Tumor Necrosis Factor Production In Response Research Articles

Modulation of lipopolysaccharide receptor expression by lactate dehydrogenase-elevating virus

Lactate dehydrogenase-elevating virus (LDV) exacerbates mouse susceptibility to endotoxin shock through enhanced tumour necrosis factor (TNF) production by macrophages exposed to lipopolysaccharide (LPS). However, the in vivo enhancement of TNF production in response to LPS induced by the virus largely exceeds that found in vitro with cells derived from infected animals. Infection was followed by a moderate increase of Toll-like receptor (TLR)-4/MD2, but not of membrane CD14 expression on peritoneal macrophages. Peritoneal macrophages from LDV-infected mice unresponsive to type I interferons (IFNs) did not show enhanced expression of TLR-4/MD2 nor of CD14, and did not produce more TNF in response to LPS than cells from infected normal counterparts, although the in vivo response of these animals to LPS was strongly enhanced. In contrast, the virus triggered a sharp increase of soluble CD14 and of LPS-binding protein serum levels in normal mice. However, production of these LPS soluble receptors was similar in LDV-infected type I IFN-receptor deficient mice and in their normal counterparts. Moreover, serum of LDV-infected mice that contained these soluble receptors had little effect if any on cell response to LPS. These results suggest that enhanced response of LDV-infected mice to LPS results mostly from mechanisms independent of LPS receptor expression.

Mechanisms of TNF induction by heat-killed Staphylococcus aureus differ upon the origin of mononuclear phagocytes

Mononuclear phagocytes are among the first immune cells activated after pathogens invasion. Although they all derive from the same progenitor in the bone marrow, their characteristics differ on the compartment from which they are derived. In this work, we investigated the contribution of phagocytosis for tumor necrosis factor (TNF) production by murine mononuclear phagocytes (monocytes, peritoneal and alveolar macrophages) in response to heat-killed Staphylococcus aureus (HKSA). Mononuclear phagocytes behaved differently, depending on their compartment of residence. Indeed, when bacterial uptake or phagosome maturation was blocked, activation through membrane receptors was sufficient for a maximal production of TNF and interleukin-10 by peritoneal macrophages. In contrast, monocytes, and to a lesser extent alveolar macrophages, required phagocytosis for optimal cytokine production. While investigating the different actors of signalization, we found that p38 kinase and phosphatidylinositol 3-kinase were playing an important role in HKSA phagocytosis and TNF production. Furthermore, blocking the α(5)β(1)-integrin significantly decreased TNF production in response to HKSA in all three cell types. Finally, using mononuclear phagocytes from NOD2 knockout mice, we observed that TNF production in response to HKSA was dependent on NOD2 for monocytes and peritoneal macrophages. In conclusion, we demonstrate that the mechanisms of activation leading to TNF production in response to HKSA are specific for each mononuclear phagocyte population and involve different recognition processes and signaling pathways. The influence of the compartments on cell properties and behavior should be taken into account, to better understand cell physiology and host-pathogen interaction, and to define efficient strategies to fight infection.

RP105 Facilitates Macrophage Activation by Mycobacterium tuberculosis Lipoproteins

RP105, phylogenetically related to Toll-like receptor (TLR)-4, is reported to facilitate B cell activation by the TLR4-agonist lipopolysaccharide (LPS)--but to limit LPS-induced cytokine production by antigen-presenting cells. Here, we show that the role of RP105 extends beyond LPS recognition and that RP105 positively regulates macrophage responses to Mycobacterium tuberculosis (Mtb) lipoproteins. Mtb-infected RP105(-/-) mice exhibited impaired proinflammatory cytokine responses associated with enhanced bacterial burden and increased lung pathology. The Mtb 19 kDa lipoprotein induced release of tumor necrosis factor in a manner dependent on both TLR2 and RP105, and macrophage activation by Mtb lacking mature lipoproteins was not RP105 dependent. Thus, mycobacterial lipoproteins are RP105 agonists. RP105 physically interacted with TLR2, and both RP105 and TLR2 were required for optimal macrophage activation by Mtb. Our data identify RP105 as an accessory molecule for TLR2, forming part of the receptor complex for innate immune recognition of mycobacterial lipoproteins.

Toll‐like Receptor Cross‐hyporesponsiveness is Functional in Interleukin‐1‐receptor‐associated Kinase‐1 (IRAK‐1)‐deficient Macrophages: Differential Role Played by IRAK‐1 in Regulation of Tumour Necrosis Factor and Interleukin‐10 Production

Signalling downstream Toll-like receptors (TLR) is regulated at several levels in order to activate the immune response and prevent excessive inflammation. Altered intracellular signalling may be one reason that repeated stimulation of various TLRs results in hyporesponsiveness and cross-tolerance. We report that TLR cross-tolerance is inducible in the absence of interleukin-1 receptor-associated kinase-1 (IRAK-1) in peritoneal macrophages. Similar to wild-type macrophages, IRAK-1-deficient macrophages respond with decreased tumour necrosis factor (TNF) production to a secondary TLR stimulation, but in opposite to IRAK-1(+/+), IRAK-1(-/-) macrophages display increased interleukin (IL)-10 production at TLR restimulation. IRAK-1-deficient peritoneal macrophages have a defective TNF and IL-10 production in response to lipoteichoic acid stimulation as well as a defective IL-10-but a normal TNF production in response to high concentration of lipopolysaccharide. Our results demonstrate that IRAK-1 is not necessary for induction of TLR cross-tolerance as judged by TNF production.

ROLE OF BACTERIAL DNA IN TRIGGERING MACROPHAGE ACTIVATION BY A USA300 ISOLATE OF COMMUNITY-ACQUIRED METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS EXPOSED TO DIFFERENT CLASSES OF ANTIBIOTICS.

Background Infections caused by community-acquired, methicillin-resistant strains of Staphylococcus aureus (CA-MRSA) have become a major problem in children and adults. We recently reported that either of two clinical CA-MRSA isolates exposed to daptomycin (vs vancomycin) stimulated less macrophage tumor necrosis factor (TNF) secretion. We hypothesized that this difference might result from reduced release of bacterial products (such as bacterial DNA) from CA-MRSA isolates exposed to daptomycin (versus vancomycin). Purpose We sought to determine whether bacterial DNA contributed to the up-regulation of macrophage TNF production in response to a live CA-MRSA isolate exposed to vancomycin, daptomycin, clindamycin, or linezolid. Methods RAW 264.7 murine macrophages were stimulated for 16 to 18 hours with 107 cfu/mL of a well-characterized CA-MRSA isolate (USA300) in the presence of either vancomycin (20 mg/L), daptomycin (20 mg/L), clindamycin (20 mg/L), or linezolid (10 mg/L). In parallel, cells were preincubated for 1 hour prior to bacterial challenge with chloroquine (2.5 mg/L), a selective inhibitor of the bacterial DNA/Toll-like receptor 9 (TLR9) pathway. After stimulation, cell supernatants were collected and assayed for TNF concentration by ELISA. Results As we have previously reported, macrophages exposed to the CA-MRSA isolate in the presence of daptomycin (vs vancomycin) secreted significantly less TNF; clindamycin and linezolid were intermediate. Interestingly, preincubation of RAW cells with chloroquine led to substantial decreases in TNF secretion in response to the CA-MRSA isolate exposed to any of the four antibiotics. Furthermore, the magnitude of inhibition was consistently greater (70% vs 20-30%) in cells exposed to the SA isolate in the presence of daptomycin (compared with vancomycin, linezolid, or clindamycin). Conclusions Our data suggest that bacterial DNA plays an important role in the stimulation of TNF secretion by macrophages exposed to this virulent USA300 CA-MRSA isolate in the presence of any of the four antibiotics tested. Additional studies are needed to define the importance of bacterial DNA in stimulating the inflammatory response to staphylococcal infections.

Metabolic disturbance and sensitivity to endotoxin in patients with advanced cancer: relationship to lymphocyte reactivity, tumour necrosis factor (TNF) production and survival.

Increased TNF production and impaired lymphocyte function have been individually linked with metabolic disturbance, endotoxaemia and mortality in humans. The inter-relationship between these observations was investigated in humans with cancer. In 13 patients with metastatic colorectal cancer and seven healthy volunteers, observations (n = 23) included peripheral blood mononuclear cell (PBMC) TNF production, IL-2 production and phytohaemagglutinin (PHA) response; the acute-phase protein response (APPR) (serum C-reactive protein (CRP), albumin, CRP/albumin ratio), and survival. APPR correlated with survival (CRP, r = -0.689, P = 0.006; CRP/albumin, r = -0.758, P = 0.002; albumin, r = 0.655, P = 0.011), but not with TNF production. TNF production in response to in vitro endotoxin correlated with impaired lymphocyte function in patients (r = 0.567, P = 0.043) and in the whole group (r = 0.65, P = 0.001). The ratio (basal PBMC TNF production)/(lymphocyte function) correlated with CRP (r = 0.569, P = 0.042), CRP/albumin (r = 0.617, P = 0.025), endotoxin sensitivity (r = 0.567, P = 0.043) and survival (r = -0.545, P = 0.038) in patients, and the whole group (P < 0.002). Impaired lymphocyte function may influence TNF production, endotoxin sensitivity and metabolic disturbance in humans with cancer. (r = Spearman correlation coefficient.)

Mycobacterium avium infection in CD14-deficient mice fails to substantiate a significant role for CD14 in antimycobacterial protection or granulomatous inflammation.

CD14 is a pattern-recognition receptor implicated in the inflammatory response to microbial components such as lipopolysaccharide, peptidoglycan and lipoarabinomannan. In this work, we made use of CD14-deficient (CD14-/-) mice to evaluate the relative importance of CD14 in response to infection with viable, intact cells of Mycobacterium avium in vitro and in vivo. Following co-incubation of either bone marrow-derived macrophages (Mphi) or thioglycollate-elicited peritoneal Mphi from CD14-/- mice with viable M. avium, tumour necrosis factor (TNF) production was significantly reduced and delayed compared to TNF secretion by infected CD14+/+ Mphi. However, following intravenous infection with a M. avium strain of either high virulence (TMC724) or intermediate virulence (SE01), there was no difference in the bacterial loads of lungs, livers or spleens at 3, 5 and 8 weeks postinfection in CD14-/- mice when compared with syngeneic CD14+/+ mice. At these time-points, TNF and interferon-gamma (IFN-gamma) mRNA expression in the liver was similar in infected CD14+/+ and CD14-/- mice, and granuloma formation and expression of inducible nitric oxide synthase within granuloma Mphi was the same in both mouse groups. In conclusion, although the absence of CD14 results in significantly reduced and delayed TNF production in response to stimulation with M. avium in vitro, there is no evidence that CD14 plays a significant role in either the antibacterial defence or the chronic granulomatous reaction to M. avium infection in vivo.

Induced TNF production in vitro as a test for familial Mediterranean fever.

We have previously demonstrated an altered pattern of tumor necrosis factor (TNF) secretion in patients with familial Mediterranean fever (FMF). To examine whether TNF determination could assist in diagnosing FMF, we stimulated heparinized blood of 51 asymptomatic FMF patients with lipopolysaccharide (LPS) and then measured TNF production in response to inducers, compared to unstimulated blood cells and to cells from a control group of 12 matched healthy subjects. Following LPS pretreatment, which induced TNF release, FMF patients produced significantly less TNF than controls, whether production was 'spontaneous' or induced by either LPS or phytohaemagglutinin (p < or = 0.003). Such 'exhaustion' did not occur in untreated cells. We then used these results to classify a further group of 29 FMF patients and 10 matched healthy controls ('validation' group) who underwent the same studies. The test correctly identified 25/29 patients as having FMF and 7/10 controls as not having FMF; a sensitivity of 86% and a specificity of 70% (likelihood ratios 2.9 (positive test) and 0.2 (negative)). Identification of a blunted TNF response following previous stimulation by a simple assay, may help the diagnosis of FMF in asymptomatic patients, provided it is interpreted in conjunction with supportive clinical data.

Effect of thalidomide on tumour necrosis factor production and anti-tumour activity induced by 5,6-dimethylxanthenone-4-acetic acid.

The investigational anti-tumour agent, 5,6-dimethylxanthenone-4-acetic acid (5,6-MeXAA), an analogue of flavone acetic acid (FAA), has been scheduled for clinical evaluation. Like FAA, 5,6-MeXAA exhibits excellent experimental anti-tumour activity and is an efficient inducer of cytokines in mice. We have examined the effect of pharmacological suppression of tumour necrosis factor (TNF) production on the anti-tumour activity of 5,6-MeXAA, taking advantage of previous observations that TNF production in response to endotoxin in vitro is inhibited by thalidomide. Thalidomide at doses of between 8 and 250 mg kg-1 efficiently suppressed serum TNF activity in response to 5,6-MeXAA at its optimal TNF inducing dose of 55 mg kg-1. Suppression was achieved when thalidomide was administered at the same time as, or up to 4 h before, 5,6-MeXAA. Under conditions in which TNF activity was suppressed, the degree of tumour haemorrhagic necrosis and the proportion of cures in the subcutaneous Colon 38 tumour were increased. In mice administered thalidomide (100 mg kg-1) together with 5,6-MeXAA (30 mg kg-1), complete tumour regression was obtained in 100% of mice, as compared with 67% in mice receiving 5,6-MeXAA alone. The results suggest a possible new application for thalidomide and pose new questions about the action of 5,6-MeXAA and related compounds.

Alteration in spleen cellularity and cytokine production in zinc-deficient mice challenged with lipopolysaccharide.

The main objective of this study was to evaluate the impact of dietary zinc deficiency on Interleukin-1α (IL-1α) and Tumor Necrosis Factor (TNF) production in an in vivo rodent model simulating an infectious process. Three to four week old BALB/c mice were fed with low zinc diet (Zn < 5 ppm) and deionized water for 4 weeks. Control group received rodent chow (43.3 μg Zn / g diet) ad libitum. A third group of mice was fed with the rodent chow but the daily consumption of food was restricted to that by the zinc-deficient group on a pair feeding basis. This group serves as a second control and takes into account the possibility of additional nutrient deficiencies that may result from restricted food intake. At the end of 4 weeks, mice were challenged with lipopolysaccharide (LPS) 20 mg/kg body weight. Spleen weight, cell numbers, IL-1α and TNF levels were monitored before and at varying intervals after LPS injection. Spleen weight, pan T cells, CD4 and CD8 T cell subsets were reduced in zinc-deficient mice as well as in the pair-fed group. The highest level of IL-1 α production by nutrient-deficient mice was slightly decreased but was not statistically different from that by normal controls. These peaks of IL-1α production appeared earlier in undernutritional conditions. Zinc-deficient mice and the pair-fed group had decreased TNF production in response to LPS challenge. The peak time of TNF production was delayed in these animals.

Differentiation-dependent modulation of TNF production by PAF in human HL-60 myeloid leukemia cells.

Platelet-activating factor (PAF) can augment tumor necrosis factor (TNF) production by human monocytes in a bimodal manner, with two peaks of activation at picomolar and micromolar concentrations. These peaks are partially associated with monocyte subsets presenting different characteristics in terms of size, density, phenotypic markers, and [Ca2+]i mobilization responses. In the present study, we used the human promyelocytic leukemia cell line HL-60, at various times during differentiation with 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] toward the monocyte lineage, in order to study the relation of cell differentiation to responsiveness to PAF in terms of cytokine production. TNF production was induced by pretreatment with interferon gamma for 24 h and treatment with muramyl dipeptide. Although detectable TNF was produced by 4 day-differentiated cells, no effect was seen with PAF (10(-16)-10(-6) M) at this or earlier stages. In contrast, 5 day-differentiated cells had a comparable baseline production of TNF but responded with a 2.5-fold increase to PAF with a single peak, maximal at 10(-8) M. Moreover, 6 day- or 7 day-differentiated HL-60 cells showed a further increase in TNF production in response to PAF, and the response was bimodal, similar to that of the less dense subset of monocytes, with peaks at 10(-14) and 10(-7) M PAF. In parallel, undifferentiated HL-60 failed to respond to PAF in terms of [Ca2+]i mobilization. The earliest responsiveness to PAF (10(-7) M) was observed by 4 days of treatment with 1,25(OH)2D3, and by day 7 the response to PAF became bimodal (10(-14) and 10(-7) M). These results indicate that myeloid cells acquire, during maturation toward the monocyte lineage, a progressive responsiveness to PAF in terms of [Ca2+]i mobilization and enhanced cytokine production, and they suggest that the heterogeneity in responses to PAF observed in normal monocytes may be related to their stage of differentiation or maturation.

Detoxified exoantigens and phosphatidylinositol derivatives inhibit tumor necrosis factor induction by malarial exoantigens.

We have previously shown that malaria parasites liberate exoantigens which, through a phospholipid component, stimulate mouse macrophages to secrete tumor necrosis factor (TNF), which are toxic to D-galactosamine-sensitized mice, and which therefore might be involved in pathology. Plasmodium yoelii exoantigens detoxified by dephosphorylation or digestion with lipases do not induce TNF production. However, these partial structures inhibited its production in response to the exoantigens, although not to bacterial lipopolysaccharide (LPS). When pure phospholipids were tested in a macrophage assay, none stimulated the production of TNF, but phosphatidylinositol (PI) inhibited TNF induction by P. yoelii exoantigens. Moreover, inositol monophosphate (IMP) was the only one of a number of monophosphate saccharides tested which was inhibitory; inositol was not. Macrophages pretreated with PI, IMP, or detoxified exoantigens and then incubated with parasite exoantigens also yielded much less TNF. PI, IMP, and lipase-digested exoantigens of P. yoelii similarly inhibited the TNF-inducing activity of exoantigens of the human parasites Plasmodium falciparum and Plasmodium vivax. Neither PI nor IMP diminished TNF production in response to LPS, in contrast to a platelet-activating factor antagonist [1-O-hexadecyl-2-acetyl- sn-glycero-3-phospho(N,N,N-trimethyl hexanolamine)] which inhibited both exoantigen- and LPS-induced production of TNF. We conclude that at least two different parts of the molecule are involved in the induction of TNF secretion by parasite exoantigens: one requires the presence of a phosphate bound to inositol, and, since dephosphorylated exoantigens were also inhibitory, one does not. It would seem that both affect interactions between parasite-derived exoantigens and the macrophage receptors.

Alterations in macrophage free radical and tumor necrosis factor production by a potassium channel activator

The potassium channel activator nicorandil, under evaluation for antianginal management, has been shown to decrease neutrophil respiratory burst. Since our laboratory has demonstrated that reactive oxygen species (ROS) increase tumor necrosis factor (TNF) production, we hypothesized that nicorandil might decrease TNF production from a lipopolysaccharide (LPS) challenge via reduction of respiratory burst. Macrophage viability and TNF production were determined after an 18-hr exposure to 5.0 μg/ml LPS and varying concentrations of nicorandil. Nicorandil was not toxic to macrophages below 12 m M (94 ± 3% viability versus control) and decreased ROS and TNF production. Intracellular superoxide production decreased from 164 ± 24 OD 550 to 99 ± 6 OD 550 with 10 m M nicorandil and extracellular superoxide decreased from 3108 ± 111 to 1760 ± 210 n M. Hydrogen peroxide production was also decreased by 10 m M nicorandil. TNF production in response to 5 μg/ml LPS decreased from 6.8 ± 0.6 to 2.7 ± 0.4 ng/ml with 10 m M nicorandil. Northern and slot blot analyses demonstrate that nicorandil acts at a post-transcriptional site. These data imply that nicorandil decreases macrophage TNF production from an LPS challenge, possibly through a reduction in respiratory burst. Such compounds may prove useful in the treatment of conditions thought to be associated with free radical-lymphokine interactions such as ischemia-reperfusion injury, oxygen toxicity, adult respiratory distress syndrome, and septic shock.

Tumor necrosis factor production in patients with leprosy.

The spectrum of host responses to Mycobacterium leprae provides a model for investigating the role of cytokines in the pathogenesis of mycobacterial disease. Of particular interest is tumor necrosis factor (TNF), a cytokine which may have both antimycobacterial and immunopathologic effects. To evaluate the potential role of TNF in leprosy, we measured TNF production in response to M. leprae and its defined constituents by peripheral blood mononuclear cells from patients across the spectrum of disease. The levels of TNF induced through the stimulation of cells with M. leprae or its dominant "lipopolysaccharide," lipoarabinomannan, were higher in patients with the tuberculoid form of the disease than in those with the lepromatous form. In patients with erythema nodosum leprosum (ENL), a reactional state of lepromatous leprosy, the levels of TNF release by peripheral blood mononuclear cells were higher than in any other form of the disease. Treatment of ENL patients with thalidomide reduced TNF secretion by more than 90%. The mycolylarabinogalactan-peptidoglycan complex of Mycobacterium species, the protein-peptidoglycan complex, and muramyl dipeptide all elicited significant TNF release. Therefore, TNF release appears to be triggered by at least two major cell wall structural constituents of M. leprae, lipoarabinomannan and segments of the cell wall skeleton. The prominent TNF release in patients with the paucibacillary tuberculoid form of the disease compared with that in patients with the multibacillary lepromatous form suggests that this cytokine contributes to a resistant immune response to mycobacterial infection. However, the marked TNF release in patients with ENL indicates that TNF may also mediate immunopathologic effects, such as fever and tissue damage.

Altered macrophage activity and tumor necrosis factor: Tumor necrosis and host cachexia

Tumor necrosis factor (TNF) may be a mediator of cancer cachexia. This study evaluates the activity of macrophages from non-tumor-bearing (NTB) and tumor-bearing (TB) rats by measuring TNF production in response to endotoxin (LPS), both in vitro and in vivo, and correlates macrophage activity with tumor burden and parameters of host cachexia. Isolated macrophages from rats with small tumors, normal food intake, and weight gain secreted more TNF in response to 10 μg/ml LPS than macrophages from control NTB rats and behaved similar to activated macrophages from rats previously treated with thioglycollate. Heightened macrophage activity (increased production of TNF in response to LPS) in TB rats increased further as tumor burden increased ( r = 0.889, P < 0.001). Tumor resection reversed the heightened macrophage activity as LPS-induced levels of TNF secreted by macrophages from resected TB rats were not different from those of sham-operated NTB control rats. TB rats had serum levels of TNF activity following an iv bolus of 10 mg/kg LPS greater than those of NTB rats ( P < 0.05). In addition, peak serum TNF activity levels following iv LPS increased directly as tumor burden increased ( r = 0.91, P < 0.001). Supernatants from tissue cultures of the tumor (MCA sarcoma) failed to have any detectable TNF activity. However, large tumors in vivo had increased amounts of necrosis (78 ± 8%), increased numbers of infiltrating macrophages, and increased levels of TNF (480 ± 68 U/ml) compared to small tumors. Rats with large tumors also had detectable TNF activity in serum (28 ± 13 U/ml), as well as reduced food intake and body weight loss, while STB animals did not. The results suggest that host macrophages are activated in response to a malignant tumor prior to clinical signs of cachexia. As tumor progresses macrophage activity further increases and elevated levels of TNF production are associated with both tumor necrosis and host cachexia.