| 1. |
- Andappan, Murugaiah M. S., et al.
(författare)
-
From the First Selective Non-Peptide AT(2) Receptor Agonist to Structurally Related Antagonists
- 2012
-
Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 55:5, s. 2265-2278
-
Tidskriftsartikel (refereegranskat)abstract
- A para substitution pattern of the phenyl ring is a characteristic feature of the first reported selective AT(2) receptor agonist M024/C21 (1) and all the nonpeptidic AT(2) receptor agonists described so far. Two series of compounds structurally related to 1 but with a meta substitution pattern have now been synthesized and biologically evaluated for their affinity to the AT(1) and AT(2) receptors. A high AT(2)/AT(1) receptor selectivity was obtained with all 41 compounds synthesized, and the majority exhibited K-i ranging from 2 to 100 nM. Five compounds were evaluated for their functional activity at the AT(2) receptor, applying a neurite outgrowth assay in NG108-15 cells.. Notably, four of the five compounds, with representatives from both series, acted as potent AT(2) receptor antagonists. These compounds were found to be considerably more effective than PD 123,319, the standard AT(2) receptor antagonist used in most laboratories. No AT(2) receptor antagonists were previously reported among the derivatives with a para substitution pattern. Hence, by a minor modification of the agonist 1 it could be transformed into the antagonist, compound 38. These compounds should serve as valuable tools in the assessment of the role of the AT(2) receptor in more complex physiological models.
|
|
| 2. |
- Botros, Milad, 1951-
(författare)
-
Characterization of Substance P (SP) Aminoterminal SP (1-7) Binding in Brain Regions and Spinal Cord of the Male Rat : Studies on the Interaction with Opioid Related Pathways
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Binding sites for substance P(1-7), SP(1-7) have been identified and characterized for the first time in crude membrane fraction from rat CNS using tritiated ([3H]) SP(1-7) as tracer. These putative receptors were investigated in relation to their affinity for tachykinins, opioid peptides and sigma receptor ligands. [3H]-SP(1-7) specifically binds to high affinity binding sites identified as receptor targets for the heptapeptide SP (1-7). Two distinct binding sites were observed in the spinal cord. One site is recognized by high affinity for SP(1-7) with a Kd of 0.5 nM, whereas the other site showed low affinity for the heptapeptide (Kd=12 nM). In the brain, the binding of SP(1-7) fitted a single site binding model with a Kd of 4.4 nM and a Ki of 4.2 nM. Further, using the spinal cord membranes the binding of [3H]-SP (1-7) was weakly displaced by SP and other N-terminal fragments thereof and no or negligible affinity was observed for ligands of the NK-1, NK-2 and NK-3 tachykinin receptors, C-terminal SP(5-11), Tyr-w-MIF-1 or the mu-opioid receptor antagonists naloxone and naloxonazine. On the other hand it was significantly displaced by endomorphin-2, DAMGO, and Try-MIF-1 and exhibit some affinity for MIF-1, ß-casomorphin and endomorphin-1. However, only endomorphin-2, DAMGO and Tyr-MIF-1 showed affinity in the close range of the native peptide SP(1-7). The affinity of endomorphin-2 for the spinal cord site was 10 times lower than that of SP(1-7) but more than 100 times higher than the affinity recorded for endomorphin-1. Tyr-MIF-1 but not Tyr-w-MIF-1 showed similar affinity as endomorphin-2 for SP(1-7) site. All peptides exhibiting high affinity at the SP(1-7) site, have a phenylalanine or a leucine residue in their C-terminal structure.Further, synthetic analogues of SP(1-7) were tested for their affinity for the SP(1-7) receptor in the rat spinal cord. An important finding here was that the receptor-ligand-interaction was favoured by the C-terminal region of SP(1-7). Residues at positions 5-7 appeared crucial for binding to the specific SP(1-7) site. The presence of the amidated Phe7 residue was extremely critical for binding to the SP(1-7) site.The analogue Gln5-Gln6-Phe7-NH2 was almost equipotent with the parent peptide in the SP (1-7) receptor binding assay.Furthermore, the SP(1-7)-amide potently and dose dependently reduced several signs of the reaction to morphine withdrawal and was significantly attenuated by the addition of the sigma agonist SK-10047.In conclusion, the work presented in this thesis has contributed the characterization of the properties of highly selective binding sites for SP(1-7) in the rat spinal cord and VTA. These sites appear to be distinct from the µ-opioid receptor or any of the known neurokinin receptors. The study further indicates that the SP(1-7)-amide mimics the effect of the nativ heptapeptide and that the mechanisms for its action involve a sigma receptor site.
|
|
| 3. |
|
|
| 4. |
- Botros, Milad, et al.
(författare)
-
Endomorphins interact with the substance P (SP) aminoterminal SP (1-7) binding in the ventral tegmental area of the rat brain
- 2008
-
Ingår i: Peptides. - : Elsevier BV. - 0196-9781 .- 1873-5169. ; 29:10, s. 1820-1824
-
Tidskriftsartikel (refereegranskat)abstract
- We have recently identified a specific binding site for the tachykinin peptide substance P (SP) fragment SP1-7 in the rat spinal cord. This site appeared very specific for SP1-7 as the binding affinity of this compound highly exceeded those of other SP fragments. We also observed that endomorphin-2 (EM-2) exhibited high potency in displacing SP1-7 from this site. In the present work using a [H-3]-labeled derivative of the heptapeptide we have identified and characterized [H-3]-SP1-7 binding in the rat ventral tegmental area (VTA). Similarly to the [H-3]-SP1-7 binding in the spinal cord the affinity of unlabeled SP1-7 to the specific site in VTA was significantly higher than those of other SP fragments. Further, the tachykinin receptor NK-1, NK-2 and NK-3 ligands showed no or negligible binding to the identified site. However, the mu-opioid peptide (MOP) receptor agonists DAMGO, EM-1 and EM-2 did, and significant difference was observed in the binding affinity between the two endomorphins. As recorded from displacement curves the affinity of EM-2 for the SP1-7 site was 4-5 times weaker than that for SP1-7 but about 5 times higher than that of EM-1. The opioid receptor antagonists naloxone and naloxonazine showed weak or negligible binding. it was concluded that the specific site identified for SP1-7 binding in the rat VTA is distinct from the MOP receptor although it exhibits high affinity for EM-2.
|
|
| 5. |
|
|
| 6. |
- Fransson, Rebecca, et al.
(författare)
-
Discovery of Dipeptides with High Affinity to the Specific Binding Site for Substance P1-7
- 2010
-
Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 53:6, s. 2383-2389
-
Tidskriftsartikel (refereegranskat)abstract
- Substance P 1-7 (SP1-7, H-Arg-Pro-Lys-Pro-Gln-Gln-Phe-OH) is the major bioactive metabolite of substance P. The interest in this heptapeptide originates from the observation that it modulates, and in certain cases opposes the effects of the parent peptide. e.g., the nociceptive effect. The p-opioid receptor agonist endomorphin-2 (EM-2, H-Tyr-Pro-Phe-Phe-NH2) has been found to also interact with the specific binding site of SP1-7 with only a 10-fold lower affinity compared to the native peptide. Considering the smaller size of EM-2 compared to the target heptapeptide, it was selected as a lead compound in the development of low-molecular-weight ligands to the SP1-7 binding site. An alanine scan and truncation study led to the unexpected discovery of the dipeptide H-Phe-Phe-NH2 (K-i = 1.5 nM), having equal affinity as the endogenous heptapeptide SP1-7. Moreover, the studies show that the C-terminal phenylalanine amide is crucial for the affinity of the dipeptide.
|
|
| 7. |
- Fransson, Rebecca, et al.
(författare)
-
Small peptides mimicking substance P (1-7) and encompassing a C-terminal amide functionality
- 2008
-
Ingår i: Neuropeptides. - : Elsevier BV. - 0143-4179 .- 1532-2785. ; 42:1, s. 31-37
-
Tidskriftsartikel (refereegranskat)abstract
- Some of the biological effects demonstrated after administration of substance P (SP) in vivo can indirectly be attributed to the fragmentation of the undecapeptide to its N-terminal bioactive fragment SP1–7. This heptapeptide (H-Arg-Pro-Lys-Pro-Gln-Gln-Phe-OH) is a major bioactive metabolite from SP that frequently exerts similar biological effects as the parent peptide but also, in several cases, completely opposite actions. Specific binding sites for the heptapeptide SP1–7 that are separate from the SP preferred NK receptors have been identified. In this study we demonstrate that (a) the C-terminal part of the SP metabolite SP1–7 is most important for binding as deduced from an Ala scan and that a replacement of Phe7 for Ala is deleterious, (b) truncation of the N-terminal amino acid residues of SP1–7 delivers peptides with retained binding activity, although with somewhat lower binding affinities than SP1–7 and (c) a C-terminal amide group as a replacement for the terminal carboxy group of SP1–7 and for all of the truncated ligands synthesized affords approximately 5–10-fold improvements of the binding affinities.
|
|
| 8. |
- Georgsson, Jennie, et al.
(författare)
-
Angiotensin II Pseudopeptides Containing 1,3,5-Trisubstituted Benzene Scaffolds with High AT2 Receptor Affinity
- 2005
-
Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 48:21, s. 6620-6631
-
Tidskriftsartikel (refereegranskat)abstract
- Two 1,3,5-trisubstituted aromatic scaffolds intended to serve as γ-turn mimetics have been synthesized and incorporated in five pseudopeptide analogues of angiotensin II (Asp-Arg-Val-Tyr-Ile-His-Pro-Phe), replacing Val-Tyr-Ile, Val-Tyr, or Tyr-Ile. All the tested compounds exhibited nanomolar affinity for the AT2 receptor with the best compound (3) having a Ki of 1.85 nM. Four pseudopeptides were AT2 selective, while one (5) also exhibited good affinity for the AT1 receptor (Ki = 30.3 nM). This pseudopeptide exerted full agonistic activity in an AT2 receptor induced neurite outgrowth assay but displayed no agonistic effect in an AT1 receptor functional assay. Molecular modeling, using the program DISCOtech, showed that the high-affinity ligands could interact similarly with the AT2 receptor as other ligands with high affinity for this receptor. A tentative agonist model is proposed for AT2 receptor activation by angiotensin II analogues. We conclude that the 1,3,5-trisubstituted benzene rings can be conveniently prepared and are suitable as γ-turn mimics.
|
|
| 9. |
- Georgsson, Jennie, et al.
(författare)
-
Short pseudopeptides containing turn scaffolds with high AT(2) receptor affinity
- 2006
-
Ingår i: Bioorganic & Medicinal Chemistry. - : Elsevier BV. - 0968-0896 .- 1464-3391. ; 14:17, s. 5963-5972
-
Tidskriftsartikel (refereegranskat)abstract
- Two pentapeptides, Ac-Tyr-Ile-His-Pro-Phe/Ile, were synthesized and shown to have angiotensin II AT(2) receptor affinity and agonistic activity. Based on these peptides, a new series of 13 pseudopeptides was synthesized via introduction of five different turn scaffolds replacing the Tyr-Ile amino acid residues. Pharmacological evaluation disclosed subnanomolar affinities for some of these compounds at the AT(2) receptor. Substitution of Phe by Ile in this series of ligands enhanced the AT(2) receptor affinity of all compounds. These results suggest that the C-terminal amino acid residues can be elaborated on to enhance the AT(2) receptor affinity in truncated Ang II analogues.
|
|
| 10. |
- Georgsson, Jennie, et al.
(författare)
-
Synthesis of a new class of druglike angiotensin II C-terminal mimics with affinity for the AT2 receptor
- 2007
-
Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 50:7, s. 1711-1715
-
Tidskriftsartikel (refereegranskat)abstract
- Four tripeptides corresponding to the C-terminal region of angiotensin II were synthesized. One of these peptides (Ac-His-Pro-Ile) showed moderate binding affinity for the AT2 receptor. Two aromatic histidine-related scaffolds were synthesized and introduced in the tripeptides to give eight new peptidomimetic structures. Three of the new peptide-derived druglike molecules exhibited selective, nanomolar affinity for the AT2 receptor. These ligands may become lead compounds in the future development of novel classes of selective AT2 receptor agonists.
|
|
