Including Lipid Mediators Research Articles

Inactivation of CES1 Blocks Prostaglandin D2 Glyceryl Ester Catabolism in Monocytes/Macrophages and Enhances Its Anti-inflammatory Effects, Whereas the Pro-inflammatory Effects of Prostaglandin E2 Glyceryl Ester Are Attenuated.

Human monocytic cells in blood have important roles in host defense and express the enzyme carboxylesterase 1 (CES1). This metabolic serine hydrolase plays a critical role in the metabolism of many molecules, including lipid mediators called prostaglandin glyceryl esters (PG-Gs), which are formed during cyclooxygenase-mediated oxygenation of the endocannabinoid 2-arachidonoylglycerol. Some PG-Gs have been shown to exhibit anti-inflammatory effects; however, they are unstable compounds, and their hydrolytic breakdown generates pro-inflammatory prostaglandins. We hypothesized that by blocking the ability of CES1 to hydrolyze PG-Gs in monocytes/macrophages, the beneficial effects of anti-inflammatory prostaglandin D2-glyceryl ester (PGD2-G) could be augmented. The goals of this study were to determine whether PGD2-G is catabolized by CES1, evaluate the degree to which this metabolism is blocked by small-molecule inhibitors, and assess the immunomodulatory effects of PGD2-G in macrophages. A human monocytic cell line (THP-1 cells) was pretreated with increasing concentrations of known small-molecule inhibitors that block CES1 activity [chlorpyrifos oxon (CPO), WWL229, or WWL113], followed by incubation with PGD2-G (10 μM). Organic solvent extracts of the treated cells were analyzed by liquid chromatography with tandem mass spectrometry to assess levels of the hydrolysis product PGD2. Further, THP-1 monocytes with normal CES1 expression (control cells) and “knocked-down” CES1 expression (CES1KD cells) were employed to confirm CES1’s role in PGD2-G catabolism. We found that CES1 has a prominent role in PGD2-G hydrolysis in this cell line, accounting for about 50% of its hydrolytic metabolism, and that PGD2-G could be stabilized by the inclusion of CES1 inhibitors. The inhibitor potency followed the rank order: CPO > WWL113 > WWL229. THP-1 macrophages co-treated with WWL113 and PGD2-G prior to stimulation with lipopolysaccharide exhibited a more pronounced attenuation of pro-inflammatory cytokine levels (interleukin-6 and TNFα) than by PGD2-G treatment alone. In contrast, prostaglandin E2-glyceryl ester (PGE2-G) had opposite effects compared to those of PGD2-G, which appeared to be dependent on the hydrolysis of PGE2-G to PGE2. These results suggest that the anti-inflammatory effects induced by PGD2-G can be further augmented by inactivating CES1 activity with specific small-molecule inhibitors, while pro-inflammatory effects of PGE2-G are attenuated. Furthermore, PGD2-G (and/or its downstream metabolites) was shown to activate the lipid-sensing receptor PPARγ, resulting in altered “alternative macrophage activation” response to the Th2 cytokine interleukin-4. These findings suggest that inhibition of CES1 and other enzymes that regulate the levels of pro-resolving mediators such as PGD2-G in specific cellular niches might be a novel anti-inflammatory approach.

P0108RESOLVIN D2 TREATMENT AMELIARATES ANGIOTENSINII-INDUCED RENAL INJURY

Abstract Background and Aims Renal inflammation is a protective response to several types of renal insults. Resolution is the ideal outcome of acute inflammation, however fail in resolution leads to chronic inflammation, progressive renal fibrosis and finally to end-stage renal failure. Recently is has been established that resolution of inflammation is mediated not only by disappearance of pro-inflammatory signals (including lipid mediators such as leukotrienes and prostaglandins) but also by activation of specialized pro-resolving mediators (SPM) including lipid mediators such as protectins (PD) and resolvins (Rvs) derived from omega-3 fatty acids precursors. Several authors have explored the role of different SPM in the treatment of experimental nephropathies. In the experimental model of bilateral ischemia/reperfusion pro-resolving mediators such as RvDs and PD1 were endogenously produced in the kidney in response to the injury. In this model, administration of RvD1 or PD1 before the ischemia or after the reperfusion showed a renoprotective effect. Moreover in the unilateral ureteral obstruction model RvE1 and RvD1administration inhibited interstitial fibrosis. One of the key mediators of renal injury is Angiotensin II (AngII) that participates in the pathogenesis of renal diseases through the regulation of two key processes, inflammation and fibrosis. Therefore, the aim of this study was to investigate the effect of the pro-resolving mediator Resolvin D2 (RvD2) in AngII-induced renal injury Method We used C57BL/6 mice that were infused with AngII (1440 µg/kg/day o 1000 ng/Kg/min). After 7 days of AngII treatment, when hypertension was already established, mice were treated with RvD2 (100ng/mouse ip) every two days for additional 7 days. At day 14 mice were sacrificed and kidneys were removed for protein and gene expression analysis and for histological examination. Results In our experimental model RvD2 ameliorated renal injury assessed by expression of NGAL both at mRNA and protein levels. In addition AngII-treated mice presented significant reduction in glomerular size that was increased by RvD2 treatment reaching values comparable to control. In addition, RvD2 inhibited the activation of inflammatory markers including COX-2, IL-6 and MCP-1 induced by AngII and reduced the number of F4/80+ infiltrated macrophages. We next evaluated the effect of RvD2 in the activation of NFκB, a key signaling pathway in inflammation. We observed that RvD2 inhibited AngII-induced NFkB activation. Moreover, RT-PCR analysis indicated that Ang II increased the expression of Tenascin C, a component of the fibrogenic niche in kidney fibrosis, as well as Type-I Collagen and Fibronectin and these levels were significantly reduced by the treatment with RvD2. These results were also confirmed by Masson-Goldner trichrome staining. Importantly, these effects were independent of changes in blood pressure. We finally studied whether the effects of RvD2 might be related to the modulation of RvDs endogenous biosynthesis pathway or RvD2 receptor GPR-18. mRNA analysis showed that AngII did not modified the expression levels of RvD2 biosynthesis enzymes including LOX-5 and LOX-15 nor GPR-18. However, RvD2 treatment increased the expression of LOX-15 and GPR-18 and downregulated LOX-5 indicating a possible auto-regulatory mechanism of RvD2 Conclusion Our results evidence a dual beneficial effect of the pro-resolvin mediator RvD2 in Ang II-induced renal injury as RvD2 treatment reversed not only renal inflammation but also tubulo-interstitial fibrosis. Hence, synthetic pro-resolving mediators would be an interesting therapeutic option for renal diseases.

Toll-like receptor signaling induces a temporal switch towards a resolving lipid profile in monocyte-derived macrophages

Inflammation is a tightly regulated process. During the past decade it has become clear that the resolution of inflammation is an active process and its dysregulation can contribute to chronic inflammation. Several cells and soluble mediators, including lipid mediators, regulate the course of inflammation and its resolution. It is, however, unclear which signals and cells are involved in initiating the resolution process. Macrophages are tissue resident cells and key players in regulating tissue inflammation through secretion of soluble mediators, including lipids. We hypothesize that persistent inflammatory stimuli can initiate resolution pathways in macrophages.In this study, we detected 21 lipids in LPS-stimulated human monocyte-derived macrophages by liquid chromatography coupled to tandem mass spectrometry. Cyclooxygenase-derived Prostaglandins were observed in the first six hours of stimulation. Interestingly, a switch towards 15-lipoxygenase products, such as the pro-resolving lipid precursors 15-HEPE and 17-HDHA was observed after 24 h. The RNA and protein expression of cyclooxygenase and 15-lipoxygenase were in line with this trend. Treatment with 17-HDHA increased IL-10 production of monocyte-derived macrophages and decreased LTB4 production by neutrophils, indicating the anti-inflammatory property of this lipid.These data reveal that monocyte-derived macrophages contribute to the resolution of inflammation in time by the production of pro-resolving lipids after an initial inflammatory stimulus.

Development and validation of a rapid, specific and sensitive LC-MS/MS bioanalytical method for eicosanoid quantification - assessment of arachidonic acid metabolic pathway activity in hypertensive rats

Lipid mediators such as eicosanoids maintain various physiological processes, and their alterations are involved in the development of numerous cardiovascular diseases. Therefore, the reliable assessment of their profile could be helpful in diagnosis as well as in eicosanoid biomarker-based treatment. Hence, the presented study aimed to develop and validate a new rapid, specific and sensitive LC-MS/MS method for quantification of arachidonic acid-derived eicosanoids in plasma, including lipid mediators generated via COX-, LOX- and CYP450-dependent pathways. The developed method features high sensitivity because the lower limit of quantification ranged from 0.05 to 0.50 ng mL−1 as well as the accuracy and precision estimated within 88.88–111.25% and 1.03–11.82%, respectively. An application of a simple and fast liquid-liquid extraction procedure for sample cleaning resulted in a highly satisfactory recovery of the analytes (>88.30%). Additionally, the method was validated using artificial plasma, an approach that enabled the elimination of the matrix effect caused by an endogenous concentration of studied lipid mediators. Importantly, the presented LC-MS/MS method allowed for simultaneous quantitative and qualitative [quan/qual] analysis of the selected eicosanoids, leading to an additional improvement of the method specificity. Moreover, the validated method was successfully applied for eicosanoid profiling in rat, mouse and human plasma samples, clearly demonstrating the heterogeneity of the profile of studied lipid mediators in those species.

Lipid metabolism in chronic obstructive pulmonary disease.

Dysregulated lipid metabolism plays crucial roles in various diseases, including diabetes mellitus, cancer, and neurodegeneration. Recent studies suggest that alterations in major lipid metabolic pathways contribute to pathogenesis of lung diseases, including chronic obstructive pulmonary disease (COPD). These changes allow lung tissue to meet the energy needs and trigger anabolic pathways that initiate the synthesis of active molecules directly involved in the inflammation. In this review, we summarize the changes of catabolism and anabolism of lipids, lipid molecules including lipid mediators, lipid synthesis transcription factors, cholesterol, and phospholipids, and how those lipid molecules participate in the initiation and resolution of inflammation in COPD.

Extracellular vesicles: lipids as key components of their biogenesis and functions

Intercellular communication has been known for decades to involve either direct contact between cells or to operate via circulating molecules, such as cytokines, growth factors, or lipid mediators. During the last decade, we have begun to appreciate the increasing importance of intercellular communication mediated by extracellular vesicles released by viable cells either from plasma membrane shedding (microvesicles, also named microparticles) or from an intracellular compartment (exosomes). Exosomes and microvesicles circulate in all biological fluids and can trigger biological responses at a distance. Their effects include a large variety of biological processes, such as immune surveillance, modification of tumor microenvironment, or regulation of inflammation. Extracellular vesicles can carry a large array of active molecules, including lipid mediators, such as eicosanoids, proteins, and nucleic acids, able to modify the phenotype of receiving cells. This review will highlight the role of the various lipidic pathways involved in the biogenesis and functions of microvesicles and exosomes.

Unique Lipid Signatures of Extracellular Vesicles from the Airways of Asthmatics

Asthma is a chronic inflammatory disease process involving the conductive airways of the human lung. The dysregulated inflammatory response in this disease process may involve multiple cell-cell interactions mediated by signaling molecules, including lipid mediators. Extracellular vesicles (EVs) are lipid membrane particles that are now recognized as critical mediators of cell-cell communication. Here, we compared the lipid composition and presence of specific lipid mediators in airway EVs purified from the bronchoalveolar lavage (BAL) fluid of healthy controls and asthmatic subjects with and without second-hand smoke (SHS) exposure. Airway exosome concentrations were increased in asthmatics, and correlated with blood eosinophilia and serum IgE levels. Frequencies of HLA-DR+ and CD54+ exosomes were also significantly higher in asthmatics. Lipidomics analysis revealed that phosphatidylglycerol, ceramide-phosphates, and ceramides were significantly reduced in exosomes from asthmatics compared to the non-exposed control groups. Sphingomyelin 34:1 was more abundant in exosomes of SHS-exposed asthmatics compared to healthy controls. Our results suggest that chronic airway inflammation may be driven by alterations in the composition of lipid mediators within airway EVs of human subjects with asthma.

Alterations in Docosahexaenoic Acid-Related Lipid Cascades in Inflammatory Bowel Disease Model Mice.

Inflammatory bowel disease (IBD) is an intestinal disorder, involving chronic and relapsing inflammation of the digestive tract. Dysregulation of the immune system based on genetic, environmental, and other factors seems to be involved in the onset of IBD, but its exact pathogenesis remains unclear. Therefore, radical treatments for ulcerative colitis and Crohn's disease remain to be found, and IBD is considered to be a refractory disease. The aim of this study is to obtain novel insights into IBD via metabolite profiling of interleukin (IL)-10 knockout mice (an IBD animal model that exhibits a dysregulated immune system). In this study, the metabolites in the large intestine and plasma of IL-10 knockout mice were analyzed. In our analytical system, two kinds of analysis (gas chromatography/mass spectrometry and liquid chromatography/mass spectrometry) were used to detect a broader range of metabolites, including both hydrophilic and hydrophobic metabolites. In addition, an analysis of lipid mediators in the large intestine and ascites of IL-10 knockout mice was carried out. The levels of a variety of metabolites, including lipid mediators, were altered in IL-10 knockout mice. For example, high large intestinal and plasma levels of docosahexaenoic acid (DHA) were observed. In addition, arachidonic acid- and DHA-related lipid cascades were upregulated in the ascites of the IL-10 knockout mice. Our findings based on metabolite profiles including lipid mediators must contribute to development of researches about IBD.

Neuroprotective Effects of Annexin A1 Tripeptide after Deep Hypothermic Circulatory Arrest in Rats.

Resolution agonists, including lipid mediators and peptides such as annexin A1 (ANXA1), are providing novel approaches to treat inflammatory conditions. Surgical trauma exerts a significant burden on the immune system that can affect and impair multiple organs. Perioperative cerebral injury after cardiac surgery is associated with significant adverse neurological outcomes such as delirium and postoperative cognitive dysfunction. Using a clinically relevant rat model of cardiopulmonary bypass (CPB) with deep hypothermic circulatory arrest (DHCA), we tested the pro-resolving effects of a novel bioactive ANXA1 tripeptide (ANXA1sp) on neuroinflammation and cognition. Male rats underwent 2 h CPB with 1 h DHCA at 18°C, and received vehicle or ANXA1sp followed by timed reperfusion up to postoperative day 7. Immortalized murine microglial cell line BV2 were treated with vehicle or ANXA1sp and subjected to 2 h oxygen–glucose deprivation followed by timed reoxygenation. Microglial activation, cell death, neuroinflammation, and NF-κB activation were assessed in tissue samples and cell cultures. Rats exposed to CPB and DHCA had evident neuroinflammation in various brain areas. However, in ANXA1sp-treated rats, microglial activation and cell death (apoptosis and necrosis) were reduced at 24 h and 7 days after surgery. This was associated with a reduction in key pro-inflammatory cytokines due to inhibition of NF-κB activation in the brain and systemically. Treated rats also had improved neurologic scores and shorter latency in the Morris water maze. In BV2 cells treated with ANXA1sp, similar protective effects were observed including decreased pro-inflammatory cytokines and cell death. Notably, we also found increased expression of ANXA1, which binds to NF-κB p65 and thereby inhibits its transcriptional activity. Our findings provide evidence that treatment with a novel pro-resolving ANXA1 tripeptide is neuroprotective after cardiac surgery in rats by attenuating neuroinflammation and may prevent postoperative neurologic complications.

Differential usage of COX-1 and COX-2 in prostaglandin production by mast cells and basophils

Basophils have been erroneously considered as minor relatives of mast cells, due to some phenotypic similarity between them. While recent studies have revealed non-redundant roles for basophils in various immune responses, basophil-derived effector molecules, including lipid mediators, remain poorly characterized, compared to mast cell-derived ones. Here we analyzed and compared eicosanoids produced by mouse basophils and mast cells when stimulated with IgE plus allergens. The production of 5-LOX metabolites such as LTB4 and 5-HETE was detected as early as 0.5h post-stimulation in both cell types, even though their amounts were much smaller in basophils than in mast cells. In contrast, basophils and mast cells showed distinct time course in the production of COX metabolites, including PGD2, PGE2 and 11-HETE. Their production by mast cells was detected at both 0.5 and 6h post-stimulation while that by basophils was detectable only at 6h. Of note, mast cells showed 8–9 times higher levels of COX-1 than did basophils at the resting status. In contrast to unaltered COX-1 expression with or without stimulation, COX-2 expression was up-regulated in both cell types upon activation. Importantly, when activated, basophils expressed 4–5 times higher levels of COX-2 than did mast cells. In accordance with these findings, the late-phase production of the COX metabolites by basophils was completely ablated by COX-2 inhibitor whereas the early-phase production by mast cells was blocked by COX-1 but not COX-2 inhibitor. Thus, the production of COX metabolites is differentially regulated by COX-1 and COX-2 in basophils and mast cells.

Insights into Soluble Toll-Like Receptor 2 as a Downregulator of Virally Induced Inflammation.

The ability to distinguish pathogens from self-antigens is one of the most important functions of the immune system. However, this simple self versus non-self assignment belies the complexity of the immune response to threats. Immune responses vary widely and appropriately according to a spectrum of threats and only recently have the mechanisms for controlling this highly textured process emerged. A primary mechanism by which this controlled decision-making process is achieved is via Toll-like receptor (TLR) signaling and the subsequent activation of the immune response coincident with the presence of pathogenic organisms or antigens, including lipid mediators. While immune activation is important, the appropriate regulation of such responses is also critical. Recent findings indicate a parallel pathway by which responses to both viral and bacterial infections is controlled via the secretion of soluble TLR2 (sTLR2). sTLR2 is able to bind a wide range of pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs). sTLR2 has been detected in many bodily fluids and is thus ubiquitous in sites of pathogen appearance. Interestingly, growing evidence suggests that sTLR2 functions to sequester PAMPs and DAMPs to avoid immune activation via detection of cellular-expressed TLRs. This immune regulatory function would serve to reduce the expression of the molecules required for cellular entry, and the recruitment of target cells following infection with bacteria and viruses. This review provides an overview of sTLR2 and the research regarding the mechanisms of its immune regulatory properties. Furthermore, the role of this molecule in regulating immune activation in the context of HIV infection via sTLR2 in breast milk provides actionable insights into therapeutic targets across a variety of infectious and inflammatory states.

Antinociceptive fatty acid patterns differ in children with psychosomatic recurrent abdominal pain and healthy controls.

Stress is considered to trigger psychosomatic recurrent abdominal pain (RAP), but the mechanism behind the pain is unclear. Because the essential fatty acids, omega-6 and omega-3, are involved in pain, by regulating lipid mediators, we analysed the fatty acid patterns in children with RAP compared to healthy children. This was a cross-sectional study of plasma phospholipid fatty acids in 22 consecutively included children with RAP, aged six to 16 years, at an outpatient clinic specialising in RAP. The controls were 100 healthy children previously reported on and analysed in the same laboratory. The children with psychosomatic RAP showed higher mean concentrations of saturated fatty acids than the controls (49.0 mol% versus 47.4 mol%) but lower mean levels of polyunsaturated fatty acids (38.6 mol% versus 39.9 mol%). Omega-3 fatty acids were lower in children with psychosomatic RAP, resulting in higher ratios of linoleic to alpha-linolenic acids (p < 0.001) and arachidonic to eicosapentaenoic acids (p = 0.01), despite a lower concentration of arachidonic acid in children with RAP (p < 0.01). The results suggested an imbalance between nociceptive omega-6 fatty acids and antinociceptive omega-3 fatty acids in psychosomatic RAP. Further studies, including lipid mediators and oxidative products, are necessary to confirm an association.

Biotherapeutics for human eosinophil associated disorders

Eosinophils which play an important role in pathophysiology of eosinophil associated diseases (EADs) contain plethora of mediators of inflammation and immune responses, including lipid mediators and eosinophil granules containing secretory cationic proteins. When secreted, they cause significant tissue damage. to circumvent the effects, numerous strategies have been employed for development of biologic medicines for EADs. strategies used for development of biotherapeutics for EADs include eosinophil modulating therapies, destruction of eosinophils by means of ADcc or opsonization with removal by reticuloendothelial system, targeting key eosinophil survival cytokines and blocking eosinophil migration into inflamed tissues is another promising strategy for the reduction of end-organ manifestation of eosinophilia. EADs are categorized as ‘‘orphan’’ diseases and most of the current treatment options for patients with these conditions are used off-label. better therapeutic targets

First report of interruption of mast cell degranulation and endothelial cells activation by anti-inflammatory drugs controlling the acute response provoked by Pseudoplatystoma fasciatum fish venom

This is the first report describing in mice the envenoming that possible to occur in humans provoked by Pseudoplatystomafasciatum and evaluated the different class of mediators involved in the inflammatory injury, identifying important targets for drugs intervention. First we demonstrate that P. fasciatum venom induces an acute inflammatory response characterized by the recruitment of immune cells into peripheral tissues choreographed by chemoattractants including lipid mediators (LTB4 and PGE2), cytokines (IL-1β and TNF-α), and chemokines (KC and MCP-1). Intravital microscopy studies showed that only high dose (60 μg) of venom promoted hemodynamic changes inducing an abundant number of thrombi of varying sizes in venules leading to transient venular stasis with reduced blood flow. We found that serotonin, leukotrine and prostaglandin are involved in edematogenic and nociceptive responses, since a selective COX-2 inhibitor, a non-specific inhibitor for cytokines and COX-2, and a non-selective 5-HT receptor antagonist were able to reduce both symptoms. In conclusion, our data show that the main symptoms of acute inflammation as pain provoked by P. fasciatum fish venom could be well managed by available drugs as COX-2 inhibitors as well dexamethasone or non-selective 5-HT receptor antagonists.

TRPC3: a multifunctional signaling molecule.

TRPC3 represents one of the first identified mammalian relative of the Drosophila trp gene product. Despite extensive biochemical and biophysical characterization as well as ambitious attempts to uncover its physiological role in native cell systems, the channel protein still represents a rather enigmatic member of the TRP superfamily. TRPC3 is significantly expressed in the brain and heart and appears of (patho)physiological importance in both non-excitable and excitable cells, being potentially involved in a wide spectrum of Ca(2+) signaling mechanisms. TRPC3 cation channels display unique gating and regulatory properties that allow for recognition and integration of multiple input stimuli including lipid mediators, cellular Ca(2+) gradients, as well as redox signals. Physiological/pathophysiological functions of this highly versatile cation channel protein are as yet incompletely understood. Its ability to associate in a dynamic manner with a variety of partner proteins enables TRPC3 to serve coordination of multiple downstream signaling pathways and control of divergent cellular functions. Here, we summarize current knowledge on ion channel features as well as possible signaling functions of TRPC3 and discuss the potential biological relevance of this signaling molecule.

Modulation of dendritic cell function by PGE2 and DHA: a framework for understanding the role of dendritic cells in neuroinflammation

Neuroinflammation characterizes various neurological disorders. Peripheral immune cells and CNS-resident glia contribute to neuroinflammation and impact CNS degeneration, recovery and regeneration. Recently, the role of dendritic cells in neuroinflammation received special attention. The function of infiltrating immune cells and resident glia is affected by various factors, including lipid mediators. Polyunsaturated fatty acids, especially n-6 arachidonic acid and n-3 docosahexaenoic acid (DHA), the most abundant in the CNS, play an important role in neuroinflammation. The major arachidonic acid bioactive derivative in immune cells, PGE2, and DHA have been reported to have opposite effects on dendritic cells in terms of cytokine production and activation/differentiation of CD4(+) T cells. Here we review the existing information on PGE2 and DHA modulation of dendritic cell function and the potential impact of these lipid mediators of dendritic cells in CNS inflammatory disorders.

Lipids in critical care medicine

While enteral nutrition is the basis for the critically ill, parenteral nutrition is often used when a sufficient enteral nutrition is not or not fully achievable. Lipids are a mainstay of caloric supply in both cases as they combine the provision of building blocks for the membranes and are precursors for function molecules including lipid mediators bearing the ability to influence immunity. Pro-inflammatory lipid mediators as prostaglandins and leukotrienes are generated from arachidonic acid (AA), a key member of the n-6 polyunsaturated fatty acids (PUFA). In contrast, lipid mediators derived from the n-3 fatty acids eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) may exhibit less inflammatory properties compared to their AA-derived counterparts. Furthermore, intercellular mediators as resolvins and protectins are generated from n-3 fatty acids. They induce the resolution of inflammation, hence the name resolution phase interaction product—resolvin. Modulating the amount of PUFA and the n-6/n-3 ratio were investigated as means to change the inflammatory response and improve the outcome of patients. Experimental data showed that n-3 fatty acids may improve acute lung injury and sepsis in animal models. Studies in patients undergoing major surgery with application of n-3 fatty acids demonstrated beneficial effects in terms of reduction of length of stay and infectious complications. Clinical data hints that this concept may also improve outcome in critically ill patients. Additionally, experimental and clinical data suggest that a reduction in n-6 PUFA may change the immune response. In conclusion, modulating the amount of PUFA, the n-6/n-3 ratio and the composition of lipid emulsions may prove to be a useful means to improve the outcome of critically ill patients.

Resolvins and protectins: mediating solutions to inflammation

Resolution of inflammation has historically been viewed as a passive process, occurring as a result of the withdrawal of pro-inflammatory signals, including lipid mediators such as leukotrienes and prostaglandins. Thus, most anti-inflammatory drugs have traditionally targeted primarily mediator pathways that are engaged at the onset of inflammation. Only recently has it been established that inflammation resolution is an active process with a distinct set of chemical mediators. Several clinical and epidemiological studies have identified beneficial effects of polyunsaturated fatty acids (PUFAs) for a variety of inflammatory diseases, yet without mechanistic explanations for these beneficial effects. Resolvins and protectins are recently identified molecules that are generated from omega-3 PUFA precursors and can orchestrate the timely resolution of inflammation in model systems. Dysregulation of pro-resolving mediators is associated with diseases of prolonged inflammation, so designing pharmacological mimetics of naturally occurring pro-resolving mediators offers exciting new targets for drug design. This review describes the discovery and synthesis of these novel lipid mediators, their receptors and mechanisms of action, and summarizes the studies to date that have uncovered roles for resolvins and protectins in disease states.

Bronchial Epithelial Cells in Allergic Reactions

Bronchial epithelial cells (BEC) are known to play an integral role in the airway defense mechanism via mucociliary system as well as mechanical barriers. Recent studies further indicate that BEC produce and release biologically active compounds including lipid mediators, growth factors, endothelin and a variety of cytokines/chemokines important in the pathogenesis of airway disorders. Cytokines and chemokines produced by BEC include IL-6, IL-8, G-CSF, GM-CSF, RANTES, eotaxin and TARC. Pro-inflammatory cytokines IL-1 and TNF-alpha, generally upregulate expression and release these cytokines/chemokines. BEC from patients with bronchial asthma showed increased levels of mRNA for these potent inflammatory peptides. BEC also interact with immune and inflammatory cells by direct adhesion as well as by humoral factors including cytokines. For example, eosinophil adhesion to BEC may be an important signal for the activation and degranulation of eosinophils. BEC is also believed to take part in the airway mucosal immunity via Toll-like receptors. Finally, BEC may play a crucial role in the processes of airway remodeling by cross-talk with mesenchymal cells. These findings strongly suggest that BEC are actively involved as regulators of allergic inflammatory responses, and become a target for therapeutic intervention.

A Novel Signaling Pathway Mediates the Inhibition of CCL3/4 Expression by Prostaglandin E2

In response to pathogen-associated molecular patterns, dendritic cells initiate an innate immune response characterized by expression and release of proinflammatory cytokines and chemokines. The extent of the inflammatory response is limited by various endogenous factors, including lipid mediators such as prostaglandin E(2) (PGE(2)). We described previously the inhibitory effect of PGE(2) on the expression and release of the inflammatory chemokines CCL3 and CCL4 from activated dendritic cells. In this study we describe a novel PGE(2) signaling pathway that proceeds through EP-2 --> cAMP --> EPAC --> phosphatidylinositol 3-kinase --> protein kinase B --> GSK-3 and results in increased DNA binding of the CCAAT displacement protein (CDP), a potent mammalian transcriptional repressor. The direct link between CDP and CCL3/4 transcription was established in knock-down experiments using CDP small interference RNA.