Dexamethasone Inhibits IL-12p40 Production in Lipopolysaccharide-Stimulated Human Monocytic Cells by Down-Regulating the Activity of c-Jun N-Terminal Kinase, the Activation Protein-1, and NF-κB Transcription Factors

Abstract

IL-12 plays a critical role in the development of cell-mediated immune responses and in the pathogenesis of inflammatory and autoimmune disorders. Dexamethasone (DXM), an anti-inflammatory glucocorticoid, has been shown to inhibit IL-12p40 production in LPS-stimulated monocytic cells. In this study, we investigated the molecular mechanism by which DXM inhibits IL-12p40 production by studying the role of the mitogen-activated protein kinases (MAPKs), and the key transcription factors involved in human IL-12p40 production in LPS-stimulated monocytic cells. A role for c-Jun N-terminal kinase (JNK) MAPK in LPS-induced IL-12p40 regulation in a promonocytic THP-1/CD14 cell line was demonstrated by using specific inhibitors of JNK activation, SP600125 and a dominant-negative stress-activated protein/extracellular signal-regulated kinase kinase-1 mutant. To identify transcription factors regulating IL-12p40 gene transcription, extensive deletion analyses of the IL-12p40 promoter was performed. The results revealed the involvement of a sequence encompassing the AP-1-binding site, in addition to that of NF-κB. The role of AP-1 in IL-12p40 transcription was confirmed by using antisense c-fos and c-jun oligonucleotides. Studies conducted to understand the regulation of AP-1 and NF-κB activation by JNK MAPK revealed that both DXM and SP600125 inhibited IL-12p40 gene transcription by inhibiting the activation of AP-1 and NF-κB transcription factors as revealed by luciferase reporter and gel mobility shift assays. Taken together, our results suggest that DXM may inhibit IL-12p40 production in LPS-stimulated human monocytic cells by down-regulating the activation of JNK MAPK, the AP-1, and NF-κB transcription factors.

Interleukin‐1β impairment of transforming growth factor β1 signaling by DOWN‐REGULATION of transforming growth factor β receptor type II and up‐regulation of Smad7 in human articular chondrocytes

“…Moreover, it has been reported that Jun or Fos can interact with the p65 subunit of NF-B (44). In addition, JNK is able to regulate the transcription activity of NF-B independently of I B degradation and NF-B nuclear translocation, and the inhibitor SP600125 decreases the activation of AP-1 as well as the DNA binding of NF-B (45). Together, these data suggest that in our system, JNK might act indirectly on TGF␤RII expression via a modulation of NF-B activation.…”

Anti-inflammatory functions of glucocorticoid-induced genes

“…In some studies anti-inflammatory effects of GCs were not accompanied by changes in DNA-binding activity of NFκB as measured by electrophoretic mobility shift assay (Brostjan et al, 1996;De Bosscher et al, 1997;Hofmann et al, 1998;Nissen and Yamamoto, 2000;Ray et al, 1997;Wissink et al, 1998). However, in other cases GCs were found to inhibit NFκB activation as measured by the same assay (Eberhardt et al, 2002;Goppelt-Struebe et al, 2000;Kurata and Yamamoto, 1999;Kurokouchi et al, 2000;Ma et al, 2004;Mukaida et al, 1994;Vital et al, 2003). The latter observations are inconsistent with the transrepression model.…”

“…IκBα expression is tissue-specifically regulated, and is enhanced by GCs in several primary or transformed cell types (Almon et al, 2005;Auphan et al, 1995;Kang et al, 2006;Kurata and Yamamoto, 1999;Kurokouchi et al, 2000;Quan et al, 2000;Ramdas and Harmon, 1998;Scheinman et al, 1995a;Shames et al, 1998;Stojadinovic et al, 2006;Thiele et al, 1999). In A c c e p t e d M a n u s c r i p t A Clark Anti-inflammatory functions of glucocorticoid-induced genes Page 17 of 53 some cases GC treatment inhibited IκBα degradation, nuclear translocation of p65 or formation of nuclear NFκB complexes (Eberhardt et al, 2002;Goppelt-Struebe et al, 2000;Kurata and Yamamoto, 1999;Kurokouchi et al, 2000;Ma et al, 2004;Mukaida et al, 1994;Vital et al, 2003). This is not consistent with a model in which GCs inhibit NFκB only at a level downstream of DNA binding, although it does not conclusively prove that upregulation of IκBα is critical.…”

Mannan-binding lectin directly interacts with Toll-like receptor 4 and suppresses lipopolysaccharide-induced inflammatory cytokine secretion from THP-1 cells

“…Primers and programs were performed as described. [39][40][41][42] Using the IL-12p40 sense primer, 59-GGA CCA GAG CAG TGA GGT CTT-39, and antisense primer, 59-CTC CTT GTT GTC CCC TCT GA-39, a product of 373 bp was amplified where primer annealing occurred at 52 uC for 35 cycles. For IL-12p35, using primers 59-CTC CTC CTT GTG GCT ACC CT-39 and 59-CTG GAA TTT AGG CAA CTC TCAT-39, a 281-bp product was amplified with annealing occurring at 55 uC for 33 cycles.…”