| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1
Department of Hematology, Oncology, and Immunology, University of Tübingen, Tübingen, Germany
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
(PPAR-), which has
anti-inflammatory properties, redirects DC toward a less
stimulatory mode. We show that activation of PPAR- during DC
differentiation profoundly affects the expression of costimulatory
molecules and of the DC hallmarker CD1a. PPAR- activation in DC
resulted in a reduced capacity to activate lymphocyte proliferation and
to prime Ag-specific CTL responses. This effect might depend on the
decreased expression of costimulatory molecules and on the impaired
cytokine secretion, but not on increased IL-10 production, because this
was reduced by PPAR- activators. Moreover, activation of PPAR- in
DC inhibited the expression of EBI1 ligand chemokine and CCR7, both
playing a pivotal role for DC migration to the lymph nodes. These
effects were accompanied by down-regulation of LPS-induced nuclear
localized RelB protein, which was shown to be important for DC
differentiation and function. Our results suggest a novel regulatory
pathway for DC function that could contribute to the regulated balance
between immunity induction and self-tolerance
maintenance. |
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Peroxisome proliferator-activated receptors (PPARs) are a family of
ligand-activated nuclear transcription factors which, upon binding of
the ligand, form heterodimers with the receptor for 9-cis retinoid
acid, retinoid X receptor, and subsequently activate target gene
transcription (8). So far, three isotypes for these
receptors have been identified: 
, 
, and . PPAR- expression
can be detected in heart, liver, kidney, adipose tissue, and skeletal
muscle. PPAR- expression appears to be less selective, as this
receptor can be found in many tissues (9). PPAR- is
expressed at high levels in adipose tissue, where it exerts critical
effects by promoting adipocyte differentiation and regulating tissue
homeostasis (10, 11). Natural ligands of PPAR- include
the cyclopentenone metabolites of PGD2,
PGJ2, and
15-deoxy-
12,14-PGJ2
(15d-PGJ2) (12, 13, 14), some
unsaturated fatty acids (9, 10, 11, 12), and oxidized
phospholipids (15). Furthermore, PPAR- was recognized
as the molecular target of the thiazolidinedione class of antidiabetic
drugs (12, 16, 17), which are currently being used for the
treatment of type II diabetes.
Detection of PPAR- expression in hematopoietic cells
(18) suggested a broader range of function for this
receptor. It was demonstrated that some PPAR- ligands, such as the
cyclooxygenase-2-derived cyclopentenone PGs, possess strong
anti-inflammatory properties and play a key role in the resolution
of inflammation (19, 20). The cyclopentenone
15d-PGJ2 and other PPAR- agonists prevent
macrophage oxidative burst and lead to impaired cytokine production in
monocytes and macrophages (21, 22, 23, 24). Ligand activation of
PPAR- induces caspase activation and apoptotic cell death in human
activated macrophages (25). Moreover, consistent with
their emerging anti-inflammatory properties, PPAR- ligands
inhibit colitis development in animal models of inflammatory bowel
disease (26, 27).
Interestingly, PPAR- was recently shown to inhibit lymphocyte
activation and to favor lymphocyte apoptotic cell death
(28, 29, 30). PPAR- expression could also be detected both
in mouse and human DC (31, 32). In this context, it was
suggested that PPAR- activation might contribute to redirect Th2
immune responses due to a down-regulated IL-12 secretion and to a
selective inhibition of Th1 lymphocyte-recruiting chemokines in DC
(32). These findings suggest that PPAR- might also play
a role in the regulation of responses mediated by adaptive immunity
effectors.
In the present work, we have explored the effect of PPAR- on the
differentiation of human monocytes into DC. We show that activation of
PPAR- affects DC properties and reverts them to a less stimulatory
mode, possibly via inhibition of RelB, an NF-
B family member playing
an important role in DC development and function.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The medium used for cell cultures was RPMI 1640 supplemented
with 10% inactivated FCS, 50 nM 2-ME, and antibiotics, all purchased
from Life Technologies (Grand Island, NY). The cell line Croft is an
EBV-immortalized HLA-A2+ B cell line kindly
donated by O. J. Finn (University of Pittsburgh,
Pittsburgh, PA). GM-CSF (Leucomax) was from Novartis (Basel,
Switzerland). LPS was obtained from (Sigma-Aldrich, Deisendorf,
Germany). IL-2, IL-4, IL-12, and TNF- were purchased from R&D
Systems (Wiesbaden, Germany). Troglitazone (TGZ) and BRL49653
were kindly donated by Sankyo (Tokyo, Japan) and
GlaxoSmithKline, respectively. 15d-PGJ2
was from Biomol (Plymouth Meeting, PA).
DC generation
DC were generated from peripheral blood adhering monocytes as described previously (33). In brief, PBMC were isolated by Ficoll (Biochrom, Berlin, Germany) density gradient centrifugation of heparinized blood from buffy coat preparations of healthy volunteers. Cells were seeded (1 x 107 cells/well) into six-well plates (Costar, Cambridge, MA) in medium. After 2 h of incubation at 37°C, nonadhering cells were removed and adherent monocytes were cultured in medium supplemented with GM-CSF (100 ng/ml) and IL-4 (1000 U/ml). Differentiating DC were fed with cytokines every 2–3 days. In some experiments DC were further induced to mature by adding LPS (100 ng/ml) at day 6 of culture. TGZ, BRL49653, or 15d-PGJ2 were added to the culture medium starting from the first day together with GM-CSF and IL-4. DC were enumerated by flow cytometry as lineage (CD14, CD3, CD19) negative and HLA-DR bright, and purity was confirmed by morphology. Furthermore, analysis of the expression of the DC markers CD1a and CD83 was performed.
Immunostaining
Cells were stained using FITC- or PE-conjugated mouse mAbs against CD14, CD80, and CD54 (BD Biosciences, Heidelberg, Germany); CD36, CD40, and CD86 (all purchased from BD PharMingen, Hamburg, Germany); CD1a (DAKO, Hamburg, Germany); CD83 (Immunotech, Marseille, France); and mouse IgG isotype control. All flow cytometry analysis were performed on a FACSCalibur (BD Biosciences).
MLR assay
A total of 105 responding cells from allogeneic PBMC were cultured in 96-well flat-bottom microplates (Nunc, Roskilde, Denmark) with various numbers of stimulator cells. Thymidine incorporation was measured on day 5 by a 16-h pulse with [3H]thymidine (0.5 µCi/well; Amersham Life Science, Little Chalfont, U.K.).
Induction of Ag-specific CTL response using the HLA-A2-restricted peptide E75 from Her-2/neu
The induction of Her-2/neu-specific CTL was performed as described (33). The Her-2/neu-derived peptides E75 (369–377: KIGSFLAFL) and GP-2 (654–662: IISAVVGIL) were synthesized using standard F-moc chemistry on a peptide synthesizer (432A; Applied Biosystems, Weiterstadt, Germany) and analyzed by reversed-phase HPLC and mass spectrometry. For CTL induction, 5 x 105 DC were pulsed with 50 µg/ml E75 peptide for 2 h, washed, and incubated with 3 x 106 autologous PBMC with or without addition of IL-12 (10 ng/ml). After 7 days of culture, cells were restimulated with autologous peptide-pulsed PBMC, and 1 ng/ml IL-2 was added on days 1, 3, and 5. The cytolytic activity of induced CTL was analyzed on day 5 after the last restimulation in a standard 51Cr-labeled release assay.
CTL assay
The standard 51Cr-labeled release assay was performed as described (33). Target cells (Croft cells) were pulsed with 50 µg/ml peptide for 2 h and labeled with 51Cr for 1 h at 37°C. Cells (104) were transferred to a well of a round-bottom 96-well plate. Varying numbers of CTLs were added to give a final volume of 200 µl and were incubated for 4 h at 37°C. At the end of the assay, supernatants (50 µl/well) were harvested and counted in a beta-plate counter. The percentage of specific lysis was calculated as follows: 100 x (experimental release - spontaneous release/maximal release - spontaneous release). Spontaneous and maximal releases were determined in the presence of either medium or 1% Triton X-100, respectively.
Cytokine determination
Cytokine concentrations in supernatants from DC cultures were
measured with commercially available two-site sandwich ELISAs from R&D
Systems (IL-15) or Immunotech Diagnostics (Hamburg, Germany; IL-12,
IL-4, IL-10, IL-6, IFN-, and TNF-), according to the
manufacturer’s instructions. DC were incubated at 1 x
106/well in 2 ml medium and stimulated with
different cytokine combinations. Supernatants were harvested after
24 h and stored at -70°C until use for cytokine
determination.
RT-PCR
RT-PCR was performed with some modifications as previously
described (33, 34, 35). Total RNA was isolated from cell
lysates using the High Pure RNA Isolation kit (Roche Diagnostics,
Mannheim, Germany) according to the instructions of the manufacturer.
This protocol includes a DNase incubation that digests
contaminating DNA. For standardization of the various PCR
experiments 250 ng of total RNA were subjected to a 20-µl cDNA
synthesis reaction (First Strand cDNA Synthesis kit for RT-PCR;
Roche Diagnostics). Oligo(dT) was used as primer. A total of 2 µl of
cDNA were used for PCR amplification. To control the integrity of the
RNA and the efficiency of the cDNA synthesis, 1 µl of cDNA was
amplified by an intron-spanning primer pair for the
2-microglobulin (2m)
gene. PCR temperature profiles and primer sequences were described
elsewhere (31), except for 2m,
IL-12 p40, and PPAR-. Primers were as follows:
2m, 5'-GATGCTGCTTACATGTCTCGA-3' and
5'-GGGTTTCATCCATCCGACAT-3'; IL-12 p40,
5'-GAGAAATGGTGGTCCTCACCTGTG-3' and
5'-GAGTGTAGCAGCTCCGCACGTC-3'; PPAR-,
5'-CAGAAATGACCATGGTTGACAC-3' and
5'-ATCCTTCACAAGCATGAACTCC-3'. PCR temperature profiles were as
follows: 5-min pretreatment at 94°C and 22 cycles at 94°C for
15 s, and annealing at 55°C for 30 s and 72°C for 30
s for the 2m cDNA; 5-min pretreatment at
94°C, 35 cycles at 94°C for 15 s, and annealing at 60°C for
30 s and 72°C for 30 s for the IL-12 p40 and PPAR- cDNA.
A total of 10 µl of the RT-PCR were electrophoresed on a 3% agarose
gel and stained with ethidium bromide for visualization under UV
light.
Preparation of nuclear extracts
Nuclear extracts were prepared from DC as described previously (31). Briefly, cell pellets were washed in 1 ml of ice-cold buffer A (10 mM HEPES (pH 7.9), 1.5 mM MgCl2, 10 mM KCl, 0.5 mM PMSF, and 1 mM DTT) and incubated for 10 min on ice in 1 ml buffer A plus 0.4% Igepal CA-630 (Sigma, Munich, Germany). Cell membranes thus obtained were centrifuged at 750 x g for 5 min. Pellets were resuspended in 200 µl buffer B (20 mM HEPES (pH 7.9), 0.42 M NaCl, 1.5 mM MgCl2, 0.2 mM EDTA, 0.5 mM PMSF, and 1 mM DTT) and nuclei were mechanically lysed for 2 h at 4°C. Cell debris were pelleted for 15 min at 7500 x g, and supernatant was recovered and stored at -70°C until use. Proteinase inhibitors (aprotinin and leupeptin; Sigma) were added to buffers just before use.
PAGE and Western blotting for detection of RelB protein
Protein concentration of nuclear extracts were determined using a bicinchoninic acid assay (Pierce, Rockford, IL). Twenty micrograms of total protein were separated on a 12% polyacrylic amide gel, blotted on a polyvinylidene difluoride membrane, and probed with a polyclonal rat RelB Ab C-19 (Santa Cruz Biotechnology, Santa Cruz, CA); bands were visualized by ECL staining (Amersham Pharmacia, Freiburg, Germany).
Western blotting for detection of PPAR- expression
Cell pellets were boiled with 5x Laemmli buffer for 5 min and
7.5% SDS-PAGE was performed. Thereafter, proteins were transferred to
nitrocellulose by electroblotting. The nitrocellulose membranes were
incubated with the first Ab (anti-PPAR-; WAK-Chemie Medical, Bad
Homburg, Germany; kindly provided by J. Auwerx, Institut Pasteur,
Paris, France) overnight at 4°C. Membranes were washed before
incubating with HRP-conjugated secondary Ab for 1 h at room
temperature. Bands were visualized by ECL staining.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
is expressed in circulating human monocytes and in human
DC at each stage of maturation
To determine whether PPAR- may play a role in DC
differentiation and function, we first analyzed its expression at mRNA
and protein levels (Fig. 1
) in peripheral
blood adherent monocytes and in different DC populations. In agreement
with a previous report (36), peripheral blood monocytes
were found to express low levels of PPAR-. DC generated from
adherent monocytes cultured in the presence of GM-CSF and IL-4 for 5–7
days were also found to be positive for PPAR-, and the expression of
this receptor was not affected by the addition of known maturation
stimuli, including LPS. PPAR- levels of expression were also not
influenced by the administration of the PPAR- ligands TGZ,
BRL49653, or 15d-PGJ2, concomitantly with GM-CSF
and IL-4 during DC development.
|
pathway skews DC differentiation
In the first series of experiments we explored whether PPAR-
ligation would have an effect on the normal differentiation of
monocytes into DC by monitoring the acquisition of a DC morphology and
phenotype. Besides the two synthetic PPAR- agonists
thiazolidinediones TGZ and BRL49653, we used the natural PG
15d-PGJ2. When cultured in the presence of GM-CSF
and IL-4 for 5–7 days, adherent peripheral blood monocytes
differentiated into large, round, loosely adherent cells showing the
typical cell protrusions in the form of veils or dendrites (data not
shown). Addition of PPAR- agonists during DC differentiation did not
substantially affect the morphological development of DC (data not
shown) and led to a significant up-regulation of the target gene CD36
in comparison with the untreated control DC, thus indicating that the
PPAR- pathway can be activated in DC (Fig. 2A). Phenotypic analysis of
GM-CSF/IL-4-genarated DC demonstrated loss of CD14 expression and
acquisition of a DC phenotype characterized by CD1a and HLA-DR
expression; the two costimulatory molecules B7.1 and B7.2 (CD80 and
CD86, respectively) were still found to be expressed at low levels.
Addition of the PPAR- agonists TGZ, BRL49653, or
15d-PGJ2, together with GM-CSF and IL-4 from the
first day of culture, skewed DC toward the acquisition of an unusual
phenotype, characterized by reduction of CD1a and CD80 expression and
selective CD86 up-regulation. CD14 down-regulation as well as CD54
(data not shown) expression were not significantly affected (Fig. 2B), whereas HLA-DR was up-regulated and CD40 was slightly
reduced.
|
expression in macrophages and to production of
endogenous PPAR- ligands (37). However, the effects on
DC phenotype observed in the presence of TGZ, BRL49653, or 15d-PGJ2
were not mimicked by the sole addition of increasing doses of IL-4
together with GM-CSF to the cultures of differentiating DC (data not
shown), suggesting that IL-4-dependent production of PPAR- ligands
might not be significant in DC.
The observed effect of PPAR- agonists was found to be concentration
dependent for all three PPAR- ligands, as monitored by evaluating
CD1a (Fig. 3), CD86, and CD80 (data not
shown) expression. According to their reported affinities for PPAR-,
BRL49653 and TGZ were the most potent modulators of DC differentiation,
because they had a significant activity at a concentration as low as
10-8 M, whereas the weakest ligand,
15d-PGJ2, significantly interfered with the
acquisition of a normal DC phenotype only upon higher concentrations.
Addition of LPS, TNF-, or soluble CD40 ligand (CD40L) to the
cultures of differentiating DC was not able to revert the effect of
PPAR- activation on CD1a, CD86, and CD80 expression (data not
shown). Importantly, PPAR- is known to promote cell death in
numerous cell types, including macrophages and lymphocytes (25, 30). However, when checking the viability of the examined cell
populations by propidium iodide cell staining, we did not detect any
increase in the rate of dead cells following exposure to PPAR-
agonists (data not shown).
|
inhibits DC maturation
To further evaluate the degree of responsiveness to a standard
activation stimulus, DC generated in the presence of PPAR- agonists
were exposed to LPS at day 6 of culture and examined for the
acquisition of a mature phenotype 24 h later. Upon activation with
LPS, DC generated from peripheral blood monocytes with GM-CSF and IL-4
reverted to an adherent, long-shaped morphology (data not shown), and,
as detected by flow cytometric analysis, they acquired high levels of
HLA-DR and CD83 expression and up-regulation of CD40, CD80, and CD86.
Cells differentiated in the presence of PPAR- ligands demonstrated
the morphological changes described for the normal control DC when
analyzed by light microscopy (data not shown). However, as shown with
TGZ, immunostaining of these cells revealed an unbalanced response to
LPS stimulation (Fig. 4): while
displaying a normal HLA-DR up-regulation, DC were found to express
lower levels of CD1a, CD83, CD80, and CD40. Again, CD86 up-regulation
prevailed.
|
ligation skews DC cytokine and chemokine expression
patterns
When evaluating whether the effects of PPAR- agonists on DC
phenotype were associated to a skewed cytokine secretion, we found that
exposure of differentiating DC to TGZ, BRL49653, or
15d-PGJ2 led to a poorer IL-6 and TNF-
secretion (Fig. 5A). Moreover,
PPAR- agonists were found to inhibit IL-10 secretion (Table I). Activation of immature DC
differentiated in the absence of PPAR- ligands with LPS at day 6 of
culture determined a severalfold increase in IL-6, IL-10, and TNF-
secretion and primed DC to produce IL-15 and IL-12. Exposure of DC
differentiated in the presence of TGZ, BRL49653, or
15-PGJ2 to LPS resulted in a reduced production
of IL-10, IL-15, and IL-12 in comparison with the control (Fig. 5B). Inhibition of cytokine secretion correlated with the
concentration of PPAR- agonist, as shown in Fig. 5C for
IL-12 down-regulation via TGZ. RT-PCR analysis also revealed a
concentration-dependent inhibition for IL-12 p40 expression at the mRNA
level in DC exposed to TGZ during differentiation (Fig. 6).
|
|
|
would have an
effect on the chemokine profile expressed by DC. Interestingly, we
found that, while not affecting the expression of
macrophage-inflammatory protein-1 and DC-CK-1 (data not
shown), activation of PPAR- during DC differentiation down-regulated
monocyte chemoattractant protein-2 (MCP-2), EBI1 ligand chemokine
(ELC), and CCR7 in a concentration-dependent fashion (Fig. 6
).
PPAR- modulates the stimulation of allogeneic lymphocytes and
Ag-specific CTL by DC
We further analyzed the ability of DC generated in vitro in the
presence of PPAR- agonists to activate lymphocyte responses. When
blood monocytes were exposed to TGZ, BRL49653, or
15d-PGJ2 concomitantly with GM-CSF and IL-4
during their differentiation, DC had an impaired capacity to stimulate
allogeneic T lymphocytes, as evaluated in standard MLR (Fig. 7A). As shown with TGZ, the
effect of PPAR- activation on DC stimulatory capacity was found to
be concentration dependent, with a significant inhibition still being
detectable at a TGZ concentration of 10-7 M
(Fig. 7B). The addition of LPS (Fig. 7C) or
soluble CD40L plus IFN- (data not shown) at day 6 of culture could
not restore the stimulatory capacity of DC differentiated in the
presence of PPAR- activators to levels comparable with the untreated
control. Because activation of PPAR- down-regulates the production
of IL-12 by DC and this cytokine is known to play a relevant role in
the induction of cell-mediated immune responses (1, 2), we
evaluated the effect of IL-12 supplementation on DC stimulatory
capacity. As shown in Fig. 7C, IL-12 addition failed to
restore DC capacity to the control level, suggesting that other factors
beside IL-12 shortening, such as the skewed expression of costimulatory
molecules and/or the down-regulated production of cytokines and
chemokines, may play a decisive role in the inhibitory effects of
PPAR- on DC function.
|
A). In contrast, stimulation
of differentiating DC by TGZ impeded activation of allogeneic
lymphocytes (Fig. 8B). Moreover, reduced levels of IFN-
were detected in the MLR cultures where DC generated in the presence of
TGZ were used as stimulators (Fig. 8C), whereas no IL-4 or
IL-10 production could be detected in the supernatants (data not
shown).
|
, CTL lines obtained after two weekly
restimulations showed high peptide-specific killing that was slightly
enhanced by IL-12 addition during CTL induction. Conversely, DC
generated in the presence of TGZ failed to activate Ag-specific CTL
and, again, IL-12 supplementation did not significantly antagonize this
effect.
|
down-regulates nuclear localized RelB transcription factor
It has recently been demonstrated that members of the NF-B
family of transcription factors are important in DC differentiation and
function (38, 39, 40, 41). We analyzed the expression of the
NF-B family member RelB in DC pretreated with the PPAR- agonist
TGZ upon stimulation with LPS. As shown in Fig. 10, expression of nuclear localized
RelB protein was found to be reduced depending on the concentration of
PPAR- ligand, thus suggesting that PPAR- inhibitory effects on DC
might be due to blocking of RelB signaling.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
(45), and T cell-derived signals
like CD40 ligation (46), which, on the contrary, promote
DC development and enhance their immunogenicity.
In this study, we show that activation of the nuclear transcription
factor PPAR- affects the differentiation of monocytes into DC. We
found that PPAR- ligands administered during GM-CSF/IL-4-induced
differentiation of peripheral blood monocytes into DC, while normally
permitting CD14 down-regulation, almost completely inhibited the
expression of the DC hallmarker CD1a. Moreover, consistent with the
results of Gosset et al. (32), we detected a selective
up-regulation of the costimulatory molecule B7.2 (CD86), which was
paralleled by B7.1 (CD80) down-regulation. In addition, we found that
PPAR- agonists also impaired CD83 and CD40 expression on DC, both
effects being enhanced upon DC activation by LPS or CD40L plus IFN-
(data not shown). Several PPAR- agonists, including TGZ, BRL49653,
and the cyclopentenone 15d-PGJ2, that were used
in our experiments have been reported to act also via
PPAR--independent mechanisms (47, 48). However, such
effects were described for very high concentrations of these agonists,
thus making it extremely unlikely that the effects we describe in DC,
which are reproduced upon concentrations of PPAR- agonists in the
nanomolar range, are mediated independently of PPAR-.
In their report, Gosset et al. (32) speculated that
activation of PPAR- in DC may switch them toward a type 2
stimulatory mode due to inhibition of IL-12 secretion and
down-regulation of chemokines capable to recruit Th1 lymphocytes.
Our data indicate a more profound effect of PPAR- activation on the
DC system: PPAR- agonists not only impeded the acquisition of a
normal DC phenotype and down-regulated DC production of TNF-, IL-6,
IL-15, and IL-12 but also severely blunted DC capacity to activate
lymphocyte proliferation in MLR and impeded the induction of
Ag-specific T cell responses by DC. Moreover, while leading to a
reduced production of IFN-, lymphocyte stimulation
by DC generated in the presence of PPAR- agonists failed to prime
the secretion of Th2 cytokines like IL-4 and IL-10. Therefore, we
suggest that PPAR- activation in DC may result in induction of
anergy/tolerance in T lymphocytes instead of committing them toward a
type 2 cytokine-secreting mode. In contrast, it is possible that the
inhibition of DC function we observed depended on the sustained
activation of PPAR-, as it was realized in our experiments, whereas
shorter activation periods like those used by Gosset et al.
(32) probably result in milder immunological
effects. The effects of PPAR- on DC stimulatory capacity were not
due to increased IL-10 secretion, the latter being reduced by PPAR-.
Moreover, the sole supplementation of IL-12 could not restore DC
stimulatory capacity in MLR and upon induction of CTL, indicating that
other factors, such as the skewed expression of the surface
costimulation molecules CD40, CD80, and CD86, reasonably could play a
decisive role in the inhibitory effects of PPAR-. Finally, while not
affecting expression of chemokines expressed by DC at the immature
state, such as macrophage-inflammatory protein-1 and DC-CK-1,
PPAR- agonists selectively down-regulated ELC and the corresponding
receptor, CCR7. These are normally up-regulated during DC maturation
and have a crucial importance for DC migration from inflamed tissues to
the afferent lymph nodes (49, 50).
RelB is a member of the NF-B family of transcription factors that
has been implicated in the differentiation of monocytes into DC and in
DC maturation (38, 39, 40, 41, 42). Because, upon DC activation by
LPS, we detected a down-regulation of nuclear localized RelB in DC
pretreated with PPAR- agonists, it seems likely that the effects of
PPAR- on DC are mediated, at least in part, via inhibition of RelB
signaling and that other molecules might be involved in the effects
mediated by PPAR-. A link between PPAR- and NF-B has already
been established (25, 27), and Chung et al.
(51) recently demonstrated that PPAR- can inhibit the
NF-B pathway by directly binding the NF-B components p50 and p65.
However, to the best of our knowledge, this is the first report
indicating RelB p68 as a target of PPAR- signaling.
Taken together, the effects of PPAR- activation on differentiating
DC delineate a novel mechanism for the regulation of DC immunogenicity
and propose a pathway for the resolution of immune responses arising
during an inflammatory process: TNF-, LPS, IL-1, and
PGE2 released during inflammation promote
activation and migration of tissue-resident DC to promptly stimulate an
Ag-specific immune response (1, 2). In contrast, at late
stages of an inflammatory event, the inducible cyclooxygenase-2
probably redirects PG synthesis toward PGD2 and
its cyclopentenone metabolites, whereas PGE2
levels may be strongly reduced (19, 20). At this time
point, cyclopentenone PGs could contribute to avoid sustained immune
stimulation by acting at the APC level, because PPAR- activation in
DC may switch them toward a less stimulatory mode with down-regulated
cytokine secretion and impaired ELC and CCR7 expression. Detection of
micromolar concentrations of PGD2 in rat tissue
homogenates including spleen, intestine, bone marrow, and lung in the
absence of inflammation (52) and the identification of APC
including DC as one major source of endogenous
PGD2 (53) raise the possibility that
this pathway of regulation is active also under steady state conditions
and contributes to modulate the acquisition of fully
immunostimulatory capacity by DC. Remarkably, some thiazolidinediones
currently represent a therapeutic option for patients with type 2
diabetes mellitus. Because these drugs reduce DC immunogenicity,
administration to diabetic patients could potentially worsen
immunodepression.
|
Acknowledgments |
|---|
expression. We also thank S. Kurtz and
S. Stephan for the excellent technical assistance. We thank Prof.
H.-U. Häring for critical reading of the manuscript. |
Footnotes |
|---|
2 Address correspondence and reprint requests to Dr. Peter Brossart, Department of Hematology, Oncology, and Immunology, University of Tübingen, Otfried Müller Strasse 10, D-72076 Tübingen, Germany. E-mail address: peter.brossart{at}med.uni-tuebingen.de
3 Abbreviations used in this paper: DC, dendritic cell; 15d-PGJ2, 15-deoxy-12,14-PGJ2; CD40L, CD40 ligand; PPAR, peroxisome proliferator-activated receptor; 2m, 2-microglobulin; TGZ, troglitazone; MCP-2, monocyte chemoattractant protein-2; ELC, EBI1 ligand chemokine; S:R, stimulator:responder.
Received for publication November 27, 2001. Accepted for publication May 31, 2002.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
2, a lipid-activated transcription factor. Cell 79:1147.[Medline]
is required for placental, cardiac, and adipose tissue development. Mol. Cell 4:585.[Medline]
and promotes adipocyte differentiation. Cell 83:813.[Medline]
12,14prostaglandin J2 is a ligand for the adipocyte determination factor PPAR-. Cell 83:803.[Medline]
ligands and agonists. J. Biol. Chem. 276:16015. (PPAR-). J. Biol. Chem. 270:12953. agonism and the antihyperglycemic activity of thiazolidinediones. J. Med. Chem. 39:665.[Medline]
cDNA: expression in hematopoietic cells and chromosomal mapping. Gene Expression 4:281.[Medline]
is a negative regulator of macrophage activation. Nature 391:79.[Medline]
12,14-prostaglandin J2 and troglitazone: evidence for heat shock-dependent and -independent inhibition of cytokine-induced inducible nitric oxide synthase expression. Diabetes 49:346.[Abstract]
agonists inhibit production of monocyte inflammatory cytokines. Nature 391:82.[Medline]
: counter-regulatory activity by IFN-. J. Leukocyte Biol. 71:677. and induces apoptosis of human monocyte-derived macrophages. J. Biol. Chem. 273:25573. ligands to inhibit the epithelial inflammatory response. J. Clin. Invest. 104:383.[Medline]
and inhibit chemically induced colitis and formation of aberrant crypt foci in rats. Cancer Res. 61:2424. (PPAR) agonists. J. Biol. Chem. 275:4541. and immunoregulation: PPAR mediates inhibition of helper T cell responses. J. Immunol. 164:1364. is expressed by mouse T lymphocytes and PPAR agonists induce apoptosis. Eur. J. Immunol. 31:1098.[Medline]
activators inhibit interleukin-12 production in murine dendritic cells. FEBS Lett. 486:261.[Medline]
activators affect the maturation of human monocyte-derived dendritic cells. Eur. J. Immunol. 31:2857.[Medline]
and CD40 ligand antagonize the inhibitory effects of interleukin 10 on T-cell stimulatory capacity of dendritic cells. Cancer Res. 60:4485. promotes monocyte/macrophage differentiation and uptake of oxidized LDL. Cell 93:241.[Medline]
ligands in macrophages by 12/15-lipoxygenase. Nature 400:378.[Medline]
B/Rel family. Cell 80:331.[Medline]
B and octamer is a hallmark of the generation and maturation of dendritic cells. Blood 95:277.B activation in hemopoietic progenitor cells. J. Immunol. 160:1224.B during human mononuclear phagocyte differentiation to macrophages and dendritic cells. Biochem. Biophys. Res. Commun. 268:99.[Medline]
. J. Exp. Med. 179:1109. cooperate in the generation of dendritic Langerhans cells. Nature 360:258.[Medline]
dependent and independent effects on macrophage-gene expression in lipid metabolism and inflammation. Nat. Med. 7:48.[Medline]
and nuclear factor-B. J. Biol. Chem. 275:32681.This article has been cited by other articles:
|
|
 |
|
  L. Klotz, S. Hucke, D. Thimm, S. Classen, A. Gaarz, J. Schultze, F. Edenhofer, C. Kurts, T. Klockgether, A. Limmer, et al. Increased Antigen Cross-Presentation but Impaired Cross-Priming after Activation of Peroxisome Proliferator-Activated Receptor {gamma} Is Mediated by Up-Regulation of B7H1 J. Immunol., July 1, 2009; 183(1): 129 - 136. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R Marion-Letellier, P Dechelotte, M Iacucci, and S Ghosh Dietary modulation of peroxisome proliferator-activated receptor gamma Gut, April 1, 2009; 58(4): 586 - 593. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 F. J. Perez-Cano, C. Ramirez-Santana, M. Molero-Luis, M. Castell, M. Rivero, C. Castellote, and A. Franch Mucosal IgA increase in rats by continuous CLA feeding during suckling and early infancy J. Lipid Res., March 1, 2009; 50(3): 467 - 476. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 F. Zapata-Gonzalez, F. Rueda, J. Petriz, P. Domingo, F. Villarroya, J. Diaz-Delfin, M. A. de Madariaga, and J. C. Domingo Human dendritic cell activities are modulated by the omega-3 fatty acid, docosahexaenoic acid, mainly through PPAR{gamma}:RXR heterodimers: comparison with other polyunsaturated fatty acids J. Leukoc. Biol., October 1, 2008; 84(4): 1172 - 1182. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Jaudszus, M. Krokowski, P. Mockel, Y. Darcan, A. Avagyan, P. Matricardi, G. Jahreis, and E. Hamelmann Cis-9,trans-11-Conjugated Linoleic Acid Inhibits Allergic Sensitization and Airway Inflammation via a PPAR{gamma}-Related Mechanism in Mice J. Nutr., July 1, 2008; 138(7): 1336 - 1342. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Smed-Sorensen, M. Moll, T.-Y. Cheng, K. Lore, A.-C. Norlin, L. Perbeck, D. B. Moody, A.-L. Spetz, and J. K. Sandberg IgG regulates the CD1 expression profile and lipid antigen-presenting function in human dendritic cells via Fc{gamma}RIIa Blood, May 15, 2008; 111(10): 5037 - 5046. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. Behshad, K. D. Cooper, and N. J. Korman A Retrospective Case Series Review of the Peroxisome Proliferator-Activated Receptor Ligand Rosiglitazone in the Treatment of Atopic Dermatitis Arch Dermatol, January 1, 2008; 144(1): 84 - 88. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. Szatmari, D. Torocsik, M. Agostini, T. Nagy, M. Gurnell, E. Barta, K. Chatterjee, and L. Nagy PPAR{gamma} regulates the function of human dendritic cells primarily by altering lipid metabolism Blood, November 1, 2007; 110(9): 3271 - 3280. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Nencioni, J. Beck, D. Werth, F. Grunebach, F. Patrone, A. Ballestrero, and P. Brossart Histone Deacetylase Inhibitors Affect Dendritic Cell Differentiation and Immunogenicity Clin. Cancer Res., July 1, 2007; 13(13): 3933 - 3941. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Zapata-Gonzalez, F. Rueda, J. Petriz, P. Domingo, F. Villarroya, A. de Madariaga, and J. C. Domingo 9-cis-Retinoic Acid (9cRA), a Retinoid X Receptor (RXR) Ligand, Exerts Immunosuppressive Effects on Dendritic Cells by RXR-Dependent Activation: Inhibition of Peroxisome Proliferator-Activated Receptor {gamma} Blocks Some of the 9cRA Activities, and Precludes Them to Mature Phenotype Development J. Immunol., May 15, 2007; 178(10): 6130 - 6139. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Geyeregger, M. Zeyda, W. Bauer, E. Kriehuber, M. D. Saemann, G. J. Zlabinger, D. Maurer, and T. M. Stulnig Liver X receptors regulate dendritic cell phenotype and function through blocked induction of the actin-bundling protein fascin Blood, May 15, 2007; 109(10): 4288 - 4295. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Dubrac, P. Stoitzner, D. Pirkebner, A. Elentner, K. Schoonjans, J. Auwerx, S. Saeland, P. Hengster, P. Fritsch, N. Romani, et al. Peroxisome Proliferator-Activated Receptor-{alpha} Activation Inhibits Langerhans Cell Function J. Immunol., April 1, 2007; 178(7): 4362 - 4372. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Klotz, I. Dani, F. Edenhofer, L. Nolden, B. Evert, B. Paul, W. Kolanus, T. Klockgether, P. Knolle, and L. Diehl Peroxisome Proliferator-Activated Receptor {gamma} Control of Dendritic Cell Function Contributes to Development of CD4+ T Cell Anergy J. Immunol., February 15, 2007; 178(4): 2122 - 2131. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Sandig, J. E. Pease, and I. Sabroe Contrary prostaglandins: the opposing roles of PGD2 and its metabolites in leukocyte function J. Leukoc. Biol., February 1, 2007; 81(2): 372 - 382. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Gogolak, B. Rethi, I. Szatmari, A. Lanyi, B. Dezso, L. Nagy, and E. Rajnavolgyi Differentiation of CD1a- and CD1a+ monocyte-derived dendritic cells is biased by lipid environment and PPAR{gamma} Blood, January 15, 2007; 109(2): 643 - 652. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Thurnher Lipids in dendritic cell biology: messengers, effectors, and antigens J. Leukoc. Biol., January 1, 2007; 81(1): 154 - 160. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. Szatmari, A. Pap, R. Ruhl, J.-X. Ma, P. A. Illarionov, G. S. Besra, E. Rajnavolgyi, B. Dezso, and L. Nagy PPAR{gamma} controls CD1d expression by turning on retinoic acid synthesis in developing human dendritic cells J. Exp. Med., October 2, 2006; 203(10): 2351 - 2362. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. Szatmari, G. Vamosi, P. Brazda, B. L. Balint, S. Benko, L. Szeles, V. Jeney, C. Ozvegy-Laczka, A. Szanto, E. Barta, et al. Peroxisome Proliferator-activated Receptor {gamma}-regulated ABCG2 Expression Confers Cytoprotection to Human Dendritic Cells J. Biol. Chem., August 18, 2006; 281(33): 23812 - 23823. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Nencioni, K. Schwarzenberg, K. M. Brauer, S. M. Schmidt, A. Ballestrero, F. Grunebach, and P. Brossart Proteasome inhibitor bortezomib modulates TLR4-induced dendritic cell activation Blood, July 15, 2006; 108(2): 551 - 558. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. August, C. Mueller, V. Weaver, T. A. Polanco, E. R. Walsh, and M. T. Cantorna Nutrients, Nuclear Receptors, Inflammation, Immunity Lipids, PPAR, and Allergic Asthma J. Nutr., March 1, 2006; 136(3): 695 - 699. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Appel, V. Mirakaj, A. Bringmann, M. M. Weck, F. Grunebach, and P. Brossart PPAR-{gamma} agonists inhibit toll-like receptor-mediated activation of dendritic cells via the MAP kinase and NF-{kappa}B pathways Blood, December 1, 2005; 106(12): 3888 - 3894. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Armeanu, M. Bitzer, I. Smirnow, S. Bossow, S. Appel, G. Ungerechts, C. Bernloehr, W. J. Neubert, U. M. Lauer, and P. Brossart Severe Impairment of Dendritic Cell Allostimulatory Activity by Sendai Virus Vectors Is Overcome by Matrix Protein Gene Deletion J. Immunol., October 15, 2005; 175(8): 4971 - 4980. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Appel, A. Rupf, M. M. Weck, O. Schoor, T. H. Brummendorf, T. Weinschenk, F. Grunebach, and P. Brossart Effects of Imatinib on Monocyte-Derived Dendritic Cells Are Mediated by Inhibition of Nuclear Factor-{kappa}B and Akt Signaling Pathways Clin. Cancer Res., March 1, 2005; 11(5): 1928 - 1940. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
X. Zhang, M. C. Rodriguez-Galan, J. J. Subleski, J. R. Ortaldo, D. L. Hodge, J.-M. Wang, O. Shimozato, D. A. Reynolds, and H. A. Young Peroxisome proliferator-activated receptor-{gamma} and its ligands attenuate biologic functions of human natural killer cells Blood, November 15, 2004; 104(10): 3276 - 3284. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
O. A. Skorokhod, M. Alessio, B. Mordmuller, P. Arese, and E. Schwarzer Hemozoin (Malarial Pigment) Inhibits Differentiation and Maturation of Human Monocyte-Derived Dendritic Cells: A Peroxisome Proliferator-Activated Receptor-{gamma}-Mediated Effect J. Immunol., September 15, 2004; 173(6): 4066 - 4074. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Nencioni and P. Brossart Cellular Immunotherapy with Dendritic Cells in Cancer: Current Status Stem Cells, July 1, 2004; 22(4): 501 - 513. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Gehrmann, M. Brunner, K. Pfister, A. Reichle, E. Kremmer, and G. Multhoff Differential Up-Regulation of Cytosolic and Membrane-Bound Heat Shock Protein 70 in Tumor Cells by Anti-Inflammatory Drugs Clin. Cancer Res., May 15, 2004; 10(10): 3354 - 3364. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Monaco and E. Paleolog Nuclear factor {kappa}B: a potential therapeutic target in atherosclerosis and thrombosis Cardiovasc Res, March 1, 2004; 61(4): 671 - 682. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Coutant, S. Agaugue, L. Perrin-Cocon, P. Andre, and V. Lotteau Sensing Environmental Lipids by Dendritic Cell Modulates Its Function J. Immunol., January 1, 2004; 172(1): 54 - 60. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Hammad, H. J. de Heer, T. Soullie, V. Angeli, F. Trottein, H. C. Hoogsteden, and B. N. Lambrecht Activation of Peroxisome Proliferator-Activated Receptor-{gamma} in Dendritic Cells Inhibits the Development of Eosinophilic Airway Inflammation in a Mouse Model of Asthma Am. J. Pathol., January 1, 2004; 164(1): 263 - 271. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Nencioni, K. Lauber, F. Grunebach, L. Van Parijs, C. Denzlinger, S. Wesselborg, and P. Brossart Cyclopentenone Prostaglandins Induce Lymphocyte Apoptosis by Activating the Mitochondrial Apoptosis Pathway Independent of External Death Receptor Signaling J. Immunol., November 15, 2003; 171(10): 5148 - 5156. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Gosset, F. Bureau, V. Angeli, M. Pichavant, C. Faveeuw, A.-B. Tonnel, and F. Trottein Prostaglandin D2 Affects the Maturation of Human Monocyte-Derived Dendritic Cells: Consequence on the Polarization of Naive Th Cells J. Immunol., May 15, 2003; 170(10): 4943 - 4952. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. Angeli, H. Hammad, B. Staels, M. Capron, B. N. Lambrecht, and F. Trottein Peroxisome Proliferator-Activated Receptor {gamma} Inhibits the Migration of Dendritic Cells: Consequences for the Immune Response J. Immunol., May 15, 2003; 170(10): 5295 - 5301. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
