Synthesis, binding studies and in vivo biological evaluation of novel non-peptide antihypertensive analogues

Synthesis of novel 2-pyrrolidinone and pyrrolidine derivatives and study of their inhibitory activity against autotaxin enzyme

Autotaxin (ATX), a glycoprotein (~125 kDa) isolated as an autocrine motility factor from melanoma cells, belongs to a seven-membered family of ectonucleotide pyrophosphatase/phosphodiesterase (ENPP), and exhibits lysophospholipase D activity. ATX is responsible for the hydrolysis of lysophosphatidylcholine (LPC) to produce the bioactive lipid lysophosphatidic acid (LPA), which is upregulated in a variety of pathological inflammatory conditions, including fibrosis, cancer, liver toxicity and thrombosis. Given its role in human disease, the ATX-LPA axis is an interesting target for therapy, and the development of novel potent ATX inhibitors is of great importance. In the present work a novel class of ATX inhibitors, optically active derivatives of 2-pyrrolidinone and pyrrolidine heterocycles were synthesized. Some of them exhibited interesting in vitro activity, namely the hydroxamic acid 16 (IC₅₀ 700 nM) and the carboxylic acid 40b (IC₅₀ 800 nM), while the boronic acid derivatives 3k (IC₅₀ 50 nM), 3l (IC₅₀ 120 nM), 3 m (IC₅₀ 180 nM) and 21 (IC₅₀ 35 nM) were found to be potent inhibitors of ATX.

Synthesis of new optically active 2-pyrrolidinones

A new class of optically active 2-pyrrolidinones was synthesized, starting from S-pyroglutamic acid, a well known natural chiral synthon. The synthetic design followed led to the insertion of various substituents at positions 1 and 5 of the 2-pyrrolidinone ring, including the imidazole moiety. Some of them possess two or three stereogenic centers, the configuration of which was retained under the mild conditions used. The new compounds also carry an imidazole moiety, which, along with the 2-pyrrolidinone template, may prove pivotal to several biological processes.

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.

Synthesis, in silico docking experiments of new 2-pyrrolidinone derivatives and study of their anti-inflammatory activity

A new class of 2-pyrrolidinone derivatives was designed, synthesized, and tested for their antioxidant and anti-inflammatory activities. The compounds were evaluated for their inhibitory activity against LOX. The most potent among them, 14d [IC(50) 0.08 (±0.005)mM], and 14e [IC(50) 0.0705 (±0.003)mM], were also tested in vivo. The compound 14d induced equipotent inhibition against rat paw edema, which is very close to the effect produced by the commonly used standard, namely indomethacin (47%). The LOX inhibitory activity of the compound 14e proceeds in parallel to the % inhibitory value of lipid peroxidation meaning that this LOX inhibitory activity is supported by the lipid peroxidation inhibition. The molecular features that govern their bioactivity were explored through in silico docking experiments. The results showed that acidic moieties must be placed in certain distance and orientation in the active site of LOX enzyme in order to productively exhibit inhibitory activity. In addition, the 2-pyrrolidinone template significantly contributes in the inhibitory properties of the new compounds.

Hypertension study in anaesthetized rabbits: protocol proposal for AT1 antagonists screening

INTRODUCTION

The aim of this study was to establish an optimized fast and safe protocol for the pharmacological screening of AT(1) antagonists.

MATERIALS AND METHODS

The pharmaceutical prototype AT(1) antagonist losartan, its active metabolite EXP3174 and the synthetic compound MMK1 were analysed in order to validate the protocol. Ang II was continuously infused while the animals received the drugs in two procedures.

RESULTS

In the post-treatment procedure drugs were administered either in a single bolus dose or in a sequential manner. When losartan was administered in a single bolus dose, efficacy was evident until the 7th min (p=0.012) whilst EXP3174 infusion extended the efficiency up to the end of the study (p=0.006). In addition, the sequential injections of losartan prolonged the inhibitory time interval until the end of the study (p=0.045). In the pre-treatment procedure, results suggested a dose-dependent inhibitory effect for both antagonists. The pressor response to Ang II was unchanged after MMK1 administration either in the post- or in the pre-treatment mode.

CONCLUSIONS

The proposed protocol appears to be safe, simple and fast for the pharmacological screening of AT(1) antagonists and enables the evaluation of new antagonists using lower doses than any other reported in the literature.

Development of a CP 31P NMR broadline simulation methodology for studying the interactions of antihypertensive AT1 antagonist losartan with phospholipid bilayers

A cross-polarization (CP) (31)P NMR broadline simulation methodology was developed for studying the effects of drugs in phospholipids bilayers. Based on seven-parameter fittings, this methodology provided information concerning the conformational changes and dynamics effects of losartan in the polar region of the dipalmitoylphosphatidylcholine bilayers. The test molecule for this study was losartan, an antihypertensive drug known to exert its effect on AT(1) transmembrane receptors. The results were complemented and compared with those of differential scanning calorimetry, solid-state (13)C NMR spectroscopy, Raman spectroscopy, and electron spin resonance. More specifically, these physical chemical methodologies indicated that the amphipathic losartan molecule interacts with the hydrophilic-head zone of the lipid bilayers. The CP (31)P NMR broadline simulations showed that the lipid molecules in the bilayers containing losartan displayed greater collective tilt compared to the tilt displayed by the load-free bilayers, indicating improved packing. The Raman results displayed a decrease in the trans/gauche ratio and increased intermolecular interactions of the acyl chains in the liquid crystalline phase. Additional evidence, suggesting that losartan possibly anchors in the realm of the headgroup, was derived from upfield shift of the average chemical shift sigma(iso) of the (31)P signal in the presence of losartan and from shift of the observed peak at 715 cm(-1) attributed to C-N stretching in the Raman spectra.