Two essential regulatory elements in the human interferon gamma promoter confer activation specific expression in T cells

Like interleukin 2 (IL-2), interferon gamma (IFN-gamma) is an early response gene in T cells and both are prototypical T helper cell type 1 (Th-1) lymphokines. Yet IL-2 and IFN-gamma production are independently regulated, as demonstrated by their differential expression in certain T cell subsets, suggesting that the regulatory elements in these two genes must differ. To explore this possibility, the 5' flank of the human IFN-gamma gene was analyzed. Expression of IFN-gamma promoter- driven beta-galactosidase reporter constructs containing 538 bp of 5' flank was similar to that by constructs driven by the IL-2 promoter in activated Jurkat T cells; expression nearly as great was observed with the construct containing only 108 bp of IFN-gamma 5' flank. These IFN- gamma promoter constructs faithfully mirrored expression of the endogenous gene, in that expression required activation both with ionomycin and PMA, was inhibited by cyclosporin A, and was not observed in U937 or THP-1 cells. The region between -108 and -40 bp in the IFN- gamma promoter was required for promoter function and contained two elements that are conserved across species. Deletion of 10 bp within either element reduced promoter function by 70%, whereas deletions in nonconserved portions of this region had little effect on promoter function. The distal conserved element (-96 to -80 bp) contained a consensus GATA motif and a potential regulatory motif found in the promoter regions of the GM-CSF and macrophage inflammatory protein (MIP) genes. Factors binding to this element, including GATA-3, were found in Jurkat nuclear extracts by electromobility shift assays and two of the three complexes observed were altered in response to activation. One or both of these motifs are present in the 5' flank of multiple, other lymphokine genes, including IL-3, IL-4, IL-5, and GM- CSF, but neither is present in the promoter of the IL-2 gene. The proximal conserved element (-73 to -48 bp) shares homology with the NFIL-2A element in the IL-2 promoter; these elements compete for binding of factors in Jurkat nuclear extracts, although the NFIL-2A element but not the IFN-gamma element binds Oct-1. Factors binding to this element in the IFN-gamma gene were present in extracts from resting and activated Jurkat T cells. However, by in vivo footprinting of intact cells, this element was protected from methylation only with activation.(ABSTRACT TRUNCATED AT 400 WORDS)     

Expression of a constitutive NF-kappa B-like activity is essential for proliferation of cultured bovine vascular smooth muscle cells.

We have recently discovered bovine and human vascular smooth muscle cells (SMCs) express a novel constitutive Nuclear Factor-kappa B (NF-kappa B)/Rel-like activity (Lawrence, R., L.-J. Chang, U. Siebenlist, P. Bressler, and G.E. Sonenshein. 1994. J. Biol. Chem. 269:28913-28918), here termed SMC-Rel. Since cytomegalovirus (CMV) infection of human vascular SMCs has been implicated in aberrant SMC proliferation during post-angioplasty restenosis, we tested the role of NF-kappa B/Rel activity in transactivation of the CMV immediate early (ie) promoter. The basal CMV ie promoter linked to three wild-type, but not mutant, copies of its NF-kappa B element was active in bovine aortic SMCs. The anti-oxidants N-acetyl cysteine (NAC) or pentoxifylline (PTX), which are used clinically to reduce NF-kappa B/Rel activity, inhibited NF-kappa B driven promoter transactivation, and SMC-Rel binding activity. Treatment with either NAC or PTX was observed to slow the growth of the SMCs in a dose dependent fashion. Microinjection of either purified I kappa B-alpha, a naturally occurring specific inhibitor of NF-kappa B/Rel activity, or double-stranded oligonucleotides harboring wild type, but not non-binding mutants of NF-kappa B elements selectively inhibited SMC proliferation. Thus constitutive NF-kappa B/Rel activity appears essential for proliferation of vascular SMCs and might be a novel target for therapeutic intervention for restenosis.     

The AP-1 site at -150 bp, but not the NF-kappa B site, is likely to represent the major target of protein kinase C in the interleukin 2 promoter

Stimulation of T cells with antigen results in activation of several kinases, including protein kinase C (PKC), that may mediate the later induction of activation-related genes. We have examined the potential role of PKC in induction of the interleukin 2 (IL-2) gene in T cells stimulated through the T cell receptor/CD3 complex. We have previously shown that prolonged treatment of the untransformed T cell clone Ar-5 with phorbol esters results in downmodulation of the alpha and beta isozymes of PKC, and abrogates induction of IL-2 mRNA and protein. Here we show that phorbol ester treatment also abolishes induction of chloramphenicol acetyltransferase activity in Ar-5 cells transfected with a plasmid containing the IL-2 promoter linked to this reporter gene. The IL-2 promoter contains binding sites for nuclear factors including NFAT-1, Oct, NF-kappa B, and AP-1, which are all potentially sensitive to activation of PKC. We show that induction of a trimer of the NFAT and Oct sites is not sensitive to phorbol ester treatment, and that mutations in the NF-kappa B site have no effect on inducibility of the IL-2 promoter. In contrast, mutations in the AP-1 site located at -150 bp almost completely abrogate induction of the IL-2 promoter, and appearance of an inducible nuclear factor binding to this site is sensitive to PKC depletion. Moreover, cotransfections with c-fos and c-jun expression plasmids markedly enhance induction of the IL-2 promoter in minimally stimulated T cells. Our results indicate that the AP-1 site at -150 bp represents a major, if not the only, site of PKC responsiveness in the IL-2 promoter.     

Genomic organization and immune regulation of the defensin gene from the mosquito, Anopheles gambiae

The defensin gene from the mosquito, Anopheles gambiae, is present as a single copy per haploid genome. Two exons, encoding a 102 residue preprodefensin, are separated by a 105 bp intron bounded by consensus splice sites. The upstream regulatory sequence includes a TATA box, arthropod initiator and numerous motifs homologous to insect and mammalian immune response elements. This promoter is capable of upregulation by immune challenge in cultured cells and activity is further stimulated by Gambif1, a mosquito Rel protein known to translocate to the nucleus and bind NF-kappa B sites in target promoters. Activity is inhibited by p50, a mammalian Rel protein that competitively binds NF-kappa B sites, and virtually abolished by p40, an avian I kappa B protein that inhibits nuclear translocation.     

The expression of the interleukin 6 gene is induced by the human immunodeficiency virus 1 TAT protein

Human immunodeficiency virus 1 (HIV1) infection is associated with severe psoriasis, B cell lymphoma, and Kaposi's sarcoma. A deregulated production of interleukin 6 (IL-6) has been implicated in the pathogenesis of these diseases. The molecular mechanisms underlying the abnormal IL-6 secretion of HIV1-infected cells may include transactivation of the IL-6 gene by HIV1. To test this hypothesis, we used the pIL6Pr-chloramphenicol acetyltransferase (CAT) plasmid, an IL- 6 promoter-CAT construct, as a target of the transactivating function of the HIV1 TAT protein. By cotransfecting the pIL6Pr-CAT and the tat- expressing pSVT8 plasmid in MC3 B-lymphoblastoid or in HeLa epithelial cells, we observed that TAT transactivates the human IL-6 promoter. These results were confirmed when pIL6Pr-CAT was transfected in MC3 or HeLa cells that constitutively expressed the tat gene in a sense (pSVT8 cells) or antisense (pSVT10 cells) orientation. 5' deletion plasmids of pIL6Pr-CAT, in which regions at -658, -287, and -172 were inserted 5' to the cat gene, were transiently transfected in pSVT10 and pSVT8 cells and showed that TAT-induced activation of the IL-6 promoter required a minimal region located between -287 and -54 bp. Moreover, experiments with plasmids carrying the -658, -287, and -172 bp regions of the IL-6 promoter inserted downstream to a TAR-deleted HIV1-LTR identified the sequence of -172 to -54 as the minimal region of the IL-6 promoter required for TAT to transactivate the TAR-deleted HIV1-LTR. By DNA- protein binding experiments, tat-transfected cells expressed a consistent increase in kappa B and nuclear factor (NF)-IL-6 binding activity. Accordingly, the pDRCAT and IL-1REK9CAT, carrying tandem repeats of NF-kappa B or NF-IL6 binding motifs, respectively, were activated in TAT-expressing cells. The biological relevance of the TAT- induced IL-6 secretion was addressed by generating 7TD1 cells, an IL-6- dependent mouse cell line, stably expressing the tat gene. These tat- positive cells expressed the endogenous IL-6 gene, secreted high amounts of murine IL-6, and grew efficiently in the absence of exogenous IL-6. Moreover, the tat-positive 7TD1 cells sustained the growth of parental 7TD1 cells and showed a dramatic increase in their tumorigenic potency. These results suggest that TAT protein may play a role in the pathogenesis of some HIV1-associated diseases by modulating the expression of host cellular genes.     

Increased nuclear factor kappa B activation in critically ill patients who die

OBJECTIVES: To determine nuclear factor kappa B (NF-kappa B) activation in mononuclear and neutrophils from critically ill patients and to compare NF-kappa B activation with circulating concentrations of interleukin (IL)-6, IL-8, and soluble intercellular adhesion molecule (sICAM)-1. DESIGN: Observational study. SETTING: University Teaching Hospital, eight-bed intensive care unit in northeast Scotland. PATIENTS: Ten patients admitted to the intensive care unit who fulfilled the criteria for systemic inflammatory response syndrome were studied at 0, 24, 48, and 72 hrs. Six healthy volunteers were also studied. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: NF-kappa B activation was significantly higher in patients compared to healthy volunteers in both neutrophils (p = .001) and mononuclear leukocytes (p = .013). In the six patients who survived to 96 hrs, the level of NF-kappa B activation in mononuclear cells remained constant (p = .9). However, in the four patients who died before 96 hrs, mononuclear cell NF-kappa B activation increased markedly and was significantly higher before death than in those who survived to 96 hrs (p = .0105). NF-kappa B activation in neutrophils similarly remained constant in patients who survived to 96 hrs (p = .4) but did not show the same increase before death. Circulating concentrations of IL-6, IL-8, and sICAM-1 were elevated but were unrelated to leukocyte NF-kappa B activation. CONCLUSIONS: We found NF-kappa B activation in mononuclear and neutrophils in patients with systemic inflammatory response syndrome, which increased markedly before death in mononuclear leukocytes and was not related to plasma IL-6, IL-8, and sICAM-1 concentrations. These data support the need for further study of the role of NF-kappa B activation in mortality from systemic inflammatory response syndrome and sepsis.     

Regulation of T lymphocyte proliferation. Interleukin 2-mediated induction of c-myb gene expression is dependent on T lymphocyte activation state

We previously reported that with time, after antigenic stimulation of antigen-regulated murine T lymphocyte clones, total IL-2-R expression decayed 10-50-fold, commensurate with a decline in the ability of the cells to proliferate to IL-2. However, late after antigenic stimulation, when the cells were refractory to the IL-2-proliferative stimulus, high levels of high affinity IL-2-R remained. In this report we further explore the basis of unresponsiveness to IL-2 in the quiescent clones. We show that the proto-oncogene c-myc is induced in the late cell population by IL-2 to comparable levels observed early after antigen stimulation. IL-2-dependent c-myb induction, however, is seen only early after activation but not in the late-activated population. Analysis of the IL-2-dependent expression of c-myb mRNA with time after antigenic stimulation showed that steadystate c-myb expression declines dramatically with kinetics closely paralleling a decay in IL-2-dependent proliferative ability. In contrast, steadystate c-myc expression remains high throughout this period. Expression of c-myb is critical for proliferation of these cells since antisense oligodeoxy-nucleotide to c-myb can inhibit their IL-2-dependent proliferation. We present evidence for a pathway of c-myb induction via the TCR that is independent of the IL-2/IL-2-R interaction. In addition, the inhibition of IL-2-R-induced c-myb expression by 2-aminopurine and enhanced induction of c-myb via the TCR demonstrate that TCR activation and IL-2-R activation lead to induction of c-myb by different mechanisms.     

Clarithromycin suppresses lipopolysaccharide-induced interleukin-8 production by human monocytes through AP-1 and NF-kappa B transcription factors

Erythromycin and other macrolides are effective for the treatment of chronic inflammatory airway diseases such as diffuse panbronchiolitis (DPB) and chronic sinusitis. The effect of macrolides in DPB is suggested to be anti-inflammatory rather than antibacterial. We investigated the effects of clarithromycin on interleukin-8 (IL-8) production using human peripheral monocytes and the human monocytic leukaemia cell line, THP-1. Bacterial extracts from Escherichia coli, Pseudomonas aeruginosa and Helicobacter pylori, as well as E. coli-derived lipopolysaccharide (LPS), induced IL-8 production. Clarithromycin suppressed this production in a dose-dependent manner in both monocytes and THP-1 cells (49.3-75.0% inhibition at 10 mg/L). A luciferase reporter gene assay with plasmids containing a serially deleted IL-8 promoter fragment showed that both the activator protein-1 (AP-1) and/or the nuclear factor-kappa B (NF-kapp aB) binding sequences were responsible for the LPS and clarithromycin responsiveness of the IL-8 promoter. Consistently, in an electromobility shift assay, LPS increased the specific binding of both AP-1 and NF-kappaB, whereas clarithromycin suppressed it. Moreover, LPS and clarithromycin regulated three other promoters that have either the NF-kappa B or the AP-1 binding sequences: two synthetic (pAP-1-Luc and pNF-kappa B-Luc) and one naturally occurring (ELAM-Luc). Our results indicate that clarithromycin modified inflammation by sup-pressing IL-8 production and that clarithromycin may affect the expression of other genes through AP-1 and NF-kappa B. In addition to treatment of airway diseases, the anti-inflammatory effect of macrolides may be beneficial for the treatment of other inflammatory diseases such as chronic gastritis caused by H. pylori.     

B7—1与B7—2对调节人IL—2基因的转录因子NF—кB和AP—1的的相同作用

为了解B7共刺激对细胞因子，特别是对IL-2mRNA及转录因子NF-кB和AP-1的影响，探讨B7介导的IL-2调节的分子机制，在异基因混合淋巴细胞反应（MLR）体系中分别或联合加入抗B7-1，抗B7-2单克隆抗体和CTLA-4Ig以阻断B7/CD28信号传导，通过竞争性PCR定量检测其对IL-2和IL-4mRNA的影响，并初步测定IFN-γmRNA的改变，同时用转染MHCⅡ类分子及联合转染等量B7-1或B7-2的NIH3T3转基因细胞tDR7,tDR7/B7-1和tDR7/B7-2刺激CD28^ T细胞，通过DNA-蛋白结合实验观察B7对（IL-2转录因子NF-кB和AP-1的影响。结果表明：抗B7-2单抗和CTLA-4Ig可明显抑制B7介导的I轼和IL-4mRNA合成，而抗B7-1单抗仅有轻度抑制作用，2种或3种抗体联合应用时抑制作用相加，MLR1-6小时，单独tDR7即可诱导NF-кB的表达，联合转染B7早期对其结合活力无明显影响，6小时后tDR7诱导作用减弱，B7却可显延长tDR7的诱导作用至72小时，tDR7早期同样可诱导AP-1的表达，联合转染B7分子在24小时内对其有一定的抑制作用，而在反应后期可延长tDR7早期同样可诱导AP-1的表达，联合转染B7分子在24小时内对其有一定的抑制作用，而在反应后期可延长tDR7对AP-1的上调作用，B7-1与B7-2间作用未见明显不同，结论：B7通过减少IL-2mRNA降解和影响基因转录而上调IL-2分泌，并可同时影响多种细胞因子分泌；在转录水平B7-1与B7-2作用未见明显不同，提示两的功能差异可能与细胞表达和时间动力学不同有关，详细了解B7介导的T细胞免疫耐受的分子机制有助于设计更好的临床方案预防移植排斥和GVHD。     

The Fas-associated death domain protein suppresses activation of NF-kappa B by LPS and IL-1 beta

Activation of NF-kappa B by bacterial LPS promotes the upregulation of proinflammatory cytokines that contribute to the pathogenesis of Gram-negative septic shock. LPS activation of NF-kappa B is dependent upon the interaction of two death domain-containing (DD-containing) proteins, MyD88 and IL-1 receptor-associated kinase IRAK. Another DD-containing protein, Fas-associated death domain (FADD), also binds MyD88 through respective DD-DD interactions. Although FADD has been classically described as a proapoptotic signaling molecule, several reports have implicated a role for FADD in mediating NF-kappa B activation. In the present report, we investigated whether FADD could mediate LPS activation of NF-kappa B. Overexpression of FADD blocked LPS-induced NF-kappa B activation, whereas absence of FADD enhanced activation of NF-kappa B by LPS. Further, LPS-induced expression of two NF-kappa B-dependent gene products, IL-6 and KC, was enhanced in FADD(-/-) mouse embryo fibroblasts (MEFs) compared with wild-type. This increase in NF-kappa B activity correlated with enhanced I kappa B degradation. FADD(-/-) MEFs were also resistant to NF-kappa B activation induced by IL-1 beta. Finally, reconstitution of full-length FADD in the FADD(-/-) MEFs completely reversed the enhanced activation of NF-kappa B elicited by either LPS or IL-1 beta. Together, these data indicate that FADD negatively regulates LPS- and IL-1 beta-induced NF-kappa B activation and that this regulation occurs upstream of I kappa B degradation.