Role of inducible nitric oxide synthase in the regulation of
VCAM-1 expression in gut inflammation
Shigeyuki
Kawachi1,
Adam
Cockrell1,
F. Stephen
Laroux1,
Laura
Gray1,
D. Neil
Granger1,
Henri C.
van der
Heyde2, and
Matthew B.
Grisham1
Departments of 1 Molecular and
Cellular Physiology and
2 Microbiology and Immunology,
Louisiana State University Medical Center, Shreveport, Louisiana 71130
 |
ABSTRACT |
The objectives of this study
were to assess the role of the inducible isoform of nitric oxide
synthase (iNOS) on vascular cell adhesion molecule 1 (VCAM-1)
expression in vivo in an acute model of inflammation induced in
iNOS-deficient
(iNOS
/
) mice and
compare these data to those obtained by pharmacological inhibition of
iNOS in a CD4+ T
lymphocyte-dependent model of chronic colitis. VCAM-1 expression was
quantified in vivo using the dual radiolabel monoclonal antibody technique. We found that intraperitoneal injection of 10 µg/kg tumor
necrosis factor-
(TNF-
) enhanced VCAM-1 expression by approximately twofold in the colon, cecum, and stomach but not small
intestine in iNOS
/
mice compared with TNF-
-injected wild-type mice. Injection of wild-type mice with 25 µg/kg TNF-
further enhanced VCAM-1
expression by approximately twofold compared with wild-type mice
injected with 10 µg/kg TNF-
; however, VCAM-1 expression was not
further enhanced in any gastrointestinal organ system in
iNOS
/
mice. In a
second series of experiments, we found that continuous inhibition of
iNOS using oral administration of
NG-iminoethyl-L-lysine
did not alter the enhanced levels of VCAM-1 expression in the colon nor
did it alter the severity of colonic inflammation in SCID mice
reconstituted with CD4+,
CD45RBhigh T cells. We conclude
that iNOS may regulate VCAM-1 expression in acute inflammation;
however, this effect is modest and tissue specific and occurs only when
VCAM-1 expression is submaximal. iNOS does not appear to modulate
VCAM-1 expression in an immune model of chronic colitis.
neutrophils; nuclear factor-
B; endothelium
 |
INTRODUCTION |
THE INFILTRATION OF leukocytes into inflamed tissues
results from the adhesive interactions between leukocytes and
endothelial cells within the postcapillary venules (6, 7). These
adhesive interactions are regulated in an orderly fashion by sequential activation of different families of membrane adherence receptors on
leukocytes and endothelial cells. One such endothelial cell adhesion
molecule (ECAM) is vascular cell adhesion molecule 1 (VCAM-1). This
member of the immunoglobulin supergene family is a redox-sensitive ECAM
whose expression is enhanced by a variety of different bacterial
products, cytokines, and oxidants (2, 18). It is thought that VCAM-1
plays an important role in adhesion and recruitment of mononuclear
leukocytes (e.g., monocytes, lymphocytes) during times of chronic
inflammation (2, 18). Several recent studies suggest that exogenous
nitric oxide (NO) donors may downregulate cytokine-induced VCAM-1
expression in cultured endothelial cells in vitro (8, 14, 20, 21,
24-27). The mechanisms by which exogenous NO exerts this
anti-inflammatory effect have not been fully delineated; however, it is
thought that NO inhibits the activation of nuclear factor-
B
(NF-
B) by enhancing expression and/or stabilization of its inhibitor
I
B and/or by inhibiting the binding of the p50/p65 heterodimer to
its consensus sequence in the promoter/enhancer region upstream of
VCAM-1 (8, 20, 21, 24, 25, 27). Because chronic gut inflammation is
associated with the upregulation of the inducible isoform of nitric
oxide synthase (iNOS) and the sustained overproduction of NO as well as
enhanced infiltration of mononuclear leukocytes (3, 9), we wished to
assess the effects of iNOS inhibition on VCAM-1 expression in vivo in
an acute model of inflammation induced in iNOS-deficient mice
(iNOS
/
) and
compare these data to those obtained in an immune-based model of
chronic colitis.
 |
MATERIALS AND METHODS |
Animals.
Male C57BL/6 mice (n = 25) and
iNOS
/
mice
(n = 13) weighing 20-30
g were obtained from Harlan Sprague Dawley (Frederick, MD) and Jackson
Laboratory (Bar Harbor, ME), respectively. Functionally inactive iNOS
was produced by disruption of the iNOS gene by insertion of the
neomycin gene into the calmodulin domain of the iNOS gene (16) and
confirmed using a mouse model of lipopolysaccharide (LPS)-induced
upregulation of iNOS-derived NO (10). Female C.B-17 and congenic C.B-17
(scid/scid)
mice between 5 and 7 wk of age were obtained from Taconic Farms
(Germantown, NY) and used for the colitis studies described in
T cell-mediated chronic
inflammation.
Tumor necrosis factor-
induced acute inflammation.
An acute animal model of inflammation was produced by intraperitoneal
injection of recombinant murine tumor necrosis factor-
(TNF-
; 10 µg/kg and 25 µg/kg) (R&D Systems, Minneapolis, MN) as previously
described (12). This model induces an acute inflammatory response in
mice characterized by increased ECAM expression in different organ
systems, including stomach, small intestine, cecum, and colon 5 h after
TNF-
administration (12). VCAM-1 expression was quantified in the
different tissues using the dual radiolabeled monoclonal antibody
method of Komatsu et al. (15).
iNOS message was assessed in colons using RT-PCR in which total RNA was
isolated, and cDNA was synthesized using reverse transcriptase and then
amplified using the following primers: sense primer, 5'-AGAGTTTGACCAGAGGACCC-3'; antisense primer,
5'-AAGACCAGAGGCAGCACATC-3'. The 559-bp products were
resolved on a 1.5% agarose gel stained with ethidium bromide. The gel
was viewed and analyzed using an Alpha Innotech gel documentation
system (San Leandro, CA).
T cell-mediated chronic inflammation.
A chronic model of colonic inflammation was produced by transfer of
CD4+,
CD45RBhigh T lymphocytes isolated
from the spleens of healthy donor mice into immunodeficient SCID mice
(5, 17). This procedure induces a chronic colitis 8 wk following
reconstitution with this lymphocyte subset, whereas injection of SCID
mice with PBS or CD4+,
CD45RBlow T cells does not produce
disease (5, 17). This model of colitis is characterized by colonic
mucosal thickening, epithelial cell hyperplasia, erosions, and crypt
abscesses as well as enhanced iNOS and VCAM-1 expression (5, 17).
Male C.B-17 SCID mice at the age of 5-7 wk were injected
(intraperitoneally) with either PBS or
CD4+ 5 × 105
CD45RBlow or
CD45RBhigh T cells suspended in
500 µl of PBS. Body weights and fecal status were followed and
recorded weekly from the time of the injection. At 4-6 wk
following reconstitution with
CD45RBhigh T cells, mice began to
lose body weight and developed loose stools. At 8 wk following
reconstitution, when animals lost ~10% of their initial body weight,
ECAM quantification was performed in these animals as well as in SCID
mice injected with PBS or
CD45RBlow T cells, which did not
develop signs of clinical disease.
The role of iNOS in regulating VCAM-1 expression was assessed in this
model of chronic gut inflammation using the selective iNOS inhibitor
NG-iminoethyl-L-lysine
(L-NIL) at a dose of 25 mg · kg
1 · day
1
po beginning on week 4 when
inflammation is minimal or absent and continuing until
week 8 when colitis is maximal.
Preliminary studies demonstrated that this dose of oral
L-NIL inhibits LPS-induced production of NO-derived nitrate and nitrite by ~80% (326 ± 3 vs. 91 ± 37 µM for vehicle and
L-NIL-treated mice injected with LPS, respectively). After 4 wk of
L-NIL treatment, animals were anesthetized and colonic VCAM-1 expression was quantified as described above. Macroscopic inflammation was scored as described previously (4).
 |
RESULTS |
We found that a single intraperitoneal injection of 10 µg/kg TNF-
significantly enhanced VCAM-1 expression in the vasculature of the
colon only; however, trends for increased expression of VCAM-1 were
observed in the cecum, small intestine, and stomach in wild-type mice
compared with their saline-injected controls (Fig.
1). This TNF-
-enhanced VCAM-1 expression
in the colon was associated with the upregulation of colonic iNOS
message (Fig. 2). Intraperitoneal injection
of 10 µg/kg TNF-
also significantly enhanced VCAM-1 expression in
the pancreas, mesentery, liver, and skeletal muscle; however, trends
for increased expression were observed in virtually all tissue analyzed
(Table 1). When these same experiments were
performed in iNOS
/
mice, colonic, cecal, and stomach but not small intestinal VCAM-1 expression was enhanced further by ~70-100% in
iNOS
/
mice given 10 µg/kg compared with the TNF-
-injected wild-type controls,
suggesting that the potential regulatory role of iNOS on VCAM-1
expression was tissue specific. Enhanced VCAM-1 expression in
iNOS
/
mice was also
observed in lung, pancreas, kidney, liver, and skin compared with that
observed in the TNF-
-injected wild-type counterparts (Table 1).
Increasing the dose of TNF-
to 25 µg/kg further enhanced VCAM-1
expression in the colon, cecum, small bowel, and stomach by
approximately twofold as well as in other tissues (Table 1) compared
with wild-type mice injected with 10 µg/kg TNF-
. Interestingly,
when TNF-
was administered to iNOS
/
mice, no
further increase in VCAM-1 expression was observed in most tissues
compared with the corresponding TNF-
-injected wild-type controls
(Fig. 1). We did, however, observe a further enhancement in VCAM-1
expression in the lung of
iNOS
/
mice injected
with this same amount of TNF-
(Table 1).

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Fig. 1.
Vascular cell adhesion molecule 1 (VCAM-1) expression in the
vasculature of the gastrointestinal tract of wild-type (wt) and
iNOS / mice injected
(intraperitoneally) with tumor necrosis factor- (TNF- ; 10 or 25 µg/kg). A total of 5 animals were used for each group.
A: colon.
B: cecum.
C: small intestine.
D: stomach.
* P < 0.05 vs. constitutive
VCAM-1 expression for wild-type or
iNOS / mice.
P < 0.05 vs. wild-type
in each dose group. iNOS, inducible isoform of nitric oxide synthase.
|
|

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Fig. 2.
RT-PCR determination of iNOS message in colons from wild-type mice
injected with either saline or 10 µg/kg TNF- . Total RNA was
isolated from colons of 3 C57BL/6 mice treated with TNF-
(lanes 1-3) and from colons of
3 saline-injected C57BL/6 mice (lanes
4-6). As controls, total RNA was isolated from
stimulated Raw264.7 macrophages and subjected to RT-PCR for iNOS in the
presence (lane 7) and absence
(lane 8) of Moloney murine leukemia
virus reverse transcriptase.
|
|
In a second series of experiments, we quantified colonic VCAM-1
expression in mice with chronic colitis induced by reconstitution of
SCID mice with CD45RBhigh T cells
(20, 21). We found that colonic VCAM-1 expression increased
approximately fourfold in SCID mice reconstituted with CD45RBhigh T cells compared with
their PBS-injected or
CD45RBlow-reconstituted SCID
controls (Fig. 3). This enhanced VCAM-1
expression correlated well with the onset of chronic inflammation and
iNOS expression in the colon as previously described (21). Continuous inhibition of iNOS in this T cell model of chronic colitis using an
oral dose of L-NIL known to
inhibit iNOS in vivo (see MATERIALS AND
METHODS) did not alter the enhanced levels of VCAM-1
expression in the colon nor did it alter macroscopic inflammation (Fig.
3).

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Fig. 3.
Effects of
NG-iminoethyl-Llysine
(L-NIL) on colonic VCAM-1
expression and macroscopic inflammation in SCID mice injected with
PBS, CD4+,
CD45RBlow T cells, or
CD4+,
CD45RBhigh T cells.
L-NIL was administered at a dose
of 25 mg · kg 1 · day 1
po beginning 4 wk following reconstitution and continuing for an
additional 4 wk. A total of 5 animals were used for each group.
* P < 0.05 vs. control SCID
mice.
|
|
 |
DISCUSSION |
There is increasing evidence to suggest that the free radical NO is
very effective at modulating leukocyte-endothelial cell interactions in
vitro and in vivo. For example, it has been demonstrated that NO
attenuates the adhesion and recruitment of leukocytes in postcapillary
venules exposed to different acute
inflammatory stimuli such as ischemia and reperfusion, oxidized
low-density lipoproteins, or reactive oxygen metabolites (6-8). An
anti-adhesive role for NO is also supported by the observation that
inhibitors of endothelial NOS elicit the recruitment of adherent
leukocytes in postcapillary venules (8). The precise mechanisms
responsible for this "anti-inflammatory" effect of NO are not
entirely clear; however, several studies using cultured endothelial
cells suggest that NO inhibits NF-
B activation by virtue of its
ability to induce and or stabilize the expression of I
B and/or by
inhibiting binding of the p50/p65 heterodimer to the enhancer-promoter
region upstream of the VCAM-1 gene (21, 24, 25). Although several studies from our laboratory as well as others have shown potent antiadhesive activity in vitro and in acute inflammation in vivo, there
is little or no evidence indicating that NO may modulate either
positively or negatively ECAM expression in chronic inflammation in
vivo. Indeed, numerous studies have demonstrated that chronic gut
inflammation is associated with the infiltration of large numbers of
mononuclear leukocytes coincident with the upregulation of iNOS and
sustained overproduction of NO (1, 4, 11, 13, 19, 22). Furthermore,
several studies have shown that certain NOS inhibitors possess
anti-inflammatory activity in different models of inflammatory bowel
disease (1, 4, 11, 13, 19, 22). These data suggest that
iNOS-derived NO may play little or no role in modulating the chronic
inflammatory response in vivo. Therefore, we wished to determine what
role, if any, iNOS played in modulating VCAM-1 expression in a
cytokine-induced model of acute inflammation vs. an immune-based model
of chronic colitis.
We found that intraperitoneal administration of TNF-
produced a
dose-dependent increase in VCAM-1 expression in vivo in several different tissues. The increase in vascular surface expression of
VCAM-1 induced by 10 µg/kg TNF-
correlated well with increases in
iNOS message in tissues such as the colon (Fig. 2). This is not
surprising in view of the fact that both VCAM-1 and iNOS expression are
induced by TNF-
via activation of NF-
B (3). Using 10 µg/kg
TNF-
, we also observed a further twofold increase in VCAM-1 expression in several different tissues, including the colon, cecum,
and stomach as well as the lung, pancreas, kidney, liver, and skin in
the iNOS
/
mice
compared with wild-type mice injected with the same dose of this
cytokine (Fig. 1 and Table 1). An equally interesting observation was
the lack of further VCAM-1 expression in a similar number of tissues
from iNOS
/
mice
injected with 10 µg/kg TNF-
compared with their wild-type controls
injected with the same amount of the cytokine (Fig. 1 and Table 1). The
reasons for this apparent tissue specificity in response to TNF-
are
not entirely clear at the present time. One possibility may be that the
physical location of iNOS in the various tissues in relation to the
postcapillary venules dictates whether iNOS-derived NO acts to modulate
VCAM-1 expression. For example, if iNOS is localized within or in close
proximity to the postcapillary venules, one would predict a modulatory
role for iNOS-derived NO. This possibility does not appear likely, since one would have to envision a completely different localization of
iNOS in the small bowel vs. the rest of the gastrointestinal tract.
Previous studies from our laboratory have determined that 10 µg/kg
TNF-
produces submaximal expression of VCAM-1 in most tissue (12,
15). Therefore, we wished to assess the modulatory role of iNOS in this
same model when the dose of TNF-
was increased to 25 µg/kg, a dose
previously shown to induce maximal VCAM-1 expression in the mouse (12,
15). We found that increasing the dose of TNF-
to 25 µg/kg
enhanced VCAM-1 expression in most tissues by approximately twofold
compared with wild-type mice injected with 10 µg/kg of the same
cytokine (Fig. 1 and Table 1). Unexpectedly, this increase was not
further enhanced in most tissues of
iNOS
/
mice as had
been shown for the 10 µg/kg dose (Fig. 1 and Table 1). The one
exception was the lung, which responded with a further increase in
VCAM-1 expression in
iNOS
/
mice. Taken
together, these data would suggest that iNOS-derived NO may modulate
VCAM-1 expression in a tissue-specific manner. Furthermore, our data
demonstrate that NO may not be an effective modulatory agent when
VCAM-1 is fully expressed, i.e., when the levels of TNF-
are
elevated to concentrations that may occur locally in more chronic
models of inflammation such as inflammatory bowel disease.
To address this possibility directly, we assessed the effects of
continuous iNOS inhibition on VCAM-1 expression in an immune-based model of chronic colitis in mice. We found that reconstitution of SCID
mice with congenic CD4+,
CD45RBhigh T cells but not with
PBS nor with CD4+,
CD45RBlow T cells produced
clinical and histopathological signs of chronic colitis beginning
5-6 wk postreconstitution, which was associated with enhanced
expression of iNOS and a fourfold increase in colonic VCAM-1 expression
compared with PBS- or
CD45RBlow-injected controls (Fig.
3). Continuous oral administration of the selective iNOS inhibitor
L-NIL beginning 4 wk
postreconstitution and continuing for an additional 4 wk did not alter
the enhanced levels of VCAM-1 expression (Fig. 3) nor did it affect the
colonic inflammation scores of these mice (Fig. 3). These data suggest that iNOS-derived NO does not modulate VCAM-1 expression to any significant extent in vivo in this model of colitis. This is not surprising in view of the data described above demonstrating the loss
of modulation of VCAM-1 by iNOS when TNF-
levels are elevated as
little as 2.5-fold. It is well known that local concentrations of
different cytokines (especially TNF-
) are enhanced in experimental models as well as in human inflammatory bowel disease
(23).
In summary, our data suggest that iNOS-derived NO may modulate VCAM-1
expression during acute inflammation; however, this modest regulatory
activity is tissue specific and occurs only within a narrow
concentration range of TNF-
. Furthermore, our data suggest that iNOS
does not appear to be involved in the regulation of VCAM-1 expression
in an immune-based model of chronic colitis.
 |
ACKNOWLEDGEMENTS |
This work was supported by grants from the Feist Foundation of
Louisiana State University Medical Center in Shreveport, the Crohn's
and Colitis Foundation of America, and National Institute of Diabetes
and Digestive and Kidney Diseases Grant DK-47663.
 |
FOOTNOTES |
The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement"
in accordance with 18 U.S.C. §1734 solely to indicate this fact.
Address for reprint requests and other correspondence: M. B. Grisham,
Dept. of Molecular and Cellular Physiology, LSU Medical Center, PO Box
33932, Shreveport, LA 71130-3932 (E-mail:
mgrish{at}lsumc.edu).
Received 19 April 1999; accepted in final form 15 June 1999.
 |
REFERENCES |
1.
Aiko, S.,
J. Fuseler,
and
M. B. Grisham.
Effects of nitric oxide synthase inhibition or sulfasalazine on the spontaneous colitis observed in HLA-B27 transgenic rats.
J. Pharmacol. Exp. Ther.
284:
722-727,
1998[Abstract/Free Full Text].
2.
Collins, T.,
M. A. Read,
A. S. Neish,
M. Z. Whitley,
D. Thanos,
and
T. Maniatis.
Transcriptional regulation of endothelial cell adhesion molecules: NF-
B and cytokine-inducible enhancers.
FASEB J.
9:
899-909,
1995[Abstract/Free Full Text].
3.
Conner, E. M.,
S. J. Brand,
J. M. Davis,
D. Y. Kang,
and
M. B. Grisham.
Role of reactive metabolites of oxygen and nitrogen in inflammatory bowel disease.
Inflam. Bowel Dis.
2:
133-147,
1996.
4.
Conner, E. M.,
S. Brand,
J. M. Davis,
F. S. Laroux,
V. J. Palombella,
J. W. Fuseler,
D. Y. Kang,
R. E. Wolf,
and
M. B. Grisham.
Proteasome inhibition attenuates nitric oxide synthase expression, VCAM-1 transcription and the development of chronic colitis.
J. Pharmacol. Exp. Ther.
282:
1615-1622,
1997[Abstract/Free Full Text].
5.
Conner, E. M.,
Z. Morise,
M. J. Eppihimer,
D. N. Granger,
and
M. B. Grisham.
Regional differences and magnitude of endothelial cell adhesion molecule expression in SCID mice reconstituted with CD45RBhigh T-lymphocytes (Abstract).
Gastroenterology
114:
A955,
1998.
6.
Granger, D. N.
Cell adhesion and migration. II. Leukocyte-endothelial cell adhesion in the digestive system.
Am. J. Physiol.
273 (Gastrointest. Liver Physiol. 36):
G982-G986,
1997[Abstract/Free Full Text].
7.
Granger, D. N.,
and
P. Kubes.
The microcirculation and inflammation: modulation of leukocyte-endothelial cell adhesion.
J. Leukoc. Biol.
55:
662-675,
1994[Abstract].
8.
Granger, D. N.,
and
P. Kubes.
Nitric oxide as anti-inflammatory agent.
Methods Enzymol.
269:
434-442,
1996[Medline].
9.
Grisham, M. B., and D. N. Granger.
Leukocyte-endothelial cell interactions in inflammatory bowel
disease. In: Inflammatory Bowel
Disease, edited by J. Kirsner. In press.
10.
Grisham, M. B.,
G. G. Johnson,
and
J. R. Lancaster, Jr.
Quantitation of nitrate and nitrite in extracellular fluids.
Methods Enzymol.
268:
237-246,
1996[Medline].
11.
Grisham, M. B.,
R. D. Specian,
and
T. E. Zimmerman.
Effects of nitric oxide synthase inhibition on the pathophysiology observed in a model of chronic granulomatous colitis.
J. Pharmacol. Exp. Ther.
271:
1114-1121,
1994[Abstract].
12.
Henninger, D. D.,
J. Panes,
M. Eppihimer,
J. Russell,
M. Gerritsen,
D. C. Anderson,
and
D. N. Granger.
Cytokine-induced VCAM-1 and ICAM-1 expression in different organs of the mouse.
J. Immunol.
158:
1825-1832,
1997[Abstract].
13.
Hogaboam, C. M.,
K. Jacobson,
S. M. Collins,
and
M. G. Blennerhassett.
The selective beneficial effects of nitric oxide inhibition in experimental colitis.
Am. J. Physiol.
268 (Gastrointest. Liver Physiol. 31):
G673-G684,
1995[Abstract/Free Full Text].
14.
Khan, B. V.,
D. G. Harrison,
M. T. Olbrych,
R. W. Alexander,
and
R. M. Medford.
Nitric oxide regulates vascular cell adhesion molecule-1 gene expression and redox-sensitive transcriptional events in human vascular endothelial cells.
Proc. Natl. Acad. Sci. USA
93:
9114-9119,
1996[Abstract/Free Full Text].
15.
Komatsu, S.,
S. Flores,
M. E. Gerritsen,
D. C. Anderson,
and
D. N. Granger.
Differential upregulation of circulating soluble and endothelial cell intercellular adhesion molecule-1 in mice.
Am. J. Pathol.
151:
205-214,
1997[Abstract].
16.
Laubach, V. E.,
E. G. Shesely,
O. Smithies,
and
P. A. Sherman.
Mice lacking inducible nitric oxide synthase are not resistant to lipopolysaccharide-induced death.
Proc. Natl. Acad. Sci. USA
92:
10688-10692,
1995[Abstract].
17.
Mackay, F.,
J. L. Browning,
P. Lawton,
S. A. Shah,
M. Comiskey,
A. K. Bhan,
E. Mizoguchi,
C. Terhorst,
and
S. J. Simpson.
Both the lymphotoxin and tumor necrosis factor pathways are involved in experimental murine models of colitis.
Gastroenterology
115:
1464-1475,
1998[Medline].
18.
Marui, N.,
M. K. Offermann,
R. Swerlock,
C. Kunsch,
C. A. Rosen,
M. Ahmad,
R. W. Alexander,
and
R. M. Medford.
Vascular cell adhesion molecule-1 (VCAM-1) gene transcription and expression are regulated through an antioxidant-sensitive mechanism in human vascular endothelial cells.
J. Clin. Invest.
92:
1866-1874,
1993[Medline].
19.
Miller, M. J.,
H. Sadowska-Krowicka,
S. Chotinaruemol,
J. L. Kakkis,
and
D. A. Clark.
Amelioration of chronic ileitis by nitric oxide synthase inhibition.
J. Pharmacol. Exp. Ther.
264:
11-16,
1993[Abstract].
20.
Peng, H. B.,
P. Libby,
and
J. K. Liao.
Induction and stabilization of I
B
by nitric oxide mediates inhibition of NF-
B.
J. Biol. Chem.
270:
14214-14219,
1995[Abstract/Free Full Text].
21.
Peng, H. B.,
M. Spiecker,
and
J. K. Liao.
Inducible nitric oxide: an autoregulatory feedback inhibitor of vascular inflammation.
J. Immunol.
161:
1970-1976,
1998[Abstract/Free Full Text].
22.
Rachmilewitz, D.,
F. Karmeli,
E. Okon,
and
M. Bursztyn.
Experimental colitis is ameliorated by inhibition of nitric oxide synthase activity.
Gut
37:
247-255,
1995[Abstract].
23.
Sartor, R. B.
Cytokines in intestinal inflammation: pathophysiological and clinical considerations.
Gastroenterology
106:
533-539,
1994[Medline].
24.
Spiecker, M.,
H. Darius,
K. Kaboth,
F. Hubner,
and
J. K. Liao.
Differential regulation of endothelial cell adhesion molecule expression by nitric oxide donors and antioxidants.
J. Leukoc. Biol.
63:
732-739,
1998[Abstract].
25.
Spiecker, M.,
H. B. Peng,
and
J. K. Liao.
Inhibition of endothelial vascular cell adhesion molecule-1 expression by nitric oxide involves the induction and nuclear translocation of I
B
.
J. Biol. Chem.
272:
30969-30974,
1997[Abstract/Free Full Text].
26.
Springer, T. A.
Traffic signals for lymphocyte recirculation and leukocyte emigration: the multistep paradigm.
Cell
76:
301-314,
1994[Medline].
27.
Takahashi, M.,
U. Ikeda,
J. Masuyama,
H. Funayama,
S. Kano,
and
K. Shimada.
Nitric oxide attenuates adhesion molecule expression in human endothelial cells.
Cytokine
8:
817-821,
1996[Medline].
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