Forebrain patterns of c-Fos and FosB induction during cancer-associated anorexia-cachexia in rat

Neurobiology of cancer: Definition, historical overview, and clinical implications

Studies published in the last two decades have clearly demonstrated that the nervous system plays a significant role in carcinogenesis, the progression of cancer, and the development of metastases. These studies, combining oncological and neuroscientific approaches, created the basis for the emergence of a new field in oncology research, the so‐called “neurobiology of cancer.” The concept of the neurobiology of cancer is based on several facts: (a) psychosocial factors influence the incidence and progression of cancer diseases; (b) the nervous system affects DNA mutations and oncogene‐related signaling; (c) the nervous system modulates tumor‐related immune responses; (d) tumor tissues are innervated; (e) neurotransmitters released from nerves innervating tumor tissues affect tumor growth and metastasis; (f) alterations or modulation of nervous system activity affects the incidence and progression of cancers; (g) tumor tissue affects the nervous system. The aim of this review is to characterize the pillars that create the basis of cancer neurobiology, to describe recent research advances of the nervous system's role in cancer diseases, and to depict potential clinical implications for oncology.

Diverging metabolic programmes and behaviours during states of starvation, protein malnutrition, and cachexia

BACKGROUND

Our evolutionary history is defined, in part, by our ability to survive times of nutrient scarcity. The outcomes of the metabolic and behavioural adaptations during starvation are highly efficient macronutrient allocation, minimization of energy expenditure, and maximized odds of finding food. However, in different contexts, caloric deprivation is met with vastly different physiologic and behavioural responses, which challenge the primacy of energy homeostasis.

METHODS

We conducted a literature review of scientific studies in humans, laboratory animals, and non-laboratory animals that evaluated the physiologic, metabolic, and behavioural responses to fasting, starvation, protein-deficient or essential amino acid-deficient diets, and cachexia. Studies that investigated the changes in ingestive behaviour, locomotor activity, resting metabolic rate, and tissue catabolism were selected as the focus of discussion.

RESULTS

Whereas starvation responses prioritize energy balance, both protein malnutrition and cachexia present existential threats that induce unique adaptive programmes, which can exacerbate the caloric insufficiency of undernutrition. We compare and contrast the behavioural and metabolic responses and elucidate the mechanistic pathways that drive state-dependent alterations in energy seeking and partitioning.

CONCLUSIONS

The evolution of energetically inefficient metabolic and behavioural responses to protein malnutrition and cachexia reveal a hierarchy of metabolic priorities governed by discrete regulatory networks.

Experimental sepsis-associated encephalopathy is accompanied by altered cerebral blood perfusion and water diffusion and related to changes in cyclooxygenase-2 expression and glial cell morphology but not to blood-brain barrier breakdown

Sepsis-associated encephalopathy (SAE) refers to brain dysfunction, including delirium, occurs during severe infection and is associated with development of post-traumatic stress disorder. SAE has been proposed to be related to reduced cerebral blood flow (CBF), blood-brain barrier breakdown (BBB), white matter edema and disruption and glia cell activation, but their exact relationships remain to be determined. In the present work, we set out to study CBF using Arterial Spin Labeling (ASL) and grey and white matter structure with T2- and diffusion magnetic resonance imaging (dMRI) in rats with cecal ligation and puncture (CLP)-induced encephalopathy. Using immunohistochemistry, the distribution of the vasoactive prostaglandin-synthesizing enzyme cyclooxygenase-2 (COX-2), perivascular immunoglobulins G (IgG), aquaporin-4 (AQP4) and the morphology of glial cell were subsequently assessed in brains of the same animals. CLP induced deficits in the righting reflex and resulted in higher T2-weighted contrast intensities in the cortex, striatum and at the base of the brain, decreased blood perfusion distribution to the cortex and increased water diffusion parallel to the fibers of the corpus callosum compared to sham surgery. In addition, CLP reduced staining for microglia- and astrocytic-specific proteins in the corpus callosum, decreased neuronal COX-2 and AQP4 expression in the cortex while inducing perivascular COX-2 expression, but did not induce widespread perivascular IgG diffusion. In conclusion, our findings indicate that experimental SAE can occur in the absence of BBB breakdown and is accompanied by increased water diffusion anisotropy and altered glia cell morphology in brain white matter.

Changes in gene expression in brain structures related to visceral sensation, autonomic functions, food intake, and cognition in melanoma-bearing mice

The brain exerts complex effects on the initiation and progression of cancer in the body. However, the influence of cancer localized in peripheral tissues on the brain has been only partially described. Therefore, we investigated gene expression in brain structures that participate in transmitting viscerosensory signals, regulating autonomic functions and food intake, as well as cognition in C57Bl/6J mice with B16-F10 melanoma. In addition, we investigated the relationship between peripheral inflammation and neuroinflammation. We found increased neuronal activity in the nucleus of the solitary tract of tumor-bearing mice, whereas neuronal activity in the A1/C1 catecholaminergic cell group, parabrachial nucleus, lateral hypothalamic area, ventromedial nucleus of the hypothalamus, paraventricular nucleus of the hypothalamus, and hippocampus was decreased. In the majority of investigated brain structures, we found increased gene expression of IL-1β, whereas gene expression of IL-6 and NF-κB was reduced or unchanged compared with controls. Melanoma-bearing mice also showed increased gene expression of tyrosine hydroxylase in the A1/C1 catecholaminergic cell group, nucleus of the solitary tract, and locus coeruleus, as well as reduced mRNA levels of hypocretin neuropeptide precursor protein in the lateral hypothalamic area, and proopiomelanocortin in the arcuate nucleus. In addition, we found reduced mRNA levels of Bcl-2, brain-derived neurotrophic factor, and doublecortin in the hippocampus. Our data indicate that skin melanoma induces complex changes in the brain, and these changes are most probably caused by cancer-related signals mediated by pro-inflammatory cytokines.

Interleukin-1 reduces food intake and body weight in rat by acting in the arcuate hypothalamus

A reduction in food intake is commonly observed after bacterial infection, a phenomenon that can be reproduced by peripheral administration of Gram-negative bacterial lipopolysaccharide (LPS) or interleukin-1beta (IL-1β), a pro-inflammatory cytokine released by LPS-activated macrophages. The arcuate nucleus of the hypothalamus (ARH) plays a major role in food intake regulation and expresses IL-1 type 1 receptor (IL-1R1) mRNA. In the present work, we tested the hypothesis that IL-1R1 expressing cells in the ARH mediate IL-1β and/or LPS-induced hypophagia in the rat. To do so, we developed an IL-1β-saporin conjugate, which eliminated IL-R1-expressing neurons in the hippocampus, and micro-injected it into the ARH prior to systemic IL-1β and LPS administration. ARH IL-1β-saporin injection resulted in loss of neuropeptide Y-containing cells and attenuated hypophagia and weight loss after intraperitoneal IL-1β, but not LPS, administration. In conclusion, the present study shows that ARH NPY-containing neurons express functional IL-1R1s that mediate peripheral IL-1β-, but not LPS-, induced hypophagia. Our present and previous findings indicate that the reduction of food intake after IL-1β and LPS are mediated by different neural pathways.

Cachexia induced by Yoshida ascites hepatoma in Wistar rats is not associated with inflammatory response in the spleen or brain

Recent data indicate that peripheral, as well as hypothalamic pro-inflammatory cytokines play an important role in the development of cancer cachexia. However, there are only a few studies simultaneously investigating the expression of inflammatory molecules in both the periphery and hypothalamic structures in animal models of cancer cachexia. Therefore, using the Yoshida ascites hepatoma rat's model of cancer cachexia we investigated the gene expression of inflammatory markers in the spleen along with the paraventricular and arcuate nuclei, two hypothalamic structures that are involved in regulating energy balance. In addition, we investigated the effect of intracerebroventricular administration of PS-1145 dihydrochloride (an Ikβ inhibitor) on the expression of selected inflammatory molecules in these hypothalamic nuclei and spleen. We observed significantly reduced food intake in tumor-bearing rats. Moreover, we found significantly decreased expression of IL-6 in the spleen as well as decreased NF-κB in the paraventricular nucleus of rats with Yoshida ascites hepatoma. Similarly, expression of TNF-α, IL-1β, NF-κB, and COX-2 in the arcuate nucleus was significantly reduced in tumor-bearing rats. Administration of PS-1145 dihydrochloride reduced only the gene expression of COX-2 in the hypothalamus. Based on our findings, we suggest that the growing Yoshida ascites hepatoma decreased food intake by mechanical compression of the gut and therefore this model is not suitable for investigation of the inflammation-related mechanisms of cancer cachexia development.

Bombesin receptor subtype-3-expressing neurons regulate energy homeostasis through a novel neuronal pathway in the hypothalamus

OBJECTIVES

Bombesin receptor subtype-3 (BRS-3) has been suggested to play a potential role in energy homeostasis. However, the physiological mechanism of BRS-3 on energy homeostasis remains unknown. Thus, we investigated the BRS-3-mediated neuronal pathway involved in food intake and energy expenditure.

MATERIALS AND METHODS

Expression of BRS-3 in the rat brain was histologically examined. The BRS-3 neurons activated by refeeding-induced satiety or a BRS-3 agonist were identified by c-Fos immunostaining. We also analyzed expression changes in feeding-relating peptides in the brain of fasted rats administered with the BRS-3 agonist.

RESULTS

In the paraventricular hypothalamic nucleus (PVH), dorsomedial hypothalamic nucleus (DMH), and medial preoptic area (MPA), strong c-Fos induction was observed in the BRS-3 neurons especially in PVH after refeeding. However, the BRS-3 neurons in the PVH did not express feeding-regulating peptides, while the BRS-3 agonist administration induced c-Fos expression in the DMH and MPA, which were not refeeding-sensitive, as well as in the PVH. The BRS-3 agonist administration changed the Pomc and Cart mRNA level in several brain regions of fasted rats.

CONCLUSION

These results suggest that BRS-3 neurons in the PVH are a novel functional subdivision in the PVH that regulates feeding behavior. As the MPA and DMH are reportedly involved in thermoregulation and energy metabolism, the BRS-3 neurons in the MPA/DMH might mediate the energy expenditure control. POMC and CART may contribute to BRS-3 neuron-mediated energy homeostasis regulation. In summary, BRS-3-expressing neurons could regulate energy homeostasis through a novel neuronal pathway.

Brainstem metabotropic glutamate receptors reduce food intake and activate dorsal pontine and medullar structures after peripheral bacterial lipopolysaccharide administration

During infection-induced inflammation food intake is reduced. Vagal and brainstem pathways are important both in feeding regulation and immune-to-brain communication. Glutamate is released by vagal afferent terminals in the nucleus of the solitary tract and by its neurons projecting to the parabrachial nuclei. We therefore studied the role of brainstem glutamate receptors in spontaneous food intake of healthy animals and during sickness-associated hypophagia after peripheral administration of bacterial lipopolysaccharides or interleukin-1beta. Brainstem group I and II metabotropic, but not ionotropic, glutamate receptor antagonism increased food intake both in saline- and lipopolysaccharide-treated rats. In these animals, expression of the cellular activation marker c-Fos in the lateral parabrachial nuclei and lipopolysaccharide-induced activation of the nucleus of the solitary tract rostral to the area postrema were suppressed. Group I metabotropic glutamate receptors did not colocalize with c-Fos or neurons regulating gastric function in these structures. Group I metabotropic glutamate receptors were, however, found on raphé magnus neurons that were part of the brainstem circuit innervating the stomach and on trigeminal and hypoglossal motor neurons. In conclusion, our findings show that brainstem metabotropic glutamate receptors reduce food intake and activate the lateral parabrachial nuclei as well as the rostral nucleus of the solitary tract after peripheral bacterial lipopolysaccharide administration. They also provide insight into potential group I metabotropic glutamate receptor-dependent brainstem circuits mediating these effects.

Proteomic profiling of the hypothalamus in a mouse model of cancer-induced anorexia-cachexia

BACKGROUND

Anorexia-cachexia is a common and severe cancer-related complication but the underlying mechanisms are largely unknown. Here, using a mouse model for tumour-induced anorexia-cachexia, we screened for proteins that are differentially expressed in the hypothalamus, the brain's metabolic control centre.

METHODS

The hypothalamus of tumour-bearing mice with implanted methylcholanthrene-induced sarcoma (MCG 101) displaying anorexia and their sham-implanted pair-fed or free-fed littermates was examined using two-dimensional electrophoresis (2-DE)-based comparative proteomics. Differentially expressed proteins were identified by liquid chromatography-tandem mass spectrometry.

RESULTS

The 2-DE data showed an increased expression of dynamin 1, hexokinase, pyruvate carboxylase, oxoglutarate dehydrogenase, and N-ethylmaleimide-sensitive factor in tumour-bearing mice, whereas heat-shock 70 kDa cognate protein, selenium-binding protein 1, and guanine nucleotide-binding protein Gα0 were downregulated. The expression of several of the identified proteins was similarly altered also in the caloric-restricted pair-fed mice, suggesting an involvement of these proteins in brain metabolic adaptation to restricted nutrient availability. However, the expression of dynamin 1, which is required for receptor internalisation, and of hexokinase, and pyruvate carboxylase were specifically changed in tumour-bearing mice with anorexia.

CONCLUSION

The identified differentially expressed proteins may be new candidate molecules involved in the pathophysiology of tumour-induced anorexia-cachexia.

The time-course of hindbrain neuronal activity varies according to location during either intraperitoneal or subcutaneous tumor growth in rats: single Fos and dual Fos/dopamine β-hydroxylase immunohistochemistry

Neuronal activity in the nucleus of the solitary tract, ventrolateral medulla, area postrema, and parabrachial nucleus was studied in rats with intraperitoneal or subcutaneous tumors on the 7th, 14th, 21st, and 28th day after injection of fibrosarcoma tumor cells. We found that the number of Fos and dopamine β-hydroxylase immunopositive neurons differs between animals with intraperitoneal and subcutaneous tumors and also between tumor-bearing rats at different times following injection. Our data indicate that responses of the brainstem structures to peripheral tumor growth depend on the localization as well as the stage of the tumor growth.

Neuronal activation in the central nervous system of rats in the initial stage of chronic kidney disease-modulatory effects of losartan and moxonidine

The effect of mild chronic renal failure (CRF) induced by 4/6-nephrectomy (4/6NX) on central neuronal activations was investigated by c-Fos immunohistochemistry staining and compared to sham-operated rats. In the 4/6 NX rats also the effect of the angiotensin receptor blocker, losartan, and the central sympatholyticum moxonidine was studied for two months. In serial brain sections Fos-immunoreactive neurons were localized and classified semiquantitatively. In 37 brain areas/nuclei several neurons with different functional properties were strongly affected in 4/6NX. It elicited a moderate to high Fos-activity in areas responsible for the monoaminergic innervation of the cerebral cortex, the limbic system, the thalamus and hypothalamus (e.g. noradrenergic neurons of the locus coeruleus, serotonergic neurons in dorsal raphe, histaminergic neurons in the tuberomamillary nucleus). Other monoaminergic cell groups (A5 noradrenaline, C1 adrenaline, medullary raphe serotonin neurons) and neurons in the hypothalamic paraventricular nucleus (innervating the sympathetic preganglionic neurons and affecting the peripheral sympathetic outflow) did not show Fos-activity. Stress- and pain-sensitive cortical/subcortical areas, neurons in the limbic system, the hypothalamus and the circumventricular organs were also affected by 4/6NX. Administration of losartan and more strongly moxonidine modulated most effects and particularly inhibited Fos-activity in locus coeruleus neurons. In conclusion, 4/6NX elicits high activity in central sympathetic, stress- and pain-related brain areas as well as in the limbic system, which can be ameliorated by losartan and particularly by moxonidine. These changes indicate a high sensitivity of CNS in initial stages of CKD which could be causative in clinical disturbances.

Food restriction-induced hyperactivity: addiction or adaptation to famine?

Increased physical activity is present in 30-80% of anorexia nervosa patients. To explain the paradox of low food intake and excessive exercise in humans and other animals, it has been proposed that increased physical activity along with food restriction activates brain reward circuits and is addictive. Alternatively, the fleeing-famine hypothesis postulates that refusal of known scarce energy-low food sources and hyperactivity facilitate migration towards new habitats that potentially contain new energy-rich foodstuffs. The use of rewarding compounds that differ in energy density, such as the energy-free sweetener saccharin and the energy rich sucrose makes it possible to critically test the reward-addiction and fleeing-famine hypotheses. The aims of the present work were to study if sucrose and/or saccharin could attenuate food restriction-induced hyperactivity, weight loss, increased plasma corticosterone, and activation of brain structures involved in neuroendocrine control, energy balance, physical activity, and reward signaling in rats. Its major findings are that access to sucrose, but not to saccharin, attenuated food restriction-induced running wheel activity, weight loss, rises in plasma corticosterone, and expression of the cellular activation marker c-Fos in the paraventricular and arcuate hypothalamus and in the nucleus accumbens. These findings suggest that the energy-richness and easy availability of sucrose interrupted a fleeing-famine-like hyperactivity response. Since corticosterone mediates food restriction-induced wheel running (Duclos et al., 2009), we propose that the attenuating effect of sucrose consumption on plasma corticosterone plays a role in reduced wheel running and weight loss by lowering activation of the nucleus accumbens and arcuate hypothalamus in these animals.

Hormonal, hypothalamic and striatal responses to reduced body weight gain are attenuated in anorectic rats bearing small tumors

Lack of compensatory or even reduced food intake is frequently observed in weight-losing cancer patients and contributes to increased morbidity and mortality. Our previous work has shown increased transcription factor expression in the hypothalamus and ventral striatum of anorectic rats bearing small tumors. mRNA expression of molecules known to be involved in pathways regulating appetite in these structures was therefore assessed in this study. Given that pain, pro-inflammatory cytokines and metabolic hormones can modify food intake, spinal cord cellular activation patterns and plasma concentrations of cytokines and hormones were also studied. Morris hepatoma 7777 cells injected subcutaneously in Buffalo rats provoked a 10% lower body weight and 15% reduction in food intake compared to free-feeding tumor-free animals 4 weeks later when the tumor represented 1-2% of body mass. No differences in spinal cord activation patterns or plasma concentration of pro-inflammatory cytokines were observed between groups. However, the changes in plasma ghrelin and leptin concentrations found in food-restricted weight-matched rats in comparison to ad libitum-fed animals did not occur in anorectic tumor-bearing animals. Real-time PCR showed that tumor-bearing rats did not display the increase in hypothalamic agouti-related peptide mRNA observed in food-restricted weight-matched animals. In addition, microarray analysis and real-time PCR revealed increased ventral striatal prostaglandin D synthase expression in food-restricted animals compared to anorectic tumor-bearing rats. These findings indicate that blunted hypothalamic AgRP mRNA expression, probably as a consequence of relatively high leptin and low ghrelin concentrations, and reduced ventral striatal prostaglandin D synthesis play a role in maintaining cancer-associated anorexia.

Fto immunoreactivity is widespread in the rodent brain and abundant in feeding-related sites, but the number of Fto-positive cells is not affected by changes in energy balance

A single nucleotide polymorphism in the FTO gene is associated with obesity in humans. Evidence gathered in animals mainly relates energy homeostasis to the central FTO mRNA levels, but our knowledge of the Fto protein distribution and regulation is limited. Fto, a demethylase and transcriptional coactivator, is thought to regulate expression of other genes. Herein, we examined Fto immunoreactivity (IR) in the mouse and rat brain with emphasis on sites governing energy balance. We also studied whether energy status affects central Fto IR. We report that Fto IR, limited to nuclear profiles, is widespread in the brain, in- and outside feeding circuits; it shows a very similar distribution in feeding-related sites in mice and rats. Several areas regulating energy homeostasis display enhanced intensity of Fto staining: the arcuate, paraventricular, supraoptic, dorsomedial, ventromedial nuclei, and dorsal vagal complex. Some regions mediating feeding reward, including the bed nucleus of the stria terminalis, have ample Fto IR. We found that differences in energy status between rats fed ad libitum, deprived or refed following deprivation, did not affect the number of Fto-positive nuclei in 10 sites governing consumption for energy or reward. We conclude that Fto IR, widespread in the rodent brain, is particularly abundant in feeding circuits, but the number of Fto-positive neurons is unaffected by changes in energy balance.

Neurobiology of inflammation-associated anorexia

Compelling data demonstrate that inflammation-associated anorexia directly results from the action of pro-inflammatory factors, primarily cytokines and prostaglandins E2, on the nervous system. For instance, the aforementioned pro-inflammatory factors can stimulate the activity of peripheral sensory neurons, and induce their own de novo synthesis and release into the brain parenchyma and cerebrospinal fluid. Ultimately, it results in the mobilization of a specific neural circuit that shuts down appetite. The present article describes the different cell groups and neurotransmitters involved in inflammation-associated anorexia and examines how they interact with neural systems regulating feeding such as the melanocortin system. A better understanding of the neurobiological mechanisms underlying inflammation-associated anorexia will help to develop appetite stimulants for cancer and AIDS patients.

Identification of rat brainstem neuronal structures activated during cancer-induced anorexia

In cancer-related anorexia, body weight loss is paradoxically associated with reduced appetite, which is contrary to the situation during starvation, implying that the normal coupling of food intake to energy expenditure is disarranged. Here we examined brainstem mechanisms that may underlie suppression of food intake in a rat model of cancer anorexia. Cultured Morris 7777 hepatoma cells were injected subcutaneously in Buffalo rats, resulting in slowly growing tumor and reduced food intake and body weight loss after about 10 days. The brainstem was examined for induced expression of the transcription factors Fos and FosB as signs of neuronal activation. The results showed that anorexia and retarded body weight growth were associated with Fos protein expression in the area postrema, the general visceral region of the nucleus of the solitary tract, and the external lateral parabrachial nucleus, structures that also display Fos after peripheral administration of satiating or anorexigenic stimuli. The magnitude of the Fos expression was specifically related to the size of induced tumor, and not associated with weight loss per se, because it was not present in pair-fed or food-deprived rats. It also appeared to be independent of proinflammatory cytokines, as determined by the absence of increased cytokine levels in plasma and induced cytokine and cyclooxygenase expression in the brain. The findings thus provide evidence that cancer-associated anorexia and weight loss in this model is associated with activation of brainstem circuits involved in the suppression of food intake, and suggest that this occurs by inflammatory-independent mechanisms.

Isolation rearing impairs wound healing and is associated with increased locomotion and decreased immediate early gene expression in the medial prefrontal cortex of juvenile rats

In addition to its maladaptive effects on psychiatric function, psychosocial deprivation impairs recovery from physical illness. Previously, we found that psychosocial deprivation, modeled by isolation rearing, depressed immediate early gene (IEG) expression in the medial prefrontal cortex (mPFC) and increased locomotion in the open field test [Levine JB, Youngs RM, et al. (2007) Isolation rearing and hyperlocomotion are associated with reduced immediate early gene expression levels in the medial prefrontal cortex. Neuroscience 145(1):42-55]. In the present study, we examined whether similar changes in behavior and gene expression are associated with the maladaptive effects of psychosocial deprivation on physical injury healing. After weaning, anesthetized rats were subjected to a 20% total body surface area third degree burn injury and were subsequently either group or isolation reared. After 4 weeks of either isolation or group rearing (a period that encompasses post-wearing and early adolescence), rats were killed, and their healing and gene expression in the mPFC were assessed. Locomotion in the open field test was examined at 3 weeks post-burn injury. We found that: 1) gross wound healing was significantly impaired in isolation-reared rats compared with group-reared rats, 2) locomotion was increased and IEG expression was suppressed for isolation-reared rats during burn injury healing, 3) the decreased activity in the open field and increased IEG expression was greater for burn injury healing group-reared rats than for uninjured group-reared rats, 4) the degree of hyperactivity and IEG suppression was relatively similar between isolation-reared rats during burn injury compared with uninjured isolation-reared rats. Thus, in the mPFC, behavioral hyperactivity to novelty (the open field test) along with IEG suppression may constitute a detectable biomarker of isolation rearing during traumatic physical injury. Implications of the findings for understanding, assessing, and treating the maladaptive effects of psychosocial deprivation on physical healing during childhood are discussed.

Brain Fos expression during 48 h after cisplatin treatment: neural pathways for acute and delayed visceral sickness

Cancer chemotherapy drugs, such as cisplatin, are extremely potent for producing nausea and vomiting. The acute effects of these treatments are partly controlled using anti-emetic drugs, but the delayed effects (>24 h), especially nausea, are much more difficult to treat. Furthermore, cisplatin induces a long-term (up to 48 h) increase in pica in rats. Pica is manifested as an increase in consumption of kaolin (clay) and is used as a measure of visceral sickness. It is unknown what brain pathways might be responsible for this sickness associated behavior. As a first attempt to define this neural system, rats were injected (i.p.) with 3, 6, or 10 mg/kg cisplatin (doses reported to produce pica) and sacrificed at 6, 24, or 48 h to determine brain Fos expression. The primary results indicate: 1) increasing the dose of cisplatin increased the magnitude and duration of brain Fos expression, 2) most excitatory effects on hindbrain nucleus of the solitary tract (NTS) and area postrema (AP) Fos expression occurred within 24 h after cisplatin injection, 3) 6 and 10 mg/kg cisplatin treatment produced large increases in Fos expression in the central amygdala (CeA) and bed nucleus of the stria terminalis (BNST), including 48 h after injection, and 4) cisplatin treatment produced little effect on Fos expression in the paraventricular and supraoptic nuclei of the hypothalamus. These results indicate that cisplatin activates a neural system that includes the dorsal vagal complex (NTS and AP), CeA, and BNST.

IL-1beta and LPS induce anorexia by distinct mechanisms differentially dependent on microsomal prostaglandin E synthase-1

Recent work demonstrated that the febrile response to peripheral immune stimulation with proinflammatory cytokine IL-1beta or bacterial wall lipopolysaccharide (LPS) is mediated by induced synthesis of prostaglandin E(2) by the terminal enzyme microsomal prostaglandin E synthase-1 (mPGES-1). The present study examined whether a similar mechanism might also mediate the anorexia induced by these inflammatory agents. Transgenic mice with a deletion of the Ptges gene, which encodes mPGES-1, and wild-type controls were injected intraperitoneally with IL-1beta, LPS, or saline. Mice were free fed, and food intake was continuously monitored with an automated system for 12 h. Body weight was recorded every 24 h for 4 days. The IL-1beta induced anorexia in wild-type but not knock-out mice, and so it was almost completely dependent on mPGES-1. In contrast, LPS induced anorexia of the same magnitude in both phenotypes, and hence it was independent of mPGES-1. However, when the mice were prestarved for 22 h, LPS induced anorexia and concomitant body weight loss in the knock-out animals that was attenuated compared with the wild-type controls. These data suggest that IL-1beta and LPS induce anorexia by distinct immune-to-brain signaling pathways and that the anorexia induced by LPS is mediated by a mechanism different from the fever induced by LPS. However, nutritional state and/or motivational factors also seem to influence the pathways for immune signaling to the brain. Furthermore, both IL-1beta and LPS caused reduced meal size but not meal frequency, suggesting that both agents exerted an anhedonic effect during these experimental conditions.