Article

Cutting Edge: A Critical Role for the G Protein-Coupled Receptor mFPR2 in Airway Inflammation and Immune Responses

Laboratory of Molecular Immunoregulation, Center for Cancer Research, National Cancer Institute at Frederick, Maryland, USA.
The Journal of Immunology (Impact Factor: 4.92). 03/2010; 184(7):3331-5. DOI: 10.4049/jimmunol.0903022
Source: PubMed
ABSTRACT
The formylpeptide receptor-like 1, now officially termed FPR2, in human and its mouse homolog mFPR2 mediate leukocyte migration in response to agonists associated with inflammation and immune responses. To clarify the in vivo role of the receptor, we generated mice deficient in mFPR2. mFPR2(-/-) mice showed markedly reduced severity in OVA/alum-induced allergic airway inflammation. This was associated with diminished recruitment of CD11c(+) dendritic cells into the airway mucosa and secondary lymphoid organs, as well as reduced production of Type 2 cytokines and Igs. We also found that the bronchoalveolar lavage fluid from wild type mice with airway inflammation contained mFPR2 agonist activity. This study reveals a critical role for mFPR2 in the progression of allergic airway inflammation and immune responses.

Full-text

Available from: Yingying Le, May 25, 2015
Cutting Edge: A Critical Role for the G Protein-Coupled
Receptor mFPR2 in Airway Inflammation and Immune
Responses
Keqiang Chen,*
,
Yingying Le,
Ying Liu,* Wanghua Gong,
x
Guoguang Ying,
{
Jian Huang,* Teizo Yoshimura,* Lino Tessarollo,
and Ji Ming Wang*
The formylpeptide receptor-like 1, now officially termed
FPR2, in human andits mousehomologmFPR2mediate
leukocyte migration in response to agonists associated
with inflammation and immune responses. To clarify
the in vivo role of the receptor, we generated mice defi-
cient in mFPR2. mFPR2
2/2
mice showed markedly re-
duced severity in OVA/alum-induced allergic airway
inflammation. This was associated with diminished re-
cruitment of CD11c
+
dendritic cells into the airway
mucosa and secondary lymphoid organs, as well as re-
duced production of Type 2 cytokines and Igs. We also
found that the bronchoalveolar lavage fluid from wild
type mice with airway inflammation contained mFPR2
agonist activity. This study reveals a critical role for
mFPR2 in the progression of allergic airway inflammation
and immune responses. The Journal of Immunology ,
2010, 184: 3331–3335.
T
he formylpeptide receptor (FPR) subfamily of the G
protein-coupled chemoattractant receptors consists of
at least three members in human and all were origi-
nally identified in phagocytic leukocytes (1, 2). The prototype
FPR (FPR1) is a high-affinity receptor for the bacterial pep-
tide formyl-methionyl-leucyl-phenylalanine (fMLF) and me-
diates fMLF-induced phagocyte chemotaxis and activation.
In vivo, FPR is likely to play a role in antimicrobial host
defense, because mice depleted of the FPR counterpart
mFPR1 are more susceptible to infection by Listeria mono-
cytogenes (3). The FPR variant formylpeptide receptor-like 1
(FPRL1 [FPR2]) and its mouse homolog mFPR2 are low
affinity receptors for fMLF, but they recognize a plethora of
agonist peptides associated with inflammation and immune
responses (1, 2). Whereas the interaction of FPR2 (FPRL1) or
mFPR2 with che motactic peptides is believed to contr ibute to
proinflammatory responses, a lipid mediator lipoxin A4
(LXA4) and the N-terminal peptides of annexi n I have been
shown to attenuate leukocyte recruitment at sites of in-
flammation (4, 5), and thus appear to elicit anti-inflammatory
signals through FPR2 (FPRL1) or mFPR2 (6). The third
human FPR subfamily member FPRL2 (FPR3) recognizes
a peptide fragment derived from Heme-binding protein (7),
and unlike FPR1 (mFPR1) and FPR2 (mFPR2) that are
mainly expressed in neutrophils and monocytes with re-
duction in mature dendritic cells (DCs), functional FPR3 is
more selectively expressed in human monocytes and DCs (8).
The identity of mouse counterpart of FPRL2 (FPR3) is not
entirely clear; however, recent studies have shown that
mFPR2 is likely a mouse receptor that is a homolog of both
human FPR2 and FPR3 (9, 10). Thus, mFPR2 might play an
important and com plex role in pathophysiologic conditions.
To clarify the role of mFPR2, and possibly human FPR2 and
FPR3, in disease states, we have generated mFPR2 knocko ut
(mFPR2
2/2
) mice. In this study, we repo rt a critical role for
mFPR2 in the progression of allergic airway inflammation
and type 2 immune responses.
Materials and Methods
Animals
Cre-loxp strategy (11) was used to deplete mouse (m) FPR2 gene (Fpr-rs2).
(Supplemental Fig. 1). mFPR2
2/2
mice were backcrossed for five generations
to wild type (WT) C57BL/6 mice before use in this study. Bone marrow
transplantation was performed according to published methods (12). mFPR2
transgenic mice (mFPR2 Tg) were generated with human b-actin promoter in
FVB background (G. Ying, unpublished observation).
*Laboratory of Molecular Immunoregulation, Cancer and Inflammation Program and
Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute
at Frederick;
x
Science Applications International Corporation-Frederick, Frederick, MD
21702;
School of Agriculture and Biology, Shanghai Jiaotong University;
Institute for
Nutritional Sciences, Shanghai Institute for Biological Sciences, Chinese Academy of
Sciences, Shanghai; and
{
Tianjin Medical University Cancer Research Institute and Hos-
pital, Tianjin, People’s Republic of China
Received for publication September 21, 2009. Accepted for publication January 29,
2010.
This work was supported in part by federal funds from the National Cancer Institute and
National Institutes of Health under Contract No. HHSN261200800001E and by the
Intramural Research Program of the National Cancer Institute and National Institutes of
Health. Y.L. was supported by Grant 2010CB529701 from the National Basic Research
Program of China.
The content of this publication does not necessarily reflect the views or policies of the
U.S. Department of Health and Human Services, nor does the mention of trade names,
commercial products, or organizations imply endorsement by the U.S. Government.
Animal studies were approved by the National Cancer Institute Frederick Animal Care
and Use Committee. Animal care was provided in accordance with the procedures out-
lined in the Guide for Care and Use of Laboratory Animals (National Research Council,
1996, National Academy Press, Washington, DC).
Address correspondence and reprint requests to Ji Ming Wang, National Cancer In-
stitute at Frederick, Building 560, Room 31-76, Frederick, MD 21702. E-mail address:
wangji@mail.nih.gov
The online version of this article contains supplemental material .
Abbreviations used in this paper: BAL, bronchoalveolar lavage; BMC, bone marrow cell;
DC, dendritic cell; Eos, eosinophil; fMLF, formyl-methionyl-leucyl-phenylalanine; FPR,
formylpeptide receptor; FPRL, formylpeptide receptor-like; m, mouse; Lym, lympho-
cyte; MF, macrophages; MLN, mediastinal draining lymph node; PMN, peritoneal
neutrophil; WT, wild type.
www.jimmunol.org/cgi/doi/10.4049/jimmunol.0903022
Page 1
Immunization and the measurement of Th2 cytokines and serum Ig
Immunization of mice with OVA/alum and airway challenge with OVA were
performed as described (13). Control mice received OVA sensitization and
airway challenge with PBS. The mice were euthanized on day 31. Cellularity in
the bronchoalveolar lavage (BAL) liquid was analyzed morphologically, and
cytokines were measured by ELISA (eBioscience, San Diego, CA). Mouse se-
rum total Igs were determined by ELISA. The Igs are expressed as the mean 6
SE of fold increase in serum Igs in immunized mice compared with naive mice.
Histology
Lung tissues fixed in formalin and embedded in paraffin were sectioned (5
mm). Tissue sections were stained with H&E or periodic acid-Schiff. Peri-
bronchial cells and goblet cell hyperplasia were quantified using a five-point
(scores, 0–4) grading system (13). At least three fields of coded lung sections
were examined by pathologists without knowledge of sample identities. Mean
scores were obtained from three to four mice after decoding the samples.
Immunohistochemistry and immunofluorescence
Eosinophils were identified by immunofluorescence using a rat anti-mouse
major basic protein Ab (Dr. J. Lee, Mayo Clinic, Scottsdale, AZ), macro-
phages with rabbit anti-Iba1 (Wako Pure Chemical Industries, Osaka, Japan),
neutrophils with Gr-1 Ab (eBioscience), and B lymphocytes with a rat anti-
mouse CD45R/B220 followed by a biotinylated anti-Ig secondary Ab (BD
Biosciences, San Diego, CA) and Streptavidin-HRP/DAB with hematoxylin
counter staining (Surgipath, Richmond, IL). For immunofluorescence, frozen
sections were stained with hamster anti-mouse CD11c and anti-mouse CD3«
Abs followed by biotinylated anti-Ig Abs (BD) with streptavidin-PE or
streptavidin-FITC and DAPI (Invitrogen). Hamster IgG (eBioscience) was
used as isotype control.
Chemotaxis
Chemotaxis of bone marrow cells (BMCs), neutrophils, and macrophages was
measured as described (14). The results are expressed as the mean 6 SE of the
chemotaxis index, representing the fold increase in the number of migrated
cells in response to chemoattractants over spontaneous cell migration.
RT-PCR
The expression of mFPR2 mRNA in mouse BMCs was examined by RT-PCR
as described (15). b-Actin transcripts were used as a control.
Flow cytometry
The expression of BAL cell surface CD11c was analyzed by flow cytometry
using hamster anti-mouse CD11c Ab and hamster IgG as the isotype control.
Statistical analysis
All experiments were performed at least three times. Representative and re-
producible results are shown. The statistical significance of the difference
between testing and control groups was analyzed by t test of the computer
software Prism (WattMaster Controls, Parkville, MO). Values of p # 0.05
was considered statistically significant.
Results and Discussion
Generation of mFPR2
2/2
mice
We used Cre-loxP strategy and 129/Svj embryonic stem cells to
generate mFPR2
2/2
mice (Supplemental Fig. 1) (11).
Southern bl otting of tail DNA (Supplemental Fig. 1A) and
RT-PCR analys is of BMC total RNA confirmed the disrup-
tion of mFPR2 gene and the absenc e of mFPR2 mRNA in
BMCs (Supplemental Fig. 1B,1C). An mFPR2 specific
chemotactic peptide MMK-1 failed to induce migration of
BMCs, neutrophils, and macrophages from mFPR2
2/2
mice
(Fig. 1A). The expression of mFPR1 mRNA, another mem-
ber of FPR family, was detected in mFPR2
2/2
neutrophils,
and the cells migrated in response to fMLF, an agonist with
relatively higher affinity for mFPR1 compared with mFPR2
(Supplemental Fig. 1C,1D). Thus, mFPR2
2/2
neutrophils
retained the expression of functional mFPR1. However,
compared with WT neutrophils, cells from mFPR2
2/2
mice
showed significantly reduced response to fMLF at low con-
centrations, whi ch presumably interact mainly with mFPR1
(Supplemental Fig. 1D). These results suggest that the func-
tion of mFPR1 in neutrophils from mFPR2
2/2
mice may be
affected, with mechanisms that are yet to be defined. In
general, mFPR2
2/2
mice appeared to develop normally, and
their lifespan in a pathogen-free facility was equivalent to WT
(mFPR2
+/+
) littermates.
Reduced severity of allergic airway inflammation in mFPR2
2/2
mice
Because mFPR2, similar to its human homolog FPR2, has
been implicated in inflammatory an d immune responses (1, 2),
we examined the responses of mFPR2
2/2
mice in OVA/
FIGURE 1. Reduced severity of allergic airway in-
flammation in mFPR2
2/2
mice. A, Migration of
BMCs, Casein-induced peritoneal neutrophils
(PMNs) and thioglycolate-induced peritoneal mac-
rophages (MF) from WT and mFPR2
2/2
mice in
response to the mFPR2 ligand MMK-1 (10
25
M).
The results are expressed as chemotaxis index repre-
senting fold increase in cell response to MMK-1
versus medium control (2). Asterisk indicates sig-
nificantly increased migration shown by BMCs,
PMNs, or Mf; from WT mice (p , 0.01). B, Total
number and differential counts of leukocytes con-
tained in the BAL liquid from mice. Eos, eosinophil;
Lym, lymphocyte. C, Histology showing infiltration
of inflammatory cells in the perivascular and peri-
bronchial regions of the lung tissues (H&E, original
magnification 3200). The severity of lung in-
flammation was scored and the asterisk indicates
significantly reduced severity in mFPR2
2/2
mice
(p , 0.01). Mice used were 8-wk-old females.
3332 CUTTING EDGE: mFPR2 DEFICIENCY REDUCES AIRWAY ALLERGIC RESPONSE
Page 2
alum-induced allergic airway inflammation, which is charac-
terized by leukocyte infiltration into the lung and type 2
immune responses. In OVA/alum-immunized and OVA
aerosol-challenged mFPR2
2/2
mice, the severity of airway
inflammation was markedly reduced, as evidenced by di-
minished exudation of leukocytes in the BAL liquid (Fig. 1B).
There was a reduced infiltration of inflammatory cells in the
lung tissue of OVA/alum-immunized and aerosol-challenged
mFPR2
2/2
mice compared with WT littermates (Fig. 1C;
Supplemental Fig. 2A). The airway epithelial layer of OVA/
alum-immunized and OVA aerosol-challenged mFPR2
2/2
mice contained considerably fewer per iodic acid-Schiff–
positive goblet cells (Supplemental Fig. 2B), suggesting at-
tenuated epithelial proliferation and secretory function.
Reduced type 2 cytokine and Ig production in mFPR2
2/2
mice
Examination of mouse immune responses revealed significantly
lower levels of type 2 cytokines IL-4, IL-5, and IL-13 in the BAL
liquid of OVA-immunized and aerosol-challenged mFPR2
2/2
mice compared with WT littermates (Fig. 2A), indicating di-
minished immune responses in mFPR2
2/2
mice. The de-
ficiency in type 2 cytokine production in mFPR2
2/2
mouse
airway was substantiated by reduced secretion of IL-4, IL-5,
and IL-13 by splenocytes isolated from OVA/alum-immunized
mFPR2
2/2
mice and then stimulated with OVA in vitro
(Supplemental Fig. 3A). Moreover, OVA-immunized and
aerosol-challenged mFPR2
2/2
mice produced lower levels of
type 2 Igs in the sera, with reduction in total IgE as well as
OVA-specific IgE, IgG1, and IgG2b (Fig. 2B). The production
of sec ondary anti-OVA IgG1 and IgG2b in the sera by OVA-
immunized mFPR2
2/2
mice was also reduced (Supplemental
Fig. 3B). However, there were no differences in the production
of type 1 cytokine interferon g between mFPR2
2/2
and WT
littermates after OVA treatment (Supplemental Fig. 3A).
To verify the involvement of mFPR2 in airway inflamma-
tion, we transplanted bone marrow-nucleated cells from WT
mice into mFPR2
2/2
mice. The chimeric mice showed
a considerable restoration of airway inflammation and immune
responses elicited by OVA/alum immunization and OVA
challenge (Supplemental Fig. 4AD), as evidenced by increased
production of Th2 cytokines, exudation of eosinophils in the
BAL liquid, and enhanced serum IgE. Furthermore, in FVB
mice overexpressing human b-actin promoter-controlled
mFPR2 transgene (G. Ying, unpublished observation), a sig-
nificantly increased immature DC migration to the CCR7 li-
gand CCL21/SLC and a markedly increased response to OVA/
alum immunization and airway challenge were observed,
compared with WT FVB mice (Supplemental Fig. 5AC).
These results support the hypothesis that mFPR2 plays an
important role in allergic airway inflammation and type 2
immune responses.
Reduced DC recruitment in OVA-immunized mFPR2
2/2
mice
The impaired innate and type 2 immune responses in
mFPR2
2/2
mice prompted us to investigate DC recruitment
in vivo, which is cru cial for proper immune responses. After
OVA/alum immunization and airway challenge, the re-
cruitment of CD11c
+
DCs into the bronchial epithelial layer
and DC exudation into the BAL liquid were markedly re-
duced in mFPR2
2/2
mice (Fig. 3A,3B). The size of the
mediastinal draining lymph nodes (MLNs; Fig. 3C ) and their
T/B lymphocyte zones (Fig. 3C, 3D) were cons iderably
smaller in mFPR2
2/2
mice with reduced number of CD11c
+
DCs in the T cell zone (Fig. 3E), indicating that the homing
of DCs carrying Ag to the draining lymph nodes was di-
minished. These results demonstrate reduced trafficking of
mFPR2
2/2
DCs into the airway and secondary lymphoid
tissues in OVA-induced allergic airway inflammation.
To clarify the role of mFPR2 in sustain ing DC function, we
pulsed DCs from WT mice in vitro with OVA and transferred
these DCs into mFPR2
2/2
mice via airway. This significantly
restored the responses of mFPR2
2/2
mice to OVA challenge.
In contrast, transfer of OVA-pulsed mFPR2
2/2
DCs did not
increase the responses of WT mice (Supplemental Fig. 6).
Thus, mFPR2 is involved in DC-mediated adaptive immune
responses.
Increased mFPR2 agonist activity contained in the BAL of
OVA/alum-immunized mice
A number of agonists for mFPR2 and its human counterpart
FPR2 have been identified and most of these agonists are
associated with inflammation and immune responses (2). We
therefore asked whether mFPR2 agonist activity is produced
in the airway in allergic inflammatory responses. We found
that the BAL liquid from immunized WT mice contained
high levels of mFPR2 agonist activity, because the BAL liquid
exhibited a much more potent chemotactic activity for human
embryonic epithelial cells (293) transfected to express mFPR2
(a gift of Dr. P. Murphy, National Institute of Allergy and
Infectious Diseases, National Institutes of Health, Bethesda,
MD) than for the parental 293 cells (Fig. 3F). mFPR2/293
FIGURE 2. Reduced type 2 cytokine and Ig production in mFPR2
2/2
mice.
A, The levels of type 2 cytokines IL-4, IL-5, and IL-13 measured in the BAL
liquid of mice. Asterisk indicates significantly lower levels of cytokines in the
BAL liquid of mFPR2
2/2
mice compared with WT littermates (p , 0.01). B,
The levels of total IgE, OVA-specific IgE (OVA-IgE), IgG1 (OVA-IgG1), and
IgG2b (OVA-IgG2b) detected in mouse sera. Asterisk indicates significantly
reduced serum Ig levels in OVA-immunized and airway-challenged mFPR2
2/2
mice (p , 0.01). All mice used were 8-wk-old female littermates.
The Journal of Immunology 3333
Page 3
cells pretreated with a defined mFPR2 ligand MMK-1
showed reduced migration in response to the BAL liquid. In
contrast, the migration of parental 293 cells was not attenu-
ated by MMK-1 (Supplemental Fig. 7), indicating that the
BAL liquid from immunized mice indeed contains mFPR2
agonists. Preliminary characterization of the nature of mFPR2
agonists in the BAL liquid suggests that the agonists are of
polypeptide in nature of ,3000 Da. Additional experiments
are required to clarify th e identity of the agonists.
Asthmaisatype2inflammatoryairwaydiseasecharacterized by
airway eosinophilia, increased mucus production by goblet cells,
and structural remodeling of the airway wall. DCs are crucial for
the initiation and progression of allergic airway inflammation
(16). In such mouse asthmatic models, DCs take up Ag in the
bronchial alveolar tissue (17) and enter the T cell zone of MLNs,
where they become functionally mature to induceproliferation of
naive T cells (18). In our study, mFPR2
2/2
mice exhibited
markedly reduced severity of OVA-induced allergic airway in-
flammation accompanied by reduction in type 2 cytokine and Ab
responses. These defects were associated with diminished re-
cruitment of mDCs in the airway draining lymph nodes. Thus,
reduction in DC homing might be responsible for attenuated
airway inflammation seen in mFPR2
2/2
mice. In addition to
reduced allergic airway inflammation, mFPR2
2/2
mice also
exhibited diminished myeloid cell exudation into peritoneal
cavity in response to thioglycollate and casein (data not shown),
suggesting decreased inflammatory responses in another location
than the airway in mFPR2
2/2
mice. Moreover, in an LPS/OVA-
induced Th1 airway inflammation model (19), mFPR2
2/2
mice
also showed diminished neutrophil exudation in the BAL liquid
and infiltration in the lung (Supplemental Fig. 8A–C). Fur-
thermore, in a model of LPS/OVA-induction of Th1 cytokines
(20), mFPR2
2/2
mice showed reduced production of IFN-g
and IL-2 (Supplemental Fig. 8D). Thus, mFPR2 might play
aroleinbothTh1andTh2responses.
FPR family members are differentially expressed in human
and mouse myeloid cells. The human mFPR2 counterpart
FPR2 is downregulated during the process of myeloid DC
maturation (8, 21), whereas another FPR variant, FPR3, was
persistently expressed (8). In mouse, mFPR2 has been shown
to function as both FPR2 and FPR3 (9, 10) and is expr essed
in mouse myeloid DCs (K. Chen, unpublished observation).
In fact, mFPR2 in mouse DCs was essential in mediating the
signaling pathways elicited by a lipid agonist LXA4 that at-
tenuates the function of the chemokine receptor CCR5, re-
sulting in reduced lethal production of IL-12 in Toxoplasma
gondii infection (15). In addition, injection of stable LXA4
analogs in T. gondii-infected mice reduced DC accumulation
in the spleen (15). These observations suggest that manipu-
lating mFPR2 function alters DC trafficking and subsequent
host immune responses.
It is intriguing that activation of mFPR2 or human FPR2
has been shown to elicit both proinflammatory and anti-in-
flammatory signals depending on the nature of the ligands (2).
FIGURE 3. Reduction of DC recruitment in OVA-immunized mFPR2
2/2
mice. A, The recruitment of CD11c
+
DCs to the airway mucosal region of OVA-
sensitized and airway-challenged mice. CD11c immunofluorescence is shown in red; nuclei are shown by DAPI in blue (original magnification 3400). CD11c
immunohistochemistry is shown in brown. B, Reduction of CD11c
+
DCs in the BAL liquid of OVA sensitized and airway challenged mFPR2
2/2
mice. Left
panels, FACS analysis of the percentage of CD11c
+
DCs in the BAL liquid. Upper right panels, CD11c immunostaining in the BAL liquid shown in red; nuclei
shown by DAPI in blue (original magnification 3400). Lower right panel, Numbers of CD11c
+
DCs in the BAL liquid. Asterisk indicates significantly lower
number of DCs in the BAL liquid of mFPR2
2/2
mice. C, The size and histology of the MLNs (original magnification 335; H&E, original magnification 3200)
from OVA-sensitized and airway-challenged mice. T zone, T cell zone. D, CD45R/B220
+
B cells (brown) in MLNs (original magnification 3400). E, CD11c
+
cells in MLNs (original magnification 3400) detected with red fluorescence. T cells were in green. Nuclei were stained with DAPI in blue. Insets, An amplified
CD11c
+
cell area among T cells in the MLN of WT mice (original magnification 31000). F, Chemotaxis of mFPR2-transfected 293 cells and parental 293 cells
in response to BAL liquid from immunized WT mice. *Significantly increased chemotaxis of mFPR2-transfected 293 cells (mFPR2/293) compared with the
response of parental 293 cells (293).
3334 CUTTING EDGE: mFPR2 DEFICIENCY REDUCES AIRWAY ALLERGIC RESPONSE
Page 4
Whereas our present study clearly demonstrated mFPR2 to be
a proinflammatory immune response mediator, results ob-
tained using anti-inflammatory mFPR2 ligands have shown
protection of the host in some disease models. For example,
LXA4 and annexin I peptides significantly reduced leukocyte
infiltration of airway tissues and type 2 responses in the airway
inflammation model (5). Clinically, the development of ex-
ercise-induced bronchoconstriction in asthmatic children was
linked to reduced biosynthesis of endogenous LXA4 (22).
However, it remains unclear how a single receptor such as
mFPR2 is capable of mediating opposing signaling events
elicited by different ligands. One possibility as suggested is
that anti-inflammatory ligands such as LXA4 may bind to
unique epitopes in mFPR2 (4). Alternatively, these ligands
may exhibit the property of partial agonists that desensitize,
and thus dampen, the proinflammatory function of mFPR2
or human FPR2 (1). In this context, although the chemical
nature of the mFPR2 agonist activity contained the in-
flammatory BAL liquid remain s to be elucidated, our present
study has revealed a nonredundant role for mFPR2 in the
development of innate and adaptive immune responses rep-
resented by allergic airway inflammation.
Acknowledgments
We thank Dr. J.J. Oppenheim, Dr. O.M.Z. Howard, and Dr. G. Trinchieri for
critically reviewing the manuscript; C. Lamb for secretarial assistance; R. Mat-
thai and K. Noer of Center for Cancer Research (National Cancer Institute at
Frederick) for flow cytometric analysis; and Steve Stull for bone marrow trans-
plantation.
Disclosures
The authors have no financial conflicts of interest.
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    • "However, the model of chemokine GPCRs alone in DC trafficking in allergic airway inflammation is inadequate and has recently had to incorporate one of the FPRs, Fpr2, as an indispensible link in the chain of events. This has been shown by greatly reduced severity of OVA-elicited allergic airway inflammation in Fpr2-deficient mice [77], in association with a marked reduction of infiltration of Ly6C + monocyte-derived inflammatory DCs in the small airways and a subsequent lack of DCs in the T cell zones in the draining mediastinal lymph nodes. These observations raise the possibility that Fpr2 might be an active participant in the sequential chemoattractant signal relay required for the trafficking of Ly6C + monocyte-derived inflammatory DCs in the inflamed lung. "
    [Show abstract] [Hide abstract] ABSTRACT: Formyl-peptide receptors are a family of 7 transmembrane domain, Gi-protein-coupled receptors that possess multiple functions in many pathophysiologic processes because of their expression in a variety of cell types and their capacity to interact with a variety of structurally diverse, chemotactic ligands. Accumulating evidence demonstrates that formyl-peptide receptors are critical mediators of myeloid cell trafficking in the sequential chemotaxis signal relays in microbial infection, inflammation, and immune responses. Formyl-peptide receptors are also involved in the development and progression of cancer. In addition, one of the formyl-peptide receptor family members, Fpr2, is expressed by normal mouse-colon epithelial cells, mediates cell responses to microbial chemotactic agonists, participates in mucosal development and repair, and protects against inflammation-associated tumorigenesis. These novel discoveries greatly expanded the current understanding of the role of formyl-peptide receptors in host defense and as potential molecular targets for the development of therapeutics.
    Full-text · Article · Dec 2015 · Journal of leukocyte biology
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    • "Responses to both full length ANX-A1 and its peptides, across macrophage ERK1/2 phosphorylation in vitro as well as leukocyte migration in air-pouch and zymosan peritonitis models of inflammation, were also reduced ( Dalli et al., 2013 ). In contrast, a reduced severity of ovalbumininduced airway inflammation was observed (in direct contrast to the mFpr2/3 −/− mouse above) (Chen et al., 2010). More recently, the same investigators observed that the inflammatory responses in the early stages of experimental colitis were both accelerated and prolonged in the mFpr2 −/− mouse, with increased susceptibility to subsequent lethality compared to wild type mice (Chen et al., 2013 ). "
    [Show abstract] [Hide abstract] ABSTRACT: Myocardial infarction (MI) and its resultant heart failure remains a major cause of death in the world. The current treatments for patients with MI are revascularization with thrombolytic agents or interventional procedures. These treatments have focused on restoring blood flow to the ischemic tissue to prevent tissue necrosis and preserve organ function. The restoration of blood flow after a period of ischemia, however, may elicit further myocardial damage, called reperfusion injury. Pharmacological interventions, such as antioxidant and Ca(2+) channel blockers, have shown premises in experimental settings; however, clinical studies have shown limited success. Thus, there is a need for the development of novel therapies to treat reperfusion injury. The therapeutic potential of glucocorticoid-regulated anti-inflammatory mediator annexin-A1 (ANX-A1) has recently been recognized in a range of systemic inflammatory disorders. ANX-A1 binds to and activates the family of formyl peptide receptors (G protein-coupled receptor family) to inhibit neutrophil activation, migration and infiltration. Until recently, studies on the cardioprotective actions of ANX-A1 and its peptide mimetics (Ac2-26, CGEN-855A) have largely focused on its anti-inflammatory effects as a mechanism of preserving myocardial viability following I-R injury. Our laboratory provided the first evidence of the direct protective action of ANX-A1 on myocardium, independent of inflammatory cells in vitro. We now review the potential for ANX-A1 based therapeutics to be seen as a "triple shield" therapy against myocardial I-R injury, limiting neutrophil infiltration and preserving both cardiomyocyte viability and contractile function. This novel therapy may thus represent a valuable clinical approach to improve outcome after MI. Copyright © 2014. Published by Elsevier Inc.
    Full-text · Article · Nov 2014 · Pharmacology [?] Therapeutics
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    • "Furthermore, FPRs regulate the inflammatory reactions in neutrophils by modulating signaling through many other receptors in a process termed receptor cross-talk21222324. The role of FPRs in regulation of inflammation is highlighted by their suggested involvement in both systemic [25] and local262728 inflammatory responses. Thus, recently various groups have suggested FPRs as therapeutic targets in inflammatory and infectious diseases [29,30] and several selective FPR agonists and inhibitors have been discovered: the cyclic undecapeptide cyclosporine H (CsH) is the most potent selective FPR1 inhibitor [31,32] , and rhodamine Blabeled PIP 2 -binding peptide of gelsolin (PBP10) is the most potent selective FPR2 inhibitor known to date [33,34]. "
    [Show abstract] [Hide abstract] ABSTRACT: Immunomodulatory host defense peptides (HDPs) are considered to be lead compounds for novel anti-sepsis and anti-inflammatory agents. However, development of drugs based on HDPs has been hampered by problems with toxicity and low bioavailability due to in vivo proteolysis. Here, a subclass of proteolytically stable HDP mimics consisting of lipidated α-peptide/β-peptoid oligomers was investigated for their effect on neutrophil function. The most promising compound, Pam-(Lys-βNSpe)6-NH2, was shown to inhibit formyl peptide receptor 2 (FPR2) agonist-induced neutrophil granule mobilization and release of reactive oxygen species. The potency of Pam-(Lys-βNSpe)6-NH2 was comparable to that of PBP10, the most potent FPR2-selective inhibitor known. The immunomodulatory effects of structural analogues of Pam-(Lys-βNSpe)6-NH2 emphasized the importance of both the lipid and peptidomimetic parts. By using imaging flow cytometry in primary neutrophils and FPR-transfected cell lines we found that a fluorescently labelled analogue of Pam-(Lys-βNSpe)6-NH2 interacted selectively with FPR2. Furthermore the interaction between Pam-(Lys-βNSpe)6-NH2 and FPR2 was found to prevent binding of the FPR2-specific activating peptide agonist Cy5-WKYMWM, while the binding of a FPR1-selective agonist was not inhibited. To our knowledge, Pam-(Lys-βNSpe)6-NH2 is the first HDP mimic found to inhibit activation of human neutrophils via direct interaction with FPR2. Hence, we consider Pam-(Lys-βNSpe)6-NH2 to be a convenient tool in the further dissection of the role of FPR2 in inflammation and homeostasis as well as for investigation of the importance of neutrophil stimulation in anti-infective therapy involving HDPs. Copyright © 2014. Published by Elsevier Inc.
    Full-text · Article · Nov 2014 · Biochemical Pharmacology
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