Role of basic science in the development of new medicines: examples from the eicosanoid field

Brown Adipose Tissue Activation in Humans Increases Plasma Levels of Lipid Mediators

CONTEXT

Activation of brown adipose tissue (BAT) thermogenesis improves insulin sensitivity and is beneficial in obesity. Emerging evidence indicates that BAT activation increases lipid mediators that play autocrine and endocrine roles to regulate metabolism and inflammation.

OBJECTIVE

The goal of the study was to determine the relationship between 2 distinct approaches of BAT activation (cold exposure and mirabegron treatment) with lipid mediators in humans.

METHODS

Healthy female subjects (n = 14) were treated with the β3-adrenergic receptor agonist mirabegron (100 mg) daily for 28 days. A subset of female subjects (n = 8) was additionally exposed to cold temperatures (14-16 °C) for 2 hours using a cooling vest prior to initiating mirabegron treatment. A panel of lipid mediators was assessed in plasma using targeted liquid chromatography-tandem mass spectrometry, and their relationship to anthropometric and metabolic parameters was determined.

RESULTS

Activation of BAT with cold exposure acutely increased levels of lipoxygenase and cyclooxygenase products, including 12-hydroxyeicosapentaenoic acid, 12-hydroxyeicosatetraenoic acid (HETE), 5-HETE, 14-hydroxydocosahexaenoic acid (HDHA), an isomer of maresin 2 (MaR2), 17-HDHA, protectin D1 (PD1), and prostaglandin E2. Mirabegron treatment similarly increased these products acutely, although levels of some mediators were blunted after chronic mirabegron treatment. Selected lipid mediators, including an MaR2 isomer, 17-HDHA, 5-HETE, and 15-HETE, positively correlated with nonesterified fatty acids and negatively correlated with the respiratory quotient, while PD1, 15-HETE, and 5-HETE positively correlated with adiponectin.

CONCLUSION

These results indicate that selected lipid mediators may serve as biomarkers of BAT activation.

The Past and Future of Inflammation as a Target to Cancer Prevention

Inflammation is an essential defense mechanism in which innate immune cells are coordinately activated on encounter of harmful stimuli, including pathogens, tissue injury, and toxic compounds and metabolites to neutralize and eliminate the instigator and initiate healing and regeneration. Properly terminated inflammation is vital to health, but uncontrolled runaway inflammation that becomes chronic begets a variety of inflammatory and metabolic diseases and increases cancer risk. Making damaged tissues behave as "wounds that do not heal" and sustaining the production of growth factors whose physiologic function is tissue healing, chronic inflammation accelerates cancer emergence from premalignant lesions. In 1863, Rudolf Virchow, a leading German pathologist, suggested a possible association between inflammation and tumor formation, but it took another 140 years to fully elucidate and appreciate the tumorigenic role of inflammation. Key findings outlined molecular events in the inflammatory cascade that promote cancer onset and progression and enabled a better appreciation of when and where inflammation should be inhibited. These efforts triggered ongoing research work to discover and develop inflammation-reducing chemopreventive strategies for decreasing cancer risk and incidence.

Stress-induced stenotic vascular remodeling via reduction of plasma omega-3 fatty acid metabolite 4-oxoDHA by noradrenaline

Stress has garnered significant attention as a prominent risk factor for inflammation-related diseases, particularly cardiovascular diseases (CVDs). However, the precise mechanisms underlying stress-driven CVDs remain elusive, thereby impeding the development of preventive and therapeutic strategies. To explore the correlation between plasma lipid metabolites and human depressive states, liquid chromatography-mass spectrometry (LC/MS) based analysis of plasma and the self-rating depression (SDS) scale questionnaire were employed. We also used a mouse model with restraint stress to study its effects on plasma lipid metabolites and stenotic vascular remodeling following carotid ligation. In vitro functional and mechanistic studies were performed using macrophages, endothelial cells, and neutrophil cells. We revealed a significant association between depressive state and reduced plasma levels of 4-oxoDHA, a specific omega-3 fatty acid metabolite biosynthesized by 5-lipoxygenase (LO), mainly in neutrophils. In mice, restraint stress decreased plasma 4-oxoDHA levels and exacerbated stenotic vascular remodeling, ameliorated by 4-oxoDHA supplementation. 4-oxoDHA enhanced Nrf2-HO-1 pathways, exerting anti-inflammatory effects on endothelial cells and macrophages. One of the stress hormones, noradrenaline, reduced 4-oxoDHA and the degraded 5-LO in neutrophils through the proteasome system, facilitated by dopamine D2-like receptor activation. Our study proposed circulating 4-oxoDHA levels as a stress biomarker and supplementation of 4-oxoDHA as a novel therapeutic approach for controlling stress-related vascular inflammation.

The biosynthetic pathways of the protectins

Evidence for the biosynthetic pathways of the specialized pro-resolving mediator (SPM) protectin D1 (PD1) and its biochemical further local metabolism were presented during the 8th European Workshop on Lipid Mediators, organized June 29th-July 1st, 2022, in Stockholm, Sweden. Herein, we provide an extended and detailed discussion of these topics. PD1, one of 43 SPMs reported so far, exhibits very potent pro-resolution and anti-inflammatory bioactions. Many research groups worldwide have confirmed these and other interesting bioactions. The protectins constitute, together with the lipoxins, resolvins, and maresins, the four individual SPM families, which have received a great interest in basic biomedical research and drug discovery efforts.

Immunomodulation of periodontitis with SPMs

Inflammation is a critical component in the pathophysiology of numerous disease processes, with most therapeutic modalities focusing on its inhibition in order to achieve treatment outcomes. The resolution of inflammation is a separate, distinct pathway that entails the reversal of the inflammatory process to a state of homoeostasis rather than selective inhibition of specific components of the inflammatory cascade. The discovery of specialized pro-resolving mediators (SPMs) resulted in a paradigm shift in our understanding of disease etiopathology. Periodontal disease, traditionally considered as one of microbial etiology, is now understood to be an inflammation-driven process associated with dysbiosis of the oral microbiome that may be modulated with SPMs to achieve therapeutic benefit.

Roles of systemic inflammatory and metabolic responses in the pathophysiology of acute-on-chronic liver failure

Acute-on-chronic liver failure (ACLF) is the most severe form of acutely decompensated cirrhosis and is characterised by the presence of one or more organ failures, intense systemic inflammation, peripheral blood lymphopenia, and a high risk of death without liver transplantation within 28 days. Herein, we propose the hypothesis that intense systemic inflammation may lead to organ failures through five different non-mutually exclusive mechanisms. First, pathogen-associated molecular patterns and inflammatory mediators (i.e. cytokines and lipid mediators) stimulate the production of the vasorelaxant nitric oxide in the walls of splanchnic arterioles, leading to enhanced splanchnic and systemic vasodilation which, in turn, induces enhanced activity of endogenous vasoconstrictor systems causing renal vasoconstriction and acute kidney injury. Second, neutrophils that reach the systemic circulation are prone to adhere to the vascular endothelium. Cytokines and lipid mediators act on the endothelium in microvessels of vital organs, an effect that favours the migration of neutrophils (and probably other leukocytes) to surrounding tissues where neutrophils can cause tissue damage and thereby contribute to organ failure. Third, cytokines and lipid mediators promote the formation of microthrombi that impair microcirculation and tissue oxygenation. Fourth, acute inflammation stimulates intense peripheral catabolism of amino acids whose products may be metabotoxins that contribute to hepatic encephalopathy. Fifth, acute inflammatory responses, which include the production of a broad variety of biomolecules (proteins and lipids), and an increase in biomass (i.e., granulopoiesis requiring de novo nucleotide synthesis), among others, are energetically expensive processes that require large amounts of nutrients. Therefore, immunity competes with other maintenance programmes for energy. The brain stem integrates the energy demand of each organ system, with immunity considered a top priority. The brain stem may "decide" to make a trade-off which involves the induction of a dormancy programme that permits the shutdown of mitochondrial respiration and oxidative phosphorylation in peripheral organs. In the context of acutely decompensated cirrhosis, the consequence of a shutdown of mitochondrial respiration and ATP production would be a dramatic decrease in organ function.

Gi/o GPCRs drive the formation of actin-rich tunneling nanotubes in cancer cells via a Gβγ/PKCα/FARP1/Cdc42 axis

The functional association between stimulation of G-protein-coupled receptors (GPCRs) by eicosanoids and actin cytoskeleton reorganization remains largely unexplored. Using a model of human adrenocortical cancer cells, here we established that activation of the GPCR OXER1 by its natural agonist, the eicosanoid 5-oxo-eicosatetraenoic acid, leads to the formation of filopodia-like elongated projections connecting adjacent cells, known as tunneling nanotube (TNT)-like structures. This effect is reduced by pertussis toxin and GUE1654, a biased antagonist for the Gβγ pathway downstream of OXER1 activation. We also observed pertussis toxin-dependent TNT biogenesis in response to lysophosphatidic acid, indicative of a general response driven by Gi/o-coupled GPCRs. TNT generation by either 5-oxo-eicosatetraenoic acid or lysophosphatidic acid is partially dependent on the transactivation of the epidermal growth factor receptor and impaired by phosphoinositide 3-kinase inhibition. Subsequent signaling analysis reveals a strict requirement of phospholipase C β3 and its downstream effector protein kinase Cα. Consistent with the established role of Rho small GTPases in the formation of actin-rich projecting structures, we identified the phosphoinositide 3-kinase-regulated guanine nucleotide exchange factor FARP1 as a GPCR effector essential for TNT formation, acting via Cdc42. Altogether, our study pioneers a link between Gi/o-coupled GPCRs and TNT development and sheds light into the intricate signaling pathways governing the generation of specialized actin-rich elongated structures in response to bioactive signaling lipids.

Stereochemistry and functions of the new cysteinyl-resolvin, 4S,5R-RCTR1, in efferocytosis and erythrophagocytosis of human senescent erythrocytes

Specialized pro-resolving lipid mediators play key functions in the resolution of the acute inflammatory response. Herein, we elucidate the stereochemical structure of the new 4S,5R-RCTR1, a cysteinyl-resolvin, recently uncovered in human leukocytes incubated with a 4S,5S-epoxy-resolvin intermediate, using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and ultra-violet (UV) spectrophotometry. With this approach, the physical properties of the new mediator prepared by total organic synthesis were matched to enzymatically produced biogenic material. In addition, we confirmed the potent biological actions of 4S,5R-RCTR1 with human M2-like macrophage phagocytosis of live bacteria, efferocytosis of apoptotic neutrophils, and erythrophagocytosis of senescent human red blood cells in a concentration-dependent manner from 0.1 to 10 nM. Taken together, these results establish the complete stereochemistry of 4S,5R-RCTR1 as 5R-glutathionyl-4S,17S-dihydroxy-6E,8E,10Z,13Z,15E,19Z-docosahexaenoic acid and give evidence of its novel bioactivities in human phagocyte responses. Moreover, they confirm and extend the stereoselective functions of the 4S,5R-RCTR1 with isolated human phagocytes of interest in the resolution of inflammation.

Protectins: Their biosynthesis, metabolism and structure-functions

Several lipoxygenase enzymes and cyclooxygenase-2 stereoselectively convert the polyunsaturated fatty acids arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and n-3 docosapentaenoic acid into numerous oxygenated products. Biosynthetic pathway studies have shown, during the resolution phase of acute inflammation, that distinct families of endogenous products are formed. These products were named specialized pro-resolving mediators, given their specialized functions in the inflammation-resolution circuit, enhancing the return of inflamed and injured tissue to homeostasis. The lipoxins, resolvins, protectins and maresins, together with the sulfido-conjugates of the resolvins, protectins and maresins, constitute the four individual families of these local mediators. When administrated in vivo in a wide range of human disease models, the specialized pro-resolving mediators display potent bioactions. The detailed and individual biosynthetic steps constituting the biochemical pathways, the metabolism, recent reports on structure-function studies and pharmacodynamic data of the protectins, are presented herein. Emphasis is on the structure-function results on the recent members of the sulfido conjugated protectins and further metabolism of protectin D1. Moreover, the members of the individual families of specialized pro-resolving mediators and their biosynthetic precursor are presented. Today 43 specialized pro-resolving mediators possessing pro-resolution and anti-inflammatory bioactions are reported and confirmed, constituting a basis for resolution pharmacology. This emerging biomedical field provides a new approach for drug discovery, that is also discussed.

Prostanoid Metabolites as Biomarkers in Human Disease

Prostaglandins (PGD₂, PGE₂, PGF_2α), prostacyclin (PGI₂), and thromboxane A₂ (TXA₂) together form the prostanoid family of lipid mediators. As autacoids, these five primary prostanoids propagate intercellular signals and are involved in many physiological processes. Furthermore, alterations in their biosynthesis accompany a wide range of pathological conditions, which leads to substantially increased local levels during disease. Primary prostanoids are chemically instable and rapidly metabolized. Their metabolites are more stable, integrate the local production on a systemic level, and their analysis in various biological matrices yields valuable information under different pathological settings. Therefore, prostanoid metabolites may be used as diagnostic, predictive, or prognostic biomarkers in human disease. Although their potential as biomarkers is great and extensive research has identified major prostanoid metabolites that serve as target analytes in different biofluids, the number of studies that correlate prostanoid metabolite levels to disease outcome is still limited. We review the metabolism of primary prostanoids in humans, summarize the levels of prostanoid metabolites in healthy subjects, and highlight existing biomarker studies. Since analysis of prostanoid metabolites is challenging because of ongoing metabolism and limited half-lives, an emphasis of this review lies on the reliable measurement and interpretation of obtained levels.

Targeting chronic inflammation as a potential adjuvant therapy for osteoporosis

Systemic, chronic, low-grade inflammation (SCLGI) underlies the pathogenesis of various widespread diseases. It is often associated with bone loss, thus connecting chronic inflammation to the pathogenesis of osteoporosis. In postmenopausal women, osteoporosis is accompanied by SCLGI development, likely owing to estrogen deficiency. We propose that SCGLI persistence in osteoporosis results from failed inflammation resolution, which is mainly mediated by specialized, pro-resolving mediators (SPMs). In corroboration, SPMs demonstrate encouraging therapeutic effects in various preclinical models of inflammatory disorders, including bone pathology. Since numerous data implicate gut dysbiosis in osteoporosis-associated chronic inflammation, restoring balanced microbiota by supplementing probiotics and prebiotics could contribute to the efficient resolution of SCGLI. In the present review, we provide evidence for this hypothesis and argue that efficient SCGLI resolution may serve as a novel approach for treating osteoporosis, complementary to traditional anti-osteoporotic medications.

Patient Stratification in Sepsis: Using Metabolomics to Detect Clinical Phenotypes, Sub-Phenotypes and Therapeutic Response

Infections are common and need minimal treatment; however, occasionally, due to inappropriate immune response, they can develop into a life-threatening condition known as sepsis. Sepsis is a global concern with high morbidity and mortality. There has been little advancement in the treatment of sepsis, outside of antibiotics and supportive measures. Some of the difficulty in identifying novel therapies is the heterogeneity of the condition. Metabolic phenotyping has great potential for gaining understanding of this heterogeneity and how the metabolic fingerprints of patients with sepsis differ based on survival, organ dysfunction, disease severity, type of infection, treatment or causative organism. Moreover, metabolomics offers potential for patient stratification as metabolic profiles obtained from analytical platforms can reflect human individuality and phenotypic variation. This article reviews the most relevant metabolomic studies in sepsis and aims to provide an overview of the metabolic derangements in sepsis and how metabolic phenotyping has been used to identify sub-groups of patients with this condition. Finally, we consider the new avenues that metabolomics could open, exploring novel phenotypes and untangling the heterogeneity of sepsis, by looking at advances made in the field with other -omics technologies.

The Synthesis of 3-(R)- and 3-(S)-Hydroxyeicosapentaenoic Acid

Monohydroxylated polyunsaturated fatty acids belonging to the oxylipin class of natural products are present in marine and terrestrial sources as well as in the human body. Due to their biological activities and role in diverse biosynthetic pathways, oxylipins biosynthesized from eicosapentaenoic acid and arachidonic acid have attracted great interest from the scientific community. One example is 3-hydroxyeicosapentaenoic acid where the absolute configuration at C-3 has only been tentatively assigned. In this paper, studies on acetate type aldol reactions that enabled the preparation of 3-(R)-hydroxyeicosapentaenoic acid (3R-HETE, 2) and its enantiomer are presented.

Identification of IL-6 as a potential mediator of the myocardial fibrosis that occurs in response to surgery with cardiopulmonary bypass in children with Tetralogy of Fallot

BACKGROUND

Tetralogy of Fallot is a common CHD. Studies have shown a close link between heart failure and myocardial fibrosis. Interleukin-6 has been suggested to be a post-independent factor of heart failure. This study aimed to explore the relationship between IL-6 and myocardial fibrosis during cardiopulmonary bypass.

MATERIAL AND METHODS

We downloaded the expression profile dataset GSE132176 from Gene Expression Omnibus. After normalising the raw data, Gene Set Enrichment Analysis and differential gene expression analysis were performed using R. Further, a weighted gene correlation network analysis and a protein-protein interaction network analysis were used to identify HUB genes. Finally, we downloaded single-cell expression data for HUB genes using PanglaoDB.

RESULTS

There were 119 differentially expressed genes in right atrium tissues comparing the post-CPB group with the pre-CPB group. IL-6 was found to be significantly up-regulated in the post-CPB group. Six genes (JUN, FOS, ATF3, EGR1, IL-6, and PTGS2) were identified as HUB genes by a weighted gene correlation network analysis and a protein-protein interaction network analysis. Gene Set Enrichment Analysis showed that IL-6 affects the myocardium during CPB mainly through the JAK/STAT signalling pathway. Finally, we used PanglaoDB data to analyse the single-cell expression of the HUB genes.

CONCLUSION

Our findings suggest that high expression of IL-6 and the activation of the JAK/STAT signalling pathway during CPB maybe the potential mechanism of myocardial fibrosis. We speculate that the high expression of IL-6 might be an important factor leading to heart failure after ToF surgery. We expect that these findings will provide a basis for the development of targeted drugs.

Dysregulation of prostaglandins, leukotrienes and lipoxin A4 in bronchiectasis

Introduction

Bronchiectasis is characterised by excessive neutrophilic inflammation. Lipid mediators such as prostaglandins and leukotrienes have crucial roles in the inflammatory response. Further characterisation of these lipids and understanding the interplay of anti-inflammatory and proinflammatory lipid mediators could lead to the development of novel anti-inflammatory therapies for bronchiectasis.

Aim

The aim of our study was to characterise the lipids obtained from serum and airways in patients with bronchiectasis in the stable state.

Methods

Six healthy volunteers, 10 patients with mild bronchiectasis, 15 with moderate bronchiectasis and 9 with severe bronchiectasis were recruited. All participants had 60 mL of blood taken and underwent a bronchoscopy while in the stable state. Lipidomics was done on serum and bronchoalveolar lavage fluid (BALF).

Results

In the stable state, in serum there were significantly higher levels of prostaglandin E₂ (PGE₂), 15-hydroxyeicosatetranoic acid (15-HETE) and leukotriene B₄ (LTB₄) in patients with moderate–severe disease compared with healthy volunteers. There was a significantly lower level of lipoxin A₄ (LXA₄) in severe bronchiectasis.

In BALF, there were significantly higher levels of PGE₂, 5-HETE, 15-HETE, 9-hydroxyoctadecadienoic acid and LTB₄ in moderate–severe patients compared with healthy volunteers.

In the stable state, there was a negative correlation of PGE₂ and LTB₄ with % predicted forced expiratory volume in 1 s and a positive correlation with antibiotic courses.

LXA₄ improved blood and airway neutrophil phagocytosis and bacterial killing in patients with bronchiectasis. Additionally LXA₄ reduced neutrophil activation and degranulation.

Conclusion

There is a dysregulation of lipid mediators in bronchiectasis with excess proinflammatory lipids. LXA₄ improves the function of reprogrammed neutrophils. The therapeutic efficacy of LXA₄ in bronchiectasis warrants further 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.

Longitudinal peripheral tissue RNA-Seq transcriptomic profiling, hyperalgesia, and wound healing in the rat plantar surgical incision model

Postoperative pain and delayed healing in surgical wounds, which require complex management strategies have understudied complicated mechanisms. Here we investigated temporal changes in behavior, tissue structure, and transcriptomic profiles in a rat model of a surgical incision, using hyperalgesic behavioral tests, histological analyses, and next‐generation RNA sequencing, respectively. The most rapidly (1 hour) expressed genes were the chemokines, Cxcl1 and Cxcl2. Consequently, infiltrating leukocytes were abundantly observed starting at 6 and peaking at 24 hours after incising which was supported by histological analysis and appearance of the neutrophil markers, S100a8 and S100a9. At this time, hyperalgesia was at a peak and overall transcriptional activity was most highly activated. At the 1‐day timepoint, Nppb, coding for natriuretic peptide precursor B, was the most strongly upregulated gene and was localized by in situ hybridization to the epidermal keratinocytes at the margins of the incision. Nppb was basically unaffected in a peripheral inflammation model transcriptomic dataset. At the late phase of wound healing, five secreted, incision‐specific peptidases, Mmp2, Aebp1, Mmp23, Adamts7, and Adamtsl1, showed increased expression, supporting the idea of a sustained tissue remodeling process. Transcripts that are specifically upregulated at each timepoint in the incision model may be potential candidates for either biomarkers or therapeutic targets for wound pain and wound healing. This study incorporates the examination of longitudinal temporal molecular responses, corresponding anatomical localization, and hyperalgesic behavioral alterations in the surgical incision model that together provide important and novel foundational knowledge to understand mechanisms of wound pain and wound healing.

Myeloid cell diversification during regenerative inflammation: Lessons from skeletal muscle

Understanding the mechanisms of tissue and organ regeneration in adult animals and humans is of great interest from a basic biology as well as a medical, therapeutical point of view. It is increasingly clear that the relatively limited ability to regenerate tissues and organs in mammals as oppose to lower vertebrates is the consequence of evolutionary trade-offs and changes during development and aging. Thus, the coordinated interaction of the immune system, particularly the innate part of it, and the injured, degenerated parenchymal tissues such as skeletal muscle, liver, lung, or kidney shape physiological and also pathological processes. In this review, we provide an overview of how morphologically and functionally complete (ad integrum) regeneration is achieved using skeletal muscle as a model. We will review recent advances about the differentiation, activation, and subtype specification of circulating monocyte to resolution or repair-type macrophages during the process we term regenerative inflammation, resulting in complete restoration of skeletal muscle in murine models of toxin-induced injury.

Regression of human coronary artery plaque is associated with a high ratio of (18-hydroxy-eicosapentaenoic acid + resolvin E1) to leukotriene B4

Inflammation in arterial walls leads to coronary artery disease (CAD). We previously reported that a high omega-3 fatty index was associated with prevention of progression of coronary atherosclerosis, a disease of chronic inflammation in the arterial wall. However, the mechanism of such benefit is unclear. The two main omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are precursors of specialized pro-resolving lipid mediators (SPMs)-resolvins and maresins-which actively resolve chronic inflammation. To explore whether SPMs are associated with coronary plaque progression, levels of SPMs and proinflammatory mediators (leukotriene B₄ [LTB₄ ] and prostaglandins) were measured using liquid chromatography-tandem mass spectrometry in 31 statin-treated patients with stable CAD randomized to either EPA and DHA, 3.36 g daily, or no EPA/DHA (control). Coronary plaque volume was measured by coronary computed tomographic angiography at baseline and at 30-month follow-up. Higher plasma levels of EPA+DHA were associated with significantly increased levels of two SPMs-resolvin E1 and maresin 1-and 18-hydroxy-eicosapentaenoic acid (HEPE), the precursor of resolvin E1. Those with low plasma EPA+DHA levels had a low (18-HEPE+resolvin E1)/LTB₄ ratio and significant plaque progression. Those with high plasma EPA+DHA levels had either low (18-HEPE+resolvin E1)/LTB₄ ratios with significant plaque progression or high (18-HEPE+resolvin E1)/LTB₄ ratios with significant plaque regression. These findings suggest that an imbalance between pro-resolving and proinflammatory lipid mediators is associated with plaque progression and potentially mediates the beneficial effects of EPA and DHA in CAD patients.

Cysteinyl-specialized proresolving mediators link resolution of infectious inflammation and tissue regeneration via TRAF3 activation

The recently elucidated proresolving conjugates in tissue regeneration (CTR) maresin-CTR (MCTR), protectin-CTR (PCTR), and resolvin-CTR (RCTR), termed cysteinyl-specialized proresolving mediators (cys-SPMs) each promotes regeneration, controls infection, and accelerates resolution of inflammation. Here, we sought evidence for cys-SPM activation of primordial pathways in planaria (Dugesia japonica) regeneration that might link resolution of inflammation and regeneration. On surgical resection, planaria regeneration was enhanced with MCTR3, PCTR3, or RCTR3 (10 nM), each used for RNA sequencing. The three cys-SPMs shared up-regulation of 175 known transcripts with fold-change > 1.25 and combined false discovery rate (FDR) < 0.002, and 199 canonical pathways (FDR < 0.25), including NF-κB pathways and an ortholog of human TRAF3 (TNFR-associated factor 3). Three separate pathway analyses converged on TRAF3 up-regulation by cys-SPMs. With human macrophages, three cys-SPMs each dose-dependently increased TRAF3 expression in a cAMP-PKA-dependent manner. TRAF3 overexpression in macrophages enhanced Interleukin-10 (IL-10) and phagocytosis of Escherichia coli IL-10 also increased phagocytosis in a dose-dependent manner. Silencing of mouse TRAF3 in vivo significantly reduced IL-10 and macrophage phagocytosis. TRAF3 silencing in vivo also relieved cys-SPMs' actions in limiting polymorphonuclear neutrophil in E. coli exudates. These results identify cys-SPM-regulated pathways in planaria regeneration, uncovering a role for TRAF3/IL-10 in regulating mammalian phagocyte functions in resolution. Cys-SPM activation of TRAF3 signaling is a molecular component of both regeneration and resolution of infectious inflammation.

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.

The need for precision nutrition, genetic variation and resolution in Covid-19 patients

The health of the individual and the population in general is the result of interaction between genetics and various environmental factors, of which diet/nutrition is the most important. The focus of this paper is on the association of high n-6 PUFA or low n-3 PUFA due to genetic variation and/or dietary intake, with changes in specialized pro-resolving mediators (SPMs), cytokine storm, inflammation-resolution and Covid-19. Human beings evolved on a diet that was balanced in the n-6 and n-3 essential fatty acids with a ratio of n-6/n-3 of 1-2/1 whereas today this ratio is 16/1. Such a high ratio due to high amounts of n-6 fatty acids leads to a prothrombotic and proinflammatory state and is associated with obesity, diabetes, cardiovascular disease, and some forms of cancer. In addition to the high intake of n-6 fatty acids that increases inflammation there is genetic variation in the biosynthesis of n-6 linoleic acid (LA) to arachidonic acid (ARA) and of linolenic (ALA) to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Present day humans have two common FADS haplotypes that differ dramatically in their ability to generate long-chain fatty acids. The more efficient, evolutionary derived haplotype increases the efficiency of synthesizing essential long-chain fatty acids from precursors and could have provided an advantage in environments with limited access to dietary long-chain fatty acids ARA, EPA and DHA. In the modern world this haplotype has been associated with lifestyle-related diseases, such as cardiovascular disease, obesity, diabetes, all of which are characterized by increased levels of inflammation. African Americans and Latino populations have increased susceptibility and higher death rates from SARS-CoV-2 than whites. These populations are characterized by increased numbers of persons (about 80%) that are fast metabolizers, leading to increased production of ARA, as well as poor intake of fruits and vegetables. The combinations of fast metabolism and high n-6 intake increases their inflammatory status and possibly susceptibility of SARS-CoV-2. In vitro and human studies indicate that the specialized pro-resolving mediators (SPM) produced from the n-3, EPA and DHA influence the resolution of inflammation, allowing the tissues to return to function and homeostasis. The SPMs each counter-regulate cytokine storms, as well as proinflammatory lipid mediators via NFκB and inflammasome down regulation and reduce the proinflammatory eicosanoids produced from ARA. The nutritional availability of dietary n-3 fatty acids from marine oils enriched with SPM intermediate precursors, along with increasing local biosynthesis of SPMs to functional concentrations may be an approach of value during SARS-CoV2 infections, as well as in prevention, and shortening their recovery from infections. It is evident that populations differ in their genetic variants and their frequencies and their interactions with the food they eat. Gene-nutrient interactions is a very important area of study that provides specific dietary advice for individuals and subgroups within a population in the form of Precision Nutrition. Nutritional science needs to focus on Precision Nutrition, genetic variants in the population and a food supply composed of Nutrients that have been part of our diet throughout evolution, which is the diet that our genes are programmed to respond.

LimeMap: a comprehensive map of lipid mediator metabolic pathways

Lipid mediators are major factors in multiple biological functions and are strongly associated with disease. Recent lipidomics approaches have made it possible to analyze multiple metabolites and the associations of individual lipid mediators. Such systematic approaches have enabled us to identify key changes of biological relevance. Against this background, a knowledge-based pathway map of lipid mediators would be useful to visualize and understand the overall interactions of these factors. Here, we have built a precise map of lipid mediator metabolic pathways (LimeMap) to visualize the comprehensive profiles of lipid mediators that change dynamically in various disorders. We constructed the map by focusing on ω-3 and ω-6 fatty acid metabolites and their respective metabolic pathways, with manual curation of referenced information from public databases and relevant studies. Ultimately, LimeMap comprises 282 factors (222 mediators, and 60 enzymes, receptors, and ion channels) and 279 reactions derived from 102 related studies. Users will be able to modify the map and visualize measured data specific to their purposes using CellDesigner and VANTED software. We expect that LimeMap will contribute to elucidating the comprehensive functional relationships and pathways of lipid mediators.

The key contribution of platelet and vascular arachidonic acid metabolism to the pathophysiology of atherothrombosis

Arachidonic acid is one of the most abundant and ubiquitous ω-6 polyunsaturated fatty acid, present in esterified form in the membrane phospholipids of all mammalian cells and released from phospholipids by several phospholipases in response to various activating or inhibitory stimuli. Arachidonic acid is the precursor of a large number of enzymatically and non-enzymatically derived, biologically active autacoids, including prostaglandins (PGs), thromboxane (TX) A2, leukotrienes, and epoxyeicosatetraenoic acids (collectively called eicosanoids), endocannabinoids and isoprostanes, respectively. Eicosanoids are local modulators of the physiological functions and pathophysiological roles of blood vessels and platelets. For example, the importance of cyclooxygenase (COX)-1-derived TXA2 from activated platelets in contributing to primary haemostasis and atherothrombosis is demonstrated in animal and human models by the bleeding complications and cardioprotective effects associated with low-dose aspirin, a selective inhibitor of platelet COX-1. The relevance of vascular COX-2-derived prostacyclin (PGI2) in endothelial thromboresistance and atheroprotection is clearly shown by animal and human models and by the adverse cardiovascular effects exerted by COX-2 inhibitors in humans. A vast array of arachidonic acid-transforming enzymes, downstream synthases and isomerases, transmembrane receptors, and specificity in their tissue expression make arachidonic acid metabolism a fine-tuning system of vascular health and disease. Its pharmacological regulation is central in human cardiovascular diseases, as demonstrated by biochemical measurements and intervention trials.

Chronic Inflammation in PCOS: The Potential Benefits of Specialized Pro-Resolving Lipid Mediators (SPMs) in the Improvement of the Resolutive Response

PCOS as the most common endocrine disorder of women in their reproductive age affects between 5–15% of the female population. Apart from its cardinal symptoms, like irregular and anovulatory cycles, hyperandrogenemia and a typical ultrasound feature of the ovary, obesity, and insulin resistance are often associated with the disease. Furthermore, PCOS represents a status of chronic inflammation with permanently elevated levels of inflammatory markers including IL-6 and IL-18, TNF-α, and CRP. Inflammation, as discovered only recently, consists of two processes occurring concomitantly: active initiation, involving “classical” mediators including prostaglandins and leukotrienes, and active resolution processes based on the action of so-called specialized pro-resolving mediators (SPMs). These novel lipid mediator molecules derive from the essential ω3-poly-unsaturated fatty acids (PUFAs) DHA and EPA and are synthesized via specific intermediates. The role and benefits of SPMs in chronic inflammatory diseases like obesity, atherosclerosis, and Diabetes mellitus has become a subject of intense research during the last years and since PCOS features several of these pathologies, this review aims at summarizing potential roles of SPMs in this disease and their putative use as novel therapeutics.

The relationship between specialized pro-resolving lipid mediators, morbid obesity and weight loss after bariatric surgery

Obesity and diabetes are associated with chronic inflammation. Specialized pro-resolving lipid mediators (SPMs)—resolvins (Rv), protectins (PD) and maresins (MaR)—actively resolve inflammation. Bariatric surgery achieves remission of diabetes, but mechanisms are unclear. We measured SPMs and proinflammatory eicosanoid levels using liquid chromatography-tandem mass spectrometry in 29 morbidly obese subjects (13 with diabetes) and 15 nondiabetic, mildly obese subjects. Compared to the mildly obese, the morbidly obese had higher levels of SPMs—RvD3, RvD4 and PD1—and white blood cells (WBC) and platelets. Post-surgery, SPM and platelet levels decreased in morbidly obese nondiabetic subjects but not in diabetic subjects, suggesting continued inflammation. Despite similar weight reductions 1 year after surgery (44.6% vs. 46.6%), 8 diabetes remitters had significant reductions in WBC and platelet counts whereas five non-remitters did not. Remitters had a 58.2% decrease (p = 0.03) in 14-HDHA, a maresin pathway marker; non-remitters had an 875.7% increase in 14-HDHA but a 36.9% decrease in MaR1 to a median of 0. In conclusion, higher levels of RvD3, PD1 and their pathway marker, 17-HDHA, are markers of leukocyte activation and inflammation in morbid obesity and diabetes and diminish with weight loss in nondiabetic but not diabetic subjects, possibly representing sustained inflammation in the latter. Lack of diabetes remission after surgically-induced weight loss may be associated with reduced ability to produce MaR1 and sustained inflammation.

Blood pro-resolving mediators are linked with synovial pathology and are predictive of DMARD responsiveness in rheumatoid arthritis

Biomarkers are needed for predicting the effectiveness of disease modifying antirheumatic drugs (DMARDs). Here, using functional lipid mediator profiling and deeply phenotyped patients with early rheumatoid arthritis (RA), we observe that peripheral blood  specialized pro-resolving mediator (SPM) concentrations are linked with both DMARD responsiveness and disease pathotype. Machine learning analysis demonstrates that baseline plasma concentrations of resolvin D4, 10S, 17S-dihydroxy-docosapentaenoic acid, 15R-Lipoxin (LX)A4 and n-3 docosapentaenoic-derived Maresin 1 are predictive of DMARD responsiveness at 6 months. Assessment of circulating SPM concentrations 6-months after treatment initiation establishes that differences between responders and non-responders are maintained, with a decrease in SPM concentrations in patients resistant to DMARD therapy. These findings elucidate the potential utility of  plasma SPM concentrations as biomarkers of DMARD responsiveness in RA.

Pro resolving inflammatory effects of the lipid mediators of omega 3 fatty acids and its implication in SARS COVID-19

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SPMs are promising substances and suggest a clinical trial be initiated to test their ability to activate resolution of lung inflammation.

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SPMs could reduce tissue damage in COVID 19 patients to influence the cytokine storm.

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The focus could be in the adjuvant management or for the improvement and resolution of chronic lung and heart inflammation in the post-acute phase of this disease.

COVID-19 is a new disease caused by coronavirus SARS-CoV-2. It was first described in 2019, developed into an epidemic in January 2020 and has spread the global to the present COVID-19 pandemic. Specialized pro‑resolving mediators (SPMs) may play a new role in the management of this lung disease because SPM actively stimulate the resolution of infectious inflammation and are organ protective in animal disease models. Many tissues have been suitable targets for treating inflammation with SPMs or their active precursors 18-HEPE, 17-HDHA and the 14-HDHA, in order to elicit dynamic resolution of inflammation.

Here we discuss the possible mode of action of these substances in the management of SARS Covid 19.

PCTR1 ameliorates lipopolysaccharide-induced acute inflammation and multiple organ damage via regulation of linoleic acid metabolism by promoting FADS1/FASDS2/ELOV2 expression and reducing PLA2 expression

Gram-negative bacterial infection causes an excessive inflammatory response and acute organ damage or dysfunction due to its outer membrane component, lipopolysaccharide (LPS). Protectin conjugates in tissue regeneration 1 (PCTR1), an endogenous lipid mediator, exerts fundamental anti-inflammation and pro-resolution during infection. In the present study, we examined the properties of PCTR1 on the systemic inflammatory response, organic morphological damage and dysfunction, and serum metabolic biomarkers in an LPS-induced acute inflammatory mouse model. The results show that PCTR1 reduced serum inflammatory factors and ameliorated morphological damage and dysfunction of the lung, liver, kidney, and ultimately improved the survival rate of LPS-induced acute inflammation in mice. In addition, metabolomics analysis and high performance liquid chromatography-mass spectrometry revealed that LPS-stimulated serum linoleic acid (LA), arachidonic acid (AA), and prostaglandin E2 (PGE2) levels were significantly altered by PCTR1. Moreover, PCTR1 upregulated LPS-inhibited fatty acid desaturase 1 (FADS1), fatty acid desaturase 2 (FADS2), and elongase of very long chain fatty acids 2 (ELOVL2) expression, and downregulated LPS-stimulated phospholipase A2 (PLA2) expression to increase the intrahepatic content of AA. However, these effects of PCTR1 were partially abrogated by a lipoxin A4 receptor (ALX) antagonist (BOC-2). In summary, via the activation of ALX, PCTR1 promotes the conversion of LA to AA through upregulation of FADS1, FADS2, and ELOVL2 expression, and inhibits the conversion of bound AA into free AA through downregulation of PLA2 expression to decrease the serum AA and PGE2 levels.

An Update of Palmitoylethanolamide and Luteolin Effects in Preclinical and Clinical Studies of Neuroinflammatory Events

The inflammation process represents of a dynamic series of phenomena that manifest themselves with an intense vascular reaction. Neuroinflammation is a reply from the central nervous system (CNS) and the peripheral nervous system (PNS) to a changed homeostasis. There are two cell systems that mediate this process: the glia of the CNS and the lymphocites, monocytes, and macrophages of the hematopoietic system. In both the peripheral and central nervous systems, neuroinflammation plays an important role in the pathogenesis of neurodegenerative diseases, such as Parkinson’s and Alzheimer’s diseases, and in neuropsychiatric illnesses, such as depression and autism spectrum disorders. The resolution of neuroinflammation is a process that allows for inflamed tissues to return to homeostasis. In this process the important players are represented by lipid mediators. Among the naturally occurring lipid signaling molecules, a prominent role is played by the N-acylethanolamines, namely N-arachidonoylethanolamine and its congener N-palmitoylethanolamine, which is also named palmitoylethanolamide or PEA. PEA possesses a powerful neuroprotective and anti-inflammatory power but has no antioxidant effects per se. For this reason, its co-ultramicronization with the flavonoid luteolin is more efficacious than either molecule alone. Inhibiting or modulating the enzymatic breakdown of PEA represents a complementary therapeutic approach to treating neuroinflammation. The aim of this review is to discuss the role of ultramicronized PEA and co-ultramicronized PEA with luteolin in several neurological diseases using preclinical and clinical approaches.

Enzymatic studies with 3-oxa n-3 DPA

Cyclooxygenase-2 and several lipoxygenases convert polyunsaturated fatty acids into a large variety of products. During inflammatory processes, these enzymes form several distinct families of specialized pro-resolving lipid mediators possessing potent anti-inflammatory and pro-resolving effects. These mediators have attracted a great interest as leads in drug discovery and have recently been the subject of biosynthetic pathway studies using docosahexaenoic and n-3 docosapentaenoic acid as substrates. Herein we present enzymatic studies with cyclooxygenase-2 and 5-, 12- and 15-lipoxygenase enzymes using 3-oxa n-3 DPA as a synthetic mimic of n-3 docosapentaenoic acid. Structural elucidation based on data from RP-HPLC UV and LC/MS-MS experiments enabled the identification of novel enzymatically formed products. These findings constitute the basis for further biosynthetic studies towards understanding the mechanisms regulating substrate utilization in the biosynthesis of specialized pro-resolving lipid mediators.

Characterization of the first insect prostaglandin (PGE2) receptor: MansePGE2R is expressed in oenocytoids and lipoteichoic acid (LTA) increases transcript expression

In arthropods, eicosanoids derived from the oxygenated metabolism of arachidonic acid are significant in mediating immune responses. However, the lack of information about insect eicosanoid receptors is an obstacle to completely decipher immune mechanisms underlying both eicosanoid downstream signal cascades and their relationship to immune pathogen-associated molecular patterns (PAMPs). Here, we cloned and sequenced a G protein-coupled receptor (MW 46.16 kDa) from the model lepidopteran, Manduca sexta (Sphingidae). The receptor shares similarity of amino acid motifs to human prostaglandin E₂ (PGE₂) receptors, and phylogenetic analysis supports its classification as a prostaglandin receptor. In agreement, the recombinant receptor was activated by PGE₂ resulting in intracellular cAMP increase, and therefore designated MansePGE₂R. Expression of MansePGE₂R in Sf9 cells in which the endogenous orthologous receptor had been silenced showed similar cAMP increase upon PGE₂ challenge. Receptor transcript expression was identified in various tissues in larvae and female adults, including Malpighian tubules, fat body, gut and hemocytes, and in female ovaries. In addition to the cDNA cloned that encodes the functional receptor, an mRNA was found featuring the poly-A tail but lacking the predicted transmembrane (TM) regions 2 and 3, suggesting the possibility that internally deleted receptor proteins exist in insects. Immunocytochemistry and in situ hybridization revealed that among hemocytes, the receptor was exclusively localized in the oenocytoids. Larval immune challenges injecting bacterial components showed that lipoteichoic acid (LTA) increased MansePGE₂R expression in hemocytes. In contrast, injection of LPS or peptidoglycan did not increase MansePGE₂R transcript levels in hemocytes, suggesting the LTA-associated increase in receptor transcript is regulated through a distinct pathway. This study provides the first characterization of an eicosanoid receptor in insects, and paves the way for establishing the hierarchy in signaling steps required for establishing insect immune responses to infections.

Some Biogenetic Considerations Regarding the Marine Natural Product (-)-Mucosin

Recently, the identity of the marine hydrindane natural product (−)-mucosin was revised to the trans-fused structure 6, thereby providing a biogenetic puzzle that remains to be solved. We are now disseminating some of our insights with regard to the possible machinery delivering the established architecture. Aspects with regard to various modes of cyclization in terms of concerted versus stepwise processes are held up against the enzymatic apparatus known to be working on arachidonic acid (8). To provide a contrast to the tentative polyunsaturated fatty acid biogenesis, the structural pattern featured in (−)-mucosin (6) is compared to some marine hydrinane natural products of professed polyketide descent. Our appraisal points to a different origin and strengthens the hypothesis of a polyunsaturated fatty acids (PUFA) as the progenitor of (−)-mucosin (6).

Proresolving mediator profiles in cerebrospinal fluid are linked with disease severity and outcome in adults with tuberculous meningitis

Tuberculous meningitis (TBM) is the most lethal form of tuberculosis infection, characterized by a dysregulated immune response that frequently leads to neurologic injury and death despite the best available treatment. The mechanisms driving the inflammatory response in TBM are not well understood. To gain insights into these mechanisms, we used a lipid mediator-profiling approach to investigate the regulation of a novel group of host protective mediators, termed specialized proresolving mediators (SPMs), in the cerebrospinal fluid (CSF) of adults with TBM. Herein, using CSF from patients enrolled into a randomized placebo-controlled trial of adjunctive aspirin treatment, we found distinct lipid mediator profiles with increasing disease severity. These changes were linked with an up-regulation of inflammatory eicosanoids in patients with severe TBM and a decrease in the production of a number of SPMs. CSF proresolving mediator concentrations were also associated with 80-d survival. In survivors, we found a significant increase in proresolving mediator concentrations, including the lipoxygenase 5-derived 13-series resolvin (RvT)2, RvT4, and 15-epi-lipoxin B4, compared with those who died. Of note, treatment of patients with high-dose aspirin led to a decrease in the concentrations of the prothrombic mediator thromboxane A2, reduced brain infarcts, and decreased death in patients with TBM. Together, these findings identify a CSF SPM signature that is associated with disease severity and 80-d mortality in TBM.-Colas, R. A., Nhat, L. T. H., Thuong, N. T. T., Gómez, E. A., Ly, L., Thanh, H. H., Mai, N. T. H., Phu, N. H., Thwaites, G. E., Dalli, J. Proresolving mediator profiles in cerebrospinal fluid are linked with disease severity and outcome in adults with tuberculous meningitis.

Novel mediators and mechanisms in the resolution of infectious inflammation: evidence for vagus regulation

Excessive chronic inflammation is linked to many diseases and considered a stress factor in humans (Robbins Pathologic Basis of Disease. Philadelphia: W.B. Saunders Co., 1999, Proc Natl Acad Sci USA, 2008, 105: 17949, Immunity, 44, 2016, 44: 463, N Engl J Med, 2011, 364: 656). Today, the resolution of inflammation is widely recognized as a cellular biochemically active process involving biosynthesis of a novel superfamily of endogenous chemical signals coined specialized pro-resolving mediators (SPMs; Nature, 2014, 510:92). Herein, we review recent evidence, indicating a role for the vagus nerve and vagotomy in the regulation of lipid mediators. Vagotomy reduces pro-resolving mediators, including the lipoxins, resolvins, protectins and maresins, delaying resolution in mouse peritonitis. Vagotomy also delays resolution of Escherichia coli infection in mice. Specifically, right vagus regulates peritoneal Group 3 innate lymphoid cell (ILC-3) number and peritoneal macrophage responses with lipid mediator profile signatures with elevated pro-inflammatory eicosanoids and reduced resolvins, including the novel protective immunoresolvent agonist protectin conjugate in tissue regeneration1 (PCTR1). Acetylcholine upregulates PCTR biosynthesis, and administration of PCTR1 to vagotomized mice restores tissue resolution and host responses to E. coli infections. Results obtained with human vagus ex vivo indicate that vagus can produce both pro-inflammatory eicosanoids, such as prostaglandins and leukotrienes, as well as the SPM. Electrical stimulation of human vagus in vitro reduces both prostaglandins and leukotrienes and enhances resolvins and the other SPM. These results elucidate a host protective mechanism mediated by vagus stimulation of SPM that includes resolvins and PCTR1 to regulate myeloid antimicrobial functions and resolution of infection. Moreover, they define a new pro-resolution of inflammation reflex operative in mice and human tissue that involves a vagus SPM circuit.

The Physiological Effect of n-3 Polyunsaturated Fatty Acids (n-3 PUFAs) Intake and Exercise on Hemorheology, Microvascular Function, and Physical Performance in Health and Cardiovascular Diseases; Is There an Interaction of Exercise and Dietary n-3 PUFA Intake?

Physical activity has a beneficial effect on systemic hemodynamics, physical strength, and cardiac function in cardiovascular (CV) patients. Potential beneficial effects of dietary intake of n-3 polyunsaturated fatty acids (n-3 PUFAs), such as α-linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid on hemorheology, vascular function, inflammation and potential to improve physical performance as well as other CV parameters are currently investigated. Recent meta-analysis suggests no effect of n-3 PUFA supplementation on CV function and outcomes of CV diseases. On the other hand, some studies support beneficial effects of n-3 PUFAs dietary intake on CV and muscular system, as well as on immune responses in healthy and in CV patients. Furthermore, the interaction of exercise and dietary n-3 PUFA intake is understudied. Supplementation of n-3 PUFAs has been shown to have antithrombotic effects (by decreasing blood viscosity, decreasing coagulation factor and PAI-1 levels and platelet aggregation/reactivity, enhancing fibrinolysis, but without effects on erythrocyte deformability). They decrease inflammation by decreasing IL-6, MCP-1, TNFα and hsCRP levels, expression of endothelial cell adhesion molecules and significantly affect blood composition of fatty acids. Treatment with n-3 PUFAs enhances brachial artery blood flow and conductance during exercise and enhances microvascular post-occlusive hyperemic response in healthy humans, however, the effects are unknown in cardiovascular patients. Supplementation of n-3 PUFAs may improve anaerobic endurance and may modulate oxygen consumption during intense exercise, may increase metabolic capacity, enhance endurance capacity delaying the onset of fatigue, and improving muscle hypertrophy and neuromuscular function in humans and animal models. In addition, n-3 PUFAs have anti-inflammatory and anti-nociceptive effects and may attenuate delayed-onset muscle soreness and muscle stiffness, and preserve joint mobility. On the other hand, effects of n-3 PUFAs were variably observed in men and women and they vary depending on dietary protocol, type of supplementation and type of sports activity undertaken, both in healthy and cardiovascular patients. In this review we will discuss the physiological effects of n-3 PUFA intake and exercise on hemorheology, microvascular function, immunomodulation and inflammation and physical performance in healthy persons and in cardiovascular diseases; elucidating if there is an interaction of exercise and diet.

Inflammatory arthritis disrupts gut resolution mechanisms, promoting barrier breakdown by Porphyromonas gingivalis

Rheumatoid arthritis is linked with altered host immune responses and severe joint destruction. Recent evidence suggests that loss of gut homeostasis and barrier breach by pathobionts, including Porphyromonas gingivalis, may influence disease severity. The mechanism(s) leading to altered gut homeostasis and barrier breakdown in inflammatory arthritis are poorly understood. In the present study, we found a significant reduction in intestinal concentrations of several proresolving mediators during inflammatory arthritis, including downregulation of the gut-protective mediator resolvin D5n-3 DPA (RvD5n-3 DPA). This was linked with increased metabolism of RvD5n-3 DPA to its inactive 17-oxo metabolite. We also found downregulation of IL-10 expression in the gut of arthritic mice that was coupled with a reduction in IL-10 and IL-10 receptor (IL-10R) in lamina propria macrophages. These changes were linked with a decrease in the number of mucus-producing goblet cells and tight junction molecule expression in the intestinal epithelium of arthritic mice when compared with naive mice. P. gingivalis inoculation further downregulated intestinal RvD5n-3 DPA and Il-10 levels and the expression of gut tight junction proteins. RvD5n-3 DPA, but not its metabolite 17-oxo-RvD5n-3 DPA, increased the expression of both IL-10 and IL-10R in macrophages via the upregulation of the aryl hydrocarbon receptor agonist l-kynurenine. Administration of RvD5n-3 DPA to arthritic P. gingivalis-inoculated mice increased intestinal Il-10 expression, restored gut barrier function, and reduced joint inflammation. Together, these findings uncover mechanisms in the pathogenesis of rheumatoid arthritis, where disruption of the gut RvD5n-3 DPA-IL-10 axis weakens the gut barrier, which becomes permissive to the pathogenic actions of the pathobiont P. gingivalis.

Identification and Complete Stereochemical Assignments of the New Resolvin Conjugates in Tissue Regeneration in Human Tissues that Stimulate Proresolving Phagocyte Functions and Tissue Regeneration

Resolvin conjugates in tissue regeneration (RCTRs) are new chemical signals that accelerate resolution of inflammation, infection, and tissue regeneration. Herein, using liquid chromatography-tandem mass spectrometry-based metabololipidomics, we identified RCTRs in human spleen, lymph node, bone marrow, and brain. In human spleen incubated with Staphylococcus aureus, endogenous RCTRs were increased along with conversion of deuterium-labeled docosahexaenoic acid, conferring pathway activation. Physical and biological properties of endogenous RCTRs were matched with those prepared by total organic synthesis. The complete stereochemical assignment of bioactive RCTR1 is 8R-glutathionyl-7S,17S-dihydroxy-4Z,9E,11E,13Z,15E,19Z-docosahexaenoic acid, RCTR2 is 8R-cysteinylglycinyl-7S,17S-dihydroxy-4Z,9E,11E,13Z,15E,19Z-docosahexaenoic acid, and RCTR3 is 8R-cysteinyl-7S,17S-dihydroxy-4Z,9E,11E,13Z,15E,19Z-docosahexaenoic acid. These stereochemically defined RCTRs stimulated human macrophage phagocytosis, efferocytosis, and planaria tissue generation. Proteome profiling demonstrated that RCTRs regulated both proinflammatory and anti-inflammatory cytokines with human macrophages. In microfluidic chambers, the three RCTRs limited human polymorphonuclear cell migration. In hind-limb ischemia-reperfusion-initiated organ injury, both RCTR2 and RCTR3 reduced polymorphonuclear cell infiltration into lungs. In infectious peritonitis, RCTR1 shortened the resolution intervals. Each RCTR (1 nmol/L) accelerated planaria tissue regeneration by approximately 0.5 days, with direct comparison to both maresin and protectin CTRs. Together, these results identify a new bioactive RCTR (ie, RCTR3) in human tissues and establish the complete stereochemistry and rank-order potencies of three RCTRs in vivo. Moreover, RCTR1, RCTR2, and RCTR3 each exert potent anti-inflammatory and proresolving actions with human leukocytes.

Dynamic changes to lipid mediators support transitions among macrophage subtypes during muscle regeneration

Muscle damage elicits a sterile immune response that facilitates complete regeneration. Here, we utilized mass spectrometry-based lipidomics to map the mediator lipidome during the transition from inflammation to resolution and regeneration in skeletal muscle injury. We observed the temporal regulation of glycerophospholipids and the production of pro-inflammatory (e.g., leukotrienes, prostaglandins) and specialized pro-resolving (e.g., resolvins, lipoxins) lipid mediators, which were modulated by ibuprofen. These time-dependent profiles were recapitulated in sorted neutrophils and Ly6C^hi and Ly6C^lo muscle-infiltrating macrophages, with a distinct pro-resolving signature observed in Ly6C^lo macrophages. RNA-seq of macrophages stimulated with resolvin D2 (RvD2) showed similarities to transcriptional changes found during the temporal Ly6C^hi to Ly6C^lo macrophage transition. In vivo, RvD2 increased Ly6C^lo macrophages and functional improvement of the regenerating muscle. These results reveal dynamic lipid mediator signatures of innate immune cells and provide a proof-of-concept for their exploitable effector roles in muscle regeneration.

The Role of Prostaglandins in Disrupted Gastric Motor Activity Associated With Type 2 Diabetes

Patients with diabetes often develop gastrointestinal motor problems, including gastroparesis. Previous studies have suggested this gastric motor disorder was a consequence of an enteric neuropathy. Disruptions in interstitial cells of Cajal (ICC) have also been reported. A thorough examination of functional changes in gastric motor activity during diabetes has not yet been performed. We comprehensively examined the gastric antrums of Lepob mice using functional, morphological, and molecular techniques to determine the pathophysiological consequences in this type 2 diabetic animal model. Video analysis and isometric force measurements revealed higher frequency and less robust antral contractions in Lepob mice compared with controls. Electrical pacemaker activity was reduced in amplitude and increased in frequency. Populations of enteric neurons, ICC, and platelet-derived growth factor receptor α+ cells were unchanged. Analysis of components of the prostaglandin pathway revealed upregulation of multiple enzymes and receptors. Prostaglandin-endoperoxide synthase-2 inhibition increased slow wave amplitudes and reduced frequency of diabetic antrums. In conclusion, gastric pacemaker and contractile activity is disordered in type 2 diabetic mice, and this appears to be a consequence of excessive prostaglandin signaling. Inhibition of prostaglandin synthesis may provide a novel treatment for diabetic gastric motility disorders.

New Areas of Interest: Is There a Role for Omega-3 Fatty Acid Supplementation in Patients With Diabetes and Cardiovascular Disease?

PURPOSE OF REVIEW

Summarize studies on omega-3 fatty acids in prevention of albuminuria in subjects with diabetes.

RECENT FINDINGS

Several small, short-term trials suggested benefit on albuminuria in subjects with diabetes; however, results were not definitive. Welty et al. showed that eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) for 1 year slowed progression of early-stage albuminuria in subjects with diabetes with clinical coronary artery disease on an angiotensin-converting enzyme inhibitor or angiotensin-receptor blocker, the majority of whom had an albumin/creatinine ratio (ACR) < 30 μg/mg. Moreover, significantly more (3-fold) subjects on EPA and DHA had a decrease in ACR compared to control, and three on EPA and DHA had a change in category from > 30 μg/mg to < 30 μg/mg, whereas no controls did. Potential mechanisms for benefit are discussed. These results suggest that there is benefit and perhaps even reversal of albuminuria with EPA and DHA at an early stage of disease in those with ACR < 30 μg/mg and those with microalbuminuria (ACR > 30).

The Protectin Family of Specialized Pro-resolving Mediators: Potent Immunoresolvents Enabling Innovative Approaches to Target Obesity and Diabetes

A western type diet and lifestyle play an important role in the development of chronic diseases, yet little insight into the precise cellular and biomolecular mechanisms has emerged. It is known that an unbalanced diet may result in obesity and diabetes. Sufficient amounts and proper balance of omega-6 and omega-3 polyunsaturated fatty acids is key for maintenance of health. The resolution of inflammation is now held to be a biosynthetically actively driven process precisely regulated and controlled by a superfamily of specialized pro-resolving mediators. Specialized pro-resolving mediators are biosynthesized from both omega-6 and omega-3 polyunsaturated fatty acids and are resolution agonists acting on distinct G-coupled protein receptors. These mediators display potent anti-inflammatory and pro-resolving bioactions with EC₅₀-values in the low nanomolar to picomolar range. The protectin (PD) family of specialized pro-resolving mediators is biosynthesized from the two omega-3 polyunsaturated fatty acids docosahexaenoic acid (DHA) and n–3 docosapentaenoic acid (n–3 DPA). All of the PDs display interesting bioactions as anti-inflammatory and pro-resolving agents. This review covers the bioactions, G-coupled protein receptors pharmacology, biosynthesis, and medicinal chemistry of the PD family of specialized pro-resolving mediators with an emphasis on obesity and anti-diabetic effects. In order to enable drug development and medicinal chemistry efforts against these diseases, stereoselective total organic synthesis of each of these mediators is required for confirmation of structure, stereochemical biosynthesis, and their functions. We provide an overview of our ongoing efforts and the current knowledge.

New pro-resolving n-3 mediators bridge resolution of infectious inflammation to tissue regeneration

While protective, the acute inflammatory response when uncontrolled can lead to further tissue damage and chronic inflammation that is now widely recognized to play important roles in many commonly occurring diseases, such as cardiovascular disease, neurodegenerative diseases, metabolic syndrome, and many other diseases of significant public health concern. The ideal response to initial challenges of the host is complete resolution of the acute inflammatory response, which is now recognized to be a biosynthetically active process governed by specialized pro-resolving mediators (SPM). These chemically distinct families include lipoxins, resolvins, protectins and maresins that are biosynthesized from essential fatty acids. The biosynthesis and complete stereochemical assignments of the major SPM are established, and new profiling procedures have recently been introduced to document the activation of these pathways in vivo with isolated cells and in human tissues. The active resolution phase leads to tissue regeneration, where we've recently identified new molecules that communicate during resolution of inflammation to activate tissue regeneration in model organisms. This review presents an update on the documentation of the roles of SPMs and the biosynthesis and structural elucidation of novel mediators that stimulate tissue regeneration, coined conjugates in tissue regeneration. The identification and actions of the three families, maresin conjugates in tissue regeneration (MCTR), protectin conjugates in tissue regeneration (PCTR), and resolvin conjugates in tissue regeneration (RCTR), are reviewed here. The identification, structural elucidation and the pathways and biosynthesis of these new mediators in tissue regeneration demonstrate the host capacity to protect from collateral tissue damage, stimulate clearance of bacteria and debris, and promote tissue regeneration via endogenous pathways and molecules in the resolution metabolome.