5-lipoxygenase: cellular biology and molecular pharmacology

Machine Learning Uncovers Natural Product Modulators of the 5-Lipoxygenase Pathway and Facilitates the Elucidation of Their Biological Mechanisms

Machine learning (ML) models have made inroads into chemical sciences, with optimization of chemical reactions and prediction of biologically active molecules being prime examples thereof. These models excel where physical experiments are expensive or time-consuming, for example, due to large scales or the need for materials that are difficult to obtain. Studies of natural products suffer from these issues─this class of small molecules is known for its wealth of structural diversity and wide-ranging biological activities, but their investigation is hindered by poor synthetic accessibility and lack of scalability. To facilitate the evaluation of these molecules, we designed ML models that predict which natural products can interact with a particular target or a relevant pathway. Here, we focused on discovering natural products that are capable of modulating the 5-lipoxygenase (5-LO) pathway that plays key roles in lipid signaling and inflammation. These computational approaches led to the identification of nine natural products that either directly inhibit the activity of the 5-LO enzyme or affect the cellular 5-LO pathway. Further investigation of one of these molecules, deltonin, led us to discover a new cell-type-selective mechanism of action. Our ML approach helped deorphanize natural products as well as shed light on their mechanisms and can be broadly applied to other use cases in chemical biology.

Molecular regulation of neutrophil swarming in health and disease: Lessons from the phagocyte oxidase

Neutrophil swarming is a complex coordinated process in which neutrophils sensing pathogen or damage signals are rapidly recruited to sites of infections or injuries. This process involves cooperation between neutrophils where autocrine and paracrine positive-feedback loops, mediated by receptor/ligand pairs including lipid chemoattractants and chemokines, amplify localized recruitment of neutrophils. This review will provide an overview of key pathways involved in neutrophil swarming and then discuss the cell intrinsic and systemic mechanisms by which NADPH oxidase 2 (NOX2) regulates swarming, including modulation of calcium signaling, inflammatory mediators, and the mobilization and production of neutrophils. We will also discuss mechanisms by which altered neutrophil swarming in disease may contribute to deficient control of infections and/or exuberant inflammation. Deeper understanding of underlying mechanisms controlling neutrophil swarming and how neutrophil cooperative behavior can be perturbed in the setting of disease may help to guide development of tools for diagnosis and precision medicine.

Substituted 1,2,4-Triazoles as Novel and Selective Inhibitors of Leukotriene Biosynthesis Targeting 5-Lipoxygenase-Activating Protein

5-Lipoxygenase-activating protein (FLAP) is a regulator of cellular leukotriene biosynthesis, which governs the transfer of arachidonic acid (AA) to 5-lipoxygenase for efficient metabolism. Here, the synthesis and FLAP-antagonistic potential of fast synthetically accessible 1,2,4-triazole derivatives based on a previously discovered virtual screening hit compound is described. Our findings reveal that simple structural variations on 4,5-diaryl moieties and the 3-thioether side chain of the 1,2,4-triazole scaffold markedly influence the inhibitory potential, highlighting the significant chemical features necessary for FLAP antagonism. Comprehensive metabololipidomics analysis in activated FLAP-expressing human innate immune cells and human whole blood showed that the most potent analogue 6x selectively suppressed leukotriene B4 formation evoked by bacterial exotoxins without affecting other branches of the AA pathway. Taken together, the 1,2,4-triazole scaffold is a novel chemical platform for the development of more potent FLAP antagonists, which warrants further exploration for their potential as a new class of anti-inflammatory agents.

Aspirin eugenol ester ameliorates LPS-induced inflammatory responses in RAW264.7 cells and mice

Introduction: Inflammation is a defensive response of the body and the pathological basis of many diseases. However, excessive inflammation and chronic inflammation impair the homeostasis of the organism. Arachidonic acid (AA) has a close relationship with inflammation and is the main mediator of the pro-inflammatory response. Based on the prodrug principle, the new pharmaceutical compound aspirin eugenol ester (AEE) was designed and synthesized. However, the effects of AEE on key enzymes, metabolites and inflammatory signaling pathways in the AA metabolic network have not been reported. Methods: In this study, the anti-inflammation effects of AEE were first investigated in mice and RAW264.7 cells in LPS induced inflammation model. Then, the changes of the key enzymes and AA metabolites were explored by RT-PCR and targeted metabolomics. Moreover, the regulatory effects on NF-kB and MAPKS signaling pathways were explored by Western Blotting. Results: Results indicated that AEE significantly reduced the number of leukocyte and increased the lymphocyte percentage. AEE decreased the expression levels of IL-1β, IL-6, IL-8 and TNF-α both in vivo and in vitro. In the liver of mice, AEE downregulated the levels of AA, prostaglandin D2 (PGD2) and upregulated 12- hydroxyeicosatetraenoic acid (12-HETE). However, the changes of PGE2, PGF2α, 6-keto-prostaglandin F1α (6-KETO-PGF1α), 9-hydroxy-octadecenoic acid (9- HODE), 13-HODE, 15-HETE, docosahexaenoic acid (DHA) and thromboxane B2 (TXB2) were not significant. Additionally, it was found that AEE decreased the relative mRNA expression levels of p65 and p38 and the ratio of p-p65/p65. Discussion: It was concluded that AEE might inhibit the LPS-induced inflammatory response through the regulation of AA metabolism. This study provides the theoretical foundation for the development of AEE as a medicinal anti-inflammatory drug.

The IRE1α Inhibitor KIRA6 Blocks Leukotriene Biosynthesis in Human Phagocytes

The ER stress and Unfolded Protein Response (UPR) component inositol-requiring enzyme 1α (IRE1α) has been linked to inflammation and lipid mediator production. Here we report that the potent IRE1α inhibitor, KIRA6, blocks leukotriene biosynthesis in human phagocytes activated with lipopolysaccharide (LPS) plus N-formyl-methionyl-leucyl-phenylalanine (fMLP) or thapsigargin (Tg). The inhibition affects both leukotriene B₄ (LTB₄) and cysteinyl leukotriene (cys-LTs) production at submicromolar concentration. Macrophages made deficient of IRE1α were still sensitive to KIRA6 thus demonstrating that the compound’s effect on leukotriene production is IRE1α-independent. KIRA6 did not exhibit any direct inhibitory effect on key enzymes in the leukotriene pathway, as assessed by phospholipase A₂ (PLA₂), 5-lipoxygenase (5-LOX), LTA₄ hydrolase (LTA4H), and LTC₄ synthase (LTC4S) enzyme activity measurements in cell lysates. However, we find that KIRA6 dose-dependently blocks phosphorylation of p38 and ERK, mitogen-activated protein kinases (MAPKs) that have established roles in activating cytosolic PLA₂α (cPLA₂α) and 5-LOX. The reduction of p38 and ERK phosphorylation is associated with a decrease in cPLA₂α phosphorylation and attenuated leukotriene production. Furthermore, KIRA6 inhibits p38 activity, and molecular modelling indicates that it can directly interact with the ATP-binding pocket of p38. This potent and unexpected, non-canonical effect of KIRA6 on p38 and ERK MAPKs and leukotriene biosynthesis may account for some of the immune-modulating properties of this widely used IRE1α inhibitor.

Treatment with the 5-Lipoxygenase Antagonist Zileuton Protects Mice from Postoperative Ileus

INTRODUCTION

Previous work of our group showed that lipoxygenase (LOX) pathways become activated upon surgical manipulation of the bowel wall and revealed a beneficial immune modulating role of the LOX-derived anti-inflammatory mediator protectin DX in postoperative ileus (POI). While we found a particular role of 12/15-LOX in the anti-inflammatory LOX action during POI, the role of 5-LOX, which produces the pro-inflammatory leukotriene B4 (LTB4), remained unknown. The purpose of this study was to investigate the role of 5-LOX within the pathogenesis of POI in a mouse model.

METHODS

POI was induced by intestinal manipulation (IM) of the small bowel in C57BL/6, 5-LOX-/-, and CX3CR1GFP/+. Mice were either treated with a vehicle or with the synthetic 5-LOX antagonist zileuton or were left untreated. Cellular localization of 5-LOX and LTB4 release were visualized by immunofluorescence or ELISA, respectively. POI severity was quantified by gastrointestinal transit (GIT) and leukocyte extravasation into the muscularis externa (ME) by immunohistochemistry.

RESULTS

5-LOX expression was detected 24 h after IM within infiltrating leukocytes in the ME. LTB4 levels increased during POI in wild type but not in 5-LOX-/- after IM. POI was ameliorated in 5-LOX-/- as shown by decreased leukocyte numbers and normalized GIT. Zileuton normalized the postoperative GIT and reduced the numbers of infiltrating leukocytes into the ME.

DISCUSSION/CONCLUSION

Our data demonstrate that 5-LOX and its metabolite LTB4 play a crucial role in POI. Genetic deficiency of 5-LOX and pharmacological antagonism by zileuton protected mice from POI. 5-LOX antagonism might be a promising target for prevention of POI in surgical patients.

In Silico, In Vitro, and In Vivo Analysis of Tanshinone IIA and Cryptotanshinone from Salvia miltiorrhiza as Modulators of Cyclooxygenase-2/mPGES-1/Endothelial Prostaglandin EP3 Pathway

Tanshinone IIA (TIIA) and cryptotanshinone (CRY) from Salvia miltiorrhiza Bunge were investigated for their inhibitory activity against the cyclooxygenase-2 (COX-2)/microsomal prostaglandin E synthase-1 (mPGES-1)/endothelial prostaglandin 3 (EP3) pathway using in silico, in vitro, in vivo, and ex vivo assays. From the analysis of the docking poses, both diterpenoids were able to interact significantly with COX-2, 5-lipoxygenase (5-LO), platelet-activating factor receptor (PAFR), and mPGES-1. This evidence was further corroborated by data obtained from a cell-free assay, where CRY displayed a significant inhibitory potency against mPGES-1 (IC50 = 1.9 ± 0.4 µM) and 5-LO (IC50 = 7.1 µM), while TIIA showed no relevant inhibition of these targets. This was consistent with their activity to increase mice bleeding time (CRY: 2.44 ± 0.13 min, p ≤ 0.001; TIIA: 2.07 ± 0.17 min p ≤ 0.01) and with the capability to modulate mouse clot retraction (CRY: 0.048 ± 0.011 g, p ≤ 0.01; TIIA: 0.068 ± 0.009 g, p ≤ 0.05). For the first time, our results show that TIIA and, in particular, CRY are able to interact significantly with the key proteins involved not only in the onset of inflammation but also in platelet activity (and hyper-reactivity). Future preclinical and clinical investigations, together with this evidence, could provide the scientific basis to consider these compounds as an alternative therapeutic approach for thrombotic- and thromboembolic-based diseases.

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.

Different forms of vitamin E and metabolite 13'-carboxychromanols inhibit cyclooxygenase-1 and its catalyzed thromboxane in platelets, and tocotrienols and 13'-carboxychromanols are competitive inhibitors of 5-lipoxygenase

Cyclooxygenase (COX-1 and COX-2)- and 5-lipoxygenase (5-LOX)-catalyzed biosynthesis of eicosanoids play important roles in inflammation and chronic diseases. The vitamin E family has four tocopherols and tocotrienols. We have shown that the metabolites of δ-tocopherol (δT) and δ-tocotrienol (δTE), i.e., δT-13'-carboxychromanol (COOH) and δTE-13'-COOH, respectively, inhibit COX-1/-2 and 5-LOX activity, but the nature of how they inhibit 5-LOX is not clear. Further, the impact of tocopherols and tocotrienols on COX-1/-2 or 5-LOX activity has not been fully delineated. In this study, we found that tocopherols and tocotrienols inhibited human recombinant COX-1 with IC50s of 1-12 µM, and suppressed COX-1-mediated formation of thromboxane in collagen-stimulated rat's platelets with IC50s of 8-50 µM. None of the vitamin E forms directly inhibited COX-2 activity. 13'-COOHs inhibited COX-1 and COX-2 enzyme activity with IC50s of 3-4 and 4-10 µM, respectively, blocked thromboxane formation in collagen- and ionophore-stimulated rats' platelets with IC50s of 1.5-2.5 µM, and also inhibited COX-2-mediated prostaglandins in stimulated cells. Using enzyme kinetics, we observed that δT-13'-COOH, δTE-13'-COOH and δTE competitively inhibited 5-LOX activity with Ki of 1.6, 0.8 and 2.2 µM, respectively. These compounds decreased leukotriene B₄ from stimulated neutrophil-like cells without affecting translocation of 5-LOX from cytosol to the nucleus. Our study reveals inhibitory effects of vitamin E forms and 13'-COOHs on COX-1 activity and thromboxane formation in platelets, and elucidates mechanisms underlying their inhibition of 5-LOX. These observations are useful for understanding the role of these compounds in disease prevention and therapy.

Mechanistic role of boswellic acids in Alzheimer's disease: Emphasis on anti-inflammatory properties

The resin/gum of Boswellia species belonging to the family of Burseraceae is a naturally occurring mixture of bioactive compounds, which was traditionally used as a folk medicine to treat conditions like chronic inflammation. Several research studies have also explored its' therapeutic potential against multiple neurodegenerative diseases such as Alzheimer's disease (AD). The main chemical constituents of this gum include boswellic acids (BAs) like 3-O-acetyl-11-keto-β boswellic acid (AKBA) that possess potent anti-inflammatory and neuroprotective properties in AD. It is also involved in inhibiting the acetylcholinesterase (AChE) activity in the cholinergic pathway and improve choline levels as well as its binding with nicotinic receptors to produce anti-inflammatory effects. Multiple shreds of evidence have demonstrated that BAs modulate key molecular targets and signalling pathways like 5-lipoxygenase/cyclooxygenase, Nrf2, NF-kB, cholinergic, amyloid-beta (Aβ), and neurofibrillary tangles formation (NFTs) that are involved in AD progression. The present review focuses on the possible mechanistic therapeutic role of BAs in modulating the 5-LOX/COX pathway in arachidonic acid metabolism, activating Nrf2 through binding of ARE, inhibiting NF-kB and AChE activity. In addition, an inhibition of amyloid plaques (Aβ) and neurofibrillary tangles (NFTs) induced neurotoxicity and neuroinflammation in AD by BAs is also discussed in this review. We have also highlighted that BAs possess beneficial effects in AD by targeting multiple molecular pathways and makes it an emerging drug candidate for treating neurodegenerative diseases.

Staphylococcus aureus-Derived α-Hemolysin Evokes Generation of Specialized Pro-resolving Mediators Promoting Inflammation Resolution

Underlying mechanisms of how infectious inflammation is resolved by the host are incompletely understood. One hallmark of inflammation resolution is the activation of specialized pro-resolving mediators (SPMs) that enhance bacterial clearance and promote tissue repair. Here, we reveal α-hemolysin (Hla) from Staphylococcus aureus as a potent elicitor of SPM biosynthesis in human M2-like macrophages and in the mouse peritoneum through selective activation of host 15-lipoxygenase-1 (15-LOX-1). S. aureus-induced SPM formation in M2 is abolished upon Hla depletion or 15-LOX-1 knockdown. Isolated Hla elicits SPM formation in M2 that is reverted by inhibition of the Hla receptor ADAM10. Lipid mediators derived from Hla-treated M2 accelerate planarian tissue regeneration. Hla but not zymosan provokes substantial SPM formation in the mouse peritoneum, devoid of leukocyte infiltration and pro-inflammatory cytokine secretion. Besides harming the host, Hla may also exert beneficial functions by stimulating SPM production to promote the resolution of infectious inflammation.

Jordan et al. reveal that α-hemolysin from Staphylococcus aureus stimulates specialized pro-resolving mediator (SPM) formation through activation of 15-lipoxygenase-1 in human macrophages involving ADAM10. The host may exploit α-hemolysin as an SPM inducer to better cope with S. aureus infections and to promote inflammation resolution and tissue regeneration.

Urine 5-Eicosatetraenoic Acids as Diagnostic Markers for Obstructive Sleep Apnea

Early detection of obstructive sleep apnea (OSA) is needed to reduce cardiovascular sequelae and mortality. Full-night polysomnography has been used for diagnosing OSA, but it is too expensive and inconvenient for patients to handle. Metabolome-wide analyses were performed to find and validate surrogate markers for OSA. We further investigated the mechanism underlying hypoxic induction of the markers in human cells and mice. Arachidonic acid derivatives 5-HETE and 5-oxoETE were detected in urine samples. The levels (mean ± SD, ng per mg creatinine) of 5-HETE and 5-oxoETE were 56.4 ± 26.2 and 46.9 ± 18.4 in OSA patients, respectively, which were significantly higher than those in controls (22.5 ± 4.6 and 18.7 ± 3.6). Both levels correlated with the apnea-hypopnea index and the lowest oxygen saturation on polysomnography. After the treatment with the continuous positive airway pressure, the metabolite levels were significantly reduced compared with those before the treatment. In human mononuclear cells subjected to intermittent hypoxia, 5-HETE and 5-oxoETE productions were induced by hypoxia-inducible factor 1 and glutathione peroxidase. When mice were exposed to intermittent hypoxia, 5-HETE and 5-oxoETE were excreted more in urine. They were identified and verified as new OSA markers reflecting hypoxic stress. The OSA markers could be used for OSA diagnosis and therapeutic evaluation.

Acceleration of Trichinella spiralis worm expulsion by leukotriene B4 receptor binding inhibition

AIMS

Helminth infection typically induces a Th2 inflammatory response that is characterized by eosinophilia, high levels of IgE and mast cells. LTB4 is generated from innate immune cells, such as neutrophils, macrophages and mast cells, in response to a range of stimuli. It mainly acts on myeloid leukocytes, inducing the activation of integrins, adhesion to endothelium walls, and chemotaxis.

METHODS AND RESULTS

The objective of the present study was to determine the role of the LTB4 receptor in Trichinella spiralis expulsion. We treated mice with the LTB4 receptor antagonist before infection with T. spiralis. We observed that the number of mast cells and worm infection decreased following treatment with the BLT antagonist during the intestinal phase. We also demonstrated that blocking the LTB4 receptor inhibited neutrophil and eosinophil infiltration.

CONCLUSIONS

Further studies are required to investigate the specific mechanism of mast cell number decrease and worm infection and the in vitro interactions between LTB4 and worm expulsion.

Identification of a Prenyl Chalcone as a Competitive Lipoxygenase Inhibitor: Screening, Biochemical Evaluation and Molecular Modeling Studies

Cyclooxygenase (COX) and lipoxygenase (LOX) are key targets for the development of new anti-inflammatory agents. LOX, which is involved in the biosynthesis of mediators in inflammation and allergic reactions, was selected for a biochemical screening campaign to identify LOX inhibitors by employing the main natural product library of Brazilian biodiversity. Two prenyl chalcones were identified as potent inhibitors of LOX-1 in the screening. The most active compound, (E)-2-O-farnesyl chalcone, decreased the rate of oxygen consumption to an extent similar to that of the positive control, nordihydroguaiaretic acid. Additionally, studies on the mechanism of the action indicated that (E)-2-O-farnesyl chalcone is a competitive LOX-1 inhibitor. Molecular modeling studies indicated the importance of the prenyl moieties for the binding of the inhibitors to the LOX binding site, which is related to their pharmacological properties.

Echinacea purpurea water extracts suppress the release of chemical mediators from mast cells

Histamine and leukotrienes (LTs), the chemical mediators released from mast cells, play an important role in type-I allergies such as hay fever. Echinacea purpurea (EP) has traditionally been used for herbal tea and has been reported to show biological functions. We evaluated the inhibitory activity of water extracts of EP petals, leaves, and stems against the chemical mediators released from mast cell lines. Petal and leaf extracts exhibited a significant inhibitory effect on histamine release from the stimulated cells, while the stem extract did not exert any effect. Activity of the petal extract was much stronger than that of the leaf extract. All the extracts significantly suppressed LTB4 production in the stimulated cells and displayed similar activities. The petal extract decreased Syk phosphorylation and Ca2+ influx associated with signal transduction in the stimulated cells. These results suggest that EP petal extract may have a relieving effect on allergic symptoms.

Simple heteroaryl modifications in the 4,5-diarylisoxazol-3-carboxylic acid scaffold favorably modulates the activity as dual mPGES-1/5-LO inhibitors with in vivo efficacy

Microsomal prostaglandin E₂ synthase-1 (mPGES-1), 5-lipoxygenase (5-LO) and 5- lipoxygenase-activating protein (FLAP) are key for biosynthesis of proinflammatory lipid mediators and pharmacologically relevant drug targets. In the present study, we made an attempt to explore the role of small heteroaromatic fragments on the 4,5-diarylisoxazol-3-carboxylic acid scaffold, which are selected to interact with focused regions in the active sites of mPGES-1, 5-LO and FLAP. We report that the simple structural variations on the benzyloxyaryl side-arm of the scaffold significantly influence the selectivity against mPGES-1, 5-LO and FLAP, enabling to produce multi-target inhibitors of these protein targets, exemplified by compound 18 (IC₅₀ mPGES-1 = 0.16 µM; IC₅₀ 5-LO = 0.39 µM) with in vivo efficacy in animal model of inflammation. The computationally modeled binding structures of these new inhibitors for three targets provide clues for rational design of modified structures as multi-target inhibitors. In conclusion, the simple synthetic procedure, and the possibility of enhancing the potency of this class of inhibitors through structural modifications pave the way for further development of new multi-target inhibitors against mPGES-1, 5-LO and FLAP, with potential application as anti-inflammatory agents.

PKC-β/Alox5 axis activation promotes Bcr-Abl-independent TKI-resistance in chronic myeloid leukemia

Bcr-Abl independent resistance to tyrosine kinase inhibitor (TKI) is a crucial factor lead to relapse or acute leukemia transformation in chronic myeloid leukemia (CML). However, its mechanism is still unclear. Herein, we found that of nine common protein kinases C (PKCs), PKC-β overexpression was significantly related with TKI resistance. Blockage of its expression in CD34+ cells and CML cell lines increased sensitivity to imatinib. Then, eighty-four leukemia related genes were compared between TKI-resistant CML cell lines with PKC-β silenced or not. Gene Ontology term and Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that Arachidonate 5-lipoxygenase (Alox5) and its relative pathway mainly participated in the resistance induced by PKC-β overexpression. It's also observed that Alox5 was increased not only in bone marrow biopsy but also in CD34⁺ cells derived from IM-resistant CML patients. The signaling pathway exploration indicated that ERK1/2 pathway mediates Alox5 upregulation by PKC-β. Meanwhile, we also proved that Alox5 induces TKI-insensitivity in CML through inactivation of PTEN. In vivo experiment, PKC-β elective inhibitor LY333531 prolonged survival time in CML-PDX mice model. In conclusion, targeted on PKC-β overexpression might be a novel therapy mechanism to overcome TKI-resistance in CML.

Leukotriene B4 licenses inflammasome activation to enhance skin host defense

The initial production of inflammatory mediators dictates host defense as well as tissue injury. Inflammasome activation is a constituent of the inflammatory response by recognizing pathogen and host-derived products and eliciting the production of IL-1β and IL-18 in addition to inducing a type of inflammatory cell death termed "pyroptosis." Leukotriene B4 (LTB4) is a lipid mediator produced quickly (seconds to minutes) by phagocytes and induces chemotaxis, increases cytokine/chemokine production, and enhances antimicrobial effector functions. Whether LTB4 directly activates the inflammasome remains to be determined. Our data show that endogenously produced LTB4 is required for the expression of pro-IL-1β and enhances inflammasome assembly in vivo and in vitro. Furthermore, LTB4-mediated Bruton's tyrosine kinase (BTK) activation is required for inflammasome assembly in vivo as well for IL-1β-enhanced skin host defense. Together, these data unveil a new role for LTB4 in enhancing the expression and assembly of inflammasome components and suggest that while blocking LTB4 actions could be a promising therapeutic strategy to prevent inflammasome-mediated diseases, exogenous LTB4 can be used as an adjuvant to boost inflammasome-dependent host defense.

The LTB4-BLT1 axis regulates actomyosin and β2-integrin dynamics during neutrophil extravasation

The eicosanoid leukotriene B4 (LTB4) relays chemotactic signals to direct neutrophil migration to inflamed sites through its receptor BLT1. However, the mechanisms by which the LTB4-BLT1 axis relays chemotactic signals during intravascular neutrophil response to inflammation remain unclear. Here, we report that LTB4 produced by neutrophils acts as an autocrine/paracrine signal to direct the vascular recruitment, arrest, and extravasation of neutrophils in a sterile inflammation model in the mouse footpad. Using intravital subcellular microscopy, we reveal that LTB4 elicits sustained cell polarization and adhesion responses during neutrophil arrest in vivo. Specifically, LTB4 signaling coordinates the dynamic redistribution of non-muscle myosin IIA and β2-integrin, which facilitate neutrophil arrest and extravasation. Notably, we also found that neutrophils shed extracellular vesicles in the vascular lumen and that inhibition of extracellular vesicle release blocks LTB4-mediated autocrine/paracrine signaling required for neutrophil arrest and extravasation. Overall, we uncover a novel complementary mechanism by which LTB4 relays extravasation signals in neutrophils during early inflammation response.

Targeting Leukotrienes as a Therapeutic Strategy to Prevent Comorbidities Associated with Metabolic Stress

Leukotrienes (LTs) are potent lipid mediators that exert a variety of functions, ranging from maintaining the tone of the homeostatic immune response to exerting potent proinflammatory effects. Therefore, LTs are essential elements in the development and maintenance of different chronic diseases, such as asthma, arthritis, and atherosclerosis. Due to the pleiotropic effects of LTs in the pathogenesis of inflammatory diseases, studies are needed to discover potent and specific LT synthesis inhibitors and LT receptor antagonists. Even though most clinical trials using LT inhibitors or antagonists have failed due to low efficacy and/or toxicity, new drug development strategies are driving the discovery for LT inhibitors to prevent inflammatory diseases. A newly important detrimental role for LTs in comorbidities associated with metabolic stress has emerged in the last few years and managing LT production and/or actions could represent an exciting new strategy to prevent or treat inflammatory diseases associated with metabolic disorders. This review is intended to shed light on the synthesis and actions of leukotrienes, the most common drugs used in clinical trials, and discuss the therapeutic potential of preventing LT function in obesity, diabetes, and hyperlipidemia.

Eicosanoid production varies by sex in mesenteric ischemia reperfusion injury

Intestinal ischemia/reperfusion (I/R)-induced injury is an inflammatory response with significant morbidity and mortality. The early inflammatory response includes neutrophil infiltration. However, the majority of rodent studies utilize male mice despite a sexual dimorphism in intestinal I/R-related diseases. We hypothesized that sex may alter inflammation by changing neutrophil infiltration and eicosanoid production. To test this hypothesis, male and female C57Bl/6 mice were subjected to sham treatment or 30 min intestinal ischemia followed by a time course of reperfusion. We demonstrate that compared to male mice, females sustain significantly less intestinal I/R-induced tissue damage and produced significant LTB₄ concentrations. Male mice release PGE₂. Finally, treatment with a COX-2 specific inhibitor, NS-398, attenuated I/R-induced injury, total peroxidase level, and PGE₂ production in males, but not in similarly treated female mice. Thus, I/R-induced eicosanoid production and neutrophil infiltration varies between sexes suggesting that distinct therapeutic intervention may be needed in clinical ischemic diseases.

Phosphorylation of 5-LOX: The Potential Set-point of Inflammation

Inflammation secondary to tissue injuries serves as a double-edged sword that determines the prognosis of tissue repair. As one of the most important enzymes controlling the inflammation process by producing leukotrienes, 5-lipoxygenase (5-LOX, also called 5-LO) has been one of the therapeutic targets in regulating inflammation for a long time. Although a large number of 5-LOX inhibitors have been explored, only a few of them can be applied clinically. Surprisingly, phosphorylation of 5-LOX reveals great significance in regulating the subcellular localization of 5-LOX, which has proven to be an important mechanism underlying the enzymatic activities of 5-LOX. There are at least three phosphorylation sites in 5-LOX jointly to determine the final inflammatory outcomes, and adjustment of phosphorylation of 5-LOX at different phosphorylation sites brings hope to provide an unrecognized means to regulate inflammation. The present review intends to shed more lights into the set-point-like mechanisms of phosphorylation of 5-LOX and its possible clinical application by summarizing the biological properties of 5-LOX, the relationship of 5-LOX with neurodegenerative diseases and brain injuries, the phosphorylation of 5-LOX at different sites, the regulatory effects and mechanisms of phosphorylated 5-LOX upon inflammation, as well as the potential anti-inflammatory application through balancing the phosphorylation-depended set-point.

Extraction, Antioxidant Capacity, 5-Lipoxygenase Inhibition, and Phytochemical Composition of Propolis from Eastern Canada

Soxhlet (SE), microwave-assisted (MAE) and ultrasound-assisted (UAE) extraction were compared using ten extraction solvents for their efficiency to extract phenolic and flavonoid antioxidants from Eastern Canada propolis. Extracts were compared for total phenolic (TPC) and total flavonoid (TFC) content, and radical scavenging activities. Anti-inflammatory activity through inhibition of 5-lipoxygenase (5-LO) products biosynthesis in HEK293 cells was also evaluated. The results showed that SE extracts using polar solvents had the highest TPC and TFC. Extracts obtained with ethanol, methanol and acetone were effective free radical scavengers, and showed 5-LO inhibition similar to zileuton. UAE was an effective extraction method since the extracts obtained were comparable to those using SE and the MAE while being done at room temperature. With UAE, extracts of less polar solvents showed similar free radical scavenging and 5-LO inhibition to extracts of much more polar solvents such as methanol or ethanol. Reversed-phase liquid chromatography tandem mass spectrometry confirmed the presence of 21 natural compounds in the propolis extracts based on the comparison of intact mass, chromatographic retention time and fragmentation patterns derived from commercial analytical standards. The current study is the first of its kind to concurrently investigate solvent polarity as well as extraction techniques of propolis.

Anti-Inflammatory Drugs as Anticancer Agents

Inflammation is strictly associated with cancer and plays a key role in tumor development and progression. Several epidemiological studies have demonstrated that inflammation can predispose to tumors, therefore targeting inflammation and the molecules involved in the inflammatory process could represent a good strategy for cancer prevention and therapy. In the past, several clinical studies have demonstrated that many anti-inflammatory agents, including non-steroidal anti-inflammatory drugs (NSAIDs), are able to interfere with the tumor microenvironment by reducing cell migration and increasing apoptosis and chemo-sensitivity. This review focuses on the link between inflammation and cancer by describing the anti-inflammatory agents used in cancer therapy, and their mechanisms of action, emphasizing the use of novel anti-inflammatory agents with significant anticancer activity.

Biological Evaluation of Naproxen-Dehydrodipeptide Conjugates with Self-Hydrogelation Capacity as Dual LOX/COX Inhibitors

The use of peptide-drug conjugates is emerging as a powerful strategy for targeted drug delivery. Previously, we have found that peptides conjugated to a non-steroidal anti-inflammatory drug (NSAID), more specifically naproxen-dehydrodipeptide conjugates, readily form nanostructured fibrilar supramolecular hydrogels. These hydrogels were revealed as efficacious nano-carriers for drug delivery applications. Moreover, the incorporation of superparamagnetic iron oxide nanoparticles (SPIONs) rendered the hydrogels responsive to external magnetic fields, undergoing gel-to-solution phase transition upon remote magnetic excitation. Thus, magnetic dehydrodipeptide-based hydrogels may find interesting applications as responsive Magnetic Resonance Imaging (MRI) contrast agents and for magnetic hyperthermia-triggered drug-release applications. Supramolecular hydrogels where the hydrogelator molecule is endowed with intrinsic pharmacological properties can potentially fulfill a dual function in drug delivery systems as (passive) nanocariers for incorporated drugs and as active drugs themselves. In this present study, we investigated the pharmacological activities of a panel of naproxen-dehydrodipeptide conjugates, previously studied for their hydrogelation ability and as nanocarriers for drug-delivery applications. A focused library of dehydrodipeptides, containing N-terminal canonical amino acids (Phe, Tyr, Trp, Ala, Asp, Lys, Met) N-capped with naproxen and linked to a C-terminal dehydroaminoacid (ΔPhe, ΔAbu), were evaluated for their anti-inflammatory and anti-cancer activities, as well as for their cytotoxicity to non-cancer cells, using a variety of enzymatic and cellular assays. All compounds except one were able to significantly inhibit lipoxygenase (LOX) enzyme at a similar level to naproxen. One of the compounds 4 was able to inhibit the cyclooxygenase-2 (COX-2) to a greater extent than naproxen, without inhibiting cyclooxygenase-1 (COX-1), and therefore is a potential lead in the search for selective COX-2 inhibitors. This hydrogelator is a potential candidate for dual COX/LOX inhibition as an optimised strategy for treating inflammatory conditions.

Design, synthesis and biological evaluation of novel pyrazole sulfonamide derivatives as dual COX-2/5-LOX inhibitors

The current therapeutic demand focuses more on the discovery of safer NSAIDs rather than exploring more potent alternatives. The dual COX-2/5-LOX inhibition is a promising strategy for designing compounds with an enhanced efficacy, reduced side-effects and a broader anti-inflammatory spectrum in comparison to classical NSAIDs. In the present study, a hybridization strategy was adopted to combine the binding features of the non-selective COX inhibitor "sulindac" and the selective COX-2 inhibitor "celecoxib" which show 5-LOX inhibitory activity with that of licofelone and a celecoxib pyridone analogue which show dual COX-2/5-LOX inhibitory activity to design new series of pyrazole sulfonamide derivatives which, by design, should possess dual COX-2/5-LOX inhibitory activity. All the newly synthesized compounds were initially tested for their potential analgesic activity, then candidates that showed potential analgesic activity, were selected for the subsequent anti-inflammatory activity evaluation, as well as, ulcerogenicity testing. Moreover, in vitro assessment of their COX-1, COX-2 and 5-LOX inhibitory activities were performed. The benzothiophen-2-yl pyrazole carboxylic acid derivative 5b showed the most potent analgesic and anti-inflammatory activities surpassing that of celecoxib and indomethacin. It showed potent COX-1, COX-2 and 5-LOX inhibitory activity with IC₅₀ of 5.40, 0.01 and 1.78 μM, respectively, showing a selectivity index of 344.56 that was much better than the used reference standards and its parent compounds, confirming its selectivity towards COX-2 over COX-1. The prodrug ester derivatives 6c and 6d showed equipotent activity to their parent compound 5b with no gastric ulcerogenicity. Molecular docking simulations confirmed that the newly synthesized compounds possess the structural features required for binding to the target enzymes COX-2 and 5-LOX.

Ginkgolic Acid is a Multi-Target Inhibitor of Key Enzymes in Pro-Inflammatory Lipid Mediator Biosynthesis

Introduction: Lipid mediators (LMs) comprise bioactive metabolites of polyunsaturated fatty acids, including pro-inflammatory prostaglandins (PGs), thromboxanes (TXs), and leukotrienes (LTs), as well as specialized pro-resolving mediators (SPMs). They are essentially biosynthesized via cyclooxygenase (COX) and lipoxygenase (LO) pathways in complex networks and regulate the progression as well as the resolution of inflammatory disorders including inflammation-triggered cancer. Ginkgolic acid (GA) is a phenolic acid contained in Ginkgo biloba L. with neuroprotective, antimicrobial, and antitumoral properties. Although LMs regulate microbial infections and tumor progression, whether GA affects LM biosynthesis is unknown and was investigated here in detail. Methods: Pharmacophore-based virtual screening was performed along with docking simulations. Activity assays were conducted for isolated human recombinant 5-LO, cytosolic phospholipase (PLA)2α, COX-2, and ovine COX-1. The activity of human mPGES-1 and thromboxane A2 synthase (TXAS) was determined in crude cellular fractions. Cellular LM formation was studied using human monocytes, neutrophils, platelets, and M1- and M2-like macrophages. LMs were identified after (ultra)high-performance liquid chromatography by UV detection or ESI-tandem mass spectrometry. Results: GA was identified as virtual hit in an mPGES-1 pharmacophore-based virtual screening. Cell-free assays revealed potent suppression of mPGES-1 activity (IC50 = 0.7 µM) that is fully reversible and essentially independent of the substrate concentration. Moreover, cell-free assays revealed COX-1 and TXAS as additional targets of GA with lower affinity (IC50 = 8.1 and 5.2 µM). Notably, 5-LO, the key enzyme in LT biosynthesis, was potently inhibited by GA (IC50 = 0.2 µM) in a reversible and substrate-independent manner. Docking simulations support the molecular interaction of GA with mPGES-1 and 5-LO and suggest concrete binding sites. Interestingly, interference of GA with mPGES-1, COX-1, TXAS, and 5-LO was evident also in intact cells with IC50 values of 2.1-3.8 µM; no radical scavenging or cytotoxic properties were obvious. Analysis of LM profiles from bacteria-stimulated human M1- and M2-like macrophages confirmed the multi-target features of GA and revealed LM redirection towards the formation of 12-/15-LO products including SPM. Conclusions: We reveal GA as potent multi-target inhibitor of key enzymes in the biosynthesis of pro-inflammatory LMs that contribute to the complex pharmacological and toxicological properties of GA.

Molecular characterization of big-belly seahorse (Hippocamus abdominalis) arachidonate 5-lipoxygenase (HaALOX5): First evidence of an immune defensive role by induced immunological stress in teleost

Arachidonate 5-lipoxygenase (ALOX5) is an essential enzyme for the biosynthesis of leukotrienes, which are pro-inflammatory and anti-inflammatory mediators. In this study, the ALOX5 paralog of the big-belly seahorse (Hippocampus abdominalis; HaALOX5) was identified from our transcriptome database, and then molecularly and functionally characterized to determine its oxygenation capability and expression under pathogenic stress. The coding sequence of HaALOX5 consisted of 2025 bp and encoded a protein of 674 amino acids in length. Sequence and phylogenetic tree analysis of HaALOX5 revealed a close relationship with its corresponding teleost HaALOX5 counterparts. Structure prediction detected an N-terminal regulatory C2-like domain and a C-terminal catalytic domain, which are the two main functional domains in ALOX5 enzymes. Quantitative PCR showed that HaALOX5 was expressed in all the analyzed tissues at different magnitudes. The highest expression was detected in the intestine and stomach. In blood cells, the liver and the intestine, HaALOX5 transcripts were significantly elevated at many post injection time points, when immune challenged with lipopolysaccharide, polyinosinic:polycytidylic acid, and Streptococcus iniae, indicating its contribution to post immune defense mechanisms in the seahorse.

Targeting Metalloenzymes for Therapeutic Intervention

Metalloenzymes are central to a wide range of essential biological activities, including nucleic acid modification, protein degradation, and many others. The role of metalloenzymes in these processes also makes them central for the progression of many diseases and, as such, makes metalloenzymes attractive targets for therapeutic intervention. Increasing awareness of the role metalloenzymes play in disease and their importance as a class of targets has amplified interest in the development of new strategies to develop inhibitors and ultimately useful drugs. In this Review, we provide a broad overview of several drug discovery efforts focused on metalloenzymes and attempt to map out the current landscape of high-value metalloenzyme targets.

Design, synthesis and identification of novel coumaperine derivatives for inhibition of human 5-LOX: Antioxidant, pseudoperoxidase and docking studies

5-Lipoxygenase (5-LOX) is a key enzyme involved in the biosynthesis of pro-inflammatory leukotrienes, leading to asthma. Developing potent 5-LOX inhibitors especially, natural product based ones, are highly attractive. Coumaperine, a natural product found in white pepper and its derivatives were herein developed as 5-LOX inhibitors. We have synthesized twenty four derivatives, characterized and evaluated their 5-LOX inhibition potential. Coumaperine derivatives substituted with multiple hydroxy and multiple methoxy groups exhibited best 5-LOX inhibition. CP-209, a catechol type dihydroxyl derivative and CP-262-F2, a vicinal trihydroxyl derivative exhibited, 82.7% and 82.5% inhibition of 5-LOX respectively at 20 µM. Their IC₅₀ values are 2.1 ± 0.2 µM and 2.3 ± 0.2 µM respectively, and are comparable to zileuton, IC₅₀ = 1.4 ± 0.2 µM. CP-155, a methylenedioxy derivative (a natural product) and CP-194, a 2,4,6-trimethoxy derivative showed 76.0% and 77.1% inhibition of 5-LOX respectively at 20 µM. Antioxidant study revealed that CP-209 and 262-F2 (at 20 µM) scavenged DPPH radical by 76.8% and 71.3% respectively. On the other hand, CP-155 and 194 showed very poor DPPH radical scavenging activity. Pseudo peroxidase assay confirmed that the mode of action of CP-209 and 262-F2 were by redox process, similar to zileuton, affecting the oxidation state of the metal ion in the enzyme. On the contrary, CP-155 and 194 probably act through some other mechanism which does not involve the disruption of the oxidation state of the metal in the enzyme. Molecular docking of CP-155 and 194 to the active site of 5-LOX and binding energy calculation suggested that they are non-competitive inhibitors. The In-Silico ADME/TOX analysis shows the active compounds (CP-155, 194, 209 and 262-F2) are with good drug likeliness and reduced toxicity compared to existing drug. These studies indicate that there is a great potential for coumaperine derivatives to be developed as anti-inflammatory drug.

Melleolides from Honey Mushroom Inhibit 5-Lipoxygenase via Cys159

5-Lipoxygenase (5-LO) initiates the biosynthesis of pro-inflammatory leukotrienes from arachidonic acid, which requires the nuclear membrane-bound 5-LO-activating protein (FLAP) for substrate transfer. Here, we identified human 5-LO as a molecular target of melleolides from honey mushroom (Armillaria mellea). Melleolides inhibit 5-LO via an α,β-unsaturated aldehyde serving as Michael acceptor for surface cysteines at the substrate entrance that are revealed as molecular determinants for 5-LO activity. Experiments with 5-LO mutants, where select cysteines had been replaced by serine, indicated that the investigated melleolides suppress 5-LO product formation via two distinct modes of action: (1) by direct interference with 5-LO activity involving two or more of the cysteines 159, 300, 416, and 418, and (2) by preventing 5-LO/FLAP assemblies involving selectively Cys159 in 5-LO. Interestingly, replacement of Cys159 by serine prevented 5-LO/FLAP assemblies as well, implying Cys159 as determinant for 5-LO/FLAP complex formation at the nuclear membrane required for leukotriene biosynthesis.

The role of phospholipase A2 in multiple Sclerosis: A systematic review and meta-analysis

Phospholipases A2 (PLA₂) are a diverse group of enzymes that cleave the fatty acids of membrane phospholipids. They play critical roles in pathogenesis of neurodegenerative diseases such as multiple sclerosis by enhancing oxidative stress and initiating inflammation. The levels of PLA₂ activity in MS patients compared to controls and role of inhibiting PLA₂ activity on severity scores in different experimental models are not comprehensively assessed in the light of varying evidence from published studies. The objective of this systematic review is to determine the association between PLA₂ activity and multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). We performed a systematic review of six studies that assessed PLA₂ activity in MS patients compared to controls and nine studies that assessed PLA₂ activity in EAE. sPLA₂ nor Lp-PLA₂ activity were not increased in MS compared to controls in five of those six studies. A difference in sPLA₂ activity was only found in a study that measured the enzyme activity in urine. However, inhibiting cPLA₂ or sPLA₂ led to lower clinical severity or no signs of EAE in mice, and a lower incidence of EAE lesions compared to animals without cPLA₂ inhibition. These findings indicate that PLA₂ appears to play a role in the pathogenesis of EAE.

Too much of a good thing: How modulating LTB4 actions restore host defense in homeostasis or disease

The ability to regulate inflammatory pathways and host defense mechanisms is critical for maintaining homeostasis and responding to infections and tissue injury. While unbalanced inflammation is detrimental to the host; inadequate inflammation might not provide effective signals required to eliminate pathogens. On the other hand, aberrant inflammation could result in organ damage and impair host defense. The lipid mediator leukotriene B₄ (LTB₄) is a potent neutrophil chemoattractant and recently, its role as a dominant molecule that amplifies many arms of phagocyte antimicrobial effector function has been unveiled. However, excessive LTB₄ production contributes to disease severity in chronic inflammatory diseases such as diabetes and arthritis, which could potentially be involved in poor host defense in these groups of patients. In this review we discuss the cellular and molecular programs elicited during LTB₄ production and actions on innate immunity host defense mechanisms as well as potential therapeutic strategies to improve host defense.

Natural products as inhibitors of prostaglandin E2 and pro-inflammatory 5-lipoxygenase-derived lipid mediator biosynthesis

Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit prostanoid formation and represent prevalent therapeutics for treatment of inflammatory disorders. However, NSAIDs are afflicted with severe side effects, which might be circumvented by more selective suppression of pro-inflammatory eicosanoid biosynthesis. This concept led to dual inhibitors of microsomal prostaglandin E₂ synthase (mPGES)-1 and 5-lipoxygenase that are crucial enzymes in the biosynthesis of pro-inflammatory prostaglandin E₂ and leukotrienes. The potential of their dual inhibition in light of superior efficacy and safety is discussed. Focus is placed on natural products, for which direct inhibition of mPGES-1 and leukotriene biosynthesis has been confirmed.

Short-Term Regulation of FcγR-Mediated Phagocytosis by TLRs in Macrophages: Participation of 5-Lipoxygenase Products

TLRs recognize a broad spectrum of microorganism molecules, triggering a variety of cellular responses. Among them, phagocytosis is a critical process for host defense. Leukotrienes (LTs), lipid mediators produced from 5-lipoxygenase (5-LO) enzyme, increase FcγR-mediated phagocytosis. Here, we evaluated the participation of TLR2, TLR3, TLR4, and TLR9 in FcγR-mediated phagocytosis and whether this process is modulated by LTs. Rat alveolar macrophages (AMs), murine bone marrow-derived macrophages (BMDMs), and peritoneal macrophages (PMs) treated with TLR2, TLR3, and TLR4 agonists, but not TLR9, enhanced IgG-opsonized sheep red blood cell (IgG-sRBC) phagocytosis. Pretreatment of AMs or BMDMs with drugs that block LT synthesis impaired the phagocytosis promoted by TLR ligands, and TLR potentiation was also abrogated in PMs and BMDMs from 5-LO^−/− mice. LTB₄ production induced by IgG engagement was amplified by TLR ligands, while cys-LTs were amplified by activation of TLR2 and TLR4, but not by TLR3. We also noted higher ERK1/2 phosphorylation in IgG-RBC-challenged cells when preincubated with TLR agonists. Furthermore, ERK1/2 inhibition by PD98059 reduced the phagocytic activity evoked by TLR agonists. Together, these data indicate that TLR2, TLR3, and TLR4 ligands, but not TLR9, amplify IgG-mediated phagocytosis by a mechanism which requires LT production and ERK-1/2 pathway activation.

The anti-inflammatory effects of Yunnan Baiyao are involved in regulation of the phospholipase A2/arachidonic acid metabolites pathways in acute inflammation rat model

The traditional Chinese medicine Yunnan Baiyao (YNB) has been reported to possess anti-inflammatory properties, however its mechanism of action remains unclear. It was previously reported that YNB ameliorated depression of arachidonic acid (AA) levels in a rat model of collagen-induced arthritis. In the current study, the capacity of YNB to ameliorate inflammation was compared in carrageenan-induced and AA-induced acute inflammation of the rat paw with celecoxib and mizolastine, respectively (n=24 per group). The capacity of YNB to affect the phospholipase A2 (PLA2)/AA pathway (using reverse transcription-quantitative polymerase chain reaction) and release of inflammatory lipid mediators (by ELISA) were investigated. Celecoxib ameliorated carrageenan-induced paw edema, and mizolastine ameliorated AA-induced rat paw edema. YNB alleviated paw edema and inhibited inflammatory cell infiltration in the two models. YNB inhibited production of 5-LOX AA metabolite leukotriene B4 (LTB4), and suppressed expression of 5-LOX, cytosolic PLA2 (cPLA2), 5-LOX-activating protein, and LTB4 receptor mRNA in the AA-induced inflammation model (P<0.05). YNB Inhibited the production of the COX-2 AA metabolite prostaglandin E2 (PGE2) and suppressed expression of COX-2, cPLA2, PGE2 mRNA in the carrageenan-induced inflammation mode (P<0.05). Taken together, the data suggest that modulation of COX and LOX pathways in AA metabolism represent a novel anti-inflammatory mechanism of YNB.

GM-CSF- and M-CSF-primed macrophages present similar resolving but distinct inflammatory lipid mediator signatures

M1 and M2 activated macrophages (Mϕs) have different roles in inflammation. Because pathogens may first encounter resting cells, we investigated lipid mediator profiles prior to full activation. Human monocytes were differentiated with granulocyte Mϕ colony-stimulating factor (GM-CSF) or Mϕ colony-stimulating factor (M-CSF), which are known to prime toward M1 or M2 phenotypes, respectively. Lipid mediators released during resting conditions and produced in response to bacterial stimuli (LPS/N-formylmethionyl-leucyl-phenylalanine or peptidoglycan) were quantified by liquid chromatography-mass spectrometry. In resting conditions, both Mϕ phenotypes released primarily proresolving lipid mediators (prostaglandin E₂ metabolite, lipoxin A₄, and 18-hydroxyeicosapentaenoic acid). A striking shift toward proinflammatory eicosanoids was observed when the same cells were exposed (30 min) to bacterial stimuli: M-CSF Mϕs produced considerably more 5-lipoxygenase products, particularly leukotriene C₄, potentially linked to M2 functions in asthma. Prostaglandins were formed by both Mϕ types. In the M-CSF cells, there was also an enhanced release of arachidonic acid and activation of cytosolic phospholipase A₂ However, GM-CSF cells expressed higher levels of 5-lipoxygenase and 5-lipoxygenase-activating protein, and in ionophore incubations these cells also produced the highest levels of 5-hydroxyeicosatetraenoic acid. In summary, GM-CSF and M-CSF Mϕs displayed similar proresolving lipid mediator formation in resting conditions but shifted toward different proinflammatory eicosanoids upon bacterial stimuli. This demonstrates that preference for specific eicosanoid pathways is primed by CSFs before full M1/M2 activation.-Lukic, A., Larssen, P., Fauland, A., Samuelsson, B., Wheelock, C. E., Gabrielsson, S., Radmark, O. GM-CSF- and M-CSF-primed macrophages present similar resolving but distinct inflammatory lipid mediator signatures.

Alterations in Epidermal Eicosanoid Metabolism Contribute to Inflammation and Impaired Late Differentiation in FLG-Mutated Atopic Dermatitis

Loss-of-function mutations in the FLG gene cause ichthyosis vulgaris (IV) and represent the major predisposing genetic risk factor for atopic dermatitis (AD). Although both conditions are characterized by epidermal barrier impairment, AD also exhibits signs of inflammation. This work was aimed at delineating the role of FLG loss-of-function mutations on eicosanoid metabolism in IV and AD. Using human epidermal equivalents (HEEs) generated with keratinocytes isolated from nonlesional skin of patients with FLG wild-type AD (WT/WT), FLG-mutated AD (FLG/WT), IV (FLG/FLG), or FLG WT control skin, we assessed the potential autocrine role of epidermal-derived eicosanoids in FLG-associated versus FLG-WT AD pathogenesis. Ultrastructural analyses demonstrated abnormal stratum corneum lipid architecture in AD and IV HEEs, independent of FLG genotype. Both AD (FLG/WT) and IV (FLG/FLG) HEEs showed impaired late epidermal differentiation. Only AD (FLG/WT) HEEs exhibited significantly increased levels of inflammatory cytokines. Analyses of lipid mediators revealed increased arachidonic acid and 12-lipoxygenase metabolites. Whereas treatment of control HEEs with arachidonic acid increased expression of inflammatory cytokines, 12-hydroxy-eicosatetraenoic acid attenuated expression of late differentiation markers. Thus, FLG mutations lead to alterations in epidermal eicosanoid metabolism that could serve as an autocrine trigger of inflammation and impaired late epidermal differentiation in AD.

Anti-inflammatory trends of new benzimidazole derivatives

Aim: In present study, the anti-inflammatory activities of a new series of benzimidazole derivatives were studied, investigating their inhibition of secretory phospholipase A2, lipoxygenase, COXs and lipopolysaccharide-induced secretion of TNF-α and IL-6 in mouse RAW264.7 macrophages. Results: Synthesized compounds effectively inhibited proinflammatory enzymes and cytokines. Conclusion: A strong inhibition of secretory phospholipases A2 was exhibited by benzimidazole derivatives with trifluoromethyl and methoxy substitutions at position 4 of attached phenyl, whereas compound 8 containing pyridine ring substituted with amino group showed very potent 5-lipoxygenase inhibition. Molecular docking experiments were carried out to elucidate the molecular basis of the observed inhibitory activities.

A broad-spectrum lipidomics screen of antiinflammatory drug combinations in human blood

Current methods of drug screening in human blood focus on the immediate products of the affected pathway and mostly rely on approaches that lack sensitivity and the capacity for multiplex analysis. We have developed a sensitive and selective method based on ultra-performance liquid chromatography-tandem mass spectrometry to scan the effect of drugs on the bioactive eicosanoid lipidome in vitro and ex vivo. Using small sample sizes, we can reproducibly measure a broad spectrum of eicosanoids in human blood and capture drug-induced substrate rediversion and unexpected shifts in product formation. Microsomal prostaglandin E synthase-1 (mPGES-1) is an antiinflammatory drug target alternative to COX-1/-2. Contrasting effects of targeting mPGES-1 versus COX-1/-2, due to differential substrate shifts across the lipidome, were observed and can be used to rationalize and evaluate drug combinations. Finally, the in vitro results were extrapolated to ex vivo studies by administration of the COX-2 inhibitor, celecoxib, to volunteers, illustrating how this approach can be used to integrate preclinical and clinical studies during drug development.

Synthesis and biological evaluation of C(5)-substituted derivatives of leukotriene biosynthesis inhibitor BRP-7

Pharmacological intervention with 5-lipoxygenase (5-LO) pathway leading to suppression of leukotriene (LT) biosynthesis is a clinically validated strategy for treatment of respiratory and cardiovascular diseases such as asthma and atherosclerosis. Here we describe the synthesis of a series of C(5)-substituted analogues of the previously described 5-LO-activating protein (FLAP) inhibitor BRP-7 (IC50 = 0.31 μM) to explore the effects of substitution at the C(5)-benzimidazole (BI) ring as a strategy to increase the potency against FLAP-mediated 5-LO product formation. Incorporation of polar substituents on the C(5) position of the BI core, exemplified by compound 11 with a C(5)-nitrile substituent, significantly enhances the potency for suppression of 5-LO product synthesis in human neutrophils (IC50 = 0.07 μM) and monocytes (IC50 = 0.026 μM).