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.
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.
Lawrence
O
O
Department of Genetics, University of Washington, Seattle 98195.
Rachie
N
N
Qureshi
N
N
Bomsztyk
K
K
Sibley
C H
CH
D000818:Animals; D001402:B-Lymphocytes / Q000187:drug effects*; D001483:Base Sequence; D004268:DNA-Binding Proteins; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D007075:Immunoglobulin M / Q000096:biosynthesis; D007145:Immunoglobulin kappa-Chains / Q000096:biosynthesis*; D008050:Lipid A / Q000031:analogs & derivatives* / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000276:immunology; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism; D050813:Octamer Transcription Factor-2; D012242:Rhodobacter sphaeroides / Q000737:chemistry*; D012485:Salmonella typhi / Q000276:immunology; D012772:Shock, Septic / Q000209:etiology; D014157:Transcription Factors / Q000096:biosynthesis; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D007075:Immunoglobulin M; D007145:Immunoglobulin kappa-Chains; D008050:Lipid A; D008070:Lipopolysaccharides; D016328:NF-kappa B; D050813:Octamer Transcription Factor-2; C489206:Pou2f2 protein, mouse; D014157:Transcription Factors; C049596:diphosphoryl lipid A