Gold Nanoclusters Enhance the Efficacy of the Polymer-Based Chaperone in Restoring and Maintaining the Native Conformation of Human Islet Amyloid Polypeptide.

The misfolding and un-natural fibrillation of proteins/peptides are associated with many conformation diseases, such as human islet amyloid polypeptide (hIAPP) in type 2 diabetes (T2D). Inspired by molecular chaperones maintaining protein homeostasis in vivo, many polymer-based artificial chaperones were introduced to regulate protein/peptide folding and fibrillation. However, the pure polymer chaperones prefer to agglomerate into large-size micelles in the physiological environment and thus lose their chaperone functions, which greatly restricts the application of polymer-based chaperones. Here, we designed and prepared a core-shell artificial chaperone based on a dozen poly-(N-isopropylacrylamide-co-N-acryloyl-O-methylated-l-arginine) (PNAMR) anchored on a gold-nanocluster (AuNC) core. The introduction of the AuNC core significantly reduced the size and enhanced the efficacy and stability of polymer-based artificial chaperones. The PNAMR@AuNCs, with a diameter of 2.5 ± 0.5 nm, demonstrated exceptional ability in maintaining the natively unfolded conformation of protein away from the misfolding and the following fibrillation by directly binding to the natively unfolded monomolecular hIAPP and hence in preventing their conversion into toxic oligomers. More excitingly, the PNAMR@AuNCs were able to restore the natural unfolded conformation of hIAPP via dissolving the ß-sheet-rich hIAPP fibrils. Considering the uniform molecular mechanism of protein misfolding and fibrillation in conformation disorders, this finding provides a generic therapeutic strategy for neurodegenerative diseases and other conformation diseases by using PNAMR@AuNC artificial chaperones to restore and maintain the native conformation of amyloid proteins.

Gold nanoclusters eliminate obesity induced by antipsychotics.

Obesity induced by antipsychotics have plagued more than 20 million people worldwide. However, no drug is available to eliminate the obesity induced by antipsychotics. Here we examined the effect and potential mechanisms of a gold nanoclusters (AuNCs) modified by N-isobutyryl-L-cysteine on the obesity induced by olanzapine, the most prescribed but obesogenic antipsychotics, in a rat model. Our results showed that AuNCs completely prevented and reversed the obesity induced by olanzapine and improved glucose metabolism profile in rats. Further mechanism investigations revealed that AuNCs exert its anti-obesity function through inhibition of olanzapine-induced dysfunction of histamine H1 receptor and proopiomelanocortin signaling therefore reducing hyperphagia, and reversing olanzapine-induced inhibition of uncoupling-protein-1 signaling which increases thermogenesis. Together with AuNCs' good biocompatibility, these findings not only provide AuNCs as a promising nanodrug candidate for treating obesity induced by antipsychotics, but also open an avenue for the potential application of AuNCs-based nanodrugs in treating general obesity.

Engineering Nanointerfaces of Au25 Clusters for Chaperone-Mediated Peptide Amyloidosis.

Synthetic nanomaterials possessing biomolecular-chaperone functions are good candidates for modulating physicochemical interactions in many bioapplications. Despite extensive research, no general principle to engineer nanomaterial surfaces is available to precisely manipulate biomolecular conformations and behaviors, greatly limiting attempts to develop high-performance nanochaperone materials. Here, we demonstrate that, by quantifying the length (-SCxR±, x = 3-11) and charges (R- = -COO-, R+ = -NH3+) of ligands on Au25 gold nanochaperones (AuNCs), simulating binding sites and affinities of amyloid-like peptides with AuNCs, and probing peptide folding and fibrillation in the presence of AuNCs, it is possible to precisely manipulate the peptides' conformations and, thus, their amyloidosis via customizing AuNCs nanointerfaces. We show that intermediate-length liganded AuNCs with a specific charge chaperone peptides' native conformations and thus inhibit their fibrillation, while other types of AuNCs destabilize peptides and promote their fibrillation. We offer a microscopic molecular insight into peptide identity on AuNCs and provide a guideline in customizing nanochaperones via manipulating their nanointerfaces.

Isomeric Effect of Nano-Inhibitors on Aß40 Fibrillation at The Nano-Bio Interface.

Chemical and physical properties of nanobio interface substantially affect the conformational transitions of adjacent biomolecules. Previous studies have reported the chiral effect and charge effect of nanobio interface on the misfolding, aggregation, and fibrillation of amyloid protein. However, the isomeric effect of nanobio interface on protein/peptides amyloidosis is still unclear. Here, three isomeric nanobio interfaces were designed and fabricated based on the same sized gold nanoclusters (AuNCs) modified with 4-mercaptobenzoic acid (p-MBA), 3-mercaptobenzoic acid (m-MBA), and 2-mercaptobenzoic acid (o-MBA). Then three isomeric AuNCs were employed as models to explore the isomeric effect on the misfolding, aggregation, and fibrillation of Aß40 at nanobio interfaces. Site-specific replacement experiments on the basis of theoretical analysis revealed the possible mechanism of Aß40 interacting with isomeric ligands of AuNCs at the nanobio interfaces. The distance and orientation of -COOH group from the surface of AuNCs can affect the electrostatic interaction between isomeric ligands and the positively charged residues (R5, K16, and K28) of Aß40, which may affect the inhibition efficiency of isomeric AuNCs on protein amyloidosis. Actually, the amyloid fibrillation kinetics results together with atomic force microscope (AFM) images, dynamic light scattering (DLS) results and circular dichroism (CD) spectra indeed proved that all the three isomeric AuNCs could inhibit the misfolding, aggregation and fibrillation of Aß40 in a dose-dependent manner, and the inhibition efficiency was definitely different from each other. The inhibition efficiency of o-MBA-AuNCs was higher than that of m-MBA-AuNCs and p-MBA-AuNCs at the same dosage. These results provide an insight for isomeric effect at nanobio interfaces, and open an avenue for structure-based nanodrug design target Alzheimer's disease (AD) and even other protein conformational diseases.

Charge effects at nano-bio interfaces: a model of charged gold nanoclusters on amylin fibrillation.

The misfolding and abnormal amyloid fibrillation of proteins/peptides are associated with more than 20 human diseases. Although dozens of nanoparticles have been investigated for the inhibition effect on the misfolding and fibrillation of pathogenesis-related proteins/peptides, there are few reports on charge effects of nano inhibitors on amyloid fibrillation. Herein, same-sized gold nanoclusters modified with 2-aminoethanethiol hydrochloride (CSH-AuNCs, positively charged in pH 7.4) or 3-mercaptopropionic acid (MPA-AuNCs, negatively charged in pH 7.4) were synthesized and adopted as models to explore the charge effect of nano inhibitors on amylin fibrillation at the nano-bio interface. ThT fluorescence kinetics analysis, AFM images and circular dichroism (CD) spectra showed that electropositive CSH-AuNCs inhibited the misfolding and fibrillation of amylin in a dosage-dependent manner, but electronegative MPA-AuNCs accelerated the misfolding and fibrillation of amylin in a dosage-dependent manner. Moreover, the theoretical and experimental results revealed the interaction mechanism between amylin and ligands of AuNCs at the nano-bio interfaces. Electropositive CSH-AuNCs could be bound to the main nucleating region of amylin via hydrogen bonding and endowed the nanocomplex with more positive net charges (amylin monomer with a positive +26.23 ± 0.80 mV zeta potential), which would inhibit the misfolding and aggregation of amylin via electrostatic repulsion and steric hindrance. In contrast, electronegative MPA-AuNCs could absorb electropositive amylin via strong electrostatic attractions, which accelerated the fibrillation process of amylin via enhancing local concentrations. Moreover, cell experiments showed that both the charged AuNCs had good biocompatibility and electronegetive MPA-AuNCs showed a better protective effect in the amylin-induced cell model than electropositive CSH-AuNCs. These results provide an insight into structure-based nanodrug design for protein conformational diseases.

Cichoric acid from witloof inhibit misfolding aggregation and fibrillation of hIAPP.

The misfolding, aggregation and fibrillation of human islet amyloid polypeptide (hIAPP) has been acknowledged as a hallmark event in type-II diabetes. Hence, inhibiting the misfolding, aggregation and fibrillation of hIAPP have been accepted as a vital factor to treat the disease. Here cichoric acid was extracted from witloof to explore its inhibition effects on misfolding, aggregation and fibrillation of hIAPP. Thioflavin-T (ThT) fluorescence assay, dynamic light scattering (DLS) and atomic force microscopy (AFM) images showed that cichoric acid inhibited the aggregation and fibrillation of hIAPP in a dosage-dependent manner. Circular dichroism (CD) spectra showed that cichoric acid inhibited the misfolding of hIAPP from unfolded to ß-sheet. Molecular docking and further experiments revealed interactions between hIAPP and cichoric acid. Cichoric acid could bind to K1 and R11 of hIAPP via electrostatic interaction. In addition, cichoric acid could form π-π stacking with hIAPP residues F15 and F23. These interactions inhibited the misfolding, aggregation and fibrillation of hIAPP. These results, together with cichoric acid's good cytocompatibility and significant protective effects in hIAPP lesioned cell models, not only showed that cichoric acid could be used to fight against amyloidosis, but also brought a new perspective for Chinese herbal medicine as natural compound's medical potential.

Kinetic study of Aß(1-42) amyloidosis in the presence of ganglioside-containing vesicles.

Alzheimer's disease (AD) is characterized by the amyloid-beta peptide (Aß) misfolding to form aberrant amyloid aggregates in the brain. Although recent evidence implicates that amyloid deposition in vivo is highly related to biomembranes, how the characteristic lipid components of neuronal membranes mediate this process remains to be fully elucidated. Herein, we established vesicle models to mimic exosomes and investigated their influence on the kinetics of Aß(1-42) amyloidosis. By using ternary vesicles composed of three brain lipids monosialoganglioside GM1, cholesterol and sphingomyelin, we found that GM1 could regulate peptide fibrillation by facilitating the conformational transition of Aß(1-42), and further quantitatively analyzed the influence of GM1-containing vesicles on the kinetics of Aß(1-42) fibrillation. In addition, GM1-containing vesicles induced the formation of Aß(1-42) fibrils at low concentrations, and these fibrils were toxic to PC12 cells. By analyzing the role of GM1 in this ternary mixture of membranes at the molecular level, we confirmed that GM1 clusters are presented as attachment sites for peptides, thus promoting the fibrillation of Aß(1-42).

Chiral Effect at Nano-Bio Interface: A Model of Chiral Gold Nanoparticle on Amylin Fibrillation.

Protein/Peptide amyloidosis is the main cause of several diseases, such as neurodegenerative diseases. It has been widely acknowledged that the unnatural fibrillation of protein/peptides in vivo is significantly affected by the physical and chemical properties of multiscale biological membranes. For example, previous studies have proved that molecule chirality could greatly influence the misfolding, fibrillation and assembly of ß-Amyloid peptides at the flat liquid-solid surface. However, how the nanoscale chirality influences this process remains unclear. Here we used gold nanoparticles (AuNPs, d = 4 ± 1 nm)-modified with N-isobutyl-L(D)-cysteine (L(D)-NIBC) enantiomers-as a model to illustrate the chiral effect on the amylin fibrillation at nano-bio interface. We reported that both two chiral AuNPs could inhibit amylin fibrillation in a dosage-dependent manner but the inhibitory effect of L-NIBC-AuNPs was more effective than that of D-NIBC-AuNPs. In-situ real time circular dichroism (CD) spectra showed that L-NIBC-AuNPs could inhibit the conformation transition process of amylin from random coils to α-helix, while D-NIBC-AuNPs could only delay but not prevent the formation of α-helix; however, they could inhibit the further conformation transition process of amylin from α-helix to ß-sheet. These results not only provide interesting insight for reconsidering the mechanism of peptides amyloidosis at the chiral interfaces provided by biological nanostructures in vivo but also would help us design therapeutic inhibitors for anti-amyloidosis targeting diverse neurodegenerative diseases.

Olanzapine-induced endoplasmic reticulum stress and inflammation in the hypothalamus were inhibited by an ER stress inhibitor 4-phenylbutyrate.

Antipsychotics are the most important treatment for schizophrenia. However, antipsychotics, particularly olanzapine and clozapine, are associated with severe weight gain/obesity side-effects. Although numerous studies have been carried out to identify the exact mechanisms of antipsychotic-induced weight gain, it is still important to consider other pathways. Endoplasmic reticulum (ER) stress signaling and its associated inflammation pathway is one of the most important pathways involved in regulation of energy balance. In the present study, we examined the role of hypothalamic protein kinase R like endoplasmic reticulum kinase- eukaryotic initiation factor 2α (PERK-eIF2α) signaling and the inflammatory IkappaB kinase ß- nuclear factor kappa B (IKKß-NFκB) signaling pathway in olanzapine-induced weight gain in female rats. In this study, we found that olanzapine significantly activated PERK-eIF2α and IKKß-NFκB signaling in SH-SY5Y cells in a dose-dependent manner. Olanzapine treatment for 8 days in rats was associated with activated PERK-eIF2α signaling and IKKß-NFκB signaling in the hypothalamus, accompanied by increased food intake and weight gain. Co-treatment with an ER stress inhibitor, 4-phenylbutyrate (4-PBA), decreased olanzapine-induced food intake and weight gain in a dose- and time-dependent manner. Moreover, 4-PBA dose-dependently inhibited olanzapine-induced activated PERK-eIF2α and IKKß-NFκB signaling in the hypothalamus. These results suggested that hypothalamic ER stress may play an important role in antipsychotic-induced weight gain.

Chiral ß-HgS quantum dots: Aqueous synthesis, optical properties and cytocompatibility.

ß-HgS quantum dots (QDs) have drawn enormous attention due to the size-tunable bandgap and the lowest quantum state in conduction band which have been applied to semiconductor transistor and photodetector. Though ß-HgS is the essential component of Tibetan medicine, the potential toxicity of ß-HgS limits its applications, especially in bio-application. Herein, chiral biomolecule enantiomers N-isobutyryl-L(D)-cysteine (L(D)-NIBC) and L(D)-cysteine (L(D)-Cys) were introduced into HgCl2 and Na2S aqueous solution to synthesize chiral ß-HgS QDs in one-pot, which significantly improved their water-solubility and cytocompatibility. Notably, all chiral ß-HgS QDs showed none cytotoxicity even at high concentration (20 mg·L-1), and the cytocompatibility of D-ß-HgS QDs was better than corresponding L-ß-HgS QDs at the concentration of 20 mg·L-1. This cytotoxicity discrimination was associated with the chirality inversion of chiral ß-HgS QDs compared with the corresponding chiral ligands. In-situ real-time circular dichroism (CD) monitoring indicated that the chirality of ß-HgS QDs originated from the asymmetrical arrangement of chiral ligands on the achiral core surface. Their chiroptical activity, near-infrared optical absorption (800 nm), fluorescence emission (900-1000 nm), high-performance photothermal conversion and good cytocompatibility, implied chiral ß-HgS QDs could be used as a candidate material for photothermal therapy or a near-infrared fluorescent probe in organism, which brings a novel insight for bio-application of ß-HgS QDs.

Gold nanoclusters for Parkinson's disease treatment.

Drug discovery for Parkinson's disease (PD) is challenging. Here we report that gold nanoclusters (AuNCs) can serve as a novel candidate for the design of anti-PD drugs. With N-isobutyryl-l-cysteine (L-NIBC) protected AuNCs as an example, we show that AuNCs effectively prevent α-Synuclein (α-Syn) fibrillation in in vitro experiments. Cell experiments demonstrate good neuroprotective effects in PD cell models. More significantly, experiments of mouse PD model further show that AuNCs largely ameliorate the behavioral disorders of sick mice. In addition, immunohistochemical and western blot (WB) analyses indicate that AuNCs can significantly reverse dopaminergic (DA) neuron loss in substantia nigra and striatum of sick mice. This study opens up a novel avenue to develop anti-PD drugs and points a new direction for AuNCs in medicinal applications.

The size-effect of gold nanoparticles and nanoclusters in the inhibition of amyloid-ß fibrillation.

A significant pathological signature of Alzheimer's disease (AD) is the deposition of amyloid-ß (Aß) plaques in the brain and the synaptic dysfunction and neurodegeneration associated with it. Compounds or drugs that inhibit Aß fibrillation are thus desirable to develop novel therapeutic strategies against AD. Conventional strategies usually require an elaborate design of their molecular structures. Here we report the size-effect of gold nanoparticles (AuNPs) and nanoclusters (AuNCs) in the inhibition of protein amyloidosis. Using l-glutathione stabilized AuNPs with different sizes and AuNCs as examples, we show that large AuNPs accelerate Aß fibrillation, whereas small AuNPs significantly suppress this process. More interestingly, AuNCs with smaller sizes can completely inhibit amyloidosis. Dynamic light scattering (DLS) experiments show that AuNCs can efficiently prevent Aß peptides from aggregation to larger oligomers (e.g. micelles) and thus avoid nucleation to form fibrils. This is crucially important for developing novel AD therapies because oligomers are the main source of Aß toxicity. This work presents a novel strategy to design anti-amyloidosis drugs, which also provides interesting insights to understand how biological nanostructures participate in vivo in Aß fibrillation from a new perspective.

Chirality-assisted ring-like aggregation of aß(1-40) at liquid-solid interfaces: a stereoselective two-step assembly process.

Molecular chirality is introduced at liquid-solid interfaces. A ring-like aggregation of amyloid Aß(1-40) on N-isobutyryl-L-cysteine (L-NIBC)-modified gold substrate occurs at low Aß(1-40) concentration, while D-NIBC modification only results in rod-like aggregation. Utilizing atomic force microscope controlled tip-enhanced Raman scattering, we directly observe the secondary structure information for Aß(1-40) assembly in situ at the nanoscale. D- or L-NIBC on the surface can guide parallel or nonparallel alignment of ß-hairpins through a two-step process based on electrostatic-interaction-enhanced adsorption and subsequent stereoselective recognition. Possible electrostatic interaction sites (R5 and K16) and a chiral recognition site (H14) of Aß(1-40) are proposed, which may provide insight into the understanding of this effect.