Superimposition of potent non-peptide AT1 receptor antagonists with angiotensin II

Docking and Molecular Dynamics Calculations of Pyrrolidinone Analog MMK16 Bound to COX and LOX Enzymes

The new molecule 4-[(2S)-2-(1H-imidazol-1-ylmethyl)-5-oxotetrahydro-1H-pyrrol-1-yl]methylbenzenecarboxylic acid (MMK16) was found to have promising anti-inflammatory activity. This biological behavior of MMK16 triggered our interest to study its binding affinity using NMR spectroscopy in LOX and its docking and molecular dynamics (MD) properties in LOX and COX enzymes. The present NMR and docking binding studies not only rationalize the obtained biological results since in all three receptors MMK16 shows high affinity and scoring but also make it a potential dual LOX-5/COX-2 inhibitor. Thus, this class of molecules must be further investigated for discovering compounds possessing better biological activity and more lasting biological effect.

An efficient synthesis of a rationally designed 1,5 disubstituted imidazole AT(1) angiotensin II receptor antagonist: reorientation of imidazole pharmacophore groups in losartan reserves high receptor affinity and confirms docking studies

A new 1,5 disubstituted imidazole AT(1) Angiotensin II (AII) receptor antagonist related to losartan with reversion of butyl and hydroxymethyl groups at the 2-, 5-positions of the imidazole ring was synthesized and evaluated for its antagonist activity (V8). In vitro results indicated that the reorientation of butyl and hydroxymethyl groups on the imidazole template of losartan retained high binding affinity to the AT(1) receptor concluding that the spacing of the substituents at the 2,5- positions is of primary importance. The docking studies are confirmed by binding assay results which clearly show a comparable binding score of the designed compound V8 with that of the prototype losartan. An efficient, regioselective and cost effective synthesis renders the new compound as an attractive candidate for advanced toxicological evaluation and a drug against hypertension.

The design and synthesis of a potent Angiotensin II cyclic analogue confirms the ring cluster receptor conformation of the hormone Angiotensin II

The novel amide linked Angiotensin II potent cyclic analogue, c-[Sar1,Lys3,Glu5] ANG II 19 has been designed and synthesized in an attempt to test the aromatic ring clustering and the charge relay bioactive conformation we have recently suggested for ANG II. This constrained cyclic analogue was synthesized by connecting the Lys3 amino and Glu5 carboxyl side chain groups, and it was found to be potent in the rat uterus assay and in anesthetized rabbits. The central part of the molecule is fixed covalently in the conformation predicted according to the backbone bend conformational model proposed for Angiotensin II. The obtained results using a combination of 2D NMR, 1D NOE spectroscopy and molecular modeling revealed a similar Tyr4-Ile5-His6 bend, a His6-Pro7 trans configuration and a side chain aromatic ring cluster of the key aminoacids Tyr4, His6, Phe8 for c-[Sar1,Lys3,Glu5] ANG II as it has been found for ANG II (Matsoukas, J. H.; Hondrelis, J.; Keramida, M.; Mavromoustakos, T.; Markriyannis, A.; Yamdagni, R.; Wu, Q.; Moore, G. J. J. Biol. Chem. 1994, 269, 5303). Previous study of the conformational properties of the Angiotensin II type I antagonist [Hser(gamma-OMe)8] ANG II (Matsoukas, J. M.; Agelis, G.; Wahhab, A.; Hondrelis, J.; Panagiotopoulos. D.; Yamdagni, R.; Wu, Q.; Mavromoustakos, T.; Maia, H.; Ganter, R.; Moore, G. J. J. Med. Chem. 1995, 38, 4660) using 1-D NOE spectroscopy coupled with the present study of the same type of lead antagonist Sarilesin revealed that the Tyr4-Ile5-His6 bend, a conformational property found in Angiotensin II is not present in type I antagonists. The obtained results provide an important conformational difference between Angiotensin II agonists and type I antagonists. It appears that our synthetic attempt to further support our proposed model was successful and points out that the charge relay system and aromatic ring cluster are essential stereoelectronic features for Angiotensin II to exert its biological activity.

An effort to understand the molecular basis of hypertension through the study of conformational analysis of losartan and sarmesin using a combination of nuclear magnetic resonance spectroscopy and theoretical calculations

Losartan is the first recently approved drug against hypertension disease that competes with the biological action of angiotensin II (AII) at the AT1 receptor. Its design was based on the mimicry of the C-terminal segment of AII. Due to the biological significance of Losartan, its structure elucidation and conformational properties are reported as determined by NMR spectroscopy and computational analysis. In addition, molecular modeling of the peptide Sarmesin [Sar1Tyr(OMe)4AII], a competitive antagonist of AII, was also developed based on NMR and computational analysis data. Sarmesin's C-terminal was used as a template for superimposition with specific molecular features of interest in the structure of Losartan such as the conformation of biphenyltetrazole, the n-butyl chain, and the orientation of hydroxymethylimidazole relative to the biphenyl template. The major conclusions derived from this study are the following: (a) Sarmesin, like the AII superagonist [Sar1]AII, adopts a conformation which keeps in close proximity the key amino acids Sar1 (or Arg2)-Tyr(OMe)4-His6-Phe8. (b) Losartan favors a low-energy conformation in which imidazole and tetrazole rings are placed in the opposite site relative to the spacer phenyl ring plane; the hydroxymethyl group is placed away from the spacer phenyl ring, the alkyl chain is oriented above the spacer phenyl ring, and the two phenyl rings deviate approximately 60 degrees from being coplanar. (c) Overlay of the C-terminal region of Sarmesin with Losartan using equivalent groups revealed an excellent match. (d) Interestingly, the matching between enantiomeric structures of Losartan was not equivalent, proposing that the chirality of this molecule is significant in order to exert its biological activity. These findings open a new avenue for synthetic chemists to design and synthesize peptidomimetic drugs based on the C-terminal segment of the proposed model of Sarmesin. The new candidate drug molecules are not restricted to structurally resemble Losartan as the design is hitherto focused.