2 activity for the detection of chemical and oxidative stress.

Beyond specific limits of exposure, chemical entities can provoke deleterious effects in mammalian cells via direct interaction with critical macromolecules or by stimulating the accumulation of reactive oxygen species (ROS). In particular, these chemical and oxidative stresses can underpin adverse reactions to therapeutic drugs, which pose an unnecessary burden in the clinic and pharmaceutical industry. Novel pre-clinical testing strategies are required to identify, at an earlier stage in the development pathway, chemicals and drugs that are likely to provoke toxicity in humans. Mammalian cells can adapt to chemical and oxidative stress via the action of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), which up-regulates the expression of numerous cell defence genes and has been shown to protect against a variety of chemical toxicities. Here, we provide a brief overview of the Nrf2 pathway and summarize novel experimental models that can be used to monitor changes in Nrf2 pathway activity and thus understand the functional consequences of such perturbations in the context of chemical and drug toxicity. We also provide an outlook on the potential value of monitoring Nrf2 activity for improving the pre-clinical identification of chemicals and drugs with toxic liability in humans.

Data Mining as a Guide for the Construction of Cross-Linked Nanoparticles with Low Immunotoxicity via Control of Polymer Chemistry and Supramolecular Assembly.

The potential immunotoxicity of nanoparticles that are currently being approved, in different phases of clinical trials, or undergoing rigorous in vitro and in vivo characterizations in several laboratories has recently raised special attention. Products with no apparent in vitro or in vivo toxicity may still trigger various components of the immune system unintentionally and lead to serious adverse reactions. Cytokines are one of the useful biomarkers for predicting the effect of biotherapeutics on modulation of the immune system and for screening the immunotoxicity of nanoparticles both in vitro and in vivo, and they were recently found to partially predict the in vivo pharmacokinetics and biodistribution of nanomaterials. Control of polymer chemistry and supramolecular assembly provides a great opportunity for the construction of biocompatible nanoparticles for biomedical clinical applications. However, the sources of data collected regarding immunotoxicities of nanomaterials are diverse, and experiments are usually conducted using different assays under specific conditions. As a result, making direct comparisons nearly impossible, and thus, tailoring the properties of nanomaterials on the basis of the available data is challenging. In this Account, the effects of chemical structure, cross-linking, degradability, morphology, concentration, and surface chemistry on the immunotoxicity of an expansive array of polymeric nanomaterials will be highlighted, with a focus on assays conducted using the same in vitro and in vivo models and experimental conditions. Furthermore, numerical descriptive values have been utilized uniquely to stand for induction of cytokines by nanoparticles. This treatment of available data provides a simple way to compare the immunotoxicities of various nanomaterials, and the values were found to correlate well with published data. On the basis of the polymeric systems investigated in this study, valuable information has been collected that will aid in the future design of nanomaterials for biomedical applications, including the following: (a) the immunotoxicity of nanomaterials is concentration- and dose-dependent; (b) the synthesis of degradable nanoparticles is essential to decrease toxicity;

Melamine-cyanurate complexes and oxidative stress markers in trout kidney following melamine and cyanuric acid long-term co-exposure and withdrawal.

In 2007, renal failure and death in pets were linked to pet food containing both melamine (MEL) and cyanuric acid (CYA). In mammals and fish, the co-administration of MEL and CYA causes renal crystal formation. Moreover, little is known about the process of crystal removal in fish. The aim of this study was to evaluate the formation of MEL-cyanurate crystals in kidney of rainbow trout (Oncorhynchus mykiss) fed combined MEL and CYA diets for 10 weeks at 250, 500 and 1,000 mg/kg in feed (equivalent to 2.5, 5, 10 mg/kg body weight of trout fed 1 % body weight per day). During the exposure trial and throughout a withdrawal period, prooxidant effects of MEL and CYA were evaluated on oxidative stress markers such as catalase, glutathione S-transferase and malondialdehyde. Crystal formation was dose and time dependent, and after six withdrawal weeks, crystals persisted in kidney of trout treated the highest triazine dose. Catalase and glutathione S-transferase activity in kidney of trout exposed to both triazines for 10 weeks indicated that MEL (with or without CYA) can exert a higher prooxidant effect than CYA dispensed singly. Although the enzymes activity increase appears to be reverted after two MEL withdrawal weeks, persistence of crystals may lead to severe damage in renal cells of fish.

Arsenic and selenium toxicity and their interactive effects in humans.

Arsenic (As) and selenium (Se) are unusual metalloids as they both induce and cure cancer. They both cause carcinogenesis, pathology, cytotoxicity, and genotoxicity in humans, with reactive oxygen species playing an important role. While As induces adverse effects by decreasing DNA methylation and affecting protein 53 expression, Se induces adverse effects by modifying thioredoxin reductase. However, they can react with glutathione and S-adenosylmethionine by forming an As-Se complex, which can be secreted extracellularly. We hypothesize that there are two types of interactions between As and Se. At low concentration, Se can decrease As toxicity via excretion of As-Se compound [(GS3)2AsSe](-), but at high concentration, excessive Se can enhance As toxicity by reacting with S-adenosylmethionine and glutathione, and modifying the structure and activity of arsenite methyltransferase. This review is to summarize their toxicity mechanisms and the interaction between As and Se toxicity, and to provide suggestions for future investigations.

Amphiphilic polysialic acid derivatives: synthesis, characterization, and in-vitro cytotoxicity.

Polysialic acid (PSA), a natural hydrophilic polysaccharide, is a potential alternative to poly(ethylene glycol) as the hydrophilic constituent of the polymeric amphiphiles for biomedical applications. In this study, amphiphilic block copolymers were prepared based on PSA as the hydrophilic block and polycaprolactone (PCL) as the hydrophobic block. The block copolymers formed micelles with spherical shapes in an aqueous environment. The average sizes of the nanoparticles were in the range of 270-390 nm, depending on the block length of PCL. The zeta potential values of the micelles were approximately -20 mV due to the negatively charged carboxylic acids of PSA. The nanoparticles showed good stability for five days in a physiological solution (pH 7.4), and had low critical micelle concentration values (1.68-8.54 microg/ml). The in-vitro cytotoxicity tests confirmed that the PSA-PCL micelles had little cytotoxicity. All these results suggest that the PSA-PCL block copolymers can form nano-sized micelles with high stability and low toxicity, implying their high potential for biomedical application.

Cholesterol-peptide hybrids to form liposome-like vesicles for gene delivery.

In this paper, four amphiphilic cholesterol-peptide conjugates (Ch-R5H5, Ch-R3H3, Ch-R5 and Ch-R5) were designed and synthesized, and their properties in gene delivery were evaluated in vitro with an aim of developing more efficient gene delivery carriers. These amphiphilic cholesterol-peptide conjugates are composed of hydrophobic cholesterol and positively charged peptides. They were able to self-assemble into micelles at low concentrations and their critical micelle concentrations in phosphate buffered saline (pH 7.4) are ≤85 µg/mL. Amphiphilic cholesterol-peptide conjugates condensed DNA more efficiently than a hydrophilic cationic oligoarginine (R10) peptide with no hydrophobic segment. Their transfection efficiencies were at least two orders of magnitude greater than that of R10 peptide in HEK-293 cells. Moreover, the introduction of histidine residues in cholesterol-peptide conjugates led to higher gene expression efficiency compared with cholesterol-peptides without histidine (Ch-R5 and Ch-R3), and the luciferase expression level was comparable or even higher than that induced by PEI at its optimal N/P ratio. In particular, Ch-R5H5 condensed DNA into smaller nanoparticles than Ch-R3H3 at higher N/P ratios, and the minimum size of Ch-R5H5/DNA complexes was 180 nm with zeta potential of 23 mV, achieved at the N/P ratio of 30. This liposome-like vesicle may be a promising gene delivery carrier for intravenous therapy.

The mechanical properties and cytotoxicity of cell-laden double-network hydrogels based on photocrosslinkable gelatin and gellan gum biomacromolecules.

A major goal in the application of hydrogels for tissue engineering scaffolds, especially for load-bearing tissues such as cartilage, is to develop hydrogels with high mechanical strength. In this study, a double-network (DN) strategy was used to engineer strong hydrogels that can encapsulate cells. We improved upon previously studied double-network (DN) hydrogels by using a processing condition compatible with cell survival. The DN hydrogels were created by a two-step photocrosslinking using gellan gum methacrylate (GGMA) for the rigid and brittle first network, and gelatin methacrylamide (GelMA) for the soft and ductile second network. We controlled the degree of methacrylation of each polymer so that they obtain relevant mechanical properties as each network. The DN was formed by photocrosslinking the GGMA, diffusing GelMA into the first network, and photocrosslinking the GelMA to form the second network. The formation of the DN was examined by diffusion tests of the large GelMA molecules into the GGMA network, the resulting enhancement in the mechanical properties, and the difference in mechanical properties between GGMA/GelMA single networks (SN) and DNs. The resulting DN hydrogels exhibited the compressive failure stress of up to 6.9 MPa, which approaches the strength of cartilage. It was found that there is an optimal range of the crosslink density of the second network for high strength of DN hydrogels. DN hydrogels with a higher mass ratio of GelMA to GGMA exhibited higher strength, which shows promise in developing even stronger DN hydrogels in the future. Three dimensional (3D) encapsulation of NIH-3T3 fibroblasts and the following viability test showed the cell-compatibility of the DN formation process. Given the high strength and the ability to encapsulate cells, the DN hydrogels made from photocrosslinkable macromolecules could be useful for the regeneration of load-bearing tissues.

Effects of macromolecular crowding on the inhibition of virus assembly and virus-cell receptor recognition.

Biological fluids contain a very high total concentration of macromolecules that leads to volume exclusion by one molecule to another. Theory and experiment have shown that this condition, termed macromolecular crowding, can have significant effects on molecular recognition. However, the influence of molecular crowding on recognition events involving virus particles, and their inhibition by antiviral compounds, is virtually unexplored. Among these processes, capsid self-assembly during viral morphogenesis and capsid-cell receptor recognition during virus entry into cells are receiving increasing attention as targets for the development of new antiviral drugs. In this study, we have analyzed the effect of macromolecular crowding on the inhibition of these two processes by peptides. Macromolecular crowding led to a significant reduction in the inhibitory activity of: 1), a capsid-binding peptide and a small capsid protein domain that interfere with assembly of the human immunodeficiency virus capsid, and 2), a RGD-containing peptide able to block the interaction between foot-and-mouth disease virus and receptor molecules on the host cell membrane (in this case, the effect was dependent on the conditions used). The results, discussed in the light of macromolecular crowding theory, are relevant for a quantitative understanding of molecular recognition processes during virus infection and its inhibition.

Instant coffee with high chlorogenic acid levels protects humans against oxidative damage of macromolecules.

SCOPE: Coffee is among the most frequently consumed beverages. Its consumption is inversely associated to the incidence of diseases related to reactive oxygen species; the phenomenon may be due to its antioxidant properties. Our primary objective was to investigate the impact of consumption of a coffee containing high levels of chlorogenic acids on the oxidation of proteins, DNA and membrane lipids; additionally, other redox biomarkers were monitored in an intervention trial. METHODS AND RESULTS: The treatment group (n=36) consumed instant coffee co-extracted from green and roasted beans, whereas the control consumed water (800 mL/P/day, 5 days). A global statistical analysis of four main biomarkers selected as primary outcomes showed that the overall changes are significant. 8-Isoprostaglandin F2α in urine declined by 15.3%, 3-nitrotyrosine was decreased by 16.1%, DNA migration due to oxidized purines and pyrimidines was (not significantly) reduced in lymphocytes by 12.5 and 14.1%. Other markers such as the total antioxidant capacity were moderately increased; e.g. LDL and malondialdehyde were shifted towards a non-significant reduction. CONCLUSION: The oxidation of DNA, lipids and proteins associated with the incidence of various diseases and the protection against their oxidative damage may be indicative for beneficial health effects of coffee.

Amyloid oligomers: dynamics and toxicity in the cytosol and nucleus.

The accumulation of misfolded proteins in the cytosol and nucleus of neuronal cells leads to neurodegenerative disorders. Polyglutamine diseases are caused by polyglutamine-expanded proteins, whereas mutations in superoxide dismutase 1 lead to amyotrophic lateral sclerosis. These structurally unstable mutant species perturb essential interactions between normal proteins and tend to aggregate because of the presence of exposed hydrophobic surfaces. Accumulating evidence suggests that soluble species, including misfolded monomers and oligomers, are more toxic than large insoluble aggregates or inclusions. Spectroscopic analysis, including fluorescence recovery after photobleaching and fluorescence loss in photobleaching, in living cells revealed that protein aggregates of misfolded proteins are dynamic structures that interact with other proteins, such as molecular chaperones. Fluorescence correlation spectroscopy analysis detected soluble oligomers/aggregates of misfolded proteins in cell extracts. Fluorescence resonance energy transfer analysis supported the notion that soluble oligomers/aggregates are formed before the formation of inclusions in vivo. Here, we reviewed the characteristics of oligomers and aggregates of misfolded proteins, with a particular focus on those revealed by spectroscopic analysis, and discussed how these oligomers may be toxic to cells.

Peptide-mediated cellular uptake of cryptophane.

Cryptophane-A has generated considerable interest based on its high affinity for xenon and potential for creating biosensors for (129)Xe nuclear magnetic resonance (NMR) spectroscopy. Here, we report the cellular delivery of three peptide-functionalized cryptophane biosensors. Cryptophanes were delivered using two cationic cell penetrating peptides into several human cancer and normal cell lines. An RGD peptide targeting alpha(v)beta(3) integrin receptor was shown to increase specificity of cryptophane cell uptake. Labeling the peptides with Cy3 made it possible to monitor cellular delivery using confocal laser scanning microscopy. The peptido-cryptophanes were determined to be relatively nontoxic by MTT assay at the micromolar cryptophane concentrations that are required for (129)Xe NMR biosensing experiments.

Production in vitro of toxic macromolecules by strains of Beauveria bassiana, and purification of a chitosanase-like protein secreted by a melanizing isolate.

The production of macromolecular insecticidal toxins in Adamek's medium by two selected strains of Beauveria bassiana was investigated. Filtrates and dialysates of the melanizing strain 618 were toxic when injected into the lepidopteran insect Galleria mellonella. Separation by DEAE chromatography revealed that peaks eluted respectively with 100 and 200 mM NaCl (P 100 and P 200) had an insecticidal activity and induced cuticular blackening. A hydrophilic protein, Bclp, which causes the formation of brownish spots of the integument, was purified from P 200 by means of chromatographic and electrophoretic methods. Bclp exhibited clear sequence homologies with fungal chitosanases of Fusarium solani. It has a molecular mass of 28 kDa, a pHI of 4 and is thermolabile. Injection of Bclp causes the same cytoxic effects and alterations of the cuticule as those observed during mycosis, and may contribute to the virulence of strain 618. Comparatively, the most obvious characteristic of the weakly melanizing strain 101 is the lack of significant toxic activity of its P 200, which does not contain Bclp. However, this strain secretes other insecticidal molecules active on lepidopterans, presently unidentified.