Specialized Pro-resolving Lipid Mediators Levels Research Articles

Exercise-stimulated Resolvin Biosynthesis in Adipose Tissue is Abrogated by High Fat Diet-induced Adrenergic Deficiency.

Diet-induced white adipose tissue inflammation is associated with insulin resistance and metabolic perturbations. Conversely, exercise (Exe) protects against the development of chronic inflammation and insulin resistance independent of changes in weight; however, the mechanisms remain largely unknown. We have recently shown that, through adrenergic stimulation of macrophages, exercise promotes resolution of acute peritoneal inflammation by enhancing the biosynthesis of specialized pro-resolving lipid mediators (SPMs). In this study, we sought to determine if exercise stimulates pro-resolving pathways in adipose tissue and whether this response is modified by diet. Specifically, we hypothesized that high fat diet feeding disrupts exercise-stimulated resolution by inhibiting adrenergic signaling, priming the development of chronic inflammation in adipose tissue (AT). To explore the dietary dependence of the pro-resolving effects of Exe, mice were fed either a control or high-fat diet (HFD) for 2 weeks prior to, and throughout, a 4 wk period of daily treadmill running. Glucose handling, body weight and composition, and exercise performance were evaluated at the end of the feeding and exercise interventions. Likewise, catecholamines and their biosynthetic enzymes were measured along with AT SPM biosynthesis and macrophage phenotype and abundance. When compared with sedentary controls (Sed), macrophages isolated from mice exposed to 4 wk of exercise display elevated expression of the SPM biosynthetic enzyme Alox15, while whole AT SPM levels and anti-inflammatory CD301+ M2 macrophages increased. These changes were dependent upon diet as 6 wk of feeding with HFD abrogated the pro-resolving effect of exercise when compared with control diet-fed animals. Interestingly, exercise-induced epinephrine production was inhibited by HFD, which diminished expression of the epinephrine biosynthetic enzyme phenylethanolamine N-methyltransferase (PNMT) in adrenal glands. Taken together, these results suggest that a diet high in fat diminishes the pro-resolving effects of exercise in adipose tissue via decreasing the biosynthesis of catecholamines.

Specialized Pro-Resolving Lipid Mediators: Endogenous Roles and Pharmacological Activities in Infections

During an infection, inflammation mobilizes immune cells to eliminate the pathogen and protect the host. However, inflammation can be detrimental when exacerbated and/or chronic. The resolution phase of the inflammatory process is actively orchestrated by the specialized pro-resolving lipid mediators (SPMs), generated from omega-3 and -6 polyunsaturated fatty acids (PUFAs) that bind to different G-protein coupled receptors to exert their activity. As immunoresolvents, SPMs regulate the influx of leukocytes to the inflammatory site, reduce cytokine and chemokine levels, promote bacterial clearance, inhibit the export of viral transcripts, enhance efferocytosis, stimulate tissue healing, and lower antibiotic requirements. Metabolomic studies have evaluated SPM levels in patients and animals during infection, and temporal regulation of SPMs seems to be essential to properly coordinate a response against the microorganism. In this review, we summarize the current knowledge on SPM biosynthesis and classifications, endogenous production profiles and their effects in animal models of bacterial, viral and parasitic infections.

Formation, Signaling and Occurrence of Specialized Pro-Resolving Lipid Mediators-What is the Evidence so far?

Formation of specialized pro-resolving lipid mediators (SPMs) such as lipoxins or resolvins usually involves arachidonic acid 5-lipoxygenase (5-LO, ALOX5) and different types of arachidonic acid 12- and 15-lipoxygenating paralogues (15-LO1, ALOX15; 15-LO2, ALOX15B; 12-LO, ALOX12). Typically, SPMs are thought to be formed via consecutive steps of oxidation of polyenoic fatty acids such as arachidonic acid, eicosapentaenoic acid or docosahexaenoic acid. One hallmark of SPM formation is that reported levels of these lipid mediators are much lower than typical pro-inflammatory mediators including the monohydroxylated fatty acid derivatives (e.g., 5-HETE), leukotrienes or certain cyclooxygenase-derived prostaglandins. Thus, reliable detection and quantification of these metabolites is challenging. This paper is aimed at critically evaluating i) the proposed biosynthetic pathways of SPM formation, ii) the current knowledge on SPM receptors and their signaling cascades and iii) the analytical methods used to quantify these pro-resolving mediators in the context of their instability and their low concentrations. Based on current literature it can be concluded that i) there is at most, a low biosynthetic capacity for SPMs in human leukocytes. ii) The identity and the signaling of the proposed G-protein-coupled SPM receptors have not been supported by studies in knock-out mice and remain to be validated. iii) In humans, SPM levels were neither related to dietary supplementation with their ω-3 polyunsaturated fatty acid precursors nor were they formed during the resolution phase of an evoked inflammatory response. iv) The reported low SPM levels cannot be reliably quantified by means of the most commonly reported methodology. Overall, these questions regarding formation, signaling and occurrence of SPMs challenge their role as endogenous mediators of the resolution of inflammation.

In This Issue

HomeCirculation ResearchVol. 129, No. 4In This Issue Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyRedditDiggEmail Jump toFree AccessIn BriefPDF/EPUBIn This Issue Ruth Williams Ruth WilliamsRuth Williams Search for more papers by this author Originally published5 Aug 2021https://doi.org/10.1161/RES.0000000000000497Circulation Research. 2021;129:455is related toUnveiling Complexity and Multipotentiality of Early Heart Fieldsis related toCoronary Disease Association With ADAMTS7 Is Due to Protease ActivityDisrupted Resolution Mechanisms Favor Altered Phagocyte Responses in COVID-19Disrupted Resolution Mechanisms Favor Altered Phagocyte Responses in COVID-19 (p e54)Download figureDownload PowerPointKoenis et al show that dysregulation of inflammation-resolving factors is a feature of severe COVID-19.Inflammation is essential in the early stages of battling an invading pathogen, but can become damaging to the host if not resolved in a timely manner. Indeed, prolonged and unresolved inflammation is responsible for the hospitalizations and deaths of many COVID-19 patients. An excess of circulating pro-inflammatory cytokines is one feature of severe COVID-19, and now Koenis and colleagues show that certain pro-resolving factors are out of balance in such patients too. While blood samples from patients with mild COVID-19 revealed an increase in specialized pro-resolving lipid mediators (SPMs), those from patients with severe disease had lower levels of these lipid factors. Expression of SPM receptors on phagocytes was also higher in patients with mild disease than those with severe COVID-19. And, in line with this, the proportion of activated pro-inflammtory phagocytes was higher in patients with severe disease. The team went on to show that patients treated with the steroid dexamethasone had increased blood levels of SPMs. Together the results reveal SPMs are dysregulated in severe cases of COVID-19 and suggest SPM modulation, whether via steroid administration or other pharmacological means, could promote resolution of out-of-control inflammation.Coronary Disease Association with ADAMTS7 Is due to Protease Activity (p 458)Download figureDownload PowerPointCatalytic function of ADAMTS7 is needed for the enzyme’s pro-atherogenic activity, say Mizoguchi et al.Several genome-wide association studies (GWAS) have identified variants at the ADAMTS7 gene and its surrounding intergenic regions as risk loci for coronary artery disease. Furthermore, animal studies suggest the ADAMTS7 protein, which is both a metalloproteinase enzyme and a proteoglycan, is pro-atherogenic. However, which of the protein’s identities is responsible for promoting atherosclerosis is unclear. Mizoguchi and colleagues now show that the enzymatic function of ADAMTS7 is to blame. The team generated mice with [a] catalytically inactive version of ADAMTS7 and compared these animals with ones that either lacked ADAMTS7 entirely or had the fully intact protein (wild type). They found that loss of either ADAMTS7 protein itself or just its catalytic function was enough to reduce plaque burden in two different models of atherosclerosis. ADAMTS7 is known to regulate migration of vascular smooth muscle cells (VSMCs), which contributes to plaque formation, and VSMCs lacking either the full protein or just its catalytic activity had impaired migratory activity, the team showed. Together the results pinpoint ADAMTS7’s enzyme activity as pro-atherogenic and suggest the catalytic domain of the protein could be a therapeutic target for curtailing atherosclerosis.Unveiling Complexity and Multipotentiality of Early Heart Fields (p 474)Download figureDownload PowerPointZhang et al discover a shared source of mesodermal progenitors contributing to both the heart and extraembryonic tissues.The developing heart is thought to originate from two populations of cells—the first and second heart fields—which are first identifiable in the stage E7.5 mouse embryo (day 15 human embryo). Genes controlling the development of these fields have been linked to congenital heart defects (CHDs), but interestingly CHDs are also sometimes linked to placental abnormalities for reasons that are unclear. Zhang and colleagues now show that the first heart field and extraembryonic tissues—those which gives rise to the yolk sac and placenta—have an unexpected link. Through lineage-tracing experiments and single-cell transcriptomics, the team discovered that the first heart field consists of two sources of mesoderm progenitors—one that is embryonic in nature, and the other that arises from the interface between extraembryonic and embryonic tissues of the early gastrula. This latter population of progenitors, which expresses the transcription factor Hand1, gives rise to extraembryonic mesoderm cells in addition to heart field cells, the team showed. The finding of this shared source of mesodermal progenitors not only blurs the lines between the embryo and its supporting tissues, but may also explain the link between placental abnormalities and CHDs. Previous Back to top Next FiguresReferencesRelatedDetailsRelated articlesUnveiling Complexity and Multipotentiality of Early Heart FieldsQingquan Zhang, et al. Circulation Research. 2021;129:474-487Coronary Disease Association With ADAMTS7 Is Due to Protease ActivityTaiji Mizoguchi, et al. Circulation Research. 2021;129:458-470Disrupted Resolution Mechanisms Favor Altered Phagocyte Responses in COVID-19Duco Steven Koenis, et al. Circulation Research. 2021;129:e54-e71 August 6, 2021Vol 129, Issue 4Article InformationMetrics © 2021 American Heart Association, Inc.https://doi.org/10.1161/RES.0000000000000497 Originally publishedAugust 5, 2021 PDF download Advertisement

Subgingival Microbiome and Specialized Pro-Resolving Lipid Mediator Pathway Profiles Are Correlated in Periodontal Inflammation.

Failure of resolution pathways in periodontitis is reflected in levels of specialized pro-resolving lipid mediators (SPMs) and SPM pathway markers but their relationship with the subgingival microbiome is unclear. This study aimed to analyze and integrate lipid mediator level, SPM receptor gene expression and subgingival microbiome data in subjects with periodontitis vs. healthy controls. The study included 13 periodontally healthy and 15 periodontitis subjects that were evaluated prior to or after non-surgical periodontal therapy. Samples of gingival tissue and subgingival plaque were collected prior to and 8 weeks after non-surgical treatment; only once in the healthy group. Metabololipidomic analysis was performed to measure levels of SPMs and other relevant lipid mediators in gingiva. qRT-PCR assessed relative gene expression (2-ΔΔCT) of known SPM receptors. 16S rRNA sequencing evaluated the relative abundance of bacterial species in subgingival plaque. Correlations between lipid mediator levels, receptor gene expression and bacterial abundance were analyzed using the Data Integration Analysis for Biomarker discovery using Latent cOmponents (DIABLO) and Sparse Partial Least Squares (SPLS) methods. Profiles of lipid mediators, receptor genes and the subgingival microbiome were distinct in the three groups. The strongest correlation existed between lipid mediator profile and subgingival microbiome profile. Multiple lipid mediators and bacterial species were highly correlated (correlation coefficient ≥0.6) in different periodontal conditions. Comparing individual correlated lipid mediators and bacterial species in periodontitis before treatment to healthy controls revealed that one bacterial species, Corynebacterium durum, and five lipid mediators, 5(S)6(R)-DiHETE, 15(S)-HEPE, 7-HDHA, 13-HDHA and 14-HDHA, were identified in both conditions. Comparing individual correlated lipid mediators and bacterial species in periodontitis before treatment to after treatment revealed that one bacterial species, Anaeroglobus geminatus, and four lipid mediators, 5(S)12(S)-DiHETE, RvD1, Maresin 1 and LTB4, were identified in both conditions. Four Selenomonas species were highly correlated with RvD1, RvE3, 5(S)12(S)-DiHETE and proinflammatory mediators in the periodontitis after treatment group. Profiles of lipid mediators, receptor gene and subgingival microbiome are associated with periodontal inflammation and correlated with each other, suggesting inflammation mediated by lipid mediators influences microbial composition in periodontitis. The role of correlated individual lipid mediators and bacterial species in periodontal inflammation have to be further studied.

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.

49193 The Association Between Specialized Pro-resolving Lipid Mediators and Markers of Neuroinflammation and Disease Severity in Acute Traumatic Brain Injury: A Prospective, Observational Cohort Study

ABSTRACT IMPACT: Characterizing specialized pro-resolving lipid mediators (SPMs) of inflammation in a cohort of adult patients with traumatic brain injury (TBI) will potentially identify novel biomarkers of disease and would generate hypotheses regarding the role of SPMs in the pathophysiology and recovery after brain injury OBJECTIVES/GOALS: Primary aim: evaluate the association between plasma and cerebrospinal fluid (CSF) SPM levels with inflammatory markers known to mediate blood brain barrier (BBB) disruption. Secondary aim: evaluate the association between SPM levels and disease severity, 14-day Glasgow Coma Scale score (GCS) and survival. METHODS/STUDY POPULATION: This is a single-center, prospective, observational cohort study (target N=50). Adult participants with moderate-to-severe non-penetrating TBI will have blood and CSF sampled serially for laboratory measures of SPMs (resolvins, protectins, lipoxins, maresins) and inflammatory peptides (TNF-α, IL-1β, IL-6, MMP-9, TIMP-1) by liquid chromatography’‘ mass spectrometry and RT-PCR & ELISA, respectively. Baseline patient characteristics, admission GCS, and 14-day GCS and mortality will be prospectively collected. To evaluate the association between SPMs and other continuous variables, Pearson’s and Spearman’s correlation will be used. Cox regression will be used to evaluate the association between SPM lipidomes and 14-day survival. RESULTS/ANTICIPATED RESULTS: As the primary outcome measure, the association between SPM levels with assayed inflammatory markers will be determined at 24 and 72 hours post-TBI. We hypothesize that SPMs will be negatively correlated with TNF-α, IL-1β, IL-6, MMP-9 and positively correlated with TIMP-1. As secondary outcome measures, the association between SPM levels with disease severity by admission GCS will be determined at 24 hours post-TBI, and the association between SPM levels and GCS and mortality will be determined at 14-days. We hypothesize that SPM levels will be positively associated with admission and 14-day GCS and will be independently associated with 14-day survival. DISCUSSION/SIGNIFICANCE OF FINDINGS: Using the SPM lipidome as a biomarker of disease is a novel tool for future translational research. It will inform a foundational mechanistic framework for TBI pathophysiology and attenuation of neuroinflammation post-TBI, providing rationale for pre-clinical and clinical research focused on 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.

703-P: Exercise-Stimulated Resolvin Biosynthesis in Adipose Tissue Is Abrogated by Obesity-Induced Adrenergic Dysfunction

Adipose tissue (AT) inflammation is associated with obesity-induced insulin resistance. Exercise (Exe) prevents the development of chronic inflammatory diseases and insulin resistance largely through unknown mechanisms. We sought to determine if changes in specialized pro-resolving lipid mediators (SPM) in AT contribute to the anti-inflammatory effect of exercise. When compared with sedentary controls (Sed), normal chow fed mice exposed to 4 wk of Exe showed elevated AT expression of SPM biosynthetic enzyme Alox15 (Sed 1.12±0.18 vs. Exe 1.68±0.13 relative expression, n=5-7), SPM levels (Sed vs. Exe; RvD1 156.7±12.02 vs. 223.0±24.71; 17R-RvD1 354.0±35.86 vs. 534.4±98.92; RvD4 31.31±6.93 vs. 123.1±30.69; and 17R-RvD3 2.92±1.08 vs. 8.20±1.70 pg/g, n=5-7), and anti-inflammatory macrophages (F4/80+CD301+; Sed 17.5±3.2 vs. Exe 40.9±4.5 %F4/80+, n=4-6). These changes were diet-dependent as feeding with high fat diet (60% kcal from fat; HFD) abrogated the pro-resolving effect of exercise in AT when compared with low fat diet (10% kcal from fat; LFD) controls. Exercise-stimulated upregulation of 15-LO expression was localized to AT macrophages in a diet-dependent manner (LFD Sed 0.11±0.03 vs. LFD Exe 0.23±0.03; HFD Sed 0.10±0.04 vs. HFD Exe 0.08±0.02 relative expression, n=3-6), as adipocytes from exercised mice showed no difference in 15-LO expression compared with sedentary controls. Given that epinephrine stimulates macrophage 15-LO expression and RvD1 production, we questioned if catecholamine biosynthesis was affected by HFD feeding. Adrenal glands from mice fed HFD show diminished expression of phenylethanolamine N-methyltransferase when compared with controls (LFD 1.0±0.25 vs. HFD 0.36±0.15, n=4). Similarly, db/db mice also displayed reduced catecholamines and expression of biosynthetic enzymes in the adrenal glands. These results suggest that obesity-induced adrenergic dysfunction abrogates exercise-stimulated resolvin production in AT. Disclosure J. Hellmann: None. W. Lynch: None. E.P. Calderin: None. B. Sansbury: None. M. Spite: None. A. Bhatnagar: None. B. Hill: None. Funding American Diabetes Association (1-16-JDF-041 to B.H.); National Institutes of Health (GM127495, GM127607)

Exercise-stimulated resolvin biosynthesis in adipose tissue is abrogated by obesity-induced adrenergic dysfunction

Abstract Adipose tissue (AT) inflammation is associated with obesity-induced insulin resistance. Exercise (Exe) prevents the development of chronic inflammatory diseases and insulin resistance largely through unknown mechanisms. We provide data that specialized proresolving lipid mediators (SPM) contribute to the anti-inflammatory effect of Exe. Compared with sedentary controls (Sed), mice exposed to 4 wk of Exe showed elevated AT expression of SPM biosynthetic enzyme Alox15 (Sed 1.12±0.2 vs Exe 1.68±0.1 relative expression, n=5–7), SPM levels (Sed vs Exe; RvD1 156.7±12.0 vs 223.0±24.7; 17R-RvD1 354.0±35.9 vs 534.4±98.9; RvD4 31.31±6.9 vs 123.1±30.7; and 17R-RvD3 2.92±1.1 vs 8.20±1.7 pg/g, n=5–7), and M2 macrophages (F4/80+CD301+; Sed 17.5±3.2 vs Exe 40.9±4.5 %F4/80+, n=4–6). These changes were diet-dependent as high fat (HFD) abrogated this Exe effect in AT when compared with low fat (LFD) controls. The exercise-stimulated Alox15 expression was restricted to AT macrophages (F4/80+ cells; LFD Sed 0.11±0.03 vs LFD Exe 0.23±0.03; HFD Sed 0.10±0.04 vs HFD Exe 0.08±0.02 relative expression, n=3–6), as adipocytes isolated from Exe mice showed no difference compared with Sed controls. That epinephrine (Epi) is released with exercise and stimulates macrophage Alox15 expression and RvD1 production, we questioned if Epi biosynthesis is affected by HFD. HFD feeding diminished expression of phenylethanolamine N-methyltransferase compared with controls (LFD 1.0±0.25 vs HFD 0.36±0.15, n=4). Similarly, obese-diabetic mice (db/db) also showed reduced catecholamine production and biosynthetic enzyme levels. These results suggest that obesity-induced adrenergic dysfunction abrogates exercise-stimulated resolvin production in AT.

Maresin1 Decreased Microglial Chemotaxis and Ameliorated Inflammation Induced by Amyloid-β42 in Neuron-Microglia Co-Culture Models.

Inflammation resolution is regulated by specialized pro-resolving lipid mediators (SPMs) and the levels of SPMs are found decreased in Alzheimer's disease (AD) brain. We have previously found that one of the SPMs, Maresin1 (MaR1), improved neuronal survival and increase microglial phagocytosis of amyloid-β 1-42 (Aβ42); however, the mechanisms underlying the protective mechanism remain further investigation. We aim to investigate the effects of MaR1 on microglial chemotaxis and activation in this study. Both indirect and direct primary neuron and microglia co-culture system was used in this study. Our results showed MaR1 downregulated the increased microglial chemotaxis induced by Aβ42. The microglial inactivation marker CD200R was downregulated by Aβ42 and upregulated by MaR1. Pro-inflammatory cytokines secretion such as tumor necrosis factor (TNF)-α were increased by Aβ42 and these changes were revised by MaR1 treatment. In addition, the levels of chemokine monocyte chemoattractant protein (MCP)-1 were increased while the levels of anti-inflammatory factor IL-10 secretion were decreased by Aβ42, and these changes were abolished by MaR1 treatment. Moreover, by proteomics analysis, we identified cell signaling pathways affected by MaR1 were not only limited to inflammation-related pathways such as P38, but also in pathways involved in cell survival, autophagy, axon formation, and apoptosis, including PI3K/AKT, mTOR, ERK, caspase3, Cdc42, and p75NTR. In conclusion, MaR1 promoted inflammation resolution by inhibiting chemotaxis and regulating activation of microglia. MaR1 played a neuroprotective role by affecting cell signaling pathways involving inflammation, cell survival, autophagy, axon formation, and apoptosis inhibition.

Omega-3 Fatty Acid-Derived Resolvin D2 Regulates Human Placental Vascular Smooth Muscle and Extravillous Trophoblast Activities.

Omega-3 fatty acids are important to pregnancy and neonatal development and health. One mechanism by which omega-3 fatty acids exert their protective effects is through serving as substrates for the generation of specialized pro-resolving lipid mediators (SPM) that potently limit and resolve inflammatory processes. We recently identified that SPM levels are increased in maternal blood at delivery as compared to umbilical cord blood, suggesting the placenta as a potential site of action for maternal SPM. To explore this hypothesis, we obtained human placental samples and stained for the SPM resolvin D2 (RvD2) receptor GPR18 via immunohistochemistry. In so doing, we identified GPR18 expression in placental vascular smooth muscle and extravillous trophoblasts of the placental tissues. Using in vitro culturing, we confirmed expression of GPR18 in these cell types and further identified that stimulation with RvD2 led to significantly altered responsiveness (cytoskeletal changes and pro-inflammatory cytokine production) to lipopolysaccharide inflammatory stimulation in human umbilical artery smooth muscle cells and placental trophoblasts. Taken together, these findings establish a role for SPM actions in human placental tissue.

Brain Cancer: Failure of Resolution of Inflammation?

Medulloblastoma therapy, including radiation and chemotherapy, induces cell death resulting in tumor cell debris assumed to be inert or inhibitory to tumor growth. However, tumor cell death (debris) produced by cytotoxic therapy can accelerate tumor progression through the inflammatory response, suggesting that every attempt to kill tumor cells is a double‐edged sword. Inflammation is regulated by endogenous specialized pro‐resolving lipid mediators (SPMs), such as resolvins and protectins, which are present in the brain and CSF. These lipid autacoids stimulate the clearance of cellular debris by macrophages, resulting in reduced localized pro‐inflammatory cytokines. A loss of SPMs is associated with several neurodegenerative diseases but has not been studied in brain cancer. We hypothesize that reduced levels of SPMs correlate with brain cancer progression and that control of tumor cell debris‐mediated inflammation through resolvins and protectins represents a novel approach to brain cancer treatment. Here, we show that SPM receptors are expressed by human brain tumors including glioblastoma and medulloblastoma. Medulloblastoma tumor cell debris generated by front‐line chemotherapy or targeted therapy stimulates primary tumor growth when co‐injected with a subthreshold (non‐tumorigenic) inoculum of tumor cells by triggering the release of pro‐inflammatory cytokines. Stimulation of the resolution of inflammation via protectins and resolvins suppressed orthotopic medulloblastoma. Protectins and resolvins down‐regulated proinflammatory cytokine release in debris‐activated microglia and stimulate the clearance of tumor debris by inducing macrophage phagocytosis of apoptotic tumor cells. Histological analysis of SPM‐treated medulloblastoma and glioblastoma tumors revealed suppressed Ki‐67‐stained tumor cell proliferation. Thus, brain tumor progression results from a loss of resolution of tumor debris‐associated inflammation. Enhancing endogenous clearance of tumor cell debris via protectins and resolvins is a novel biological target to complement current cytotoxic brain cancer therapy and addresses the intrinsic limitation of current cancer therapy involving cell death. Our studies provide a new strategy for the prevention and treatment of therapy‐induced resistance in medulloblastoma and other brain cancers.Support or Funding InformationThis work was supported by the National Cancer Institute grant RO1 01CA170549‐02 (D.P.); ROCA148633‐01A4 (D.P.); and the Credit Unions Kids at Heart Team (D.P.)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Omega-3 Fatty Acid Supplementation, Pro-Resolving Mediators, and Clinical Outcomes in Maternal-Infant Pairs.

Omega (n)-3 fatty acids are vital to neonatal maturation, and recent investigations reveal n-3 fatty acids serve as substrates for the biosynthesis of specialized pro-resolving lipid mediators (SPM) that have anti-inflammatory and immune-stimulating effects. The role SPM play in the protection against negative maternal-fetal health outcomes is unclear, and there are no current biomarkers of n-3 fatty acid sufficiency. We sought to ascertain the relationships between n-3 fatty acid intake, SPM levels, and maternal-fetal health outcomes. We obtained n-3 fatty acid intake information from 136 mothers admitted for delivery using a food frequency questionnaire and measured docosahexaenoic acid (DHA)-derived SPMs resolvin D1 (RvD1) and RvD2 in maternal and cord plasma. We found significantly elevated SPM in maternal versus cord plasma, and increased SPM levels were associated with at-risk outcomes. We also identified that increased DHA intake was associated with elevated maternal plasma RvD1 (p = 0.03; R2 = 0.18) and RvD2 (p = 0.04; R2 = 0.20) in the setting of neonatal intensive care unit (NICU) admission. These findings indicate that increased n-3 fatty acid intake may provide increased substrate for the production of SPM during high-risk pregnancy/delivery conditions, and that increased maternal plasma SPM could serve as a biomarker for negative neonatal outcomes.

Resolution of inflammation in neuromyelitis optica spectrum disorders

BackgroundNeuromyelitis optica spectrum disorders (NMOSD) are a spectrum of neuroinflammatory disorders associated with autoimmune antibodies against aquaporin-4 (AQP4). Accumulating evidence suggests that inflammation is involved in NMOSD pathogenesis. Resolution of inflammation, which is a highly regulated process mediated by specialized pro-resolving lipid mediators (SPMs) is important to prevent over-responsive inflammation. Deficiency in resolution of inflammation may lead to or accelerates inflammatory diseases. However, whether resolution of inflammation is impaired in NMOSD is not known. The objective of this study was to analyze the levels of SPMs in the serum and cerebrospinal fluid (CSF) of NMOSD patients, and to explore the roles of SPMs in clinical features of NMOSD. MethodsThirty-five patients with NMOSD, 34 patients with multiple sclerosis, and 36 patients with non-inflammatory neurological diseases were enrolled in this study. Pro-resolving mediators including Annexin A1 (ANXA1) and resolvin D1 (RvD1), as well as pro-inflammatory lipid mediator leukotriene B4 (LTB4) levels were analyzed by enzyme-linked immunosorbent assay. Pro- and anti-inflammatory cytokines as well as chemokine levels were analyzed using cytometric beads array (CBA). ResultsOur results showed RvD1 levels were significantly decreased, whereas LTB4 levels were significantly increased in the CSF of NMOSD patients. AQP4-IgG titer was negatively correlated with RvD1 levels in the CSF of NMOSD patients. ConclusionsDecreased RvD1 levels indicate impaired resolution of inflammation in NMOSD patients. AQP4-IgG may contribute to increased inflammation and lead to unresolved inflammation in NMOSD.

Combined administration of resolvin E1 and lipoxin A4 resolves inflammation in a murine model of Alzheimer's disease

Dysfunction in the resolution of inflammation may play a key role in Alzheimer's disease (AD). In this study, we found that the levels of specialized pro-resolving lipid mediators (SPMs) in the hippocampus of 5xFAD mice are significantly lower than in non-transgenic littermates. We, therefore, tested the hypothesis that treatment with resolvin E1 (RvE1) and lipoxin A4 (LXA4) alone or in combination will reverse the neuroinflammatory process and decrease Aβ pathology. 5xFAD mice were treated intraperitoneally starting at 1month of age with RvE1 or LXA4 alone or in combination at a dose of 1.5 μg/kg, 3 times a week until 3months of age. We found that treatment with RvE1 or LXA4 alone or in combination increased the concentration of RvE1, LXA4, and RvD2 in the hippocampus as measured by ELISA. Combination treatment of RvE1 and LXA4 had a more potent effect on the activation of microglia and astrocytes than either treatment alone, measured by immunohistochemistry with Iba1 and GFAP antibodies, respectively. The concentrations of Aβ40 and Aβ42 were measured by ELISA and the percentage of Aβ plaques were analyzed by immunohistochemistry. All treatments single and in combination, decreased the measures of Aβ pathology and restored the homeostasis reversing the inflammatory process for inflammatory cytokines and chemokines (GM-CSF, IFN-γ, IL-1β, IL-6, IL-10, TNF-α, MCP-1, MIP-1α, MIP-1β, and RANTES) as measured by multiplex immunoassay. Overall, the study showed that the levels of SPMs in the hippocampus of 5xFAD mice were significantly lower than in wild-type mice; that treatment with RvE1 and LXA4 restored the level of these compounds, reversed the inflammatory process, and decreased the neuroinflammation associated with Aβ pathology in 5xFAD mice.

Plasma lipoxin A4 and resolvin D1 are not associated with reduced adenoma risk in a randomized trial of aspirin to prevent colon adenomas.

Inflammation plays a major role in colon carcinogenesis. Endogenously produced specialized proresolving lipid mediators (SPMs) play a central role in inflammation and tissue homeostasis, and have been implicated in carcinogenesis. We studied the associations of plasma levels of two SPMs [lipoxin A4 (LXA4 ) and resolvin D1(RvD1)] with risk for recurrent adenoma. In this pilot study, we used data and biosamples from an adenoma chemoprevention study investigating the effects of aspirin and/or folic acid on the occurrence of colorectal adenomas. In the parent study, 1121 participants with a recent adenoma were randomized to study agents to be taken until the next surveillance colonoscopy about 3 years later. In this pilot study, LXA4 and RvD1 from samples taken near the end of study treatment were measured in a randomly selected sub-set of 200 participants. Commercially available ELISA kits to assay the analytes were validated using a metabololipidomic LC-MS/MS assay. Poisson regression with a robust error variance was used to calculate risk ratios and 95% confidence intervals. Plasma LXA4 and RvD1 were not associated with the risk of adenoma occurrence. LXA4 at the end of study follow-up was 32% (P = 0.01) proportionately higher in women compared to men. A similar non-significant trend toward higher levels among women was observed for RvD1. Our preliminary findings provided no evidence that plasma LXA4 or RvD1 are associated with reduced risk of colorectal adenoma occurrence, but suggest LXA4 may differ among men and women. Future studies focusing on SPM's local effects and levels in the colon are needed.

An imbalance between specialized pro-resolving lipid mediators and pro-inflammatory leukotrienes promotes instability of atherosclerotic plaques

Chronic unresolved inflammation plays a causal role in the development of advanced atherosclerosis, but the mechanisms that prevent resolution in atherosclerosis remain unclear. Here, we use targeted mass spectrometry to identify specialized pro-resolving lipid mediators (SPM) in histologically-defined stable and vulnerable regions of human carotid atherosclerotic plaques. The levels of SPMs, particularly resolvin D1 (RvD1), and the ratio of SPMs to pro-inflammatory leukotriene B4 (LTB4), are significantly decreased in the vulnerable regions. SPMs are also decreased in advanced plaques of fat-fed Ldlr−/− mice. Administration of RvD1 to these mice during plaque progression restores the RvD1:LTB4 ratio to that of less advanced lesions and promotes plaque stability, including decreased lesional oxidative stress and necrosis, improved lesional efferocytosis, and thicker fibrous caps. These findings provide molecular support for the concept that defective inflammation resolution contributes to the formation of clinically dangerous plaques and offer a mechanistic rationale for SPM therapy to promote plaque stability.

Proresolving and cartilage-protective actions of resolvin D1 in inflammatory arthritis.

Rheumatoid arthritis (RA) is a debilitating disease characterized by persistent accumulation of leukocytes within the articular cavity and synovial tissue. Metabololipidomic profiling of arthritic joints from omega-3 supplemented mice identified elevated levels of specialized proresolving lipid mediators (SPM) including resolvin D1 (RvD1). Profiling of human RA synovial fluid revealed physiological levels of RvD1, which — once applied to human neutrophils — attenuated chemotaxis. These results prompted analyses of the antiarthritic properties of RvD1 in a model of murine inflammatory arthritis. The stable epimer 17R-RvD1 (100 ng/day) significantly attenuated arthritis severity, cachexia, hind-paw edema, and paw leukocyte infiltration and shortened the remission interval. Metabololipidomic profiling in arthritic joints revealed 17R-RvD1 significantly reduced PGE2 biosynthesis, while increasing levels of protective SPM. Molecular analyses indicated that 17R-RvD1 enhanced expression of genes associated with cartilage matrix synthesis, and direct intraarticular treatment induced chondroprotection. Joint protective actions of 17R-RvD1 were abolished in RvD1 receptor–deficient mice termed ALX/fpr2/3–/–. These investigations open new therapeutic avenues for inflammatory joint diseases, providing mechanistic substance for the benefits of omega-3 supplementation in RA.