Andrographolide inhibits human serum albumin fibril formations through site-specific molecular interactions
30 Aug 2018-RSC Advances (The Royal Society of Chemistry)-Vol. 8, Iss: 54, pp 30717-30724
TL;DR: The results demonstrated that the compound possesses anti-amyloidogenic properties and can be promising against some human degenerative diseases.
Abstract: Protein misfolding and fibrillation are the fundamental traits in degenerative diseases like Alzheimer's, Parkinsonism, and diabetes mellitus Bioactives such as flavonoids and terpenoids from plant sources are known to express protective effects against an array of diseases including diabetes, Alzheimer's and obesity Andrographolide (AG), a labdane diterpenoid is prescribed widely in the Indian and Chinese health care systems for classical efficacy against a number of degenerative diseases This work presents an in depth study on the effects of AG on protein fibrillating pathophysiology Thioflavin T fluorescence spectroscopy and DLS results indicated concentration dependent inhibition of human serum albumin (HSA) fibrillation The results were confirmed by electron microscopy studies HSA fibril formations were markedly reduced in the presence of AG Fluorescence studies and UV-Vis experiments confirmed further that AG molecularly interacts with HSA at site In silico molecular docking studies revealed hydrogen bonding and hydrophobic interactions with HSA in the native state Thus AG interacts with HSA, stabilizes the native protein structure and inhibits fibrillation The results demonstrated that the compound possesses anti-amyloidogenic properties and can be promising against some human degenerative diseases
TL;DR: Wang et al. as discussed by the authors presented a comprehensive review of andrographis paniculata (Burm. f. ex Nees), including its pharmacology, pharmacokinetics, toxicity and pharmaceutical researches.
Abstract: Andrographis paniculata (Burm. f.) Wall. ex Nees, a renowned herb medicine in China, is broadly utilized in traditional Chinese medicine (TCM) for the treatment of cold and fever, sore throat, sore tongue, snake bite with its excellent functions of clearing heat and toxin, cooling blood and detumescence from times immemorial. Modern pharmacological research corroborates that andrographolide, the major ingredient in this traditional herb, is the fundamental material basis for its efficacy. As the main component of Andrographis paniculata (Burm. f.) Wall. ex Nees, andrographolide reveals numerous therapeutic actions, such as antiinflammatory, antioxidant, anticancer, antimicrobial, antihyperglycemic and so on. However, there are scarcely systematic summaries on the specific mechanism of disease treatment and pharmacokinetics. Moreover, it is also found that it possesses easily ignored security issues in clinical application, such as nephrotoxicity and reproductive toxicity. Thereby it should be kept a lookout over in clinical. Besides, the relationship between the efficacy and security issues of andrographolide should be investigated and evaluated scientifically. In this review, special emphasis is given to andrographolide, a multifunctional natural terpenoids, including its pharmacology, pharmacokinetics, toxicity and pharmaceutical researches. A brief overview of its clinical trials is also presented. This review intends to systematically and comprehensively summarize the current researches of andrographolide, which is of great significance for the development of andrographolide clinical products. Noteworthy, those un-cracked issues such as specific pharmacological mechanisms, security issues, as well as the bottleneck in clinical transformation, which detailed exploration and excavation are still not to be ignored before achieving integration into clinical practice. In addition, given that current extensive clinical data do not have sufficient rigor and documented details, more high-quality investigations in this field are needed to validate the efficacy and/or safety of many herbal products.
TL;DR: Docking results suggested that both the flavonoids interact with various amino acid residues of subdomain IIA including glycation prone lysines and arginines via non-covalent forces and further stabilized the structure of HSA, which further explains their mechanisms of action as antiglycating and antifibrillating agents.
Abstract: The post-translational modification of proteins by nonenzymatic glycation (NEG) and the accumulation of AGEs are the two underlying factors associated with the long-term pathogenesis in diabetes. Glyoxal (GO) is a reactive intermediate which has the ability to modify proteins and generate AGEs at a faster rate. Human serum albumin (HSA) being the most abundant serum protein has a higher chance to be modified by NEG. The key objective of the present study is to investigate the potency of chrysin and luteolin as antiglycating and antifibrillating agents in the GO-mediated glycation and fibril formation of HSA. AGEs formation were confirmed from the absorption and fluorescence spectral measurements. Both the flavonoids were able to quench the AGEs fluorescence intensity in vitro indicating the antiglycating nature of the molecules. The formation of fibrils in the GO-modified HSA was confirmed by the Thioflavin T (ThT) fluorescence assay and the flavonoids were found to exihibit the antifibrillation properties in vitro. Docking results suggested that both the flavonoids interact with various amino acid residues of subdomain IIA including glycation prone lysines and arginines via non-covalent forces and further stabilized the structure of HSA, which further explains their mechanisms of action as antiglycating and antifibrillating agents.
TL;DR: In this paper, Andrographolide nanocrystals (AGNC) were prepared through solvent-diffusion followed by homogenization, which led to significant increase of aqueous solubility and intestinal permeation ex vivo.
Abstract: Andrographolide (AG) is a labdane di-terpenoid obtained from aerial parts of Andrographis paniculata. Though known as a potent bioactive in a myriad of biological conditions, the applications of AG in translational medicine are mostly limited due to its low aqueous solubility and poor bioavailability. Nanocrystal technology was envisaged as a possible solution. Andrographolide nanocrystals (AGNC) were prepared through solvent-diffusion followed by homogenization. AGNC hydrodynamic diameter of 630 ± 12 nm and crystallinity changes led to significant increase of aqueous solubility and intestinal permeation ex vivo. Pharmacodynamic studies on mice showed that AGNC exerted hepatoprotective activity at a lower dose against paracetamol induced liver injury, in comparison to crude AG. The work highlighted that nanocrystal technology can be considered as one platform for circumventing the biopharmaceutical limitations of AG. This also ensures significant successes in biological applications.
TL;DR: Wang et al. as discussed by the authors designed and prepared highly stabilized AND nanocrystals (AND-MPN Ns) with high drug loading capacity to facilitate the clinical application of AND. Andrographolide is a potent anti-inflammatory drug that can reduce pro-inflammatory cytokines and suppress NF-κB /MAPK pathway in activated macrophages.
Abstract: Macrophages play a crucial role in initiating, maintaining, and resolving inflammation through the phenotypic shift, inducing or inhibiting the production of inflammatory cytokines. Therefore, macrophages are potential targets for treating inflammatory diseases. Andrographolide (AND) is a potent anti-inflammatory drug that can reduce pro-inflammatory cytokines and suppress NF-κB /MAPK pathway in activated macrophages. Although AND has many medicinal properties, its lower water solubility and first-pass effect in the liver have hindered its clinical application. In this context, by using a metal phenolic network as a stabilizer, we designed and prepared highly stabilized AND nanocrystals (AND-MPN Ns) with high drug loading capacity to facilitate the clinical application of AND. Our findings showed that AND-MPN Ns could be used to enhance the anti-inflammation in-vitro via macrophage polarization, reducing pro-inflammatory cytokines IL-6 and TNF-α, and suppressing the NF-κB signaling pathway activation. The results demonstrated the potential of AND-MPN Ns to combat inflammatory diseases effectively.
TL;DR: Findings have provided some important insights into the binding mechanism of Bra with BSA, and would be helpful in designing suitable agents against amyloid diseases.
Abstract: Free and active concentration of drug in the blood plays a vital role in the disease treatment. Binding of drug to serum albumin, an important transport protein in plasma, usually improves its aqueous solubility, stability and bioactivity. Brazilin (Bra) is a natural compound extracted from Caesalpinia sappan with numerous pharmacological applications, while the behavior of Bra in circulatory system is still unknown. Therefore, in the present work, we firstly examined the interaction of Bra with bovine serum albumin (BSA) using various spectroscopic and computer simulation techniques. The static quenching mechanism and moderate binding affinity (2.18 × 104 M−1 at 298 K) were obtained through fluorescence spectroscopic measurement. Thermodynamic analysis results indicated that hydrophobic interactions and hydrogen bonds played a major role in the binding process. Site marker competitive experiments and molecular simulation suggested that the probable Bra-binding position was located in subdomain IIA of BSA. UV–vis absorption, circular dichroism (CD) and dynamic light scattering (DLS) experiments suggested the conformational changes of BSA induced by Bra. Additionally, the potential of Bra to inhibit the formation of amyloid fibrils, in vitro, has also been analyzed. Thioflavin T (ThT) binding, 8-anilino-1-naphthalenesulfonic acid (ANS) binding, Congo red binding, DLS, CD, fluorescence microscopic image, atomic force microscopy (AFM), size-exclusion chromatography (SEC) and native gel-electrophoresis methods were used, and all confirmed the anti-amyloidogenic behavior of Bra. In short, our findings have provided some important insights into the binding mechanism of Bra with BSA, and would be helpful in designing suitable agents against amyloid diseases.
TL;DR: In this paper, it was shown that the position of the absorption bands of iodine solutions in the visible region moved gradually from violet to brown, the shift being only small in the case of benzene in which the color of iodine is a red-violet.
Abstract: Introduction The various colors of iodine in different solvents have attracted the attention of investigators for over half a century. Beckmann’ showed that the differences are not due to any change in the molecular weight of iodine and suggested solvation as the cause of brown color. Lachman2 supported this explanation, pointing out that the solvents which give a violet color are saturated, those which give brown colors are unsaturated. He stated that small additions of alcohol to a solution of iodine in chloroform suffice to shift the color stepwise from violet to brown. Hildebrand and Glascock3 found that when iodine and an alcohol were both added to a “violet” solvent, bromoform or ethylene bromide, the molal lowering of the freezing point was considerably less than additive, indicating combination of iodine with alcohol. Furthermore, they investigated colorimetrically the equilibria of iodine with ethyl alcohol, ethyl acetate and nitrobenzene dissolved together in a “violet” solvent such as carbon tetrachloride, chloroform or carbon disulfide, and found in each case an equilibrium constant corresponding to a 1 : 1 compound. They calculated the heat of combination in one case. There followed a long series of investigations of the general problem, well summarized by Gmelin4 and in a recent review by Kleinberg and Davidson.6 But the original division of iodine solutions into two or more distinct color classes became untenable with the work of Waentig, Groh’ and \\X7alkers which showed that the position of the absorption bands of iodine solutions in the visible region moved gradually from violet to brown, the shift being only small in the case of benzene in which the color of iodine is a red-violet. We have long been curious about the chemical basis for iodine solvates. It is not a question of dipole moment, as Walkers concluded, for we have recently shown rather conclusively that the iodine solubility, which would be altered by solvation effects, bears little or no relation to the dipole moment of the solvent mole~ule .~ The alcohols are extraordinary dipoles, and their effect is readily understandable, but the case of benzene seemed
TL;DR: Enrichment results demonstrate the importance of the novel XP molecular recognition and water scoring in separating active and inactive ligands and avoiding false positives.
Abstract: A novel scoring function to estimate protein-ligand binding affinities has been developed and implemented as the Glide 4.0 XP scoring function and docking protocol. In addition to unique water desolvation energy terms, protein-ligand structural motifs leading to enhanced binding affinity are included: (1) hydrophobic enclosure where groups of lipophilic ligand atoms are enclosed on opposite faces by lipophilic protein atoms, (2) neutral-neutral single or correlated hydrogen bonds in a hydrophobically enclosed environment, and (3) five categories of charged-charged hydrogen bonds. The XP scoring function and docking protocol have been developed to reproduce experimental binding affinities for a set of 198 complexes (RMSDs of 2.26 and 1.73 kcal/mol over all and well-docked ligands, respectively) and to yield quality enrichments for a set of fifteen screens of pharmaceutical importance. Enrichment results demonstrate the importance of the novel XP molecular recognition and water scoring in separating active and inactive ligands and avoiding false positives.
TL;DR: Thioflavine T associates rapidly with aggregated fibrils of the synthetic β/A4‐derived peptides β( 1–28) and β(1–40), giving rise to a new excitation maximum at 450 nm and enhanced emission at 482 nm, as opposed to the 385 nm and 445 nm of the free dye.
Abstract: Thioflavine T (ThT) associates rapidly with aggregated fibrils of the synthetic beta/A4-derived peptides beta(1-28) and beta(1-40), giving rise to a new excitation (ex) (absorption) maximum at 450 nm and enhanced emission (em) at 482 nm, as opposed to the 385 nm (ex) and 445 nm (em) of the free dye. This change is dependent on the aggregated state as monomeric or dimeric peptides do not react, and guanidine dissociation of aggregates destroys the signal. There was no effect of high salt concentrations. Binding to the beta(1-40) is of lower affinity, Kd 2 microM, while it saturates with a Kd of 0.54 microM for beta(1-28). Insulin fibrils converted to a beta-sheet conformation fluoresce intensely with ThT. A variety of polyhydroxy, polyanionic, or polycationic materials fail to interact or impede interaction with the amyloid peptides. This fluorometric technique should allow the kinetic elucidation of the amyloid fibril assembly process as well as the testing of agents that might modulate their assembly or disassembly.
TL;DR: Crystallographic analysis of 17 different complexes of HSA with a wide variety of drugs and small-molecule toxins reveals the precise architecture of the two primary drug-binding sites on the protein, identifying residues that are key determinants of binding specificity and illuminating the capacity of both pockets for flexible accommodation.
Abstract: Human serum albumin (HSA) is an abundant plasma protein that binds a remarkably wide range of drugs, thereby restricting their free, active concentrations. The problem of overcoming the binding affinity of lead compounds for HSA represents a major challenge in drug development. Crystallographic analysis of 17 different complexes of HSA with a wide variety of drugs and small-molecule toxins reveals the precise architecture of the two primary drug-binding sites on the protein, identifying residues that are key determinants of binding specificity and illuminating the capacity of both pockets for flexible accommodation. Numerous secondary binding sites for drugs distributed across the protein have also been identified. The binding of fatty acids, the primary physiological ligand for the protein, is shown to alter the polarity and increase the volume of drug site 1. These results clarify the interpretation of accumulated drug binding data and provide a valuable template for design efforts to modulate the interaction with HSA.
TL;DR: This work has developed a method called β-structure selection (BeStSel) for the secondary structure estimation that takes into account the twist of β-structures, and can predict the protein fold down to the topology level following the CATH classification from a single CD spectrum.
Abstract: Circular dichroism (CD) spectroscopy is a widely used technique for the study of protein structure. Numerous algorithms have been developed for the estimation of the secondary structure composition from the CD spectra. These methods often fail to provide acceptable results on α/β-mixed or β-structure–rich proteins. The problem arises from the spectral diversity of β-structures, which has hitherto been considered as an intrinsic limitation of the technique. The predictions are less reliable for proteins of unusual β-structures such as membrane proteins, protein aggregates, and amyloid fibrils. Here, we show that the parallel/antiparallel orientation and the twisting of the β-sheets account for the observed spectral diversity. We have developed a method called β-structure selection (BeStSel) for the secondary structure estimation that takes into account the twist of β-structures. This method can reliably distinguish parallel and antiparallel β-sheets and accurately estimates the secondary structure for a broad range of proteins. Moreover, the secondary structure components applied by the method are characteristic to the protein fold, and thus the fold can be predicted to the level of topology in the CATH classification from a single CD spectrum. By constructing a web server, we offer a general tool for a quick and reliable structure analysis using conventional CD or synchrotron radiation CD (SRCD) spectroscopy for the protein science research community. The method is especially useful when X-ray or NMR techniques fail. Using BeStSel on data collected by SRCD spectroscopy, we investigated the structure of amyloid fibrils of various disease-related proteins and peptides.