STAT3 regulates NF-κB recruitment to the IL-12p40 promoter in dendritic cells

Abstract

Interleukin-10-deficient (IL-10 IntroductionInterleukin-10-deficient (IL-10 Ϫ/Ϫ ) mice develop spontaneous T-helper 1 (Th-1)-mediated colitis when housed under specific pathogen-free (SPF) conditions. [1][2][3] In this experimental model, enhanced IL-12p40 production by immune cells represents a key feature of intestinal inflammation, as demonstrated by the prevention and partial treatment of colitis by anti-IL-12 antibodies. 4,5 This suggests that in absence of IL-10, the host mounts a dysregulated innate response to the commensal intestinal microflora. Dendritic cells (DCs) are at the interface of innate and adaptive immunity by virtue of their ability to secrete various cytokines including tumor necrosis factor ␣ (TNF␣), 7 For instance, IL-12p40-producing DCs skewed T-cell differentiation toward a Th-1 profile, a hallmark in the IL-10 Ϫ/Ϫ experimental mouse model. 8,9 However, the molecular mechanisms of dysregulated IL-12p40 gene expression in IL-10 Ϫ/Ϫ mice following SPF transfer are still poorly understood.IL-10 is a potent immunoregulatory cytokine with numerous effects, such as down-regulation of proinflammatory cytokines, chemokines, and costimulatory molecules. 10 Several mechanisms have been proposed for the IL-10-mediated inhibition of lipopolysaccharide (LPS)-induced proinflammatory gene expression, including activation of the heme oxygenase (HO)/carbon monoxide pathway, 11 inhibition of the nuclear factor-B (NF-B) pathway 12-14 and mitogen-activated protein (MAP) kinase activity, 15 mRNA stability, 16 signal transducers and activators of transcription 3 (STAT3) activation, 17 and induction of B-cell/lymphoma 3 (Bcl3). 18 However, the molecular mechanisms for dysregulated host innate responses in the IL-10 Ϫ/Ϫ mouse model are still unknown. IL-10 mediates its inhibitory effects through binding to its receptor complex, which induces activation of the cytoplasmic receptor-associated Janus kinase 1 (JAK1) and tyrosine kinase-2 (Tyk2). 10 This is followed by STAT3 phosphorylation, homodimerization, and translocation to the nucleus where it binds to STATbinding elements in the promoters of various IL-10-inducible genes, including suppressor of cytokine signaling 3 (SOCS3) and Bcl3. 10,18 The pivotal role of STAT3 in maintaining host homeostasis is clearly demonstrated by studies using genetic deletion. For example, STAT3 deletion is embryogenically lethal, 19 and myeloid cell-specific STAT3-deficient mice develop severe enterocolitis. 20 STAT3 deletion in bone marrow cells leads to overly activated innate immune responses 21 and interferes with the adaptive immune system by inhibiting the induction of antigen-specific T-cell tolerance. 22 Moreover, STAT3 gene inactivation leads to an aggressive and fatal form of enterocolitis mediated by These data highlight the pivotal role of STAT3 in controlling innate immunity. The absence of endogenous IL-10 in IL-10 Ϫ/Ϫ mice provides a powerful means to investigate the immunoregulatory mechanisms of this cytokine. To date, the Materials and methods Cell isolation...

Gnotobiotic IL-10−/−;NF-κBEGFP Mice Reveal the Critical Role of TLR/NF-κB Signaling in Commensal Bacteria-Induced Colitis

“…with a previous finding showing higher LPS-induced IL-12p40 secretion in IL-10 Ϫ/Ϫ compared with IL-10 wt/wt mice (33). Importantly, E. faecalis/E.…”

“…BMDC were generated from the femur and tibia of IL-10 wt/wt ;NF-B EGFP , IL-10 Ϫ/Ϫ ;NF-B EGFP and IL-10 Ϫ/Ϫ ;MyD88 Ϫ/Ϫ mice as described previously (33). Bone marrow cells were flushed and depleted of RBC using RBC lysing buffer (Sigma-Aldrich), and then cultured in ultralow-adherence 24-well plates (Costar) in complete medium (RPMI 1640) supplemented with 10% FCS, 2 mM L-glutamine, 50 M 2-ME, 10 ng/ml murine rGM-CSF, and 10 ng/ml murine rIL-4 (both from PeproTech).…”

Role of Stat3 in suppressing anti-tumor immunity

“…The ability of Stat3 to inhibit expression of similar immunostimulatory molecules in immune cells in tumor setting and in normal cells has also been demonstrated [4]. The underlying molecular mechanism(s) for downregulating Th1 immune responses remain fully unexplored, although it has been suggested that Stat3 has an antagonistic effect on immunostimulatory effects of NF-κB [11,12] and Stat1 [13], both of which are critical for inducing Th1 immune responses.…”

Cell‐extrinsic CTLA4‐mediated regulation of dendritic cell maturation depends on STAT3

“…These data suggest that CTLA4Fc exerts its regulatory effect downstream of the proximal NF-κB signaling pathway. STAT3 is a transcription factor that can modulate NF-κB binding to the IL-12p40 promoter [42] and negatively regulate LPS signaling [20]. IL-10 is a well-characterized STAT3 activator, which has been previously associated with Treg cell-DC crosstalk [43].…”