| 23701329 |
Pharmacology of polymyxins: new insights into an 'old' class of antibiotics |
10.2217/fmb.13.39. |
Future Microbiol |
Pharmacology of polymyxins: new insights into an 'old' class of antibiotics
Abstract
- Increasing antibiotic resistance in Gram-negative bacteria, particularly in Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae, presents a global medical challenge. No new antibiotics will be available for these 'superbugs' in the near future due to the dry antibiotic discovery pipeline. Colistin and polymyxin B are increasingly used as the last-line therapeutic options for treatment of infections caused by multidrug-resistant Gram-negative bacteria. This article surveys the significant progress over the last decade in understanding polymyxin chemistry, mechanisms of antibacterial activity and resistance, structure-activity relationships and pharmacokinetics/pharmacodynamics. In the 'Bad Bugs, No Drugs' era, we must pursue structure-activity relationship-based approaches to develop novel polymyxin-like lipopeptides targeting polymyxin-resistant Gram-negative 'superbugs'. Before new antibiotics become available, we must optimize the clinical use of polymyxins through the application of pharmacokinetic/pharmacodynamic principles, thereby minimizing the development of resistance.
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| 23702710 |
CYCLONE--a utility for de novo sequencing of microbial cyclic peptides |
10.1007/s13361-013-0652-7. |
J Am Soc Mass Spectrom |
CYCLONE--a utility for de novo sequencing of microbial cyclic peptides
Abstract
- We have developed a de novo sequencing software tool (CYCLONE) and applied it for determination of cyclic peptides. The program uses a non-redundant database of 312 nonribosomal building blocks identified to date in bacteria and fungi (more than 230 additional residues in the database list were isobaric). The software was used to fully characterize the tandem mass spectrum of several cyclic peptides and provide sequence tags. The general strategy of the script was based on fragment ion pre-characterization to accomplish unambiguous b-ion series assignments. Showcase examples were a cyclic tetradepsipeptide beauverolide, a cyclic hexadepsipeptide roseotoxin A, a lasso-like hexapeptide pseudacyclin A, and a cyclic undecapeptide cyclosporin A. The extent of ion scrambling in smaller peptides was as low as 5 % of total ion current; this demonstrated the feasibility of CYCLONE de novo sequencing. The robustness of the script was also tested against database sets of various sizes and isotope-containing data. It can be downloaded from the http://ms.biomed.cas.cz/MSTools/ website. ᅟ
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| 23707282 |
Neurohormonal effects of oxytocin and vasopressin receptor agonists on spinal pain processing in male rats |
10.1016/j.pain.2013.05.003. |
Pain |
Neurohormonal effects of oxytocin and vasopressin receptor agonists on spinal pain processing in male rats
Abstract
- Oxytocin (OT) and arginine vasopressin (AVP) are 2 neuropeptides that display well-known effects on the reproductive system. Although still controversial, oxytocin and vasopressin were demonstrated to exert potent effects on the nociceptive system when administered directly in various central nervous structures. On the other hand, little is known about their peripheral (hormonal) actions on nociception and pain responses. The aim of the present work was to characterize the effects of physiological blood concentrations of OT and AVP on spinal nociception and on pain responses. To do so, growing doses of OT or AVP were administered intravenously and the nociceptive processing by spinal cord neurons was analyzed in anesthetized male rats in vivo. We observed that the action potentials mediated by C-type nociceptive fibers was strongly reduced (antinociception) after intravenous injections of low doses of OT (<5 μg) or AVP (<500 pg), whereas an increase (pronociception) was observed at higher doses. Interestingly, antinociceptive and pronociceptive effects were fully abolished in the presence of the OT receptor antagonist and the AVP receptor antagonist type 1A (V1A), respectively. We confirmed this result with a behavioral model of forced swim stress-induced analgesia associated with plasmatic release of OT (and not vasopressin). Stress-induced analgesia was transiently lost after i.v. administration of OTR antagonist. Together, the present work provides straightforward evidence that blood levels of OT and AVP modulate nociception, windup plasticity and pain responses. The final target structures explaining these effects remains to be identified but are likely to be C-type nociceptors.
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| 23718637 |
Metabolites from Microcystis aeruginosa bloom material collected at a water reservoir near Kibbutz Hafetz Haim, Israel |
10.1021/np400281q. |
J Nat Prod |
Metabolites from Microcystis aeruginosa bloom material collected at a water reservoir near Kibbutz Hafetz Haim, Israel
Abstract
- An aqueous MeOH extract of Microcystis aeruginosa (IL-399) afforded three new protease inhibitors, micropeptin HH978 (1), micropeptin HH960 (2), and micropeptin HH992 (3), as well as the known aeruginosin GH553 and microguanidine AL772. The structures of the compounds were elucidated using 1D and 2D NMR techniques, as well as high-resolution mass spectrometry. The absolute configurations of 1-3 were determined using Marfey's method for amino acid and chiral-phase HPLC for hydroxy acids. The inhibitory activity of the compounds was determined for the serine proteases trypsin, thrombin, elastase, and chymotrypsin. The structure elucidation and biological activities of the new natural products are discussed.
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| 23721918 |
Synthesis and functional analysis of deferriferrichrysin derivatives: application to colorimetric pH indicators |
10.1016/j.bmc.2013.04.078. |
Bioorg Med Chem |
Synthesis and functional analysis of deferriferrichrysin derivatives: application to colorimetric pH indicators
Abstract
- Deferriferrichrysin belongs to the siderophore peptide family which are Fe(III)-coordinating cyclic peptides. The common structure of this family is three consecutive hydroxamate moieties, such as N(δ)-acetyl-N(δ)-hydroxy-l-ornithine (Aho). We have designed two deferriferrichrysin derivatives where three Aho residues were arranged as: cyclo(-Aho-Gly-Aho-Gly-Aho-Gly-) and cyclo(-Aho-Ser-Aho-Ser-Aho-Ser-). Comparative evaluation of the physicochemical properties of their Fe(III) complexes revealed that naturally occurring deferriferrichrysin formed a more stable Fe(III) complex when compared with the two derivatives. This result shows that three consecutive Aho residues are indispensable for high affinity Fe(III) binding by deferriferrichrysin. Of note, the observed pH-dependent chromogenic response of the Fe(III) complexes of the derivatives suggests that these two derivatives should function as sensitive pH indicators in acidic environments.
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| 23748293 |
Controlled surface modification of tissue culture polystyrene for selective cell binding using resilin-inspired polypeptides |
10.1088/1758-5082/5/3/035005. |
Biofabrication |
Controlled surface modification of tissue culture polystyrene for selective cell binding using resilin-inspired polypeptides
Abstract
- Modified tissue culture polystyrene (TCP) surfaces have been fabricated by attachment of recombinant polypeptides based on Drosophila melanogaster resilin and the Anopheles gambiae resilin-like protein. The D. melanogaster polypeptide (Rec-1) was from the first exon of resilin and consisted of 17 very similar repeats of a 15 residue sequence. The A. gambiae polypeptide consisted of 16 repeats of an 11 residue consensus sequence (An16). Polypeptides were attached to the TCP surface through tyrosine-based photo-crosslinking using blue light in combination with (RuII(bpy)3)Cl2 and sodium persulfate. TCP that has been manufactured by mild oxidation has surface phenolic groups that are believed to participate in this crosslinking process. X-ray photoelectron spectroscopy and contact angle analyses were used to demonstrate polypeptide binding. At higher coating concentrations of Rec-1 and An16, the surface was passivated and fibroblasts no longer attached and spread. At coating concentrations of 1 mg ml(-1) for Rec-1 and 0.1 mg ml(-1) for An16, where the surface was fully passivated against fibroblast attachment, addition of a cell attachment peptide, cyclo(Arg-Gly-Asp-D-Tyr-Lys) during coating and photo-crosslinking at >0.1 mg ml(-1), led to the restoration of fibroblast binding that was dependent on the integrin αV chain.
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| 23756682 |
Synergistic antifungal activity of KB425796-C in combination with micafungin against Aspergillus fumigatus and its efficacy in murine infection models |
10.1038/ja.2013.57. |
J Antibiot (Tokyo) |
Synergistic antifungal activity of KB425796-C in combination with micafungin against Aspergillus fumigatus and its efficacy in murine infection models
Abstract
- KB425796-C is a novel antifungal metabolite produced by the newly isolated bacterial strain Paenibacillus sp. No. 530603. This compound is a 40-membered macrocyclic lipopeptidolactone consisting of 12 amino acids and a 3-hydroxy-15-methylpalmitoyl moiety. KB425796-C displayed antifungal activity against micafungin-resistant fungi and was fungicidal to Trichosporon asahii in vitro. In a murine systemic infection model of T. asahii, KB425796-C showed excellent efficacy upon i.p. administration at 32 mg kg(-1). In addition, KB425796-C induced morphological changes in the hyphae of Aspergillus fumigatus and had fungicidal effects in combination with micafungin. In a mouse model of septic A. fumigatus infection, although non-treated mice survived for a maximum of only 6 days, the survival rate of micafungin-treated mice (0.1 mg kg(-1)) increased to 20%, while the survival rate of mice treated with a combination of micafungin (0.1 mg kg(-1)) and KB425796-C (32 mg kg(-1)) increased to 100% during the 31-day post-infection period. Our findings suggest that KB425796-C is a good candidate for the treatment of aspergillosis in combination with micafungin.
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| 23756961 |
Efficacy of emodepside plus toltrazuril oral suspension for dogs (Procox®, Bayer) against Trichuris vulpis in naturally infected dogs |
10.1007/s00436-013-3287-5. |
Parasitol Res |
Efficacy of emodepside plus toltrazuril oral suspension for dogs (Procox®, Bayer) against Trichuris vulpis in naturally infected dogs
Abstract
- The efficacy of emodepside plus toltrazuril oral suspension for dogs (Procox®, Bayer) against Trichuris vulpis was evaluated in a controlled, blinded and randomised laboratory study. Twenty naturally infected dogs were included. Dogs in the treatment group received the minimum therapeutic dose of 0.45 mg emodepside and 9 mg toltrazuril per kg body weight, while dogs in the control group were left untreated. Efficacy was calculated based on worm counts after necropsy on Day 7 post treatment. Additionally, all faeces were collected and examined for expelled worms. The treatment was 100 % effective. A total of 233 adult worms (geometric mean 17.0) and 3 immature adult worms were found in the control group at necropsy. Adequacy of infection was demonstrated. The treated group excreted a total of 186 adult worms within 2 days after treatment. Additionally, all dogs were co-infected with Uncinaria stenocephala. Efficacy against this parasite was 99.8 %. No side effects of the treatment were observed. This study demonstrates that in addition to the formerly proven efficacy against Toxocara canis, Ancylostoma caninum and Uncinaria stenocephala, emodepside plus toltrazuril suspension is also effective against T. vulpis and thus represents a convenient treatment option for dogs co-infected with whipworms and coccidia.
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| 23762328 |
Coibamide A induces mTOR-independent autophagy and cell death in human glioblastoma cells |
10.1371/journal.pone.0065250. |
PLoS One |
Coibamide A induces mTOR-independent autophagy and cell death in human glioblastoma cells
Abstract
- Coibamide A is an N-methyl-stabilized depsipeptide that was isolated from a marine cyanobacterium as part of an International Cooperative Biodiversity Groups (ICBG) program based in Panama. Previous testing of coibamide A in the NCI in vitro 60 cancer cell line panel revealed a potent anti-proliferative response and "COMPARE-negative" profile indicative of a unique mechanism of action. We report that coibamide A is a more potent and efficacious cytotoxin than was previously appreciated, inducing concentration- and time-dependent cytotoxicity (EC50<100 nM) in human U87-MG and SF-295 glioblastoma cells and mouse embryonic fibroblasts (MEFs). This activity was lost upon linearization of the molecule, highlighting the importance of the cyclized structure for both anti-proliferative and cytotoxic responses. We show that coibamide A induces autophagosome accumulation in human glioblastoma cell types and MEFs via an mTOR-independent mechanism; no change was observed in the phosphorylation state of ULK1 (Ser-757), p70 S6K1 (Thr-389), S6 ribosomal protein (Ser-235/236) and 4EBP-1 (Thr-37/46). Coibamide A also induces morphologically and biochemically distinct forms of cell death according to cell type. SF-295 glioblastoma cells showed caspase-3 activation and evidence of apoptotic cell death in a pattern that was also seen in wild-type and autophagy-deficient (ATG5-null) MEFs. In contrast, cell death in U87-MG glioblastoma cells was characterized by extensive cytoplasmic vacuolization and lacked clear apoptotic features. Cell death was attenuated, but still triggered, in Apaf-1-null MEFs lacking a functional mitochondria-mediated apoptotic pathway. From the study of ATG5-null MEFs we conclude that a conventional autophagy response is not required for coibamide A-induced cell death, but likely occurs in dying cells in response to treatment. Coibamide A represents a natural product scaffold with potential for the study of mTOR-independent signaling and cell death mechanisms in apoptotic-resistant cancer cells.
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| 23768016 |
Dicarba α-conotoxin Vc1.1 analogues with differential selectivity for nicotinic acetylcholine and GABAB receptors |
10.1021/cb4002393. |
ACS Chem Biol |
Dicarba α-conotoxin Vc1.1 analogues with differential selectivity for nicotinic acetylcholine and GABAB receptors
Abstract
- Conotoxins have emerged as useful leads for the development of novel therapeutic analgesics. These peptides, isolated from marine molluscs of the genus Conus, have evolved exquisite selectivity for receptors and ion channels of excitable tissue. One such peptide, α-conotoxin Vc1.1, is a 16-mer possessing an interlocked disulfide framework. Despite its emergence as a potent analgesic lead, the molecular target and mechanism of action of Vc1.1 have not been elucidated to date. In this paper we describe the regioselective synthesis of dicarba analogues of Vc1.1 using olefin metathesis. The ability of these peptides to inhibit acetylcholine-evoked current at rat α9α10 and α3β4 nicotinic acetylcholine receptors (nAChR) expressed in Xenopus oocytes has been assessed in addition to their ability to inhibit high voltage-activated (HVA) calcium channel current in isolated rat DRG neurons. Their solution structures were determined by NMR spectroscopy. Significantly, we have found that regioselective replacement of the native cystine framework with a dicarba bridge can be used to selectively tune the cyclic peptide's innate biological activity for one receptor over another. The 2,8-dicarba Vc1.1 isomer retains activity at γ-aminobutyric acid (GABAB) G protein-coupled receptors, whereas the isomeric 3,16-dicarba Vc1.1 peptide retains activity at the α9α10 nAChR subtype. These singularly acting analogues will enable the elucidation of the biological target responsible for the peptide's potent analgesic activity.
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| 23778114 |
Identification of ten KB425796-A congeners from Paenibacillus sp. 530603 using an antifungal assay against Aspergillus fumigatus in combination with micafungin |
10.1038/ja.2013.64. |
J Antibiot (Tokyo) |
Identification of ten KB425796-A congeners from Paenibacillus sp. 530603 using an antifungal assay against Aspergillus fumigatus in combination with micafungin
Abstract
- The discovery and characterization of natural congeners is one approach for understanding the relationship between chemical structure and biological function. We recently isolated the novel antifungal metabolite KB425796-A produced by the recently isolated bacterium Paenibacillus sp. 530603. On the basis of morphological changes of Aspergillus fumigatus induced by KB425796-A in combination with micafungin, we developed a highly sensitive screening method for the specific detection of KB425796-A congeners. Using this method, we isolated ten congeners of KB425796-A, named KB425796-B, -C, -D, -E, -F, -G, -H, -I, -J and -K, which exhibited diverse antifungal potencies against A. fumigatus. One of the most potent congeners, KB425796-C, had antifungal activities against several micafungin-resistant infectious fungi. KB425796-C can be a potential drug candidate for treating micafungin-resistant fungal infections.
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| 23778117 |
KB425796-A, a novel antifungal antibiotic produced by Paenibacillus sp. 530603 |
10.1038/ja.2013.63. |
J Antibiot (Tokyo) |
KB425796-A, a novel antifungal antibiotic produced by Paenibacillus sp. 530603
Abstract
- The novel antifungal macrocyclic lipopeptidolactone, KB425796-A (1), was isolated from the fermentation broth of bacterial strain 530603, which was identified as a new Paenibacillus species based on morphological and physiological characteristics, and 16S rRNA sequences. KB425796-A (1) was isolated as white powder by solvent extraction, HP-20 and ODS-B column chromatography, and lyophilization, and was determined to have the molecular formula C79H115N19O18. KB425796-A (1) showed antifungal activities against Aspergillus fumigatus and the micafungin-resistant infectious fungi Trichosporon asahii, Rhizopus oryzae, Pseudallescheria boydii and Cryptococcus neoformans.
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| 23800264 |
Comparison of the antimicrobial effects of semipurified cyclotides from Iranian Viola odorata against some of plant and human pathogenic bacteria |
10.1111/jam.12251. |
J Appl Microbiol |
Comparison of the antimicrobial effects of semipurified cyclotides from Iranian Viola odorata against some of plant and human pathogenic bacteria
Abstract
- Cyclotides are mini-proteins that are synthesized via the ribosomal pathway. They have a variety of biological activities such as antimicrobial, antitumour, anti-HIV activities. Because of their various bioactivities and unique stability, they are suitable candidate in drug design applications. The main aim of this study was to determine new antimicrobial agents, which can be used instead of chemical antibiotics. For this reason, we compared the antimicrobial effects of semipurified cyclotides against human and plant pathogenic bacteria.
The cyclotides were isolated from the Iranian plant Viola odorata by fractionation methods and semipurified on a SPE-C18 column chromatography. Antimicrobial activities of extracted cyclotides were studied by radial diffusion assays (RDAs), minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). Data analysis showed that MIC of semipurified cyclotides was 1.6 mg ml(-1) against Staphylococcus aureus, gram-positive bacteria. It was also revealed they are the most susceptible among human pathogenic bacteria used in this research. On the other hand, plant pathogenic bacteria are more susceptible than human pathogenic bacteria.
The results of the study show that cyclotides from Iranian V. odorata have potent antimicrobial activity against gram-negative, plant pathogenic bacteria.
This study is a part of our extended researches on finding new pharmaceutical potentials of plants and on developing new peptides for special purposes in a way that does not have harmful side effects or have the least side effects.
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| 23819826 |
Cyclopeptide alkaloids: stereochemistry and synthesis of the precursors of discarines C and D and myrianthine A |
10.1021/np400313w. |
J Nat Prod |
Cyclopeptide alkaloids: stereochemistry and synthesis of the precursors of discarines C and D and myrianthine A
Abstract
- The stereochemistry of discarines C (1) and D (2) and myrianthine A (3), three cyclopeptide alkaloids isolated from Discaria febrifuga, was determined by a combination of NMR studies of 1-3, enantioselective gas chromatography, and comparison of NMR data with those of synthetic tripeptides. For the synthesis of peptides, the nonproteinogenic amino acid 3-phenylserine was also obtained in its four diastereoisomeric forms (l and d threo, obtained by recrystallization of the diastereoisomeric tripeptide, and l and d erythro, obtained by a Mitsunobu reaction with the threo-tripeptides). The general synthetic strategy described in this paper allows the tripeptide to be obtained with the free N-terminal extremity protected or dimethylated. This strategy also allows the synthesis of the corresponding peptide with an imidazolidi ring.
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| 23822585 |
Suberoylanilide hydroxamic acid, a histone deacetylase inhibitor, induces the production of anti-inflammatory cyclodepsipeptides from Beauveria felina |
10.1021/np400143j. |
J Nat Prod |
Suberoylanilide hydroxamic acid, a histone deacetylase inhibitor, induces the production of anti-inflammatory cyclodepsipeptides from Beauveria felina
Abstract
- The addition of the histone deacetylase inhibitor suberoylanilide hydroxamic acid to a culture of the filamentous fungus Beauveria felina significantly changed its secondary metabolite profile and led to the isolation of eight compounds, including three new cyclodepsipeptides, desmethylisaridin E (1), desmethylisaridin C2 (2), and isaridin F (3), along with five known cyclodepsipeptide compounds. Isaridin F (3) possesses a cyclodepsipeptide ring with N-methylbutyric acid, which is rare in natural peptides. Absolute configurations of the new cyclodepsipeptides were achieved by Marfey's method. The anti-inflammatory activity of the isolated compounds was investigated through evaluating their effect on superoxide anion production and elastase release by FMLP-induced human neutrophils. Among the tested compounds, desmethylisaridin E (1) inhibited superoxide anion production and desmethylisaridin C2 (2) inhibited elastase release, with IC50 values of 10.00 ± 0.80 and 10.01 ± 0.46 μM, respectively.
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