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Infect. Immun., 03 1995, 1040-1046, Vol 63, No. 3
O Lawrence, N Rachie, N Qureshi, K Bomsztyk and CH Sibley
Lipopolysaccharide (LPS) is implicated in much of the pathophysiology
associated with gram-negative septic shock. One approach to this serious
clinical problem is to develop new drugs that antagonize the action of
toxic LPS. A model system to study LPS action and test for potential
antagonists is readily provided by LPS regulation of the kappa gene in the
murine B-cell line 70Z/3. Rhodobacter sphaeroides diphosphoryl lipid A
(RsDPLA) effectively blocked toxic LPS induction of kappa light-chain
immunoglobulin expression in 70Z/3 cells. Induction of kappa expression by
LPS is dependent on the activation of at least two transcription factors,
Oct-2 and NF-kappa B. RsDPLA completely repressed the long-term activation
of NF-kappa B observed after 24 h of Salmonella typhosa LPS treatment and
antagonized activation of oct-2 mRNA expression. However, RsDPLA was not an
inert competitor of LPS. RsDPLA alone strongly activated NF-kappa B binding
activity by 30 min but not beyond 9 h of treatment. It also induced a small
increase in oct-2 mRNA levels. RsDPLA is not simply a weak agonist; we
found no graded increase in kappa expression with increasing RsDPLA
concentrations up to 50 micrograms/ml. The NF-kappa B complexes activated
by RsDPLA and S. typhosa LPS were both composed of the p50-p65 heterodimer.
These results suggest that the physiological LPS receptor(s) on B cells
transmits qualitatively different signals depending on the nature of the
binding ligand and that the fatty acyl groups of LPS play an important role
in activating signal transduction.
Copyright © 1995, American Society for Microbiology
Diphosphoryl lipid A from Rhodobacter sphaeroides transiently activates NF-kappa B but inhibits lipopolysaccharide induction of kappa light chain and Oct-2 in the B-cell lymphoma line 70Z/3
Department of Genetics, University of Washington, Seattle 98195.
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