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*
Amgen Institute, Toronto, Ontario, Canada;
Department of Inflammation, Amgen Boulder, Boulder, CO 80301;
Ontario Cancer Institute, Departments of Medical Biophysics and Immunology, University of Toronto, Toronto, Ontario, Canada;
§
Amgen, Thousand Oaks, CA 91320; and
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Department of Pathology, Cornell University Medical College, New York, NY 10021
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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CD31 is a 130-kDa glycoprotein consisting of a single chain molecule of
six Ig-like extracellular domains, a transmembrane portion, and a
cytoplasmic tail 4, 5 . CD31 is concentrated at cell-cell borders of
EC, and is expressed at a lower level diffusely on the surfaces of
platelets and most leukocytes 6, 7 . It has been demonstrated that
CD31 can support cell-cell adhesion via either homophilic 5, 8, 9, 10 or
heterophilic interactions 11 . Proposed heterophilic ligands include
the integrin 
vß3 12, 13 , and as yet
uncharacterized molecules found on activated T cells 14 and
parasitized RBC 15 . These observations make CD31 an ideal candidate
for mediating leukocyte migration across EC, and indeed CD31 has been
demonstrated to play a role in the TEM of PMN, monocytes, and NK
cells in both in vitro and in vivomodels 3, 16 .
The processes of vasculogenesis and angiogenesis also involve cell-cell adhesive interactions, in the form of endothelial cell interactions both with each other and extracellular matrix components 17 . CD31 is expressed on all continuous EC linings in vivo 18 , and has been shown to play an important role in the initiation of EC contact, EC tube formation, and in vivo murine angiogenesis 19, 20 . The tyrosine phosphorylation state of CD31 also correlates with angioblast development in the murine conceptus 21 , implying involvement of CD31 in the development of blood islands and vessels.
In addition to direct cell-cell adhesion, it would appear that engagement of CD31 facilitates outside-in signaling. A number of studies have demonstrated a CD31-dependent increase in the integrin-mediated adhesion of a variety of leukocytes, including monocytes, PMN, NK cells, lymphokine-activated killer cells, CD34+ hemopoietic progenitor cells, and T lymphocytes 22, 23, 24, 25, 26, 27, 28 . A potential role for CD31 in platelet function has also been proposed. Distinct signaling complexes involving CD31 were formed during human platelet aggregation 29 , and CD31 has been proposed as a costimulatory agonist receptor capable of modulating integrin function in human platelets during adhesion and aggregation 30 . In vivo, treatment with anti-CD31 Abs delayed platelet adhesion/aggregation in the mouse 31, 32 .
In this study, we show that CD31KO mice are viable and undergo normal vascular development, suggesting that CD31 is not critical for vasculogenesis. Although electron-microscopic examination of mesenteric postcapillary venules revealed an accumulation of PMN at the perivascular BM in CD31KO mice, similar numbers of leukocytes migrate into the peritoneal cavity in both wild-type (WT) and CD31KO mice after challenge with IL-1ß or thioglycolate (TG). We observed no defect in migration of PMN in vitro that could account for these disparate findings. No defect in T lymphocyte homing to lymphoid organs, or in the mounting of a cutaneous hypersensitivity response, is evident in CD31KO mice. No dependence on CD31-mediated adhesion in ADP-stimulated platelet-platelet in vitro aggregation was found. In conclusion, the creation of a CD31-deficient mouse confirms that CD31 is involved in TEM of neutrophils at the level of passage across the BM. However, PECAM is not essential for the processes of leukocyte migration and vascular development, implying the existence of compensatory mechanisms in the mouse.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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A 129/J mouse genomic library was screened with a CD31 cDNA probe, and a phage clone containing exons 6–8 was isolated. A targeting vector was designed to disrupt exon 7 by inserting a pGK1neo resistance expression cassette in reverse orientation of CD31 transcription. The targeting vector (20 µg) was linearized with KpnI and electroporated into 5 x 106 E14K embryonic stem (ES) cells (derived from 129/Ola mice) maintained on a layer of mitomycin C-treated embryonic fibroblasts in DMEM, supplemented with leukemia-inhibitory factor, 15% FCS, L-glutamine, and 2-ME. The electroporated cells were subsequently cultured in 300 µg/ml G418 for 8 days. Homologous recombinants were identified by PCR using the following primers: 5'-AGG TAA GGA CCT ACA GGT GTG TTC-3' plus 3'-CTT CCT CGT GCT TTA CGG TAT C-5', yielding a mutant band of 1 kb. PCR conditions were as follows: 1 min at 94°C, 1 min at 63°C, and 1 min at 72°C for 30 cycles. Colonies positive for PCR were genotyped by Southern blotting analysis using a PCR-amplified flanking probe and a neomycin-specific probe (data not shown).
Chimeric mice were produced by microinjection of targeted ES cells into 3.5-day C57BL/6J blastocysts that were subsequently transferred to CD1 pseudopregnant foster mothers. Chimeric males were mated with C57BL/6J females. Germline transmission of the mutant allele was verified by Southern blotting analysis of tail DNA from F1 offspring with agouti coat color. Both of the two targeted ES clones contributed to the germline transmission of the mutation. F2 offspring from heterozygous intercrosses were genotyped by Southern blotting analysis and analyzed by flow-cytometric analysis of surface expression of CD31 on the surface of leukocytes. Mutant mice derived from the two targeted ES cell clones showed the same phenotype.
Flow-cytometric analysis of leukocytes
PBL and leukocytes obtained from organs were preincubated with anti-FcR (anti-murine CD16/CD32, Fc block; PharMingen, San Diego, CA) and subsequently stained with mAbs in 100 µl of PBS (2 mM EDTA/5% BSA and 0.1% azide) for 30 min at 4°C. Cells were analyzed for single-, double-, and triple-color immunofluorescence using a FACScalibur flow cytometer (Becton Dickinson, San Jose, CA). mAbs used were MEC 13.3 and 390 (anti-CD31), M1/70 (anti-CD11b, Mac-1), RB6-8C5 (anti-Ly-6G, GR-1, and 145-2C11 (anti-CD3) (all mAbs from PharMingen, San Diego, CA).
PBL, RBC, and platelet counts
Circulating cell numbers were determined on a Sysmex F-800 semiautomated hemologic analyzer and by direct counting using a hemocytometer. Additional determinations of blood composition were performed by FACS analysis of blood.
Preparation of whole embryo sections
Immunohistochemistry for CD31 (anti-CD31, clone MEC13.3, 1:100; PharMingen) was performed on sectioned material, as previously described 33 .
IL-1ß- and TG-induced peritonitis model
Acute peritonitis was induced by i.p. injection of 10 ng of murine rIL-1ß (Genzyme, Cambridge, MA) in 0.5 ml PBS or by 1.5 ml of 4% TG broth (Difco, Detroit, MI). At various time points, mice were sacrificed by CO2 inhalation, and peritoneal exudate cells were harvested by lavage with 7 ml of PBS containing 2 mM EDTA and 50 U/ml heparin. Cells recovered were washed three times in Ca2+/Mg2+-free PBS and counted using a hemocytometer. Cytospins were prepared to perform differential counts, and infiltrating cells were subsequently identified as being either PMN, monocytes, macrophages, or lymphocytes.
Mouse air pouch model
Air pouches were formed by the dorsal s.c. injection of 6 ml
sterile air on day 0 and 5 ml on day 3. On day 6, 10 ng murine IL-1ß
(Genzyme), approximately 108 Formalin-inactivated
Staphylococcus aureus (American Type Culture Collection,
Manassas, VA; 25923), or 100 ng murine macrophage inflammatory
protein-1 (Genzyme) was injected locally into the air pouch
in 1.5 ml vehicle (0.5% carboxymethyl cellulose, CMC, medium
viscosity; Sigma, St Louis, MO). At various time points, air pouches
were lavaged with 2 ml PBS containing 2 mM EDTA and 50 U/ml heparin.
Collected cells were washed three times in
Ca2+/Mg2+-free PBS and counted, and cytospins
were performed.
Electron-microscopic examination of mesenteric postcapillary venules
Portions of mesentery containing blood vessels were dissected
out of the original sample (4 h postinjection of 10 ng IL-1ß or 1.5
ml TG), immersed overnight in fixation buffer (2.5% glutaraldehyde in
0.05 M sodium cacodylate buffer, pH 7.2), postfixed in 1% aqueous
osmium tetroxide, rinsed in water, dehydrated in ethanol, and embedded
in epoxy resin. One-micrometer sections were initially cut, stained
with toluidine blue, and screened by light microscopy for the presence
of postcapillary venules. Samples containing postcapillary venules were
ultra-thin sectioned, and the resultant sections were collected onto
both mesh grids and formvar-coated keyhole grids. Sections were
contrast enhanced with uranyl acetate and lead citrate before
examination under a CM120 transmission electron microscope (Philips
Electron Optics, Eindhoven, The Netherlands). Five mesenteric portions
were analyzed from three WT, and five from three CD31KO mice, allowing
the scanning of 4.1 mm of vessel in the WT and 4.12 mm in the CD31KO.
The postcapillary venules studied in both WT and CD31KO exhibited the
same number of EC, with approximately the same thickness of basal
lamina and number of pericytes. Leukocytes within postcapillary venules
were included for analysis only if they showed both nucleus and
cytoplasm in the plane of the section and if they were considered to be
potentially transmigrating, i.e., they were either proximal to the
endothelium (within one cell diameter or in contact with endothelium),
or trapped between the endothelium and the BM. Migrating leukocytes
were identified either as PMN or monocytes based on their morphology.
Counts of PMN and monocytes were compared using the Student’s
t test or, when the distribution was skewed, the Wilcoxon’s
rank sum test. The distribution of leukocytes in the proximal and
trapped position was compared between the CD31KO and WT mice using the
2 test with continuity correction factor.
Contact hypersensitivity model
Mice were sensitized on days 1 and 2 with oxazalone (Sigma; freshly dissolved in a 4:1 acetone/sesame oil mixture) on the shaved abdomen (50 µl) and right front paw (5 µl). On day 5, mice were challenged with 1% oxazalone in the same solvent mixture. For challenge, 10 µl of oxazalone was applied topically to both dorsal and ventral surfaces of the right ear, while the left ear was treated with vehicle alone. After 24 h, both ears were measured with a force calibrated digital thickness gauge, and data were expressed as percentage of increase in ear thickness between right and left ears.
Analysis of lymphocyte trafficking
Lymphocytes (5 x 107/ml) were taken from mesenteric and peripheral lymph nodes and labeled with 100 µCi of 51Cr in PBS. Labeled cells were centrifuged over a FCS gradient to remove dead cells and debris, washed three times, and resuspended at 3 x 106/ml in PBS. A total of 100 µl labeled cells was injected i.v. via the tail vein, while an uninjected fraction of labeled cells was kept for determination of total counts injected. At 2- or 24-h postinjection, mice were sacrificed and lymphoid organs were removed for determination of 51Cr activity using a gamma counter.
In vitro analysis of bEND3 cell transmigration
Transwell membranes (5 µm, 24 mm; Costar, Cambridge, MA) were coated with 1% gelatin in PBS. After 30 min, the gelatin was removed and 2 x 105 bEND.3 cells (kindly provided by Dr. Werner Risau, Max Planck Institute for Physiology and Clinical Research, Bad Nauheim, Germany) were added to each membrane and cultured for 3 days, after which the membranes were washed twice in adhesion media (RPMI containing 10% FCS). A total of 500 µl adhesion media containing 500 ng/ml human rIL-8 (Genzyme) was added to the lower wells, and 2 x 105 PMN was added to the top well, respectively.
As a source of mouse PMN, mice were challenged i.p. with 1.5 ml of 4% TG and cells were collected 4 h later. There was no difference in the percentage of PMN between WT and CD31KO in these samples, as assessed by differential counts. PMN were then examined for their ability to migrate across bEND3 monolayers in response to a chemoattractant gradient of human rIL-8. Migration was allowed to proceed up to 4 h, after which membranes were removed and cells in the lower wells were fixed for 20 min with 1 ml PBS containing 1% paraformaldehyde. Fixed cells were enumerated using a fixed flow rate over a period of 1 min on a FACScan flow cytometer gated to eliminate cell debris.
Analysis of platelet function
Platelet aggregation in response to ADP was measured in vitro using an optical platelet aggregometer. Approximately 1 ml heparinized blood (final concentration 5 U/ml heparin) was collected from the inferior vena cava of wild-type, heterozygous, or homozygous mutant mice; blood from five mice of each genotype was pooled for each experiment. Platelet-rich plasma (PRP) was prepared by centrifugation of whole blood at 350 x g for 15 min, and platelet counts in the aspirated PRP were conducted. Platelet-poor plasma (PPP) was prepared by centrifugation of the remaining pellet at 2000 x g for 15 min. Platelet number was adjusted to 1 x 105 platelets/ml PRP using autologous PPP as diluent. Aggregometry was conducted in a Chronolog lumi-aggregometer using 250 µl PRP added to prewarmed siliconized glass cuvettes continuously stirred at 100 rpm. Increases in light transmission were recorded on an analogue chart recorder and converted to percentage of platelet aggregation, using PRP as a reference for 0% and PPP as a reference for 100% platelet aggregation.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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CD31 null mice were generated using homologous recombination in
E14K embryonic stem (ES) cells. The targeting vector consisted of a
neomycin resistance gene inserted into exon 7 of the CD31 gene (Fig. 1
). Of nine ES cell clones selected on
the basis of G418 resistance and Southern blot analysis (data not
shown), two were injected into blastocysts. Both gave germline
transmission and produced two independent CD31-deficient mouse lines
that were identical phenotypically. Interbreeding of heterozygous
CD31-deficient mice generated WT, heterozygous, and homozygous
offspring in the correct Mendelian ratios, and interbreeding of
homozygous CD31KO mice up to 6 mo in age produced viable offspring in
normal numbers. These results indicate that PECAM is required neither
for embryogenesis, fetal maturation, nor fertility in the mouse.
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A, PBL of WT mice
constitutively express detectable levels of CD31, as assessed by
surface staining using mAb MEC13.3, while CD31KO mice display only
background fluorescence. Interestingly, analysis of CD31 heterozygous
mice (CD31+/-) revealed an approximately 50% decrease in
cell surface staining for CD31 compared with WT mice, indicating that
loss of one functional allele reduces CD31 protein synthesis and
subsequent cell surface expression. CD31-specific staining was also
undetectable on leukocytes obtained from spleen, lymph nodes, and
thymus of CD31KO mice. An identical pattern of cell surface staining
was obtained using mAb 390.
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C), compared with that of WT embryos
(Fig. 2B), confirming that mutation of the CD31 gene results
in the absence of cell surface expression on both vascular endothelium
and circulating leukocytes. PBL, RBC, and platelet counts in CD31KO mice
No significant difference in the number of PBL was apparent
between WT and CD31KO mice, either before, or after, injection of TG
i.p. (Table I). TG challenge resulted in
an overall reduction in PBL numbers of approximately 50% in both WT
and CD31KO mice, most likely due to increased interaction of cells with
vasculature, and subsequent migration into the inflamed tissues. This
reduction in PBL number can largely be accounted for by a decrease in
circulating lymphocytes, the absolute number of which was similar in WT
and CD31KO mice, both before, and after, challenge with TG. A profound
neutrophilia occurred in both WT and CD31KO mice 4 h after
injection of TG (and IL-1ß, data not shown), probably due to an
increased release of PMN from bone marrow and a marginated pool of
leukocytes. Although naive CD31KO mice had significantly fewer
circulating PMN than their WT counterparts, circulating PMN numbers
increased 2.5-fold after TG in both WT and CD31KO mice. Circulating
monocyte numbers declined slightly, and to a similar extent, in both WT
and CD31KO mice. Thus, the mobilization of PMN after inflammatory
challenge appears to be normal in CD31KO mice. RBC and platelet numbers
in CD31KO mice were normal, as was the cellularity and composition of
thymus, spleen, and lymph nodes (Table II).
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To investigate the role of CD31 in TEM, we examined leukocyte
influx into acute inflammatory sites using three in vivo models:
IL-1ß- or TG-induced peritonitis, and the mouse air pouch model.
Injection of IL-1ß or TG into the peritoneal cavity of the mouse
results in a rapid influx of inflammatory cells into the area that, at
4 h, consists mainly of PMN. Contrary to previously reported
results in which PMN transendothelial migration into sites of acute
inflammation in wild-type mice is clearly blocked by anti-CD31 Ab
34, 35, 36, 37 , influx of PMN into the peritoneal cavities of CD31KO mice
injected with 10 ng IL-1ß or 1.5 ml TG was identical to that observed
in wild-type mice, as assessed by the number of leukocytes in lavage
fluid at 4 h postinjection (Table III). The proportion of PMN in these
samples was approximately equivalent in WT and CD31KO mice
(approximately 90%) after IL-1 (data not shown) or TG (Table III).
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, total cell numbers
obtained 24 h after TG were identical in WT and CD31KO mice.
Differential counts on recovered cells revealed no significant
differences in the cell populations recovered: PMN and mononuclear
cells recovered from both WT and CD31KO were present at approximately
equivalent percentages of total cells, although as at 4 h, CD31KO
mice exhibited a small increase in the percentage of PMN recovered.
The role of CD31 in migration across an alternative site of
vasculature, the mouse air pouch, was also examined. Proinflammatory
stimuli or chemoattractants can be introduced locally into the air
pouch, and subsequent cell migration can be assessed by lavage of the
resulting infiltrate 38 . Injection of IL-1ß 39 or nonviable
(Formalin-inactivated) Gram-positive bacteria, S. aureus
40 , resulted in an influx of largely PMN into the air pouch cavity at
4 h, and of PMN, macrophages, and monocytes after 24 h.
CD31KO mice again displayed no defect in leukocyte migration in
response to either IL-1ß or S. aureus (Table III). The
relative influx of the various cell types, as assessed by differential
counts of cells recovered from the air pouch, was also essentially the
same in WT and CD31KO mice (Table III). In addition, no significant
difference was apparent in monocyte, macrophage, PMN, or lymphocyte
migration between WT and CD31KO mice in response to to macrophage
inflammatory protein-1 41 , demonstrating that C-C
chemokine-mediated TEM was normal in the absence of CD31 (data not
shown).
Interestingly, despite the recovery of equivalent numbers of leukocytes
from the peritoneal cavities of WT and CD31KO mice injected i.p. with
10 ng IL-1ß, electron-microscopic examination of the mesenteric
postcapillary venules of these mice revealed trapping of PMN at the
perivascular BM in CD31KO mice (Fig. 3,
A and B). As shown in Table IV, in CD31KO mice there was a
significant decrease in the number of PMN that were situated proximally
to the endothelium within one cell diameter, or in contact with the
endothelium, and a corresponding significant increase in the number of
PMN found between the EC and BM (trapped cells). This phenomenon
appears specific to PMN in the case of IL-1ß stimulation, the number
of monocytes proximal to endothelium or trapped at the BM being
equivalent in WT and CD31KO mice. The accumulation of leukocytes at the
BM of CD31KO mice was also clearly apparent after i.p. injection of TG
(Fig. 3, E and F), with large numbers of
leukocytes visible between EC and the BM in all five CD31KO mice
observed. None of the five WT mice tested displayed this phenomenon.
Thus, CD31 is required for the normal migration of PMN, but apparently
not monocytes, across the BM at an early time point after an
inflammatory stimulus.
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Despite slightly lower numbers of circulating PMN after TG
injection in CD31KO mice (Table I), and the observed accumulation of
PMN at the BM, similar numbers of PMN were recovered from peritoneal
lavage 4 h post-TG in both WT and CD31KO (Table III). A possible
explanation for this phenomenon could be that CD31KO PMN have a higher
rate of migration than their WT counterparts. Augmented rate of
migration across EC could also conceivably manifest itself as an
accumulation of PMN at the BM. In an attempt to elucidate the mechanism
underlying the accumulation of PMN at the BM in CD31KO mice, PMN
migration in vitro across bEND3 cells in response to IL-8 was
investigated. As shown in Fig. 4,
CD31-deficient PMN migrate across bEND3 cells to the same extent, and
with the same kinetics, as WT PMN, suggesting that an increased rate of
TEM is not an explanation for our findings.
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Given the expression of CD31 on approximately 50% of human
lymphocytes 7 and on almost all circulating lymphocytes in the
peripheral blood of mice (Fig. 2A), it was of interest to
assess the ability of T lymphocytes to undergo transendothelial
migration in the absence of CD31. Two in vivo models were used: 1)
oxazalone-mediated contact sensitivity, which in the mouse involves
both mononuclear and PMN infiltration, and 2) the homing of labeled
donor lymphocytes to lymphoid organs of recipient mice.
Leukocyte influx after oxazalone sensitization and subsequent challenge
was assessed in WT, CD31KO, and LFA-1-deficient 42 mice. After
topical oxazalone treatment, ear thickness in WT mice was increased
postchallenge by approximately 100% over that of the control,
vehicle-treated ear (Fig. 5A).
As a positive control, ear swelling was not apparent in LFA-1-deficient
mice, demonstrating that CD11a-mediated cell-cell adhesion and/or
activation is essential for the mounting of a normal cutaneous
hypersensitivity response. In contrast, on challenge with oxazalone,
CD31KO mice exhibited an identical response to that of WT mice,
indicating no role for CD31 either in the priming or effector phase of
the cutaneous hypersensitivity response.
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B)
and 24 h (Fig. 5C) postinjection of labeled donor WT
cells, and clearly shows that CD31 present on the EC of the lymphoid
organ vasculature of the recipient is not required for the homing of
lymphocytes to lymphoid organs. Homing of CD31KO and WT lymph node
cells in WT mice was also examined, and at 2 h postinjection, no
difference in counts was found in WT recipients that had received WT or
CD31KO donor cells (data not shown), implying that leukocyte CD31 has
no role in the homing of resting T lymphocytes. Platelet function in CD31KO mice
In addition to leukocytes and EC, CD31 is also expressed on the
surface of platelets. To examine the potential role of CD31 in
platelet-platelet interaction, we assessed platelet aggregation in
vitro in response to varying doses of ADP, a potent proaggregatory
agent. The aggregation response to ADP was identical in both wild-type
and CD31KO mice, with half-maximal responses occurring at essentially
the same concentration of ADP (Fig. 6).
These results suggest that platelet CD31 is not critically involved in
the general phenomenon of platelet-platelet adhesion during platelet
aggregation.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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It has been proposed that CD31 may play a role in hemopoiesis, either through the formation of a stromal cell/extracellular matrix network, in the commitment of multipotential progenitor cells to myeloid and lymphoid lineages, or through the exit of hemopoietic cells via the bone marrow sinus endothelia into the circulation 7 . There have been, however, no published reports to substantiate these hypotheses, and the essentially normal number and composition of hemopoietic cells found in the CD31KO mouse suggest that CD31 is not crucial for the normal production of peripheral blood cells.
Large numbers of monocytes and PMN migrate from the peripheral blood into tissues in response to inflammatory stimuli. The final stage in the emigration of leukocytes into tissues involves the movement of leukocytes across EC and their subsequent passage through the BM into the subendothelial tissues 1 . This step has been shown to be mediated, at least in part, by CD31 16 , and many studies, both in vitro and in vivo, have demonstrated the ability of anti-CD31 Ab to block leukocyte migration 3, 34, 35, 36, 37, 49 . Given the abundant number of reports detailing the importance of CD31 in the TEM of monocytes and PMN, the testing of this observation in the CD31KO mouse was a primary objective. Surprisingly, no significant differences in leukocyte TEM in response to TG, IL-1ß, and Formalin-inactivated S. aureus were detected between CD31KO and WT mice. Total numbers of cells recovered and the cellular composition of the lavage were similar. Monocytes and lymphocytes underwent TEM in essentially equal numbers in both CD31KO and WT mice independent of the stimulus used, organ systems studied, or time point of observation. It should be noted that, in none of the cited studies demonstrating a role for CD31 in leukocyte emigration was TEM blocked completely, suggesting that CD31-independent pathways normally exist, although they are quantitatively less important. These CD31-independent pathways are apparently sufficient to support acute inflammation in mice that have developed in the absence of CD31.
Interestingly, although similar numbers of cells were recovered from the peritoneal cavities of both CD31KO and WT mice after i.p. injection of IL-1ß or TG, electron-microscopic examination of the postcapillary venules in mesentery taken from treated animals revealed a disparity. Only in the CD31KO samples were leukocytes routinely visible between the EC lining, the lumen of the vessels, and the perivascular BM. Selecting only leukocytes whose nuclei were present in the field of view (which could therefore be classified as either PMN or monocytes), this accumulation of leukocytes was found to be specific to PMN 4 h after IL-1ß injection.
Liao et al. 49 showed that mAbs to domain 6 of human CD31, which have no effect on TEM, block migration of monocytes across the subendothelial basal lamina. A parallel to this finding was demonstrated in vivo: administration of an anti-CD31 Ab inhibited extravasation of leukocytes in rat mesenteric microvessels 4 h after IL-1ß treatment 50 . The mechanism underlying this phenomenon remains unclear, although proteoglycans may interact in some indirect way with domain 6 of leukocyte CD31 49 , with subsequent increases in adhesive interactions and/or proteolytic degradation of the BM components 50 . Outside-in signaling involving CD31 has been demonstrated in a number of systems; amplification of integrin-mediated adhesion on CD31 ligation has been shown in human PMN, monocytes, T cell subsets, murine lymphokine-activated killer cells, and human NK cells 22, 23, 24, 25, 26, 27, 28 . The trapping of PMN at the BM in the CD31KO mouse suggests that CD31 is indeed involved in trans-BM passage. That an equal number of cells were recovered after peritoneal lavage from both WT and CD31KO mice suggested to us that CD31 may affect the rate of passage (while not affecting the overall outcome) of the migration process, via a decrease in the rate of passage across the BM or, possibly, an increase in the rate of passage across the EC. Our study of in vitro migration of CD31-deficient PMN over a period of 4 h in response to a chemotactic gradient of IL-8 would appear to argue against an increased rate of passage across EC as being the mechanism behind the observed accumulation of PMN at the BM. It must be pointed out, however, that the in vitro system used does not fully mimic the in vivo situation, in that bEND3 cells express CD31, unlike the CD31KO EC. The accumulation of PMN at the BM could be explained by a reduction in the ability of PMN to pass through this subendothelial barrier in the absence of CD31, for reasons yet to be elucidated, but possibly related to an absence of CD31-mediated activatory signals. The equal cell counts recovered in this study suggest that if there is a retardation of passage across BM in CD31KO mice, then it must be transient and subtle, and could be compensated for by an increased ability of CD31-deficient PMN to migrate through the interstitium. This hypothesis would reconcile the disparate findings of equal numbers of cells recovered from lavage fluid at 4 h postinflammatory stimulus and of PMN accumulation at the BM in CD31KO mice. In summary, our in vitro findings in the CD31KO mouse indicate that the role of CD31 in migration across the basal lamina is most likely independent of any role for CD31 in migration across the intercellular junctions of endothelium.
The apparent importance of CD31 in the modulation of lymphocyte
function 25, 26, 28 , and the expression of CD31 on almost all murine
PBL (Fig. 2A) suggested that CD31 may be involved in
lymphocyte migration. However, in an oxazalone-mediated model of
contact sensitivity, CD31KO mice did not display the reduction in ear
swelling expected if the absence of CD31 were to affect either the
priming or effector phase of this response. Similarly, specific homing
of radiolabeled WT or CD31KO lymph node cells to lymphoid organs in a
WT host was equivalent. Neither was the homing of labeled CD31KO cells
injected into WT recipient mice impaired. CD31 does not therefore
appear to play a role in T lymphocyte migration.
CD31 is also highly expressed on the surface of platelets, although its role here remains unclear. Differential CD31 phosphorylation has been reported in nonaggregated and aggregated platelets 51, 52 , and the protein tyrosine phosphatase SHP-2 has been shown to interact with CD31 during platelet aggregation 29 . In addition, it has recently been reported that CD31 can act as a costimulatory molecule for integrin-mediated adhesion and aggregation in platelets 30 . In vivo, CD31 has been implicated in platelet aggregation in a model of EC injury in mouse cerebral arterioles in which platelet aggregation is dependent on EC injury without exposure of basal lamina 31, 32 . In these studies, treatment with two independent anti-CD31 mAb doubled the time required for platelet aggregates to form after EC damage. The finding in this study that ADP-induced in vitro aggregation of CD31KO platelets is normal is in agreement with an ex vivo study on the effect of anti-CD31 Ab on platelet aggregation in response to ADP and arachidonate 32 . Taken together, these data suggest that CD31 expression on platelets is not essential for platelet-platelet aggregation, but that EC injury may expose or activate CD31 on EC, resulting in augmentation of aggregate formation. The relative roles of EC and platelet CD31 in hemostasis therefore remain unknown, and are currently under investigation.
There has been a plethora of reports published recently detailing studies demonstrating the importance of CD31 in vascular development and angiogenesis, leukocyte migration, and functional regulation of integrins via outside-in signaling. Based on these reports, a null mutation of the gene encoding CD31 would be expected to result in a variety of phenotypes involving both vascular development and/or transendothelial migration of leukocytes. This study of such a CD31-null mouse provides genetic evidence that CD31 does not have an essential exclusive role in any of these biological processes, and that CD31-deficient mice are able to utilize CD31-independent pathways to sustain leukocyte migration in inflammatory situations. Whether these CD31-independent pathways are mediated through the compensatory induction of known, but normally redundant, adhesion molecules in the KO mouse cannot be fully resolved until these molecules are identified and their functional role examined in both CD31KO and WT mice. Identification of the cell adhesion molecules used by CD31KO mice for TEM may yield valuable information about CD31-independent pathways of TEM in humans and WT animals. The modification of these molecules may provide important adjuncts to antiinflammatory therapies aimed at inhibiting CD31.
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Acknowledgments |
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Footnotes |
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2 These authors have contributed equally to this work.
3 Address correspondence and reprint requests to Dr. Tak W. Mak, Amgen Institute, 620 University Avenue, Toronto, Ontario, Canada. M5G 2C1.
4 Abbreviations used in this paper: BM, basement membrane; EC, endothelial cell; ES, embryonic stem; PECAM, platelet/endothelial cell adhesion molecule; PMN, polymorphonuclear; PPP, platelet-poor plasma; PRP, platelet-rich plasma; TEM, transendothelial migration; TG, thioglycolate; WT, wild-type.
Received for publication September 10, 1998. Accepted for publication November 20, 1998.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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vß3 integrin involved in adhesion of leukocytes to endothelium. J. Cell Biol. 130:451.vß3 as a heterotypic ligand for CD31/PECAM-1. J. Cell Sci. 109:437.[Abstract]
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  A. Woodfin, M.-B. Voisin, B. A. Imhof, E. Dejana, B. Engelhardt, and S. Nourshargh Endothelial cell activation leads to neutrophil transmigration as supported by the sequential roles of ICAM-2, JAM-A, and PECAM-1 Blood, June 11, 2009; 113(24): 6246 - 6257. [Abstract] [Full Text] [PDF]
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 M. L. Fehrenbach, G. Cao, J. T. Williams, J. M. Finklestein, and H. M. DeLisser Isolation of murine lung endothelial cells Am J Physiol Lung Cell Mol Physiol, June 1, 2009; 296(6): L1096 - L1103. [Abstract] [Full Text] [PDF]
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 R. Goel, B. R. Schrank, S. Arora, B. Boylan, B. Fleming, H. Miura, P. J. Newman, R. C. Molthen, and D. K. Newman Site-Specific Effects of PECAM-1 on Atherosclerosis in LDL Receptor-Deficient Mice Arterioscler. Thromb. Vasc. Biol., November 1, 2008; 28(11): 1996 - 2002. [Abstract] [Full Text] [PDF]
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T. Korff, J. Braun, D. Pfaff, H. G. Augustin, and M. Hecker Role of ephrinB2 expression in endothelial cells during arteriogenesis: impact on smooth muscle cell migration and monocyte recruitment Blood, July 1, 2008; 112(1): 73 - 81. [Abstract] [Full Text] [PDF]
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 C. Bergom, C. Paddock, C. Gao, T. Holyst, D. K. Newman, and P. J. Newman An alternatively spliced isoform of PECAM-1 is expressed at high levels in human and murine tissues, and suggests a novel role for the C-terminus of PECAM-1 in cytoprotective signaling J. Cell Sci., April 15, 2008; 121(8): 1235 - 1242. [Abstract] [Full Text] [PDF]
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 R. Goel, B. Boylan, L. Gruman, P. J. Newman, P. E. North, and D. K. Newman The proinflammatory phenotype of PECAM-1-deficient mice results in atherogenic diet-induced steatohepatitis Am J Physiol Gastrointest Liver Physiol, December 1, 2007; 293(6): G1205 - G1214. [Abstract] [Full Text] [PDF]
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A. Woodfin, M.-B. Voisin, and S. Nourshargh PECAM-1: A Multi-Functional Molecule in Inflammation and Vascular Biology Arterioscler. Thromb. Vasc. Biol., December 1, 2007; 27(12): 2514 - 2523. [Abstract] [Full Text] [PDF]
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 P. Baluk, J. Fuxe, H. Hashizume, T. Romano, E. Lashnits, S. Butz, D. Vestweber, M. Corada, C. Molendini, E. Dejana, et al. Functionally specialized junctions between endothelial cells of lymphatic vessels J. Exp. Med., October 1, 2007; 204(10): 2349 - 2362. [Abstract] [Full Text] [PDF]
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 J. L. Lucitti, E. A. V. Jones, C. Huang, J. Chen, S. E. Fraser, and M. E. Dickinson Vascular remodeling of the mouse yolk sac requires hemodynamic force Development, September 15, 2007; 134(18): 3317 - 3326. [Abstract] [Full Text] [PDF]
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A. Woodfin, C. A. Reichel, A. Khandoga, M. Corada, M.-B. Voisin, C. Scheiermann, D. O. Haskard, E. Dejana, F. Krombach, and S. Nourshargh JAM-A mediates neutrophil transmigration in a stimulus-specific manner in vivo: evidence for sequential roles for JAM-A and PECAM-1 in neutrophil transmigration Blood, September 15, 2007; 110(6): 1848 - 1856. [Abstract] [Full Text] [PDF]
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E. Rijcken, R. B. Mennigen, S. D. Schaefer, M. G. Laukoetter, C. Anthoni, H.-U. Spiegel, M. Bruewer, N. Senninger, and C. F. Krieglstein PECAM-1 (CD 31) mediates transendothelial leukocyte migration in experimental colitis Am J Physiol Gastrointest Liver Physiol, August 1, 2007; 293(2): G446 - G452. [Abstract] [Full Text] [PDF]
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 A. Schmidt, K. Brixius, and W. Bloch Endothelial Precursor Cell Migration During Vasculogenesis Circ. Res., July 20, 2007; 101(2): 125 - 136. [Abstract] [Full Text] [PDF]
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 S. Kondo, E. A. Scheef, N. Sheibani, and C. M. Sorenson PECAM-1 isoform-specific regulation of kidney endothelial cell migration and capillary morphogenesis Am J Physiol Cell Physiol, June 1, 2007; 292(6): C2070 - C2083. [Abstract] [Full Text] [PDF]
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T. S. Dhanjal, C. Pendaries, E. A. Ross, M. K. Larson, M. B. Protty, C. D. Buckley, and S. P. Watson A novel role for PECAM-1 in megakaryocytokinesis and recovery of platelet counts in thrombocytopenic mice Blood, May 15, 2007; 109(10): 4237 - 4244. [Abstract] [Full Text] [PDF]
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D. M. Shasby Cell-cell adhesion in lung endothelium Am J Physiol Lung Cell Mol Physiol, March 1, 2007; 292(3): L593 - L607. [Abstract] [Full Text] [PDF]
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E. Ortolan, E. V. Tibaldi, B. Ferranti, L. Lavagno, G. Garbarino, R. Notaro, L. Luzzatto, F. Malavasi, and A. Funaro CD157 plays a pivotal role in neutrophil transendothelial migration Blood, December 15, 2006; 108(13): 4214 - 4222. [Abstract] [Full Text] [PDF]
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S. Perkowski, A. Scherpereel, J.-C. Murciano, E. Arguiri, C. C. Solomides, S. M. Albelda, V. Muzykantov, and M. Christofidou-Solomidou Dissociation between alveolar transmigration of neutrophils and lung injury in hyperoxia Am J Physiol Lung Cell Mol Physiol, November 1, 2006; 291(5): L1050 - L1058. [Abstract] [Full Text] [PDF]
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 S. Nourshargh, F. Krombach, and E. Dejana The role of JAM-A and PECAM-1 in modulating leukocyte infiltration in inflamed and ischemic tissues J. Leukoc. Biol., October 1, 2006; 80(4): 714 - 718. [Abstract] [Full Text] [PDF]
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 C. M. Udell, L. A. Samayawardhena, Y. Kawakami, T. Kawakami, and A. W. B. Craig Fer and Fps/Fes Participate in a Lyn-dependent Pathway from Fc{epsilon}RI to Platelet-Endothelial Cell Adhesion Molecule 1 to Limit Mast Cell Activation J. Biol. Chem., July 28, 2006; 281(30): 20949 - 20957. [Abstract] [Full Text] [PDF]
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 R. E. Conway, N. Petrovic, Z. Li, W. Heston, D. Wu, and L. H. Shapiro Prostate-specific membrane antigen regulates angiogenesis by modulating integrin signal transduction. Mol. Cell. Biol., July 1, 2006; 26(14): 5310 - 5324. [Abstract] [Full Text] [PDF]
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M.-T. Huang, K. Y. Larbi, C. Scheiermann, A. Woodfin, N. Gerwin, D. O. Haskard, and S. Nourshargh ICAM-2 mediates neutrophil transmigration in vivo: evidence for stimulus specificity and a role in PECAM-1-independent transmigration Blood, June 15, 2006; 107(12): 4721 - 4727. [Abstract] [Full Text] [PDF]
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H. M. DeLisser, B. P. Helmke, G. Cao, P. M. Egan, D. Taichman, M. Fehrenbach, A. Zaman, Z. Cui, G. S. Mohan, H. S. Baldwin, et al. Loss of PECAM-1 Function Impairs Alveolarization J. Biol. Chem., March 31, 2006; 281(13): 8724 - 8731. [Abstract] [Full Text] [PDF]
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E. A. Eugenin, R. Gamss, C. Buckner, D. Buono, R. S. Klein, E. E. Schoenbaum, T. M. Calderon, and J. W. Berman Shedding of PECAM-1 during HIV infection: a potential role for soluble PECAM-1 in the pathogenesis of NeuroAIDS. J. Leukoc. Biol., March 1, 2006; 79(3): 444 - 452. [Abstract] [Full Text] [PDF]
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S. Falati, S. Patil, P. L. Gross, M. Stapleton, G. Merrill-Skoloff, N. E. Barrett, K. L. Pixton, H. Weiler, B. Cooley, D. K. Newman, et al. Platelet PECAM-1 inhibits thrombus formation in vivo Blood, January 15, 2006; 107(2): 535 - 541. [Abstract] [Full Text] [PDF]
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 S. C. Wassmer, V. Combes, F. J. Candal, I. Juhan-Vague, and G. E. Grau Platelets Potentiate Brain Endothelial Alterations Induced by Plasmodium falciparum Infect. Immun., January 1, 2006; 74(1): 645 - 653. [Abstract] [Full Text] [PDF]
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 D. Mehta and A. B. Malik Signaling Mechanisms Regulating Endothelial Permeability Physiol Rev, January 1, 2006; 86(1): 279 - 367. [Abstract] [Full Text] [PDF]
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B.-S. Ding, C. Gottstein, A. Grunow, A. Kuo, K. Ganguly, S. M. Albelda, D. B. Cines, and V. R. Muzykantov Endothelial targeting of a recombinant construct fusing a PECAM-1 single-chain variable antibody fragment (scFv) with prourokinase facilitates prophylactic thrombolysis in the pulmonary vasculature Blood, December 15, 2005; 106(13): 4191 - 4198. [Abstract] [Full Text] [PDF]
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J. L. Wee and D. E. Jackson The Ig-ITIM superfamily member PECAM-1 regulates the "outside-in" signaling properties of integrin {alpha}IIb{beta}3 in platelets Blood, December 1, 2005; 106(12): 3816 - 3823. [Abstract] [Full Text] [PDF]
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 Y. Wu, P. Stabach, M. Michaud, and J. A. Madri Neutrophils Lacking Platelet-Endothelial Cell Adhesion Molecule-1 Exhibit Loss of Directionality and Motility in CXCR2-Mediated Chemotaxis J. Immunol., September 15, 2005; 175(6): 3484 - 3491. [Abstract] [Full Text] [PDF]
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I. Fleming, B. Fisslthaler, M. Dixit, and R. Busse Role of PECAM-1 in the shear-stress-induced activation of Akt and the endothelial nitric oxide synthase (eNOS) in endothelial cells J. Cell Sci., September 15, 2005; 118(18): 4103 - 4111. [Abstract] [Full Text] [PDF]
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L.-k. Tai, Q. Zheng, S. Pan, Z.-G. Jin, and B. C. Berk Flow Activates ERK1/2 and Endothelial Nitric Oxide Synthase via a Pathway Involving PECAM1, SHP2, and Tie2 J. Biol. Chem., August 19, 2005; 280(33): 29620 - 29624. [Abstract] [Full Text] [PDF]
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 M. Corada, S. Chimenti, M. R. Cera, M. Vinci, M. Salio, F. Fiordaliso, N. De Angelis, A. Villa, M. Bossi, L. I. Staszewsky, et al. Junctional adhesion molecule-A-deficient polymorphonuclear cells show reduced diapedesis in peritonitis and heart ischemia-reperfusion injury PNAS, July 26, 2005; 102(30): 10634 - 10639. [Abstract] [Full Text] [PDF]
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S. Wang, J. P. Dangerfield, R. E. Young, and S. Nourshargh PECAM-1, {alpha}6 integrins and neutrophil elastase cooperate in mediating neutrophil transmigration J. Cell Sci., May 1, 2005; 118(9): 2067 - 2076. [Abstract] [Full Text] [PDF]
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J. M. Cook-Mills and T. L. Deem Active participation of endothelial cells in inflammation J. Leukoc. Biol., April 1, 2005; 77(4): 487 - 495. [Abstract] [Full Text] [PDF]
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B. E. Sumpio, S. Yun, A. C. Cordova, M. Haga, J. Zhang, Y. Koh, and J. A. Madri MAPKs (ERK1/2, p38) and AKT Can Be Phosphorylated by Shear Stress Independently of Platelet Endothelial Cell Adhesion Molecule-1 (CD31) in Vascular Endothelial Cells J. Biol. Chem., March 25, 2005; 280(12): 11185 - 11191. [Abstract] [Full Text] [PDF]
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P. L. W. Yun, A. A. Decarlo, C. C. Chapple, and N. Hunter Functional Implication of the Hydrolysis of Platelet Endothelial Cell Adhesion Molecule 1 (CD31) by Gingipains of Porphyromonas gingivalis for the Pathology of Periodontal Disease Infect. Immun., March 1, 2005; 73(3): 1386 - 1398. [Abstract] [Full Text] [PDF]
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J. P. Dangerfield, S. Wang, and S. Nourshargh Blockade of {alpha}6 integrin inhibits IL-1{beta}- but not TNF-{alpha}-induced neutrophil transmigration in vivo J. Leukoc. Biol., February 1, 2005; 77(2): 159 - 165. [Abstract] [Full Text] [PDF]
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 M. Carrithers, S. Tandon, S. Canosa, M. Michaud, D. Graesser, and J. A. Madri Enhanced Susceptibility to Endotoxic Shock and Impaired STAT3 Signaling in CD31-Deficient Mice Am. J. Pathol., January 1, 2005; 166(1): 185 - 196. [Abstract] [Full Text] [PDF]
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 M. Maas, M. Stapleton, C. Bergom, D. L. Mattson, D. K. Newman, and P. J. Newman Endothelial cell PECAM-1 confers protection against endotoxic shock Am J Physiol Heart Circ Physiol, January 1, 2005; 288(1): H159 - H164. [Abstract] [Full Text] [PDF]
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A. R. Schenkel, T. W. Chew, and W. A. Muller Platelet Endothelial Cell Adhesion Molecule Deficiency or Blockade Significantly Reduces Leukocyte Emigration in a Majority of Mouse Strains J. Immunol., November 15, 2004; 173(10): 6403 - 6408. [Abstract] [Full Text] [PDF]
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S. A. Vokes, T. A. Yatskievych, R. L. Heimark, J. McMahon, A. P. McMahon, P. B. Antin, and P. A. Krieg Hedgehog signaling is essential for endothelial tube formation during vasculogenesis Development, September 1, 2004; 131(17): 4371 - 4380. [Abstract] [Full Text] [PDF]
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 S. M. Albelda, K. C. Lau, P. Chien, Z.-Y. Huang, E. Arguiris, A. Bohen, J. Sun, J. A. Billet, M. Christofidou-Solomidou, Z. K. Indik, et al. Role for Platelet-Endothelial Cell Adhesion Molecule-1 in Macrophage Fc{gamma} Receptor Function Am. J. Respir. Cell Mol. Biol., August 1, 2004; 31(2): 246 - 255. [Abstract] [Full Text] [PDF]
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G. Bazzoni and E. Dejana Endothelial Cell-to-Cell Junctions: Molecular Organization and Role in Vascular Homeostasis Physiol Rev, July 1, 2004; 84(3): 869 - 901. [Abstract] [Full Text] [PDF]
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A. K. Nath, J. Enciso, M. Kuniyasu, X.-Y. Hao, J. A. Madri, and E. Pinter Nitric oxide modulates murine yolk sac vasculogenesis and rescues glucose induced vasculopathy Development, May 15, 2004; 131(10): 2485 - 2496. [Abstract] [Full Text] [PDF]
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J. D. van Buul and P. L. Hordijk Signaling in Leukocyte Transendothelial Migration Arterioscler. Thromb. Vasc. Biol., May 1, 2004; 24(5): 824 - 833. [Abstract] [Full Text]
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 T. Furusawa, K. Ohkoshi, C. Honda, S. Takahashi, and T. Tokunaga Embryonic Stem Cells Expressing Both Platelet Endothelial Cell Adhesion Molecule-1 and Stage-Specific Embryonic Antigen-1 Differentiate Predominantly into Epiblast Cells in a Chimeric Embryo Biol Reprod, May 1, 2004; 70(5): 1452 - 1457. [Abstract] [Full Text] [PDF]
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R. E. Young, R. D. Thompson, K. Y. Larbi, M. La, C. E. Roberts, S. D. Shapiro, M. Perretti, and S. Nourshargh Neutrophil Elastase (NE)-Deficient Mice Demonstrate a Nonredundant Role for NE in Neutrophil Migration, Generation of Proinflammatory Mediators, and Phagocytosis in Response to Zymosan Particles In Vivo J. Immunol., April 1, 2004; 172(7): 4493 - 4502. [Abstract] [Full Text] [PDF]
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 G. W. PAYNE, J. A. MADRI, W. C. SESSA, and S. S. SEGAL Histamine inhibits conducted vasodilation through endothelium-derived NO production in arterioles of mouse skeletal muscle FASEB J, February 1, 2004; 18(2): 280 - 286. [Abstract] [Full Text] [PDF]
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V. Rathore, M. A. Stapleton, C. A. Hillery, R. R. Montgomery, T. C. Nichols, E. P. Merricks, D. K. Newman, and P. J. Newman PECAM-1 negatively regulates GPIb/V/IX signaling in murine platelets Blood, November 15, 2003; 102(10): 3658 - 3664. [Abstract] [Full Text] [PDF]
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T. Ishida, R. K. Kundu, E. Yang, K.-i. Hirata, Y.-D. Ho, and T. Quertermous Targeted Disruption of Endothelial Cell-selective Adhesion Molecule Inhibits Angiogenic Processes in Vitro and in Vivo J. Biol. Chem., September 5, 2003; 278(36): 34598 - 34604. [Abstract] [Full Text] [PDF]
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D. GRATZINGER, S. CANOSA, B. ENGELHARDT, and J. A. MADRI Platelet endothelial cell adhesion molecule-1 modulates endothelial cell motility through the small G-protein Rho FASEB J, August 1, 2003; 17(11): 1458 - 1469. [Abstract] [Full Text] [PDF]
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G. W. Payne, J. A. Madri, W. C. Sessa, and S. S. Segal Abolition of arteriolar dilation but not constriction to histamine in cremaster muscle of eNOS-/- mice Am J Physiol Heart Circ Physiol, July 11, 2003; 285(2): H493 - H498. [Abstract] [Full Text] [PDF]
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P. J. Newman and D. K. Newman Signal Transduction Pathways Mediated by PECAM-1: New Roles for an Old Molecule in Platelet and Vascular Cell Biology Arterioscler. Thromb. Vasc. Biol., June 1, 2003; 23(6): 953 - 964. [Abstract] [Full Text] [PDF]
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A. R. Burns, C. W. Smith, and D. C. Walker Unique Structural Features That Influence Neutrophil Emigration Into the Lung Physiol Rev, April 1, 2003; 83(2): 309 - 336. [Abstract] [Full Text] [PDF]
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C. D. O'Brien, P. Lim, J. Sun, and S. M. Albelda PECAM-1-dependent neutrophil transmigration is independent of monolayer PECAM-1 signaling or localization Blood, April 1, 2003; 101(7): 2816 - 2825. [Abstract] [Full Text] [PDF]
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A. Solowiej, P. Biswas, D. Graesser, and J. A. Madri Lack of Platelet Endothelial Cell Adhesion Molecule-1 Attenuates Foreign Body Inflammation because of Decreased Angiogenesis Am. J. Pathol., March 1, 2003; 162(3): 953 - 962. [Abstract] [Full Text] [PDF]
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 S. Tasaka, L. Qin, A. Saijo, S. M. Albelda, H. M. DeLisser, and C. M. Doerschuk Platelet Endothelial Cell Adhesion Molecule-1 in Neutrophil Emigration during Acute Bacterial Pneumonia in Mice and Rats Am. J. Respir. Crit. Care Med., January 15, 2003; 167(2): 164 - 170. [Abstract] [Full Text] [PDF]
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J. Dangerfield, K. Y. Larbi, M.-T. Huang, A. Dewar, and S. Nourshargh PECAM-1 (CD31) Homophilic Interaction Up-Regulates {alpha}6{beta}1 on Transmigrated Neutrophils In Vivo and Plays a Functional Role in the Ability of {alpha}6 Integrins to Mediate Leukocyte Migration through the Perivascular Basement Membrane J. Exp. Med., November 4, 2002; 196(9): 1201 - 1212. [Abstract] [Full Text] [PDF]
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 M. Osawa, M. Masuda, K.-i. Kusano, and K. Fujiwara Evidence for a role of platelet endothelial cell adhesion molecule-1 in endothelial cell mechanosignal transduction: is it a mechanoresponsive molecule? J. Cell Biol., August 19, 2002; 158(4): 773 - 785. [Abstract] [Full Text] [PDF]
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P. F. Lalor, S. Edwards, G. McNab, M. Salmi, S. Jalkanen, and D. H. Adams Vascular Adhesion Protein-1 Mediates Adhesion and Transmigration of Lymphocytes on Human Hepatic Endothelial Cells J. Immunol., July 15, 2002; 169(2): 983 - 992. [Abstract] [Full Text] [PDF]
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R. Wilkinson, A. B. Lyons, D. Roberts, M.-X. Wong, P. A. Bartley, and D. E. Jackson Platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31) acts as a regulator of B-cell development, B-cell antigen receptor (BCR)-mediated activation, and autoimmune disease Blood, June 17, 2002; 100(1): 184 - 193. [Abstract] [Full Text] [PDF]
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M.-X. Wong, D. Roberts, P. A. Bartley, and D. E. Jackson Absence of Platelet Endothelial Cell Adhesion Molecule-1 (CD31) Leads to Increased Severity of Local and Systemic IgE-Mediated Anaphylaxis and Modulation of Mast Cell Activation J. Immunol., June 15, 2002; 168(12): 6455 - 6462. [Abstract] [Full Text] [PDF]
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D. Broide Fast Flowing Eosinophils . Signals for Stopping and Stepping Out of Blood Vessels Am. J. Respir. Cell Mol. Biol., June 1, 2002; 26(6): 637 - 640. [Full Text] [PDF]
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J. R. Allport, Y.-C. Lim, J. M. Shipley, R. M. Senior, S. D. Shapiro, N. Matsuyoshi, D. Vestweber, and F. W. Luscinskas Neutrophils from MMP-9- or neutrophil elastase-deficient mice show no defect in transendothelial migration under flow in vitro J. Leukoc. Biol., May 1, 2002; 71(5): 821 - 828. [Abstract] [Full Text] [PDF]
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L.-P. Berg, M. J. James, M. Alvarez-Iglesias, S. Glennie, R. I. Lechler, and F. M. Marelli-Berg Functional Consequences of Noncognate Interactions Between CD4+ Memory T Lymphocytes and the Endothelium J. Immunol., April 1, 2002; 168(7): 3227 - 3234. [Abstract] [Full Text] [PDF]
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 I. M. Fierro, J. L. Kutok, and C. N. Serhan Novel Lipid Mediator Regulators of Endothelial Cell Proliferation and Migration: Aspirin-Triggered-15R-Lipoxin A4 and Lipoxin A4 J. Pharmacol. Exp. Ther., February 1, 2002; 300(2): 385 - 392. [Abstract] [Full Text] [PDF]
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M. Cicmil, J. M. Thomas, M. Leduc, C. Bon, and J. M. Gibbins Platelet endothelial cell adhesion molecule-1 signaling inhibits the activation of human platelets Blood, January 1, 2002; 99(1): 137 - 144. [Abstract] [Full Text] [PDF]
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S. K. Shaw, B. N. Perkins, Y.-C. Lim, Y. Liu, A. Nusrat, F. J. Schnell, C. A. Parkos, and F. W. Luscinskas Reduced Expression of Junctional Adhesion Molecule and Platelet/Endothelial Cell Adhesion Molecule-1 (CD31) at Human Vascular Endothelial Junctions by Cytokines Tumor Necrosis Factor-{alpha} Plus Interferon-{gamma} Does Not Reduce Leukocyte Transmigration Under Flow Am. J. Pathol., December 1, 2001; 159(6): 2281 - 2291. [Abstract] [Full Text] [PDF]
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K. L. Jones, S. C. Hughan, S. M. Dopheide, R. W. Farndale, S. P. Jackson, and D. E. Jackson Platelet endothelial cell adhesion molecule-1 is a negative regulator of platelet-collagen interactions Blood, September 1, 2001; 98(5): 1456 - 1463. [Abstract] [Full Text] [PDF]
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M. Miller, K.-L. P. Sung, W. A. Muller, J. Y. Cho, M. Roman, D. Castaneda, J. Nayar, T. Condon, J. Kim, P. Sriramarao, et al. Eosinophil Tissue Recruitment to Sites of Allergic Inflammation in the Lung Is Platelet Endothelial Cell Adhesion Molecule Independent J. Immunol., August 15, 2001; 167(4): 2292 - 2297. [Abstract] [Full Text] [PDF]
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T. M. Carlos Leukocyte recruitment at sites of tumor: dissonant orchestration J. Leukoc. Biol., August 1, 2001; 70(2): 171 - 184. [Abstract] [Full Text] [PDF]
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B. Wang, C. Feliciani, I. Freed, Q. Cai, and D. N. Sauder Insights into molecular mechanisms of contact hypersensitivity gained from gene knockout studies J. Leukoc. Biol., August 1, 2001; 70(2): 185 - 191. [Abstract] [Full Text] [PDF]
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S. Patil, D. K. Newman, and P. J. Newman Platelet endothelial cell adhesion molecule-1 serves as an inhibitory receptor that modulates platelet responses to collagen Blood, March 15, 2001; 97(6): 1727 - 1732. [Abstract] [Full Text] [PDF]
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R. D. Thompson, K. E. Noble, K. Y. Larbi, A. Dewar, G. S. Duncan, T. W. Mak, and S. Nourshargh Platelet-endothelial cell adhesion molecule-1 (PECAM-1)-deficient mice demonstrate a transient and cytokine-specific role for PECAM-1 in leukocyte migration through the perivascular basement membrane Blood, March 15, 2001; 97(6): 1854 - 1860. [Abstract] [Full Text] [PDF]
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E. Prager, G. Staffler, O. Majdic, M. D. Saemann, S. Godar, G. J. Zlabinger, and H. Stockinger Induction of Hyporesponsiveness and Impaired T Lymphocyte Activation by the CD31 Receptor:Ligand Pathway in T Cells J. Immunol., February 15, 2001; 166(4): 2364 - 2371. [Abstract] [Full Text] [PDF]
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N. ILAN, A. MOHSENIN, L. CHEUNG, and J. A. MADRI PECAM-1 shedding during apoptosis generates a membrane-anchored truncated molecule with unique signaling characteristics FASEB J, February 1, 2001; 15(2): 362 - 372. [Abstract] [Full Text] [PDF]
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S. TOHKA, M.-L. LAUKKANEN, S. JALKANEN, and M. SALMI Vascular adhesion protein 1 (VAP-1) functions as a molecular brake during granulocyte rolling and mediates recruitment in vivo FASEB J, February 1, 2001; 15(2): 373 - 382. [Abstract] [Full Text] [PDF]
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E. Sans, E. Delachanal, and A. Duperray Analysis of the Roles of ICAM-1 in Neutrophil Transmigration Using a Reconstituted Mammalian Cell Expression Model: Implication of ICAM-1 Cytoplasmic Domain and Rho-Dependent Signaling Pathway J. Immunol., January 1, 2001; 166(1): 544 - 551. [Abstract] [Full Text] [PDF]
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 A. Marszalek, T. Daa, K. Kashima, I. Nakayama, and S. Yokoyama Ultrastructural and Morphometric Studies Related to Expression of the Cell Adhesion Molecule PECAM-1/CD31 in Developing Rat Lung J. Histochem. Cytochem., September 1, 2000; 48(9): 1283 - 1290. [Abstract] [Full Text]
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 C. W.Y. Wong, G. Wiedle, C. Ballestrem, B. Wehrle-Haller, S. Etteldorf, M. Bruckner, B. Engelhardt, R. H. Gisler, and B. A. Imhof PECAM-1/CD31 Trans-homophilic Binding at the Intercellular Junctions Is Independent of Its Cytoplasmic Domain; Evidence for Heterophilic Interaction with Integrin alpha vbeta 3 in Cis Mol. Biol. Cell, September 1, 2000; 11(9): 3109 - 3121. [Abstract] [Full Text]
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R. D. Thompson, M. W. Wakelin, K. Y. Larbi, A. Dewar, G. Asimakopoulos, M. A. Horton, M. T. Nakada, and S. Nourshargh Divergent Effects of Platelet-Endothelial Cell Adhesion Molecule-1 and {beta}3 Integrin Blockade on Leukocyte Transmigration In Vivo J. Immunol., July 1, 2000; 165(1): 426 - 434. [Abstract] [Full Text] [PDF]
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K. A. Reedquist, E. Ross, E. A. Koop, R. M.F. Wolthuis, F. J.T. Zwartkruis, Y. van Kooyk, M. Salmon, C. D. Buckley, and J. L. Bos The Small GTPase, Rap1, Mediates CD31-induced Integrin Adhesion J. Cell Biol., March 20, 2000; 148(6): 1151 - 1158. [Abstract] [Full Text] [PDF]
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C. J. Drake and P. A. Fleming Vasculogenesis in the day 6.5 to 9.5 mouse embryo Blood, March 1, 2000; 95(5): 1671 - 1679. [Abstract] [Full Text] [PDF]
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J. R. Allport, W. A. Muller, and F. W. Luscinskas Monocytes Induce Reversible Focal Changes in Vascular Endothelial Cadherin Complex during Transendothelial Migration Under Flow J. Cell Biol., January 10, 2000; 148(1): 203 - 216. [Abstract] [Full Text] [PDF]
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C Johnson-Leger, M Aurrand-Lions, and B. Imhof The parting of the endothelium: miracle, or simply a junctional affair? J. Cell Sci., January 3, 2000; 113(6): 921 - 933. [Abstract] [PDF]
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F. Liao, A. R. Schenkel, and W. A. Muller Transgenic Mice Expressing Different Levels of Soluble Platelet/Endothelial Cell Adhesion Molecule-IgG Display Distinct Inflammatory Phenotypes J. Immunol., November 15, 1999; 163(10): 5640 - 5648. [Abstract] [Full Text] [PDF]
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D. K. Newton-Nash and P. J. Newman A New Role for Platelet-Endothelial Cell Adhesion Molecule-1 (CD31): Inhibition of TCR-Mediated Signal Transduction J. Immunol., July 15, 1999; 163(2): 682 - 688. [Abstract] [Full Text] [PDF]
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N. Ilan, L. Cheung, E. Pinter, and J. A. Madri Platelet-Endothelial Cell Adhesion Molecule-1 (CD31), a Scaffolding Molecule for Selected Catenin Family Members Whose Binding Is Mediated by Different Tyrosine and Serine/Threonine Phosphorylation J. Biol. Chem., July 7, 2000; 275(28): 21435 - 21443. [Abstract] [Full Text] [PDF]
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M. Cicmil, J. M. Thomas, T. Sage, F. A. Barry, M. Leduc, C. Bon, and J. M. Gibbins Collagen, Convulxin, and Thrombin Stimulate Aggregation-independent Tyrosine Phosphorylation of CD31 in Platelets. EVIDENCE FOR THE INVOLVEMENT OF Src FAMILY KINASES J. Biol. Chem., August 25, 2000; 275(35): 27339 - 27347. [Abstract] [Full Text] [PDF]
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K.-i. Hirata, T. Ishida, K. Penta, M. Rezaee, E. Yang, J. Wohlgemuth, and T. Quertermous Cloning of an Immunoglobulin Family Adhesion Molecule Selectively Expressed by Endothelial Cells J. Biol. Chem., May 4, 2001; 276(19): 16223 - 16231. [Abstract] [Full Text] [PDF]
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