(Journal of Leukocyte Biology. 2001;70:708-714.)
© 2001
by Society for Leukocyte Biology
Uptake of apoptotic leukocytes by synovial lining macrophages inhibits immune complexmediated arthritis
P.L.E.M. van Lent*,
R. Licht
,
H. Dijkman,
A.E.M. Holthuysen*,
J.H.M. Berden and
W.B. van den Berg
Division of Rheumatology, University Medical Centre Nijmegen, the Netherlands,
* Division of Nephrology, University Medical Centre Nijmegen, the Netherlands,
Division of Pathology, University Medical Centre Nijmegen, the Netherlands
Correspondence: P.L.E.M. van Lent, Division of Rheumatology, University Medical Center Nijmegen, Geert Grooteplein 26-28, 6500 HB Nijmegen, the Netherlands. E-mail: p.vanlent{at}reuma.azn.nl.
 |
ABSTRACT
|
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Previously we have shown that synovial lining macrophages (SLMs)
determine the onset of experimental immune complexmediated arthritis
(ICA). During joint inflammation, many leukocytes undergo apoptosis,
and removal of leukocytes by SLMs may regulate resolution of
inflammation. In this study we investigated binding and uptake of
apoptotic leukocytes by SLMs and its impact on the onset of murine
experimental arthritis. We used an in vitro model to evaluate
phagocytosis of apoptotic cells on chemotaxis. Phagocytosis of
apoptotic thymocytes resulted in a significant decrease (58%) of
chemotactic activity for polymorphonuclear neutrophils (PMNs). If
apoptotic cells were injected directly into a normal murine knee joint,
SLMs resulted in a prominent uptake of cells. After ICA induction,
electron micrographs showed that apoptotic leukocytes were evidently
present in SLMs on days 1 and 2. Injection of apoptotic leukocytes into
the knee joint 1 h before induction of ICA significantly inhibited
PMN infiltration into the knee joint at 24 h (61% decrease). This
study indicates that uptake of apoptotic leukocytes by SLM reduces
chemotactic activity and inhibits the onset of experimental arthritis.
These findings indicate an important mechanism in the resolution of
joint inflammation.
Key Words: joint inflammation immune complexes synovium apoptotic cells synovial lining macrophages chemotaxis
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INTRODUCTION
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During arthritis, large numbers of inflammatory cells migrate into
the joint cavity [1
]. Many of them undergo apoptosis, a
process that follows programmed pathways leading to well-defined
biochemical and morphological characteristics [2
,
3
]. Characteristic features of apoptosis are DNA
digestion in the internucleosomal linker regions, nuclear
fragmentation, aggregation of dense masses of chromatin beneath the
nuclear membrane, and cell shrinkage. During apoptosis, the cells
surfaces are altered, which leads to their removal by phagocytosis
[4
]. Macrophages can identify a cell as apoptotic, and
they have been shown to phagocytose apoptotic cells. Many receptors may
be important in the interaction between apoptotic cells and
macrophages. On the macrophage surface, the vitronectin receptor
vß3 [5
], CD36 [6
], the ATP-binding
cassette transporter ABC-1 [7
], class A scavenger
receptor [8
], CD14 [9
], and possible
low-density lipoprotein receptor CD68 [10
] have been
involved in apoptotic cell clearance. On the apoptotic cell, however,
only one surface changethe exposure of phosphatidylserinehas been
firmly linked with the clearance mechanism [11
], whereas
recently it was found that ICAM-3 (CD50) is also important in the
recognition of apoptotic leukocytes by macrophages [12
].
Both apoptosis and the removal of apoptotic cells are essential to
prevent leakage of potentially harmful intracellular contents into the
micro-environment [13
, 14
]. In contrast to
complement or Fc-mediated phagocytosis, the uptake of apoptotic cells
does not promote inflammation [15
]. In fact, recent data
even indicate that the phagocytosis of apoptotic material by
macrophages causes the release of mediators that actively inhibit the
inflammatory response [16
17
18
19
].
Di-arthrodial joints are covered by a thin layer of cells, the synovial
intima [20
]. In the mouse, the synovial intima consists
mainly of macrophage-like type A cells. Recent studies have shown that
these cells are of utmost importance for the onset
[21
22
], propagation [23
], and
exacerbation [24
] of experimental arthritis. They
probably form an important source of chemokines, which are released on
activation by cytokines such as interleukin-1 [22
].
Earlier we developed a model of immune complexmediated arthritis
(ICA) in the mouse. Arthritis is induced by local injection of the
antigen lysozyme into the knee joint of mice that previously were given
specific antilysozyme antibodies intravenously [25
].
Maximal knee joint inflammation is found at day 2. At that stage, many
inflammatory cells undergo apoptosis in the knee joint cavity.
Apoptotic cells can be removed by polymorphonuclear cells present in
the joint cavity or by synovial lining macrophages. Inhibition of
synovial macrophages due to apoptotic cell uptake may have implications
for the onset and propagation of joint inflammation.
In this study, we investigated whether apoptotic leukocytes can be
phagocytosed by synovial lining cells during experimental ICA, whether
macrophages that have phagocytosed apoptotic cells modulate the
chemotactic activity in vitro, and the impact of apoptotic cell uptake
by SLMs on the onset of experimental arthritis. Our study indicates
that apoptotic cells are phagocytosed by synovial lining macrophages
and that this leads to inhibition of the cell influx into the joint
cavity in which experimental arthritis is subsequently elicited.
 |
MATERIALS AND METHODS
|
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Animals
Female inbred BALB/c mice younger than 15 weeks were used for
all experiments. The mice were purchased from Harlan (Horst, the
Netherlands) and housed under specific pathogen-free conditions. The
animals were fed standard food (Hope Farms, Woerden, the Netherlands)
and acidified tap water ad libitum and treated according to university
guidelines.
Induction of ICA
ICA was induced as described earlier [25
]. Three
micrograms of Henn Egg Lysozyme coupled to poly-L-lysine was injected
into the knee joints of mice that had previously been given 0.2 mL
antilysozyme antibodies intravenously. The first signs of arthritis
were observed at 6 h, and maximal inflammation was found at day 2
after arthritis induction.
Light microscopy
Knee joints were fixed in buffered formalin, decalcified in
formic acid, and embedded in paraffin. Whole knee joint sections (6
m) were cut on a Reichert microtome, mounted on gelatin-coated
slides, and stained with hematoxylin/eosin as described earlier
[26
].
Electron microscopy
Synovia were dissected from the knee joint and fixed in 2%
glutaraldehyde in 0.1 M cacodylate buffer pH 7.4 for 2 h.
Subsequently, the synovia were washed in cacodylate buffer, postfixed
in 1% OsO4 for 1 h, and washed and dehydrated in increasing
concentrations of ethanol. The 100% ethanol was replaced by 1,2
propylene-oxide and subsequently embedded in epon 812. Sections (90 nM)
were cut with a Reichert microtome and stained with uranyl acetate and
lead citrate. The sections were studied with an electron microscope
(Jeol 1200EX, Japan).
Isolation of thymocytes and apoptosis induction
After cervical dislocation, the thymus of a BALB/c mouse was
removed and stored in 10% fetal bovine serum (FBS) on ice. Apoptosis
was induced as described [27
]. Briefly, a single-cell
suspension of thymocytes was seeded in 10% FBS in Dulbeccos modified
Eagles medium (DMEM) (10% FBS/DMEM) supplemented with 1
m
dexamethasone (Genfarma, Maarssen, the Netherlands). After 3 h of
incubation, the cells were washed 3 times in medium and resuspended in
1 mL of 10% FBS/DMEM. Apoptosis was determined by
annexin-V-FITC/propidium iodide double staining [28
,
29
], which was analyzed in a Coulter EpicsXL flow
cytometer (Coulter Corporation, Hialiah, FL) equipped with a 488-nM
Argon laser.
Isolation of resident peritoneal macrophages
Resident peritoneal macrophages were isolated as previously
described [27
]. Briefly, closed peritoneal lavage was
performed on non-anesthetized mice. The peritoneal lavage was kept on
ice until seeding on plastic coverslips in 10% FBS/DMEM and allowed to
settle and adhere for 1.5 h, after which nonadherent cells were
removed by washing with 10% FBS.
Macrophage and apoptotic cell interaction in vitro
In vitro phagocytosis and subsequent scoring were performed as
described previously [26
]. In short, macrophages and
apoptotic thymocytes were allowed to interact for 10 min or 1 h,
after which the coverslips were rinsed with 10% FBS/DMEM, using a
Pasteur pipette to remove nonphagocytosed thymocytes. Immediately after
interaction, coverslips were spin-dried, fixed, and stained.
Preparations were scored at 400x magnification by regular light
microscopy.
Determination of chemotactic activity
Isolation of PMNs
Murine neutrophil granulocytes (PMNs) were isolated after
implantation of gelatin sponges (Willospon; Will-Pharma, Zwanenburg,
the Netherlands), a method developed by Middleton and Campbell
[30
]. After cells were collected, analysis of the
cytospin products showed that the cell suspension consisted
predominantly of neutrophil granulocytes (99%).
Chemotactic assay
PMN chemotaxis was measured using 12-well 6.5-mm Costar
Transwell culture plate inserts equipped with polycarbonate filters
(no. 3415, pore size 3 µm, polyvinyl pyrrolidone free; Costar,
Cambridge, MA). Next, 105 peritoneal macrophages were
attached to coverslips and 5 x 105 apoptotic cells or
non-apoptotic control cells were added and incubated for 1 h.
Non-ingested apoptotic or intact thymocytes were washed away by rinsing
the coverslips in 37oC DMEM. Macrophages were activated by
lipopolysaccharides (LPSs) (5 µg/ml) for 5 h. Then 500 µL of
culture supernatant was added to the bottom chamber of the transwell.
Subsequently, 100 µL of PMN suspension (105 cells/mL) was
loaded above the filter and incubated for 2 h at 37oC
in humified 5% CO2. As a positive control, 5%
zymosan-activated serum was used. Fresh serum was activated by 10%
zymosan for 1 h at 37oC. Phosphate-buffered saline
(PBS) was used as a negative control. Thereafter, cells in the bottom
chamber were counted by using a hemocytometer. We also made a
cytocentrifuge of 100 µL of supernatant. PMNs were stained with
Giemsa-May-Grünwald and counted under the microscope. Results are
expressed as the total number of cells in the bottom chamber 2 h
after incubation.
Injection of apoptotic cells into murine knee joints
Apoptotic (AN+/PI-) cells were injected (2 x
106 /6
L 10% FBS/DMEM) into the knee joint of BALB/c
mice. Apoptotic cells were injected in normal knee joints. At several
time points (10, 30, and 60 min) after injection of apoptotic cells,
mice were sacrificed and total knee joints or synovial specimens were
processed by light and electron microscopy. Furthermore, apoptotic
cells were injected in knee joints 1 h before arthritis induction.
Total knee joint sections were stained with hematoxylin/eosin or
immunostained with NIMP-R14 (an antibody that specifically binds a
2530-kD epitope mainly found on PMNs [31
]).
Briefly, sections were deparaffinized and pre-incubated for 15 min at
RT with 20% normal rabbit serum. Thereafter, sections were incubated
with NIMP-R14 antibodies for 1 h. After incubation with the second
antibody rabbit anti-rat peroxidase for 30 min, the sections were
stained for hematoxylin for 30 s. As a negative control, sections
were incubated with normal rat IgG instead of NIMP-R14. Joint
inflammation was scored as the total amount of PMNs found in synovium
(infiltrate) and knee joint cavity (exsudate) using an arbitrary scale
of 03 (0=no PMNs; 1=few; 2=some; 3=many).
 |
RESULTS
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Uptake of apoptotic cells by synovial lining macrophages during
early experimental ICA
To investigate whether the uptake of early apoptotic cells by
synovial lining cells takes place, we first checked the occurrence of
significant uptake of apoptotic leukocytes by synovial intimal cells
during experimental arthritis. In our model, large amounts of
leukocytes (mainly PMNs) migrated into the joint cavity and maximal
inflammation was found at day 2. After ICA induction, many inflammatory
cells were observed in close association with the synovial lining
(Fig. 1A
). We used electron microscopy for more detailed analysis. We were
able to demonstrate clear uptake of apoptotic cells in synovial
macrophages 1 and 2 days after ICA induction (Fig. 1B) .

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Figure 1. Murine knee joints were isolated 48 h after induction of immune
complexmediated arthritis. Prominent binding and uptake of leukocytes
by synovial lining macrophages (SLMs) in knee joint sections stained
with hematoxylin and eosin (A) was found by light microscopy. The upper
half of (A) represents the joint cavity infiltrated mainly with PMN,
whereas the lower half shows the synovial layer with the thin lining
layer containing predominantly type A macrophages (see arrows). The
electron micrograph shows binding of PMNs and phagocytosis of an
apoptotic PMN (Fig. 2B)
. Uptake was only found in synovial lining
macrophages. JC = joint cavity, SM = synovial macrophages,
L = leukocyte, S = synovium, AC = apoptotic cell.
Original magnification of light micrographs x200 and electron
micrographs x6750.
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Uptake of apoptotic cells by macrophages in vitro inhibits
chemotactic activity for PMNs
To obtain a model system to analyze the impact of phagocytosis of
apoptotic cells, apoptotic thymocytes (AN+/PI- cells) were incubated
with murine peritoneal macrophages attached to plastic coverslips.
AN+/PI- cells did bind and then were rapidly taken up by residential
macrophages within 10 min of incubation. After 60 min of incubation,
90% of the macrophages had taken up apoptotic thymocytes (Fig. 2
). Staining of these thymocytes with annexin V and PI showed that
mostly AN+/PI- were taken up by peritoneal macrophages whereas
AN-/PI- cells stayed outside the macrophage (data not shown).

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Figure 2. Uptake of early apoptotic cells by murine peritoneal macrophages
attached to coverslips. Coverslips were fixed 60 min after the addition
of apoptotic cells and were stained with hematoxylin/eosin. Original
magnification x1000.
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To directly investigate whether the uptake of apoptotic cells has
consequences for chemotaxis for PMNs, the supernatant of macrophages
given apoptotic cells or intact cells and subsequently activated by LPS
for 5 h was tested for its ability to attract PMN in a chemotactic
assay. Within 2 h, PMN migrated through the filter from the upper
to the lower compartment, which contained the supernatant of activated
macrophages. Migration of PMN induced by the supernatant of macrophages
that had phagocytosed apoptotic cells was significantly lower (58%)
(Fig. 3
).

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Figure 3. Migration of purified mouse PMNs in the transwell chemotaxis assay.
Significantly reduced migration of PMN was seen to culture supernatants
of LPS-activated macrophages that previously had engulfed early
apoptotic cells as compared to LPS-activated control macrophages. As a
positive control, 5% zymosan-activated serum (ZAS)/DMEM was used. We
used DMEM as a negative control. Values represent the mean
±SD of six measurements. data were evaluated with the
mann-whitney u test (**P<0.05).
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Uptake of apoptotic cells by macrophages in vivo
We further investigated whether apoptotic (AN+/PI-) cells were
also phagocytosed in vivo. Synovial lining type A macrophages differ
from other tissue macrophages. Type A cells are surrounded by a
collagen type IV matrix, which may disturb an efficient uptake.
AN+/PI- or intact cells (AN+/PI-) were injected directly into the
knee joint (2 x 106 in 6 µL).
Histological examination of total knee joints at 10, 20, and 30 min
after injection of intact AN+/PI- cells showed no binding and uptake
of these cells by synovial lining cells (data not shown). In contrast,
a clear binding to and uptake of AN+/PI- apoptotic cells was found
(Fig. 4A
). About 10% of the cells injected in the joint cavity bound to
the lining layer 10 min after injection. The binding decreased
thereafter. Electron microscopy identified type A cells, characterized
by large cell protrusions, as the cell type that phagocytosed apoptotic
cells (Fig. 4B)
. Type B cells, which have a more fibroblastic
appearance, did not bind or phagocytose apoptotic cells.

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Figure 4. Light (A) and electron micrographs (B) of knee joints, shortly after
injection of apoptotic cells directly into the knee joint (2 x
106 apoptotic cells in 6 l 10% FBS/DMEM). In the knee
joints, apoptotic cells were ungulfed by type A lining macrophages
covering the inside of the knee joints 10 min after intra-articular
injection. SM = synovial macrophage, AC = apoptotic cell.
Magnification light micrograph (A) = x1000 and electron
micrograph (B) = x9700.
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Uptake of apoptotic cells by synovial lining macrophages inhibits
the onset of ICA
To investigate whether lining cells that have phagocytosed apoptotic
cells influence the onset of ICA, 2 x 106 apoptotic
cells or intact control cells were injected directly into the knee
joint 1 h before arthritis induction. At 6 h and 24 h
after induction, mice were sacrificed and total knee joints were
processed for histology. In addition, total knee joints were either
stained with hematoxylin or immunostained with NIMP-R14, an antibody
that specifically stains PMNs. This allowed us to score the amount of
PMN in infiltrate and exsudate using an arbitrary scale. We found that
the infiltrate in the synovial layer was the same at 6 and 24 h
among the groups that received either apoptotic cells or intact control
cells (Fig. 5A
). The amount of PMNs in the exsudate, however, was significantly
lower (61%) in the joints pretreated with apoptotic cells at 24 h
but not at 6 h after ICA induction when compared to controls (Fig. 5A
5B
5C)
.

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Figure 5. Cell influx into the joint cavity (exudate) or synovium (infiltrate) in
arthritic knee joint sections stained with hematoxylin and eosin was
scored on a 03 scale (0=no influx, 1=minor, 2=moderate, 3=marked).
One hour before arthritis induction, 2 x 106
apoptotic cells in 6 µL 10% FBS/DMEM were injected into the knee
joints. Note the significant reduction in cell influx in the exudate at
24 h but not at 6 h after arthritis induction (A and
micrographs B = intact cells injected versus C = apoptotic cell
injected). No differences were found in the infiltrate both at 6 and
24 h. Values represent 2 experiments with 5 mice per group.
*P < 0.05 versus PBS alone by Mann-Whitney U test. P =
patella, F = femur, JS = joint space, S = synovium.
Original magnification of photographs x400.
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 |
DISCUSSION
|
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In this study we find clear uptake of apoptotic cells by synovial
lining macrophages during ICA. Apoptotic cells are taken up by almost
every cell type in the body, but macrophages have been very efficient
in clearing these cells. During rheumatoid arthritis (RA), prominent
apoptosis occurs within the synovial tissue. Using in situ end labeling
and agarose gel electrophoresis detecting DNA strand breaks, it was
found that the primary localization of the apoptotic cells was within
the synovial lining macrophages [32
]. Another study
showed a close correlation between the increasing propensity of
apoptosis in neutrophils and the degree of macrophage recognition of
the aging neutrophil population [33
].
First we studied the effect of apoptotic cell uptake by macrophages on
chemotactic activity for PMN. Using a transwell chemotactic assay for
PMNs, we found that chemotactic activity produced by activated
macrophages was significantly decreased when they had engulfed
apoptotic cells. Dexamethasone used for induction of apoptotis in
thymocytes may have an effect on macrophage function. However, the
dexamethasone concentration measured in the apoptotic cell suspension
was lower than 10-11 mM, and this concentration had no
effect on cytokine production (IL-1ß, TNF
) by macrophages after
stimulation by LPS (data not shown). Earlier studies revealed that
apoptotic cell uptake by mouse J744 macrophages inhibited synthesis and
secretion of the chemokines macrophage inflammatory protein-2 (MIP-2)
and macrophage inflammatory protein-1
(MIP-1
), which
predominantly attract PMNs. The predominantly monocyte-attracting
chemokine monocyte chemotactic protein (MCP-1/JE), however, was not
inhibited [18
]. Furthermore, the production of other
mediators such as IL-1 [34
] and enzymes
[35
] was decreased. Inhibition of chemokine production
is probably regulated by TGF-ß since this growth factor was increased
[18
, 19
, 36
], whereas
anti-TGF-ß neutralizing antibodies reversed the inhibiting effect of
apoptotic cell uptake [34
]. Moreover, TGF-ß is
released by human macrophages in response to ingestion of apoptotic
neutrophils [34
], whereas exogenous TGF-ß
down-regulated the synthesis of the PMN-specific chemokine production
[18
].
To determine whether this in vitro inhibitory effect was also found in
vivo, we first investigated whether early apoptotic cells are engulfed
by type A intimal cells if injected into the joint. Type A intimal
cells lie within a reticular network that is presumably a product of
type B synovial cells and consists of collagen type IV, heparan sulfate
proteoglycan, and laminin [37
]. Despite the layer
surrounding the synovial type A cells, we found prominent binding and
uptake of apoptotic cells at 10 min after intra-articular injection.
More than 18 distinct integrins have been described on the synovial
macrophage that may be involved in this process [37
].
During joint inflammation, the components of the reticular network
surrounding the macrophage are partly degraded by enzymes, which may
thus lead to exposure of receptors that are more efficiently involved
in clearance of apoptotic cells.
We further analyzed whether apoptotic cell uptake by type A cells had
consequences for joint inflammation. When injected into murine knee
joints before experimental arthritis induction, apoptotic cells caused
inhibition of PMN influx within the joint cavity. In the immune complex
arthritis model, two chemotactic factors seem of utmost importance for
PMN migration: namely, C5a and IL-1. Elimination of C5a by Cobra venom
factor pretreatment before arthritis induction prevented PMN migration
for the most part [25
]. C5a probably forms the main
PMN-attracting component during the first hours of this arthritis.
Since we found no effect of apoptotic cell uptake by synovial
macrophages on arthritis development after 6 h, we concluded that
apoptotic cells probably do not alter C5a generation. The second major
regulating factor is IL-1, which is formed several hours after the
onset of arthritis [25
]. Neutralization of the formed
IL-1 using anti-IL-1 antibodies [25
] or IL-1ra
[38
] largely prevented the influx of PMNs. IL-1 is not
chemotactic but probably acts by mediating the production of
PMN-attractive factors such as MIP-2 and MIP-1
by synovial
macrophages. Engulfment of apoptotic cells by macrophages may thus
inhibit synthesis and secretion of these PMN-attracting chemokines
either directly or indirectly by lowering IL-1 production. Synovial
lining macrophages were important producers of chemokines in this model
since selective removal of these cells using clodronate-containing
liposomes before arthritis induction prevented both joint inflammation
and chemokine production [39
].
Engulfment of apoptotic cells by lining macrophages significantly
inhibited PMN migration into the joint cavity but not in the synovial
layer 24 h after arthritis induction. In earlier studies we found
that complete removal of type A cells before ICA induction completely
blocked synovial and joint cavity cell influx [39
]. It
seems likely that apoptotic cell engulfment blocks superficial lining
macrophage activation only in part, because the local chemokine levels
are sufficient to attract inflammatory cells into the synovium but
insufficient to promote traffic to the joint space. When other
particles, such as empty liposomes, were injected, they were also
selectively taken up by lining macrophages, but this did not alter the
onset and severity of ICA [21
], which means that the
uptake of particles alone does not lower the inflammatory function of
the lining macrophage.
During RA, large amounts of inflammatory cells are found within the
synovial fluid. These cells posses potent degrading enzymes and
pro-inflammatory mediators, and their removal is vital for resolution
of the inflammation. Apoptosis and subsequent disposal by macrophages
have been a major route for direct removal of effete inflammatory
cells. This study shows that apoptotic cells are engulfed by resident
synovial lining macrophages, which are crucial in the onset,
propagation, and exacerbation of arthritis. Inhibition of residential
synovial macrophages lining the joint cavity, by uptake of apoptotic
cells, may be an important physiological mechanism contributing to the
resolution of joint inflammation.
Received March 17, 2001;
revised July 1, 2001;
accepted July 9, 2001.
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REFERENCES
|
|---|
-
Klippel, J. H. eds. Primer on the rheumatic diseases 1997 Arthritis Foundation Atlanta.
-
Wyllie, A.H., Kerr, J. F., Currie, A. R. (1980) Cell death: The significance of apoptosis Int. Rev. Cytol. 68,251-306[Medline]
-
Hengartner, M. O. (2000) The biochemistry of apoptosis Nature 407(6805),770-776[Medline]
-
Casciola-Rosen, L. A., Anhalt, G., Rosen, A. (1994) Autoantigens targeted in systemic lupus erythematosus are clustered in two populations of surface structures on apoptotic keratinocytes J. Exp. Med. 179(4),1317-1330[Abstract/Free Full Text]
-
Savill, J., Dransfield, I., Hogg, N., Haslett, C. (1990) Vitronectin receptor mediated phagocytosis of cells undergoing apoptosis Nature 343,170-173[Medline]
-
Savill, J., Hogg, N., Ren, Y., Haslett, C. (1992) Thrombospondin cooperates with CD36 and the vitronectin receptor in macrophage recognition of neutrophils undergoing apoptosis J. Clin. Invest. 90,1513-1522
-
Luciani, M. F., Chimini, G. (1996) The ATP binding cassette transporter ABC1 is required for the engulfment of corpses generated by apoptotic cell death EMBO J 15,226-235[Medline]
-
Platt, N., Susuki, H., Kurihara, Y., Kodama, T., Gordon, S. (1996) Role for the class A macrophage scavenger receptor in the phagocytosis of apoptotic thymocytes in vitro Proc. Natl. Acad. Sci.USA 93,2456-2460
-
Devitt, A., Moffatt, O. D., Raykundalia, C., Capra, J. D., Simmons, D. L., Gregory, C. D. (1998) Human CD14 mediates recognition and phagocytosis of apoptotic cells Nature 392,505-509[Medline]
-
Sambrano, G. R., Steinberg, D. (1995) Recognition of oxidatively damaged and apoptotic cells by an oxidized low-density-lipoprotein receptor on mouse peritoneal macrophages of membrane phosphatidylserine Proc. Natl. Acad. Sci.USA 92,1396-1400[Abstract/Free Full Text]
-
Fadok, V. A., Voelker, D. R., Campbell, P. A., Cohen, J. J., Bratton, D. L., Henson, P. M. (1992) Exposure of phosphatidylserine on the surface of apoptotic lymphocytes triggers specific recognition and removal by macrophages J. Immunol. 148,2207-2216[Abstract]
-
Mofatt, O. D., Devitt, A., Bell, E. D., Simmons, D. L., Gregory, C. D. (1999) Macrophage recognition of ICAM-3 on apoptotic leukocytes J. Immunol. 162,6800-6810[Abstract/Free Full Text]
-
Savill, J. S., Wyllie, A. H., Henson, J. E., Walport, M. J., Henson, P. M., Haslett, C. (1989) Macrophage phagocytosis of aging neutrophils in inflammation programmed cell death in the neutrophil leads to its recognition by macrophages J. Clin. Invest. 83(3),865-875
-
Savill, J. S. (1997) Apoptosis in resolution of inflammation J. Leuk. Biol. 61(4),375-380[Abstract]
-
Squier, M. K., Sehnert, A. J., Cohen, J. J. (1995) Apoptosis in leukocytes J. Leuk. Biol. 57(1),2-10[Abstract]
-
Voll, R. E., Herrmann, M., Roth, E. A., Stach, C., Kalden, J. R., Girkontaite, I. (1997) Immunosuppressive effects of apoptotic cells Nature 27(390(6658)),350-351
-
Fadok, V. A., McDonald, P. P., Bratton, D. L., Bratton, D. L., Henson, P. M. (1998) Regulation of macrophage cytokine production by phagocytosis of apoptotic and post-apoptotic cells Biochem. Soc. Trans. 26(4),653-656[Medline]
-
McDonald, P. P., Fadok, V. A., Bratton, D., Henson, P. M. (1999) Transcriptional and translational regulation of inflammatory mediator production by endogenous TGFbeta in macrophages that have ingested apoptotic cells J. Immunol. 163(11),6164-6172[Abstract/Free Full Text]
-
Freire-de-Lima, C. G., Nascimento, D. O., Soares, M. B., Bozza, P. T., Castro Neto, H. C., de Mello, F. G., DosReis, G. A., Lopes, M. F. (2000) Uptake of apoptotic cells drives the growth of a pathogenic trypanosome in macrophages Nature 403(6766),199-203[Medline]
-
Henderson, B. (1988) The synovial lining cell and synovitis Scand. J. Rheum. 76,33-38
-
Van Lent, P.L.E.M., Holthuysen, A.E.M., van den Bersselaar, L.A.M., van Rooijen, N., van de Putte, L.B.A., van den Berg, W. B. (1995) Role of macrophage-like synovial lining cells in localisation and expression of experimental arthritis Scand. J. Rheumatol. 24(suppl 101),83-89
-
Van Lent, P.L.E.M., Holthuysen, A.E.M., van den Bersselaar, L.A.M., van Rooijen, N., Joosten, L.A.B., van de Loo, F.A.J., van de Putte, L.B.A., van den Berg, W. B. (1996) Phagocytic lining cells determine local expression of inflammation in type II collagen-induced arthritis Arthritis Rheum 39,1545-1555[Medline]
-
Van Lent, P.L.E.M., van den Bersselaar, L.A.M., Holthuysen, A.E.M., van Rooijen, N., van de Putte, L.B.A., van den Berg, W. B. (1994) Phagocytic lining cells in experimentally arthritis: downregulation of synovitis by CL2MDP-liposomes Rheumatol. Int. 13,221-228
-
Van Lent, P.L.E.M., Holthuysen, A.E.M., van Rooijen, N., van de Loo, F.A.J., van de Putte, L.B.A., van den Berg, W. B. (1998) Phagocytic synovial lining cells regulate acute and chronic joint inflammation after antigenic exacerbation of smouldering experimental murine arthritis J. Rheumatol. 25,1135-1145[Medline]
-
Van Lent, P.L.E.M., Van den Bersselaar, L.A.M., Van den Hoek, A.E.M., van de Loo, A.A.J., van den Berg, W. B. (1992) Cationic immune complex arthritis in mice: a new model. Synergistic effect of complent and interleukin-1 Am. J. Pathol. 140(6),1451-1461[Abstract]
-
Van den Berg, W. B., van de Putte, L.B.A. (1985) Electrical charge of the antigen determines its localisation in the mouse knee joint: deep penetration of cationic BSA in hyaline articular cartilage Am. J. Pathol. 121,224-234[Abstract]
-
Licht, R., Jacobs, C.W.M., Tax, W.J.M., Berden, J.H.M. (1999) An assay for the quantitative measurement of in vitro phagocytosis of early apoptotic thymocytes by murine resident peritoneal macrophages J. Immunol. Methods 223(2),237-248[Medline]
-
Vermes, I., Haanen, C., Steffens-Nakken, H., Reutelingsperger, C. (1995) A novel assay for apoptosis. Flow cytometric detection of phosphatidylserine expression on early apoptotic cells using fluorescein labelled Annexin V J. Immunol. Methods 184(1),39-51[Medline]
-
Martin, S. J., Reutelingsperger, C. P., McGahon, A. J., Rader, J. A., Van Schie, R. C., LaFace, D. M., Green, D. R. (1995) Early redistribution of plasma membrane phosphatidylserine is a general feature of apoptosis regardless of the initiating stimulus. Inhibition by overexpression of Bcl-2 and Abl J. Exp. Med. 182(5),1545-1556[Abstract/Free Full Text]
-
Middleton, M. M., Campbell, P. A. (1983) Functions of purified mouse neutrophils isolated from gelatin sponges J. Leuk. Biol. 46,461-466[Abstract]
-
Chang, H. R., Vesin, C., Grau, G. E., Pointaire, P., Arsenijevic, D., Strath, M., Pechère, J. C., Piquet, P. F. (1993) Respective role of polymorphonuclear leukocytes and their integrins (CD-11/18) in the local or systemic toxicity of lipopolysaccharide J. Leuk. Biol. 53,636-639[Abstract]
-
Firestein, G. S., Yeo, M., Zvaifler, N. J. (1995) Apoptosis in rheumatoid synovium J. Clin. Invest. 96(3),1631-1638
-
Jones, S. T., Denton, J., Holt, P. J., Freemont, A. J. (1993) Possible clearance of effete polymorphonuclear leukocytes from synovial fluid by cytophagocytic mononuclear cells: implications for pathogenesis and chronicity in inflammatory arthritis Ann. Rheum. Dis. 52(2),121-126[Abstract/Free Full Text]
-
Fadok, V. A., Bratton, D. L., Konowal, K., Freed, P. W., Westcott, J. Y., Henson, P. M. (1998) Macrophages that have ingested apoptotic cells in vitro inhibit pro-inflammatory cytokine production through autocrine/paracrine mechanisms involving TGFß,GE2, and PAF J. Clin. Invest. 101,890-898[Medline]
-
Stern, M., Savill, J., Haslett, C. (1996) Human monocyte-derived macrophages phagocytosis of senescent eosinophils undergoing apoptosis: mediation by
vB3/CD36/thrombospondin recognition mechanism and lack of phlogistic response Am. J. Pathol. 149,911-921[Abstract]
-
Barker, R. N., Erwig, L., Pearce, W. P., Devine, A., Rees, A. J. (1999) Differential effects of necrotic or apoptotic cell uptake on antigen presentation by macrophages Pathobiol 67,302-305
-
Zvaifler, N. J. (1995) Macrophages and the synovial lining Scand. J. Rheumatol. 24(suppl 101),67-75
-
Van Lent, P.L.E.M., Blom, A., Holthuysen, A.E.M., Jacobs, C.W.M., van de Putte, L.B.A., van den Berg, W. B. (1997) Monocytes rather than PMN are involved in early cartilage degradation in cationic immune complex complex arthritis in mice J. Leuk. Biol. 61,267-278[Abstract]
-
Van Lent, P. L., van den Hoek, A. E., van den Bersselaar, L. A., Spanjaards, M. F., van Rooijen, N., Dijkstra, C. D., van de putte, L. B., van den Berg, W. B. (1993) In vivo role of phagocytic synovial lining cells in the onset of experimental arthritis Am. J. Pathol. 143(4),1226-1237[Abstract]