Differential insular cortex subregional vulnerability to α-synuclein pathology in Parkinson's disease and dementia with Lewy bodies.

AIM: The insular cortex consists of a heterogenous cytoarchitecture and diverse connections and is thought to integrate autonomic, cognitive, emotional and interoceptive functions to guide behaviour. In Parkinson's disease (PD) and dementia with Lewy bodies (DLB), it reveals α-synuclein pathology in advanced stages. The aim of this study is to assess the insular cortex cellular and subregional vulnerability to α-synuclein pathology in well-characterized PD and DLB subjects. METHODS: We analysed postmortem insular tissue from 24 donors with incidental Lewy body disease, PD, PD with dementia (PDD), DLB and age-matched controls. The load and distribution of α-synuclein pathology and tyrosine hydroxylase (TH) cells were studied throughout the insular subregions. The selective involvement of von Economo neurons (VENs) in the anterior insula and astroglia was assessed in all groups. RESULTS: A decreasing gradient of α-synuclein pathology load from the anterior periallocortical agranular towards the intermediate dysgranular and posterior isocortical granular insular subregions was found. Few VENs revealed α-synuclein inclusions while astroglial synucleinopathy was a predominant feature in PDD and DLB. TH neurons were predominant in the agranular and dysgranular subregions but did not reveal α-synuclein inclusions or significant reduction in density in patient groups. CONCLUSIONS: Our study highlights the vulnerability of the anterior agranular insula to α-synuclein pathology in PD, PDD and DLB. Whereas VENs and astrocytes were affected in advanced disease stages, insular TH neurons were spared. Owing to the anterior insula's affective, cognitive and autonomic functions, its greater vulnerability to pathology indicates a potential contribution to nonmotor deficits in PD and DLB.

Anti-inflammatory effect by lentiviral-mediated overexpression of IL-10 or IL-1 receptor antagonist in rat glial cells and macrophages.

Neuroinflammation, as defined by activation of local glial cells and production of various inflammatory mediators, is an important feature of many neurological disorders. Expression of pro-inflammatory mediators produced by glial cells in the central nervous system (CNS) is considered to contribute to the neuropathology observed in those diseases. To diminish the production or action of pro-inflammatory mediators, we have used lentiviral (LV) vector-mediated encoding rat interleukin-10 (rIL-10) or rat interleukin-1 receptor antagonist (rIL-1ra) to direct the local, long-term expression of these anti-inflammatory cytokines in the CNS. We have shown that cultured macrophages or astroglia transduced with LV-rIL-10 or LV-rIL-1ra produced far less tumor necrosis factor (TNF)alpha or IL-6, respectively in response to pro-inflammatory stimuli. Moreover, intracerebroventricular (i.c.v.) administration of LV-rIL-10 or LV-rIL-1ra resulted in transduction of glial cells and macrophages and, subsequently reduced TNFalpha, IL-6 and inducible nitric oxide synthase (iNOS) expression in various brain regions induced by inflammatory stimuli, whereas peripheral expression of these mediators remained unaffected. In addition, expression levels of the anti-inflammatory cytokines IL-4 and transforming growth factor-beta were not altered in either brain or pituitary gland. Furthermore, i.c.v. administration of LV-rIL-10 or LV-rIL-1ra given during the remission phase of chronic-relapsing experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis, improved the clinical outcome of the relapse phase. Thus, local application of LV vectors expressing anti-inflammatory cytokines could be of therapeutic interest to counteract pro-inflammatory processes in the brain without interfering with the peripheral production of inflammatory mediators.

Anti-inflammatory cytokine gene therapy decreases sensory and motor dysfunction in experimental Multiple Sclerosis: MOG-EAE behavioral and anatomical symptom treatment with cytokine gene therapy.

Multiple Sclerosis (MS) is an autoimmune inflammatory disease that presents clinically with a range of symptoms including motor, sensory, and cognitive dysfunction as well as demyelination and lesion formation in brain and spinal cord. A variety of animal models of MS have been developed that share many of the pathological hallmarks of MS including motor deficits (ascending paralysis), demyelination and axonal damage of central nervous system (CNS) tissue. In recent years, neuropathic pain has been recognized as a prevalent symptom of MS in a majority of patients. To date, there have been very few investigations into sensory disturbances in animal models of MS. The current work contains the first assessment of hind paw mechanical allodynia (von Frey test) over the course of a relapsing-remitting myelin oligodendrocyte glycoprotein induced experimental autoimmune encephalomyelitis (MOG-EAE) rat model of MS and establishes the utility of this model in examining autoimmune induced sensory dysfunction. We demonstrate periods of both decreased responsiveness to touch that precedes the onset of hind limb paralysis, and increased responsiveness (allodynia) that occurs during the period of motor deficit amelioration traditionally referred to as symptom remission. Furthermore, we tested the ability of our recently characterized anti-inflammatory IL-10 gene therapy to treat the autoimmune inflammation induced behavioral symptoms and tissue histopathological changes. This therapy is shown here to reverse inflammation induced paralysis, to reduce disease associated reduction in sensitivity to touch, to prevent the onset of allodynia, to reverse disease associated loss of body weight, and to suppress CNS glial activation associated with disease progression in this model.

Mature astrocytes in the adult human neocortex express the early neuronal marker doublecortin.

Doublecortin (DCX) is a microtubule-associated protein expressed by migrating neuroblasts and is considered to be a reliable marker of neurogenesis. DCX has been used to study the relation between neurogenesis in adult human brain and neurological and neurodegenerative disease processes in the search for putative therapeutic strategies. Using autopsy and surgically resected tissue from a total of 60 patients, we present evidence that DCX is present in several cellular compartments of differentiated astrocytes in the adult human neocortex. One of these compartments consisted of peripheral processes forming punctate envelopes around mature neuronal cell bodies. Markers of glial activation, such as GFAP and HLA, were not associated with DCX immunoreactivity, however, the presence of cytoarchitectural alterations tended to correlate with reduced DCX staining of astrocytic somata. Interestingly, local Alzheimer pathology that showed no relation with cytoarchitectural abnormalities appeared to correlate negatively with the expression of DCX in the astrocytic somata. In combination with the literature our data support the view that DCX in the adult human neocortex may have a function in glia-to-neuron communication. Furthermore, our results indicate that in the adult human neocortex DCX is neither a reliable nor a selective marker of neurogenesis.

High cholesterol diet results in increased expression of interleukin-6 and caspase-1 in the brain of apolipoprotein E knockout and wild type mice.

Inflammation in the central nervous system is an early hallmark of many neurodegenerative diseases including Alzheimer's disease (AD). Recently, increasing evidence suggests that hypercholesterolemia during midlife and abnormalities in the cholesterol metabolism could have an important role in the pathogenesis of AD. In the present study, we have evaluated the effect of high cholesterol (HC) diet on the expression of interleukin-6 (IL-6), a cytokine involved in neurodegeneration, and caspase-1, that is responsible for the cleavage of the precursors of interleukin-1 beta (IL-1 beta) and interleukin-18 (IL-18) in the brain of apolipoprotein E (Apo E) knock-out (KO) and wild type (WT) mice. The density of IL-6-positive cells was increased in the hippocampus (p<0.0001) and the dorsal part of the cortex (p<0.001) of KO and WT mice on HC diet (KOHC and WTHC mice, respectively) compared to KO and WT mice on ND (KOND and WTND mice, respectively). KOHC mice had increased caspase-1 positive cells and staining intensity in the hippocampus in comparison with WTHC mice (p<0.01). In the hippocampus, the density of caspase-1 positive cells was also higher in KOHC compared to KOND mice (p<0.05) and KOHC compared with WTHC mice (p<0.01). There was a major increase in caspase-1 immunoreactivity and cell density in both the dosal part of the cortex (p<0.001) and the lateral part of the cortex (p<0.005) in KO and WT mice on HC diet compared to ND. The findings of the present study indicate that chronic exposure to HC diet increases the expression of the two important inflammatory mediators IL-6 and caspase-1 in the brain of KO and WT mice. In the case of caspase-1, we report a major difference in the effect of HC diet on the KO mice compared to WT mice in the hippocampus. Increased expression of inflammatory mediators involved in neurodegeneration could be a potential mechanism by which hypercholesterolemia and HC diet increase the risk of AD.

Nitric oxide synthase expression and apoptotic cell death in brains of AIDS and AIDS dementia patients.

OBJECTIVES: To determine the occurrence and cellular localization of inducible nitric oxide synthase (iNOS), NOS activity and its association with cell death in brains of AIDS and AIDS dementia complex (ADC) patients. DESIGN AND METHODS: Post-mortem cerebral cortex tissue of eight AIDS patients, eight ADC patients and eight control subjects was processed for iNOS immunocytochemistry, NADPH-diaphorase activity staining as an index of NOS activity, and in situ end-labelling to detect cell death. RESULTS: iNOS-positive cells were present in the white matter of 14 out of 16 AIDS and ADC patients, whereas two out of eight control subjects showed iNOS-positive cells. iNOS immunoreactivity was exclusively localized in activated macrophages and microglial cells that both showed NADPH-diaphorase activity. In addition, NADPH-diaphorase activity, not related to iNOS immunoreactivity, was observed in astrocytes in both white and grey matter of AIDS and ADC patients. All AIDS and ADC patients, and only one control subject showed characteristic features of apoptotic cell death. CONCLUSIONS: Different forms of NOS are present in microglial cells and astrocytes of AIDS and ADC patients but are largely absent in control subjects. Although more NOS-expressing cells occur in ADC than in AIDS patients, apoptotic cell death was found in both patient groups to the same extent. We postulate that NO production in brains of AIDS patients results in cumulative cortical cell loss, which becomes neurologically evident at later stages of disease and is expressed as ADC.

Demonstration of interleukin-1 beta in Lewis rat brain during experimental allergic encephalomyelitis by immunocytochemistry at the light and ultrastructural level.

Interleukin-1 beta (IL-1) is a cytokine which exerts many biological effects during inflammation. In the present study, experimental allergic encephalomyelitis (EAE) was induced in Lewis rats. During the various stages of EAE, the presence of IL-1 in the brain was investigated using immunocytochemistry at both the light and ultrastructural level. Ten days after immunization, IL-1 immunoreactivity was found in brains of animals which at this time showed mild clinical signs. Outside the blood-brain barrier, IL-1 was localized in the cytoplasm of meningeal macrophages and perivascular cells. Within the brain parenchyma, IL-1 immunoreactivity was distributed in perivascular lesions in the cytoplasm of infiltrated macrophages and activated microglia. On day 13, animals had developed a full blown EAE. At this stage the number of lesions with IL-1-positive cells had increased. In the remission phase (day 25), lesions with IL-1-positive cells could still be detected but were less pronounced as compared to day 13. Other presumptive IL-1-producing cell types like endothelial cells or astrocytes were, at none of the various stages, found to stain for IL-1.

Induction of immunoreactive interleukin-1 beta and tumor necrosis factor-alpha in the brains of rabies virus infected rats.

Interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF alpha) are important cytokines in the development of brain inflammation during pathological process. During rabies virus infection, the level of these proinflammatory cytokines are enhanced in the brain. In the present study we determined the cellular localization of these two cytokines by immunocytochemistry in brains of rats infected with rabies virus, at different time-intervals of the disease (day 1, 3, 4, 5 and at final stage day 6 post-infection (p.i.)). Cellular identification of IL-1 beta (irIL-1 beta) and TNF alpha (irTNF alpha) immunopositive cells was studied using a polyclonal antibody against these cytokines and against glial fibrillary acidic protein (GFAP) to detect astrocytes and GSA-I-B4 isolectin to detect microglial cells and/or infiltrating macrophages. In brains of control and early infected rats, irIL-1 beta was only detected in fibers located in the hypothalamus, supraoptic and tractus optic nuclei and infundibular nucleus. From day 4 onwards until day 6 p.i., enhanced irIL-1 beta was found and identified either in activated ameboid and/or infiltrated macrophages (amygdala, thalamus, internal capsula, subtantia nigra, septal nuclei and around blood vessels), or in activated ramified cells (hypothalamus and periventricular nucleus, piriformis and cingulate cortex, hippocampus). IrTNF alpha was observed in the brains of rats at a final stage of disease (day 5 and 6 p.i.): in the hypothalamus, the amygdala, the internal capsula, the thalamus, the septal nuclei, the hippocampus, the habenular nuclei and around the blood vessels. Ir-TNF alpha was detected in round cells identified as ameboid microglia and/or infiltrated macrophages. A marked activation of microglial and astroglial cells was observed mainly in the hypothalamus, the thalamus and hippocampus and around the blood vessels, at day 4 p.i. and later, revealing a high central inflammatory reaction in brains of rabies virus infected rats. These results showed that IL-1 beta and TNF alpha are produced in the brain both by local microglial cells and infiltrating macrophages during rabies infection. Thus, these cytokines may play an important role in coordinating the dramatic inflammatory response associated with the rabies-encephalopathy as well as in the neural modification and alteration of brain functions.

Eicosanoid production by rat cerebral endothelial cells: stimulation by lipopolysaccharide, interleukin-1 and interleukin-6.

The capacity of rat cerebral endothelial cells (RCEC) to form eicosanoids was determined after incubation with 14C-labelled arachidonic acid. Prostaglandin E2 (PGE2) was the main metabolite formed by RCEC and was responsible for 54% of the total amount of eicosanoids produced. In contrast, in primary cultures of rat aorta endothelial cells, 32% of the amount of prostaglandins was 6-keto-PGF1 alpha). RCEC treated with 50 ng/ml LPS for 24 h responded with an augmented PGE2 synthesis and 6-keto-PGF1 alpha of 3.4-fold and 2.2-fold, respectively. Cultures treated with IL-1 beta (50 ng/ml) for 3 h showed a stimulation of the release of PGE2 and 6-keto-PGF1 alpha of 2.5- and 4.5-fold, respectively, and 2.0-fold and 2.3-fold, respectively, after IL-6 (50 ng/ml) incubation for 3 h. PGE2 is the main eicosanoid formed by RCEC in response to inflammatory agents, suggesting an important role of the cerebral endothelial cells in the transduction of an inflammatory response in the central nervous system.

Expression of interleukin-1 beta in rat dorsal root ganglia.

The expression of interleukin-1beta was examined in dorsal root ganglion (DRG) neurons from adult rats using non-radioactive in situ hybridization and immunocytochemistry. At all spinal levels, approximately 70% of the DRG neurons appeared to express IL-1beta mRNA; about 80% of these DRG neurons actually appeared to produce the IL-1beta protein at markedly varying levels. The expression of IL-1beta was found in large as well as in intermediate diameter sensory neurons but only sporadically in the population of small sensory neurons. The population of IL-1beta immunopositive sensory neurons included most of the large calretinin-positive Ia afferents, but only a few of the small substance P/CGRP positive sensory neurons. In situ hybridization staining for the detection of type 1 IL-1 receptor showed expression of this receptor by most of the sensory neurons as well as by supportive glial-like cells, presumably satellite cells. The functional significance of IL-1beta in the DRG neurons needs to be elucidated, but we speculate that IL-1beta produced by DRG neurons may be an auto/paracrine signalling molecule in sensory transmission.

Co-localization of interleukin-1 receptor type I and interleukin-1 receptor antagonist with vasopressin in magnocellular neurons of the paraventricular and supraoptic nuclei of the rat hypothalamus.

Interleukin-1 receptor type I and interleukin-1 receptor antagonist were found in magnocellular neurons of the paraventricular and supraoptic nuclei of the rat hypothalamus by immunohistochemical detection. Double-labelling experiments revealed that both proteins occurred in vasopressin-containing neurons. A similar distribution pattern was observed in a group of vasopressin-positive accessory magnocellular neurons. Axons emanating from the interleukin-1 receptor type I- and interleukin-1 receptor antagonist-immunoreactive neuronal cell bodies could be seen within the hypothalamic nuclei, and varicosities expressing interleukin-1 receptor antagonist immunoreactivity were observed in the internal zone of the median eminence, as well as in the hypothalamo-pituitary projection. The co-localization of interleukin-1 receptor type I with vasopressin is in agreement with findings that interleukin-1 has a stimulatory effect on vasopressin synthesis and release. The hypothalamic neurons may serve as a source of interleukin-1 receptor antagonist to balance the effects of interleukin-1.

Endotoxin-induced appearance of immunoreactive interleukin-1 beta in ramified microglia in rat brain: a light and electron microscopic study.

Interleukin-1 plays an important role as mediator of endotoxin-induced responses in the brain such as fever, sleep, anorexia, behavioural and neuroendocrine changes. In the present study, interleukin-1 beta immunocytochemistry has been performed at the light and electron microscopic level to study the cellular and subcellular localization of interleukin-1 beta in the brains of rats given endotoxin or saline. Light microscopic analysis of rats killed 4, 8 or 24h after endotoxin (2.5 mg/kg) given intraperitoneally or intravenously revealed a region-specific localization of immunoreactive interleukin-1 beta in macrophages and microglial cells. After saline treatment, no induction of interleukin-1 beta immunoreactivity occurred in the brain. After administration of endotoxin, many interleukin-1 beta-positive cells were found in the meninges, choroid plexus, circumventricular organs, cerebral cortex and hypothalamus. The number of interleukin-1 beta-positive microglial cells reached a maximum 8 h after administration of endotoxin, irrespective of the route of administration. In general, more interleukin-1 beta-positive microglial cells were found after intravenous than after intraperitoneal administration of endotoxin. Interleukin-1 beta-positive microglial cells were often grouped in patches in the vicinity of blood vessels. At the surface of the cerebral cortex, in the meninges, intermediate cell forms between interleukin-1 beta-positive macrophages and microglial cells were found. interleukin-1 beta-positive perivascular microglia were localized at the brain side of the basal lamina. Immunoreactive interleukin-1 beta was found at the luminal side of the endothelial cells lining the venules. Furthermore, microglial cells that extended their processes into the ependymal layer of the third ventricle were observed. Results of the electron microscopic studies revealed immunoreactive interleukin-1 beta in many cells with the cellular characteristics of microglial cells, but also, in some cells, identified as astrocytes. In microglial cells, immunoreactive interleukin-1 beta was found in the cytoplasm but not in the endoplasmatic reticulum or Golgi apparatus. These results show that after peripheral administration of endotoxin, immunoreactive interleukin-1 beta is induced in macrophages in the meninges and in the choroid plexus, as well as in microglial cells in parenchyma. Interleukin-1 beta produced by these cells may serve as a signal for adjacent or more distant targets (neurons, endothelial cells, microglial cells) to play a role in the induction of non-specific symptoms of sickness.

Immunohistochemical localization of interleukin-1beta, interleukin-1 receptor antagonist and interleukin-1beta converting enzyme/caspase-1 in the rat brain after peripheral administration of kainic acid.

The temporal and anatomical distribution of members of the interleukin-1 system in the rat brain following intraperitoneal kainic acid administration was studied in relation to neurodegeneration as detected with in situ end labelling. Kainic acid administration (10 mg/kg, i.p.) resulted in the induced expression of interleukin-1beta, interleukin- receptor antagonist and caspase-1p10 immunoreactivity in areas known to display neuronal and tissue damage upon excitotoxic lesions. The induction of these proteins was transient. Interleukin-1 immunoreactivity appeared at 5 h, and the interleukin-1 receptor antagonist-immunoreactive cells were first detected at 12 h, whereas the induction of caspase- 1p10 expression was first detected 24 h after kainic acid injection. Double labelling with the microglial marker Ox42 confirmed that both interleukin-1beta and interleukin-1 receptor antagonist were mainly localized in microglial cells. The regional distribution of in situ end-labelled neurons was similar to the distribution of cells expressing interleukin-1beta and interleukin-1 receptor antagonist, whereas the distribution of caspase-1 was more limited. The in situ end-labelled neurons, were, similarly to the interleukin-1beta-positive cells, first detected at 5 h, which is earlier than the induction of caspase-1. Our results show that the induction of IL-1beta and IL-1 receptor antagonist proteins after kainic acid are closely associated with the temporal as well as the anatomical distribution of in situ end-labelled neurons, whereas the induction of caspase-1 protein exhibited a delayed temporal profile and limited distribution. Since cytokine production occurs in activated microglial cells, the inflammatory component seems to be a strong mediator of this type of excitotoxic damage. The late onset of the caspase-1 expression would seem to indicate that this enzyme has no fundamental role in directly causing neuronal cell death induced by systemic kainic acid.

Peripheral macrophage depletion prevents down regulation of central interleukin-1 receptors in mice after endotoxin administration.

Interleukin-1 receptors (IL-1R) have been characterized in the brain and pituitary gland of mice. Previous studies have demonstrated that following lipopolysaccharide (LPS) injection, IL-1R density decreases in the dentate gyrus and in the choroid plexus. Receptors present in the anterior pituitary gland remain unchanged under the same experimental conditions. In this study, we investigated the role of peripheral macrophages in LPS-induced downregulation of IL-1 receptors. Mice were injected with liposomes encapsulated with dichloromethylene diphosphonate (Cl2MDP), which induced a profound depletion of peripheral macrophages. Immunocytochemistry was used to determine the efficiency of macrophage elimination. Depletion of macrophages did not affect the density of central and pituitary IL-1R in non-LPS-challenge mice. However, the liposome treatment prevented downregulation of IL-1R in the dentate gyrus observed following LPS administration. In addition, LPS induced a slight decrease in IL-1R density in the choroid plexus but not in the anterior pituitary gland of liposome treated mice. These results suggest that peripheral macrophages play an important role in the LPS-induced modulation of central IL-1R.

Activation of the hypothalamus-pituitary-adrenal axis by bacterial endotoxins: routes and intermediate signals.

Peripheral administration of endotoxin induces brain-mediated responses, including activation of the hypothalamus-pituitary-adrenal (HPA) axis and changes in thermoregulation. This paper reviews the mechanisms by which endotoxin affects these responses. The effects on thermoregulation are complex and include macrophage-dependent hyperthermic and hypothermic responses. Low doses of endotoxin, given IP, activate peripheral macrophages to produce interleukin (IL)-1 beta, which enters the circulation and acts as a hormonal signal. IL-1 may pass fenestrated endothelium in the median eminence to stimulate corticotropin-releasing hormone (CRH) secretion from the CRH nerve-terminals. In addition, IL-1 may activate brain endothelial cells to produce IL-1, IL-6, prostaglandins, etc., and secrete these substances into the brain. By paracrine actions, these substances may affect neurons (e.g., CRH neurons) or act on microglial cells, which show IL-1-induced IL-1 production and therefore amplify and prolong the intracerebral IL-1 signal. In contrast, high doses of endotoxin given i.v. may directly stimulate endothelial cells to produce IL-1, IL-6, and prostaglandin-E2 (PGE2) and thereby activate the HPA axis in a macrophage-independent manner.

Effects of peripheral administration of LPS on the expression of immunoreactive interleukin-1 alpha, beta, and receptor antagonist in rat brain.

The cytokine interleukin-1 (IL-1) appears to play a pivotal role in the orchestration of brain-mediated, nonspecific illness symptoms during an infection. In the present study, we examine the possibility that IL-1 is produced in the central nervous system itself, which may be responsible for the induction of brain-mediated responses. Using immunocytochemical techniques, we demonstrated that peripheral administration of bacterial endotoxin to rats caused a time- (1.5-24 hr) and dose-dependent (4 micrograms/kg-2.5 mg/kg) induction of IL 1 beta immunoreactivity in cells identified as macrophages in meninges and choroid plexus and microglial cells in various brain regions. At 8 hr after endotoxin (2.5 mg/kg), immunoreactive IL-1 alpha was observed in the same areas and cell types as IL-1 beta. Although no quantitative measurements have been performed, it appears that fewer cells express immunoreactive IL-1 alpha than IL-1 beta. Furthermore, IL-1ra was found to be constitutively expressed in neurons in the paraventricular nucleus and supraoptic nucleus, which is in accordance with mRNA data. After administration of endotoxin, we observed no additional cells that expressed immunoreactive IL-1ra. We conclude that IL-1 alpha and IL-1 beta production in the brain is induced in the same cell types, whereas IL-1ra is expressed constitutively by a different cell type--probably neurons.

Individual variation in hypothalamus-pituitary-adrenal responsiveness of rats to endotoxin and interleukin-1 beta.

Intraperitoneal (i.p.) administration of lipopolysaccharide (LPS) or interleukin (IL)-1 beta induces activation of the hypothalamus-pituitary-adrenal (HPA) axis. In some experiments, a marked individual variation has been observed in HPA responses to these stimuli. We reasoned that only parameters that correlate with this variability may reflect signals involved in HPA activation. Although IL-1 beta is found in the peritoneal cavity and has been implicated in the HPA response to i.p. LPS, IL-1 beta levels in peritoneal lavage fluid did not correlate with the variation in HPA responsiveness and neither did IL-1 beta concentrations in plasma. In contrast, IL-6 concentrations in plasma, but not in peritoneal lavage fluid, correlated with this variation to i.p. LPS or IL-1 beta. We conclude that IL-6 in the plasma represents a major determinant of the individual variation in HPA responses to i.p. LPS or IL-1 beta. Because of its positive correlation with Fos expression in various brain-stem nuclei, we suggest that circulating IL-6 may facilitate the generation of signals in vagal afferents or potentiate vagal information transfer to lower brain-stem nuclei.

Appearance of interleukin-1 in macrophages and in ramified microglia in the brain of endotoxin-treated rats: a pathway for the induction of non-specific symptoms of sickness?

The presence and cellular localization of interleukin-1 beta immunoreactivity (irIL-1) in and around the brain was investigated using immunocytochemistry on Bouin's fixed vibratome brain sections of control and endotoxin-treated rats. Peripheral administration of endotoxin resulted in the appearance of irIL-1 in cells in the meninges, choroid plexus, brain blood vessels and in non-neuronal cells in the brain parenchyma. Using monoclonal and polyclonal antibodies to macrophage and astrocyte antigens, the endotoxin-induced irIL-1 positive cells could be identified as macrophages in the meninges and choroid plexus (ED2), perivascular cells (ED2) and ramified microglial cells (GSA-I-B4 isolectin). Our data demonstrate a pathway for the induction of non-specific sickness symptoms in response to endotoxin.

Distribution of interleukin 1 beta immunoreactivity within the porcine hypothalamus.

The presence and localization of interleukin 1 beta immunoreactivity (IL 1 beta i.r.) was studied in the hypothalamus of four healthy, male pigs at 7 months of age, using immunocytochemical techniques on 100 mu vibratome and 10 mu paraffin sections. IL 1 beta i.r. was found in neuronal cell bodies and their processes within nuclei and fiber tracts of the hypothalamus as well as in varicose fibers, terminals and deposits within the median eminence. In addition, IL 1 beta i.r. was found in the walls of several, but not all, blood vessels and in very few glial cells.

Immunocytochemical detection of prostaglandin E2 in microvasculature and in neurons of rat brain after administration of bacterial endotoxin.

The aim of the present study was to identify the site of prostaglandin E2 (PGE2) production in the brain in response to a pyrogenic dose of endotoxin. The presence of PGE2 was detected using immunocytochemistry on Bouin's fixed vibratome sections of control and endotoxin-treated rats. Peripheral administration of endotoxin caused a time-related stimulation of PGE2 immunoreactivity (irPGE2) in the choroid plexus and in the microvasculature of the brain. In addition to these sites, hypophysiotrophic neurons of the paraventricular nucleus (PVN) and supraopticus nucleus (SON) responded with induction of irPGE2 to endotoxin administration. Our data demonstrate that alterations in brain function in response to endotoxin may involve arachidonic metabolites such as PGE2 that are induced at the blood-brain barrier (microvasculature) and blood-liquor barrier (choroid plexus) and in hypophysiotrophic neurons of the rat brain.