Novel Endogenous Proresolving Molecules:Essential Fatty Acid-Derived and Gaseous Mediators in the Resolution of Inflammation

Chronic stress alters lipid mediator profiles associated with immune-related gene expressions and cell compositions in mouse bone marrow and spleen

Despite the importance of lipid mediators in stress and depression and their link to inflammation, the influence of stress on these mediators and their role in inflammation is not fully understood. This study used RNA-seq, LC-MS/MS, and flow cytometry analyses in a mouse model subjected to chronic social defeat stress to explore the effects of acute and chronic stress on lipid mediators, gene expression, and cell population in the bone marrow and spleen. In the bone marrow, chronic stress induced a sustained transition from lymphoid to myeloid cells, accompanied by corresponding changes in gene expression. This change was associated with decreased levels of 15-deoxy-d12,14-prostaglandin J2, a lipid mediator that inhibits inflammation. In the spleen, chronic stress also induced a lymphoid-to-myeloid transition, albeit transiently, alongside gene expression changes indicative of extramedullary hematopoiesis. These changes were linked to lower levels of 12-HEPE and resolvins, both critical for inhibiting and resolving inflammation. Our findings highlight the significant role of anti-inflammatory and pro-resolving lipid mediators in the immune responses induced by chronic stress in the bone marrow and spleen. This study paves the way for understanding how these lipid mediators contribute to the immune mechanisms of stress and depression.

Chronic social defeat stress increases the amounts of 12-lipoxygenase lipid metabolites in the nucleus accumbens of stress-resilient mice

Severe and prolonged social stress induces mood and cognitive dysfunctions and precipitates major depression. Neuroinflammation has been associated with chronic stress and depression. Rodent studies showed crucial roles of a few inflammation-related lipid mediators for chronic stress-induced depressive-like behaviors. Despite an increasing number of lipid mediators identified, systematic analyses of synthetic pathways of lipid mediators in chronic stress models have not been performed. Using LC–MS/MS, here we examined the effects of chronic social defeat stress on multiple synthetic pathways of lipid mediators in brain regions associated with stress susceptibility in mice. Chronic social defeat stress increased the amounts of 12-lipoxygenase (LOX) metabolites, 12-HETE and 12-HEPE, specifically in the nucleus accumbens 1 week, but not immediately, after the last stress exposure. The increase was larger in stress-resilient mice than stress-susceptible mice. The S isomer of 12-HETE was selectively increased in amount, indicating the role of 12S-LOX activity. Among the enzymes known to have 12S-LOX activity, only Alox12 mRNA was reliably detected in the brain and enriched in brain endothelial cells. These findings suggest that chronic social stress induces a late increase in the amounts of 12S-LOX metabolites derived from the brain vasculature in the nucleus accumbens in a manner associated with stress resilience.

Atherosclerosis is a major human killer and non-resolving inflammation is a prime suspect

The resolution of inflammation (or inflammation-resolution) is an active and highly coordinated process. Inflammation-resolution is governed by several endogenous factors, and specialized pro-resolving mediators (SPMs) are one such class of molecules that have robust biological function. Non-resolving inflammation is associated with a variety of human diseases, including atherosclerosis. Moreover, non-resolving inflammation is a hallmark of ageing, an inevitable process associated with increased risk for cardiovascular disease. Uncovering mechanisms as to why inflammation-resolution is impaired in ageing and in disease and identifying useful biomarkers for non-resolving inflammation are unmet needs. Recent work has pointed to a critical role for balanced ratios of SPMs and pro-inflammatory lipids (i.e. leucotrienes and/or specific prostaglandins) as a key determinant of timely inflammation resolution. This review will focus on the accumulating findings that support the role of non-resolving inflammation and imbalanced pro-resolving and pro-inflammatory mediators in atherosclerosis. We aim to provide insight as to why these imbalances occur, the importance of ageing in disease progression, and how haematopoietic function impacts inflammation-resolution and atherosclerosis. We highlight open questions regarding therapeutic strategies and mechanisms of disease to provide a framework for future studies that aim to tackle this important human disease.

Effect of resolvin D5 on T cell differentiation and osteoclastogenesis analyzed by lipid mediator profiling in the experimental arthritis

Resolvins, are specialized pro-resolving mediators (SPMs) derived from n-3 polyunsaturated fatty acids. They contribute actively to the resolution of inflammation, but little is known concerning their role in chronic inflammation, such as in rheumatoid arthritis (RA). Here, we performed lipid mediator (LM) profiling in tissues from the paws of SKG arthritic mice using lipid chromatography (LC)/mass spectrometry (MS)/MS-based LM metabololipidomics. We found elevated levels of SPMs including resolvin D5 (RvD5) in these tissues. Moreover, RvD5 levels were significantly correlated with arthritis disease activity. From experiments to assess the role of RvD5 in the pathology of RA, we concluded that RvD5 suppressed Th17 cell differentiation and facilitated regulatory T cell differentiation, as well as inhibiting CD4⁺ T cell proliferation. Furthermore, RvD5 attenuated osteoclast differentiation and interfered with osteoclastogenesis. Targeting the resolution of inflammation could be promising as a novel treatment for RA.

Regulation of Neutrophil Function by Marine n-3 Fatty Acids-A Mini Review

While normal functioning neutrophils contribute in various, critical ways to the maintenance of a stable immune system, their hypo- or hyper-activation has been implicated in the onset or exacerbation of multiple inflammatory conditions often affecting the vulnerable, aging population. As such, many would benefit from interventions capable of targeting neutrophils in disease-specific ways without disrupting their primary role in maintaining immune function. After consumption, marine omega-3 fatty acids are rapidly incorporated into the phospholipid bilayer of neutrophils, changing the fatty acid composition and consequently modifying neutrophil function. In addition to eicosanoid synthesis, the mechanisms by which marine n-3 fatty acids and their metabolites alter neutrophil function involve blockage of transcription factors that subsequently reduce pro-inflammatory gene expression by neutrophils and through the disruption of lipid rafts. In the current mini-review, a brief explanation of marine n-3 fatty acid metabolism is provided and the subsequent impact on neutrophil function is discussed. In addition, current evidence of the effects of marine n-3 fatty acid supplementation on neutrophil function from clinical trials conducted in the past 15 years is summarized.

Specialized Pro-Resolving Mediators and the Lymphatic System

Diminished lymphatic function and abnormal morphology are common in chronic inflammatory diseases. Recent studies are investigating whether it is possible to target chronic inflammation by promoting resolution of inflammation, in order to enhance lymphatic function and attenuate disease. Resolution of inflammation is an active process regulated by bioactive lipids known as specialized pro-resolving mediators (SPMs). SPMs can modulate leukocyte migration and function, alter cytokine/chemokine release, modify autophagy, among other immune-related activities. Here, we summarize the role of the lymphatics in resolution of inflammation and lymphatic impairment in chronic inflammatory diseases. Furthermore, we discuss the current literature describing the connection between SPMs and the lymphatics, and the possibility of targeting the lymphatics with innovative SPM therapy to promote resolution of inflammation and mitigate disease.

15-Deoxy-△12,14-Prostaglandin J2 Promotes Resolution of Experimentally Induced Colitis

Uncontrolled macrophage functions cause failure to resolve gut inflammation and has been implicated in the pathogenesis of inflammatory bowel disease (IBD). 15-Deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂), one of endogenous lipid mediators formed from arachidonic acid during the inflammatory process, has been reported to terminate inflammation. However, the pro-resolving effect of 15d-PGJ₂ on intestinal inflammation and underlying molecular mechanisms remain largely unknown. In the present study, we examined the effects of 15d-PGJ₂ on the resolution of dextran sulfate sodium (DSS)-induced murine colitis that mimics human IBD. Pharmacologic inhibition of prostaglandin D synthase (PGDS) responsible for the synthesis of 15d-PGJ₂ hampered resolution of inflammation in the colonic mucosa of mice treated with DSS. Notably, intraperitoneal injection of 15d-PGJ₂ accelerated the resolution of experimentally induced colitis. 15d-PGJ₂ treatment reduced the number of neutrophils and M1 macrophages, while it increased the proportion of M2 macrophages. Moreover, 15d-PGJ₂ treated mice exhibited the significantly reduced proportion of macrophages expressing the pro-inflammatory cytokine, IL-6 with concomitant suppression of STAT3 phosphorylation in the colonic mucosa of mice administered 2.5% DSS in drinking water. Taken together, these findings clearly indicate that 15d-PGJ₂, endogenously generated from arachidonic acid by cyclooxygenase-2 and PGDS activities in inflamed tissue, promotes resolution of intestinal colitis.

Molecular Pathways Linking Oxylipins to Nociception in Rats

Oxylipins are lipid peroxidation products that participate in nociceptive, inflammatory, and vascular responses to injury. Effects of oxylipins depend on tissue-specific differences in accumulation of precursor polyunsaturated fatty acids and the expression of specific enzymes to transform the precursors. The study of oxylipins in nociception has presented technical challenges leading to critical knowledge gaps in the way these molecules operate in nociception. We applied a systems-based approach to characterize oxylipin precursor fatty acids, and expression of genes coding for proteins involved in biosynthesis, transport, signaling and inactivation of pro- and antinociceptive oxylipins in pain circuit tissues. We further linked these pathways to nociception by demonstrating intraplantar carrageenan injection induced gene expression changes in oxylipin biosynthetic pathways. We determined functional-biochemical relevance of the proposed pathways in rat hind paw and dorsal spinal cord by measuring basal and stimulated levels of oxylipins throughout the time-course of carrageenan-induced inflammation. Finally, when oxylipins were administered by intradermal injection we observed modulation of nociceptive thermal hypersensitivity, providing a functional-behavioral link between oxylipins, their molecular biosynthetic pathways, and involvement in pain and nociception. Together, these findings advance our understanding of molecular lipidomic systems linking oxylipins and their precursors to nociceptive and inflammatory signaling pathways in rats. PERSPECTIVE: We applied a systems approach to characterize molecular pathways linking precursor lipids and oxylipins to nociceptive signaling. This systematic, quantitative evaluation of the molecular pathways linking oxylipins to nociception provides a framework for future basic and clinical research investigating the role of oxylipins in pain.

Docosahexaenoic acid,22:6n-3: Its roles in the structure and function of the brain

Docosahexaenoic acid,22:6n-3 (DHA) and its metabolites are vital for the structure and functional brain development of the fetus and infants, and also for maintenance of healthy brain function of adults. DHA is thought to be an essential nutrient required throughout the life cycle for the maintenance of overall brain health. The mode of actions of DHA and its derivatives at both cellular and molecular levels in the brain are emerging. DHA is the major prevalent fatty acid in the brain membrane. The brain maintains its fatty acid levels mainly via the uptake of plasma free fatty acids. Therefore, circulating plasma DHA is significantly related to cognitive abilities during ageing and is inversely associated with cognitive decline. The signaling pathways of DHA and its metabolites are involved in neurogenesis, antinociceptive effects, anti-apoptotic effect, synaptic plasticity, Ca²⁺ homeostasis in brain diseases, and the functioning of nigrostriatal activities. Mechanisms of action of DHA metabolites on various processes in the brain are not yet well known. Epidemiological studies support a link between low habitual intake of DHA and a higher risk of brain disorders. A diet characterized by higher intakes of foods containing high in n-3 fatty acids, and/or lower intake of n-6 fatty acids was strongly associated with a lower Alzheimer's Disease and other brain disorders. Supplementation of DHA improves some behaviors associated with attention deficit hyperactivity disorder, bipolar disorder, schizophrenia, and impulsive behavior, as well as cognition. Nevertheless, the outcomes of trials with DHA supplementation have been controversial. Many intervention studies with DHA have shown an apparent benefit in brain function. However, clinical trials are needed for definitive conclusions. Dietary deficiency of n-3 fatty acids during fetal development in utero and the postnatal state has detrimental effects on cognitive abilities. Further research in humans is required to assess a variety of clinical outcomes, including quality of life and mental status, by supplementation of DHA.

Neuroinflammation in hypertension: the renin-angiotensin system versus pro-resolution pathways

Overstimulation of the pro-inflammatory pathways within brain areas responsible for sympathetic outflow is well evidenced as a primary contributing factor to the establishment and maintenance of neurogenic hypertension. However, the precise mechanisms and stimuli responsible for promoting a pro-inflammatory state are not fully elucidated. Recent work has unveiled novel compounds derived from omega-3 polyunsaturated fatty acids (ω-3 PUFAs), termed specialized pro-resolving mediators (SPMs), which actively regulate the resolution of inflammation. Failure or dysregulation of the resolution process has been linked to a variety of chronic inflammatory and neurodegenerative diseases. Given the pathologic role of neuroinflammation in the hypertensive state, SPMs and their associated pathways may provide a link between hypertension and the long-standing association of dietary ω-3 PUFAs with cardioprotection. Herein, we review recent progress in understanding the RAS-driven pathophysiology of neurogenic hypertension, particularly in regards to the chronic low-grade neuroinflammatory response. In addition, we examine the potential for an impaired resolution of inflammation process in the context of hypertension.

Cellular and Molecular Therapeutic Targets in Inflammatory Bowel Disease-Focusing on Intestinal Barrier Function

The human gut relies on several cellular and molecular mechanisms to allow for an intact and dynamical intestinal barrier. Normally, only small amounts of luminal content pass the mucosa, however, if the control is broken it can lead to enhanced passage, which might damage the mucosa, leading to pathological conditions, such as inflammatory bowel disease (IBD). It is well established that genetic, environmental, and immunological factors all contribute in the pathogenesis of IBD, and a disturbed intestinal barrier function has become a hallmark of the disease. Genetical studies support the involvement of intestinal barrier as several susceptibility genes for IBD encode proteins with key functions in gut barrier and homeostasis. IBD patients are associated with loss in bacterial diversity and shifts in the microbiota, with a possible link to local inflammation. Furthermore, alterations of immune cells and several neuro-immune signaling pathways in the lamina propria have been demonstrated. An inappropriate immune activation might lead to mucosal inflammation, with elevated secretion of pro-inflammatory cytokines that can affect the epithelium and promote a leakier barrier. This review will focus on the main cells and molecular mechanisms in IBD and how these can be targeted in order to improve intestinal barrier function and reduce inflammation.

Pro-resolution of Inflammation: New Hints to Manage Sepsis?

Sepsis is newly defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. The pathophysiological mechanism of sepsis is highly complex, and the mortality of in-patients suffering from sepsis is more than 10%. Severe unmanaged inflammation and inappropriate immune response characterize sepsis. Anti-inflammation therapies alone are not successful for the reason that disbalance of anti-inflammatory and pro-resolving agents. In the recent researches, the host responses during the course of self-resolving infections are found to have the involvements of specialized pro-resolution mediators (SPMs), namely, lipoxins, resolvins, protectins and maresins. These endogenous lipid metabolites are core signal molecules in the resolution of inflammation, playing a key role in regulating the inflammation and promoting return to homeostasis. Besides, heme oxygenase-1 (HO-1, a sensitive marker for oxidative stress) is also known for upregulation in inflammation profiling. Carbon monoxide, synthesized by HO-1, performs multiple stances of anti-inflammation and pro-resolution along with the SPMs. If the potentially beneficial effects of these mediators would be well evaluated in clinical trials, they present encouraging new hints in managing infectious maladies especially sepsis.

Inflammatory and Pro-resolving Lipids in Trypanosomatid Infections: A Key to Understanding Parasite Control

Pathogenic trypanosomatids (Trypanosoma cruzi, Trypanosoma brucei, and Leishmania spp.) are protozoan parasites that cause neglected diseases affecting millions of people in Africa, Asia, and the Americas. In the process of infection, trypanosomatids evade and survive the immune system attack, which can lead to a chronic inflammatory state that induces cumulative damage, often killing the host in the long term. The immune mediators involved in this process are not entirely understood. Most of the research on the immunologic control of protozoan infections has been focused on acute inflammation. Nevertheless, when this process is not terminated adequately, permanent damage to the inflamed tissue may ensue. Recently, a second process, called resolution of inflammation, has been proposed to be a pivotal process in the control of parasite burden and establishment of chronic infection. Resolution of inflammation is an active process that promotes the normal function of injured or infected tissues. Several mediators are involved in this process, including eicosanoid-derived lipids, cytokines such as transforming growth factor (TGF)-β and interleukin (IL)-10, and other proteins such as Annexin-V. For example, during T. cruzi infection, pro-resolving lipids such as 15-epi-lipoxin-A4 and Resolvin D1 have been associated with a decrease in the inflammatory changes observed in experimental chronic heart disease, reducing inflammation and fibrosis, and increasing host survival. Furthermore, Resolvin D1 modulates the immune response in cells of patients with Chagas disease. In Leishmania spp. infections, pro-resolving mediators such as Annexin-V, lipoxins, and Resolvin D1 are related to the modulation of cutaneous manifestation of the disease. However, these mediators seem to have different roles in visceral or cutaneous leishmaniasis. Finally, although T. brucei infections are less well studied in terms of their relationship with inflammation, it has been found that arachidonic acid-derived lipids act as key regulators of the host immune response and parasite burden. Also, cytokines such as IL-10 and TGF-β may be related to increased infection. Knowledge about the inflammation resolution process is necessary to understand the host–parasite interplay, but it also offers an interesting opportunity to improve the current therapies, aiming to reduce the detrimental state induced by chronic protozoan infections.

Altered Serum n-6 Polyunsaturated Fatty Acid Profile and Risks of Mortality and Cardiovascular Events in a Cohort of Hemodialysis Patients

OBJECTIVE

Alterations in the balance between serum n-3 and n-6 polyunsaturated fatty acids (PUFAs) is predictive of cardiovascular events among hemodialysis patients, although little is known about the serum ratio of n-6 arachidonic acid (AA) to n-6 dihomo-γ-linoleic acid (DGLA) in renal failure. We hypothesized that AA/DGLA ratio is altered in hemodialysis patients resulting in poor clinical outcomes.

METHODS

This was a single center cohort study in an urban area in Japan with cross-sectional analyses. Subjects were 517 hemodialysis patients and 122 control subjects. The main exposure was serum AA/DGLA ratio, and the main outcome measures were all-cause mortality and cardiovascular events during 5 years.

RESULTS

The hemodialysis patients showed a higher median (interquartile range) AA/DGLA ratio than the control subjects (6.46 [5.22-7.81] versus 4.56 [3.74-6.34], P < .001). In a Cox proportional hazard model adjusted for age, sex, dialysis duration, diabetic nephropathy, prior cardiovascular disease, and the ratio of serum n-3 polyunsaturated fatty acids (eicosapentaenoic acid plus docosahexaenoic acid) to AA, the higher quartiles of AA/DGLA ratio were associated with higher risk for all-cause mortality with hazard ratios (95% confidence interval) of 1.50 (0.84-2.76) for quartile 2, 2.10 (1.18-3.86) for quartile 3, and 2.02 (1.10-3.78) for quartile 4 compared with quartile 1. AA/DGLA ratio showed a similar association with the risk of cardiovascular events.

CONCLUSIONS

AA/DGLA ratio was elevated in patients with end-stage renal disease requiring hemodialysis, and a high AA/DGLA ratio was an independent predictor of poor clinical outcomes in this population.

Actors and Factors in the Resolution of Intestinal Inflammation: Lipid Mediators As a New Approach to Therapy in Inflammatory Bowel Diseases

In the last few decades, the pathogenesis of inflammatory bowel disease (IBD) in genetically predisposed subjects susceptible to specific environmental factors has been attributed to disturbance of both the immune and non-immune system and/or to the imbalanced interactions with microbes. However, increasing evidences support the idea that defects in pro-resolving pathways might strongly contribute to IBD onset. The resolution of inflammation is now recognized as a dynamic event coordinated by specialized pro-resolving lipid mediators (LMs), which dampen inflammation-sustaining events, such as angiogenesis, release of pro-inflammatory cytokines, clearance of apoptotic cells, and microorganisms. Among these pro-resolving molecules, those derived from essential polyunsaturated fatty acids (PUFAs) have been shown to induce favorable effects on a plethora of human inflammatory disorders, including IBD. Here, we offer a summary of mechanisms involving both cellular and molecular components of the immune response and underlying the anti-inflammatory and pro-resolving properties of PUFAs and their derivatives in the gut, focusing on both ω-3 and ω-6 LMs. These fatty acids may influence IBD progression by: reducing neutrophil transmigration across the intestinal vasculature and the epithelium, preventing the release of pro-inflammatory cytokines and the up-regulation of adhesion molecules, and finally by promoting the production of other pro-resolving molecules. We also discuss the numerous attempts in using pro-resolving PUFAs to ameliorate intestinal inflammation, both in patients with IBD and mouse models. Although their effects in reducing inflammation is incontestable, results from previous works describing the effects of PUFA administration to prevent or treat IBD are controversial. Therefore, more efforts are needed not only to identify and explain the physiological functions of PUFAs in the gut, but also to unveil novel biosynthetic pathways of these pro-resolving LMs that may be dysregulated in these gut-related disorders. We suppose that either PUFAs or new medications specifically promoting resolution-regulating mediators and pathways will be much better tolerated by patients with IBD, with the advantage of avoiding immune suppression.

Comparative effects of the ω3 polyunsaturated fatty acid derivatives resolvins E1 and D1 and protectin DX in models of inflammation and pain

Purpose

Specialized pro-resolving lipid mediators (SPMs), also known as lipoxins, resolvins (Rvs), protectins and maresins, have been implicated in the resolution of the inflammatory process. However, a systematic comparison of their activity in the relief of inflammation and pain models is still lacking.

Materials and methods

The effects of Rvs E1 and D1 and protectin DX (PDX) were assessed in rat paws inflamed by the standard proinflammatory stimulus carrageenan or by histamine, 5-hydroxytryptamine, substance P or prostaglandin E₂. The experimental outcomes were the mechanical nociceptive threshold and increase in paw volume as a measure of pain and edema formation, respectively. The analgesic and anti-inflammatory activities of the indicated SPMs were also compared with nonsteroidal (indomethacin and celecoxib) and steroidal (dexamethasone) anti-inflammatory drugs.

Results

Only RvE1 and RvD1 presented analgesic and anti-inflammatory activities in the carrageenan model, and RvE1 was twice as potent as RvD1. Both substances tended to be better analgesics than anti-inflammatory agents, with a modeling profile similar to steroidal anti-inflammatory drugs. However, proinflammatory effects (edema formation) were also detected when the mediators histamine, 5-hydroxytryptamine or substance P replaced carrageenan as the proinflammatory stimuli. The analgesic and anti-inflammatory effects of resolvins were specifically prevented by an antagonist of the leukotriene B₄ receptor 1 (BLT1).

Conclusion

Rvs, as analgesic agents, may be better therapeutic agents than nonsteroidal anti-inflammatory drugs, the current choice in the relief of pain of an inflammatory origin. However, the possibility of developing adverse effects cannot be overlooked.

Boosting Inflammation Resolution in Atherosclerosis: The Next Frontier for Therapy

Defective inflammation resolution is the underlying cause of prevalent chronic inflammatory diseases, such as arthritis, asthma, cancer, and neurodegenerative and cardiovascular diseases. Inflammation resolution is governed by several endogenous factors, including fatty acid-derived specialized proresolving mediators and proteins, such as annexin A1. Specifically, specialized proresolving mediators comprise a family of mediators that include arachidonic acid-derived lipoxins, omega-3 fatty acid eicosapentaenoic acid-derived resolvins, docosahexaenoic acid-derived resolvins, protectins, and maresins. Emerging evidence indicates that imbalances between specialized proresolving mediators and proinflammatory mediators are associated with several prevalent human diseases, including atherosclerosis. Mechanisms that drive this imbalance remain largely unknown and will be discussed in this review. Furthermore, the concept of dysregulated inflammation resolution in atherosclerosis has been known for several decades. Recently, there has been an explosion of new work with regard to the therapeutic application of proresolving ligands in experimental atherosclerosis. Therefore, this review will highlight recent advances in our understanding of how inflammation resolution may become defective in atherosclerosis and the potential for proresolving therapeutics in atherosclerosis. Last, we offer insight for future implications of the field.

Eicosapentaenoic Acid-Enriched High-Density Lipoproteins Exhibit Anti-Atherogenic Properties

BACKGROUND

It has previously been reported that oral administration of purified eicosapentaenoic acid (EPA) generates EPA-rich high-density lipoprotein (HDL) particles with a variety of anti-inflammatory properties. In this study, the mechanism underlying the anti-atherogenic effects of EPA-rich HDL using reconstituted HDL (rHDL) was investigated.Methods and Results:rHDL was generated by the sodium cholate dialysis method, using apolipoprotein A-1 protein, cholesterol, and various concentrations of EPA-phosphatidylcholine (PC) or egg-PC. Increased EPA-PC contents in rHDL resulted in decreased particle size. Next, the effects of rHDL containing various amounts (0-100% of total PC) of EPA-PC on vascular cell adhesion molecule-1 (VCAM-1) expression in human umbilical vein endothelial cells (HUVECs) was examined. Cytokine-stimulated VCAM-1 expression was inhibited in a dose-dependent manner based on the amount of EPA-PC in rHDL. Surprisingly, the incubation of HUVECs with EPA-rich rHDL resulted in the production of resolvin E3 (RvE3), an anti-inflammatory metabolite derived from EPA. Incubation with EPA-PC alone did not adequately induce RvE3 production, suggesting that RvE3 production requires an endothelial cell-HDL interaction. The increased anti-inflammatory effects of EPA-rich HDL may be explained by EPA itself and RvE3 production. Furthermore, the increase in EPA-PC content enhanced cholesterol efflux.

CONCLUSIONS

The EPA-enriched HDL particles exhibit cardioprotective properties via the production of anti-inflammatory lipid metabolites and the increase in cholesterol efflux.

Microglia mediate postoperative hippocampal inflammation and cognitive decline in mice

Surgery can induce cognitive decline, a risk that increases with advancing age. In rodents, postoperative cognitive decline (POCD) is associated with the inflammatory activation of hippocampal microglia. To examine the role of microglia in POCD, we inhibited the colony-stimulating factor 1 receptor (CSF1R) in adult mice, effectively depleting CNS microglia. Surgical trauma (tibial fracture) reduced the ability of mice to remember a conditioned response learned preoperatively, a deficit more pronounced and persistent in mice with diet-induced obesity (DIO). Whereas microglial depletion by itself did not affect learning or memory, perioperative microglial depletion remarkably protected mice, including those with DIO, from POCD. This protection was associated with reduced hippocampal levels of inflammatory mediators, abrogation of hippocampal recruitment of CCR2⁺ leukocytes, and higher levels of circulating inflammation-resolving factors. Targeting microglia may thus be a viable strategy to mitigate the development of POCD, particularly in those with increased vulnerability.

Specialized pro-resolving mediators in cardiovascular diseases

The resolution of inflammation is a highly regulated process enacted by endogenous mediators including specialized pro-resolving lipid mediators (SPMs): the lipoxins, resolvins, protectins and maresins. SPMs activate specific cellular receptors to temper the production of pro-inflammatory mediators, diminish the recruitment of neutrophils, and promote the clearance of dead cells by macrophages. These mediators also enhance host-defense and couple resolution of inflammation to subsequent phases of tissue repair. Given that unresolved inflammation plays a causal role in the development of cardiovascular diseases, an understanding of these endogenous pro-resolving processes is critical for determining why cardiovascular inflammation does not resolve. Here, we discuss the receptor-dependent actions of resolvins and related pro-resolving mediators and highlight their emerging roles in the cardiovascular system. We propose that stimulating resolution could be a novel approach for treating chronic cardiovascular inflammation without promoting immunosuppression.

The time course of erythrocyte membrane fatty acid concentrations during and after treatment of non-human primates with increasing doses of an omega-3 rich phospholipid preparation derived from krill-oil

Background

A commonly used measure to reflect the intake of the long-chain omega-3 fatty acids EPA and DHA is the omega-3 index, defined as the sum of EPA + DHA as % of total fatty acids in erythrocyte membrane. When the omega-3 index changes it follows that the relative fractions of other fatty acids in the membrane are also changed. In the present study, increasing doses of a preparation of omega-3 rich phospholipids extracted from krill oil were administered orally to non-human primates for 12 weeks and the time course of EPA, DHA and 22 other fatty acids in erythrocytes was determined bi-weekly during treatment and for 8 weeks after cessation of treatment. Plasma concentrations of six endocannabinoid-type mediators being downstream metabolites of some fatty acids analyzed in erythrocytes were also determined.

Methods

Six diabetic, dyslipidemic non-human primates were included, three in a vehicle control group and three being treated with the omega-3 rich phospholipid preparation. The vehicle control and test items were given daily by gavage and the test item doses were 50, 150 and 450 mg phospholipids/kg/day. Each dose level was given for four weeks. Blood was sampled at baseline and thereafter bi-weekly. Fatty acids were determined in erythrocytes by methylation followed by gas-chromatography. Endocannabinoids and endocannabinoid-like mediators were analyzed in plasma by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry.

Results

The treatment resulted in a dose-related increase in the fraction of EPA and DHA in erythrocyte membranes and a dose-related decrease of other poly-unsaturated fatty acids, in particular omega-6 polyunsaturated fatty acids. Erythrocyte concentrations of saturated fatty acids remained unchanged throughout the experiment. Plasma concentrations of endocannabinoids and endocannabinoid-like mediators changed accordingly as those being downstream arachidonic acid decreased, downstream of the saturated palmitic and oleic acids remained unchanged while a downstream EPA metabolite increased.

Conclusion

Increasing the omega-3 index by administering an omega-3 rich phospholipid extracted from krill oil did not alter the ratio of unsaturated vs. saturated fatty acids in the erythrocyte membranes but only the relative concentrations of unsaturated fatty acids, in particular unsaturated omega-6 fatty acids. Concentrations of saturated fatty acids remained unchanged.

Pro-Resolving Effects of Resolvin D2 in LTD4 and TNF-α Pre-Treated Human Bronchi

Inflammation is a major burden in respiratory diseases, resulting in airway hyperresponsiveness. Our hypothesis is that resolution of inflammation may represent a long-term solution in preventing human bronchial dysfunctions. The aim of the present study was to assess the anti-inflammatory effects of RvD₂, a member of the D-series resolving family, with concomitant effects on ASM mechanical reactivity. The role and mode of action of RvD₂ were assessed in an in vitro model of human bronchi under pro-inflammatory conditions, induced either by 1 μM LTD₄ or 10 ng/ml TNF-α pre-treatment for 48h. TNF-α and LTD₄ both induced hyperreactivity in response to pharmacological stimuli. Enhanced 5-Lipoxygenase (5-LOX) and cysteinyl leukotriene receptor 1 (CysLTR1) detection was documented in LTD₄ or TNF-α pre-treated human bronchi when compared to control (untreated) human bronchi. In contrast, RvD₂ treatments reversed 5-LOX/β-actin and CysLTR1/β-actin ratios and decreased the phosphorylation levels of AP-1 subunits (c-Fos, c-Jun) and p38-MAP kinase, while increasing the detection of the ALX/FPR2 receptor. Moreover, various pharmacological agents revealed the blunting effects of RvD₂ on LTD₄ or TNF-α induced hyper-responsiveness. Combined treatment with 300 nM RvD₂ and 1 μM WRW4 (an ALX/FPR2 receptor inhibitor) blunted the pro-resolving and broncho-modulatory effects of RvD₂. The present data provide new evidence regarding the role of RvD₂ in a human model of airway inflammation and hyperrresponsiveness.

Polyunsaturated Fatty Acids and Their Derivatives: Therapeutic Value for Inflammatory, Functional Gastrointestinal Disorders, and Colorectal Cancer

Polyunsaturated fatty acids (PUFAs) are bioactive lipids which modulate inflammation and immunity. They gained recognition in nutritional therapy and are recommended dietary supplements. There is a growing body of evidence suggesting the usefulness of PUFAs in active therapy of various gastrointestinal (GI) diseases. In this review we briefly cover the systematics of PUFAs and their metabolites, and elaborate on their possible use in inflammatory bowel disease (IBD), functional gastrointestinal disorders (FGIDs) with focus on irritable bowel syndrome (IBS), and colorectal cancer (CRC). Each section describes the latest findings from in vitro and in vivo studies, with reports of clinical interventions when available.