Eoxins are proinflammatory arachidonic acid metabolites produced via the 15-lipoxygenase-1 pathway in human eosinophils and mast cells

Novel 15-lipoxygenase-1 inhibitor protects cells from RSL3-induced cell death

Ferroptosis is a form of regulated cell death characterized by the accumulation of lipid peroxides. The enzyme 15-lipoxygenase-1 (15-LOX-1) plays a key role in catalyzing the formation of lipid peroxides. Therefore, inhibition of 15-LOX-1 enzyme activity holds promise to decrease the levels of lipid peroxidation. In this study, a novel potent 15-LOX-1 inhibitor, 5i, was developed and structure-activity relationships were explored. In vitro, this inhibitor inhibited lipid peroxidation and protected cells from RSL3-induced cell death. Thus, we report a potent 15-LOX-1 inhibitor, which can be used as a tool to investigate the role of 15-LOX-1.

Eosinophils and Bioactive Lipid Mediators Regulate Skin Inflammation and Cancer Growth

Cutaneous squamous cell carcinoma (cSCC) is the second most common form of skin cancer, with local immunity playing a key role in regulating outcome. Nonresolving inflammation has been suggested to drive cancer growth; however, a fundamental understanding of the tumor immune microenvironment in cSCC is still lacking. In this study, we demonstrate tissue-associated tumor eosinophilia in both human and murine cSCC and show that eosinophils promote epithelial hyperplasia and tumor outgrowth. The skin eosinophils display tissue adaptation and dynamically alter their transcriptome according to the microenvironment. Furthermore, we show that the skin bioactive lipidome is significantly altered during inflammation and in cSCC and that this is regulated by eosinophils. Inflamed skin and cSCC tissue are dominated by lipid mediators synthesized by lipoxygenase enzymes, and our results suggest that eosinophils influence the balance between proinflammatory and proresolving lipid mediators. We demonstrate that lipid mediators can regulate epithelial cell expansion, with PCTR1 reducing inflammation-driven growth of tumor cells and eosinophil-driven eoxin C4 blocking this effect. Together, these findings highlight that eosinophils and specific bioactive lipid mediators play important roles in skin biology and carcinogenesis and point to potential previously unreported strategies for treatment of inflammatory disorders and epithelial malignancies.

Eosinophils and pleural macrophages counter regulate IL-33-elicited airway inflammation via the 12/15-lipoxygenase pathway

Introduction

Fatty acid metabolism plays a crucial role in regulating airway inflammation through the synthesis of lipid mediators. We have previously demonstrated that a 12/15-lipoxygenase (12/15-LOX or Alox15)-derived mediator attenuates IL-33-induced eosinophilic airway inflammation in mice. However, the cellular sources of these mediators remain unclear.

Methods

To identify the cellular sources, we used several cell type-specific conditional 12/15-LOX-deficient mice.

Results

We found that eosinophils and pleural macrophages were the major 12/15-LOX-expressing cell types responsible for attenuating airway inflammation. Eosinophils were the major population of 12/15-LOX-expressing cells found in inflamed lung tissue. In addition, pleural macrophages were the major population of 12/15-LOX-expressing cells in the thoracic cavity and were found to translocate into inflamed lung tissue in response to airway inflammation.

Discussion

This study suggests that eosinophils and pleural macrophages cooperatively regulate eosinophilic airway inflammation via 12/15-LOX expression. Targeting 12/15-LOX metabolism in these cells may offer new therapeutic strategies for severe asthma.

Discovery of GJG057, a Potent and Highly Selective Inhibitor of Leukotriene C4 Synthase

Leukotriene C4 synthase (LTC4S) is a glutathione S-transferase that mediates the biosynthesis of cysteinyl leukotriene C4 (LTC4). Cysteinyl leukotrienes (CysLTs) are lipid mediators that drive type 2 inflammation, bronchoconstriction, and itch. Thus, LTC4S represents an attractive drug target for the treatment of allergic inflammatory diseases, but to date, no LTC4S inhibitor has been tested in patients. Herein, we disclose the discovery and preclinical profiling of the highly selective, oral LTC4S inhibitor GJG057 (compound 1), which exhibits 20-fold improved potency (IC50 = 44 nM) versus clinical candidate AZD9898 (IC50 = 900 nM) in a human whole blood LTC4 release assay. GJG057 showed efficacy in a murine asthma exacerbation model as well as in a mastoparan-induced skin challenge PK/PD model and was profiled in GLP toxicology studies. Despite its promising properties, GJG057 was not progressed into clinical trials as an oral drug. Its potential as a topical drug is currently being evaluated.

The Role of Endogenous Specialized Proresolving Mediators in Mast Cells and Their Involvement in Inflammation and Resolution

Many polyunsaturated fatty acids within cells exhibit diverse physiological functions. Particularly, arachidonic acid is the precursor of highly bioactive prostaglandins and leukotrienes, which are pro-inflammatory mediators. However, polyunsaturated fatty acids, such as arachidonic, docosahexaenoic, and eicosapentaenoic acids, can be metabolized into specialized proresolving mediators (SPMs), which have anti-inflammatory properties. Given that pro-inflammatory mediators and SPMs are produced via similar enzymatic pathways, SPMs can play a crucial role in mitigating excessive tissue damage induced by inflammation. Mast cells are immune cells that are widely distributed and strategically positioned at interfaces with the external environment, such as the skin and mucosa. As immune system sentinels, they respond to harmful pathogens and foreign substances. Upon activation, mast cells release various pro-inflammatory mediators, initiating an inflammatory response. Furthermore, these cells secrete factors that promote tissue repair and inhibit inflammation. This dual function positions mast cells as central regulators, balancing between the body's defense mechanisms and the need to minimize tissue injury. This review investigates the production of SPMs by mast cells and their subsequent effects on these cells. By elucidating the intricate relationship between mast cells and SPMs, this review aims to provide a comprehensive understanding of the mechanism by which these cells regulate the delicate balance between tissue damage and repair at inflammatory sites, ultimately contributing to the resolution of inflammatory responses.

Metabolic pathways of eicosanoids-derivatives of arachidonic acid and their significance in skin

The skin is a barrier that protects the human body against environmental factors (physical, including solar radiation, chemicals, and pathogens). The integrity and, consequently, the effective metabolic activity of skin cells is ensured by the cell membrane, the important structural and metabolic elements of which are phospholipids. Phospholipids are subject to continuous transformation, including enzymatic hydrolysis (with the participation of phospholipases A, C, and D) to free polyunsaturated fatty acids (PUFAs), which under the influence of cyclooxygenases (COX1/2), lipoxygenases (LOXs), and cytochrome P450 (CYPs P450) are metabolized to various classes of oxylipins, depending on the type of PUFA being metabolized and the enzyme acting. The most frequently analyzed oxylipins, especially in skin cells, are eicosanoids, which are derivatives of arachidonic acid (AA). Their level depends on both environmental factors and endogenous metabolic disorders. However, they play an important role in homeostasis mechanisms related to the structural and functional integrity of the skin, including maintaining redox balance, as well as regulating inflammatory processes arising in response to endogenous and exogenous factors reaching skin cells. Therefore, it is believed that dysregulation of eicosanoid levels may contribute to the development of skin diseases, such as psoriasis or atopic dermatitis, which in turn suggests that targeted control of the generation of specific eicosanoids may have diagnostic significance and beneficial therapeutic effects. This review is the first systemic and very detailed approach presenting both the causes and consequences of changes in phospholipid metabolism leading to the generation of eicosanoids, changes in the level of which result in specific metabolic disorders in skin cells leading to the development of various diseases. At the same time, existing literature data indicate that further detailed research is necessary to understand a clear relationship between changes in the level of specific eicosanoids and the pathomechanisms of specific skin diseases, as well as to develop an effective diagnostic and therapeutic approach.

Pro-resolving lipid mediators and therapeutic innovations in resolution of inflammation

This review summarizes findings presented at the 19th World Congress of Basic & Clinical Pharmacology 2023 (Glasgow, Scotland, July 3rd to 7th, 2023) from 8 speakers in the field of resolution of inflammation, resolution pharmacology and resolution biology. It is now accepted that the acute inflammatory response is protective to defend the host against infection or tissue injury. Acute inflammation is self-limited and programmed to be limited in space and time: this is achieved through endogenous resolution processes that ensure return to homeostasis. Resolution is brought about by agonist mediators that include specialized pro-resolving lipid mediators (SPMs) and pro-resolving proteins and peptides such as annexin A1 and angiotensin-(1-7), all acting to initiate anti-inflammatory and pro-resolving processes. If the inflammatory reaction remains unchecked through dysfunctional resolution mechanism, it can become chronic and contribute to a plethora of human diseases, including respiratory, cardiovascular, metabolic, allergic diseases, and arthritis. Herein, we discuss how non-resolving inflammation plays a role in the pathogenesis of these diseases. In addition to SPMs, we highlight the discovery, biosynthesis, biofunctions, and latest research updates on innovative therapeutics (including annexin-A1 peptide-mimetic RTP-026, small molecule FPR2 agonist BM-986235/LAR-1219, biased agonist for FPR1/FPR2 Cmpd17b, lipoxin mimetics AT-01-KG and AT-02-CT, melanocortin receptor agonist AP1189, gold nanoparticles, angiotensin-(1-7), and CD300a) that can promote resolution of inflammation directly or through modulation of SPMs production. Drug development strategies based on the biology of the resolution of inflammation can offer novel therapeutic means and/or add-on therapies for the treatment of chronic diseases.

Unique effect of aspirin on local 15-oxo-eicosatetraenoic acid synthesis in asthma patients with aspirin hypersensitivity

BACKGROUND

Nonsteroidal anti-inflammatory drugs-exacerbated respiratory disease (NSAIDs-ERD) is characterized by altered arachidonic acid (AA) metabolism. Aspirin hypersensitivity is diagnosed using aspirin challenge, while induced sputum is collected to perform cell counts and to identify local biomarkers in induced sputum supernatant (ISS). This study aimed to assess the levels of a newly identified eicosanoid, 15-oxo-eicosatetraenoic acid (15-oxo-ETE), in ISS at baseline and during aspirin-induced bronchospasm in patients with NSAIDs-ERD.

METHODS

Oral aspirin challenge was performed in 27 patients with NSAIDs-ERD and in 17 patients with aspirin-tolerant asthma (ATA) serving as controls. Sputum was collected before and after aspirin challenge to determine eosinophil, neutrophil, macrophage, and lymphocyte counts as well as the concentration of AA metabolites via 15-lipoxygenase-1 (15-LOX-1) and 5-LOX pathways in ISS. Chromatography-tandem mass spectrometry was used to measure ISS levels of 15-oxo-ETE, 15-hydroxyeicosatetranoic acid (15-HETE), and leukotriene E4 (LTE4).

RESULTS

At baseline, ISS levels of 15-oxo-ETE were higher in NSAIDs-ERD than in ATA (p = 0.04). In contrast, baseline 15-HETE levels in ISS were lower in patients with NSAIDs-ERD (p = 0.03). After aspirin challenge, 15-oxo-ETE levels decreased only in patients with NSAIDs-ERD (p = 0.001) who developed bronchospasm. In both study groups, there was a reduction in sputum macrophage count after aspirin challenge (p = 0.03 and p = 0.02, respectively) irrespective of bronchospasm.

CONCLUSIONS

Patients with NSAIDs-ERD are characterized by higher baseline 15-oxo-ETE levels in ISS than patients with ATA. Aspirin-induced bronchospasm inhibited the local generation of 15-oxo-ETE.

Real time changes in the expression of eicosanoid synthesizing enzymes during inflammation

Immune responses during inflammation involve complex, well-coordinated lipid signaling pathways. Eicosanoids are a class of lipid signaling molecules derived from polyunsaturated fatty acids such as arachidonic acid and constitute a major network that controls inflammation and its subsequent resolution. Arachidonic acid is metabolized by enzymes in three different pathways to form a variety of lipid metabolites that can be either pro- or anti-inflammatory. Therefore, an understanding of the time-dependent gene expression, lipid metabolite profiles and cytokine profiles during the initial inflammatory response is necessary, as it will allow for the design of time-dependent therapeutics. Herein, we investigate the multi-level regulation of this process. After stimulating RAW 264.7 cells, a mouse-derived macrophage cell line commonly used to examine inflammatory responses, we examine the gene expression of 44 relevant lipid metabolizing enzymes from the different eicosanoid synthesizing classes. We also measure the formation of lipid metabolites and production of cytokines at selected time points. Results reveal a dynamic relationship between the time-course of inflammation dependent gene expression of the three eicosanoid synthesizing enzymes.

Expression and putative biological roles of lipoxygenases and leukotriene receptors in leukemia and lymphoma

This mini-review addresses lipoxygenases and receptors for leukotrienes in hematological malignancies. Potential novel biomarkers and drug targets in leukemia and B-cell lymphoma are discussed.

Air pollution, genetic factors, and chronic rhinosinusitis: A prospective study in the UK Biobank

BACKGROUND

Chronic rhinosinusitis (CRS) is a prevalent upper respiratory condition that manifests in two primary subtypes: CRS with nasal polyps (CRSwNP) and CRS without nasal polyps (CRSsNP). While previous studies indicate a correlation between air pollution and CRS, the role of genetic predisposition in this relationship remains largely unexplored. We hypothesized that higher air pollution exposure would lead to the development of CRS, and that genetic susceptibility might modify this association.

METHODS

This cohort study involving 367,298 adult participants from the UK Biobank, followed from March 2006 to October 2021. Air pollution metrics were estimated at residential locations using land-use regression models. Cox proportional hazard models were employed to explore the associations between air pollution exposure and CRS, CRSwNP, and CRSsNP. A polygenic risk score (PRS) was constructed to evaluate the joint effect of air pollution and genetic predisposition on the development of CRS.

RESULTS

We found that the risk of CRS increased under long-term exposure to PM2.5 [the hazard ratios (HRs) with 95 % CIs: 1.59 (1.26-2.01)], PM10 [1.64 (1.26-2.12)], NO2 [1.11 (1.04-1.17)], and NOx [1.18 (1.12-1.25)], respectively. These effects were more pronounced among participants with CRSwNP, although the differences were not statistically significant. Additionally, we found that the risks for CRS and CRSwNP increased in a graded manner among participants with higher PRS or higher exposure to PM2.5, PM10, or NOx concentrations. However, no multiplicative or additive interactions were observed.

CONCLUSIONS

Long-term exposure to air pollution increases the risk of CRS, particularly CRSwNP underscoring the need to prioritize clean air initiatives and environmental regulations.

Eosinophil biology from the standpoint of metabolism: implications for metabolic disorders and asthma

Eosinophils, recognized for their immune and remodeling functions and participation in allergic inflammation, have recently garnered attention due to their impact on host metabolism, especially in the regulation of adipose tissue. Eosinophils are now known for their role in adipocyte beiging, adipokine secretion, and adipose tissue inflammation. This intricate interaction involves complex immune and metabolic processes, carrying significant implications for systemic metabolic health. Importantly, the interplay between eosinophils and adipocytes is bidirectional, revealing the dynamic nature of the immune-metabolic axis in adipose tissue. While the homeostatic regulatory role of eosinophils in adipose tissue is appreciated, this relationship in the context of obesity or allergic inflammation is much less understood. Mechanistic details of eosinophil-adipose interactions, especially the direct regulation of adipocytes by eosinophils, are also lacking. Another poorly understood aspect is the metabolism of the eosinophils themselves, encompassing metabolic shifts during eosinophil subset transitions in different tissue microenvironments, along with potential effects of host metabolism on the programming of eosinophil hematopoiesis and the resulting plasticity. This review consolidates recent research in this emerging and fascinating frontier of eosinophil investigation, identifying unexplored areas and presenting innovative perspectives on eosinophil biology in the context of metabolic disorders and associated health conditions, including asthma.

Trisomy 21-driven metabolite alterations are linked to cellular injuries in Down syndrome

Down syndrome (DS) arises from a genetic anomaly characterized by an extra copy of chromosome 21 (exCh21). Despite high incidence of congenital diseases among DS patients, direct impacts of exCh21 remain elusive. Here, we established a robust DS model harnessing human-induced pluripotent stem cells (hiPSCs) from mosaic DS patient. These hiPSC lines encompassed both those with standard karyotype and those carrying an extra copy of exCh21, allowing to generate isogenic cell lines with a consistent genetic background. We unraveled that exCh21 inflicted disruption upon the cellular transcriptome, ushering in alterations in metabolic processes and triggering DNA damage. The impact of exCh21 was also manifested in profound modifications in chromatin accessibility patterns. Moreover, we identified two signature metabolites, 5-oxo-ETE and Calcitriol, whose biosynthesis is affected by exCh21. Notably, supplementation with 5-oxo-ETE promoted DNA damage, in stark contrast to the protective effect elicited by Calcitriol against such damage. We also found that exCh21 disrupted cardiogenesis, and that this impairment could be mitigated through supplementation with Calcitriol. Specifically, the deleterious effects of 5-oxo-ETE unfolded in the form of DNA damage induction and the repression of cardiogenesis. On the other hand, Calcitriol emerged as a potent activator of its nuclear receptor VDR, fostering amplified binding to chromatin and subsequent facilitation of gene transcription. Our findings provide a comprehensive understanding of exCh21's metabolic implications within the context of Down syndrome, offering potential avenues for therapeutic interventions for Down syndrome treatment.

Chromone-based small molecules for multistep shutdown of arachidonate pathway: Simultaneous inhibition of COX-2, 15-LOX and mPGES-1 enzymes

As a new approach to the management of inflammatory disorders, a series of chromone-based derivatives containing a (carbamate)hydrazone moiety was designed and synthesized. The compounds were assessed for their ability to inhibit COX-1/2, 15-LOX, and mPGES-1, as a combination that should effectively impede the arachidonate pathway. Results revealed that the benzylcarbazates (2a-c) demonstrated two-digit nanomolar COX-2 inhibitory activities with reasonable selectivity indices. They also showed appreciable 15-LOX inhibition, in comparison to quercetin. Further testing of these compounds for mPGES-1 inhibition displayed promising activities. Intriguingly, compounds 2a-c were capable of suppressing edema in the formalin-induced rat paw edema assay. They exhibited an acceptable gastrointestinal safety profile regarding ulcerogenic liabilities in gross and histopathological examinations. Additionally, upon treatment with the test compounds, the expression of the anti-inflammatory cytokine IL-10 was elevated, whereas that of TNF-α, iNOS, IL-1β, and COX-2 were downregulated in LPS-challenged RAW264.7 macrophages. Docking experiments into the three enzymes showed interesting binding profiles and affinities, further substantiating their biological activities. Their in silico physicochemical and pharmacokinetic parameters were advantageous.

Polyunsaturated Fatty Acids: Conversion to Lipid Mediators, Roles in Inflammatory Diseases and Dietary Sources

Polyunsaturated fatty acids (PUFAs) are important components of the diet of mammals. Their role was first established when the essential fatty acids (EFAs) linoleic acid and α-linolenic acid were discovered nearly a century ago. However, most of the biochemical and physiological actions of PUFAs rely on their conversion to 20C or 22C acids and subsequent metabolism to lipid mediators. As a generalisation, lipid mediators formed from n-6 PUFAs are pro-inflammatory while those from n-3 PUFAs are anti-inflammatory or neutral. Apart from the actions of the classic eicosanoids or docosanoids, many newly discovered compounds are described as Specialised Pro-resolving Mediators (SPMs) which have been proposed to have a role in resolving inflammatory conditions such as infections and preventing them from becoming chronic. In addition, a large group of molecules, termed isoprostanes, can be generated by free radical reactions and these too have powerful properties towards inflammation. The ultimate source of n-3 and n-6 PUFAs are photosynthetic organisms which contain Δ-12 and Δ-15 desaturases, which are almost exclusively absent from animals. Moreover, the EFAs consumed from plant food are in competition with each other for conversion to lipid mediators. Thus, the relative amounts of n-3 and n-6 PUFAs in the diet are important. Furthermore, the conversion of the EFAs to 20C and 22C PUFAs in mammals is rather poor. Thus, there has been much interest recently in the use of algae, many of which make substantial quantities of long-chain PUFAs or in manipulating oil crops to make such acids. This is especially important because fish oils, which are their main source in human diets, are becoming limited. In this review, the metabolic conversion of PUFAs into different lipid mediators is described. Then, the biological roles and molecular mechanisms of such mediators in inflammatory diseases are outlined. Finally, natural sources of PUFAs (including 20 or 22 carbon compounds) are detailed, as well as recent efforts to increase their production.

Thiocarbohydrazone and Chalcone-Derived 3,4-Dihydropyrimidinethione as Lipid Peroxidation and Soybean Lipoxygenase Inhibitors

The potential of the 4,6-diphenyl-3,4-dihydropyrimidine-2(1H)-thione (abbreviated as KKII5) and (E)-N'-benzylidenehydrazinecarbothiohydrazide (abbreviated as DKI5) compounds as possible drug leads is investigated. KKII5 and DKI5 are synthesized in high yield of up to 97%. Their structure, binding in the active site of the LOX-1 enzyme, and their toxicity are studied via joint experimental and computational methodologies. Specifically, the structure assignment and conformational analysis were achieved by applying homonuclear and heteronuclear 2D nuclear magnetic resonance (NMR) spectroscopy (2D-COSY, 2D-NOESY, 2D-HSQC, and 2D-HMBC) and density functional theory (DFT). The obtained DFT lowest energy conformers were in agreement with the NOE correlations observed in the 2D-NOESY spectra. Additionally, docking and molecular dynamics simulations were performed to discover their ability to bind and remain stabile in the active site of the LOX-1 enzyme. These in silico experiments and DFT calculations indicated favorable binding for the enzyme under study. The strongest binding energy, -9.60 kcal/mol, was observed for dihydropyrimidinethione KKII5 in the active site of LOX-1. ADMET calculations showed that the two molecules lack major toxicities and could serve as possible drug leads. The redox potential of the active center of LOX-1 with the binding molecules was calculated via DFT methodology. The results showed a significantly smaller energy attachment of 2.8 eV with KKII5 binding in comparison to DKI5. Thus, KKII5 enhanced the ability of the active center to receive electrons compared to DKI5. This is related to the stronger binding interaction of KKII5 relative to that of DK15 to LOX-1. The two very potent LOX-1 inhibitors exerted IC₅₀ 19 μΜ (KKII5) and 22.5 μΜ (DKI5). Furthermore, they both strongly inhibit lipid peroxidation, namely, 98% for KKII5 and 94% for DKI5.

Synthesis and Significance of Arachidonic Acid, a Substrate for Cyclooxygenases, Lipoxygenases, and Cytochrome P450 Pathways in the Tumorigenesis of Glioblastoma Multiforme, Including a Pan-Cancer Comparative Analysis

Glioblastoma multiforme (GBM) is one of the most aggressive gliomas. New and more effective therapeutic approaches are being sought based on studies of the various mechanisms of GBM tumorigenesis, including the synthesis and metabolism of arachidonic acid (ARA), an omega-6 polyunsaturated fatty acid (PUFA). PubMed, GEPIA, and the transcriptomics analysis carried out by Seifert et al. were used in writing this paper. In this paper, we discuss in detail the biosynthesis of this acid in GBM tumors, with a special focus on certain enzymes: fatty acid desaturase (FADS)1, FADS2, and elongation of long-chain fatty acids family member 5 (ELOVL5). We also discuss ARA metabolism, particularly its release from cell membrane phospholipids by phospholipase A₂ (cPLA₂, iPLA₂, and sPLA₂) and its processing by cyclooxygenases (COX-1 and COX-2), lipoxygenases (5-LOX, 12-LOX, 15-LOX-1, and 15-LOX-2), and cytochrome P450. Next, we discuss the significance of lipid mediators synthesized from ARA in GBM cancer processes, including prostaglandins (PGE₂, PGD₂, and 15-deoxy-Δ^12,14-PGJ₂ (15d-PGJ₂)), thromboxane A₂ (TxA₂), oxo-eicosatetraenoic acids, leukotrienes (LTB₄, LTC₄, LTD₄, and LTE₄), lipoxins, and many others. These lipid mediators can increase the proliferation of GBM cancer cells, cause angiogenesis, inhibit the anti-tumor response of the immune system, and be responsible for resistance to treatment.

Male infertility and somatic health - insights into lipid damage as a mechanistic link

Over the past decade, mounting evidence has shown an alarming association between male subfertility and poor somatic health, with substantial evidence supporting the increased incidence of oncological disease, cardiovascular disease, metabolic disorders and autoimmune diseases in men who have previously received a subfertility diagnosis. This paradigm is concerning, but might also provide a novel window for a crucial health reform in which the infertile phenotype could serve as an indication of potential pathological conditions. One of the major limiting factors in this association is the poor understanding of the molecular features that link infertility with comorbidities across the life course. Enzymes involved in the lipid oxidation process might provide novel clues to reconcile the mechanistic basis of infertility with incident pathological conditions. Building research capacity in this area is essential to enhance the early detection of disease states and provide crucial information about the disease risk of offspring conceived through assisted reproduction.

Identification of PCSK9-like human gene knockouts using metabolomics, proteomics, and whole-genome sequencing in a consanguineous population

Natural human knockouts of genes associated with desirable outcomes, such as PCSK9 with low levels of LDL-cholesterol, can lead to the discovery of new drug targets and treatments. Rare loss-of-function variants are more likely to be found in the homozygous state in consanguineous populations, and deep molecular phenotyping of blood samples from homozygous carriers can help to discriminate between silent and functional variants. Here, we combined whole-genome sequencing with proteomics and metabolomics for 2,935 individuals from the Qatar Biobank (QBB) to evaluate the power of this approach for finding genes of clinical and pharmaceutical interest. As proof-of-concept, we identified a homozygous carrier of a very rare PCSK9 variant with extremely low circulating PCSK9 levels and low LDL. Our study demonstrates that the chances of finding such variants are about 168 times higher in QBB compared with GnomAD and emphasizes the potential of consanguineous populations for drug discovery.

Single-cell profiling identifies mechanisms of inflammatory heterogeneity in chronic rhinosinusitis

The heterogeneous cellular microenvironment of human airway chronic inflammatory diseases, including chronic rhinosinusitis (CRS) and asthma, is still poorly understood. Here, we performed single-cell RNA sequencing (scRNA-seq) on the nasal mucosa of healthy individuals and patients with three subtypes of CRS and identified disease-specific cell subsets and molecules that specifically contribute to the pathogenesis of CRS subtypes. As such, ALOX15+ macrophages contributed to the type 2 immunity-driven pathogenesis of one subtype of CRS, eosinophilic CRS with nasal polyps (eCRSwNP), by secreting chemokines that recruited eosinophils, monocytes and T helper 2 (TH2) cells. An inhibitor of ALOX15 reduced the release of proinflammatory chemokines in human macrophages and inhibited the overactivation of type 2 immunity in a mouse model of eosinophilic rhinosinusitis. Our findings advance the understanding of the heterogeneous immune microenvironment and the pathogenesis of CRS subtypes and identify potential therapeutic approaches for the treatment of CRS and potentially other type 2 immunity-mediated diseases.

Effects of Levofloxacin, Aztreonam, and Colistin on Enzyme Synthesis by P. aeruginosa Isolated from Cystic Fibrosis Patients

(1) Background: Cystic fibrosis (CF) is characterized by chronic pulmonary inflammation and persistent bacterial infections. P. aeruginosa is among the main opportunistic pathogens causing infections in CF. P. aeruginosa is able to form a biofilm, decreasing antibiotic permeability. LOX, a lipoxygenase enzyme, is a virulence factor produced by P. aeruginosa and promotes its persistence in lung tissues. The aim of this study is to evaluate if antibiotics currently used for aerosol therapy in CF are able to interfere with the production of lipoxygenase from open isolates of P. Aeruginosa from patients with CF. (2) Methods: Clinical isolates of P. aeruginosa from patients with CF were grown in Luria broth (LB). Minimum inhibitory concentration (MIC) was performed and interpreted for all isolated strains according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. We selected four antibiotics with different mechanisms of action: aztreonam, colistin, amikacin, and levofloxacin. We used human pulmonary epithelial NCI-H929 cells to evaluate LOX activity and its metabolites according to antibiotic action at increasing concentrations. (3) Results: there is a correlation between LOX secretion by clinical isolates of P. aeruginosa and biofilm production. Levofloxacin exhibits highly significant inhibitory activity compared to the control. Amikacin also exhibits significant inhibitory activity against LOX production. Aztreonam and colistin do not show inhibitory activity. These results are also confirmed for LOX metabolites. (4) Conclusions: among the evaluated antibiotics, levofloxacin and amikacin have an activity on LOX secretion.

The role of 15 lipoxygenase 1 in asthma comes into focus

IL-4– and IL-13–driven epithelial cell expression of 15 lipoxygenase 1 (15LO1) is a consistent feature of eosinophil-dominated asthma known as type 2–high (T2-high) asthma. The abundant soluble products of arachidonic acid (AA) metabolized by 15LO1 reflect a high level of enzymatic activity in asthma and chronic rhinosinusitis. However, the precise role of 15LO1 and its products in disease pathogenesis remains enigmatic. In this issue of the JCI, Nagasaki and colleagues demonstrate a role for 15LO1 in controlling redox balance and epithelial homeostasis in T2-high asthma by metabolizing AA that is esterified to membrane phospholipids. The findings may pave the way toward the development of 15LO1 inhibitors as asthma treatments.

Human and Mouse Eosinophils Differ in Their Ability to Biosynthesize Eicosanoids, Docosanoids, the Endocannabinoid 2-Arachidonoyl-glycerol and Its Congeners

High eosinophil (EOS) counts are a key feature of eosinophilic asthma. EOS notably affect asthmatic response by generating several lipid mediators. Mice have been utilized in hopes of defining new pharmacological targets to treat asthma. However, many pinpointed targets in mice did not translate into clinics, underscoring that key differences exist between the two species. In this study, we compared the ability of human (h) and mouse (m) EOS to biosynthesize key bioactive lipids derived from arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). hEOS were isolated from the blood of healthy subjects and mild asthmatics, while mEOSs were differentiated from the bone marrow. EOSs were treated with fatty acids and lipid mediator biosynthesis assessed by LC-MS/MS. We found that hEOS biosynthesized leukotriene (LT) C₄ and LTB₄ in a 5:1 ratio while mEOS almost exclusively biosynthesized LTB₄. The biosynthesis of the 15-lipoxygenase (LO) metabolites 15-HETE and 12-HETE also differed, with a 15-HETE:12-HETE ratio of 6.3 for hEOS and 0.727 for mEOS. EOS biosynthesized some specialized pro-resolving mediators, and the levels from mEOS were 9-times higher than those of hEOS. In contrast, hEOS produced important amounts of the endocannabinoid 2-arachidonoyl-glycerol (2-AG) and its congeners from EPA and DHA, a biosynthetic pathway that was up to ~100-fold less prominent in mEOS. Our data show that hEOS and mEOS biosynthesize the same lipid mediators but in different amounts. Compared to asthmatics, mouse models likely have an amplified involvement of LTB₄ and specialized pro-resolving mediators and a diminished impact of the endocannabinoid 2-arachidonoyl-glycerol and its congeners.

Longitudinal exposure to consumer product chemicals and changes in plasma oxylipins in pregnant women

BACKGROUND

Exposure to consumer product chemicals during pregnancy may increase susceptibility to pregnancy disorders by influencing maternal inflammation. However, effects on specific inflammatory pathways have not been well characterized. Oxylipins are a diverse class of lipids that act as important mediators and biomarkers of several biological pathways that regulate inflammation. Adverse pregnancy outcomes have been associated with circulating oxylipin levels in pregnancy. In this study, we aimed to determine the longitudinal associations between plasma oxylipins and urinary biomarkers of three classes of consumer product chemicals among pregnant women.

METHODS

Data come from a study of 90 pregnant women nested within the LIFECODES cohort. Maternal plasma and urine were collected at three prenatal visits. Plasma was analyzed for 61 oxylipins, which were grouped according to biosynthetic pathways that we defined by upstream: 1) fatty acid precursor, including linoleic, arachidonic, docosahexaenoic, or eicosapentaenoic acid; and 2) enzyme pathway, including cyclooxygenase (COX), lipoxygenase (LOX), or cytochrome P450 (CYP). Urine was analyzed for 12 phenol, 12 phthalate, and 9 organophosphate ester (OPE) biomarkers. Linear mixed effect models were used for single-pollutant analyses. We implemented a novel extension of quantile g-computation for longitudinal data to examine the joint effect of class-specific chemical mixtures on individual plasma oxylipin concentrations.

RESULTS

We found that urinary biomarkers of consumer product chemicals were positively associated with pro-inflammatory oxylipins from several biosynthetic pathways. Importantly, these associations depended upon the chemical class of exposure biomarker. We estimated positive associations between urinary phenol biomarkers and oxylipins produced from arachidonic acid by LOX enzymes, including several important pro-inflammatory hydroxyeicosatetraenoic acids (HETEs). On average, mean concentrations of oxylipin produced from the arachidonic acid/LOX pathway were 48%-71% higher per quartile increase in the phenol biomarker mixture. For example, a simultaneous quartile increase in all urinary phenols was associated with 53% higher (95% confidence interval [CI]: 11%, 111%) concentrations of 12-HETE. The positive associations among phenols were primarily driven by methyl paraben, 2,5-dichlorophenol, and triclosan. Additionally, we observed that phthalate and OPE metabolites were associated with higher concentrations of oxylipins produced from linoleic acid by CYP enzymes, including the pro-inflammatory dihydroxy-octadecenoic acids (DiHOMEs). Associations among DiHOME oxylipins were driven by metabolites of benzylbutyl and di-isodecyl phthalate, and by the metabolite of tris(1,3-dichloro-2-propyl) phosphate among OPEs. We also observed inverse associations between phthalate and OPE metabolites and oxylipins produced from other pathways; however, adjusting for a plasma indicator of dietary fatty acid intake attenuated those results.

CONCLUSIONS

Our findings support the hypothesis that consumer product chemicals may have diverse impacts on inflammation processes in pregnancy. Certain pro-inflammatory oxylipins were generally higher among participants with higher urinary chemical biomarker concentrations. Associations varied by class of chemical and by the biosynthetic pathway of oxylipin production, indicating potential specificity in the inflammatory effects of these environmental chemicals during pregnancy that warrant investigation in larger studies.

Loss of 15-lipoxygenase disrupts Treg differentiation altering their pro-resolving functions

Regulatory T-cells (Tregs) are central in the maintenance of homeostasis and resolution of inflammation. However, the mechanisms that govern their differentiation and function are not completely understood. Herein, we demonstrate a central role for the lipid mediator biosynthetic enzyme 15-lipoxygenase (ALOX15) in regulating key aspects of Treg biology. Pharmacological inhibition or genetic deletion of ALOX15 in Tregs decreased FOXP3 expression, altered Treg transcriptional profile and shifted their metabolism. This was linked with an impaired ability of Alox15-deficient cells to exert their pro-resolving actions, including a decrease in their ability to upregulate macrophage efferocytosis and a downregulation of interferon gamma expression in Th1 cells. Incubation of Tregs with the ALOX15-derived specilized pro-resolving mediators (SPM)s Resolvin (Rv)D3 and RvD5n-3 DPA rescued FOXP3 expression in cells where ALOX15 activity was inhibited. In vivo, deletion of Alox15 led to increased vascular lipid load and expansion of Th1 cells in mice fed western diet, a phenomenon that was reversed when Alox15-deficient mice were reconstituted with wild type Tregs. Taken together these findings demonstrate a central role of pro-resolving lipid mediators in governing the differentiation of naive T-cells to Tregs.

O-prenylated carbostyrils as a novel class of 15-lipoxygenase inhibitors: Synthesis, characterization, and inhibitory assessment

Catalyzed peroxidation of unsaturated lipid in animals and plants intimately is linked to the activity of 15-Lipoxygenase enzymes. Lipoxygenases (LOXs) are well known to play an important role in many acute and chronic syndromes such as inflammation, asthma, cancer, and allergy. In this study, a series of mono prenyloxycarbostyrils were synthesized and evaluated as potential inhibitors of soybean 15-Lipoxygenase (SLO) and their inhibitory potencies were compared to mono prenyloxycoumarins which had been reported in the previous works. The synthetic compounds inhibit lipoxygenase enzyme by competitive mechanism like the prenyloxy coumarins. The results showed that position and length of the prenyl moiety play the important role in lipoxygenase inhibitory activity. Among all of the synthetic compounds (coumarin and carbostyril derivatives), 5-farnesyloxycoumarin and 8-farnesyloxycarbostyril demonstrated the best inhibitory activity by IC50  values of 1.1 µM and 0.53 µM, respectively.

Metastasis-Entrained Eosinophils Enhance Lymphocyte-Mediated Antitumor Immunity

The recognition of the immune system as a key component of the tumor microenvironment (TME) led to promising therapeutics. Because such therapies benefit only subsets of patients, understanding the activities of immune cells in the TME is required. Eosinophils are an integral part of the TME especially in mucosal tumors. Nonetheless, their role in the TME and the environmental cues that direct their activities are largely unknown. We report that breast cancer lung metastases are characterized by resident and recruited eosinophils. Eosinophil recruitment to the metastatic sites in the lung was regulated by G protein-coupled receptor signaling but independent of CCR3. Functionally, eosinophils promoted lymphocyte-mediated antitumor immunity. Transcriptome and proteomic analyses identified the TME rather than intrinsic differences between eosinophil subsets as a key instructing factor directing antitumorigenic eosinophil activities. Specifically, TNFα/IFNγ-activated eosinophils facilitated CD4⁺ and CD8⁺ T-cell infiltration and promoted antitumor immunity. Collectively, we identify a mechanism by which the TME trains eosinophils to adopt antitumorigenic properties, which may lead to the development of eosinophil-targeted therapeutics. SIGNIFICANCE: These findings demonstrate antitumor activities of eosinophils in the metastatic tumor microenvironment, suggesting that harnessing eosinophil activity may be a viable clinical strategy in patients with cancer.

Pathomechanisms of AERD—Recent Advances

The pathomechanisms behind NSAID-exacerbated respiratory disease are complex and still largely unknown. They are presumed to involve genetic predisposition and environmental triggers that lead to dysregulation of fatty acid and lipid metabolism, altered cellular interactions involving transmetabolism, and continuous and chronic inflammation in the respiratory track. Here, we go through the recent advances on the topic and sum up the current understanding of the background of this illness that broadly effects the patients' lives.

Endocannabinoid signaling pathways: beyond CB1R and CB2R

The search for cannabinoid receptors other than CB1R and CB2R has been ongoing for over a decade. A number of orphan receptors have been proposed as potential cannabinoid receptors primarily based on phylogenic arguments and reactivity towards known endocannabinoids and phytocannabinoids. Seven putative cannabinoid receptors are described and discussed, and evidence for and against their inclusion in this category are presented.

Discovery of natural 15-LOX small molecule inhibitors from Chinese herbal medicine using virtual Screening, biological evaluation and molecular dynamics studies

Chinese herbal medicines (CHM) are frequently used to treat different types of inflammatory diseases and 15-Lipoxygenase (15-LOX) is a critical target enzyme for treating various inflammatory diseases. In this study, natural 15-LOX inhibitors were identified in CHM using an approach of virtual screening combined with the biological assays. First, an in-house Chinese medicine database containing 360 compounds was screened using a virtual screening approach based on pharmacophore and molecular docking to uncover several novel potential 15-LOX inhibitors. Secondly, the inhibitory effect of virtual screening hits against the 15-LOX enzyme was validated in an in vitro enzyme inhibition assay. Then, a tumor necrosis factor-α (TNF-α) release assay was carried out to explore the anti-inflammatory response of the active compounds. Furthermore, molecular dynamics (MD) simulation and binding free energy calculation were applied to analyze the process of inhibitors binding and also compared the mode of binding of the inhibitors by using the Molecular Mechanics-Generalized Born Surface Area (MM/GBSA) method. Finally, licochalcone B and eriodictyol were confirmed as inhibitors of the 15-LOX enzyme with IC₅₀ values of 9.67 and 18.99 μM, respectively. In vitro cell-based assay showed that licochalcone B and eriodictyol inhibited the release of TNF-α factor in RAW264.7 cells stimulated by lipopolysaccharides (LPS) in a dose-dependent manner. Molecular dynamics and binding free energy analysis showed that the two 15-LOX-ligand systems immediately attained equilibrium with almost 1 Å fluctuation, the calculated binding free energies were found around -18.89 and -12.96 kcal/mol for licochalcone B and eriodictyol, respectively. Thr412, Arg415, Val420, Thr429, Ile602 and Trp606 were the main amino acid residues for the inhibition of 15-LOX enzyme activity. The current study confirms that licochalcone B and eriodictyol are 15-LOX inhibitors and can suppress the release of the TNF-α factor in RAW264.7 cells stimulated by LPS, thus providing a basis for the follow-up research and development for 15-LOX inhibitors.

Utility of novel 2-furanones in synthesis of other heterocyclic compounds having anti-inflammatory activity with dual COX2/LOX inhibition

Inflammation is associated with the development of several diseases comprising cancer and cardiovascular disease. Agents that suppress cyclooxygenase (COX) and lipoxygenase (LOX) enzymes, besides chemokines have been suggested to minimise inflammation. Here, a variety of novel heterocyclic and non-heterocyclic compounds were prepared from novel three furanone derivatives. The structures of all synthesised compounds were confirmed by elemental and spectral analysis including mass, IR, and ¹H-NMR spectroscopy. Anti-inflammatory activities of these synthesised compounds were examined in vitro against COX enzymes, 15-LOX, and tumour necrosis factor-α (TNF-α), using inhibition screening assays. The majority of these derivatives showed significant to high activities, with three pyridazinone derivatives (5b, 8b, and 8c) being the most promising anti-inflammatory agents with dual COX-2/15-LOX inhibition activities along with high TNF-α inhibition activity.

The Emerging Role of COX-2, 15-LOX and PPARγ in Metabolic Diseases and Cancer: An Introduction to Novel Multi-target Directed Ligands (MTDLs)

Emerging evidence supports an intertwining framework for the involvement of different inflammatory pathways in a common pathological background for a number of disorders. Of importance are pathways involving arachidonic acid metabolism by cyclooxygenase-2 (COX-2) and 15-lipoxygenase (15-LOX). Both enzyme activities and their products are implicated in a range of pathophysiological processes encompassing metabolic impairment leading to adipose inflammation and the subsequent vascular and neurological disorders, in addition to various pro- and antitumorigenic effects. A further layer of complexity is encountered by the disparate, and often reciprocal, modulatory effect COX-2 and 15-LOX activities and metabolites exert on each other or on other cellular targets, the most prominent of which is peroxisome proliferator-activated receptor gamma (PPARγ). Thus, effective therapeutic intervention with such multifaceted disorders requires the simultaneous modulation of more than one target. Here, we describe the role of COX-2, 15-LOX, and PPARγ in cancer and complications of metabolic disorders, highlight the value of designing multi-target directed ligands (MTDLs) modifying their activity, and summarizing the available literature regarding the rationale and feasibility of design and synthesis of these ligands together with their known biological effects. We speculate on the potential impact of MTDLs in these disorders as well as emphasize the need for structured future effort to translate these early results facilitating the adoption of these, and similar, molecules in clinical research.

Emerging Role of Phospholipase-Derived Cleavage Products in Regulating Eosinophil Activity: Focus on Lysophospholipids, Polyunsaturated Fatty Acids and Eicosanoids

Eosinophils are important effector cells involved in allergic inflammation. When stimulated, eosinophils release a variety of mediators initiating, propagating, and maintaining local inflammation. Both, the activity and concentration of secreted and cytosolic phospholipases (PLAs) are increased in allergic inflammation, promoting the cleavage of phospholipids and thus the production of reactive lipid mediators. Eosinophils express high levels of secreted phospholipase A2 compared to other leukocytes, indicating their direct involvement in the production of lipid mediators during allergic inflammation. On the other side, eosinophils have also been recognized as crucial mediators with regulatory and homeostatic roles in local immunity and repair. Thus, targeting the complex network of lipid mediators offer a unique opportunity to target the over-activation and 'pro-inflammatory' phenotype of eosinophils without compromising the survival and functions of tissue-resident and homeostatic eosinophils. Here we provide a comprehensive overview of the critical role of phospholipase-derived lipid mediators in modulating eosinophil activity in health and disease. We focus on lysophospholipids, polyunsaturated fatty acids, and eicosanoids with exciting new perspectives for future drug development.

Targetable pathogenic mechanisms in nasal polyposis

Chronic rhinosinusitis with nasal polyps (CRSwNP) represents a challenging disease entity with significant rates of recurrence following appropriate medical and surgical therapy. Recent approval of targeted biologics in CRSwNP compels deeper understanding of underlying disease pathophysiology. Both of the approved biologics for CRSwNP modulate the type 2 inflammatory pathway, and the majority of drugs in the clinical trials pathway are similarly targeted. However, there remain multiple other pathogenic mechanisms relevant to CRSwNP for which targeted therapeutics already exist in other inflammatory diseases that have not been studied directly. In this article we summarize pathogenic mechanisms of interest in CRSwNP and discuss the results of ongoing clinical studies of targeted therapeutics in CRSwNP and other related human inflammatory diseases.

Oxidation of polyunsaturated fatty acids to produce lipid mediators

The chemistry, biochemistry, pharmacology and molecular biology of oxylipins (defined as a family of oxygenated natural products that are formed from unsaturated fatty acids by pathways involving at least one step of dioxygen-dependent oxidation) are complex and occasionally contradictory subjects that continue to develop at an extraordinarily rapid rate. The term includes docosanoids (e.g. protectins, resolvins and maresins, or specialized pro-resolving mediators), eicosanoids and octadecanoids and plant oxylipins, which are derived from either the omega-6 (n-6) or the omega-3 (n-3) families of polyunsaturated fatty acids. For example, the term eicosanoid is used to embrace those biologically active lipid mediators that are derived from C₂₀ fatty acids, and include prostaglandins, thromboxanes, leukotrienes, hydroxyeicosatetraenoic acids and related oxygenated derivatives. The key enzymes for the production of prostanoids are prostaglandin endoperoxide H synthases (cyclo-oxygenases), while lipoxygenases and oxidases of the cytochrome P450 family produce numerous other metabolites. In plants, the lipoxygenase pathway from C₁₈ polyunsaturated fatty acids yields a variety of important products, especially the jasmonates, which have some comparable structural features and functions. Related oxylipins are produced by non-enzymic means (isoprostanes), while fatty acid esters of hydroxy fatty acids (FAHFA) are now being considered together with the oxylipins from a functional perspective. In all kingdoms of life, oxylipins usually act as lipid mediators through specific receptors, have short half-lives and have functions in innumerable biological contexts.

Eicosanoids

This article describes the pathways of eicosanoid synthesis, eicosanoid receptors, the action of eicosanoids in different physiological systems, the roles of eicosanoids in selected diseases, and the major inhibitors of eicosanoid synthesis and action. Eicosanoids are oxidised derivatives of 20-carbon polyunsaturated fatty acids (PUFAs) formed by the cyclooxygenase (COX), lipoxygenase (LOX) and cytochrome P450 (cytP450) pathways. Arachidonic acid (ARA) is the usual substrate for eicosanoid synthesis. The COX pathways form prostaglandins (PGs) and thromboxanes (TXs), the LOX pathways form leukotrienes (LTs) and lipoxins (LXs), and the cytP450 pathways form various epoxy, hydroxy and dihydroxy derivatives. Eicosanoids are highly bioactive acting on many cell types through cell membrane G-protein coupled receptors, although some eicosanoids are also ligands for nuclear receptors. Because they are rapidly catabolised, eicosanoids mainly act locally to the site of their production. Many eicosanoids have multiple, sometimes pleiotropic, effects on inflammation and immunity. The most widely studied is PGE2. Many eicosanoids have roles in the regulation of the vascular, renal, gastrointestinal and female reproductive systems. Despite their vital role in physiology, eicosanoids are often associated with disease, including inflammatory disease and cancer. Inhibitors have been developed that interfere with the synthesis or action of various eicosanoids and some of these are used in disease treatment, especially for inflammation.

12-Oxo-10-glutathionyl-5,8,14-eicosatrienoic acid (TOG10), a novel glutathione-containing eicosanoid generated via the 12-lipoxygenase pathway in human platelets

Biologically active glutathione (GSH) conjugates of oxygenated fatty acids comprise a group of pro- and anti-inflammatory lipid mediators. While arachidonic acid (AA)-derived conjugates, as the cysteinyl leukotrienes (cys-LTs) and eoxins (EXs) have pro-inflammatory properties, conjugates in tissue regeneration (CTRs) biosynthesized from docosahexaenoic acid (DHA) exhibit pro-resolving activity. Human platelets express abundant amounts of platelet-type 12-lipoxygenase (pt12-LOX) and leukotriene C4 synthase (LTC4S). However, the only two described GSH conjugates formed by platelets are the AA-derived cys-LTs and the recently reported maresin CTRs (MCTRs). While cys-LTs are biosynthesized in a transcellular mechanism via the action of 5-LOX and LTC4S, MCTR1 is formed by 12-LOX and a yet unidentified GSH S-transferase (GST). Here, we present a novel GSH conjugate formed from AA via the 12-LOX pathway in human platelets. The 12-oxo-glutathione adduct, 12-oxo-10-glutathionyl-5,8,14-eicosatrienoic acid (TOG10), was identified by mass spectrometry using positive electrospray ionization. The structural proposal is supported by fragmentation data of the labeled metabolite obtained after incubation of deuterated AA (AA-d8). In platelets as well as in HEK293 cells stably expressing pt12-LOX, TOG10 biosynthesis was inhibited by the 12-LOX inhibitor ML-355 (5 μM), which confirms the involvement of pt12-LOX. Interestingly, TOG10 was formed independently of LTC4S in platelets. This is in accordance with the observation that the conjugate was also generated by AA-stimulated HEK_12-LOX cells in absence of LTC4S. Nevertheless, TOG10 can also be formed by LTC4S as the biosynthesis in HEK_12-LOX_LTC4S cells was reduced by the specific LTC4S inhibitor TK04a. In summary, TOG10 was identified as a new AA-derived GSH conjugate generated in human platelets via the action of pt12-LOX in combination with a GST.

COX-1 dependent biosynthesis of 15-hydroxyeicosatetraenoic acid in human mast cells

15-hydroxyeicosatetraenoic acid (15-HETE) is an arachidonic acid derived lipid mediator which can originate both from 15-lipoxygenase (15-LOX) activity and cyclooxygenase (COX) activity. The enzymatic source determines the enantiomeric profile of the 15-HETE formed. 15-HETE is the most abundant arachidonic acid metabolite in the human lung and has been suggested to influence the pathophysiology of asthma. Mast cells are central effectors in asthma, but there are contradictory reports on whether 15-HETE originates from 15-LOX or COX in human mast cells. This prompted the current study where the pathway of 15-HETE biosynthesis was examined in three human mast cell models; the cell line LAD2, cord blood derived mast cells (CBMC) and tissue isolated human lung mast cells (HLMC). Levels and enantiomeric profiles of 15-HETE and levels of the downstream metabolite 15-KETE, were analyzed by UPLC-MS/MS after stimulation with anti-IgE or calcium ionophore A23187 in the presence and absence of inhibitors of COX isoenzymes. We found that 15-HETE was produced by COX-1 in human mast cells under these experimental conditions. Unexpectedly, chiral analysis showed that the 15(R) isomer was predominant and gradually accumulated, whereas the 15(S) isomer was metabolized by the 15-hydroxyprostaglandin dehydrogenase. We conclude that during physiological conditions, i.e., without addition of exogenous arachidonic acid, both enantiomers of 15-HETE are produced by COX-1 in human mast cells but that the 15(S) isomer is selectively depleted by undergoing further metabolism. The study highlights that 15-HETE cannot be used as an indicator of 15-LOX activity for cellular studies, unless chirality and sensitivity to pharmacologic inhibition is determined.

Design, synthesis, molecular modelling and biological evaluation of novel 3-(2-naphthyl)-1-phenyl-1H-pyrazole derivatives as potent antioxidants and 15-Lipoxygenase inhibitors

Oxidative stress is one of the main causes of significant severe diseases. The discovery of new potent antioxidants with high efficiency and low toxicity is a great demand in the field of medicinal chemistry. Herein, we report the design, synthesis molecular modelling and biological evaluation of novel hybrids containing pyrazole, naphthalene and pyrazoline/isoxazoline moiety. Chalcones 2a–e were synthesized efficiently and were used as starting materials for synthesis of a variety of heterocycles. A novel series of pyrazoline 3a–e, phenylpyrazoline 4a–e, isoxazoline 5a–e and pyrazoline carbothioamide derivatives 6a–e were synthesized and screened for in vitro antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH), nitric oxide (NO) and superoxide radical scavenging assay as well as 15-lipoxygenase (15-LOX) inhibition activity. Compounds 3a, 4e, 5b, 5c, 6a, 6c, and 6e showed excellent radical scavenging activity in all three methods in comparison with ascorbic acid and 15-LOX inhibition potency using quercetin as standard then were subjected to in vivo study. Catalase (CAT) activity, glutathione (GSH) and malondialdehyde (MDA) levels were assayed in liver of treated rats. Compounds 5b, 5c, and 6e showed significant in vivo antioxidant potentials compared to control group at dose of 100 mg/kg B.W. Molecular docking of compound 6a endorsed its proper binding at the active site pocket of the human 15-LOX which explains its potent antioxidant activity in comparison with standard ascorbic acid.

Enhanced 15-Lipoxygenase 1 Production is Related to Periostin Expression and Eosinophil Recruitment in Eosinophilic Chronic Rhinosinusitis

BACKGROUND

The pathological features of chronic rhinosinusitis (CRS) with nasal polyps (CRSwNP) tissues include an eosinophilic infiltration pattern (eosinophilic CRS (ECRS)) or a less eosinophilic pattern (non-ECRS). Recently, it has been suggested that 15-lipoxygenase 1 (15-LOX-1) may have significant roles in allergic disease; however, the significance of 15-LOX-1 in CRS is not well understood. The objective of this study was to demonstrate the expression of 15-LOX-1 in CRS.

METHODS

The mRNA expression levels of 15-LOX-1 and periostin in nasal tissues were measured by quantitative real-time polymerase chain reaction. We also performed an immunofluorescence study of nasal tissues. Cells of the Eol-1 eosinophilic leukemic cell line were stimulated with interleukin-33 to test the induction of 15-LOX-1.

RESULTS

The expression level of 15-LOX-1 mRNA in nasal polyps (NPs) was significantly higher in ECRS patients than in non-ECRS patients. The immunofluorescence study revealed that both airway epithelial cells and eosinophils in NPs expressed 15-LOX-1. A significant correlation was seen between the number of eosinophils and the mRNA expression levels of 15-LOX-1 and periostin in nasal polyps. Moreover, interleukin-33 enhanced 15-LOX-1 expression in Eol-1 cells.

CONCLUSIONS

15-LOX-1 was shown to be a significant molecule that facilitates eosinophilic inflammation in ECRS.

Role of oxylipins generated from dietary PUFAs in the modulation of endothelial cell function

Oxylipins, which are circulating bioactive lipids generated from polyunsaturated fatty acids (PUFAs) by cyclooxygenase, lipooxygenase and cytochrome P450 enzymes, have diverse effects on endothelial cells. Although studies of the effects of oxylipins on endothelial cell function are accumulating, a review that provides a comprehensive compilation of current knowledge and recent advances in the context of vascular homeostasis is lacking. This is the first compilation of the various in vitro, ex vivo and in vivo reports to examine the effects and potential mechanisms of action of oxylipins on endothelial cells. The aggregate data indicate docosahexaenoic acid-derived oxylipins consistently show beneficial effects related to key endothelial cell functions, whereas oxylipins derived from other PUFAs exhibit both positive and negative effects. Furthermore, information is lacking for certain oxylipin classes, such as those derived from α-linolenic acid, which suggests additional studies are required to achieve a full understanding of how oxylipins affect endothelial cells.

The enzymology of human eicosanoid pathways: the lipoxygenase branches

Eicosanoids are short-lived derivatives of polyunsaturated fatty acids that serve as autocrine and paracrine signaling molecules. They are involved numerous biological processes of both the well state and disease states. A thorough understanding of the progression the disease state and homeostasis of the well state requires a complete evaluation of the systems involved. This review examines the enzymology for the enzymes involved in the production of eicosanoids along the lipoxygenase branches of the eicosanoid pathways with particular emphasis on those derived from arachidonic acid. The enzymatic parameters, protocols to measure them, and proposed catalytic mechanisms are presented in detail.

Non-targeted and targeted analysis of oxylipins in combination with charge-switch derivatization by ion mobility high-resolution mass spectrometry

Eicosanoids and other oxylipins play an important role in mediating inflammation as well as other biological processes. For the investigation of their biological role(s), comprehensive analytical methods are necessary, which are able to provide reliable identification and quantification of these compounds in biological matrices. Using charge-switch derivatization with AMPP (N-(4-aminomethylphenyl)pyridinium chloride) in combination with liquid chromatography ion mobility quadrupole time-of-flight mass spectrometry (LC-IM-QTOF-MS), we developed a non-target approach to analyze oxylipins in plasma, serum, and cells. The developed workflow makes use of an ion mobility resolved fragmentation to pinpoint derivatized molecules based on the cleavage of AMPP, which yields two specific fragment ions. This allows a reliable identification of known and unknown eicosanoids and other oxylipins. We characterized the workflow using 52 different oxylipins and investigated their fragmentation patterns and ion mobilities. Limits of detection ranged between 0.2 and 10.0 nM (1.0-50 pg on column), which is comparable with other state-of-the-art methods using LC triple quadrupole (QqQ) MS. Moreover, we applied this strategy to analyze oxylipins in different biologically relevant matrices, as cultured cells, human plasma, and serum. Graphical abstract.

Importance of the Role of ω-3 and ω-6 Polyunsaturated Fatty Acids in the Progression of Brain Cancer

Brain cancer is one of the most malignant types of cancer in both children and adults. Brain cancer patients tend to have a poor prognosis and a high rate of mortality. Additionally, 20-40% of all other types of cancer can develop brain metastasis. Numerous pieces of evidence suggest that omega-3-polyunsaturated fatty acids (ω-PUFAs) could potentially be used in the prevention and therapy of several types of cancer. PUFAs and oxylipins are fundamental in preserving physiological events in the nervous system; it is, therefore, necessary to maintain a certain ratio of ω-3 to ω-6 for normal nervous system function. Alterations in PUFAs signaling are involved in the development of various pathologies of the nervous system, including cancer. It is well established that an omega-6-polyunsaturated fatty acid (ω-6 PUFA)-rich diet has a pro-tumoral effect, whereas the consumption of an ω-3 rich diet has an anti-tumoral effect. This review aims to offer a better understanding of brain cancer and PUFAs and to discuss the role and impact of PUFAs on the development of different types of brain cancer. Considering the difficulty of antitumor drugs in crossing the blood-brain barrier, the therapeutic role of ω-3/ω-6 PUFAs against brain cancer would be a good alternative to consider. We highlight our current understanding of the role of PUFAs and its metabolites (oxylipins) in different brain tumors, proliferation, apoptosis, invasion, angiogenesis, and immunosuppression by focusing on recent research in vitro and in vivo.

Human health benefits of very-long-chain polyunsaturated fatty acids from microalgae

Microalgae are single-cell, photosynthetic organisms whose biodiversity places them at the forefront of biological producers of high-value molecules including lipids and pigments. Some of these organisms particular are capable of synthesizing n-3 very long chain polyunsaturated fatty acids (VLC-PUFAs), known to have beneficial effects on human health. Indeed, VLC-PUFAs are the precursors of many signaling molecules in humans involved in the complexities of inflammatory processes. This mini-review provides an inventory of knowledge on the synthesis of VLC-PUFAs in microalgae and on the diversity of signaling molecules (prostanoids, leukotrienes, SPMs, EFOX, isoprostanoids) that arise in humans from VLC-PUFAs.

Synthesis and function of fatty acids and oxylipins, with a focus on Caenorhabditis elegans

Polyunsaturated fatty acids (PUFAs) exhibit a diverse range of important biological functions in most biological systems. These PUFAs can be oxygenated via enzymatic or free radical-mediated reactions to form bioactive oxygenated lipid mediators termed oxylipins. Eicosanoids are broad class of oxylipins that are transient and locally synthesized signalling molecules, including prostaglandins, leukotrienes, lipoxins and thromboxanes, which mediate various physiological responses, such as inflammation. In addition to arachidonic acid-derived eicosanoids, current developments in lipidomic methodologies have brought attention to vast number of oxylipins produced from other PUFAs, including omega-3. Although, the molecular mechanisms of how PUFAs and oxylipins contribute to majority of the fundamental biological processes are largely unclear, a model organism Caenorhabditis elegans remains a powerful model for exploring lipid metabolism and functions of PUFAs and oxylipins. For instance, the ability of C. elegans to modify fatty acid composition with dietary supplementation and genetic manipulation enables the dissection of the roles of omega-3 and omega-6 PUFAs in many biological processes that include aging, reproduction, and neurobiology. However, much remains to be elucidated concerning the roles of oxylipins, but thus far, C. elegans is well-known for the synthesis of vast set of cytochrome (CYP) eicosanoids. These CYP eicosanoids are extremely susceptible to changes in the relative bioavailability of the different PUFAs, thus providing a better insight into complex mechanisms connecting essential dietary fatty acids to various biological processes. Therefore, this review provides an overview of the synthesis and function of PUFAs and oxylipins in mammals. It also focusses on what is known regarding the production of PUFAs and oxylipins in C. elegans and their functions.

The Biosynthesis of Enzymatically Oxidized Lipids

Enzymatically oxidized lipids are a specific group of biomolecules that function as key signaling mediators and hormones, regulating various cellular and physiological processes from metabolism and cell death to inflammation and the immune response. They are broadly categorized as either polyunsaturated fatty acid (PUFA) containing (free acid oxygenated PUFA "oxylipins", endocannabinoids, oxidized phospholipids) or cholesterol derivatives (oxysterols, steroid hormones, and bile acids). Their biosynthesis is accomplished by families of enzymes that include lipoxygenases (LOX), cyclooxygenases (COX), cytochrome P450s (CYP), and aldo-keto reductases (AKR). In contrast, non-enzymatically oxidized lipids are produced by uncontrolled oxidation and are broadly considered to be harmful. Here, we provide an overview of the biochemistry and enzymology of LOXs, COXs, CYPs, and AKRs in humans. Next, we present biosynthetic pathways for oxylipins, oxidized phospholipids, oxysterols, bile acids and steroid hormones. Last, we address gaps in knowledge and suggest directions for future work.

Mechanistic Links Between Obesity, Diabetes, and Blood Pressure: Role of Perivascular Adipose Tissue

Obesity is increasingly prevalent and is associated with substantial cardiovascular risk. Adipose tissue distribution and morphology play a key role in determining the degree of adverse effects, and a key factor in the disease process appears to be the inflammatory cell population in adipose tissue. Healthy adipose tissue secretes a number of vasoactive adipokines and anti-inflammatory cytokines, and changes to this secretory profile will contribute to pathogenesis in obesity. In this review, we discuss the links between adipokine dysregulation and the development of hypertension and diabetes and explore the potential for manipulating adipose tissue morphology and its immune cell population to improve cardiovascular health in obesity.