Neurochemical and neuroendocrine responses to Newcastle disease virus administration in mice

Effects of invasion history on physiological responses to immune system activation in invasive Australian cane toads

The cane toad (Rhinella marina) has undergone rapid evolution during its invasion of tropical Australia. Toads from invasion front populations (in Western Australia) have been reported to exhibit a stronger baseline phagocytic immune response than do conspecifics from range core populations (in Queensland). To explore this difference, we injected wild-caught toads from both areas with the experimental antigen lipopolysaccharide (LPS, to mimic bacterial infection) and measured whole-blood phagocytosis. Because the hypothalamic-pituitary-adrenal axis is stimulated by infection (and may influence immune responses), we measured glucocorticoid response through urinary corticosterone levels. Relative to injection of a control (phosphate-buffered saline), LPS injection increased both phagocytosis and the proportion of neutrophils in the blood. However, responses were similar in toads from both populations. This null result may reflect the ubiquity of bacterial risks across the toad’s invaded range; utilization of this immune pathway may not have altered during the process of invasion. LPS injection also induced a reduction in urinary corticosterone levels, perhaps as a result of chronic stress.

Mechanisms of Changes in Immune Response during Bacterial Coinfections of the Respiratory Tract

Acute diseases of the respiratory tract are often caused by viral pathogens and accompanying secondary bacterial infections. It is known that the development of such bacterial complications is caused mainly by a decreased infiltration with immune system cells and by suppressed inflammation in the lungs. There are significant advances in understanding the mechanisms of secondary infections, although many details remain unclear. This review summarizes current knowledge of the molecular and cellular changes in the host organism that can influence the course of bacterial coinfections in the respiratory tract.

Psychoneuroimmunology: Then and Now

Psychoneuroimmunology (PNI) emerged in the neurosciences in the late 1970s to early 1980s and has extended to influence the fields of psychology, psychiatry, endocrinology, physiology, and the biomedical research community. This review documents the journey of PNI from the early 1980s to the present. Today, we recognize that the highly complex immune system interacts with an equally complex nervous system in a bidirectional manner. Evolutionarily old signals continue to play a role in these communications, as do mechanisms for protection of the host. The disparity between physical and psychological stressors is only an illusion. Host defense mechanisms respond in adaptive and meaningful ways to both. The present review will describe a new way of thinking about evolutionarily old molecules, heat shock proteins, adding to a body of evidence suggesting that activation of the acute stress response is a double-edged sword that can both benefit and derail optimal immunity.

Cerebral Response to Peripheral Challenge with a Viral Mimetic

It has been well established that peripheral inflammation resulting from microbial infections profoundly alters brain function. This review focuses on experimental systems that model cerebral effects of peripheral viral challenge. The most common models employ the induction of the acute phase response via intraperitoneal injection of a viral mimetic, polyinosinic-polycytidylic acid (PIC). The ensuing transient surge of blood-borne inflammatory mediators induces a "mirror" inflammatory response in the brain characterized by the upregulated expression of a plethora of genes encoding cytokines, chemokines and other inflammatory/stress proteins. These inflammatory mediators modify the activity of neuronal networks leading to a constellation of behavioral traits collectively categorized as the sickness behavior. Sickness behavior is an important protective response of the host that has evolved to enhance survival and limit the spread of infections within a population. However, a growing body of clinical data indicates that the activation of inflammatory pathways in the brain may constitute a serious comorbidity factor for neuropathological conditions. Such comorbidity has been demonstrated using the PIC paradigm in experimental models of Alzheimer's disease, prion disease and seizures. Also, prenatal or perinatal PIC challenge has been shown to disrupt normal cerebral development of the offspring resulting in phenotypes consistent with neuropsychiatric disorders, such as schizophrenia and autism. Remarkably, recent studies indicate that mild peripheral PIC challenge may be neuroprotective in stroke. Altogether, the PIC challenge paradigm represents a unique heuristic model to elucidate the immune-to-brain communication pathways and to explore preventive strategies for neuropathological disorders.

Common biological pathways underlying the psychoneurological symptom cluster in cancer patients

BACKGROUND

A symptom cluster is a group of symptoms that occur together and are interrelated. The clinical implication of symptom cluster research is to use the clustering patterns of symptoms to understand the mechanisms for these symptoms and develop management strategies targeted at multiple symptoms.

OBJECTIVE

The purposes of this review were to summarize the evidence for a psychoneurological symptom cluster in cancer patients, to provide information regarding the underlying biological mechanisms for each of the psychoneurological symptoms within the cluster, and to propose possible common biological pathways that may underlie this cluster.

METHODS

A systematic review of the literature was conducted.

RESULTS

Empirical evidence exists to support a cluster of psychoneurological symptoms (ie, depressive symptoms, cognitive disturbance, fatigue, sleep disturbance, pain). At a molecular level, common biological pathways (ie, proinflammatory cytokines, hypothalamic-pituitary-adrenal axis, and monoamine neurotransmission system) may underlie the development of symptoms within this cluster. Activation of proinflammatory cytokines is proposed as a first stage of mechanistic pathway. However, other biological factors, such as lowered estrogen or hemoglobin levels, may influence psychoneurological cluster.

CONCLUSION

Additional studies are needed to confirm the roles of cytokines as well as other biological factors in the development of the psychoneurological cluster and to determine the biomarkers to identify the subgroups of cancer patients who are at greatest risk for this cluster.

IMPLICATIONS FOR PRACTICE

This information can be used by researchers and clinicians to guide the selection of symptom management strategies that are ideally targeted to the biological mechanisms that underlie this symptom cluster.

Poly I:C-induced activation of the immune response is accompanied by depression and anxiety-like behaviours, kynurenine pathway activation and reduced BDNF expression

In this study we characterised the ability of the viral mimetic poly I:C to induce a neuroinflammatory response and induce symptoms of depression and anxiety in rats. Furthermore, the ability of poly I:C to deplete central tryptophan and serotonin via induction of indolamine 2,3 dioxygenase (IDO), and also the ability of poly I:C to impact upon expression of the neurotrophin BDNF and its receptor TrkB were examined as potential mechanisms to link inflammation to depression. Poly I:C induced a neuroinflammatory response characterised by increased expression of IL-1β, IL-6, TNF-α and CD11b in frontal cortex and hippocampus. In the first 24h following poly I:C administration rats displayed sickness behaviour characterised by reduced locomotor activity and weight gain. Anhedonia measured using the saccharin preference test was used as an indicator of depressive behaviour, and poly I:C induced depressive behaviour that persisted for up to 72h following administration. Anxiety was measured using the open field test and anxious behaviour was observed 24h following poly I:C, a time-point when sickness behaviour had resolved. These behavioural changes were accompanied by decreased expression of BDNF and TrkB in hippocampus and frontal cortex. In addition, poly I:C increased central IDO expression and increased concentrations of tryptophan, and its metabolite kynurenine. However this activation of the kynurenine pathway did not result in reduced central serotonin concentrations. These findings suggest that depressive and anxiety-like behaviours elicited by poly I:C are associated with a reduction in BDNF signalling, and activation of the kynurenine pathway, but not a reduction in serotonin.

Effects of stressors and immune activating agents on peripheral and central cytokines in mouse strains that differ in stressor responsivity

The impact of inflammatory immune activation on behavioral and physiological processes varies with antecedent stressor experiences. We assessed whether immune activation would differentially influence such outcomes as a function of stressor reactivity related to genetic differences. To this end, we assessed the influence of a social stressor (exposure to a dominant mouse) in combination with an acute immune challenge on behavior and on peripheral and central cytokines in stressor-reactive BALB/cByJ mice and the less reactive C57BL/6ByJ strain. As C57BL/6ByJ and BALB/cByJ mice are highly T helper type-1 (Th1) and Th2 responsive, respectively, the stressor effects were assessed in response to different challenges, namely the viral analogue poly I:C and the bacterial endotoxin lipopolysaccharide (LPS). The stressor enhanced the effects of LPS on sickness behaviors and plasma corticosterone particularly in BALB/cByJ mice, whereas the effects of poly I:C, which primarily affects Th1 processes, were not augmented by the stressor. As well, the stressor increased circulating cytokines in LPS treated C57BL/6ByJ mice, whereas the effects of poly I:C were diminished. Finally, like circulating cytokines, mRNA expression of pro-inflammatory cytokines within the prefrontal cortex and hippocampus varied with the mouse strain and with the stressor experience, and with the specific cytokine considered. Together, the experiments indicated that the impact of stressors vary with the nature of the immune challenge to which animals had been exposed. Moreover, given the diversity of the stressor effects on central and peripheral processes, it seems likely that the cytokine changes, HPA activity and sickness operate through independent mechanisms.

Influenza virus-induced glucocorticoids compromise innate host defense against a secondary bacterial infection

Multicellular organisms are continuously exposed to many different pathogens. Because different classes of pathogens require different types of immune responses, understanding how an ongoing immune response to one type of infection affects the host's ability to respond to another pathogen is essential for a complete understanding of host-pathogen interactions. Here, we used a mouse model of coinfection to gain insight into the effect of respiratory influenza virus infection on a subsequent systemic bacterial infection. We found that influenza infection triggered a generalized stress response leading to a sustained increase in serum glucocorticoid levels, resulting in a systemic suppression of immune responses. However, virus-induced glucocorticoid production was necessary to control the inflammatory response and prevent lethal immunopathology during coinfection. This study demonstrates that activation of the hypothalamic-pituitary-adrenal axis controls the balance between immune defense and immunopathology and is an important component of the host response to coinfection.

Can cocaine abuse exacerbate the cardiac toxicity of human immunodeficiency virus?

Both cocaine use and human immunodeficiency virus (HIV) infection alone have been associated with an increased incidence of cardiac dysfunction. Concomitant exposure to cocaine and HIV infection may exacerbate the cardiac toxicity of either agent alone, a hypothesis that is examined in this review article. A possible unifying hypothesis based on enhancement of adrenergic stimulation is proposed.

Interleukin-1 (IL-1): a central regulator of stress responses

Ample evidence demonstrates that the pro-inflammatory cytokine interleukin-1 (IL-1), produced following exposure to immunological and psychological challenges, plays an important role in the neuroendocrine and behavioral stress responses. Specifically, production of brain IL-1 is an important link in stress-induced activation of the hypothalamus-pituitary-adrenal axis and secretion of glucocorticoids, which mediate the effects of stress on memory functioning and neural plasticity, exerting beneficial effects at low levels and detrimental effects at high levels. Furthermore, IL-1 signaling and the resultant glucocorticoid secretion mediate the development of depressive symptoms associated with exposure to acute and chronic stressors, at least partly via suppression of hippocampal neurogenesis. These findings indicate that whereas under some physiological conditions low levels of IL-1 promote the adaptive stress responses necessary for efficient coping, under severe and chronic stress conditions blockade of IL-1 signaling can be used as a preventive and therapeutic procedure for alleviating stress-associated neuropathology and psychopathology.

Glucocorticoids modulate NF-kappaB-dependent gene expression by up-regulating FKBP51 expression in Newcastle disease virus-infected chickens

FK506-binding protein 51(FKBP51, coded by FKBP5) is a co-chaperone molecule that interacts with the chaperone HSP90 and the glucocorticoid receptor (GR) in an inactive GR complex. It is a negative regulator of glucocorticoid action and is replaced by the positive regulator, FK506-binding protein 52 (FKBP52, coded by FKBP4) when hormone binds to GR, which renders the GR complex active. In this study, we found that the expression of FKBP51 mRNA in 12 organs of Newcastle disease virus (NDV)-infected chickens was robustly induced. The level of corticosterone in NDV-infected chickens was also elevated, approximately 2- to 6.5-fold in the organs compared to non-infected control chickens. The induction of FKBP51 mRNA expression was reproduced by dexamethasone treatment, indicating a role for glucocorticoids in the systemic induction of FKBP51 mRNA expression. In chicken UMNSAH/DF-1 cells, nuclear factor kappaB (NF-kappaB) was activated in an FKBP51-dependent manner. Regulation of the three NF-kappaB-dependent, anti-apoptotic genes, bcl-2, bcl-x and bfl-1/A1 was investigated in UMNSAH/DF-1 cells. Dexamethasone treatment of UMNSAH/DF-1 cells resulted in up-regulation of bcl-2, and down-regulation of bcl-x and bfl-1/A1. Expression of FKBP51 also resulted in down-regulation of bfl-1/A1, but had no effect on bcl-2 and bcl-x, suggesting the involvement of glucocorticoid-FKBP51-NF-kappaB signaling in the regulation of expression of bfl-1/A1 in UMNSAH/DF-1 cells. We observed organ-specific up- or down-regulation of expression of, bcl-2, bcl-x and bfl-1/A1 in NDV-infected and dexamethasone-treated chickens. Differential regulation of bfl-1/A1, bcl-2 and bcl-x upon NDV-infection and dexamethasone treatment suggests that additional factors are involved in the regulation of these genes. These results suggest that systemic elevation of FKBP51 in NDV-infected chickens activates NF-kappaB, which cooperates with other factors to regulate the expression of NF-kappaB-dependent genes.

The sickness behaviour and CNS inflammatory mediator profile induced by systemic challenge of mice with synthetic double-stranded RNA (poly I:C)

Poly inosinic:poly cytidylic acid (poly I:C) is a synthetic double-stranded RNA and is a ligand for the Toll like receptor-3. This receptor is involved in the innate immune response to viral infection and poly I:C has been used to mimic the acute phase of a viral infection. The effects of TLR3 activation on brain function have not been widely studied. In the current study we investigate the spectrum of sickness behavioural changes induced by poly I:C in C57BL/6 mice and the CNS expression of inflammatory mediators that may underlie this. Poly I:C, at doses of 2, 6 and 12 mg/kg, induced a dose-responsive sickness behaviour, decreasing locomotor activity, burrowing and body weight, and caused a mild hyperthermia at 6h. The 12 mg/kg dose caused significant hypothermia at later times. The Remo400 remote Telemetry system proved a sensitive measure of this biphasic temperature response. The behavioural responses to poly I:C were not significantly blunted upon a second poly I:C challenge either 1 or 3 weeks later. Plasma concentrations of IL-6, TNF-alpha and IFN-beta were markedly elevated and IL-1 beta was also detectable. Cytokine synthesis within the CNS, as determined by quantitative PCR, was dominated by IL-6, with lesser inductions of IL-1 beta, TNF-alpha and IFN-beta and there was a clear activation of cyclooxygenase-2 at the brain endothelium. These findings demonstrate clear CNS effects of peripheral TLR3 stimulation and will be useful in studying aspects of the effects of systemic viral infection on brain function in both normal and pathological situations.

Influence of poly I:C on sickness behaviors, plasma cytokines, corticosterone and central monoamine activity: moderation by social stressors

Stressor and cytokine challenges provoke several common effects, and may synergistically influence behavioral and neurochemical functioning. In the present investigation, we assessed whether the effects of poly I:C would be influenced when administered on a backdrop of a psychosocial stressor. In naïve mice, poly I:C (2mg/kg) modestly increased sickness behaviors, plasma IL-6, TNF-alpha and IL-10 levels, but did not affect IL-1, IL-4, or IFN-gamma. The viral analogue also increased plasma corticosterone levels and norepinephrine (NE) utilization within the paraventricular hypothalamus (PVN) and hippocampus. However, among mice that had experienced social disruption (comprising 14 days of isolation followed by regrouping), the behavioral, IL-6, IL-10, and corticoid alterations provoked by poly I:C were markedly augmented. Moreover, following social disruption the effect of poly I:C on NE utilization was increased within the PVN, prefrontal cortex and central amygdala, as was serotonin utilization within the hippocampus. The effects of poly I:C were likewise augmented following social disruption engendered by introducing mice to strangers.. However, among mice that had previously been exposed to a chronic, variable psychosocial stressor regimen, the augmented behavioral, neuroendocrine and monoamine effects of poly I:C were absent, and IL-6 and IL-10 levels were reduced relative to mice that had not been chronically stressed. In contrast, levels of IL-1 beta and IFN-gamma were increased. Mechanisms that might be responsible for the interactive effects of social disruption and immune activation are presented, and the data were related to depressive symptoms associated with stressor and cytokine treatments.

Effects of cytokines and infections on brain neurochemistry

Administration of cytokines to animals can elicit many effects on the brain, particularly neuroendocrine and behavioral effects. Cytokine administration also alters neurotransmission, which may underlie these effects. The most well studied effect is the activation of the hypothalamo-pituitary-adrenocortical (HPA) axis, especially that by interleukin-1 (IL-1). Peripheral and central administration of IL-1 also induces norepinephrine (NE) release in the brain, most markedly in the hypothalamus. Small changes in brain dopamine (DA) are occasionally observed, but these effects are not regionally selective. IL-1 also increases brain concentrations of tryptophan, and the metabolism of serotonin (5-HT) throughout the brain in a regionally nonselective manner. Increases of tryptophan and 5-HT, but not NE, are also elicited by IL-6, which also activates the HPA axis, although it is much less potent in these respects than IL-1. IL-2 has modest effects on DA, NE and 5-HT. Like IL-6, tumor necrosis factor-α (TNFα) activates the HPA axis, but affects NE and tryptophan only at high doses. The interferons (IFN's) induce fever and HPA axis activation in man, but such effects are weak or absent in rodents. The reported effects of IFN's on brain catecholamines and serotonin have been very varied. However, interferon-γ, and to a lesser extent, interferon-α, have profound effects on the catabolism of tryptophan, effectively reducing its concentration in plasma, and may thus limit brain 5-HT synthesis.Administration of endotoxin (LPS) elicits responses similar to those of IL-1. Bacterial and viral infections induce HPA activation, and also increase brain NE and 5-HT metabolism and brain tryptophan. Typically, there is also behavioral depression. These effects are strikingly similar to those of IL-1, suggesting that IL-1 secretion, which accompanies many infections, may mediate these responses. Studies with IL-1 antagonists, support this possibility, although in most cases the antagonism is incomplete, suggesting the existence of multiple mechanisms. Because LPS is known to stimulate the secretion of IL-1, IL-6 and TNFα, it seems likely that these cytokines mediate at least some of the responses, but studies with antagonists indicate that there are multiple mechanisms. The neurochemical responses to cytokines are likely to underlie the endocrine and behavioral responses. The NE response to IL-1 appears to be instrumental in the HPA activation, but other mechanisms exist. Neither the noradrenergic nor the serotonergic systems appear to be involved in the major behavioral responses. The significance of the serotonin response is unknown.

Immune modulation of the hypothalamic-pituitary-adrenal (HPA) axis during viral infection

Compelling data has been amassed indicating that soluble factors, or cytokines, emanating from the immune system can have profound effects on the neuroendocrine system, in particular the hypothalamic- pituitary-adrenal (HPA) axis. HPA activation by cytokines (via the release of glucocorticoids), in turn, has been found to play a critical role in restraining and shaping immune responses. Thus, cytokine-HPA interactions represent a fundamental consideration regarding the maintenance of homeostasis and the development of disease during viral infection. Although reviews exist that focus on the bi-directional communication between the immune system and the HPA axis during viral infection (188,235), others have focused on the immunomodulatory effects of glucocorticoids during viral infection (14,225). This review, however, concentrates on the other side of the bi-directional loop of neuroendocrine-immune interactions, namely, the characterization of HPA axis activity during viral infection and the mechanisms employed by cytokines to stimulate glucocorticoid release.

Intratracheal double-stranded RNA plus interferon-γ: A model for analysis of the acute phase response to respiratory viral infections

Double-stranded (ds)RNA is made as a by-product of viral replication. Synthetic dsRNA induces virtually all of the same systemic symptoms as acute viral infections, such as fever and malaise. In order to develop a model of respiratory viral infections (such as influenza) suitable for use in gene knockout mice (where the deleted gene may affect viral replication), we examined C57BL/6 mouse body temperature and locomotor activity responses to the synthetic dsRNA polyriboinosinic.polyribocytidylic acid (poly[rI.rC]) introduced via the intratracheal (IT) route. We compared the IT poly[rI.rC] responses to the well-characterized intraperitoneal (IP) poly[rI.rC] responses. IT poly[rI.rC] failed to induce an acute phase response (APR) in mice, in contrast to IP poly[rI.rC]. However, addition of interferon (IFN)gamma to the IT poly[rI.rC] inoculum induced sustained hypothermia and suppressed locomotor activity responses with similar kinetics to those responses seen in acute mouse influenza. We further examined cytokine, antiviral, muscarinic M2 receptor and inducible nitric oxide synthase gene expression at 5 hr in the lungs of IT challenged mice. These studies suggested that priming the lung with IFNgamma could enhance proinflammatory (IL1beta, IL6, TNFalpha) cytokine gene expression and suppress interferon gene expression compared to IT poly[rI.rC] alone. No differences were detected for the other genes examined. While further molecular characterization of the model is required, we demonstrate that IT challenge with combined poly[rI.rC] and IFNgamma closely simulates the APR to an acute respiratory virus, and may serve as a suitable model for analyzing the molecular basis of the viral APR in gene knockout mice.

Endocrine aspects of cancer gene therapy

The field of cancer gene therapy is in continuous expansion, and technology is quickly moving ahead as far as gene targeting and regulation of gene expression are concerned. This review focuses on the endocrine aspects of gene therapy, including the possibility to exploit hormone and hormone receptor functions for regulating therapeutic gene expression, the use of endocrine-specific genes as new therapeutic tools, the effects of viral vector delivery and transgene expression on the endocrine system, and the endocrine response to viral vector delivery. Present ethical concerns of gene therapy and the risk of germ cell transduction are also discussed, along with potential lines of innovation to improve cell and gene targeting.

Interleukin-6 is an afferent signal to the hypothalamo-pituitary-adrenal axis during local inflammation in mice

The cytokines IL-1 and IL-6 are able to induce prostaglandin (PG)-dependent activation of the hypothalamo-pituitary-adrenal axis (HPAA) and are thought to play key roles in immune-neuroendocrine interactions during inflammation. The present study shows that inflammation induced by im injection of turpentine (TPS) in the hind limb of mice causes an increase in the plasma concentration of IL-6, but not that of IL-1 alpha or IL-1 beta, together with a prolonged (>18-h) activation of the HPAA. IL-6 plays a causal role in the TPS-induced elevation in HPAA activity, because the sustained (8-18 h) increases in 1) plasma corticosterone, 2) plasma ACTH, and 3) induction of c-Fos in the hypothalamic paraventricular nucleus are all markedly blunted in IL-6-deficient (IL-6(-/-)) mice. Peripheral administration of a neutralizing IL-6 antiserum inhibited the plasma corticosterone response of normal (C57BL/6) mice to hind limb inflammation to an extent similar to that seen in IL-6(-/-) mice, suggesting that the IL-6 responsible for the increased HPAA activity is produced, or acts, on the blood side of the blood-brain barrier. We also show that IL-6 in the circulation is induced almost exclusively at the local inflammatory site, where IL-1 beta is produced. Induction of IL-6 and activation of the HPAA are dependent upon prior activation of an IL-1 type I receptor, as both are inhibited in type I IL-1 receptor-deficient mice. Furthermore, hind limb inflammation induced cyclooxygenase-2 protein expression around the cerebrovasculature of normal (IL-6(+/+)), but not IL-6(-/-), mice. Based on these data, we propose that IL-6 is produced at the local inflammatory site under the control of IL-1 beta and is the circulating afferent signal that is in part responsible for elevated HPAA activity, possibly acting via eicosanoid production within the cerebrovasculature.

Inhibitory effect of neurogenic and immune stressors on testosterone secretion in rats

OBJECTIVE

We investigated the ability of foot shocks, endotoxemia and turpentine-induced tissue injury, to interfere with luteinizing hormone (LH) and testosterone (T) secretion, and the putative role of beta-adrenergic, opiate- and corticotropin-releasing factor (CRF) receptors in these responses.

METHODS

Adult male rats were exposed to mild intermittent foot shocks for 1 h, administered endotoxin [lipopolysaccharide (LPS)] intravenously (i.v., 5 microg/kg), or injected with turpentine intradermally (i.m., 400 microl/kg), prior to injection with human chorionic gonadotropin (hCG, 1 U/kg i.v.). In some cases, antagonists to CRF, adrenergic or opiate receptors, or their vehicle were administered prior to the stressors. Levels of LH, T, tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), adrenocorticotropin (ACTH) and/or corticosterone were measured in serial blood samples.

RESULTS

All three challenges significantly lowered basal LH and T levels and blunted the T response to hCG, though the magnitude of this inhibition was significantly (p < 0.01) smaller in shocked rats (42%), compared to animals injected with LPS (92%) or turpentine (78%). Shocks, LPS and turpentine all significantly stimulated ACTH and corticosterone release, and the magnitude and time course of these responses were also stressor specific. While turpentine only increased circulating IL-6 concentrations, shocks and LPS both significantly increased circulating TNF-alpha and IL-6 levels, but the effect of shocks was markedly smaller. Pretreatment with propranolol did not restore T responses, while naloxone produced small and inconsistent effects. However, the CRF antagonist Astressin B, which significantly prevented stressor-induced increase in circulating levels of ACTH and corticosterone, partially reversed the inhibitory effect of LPS on hCG-induced T release.

CONCLUSION

(1) Both neurogenic and systemic stressors lower basal plasma LH and T levels and blunt the T response to hCG. (2) LPS, whose ability to release ACTH and corticosterone was similar to that of shocks, but caused increases in circulating TNF-alpha and IL-6 levels that were significantly larger than those due to the other stressors, was the most potent inhibitor of the T response to hCG. (3) Neither beta-adrenergic nor opiate receptors play a major role in the ability of the stressors we used to inhibit T release.

Acute effects of purified and UV-inactivated Herpes simplex virus type 1 on the hypothalamo-pituitary-adrenocortical axis

Herpes simplex virus type 1 (HSV-1) is a common cause of viral encephalitis, manifested by neuroendocrine and behavioral changes. We have previously demonstrated that HSV-1 induces marked hypothalamo-pituitary-adrenocortical (HPA) axis activation. In this study we characterized the acute effects of HSV-1 on the HPA axis occurring before viral replication and appearance of clinical signs of encephalitis. Since in previous studies we used crude virus preparations which may contain immune factors produced by the infected cells, we tested here the effects of purified HSV-1 virions. HSV-1 was propagated on Vero cells and virions were purified by centrifugation in sucrose gradients. Inactivation of viral infectivity was achieved by UV-irradiation, which caused a million-fold decrease in virus titer, as determined by plaque assay. Intracerebroventricular (ICV) inoculation of crude or purified virions induced a dose dependent increase in serum corticosterone and corticotropin (ACTH). This effect was maximal within 3.5 h postinfection and lasted for 72 h. ICV inoculation of UV-inactivated purified virions caused a marked increase in serum corticosterone and ACTH at 3.5 h, but in contrast to the effect of the active virus, the hormone levels gradually decreased at 24 h, and returned to basal levels at 72 h postinfection. HSV-1-induced HPA axis activation at 3.5 h was completely abolished by pretreatment with interleukin-1 receptor antagonist, injected ICV. Adrenalectomized rats failed to respond to ICV inoculation of purified HSV-1 by increase in ACTH. In contrast, these rats responded to ICV injection of LPS.

IN CONCLUSION

(1) HSV-1 can acutely activate the HPA axis before and independently of any viral replication; (2) HSV-1-induced HPA axis activation depends on a permissive action of circulating glucocorticoids and on host derived brain interleukin-1.

Cytokine activation of the HPA axis

The observation that administration of interleukin-1 (IL-1) to animals activates the hypothalamo-pituitary-adrenocortical (HPA) axis stimulated great interest in the significance and mechanism of this response, and in whether other cytokines have similar activities. Interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF alpha) share HPA-activating activity, although they are less potent and effective than IL-1, whereas IL-2 and interferon alpha(IFN alpha) lack activity. Small increases in body temperature occur in response to IL-1, IL-6 and TNF alpha, but these changes are prevented by inhibitors of cyclooxygenase (COX) and do not appear to be related to the HPA-activation. The rapid HPA-activating effects of IL-1 are impaired by COX inhibitors, but the more prolonged HPA activation associated with intraperitoneal injections is not affected, indicating multiple mechanisms for IL-1-induced HPA activation. The HPA response to IL-6 is not sensitive to COX inhibitors, but that to TNF alpha appears to be. The HPA-activating activity of IL-1 is associated with increases in the apparent release of brain noradrenaline (NA) and serotonin (5-HT), but not dopamine, as well as with increased brain tryptophan. The NA changes, but not these in serotonin metabolism and tryptophan, are prevented by COX inhibitors. IL-6 has effects on serotonin and tryptophan like those of IL-1, but no detected effect on NA. TNF alpha has some effect on NA and tryptophan, but only at relatively high doses. IFN alpha lacks activity on these neurochemicals. Manipulation of noradrenergic, but not serotonergic systems alters the IL-1-induced HPA activation, suggesting the involvement of NA. However, brain NA does not appear to be essential for HPA activation in mice.

Effect of acute lipopolysaccharide administration on (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2 aminopropane-induced wet dog shake behavior in rats: comparison with body weight change and locomotor activity

1. Several reports have shown that serotonin (5-HT)2A receptor density and its function are altered after physiological or pharmacological stress. To examine whether an acute administration of lipopolysaccharide (LPS), a bacterial endotoxin, affected 5-HT2A receptor function, wet dog shakes of male Wistar rats were observed after a subcutaneous injection of DOI, a 5-HT2A receptor agonist following LPS treatment. Body weight change and locomotor activity were also observed. 2. DOI (1 mg/kg)-induced WDS significantly decreased after 400 or 1000 microg/kg LPS treatment compared with that of control rats 1 and 3 hr after injection, and WDS completely recovered 8 hr after LPS treatment. Treatment with 10 mg/kg indomethacin (IND) or 1 mg/kg naltrexone (NLTX) canceled the effect of 400 microg/kg LPS on DOI-induced WDS. 3. Body weight decrease was significantly greater in LPS-treated rats compared with control rats 3, 5 and 8 hr after treatment. Treatment with IND (10 mg/kg) significantly recovered the reduction in body weight induced by 400 microg/kg LPS. Treatment with NLTX (1 mg/kg) also prevented the LPS effect on body weight decrease. 4. Eight hr after treatment with LPS (400 microg/kg), the rats showed significant attenuation of locomotor activity. IND (10 mg/kg) treatment abolished the inhibitory effect of LPS on locomotor activity, and NLTX (1 mg/kg) also improved the decrease in locomotion 8 hr after LPS treatment. 5. Plasma tumor necrosis factor (TNF)-alpha concentration dramatically increased 1 hr after the injection of 400 microg/kg LPS, and returned almost to the basal level 3 hr later. Next, rats were injected with 50 microg/kg TNF-alpha intraperitoneally, and body weight change and DOI-induced WDS was determined 3 hr after TNF-alpha injection. Body weight loss was significantly greater in rats treated with TNF-alpha. On the other hand, DOI-induced WDS was not altered when rats were treated with TNF-alpha. 6. These results suggest that acute treatment with LPS inhibited 5-HT2A receptor-mediated behavior via cyclooxygenase and opioid receptor activation, but that the inhibition of the WDS by LPS appears to be independent of TNF-alpha production.

Viral double-stranded RNA, cytokines, and the flu

The symptoms of the flu, such as fever, drowsiness, and malaise, are the sole means by which this common clinical syndrome is defined. The syndrome is usually the first clinical manifestation of both acute bacterial and viral infections. In the case of acute bacterial infections, several proinflammatory cytokines induced by bacterial products have been implicated as the causative agents of the flu syndrome. Viruses induce similar cytokines to bacteria, plus substantial amounts of interferon-alpha (IFN-alpha), although the direct association of these cytokines with the viral flu syndrome is less clear. Furthermore, the viral inducer(s) of cytokines has not been defined. The best candidate cytokine inducer associated with a majority of viral infections is virus-associated double-stranded RNA (dsRNA). This review examines the essential physical properties of toxic dsRNA, the cytokines induced by it, its viral and cellular sources, evidence for its presence in infected cells, its quantities in normal and infected cells, its cytotoxic mechanisms, and its cell-penetration properties. Toxic effects of viruses and dsRNA are compared. Energetics and extraction artifact issues are also discussed. Whereas most research on dsRNA toxicity has employed synthetic dsRNA, studies with virus-associated dsRNA are featured when available. Finally, a model for how viral dsRNA might initiate systemic disease is presented.

Newcastle disease virus (NDV): brief history of its oncolytic strains

BACKGROUND

While genetically engineered viruses are now being tested for the virus therapy of human cancers, some naturally occurring viruses display unmatched oncolytic activity. Newcastle disease virus (NDV) excels as an oncolytic agent.

OBJECTIVES

As its virulence versus attenuation can be explained on molecular biological bases, it may be possible to develop or select highly oncolytic strains of NDV without adverse toxicity.

STUDY DESIGN

Questions are posed as to the mechanisms of viral oncolysis, the appropriateness of tests to predict oncolytic activity of a given NDV strain and the best modes of administration for oncolytic effects. Answers are provided based on specific data or on considerations drawn from experience (the authors use NDV oncolysates to immunize against melanoma and kidney carcinoma) or from analogous clinical situations (therapeutic use of mumps or measles viruses).

RESULTS AND CONCLUSIONS

NDV oncolysates probably suit better for immunotherapy (providing also active tumor-specific immunization) than massive repeated inoculations of NDV strains, especially when the NDV strain used is not proven to be oncolytic by appropriate pre-clinical tests.

Catecholamine, indoleamine and corticosteroid responses in mice bearing tumors

The neurochemical and endocrine responses to inoculation of mice with the murine lymphoma cell line AW5E was studied. This cell line was chosen because it is NK cell lysis resistant and thus does not induce a normal immune response. Immune activation has long been known to be a potent stimulator of the hypothalamo-pituitary-adrenocortical (HPA) axis as well as brain catecholamine and indoleamine metabolism, involving increases in the brain concentrations of catabolites of norepinephrine (NE) and serotonin (5-HT), as well as free tryptophan. Mice injected intravenously with AW5E tumor cells exhibited small increases in plasma corticosterone and hypothalamic NE and 5-HT catabolites one day after injection. There were no significant changes after 6 or 8 days, but a sustained increase in hypothalamic NE and 5-HT metabolism appeared 10 days after injection. There were similar, but more limited changes in the brain stem and prefrontal cortex. On the last day tested (day 14), plasma corticosterone was slightly elevated, as were hypothalamic dopamine, NE and 5-HT catabolites and tryptophan. These results indicate that inoculation with AW5E tumor cells increases brain catecholamine and serotonin metabolism, the hypothalamus being the most sensitive region. The most marked increases occurred in the few days preceding death, and thus may be associated with the pathology of the tumor growth.

Activation of the adrenocortical axis by surgical stress: involvement of central norepinephrine and interleukin-1

In the present study, we examined the mechanisms involved in the activation of the adrenocortical axis following surgical stress. Adult male rats underwent surgical laparotomy or craniotomy under ether anesthesia while control rats were only ether-anesthetized. Four hours following laparotomy or craniotomy, serum adrenocorticotropin (ACTH) and corticosterone (CS) were significantly increased and returned to almost basal levels after 24 h. Laparotomy also caused a significant depletion of corticotropin-releasing hormone (CRH-41) in the median eminence (ME). Pretreatment with dexamethasone 50 microg/kg completely abolished the pituitary-adrenal response while pretreatment with type II corticosteroid receptor antagonist caused a significant hypersecretion of both ACTH and CS and inhibited the effect of dexamethasone. The response to laparotomy was markedly attenuated in rats injected with 6-hydroxydopamine into the paraventricular nucleus (PVN) which significantly depletes norepinephrine (NE) PVN content. Intracerebroventricular injection of interleukin-1 receptor antagonist (IL-1ra) also inhibited the pituitary-adrenal response to laparotomy. The results suggest that (1) surgical stress activates the hypothalamo-pituitary-adrenal (HPA) axis via a mechanism which involves the release of CRH from the ME and NE input to the PVN; (2) the adrenocortical response is sensitive to the negative feedback of glucocorticoids via the mediation of type II glucocorticoid receptors, and (3) central IL-1 may be a mediator in the HPA axis response to surgical stress.

Regulation of the hypothalamic-pituitary-adrenal axis by cytokines: actions and mechanisms of action

Glucocorticoids are hormone products of the adrenal gland, which have long been recognized to have a profound impact on immunologic processes. The communication between immune and neuroendocrine systems is, however, bidirectional. The endocrine and immune systems share a common "chemical language," with both systems possessing ligands and receptors of "classical" hormones and immunoregulatory mediators. Studies in the early to mid 1980s demonstrated that monocyte-derived or recombinant interleukin-1 (IL-1) causes secretion of hormones of the hypothalamic-pituitary-adrenal (HPA) axis, establishing that immunoregulators, known as cytokines, play a pivotal role in this bidirectional communication between the immune and neuroendocrine systems. The subsequent 10-15 years have witnessed demonstrations that numerous members of several cytokine families increase the secretory activity of the HPA axis. Because this neuroendocrine action of cytokines is mediated primarily at the level of the central nervous system, studies investigating the mechanisms of HPA activation produced by cytokines take on a more broad significance, with findings relevant to the more fundamental question of how cytokines signal the brain. This article reviews published findings that have documented which cytokines have been shown to influence hormone secretion from the HPA axis, determined under what physiological/pathophysiological circumstances endogenous cytokines regulate HPA axis activity, established the possible sites of cytokine action on HPA axis hormone secretion, and identified the potential neuroanatomic and pharmacological mechanisms by which cytokines signal the neuroendocrine hypothalamus.

Cytokine release and its modulation by dexamethasone in whole blood following exercise

Glucocorticoids (GC) play an important role in the treatment of inflammatory diseases like asthma. However, in selected patients a relative resistance to GC has been reported. Recently, it has been suggested that GC sensitivity of peripheral blood leucocytes may be regulated in a dynamic fashion during exercise, in association with activation of the hypothalamic-pituitary-adrenal (HPA) axis. The aim of the present study was to explore changes in the GC sensitivity of cytokine production by leucocytes following strenuous exercise by well trained oarsmen. These changes were studied using lipopolysaccharide (LPS)-induced and anti-CD2/anti-CD28 MoAb-stimulated cytokine release in whole blood and its modulation by dexamethasone. Following exercise, significant decreases in LPS-induced release of IL-6, tumour necrosis factor-alpha (TNF-alpha) and IL-10 and anti-CD2/anti-CD28 MoAb-stimulated secretion of interferon-gamma (IFN-gamma) were observed. In addition, the inhibitory effect of dexamethasone on both IL-6 and TNF-alpha secretion was significantly reduced following exercise, whereas that on IL-10 and IFN-gamma release was not affected. These exercise-induced changes were accompanied by activation of the HPA axis, as indicated by an increase in circulating adrenocorticotropic hormone (ACTH) levels immediately following exercise. The results from the present study suggest that GC sensitivity of whole blood cytokine release can be regulated in a dynamic fashion and that this can be assessed using an ex vivo stimulation assay. Moreover, since dexamethasone responsiveness of anti-CD2/anti-CD28 MoAb-induced IFN-gamma secretion in whole blood is not affected by exercise, it may suggest that exercise differentially affects monocytes and lymphocytes. The dynamic regulation of steroid responsiveness of leucocytes, as observed in the present study, could have important consequences for the effectiveness of GC treatment in inflammatory diseases.

Early induction of proinflammatory cytokine and type I interferon mRNAs following Newcastle disease virus, poly [rI:rC], or low-dose LPS challenge of the mouse

Numerous cytokines induce symptoms characteristic of the flu syndrome common to acute viral infections. To better characterize the cytokine mRNA profile associated with the early phase of this syndrome, we examined the induction of cytokine mRNAs in spleens of mice 1, 2, and 4 h following intraperitoneal inoculation of Newcastle disease virus (NDV). The reverse transcriptase-polymerase chain reaction was used to detect mRNAs for mouse proinflammatory cytokines [interleukin (IL)-1 alpha, IL-1 beta, IL-6, tumor necrosis factor-alpha (TNF-alpha), macrophage colony-stimulating factor (M-CSF), and interferon (IFN)-gamma] and type I IFNs (IFN-alpha 4 and IFN-beta). We observed a rapid (within 2 h) induction of most of these cytokine mRNAs in the mouse spleen following challenge with live NDV or the viral stimulant poly[rI:rC]. IL-1 beta, M-CSF, and IFN-gamma mRNAs were also induced by heat-inactivated NDV, suggesting the possibility of endotoxin contamination of the virus (confirmed by Limulus lysate assay). Examination of cytokine induction by comparable doses of lipopolysaccharide indicated that endotoxin contamination could account for the cytokine mRNA-inducing activity of the heat-inactivated virus. These studies point to a critical control (heat-inactivated virus) for viral cytokine studies. In addition, they indicate that certain cytokine mRNAs (IL-1 alpha, IL-6, M-CSF, IFN-gamma, IFN-alpha, and IFN-beta) are rapidly induced in the spleen when live virus is inoculated intraperitoneally, independently of contaminating endotoxin.

Prefrontal cortex dysfunction in Borna disease virus (BDV)--infected rats

Viruses have been proposed to play a role in the pathogenesis of schizophrenia; however, the mechanisms by which infection could cause the affective, cognitive, and movement disorders of schizophrenia are not understood. The neurotropic RNA virus, Borna disease (BD) virus, linked to schizophrenia by serologic studies, causes movement and behavior disorders in a wide variety of mammalian and bird hosts. BD rats have hyperactivity and stereotyped behaviors similar to those that follow neurotoxic or electrolytic lesions in frontal cortex or its catecholamine afferents in rats. BD rats have high levels of viral nucleic acid in the prefrontal cortex (PFC), abnormal mesocortical dopamine activity (elevated levels of DOPAC in PFC), yet no alteration in specific binding of D1 or D2 receptor radioligands in PFC. Since frontal lobe dysfunction is frequently reported in schizophrenia, the BD rat model may provide insights into pathogenesis and management of this debilitating psychiatric disease.

Endotoxin produces a depressive-like episode in rats

Activation of the immune system produces psychological and physiological effects, which resemble the characteristics of depression. The present study was designed to investigate further, in rats, the similarity between the behavioral effects of immune activation and a model of depression in animals. Reduction in the preference for and consumption of saccharin solutions and suppression of sexual behavior were used as models of one essential feature of depression, the inability to experience pleasure (anhedonia). Other measures testing this model were the reduction in food consumption, body weight, locomotor activity, and social interaction. It was found that systemic injection of lipopolysaccharide (endotoxin), which is a potent activator of the immune system, significantly decreased saccharin preference in fluid-deprived rats. Lipopolysaccharide (LPS) also decreased free consumption of saccharin, but not water, in non-deprived rats. Several indices of male sexual behavior were significantly suppressed following LPS administration. Chronic, but not acute, treatment with the tricyclic antidepressant imipramine abolished the suppressive effect of LPS on saccharin preference. Moreover, chronic, but not acute, treatment with imipramine also reduced and facilitated the recovery from the suppressive effects of LPS on food consumption, body weight, social interaction and activity in the open-field test. The results suggest that activation of the immune system in rats produces anhedonia and other depressive-like symptoms, which can be attenuated or completely blocked by chronic treatment with an antidepressant drug.

Endotoxin administration induced differential neurochemical activation of the rat brain stem nuclei

Lipopolisaccharide (LPS) is a potent activator of the immune system, but also activates the hypothalamic-pituitary-adrenocortical (HPA) axis and cerebral catecholamine systems. In the present study, the effect of peripheral LPS administration on catecholaminergic and serotonergic neurotransmission in discrete brainstem nuclei was examined. Two hours following systemic administration of LPS (1, 10, or 100 micrograms/kg) norepinephrine (NE) content in the locus coeruleous (LC) was significantly increased in a dose related manner. An increased dopamine (DA) turnover as reflected by the 3,4-dihydroxyphenylacetic (DOPAC) + Homovanillic acid (HVA)/DA ratio, [DO-PAC + HVA]/[DA], was also observed at the LC with the medium and high doses of LPS administered. Endotoxin caused the main effects in the nucleus of the tractus solitarii (NTS) in which (a) it was found NE content increased in a dose related fashion, (b) DA turnover index was elevated with 10 and 100 micrograms/kg LPS doses, and (c) levels of serotonin (5-HT) and its catabolite, 5-hydroxyindole-3-acetic acid (5-HIAA), were also significantly elevated following the injection of 10 or 100 micrograms/kg LPS. By contrast, a consistent lack of catecholaminergic and serotonergic responses to endotoxin treatment was observed at the level of midbrain Raphe nuclei (MRN). These results demonstrate that differential neurochemical changes may occur in the brainstem region with a rank order of activation by LPS that was NTS > LC > MRN, suggesting different neural substrate for central effects of peripheral immune activation.

Effects of HSV-1, a neurotropic virus, on the hypothalamic-pituitary-adrenocortical axis in rats

It is well established that the hypothalamic-pituitary-adrenocortical (HPA) axis is activated during systemic viral diseases. In this study we examined the effects of a neurotropic virus, herpes simplex virus type 1 (HSV-1), on the HPA axis in male rats. Following corneal inoculation with HSV-1, the virus invaded the nervous system and replicated in the brainstem without clinical signs of disease. During this asymptomatic brainstem infection with HSV-1, significant changes were found in the function of the HPA axis: On days 3, 7 and 14 post-infection (p.i.) basal ACTH and corticosterone (CS) levels were markedly elevated, and photic stressful stimulation failed to further increase the levels of these hormones. In addition, the elevated basal serum levels of ACTH and CS could not be suppressed by pretreatment with dexamethasone. The content of CRF-41 in the paraventricular nucleus of the hypothalamus and in the median eminence measured at 6 days p.i. was similar to that of vehicle inoculated rats. By 4 weeks p.i. the basal levels of ACTH and CS returned to normal and these animals responded to photic stimulation and dexamethasone similar to vehicle inoculated rats. Systemic (intraperitoneal) inoculation of HSV-1 did not induce any changes in the HPA axis responses. We therefore suggest that asymptomatic acute infection of the brainstem with HSV-1 may affect brain regions involved in the regulation of the HPA axis, and that those effects are mediated centrally and not by a systemic mechanism.

The effect of the adrenocortical axis upon recovery from closed head injury

Fragments and analogs of the hormone ACTH were previously shown to have beneficial effect on the outcome of head injury, while elevated levels of corticosterone (CS) exacerbate it. In the present study we investigated the role of the hypothalamo-pituitary-adrenal (HPA) axis in the pathophysiology of closed head injury (CHI). CHI was produced in ether-anesthetized rats by a calibrated weight-drop device. After evaluating the functional status according to a set of criteria, at 1 and 24 h, the rats were sacrificed and cortical tissue was removed to determine its water content. CHI was also produced in rats that underwent surgical procedures to remove their adrenal gland (ADEX) or the pituitary (HypoX), thus altering the levels of their circulating HPA hormones. Given after CHI, to rats with intact HPA axis, ACTH reduced edema and improved recovery. ADEX rats (6 days postsurgery) had 10-fold higher levels of plasma ACTH. ADEX rats subjected to CHI showed improved functional outcome (p = 0.008) and reduced edema (p = 0.02). We then produced CHI in three groups of rats: HypoX (15 days postsurgery), HypoX treated with ACTH, and controls. In HypoX rats, CHI resulted in increased mortality (35% vs 0) and edema in the surviving rats, and a slower recovery, as compared with the control. Mortality was prevented, edema slightly reduced, and recovery significantly improved after administration of 1-24-ACTH to HypoX rats with CHI. Our results suggest that ACTH has a cerebroprotective effect on the outcome of CHI.