Does promoting resolution instead of inhibiting inflammation represent the new paradigm in treating infections?

The Lipid Intensive Drug Therapy for Sepsis Phase II Pilot Clinical Trial

OBJECTIVES

Low cholesterol levels in early sepsis patients are associated with mortality. We sought to test if IV lipid emulsion administration to sepsis patients with low cholesterol levels would prevent a decline or increase total cholesterol levels at 48 hours.

DESIGN

Phase II, adaptive, randomized pilot clinical trial powered for 48 patients.

SETTING

Emergency department or ICU of an academic medical center.

PATIENTS

Sepsis patients (first 24 hr) with Sequential Organ Failure Assessment greater than or equal to 4 or shock.

INTERVENTIONS

Patients meeting study criteria, including screening total cholesterol levels less than or equal to 100 mg/dL or high-density lipoprotein cholesterol (HDL-C) + low-density lipoprotein cholesterol (LDL-C) less than or equal to 70 mg/dL, were randomized to receive one of three doses of lipid emulsion administered twice in 48 hours or no drug (controls). The primary endpoint was a change in serum total cholesterol (48 hr - enrollment) between groups.

MEASUREMENTS AND MAIN RESULTS

Forty-nine patients were enrolled and randomized. Two patients randomized to lipid emulsion were withdrawn before drug administration. Data for 24 control patients and 23 lipid emulsion patients were analyzed. The mean change in total cholesterol from enrollment to 48 hours was not different between groups and was 5 mg/dL ( sd 20) for lipid emulsion patients, and 2 mg/dL ( sd 18) for control patients ( p = 0.62). The mean changes in HDL-C and LDL-C were similar between groups. Mean change in triglycerides was elevated in lipid emulsion patients (61 mg/dL, sd 87) compared with controls (20 mg/dL, sd 70, p = 0.086). The 48-hour change in SOFA score was -2 (interquartile range [IQR] -4, -1) for control patients and -2 (IQR -3, 0) for lipid emulsion patients ( p = 0.46).

CONCLUSIONS

Administration of IV lipid emulsion to early sepsis patients with low cholesterol levels did not influence change in cholesterol levels from enrollment to 48 hours.

Biology and Total Synthesis of n-3 Docosapentaenoic Acid-Derived Specialized Pro-Resolving Mediators

Research over the last 25 years related to structural elucidations and biological investigations of the specialized pro-resolving mediators has spurred great interest in targeting these endogenous products in total synthesis. These lipid mediators govern the resolution of inflammation as potent and stereoselective agonists toward individual G-protein-coupled receptors, resulting in potent anti-inflammatory activities demonstrated in many human disease models. Specialized pro-resolving mediators are oxygenated polyunsaturated products formed in stereoselective and distinct biosynthetic pathways initiated by various lipoxygenase and cyclooxygenase enzymes. In this review, the reported stereoselective total synthesis and biological activities of the specialized pro-resolving mediators biosynthesized from the polyunsaturated fatty acid n-3 docosapentaenoic acid are presented.

Metabolization of Resolvin E4 by ω-Oxidation in Human Neutrophils: Synthesis and Biological Evaluation of 20-Hydroxy-Resolvin E4 (20-OH-RvE4)

Resolvin E4 (RvE4) belongs to the resolvin family of specialized pro-resolving mediators (SPMs). The resolvins are endogenously formed mediators with both potent pro-resolving and anti-inflammatory biological activities and have attracted considerable attention in both inflammation research and drug discovery. Hence, further metabolism of the resolvins is of interest. Gaining knowledge about the structure-function of further metabolites of the resolvins is important due to their interest in drug-discovery efforts. For the first time, the total synthesis and biological evaluations of the ω-20 hydroxylated metabolite of RvE4, named herein 20-OH-RvE4, are presented. RvE4 was converted to 20-OH-RvE4 by human polymorphonuclear leukocytes. LC-MS/MS analysis and UV spectrophotometry reveal that the synthetic 20-OH-RvE4 matched RvE4-converted product 20-OH-RvE4 by human neutrophils. Cellular studies have revealed that RvE4 is formed from eicosapentaenoic acid in physiologic hypoxia by human neutrophils and macrophages, and we herein established that 20-OH-RvE4 is a secondary metabolite formed by the ω-oxidation of RvE4 in human neutrophils. A direct comparison of the biological actions between RvE4 and its metabolic product suggested that 20-OH-RvE4 displayed reduced bioactions in stimulating the efferocytosis of human senescent erythrocytes by human M2-like macrophages. At concentrations down to 0.1 nM, RvE4 increased macrophage erythrophagocytosis, an important pro-resolving function that was diminished due to metabolic transformation. The results provided herein contribute to a novel molecular insight on the further local metabolization of RvE4, the newest member among the SPM superfamily.

Stereoselective Synthesis, Pro-resolution, and Anti-inflammatory Actions of RvD5n-3 DPA

The methyl ester of resolvin D5n-3 DPA, a lipid mediator biosynthesized from the omega-3 fatty acid n-3 docosapentaenoic acid, was stereoselectively prepared in 8% yield over 12 steps (longest linear sequence). The key steps for the introduction of the two stereogenic secondary alcohols were an organocatalyzed oxyamination and the Midland Alpine borane reduction. For the assembly of the carbon chain, the Sonogashira cross-coupling reaction and the Takai olefination were utilized. The physical properties, including retention time in liquid chromatography and tandem mass spectra, of the synthetic material were matched against material from human peripheral blood and mouse infectious exudates. Synthetic RvD5n-3 DPA, obtained just prior to biological experiments, displayed potent leukocyte-directed activities, upregulating the ability of neutrophils and macrophages to phagocytose bacteria, known as hallmark bioactions of specialized pro-resolving endogenous mediators.

Novel nutrition strategies to enhance recovery after surgery

Surgery and traumatic injury set off a cascade of metabolic changes that are becoming better understood. Recently, strategies and protocols have been developed for optimizing outcomes, and this has yielded beneficial results. This brief review evaluates three specific nutrition or metabolic interventions in the postoperative setting that attempt to optimize outcomes. We limited this to three subspecialty areas including oncologic surgery, orthopedic surgery, and cardiac surgery. These agents included fish oils, factors to prevent dysbiosis, and resistance exercise and its role in enhancing protein update. Where these novel agents fit into the basic tenets of postoperative nutrition interventions does not change the narrative: deliver graduated early enteral feeding to attenuate the metabolic response to surgical stress, maintain the gastrointestinal mucosal barrier, use immune/metabolic modulation to enhance immune response while attenuating excessive inflammation, and support the microbiome.

The function of specialized pro-resolving endogenous lipid mediators, vitamins, and other micronutrients in the control of the inflammatory processes: Possible role in patients with SARS-CoV-2 related infection

Inflammation is an essential protective response against harmful stimuli, such as invading pathogens, damaged cells, or irritants. Physiological inflammation eliminates pathogens and promotes tissue repair and healing. Effective immune response in humans depends on a tightly regulated balance among inflammatory and anti-inflammatory mechanisms involving both innate and adaptive arms of the immune system. Excessive inflammation can become pathological and induce detrimental effects. If this process is not self-limited, an inappropriate remodeling of the tissues and organs can occur and lead to the onset of chronic degenerative diseases. A wide spectrum of infectious and non-infectious agents may activate the inflammation, via the release of mediators and cytokines by distinct subtypes of lymphocytes and macrophages. Several molecular mechanisms regulate the onset, progression, and resolution of inflammation. All these steps, even the termination of this process, are active and not passive events. In particular, a complex interplay exists between mediators (belonging to the group of Eicosanoids), which induce the beginning of inflammation, such as Prostaglandins (PGE2), Leukotrienes (LT), and thromboxane A2 (TXA2), and molecules which display a key role in counteracting this process and in promoting its proper resolution. The latter group of mediators includes: ω-6 arachidonic acid (AA)-derived metabolites, such as Lipoxins (LXs), ω -3 eicosapentaenoic acid (EPA)-derived mediators, such as E-series Resolvins (RvEs), and ω -3 docosahexaenoic (DHA)-derived mediators, such as D-series Resolvins (RvDs), Protectins (PDs) and Maresins (MaRs). Overall, these mediators are defined as specialized pro-resolving mediators (SPMs). Reduced synthesis of these molecules may lead to uncontrolled inflammation with possible harmful effects. ω-3 fatty acids are widely used in clinical practice as rather inexpensive, safe, readily available supplemental therapy. Taking advantage of this evidence, several researchers are suggesting that SPMs may have beneficial effects in the complementary treatment of patients with severe forms of SARS-CoV-2 related infection, to counteract the "cytokine storm" observed in these individuals. Well-designed and sized trials in patients suffering from COVID-19 with different degrees of severity are needed to investigate the real impact in the clinical practice of this promising therapeutic approach.

Theoretical Characterization of the Step-by-Step Mechanism of Conversion of Leukotriene A4 to Leukotriene B4 Catalysed by the Enzyme Leukotriene A4 Hydrolase

LTA₄H is a bifunctional zinc metalloenzyme that converts leukotriene A₄ (LTA₄) into leukotriene B₄ (LTB₄), one of the most potent chemotactic agents involved in acute and chronic inflammatory diseases. In this reaction, LTA₄H acts as an epoxide hydrolase with a unique and fascinating mechanism, which includes the stereoselective attachment of one water molecule to the carbon backbone of LTA₄ several methylene units away from the epoxide moiety. By combining Molecular Dynamics simulations and Quantum Mechanics/Molecular Mechanics calculations, we obtained a very detailed molecular picture of the different consecutive steps of that mechanism. By means of a rather unusual 1,7-nucleophilic substitution through a clear S_N1 mechanism, the epoxide opens and the triene moiety of the substrate twists in such a way that the bond C₆-C₇ adopts its cis (Z) configuration, thus exposing the R face of C₁₂ to the addition of a water molecule hydrogen-bonded to ASP375. Thus, the two stereochemical features that are required for the bioactivity of LTB₄ appear to be closely related. The noncovalent π-π stacking interactions between the triene moiety and two tyrosines (TYR267 and, especially, TYR378) that wrap the triene system along the whole reaction explain the preference for the cis configuration inside LTA₄H.

Activating endogenous resolution pathways by soluble epoxide hydrolase inhibitors for the management of COVID-19

Anti-inflammatory, specialized proresolving mediators such as resolvins, protectins, maresins, and lipoxins derived from polyunsaturated acids may play a potential role in lung diseases as they protect different organs in animal disease models. Polyunsaturated fatty acids are an important resource for epoxy fatty acids (EET, EEQ, and EDP) that mediate a broad array of anti-inflammatory and proresolving mechanisms, such as mitigation of the cytokine storm. However, epoxy fatty acids are rapidly metabolized by soluble epoxide hydrolase (sEH). In animal studies, administration of sEH inhibitors (sEHIs) increases epoxy fatty acid levels, reduces lung inflammation, and improves lung function, making it a viable COVID-19 treatment approach. Thus, using sEHIs to activate endogenous resolution pathways might be a novel method to minimize organ damage in severe cases and improve outcomes in COVID-19 patients. This review focuses on the use of sEH inhibitors to activate endogenous resolution mechanisms for the treatment of COVID-19.

Shifting the Biosynthesis of Leukotrienes Toward Specialized Pro-Resolving Mediators by the 5-Lipoxygenase-Activating Protein (FLAP) Antagonist BRP-201

Background and Purpose

Lipid mediators (LM) play crucial roles in the complex inflammation process with respect to initiation, maintenance, and resolution. Proinflammatory leukotrienes (LTs), generated by 5-lipoxygenase (LOX) and the 5-LOX-activating protein (FLAP), initiate and maintain inflammation while specialized pro-resolving mediators (SPMs) formed by various LOXs as key enzymes promote inflammation resolution and the return to homeostasis. Since 5-LOX also contributes to SPM biosynthesis, smart pharmacological manipulation of the 5-LOX pathway and accompanied activation of 12-/15-LOXs may accomplish suppression of LT formation but maintain or even elevate SPM formation. Here, we demonstrated that the FLAP antagonist BRP-201 possesses such pharmacological profile and causes a switch from LT toward SPM formation.

Methods and Results

Comprehensive LM metabololipidomics with activated human monocyte-derived macrophages (MDM) of M1 or M2 phenotype showed that BRP-201 strongly inhibits LT formation induced by bacterial exotoxins. In parallel, SPM levels and 12/15-LOX-derived products were markedly elevated, in particular in M2-MDM. Intriguingly, in unstimulated MDM, BRP-201 induced formation of 12/15-LOX products including SPM and caused 15-LOX-1 subcellular redistribution without affecting 5-LOX. Experiments with HEK293 cells stably expressing either 5-LOX with or without FLAP, 15-LOX-1 or 15-LOX-2 confirmed suppression of 5-LOX product formation due to FLAP antagonism by BRP-201 but activated 15-LOX-1 in the absence of FLAP. Finally, in zymosan-induced murine peritonitis, BRP-201 (2 mg/kg, ip) lowered LT levels but elevated 12/15-LOX products including SPMs.

Conclusion

BRP-201 acts as FLAP antagonist but also as 12/15-LOX activator switching formation of pro-inflammatory LTs toward inflammation-resolving SPM, which reflects a beneficial pharmacological profile for intervention in inflammation.

Stereoselective Synthesis, Configurational Assignment and Biological Evaluations of the Lipid Mediator RvD2n-3 DPA

Herein we report the first total synthesis of RvD2n-3 DPA , an endogenously formed mediator biosynthesized from the omega-3 fatty acid n-3 docosapentaenoic acid. The key steps are the Midland Alpine borane reduction, Sonogashira cross-coupling reactions, and a Z-selective alkyne reduction protocol, yielding RvD2n-3 DPA methyl ester in 13 % yield over 12 steps (longest linear sequence). The physical property data (UV chromophore, chromatography and MS/MS fragmentation) of the synthetic lipid mediator matched those obtained from biologically produced material. Moreover, synthetic RvD2n-3 DPA also carried the potent biological activities of enhancing macrophage uptake of Staphylococcus aureus and zymosan A bioparticles.

Natural chalcones elicit formation of specialized pro-resolving mediators and related 15-lipoxygenase products in human macrophages

Specialized pro-resolving mediators (SPMs) comprise lipid mediators (LMs) produced from polyunsaturated fatty acids (PUFAs) via stereoselective oxygenation particularly involving 12/15-lipoxygenases (LOXs). In contrast to pro-inflammatory LMs such as leukotrienes formed by 5-LOX and prostaglandins formed by cyclooxygenases, the SPMs have anti-inflammatory and inflammation-resolving properties. Although glucocorticoids and non-steroidal anti-inflammatory drugs (NSAIDs) that block prostaglandin production are still prime therapeutics for inflammation-related diseases despite severe side effects, novel concepts focus on SPMs as immunoresolvents for anti-inflammatory pharmacotherapy. Here, we studied the natural chalcone MF-14 and the corresponding dihydrochalcone MF-15 from Melodorum fruticosum, for modulating the biosynthesis of LM including leukotrienes, prostaglandins, SPM and their 12/15-LOX-derived precursors in human monocyte-derived macrophage (MDM) M1- and M2-like phenotypes. In MDM challenged with Staphylococcus aureus-derived exotoxins both compounds (10 µM) significantly suppressed 5-LOX product formation but increased the biosynthesis of 12/15-LOX products, especially in M2-MDM. Intriguingly, in resting M2-MDM, MF-14 and MF-15 strikingly evoked generation of 12/15-LOX products and of SPMs from liberated PUFAs, along with translocation of 15-LOX-1 to membranous compartments. Enhanced 12/15-LOX product formation by the chalcones was evident also when exogenous PUFAs were supplied, excluding increased substrate supply as sole underlying mechanism. Rather, MF-14 and MF-15 stimulate the activity of 15-LOX-1, supported by experiments with HEK293 cells transfected with either 5-LOX, 15-LOX-1 or 15-LOX-2. Together, the natural chalcone MF-14 and the dihydrochalcone MF-15 favorably modulate LM biosynthesis in human macrophages by suppressing pro-inflammatory leukotrienes but stimulating formation of SPMs by differential interference with 5-LOX and 15-LOX-1.

Long COVID a New Derivative in the Chaos of SARS-CoV-2 Infection: The Emergent Pandemic?

Coronavirus disease 2019 (COVID-19) is a multisystem illness caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), which can manifest with a multitude of symptoms in the setting of end-organ damage, though it is predominantly respiratory. However, various symptoms may remain after acute SARS-CoV-2 infection, and this condition is referred to as "Long COVID" (LC). Patients with LC may develop multi-organ symptom complex that remains 4-12 weeks after the acute phase of illness, with symptoms intermittently persisting over time. The main symptoms are fatigue, post-exertional malaise, cognitive dysfunction, and limitation of functional capacity. Pediatric patients developed the main symptoms of LC like those described in adults, although there may be variable presentations of LC in children. The underlying mechanisms of LC are not clearly known, although they may involve pathophysiological changes generated by virus persistence, immunological alterations secondary to virus-host interaction, tissue damage of inflammatory origin and hyperactivation of coagulation. Risk factors for developing LC would be female sex, more than five early symptoms, early dyspnea, previous psychiatric disorders, and alterations in immunological, inflammatory and coagulation parameters. There is currently no specific treatment for LC, but it could include pharmacological treatments to treat symptoms, supplements to restore nutritional, metabolic, and gut flora balance, and functional treatments for the most disabling symptoms. In summary, this study aims to show the scientific community the current knowledge of LC.

Inflammation and Periodontal Regeneration

Technological innovations in cellular and molecular aspects of tissue engineering --scaffolds, stem cells and 3D printed tissues --have been dramatically increased in the last decade. However, regenerative treatment still has challenges in translation to clinic. This is partly due to failure of addressing an essential element of wound healing, inflammation. It is now well-recognized that inflammation is an active process. This paradigm shift opened up a new avenue of therapeutic approaches called "host-modulation." Host-modulation therapies capable of modulating inflammatory response at multiple levels and mimicking the natural sequence of wound healing offer a new direction and promising clinical translation.

Loss of 15-lipoxygenase disrupts Treg differentiation altering their pro-resolving functions

Regulatory T-cells (Tregs) are central in the maintenance of homeostasis and resolution of inflammation. However, the mechanisms that govern their differentiation and function are not completely understood. Herein, we demonstrate a central role for the lipid mediator biosynthetic enzyme 15-lipoxygenase (ALOX15) in regulating key aspects of Treg biology. Pharmacological inhibition or genetic deletion of ALOX15 in Tregs decreased FOXP3 expression, altered Treg transcriptional profile and shifted their metabolism. This was linked with an impaired ability of Alox15-deficient cells to exert their pro-resolving actions, including a decrease in their ability to upregulate macrophage efferocytosis and a downregulation of interferon gamma expression in Th1 cells. Incubation of Tregs with the ALOX15-derived specilized pro-resolving mediators (SPM)s Resolvin (Rv)D3 and RvD5n-3 DPA rescued FOXP3 expression in cells where ALOX15 activity was inhibited. In vivo, deletion of Alox15 led to increased vascular lipid load and expansion of Th1 cells in mice fed western diet, a phenomenon that was reversed when Alox15-deficient mice were reconstituted with wild type Tregs. Taken together these findings demonstrate a central role of pro-resolving lipid mediators in governing the differentiation of naive T-cells to Tregs.

Prostanoids and Resolution of Inflammation - Beyond the Lipid-Mediator Class Switch

Bioactive lipid mediators play a major role in regulating inflammatory processes. Herein, early pro-inflammatory phases are characterized and regulated by prostanoids and leukotrienes, whereas specialized pro-resolving mediators (SPM), including lipoxins, resolvins, protectins, and maresins, dominate during the resolution phase. While pro-inflammatory properties of prostanoids have been studied extensively, their impact on later phases of the inflammatory process has been attributed mainly to their ability to initiate the lipid-mediator class switch towards SPM. Yet, there is accumulating evidence that prostanoids directly contribute to the resolution of inflammation and return to homeostasis. In this mini review, we summarize the current knowledge of the resolution-regulatory properties of prostanoids and discuss potential implications for anti-inflammatory, prostanoid-targeted therapeutic interventions.

Disrupted Resolution Mechanisms Favor Altered Phagocyte Responses in COVID-19

Supplemental Digital Content is available in the text.

Resolution mechanisms are central in both the maintenance of homeostasis and the return to catabasis following tissue injury and infections. Among the proresolving mediators, the essential fatty acid-derived specialized proresolving lipid mediators (SPM) govern immune responses to limit disease severity. Notably, little is known about the relationship between the expression and activity of SPM pathways, circulating phagocyte function and disease severity in patients infected with the novel severe acute respiratory syndrome coronavirus 2 leading to coronavirus disease 2019 (COVID-19).

Synthetic high-density lipoprotein nanoparticles: Good things in small packages

Medicine has been a great beneficiary of the nanotechnology revolution. Nanotechnology involves the synthesis of functional materials with at least one size dimension between 1 and 100 nm. Advances in the field have enabled the synthesis of bio-nanoparticles that can interface with physiological systems to modulate fundamental cellular processes. One example of a diverse acting nanoparticle-based therapeutic is synthetic high-density lipoprotein (HDL) nanoparticles (NP), which have great potential for treating diseases of the ocular surface. Our group has developed a spherical HDL NP using a gold nanoparticle core. HDL NPs: (i) closely mimic the physical and chemical features of natural HDLs; (ii) contain apoA-I; (iii) bind with high-affinity to SR-B1, which is the major receptor through which HDL modulates cell cholesterol metabolism and controls the selective uptake of HDL cargo into cells; (iv) are non-toxic to cells and tissues; and (v) can be chemically engineered to display nearly any surface or core composition desired. With respect to the ocular surface, topical application of HDL NPs accelerates re-epithelization of the cornea following wounding, attenuates inflammation resulting from chemical burns and/or other stresses, and effectively delivers microRNAs with biological activity to corneal cells and tissues. HDL NPs will be the foundation of a new class of topical eye drops with great translational potential and exemplify the impact that nanoparticles can have in medicine.

Role of arachidonic cascade in COVID-19 infection: A review

The World Health Organization has described the 2019 Coronavirus disease caused by an influenza-like virus called SARS-CoV-2 as a pandemic. Millions of people worldwide are already infected by this virus, and severe infection causes hyper inflammation, thus disrupting lung function, exacerbating breath difficulties, and death. Various inflammatory mediators bio-synthesized through the arachidonic acid pathway play roles in developing cytokine storms, injuring virus-infected cells. Since pro-inflammatory eicosanoids, including prostaglandins, and leukotrienes, are key brokers for physiological processes such as inflammation, fever, allergy, and pain but, their function in COVID-19 is not well defined. This study addresses eicosanoid's crucial role through the arachidonic pathway in inflammatory cascading and recommends using bioactive lipids, NSAIDs, steroids, cell phospholipase A2 (cPLA2) inhibitors, and specialized pro-resolving mediators (SPMs) to treat COVID-19 disease. The role of soluble epoxide hydrolase inhibitors (SEHIs) in promoting the activity of epoxyeicosatrienoic acids (EETs) and 17-hydroxide-docosahexaenoic acid (17-HDHA) is also discussed. Additional research that assesses the eicosanoid profile in COVID-19 patients or preclinical models generates novel insights into coronavirus-host interaction and inflammation regulation.

Erythropoietin Promotes Infection Resolution and Lowers Antibiotic Requirements in E. coli- and S. aureus-Initiated Infections

Endogenous mechanisms underlying bacterial infection resolution are essential for the development of novel therapies for the treatment of inflammation caused by infection without unwanted side effects. Herein, we found that erythropoietin (EPO) promoted the resolution and enhanced antibiotic actions in Escherichia coli (E. coli)- and Staphylococcus aureus (S. aureus)-initiated infections. Levels of peritoneal EPO and macrophage erythropoietin receptor (EPOR) were elevated in self-limited E. coli-initiated peritonitis. Myeloid-specific EPOR-deficient mice exhibited an impaired inflammatory resolution and exogenous EPO enhanced this resolution in self-limited infections. Mechanistically, EPO increased macrophage clearance of bacteria via peroxisome proliferator-activated receptor γ (PPARγ)-induced CD36. Moreover, EPO ameliorated inflammation and increased the actions of ciprofloxacin and vancomycin in resolution-delayed E. coli- and S. aureus-initiated infections. Collectively, macrophage EPO signaling is temporally induced during infections. EPO is anti-phlogistic, increases engulfment, promotes infection resolution, and lowers antibiotic requirements.

Stereoselective Synthesis and Structural Confirmation of the Specialized Pro-Resolving Mediator Resolvin E4

Herein, we report the stereoselective and convergent synthesis of resolvin E4, a newly identified specialized pro-resolving mediator. This synthesis proves the absolute configuration and exact olefin geometry. Key elements of the successful strategy include a highly stereoselective MacMillan organocatalytic oxyamination, a Midland Alpine borane reduction, and the use of a 1,4-pentadiyne unit as a linchpin building block. The application of reaction telescoping in several of the synthetic transformations enabled the preparation of the resolvin E4 methyl ester in 10% yield over 10 steps (longest linear sequence). The physical property (UV–Vis and LC–MS/MS) data of synthetic resolvin E4 matched those obtained from biologically produced material.

Proresolving Mediators in Endodontics: A Systematic Review

INTRODUCTION

Proresolving lipid mediators are specialized molecules (SPMs) involved in the active resolution of the inflammatory process by regulating tissue homeostasis. The aim of this study was to investigate the scientific literature to assess the potential of SPMs as an adjunct in the treatment of endodontic infection.

METHODS

Three electronic databases (PubMed, Web of Science, and Scopus) were searched from their inception until February 2020 (PROSPERO CRD42020164743). Supplemental research was performed by screening the references of the relevant studies eligible for inclusion. A quality assessment of animal studies was performed using the Animal Research: Reporting of In Vivo Experiments guidelines, whereas the Systematic Review Centre for Laboratory animal Experimentation Risk of Bias tool was used to assess the risk of bias.

RESULTS

A total of 3295 records were screened, and 8 articles meeting the criteria were included for this qualitative review. The eligible studies showed a high to moderate overall quality and a low to moderate risk of bias. SPMs positively affected the development of pulpitis and apical periodontitis in experimental animal models. The early treatment of pulpitis with the topical application of SPMs was beneficial to control inflammation within 24 hours from contamination. In addition, SPMs delivered within the root canals after disinfection were found effective in promoting periapical healing.

CONCLUSIONS

Our findings suggest that SPMs may play a role in the inception and treatment of pulpal-periapical diseases, and they should be considered for future research for developing new therapeutics as an adjunct to endodontic treatment.

Cytokine Storm and Failed Resolution in COVID-19: Taking a Cue from Multiple Sclerosis

INTRODUCTION

Excessive inflammatory responses and failed resolution are major common causes of tissue injury and organ dysfunction in a variety of diseases, including multiple sclerosis (MS), diabetes, and most recently, COVID-19, despite the distinct pathoetiology of the diseases. The promotion of the natural process of inflammatory resolution has been long recognized to improve functional recovery and disease outcomes effectively. To mitigate the excessive inflammation in MS, scientific investigations identified a group of derivatives of omega fatty acids, known as specialized pro-resolving lipid mediators (SPM) that have been significantly effective in treating preclinical disease models of MS.

METHODS

This chapter is based on our observations from MS. It is being increasingly deliberated that the ongoing COVID-19 infection induces severe cytokine storm that ultimately triggers rampant inflammation. The impact of infection and associated mortality is much higher in patients with co-morbid diseases. Also, reports suggest a better outcome in diabetic patients with reasonable glycemic control, which certainly hints towards a hidden role of anti-hyperglycemic drugs such as metformin in alleviating disease pathology through its anti-inflammatory feature. Notably, SPM and metformin share common therapeutic features in exerting a broad-spectrum anti-inflammatory activity in human patients with a superior safety profile.

RESULTS

When there is an immediate need to encounter the fast-rampant infection of COVID-19 and control the viral-infection associated morbid inflammatory cytokine storm causing severe organ damage, SPM and metformin should be seriously considered as a potential adjunctive treatment.

CONCLUSION

Given the fact that current treatment for COVID-19 is only supportive, global research is aimed at developing safe and effective therapeutic options that can result in a better clinical course in patients with comorbid conditions. Accordingly, taking a cue from our experiences in controlling robust inflammatory response in MS and diabetes by simultaneously inhibiting inflammatory process and stimulating its resolution, combinatorial therapy of metformin and SPM in COVID-19 holds significant promise in treating this global health crisis.

Exploiting the pro-resolving actions of glucocorticoid-induced proteins Annexin A1 and GILZ in infectious diseases

For decades, glucocorticoids (GC) have been used to treat several inflammatory conditions, including chronic and autoimmune diseases, due to their potent anti-inflammatory properties. In the context of infectious diseases, the use of GCs may be effective as adjuvant to antibiotic therapy by controlling excessive inflammatory responses resulting in better outcome in some cases. However, the use of GCs has been associated with a vast number of side effects, including increased probability of immunosuppression and consequent risk of opportunistic infection. Glucocorticoid-induced leucine zipper (GILZ) and Annexin A1 (AnxA1) are GC-induced proteins intrinsically involved with the anti-inflammatory functions of GCs without the associated adverse metabolic effects. Recent studies have shown that these GC-proteins exhibit pro-resolving effects. An essential characteristic of pro-resolving molecules is their ability to coordinate the resolution of inflammation and promote host defense in most experimental models of infection. Although the role of GILZ and AnxA1 in the context of infectious diseases remain to be better explored, herein we provide an overview of the emerging functions of these GC-proteins obtained from pre-clinical models of infectious diseases.

Clinical application of fish-oil intravenous lipid emulsion in adult home parenteral nutrition patients

BACKGROUND

High-ω-6 polyunsaturated fatty acids (PUFAs) are noted to contribute to development of intestinal failure-associated liver disease (IFALD) in home parenteral nutrition (HPN). Fish oil (FO) has been added to latest generation of lipid injectable emulsion (ILE) to increase ω-3:ω-6 PUFA ratio; however, appropriate dose of FO to treat IFALD is unknown.

METHODS

After approval of exclusive FO ILE in the US for pediatric patients, we noted 2 adult patients with ongoing IFALD despite transition to mixed-oil (MO) ILE. They were transitioned to off-label FO ILE after review of literature regarding use of FO ILE in adult HPN patients was conducted to guide management.

RESULTS

The first case involves a 40-year-old female receiving HPN with IFALD refractory to MO ILE. MO ILE (with 15% FO) was provided at 50 g/d for 3 d/wk and combined with FO ILE at 50 g/d for 4 d/wk. This combination resulted in improvement in liver studies and allowed for decrease in dextrose calories. The second case involves a 49-year-old male receiving HPN (secondary to complications of necrotizing pancreatitis) who developed IFALD. FO ILE was used as the sole source of lipids and led to improvement in liver function tests. No evidence of essential fatty acid deficiency was found in either case.

CONCLUSIONS

Current case presentations and review of literature support the use of FO ILE to increase ω-3 PUFAs in patients with IFALD refractory to MO ILE. Additional research is necessary to delineate the dose of FO ILE necessary to achieve benefit.

The First Total Synthesis of the Lipid Mediator PD2n-3 DPA

The resolution of inflammation is governed by the active biosynthesis of specialized pro-resolving mediators using ω-6 and ω-3 polyunsaturated fatty acids as substrates. These mediators act as resolution agonists and display several interesting bioactivities. PD2n-3 DPA is an oxygenated polyunsaturated fatty acid biosynthesized from n-3 docosapentaenoic acid belonging to the specialized pro-resolving lipid mediator family named protectins. The protectins exhibit anti-inflammatory properties and pro-resolving bioactivities. These endogenously produced compounds are of interest as leads in resolution pharmacology and drug development. Herein, together with its NMR, MS, and UV data, a stereoselective total synthesis of PD2n-3 DPA is presented.

Use of DAMPs and SAMPs as Therapeutic Targets or Therapeutics: A Note of Caution

This opinion article discusses the increasing attention paid to the role of activating damage-associated molecular patterns (DAMPs) in initiation of inflammatory diseases and suppressing/inhibiting DAMPs (SAMPs) in resolution of inflammatory diseases and, consequently, to the future roles of these novel biomarkers as therapeutic targets and therapeutics. Since controlled production of DAMPs and SAMPs is needed to achieve full homeostatic restoration and repair from tissue injury, only their pathological, not their homeostatic, concentrations should be therapeutically tackled. Therefore, distinct caveats are proposed regarding choosing DAMPs and SAMPs for therapeutic purposes. For example, we discuss the need to a priori identify and define a context-dependent “homeostatic DAMP:SAMP ratio” in each case and a “homeostatic window” of DAMP and SAMP concentrations to guarantee a safe treatment modality to patients. Finally, a few clinical examples of how DAMPs and SAMPs might be used as therapeutic targets or therapeutics in the future are discussed, including inhibition of DAMPs in hyperinflammatory processes (e.g., systemic inflammatory response syndrome, as currently observed in Covid-19), administration of SAMPs in chronic inflammatory diseases, inhibition of SAMPs in hyperresolving processes (e.g., compensatory anti-inflammatory response syndrome), and administration/induction of DAMPs in vaccination procedures and anti-cancer therapy.

Stereoselective synthesis of MaR2n-3 DPA

The first total synthesis of the n-3 docosapentaenoic derived oxygenated product MaR2n-3 DPA has been achieved. The 13R and 14S stereogenic centers were introduced using 2-deoxy-d-ribose in a chiral pool strategy. The geometry of the Z,E,E-triene moiety was prepared using highly E-selective Wittig- and Takai-olefination reactions as well as the Z-stereoselective Lindlar reduction. LC/MS-MS data of synthetic MaR2n-3 DPA matched data for the biosynthetic formed product that enabled the configurational assignment of this oxygenated natural product to be (7Z,9E,11E,13R,14S,16Z,19Z)-13,14-dihydroxydocosa-7,9,11,16,19-pentaenoic acid.

Plant- and Fish-Derived n-3 PUFAs Suppress Citrobacter Rodentium-Induced Colonic Inflammation

SCOPE

Marine-derived n-3 PUFAs may ameliorate inflammation associated with inflammatory bowel diseases. Plant-derived n-3 PUFAs are thought to be inferior owing to shorter chain lengths. The aim of this study is to compare the impact of plant- and fish-derived PUFAs on murine colitis.

METHODS AND RESULTS

C57BL/6 mice are fed high fat (36% kcal) diets with either 2.5% w/w sunflower oil (SO), flaxseed oil (FSO), ahiflower oil (AO), or fish oil (FO). After 4 weeks, mice are orogastrically challenged with Citrobacter rodentium (10⁸ CFU) or sham gavaged. Fecal shedding is assayed at 2, 7, 10, and 14 days post infection (PI), and fecal microbiota at 14 days PI. Colonic inflammation and lipid mediators are measured. Supplementation regulates intestinal inflammation with crypt lengths being 66, 73, and 62 ±17 µm shorter (compared to SO) for FSO, AO, and FO respectively, p < 0.01. FSO blunts pathogen shedding at the peak of infection and FSO and AO both enhance fecal microbial diversity. FO attenuates levels of lipoxin and leukotriene B₄ while plant oils increase pro-resolving mediator concentrations including D, E, and T-series resolvins.

CONCLUSION

Plant and fish n-3 PUFAs attenuate colitis-induced inflammation while exhibiting characteristic pro-resolving lipid mediator metabolomes. Plant oils additionally promote microbial diversity.

The Annexin A1/FPR2 pathway controls the inflammatory response and bacterial dissemination in experimental pneumococcal pneumonia

Streptococcus pneumoniae is a major cause of community-acquired pneumonia leading to high mortality rates. Inflammation triggered by pneumococcal infection is necessary for bacterial clearance but must be spatially and temporally regulated to prevent further tissue damage and bacterial dissemination. Annexin A1 (AnxA1) mainly acts through Formyl Peptide Receptor 2 (FPR2) inducing the resolution of inflammation. Here, we have evaluated the role of AnxA1 and FPR2 during pneumococcal pneumonia in mice. For that, AnxA1, Fpr2/3 knockout (KO) mice and wild-type (WT) controls were infected intranasally with S pneumoniae. AnxA1 and Fpr2/3 KO mice were highly susceptible to infection, displaying uncontrolled inflammation, increased bacterial dissemination, and pulmonary dysfunction compared to WT animals. Mechanistically, the absence of AnxA1 resulted in the loss of lung barrier integrity and increased neutrophil activation upon S pneumoniae stimulation. Importantly, treatment of WT or AnxA1 KO-infected mice with Ac2-26 decreased inflammation, lung damage, and bacterial burden in the airways by increasing macrophage phagocytosis. Conversely, Ac2-26 peptide was ineffective to afford protection in Fpr2/3 KO mice during infection. Altogether, these findings show that AnxA1, via FPR2, controls inflammation and bacterial dissemination during pneumococcal pneumonia by promoting host defenses, suggesting AnxA1-based peptides as a novel therapeutic strategy to control pneumococcal pneumonia.

Synthesis, Structural Confirmation, and Biosynthesis of 22-OH-PD1n-3 DPA

PD1_{n-3 DPA} belongs to the protectin family of specialized pro-resolving lipid mediators. The protectins are endogenously formed mediators that display potent anti-inflammatory properties and pro-resolving bioactivities and have attracted interest in drug discovery. However, few studies have been reported of the secondary metabolism of the protectins. To investigate the metabolic formation of the putative C22 mono-hydroxylated product, coined 22-OH-PD1_{n-3 DPA}, a stereoselective synthesis was performed. LC/MS-MS data of synthetic 22-OH-PD1_{n-3 DPA} matched the data for the biosynthetic formed product. Cellular studies revealed that 22-OH-PD1_{n-3 DPA} is formed from n-3 docosapentaenoic acid in human serum, and we confirmed that 22-OH-PD1_{n-3 DPA} is a secondary metabolite produced by ω-oxidation of PD1_{n-3 DPA} in human neutrophils and in human monocytes. The results reported are of interest for enabling future structure–activity relationship studies and provide useful molecular insight of the metabolism of the protectin class of specialized pro-resolving mediators.

Host⁻Microbe Interactions and Gut Health in Poultry-Focus on Innate Responses

Commercial poultry are continually exposed to, frequently pathogenic, microorganisms, usually via mucosal surfaces such as the intestinal mucosa. Thus, understanding host–microbe interactions is vital. Many of these microorganisms may have no or limited contact with the host, while most of those interacting more meaningfully with the host will be dealt with by the innate immune response. Fundamentally, poultry have evolved to have immune responses that are generally appropriate and adequate for their acquired microbiomes, although this is challenged by commercial production practices. Innate immune cells and their functions, encompassing inflammatory responses, create the context for neutralising the stimulus and initiating resolution. Dysregulated inflammatory responses can be detrimental but, being a highly conserved biological process, inflammation is critical for host defence. Heterogeneity and functional plasticity of innate immune cells is underappreciated and offers the potential for (gut) health interventions, perhaps including exogenous opportunities to influence immune cell metabolism and thus function. New approaches could focus on identifying and enhancing decisive but less harmful immune processes, improving the efficiency of innate immune cells (e.g., targeted, efficient microbial killing) and promoting phenotypes that drive resolution of inflammation. Breeding strategies and suitable exogenous interventions offer potential solutions to enhance poultry gut health, performance and welfare.

Pathological mechanisms and therapeutic outlooks for arthrofibrosis

Arthrofibrosis is a fibrotic joint disorder that begins with an inflammatory reaction to insults such as injury, surgery and infection. Excessive extracellular matrix and adhesions contract pouches, bursae and tendons, cause pain and prevent a normal range of joint motion, with devastating consequences for patient quality of life. Arthrofibrosis affects people of all ages, with published rates varying. The risk factors and best management strategies are largely unknown due to a poor understanding of the pathology and lack of diagnostic biomarkers. However, current research into the pathogenesis of fibrosis in organs now informs the understanding of arthrofibrosis. The process begins when stress signals stimulate immune cells. The resulting cascade of cytokines and mediators drives fibroblasts to differentiate into myofibroblasts, which secrete fibrillar collagens and transforming growth factor-β (TGF-β). Positive feedback networks then dysregulate processes that normally terminate healing processes. We propose two subtypes of arthrofibrosis occur: active arthrofibrosis and residual arthrofibrosis. In the latter the fibrogenic processes have resolved but the joint remains stiff. The best therapeutic approach for each subtype may differ significantly. Treatment typically involves surgery, however, a pharmacological approach to correct dysregulated cell signalling could be more effective. Recent research shows that myofibroblasts are capable of reversing differentiation, and understanding the mechanisms of pathogenesis and resolution will be essential for the development of cell-based treatments. Therapies with significant promise are currently available, with more in development, including those that inhibit TGF-β signalling and epigenetic modifications. This review focuses on pathogenesis of sterile arthrofibrosis and therapeutic treatments.

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.

Total Synthesis of the Antidiabetic (Type 2) Lipid Mediator Protectin DX/PDX

The first total synthesis of a lipid mediator derived from natural ω-3-fatty acid docosahexaenoic acid (DHA), 10 S,17 S-diHDHA (also referred to as protectin DX/PDX), was achieved in a convergent route (29 steps). The two chiral hydroxyl groups at C-10 and C-17 were derived from readily available ( S)-1,2,4-butanetriol and ( R)-glycidol, respectively. The two stereodefined E-double bonds were generated by a Takai olefination, and the skipped diene side chain was introduced with a stereocontrolled Wittig olefination. Importantly, the sensitive conjugated E, Z, E-triene intermediate was generated by a Boland reduction of the central triple bond of a E, E-dienyne. Overall, this synthetic strategy should allow the preparation of a larger quantity of PDX, which is inaccessible via previously reported biosynthetic approaches.

Specialized Pro-resolving Lipid Mediators: Modulation of Diabetes-Associated Cardio-, Reno-, and Retino-Vascular Complications

Diabetes and its associated chronic complications present a healthcare challenge on a global scale. Despite improvements in the management of chronic complications of the micro-/macro-vasculature, their growing prevalence and incidence highlights the scale of the problem. It is currently estimated that diabetes affects 425 million people globally and it is anticipated that this figure will rise by 2025 to 700 million people. The vascular complications of diabetes including diabetes-associated atherosclerosis and kidney disease present a particular challenge. Diabetes is the leading cause of end stage renal disease, reflecting fibrosis leading to organ failure. Moreover, diabetes associated states of inflammation, neo-vascularization, apoptosis and hypercoagulability contribute to also exacerbate atherosclerosis, from the metabolic syndrome to advanced disease, plaque rupture and coronary thrombosis. Current therapeutic interventions focus on regulating blood glucose, glomerular and peripheral hypertension and can at best slow the progression of diabetes complications. Recently advanced knowledge of the pathogenesis underlying diabetes and associated complications revealed common mechanisms, including the inflammatory response, insulin resistance and hyperglycemia. The major role that inflammation plays in many chronic diseases has led to the development of new strategies aiming to promote the restoration of homeostasis through the "resolution of inflammation." These strategies aim to mimic the spontaneous activities of the 'specialized pro-resolving mediators' (SPMs), including endogenous molecules and their synthetic mimetics. This review aims to discuss the effect of SPMs [with particular attention to lipoxins (LXs) and resolvins (Rvs)] on inflammatory responses in a series of experimental models, as well as evidence from human studies, in the context of cardio- and reno-vascular diabetic complications, with a brief mention to diabetic retinopathy (DR). These data collectively support the hypothesis that endogenously generated SPMs or synthetic mimetics of their activities may represent lead molecules in a new discipline, namely the 'resolution pharmacology,' offering hope for new therapeutic strategies to prevent and treat, specifically, diabetes-associated atherosclerosis, nephropathy and retinopathy.

Specialized Pro-resolving Mediators Regulate Alveolar Fluid Clearance during Acute Respiratory Distress Syndrome

Objective

Acute respiratory distress syndrome (ARDS) is an acute and lethal clinical syndrome that is characterized by the injury of alveolar epithelium, which impairs active fluid transport in the lung, and impedes the reabsorption of edema fluid from the alveolar space. This review aimed to discuss the role of pro-resolving mediators on the regulation of alveolar fluid clearance (AFC) in ARDS.

Data Sources

Articles published up to September 2017 were selected from the PubMed, with the keywords of "alveolar fluid clearance" or "lung edema" or "acute lung injury" or "acute respiratory distress syndrome", and "specialized pro-resolving mediators" or "lipoxin" or "resolvin" or "protectin" or "maresin" or "alveolar epithelial cells" or "aspirin-triggered lipid mediators" or "carbon monoxide and heme oxygenase" or "annexin A1".

Study Selection

We included all relevant articles published up to September 2017, with no limitation of study design.

Results

Specialized pro-resolving mediators (SPMs), as the proinflammatory mediators, not only upregulated epithelial sodium channel, Na,K-ATPase, cystic fibrosis transmembrane conductance regulator (CFTR), and aquaporins levels, but also improved Na,K-ATPase activity to promote AFC in ARDS. In addition to the direct effects on ion channels and pumps of the alveolar epithelium, the SPMs also inhibited the inflammatory cytokine expression and improved the alveolar epithelial cell repair to enhance the AFC in ARDS.

Conclusions

The present review discusses a novel mechanism for pulmonary edema fluid reabsorption. SPMs might provide new opportunities to design "reabsorption-targeted" therapies with high degrees of precision in controlling ALI/ARDS.

Autotherapies: Enhancing Endogenous Healing and Regeneration

The promise of tissue engineering and regenerative medicine to reduce the burden of disease and improve quality of life are widely acknowledged. Traditional tissue engineering and regenerative medicine approaches rely on generation of tissue constructs in vitro for subsequent transplantation or injection of exogenously manipulated cells into a host. While promising, few such therapies have succeeded in clinical practice. Here, we propose that recent advances in stem cell and developmental biology, immunology, bioengineering, and material sciences, position us to develop a new generation of in vivo regenerative medicine therapies, which we term autotherapies. Autotherapies are strategies based on optimizing endogenous tissue responses and capitalizing on manipulation of stem cell niches and endogenous tissue microenvironments to enhance tissue healing and regeneration.

Identification and structure elucidation of the pro-resolving mediators provides novel leads for resolution pharmacology

Inflammatory diseases are a major socio‐economic burden, with the incidence of such conditions on the rise, especially in western societies. For decades, the primary treatment paradigm for many of these conditions was to develop drugs that inhibit or antagonize the production and biological actions of molecules that were thought to be the culprits in propagating disease; these include cytokines and eicosanoids. This approach is effective in controlling disease propagation; however, long‐term exposure to these anti‐inflammatories is also associated with many side effects, some of which are severe, including immune‐suppression. The discovery that termination of self‐limited acute inflammation is an active process orchestrated by endogenous mediators, including the essential fatty acid‐derived resolvins, protectins and maresins, has provided novel opportunities for the design of therapeutics that control inflammation with a lower burden of side effects. This is because at variance to anti‐inflammatories, pro‐resolving mediators do not completely inhibit inflammatory responses; instead, these mediators reprogramme the immune response to accelerate the termination of inflammation, facilitating the regain of function. The scope of this review is to highlight the biological actions of these autacoids and their potential utility as lead compounds in developing resolution pharmacology‐based therapeutics.

Linked Articles

This article is part of a themed section on Eicosanoids 35 years from the 1982 Nobel: where are we now? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.8/issuetoc

Immunoresolvents signaling molecules at intersection between the brain and immune system

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The vagus nerve regulates ILC-3 and macrophage trafficking to the peritoneum.

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Vagotomy reduces peritoneal PCTR concentrations and alters tissue resolution tone.

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Resection of the vagus nerve impairs resolution responses to sterile and infectious insults.

Understanding mechanisms that control immunity is central in the quest to gain insights into the etiopathology of many of the diseases that afflict modern societies. New results implicate the nervous system as a central player in controlling many aspects of both the innate and adaptive arms of the immune response. Furthermore it is now well appreciated that a novel group of autacoids termed as specialized proresolving mediators, which are enzymatically produced from essential fatty acids, orchestrate the immune response promoting the termination of inflammation as well as tissue repair and regeneration. The present brief review discusses evidence for the crosstalk between the nervous system and leukocytes in regulating SPM production. We will also discuss the impact that this has on controlling tissue resolution tone and the resolution of both infectious and sterile inflammation.

Pro-Resolving Mediators in Regulating and Conferring Macrophage Function

Macrophages are central in coordinating the host response to both sterile and infective insults. Clearance of apoptotic cells and cellular debris is a key biological action preformed by macrophages that paves the way to the resolution of local inflammation, repair and regeneration of damaged tissues, and re-establishment of function. The essential fatty acid-derived autacoids termed specialized pro-resolving mediators (SPM) play central roles in promoting these processes. In the present article, we will review the role of microvesicles in controlling macrophage efferocytosis and SPM production. We will also discuss the role of both apoptotic cells and microvesicles in providing substrate for transcellular biosynthesis of several SPM families during efferocyotsis. In addition, this article will discuss the biological actions of the recently uncovered macrophage-derived SPM termed maresins. These mediators are produced via 14-lipoxygenation of docosahexaenoic acid that is either enzymatically converted to mediators carrying two hydroxyl groups or to autacoids that are peptide-lipid conjugates, coined maresin conjugates in tissue regeneration. The formation of these mediators is temporally regulated during acute self-limited infectious-inflammation where they promote the uptake and clearance of apoptotic cells, regulate several aspects of the tissue repair and regeneration, and display potent anti-nociceptive actions.

Annexin A1 and specialized proresolving lipid mediators: promoting resolution as a therapeutic strategy in human inflammatory diseases

INTRODUCTION

The timely resolution of inflammation is essential to restore tissue homeostasis and to avoid chronic inflammatory diseases. Resolution of inflammation is an active process modulated by various proresolving mediators, including annexin A1 (AnxA1) and specialized proresolving lipid mediators (SPMs), which counteract excessive inflammatory responses and stimulate proresolving mechanisms. Areas covered: The protective effects of AnxA1 and SPMs have been extensively explored in pre-clinical animal models. However, studies investigating the function of these molecules in human diseases are just emerging. This review highlights recent advances on the role of proresolving mediators, and pharmacological opportunities of promoting resolution pathways in preclinical models and patients with various human diseases. Expert opinion: Dysregulation or 'failure' in proresolving mechanisms might be involved in the pathogenesis of chronic inflammatory diseases. Altered levels of proresolving mediators were found in a wide range of human diseases. In some cases, AnxA1 and SPMs are up-regulated in human blood and tissues but fail to engage in proresolving signaling and, hence, to regulate excessive inflammation. Thus, the new concept of 'resolution pharmacology' could be applied to compensate deficiency of endogenous proresolving mediators' generation and/or possible failures in the engagement of resolution pathways observed in many chronic inflammatory diseases.

Stereocontrolled synthesis and investigation of the biosynthetic transformations of 16(S),17(S)-epoxy-PDn-3 DPA

Biomolecular investigations using synthetic ePD_{n-3 DPA} have been performed to study its role in the biosynthesis of the specialized pro-resolving mediator PD1_{n-3 DPA}.