Dexamethasone inhibits food intake suppression induced by low doses of interleukin-1 beta administered intracerebroventricularly

Invited review: Mechanisms of hypophagia during disease

Suppression of appetite, or hypophagia, is among the most recognizable effects of disease in livestock, with the potential to impair growth, reproduction, and lactation. The continued evolution of the field of immunology has led to a greater understanding of the immune and endocrine signaling networks underlying this conserved response to disease. Inflammatory mediators, especially including the cytokines tumor necrosis factor-α and interleukin-1β, are likely pivotal to disease-induced hypophagia, based on findings in both rodents and cattle. However, the specific mechanisms linking a cytokine surge to decreased feeding behavior are more difficult to pin down and likely include direct effects on appetite centers in the brain, alteration of gastric motility, and modulation of other endocrine factors that influence appetite and satiety. These insights into the mechanisms for disease-induced hypophagia have great relevance for management of neonatal calves, mature cows transitioning to lactation, and cows experiencing mastitis; however, it is not necessarily the case that increasing feed intake by any means possible will improve health outcomes for diseased cattle. We explore conflicting effects of hypophagia on immune responses, which may be impaired by the lack of specific substrates, versus apparent benefits for controlling the growth of some pathogens. Anti-inflammatory strategies have shown promise for promoting recovery of feed intake following some conditions but not others. Finally, we explore the potential for early disease detection through automated monitoring of feeding behavior and consider which strategies may be implemented to respond to early hypophagia.

Activation of orexinergic and histaminergic pathway involved in therapeutic effect of histamine H4 receptor antagonist against cisplatin-induced anorexia in mice

We previously reported that hypothalamic tumor necrosis factor-alpha (TNF-α) mRNA expression via histamine H₄ receptors contributes to the development of cisplatin-induced anorexia; however, its precise mechanisms remain unclear. It has been reported that chemotherapeutic agents induce the suppression of orexin neuron activity, and the administration of orexin inhibits chemotherapeutic agent-induced gastric discomfort. Other studies demonstrated that the central administration of TNF-α impairs the orexinergic system, and that orexin excites the histaminergic system. We investigated the involvement of orexinergic and histaminergic systems in the therapeutic effect of an H₄ receptor antagonist against cisplatin-induced anorexia. Cisplatin decreased the expression of prepro-orexin mRNA, which encodes precursors of orexin, in the hypothalamus of mice. The period of expression decreased in parallel with the onset of anorexia, and treatment with an H₄ receptor antagonist (JNJ7777120, 10 mg/kg) inhibited the decrease in expression. The effect of the H₄ receptor antagonist on cisplatin-induced anorexia in mice was antagonized by an orexin OX₂ receptor antagonist (JNJ10397049, 5 mg/kg) rather than an orexin OX₁ receptor antagonist (SB408124, 30 mg/kg). Although an OX₂ receptor agonist (YNT-185, 20 mg/kg) or a histamine H₃ receptor inverse agonist (ciproxifan, 1 mg/kg) inhibited the cisplatin-induced anorexia, the inhibitory effect of the OX₂ receptor agonist was antagonized by an H₃ receptor silent antagonist (VUF5681, 5 mg/kg). The combination of JNJ7777120 (10 mg/kg) and ciproxifan (0.5 mg/kg) completely resolved the cisplatin-induced anorexia. These results suggest that activation of the orexinergic and histaminergic pathway is involved in the therapeutic effect of an H₄ receptor antagonist against cisplatin-induced anorexia.

Effects of a histamine H4 receptor antagonist on cisplatin-induced anorexia in mice

Cancer chemotherapy often induces gastrointestinal symptoms such as anorexia, nausea, and vomiting. Antiemetic agents are effective in inhibiting nausea and vomiting, but patients still experience anorexia. We previously reported that chemotherapeutic agent-induced anorexia is associated with an increase of inflammatory cytokines. Other studies also reported that antagonism of the histamine H₄ receptor is anti-inflammatory. In this study, we investigated the involvement of the H₄ receptor in the development of chemotherapy-induced anorexia in mice. Cisplatin-induced anorexia occurred within 24 h of its administration and continued for 3 days. The early phase (day 1), but not the delayed phase (days 2 and 3), of anorexia was inhibited by the daily injection of a 5-HT₃ receptor antagonist (granisetron). However, a corticosteroid (dexamethasone) or selective H₄ receptor antagonist (JNJ7777120) abolished the delayed phases of anorexia. Cisplatin significantly increased TNF-α mRNA expression in the hypothalamus and spleen, and the period of expression increase paralleled the onset period of anorexia. In addition, pretreatment with JNJ7777120 completely inhibited the increased expression. These results suggest that TNF-α mRNA expression via H₄ receptors may contribute to the development of cisplatin-induced anorexia, and that H₄ receptor antagonists are potentially useful treatments.

Oxidative Stress and Inflammation Induced by Environmental and Psychological Stressors: A Biomarker Perspective

SIGNIFICANCE

The environment can elicit biological responses such as oxidative stress (OS) and inflammation as a consequence of chemical, physical, or psychological changes. As population studies are essential for establishing these environment-organism interactions, biomarkers of OS or inflammation are critical in formulating mechanistic hypotheses. Recent Advances: By using examples of stress induced by various mechanisms, we focus on the biomarkers that have been used to assess OS and inflammation in these conditions. We discuss the difference between biomarkers that are the result of a chemical reaction (such as lipid peroxides or oxidized proteins that are a result of the reaction of molecules with reactive oxygen species) and those that represent the biological response to stress, such as the transcription factor NRF2 or inflammation and inflammatory cytokines.

CRITICAL ISSUES

The high-throughput and holistic approaches to biomarker discovery used extensively in large-scale molecular epidemiological exposome are also discussed in the context of human exposure to environmental stressors.

FUTURE DIRECTIONS

We propose to consider the role of biomarkers as signs and to distinguish between signs that are just indicators of biological processes and proxies that one can interact with and modify the disease process. Antioxid. Redox Signal. 28, 852-872.

Food and water intake, body temperature and metabolic consequences of interleukin-1β microinjection into the cingulate cortex of the rat

In order to elucidate whether cytokine mechanisms of the cingulate cortex (cctx) are important in the central regulation of homeostasis, in the present study, feeding-metabolic effects of direct bilateral microinjection of interleukin-1β (IL-1β) into the cctx of the rat have been investigated. Short- (2h), medium (12h) and long-term (24h) food and water intakes and body temperature were measured after the intracerebral administration of this primary cytokine or vehicle solution, with or without paracetamol pretreatment. The effect of IL-1β on the blood glucose level of animals was examined in glucose tolerance test (GTT), and concentrations of relevant plasma metabolites (total cholesterol, HDL, LDH, triglycerides, uric acid) were additionally also determined following the above microinjections. In contrast to causing no major alteration in the food and water intakes, the cytokine treatment evoked significant increase in the body temperature of the rats. Prostaglandin-mediated mechanisms were shown to have important role in the mode of this action of IL-1β, since paracetamol pretreatment partially prevented the development of the above mentioned hyperthermia. In the GTT, no considerable difference was observed between the blood glucose levels of the cytokine treated and control animals. Following IL-1β microinjection, however, significant decrease of HDL and total cholesterol was found. Our present findings indicate that elucidating the IL-1β mediated homeostatic control mechanisms in the cingulate cortex may lead to the better understanding not only the regulatory entities of the healthy organism but also those found in obesity, diabetes mellitus and other worldwide rapidly spreading feeding-metabolic disorders.

Antihypertensive effect of allicin in dexamethasone-induced hypertensive rats

BACKGROUND

Glucocorticoid is among the most commonly prescribed medicine. Unfortunately, Excess glucocorticoid level leads hypertension in 80-90% patients. Garlic (Allium sativum) has been used since ancient times and even nowadays as a part of popular medicine for various ailments and physiological disorders. Hence this study was undertaken to investigate the antihypertensive activity of allicin in dexamethasone induced hypertension in wistar rats.

METHODS

The animals were randomly divided into four groups comprising of six rats per group. Hypertension was induced by subcutaneous injection of dexamethasone (10 μg/rat/day) in hypertensive rats. Two hypertensive group animals were treated with nicorandil (6 mg/kg/day, po) and allicin (8 mg/kg/day, po) respectively for 8 weeks. While systolic blood pressure (SBP) was measured by the tail-cuff method weekly up to 8 weeks.

RESULTS

Dexamethasone treatment resulted in significant increase in SBP while allicin treatment significantly decreases the SBP. Thus, this study confirmed that allicin treatment for 8 weeks partially reverse dexamethasone induced hypertension in rats. Allicin treatment also attenuated dexamethasone-induced anorexia and loss of total body weight.

CONCLUSION

This result suggests antihypertensive effects of allicin in dexamethasone induced hypertension. However, further studies are needed to explore the detailed mechanism of antihypertensive effect of allicin.

Pancreatic cancer cachexia: a review of mechanisms and therapeutics

Over the last decade, we have gained new insight into the pathophysiology of cachexia associated with pancreatic cancer. Unfortunately, its treatment is complex and remains a challenge. Pancreatic cancer cachexia is a multifactorial syndrome characterized by uncompensated adipose tissue and skeletal muscle loss in the setting of anorexia that leads to progressive functional impairment. This paper will review the current concepts of pancreatic cancer cachexia, its assessment and pathophysiology as well as current and future treatments. The successful management of pancreatic cancer cachexia will likely require a multimodal approach that includes nutritional support and combination pharmaceutical interventions.

Glucocorticoids as cytokine inhibitors: role in neuroendocrine control and therapy of inflammatory diseases

Glucocorticoids are potent inhibitors of inflammation and endotoxic shock. This probably occurs through an inhibition of the synthesis of pro-inflammatory cytokines as well as of many of their toxic activities. Therefore, endogenous glucocorticoids (GC) might represent a major mechanism in the control of cytokine mediated pathologies. GC inhibit the synthesis of cytokines in various experimental models. Adrenalectomy or GC antagonists potentiate TNF, IL-1 and IL-6 production in LPS treated mice. GC inhibit the formation of arachidonic acid metabolites and the induction of NO synthase. They also inhibit various activities of cytokines including toxicity, haemodynamic shock and fever. Adrenalectomy sensitizes to the toxic effects of LPS, TNF and IL-1. On the other hand, GC potentiate the synthesis of several cytokine induced APP by the liver. Since many of these proteins have anti-toxic activities (antioxidant, antiprotease etc.) or bind cytokines, this might well represent a GC mediated protective feedback mechanism involving the liver. Not only do GC inhibit cytokines, but in vivo LPS and various cytokines (TNF, IL-1, IL-6) increase blood GC levels through a central mechanism involving the activation of the HPA. Thus, this neuroendocrine response to cytokines constitutes an important immunoregulatory feedback involving the brain.

The effect of non-steroidal anti-inflammatory agents on behavioural changes and cytokine production following systemic inflammation: Implications for a role of COX-1

Systemic inflammation gives rise to metabolic and behavioural changes, largely mediated by pro-inflammatory cytokines and prostaglandin production (PGE(2)) at the blood-brain barrier. Despite numerous studies, the exact biological pathways that give rise to these changes remains elusive. This study investigated the mechanisms underlying immune-to-brain communication following systemic inflammation using various anti-inflammatory agents. Mice were pre-treated with selective cyclo-oxygenase (COX) inhibitors, thromboxane synthase inhibitors or dexamethasone, followed by intra-peritoneal injection of lipopolysaccharide (LPS). Changes in body temperature, open-field activity, and burrowing were assessed and mRNA and/or protein levels of inflammatory mediators measured in serum and brain. LPS-induced systemic inflammation resulted in behavioural changes and increased production of IL-6, IL-1beta and TNF-alpha, as well as PGE(2) in serum and brain. Indomethacin and ibuprofen reversed the effect of LPS on behaviour without changing peripheral or central IL-6, IL-1beta and TNF-alpha mRNA levels. In contrast, dexamethasone did not alter LPS-induced behavioural changes, despite complete inhibition of cytokine production. A selective COX-1 inhibitor, piroxicam, but not the selective COX-2 inhibitor, nimesulide, reversed the LPS-induced behavioural changes without affecting IL-6, IL-1beta and TNF-alpha protein expression levels in the periphery or mRNA levels in the hippocampus. Our results suggest that the acute LPS-induced changes in burrowing and open-field activity depend on COX-1. We further show that COX-1 is not responsible for the induction of brain IL-6, IL-1beta and TNF-alpha synthesis or LPS-induced hypothermia. Our results may have implications for novel therapeutic strategies to treat or prevent neurological diseases with an inflammatory component.

Systemic infection and inflammation in acute CNS injury and chronic neurodegeneration: underlying mechanisms

We have all at some time experienced the non-specific symptoms that arise from being ill following a systemic infection. These symptoms, such as fever, malaise, lethargy and loss of appetite are often referred to as "sickness behavior" and are a consequence of systemically produced pro-inflammatory mediators. These inflammatory mediators signal to the brain, leading to activation of microglial cells, which in turn, signal to neurons to induce adaptive metabolic and behavioral changes. In normal healthy persons this response is a normal part of our defense, to protect us from infection, to maintain homeostasis and causes no damage to neurons. However, in animals and patients with chronic neurodegenerative disease, multiple sclerosis, stroke and even during normal aging, systemic inflammation leads to inflammatory responses in the brain, an exaggeration of clinical symptoms and increased neuronal death. These observations imply that, as the population ages and the number of individuals with CNS disorders increases, relatively common systemic infections and inflammation will become significant risk factors for disease onset or progression. In this review we discuss the underlying mechanisms responsible for sickness behavior induced by systemic inflammation in the healthy brain and how they might be different in individuals with CNS pathology.

Central adaptation to chronic administration of interleukin-1beta (IL-1beta) in rats

Interleukin-1beta (IL-1beta), a cytokine, has been shown to induce a number of central and neuroendocrine effects. Prolonged treatment with IL-1beta is associated with adaptive responses in feeding, body temperature and hormone profiles. The purpose of the present study was to see if these effects are accompanied by changes in hypothalamic norepinephrine (NE) and to compare it with the acute effects of IL-1beta. Adult male Sprague-Dawley rats were treated (i.p.) with 5 microg of IL-1beta once (acute) or daily for 5 consequent days (chronic). The control animals received an injection of the vehicle for IL-1beta (0.1% PBS-BSA). Body weight, food intake, and rectal temperature were monitored daily. At the end of treatment, the animals were sacrificed, and specific areas of the hypothalamus were microdissected and analyzed for NE concentrations. Corticosterone levels were measured in the serum. Both acute and chronic IL-1beta treatment produced significant changes in a number of parameters. However, there were marked differences between the two treatment regimens. While acute treatment with IL-1beta increased NE concentrations in both the paraventricular nucleus and the median eminence (ME), chronic treatment increased NE concentrations only in the ME. A corresponding increase in serum corticosterone levels was observed with acute IL treatment. Chronic treatment with IL-1beta decreased body weight, and produced an initial decrease in food intake which returned to control levels by the fourth day of treatment. Chronic IL treatment also produced an initial increase in body temperature that returned to control levels by day 4. These results indicate that the effects of IL-1beta on central and neuroendocrine functions are dependent on the duration of the treatment and that the adaptive responses observed in feeding and body temperature after chronic IL treatment are accompanied by similar responses in brain NE.

Inhibition of leptin-induced IL-1beta expression by glucocorticoids in the brain

Leptin is an important circulating signal for the regulation of food intake and body weight. Glucocorticoids were suggested to play a physiological role in the feedback inhibition of immune/inflammatory responses. In the present study, we examined whether these neuroendocrine effects of glucocorticoids are linked to changes in the leptin-induced expression of IL-1beta and STAT3 activation in the brain. Intravenous injection of leptin induced IL-1beta expression in the hypothalamus. Pretreatment with dexamethasone dose dependently inhibited leptin-induced IL-1beta expression in the hypothalamus. Moreover, dexamethasone inhibited leptin-induced IL-1beta expression in the primary cultured glial cells. In contrast, pretreatment with dexamethasone did not inhibit leptin-induced STAT3 phosphorylation in the hypothalamus. These effects of dexamethasone may not be due to the change in the expression level of the leptin receptor Ob-Ra and Ob-Rb isoforms. Therefore, it is suggested that glucocorticoid negatively regulates leptin-induced IL-1beta expression in the brain.

Peripheral endotoxin causes long-lasting changes in locus coeruleus activity via IL-1 in the brain

Activity of locus coeruleus (LC) neurons, the major noradrenergic cell-body group in the brain whose axons give rise to approximately 70% of norepinephrine (NE) in the brain, is believed to play an important role in attention/vigilance, cognitive functions and behavioral disorders, particularly depression. Results described here show that in the rat, intraperitoneal (i.p.) injection of lipopolysaccharide (LPS, a bacterial endotoxin) causes long-lasting changes in electrophysiological activity of LC neurons that are mediated by interleukin-1 (IL-1) acting locally in the LC region. First, it was found that IL-1, when microinjected into the LC region or stimulated/expressed in that brain region, increased activity of LC neurons. The only exception to this was that a very low dose of microinjected IL-1 (5 pg) decreased LC activity, which could be blocked by an antagonist to corticotropin-releasing hormone (CRH), thus suggesting that the decrease was due to IL-1 stimulation of CRH release. All of these effects could be blocked by injection and/or infusion of IL-1 receptor antagonist (IL-1RA) specifically into the LC region. Next, intraperitoneal (i.p.) injection of a low dose of LPS(10 µg/kg or 100 ng/kg) was also found to increase LC activity. The excitation of LC produced by 10 µg/kg i.p. LPS increased progressively for at least 1 week, with LC neurons firing at more than twice their normal rate at 1 week after the i.p. LPS injection. Alteration of LC activity lasted for 3 weeks after a single i.p. injection of 10 µg/kg LPS. The effects of i.p. LPS on LC activity at any time after i.p. injection could be blocked by a brief microinfusion of IL-1RA into the LC region, thereby indicating that changes in LC activity seen after the i.p. LPS were caused by IL-1 acting in the LC region. Finally, i.p. injection of peptidoglycan, representing gram-positive bacteria, and polyinsinic-polycytidylic acid [poly(I):(C)], representing viral infection, also caused increases in LC activity, and the effects of peptidoglycan [but not those of poly(I):(C)] were blocked by microinfusion of IL-1RA into LC. These findings suggest that bacterial infections can give rise to prolonged changes in brain activity through cytokine action in brain.

Managing cancer-related anorexia/cachexia

Cancer-related anorexia/cachexia (CAC) is a complex phenomenon in which metabolic abnormalities, proinflammatory cytokines produced by the host immune system, circulating tumour-derived catabolic factors, decreased food intake, and probably additional unknown factors, all play different roles. This review examines the mechanisms of CAC and its management. All the potential modalities of intervention from nutritional to pharmacological approaches are included with a clear distinction between unproven, investigational and well established treatments. Among the latter, the progestogens are currently considered the most effective and safest drugs for the management of CAC. Agents currently under investigation for CAC include thalidomide, pentoxifylline and melatonin, which most probably act on cytokine release, and clenbuterol, which acts on muscle mass and to antagonise protein wasting. Our personal experience with the synthetic progestogens megestrol and medroxyprogesterone supports their use as first-line agents. In addition, our work on the potential role of antioxidant agents in counteracting the oxidative stress, which appears to be involved in CAC, shows them to be promising agents when used in combination chemotherapy regimens either alone or with other 'biologics'. There is an ongoing need for quality of life questionnaires which specifically address the most significant symptoms present in patients with CAC.

1998 Curt P. Richter Award. Brain mechanisms in cytokine-induced anorexia

Our research focuses on the mechanisms underlying cytokine action in the central nervous system (CNS) using an integrative and multidisciplinary strategy organized through supracellular (behavioral analysis by computerized monitoring systems), cellular (extracellular and intracellular neurophysiological recording), and molecular (patch-clamp recording, and DNA, RNA and protein analyses) approaches. An integrative strategy that combines computerized meal pattern analyses with cellular and molecular biology approaches allows the study of underlying brain mechanisms in cytokine- and disease-associated anorexia. This paper presents a comprehensive discussion of our laboratory's previously published data on brain mechanisms involved in cytokine-induced anorexia including the relevance of meal pattern analysis (meal size, meal duration, meal frequency, intermeal intervals), modulation of hypothalamic neuronal activity, molecular processes involving ionic conductances, cytokine-cytokine and cytokine-peptide interactions, and modulation of cytokine and peptide/neuropeptide system components (ligands, endogenous inhibitors, receptor subtypes, signal transduction molecules, intracellular mediators) and cytokine feedback systems.

The uses of psychotropics in symptom management in advanced cancer

Approximately 50% of patients diagnosed with cancer die because of progressive disease. Psychotropic drugs are frequently used for the management of physical and psychosocial symptoms in these patients. Thalidomide, cannabinoids and melatonin are emerging agents for the management of cachexia. Psychostimulants have a defined role in the management of opioid-induced sedation. Haloperidol, tricyclic anti-depressants and newer anti-depressants also have an established role in the management of neuropsychiatric symptoms such as delirium or depression. Cancer patients present unique challenges for successful psychotropic therapy including older age, malnutrition, autonomic failure, borderline cognition, opioid and psychotropic therapy. A practical clinical approach which defines a specific target symptom, an outcome latency period, expected side effects, and reviews possible drug interactions, and frequent monitoring is outlined. Continued research is needed to further define the role of psychotropics in the management of the different physical and psychosocial symptoms in advanced cancer patients.

Effects of systemic interleukin-1beta administration on daily drinking and renal excretory function in conscious rats

To elucidate the roles of interleukin-1beta (IL-1beta), a cytokine with several diverse actions, in the control of body fluid balance, its effects on daily drinking behavior and renal excretory function were examined in conscious rats. Administration of IL-1beta (4 microg/kg, I.P.) resulted in the suppression of both daily drinking and food intake and a decrease in daily urinary sodium and potassium excretion, but had no effect on urine volume. The IL-1beta-induced decrease in sodium excretion was abolished in renal-denervated rats. Kainic acid was then injected into the anteroventral third ventricle region, including the organum vasculosum of the lamina terminalis, to examine whether neurons in this region are involved in the IL-1beta-induced responses; the effects on daily drinking and urinary sodium and potassium excretion were abolished, whereas the effects on food intake, although attenuated, were still present. In contrast, electrical lesion of the subfomical organ did not affect the IL-1beta-induced responses. Thus, IL-1beta seems exert its effects on body fluid balance at several distinct sites in the central nervous system.

Bacterial products and the control of ingestive behavior: clinical implications

Bacterial products such as lipopolysaccharides (LPS) and muramyl peptides are delivered in the course of infections. They trigger the host's acute phase responses to bacterial infections and are probably involved in the accompanying hypophagia because LPS and muramyl dipeptide (MDP, the minimal immunologically active muramyl peptide) reduce food intake after parenteral administration in animals. LPS and MDP inhibit feeding synergistically through separate but interacting mechanisms. The hypophagic effects of LPS and MDP are presumably mediated by the combined actions of interleukin-1, tumor necrosis factor, and other cytokines. More work is required to understand the interactions between these cytokines, and between bacterial products and cytokines, before cytokine antagonists can be used for treatment of the hypophagia during bacterial infections. As the hypophagia seems to be an early mechanism of host defense, a treatment should be carefully considered. If an intervention is indicated because of a patient's poor condition, inhibitors of eicosanoid synthesis and glucocorticoids may hold more promise for therapy because such substances block LPS and MDP hypophagia. Although LPS can reduce food intake by direct action on the brain, presently available evidence indicates that systemic LPS acts primarily in the periphery to generate a neural signal that is transmitted to the brain and inhibits feeding through the vagus. The exact site where LPS acts on peripheral nerves remains to be identified. LPS hypophagia is conditionable, but conditioning cannot solely account for LPS hypophagia under most test conditions. Whether MDP hypophagia is also conditionable and mediated by vagal afferents is not yet known. All in all, the putative mediators and mechanisms of LPS and MDP hypophagia suggest some options for a treatment of the hypophagia during bacterial infection, but present knowledge about the mechanisms and interactions of the involved substances is still fragmentary and requires further investigation.

Corticosterone controls interleukin-1 beta expression and sickness behavior in the rat

We studied the effect of corticosterone on interleukin (IL)-1 beta synthesis, body temperature, general activity, food consumption and fluid intake in rats treated with bacterial lipopolysaccharide (LPS). Radiotelemetry was used to assess body temperature and locomotor activity in combination with continuous automated recordings of feeding and drinking. This technique was developed as a novel method to identify and measure sickness behavior in rodents. The animals were (a) sham-operated, (b) adrenalectomized or (c) sham-operated and treated with corticosterone (10 mg/kg, subcutaneously). They were then intraperitoneally injected with vehicle or LPS at a dose (100 micrograms/kg) that in sham-operated rats induced fever and anorexia, reduced spontaneous activity and increased IL1-beta mRNA in spleen and adrenals as determined by Northern blot analysis. Adrenalectomized rats produced larger amounts of splenic IL-1 beta mRNA, reduced their general activity much more and developed a mild adipsia as compared with adrenal-intact animals. Administration of corticosterone 1 h before LPS lowered the splenic IL-1 beta mRNA content compared to LPS-treated adrenal-intact rats that did not receive corticosterone and inhibited fever and anorexia, whereas the glucocorticoid did not attenuate the endotoxin-induced suppression of locomotor activity. Our data suggest that during inflammatory conditions body temperature, sickness behavior and the synthesis of IL-1 beta are controlled by corticosterone. Different components of sickness behavior seem to be independently regulated and are under differential control by glucocorticoids.

Anorexia during acute and chronic disease

Anorexia is associated with disorders of all systems. Anorexia represents a consistent clinical manifestation during acute and chronic pathophysiological processes (infection, inflammation, injury, toxins, immunological reactions, malignancy and necrosis). Anorexia during disease can be beneficial or deleterious depending on the timing and duration. Temporary anorexia during acute disease may be beneficial to an organism since a restriction in the intake of micro- and macro-nutrients will inhibit bacterial growth. Long-term anorexia during chronic disease, however, is deleterious to an organism and may be associated with cachexia, which can ultimately result in death. Various mechanisms participate in the anorexia observed during disease, including cytokine action. Anorexia induced by cytokines is proposed to involve modulation of hypothalamic-feeding associated sites, prostaglandin-dependent mechanisms, modifications of neurotransmitter systems, gastrointestinal, metabolic, and endocrine factors. In addition, the anorexia-cachexia syndrome is multifactorial and may involve chronic pain, depression or anxiety, hypogeusia and hyposmia, chronic nausea, early satiety, malfunction of the gastrointestinal system, metabolic alterations, cytokine action, production of other anorexigenic substances and/or iatrogenic causes (chemotherapy, radiotherapy). Cachexia may result not only from anorexia and a decreased caloric intake, but also from malabsorption and losses from the body (ulcers, hemorrhage, effusions), or a change in body metabolism. Research has focused on potential interventions to modify anorexia during disease and the anorexia-cachexia syndrome. Nutritional modifications and the use of specific steroids (such as megestrol acetate) are being tested in the clinical setting. Understanding the specific mechanisms responsible for anorexia during disease as well as their interactions is essential to develop interventions for the control of anorexia (during a critical time in a specific disease), and to devise less toxic immunotherapeutic regimens using cytokines.

On the Inseparability of Mental and Physical Health in Aged Persons: Lessons From Depression and Medical Comorbidity

Recent research findings demonstrate that general medical and mental health are inseparable in older individuals. The medical consequences of depression can be summarized with the unifying hypothesis that depression interacts with medical or neurological illness to modify the course of disease and to amplify its associated effects. The medical causes of depression can be divided into specific mechanisms of certain diseases or medications and general mechanisms that may integrate effects of a number of the common chronic disorders of late life. The authors discuss two general hypotheses: One suggests that depression may be associated with subclinical cerebrovascular disease in older patients with cerebrovascular risk factors; the other suggests that depression occurring in association with various conditions may be related to cytokine-mediated "sickness behavior." The research literature makes a compelling case for the need to address psychiatric-medical comorbidity in late life as a central issue in public policy and the design of health care systems.

Meal patterns in response to the intracerebroventricular administration of interleukin-1 beta in rats

Interleukin-1 beta (IL-1 beta) depresses feeding in rats when administered peripherally (in the microgram range) or centrally (in the nanogram range). In the present study, the effects of the intracerebroventricular (ICV, into the third ventricle) microinfusion of recombinant human IL-1 beta (rhIL-1 beta) on the microstructure of feeding in rats maintained ad lib were investigated with a computerized behavioral monitoring system. ICV microinfusion of rhIL-1 beta (0.5 to 4.0 ng/rat) decreased the short- (2 h) and long-term (nighttime) intake of pellets by reducing meal size and meal duration. Eating rate decreased, indicating a greater effect on meal size than on meal duration. Only the highest dose (4.0 ng/rat) decreased nighttime meal frequency and prolonged nighttime postprandial intermeal intervals. Water intake and locomotor activity also decreased. Water intake-to-food intake ratios in the 2.0 and 4.0 ng/rat rhIL-1 beta-treated groups increased, and this indicated a greater effect of rhIL-1 beta on food intake than on water intake. During the following daytime, meal parameters increased, suggesting compensation for the previous nighttime changes. However, these daytime compensatory responses were limited, and the total daily meal parameters were still decreased. The concomitant ICV microinfusion of rhIL-1 beta (1.0 ng) and recombinant human interleukin-1 receptor antagonist (rhIL-1ra, 500 ng) completely blocked the changes in the microstructure of behavior induced by rhIL-1 beta. This evidence suggests specificity of IL-1 beta inducing behavioral changes by direct action in the central nervous system.

Centrally administered bacterial lipopolysaccharide depresses feeding in rats

Bacterial lipopolysaccharide (LPS) suppresses feeding in rats when administered peripherally in the microgram range. In the present study, the effects of LPS (Escherichia coli serotype 0111:B4) on the central regulation of feeding in rats maintained ad lib was investigated. Intracerebroventricular (ICV) microinfusion of LPS (0.1 to 1000 ng/rat) suppressed the short-term (2-h) and long-term (nighttime and total daily) food intakes, dose dependently. Computerized analysis of behavioral patterns demonstrated a significant reduction of meal size during the nighttime, whereas meal frequency and meal duration were also decreased, but not significantly. Water intake and locomotor activity also decreased. Intraperitoneal administration of LPS in doses equivalent to those administered centrally had no effect on food intake. The results suggest that centrally administered LPS acts directly in the central nervous system (CNS) to depress feeding.

Corticotropin-releasing factor in the paraventricular nucleus modulates feeding induced by neuropeptide Y

Central administration of neuropeptide Y (NPY) exerts a potent orexigenic effect in rats, whereas injection of corticotropin-releasing factor (CRF) suppresses food intake. Anatomical evidence of NPY-containing terminals located in close proximity to CRF-containing neurons and terminals of the hypothalamus and amygdala suggests possible interactions of these neuropeptide systems in food-intake regulation. The present study examined the effect of local administration of the CRF antagonist, alpha-helical CRF9-41, or peripheral treatment with dexamethasone on NPY-induced hyperphagia. Injection of a 250-ng dose of alpha-hel CRF within the paraventricular nucleus (PVN) of the hypothalamus significantly potentiated the feeding induced by a 500-ng dose of NPY injected into the same locus. In contrast, feeding induced by administration of the 500-ng dose of NPY into the ventromedial hypothalamus (VMH) was not modified by intra-VMH pre-treatment with a 250-ng dose of CRF antagonist. No effects of NPY or alpha-hel CRF on feeding were observed after administration into the central nucleus of the amygdala. Systemic pre-treatment with the synthetic glucocorticoid dexamethasone at a dose known to downregulate the function of CRF neurons in the PVN (100 micrograms/kg) enhanced feeding induced by intra-PVN administration of a 500-ng dose of NPY. These results suggest that hypothalamic CRF systems in the PVN exert inhibitory control over NPY-induced food intake.

Adrenalectomy does not change CRF secretion induced by interleukin-1 from rat perifused hypothalami

Interleukin-1 (IL-1) is a potent hypothalamic-pituitary-adrenal (H-P-A) axis activator. The hypothalamus is considered one of the main sites of action of IL-1 on the H-P-A axis, inducing CRF secretion, which is modulated by glucocorticoids. Glucocorticoids, which modulate CRF release by a negative feedback inhibition, have been postulated to exert a permissive action on the IL-1 effect on CRF secretion. Using a continuous perifusion system of rat hypothalami, the results of the present study indicate that at the same concentrations, IL-1 beta exerted a more potent effect than IL-1 alpha stimulating CRF secretion. The increase in hypothalamic CRF release induced by IL-1 was rapidly inhibited by both dexamethasone and corticosterone. However, adrenalectomy 2 or 8 days before did not modify CRF secretion induced by IL-1 from the in vitro perifused hypothalami. These data indicate that IL-1 does not seem to induce CRF secretion by interfering with an impeding action of glucocorticoids, although the cytokine effect is negatively modulated by corticosteroids.

Intracerebroventricular administration of a specific IL-1 receptor antagonist blocks food and water intake suppression induced by interleukin-1 beta

Intracerebroventricular (ICV) microinfusion of recombinant human interleukin-1 beta (rhIL-1 beta, 1.0 ng/rat) suppressed the short-term (2 h) food and water intakes in rats. ICV infusion of recombinant human IL-1 receptor antagonist (rhIL-1ra) had no effect on food or water intake. Concomitant ICV infusion of rhIL-1 beta (1.0 ng/rat) and increasing concentrations of rhIL-1ra (25 to 1000 ng/rat) resulted in a dose-dependent inhibition of the short-term food and water intake suppression induced by rhIL-1 beta. The highest doses of rhIL-1ra (500 and 1000 ng/rat) completely blocked the food and water intake suppression induced by rhIL-1 beta. This suggests specificity of IL-1 beta suppression of short-term feeding and drinking by a direct action in the central nervous system (CNS). This ability of rhIL-1ra may have potential therapeutic implications in acute and chronic pathological processes associated with increased levels of IL-1 and appetite suppression.