novel lipid mediators promote resolution of acute...

This Review is part of a thematic series on Lipid Oxidation and Cardiovascular Disease, which includes the following articles:Lipid Oxidation and Cardiovascular Disease: Introduction to a Review Series

Novel Lipid Mediators Promote Resolution of Acute Inflammation: Impact of Aspirin and Statins

Oxidation-Specific Epitopes Are Danger-Associated Molecular Patterns Recognized by Pattern Recognition Receptors of

Innate Immunity

Aldehydic Lipid Peroxidation Products and Cardiovascular Disease

Phospholipid Oxidation Products in Cardiovascular Disease Stan Hazen and Thomas M. McIntyre, Guest Editors

Novel Lipid Mediators Promote Resolution ofAcute Inflammation

Impact of Aspirin and Statins

Matthew Spite, Charles N. Serhan

Abstract: The resolution of acute inflammation is a process that allows for inflamed tissues to return tohomeostasis. Resolution was held to be a passive process, a concept now overturned with new evidencedemonstrating that resolution is actively orchestrated by distinct cellular events and endogenous chemicalmediators. Among these, lipid mediators, such as the lipoxins, resolvins, protectins, and newly identifiedmaresins, have emerged as a novel genus of potent and stereoselective players that counter-regulate excessiveacute inflammation and stimulate molecular and cellular events that define resolution. Given that uncontrolled,chronic inflammation is associated with many cardiovascular pathologies, an appreciation of the endogenouspathways and mediators that control timely resolution can open new terrain for therapeutic approaches targetedat stimulating resolution of local inflammation, as well as correcting the impact of chronic inflammation incardiovascular disorders. Here, we overview and update the biosynthesis and actions of proresolving lipidmediators, highlighting their diverse protective roles relevant to vascular systems and their relation to aspirinand statin therapies. (Circ Res. 2010;107:1170-1184.)

Key Words: resolution � lipid mediators � eicosanoids � omega-3 fatty acids � proresolving mediators

Ungoverned inflammation is a prominent characteristic ofmany chronic diseases, such as arthritis and diabetes, as

well as cardiovascular diseases, including atherosclerosis,myocarditis, heart failure, and vasculitis.1–4 Antiinflamma-tory therapies aimed at blocking proinflammatory pathwaysare widely used. Among these, synthetic corticosteroids,cyclooxygenase (COX) inhibitors, and anti–tumor necrosisfactor (TNF)-� antibodies are prominent examples.5–10 Al-though this approach has proven efficacious in certain clinical

settings, inhibiting proinflammatory pathways can in somecases be detrimental (eg, selective COX-2 inhibitors); thus,effective therapeutics aimed at controlling chronic inflamma-tion remain of interest.6,9–11 We focused on mapping endog-enous cellular and biochemical pathways that operate duringself-limited acute inflammatory responses that enable thereturn to homeostasis.12,13 This systematic approach with invivo inflammatory exudates uncovered novel chemical me-diators that are actively biosynthesized during resolution of

Original received May 10, 2010; revision received August 17, 2010; accepted September 10, 2010. In August 2010, the average time from submissionto first decision for all original research papers submitted to Circulation Research was 13.2 days.

From the Center for Experimental Therapeutics and Reperfusion Injury (M.S., C.N.S.), Brigham and Women’s Hospital and Harvard Medical School,Boston, Mass. Present address for M.S.: Division of Cardiovascular Medicine, University of Louisville, Ky.

Correspondence to Prof Charles N. Serhan, Brigham and Women’s Hospital, Harvard Medical School, Harvard Institutes of Medicine Bldg, 77 AveLouis Pasteur, HIM 829, Boston, MA 02115. E-mail [email protected]

© 2010 American Heart Association, Inc.

Circulation Research is available at http://circres.ahajournals.org DOI: 10.1161/CIRCRESAHA.110.223883

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inflammation and potently stimulate this vital process. Theidentification of these new mechanisms and pathways chal-lenged the preexisting paradigm that inflammation passivelyterminates.13 Within this context, a detailed appreciation ofthe endogenous pathways that actively turn off acute inflamma-tion and stimulate resolution opens many new avenues fortherapeutics and prevention that are aimed at controlling exces-sive inflammation without apparent immunosuppression.

Inflammation and Its Natural ResolutionThe acute inflammatory response is a protective, physiolog-ical program that protects the host against invading patho-gens. Local chemical mediators biosynthesized during acuteinflammation give rise to the macroscopic events character-ized by Celsus in the first century, namely, rubor (redness),tumor (swelling), calor (heat), and dolor (pain).12 Althoughthese cardinal signs of inflammation were evident more than2000 years ago, the cellular and molecular events that regulatethe inflammatory response and its timely resolution are onlyrecently beginning to be appreciated. Tissue edema is one of theearliest events of the acute inflammatory response that arisesfrom increased permeability of microvasculature. Polymorpho-nuclear neutrophils (PMNs) are the first line of defense againstmicrobial invasion, which contain potentially harmful stimuli viaphagocytosis. PMNs traverse postcapillary venules at sites ofinflammation, degrade pathogens within phagolysosomes, andundergo apoptosis. Next, mononuclear cells infiltrate, differ-entiate into macrophages, and clear apoptotic PMNs byphagocytosis in a noninflammatory manner termed efferocy-tosis.14 Ultimately, clearance of microbes and efflux ofphagocytes allows for the tissue to return to homeostasis.13

Disruption of any of these specific checkpoints could poten-tially give rise to chronic inflammation, which is character-ized primarily by excessive leukocyte infiltration and activa-tion, delayed clearance, resultant tissue damage, and loss offunction.15 Indeed, cardiovascular diseases such as athero-sclerosis display many of these features.16–18

Lipid mediators (LMs) biosynthesized from essential fattyacids play pivotal roles in distinct phases of the inflammatoryresponse,13 with prostaglandin (PG)E2 and cysteinyl leuko-trienes (cysLTs) promoting early vascular permeability andleukotriene (LT)B4 stimulating leukocyte chemotaxis.19 Pros-taglandins play additional roles during the acute inflamma-tory response, including the regulation of local changes inblood flow and pain sensitization (reviewed elsewhere20).During evolution of an inflammatory exudate, the profile ofLM autacoids changes to biosynthesis of counter-regulatorymediators that limit further PMN congregation and stimulateresolution.21–23 Although the mechanisms that mediate pro-gression from acute to chronic inflammation are not com-pletely understood, chronic inflammation is widely viewed asan excess of proinflammatory mediators.11 In view of mount-ing evidence from our laboratory, and now many othergroups, it is also plausible that disruptions in endogenousproresolving circuits could underlie some of the aberrantmechanisms that lead to chronic inflammation.1,11,13,15

Complete resolution of an acute inflammatory response isthe ideal outcome following an insult.12 For resolution to ensue,further leukocyte recruitment must be halted and accompanied

by removal of leukocytes from inflammatory sites. These keyevents governing resolution of inflammation are the focus of ourwork and collaborators. In particular, we sought to identifymechanisms that regulate these key histological events in reso-lution using an unbiased systems approach to profile self-limitedinflammation using liquid chromatography/tandem mass spec-trometry (LC-MS/MS).21,22,24–26 These analyses identified novelLMs and also provided information regarding their biosyntheticpathways and further metabolic inactivation products. It isnoteworthy that, in addition to novel LMs reviewed here, otherimportant components of resolution are emerging (ie, nuclearfactor [NF]-�B, annexin-1, specific prostanoids). They are be-yond the scope of this concise update and interested readers aredirected to.8,11,23,27

Non-standard Abbreviations and Acronyms

AA arachidonic acid

ATL aspirin-triggered LXA4 (5S,6R,15R-trihydroxy-7,9,13-trans-11-cis-eicosatetraenoic acid)

AT-RvD1 aspirin-triggered-RvD1 (7S,8R,17R-trihydroxy-docosa-4Z,9E,11E,13Z,15E,19Z-hexaenoic acid)

AT-RvD2 aspirin-triggered RvD2 (7S,16R,17R-trihydroxy-docosa-4Z,8E,10Z,12E,14E,19Z-hexaenoic acid)

COX cyclooxygenase

cysLT cysteinyl leukotriene

DHA docosahexaenoic acid

EPA eicosapentaenoic acid

GPCR G protein–coupled receptor

HO heme oxygenase

IL interleukin

LC-MS/MS liquid chromatography/tandem mass spectrometry

LDL low-density lipoprotein

LM lipid mediator

LOX lipoxygenase

LT leukotriene

LXA4 5S,6R,15S-trihydroxy-7,9,13-trans-11-cis-eicosatetraenoic acid

MaR1 maresin 1 (7,14-dihydroxydocosa-4Z,8,10,12,16Z,19Z-hexaenoic acid)

NF-�B nuclear factor �B

NPD1/PD1 10R,17S-dihydroxy-docosa-4Z,7Z,11E,13E,15Z,19Z-hexaenoic acid

PDGF platelet-derived growth factor

PG prostaglandin

PMN polymorphonuclear neutrophil

Rv resolvin

RvD1 resolvin D1 (7S,8R,17S-trihydroxy-docosa-4Z,9E,11E,13Z,15E,19Z-hexaenoic acid)

RvD2 resolvin D2 (7S,16R,17S-trihydroxy-docosa-4Z,8E,10Z,12E,14E,19Z-hexaenoic acid)

RvE1 resolvin E1 (5S,12R,18R-trihydroxy-eicosa-6Z,8E,10E,14Z,16E-pentaenoic acid)

TNF tumor necrosis factor

VEGF vascular endothelial growth factor

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Proresolving Lipid Mediators: AutacoidSignals in Exudates

Using experimental models of self-resolving acute inflamma-tion, we uncovered a new genus of autacoids that possesspotent antiinflammatory and proresolving actions. Theseinclude lipoxins, which are generated from arachidonic acid(AA), resolvins, protectins, and newly identified maresins,which are generated from omega-3 fatty acids. The enzymaticgeneration of these families occurs primarily via transcellularbiosynthesis, and in some cases within a single cell type, vialipoxygenase (LOX) enzymes. They are potent, stereoselec-tive agonists controlling both the magnitude and duration ofan acute inflammatory response. The biosynthesis and actionsof each of these families of endogenous counter-regulatoryautacoids are reviewed herein.

LipoxinsLipoxins are generated in humans from AA via LOX en-zymes and comprise 2 distinct regioisomers, lipoxin (LX)A4

and LXB4. Lipoxins were the first mediators recognized tohave both antiinflammatory and proresolving actions.28 Theirbiosynthesis proceeds via 15-LOX–mediated conversion ofAA to 15-hydroxyeicosatetraenoic acid (HETE), which isfurther transformed via 5-LOX and subsequent reactions toLXA4 and LXB4 during cell:cell interactions (eg, epithelial:

leukocyte, leukocyte:leukocyte). Lipoxins are also generatedin the vasculature during platelet:leukocyte interactions, inwhich the intermediate in leukotriene biosynthesis, leukotri-ene (LT)A4, is produced within leukocytes and converted tolipoxins by platelet 12-LOX.29 In addition to LOX-initiatedlipoxin biosynthesis, an intriguing novel route involvingCOX-2 was uncovered. In the presence of aspirin, acetylatedCOX-2 loses activity required to form prostaglandin (PG)H2

but retains oxygenase activity to produce 15R-HETE fromarachidonate. This intermediate, like 15S-HETE, is transformedvia 5-LOX to generate epimeric lipoxins, termed aspirin-triggered (AT) or 15-epi-lipoxins.30 The 15-epi-lipoxins sharethe potent bioactions of lipoxins, suggesting that their formationcould underlie the antiinflammatory actions of aspirin thatcannot be attributed only to the inhibition of prostanoid forma-tion (vide infra). Of note, 15-epi-lipoxin biosynthesis can also beinitiated by cytochrome P450 enzymes and this importantpathway may underlie the generation of 15-epi-lipoxins in theabsence of aspirin.31 In humans, low dose aspirin limits PMNinfiltration via local 15-epi-lipoxin formation that in turn stim-ulates nitric oxide (NO) production (vide infra).32,33

The temporal generation and biological role of endogenouslipoxins was elucidated using animal models of sterile in-flammation. The initial formation of leukotrienes correspondswith an increase in PMN infiltration and is followed by a

Table 1. Cellular Actions of Lipoxins, Resolvins, and Maresins

Lipid Mediator and Target Cell Action(s) References

Lipoxin A4 (or aspirin-triggeredlipoxin A4)

Endothelial cells Blocks ROS generation; inhibits VEGF-induced migration/proliferation; decreases ICAM-1 expression;stimulates PGI2 and NO formation; stimulates HO-1 expression

33, 93–95, 113

Vascular smooth musclecells

Decreases PDGF-stimulated migration 96

Macrophages Stimulates nonphlogistic phagocytosis 25, 35

T cells Upregulates CCR5 expression; inhibits TNF secretion 69, 123

Fibroblasts Blocks MMP-3 production 124

Neutrophils Blocks superoxide generation; reduces CD11b/CD18 expression; blocks neutrophil:endothelialinteractions; inhibits peroxynitrite formation

125–127

Resolvin E1

Macrophages Stimulates nonphlogistic phagocytosis; binds to ChemR23 in a stereospecific manner 25, 47

Vascular smooth musclecells

Decreases PDGF-stimulated migration 96

Platelets Reduces aggregation/activation 54

Neutrophils Blocks transmigration; acts as partial agonist/antagonist of BLT-1 and blocks LTB4-stimulated Ca2�

mobilization22

Dendritic cells Reduces IL-12 production 47

Resolvin D1

Neutrophils Binds ALX and GPR32 & decreases LTB4-stimulated actin polymerization; Blocks transmigration 61, 63

Macrophages Enhances phagocytosis in a receptor-dependent manner 63

Resolvin D2

Endothelial cells Stimulates NO and PGI2 production; blocks leukocyte:endothelial interactions 62

Neutrophils Enhances microbial phagocytosis; decreases extracellular ROS generation; reduces CD18expression and L-selectin shedding

62

Macrophages Enhances phagocytosis 62

Maresin 1

Macrophages Enhances phagocytosis 76

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progressive increase in prostaglandin formation, namelyPGE2 and PGD2.21 Next, the profile of lipid mediatorsswitches from proinflammatory eicosanoids to lipoxins,whereby PGE2 and PGD2 stimulate upregulation of 15-LOX,a process termed “lipid mediator class switching”.21 Thus,although COX-2–derived proinflammatory eicosanoids arecommonly viewed as harmful, they are critical for positivefeed-forward regulation of antiinflammatory LM circuits.Importantly, recent studies have shown that inhibition ofCOX-2 delays resolution of inflammation.25,27 Thus, in addi-tion to inhibiting the formation of protective prostaglandins(eg, prostacyclin),10 selective COX-2 inhibitors also interferewith endogenous resolution programs. The role of lipoxins incounter-regulating leukocyte trafficking was demonstrated inboth animal and human systems, where administration ofLXA4 reduces PMN transmigration, adhesion receptor ex-pression, proinflammatory cytokine generation and excessivePMN infiltration into inflamed tissues (Tables 1 and 2).13,24,34

Proresolving SignalsAlong with the antiinflammatory role of lipoxins in negativelyregulating leukocyte infiltration into tissues, lipoxins also stim-ulate resolution. Within inflammatory exudates, PMNs undergoapoptosis and must be cleared to prevent unwarranted tissuedamage. In this regard, lipoxins and 15-epi-lipoxins stimulatephagocytosis of apoptotic PMNs by macrophages in a nonphlo-gistic (non–fever-causing) manner.25,35 Lipoxins also stimulatethe production of antiinflammatory cytokines, such as interleu-kin (IL)-10, in macrophages and promote macrophage efflux toperipheral lymph nodes. Thus, lipoxins are dual acting mediatorsthat not only reduce further leukocyte infiltration, but alsopromote their removal from inflamed sites.1,25

LXA4 elicits its actions in nanomolar concentrations viaagonist signaling by a specific G protein–coupled receptor(GPCR) termed ALX (also denoted formyl peptide receptor

2; FPR2).29 Specific binding of LXA4 to ALX is stereoselec-tive and ALX signaling mediates the protective actions ofLXA4 in myeloid cells, which include inhibition of NF-�Bactivation, blockade of leukotriene biosynthesis, attenuationof superoxide production and regulation of leukocyte chemo-taxis (Figure 1 and Table 1). Regulation of leukocyte traf-ficking by LXA4 is partly dependent on direct stimulation ofthe suppressor of cytokine synthesis (SOCS-2) pathway.36 Ofnote, LXA4 counter-regulates vascular smooth muscle cellmigration37 induced by cysLTs and serves as a cysLT1receptor antagonist.38 The role of specific GPCRs in mediat-ing diverse protective actions of lipoxins is evidenced bytargeted overexpression and genetic deletion of both humanand murine homologs of ALX/FPR239 in murine systems.40,41

The Omega-3 Proresolution Mediators:Resolvins, Protectins, and Maresins

The importance of essential omega-3 polyunsaturated fattyacids in humans is evidenced by multiple studies demonstrat-ing that dietary omega-3 fatty acids have beneficial cardio-vascular effects.42 Of note, a diet rich in omega-3 fatty acidsis recommended by the American Heart Association(www.americanheart.org). It was first observed that Green-land Eskimos, who have a diet high in cold water fish, havea low rate of ischemic heart disease.43 These findings werevalidated in numerous human and animal studies usingpurified fish oil extracts rich in omega-3 fatty acids, eicosa-pentaenoic acid (EPA) and docosahexaenoic acid (DHA).Most notably, the Gruppo Italiano per lo Studio della Soprav-vivenza nell’Infarto miocardico (GISSI) Prevenzione trialdemonstrated that omega-3 dietary supplementation (1 g/d)reduced the risk of cardiovascular death in a patient popula-tion of �2000 that had experienced a previous myocardialinfarction.44 More recently, GISSI Prevenzione determinedthat omega-3 supplementation also reduces the risk of deathfrom congestive heart failure in a placebo-controlled, doubleblind, randomized study of more than 6,000 heart failurepatients.45 Although multiple beneficial actions of omega-3supplementation are widely appreciated, the mechanisms under-lying their protection in complex disease remained to be identi-fied. At higher concentrations, omega-3 fatty acids act on ionchannels, are metabolized to inactive eicosanoids of the 3-seriesprostaglandins and 5-series leukotrienes, and change cell mem-brane physical properties. However, the role of omega-3 fattyacids in resolution of inflammation was unknown.

To address the molecular basis for antiinflammatory prop-erties of omega-3 fatty acids, an unbiased LC-MS/MS-basedinformatics approach was devised to identify novel mediatorsgenerated from omega-3 precursors during acute inflamma-tion in vivo. Using this approach, EPA and DHA were foundto be enzymatically converted into novel potent LMs coinedresolvins for resolution phase interaction products.22,24,26

Resolvins represent a new distinct family of mediatorsgenerated from omega-3 fatty acids during resolution. Impor-tantly, biosynthesis of resolvins gives rise to stereospecificlocal mediators that have potent actions and activate specificreceptors. Therefore, resolvins are distinct from auto-oxidation products that can arise from EPA and DHA on foodspoiling or in vivo during oxidative stress.46

Table 2. Lipoxins and Aspirin-Triggered Lipoxins in AnimalModels of Disease

Disease Model Species Action(s) References

Asthma Mouse Attenuates pulmonaryinflammation and airway

hyperresponsiveness

128

Ischemia/reperfusioninjury

Mouse Decreases hindlimbischemia/reperfusion injury in

the lung; attenuates renalischemia/reperfusion injury

34, 129

Dermal Inflammation Mouse Decreases vascularpermeability

130

Periodontitis Rabbit Decreases bone loss; reducesPMN accumulation

131

Peritonitis Mouse Decreases PMN infiltration;enhances phagocytosis andclearance of apoptotic cells

24, 25

Cystic Fibrosis Mouse Decreases disease severity,inflammation, and bacterial

burden

81

Angiogenesis Mouse CounterregulatesVEGF-induced pathological

neovascularization

113




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E-Series ResolvinsThe first evidence that EPA serves as a precursor forbioactive mediators during resolution of inflammation wasobtained in sterile, self-limited inflammation in mice. As�90% of patients enrolled in the GISSI Prevenzione trialwere taking aspirin in addition to omega-3 fatty acids,44 andour earlier finding that aspirin-acetylated COX-2 gives rise to15-epi-lipoxins, it was of interest to determine whether thiscombination would promote the formation of unique chemi-cal mediators generated from EPA during resolution. In miceadministered EPA and aspirin, PMN infiltration into inflamedtissues decreased and correlated with conversion of EPA to18R-hydroxyeicosapentaenoic acid (18R-HEPE), as well asother related bioactive compounds. LM-lipidomics revealedthat EPA is converted in vivo to a novel bioactive trihydroxy-conjugated triene and diene-containing mediator.22 This bio-synthetic pathway was recapitulated with hypoxic humanendothelial cells exposed to EPA and aspirin, in which18R-HEPE was generated and converted to the mediator byactivated human PMNs via 5-LOX.22 The complete structureof this mediator, coined resolvin E1 (RvE1), was elucidatedvia total organic synthesis based on the proposed biosynthesisand basic structure (see abbreviations).22,47 Add back of RvE1

during acute inflammation markedly reduced PMN infiltra-tion and decreased proinflammatory cytokines, results thatprovided the first evidence for the in vivo molecular basis ofantiinflammatory, anti-PMN actions of EPA.

Given these potent actions, we reasoned that RvE1 mightactivate specific receptors to promote resolution. Screening ofcandidate GPCRs related in sequence to ALX revealed thatRvE1 stereoselectively binds ChemR23, a previous orphanreceptor.47 In isolated cells transfected with ChemR23, RvE1inhibits TNF-� stimulated NF-�B activation, consistent within vivo actions of RvE1 in blocking TNF-� stimulatedleukocyte trafficking. Of note, the endogenous role ofChemR23 in counter-regulating inflammation was recentlydemonstrated in mice with a genetic deletion of ChemR23.48

Acting via ChemR23, RvE1 stimulates downstream signalingthrough the phosphatidylinositol-3 kinase (PI3K)/Akt path-way, leading to activation of the translational regulator,ribosomal protein S6.49 This pathway is involved in RvE1stimulation of macrophage phagocytosis. ChemR23 is highlyexpressed on dendritic cells and monocytes, although itsexpression is low on PMNs.47,50 As RvE1 blocks PMNmigration in vitro and displays specific binding on humanPMNs, this suggested that RvE1 might bind additional

Figure 1. Key cellular actions of lipoxins and resolvins. LXA4 is generated from AA, whereas omega-3 fatty acids, EPA, and DHAserve as precursors for E-series and D-series resolvins, respectively. Lipoxins and resolvins act in a stereospecific manner on distinctcell types through interaction with GPCRs to stimulate nonphlogistic macrophage phagocytosis, increase antiinflammatory cytokines,and decrease proinflammatory cytokine generation in macrophages, neutrophils (PMNs), endothelial cells, and dendritic cells. Lipoxinsand resolvins also stimulate endothelial production of nitric oxide (NO) and vasoprotective prostacyclin (PGI2).




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GPCRs. Indeed, RvE1 signals as a partial agonist/antagonistvia the LTB4 receptor, BLT1, and attenuates LTB4-inducedproinflammatory signaling in PMNs.50

The multilevel potent actions of RvE1 were demonstrated onhuman cells and in acute and chronic inflammatory pathologies.As summarized in Table 3, RvE1 regulates leukocyte traffickingand proinflammatory signaling to promote resolution of perito-nitis, colitis, periodontitis (a chronic infectious inflammation)and retinopathy.25,51–53 RvE1 also displays potent actions onhuman platelets. Humans taking both aspirin and EPA increaseRvE1 levels in plasma,50 and RvE1 blocks ADP andthromboxane-stimulated platelet aggregation without affectingeither collagen or thrombin-stimulated activation.54

A second bioactive member of the E-series was identified thatshares an intermediate in RvE1 biosynthesis. It was earlierproposed that enzymatic conversion of 18R-HEPE to RvE1involves the formation of an epoxide. The 5S-hydroperoxideformed before epoxidation can undergo reduction to 5S,18(R/S)-dihydroxy-eicosapentaenoic acid, denoted resolvin E2 (RvE2).55

RvE2 shares some of the potent actions of RvE1, namelyreducing PMN infiltration in peritonitis, and acts in an additivefashion with RvE1. Interestingly, differences in biological activ-ity were observed that depend on the route of administration (ie,intravenous versus intraperitoneal), suggesting that the targetsand receptors for RvE1 and RvE2 may be distinct. Furtherstudies are warranted to appreciate the specific biosynthesis ofRvE1 and RvE2 and their respective sites of action. Thus, giventhat E-series resolvins are biosynthesized and have direct actionswithin the vasculature, the importance of this pathway and

related products in cardiovascular disease is an area of ongoinginvestigation.

D-Series ResolvinsDHA also has numerous beneficial actions in the cardiovascularsystem.42,56–59 Exogenous DHA reduces expression of vascularendothelial adhesion molecules, such as VCAM-1 and ICAM-1,induced by proinflammatory stimuli and thus regulates leu-kocyte:endothelial interactions.57 However, the amounts ofDHA required to elicit these effects are generally high, ie,micromolar range in vitro or gram dose ranges in vivo. Thus,it was important to determine whether DHA might also serveas a precursor to endogenous autacoids. In mice given DHAplus aspirin, a monohydroxy product, namely 17R-hydroxydocosahexaenoic acid, was generated during resolu-tion. Both dihydroxy and trihydroxy structures biosynthe-sized from DHA were also identified within resolvingexudates. These bioactive molecules were coined aspirin-triggered (AT) D-series resolvins because they enhanceresolution.26 To identify potential cellular sources of these,the proposed biosynthetic pathway was recapitulated in hu-man cells. Hypoxic endothelial cells treated with aspirinconvert DHA to 17R-hydroxydocosahexaenoic acid, which istransformed by leukocytes into D-series resolvins. Impor-tantly, DHA is converted into resolvins in human wholeblood in the absence of aspirin.60 Notably, D-series resolvinsgenerated in the absence of aspirin carry the alcohol at the 17position in predominantly the S configuration, rather than Rconfiguration.60 Addition of this precursor to activated humanPMNs also generated D-series resolvins, again highlighting

Table 3. Antiinflammatory and Proresolving Actions of Resolvins and Maresins in Animal Models of Disease

Disease Model Species Action(s) References

Resolvin E1

Peritonitis Mouse Stops neutrophil recruitment; regulates chemokine/cytokine production; promoteslymphatic removal of phagocytes

22, 24, 47

Retinopathy Mouse Protects against neovascularization 52

Colitis Mouse Decreases neutrophil recruitment and proinflammatory gene expression; improves survival;reduces weight loss

51

Pneumonia Mouse Improves survival; decreases neutrophil infiltration; enhances bacterial clearance; reducesproinflammatory cytokines

109

Inflammatory pain Mouse Reduces inflammatory pain induced by formalin, carrageenan, or Freund’s completeadjuvant; blocks capsaicin- and TNF-�–induced heat and mechanical hypersensitivity

132

Resolvin D1

Peritonitis Mouse Reduces neutrophil recruitment; blocks oxidative-stress induced peritonitis 60, 61, 133

Kidneyischemia/reperfusion

Mouse Decreases fibrosis and protects from ischemia/reperfusion-induced kidney damage andloss of function

72

Retinopathy Mouse Reduces pathological neovascularization 52

Inflammatory Pain Mouse Reduces inflammatory pain induced by formalin, carrageenan, or Freund’s completeadjuvant

132

Resolvin D2

Sepsis (CLP) Mouse Reduces systemic cytokine storm; enhances bacterial clearance; improves survival;regulates leukocyte trafficking; protects from hypothermia

62

Peritonitis Mouse Decreases neutrophil recruitment 62

Maresin 1

Peritonitis Mouse Reduces neutrophil recruitment 76




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the importance of cell-cell interactions (as occurs during reso-lution of inflammation). The enzymatic pathway leading tothe formation of D-series resolvins is shown in Figure 2.Additional bioactive members of this family were identifiedand characterized (RvD3-RvD6). Each of these arises bysimilar biosynthetic routes, but have distinct structures andpotentially additional bioactions.13

Following complete structural elucidation, stereochemicalassignment and total organic synthesis, the bioactions of bothnative and AT D-series resolvins were elucidated.13,26,61 Werecently established the complete structure and stereochemi-cal assignment of RvD2.62 D-series resolvins have multiplebeneficial actions both in vivo, and in isolated human cells(Figure 1 and Tables 1 and 3). In particular, they reduceexcessive PMN infiltration into inflamed tissues, decrease PMNactivation and promote phagocytosis and clearance of apoptoticcells and microbes. Protective actions of D-series resolvins havebeen observed in both acute and chronic inflammatory diseases,such as peritonitis, ischemia/reperfusion injury, and sepsis (Ta-ble 3). The unique mechanism of action for resolvins involvesboth limiting PMN infiltration and enhanced macrophagephagocytosis that uses specific receptors recently identified onhuman PMNs, monocytes, and macrophages.63 RvD1 signals viaa GPCR denoted GPR32 that was an orphan human receptor.Interestingly, RvD1 was also found to activate ALX, in additionto serving as an agonist for GPR32. Signaling through thesereceptors, RvD1 counter-regulates LTB4-stimulated surface ex-pression of �2 integrins, reduces actin polymerization, andenhances macrophage phagocytosis. Of note, classic GPCRsecond messengers, cAMP and Ca2�, are not activated by RvD1signaling in PMNs.

Protectins: Docosatrienes and OtherNovel Products

In addition to DHA-derived resolvins, resolving exudates alsocontained novel 10,17S-dihydroxydocosatrienes, as well asother novel products including 7S,17S-diHDHA and 4S,17S-diHDHA. These dihydroxy-containing products and theirregulatory actions in dermal inflammation and peritonitiswere first reported in.26 Further experiments revealed thatDHA was transformed to 10,17S-docosatriene, 16,17S-docosatriene and D-series resolvins in whole blood, leuko-cytes, brain and glial cells.60 In human glial cells, 10,17S-docosatriene potently regulated IL-1� and extracellularacidification, providing evidence that this compound is aligand, evoking rapid cellular responses. Also, an omega-22hydroxylation product of 10,17S-docosatriene was identified,suggesting that once 10,17S-docosatriene evokes its action, itis inactivated.60 Studies with Bazan and colleagues demon-strated that 10,17S-docosatriene reduces stroke damage inpart by limiting neutrophilic infiltration.64 Based on its potentactions in human retinal pigmented epithelial cells andneutrophils, this 10,17-docosatriene was coined NPD1 (neu-roprotectin D1) when produced in the vicinity of neuraltissues, and PD1 (protectin D1) in the immune system.65,66

The identification of these biologically active endogenousproducts, isomers and related compounds biosynthesizedfrom DHA provided evidence that a larger family with this

basic structure from a 22-carbon backbone was warranted,and the family was coined protectins.67

PD1 is also biosynthesized by T cells and regulatesapoptosis.68 During peritonitis, PD1 is formed from endoge-nous DHA and accumulates during resolution.24 PD1 has anumber of potent bioactions evident in the picogram tonanogram range, including the ability to limit PMN infiltra-tion and reduce cytokine/chemokine levels during acuteinflammation. Importantly, PD1 shortens the resolution inter-val.24,25 Hence, it was important to establish the completestereochemistry of NPD1/PD1, which was assigned bymatching with compounds prepared via total organic synthe-sis. PD1 proved additive with RvE1, and halted leukocyticinfiltration following the initiation of an inflammatory re-sponse when administered �2 hours following exposure tochallenge. LXA4, RvE1, and PD1 stimulate resolution in partby stimulating the sequestration of chemokines on T cells andapoptotic PMNs by their ability to regulate CCR5 expres-sion.69 This event results in macrophage engulfment andclearing of chemokines from inflammatory sites. Transgenicmice overexpressing the fat-1 gene, which encodes a desatu-rase enzyme that enables the endogenous conversion ofomega-6 to omega-3 fatty acids, are protected from a numberof inflammatory insults and have higher levels of resolvinsand protectins.70 Levels of NPD1/PD1 are also increased inthe bone marrow of mice consuming a diet rich in omega-3fatty acids,71 which is renal-protective via the ability ofNPD1/PD1 to regulate leukocyte trafficking.72 Along theselines, PD1 was identified in human breath condensatesobtained from healthy subjects and is diminished in exhaledbreath condensates obtained from asthmatics. In murineairways, PD1 markedly accelerates resolution of airwayinflammation and regulates eosinophil, T lymphocyte, mucusand proinflammatory mediator levels, including IL-13, leu-kotrienes, and prostaglandins.73 The important role of NPD1/PD1 in regulating retinal and neural pathophysiology wasrecently reviewed.74 Trapping products indicate the involve-ment of an epoxide intermediate in the biosynthesis of NPD1in retinal pigment epithelial cells, and evidence for stereose-lective specific binding sites with human PMNs and retinalpigmented epithelial cells was obtained.75

MaresinsMacrophages are key players in resolution and theirpresence in inflamed tissues is vital for tissue repair,wound healing and the restoration of homeostasis.11 Re-cently, a new lipid mediator biosynthetic pathway wasidentified that involves enzymatic conversion of DHA bymacrophages during resolution. Late-stage resolving exu-dates accumulated 14S-hydroxydocosahexaenoic acid, in ad-dition to 17-hydroxydocosahexaenoic acid, a marker of re-solvin biosynthesis. Given that monohydroxy fatty acids aremarkers of biosynthetic pathways leading to potent down-stream mediators, as is the case for leukotrienes, lipoxins andresolvins, it was reasoned that 14-hydroxydocosahexaenoicacid might be a marker of previously unrecognized mediatorpathway operative during resolution and homeostasis. Usingisolated human and murine macrophages, we found that thesecells convert DHA into 14-hydroxydocosahexaenoic acid and




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a novel 7,14-dihydroxy-containing product that showed po-tent antiinflammatory and proresolving actions.76 Addition ofeither DHA or 14S-hydroperoxydocosahexaenoic acid tomacrophages transformed these substrates into the dihydroxymediator, the complete structure of which was established.76

Given its potent stereoselective actions and in vivo produc-tion, we coined this new family the maresins (macrophagemediators in resolving inflammation); specifically the leadmediator as maresin 1 (MaR1).76 These findings lend furthersupport to the concept that local enzymatic conversion ofDHA to bioactive and stereoselective mediators could indeedunderlie the essential role of DHA.

Aspirin, COX-2, and Proresolving Pathway ofLocal Mediators

Aspirin is one of the most widely used antiinflammatory drugs,and low-dose aspirin (81 mg) is currently recommended by theAmerican Heart Association (www.americanheart.org) for bothprimary and secondary prevention of myocardial infarction,stroke, and unstable angina. The beneficial actions of aspirin inthe cardiovascular system have been widely attributed to thewell-documented ability of aspirin to block prostaglandin andprothrombotic thromboxane (TXA2) generation via acetylationof COX-1.77 Notably, aspirin has additional antiinflammatoryactions, such as blocking leukocyte trafficking to inflamedtissues, which cannot be attributed only to aspirin’s ability toinhibit prostanoid biosynthesis.27,78 As noted above, aspirinacetylation of COX-2 not only inhibits prostanoid formation butalters the active site of COX-2 and thereby permits conversion ofAA to 15R-HETE in vascular endothelial cells. This intermedi-ate can be further transformed to epimeric lipoxins by leukocytes(Figure 3). The formation of 15-epi-lipoxins is documented in

healthy individuals taking low-dose aspirin and was shown to beboth age and gender dependent.79,80 Recently, the antiinflamma-tory actions of aspirin were documented during acute inflamma-tion in humans. Oral administration of low-dose aspirin reducedleukocyte accumulation in cantharidin-induced skin blisters andwas associated with both 15-epi-lipoxin biosynthesis and anincrease in ALX expression.33

As noted, both EPA and DHA are substrates for acetylatedCOX-2, which generates biosynthetic precursors to AT-resolvins. The AT-resolvins share potent antiinflammatoryactions of native resolvins.61 Thus, it can be considered thataspirin, in addition to blocking proinflammatory lipid medi-ator production, stimulates resolution via the generation ofbioactive epimers of lipoxins and resolvins. These actionscould underlie the multiple beneficial effects of aspirin incomplex cardiovascular diseases and suggest that formationof proresolving lipid mediators could, in part, explain thedistinct antiinflammatory and proresolution actions of aspirin.

LXA4 and Aspirin-Triggered 15-Epi-LXA4 inAnimal Models and Human Diseases

The potent antiinflammatory and proresolving actions oflipoxins and epi-lipoxins have been demonstrated in multipleanimal models of human diseases (Table 2). Both nativeLXA4 and 15-epi-LXA4 bind and activate ALX and decreasePMN infiltration in murine and rat models of acute peritoni-tis.29 The endogenous protective role of ALX mediating thebiological actions of lipoxins has been demonstrated in miceoverexpressing the human lipoxin receptor in myeloid cells

Figure 2. Biosynthetic scheme of D-series resolvins. DHA isenzymatically converted to 17-hydroperoxydocosahexaenoicacid by 15-LOX. The 17-hydroperoxy intermediate is furthertransformed by 5-LOX via transcellular biosynthesis to form a7,8-epoxide intermediate, which is enzymatically hydrolyzed toeither resolvin D1 (RvD1) or RvD2. In the presence of aspirin, acet-ylated COX-2 converts DHA into 17-hydroxydocosahexaenoic acidin which the hydroxyl group is in the R configuration, rather thanthe S configuration. This intermediate is further transformed intoaspirin-triggered RvD1 and RvD2.

Figure 3. Aspirin and statins promote the formation of15-epi-LXA4. Both aspirin and statins promote the generation of15R-hydroxyeicosatetraenoic acid (HETE) from AA via the acety-lation or S-nitrosylation of COX-2, respectively. Through trans-cellular biosynthesis, 15R-HETE is further converted to 15-epi-LXA4 by 5-LOX.




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and more recently in mice lacking the murine homolog ofALX, FPR2.40,41 Numerous studies have further demonstratedthat the progression of inflammation in chronic diseases, suchas asthma, scleroderma lung disease and cystic fibrosis, isassociated with deficiencies in lipoxin production and/or animbalance between proinflammatory eicosanoids and li-poxins.81–83 Accordingly, restoration of these deficiencies re-solves inflammation associated with these diseases, decreasingleukocyte accumulation and proinflammatory cytokine genera-tion. In addition to regulating excessive leukocyte responses,lipoxins also decrease fibrosis in lung injury and in renalmesangial cells.84,85 It is noteworthy that several generations ofstable analogs of lipoxins and 15-epi-lipoxins were prepared thatare longer lived, and share the potent biological actions ofendogenous lipoxins in vitro and in vivo.86 Lipoxins are cur-rently in clinical development, and it is clear that their potentactions in regulating leukocyte responses, fibrosis and tissueinjury can have far-reaching clinical implications.

Statins and Proresolving Lipid MediatorsStatins (3-hydroxy-3-methylglutaryl [HMG]-CoA reductaseinhibitors) represent a widely used class of therapeutics thathave well-documented actions in reducing low-density li-poprotein (LDL) cholesterol levels in humans. Althoughreducing LDL levels provides a prominent mechanismwhereby statins reduce the risk of cardiovascular events (eg,myocardial infarction, sudden cardiac death), accumulatingevidence suggests that statins have additional antiinflamma-tory properties that may underlie their diverse protectiveactions in the cardiovascular system.5 Indeed, numerousstudies have demonstrated that statins reduce acute inflam-mation in vivo, in part via direct regulation of leukocyte-en-dothelial interactions.5,87 Recently, results of the JUPITERtrial (Justification for the Use of Statins in Prevention: AnIntervention Trial Evaluating Rosuvastatin) demonstratedthat rosuvastatin (20 mg/d) reduced systemic markers ofinflammation (eg, C-reactive protein) and provided an addi-tional clinical benefit beyond lowering cholesterol levels inpatients, namely reducing major cardiovascular events.88

Recent results demonstrate that, as with aspirin, formation of15-epi-lipoxins may underlie some of the beneficial actionsof statins. Studies from Birnbaum et al demonstrate thatatorvastatin promotes the myocardial generation of 15-epi-LXA4 via S-nitrosylation of COX-2.89 Similar to aspirinacetylation of COX-2, S-nitrosylated COX-2 produces 15R-HETE, which is converted by leukocyte 5-LOX to generate15-epi-LXA4 (Figure 3). It was further elucidated that theantidiabetic thiazolidinedione pioglitazone also promotes thegeneration of 15-epi-lipoxins in the myocardium and isadditive when given together with statins.89 COX-2 and5-LOX coprecipitate in adult rat hearts after treatment withthese commonly-used therapeutics.90 In isolated adult ratcardiac myocytes, 5-LOX cellular distribution was regulatedby statin and thiazolidinedione treatment, and it was proposedthat protein kinase A-dependent phosphorylation of 5-LOXinduced by these therapeutics promotes its association withCOX-2 to generate 15-epi-lipoxins, whereas in absence ofphosphorylation, 5-LOX associates with membranous cyto-solic phospholipase A2 to promote generation of leukotri-

enes.90 Thus, these findings illustrate the delicate balancebetween proinflammatory and antiinflammatory-proresolvingLM pathways and suggest that commonly used therapeuticsmay exert antiinflammatory effects and potentially proresolv-ing actions via the regulation of LM biosynthesis.

The enhanced formation of 15-epi-LXA4 by statins wasrecently confirmed and extended in a report showing thatlovastatin promotes 15-epi-LXA4 formation and coincideswith protection from murine lung inflammation.91 It is note-worthy that potential adverse interactions can occur whenCOX-2 is both acetylated and S-nitrosylated, in that theactivity of COX-2 in promoting 15-epi-LXA4 formation isinhibited.92 Given that many cardiovascular disease patientsare on both antiplatelet therapy and cholesterol-loweringtherapy, further studies on the impact of this combinationtherapy on inflammation-resolution pathways will be impor-tant. It remains of interest whether these results, from both invitro and in vivo studies, translate to humans. It is likely thatthis mechanism will also impact the biosynthesis of epimericforms of resolvins.

Vascular Actions of ProresolvingLipid Mediators

Lipoxins and resolvins each exhibit direct actions on endo-thelial cells and regulate leukocyte:endothelial interactions inisolated cells and in vivo (Figure 4). Recent evidence dem-onstrates that receptors for these mediators, namely ALX andGPR32, are expressed on human endothelial cells.29,63 Li-poxins directly stimulate the endothelial production of vaso-protective and antithrombotic mediators, NO and prostacyclin(PGI2).78,93 Of interest, aspirin-stimulated NO production wasfound to be dependent on the formation of 15-epi-LXA4 invivo. Notably, the antiinflammatory actions of aspirin aredependent on both constitutive and inducible nitric oxidesynthase (eNOS and iNOS)-derived NO, and both aspirin and15-epi-LXA4 have reduced effects on leukocyte:endothelialinteractions in eNOS and iNOS knock-out mice.78 Theseresults provide further support that 15-epi-lipoxin productionunderlies some of the beneficial cardiovascular effects ofaspirin treatment. Lastly, 15-epi-lipoxin potently reduces theformation of reactive oxygen species (ROS) in endothelialcells by preventing NADPH-oxidase activation.94 Recently,we determined that resolvin D2 (RvD2) directly stimulatesthe endothelial production of NO and that RvD2 potentlyreduces leukocyte infiltration in a murine model of peritonitisin an eNOS-dependent manner.62 Leukocyte adhesion topostcapillary venules was largely abolished by RvD2, asassessed by intravital microscopy, and this is also partiallydependent on endogenous NO production, as a nonselectiveNOS inhibitor reversed this effect.62

In addition to regulating the vascular production of NO andprostacyclin, 15-epi-lipoxins have been shown to underlieaspirin-induced heme oxygenase (HO)-1 expression in endo-thelial cells. A stable analog of 15-epi-LXA4, denoted ATL-1,directly stimulates HO-1 expression in isolated human endo-thelial cells to a similar extent as aspirin alone.95 Theseeffects of ATL-1 were shown to be receptor-dependent andtranslated to reduced surface expression of VCAM-1 in aHO-1–dependent manner.95 Lastly, recent evidence indicates




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that both lipoxins and resolvins have direct actions onvascular smooth muscle cells (VSMCs). Receptors for bothLXA4 and RvE1, ALX, and ChemR23, respectively, wereidentified on human saphenous vein SMC. Both RvE1 and15-epi-LXA4 counter-regulate platelet-derived growth factor(PDGF)-stimulated VSMC migration in a dose-dependentmanner and decrease PDGF receptor phosphorylation.96

Thus, these and related results suggest that proresolution LMsmay have multiple diverse and protective actions beyondmyeloid cells. It will be important to determine whether thesenovel actions of proresolution lipid mediators translate intoprotective actions in complex cardiovascular pathologies.

AtherosclerosisAtherosclerosis is widely viewed as a chronic inflammatorydisease characterized by the excessive recruitment and acti-vation of peripheral blood mononuclear cells, such as mono-cytes and T-cells.18 Monocytes differentiate into macro-phages within the plaque milieu and attempt to clear excessoxidized lipoproteins and cholesterol from the tissue. Thisprecipitates the generation of lipid-laden foam cells that failto clear from the plaque, continue to secrete proinflammatorymediators and eventually undergo postapoptotic secondarynecrosis.17 Emerging evidence highlights that atherosclerosiscould be viewed as a state of failed resolution of inflamma-tion.17 Indeed, recent results demonstrate that peripheralartery disease patients have a defect in generation of proreso-lution LM, 15-epi-LXA4.96 Given the indispensable role ofmacrophage efferocytosis in resolution, new evidence sug-gests that defective clearance of plaque macrophages mayunderlie the progression of advanced atherosclerotic lesions,characterized by macrophage necrosis. Li et al demonstratedthat peritoneal macrophages isolated from obese-diabeticmice crossed with LDL-receptor deficient mice (LDLR�/�)

display defects in their ability to phagocytose apoptotic cells.16

Moreover, defective phagocytosis and clearance of apoptoticcells was observed in advanced atherosclerotic lesions fromthese mice. Interestingly, saturated fatty acids (palmitic andstearic) were increased in obese mice relative to endogenousomega-3 fatty acids and were implicated in defective macro-phage efferocytosis. Accordingly, supplementation of omega-3fatty acids, EPA and DHA, reversed deficits in macrophageefferocytosis in obese/LDLR�/� mice.16 These studies highlightthat progression of chronic inflammatory diseases could result inpart because of altered resolution and implicates a role forendogenous lipid mediator pathways.

In accordance with the view that altered resolution con-tributes to atherogenesis, mice lacking both 12/15-LOX andapoE display exacerbated atherosclerotic lesion formationcompared to apoE-null mice.97 Similarly, targeted macro-phage-specific overexpression of 12/15-LOX protected fromlesion development. Importantly, 12/15-LOX gene dosagecorrelated with LXA4 formation in isolated macrophages, aswell as the production of 17-hydroxydocosahexaenoic acid, amarker of the D-series resolvin biosynthetic pathway. Bothlipoxins and resolvins display potent actions on isolatedmacrophages and endothelial cells, regulating production ofproinflammatory cytokines/chemokines and adhesion recep-tors (VCAM-1 and P-selectin).97 Notably, LXA4 and RvD1each enhance macrophage phagocytosis of apoptotic cells.These results corroborate earlier findings in rabbits demon-strating the atheroprotective effect of macrophage-specifictransgenic overexpression of 15-LOX.98 The antiinflamma-tory proresolving role of this pathway was recently indepen-dently confirmed.99–101

Containing and Clearing MicrobesPrevalence of polymicrobial sepsis is increasing and mortal-ity rates associated with septic shock remain as high as 20%

Figure 4. Novel antiinflammatory andproresolving actions of lipoxins, resolvins,and protectins in the vasculature. Tissueinjury and microbial invasion precipitates therelease of endogenous chemical mediatorsthat increase vascular permeability and pro-mote leukocyte chemotaxis in postcapillaryvenules, which characterizes the initiation ofthe acute inflammatory response. After kill-ing the invading microbes, PMNs undergoapoptosis and must be cleared by macro-phages to allow for tissue homeostasis to berestored. During the time course of the acuteinflammatory response, endogenous lipidmediators, such as the lipoxins, resolvins,and protectins are generated and act locallyto stop further vascular permeability andleukocyte chemotaxis and promote the for-mation of antiadhesive and antithromboticmediators, NO, and prostacyclin (PGI2).These novel lipid mediators also stimulatephagocytosis and clearance of apoptoticPMNs and microbes. Ungoverned activationof leukocytes and endothelial cells can leadto extracellular release of reactive oxygenspecies (ROS) and excessive leukocyterecruitment and/or altered clearance, whichare prominent characteristics of chronicinflammatory diseases. (Illustration Credit:Ben Smith/Cosmocyte.)




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to 60% despite clinical efforts to control infection.102 Al-though sepsis precipitates a robust systemic inflammatoryresponse, antiinflammatory therapies have largely failed inhuman studies, in part, because of sustained immunosuppres-sion and bacterial proliferation.102 Infection progresses rap-idly in sepsis and must be contained by phagocytes to preventbacterial proliferation, multiple-organ failure and ultimately,death. Thus, therapeutic strategies to control excessive in-flammation without promoting immune suppression are war-ranted. Of note, omega-3 supplementation has protectiveactions in animal models of sepsis and blunts the inflamma-tory response to endotoxin in humans, although the mecha-nistic basis underlying this protection is not known.103–105

Using a widely established murine model of polymicrobialsepsis that most closely resembles the human clinical picture,namely cecal ligation and puncture (CLP), we recentlydetermined that the bioactive DHA-derived mediator RvD2enhances survival of septic mice.62 Pre- or postoperativetreatment with synthetic RvD2 at nanogram doses reducedexcessive leukocyte infiltration, whereas enhancing phagocyte-dependent bacterial clearance to inguinal lymph nodes. Bothlocal and systemic bacteremia were largely blunted withRvD2 treatment, which protected mice from the systemic‘cytokine storm’ and CLP-induced hypothermia. Notably,RvD2 treatment blunted systemic increases in both pro- andantiinflammatory cytokines, such as IL-17, IL-1�, and IL-10,which have been documented to have detrimental actions insepsis.106–108 Importantly, RvD2 also regulated the produc-tion of proinflammatory eicosanoids, such as PGE2 andLTB4. Corroboratory results were obtained with humanPMNs in vitro where RvD2 (nanomolar range) enhancedphagocytosis and killing of Escherichia coli. These resultsfurther demonstrate the potent and distinct antiinflammatoryversus proresolution actions of RvD2 and highlight thatresolvins may represent a new class of therapeutics that arenot immunosuppressive, but rather stimulate resolution ofcomplex disease pathologies. Along these lines, RvE1 alsodisplays anti-infective actions, enhancing clearance of bacte-ria from mouse lungs in a model of pneumonia, leading toincreased survival.109 Thus, these novel mediators displaypotent antiinflammatory, antifibrotic, and recently demon-strated antiinfective actions in several widely used experi-mental models of inflammation and in human cells.

AngiogenesisVessel sprouting induced by mitogenic stimuli, such asvascular endothelial growth factor (VEGF) and fibroblastgrowth factor (FGF), plays an important role in woundhealing, recovery from myocardial ischemia/reperfusion in-jury, and organ regeneration.110 In contrast, pathologicalangiogenesis, as occurs during retinopathy and tumor growth,can be detrimental if not properly regulated.110 Lipid media-tors are key players in angiogenesis, with proinflammatoryeicosanoids such as 12-HETE and prostaglandins (PGE2)promoting VEGF-stimulated angiogenesis.111,112 Like mostbiological processes, angiogenesis is tightly controlled byboth positive and negative inputs and, although multiplechemical mediators have been shown to operate in thisregard, we have recently learned that lipoxins and resolvins

also regulate pathological angiogenesis. In isolated humanendothelial cells, lipoxins and their AT-epimers regulateVEGF, as well as cysteinyl leukotriene (LTD4)-stimulatedmigration and proliferation.113–115 Godson et al elucidated themechanistic basis for this regulation and found that LXA4

regulates VEGF receptor-2 phosphorylation and downstreamsignaling.115 This concept of growth factor receptor transin-hibition was extended to other growth factor receptors,including PDGF receptor � in mesangial cells.85 These potentactions of lipoxins were validated in vivo, where 15-epi-lipoxin stable analog (ATL-1) blocked angiogenesis in agranuloma model of inflammatory angiogenesis.113 Gronertand colleagues demonstrated the role of endogenous lipoxincircuits in protecting from pathological neovascularizationinduced by corneal injury.100 Both the murine homolog of thelipoxin receptor and 15-LOX were upregulated during cor-neal injury, and genetic ablation of either 15-LOX or 5-LOX(both enzymes involved in lipoxin biosynthesis) exacerbatedpathological neovascularization and correlated with increasedVEGF-A and VEGF-3 receptor expression. Along these lines,topical administration of synthetic lipoxins decreases VEGF-Aexpression and protects from pathological angiogenesis.100

In addition to the role of AA-derived eicosanoids in regulatingangiogenesis, recent evidence also indicates a protective role foromega-3–derived LMs in pathological angiogenesis. Transgenicmice overexpressing the fat-1 gene (as noted above) are pro-tected from hypoxia-induced neovascularization.52 Interestingly,resolvins are biosynthesized in fat-1 transgenic mice and admin-istration of synthetic resolvins protect from pathological neovas-cularization.52 The protective actions of resolvins in this contextwere mediated in part through the direct regulation of retinalTNF-� production. These results were extended in furtherstudies which showed that both lipoxins and resolvins modulateleukocyte infiltration into injured corneas, regulate proinflam-matory cytokine generation, VEGF-A production, and decreaseangiogenesis.116 Importantly, receptors for both LXA4 andRvE1, ALX and ChemR23, are expressed in epithelial cells,stromal keratinocytes and infiltrated CD11b� cells.116 Overall,these results suggest that lipoxins and resolvins have diverseprotective actions on multiple cell types and endogenous pro-resolution circuits protect against pathological angiogenesis.

Ischemia/Reperfusion InjurySeveral recent reports demonstrate that proresolution LMselicit organ-protective actions during ischemia/reperfusion. Inthe kidney, reperfusion following an ischemic insult results inincreased circulating DHA and correlates with local produc-tion of D-series resolvins, including RvD2.72 This is consis-tent with recent results demonstrating that free plasma DHAis rapidly delivered to inflammatory sites for local generationof resolvins.117 Synthetic resolvins largely abolish leukocyteinfiltration into reperfused kidneys and protect from second-organ reperfusion injury in a murine model of hind-limbischemia.72,117 Importantly, the protective actions of syntheticresolvins and their stable analogs are retained after therapeu-tic administration (ie, after the initiation of reperfusion). Theendogenous protective role of proresolution mediators wasdemonstrated in mice lacking the murine homolog of theLXA4 receptor (ALX/FPR2), in which ischemia/reperfusion




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resulted in excessive leukocyte adhesion and emigration inthe mesenteric microcirculation.41 Of note, in addition toregulating excessive leukocyte-mediated tissue injury in re-sponse to reperfusion, proresolution LMs also reduce organfibrosis.72,85 Recently, it was shown that RvE1 stimulatesphosphorylation of eNOS and Akt, and prevents apoptosis incardiac myocytes exposed to hypoxia/reoxygenation by attenu-ating the level of activated caspase-3. These direct actions weredemonstrated in vivo where RvE1 decreased infarct size in a ratmodel of myocardial ischemia/reperfusion injury.118 Of note,these protective actions of RvE1 are dependent on activation ofthe epidermal growth factor receptor (EGFR) and are consistentwith a recent report documenting transactivation of EGFR byRvE1 in corneal epithelial cells.118,119

Obesity and Diabetes: LipidMediator Interplay

Obesity is one of the most robust risk factors for thedevelopment of type 2 diabetes, and chronic low-gradeinflammation is currently held to be a prominent link betweenthe two syndromes.120 Given the indispensable role of LMs inorchestrating macrophage-dependent inflammatory re-sponses, it is not surprising that operational LM pathwayswere recently found to play both positive and negativeregulatory roles within the context of obesity-induced diabe-tes. Claria et al recently found that the leukotriene pathwayplays a role in the development of adipose tissue inflamma-tion in experimental obesity.121 Enzymes involved in LTB4

biosynthesis, including 5-LOX and 5-LOX activating protein(FLAP), were expressed in adipose tissue, and the level ofFLAP increases with high fat feeding. Importantly, receptorsfor LTB4 (BLT-1 and 2), as well as the cysteinyl leukotrienes(cysLT1 and -2) are expressed in adipocytes and stromalvascular cells. Modulation of the leukotriene biosynthetic path-way with a FLAP inhibitor decreased systemic proinflammatorycytokines, adipose tissue macrophage content and systemicinsulin resistance.121 In a separate study, omega-3 feeding wasprotective in obesity-induced inflammation and associated withresolvin biosynthesis in adipose tissue.122 Synthetic RvE1 in-creased mRNA expression of genes known to be protectiveagainst systemic insulin resistance, such as adiponectin, PPAR�,and insulin-receptor substrate-1.122

Summary and Future DirectionsProresolving LMs, including the lipoxins, resolvins, protec-tins, and recently identified maresins, represent a new genusof endogenous LMs that carry out multilevel antiinflamma-tory and proresolution actions to hasten the return to ho-meostasis. These novel mediators possess unique and specificprotective functions demonstrated in animal models of acuteand chronic diseases, and also have potent actions on, and arebiosynthesized by, human cells. The discovery of these opensup entirely new terrain for therapeutics based on endogenousbiotemplates for treating inflammatory diseases by stimulat-ing resolution. Although these new families of autacoidsshare many protective actions, an appreciation of their dis-tinct, targeted roles in regulating local diverse events inresolution is rapidly emerging.

In ongoing studies, it will be important to elucidate howproresolution pathways are modulated with the progression ofchronic diseases and the impact of blocking these pathways inhumans. Although both aspirin and statins can promote theformation of endogenous protective LMs and thereby exertantiinflammatory and proresolving actions, other commonlyused therapeutics can delay resolution.15 In summation, thisnew area of “resolution pharmacology” is likely to lead tobetter targeted approaches to treat inflammatory diseaseswithout precipitating sustained immunosuppression that maybe relevant in vascular medicine.

AcknowledgmentsWe thank Mary H. Small for expert assistance in manuscriptpreparation.

Sources of FundingResults from the laboratory of C.N.S. reviewed here were supportedin part by NIH grants GM38765, DK074448, and DE019938. Wealso acknowledge the support of the NIH Diabetes and ObesityCenter 1P20RR024489 (to M.S.).

DisclosuresC.N.S. is inventor on patents covering structural elucidation andcomposition of matter of the resolvins and protectins, as well as theiruses. These patents are assigned to Brigham and Women’s Hospitaland are licensed for clinical development to Resolvyx Pharmaceuti-cal Company. C.N.S. is a founder and retains founder stock.

References1. Serhan CN, Savill J. Resolution of inflammation: the beginning

programs the end. Nat Immunol. 2005;6:1191–1197.2. Braunwald E. Biomarkers in heart failure. N Engl J Med. 2008;358:

2148–2159.3. Ellis CR, Di Salvo T. Myocarditis: basic and clinical aspects. Cardiol

Rev. 2007;15:170–177.4. Rocha VZ, Libby P. Obesity, inflammation, and atherosclerosis. Nat Rev

Cardiol. 2009;6:399–409.5. Dinarello CA. Anti-inflammatory agents: present and future. Cell. 2010;

140:935–950.6. Flower RJ. The development of COX2 inhibitors. Nat Rev Drug Discov.

2003;2:179–191.7. Taylor PC, Feldmann M. Anti-TNF biologic agents: still the therapy of

choice for rheumatoid arthritis. Nat Rev Rheumatol. 2009;5:578–582.8. Perretti M, D’Acquisto F. Annexin A1 and glucocorticoids as effectors

of the resolution of inflammation. Nat Rev Immunol. 2009;9:62–70.9. Patrono C, Rocca B. Aspirin: promise and resistance in the new mil-

lennium. Arterioscler Thromb Vasc Biol. 2008;28:s25–32.10. Funk CD, FitzGerald GA. COX-2 inhibitors and cardiovascular risk.

J Cardiovasc Pharmacol. 2007;50:470–479.11. Nathan C, Ding A. Nonresolving inflammation. Cell. 2010;140:871–882.12. Kumar V, Abbas A, Fausto N. Robbins and Cotran Pathologic Basis of

Disease. Philadelphia: W.B. Saunders; 2005.13. Serhan CN. Resolution phase of inflammation: novel endogenous anti-

inflammatory and proresolving lipid mediators and pathways. Annu RevImmunol. 2007;25:101–137.

14. Rossi AG, Sawatzky DA, eds. The Resolution of Inflammation. Basel,Switzerland: Birkhauser Verlag AG; 2008.

15. Serhan CN, Brain SD, Buckley CD, Gilroy DW, Haslett C, O’Neill LA,Perretti M, Rossi AG, Wallace JL. Resolution of inflammation: state ofthe art, definitions and terms. FASEB J. 2007;21:325–332.

16. Li S, Sun Y, Liang CP, Thorp EB, Han S, Jehle AW, Saraswathi V,Pridgen B, Kanter JE, Li R, Welch CL, Hasty AH, Bornfeldt KE,Breslow JL, Tabas I, Tall AR. Defective phagocytosis of apoptotic cellsby macrophages in atherosclerotic lesions of ob/ob mice and reversal bya fish oil diet. Circ Res. 2009;105:1072–1082.

17. Tabas I. Macrophage death and defective inflammation resolution inatherosclerosis. Nat Rev Immunol. 2010;10:36–46.




ownloaded from


18. Hansson GK, Libby P. The immune response in atherosclerosis: adouble-edged sword. Nat Rev Immunol. 2006;6:508–519.

19. Samuelsson B, Dahlen SE, Lindgren JA, Rouzer CA, Serhan CN. Leu-kotrienes and lipoxins: structures, biosynthesis, and biological effects.Science. 1987;237:1171–1176.

20. Flower RJ. Prostaglandins, bioassay and inflammation. Br J Pharmacol.2006;147(Suppl 1):S182–S192.

21. Levy BD, Clish CB, Schmidt B, Gronert K, Serhan CN. Lipid mediatorclass switching during acute inflammation: signals in resolution. NatImmunol. 2001;2:612–619.

22. Serhan CN, Clish CB, Brannon J, Colgan SP, Chiang N, Gronert K.Novel functional sets of lipid-derived mediators with antiinflammatoryactions generated from omega-3 fatty acids via cyclooxygenase2-nonsteroidal antiinflammatory drugs and transcellular processing.J Exp Med. 2000;192:1197–1204.

23. Lawrence T, Fong C. The resolution of inflammation: anti-inflammatoryroles for NF-kappaB. Int J Biochem Cell Biol. 2010;42:519–523.

24. Bannenberg GL, Chiang N, Ariel A, Arita M, Tjonahen E, GotlingerKH, Hong S, Serhan CN. Molecular circuits of resolution: formation andactions of resolvins and protectins. J Immunol. 2005;174:4345–4355.

25. Schwab JM, Chiang N, Arita M, Serhan CN. Resolvin E1 and protectinD1 activate inflammation-resolution programmes. Nature. 2007;447:869–874.

26. Serhan CN, Hong S, Gronert K, Colgan SP, Devchand PR, Mirick G,Moussignac RL. Resolvins: a family of bioactive products of omega-3fatty acid transformation circuits initiated by aspirin treatment thatcounter proinflammation signals. J Exp Med. 2002;196:1025–1037.

27. Gilroy DW, Colville-Nash PR, Willis D, Chivers J, Paul-Clark MJ,Willoughby DA. Inducible cyclooxygenase may have anti-inflammatoryproperties. Nat Med. 1999;5:698–701.

28. Serhan CN, Chiang N, Van Dyke TE. Resolving inflammation: dualanti-inflammatory and pro-resolution lipid mediators. Nat Rev Immunol.2008;8:349–361.

29. Chiang N, Arita M, Serhan CN. Anti-inflammatory circuitry: lipoxin,aspirin-triggered lipoxins and their receptor ALX. ProstaglandinsLeukot Essent Fatty Acids. 2005;73:163–177.

30. Claria J, Serhan CN. Aspirin triggers previously undescribed bioactiveeicosanoids by human endothelial cell-leukocyte interactions. Proc NatlAcad Sci U S A. 1995;92:9475–9479.

31. Claria J, Lee MH, Serhan CN. Aspirin-triggered lipoxins (15-epi-lx) aregenerated by the human lung adenocarcinoma cell line (A549)-neutrophil interactions and are potent inhibitors of cell proliferation. MolMed. 1996;2:583–596.

32. Morris T, Stables M, Colville-Nash P, Newson J, Bellingan G, de SouzaPM, Gilroy DW. Dichotomy in duration and severity of acute inflam-matory responses in humans arising from differentially expressed pro-resolution pathways. Proc Natl Acad Sci U S A. 2010;107:8842–8847.

33. Morris T, Stables M, Hobbs A, de Souza P, Colville-Nash P, Warner T,Newson J, Bellingan G, Gilroy DW. Effects of low-dose aspirin on acuteinflammatory responses in humans. J Immunol. 2009;183:2089–2096.

34. Scalia R, Gefen J, Petasis NA, Serhan CN, Lefer AM. Lipoxin A4 stableanalogs inhibit leukocyte rolling and adherence in the rat mesentericmicrovasculature: role of P-selectin. Proc Natl Acad Sci U S A. 1997;94:9967–9972.

35. Godson C, Mitchell S, Harvey K, Petasis NA, Hogg N, Brady HR.Cutting edge: lipoxins rapidly stimulate nonphlogistic phagocytosis ofapoptotic neutrophils by monocyte-derived macrophages. J Immunol.2000;164:1663–1667.

36. Machado FS, Johndrow JE, Esper L, Dias A, Bafica A, Serhan CN,Aliberti J. Anti-inflammatory actions of lipoxin A4 and aspirin-triggeredlipoxin are socs-2 dependent. Nat Med. 2006;12:330–334.

37. Parameswaran K, Radford K, Fanat A, Stephen J, Bonnans C, Levy BD,Janssen LJ, Cox PG. Modulation of human airway smooth musclemigration by lipid mediators and th-2 cytokines. Am J Respir Cell MolBiol. 2007;37:240–247.

38. Gronert K, Martinsson-Niskanen T, Ravasi S, Chiang N, Serhan CN.Selectivity of recombinant human leukotriene D(4), leukotriene B(4),and lipoxin A(4) receptors with aspirin-triggered 15-epi-LXA(4) andregulation of vascular and inflammatory responses. Am J Pathol. 2001;158:3–9.

39. Ye RD, Boulay F, Wang JM, Dahlgren C, Gerard C, Parmentier M,Serhan CN, Murphy PM. International Union of Basic and ClinicalPharmacology. LXXIII. Nomenclature for the formyl peptide receptor(FPR) family. Pharmacol Rev. 2009;61:119–161.

40. Devchand PR, Arita M, Hong S, Bannenberg G, Moussignac RL,Gronert K, Serhan CN. Human ALX receptor regulates neutrophilrecruitment in transgenic mice: roles in inflammation and host defense.FASEB J. 2003;17:652–659.

41. Dufton N, Hannon R, Brancaleone V, Dalli J, Patel HB, Gray M,D’Acquisto F, Buckingham JC, Perretti M, Flower RJ. Anti-inflammatory role of the murine formyl-peptide receptor 2: ligand-specific effects on leukocyte responses and experimental inflammation.J Immunol. 2010;184:2611–2619.

42. Simopoulos AP. Omega-3 fatty acids in the prevention-management ofcardiovascular disease. Can J Physiol Pharmacol. 1997;75:234–239.

43. Burr ML, Fehily AM, Gilbert JF, Rogers S, Holliday RM, SweetnamPM, Elwood PC, Deadman NM. Effects of changes in fat, fish, and fibreintakes on death and myocardial reinfarction: Diet and ReinfarctionTrial (DART). Lancet. 1989;2:757–761.

44. Dietary supplementation with n-3 polyunsaturated fatty acids andvitamin E after myocardial infarction: results of the GISSI-Prevenzionetrial. Gruppo Italiano per lo Studio della Sopravvivenza nell’Infartomiocardico. Lancet. 1999;354:447–455.

45. Tavazzi L, Maggioni AP, Marchioli R, Barlera S, Franzosi MG, LatiniR, Lucci D, Nicolosi GL, Porcu M, Tognoni G. Effect of n-3 polyun-saturated fatty acids in patients with chronic heart failure (the GISSI-HFtrial): a randomised, double-blind, placebo-controlled trial. Lancet.2008;372:1223–1230.

46. Roberts LJ, II, Fessel JP. The biochemistry of the isoprostane, neuro-prostane, and isofuran pathways of lipid peroxidation. Chem PhysLipids. 2004;128:173–186.

47. Arita M, Bianchini F, Aliberti J, Sher A, Chiang N, Hong S, Yang R,Petasis NA, Serhan CN. Stereochemical assignment, antiinflammatoryproperties, and receptor for the omega-3 lipid mediator resolvin E1.J Exp Med. 2005;201:713–722.

48. Cash JL, Hart R, Russ A, Dixon JP, Colledge WH, Doran J, HendrickAG, Carlton MB, Greaves DR. Synthetic chemerin-derived peptidessuppress inflammation through Chemr23. J Exp Med. 2008;205:767–775.

49. Ohira T, Arita M, Omori K, Recchiuti A, Van Dyke TE, Serhan CN.Resolvin E1 receptor activation signals phosphorylation and phago-cytosis. J Biol Chem. 2010;285:3451–3461.

50. Arita M, Ohira T, Sun YP, Elangovan S, Chiang N, Serhan CN.Resolvin E1 selectively interacts with leukotriene B4 receptor BLT1 andChemR23 to regulate inflammation. J Immunol. 2007;178:3912–3917.

51. Arita M, Yoshida M, Hong S, Tjonahen E, Glickman JN, Petasis NA,Blumberg RS, Serhan CN. Resolvin E1, an endogenous lipid mediatorderived from omega-3 eicosapentaenoic acid, protects against 2,4,6-trinitrobenzene sulfonic acid-induced colitis. Proc Natl Acad Sci U S A.2005;102:7671–7676.

52. Connor KM, SanGiovanni JP, Lofqvist C, Aderman CM, Chen J,Higuchi A, Hong S, Pravda EA, Majchrzak S, Carper D, Hellstrom A,Kang JX, Chew EY, Salem N Jr, Serhan CN, Smith LE. Increaseddietary intake of omega-3-polyunsaturated fatty acids reduces patho-logical retinal angiogenesis. Nat Med. 2007;13:868–873.

53. Hasturk H, Kantarci A, Ohira T, Arita M, Ebrahimi N, Chiang N, PetasisNA, Levy BD, Serhan CN, Van Dyke TE. Rve1 protects from localinflammation and osteoclast-mediated bone destruction in periodontitis.FASEB J. 2006;20:401–403.

54. Dona M, Fredman G, Schwab JM, Chiang N, Arita M, Goodarzi A,Cheng G, von Andrian UH, Serhan CN. Resolvin E1, an EPA-derivedmediator in whole blood, selectively counter-regulates leukocytes andplatelets. Blood. 2008;112:848–855.

55. Tjonahen E, Oh SF, Siegelman J, Elangovan S, Percarpio KB, Hong S,Arita M, Serhan CN. Resolvin E2: identification and anti-inflammatoryactions: pivotal role of human 5-lipoxygenase in resolvin E seriesbiosynthesis. Chem Biol. 2006;13:1193–1202.

56. Stirban A, Nandrean S, Gotting C, Tamler R, Pop A, Negrean M,Gawlowski T, Stratmann B, Tschoepe D. Effects of n-3 fatty acids onmacro- and microvascular function in subjects with type 2 diabetesmellitus. Am J Clin Nutr. 2010;91:808–813.

57. De Caterina R, Cybulsky MA, Clinton SK, Gimbrone MA Jr, Libby P.Omega-3 fatty acids and endothelial leukocyte adhesion molecules.Prostaglandins Leukot Essent Fatty Acids. 1995;52:191–195.

58. De Caterina R, Liao JK, Libby P. Fatty acid modulation of endothelialactivation. Am J Clin Nutr. 2000;71:213S–223S

59. Massaro M, Habib A, Lubrano L, Del Turco S, Lazzerini G, Bourcier T,Weksler BB, De Caterina R The omega-3 fatty acid docosahexaenoateattenuates endothelial cyclooxygenase-2 induction through both




ownloaded from


NADP(H) oxidase and PKC epsilon inhibition. Proc Natl Acad SciU S A. 2006;103:15184–15189.

60. Hong S, Gronert K, Devchand PR, Moussignac RL, Serhan CN. Noveldocosatrienes and 17S-resolvins generated from docosahexaenoic acidin murine brain, human blood, and glial cells. Autacoids in anti-inflammation. J Biol Chem. 2003;278:14677–14687.

61. Sun YP, Oh SF, Uddin J, Yang R, Gotlinger K, Campbell E, Colgan SP,Petasis NA, Serhan CN. Resolvin D1 and its aspirin-triggered 17Repimer. Stereochemical assignments, anti-inflammatory properties, andenzymatic inactivation. J Biol Chem. 2007;282:9323–9334.

62. Spite M, Norling LV, Summers L, Yang R, Cooper D, Petasis NA,Flower RJ, Perretti M, Serhan CN. Resolvin D2 is a potent regulator ofleukocytes and controls microbial sepsis. Nature. 2009;461:1287–1291.

63. Krishnamoorthy S, Recchiuti A, Chiang N, Yacoubian S, Lee CH, YangR, Petasis NA, Serhan CN. Resolvin D1 binds human phagocytes withevidence for proresolving receptors. Proc Natl Acad Sci U S A. 2010;107:1660–1665.

64. Marcheselli VL, Hong S, Lukiw WJ, Tian XH, Gronert K, Musto A,Hardy M, Gimenez JM, Chiang N, Serhan CN, Bazan NG. Noveldocosanoids inhibit brain ischemia-reperfusion-mediated leukocyteinfiltration and pro-inflammatory gene expression. J Biol Chem. 2003;278:43807–43817.

65. Mukherjee PK, Marcheselli VL, Serhan CN, Bazan NG. NeuroprotectinD1: a docosahexaenoic acid-derived docosatriene protects human retinalpigment epithelial cells from oxidative stress. Proc Natl Acad Sci U S A.2004;101:8491–8496.

66. Serhan CN, Gotlinger K, Hong S, Lu Y, Siegelman J, Baer T, Yang R,Colgan SP, Petasis NA. Anti-inflammatory actions of neuroprotectinD1/protectin D1 and its natural stereoisomers: assignments ofdihydroxy-containing docosatrienes. J Immunol. 2006;176:1848–1859.

67. Serhan CN. A search for endogenous mechanisms of anti-inflammationuncovers novel chemical mediators: missing links to resolution. His-tochem Cell Biol. 2004;122:305–321.

68. Ariel A, Li PL, Wang W, Tang WX, Fredman G, Hong S, Gotlinger KH,Serhan CN. The docosatriene protectin D1 is produced by TH2 skewingand promotes human T cell apoptosis via lipid raft clustering. J BiolChem. 2005;280:43079–43086.

69. Ariel A, Fredman G, Sun YP, Kantarci A, Van Dyke TE, Luster AD,Serhan CN. Apoptotic neutrophils and t cells sequester chemokinesduring immune response resolution through modulation of ccr5expression. Nat Immunol. 2006;7:1209–1216.

70. Hudert CA, Weylandt KH, Lu Y, Wang J, Hong S, Dignass A, SerhanCN, Kang JX. Transgenic mice rich in endogenous omega-3 fatty acidsare protected from colitis. Proc Natl Acad Sci U S A. 2006;103:11276–11281.

71. Poulsen RC, Gotlinger KH, Serhan CN, Kruger MC. Identification ofinflammatory and proresolving lipid mediators in bone marrow and theirlipidomic profiles with ovariectomy and omega-3 intake. Am J Hematol.2008;83:437–445.

72. Duffield JS, Hong S, Vaidya VS, Lu Y, Fredman G, Serhan CN,Bonventre JV. Resolvin D series and protectin D1 mitigate acute kidneyinjury. J Immunol. 2006;177:5902–5911.

73. Levy BD, Kohli P, Gotlinger K, Haworth O, Hong S, Kazani S, Israel E,Haley KJ, Serhan CN. Protectin D1 is generated in asthma and dampensairway inflammation and hyperresponsiveness. J Immunol. 2007;178:496–502.

74. Bazan NG, Calandria JM, Serhan CN. Rescue and repair during photo-receptor cell renewal mediated by docosahexaenoic acid-derived neuro-protectin D1. J Lipid Res. 2010;51:2018–2031.

75. Marcheselli VL, Mukherjee PK, Arita M, Hong S, Antony R, Sheets K,Winkler JW, Petasis NA, Serhan CN, Bazan NG. NeuroprotectinD1/protectin D1 stereoselective and specific binding with human retinalpigment epithelial cells and neutrophils. Prostaglandins Leukot EssentFatty Acids. 2010;82:27–34.

76. Serhan CN, Yang R, Martinod K, Kasuga K, Pillai PS, Porter TF, Oh SF,Spite M. Maresins: novel macrophage mediators with potent antiinflam-matory and proresolving actions. J Exp Med. 2009;206:15–23.

77. Vane JR, Botting RM. The mechanism of action of aspirin. Thromb Res.2003;110:255–258.

78. Paul-Clark MJ, Van Cao T, Moradi-Bidhendi N, Cooper D, Gilroy DW.15-Epi-lipoxin A4-mediated induction of nitric oxide explains howaspirin inhibits acute inflammation. J Exp Med. 2004;200:69–78.

79. Chiang N, Bermudez EA, Ridker PM, Hurwitz S, Serhan CN. Aspirintriggers antiinflammatory 15-epi-lipoxin A4 and inhibits thromboxane

in a randomized human trial. Proc Natl Acad Sci U S A. 2004;101:15178–15183.

80. Chiang N, Hurwitz S, Ridker PM, Serhan CN. Aspirin has a gender-dependent impact on antiinflammatory 15-epi-lipoxin A4 formation: arandomized human trial. Arterioscler Thromb Vasc Biol. 2006;26:e14–e17.

81. Karp CL, Flick LM, Park KW, Softic S, Greer TM, Keledjian R, YangR, Uddin J, Guggino WB, Atabani SF, Belkaid Y, Xu Y, Whitsett JA,Accurso FJ, Wills-Karp M, Petasis NA. Defective lipoxin-mediatedanti-inflammatory activity in the cystic fibrosis airway. Nat Immunol.2004;5:388–392.

82. Levy BD, Bonnans C, Silverman ES, Palmer LJ, Marigowda G, Israel E.Diminished lipoxin biosynthesis in severe asthma. Am J Respir CritCare Med. 2005;172:824–830.

83. Kowal-Bielecka O, Kowal K, Distler O, Rojewska J, Bodzenta-Lukaszyk A, Michel BA, Gay RE, Gay S, Sierakowski S. Cyclooxy-genase- and lipoxygenase-derived eicosanoids in bronchoalveolarlavage fluid from patients with scleroderma lung disease: an imbalancebetween proinflammatory and antiinflammatory lipid mediators.Arthritis Rheum. 2005;52:3783–3791.

84. Martins V, Valenca SS, Farias-Filho FA, Molinaro R, Simoes RL,Ferreira TP, e Silva PM, Hogaboam CM, Kunkel SL, Fierro IM, CanettiC, Benjamim CF. Atla, an aspirin-triggered lipoxin A4 synthetic analog,prevents the inflammatory and fibrotic effects of bleomycin-inducedpulmonary fibrosis. J Immunol. 2009;182:5374–5381.

85. Rodgers K, McMahon B, Mitchell D, Sadlier D, Godson C. Lipoxin A4modifies platelet-derived growth factor-induced pro-fibrotic geneexpression in human renal mesangial cells. Am J Pathol. 2005;167:683–694.

86. Petasis NA, Akritopoulou-Zanze I, Fokin VV, Bernasconi G, KeledjianR, Yang R, Uddin J, Nagulapalli KC, Serhan CN. Design, synthesis andbioactions of novel stable mimetics of lipoxins and aspirin-triggeredlipoxins. Prostaglandins Leukot Essent Fatty Acids. 2005;73:301–321.

87. Fischetti F, Carretta R, Borotto G, Durigutto P, Bulla R, Meroni PL,Tedesco F. Fluvastatin treatment inhibits leucocyte adhesion and extrav-asation in models of complement-mediated acute inflammation. ClinExp Immunol. 2004;135:186–193.

88. Ridker PM, Danielson E, Fonseca FA, Genest J, Gotto AM Jr, KasteleinJJ, Koenig W, Libby P, Lorenzatti AJ, MacFadyen JG, NordestgaardBG, Shepherd J, Willerson JT, Glynn RJ. Rosuvastatin to preventvascular events in men and women with elevated C-reactive protein.N Engl J Med. 2008;359:2195–2207.

89. Birnbaum Y, Ye Y, Lin Y, Freeberg SY, Nishi SP, Martinez JD, HuangMH, Uretsky BF, Perez-Polo JR. Augmentation of myocardial produc-tion of 15-epi-lipoxin-A4 by pioglitazone and atorvastatin in the rat.Circulation. 2006;114:929–935.

90. Ye Y, Lin Y, Perez-Polo JR, Uretsky BF, Ye Z, Tieu BC, Birnbaum Y.Phosphorylation of 5-lipoxygenase at Ser523 by protein kinase adetermines whether pioglitazone and atorvastatin induce proinflam-matory leukotriene B4 or anti-inflammatory 15-epi-lipoxin A4 produc-tion. J Immunol. 2008;181:3515–3523.

91. Planaguma A, Pfeffer MA, Rubin G, Croze R, Uddin M, Serhan CN,Levy BD. Lovastatin decreases acute mucosal inflammation via 15-epi-lipoxin A(4). Mucosal Immunol. 2010;3:270–279.

92. Birnbaum Y, Ye Y, Lin Y, Freeberg SY, Huang MH, Perez-Polo JR,Uretsky BF. Aspirin augments 15-epi-lipoxin A4 production by lipo-polysaccharide, but blocks the pioglitazone and atorvastatin induction of15-epi-lipoxin A4 in the rat heart. Prostaglandins Other Lipid Mediat.2007;83:89–98.

93. Brezinski ME, Gimbrone MA Jr, Nicolaou KC, Serhan CN. Lipoxinsstimulate prostacyclin generation by human endothelial cells. FEBS Lett.1989;245:167–172.

94. Nascimento-Silva V, Arruda MA, Barja-Fidalgo C, Fierro IM. Aspirin-triggered lipoxin A4 blocks reactive oxygen species generation in en-dothelial cells: a novel antioxidative mechanism. Thromb Haemost.2007;97:88–98.

95. Nascimento-Silva V, Arruda MA, Barja-Fidalgo C, Villela CG, FierroIM. Novel lipid mediator aspirin-triggered lipoxin A4 induces hemeoxygenase-1 in endothelial cells. Am J Physiol Cell Physiol. 2005;289:C557–C563.

96. Ho KJ, Spite M, Owens CD, Lancero H, Kroemer AH, Pande R, CreagerMA, Serhan CN, Conte MS. Aspirin-triggered lipoxin and resolvin E1modulate vascular smooth muscle cell phenotype and correlate withperipheral atherosclerosis. Am J Pathol. 2010;177:2116–2123.




ownloaded from


97. Merched AJ, Ko K, Gotlinger KH, Serhan CN, Chan L. Atherosclerosis:evidence for impairment of resolution of vascular inflammationgoverned by specific lipid mediators. FASEB J. 2008;22:3595–3606.

98. Shen J, Herderick E, Cornhill JF, Zsigmond E, Kim HS, Kuhn H,Guevara NV, Chan L. Macrophage-mediated 15-lipoxygenaseexpression protects against atherosclerosis development. J Clin Invest.1996;98:2201–2208.

99. Gronert K, Maheshwari N, Khan N, Hassan IR, Dunn M, LaniadoSchwartzman M. A role for the mouse 12/15-lipoxygenase pathway inpromoting epithelial wound healing and host defense. J Biol Chem.2005;280:15267–15278.

100. Leedom AJ, Sullivan AB, Dong B, Lau D, Gronert K. EndogenousLXA4 circuits are determinants of pathological angiogenesis in responseto chronic injury. Am J Pathol. 2010;176:74–84.

101. Kronke G, Katzenbeisser J, Uderhardt S, Zaiss MM, Scholtysek C,Schabbauer G, Zarbock A, Koenders MI, Axmann R, Zwerina J,Baenckler HW, van den Berg W, Voll RE, Kuhn H, Joosten LA, SchettG. 12/15-lipoxygenase counteracts inflammation and tissue damage inarthritis. J Immunol. 2009;183:3383–3389.

102. Ward PA. The dark side of C5a in sepsis. Nat Rev Immunol. 2004;4:133–142.

103. Farolan LR, Goto M, Myers TF, Anderson CL, Zeller WP. Perinatalnutrition enriched with omega-3 polyunsaturated fatty acids attenuatesendotoxic shock in newborn rats. Shock. 1996;6:263–266.

104. Singer P, Shapiro H, Theilla M, Anbar R, Singer J, Cohen J. Anti-inflammatory properties of omega-3 fatty acids in critical illness: novelmechanisms and an integrative perspective. Intensive Care Med. 2008;34:1580–1592.

105. Pluess TT, Hayoz D, Berger MM, Tappy L, Revelly JP, Michaeli B,Carpentier YA, Chiolero RL. Intravenous fish oil blunts the physiolog-ical response to endotoxin in healthy subjects. Intensive Care Med.2007;33:789–797.

106. Osuchowski MF, Welch K, Siddiqui J, Remick DG. Circulating cyto-kine/inhibitor profiles reshape the understanding of the SIRS/CARScontinuum in sepsis and predict mortality. J Immunol. 2006;177:1967–1974.

107. Huang X, Venet F, Wang YL, Lepape A, Yuan Z, Chen Y, Swan R,Kherouf H, Monneret G, Chung CS, Ayala A. Pd-1 expression bymacrophages plays a pathologic role in altering microbial clearance andthe innate inflammatory response to sepsis. Proc Natl Acad Sci U S A.2009;106:6303–6308.

108. Flierl MA, Rittirsch D, Gao H, Hoesel LM, Nadeau BA, Day DE,Zetoune FS, Sarma JV, Huber-Lang MS, Ferrara JL, Ward PA. Adversefunctions of il-17a in experimental sepsis. FASEB J. 2008;22:2198–2205.

109. Seki H, Fukunaga K, Arita M, Arai H, Nakanishi H, Taguchi R,Miyasho T, Takamiya R, Asano K, Ishizaka A, Takeda J, Levy BD. Theanti-inflammatory and proresolving mediator resolvin E1 protects micefrom bacterial pneumonia and acute lung injury. J Immunol. 2010;184:836–843.

110. Carmeliet P. Angiogenesis in life, disease and medicine. Nature. 2005;438:932–936.

111. Nie D, Tang K, Diglio C, Honn KV. Eicosanoid regulation of angio-genesis: role of endothelial arachidonate 12-lipoxygenase. Blood. 2000;95:2304–2311.

112. Finetti F, Donnini S, Giachetti A, Morbidelli L, Ziche M. ProstaglandinE(2) primes the angiogenic switch via a synergic interaction with thefibroblast growth factor-2 pathway. Circ Res. 2009;105:657–666.

113. Fierro IM, Kutok JL, Serhan CN. Novel lipid mediator regulators ofendothelial cell proliferation and migration: aspirin-triggered-15R-lipoxin A(4) and lipoxin A(4). J Pharmacol Exp Ther. 2002;300:385–392.

114. Badr KF, DeBoer DK, Schwartzberg M, Serhan CN. Lipoxin A4 antag-onizes cellular and in vivo actions of leukotriene D4 in rat glomerularmesangial cells: evidence for competition at a common receptor. ProcNatl Acad Sci U S A. 1989;86:3438–3442.

115. Baker N, O’Meara SJ, Scannell M, Maderna P, Godson C. Lipoxin A4:anti-inflammatory and anti-angiogenic impact on endothelial cells.J Immunol. 2009;182:3819–3826.

116. Jin Y, Arita M, Zhang Q, Saban DR, Chauhan SK, Chiang N, SerhanCN, Dana R. Anti-angiogenesis effect of the novel anti-inflammatoryand pro-resolving lipid mediators. Invest Ophthalmol Vis Sci. 2009;50:4743–4752.

117. Kasuga K, Yang R, Porter TF, Agrawal N, Petasis NA, Irimia D, TonerM, Serhan CN. Rapid appearance of resolvin precursors in inflammatoryexudates: novel mechanisms in resolution. J Immunol. 2008;181:8677–8687.

118. Keyes KT, Ye Y, Lin Y, Zhang C, Perez-Polo JR, Gjorstrup P,Birnbaum Y. Resolvin E1 protects the rat heart against reperfusioninjury. Am J Physiol Heart Circ Physiol. 2010;299:H153–H164.

119. Zhang F, Yang H, Pan Z, Wang Z, Wolosin JM, Gjorstrup P, ReinachPS. EGF receptor transactivation mediates resolvin-induced increases incorneal epithelial cell migration. Invest Ophthalmol Vis Sci. 2010; Epub6/10/10; doi: 10.1167/iovs.09-4468.

120. Hotamisligil GS, Erbay E. Nutrient sensing and inflammation in meta-bolic diseases. Nat Rev Immunol. 2008;8:923–934.

121. Horrillo R, Gonzalez-Periz A, Martínez-Clemente M, Lopez-Parra M,Ferre N, Titos E, Moran-Salvador E, Deulofeu R, Arroyo V, Claria J.5-lipoxygenase activating protein signals adipose tissue inflammationand lipid dysfunction in experimental obesity. J Immunol. 2010;184:3978–3987.

122. Gonzalez-Periz A, Horrillo R, Ferre N, Gronert K, Dong B, Moran-Salvador E, Titos E, Martinez-Clemente M, Lopez-Parra M, Arroyo V,Claria J. Obesity-induced insulin resistance and hepatic steatosis arealleviated by omega-3 fatty acids: a role for resolvins and protectins.FASEB J. 2009;23:1946–1957.

123. Ariel A, Chiang N, Arita M, Petasis NA, Serhan CN. Aspirin-triggeredlipoxin A4 and B4 analogs block extracellular signal-regulated kinase-dependent TNF-alpha secretion from human t cells. J Immunol. 2003;170:6266–6272.

124. Sodin-Semrl S, Taddeo B, Tseng D, Varga J, Fiore S. Lipoxin A4inhibits IL-1 beta-induced IL-6, IL-8, and matrix metalloproteinase-3production in human synovial fibroblasts and enhances synthesis oftissue inhibitors of metalloproteinases. J Immunol. 2000;164:2660–2666.

125. Fiore S, Serhan CN. Lipoxin A4 receptor activation is distinct from thatof the formyl peptide receptor in myeloid cells: inhibition of CD11/18expression by lipoxin A4-lipoxin A4 receptor interaction. Biochemistry.1995;34:16678–16686.

126. Jozsef L, Zouki C, Petasis NA, Serhan CN, Filep JG. Lipoxin A4 andaspirin-triggered 15-epi-lipoxin A4 inhibit peroxynitrite formation,NF-kappa B and AP-1 activation, and IL-8 gene expression in humanleukocytes. Proc Natl Acad Sci U S A. 2002;99:13266–13271.

127. Papayianni A, Serhan CN, Brady HR. Lipoxin A4 and B4 inhibitleukotriene-stimulated interactions of human neutrophils and endothelialcells. J Immunol. 1996;156:2264–2272.

128. Levy BD, De Sanctis GT, Devchand PR, Kim E, Ackerman K, SchmidtBA, Szczeklik W, Drazen JM, Serhan CN. Multi-pronged inhibition ofairway hyper-responsiveness and inflammation by lipoxin A(4). NatMed. 2002;8:1018–1023.

129. Chiang N, Gronert K, Clish CB, O’Brien JA, Freeman MW, Serhan CN.Leukotriene B4 receptor transgenic mice reveal novel protective rolesfor lipoxins and aspirin-triggered lipoxins in reperfusion. J Clin Invest.1999;104:309–316.

130. Takano T, Clish CB, Gronert K, Petasis N, Serhan CN. Neutrophil-mediated changes in vascular permeability are inhibited by topicalapplication of aspirin-triggered 15-epi-lipoxin A4 and novel lipoxin b4stable analogues. J Clin Invest. 1998;101:819–826.

131. Serhan CN, Jain A, Marleau S, Clish C, Kantarci A, Behbehani B,Colgan SP, Stahl GL, Merched A, Petasis NA, Chan L, Van Dyke TE.Reduced inflammation and tissue damage in transgenic rabbits overex-pressing 15-lipoxygenase and endogenous anti-inflammatory lipidmediators. J Immunol. 2003;171:6856–6865.

132. Xu ZZ, Zhang L, Liu T, Park JY, Berta T, Yang R, Serhan CN, Ji RR.Resolvins RVE1 and RVD1 attenuate inflammatory pain via central andperipheral actions. Nat Med. 2010;16:592–597.

133. Spite M, Summers L, Porter TF, Srivastava S, Bhatnagar A, Serhan CN.Resolvin D1 controls inflammation initiated by glutathione-lipid con-jugates formed during oxidative stress. Br J Pharmacol. 2009;158:1062–1073.




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novel lipid mediators promote resolution of acute...

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