| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
*
Department of Immunology and Cell Biology, Istituto di Ricerche Farmacologiche "Mario Negri," Milan, Italy; and
Section of General Pathology, Department of Biotechnology, Università di Brescia, Brescia, Italy
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
and IL-1ß), which
are among the most potent and multifunctional cell activators described
in immunology and cell biology. The spectrum of action of IL-1
encompasses cells of hematopoietic origin (from immature precursors to
differentiated leukocytes); vessel wall elements; and cells of
mesenchymal, nervous, and epithelial origin 1, 2 . The production and
action of IL-1 are regulated by multiple control pathways, some of
which are unique to this cytokine. This complexity and uniqueness is
best represented by the term "IL-1 system" 3 . The IL-1 system
consists of two agonists, IL-1 and IL-1ß, a specific activation
system, IL-1 converting enzyme, IL-1 receptor antagonist
(IL-1Ra)5 produced in
different isoforms 4, 5 , and high affinity surface binding molecules
3 . Two distinct forms of receptors for IL-1 have been cloned in mammalian cells, IL-1RI and IL-1RII 6, 7, 8 . IL-1RI mediates the biological effects of the IL-1 9, 10, 11, 12 . IL-1R accessory protein (IL-1RAcP) cooperates in ligand recognition and in signal transduction with IL-1RI 13, 14, 15, 16 . MyD88 couples the receptor complex to the IL-1R-associated kinase/TNFR-associated factor 6 (IRAK/TRAF6) signaling cascade 17, 18 . IL-1RII binds IL-1 but does not transduce signals. Available data are consistent with a model in which IL-1RII competes with IL-1RI for IL-1 binding, acting as a decoy for IL-1 and inhibiting its activity 11, 19, 20, 21, 22 . Complexing with IL-1RAcP may also contribute to the anti-IL-1 action of high numbers of decoy IL-1RII (Refs. 19, 23, and 24, and M. Martin, personal communication). The decoy model for IL-1RII was recently confirmed in vivo in transgenic mice 22 .
Expression and release of the decoy IL-1RII are strictly regulated by multiple control mechanisms. It has long been known that the decoy IL-1RII is found in culture supernatants and biological fluids 25, 26, 27, 28 . It was found that chemoattractants and agents that recapitulate key elements in the signal-transduction pathway of chemotactic receptors cause rapid release of the decoy IL-1RII 29 . Rapid shedding of the decoy IL-1RII, which is also induced by TNF but not by other cytokines 30 , depends on activation of preformed metalloprotease(s) 31 . Rapid shedding of the decoy IL-1RII during the early steps of myelomonocytic cell extravasation would buffer IL-1 leaking from sites of inflammation 27, 29, 31 . A second pathway of regulation of the decoy IL-1RII depends on gene expression and protein synthesis and is activated by antinflammatory molecules, including glucocorticoid hormones, IL-4, and IL-13 11, 32, 33 . These agents augment expression and subsequent release of the decoy IL-1RII with little or no effect on IL-1RI 11, 32, 33 .
The finding that antinflammatory mediators augment expression of the decoy IL-1RII is consistent with IL-1RII being an important anti-IL-1 pathway. The present study was designed to investigate whether bacterial LPS, a prototypic proinflammatory molecule, affects IL-1Rs in human monocytes. LPS caused a rapid (10–20-min) release of the decoy IL-1RII via metalloprotease activation. Rapid stripping of the decoy IL-1RII was followed by profound inhibition of decoy IL-1RII mRNA expression. Concomitantly, expression of IL-1RI and IL-1RAcP mRNAs were up-regulated. Stimulation of IL-1RI expression by LPS was associated with the appearance of novel 2.4-kb mRNAs, which were characterized by PCR and cDNA cloning as heterogeneous, incompletely spliced, polyadenylated transcripts.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Human monocytes were separated from peripheral blood of human healthy donors by Percoll gradient centrifugation 11 . Briefly, whole blood was fractionated on Ficoll gradient centrifugation (Seromed-Biochem KG, Berlin, Germany), and mononuclear cells were collected from the ring, layered on top of 46% Percoll (Pharmacia, Uppsala, Sweden), and centrifuged at 2000 rpm for 30 min at room temperature. Monocytes (>98% pure as assessed by morphology) were resuspended at 5 x 106 cells/ml in RPMI 1640 (Seromed-Biochem) and 2 mM HEPES (Merck, Darmstadt, Germamy). All reagents contained <0.125 EU/ml of endotoxin as checked by Limulus amoebocyte lysate assay (Microbiological Associates, Rockville, MD).
Stimulation conditions and reagents
Monocytes were incubated in endotoxin-free RPMI 1640 at 5
x 106 cells/ml with or without stimuli for the indicated
times at 37°C in the presence of 5% CO2. LPS
(Escherichia coli 005:B5; Difco, Detroit, MI) was used at
500 ng/ml. Actinomycin D (ActD; Sigma Chemical Co., St. Louis, MO) was
used at 1 µg/ml. Cycloheximide (CH; Sigma) was used at 10 µg/ml.
Human rIL-1ß (Dompe, Aquila, Italy) was used at 10 ng/ml. TNF-
(BASF/Knoll, Ludwigshafen, Germany) was used at 500 U/ml. IL-1Ra
(Cetus, Emeryville, CA) was used at 10 µg/ml. The mAb against
TNF-, B154.2, was a kind gift from Dr G. Trinchieri (Wistar
Institute, Philadelphia, PA). A 1:2000 dilution of ascites neutralized
1000 U/ml of rTNF-. The metalloprotease inhibitor BB-94 was from
British Biotech (Oxford, U.K.); L,680833, a specific elastase inhibitor
was from Pharmacia Upjohn (Nerviano, Italy); E-64, a
cysteine-protease inhibitor, was from Calbiochem Corp. (La Jolla, CA).
IL-1 binding assay
The assay was conducted as described 29 . Briefly, 10 x 106 cells were incubated with or without the indicated stimuli in serum-free medium at 37°C in 5% CO2 for 20 min in 50-ml conical polypropylene tubes (Falcon-Becton Dickinson Labware, Lincoln Park, NJ). Cells were then washed with binding buffer (RPMI 1640, 0.2% BSA, pH 7.4), and 4 x 106 cells were incubated with 600 pM 125I-labeled IL-1ß (sp. act. 180 µCi/mg; NEN, Bad Homburg, Germany) in the presence or absence of a 100 M excess of cold cytokine in 50 µl of binding buffer at 4°C for 4 h in polystyrene 96 round-bottom well microplates (Falcon) on a shaking platform. Preliminary experiments showed that binding reached the plateau (4 h) under these conditions. To separate bound from free 125I-labeled IL-1ß, cells were resuspended, transferred to Eppendorf tubes, washed in binding buffer, resuspended in 70 µl of binding buffer, and finally layered on the top of a 200-µl cushion of 20% sucrose (Merck) and 1% BSA in 400-µl polypropylene tubes (Beckman Instruments, Palo Alto, CA) and centrifuged at 10,000 rpm for 30 s at room temperature. The cellular pellets were counted in a gamma counter. To obtain a saturation curve, untreated or LPS-treated monocytes were incubated with increasing amounts of 125I-labeled IL-1ß, in the presence or absence of a 100 M excess of cold cytokine. Scatchard analysis was performed by the LIGAND program (Version 4.1; National Institutes of Health, Bethesda, MD) to determine the affinity and numbers of receptors for IL-1ß.
Affinity cross-linking
Cells (30 x 106) were stimulated with 50 ng/ml LPS in 1 ml of RPMI 1640 at 37°C for 20 min. Medium was recovered and concentrated 10 times by membrane filtration (cutoff, 10,000; Amicon, Beverly, MA). One hundred microliters were added to 1 nM 125I-labeled IL-1ß, with or without a 200 M excess of cold IL-1ß or 10 µg/ml M1 (blocking mAb anti-IL-1RI) or M22 (blocking mAb anti-IL-1RII) 7, 34 kindly provided by Dr. J. E. Sims (Immunex, Seattle, WA), and incubated at 4°C for 4 h. After addition of 1 mM disuccinimidyl suberate (Pierce, Rockford, IL) at 4°C for 30 min, samples were analyzed by 8% SDS-PAGE under reducing conditions, and dried gels were exposed to autoradiography for 1–3 days.
RNA extraction and Northern blots
RNA was extracted and purified using the guanidine isothiocyanate (Merck) method as described previously 35, 36 . Total cellular RNA (10 µg) was run in standard formaldehyde-agarose gel, blotted onto Gene Screen Plus membranes (New England Nuclear, Boston, MA), and fixed at 80°C for 2 h. Membranes were pretreated and hybridized in 50% formamide (Merck) with 10% dextran sulfate (Sigma) and washed twice with 2x SSC (1x SSC, 0.15 mol/L NaCl, and 0.015 mol/L sodium citrate) and 0.1% SDS (Merck) at 60°C for 1 h, and finally washed twice with 0.1x SSC at room temperature for 5 min. Membranes were exposed for 4–24 h at -80°C with intensifying screens. RNA transfer to membranes was checked by UV irradiation, as shown in each figure.
Hybridizations for detection of IL-1RI transcript were performed, with
HindIII-EcoRI cDNA probe corresponding to probe b
in Fig. 7
A. Hybridizations for detection of IL-1RII
transcript were performed using the probe corresponding to the 750-bp
fragment subcloned in the EcoRI site of the plasmid pHuII75
gift by Dr. J. E. Sims (Immunex).
|
RT-PCR
To amplify different sequences of coding or noncoding regions of the IL-1RI gene, we performed RT-PCR 37 . Briefly, 1 µg of total RNA from LPS-treated monocytes was reverse transcribed in reverse transcriptase buffer (5 mmol/L MgCl2, 50 mmol/L KCl, and 10 mmol/L Tris-HCl, pH 8.3) with 2.5 µmol/L random hexamers, 1 mmol/L each deoxynucleotide triphosphate, 1 U/µl RNase inhibitor, and 2.5 U/µl Moloney leukemia virus reverse transcriptase (Perkin-Elmer/Cetus, Norwalk, CT). Samples were incubated for 10 min at room temperature and then at 42°C for 15 min, 99°C for 5 min, and 5°C for 5 min. Then, each cDNA reaction was divided into two Eppendorf tubes, and a specific pair of primers designed to amplify cDNAs coding for IL-1RI, and as an internal control human ß actin, was added to each. Amplification was performed in 2 mmol/L MgCl2, 50 mmol/L KCl, 10 mmol/L Tris-HCl, 0.2 mol/L each deoxynucleotide triphosphate, 2.5 U/100 µl Taq DNA polymerase (Perkin-Elmer Cetus), and 4 µg/ml of each specific primer (see below). Amplification was performed in an automated thermal cycler (Perkin-Elmer Cetus) at 95°C for 1.5 min, 55°C for 1.5 min, and 72°C for 1.5 min. Amplification was stopped at 35 cycles. The specific primers were designed to amplify the following sequences: probe a, sequence 123–694 (exons 4–6, extracellular region); probe b, sequence 765-1192 (exons 7–10, extracellular and transmembrane regions); probe c, sequence 1051–1231 (exon 10, transmembrane region); probe d, sequence 1199–1399 (exon 11, intracellular region); probe e, sequence 1470–1970 (exon 12, intracellular region and a part of 3' untranslated); probe f, sequence 2427–2966 (3' untranslated); probe g, sequence 3201–3683 (3' untranslated); and probe h, sequence 4003–4476 (3' untranslated).
The nucleotides in these sequences can be found under GenBank accession number M27492. In this sequence, the translation termination codon is at nucleotide 1790, and the alternative consensus sequence for poly(A)+ addition is at nucleotide 2309. The PCR products were subcloned in pMOS Blue T-vector (pMOS Blue T-vector kit, RPN 1719; Amersham, Arlington Heights, IL) and sequenced by the T7 sequencing kit (Pharmacia).
cDNA cloning
Total RNA was isolated from monocytes stimulated for 4 h
with 500 µg/ml LPS. Poly(A)+ RNA was further purified by
affinity chromatography on oligo(dT) cellulose. A cDNA library was
constructed in the 
-ZAP II vector (Stratagene, La Jolla, CA) as
described 38 . A total of 3 x 105 plaques were
transferred onto nitrocellulose membranes in duplicate by standard
procedures and screened as described 38 . Eighty-four plaques were
found to be positive for probes b and e, and only three plaques were
found to hybridize with probe b and not with probe e.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
In a first series of experiments, we examined whether LPS affected
rapid release of the decoy IL-1RII in human monocytes, a cell type that
expresses predominantly (>80% of the IL-1 binding capacity) the type
II decoy R, IL-1RII 3, 11 . As shown in Fig. 1A, exposure to LPS for 30 min
caused a profound reduction of the monocyte capacity to bind IL-1, with
an ED50 of 
1 ng/ml and virtually complete inhibition at
10 ng/ml. The number of IL-1R/cell was 5016 ± 214 in the
untreated population and 356 ± 11 in LPS-treated monocytes. No
substantial change in receptor affinity was detected (4.12 x
10-9 M in untreated cells and 1.88 x
10-9 M in LPS-treated cells) (Fig. 1B). The
effect of LPS was detected at 10 min and was maximal at 20 min (not
shown).
|
C, LPS-treated monocytes released an IL-1 binding molecule
of 78 kDa; after subtraction of the IL-1 mass, the molecular
mass of this protein was 60 kDa, as expected for a soluble
form of IL-1RII 11, 32, 33 . The specific nature of the cross-linking
was demonstrated by competition with an excess of unlabeled IL-1. The
IL-1 soluble binding material was totally inhibited by the presence of
a blocking mAb (M22) directed against the IL-1 decoy IL-1RII but not of
an anti-IL-1RI mAb (M1). Thus, the loss of IL-1 binding induced by
LPS is largely, if not exclusively, accounted for by the release of the
soluble form of the IL-1 decoy IL-1RII from the monocyte surface.
TNF- is a potent inducer of decoy IL-1RII release on monocytes and
polymorphonuclear neutrophils 30 , and LPS induces TNF-
production in monocytes. We tested whether LPS-induced decoy IL-1RII
release was mediated by TNF- produced by monocytes after incubation
with LPS. We incubated monocytes with a blocking mAb specific for
TNF-, in the presence or absence of LPS. As a positive control, we
also incubated monocytes with TNF- and mAb. As shown in Fig. 2A, while the TNF- action
on decoy IL-1RII release was blocked by the specific Ab, the LPS effect
was not significantly modified.
|
B, when cells were treated with different protease
inhibitors, BB-94, a specific metalloprotease inhibitor, significantly
blocked the LPS-induced release of decoy IL-1RII. Effects on IL-1R expression
Having identified a rapid action of LPS on surface levels of the
IL-1 decoy IL-1RII, we investigated "late" effects on mRNA levels.
As shown in Fig. 3A, resting
monocytes express high levels of decoy IL-1RII mRNA, and these were
markedly reduced by LPS in a dose-dependent way (at a dose of 500
ng/ml, 10-fold, mean of 20 experiments). This effect was maximal
between 6 and 8 h after treatment with LPS (Fig. 3B).
|
A). Upon exposure to LPS, monocytes showed a dramatic
augmentation of steady-state IL-1RI transcripts (at a dose of 500
ng/ml, 30-fold, mean of 35 experiments). The effect of LPS on IL-1RI
expression was maximal at 4 h and declined thereafter (Fig. 3B). As shown in Fig. 3C, expression of IL-1RAcP
was also augmented by LPS (8-fold, two experiments).
To obtain initial indications as to the mechanisms involved in LPS
stimulation of IL-1RI expression, we used metabolic inhibitors and
measured transcript half-life. As shown in Fig. 4, A and B, the
transcriptional inhibitor ActD and the protein synthesis inhibitor CH
completely abolished the divergent effects of LPS on expression of
IL-1RI and of the decoy IL-1RII. In an effort to assess whether LPS
affected mRNA stability, monocytes were exposed to LPS for 4 h,
treated with ActD to inhibit transcription, and analyzed by Northern
blot at different times to evaluate the mRNA half-lives (Fig. 4C). The estimated mRNA half-lives were 2 and 2.45 h
for IL-IRI in control and LPS-treated cells, respectively, and 2.15 and
1.30 h for IL-1RII in control and LPS-treated monocytes,
respectively.
|
augmented expression of IL-1RI and inhibited that of
decoy IL-1RII in human monocytes (not shown). However, addition of
excessive amounts of IL-1Ra and of a blocking anti-TNF- mAb,
alone or in combination, did not affect LPS with regard to
expression of IL-1RI and decoy IL-1RII (Fig. 5).
|
In the course of these studies we observed that LPS induced the
appearance of a 2.4-kb IL-1R-related band, visible after more prolonged
exposure of the blots (after 24 h). Blots from resting and
LPS-treated monocytes were therefore hybridized with the IL-1RI and
IL-1RII probes separately. As shown in Fig. 6 (representative of 15 experiments), LPS
induced expression of a novel 2.4-kb transcript, which hybridized with
the IL-1RI probe and was detected after longer (24-h) exposure of
the blots. By densitometric analysis of results at an LPS concentration
of 500 ng/ml, the intensity of the 2.4-kb band was 10–20-fold lower
than that of the 5-kb one in this series of experiments. Induction of
the 2.4-kb IL-1RI transcript closely paralleled that of the canonical
5-kb mRNA in terms of time course (not shown) and dose-response
relationship.
|
A) of IL-1RI mRNA, were used
in Northern analysis of RNA from resting and LPS-stimulated cells.
All probes recognized the 5-kb IL-1RI transcript. In contrast, probes
e, f, g, and h did not hybridize to the 2.4-kb IL-1R transcripts;
therefore a 3' part of the coding sequence (exon 12) and the 3'
untranslated region were not present in the smaller 2.4-kb mRNA species
(Fig. 7B). Since probe e comprises coding and noncoding
sequences of the IL-1RI, we constructed two new probes, e1 and e2 (Fig. 7A), which correspond to the coding and noncoding regions,
respectively. Neither the e1 nor the e2 probe hybridized to the small
2.4-kb transcript (Fig. 7C), which indicated that part of
the 3' coding sequence may have been missing in this band.
To define the structure of the 2.4-kb IL-1RI-transcripts, we
constructed a cDNA library from LPS-stimulated monocytes. The library
was screened in duplicate using probes b and e; we selected for
analysis clones negative with probe e and positive with probe b. We
obtained 84 positive clones with probes b and e (IL-1RI wild-type) and
3 positive clones (clones 27, 21, and 25) that were positive with probe
b and negative with probe e. These clones were sequenced; Fig. 8A shows a schematic
representation of the structure of these clones. In all 3 clones, exon
12 and the 3' untranslated region are absent and polyadenylation is
present. Intronic sequences 39 corresponding to introns 7 and 9 were
present in clone 27, those of introns 5 and 6 in clone 21, and those of
intron 11 in clone 25. In clone 21, the poly(A) tail was preceded by a
novel sequence, X (GenBank accession number AF054830).
|
B, a probe
corresponding to intron 9 of IL-1RI recognized the 2.4 transcript in
total (Fig. 8B, lanes 1 and 2) and
poly(A)+ RNA (Fig. 8B, lane 3) from
LPS-induced monocytes. The same 2.4-kb band was also recognized by a
probe representative of sequence X (data not shown).
To confirm these data, we used primers corresponding to a fragment
spanning exonic (exon 8) and intronic (intron 9) regions to amplify
total RNA of LPS-stimulated monocytes. As expected, a band of 970 bp
was amplified (Fig. 8C), further supporting the existence of
these transcripts in LPS-treated monocytes.
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
LPS induced rapid (within minutes) loss of the IL-1 binding capacity in
monocytes. The loss of IL-1 binding capacity in LPS-treated monocytes
was due to the disappearance of the receptors from the cell surface and
associated with the rapid release of a 60-kDa IL-1 binding molecule.
The rate of IL-1R internalization was not affected by LPS. The 60-kDa
IL-1 binding molecule was identified as the IL-1 decoy receptor, which
represents the main IL-1R in myelomonocytic cells and an anti-IL-1
pathway 3, 11 . Since TNF- is a potent inducer of decoy IL-1RII
release in monocytes and polymorphonuclear neutrophils 30 and
LPS induces production of TNF- in monocytes, it was important to
investigate whether the effect of LPS on release of decoy IL-1RII was
mediated by TNF-. Using a blocking mAb specific for TNF-, we
found that the action of LPS was not mediated by TNF-, indicating
that LPS directly induced release of the decoy IL-1RII.
We recently showed that release of decoy IL-1RII mediated by TNF, chemoattractant molecules, and phorbol ester is mediated by metalloprotease(s) 31 . Therefore, we investigated whether the LPS-induced release of decoy IL-1RII was also mediated by metalloprotease(s). BB-94, a classical metalloprotease inhibitor, blocked the LPS-induced release of the receptor, indicating that a common mechanism is responsible for decoy IL-1RII shedding.
LPS induces production of a number of mediators in mononuclear phagocytes, including the primary cytokines IL-1 and TNF. In preliminary experiments we found that IL-1 and, to some extent, TNF mimicked the action of LPS, having divergent effects on mRNA expression of IL-1Rs. However, IL-1Ra and anti-TNF mAb did not affect the regulation of IL-1R expression by LPS. Therefore, we conclude conclude that induction of IL-1 and TNF does not account for the contrasting actions of LPS on IL-1R transcripts.
LPS induced expression of novel 2.4-kb IL-1RI transcripts. Others have noted the presence of similar IL-1RI-related mRNA and speculated that it might originate from usage of an alternative polyadenylation site located 518 bases 3' of the termination codon 34 . Using probes spanning the whole conventional IL-1RI transcript, we determined that the 2.4-kb transcripts lack a portion of the 3' coding region as well as 3' untranslated sequences.
Using a combination of RT-PCR and cDNA cloning strategies, we
determined that the 2.4-kb band contains polyadenylated transcripts,
which all lack exon 12 (two cDNAs also lack exon 10 and 11) and contain
intronic sequences. Since only three clones were sequenced, the
relative abundance of different, incompletely spliced transcripts in
the 2.4-kb band cannot be estimated based on these results. Based on
Northern analysis with probes representative of different regions (Fig. 7), one would infer that most transcripts in the 2.4-kb band include
exons 3–11. The occurrence of incompletely spliced transcripts with
intronic sequences in mature polyadenylated mRNA has already been
described 40, 41, 42, 43, 44 . LPS-induced overexpression may override the
capacity of the splicing machinery to generate conventional transcripts
of IL-1RI.
The significance of these LPS-inducible anomalous IL-1RI 2.4-kb transcripts remains a matter of speculation. The membrane-bound, conventional IL-1RI is not susceptible to proteolytic shedding, unlike IL-1RII (Refs. 29–31 and 45 and our unpublished data). Soluble IL-1RI has been detected in normal serum 46 and in inflammatory conditions such as rheumatoid arthritis 47 . One could therefore speculate that incompletely spliced transcripts may encode truncated, releasable isoforms of IL-1RI. Given the relative affinity of IL-1RI for different ligands and their relative concentration in biological fluids 1, 2, 3 , soluble IL-1RI may primarily interact with and block IL-1Ra. Alternatively, the 2.4-kb band may not have physiological significance and may be a consequence of overriding of the splicing system under the pressure of LPS stimulation.
Available information is consistent with the view that IL-1RI and decoy IL-1RII have opposite roles in responses to IL-1, one being a signaling molecule in concert with IL-1AcP and the other a molecular trap for IL-1. LPS augments the expression of IL-1RI and IL-1AcP and decreases that of IL-1RII. We speculate that these effects on IL-1Rs play a role in the synergism between LPS and IL-1 observed in certain cellular systems 1, 2, 48 .
Available information is consistent with a "decoy" model of function of the type II R, while the signal-transducing capacity of IL-1RI and IL-1RAcP is well established 3, 10, 11, 19 . Consistently with this model, anti-inflammatory molecules, including glucocorticoid hormones and cytokines (e.g., IL-13) induce augmented expression of the decoy IL-1RII 32, 33 . The observation of divergent effects of proinflammatory molecules on IL-1Rs, with stimulation of IL-1RI and inhibition of IL-1RII, is consistent with the view that these molecules subserve opposite functions in the pathophysiology of the IL-1 system. In particular, the rapid shedding of decoy IL-1RII by monocytes early in recruitment may serve to buffer the systemic action of IL-1 leaking from sites of inflammation. This early event, followed by prolonged inhibition of IL-1RII expression and up-regulation of IL-1RI and IL-1RAcP, may render monocytes more responsive to IL-1 at sites of inflammation.
|
Footnotes |
|---|
2 The sequences reported herein have been deposited in the GenBank/EMBL database and assigned accession numbers M27492 and AF054830.
3 G.P.-R. and S.O. contributed equally to this work.
4 Address correspondence and reprint requests to Alberto Mantovani, Istituto di Ricerche Farmacologiche "Mario Negri," via Eritrea 62, 20157 Milan, Italy. E-mail address:
5 Abbreviations used in this paper: IL-1Ra, IL-1R antagonist; IL-1RAcP, IL-1R accessory protein; ActD, actinomycin D; CH, cycloheximide.
Received for publication August 10, 1998. Accepted for publication November 12, 1998.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
, unlike other pro- and anti-inflammatory cytokines, induces rapid release of the IL-1 type II decoy receptor in human myelomonocytic cells. J. Immunol. 158:3861.[Abstract]
, IL-1ß, and IL-1 receptor antagonist by soluble IL-1 receptors and levels of soluble IL-1 receptors in synovial fluids. J. Immunol. 153:4766.[Abstract]
. J. Immunol. 160:3869.This article has been cited by other articles:
|
|
 |
|
  Z. Zhou, R. P. Barrett, S. A. McClellan, Y. Zhang, E. A. Szliter, N. van Rooijen, and L. D. Hazlett Substance P Delays Apoptosis, Enhancing Keratitis after Pseudomonas aeruginosa Infection Invest. Ophthalmol. Vis. Sci., October 1, 2008; 49(10): 4458 - 4467. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 X. Huang, L. D. Hazlett, W. Du, and R. P. Barrett SIGIRR Promotes Resistance against Pseudomonas aeruginosa Keratitis by Down-Regulating Type-1 Immunity and IL-1R1 and TLR4 Signaling J. Immunol., July 1, 2006; 177(1): 548 - 556. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Verbruggen Chondroprotective drugs in degenerative joint diseases Rheumatology, February 1, 2006; 45(2): 129 - 138. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Huber-Lang, J. V. Sarma, D. Rittirsch, H. Schreiber, M. Weiss, M. Flierl, E. Younkin, M. Schneider, H. Suger-Wiedeck, F. Gebhard, et al. Changes in the Novel Orphan, C5a Receptor (C5L2), during Experimental Sepsis and Sepsis in Humans J. Immunol., January 15, 2005; 174(2): 1104 - 1110. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
X. Cui, F. N. Rouhani, F. Hawari, and S. J. Levine Shedding of the Type II IL-1 Decoy Receptor Requires a Multifunctional Aminopeptidase, Aminopeptidase Regulator of TNF Receptor Type 1 Shedding J. Immunol., December 15, 2003; 171(12): 6814 - 6819. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. M. Prevost, J. L. Pelley, W. Zhu, G. E. D'Egidio, P. P. Beaudry, C. Pihl, G. G. Neely, E. Claret, J. Wijdenes, and C. B. Brown Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) and Inflammatory Stimuli Up-Regulate Secretion of the Soluble GM-CSF Receptor in Human Monocytes: Evidence for Ectodomain Shedding of the Cell Surface GM-CSF Receptor {alpha} Subunit J. Immunol., November 15, 2002; 169(10): 5679 - 5688. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. Muller, G. Peri, A. Doni, A. P. Perruchoud, R. Landmann, F. Pasqualini, and A. Mantovani High circulating levels of the IL-1 type II decoy receptor in critically ill patients with sepsis: association of high decoy receptor levels with glucocorticoid administration J. Leukoc. Biol., October 1, 2002; 72(4): 643 - 649. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. A. Hintz, A. J. Rassias, K. Wardwell, M. L. Moss, P. M. Morganelli, P. A. Pioli, A. L. Givan, P. K. Wallace, M. P. Yeager, and P. M. Guyre Endotoxin induces rapid metalloproteinase-mediated shedding followed by up-regulation of the monocyte hemoglobin scavenger receptor CD163 J. Leukoc. Biol., October 1, 2002; 72(4): 711 - 717. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Muzio, D. Bosisio, N. Polentarutti, G. D'amico, A. Stoppacciaro, R. Mancinelli, C. van't Veer, G. Penton-Rol, L. P. Ruco, P. Allavena, et al. Differential Expression and Regulation of Toll-Like Receptors (TLR) in Human Leukocytes: Selective Expression of TLR3 in Dendritic Cells J. Immunol., June 1, 2000; 164(11): 5998 - 6004. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. E. Jensen, M. Muzio, A. Mantovani, and A. S. Whitehead IL-1 Signaling Cascade in Liver Cells and the Involvement of a Soluble Form of the IL-1 Receptor Accessory Protein ,2 J. Immunol., May 15, 2000; 164(10): 5277 - 5286. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. M. Daun, R. W. Ball, and J. G. Cannon Glucocorticoid sensitivity of interleukin-1 agonist and antagonist secretion: the effects of age and gender Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2000; 278(4): R855 - R862. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||
