Effect of platelet-activating factor on monocyte activation and production of tumor necrosis factor

The effect of platelet-activating factor (PAF) or human peripheral-blood-derived monocytes (PBM) was examined. The addition of PAF to monocyte cultures did not activate the cells to mediate cytotoxicity activity against 51Cr-labeled target cells. Furthermore, supernatants derived from the treated cultures were not cytotoxic. However, these supernatants contained tumor necrosis factor (TNF) when assayed by a sensitive radioimmunoassay. Further kinetic studies indicated that cytotoxic supernatant is detected at 2-4 h following PAF treatment but not overnight treatment, suggesting, perhaps, the presence of inhibitors interfering with the cytotoxic activity. Cells pretreated with PAF responded poorly to a second stimulation with phorbol myristate acetate whereas a secondary response was seen with cells pretreated with interferon-gamma. These results suggest that PAF is involved in regulating cytokine production by monocytes and thus plays a role in the immune response to foreign antigens.     

Differential production of tumor necrosis factor, macrophage colony stimulating factor, and interleukin 1 by human alveolar macrophages

Human alveolar macrophages (AMO) have been investigated for their ability to produce three monokines, tumor necrosis factor-alpha (TNF), macrophage colony stimulating factor (CSF-1), and interleukin 1-beta (IL-1). No TNF activity was found in supernatants of unstimulated AMO cultured for 20 h, although TNF mRNA was detected in the cells by Northern blot analysis. Stimulation of the cells with lipopolysaccharide (LPS) induced production and release of high levels of TNF into the culture supernatant. Increased levels of TNF mRNA were detectable at 90 min after LPS stimulation by dot blot analysis, reaching maximum expression between 4 and 8 h and declining thereafter. TNF activity peaked at approximately 8 h in the AMO supernatants. After 24 h TNF production had ended. Compared to autologous monocytes the AMO produced 5.7 times more TNF on a per cell basis (activity accumulated in 20 h supernatants). Uncultured AMO expressed CSF-1 mRNA which was translated into active protein recovered in supernatants upon culture in the absence of stimulus. The addition of LPS to AMO slightly reduced both mRNA levels and amount of factor in the supernatants. In contrast to the AMO, monocyte production of CSF-1 was enhanced by LPS. CSF-1 production by AMO continued for at least 48 h of culture. Spontaneous production of low amounts of IL-1 was found in one-third of the AMO samples, while low levels of IL-1 mRNA were present in all tested preparations. LPS stimulation induced increase in IL-1 mRNA within 90 min; mRNA levels peaked between 12 and 20 h and stayed high for at least 42 h. However, while all LPS-stimulated AMO expressed high levels of IL-1 mRNA biologically active IL-1 was again detected only in a fraction of the AMO supernatants. These results show that the production of monokines CSF-1, TNF, and IL-1 is differentially regulated by LPS in alveolar macrophages and has different responses as compared to monocytes. The longevity of the messages for each of the factors is possible indicators of the relative contribution of these factors to the response to endotoxin-induced injury and repair processes in the lung.     

Effect of histamine on tumor necrosis factor production by human monocytes

This study was aimed at evaluating the effect of histamine on tumor necrosis factor (TNF alpha) secretion by purified human blood monocytes. TNF alpha was measured by radioimmunoassay. Histamine caused a dose-dependent inhibition of lipopolysaccharide-induced TNF alpha production from human blood monocytes, averaging maximally 50% at 10(-5) M. Preincubation of mononuclear cells with an H2 antagonist (cimetidine), but not with an H1 antagonist (promethazine) prevented this inhibitory effect of histamine. In conclusion, histamine causes, in vitro, a depression of TNF alpha secretion by human monocytes through activation of H2 receptors.     

Effects of quinolones on tumor necrosis factor production by human monocytes.

Previous studies have shown that in lipopolysaccharide (LPS)-stimulated human monocytes, interleukin 1 (IL-1) production is altered by quinoline derivative antibiotics (quinolones), in a way which depends both on the dose and on the agents used. Given that IL-1 and tumor necrosis factor alpha (TNF) are produced in response to LPS and have some overlapping and synergistic activities, we sought to determine if TNF production was altered under the above-mentioned conditions. We investigated the effects of three quinolones: ciprofloxacin (Cip), pefloxacin (Pef) and ofloxacin (Ofl). These quinolones were found to decrease extracellular TNF production in a dose-dependent manner at concentrations higher than 25 micrograms/ml as previously described by our laboratory with regard to IL-1 production. Moreover, the order of the extracellular decrease in TNF and IL-1 induced by each drug was similar. However, in contrast to IL-1 activity, the quinolones studied also reduced cell-associated TNF. The kinetics of TNF production suggested that the quinolones affected TNF production at a very early step, probably during TNF synthesis rather than during its secretion into the extracellular medium. Furthermore, the quinolone-induced accumulation of intracellular cAMP could explain the extracellular decrease in both IL-1 and TNF production.     

Differential ability of human blood monocyte subsets to release various cytokines

We have shown that two human monocyte subsets can be isolated from the peripheral blood of healthy donors; these subsets possess different morphological, cytochemical, functional, and in vivo trafficking properties [1]. In this report, these two subsets were further characterized. One subset (intermediate monocytes, IM) has been shown to have significantly lower acid phosphatase activity and total cellular protein content as well as lower peroxidase activity when compared with another subset (regular monocytes, RM). The overall activation status of the two subsets (as determined by their alkaline phosphodiesterase activity) was identical. We also examined the capacity of these subsets to release various cytokines with or without polyriboinosinic and polyribocytidylic acid (Poly I:C) stimulation. There was no appreciable difference in their ability to release interferon (IFN), interleukin 1 (IL-1), and prostaglandin E (PGE) without stimulation, while IM produced slightly, but significantly, higher amounts of colony-stimulating factor (CSF) than RM. The amount of IFN released by IM in response to poly I:C was approximately three times higher than the amount of IFN released by RM. IL-1 was also released in higher amounts by IM than by RM in response to poly I:C. IM were also found to release more CSF than RM in response to poly I:C. In contrast, it was noted that IM secrete significantly less PGE response to poly I:C than do RM. These findings indicate that two purified human monocyte subsets, distinguishable by maturation markers, differ significantly in their ability to release various cytokines after stimulation; this difference may be relevant to potential in vivo roles of these immunoregulatory cells.     

Tumor necrosis factor production by human granulocytes.

Human polymorphonuclear leukocytes kill WEHI 164 cells in an 18-hour 51Cr release assay. Antibody to human tumor necrosis factor (TNF) blocks the lysis of targets mediated by human granulocytes. Resting granulocytes produce an undetectable amount of TNF, if any. Granulocytes stimulated with Staphylococcus aureus release 250-500 U/ml TNF alpha. The specificity of the released TNF in the WEHI 164 cytotoxicity assay was confirmed by using neutralizing anti-TNF alpha monoclonal antibodies. The thymidine uptake of endothelial cells was inhibited by granulocyte-derived TNF. The identity of TNF alpha was further confirmed by molecular weight determination, by gel filtration on Sephacryl S-200, with a result of approximately 44,000. Besides their antimicrobial capacity, therefore, granulocytes may contribute to tumor rejection, inflammation and septic infections by releasing TNF.     

Regulation of tumor necrosis factor production by monocyte-macrophages and lymphocytes

TNF, a cytokine originally considered the product of only one cell type, the monocyte-macrophages, is now known to be produced by cells of many different lineages, with mechanisms of stimulation typical for each cell type analyzed. The fact that many different cell types can produce a cytokine such as TNF that has a very large spectrum of biologic functions on almost any target cell type is suprising. The functions of the cell types that produce TNF, e.g. monocyte-macrophages, neutrophils, T and B cells, are profoundly affected by TNF itself. Furthermore, TNF is able to induce its own gene, making these autocrine circuits even more complex. Because TNF has important systemic effects and it has been shown to be in vivo a major and necessary pathogenetic factor in situations such as endotoxin shock, graft-versus-host disease, and hypothermia induced by anti-T cell antibodies, it is clear that its production and its localization should be highly regulated in vivo and that our understanding of the regulation of TNF production based almost exclusively on in vitro observation is still very limited. Further analysis of the fine mechanisms of regulation of TNF production in vivo is required for a better under standing of the role of TNF in physiological and pathological conditions.     

Neopterin augmentation of tumor necrosis factor production

Gamma interferon (gamma-IFN), lipopolysaccharide (LPS)-gamma or interleukin-2 (IL-2)-induced tumor necrosis factor alpha (TNF alpha) production by both macrophages and peripheral blood mononuclear cells (PBMC), was increased in the presence of neopterin. Addition of neopterin caused an increased level of TNF alpha, but did not affect the kinetics of the TNF alpha production, which showed peak levels of cytotoxic activity 4 h after stimulatory treatment. Using anticytokine antibodies, we concluded that the neopterin effect was mainly gamma-IFN mediated, and only slightly affected by anti IL-2 receptor antibodies. The neopterin augmented TNF alpha production can be attributed to an immunological role for neopterin in the enhancement of cell-mediated immune (CMI) response.     

Danazol suppresses the production of interleukin-1 beta and tumor necrosis factor by human monocytes

The effects of estradiol (E2), progesterone (P), and danazol on the production of interleukin-1 beta (IL-1 beta) and tumor necrosis factor (TNF) by OK-432 (a streptococcal preparation)-stimulated monocytes were examined. E2 and P at physiologic concentrations enhanced IL-1 beta and TNF production by monocytes from donors with lower control levels (without steroids added) of IL-1 beta and TNF. However, E2 and P at physiologic concentrations did not affect IL-1 beta and TNF production by monocytes from donors with higher control levels of IL-1 beta and TNF. Danazol inhibited IL-1 beta and TNF production by monocytes in a dose-dependent manner from not only donors with lower control levels of IL-1 beta and TNF but also donors with higher control levels of IL-1 beta and TNF. Danazol at a concentration of 10(-6) M significantly suppressed IL-1 beta and TNF production in the presence of E2 and/or P at concentrations giving peak responses of IL-1 beta production. These findings suggest possible new mechanisms of action for danazol in the treatment of endometriosis and infertility associated with immune abnormalities.     

Inhibition by delta-9-tetrahydrocannabinol of tumor necrosis factor alpha production by mouse and human macrophages.

Suppression by delta-9-tetrahydrocannabinol (THC) of tumor necrosis factor (TNF) production by macrophages has not been reported previously. The present study evaluated the effect in vitro of THC on soluble TNF-alpha production by cultured murine peritoneal macrophages. THC at 5 or 10 micrograms/ml added to medium [RPMI 1640 containing 10 ng LPS/ml, mouse IFN-gamma (100 u/ml), and 0.5% bovine serum albumin (BSA)] used to induce TNF significantly decreased TNF-alpha production by BALB/c mouse macrophages. Macrophages pretreated with THC at 0.1, 0.5, or 1.0 micrograms/ml in protein-free medium for 3 h at 37 degrees C, prior to TNF induction, also showed a decreased ability to produce TNF-alpha in a dose-dependent manner. Increasing the protein concentration from 0.5 to 5% BSA in the medium which was used to induce TNF prevented the inhibitory activity of THC. Human peripheral blood adherent cells treated with THC-containing medium produced less TNF-alpha than controls that were not exposed to THC. Thus, our data provide evidence that THC can inhibit TNF production by mouse and human macrophages. The drug's activity is concentration dependent and is related to the amount of serum protein in the medium used to induce this cytokine.     

Interleukin-8 and tumor necrosis factor alpha production in human epidermal keratinocytes induced by Trichophyton mentagrophytes

Production of interleukin-8 (IL-8) and tumor necrosis factor alpha (TNF-alpha) was confirmed by enzyme-linked immunosorbent assay in a medium where human epidermal keratinocytes were cocultured with Trichophyton mentagrophytes for 1 to 12 h. IL-8 and TNF-alpha mRNAs were also detected in the keratinocytes cocultured with T. mentagrophytes.     

Suppression of tumor necrosis factor alpha production by a human immunoglobulin preparation for intravenous use.

We investigated the effect of a pH 4-treated human immunoglobulin preparation for intravenous use (pH4-G) on the production of tumor necrosis factor alpha (TNF-alpha) in vivo. The level of TNF-alpha in the sera of rabbits receiving pH4-G before lipopolysaccharide (LPS) injection was lower than that in rabbits receiving only LPS. Similarly, the in vitro production of TNF-alpha was suppressed by pH4-G. Rabbit peritoneal exudate cells stimulated with LPS in the presence of pH4-G produced less TNF-alpha than did those stimulated only with LPS. pH4-G, however, had no effect on various TNF-alpha activities, such as cytotoxicity against tumorigenic murine fibroblasts (L929 cells), induction of interleukin-1 production, or fever induction. These results indicate that pH4-G suppresses TNF-alpha production without affecting TNF-alpha activities. A suppressive effect on the expression of TNF-alpha mRNA was also observed.     

Ambroxol inhibits interleukin 1 and tumor necrosis factor production in human mononuclear cells

We have studied the effect of Ambroxol on the production of Interleukin-1 (IL-1) and Tumor Necrosis Factor (TNF) in human mononuclear cells (MNC). For this purpose MNC were cultured for 24 h in the presence of endotoxin and different doses of Ambroxol. The results indicate that Ambroxol markedly inhibited IL-1 and TNF production at doses of 10–100 g/ml, without any apparent toxicity.     

Tumor necrosis factor production by human sarcoid alveolar macrophages.

Tumor necrosis factor (TNF) is an oncolytic peptide that may also exert many other biologic effects. Experimentally, immunologically activated mononuclear phagocytes stimulated with endotoxin (LPS) produce TNF, while resting mononuclear phagocytes stimulated with LPS produce little TNF. To date, the ability of human alveolar macrophages (AMs) to produce TNF has not been clearly delineated. As pulmonary sarcoidosis is a granulomatous inflammatory disorder characterized by immunologically activated AMs, we investigated the production of TNF by AMs obtained by bronchoalveolar lavage from 7 normal volunteers and 13 patients with pulmonary sarcoidosis. The AMs were cultured with and without LPS, and TNF production was assessed by an in vitro cytotoxicity assay. Unstimulated sarcoid and normal AMs produced little TNF, but LPS stimulation enhanced TNF production by both normal and sarcoid AMs. Furthermore, LPS-stimulated sarcoid AMs produced more TNF than normal AMs (84.9 +/- 16.7 versus 32.5 +/- 10.2 units/million cells, P less than 0.05). It is concluded that human AMs can produce TNF and that sarcoid AMs are primed and can produce significantly more TNF, compared with normal AMs.     

Glomerular basement membrane-containing immune complexes stimulate tumor necrosis factor and interleukin-1 production by human monocytes.

The ability of human peripheral blood monocytes to produce tumor necrosis factor (TNF) and interleukin-1 (IL-1) in an in vitro model of immune complex-mediated glomerulonephritis was investigated. When isolated monocytes were incubated with human glomerular basement membrane (GBM) containing anti-GBM immune complexes, both TNF and IL-1 were produced and secreted into the medium. The time course of secretion differed, with IL-1 production being maximal after approximately 8 hours, whereas TNF levels continued to rise for 30 hours. The activities of the monocyte-derived TNF and IL-1 were inhibitable by specific antibodies. No effect was seen when monocytes were incubated separately with either GBM alone or anti-GBM IgG. The levels of TNF and IL-1 released were comparable with those induced by high concentrations of LPS, indicating that production was close to the maximal levels reported for these cells. High levels of TNF and IL-1 also were produced in response to soluble immune complexes. The results show that monocytes can produce significant levels of TNF and IL-1 in response to both surface-bound and soluble immune complexes and provide support for the participation of these monokines in glomerulonephritis.     

Interleukin-6 production by tumor necrosis factor and lipopolysaccharide-stimulated rat renal cells

Interleukin-6 (IL-6) is produced by various cell types, including monocytes, fibroblasts, and endothelial cells. IL-6 has also been detected in the urine of normal and renal transplant patients. Thus, the possible production of this cytokine by glomeruli and mesangial cells was investigated. Rat glomeruli were obtained by serial sieving of cortical homogenates of blood-free kidneys. Mesangial cells were obtained from the glomeruli and cultured under standard methods in RPMI 1640 medium containing 15% fetal calf serum. Glomeruli or confluent monolayers cells were then incubated in RPMI 1640 for 18 hr, in the presence or not of tumor necrosis factor-alpha (TNF alpha), lipopolysaccharide (LPS), or platelet-activating factor (PAF). IL-6 activity was measured using the IL-6-dependent cell line subclone (B 9-9) and expressed with respect to a standard curve established with recombinant IL-6. Glomeruli generate IL-6 upon TNF alpha (100 ng/ml) and LPS (1 microgram/ml), 11,500 +/- 3000 and 22,000 +/- 7500 U/ml, respectively. Nonstimulated mesangial cells produced 50 +/- 5 U/ml (mean +/- SEM, n = 4) of IL-6. TNF alpha (1 ng/ml) and LPS (1 microgram/ml) induced the production of 800 +/- 90 and 40,000 +/- 5000 U/ml, respectively (n = 4). In contrast, PAF (0.1 nM-1 microM) did not increase IL-6 production from glomeruli or mesangial cells. These results demonstrate that renal cells spontaneously generate minimal amounts of IL-6 and that this production is significantly increased by TNF alpha or LPS. A synergy between LPS and TNF alpha was induced in glomerular cells with 10 ng/ml of TNF alpha and graded concentrations of LPS. Thus, the production of IL-6 by glomerular cells and its modulation by other cytokines or endotoxins may play a role in the local immunological processes leading to immune glomerular diseases.     

Pneumolysin stimulates production of tumor necrosis factor alpha and interleukin-1 beta by human mononuclear phagocytes.

Human peripheral blood monocytes and a human monocyte cell line were exposed to the toxin pneumolysin. Pneumolysin-exposed cells produced significantly larger amounts of tumor necrosis factor alpha and interleukin-1 beta than cells not exposed to the toxin. The viability of cells was not affected by the concentrations of pneumolysin used in the experiments.     

Peripheral blood monocyte/macrophages and serum tumor necrosis factor in Kawasaki disease

We analyzed the populations of peripheral blood monocyte/macrophages in 27 patients using a fluorescence-activated cell sorter, and investigated the possibility, in another 30 patients, that tumor necrosis factor (TNF) might be detectable in serum during the acute phase of Kawasaki disease (KD). Percentages of peripheral blood monocyte/macrophages among mononuclear cells and serum TNF levels were both seen to increase during the acute phase of the illness in patients with KD. The percentage of TNF positive cases in KD patients with coronary involvement was higher than that of patients without coronary involvement. These results suggest the possibility that immunological activation, accompanied by the secretion of TNF from monocyte/macrophages, is an important predisposing condition for the exacerbation of vascular damage in KD.     

Fibronectin fragments stimulate tumor necrosis factor secretion by human monocytes.

Fibronectin (Fn) is a high molecular-weight glycoprotein that can influence many aspects of monocyte function. The purpose of this study was to determine whether Fn could stimulate monocyte tumor necrosis factor (TNF) secretion. Monocytes were isolated from the peripheral blood of healthy volunteers by density gradient centrifugation and adherence to plastic (2 h). Plasma Fn was purified from the blood by gelatin-Sepharose affinity chromatography. Monocytes were stimulated with Fn for 18 h and the supernatants were assayed for TNF activity using the L929 bioassay. Intact Fn stimulated the secretion of TNF in a dose-dependent manner. Intact Fn-induced TNF secretion by monocytes was inhibited (50%) but not eliminated by the addition of the R-G-D-containing peptide GRGDSP. Limited proteolysis of the Fn molecule using insoluble chymotrypsin resulted in a fragment preparation that was dramatically more stimulatory than the intact Fn preparation. High-performance liquid chromatographic (HPLC) purification of the fragments demonstrated that at least two fragments were capable of stimulating TNF secretion. Further purification by affinity chromatography and HPLC localized the stimulatory activity to the 120-kd cell-binding fragment. The possibility that the stimulatory activity was the result of endotoxin contamination was ruled out using macrophages from C3H/Hej mice. These results suggest that Fn fragments are potentially important molecules for activation of monocytes and may stimulate monocyte cytotoxic activity.