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Rationale: Sepsis, a life-threatening organ dysfunction caused by a dysregulated host response to infection, is a major public health concern with high mortality and morbidity. Although inflammatory responses triggered by infection are crucial for host defense against invading microbes, the excessive inflammation often causes tissue damage leading to organ dysfunction. Resolution of inflammation, an active immune process mediated by endogenous lipid mediators (LMs), is important to maintain host homeostasis.Objectives: We sought to determine the role of the nucleotide-binding domain, leucine-rich repeat-containing receptor, pyrin domain-containing-3 (NLRP3) inflammasome in polymicrobial sepsis and regulation of LM biosynthesis.Methods: We performed cecal ligation and puncture (CLP) using mice lacking NLRP3 inflammasome-associated molecules to assess mortality. Inflammation was evaluated by using biologic fluids including plasma, bronchoalveolar, and peritoneal lavage fluid. Local acting LMs in peritoneal lavage fluid from polymicrobacterial septic mice were assessed by mass spectrometry-based metabololipidomics.Measurements and Main Results: Genetic deficiency of NLRP3 inhibited inflammatory responses and enhanced survival of CLP-induced septic mice. NLRP3 deficiency reduced proinflammatory LMs and increased proresolving LM, lipoxin B4 (LXB4) in septic mice, and in macrophages stimulated with LPS and ATP. Activation of the NLRP3 inflammasome induced caspase-7 cleavage and pyroptosis. Caspase-7 deficiency similarly reduced inflammation and mortality in CLP-induced sepsis, and increased LXB4 production in vivo and in vitro. Exogenous application of LXB4 reduced inflammation, pyroptosis, and mortality of mice after CLP.Conclusions: Genetic deficiency of NLRP3 promoted resolution of inflammation in polymicrobial sepsis by relieving caspase-7-dependent repression of LXB4 biosynthesis, and increased survival potentially via LXB4 production and inhibition of proinflammatory cytokines. [ABSTRACT FROM AUTHOR]

The resolution of inflammation is an active process orchestrated by specialized proresolving lipid mediators (SPM) that limit the host response within the affected tissue; failure of effective resolution may lead to tissue injury. Because persistence of inflammatory signals is a main feature of chronic inflammatory conditions, including inflammatory bowel diseases (IBDs), herein we investigate expression and functions of SPM in intestinal inflammation. Targeted liquid chromatography-tandem mass spectrometry-based metabololipidomics was used to identify SPMs fromn-3 polyunsaturated fatty acids in human IBD colon biopsies, quantifying a significant upregulation of the resolvin and protectin pathway compared with normal gut tissue. Systemic treatment with protectin (PD)1n-3 DPA or resolvin (Rv)D5n-3 DPA protected against colitis and intestinal ischemia/reperfusion-induced inflammation in mice. Inhibition of 15-lipoxygenase activity reduced PD1n-3 DPA and augmented intestinal inflammation in experimental colitis. Intravital microscopy of mouse mesenteric venules demonstrated that PD1n-3 DPA and RvD5n-3 DPA decreased the extent of leukocyte adhesion and emigration following ischemia-reperfusion. These data were translated by assessing human neutrophil-endothelial interactions under flow: PD1n-3 DPA and RvD5n-3 DPA reduced cell adhesion onto TNF-α-activated human endothelial monolayers. In conclusion, we propose that innovative therapies based on n-3 DPA-derived mediators could be developed to enable antiinflammatory and tissue protective effects in inflammatory pathologies of the gut. [ABSTRACT FROM AUTHOR]

Acute inflammation is accompanied from its outset by the release of specialized pro-resolving mediators (SPMs), including resolvins, that orchestrate the resolution of local inflammation. We showed earlier that, in rats with subcutaneous inflammation of the back induced by carrageenan, stretching for 10 min twice daily reduced inflammation and improved pain, 2 weeks after carrageenan injection. In this study, we hypothesized that stretching of connective tissue activates local pro-resolving mechanisms within the tissue in the acute phase of inflammation. In rats injected with carrageenan and randomized to stretch versus no stretch for 48 h, stretching reduced inflammatory lesion thickness and neutrophil count, and increased resolvin (RvD1) concentrations within lesions. Furthermore, subcutaneous resolvin injection mimicked the effect of stretching. In ex vivo experiments, stretching of connective tissue reduced the migration of neutrophils and increased tissue RvD1 concentration. These results demonstrate a direct mechanical impact of stretching on inflammation-regulation mechanisms within connective tissue. J. Cell. Physiol. 231: 1621-1627, 2016. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Summary The role of inflammation in obesity-related pathologies is well established. We investigated the therapeutic potential of LipoxinA 4 (LXA 4 :5( S ),6( R ),15( S )-trihydroxy-7E,9E,11Z,13E, - eicosatetraenoic acid) and a synthetic 15( R )-Benzo-LXA 4 -analog as interventions in a 3-month high-fat diet (HFD; 60% fat)-induced obesity model. Obesity caused distinct pathologies, including impaired glucose tolerance, adipose inflammation, fatty liver, and chronic kidney disease (CKD). Lipoxins (LXs) attenuated obesity-induced CKD, reducing glomerular expansion, mesangial matrix, and urinary H 2 O 2 . Furthermore, LXA 4 reduced liver weight, serum alanine-aminotransferase, and hepatic triglycerides. LXA 4 decreased obesity-induced adipose inflammation, attenuating TNF-α and CD11c + M1-macrophages (MΦs), while restoring CD206 + M2-MΦs and increasing Annexin-A1. LXs did not affect renal or hepatic MΦs, suggesting protection occurred via attenuation of adipose inflammation. LXs restored adipose expression of autophagy markers LC3-II and p62. LX-mediated protection was demonstrable in adiponectin −/− mice, suggesting that the mechanism was adiponectin independent. In conclusion, LXs protect against obesity-induced systemic disease, and these data support a novel therapeutic paradigm for treating obesity and associated pathologies. [ABSTRACT FROM AUTHOR]

Negative regulators of white adipose tissue (WAT) expansion are poorly documented in vivo. Prostaglandin F2α (PGF2α) is a potent antiadipogenic factor in cultured preadipocytes, but evidence for its involvement in physiological context is lacking. We previously reported that Akr1b7, an aldo-keto reductase enriched in adipose stromal vascular fraction but absent from mature adipocytes, has antiadipogenic properties possibly supported by PGF2α synthase activity. To test whether lack of Akr1b7 could influence WAT homeostasis in vivo, we generated Akr1b7-/- mice in 129/Sv background. Akr1b7-/- mice displayed excessive basal adiposity resulting from adipocyte hyperplasia/hypertrophy and exhibited greater sensitivity to diet-induced obesity. Following adipose enlargement and irrespective of the diet, they developed liver steatosis and progressive insulin resistance. Akr1b7 loss was associated with decreased PGF2α WAT contents. Cloprostenol (PGF2α agonist) administration to Akr1b7-/- mice normalized WAT expansion by affecting both de novo adipocyte differentiation and size. Treatment of 3T3-L1 adipocytes and Akr1b7-/- mice with cloprostenol suggested that decreased adipocyte size resulted from inhibition of lipogenic gene expression. Hence, Akr1b7 is a major regulator of WAT development through at least two PGF2α-dependent mechanisms: inhibition of adipogenesis and lipogenesis. These findings provide molecular rationale to explore the status of aldo-keto reductases in dysregulations of adipose tissue homeostasis. [ABSTRACT FROM AUTHOR]

Bacterial pneumonia is a leading cause of morbidity and mortality worldwide. Host responses to contain infection and mitigate pathogen-mediated lung inflammation are critical for pneumonia resolution. Aspirin-triggered resolvin D1 (AT-RvD1; 7S,8R,17R trihydroxy-4Z,9E,11E,13Z,15E,19Z docosahexaenoic acid) is a lipid mediator that displays organ protective actions in sterile lung inflammation, and regulates pathogen-initiated cellular responses. Here, in a self-resolving murine model of Escherichia coli pneumonia, lipid mediator metabololipidomics performed on lungs obtained at baseline, 24 hours and 72 hours after infection uncovered temporal regulation of endogenous AT-RvD1 production. Early treatment with exogenous AT-RvD1 (1 hr post-infection) enhanced clearance of E.coli and Pseudomonas aeruginosa in vivo, and lung macrophage phagocytosis of fluorescent bacterial particles ex vivo. Characterization of macrophage subsets in the alveolar compartment during pneumonia identified efferocytosis by infiltrating macrophages (CD11bHi CD11cLow) and exudative macrophages (CD11bHi CD11cHi). AT-RvD1 increased efferocytosis by these cells ex vivo, and accelerated neutrophil clearance during pneumonia in vivo. These anti-bacterial and pro-resolving actions of AT-RvD1 were additive to antibiotic therapy. Taken together, these findings suggest that the pro-resolving actions of AT-RvD1 during pneumonia represent a novel host-directed therapeutic strategy to complement the current antibiotic centered approach to combatting infections.

Obesity is among the leading causes of elevated cardiovascular disease mortality and morbidity. Adipose tissue dysfunction, insulin resistance and inflammation are recognized as important risk factors for the development of cardiovascular disorders in obesity. Hypoxia appears to be a key factor in adipose tissue dysfunction affecting not only adipocytes but also immune cell function. Here we examined the effect of hypoxia-induced transcription factor HIF1α activation on classical dendritic cell (cDCs) function during obesity. We found that deletion of Hif1α on cDCs results in enhanced adipose-tissue inflammation and atherosclerotic plaque formation in a mouse model of obesity. This effect is mediated by HIF1α-mediated increased lipid synthesis, accumulation of lipid droplets and alter synthesis of lipid mediators. Our findings demonstrate that HIF1α activation in cDCs is necessary to control vessel wall inflammation. [ABSTRACT FROM AUTHOR]

Infection is a common cause of death in patients with cirrhosis. We investigated the association between the innate immune response and death within 3 months of hospitalization. Plasma samples were collected on days 1, 5, 10, and 15 from participants recruited into the albumin to prevent infection in chronic liver failure feasibility study. Patients with acute decompensated cirrhosis were given albumin infusions at 10 hospitals in the United Kingdom. Data were obtained from 45 survivors and 27 non-survivors. We incubated monocyte-derived macrophages from healthy individuals with patients' plasma samples and measured activation following lipopolysaccharide administration, determined by secretion of tumor necrosis factor and soluble mediators of inflammation. Each analysis included samples from 4 to 14 patients. Plasma samples from survivors vs non-survivors had different inflammatory profiles. Levels of prostaglandin E2 were high at times of patient hospitalization and decreased with albumin infusions. Increased levels of interleukin 4 (IL4) in plasma collected at day 5 of treatment were associated with survival at 3 months. Incubation of monocyte-derived macrophages with day 5 plasma from survivors, pre-incubated with a neutralizing antibody against IL4, caused a significant increase in tumor necrosis factor production to the level of non-survivor plasma. Although baseline characteristics were similar, non-survivors had higher white cell counts and levels of C-reactive protein and renal dysfunction. We identified profiles of inflammatory markers in plasma that are associated with 3-month mortality in patients with acute decompensated cirrhosis given albumin. Increases in prostaglandin E2 might promote inflammation within the first few days after hospitalization, and increased levels of plasma IL4 at day 5 are associated with increased survival. Clinicaltrialsregister.eu: EudraCT 2014-002300-24 [ABSTRACT FROM AUTHOR]

(1) Ligand receptor interactions were monitored using the PathHunter SP ® sp -arrestin cell-based assays (Eurofins DiscoverX Corporation, Fremont, CA, USA) essentially as described earlier. SP [1] sp CHO- -arrestin-GPR32 cells and HEK- -arrestin-FPR2/ALX cells were purchased from DiscoverX, and maintained in HAM F-12 and DMEM media, respectively, supplemented with 10% FBS, 1X pen/strip, G418 (0.8 mg ml SP -1 sp ) and hygromycin (0.3 mg ml SP -1 sp ). (5) DiscoverX PathHunter Detection Reagent (Eurofins DiscoverX Corporation, Fremont, CA, USA) was then used following the manufacturer's instruction; namely, 55 microliters of Working Detection Solution (mixture of Cell Assay Buffer: Substrate Reagent 1: Substrate Reagent 2; 19:5:1) was added to each well, and assay plates incubated in the dark at room temperature for 60 min. Note that the receptor denoted ALX/FPR2 was demonstrated bias in intracellular signaling with specific ligands and with pro-resolving mediator ligands, SP [2] sp confirmed in >175 publications in PubMed to date. [Extracted from the article]

Background & Aims Patients with acute decompensation and acute-on-chronic liver failure (AD/ACLF) have immune dysfunction, which increases their risk for infections; however, there are no effective treatments to restore their immune function. We investigated whether the potentially immune-restorative effects of albumin are mediated by its effects on prostaglandin E 2 (PGE 2 ) and other lipids. Methods We analyzed bloods samples from 45 of 79 patients with AD/ACLF and serum levels of albumin less than 30 g/L for whom infusion of 20% human albumin solution (HAS) increased serum levels of albumin 30 g/L or more in a feasibility study of effects of 20% HAS. Immune function was determined by comparison of macrophage function following addition of plasma samples. We also used samples from 12 healthy individuals. We measured binding of plasma proteins to PGE 2 and serum levels of endotoxin (lipopolysaccharide) and cytokines; using 10 patients’ samples, we investigated the effects of PGE 2 inhibitors. We performed a comprehensive lipid metabolomic analysis using samples from 10 different patients, before and after HAS administration. Results At baseline, AD/ACLF patient plasma induced significantly lower production of tumor necrosis factor by healthy macrophages than plasma from healthy individuals ( P < .0001). Plasma from patients after HAS infusion induced significantly higher levels of tumor necrosis factor production by macrophages (19.5 ± 4.8 ng/mL) compared with plasma collected before treatment (17.7 ± 4.5 ng/mL; P = .0013). There was a significantly lower proportion of plasma protein (albumin) binding to PGE 2 from patients with AD/ACLF plasma (mean, 61.9%) compared with plasma from control subjects (77.1%; P = .0012). AD/ACLF plasma protein binding to PGE 2 increased following HAS treatment compared with baseline (mean increase, 8.7%; P < .0001). Circulating levels of PGE 2 , lipopolysaccharide, and inflammatory or anti-inflammatory cytokines were higher in patients with AD/ACLF than healthy volunteers. Unexpectedly, HAS infusion had no effect on mediator levels. Principal component analysis of baseline levels of lipids that induce or resolve inflammation identified 2 distinct groups of patients that differed according to baseline plasma level of lipopolysaccharide. Sample analyses after HAS treatment indicated that albumin regulates circulating levels of lipid mediators, but this effect was distinct in each group. Conclusions Analysis of blood samples from patients with AD/ACLF participating in a feasibility study of 20% HAS infusions has shown that infusions to raise serum albumin above 30 g/L reversed plasma-mediated immune dysfunction by binding and inactivating PGE 2 . We also describe a method to classify the inflammatory response in AD/ACLF, based on lipid profile, which could improve identification of patients most likely to respond to HAS treatment. A randomized controlled trial is needed to determine whether these effects of HAS reduce infections in AD/ACLF. Trial registered with European Medicines Agency (EudraCT 2014-002300-24) and adopted by NIHR (ISRCTN14174793). [ABSTRACT FROM AUTHOR]

A correction to the article "Novel n-3 Immunoresolvents: Structures and Actions" by Jesmond Dalli, Romain A. Colas and Charles N. Serhan is presented.

Platelets are collected for transfusion to patients with different haematological disorders, and for logistical reasons, platelets are stored as concentrates. Despite carefully controlled conditions, platelets become activated during storage, and platelet concentrates (PlaCs) may cause adverse inflammatory reactions in recipients. The time-dependent changes in the lipidome of clinical PlaCs, platelets isolated from PlaCs, and extracellular vesicles (EVs) thereof were examined by mass spectrometry. The relative amount of arachidonic acid containing glycerophospholipids, especially those in the phosphatidylethanolamine and phosphatidylserine classes during storage, but the relative amount of other polyunsaturated fatty acid containing glycerophospholipids remained stable in all sample types. These changes were not directly translated to lipid mediator (LM) profile since the levels of arachidonic acid-derived proinflammatory LMs were not specifically elevated. Instead, several monohydroxy pathway markers and functionally relevant LMs, both proinflammatory and proresolving, were detected in the PlaCs and the EVs, and some representatives of both kind clearly accumulated during storage. By Western blot, the key enzymes of these pathways were shown to be present in platelets, and in many cases, EVs. Since the EVs were enriched in the fatty acid precursors of LMs in their (phospholipid) membranes, harboured LM-producing enzymes, contained the related monohydroxy pathway markers, and secreted the final LM products, PlaC-derived EVs could participate in the regulation of inflammation and healing, and thereby aid the platelets in exerting their essential physiological functions. • AA-containing FA species increase in major GPL classes of platelet concentrates. • Enzymes processing FAs to lipid mediators were detected in all sample types. • Lipid mediator pathway markers were found to be a result of enzymatic processing. • Lipid mediators were detected in platelet concentrates and extracellular vesicles. [ABSTRACT FROM AUTHOR]

Unresolved inflammation is a major contributor to the development of heart failure following myocardial infarction (MI). Pro-resolving lipid mediators, such as resolvins (e.g. RvD1), are biosynthesized endogenously. The role of RvD1 in resolving post-MI inflammation has not been elucidated due to its unstable nature. Here, we have tested the role for two forms of RvD1, after incorporation into liposomes (Lipo-RvD1) and its free acid form (RvD1) in the left ventricle (LV) and splenic remodeling post-MI. 8 to 12-week old male, C57BL/6J-mice were subjected to coronary artery ligation and Lipo-RvD1 or RvD1 (3 μg/kg/day) was injected 3 h post-MI for day (d)1 or until d5. No-MI mice and saline-injected MI mice served as controls. RvD1 injected groups showed improved fractional shortening post-MI; preserving transient changes in the splenic reservoir compared to MI-saline. RvD1-groups showed an early exit of neutrophils from LV and spleen at d5 post-MI with an increased expression of lipoxin A 4 receptor (ALX; synonym formyl peptide receptor; FPR2) compared to the MI-saline group. The levels of pro-resolving mediators RvD1, RvD2, Maresin 1 (MaR1) and Lipoxin A 4 (LXA 4 ) were increased in spleens from RvD1 injected mice at d5 post-MI. RvD1 administration reduced macrophage density, ccr5 and cxcl5 levels at d5 post-MI compared to saline injected mice (both, p < 0.05). Increased transcripts of mrc-1 , arg-1 and Ym-1 (all, p < 0.05) suggest macrophage-mediated clearance of necrotic cells in RvD1-groups. RvD1 reduced the pro-fibrotic genes ( colla1 , coll2a1 and tnc (all; p < 0.05)) and decreased collagen deposition, thereby reducing post-MI fibrosis and thus stabilizing the extracellular matrix. In summary, RvD1 and Lipo-RvD1 promote the resolution of acute inflammation initiated by MI, thereby delaying the onset of heart failure. [ABSTRACT FROM AUTHOR]

Acute inflammatory responses are protective, yet without timely resolution can lead to chronic inflammation and organ fibrosis. A systems approach to investigate self-limited (self-resolving) inflammatory exudates in mice and structural elucidation uncovered novel resolution phase mediators in vivo that stimulate endogenous resolution mechanisms in inflammation. Resolving inflammatory exudates and human leukocytes utilize DHA and other n− 3 EFA to produce three structurally distinct families of potent di- and trihydroxy-containing products, with several stereospecific potent mediators in each family. Given their potent and stereoselective picogram actions, specific members of these new families of mediators from the DHA metabolome were named D-series resolvins (Resolvin D1 to Resolvin D6), protectins (including protectin D1 –neuroprotectin D1), and maresins (MaR1 and MaR2). In this review, we focus on a) biosynthesis of protectins and maresins as anti-inflammatory–pro-resolving mediators; b) their complete stereochemical assignments and actions in vivo in disease models. Each pathway involves the biosynthesis of epoxide-containing intermediates produced from hydroperoxy-containing precursors from human leukocytes and within exudates. Also, aspirin triggers an endogenous DHA metabolome that biosynthesizes potent products in inflammatory exudates and human leukocytes, namely aspirin-triggered Neuroprotectin D1/Protectin D1 [AT-(NPD1/PD1)]. Identification and structural elucidation of these new families of bioactive mediators in resolution has opened the possibility of diverse patho-physiologic actions in several processes including infection, inflammatory pain, tissue regeneration, neuroprotection-neurodegenerative disorders, wound healing, and others. This article is part of a Special Issue entitled “Oxygenated metabolism of PUFA: analysis and biological relevance”. [ABSTRACT FROM AUTHOR]