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B Activation and Augmentation of IBß by Secretory Leukocyte Protease Inhibitor during Lung Inflammation
From the Department of Surgery,*
University of
Louisville School of Medicine, Louisville, Kentucky; the Departments of
Pathology and
Surgery,
University of Michigan Medical
School, Ann Arbor, Michigan; and the Department of Trauma
Surgery,§
University of Freiburg,
Freiburg/Breisgau, Germany
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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B (NF-B) in lung cells but
did not suppress activation of lung mitogen-activated protein kinase.
SLPI did not alter NF-B activation in alveolar macrophages harvested
30 minutes after initiation of lung inflammation. In the presence of
SLPI, content of tumor necrosis factor-
, CXC
chemokines, and C5a in bronchoalveolar fluids was unaffected.
In the inflamed lungs, inhibition of NF-B activation by SLPI
was associated with elevated levels of lung IBß (but not IB)
protein in the absence of elevated mRNA for IBß. When instilled
into normal lung, SLPI also caused similar changes (increases)
in lung IBß. Finally, in the lung inflammatory model
used, the presence of anti-SLPI caused accentuated activation
of NF-B. These data confirm the anti-inflammatory effect of SLPI in
lung and point to a mechanism of anti-inflammatory effects of SLPI.
SLPI appears to function as an endogenous regulator of lung
inflammation.
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Acute lung injury induced by intrapulmonary deposition of IgG immune
complexes in rats exhibits a pathophysiology similar to that observed
during sepsis, ischemia/reperfusion, or trauma.12-15
In
this model, enhanced production of tumor necrosis factor- (TNF-)
and interleukin-1ß (IL-1ß) by activated lung macrophages causes
up-regulation of the adhesion molecules, intercellular adhesion
molecule-1 (ICAM-1), and E-selectin on the pulmonary
endothelium.16,17
Interactions of these vascular adhesion
molecules with their respective ligands on blood neutrophils cause
leukocyte adhesion to the endothelium and recruitment of neutrophils
into the alveolar compartment. The ensuing lung injury is mediated by
oxidants and proteases released by neutrophils and lung macrophages and
is characterized by increased vascular permeability and alveolar
hemorrhage.18,19
During this inflammatory
response, activation of the transcription factor, nuclear factor-B
(NF-B), occurs in a time course similar to that for the production
of TNF-, IL-1ß, and the expression of adhesion molecules in the
pulmonary vasculature.20
Administration of SLPI attenuates pulmonary recruitment of neutrophils
and decreases lung injury induced by intrapulmonary deposition of IgG
immune complexes.21
Blockade of endogenous SLPI
results in an augmented inflammatory response with increased
recruitment of neutrophils and lung injury (Gipson TS, Bless NM, Crouch
LD, Shanley TP, Bleavins MR, Tefera W, McConnell PC, Mueller WT,
Johnson KJ, Ward PA: Role of endogenous protease inhibitors in
regulation of acute lung inflammatory injury. Submitted). However, the
exact mechanisms by which SLPI exerts its anti-inflammatory effects in
lung are unclear. Although SLPI inhibits serine proteases released by
activated phagocytes, more recent studies have shown that SLPI
interferes with the signal transduction pathway involved in the
generation of matrix metalloproteinases.22
In the
current studies, we sought to determine whether the protective effects
of SLPI during lung inflammation might be caused by effects on other
signal transduction mechanisms including NF-B and mitogen-activated
protein kinase (MAPK).
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Materials and Methods |
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Recombinant human SLPI and tissue inhibitor of metalloproteinases-2 (TIMP-2) were kindly provided by Dr. Thomas R. Ulich, (Amgen Inc., Thousand Oaks, CA). Rabbit polyclonal antibody to rat SLPI was prepared as described elsewhere.1 New Zealand White rabbits were immunized with rat SLPI in incomplete Freund's adjuvant. Immune serum (10-6 titer) was affinity purified, and the IgG administered intratracheally at a dose of 300 µg.
IgG Immune Complex-Induced Alveolitis
Pathogen-free male Long-Evans rats (275 to 300 g; Harlan
Sprague-Dawley, Indianapolis, IN) were anesthetized with Ketamine HCl
(150 mg/kg, intraperitoneally). A total of 1.5 mg of rabbit polyclonal
IgG anti-bovine serum albumin (BSA) (ICN Biomedicals, Inc., Costa Mesa,
CA) in a volume of 0.3 ml of phosphate-buffered saline (PBS) was
instilled via an intratracheal catheter during inspiration. Immediately
thereafter, 10 mg of BSA in 0.5 ml of PBS were injected intravenously.
Negative control rats received PBS intratracheally. For analysis of
pulmonary vascular permeability, trace amounts of
125I-labeled BSA were injected intravenously.
Four hours after IgG immune complex deposition, rats were
exsanguinated, the pulmonary circulation was flushed with 10 ml of PBS
by pulmonary artery injection and the lungs were surgically dissected.
The extent of lung injury was quantified by calculating the lung
permeability index (dividing the amount of radioactivity
(125I-labeled BSA) in the perfused lungs by the
amount of radioactivity in 1.0 ml of blood obtained at the time of
death). For analysis of NF-B and MAPK activation, lungs were
immediately frozen in liquid nitrogen after vascular perfusion with
PBS.
NF-B Activation
Nuclear extracts of whole lung tissues and alveolar macrophages
were prepared as previously described20
and
analyzed by electrophoretic mobility shift assay (EMSA). Briefly,
double-stranded NF-B consensus oligonucleotide
(5'-GTGAGGGGACTTTCCCAGGC-3'; Promega, Madison, WI) was end-labeled with
[32P]ATP (3000 Ci/mmol at 10 mCi/ml,
Amersham, Arlington Heights, IL). Binding reactions containing equal
amounts of nuclear protein extract (10 µg) and 35 fmols (~50,000
cpm, Cherenkov counting) of oligonucleotide were performed for 30
minutes in binding buffer (4% glycerol, 1 mmol/L
MgCl2, 0.5 mmol/L EDTA, pH 8.0, 0.5 mmol/L
dithiothreitol, 50 mmol/L NaCl, 10 mmol/L Tris, pH 7.6, 50 µg/ml
poly(dI-dC); Pharmacia, Piscataway, NJ). Reaction volumes were held
constant to 15 µl. Reaction products were separated in a 4%
polyacrylamide gel in 0.25 x TBE buffer (25 mmol/L
Tris, 22.5 mmol/L boric acid, 0.25 mmol/L EDTA) and analyzed by
autoradiography. NF-B activation was quantitated from digitized
autoradiography films using image analysis software (Adobe Systems, San
Jose, CA).
MAPK Activation and Western Blot Analysis
Whole lung tissue or alveolar macrophages obtained by BAL
(bronchoalveolar lavage) were homogenized in lysis buffer (10 mmol/L
HEPES, pH 7.9, 150 mmol/L NaCl, 1 mmol/L EDTA, 0.6% Nonidet P-40, 0.5
mmol/L phenylmethylsulfonyl fluoride, 1 µg/ml leupeptin, 1
µg/ml aprotinin, 10 µg/ml soybean trypsin inhibitor, 1
µg/ml pepstatin) on ice. Homogenates were sonicated and centrifuged
at 14,000 rpm to remove cellular debris. Interfering IgG anti-BSA in
homogenates was removed with GammaBind G sepharose (Pharmacia). Protein
concentrations were determined as described for nuclear extracts.
Samples (10 µg for MAPK analysis, 100 µg for IB proteins) were
separated in a denaturing 12.5% polyacrylamide gel and transferred to
a nitrocellulose membrane. Nonspecific binding sites were blocked with
Tris-buffered saline containing Tween 20 (40 mmol/L Tris, pH 7.6, 300
mmol/L NaCl, 0.1% Tween 20) containing 5% nonfat dry milk for 12
hours at 4°C. For analysis of MAPK proteins, membranes were incubated
in a 1:1000 dilution of rabbit polyclonal anti-phospho p42/p44 or
anti-nonphosphorlyated p42/p44 (New England Biolabs, Inc., Beverly,
MA). For analysis of IB proteins, membranes were incubated in a
1:1000 dilution of rabbit polyclonal anti-IB or anti-IBß
(Santa Cruz Biotechnology, Santa Cruz, CA) in TBST. After three
washes in TBST, membranes were incubated in a 1:50,000 dilution
of horseradish peroxidase-conjugated donkey anti-rabbit IgG (Amersham
Corp., Arlington Heights, IL). Immunoreactive proteins were detected by
enhanced chemiluminescence.
Northern Blot Analysis
Total RNA from whole lung tissue was extracted using a
guanidinium-isothiocyanate method as described
previously.23
Samples (20 µg of RNA) were
fractionated electrophoretically in a 1% formaldehyde gel and
transferred to a nylon membrane (MSI, Westboro, MA). cDNA for rat
IBß was generated by reverse transcriptase-polymerase chain
reaction using the following oligonucleotide primers based on the
murine sequence:24
5' primer:
5'-CATGTAGCTGTCATCCACA-3' and 3' primer: 5'-TGTGCACGGAGGAGGCG-3'. The
polymerase chain reaction product was sequenced for verification, and
the rat IBß cDNA probe was end labeled with
[32P]dCTP (NEN-DuPont, Boston, MA) using Random
Prime (Amersham Corp.). Northern blots were hybridized with the cDNA
probe in QuikHyb® hybridization solution
(Stratagene Cloning Systems, La Jolla, CA) at 68°C for 4 hours and an
autoradiogram developed on Kodak BioMax-MR film (Rochester, NY). Equal
loading of RNA samples was confirmed by probing Northern blots with
cDNA to ß-actin (Stratagene Cloning Systems) end-labeled with
[32P]dCTP.
BAL Fluid Analyses
BAL fluids were collected by instilling and withdrawing 5 ml of
sterile PBS three times from the lungs via an intratracheal cannula.
BAL content of TNF- was measured using a standard WEHI cell
cytotoxicity assay as previously reported.25
Measurement of macrophage inflammatory protein-2 (MIP-2),
cytokine-induced neutrophil chemoattractant (CINC), and C5a in BAL
fluids were by enzyme-linked immunosorbent assay as described
elsewhere.26,27
Lung Vascular Expression of ICAM-1
Rats were injected intravenously with 1.5 µCi of 125I-labeled anti-ICAM-1 (clone 1A29; PharMingen, Inc. San Diego, CA) 3.75 hours after induction of lung injury. The specific activity of the anti-ICAM-1 was 11.3 µCi/µg. Fifteen minutes later (4 hours after induction of lung injury), rats were sacrificed, and the lung vasculature was flushed with 10 ml of PBS. Lung vascular ICAM-1 expression (binding index) was calculated by dividing the amount of radioactivity (125I-labeled antibody) in lungs by the amount of radioactivity in 1.0 ml of blood. To control for nonspecific binding and potential accumulation of anti-ICAM-1 antibody in lung parenchyma caused by injury, 1.5 µCi of 125I-labeled nonspecific isotype-matched mouse IgG (clone MOPC-21, ICN Biomedicals, Inc.) were administered in a separate set of rats. The specific activity of the irrelevant IgG antibody was 13.0 µCi/µg.
Lung Myeloperoxidase (MPO) Content
Whole lung MPO activity was quantitated as described previously.28 Briefly, whole lungs homogenates were diluted in 50 mmol/L potassium phosphate buffer containing 0.5% hexadecyltrimethylammonium bromide, pH 6.0. After sonication and two freeze-thaw cycles, samples were centrifuged at 4000 x g for 30 minutes. The supernatants were reacted with H2O2 (0.3 mmol/L) in the presence of tetramethylbenzidine (1.6 mmol/L). MPO activity was assessed by measuring the change in absorbance at 655 nm.
Statistical Analyses
All values are expressed as mean ± SEM. Data were analyzed with a one-way analysis of variance and individual group means were then compared with a Student-Newman-Keuls test. Differences were considered significant when P < 0.05. For calculations of percent change, negative control values were subtracted from positive control and treatment group values.
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Results |
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Previous studies demonstrated that when administered
intratracheally, 1 mg of SLPI suppressed IgG immune complex-induced
lung injury.21
To determine the lowest effective
dose of intratracheally administered SLPI, dose response experiments
were performed with the endpoint of extravascular leakage of
125I-albumin. As shown in Figure 1
, neither 5 nor 25 µg of SLPI (given
intratracheally along with the anti-BSA) caused any significant
reduction in IgG immune complex-induced lung vascular permeability.
However, 100 µg of SLPI reduced lung vascular permeability by 45%
(P = 0.006). TIMP-2 had similar effects,
reducing albumin leak by 40% (Figure 1)
. The effects of 100 µg SLPI
on IgG immune complex-induced increases in proinflammatory mediators in
BAL fluids were assessed. As anticipated, intrapulmonary deposition of
IgG immune complexes caused significant increases in BAL content of
TNF-, MIP-2, CINC, and C5a (Table 1)
.
Co-treatment with 100 µg of SLPI did not significantly alter BAL
levels of any of these proinflammatory mediators.
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. The increase in binding index for the
anti-ICAM-1 antibody could not be attributed to nonspecific binding or
sequestration from lung injury as the binding index for the irrelevant
IgG control antibody was only 0.091 ± 0.011 in inflamed lungs
(versus 0.065 ± 0.015 in noninflamed lungs). In
the presence of 100 µg of SLPI, there was a 67% reduction
(P = 0.041) in ICAM-1 expression in the
pulmonary vasculature. Because SLPI caused a substantial decrease in
lung vascular ICAM-1 expression, we examined whether this effect was
associated with decreased lung recruitment of neutrophils. Pulmonary
accumulation of neutrophils was quantitated by lung content of MPO. As
expected, intrapulmonary deposition of IgG immune complexes caused a
greater than sevenfold increase in lung MPO content (Figure 3)
. Co-treatment with SLPI reduced IgG
immune complex-induced lung MPO content by 39%
(P < 0.001).
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B and MAPK
To investigate whether the protective effects of SLPI might be
related to inhibition of pulmonary NF-B activation (defined as
nuclear translocation), nuclear extracts from whole lungs harvested 4
hours after IgG immune complex deposition were analyzed by EMSA. As
expected, little NF-B was present in lung nuclei from rats treated
intratracheally with PBS (Figure 4)
.
Treatment with IgG immune complexes resulted in a significant increase
in nuclear translocation of NF-B. In the presence of 100 µg of
SLPI, NF-B activation was greatly reduced. Image analysis of
digitized EMSA blots demonstrated that the presence of SLPI reduced
nuclear localization of lung NF-B by 64% (P
= 0.005). Interestingly, 100 µg of TIMP-2 had no effect on lung
NF-B activation.
|
. Four hours after intrapulmonary
deposition of IgG immune complexes, phosphorylation (a measure of
activation) of MAPK was evident. No phosphorylation of p42 or p44 was
found in extracts from lungs instilled with PBS, in striking contrast
to phosphorylation of p42 and p44 in inflamed lungs (Figure 5
, upper
frame). Phosphorylation was primarily associated with the p44 form of
MAPK (slower migrating band) as contrasted to the p42 form. It also
seems likely that in this model of inflammation there is induction of
p44 because the Western blot bands were more intense in lungs receiving
IgG immune complexes (Figure 5
, lower frame, second lane
versus third and fourth lanes). Quite clearly, co-treatment
with SLPI did not seem to interfere with MAPK activation in lung.
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B activation in alveolar
macrophages in vivo is increased as early as 30 minutes
after deposition of IgG immune complexes.29
Furthermore, in a macrophage cell line transgenically over-expressing
SLPI, LPS-induced NF-B activation was
attenuated.5
Therefore, we assessed whether 100
µg of SLPI administered intratracheally reduced NF-B activation in
alveolar macrophages following intrapulmonary deposition of IgG immune
complexes. Treatment with SLPI had no effect on NF-B activation in
alveolar macrophages retrieved by BAL 30 minutes after initiation of
IgG immune complex deposition (Figure 6)
.
Similarly, NF-B activation in alveolar macrophages stimulated
in vitro with 100 µg/ml IgG-BSA immune complexes or LPS
(50 ng/ml) was unaffected by co-treatment with 10 µg/ml SLPI (data
not shown). Intrapulmonary instillation of SLPI failed to inhibit MAPK
activation in alveolar macrophages retrieved by BAL 30 minutes after
IgG immune complex deposition (data not shown). Thus, it would appear
that the effects of SLPI in lung are not directed toward alveolar
macrophages.
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B Activation
Because treatment with SLPI almost completely ameliorated IgG
immune complex-induced NF-B activation in whole lung tissues, we
investigated whether endogenous SLPI regulated activation of lung
NF-B. For these experiments, a reduced intratracheal dose of
anti-BSA (250 µg) was used to produce minimal activation of NF-B.
Endogenous SLPI was blocked by intratracheal administration of 300 µg
of anti-rat SLPI together with the anti-BSA. This dose of anti-SLPI was
shown to effectively neutralize endogenous SLPI in this model of lung
inflammation.1
Positive controls received 300
µg of preimmune rabbit IgG. Four hours after intrapulmonary
deposition of IgG immune complexes there was a detectable increase in
lung NF-B activation (Figure 7)
. In
the presence of anti-SLPI there was significantly increased NF-B
activation in lung. Image analysis of digitized EMSA blots
dem- onstrated that anti-SLPI increased nuclear localization of
lung NF-B by 141% (P = 0.006). Blockade of
endogenous SLPI had no effect on lung MAPK activation (data not shown).
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B and IBß
As SLPI inhibited NF-B activation in whole lungs (Figure 4)
, we
designed experiments to determine whether the inhibitory effects of
SLPI during lung inflammation might be related to effects on the
cytoplasmic NF-B regulatory proteins, IB and IBß. Western
blot analysis of whole lung homogenates obtained 4 hours after
initiation of lung injury confirmed decreases in the amounts of
detectable IB protein after intrapulmonary deposition of IgG
immune complexes as compared with intrapulmonary instillation of PBS
(Figure 8A
, upper panel). Neither
co-treatment with SLPI nor TIMP-2 had any measurable effect on
decreases in IB protein in the inflamed lung. In striking
contrast, IgG immune complex deposition appeared to cause an increase
in the amount of detectable IBß protein compared with treatment
with PBS (Figure 8A
, lower panel). Image analysis of digitized Western
blots is shown in Figure 8B
. Western blots of samples from lungs
treated with IgG immune complexes showed a second, faint, and more
rapidly migrating IBß band. Other studies have identified this
band to be a dephosphorylated form of IBß, which is an
intermediate during IBß degradation.30
Co-treatment with SLPI resulted in a marked increase in the slower
migrating, presumably hyperphosphorylated, form of IBß when
compared with treatment with IgG immune complexes. Co-treatment with
TIMP-2 had no effect on IgG immune complex-induced changes in IBß
protein (Figure 8A
, lower panel).
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Bß and/or suppressing IBß degradation, rats received lung
instillation of PBS, SLPI, or TIMP-2 (each at 100 µg) in the absence
of IgG immune complexes. Neither SLPI nor TIMP-2 had any detectable
effect on IB protein expression compared with treatment with PBS
(Figure 9
, upper panel). However,
treatment with SLPI, but not with TIMP-2, resulted in a marked increase
in IBß protein expression compared with treatment with PBS (Figure 9
, lower panel). In these experiments only the slower migrating
IBß band was observed, suggesting that under these conditions
degraded IBß could not be detected.
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Bß protein
expression were related to enhanced IBß gene activation, Northern
blot analysis of IBß mRNA in whole lung extracts was performed.
Lung extracts from rats undergoing 4 hours of injury were analyzed. As
shown in Figure 10
, intrapulmonary
deposition of IgG immune complexes caused a marked increase in IBß
mRNA expression compared with PBS controls. Co-treatment with SLPI
failed to provide any clear evidence for IgG immune complex-induced
increases in IBß mRNA expression. Finally, lung instillation of
SLPI in otherwise unmanipulated rats did not induce expression of mRNA
for IBß (Figure 10)
.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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B (but not MAPK) during
lung inflammatory injury and that the inhibitory effects on NF-B
seem linked to preserved expression of IBß but not IB.
The administration of exogenous SLPI at the onset of IgG immune
complex-induced lung injury caused a dramatic reduction in the nuclear
translocation (activation) of NF-B in lung tissues. In parallel,
blockade of endogenous SLPI using polyclonal antibody resulted in
significant enhancement of NF-B activation. The activation of
NF-B is regulated by cytoplasmic proteins of the IB family. Two
of these proteins, IB and IBß, are known to be largely
responsible for the control of NF-B
activation.24,31
We found that exogenously
administered SLPI had no measurable effect on IB protein
expression in lung but clearly caused increased levels of IBß
protein (as determined by Western blot technique) in otherwise normal
lungs and in lungs undergoing IgG immune complex-induced inflammation.
SLPI had no measurable effects on IBß mRNA expression, suggesting
that SLPI may operate by preventing degradation of IBß protein.
The inhibitory effects of SLPI on lung NF-B activation was not a
generalized effect of protease inhibitors. Treatment with TIMP-2, a
potent inhibitor of matrix metalloproteinases, had no effect on NF-B
activation induced by intrapulmonary deposition of IgG immune
complexes, even though it is known that TIMP-2 is protective in this
model of lung injury.21
Furthermore, in contrast
to SLPI, lung instillation of TIMP-2 into otherwise normal lungs had no
effect on the protein expression of either IB or IBß. These
data suggest that the inhibitory effects of SLPI are selective for the
signal transduction pathway leading to NF-B activation. IgG immune
complex-induced activation of MAPK in alveolar macrophages and lung
tissues was not reduced in the presence of SLPI.
Endogenous SLPI has been shown to regulate the lung inflammatory
response. Studies of the IgG immune complex model of lung injury have
demonstrated that blockade of endogenous SLPI with neutralizing
antibody causes enhanced pulmonary accumulation of neutrophils and
increased lung vascular permeability.1
The data
presented here suggest that the deleterious effects of SLPI blockade
are associated with greatly enhanced (by 141%) intrapulmonary
activation of NF-B. Interestingly, these effects cannot be
attributed to augmented production of TNF- as SLPI blockade does not
result in increased BAL levels of TNF-.1
The
lack of an effect of SLPI blockade on lung TNF- is consistent with
the current data demonstrating an inability of exogenous SLPI to reduce
BAL levels of TNF-. Thus, it appears that endogenous SLPI regulates
lung inflammatory reactions, at least in part, through effects on lung
NF-B. However, alveolar macrophages, which are the primary source of
lung TNF-, seem not to be a target of the suppressive effects of
SLPI. Rather, vascular endothelial cells seem to be the target for
SLPI-induced inhibition of NF-B activation. This would be consistent
with the findings that SLPI does not interfere with levels of TNF-
but nevertheless reduces up-regulation of lung vascular ICAM-1.
Alveolar macrophage activation is an initial event in the genesis of
lung inflammatory reactions. In lung inflammation induced by
intrapulmonary deposition of IgG immune complexes, we have shown that
early activation (within 30 minutes) of alveolar macrophages occurs in
an NF-B-dependent manner.29
Furthermore,
NF-B activation in alveolar macrophages in vivo occurs
prior to NF-B activation in whole lung tissues, suggesting that
products of activated alveolar macrophages are required to stimulate
nuclear translocation of NF-B in other lung cell types. Indeed,
TNF- and IL-1ß, which are required for the full induction of lung
injury in this model,32,33
seem to operate as
autocrine/paracrine stimulators of alveolar
macrophages.20
Administration of the
anti-inflammatory cytokines IL-10 or IL-13 greatly suppresses NF-B
activation in alveolar macrophages in association with preserved levels
of IB and decreased lung production of
TNF-.29,34
In the current studies,
administration of SLPI neither suppressed IgG immune complex-induced
increases in alveolar macrophage NF-B activation nor reduced BAL
levels of TNF-, MIP-2, CINC, or C5a. These data suggest that SLPI
does not affect the activation of alveolar macrophages but inhibits the
subsequent activation of NF-B in nonmacrophage lung cells and
reduces the development of lung injury.
Our data suggest that one such candidate for the effects of SLPI may be
the pulmonary vascular endothelial cell. SLPI greatly reduced IgG
immune complex-induced expression of ICAM-1 in the lung vasculature.
Although the expression of lung vascular ICAM-1 is known to be
regulated primarily by TNF-,16
treatment with
SLPI in this lung inflammation model did not reduce levels of TNF-
in BAL fluids. One possible explanation for this phenomenon is that
SLPI directly reduces ICAM-1 expression through suppression of
endothelial NF-B activation. It is known that NF-B regulates the
transcriptional activation of genes for ICAM-1 and other vascular
adhesion molecules.35
Treatment with SLPI also
reduced IgG immune complex-induced lung neutrophil accumulation.
Because SLPI did not reduce BAL levels of the CXC chemokines
MIP-2 or CINC, it would appear that SLPI reduced pulmonary neutrophil
recruitment by decreasing lung vascular ICAM-1 expression, thus
interfering with adhesion events required for recruitment of
neutrophils.
This study identifies a novel function for SLPI, namely suppression of
NF-B activation during lung inflammation. The data suggest that SLPI
suppresses NF-B in cell types other than lung macrophages, as these
effects are associated with augmented protein expression of IBß.
As indicated above, it seems possible that SLPI directly blocks
endothelial cell activation of NF-B, preventing full expression of
ICAM-1. Although it is not known if receptors for SLPI exist on
endothelial cells, high affinity binding to monocytes has been
reported.36
These studies also indicate that
endogenous SLPI may regulate the extent of the lung inflammatory
response by suppressing pulmonary NF-B activation.
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Footnotes |
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Supported in part by the National Institutes of Health Grants GM-29587 and HL-31963 (P. A. Ward) and a grant from the American Lung Association (V. Sarma).
Accepted for publication September 24, 1998.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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regulates in vivo intrapulmonary expression of ICAM-1. Am J Pathol 1993, 142:1739-1749[Abstract]
B activation during IgG immune complex-induced lung injury: requirements for TNF- and IL-1ß but not complement. Am J Pathol 1998, 152:1327-1336[Abstract]
by interleukin-10, and interleukin-13. J Clin Invest 1997, 100:2443-2448[Medline]
Bß degradation: similarities to and differences from IB. J Biol Chem 1997, 272:9942-9949This article has been cited by other articles:
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J. Lee, Y.-S. Kim, D.-H. Choi, M. S. Bang, T. R. Han, T. H. Joh, and S.-Y. Kim Transglutaminase 2 Induces Nuclear Factor-{kappa}B Activation via a Novel Pathway in BV-2 Microglia J. Biol. Chem., December 17, 2004; 279(51): 53725 - 53735. [Abstract] [Full Text] [PDF]
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 K. Heckel, R. Kiefmann, M. Dorger, M. Stoeckelhuber, and A. E. Goetz Colloidal gold particles as a new in vivo marker of early acute lung injury Am J Physiol Lung Cell Mol Physiol, October 1, 2004; 287(4): L867 - L878. [Abstract] [Full Text] [PDF]
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 C. M. Greene, N. G. McElvaney, S. J. O'Neill, and C. C. Taggart Secretory Leucoprotease Inhibitor Impairs Toll-Like Receptor 2- and 4-Mediated Responses in Monocytic Cells Infect. Immun., June 1, 2004; 72(6): 3684 - 3687. [Abstract] [Full Text] [PDF]
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P. A. Henriksen, M. Hitt, Z. Xing, J. Wang, C. Haslett, R. A. Riemersma, D. J. Webb, Y. V. Kotelevtsev, and J.-M. Sallenave Adenoviral Gene Delivery of Elafin and Secretory Leukocyte Protease Inhibitor Attenuates NF-{kappa}B-Dependent Inflammatory Responses of Human Endothelial Cells and Macrophages to Atherogenic Stimuli J. Immunol., April 1, 2004; 172(7): 4535 - 4544. [Abstract] [Full Text] [PDF]
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J. C. Parker and M. I. Townsley Evaluation of lung injury in rats and mice Am J Physiol Lung Cell Mol Physiol, February 1, 2004; 286(2): L231 - L246. [Abstract] [Full Text] [PDF]
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C. Odaka, T. Mizuochi, J. Yang, and A. Ding Murine Macrophages Produce Secretory Leukocyte Protease Inhibitor During Clearance of Apoptotic Cells: Implications for Resolution of the Inflammatory Response J. Immunol., August 1, 2003; 171(3): 1507 - 1514. [Abstract] [Full Text] [PDF]
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 A. Churg, R. D. Wang, C. Xie, and J. L. Wright {alpha}-1-Antitrypsin Ameliorates Cigarette Smoke-induced Emphysema in the Mouse Am. J. Respir. Crit. Care Med., July 15, 2003; 168(2): 199 - 207. [Abstract] [Full Text] [PDF]
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