Tumor Necrosis Factor-alpha Activity Research Articles

An update on the cytokine network in rheumatoid arthritis.

To update the knowledge accumulated on the contribution of cytokines to rheumatoid arthritis and related animal models. Publications from the end of 2002 and 2003 period were analyzed for a selection. A better understanding of the clinical results with tumor necrosis factor-alpha inhibitors has come from studies in treated patients. The expected effect of infliximab on the apoptosis of cells expressing tumor necrosis factor-alpha was not observed in synovium biopsy specimens. The mode of action of tumor necrosis factor-alpha on bone destruction has been clarified in gene-defective mice. Tumor necrosis factor-alpha acts through osteoclasts--an effect that is inhibited with osteoprotegerin. New interleukin-1 inhibitors with a potential for increased efficacy, such as interleukin-1trap, have been manufactured and are now being tested in rheumatoid arthritis. The list of cytokines of interest for therapeutic intervention has been growing rapidly. The results with animal models have provided clues to control arthritis with natural interleukin-18 inhibitors, such as interleukin-18 BP. Additional results have been accumulated that indicate the contribution of T cell subsets in inflammation and destruction through the production of interleukin-17. Synergistic interactions with other cytokines are critical in the interleukin-17 tuning effects. Macrophage inhibitory factor was described many years ago. Its comeback is based on properties of synoviocyte activation and proliferation. Such findings are critical for a better understanding of response heterogeneity in patients treated with the cytokine inhibitors now on the market. New therapeutic approaches are been planned from these results.

Activation of RAW264.7 Macrophages by Bacterial DNA and Lipopolysaccharide Increases Cell Surface DNA Binding and Internalization

Bacterial DNA containing unmethylated CpG motifs is a pathogen-associated molecular pattern (PAMP) that interacts with host immune cells via a toll-like receptor (TLR) to induce immune responses. DNA binding and internalization into cells is independent of TLR expression, receptor-mediated, and required for cell activation. The objective of this study was to determine whether exposure of immune cells to bacterial DNA affects DNA binding and internalization. Treatment of RAW264.7 cells with CpG oligodeoxynucleotide (ODN) for both 18 and 42 h resulted in a significant increase in DNA binding, whereas non-CpG ODN had no effect on DNA binding. Enhanced DNA binding was non-sequence-specific, inhibited by unlabeled DNA, showed saturation, was consistent with increased cell surface DNA receptors, and resulted in enhanced internalization of DNA. Treatment with Escherichia coli DNA or lipopolysaccharide (LPS) also resulted in a significant increase in DNA binding, but treatment with interleukin-1alpha, tumor necrosis factor-alpha, or phorbol 12-myristate 13-acetate had no effect on DNA binding. Soluble factors produced in response to treatment with CpG ODN or LPS did not affect DNA binding. These studies demonstrate that one consequence of activating the host innate immune response by bacterial infection is enhanced binding and internalization of DNA. During this period of increased DNA internalization, RAW264.7 cells were hypo-responsive to continued stimulation by CpG ODN, as assessed by tumor necrosis factor-alpha activity. We speculate the biological significance of increasing DNA binding and internalization following interaction with bacterial PAMPs may provide a mechanism to limit an ongoing immune inflammatory response by enhancing clearance of bacterial DNA from the extracellular environment.

Alcoholic liver injury in the rat is associated with reduced expression of peroxisome proliferator-alpha (PPARalpha)-regulated genes and is ameliorated by PPARalpha activation.

Alcoholic liver disease is associated with a state of hepatic fatty acid overload. We examined the effect of ethanol and different types of dietary fat on the expression of mRNA for liver fatty acid binding protein (L-FABP), peroxisome proliferator-activated receptor-alpha (PPARalpha), and peroxisomal fatty acyl CoA oxidase (FACO). Four groups of rats (n = 5) were fed intragastrically, a liquid diet with or without ethanol (10-16 g/kg/day) for 4 weeks. Pair-fed controls received isocaloric amounts of dextrose. The source of fat was either corn oil or fish oil. Ethanolfed rats developed fatty liver, necrosis, and inflammation; the changes were more severe in the fish oil-ethanol (FE) rats. PPARalpha mRNA levels were not different between groups, although there was a trend toward increased levels in ethanol-fed rats. We calculated L-FABP/PPARalpha and FACO/PPARalpha ratios as a measure of FACO and L-FABP up-regulation relative to PPARalpha expression. Both FACO/PPARalpha and L-FABP/PPARalpha ratios were significantly decreased in FE rats. However, only L-FABP/PPARalpha was decreased in corn oil plus ethanol rats. Also, the level of L-FABP/mRNA correlated inversely with the degree of fatty liver in ethanol-fed rats. Since expression of PPARalpha response genes was impaired in ethanol-fed rats, we determined whether activation of PPARalpha would normalize the PPARalpha response and prevent the pathological changes in ethanol-fed rats. Treatment with clofibrate, a PPARalpha-activating ligand, led to a marked decrease in fatty liver and complete abrogation of necroinflammatory changes in FE rats. Also, nuclear factor kappaB activation and up-regulation of tumor necrosis factor-alpha and cyclooxygenase-2 was also abolished in clofibrate-treated rats. We conclude that adaptive gene regulation of FACO and L-FABP by PPARalpha is impaired in ethanol-fed rats and that treatment with clofibrate, a PPARalpha ligand, prevents alcohol-induced pathological liver injury, possibly by reversing the above changes.

Development of multiple nonmelanoma skin cancers after treatment with infliximab

Infliximab is a chimeric mouse-human monoclonal antibody targeting tumor necrosis factor-alpha. Blocking the actions of tumor necrosis factor-alpha is highly effective in treating several inflammatory disorders. Although safety data has been encouraging, there are reports of immunosuppressive sequelae resulting from the use of the drug. We report a case of multiple squamous cell carcinomas arising in a patient receiving infliximab for treatment of her rheumatoid arthritis.

Intravenous immunoglobulin inhibits NF-kappaB activation and affects Fcgamma receptor expression in monocytes/macrophages.

High-dose intravenous immunoglobulin (IVIG) therapy is well established as a standard therapy for Kawasaki disease (KD) that reduces the risk of developing coronary artery aneurysms. Activation of monocytes/macrophages and tumor necrosis factor-alpha (TNF-alpha) activity are responsible for severe vascular injury in acute KD. We examined whether or not IVIG inhibits TNF-alpha-induced activation of transcription factor NF-kappaB, a factor that is essential for the expression of proinflammatory cytokines, in human monocytic U-937 cells. The inhibitory effect of IVIG on NF-kappaB activation induced by TNF-alpha was evaluated by Western blotting and flow cytometry. In addition, we examined the effect of IVIG on the expression of FcgammaIII (CD16) and FcgammaRIIb (CD32b) in U-937 cells and peripheral blood CD14+ monocytes/macrophages by flow cytometry. Western blotting demonstrated that IVIG inhibits NF-kappaB activation in U-937 cells, and flow cytometry that IVIG inhibits NF-kappaB activation in U-937 cells in a dose-related manner. Western blotting of cytoplasmic extracts of U-937 cells revealed that IVIG inhibited degradation of the IkappaBalpha protein. Moreover, flow cytometry demonstrated that IVIG decreased the expression of FcgammaRIII in U-937 cells and peripheral blood CD14+ monocytes/macrophages. However, Western blotting revealed that IVIG did not affect the quantity of FcgammaRIII protein, and PCR that IVIG did not affect the quantity of FcgammaRIII mRNA in the cells. These findings suggest that IVIG inhibits TNF-alpha-induced NF-kappaB activation in monocytes/macrophages, and blocks FcgammaRIII on the membranes of monocytes/macrophages.

Molecular cloning and characterization of mouse LITAF cDNA: role in the regulation of tumor necrosis factor-alpha (TNF-alpha) gene expression.

The inflammatory response to bacteria and bacterial products, such as lipopolysaccharides (LPSs), is mediated by a variety of secreted factors, but cytotoxic effects of LPS have been ascribed to the tumor necrosis factor alpha (TNF-alpha) activity. TNF-alpha is probably the most pleiotropic cytokine and, given the deleterious effects to the host of this factor, it has been postulated that its expression must be tightly regulated. Our laboratory has recently isolated, cloned and characterized a novel human transcription factor named LITAF or LPS-induced TNF-alpha factor. The present study reports the isolation, cloning and characterization of the mouse LITAF cDNA. Chromosomal localization revealed that mouse LITAF mapped to mouse chromosome 16, in a region highly homologous with the area on which human LITAF was previously located. Northern blot analysis shows that mouse LITAF is already expressed at embryonic day 7 of development, and is highly expressed in adult liver, heart and kidney. Moreover, upon LPS stimulation, we show that: (i) LITAF expression is increased in a mouse monocyte/macrophage cell line; and (ii) TNF-alpha expression is reduced in ES cell-derived macrophages lacking one copy of LITAF gene. Taken together, these results highlight the important role of LITAF in the regulation of TNF-alpha gene expression and suggest a potential role of LITAF in mouse organogenesis.

Molecular cloning and characterization of mouse LITAF cDNA: role in the regulation of tumor necrosis factor-α (TNF-α) gene expression

The inflammatory response to bacteria and bacterial products, such as lipopolysaccharides (LPSs), is mediated by a variety of secreted factors, but cytotoxic effects of LPS have been ascribed to the tumor necrosis factor alpha (TNF-α) activity. TNF-α is probably the most pleiotropic cytokine and, given the deleterious effects to the host of this factor, it has been postulated that its expression must be tightly regulated. Our laboratory has recently isolated, cloned and characterized a novel human transcription factor named LITAF or LPS-induced TNF-alpha factor. The present study reports the isolation, cloning and characterization of the mouse LITAF cDNA. Chromosomal localization revealed that mouse LITAF mapped to mouse chromosome 16, in a region highly homologous with the area on which human LITAF was previously located. Northern blot analysis shows that mouse LITAF is already expressed at embryonic day 7 of development, and is highly expressed in adult liver, heart and kidney. Moreover, upon LPS stimulation, we show that: (i) LITAF expression is increased in a mouse monocyte/macrophage cell line; and (ii) TNF-α expression is reduced in ES cell-derived macrophages lacking one copy of LITAF gene. Taken together, these results highlight the important role of LITAF in the regulation of TNF-α gene expression and suggest a potential role of LITAF in mouse organogenesis.

Etanercept

Etanercept (Enbrel), which inhibits the activity of tumour necrosis factor-alpha, is indicated in the treatment of patients with active rheumatoid arthritis (RA). A lifetime cost-utility analysis in patients with severe disease-modifying antirheumatic drug (DMARD)-resistant RA in the UK suggested that etanercept is associated with acceptable cost-utility ratios relative to traditional nonbiological DMARDs. In a 12-month cost-utility study in Spain, etanercept was predicted to be dominant over infliximab plus methotrexate in patients with active, refractory RA with regards to the cost per QALY gained and cost per American College of Rheumatology (ACR) 20 response achieved. In short-term cost-effectiveness analyses conducted in the US, the cost effectiveness of etanercept relative to other treatments in patients with methotrexate-naive or -resistant RA depends on whether predicted incremental cost-effectiveness ratios of at least USD 41,900 per ACR 20 response or USD 34,800 per ACR 70 weighted response over a 6-month period are considered acceptable (1999 values). The relative efficacy and cost effectiveness of etanercept and other biological DMARDs will be clarified when appropriate data from directly comparative clinical and/or long-term pharmacoeconomic studies become available. Etanercept may prevent or delay disability, which may produce reductions in nondrug costs that could help offset its acquisition cost.

Infliximab: a pharmacoeconomic review of its use in rheumatoid arthritis.

Infliximab (Remicade), a biological disease-modifying antirheumatic drug (DMARD), binds to and inhibits the activity of tumour necrosis factor-alpha, which is thought to play an important role in the pathophysiology of rheumatoid arthritis. Intravenous infliximab plus methotrexate is recommended in patients with rheumatoid arthritis who have not achieved satisfactory disease control with adequate courses of other DMARDs. Pharmacoeconomic analyses have been based on efficacy data from the pivotal placebo-controlled Anti-Tumour Necrosis Factor Trial in Rheumatoid Arthritis with Concomitant Therapy (ATTRACT) trial in patients with active, refractory rheumatoid arthritis. Infliximab every 8 weeks plus methotrexate demonstrated rapid and sustainable improvements in clinical response, delayed radiographic progression, and/or improved functional status and health-related QOL compared with placebo plus methotrexate at weeks 30, 54 and 102. In cost-utility analyses of infliximab plus methotrexate conducted from a healthcare payer and/or societal perspective in the US, Europe, Portugal, Sweden and the UK, infliximab 3 mg/kg every 8 weeks plus methotrexate was associated with acceptable (<$US50,000 per discounted QALY gained) cost-utility ratios relative to methotrexate alone in patients with active, refractory rheumatoid arthritis. When only direct costs were considered, the lifetime incremental cost per discounted QALY gained with infliximab plus methotrexate relative to methotrexate alone was $US30,500-38,700 (year of costing 1998 or not reported; treatment duration 54 or 102 weeks or lifelong) in the US and Europe analyses, and euro39 500 (year of costing not reported; lifelong treatment) in the Portuguese analysis. The cost-utility ratios were more favourable when lost productivity costs or the additional benefit of infliximab on radiographic stabilisation were considered. In the Swedish and UK analyses with a 10-year time horizon, infliximab plus methotrexate for 1 or 2 years was associated with cost-utility ratios of euro28 600-56 100 (year of costing not reported) when direct costs were considered, and euro3440-48 200 when direct costs plus loss-of-productivity costs were considered. In conclusion, cost-utility analyses, which were based on modelling of data from the pivotal clinical trial of infliximab plus methotrexate, indicate that infliximab plus methotrexate is associated with acceptable cost-effectiveness ratios (<$US50,000 per discounted QALY gained) relative to methotrexate monotherapy in patients with active rheumatoid arthritis who have not responded to previous methotrexate or other DMARD therapy. The cost effectiveness of infliximab versus other DMARDs is at present unclear, but will be clarified when appropriate data from directly comparative clinical and/or pharmacoeconomic studies become available. In patients in whom adequate courses of other DMARDs have failed to achieve satisfactory disease control, infliximab plus methotrexate may prevent or delay disability, which may produce reductions in nondrug costs that can help offset its acquisition cost.

Effect of cold-ischemia time on nuclear factor-kappaB activation and inflammatory response in graft after orthotopic liver transplantation in rats.

To study the mechanism and effect of nuclear factor-kappaB (NF-kappaB) activation and inflammatory response on the extended cold-preserved graft injury after orthotopic liver transplantation (OLT). OLT was performed in rats with varying time of cold ischemia grafts (6, 18 and 24 h in University Wisconsin solution at 4 degrees ). We determined the time of NF-kappaB activation and expression of tumor necrosis factor-alpha (TNF-alpha), cytokine-inducible neutrophil chemoattractant (CINC), and intercellular adhesion molecule-1 (ICAM-1) within 6 h after reperfusion. Serum alarming aminotransferase (ALT), neutrophil sequestration, circulating neutrophil CD11b and L- selectin expression were also evaluated. The accumulation of neutrophils in the graft was significantly increased in the 18 h and 24 h cold-ischemia groups within 0.5 h after reperfusion, compared with the 6 h group. But the strongly activated neutrophils was slightly increased at 2 h after reperfusion and remained at high levels 4 h after reperfusion, which was synchronized with the common situation of recipients after transplantation. Prolonged cold-preservation did not affect neutrophil accumulation and activation. NF-kappaB activation preceded the expression of TNF-alpha, CINC, and ICAM-1 in the liver, which was significantly increased with prolonged cold preservation. In prolonged cold preserved grafts, prominently elevated NF-kappaB activation occurred at 0.5 h and 1 h, compared with that at 2 h after reperfusion, which was consistent with greatly increased intrahepatic TNF-alpha response. NF-kappaB activation is correlated with the expression of TNF-alpha, CINC, and ICAM-1 in vivo in OLT rats. Extended cold preservation of grafts might up-regulate TNF-alpha, CINC, and ICAM-1 expression in the grafts, most probably through elevated NF-kappaB activation, and might contribute to neutrophil infiltration in the grafts after reperfusion. Elevated NF-kappaB activity is harmful to inflammatory response in the grafts, and inhibited NF-kappaB activity might protect against early graft injury after liver transplantation.

Protective effect of melatonin against liver injury in mice induced by Bacillus Calmette-Guerin plus lipopolysaccharide.

To investigate the effects and mechanisms of melatonin on immunological liver injury in mice. A model of liver injury was induced by tail vein injection of Bacillus Calmette Guerin (BCG) and lipopolysaccharide (LPS) in mice. Kupffer cells and hepatocytes were isolated and cultured according to a modified two-step collagenase perfusion technique. Levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and nitric oxide (NO), content of malondiadehyde (MDA), activity of superoxide dismutase (SOD), were measured by biochemical methods. Tumor necrosis factor-alpha (TNF-alpha) activity was determined by RIA. Interleukin (IL)-1 activity was measured by thymocyte proliferation bioassay. Hepatic tissue sections were stained with hematoxylin and eosin and examined under a light microscope. Immunological liver injury induced by BCG+LPS was successfully duplicated. Serum transaminase (ALT, AST) activities were significantly decreased by melatonin (0.25, 1.0, 4.0 mg/kg bm). Meanwhile, MDA content was decreased and SOD in liver homogenates was upregulated. Furthermore, pro-inflammatory mediators (TNF-alpha, IL-1, NO) in serum and liver homogenates were significantly reduced by melatonin. Histological examination demonstrated that melatonin could attenuate the area and extent of necrosis, reduce the immigration of inflammatory cells. In in vitro experiment, TNF-alpha was inhibited at the concentrations of 10(-8)-10(-6) mol/L of melatonin, while IL-1 production of Kupffer cells induced by LPS (5 microg/mL) was decreased only at the concentration of 10(-6) mol/L of melatonin, but no effect on NO production was observed. Immunological liver injury model in vitro was established by incubating hepatocytes with BCG- and LPS-induced Kupffer cells. Activities of ALT, TNF-alpha, IL-1, and MDA in supernatant were significantly increased. Melatonin had little effect on the level of ALT, but reduced the content of TNF-alpha and MDA at concentrations of 10(-7)-10(-5) mol/L and decreased the content of IL-1 at concentrations of 10(-6)-10(-5) mol/L. Melatonin could significantly protect liver injury in mice, which was related to free radical scavenging, increased SOD activity and pro-inflammatory mediators.

What is the contribution of differences in three measures of tumor necrosis factor-alpha activity to insulin resistance in healthy volunteers?

To address the potential role that tumor necrosis factor-alpha (TNF-α) might play in modulation of insulin resistance in healthy, nondiabetic individuals, we compared plasma TNF-α and soluble TNF-α receptor 2 (sTNF-R2) concentrations, as well as TNF-α polymorphisms, in 94 healthy individuals, stratified into insulin-resistant (IR) and insulin-sensitive (IS) groups based on their plasma insulin concentrations 120 minutes after oral glucose on 2 occasions (1993 and 2000). The IR group (n = 50; 29 men and 21 women) was in the upper quartile and the IS group (n = 44; 24 men and 20 women) in the lowest quartile of the distribution of post-glucose challenge insulin concentrations in a large unselected population (>50 v <23 μU/mL). The IR group had significantly higher values for body mass index, waist-to-hip girth, fasting and post-glucose challenge insulin concentrations, and fasting triglyceride concentrations, and lower high-density lipoprotein cholesterol concentrations as compared to the IS group. Despite the fact that they were relatively more obese, and insulin-resistant, plasma concentrations of TNF-α were similar in the IR (1.6 ± 0.6 pg/mL) and IS (1.7 ± 0.6 pg/mL) groups, as were the concentrations (5.4 ± 1.4 v 5.8 ± 2.0 pg/mL) of sTNF-R2. Furthermore, TNF-α polymorphisms (detected by polymerase chain reaction [PCR]) were similar in the 2 groups, with essentially identical allelic frequencies of the 238 (10.3% v 9.4%) and 308 polymorphisms (17.9% v 18.7%). In conclusion, plasma TNF-α and sTNF-R2 concentrations, as well as TNF-α gene polymorphisms, were not different in healthy volunteers stratified into IR and IS groups on the basis of their plasma insulin response to an oral glucose challenge. Given these data, it does not appear that differences in TNF-α activity contribute to the marked variations in insulin action that occur in healthy individuals.

The priming action of tumour necrosis factor-alpha (TNF-alpha) and granulocyte-macrophage colony-stimulating factor (GM-CSF) on neutrophils activated by inflammatory microcrystals.

We studied the effects of TNF-alpha or GM-CSF on the production of reactive oxygen species (as measured by chemiluminescence) and degranulation responses of neutrophils to opsonized inflammatory microcrystals. TNF-alpha in the 10-2000 pM or GM-CSF in the 2-200 pM concentration range caused the concentration-dependent amplification of neutrophil chemiluminescence responses to both calcium pyrophosphate dihydrate (CPPD) and monosodium urate monohydrate (MSUM) crystals. Degranulation responses, as measured by the extracellular release of the granule enzymes myeloperoxidase or lysozyme, were amplified by approximately 50-100% for both MSUM or CPPD crystal-induced neutrophil activation when cells were pretreated with TNF-alpha at 2000 pM or GM-CSF at 75 pM.

Actions of tumor necrosis factor-alpha on oocyte maturation and embryonic development in cattle.

Infertility can accompany mastitis in cattle. Involvement of tumor necrosis factor-alpha (TNF-alpha) in this phenomenon is suggested by observations that circulating concentrations of TNF-alpha are elevated after intramammary infection or infusion of endotoxin. It was hypothesized that (1) TNF-alpha acts on the oocyte during maturation to decrease the percent of oocytes that cleave and develop following fertilization; (2) exposure of embryos to TNF-alpha after fertilization reduces development to the blastocyst stage; and (3) TNF-alpha increases the proportion of blastomeres that undergo apoptosis in a stage-of-development dependent manner. In one experiment, oocytes were matured with various concentrations of TNF-alpha and then fertilized and cultured without TNF-alpha. In another study, embryos were cultured with TNF-alpha for 8 days beginning after fertilization. Finally, embryos were collected at the two or four-cell stage (at 28-30 hr after insemination) or when > or = 9-cells (at day 4 after insemination) and cultured +/- TNF-alpha for 24 hr. The proportion of blastomeres undergoing apoptosis was then determined by the TUNEL procedure. Addition of TNF-alpha to maturation medium did not affect the proportion of oocytes that cleaved. However, the percent of oocytes that developed to the blastocyst stage at day 8 after insemination was reduced (P = 0.05) at all TNF-alpha concentrations tested (0.1-100 ng/mL). When added during embryo culture, there was no significant effect of TNF-alpha on the proportion of oocytes that became blastocysts. In addition, TNF-alpha did not induce apoptosis in two and four-cell embryos. For embryos > or = 9-cells, however, 10 and 100 ng/mL TNF-alpha increased (P < 0.05) the percent of blastomeres labeling as TUNEL-positive. TNF-alpha can have deleterious actions on oocyte maturation that compromise development of the resultant embryo. While exposure of fertilized embryos to TNF-alpha did not inhibit development to the blastocyst stage, TNF-alpha increased the percentage of blastomeres undergoing apoptosis when exposure occurred for embryos > or = 9-cells. Increased blastomere apoptosis could conceivably compromise subsequent embryo survival.

Immunobiological effects of glucosamine in vitro.

Glucosamine (GlcN) and N-acetyl-d-glucosamine (GlcNAc) were assayed in vitro for their effects on proliferation, cytotoxicity and cytokine secretion in primary and secondary mixed lymphocyte cultures (MLCs). In addition, we studied the effect of GlcN and GlcNAc on the proliferation of purified CD4+ T cells exposed to immobilized anti-CD3 antibody. The present data show that GlcN, but not GlcNAc, inhibits CD4+ T-cell proliferation, the generation of alloreactive cytotoxic T lymphocytes (CTLs) and the secretion of interferon-gamma (IFN-gamma) and interleukin-5 (IL-5) in primary MLC. In secondary T helper-2 (Th2)-polarized MLC, GlcN, but not GlcNAc, inhibits IL-4 and IL-5 secretion, whereas no effect was found on IFN-gamma secretion in Th1-polarized MLC. Dendritic cells treated with GlcN showed a 75-80% decreased capacity for antigen cross-presentation and allostimulation. In cellular bioassays, GlcN was shown to inhibit the stimulatory activity of IL-4 and IL-2, as well as the cytotoxic activity of tumour necrosis factor-alpha (TNF-alpha). In conclusion, GlcN suppresses unprimed T-cell responses by interfering with antigen-presenting cell functions and by a direct inhibitory effect on T-cell proliferation. In addition, GlcN inhibits the secretion of cytokines in antigen-stimulated unprimed T cells and primed Th2-polarized cells.

502 Repopulation of the moderately well differentiated GL human squamous cell carcinoma growing in nude mice

Purpose: To evaluate the antitumor activity of recombinant human tumor necrosis factor-alpha (rHuTNF-α) on a human glioblastoma multiforme (U87) xenograft in nude mice, and to study the effect of combining rHuTNF-α with local radiation on the tumor control probability of this tumor model.Methods and Materials: U87 xenograft was transplanted SC into the right hindleg of NCr/Sed nude mice (7–8 weeks old, male). When tumors reached a volume of about 110 mm3, mice were randomly assigned to treatment: rHuTNF-α alone compared with normal saline control; or local radiation plus rHuTNF-α vs. local radiation plus normal saline. Parameters of growth delay, volume doubling time, percentage of necrosis, and cell loss factor were used to assess teh antitumor effects of rHuTNF-α on this tumor. The TCD50 (tumor control dose 50%) was used as an endoint to determine the effect of combining rHuTNF-α with local radiation.Results: Tumor growth in mice treated with a dose of 150 μg/kg body weight rHuTNF-α, IP injection daily for 7 consecutive days, was delayed about 8 days comapred to that in controls. Tumors in the treatment group had a significantly longer volume doubling time, and were smaller in volume and more necrotic than matched tumors in control group. rHuTNF-α also induced a 2.3 times increase of cell loss factor. The administration ofthe above-mentioned dose of rHuTNF-α starting 24 h after single doses of localized irradiation under hypoxic condition, resulted in a significant reduction in TCD50 from the control value of 60.9 Gy to 5035 Gy (p < 0.01).Conclusion: rHuTNF-α exhibits an antitumor effect against U87 xnograft in nude mice, as evidence by an increased delay in tumor growth as well as cell loss factor. Also, there was an augmentation of tumor curability when given in combination with radiotherapy, resulting in a significantly lower TCD50 value in the treatment vs. the control groups.

The sphingosine kinase 1/sphingosine-1-phosphate pathway mediates COX-2 induction and PGE2 production in response to TNF-alpha.

In this study we addressed the role of sphingolipid metabolism in the inflammatory response. In a L929 fibroblast model, tumor necrosis factor-alpha (TNF) induced prostaglandin E2 (PGE2) production by 4 h and cyclooxygenase-2 (COX-2) induction as early as 2 h. This TNF-induced PGE2 production was inhibited by NS398, a COX-2 selective inhibitor. GC-MS analysis revealed that only COX-2-generated prostanoids were produced in response to TNF, thus providing further evidence of COX-2 selectivity. As sphingolipids have been implicated in mediating several actions of TNF, their role in COX-2 induction and PGE2 production was evaluated. Sphingosine-1-phosphate (S1P) induced both COX-2 and PGE2 in a dose-responsive manner with an apparent ED50 of 100-300 nM. The related sphingolipid sphingosine also induced PGE2, though with much less efficacy. TNF induced a 3.5-fold increase in sphingosine-1-phosphate levels at 10 min that rapidly returned to baseline by 40 min. Small interfering RNAs (siRNAs) directed against mouse SK1 decreased (typically by 80%) SK1 protein and inhibited TNF-induced SK activity. Treatment of cells with RNAi to SK1 but not SK2 almost completely abolished the ability of TNF to induce COX-2 or generate PGE2. By contrast, cells treated with RNAi to S1P lyase or S1P phosphatase enhanced COX-2 induction leading to enhanced generation of PGE2. Treatment with SK1 RNAi also abolished the effects of exogenous sphingosine and ceramide on PGE2, revealing that the action of sphingosine and ceramide are due to intracellular metabolism into S1P. Collectively, these results provide novel evidence that SK1 and S1P are necessary for TNF to induce COX-2 and PGE2 production. Based on these findings, this study indicates that SK1 and S1P could be implicated in pathological inflammatory disorders and cancer.

Functional identification of the alveolar edema reabsorption activity of murine tumor necrosis factor-alpha.

Tumor necrosis factor-alpha (TNF-alpha) activates sodium channels in Type II alveolar epithelial cells, an important mechanism for the reported fluid resorption capacity of the cytokine. Both TNF-alpha receptor-dependent and -independent effects were proposed for this activity in vitro, the latter mechanism mediated by the lectin-like domain of the molecule. In this study, the relative contribution of the receptor-dependent versus receptor-independent activities was investigated in an in situ mouse lung model and an ex vivo rat lung model. Fluid resorption due to murine TNF-alpha (mTNF-alpha) was functional in mice that were genetically deficient in both types of mTNF-alpha receptor, establishing the importance of mTNF-alpha receptor-independent effects in this species. In addition, we assessed the capacity of an mTNF-alpha-derived peptide (mLtip), which activates sodium transport by a receptor-independent mechanism, to reduce lung water content in an isolated, ventilated, autologous blood-perfused rat lung model. The results show that in this model, mLtip, in contrast to mTNF-alpha, produced a progressive recovery of dynamic lung compliance and airway resistance after alveolar flooding. There was also a significant reduction in lung water. These results indicate that the receptor-independent lectin-like domain of mTNF-alpha has a potential physiological role in the resolution of alveolar edema in rats and mice.

Iron-dependent activation of NF-κB in Kupffer cells: a priming mechanism for alcoholic liver disease

Alcoholic liver disease is associated with hepatic iron accumulation, and iron supplementation exacerbates alcoholic liver disease, suggesting the pathogenic role of iron in alcoholic liver disease. We have tested a hypothesis that iron plays a signaling role in activation of redox-sensitive nuclear factor-kappa B (NF-κB) and that increased iron content results in heightened expression of proinflammatory cytokines in Kupffer cells because of this signaling. In cultured Kupffer cells isolated from normal rats, treatment with a lipophilic iron chelator, 1,2-dimethyl-3-hydroxypyrid-4-one (L1), markedly reduced lipopolysaccharide (LPS)-induced NF-κB activation and expression of tumor necrosis factor-alpha (TNF-α) and interleukin-6. Kupffer cells, isolated from rats with experimentally induced alcoholic liver disease, had significant increases in nonheme iron content, NF-κB binding, and mRNA expression for TNF-α and macrophage inflammatory protein-1. Ex vivo L1 treatment normalized all these parameters. Addition of ferrous iron to cultured normal rat Kupffer cells increased I-kappa B kinase (IKK) activity at 15 min and NF-κB binding at 30 min. L1 pretreatment completely abrogated both effects. Moreover, the iron treatment increased TNF-α release and TNF-α promoter activity in a NF-κB-dependent manner. Ferrous iron also transiently decreased cytoplasmic I-kappa B-alpha (IκB-α), with concomitant increases in nuclear p65 protein and DNA binding of p65/p50. Taken together, these results support the existence of iron-dependent signaling for activation of IKK/NF-κB in Kupffer cells, and this iron signaling serves as a target for a potential priming effect for the pathogenesis of experimental alcoholic liver disease.

Effects on plasma endotoxin and eicosanoid concentrations and serum cytokine activities in horses competing in a 48-, 83-, or 159-km endurance ride under similar terrain and weather conditions.

To determine plasma endotoxin concentration in horses competing in a 48-, 83-, or 159-km endurance race and its importance with regard to physical, hematologic, or serum and plasma biochemical variables. 3 horses. Weight and rectal temperature measurements and blood samples were obtained before, during, and after exercise. Blood samples were analyzed for plasma endotoxin concentration; serum antiendotoxin antibody titers; thromboxane B2 (TxB2) and 6-keto-prostaglandin F1alpha (PGF1alpha) concentrations; tumor necrosis factor alpha (TNFalpha) and interleukin-6 (IL-6) activities; WBC, plasma protein, lactate, serum electrolyte, and calcium concentrations; PCV; and creatine kinase activity. Detection of plasma endotoxin increased during exercise for horses competing at all distances but occurred more frequently in the 48- and 83-km groups. Plasma lactate concentration was significantly greater when endotoxin was concurrently detected. Endotoxin in plasma was not significantly associated with success of race completion. Plasma TxB2 and PGF1alpha concentrations and serum IL-6 activity significantly increased with exercise. Horses that had an excellent fitness level (as perceived by their owners) had greater decreases in serum antiendotoxin antibody titers during exercise than did horses perceived as less fit. In horses with better finish times, TxB2 and PGF1alpha concentrations were significantly greater and TNFalpha activity was significantly less than that of slower horses. Endotoxemia developed during endurance racing, but was significantly correlated with increased plasma lactate concentration and not with other variables indicative of endotoxemia. Plasma TxB2 and PGF1alpha concentrations and serum TNFalpha activity may be associated with performance success.