Biological Activity Of TNF-alpha Research Articles

Delayed addition of tumor necrosis factor (TNF) antagonists inhibits the generation of CD11c+ dendritic cells derived from CD34+ cells exposed to TNF-α

We have developed a method that cells exhibiting typical dendritic cell (DC) characteristics are generated from human CD34(+) cells and phagocytose cogenerating erythroid progenitor cells in the presence of tumor necrosis factor-alpha (TNF-alpha), interleukin-3, stem cell factor and erythropoietin. Using this system, we titrated the effects of TNF antagonists, etanercept and infliximab, on TNF-alpha activity. We found that 1 microg/ml etanercept dramatically inhibited the generation of CD11c(+) cells accompanying with a complete recovery of the generation of erythroid progenitors. Infliximab at 200 microg/ml exhibited a similar effect to that observed for etanercept. The delayed addition of etanercept to this culture system at day five resulted in significant inhibitory effects on the generation of CD11c(+), CD4(+) and CD86(+) cells. These results indicate that TNF antagonists administered at a concentration that is achievable in vivo, neutralize the biologic effects of TNF-alpha in generating CD11c(+) cells and that a delay in the administration of these antagonists for as long as 5 days partially inhibits the biologic activity of TNF-alpha. These findings may contribute to a great understanding of anti-TNF therapy in patients with an overproduction of cytokines such as hemophagocytic syndromes.

The type 1 TNF receptor and its associated adapter protein, FAN, are required for TNFα-induced sickness behavior

During the course of an infection, the pro-inflammatory cytokine tumor necrosis factor alpha (TNFalpha) acts in the brain to trigger development of behavioral responses, collectively termed sickness behavior. Biological activities of TNFalpha can be mediated by TNF receptor type 1 (TNF-R1) and type 2 (TNF-R2). TNFalpha activates neutral sphingomyelinase through the TNF-R1 adapter protein FAN (factor associated with neutral sphingomyelinase activation), but a behavioral role of FAN in the brain has never been reported. We hypothesized that TNFalpha-induced sickness behavior requires TNF-R1 and that FAN is a necessary component for this response. We determined the role of brain TNF-R1 in sickness behavior by administering an optimal amount of TNFalpha intracerebroventricularly (i.c.v., 50 ng/mouse) to wild-type (WT), TNF-R1-, TNF-R2-, and FAN-deficient mice. Sickness was assessed by decreased social exploration of a novel juvenile, induction of immobility, and loss of body weight. TNF-R1-deficient mice were resistant to the sickness-inducing properties of i.c.v. TNFalpha, whereas both TNF-R2-deficient and WT mice were fully responsive. Furthermore, the complete absence of TNFalpha-induced sickness behavior in FAN-deficient mice provided in vivo evidence that FAN-dependent TNF-R1 signaling is critical for this central action of TNFalpha. This is the first report to demonstrate that TNFalpha-induced sickness behavior is fully mediated by TNF-R1 and that the adaptor protein FAN is a necessary intracellular intermediate for sickness behavior.

The use of infliximab in dermatology

Autoimmune diseases like Crohn's disease, rheumatoid arthritis (RA) and psoriasis are often difficult to treat due to complex underlying immunologic pathways. Tumor necrosis factor (TNFalpha) is an important proinflammatory cytokine that seems to play an important role in the pathogenesis of these diseases. After the approval of a variety of drugs which block the biological activity of TNFalpha, new therapeutic options were available and especially infliximab became widely used. TNFalpha, as a member of the proinflammatory cytokine family, is a major cytokine in different inflammatory dermatological diseases such as cutaneous vasculitis, lupus erythematosus, eczema or psoriasis. Therefore infliximab has been used in a variety of inflammatory dermatoses lately, sometimes with great success. Several case reports showing new indications for a successful use of TNFalpha-inhibitors in dermatology have been published and will be reviewed in the following article. Nevertheless, infliximab is not approved for these indications at the moment and has to be considered as off-label use.

Effects of ultrasound on the structure and function of tumor necrosis factor–α

The objective of this study was to investigate the effects of ultrasound on the structure and function of human tumor necrosis factor–alpha (TNF-α) and to study whether TNF-alpha underwent a denaturation process and the molecular structure was damaged when it was irradiated by ultrasound. The samples of TNF-alpha were dissolved in aqueous solution and filled into polystyrene tubes. High intensity ultrasound processor (20 kHz frequency, burst mode, 0.5 duty factor, 100–500 W total electrical power, 0–20 min total treatment time) was used during the treatment. The biologic activity of TNF-alpha was determined by its toxic activity towards TNF-alpha sensitive cell line L 929 in the presence of actinomycin D. The methods of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) were used to detect the integrity of TNF-alpha molecule after it was irradiated by ultrasound. The results showed TNF-alpha could keep its biological activity, instead of undergoing a denaturation process, when it is irradiated by ultrasound in the aqueous solution; at the same time, the aggregates of TNF-alpha formed by the recombinant DNA E. coli could be dissociated through the molecular vibration induced by ultrasound energy. The biologic activity of TNF-alpha was not reduced, but small quantities of TNF-alpha molecular structure were damaged during the process of sonication. These features of TNF-α molecule irradiated by ultrasound probably gave TNF-α the advantage in being used in the drug microencapsulation and provided a new drugs formulation for tumor therapy. (mxwan@mail.xjtu.edu.cn)

Treatment of Crohn's disease with infliximab.

The role of infliximab in managing Crohn's disease (CD) is described. CD is characterized by chronic transmural inflammation at various sites of the gastrointestinal tract, particularly the ileum and colon. The major symptoms are diarrhea, abdominal pain, enterocutaneous and perianal fistulas, and weight loss. Management goals include alleviating symptoms, inducing remission, promoting healing of the intestinal mucosa and fistulas, and modifying the disease process. Drugs traditionally used to manage CD are aminosalicylates, antimicrobials, immunomodulatory agents, and corticosteroids. Infliximab is a chimeric (human-mouse) monoclonal antibody targeted at human tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine important in the pathogenesis of CD. Infliximab antagonizes the biological activity of TNF-alpha by binding to it on macrophage and T-cell surfaces. Clinical trials have shown infliximab to be effective in producing and maintaining a clinical response in patients with refractory, moderate to severe CD. Treatment helps promote healing of intestinal mucosa and closure of fistulas. Infliximab may act more rapidly than most traditional agents and produces less severe adverse effects. The most frequent adverse effects are headache, nausea, and upper-respiratory-tract infections. The recommended dosage is 5 mg/kg i.v. infused over a two-hour period. Infliximab may be given at eight-week intervals for maintenance or management of flare-ups. Infliximab appears useful in the treatment of CD and may improve patients' quality of life.

Plasma concentrations of tumor necrosis factor-alpha (TNF-alpha) and soluble TNF receptors in patients with bulimia nervosa.

Tumor necrosis factor-alpha (TNF-alpha) is a cytokine with numerous immunological and metabolic activities. In addition, TNF-alpha can stimulate a variety of physiological, neuroendocrine and behavioural responses of the central nervous system. In experimental animals, TNF-alpha induces changes in physiological and behavioural parameters which have also been observed in eating disorders. The biological activities of TNF-alpha are mediated by two structurally related, but functionally distinct receptors, TNF-RI and TNF-RII. Since injection of TNF-alpha results in increased shedding of TNF-alpha receptors, it is likely that TNF-alpha release is reflected by soluble TNF-receptors (sTNF-Rs) levels. We studied plasma concentrations of TNF-alpha and two sTNF-Rs (sTNF-RI and sTNF-RII) in female patients with bulimia nervosa. Twenty female patients with bulimia nervosa (BN) and 20 age-matched normal women (N) were studied. Plasma TNF-alpha concentrations were measured by enzyme immunoassay kit and plasma concentrations of sTNF-RI and sTNF-RII were measured by enzyme-linked immunosorbent assay. Plasma TNF-alpha concentrations in BN were significantly higher than those in N (4.7+/- 0.5 ng/l vs. 1.6+/-0.1 ng/l; P<0.01). Although no significant difference was observed in plasma sTNF-RI concentrations between the two groups, plasma sTNF-RII concentrations in BN were significantly higher than those in N (2080.0+/-107.5 ng/l vs. 1569.5 +/-84.0 ng/l; P<0.01). Plasma TNF-alpha concentrations were significantly related to plasma sTNF-RI concentrations (r = 0.511, P<0.05) and to plasma sTNF-RII concentrations (r = 0.532, P<0.05) in bulimic patients. However, plasma TNF-alpha concentrations were not related to body fat mass or to bulimic behaviours in these patients. Our present findings suggest that the adipose tissue may not be the immediate source of TNF-alpha in bulimic patients but the increase in plasma TNF-alpha in these patients may be derived from the central nervous system sources. The elevated sTNF-RII may reflect different shedding kinetics compared with sTNF-RI in bulimic patients.

Circulating levels of sTNFR and discrepancy between cytotoxicity and immunoreactivity of TNF-α in patients with visceral leishmaniasis

To study the influence of soluble tumour necrosis factor (TNF) receptors (sTNFR) on bioactivity and immunoreactivity of TNF-alpha in patients with visceral leishmaniasis (Kala-azar) and to examine the association between circulating levels of sTNFR type I and type II with clinical manifestations of the disease. Ten patients with Kala-azar were enrolled. Plasma samples for TNF-alpha and sTNFR were obtained on days 0, 7 and 21-28 of antimonial therapy. Bioactivity of TNF-alpha was measured by cytotoxicity to L-929 cells and immunoreactivity by enzyme-linked immunosorbent assay (ELISA). sTNFR-I and sTNFR-II were measured by ELISA. Measured by ELISA, TNF-alpha was detected at baseline in all patients (range from 22.3 to 163 pg/mL) and showed a linear decline over time on therapy (r = -0.49, P = 0.007). In contrast, when measured by cytotoxicity assay, TNF-alpha was detected in only one patient at baseline (193 pg/mL) and in four patients at the end of therapy (38.7, 95, 133 and 232 pg/mL) and there was no linear association between TNF-alpha and duration of therapy (r = -0.18, P = 0.45). sTNFR-I and sTNFR-II were detected in all patients before therapy. There was a strong positive correlation between plasma concentrations of sTNFR-I and sTNFR-II (r = 0.8, P = 0.006). Levels of sTNFR-I and sTNFR-II declined exponentially with time on therapy. We concluded that sTNFR-I and sTNFR-II are related to disease activity in patients with Kala-azar and that these circulating receptors may interfere with the biological activity of TNF-alpha in patients with Kala-azar.

Monoclonal antibody-mediated, complement-independent binding of human tumor necrosis factor-alpha to primate erythrocytes via complement receptor 1.

Monoclonal antibody (MAb)-based heteropolymers (HP) were used to simulate immune adherence. The HP is constructed by cross-linking MAbs that recognize complement receptor 1 (CR1) and tumor necrosis factor-alpha (TNF-alpha). 125I-labeled TNF-alpha was cocultured with either sheep, monkey, or human erythrocytes in the presence or absence of HP. Human erythrocytes demonstrated 63% +/- 0 (mean +/- SD) binding of 125I-labeled TNF-alpha, while binding of 125I-labeled TNF-alpha in the absence of HP was 4% +/- 1% (P < .001). Monkey erythrocytes showed similar results, while sheep erythrocytes (which lack CR1) demonstrated low binding. The effect of HP binding on biologic activity of TNF-alpha was examined in an assay of stimulated human neutrophils. The HP completely inhibited the ability of TNF-alpha to prime neutrophils, occurring regardless of the presence or absence of erythrocytes but solely dependent on the addition of HP. Thus, the HP facilitated specific, saturable, and significant binding of 125I-labeled TNF-alpha to primate erythrocytes in vitro.

Tumor necrosis factor (TNF) receptor type 1 (p55) is a main mediator for TNF-alpha-induced skin inflammation.

Tumor necrosis factor alpha (TNF-alpha) is a pleiotropic proinflammatory cytokine that elicits a large number of biological effects, including inflammatory and immunoregulatory responses. Biological activities of TNF-alpha are mediated by two distinct TNF receptors, p55 type 1 receptor (TNFR1) and p75 type 2 receptor (TNFR2). To determine the role of TNF-alpha in the induction of inflammatory responses in the skin, gene-targeted mutant mice lacking either TNFR1 or TNFR2 were painted with irritant chemicals. Both phenol and croton oil painting onto the ears induced less inflammation in TNFR1(-) mice than normal and TNFR2(-) mice. Intradermal injection of TNF-alpha (0.2-200 ng for 3 days) into the ear induced less inflammation in TNFR1(-) mice than in normal mice. TNFR2(-) mice developed a normal inflammatory reaction to high doses of TNF-alpha (20-200 ng for 3 days), while they showed minimal reactivity to low doses of TNF-alpha (0.2-2 ng for 3 days). TNF-alpha is known to trigger the release of a series of other cytokines and to induce the expression of cell adhesion molecules, thus contributing to the development of inflammation. The levels of protein and mRNA for interleukin (IL)-6 were elevated in keratinocytes from normal as well as TNFR2(-) mice after treatment with TNF-alpha, while keratinocytes from TNFR1(-) mice did not show any up-regulation of IL-6. TNF-alpha induced intercellular adhesion molecule (ICAM)-1 expression in the keratinocytes from normal and TNFR2(-) mice, but not in those from TNFR1(-) mice. These results indicate that TNFR1 is critical for induction of skin inflammation by TNF-alpha.

Plasma levels of tumor necrosis factor (TNF) and soluble TNF receptors in kidney transplant recipients.

Tumor necrosis factor-alpha is elevated in plasma during kidney transplant rejection. However, the measurement and biological activity of TNF alpha is influenced by inhibitory soluble TNF receptors. We therefore determined plasma levels of TNF alpha and the 2 soluble TNF receptors, the 55-kDa TNF receptor (TNF-sR55) and the 75-kDa TNF receptor (TNF-sR75), by immunoassays in 25 patients before and daily after kidney transplantation. Plasma samples were retrospectively assigned to 3 groups: (1) patients with well-functioning grafts (n = 14); (2) patients with biopsy-proven graft rejections (n = 7 patients with 10 rejections); and (3) patients with episodes of CsA nephrotoxicity (n = 4 patients with 9 samples). On the day of biopsy-proven graft rejection, TNF alpha increased from 8.6 +/- 0.9 pg/ml to 14.8 +/- 3.5 pg/ml (P < 0.02), TNF-sR55 from 6.6 +/- 1.3 ng/ml to 9.0 +/- 1.2 ng/ml (NS), and TNF-sR75 from 10.3 +/- 1.0 ng/ml to 15.3 +/- 2.0 ng/ml (P < 0.01). During episodes of CsA toxicity, TNF alpha levels did not change, TNF-sR55 increased from 5.2 +/- 0.5 ng/ml to 10.5 +/- 0.5 ng/ml (P < 0.01), and TNF-sR75 increased from 10.2 +/- 0.8 ng/ml to 17.5 +/- 0.9 ng/ml (P < 0.01). There was a strong correlation between serum creatinine and plasma TNF-sR55 (r = 0.7, P < 0.001) and TNF-sR75 (r = 0.7, P < 0.001), but not with TNF alpha. Therefore, levels of TNF-sR55 and TNF-sR75 were corrected for serum creatinine. An index expressing TNF alpha over actively released soluble receptors (index = TNF alpha/(corr.TNF-sR55 + corr.TNF-sR75)) detected rejection episodes with a sensitivity of 70-80% and a specificity of 89%. We conclude that the measurement of plasma TNF alpha in combination with its soluble receptors is superior to isolated TNF alpha determinations in discriminating acute graft rejection from episodes of CsA toxicity in kidney transplant recipients.

Selective enhancement of the tumour necrotic activity of TNF alpha with monoclonal antibody.

The binding and biological activity of human TNF alpha on endothelial and tumour cells has been studied in the presence of monoclonal antibodies (MAbs). In particular, one monoclonal antibody to TNF alpha (MAb 32) has been identified which failed to inhibit binding and cytotoxicity of TNF alpha on WEHI-164 tumour cells but which was a potent inhibitor of TNF alpha-induced endothelial cell procoagulant activity on bovine aortic endothelial cells. The ability of MAb 32 to inhibit selectively the actions of TNF alpha on endothelial cells but not on tumour cells suggests a mechanism for enhancement of the anti-tumour action of TNF alpha in vivo when in complex with this antibody. Treatment of tumour bearing mice (WEHI-164 and Meth A fibrosarcoma) with TNF alpha-MAb 32 complex resulted in a 5- to 10-fold enhancement in the potency of the cytokine in comparison to free TNF alpha. Complexes between this cytokine and other MAbs generally resulted in either no effect or inhibition of TNF alpha activity in vivo and in vitro. Neither intact MAb 32 nor FAb' fragments of MAb 32 showed any tumour regressive activity in the absence of TNF alpha. The FAb' fragments were equipotent to the bivalent form of the antibody in enhancing TNF alpha activity. These data provide evidence that it is possible to segregate the individual biological activities of TNF alpha with concomitant enhancement of the tumour regressive activity of the cytokine in vivo.