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Infect Immun, April 1998, p. 1638-1647, Vol. 66, No. 4
Departments of Medical Microbiology and
Immunology,1
Biomolecular
Chemistry,2
Pharmacology,3 and
Medicine,4 University of Wisconsin
Medical School, Madison, Wisconsin 53706
Received 15 May 1997/Returned for modification 7 August
1997/Accepted 15 December 1997
Elucidation of a signal transduction pathway essential to
lipopolysaccharide (LPS)-induced macrophage activation has the
capacity to provide new targets for the treatment of septic shock. In
this regard, activation of the transcription factor NF-
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Nuclear Translocation of NF-
B in
Lipopolysaccharide-Treated Macrophages Fails To Correspond to
Endotoxicity: Evidence Suggesting a Requirement for a Gamma
Interferon-Like Signal
B is commonly thought to be critical to LPS-stimulated macrophage inflammatory mediator production, although certain immunological, genetic, and
molecular evidence suggests that other factors are involved. To address
this issue, we hypothesized that the degree of LPS-induced NF-
B
mobilization should correlate with the murine endotoxicity of the
species of LPS used for in vitro study. Therefore, using D-galactosamine-sensitized mice, we assessed
the lethal potencies of eight LPS preparations from
Escherichia, Salmonella,
Klebsiella, Bacteroides,
Pseudomonas, Neisseria, and
Rhodobacter species as well as that of the endotoxin
substructure lipid X. The lethal potencies of these LPS preparations
varied by >160-fold. Treatment of RAW 264.7 cells with the same LPS
preparations induced levels of tumor necrosis factor alpha (TNF-
)
and NO production that correlated with the LPS 50% lethal dose. The
combined analysis of the levels of these two mediators produced in
response to LPS in RAW cells was found to be a strong predictor of
murine endotoxic lethality. Interestingly, while relatively nontoxic in
mice, Rhodobacter capsulatus LPS stimulated RAW cell
NF-
B-like DNA binding protein mobilization and TNF-
production to
levels comparable to those of more toxic species of LPS but was unable
to induce NO generation in RAW cells. These data indicate that neither
NF-
B activation nor TNF-
production alone is a dependable
predictor of LPS lethality. Additionally, cotreatment of
RAW cells with the potent inflammatory mediator ADP had no effect on
the ability of R. capsulatus LPS to stimulate NO production
but significantly enhanced induction of NO production by the toxic
species of LPS. In contrast, cotreatment of RAW cells or peritoneal
macrophages with gamma interferon (IFN-
) normalized the abilities of
both toxic and nontoxic LPS preparations to induce NO production,
suggesting that selected preparations of LPS may preferentially
generate an IFN-
-like signal that accounts for enhanced
toxicity. In sum, the activation of NF-
B does not correspond to LPS lethality, thereby complicating models of
macrophage activation that highlight NF-
B alone as a signal
transduction factor necessary for LPS-mediated toxicity.
*
Corresponding author. Mailing address for Paul J. Bertics: Department of Biomolecular Chemistry, University of Wisconsin
Medical School, 1300 University Ave., Room 571 Bardeen, Madison, WI
53706. Phone: (608) 262-8667. Fax: (608) 262-5253. E-mail:
pbertics{at}macc.wisc.edu. Mailing address for Richard A. Proctor: Department of Medical Microbiology and Immunology, University
of Wisconsin Medical School, 1300 University Ave., Room 407 SMI,
Madison, WI 53706. Phone: (608) 263-5591. Fax: (608) 262-5253. E-mail:
pbertics{at}macc.wisc.edu.
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