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TNFalpha is an important mediator of catabolism in cachexia. Most of its effects have been characterized in peripheral tissues, such as skeletal muscle and fat. However, by acting directly in the hypothalamus, TNFalpha can activate thermogenesis and modulate food intake. Here we show that high concentration TNFalpha in the hypothalamus leads to increased O(2) consumption/CO(2) production, increased body temperature, and reduced caloric intake, resulting in loss of body mass. Most of the thermogenic response is produced by beta 3-adrenergic signaling to the brown adipose tissue (BAT), leading to increased BAT relative mass, reduction in BAT lipid quantity, and increased BAT mitochondria density. The expression of proteins involved in BAT thermogenesis, such as beta 3-adrenergic receptor, peroxisomal proliferator-activated receptor-gamma coactivator-1 alpha, and uncoupling protein-1, are increased. In the hypothalamus, TNFalpha produces reductions in neuropeptide Y, agouti gene-related peptide, proopiomelanocortin, and melanin-concentrating hormone, and increases CRH and TRH. The activity of the AMP-activated protein kinase signaling pathway is also decreased in the hypothalamus of TNFalpha-treated rats. Upon intracerebroventricular infliximab treatment, tumor-bearing and septic rats present a significantly increased survival. In addition, the systemic inhibition of beta 3-adrenergic signaling results in a reduced body mass loss and increased survival in septic rats. These data suggest hypothalamic TNFalpha action to be important mediator of the wastage syndrome in cachexia.

Objectives: Rheumatoid arthritis (RA) is accompanied by increased resting energy expenditure (REE) and decreased fat-free mass (FFM). This is referred to as rheumatoid cachexia and is attributed to high levels of tumour necrosis factor-alpha (TNF-alpha). This study aimed to investigate the effects of anti-TNF-alpha therapy on REE, body composition, physical activity and protein intake in RA patients., Methods: Twenty RA patients [50% female; age: (mean +/- s.d.) 61.1 +/- 6.8 yrs; body mass index (BMI): 28.3 +/- 3.7 kg/m2] and 12 age-sex-BMI-matched healthy controls were assessed. REE (indirect calorimetry), body composition (bioelectrical impedance), the International Physical Activity Questionnaire (IPAQ), diet, Health Assessment Questionnaire (HAQ), disease activity [disease activity score 28 (DAS28), erythrocyte sedimentation rate (ESR), C-reactive protein] and serum TNF-alpha were measured before (Baseline) as well as 2 weeks (Time-1) and 12 weeks (Time-2) after initiation of anti-TNF-alpha treatment. Controls were only assessed at Baseline., Results: RA patients had significantly higher REE than controls at Baseline (1799.4 +/- 292.0 vs 1502.9 +/- 114.5 kcal/day, P = 0.002). Within the RA group, REE increased significantly between Time-1 and Time-2 (P = 0.001) but not between Baseline and Time-2. Sustained significant increases were observed in IPAQ (P = 0.001) and protein intake (P = 0.001). There were no significant changes in FFM or body fat. ESR (P = 0.002), DAS28 (P < 0.001), HAQ (P < 0.001) and TNF-alpha (P = 0.024) improved significantly. Physical activity (P = 0.001) and protein intake (P = 0.024) were significant between-subject factors for the elevation of REE., Conclusions: After 12 weeks of anti-TNF-alpha therapy, there were significant improvements in disease activity and physical function, as well as physical activity and protein intake, but no significant changes in REE or FFM. There is a need for longer-term studies in this field.

TNF-alpha, generated during the systemic inflammatory response, triggers a wide range of biological activities that mediate the neurologic manifestations associated with cancer and infection. Since this cytokine regulates ion channels in vitro (especially Kv1.3 and Kir2.1), we aimed to study Kv1.3 and Kir2.1 expression in brain in response to in vivo systemic inflammation. Cancer-induced cachexia and LPS administration increased plasma TNF-alpha. Kv1.3 and Kir2.1 expression was impaired in brain during cancer cachexia. However, LPS treatment induced Kv1.3 and downregulated Kir2.1 expression, and TNF-alpha administration mimicked these results. Experiments using TNF-alpha double receptor knockout mice demonstrated that the systemic inflammatory response mediates K(+) channel regulation in brain via TNF-alpha-dependent and -independent redundant pathways. In summary, distinct neurological alterations associated with systemic inflammation may result from the interaction of various cytokine pathways tuning ion channel expression in response to neurophysiological and neuroimmunological processes.

Cachexia is associated with poor prognosis in patients with chronic disease. Tumor necrosis factor-alpha (TNFalpha) plays a pivotal role in mediating cachexia and has been demonstrated to inhibit skeletal muscle differentiation in vitro. It has been proposed that TNFalpha-mediated activation of NFkappaB leads to down regulation of MyoD, however the mechanisms underlying TNFalpha effects on skeletal muscle remain poorly understood. We report here a novel pathway by which TNFalpha inhibits muscle differentiation through activation of caspases in the absence of apoptosis. TNFalpha-mediated caspase activation and block of differentiation are dependent upon the expression of PW1, but occur independently of NFkappaB activation. PW1 has been implicated previously in p53-mediated cell death and can induce bax translocation to the mitochondria. We show that bax-deficient myoblasts do not activate caspases and differentiate in the presence of TNFalpha, highlighting a role for bax-dependent caspase activation in mediating TNFalpha effects. Taken together, our data reveal that TNFalpha inhibits myogenesis by recruiting components of apoptotic pathways through PW1.

Leptin is a recently identified hormone produced by the adipocyte ob gene which acts as a negative feedback signal critical to the normal control of food intake and body weight. A number of proinflammatory cytokines, such as interleukin 6, tumor necrosis factor alpha, and interferon gamma, have been proposed as mediators of cancer cachexia; these data suggest that abnormalities in leptin production/release or in its feedback mechanism play a role in cancer patients. We therefore studied the relationship between serum leptin and serum cytokines interleukin 6 and tumor necrosis factor alpha levels in advanced-stage cancer patients. Twenty-nine advanced stage cancer patients (all but one stage IV) with tumors at various sites were included in the study. A direct correlation between body mass index and serum leptin levels was found both in cancer patients and in healthy individuals. The serum levels of interleukin 6 were significantly higher in cancer patients than in healthy individuals. In cancer patients an inverse correlation was found between serum levels of leptin and proinflammatory cytokines. There was an inverse correlation between the Eastern Cooperative Oncology Group performance status scale and serum levels of leptin. Regarding survival, patients with very high serum levels of proinflammatory cytokines and very low levels of leptin had very short survival. Although obtained in a cancer patient population not overtly cachectic, our results provide further evidence that a simple dysregulation of leptin production and/or release cannot be involved in cancer-associated pathophysiological changes leading to cachexia.

Muscle wasting is often associated with chronic inflammation. Because tumor necrosis factor alpha (TNF-alpha) has been implicated as a major mediator of cachexia, its effects on C2C12 myocytes were examined. TNF-alpha activated nuclear factor-kappaB (NF-kappaB) and interfered with the expression of muscle proteins in differentiating myoblasts. Introduction of a mutant form of inhibitory protein kappaBalpha (IkappaBalpha) restored myogenic differentiation in myoblasts treated with TNF-alpha or interleukin 1beta. Conversely, activation of NF-kappaB by overexpression of IkappaB kinase was sufficient to block myogenesis, illustrating the causal link between NF-kappaB activation and inhibition of myogenic differentiation. The inhibitory effects of TNF-alpha on myogenic differentiation were reversible, indicating that the effects of the cytokine were not due to nonspecific toxicity. Treatment of differentiated myotubes with TNF-alpha did not result in a striking loss of muscle-specific proteins, which shows that myogenesis was selectively affected in the myoblast stage by TNF-alpha. An important finding was that NF-kappaB was activated to the same extent in differentiating and differentiated cells, illustrating that once myocytes have differentiated they become refractory to the effects of NF-kappaB activation. These results demonstrate that inflammatory cytokines may contribute to muscle wasting through the inhibition of myogenic differentiation via a NF-kappaB-dependent pathway.

A20 is a cytoplasmic zinc finger protein that inhibits nuclear factor kappaB (NF-kappaB) activity and tumor necrosis factor (TNF)-mediated programmed cell death (PCD). TNF dramatically increases A20 messenger RNA expression in all tissues. Mice deficient for A20 develop severe inflammation and cachexia, are hypersensitive to both lipopolysaccharide and TNF, and die prematurely. A20-deficient cells fail to terminate TNF-induced NF-kappaB responses. These cells are also more susceptible than control cells to undergo TNF-mediated PCD. Thus, A20 is critical for limiting inflammation by terminating TNF-induced NF-kappaB responses in vivo.

Although circulating tumor necrosis factor (TNF)-alpha levels have been found to be increased in weight-losing patients with chronic obstructive pulmonary disease (COPD), the main causes for this phenomenon remain to be elucidated. Since hypoxia itself can enhance the production of the TNF-alpha in vitro, we studied the relationship between hypoxemia and activities of the TNF-alpha system, including circulating TNF-alpha and soluble TNF-receptors (sTNF-R; sTNF-R55 and -R75) levels, in 27 COPD patients and 15 age-matched healthy controls. The COPD patients showed a significant weight loss (body mass index = 18.1 +/- 2.8 versus 22.8 +/- 2.2 [mean +/- SD] kg/m(2); p < 0.0001. % fat = 16.3 +/- 5.9 versus 24.3 +/- 4.9 %; p < 0.001), and hypoxemia (Pa(O2 )= 62.2 +/- 9.5 versus 88.6 +/- 5.9 mm Hg; p < 0.0001) as compared with the healthy controls. Serum TNF-alpha (6.15 +/- 1.08 versus 5.41 +/- 1.60 pg/ml; p < 0.05) and plasma sTNF-R55 (1.15 +/- 0.49 versus 0.67 +/- 0.13 ng/ml; p < 0.0001) and sTNF-R75 (3.54 +/- 1.16 versus 2.25 +/- 0.43; p < 0.0001) levels were significantly higher in the COPD patients than in the healthy controls. There were inverse correlations between Pa(O(2)) and circulating TNF-alpha and sTNF-R levels in patients with COPD (TNF-alpha; r = -0.426, p = 0.0297; sTNF-R55: r = -0.587, p = 0.0027; sTNF-R75: r = -0.573, p = 0.0035). In addition, we found inverse correlations between sTNF-R levels and % fat in COPD patients (sTNF-R55: r = -0.442, p = 0.0272; sTNF-R75: r = -0. 484, p = 0.0155). TNF-alpha levels correlated well with sTNF-R levels (sTNF-R55: r = 0.488, p = 0.0127; sTNF-R75: r = 0.609, p = 0. 0019). These relationships were not observed in the healthy controls. These data suggest that systemic hypoxemia noted in patients with COPD is associated with activation of the TNF-alpha system in vivo, which may be a factor contributing to the weight loss in patients with the disease.

Tumor necrosis factor-alpha (TNF-alpha) is a cytokine involved in the physiological and metabolic abnormalities found in cachectic states. Until very recently, it was inconceivable to think of TNF-alpha in obesity. However, recent studies have shown that TNF-alpha can also play a key role in obesity, the cytokine being overexpressed in adipose tissue of obese rodents and humans. The aim of this review is to reconcile the role of TNF-alpha in these two opposite metabolic situations: obesity and cachexia. It is suggested that TNF-alpha may have a key role in the control of body mass in normal weight-controlled situations and that abnormalities in either its production (during cachexia) or action (during obesity) are responsible for the lack of control of body weight.

To examine the role of the Th2-type response during schistosomiasis mansoni we compared disease progression in wild type (wt), and Th2-response deficient IL-4(-/-) mice. Whereas wt C57BL/6 mice tolerate infection and develop chronic disease, IL-4(-/-) C57BL/6 animals are highly susceptible, exhibiting severe acute cachexia followed by death. Data point toward morbidity in the IL-4(-/-) C57BL/6 mice being mediated by TNF-alpha, possibly through the uncontrolled production of nitric oxide in target organs such as the ileum. We propose that IL-4 prevents severe disease during schistosomiasis by regulating macrophage activation.

In a group of patients with New York Heart Association class IV heart failure, significant relations between interleukin-6 and tumor necrosis factor-alpha, and between levels of both interleukin-6 and tumor necrosis factor-alpha and plasma levels of norepinephrine were observed. The present study also demonstrates that in patients with heart failure, elevated levels of tumor necrosis factor-alpha and interleukin-6 may be present even without cachexia.

Lentinan (LNT), a beta-glucan derived from Lentinus edodes (Berk.) Sign., is known to work positively against cachexia in patients with malignant tumors. Because the cachectin/tumor necrosis factor (TNF) is supposed to be one of the factors that mediate cancer cachexia, we tested the effects of LNT on TNF-induced cachexia in rats. First, we analyzed in detail the cachectic actions of TNF (0.2 mg/kg/day, 5 days, IV) on food and water intake, body weight, and locomotor activity. The day after the first administration of TNF (acute phase), food and water intake, as well as body weight, of all rats decreased. However, over the next few days of treatment (chronic phase), the rats gradually developed a tolerance to the cachectic actions of TNF. Specifically, after the third administration, the rats treated with TNF had a higher amount of water intake than the control rats. This was mainly due to an increase in daytime water intake. We also analyzed the effects of LNT (0.1 or 1.0 mg/kg, twice/wk. IV) on TNF-induced cachexia, and compared the data with those from the rats treated with TNF alone. The higher dosage of LNT significantly suppressed TNF-induced daytime polydipsia and increased the amount of nighttime water intake, as well as the meal size of nighttime food intake. These results suggest that LNT partially normalizes TNF-induced cachexia in rats.

This study determined the effects of chronic administration of the two principal proximate cytokines, interleukin-1 (IL-1) and tumor necrosis factor (TNF), on host wasting in rats. The effects were compared with those observed in a matched pair-fed group to distinguish the contribution from anorexia. Both TNF and IL-1 produced weight loss, net nitrogen loss, and skeletal muscle catabolism and increased liver weight. Such effects were independent from and additive to those resulting from semistarvation. However, under equivalent nutritional conditions, TNF infusion led to a greater effect on muscle protein catabolism and liver weight and caused liver protein anabolism, whereas only the group receiving IL-1 had altered glucose metabolism in the postabsorptive state. Tachyphylaxis was seen in the response of food intake over time after administration of IL-1. These actions define the two principal mechanisms for the development of protein calorie malnutrition that occur because of cytokine action, anorexia producing semistarvation and an increased net protein catabolic rate reducing anabolic efficiency.

The mechanisms responsible for impaired wound healing in patients with cachexia-associated infection, inflammation, and cancer are unknown. As tumor necrosis factor (TNF)-alpha is elevated in these diseases, and TNF-alpha inhibits collagen alpha1(I) gene expression in cultured fibroblasts, we analyzed whether chronically elevated serum TNF-alpha affects collagen metabolism in vivo by inoculating nude mice with Chinese hamster ovary cells secreting TNF-alpha (TNF-alpha mice) or control Chinese hamster ovary cells (control mice). Before the onset of weight loss, TNF-alpha mice had a selective decrease in collagen synthesis and collagen alpha1(I) mRNA in the skin. In addition, TNF-alpha mice displayed impaired healing of incisional and excisional skin wounds, compared with control animals, before the onset of cachexia. The expression of transforming growth factor-beta1, a potent fibrogenic factor, was inhibited by TNF-alpha in the skin. In studies with transgenic mice expressing the human growth hormone under the direction of 5' regulatory regions of the human collagen alpha1(I) gene, TNF-alpha treatment inhibited the expression of the collagen alpha1(I) human growth hormone transgene containing -2.3 kb of the 5' region, whereas transgene expression directed by -0.44 kb of the 5' region was not affected. These experiments suggest that TNF-alpha may play an important role in the impaired wound healing of chronic diseases that are characterized by a high production of this cytokine and provide insights for potential therapeutic approaches.

This study was conducted to investigate the role of tumor necrosis factor-alpha (TNF-alpha) and interleukin-2 (IL-2) in inducing cancer cachexia, and the results were compared with those obtained from our previous study on Fisher 344 rats with methylcholanthrene-induced sarcoma. Three groups of male Fisher 344 rats received one of the following regimens: 4 x 10(4) IU of human recombinant TNF-alpha per rat per day subcutaneously (sc) for 5 consecutive days (n = 5), 3.5 x 10(5) U human recombinant IL-2 per rat per day sc for 14 consecutive days (n = 5), or normal saline (n = 5). The activities of both phosphoenolpyruvate carboxykinase (PEPCK) and malic enzyme (ME) were increased slightly in the IL-2 group. Furthermore, LPL activity was significantly increased in the adipose tissue of the TNF group and in the cardiac muscle of the IL-2 group, but not in that of the TNF group. These results show that there is a significant difference between the metabolic alterations seen in the tumor-bearing state and those induced by either TNF-alpha or IL-2 alone. Thus, it is unlikely that IL-2 or TNF-alpha is the sole mediator of cancer cachexia in this tumor and rat model.

The pleiotropic cytokine tumour necrosis factor-alpha (TNF) is thought to play a central role in infectious, inflammatory and autoimmune diseases. Critical to the understanding and management of TNF-associated pathology is the development of highly specific agents capable of modifying TNF activity. We evaluated the ability of a high affinity mouse/human chimeric anti-TNF monoclonal antibody (cA2) to neutralize the in vitro and in vivo biological effects of TNF. cA2 inhibited TNF-induced mitogenesis and IL-6 secretion by human fibroblasts, TNF-priming of human neutrophils, and the stimulation of human umbilical vein endothelial cells by TNF as measured by the expression of E-selectin, ICAM-1 and procoagulant activity. cA2 also specifically blocked TNF-induced adherence of human neutrophils to an endothelial cell monolayer. Receptor binding studies suggested that neutralization resulted from cA2 blocking of TNF binding to both p55 and p75 TNF receptors on the cells. In vivo, repeated administration of cA2 to transgenic mice that constitutively express human TNF reversed the cachectic phenotype and prevented subsequent mortality. These results demonstrated that cA2 effectively neutralized a broad range of TNF biological activities both in vitro and in vivo.

Anorexia, net proteolysis of skeletal muscle and consumption of body fat are hallmarks of the cachexia syndrome associated with chronic disease states. While inanition contributes to cachexia, this wasting diathesis has little in common with simple starvation. The cachexia syndrome is characterized by progressive weight loss and depletion of lean body mass in excess to that resulting from comparable caloric restriction. Accelerated mobilization and consumption of host protein stores from peripheral tissues occurs to support gluconeogenesis and acute phase protein synthesis [1, 2]. In contrast, simple starvation is associated with a relative sparing of lean tissue with the preferential consumption of fat. While the clinical manifestations of cachexia are readily apparent, identification of the specific mechanisms responsible for the development of cachexia remains an enigma. In recent years, interest has focused on the role that the immune system plays in the development of cachexia. Investigators initially hypothesized that the chronic production of two inflammatory cytokines, tumour necrosis factor alpha (TNF alpha) and/or interleukin-1 (IL-1), could explain the host non-specific responses resulting in cachexia [3-5]. Other pro-inflammatory cytokines, including interleukin-6 (IL-6) [6, 7] and interferon-gamma [8, 9], have been more recently proposed to be involved in this complex process. Although no consensus exists for the exclusive role of any one cytokine in the pathogenesis of cachexia, there is growing acceptance that the progression of cachexia results in part from the inappropriate release of one or more pro-inflammatory cytokines [10, 11]. In the present review, the current role of TNF alpha as a mediator of cachexia is examined.

Tumor necrosis factor is a cytokine made by macrophages, monocytes and T cells that has been formed to play an important role in shock, cachexia and inflammation. The importance of this cytokine eliciting shock and cachexia in mammals is reviewed.

Objective: To investigate body composition and serum tumor necrosis factor (TNF) levels in a series of 24 patients with rheumatoid arthritis (RA)., Methods: Body composition assessment by anthropometric measures and bioelectrical impedance. Cytokine determination in serum by ELISA:, Results: When compared to United States population norms, 16 of the subjects (67%) were cachectic. In regression models, lean body mass (LBM) was inversely associated with the number of swollen joints (p < 0.025). Elevated TNF-alpha was found in 3 of 5 flaring patients vs 0 of 18 patients with less active disease (p = 0.001). These 3 were all cachectic, while the 2 flaring patients without detectable TNF had normal LBM (p < 0.03). Among the whole group, there was a trend toward increasing disability with decreased LBM after adjusting for joint pain and disease duration (p < 0.07)., Conclusion: Cachexia is common in RA, and may be cytokine driven. Given the prognostic impact of LBM wasting in other diseases, the effect of rheumatoid cachexia on outcome in RA deserves further study.

Daily administration of an escalating dose of tumour necrosis factor-alpha (TNF-alpha) to female NMRI mice caused a progressive loss of body weight representing 12% of the original weight over a 6-day period. Weight loss was associated with a decreased food intake and pair-fed controls exhibited a weight loss of similar magnitude to that caused by TNF-alpha. However, weight loss in animals bearing a murine adenocarcinoma (MAC16) occurred without a change in energy intake and thus differed from that produced by TNF-alpha. Anti-TNF-alpha monoclonal antibodies at levels capable of protecting mice against lethal endotoxaemia were ineffective in reversing weight loss in animals bearing the MAC16 tumour and had no effect on the increase in tumour volume. Circulating levels of interleukin-6 were not elevated in animals bearing the MAC16 tumour and with a weight loss between 1.8 and 5.4 g. These results suggest that these cytokines are not involved in the cachexia produced by this murine tumour.

This review presents a history of tumor necrosis factor, considers the biology of this pleiotropic mediator, and summarizes the evidence that implicates it as a mediator of cachexia.

Tumour necrosis factor (TNF) is a pleiotropic cytokine with activities that extend beyond its antitumour effect. There is now increasing evidence that TNF can be either constitutively produced or induced in human tumours. Tumour cells may also lead to TNF induction in normal cells. Experimental studies implicate TNF in processes that contribute to cancer progression. These range from stimulation of cancer growth and metastasis, to metabolic and haematological disturbances, e.g. cancer cachexia, anaemia, and hypercalcaemia. Future cancer therapies may therefore involve neutralisation of TNF activity in cancer patients.

Tumor necrosis factor is a cytokine that participates in the mediation of numerous diseases associated with inflammation, cachexia, shock, and tissue injury. Early studies of the biology of TNF delineated its hormonal actions as well as its systemic toxicity. More recent investigations have drawn attention to its paracrine actions that predominate when it is produced locally in the brain or vital organs. For instance, when compartmentalized production of TNF occurs in the central nervous system it directly mediates fever, anorexia, and altered whole-body metabolism. Since these changes are mediated within the neural network they occur independently of simultaneously sampled serum TNF levels. These paracrine actions of TNF have implications for diseases associated with production of TNF in tissues (e.g. HIV cerebritis, multiple sclerosis, cerebral malaria and cancer), because they may differ markedly from the hormone like-actions associated with systemic release. Since TNF may be beneficial in some diseases yet injurious in others, both the hormonal and paracrine actions must be precisely defined in order to formulate novel treatment strategies based on either enhancing its useful effects, or suppressing toxicity.

The relationship between detrimental (cachectic) and beneficial (antitumor) effects of tumor necrosis factor (TNF) was studied in mice bearing murine tumors transfected to secrete human TNF. In vitro, the TNF-producing transfectants were resistant to the secreted TNF and grew at rates similar to those of untransfected cells or transfected cells that did not secrete TNF. However, tumors formed by the TNF-secreting cells in vivo remained much smaller than the nonsecreting (transfected and untransfected) tumors. This inhibition of tumor growth required only relatively low serum levels of TNF, persisted for many weeks, and was independent of T cells since it occurred in nude mice. Growth of the TNF-secreting tumors increased dramatically after treatment with anti-human TNF antibody, indicating that extracellular TNF secreted by the tumor cells was necessary for the tumor inhibition. Severe weight loss characteristic of cachexia only occurred in animals with very high serum TNF levels (250 pg/ml) and could be prevented or reversed by anti-TNF antibody treatment. These data are consistent with the existence of a therapeutic window in which persistent exposure to human TNF can lead to prolonged inhibition of tumor growth in the absence of T-cell immunity or severe weight loss and without development of resistant tumor variants.

Recently, we have established a human squamous cell carcinoma of the maxilla (called MH-85) associated with hypercalcemia, leukocytosis, and cachexia in culture. MH-85 tumor cells caused the same paraneoplastic syndromes in tumor-bearing nude mice. We found that there was a sixfold increase in splenic size in MH-85 tumor-bearing mice. This increase paralleled tumor growth and was reversed by surgical removal of the tumor. Splenectomy in nude mice 1 wk before or 6 wk after tumor inoculation resulted in a decrease in tumor growth, and impairment of hypercalcemia, leukocytosis, and cachexia. In MH-85 tumor-bearing animals that had been pretreated by splenectomy, intravenous injection of fresh normal spleen cells caused an immediate reversal of leukocytosis, hypercalcemia, and cachexia. Since the presence of cachexia in both the patient and the mice carrying the tumor suggested tumor necrosis factor (TNF) may be overproduced, we injected polyclonal neutralizing antibodies raised against murine TNF into tumor-bearing mice. There was a rapid and reproducible decrease in blood ionized calcium, accompanied by suppression of osteoclast activity. No changes in blood ionized calcium were seen in mice injected with normal immune sera. In addition, there was an increase in body weight and decrease in white cell count. Plasma immunoreactive TNF was increased almost fourfold in tumor-bearing nude mice compared with control nude mice. Although TNF activity was undetectable in MH-85 culture supernatants, cells of the macrophage lineage, including spleen cells, released increased amounts of TNF when cultured with MH-85 tumor-conditioned media. These results suggest that splenic cytokines such as TNF may influence the development of the paraneoplastic syndromes of hypercalcemia, leukocytosis, and cachexia in these animals, as well as tumor growth. They also show that paraneoplastic syndromes may be due to factors produced by normal host cells stimulated by the presence of the tumor.

The aim of this study was to evaluate to what extent tumor necrosis factor alpha (TNF-alpha) and interleukin 1 may explain the development of experimental cancer cachexia. For this purpose, C57BL/6J mice bearing a transplantable low differentiated rapidly growing tumor were passively immunized every other day with rabbit or rat neutralizing immunoglobulins against either TNF-alpha (anti-TNF) or against an interleukin 1 receptor (anti-IL-1r). Anti-IL-1r in itself had no agonistic effect to the type I, T-cell/fibroblast IL-receptor. Tumor-bearing mice receiving either preimmune antiserum or nonimmune rat hybridoma IgG served as controls. Anti-TNF and anti-IL-1r inhibited tumor growth significantly, as measured by a lower wet and dry tumor weight at the end of 11 days of antiserum treatment (P less than 0.05). The acute phase response in tumor-bearing animals, measured as an increase in liver weight, hepatic RNA content, and increases in plasma concentrations of circulating IL-6, serum amyloid P, transferrin, complement (C3), and a decrease in plasma albumin, were unaffected by the specific antiserum treatments. Food intake, which declined significantly in pre/nonimmune injected tumor-bearing controls, was significantly improved in tumor-bearing animals immunized against TNF-alpha or the IL-1r. Whole body lipid content showed a trend to improvement in specifically immunized animals (P less than 0.07). The effects on whole body fat-free dry weight were insignificant, although numerically higher in specifically immunized tumor-bearing animals. The combination of anti-TNF and anti-IL-1r antiserum had no additive effects compared to single antiserum treatment suggesting that the two antibody treatments acted through a common mechanism. Cultured tumor cells, established from growing tumors, were sensitive to anti-TNF and anti-IL-1r, which both reduced tumor growth in vitro. This inhibitory effect by the antiserum could in part be reversed by the addition of recombinant IL-1 alpha and TNF alpha. We conclude that both TNF and IL-1 are involved in tumor growth and thus the progression of cancer cachexia. It seems as if the role of TNF and IL-1 was to promote tumor growth rather than restrict tumor growth in the present model. In this sense both TNF and IL-1 may act as tumor growth factors.

We have developed a murine model of wasting by injecting intracerebrally cells which continuously secrete h-cachectin/TNF (CHO-TNF) to: (a) determine the effects of cachectin/TNF produced continuously in the central nervous system (CNS), and (b) compare the metabolic effects of cachectin/TNF-secreting tumor in the brain to the cachexia caused by CHO-TNF tumor in peripheral tissue (IM). Intracerebral CHO-TNF tumors produced increased serum h-cachectin/TNF levels with lethal hypophagia and weight loss (mean survival time of 11 d); these changes were not observed in association with nonsecretory control brain tumors. The metabolic consequences of intracerebral cachectin/TNF production were indistinguishable from acute, lethal starvation: whole-body lipid content was decreased significantly but protein was conserved. Although intramuscular cachectin/TNF-secreting tumors caused similar increases of serum h-cachectin/TNF levels, profound anorexia did not develop; wasting developed after a longer period of tumor burden (50 d) with classical signs of cachexia (i.e., anemia and depletion of both protein and lipid). These studies provide a reproducible animal model of site-specific cytokine production and suggest that, regardless of serum levels, cachectin/TNF produced locally in brain influences both the rate of development of wasting and its net metabolic effects.

Wasting and secretion of the catabolic cytokines tumor necrosis factor (TNF)/cachectin and interleukin 1 (IL-1) were assessed in weanling Syrian hamsters infected with Leishmania donovani amastigotes. Whereas the mean weight of uninfected animals increased progressively over 9 weeks, the mean weight of infected animals plateaued at 4-6 weeks and then decreased progressively until death. Splenic mononuclear cells from control hamsters produced 11.3 +/- 8.3 (SD) ng TNF/10(6) mononuclear cells/24 hr. TNF secretion in infected animals was greater than the mean +/- 2 SD of controls in 1 of 3 hamsters at 2 weeks post-infection and in 8 of 9 hamsters at weeks 4-8. The mean TNF secreted by infected animals studied at weeks 4-8 was 371 (range 28-800) ng TNF/10(6) mononuclear cells/24 hr (P = 0.005). Control hamsters produced 7.7 +/- 2.7 pg IL-1/10(6) mononuclear cells/24 hr. At 2 weeks, mononuclear cells from 2 of 3 infected animals secreted amounts of IL-1 greater than the mean +/- 2 SD of controls. All of 8 infected hamsters secreted increased amounts of IL-1 at 4-8 weeks. The mean was 164 (range 17-370) pg IL-1/10(6) mononuclear cells/24 hr (P = 0.002). In comparison to infected animals, mononuclear cells from control hamsters incubated with lipopolysaccharide, 10 micrograms/ml, produced 172.5 ng TNF and 44.6 pg of IL-1/10(6) mononuclear cells/24 hr. The effect of visceral leishmaniasis on food intake was assessed in a separate group of animals housed individually in metabolic cages. Significant reductions in weight and food intake were first observed at 2 and 3 weeks of infection, respectively. By 5 weeks, the food intake of infected animals was 46% that of controls. Syrian hamsters infected with L. donovani provide an excellent model with which to study the mechanism of wasting.

The mechanisms responsible for decreased serum albumin levels in patients with cachexia-associated infection, inflammation, and cancer are unknown. Since tumor necrosis factor-alpha (TNF alpha) is elevated in cachexia-associated diseases, and chronic administration of TNF alpha induces cachexia in animal models, we assessed the regulation of albumin gene expression by TNF alpha in vivo. In this animal model of cachexia, Chinese hamster ovary cells transfected with the functional gene for human TNF alpha were inoculated into nude mice (TNF alpha mice). TNF alpha mice became cachectic and manifested decreased serum albumin levels, albumin synthesis, and albumin mRNA levels. However, even before the TNF alpha mice lost weight, their albumin mRNA steady-state levels were decreased approximately 90%, and in situ hybridization revealed a low level of albumin gene expression throughout the hepatic lobule. The mRNA levels of several other genes were unchanged. Hepatic nuclei from TNF alpha mice before the onset of weight loss were markedly less active in transcribing the albumin gene than hepatic nuclei from control mice. Therefore, TNF alpha selectively inhibits the genetic expression of albumin in this model before weight loss.

Human Tumor Necrosis Factor-alpha (TNF-alpha) is a multifaceted cytokine mainly produced by activated monocytes or macrophages. Several recent studies have shown that TNF-alpha can exert a variety of in vitro and in vivo effects including: modulation of normal and malignant haemopoiesis, antineoplastic activity, activation of neutrophils, induction of IL-1 production, hyperpyrexia and induction of cachexia. Furthermore this cytokine is thought to play an important role in the pathogenesis of septic shock. The principal biochemical characteristics and biological activities of this cytokine will be here summarized.

Tumour necrosis factor, TNF, possesses the attributes of a typical cytokine, being a pleiotropic cell regulatory protein whose activity is largely determined by the cell type to which it binds and the presence of other protein regulators. Thus TNF can be a growth factor, cytotoxin, cytostatic agent or inducer of differentiation. This cytokine is also an important inflammatory mediator regulating the activity of neutrophils, eosinophils, T and B lymphocytes and modulating the properties of the vascular endothelium. All of these actions may play a role in the ability of TNF to induce necrosis of experimental animal tumours, but the potential of this cytokine in therapy of human cancer is uncertain. The increasing evidence for a role for TNF in the pathophysiology of acute and chronic disease makes the use of specific TNF antagonists an equally interesting therapeutic possibility.

The mechanism by which cord factor (CF), a toxic glycolipid from mycobacteria, induces cachexia was studied in BALB/c mice. Body weight was markedly reduced 48 h after CF administration; the animals became severely wasted and exhibited hypertriglyceridemia, hypoglycemia, and high levels of tumor necrosis factor (TNF) in plasma. After CF administration, a transferable factor which caused cachexia and hypertriglyceridemia in recipient mice was detected in the blood. Dexamethasone partially inhibited the cachexia-inducing action of CF. Conditioned medium from adherent peritoneal cell cultures incubated with CF produced the same wasting symptoms when inoculated intravenously into mice. These studies also demonstrated that adherent peritoneal cells produced a humoral factor in response to CF which was related to CF-induced cachexia. Antiserum to recombinant TNF-alpha prevented the cachectin action in passive-transfer experiments. Our findings indicate that cachectin (TNF) plays a role as a central mediator of the wasting induced by CF.

The studies reviewed here represent but a fraction of those published in the field last year, but they serve to illustrate two important points: (1) the cytokine network possesses enormous diversity of biological function, and (2) it is redundant, such that overlapping and synergistic effects are observed between many different cytokines. The impact of this system on the host is pervasive and readily amplifiable, and integrates the diverse responses to infectious disease which may be either beneficial, protecting against infection, or deleterious, causing tissue injury and death. The example of cachectin/TNF illustrates this type of scenario: during local infection or inflammation, low levels of cachectin/TNF act to enhance immune responsiveness, stimulate blood-vessel growth, increase energy mobilization, induce the release of other cytokines, and promote wound-healing; when overwhelming infection occurs, as in septicemia, large quantities of cachectin/TNF reach the circulation and cause shock, MSOF, and death; if a persisting infection develops and cachectin/TNF is chronically secreted, it mediates a state of cachexia which may be fatal. Future studies will undoubtedly advance our understanding of these effects, and that of the other cytokines. The development of novel therapies for inflammation, septic shock, and cachexia may be based on such advances.

A comparison has been made of the cachectic effects produced by the transplantable murine adenocarcinoma of the mouse colon (MAC16) with tumour necrosis factor-alpha (cachectin). Tumour necrosis factor-alpha (TNF-alpha) produced a dose-related weight reduction that was accompanied by a decrease in both food and water intake. The degree of weight loss was directly proportional to the decreased food and water intake. In contrast weight loss produced by the MAC16 tumour occurred without a reduction in fluid or nutrient intake. Both the MAC16 tumour and TNF-alpha produced hypoglycaemia and a reduction in the circulatory level of free fatty acids (FFA), but had opposite effects on the level of plasma triglycerides with the MAC16 tumour-induced cachexia causing a decrease and TNF-alpha producing an increase. The MAC16 tumour elaborated a lipolytic factor which caused an immediate release of FFA from adipose tissue. In contrast TNF-alpha had no effect on mobilization of adipose triglycerides over a short time period. Both TNF-alpha and extracts from the MAC16 tumour caused an enhanced release of amino acids from mouse diaphragm, which was suppressible with indomethacin and heat labile. No TNF was detected in the MAC16 tumour or in the serum of tumour-bearing animals. Both tumour and non-tumour-bearing animals responded with a similar elevation of their serum TNF levels 90 min after a single injection of endotoxin. It is concluded that weight loss produced by TNF-alpha arises from an anorexic effect and that this differs from the complex metabolic changes associated with cancer cachexia.