An NF-κB–Dependent Role for JunB in the Induction of Proinflammatory Cytokines in LPS-Activated Bone Marrow–Derived Dendritic Cells

Abstract

BackgroundDendritic cells (DCs) play a key role in the induction of adaptive and memory immune responses. Upon encounter with pathogens, they undergo a complex maturation process and migrate toward lymphoid organs where they stimulate immune effector cells. This process is associated with dramatic transcriptome changes, pointing to a paramount role for transcription factors in DC activation and function. The regulation and the role of these transcription factors are however ill-defined and require characterization. Among those, AP-1 is a family of dimeric transcription complexes with an acknowledged role in the control of immunity. However, it has not been studied in detail in DCs yet.Methodology/Principal FindingsHere, we have investigated the regulation and function of one of its essential components, JunB, in primary bone marrow–derived DCs induced to maturate upon stimulation by Escherichia coli lipopolysaccharide (LPS). Our data show fast and transient NF-κB–dependent transcriptional induction of the junb gene correlating with the induction of the TNFα, IL-6, and IL-12 proinflammatory cytokines. Inhibition of JunB protein induction by RNA interference hampered the transcriptional activation of the TNF-α, IL-6, and IL-12p40 genes. Consistently, chromatin immunoprecipitation experiments showed LPS-inducible binding of JunB at AP-1–responsive sites found in promoter regions of these genes. Concomitant LPS-inducible NF-κB/p65 binding to these promoters was also observed.Conclusions/SignificanceWe identified a novel role for JunB—that is, induction of proinflammatory cytokines in LPS-activated primary DCs with NF-κB acting not only as an inducer of JunB, but also as its transcriptional partner.

HSP90 inhibition by 17-DMAG reduces inflammation in J774 macrophages through suppression of Akt and nuclear factor-κB pathways

“…However, we found that a 1-h treatment with 17-DMAG followed by stimulation from LPS/IFN-c only reduced phosphorylation of IjB prior to and at 15 min stimulation. Our data suggests that HSP90 does not directly affect IjB activity; however, our data would also suggest that inhibition of IjB phosphorylation requires a 17-DMAG treatment time greater than 1 h. Upon phosphorylation of IjB, it dissociates from NF-jB, which allows NF-jB to translocate to the nucleus and bind to specific inflammatory gene promoters [51]. Recently, 17-DMAG was shown to reduce NF-jB activation in human macrophage cells by preventing IjB deactivation [50].…”

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“…Chromatin immunoprecipitation (ChIP) analysis was performed as described previously (38). For each ChIP experiment, chromatin was isolated from 2 3 10 7 T cells.…”

Human Intervention Study to Assess the Effects of Supplementation with Olive Leaf Extract on Peripheral Blood Mononuclear Cell Gene Expression

“…JUNB is an AP1 transcription factor correlated to immune function, and recent experimental work has demonstrated its pivotal role in macrophage activation [22,35]. JUNB can be directly activated by NF-κB in dendritic cells with LPS stimulation [36] and is required for the full activation of IL1β and tumor necrosis factor (TNF) in macrophages stimulated by LPS [22]. …”