1 Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, Georgia; 2 Department of Chemistry, University of Southern California, Los Angeles, California; and 3 Center for Experimental Therapeutics and Reperfusion Injury, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
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ABSTRACT |
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The eicosanoid lipoxin A4 (LXA4) is biosynthesized in vivo by cells present at inflammatory sites and appears to be an endogenous anti-inflammatory mediator. Further, in the presence of aspirin, the 15-epimer of LXA4 (15-epi-LXA4) is biosynthesized and may mediate some of aspirin's desirable bioactions. LXA4, 15-epi-LXA4, and their stable analogs inhibit inflammation in established animal models, indicating that these compounds may be useful for treating inflammatory disease states. To investigate the cellular mechanisms by which these lipid mediators downregulate inflammation, we investigated whether these eicosanoids could influence receptor-mediated degranulation of human neutrophils, an event thought to play a major causative role in several inflammatory disease states. LXA4, 15-epi-LXA4, and their stable analogs potently (IC50 < 1 nM) and selectively downregulated neutrophil release of azurophilic granule contents but did not affect other neutrophil secretory functions. Thus the cellular basis of action of these natural off-switches to inflammation appears to involve downregulation of neutrophil azurophilic granule release.
anti-inflammatory mediators; elastase; eicosanoids; Fc
receptors; immune complexes; neutrophils
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INTRODUCTION |
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THE LIPOXYGENASE INTERACTION PRODUCTS, lipoxins (LX), appear to play an important role in downregulating inflammation (25, 30, 31). In humans, these eicosanoids are cooperatively (i.e., involves multiple cell types) biosynthesized from arachidonate by cells present at sites of inflammation (25). In contrast to other eicosanoids (e.g., leukotrienes, prostaglandins) that promote leukocyte infiltration (i.e., inflammation), LX have bioactivities that downregulate polymorphonuclear leukocytes (PMN or neutrophils) movement, thus making these eicosanoids "anti-inflammatory." Particularly potent anti-inflammatory activity is exhibited by LXA4 and its stable analogs (26). One compound that behaves as an LXA4 stable analog, in that it competes for the LXA4 receptor, is resistant to enzymatic degradation, and has anti-inflammatory bioactivity, is the 15-epimer of LXA4 (15-epi-LXA4) (3, 31). However, 15-epi-LXA4 is in fact biosynthesized in vivo by a pathway involving cyclooxygenase that has been acetylated by aspirin. 15-Epi-LXA4 biosynthesized in this manner may play a role in mediating some of aspirin's bioactions.
LXA4 (as well as 15-epi-LXA4 and LXA4 analogs) potently downregulate inflammation in vivo in well-defined animal models such as the hamster cheek pouch (21) and the mouse ear (31). LX also exhibit anti-inflammatory bioactivity in isolated model systems with isolated cells or cell systems, including inhibition of PMN chemotaxis (14) as well as migration across model endothelium (19) and epithelium (6). Additionally, LXA4 can attenuate PMN movement by downregulating (in epithelial cells) secretion of chemokines that direct PMN movement (9, 12). LX can also downregulate vascular endothelial P-selectin expression, resulting in reduced PMN adherence to endothelium (23) (an early step in PMN movement to inflammatory sites). Although these in vitro LX bioactions are likely partially responsible for the in vivo anti-inflammatory effects of LX, the profound downregulation of inflammation in animal models [e.g., mouse ear (31)] by LX suggests that, in addition to these known cellular mechanisms, LX likely have as yet still unrecognized bioactions that can account, in part, for their overall in vivo anti-inflammatory effect.
We reasoned that perhaps LX could downregulate PMN secretion, thus providing an additional means by which LX could attenuate inflammation. When appropriately activated, PMN secrete their antibacterial arsenal of superoxide anions and the contents of their two major granule populations. Although PMN-secreted products play an important role in host defense, in some inflammatory disease states PMN granule contents also appear to be responsible for damage to host tissue and subsequently for promoting the inflammatory state (7, 33, 34). This can occur if PMN are lysed by phagocytosing urate crystals that are present in gout patients (35). Alternatively, PMN granule contents are also released extracellularly during the receptor-mediated ingestion of immune complexes, which are abundant in rheumatoid arthritis, via a process that has been termed "regurgitation during feeding" (36). Some PMN azurophilic granule contents are directly chemotactic for PMN (2), whereas others induce chemokine release from other cells (17), perhaps long after any foreign entities have been eliminated. One particularly important secreted molecule thought to be involved in host tissue damage in chronic inflammatory disease states is the protease elastase, the source of which is PMN azurophilic granules.
PMN secretion of azurophilic granule contents can be mediated via Fc
receptors. These receptors are activated by IgG-coated entities
(bacteria or other antigens) or high-valency immune complexes (HIC) (1,
15, 28). Thus we investigated whether
LXA4 and its stable analogs could
regulate PMN secretion induced by HIC. We report that
LXA4 attenuated PMN Fc
receptor-mediated release of azurophilic granule contents, indicating
that LX downregulation of inflammation in vivo may involve attenuation
of PMN degranulation. This effect was selective for release of
azurophilic granules and did not extend to specific granules or
superoxide release evoked by Fc
receptor-mediated activation. This
selective inhibition of specific PMN activation responses by an
endogenously biosynthesized compound is unique for LX.
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MATERIALS AND METHODS |
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LX. LXA4 and LXB4 were obtained from Cayman (Ann Arbor, MI). LXA4 analogs (15[R/S]-methyl-LXA4, 16-phenoxy-LXA4, and 15-deoxy-LXA4) as well as 15-epi-LXA4 and its stable analog [15-epi-16-(para-fluoro)-phenoxy-LXA4] were prepared as methyl esters by total organic synthesis as previously described (26, 30).
LX exposure to PMN. PMN [50 × 106/ml Hanks' balanced salt solution (not supplemented with Ca2+)], isolated from healthy volunteers as previously described (20), were exposed to indicated LX or vehicle (always 0.1% ethanol) for 2.5 h unless otherwise indicated. PMN were kept at 37°C and mixed every 15 min by gentle pipetting. PMN were then used within 20 min or placed on ice and used within 1 h.
Secretion assays. Elastase release was measured in real time by spectrofluorometry as modified from Sklar et al. (27) as previously described (24). Unless otherwise noted, HIC [prepared as previously described (11, 28, 29)] was added at a final concentration of 100 µg/ml. The assay was calibrated with purified elastase generously supplied by Dr. Mustapha Si-Tahar (Pasteur Institute, Paris, France). Lactoferrin was measured by ELISA as previously described (10), except that standardization was performed with purified lactoferrin (Sigma) instead of PMN lysates. Myeloperoxidase activity was measured in supernatants of stimulated PMN, which had been centrifuged for 2 min after activation by HIC [using a peroxidase substrate as previously described (20)]. Superoxide release was measured by following the superoxide dismutase (SOD)-inhibitable reduction of ferricytochrome C at 550 nm (5). An endpoint version of this assay was utilized by measuring the total amount of SOD-inhibitable reduction of ferricytochrome C that occurred within 2 min following addition of HIC. Chelation of intracellular Ca2+ with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), as well as measurement of intracellular Ca2+, were performed as previously described (24).
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RESULTS |
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To investigate whether LX could regulate PMN secretion, PMN were
treated with LXA4 before being
stimulated with HIC, an agonist that, via an Fc receptor-mediated
mechanism, induces secretion in intact PMN (1).
LXA4 attenuated PMN release of
azurophilic granule contents (Fig.
1), as measured by release of
elastase (utilizing an assay that continuously measures release of this protease). LXA4 did not by itself
induce release of elastase (indicated by the fluorescence before
addition of HIC being comparable with control) or affect the time at
which maximal release in response to HIC occurred (~1 min, the time
at which the slope becomes maximal). Inhibition of HIC-induced elastase
release by LXA4 was concentration dependent, with IC50
1.0 nM
and maximal inhibition occurring at 100 nM (Fig.
1B).
LXA4 attenuation of azurophilic
degranulation was also time dependent, requiring that PMN be exposed to
LXA4 for 2 h or more before
activation with HIC for significant inhibition to occur (Fig.
2).
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We next ascertained whether LXA4
treatment led to inhibition of all Fc receptor-mediated secretion or
selectively attenuated azurophilic degranulation. We measured PMN
release of superoxide anions as well as the specific granule component,
lactoferrin, in response to HIC.
LXA4 treatment, which inhibited
HIC-induced elastase release by >50%, did not significantly affect
HIC-induced secretion of lactoferrin or superoxide anions (Fig.
3). Next, we measured whether elastase
release induced by another agonist was also inhibited by
LXA4. If PMN are pretreated with
cytochalasins (fungal metabolites that prevent actin polymerization),
stimulation with chemoattractants such as
N-formyl-methionyl-leucyl-phenylalanine (FMLP) results in elastase release (37). In these experiments, cytochalasin-treated PMN that were stimulated with a subsaturating dose
of FMLP (2.0 × 10
8 M)
exhibited elastase release, which was attenuated by pretreatment with
LXA4 (Fig.
4). PMN (vehicle or
LXA4 treated) stimulated with 1.0 × 10
8 M
FMLP did not secrete detectable amounts of elastase, whereas stimulation with higher concentrations of FMLP gave a maximal response
that was not affected by LXA4
(Fig. 4). In contrast, Fc
receptor-mediated elastase
release was attenuated by LXA4 in
response to all tested concentrations of HIC (Fig. 4). These results
indicate that LXA4 downregulated
azurophilic degranulation in response to a physiological agonist as
well as an unrelated receptor-mediated agonist but blocked neither
other Fc
receptor-mediated superoxide generation nor azurophilic
degranulation induced by saturating stimulation. To verify that the
inhibition of elastase release that we measured truly reflected
inhibition of azurophilic degranulation rather than specific inhibition
of only elastase release, we also measured HIC-induced myeloperoxidase
release (another azurophilic granule component) in the absence and
presence of LXA4. This response
was similarly inhibited by LXA4
(inhibition ranged from 40 to 65% among 3 different PMN donors,
P < 0.01), indicating that, indeed,
LXA4 attenuation of elastase
release represented an attenuation of azurophilic degranulation.
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We next began to explore potential mechanisms by which
LXA4 downregulated PMN Fc
receptor-mediated elastase release. The previously characterized
bioactions of LXA4 appear to be
mediated via the LXA4 receptor (8,
9, 12, 31). To find out whether LX attenuation of degranulation was
also mediated via the LXA4 receptor, we investigated which members of a panel of
LXA4 stable analogs, which are or
are not specific ligands for the
LXA4 receptor, could mimic the
ability of LXA4 to downregulate
Fc
receptor-mediated azurophilic degranulation. The
LXA4 stable analogs that are
specific ligands for the LXA4
receptor
(15-[R/S]-methyl-LXA4,
16-phenoxy-LXA4; Ref. 26) were
able to mimic the ability of LXA4
to downregulate Fc
receptor-mediated azurophilic degranulation,
whereas two compounds that are not specific ligands for the
LXA4 receptor
(15-deoxy-LXA4, an inactive
LXA4 stable analog, and lipoxin
B4, an eicosanoid whose
bioactivity differs in some cases from
LXA4) were without significant
effect (Fig.
5A).
Aspirin-triggered 15-epi-LXA4,
which is also a specific ligand for the
LXA4 receptor (3), and its stable
analog
[15-epi-16-(para-fluoro)-phenoxy-LXA4
(30)] also downregulated PMN elastase release to an extent
similar or perhaps slightly greater than
LXA4.
15-Epi-LXA4 exhibited this
bioactivity at subnanomolar concentrations with an
IC50 of ~0.2 nM. An analog of
this compound,
15-epi-16-(para-fluoro)-phenoxy-LXA4,
exhibited similar bioactivity at saturating concentrations but had an
IC50 approximately one log
unit less potent (Fig.
5B).
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One intracellular signaling event that occurs in PMN in response to
LXA4 is a small increase in
cytosolic Ca2+ concentration
([Ca2+]) (18). Our
bioactive LXA4 stable analogs also
induce a small increase in cytosolic
[Ca2+] in PMN
(increase was ~25 nM above baseline, reaching maximal levels ~1 min
after addition of LXA4 analog). To
investigate whether this small
Ca2+ mobilization was required for
LX attenuation of PMN Fc receptor degranulation, the
Ca2+ increase was inhibited by the
intracellular Ca2+ chelator BAPTA.
First, we verified the effectiveness of our BAPTA loading procedure by
checking that, as previously shown (24), this BAPTA treatment prevented
any detectable increase of
[Ca2+] in response to
FMLP. We then measured intracellular
[Ca2+] in control
(DMSO-treated) and BAPTA-loaded cells in response to our most potent
LXA4 stable analog. As expected,
the small increase in intracellular
[Ca2+] observed in
response to
15-[R/S]-methyl-LXA4
was completely prevented by BAPTA. Preventing the
LXA4 analog-induced increase in
intracellular [Ca2+]
in this manner did not affect LXA4
analog attenuation of Fc
receptor-mediated elastase release (100 nM
15-[R/S]-methyl
LXA4 attenuated HIC-induced
elastase release by 46 ± 7.5% in DMSO-treated PMN and by 54 ± 5.0% in BAPTA-loaded PMN). Thus the small increase in intracellular
[Ca2+] observed in
response to LXA4 and its stable
analogs does not appear to mediate this
LXA4 bioaction.
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DISCUSSION |
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Inflammation appears to be downregulated via the biosynthesis of LX by
cells present at inflammatory sites. These LX can then act to counter
the bioactions of proinflammatory mediators (e.g., leukotrienes,
platelet-activating factor, tumor necrosis factor) (12,
31). In part, LX attenuate inflammation by downregulating PMN motility
to chemoattractants as well as by downregulating secretion of the
chemokines that direct PMN movement (9, 12). Here we demonstrate that
LXA4 and its stable analogs can
also downregulate Fc receptor-mediated release of azurophilic
granules. This previously unappreciated bioaction of
LXA4 may be an important means by
which LX regulates inflammation in vivo. Because the proteases released
from PMN azurophilic granules are thought to play an important role in
the pathologies of a number of chronic inflammatory disease states,
these results suggest that LXA4, aspirin-triggered LX, and their stable analogs are not merely tools for
studying LX action but may have therapeutic potential for treating
these disease states. This newly described bioaction of LX likely adds
to the ability of LX to attenuate PMN movement in reducing inflammation
in vivo.
Although both azurophilic degranulation and superoxide secretion are
important components of the PMN arsenal,
LXA4 treatment downregulated the
former but had no detectable effect on the latter in response to an
Fc receptor-mediated agonist. A possible rationale for this can be
envisaged by considering the physiological role of Fc
receptor-mediated secretion as well as some of the fundamental differences between superoxide anions and azurophilic granule components. Fc
receptors mediate the phagocytosis of microorganisms, various other foreign entities, and host-generated immune complexes (4). Accompanying phagocytosis are PMN generation of superoxide anions
and secretion of granule contents into the phagovacuole and
extracellular space, which act to kill microorganisms (32) and possibly
to digest immune complexes. Although both superoxide anions and
azurophilic granule proteases are also capable of damaging host tissue
and subsequently promoting inflammation, azurophilic granule enzymes
(especially proteases like elastase and cathepsin G) have
characteristics that may make them much more proinflammatory than
superoxide anions. First, superoxide is rapidly reduced by superoxide
dismutase, whereas azurophilic granule proteases like elastase can
subsist for many hours (especially perhaps in nonserosal environments
such as the lumens of the lung and gastrointestinal tract). Second, the
azurophilic granule proteases (elastase and cathepsin G) are directly
chemotactic for immune cells (2). Third, granule proteases (and
azurophilic glycosidases) can digest matrix tissue, thus providing
access routes for immune cells to the inflammatory site and perhaps
also for locally generated proinflammatory molecules back to the
vasculature. This latter event results in the recruitment of yet more
immune cells. Considering that LX biosynthesized at inflammatory sites
in vivo are likely generated from products of PMN 5-lipoxygenase
(and/or 15-lipoxygenase interactions), LX will not likely
be present until many immune cells have already arrived at the
infected/inflamed site. Thus, perhaps by selectively downregulating
extracellular release of their azurophilic granule contents, but not
Fc
receptor-mediated superoxide generation, PMN can maintain their
ability to kill microorganisms while minimizing tissue damage. Coherent
with this view, release of specific granules was also not affected by
LX, and the content of these granules is antibacterial but does not
seem to pose a threat to host tissue or to promote the inflammatory state.
The intracellular mechanisms that mediate downregulation of azurophilic granule secretion by LXA4, aspirin-triggered LX, and their stable analogs are not yet clear, although some insights can be drawn. Because, of the compounds tested, only those that are specific ligands for the LXA4 receptor (26, 30) were able to downregulate azurophilic degranulation, it is likely that ligand binding of this receptor is a prerequisite for such attenuation of this secretory response. One postreceptor signal induced by LXA4 is a small increase in cytosolic [Ca2+]. However, since preventing the generation of this signal had no effect on the ability of LXA4 to attenuate azurophilic degranulation, this Ca2+ mobilization appears not to be required for this anti-inflammatory action of this eicosanoid. Analogously, LXA4-induced Ca2+ mobilization does not play a role in mediating LXA4 effects on monocyte adherence, indicating that intracellular Ca2+ is not a second messenger of LX receptor activation (16, 22). Identification of the signaling pathway by which LXA4 acts to downregulate PMN azurophilic granule release will be important for developing rational therapeutic strategies for disease states mediated by PMN tissue destruction.
This report is the first description of an agent that selectively attenuates azurophilic degranulation but not oxidative burst in response to a receptor-mediated agonist. This downregulation was exhibited not by a pharmacological compound but by a biomolecule that is naturally biosynthesized in vivo at inflammatory sites. Furthermore, this downregulation of azurophilic degranulation was observed in response to HIC analogous to those that are characteristically found in inflammation in the lung and joints (in rheumatoid arthritis) (13). Because azurophilic granule components (especially the protease elastase) are thought to damage host tissue in these and other inflammatory disease states, downregulating release of these granules via LXA4 and LXA4 stable analogs may offer therapeutic potential for these conditions. Because LXA4 stable analogs are much more resistant to degradation than the native eicosanoid, these compounds might be especially useful in treating inflammatory disease states. Further, it is possible that some of the therapeutic benefits of currently used nonsteroidal anti-inflammatory agents, specifically aspirin, are in fact due to the endogenous biosynthesis of 15-epi-LX that is induced by this drug. If this notion (supported in part by our observations that this aspirin-triggered compound downregulated elastase release at subnanomolar concentrations) is correct, then direct administration of 15-epi-LX (or the analogs studied here) may offer potent anti-inflammatory activity while avoiding some of the potential undesirable side effects caused by drugs that interfere with eicosanoid production via inhibition of cyclooxygenases and lipoxygenases.
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ACKNOWLEDGEMENTS |
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These studies were supported by National Institutes of Health Grants DK-47662 and DK-35932 (to J. L. Madara) and DK-50305 and GM-38765 (to C. N. Serhan) and by a discovery grant from Schering AG (to J. L. Madara, C. N. Serhan, and N. A. Petasis). A. Gewirtz was supported by an individual National Research Service Award.
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FOOTNOTES |
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The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.
Address for reprint requests and other correspondence: A. Gewirtz, Dept. of Pathology and Laboratory Medicine, Emory Univ. Hospital, Atlanta, GA 30322 (E-mail: agewirt{at}emory.edu).
Received 11 November 1998; accepted in final form 8 January 1999.
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REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Brunkhorst, B. A.,
G. R. Strohmeier,
K. G. Lazzari,
G. Weil,
D. Melnick,
H. B. Fleit,
and
E. R. Simons.
Differential roles of FcRII and Fc
RIII in immune complex stimulation of human neutrophils.
J. Biol. Chem.
267:
20659-20666,
1992
2.
Chertov, O.,
H. Ueda,
L. L. Xu,
K. Tani,
W. J. Murphy,
J. M. Wang,
O. M. Howard,
T. J. Sayers,
and
J. J. Oppenheim.
Identification of human neutrophil-derived cathepsin G and azurocidin/CAP37 as chemoattractants for mononuclear cells and neutrophils.
J. Exp. Med.
186:
739-747,
1997
3.
Claria, J.,
and
C. N. Serhan.
Aspirin triggers previously undescribed bioactive eicosanoids by human endothelial cell-leukocyte interactions.
Proc. Natl. Acad. Sci. USA
92:
9475-9479,
1995[Abstract].
4.
Clarkson, S. B.,
R. P. Kimberly,
J. E. Valinsky,
M. D. Witmer,
J. B. Bussel,
R. L. Nachman,
and
J. C. Unkeless.
Blockade of clearance of immune complexes by an anti-Fc gamma receptor monoclonal antibody.
J. Exp. Med.
164:
474-489,
1986
5.
Cohen, H. J.,
and
M. E. Chovaniec.
Superoxide generation by digitonin-stimulated guinea pig granulocytes. A basis for a continuous assay for monitoring superoxide production and for the study of the activation of the generating system.
J. Clin. Invest.
61:
1081-1087,
1978[Medline].
6.
Colgan, S. P.,
C. N. Serhan,
C. A. Parkos,
C. Delp-Archer,
and
J. L. Madara.
Lipoxin A4 modulates transmigration of human neutrophils across intestinal epithelial monolayers.
J. Clin. Invest.
92:
75-82,
1993[Medline].
7.
Downey, G. P.,
L. Fialkow,
and
T. Fukushima.
Initial interaction of leukocytes within the microvasculature: deformability, adhesion, and transmigration.
New Horizons
3:
219-228,
1995[Medline].
8.
Fiore, S.,
M. Romano,
E. Reardon,
and
C. N. Serhan.
Induction of functional lipoxin A4 receptors in HL-60 cells.
Blood
81:
3395-3403,
1993[Abstract].
9.
Gewirtz, A. T.,
B. A. McCormick,
A. S. Neish,
A. S. Petasis,
K. G. Gronert,
C. N. Serhan,
and
J. L. Madara.
Pathogen-induced chemokine secretion from model intestinal epithelium is inhibited by lipoxin A4 analogs.
J. Clin. Invest.
101:
1860-1869,
1998
10.
Gewirtz, A. T.,
K. F. Seetoo,
and
E. R. Simons.
Neutrophil degranulation and phospholipase D activation are enhanced if the Na+/H+ antiport is blocked.
J. Leukoc. Biol.
64:
98-103,
1998[Abstract].
11.
Gewirtz, A. T.,
and
E. R. Simons.
Phospholipase D mediates Fc receptor activation of neutrophils and provides signaling specificity between signaling pathways activated by fMLP and HIC.
J. Leukoc. Biol.
61:
131-138,
1997.
12.
Gronert, K. G.,
A. T. Gewirtz,
J. L. Madara,
and
C. N. Serhan.
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:
1285-1294,
1998
13.
Kronborg, G. Lipopolysaccharide (LPS), LPS-immune complexes
and cytokines as inducers of pulmonary inflammation in patients with
cystic fibrosis and chronic Pseudomonas
aeruginosa lung infection.
APMIS 50, Suppl.: 1-30, 1995.
14.
Lee, T. H.,
C. E. Horton,
U. Kyan-Aung,
D. Haskard,
A. E. Crea,
and
B. W. Spur.
Lipoxin A4 and lipoxin B4 inhibit chemotactic responses of human neutrophils stimulated by leukotriene B4 and N-formyl-L-methionyl-L-leucyl-L-phenylalanine.
Clin. Sci.
77:
195-203,
1989[Medline].
15.
Luscinskas, F. W.,
D. E. Mark,
B. Brunkhorst,
F. J. Lionetti,
E. J. J. Cragoe,
and
E. R. Simons.
The role of transmembrane cationic gradients in immune complex stimulation of human polymorphonuclear leukocytes.
J. Cell. Physiol.
134:
211-219,
1988[Medline].
16.
Maddox, J. F.,
M. Hachicha,
T. Takano,
N. A. Petasis,
V. V. Fokin,
and
C. N. Serhan.
Lipxin 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:
6972-6978,
1997
17.
Nakamura, H.,
K. Yoshimura,
N. G. McElvaney,
and
R. G. Crystal.
Neutrophil elastase in respiratory epithelial lining fluid of individuals with cystic fibrosis induces interleukin-8 gene expression in a human bronchial epithelial cell line.
J. Clin. Invest.
89:
1478-1484,
1992[Medline].
18.
Nigam, S.,
S. Fiore,
F. W. Luscinskas,
and
C. N. Serhan.
Lipoxin A4 and lipoxin B4 stimulate the release but not the oxygenation of arachidonic acid in human neutrophils: dissociation between lipid remodeling and adhesion.
J. Cell. Physiol.
143:
512-523,
1990[Medline].
19.
Papayianni, A.,
S. Takata,
C. N. Serhan,
and
H. R. Brady.
Counterregulatory actions of leukotrienes and lipoxins on P-selectin expression on human endothelial cell adhesion (Abstract).
J. Am. Soc. Nephrol.
4:
627,
1993.
20.
Parkos, C. A.,
C. G. Cochrane,
M. Schmitt,
and
A. J. Jesaitis.
Regulation of the oxidative response of human granulocytes to chemoattractants. No evidence for stimulated traffic of redox enzymes between endo and plasma membranes.
J. Biol. Chem.
260:
6541-6547,
1985
21.
Raud, J.,
U. Palmertz,
S. E. Dahlen,
and
P. Hedqvist.
Lipoxins inhibit microvascular inflammatory actions of leukotriene B4.
Adv. Exp. Med. Biol.
314:
185-192,
1991[Medline].
22.
Romano, M.,
J. F. Maddox,
and
C. N. Serhan.
Activation of human monocytes and the acute monocytic leukemia cell line (THP-1) by lipoxins involves unique signaling pathways for lipoxin A4 versus lipoxin B4: evidence for differential Ca2+ mobilization.
J. Immunol.
157:
2149-2154,
1996[Abstract].
23.
Scalia, R.,
J. Gefen,
N. A. Petasis,
C. N. Serhan,
and
A. M. Lefer.
Lipoxin A4 stable analogs inhibit leukocyte rolling and adherence in the rat mesenteric microvasculature: role of P-selectin.
Proc. Natl. Acad. Sci. USA
94:
9967-9972,
1997
24.
Seetoo, K. F.,
J. E. Schonhorn,
A. T. Gewirtz,
M. J. Zhou,
M. E. McMenamin,
L. Delva,
and
E. R. Simons.
A cytosolic calcium transient is not necessary for degranulation or oxidative burst in immune complex-stimulated neutrophils.
J. Leukoc. Biol.
62:
329-340,
1997[Abstract].
25.
Serhan, C. N.
Lipoxins and novel aspirin-triggered 15-epi-lipoxins (ATL): a jungle of cell-cell interactions or a therapeutic opportunity?
Prostaglandins
53:
107-137,
1997[Medline].
26.
Serhan, C. N.,
J. F. Maddox,
N. A. Petasis,
I. Akritopoulou-Zanze,
A. Papayianni,
H. R. Brady,
S. P. Colgan,
and
J. L. Madara.
Design of lipoxin A4 stable analogs that block transmigration and adhesion of human neutrophils.
Biochemistry
34:
14609-14615,
1995[Medline].
27.
Sklar, L. A.,
V. M. McNeil,
A. J. Jesaitis,
R. G. Painter,
and
C. G. Cochrane.
A continuous spectroscopic analysis of the kinetics of elastase secretion by neutrophils.
J. Biol. Chem.
257:
5471-5475,
1982
28.
Strohmeier, G. R.,
B. A. Brunkhorst,
K. F. Seetoo,
J. Bernardo,
G. J. Weil,
and
E. R. Simons.
Neutrophil functional responses depend on immune complex valency.
J. Leukoc. Biol.
58:
403-414,
1995[Abstract].
29.
Strohmeier, G. R.,
B. A. Brunkhorst,
K. F. Seetoo,
T. Meshulam,
J. Bernardo,
and
E. R. Simons.
Role of the FcR subclasses Fc
RII and Fc
RIII in the activation of human neutrophils by low and high valency immune complexes.
J. Leukoc. Biol.
58:
415-422,
1995[Abstract].
30.
Takano, T.,
C. B. Clish,
K. Gronert,
N. Petasis,
and
C. N. Serhan.
Neutrophil-mediated changes in vascular permeability are inhibited by topical application of aspirin-triggered 15-epi-lipoxin A4 and novel lipoxin B4 stable analogues.
J. Clin. Invest.
101:
819-826,
1998
31.
Takano, T.,
S. Fiore,
J. F. Maddox,
H. R. Brady,
N. A. Petasis,
and
C. N. Serhan.
Aspirin-triggered 15-epi-lipoxin A4 and LXA4 stable anaolgs are potent inhibitors of acute inflammation: evidence for anti-inflammatory receptors.
J. Exp. Med.
185:
1693-1704,
1997
32.
Van Kessel, K. P.,
and
J. Verhoef.
A view to a kill: cytotoxic mechanisms of human polymorphonuclear leukocytes compared with monocytes and natural killer cells.
Pathobiology
58:
249-264,
1990[Medline].
33.
Varani, J.,
and
P. A. Ward.
Mechanisms of endothelial cell injury in acute inflammation.
Shock
2:
311-319,
1994[Medline].
34.
Weiss, S. J.
Tissue destruction by neutrophils.
N. Engl. J. Med.
320:
365-376,
1989[Medline].
35.
Weissmann, G.,
and
G. A. Rita.
Molecular basis of gouty inflammation: interaction of monosodium urate crystals with lysosomes and liposomes.
Nat. New Biol.
240:
167-172,
1972[Medline].
36.
Weissmann, G.,
R. B. Zurier,
P. J. Spieler,
and
I. M. Goldstein.
Mechanisms of lysosomal enzyme release from leukocytes exposed to immune complexes and other particles.
J. Exp. Med.
134:
149s-165s,
1971[Medline].
37.
Zurrier, R. B.,
S. Hoffstein,
and
G. Weissmann.
Cytochalasin B. Effect on lysozomal enzyme release from human leukocytes.
Proc. Natl. Acad. Sci. USA
70:
844-849,
1973[Abstract].