| 31155628 |
Total synthesis and antimalarial activity of mortiamides A-D |
10.1039/c9cc02864a. |
Chem Commun (Camb) |
Total synthesis and antimalarial activity of mortiamides A-D
Abstract
- Mortiamides A-D (1-4) are head-to-tail cyclic heptapeptides that were identified from a novel Mortierella sp. isolate obtained from marine sediments from Northern Canada. Herein we report the first total synthesis of mortiamides A-D (1-4) on a solid support by concomitant cyclization/cleavage without any oligomerization side reactions, and overall yields up to 48%. We also report on the antiplasmodial activity of mortiamides A-D (1-4). We show that three out of the four tested mortiamides (A, B and D) have moderate antiplasmodial activity, while mortiamide D (4) exhibits low micromolar activity.
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| 31180597 |
Effect of natural toxins and adipokinetic hormones on the activity of digestive enzymes in the midgut of the cockroach Periplaneta americana |
10.1002/arch.21586. |
Arch Insect Biochem Physiol |
Effect of natural toxins and adipokinetic hormones on the activity of digestive enzymes in the midgut of the cockroach Periplaneta americana
Abstract
- This study examined the effect of two natural toxins (a venom from the parasitic wasp Habrobracon hebetor and destruxin A from the entomopathogenic fungus Metarhizium anisopliae), and one pathogen (the entomopathogenic fungus Isaria fumosorosea) on the activity of basic digestive enzymes in the midgut of the cockroach Periplaneta americana. Simultaneously, the role of adipokinetic hormones (AKH) in the digestive processes was evaluated. The results showed that all tested toxins/pathogens elicited stress responses when applied into the cockroach body, as documented by an increase of AKH level in the central nervous system. The venom from H. hebetor showed no effect on digestive enzyme activities in the ceca and midgut in vitro. In addition, infection by I. fumosorosea caused a decrease in activity of all enzymes in the midgut and a variable decrease in activity in the ceca; application of AKHs did not reverse the inhibition. Destruxin A inhibited the activity of all enzymes in the midgut but in the ceca in vitro; application of AKHs did reverse this inhibition, and no differences between both cockroach AKHs were found. Overall, the results demonstrated the variable effect of the tested toxins/pathogens on the digestive processes of cockroaches as well as the variable ability of AKH to counteract these effects.
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| 31181107 |
The cyclophilin inhibitor CRV431 inhibits liver HBV DNA and HBsAg in transgenic mice |
10.1371/journal.pone.0217433. |
PLoS One |
The cyclophilin inhibitor CRV431 inhibits liver HBV DNA and HBsAg in transgenic mice
Abstract
- Hepatitis B virus (HBV) infection is a major health burden worldwide with 240 million chronically infected individuals. Nucleos(t)ide analogs and interferons are the current standards of care due to their suppression of HBV replication, but the treatments rarely eradicate HBV from individuals. Similar to current treatments for human immunodeficiency virus type-1 (HIV-1) and hepatitis C virus (HCV) patients, improved HBV therapies will require the combination of multiple drugs which target distinct steps of the HBV life cycle. In this study, we tested the potential of a cyclophilin inhibitor, CRV431, to affect HBV replication in transgenic mice. We found that oral treatment with CRV431 (50 mg/kg/day) for a period of 16 days significantly reduced liver HBV DNA levels and moderately decreased serum HBsAg levels. We observed an additive inhibitory effect on liver HBV DNA levels in mice treated with a combination of low doses of CRV431 (10 mg/kg/day) and the nucleotide prodrug, tenofovir exalidex (TXL), (5 mg/kg/day). No toxicity was observed in CRV431-treated mice. Although it is well known that CRV431 neutralizes the peptidyl-prolyl isomerase activity of cyclophilins, its anti-HBV mechanism(s) of action remains unknown. Nevertheless, this study provides the first demonstration of a beneficial effect of a cyclophilin inhibitor in vivo in an HBV transgenic mouse model. Altogether our data reveal the potential of CRV431 to be part of improved new therapies for HBV patients.
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| 31184497 |
Four pairs of proline-containing cyclic dipeptides from sp. HT88, an endophytic bacterium of L |
10.1080/14786419.2019.1577834. |
Nat Prod Res |
Four pairs of proline-containing cyclic dipeptides from sp. HT88, an endophytic bacterium of L
Abstract
- Strain HT88 was isolated from the fresh stems of , and it was identified as sp. by analyzing its morphology and the 16S rRNA sequence. The extracts of fermented HT88 showed potent antimicrobial activities. Bioassay guided separation of extracts led to eight proline -containing cyclic dipeptides. Their structures were determined by 1D and 2D NMR spectroscopy and ESI mass spectrometry and further comparison with existing H and C NMR, melting points and specific rotation data. The eight 2,5-diketopiperazines (DKPs) were identified as cyclo(-Pro-Leu) (), cyclo(Pro-Leu) (), cyclo(--Hyp--Leu) (), cyclo(--Hyp--Leu) (), and cyclo(-Pro--Phe) (), cyclo(-Pro--Phe) (, and cyclo(--Hyp--Phe) (), cycloHyp-Phe) (), respectively. Up to date, this is the first isolation of four pairs of proline based DKPs from sp.
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| 31214027 |
Periplasmic Expression of 4/7 α-Conotoxin TxIA Analogs in Favors Ribbon Isomer Formation - Suggestion of a Binding Mode at the α7 nAChR |
10.3389/fphar.2019.00577. |
Front Pharmacol |
Periplasmic Expression of 4/7 α-Conotoxin TxIA Analogs in Favors Ribbon Isomer Formation - Suggestion of a Binding Mode at the α7 nAChR
Abstract
- Peptides derived from animal venoms provide important research tools for biochemical and pharmacological characterization of receptors, ion channels, and transporters. Some venom peptides have been developed into drugs (such as the synthetic ω-conotoxin MVIIA, ziconotide) and several are currently undergoing clinical trials for various clinical indications. Challenges in the development of peptides include their usually limited supply from natural sources, cost-intensive chemical synthesis, and potentially complicated stereoselective disulfide-bond formation in the case of disulfide-rich peptides. In particular, if extended structure-function analysis is performed or incorporation of stable isotopes for NMR studies is required, the comparatively low yields and high costs of synthesized peptides might constitute a limiting factor. Here we investigated the expression of the 4/7 α-conotoxin TxIA, a potent blocker at α3β2 and α7 nicotinic acetylcholine receptors (nAChRs), and three analogs in the form of maltose binding protein fusion proteins in . Upon purification via nickel affinity chromatography and release of the toxins by protease cleavage, HPLC analysis revealed one major peak with the correct mass for all peptides. The final yield was 1-2 mg of recombinant peptide per liter of bacterial culture. Two-electrode voltage clamp analysis on oocyte-expressed nAChR subtypes demonstrated the functionality of these peptides but also revealed a 30 to 100-fold potency decrease of expressed TxIA compared to chemically synthesized TxIA. NMR spectroscopy analysis of TxIA and two of its analogs confirmed that the decreased activity was due to an alternative disulfide linkage rather than the missing C-terminal amidation, a post-translational modification that is common in α-conotoxins. All peptides preferentially formed in the ribbon conformation rather than the native globular conformation. Interestingly, in the case of the α7 nAChR, but not the α3β2 subtype, the loss of potency could be rescued by an R5D substitution. In conclusion, we demonstrate efficient expression of functional but alternatively folded ribbon TxIA variants in and provide the first structure-function analysis for a ribbon 4/7-α-conotoxin at α7 and α3β2 nAChRs. Computational analysis based on these data provide evidence for a ribbon α-conotoxin binding mode that might be exploited to design ligands with optimized selectivity.
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| 31263151 |
Two novel cyclic depsipeptides Xenematides F and G from the entomopathogenic bacterium Xenorhabdus budapestensis |
10.1038/s41429-019-0203-y. |
J Antibiot (Tokyo) |
Two novel cyclic depsipeptides Xenematides F and G from the entomopathogenic bacterium Xenorhabdus budapestensis
Abstract
- Two novel depsipeptides xenematides F and G (1, 2), were isolated from entomopathogenic Xenorhabdus budapestensis SN84 along with a known compound xenematide B. The structures of the two new molecules were elucidated using NMR, MS and Marfey's method. The xenematide G (2) contains α-aminoheptanoic acid, a non-protein amino acid that is rarely found in secondary metabolites from entomopathogenic bacteria. Xenematides F and G were tested for antibacterial activity. Xenematide G (2) exhibited moderate antibacterial activity.
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| 31361305 |
Apratoxin S4 Inspired by a Marine Natural Product, a New Treatment Option for Ocular Angiogenic Diseases |
10.1167/iovs.19-26936. |
Invest Ophthalmol Vis Sci |
Apratoxin S4 Inspired by a Marine Natural Product, a New Treatment Option for Ocular Angiogenic Diseases
Abstract
- Abnormal blood vessel formation is a defining feature of many blinding eye diseases. Targeting abnormal angiogenesis by inhibiting VEGF has revolutionized the treatment of many ocular angiogenic diseases over the last decade. However, a substantial number of patients are refractory to anti-VEGF treatment or may develop resistance over time. The objective of this study was to determine the efficacy and the mechanism of action of Apratoxin S4 in ocular angiogenesis.
Retinal vascular cell proliferation, migration, and the ability to form tube-like structure were studied in vitro. Ex vivo aortic ring, choroid, and metatarsal assays were used to study Apratoxin S4's impact on vessel outgrowth in a multicellular environment. Apratoxin S4 was also tested in mouse models of oxygen-induced retinopathy (OIR) and laser-induced choroidal neovascularization (CNV), and in a rabbit model of persistent retinal neovascularization (PRNV). Western blot and ELISA were used to determine the expression of key angiogenic regulators after Apratoxin S4 treatment.
Apratoxin S4 strongly inhibits retinal vascular cell activation by suppressing multiple angiogenic pathways. VEGF-activated vascular cells and angiogenic vessels are more susceptible to Apratoxin S4 treatment than quiescent vascular cells and vessels. Both intraperitoneal and intravitreal delivery of Apratoxin S4 are able to impede ocular neovascularization in vivo. Apratoxin S4 specifically attenuates pathological ocular angiogenesis and exhibits a combinatorial inhibitory effect with standard-of-care VEGF inhibitor drug (aflibercept).
Apratoxin S4 is a potent antiangiogenic drug that inhibits the activation of retinal endothelial cells and pericytes through mediating multiple angiogenic pathways.
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| 31392883 |
An Orbitide from Seed Containing 16 Amino Acid Residues |
10.1021/acs.jnatprod.9b00111. |
J Nat Prod |
An Orbitide from Seed Containing 16 Amino Acid Residues
Abstract
- Cyclic peptides are abundant in plants and have attracted interest due to their bioactivity and potential as drug scaffolds. Orbitides are head-to-tail cyclic peptides that are ribosomally synthesized, post-translationally modified, and lack disulfide bonds. All known orbitides contain 5-12 amino acid residues. Here we describe PLP-53, a novel orbitide from the seed of . PLP-53 consists of 16 amino acids, four residues larger than any known orbitide. NMR structural studies showed that, compared to previously characterized orbitides, PLP-53 is more flexible and, under the studied conditions, did not adopt a single ordered conformation based on analysis of NOEs and chemical shifts.
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| 31406003 |
A Pan-Cyclophilin Inhibitor, CRV431, Decreases Fibrosis and Tumor Development in Chronic Liver Disease Models |
10.1124/jpet.119.261099. |
J Pharmacol Exp Ther |
A Pan-Cyclophilin Inhibitor, CRV431, Decreases Fibrosis and Tumor Development in Chronic Liver Disease Models
Abstract
- Previous studies show that cyclophilins contribute to many pathologic processes, and cyclophilin inhibitors demonstrate therapeutic activities in many experimental models. However, no drug with cyclophilin inhibition as the primary mode of action has advanced completely through clinical development to market. In this study, we present findings on the cyclophilin inhibitor, CRV431, that highlight its potential as a drug candidate for chronic liver diseases. CRV431 was found to potently inhibit all cyclophilin isoforms tested-A, B, D, and G. Inhibitory constant or IC values ranged from 1 to 7 nM, which was up to 13 times more potent than the parent compound, cyclosporine A (CsA), from which CRV431 was derived. Other CRV431 advantages over CsA as a nontransplant drug candidate were significantly diminished immunosuppressive activity, less drug transporter inhibition, and reduced cytotoxicity potential. Oral dosing to mice and rats led to good blood exposures and a 5- to 15-fold accumulation of CRV431 in liver compared with blood concentrations across a wide range of CRV431 dosing levels. Most importantly, CRV431 decreased liver fibrosis in a 6-week carbon tetrachloride model and in a mouse model of nonalcoholic steatohepatitis (NASH). Additionally, CRV431 administration during a late, oncogenic stage of the NASH disease model resulted in a 50% reduction in the number and size of liver tumors. These findings are consistent with CRV431 targeting fibrosis and cancer through multiple, cyclophilin-mediated mechanisms and support the development of CRV431 as a safe and effective drug candidate for liver diseases. SIGNIFICANCE STATEMENT: Cyclophilin inhibitors have demonstrated therapeutic activities in many disease models, but no drug candidates have yet advanced completely through development to market. In this study, CRV431 is shown to potently inhibit multiple cyclophilin isoforms, possess several optimized pharmacological properties, and decrease liver fibrosis and tumors in mouse models of chronic liver disease, which highlights its potential to be the first approved drug primarily targeting cyclophilin isomerases.
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| 31411453 |
α-Conotoxin Vc1.1 Structure-Activity Relationship at the Human α9α10 Nicotinic Acetylcholine Receptor Investigated by Minimal Side Chain Replacement |
10.1021/acschemneuro.9b00389. |
ACS Chem Neurosci |
α-Conotoxin Vc1.1 Structure-Activity Relationship at the Human α9α10 Nicotinic Acetylcholine Receptor Investigated by Minimal Side Chain Replacement
Abstract
- α-Conotoxin Vc1.1 inhibits the nicotinic acetylcholine receptor (nAChR) α9α10 subtype and has the potential to treat neuropathic chronic pain. To date, the crystal structure of Vc1.1-bound α9α10 nAChR remains unavailable; thus, understanding the structure-activity relationship of Vc1.1 with the α9α10 nAChR remains challenging. In this study, the Vc1.1 side chains were minimally modified to avoid introducing large local conformation perturbation to the interactions between Vc1.1 and α9α10 nAChR. The results suggest that the hydroxyl group of Vc1.1, Y10, forms a hydrogen bond with the carbonyl group of α9 N107 and a hydrogen bond donor is required. However, Vc1.1 S4 is adjacent to the α9 D166 and D169, and a positive charge residue at this position increases the binding affinity of Vc1.1. Furthermore, the carboxyl group of Vc1.1, D11, forms two hydrogen bonds with α9 N154 and R81, respectively, whereas introducing an extra carboxyl group at this position significantly decreases the potency of Vc1.1. Second-generation mutants of Vc1.1 [S4 Dab, N9A] and [S4 Dab, N9W] increased potency at the α9α10 nAChR by 20-fold compared with that of Vc1.1. The [S4 Dab, N9W] mutational effects at positions 4 and 9 of Vc1.1 are not cumulative but are coupled with each other. Overall, our findings provide valuable insights into the structure-activity relationship of Vc1.1 with the α9α10 nAChR and will contribute to further development of more potent and specific Vc1.1 analogues.
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| 31427820 |
Design of stapled antimicrobial peptides that are stable, nontoxic and kill antibiotic-resistant bacteria in mice |
10.1038/s41587-019-0222-z. |
Nat Biotechnol |
Design of stapled antimicrobial peptides that are stable, nontoxic and kill antibiotic-resistant bacteria in mice
Abstract
- The clinical translation of cationic α-helical antimicrobial peptides (AMPs) has been hindered by structural instability, proteolytic degradation and in vivo toxicity from nonspecific membrane lysis. Although analyses of hydrophobic content and charge distribution have informed the design of synthetic AMPs with increased potency and reduced in vitro hemolysis, nonspecific membrane toxicity in vivo continues to impede AMP drug development. Here, we analyzed a 58-member library of stapled AMPs (StAMPs) based on magainin II and applied the insights from structure-function-toxicity measurements to devise an algorithm for the design of stable, protease-resistant, potent and nontoxic StAMP prototypes. We show that a lead double-stapled StAMP named Mag(i+4)1,15(A9K,B21A,N22K,S23K) can kill multidrug-resistant Gram-negative pathogens, such as colistin-resistant Acinetobacter baumannii in a mouse peritonitis-sepsis model, without observed hemolysis or renal injury in murine toxicity studies. Inputting the amino acid sequences alone, we further generated membrane-selective StAMPs of pleurocidin, CAP18 and esculentin, highlighting the generalizability of our design platform.
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| 31464123 |
" " No More: An Analysis of Antibacterial Cyclotides |
10.1021/acs.jnatprod.9b00359. |
J Nat Prod |
" " No More: An Analysis of Antibacterial Cyclotides
Abstract
- The emergence of rapidly evolving multidrug-resistant pathogens and a deficit of new compounds entering the clinical pipeline necessitate the exploration of alternative sources of antimicrobial therapeutics. Cyclotides revealed in . are a class of highly stable, cyclic, and disulfide-bound peptides with diverse intrinsic bioactivities. Herein we have identified a novel complement of 42 putative cyclotide masses in the plant species . Cyclotide-containing fractions of a peptide library revealed potent bioactivities against the Gram-negative bacteria ATCC 25922 and the highly virulent and multidrug-resistant VK148. As such, six previously uncharacterized cyclotides, cycloviolacins I1-6 (cyI1-cyI6), were prioritized for molecular characterization. Cyclotides cyI3-cyI6 contain a novel "TLNGNPGA" motif in the highly variable loop six region, expanding the already substantial sequence diversity of this peptide class. Library fractions comprised of cyclotides cyI3-cyI6 exhibited MIC values of 18 and 35 μM against and , respectively, whereas isolated cyI3 killed ∼50% of at 60 μM and isolated cyI4 demonstrated no killing at concentrations >60 μM against both pathogens. This work expands the repertoire of bioactive cyclotides found in . and highlights the potential of these antibacterial cyclic peptides.
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| 31557052 |
Generating the Blood Exposome Database Using a Comprehensive Text Mining and Database Fusion Approach |
10.1289/EHP4713. |
Environ Health Perspect |
Generating the Blood Exposome Database Using a Comprehensive Text Mining and Database Fusion Approach
Abstract
- Blood chemicals are routinely measured in clinical or preclinical research studies to diagnose diseases, assess risks in epidemiological research, or use metabolomic phenotyping in response to treatments. A vast volume of blood-related literature is available via the PubMed database for data mining.
We aimed to generate a comprehensive blood exposome database of endogenous and exogenous chemicals associated with the mammalian circulating system through text mining and database fusion.
Using NCBI resources, we retrieved PubMed abstracts, PubChem chemical synonyms, and PMC supplementary tables. We then employed text mining and PubChem crowdsourcing to associate phrases relating to blood with PubChem chemicals. False positives were removed by a phrase pattern and a compound exclusion list.
A query to identify blood-related publications in the PubMed database yielded 1.1 million papers. Matching a total of 15 million synonyms from 6.5 million relevant PubChem chemicals against all blood-related publications yielded 37,514 chemicals and 851,999 publications records. Mapping PubChem compound identifiers to the PubMed database yielded 49,940 unique chemicals linked to 676,643 papers. Analysis of open-access metabolomics papers related to blood phrases in the PMC database yielded 4,039 unique compounds and 204 papers. Consolidating these three approaches summed up to a total of 41,474 achiral structures that were linked to 65,957 PubChem CIDs and to over 878,966 PubMed articles. We mapped these compounds to 50 databases such as those covering metabolites and pathways, governmental and toxicological databases, pharmacology resources, and bioassay repositories. In comparison, HMDB, the Human Metabolome Database, links 1,075 compounds to blood-related primary publications.
This new Blood Exposome Database can be used for prioritizing chemicals for systematic reviews, developing target assays in exposome research, identifying compounds in untargeted mass spectrometry, and biological interpretation in metabolomics data. The database is available at http://bloodexposome.org. https://doi.org/10.1289/EHP4713.
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| 31607609 |
Photo-induced synthesis of Axinastatin 3 analogs, the secondary structures and their in vitro antitumor activities |
10.1016/j.bmcl.2019.126730. |
Bioorg Med Chem Lett |
Photo-induced synthesis of Axinastatin 3 analogs, the secondary structures and their in vitro antitumor activities
Abstract
- Cyclic peptides combine several favorable properties such as good binding affinity, target selectivity and low toxicity that make them an attractive modality for drug development. In an effort to identify what conformation could be accounting for the bioactive disparity of natural and synthetic cyclic peptides, some structurally-constrained analogs of cyclopeptide Axinastatin 3 were prepared by photo-induced single electron transfer (SET) reaction. Detailed stereochemistry study was performed by experimental electronic circular dichroism combined with theoretical calculations. Our study suggested that the cyclopeptide 1 with βI-turn presented stronger antitumor activity comparing with those without such secondary structures. Moreover, a rare 'π helix unit' (compound 3) was realized because of the constrained cyclic structure, which could be considered an important research object for future study of unique helix secondary structures.
|
| 31636431 |
Pass-back chain extension expands multimodular assembly line biosynthesis |
10.1038/s41589-019-0385-4. |
Nat Chem Biol |
Pass-back chain extension expands multimodular assembly line biosynthesis
Abstract
- Modular nonribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) enzymatic assembly lines are large and dynamic protein machines that generally effect a linear sequence of catalytic cycles. Here, we report the heterologous reconstitution and comprehensive characterization of two hybrid NRPS-PKS assembly lines that defy many standard rules of assembly line biosynthesis to generate a large combinatorial library of cyclic lipodepsipeptide protease inhibitors called thalassospiramides. We generate a series of precise domain-inactivating mutations in thalassospiramide assembly lines, and present evidence for an unprecedented biosynthetic model that invokes intermodule substrate activation and tailoring, module skipping and pass-back chain extension, whereby the ability to pass the growing chain back to a preceding module is flexible and substrate driven. Expanding bidirectional intermodule domain interactions could represent a viable mechanism for generating chemical diversity without increasing the size of biosynthetic assembly lines and challenges our understanding of the potential elasticity of multimodular megaenzymes.
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