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*
Maxwell Finland Laboratory for Infectious Diseases, Department of Medicine, Boston Medical Center and Boston University School of Medicine, Boston, MA 02118;
Eisai Research Institute, Andover, MA 01810;
Department of Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02118; and
§
Norwegian University of Science and Technology, Trondheim, Norway
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The identification of CD14 as a signaling receptor for complexes of LPS was a seminal event in understanding the mechanism by which LPS-induced cellular activation occurs. CD14, a 55-kDa glycosyl phosphatidylinositol (GPI)4-linked protein present on the surface of phagocytic leukocytes, has been shown to bind LPS and to mediate cellular activation (4, 5, 6). In addition, a soluble form of CD14 (sCD14) is also capable of binding LPS and activating some CD14-deficient cells, such as endothelial cells (7, 8, 9, 10). Several lines of evidence support a role for CD14 in LPS signaling, including: 1) LPS binds membrane and sCD14 as a complex with LPS-binding protein (5, 6, 11, 12); 2) mAbs to CD14 inhibit the ability of LPS to stimulate phagocytes (5, 13, 14, 15, 16) and endothelial cells (8); 3) cells that are LPS hyporesponsive or unresponsive become sensitive to LPS when transfected with CD14 (17, 18); and 4) CD14-deficient mice have severely diminished responses to LPS (19).
One interesting aspect of CD14-mediated signal transduction is that it is greatly enhanced by two serum proteins: LPS-binding protein (LBP) and sCD14. Soluble CD14, as described above, acts as an LPS receptor for some non-CD14 bearing cells, such as endothelial cells (7, 8, 9, 10). LBP, in contrast, is a lipid transfer protein. Although CD14 can bind LPS in its absence, LBP accelerates the binding of LPS monomers to both membrane and sCD14 (12, 20), thus enhancing the sensitivity of cells to LPS (5, 12, 21, 22).
It is generally agreed that the interaction between lipid A and CD14 is central to cellular activation by LPS; however, details of the downstream signaling events remain obscure. For example, since CD14 lacks a transmembrane domain, it seems probable that CD14 utilizes an accessory receptor to transmit a signal across the plasma membrane. Furthermore, pharmacologic studies with lipid A antagonists suggest that CD14 activates cells via an ancillary-signaling molecule. For example, the biologically derived lipid A analogues Rhodobacter sphaeroides lipid A (RSLA) and lipid IVA are potent LPS antagonists in LPS-responsive human cells (23, 24, 25). In hamster and mouse cells these compounds have very different effects: in hamsters, both compounds are LPS mimetics (26), while in mice lipid IVA is a LPS mimetic and RSLA is a LPS antagonist (23, 24, 27, 28). Data from transfected cell lines have shown that the species-specific effects of the lipid A-like compounds are determined not by the species of CD14, but by the genome of the host cell on which it is expressed (26). In addition, careful binding studies by Kitchens et al. (15) and Kitchens and Munford (29) demonstrated that these compounds inhibit the ability of LPS to activate cells at concentrations that are too low to inhibit binding of LPS to CD14. Taken together, these data suggest that the inhibitors are not simply competing with LPS for binding to CD14, but that they are antagonizing LPS at a site distinct from CD14. Thus, while CD14 plays a major role in LPS recognition by phagocytes, it is not felt to be a direct signaling receptor.
The CD11/CD18 (ß2) integrins represent a second group of LPS
receptors. Although Wright and Jong demonstrated that the integrins
were capable of binding unopsonized bacteria and LPS (30),
it was initially unclear if this interaction triggered a cellular
response independent of CD14. For example, it was demonstrated that
PBMCs from CD18-deficient patients responded normally to LPS
(31). Studies in our laboratory recently demonstrated that
the CD11/CD18 integrins enable LPS-induced signal transduction when
transfected into Chinese hamster ovary (CHO) cells, thus demonstrating
that CD11/CD18 can enable LPS responsiveness independent of CD14
(32, 33). Although the integrins are transmembrane
receptors, the cytoplasmic domains do not appear to be necessary for
signaling translocation of nuclear factor-
B (NF-B) in response to
LPS binding. This is based on the observation that a mutant CD11b/CD18,
deficient in the cytoplasmic domains and incapable of internalization
of Gram-negative bacteria, is still competent for LPS-induced cellular
activation (33). Thus, the integrins, like CD14, may
function to transfer LPS to a second receptor that transduces the
signal.
We sought to identify further similarities and differences between the signaling systems utilized by CD14 and CD11/CD18. First, we found that LBP was capable of enhancing CD11/CD18-dependent binding of whole Gram-negative bacteria to cells, as well as cellular activation via LPS in the CD11/CD18-transfected CHO cells. In addition, we found that lipid IVA and two synthetic lipid A analogues demonstrated the same species specificity in CD11/CD18-transfected cell lines as they did in CD14 transfectants. In light of the similarities between CD14- and CD11/CD18-mediated signal transduction, we hypothesize that both LPS receptors form a signaling complex that utilizes a common lipid A recognition molecule that functions as the true signal transducer in LPS-mediated cellular activation.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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All solutions were guaranteed sterile and pyrogen free by the
manufacturer unless otherwise stated. PBS, Ham’s F-12, DMEM, and RPMI
1640 were obtained from BioWhittaker (Walkersville, MD). Ex-Cell 301
serum-free medium was obtained from JRH Biosciences (Lenexa, KS). FCS
(LPS 
10 pg/ml) was obtained from HyClone Laboratories (Logan,
UT). Human serum was derived from clotted whole blood from healthy
volunteers and heat inactivated in a water bath at 56°C for 20 min.
Ciprofloxacin was a gift from Miles Pharmaceuticals (West Haven, CT).
G418 was obtained from Sigma (St. Louis, MO). Murine LBP was a gift of
Ralf Schumann (Humboldt University, Berlin, Germany); human LBP and
soluble CD14 were gifts of Henry Lichenstein (Amgen, Thousand Oaks,
CA). LPS from Salmonella minnesota R595 (ReLPS) was the gift
of Drs. N. Qureshi and K. Takayama (University of Wisconsin, Madison,
WI). The generation of compound B287 has been published previously
(34). Compound B1287 was prepared at Eisai Research
Institute (Andover, MA; patent reference no. WO-9639411-A1). Synthetic
lipid IVA was purchased from ICN (Costa Mesa, CA). Lipids
were prepared as 1 mg/ml dispersed sonicates in pyrogen-free PBS and
stored at -20°C. Prior to use, the suspensions were thawed and
sonicated for 3 min in a water bath sonicator (Laboratory Supplies,
Hicksville, NY) before diluting to final concentration. Mycobacterial
lipoarabinomannan (noncapped araLAM from a rapidly growing
mycobacterial species) was provided by Drs. J. Belisle and P. Brennan
(Colorado State University, Fort Collins, CO) under National Institutes
of Health Contract NO1-A1-25147. The LPS content of this preparation,
as assayed by Limulus amebocyte lysate assay, was 14 ng/mg
of LAM. Peptidoglycan (PG; soluble polymeric peptidoglycan isolated
from the cell walls of Staphylococcus aureus) was a gift
from Dr. R. Dziarski (Indiana University School of Medicine, Gary, IN).
PG contained <12 pg of LPS/mg as determined by the Limulus
amebocyte lysate assay.
Cell lines
The following cell lines were obtained from the American Type
Culture Collection (Manassas, VA): CHO-K1, a hamster fibroblast cell
line; HT1080, human fibrosarcoma cell line; RAW 264.7, an
LPS-responsive murine macrophage cell line (35); and
THP-1, a human promonomyelocytic line (36). The following
stably transfected cell lines were engineered as previously described:
HT1080/CD14human and HT1080/CD14murine, human
and murine CD14-transfected HT1080 lines (26); CHO/Neo,
CHO-K1 transfected with the pCDNA1/Neo vector (18);
CHO/CD14 human CD14-transfected CHO-K1 (18); and
CHO/CD11b, CHO-K1 transfected with full length human CD11b and CD18,
and CHO/CD11bmutant, which contains a cytoplasmic deletion
mutant form of CD11b and CD18 (33). CHO/CD11c, CHO-K1
transfected with human CD11c and CD18, was engineered by the same
method as described for CHO/CD11b (33) using human CD11c
and CD18 cDNA in 
H3M vectors (37) and pcDNA1/Neo.
Cell culture and stimulation conditions
Cell lines were maintained as follows: RAW 264.7 and HT1080 in DMEM/HG; THP-1 in RPMI 1640; and CHO-K1 cells in Ham’s F-12. Tissue culture medium was supplemented with 10% FCS and 10 µg ciprofloxacin/ml (complete medium). Transfected CHO cell lines were maintained in complete medium supplemented with G418 (500 µg active drug/ml). Cell lines were grown as adherent monolayers in tissue culture dishes at 37°C in 5% CO2, and passaged twice a week to maintain logarithmic growth. THP-1 cells were differentiated with vitamin D3 (0.1 µM) for 72 h prior to stimulation (15).
One day prior to stimulation, cells growing as adherent monolayers in tissue culture dishes were trypsinized, resuspended in complete medium, and plated in 6-well tissue culture dishes at a density of 5 x 105 per well. Plates were incubated overnight at 37°C in 5% CO2. On the day of stimulation, wells were aspirated and washed three times with PBS to remove FCS. For RAW and THP-1 cells, medium was replaced with 1 ml of DMEM or RPMI 1640, respectively, and supplemented with 2% heat-inactivated human serum. For the CHO cells, medium was replaced with Ham’s F-12 with 2% FCS or Ex-Cell serum-free medium. When LBP was used in assays, it was added to Ex-Cell for a final concentration of 150 ng/ml. Compound B1287, also diluted in PBS, was added at the same time as the stimulant. Culture dishes were returned to 37°C/5% CO2 for 1 h.
Preparation of nuclear extracts
The procedure used for the preparation of nuclear extracts has been published in detail (38). After stimulation, cells were washed in tissue culture plates with PBS/2% FCS, harvested using a rubber policeman, and pelleted in a microcentrifuge (Beckman Microfuge 11). Cell pellets were resuspended in 0.4 ml buffer I (10 mM Tris-HCl, pH 7.8, 5 mM MgCl2, 10 mM KCl, 0.5 mM DTT, 1 mM EGTA, 1 mM PMSF, 10 mM ß-glycerol phosphate, 0.3 M sucrose, and 1.0 µg/ml each of the following protease inhibitors: aprotinin, antipain, leupeptin, chymostatin, and pepstatin), incubated on ice for 15 min, and lysed by adding Nonidet P-40 to a final concentration of 0.5%. Nuclei were collected by centrifugation and resuspended in 50 µl of buffer II (20 mM Tris-HCl, pH 7.8, 5 mM MgCl2, 320 mM KCl, 0.5 mM DTT, 0.2 mM EGTA, 0.5 mM PMSF, 10 mM ß-glycerol-phosphate, 25% glycerol, and 1.0 µg/ml protease inhibitors as above). After a 15-min incubation on ice, the nuclear extracts were cleared by centrifugation and transferred to a new tube. Protein concentration was determined using Bio-Rad protein assay dye reagent concentrate (Bio-Rad Laboratories, Hercules, CA).
Electrophoretic mobility shift assay (EMSA)
Nuclear extract pellets were assayed for the presence of
(NF-B) as described in detail (38). Briefly, 4 µg of
the crude nuclear protein was incubated with 32P-labeled
oligonucleotides containing the consensus sequence for NF-B binding
from the murine Ig light chain gene enhancer. The DNA-protein
binding reactions were analyzed by nondenaturing gel electrophoresis.
Gels were transferred to filter paper, dried, and exposed to x-ray
film. Scanning densitometry of the autoradiographs was performed using
Sigma Gel (version 1.0; Jandel Scientific, San Rafael, CA).
Binding assays
Binding assays were performed as previously described (33). Briefly, Escherichia coli MC1061/P3 were cultured to a density of 1 x 109/ml, heat fixed, and labeled with FITC (0.1 mg/ml) for 30 min at room temperature. Monolayers of CHO transfectants growing at a density of 1 x 105 per well were incubated with 108 bacteria at 37°C for 1 h and analyzer for fluorescence signal (18).
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The serum protein LBP is a lipotransferase, catalytically transferring LPS from aggregates to CD14. LBP does not form detectable complexes with LPS and CD14, and it is not required for LPS-induced cellular activation. However, by facilitating the interaction between LPS and CD14, LBP enhances the sensitivity of cells to LPS (12). In addition to transferring LPS to CD14, LBP is also capable of transferring LPS to lipoprotein particles, such as high density lipoprotein, where it may play a role in LPS neutralization (20).
We asked whether LBP could perform a similar function in the
interaction between LPS and CD11/CD18. We had previously reported that,
unlike CD14-dependent signaling, activation of CD11c/CD18-transfected
CHO cells was not enhanced by the addition of human serum
(32). When we attempted to examine this observation
further, we found recombinant sCD14 had no effect on LPS-induced
activation in either the CHO/CD11b or CHO/CD11c cell lines (data not
shown). However, with LBP, the results were quite different. Here we
found another similarity between CD11/CD18 and CD14 with respect to
signaling: the addition of recombinant human LBP (150 ng/ml) to
serum-free medium increased the sensitivity of CHO/CD11b to LPS by
approximately 30-fold (Fig. 1
). A similar
effect was also seen with the cytoplasmic deletion mutant
CHO/CD11bmutant (data not shown). This suggested to us that
LBP was also capable of transferring LPS to CD11/CD18.
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, opsonization of FITC-labeled E.
coli with recombinant murine LBP (200 ng/ml) resulted in a
dramatic increase in binding to CHO cells expressing CD11/CD18. An
increase in binding of bacteria to CHO/CD14 could also be seen in the
presence of LBP, although overall the binding was much lower than that
seen in the CD11b/CD18-transfected CHO cells. In contrast, the control
line CHO/Neo cell line failed to bind significant bacteria whether or
not LBP was present.
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Several biosynthetic inhibitors of lipid A, such as RSLA and lipid
IVA, have been useful in the study of LPS-induced cellular
activation. The development of new methodologies for the preparation of
synthetic lipid A has greatly benefited the study of LPS antagonists.
One such compound, compound B287, is based on the proposed structure of
RSLA, and has activity identical to that of natural RSLA when tested in
macrophage cell lines and whole human blood ex vivo (34).
Christ et al. recently reported on the activity of E5531, a potent LPS
antagonist similar in structure to Rhodobacter capsulatus
lipid A (39). They found that this compound blocked
LPS-mediated cellular activation in human macrophages and protected
mice from lethality induced by LPS. This compound also inhibits a broad
range of effects in LPS-challenged humans (39) (M. Lynn,
personal communication), and is currently in human clinical trails as
an antiendotoxic agent. The structure of E5531, as well as the nontoxic
lipid A moieties from R. capsulatus and R.
sphaeroides lipid A, served as the foundation for the development
of compound B1287. Figure 3 depicts the
structure of compound B1287 in comparison with compound B287 and ReLPS
lipid A. Compound B287 differs from lipid A by the presence of a
3-keto-myristoyl group at the 2 position, a double bond in the
acyloxyacyl chain at the 2' position, and the absence of an oxyacyl
chain at the 3' position. It also has shorter 3 and 3' acyl groups.
Compound B1287 is similar in structure to B287 with the following
exceptions: the ester linkage of the fatty acyl side chains at the 3
and 3' positions have been replaced by ether linkages; the hydroxyl
groups at the C-6' position and on the 3' acyl chain have been replaced
by MeO groups; the oxyacyl chain at the 2' position has been removed;
and a double bond has been introduced in the 2' acyl chain. In
addition, the 2' acyl chain has been lengthened to C18.
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RAW and vitamin D3-differentiated THP-1 cells were
treated with increasing doses of LPS in the presence or absence of
compound B1287, and the nuclear extracts were assayed for the presence
of NF-B. As predicted by the activity of RSLA, which is an
antagonist in human and murine cells, B1287 blocked LPS-induced NF-B
translocation in both cell lines. A comparison of the sensitivity of
the two cell lines by scanning densitometry to the antagonist reveals
that THP-1 (Fig. 4) and RAW (Fig. 5) have an IC50 of <1 ng/ml
and 100 ng/ml, respectively. However, in both cases, the ability of
B1287 to block LPS-induced signal transduction could be overcome with
sufficiently high concentrations of LPS. Similar results were observed
with the HT1080 transfectants expressing either human
(HT1080/CD14human) or murine
(HT1080/CD14murine) CD14 (data not shown).
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Phagocytic leukocytes respond to a variety of bacterial products, and CD14 has been implicated as a component of the cell-activating receptor system for outer wall microbial components other than LPS. This includes the glycolipid LAM from mycobacterial species (40, 41, 42, 43, 44, 45), Gram-positive metabolites, such as PG (41, 46, 47, 48, 49, 50), and mannuronic acid polymers (51, 52). The conclusion that LAM activation is CD14 dependent is based, in part, on the ability of anti-CD14 mAbs to inhibit macrophage responses to these substances and the dependence upon the presence of LBP (45). While CD14 appears to be necessary for cellular activation by LAM and PG, it is not sufficient by itself, as CD14-transfected CHO cells fail to respond to either compound (45) (data not shown). Interestingly, lipid A partial structures have been shown to inhibit LAM- (45) and PG-induced cellular activation (48) as well.
When the ability of compound B1287 to block LAM-induced NF-B
translocation in THP-1 cells was examined, we found similar results.
Like RSLA (45), B1287 was a potent antagonist of NF-B
translocation by LAM (Fig. 6). Similar
data was found using B1287 to block PG-induced NF-B translocation in
the same system (data not shown). These data support the hypothesis
that LPS, LAM, and PG signal cells through a shared receptor complex,
which includes CD14 and a common lipid A recognition molecule
(45).
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Based on the ability of the synthetic LPS analogues B287 and lipid
IVA to stimulate hamster macrophages and CD14-transfected
CHO cells (26), we predicted that the same
species-specific effects would be seen in the CHO cells expressing
CD11/CD18. In fact, we found compound B287 to be an LPS mimetic in both
CHO/CD11b and CHO/CD11c cells (Fig. 7).
Lipid IVA showed similar LPS-mimetic activity (data not
shown).
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). In addition, B1287
was found to be an LPS antagonist in CD11b/CD18-transfected CHO cells
(Fig. 9). In contrast to CHO/CD14, which
are more sensitive to LPS, CHO/CD11b required higher doses of LPS for
stimulation and, consequently, higher doses of B1287 to completely
block signaling. We estimate the IC50 in CHO/CD11b to be
approximately 100 to 1000 ng/ml (data not shown).
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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There are important differences between CD14 and CD11/CD18. In the CHO-K1 system, CD14 appears to be more sensitive to LPS compared with CD11/CD18, and the activation of cells appears to occur more rapidly (32, 33). While sCD14 is capable of activating many non-CD14-bearing cell types, there is no evidence, at least with a soluble form of CD11c/CD18, that the integrins can function in this manner (R. R. Ingalls, M. A. Arnaout, and D. T. Golenbock, unpublished observations). There are also significant similarities between CD14 and CD11/CD18 that suggest a shared signaling system may exist. First, the extracellular LPS-binding domain of the two receptors appears to be the most important feature of the receptor; the mechanism by which it is anchored to the membrane (i.e., GPI-anchored vs transmembrane) does not appear to be relevant. For example, CD14 functions equally as well when it exists as an integral protein as it does when it is GPI anchored (55). In addition, the cytoplasmic domains of CD11/CD18, while essential for functions such as phagocytosis, are not required for LPS-induced signaling (33).
Second, both CD14 and CD11/CD18 appear to interact not only with LPS, but also with LPS complexed to LBP. While it is agreed that LBP functions to move LPS onto CD14 (5, 12, 22, 56), no role for LBP has ever been established with respect to the CD11/18 integrins. Our data support the observation by Wright et al. that LBP can act as an opsonin for Gram-negative bacteria (11). In addition, we have observed that LBP enhances LPS-induced activation of CD11/CD18-transfected CHO cells by approximately 30-fold. The physiologic relevance of this opsonic function is currently unproved, although one can imagine that this process would not only amplify CD11/18-mediated signaling (resulting in bacterial engulfment, mobilization of anti-bacterial machinery such as toxic radical production), but also increase other aspects of host defenses (e.g., cytokine production) via CD14.
Finally, the species-specific effects of the natural and synthetic lipid A-like compounds appear to be identical in CD14- and CD11/CD18-mediated signaling. Detailed pharmacologic studies with lipid A analogues have provided a framework for understanding how the LPS receptors are coupled to immediate events following LPS binding. Indeed, all proposed models to explain LPS-induced signal transduction must take into account the complex observations made with the LPS-receptor antagonists. The existence of a lipid A recognition molecule, which is capable of discriminating between the lipid A of LPS and the LPS antagonists, has been postulated by many groups (reviewed in Ref. 57). However, the mechanism by which the antagonists would block LPS-induced cellular activation at the level of this postulated lipid A recognition molecule remains unclear. For example, the antagonists could compete directly with LPS for binding to the lipid A recognition molecule. Alternatively, the antagonists could induce a negative signal at the level of the lipid A recognition molecule which rapidly inhibits the ability of LPS to activate cells (15). It is unlikely that these conflicting models will be reconciled until the identification and precise cellular location of this associated effector molecule is determined.
Table I summarizes the work on the
species-specific effects of the lipid A analogues
(23, 24, 25, 26, 27, 28). These data, combined with binding studies
(29), provide additional evidence for the hypothesis that
the biologic target of lipid A partial structure is neither CD14 nor
CD11/CD18, but a second LPS recognition molecule that associates with
CD14- or CD11/CD18-bound LPS. Because CD14 is unable to discriminate
between agonist and antagonist, it seems unlikely that the antagonists
are simply competing with LPS for binding to CD14. Based on our
hypothesis that CD11/CD18 utilizes the same signal transduction pathway
as CD14, we would support the same model for the antagonist’s action
in the CD11/CD18 system. We propose that it is this lipid A recognition
molecule that is activated (or inhibited) by lipid A, RSLA, lipid
IVA, or compound B1287. In our view, the interaction of
lipid A with its signaling receptor is facilitated when ligand is
presented by either CD14 or CD11/CD18. This ligand presentation thus
represents the primary role of these LPS-binding receptors in
endotoxin-induced signaling (Fig. 10).
The ability of B1287 and similar compounds to inhibit a variety of
CD14-dependent ligands, such as LPS, PG, and LAM, implies that
different bacterial products share CD14 and this putative lipid A
recognition molecule as part of their receptor complex
(45).
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Compound B1287 is unique among the previously studied antagonists in its ability to block the activation of human, mouse, and hamster LPS-responsive cells. As such, it will be a useful research tool for the study of LPS responses in a variety of animal systems. In addition, the unique ability of compound B1287 to inhibit the inflammatory effects of LPS in cells from multiple animal species implies that animal studies with this antisepsis agent can produce clinically relevant data. This is in contrast to other potentially useful compounds, such as RSLA, to which human and animal responses are very different. More importantly, however, its ability to block diverse bacterial virulence factors such as LPS, LAM, and PG suggest that this form of therapy may be advantageous in the early treatment of sepsis and other life-threatening infections, where the ability to distinguish clinically between Gram-negative, Gram-positive, and mycobacterial infections is often not possible. The ability of B1287 and similar compounds to inhibit diverse bacterial products also implies that the innate immune system has a relatively limited repertoire of proteins involved in bacterial recognition.
The host immune response to infection is necessary to maintain homeostasis and eradicate an invading microorganism. However, it is clear that in many cases the bystander injury produced by the inflammatory response can be more deleterious to the host than the inciting event. This appears to be the case in the sepsis syndrome. By better understanding the complex interactions of the multiple receptors involved in LPS recognition and the subsequent cellular activation, clinically useful therapies can be developed for the treatment of Gram-negative sepsis and septic shock.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Robin
R. Ingalls, Maxwell Finland Laboratory for Infectious Diseases, Boston
Medical Center, Boston University School of Medicine, 774 Albany
Street, Boston, MA 02118.
3 Current address: Department of Microbiology and
Immunology, Uniformed Services of the Health Sciences, Bethesda, MD
20814.
4 Abbreviations used in this paper: GPI, glycosyl phosphatidylinositol; sCD14, soluble form of CD14; LBP, lipopolysaccharide-binding protein; RSLA, Rhodobacter sphaeroides lipid A; CHO, Chinese hamster ovary; NF-B, nuclear factor-B; PG, peptidoglycan; IC50, 50% inhibitory concentration; EMSA, electrophoretic mobility shift assay; ReLPS, lipopolysaccharide from Salmonella minnesota R595; LAM, lipoarabinomannan.
Received for publication September 9, 1997. Accepted for publication June 25, 1998.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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B induced by LPS does not required tyrosine kinase activity. J. Biol. Chem. 269:22252.
by Mycobacterium tuberculosis components. J. Clin. Invest. 91:2076.
B. Proc. Natl. Acad. Sci. USA 91:2225.This article has been cited by other articles:
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 M. M. Monick, L. Powers, N. Butler, T. Yarovinsky, and G. W. Hunninghake Interaction of matrix with integrin receptors is required for optimal LPS-induced MAP kinase activation Am J Physiol Lung Cell Mol Physiol, August 1, 2002; 283(2): L390 - L402. [Abstract] [Full Text] [PDF]
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 M.M. Monick and G.W. Hunninghake Activation of second messenger pathways in alveolar macrophages by endotoxin Eur. Respir. J., July 1, 2002; 20(1): 210 - 222. [Abstract] [Full Text] [PDF]
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 G. Hajishengallis, M. Martin, H. T. Sojar, A. Sharma, R. E. Schifferle, E. DeNardin, M. W. Russell, and R. J. Genco Dependence of Bacterial Protein Adhesins on Toll-Like Receptors for Proinflammatory Cytokine Induction Clin. Vaccine Immunol., March 1, 2002; 9(2): 403 - 411. [Abstract] [Full Text] [PDF]
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P. Massari, P. Henneke, Y. Ho, E. Latz, D. T. Golenbock, and L. M. Wetzler Cutting Edge: Immune Stimulation by Neisserial Porins Is Toll-Like Receptor 2 and MyD88 Dependent J. Immunol., February 15, 2002; 168(4): 1533 - 1537. [Abstract] [Full Text] [PDF]
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S. H. Diks, S. J.H. van Deventer, and M. P. Peppelenbosch Invited review: Lipopolysaccharide recognition, internalisation, signalling and other cellular effects Innate Immunity, October 1, 2001; 7(5): 335 - 348. [Abstract] [PDF]
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C. Alexander and E. Th. Rietschel Invited review: Bacterial lipopolysaccharides and innate immunity Innate Immunity, June 1, 2001; 7(3): 167 - 202. [Abstract] [PDF]
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R. R. Ingalls, E. Lien, and D. T. Golenbock Membrane-Associated Proteins of a Lipopolysaccharide-Deficient Mutant of Neisseria meningitidis Activate the Inflammatory Response through Toll-Like Receptor 2 Infect. Immun., April 1, 2001; 69(4): 2230 - 2236. [Abstract] [Full Text] [PDF]
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T. H. Flo, L. Ryan, L. Kilaas, G. Skjak-Brak, R. R. Ingalls, A. Sundan, D. T. Golenbock, and T. Espevik Involvement of CD14 and beta 2-Integrins in Activating Cells with Soluble and Particulate Lipopolysaccharides and Mannuronic Acid Polymers Infect. Immun., December 1, 2000; 68(12): 6770 - 6776. [Abstract] [Full Text] [PDF]
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K. J. Moore, L. P. Andersson, R. R. Ingalls, B. G. Monks, R. Li, M. A. Arnaout, D. T. Golenbock, and M. W. Freeman Divergent Response to LPS and Bacteria in CD14-Deficient Murine Macrophages J. Immunol., October 15, 2000; 165(8): 4272 - 4280. [Abstract] [Full Text] [PDF]
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 J. G. Wagner and R. A. Roth Neutrophil Migration Mechanisms, with an Emphasis on the Pulmonary Vasculature Pharmacol. Rev., September 1, 2000; 52(3): 349 - 374. [Abstract] [Full Text] [PDF]
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Y. Mokuno, T. Matsuguchi, M. Takano, H. Nishimura, J. Washizu, T. Ogawa, O. Takeuchi, S. Akira, Y. Nimura, and Y. Yoshikai Expression of Toll-Like Receptor 2 on {gamma}{delta} T Cells Bearing Invariant V{gamma}6/V{delta}1 Induced by Escherichia coli Infection in Mice J. Immunol., July 15, 2000; 165(2): 931 - 940. [Abstract] [Full Text] [PDF]
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T. H. Flo, O. Halaas, E. Lien, L. Ryan, G. Teti, D. T. Golenbock, A. Sundan, and T. Espevik Human Toll-Like Receptor 2 Mediates Monocyte Activation by Listeria monocytogenes, But Not by Group B Streptococci or Lipopolysaccharide J. Immunol., February 15, 2000; 164(4): 2064 - 2069. [Abstract] [Full Text] [PDF]
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 T. Matsuguchi, K. Takagi, T. Musikacharoen, and Y. Yoshikai Gene expressions of lipopolysaccharide receptors, toll-like receptors 2 and 4, are differently regulated in mouse T lymphocytes Blood, February 15, 2000; 95(4): 1378 - 1385. [Abstract] [Full Text] [PDF]
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E. Cario, I. M. Rosenberg, S. L. Brandwein, P. L. Beck, H.-C. Reinecker, and D. K. Podolsky Lipopolysaccharide Activates Distinct Signaling Pathways in Intestinal Epithelial Cell Lines Expressing Toll-Like Receptors J. Immunol., January 15, 2000; 164(2): 966 - 972. [Abstract] [Full Text] [PDF]
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R. R. Ingalls, B. G. Monks, and D. T. Golenbock Surface presentation of LPS is sufficient for initiation of signaling events Innate Immunity, August 1, 1999; 5(4): 244 - 248. [Abstract] [PDF]
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N. Bhat, P.-Y. Perera, J. M. Carboni, J. Blanco, D. T. Golenbock, T. N. Mayadas, and S. N. Vogel Use of a Photoactivatable Taxol Analogue to Identify Unique Cellular Targets in Murine Macrophages: Identification of Murine CD18 as a Major Taxol-Binding Protein and a Role for Mac-1 in Taxol-Induced Gene Expression J. Immunol., June 15, 1999; 162(12): 7335 - 7342. [Abstract] [Full Text] [PDF]
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 R. R. Ingalls, B. G. Monks, and D. T. Golenbock Membrane Expression of Soluble Endotoxin-binding Proteins Permits Lipopolysaccharide Signaling in Chinese Hamster Ovary Fibroblasts Independently of CD14 J. Biol. Chem., May 14, 1999; 274(20): 13993 - 13998. [Abstract] [Full Text] [PDF]
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E. Lien, J. C. Chow, L. D. Hawkins, P. D. McGuinness, K. Miyake, T. Espevik, F. Gusovsky, and D. T. Golenbock A Novel Synthetic Acyclic Lipid A-like Agonist Activates Cells via the Lipopolysaccharide/Toll-like Receptor 4 Signaling Pathway J. Biol. Chem., January 12, 2001; 276(3): 1873 - 1880. [Abstract] [Full Text] [PDF]
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