Signal transducers and activators of transcription 3 (STAT3) inhibits transcription of the inducible nitric oxide synthase gene by interacting with nuclear factor κB

Abstract

Prolific generation of NO by inducible nitric oxide synthase (iNOS) can cause unintended injury to host cells during glomerulonephritis and other inflammatory diseases. While much is known about the mechanisms of iNOS induction, few transcriptional repressors have been found. We explored the role of signal transducers and activators of transcription 3 (STAT3) proteins in interleukin (IL)-1beta- and lipopolysaccharide (LPS)+interferon (IFN)-gamma-mediated iNOS induction in murine mesangial cells. Both stimuli induced rapid phosphorylation of STAT3 and sequence-specific STAT3 DNA-binding activity. Supershift assays with a STAT3 element probe demonstrated that nuclear factor kappaB (NF-kappaB) p65 and p50 complexed with STAT3 in the DNA-protein complex. The direct interaction of STAT3 and NF-kappaB p65 was verified in vivo by co-immunoprecipitation and in vitro by pull-down assays with glutathione S-transferase-NF-kappaB p65 fusion protein and in vitro -translated STAT3alpha. Overexpression of STAT3 dramatically inhibited IL-1beta- or LPS+IFN-gamma-mediated induction of iNOS promoter-luciferase constructs that contained the wild-type iNOS promoter or ones harbouring mutated STAT-binding elements. In tests of indirect inhibitory effects of STAT3, overexpression of STAT3 dramatically inhibited the activity of an NF-kappaB-dependent promoter devoid of STAT-binding elements without affecting NF-kappaB DNA-binding activity. Thus STAT3, via direct interactions with NF-kappaB p65, serves as a dominant-negative inhibitor of NF-kappaB activity to suppress indirectly cytokine induction of the iNOS promoter in mesangial cells. These results provide a new model for the termination of NO production by activated iNOS following exposure to pro-inflammatory stimuli.

STAT1 Signaling Regulates Tumor-Associated Macrophage-Mediated T Cell Deletion

“…These cells had no detectable STAT3 activity, but increased STAT1. These data are consistent with recent observation that STAT3 inhibits transcription of the iNOS by interacting with NF-B (45). These data are also consistent with recent observation that pharmacological inhibition of STAT3 activity in macrophages with AG490 did not affect the level of NO production (E. Sotomayor, unpublished observation).…”

Nuclear factor κB (NF-κB) suppresses food intake and energy expenditure in mice by directly activating the Pomc promoter

“…Consistent with previous reports [27][28][29][30], STAT3 and RELA were coimmunoprecipitated from 293-OBRb cells (Fig. 5a).…”

“…Nonetheless, we tested the second hypothesis, which may work in parallel with the first one, by examining the pSTAT3 levels in the cytosolic and nuclear fractions of leptin-stimulated 293-OBRb cells. Although STAT3 may directly interact with RELA [27][28][29][30] (also see Fig. 5a), increasing amounts of RELA did not affect pSTAT3 nuclear translocation (Fig.…”

“…For example, FOXO1 inhibits pSTAT3 binding to the SP1-Pomc complex by sequestering STAT3 through direct interaction [10]. The fact that RELA interacts with STAT3 [27][28][29][30] and inhibits STAT3-mediated promoter activity further highlights the connection between inflammation and leptin signalling, and offers a novel direct link between the inflammatory pathway and leptin resistance. Similar to FOXO1 action in leptin resistance, RELA may also block leptin-induced POMC activity through direct interaction (Fig.…”

NF-κB and STAT3 signaling pathways collaboratively link inflammation to cancer

“…There are seven mammalian STAT Protein Cell & teract with each other at many different layers. First, the members of NF-κB like RelA can physiologically interact with STAT3 and their association can modify their transcriptional activity (Yu et al, 2002;Lee et al, 2009). Second, as two important transcriptional factors, NF-κB and STAT3 cooperatively bind at a subset of gene promoters to collaboratively induce their target genes expression (Yang et al, 2007).…”