IFN-γInhibits Lipopolysaccharide-Induced Interleukin-1βin Primary Murine Macrophages via a Stat1-Dependent Pathway

Abstract

Interleukin-1 (IL-1) plays an important role in host defenses against microbial pathogens. Excessive production of this cytokine, however, may be responsible in part for the lethality observed during sepsis. Our studies show that interferon-gamma (IFN-gamma) downregulates lipopolysaccharide (LPS)-induced interleukin-1beta (IL-1beta) transcription in primary macrophages. This phenomenon does not occur in splenocytes or bone marrow-derived macrophages from signal transducer and activator of transcription (Stat1)-deficient mice, suggesting that Stat1, a transcription factor involved in IFN signaling, plays a critical role in this process. Moreover, nitric oxide (NO) was also involved in the downregulation of LPS-induced IL-1 by IFN, as addition of the inducible nitric oxide synthase (iNOS) inhibitor L-N(6)-(1-iminoethyl)lysine (NIL) negated the effect. Kinetic analysis of IL-1 and IFN levels in LPS-treated mice in vivo suggests that IFN-mediated inhibition of IL-1 might be an important negative feedback mechanism for limiting IL-1 generation in vivo.

Early Inhibition of IL-1β Expression by IFN-γ Is Mediated by Impaired Binding of NF-κB to the IL-1β Promoter but Is Independent of Nitric Oxide

“…3D), confirming the results of previous studies (22,24). Of note, under these conditions, downregulation of IL-1b was accompanied by increased NO concentrations and vice versa (compare Fig.…”

“…It was reported that IFN-g can downregulate IL-1b production in response to LPS stimulation and infection with Mycobacterium tuberculosis, as well as in models of autoimmune diseases, like collagen-induced arthritis, both in vitro and in vivo (21-24, 36, 37). Several reports indicated that IFN-g-mediated suppression of LPS-induced IL-1b occurred at the level of transcription (21)(22)(23). Although most studies did not further analyze the underlying mechanism, De Boer et al (22) demonstrated that this transcriptional silencing was crucially dependent on IFN-g-induced NO, because pharmacological inhibition of iNOS reversed the IFN-gmediated phenotype.…”

“…Inhibition of IL-1b secretion by costimulation with IFN-g is independent of NO It was reported that IFN-g can inhibit IL-1b production through intermediate production of NO (22,24). However, NO synthesis is known to be a late event after IFN-g stimulation (25)(26)(27).…”

“…Further, IFN-g enhances Th1 cell development. Despite those clearly proinflammatory features, IFN-g was described to suppress the generation of activeg-induced NO was demonstrated in both cases (22,24). Because NO production occurs with delayed kinetics (25)(26)(27), these effects were observed most prominently after long-term stimulation.…”

IL-18 Levels and the Outcome of Innate Immune Response to Lipopolysaccharide: Importance of a Positive Feedback Loop with Caspase-1 in IL-18 Expression

“…Serum IFN-␥ and IL-1␤ concentrations were determined by ELISA using R4-6A2/XMG1.1 (BD PharMingen, San Diego, CA; IFN-␥) and PM425B/MM 425B (Endogen, Woburn, MA; IL-1␤) Ab pairs, as described (37). IL-18 was measured using a mouse IL-18 detection ELISA kit (Medical and Biological Laboratories, Naka-ku Nagoya, Japan), according to the manufacturer's instructions, while ELISA for IL-12 (p70) was performed using Duoset system (R&D Systems), according to the manufacturer's instructions.…”