Development of a fluorescence-based enzyme assay of human 5-lipoxygenase

Structure-Based Identification of Organoruthenium Compounds as Nanomolar Antagonists of Cannabinoid Receptors

Metal complexes exhibit a diverse range of coordination geometries, representing novel privileged scaffolds with convenient click types of preparation inaccessible for typical carbon-centered organic compounds. Herein, we explored the opportunity to identify biologically active organometallic complexes by reverse docking of a rigid, minimum-size octahedral organoruthenium scaffold against thousands of protein-binding pockets. Interestingly, cannabinoid receptor type 1 (CB1) was identified based on the docking scores and the degree of overlap between the docked organoruthenium scaffold and the hydrophobic scaffold of the cocrystallized ligand. Further structure-based optimization led to the discovery of organoruthenium complexes with nanomolar binding affinities and high selectivity toward CB2. Our work indicates that octahedral organoruthenium scaffolds may be advantageous for targeting the large and hydrophobic binding pockets and that the reverse docking approach may facilitate the discovery of novel privileged scaffolds, such as organometallic complexes, for exploring chemical space in lead discovery.

Boesenbergia rotunda and Its Pinostrobin for Atopic Dermatitis: Dual 5-Lipoxygenase and Cyclooxygenase-2 Inhibitor and Its Mechanistic Study through Steady-State Kinetics and Molecular Modeling

Human 5-lipoxygenase (5-LOX) and cyclooxygenase-2 (COX-2) are potential targets for suppressing pruritic skin inflammation in atopic dermatitis (AD). In addition, Staphylococcus aureus colonization and oxidative stress worsen AD skin conditions. We aimed to investigate anti-inflammatory activity, using 5-LOX and COX-2 inhibitions, and the anti-staphylococcal, and antioxidant potentials of several medicinal plants bio-prospected from traditional medicine related to AD pathogenesis. Essential oils and hexane fractions were prepared and analyzed using gas chromatography-mass spectrometry. Boesenbergia rotunda hexane extract displayed anti-Staphylococcus aureus (MIC = 10 µg/mL) and antioxidant activities (IC50 = 557.97 and 2651.67 µg/mL against DPPH and NO radicals, respectively). A major flavonoid, pinostrobin, was further nonchromatographically isolated. Pinostrobin was shown to be a potent 5-LOX inhibitor (IC50 = 0.499 µM) compared to nordihydroguaiaretic acid (NDGA; IC50 = 5.020 µM) and betamethasone dipropionate (BD; IC50 = 2.077 µM) as the first-line of AD treatment. Additionally, pinostrobin inhibited COX-2 (IC50 = 285.67 µM), which was as effective as diclofenac sodium (IC50 = 290.35 µM) and BD (IC50 = 240.09 µM). This kinetic study and molecular modeling showed the mixed-type inhibition of NDGA and pinostrobin against 5-LOX. This study suggests that B. rotunda and its bioactive pinostrobin have promising properties for AD therapy.

Natural pentacyclic triterpenoid as allosteric modulators of human 5-lipoxygenase with potential anti-inflammatory activity

This study explored new methods to inhibit human 5-lipoxygenase (5-hLOX) by analyzing natural terpenes that share structural similarities with acetoxyboswellic acid (AKBA). Enzymatic assays were used to evaluate the terpene's ability to inhibit the enzyme, potentially providing anti-inflammatory benefits. Our research focused on how certain types of triterpenes can inhibit 5-hLOX allosterically via a newly discovered allosteric site identified by enzyme crystallization. To determine whether natural boswellic acid analogs mimicked the allosteric known inhibitor AKBA, we combined 5-hLOX inhibition with in silico modeling. Our research has discovered that certain amino acids, specifically Arg 138, Arg 101, Arg 68, and Gln129, located in the allosteric 5-hLOX pocket, play a critical role in stabilizing glycyrrhetinic isomers. These amino acids form hydrogen bonds and hydrophobic interactions that contribute to the inhibitory potency of boswellic acid derivatives. We have found that α and β glycyrrhetinic acid isomers, carbenoxolone, and to a minor extent, prednisolone, have a potent inhibitory effect against 5-hLOX with IC50 values of 8.64, 3.94, 52.98, and 291.20 µM, respectively. These values are in line with our calculated in silico allosteric site binding energy estimations. In contrast, other steroidal or non-steroidal anti-inflammatory agents exhibited inhibitory potencies larger than 500 μM. However, the specific pharmacodynamic mechanisms are currently unknown. We propose that AKBA analogs may lead to the future development of novel anti-inflammatory agents.Communicated by Ramaswamy H. Sarma.

Anti-inflammatory constituents from the stems and leaves of Glycosmis ovoidea Pierre

Seven undescribed compounds, including four acridones, two coumarins, and a phenylpropanoid, together with 13 known acridone analogues were isolated from the ethanolic extract of the stems and leaves of Glycosmis ovoidea Pierre. Their structures were elucidated on the basis of comprehensive analysis of 1D and 2D NMR and HRESIMS spectroscopic data, and the absolute configurations were assigned by comparison of the experimental and calculated ECD data. Five compounds showed moderate inhibitory effects on nitric oxide production stimulated by lipopolysaccharide in BV-2 microglial cells with IC₅₀ values in the range of 18.30-30.84 μM, and three compounds showed potent inhibition on 5-lipoxygenase (5-LOX) with IC₅₀ values in the range of 2.08-10.26 μM. The possible binding sites of the active compounds with 5-LOX were further performed by molecular docking.

Flavonoids as dual inhibitors of cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX): molecular docking and in vitro studies

Background

Inflammation is known to involve in many pathological processes of different diseases, but the current therapy causes adverse effects. Thus, there is a great interest for the discovery of flavonoids as a valuable alternative to classical analgesic and anti-inflammatory agent with dual-inhibitory action, especially on both COX-2 and 5-LOX which can minimize or overcome this problem.

Results

In the present work, drug-likeness properties of the synthesized flavonoids via Lipinski’s Rule of Five were predicted using QikProp prior to evaluation of their COX and LOX inhibitory activities using enzyme assays. Subsequently, molecular docking was performed using GLIDE to analyse their binding behaviour. The results showed that all compounds obeyed the Lipinski’s Rule of Five. NPC6 and NPC7 had displayed better selectivity towards COX-2 as compared to Indomethacin with less than 50% inhibition against COX-1. In addition, these compounds also inhibited activity of 5-LOX. Their selectivity to COX-2 was due to the binding to hydrophobic region and extends to lobby region near the entrance of COX binding site forming hydrogen bond with Ser530. Interestingly, these compounds showed a similar binding mode as Zileuton in the active site of 5-LOX and formed hydrogen bond interaction with Ala424.

Conclusion

NPC6 and NPC7 had potential as dual inhibitor of COX-2 and 5-LOX. The scaffolds of these chemical entities are useful to be as lead compounds for the dual inhibition of COX-2 and 5-LOX.

Discovery of polymethoxyflavones as potential cyclooxygenase-2 (COX-2), 5-lipoxygenase (5-LOX) and phosphodiesterase 4B (PDE4B) inhibitors

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely prescribed to treat inflammatory-related diseases, pain and fever. However, the prolong use of traditional NSAIDs leads to undesirable side effects such as gastric, ulceration, and renal toxicity due to lack of selectivity toward respective targets for COX-2, 5-LOX, and PDE4B. Thus, targeting multiple sites can reduce these adverse effects of the drugs and increase its potency. A series of methoxyflavones (F1-F5) were synthesized and investigated for their anti-inflammatory properties through molecular docking and inhibition assays. Among these flavones, only F2 exhibited selectivity toward COX-2 (Selectivity Index, SI: 3.90, COX-2 inhibition: 98.96 ± 1.47%) in comparison with celecoxib (SI: 7.54, COX-2 inhibition: 98.20 ± 2.55%). For PDEs, F3 possessed better selectivity to PDE4B (SI: 4.67) than rolipram (SI: 0.78). F5 had the best 5-LOX inhibitory activity among the flavones (33.65 ± 4.74%) but less than zileuton (90.81 ± 0.19%). Docking analysis indicated that the position of methoxy group and the substitution of halogen play role in determining the bioactivities of flavones. Interestingly, F1-F5 displayed favorable pharmacokinetic profiles and acceptable range of toxicity (IC₅₀>70 µM) in cell lines with the exception for F1 (IC₅₀: 16.02 ± 1.165 µM). This study generated valuable insight in designing new anti-inflammatory drug based on flavone scaffold. The newly synthesized flavones can be further developed as future therapeutic agents against inflammation.

From the Design to the In Vivo Evaluation of Benzohomoadamantane-Derived Soluble Epoxide Hydrolase Inhibitors for the Treatment of Acute Pancreatitis

The pharmacological inhibition of soluble epoxide hydrolase (sEH) is efficient for the treatment of inflammatory and pain-related diseases. Numerous potent sEH inhibitors (sEHIs) present adamantyl or phenyl moieties, such as the clinical candidates AR9281 or EC5026. Herein, in a new series of sEHIs, these hydrophobic moieties have been merged in a benzohomoadamantane scaffold. Most of the new sEHIs have excellent inhibitory activities against sEH. Molecular dynamics simulations suggested that the addition of an aromatic ring into the adamantane scaffold produced conformational rearrangements in the enzyme to stabilize the aromatic ring of the benzohomoadamantane core. A screening cascade permitted us to select a candidate for an in vivo efficacy study in a murine model of cerulein-induced acute pancreatitis. The administration of 22 improved the health status of the animals and reduced pancreatic damage, demonstrating that the benzohomoadamantane unit is a promising scaffold for the design of novel sEHIs.

Identification of NSAIDs as lipoxygenase inhibitors through highly sensitive chemiluminescence method, expression analysis in mononuclear cells and computational studies

Here we report the inhibitory effects of nine non-steroidal anti-inflammatory drugs (NSAIDs) on soybean 15-lipoxygenase (15-LOX) enzyme (EC 1.13.11.12) by three different methods; UV-absorbance, colorimetric and chemiluminescence methods. Only two drugs, Ibuprofen and Ketoprofen, exhibited enzyme inhibition by UV-absorbance method but none of the drug showed inhibition through colorimetric method. Chemiluminescence method was found highly sensitive for the identification of 15-LOX inhibitors and it was more sensitive and several fold faster than the other methods. All tested drugs showed 15-LOX-inhibition with IC₅₀ values ranging from 3.52 ± 0.08 to 62.6 ± 2.15 µM by chemiluminescence method. Naproxen was the most active inhibitor (IC₅₀ 3.52 ± 0.08 µM) followed by Aspirin (IC₅₀ 4.62 ± 0.11 µM) and Acetaminophen (IC₅₀ 6.52 ± 0.14 µM). Ketoprofen, Diclofenac and Mefenamic acid showed moderate inhibitory profiles (IC₅₀ 24.8 ± 0.24 to 39.62 ± 0.27 µM). Piroxicam and Tenoxicam were the least active inhibitors with IC₅₀ values of 62.6 ± 2.15 µM and 49.5 ± 1.13 µM, respectively. These findings are supported by expression analysis, molecular docking studies and density functional theory calculations. The expression analysis and flow cytometry apoptosis analysis were carried out using mononuclear cells (MNCs) which express both human 15-LOX and 5-LOX. Selected NSAIDs did not affect the cytotoxic activity of MNCs at IC₅₀ concentrations and the cell death showed dose dependent effect. However, MNCs apoptosis increased only at the higher concentrations, demonstrating that these drugs may not induce loss of immunity in septic and other inflammatory conditions at the acceptable inhibitory concentrations. The data collectively suggests that NSAIDs not only inhibit COX enzymes as reported in the literature but soybean 15-LOX and MNCs LOXs are also inhibited at differential values. A comparison of the metabolomics studies of arachidonic acid pathway after inhibition of either COX or LOX enzymes may reconfirm these findings.

Synthesis and structure-activity relationships of novel 5-(hydroxamic acid)methyl oxazolidinone derivatives as 5-lipoxygenase inhibitors

Oxazolidinone hydroxamic acid derivatives were synthesised and evaluated for inhibitory activity against leukotriene (LT) biosynthesis in three in vitro cell-based test systems and on direct inhibition of recombinant human 5-lipoxygenase (5-LO). Thirteen of the 19 compounds synthesised were considered active ((50% inhibitory concentration (IC₅₀) ≤ 10 µM in two or more test systems)). Increasing alkyl chain length on the hydroxamic acid moiety enhanced activity and morpholinyl-containing derivatives were more active than N-acetyl-piperizinyl derivatives. The IC₅₀ values in cell-based assay systems were comparable to those obtained by direct inhibition of 5-LO activity, confirming that the compounds are direct inhibitors of 5-LO. Particularly, compounds PH-249 and PH-251 had outstanding potencies (IC₅₀ < 1 µM), comparable to that of the prototype 5-LO inhibitor, zileuton. Pronounced in vivo activity was demonstrated in zymosan-induced peritonitis in mice. These novel oxazolidinone hydroxamic acid derivatives are, therefore, potent 5-LO inhibitors with potential application as anti-allergic and anti-inflammatory agents.

Evaluation of cyrhetrenyl and ferrocenyl precursors as 5-lipoxygenase inhibitors – biological and computational studies

Synthesis and biological evaluation of precursors derived from ferrocene and cyrhetrene as inhibitors of enzyme 5-hLOX.

2-Oxaadamant-1-yl Ureas as Soluble Epoxide Hydrolase Inhibitors: In Vivo Evaluation in a Murine Model of Acute Pancreatitis

In vivo pharmacological inhibition of soluble epoxide hydrolase (sEH) reduces inflammatory diseases, including acute pancreatitis (AP). Adamantyl ureas are very potent sEH inhibitors, but the lipophilicity and metabolism of the adamantane group compromise their overall usefulness. Herein, we report that the replacement of a methylene unit of the adamantane group by an oxygen atom increases the solubility, permeability, and stability of three series of urea-based sEH inhibitors. Most of these oxa-analogues are nanomolar inhibitors of both the human and murine sEH. Molecular dynamics simulations rationalize the molecular basis for their activity and suggest that the presence of the oxygen atom on the adamantane scaffold results in active site rearrangements to establish a weak hydrogen bond. The 2-oxaadamantane 22, which has a good solubility, microsomal stability, and selectivity for sEH, was selected for further in vitro and in vivo studies in models of cerulein-induced AP. Both in prophylactic and treatment studies, 22 diminished the overexpression of inflammatory and endoplasmic reticulum stress markers induced by cerulein and reduced the pancreatic damage.

Screening for natural inhibitors of 5-lipoxygenase from Zi-shen pill extract by affinity ultrafiltration coupled with ultra performance liquid chromatography-mass spectrometry

ETHNOPHARMACOLOGICAL RELEVANCE

Zi-shen pill (ZSP), a traditional Chinese medicine, is widely used for the treatment of benign prostatic hyperplasia (BPH) and has remarkable curative effect.

AIM OF THE STUDY

To screen the potential 5-Lipoxygenase(5-LOX) inhibitors from ZSP extract.

MATERIALS AND METHODS

A new approach based on affinity ultrafiltration-ultra performance liquid chromatography-mass spectrometry(UPLC-MS) was established and validated. Zileuton and glipizide were chosen as positive and negative control drug, respectively. For better screening result, the concentration of 5-LOX enzyme, incubation temperature and time, pH and ion strength were optimized. In addition, 5-LOX inhibitory assay in vitro and molecular docking technique were used for further verification.

RESULTS

20 compounds were characterized in the ultrafiltrate by high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and 16 ligands showed binding ability to 5-LOX. Among them, six ligands were deduced as high-potential 5-LOX inhibitors with their high specific binding values (>2.0). The inhibitory activities of anemarrhenasaponin I, timosaponin AI, nyasol and demethyleneberberine were confirmed by the 5-LOX inhibitory assay for validating the reliability of affinity ultrafiltration approach and the computer-simulated molecular docking technique further clarified the possible mechanism of action between the active compounds and the 5-LOX active sites.

New flavonoid - N,N-dibenzyl(N-methyl)amine hybrids: Multi-target-directed agents for Alzheimer´s disease endowed with neurogenic properties

The design of multi-target directed ligands (MTDLs) is a valid approach for obtaining effective drugs for complex pathologies. MTDLs that combine neuro-repair properties and block the first steps of neurotoxic cascades could be the so long wanted remedies to treat neurodegenerative diseases (NDs). By linking two privileged scaffolds with well-known activities in ND-targets, the flavonoid and the N,N-dibenzyl(N-methyl)amine (DBMA) fragments, new CNS-permeable flavonoid - DBMA hybrids (1-13) were obtained. They were subjected to biological evaluation in a battery of targets involved in Alzheimer's disease (AD) and other NDs, namely human cholinesterases (hAChE/hBuChE), β-secretase (hBACE-1), monoamine oxidases (hMAO-A/B), lipoxygenase-5 (hLOX-5) and sigma receptors (σ₁R/σ₂R). After a funnel-type screening, 6,7-dimethoxychromone - DBMA (6) was highlighted due to its neurogenic properties and an interesting MTD-profile in hAChE, hLOX-5, hBACE-1 and σ₁R. Molecular dynamic simulations showed the most relevant drug-protein interactions of hybrid 6, which could synergistically contribute to neuronal regeneration and block neurodegeneration.

New antibacterial and 5-lipoxygenase activities of synthetic benzyl phenyl ketones: Biological and docking studies

We investigated twelve benzyl phenyl ketone derivatives which are synthetic precursors of isoflavonoids that are shown be good 5-hLOX inhibitors, especially those that have the catechol group, but these precursors never have been assayed as 5-hLOX inhibitors being a novelty as inhibitors of the enzyme, due to sharing important structural characteristics. Screening assays, half maximal inhibitory concentration (IC₅₀) and kinetic assays of all the studied molecules (5 µg/ml in media assay) showed that 1-(2,4-dihydroxy-3-methylphenyl)-2-(3-chlorophenyl)-ethanone (K205; IC₅₀ = 3.5 µM; K_i = 4.8 µM) and 1-(2,4-dihydroxy-3-methylphenyl)-2-(2-nitrophenyl)-ethanone (K206; IC₅₀ = 2.3 µM; K_i = 0.7 µM) were potent, selective, competitive and nonredox inhibitors of 5-hLOX. Antioxidant behavior was also assayed by DPPH, FRAP, and assessing ROS production, and those with antibacterial and antiproliferative properties relating to 1-(2,4-dihydroxy-3-methylphenyl)-2-(2-chlorophenyl)-ethanone (K208) established it as the most interesting and relevant compound studied, as it showed nearly 100% inhibition of bacterial growth of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Finally, docking studies were done that helped to characterize how the inhibitor structures correlated to decreased 5-hLOX activity.

Activation of Glutathione Peroxidase 4 as a Novel Anti-inflammatory Strategy

The anti-oxidative enzyme, glutathione peroxidase 4 (GPX4), helps to promote inflammation resolution by eliminating oxidative species produced by the arachidonic acid (AA) metabolic network. Up-regulating its activity has been proposed as a promising strategy for inflammation intervention. In the present study, we aimed to study the effect of GPX4 activator on the AA metabolic network and inflammation related pathways. Using combined computational and experimental screen, we identified a novel compound that can activate the enzyme activity of GPX4 by more than two folds. We further assessed its potential in a series of cellular assays where GPX4 was demonstrated to play a regulatory role. We are able to show that GPX4 activation suppressed inflammatory conditions such as oxidation of AA and NF-κB pathway activation. We further demonstrated that this GPX4 activator can decrease the intracellular ROS level and suppress ferroptosis. Our study suggests that GPX4 activators can be developed as anti-inflammatory or cyto-protective agent in lipid-peroxidation-mediated diseases.

Neurogenic and neuroprotective donepezil-flavonoid hybrids with sigma-1 affinity and inhibition of key enzymes in Alzheimer's disease

In this work we describe neurogenic and neuroprotective donepezil-flavonoid hybrids (DFHs), exhibiting nanomolar affinities for the sigma-1 receptor (σ1R) and inhibition of key enzymes in Alzheimer's disease (AD), such as acetylcholinesterase (AChE), 5-lipoxygenase (5-LOX), and monoamine oxidases (MAOs). In general, new compounds scavenge free radical species, are predicted to be brain-permeable, and protect neuronal cells against mitochondrial oxidative stress. N-(2-(1-Benzylpiperidin-4-yl)ethyl)-6,7-dimethoxy-4-oxo-4H-chromene-2-carboxamide (18) is highlighted due to its interesting biological profile in σ1R, AChE, 5-LOX, MAO-A and MAO-B. In phenotypic assays, it protects a neuronal cell line against mitochondrial oxidative stress and promotes maturation of neural stem cells into a neuronal phenotype, which could contribute to the reparation of neuronal tissues. Molecular modelling studies of 18 in AChE, 5-LOX and σ1R revealed the main interactions with these proteins, which will be further exploited in the optimization of new, more efficient DFHs.

Novel Allosteric Activators for Ferroptosis Regulator Glutathione Peroxidase 4

Glutathione peroxidase 4 (GPX4) is essential for cell membrane repair, inflammation suppression, and ferroptosis inhibition. GPX4 upregulation provides unique drug discovery opportunities for inflammation and ferroptosis-related diseases. However, rational design of protein activators is challenging. Until now, no compound has been reported to activate the enzyme activity of GPX4. Here, we identified a potential allosteric site in GPX4 and successfully found eight GPX4 activators using a novel computational strategy and experimental studies. Compound 1 from the virtual screen increased GPX4 activity, suppressed ferroptosis, reduced pro-inflammatory lipid mediator production, and inhibited NF-κB pathway activation. Further chemical synthesis and structure-activity relationship studies revealed seven more activators. The strongest compound, 1d4, increased GPX4 activity to 150% at 20 μM in the cell-free assay and 61 μM in cell extracts. Therefore, we demonstrated that GPX4 can be directly activated using chemical compounds to suppress ferroptosis and inflammation. Meanwhile, the discovery of GPX4 activators verified the possibility of rational design of allosteric activators.

Discovery of an Inhibitor of the Proteasome Subunit Rpn11

The proteasome plays a crucial role in degradation of normal proteins that happen to be constitutively or inducibly unstable, and in this capacity it plays a regulatory role. Additionally, it degrades abnormal/damaged/mutant/misfolded proteins, which serves a quality-control function. Inhibitors of the proteasome have been validated in the treatment of multiple myeloma, with several FDA-approved therapeutics. Rpn11 is a Zn²⁺-dependent metalloisopeptidase that hydrolyzes ubiquitin from tagged proteins that are trafficked to the proteasome for degradation. A fragment-based drug discovery (FBDD) approach was utilized to identify fragments with activity against Rpn11. Screening of a library of metal-binding pharmacophores (MBPs) revealed that 8-thioquinoline (8TQ, IC₅₀ value ∼2.5 μM) displayed strong inhibition of Rpn11. Further synthetic elaboration of 8TQ yielded a small molecule compound (35, IC₅₀ value ∼400 nM) that is a potent and selective inhibitor of Rpn11 that blocks proliferation of tumor cells in culture.

Computer modeling in predicting the bioactivity of human 5-lipoxygenase inhibitors

5-Lipoxygenase (5-LOX) is a key enzyme in the inflammatory path. Inhibitors of 5-LOX are useful for the treatment of diseases like arthritis, cancer, and asthma. We have collected a dataset including 220 human 5-LOX inhibitors for classification. A self-organizing map (SOM), a support vector machine (SVM), and a multilayer perceptron (MLP) algorithm were used to build models with selected descriptors for classifying 5-LOX inhibitors into active and weakly active ones. MACCS fingerprints were used in this model building process. The accuracy (Q) and Matthews correlation coefficient (MCC) of the best SOM model (Model 1A) were 86.49% and 0.73 on the test set, respectively. The Q and MCC of the best SVM model (Model 2A) were 82.67% and 0.64 on the test set, respectively. The Q and MCC of the best MLP model (Model 3B) were 84.00% and 0.67 on the test set, respectively. In addition, 180 inhibitors with bioactivities measured by fluorescence method were further used for a quantitative prediction. Multiple linear regression (MLR) and SVM algorithms were used to build models to predict the [Formula: see text] values. The correlation coefficients (R) of the MLR model (Model Q1) and the SVM model (Model Q2) were 0.72 and 0.74 on the test set, respectively.

Structural optimization and biological evaluation of 1,5-disubstituted pyrazole-3-carboxamines as potent inhibitors of human 5-lipoxygenase

Human 5-lipoxygenase (5-LOX) is a well-validated drug target and its inhibitors are potential drugs for treating leukotriene-related disorders. Our previous work on structural optimization of the hit compound 2 from our in-house collection identified two lead compounds, 3a and 3b, exhibiting a potent inhibitory profile against 5-LOX with IC₅₀ values less than 1 µmol/L in cell-based assays. Here, we further optimized these compounds to prepare a class of novel pyrazole derivatives by opening the fused-ring system. Several new compounds exhibited more potent inhibitory activity than the lead compounds against 5-LOX. In particular, compound 4e not only suppressed lipopolysaccharide-induced inflammation in brain inflammatory cells and protected neurons from oxidative toxicity, but also significantly decreased infarct damage in a mouse model of cerebral ischemia. Molecular docking analysis further confirmed the consistency of our theoretical results and experimental data. In conclusion, the excellent in vitro and in vivo inhibitory activities of these compounds against 5-LOX suggested that these novel chemical structures have a promising therapeutic potential to treat leukotriene-related disorders.

A high-throughput mass spectrometric assay for discovery of human lipoxygenase inhibitors and allosteric effectors

Lipoxygenases (LOXs) regulate inflammation through the production of a variety of molecules whose specific downstream effects are not entirely understood due to the complexity of the inflammation pathway. The generation of these biomolecules can potentially be inhibited and/or allosterically regulated by small synthetic molecules. The current work describes the first mass spectrometric high-throughput method for identifying small molecule LOX inhibitors and LOX allosteric effectors that change the substrate preference of human lipoxygenase enzymes. Using a volatile buffer and an acid-labile detergent, enzymatic products can be directly detected using high-performance liquid chromatography-mass spectrometry (HPLC-MS) without the need for organic extraction. The method also reduces the required enzyme concentration compared with traditional ultraviolet (UV) absorbance methods by approximately 30-fold, allowing accurate binding affinity measurements for inhibitors with nanomolar affinity. The procedure was validated using known LOX inhibitors and the allosteric effector 13(S)-hydroxy-9Z,11E-octadecadienoic acid (13-HODE).

The expression and activity of 5-LOX in the large intestine of horses harbouring encysted cyathostomin larvae

Leukotrienes are products of the arachidonic acid metabolism and act as potent inflammatory mediators modulating the immune response and various physiological processes. This study evaluated the expression and activity of 5-lipoxygenase (5-LOX), the enzyme that catalyzes the first two steps in the biosynthesis of leukotrienes, in horses infected by larval cyathostomins. Tissue samples from dorsal and ventral colon, and from the cecum were collected from 16 horses slaughtered for human consumption. Samples were analyzed to estimate the burdens of encysted cyathostomin larvae and adult luminal stages, and then processed for the evaluation of biochemical parameters. No significant differences were found in the protein expression and enzymatic activity of 5-LOX between animals harbouring only adult parasites and negative horses. The protein expression and enzyme activity of 5-LOX were significantly higher in horses harbouring encysted larvae in comparison with horses free of encysted larvae. Although preliminary, these results indicate that 5-LOX is an important mediator in the course of horse cyathostominosis and further studies are warranted to unveil the possible role this enzyme plays in the pathogenesis of horse cyathostominosis, and its potential as a diagnostic marker.

Benzo[d]isothiazole 1,1-dioxide derivatives as dual functional inhibitors of 5-lipoxygenase and microsomal prostaglandin E(2) synthase-1

A series of 6-nitro-3-(m-tolylamino) benzo[d]isothiazole 1,1-dioxide analogues were synthesized and evaluated for their inhibition activity against 5-lipoxygenase (5-LOX) and microsomal prostaglandin E2 synthase (mPGES-1). These compounds can inhibit both enzymes with IC50 values ranging from 0.15 to 23.6μM. One of the most potential compounds, 3g, inhibits 5-LOX and mPGES-1 with IC50 values of 0.6μM, 2.1μM, respectively.

A fluorescence-based assay for measuring the redox potential of 5-lipoxygenase inhibitors

The activities and side effects of 5-lipoxygenase (5-LO) inhibitors can be predicted by identifying their redox mechanisms. In this study, we developed a fluorescence-based method to measure the redox potential of 5-LO inhibitors and compared it to the conventional, absorbance-based method. After the pseudo-peroxidase reaction, the amount of remaining lipid peroxide was quantified using the H2DCFDA (2′,7′-dichlorodihydrofluorescein diacetate) fluorescence dye. Our method showed large signal windows and provided comparable redox potential values. Importantly, the redox mechanisms of known inhibitors were accurately measured with the fluorescence assay, whereas the conventional, absorbance-based method showed contradictory results. Our findings suggest that our developed method is a better alternative for classifying the redox potential of 5-LO inhibitors, and the fluorescence assay can be effectively used to study the mechanisms of action that are related to redox cycling.

Bioguidage search of active compounds from Waltheria indica L. (Malvaceae) used for asthma and inflammation treatment in Burkina Faso

Waltheria indica is used in traditional pharmacopeia in Burkina Faso for the treatment of asthma and conditions of inflammation. To evaluate its pharmacological properties and isolate the active compounds, a study through a bioguided phytochemical approach was conducted. This search was guided by a two-level investigation. First, we evaluated the impact of various fractions on the activity of enzymes involved in smooth muscle contraction (PDE4A1α) and inflammatory processes (PLA2 , 5-LOX). Second, we investigated the inhibitory effect of fractions on isolated rat trachea. The initial hydroalcoholic extract from roots of W. indica (HA), n-hexane fraction (F1 ), dichloromethane fraction (F2 ), ethyl acetate fraction (F3 ), residuary fraction (F4 ) reduced enzyme activity of PDE4A1α (inhibition of 22-42% at 50 μg/mL), 5-LOX (60-80% at 10 μg/mL), and PLA2 (42-94% at 100 μg/mL). On isolated rat trachea, only HA, F3 , and fractions obtained from F3 by chromatography on silica gel column, using dichloromethane/methanol, dose dependently inhibited contraction induced by acetylcholine. IC50 was 1051 μg/mL for HA and comprised between 181 and 477 μg/mL for F3 and its fractions. The most active fractions were purified and led to the identification of (-)-epicatechin. (-)-epicatechin from W. indica dose dependently inhibited PLA2 (IC50 = 154.7 μm) and 5-LOX (IC50 = 15.8 μm). In conclusion, both inhibition of PDE4A1α, 5-LOX, and PLA2 activities and rat trachea relaxation by W. indica validate its use in traditional management of asthma and other conditions of inflammation. These effects should be, at least in part, attributed to the presence of (-)-epicatechin in roots of W. indica.

5-Lipoxygenase inhibitors: a patent evaluation (WO2011161615)

1,5-Diarylpyrazoles are privileged scaffolds used for the development of COX-2 (cyclooxygenase 2) selective inhibitors (coxibs). Derivatives of 1,5-diarylpyrazoles are currently being used as 5-lipoxygenase (5-LO) inhibitors for the treatment of respiratory diseases, inflammatory and autoimmune disorders. The following article, which evaluates this patent application, describes 1,5-arylpyrazoles and their pharmacological ability to inhibit 5-LO. Furthermore, the authors describe how these compounds relate to pyrazole derivatives in terms of their synthesis and how they are used for treating several respiratory diseases including: chronic obstructive pulmonary disease (COPD), bronchial asthma and other disorders. The authors have come to the conclusion that this current patent evaluation is insufficient for the complete evaluation of these compounds. However, this does not diminish the importance of the versatile synthesis of 1,5-pyrazole derivatives and their use in the treatment of inflammatory-related pathologies.

5-Lipoxygenase and cyclooxygenase-2 in the lungs of pigs naturally affected by enzootic pneumonia and porcine pleuropneumonia

Enzootic pneumonia by Mycoplasma hyopneumoniae and pleuropneumonia by Actinobacillus pleuropneumoniae are among the most common and economically relevant pulmonary diseases in swine herds. We herein investigated the activity and expression of 5-lipoxygenase (5-LOX) and cyclooxygenase-2 (COX-2) in healthy and diseased porcine lungs, by means of immunohistochemical, immunochemical and biochemical assays. Diseased lungs showed a significantly higher activity and expression of 5-LOX and COX-2 in a wide range of cell types, thus suggesting the likely involvement of both enzymes in the pathogenesis of bacterial porcine pneumonia. Consistently, increased enzyme activities were paralleled by increased leukotriene B(4) (LTB(4)), a 5-LOX product and prostaglandin E(2) (PGE(2)), a COX-2 product, content in diseased versus healthy lungs.

Synthesis and evaluation of 5-lipoxygenase translocation inhibitors from acylnitroso hetero-Diels-Alder cycloadducts

Acylnitroso cycloadducts have proven to be valuable intermediates in the syntheses of a plethora of biologically active molecules. Recently, organometallic reagents were shown to open bicyclic acylnitroso cycloadducts and, more interestingly, the prospect of highly regioselective openings was raised. This transformation was employed in the synthesis of a compound with excellent inhibitory activity against 5-lipoxygenase ((±)-4a, IC(50) 51 nM), an important mediator of inflammation intimately involved in a number of disease states including asthma and cancer. Optimization of the copper-mediated organometallic ring opening reaction was accomplished allowing the further exploration of the biological activity. Synthesis of a number of derivatives with varying affinity for metal binding as well as pendant groups in a range of sizes was accomplished. Analogues were tested in a whole cell assay which revealed a subset of the compounds to be inhibitors of enzyme translocation, a mode of action not previously known and, potentially, extremely important for better understanding of the enzyme and inhibitor development. Additionally, the lead compound was tested in vivo in an established colon cancer model and showed very encouraging anti-tumorogenic properties.

Localization of lipoxygenase activity on the oil bodies and in protoplasts using a novel fluorescence imaging method

Lipoxygenase (linoleate:oxygen oxidoreductase; EC 1.13.11.12; LOX) catalyzes oxygenation of polyenoic fatty acids, which precedes the degradation of storage lipids during seed germination in sunflower. In the present work, it has been confirmed that 2',7'-dichlorodihydrofluorescein diacetate (H(2)DCFDA) produces fluorescence in presence of lipid hydroperoxides (LOX reaction products). This work provides new information on spatial localization of transiently enhanced LOX activity in protoplasts from 5 d old seedling cotyledons of sunflower (Helianthus annuus L. cv. Morden) by exploiting H(2)DCFDA as a probe for fluorescence detection from LOX activity sites. Use of LOX inhibitors [nordihydroguaiaretic acid (NDGA) and propyl gallate (PG)] confirms oil bodies as LOX activity sites. Oil body surface has been shown to possess LOX activity in 5 d old seedling cotyledons.

Identifying chelators for metalloprotein inhibitors using a fragment-based approach

Fragment-based lead design (FBLD) has been used to identify new metal-binding groups for metalloenzyme inhibitors. When screened at 1 mM, a chelator fragment library (CFL-1.1) of 96 compounds produced hit rates ranging from 29% to 43% for five matrix metalloproteases (MMPs), 24% for anthrax lethal factor (LF), 49% for 5-lipoxygenase (5-LO), and 60% for tyrosinase (TY). The ligand efficiencies (LE) of the fragment hits are excellent, in the range of 0.4-0.8 kcal/mol. The MMP enzymes all generally elicit the same chelators as hits from CFL-1.1; however, the chelator fragments that inhibit structurally unrelated metalloenzymes (LF, 5-LO, TY) vary considerably. To develop more advanced hits, one hit from CFL-1.1, 8-hydroxyquinoline, was elaborated at four different positions around the ring system to generate new fragments. 8-Hydroxyquinoline fragments substituted at either the 5- or 7-positions gave potent hits against MMP-2, with IC(50) values in the low micromolar range. The 8-hydroxyquinoline represents a promising new chelator scaffold for the development of MMP inhibitors that was discovered by use of a metalloprotein-focused chelator fragment library.

Pharmacology of PF-4191834, a novel, selective non-redox 5-lipoxygenase inhibitor effective in inflammation and pain

5-Lipoxygenase (LOX) is an important arachidonic acid-metabolizing enzyme producing leukotrienes and other proinflammatory lipid mediators with potent pathophysiological functions in asthma and other inflammatory diseases. 4-(3-(4-(1-Methyl-1H-pyrazol-5-yl)phenylthio)phenyl)-tetrahydro-2H-pyran-4-carboxamide (PF-4191834) is a novel, selective non-redox 5-lipoxygenase inhibitor effective in inflammation and pain. In vitro and in vivo assays were developed for the evaluation of a novel 5-LOX inhibitor using conditions of maximal enzyme activity. PF-4191834 exhibits good potency in enzyme- and cell-based assays, as well as in a rat model of acute inflammation. Enzyme assay results indicate that PF-4191834 is a potent 5-LOX inhibitor, with an IC(50) = 229 +/- 20 nM. Furthermore, it demonstrated approximately 300-fold selectivity for 5-LOX over 12-LOX and 15-LOX and shows no activity toward the cyclooxygenase enzymes. In addition, PF-4191834 inhibits 5-LOX in human blood cells, with an IC(80) = 370 +/- 20 nM. This inhibitory concentration correlates well with plasma exposures needed for in vivo efficacy in inflammation in models of inflammatory pain. The combination of potency in cells and in vivo, together with a sustained in vivo effect, provides PF-4191834 with an overall pharmacodynamic improvement consistent with once a day dosing.

5-lipoxygenase and cyclooxygenase-2 in porcine parasitic bronchopneumonia: immunohistochemical and biochemical investigations

Eicosanoids are products of arachidonic acid metabolism and have numerous biological roles. The present study aimed to investigate the role of 5-lipoxygenase (5-LOX)- and cyclooxygenase-2 (COX-2)- dependent enzymatic pathways in the pathogenesis of porcine parasitic bronchopneumonia caused by Metastrongylus spp. Pulmonary tissue samples from healthy control and parasitized pigs were processed for histopathological, immunohistochemical and biochemical investigations. In control animals, immunohistochemistry demonstrated that 5-LOX and COX-2 expression was almost exclusively limited to the bronchiolar epithelial cells. Parasitized pigs had greater 5-LOX- and COX-2- specific immunoreactivity, involving a wide range of cell types within foci of granulomatous and eosinophilic bronchopneumonia. Biochemical investigations demonstrated the presence of 5-LOX (and the related product Leukotriene B(4)) and COX-2 (and the related product prostaglandin E(2); PGE(2)) in all tissues under study. COX-2 activity and PGE(2) concentration were significantly higher in diseased lungs compared with normal healthy controls. These findings demonstrate that 5-LOX and COX-2 are differentially expressed in normal versus lungworm-infected lungs and therefore suggest that both biochemical pathways are likely to be involved in the pathogenesis of porcine parasitic bronchopneumonia.

A cell-based assay for screening lipoxygenase inhibitors

Lipoxygenases (LOX) form a family of lipid peroxidizing enzymes within the plant and animal kingdoms. In humans, six functional lipoxygenase isoforms have been identified. 5-LOX, "platelet-type" 12-LOX (p12-LOX) and 15-LOX type 1 (15-LOX1), originally identified in leukocytes, platelets, and reticulocytes, respectively, generate lipid mediators involved in host cellular functions and in the pathophysiology of asthma, cardiovascular diseases, and cancer. The pharmaceutical industry has reinvigorated their programs to develop novel LOX inhibitors in view of recent findings. However, high throughput LOX screening assays to test novel agents against these intracellular enzymes are limited. We describe a cell-based 96-well microplate fluorescence assay tested against several existing LOX inhibitors, and validate the assay by comparing known IC(50) values and HPLC analysis, which may provide a useful screen for novel LOX inhibitors.

A rat air pouch model for evaluating the efficacy and selectivity of 5-lipoxygenase inhibitors

The 5-lipoxygenase (5-LOX) pathway has been associated with a variety of inflammatory diseases including asthma, atherosclerosis, rheumatoid arthritis, pain, cancer and liver fibrosis. Several classes of 5-LOX inhibitors have been identified, but only one drug, zileuton, a redox inhibitor of 5-LOX, has been approved for clinical use. To better evaluate the efficacy of 5-LOX inhibitors for pharmacological intervention, a rat model was modified to test the in vivo efficacy of 5-LOX inhibitors. Inflammation was produced by adding carrageenan into a newly formed air pouch and prostaglandins produced. While macrophages and neutrophils are present in the inflamed pouch, little 5-LOX products are formed. Cellular 5-LOX activation was obtained by adding calcium ionophore (A23187) into the pouch thus providing a novel model to evaluate the efficacy and selectivity of 5-LOX inhibitors. Also, we described modifications to the in vitro 5-LOX enzyme and cell assays. These assays included a newly developed fluorescence-based enzyme assay, a 5-LOX redox assay, an ex vivo human whole blood assay and an IgE-stimulated rat mast cell assay, all designed for maximal production of leukotrienes. Zileuton and CJ-13,610, a competitive, non-redox inhibitor of 5-LOX, were evaluated for their pharmacological properties using these assays. Although both compounds achieved dose-dependent inhibition of 5-LOX enzyme activity, CJ-13,610 was 3-4 fold more potent than zileuton in all-assays. Evaluation of 5-LOX metabolites-by LC/MS/MS and ELISA confirmed that both compounds selectively inhibited all products downstream of 5-hydroperoxy eicosatetraenoic acid (5-HPETE), including 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxoETE), without inhibition of 12-lipoxygenase (12-LOX), 15-lipoxygenase (15-LOX), or cyclooxygenase (COX) products. In the rat air pouch model, oral dosing of CJ-13,610 and zileuton resulted in selective inhibition 5-LOX activity from pouch exudate and ex vivo rat whole blood with similar potency to in vitro assay. These data show that the rat air pouch model is a reliable and useful tool for evaluating in vivo efficacy of 5-LOX inhibitors and may aid in the development of the next generation of 5-LOX inhibitors, such as the non-redox inhibitors similar to CJ-13,610.