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Regular Articles |
From the Department of Vascular Biology,*
SmithKline
Beecham Pharmaceuticals, New Frontiers Science Park North, Coldharbour
Road, Harlow, Essex, the United Kingdom, Department of Pulmonary
Pharmacology,
SmithKline Beecham
Pharmaceuticals, King of Prussia, Pennsylvania, and Department of
Surgery,
St. Thomas's Hospital, London,
the United Kingdom
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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and interferon-
but not in SMC stimulated with serum.
Both PARC and ELC mRNA were expressed by monocyte-derived macrophages
but not monocytes. The expression patterns of PARC and ELC mRNA in
human atherosclerotic lesions suggest a potential role for these two
recently described CC chemokines in attracting T lymphocytes into
atherosclerotic lesions.
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The presence of T cells in addition to macrophages in atherosclerotic
lesions indicates that there are immunological events occurring in
conjunction with inflammatory ones.1,2
The earliest visible
stage of the disease, the so-called "fatty streak" is characterized
by the presence of monocyte/macrophages and T lymphocytes in the
intima. After entry into the arterial intima, monocytes differentiate
into macrophages, many of which become foam cells following ingestion
of modified lipoprotein particles, notably oxidized LDL (low density
lipoprotein). Both CD4+ and CD8+ T cells have
been found in human plaques, and many of these cells have been shown to
be in an activated state and producing the cytokine interferon-
(INF-), a potent macrophage activating factor.3
The
occurrence of activated T cells in plaques supports the idea that there
may be a specific immune response in operation during atherosclerosis.
Additional evidence for the implication of local immunological
mechanisms in atherosclerosis comes from the finding of
CD4+ T cells in lesions of the apolipoprotein E (ApoE)
knockout mouse throughout all stages of development.4
T cells and macrophages, in addition to the arterial smooth muscle
cells (SMC) and endothelium, are capable of producing a wide range of
cytokines and growth factors.5
Chemokines are a superfamily
of small (8 to 10 kd) cytokines with four conserved cysteine residues,
which are potent chemoattractants for leukocytes.6,7
To date, four classes of chemokines, containing approximately 40
members, have been identified based on the arrangement of the conserved
cysteines. In the CC chemokine family (eg, monocyte chemoattractant
protein-1 (MCP-1) and macrophage inflammatory protein-1 (MIP-1))
these cysteine residues are adjacent, whereas the CXC chemokines (eg,
interleukin (IL)-8 and IP (inducible protein)-10) have an intervening
amino acid between the first two cysteines.7
The C
chemokine family contains just one member to date, lymphotactin, which
lacks two of the four conserved cysteines.8
Fractalkine,
the only CX3C chemokine family member, has three
intervening amino acid residues between the first two cysteines and is
encoded as a membrane bound molecule with the chemokine domain attached
to a mucin-like stalk.9
Different chemokine classes tend to
display different ranges of leukocyte specificity. CXC chemokines
preferentially attract neutrophils, whereas CC chemokines attract
monocytes, T and B cells and eosinophils. Chemokine activities are
mediated by seven transmembrane domain G protein coupled receptors. To
date, at least eight receptors for CC chemokines and five for CXC
chemokines have been characterized.7
MCP-1, a potent monocyte chemoattractant, is the prototype for the CC
chemokine family.10
MCP-1, 2, 3, and 4, RANTES (regulated
on activation normal T expressed and secreted chemokine), MIP-1, and
MIP-1ß are all chemoattractants for monocytes albeit with differing
potencies.10-12
MCP-1 was the first CC chemokine found to
be expressed in human atherosclerotic lesions13,14
and its
production either singularly or in combination with other chemokines is
postulated to be responsible for the continued influx of monocytes into
atherosclerotic plaques. All of the aforementioned CC chemokines are
capable of attracting several classes of blood
leukocytes7,15
and many can bind and signal through a
number of different receptors.7
Recently, four CC
chemokines have been characterized and shown to selectively attract T
cells: PARC/DC-CK1 (dendritic cell derived CC
chemokine),16,17
ELC/MIP-3ß,18,19
SLC,20
and LARC.21
Of particular interest in
the context of atherosclerosis is the finding that PARC shows a
specificity for naive, resting T cells.17
This property is
not shared by other T-cell chemoattractants such as RANTES, MIP1-,
and IL-8.17
ELC and SLC are known to act through
CCR7/EBI122,23
and LARC through CCR6.22
The
receptor for PARC has not yet been identified. Given the fact that T
cells are present throughout plaque development2,4
and
their presence is thought to be caused by active recruitment and local
polyclonal T-cell activation rather than clonal antigenic
expansion,24
we investigated the gene expression of these
new lymphocyte specific chemoattractants in human atherosclerotic
lesions.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Plaque samples used in this study were carotid endarterectomy specimens (n = 14 for ELC and n = 18 for PARC) from patients undergoing vascular reconstructive surgery for arterial occlusive disease and internal mammary arteries (n = 4). Tissues were either mounted in OCT compound-embedding medium (Agar Scientific Ltd., Essex, UK) and frozen in liquid nitrogen or snap-frozen in liquid nitrogen and mounted in OCT prior to cryostat sectioning. All specimens were stored at -70°C.
Cell Culture
Human Monocyte-Derived CD1a+ Dendritic Cells
Human peripheral blood monocytes were prepared from blood as
previously described.25
Monocyte derived dendritic cells
were prepared essentially as described by Zhou and
Tedder.26
The purified monocyte fraction was resuspended in
supplemented RPMI 1640 medium supplemented with 10% fetal bovine serum
(FBS), 20 mmol/L L-glutamine, 100 U/ml penicillin, and 100
µg/ml streptomycin (Gibco BRL, Grand Island, New York). Cells were
maintained in T-75 flasks with IL-4 (500 U/ml) and 800 U/ml GM-CSF and
100 U/ml tumor necrosis factor (TNF)- was added on day 5 (all
cytokines from Peprotech, Rocky Hill, NJ). Medium was changed on days
3 and 5. On day 8, cells were harvested by centrifugation,
washed with phosphate-buffered saline (PBS), 1% bovine
serum albumin (BSA), 0.1% NaN3 and stained with
phycoerythrin-conjugated anti-human CD1a (DAKO, Glostrup, Denmark).
Positively stained cells were sorted on a FACSort
(Becton-Dickinson, Bedford, MA) to a purity >98%.
Human CD4+ Blood Dendritic Cells
Cells were purified from peripheral blood using the MACS immunomagnetic blood dendritic cell isolation kit (Miltenyi Biotec, Auburn, CA) according to the manufacturer's protocol.
Monocyte Stimulation
The monocyte enriched fraction from a Percoll separation was further enriched by incubation for 1 hour in RPMI 1640 medium, 10% FBS, after which nonadherent cells were washed off. Monocytes were resuspended in RPMI/FBS and treated with 0.1 µg/ml lipopolysaccharide (LPS) (E. coli serotype 055.B5) (Sigma, St. Louis, MO) for 18 hours.
THP-1 Cell Culture, Differentiation and Foam Cell Formation
The human monocyte cell-line THP-1 was cultured in RPMI 1640 medium supplemented with 10% fetal calf serum (FCS) 100 units/ml penicillin, 100 µg/ml streptomycin, 2 mmol/L Glutamax, and 18 µmol/L 2-mercaptoethanol. All media and supplements were obtained from Gibco BRL Life Technologies Ltd. (Paisley, UK).
THP-1 cells were differentiated to anchorage-dependent macrophages by the addition of 0.2 µg/ml phorbol-12-myristate-13-acetate (PMA, Sigma Chemical Co, Dorset, UK) to T225 flasks 7 days after seeding. Cells became anchorage dependent within 24 hours and took on macrophage morphology within 48 hours. At this point either RNA was extracted from the cells or 50 µg/ml oxidized human LDL (ox-LDL) was added in 100 ml of fresh medium for an additional 72 hours. Human LDL was purchased from Calbiochem-Novabiochem Ltd. (Nottingham U.K.) and oxidized with 5 µmol/L CuSO4 for 24 hours at 37°C in the absence of EDTA. Uptake of the ox-LDL resulted in accumulation of fat droplets within the cells. This was confirmed by positive staining with oil red-O.
Human Aortic Smooth Muscle Cells
Cryopreserved human aortic SMC were obtained from
BioWhittaker (Berkshire, UK). SMC were cultured according to
manufacturer's instructions in smooth muscle cell basal medium (SmBM)
supplemented with smooth muscle cell growth medium SingleQuot
BulletKit-2. The resulting smooth muscle cell growth medium (SmGM-2)
contained 0.5 ng/ml human epidermal growth factor, 5 ug/ml insulin, 2
ng/ml human fibroblast growth factor, 50 ug/ml gentamicin, 50 pm/ml
amphotericin-B, and 5% FBS. Cultures were maintained at 37°C in a
humidified 95% air, 5% CO2 atmosphere in T75 flasks
(Costar UK Ltd., Buckinghamshire, UK). SmGM-2 was replaced with fresh
medium every 2 to 3 days until confluence was reached, and SMC were
subsequently subcultured after treatment with 0.025% trypsin and
0.01% EDTA. SMCs used in these experiments were between passage 4 and
8. Cells stained positive for SMC -actin.
For cytokine stimulation experiments, SMCs were cultured in T75 flasks
for 4 days in SmGM-2 until semiconfluent. SmGM-2 supplements were then
reduced to 50% for 24 hours and subsequently made fully quiescent in
SmBM containing only 0.5% FBS for an additional 18 hours. SMC were
then treated with 10 ng/ml TNF- and 10 ng/ml INF- in SmBM, 0.5%
FBS for 8 and 24 hours. For the serum stimulation experiments, the
cells were made quiescent as described above and then stimulated with
10% FBS for 1, 2, 4, 8, 24, and 48 hours.
Oligonucleotide Primers
Oligonucleotide primers were designed using DNASTAR software and
obtained from Cruachem Ltd. (Glasgow, UK). Primer pairs for the
chemokines and ß-actin were designed in the coding region of the cDNA
(Table 1)
.
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RNA was isolated from human carotid endarterectomy specimens and cell lines using either Trizol reagent (Gibco BRL) or RNAzol B (Biotecx, Houston, TX) as per manufacturer's instructions. cDNA was reverse transcribed from 1 µg of DNase (Gibco BRL) treated total RNA using Superscript II (Gibco BRL) as per manufacturer's instructions. For each sample, a parallel RNA was run with no Superscript II. Polymerase chain reaction (PCR) was carried out in 50 µl of reaction volumes containing 5 µl of 5x diluted cDNA, 1.5 mmol/L MgCl2, 0.5 µmol/L of each primer, 0.2 mmol/L of each NTP, and 5 units of Taq polymerase (Gibco BRL). The amplification profile consisted of 30 cycles (35 cycles for LARC) of 94°C for 1 minute, annealing temperatures of 50 to 55°C for 1 minute, and extension for 30 seconds at 72°C with one final cycle of extension at 72°C for 5 minutes. Each PCR reaction was run with the following negative controls: human genomic DNA, water instead of RNA, and a parallel no reverse transcriptase sample for each cDNA used. The positive control for size of products was pBluescript SK containing the cDNA of interest.
Probes
The chemokine cDNAs used in this study were initially identified at Human Genome Sciences (HGS) (Rockville, MD) by random sequencing of expressed tags in cDNA libraries from human pulmonary artery (PARC), human fetal spleen (ELC), human fetal lung (SLC), and monocytes (LARC). Full length clones were identified and sequenced at HGS and found to be identical to PARC, ELC, SLC, and LARC (clone numbers 35312, 49487, 50795, and 220914, respectively). The cDNA probes used for preparing riboprobes were the full length clones inserted between the EcoRI (5') and Xhol (3') sites of pBluescript SK- (Strategene, Cambridge, UK). Sense and antisense RNA probes were labeled with 35S UTP (Amersham Pharmacia Biotech Buckinghamshire, UK) using T3 or T7 polymerase (Promega, Southampton, UK), respectively. Prior to ethanol precipitation of the probe, 1 µl of the reaction was run on a 4% polyacrylamide/urea gel (Gibco BRL) to check for full length transcripts. Transcript sizes were approximately 750, 650, 850, and 800 bp for PARC, ELC, SLC, and LARC, respectively.
In Situ Hybridization
Transverse tissue sections (10 µm) were thaw mounted onto Superfrost+ microscope slides (BDH, Leicestershire, UK). Sections were fixed in fresh 4% paraformaldehyde in PBS, pH 7.4, acetylated in 0.25% acetic anhydride/0.1 mmol/L triethanolamine/0.1 mol/L NaCl and dehydrated and delipidated through a graded series of alcohols and chloroform. Sections were air dried and stored at -70°C until use.
RNA sense and antisense probes were resuspended at 25,000 cpm/µl in hybridization buffer (50% formamide, 0.02% w/v BSA, 0.02% polyvinylpyrrolidone, 0.02% ficoll, 100 µg/ml polyadenylate, 100 µg/ml denatured salmon sperm DNA, 100 µg/ml yeast tRNA, 4x SSC, 10% dextran sulphate, 10 mmol/L dithiothreitol), and slides were incubated overnight in a sealed humid chamber at 55°C. After hybridization, the sections were washed with 1x SSC at room temperature for 30 minutes, treated with 20 µg/ml RNase A in buffer and then with buffer alone (500 mmol/L NaCl, 10 mmol/L Tris, pH 8.0, 1 mmol/L EDTA, 30 minutes each at 37°C), washed with 1x SSC (room temperature, 30 minutes), followed by a high stringency wash (0.5x SSC at 65°C for 30 minutes) and 0.5x SSC at room temperature for 2 x 10 minutes. Slides were dehydrated through a series of alcohols, air dried, and dipped in photographic emulsion (Amersham Pharmacia Biotech). Slides were exposed for 3 to 9 weeks at 4°C and developed using Kodak D19 (1:1 water), counterstained in toluidine blue, dehydrated through a graded series of alcohols, and coverslipped for microscope analysis.
Immunohistochemistry
Serial transverse tissue sections (10 µm) were thaw mounted onto
Superfrost+ microscope slides, refrozen, and stored at -70°C until
use. For immunohistochemistry (IHC), sections were air-dried for 1 hour
and fixed in acetone for 10 minutes. IHC was performed using the
avidin-biotin-peroxidase complex method. All incubations were done at
room temperature unless otherwise stated. Briefly, endogenous
peroxidase activity was blocked by incubating slides in 0.6%
H2O2 in methanol. Nonspecific binding was
blocked by incubating sections in normal rabbit serum before applying
the primary antibody. Optimal primary antibody concentrations were
predetermined by titration and slides were incubated for 60 minutes in
the appropriate primary antibody dilutions. Slides were then incubated
in biotinylated rabbit anti-mouse secondary antibody (DAKO Ltd.,
Buckinghamshire, UK) for 30 minutes, washed, and incubated with
avidin/biotinylated horseradish peroxidase complex for 30 minutes.
Slides were then stained with diaminobenzidine tetrahydrochloride
substrate. The sections were counterstained with haematoxylin,
dehydrated through a graded series of alcohols, and mounted in
DPX. Negative controls were omission of primary antibody and
substitution of primary antibody with appropriate isotype. The cellular
composition of the plaques was determined using a panel of
characterized antibodies: HHF35 (specific for smooth muscle -actin),
CD68, a specific macrophage marker, Von Willebrand factor for
endothelial cells, CD1a, a dendritic cell marker (all from DAKO) and
CD3 leu, a marker for T cells (Becton Dickinson, Oxford, UK).
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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In order to study PARC, ELC, SLC, and LARC gene expression in
human atherosclerotic plaques, we initially screened a number of cDNAs
derived from carotid endarterectomy specimens using gene specific
primers (Table 1)
. A clear product for PARC was obtained from all six
samples and for ELC in four of six samples. However, products for LARC
and SLC were less clear (Figure 1)
.
ß-actin was used to assess the quality of the carotid endarterectomy
RNA. The plasmid containing the cDNA insert for the gene of interest
was used in all four cases as a positive control for PCR product size.
|
In order to further characterize the gene expression of PARC, ELC,
SLC, and LARC in normal and diseased human arteries, we carried out
in situ hybridization using 35S-labeled
riboprobes. After 3 weeks development time in photographic emulsion,
strong signals were observed for PARC and ELC in a large number of the
carotid endarterectomy sections studied (n = 14
of 18 and 12 of 14, respectively). Replicate slides were developed at
intervals and, in agreement with reverse transcriptase (RT)-PCR data,
no signal was observed for SLC or LARC in the plaque sections even
after 9 weeks in emulsion. To determine the cellular composition of
lesions and determine the cell types expressing PARC and ELC mRNA, we
carried out immunohistochemical staining of serial sections
with markers for SMC (-actin), macrophages (CD68), endothelial
cells (Von Willebrand Factor), T cells (CD3), and dendritic cells
(CD1a) (all results are not shown). Figure 2
shows PARC mRNA expression in a
representative carotid endarterectomy sample. In all positive cases (14
of 18), PARC mRNA expression was detected in macrophage-rich areas of
the lesion as determined by positive CD68 staining. Expression was
detected around necrotic regions and, where present, in areas of
calcification. However, PARC was not expressed in all CD68 positive
areas. All specimens were probed using the PARC sense strand and in all
cases the sections were devoid of silver grain clusters. mRNA
expression for ELC in lesions was found to be more widespread than PARC
mRNA and was associated with both intimal SMC and macrophages. Figure 3
shows ELC mRNA expression by
macrophages and some diffuse mRNA expression can also be observed in
the underlying SMC. In lesions displaying severe calcification
(n = 4), ELC mRNA was also found to be expressed
strongly by medial SMC in addition to lesion associated cells (Figure 4)
. No expression was observed in the
panel of sections probed with the ELC sense strand. In control mammary
arteries, no positive signal was detected for PARC nor SLC or LARC
(results not shown). However, low levels of expression of ELC were
detected in the medial SMC of mammary arteries. Some signal over
background is also visible in the adventitia of these vessels (Figure 5)
.
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In order to gain some information on the regulation of expression
of PARC and ELC in SMC and monocyte/macrophages, we carried out
RT-PCR on cDNAs derived from a range of stimulated and nonstimulated
cells. No PCR products were found for PARC in quiescent SMC or SMC
stimulated with serum for 1, 2, 4, 8, 16, 24, or 48 hours. It was also
not expressed by naive THP-1 cells or THP-1 cells treated with PMA or
incubated with oxidized LDL (results not shown). SMC stimulated with
TNF- and INF- also failed to express PARC. We did, however, find
PARC to be clearly expressed by human monocyte-derived
CD1a+ dendritic cells but not by human peripheral blood
derived dendritic cells. Human blood-derived monocytes also failed to
show a specific PCR product, but clear expression was detected in
monocytes that had been activated with LPS (Figure 6)
.
|
and IFN- for
24 hours. Clear PCR products could also be detected in human blood
derived monocytes that had been activated with LPS but not in
unstimulated monocytes (Figure 6)
. No PCR products for ELC were
detected in CD4+ dendritic cells. All cell preparations and
PCR reactions were done in duplicate. Clear ß-actin product can be
seen for all the cells used in this experiment. |
Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The presence of chemokines in atherosclerosis and related conditions is
well documented, suggesting an important role for these molecules in
the pathogenesis of the disease. MCP-1, MCP-4, and RANTES have all been
found to be expressed by plaque macrophages.11,13,27
In
addition, other cell types have been found to express these chemokines:
MCP-1 by SMC and MCP-4 by endothelial cells of the vasa
vasorum.11,13
Chemokine expression is also associated with
abdominal aortic aneurysms and transplant-associated accelerated
atherosclerosis.28,29
In this study, we have found ELC mRNA
to be expressed in atherosclerotic lesions by both intimal SMC and
macrophages. Both cell types in plaques are known to be responsible for
local production of a wide range of growth factors and
cytokines.5
Furthermore, our data also indicate strong
expression of ELC mRNA in the medial SMC of lesions that are highly
calcified. The ability of SMC to express ELC in carotid endarterectomy
specimens suggests a pro-inflammatory role for these cells in human
atherosclerosis. Indeed, we found that ELC mRNA could be up-regulated
in human aortic SMC by INF- and TNF- but not by serum alone.
Several other in vitro studies have shown that
pro-inflammatory cytokine treatment of SMC results in increased levels
of expression/secretion of CC chemokines, eg, human vascular SMC
treated with IL-1- or TNF- secrete increased amounts of IL-8,
MCP-1, and RANTES,30
whereas human airway SMC can express
RANTES mRNA and protein in response to treatment with TNF- alone and
to a greater extent with TNF- in combination with
INF-.31
These inflammatory cytokines are known to be
expressed in atherosclerotic plaques, INF- by T cells,3
and TNF- by macrophages.27
As indicated above, we found
that ELC mRNA was also expressed by macrophages in atherosclerotic
lesions. ELC was independently identified as MIP-3ß and found to be
expressed in an activated monocyte cDNA library.19
We found
expression of ELC mRNA by monocytes activated by LPS but not in naive
monocytes, further suggesting a role for ELC in the pro-inflammatory
processes occurring during atherogenesis.
Our studies revealed PARC mRNA to show a more restricted pattern of expression in atherosclerotic plaques, localizing with CD68+ macrophages. Of all the stimulated/unstimulated cells we examined in vitro, PARC mRNA expression was confined to monocyte-derived dendritic cells and LPS-activated monocytes. Previously, Adema et al.17 found DC-CK1/PARC mRNA to be expressed in monocyte-derived dendritic cells in vitro but in contrast to our findings, not to be expressed by LPS activated monocytes. Our in situ hybridization showed mRNA expression for PARC in CD68+ macrophages in line with our in vitro findings. We did find sparse CD1a+ dendritic cells in carotid endarterectomy specimens (results not shown) but these cells were not associated with PARC mRNA expression. The presence of CD1a+ dendritic cells in atherosclerotic plaques has been reported in the literature.32,33 However, it has not yet been clarified as to whether these cells play a role in antigen presentation during atherosclerosis. It is thought that destruction of these cells may be involved in the calcification process through release of the calcium binding protein S-100.33 In agreement with our data, Hieshima et al.16 found that PARC mRNA could be induced in monocytes differentiated with LPS and in U937 cells stimulated with PMA. Also, in situ studies in lung sections showed high PARC expression in a subset of alveolar macrophages that stained positive for EBM11/CD68.16 The expression pattern for PARC mRNA by macrophages in human atherosclerosis strongly suggests a pro-inflammatory role for this chemokine in the disease.
The target cell type for both PARC and ELC is the
lymphocyte.16-18
The receptor for ELC is EBI1
(Epstein-Barr virus (EBV)-induced gene 1),34,35
which is
known to be expressed on T and B cells.35
Although the
receptor for PARC has not yet been identified, saturation studies have
shown that human blood lymphocytes express a single class of high
affinity receptors for PARC.16
T cells are present
throughout atherosclerotic lesion development,2
and many
are in an activated state.3
The presence of these two T
cell-specific chemokines, PARC and ELC, in plaques strongly suggests an
active recruitment of this cell type into lesions rather than a
nonspecific "trapping" of T cells in atherosclerotic plaques.
Indeed, unlike other chemokines known to attract T cells, such as
RANTES, MIP-1, and IL-8, PARC shows a specificity for attracting
naive resting T cells.17
Atherosclerotic plaques contain
all of the molecular components required for antigen presentation to
CD4+ T cells. Expression of MHC (major histocompatibility
complex) molecules have not only been found on macrophages in human
lesions but also on SMC and endothelial cells.36
There are
still conflicting reports in the literature on the role of T cells in
atherosclerosis. A study has shown that total lymphocyte deficiency in
the ApoE-/- mouse, achieved by deletion of the recombinase activator
gene 2, has no effect on the extent of aortic atherosclerosis in these
mice.37
However, this study does not rule out the
involvement of T cells at different time points or stages of the
disease. It is also important to note that lesions of atherosclerotic
mice do not rupture. Therefore, a study of this type would not address
the modulatory effects that T cells extert on other plaque cell types,
which may have an important effect on overall plaque stability. For
example, it is known that T cell-secreted pro-inflammatory cytokines
are capable of inducing metalloproteinase expression by
macrophages.36
The CD40 receptor and CD40L (ligand) are
important co-stimulatory factors in antigen presentation and
autoimmunity in addition to T cell and macrophage activation. Both
receptor and ligand have also been detected on all cell types in
atherosclerotic plaques.38
A recent study has shown that
treatment of the LDL receptor knockout mouse with an antibody against
CD40L results in a reduction in the size of aortic lesions and their
lipid content and also reduces the number of macrophages and T cells in
plaques.39
These data provide strong evidence for a
specific immune response occurring during atherosclerosis. A pivotal
role for the chemokines PARC and ELC can easily be envisaged during the
sequence of events occurring prior to and after antigen presentation.
PARC may be used by plaque macrophages to attract naive T cells, which
after recognition of MHC molecule/peptide presented by activated
macrophages and/or SMC results in induction of a primary immune
response. ELC may participate in a similar fashion, although recent
reports have shown further functions for this chemokine. In addition to
its chemotactic properties, ELC has been shown to be capable of
inducing adhesion of circulating lymphocytes to intercellular adhesion
molecule-1 and induce the arrest of rolling cells under physiological
shear,40
suggesting a role for ELC in T
cell-endothelial cell recognition.
In conclusion, the data presented in this report suggest a role for PARC and ELC in the recruitment of T cells into atherosclerotic lesions. Through paracrine interactions, T cells could perpetuate their infiltration into the plaque through local secretion of inflammatory cytokines capable of up-regulating the production of the lymphocyte specific chemokines, PARC and ELC, in neighboring cells.
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Acknowledgements |
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Footnotes |
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Accepted for publication November 5, 1998.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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and MIP-1ß on human monocytes. Eur J Immunol 1995, 25:64-68[Medline]
/LD78 and chemotactic for T lymphocytes, but not for monocytes. J Immunol 1997, 159:1140-1149[Abstract]
and MIP-3ß. J Immunol 1997, 158:1033-1036[Abstract]
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C. A. Bursill, R. P. Choudhury, Z. Ali, D. R. Greaves, and K. M. Channon Broad-Spectrum CC-Chemokine Blockade by Gene Transfer Inhibits Macrophage Recruitment and Atherosclerotic Plaque Formation in Apolipoprotein E-Knockout Mice Circulation, October 19, 2004; 110(16): 2460 - 2466. [Abstract] [Full Text] [PDF]
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M. S. Smith, G. L. Bentz, P. M. Smith, E. R. Bivins, and A. D. Yurochko HCMV activates PI(3)K in monocytes and promotes monocyte motility and transendothelial migration in a PI(3)K-dependent manner J. Leukoc. Biol., July 1, 2004; 76(1): 65 - 76. [Abstract] [Full Text] [PDF]
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S. Senechal, P. de Nadai, N. Ralainirina, A. Scherpereel, H. Vorng, P. Lassalle, A.-B. Tonnel, A. Tsicopoulos, and B. Wallaert Effect of Diesel on Chemokines and Chemokine Receptors Involved in Helper T Cell Type 1/Type 2 Recruitment in Patients with Asthma Am. J. Respir. Crit. Care Med., July 15, 2003; 168(2): 215 - 221. [Abstract] [Full Text] [PDF]
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A. Gibejova, F. Mrazek, D. Subrtova, V. Sekerova, J. Szotkowska, V. Kolek, R. M. du Bois, and M. Petrek Expression of Macrophage Inflammatory Protein-3{beta}/CCL19 in Pulmonary Sarcoidosis Am. J. Respir. Crit. Care Med., June 15, 2003; 167(12): 1695 - 1703. [Abstract] [Full Text] [PDF]
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M. Vulcano, S. Struyf, P. Scapini, M. Cassatella, S. Bernasconi, R. Bonecchi, A. Calleri, G. Penna, L. Adorini, W. Luini, et al. Unique Regulation of CCL18 Production by Maturing Dendritic Cells J. Immunol., April 1, 2003; 170(7): 3843 - 3849. [Abstract] [Full Text] [PDF]
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 A M A. El-Asrar, S Struyf, S A Al-Kharashi, L Missotten, J Van Damme, and K Geboes Expression of T lymphocyte chemoattractants and activation markers in vernal keratoconjunctivitis Br. J. Ophthalmol., October 1, 2002; 86(10): 1175 - 1180. [Abstract] [Full Text] [PDF]
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S. A. Luther, A. Bidgol, D. C. Hargreaves, A. Schmidt, Y. Xu, J. Paniyadi, M. Matloubian, and J. G. Cyster Differing Activities of Homeostatic Chemokines CCL19, CCL21, and CXCL12 in Lymphocyte and Dendritic Cell Recruitment and Lymphoid Neogenesis J. Immunol., July 1, 2002; 169(1): 424 - 433. [Abstract] [Full Text] [PDF]
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