HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Godson, C. Articles by Brady, H. R. Search for Related Content PubMed PubMed Citation Articles by Godson, C. Articles by Brady, H. R.

Cutting Edge: Lipoxins Rapidly Stimulate Nonphlogistic Phagocytosis of Apoptotic Neutrophils by Monocyte-Derived Macrophages¹

Catherine Godson^2,3,*, Siobhan Mitchell^2,*, Killeen Harvey^*, Nicos A. Petasis, Nancy Hogg and Hugh R. Brady^*

^* Centre for Molecular Inflammation and Vascular Research, Mater Misericordiae Hospital and Department of Medicine and Therapeutics, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin, Ireland; Department of Chemistry, University of Southern California, Los Angeles, CA 90089; and Imperial Cancer Research Fund, London, United Kingdom

	Abstract

Top Abstract Introduction Materials and Methods Results and Discussion References

 
Lipoxins (LX) are lipoxygenase-derived eicosanoids generated during inflammation. LX inhibit polymorphonuclear neutrophil (PMN) chemotaxis and adhesion and are putative braking signals for PMN-mediated tissue injury. In this study, we report that LXA₄ promotes another important step in the resolution phase of inflammation, namely, phagocytosis of apoptotic PMN by monocyte-derived macrophages (M). LXA₄ triggered rapid, concentration-dependent uptake of apoptotic PMN. This bioactivity was shared by stable synthetic LXA₄ analogues (picomolar concentrations) but not by other eicosanoids tested. LXA₄-triggered phagocytosis did not provoke IL-8 or monocyte chemoattractant protein-1 release. LXA₄-induced phagocytosis was attenuated by anti-CD36, _vß₃, and CD18 mAbs. LXA₄-triggered PMN uptake was inhibited by pertussis toxin and by 8-bromo-cAMP and was mimicked by Rp-cAMP, a protein kinase A inhibitor. LXA₄ attenuated PGE₂-stimulated protein kinase A activation in M. These results suggest that LXA₄ is an endogenous stimulus for PMN clearance during inflammation and provide a novel rationale for using stable synthetic analogues as anti-inflammatory compounds in vivo.

	Introduction

Top Abstract Introduction Materials and Methods Results and Discussion References

 
It is increasingly appreciated that the resolution of inflammation is a dynamically regulated process. Of particular relevance in this context is the clearance of accumulated leukocytes (1, 2). Evidence from in vitro models and from histopathology suggests that neutrophil-mediated tissue damage is limited by polymorphonuclear neutrophil (PMN)⁴ apoptosis and subsequent phagocytosis by macrophages (M) and other "nonprofessional" phagocytes. It is noteworthy that such phagocytic clearance is nonphlogistic; i.e., in contrast to phagocytosis of particles opsonized with complement or Ig, phagocytosis of apoptotic leukocytes does not provoke the release of proinflammatory mediators (reviewed in Refs. 1, 2). These observations suggest the existence of a specialized phagocytic process for removal of apoptotic PMN from an inflammatory milieu. Several aspects of phagocyte-apoptotic cell recognition systems have been described involving the concerted action of cell surface molecules (reviewed in Refs. 1, 2, 3). To date, rapid modulation of PMN phagocytosis has not been described (4, 5).

Lipoxins (lipoxygenase interaction products; LX) are lipid-derived mediators typically generated by transcellular lipoxygenation of arachidonic acid. Several lines of evidence suggest that LX are braking signals for PMN recruitment in host defense, inflammation, and hypersensitivity reactions (reviewed in Ref. 6). LX have been detected in tissues and inflammatory exudates in experimental and human diseases. LX, at nanomolar concentrations, inhibit PMN chemotaxis, ß₂ integrin and P-selectin-dependent PMN adhesion to endothelial cells, and PMN transmigration across confluent monolayers of endothelial and epithelial cells in vitro in response to leukotrienes and other inflammatory mediators (6, 7, 8). LX inhibit several other proinflammatory responses of leukocytes and parenchymal cells, including PMN degranulation and cytokine release by colonic epithelial cells (9, 10). Furthermore, ex vivo treatment of PMN with LXA₄ blunts their subsequent recruitment to inflamed renal glomeruli in experimental immune complex glomerulonephritis, and impaired LXA₄ biosynthesis has been associated with exaggerated PMN recruitment in the latter setting (11). Interestingly, the topical and systemic administration of LX and/or synthetic LX analogues inhibits PMN recruitment and plasma exudation induced by leukotriene B₄ and other insults in various models of acute inflammation (12, 13). Aspirin promotes the generation of LX epimers during leukocyte interactions with endothelial and epithelial cells which may account for some of the efficacy of this classic nonsteroidal anti-inflammatory agent (6, 12, 13, 14, 15). Together these observations raise the possibility that the LX play dynamic roles in the resolution phase of PMN-mediated inflammation.

In this study, we further expand on the anti-inflammatory actions of LX by determining their effects on M phagocytosis of apoptotic PMN. We demonstrate that exposure of M to LX causes rapid enhancement of phagocytosis of apoptotic PMN; this response is concentration dependent, involves multiple adhesion molecules, can be mimicked by stable synthetic LX analogues, and is associated with modulation of protein kinase A (PKA) activity.

	Materials and Methods

Top Abstract Introduction Materials and Methods Results and Discussion References

 
Leukocyte isolation and culture

Human monocytes and PMN were isolated from peripheral venous blood drawn from healthy volunteers following informed written consent. PMN were isolated by density gradient centrifugation and dextran sedimentation (16). M were prepared from monocytes collected over Ficoll-Paque as reported previously (17). Adherent monocytes were cultured for 5–7 days in RPMI 1640 supplemented with 10% autologous serum and 1% penicillin-streptomycin.

Induction and monitoring of PMN apoptosis

Spontaneous apoptosis of PMN was achieved by culturing 0.5 x 10⁶–1.5 x 10⁶ PMN/ml for 4–48 h (16). Apoptosis was monitored by a combination of light microscopy and dual laser flow cytometry (Epics Elite flow cytometer, Coulter, Hialeah, FL) using Hoechst 33342 and propidium iodide (16).

M phagocytosis of apoptotic PMN

M were exposed to experimental stimuli, washed with RPMI 1640, and coincubated with aged PMN in 24-well tissue culture plates (4 x 10⁶ PMN/ml RPMI 1640/well) at 37°C for 30 min. After coincubation, the cells were washed with PBS, fixed with 2.5% glutaraldehyde, and stained for myeloperoxidase (MPO) activity with dimethoxybenzidine in the presence of hydrogen peroxide. M were routinely negative for peroxidase staining. For each experiment, the number of M containing one or more PMN was counted by two independent observers in at least five fields (minimum of 400 cells) and expressed as a percentage of the total number of M in duplicate wells. In initial experiments, phagocytosis of apoptotic PMN was confirmed by electron microscopy.

Determination of IL-8 and monocyte chemoattractant protein-1 (MCP-1) release

IL-8 and MCP-1 were assayed in supernatants of PMN-M cocultures by ELISA according to the manufacturer’s instruction (R&D Systems, Minneapolis, MN).

Determination of PKA activity

PKA activity was determined by a Non-Radioactive PepTag assay (Promega, Madison, WI) using a fluorescent peptide substrate specific for PKA-dependent phosphorylation. M were pretreated with isobutylmethylxanthine (250 µM in RPMI 1640, 15 min), washed once with RPMI 1640, treated with either LXA₄ (10^-9 M in RPMI 1640 containing 250 µM isobutylmethylxanthine, 15 min) or vehicle, and then stimulated with either PGE₂ (10^-5 M, 15 min), forskolin (10^-5 M, 15 min), or diluent at 37°C. Lysates were harvested and PKA activity was assayed. Phosphorylated and unphosphorylated substrates were resolved by agarose gel electrophoresis.

Statistics

Results are expressed as means ± SEM. Statistical significance was determined by Student’s t test.

Materials

Anti-CD18 mouse mAb (MHM 23) was purchased from Dako (Cambridge, U.K.), anti-_vß₃ mouse mAb (23C6) from Serotec (Oxford, U.K.), and anti-CD44 mouse mAb (J-173), FITC-conjugated anti-CD36 (FA6-152) and anti-_vß₃ (anti-CD51/61)(AMF-7) mAbs from Beckman Coulter (Luton, U.K.). LXA₄ was obtained from Cascade Biologicals (Berkshire, U.K.). The stable LXA₄ analogues 15-(R,S)-methyl-LXA₄ and 16-phenoxy-LXA₄ were prepared by total organic synthesis (18).

	Results and Discussion

Top Abstract Introduction Materials and Methods Results and Discussion References

 
An important determinant of the resolution of inflammation is the nonphlogistic clearance of apoptotic leukocytes by phagocytosis. Prolonged exposure of cultured human monocyte-derived M to several cytokines, namely, GM-CSF, TNF-, IFN-, IL-1, and IL-10, enhances their capacity to phagocytose apoptotic PMN in vitro, suggesting that this process is dynamically regulated within inflamed tissue (4). Recent work has shown that exposure of macrophages to corticosteroids enhances their phagocytic capacity by a cycloheximide-sensitive process, raising the intriguing possibility that these agents may suppress inflammation, at least in part, by promoting clearance of PMN (5). Rapidly acting endogenous modulators of phagocytosis in this context remain relatively enigmatic. In the present study, we have investigated whether LX, endogenously produced eicosanoids with anti-inflammatory activities, could influence this process.

LXA₄ stimulates nonphlogistic phagocytosis of apoptotic PMN

PMN undergo spontaneous apoptosis during aging in vitro. This process is characterized morphologically by progression through an initial apoptotic phase typified by chromatin condensation and coalescence of nuclear lobes to a later apoptotic phase characterized by nuclear degradation, evanescence, and secondary necrosis (16). For phagocytosis assays, PMN were studied after 24 h in culture, a time point at which 25% were in the initial phase of apoptosis and <3% had undergone secondary necrosis as monitored by dual laser flow cytometry (Fig. 1A). Pretreatment of M with LXA₄ (1 nM, 15 min, 37°C) resulted in a 3-fold increase in MPO-positive M (Fig. 1B). In parallel experiments, we included M pretreated with anti-CD44 mAb (J-173, 80 µg/ml, 20 min, 22°C) before the addition of aged PMN as a positive control (19). Consistent with published data CD44 receptor cross-linking augmented phagocytosis of apoptotic cells (Fig. 1B) (19). PMN uptake was not observed with freshly isolated PMN (data not shown).

View larger version (29K): [in this window] [in a new window]   FIGURE 1. LXA4 rapidly stimulates nonphlogistic phagocytosis of apoptotic PMN by M. A, Dual laser flow cytometry demonstrating progression of PMN from normal (gate C) through early apoptotic (gate D) to late apoptotic/secondary necrotic (gate M) phases during aging for 4 h (left), 24 h (middle), and 48 h (right) (14 ). For M phagocytosis assays, PMN were aged for 24 h. B, Exposure of M to LXA4 (10-9 M, 15 min) enhances their phagocytosis of apoptotic PMN during a 30-min coincubation at 37°C. As a positive control in parallel experiments, M were pretreated with anti-CD44 mAb (J-173, 80 µg/ml, 20 min, 22°C). Data are means ± SEM and are expressed as percent M staining positively for MPO (n = 10, p < 0.01). C, IL-8 release from M-PMN coincubations. IL-8 was determined by ELISA (R&D Systems) of supernatants harvested after 30 min from M cultures, cocultures of aged PMN with M pretreated with LXA4 (1 nM) or vehicle (15 min), or M exposed to opsonized zymosan (10 mg/ml). Data are means ± SEM (n = 5) and are expressed as percent zymosan-stimulated IL-8 release.

LXA₄-mediated phagocytosis of apoptotic PMN is concentration dependent, specific, and mimicked by stable LXA₄ analogues

LXA₄-triggered phagocytosis was concentration dependent (EC₅₀ 0.5 x 10^-9 M; Fig. 2A); this value is consistent with the reported K_d of the cloned LXA₄ receptor which is expressed by M (22). The specificity of the effect of LXA₄ relative to other eicosanoids was investigated. LX-augmented phagocytosis was not mimicked by exposure of M to either the LX precursors arachidonic acid (10^-9 M) or 15(S)-hydroxyeicosatetraenoic acid (10^-9 M), or by exposure to the proinflammatory product of the 5-lipoxygenase pathway, leukotriene B₄ (1 nM; Table I), or to PGE₂ (1 nM; data not shown). LXA₄ is metabolized rapidly via pathways initially involving dehydrogenation at carbon-15. To circumvent such degradation, a panel of synthetic, stable LXA₄ analogues have been designed (18). These analogues act as ligands for the human myeloid LXA₄ receptor and retain the ability of the native compound to inhibit PMN-endothelial cell adhesion and PMN recruitment in vitro and in vivo (12, 13, 18, 22). We investigated whether the stable synthetic LXA₄ analogues 15-(R,S)-methyl-LXA₄ and 16-phenoxy-LXA₄ could mimic the effects of the native compound on M phagocytosis. Both analogues stimulated M phagocytosis of apoptotic PMN at picomolar concentrations (Fig. 2B). The potency of the analogues relative to the native compound are remarkable given the previously described rapid inactivation of LXA₄ by monocytes (22). The data with 15-(R,S)-methyl-LXA₄ are particularly interesting as this is a racemate of both native LXA₄ and aspirin-triggered 15-epi-LXA₄ (12, 13). Thus, acceleration of PMN clearance is a potential component of aspirin-related bioactivities within a local inflammatory milieu.

View larger version (22K): [in this window] [in a new window]   FIGURE 2. LXA4-triggered phagocytosis of apoptotic PMN by M is concentration dependent and mimicked by stable synthetic LX analogues. A, M were pretreated with the indicated concentrations of LXA4 for 15 min and phagocytosis was determined as described for Fig. 1. Data are means ± SEM (n = 5) and are expressed as percent M staining positively for MPO. B, M were pretreated with the stable LX analogues 15-(R,S)-methyl-LXA4 and 16-phenoxy-LXA4 (10-11 M), and phagocytosis was assayed as described above. Data are means ± SEM (n = 5, *, p < 0.05).

View this table: [in this window] [in a new window]   Table I. Influence of arachidonic acid and lipoxygenase-derived eicosanoids on M phagocytosis of apoptotic PMN1

M recognize apoptotic cells via several mechanisms, including integrins, phosphatidylserine recognition systems, lectins, and scavenger receptors, frequently acting in concert (23, 24, 25, 26, 27). In the present study, treatment of M with mAbs against either CD36 or _vß₃ blocked phagocytosis of apoptotic PMN induced by LXA₄ (Table II), indicating a role for the _vß₃-CD36 complex in LXA₄-stimulated phagocytosis. In parallel experiments, treatment of M with LXA₄ (10^-9 M, 15 min) did not alter cell surface expression of either _vß₃ or CD36, as determined by flow cytometry (n = 3; data not shown). These results suggest that LXA₄ promotes M phagocytosis of apoptotic PMN either by increasing the avidity of the _vß₃-CD36 complex for PMN ligands or by influencing subsequent cytoskeletal events that are dependent on initial macrophage-PMN adhesion. There is compelling evidence that a M adhesion complex involving the CD36 scavenger receptor and _vß₃ integrin (CD51/61, vitronectin receptor) plays a central role in the recognition of apoptotic PMN (23, 24, 25, 26, 27, 28).

View this table: [in this window] [in a new window]   Table II. M phagocytosis of apoptotic PMN: adhesion requirements1

LXA₄-stimulated phagocytosis and PKA activity

M high-affinity LXA₄ receptors have previously been shown to be coupled through pertussis toxin (PTX)-sensitive G proteins (22). In the present study, prior exposure of M to pertussis toxin (200 ng/ml, 18 h) inhibited phagocytosis (percent phagocytosis: vehicle, 11.0 ± 1.3; LXA₄, 20.8 ± 5.4; PTX alone, 5.1 ± 0.8; and LXA₄ plus PTX, 4.5 ± 0.8, n = 3), consistent with a receptor-mediated response involving G_i proteins. Elevation of intracellular cAMP by prior exposure of M with the cell permeant analogue 8-bromo-cAMP inhibited LX-stimulated phagocytosis and, conversely, the PKA inhibitor Rp-cAMP mimicked the effects of LXA₄ (Table III). Interestingly, the effects of Rp-cAMP and LXA₄ on promoting phagocytosis were not additive (Table III), suggesting that they may act at a common target. This observation was further characterized by direct assay of PKA activity. Exposure of macrophages to LXA₄ (10^-9 M) consistently blunted PKA activation induced by addition of exogenous PGE₂ (10^-5 M, 15 min, n = 5; Fig. 3) and by forskolin (10^-5 M, 15 min, n = 5; data not shown), known activators of M adenylyl cyclase. These data are of interest in the context of cAMP-dependent regulation of cytoskeletal functions such as F-actin assembly, cell adhesion, and cell spreading. Recent data from others have shown that increased intracellular cAMP is associated with decreased M phagocytosis of apoptotic cells, reduced M adhesiveness, and a perturbation in actin and talin colocalization at contact points (29). Our data showing blockade of M phagocytosis of apoptotic PMN with anti-CD36 mAb is particularly interesting given that CD36 is a PKA substrate (30). Platelet CD36 is constitutively phosphorylated and its dephosphorylation is associated with increased cytoadhesion (31). Consistent with the hypothesis that LX-mediated protein dephosphorylation is an important determinant of phagocyte-apoptotic cell recognition are our preliminary observations that the phosphatase inhibitor okadaic acid blocks LXA₄-stimulated phagocytosis (data not shown).

View this table: [in this window] [in a new window]   Table III. M phagocytosis of apoptotic PMN: role of cAMP and PKA1

View larger version (35K): [in this window] [in a new window]   FIGURE 3. LXA4 inhibits PGE2-stimulated PKA activation in human monocyte-derived M. M were pretreated with LXA4 (1 nM, 15 min.) or vehicle followed by exposure to either PGE2 (10 µM) or vehicle (15 min). PKA activity was assayed using the Non-Radioactive PepTag kit (Promega). These results are representative of five experiments, each conducted in duplicate.

	Acknowledgments

 
We thank Ian Dransfield, John Savill, Finian Martin, and Bill Watson for helpful discussions.

	Footnotes

 
¹ This research was funded by grants from the Health Research Board, the Wellcome Trust, Forbairt (Enterprise Ireland) a President’s Research Award from University College Dublin, and the Mater College. The results were presented in preliminary form at the 31st and 32nd Annual Meetings of the American Society of Nephrology and published in abstract form in J. Am. Soc. Nephrol. 1998; 9:482A and J. Am. Soc. Nephrol. 1999; 10: 532A.

² C.G. and S.M. contributed equally to this work.

³ Address correspondence and reprint requests to Dr. Catherine Godson, Department of Medicine and Therapeutics, University College Dublin, 41 Eccles Street, Dublin 7, Ireland. E-mail address:

⁴ Abbreviations used in this paper: PMN, polymorphonuclear neutrophil; M, macrophage; LX, lipoxin; PKA, protein kinase A; MPO, myleoperoxidase; MCP-1. monocyte chemoattractant protein-1; PTX, pertussis toxin.

Received for publication October 13, 1999. Accepted for publication December 17, 1999.

	References

Top Abstract Introduction Materials and Methods Results and Discussion References

 

1. Savill, J., V. Fadok, P. Henson, C. Haslett. 1993. Phagocyte recognition of cells undergoing apoptosis. Immunol. Today 14:131.[Medline]
2. Hart, S. P., C. Haslett, I. Dransfield. 1996. Recognition of apoptotic cells by phagocytes. Experientia 52:950.[Medline]
3. Savill, J.. 1998. Phagocytic docking without shocking. Nature 392:442.[Medline]
4. Ren, Y., J. Savill. 1995. Proinflammatory cytokines potentiate thrombospondin-mediated phagocytosis of neutrophils undergoing apoptosis. J. Immunol. 154:2355.
5. Liu, Y., J. M. Cousin, J. Hughes, J. Van Damme, J. R. Seckle, C. Haslett, I. Dransfield, J. Savill, A. G. Rossi. 1999. Glucocorticoids promote nonphlogistic phagocytosis of apoptotic leukocytes. J. Immunol. 162:3639.[Abstract/Free Full Text]
6. Serhan, C. N.. 1997. Lipoxins and novel aspirin-triggered 15-epi-lipoxins (ATL): a jungle of cell-cell interactions or a therapeutic opportunity?. Prostaglandins 53:107.[Medline]
7. Papayianni, A., C. N. Serhan, H. R. Brady. 1996. Lipoxin A₄ and B₄ inhibit leukotriene-stimulated interactions of human neutrophils and endothelial cells. J. Immunol. 156:2264.[Abstract]
8. Colgan, S. P., C. N. Serhan, C. A. Parkos, C. Delp-Archer, J. L. Madara. 1993. Lipoxin A₄ modulates transmigration of human neutrophils across intestinal epithelial cell monolayers. J. Clin. Invest. 92:75.
9. Gronert, K., A. Gewirtz, J. L. Madara, C. N. Serhan. 1998. Identification of a human enterocyte lipoxin A₄ receptor that is regulated by interleukin(IL)-13 and interferon- and inhibits tumor necrosis factor -induced IL-8 release. J. Exp. Med. 187:1285.[Abstract/Free Full Text]
10. Gewirtz, A., V. V. T, N. A. Fokin, C. N. Petasis, C. N. Serhan, J. L. Madara. 1999. LXA₄, aspirin-triggered 15-epi-LXA4 and their analogs selectively downregulate PMN azurophilic degranulation. Am. J. Physiol. 276:C988.[Abstract/Free Full Text]
11. Papayanni, A., C. N. Serhan, M. L. Phillips, H. G. Rennke, H. R. Brady. 1994. Transcellular biosynthesis of lipoxin A₄ during adhesion of platelets and neutrophils in experimental immune complex glomerulonephritis. Kidney Int. 47:1295.
12. Takano, T., S. Fiore, J. F. Maddox, H. R. Brady, N. A. Petasis, C. N. Serhano. 1997. Aspirin-triggered epi-lipoxin A₄ (LXA₄) and LXA₄ stable analogues are potent inhibitors of acute inflammation: evidence for anti-inflammatory receptors. J. Exp. Med. 185:1693.[Abstract/Free Full Text]
13. Clish, C.B, J. A. O’Brien, K. Gronert, G. L. Stahl, N. A. Petasis., C. N. Serhan. 1999. Local and systemic delivery of a stable-aspirin triggered lipoxin prevents neutrophil recruitment in vivo. Proc. Natl. Acad. Sci. USA 96:8247.[Abstract/Free Full Text]
14. Hachicha, M., M. Pouliot, N. A. Petasis, C. N. Serhan. 1999. Lipoxin (LX)A₄ and aspirin-triggered 15-epi-LXA₄ inhibit tumor necrosis factor alpha-initiated neutrophil responses and trafficking: regulators of a cytokine-chemokine axis. J. Exp. Med. 189:1923.[Abstract/Free Full Text]
15. Chiang, N., T. Takano, C. B. Clish, N. A. Petasis, H. H. Tai, C. N. Serhan. 1998. Aspirin-triggered 15-epi-lipoxin A₄ (ATL) generation by human leukocytes and murine peritonitis exudates: development of a specific 15-epi-LXA₄ ELISA. J. Pharmacol. Exp. Ther. 287:779.[Abstract/Free Full Text]
16. Hebert, M.J., T. Takano, H. Holthofer, H. R. Brady. 1996. Sequential morphologic events during apoptosis of human neutrophils: modulation by lipoxygenase-derived eicosanoids. J. Immunol. 157:3105.[Abstract]
17. Tremoli, E., S. Eligini, S. Colli, P. Maderna, P. Pise, F. Pazzucconi, F. Marangoni, C. R. Sirtoriand, C. Galli. 1994. n-3 Fatty acid ethyl ester administration to healthy subjects and to hypertriglyceridemic patients reduces tissue factor activity in adherent monocytes. Arterioscler. Thromb. 14:1600.[Abstract/Free Full Text]
18. Serhan, C. N., J. F. Maddox, N. A. Petasis, I. Akritopoulou-Zanze, A. Papayianni, H. R. Brady, S. P. Colgan, J. L. Madara. 1995. Design of lipoxin A₄ stable analogs that block transmigration and adhesion of human neutrophils. Biochemistry 34:14609.[Medline]
19. Hart, S. P., G. J. Dougherty, C. Haslett, I. Dransfield. 1997. CD44 regulates phagocytosis of apoptotic neutrophil granulocytes, but not apoptotic lymphocytes, by human macrophages. J. Immunol. 159:919.[Abstract]
20. Meagher, L. C., J. S. Savill, A. Baker, R. W. Fuller, C. Haslett. 1992. Phagocytosis of apoptotic neutrophils does not induce macrophage release of thromboxane B₂. J. Leukocyte Biol. 52:269.[Abstract]
21. Fadok, V. A., D. L. Bratton. A. Konowal, P. W. Freed, J. Y. Westcott, P. M. Henson. 1998. Macrophages that have ingested apoptotic cells in vitro inhibit proinflammatory cytokine production through autocrine/paracrine mechanisms involving TGF-ß, PGE₂ and PAF. J. Clin. Invest. 101:890.[Medline]
22. Maddox, J. F., M. Hachicha, T. Takano, N. A. Petasis, V. V. Fokin, C. N. Serhan. 1997. Lipoxin A₄ stable analogs are potent mimetics that stimulate human monocytes and THP-1 cells via a G-protein-linked lipoxin A₄ receptor. J. Biol. Chem. 272:6972.[Abstract/Free Full Text]
23. Savill, J., N. Hogg, Y. Ren, C. Haslett. 1992. Thrombospondin cooperates with CD36 and the vitronectin receptor in macrophage recognition of neutrophils undergoing apoptosis. J. Clin. Invest. 90:1513.
24. Fadok, V. A., J. Savill, C. Haslett, D. L. Bratton, D. E. Doherty, P. A. Campbell, P. M. Henson. 1998. Different populations of macrophages use either the vitronectin receptor or the phosphatidylserine receptor to recognize and remove apoptotic cells. J. Immunol. 149:4029.[Abstract]
25. Fadok, V. A., M. L. Warner, D. L. Bratton, P. M. Henson. 1998. CD36 is required for phagocytosis of apoptotic cells by human macrophages that use either a phosphatidylserine receptor or the vitronectin receptor (_vß₃). J. Immunol. 161:6250.[Abstract/Free Full Text]
26. Flora, P. K., C. D. Gregory. 1994. Recognition of apoptotic cells by human macrophages: inhibition by a monocyte/macrophage-specific monoclonal antibody. Eur. J. Immunol. 24:2625.[Medline]
27. Devitt, A. C., O. D. Raykundalia, J. D. Moffat, D. L. Simmons Capra, C. D. Gregory. 1998. Human CD14 mediates recognition and phagocytosis of cells undergoing apoptosis. Nature 392:505.[Medline]
28. McCutcheon, J. C., S. P. Hart, M. Canning, K. Ross, M. J. Humphries, I. Dransfield. 1998. Regulation of macrophage phagocytosis of apoptotic neutrophils by adhesion to fibronectin. J. Leukocyte Biol. 64:600.[Abstract]
29. Rossi, A. G., J. C. McCutcheon, N. Roy, E. R. Chilvers, C. Haslett, I. Dransfield. 1998. Regulation of macrophage phagocytosis of apoptotic cells by cAMP. J. Immunol. 160:3562.[Abstract/Free Full Text]
30. Hatmi, M., J. M. Gavaret, I. Elalamy, B. Boris Vargaftig, C. Jacquemin. 1996. Evidence for cAMP-dependent platelet ectoprotein kinase activity that phosphorylates platelet glycoprotein IV (CD36). J. Biol. Chem. 271:24776.[Abstract/Free Full Text]
31. Asch, A. S., I. Liu, F. M. Briccetti, J. W. Barnwell, F. Kwakye-Berko, A. Dokun, J. Goldberger, M. Pernambuco. 1993. Analysis of CD36 binding domains: ligand specificity controlled by dephosphorylation of an ectodomain. Science 262:1436.[Abstract/Free Full Text]

This article has been cited by other articles:

				S. Hong, T. F. Porter, Y. Lu, S. F. Oh, P. S. Pillai, and C. N. Serhan Resolvin E1 Metabolome in Local Inactivation during Inflammation-Resolution J. Immunol., March 1, 2008; 180(5): 3512 - 3519. [Abstract] [Full Text] [PDF]

				K. Gronert Lipid Autacoids in Inflammation and Injury Responses: A Matter of Privilege Mol. Interv., February 1, 2008; 8(1): 28 - 35. [Abstract] [Full Text] [PDF]

				H. Hasturk, A. Kantarci, E. Goguet-Surmenian, A. Blackwood, C. Andry, C. N. Serhan, and T. E. Van Dyke Resolvin E1 Regulates Inflammation at the Cellular and Tissue Level and Restores Tissue Homeostasis In Vivo J. Immunol., November 15, 2007; 179(10): 7021 - 7029. [Abstract] [Full Text] [PDF]

				O. Haworth and B. D. Levy Endogenous lipid mediators in the resolution of airway inflammation Eur. Respir. J., November 1, 2007; 30(5): 980 - 992. [Abstract] [Full Text] [PDF]

				D. El Kebir, L. Jozsef, T. Khreiss, W. Pan, N. A. Petasis, C. N. Serhan, and J. G. Filep Aspirin-Triggered Lipoxins Override the Apoptosis-Delaying Action of Serum Amyloid A in Human Neutrophils: A Novel Mechanism for Resolution of Inflammation J. Immunol., July 1, 2007; 179(1): 616 - 622. [Abstract] [Full Text] [PDF]

				M. Scannell, M. B. Flanagan, A. deStefani, K. J. Wynne, G. Cagney, C. Godson, and P. Maderna Annexin-1 and Peptide Derivatives Are Released by Apoptotic Cells and Stimulate Phagocytosis of Apoptotic Neutrophils by Macrophages J. Immunol., April 1, 2007; 178(7): 4595 - 4605. [Abstract] [Full Text] [PDF]

				C. Bonnans and B. D. Levy Lipid Mediators as Agonists for the Resolution of Acute Lung Inflammation and Injury Am. J. Respir. Cell Mol. Biol., February 1, 2007; 36(2): 201 - 205. [Abstract] [Full Text] [PDF]

				S.-W. Jin, L. Zhang, Q.-Q. Lian, D. Liu, P. Wu, S.-L. Yao, and D.-Y. Ye Posttreatment with Aspirin-Triggered Lipoxin A4 Analog Attenuates Lipopolysaccharide-Induced Acute Lung Injury in Mice: The Role of Heme Oxygenase-1 Anesth. Analg., February 1, 2007; 104(2): 369 - 377. [Abstract] [Full Text] [PDF]

				D. M. Schrijvers, G. R.Y. De Meyer, A. G. Herman, and W. Martinet Phagocytosis in atherosclerosis: Molecular mechanisms and implications for plaque progression and stability Cardiovasc Res, February 1, 2007; 73(3): 470 - 480. [Abstract] [Full Text] [PDF]

				A. Daryadel, R. F. Grifone, H.-U. Simon, and S. Yousefi Apoptotic Neutrophils Release Macrophage Migration Inhibitory Factor upon Stimulation with Tumor Necrosis Factor-{alpha} J. Biol. Chem., September 15, 2006; 281(37): 27653 - 27661. [Abstract] [Full Text] [PDF]

				N. Chiang, C. N. Serhan, S.-E. Dahlen, J. M. Drazen, D. W. P. Hay, G. E. Rovati, T. Shimizu, T. Yokomizo, and C. Brink The Lipoxin Receptor ALX: Potent Ligand-Specific and Stereoselective Actions in Vivo Pharmacol. Rev., September 1, 2006; 58(3): 463 - 487. [Abstract] [Full Text] [PDF]

				R. Rajakariar, M. M. Yaqoob, and D. W. Gilroy COX-2 in Inflammation and Resolution Mol. Interv., August 1, 2006; 6(4): 199 - 207. [Abstract] [Full Text] [PDF]

				R. W. Vandivier, P. M. Henson, and I. S. Douglas Burying the Dead: The Impact of Failed Apoptotic Cell Removal (Efferocytosis) on Chronic Inflammatory Lung Disease Chest, June 1, 2006; 129(6): 1673 - 1682. [Abstract] [Full Text] [PDF]

				C. N. Serhan, K. Gotlinger, S. Hong, Y. Lu, J. Siegelman, T. Baer, R. Yang, S. P. Colgan, and N. A. Petasis Anti-Inflammatory Actions of Neuroprotectin D1/Protectin D1 and Its Natural Stereoisomers: Assignments of Dihydroxy-Containing Docosatrienes J. Immunol., February 1, 2006; 176(3): 1848 - 1859. [Abstract] [Full Text] [PDF]

				K. Reville, J. K. Crean, S. Vivers, I. Dransfield, and C. Godson Lipoxin A4 Redistributes Myosin IIA and Cdc42 in Macrophages: Implications for Phagocytosis of Apoptotic Leukocytes J. Immunol., February 1, 2006; 176(3): 1878 - 1888. [Abstract] [Full Text] [PDF]

				I. Tabas Consequences and Therapeutic Implications of Macrophage Apoptosis in Atherosclerosis: The Importance of Lesion Stage and Phagocytic Efficiency Arterioscler. Thromb. Vasc. Biol., November 1, 2005; 25(11): 2255 - 2264. [Abstract] [Full Text] [PDF]

				M.-L. N. Huynh, K. C. Malcolm, C. Kotaru, J. A. Tilstra, J. Y. Westcott, V. A. Fadok, and S. E. Wenzel Defective Apoptotic Cell Phagocytosis Attenuates Prostaglandin E2 and 15-Hydroxyeicosatetraenoic Acid in Severe Asthma Alveolar Macrophages Am. J. Respir. Crit. Care Med., October 15, 2005; 172(8): 972 - 979. [Abstract] [Full Text] [PDF]

				B. D. Levy, C. Bonnans, E. S. Silverman, L. J. Palmer, G. Marigowda, E. Israel, and for the Severe Asthma Research Program, National H Diminished Lipoxin Biosynthesis in Severe Asthma Am. J. Respir. Crit. Care Med., October 1, 2005; 172(7): 824 - 830. [Abstract] [Full Text] [PDF]

				T. Iyoda, K. Nagata, M. Akashi, and Y. Kobayashi Neutrophils Accelerate Macrophage-Mediated Digestion of Apoptotic Cells In Vivo as Well as In Vitro J. Immunol., September 15, 2005; 175(6): 3475 - 3483. [Abstract] [Full Text] [PDF]

				K. Rodgers, B. McMahon, D. Mitchell, D. Sadlier, and C. Godson Lipoxin A4 Modifies Platelet-Derived Growth Factor-Induced Profibrotic Gene Expression in Human Renal Mesangial Cells Am. J. Pathol., September 1, 2005; 167(3): 683 - 694. [Abstract] [Full Text] [PDF]

				V. Nascimento-Silva, M. A. Arruda, C. Barja-Fidalgo, C. G. Villela, and I. M. Fierro Novel lipid mediator aspirin-triggered lipoxin A4 induces heme oxygenase-1 in endothelial cells Am J Physiol Cell Physiol, September 1, 2005; 289(3): C557 - C563. [Abstract] [Full Text] [PDF]

				R. L. Simoes and I. M. Fierro Involvement of the Rho-Kinase/Myosin Light Chain Kinase Pathway on Human Monocyte Chemotaxis Induced by ATL-1, an Aspirin-Triggered Lipoxin A4 Synthetic Analog J. Immunol., August 1, 2005; 175(3): 1843 - 1850. [Abstract] [Full Text] [PDF]

				G. L. Bannenberg, N. Chiang, A. Ariel, M. Arita, E. Tjonahen, K. H. Gotlinger, S. Hong, and C. N. Serhan Molecular Circuits of Resolution: Formation and Actions of Resolvins and Protectins J. Immunol., April 1, 2005; 174(7): 4345 - 4355. [Abstract] [Full Text] [PDF]

				P. Maderna, S. Yona, M. Perretti, and C. Godson Modulation of Phagocytosis of Apoptotic Neutrophils by Supernatant from Dexamethasone-Treated Macrophages and Annexin-Derived Peptide Ac2-26 J. Immunol., March 15, 2005; 174(6): 3727 - 3733. [Abstract] [Full Text] [PDF]

				T. Ohse, T. Ota, N. Kieran, C. Godson, K. Yamada, T. Tanaka, T. Fujita, and M. Nangaku Modulation of Interferon-Induced Genes by Lipoxin Analogue in Anti-Glomerular Basement Membrane Nephritis J. Am. Soc. Nephrol., April 1, 2004; 15(4): 919 - 927. [Abstract] [Full Text] [PDF]

				D. W. GILROY, J. NEWSON, P. SAWMYNADEN, D. A. WILLOUGHBY, and J. D. CROXTALL A novel role for phospholipase A2 isoforms in the checkpoint control of acute inflammation FASEB J, March 1, 2004; 18(3): 489 - 498. [Abstract] [Full Text] [PDF]

				B. McMahon and C. Godson Lipoxins: endogenous regulators of inflammation Am J Physiol Renal Physiol, February 1, 2004; 286(2): F189 - F201. [Abstract] [Full Text] [PDF]

				K. Asada, S. Sasaki, T. Suda, K. Chida, and H. Nakamura Antiinflammatory Roles of Peroxisome Proliferator-activated Receptor {gamma} in Human Alveolar Macrophages Am. J. Respir. Crit. Care Med., January 15, 2004; 169(2): 195 - 200. [Abstract] [Full Text] [PDF]

P. Boutet, F. Bureau, G