Scott E. Plevy

A Prominent Role for Sp1 During Lipopolysaccharide- Mediated Induction of the IL-10 Promoter in Macrophages

IL-10 is an antiinflammatory cytokine secreted by activated macrophages and Th2 cells. IL-10 secretion promotes the down-regulation of proinflammatory cytokine synthesis and the development of Th2 responses. In macrophages, proinflammatory cytokines appear to be induced by similar mechanisms, but the IL-10 induction mechanisms have not been examined. We have analyzed the murine IL-10 promoter in the RAW264.7 macrophage line activated with LPS. A comprehensive mutant analysis revealed only one element upstream of the core promoter that was essential for promoter induction. A refined mutant analysis localized this element to nucleotides −89 to −78, and gel shift experiments revealed that it represents a nonconsensus binding site for Sp1. The functional relevance of Sp1 was supported by the high affinity of the interaction, the close correlation between the nucleotides required for Sp1 binding and promoter function, and the ability of an Sp1 consensus sequence to substitute for the −89/−78 promoter sequence. Evidence that Sp1 may be a target of signaling pathways involved in IL-10 induction was provided by the exclusive requirement for the Sp1 binding site, by the ability of the Sp1 site to confer induction to a heterologous promoter, and by the delineation of an Sp1 domain that can mediate induction. No relevant contribution from Rel, C/EBP (CCAAT/enhancer-binding protein), or AP-1 binding sites, which regulate most proinflammatory cytokine promoters, was observed. Together, these results demonstrate that IL-10 gene regulation is distinct from the regulation of proinflammatory cytokine genes, and suggest that Sp1 may be a central mediator of IL-10 induction.

Rapid and Selective Remodeling of a Positioned Nucleosome during the Induction of IL-12 p40 Transcription

Nucleosomes are important for gene regulation, but comprehensive studies of nucleosome positioning, remodeling, and transcription factor binding at inducible mammalian promoters have not been reported. We have analyzed the IL-12 p40 promoter, which is induced in macrophages by bacterial products. High-resolution micrococcal nuclease analyses revealed that a positioned nucleosome, nucleosome 1, spans the promoter, with three positioned nucleosomes further upstream. Upon activation, nucleosome 1 was rapidly and selectively remodeled in a protein synthesis-dependent manner. In primary macrophages, IFNgamma synergistically enhanced p40 expression, but little effect on remodeling or promoter occupancy was observed. These results suggest that remodeling complexes are selectively targeted to a single, promoter-encompassing nucleosome and that IFNgamma influences an event that is independent or downstream of remodeling.

Factors predictive of response to cyclosporin treatment for severe, steroid-resistant ulcerative colitis

OBJECTIVE:Cyclosporin-A (CSA) has been demonstrated to be effective for treatment of severe, steroid-resistant ulcerative colitis (UC). Use of CSA has been limited, however, because of low 1-yr response rates and the potential for complications. The aim of this study is to define clinical and laboratory factors predictive of response in severe, steroid-resistant UC.METHODS:A retrospective review of 36 cases of severe, steroid-resistant UC treated with CSA was performed. Intravenous (i.v.) CSA was administered at an initial dose of 2.5 mg/kg, and oral (p.o.) CSA was given as twice the i.v. dose. Clinical response was recorded and logistic regression analysis was performed on clinical and laboratory factors for prediction of response to CSA.RESULTS:Of 36 patients, 25 responded to i.v. CSA and were switched to p.o. CSA. Of the 25, 13 required colectomy by 9 months. The other 12 patients had a sustained response to CSA and avoided colectomy at 9 months. Overall, 24 of 36 patients treated with CSA required colectomy by 9 months. A high percentage of band neutrophils (bands) on admission was found to be a significant predictor of response to CSA.CONCLUSIONS:Bands on admission are predictive of response to CSA and ultimately, the requirement for surgery in steroid-resistant UC.

Characterization of an activation protein-1-binding site in the murine interleukin-12 p40 promoter. Demonstration of novel functional elements by a reductionist approach.

Interleukin (IL)-12 is a heterodimeric cytokine produced by macrophages in response to intracellular pathogens and provides an obligatory signal for the differentiation of T-helper-1 cells. We previously reported an analysis of the IL-12 p40 promoter in RAW264.7 macrophages. Multiple control elements were involved in activation of transcription by bacterial products. A critical control element, located between −96 and −88, interacts with C/EBP family members. In this study, using a strategy to demonstrate functional activity in a minimal promoter context, three novel cis-acting elements are found to have an important role in IL-12 p40 promoter activation by lipopolysaccharide. One of these elements is characterized in detail. Mutations from −79 to −74 in the murine IL-12 p40 promoter significantly reduce lipopolysaccharide-induced promoter activity. Electrophoretic mobility shift assays demonstrate binding of AP-1 family members to this region. Spacing between the C/EBP and AP-1 site is important for promoter activation, suggesting cooperativity between these elements. c-Jun and a mutant c-Jun molecule activate the IL-12 p40 promoter and synergistically activate the promoter when co-expressed with C/EBPβ. Finally, this region of the promoter is demonstrated to be a target for mitogen-activated protein kinase and toll-like receptor signaling pathways.

Toward an Understanding of the Gene-Specific and Global Logic of Inducible Gene Transcription

Virtually all living organisms have evolved mechanisms to adapt to their environment by sensing environmental stresses and inducing the transcription of appropriate sets of response genes in a coordinated fashion. In the vertebrate immune system, the highly selective response to an environmental stimulus, often an invading microorganism, plays an especially important role in regulating the activities of, and interactions among, the many cell types involved in innate and adaptive immunity. It is now widely appreciated that the selective response to a stimulus requires the concerted action of signal transduction pathways, transcription factors, and chromatin structure. Many proteins and pathways that help to regulate a response have been characterized. However, our understanding of the gene-specific and global logic through which a highly selective response is elicited has only recently begun to emerge.