1.
El-Seedi, Hesham R., et al.
(författare)
Recent insights into the biosynthesis and biological activities of natural xanthones
2010
Ingår i: Current Medicinal Chemistry. - : Bentham Science Publishers Ltd.. - 0929-8673 .- 1875-533X. ; 17:9, s. 854-901
Forskningsöversikt (refereegranskat) abstract
This review focuses on recent advances in our understanding of the complex biosynthetic pathways and diverse biological activities of naturally occurring xanthones. The biosynthesis section covers studies published from 1989 to 2008 on xanthone production in plants and fungi, while the bioactivity review presents tabulated activities of more than 250 xanthones described in studies published from 2001 to 2008, together with structural information and indications of their wide-ranging potential uses as pharmacological tools. A large number of relevant papers have been published on these subjects (128 cited here), illustrating the diversity of the xanthones and their possible uses.
2.
Strand, Malin, et al.
(författare)
The Bacterial (Vibrio alginolyticus) Production of Tetrodotoxin in the Ribbon Worm Lineus longissimus-Just a False Positive?
2016
Ingår i: Marine Drugs. - Basel : MDPI AG. - 1660-3397. ; 14:4
Tidskriftsartikel (refereegranskat) abstract
We test previous claims that the bacteria Vibrio alginolyticus produces tetrodotoxin (TTX) when living in symbiosis with the nemertean Lineus longissimus by a setup with bacteria cultivation for TTX production. Toxicity experiments on the shore crab, Carcinus maenas, demonstrated the presence of a paralytic toxin, but evidence from LC-MS and electrophysiological measurements of voltage-gated sodium channel-dependent nerve conductance in maleWistar rat tissue showed conclusively that this effect did not originate from TTX. However, a compound of similar molecular weight was found, albeit apparently non-toxic, and with different LC retention time and MS/MS fragmentation pattern than those of TTX. We conclude that C. maenas paralysis and death likely emanate from a compound <5 kDa, and via a different mechanism of action than that of TTX. The similarity in mass between TTX and the Vibrio-produced low-molecular-weight, non-toxic compound invokes that thorough analysis is required when assessing TTX production. Based on our findings, we suggest that re-examination of some published claims of TTX production may be warranted.
3.
Kerr White, John, et al.
(författare)
A Synthetic Cyclized Antimicrobial Peptide with Potent Effects against Drug-Resistant Skin Pathogens
2023
Ingår i: ACS - Infectious Diseases. - : American Chemical Society (ACS). - 2373-8227. ; 9:5, s. 1056-1063
Tidskriftsartikel (refereegranskat) abstract
Dermal infections requiring treatment are usually treated with conventional antibiotics, but the rise of bacterial resistance to first-line antibiotics warrants alternative therapeutics. Here, we report that a backbone-cyclized antimicrobial peptide, CD4-PP, designed from the human host defense peptide LL-37, has strong direct antibacterial effects on antibiotic sensitive as well as resistant-type strains and clinical isolates of common skin pathogens in the low (<2) μM range. In addition, it influences innate immunity in keratinocytes, and treatment with CD4-PP is able to clear bacterial infections in infected keratinocytes. Additionally, CD4-PP treatment significantly reduces the wound area in a lawn of keratinocytes infected with MRSA. In conclusion, CD4-PP has the potential to serve as a future drug treating wounds infected with antibiotic-resistant bacteria.
4.
Pränting, Maria, et al.
(författare)
The cyclotide cycloviolacin O2 from Viola odorata has potent bactericidal activity against Gram-negative bacteria
2010
Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press (OUP). - 0305-7453 .- 1460-2091. ; 65:9, s. 1964-1971
Tidskriftsartikel (refereegranskat) abstract
OBJECTIVES:To determine the antibacterial activity of small cyclic plant proteins, i.e. cyclotides, and the importance of the surface exposed charged residues for activity.METHODS:Prototypic cyclotides, including the Möbius kalata B1 and the bracelet cycloviolacin O2 (cyO2), were isolated using reversed-phase HPLC. Initial activity screenings were conducted using radial diffusion assays (RDAs) and MIC assays with Salmonella enterica serovar Typhimurium LT2, Escherichia coli and Staphylococcus aureus as test strains. For the most active peptide, cyO2, time-kill kinetics was determined in sodium phosphate buffer (containing 0.03% trypticase soy broth) against several Gram-negative and Gram-positive bacterial species. Charged residues in cyO2 were chemically modified and activity was determined in time-kill assays.RESULTS:CyO2 was the most active cyclotide and efficiently inhibited the growth of S. enterica serovar Typhimurium LT2 and E. coli in RDAs and MIC assays, while the other peptides were less active. In time-kill assays, cyO2 also had bactericidal activity against the Gram-negative species Klebsiella pneumoniae and Pseudomonas aeruginosa. In contrast, none of the cyclotides had high activity against S. aureus. Chemical masking of the charged Glu and Lys residues in cyO2 caused a near total loss of activity against Salmonella, while masking Arg caused a less pronounced activity reduction.CONCLUSIONS:CyO2 is a cyclotide with potent activity against Gram-negative bacteria. The charged residues in cyO2 are all required for optimum antibacterial activity. In combination with its previously demonstrated cytotoxic activity against cancer cells and the general stability of cyclotides, cyO2 provides a promising scaffold for future drug design.
5.
Aboye, Teshome L., et al.
(författare)
A Cactus-Derived Toxin-Like Cystine Knot Peptide with Selective Antimicrobial Activity
2015
Ingår i: ChemBioChem. - : Wiley. - 1439-4227 .- 1439-7633. ; 16:7, s. 1068-1077
Tidskriftsartikel (refereegranskat) abstract
Naturally occurring cystine knot peptides show a wide range of biological activity, and as they have inherent stability they represent potential scaffolds for peptide-based drug design and biomolecular engineering. Here we report the discovery, sequencing, chemical synthesis, three-dimensional solution structure determination and bioactivity of the first cystine knot peptide from Cactaceae (cactus) family: Ep-AMP1 from Echinopsis pachanoi. The structure of Ep-AMP1 (35 amino acids) conforms to that of the inhibitor cystine knot (or knottin) family but represents a novel diverse sequence; its activity was more than 500 times higher against bacterial than against eukaryotic cells. Rapid bactericidal action and liposome leakage implicate membrane permeabilisation as the mechanism of action. Sequence homology places Ec-AMP1 in the plant C6-type of antimicrobial peptides, but the three dimensional structure is highly similar to that of a spider neurotoxin.
6.
Melander, Erik
(författare)
A pharmacokinetic approach to intra-brain distribution with a focus on cyclic peptides
2022
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
When designing treatments for disorders of the central nervous system (CNS) reaching the site of action is a major hurdle in the development process. Regardless if the target is extra- or intracellular, precise measurements to understand the distribution within the CNS are required. There is however a lack of understanding of differences in blood-brain barrier transport and intra-brain distribution of both small and large molecules. In this thesis the regional Blood-Brain Barrier transport of antipsychotic agents, along with their brain tissue binding and regional cellular accumulation was quantified. Furthermore, a novel LC-MS/MS method was developed for the quantitative analysis of the cyclic peptide kalata B1 was developed for analysis of brain tissue and plasma samples. The Blood-Brain Barrier transport, permeability, intra-brain distribution and cellular accumulation were assessed for two cyclic peptides, SFTI-1 and kalata B1. The antipsychotics exhibited clear differences in their regional BBB transport as well as their brain tissue binding, with the most dramatic spatial differences in BBB transport being observed for the p-glycoprotein substrates risperidone and paliperidone. The highest level of transporter mediated protection was observed in the cerebellum, with pronounced efflux for several of the antipsychotics. The development of a quantitative method for the cyclic peptide kalata B1 was successfully validated and applied to measure low concentration of the peptide in biological matrices. The BBB transport of SFTI-1 was markedly higher than that of kalata B1 whereas both peptides exhibited similar permeability across an in vitro BBB model. It was also shown that SFTI-1 resides mainly within the interstitial fluid within the brain, but that kalata B1 readily enters the cells of the brain parenchyma. The cellular accumulation of kalata B1 was abolished under cold conditions, and was not observable in lung tissue, suggesting an active process that is tissue specific. It was also shown that both peptides are taken up into cell cultures of neurons and astrocytes.In conclusion this thesis and the studies herein contribute to a better understanding of distribution patterns of both antipsychotics and cyclic peptides and provides valuable lessons in terms of what types of studies should be prioritized for the development of such molecules into therapeutic agents.
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8.
9.
Aboye, Teshome Leta, 1975-
(författare)
Engineering of the Ultra-stable Cystine Knot Framework of Microproteins : Design, Chemical Synthesis and Structural Studies
2011
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Ultra-stable cystine knotted microproteins, in which two disulfides and their connecting backbones form a circle that is penetrated by the third disulfide bonds, have attracted high interest due to their resistance to degradation in vitro and potential for the development of peptide drugs. This thesis gives new insights into engineering of that framework of microproteins, including approaches to their chemical synthesis, backbone engineering, structural and biological evaluations. Synthetic and oxidative folding approaches for bracelet cyclotides, a family of cyclic cystine knotted microproteins, was developed using a model peptide, cycloviolacin O2. Following assembly of the peptide chain, protected peptide was generated by mild cleavage that was subsequently thioesterified and cyclized in solution. The cyclic peptide was oxidatively folded under optimized conditions containing co-solvent and non-ionic detergent affording native cycloviolacin O2 as a major product. To gain further insights into the heterogeneity, efficiency and kinetics of cyclotides’ oxidative folding, the intermediates that accumulate in oxidative refolding pathways of all cyclotide subfamilies: Möbius, bracelet and the hybrid cyclotides were quantitatively determined under four different folding conditions. The results were used for defining major folding pathways, which indicated that Möbius cyclotides might accumulate heterogeneous folding intermediates with one-, two- and three-disulfides, whereas bracelet tend to accumulate a homogenous intermediate with three-disulfides, depending on the buffer systems used. Furthermore, to probe the internal factors contributing to inefficiency of oxidative folding, as well as undesired bioactivities of bracelet cyclotides (e.g., cytotoxic activity), polymer-hybridized cyclotides were designed by replacing non-conserved residues with small isosteric polymers. The designed hybrid analogs in which hybridization involved replacement of loop 3 with isosteric polymers showed improved synthetic and oxidative folding properties. The cytoxicity of a model hybrid designed with replacement of loop 3 and 5 exhibited no cytotoxic activity at concentration of 128-fold relative to that of native peptide. Furthermore, 1D and 2D 1H NMR analysis of this hybrid showed that it had well structured fold.
10.
Aboye, Teshome Leta, et al.
(författare)
Interlocking disulfides in circular proteins : toward efficient oxidative folding of cyclotides.
2011
Ingår i: Antioxidants and Redox Signaling. - : Mary Ann Liebert Inc. - 1523-0864 .- 1557-7716. ; 14:1, s. 77-86
Tidskriftsartikel (refereegranskat) abstract
Cyclotides are ultrastable plant proteins characterized by the presence of a cyclic amide backbone and three disulfide bonds that form a cystine knot. Because of their extreme stability, there has been significant interest in developing these molecules as a drug design scaffold. For this potential to be realized, efficient methods for the synthesis and oxidative folding of cyclotides need to be developed, yet we currently have only a basic understanding of the folding mechanism and the factors influencing this process. In this study, we determine the major factors influencing oxidative folding of the different subfamilies of cyclotides. The folding of all the cyclotides examined was heavily influenced by the concentration of redox reagents, with the folding rate and final yield of the native isomer greatly enhanced by high concentrations of oxidized glutathione. Addition of hydrophobic solvents to the buffer also enhanced the folding rates and appeared to alter the folding pathway. Significant deamidation and isoaspartate formation were seen when oxidation conditions were conducive to slow folding. The identification of factors that influence the folding and degradation pathways of cyclotides will facilitate the development of folding screens and optimized conditions for producing cyclotides and grafted analogs as stable peptide-based therapeutics.
