Second-generation beta-oxidation resistant 3-oxa-lipoxin A4 analogs

Therapeutic potential of pro-resolving mediators in diabetic kidney disease

Renal microvascular disease associated with diabetes [Diabetic kidney disease - DKD] is the leading cause of chronic kidney disease. In DKD, glomerular basement membrane thickening, mesangial expansion, endothelial dysfunction, podocyte cell loss and renal tubule injury contribute to progressive glomerulosclerosis and tubulointerstitial fibrosis. Chronic inflammation is recognized as a major pathogenic mechanism for DKD, with resident and circulating immune cells interacting with local kidney cell populations to provoke an inflammatory response. The onset of inflammation is driven by the release of well described proinflammatory mediators, and this is typically followed by a resolution phase. Inflammation resolution is achieved through the bioactions of endogenous specialized pro-resolving lipid mediators (SPMs). As our understanding of SPMs advances 'resolution pharmacology' based approaches using these molecules are being explored in DKD.

Recent advances in the design and development of formyl peptide receptor 2 (FPR2/ALX) agonists as pro-resolving agents with diverse therapeutic potential

Under physiological conditions the initiation, duration and amplitude of inflammatory responses are tightly regulated to ensure the restoration of homeostasis. The resolution of inflammation in these circumstances is dictated by responses to endogenously generated mediators. Mimicry of such mediators underpins the principle of promoting the resolution of inflammation in treating inflammatory pathologies. The formyl peptide receptor 2 (FPR2/ALX) is a G-protein coupled receptor known to play a crucial role in maintaining host defence and orchestrating the inflammatory process. FPR2/ALX can be activated by a wide range of distinct agonists, including lipids, proteins, peptides, and an array of synthetic small molecule agonists. The focus of this review is to provide a comprehensive overview of recent progress made in the development of FPR2/ALX agonists which promote resolution and tissue regeneration.

Pro-resolving lipid mediators: regulators of inflammation, metabolism and kidney function

Obesity, diabetes mellitus, hypertension and cardiovascular disease are risk factors for chronic kidney disease (CKD) and kidney failure. Chronic, low-grade inflammation is recognized as a major pathogenic mechanism that underlies the association between CKD and obesity, impaired glucose tolerance, insulin resistance and diabetes, through interaction between resident and/or circulating immune cells with parenchymal cells. Thus, considerable interest exists in approaches that target inflammation as a strategy to manage CKD. The initial phase of the inflammatory response to injury or metabolic dysfunction reflects the release of pro-inflammatory mediators including peptides, lipids and cytokines, and the recruitment of leukocytes. In self-limiting inflammation, the evolving inflammatory response is coupled to distinct processes that promote the resolution of inflammation and restore homeostasis. The discovery of endogenously generated lipid mediators - specialized pro-resolving lipid mediators and branched fatty acid esters of hydroxy fatty acids - which promote the resolution of inflammation and attenuate the microvascular and macrovascular complications of obesity and diabetes mellitus highlights novel opportunities for potential therapeutic intervention through the targeting of pro-resolution, rather than anti-inflammatory pathways.

Pathogenetic Substantiation of Therapeutic and Preventive Measures in Severe Coronavirus Infection

The basis of coronavirus disease is an infectious process, accompanied by a varying degree of activity of pathological processes. Based on the study of the pathological course of infection, modern approaches to the treatment and prevention of complications of coronavirus infection are presented. The main strategic pathogenetic direction in the creation of effective programs for the treatment of COVID-19, as well as the prevention of fatal complications, should be a set of measures enhancing permissive regulatory influences and events. Endothelium, being a source of inflammatory mediators and a transducer of their regulatory effects on the vascular tone, is involved in the development and alternation of vascular reactions, changing the volume of perfusion. The main mechanism for the development of endothelial dysfunction and damage is associated with an imbalance between the generation of reactive oxygen species and the power of the antioxidant defense system. Any measures to protect the endothelium, reducing the severity of microcirculatory disorders and hypoxia, will have a therapeutic and preventive effect on fatal complications. In this regard, in the treatment of COVID-19, the use of synthetic gas transport preparations based on perfluorocarbon nanodispersed emulsions with a clinical effect directed at once to several patho-genetic links underlying the progression of COVID-19 disease can be quite effective. The necessity of a comprehensive effect on pathogenesis using sanogenetic principles of treatment, allowing influencing the speed and time of onset of resolution of inflammation, which can reduce the number of complications and deaths of the disease, is substantiated.

Specialized pro-resolving mediators in diabetes: novel therapeutic strategies

Diabetes mellitus (DM) is an important metabolic disorder characterized by persistent hyperglycemia resulting from inadequate production and secretion of insulin, impaired insulin action, or a combination of both. Genetic disorders and insulin receptor disorders, environmental factors, lifestyle choices and toxins are key factors that contribute to DM. While it is often referred to as a metabolic disorder, modern lifestyle choices and nutrient excess induce a state of systemic chronic inflammation that results in the increased production and secretion of inflammatory cytokines that contribute to DM. It is chronic hyperglycemia and the low-grade chronic-inflammation that underlies the development of microvascular and macrovascular complications leading to damage in a number of tissues and organs, including eyes, vasculature, heart, nerves, and kidneys. Improvements in the management of risk factors have been beneficial, including focus on intensified glycemic control, but most current approaches only slow disease progression. Even with recent studies employing SGLT2 inhibitors demonstrating protection against cardiovascular and kidney diseases, kidney function continues to decline in people with established diabetic kidney disease (DKD). Despite the many advances and a greatly improved understanding of the pathobiology of diabetes and its complications, there remains a major unmet need for more effective therapeutics to prevent and reverse the chronic complications of diabetes. More recently, there has been growing interest in the use of specialised pro-resolving mediators (SPMs) as an exciting therapeutic strategy to target diabetes and the chronic complications of diabetes.

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.

Proresolving actions of a new resolvin D1 analog mimetic qualifies as an immunoresolvent

Resolution of inflammation is an active process driven by several new families of endogenous lipid mediators collectively coined specialized proresolving mediators (SPM). Here, we report a synthetic analog of resolvin D1 (RvD1) and aspirin-triggered RvD1, benzo-diacetylenic-17R-RvD1-methyl ester (BDA-RvD1), which was prepared using fewer steps than required for total organic synthesis of natural SPM. BDA-RvD1 was resistant to further metabolism by human recombinant 15-prostaglandin dehydrogenase, a major inactivation pathway for RvD1. In ischemia-reperfusion-initiated second organ injury, BDA-RvD1 intravenously (1 μg) reduced neutrophil infiltration into the lungs by 58 ± 9% and was significantly more potent than native RvD1. BDA-RvD1 at 100 ng/mouse also shortened the resolution interval, Ri, of Escherichia coli peritonitis with a similar potency as RvD1, by ~57%, from Ri 10.5 h to 4.5 h. With isolated human phagocytes, BDA-RvD1 at picomolar concentrations (10(-12) M) stimulated phagocytosis of zymosan A particles. BDA-RvD1 activated human recombinant G protein-coupled receptor 32/DRV1, an RvD1 receptor, in a dose-dependent manner. These results indicate that, both in vivo in mice and with isolated human cells, BDA-RvD1 shares defining proresolving actions of RvD1, including inhibiting leukocyte infiltration and stimulating phagocytosis. Moreover, they provide evidence for a new analog mimetic and example of an immunoresolvent, namely an agent that stimulates active resolution of inflammation, for a potential new therapeutic class.

Efficacy and safety of 15(R/S)-methyl-lipoxin A(4) in topical treatment of infantile eczema

BACKGROUND

 Lipoxins are potential anti-inflammatory mediators and serve as an endogenous 'braking signal' in the inflammatory process. Accumulating evidence has indicated the efficacy of lipoxin A(4) (LXA(4) ) and its analogs in the treatment of many animal models of inflammatory diseases.

OBJECTIVES

 This study investigates the efficacy and safety of 15(R/S)-methyl-lipoxin A(4) in the topical treatment of infantile eczema.

PATIENTS AND METHODS

In this two-centre, double-blind, placebo-controlled, randomized, parallel-groups comparative study, 60 patients were randomly assigned to receive either the 15(R/S)-methyl-lipoxin A(4) cream, mometasone furoate (Eloson, Schering-Plough, Shanghai, China) or placebo for 10days. The efficacy was determined using the Severity Scale Score (SSS), Eczema Area and Severity Index (EASI) and the Infants' Dermatitis Quality of Life Index (IDQOL). Safety was monitored by physical examination, laboratory investigation and documentation of clinical adverse events.

RESULTS

 The treatment of eczema with 15(R/S)-methyl-LXA(4) cream significantly relieved the severity, induced a recovery, and improved the quality of life of the patients, as demonstrated by significantly reduced SSS, EASI and IDQOL, respectively, in a way similar to the efficacy of Eloson. All safety parameters remained within normal limits. No clinical adverse event was found in the three patient groups.

CONCLUSIONS

 15(R/S)-methyl-LXA(4) was well tolerated, and significantly reduced the severity of eczema. The results of this small exploratory study suggest that 15(R/S)-methyl-LXA(4) warrants further investigation in the treatment of eczema.

Controlled formation of mono- and dihydroxy-resolvins from EPA and DHA using soybean 15-lipoxygenase

Resolvins and protectins are important anti-inflammatory and pro-resolution compounds derived from the enzymatic oxidation of omega-3 fatty acids all-cis-5,8,11,14,17-eicosapentaenoic acid (EPA) and all-cis-4,7,10,13,16,19-docosahexaenoic acid (DHA). We have developed a simple, controlled method to synthesize an array of resolvin and protectin analogs from fatty acid starting materials using soybean 15-lipoxygenase. The conditions were optimized for the production of both mono- and dihydroxy derivatives, with enzyme concentration and pH found to have a significant effect on the reaction products. The methods were applied to five biologically important omega-3 and omega-6 fatty acid substrates. Mono- and dihydroxy compounds were successfully synthesized from all substrates and the products were characterized by normal phase (NP) HPLC, GC-MS, TOF-MS, UV-visible (UV-vis) spectroscopy, and NMR spectroscopy. The methods could be further applied to any polyunsaturated fatty acids containing the cis-1,4,7,10-undecatetraene moiety to produce a range of novel compounds with potential biological activity.

Lipoxins, resolvins and protectins: new leads for the treatment of asthma

BACKGROUND

The pathobiology of asthma is characterized by the production of pro-inflammatory eicosanoids that play important roles in regulating airway responses. Recognition of the biosynthetic pathways and sites of action for 5-lipoxygenase-derived leukotrienes has led to the successful development of two different classes of asthma therapeutics.

OBJECTIVES

In this review, we describe structurally distinct lipid mediators derived from arachidonic acid and ω-3 fatty acids that have anti-inflammatory and pro-resolving actions. These counter-regulatory lipid mediators are generated in the airway during asthma and defects in their production are associated with disease severity.

CONCLUSION

These natural small molecules are rapidly inactivated, but serve as rationale templates for the design of stable analogues with protective actions that could serve as new therapeutic leads for asthma.

Resolution of inflammation: therapeutic potential of pro-resolving lipids in type 2 diabetes mellitus and associated renal complications

The role of inflammation in the pathogenesis of type 2 diabetes mellitus (T2DM) and its associated complications is increasingly recognized. The resolution of inflammation is actively regulated by endogenously produced lipid mediators such as lipoxins, resolvins, protectins, and maresins. Here we review the potential role of these lipid mediators in diabetes-associated pathologies, specifically focusing on adipose inflammation and diabetic kidney disease, i.e., diabetic nephropathy (DN). DN is one of the major complications of T2DM and we propose that pro-resolving lipid mediators may have therapeutic potential in this context. Adipose inflammation is also an important component of T2DM-associated insulin resistance and altered adipokine secretion. Promoting the resolution of adipose inflammation would therefore likely be a beneficial therapeutic approach in T2DM.

The medicinal chemistry of stable synthetic leukotriene B3 and B4 analogues

Leukotriene B3 and B4 are part of an important class of signaling molecules – the leukotrienes, implicated in the inflammation process. Their pro-inflammatory effects have been widely recognized for almost three decades but it is only recently that their benefit in host defense has begun to be acknowledged. Their use as therapeutic agents is, unfortunately, limited by rapid metabolism. However, over the past 25 years, a number of stable leukotriene B3 and B4 analogues have been produced. In this review, we examine their medicinal chemistry and biological evaluation.

Therapeutic anti-inflammatory potential of formyl-peptide receptor agonists

The need for novel anti-inflammatory drugs justifies the search for innovative targets that could satisfy this goal. For quite some time now, we have proposed the study of endogenous anti-inflammation as a distinctive approach to the discovery of new drugs. This approach requires development of new compounds that activate specific receptor targets to downregulate the cellular and tissue pathways operative in the host during inflammation. Here we dwell on a family of G-protein coupled receptors (GPCR) termed FPRs, acronym for formyl-peptide receptors. With three and seven members in man and mouse, respectively, these receptors harness many biological functions, spanning odour perception and hair growth, to the control of multiple facets (pain; cell migration; oxidative burst; xenobiotic engulfment) of the inflammatory reaction. We focus on FPR biology with particular attention to molecules able to produce pharmacological effects by interacting with these GPCRs, describing endogenous agonists of FPRs and, more relevantly, the current development of synthetic agonists. Besides being potential leads for the development of the anti-inflammatory therapeutics of the future, these compounds could also help clarify the properties and roles that each FPR might play in the complex network of pathways that is inflammation. We conclude that FPR2 agonists could be valid warhorses for defining a novel philosophy for anti-inflammatory drug discovery programmes: mimicking - with new compounds - the way our body disposes of inflammation could be a viable approach to regulate aberrant inflammatory responses as in the case of several chronic rheumatic and cardiovascular pathologies.

Oxidative stress induced mechanisms in the progression of periodontal diseases and cancer: a common approach to redox homeostasis?

There is documented evidence of significant associations between cancer of the lung, kidney, pancreas, hematological and oral cancers and periodontal diseases of the supporting structures of the teeth. Enhanced lipid peroxidation, raised levels of TBARS and the oxidative stress marker malondealdehyde have been detected in breast cancer with reduced antioxidant capacity, also characteristic of periodontal diseases. Antioxidants could overcome this deficit and attenuate disease progression by down regulating glutathione detoxification/redox buffering system and inhibiting key transcription factors. Periodontal disease may be a critical marker of a susceptible immune system, or initiate cancer risk with a pro-oxidant inflammatory profile.

Lipids as targets for novel anti-inflammatory therapies

Lipids serve important functions as membrane constituents and also as energy storing molecules. Besides these functions certain lipid species have now been recognized as signalling molecules that regulate a multitude of cellular responses including cell growth and death, and also inflammatory reactions. Bioactive lipids are generated by hydrolysis from membrane lipids mainly by phospholipases giving rise to fatty acids and lysophospholipids that either directly exert their function or are further converted to active mediators. This review will summarize the present knowledge about bioactive lipids that either promote or attenuate inflammatory reactions. These lipids include polyunsaturated fatty acids (PUFA), eicosanoids including the epoxyeicosatrienoic acids (EET), peroxisome proliferation activating receptor (PPAR) activators, cannabinoids and the sphingolipids ceramide, sphingosine 1-phosphate and sphingosylphosphorylcholine.

Thematic Review Series: Proteomics. An integrated omics analysis of eicosanoid biology

Eicosanoids have been implicated in a vast number of devastating inflammatory conditions, including arthritis, atherosclerosis, pain, and cancer. Currently, over a hundred different eicosanoids have been identified, with many having potent bioactive signaling capacity. These lipid metabolites are synthesized de novo by at least 50 unique enzymes, many of which have been cloned and characterized. Due to the extensive characterization of eicosanoid biosynthetic pathways, this field provides a unique framework for integrating genomics, proteomics, and metabolomics toward the investigation of disease pathology. To facilitate a concerted systems biology approach, this review outlines the proteins implicated in eicosanoid biosynthesis and signaling in human, mouse, and rat. Applications of the extensive genomic and lipidomic research to date illustrate the questions in eicosanoid signaling that could be uniquely addressed by a thorough analysis of the entire eicosanoid proteome.

Biogenic synthesis, purification, and chemical characterization of anti-inflammatory resolvins derived from docosapentaenoic acid (DPAn-6)

Enzymatically oxygenated derivatives of the omega-3 fatty acids cis-4,7,10,13,16,19-docosahexaenoic acid (DHA) and cis-5,8,11,14,17-eicosapentaenoic acid, known as resolvins, have potent inflammation resolution activity (Serhan, C. N., Clish, C. B., Brannon, J., Colgan, S. P., Chiang, N., and Gronert, K. (2000) J. Exp. Med. 192, 1197-1204; Hong, S., Gronert, K., Devchand, P. R., Moussignac, R., and Serhan, C. N. (2003) J. Biol. Chem. 278, 14677-14687). Our objective was to determine whether similar derivatives are enzymatically synthesized from other C-22 fatty acids and whether these molecules possess inflammation resolution properties. The reaction of DHA, DPAn-3, and DPAn-6 with 5-, 12-, and 15-lipoxygenases produced oxylipins, which were identified and characterized by liquid chromatography coupled with tandem mass-spectrometry. DPAn-6 and DPAn-3 proved to be good substrates for 15-lipoxygenase. 15-Lipoxygenase proved to be the most efficient enzyme of the three tested for conversion of long chain polyunsaturated fatty acids to corresponding oxylipins. Since DPAn-6 is a major component of Martek DHA-S oil, we focused our attention on reaction products obtained from the DPAn-6 and 15-lipoxygenase reaction. (17S)-hydroxy-DPAn-6 and (10,17S)-dihydroxy-DPAn-6 were the main products of this reaction. These compounds were purified by preparatory high performance liquid chromatography techniques and further characterized by NMR, UV spectrophotometry, and tandem mass spectrometry. We tested both compounds in two animal models of acute inflammation and demonstrated that both compounds are potent anti-inflammatory agents that are active on local intravenous as well as oral administration. These oxygenated DPAn-6 compounds can thus be categorized as a new class of DPAn-6-derived resolvins.

Uncontrolled airway inflammation in lung disease represents a defect in counter-regulatory signaling

Counter-regulatory lipid mediators are generated during airway inflammation to promote resolution. Defects in the production of these lipid mediators have now been associated with several diseases of persistent airway inflammation. Lipoxins are the lead members of this class of anti-inflammatory and proresolving chemical mediators. Recently, several new families of fatty acid-derived counter-regulatory mediators have been discovered, including the resolvins and protectins. Diminished formation of these endogenous protective signals would interrupt the natural resolution of inflammation. Here, we review how rapidly emerging information on lipoxins, resolvins and protectins is providing new insights into the pathophysiology of chronic airway inflammation in several common illnesses, including asthma.

Systems approach with inflammatory exudates uncovers novel anti-inflammatory and pro-resolving mediators

Using a systems approach to mine spontaneously resolving inflammatory exudates, novel families of lipid- derived mediators were identified in animal systems that control both the duration and magnitude of acute inflammation. These new families were coined with the resolvins and protectins because they possess potent bioactions and novel chemical structures. The mapping of these new resolution circuits has already provided new avenues for appreciating the molecular basis of many inflammatory diseases. This presentation/mini review gives recent advances from our studies on resolvin and protectin biosynthesis and the actions of these novel mediators. These previously unappreciated families of lipid-derived mediators were originally isolated from murine models of acute inflammation captured during the natural spontaneous resolution phase. They are biosynthesized from omega-3 fatty acids and possess potent anti-inflammatory, pro-resolving and anti-fibrotic in vivo actions. These new families of endogenous pro-resolving and anti-inflammatory agonists were also used as biotemplates to design potent mimetics/analogs which were used to confirm each of their structures and specific functions. Moreover, together the identification of these mediators indicate that resolution is an active process at the tissue level in vivo as well as constitute a new genus of anti-inflammatories with a previously unknown pro-resolving mechanism of action.

Design and synthesis of benzo-lipoxin A4 analogs with enhanced stability and potent anti-inflammatory properties

A new class of chemically and metabolically stable lipoxin analogs featuring a replacement of the tetraene unit of native LXA(4) with a substituted benzo-fused ring system have been designed and studied. These molecules were readily synthesized via a convergent synthetic route involving iterative palladium-mediated cross-coupling, and exhibit enhanced chemical stability, as well as resistance to metabolic inactivation via eicosanoid oxido-reductase. These new LX analogs were evaluated in a model of acute inflammation and were shown to exhibit potent anti-inflammatory properties, significantly decreasing neutrophil infiltration in vivo. The most potent among these was compound 9 (o-[9,12]-benzo-15-epi-LXA(4) methyl ester. Taken together, these findings help identify a new class of stable and easily prepared LX analogs that may serve as novel tools and as promising leads for new anti-inflammatory agents with improved therapeutic profile.

Anti-inflammatory and proresolving lipid mediators

The popular view that all lipid mediators are pro-inflammatory arises largely from the finding that nonsteroidal anti-inflammatory drugs block the biosynthesis of prostaglandins. The resolution of inflammation was widely held as a passive event until recently, with the characterization of novel biochemical pathways and lipid-derived mediators that are actively turned on in resolution and that possess potent anti-inflammatory and proresolving actions. A lipid-mediator informatics approach was employed to systematically identify new families of endogenous local-acting mediators from omega-3 polyunsaturated fatty acids (eicosapentaenoic acid and docosahexaenoic acid) in resolving exudates, which also contain lipoxins and aspirin-triggered lipoxins generated from arachidonic acid. Given their potent bioactions, these new chemical mediator families were termed resolvins and protectins. Here, we review the recent advances in our understanding of the biosynthesis and stereospecific actions of these new proresolving mediators, which have also proven to be organ protective and antifibrotic.

New endogenous anti-inflammatory and proresolving lipid mediators: implications for rheumatic diseases

Prostaglandins and leukotrienes are lipid mediators that carry out pivotal roles in host defense and acute inflammation. Failure to completely resolve an acute inflammatory response can lead to chronic inflammation, scarring, and eventual loss of tissue function. Until recently, it was thought that tissue resolution of acute inflammation was a passive event. However, it is now known than lipoxins, which--like prostaglandins and leukotrienes--are also derived from arachidonic acid, are active anti-inflammatory and proresolution mediators, acting in part by reducing neutrophil entry to the inflammation site and stimulating the uptake of apoptotic polymorphonuclear leukocytes by macrophages. Novel families of locally acting and locally generated mediators derived from omega-3 polyunsaturated fatty acids have also been identified as biosynthetically active components in the resolution phase of inflammation. The new families of chemical mediators are termed 'resolvins' and 'protectins' because individual members of each family are stereospecific in controlling the duration and magnitude of inflammation in animal models. Possible deficiencies in the biosynthesis of lipoxins, resolvins, and protectins, and/or their signal transduction, might underlie some aspects of pathogenesis in chronic inflammatory diseases.

Lipoxin A4 stable analogs reduce allergic airway responses via mechanisms distinct from CysLT1 receptor antagonism

Cellular recruitment during inflammatory/immune responses is tightly regulated. The ability to dampen inflammation is imperative for prevention of chronic immune responses, as in asthma. Here we investigated the ability of lipoxin A4 (LXA4) stable analogs to regulate airway responses in two allergen-driven models of inflammation. A 15-epi-LXA4 analog (ATLa) and a 3-oxa-15-epi-LXA4 analog (ZK-994) prevented excessive eosinophil and T lymphocyte accumulation and activation after mice were sensitized and aerosol-challenged with ovalbumin. At <0.5 mg/kg, these LXA4 analogs reduced leukocyte trafficking into the lung by >50% and to a greater extent than equivalent doses of the CysLT1 receptor antagonist montelukast. Distinct from montelukast, ATLa treatment led to marked reductions in cysteinyl leukotrienes, interleukin-4 (IL-4), and IL-10, and both ATLa and ZK-994 inhibited levels of IL-13. In cockroach allergen-induced airway responses, both intraperitoneal and oral administration of ZK-994 significantly reduced parameters of airway inflammation and hyper-responsiveness in a dose-dependent manner. ZK-994 also significantly changed the balance of Th1/Th2-specific cytokine levels. Thus, the ATLa/LXA4 analog actions are distinct from CysLT1 antagonism and potently block both allergic airway inflammation and hyper-reactivity. Moreover, these results demonstrate these analogs' therapeutic potential as new agonists for the resolution of inflammation.

Synthesis of 3-oxalinolenic acid and β-oxidation-resistant 3-oxa-oxylipins

3-Oxalinolenic acid (3-oxa-9(Z),12(Z),15(Z)-octadecatrienoic acid or (6(Z),9(Z),12(Z)-pentadecatrienyloxy)acetic acid) was synthesized from 5(Z),8(Z),11(Z),14(Z),17(Z)-eicosapentaenoic acid by a sequence involving the C15 aldehyde 3(Z),6(Z),9(Z),12(Z)-pentadecatetraenal as a key intermediate. Conversion of the aldehyde by isomerization and two steps of reduction afforded 6(Z),9(Z),12(Z)-pentadecatrienol, which was coupled to bromoacetate to afford after purification by HPLC >99%-pure 3-oxalinolenic acid in 10-15% overall yield. 3-Oxalinolenic acid was efficiently oxygenated by soybean lipoxygenase-1 into 3-oxa-13(S)-hydroperoxy-9(Z),11(E),15(Z)-octadecatrienoic acid, and this hydroperoxide could be further converted chemically into 3-oxa-13(S)-hydroxy-9(Z),11 (E),15(Z)-octadecatrienoic acid and 3-oxa-13-oxo-9(Z),11 (E),15(Z)-octadecatrienoic acid. The 3-oxa-hydroperoxide also served as the substrate for the plant enzymes allene oxide synthase, divinyl ether synthase, and hydroperoxide lyase to produce 3-oxa-12-oxo-10,15(Z)-phytodienoic acid and other 3-oxa-oxylipins that were characterized by MS. 3-Oxalinolenic acid was not oxygenated by 9-lipoxygenase from tomato but was converted at a slow rate into 3-oxa-9(S)-hydroperoxy-10(E),12(Z),15(Z)-octadecatrienoic acid by recombinant maize 9-lipoxygenase. Recombinant alpha-dioxygenase-1 from Arabidopsis thaliana catalyzed the conversion of 3-oxalinolenic acid into a 2-hydroperoxide, which underwent spontaneous degradation into a mixture of 6,9,12-pentadecatrienol and 6,9,12-pentadecatrienyl formate. A novel alpha-dioxygenase from the moss Physcomitrella patens was cloned and expressed and was found to display the same activity with 3-oxalinolenic acid as Arabidopsis thaliana alpha-dioxygenase-1. Lipoxygenase-generated 3-oxa-oxylipins are resistant toward beta-oxidation and have the potential for displaying enhanced biological activity in situations where activity is limited by metabolic degradation.