Publications by authors named "Dirk Tourwé"

108 Publications

Using conformational constraints at position 6 of Angiotensin II to generate compounds with enhanced AT2R selectivity and proteolytic stability.

Bioorg Med Chem Lett 2021 Jul 7;43:128086. Epub 2021 May 7.

Laboratory of Organic Chemistry and Biochemistry, Department of Chemistry, University of Ioannina, Ioannina 45110, Greece; University Research Center of Ioannina (URCI), Institute of Materials Science and Computing, Ioannina, Greece. Electronic address:

The Renin-Angiotensin System (RAS) plays a crucial role in numerous pathological conditions. Two of the critical RAS players, the angiotensin receptors AT1R and AT2R, possess differential functional profiles, although they share high sequence similarity. Although the main focus has been placed on AT1R, several epidemiological studies have evidenced that activation of AT2R could operate as a multimodal therapeutic target for different diseases. Thus, the development of selective AT2R ligands could have a high clinical potential for different therapeutic directions. Furthermore, they could serve as a powerful tool to interrogate the molecular mechanisms that are mediated by AT2R. Based on our recently established high affinity and AT2R selective compound [Y]-AII we developed several analogues through modifying aminoacids located at positions 6 and 7 with various conformationally constrained analogues to enhance both the selectivity and stability. We report the development of high-affinity AT2R binders, which displayed high selectivity for AT2R versus AT1R. Furthermore, all analogues presented enhanced stability in human plasma with respect to the parent hormone Angiotensin II as also [Y]-AII.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bmcl.2021.128086DOI Listing
July 2021

Structure-Based Design of Melanocortin 4 Receptor Ligands Based on the SHU-9119-hMC4R Cocrystal Structure†.

J Med Chem 2021 01 14;64(1):357-369. Epub 2020 Nov 14.

Research Group of Organic Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.

The melanocortin receptors (MC1R-MC5R) belong to class A G-protein-coupled receptors (GPCRs) and are known to have receptor-specific roles in normal and diseased states. Selectivity for MC4R is of particular interest due to its involvement in various metabolic disorders, including obesity, feeding regulation, and sexual dysfunctions. To further improve the potency and selectivity of MC4R (ant)agonist peptide ligands, we designed and synthesized a series of cyclic peptides based on the recent crystal structure of MC4R in complex with the well-characterized antagonist (Ac-Nle-c[Asp-His-DNal(2')-Arg-Trp-Lys]-NH). These analogues were pharmacologically characterized , giving key insights into exploiting binding site subpockets to deliver more selective ligands. More specifically, the side chains of the Nle, DNal(2'), and Trp residues in , as well as the amide linkage between the Asp and Lys side chains, were found to represent structural features engaging a hMC4R/hMC3R selectivity switch.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jmedchem.0c01620DOI Listing
January 2021

Optimized Opioid-Neurotensin Multitarget Peptides: From Design to Structure-Activity Relationship Studies.

J Med Chem 2020 11 23;63(21):12929-12941. Epub 2020 Sep 23.

Research Group of Organic Chemistry, Departments of Chemistry and Bioengineering Sciences, Vrije Universiteit Brussel, 1050 Brussels, Belgium.

Fusion of nonopioid pharmacophores, such as neurotensin, with opioid ligands represents an attractive approach for pain treatment. Herein, the μ-/δ-opioid agonist tetrapeptide H-Dmt-d-Arg-Aba-β-Ala-NH () was fused to analogues. Since the NTS1 receptor has been linked to adverse effects, selective MOR-NTS2 ligands are preferred. Modifications were introduced within the native NT sequence, particularly a β-homo amino acid in position 8 and Tyr substitutions. Combination of βhArg and Dmt led to peptide , a MOR agonist, showing the highest NTS2 affinity described to date ( = 3 pM) and good NTS1 affinity ( = 4 nM), providing a >1300-fold NTS2 selectivity. The (6-OH)Tic-containing analogue also exhibited high NTS2 affinity ( = 1.7 nM), with low NTS1 affinity ( = 4.7 μM), resulting in an excellent NTS2 selectivity (>2700). In mice, hybrid produced significant and prolonged antinociception (up to 8 h), as compared to the opioid parent compound.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jmedchem.0c01376DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7667639PMC
November 2020

Neurotensin Analogues Containing Cyclic Surrogates of Tyrosine at Position 11 Improve NTS2 Selectivity Leading to Analgesia without Hypotension and Hypothermia.

ACS Chem Neurosci 2019 11 21;10(11):4535-4544. Epub 2019 Oct 21.

Département de pharmacologie et physiologie, Institut de pharmacologie de Sherbrooke, Centre de Recherche du Centre Hospitalier Universitaire de Sherbrooke, Faculté de médecine et des sciences de la santé , Université de Sherbrooke , Sherbrooke , Québec J1H 5H4 , Canada.

Neurotensin (NT) exerts its analgesic effects through activation of the G protein-coupled receptors NTS1 and NTS2. This opioid-independent antinociception represents a potential alternative for pain management. While activation of NTS1 also induces a drop in blood pressure and body temperature, NTS2 appears to be an analgesic target free of these adverse effects. Here, we report modifications of NT at Tyr to increase selectivity toward NTS2, complemented by modifications at the N-terminus to impair proteolytic degradation of the biologically active NT(8-13) sequence. Replacement of Tyr by either 6-OH-Tic or 7-OH-Tic resulted in a significant loss of binding affinity to NTS1 and subsequent NTS2 selectivity. Incorporation of the unnatural amino acid βhLys at position 8 increased the half-life to over 24 h in plasma. Simultaneous integration of both βhLys and 6-OH-Tic into NT(8-13) produced a potent and NTS2-selective analogue with strong analgesic action after intrathecal delivery in the rat formalin-induced pain model with an ED of 1.4 nmol. Additionally, intravenous administration of this NT analogue did not produce persistent hypotension or hypothermia. These results demonstrate that NT analogues harboring unnatural amino acids at positions 8 and 11 can enhance crucial pharmacokinetic and pharmacodynamic features for NT(8-13) analogues, i.e., proteolytic stability, NTS2 selectivity, and improved analgesic/adverse effect ratio.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acschemneuro.9b00390DOI Listing
November 2019

Neuromedin U and Structural Analogs: An Overview of their Structure, Function and Selectivity.

Curr Med Chem 2020 ;27(39):6744-6768

Research Group of Organic Chemistry, Departments of Chemistry and Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.

The neuromedin U peptide sequence is highly conserved between various species. Neuromedin U is involved in a variety of physiological processes. It exerts its effects via two neuromedin U receptors, NMUR1 and NMUR2. These receptors are characterized by a distinct, yet complementary, tissue distribution with NMUR1 mostly found in the periphery, while NMUR2 is most abundant in the central nervous system. The capability of the neuropeptide to reduce food intake in rodents triggered the design and synthesis of a broad range of modified peptide ligands. The purpose of these ligands is to develop novel therapeutics which could be beneficial in the treatment of obesity and diabetes. Most compounds are derived either from the full-length neuromedin U sequence or are based on the truncated orthologs of this neuropeptide. Only a few non-peptidic ligands were developed. This review provides an overview on various neuromedin U analogs and mimetics that have been reported to date.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2174/0929867326666190916143028DOI Listing
January 2021

Trifluoromethylated Proline Surrogates as Part of "Pro-Pro" Turn-Inducing Templates.

Chembiochem 2019 10 15;20(19):2513-2518. Epub 2019 Jul 15.

Research Group of Organic Chemistry, Departments of Bioengineering Sciences and Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium.

Proline is often found as a turn inducer in peptide or protein domains. Exploitation of its restricted conformational freedom led to the development of the d-Pro-l-Pro (corresponding to (R)-Pro-(S)-Pro) segment as a "templating" unit, frequently used in the design of β-hairpin peptidomimetics, in which conformational stability is, however, inherently linked to the cis-trans isomerization of the prolyl amide bonds. In this context, the stereoelectronic properties of the CF group can aid in conformational control. Herein, the impact of α-trifluoromethylated proline analogues is examined for the design of enhanced β-turn inducers. A theoretical conformational study permitted the dipeptide (R)-Pro-(R)-TfmOxa (TfmOxa: 2-trifluoromethyloxazolidine-2-carboxylic acid) to be selected as a template with an increased trans-cis rotational energy barrier. NMR spectroscopic analysis of the Ac-(R)-Pro-(R)-TfmOxa-(S)-Val-OtBu β-turn model, obtained through an original synthetic pathway, validated the prevalence of a major trans-trans conformer and indicated the presence of an internal hydrogen bond. Altogether, it was shown that the (R)-Pro-(R)-TfmOxa template fulfilled all crucial β-turn-inducer criteria.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/cbic.201900294DOI Listing
October 2019

Synthesis and Evaluation of Stabilized and Selective Neuromedin U-1 Receptor Agonists.

ACS Med Chem Lett 2018 May 23;9(5):496-501. Epub 2018 Apr 23.

Research Group of Organic Chemistry, Departments of Chemistry and Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium.

Neuromedin U (NMU) is a multifunctional neuropeptide which is characterized by a high conservation through all species. Herein, we describe the synthesis of a novel set of NMU-analogs based on the truncated NMU-8. Through combination of previously reported modifications, an elaborate structure-activity relationship study was performed aiming for the development of peptides with an increased selectivity toward NMU receptor 1 (NMUR1). Compound possessed the highest NMUR1 selectivity (IC = 0.54 nM, selectivity ratio = 5313) together with an increased potency (EC = 3.7 nM), an 18% increase of the maximal effect at NMUR1, and a higher resistance against enzymatic degradation as compared to the native NMU-8. The development of a potent NMUR1 agonist with extended half-life could represent an attractive tool to further unveil the role of NMUR1 in NMU signaling.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsmedchemlett.8b00105DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5949835PMC
May 2018

Indoloazepinone-Constrained Oligomers as Cell-Penetrating and Blood-Brain-Barrier-Permeating Compounds.

Chembiochem 2018 04 28;19(7):696-705. Epub 2018 Feb 28.

Research Group of Organic Chemistry, Departments of Chemistry and Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium.

Non-cationic and amphipathic indoloazepinone-constrained (Aia) oligomers have been synthesized as new vectors for intracellular delivery. The conformational preferences of the [l-Aia-Xxx] oligomers were investigated by circular dichroism (CD) and NMR spectroscopy. Whereas Boc-[l-Aia-Gly] -OBn oligomers 12 and 13 and Boc-[l-Aia-β -h-l-Ala] -OBn oligomers 16 and 17 were totally or partially disordered, Boc-[l-Aia-l-Ala] -OBn (14) induced a typical turn stabilized by C - and C -membered H-bond pseudo-cycles and aromatic interactions. Boc-[l-Aia-l-Ala] -OBn (15) exhibited a unique structure with remarkable T-shaped π-stacking interactions involving the indole rings of the four l-Aia residues forming a dense hydrophobic cluster. All of the proposed FITC-6-Ahx-[l-Aia-Xxx] -NH oligomers 19-23, with the exception of FITC-6-Ahx-[l-Aia-Gly] -NH (18), were internalized by MDA-MB-231 cells with higher efficiency than the positive references penetratin and Arg . In parallel, the compounds of this series were successfully explored in an in vitro blood-brain barrier (BBB) permeation assay. Although no passive diffusion permeability was observed for any of the tested Ac-[l-Aia-Xxx] -NH oligomers in the PAMPA model, Ac-[l-Aia-l-Arg] -NH (26) showed significant permeation in the in vitro cell-based human model of the BBB, suggesting an active mechanism of cell penetration.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/cbic.201700678DOI Listing
April 2018

Development of potent and proteolytically stable human neuromedin U receptor agonists.

Eur J Med Chem 2018 Jan 14;144:887-897. Epub 2017 Dec 14.

Research Group of Organic Chemistry, Departments of Chemistry and Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium. Electronic address:

Neuromedin U (NMU) is a highly conserved endogenous peptide that is involved in a wide range of physiological processes such as regulation of feeding behavior, the stress response and nociception. The major limitation to use NMU as a therapeutic is its short half-life. Here, we describe the development of a set of novel NMU-analogs based on NMU-8, by introducing unnatural amino acids into the native sequence. This approach shows that it is possible to generate molecules with increased potency and improved plasma stability without major changes of the peptidic nature or the introduction of large conjugates. When compared to the native NMU-8 peptide, compounds 16, 18 and 20 have potent agonist activity and affinity for both NMU receptors. Selectivity towards NMUR1 was observed when the Phe residue in position 4 was modified, whereas higher potencies at NMUR2 were found when substitutions of the Pro residue in position 6 were executed. To study the effect of the modifications on the proteolytic stability of the molecules, an in vitro stability assay in human plasma at 37 °C was performed. All analyzed analogs possessed an increased resistance against enzymatic degradation in human plasma resulting in half-lifes from 4 min for NMU-8, up to more than 23 h for compound 42.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ejmech.2017.12.035DOI Listing
January 2018

χ-Space Screening of Dermorphin-Based Tetrapeptides through Use of Constrained Arylazepinone and Quinolinone Scaffolds.

ACS Med Chem Lett 2017 Nov 4;8(11):1177-1182. Epub 2017 Oct 4.

Research Group of Organic Chemistry, Departments of Chemistry and Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium.

Herein, the synthesis of novel conformationally constrained amino acids, 4-amino-8-bromo-2-benzazepin-3-one (8-Br-Aba), 3-amino-3,4-dihydroquinolin-2-one, and regioisomeric 4-amino-naphthoazepinones (1- and 2-Ana), is described. Introduction of these constricted scaffolds into the -terminal tetrapeptide of dermorphin (i.e., H-Tyr-d-Ala-Phe-Gly-NH) induced significant shifts in binding affinity, selectivity, and in vitro activity at the μ- and δ-opioid receptors (MOP and DOP, respectively). A reported constrained μ-/δ-opioid lead tetrapeptide H-Dmt-d-Arg-Aba-Gly-NH was modified through application of various constrained building blocks to identify optimal spatial orientations in view of activity at the opioid receptors. Interestingly, when the aromatic moieties were turned toward the -terminus of the peptide sequences, (partial) (ant)agonism at MOP and weak (ant)agonism at DOP were noticed, whereas the incorporation of the 1-Ana residue led toward balanced low nanomolar MOP/DOP binding and in vitro agonism.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsmedchemlett.7b00347DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5683700PMC
November 2017

Efficient One-Pot Access to Trisubstituted 2-Benzazepin-3-ones as Constrained Pseudopeptide Analogues and Privileged Scaffolds.

Med Chem 2018 ;14(4):400-408

Research Group of Organic Chemistry, Departments of Chemistry and Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, B-1050, Brussels, Belgium.

Background: Benzazepines received great attention in the field of medicinal chemistry since this scaffold has been recognized to belong to the important family of privileged templates. More specifically, the 4-amino-1,2,4,5-tetrahydro-2-benzazepin-3-one (Aba) is used as a core structure in a variety of constrained therapeutic peptide (turn) mimetics.Most of the synthetic approaches towards this template have focused on cyclizations which form the central 7-membered azepine ring.

Objective: Previous investigations in our group allowed an expansion of the substitution patterns in the 4-amino-benzazepin-3-one scaffold by introduction of methyl substituents at positions 4 and 5 of the azepinone ring system, but also to 1-aryl substituted compounds. These were the only trisubstituted analogues obtained to date. To introduce an additional point of diversification and conformational constraint useful for peptide mimicry, one can use bifunctional substrates in the Ugi reaction as reported in the present manuscript.

Method: The 1-carboxamido-substituted Aba scaffold has been synthesized via the Ugi-3CR reaction starting from N-Phth-protected 2-formyl-L-Phe-OH with a set of amine and isocyanide derivatives. The most suited reaction conditions were applied, involving preformation of the imine in MeOH (0.1 M) in the presence of anhydrous Na2SO4 during 2 hours at room temperature, followed by the addition of an equimolar quantity of isocyanide prior to heating the reaction mixture at 80 °C for 20 hours, using sealed vial reaction conditions.

Results: The substituted Aba scaffolds were isolated in moderate yields (and diastereomeric ratio). This is due to the requirement for a double N-phthaloyl protection of the bifunctional building block, which prevents the use of an excess of amine reagent to drive the reaction conversion to completion, and some starting substrate always remains. Despite the moderate yields, the methodology is efficient since it only requires a limited number of synthetic steps in a final one-pot reaction. In most cases, the diastereomers could be separated by preparative RP-HPLC or via silica gel column chromatography. This is interesting from a medicinal chemistry point of view, since access is provided to the individual diastereomers.

Conclusion: We have developed an efficient and useful one-pot strategy to access 1-substituted 4- aminobenzazepinone (Aba) derivatives via the Ugi-3CR reaction. To the best of our knowledge, these scaffolds are only accessible through the presented methodology. The obtained structural complexity, as well as the substitution versatility of these trisubstituted scaffolds, will allow their use in various biological applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2174/1573406413666171002122233DOI Listing
August 2018

Analgesic Properties of Opioid/NK1 Multitarget Ligands with Distinct in Vitro Profiles in Naive and Chronic Constriction Injury Mice.

ACS Chem Neurosci 2017 10 26;8(10):2315-2324. Epub 2017 Jul 26.

Institute of Pharmacology, Polish Academy of Sciences, Department of Pain Pharmacology , 31-343 Krakow, Poland.

The lower efficacy of opioids in neuropathic pain may be due to the increased activity of pronociceptive systems such as substance P. We present evidence to support this hypothesis in this work from the spinal cord in a neuropathic pain model in mice. Biochemical analysis confirmed the elevated mRNA and protein level of pronociceptive substance P, the major endogenous ligand of the neurokinin-1 (NK1) receptor, in the lumbar spinal cord of chronic constriction injury (CCI)-mice. To improve opioid efficacy in neuropathic pain, novel compounds containing opioid agonist and neurokinin 1 (NK1) receptor antagonist pharmacophores were designed. Structure-activity studies were performed on opioid agonist/NK1 receptor antagonist hybrid peptides by modification of the C-terminal amide substituents. All compounds were evaluated for their affinity and in vitro activity at the mu opioid (MOP) and delta opioid (DOP) receptors, and for their affinity and antagonist activity at the NK1 receptor. On the basis of their in vitro profiles, the analgesic properties of two new bifunctional hybrids were evaluated in naive and CCI-mice, representing models for acute and neuropathic pain, respectively. The compounds were administered to the spinal cord by lumbar puncture. In naive mice, the single pharmacophore opioid parent compounds provided better analgesic results, as compared to the hybrids (max 70% MPE), raising the acute pain threshold close to 100% MPE. On the other hand, the opioid parents gave poor analgesic effects under neuropathic pain conditions, while the best hybrid delivered robust (close to 100% MPE) and long lasting alleviation of both tactile and thermal hypersensitivity. The results presented emphasize the potential of opioid/NK1 hybrids in view of analgesia under nerve injury conditions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acschemneuro.7b00226DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5647227PMC
October 2017

Hydrazone Linker as a Useful Tool for Preparing Chimeric Peptide/Nonpeptide Bifunctional Compounds.

ACS Med Chem Lett 2017 Jan 1;8(1):73-77. Epub 2016 Nov 1.

Department of Neuropeptides, Mossakowski Medical Research Centre Polish Academy of Sciences , 5 Pawińskiego Str., 02-106 Warsaw, Poland.

The area of multitarget compounds, joining two pharmacophores within one molecule, is a vivid field of research in medicinal chemistry. Not only pharmacophoric elements are essential for the design and activity of such compounds, but the type and length of linkers used to connect them are also crucial. In the present contribution, we describe compound in which a typical opioid peptide sequence is combined with a fragment characteristic for neurokinin-1 receptor (NK1R) antagonists through a hydrazone bridge. The compound has a high affinity for μ- and δ-opioid receptors (IC= 12.7 and 74.0 nM, respectively) and a weak affinity for the NK1R. Molecular modeling and structural considerations explain the observed activities. In in vivo test, intrathecal and intravenous administrations of exhibited a strong analgesic effect, which indicates potential BBB penetration. This letter brings an exemplary application of the hydrazone linker for fast, facile, and successful preparation of chimeric compounds.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsmedchemlett.6b00381DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5238479PMC
January 2017

Side Chain Cyclized Aromatic Amino Acids: Great Tools as Local Constraints in Peptide and Peptidomimetic Design.

J Med Chem 2016 12 12;59(24):10865-10890. Epub 2016 Oct 12.

Research Group of Organic Chemistry, Departments of Chemistry and Bio-Engineering Sciences, Vrije Universiteit Brussel , Pleinlaan 2, 1050 Brussels, Belgium.

Constraining the conformation of flexible peptides is a proven strategy to increase potency, selectivity, and metabolic stability. The focus has mostly been on constraining the backbone dihedral angles; however, the correct orientation of the amino acid side chains (χ-space) that constitute the peptide pharmacophore is equally important. Control of χ-space utilizes conformationally constrained amino acids that favor, disfavor, or exclude the gauche (-), the gauche (+), or the trans conformation. In this review we focus on cyclic aromatic amino acids in which the side chain is connected to the peptide backbone to provide control of χ- and χ-space. The manifold applications for cyclized analogues of the aromatic amino acids Phe, Tyr, Trp, and His within peptide medicinal chemistry are showcased herein with examples of enzyme inhibitors and ligands for G protein-coupled receptors.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jmedchem.6b01029DOI Listing
December 2016

Bifunctional Peptide-Based Opioid Agonist-Nociceptin Antagonist Ligands for Dual Treatment of Acute and Neuropathic Pain.

J Med Chem 2016 04 14;59(8):3777-92. Epub 2016 Apr 14.

Research Group of Organic Chemistry, Departments of Chemistry and Bio-engineering Sciences, Vrije Universiteit Brussel , Pleinlaan 2, 1050 Brussels, Belgium.

Herein, the opioid pharmacophore H-Dmt-d-Arg-Aba-β-Ala-NH2 (7) was linked to peptide ligands for the nociceptin receptor. Combination of 7 and NOP ligands (e.g., H-Arg-Tyr-Tyr-Arg-Ile-Lys-NH2) led to binding affinities in the low nanomolar domain. In vitro, the hybrids behaved as agonists at the opioid receptors and antagonists at the nociceptin receptor. Intravenous administration of hybrid 13a (H-Dmt-d-Arg-Aba-β-Ala-Arg-Tyr-Tyr-Arg-Ile-Lys-NH2) to mice resulted in potent and long lasting antinociception in the tail-flick test, indicating that 13a was able to permeate the BBB. This was further supported by a cell-based BBB model. All hybrids alleviated allodynia and hyperalgesia in neuropathic pain models. Especially with respect to hyperalgesia, they showed to be more effective than the parent compounds. Hybrid 13a did not result in significant respiratory depression, in contrast to an equipotent analgesic dose of morphine. These hybrids hence represent a promising avenue toward analgesics for the dual treatment of acute and neuropathic pain.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jmedchem.5b01976DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4850106PMC
April 2016

Dual Alleviation of Acute and Neuropathic Pain by Fused Opioid Agonist-Neurokinin 1 Antagonist Peptidomimetics.

ACS Med Chem Lett 2015 Dec 31;6(12):1209-14. Epub 2015 Oct 31.

Department of Organic Chemistry, Vrije Universiteit Brussel , Brussels, Belgium.

Herein, the synthesis and biological evaluation of dual opioid agonists-neurokinin 1 receptor (NK1R) antagonists is described. In these multitarget ligands, the two pharmacophores do not overlap, and this allowed maintaining high NK1R affinity and antagonist potency in compounds 12 and 13. Although the fusion of the two ligands resulted in slightly diminished opioid agonism at the μ- and δ-opioid receptors (MOR and DOR, respectively), as compared to the opioid parent peptide, balanced MOR/DOR activities were obtained. Compared to morphine, compounds 12 and 13 produced more potent antinociceptive effects in both acute (tail-flick) and neuropathic pain models (von Frey and cold plate). Similarly to morphine, analgesic tolerance developed after repetitive administration of these compounds. To our delight, compound 12 did not produce cross-tolerance with morphine and high antihyperalgesic and antiallodynic effects could be reinstated after chronic administration of each of the two compounds.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsmedchemlett.5b00359DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4677362PMC
December 2015

Synthesis and binding characteristics of [(3)H]neuromedin N, a NTS2 receptor ligand.

Neuropeptides 2016 Jun 8;57:15-20. Epub 2015 Dec 8.

Department of Neuropeptides, Mossakowski Medical Research Centre, Polish Academy of Sciences, 5 Pawinskiego Street, 02106 Warsaw, Poland; Department of Pharmacodynamics, Centre for Preclinical Research and Technology, Medical University of Warsaw, 1B Banacha Str., 02-106 Warsaw, Poland. Electronic address:

Neurotensin (NT) and its analog neuromedin N (NN) are formed by the processing of a common precursor in mammalian brain tissue and intestines. The biological effects mediated by NT and NN (e.g. analgesia, hypothermia) result from the interaction with G protein-coupled receptors. The goal of this study consisted of the synthesis and radiolabeling of NN, as well as the determination of the binding characteristics of [(3)H]NN and G protein activation by the cold ligand. In homologous displacement studies a weak affinity was determined for NN, with IC50 values of 454nM in rat brain and 425nM in rat spinal cord membranes. In saturation binding experiments the Kd value proved to be 264.8±30.18nM, while the Bmax value corresponded to 3.8±0.2pmol/mg protein in rat brain membranes. The specific binding of [(3)H]NN was saturable, interacting with a single set of homogenous binding sites. In sodium sensitivity experiments, a very weak inhibitory effect of Na(+) ions was observed on the binding of [(3)H]NN, resulting in an IC50 of 150.6mM. In [(35)S]GTPγS binding experiments the Emax value was 112.3±1.4% in rat brain and 112.9±2.4% in rat spinal cord membranes and EC50 values of 0.7nM and 0.79nM were determined, respectively. NN showed moderate agonist activities in stimulating G proteins. The stimulatory effect of NN could be maximally inhibited via use of the NTS2 receptor antagonist levocabastine, but not by the opioid receptor specific antagonist naloxone, nor by the NTS1 antagonist SR48692. These observations allow us to conclude that [(3)H]NN labels NTS2 receptors in rat brain membranes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.npep.2015.12.004DOI Listing
June 2016

T3P-Promoted, Mild, One-Pot Syntheses of Constrained Polycyclic Lactam Dipeptide Analogues via Stereoselective Pictet-Spengler and Meyers Lactamization Reactions.

Org Lett 2015 Sep 31;17(18):4482-5. Epub 2015 Aug 31.

Research Group of Organic Chemistry, Departments of Chemistry and Bio-Engineering Sciences, Vrije Universiteit Brussel , Pleinlaan 2, B-1050 Brussels, Belgium.

A new convenient, mild, one-pot procedure is described for the diastereoselective synthesis of constrained 7,5- and 7,6-fused azabicycloalkanes. Using 2-formyl-L-tryptophan and 2-formyl-l-phenylalanine as bielectrophilic building blocks, T3P-mediated Pictet-Spengler and Meyers lactamization reactions were developed to present chiral and polycyclic aminoindolo- and aminobenzazepinone compounds in excellent yields. The conformationally constrained compounds can serve as templates for peptidomimetic research or polyheterocyclic privileged scaffolds.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.orglett.5b02145DOI Listing
September 2015

Neuropeptide FF receptors as novel targets for limbic seizure attenuation.

Neuropharmacology 2015 Aug 9;95:415-23. Epub 2015 May 9.

Center for Neurosciences, Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Vrije Universiteit Brussel, Laarbeeklaan 103, 1090 Brussels, Belgium. Electronic address:

Neuropeptide Y (NPY) is a well established anticonvulsant and first-in-class antiepileptic neuropeptide. In this study, the controversial role of NPY1 receptors in epilepsy was reassessed by testing two highly selective NPY1 receptor ligands and a mixed NPY1/NPFF receptor antagonist BIBP3226 in a rat model for limbic seizures. While BIBP3226 significantly attenuated the pilocarpine-induced seizures, neither of the highly selective NPY1 receptor ligands altered the seizure severity. Administration of the NPFF1/NPFF2 receptor antagonist RF9 also significantly attenuated limbic seizure activity. To further prove the involvement of NPFF receptors in these seizure-modulating effects, low and high affinity antagonists for the NPFF receptors were tested. We observed that the low affinity ligand failed to exhibit anticonvulsant properties while the two high affinity ligands significantly attenuated the seizures. Continuous NPFF1 receptor agonist administration also inhibited limbic seizures whereas bolus administration of the NPFF1 receptor agonist was without effect. This suggests that continuous agonist perfusion could result in NPFF1 receptor desensitization and mimic NPFF1 receptor antagonist administration. Our data unveil for the first time the involvement of the NPFF system in the management of limbic seizures.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuropharm.2015.04.030DOI Listing
August 2015

Azepinone-Containing Tetrapeptide Analogues of Melanotropin Lead to Selective hMC4R Agonists and hMC5R Antagonist.

ACS Med Chem Lett 2015 Feb 3;6(2):192-7. Epub 2014 Dec 3.

Research Group of Organic Chemistry, Vrije Universiteit Brussel , Pleinlaan 2, B-1050 Brussels, Belgium.

To address the need for highly potent, metabolically stable, and selective agonists, antagonists, and inverse agonists at the melanocortin receptor subtypes, conformationally constrained indolo- and benzazepinone residues were inserted into the α-MSH pharmacophore, His(6)-Phe(7)-Arg(8)-Trp(9)-domain. Replacement of His(6) by an aminoindoloazepinone (Aia) or aminobenzazepinone (Aba) moiety led to hMC4R and hMC5R selective agonist and antagonist ligands, respectively (tetrapeptides 1 to 3 and 4, respectively). In peptides 1 to 3 and depending on the para-substituent of the d-Phe residue in position 2, the activity goes from allosteric partial agonism (1, R = H) to allosteric full agonism (2, R = F) and finally allosteric partial agonism (3, R = Br).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ml500436sDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4329577PMC
February 2015

Structural basis for bifunctional peptide recognition at human δ-opioid receptor.

Nat Struct Mol Biol 2015 Mar 16;22(3):265-8. Epub 2015 Feb 16.

1] Department of Chemistry, Vrije Universiteit Brussel, Brussels, Belgium. [2] Department of Bioengineering Sciences, Vrije Universiteit Brussel, Brussels, Belgium.

Bifunctional μ- and δ-opioid receptor (OR) ligands are potential therapeutic alternatives, with diminished side effects, to alkaloid opiate analgesics. We solved the structure of human δ-OR bound to the bifunctional δ-OR antagonist and μ-OR agonist tetrapeptide H-Dmt-Tic-Phe-Phe-NH2 (DIPP-NH2) by serial femtosecond crystallography, revealing a cis-peptide bond between H-Dmt and Tic. The observed receptor-peptide interactions are critical for understanding of the pharmacological profiles of opioid peptides and for development of improved analgesics.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nsmb.2965DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4351130PMC
March 2015

Synthesis and biological evaluation of compact, conformationally constrained bifunctional opioid agonist - neurokinin-1 antagonist peptidomimetics.

Eur J Med Chem 2015 Mar 19;92:64-77. Epub 2014 Dec 19.

Laboratory of Organic Chemistry, Departments of Chemistry and Bio-engineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium. Electronic address:

A reported mixed opioid agonist - neurokinin 1 receptor (NK1R) antagonist 4 (Dmt-D-Arg-Aba-Gly-(3',5'-(CF3)2)NMe-benzyl) was modified to identify important features in both pharmacophores. The new dual ligands were tested in vitro and subsequently two compounds (lead structure 4 and one of the new analogues 22, Dmt-D-Arg-Aba-β-Ala-NMe-Bn) were selected for in vivo behavioural assays, which were conducted in acute (tail-flick) and neuropathic pain models (cold plate and von Frey) in rats. Compared to the parent opioid compound 33 (without NK1R pharmacophore), hybrid 22 was more active in the neuropathic pain models. Attenuation of neuropathic pain emerged from NK1R antagonism as demonstrated by the pure NK1R antagonist 6. Surprisingly, despite a lower in vitro activity at NK1R in comparison with 4, compound 22 was more active in the neuropathic pain models. Although potent analgesic effects were observed for 4 and 22, upon chronic administration, both manifested a tolerance profile similar to that of morphine and cross tolerance with morphine in a neuropathic pain model in rat.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ejmech.2014.12.033DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4336569PMC
March 2015

Synthesis of fused 3-aminoazepinones via trapping of a new class of cyclic seven-membered allenamides with furan.

Org Lett 2014 Jul 9;16(14):3712-5. Epub 2014 Jul 9.

Research Group of Organic Chemistry, Department of Chemistry and Department of Bio-engineering Sciences, Faculty of Science and Bio-engineering Sciences and ‡Department of General Chemistry, Vrije Universiteit Brussel , Pleinlaan 2, B-1050 Brussels, Belgium.

Novel tricyclic tetrahydroazepinones were synthesized via an in situ Diels-Alder reaction of furan with cyclic allenamides. These reactive intermediates are the first examples of cyclic seven-membered allenamides and were prepared starting from N-(2-chloroallyl)-2-allylglycine derivatives via ring-closing metathesis followed by dehydrochlorination. The trapping of the intermediate cycloallene with furan occurred endo- and regioselectively and provided a convenient entry into new building blocks for medicinal chemistry. The diastereoselectivity of the cycloaddition was confirmed using quantum chemical computations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ol501529zDOI Listing
July 2014

One-pot isomerization-cross metathesis-reduction (ICMR) synthesis of lipophilic tetrapeptides.

ACS Comb Sci 2014 Jul 18;16(7):342-51. Epub 2014 Jun 18.

Department of Organic Chemistry, Vrije Universiteit Brussel , Pleinlaan 2, B-1050 Brussels, Belgium.

An efficient, versatile and rapid method toward homologue series of lipophilic tetrapeptide derivatives (herein, the opioid peptides H-TIPP-OH and H-DIPP-OH) is reported. High atom economy and a minimal number of synthetic steps resulted from a one-pot tandem isomerization-cross metathesis-reduction sequence (ICMR), applicable both in solution and solid phase methodology. The broadly applicable synthesis proceeds with short reaction times and simple work-up, as illustrated in this work for alkylated opioid tetrapeptides.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/co500020aDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4140390PMC
July 2014

In Vitro Membrane Permeation Studies and in Vivo Antinociception of Glycosylated Dmt-DALDA Analogues.

ACS Med Chem Lett 2014 Apr;5(4):352-357

Laboratory of Chemical Biology and Peptide Research, Clinical Research Institute of Montreal, Montreal, QC H2W 1R7, Canada.

In this study the μ opioid receptor (MOR) ligands DALDA (Tyr-d-Arg-Phe-Lys-NH) and Dmt-DALDA (Dmt-d-Arg-Phe-Lys-NH, Dmt = 2',6'-dimethyltyrosine) were glycosylated at the N- or C-terminus. Subsequently, the modified peptides were subjected to in vitro and in vivo evaluation. In contrast to the N-terminally modified peptide (), all peptide analogues derivatized at the C-terminus (-) proved to possess high affinity and agonist potency at both MOR and DOR (δ opioid receptor). Results of the Caco-2 monolayer permeation, as well as in vitro blood-brain barrier model experiments, showed that, in the case of compound , the glycosylation only slightly diminished the lumen-to-blood and blood-to-lumen transport. Altogether, these experiments were indicative of transcellular transport but not active transport. In vivo assays demonstrated that the peptides were capable of (i) crossing the blood-brain barrier (BBB) and (ii) activating both the spinal ascending as well as the descending opioid pathways, as determined by the tail-flick and hot-plate assays, respectively. In contrast to the highly selective MOR agonist Dmt-DALDA , compounds - are mixed MOR/DOR agonists, expected to produce reduced opioid-related side effects.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ml4004765DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4023695PMC
April 2014

Presence and regulation of insulin-regulated aminopeptidase in mouse macrophages.

J Renin Angiotensin Aldosterone Syst 2014 Dec 14;15(4):466-79. Epub 2014 Feb 14.

Myeloid Cell Immunology Laboratory, VIB, Belgium Cellular and Molecular Immunology Unit, Vrije Universiteit Brussel, Belgium.

Introduction: The insulin-regulated aminopeptidase (IRAP) is expressed in several cell types, where it is mainly located in specialized secretory endosomes that are quickly recruited to the cell surface upon cell type-specific activation. Here we describe for the first time the expression and subcellular distribution of IRAP in macrophages.

Methods: IRAP mRNA expression, protein expression and presence at the cell surface was investigated by real-time polymerase chain reaction (PCR), Western blot and [(3)H]IVDE77 binding, respectively.

Results: IRAP mRNA expression was increased by interferon-γ (IFN-γ) and lipopolysaccharide (LPS), but not by anti-inflammatory cytokines (interleukin (IL)-4, IL-10, transforming growth factor β (TGF-β)). IFN-γ increased [(3)H]IVDE77 binding steadily over time, while LPS quickly and transiently recruited IRAP to the cell surface. Combined stimulations with IFN-γ and LPS showed the same pattern as LPS alone. Latex particles also induced a transient recruitment of IRAP to the cell surface, but no difference was observed in phagocytic uptake between wild-type and IRAP(-/-) macrophages, suggesting that the enzymatic activity of IRAP is not required for the ingestion of particles.

Conclusion: IRAP is more highly expressed in pro-inflammatory M1-activated macrophages and its presence at the cell surface is modulated upon exposure to IFN-γ, LPS or exogenous particles.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1177/1470320313507621DOI Listing
December 2014

Development and pharmacological characterization of conformationally constrained urotensin II-related peptide agonists.

J Med Chem 2013 Dec 26;56(23):9612-22. Epub 2013 Nov 26.

INRS-Institut Armand-Frappier, Institut national de la recherche scientifique, Université du Québec , Ville de Laval, Québec, QC H7V 1B7, Canada.

Urotensin II (UII) and its paralog peptide, urotensin II-related peptide (URP), exert not only common but also divergent actions through the activation of UT, a specific membrane-bound receptor that belongs to the 1A G protein-coupled receptor subclass. In this study, we have designed and synthesized new URP analogues in which the intracyclic Trp residue was replaced with natural, unnatural, and constrained amino acids to determine important physicochemical features for receptor binding and activation. The biological data, highlighting the potent agonistic behavior of [Tiq(4)]URP and [Tpi(4)]URP, also suggest that the Trp residue, and more specifically the indole ring, is not critical for receptor interaction and could in fact be involved in the intramolecular stabilization of the bioactive conformation of URP. Finally, these analogues, which are intracyclic constrained URP-based agonists, could represent useful pharmacological tools for the study of the urotensinergic system.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jm401153jDOI Listing
December 2013

Highly diastereoselective synthesis of 1-carbamoyl-4-aminoindoloazepinone derivatives via the Ugi reaction.

Org Lett 2013 Nov 25;15(22):5866-9. Epub 2013 Oct 25.

Department of Organic Chemistry, Vrije Universiteit Brussel , Pleinlaan 2, B-1050 Brussels, Belgium , and Institute of Organic Chemistry , Polish Academy of Sciences, Kasprzaka Str. 44/52, 01-224 Warsaw, Poland.

A one-pot procedure for the highly diastereoselective synthesis of 1-carbamoyl-4-amino-1,2,4,5-tetrahydroindolo[2,3-c]azepin-3-one derivatives is described. Using 2-formyl-L-tryptophan as a bifunctional building block, a catalyst-free Ugi-three-component reaction (Ugi-3CR) was developed to present trisubstituted indoloazepinones in good yields and excellent diastereomeric excess.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ol402940xDOI Listing
November 2013

Identification of Dmt-D-Lys-Phe-Phe-OH as a highly antinociceptive tetrapeptide metabolite of the opioid-neurotensin hybrid peptide PK20.

Pharmacol Rep 2013 ;65(4):836-46

Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawińskiego 5, PL 02-106 Warszawa, Poland.

Background: Recently, we presented a novel compound (PK20, Dmt-D-Lys-Phe-Phe-Lys-Lys-Pro-Phe-Tle-Leu-OH) that targets single entity opioid and neurotensin pharmacophores. This endomorphin-2-like opioid peptide was introduced as a highly active analgesic because it elicited a strong dose- and time-dependent antinociceptive response when administered centrally and peripherally. Its pain-relieving activity was observed as rapidly as 5 min after drug injection. Such promising results led us to perform further studies, such as determining the resistance to enzymatic degradation, which resulted in obtaining a very stable opioid pharmacore PK20 metabolite.

Methods: The synthesis of PK20 and its N-terminal tetrapeptide fragment has been accomplished using solid phase peptide chemistry. The biological stability of peptides has been measured in human serum and analyzed by HPLC/MS. Peptides were pharmacologically characterized in in vitro MOP and DOP receptor binding as well as [(35)S]GTPγS receptor binding assays. Antinociceptive properties of compounds were measured by in vivo assays in C57Bl6 mice after intravenous or intrathecal applications.

Results: Dmt-D-Lys-Phe-Phe-OH (PK20M), an N-terminal tetrapeptide metabolite of the opioid-neurotensin hybrid peptide PK20, is characterized by a long duration of action, as demonstrated by a preserved, long-lasting analgesic effect even 2 h post-injection (average % MPE = 69.33). In rat brain membranes, PK20M efficiently displaced both the MOP and DOP receptor selective radioprobes [(3)H]DAMGO and [(3)H]DIDI (pKi of 9.52 and 7.86, respectively) and potently stimulated [(35)S]GTPγS binding, proving full agonism at both receptor types. In the [(35)S]GTPγS assay, which measured the agonist-mediated G protein activation, PK20M together with PK20 and Met-enkephalin were potent stimulators of the regulatory G proteins. The relative affinities of PK20M for the μ and δ receptor subtypes revealed μ-receptor selectivity.

Conclusion: The novel MOP receptor selective metabolite has been shown to possess opioid subtype receptor selectivity, high potency, and effective analgesic activities as measured in various bioassays.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/s1734-1140(13)71064-8DOI Listing
June 2014

Stabilisation of a short α-helical VIP fragment by side chain to side chain cyclisation: a comparison of common cyclisation motifs by circular dichroism.

J Pept Sci 2013 Jul 27;19(7):423-32. Epub 2013 May 27.

Department of Organic Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, B-1050, Brussels, Belgium.

A model octapeptide segment derived from vasoactive intestinal peptide (VIP) was utilised to investigate the effect of several conventional cyclisation methods on the α-helical conformation in short peptide fragments. Three of the classical macrocyclisation techniques (i.e. lactamisation, ring-closing metathesis and Huisgen cycloaddition) were applied, and the conformations of the resulting cyclic peptides, as well as their linear precursors, were compared by CD analysis. The visibly higher folding propensity of the triazole-tethered peptide after azide-alkyne CuAAC macrocyclisation illustrates that the secondary structure of a short peptide fragment can differ significantly depending on the chemical strategy used to covalently cross-link side chain residues in a 'helical' fragment.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/psc.2515DOI Listing
July 2013