Early Tumor Necrosis Factor Research Articles

Cell surface 4-1BBL mediates sequential signaling pathways 'downstream' of TLR and is required for sustained TNF production in macrophages

The stimulation of Toll-like receptors (TLRs) on macrophages triggers production of the cytokine tumor necrosis factor (TNF). TNF production occurs within 1 h of TLR stimulation and is sustained for 1 d. Here we document a function for the TNF family member 4-1BB ligand (4-1BBL) in sustaining TLR-induced TNF production. TLR signaling induced 4-1BBL, and 4-1BBL interacted with TLRs on the macrophage surface. The influence of 4-1BBL on TNF production was independent of its receptor (4-1BB) and did not require the adaptors MyD88 or TRIF. It did not influence TLR4-induced activation of transcription factor NF-kappaB (an early response) but was required for TLR4-induced activation of transcription factors CREB and C/EBP (a late event). Transient TLR4-MyD88 complexes appeared during the first hour after lipopolysaccharide stimulation, and TLR4-4-1BBL interactions were detected between 2 h and 8 h after lipopolysaccharide stimulation. Our results indicate that two different TLR4 complexes sequentially form and selectively control early and late TNF production.

Dynamics of Early Synovial Cytokine Expression in Rodent Collagen-Induced Arthritis: A Therapeutic Study Using a Macrophage-Deactivating Compound

This study was performed to elucidate pathophysiological events before and during the course of collagen-induced arthritis in Dark Agouti rats, a model for rheumatoid arthritis. Kinetic studies of local cytokine responses were determined using immunohistochemical techniques, quantified by computer-assisted image analysis. We recently reported that the macrophage-pacifying agent CNI-1493 successfully ameliorated collagen-induced arthritis. In the present trial, we investigated the potential of CNI-1493 to down-regulate pro-inflammatory cytokines. Synovial cryosections were analyzed at various time points for the presence of interleukin (IL)-1beta, tumor necrosis factor (TNF), and transforming growth factor (TGF)-beta. Unexpectedly, an early simultaneous TNF and IL-1beta expression was detected in resident cells in the lining layer, preceding disease onset and inflammatory cell infiltration by >1 week. The predominant cytokine synthesis by synovial (ED1+) macrophages coincided with clinical disease. TNF production greatly exceeded that of IL-1beta. CNI-1493 treatment did not affect the early disease-preceding TNF and IL-1beta synthesis in the lining layer. However, after disease onset, CNI-1493 intervention resulted in a pronounced reduced IL-1beta and in particular TNF expression. Furthermore, CNI-1493 significantly up-regulated synthesis of the anti-inflammatory cytokine TGF-beta and thereby shifted the balance of pro-inflammatory and anti-inflammatory cytokines in the arthritic joint in a beneficial way.

Sublethal hemorrhage blunts the inflammatory cytokine response to endotoxin in a rat model.

Tolerance to lipopolysaccharide (LPS) induced by previous hemorrhage in mice is associated with a blunted interleukin 1 (IL-1) response, suggesting down-regulation of the cytokine cascade as a possible protective mechanism. This study was undertaken to determine whether prehemorrhage induces attenuation of the cytokine response to sepsis beyond IL-1 in a rat model and whether this response occurs at the level of gene transcription. Sprague-Dawley rats underwent sublethal hemorrhage, lethal intraperitoneal endotoxin, or sublethal hemorrhage with delayed lethal endotoxin. Animals were killed 12 hours after LPS injection or 24 hours after hemorrhage. IL-1 and tumor necrosis factor (TNF) mRNA levels were determined on total splenic RNA using reverse-transcriptase polymerase chain reaction, and serum cytokine levels were determined using enzyme-linked immunosorbent assay. Animals that received LPS alone mounted an IL-1 and TNF response (RNA and protein) much higher than animals subjected to hemorrhage alone. TNF and IL-1 gene expression and protein levels in prehemorrhaged animals that received LPS, however, were significantly lower than those of animals that received LPS alone. Hemorrhage induces early IL-1 and TNF gene expression, which blunts their subsequent expected increase after endotoxic challenge. These findings validate previously documented immune-modulated protective effects of the first insult in a two-hit model.

Timing of tumor necrosis factor antagonism is critical in determining outcome in murine lethal acute pancreatitis

Tumor necrosis factor (TNF) is produced in large amounts within the pancreas, lungs, and liver during severe acute pancreatitis and is believed to mediate many of the detrimental consequences typical of this disease. Investigations into the benefit of TNF antagonism have suggested that TNF may also mediate processes that are protective to the host. With the hypothesis that timing plays a role in these dissenting views, TNF was antagonized either prophylactically or therapeutically with a recombinant form of the soluble type I TNF receptor (TNFbp) during a lethal model of necrotizing pancreatitis induced by feeding a choline-deficient diet. Mortality was determined for 10 days in 390 female mice divided into three groups: control, TNFbp early (time, 0 to 5 days), and TNFbp late (time, 1.5 to 5 days). Pancreatitis severity and cytokine production were assessed daily. Animals in the control group had a 75% mortality rate that was significantly decreased by prophylactic TNF blockade (64%, p < 0.05). Delaying TNF antagonism until serum cytokines were elevated and pancreatitis was manifest decreased mortality to 42% (p < 0.001 versus control, p < 0.01 versus early). Early and late TNF blockade decreased pancreatic edema and serum amylase, lipase, interleukin-1, and interleukin-6 (all p < 0.05) but not TNF. Late antagonism typically resulted in the greatest attenuation of all these parameters. Blockade of TNF by the administration of a soluble TNF receptor attenuates the severity of pancreatitis, decreases the production of associated inflammatory cytokines, and significantly improves survival. Delaying antagonism until pancreatitis is manifest and circulating cytokines are elevated but not yet maximal appears to be more protective than simple prophylactic TNF antagonism.

Simultaneous block of interleukin-1 and tumor necrosis factor is required to completely prevent bone loss in the early postovariectomy period.

Considerable evidence supports the hypothesis that estrogen prevents bone loss by blocking the production of cytokines in bone or bone marrow. However, controversy remains on the role of candidate factors, such as interleukin-1 (IL-1), IL-6, and tumor necrosis factor (TNF). As IL-1 and TNF have many additive and/or synergistic effects in bone, we tested the hypothesis that the simultaneous block of IL-1 and TNF is required to prevent the initial phase of rapid bone loss that follows ovariectomy (ovx). To this aim, rats were ovariectomized and treated for 2 weeks with either IL-1 receptor antagonist (IL-1ra), an inhibitor of IL-1, or TNF-binding protein (TNFbp), an inhibitor of TNF. Ovx increased bone marrow cell secretion of IL-1 and TNF and decreased the bone density of the distal femur, as measured by dual energy x-ray absorptiometry. Ovx-induced bone loss was decreased by both IL-1ra and TNFbp and completely prevented by simultaneous treatment with IL-1ra and TNFbp. Combined treatment with IL-1ra and TNFbp decreased urinary pyridinoline cross-links, a marker of bone resorption that reflects osteoclast number and osteoclast activity, whereas treatment with either inhibitor alone was less effective. Both IL-1ra and TNFbp decreased the number of osteoclasts on the endocortical surfaces and stimulated bone formation, but the two inhibitors had no additive effects on these indexes, suggesting that inhibition of osteoclastogenesis and stimulation of bone formation do not account for the additive bone-sparing effects of IL-1ra and TNFbp. These inhibitors had no effect in sham-operated rats, indicating that they specifically blocked estrogen-dependent events. In conclusion, these data indicate that in the early post-ovx period, IL-1 and TNF play a critical causal role in inducing bone loss and do so by stimulating bone resorption and inhibiting bone formation.

Regulation of interleukin 10 release by tumor necrosis factor in humans and chimpanzees.

Interleukin 10 (IL-10) has been shown to inhibit endotoxin-induced tumor necrosis factor (TNF) production. To assess the role of TNF in the induction of IL-10 in endotoxemia, four healthy men were studied after a bolus intravenous injection of recombinant human TNF (50 micrograms/m2). In addition, 13 healthy chimpanzees were investigated after a bolus intravenous injection of Escherichia coli endotoxin (4 ng/kg), 6 animals received endotoxin only, 4 animals received a simultaneous intravenous injection of a monoclonal anti-TNF antibody, whereas 3 chimpanzees were treated with an anti-TNF F(ab')2 fragment 30 min after the administration of endotoxin. TNF induced a modest rise in IL-10 concentrations peaking after 45 min (47 +/- 32 pg/ml; p < 0.05). IL-10 peaked 2 h after injection of endotoxin (202 +/- 61 pg/ml; p < 0.005). In both anti-TNF-treated groups, the early endotoxin-induced TNF activity was completely neutralized. Simultaneous anti-TNF treatment attenuated endotoxin-induced IL-10 release (73 +/- 13 pg/ml; p < 0.01 versus endotoxin alone), whereas postponed anti-TNF treatment did not significantly affect this response (p = 0.21). These results indicate that TNF, in part, mediates the induction of IL-10 in endotoxemia, resulting in an autoregulatory feedback loop.

Tumor necrosis factor is involved in the appearance of interleukin-1 receptor antagonist in endotoxemia.

To assess the role of tumor necrosis factor (TNF) in the appearance of interleukin-1 receptor antagonist (IL-1RA) in endotoxemia, 4 healthy humans were studied after a bolus intravenous injection of recombinant human TNF (50 micrograms/m2). In addition, 8 healthy chimpanzees were investigated after a bolus intravenous injection of Escherichia coli endotoxin (4 ng/kg) with (n = 4) or without (n = 4) a simultaneous intravenous injection of a monoclonal anti-TNF antibody (15 mg/kg). TNF induced a pronounced rise in IL-1RA concentrations, becoming apparent after 1 h and peaking after 3 h (P < .05). The rise in IL-1RA after administration of endotoxin started 2 h later. Neutralization of the early endotoxin-induced TNF activity by anti-TNF caused a marked reduction in IL-1RA concentrations (P < .05). These results indicate that TNF is an intermediate factor in IL-1RA release in endotoxemia.