Discovery of the first dual inhibitor of the 5-lipoxygenase-activating protein and soluble epoxide hydrolase using pharmacophore-based virtual screening

Identification of potentially high drug-like VEGFR2/c-Met dual-target type II kinase inhibitors with symmetric skeletons based on structural screening

Vascular endothelial growth factor receptor 2 (VEGFR2) and c-Mesenchymal epithelial transition factor (c-Met) are tyrosine kinase receptors associated with the occurrence of malignant tumors. Studies have shown that inhibition of VEGFR2 promotes a feedback increase in c-Met, a mechanism linked to the emergence of resistance to VEGFR2 inhibitors. Therefore, treatment targeting both VEGFR2 and c-Met will have better application prospects. In this study, hierarchical virtual screening was performed on ZINC15, Molport and Mcule-ULTIMATE databases to identify potential VEGFR2/c-Met dual inhibitors. Firstly, the best pharmacophore model for each target was used to cross-screen the three databases, and the compounds that could match the two pharmacophore models were then retained based on the Fit Value of the respective crystal ligands. Compounds ZINC, MOL, and MLB named after their database sources were retained by binding pattern analysis and docking assessment. ADMET predictions indicated that ZINC had significantly higher oral bioavailability compared to the approved drug cabozantinib. This is likely due to ZINC's unique symmetrical backbone with less structure complexity, which may reduce the occurrence of adverse effects. Molecular dynamics simulations and binding free energy analysis showed that all three hit compounds were able to stably bind at the active site, but only ZINC could form high occupancy of hydrogen bonds with both VEGFR2 and c-Met, and also only ZINC had a higher binding free energy than crystal ligands, suggesting that ZINC was the most likely potential VEGFR2/c-Met dual-target inhibitor. This finding provides a promising starting point for the development of VEGFR2/c-Met dual-target inhibitors.Communicated by Ramaswamy H. Sarma.

Novel thiazolopyridine derivatives of diflapolin as dual sEH/FLAP inhibitors with improved solubility

Inflammatory responses are orchestrated by a plethora of lipid mediators, and perturbations of their biosynthesis or degradation hinder resolution and lead to uncontrolled inflammation, which contributes to diverse pathologies. Small molecules that induce a switch from pro-inflammatory to anti-inflammatory lipid mediators are considered valuable for the treatment of chronic inflammatory diseases. Commonly used non-steroidal anti-inflammatory drugs (NSAIDs) are afflicted with side effects caused by the inhibition of beneficial prostanoid formation and redirection of arachidonic acid (AA) into alternative pathways. Multi-target inhibitors like diflapolin, the first dual inhibitor of soluble epoxide hydrolase (sEH) and 5-lipoxygenase-activating protein (FLAP), promise improved efficacy and safety but are confronted by poor solubility and bioavailability. Four series of derivatives bearing isomeric thiazolopyridines as bioisosteric replacement of the benzothiazole core and two series additionally containing mono- or diaza-isosteres of the phenylene spacer were designed and synthesized to improve solubility. The combination of thiazolo[5,4-b]pyridine, a pyridinylen spacer and a 3,5-Cl2-substituted terminal phenyl ring (46a) enhances solubility and FLAP antagonism, while preserving sEH inhibition. Moreover, the thiazolo[4,5-c]pyridine derivative 41b, although being a less potent sEH/FLAP inhibitor, additionally decreases thromboxane production in activated human peripheral blood mononuclear cells. We conclude that the introduction of nitrogen, depending on the position, not only enhances solubility and FLAP antagonism (46a), but also represents a valid strategy to expand the scope of application towards inhibition of thromboxane biosynthesis.

Pharmacophore-based virtual screening and in-silico study of natural products as potential DENV-2 RdRp inhibitors

Dengue fever is a significant public health concern throughout the world, causing an estimated 500,000 hospitalizations and 20,000 deaths each year, despite the lack of effective therapies. The DENV-2 RdRp has been identified as a potential target for the development of new and effective dengue therapies. This research's primary objective was to discover an anti-DENV inhibitor using in silico ligand- and structure-based approaches. To begin, a ligand-based pharmacophore model was developed, and 130 distinct natural products (NPs) were screened. Docking of the pharmacophore-matched compounds were performed to the active site of DENV-2 RdRp protease . Eleven compounds were identified as potential DENV-2 RdRp inhibitors based on docking energy and binding interactions. ADMET and drug-likeness were done to predict their pharmacologic, pharmacokinetic, and drug-likeproperties . Compounds ranked highest in terms of pharmacokinetics and drug-like appearances were then subjected to additional toxicity testing to determine the leading compound. Additionally, MD simulation of the lead compound was performed to confirm the docked complex's stability and the binding site determined by docking. As a result, the lead compound (compound-108) demonstrated an excellent match to the pharmacophore, a strong binding contact and affinity for the RdRp enzyme, favourable pharmacokinetics, and drug-like characteristics. In summary, the lead compound identified in this study could be a possible DENV-2 RdRp inhibitor that may be further studied on in vitro and in vivo models to develop as a drug candidate.Communicated by Ramaswamy H. Sarma.

Pharmacophore model-aided virtual screening combined with comparative molecular docking and molecular dynamics for identification of marine natural products as SARS-CoV-2 papain-like protease inhibitors

Targeting SARS-CoV-2 papain-like protease using inhibitors is a suitable approach for inhibition of virus replication and dysregulation of host anti-viral immunity. Engaging all five binding sites far from the catalytic site of PLpro is essential for developing a potent inhibitor. We developed and validated a structure-based pharmacophore model with 9 features of a potent PLpro inhibitor. The pharmacophore model-aided virtual screening of the comprehensive marine natural product database predicted 66 initial hits. This hit library was downsized by filtration through a molecular weight filter of ≤ 500 g/mol. The 50 resultant hits were screened by comparative molecular docking using AutoDock and AutoDock Vina. Comparative molecular docking enables benchmarking docking and relieves the disparities in the search and scoring functions of docking engines. Both docking engines retrieved 3 same compounds at different positions in the top 1 % rank, hence consensus scoring was applied, through which CMNPD28766, aspergillipeptide F emerged as the best PLpro inhibitor. Aspergillipeptide F topped the 50-hit library with a pharmacophore-fit score of 75.916. Favorable binding interactions were predicted between aspergillipeptide F and PLpro similar to the native ligand XR8-24. Aspergillipeptide F was able to engage all the 5 binding sites including the newly discovered BL2 groove, site V. Molecular dynamics for quantification of Cα-atom movements of PLpro after ligand binding indicated that it exhibits highly correlated domain movements contributing to the low free energy of binding and a stable conformation. Thus, aspergillipeptide F is a promising candidate for pharmaceutical and clinical development as a potent SARS-CoV-2 PLpro inhibitor.

Synthesis and structure-activity relationships for some novel diflapolin derivatives with benzimidazole subunit

A series of derivatives of the potent dual soluble epoxide hydrolase (sEH)/5-lipoxygenase-activating protein (FLAP) inhibitor diflapolin was designed, synthesised, and characterised. These novel compounds, which contain a benzimidazole subunit were evaluated for their inhibitory activity against sEH and FLAP. Molecular modelling tools were applied to analyse structure-activity relationships (SAR) on both targets and to predict solubility and gastrointestinal (GI) absorption. The most promising dual inhibitors of these series are 5a, 6b, and 6c.

Quinazoline-4(3H)-one-7-carboxamide Derivatives as Human Soluble Epoxide Hydrolase Inhibitors with Developable 5-Lipoxygenase Activating Protein Inhibition

Soluble epoxide hydrolase (sEH) metabolizes epoxyeicosatrienoic acids (EETs), which are endowed with beneficial biological activities as they reduce inflammation, regulate endothelial tone, improve mitochondrial function, and decrease oxidative stress. Therefore, inhibition of sEH for maintaining high EET levels is implicated as a new therapeutic modality with broad clinical applications for metabolic, renal, and cardiovascular disorders. In our search for new sEH inhibitors, we designed and synthesized novel amide analogues of the quinazolinone-7-carboxylic acid derivative 5, a previously discovered 5-lipoxygenase-activating protein (FLAP) inhibitor, to evaluate their potential for inhibiting sEH. As a result, we identified new quinazolinone-7-carboxamides that demonstrated selective sEH inhibition with decreased FLAP inhibitor properties. The tractable SAR results indicated that the amide and thiobenzyl fragments flanking the quinazolinone nucleus are critical features governing the potent sEH inhibition, and compounds 34, 35, 37, and 43 inhibited the sEH activity with IC₅₀ values of 0.30-0.66 μM. Compound 34 also inhibited the FLAP-mediated leukotriene biosynthesis (IC₅₀ = 2.91 μM). In conclusion, quinazolinone-7-carboxamides can be regarded as novel lead structures, and newer analogues with improved efficiency against sEH along with or without FLAP inhibition can be generated.

Repositioning of tubocurarine as analgesic and anti-inflammatory agent: Exploring beyond myorelaxant activity

BACKGROUND AND PURPOSE

Tubocurarine (d-TC), a non-depolarizing competitive blocker of nicotinic acetylcholine receptors is extensively utilized for the relaxation of skeletal muscles. Drug repositioning is a forthright approach to reduce the cost and speed up drug development process. Herein, we have attempted to evaluate the analgesic and anti-inflammatory activity of d-TC for its possible repurposing in pain and inflammation-related issues.

EXPERIMENTAL APPROACH

We examined the soluble epoxide hydrolase inhibitory (sEHI) activity of d-TC employing in silico high throughput screening protocols, in vitro cell-free sEH inhibitory assay, and in in vivo rodent models for its repositioning in pain and inflammation-related disorders.

KEY RESULTS

In molecular docking study, d-TC displayed impressive hydrogen bonding interactions within the cavity of sEH enzyme with good docking score. d-TC also exhibited notable sEH inhibitory activity (IC₅₀ 3.72 nm) at the in vitro assay. Oral absorption capability of d-TC (0.1 and 0.2 mg/mL) was determined using an in vitro everted intestinal sac model employing rat ileum tissue that revealed significant oral absorption of d-TC. Besides, in vivo studies revealed that oral administration of d-TC (0.1 and 0.2 mg/kg) in rodents significantly attenuated hyperalgesia (cold plate test, tail immersion test and formalin test) and inflammation (estimation of rectal temperature, acetic acid induced pleurisy test and cotton pellet-induced granuloma test) induced in robust preclinical models. Conclusion and implications These findings are novel and warrant immediate efforts to reposition d-TC as a new therapeutic candidate in the management of hyperalgesia, inflammation, and associated conditions.

Soluble epoxide hydrolase inhibitors: an overview and patent review from the last decade

INTRODUCTION

Biological effects mediated by the CYP450 arm of arachidonate cascade implicate the enzyme-soluble epoxide hydrolase (sEH) in hydrolyzing anti-inflammatory epoxy fatty acids to pro-inflammatory diols. Hence, inhibiting the sEH offers a therapeutic approach to treating inflammatory diseases. Over three decades of work has shown the role of sEH inhibitors (sEHis) in treating various disorders in rodents and larger veterinary subjects. Novel chemical strategies to enhance the efficacy of sEHi have now appeared.

AREAS COVERED

A comprehensive review of patent literature related to soluble epoxide hydrolase inhibitors in the last decade (2010-2021) is provided.

EXPERT OPINION

Soluble epoxide hydrolase (sEH) is an important enzyme that metabolizes the bioactive epoxy fatty acids (EFAs) in the arachidonic acid signaling pathway and converts them to vicinal diols, which appear to be pro-inflammatory. Inhibition of sEH hence offers a mechanism to increase in vivo epoxyeicosanoid levels and resolve pro-inflammatory pathways in disease states. Significant efforts in the field have led to potent single target as well as multi-target inhibitors with promising in vitro and widely encompassing in vivo activities. Successful clinical translation of compounds targeting sEH inhibition will further validate the promised therapeutic potential of this pathway in treating human diseases.

Repurposing of digoxin in pain and inflammation: An evidence-based study

In recent years, the drug repositioning strategy has gained considerable attention in the drug discovery process that involves establishing new therapeutic uses of already known drugs. In line with this, we have identified digoxin a cardiac glycoside, as a potent inhibitor of soluble epoxide hydrolase (sEH) enzyme employing in silico high throughput screening protocols and further confirmed using in vitro cell-free sEH inhibitory assay and in vivo preclinical studies in rodents for its repurposing in hyperalgesia, inflammation, and related disorders. Oral administration of digoxin at dose 0.2 mg/kg significantly reduced (p < .0001) the allodynia in mice induced by using hot plate (3.6 ± 1.9) and tail-flick test (7.58 ± 0.9). In addition, digoxin at a dose of 0.2 mg/kg showed marked reduction (94%, p < .0001) in acetic acid-induced abdominal contraction in rats. Further, digoxin also demonstrated antipyretic activity (37.04 ± 0.2, p < .0001) and showed notable reduction (0.60 ± 0.06) in carrageenan-induced paw edema in rats. Also, the histopathological evaluation revealed that digoxin treatment attenuated the edema, neutrophil infiltration, and alveolar septal thickening in lung tissue. These findings are novel and highlight the newer insights towards repurposing digoxin as a new lead in the treatment of hyperalgesia, inflammation, and related disorders.

Combined Machine Learning and GRID-Independent Molecular Descriptor (GRIND) Models to Probe the Activity Profiles of 5-Lipoxygenase Activating Protein Inhibitors

Leukotrienes (LTs) are pro-inflammatory lipid mediators derived from arachidonic acid (AA), and their high production has been reported in multiple allergic, autoimmune, and cardiovascular disorders. The biological synthesis of leukotrienes is instigated by transfer of AA to 5-lipoxygenase (5-LO) via the 5-lipoxygenase-activating protein (FLAP). Suppression of FLAP can inhibit LT production at the earliest level, providing relief to patients requiring anti-leukotriene therapy. Over the last 3 decades, several FLAP modulators have been synthesized and pharmacologically tested, but none of them could be able to reach the market. Therefore, it is highly desirable to unveil the structural requirement of FLAP modulators. Here, in this study, supervised machine learning techniques and molecular modeling strategies are adapted to vaticinate the important 2D and 3D anti-inflammatory properties of structurally diverse FLAP inhibitors, respectively. For this purpose, multiple machine learning classification models have been developed to reveal the most relevant 2D features. Furthermore, to probe the 3D molecular basis of interaction of diverse anti-inflammatory compounds with FLAP, molecular docking studies were executed. By using the most probable binding poses from docking studies, the GRIND model was developed, which indicated the positive contribution of four hydrophobic, two hydrogen bond acceptor, and two shape-based features at certain distances from each other towards the inhibitory potency of FLAP modulators. Collectively, this study sheds light on important two-dimensional and three-dimensional structural requirements of FLAP modulators that can potentially guide the development of more potent chemotypes for the treatment of inflammatory disorders.

Structure-Based Pharmacophore Modeling, Virtual Screening, Molecular Docking, ADMET, and Molecular Dynamics (MD) Simulation of Potential Inhibitors of PD-L1 from the Library of Marine Natural Products

Background: In the past decade, several antibodies directed against the PD-1/PD-L1 interaction have been approved. However, therapeutic antibodies also exhibit some shortcomings. Using small molecules to regulate the PD-1/PD-L1 pathway may be another way to mobilize the immune system to fight cancer. Method: 52,765 marine natural products were screened against PD-L1(PDBID: 6R3K). To identify natural compounds, a structure-based pharmacophore model was generated, following by virtual screening and molecular docking. Then, the absorption, distribution, metabolism, and excretion (ADME) test was carried out to select the most suitable compounds. Finally, molecular dynamics simulation was also performed to validate the binding property of the top compound. Results: Initially, 12 small marine molecules were screened based on the pharmacophore model. Then, two compounds were selected for further evaluation based on the molecular docking scores. After ADME and toxicity studies, molecule 51320 was selected for further verification. By molecular dynamics analysis, molecule 51320 maintains a stable conformation with the target protein, so it has the chance to become an inhibitor of PD-L1. Conclusions: Through structure-based pharmacophore modeling, virtual screening, molecular docking, ADMET approaches, and molecular dynamics (MD) simulation, the marine natural compound 51320 can be used as a small molecule inhibitor of PD-L1.

Role of arachidonic acid lipoxygenase pathway in Asthma

The arachidonic acid (AA) metabolism pathways play a key role in immunological response and inflammation diseases, such as asthma, etc. AA in cell membranes can be metabolized by lipoxygenases (LOXs) to a screen of bioactive substances that include leukotrienes (LTs), lipoxins (LXs), and eicosatetraenoic acids (ETEs), which are considered closely related to the pathophysiology of respiratory allergic disease. Studies also verified that drugs regulating AA LOXs pathway have better rehabilitative intervention for asthma. This review aims to summarize the physiological and pathophysiological importance of AA LOXs metabolism pathways in asthma and to discuss its prospects of therapeutic strategies.

Encapsulation of the Anti-inflammatory Dual FLAP/sEH Inhibitor Diflapolin Improves the Efficiency in Human Whole Blood

Diflapolin is a dual FLAP/sEH inhibitor with potent anti-inflammatory efficiency in cellular assays and experimental in vivo studies. Despite these outstanding characteristics, its high lipophilicity and plasma protein binding hamper the bioactivity in blood. To overcome these limitations, diflapolin was encapsulated in poly(lactic-co-glycolic acid) nanoparticles to develop an efficient and biocompatible drug delivery system. Two different cosolvent approaches were tested showing the possibility to exchange dimethyl sulfoxide in the organic phase by the sustainable 400 g/mol poly(ethylene glycol). A particle size of 220 nm and the amorphous encapsulation of diflapolin in high amounts rendered the nanoparticles appropriate for the intended application. Excellent biocompatibility of the nanoparticles was demonstrated in an ex ovo hen's egg model. The potent suppression of FLAP-dependent 5-lipoxygenase product formation by the nanoparticles in human whole blood, superior to the free drug, makes them to a promising drug delivery system to improve the bioactivity of diflapolin.

Structure-based molecular modeling in SAR analysis and lead optimization

In silico methods like molecular docking and pharmacophore modeling are established strategies in lead identification. Their successful application for finding new active molecules for a target is reported by a plethora of studies. However, once a potential lead is identified, lead optimization, with the focus on improving potency, selectivity, or pharmacokinetic parameters of a parent compound, is a much more complex task. Even though in silico molecular modeling methods could contribute a lot of time and cost-saving by rationally filtering synthetic optimization options, they are employed less widely in this stage of research. In this review, we highlight studies that have successfully used computer-aided SAR analysis in lead optimization and want to showcase sound methodology and easily accessible in silico tools for this purpose.

Structure based pharmacophore modeling, virtual screening, molecular docking and ADMET approaches for identification of natural anti-cancer agents targeting XIAP protein

X-linked inhibitor of apoptosis protein (XIAP) is a member of inhibitor of apoptosis protein (IAP) family responsible for neutralizing the caspases-3, caspases-7, and caspases-9. Overexpression of the protein decreased the apoptosis process in the cell and resulting development of cancer. Different types of XIAP antagonists are generally used to repair the defective apoptosis process that can eliminate carcinoma from living bodies. The chemically synthesis compounds discovered till now as XIAP inhibitors exhibiting side effects, which is making difficulties during the treatment of chemotherapy. So, the study has design to identifying new natural compounds that are able to induce apoptosis by freeing up caspases and will be low toxic. To identify natural compound, a structure-based pharmacophore model to the protein active site cavity was generated following by virtual screening, molecular docking and molecular dynamics (MD) simulation. Initially, seven hit compounds were retrieved and based on molecular docking approach four compounds has chosen for further evaluation. To confirm stability of the selected drug candidate to the target protein the MD simulation approach were employed, which confirmed stability of the three compounds. Based on the finding, three newly obtained compounds namely Caucasicoside A (ZINC77257307), Polygalaxanthone III (ZINC247950187), and MCULE-9896837409 (ZINC107434573) may serve as lead compounds to fight against the treatment of XIAP related cancer, although further evaluation through wet lab is necessary to measure the efficacy of the compounds.

Structure-based, multi-targeted drug discovery approach to eicosanoid inhibition: Dual inhibitors of mPGES-1 and 5-lipoxygenase activating protein (FLAP)

BACKGROUND

Due to the importance of both prostaglandins (PGs) and leukotrienes (LTs) as pro-inflammatory mediators, and the potential for eicosanoid shunting in the presence of pathway target inhibitors, we have investigated an approach to inhibiting the formation of both PGs and LTs as part of a multi-targeted drug discovery effort.

METHODS

We generated ligand-protein X-ray crystal structures of known inhibitors of microsomal prostaglandin E2 synthase-1 (mPGES-1) and the 5-Lipoxygenase Activating Protein (FLAP), with their respective proteins, to understand the overlapping pharmacophores. We subsequently used molecular modeling and structure-based drug design (SBDD) to identify hybrid structures intended to inhibit both targets.

RESULTS

This work enabled the preparation of compounds 4 and 5, which showed potent in vitro inhibition of both targets.

SIGNIFICANCE

Our findings enhance the structural understanding of mPGES-1 and FLAP's unique ligand binding pockets and should accelerate the discovery of additional dual inhibitors for these two important integral membrane protein drug targets.

Small Molecule Soluble Epoxide Hydrolase Inhibitors in Multitarget and Combination Therapies for Inflammation and Cancer

The enzyme soluble epoxide hydrolase (sEH) plays a central role in metabolism of bioactive lipid signaling molecules. The substrate-specific hydrolase activity of sEH converts epoxyeicosatrienoic acids (EETs) to less bioactive dihydroxyeicosatrienoic acids. EETs exhibit anti-inflammatory, analgesic, antihypertensive, cardio-protective and organ-protective properties. Accordingly, sEH inhibition is a promising therapeutic strategy for addressing a variety of diseases. In this review, we describe small molecule architectures that have been commonly deployed as sEH inhibitors with respect to angiogenesis, inflammation and cancer. We juxtapose commonly used synthetic scaffolds and natural products within the paradigm of a multitarget approach for addressing inflammation and inflammation induced carcinogenesis. Structural insights from the inhibitor complexes and novel strategies for development of sEH-based multitarget inhibitors are also presented. While sEH inhibition is likely to suppress inflammation-induced carcinogenesis, it can also lead to enhanced angiogenesis via increased EET concentrations. In this regard, sEH inhibitors in combination chemotherapy are described. Urea and amide-based architectures feature prominently across multitarget inhibition and combination chemotherapy applications of sEH inhibitors.

Fingerprint-based computational models of 5-lipo-oxygenase activating protein inhibitors: Activity prediction and structure clustering

Inflammatory diseases can be treated by inhibiting 5-lipo-oxygenase activating protein (FLAP). In this study, a data set containing 2,112 FLAP inhibitors was collected. A total of 25 classification models were built by five machine learning algorithms with five different types of fingerprints. The best model, which was built by support vector machine algorithm with ECFP_4 fingerprint had an accuracy and a Matthews correlation coefficient of 0.862 and 0.722 on the test set, respectively. The predicted results were further evaluated by the application domain d_STD-PRO (a distance between one compound to models). Each compound had a d_STD-PRO value, which was calculated by the predicted probabilities obtained from all 25 models. The application domain results suggested that the reliability of predicted results depended mainly on the compounds themselves rather than algorithms or fingerprints. A group of customized 10-bit fingerprint was manually defined for clustering the molecular structures of 2,112 FLAP inhibitors into eight subsets by K-Means. According to the clustering results, most of inhibitors in two subsets (subsets 2 and 4) were highly active inhibitors. We found that aryl oxadiazole/oxazole alkanes, biaryl amino-heteroarenes, two aromatic rings (often N-containing) linked by a cyclobutene group, and 1,2,4-triazole group were typical fragments in highly active inhibitors.

In silico drug repositioning of FDA-approved drugs to predict new inhibitors for alpha-synuclein aggregation

One of the hallmarks of Parkinson's disease (PD), a long-term neurodegenerative syndrome, is the accumulation of alpha-synuclein (α-syn) fibrils. Despite numerous studies and efforts, inhibition of α-syn protein aggregation is still a challenge. To overcome this issue, we propose an in silico pharmacophore-based repositioning strategy, to find a pharmaceutical drug that, in addition to their defined role, can be used to prevent aggregation of the α-syn protein. Ligand-based pharmacophore modeling was developed and the best model was selected with validation parameters including 72 % sensitivity, 98 % specificity and goodness score about 0.7. The optimal model has three groups of hydrogen bond donor (HBD), three groups of hydrogen bond acceptor (HBA), and two aromatic rings (AR). The FDA-Approved reports in the ZINC15 database were screened with the pharmacophore model taken from inhibitor compounds. The model identified 22 hits, as promising candidate drugs for Parkinson's therapy. It is noteworthy that among these, 10 drugs have been reported to inhibition of α-syn aggregation or treat/reduce Parkinson's pathogenesis. This model was used to virtual screen ZINC, NCI databases, and natural products from the pomegranate. The results of this screen were filtered for their inability to cross the blood-brain barrier, poor oral bioavailability, etc. Finally, the selected compounds of two ZINC and NCI databases were combined and structurally clustered. Remained compounds were clustered in 28 different clusters, and the 17 compounds were introduced as final candidates.

Inhibition of 5-Lipoxygenase-Derived Leukotrienes and Hemiketals as a Novel Anti-Inflammatory Mechanism of Urolithins

SCOPE

Urolithins (Uro), gut microbial metabolites derived from ellagic acid (EA), reach significant concentrations in the human colon. Uro-A exerts anti-inflammatory activity in animal models of inflammatory bowel diseases (IBDs). It is hypothesized that Uro can modulate the biosynthesis of leukocyte-derived inflammatory eicosanoids from the 5-lipoxygenase (5-LOX), cyclooxygenase-2 (COX-2), and 5-LOX/COX-2 pathways, relevant in the onset and progression of IBDs, including 5-hydroxyeicosatetraenoic acids (5-HETEs), leukotriene-B₄ (LTB₄ ), prostaglandin E₂ (PGE₂ ), and hemiketals (HKE₂ and HKD₂ ).

METHODS AND RESULTS

Leukocytes, obtained from six healthy donors, are stimulated with lipopolysaccharide and calcium ionophore A23187. Uro, at concentrations found in the human colon (1-15 µm), decrease eicosanoid biosynthesis and COX-2 levels in the activated leukocytes. In contrast, EA and conjugated Uro (glucuronides and sulfates) are inactive. Uro-A and isourolithin-A reduce the formation of the 5-LOX/COX-2 products HKE₂ and HKD₂ through the COX-2 pathway (down-regulation of COX-2 and PGE2), whereas Uro-C reduces 5-HETE and LTB₄ via inhibition of 5-LOX.

CONCLUSIONS

The results show that physiologically relevant colonic Uro target eicosanoid biosynthetic pathways. The effect on HKs and LTB₄ formation is unprecedented and expands the knowledge on anti-inflammatory mechanisms of Uro against IBDs.

Development of multitarget agents possessing soluble epoxide hydrolase inhibitory activity

Over the last two decades polypharmacology has emerged as a new paradigm in drug discovery, even though developing drugs with high potency and selectivity toward a single biological target is still a major strategy. Often, targeting only a single enzyme or receptor shows lack of efficacy. High levels of inhibitor of a single target also can lead to adverse side effects. A second target may offer additive or synergistic effects to affecting the first target thereby reducing on- and off-target side effects. Therefore, drugs that inhibit multiple targets may offer a great potential for increased efficacy and reduced the adverse effects. In this review we summarize recent findings of rationally designed multitarget compounds that are aimed to improve efficacy and safety profiles compared to those that target a single enzyme or receptor. We focus on dual inhibitors/modulators that target the soluble epoxide hydrolase (sEH) as a common part of their design to take advantage of the beneficial effects of sEH inhibition.

Synthesis, Biological Evaluation and Structure-Activity Relationships of Diflapolin Analogues as Dual sEH/FLAP Inhibitors

A series of derivatives of the potent dual soluble epoxide hydrolase (sEH)/5-lipoxygenase-activating protein (FLAP) inhibitor diflapolin was designed, synthesized, and characterized by 1H NMR, 13C NMR, and elemental analysis. These novel compounds were biologically evaluated for their inhibitory activity against sEH and FLAP. Molecular modeling tools were applied to analyze structure-activity relationships (SAR) on both targets. Results show that even small modifications on the lead compound diflapolin markedly influence the inhibitory potential, especially on FLAP, suggesting very narrow SAR.

Prospective for cytochrome P450 epoxygenase cardiovascular and renal therapeutics

Therapeutics for arachidonic acid pathways began with the development of non-steroidal anti-inflammatory drugs that inhibit cyclooxygenase (COX). The enzymatic pathways and arachidonic acid metabolites and respective receptors have been successfully targeted and therapeutics developed for pain, inflammation, pulmonary and cardiovascular diseases. These drugs target the COX and lipoxygenase pathways but not the third branch for arachidonic acid metabolism, the cytochrome P450 (CYP) pathway. Small molecule compounds targeting enzymes and CYP epoxy-fatty acid metabolites have evolved rapidly over the last two decades. These therapeutics have primarily focused on inhibiting soluble epoxide hydrolase (sEH) or agonist mimetics for epoxyeicosatrienoic acids (EET). Based on preclinical animal model studies and human studies, major therapeutic indications for these sEH inhibitors and EET mimics/analogs are renal and cardiovascular diseases. Novel small molecules that inhibit sEH have advanced to human clinical trials and demonstrate promise for cardiovascular diseases. Challenges remain for sEH inhibitor and EET analog drug development; however, there is a high likelihood that a drug that acts on this third branch of arachidonic acid metabolism will be utilized to treat a cardiovascular or kidney disease in the next decade.

Recent development of lipoxygenase inhibitors as anti-inflammatory agents

Inflammation is favorable in most cases, because it is a kind of body defensive response to external stimuli; sometimes, inflammation is also harmful, such as attacks on the body's own tissues. It could be that inflammation is a unified process of injury and resistance to injury. Inflammation brings extreme pain to patients, showing symptoms of rubor, swelling, fever, pain and dysfunction. As the specific mechanism is not clear yet, the current anti-inflammatory agents are given priority for relieving suffering of patients. Thus it is emergent to find new anti-inflammatory agents with rapid effect. Lipoxygenase (LOX) is a kind of rate-limiting enzyme in the process of arachidonic acid metabolism into leukotriene (LT) which mediates the occurrence of inflammation. The inhibition of LOX can reduce LT, thereby producing an anti-inflammatory effect. In this review, the LOX inhibitors reported in recent years are summarized, and, in particular, their activities, structure-activity relationships and molecular docking studies are emphasized, which will provide new ideas to design novel LOX inhibitors.

Pharmacological profile and efficiency in vivo of diflapolin, the first dual inhibitor of 5-lipoxygenase-activating protein and soluble epoxide hydrolase

Arachidonic acid (AA) is metabolized to diverse bioactive lipid mediators. Whereas the 5-lipoxygenase-activating protein (FLAP) facilitates AA conversion by 5-lipoxygenase (5-LOX) to pro-inflammatory leukotrienes (LTs), the soluble epoxide hydrolase (sEH) degrades anti-inflammatory epoxyeicosatrienoic acids (EETs). Accordingly, dual FLAP/sEH inhibition might be advantageous drugs for intervention of inflammation. We present the in vivo pharmacological profile and efficiency of N-[4-(benzothiazol-2-ylmethoxy)-2-methylphenyl]-N′-(3,4-dichlorophenyl)urea (diflapolin) that dually targets FLAP and sEH. Diflapolin inhibited 5-LOX product formation in intact human monocytes and neutrophils with IC₅₀ = 30 and 170 nM, respectively, and suppressed the activity of isolated sEH (IC₅₀ = 20 nM). Characteristic for FLAP inhibitors, diflapolin (I) failed to inhibit isolated 5-LOX, (II) blocked 5-LOX product formation in HEK cells only when 5-LOX/FLAP was co-expressed, (III) lost potency in intact cells when exogenous AA was supplied, and (IV) prevented 5-LOX/FLAP complex assembly in leukocytes. Diflapolin showed target specificity, as other enzymes related to AA metabolism (i.e., COX1/2, 12/15-LOX, LTA₄H, LTC₄S, mPGES₁, and cPLA₂) were not inhibited. In the zymosan-induced mouse peritonitis model, diflapolin impaired vascular permeability, inhibited cysteinyl-LTs and LTB₄ formation, and suppressed neutrophil infiltration. Diflapolin is a highly active dual FLAP/sEH inhibitor in vitro and in vivo with target specificity to treat inflammation-related diseases.