CD8 T cells drive anorexia, dysbiosis, and blooms of a commensal with immunosuppressive potential after viral infection

Infections elicit immune adaptations to enable pathogen resistance and/or tolerance and are associated with compositional shifts of the intestinal microbiome. However, a comprehensive understanding of how infections with pathogens that exhibit distinct capability to spread and/or persist differentially change the microbiome, the underlying mechanisms, and the relative contribution of individual commensal species to immune cell adaptations is still lacking. Here, we discovered that mouse infection with a fast-spreading and persistent (but not a slow-spreading acute) isolate of lymphocytic choriomeningitis virus induced large-scale microbiome shifts characterized by increased Verrucomicrobia and reduced Firmicute/Bacteroidetes ratio. Remarkably, the most profound microbiome changes occurred transiently after infection with the fast-spreading persistent isolate, were uncoupled from sustained viral loads, and were instead largely caused by CD8 T cell responses and/or CD8 T cell-induced anorexia. Among the taxa enriched by infection with the fast-spreading virus, Akkermansia muciniphila, broadly regarded as a beneficial commensal, bloomed upon starvation and in a CD8 T cell-dependent manner. Strikingly, oral administration of A. muciniphila suppressed selected effector features of CD8 T cells in the context of both infections. Our findings define unique microbiome differences after chronic versus acute viral infections and identify CD8 T cell responses and downstream anorexia as driver mechanisms of microbial dysbiosis after infection with a fast-spreading virus. Our data also highlight potential context-dependent effects of probiotics and suggest a model in which changes in host behavior and downstream microbiome dysbiosis may constitute a previously unrecognized negative feedback loop that contributes to CD8 T cell adaptations after infections with fast-spreading and/or persistent pathogens.

The role of hypothalamic inflammation, the hypothalamic-pituitary-adrenal axis and serotonin in the cancer anorexia-cachexia syndrome

PURPOSE OF REVIEW

In cancer patients, the development of cachexia (muscle wasting) is frequently aggravated by anorexia (loss of appetite). Their concurrence is often referred to as anorexia-cachexia syndrome. This review focusses on the recent evidence underlining hypothalamic inflammation as key driver of these processes. Special attention is given to the involvement of hypothalamic serotonin.

RECENT FINDINGS

The anorexia-cachexia syndrome is directly associated with higher mortality in cancer patients. Recent reports confirm its severe impact on the quality of life of patients and their families.Hypothalamic inflammation has been shown to contribute to muscle and adipose tissue loss in cancer via central hypothalamic interleukine (IL)1β-induced activation of the hypothalamic-pituitary-adrenal axis. The resulting release of glucocorticoids directly stimulates catabolic processes in these tissues via activation of the ubiquitin-proteosome pathway. Next to this, hypothalamic inflammation has been shown to reduce food intake in cancer by triggering changes in orexigenic and anorexigenic responses via upregulation of serotonin availability and stimulation of its signalling pathways in hypothalamic tissues. This combination of reduced food intake and stimulation of tissue catabolism represents a dual mechanism by which hypothalamic inflammation contributes to the development and maintenance of anorexia and cachexia in cancer.

SUMMARY

Hypothalamic inflammation is a driving force in the development of the anorexia-cachexia syndrome via hypothalamic-pituitary-adrenal axis and serotonin pathway activation.

ICF-specific DNMT3B dysfunction interferes with intragenic regulation of mRNA transcription and alternative splicing

Hypomorphic mutations in DNA-methyltransferase DNMT3B cause majority of the rare disorder Immunodeficiency, Centromere instability and Facial anomalies syndrome cases (ICF1). By unspecified mechanisms, mutant-DNMT3B interferes with lymphoid-specific pathways resulting in immune response defects. Interestingly, recent findings report that DNMT3B shapes intragenic CpG-methylation of highly-transcribed genes. However, how the DNMT3B-dependent epigenetic network modulates transcription and whether ICF1-specific mutations impair this process remains unknown. We performed a transcriptomic and epigenomic study in patient-derived B-cell lines to investigate the genome-scale effects of DNMT3B dysfunction. We highlighted that altered intragenic CpG-methylation impairs multiple aspects of transcriptional regulation, like alternative TSS usage, antisense transcription and exon splicing. These defects preferentially associate with changes of intragenic H3K4me3 and at lesser extent of H3K27me3 and H3K36me3. In addition, we highlighted a novel DNMT3B activity in modulating the self-regulatory circuit of sense-antisense pairs and the exon skipping during alternative splicing, through interacting with RNA molecules. Strikingly, altered transcription affects disease relevant genes, as for instance the memory-B cell marker CD27 and PTPRC genes, providing us with biological insights into the ICF1-syndrome pathogenesis. Our genome-scale approach sheds light on the mechanisms still poorly understood of the intragenic function of DNMT3B and DNA methylation in gene expression regulation.

A central role for the mammalian target of rapamycin in LPS-induced anorexia in mice

Bacterial lipopolysaccharide (LPS), also known as endotoxin, induces profound anorexia. However, the LPS-provoked pro-inflammatory signaling cascades and the neural mechanisms underlying the development of anorexia are not clear. Mammalian target of rapamycin (mTOR) is a key regulator of metabolism, cell growth, and protein synthesis. This study aimed to determine whether the mTOR pathway is involved in LPS-induced anorexia. Effects of LPS on hypothalamic gene/protein expression in mice were measured by RT-PCR or western blotting analysis. To determine whether inhibition of mTOR signaling could attenuate LPS-induced anorexia, we administered an i.c.v. injection of rapamycin, an mTOR inhibitor, on LPS-treated male mice. In this study, we showed that LPS stimulates the mTOR signaling pathway through the enhanced phosphorylation of mTOR(Ser2448) and p70S6K(Thr389). We also showed that LPS administration increased the phosphorylation of FOXO1(Ser256), the p65 subunit of nuclear factor kappa B (P<0.05), and FOXO1/3a(Thr) (24) (/) (32) (P<0.01). Blocking the mTOR pathway significantly attenuated the LPS-induced anorexia by decreasing the phosphorylation of p70S6K(Thr389), FOXO1(Ser256), and FOXO1/3a(Thr) (24) (/) (32). These results suggest promising approaches for the prevention and treatment of LPS-induced anorexia.

Advances in deoxynivalenol toxicity mechanisms: the brain as a target

Deoxynivalenol (DON), mainly produced by Fusarium fungi, and also commonly called vomitoxin, is a trichothecene mycotoxin. It is one of the most abundant trichothecenes which contaminate cereals consumed by farm animals and humans. The extent of cereal contamination is strongly associated with rainfall and moisture at the time of flowering and with grain storage conditions. DON consumption may result in intoxication, the severity of which is dose-dependent and may lead to different symptoms including anorexia, vomiting, reduced weight gain, neuroendocrine changes, immunological effects, diarrhea, leukocytosis, hemorrhage or circulatory shock. During the last two decades, many studies have described DON toxicity using diverse animal species as a model. While the action of the toxin on peripheral organs and tissues is well documented, data illustrating its effect on the brain are significantly less abundant. Yet, DON is known to affect the central nervous system. Recent studies have provided new evidence and detail regarding the action of the toxin on the brain. The purpose of the present review is to summarize critical studies illustrating this central action of the toxin and to suggest research perspectives in this field.

The role of anorexia in resistance and tolerance to infections in Drosophila

Most infections induce anorexia but its function, if any, remains unclear. Because this response is common among animals, we hypothesized that infection-induced diet restriction might be an adaptive trait that modulates the host's ability to fight infection. Two defense strategies protect hosts against infections: resistance, which is the ability to control pathogen levels, and tolerance, which helps the host endure infection-induced pathology. Here we show that infected fruit flies become anorexic and that diet restriction alters defenses, increasing the fly's tolerance to Salmonella typhimurium infections while decreasing resistance to Listeria monocytogenes. This suggests that attempts to extend lifespan through diet restriction or the manipulation of pathways mimicking this process will have complicated effects on a host's ability to fight infections.

Tryptophan in wasting diseases: at the crossing between immune function and behaviour

PURPOSE OF REVIEW

Wasting diseases are characterized by progressive deterioration of nutritional status that negatively influences patients' outcome. The better understanding of the pathogenic mechanisms of wasting may lead to effective therapies. Tryptophan metabolism has unique features suggesting a critical role in influencing human metabolism under normal and pathological conditions.

RECENT FINDINGS

During disease, inflammatory response favours the local depletion of the essential amino acid tryptophan, thereby inhibiting cellular proliferation. Tryptophan depletion may also mediate immunotolerance to foreign antigens. In contrast, brain accumulation of tryptophan contributes to wasting by increasing oxidative stress and hypothalamic serotonin neurotransmission, and thereby triggering the onset of sickness behaviour followed by depressive-like behaviour.

SUMMARY

Tryptophan metabolism is critical in mediating a number of important biological responses. Restoring tryptophan metabolism may well result in enhanced recovery from disease.

Evidence for hypothalamic dysregulation in mouse models of anorexia as well as in humans

Eating disorders constitute major medical health problems in the western world. Even though little is known about the molecular mechanisms behind abnormal eating behavior, it has become clear that the central nervous system (CNS), particularly the hypothalamus, plays a significant role. The anorexic anx/anx mouse is a unique model for studying food intake and energy expenditure. The anx mutation is linked to marked alterations in hypothalamic distributions of signal substances known to have potent regulatory roles in the control of food intake. Another mouse model that displays an anorectic phenotype similar to the anx/anx mouse is the Contactin KO mouse. This model displays very similar hypothalamic alterations as seen in the anx/anx mouse, arguing for a role of these specific hypothalamic changes in an anorectic phenotype. In human eating disorders, hypothalamic systems corresponding to those defective in mouse models could be compromised since autoantibodies against melanocortin peptides have been detected in anorectic and bulimic patients. These findings represent research avenues that may lead to a better understanding of eating disorders and development of targeted therapeutic approaches.

Neonatal immune challenge does not affect body weight regulation in rats

The perinatal environment plays a crucial role in programming many aspects of adult physiology. Myriad stressors during pregnancy, from maternal immune challenge to nutritional deficiency, can alter long-term body weight set points of the offspring. In light of the increasing concern over body weight issues, such as obesity and anorexia, in modern societies and accumulating evidence that developmental stressors have long-lasting effects on other aspects of physiology (e.g., fever, pain), we explored the role of immune system activation during neonatal development and its impact on body weight regulation in adulthood. Here we present a thorough evaluation of the effects of immune system activation (LPS, 100 microg/kg ip) at postnatal days 3, 7, or 14 on long-term body weight, adiposity, and body weight regulation after a further LPS injection (50 microg/kg ip) or fasting and basal and LPS-induced circulating levels of the appetite-regulating proinflammatory cytokine leptin. We show that neonatal exposure to LPS at various times during the neonatal period has no long-term effects on growth, body weight, or adiposity. We also observed no effects on body weight regulation in response to a short fasting period or a further exposure to LPS. Despite reductions in circulating leptin levels in response to LPS during the neonatal period, no long-term effects on leptin were seen. These results convincingly demonstrate that adult body weight and weight regulation are, unlike many other aspects of adult physiology, resistant to programming by a febrile-dose neonatal immune challenge.

Brain activation in uremic anorexia

This article reviews current knowledge about mechanisms responsible for uremic events, especially those that involve the central nervous system (CNS). Anorexia is a frequent complication of the uremic syndrome that contributes to malnutrition in patients on dialysis. Uremic anorexia has been associated with many factors. Traditionally, anorexia in dialysis patients has been regarded as a sign of uremic toxicity; therefore, 2 hypotheses have been proposed: the "middle molecule" and "peak concentration" hypotheses; both of these remain unproved. Recently, our group has proposed the tryptophan-serotonin hypothesis, which is based on a disorder in the amino acid profile that may be acquired when the patient is in uremic status. It is characterized by low concentrations of large neutral and branched chain amino acids in the cerebrospinal fluid. This situation permits a high level of tryptophan transport across the blood-brain barrier and enhances the synthesis of serotonin (the final target responsible for inhibiting appetite). The role of inflammation in the genesis of anorexia-malnutrition is also emphasized. In summary, in the CNS, factors associated with uremic anorexia include high levels within the cerebrospinal fluid of proinflammatory cytokines, leptin, and free tryptophan and serotonin (hyperserotoninergic-like syndrome), along with deficiency of neural nitric oxide (nNO) and disorders in various receptors such as melanocortin receptor-4 (MC4-R). Uremic anorexia is a complex complication associated with malnutrition and high levels of morbidity and mortality. Several uremia-acquired disorders in the CNS such as high cerebrospinal fluid levels of anorexigen substances and disorders in appetite regulator receptors may explain the lack of appetite.

Illness-induced anorexia and its possible function in the caterpillar, Manduca sexta

Although many animals exhibit illness-induced anorexia when immune-challenged, the adaptive significance of this behavior remains unclear. Injecting Manduca sexta larvae (caterpillars) with live bacteria (Serratia marcescens), heat-killed bacteria or bacterial lipopolysaccharides resulted in a decline in feeding, demonstrating illness-induced anorexia in this species. We used M. sexta to test four commonly suggested adaptive functions for illness-induced anorexia. (1) Food deprivation did not reduce the iron content of the hemolymph. (2) Immune-challenged M. sexta were not more likely to move to a different part of the plant. Therefore, the decline in feeding is unlikely to be an adaptive response allowing the animal to move away from a patch of contaminated food. (3) M. sexta force-fed S. marcescens bacteria were not more susceptible to a S. marcescens systemic infection than were M. sexta force-fed nutrient broth. (4) Force-feeding infected M. sexta during illness-induced anorexia did not increase mortality and short-term food deprivation did not enhance survival. However, force-feeding M. sexta with a high lipid diet (linseed oil and water) resulted in an increase in mortality when challenged with S. marcescens. Force-feeding sucrose or water did not reduce resistance. Force-feeding a high lipid diet into healthy animals did not reduce weight gain, suggesting that it was not toxic. We hypothesize that there is a conflict between lipid metabolism and immune function, although whether this conflict has played a role in the evolution of illness-induced anorexia remains unknown. The adaptive function of illness-induced anorexia requires further study in both vertebrates and invertebrates.

A putative role for cytokines in the impaired appetite in depression

Impaired appetite and weight changes are commonly seen in patients with depression, but the pathophysiology behind this imbalance between energy intake and energy expenditure remains largely unknown. The aim of this paper is to review the literature regarding a possible role for cytokines in the regulation of appetite and body weight, with special emphasis on depression. There now exists a substantial amount of evidence that depressed patients show signs of immune activation including increased levels of proinflammatory cytokines. Cytokines, which by themselves have anorectic properties, stimulate the release of the cytokine-like anorexogenic peptide leptin. In addition to their anorectic properties, both proinflammatory cytokines and leptin interact with the hypothalamic-pituitary-adrenal (HPA) axis, the sympathetic nervous system (SNS) and the immune system. In turn, these systems regulate energy balance as well as they are dysfunctional in depression. Furthermore, both proinflammatory cytokines and leptin can induce anhedonia, one of the cardinal symptoms of depression. In view of the different effects on appetite and/or body weight observed in melancholic versus atypical depression, we suggest that cytokines are differentially altered in these subtypes of depression, and that this may explain some of the inconsistency in the reported findings of cytokine as well as leptin levels in depressed patients. Finally, we propose that the immune system uses the interoceptive pathway projecting to the insular cortex, a brain region where cytokine-induced changes in appetite could be partly mediated, and that this pathway is activated in depression.

Comparative psychoneuroimmunology: evidence from the insects

Interactions between immune systems, nervous systems, and behavior are well established in vertebrates. A comparative examination of these interactions in other animals will help us understand their evolution and present adaptive functions. Insects show immune-behavioral interactions similar to those seen in vertebrates, suggesting that many of them may have a highly conserved function. Activation of an immune response in insects results in illness-induced anorexia, behavioral fever, changes in reproductive behavior, and decreased learning ability in a broad range of species. Flight-or-fight behaviors result in a decline in disease resistance. In insects, illness-induced anorexia may enhance immunity. Stress-induced immunosuppression is probably due to physiological conflicts between the immune response and those of other physiological processes. Because insects occupy a wide range of ecological niches, they will be useful in examining how some immune-behavioral interactions are sculpted by an animal's behavioral ecology.

Anorexia in chronic obstructive pulmonary disease--association to cachexia and hormonal derangement

BACKGROUND

In patients with chronic obstructive pulmonary disease (COPD) weight loss frequently occurs that may ultimately lead to cachexia as a serious co-morbidity, indicating severely impaired functional capacity, health status and increased mortality. Increased energy expenditure due to mechanic and metabolic inefficiency and systemic inflammation are determinants of a hypermetabolic state that is not balanced by dietary intake. Anorexia may importantly contribute to weight loss in COPD, however, the association between immune and hormonal derangement and altered appetite has not been studied in detail.

AIM

The aim of the present study was to investigate whether anorexia in COPD is related to inflammation and hormonal derangement in association to weight loss.

METHODS

We prospectively enrolled 103 consecutive patients with COPD (age 59.8+/-1.3 years, 35% female, mean FEV1 38.3+/-1.7%) in comparison to healthy controls of similar age (n=15).

RESULTS

In 34 patients (33%) cachexia was diagnosed (weight loss >7.5%, BMI < or = 24 kg/m2). Cachectic COPD patients had lower BMI (19.0+/-0.5 vs 25.6+/-0.7 kg/m2) and impaired lung function (FEV1 31+/-2% vs 42+/-2%, FVC 51+/-3 vs 59+/-3%, both p<0.001). Inflammatory immune activation (IL-6 and IL-6/IL-10 ratio) was significantly higher in cachectic COPD patients. Analysis of the extent of anorexia (visual analogue scale) revealed that cachectic COPD patients had significantly decreased subjective desire to eat compared to non-cachectic patients (3.5+/-0.3 vs 6.3+/-0.2, p<0.001). Patients with COPD and cachexia showed evidence of acquired GH resistance (decreased IGF-1/GH ratio) and insulin resistance (HOMA). Anorexia showed a direct correlation with the IGF-1/GH ratio (r=0.34, p<0.05) and was further related to BMI and % weight loss (both p<0.001).

CONCLUSION

In COPD anorexia relates to hormonal derangement and inflammatory immune activation. Anorexia contributes to development of cachexia. The concept of appetite stimulating therapy emerges as a novel therapeutic option in cachectic COPD patients.

Neuronal, endocrine, and anorexic responses to the T-cell superantigen staphylococcal enterotoxin A: dependence on tumor necrosis factor-alpha

Staphylococcal enterotoxin A (SEA) is a microbial superantigen that activates T-lymphocytes and induces production of various cytokines, including tumor necrosis factor-alpha (TNFalpha). Previously, it was shown that SEA activates the hypothalamic-pituitary-adrenal axis and augments gustatory neophobic behaviors. In the present study, it was hypothesized that these effects involve neuronal activation in forebrain regions mediating fear and/or anxiety and are dependent on the production of TNFalpha. Male C57BL/6J mice were given intraperitoneal injections of 10 microg of SEA and 5 microg of lipopolysaccharide (LPS) or saline and perfused 2 h later for histochemical determination of brain c-Fos immunoreactivity (IR). The results showed increased c-Fos IR in the paraventricular nucleus, arcuate nucleus, central nucleus of the amygdala, bed nucleus of the stria terminalis, and lateral septum. Challenge of TNF-/- mice with SEA did not produce a significant increase in brain c-Fos IR, although c-Fos was increased after exposure to a psychogenic stressor (i.e., open field). In additional experiments, the elevated corticosterone response to SEA was abrogated in TNF-/- mice and was shown to be corticotropin-releasing hormone dependent. Finally, the augmented reduction in novel food intake after SEA challenge was attenuated in TNF-/- mice as well as in wild-type mice administered antibody to TNFalpha. In conclusion, challenge with SEA recruits brain regions mediating stress and anxiety responses, an effect that requires endogenous TNFalpha. Whether this is indicative of all T-cell superantigens remains to be determined, although it stands in contrast to other models of neuroimmunomodulation (e.g., LPS) that involve multiple cytokine influences.

Current perspectives on behavioural and cellular mechanisms of illness anorexia

Here we review our current understanding of the integration of immune, neural, metabolic and endocrine signals involved in the generation of anorexia during acute infection, with the focus on anorexia elicited by peripheral administration of bacterial lipopolysaccharide (LPS). We chose to limit this review to peripheral LPS-anorexia because the mechanisms underlying this response may also be valid for anorexia during other types of acute or chronic infections, with slight differences in the duration of anorexia, levels of circulating concentrations of pro-inflammatory cytokines and hypermetabolism. Evidence so far indicates that LPS-anorexia is a complex response beneficial to host defence that involves both peripheral and central action of pro-inflammatory cytokines, other immune factors, such as prostanoids, and neurotransmitters, such as serotonin. One interesting characteristic of LPS-anorexia is its sexual differentiation, an aspect mainly mediated by the gonadal hormone estradiol. Understanding the behavioural and molecular mechanisms of LPS-anorexia may even provide useful leads for identifying mechanisms of eating disorders in humans.

Interleukin-6 and human immunodeficiency virus load, but not plasma leptin concentration, predict anorexia and wasting in adults with pulmonary tuberculosis in Malawi

BACKGROUND

Wasting is a prominent feature of tuberculosis and may be more severe among individuals with HIV coinfection. It is likely that several biological mechanisms, including the anorexia of infection, are contributing to wasting.

OBJECTIVE

The purpose of this study was to determine whether leptin concentrations, in relation to the inflammatory cytokine response and level of HIV infection, are contributing to loss of appetite and wasting in adults with pulmonary tuberculosis and HIV infection.

DESIGN

We characterized plasma leptin concentrations in relationship with self-reported loss of appetite, body mass index, fat mass (FM), IL-6, and HIV load in a cross-sectional study of 500 adults who presented with pulmonary tuberculosis in Zomba, Malawi.

RESULTS

Plasma leptin concentrations, associated with FM, significantly decreased by increasing tertile of plasma HIV load (P = 0.0001). Leptin concentrations were inversely associated with plasma IL-6 concentrations after adjusting for sex, age, FM, and HIV load. Plasma leptin concentrations were associated with neither loss of appetite nor wasting. Inflammation, reflected by increased IL-6 concentrations, was associated with loss of appetite (odds ratio, 3.41; 95% confidence interval, 1.91-6.09), when adjusted for sex, age, FM, leptin concentrations, and HIV load. A high plasma HIV load was associated with severe wasting, defined as body mass index less than 16.0 kg/m2 (odds ratio, 2.14; 95% confidence interval, 1.09-4.19) when adjusted for sex, age, IL-6, FM, and leptin concentrations.

CONCLUSION

This study suggests that the anorexia and wasting seem primarily determined by the level of inflammation and the level of HIV infection in patients with tuberculosis and HIV coinfection.

The role of central corticotropin-releasing hormone in the anorexic and endocrine effects of the bacterial T cell superantigen, Staphylococcal enterotoxin A

Bacterial superantigens, such as the staphylococcal enterotoxins, exert a strong capacity for in vivo stimulation of T cell proliferation and cytokine production. Previously, staphylococcal enterotoxin A (SEA) was shown to induce an anorexic effect under novel contextual conditions of testing, and produced an increase in plasma ACTH and corticosterone levels in C57BL/6J mice. In the present study, the role of corticotropin releasing hormone (CRH) in promoting these effects of SEA was addressed via intracerebroventricular (icv) administration of alpha-helical CRH(9-41) ((alpha)hCRH), a non-selective CRH receptor antagonist, and astressin-2B, a selective CRH receptor 2 antagonist. The efficacy of (alpha)hCRH and astressin-2B in blocking anorexic responses to CRH and urocortin under the current conditions of testing was first confirmed. Subsequently, it was found that (alpha)hCRH (20 microg icv), but not astressin-2B (10 and 25 microg icv), significantly attenuated the anorexia induced by SEA. This suggested that central CRH is involved in mediating the anorexia induced by SEA, but potentially through CRH receptor 1. Additional results revealed that plasma ACTH stimulation in response to SEA was not significantly attenuated by either antagonist administered icv. However, the plasma corticosterone elevation showed a modest, but significant, attenuation in SEA challenged mice given (alpha)hCRH. These data suggest a possible influence of central CRH on adrenocorticoid activity subsequent to SEA challenge. More importantly, it appears that central activation of CRH receptors is a consequence of SEA challenge, and this likely contributes to its anorexic effects.

“Starve a fever and feed a cold”: feeding and anorexia may be adaptive behavioral modulators of autonomic and T helper balance

Anorexia is a common symptom accompanying infections, but the teleology of the phenomenon remains unexplained. We hypothesize that anorexia may represent a prehistoric behavioral adaptation to fight infection by maintaining T helper (Th)2 bias, which is particularly vital in fighting bacterial pathogens. Specifically, we propose that anorexia may avert the reduction of Th2/Th1 ratio by preventing feeding-induced neurohormonal and vagal output from the gut. Emerging evidence suggests that the vagal and neurohormonal output of the gut during feeding promotes Th1 function, which is desirable in fighting viral infections. Since fever may be an adaptation to fight bacteria and "colds" are generally viral in origin, the adage "starve a fever and feed a cold" may reflect a sensible behavioral strategy to tilt autonomic and Th balance in directions that are optimal for fighting the particular type of infection. The ability to modulate T helper balance through the neurohormonal and autonomic axis by adjusting food intake may be the mechanism behind other unexplained clinical observations such as the improved outcomes of ICU patients after enteric versus parenteric feedings. Compared to the prehistoric period when bacterial infection was commonplace, the anorexic response may be less adaptive today when viruses and cancers have become common triggers of anorexia. By promoting host anorexia, cachexia, and insomnia, cancers and viruses can deter behaviors such as digestion and sleep that would raise vagal and Th1 activity against tumors and viruses. Hydration and sleep, unexplained but widely accepted recommendations for flu patients, may also work by promoting vagal and Th1 functions. Modulating feeding, hydration, and sleep may prove beneficial in treating other conditions associated with abnormal autonomic and Th balance.

Circulating leptin mediates lipopolysaccharide-induced anorexia and fever in rats

Anorexia and fever are important features of the host's response to inflammation that can be triggered by the bacterial endotoxin lipopolysaccharide (LPS) and the appetite suppressant leptin. Previous studies have demonstrated that LPS induces leptin synthesis and secretion in the periphery, and that the action of leptin on appetite suppression and fever are dependent on brain interleukin (IL)-1beta. However, the role of leptin as a neuroimmune mediator of LPS-induced inflammation has not been fully elucidated. To address this issue, we neutralized circulating leptin using a leptin antiserum (LAS) and determined how this neutralization affected LPS-induced anorexia, fever and hypothalamic IL-1beta. Adult male rats were separated into four treatment groups, namely LPS + normal sheep serum (NSS), LPS + LAS, saline + LAS and saline + NSS. Intraperitoneal injection of LPS (100 microg kg(-1)) induced a significant reduction in food intake and body weight, which were significantly reversed in the presence of LAS (1 ml kg(-1)), 8 and 24 h after treatment. In addition, LPS-induced fever was significantly attenuated by LAS over the duration of the fever response (8 h). Lipopolysaccharide induced an increase of circulating IL-6, another potential circulating pyrogen, which was not affected by neutralization of leptin at 2 h. Interleukin-1beta mRNA at 1 and 8 h, and IL-1 receptor antagonist (ra) at 2 h were significantly upregulated in the hypothalamus of LPS-treated animals. The induction of these cytokines was attenuated in the presence of LAS. These results are the first to demonstrate that leptin is a circulating mediator of LPS-induced anorexia and fever, probably through a hypothalamic IL-1beta-dependent mechanism.

Influence of chronic interleukin-2 infusion and stressors on sickness behaviors and neurochemical change in mice

OBJECTIVES

Major depression is associated with increased circulating interleukin-2 (IL-2) levels, and IL-2 immunotherapy may provoke depressive symptoms, leading to the suggestion that this cytokine may contribute to the evolution of affective disorders. Although depression is a relatively chronic condition, and immunotherapy involves repeated cytokine administration, animal studies have typically assessed the consequences of acute cytokine treatment. The present investigation assessed several behavioral and neurochemical effects of chronic IL-2 infusion.

METHODS

Behaviors reflecting anhedonia and/or anorexia, sickness behavior, plasma corticosterone and norepinephrine (NE) activity in the paraventricular nucleus (PVN) of the hypothalamus were assessed following continuous infusion of IL-2 over 7 days in CD-1 mice.

RESULTS

The cytokine treatment reduced the consumption of a highly favored palatable substance (chocolate milk) and reduced locomotor activity monitored over the course of the 7-day period. Although sickness behaviors were also increased significantly by the treatment, the degree of sickness behavior was actually modest. While a chronic, variable stressor also affected consumption of the palatable food, this treatment did not enhance the effects of IL-2. Furthermore, in contrast to acute and chronic stressors that increased plasma corticosterone levels and the utilization of NE within the PVN of the hypothalamus, IL-2 did not promote such effects and did not modify the impact of the stressors.

CONCLUSION

While IL-2 may induce anorexia or anhedonia, the effects of this treatment are distinguishable from those elicited by stressors and those typically elicited by proinflammatory cytokines. The data are related to findings suggesting a link between IL-2 and depressive illness.

Cancer anorexia: clinical implications, pathogenesis, and therapeutic strategies

Anorexia and reduced food intake are important issues in the management of patients with cancer because they contribute to the development of malnutrition, increase morbidity and mortality, and impinge on quality of life. Accumulating evidence indicates that cancer anorexia is multifactorial in its pathogenesis, and most of the hypothalamic neuronal signalling pathways modulating energy intake are likely to be involved. Several factors are considered to be putative mediators of cancer anorexia, including hormones (eg, leptin), neuropeptides (eg, neuropeptide Y), cytokines (eg, interleukin 1 and 6, and tumour necrosis factor), and neurotransmitters (eg, serotonin and dopamine). These pathways are not isolated and distinct pathogenic mechanisms but are closely inter-related. However, convincing evidence suggests that cytokines have a vital role, triggering the complex neurochemical cascade which leads to the onset of cancer anorexia. Increased expression of cytokines during tumour growth prevents the hypothalamus from responding appropriately to peripheral signals, by persistently activating anorexigenic systems and inhibiting prophagic pathways. Hypothalamic monoaminergic neurotransmission may contribute to these effects. Thus, the optimum therapeutic approach to anorectic cancer patients should include changes in dietary habits, achieved via nutritional counselling, and drug therapy, aimed at interfering with cytokine expression or hypothalamic monoaminergic neurotransmission.

[Cytokines and nutritional disorders]

During an infection, a decrease in food intake together with elevated energy expenditure appears. Anorexia is one of the most common signs of illness and is often considered as an undesirable manifestation of sickness. However, compelling data demonstrate that anorexia constitutes an adaptative strategy systematically organised for pathogens elimination. Microbial products stimulate the production by immunocompetent cells of cytokines, which orchestrate the immune response. Since the administration of cytokines reduces food intake, it has been suggested that these agents play a key role in mediating anorexia during infection. This review details the mechanisms of cytokine-induced anorexia, focusing on the role of endogenously produced brain cytokines and more particularly interleukin-1 (IL-1). De novo synthesis of IL-1 occurs in the brain during peripheral infection mimicked by the administration of bacterial endotoxin lipopolysaccharide (LPS). Centrally produced IL-1 acts on its receptors to mediate anorexia as demonstrated by the use of knockout mice and specific IL-1 receptor antagonist. Functional neuroanatomy demonstrates further that LPS or IL-1 specifically activates the hypothalamic neurons that control food intake. Leptin is tightly regulated by IL-1, suggesting the involvement of this hormone in the anorexia of infection. The mechanisms by which hypothalamic arcuate nucleus neuropeptides, which are regulated by IL-1 and leptin, could mediate anorexia during infection are discussed.

Leptin surge precedes onset of autoimmune encephalomyelitis and correlates with development of pathogenic T cell responses

In the work presented here, we explored the influence of leptin on the kinetics of experimental autoimmune encephalomyelitis (EAE) onset, in the EAE-associated inflammatory anorexia, and in the development of pathogenic T cell responses. We found that the expression of serum leptin increased before the clinical onset of EAE in disease-susceptible C57BL/6J (H-2(b)) and SJL/J (H-2(s)) strains of mice, which are models of chronic-progressive and relapsing-remitting EAE, respectively. This increase in serum leptin correlated with disease susceptibility, reduction in food intake, and decrease in body weight. Indeed, acute starvation, which is able to prevent the increase in serum leptin, delayed disease onset and attenuated clinical symptoms by inducing a T helper 2 cytokine switch. Furthermore, immunohistochemical analysis revealed a parallel in situ production of leptin in inflammatory infiltrates and in neurons only during the acute/active phase of both chronic-progressive and relapsing-remitting EAE. We also found that leptin secretion by activated T cells sustained their proliferation in an autocrine loop, since antileptin receptor antibodies were able to inhibit the proliferative response of autoreactive T cells in vitro. Given that leptin appears to regulate EAE susceptibility, inflammatory anorexia, and pathogenic T-cell immune function, we postulate that it may offer a potential target in the treatment of multiple sclerosis.

Autoantibodies against alpha -MSH, ACTH, and LHRH in anorexia and bulimia nervosa patients

The hypothalamic arcuate nucleus is involved in the control of energy intake and expenditure and may participate in the pathogenesis of eating disorders such as anorexia nervosa (AN) and bulimia nervosa (BN). Two systems are of particular interest in this respect, synthesizing alpha-melanocyte-stimulating hormone (alpha-MSH) and synthesizing neuropeptide Y, respectively. We report here that 42 of 57 (74%) AN andor BN patients studied had in their plasma Abs that bind to melanotropes andor corticotropes in the rat pituitary. Among these sera, 8 were found to bind selectively to alpha-MSH-positive neurons and their hypothalamic and extrahypothalamic projections as revealed with immunostaining on rat brain sections. Adsorption of these sera with alpha-MSH peptide abolished this immunostaining. In the pituitary, the immunostaining was blocked by adsorption with alpha-MSH or adrenocorticotropic hormone. Additionally, 3 ANBN sera bound to luteinizing hormone-releasing hormone (LHRH)-positive terminals in the rat median eminence, but only 2 of them were adsorbed with LHRH. In the control subjects, 2 of 13 sera (16%) displayed similar to ANBN staining. These data provide evidence that a significant subpopulation of ANBN patients have autoantibodies that bind to alpha-MSH or adrenocorticotropic hormone, a finding pointing also to involvement of the stress axis. It remains to be established whether these Abs interfere with normal signal transduction in the brain melanocortin circuitryLHRH system andor in other central and peripheral sites relevant to food intake regulation, to what extent such effects are related to andor could be involved in the pathophysiology or clinical presentation of ANBN, and to what extent increased stress is an important factor for production of these autoantibodies.

[Effect of fuzheng jianpi recipe on content of trace element and immune function in children with spleen deficiency anorexia]

OBJECTIVE

To evaluate the efficacy and prospect of Fuzheng Jianpi Recipe (FZJPR) in treating children's Spleen deficiency anorexia (CSDA) by means of observing its effect on trace element content and immune function.

METHODS

One hundred and thirty cases of CSDA were treated with FZJPR, one dose per day in decoction, orally taken, 30 days for one therapeutic course. Levels of T-lymphocyte subsets, IL-2R, immunoglobulin and trace elements were determined before and after treatment, and compared with those in the control group consisted of 60 healthy children.

RESULTS

In the treated group, abnormal figures were shown in T-lymphocyte subsets, especially in lowering of CD3 and CD4 count before treatment, and IgG content was reduced also. After treatment, CD3, CD4, CD4/CD8 ratio as well as IgG and IgA were improved significantly (P < 0.01), IL-2R percentage approached normal. Moreover, the levels of Zn and Fe changed significantly (P < 0.01).

CONCLUSION

FZJPR could improve the trace elements content and immune function in CSDA children, so it is effective in treating CSDA.

The leptin defense against wasting is abolished in the IL-2-deficient mouse model of inflammatory bowel disease

Anorexia is a major complication of inflammatory bowel disease (IBD). We postulated that chronic intestinal inflammation with increased proinflammatory cytokines elevates serum leptin concentration, thereby contributing to anorexia. This hypothesis was studied in interleukin-2-deficient (IL-2(-/-)) mice, a model of IBD with elevated proinflammatory cytokine production. IL-2(-/-), wild-type pair-fed and wild-type control male mice (8 wk old) were fed regular laboratory mouse food for 2 wk. The IL-2(-/-) and pair-fed groups consumed less food and lost weight. Serum leptin concentrations in the IL-2(-/-) mice in the fed state were lower than controls, but not different from pair-fed mice, and paradoxically increased in the starved state to levels significantly higher than both starved control and pair-fed groups. This result did not change when serum leptin was adjusted for amount of body fat. These data show abnormal leptin responses in IL-2(-/-) mice with increased leptin concentrations disproportionate to fat mass and prevention of the normal decline in leptin with food restriction.

COX-2 inhibition attenuates anorexia during systemic inflammation without impairing cytokine production

Anorexia and weight loss are frequent complications of acute and chronic infections and result from induction of cytokines, prostaglandins, and other inflammatory mediators that are critical for pathogen elimination. Selective attenuation of the hypophagic response to infection and maintenance of the production of factors essential for infection control would be a useful addition to antimicrobial therapy in the treatment of human disease. Here, we evaluate the relative contribution of cyclooxygenase (COX)-1- and COX-2-derived prostaglandins to anorexia and weight loss precipitated by systemic immune activation by lipopolysaccharide (LPS). Using COX isoform-selective pharmacological inhibitors and gene knockout mice, we found that COX-2 inhibition during LPS-induced inflammation results in preserved food intake and maintenance of body weight, whereas COX-1 inhibition results in augmented and prolonged weight loss. Regulation of neuropeptide Y, corticotropin-releasing hormone, leptin, and interleukin-6 does not change as a function of COX-2 inhibition after LPS administration. Our data implicate COX-2 inhibition as a therapeutic target to maintain nutritional status while still allowing a normal cytokine response during infection.

Cytokine-induced sickness behaviour: mechanisms and implications

Sickness behaviour represents the expression of the adaptive reorganization of the priorities of the host during an infectious episode. This process is triggered by pro-inflammatory cytokines produced by peripheral phagocytic cells in contact with invading micro-organisms. The peripheral immune message is relayed to the brain via a fast neural pathway and a slower humoral pathway, resulting in the expression of pro-inflammatory cytokines in macrophage-like cells and microglia in the brain. The cellular and molecular components of this previously unsuspected system are being progressively identified. These advances are opening new avenues for understanding brain disorders, including depression.

Anorexia in a rat model of colitis: interaction of interleukin-1 and hypothalamic serotonin

BACKGROUND AND AIMS

Anorexia induced by experimental colitis in rats is mediated, in part, by increased release of serotonin (5-HT) from the hypothalamic paraventricular nucleus (PVN). In this model, anorexia is attenuated by treatment with an interleukin-1 (IL)-1 receptor antagonist (ra). However, a functional link between central IL-1 receptors and 5-HT release remains unproven. We have tested the hypothesis that anorexia associated with experimental colitis is mediated by IL-1 induced release of 5-HT.

METHODS

In vivo 5-HT release in the PVN was measured in rats with 2,4,6-trinitrobenzenesulphonic acid (TNBS)-induced colitis, treated with intracerebroventricular infusion of IL-1ra or vehicle treated controls. The effect of inhibition of tumour necrosis factor-alpha on food intake and PVN 5-HT release in TNBS-colitis was also tested.

RESULTS

In rats with TNBS-induced colitis, intracerebroventricular infusion of IL-1ra resulted in a 18-fold reduction in PVN 5-HT release compared to vehicle-treated controls. This was associated with a significant increase in food intake in IL-1ra treated rats. In contrast intracerebroventricular administration of anti-tumour necrosis factor antibodies had no effect on either PVN 5-HT release or food intake in rats with TNBS-induced colitis.

CONCLUSIONS

In animals with TNBS-colitis, anorexia is mediated, in part, by the stimulatory effect of IL-1 on medial hypothalamic 5-HT.

Dietary supplementation with conjugated linoleic acid does not improve nutritional status of tumor-bearing rats

Tumor necrosis factor-alpha (TNF) is an immunoregulatory cytokine that plays a major role in tumor-induced anorexia and weight loss. Conjugated linoleic acids (CLA) are naturally occurring isomers of linoleic acid that, when added to the diet, improve food intake and body weight in mice injected with TNF. The purpose of the present study was to examine the effects of a diet supplemented with 0.5% CLA on the nutritional status of rats implanted with the Morris 7777 hepatoma. Body weight, food intake, serum levels of insulin-like growth factor, and splenocyte synthesis of TNF were not different in tumor-bearing animals fed CLA versus the control diet. However, insulin levels were increased in both tumor-bearing and control animals given CLA. The 0.5% CLA did not improve the nutritional status nor alter TNF synthesis in hypophagic tumor-bearing rats. The biological significance of increased insulin levels in animals given CLA remains to be determined.

Feeding-related immune responsive brain stem neurons: association with CGRP

Using dual-labeling in situ hybridization histochemistry, the neurotransmitter expression of immune-responsive neurons in the pontine parabrachial nucleus, a major relay for interoceptive information, was investigated. Intravenous injection of bacterial wall lipopolysaccharide resulted in dense c-fos mRNA expression in the external lateral parabrachial nucleus, and a majority of the c-fos expressing cells also expressed calcitonin gene-related peptide (CGRP) mRNA. In contrast CGRP-positive cells in the adjoining external medial subnucleus were c-fos negative. Taken together with previous hodological and behavioral studies, these data suggest that CGRPergic parabrachial neurons may mediate lipopolysaccharide-induced anorexia by means of their projection to central nucleus of the amygdala.

Social stress in anorexia nervosa: a review of immuno-endocrine relationships

Anorexia nervosa (AN) patients have difficulty in establishing social contacts, leading to tension, anxiety and full-blown stress reactions. Stress hormones are chronically increased in AN, while immune function, which is involved in physical and psychological coping capacities, is mostly unimpaired. We examined immune function in a group of anorexics by measuring the T-lymphocyte proliferative response to stimulation with phytohemagglutinin (PHA), before and after in vivo acute administration of corticotropin-releasing hormone (CRH), to mirror a stress reaction. The responses of anorexics, before and after CRH stimulation, did not differ from those of controls. In a second group of anorexics, we measured plasma concentrations of interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) before and after psychopharmacological (fluoxetine, amineptine) therapy. Basal values of the cytokines were not different in patients and controls, and did not change during therapy. In the same patients, we measured basal concentrations of soluble IL-1 beta receptor antagonist (s-IL-1 beta-RA), soluble IL-6 receptor (sIL-6-R) and soluble TNF-alpha receptors I and II (sTNF-alpha-R-I and -II). S-IL-1 beta-RA and sTNF-alpha-R-I and -II levels were not different in patients and controls, while those of s-IL-6-R were lower than normal in anorexics. The normality of most of the immune parameters in our anorexics, in basal conditions, after a stressful stimulation and after pharmacological manipulation of neurotransmitters suggests that the well-known interrelation among immune, neuroendocrine and central nervous system functions is not maintained in AN, the immune system being somehow unresponsive to stimuli.

Immunopathologic weight loss in intracranial LCMV infection initiated by the anorexigenic effects of IL-1beta

Lymphocytic choriomeningitis virus (LCMV) infection of beta2-microglobulin-deficient (beta2m-/-) mice results in a substantial loss of body weight that is not mediated by the virus itself, but rather by CD4+ T cells responding to the viral infection. In this study, we further characterized LCMV-induced weight loss in immunocompetent and beta32m-/- mice. We show that intracranial (i.c.), but not intraperitoneal (i.p.) LCMV infection elicited significant weight loss and that weight loss was preceded by anorexia. Also, uninfected mice fed an equivalent amount as eaten by infected mice had similar weight loss compared to their infected counterparts. Interestingly, both weight loss and anorexia were greater in female than male beta2m-/- mice. LCMV-infected female beta2m-/- mice also had significantly more interleukin (IL)-betag in their cerebrospinal fluid (CSF) than did male beta2m-/- mice. Finally, intracerebroventricular (i.c.v.) administration of anti-IL-1beta antibody, but not control immunoglobulin G (IgG), attenuated the initial weight loss and increased food intake. Taken together, these results suggest that the majority of weight loss after intracranial LCMV infection is the result of anorexia and IL-1beta mediates initial anorexic weight loss.

Behavioral effects of infection with IL-6 adenovector

The onset of autoimmunity in lupus-prone mice is accompanied by a constellation of behavioral deficits, termed Autoimmunity-Associated Behavioral Syndrome (AABS). In particular, a spontaneous increase in serum interleukin-6 (IL-6) levels in five-week old MRL-lpr mice coincides temporally with blunted responsiveness to sucrose and excessive immobility in the forced swim test. These relationships, along with evidence that sucrose intake drops after systemic IL-6 overexpression is induced in healthy mice, have led to the hypothesis that sustained elevation in serum IL-6 also induces other aspects of AABS. This hypothesis is tested by comparing the behavioral profiles of healthy mice infected with Ad5mIL6 adenovirus (2 x 10(8) pfu of virus/mouse i.p.) with those of animals infected with control Ad5 virus. This methodology was used to achieve high circulating levels of IL-6, to overcome the problem of its short half-life, and to avoid the stressful effects of repeated injections. The Ad5mIL6 infection (known to induce excessive IL-6 levels over five days) transiently reduced food, water, and sucrose intake, as well as rectal temperature in MRL +/+ and AKR/J mice. Although the level of locomotor activity did not decline, Ad5mIL6-infected AKR/J mice demonstrated less novel object exploration. Performance in the step-down, plus-maze, and spontaneous alternation tests were disturbed to various degrees in all infected animals. The present results suggest that prolonged exposure to circulating IL-6 primarily impairs ingestive behavior, likely reflecting enhanced catabolism. The inability of circulating IL-6 to alter other aspects of behavior supports the hypothesis that multiple immuno-neuroendocrine mechanisms contribute to the pathogenesis of AABS.

Modulation of the acute phase response by altered expression of the IL-1 type 1 receptor or IL-1ra

A complete understanding of the role for endogenously produced interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-alpha), and IL-1 receptor antagonist (IL-1ra) in the acute phase response to inflammation remains unknown. In the present studies, knockout mice lacking either a functional IL-1 type I receptor (IL-1RI(-/-)), a TNF type I receptor (TNFR-I(-/-)), or both IL-1 type I and TNF type I receptors (IL-1RI(-/-)/TNFR-I(-/-)) received a turpentine abscess. Additional mice deficient in IL-1ra protein (IL-1ra(-/-)) or overexpressing IL-1ra protein (IL-1ra(tg)) were similarly treated. After a turpentine abscess, IL-1 receptor knockout mice exhibited an attenuated inflammatory response compared with wild-type or animals lacking a functional TNFR-I. Mice overexpressing IL-1ra also had an attenuated hepatic acute phase protein response, whereas IL-1ra knockout mice had a significantly greater hepatic acute phase response. We conclude that the inflammatory response to a turpentine abscess is the result of a balance between IL-1ra expression and IL-1 binding to its type I receptor. Endogenously produced IL-1ra plays a central role in mitigating the magnitude of the IL-1-mediated inflammatory response and, ultimately, the outcome to a turpentine abscess.

Nutritional effects on vaccination

Immune-induced cachetic response is an example of a biological opportunity to develop technologies that ensure improved performance in animal agriculture. We have estimated that reduced performance of immune stimulated animals, whether by exposure to conventional environments or through vaccination, results in more than U.S. $500 million in reduced productivity. Nontraditional methods to alleviate the adverse effects of the immune response provide an opportunity for those skilled in the art of vaccinology and immunology to develop new technologies and feeding practices. Too often, biologists are blinded by the limits of their disciplines and rarely venture to the fringe of their field to engage in collaborations that at first glance do not seem logical. The examples of CLA and antigastrointestinal peptides suggest that new opportunities await in ensuring that the cost of the immune response is minimized and that new approaches to animal agriculture await discovery.

Immune and endocrine regulation of food intake in sick animals

To understand why sick animals do not eat, investigators have studied how the immune system interacts with the central nervous system (CNS), where motivation to eat is ultimately controlled. The focus has been on the cytokines secreted by activated mononuclear myeloid cells, which include interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha). Either central or peripheral injection of recombinant IL-1 beta, IL-6, and TNF-alpha reduce food-motivated behavior and food intake in rodents. Moreover, these cytokines and their receptors are present in the endocrine system and brain, and antagonism of this system (i.e., the cytokine network) has been shown to block or abrogate anorexia induced by inflammatory stimuli. Recent studies indicate that the same cytokines act on adipocytes and induce secretion of leptin, a protein whose activity has been neuroanatomically mapped to brain areas involved in regulating food intake and energy expenditure. Therefore, many findings converge to suggest that the reduction of food intake in sick animals is mediated by inflammatory cytokines, which convey a message from the immune system to the endocrine system and CNS. The nature of this interaction is the focus of this short review.

Brain cytokine mRNAs in anorectic rats bearing prostate adenocarcinoma tumor cells

Cancer is consistently associated with anorexia. The Lobund-Wistar rat model of prostate cancer exhibits clinical manifestations (including anorexia) that resemble many aspects of the human disease. Cytokines are proposed to be involved in cancer-associated anorexia. Here we investigated mRNA profiles of feeding-modulatory cytokines and neuropeptides in specific brain regions of anorectic Lobund-Wistar rats bearing prostate adenocarcinoma tumor cells. Interleukin (IL)-1beta system components (ligand, signaling receptor, receptor accessory proteins, receptor antagonist), tumor necrosis factor-alpha, transforming growth factor-beta1, glycoprotein 130 (IL-6 receptor signal transducer), proopiomelanocortin (POMC, opioid peptide precursor), and neuropeptide Y (NPY) mRNAs were analyzed with sensitive and specific RNase protection assays. The same brain region sample was assayed for all components. The data show that early anorexia in tumor-bearing rats was associated with an upregulation of IL-1beta mRNA in the brain regions examined (cerebellum, cortex, and hypothalamus). IL-1 receptor antagonist (IL-1Ra) mRNA and IL-1 receptor type I mRNA levels were also significantly increased in the cortex and hypothalamus. All other cytokine components, POMC, or NPY mRNA levels were not significantly different between tumor-bearing and pair-fed (control) rats. IL-1beta mRNA and IL-1Ra mRNA were also significantly upregulated in the spleen of tumor-bearing rats. These data suggest that 1) IL-1beta mRNA upregulation in the brain may be relevant to the anorexia exhibited by the tumor-bearing Lobund-Wistar rat and 2) in vivo characterization of cytokine components in discrete brain regions during cancer is necessary to understand underlying molecular mechanisms responsible for cancer-associated neurological manifestations.

Blockade of brain type II interleukin-1 receptors potentiates IL1beta-induced anorexia in mice

Interleukin-1beta (IL1beta) peripheral activities are mediated by type I IL1 receptors (IL1RI), whereas type II IL1 receptors (IL1RII) act as 'decoy' targets. To study the functionality of IL1RII in the brain, mice were treated with an intracerebroventricular injection of a neutralising MoAb directed against IL1RII (4E2, 1 microg) followed by recombinant rat IL1beta at a dose (2 ng) that produced a moderate but significant decrease of food intake 1 h 30 min after injection. The administration of 4E2 to IL-1beta treated mice significantly potentiated IL1beta-induced decrease in food intake without altering hypothermia. The effects of IL1beta were abrogated in the positive control group treated with IL1ra (2 microg, i.c.v). These results suggest that brain IL1RII down-regulate the effects of IL1beta on its cell targets in the brain.

Cytokine activity in cancer-related anorexia/cachexia: role of megestrol acetate and medroxyprogesterone acetate

The characteristic clinical picture of anorexia, tissue wasting, loss of body weight accompanied by a decrease in muscle mass and adipose tissue, and poor performance status that often precedes death has been named the cancer-related anorexia/cachexia syndrome (CACS). Chronic administration of pro-inflammatory cytokines, including interleukin-I (IL-I), IL-6, and tumor necrosis factor (TNF), either alone or in combination, is capable of reproducing the different features of CACS. High serum levels of these cytokines have been found in cancer patients, which seem to correlate with progression of the tumor. This article describes a series of experimental and clinical studies demonstrating that: (1) high serum levels of some cytokines, including IL-I, IL-6, and TNF, are present in advanced-stage cancer patients, particularly those with CACS; (2) megestrol acetate (MA) has a beneficial therapeutic effect on CACS symptoms, such as appetite, body weight, and quality of life; (3) MA downregulates the synthesis and release of cytokines and relieves the symptoms of CACS; (4) cytokines play a key role in the onset of CACS; (5) medroxyprogesterone acetate (MPA) reduces the in vitro production of cytokines and serotonin (5-hydroxytryptamine, 5-HT) by peripheral blood mononuclear cells (PBMC) of cancer patients; and (6) MA and MPA reduce the cisplatin-induced 5-HT release in vitro from PBMC of cancer patients. Based on these results, a clinical study incorporating MA/MPA in combination with chemotherapy or chemoimmunotherapy may be warranted. In addition, it has been recently shown that "oxidative stress" resulting from reactive oxygen species, which can be induced by pro-inflammatory cytokines, is involved in tissue wasting and CACS. These results suggest promising approaches for the prevention and treatment of cytokine-induced CACS based on MA, MPA, and metabolic antioxidants.

Anticytokine approaches to the treatment of anorexia and cachexia

Proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) have a prominent role in the pathogenesis of anorexia and cachexia of chronic disease. Pentoxyfylline and thalidomide are inhibitors of TNF-alpha that have been tried as rational therapeutic interventions in cachexia. Preliminary studies with pentoxyfylline have not shown efficacy in reversing weight loss, despite evidence of TNF-alpha inhibition. In contrast, the administration of thalidomide to patients with human immunodeficiency virus- and/or tuberculosis-associated weight loss has consistently resulted in weight gain. However, the relationship of the metabolic benefits of thalidomide treatment to its complex effects on the immune system is imperfectly understood. Studies of thalidomide, either alone or in combination with other therapies for the treatment of cancer cachexia, are warranted.

Interleukin-1beta system (ligand, receptor type I, receptor accessory protein and receptor antagonist), TNF-alpha, TGF-beta1 and neuropeptide Y mRNAs in specific brain regions during bacterial LPS-induced anorexia

Bacterial lipopolysaccharide (LPS) or endotoxin induces neurological manifestations including anorexia. It is proposed that LPS-induced cytokine production is involved in the generation of neurological manifestations and in neuroinflammatory/immunological responses during gram-negative infections. For example, LPS-induced effects can be blocked or ameliorated by the interleukin-1 receptor antagonist (IL-1Ra). Here, sensitive and specific RNase protection assays were used to investigate the effects of the intracerebroventricular (i.c.v.) administration of LPS on mRNA levels of interleukin-1beta (IL-1beta) system components, tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta1, and neuropeptide Y (NPY) in the cerebellum, hippocampus, and hypothalamus. The same brain region sample was analyzed with all of the antisense probes. The data show simultaneous local induction of multiple cytokine components messenger ribonucleic acids (mRNAs) within specific brain regions in anorectic rats responding to i.c.v. administered LPS (500 ng/rat). Interleukin-1beta and IL-1Ra had a similar mRNA induction profile (hypothalamus > cerebellum > hippocampus). Interleukin-1 receptor type I (IL-1RI) mRNA also increased in all three brain regions examined, and the soluble form of IL-1 receptor accessory protein (IL-1R AcP II) mRNA was induced in the hypothalamus. Tumor necrosis factor-alpha mRNA levels increased in the hypothalamus > hippocampus > cerebellum. Levels of membrane bound IL-1R AcP, TGF-beta1, and NPY mRNAs did not change significantly in any brain region. The results suggest that: (1) endogenous up-regulation of IL-1beta and TNF-alpha in the hypothalamus contribute to LPS-induced anorexia; and (2) the ratio IL-1Ra/IL-1beta, and IL-1beta <--> TNF-alpha interactions may have implications for gram-negative infections associated with high levels of LPS in the brain-cerebrospinal fluid.

Infection-induced anorexia: active host defence strategy

In association with fever production, decreased food consumption is the most common sign of infection. This effect is often regarded as an undesirable manifestation of sickness. However, evidence suggests that just as many behaviours have now been shown to modify immunocompetence, infection-induced anorexia is a behaviour systematically organised for pathogen elimination. That is, anorexia is an active defence mechanism that is beneficial for host defence. This review details the mechanism of infection-induced anorexia, placing it within the framework of the intricately organised acute phase response--the host response to infection. Furthermore, the evolutionary, behavioural, metabolic and immunological consequences of infection-induced anorexia are outlined, each providing evidence for the beneficial nature of this response. The evidence suggests that food restriction is one of the important behavioural strategies that organisms have evolved for the fight against pathogenic invasion. Nevertheless, such benefits require fine homeostatic control, as chronic undernutrition has deleterious consequences for host defence.

Interactions between nutrition and immunity in anorexia nervosa: a 1-y follow-up study

Nutritional status and immunocompetence were evaluated in 15 patients suffering from anorexia nervosa in comparison with a control group (n = 15). After 1 y, data from six phases of the study were evaluated: immediately after admittance to the hospital (AN1), after 1 mo (AN2), after 2 mo (AN3), after 3 mo (AN4), after 6 mo (AN5), and after 1 y, (AN6). Patients recovered weight from AN4 until AN6 although, according to body mass index values, all patients had low weights during the 1-y follow-up. Likewise, leukocyte and lymphocyte values were borderline and lower in patients in all phases tested than in control subjects. All lymphocyte subpopulations were lower in AN1 and AN2 patients (inpatients) than in control subjects, except for CD19 cells, which remained unmodified. There seemed to be a recovery of lymphocyte subsets after hospitalization in AN3 and AN4 patients (outpatients), except for CD57, which remained below control values. However, there was a global decrease of the lymphocyte subsets in AN5 and AN6. Ratios of CD4 to CD8 cells were not altered but the ratio of CD2 to CD19 cells was lower in all phases except AN6. Moreover, cell-mediated immune function was impaired and none of the patients showed normal responses. Thus, despite the slight weight increase found in AN4, AN5, and AN6 and the apparent cell subset recovery after hospitalization, these results suggest a greatly depleted nutritional status that remained during the whole year in all patients.

Medroxyprogesterone acetate reduces the in vitro production of cytokines and serotonin involved in anorexia/cachexia and emesis by peripheral blood mononuclear cells of cancer patients

Medroxyprogesterone acetate (MPA) is widely used in oncology both in the treatment of hormone-related cancers and as supportive therapy in anorexia/cachexia syndrome (ACS), but conclusive data are not yet available to explain its anticachectic effect. ACS is characterised by weight loss, changes in metabolism, reduction of appetite, nausea and vomiting. Several cytokines, mainly interleukin (IL)-1, IL-2, IL-6 and tumour necrosis factor alpha (TNF alpha), are involved in the pathogenesis of ACS. Additionally, nausea and vomiting can be mediated by factors inducing serotonin (5-HT) production and/or release by pleiotropic cells including activated T lymphocytes. In the present study, we report the effect of MPA on peripheral blood mononuclear cells (PBMC) from 10 cancer patients in advanced stage of disease (6 head and neck, 2 colon, 1 lung and 1 ovary). The proliferative response of PBMC to PHA, anti-CD3 monoclonal antibody (MAb) or recombinant IL-2 (rIL-2), the production of IL-1 beta, IL-2, IL-6, TNF alpha and 5-HT by PHA-stimulated PBMC and the expression of lymphocyte membrane-bound IL-2 receptor (IL-2R) subunities (CD25 and CD122) were studied. The addition of MPA significantly reduced the PBMC proliferative response to PHA and anti-CD3 MAb but not to rIL-2. MPA 0.2 microgram/ml was also capable of reducing the levels of IL-1 beta, IL-6, TNF alpha and 5-HT produced in culture by PHA-stimulated PBMC, whereas it did not induce any change in the percentage of PBMC expressing either CD25 or CD122 or both molecules after stimulation with PHA or anti-CD3 mAb.

Immunopathology of experimental Jembrana disease in Bali cattle

Sequential immunohistochemical studies of the lymphoreticular responses of Bali cattle (Bos javanicus syn. Bos sondaicus) after inoculation with the Jembrana disease virus were carried out using the peroxidase-antiperoxidase test for immunoglobulin containing cell assessment and the indirect immunoperoxidase test for lymphocyte subset assessment. The prevalence of immunoglobulin G-containing cells declined during the acute phase of the disease but became significantly elevated during convalescence. This trend was consistent with serological responses previously observed using an enzyme linked immunosorbent assay. Temporary immunosuppression appeared to occur during the acute phase of the disease as indicated by a decrease in the immunoglobulin G-containing cells in the lymphoid organs and an observed decrease in the BoCD4/BoCD8 lymphocyte ratio in lymph node follicles.