Regulation of p100 (NFKB2) expression in human monocytes in response to inflammatory mediators and lymphokines

Abstract

The transcription factor NF-B plays an important role in the regulated expression of cytokines in human monocytes. A p100 subunit of NF-B has IB-like properties by sequestering the p65 transactivating subunit in the cytosol of cells. In transient transfection assays we demonstrated that p100 has an inhibitory effect on the NF-B-dependent IL-6 promoter activity. In view of this finding, we studied the regulation of the p100 subunit in human monocytes in response to LPS, the inflammatory cytokines IL-1␤ and TNF-␣ and lymphokines. The results demonstrate that LPS, IL-1␤, and TNF-␣ induce p100 expression at mRNA and protein level while IFN-␥, IL-3 and IL-4/IL-10 have no effect. The induction of p100 expression was shown to be mediated by a two-fold increase in the p100 transcription rate and a two-fold increase in p100 mRNA stability. Furthermore the p100 mediated upregulation was dependent on a tyrosine kinase dependent pathway rather than the protein kinase C pathway. NF-B is a complex of either p50 homodimers or a p50/p65 heterodimer. The latter is known to strongly autoregulate p100 transcription. We therefore examined the composition of NF-B induced by LPS vs the different lymphokines. LPSinduced NF-B showed a distinct p65 supershift whereas the composition of NF-B induced by different lymphokines did not show a change in p65. We conclude that the p100 subunit of the transcription factor NF-B is induced by different inflammatory mediators while lymphokines fail to induce p100 expression which may be caused by the induction of NF-B predominantly consisting of p50 homodimers.

A Genomic and Proteomic Analysis of Activation of the Human Neutrophil by Lipopolysaccharide and Its Mediation by p38 Mitogen-activated Protein Kinase

“…As will be discussed below, our study identifies, in particular, novel aspects of the LPS-stimulated PMN transcriptional regulation, activity in the innate immune response, signaling, cytoskeletal reorganization, and priming for granule release. In the present study, the increase in NF-B transcript abundance (Table I) detected by the microarrays corroborates the findings of other studies of PMNs and monocytes (40) and indicates a mechanism for the responsiveness and scope of the PMN transcriptional machinery following LPS exposure. NF-B, recently described to be activated by LPS through the TLR/MyD88/interleukin-1 receptor-associated kinase pathway (1,4), is the only transcriptional complex reported to be induced by LPS in the PMN.…”

NFκB2/p100 Is a Key Factor for Endotoxin Tolerance in Human Monocytes: A Demonstration Using Primary Human Monocytes from Patients with Sepsis

“…However, our data confirm a new important player in the control of ET. Previous studies from our group and others had suggested the involvement of p100 in this phenomenon (8,14). In addition to the high expression of p100 during endotoxin tolerance, our findings demonstrated that p100 knockdown restored tolerant cells to an inflammatory status, including the following: tolerant human monocytes from an in vitro model, bone marrow-derived macrophages from p100…”

“…Previous studies on human models have indicated that IRAK-M and members of the NF-kB pathway might be crucial for the development of the ET refractory state (4,13). Along these lines, previous findings suggested a potential role for NFkB2/p100 in the ET of human monocytes (8,14). A genome-wide microarray analysis showed that p100 is upregulated during the ET state (8).…”

Bruton’s Tyrosine Kinase Mediates NF-κB Activation and B Cell Survival by B Cell-Activating Factor Receptor of the TNF-R Family

“…cells have reduced levels of p100 (47,52,53). Our studies reveal that loss of two additional components of the classical NF-B pathway, Btk and PLC-␥2, results in reduced p100 mRNA and protein.…”