| 29745052 |
Sensitive quantification of the somatostatin analog AP102 in plasma by ultra-high pressure liquid chromatography-tandem mass spectrometry and application to a pharmacokinetic study in rats |
10.1002/dta.2400. |
Drug Test Anal |
Sensitive quantification of the somatostatin analog AP102 in plasma by ultra-high pressure liquid chromatography-tandem mass spectrometry and application to a pharmacokinetic study in rats
Abstract
- AP102 is a di-iodinated octapeptide somatostatin agonist (SSA) designed to treat acromegaly and neuroendocrine tumors. A sensitive and selective method was validated for the quantification of AP102 in plasma following the European Medicines Agency (EMA) and Food and Drug Administration (FDA) guidelines. Sample preparation was performed using solid-phase extraction microplates. Chromatographic separation was achieved on an ultra-high pressure liquid chromatography (UHPLC) C18 column in 6.0 minutes. The compounds were quantified using multiple reaction monitoring on a tandem quadrupole mass spectrometer with C, N-labeled AP102 as internal standard. Calibration ranged from 50 to 10000 pg/mL. The lower limit of quantification (LLOQ) was measured at 20 pg/mL, and robust analytical performances were obtained with trueness at 99.2%-100.0%, intra-assay imprecision at 2.5%-4.4%, and inter-assay imprecision at 8.9%-9.7%. The accuracy profiles (total error) built on the 3 concentrations levels showed accuracy within the 70%-130% range. AP102 is remarkably stable since no proteolytic fragments were detected on plasma samples analyzed by Orbitrap-MS. Pharmacokinetic studies were conducted in rats, after single dose (1, 3, and 10 μg/kg, sc) and continuous subcutaneous administration (osmotic minipumps for 28 days, 3.0 or 10.0 μg/kg/h). AP102 showed a rapid absorption by the subcutaneous route (T : 15-30 minutes) and a fast elimination (t : 33-86 minutes). The PK profile of AP102 exhibited a mean clearance of 1.67 L/h and a mean distribution volume at steady state of 7.16 L/kg, about 10-fold higher than those observed with other SSA or non- and mono-iodinated AP102. LogD determination confirmed the lipophilic properties of AP102 that might influence its distribution in tissues.
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| 29746088 |
Structure-Activity Studies Reveal the Molecular Basis for GABA-Receptor Mediated Inhibition of High Voltage-Activated Calcium Channels by α-Conotoxin Vc1.1 |
10.1021/acschembio.8b00190. |
ACS Chem Biol |
Structure-Activity Studies Reveal the Molecular Basis for GABA-Receptor Mediated Inhibition of High Voltage-Activated Calcium Channels by α-Conotoxin Vc1.1
Abstract
- α-Conotoxins are disulfide-bonded peptides from cone snail venoms and are characterized by their affinity for nicotinic acetylcholine receptors (nAChR). Several α-conotoxins with distinct selectivity for nAChR subtypes have been identified as potent analgesics in animal models of chronic pain. However, a number of α-conotoxins have been shown to inhibit N-type calcium channel currents in rodent dissociated dorsal root ganglion (DRG) neurons via activation of G protein-coupled GABA receptors (GABAR). Therefore, it is unclear whether activation of GABAR or inhibition of α9α10 nAChRs is the analgesic mechanism. To investigate the mechanisms by which α-conotoxins provide analgesia, we synthesized a suite of Vc1.1 analogues where all residues, except the conserved cysteines, in Vc1.1 were individually replaced by alanine (A), lysine (K), and aspartic acid (D). Our results show that the amino acids in the first loop play an important role in binding of the peptide to the receptor, whereas those in the second loop play an important role for the selectivity of the peptide for the GABAR over α9α10 nAChRs. We designed a cVc1.1 analogue that is >8000-fold selective for GABAR-mediated inhibition of high voltage-activated (HVA) calcium channels over α9α10 nAChRs and show that it is analgesic in a mouse model of chronic visceral hypersensitivity (CVH). cVc1.1[D11A,E14A] caused dose-dependent inhibition of colonic nociceptors with greater efficacy in ex vivo CVH colonic nociceptors relative to healthy colonic nociceptors. These findings suggest that selectively targeting GABAR-mediated HVA calcium channel inhibition by α-conotoxins could be effective for the treatment of chronic visceral pain.
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| 29750913 |
Synthesis, biophysical and functional studies of two BP100 analogues modified by a hydrophobic chain and a cyclic peptide |
10.1016/j.bbamem.2018.05.003. |
Biochim Biophys Acta Biomembr |
Synthesis, biophysical and functional studies of two BP100 analogues modified by a hydrophobic chain and a cyclic peptide
Abstract
- Antimicrobial peptides (AMPs) work as a primary defense against pathogenic microorganisms. BP100, (KKLFKKILKYL-NH), a rationally designed short, highly cationic AMP, acts against many bacteria, displaying low toxicity to eukaryotic cells. Previously we found that its mechanism of action depends on membrane surface charge and on peptide-to-lipid ratio. Here we present the synthesis of two BP100 analogs: BP100‑alanyl‑hexadecyl‑1‑amine (BP100-Ala-NH-CH) and cyclo(1‑4)‑d‑Cys, Ile, Leu, Cys-BP100 (Cyclo(1‑4)‑cILC-BP100). We examined their binding to large unilamellar vesicles (LUV), conformational and functional properties, and compared with those of BP100. The analogs bound to membranes with higher affinity and a lesser dependence on electrostatic forces than BP100. In the presence of LUV, BP100 and BP100-Ala-NH-CH acquired α-helical conformation, while Cyclo(1‑4)‑cILC-BP100) was partly α-helical and partly β-turn. Taking in conjunction: 1. particle sizes and zeta potential, 2. effects on lipid flip-flop, 3. leakage of LUVs internal contents, and 4. optical microscopy of giant unilamellar vesicles, we concluded that at high concentrations, all three peptides acted by a carpet mechanism, while at low concentrations the peptides acted by disorganizing the lipid bilayer, probably causing membrane thinning. The higher activity and lesser membrane surface charge dependence of the analogs was probably due to their greater hydrophobicity. The MIC values of both analogs towards Gram-positive and Gram-negative bacteria were similar to those of BP100 but both analogues were more hemolytic. Confocal microscopy showed Gram-positive B. subtilis killing with concomitant extensive membrane damage suggestive of lipid clustering, or peptide-lipid aggregation. These results were in agreement with those found in model membranes.
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| 29757646 |
Inhibition of Breast Cancer Cell Migration by Cyclotides Isolated from Pombalia calceolaria |
10.1021/acs.jnatprod.7b00969. |
J Nat Prod |
Inhibition of Breast Cancer Cell Migration by Cyclotides Isolated from Pombalia calceolaria
Abstract
- Two new bracelet cyclotides from roots of Pombalia calceolaria with potential anticancer activity have been characterized in this work. The cyclotides Poca A and B (1 and 2) and the previously known CyO4 (3) were de novo sequenced by MALDI-TOF/TOF mass spectrometry (MS). The MS spectra were examined and the amino acid sequences were determined. The purified peptides were tested for their cytotoxicity and effects on cell migration of MDA-MB-231, a triple-negative breast cancer cell line. The isolated cyclotides reduced the number of cancer cells by more than 80% at 20 μM, and the concentration-related cytotoxic responses were observed with IC values of 1.8, 2.7, and 9.8 μM for Poca A (1), Poca B (2), and CyO4 (3), respectively. Additionally, the inhibition of cell migration (wound-healing assay) exhibited that CyO4 (3) presents an interesting activity profile, in being able to inhibit cell migration (50%) at a subtoxic concentration (2 μM). The distribution of these cyclotides in the roots was analyzed by MALDI imaging, demonstrating that all three compounds are present in the phloem and cortical parenchyma regions.
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| 29843182 |
A Cyclotide Isolated from Noisettia orchidiflora (Violaceae) |
10.1055/a-0632-2204. |
Planta Med |
A Cyclotide Isolated from Noisettia orchidiflora (Violaceae)
Abstract
- Biologically active cyclotides have been found on some flowering plants species and are involved in the role of the plant protection. As part of studies focusing on peptides from Brazilian plant species, we are reporting the detection by LC-MS of several cyclotides from leaves and stems of (Violaceae). From stems it was possible to isolate and characterize a cyclotide named Nor A. Its primary structure (amino acid sequence) was established by MALDI-TOF-MS, based on the and type ion series, after reduction and alkylation reactions, as well as enzymatic digestion using the enzymes endoproteinase glutamic acid (endoGlu-C), trypsin, and chymotrypsin. Furthermore, the amino acid analysis was also described.
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| 29901750 |
Murepavadin activity tested against contemporary (2016-17) clinical isolates of XDR Pseudomonas aeruginosa |
10.1093/jac/dky227. |
J Antimicrob Chemother |
Murepavadin activity tested against contemporary (2016-17) clinical isolates of XDR Pseudomonas aeruginosa
Abstract
- Murepavadin (POL7080) represents the first member of a novel class of outer membrane protein-targeting antibiotics. Murepavadin acts by binding to LPS transport protein D and is being developed for the treatment of hospital-acquired and ventilator-associated pneumonia caused by Pseudomonas aeruginosa.
To evaluate the antimicrobial activity of murepavadin against XDR P. aeruginosa.
A total of 785 clinical isolates of XDR P. aeruginosa were collected in 2016-17 through the SENTRY Antimicrobial Surveillance Program from 34 medical centres in 21 European nations (n = 353) and 75 medical centres in North America (n = 432). Isolates were categorized as XDR when susceptible (CLSI) to ≤2 of the following antimicrobial classes: antipseudomonal cephalosporins, carbapenems, broad-spectrum penicillin/β-lactamase inhibitor combinations, fluoroquinolones, aminoglycosides and polymyxins. Susceptibility testing was performed by the reference broth microdilution method and EUCAST and CLSI interpretative criteria were applied.
Murepavadin (MIC50/90, 0.12/0.25 mg/L) inhibited 96.7% of isolates at ≤0.5 mg/L and was 8-fold more active than colistin (MIC50/90, 1/2 mg/L). Only seven isolates (0.9%) exhibited murepavadin MIC values >4 mg/L. Colistin (MIC50/90, 1/2 mg/L; 93.6% susceptible) was the most active comparator, followed by ceftolozane/tazobactam (MIC50/90, 2/>32 mg/L; 70.6% susceptible) and tobramycin (MIC50/90, 8/>8 mg/L; 47.5% susceptible). Murepavadin remained active against isolates that were non-susceptible to colistin (n = 50; MIC50/90, 0.25/0.25 mg/L), ceftolozane/tazobactam (n = 231; MIC50/90, 0.12/0.25 mg/L) and/or tobramycin (n = 412; MIC50/90, 0.12/0.25 mg/L).
Murepavadin exhibited potent activity against a large collection of clinical XDR P. aeruginosa isolates from Europe and North America, including isolates that were non-susceptible to colistin, ceftolozane/tazobactam and/or tobramycin.
|
| 29902438 |
Accessing Bioactive Natural Products from the Human Microbiome |
10.1016/j.chom.2018.05.013. |
Cell Host Microbe |
Accessing Bioactive Natural Products from the Human Microbiome
Abstract
- Natural products have long played a pivotal role in the development of therapeutics for a variety of diseases. Traditionally, soil and marine environments have provided a rich reservoir from which diverse chemical scaffolds could be discovered. Recently, the human microbiome has been recognized as a promising niche from which secondary metabolites with therapeutic potential have begun to be isolated. In this Review, we address how the expansive history of identifying bacterial natural products in other environments is informing the approaches being brought to bear on the study of the human microbiota. We also touch on how these tools can lead to insights about microbe-microbe and host-microbe interactions and help generate biological hypotheses that may lead to developments of new therapeutic modalities.
|
| 29904274 |
Evaluation of the bioactivity of a mastoparan peptide from wasp venom and of its analogues designed through targeted engineering |
10.7150/ijbs.23419. |
Int J Biol Sci |
Evaluation of the bioactivity of a mastoparan peptide from wasp venom and of its analogues designed through targeted engineering
Abstract
- Mastoparan is a typical cationic and amphipathic tetradecapeptide found in wasp venom and exhibits potent biological activities. Yet, compared with other insect-derived peptides, such as melittin from the bee venom, this family have been underrated. Herein, we evaluated the biological activities of mastoparan-C (MP-C), which was identified from the venom of the European Hornet (), and rationally designed two analogues (a skeleton-based cyclization by two cysteine residues and an N-terminal extension via tat-linked) for enhancing the stability of the biological activity and membrane permeability, respectively. Three peptides possessed broadly efficacious inhibiting capacities towards common pathogens, resistant strains, as well as microbial biofilm. Although, cyclized MP-C showed longer half-life time than the parent peptide, the lower potency of antimicrobial activity and higher degree of haemolysis were observed. The tat-linked MP-C exhibited more potent anticancer activity than the parent peptide, but it also loses the specificity. The study revealed that MP-C is good candidate for developing antimicrobial agents and the targeted-design could improve the stability and transmembrane delivery, but more investigation would be needed to adjust the side effects brought from the design.
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| 29916519 |
Natural products from thioester reductase containing biosynthetic pathways |
10.1039/c8np00013a. |
Nat Prod Rep |
Natural products from thioester reductase containing biosynthetic pathways
Abstract
- Covering: up to 2018 Thioester reductase domains catalyze two- and four-electron reductions to release natural products following assembly on nonribosomal peptide synthetases, polyketide synthases, and their hybrid biosynthetic complexes. This reductive off-loading of a natural product yields an aldehyde or alcohol, can initiate the formation of a macrocyclic imine, and contributes to important intermediates in a variety of biosyntheses, including those for polyketide alkaloids and pyrrolobenzodiazepines. Compounds that arise from reductase-terminated biosynthetic gene clusters are often reactive and exhibit biological activity. Biomedically important examples include the cancer therapeutic Yondelis (ecteinascidin 743), peptide aldehydes that inspired the first therapeutic proteasome inhibitor bortezomib, and numerous synthetic derivatives and antibody drug conjugates of the pyrrolobenzodiazepines. Recent advances in microbial genomics, metabolomics, bioinformatics, and reactivity-based labeling have facilitated the detection of these compounds for targeted isolation. Herein, we summarize known natural products arising from this important category, highlighting their occurrence in Nature, biosyntheses, biological activities, and the technologies used for their detection and identification. Additionally, we review publicly available genomic data to highlight the remaining potential for novel reductively tailored compounds and drug leads from microorganisms. This thorough retrospective highlights various molecular families with especially privileged bioactivity while illuminating challenges and prospects toward accelerating the discovery of new, high value natural products.
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| 29922855 |
Hyporientalin A, an anti-Candida peptaibol from a marine Trichoderma orientale |
10.1007/s11274-018-2482-z. |
World J Microbiol Biotechnol |
Hyporientalin A, an anti-Candida peptaibol from a marine Trichoderma orientale
Abstract
- A Trichoderma orientale strain LSBA1 was isolated from the Mediterranean marine sponge Cymbaxinella damicornis. The crude extract of T. orientale mycelium showed inhibitory activity against growth of Gram-positive and Gram-negative bacteria as well as clinical isolates of Candida albicans. Purification of the anti-Candida component was performed using a combination of open silica gel-60 column and reverse phase high performance liquid chromatography. The active compound called hyporientalin A has been identified as a peptaibol analogue of longibrachin-A-II using mass spectrometry. It exhibited fungicidal activity against clinical isolates of C. albicans with minimal inhibitory concentrations (MICs) ranging from 2.49 to 19.66 µM, comparable to that of the antifungal agent amphotericin B. Our data support the use of hyporientalin A as a promising new and efficient antifungal drug in the treatment of candidiasis while controlling toxicity.
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| 29947227 |
Cone Snail Glutaminyl Cyclase Sequences from Transcriptomic Analysis and Mass Spectrometric Characterization of Two Pyroglutamyl Conotoxins |
10.1021/acs.jproteome.8b00132. |
J Proteome Res |
Cone Snail Glutaminyl Cyclase Sequences from Transcriptomic Analysis and Mass Spectrometric Characterization of Two Pyroglutamyl Conotoxins
Abstract
- The post-translational modification of N-terminal glutamine (Q) to a pyroglutamyl (Z) residue is observed in the conotoxins produced by marine cone snails. This conversion requires the action of the enzyme glutaminyl cyclase (QC). Four complete QC sequences from the species C. araneosus, C. frigidus, C. litteratus, and C. monile and two partial sequences from C. amadis and C. miles have been obtained by analysis of transcriptomic data. Comparisons with mammalian enzyme sequences establish a high level of identity and complete conservation of functional active site residues, including a cluster of hydrogen-bonded acidic side chains. Mass spectrometric analysis of crude venom samples coupled to conotoxin precursor protein sequences obtained from transcriptomic data establishes the presence of pyroglutamyl conotoxins in the venom of C. frigidus and C. amadis. The C. frigidus peptide belongs to the M superfamily, with cysteine framework III, whereas the C. amadis peptide belongs to the divergent superfamily with cysteine framework VI/VII. Additionally, gamma carboxylation of glutamic acid and hydroxylation of proline are observed in the C. frigidus peptide. Mass spectral data are available via ProteomeXchange with identifier PXD009006.
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| 29974638 |
Biosynthetic Gene Cluster of a d-Tryptophan-Containing Lasso Peptide, MS-271 |
10.1002/cbic.201800315. |
Chembiochem |
Biosynthetic Gene Cluster of a d-Tryptophan-Containing Lasso Peptide, MS-271
Abstract
- MS-271, produced by Streptomyces sp. M-271, is a lasso peptide natural product comprising 21 amino acid residues with a d-tryptophan at its C terminus. Because lasso peptides are ribosomal peptides, the biosynthesis of MS-271, especially the mechanism of d-Trp introduction, is of great interest. The MS-271 biosynthetic gene cluster was identified by draft genome sequencing of the MS-271 producer, and it was revealed that the precursor peptide contains all 21 amino acid residues including the C-terminal tryptophan. This suggested that the d-Trp residue is introduced by epimerization. Genes for modification enzymes such as a macrolactam synthetase (mslC), precursor peptide recognition element (mslB1), cysteine protease (mslB2), disulfide oxidoreductases (mslE, mslF), and a protein of unknown function (mslH) were found in the flanking region of the precursor peptide gene. Although obvious epimerase genes were absent in the cluster, heterologous expression of the putative MS-271 cluster in Streptomyces lividans showed that it contains all the necessary genes for MS-271 production including a gene for a new peptide epimerase. Furthermore, a gene-deletion experiment indicated that MslB1, -B2, -C and -H were indispensable for MS-271 production and that some interactions of the biosynthetic enzymes were essential for the biosynthesis of MS-271.
|
| 30025921 |
Species specificity of rat and human α7 nicotinic acetylcholine receptors towards different classes of peptide and protein antagonists |
10.1016/j.neuropharm.2018.07.019. |
Neuropharmacology |
Species specificity of rat and human α7 nicotinic acetylcholine receptors towards different classes of peptide and protein antagonists
Abstract
- Peptide and protein neurotoxins, such as α-conotoxins from Cone snails and α-neurotoxins from snake venoms, are excellent tools to identify distinct nicotinic acetylcholine receptor (nAChR) subtypes. Here we compared the rat/human species specificity of α7 nAChR towards peptide and protein neurotoxins and found that α-conotoxin analogues [K11A]TxIB and [H5D]RegIIA are much more potent on the rat versus human α7 receptor expressed in Xenopus oocytes. In the hope to determine the key residue responsible for the difference in α-conotoxin analogues affinities, ten single mutants of rat α7 nAChR were obtained because there are 10 differences in the extracellular ligand-binding domains of these species, and only K185R mutation decreased the affinity for α-conotoxins [K11A]TxIB and [H5D]RegIIA, down to their low affinities for human α7 nAChR. On the other hand, the reverse mutation R185K in human α7 nAChR resulted in the greatest increase in the affinity for both conotoxins, while a double mutation hα7[S183N, R185K] made the potency of the receptor for them as high as that of rat α7 nAChR. The effects of mutations at position 185 were investigated also with some other α-conotoxins and cobra venom α-cobratoxin and found to have similar but much less pronounced effects on their species specificity. Molecular modeling provided possible explanation for the high species selectivity of [K11A]TxIB and [H5D]RegIIA towards α7 nAChR, opening the new way for design of their analogues with improved affinity to the human receptor.
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| 30031620 |
An efficient synthetic route for preparation of antimycobacterial wollamides and evaluation of their in vitro and in vivo efficacy |
10.1016/j.bmcl.2018.07.021. |
Bioorg Med Chem Lett |
An efficient synthetic route for preparation of antimycobacterial wollamides and evaluation of their in vitro and in vivo efficacy
Abstract
- A convenient solid phase peptide synthetic (SPPS) route is reported for the preparation of antimycobacterial wollamides. The method is based on on-resin head-to-tail cyclization and is fast, efficient and amenable to automation. The in vitro antimycobacterial activities of the newly synthesized wollamides were evaluated against M. tuberculosis H37Rv (Mtb H37Rv). To assess their drug-likeness, in vitro pharmacokinetic (ADME) profiling was also performed. For wollamides with potent extracellular potency, intracellular activities and in vivo efficacy were determined. The results disclose the potent antimycobacterial (MIC = 1.1 µM) and suitable drug-like properties of wollamide A (4b). Out of the synthesized wollamides, four compounds (4b-e) exhibited potent intracellular activities against Mtb H37Rv infected human macrophages (IC = 0.2-1.3 µM). Results of in vivo blood exposure and efficacy assays for 4d and 4e are discussed.
|
| 30102220 |
CXCR4-targeted therapy in breast cancer |
10.1016/S1470-2045(18)30480-7. |
Lancet Oncol |
CXCR4-targeted therapy in breast cancer
Abstract
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