title: Contribution of interferon-beta to the murine macrophage response to the toll-like receptor 4 agonist, lipopolysaccharide.
abstract: Interferon-beta (IFN-beta) has been identified as the signature cytokine induced via the Toll-like receptor (TLR) 4, "MyD88-independent" signaling pathway in macrophages stimulated by Gram-negative bacterial lipopolysaccharide (LPS). In this study, we analyzed the responses of macrophages derived from wild-type (IFN-beta(+/+)) mice or mice with a targeted mutation in IFN-beta (IFN-beta(-/-)) to the prototype TLR4 agonist, Escherichia coli LPS. A comparison of basal and LPS-induced gene expression (by reverse transcription-PCR, real-time PCR, and Affymetrix microarray analyses) resulted in the identification of four distinct patterns of gene expression affected by IFN-beta deficiency. Analysis of a subset of each group of differentially regulated genes by computer-assisted promoter analysis revealed putative IFN-responsive elements in all genes examined. LPS-induced activation of intracellular signaling molecules, STAT1 Tyr-701, STAT1 Ser-727, and Akt, but not p38, JNK, and ERK MAPK proteins, was significantly diminished in IFN-beta(-/-) versus IFN-beta(+/+) macrophages. "Priming" of IFN-beta(-/-) macrophages with exogenous recombinant IFN-beta significantly increased levels of LPS-induced gene expression for induction of monocyte chemotactic protein 5, inducible nitric-oxide synthase, IP-10, and IL-12 p40 mRNA, whereas no increase or relatively small increases were observed for IL-1beta, IL-6, monocyte chemotactic protein 1, and MyD88 mRNA. Finally, IFN-beta(-/-) mice challenged in vivo with LPS exhibited increased survival when compared with wild-type IFN-beta(+/+) controls, indicating that IFN-beta contributes to LPS-induced lethality; however, not to the extent that one observes in mice with more complete pathway deficiencies (e.g. TLR4(-/-) or TRIF(-/-) mice). Collectively, these findings reveal unanticipated regulatory roles for IFN-beta in response to LPS in vitro and in vivo.
authors.affiliation: Department of Microbiology and Immunology, University of Maryland, Baltimore, Maryland 21201, USA.
authors.forename: Karen E
authors.initials: KE
authors.lastname: Thomas
authors.forename: Carole L
authors.initials: CL
authors.lastname: Galligan
authors.forename: Raj Deonarain
authors.initials: RD
authors.lastname: Newman
authors.forename: Eleanor N
authors.initials: EN
authors.lastname: Fish
authors.forename: Stefanie N
authors.initials: SN
authors.lastname: Vogel
mesh_terms: D000818:Animals; D004926:Escherichia coli / Q000378:metabolism; D016899:Interferon-beta / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008957:Models, Genetic; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000819:agonists* / Q000502:physiology*
chemical_list: D008070:Lipopolysaccharides; D012333:RNA, Messenger; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D016899:Interferon-beta