Novel bis-arylalkylamines as myeloperoxidase inhibitors: Design, synthesis, and structure-activity relationship study

Structure-Activity Relationship of 7-Chloro-4-(Phenylselanyl) Quinoline: Novel Antinociceptive and Anti-Inflammatory Effects in Mice

The 7-chloro-4-(phenylselanyl) quinoline (4-PSQ) shows promise for its antinociceptive and anti-inflammatory properties. Here, we explored the structure-activity relationship of 4-PSQ and its analogues: 7-chloro-4-[(4-fluorophenyl) selanyl]quinoline (a), 7-chloro-4-{[3-trifluoromethyl)phenyl] selanyl} quinoline (b), 4-((3,5-Bis(trifluoromethyl)phenyl) selanyl-7-chloroquinoline (c), 7-chloro-4-[(2,4,6-trimethyl)selanyl]quinolinic acid (d) and 7-chloroquinoline-4-selenium acid (e) in models of acute inflammation and chemical, thermal and mechanical nociception in mice, alongside in silico analysis. Compounds a (-F), b (-CF3), c (-Bis-CF3), d (-CH3), e (-OOH), and 4-PSQ exhibited antinociceptive effects in chemical and thermal nociception models, except d (-CH3) and e (-OOH) in the hot plate test. None induced locomotor changes. In silico, only c (-Bis-CF3) showed low gastrointestinal absorption, and c (-Bis-CF3) and e (-OOH) lacked blood-brain barrier penetration, suggesting e (-OOH) lacked central antinociceptive effect. These compounds had higher COX-2 affinity than COX-1. Our findings suggest substituent insertion alters 4-PSQ's efficacy as an antinociceptive and anti-inflammatory agent.

Potential preventative impact of aloe-emodin nanoparticles on cerebral stroke-associated myocardial injury by targeting myeloperoxidase: In supporting with In silico and In vivo studies

The present study examined the potential neuroprotective effects of aloe-emodin (AE) nanoparticles on the cerebral stroke-associated target protein myeloperoxidase (MPO). We investigated the binding interactions between AE and MPO through molecular docking and molecular dynamics simulations. Molecular docking results indicated that AE exhibited a binding energy of -6.9 kcal/mol, whereas it was -7.7 kcal/mol for 2-{[3,5-bis(trifluoromethyl)benzyl]amino}-n-hydroxy-6-oxo-1,6-dihydropyrimidine-5-carboxamide (CCl). Furthermore, molecular dynamics studies demonstrated that AE possesses a stronger binding affinity (-57.137 ± 13.198 kJ/mol) than does CCl (-22.793 ± 30.727 kJ/mol), suggesting that AE has a more substantial inhibitory effect on MPO than does CCl. Despite the therapeutic potential of AE for neurodegenerative disorders, its bioavailability is limited within the body. A proposed hypothesis to enhance the bioavailability of AE is its conversion into aloe-emodin nanoparticles (AENP). The AENPs synthesized through a fabrication method were spherical with a consistent diameter of 104.4 ± 7.9 nm and a polydispersity index ranging from 0.525 to 0.586. In rats experiencing cerebral stroke, there was a notable increase in cerebral infarction size; abnormalities in electrocardiogram (ECG) and electroencephalogram (EEG) patterns; a decrease in brain and cardiac antioxidant activities; and an increase in myeloperoxidase levels compared to those in normal rats. Compared with AE treatment, AENP treatment significantly ameliorated cerebral infarction, normalized ECG and EEG patterns, enhanced brain and cardiac antioxidant activities, and reduced MPO levels in stroke rats. Histopathological evaluations revealed pronounced alterations in the rat hippocampus, with pyknotic nuclei, disarray and loosely packed cells, deterioration of cardiac muscle fibers, and extensive damage to cardiac myocytes, in contrast to those in normal rats. AENP treatment mitigated these pathological changes more effectively than AE treatment in both brain and cardiac cells. These findings support that AENP provides considerable protection against stroke-associated myocardial infarction.

Potential effect of novel thiadiazole derivatives against radiation induced inflammation with low cardiovascular risk in rats

The aim of the present study is to explore new selective anti-inflammatory compounds with low cardiovascular risk. Twelve thiadiazole derivatives incorporating different amino acid moieties were newly synthesized (4–15) as potential anti-inflammatory agents with low cardiovascular risks through dual COX-2/MPO inhibition. Compounds were initially screened for their anti-inflammatory effect by assay of COX-2, the most potent (4–6, 8) were further tested for COX-1 inhibition, myeloperoxidase MPO activity as well as total nitric oxide content NO in heart of irradiated rats. Cardiac toxicity potential was evaluated by assay of creatine kinase-MB (CK-MB), troponin-I (Tn-I) and lactate dehydrogenase (LDH). Celcoxcib was used as reference drug. S-(5-((4-Methoxybenzylidene)amino)-2,3-dihydro-1,3,4-thiadiazol-2-yl)2-amino propanethioate (5) was the most potent anti-inflammatory with the least cardiotoxicity effect. It exhibited IC50 0.09 µM on COX-2 inhibition with very low activity on COX-1. Troponin I was elevated by 11% using compound 5 in non-irradiated rats. Moreover, compound (5) showed 73% reduction in MPO level. Results were supported by molecular docking into the active sites of COX-2 and MPO enzymes to have more insights about the possible dual inhibition of compound 5 of both enzymes.

Assessment of anti-inflammatory-like, antioxidant activities and molecular docking of three alkynyl-substituted 3-ylidene-dihydrobenzo[d]isothiazole 1,1-dioxide derivatives

The presence of enyne and benzoisothiazole functions in the molecular architecture of compounds 1, 2 and 3 were expected to provide biochemical activities. In the present work, we first examined the molecular surface contact of three alkynyl-substituted 3-ylidenedihydrobenzo[d] isothiazole 1,1-dioxides. The analysis of the Hirshfeld surfaces reveals that only compound 3 exhibited a well-defined red spots, indicating intermolecular interactions identified as S-O⋯H, C-H⋯O and C-O⋯H contacts. Comparative fingerprint histograms of the three compounds show that close pair interactions are dominated by C-H⋯H-C contact. By UV-visible analysis, compound 1 showed the most intense absorbances at 407 and 441 nm, respectively. The radical scavenging activity explored in the DPPH test, shows that only 1 exhibited low anti-radical activity. Furthermore, cellular antioxidant capacity of benzoisothiazoles 1-3 was investigated with PMA-activated HL-60 cells using chemiluminescence and fluorescence techniques in the presence of L-012 and Amplex Red probe, respectively. Results highlight that compound 1 exhibited moderate anti-ROS capacity while compounds 2 and 3 enhanced ROS production. The cytotoxicity test performed on HL-60 cells, using the MTS assay, confirmed the lack of toxicity of the tested benzoisothiazole 1 compared to 2 and 3 which show low cytotoxicity (≤30%). Anti-catalytic activity was evaluated by following the inhibitory potential of the benzoisothiazoles on MPO activity and depicted benzoisothiazoles-MPO interactions by docking. Both SIEFED and docking studies demonstrated an anti-catalytic activity of the tested benzoisothiazoles towards MPO with the best activity for compound 2.

Boron insertion into alkyl ether bonds via zinc/nickel tandem catalysis

Mild methods to cleave the carbon-oxygen (C-O) bond in alkyl ethers could simplify chemical syntheses through the elaboration of these robust, readily available precursors. Here we report that dibromoboranes react with alkyl ethers in the presence of a nickel catalyst and zinc reductant to insert boron into the C-O bond. Subsequent reactivity can effect oxygen-to-nitrogen substitution or one-carbon homologation of cyclic ethers and more broadly streamline preparation of bioactive compounds. Mechanistic studies reveal a cleavage-then-rebound pathway via zinc/nickel tandem catalysis.

Integration of an Inhibitor-like Rule and Structure-based Virtual Screening for the Discovery of Novel Myeloperoxidase Inhibitors

Myeloperoxidase (MPO) is an attractive therapeutic target against inflammation. Herein, we developed an inhibitor-like rule, based on known MPO inhibitors, and generated a target database containing 6546 molecules with privileged inhibitory properties. Using a structure-based approach validated by decoys, robust statistical metrics, redocking, and cross-docking, we selected 10 putative MPO inhibitors with high chemical diversity. At 20 μM, six of these 10 compounds (i.e., 60% success rate) inhibited more than 20% of the chlorinating activity of the enzyme. Additionally, we found that compound ZINC9089086 forms hydrogen bonds with Arg233 and with the hemic carboxylate. It makes a π-stacking interaction with the heme group and displays a high affinity for the enzyme active site. When incubated with purified MPO, ZINC9089086 inhibited the chlorinating activity of the enzyme with an IC₅₀ of 2.2 ± 0.1 μM in a reversible manner. Subsequent experiments revealed that ZINC9089086 inhibited hypochlorous acid production in dHL-60 cells and human neutrophils. Furthermore, the theoretical ADME/Tox profile indicated that this compound exhibits low toxicity risks and adequate pharmacokinetic parameters, thus making ZINC9089086 a very promising candidate for preclinical anti-inflammatory studies. Overall, our study shows that integrating an inhibitor-like rule with a validated structure-based methodology is an excellent approach for improving the success rate and molecular diversity of novel MPO inhibitors with good pharmacokinetics and toxicological profiles. By combining these tools, it was possible to increase the assurance rate, which ultimately diminishes the costs and time needed for the acquisition, synthesis, and evaluation of new compounds.

Myeloperoxidase: A versatile mediator of endothelial dysfunction and therapeutic target during cardiovascular disease

Myeloperoxidase (MPO) is a prominent mammalian heme peroxidase and a fundamental component of the innate immune response against microbial pathogens. In recent times, MPO has received considerable attention as a key oxidative enzyme capable of impairing the bioactivity of nitric oxide (NO) and promoting endothelial dysfunction; a clinically relevant event that manifests throughout the development of inflammatory cardiovascular disease. Increasing evidence indicates that during cardiovascular disease, MPO is released intravascularly by activated leukocytes resulting in its transport and sequestration within the vascular endothelium. At this site, MPO catalyzes various oxidative reactions that are capable of promoting vascular inflammation and impairing NO bioactivity and endothelial function. In particular, MPO catalyzes the production of the potent oxidant hypochlorous acid (HOCl) and the catalytic consumption of NO via the enzyme's NO oxidase activity. An emerging paradigm is the ability of MPO to also influence endothelial function via non-catalytic, cytokine-like activities. In this review article we discuss the implications of our increasing knowledge of the versatility of MPO's actions as a mediator of cardiovascular disease and endothelial dysfunction for the development of new pharmacological agents capable of effectively combating MPO's pathogenic activities. More specifically, we will (i) discuss the various transport mechanisms by which MPO accumulates into the endothelium of inflamed or diseased arteries, (ii) detail the clinical and basic scientific evidence identifying MPO as a significant cause of endothelial dysfunction and cardiovascular disease, (iii) provide an up-to-date coverage on the different oxidative mechanisms by which MPO can impair endothelial function during cardiovascular disease including an evaluation of the contributions of MPO-catalyzed HOCl production and NO oxidation, and (iv) outline the novel non-enzymatic mechanisms of MPO and their potential contribution to endothelial dysfunction. Finally, we deliver a detailed appraisal of the different pharmacological strategies available for targeting the catalytic and non-catalytic modes-of-action of MPO in order to protect against endothelial dysfunction in cardiovascular disease.

Synthesis of novel 3,5,6-trisubstituted 2-pyridone derivatives and evaluation for their anti-inflammatory activity

The inflammatory response is the reaction of living tissue to an injury of a foreign nature, such as infection and irritants, and occurs as part of the body's natural defence response. Compounds capable of inhibiting cyclooxygenase (COX) enzymes, especially COX-2, have great potential as anti-inflammatory agents. Herein we present the regioselective synthesis of 49 novel compounds based on the 2-pyridone nucleus. The topical anti-inflammatory activity of seventeen compounds was evaluated in mice by croton oil (CO) induced ear edema assay. Most of the compounds exhibited a high level of in vivo anti-inflammatory activity, reducing ear edema and myeloperoxidase (MPO) activity. The most active compounds (2a and 7a) were inhibitors of COX enzymes. Compound 2a selectively inhibited the COX-2, while 7a was nonselective. Further, the compound 2a showed effective binding at the active site of COX-2 co-crystal by docking molecular study.

Discovery of a novel indole pharmacophore for the irreversible inhibition of myeloperoxidase (MPO)

Myeloperoxidase (MPO) activity and subsequent generation of hypochlorous acid has been associated with the killing of host-invading microorganisms (e.g. bacteria, viruses, and fungi). However, during oxidative stress, high MPO activity can damage host tissue and is linked to several chronic inflammatory conditions. Herein, we describe the development of a novel biaryl, indole-pyrazole series of irreversible mechanism-based inhibitors of MPO. Derived from an indole-containing high-throughput screen hit, optimization efforts resulted in potent and selective 6-substituted indoles with good oral bioavailability and in vivo activity.

The soluble curcumin derivative NDS27 inhibits superoxide anion production by neutrophils and acts as substrate and reversible inhibitor of myeloperoxidase

A water-soluble curcumin lysinate incorporated into hydroxypropyl-β-cyclodextrin (NDS27) has been developed and shown anti-inflammatory properties but no comparative study has been made in parallel with its parent molecule, curcumin on polymorphonuclear neutrophils (PMNs) and myeloperoxidase (MPO) involved in inflammation. The effect of NDS27, its excipients (hydroxypropyl-β-cyclodextrin and lysine), curcumin lysinate and curcumin were compared on the release of superoxide anion by PMNs using a chemiluminescence assay and on the enzymatic activity of MPO. It was shown that curcumin and NDS27 exhibit similar inhibition activities on superoxide anion release by stimulated PMNs but also on MPO peroxidase and halogenation activities. The action mechanism of curcumin and NDS27 on the MPO activity was refined by stopped-flow and docking analyses. We demonstrate that both curcumin and NDS27 are reversible inhibitors of MPO by acting as excellent electron donors for redox intermediate Compound I (∼10⁷ M^-1 s^-1) but not for Compound II (∼10³ M^-1 s^-1) in the peroxidase cycle of the enzyme, thereby trapping the enzyme in the Compound II state. Docking calculations show that curcumin is able to enter the enzymatic pocket of MPO and bind to the heme cavity by π-stacking and formation of hydrogen bonds involving substituents from both aromatic rings. Hydroxypropyl-β-cyclodextrin is too bulky to enter MPO channel leading to the binding site suggesting a full release of curcumin from the cyclodextrin thereby allowing its full access to the active site of MPO. In conclusion, the hydroxypropyl-β-cyclodextrin of NDS27 enhances curcumin solubilization without affecting its antioxidant capacity and inhibitory activity on MPO.

Molecular Mechanisms of Drug Action: X-ray Crystallography at the Basis of Structure-based and Ligand-based Drug Design

Biological systems are recognized for their complexity and diversity and yet we sometimes manage to cure disease via the administration of small chemical drug molecules. At first, active ingredients were found accidentally and at that time there did not seem a need to understand the molecular mechanism of drug functioning. However, the urge to develop new drugs, the discovery of multipurpose characteristics of some drugs, and the necessity to remove unwanted secondary drug effects, incited the pharmaceutical sector to rationalize drug design. This did not deliver success in the years directly following its conception, but it drove the evolution of biochemical and biophysical techniques to enable the characterization of molecular mechanisms of drug action. Functional and structural data generated by biochemists and structural biologists became a valuable input for computational biologists, chemists and bioinformaticians who could extrapolate in silico, based on variations in the structural aspects of the drug molecules and their target. This opened up new avenues with much improved predictive power because of a clearer perception of the role and impact of structural elements in the intrinsic affinity and specificity of the drug for its target. In this chapter, we review how crystal structures can initiate structure-based drug design in general.