BCL-3 and NF-kappaB p50 attenuate lipopolysaccharide-induced inflammatory responses in macrophages.
Lipopolysaccharide (LPS) induces expression of tumor necrosis factor alpha (TNFalpha) and other pro-inflammatory cytokines in macrophages. Following its induction, TNFalpha gene transcription is rapidly attenuated, in part due to the accumulation of NF-kappaB p50 homodimers that bind to three kappaB sites in the TNFalpha promoter. Here we have investigated the inhibitory role of BCL-3, an IkappaB-like protein that interacts exclusively with p50 and p52 homodimers. BCL-3 was induced by LPS with delayed kinetics and was associated with p50 in the nucleus. Forced expression of BCL-3 suppressed LPS-induced transcription from the TNFalpha promoter and inhibited two artificial promoters composed of TNFalphakappaB sites that preferentially bind p50 dimers. BCL-3-mediated repression was reversed by trichostatin A and was enhanced by overexpression of HDAC-1, indicating that transcriptional attenuation involves recruitment of histone deacetylase. Analysis of macrophages from p50 and BCL-3 knock-out mice revealed that both transcription factors negatively regulate TNFalpha expression and that BCL-3 inhibits IL-1alpha and IL-1beta. In contrast, induction of the anti-inflammatory cytokine IL-10 was reduced in BCL-3 null macrophages. BCL-3 was not required for the production of p50 homodimers but BCL-3 expression was severely diminished in p50-deficient cells. Together, these findings indicate that p50 and BCL-3 function as anti-inflammatory regulators in macrophages by attenuating transcription of pro-inflammatory cytokines and activating IL-10 expression.
Laboratory of Protein Dynamics and Signaling, NCI-Frederick, Frederick, Maryland 21702-1201, USA.
Jennifer
J
Wessells
Mark
M
Baer
Howard A
HA
Young
Estefania
E
Claudio
Keith
K
Brown
Ulrich
U
Siebenlist
Peter F
PF
Johnson
D000818:Animals; D000081242:B-Cell Lymphoma 3 Protein; D005786:Gene Expression Regulation / Q000502:physiology; D016753:Interleukin-10 / Q000096:biosynthesis / Q000235:genetics; D008070:Lipopolysaccharides / Q000276:immunology / Q000378:metabolism*; D008264:Macrophages / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics
D000081242:B-Cell Lymphoma 3 Protein; C000631345:Bcl3 protein, mouse; D008070:Lipopolysaccharides; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10