IL-12p40 Production In Macrophages Research Articles

Nfkb1 Inhibits LPS-Induced IFN-β and IL-12 p40 Production in Macrophages by Distinct Mechanisms

Background Nfkb1-deficient murine macrophages express higher levels of IFN-β and IL-12 p40 following LPS stimulation than control macrophages, but the molecular basis for this phenomenon has not been completely defined. Nfkb1 encodes several gene products including the NF-κB subunit p50 and its precursor p105. p50 is derived from the N-terminal of 105, and p50 homodimers can exhibit suppressive activity when overexpressed. The C-terminal region of p105 is necessary for LPS-induced ERK activation and it has been suggested that ERK activity inhibits both IFN-β and IL-12 p40 following LPS stimulation. However, the contributions of p50 and the C-terminal domain of p105 in regulating endogenous IFN-β(Ifnb) and IL-12 p40 (Il12b) gene expression in macrophages following LPS stimulation have not been directly compared.Methodology/Principal FindingsWe have used recombinant retroviruses to express p105, p50, and the C-terminal domain of p105 (p105ΔN) in Nfkb1-deficient murine bone marrow-derived macrophages at near endogenous levels. We found that both p50 and p105ΔN inhibited expression of Ifnb, and that inhibition of Ifnb by p105ΔN depended on ERK activation, because a mutant of p105ΔN (p105ΔNS930A) that lacks a key serine necessary to support ERK activation failed to inhibit. In contrast, only p105ΔN but not p50 inhibited Il12b expression. Surprisingly, p105ΔNS930A retained inhibitory activity for Il12b, indicating that ERK activation was not necessary for inhibition. The differential effects of p105ΔNS930A on Ifnb and Il12b expression inversely correlated with the function of one of its binding partners, c-Rel. This raised the possibility that p105ΔNS930A influences gene expression by interfering with the function of c-Rel.ConclusionsThese results demonstrate that Nfkb1 exhibits multiple gene-specific inhibitory functions following TLR stimulation of murine macrophages.

GSK3β Inhibitor Peptide Protects Mice from LPS-induced Endotoxin Shock

BackgroundGlycogen synthase kinase 3β (GSK3β) is a ubiquitous serine/threonine kinase that is regulated by serine phosphorylation at 9. Recent studies have reported the beneficial effects of a number of the pharmacological GSK3β inhibitors in rodent models of septic shock. Since most of the GSK3β inhibitors are targeted at the ATP-binding site, which is highly conserved among diverse protein kinases, the development of novel non-ATP competitive GSK3β inhibitors is needed.MethodsBased on the unique phosphorylation motif of GSK3β, we designed and generated a novel class of GSK3β inhibitor (GSK3i) peptides. In addition, we investigated the effects of a GSK3i peptide on lipopolysaccharide (LPS)-stimulated cytokine production and septic shock. Mice were intraperitoneally injected with GSK3i peptide and monitored over a 7-day period for survival.ResultsWe first demonstrate its effects on LPS-stimulated pro-inflammatory cytokine production including interleukin (IL)-6 and IL-12p40. LPS-induced IL-6 and IL-12p40 production in macrophages was suppressed when macrophages were treated with the GSKi peptide. Administration of the GSK3i peptide potently suppressed LPS-mediated endotoxin shock.ConclusionCollectively, we present a rational strategy for the development of a therapeutic GSK3i peptide. This peptide may serve as a novel template for the design of non-ATP competitive GSK3 inhibitors.

Azithromycin suppresses interleukin-12p40 expression in lipopolysaccharide and interferon-γ stimulated macrophages

Azithromycin (AZM), a 15-member macrolide antibiotic, possesses anti-inflammatory activity. Macrophages are important in innate and acquired immunity, and produce pro-inflammatory cytokines such as interleukin (IL)-12, which are composed of subunit p40 and p35. The key function of IL-12 is the induction and maintenance of T-helper-1 responses, which is associated with the pathogenesis of chronic inflammatory diseases. We investigated the effect of azithromycin on IL-12p40 production in macrophages after lipopolysaccharide (LPS)/interferon (IFN)-gamma stimulation. RAW264.7 macrophage cell line was pre-treated with vehicle or AZM, followed by the stimulation with LPS/IFN-gamma. We measured IL-12 production by RT-PCR and ELISA. IL-12 transcriptional regulation was assessed by electrophoretic mobility shift assay and reporter assay. Phosphorylation of activator protein (AP)-1 and interferon consensus sequence binding protein (ICSBP) was assessed by immunoprecipitation using phosphotyrosine antibody, and immunoblotting using specific antibodies against JunB and ICSBP. AZM reduced the induction of IL-12p40 by LPS/IFN-gamma in a dose dependent manner. AZM inhibited the binding of AP-1, nuclear factor of activated T cells (NFAT), and ICSBP, to the DNA binding site in the IL-12p40 promoter. AZM also reduced LPS/IFN-gamma-induced IL-12p40 promoter activity. Phosphorylation of JunB and ICSBP was inhibited by azithromycin-treatment in stimulated cells. In conclusion, AZM reduced IL-12p40 transcriptional activity by inhibiting the binding of AP-1, NFAT, and ICSBP to the promoter site. This may represent an important mechanism for regulating the anti-inflammatory effects of AZM in macrophages.

Prolactin-induced production of cytokines in macrophages in vitro involves JAK/STAT and JNK MAPK pathways

Macrophages play a crucial role in host immunosurveillance against pathogens and malignancies. The enhanced productions of pro-inflammatory cytokines are central to the regulatory role of macrophages and induction of robust immune response. The excessive inflammatory response of macrophages can result into pathological conditions in host. We have previously reported that prolactin (PRL) induces the production of nitric oxide (NO) and tumor necrosis factor (TNF)-alpha in murine peritoneal macrophages. It was suggested that protein tyrosine kinases (PTKs), mitogen-activated protein kinases (MAPKs) and Ca(++) signaling were involved in the NO production by macrophages on PRL treatment. In this manuscript, we investigated the role of PTKs [Janus kinase (JAK) 2 and phosphoinositide 3-kinase (PI3K)] and c-Jun N-terminal kinase (JNK) MAPK in PRL-induced activation of murine peritoneal macrophages. It is reported that PRL-induced activation of macrophages in vitro is dependent on JAK/signal transducers and activators of transcription (STAT) and JNK MAPK-signaling pathways. It is observed that pre-treatment of macrophages with JNK inhibitor, SP600125; tyrosine kinase inhibitor, genistein; PI3K inhibitor, Wortmannin and JAK2 inhibitor, AG490 inhibited the phosphorylation of JNK MAPK. Further, pre-treatment of macrophages with SP600125 inhibited the PRL-induced production of IFN-gamma and TNF-alpha. AG490, inhibitor of JAK2, down-regulated transcription factors c-jun and STAT1 and inhibited the PRL-induced IFN-gamma, TNF-alpha, IL-1 beta and IL-12p40 production in macrophages.

Activation and Repression of Interleukin-12 p40 Transcription by Erythroid Kruppel-like Factor in Macrophages

Transcription of interleukin (IL)-12 p40 in myeloid cells is attributed to the recruitment of multiple activated transcription factors such as nuclear factor kappaB (NFkappaB), CCAAT enhancer-binding protein beta, ets-2, PU.1, and so forth. We now provide the first description of the human erythroid Kruppel-like factor (EKLF) in human primary macrophages and identify the role of EKLF in IL-12 p40 expression. EKLF-specific binding to the CACCC element (-224 to -220) on the human IL-12 p40 promoter was observed in resting human primary macrophages. Functional analysis of the CACCC element revealed a dependent role for EKLF binding in activating IL-12 p40 transcription in resting RAW264.7 cells, whereas EKLF overexpression in the presence or absence of this element repressed IL-12 p40 transcription in interferon gamma/lipopolysaccharide-stimulated RAW264.7 cells. Murine endogenous IL-12 p40 mRNA was consistently induced by overexpressed EKLF in resting RAW264.7 cells, whereas EKLF suppressed IL-12 p40 expression in activated RAW264.7 cells. Modulation of nuclear binding activities at the IL-12 p40 NFkappaB half-site was induced by EKLF for down-regulation of IL-12 p40 transcription in activated RAW264.7 cells, but no effect of EKLF on NFkappaB activity was observed in resting RAW264.7 cells. Taken together, we identify EKLF as a transcription factor in macrophages able to regulate IL-12 p40 transcription depending on the cellular activation status. The bifunctional control of IL-12 p40 by EKLF and its modulation of NFkappaB support a potential function for this factor in orchestrating IL-12 p40 production in macrophages.