Endotoxin-responsive sequences control cachectin/tumor necrosis factor biosynthesis at the translational level

Protein tyrosine kinase inhibitors decrease lipopolysaccharide-induced proinflammatory cytokine production in mixed glia, microglia-enriched or astrocyte-enriched cultures

Proinflammatory cytokines, tumor necrosis factor-alpha (TNF alpha), interleukin-1 (IL-1), and interleukin-6 (IL-6), produced by glial cells have been implicated in the neuropathogenesis of various diseases. However, the signal transduction pathway(s) for the production of these cytokines in glial cells are not well understood. This study examined the effects of two potent protein tyrosine kinase inhibitors, genistein and tyrphostin A25, on lipopolysaccharide (LPS)-induced production of TNF alpha, IL-1 alpha, and IL-6 in mouse primary mixed glia, microglia- or astrocyte-enriched cultures. LPS dose-dependently increased the production of TNF alpha, IL-1 alpha, and IL-6 from the mixed glia cultures. Genistein or tyrphostin A25 significantly inhibited the LPS-induced production of these cytokines. The LPS-induced TNF alpha, IL-1 alpha, and IL-6 production in microglia- or astrocyte-enriched cultures were also inhibited by tyrphostin A25. These results demonstrate that protein tyrosine kinases are involved in the signaling events of the LPS-induced production of TNF alpha, IL-1 alpha, or IL-6 in microglia or astrocytes, which may provide insights into therapeutic interventions in the pathway for cytokine production in the brain.

Mice heterozygous for a deletion of the tumor necrosis factor-alpha and lymphotoxin-alpha genes: biological importance of a nonlinear response of tumor necrosis factor-alpha to gene dosage

The tumor necrosis factors (TNF-alpha and lymphotoxin, or LT-alpha) are important mediators of the immune and inflammatory responses, and it has been proposed that a positive feedback loop could boost the expression of the TNF to sufficiently high levels to fend off infections. To investigate this phenomenon and its biological consequences, we have generated LT-alpha/TNF-alpha knockout mice and compared mice having one or two functional LT-alpha/TNF-alpha alleles. In response to lipopolysaccharide (LPS) stimulation, TNF-alpha levels in the circulation or in the supernatant of macrophage cultures were 20- to 100-fold lower in heterozygous samples than in their wild-type counterparts. This differential increased with the intensity of stimulation and throughout the response, supporting the involvement of a positive feedback loop. Moreover, the heterozygous mice had an increased bacterial load following Listeria monocytogenes infection and exhibited a bimodal response to the association of D-galactosamine and LPS which was similar to that of wild-type mice at low doses of LPS and more like that of homozygous mutants at high doses. These results therefore establish the biological importance of the nonlinear response of TNF-alpha levels to gene dosage, and these mice provide a unique tool to study how the propensity to produce TNF can determine the immunological fitness of individuals.

Activation of the transcription factor MEF2C by the MAP kinase p38 in inflammation

For cells of the innate immune system to mount a host defence response to infection, they must recognize products of microbial pathogens such as lipopolysaccharide (LPS), the endotoxin secreted by Gram-negative bacteria. These cellular responses require intracellular signalling pathways, such as the four MAP kinase (MAPK) pathways. In mammalian cells the MAPK p38 is thought to play an important role in the regulation of cellular responses during infection through its effects on the expression of proinflammatory molecules. One means of understanding the role of p38 in these responses is to identify proteins with functions regulated by p38-catalysed phosphorylation. Here we demonstrate a link between the p38 pathway and a member of the myocyte-enhancer factor 2 (MEF2) group of transcription factors. We found that in monocytic cells, LPS increases the transactivation activity of MEF2C through p38-catalysed phosphorylation. One consequence of MEF2C activation is increased c-jun gene transcription. Our results show that p38 may influence host defence and inflammation by maintaining the balance of c-Jun protein consumed during infection.

Diurnal variation of TNF alpha in the rat brain

Tumor necrosis factor-alpha (TNF alpha) is thought to play a physiological role in the brain. These studies were performed to determine whether a diurnal rhythm of TNF alpha exist in the rat brain. Samples were collected from hippocampus, hypothalamus, cerebral cortex, cerebellum, pons and midbrain at light onset and at 6 h intervals thereafter over a day. A TNF alpha bioassay was used to measure TNF alpha in each area. TNF alpha was highest at light onset in the hypothalamus, hippocampus and cerebral cortex. Levels at light onset were about 10-fold greater than minimal night-time levels. Changes in TNF alpha activity in other brain areas were also evident, but smaller. These results support the hypothesis that TNF alpha has physiological roles in the brain.

NcoI restriction fragment length polymorphism at -308 of the tumor necrosis factor alpha (TNFA) promoter region in Korean

Tumor necrosis factor alpha (TNFA) is a cytokine, which is secreted from activated macrophage, with a broad range of biological activities. The gene encoding TNFA is located in tandem with the TNFB gene within the HLA complex on chromosome 6p21.3. We detected a single base polymorphism in the human TNFA gene promoter region in 300 unrelated Korean individuals. The TNFA promoter region which showed a G to A transition at position of -308 was investigated by NcoI restriction fragment length polymorphism analysis. A biallelic polymorphism of TNFA gene showed fragments of 87/20 bp and 107 bp acting as TNFA*1 allele and TNFA*2 allele, respectively. The allele frequencies of TNFA*1 and TNFA*2 were 0.8783 and 0.1217, respectively. The 21.7% of heterozygosity was observed. No association between promoter region phenotypes of TNFA and the first intron phenotypes of TNFB was observed in Korean. Allele frequencies of Koreans were compared with that of Europeans.

Scarring trachoma is associated with polymorphism in the tumor necrosis factor alpha (TNF-alpha) gene promoter and with elevated TNF-alpha levels in tear fluid

Tumor necrosis factor alpha (TNF-alpha) may play a central role in the disease pathogenesis which occurs as a consequence of chlamydial infection. To investigate the importance of TNF-alpha gene promoter polymorphisms and TNF-alpha levels in tear fluid in scarring trachoma, a large matched-pair case-control study was performed in The Gambia. The -308A allele was present in a higher proportion of patients (28.4%) than controls (18.4%), with an increasing association for homozygotes (chi2 for trend, P = 0.032; allele frequency, 0.163 in patients and 0.099 in controls; chi2, P = 0.025). For the -238A allele, the association was similar but not significant. The disease association was highly significant when the number of either -308A or -238A sites in an individual was considered (P = 0.003). TNF-alpha promoter alleles are tightly linked to some HLA class I and II alleles, but multivariate analysis confirmed that the disease associations were independent of HLA, although a class I allele, A*6802, is also associated with disease. TNF-alpha was more frequently detected in tear samples from patients (27.6%) than from controls (15.9%), increasingly so for higher levels of detectable TNF-alpha (P = 0.015). Among patients, detectable TNF-alpha in tears was highly associated with the presence of ocular chlamydial infection (P < 0.001). The results indicate that TNF-alpha plays a major role in the tissue damage and scarring which occurs as a consequence of Chlamydia trachomatis infection.

Proteasome (prosome) associated endonuclease activity

The 20S proteasome (prosome) is a highly organized multiprotein complex with approximate molecular weight of about 700 kDa. Whilst the role of the proteasome in the processing and turnover of cellular proteins is becoming clearer, its relationship with RNA remains still obscure. Here we focus on the nature and function of proteasome associated endonuclease activity. Thus the involvement of a proteasome alpha-type subunit in RNA-degradation, the catalytic requirements, the interaction of proteasomes with their RNA-substrate and the identification of a well defined cleavage site in the 3'UTR of short-lived cellular mRNAs will be described in detail. All data indicate that proteasomes associated endonuclease activity could be involved in post-transcriptional gene control at the level of translation.

Inhibition of release of tumor necrosis factor-alpha from human vascular tissue and smooth muscle cells by glucocorticoids

OBJECTIVES

Based on our previous study that bacterial lipopolysaccharide stimulates release of tumor necrosis factor (TNF)-alpha from human vascular tissue and smooth muscle cells, we tested the hypothesis that release of TNF could be inhibited by pretreatment with glucocorticoids.

DESIGN

Prospective, repeated-measures analysis of concentration-response relationships.

SETTING

Academic anesthesiology research laboratory.

SUBJECTS

Segments of internal mammary artery and saphenous vein were obtained during coronary artery bypass surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Confluent human smooth muscle cells, cultured from saphenous vein and internal mammary artery, were exposed to 20 micrograms/mL of bacterial lipopolysaccharide following pretreatment for 18 hrs with either 0.1, 1.0, or 10.0 microM of dexamethasone. At 1, 3, 6, 18, and 24 hrs, the culture medium was removed and analyzed for biologically active TNF-alpha using the L929 cell cytotoxicity assay. Smooth muscle cells exposed to bacterial lipopolysaccharide but not treated with dexamethasone served as controls. In control internal mammary cells, bacterial lipopolysaccharide stimulated TNF-alpha release in a time-dependent manner to a peak of 36 +/- 2.3 U/mg of cell protein at 6 hrs, compared with 0.7 +/- 0.3 U/mg of cell protein in cells not exposed to lipopolysaccharide. Dexamethasone inhibited bacterial lipopolysaccharide-stimulated release at all time points in a concentration-dependent manner. For instance, at 6 hrs, TNF-alpha was 12 +/- 2.2, 6.9 +/- 1.7, and 2.3 +/- 0.9 U/mg of cell protein for cells pretreated with 0.1, 1.0, and 10.0 microM of dexamethasone, respectively (p < .05 vs. control). In separate experiments, segments of internal mammary artery and saphenous vein were obtained from five patients who received 1 g of methylprednisolone intravenously during induction of anesthesia, and from seven patients who did not receive methylprednisolone. Bacterial lipopolysaccharide induced release of TNF-alpha from vascular tissues of untreated patients in a time-dependent manner (e.g., 733 +/- 44 U/g of tissue at 6 hrs in saphenous vein). In contrast, in patients treated with methylprednisolone, bacterial lipopolysaccharide did not stimulate release from vascular tissues incubated for up to 24 hrs.

CONCLUSIONS

These results indicate that human vascular tissue, particularly the smooth muscle cell, may be a source of TNF-alpha and that glucocorticoids inhibit release stimulated by bacterial lipopolysaccharide.

Alteration of major cytokines produced by mitogen-activated peritoneal macrophages and splenocytes in T-2 toxin-treated male CD-1 mice

Fusarium T-2 toxin has immunotoxic properties that may be related to the modulation of cytokine expression by cells of the immune system. Male CD-1 mice were used to study the effect of in vivo exposure to T-2 toxin on the alteration of interleukin (IL)-1α, tumor necrosis factor α (TNF), and IL-6 in lipopolysaccharide-stimulated peritoneal macrophages, and IL-2, IL-3, and interferon γ (IFNγ) in concanavalin A (Con A)-stimulated splenocytes. Mice were orally dosed with 0, 0.1, 0.5, and 2.5 mg T-2 toxin/kg body weight for 2 weeks on alternate days. Northern blot analysis of IL-1α, TNF, and IL-6 mRNA from activated peritoneal macrophages showed no significant differences between control and treated groups. Measurements of secreted protein by immunoassay demonstrated suppression of these cytokines in all treated groups, suggesting that T-2 toxin affects the translational or post-translational regulation of these cytokines from peritoneal macrophages. Levels of IL-2, IL-3, and IFNγ mRNA from Con A-activated splenocytes were higher in all treated groups. The increases were significant for IL-2 and IFNγ in the groups receiving low (0.1 mg/kg) and high (2.5 mg/kg) doses of T-2 toxin, and for IL-3 in the group receiving a medium (0.5 mg/kg) dose of this toxin (P ≤ 0.05). Results indicated that T-2 toxin given orally at low or medium doses induces transcription or increases mRNA stability of IL-2, IFNγ, and IL-3. Protein levels of all three cytokines were also increased, indicating that T-2 toxin also increases translational/post-translational efficiency of IFNγ, IL-2, and IL-3. Possible mechanisms in the immunosuppressive effects of T-2 toxin may involve endotoxemia resulting after the toxin administration, alteration of the stability of mRNA, or previously described effects of T-2 toxin on protein synthesis.

Effects of benzoxazinorifamycin KRM-1648 on cytokine production at sites of Mycobacterium avium complex infection induced in mice

Although various antimicrobial agents exhibit appreciable microbicidal activity in the early phase (weeks 2 t0 4) of Mycobacterium avium complex (MAC) infection induced in mice, progressive bacterial regrowth subsequently occurs. To clarify the reason for this pattern of changes, we studied changes in the levels of various cytokines in tissue at sites of infection (spleens and lungs) of MAC-infected mice which were or were not given a benzoxazinorifamycin, KRM-1648 (KRM). Levels of the proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha) and gamma interferon (IFN-gamma) in tissues temporarily increased at around weeks 2 to 4 after infection, rapidly decreased thereafter, and returned to normal by week 8. Similar but somewhat delayed changes were noted for levels of interleukin 10 (IL-10) and transforming growth factor beta (TGF-beta), immunosuppressive cytokines with macrophage (M phi)-deactivating activity, in tissue, except that TGF-beta levels in the spleen remained high during weeks 4 to 8. KRM treatment blocked the increase in the levels of all of those cytokines in tissue in the early phase of infection, most strongly at week 4. IL-6 levels were beneath the limit of detection throughout the observation period. Bacterial loads in the visceral organs decreased during the first 2 weeks, and KRM treatment markedly promoted this decrease. However, regrowth of MAC organisms began at weeks 2 to 4 and continued thereafter, even in KRM-treated mice. Splenocytes and splenic M phi s of MAC-infected mice (week 2) produced and/or released into the culture fluid significant amounts of TNF-alpha (in a cell-bound form), IFN-gamma, and IL-10, but not TGF-beta, during 3 days of cultivation. A substantial amount of TGF-beta was produced during 2 weeks of cultivation of peritoneal M phi s. KRM itself did not significantly affect the IL-10- and TGF-beta-producing ability of cultured M phi s. These findings suggest that IL-10 and TGF-beta play important roles in the regrowth of MAC organisms seen during the course of KRM treatment.

Detection of interleukin-8 mRNA and protein in human colorectal carcinoma cells

Interleukin-8 (IL-8) is a member of the chemokine family of pro-inflammatory chemotactic cytokines and is secreted by some human colorectal carcinoma cell lines. We have used in situ hybridisation and immunohistochemistry to determine whether IL-8 mRNA and protein, respectively, are produced by human colorectal carcinoma cells in vivo. IL-8 mRNA was detected within the cytoplasm of tumour cells in all nine samples tested, including that of a tumour which had metastasised to a lymph node. Non-involved colonic mucosa within the same tissue blocks showed much weaker labelling. IL-8 protein was detected in 74% (23/31) of tumour samples and was mainly localised to the tumour cell cytoplasm. In 30% of cases, staining was heterogeneous, with between 1 and 30% of cells being positive. In some tumour cells, IL-8 showed a perinuclear distribution resembling that found by in situ hybridisation. Some infiltrating leucocytes, endothelial cells and fibroblast-like cells within the tumour sections were also positive for IL-8 mRNA and protein. The possibilities that colorectal tumours produce IL-8 to aid invasion and/or metastasis or as a tumour growth factor are discussed.

Molecular cloning and characterization of a novel mouse macrophage gene that encodes a nuclear protein comprising polyglutamine repeats and interspersing histidines

Simple tandem repeats of the trinucleotide sequence CAG encode homopolymeric stretches of glutamine. Although polyglutamine has been identified in diverse proteins, it is present predominantly in transcription factors. We observed that oncogene-immortalized mouse macrophages express several genes that contain a CAG repeat motif. Therefore, we attempted to clone a novel gene that contains a CAG repeat and is associated with cytokine activation of macrophages. Screening of a mouse macrophage cDNA library with a probe comprising 12 consecutive CAG triplets identified at least one unique clone. The cDNA encodes a protein (named GRP-1 or glutamine repeat protein-1) with 171 amino acids, a calculated molecular mass of 21.6 kDa, and a predicted pI of 10.67. Greater than two-thirds of GRP-1 are only two amino acids, namely glutamine (50%) and histidine (18%). There are four polyglutamine motifs interspersed with histidine-rich regions. There is also a putative nuclear localization signal flanked by sites for possible serine phosphorylation. GRP-1 mRNA was expressed constitutively in some macrophage cell lines and B and T cell lines. Interferon-gamma or lipopolysaccharide augmented GRP-1 mRNA expression in the mouse macrophage cell line ANA-1. Western blot analyses using an antipeptide serum revealed that GRP-1 was localized in the nucleus of ANA-1 macrophages and transfected 3T3 fibroblasts. Overexpression of GRP-1 decreased Sp1-driven chloramphenicol acetyltransferase gene expression in transient cotransfection experiments. Because polyglutamine motifs can cause protein oligomerization and can function as transcriptional activation domains, we suggest that GRP-1 may be a transcription factor associated with interferon-gamma- or lipopolysaccharide-induced activation of macrophages.

Transcriptional and translational control of TNF-alpha gene expression in human monocytes by major histocompatibility complex class II ligands

While non-stimulated primary human monocytes exhibit very low levels of tumor necrosis factor (TNF)-alpha mRNA, direct binding of the staphylococcal exotoxin toxic shock syndrome toxin-1 (TSST-1) to major histocompatibility complex (MHC) class II molecules results in a fast (peak 1 h after stimulation), transient induction (sevenfold) of TNF-alpha mRNA. This induction correlates with a fourfold increase in transcription rates of the TNF-alpha gene, as detected by run-on assays, and does not require de novo protein synthesis. Mapping of DNase-I hypersensitive sites (DHS) discloses two constitutive DHS, one located far upstream (within the TNF-beta promoter) and the other centered at -39 +/- 40 bp relative to the major TNF-alpha transcription start site, suggesting that the TNF-alpha gene was transcriptionally competent even prior to MHC class II engagement. Furthermore, stimulation of human monocytes with either TSST-1 or lipopolysaccharide increases the translational efficiency of TNF-alpha mRNA, as shown by a shift in the distribution of this mRNA species in polysome gradients and the translation rates of TNF-alpha measured by immunoprecipitation from cells pulsed with [35S] methionine. The increase in translation efficiency of TNF-alpha mRNA is independent of the half-life of TNF-alpha transcripts, which under the conditions used is unchanged. Taken together, our data indicate that TNF-alpha expression is tightly regulated by MHC class II ligands, both at the transcriptional and translational levels.

Inhibition of LPS-induced tumor necrosis factor-alpha production by colchicine and other microtubule disrupting drugs

Colchicine has been shown to act as an antiinflammatory agent. In this study, we examined whether colchicine and other microtubule-depolymerizing drugs affected the production of TNF-alpha. When rat peritoneal macrophages were stimulated by LPS, addition of colchicine, vincristine, vinblastine or nocodazole was found to inhibit TNF-alpha release in a concentration-dependent manner. Suppression of TNF-alpha release was not due to interference with secretion as the cytokine did not accumulate intracellularly following colchicine treatment. Colchicine markedly enhanced PGE2 release from LPS-stimulated macrophages. However, addition of the cyclooxygenase inhibitor indomethacin only partially reversed the suppressive effect of colchicine on TNF-alpha production. Colchicine caused a strong reduction of LPS-induced TNF-alpha mRNA accumulation, suggesting that a pretranslational effect may represent the primary mechanism by which colchicine reduced TNF-alpha production. These observations could have clinical relevance in ameliorating undesirable effects due to excessive TNF-alpha production, for example following LPS stimulation of monocytes/macrophages in gram-negative sepsis. Furthermore, these drugs may provide useful tools to study the apparent involvement of the microtubular system in cytokine gene expression and cytokine production.

Two distinct regions in the 3' untranslated region of tumor necrosis factor alpha mRNA form complexes with macrophage proteins

The production of tumor necrosis factor alpha (TNF-alpha), a key proinflammatory cytokine essential for the function of the immune system, is regulated at both the transcriptional and posttranscriptional levels. In this report, we focus on the interaction of TNF-alpha mRNA with macrophage proteins, likely mediators of its post-transcriptional control. Mapping of murine TNF-alpha mRNA by using a combination of RNase protection and RNA gel shift assays revealed that two distinct sites within the 3' untranslated region (3'-UTR) engage in the formation of four major RNA-protein complexes, while no protein binding to the 5'-UTR or coding sequences was detected. The protein-binding site of three RNA-protein complexes, A, B, and C, is positioned between bases 1291 and 1320 inside the AU-rich sequence, a region previously shown to be crucial for both translational repression and lipopolysaccharide inducibility of TNF-alpha. An additional protein complex (complex D) whose binding to the TNF-alpha 3'-UTR was independent of the presence of AU-rich sequences was identified. At least six protein species with apparent molecular masses of 48, 52, 54, 81, 101, and 150 kDa are in direct contact with TNF-alpha mRNA. The RNA-binding proteins are differentially distributed in the cell: complexes A and D are present predominantly in the cytosol, while complexes B and C are found in the nucleus and associated with particulate cytoplasmic fractions. Cytosolic complex A displays comparatively high specificity for TNF-alpha mRNA, while the binding of complexes B and C to TNF-alpha mRNA is readily competed for by other AU-rich sequence-containing RNAs. In summary, these findings demonstrate that two regions of the TNF-alpha mRNA molecule interact with macrophage RNA-binding protein complexes that differ in their core protein composition, cellular distribution, and affinity to TNF-alpha mRNA.

Post-transcriptional stabilization by interleukin-1beta of interleukin-6 mRNA induced by c-kit ligand and interleukin-10 in mouse bone marrow-derived mast cells

We demostrate that a specific combination of cytokines elicits high levels of interleukin (IL)-6 gene expression in mast cells and define the cellular mechanisms of the exogenous cytokine action. The addition of c-kit ligand (KL) and IL-10 to IL-3-derived mouse bone marrow mast cells (BMMC) elicited an approximately 2-fold increase in steady-state IL-6 mRNA levels that peaked after 0.5 h and was followed by the release of approximately 0.2 ng of IL-6/10(6) cells by 5-7 h. The addition of IL-1beta to KL + IL-10 elicited a prolonged approximately 12-fold increase in the level of IL-6 mRNA by 3-5 h and an approximately 50-fold increase in the level of IL-6 protein released by 7 h. As determined by nuclear run-on analysis, KL + IL-10 stimulated IL-6 gene transcription within 0.5 h, and the addition of IL-1beta did not increase transcription. Instead, IL-1beta slowed by approximately 8-fold the decay of IL-6 mRNA as compared to its decay in BMMC stimulated with KL + IL-10 alone. The exposure of BMMC to cycloheximide 0.5 h before the addition of the three exogenous cytokines inhibited by approximately 50% the level of IL-6 mRNA generated but did not inhibit the effects of KL + IL-10, indicating that IL-1beta induces the synthesis of a protein that stabilizes IL-6 mRNA. The stabilization of IL-6 mRNA was inhibited by the addition of actinomycin D at 0.5 but not 3 h after BMMC were stimulated with IL-1beta in combination with KL + IL-10, suggesting that once transcribed, the stabilizing protein is long-lived. The addition of cycloheximide to BMMC after stimulation with KL + IL-10 with or without IL-1beta increased the levels of steady-state IL-6 mRNA compared to levels in cells without drug, indicating that in addition to stimulating IL-6 transcription, KL + IL-10 induces a protein factor that destabilizes IL-6 mRNA. Thus, there exists a novel Fcepsilon receptor type I-independent mechanism by which a mast cell can provide substantial amounts of IL-6 protein in response to the synergistic action of KL and IL-10 to induce IL-6 gene transcription, and IL-1beta to stabilize otherwise short-lived IL-6 transcripts.

The antiangiogenic agent linomide inhibits tumor necrosis factor-alpha secretion via inhibition of its synthesis

We have previously reported that linomide, a quinoline-3-carboxamide, has antitumor effects against prostatic cancers in vivo through its ability to inhibit tumor angiogenesis. Subsequently, we reported that linomide inhibits several steps in the process of angiogenesis, including direct effects on endothelial cell proliferation and their chemotactic migration and invasion. Besides these direct effects, linomide's antiangiogenic activity also involves indirect effects secondary to inhibition of tumor infiltration of macrophages and their ability to secrete the angiogenic factor tumor necrosis factor-alpha (TNF-alpha). The current studies were conducted to gain insight into the mechanism by which linomide inhibits macrophage TNF-alpha secretion. The virally transformed RAW 264.7 mouse macrophage cell line was used as a model system. Chronic in vitro exposure (7 days) to 81-650 microM linomide is cytostatic to RAW cells. Such chronic exposure to linomide significantly decreased (P < 0.05) RAW cells' baseline ability to secrete TNF-alpha and also their ability to up-regulate TNF-alpha secretion in response to lipopolysaccharide (LPS) challenge. Ribonuclease protection assays demonstrated that linomide's ability to inhibit baseline and LPS-challenged TNF-alpha secretion is not functioning at the mRNA level, because steady-state levels of TNF-alpha mRNA do not change in response to linomide. Linomide's ability to inhibit TNF-alpha secretion is not associated with an increase in cell-associated TNF-alpha levels. Immunoprecipitation experiments demonstrated that linomide did not inhibit the normal proteolytic processing of the initial 26 kDa plasma membrane-bound TNF-alpha to the secreted 17 kDa soluble form. These results demonstrate that linomide inhibits TNF-alpha secretion by inhibition of the synthesis of the TNF-alpha protein. Linomide's ability to inhibit TNF-alpha protein synthesis is not due to an inhibition of general protein synthesis or secretion and is not mediated via a change in cyclic adenosine monophosphate levels.

Increased levels of tumor necrosis factor-alpha and interleukin-6 protein and messenger RNA in human peripheral blood monocytes due to titanium particles

Cytokines produced by macrophages in the periprosthetic membranes surrounding joint replacements have been implicated as causal agents in osteolysis and prosthetic loosening. The present study characterizes the response of human peripheral blood monocytes to titanium particles. Monocytes were obtained from volunteers and blood that had been donated to the American Red Cross and were cultured in the presence of titanium particles (one to three micrometers in diameter). There were consistent dose-dependent increases in the production of TNF-alpha (tumor necrosis factor-alpha) and IL-6 (interleukin-6) protein, with the greatest stimulation generally observed with a concentration of 6 x 10(5) to 6 x 10(6) particles of titanium per milliliter. The level of TNF-alpha was the greatest (fifty to 1000 times greater than the control level) after eight hours of exposure to titanium particles; the level of IL-6 was two to five times greater than the control level after sixteen hours of exposure. These increases were similar to those observed after stimulation with lipopolysaccharide and depended on de novo synthesis rather than on release from intracellular stores. The production of TNF-alpha was inhibited in a dose-dependent manner by the translational inhibitor cycloheximide and the transcriptional inhibitor actinomycin D, indicating the requirement for both mRNA (messenger RNA) and protein synthesis for the induction of cytokine synthesis by titanium particles. Although the increase in the levels of cytokine mRNA in response to titanium was rapid (thirty to ninety minutes), the increase in the level of TNF-alpha mRNA preceded that of IL-6 mRNA. The level of TNF-alpha mRNA was the greatest at ninety minutes and the level of IL-6 mRNA was the greatest at three hours. After stimulation with titanium particles, the level of TNF-alpha mRNA was increased as much as fivefold and the level of IL-6 mRNA, as much as twelvefold.

Evidence for a predominant proinflammatory conjunctival cytokine response in individuals with trachoma

Immune responses to Chlamydia trachomatis infection in trachoma do not protect against reinfection or the development of scarring and blindness. In addition, the immunoregulatory contribution of cytokines to the development of conjunctival histopathology or protection is undefined. In this study, conjunctival cytokine mRNA transcripts were compared among subgroups of chlamydia infection status and ocular disease presentations of 50 individuals from an area where trachoma is endemic. There was a significant association of elevated interleukin (IL)-1beta, transforming growth factor beta1, and tumor necrosis factor alpha transcripts with infection, follicular inflammation, and scarring. Both gamma interferon (IFN-gamma) and IL-2 transcripts were significantly associated with infection; slightly elevated IL-2 levels were found in inflammatory disease. High IFN-gamma transcript levels were present with follicles and inflammatory disease and to a lesser extent with inflammatory scarring. The role of IFN-gamma in protection from infection or disease was not apparent from this study, since transcripts were frequently present in both chlamydial infection and disease. IL-12 (p40) transcripts were elevated in adults and children in association with follicular inflammation but not with scarring. IL-4, IL-5, and IL-10 transcripts were not detected in any samples. In conclusion, C. trachomatis infection stimulates local cytokines which favor a strong cell-mediated and proinflammatory response in both the early and later manifestations of trachoma. In addition, cytokine transcript levels that were associated with disease but no infection were characteristically lower overall than when chlamydia was present.

Promoter region polymorphism in the human TNF-alpha gene is not associated with lichen sclerosus

The pathogenesis of lichen sclerosus remains unknown. However, it has been frequently associated clinically with autoimmunity. The MHC haplotype A1, B8, DR3 is associated with many autoimmune conditions and has also been associated with the uncommon allele of the tumour necrosis factor (TNF-alpha) promoter polymorphism. This allele is also associated with higher production of TNF in vivo and in vitro, and thus it has been speculated that it is the TNF-alpha gene which underlies the genetic association of many diseases with the autoimmune haplotype. There have been many reports of HLA associations with lichen scleroses, but these have not been concordant. We therefore decided to analyse the TNF-alpha polymorphism in patients with lichen scleroses to determine if TNF-alpha was likely to play a role in susceptibility or severity of lichen scleroses. No association between alleles of the TNF-alpha polymorphism and lichen scleroses was found.

Engagement of tumor necrosis factor mRNA by an endotoxin-inducible cytoplasmic protein

BACKGROUND

Tumor necrosis factor (TNF) production by macrophages plays an important role in the host response to infection. TNF-alpha gene expression in RAW 264.7 macrophages is predominantly regulated at the translational level. A key element in this regulation is an AU-rich (AUR) sequence located in the 3' untranslated region (UTR) of TNF mRNA. In unstimulated macrophages, the translation of TNF mRNA is inhibited via this AUR sequence. Upon stimulation with LPS, this repression is overcome and translation occurs. In this study, we attempted to identify cellular proteins that interact with the AUR sequence and thereby regulate TNF mRNA translation.

MATERIALS AND METHODS

RNA probes corresponding to portions of TNF mRNA 3' UTR were synthesized. These labeled RNAs were incubated with cytoplasmic extracts of either unstimulated or lipopolysaccharides (LPS)-stimulated RAW 264.7 macrophages. The RNA/protein complexes formed were analyzed by gel retardation. Ultraviolet (UV) cross-linking experiments were performed to determine the molecular weight of the proteins involved in the complexes.

RESULTS

TNF mRNA AUR sequence formed two complexes (1 and 2) of distinct electrophoretic mobilities. While the formation of complex 1 was independent of the activation state of the macrophages from which the extracts were obtained, complex 2 was detected only using cytoplasmic extracts from LPS-stimulated macrophages. Upon UV cross-linking, two proteins, of 50 and 80 kD, respectively, were capable of binding the UAR sequence. The 50-kD protein is likely to be part of the LPS-inducible complex 2, since its binding ability was enhanced upon LPS stimulation. Interestingly, complex 2 formation was also triggered by Sendaï virus infection, another potent activator of TNF mRNA translation in RAW 264.7 macrophages. In contrast, complex 2 was not detected with cytoplasmic extracts obtained from B and T cell lines which are unable to produce TNF in response to LPS. Protein tyrosine phosphorylation is required for LPS-induced TNF mRNA translation. Remarkably, the protein tyrosine phosphorylation inhibitor herbimycin A abolished LPS-induced complex 2 formation. Complex 2 was already detectable after 0.5 hr of LPS treatment and was triggered by a minimal LPS dose of 10 pg/ml.

CONCLUSIONS

The tight correlation between TNF production and the formation of an LPS-inducible cytoplasmic complex suggests that this complex plays a role in the translational regulation of TNF mRNA.

Effect of a novel topical immunomodulator, S-28463, on keratinocyte cytokine gene expression and production

A new immunomodulating agent, imiquimod, has been reported to have antiviral and antitumor activities in animal models. S-28463 (4-amino-2-ethoxymethyl-alpha, alpha-dimethyl-1H-imidazo[4, 5-c]quinoline-1-ethanol), an analog of imiquimod, has more potent antiviral activity in animals than imiquimod. It has also been shown to be more potent at inducing cytokines in human blood in vitro. However, its precise role as an immunomodulator in the skin has not been determined. We investigated the effect of S-28463 on human keratinocyte (KC) production of interferon-alpha (IFN-alpha) and other proinflammatory cytokines, including interleukin (IL)-1alpha, IL-8, and tumor necrosis factor-alpha (TNF-alpha). Human KC were incubated with S-28463 at two concentrations (1 microgram/ml and 10 micrograms/ml) for 6 h. Cytokine gene expression was analyzed by reverse-transcriptase PCR. In human KC, S-28463 stimulated significant increases in IFN-alpha mRNA at both concentrations. IL-1alpha mRNA increased 1.4-fold at 10 micrograms/ml. IL-8 mRNA was upregulated 2.5-fold at 10 micrograms/ml. Twenty-four hours after treatment, IL-1 alpha, IL-8, and TNF-alpha protein were increased, but IFN-alpha was below the level of detection. These results suggest that in the skin, S-28463-induced-IL-1 alpha, IL-8, and TNF-alpha production may be involved in the immunomodulating action of S-28463.

Tumour necrosis factor is expressed in cardiac tissues of patients with heart failure

Tumour necrosis factor (TNF), a cytokine produced mainly by macrophages, has also been found in vascular smooth muscle cells. Elevated serum levels of TNF have been reported in various cardiac diseases, especially congestive heart failure (CHF). Although the myocardium produces several cytokines, the expression of TNF in human cardiac tissue has not yet been demonstrated. We examined TNF expression in right atrial (RA) specimens obtained from 15 patients during cardiac surgery with immunohistochemistry using an anti-human TNF monoclonal antibody, enzyme-linked immunosorbent assay (ELISA) and reverse transcriptase polymerase chain reaction (RT-PCR). TNF immunoreactivity was found only in cardiac myocytes and some vascular smooth muscle cells of small vessels of specimens from patients with severe CHF (3/5), and not in those from patients without severe CHF (0/10). ELISA of four RA specimens revealed that RA tissues from two patients with severe CHF contained more TNF than did those from two patients without severe CHF (3.1 and 4.7 pg/mg vs. 0.1 and 0.3 pg/mg). RT-PCR revealed TNF mRNA in all seven cases we examined. It was concluded that TNF mRNA is expressed by atrial tissue. The production of immunoreactive TNF-like peptides by myocytes and vascular smooth muscle cells is augmented in patients with severe CHF.

In situ changes in the relative abundance of human epidermal cytokine messenger RNA levels following exposure to the poison ivy/oak contact allergen urushiol

Abstract: Epidermal keratinocytes in culture have been shown to produce many cytokines, and their proteins have been identified in skin tissue samples. It has therefore been assumed that these cytokines are transcribed in vivo by the epidermis in response to contact allergens. In this report, in situ hybridization was used to detect the messenger RNAs for interleukin-1 alpha (IL-1 alpha), interleukin-1 beta (IL-1 beta) and tumour necrosis factor-alpha (TNF-alpha) in samples of human skin prior to and at various times after application of urushiol, the immunogenic component of poison ivy/oak. In sensitive subjects, IL-1 alpha and TNF-alpha mRNAs showed a progressive increase in transcript levels that paralleled the clinical and histological features of the inflammatory process. The time-course of the IL-1 beta response differed from that of IL-1 alpha and TNF-alpha, in that there was an early (by 6 h after urushiol administration) elevation in IL-1 beta mRNA that occurred before there was evidence of inflammation and had returned to background levels by 72 h when the reaction had reached its peak. In contrast to urushiol-sensitive subjects, urushiol-anergic individuals did not exhibit an increase in IL-1 alpha, IL-1 beta or TNF-alpha mRNA levels. The data provide evidence for an in vivo role for epidermal IL-1 alpha, IL-1 beta and TNF-alpha transcription in the regulation of IL-1 beta and TNF-alpha polypeptide levels in the epidermis in response to this common contact allergen.

Dissociation between cytokine mRNA expression and protein production in shigellosis

In our study, infection with Shigella dysenteriae type 1 (n = 16) or Shigella flexneri in adults (n = 5) was associated with a gradual accumulation of mRNA for interleukin (IL)-1 beta, tumor necrosis factor (TNF)-alpha, IL-6, transforming growth factor-beta, IL-10, IL-4, TNF-beta, interferon (IFN)-gamma and perforin in the rectal biopsy samples during the convalescent stage of the disease demonstrated by in situ hybridization. In contrast, immunohistochemical staining in rectal tissues of cytokine protein-producing cells at the single-cell level exhibited a steady-state expression during 2-36 days after the onset of the disease. The frequency of cytokine mRNA-expressing cells varied in the range of 3-100-fold higher than that of the corresponding protein-synthesizing cells. The accumulation of cytokine mRNA in vivo during shigellosis represented a long-lasting phenomenon throughout the disease course, and may be linked to its immunopathogenesis. The results also indicate that assessment of both protein and mRNA in vivo may provide complementary information. Stimulation in vitro of peripheral blood mononuclear cells from normal healthy donors with Shigella-derived lipopolysaccharide or shiga toxin was carried out to elucidate the role of Shigella antigens in the regulation of translation of cytokine-specific mRNA. The incidence of cytokine (IFN-gamma, IL-6 and TNF-alpha) mRNA- and cytokine protein-expressing cells was very similar and congruent after both these Shigella-derived stimuli. We could, thus, not find evidence for shiga toxin-induced down-regulation of cytokine mRNA translation as the explanation for the observed discrepancy between cytokine mRNA and protein levels in the tissue biopsies.

CNI-1493 inhibits monocyte/macrophage tumor necrosis factor by suppression of translation efficiency

Tumor necrosis factor (TNF) mediates a wide variety of disease states including septic shock, acute and chronic inflammation, and cachexia. Recently, a multivalent guanylhydrazone (CNI-1493) developed as an inhibitor of macrophage activation was shown to suppress TNF production and protect against tissue inflammation and endotoxin lethality [Bianchi, M., Ulrich, P., Bloom, O., Meistrell, M., Zimmerman, G. A., Schmidtmayerova, H., Bukrinsky, M., Donnelley, T., Bucala, R., Sherry, B., Manogue, K. R., Tortolani, A. J., Cerami, A. & Tracey, K. J. (1995) Mol. Med. 1, 254-266, and Bianchi, M., Bloom, O., Raabe, T., Cohen, P. S., Chesney, J., Sherry, B., Schmidtmayerova, H., Zhang, X., Bukrinsky, M., Ulrich, P., Cerami, A. & Tracey, J. (1996) J. Exp. Med., in press]. We have now elucidated the mechanism by which CNI-1493 inhibits macrophage TNF synthesis and show here that it acts through suppression of TNF translation efficiency. CNI-1493 blocked neither the lipopolysaccharide (LPS)-induced increases in the expression of TNF mRNA nor the translocation of nuclear factor NF-kappa B to the nucleus in macrophages activated by 15 min of LPS stimulation, indicating that CNI-1493 does not interfere with early NF-kappa B-mediated transcriptional regulation of TNF. However, synthesis of the 26-kDa membrane form of TNF was effectively blocked by CNI-1493. Further evidence for the translational suppression of TNF is given by experiments using chloram-phenicol acetyltransferase (CAT) constructs containing elements of the TNF gene that are involved in TNF translational regulation. Both the 5' and 3' untranslated regions of the TNF gene were required to elicit maximal translational suppression by CNI-1493. Identification of the molecular target through which CNI-1493 inhibits TNF translation should provide insight into the regulation of macrophage activation and mechanisms of inflammation.

Interleukin 1 beta and phorbol ester induce tumour necrosis factor alpha production in a hepatic cell line (HepG2)

Tumour necrosis factor "alpha" (TNF "alpha") is a pleiotropic cytokine that is produced mainly by monocytes and macrophages. TNF "alpha" appears to be responsible for many of the inflammatory and necrotic changes seen in malignant or infectious liver diseases. In addition, blood levels of TNF "alpha" have been reported to be elevated in those with hepatic diseases. Although TNF "alpha" is synthesized mainly by monocytes and macrophages, its production has recently been found in nonhaemopoietic cells as well. Therefore we have used the human liver cell line HepG2 to test for the inducible production of TNF "alpha" in hepatic parenchymal cells. No constitutive TNF "alpha" gene expression was detected by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). However, treatment with the proinflammatory cytokine interleukin 1 "beta" (IL-1 "beta") or phorbol 12-myristate-acetate (PMA) led to a marked increase in TNF "alpha" mRNA levels. Maximal TNF "alpha" mRNA levels were observed after 3-h incubation periods, decreased thereafter and became undetectable after 12 h. The culture supernatant from cells treated with IL-1 "beta" or PMA contained significant amounts of TNF "alpha" protein which was immunologically detectable and biologically active. We believe that our report of inducible TNF "alpha" production in this widely available hepatic cell line adds a valuable tool for understanding TNF "alpha" gene expression in nonhaematopoietic cells.

Distinct mRNA-binding proteins interacting with short repeat sequences of the 3' UTR may be involved in the post-transcriptional regulation of the mouse catalase gene, Cas-1

The 3' untranslated region (UTR) of the mouse catalase gene (Cas-1) is demonstrated to be an active site for specific protein interactions. We have identified two regions of the Cas-1 3' UTR mRNA that bind to distinct cytoplasmic proteins: one containing a (CA)31 repeat with UA octomer (RNA 5) and another with a (U)15 tract (RNA 6). RNA 5 interacts with one set of protein complexes (a, b, and c) whereas RNA 6 interacts with another (x, y, and z) in a sequence-specific manner. These RNA-protein complexes are development-, tissue-, and genotype-specific. The proteins involved in the two sets of complexes are different. Further characterization of the proteins involved in these interactions has revealed the presence of a single protein of approximately 70 kD that binds RNA 5, and two proteins approximately 38 kD and approximately 47 kD that bind to RNA 6. The approximately 70-k D and approximately 38-kD proteins are also associated with the polysomal fractions and may play a role in the post-transcriptional regulation of Cas-1. Although the observed 3' UTR RNA-protein interactions are hypothesized to be important in post-transcriptional regulation of this gene in rodents, specific RNA sequences and their associated proteins identified in this report would now permit the elucidation of the mechanisms of their action at the molecular level.

Differential regulation of tumour necrosis factor-alpha mRNA degradation in macrophages by interleukin-4 and interferon-gamma

Interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) have been reported previously to mediate similar as well as antagonistic effects on murine macrophage functions. One effect common to both is the enhancement of tumour necrosis factor-alpha (TNF-alpha) secretion in macrophages. To assess further the effects of these two lymphokines on macrophage TNF-alpha production, we investigated the role of these lymphokines in the induction and stability of TNF-alpha messages along with interleukin-1 (IL-1) as a comparison. IFN-gamma and IL-4 increased lipopolysaccharide (LPS)-induced TNF-alpha, IL-1 steady-state message levels. In contrast to IL-1 messages, whose degradation was not significantly affected by either lymphokine, the stability of TNF-alpha messages differed after IFN-gamma and IL-4 treatment. Although IL-4 treatment increased the TNF-alpha transcription rate, an increase in the degradation rate of TNF-alpha mRNA in the IL-4-treated cells resulted in a lower level of steady-state mRNA than in the IFN-gamma-treated cells. Additionally, a 18,000 MW cytoplasmic factor was found to have specific binding activity to the AU-rich sequences of the TNF-alpha message in peritoneal macrophages. Although the binding activity of this factor was not affected by either IFN-gamma or IL-4, the binding of the factor to AU-rich sequences appeared to be important in the rapid degradation of TNF-alpha messages. Thus IFN-gamma and IL-4 may differentially affect the post-transcriptional control of TNF-alpha gene expression. And this lymphokine-mediated post-transcriptional control of the TNF-alpha gene does not appear to involve the alteration of binding activity of the 18,000 MW AU-rich sequence binding factor.

Dialysable leucocyte extract (DLE) reduces lipopolysaccharide-induced tumour necrosis factor secretion in human leucocytes

Dialysable leucocyte extract (DLE), obtained from lysed leucocytes, provide clinical effectiveness in a broad spectrum of diseases. Tumour necrosis factor (TNF) is raised in AIDS patients leading to an increase in human immunodeficiency virus (HIV) replication in vitro [1,2], whereas progression to AIDS in asymptomatic HIV infected individuals is retarded under treatment with DLE. In the present study we tested the DLE effect in vitro on both TNF biological activity (cytotoxicity) in L929 cells and its induction by lipopolysaccharide (LPS) in human monocytes as well as in whole blood from healthy donors. When monocytic cells were simultaneously exposed to LPS and DLE during a period of 5 1/2 hours, the induction of TNF was strongly diminished. The same inhibitory effect of DLE on TNF induction was observed when LPS was added to the culture medium prior to DLE. No significant effect of DLE on TNF-mediated cytotoxicity, even in the presence of the highest concentrations of DLE tested, was detected. DLE treatment of whole human blood regulates responses to LPS: simultaneous in vitro exposure to endotoxin provokes a remarkable decrease (4- and 1.6-fold) of TNF release. In pre-incubation experiments, TNF production was largely reduced or completed abrogated. These results could, in part, explain the in vivo observed effect, when under treatment with this extract, the progression to AIDS of HIV-infected individuals was retarded. The results suggest that "natural' substances like DLE may be important immunomodulators in inflammatory diseases.

Characterization of the distal promoter element of halobacteria in vivo using saturation mutagenesis and selection

The sequence and spacing requirements of the archaeal "distal promoter element' (DPE) were examined by randomizing positions -19 to -32 upstream of the transcriptional start site of the ferredoxin (fdx) promoter of Halobacterium salinarium. This randomized promoter library containing 4(14) entries was cloned in front of the dihydrofolate reductase (DHFR) reporter gene and transformed into Haloferax volcanii. Two approaches were used to characterize these synthetic promoters. First, 1040 independent clones were randomly chosen and their degrees of trimethoprim resistance were determined. The sequences of 20 clones that were either sensitive, partially resistant or very resistant, respectively, were determined. Secondly, the transformed library was screened by direct selection for high-activity promoters by growing transformants in the presence of trimethoprim. Both approaches produced the following consensus sequence for a halobacterial promoter: (Formula: see text) (where R = A or G; Y = C or T; W = A or T; S = G or C; N = A, C, G or T). Further characterization of two sensitive, two partially resistant, and two very resistant clones verified that DHFR activity and cell phenotype are directly correlated. Sensitive clones did not contain detectable dhfr mRNA, whereas partially resistant clones contained a 700 nucleotide (nt)-long transcript, and very resistant clones contained both the 700nt-long transcript and a second, more abundant, 500nt-long truncated transcript. Quantification of the dhfr mRNA and DHFR enzyme activity suggests that the 3'-untranslated region of the dhfr transcript, missing from the shorter transcript, functions as a negative regulator of translation.

MKK3- and MKK6-regulated gene expression is mediated by the p38 mitogen-activated protein kinase signal transduction pathway

The p38 mitogen-activated protein (MAP) kinase signal transduction pathway is activated by proinflammatory cytokines and environmental stress. The detection of p38 MAP kinase in the nucleus of activated cells suggests that p38 MAP kinase can mediate signaling to the nucleus. To test this hypothesis, we constructed expression vectors for activated MKK3 and MKK6, two MAP kinase kinases that phosphorylate and activate p38 MAP kinase. Expression of activated MKK3 and MKK6 in cultured cells caused a selective increase in p38 MAP kinase activity. Cotransfection experiments demonstrated that p38 MAP kinase activation causes increased reporter gene expression mediated by the transcription factors ATF2 and Elk-1. These data demonstrate that the nucleus is one target of the p38 MAP kinase signal transduction pathway.

Interleukin 10 (IL-10) regulation of tumour necrosis factor alpha (TNF-alpha) from human alveolar macrophages and peripheral blood monocytes

BACKGROUND

Regulation of the inflammatory response within the human lung is essential to prevent this important part of the normal host defence response becoming a pathological process. Tumour necrosis factor alpha (TNF-alpha) is a cytokine involved in the pathogenesis of shock and in granuloma formation, tissue necrosis, and fibrosis in many organ systems including the lung. Interleukin 10 (IL-10) has been proposed as having an inhibitory effect on the production of several inflammatory cytokines including TNF-alpha.

METHODS

The effect of IL-10 administration on TNF-alpha production was explored in human alveolar macrophages and peripheral blood monocytes from matched individuals. The effects of IL-10 on TNF-alpha protein production were determined by sandwich enzyme linked immunosorbant assay (ELISA), whereas the TNF-alpha mRNA response was established by Northeren blotting using a TNF-alpha specific oligonucleotide probe. The protein synthesis inhibitors actinomycin D and cyclohexamide were utilised to monitor IL-10 effects on mRNA degradation and de novo protein synthesis, respectively.

RESULTS

The lipopolysaccharide-mediated TNF-alpha production in alveolar macrophages was reduced from 3.508 (0.629) to 2.035 (0.385) ng/ml by 100 U/ml IL-10. Lipopolysaccharide-induced TNF-alpha production in peripheral blood monocytes was reduced from 2.035 (0.284) to 0.698 (0.167) ng/ml. TNF-alpha gene expression was also inhibited in both alveolar macrophages and peripheral blood monocytes; lipopolysaccharide-induced TNF-alpha mRNA was reduced by 47.8 (15.2)% and 83.1 (4.2)%, respectively, by IL-10. The IL-10 mediated suppression of TNF-alpha mRNA was unaffected by addition of cyclohexamide, suggesting that de novo protein synthesis was not required for TNF-alpha inhibition. mRNA stability experiments indicated no acceleration in lipopolysaccharide-induced TNF-alpha mRNA degradation in response to IL-10.

CONCLUSIONS

These findings suggest that IL-10 is a potent inhibitor of TNF-alpha expression and release from alveolar macrophages and peripheral blood monocytes, and thus it may have an important role in the cytokine network of the pulmonary immune response.

Human blood vessels release tumor necrosis factor-alpha from a smooth muscle cell source

OBJECTIVES

In septic shock, the principal source of increased plasma concentrations of tumor necrosis factor alpha (TNF) is considered to be the macrophage. Release from the macrophage is stimulated by bacterial lipopolysaccharide (endotoxin). We tested the hypothesis that vascular tissue also responds to endotoxin by releasing TNF.

DESIGN

Prospective repeated measures analysis of timed-release curves.

SETTING

Anesthesia research laboratory in an academic medical center.

SUBJECTS

With Institutional Review Board approval and patient consent, segments of internal mammary artery and saphenous vein were obtained during coronary artery bypass surgery.

INTERVENTIONS

None

MEASUREMENTS AND MAIN RESULTS

Segments of saphenous veins were incubated for 24 hrs in the presence or absence of bacterial lipopolysaccharide. At 0.5, 1, 3, 6, and 24 hrs, medium was assayed for TNF. In other experiments, smooth muscle cells were cultured from saphenous veins, incubated with our without bacterial lipopolysaccharide, and a time-course of TNF release determined. Bacterial lipopolysaccharide (20 micrograms/mL) significantly stimulated release of TNF from venous tissue in a time-dependent manner. At 0.5 hrs, TNF was undetectable in untreated tissue and was 48 +/- 8 U/g wet tissue weight in the presence of bacterial lipopolysaccharide. At 3 hrs, TNF was 43 +/- 27 U/g wet tissue weight in untreated and 388 +/- 185 U/g wet tissue weight in treated (p < .01 vs. control) tissue. Segments of internal mammary artery responded in a similar manner. In smooth muscle cells cultured from saphenous vein and internal mammary artery, bacterial lipopolysaccharide triggered the release of TNF. At 3 hrs, the release of TNF in control cells was 0.2 +/- 0.15 U/mg cell protein and 17 +/- 2 U/mg in the presence of 20 micrograms/mL of bacterial lipopolysaccharide (p < .01 vs. control).

CONCLUSIONS

Human blood vessels, both artery and vein, produce TNF potentially from a smooth muscle cell source in response to bacterial lipopolysaccharide.

Regulation of inducible nitric oxide synthase expression by macrophage purinoreceptors and calcium

Macrophage activation is central to the progression of multiple diseases via the release of inflammatory mediators such as cytokines and nitric oxide. Despite the recognized overlap in the regulatory mechanisms involved in mediator production, little formation exists regarding receptor-initiated signaling pathways that coordinately control multiple end points, such as tumor necrosis factor-alpha (TNF-alpha) and nitric oxide production. In this study, the expression of inducible nitric oxide synthase (iNOS) in macrophages is shown to be regulated by calcium and by a purinoreceptor signaling system. The P2Y purinoreceptor partial agonist, 2-methylthio-ATP (2-MeS-ATP), inhibits the expression of iNOS induced by lipopolysaccharide (LPS) plus interferon-gamma (IFN-gamma) in primary macrophages. Additionally, 2-MeS-ATP attenuates the expression of iNOS in macrophages isolated from CD-1 mice challenged with LPS, and it inhibits LPS-induced TNF-alpha and interleukin-1 alpha (IL-1 alpha) release, thereby preventing endotoxic death. Thus, purinoreceptors and calcium are likely to be critical for macrophage activation and the production of inflammatory mediators stimulated by LPS.

Short- or long-term effects of a low-protein diet on fibronectin and transforming growth factor-beta synthesis in Adriamycin-induced nephropathy

Increased synthesis and gene expression of fibronectin or transforming growth factor-beta (TGF-beta) have been reported to be involved in the progressive process of doxorubicin hydrochloride (Adriamycin)-induced nephropathy. In the present study, the effects of dietary protein restriction on the synthesis and gene expression of fibronectin or TGF-beta were investigated by immunoprecipitation, Northern blotting, and TGF-beta bioassay in this model after subjects were given either short- or long-term low-protein diets. In the long-term diet experiment, either a normal protein diet (NPD, 20%) or low-protein diet (LPD, 5%) was fed to the Adriamycin rats for 8 weeks after the injection of Adriamycin. An 8-week LPD significantly ameliorated kidney destruction and remarkably reduced the fibronectin synthesis. Furthermore, the significant decreases of the latent TGF-beta secretion and the expression of TGF-beta 1 mRNA were observed in the Adriamycin rats fed an 8-week LPD. In the short-term diet experiment, an NPD or LPD was fed to the Adriamycin rats for 2 weeks at weeks 4, 8, or 16 after the injection of Adriamycin. A 2-week LPD did not ameliorate kidney damage. Although fibronectin synthesis by the renal cortex in the Adriamycin rats was remarkably reduced by a 2-week LPD, there was no significant decrease in the latent TGF-beta secretion in the Adriamycin rats. The mRNA expressions of fibronectin or TGF-beta 1 were not affected by a 2-week LPD in the Adriamycin rats at any stage. In conclusion, decreased fibronectin and TGF-beta synthesis may be one of the mechanisms by which the long-term dietary protein restriction ameliorates kidney damage. On the other hand, a 2-week LPD affected the only fibronectin synthesis, which thus suggested that an LPD might exert a quicker influence on the protein synthesis of fibronectin than on the transcriptional events of fibronectin.

Regulatory mechanisms of antitumor T cell responses in the tumor-bearing state

Tumor-bearing hosts develop antitumor immune responses. However, a number of immunosuppressive mechanisms come into operation with the progression of tumor growth. This article will review the observations regarding the modulation of antitumor immune responses in the tumor-bearing state, and consider the mechanisms underlying tumor-induced immune defects, especially in the light of the induction of an abnormal cytokine network. We will also describe the restoration of suppressed antitumor immune responses by administration of a particular cytokine, interleukin-12.

Effects of 3' untranslated and intergenic regions on gene expression in Trypanosoma cruzi

The effects of 3' untranslated regions (UTR) and intergenic regions (INT), from various Trypanosoma cruzi stage-specific and constitutive genes, on the expression of the reporter firefly luciferase gene (luc), were studied using stable episomal transformation. The 3' UTR influenced luciferase expression by changing the steady-state level and/or the translation efficiency of luc mRNA. Glycoprotein 72 gene (gp72), glycoprotein 85 gene (gp85) or amastin gene (ama) 3' UTR decreased the luc mRNA level 6- to 14-fold, compared to the glyceraldehyde 1-phosphate dehydrogenase gene (gapdh) 3' UTR, in epimastigotes. Luciferase activity decreased in parallel with the luc mRNA level in transformants utilizing the gp85 or ama 3' UTR, whereas luc mRNA containing the gp72 3' UTR showed approximately 5-fold higher translation efficiency than luc mRNA containing a minimal 3' UTR. In amastigotes, the inhibitory effect of the ama 3' UTR observed in other life cycle stages was abolished and luciferase expression was stimulated 16-fold. The overall stage-specific difference mediated by the ama 3' UTR, between epimastigotes and amastigotes, was approximately 100-fold. INT, which was expected to influence polyadenylation efficiency, of gapdh, gp72, or heat shock protein 60 gene inserted after gapdh 3' UTR increased luc mRNA 2- to 8-fold, whereas gp85 INT slightly decreased luc mRNA. By separating effects attributable to the 3' UTR and INT, this study shows the effects of 3' UTR on RNA levels and translational efficiency in T. cruzi.

Tumor necrosis factor alpha activity in genital tract secretions of guinea pigs infected with chlamydiae

Previous studies using the guinea pig model of chlamydial genital infection demonstrated that primary infection is associated with a marked acute inflammatory response early on, while chronic inflammation appears later, at a time when the level of infection is reduced. Challenge infections result primarily in a chronic inflammatory response. The stimuli that initiate inflammation and lead to tissue damage have not been defined. We investigated the possibility that tumor necrosis factors (TNFs) play a role in the inflammatory response to chlamydial genital tract infection. Cytotoxicity assays for TNF were performed on genital tract secretions collected from female guinea pigs during infection with the Chlamydia psittaci agent of guinea pig inclusion conjunctivitis. During the early days of primary infection, high levels of TNF-alpha were detected in genital tract secretions from inbred S2 strain and outbred Hartley strain guinea pigs. Significantly lower levels of TNF-alpha were detected in secretions from both strains during challenge infection. In general, the intensity of the TNF-alpha response was proportional to the intensity of infection. High TNF-alpha levels were present during primary infection at a time of marked neutrophil influx. Thus, TNF-alpha may play an important role in the response to primary chlamydial genital tract infection.

Messenger RNAs for the multifunctional cytokines interleukin-1 alpha, interleukin-1 beta and tumor necrosis factor-alpha are present in adnexal tissues and in dermis of normal human skin

Interleukin-1 alpha (IL-1 alpha), interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) are 3 cytokines that play a key rôle in cutaneous homeostasis and in the immunopathogenesis of a number of dermatologic diseases. Most studies have focused on their production by keratinocytes and Langerhans cells. To determine whether there are non-epidermal sites of cytokine transcription, biopsy specimens of normal human skin were probed for IL-1 alpha, IL-1 beta and TNF-alpha messenger RNAs using the method of in situ hybridization. The results demonstrate that each cytokine mRNA is present at multiple sites within the skin, including epidermal appendages and adnexal structures (hair follicles, sebaceous glands), the dermal microvasculature, arrectores pilorum smooth muscle, and the dermal connective tissue. These data provide evidence that in vivo there are multiple sites other than the epidermis of constitutive IL-1 alpha, IL-1 beta, and TNF-alpha gene transcription in normal human skin.

Warming macrophages to febrile range destabilizes tumor necrosis factor-alpha mRNA without inducing heat shock

We have previously reported that sustained tumor necrosis factor (TNF)-alpha expression is suppressed by temperatures in the febrile range in human macrophages. In this study, we examined the mechanisms of high-temperature-induced macrophage TNF suppression in the RAW 264.7 macrophage cell line. Incubating lipopolysaccharide (LPS)-stimulated RAW 264.7 cells at 40 degrees C reduced TNF secretion by 92% and peak TNF mRNA levels by 43% compared with cells incubated at 37 degrees C (P < 0.05) but did not affect levels of glyceraldehyde-3-phosphate dehydrogenase, beta-actin, or interleukin-6 mRNA. TNF mRNA half-life, measured after transcriptional arrest with actinomycin D, was reduced from 21.8 +/- 3.6 min in LPS-stimulated RAW 264.7 cells at 37 degrees C to 16.0 +/- 1.8 min at 40 degrees C (P < 0.03), but these cells at 40 degrees C did not alter transcription rate or TNF mRNA polysome association. TNF mRNA destabilization occurred at temperatures below the threshold (43 degrees C) for the generalized heat shock response in these cells. We conclude that heating macrophages to febrile-range temperatures attenuates sustained TNF expression by modulating posttranscriptional processing, including acceleration of TNF mRNA decay.

Chemokine response in mice infected with Mycobacterium tuberculosis

We show here that infection of murine macrophages with various strains of Mycobacterium tuberculosis induces the rapid in vitro expression of genes encoding chemokines macrophage inflammatory protein 1 alpha and macrophage inflammatory protein 2, which recruit neutrophils to sites of infection, and macrophage-recruiting chemokines 10-kDa, interferon-inducible protein (IP-10) and macrophage chemotactic protein 1. Three strains of M. tuberculosis, Erdman and the clinical isolates CSU 22 and CSU 46, induced similar levels of secretion of macrophage chemotactic protein 1 from infected macrophage monolayers; however, the Erdman strain failed to induce levels of secretion of tumor necrosis factor alpha similar to those induced by either CSU 22 or CSU 46. Using a low-dose aerosol infection model, we also found that while the Erdman strain induced negligible increases in chemokine mRNA levels in the lungs, infection with either CSU 22 or CSU 46 resulted in greater levels of mRNA production for all four chemokines tested. The growth of these strains in the lungs was, however, equally well contained by acquired host immunity. These data allow us to hypothesize that the chemokine response in the lungs probably does not control the protective granulomatous response and that perhaps other T-cell- or macrophage-associated cytokines such as tumor necrosis factor alpha or interleukin 12 may be involved in this process.

Functional analysis of a new polymorphism in the human TNF alpha gene promoter

In this paper the functional relevance of a TNFA promoter polymorphism, a G/A polymorphic sequence at position -238, was tested by analysing its influence on TNF alpha production upon in vitro stimulation of monocytes from 78 healthy, unrelated individuals by lipopolysaccharide (LPS) or after allogenic stimulation in a panel of 32 healthy individuals. All TNFA-A positive individuals were either DR3 or DR7 positive, confirming the previously reported strong linkage disequilibrium of the TNFA-A allele with the two extended haplotypes (B18, F1C30, DR3) and (B57, SC61, DR7). No individuals homozygous for the TNFA-A allele were present in the panel. The mean level of TNF alpha production was not significantly different in TNFA-G/G homozygous and in TNFA-A/G heterozygous individuals after LPS stimulation of monocytes (P = 0.35) or after allogenic stimulation (P = 0.7). After LPS and allogenic stimulation DR3 positive individuals had a higher mean TNF production. This could not be further differentiated by typing for TNF -283.

Interleukin-3 mRNA stabilization by a trans-acting mechanism in autocrine tumors lacking interleukin-3 gene rearrangements

Tumors obtained from v-Ha-ras-transformed PB-3c cells are characterized by autocrine interleukin-3 (IL3) expression, which occurs either without (class I tumors) or with enhanced transcription (class II tumors). To address possible post-transcriptional mechanisms of IL3 expression, IL3 mRNA stability was examined in both tumor classes. Increased stability of IL3 mRNA was detected in class I tumor lines (t1/2 > 3 h), whereas rapid decay of IL3 transcripts (t1/2 < 0.5 h) was found in class II tumor lines. In both tumor classes, the c-myc and interleukin-6 transcripts were short-lived. Transcripts of a constitutively expressed IL3 reporter gene were stable in class I tumor cells but unstable in class II tumor cells, suggesting that IL3 mRNA stabilization involved a trans-acting mechanism. Rapid decay of IL3 reporter transcripts was observed in untransformed PB-3c as well as in v-Ha-ras expressing precursor cells linking transcript stabilization to the tumor stage. Reporter transcript stabilization in class I tumor cells correlated with increased IL3 production. Deletion of the AU-rich element from the IL3 reporter gene further augmented IL3 mRNA levels as well as IL3 production, suggesting that the stabilizing mechanism in class I tumor cells is not equivalent to AU-rich element deletion.

Linkage between obesity and a marker near the tumor necrosis factor-alpha locus in Pima Indians

Because tumor necrosis factor-alpha (TNF-alpha) expression is increased in adipose tissue of both rodent models of obesity and obese humans, it has been considered as a candidate gene for obesity. Pima Indians were scored for genotypes at three polymorphic dinucleotide repeat loci (markers) near the gene TNF-alpha at 6p21.3. In a sib-pair linkage analysis, percent body fat, as measured by hydrostatic weighing, was linked (304 sib-pairs, P = 0.002) to the marker closest (10 kb) to TNF-alpha. The same marker was associated (P = 0.01) by analysis of variance with BMI. To search for possible DNA variants in TNF-alpha that contribute to obesity, single stranded conformational polymorphism analysis was performed from 20 obese and 20 lean subjects. Primer pairs were designed for the entire TNF-alpha protein coding region and part of the promoter. Only a single polymorphism located in the promoter region was detected. No association could be demonstrated between alleles at this polymorphism and percent body fat. We conclude that the linkage of TNF-alpha to obesity might be due to a sequence variant undetected in TNF-alpha or due to a variant in some other closely linked gene.

Activation of Raf-1 and mitogen-activated protein kinase in murine macrophages partially mimics lipopolysaccharide-induced signaling events

Lipopolysaccharide (LPS), a highly conserved component of the outer membrane of gram-negative bacteria, stimulates macrophages to release various cytokine and eicosanoid mediators of the immune response. The mechanism by which LPS stimulates these cells is poorly characterized. One of the most rapid LPS-stimulated events is the phosphorylation and activation of the p42 and p44 isoforms of mitogen-activated protein (MAP) kinase. We wished to examine the role of MAP kinase in LPS-induced signaling in murine macrophages by activating MAP kinase independently of LPS. An expression vector encoding a Raf-1:estrogen receptor (ER) chimeric protein was transfected into the murine macrophage cell line RAW 264.7. Activation of this chimeric protein (delta Raf-1:ER) by estradiol resulted in rapid and prolonged activation of MAP kinase, as expected from previous results implicating Raf-1 as an upstream activator of this signaling cascade. LPS stimulation induced accumulation of MAP kinase phosphatase 1 messenger RNA, whereas delta Raf-1:ER activation did not, perhaps accounting for the more prolonged activation of MAP kinase seen in response to delta Raf-1:ER activation. Similarly, activation of DNA binding by the transcription factor, nuclear factor (NF) kappa B, as assessed by electrophoretic mobility shift assay, occurred in response to LPS stimulation but not in response to delta Raf-1:ER activation or phorbol myristate acetate (PMA) stimulation. Using an enzyme-linked immunosorbent assay for murine tumor necrosis factor alpha (TNF-alpha), we found that LPS and PMA stimulation and delta Raf-1:ER activation induced secretion of TNF-alpha, although the amount of TNF-alpha secreted in response to delta Raf-1:ER activation and PMA stimulation was approximately 20-fold less than that secreted in response to LPS. Correspondingly, accumulation of TNF-alpha messenger RNA was weakly induced by delta Raf-1:ER activation or PMA stimulation, whereas strong induction was noted in response to LPS. These results suggest that Raf-1 or PMA activation of MAP kinase in murine macrophages is sufficient for a small amount of TNF-alpha production and secretion in the absence of NF-kappa B activation, but LPS stimulation involves additional signaling events, such as NF-kappa B activation, that augment the response seen with activation of MAP kinase alone.

Comparative genetic association of human leukocyte antigen class II and tumor necrosis factor-alpha with dermatitis herpetiformis

Dermatitis herpetiformis is a chronic subepidermal vesicular autoimmune skin disease characterized by a strong association with the human leukocyte antigen A1-B8-DR3-DQ2 haplotype. Although the strongest major histocompatibility complex association has been shown to be with the DQw2 (DQB1*0201/DQA1*0501) heterodimer, recent evidence has suggested that there may be up to three susceptibility loci within the major histocompatibility complex. Tumor necrosis factor-alpha (TNF-alpha) is a cytokine with a broad range of proinflammatory, immunomodulating, and catabolic activities. We have recently described the first known polymorphism in the human TNF-alpha gene, which is biallelic and lies in the promoter region. The rare allele, TNF2, is in strong linkage disequilibrium with the human leukocyte antigen A1-B8-DR3-DQ2 haplotype. We therefore examined TNF-alpha genotypes in patients with dermatitis herpetiformis and controls and compared the association with that of the class II alleles. Although TNF2 is strongly associated with dermatitis herpetiformis, this was weaker than the association with the class II loci, with DQw2 (DQB1*0201/DQA1*0501) showing the strongest disease association. Of the four patients negative for this marker, only one carried the TNF2 allele. These results indicate that TNF2 is not a major disease susceptibility marker, although our results do not exclude a minor role.