Tumor necrosis factor (cachectin) in the biology of septic shock syndrome.

The high mortality of septic shock syndrome has prompted extensive investigation into its pathogenesis. Tumor necrosis factor (TNF), a cytokine that is often over-produced during Gram-negative or Gram-positive infection, occupies a critical role in triggering this catastrophic illness. The net effects of TNF are dependent upon its concentration in certain vital tissues, and may be dissociated from the presence of the invading pathogens. Agents that inhibit TNF have been developed; these protect against shock and tissue injury and are currently being investigated in clinical trials of septic shock syndrome.     

Tumor necrosis factor-alpha (cachectin) stimulates bone resorption in mouse calvaria via a prostaglandin-mediated mechanism

Recombinant human (h) and murine (m) tumor necrosis factor (TNF)-alpha stimulated bone resorption and the production of prostaglandin (PG) E2 in neonatal mouse calvaria in organ culture. In experiments of 72-h duration, the effect on bone resorption was of large magnitude (an average increase in medium calcium of 3.3 mg/dl above control values in 11 separate experiments) and occurred over a concentration range of 0.1-20 ng/ml mTNF and 0.5-50 ng/ml hTNF. Accompanying the TNF-enhanced release of bone calcium there was enhanced accumulation of PGE2 in the culture medium. The increases in medium calcium and PGE2 were both inhibited completely by nontoxic concentrations of 4 different PG cyclooxygenase inhibitors (indomethacin, piroxicam, ibuprofen, and acetylsalicylic acid) but not by the noncyclooxygenase inhibitor salicylic acid. The magnitude of the PGE2 response, but not the calcium release, was less for bones treated with TNF than for those treated with equipotent doses of epidermal growth factor or human transforming growth factors-alpha or -beta, suggesting that the local site of production of PGE2 in bone may be different for TNF than for the other factors. Repeated sc injections of hTNF to intact mice for a 48-h period produced a statistically significant elevation of the plasma calcium concentration. Because TNF is produced by cells of the monocyte/macrophage lineage in response to invasive stimuli such as the presence of tumor, our findings indicate that a host factor produced in response to malignant cells can cause enhanced bone resorption. Thus, the concept of the humoral hypercalcemias of malignancy must be expanded to include mediators not produced by the tumor cells themselves.     

Tumor necrosis factor/cachectin and lymphotoxin gene expression in lymph nodes from lymphoma patients

We investigated the mRNA content for tumor necrosis factor (TNF)/cachectin and lymphotoxin (LT) in tumoral tissues of a prospective series of 35 non-Hodgkin's (NHL) and 23 Hodgkin's (HL) lymphomas, to assess their postulated contribution to systemic symptoms. Total RNAs were extracted from diagnostic tissue specimens and submitted to Northern blot analysis, using specific TNF and LT cRNA probes. High amounts of TNF mRNA were found exclusively in NHL (12/35). The majority (9/12) of these were low grade B-cell NHL, which contained a uniform population of malignant cells. In contrast, abundant LT mRNA production was detected in most HL (21/23) and in 19 of 35 NHL. The highest LT mRNA levels were observed in high grade NHL and in lymphocytic predominant subtypes of HL specimens. A significant correlation was found between TNF/cachectin and LT gene expression in NHL and the presence of constitutional symptoms. The biologic and prognostic implications of these preliminary findings are presently unknown, but they demonstrate that lymphoma tissues sharing common histologic features are highly heterogeneous in their ability to synthesize cytokines susceptible to playing a role in the growth control of malignant cells. These results suggest that the evaluation of TNF/cachectin and LT production in lymphomas may help to elucidate the mechanisms of tumoral fever and cachexia.     

Tumor necrosis factor-alpha/cachectin enhances human immunodeficiency virus type 1 replication in primary macrophages

Macrophages are important target cells for human immunodeficiency virus type 1 (HIV-1). The ability of HIV-1 to productively infect macrophages may be influenced by endogenous cytokines that alter the activation state of these cells. In this study, the effect of tumor necrosis factor-alpha/cachectin (TNF alpha), a cytokine with macrophage-activating properties, on HIV-1 replication in primary blood monocyte-derived macrophages was examined. Treatment of macrophages with recombinant human TNF alpha (rTNF alpha), starting before or after HIV-1 infection, consistently enhanced viral production fivefold or greater above control (P less than .01). rTNF alpha was active at low concentrations (0.05-50 ng/ml) and increased the replication of both lymphocyte-tropic (human T lymphotropic virus type IIIB) and macrophage-tropic (human T lymphotropic virus type III BaL) strains of HIV-1. These findings provide additional evidence that TNF alpha may play a role in the pathogenesis of HIV-1 infection by upregulating viral expression in macrophages.     

Circulating tumour necrosis factor-alpha (cachectin) in myocardial infarction

In a prospective study, 22 patients with prolonged chest pain were monitored by serial serum tumour necrosis factor-alpha (TNF; cachectin) measurements. In five patients serum TNF markedly increased, peaking at greater than 145 ng l-1; all these patients had large infarcts complicated by hypotension, pulmonary oedema and/or arrhythmia. Two of these patients died. In contrast, TNF levels were either normal or only slightly raised in patients with small or uncomplicated infarcts and in patients with prolonged angina without evidence of infarction. The results show that extensive myocardial infarction induces the release of the monocyte/macrophage-derived polypeptide hormone TNF into circulation. This finding may be clinically relevant with respect to systemic metabolic consequences of myocardial infarction.     

Hormonal disturbances in visceral leishmaniasis (kala-azar)

This study presents a cross-sectional analysis of the hormonal alterations of patients with visceral leishmaniasis. The diagnosis was established by the bone marrow aspiration and polymerase chain reaction test. Primary adrenal insufficiency was observed in 45.8% of patients; low aldosterone/renin plasma ratio in 69.4%; low daily urinary aldosterone excretion in 61.1%; and low transtubular potassium gradient in 68.0%. All patients had normal plasma antidiuretic hormone (ADH) concentrations, hyponatremia, and high urinary osmolality. Plasma parathyroid hormone was low in 63%; hypomagnesemia was present in 46.4%, and increased Mg(++)(EF) in 100%. Primary thyroid insufficiency was observed in 24.6%, and secondary thyroid insufficiency in 14.1%. Normal follicle-stimulating hormone plasma levels were present in 81.4%; high luteinizing hormone and low testosterone plasma levels in 58.2% of men. There are evidences of hypothalamus-pituitary-adrenal axis abnormalities, inappropriate aldosterone and ADH secretions, and presence of hypoparathyroidism, magnesium depletion, thyroid and testicular insufficiencies.     

Tumor necrosis factor

Bronchial asthma is currently considered as basically an inflammatory disorder. In children there is a clear association between the allergy to aeroallergens and the development of asthma. By means of a complex interaction between environmental and genetic factors, the cellular mechanisms responsible for their pathophysiology are set off. The lymphocytes with a phenotype similar to those describe in the TH-2 mouse, are considered to be responsible for controlling this inflammatory process. By means of the production of Il-4 they would induce the hyper-production of IgE, the main alteration of the immunologic system in people who are allergic and it is eventually responsible for setting off the allergic reaction. The main effector cells involved are the eosinophils and the mastocytes, due to their capacity to segregate preformed and synthesised mediators of the inflammation again. Over the last few years the research work has been multiplied in search of the inflammatory markers of the illness, trying to co-relate them to the seriousness. In theory, the higher the level of inflammatory markers should correspond to a more serious inflammation, in this way the use of these markers would be aimed at monitoring the treatment, the response and the performance, the identification of risk patients and their application to the differential diagnosis of asthma. The TNF-alpha is a very versatile and ubiquitous cytokine that has been involved in the pathophysiology of bronchial asthma, both in the inflammatory process as well as in the bronchial hyper-reactivity. Our aim is to review the role of this inflammatory mediator in bronchial asthma in general and the specific problems of asthma in children.     

Tumor necrosis factor and interferon as prognostic markers in human immunodeficiency virus (HIV) infection

Peripheral blood cells were obtained from patients at different stages of their human immunodeficiency virus (HIV) infection. It was found that the capacity to generate interferon alpha was reduced already at Walter Reed stage 2 (WR) while the interferon gamma capacity remained largely unaffected until WR stage 4. Endogenous tumor necrosis factor (TNF) alpha production increased as the HIV disease progressed. The data obtained add to our knowledge on destruction of the immune system by the HIV. Moreover TNF and acid labile interferon alpha might contribute to HIV replication and disease progression. Nevertheless the tests performed are too time-consuming to be introduced into routine analysis of HIV infection or for monitoring its therapy and can so far not be used for intervention strategies. Further studies are needed.Periphere Blutzellen von Patienten mit unterschiedlichen Stadien der HIV-Infektion wurden auf ihre Fähigkeit, alpha-oder gamma-Interferon oder Tumornekrosefaktor-alpha zu bilden, untersucht. Die endogene alpha-Interferon Produktion war im Walter-Reed-Stadium 2 (WR) bereits reduziert, während dies für gamma-Interferon erst im WR-Stadium 4 zutraf. Die endogene TNF Produktion stieg mit Fortschritt der HIV-Erkrankung an. Die Untersuchungen ergeben neue Informationen über die progressive Zerstörung des Immunsystemes durch HIV. TNF und das säurelabile alpha-Interferon können zusätzlich HIV Replikation und Krankheitsfortschritt begünstigen. Die vorgestellten Tests sind wegen ihres Zeitaufwandes nicht in der Routineanalyse der HIV Infektion, der Therapiekontrolle oder bei Interventionsstrategien sinnvoll. Weitere klinische Untersuchungen sind notwendig.     

Impairment of hypothalamic-pituitary-thyroid function in rats treated with human recombinant tumor necrosis factor-alpha (cachectin)

Tumor necrosis factor-alpha (TNF; cachectin), a peptide secreted from stimulated macrophages, mediates some of the metabolic derangements in inflammatory and neoplastic disorders. To determine whether TNF is responsible for the changes in hypothalamic-pituitary-thyroid (HPT) function in nonthyroid illnesses, we administered synthetic human TNF to male Sprague-Dawley rats. The rats were given TNF or saline (control; both pair fed and nonpair fed) iv (six to eight per group). HPT function was tested 8 h after administration of 200 micrograms TNF/kg BW, 8 h after 5 days of 150 micrograms TNF/kg BW, and 8 h after a 3-day series of 50, 200, and 800 micrograms TNF/kg BW. The single injection of 200 micrograms TNF/kg significantly reduced (all P less than 0.05) serum TSH, T4, free T4, T3, and hypothalamic TRH compared to the corresponding hormone levels in saline-injected control rats. Serum TSH and hypothalamic TRH recovered to normal levels after 5 days of 150 micrograms/kg TNF treatment. With the increasing daily doses of TNF, serum TSH and hypothalamic TRH fell significantly. Hepatic 5'-deiodinase activity was reduced after 1 day of TNF treatment, but increased after the 3-day series of injections. TNF treatment reduced pituitary TSH beta mRNA, but did not affect alpha-subunit mRNA. TNF treatment also reduced thyroid 125I uptake and reduced thyroidal release of T4 and T3 in response to bovine TSH, but did not change the TSH response to TRH. TNF treatment reduced the binding of pituitary TSH to Concanavalin-A, indicating that it alters the glycosylation of TSH. The TSH with reduced affinity for this lectin had reduced biological activity when tested in cultured FRTL-5 rat thyroid cells. In vitro, TNF inhibited 125I uptake by cultured FRTL-5 rat thyroid cells and blocked the stimulation of [3H]thymidine uptake by these cells. The data indicate that TNF acts on the HPT axis at multiple levels and suggest that TNF is one of the mediators responsible for alterations in thyroid function tests in patients with nonthyroidal illnesses.     

Tumour necrosis factor (cachectin) and other cytokines in septic shock: a review of the literature

The role of bacterial endotoxin in the pathogenesis of septic shock has been studied extensively. Endotoxin does not seem to exert most of its effects on the host directly, but rather it elicits the production of host factors that may in turn lead to shock and death. These factors, called cytokines, appear to be produced by cells of haematopoietic origin such as macrophages/monocytes, but can also be produced by other cells such as endothelium and fibroblasts. Three important cytokines associated with septic shock are tumour necrosis factor/cachectin (TNF), interleukin 1 (IL-1) and interleukin 6 (IL-6). The macrophage-derived TNF has been implicated as the most important host mediator in the pathogenesis of septic shock. TNF, alone or together with endotoxin or IL-1, is capable of inducing lethal shock and tissue injury resembling that of septic shock. It has also been suggested that IL-6 is involved in the pathogenesis of septic shock. The major biologic activities of IL-6 include B-cell differentiation and induction of the acute-phase proteins. In the present paper, reports addressing the current understanding of the biological, regulatory and clinical aspects of these cytokines are reviewed.     

Standardization of the dot enzyme-linked immunosorbent assay (Dot-ELISA) for human visceral leishmaniasis

The Dot-ELISA, a rapid, visually read micro enzyme immunoassay for visceral leishmaniasis utilizing minute volumes of antigen "dotted" on nitrocellulose filter discs and precipitable chromogenic substrate, was analyzed under a variety of experimental parameters. Raising assay incubation temperatures from 23 degrees C to 28 degrees C resulted in titer increases in three of five leishmaniasis patient sera; at 37 degrees C, all five patient sera and one of five normal human sera showed titer increases. The amount of antigen used could be reduced 50% by incubating patient serum overnight at 4 degrees C. Antigen discs stored at - 20 degrees C were optimally reactive with leishmaniasis sera over a 270-day period. Antigen discs stored at 4 degrees C and 23 degrees C showed reproducible titer decreases at 90 days. Aging either peroxidase-conjugated antibody or substrate for up to 28 days at 4 degrees C did not adversely affect titers of positive and negative control sera and reagent controls. Activated substrate stored at 23 degrees C was optimally reactive in the assay for at least 24 hours. No changes in titers of positive and negative control sera or nonspecific reactions in reagent controls occurred when using different brands of microtiter plates. The long shelf lives and stabilities of Dot-ELISA antigen and reagents indicate this test should prove useful both in the laboratory and in the field.     

Dexamethasone modulation of tumour necrosis factor-alpha (cachectin) release by activated normal human alveolar macrophages.

Recurrent infections of the lower respiratory tract are a frequent and serious side-effect of chronic corticosteroid treatment. Since alveolar macrophages (AM) are currently thought to play a central role in the protection of the lower respiratory tract against infectious agents, it is likely that a steroid-induced deficiency of AM is involved in this process. In this respect, when activated, AM are major producers of tumour necrosis factor-alpha (TNF or cachectin), a versatile cytokine with several biological properties including antiviral and anti-infectious activities. A deficit of TNF production induced by corticosteroid may be one mechanism of the sensitivity to infections. Thus normal human AM obtained by bronchoalveolar lavage were pretreated with dexamethasone (DXM) before activation with lipopolysaccharides (LPS) and the amounts of TNF released in culture were quantified. Pretreatment with DXM resulted in a marked decrease of TNF release in a dose-dependent fashion. In contrast, when AM were activated with LPS before DXM treatment, TNF release by AM was suppressed in a more limited fashion. Thus DXM suppression of LPS-activated AM ability to release TNF may play a role in the susceptibility to infections of patients chronically treated with corticosteroids.     

Tumor necrosis factor in malaria-induced abortion

The cause of fetal loss in malaria is not known. We report that a small (1.5-5.0 micrograms) intravenous dose of recombinant human tumor necrosis factor (TNF) caused fetal death and abortion in 16 day pregnant mice that were carrying low densities of Plasmodium vinckei. In contrast, 50 micrograms human TNF did not cause fetal death or abortion in uninfected 16 day pregnant mice. Endogenous TNF, which was not detectable in plasma of low parasitemia animals, pregnant or not, was present (1.6 +/- 0.9 ng/ml) in samples from malarial pregnant mice when, on day 17, parasitemia was high and the first signs of impending abortion were evident. No TNF was detectable in the plasma of uninfected mice at day 17 of pregnancy. A small dose of TNF also caused fetal death in 16 day pregnant mice that had received an intravenous injection of Coxiella burneti extract 9-10 days earlier. Thus, TNF-induced abortion may occur in a range of infections in which systemic macrophage activation occurs and a trigger for TNF release is present.