Neural control of immune cell trafficking.

Leukocyte trafficking between blood and tissues is an essential function of the immune system that facilitates humoral and cellular immune responses. Within tissues, leukocytes perform surveillance and effector functions via cell motility and migration toward sites of tissue damage, infection, or inflammation. Neurotransmitters that are produced by the nervous system influence leukocyte trafficking around the body and the interstitial migration of immune cells in tissues. Neural regulation of leukocyte dynamics is influenced by circadian rhythms and altered by stress and disease. This review examines current knowledge of neuro-immune interactions that regulate leukocyte migration and consequences for protective immunity against infections and cancer.

Prurigo nodularis: Pathogenesis and management.

Prurigo nodularis is a chronic skin condition characterized by severely pruritic nodules that cause a profound negative impact on quality of life. The second article in this 2-part continuing medical education series focuses on reviewing the pathogenesis of prurigo nodularis and exploring management algorithms for this condition. In addition, we discuss some emerging and novel therapies for treating prurigo nodularis. The first article in this 2-part series describes the broader epidemiology, patient demographics, physical examination findings, and symptoms to aid in the timely recognition and diagnosis of prurigo nodularis.

Crosstalk between the immune system and neural pathways in interstitial cystitis/bladder pain syndrome.

Interstitial Cystitis/Bladder Pain Syndrome (IC/BPS) is a condition causing intense pelvic pain and urinary symptoms. While it is thought to affect millions of people and significantly impair quality of life, difficulty with diagnosis and a lack of reliably effective treatment options leave much progress to be made in managing this condition. We describe what is currently known about the immunological and neurological basis of this disease, focusing on the interactions between the immune and nervous system. Evidence for immune involvement in IC/BPS comes from its high co-occurrence with known autoimmune diseases, altered cytokine profiles, and immune cell infiltration in patients. These cytokines have the ability to cross-talk with the nervous system via NGF signaling, resulting in hyper-sensitization of pain receptors, causing them to release substance P and creating a positive feedback loop of neuroinflammation. While it seems that the crosstalk between the immune and nervous system in IC is understood, much of the information comes from studying other diseases or from animal models, and it remains to be confirmed in patients with the disease. Identifying biomarkers and confirming the mechanism of IC/BPS are ultimately important for selecting drug targets and for improving the lives of patients with this disease.

Central neural activation following contact sensitivity peripheral immune challenge: evidence of brain-immune regulation through C fibres.

This study tested the hypothesis that peripheral immune challenges will produce predictable activation patterns in the rat brain consistent with sympathetic excitation. As part of examining this hypothesis, this study asked whether central activation is dependent on capsaicin-sensitive C-fibres. We induced skin contact sensitivity immune responses with 2,4-dinitrochlorobenzene (DNCB), in the presence or absence of the acute C-fibre toxin capsaicin (8-methyl-N-vanillyl-6-nonenamide) to trigger immune responses with and without diminished activity of C-fibres. Innovative blood-oxygen-level-dependent functional magnetic resonance imaging data revealed that the skin contact sensitivity immune responses induced with DNCB were associated with localized increases in brain neuronal activity in treated rats. This response was diminished by pre-treatment with capsaicin 1 week before scans. In the same animals, we found expression of the immediate early gene c-Fos in sub-regions of the amygdala and hypothalamic sympathetic brain nuclei. Significant increases in c-Fos expression were found in the supraoptic nucleus, central amygdala and medial habenula following immune challenges. Our results support the idea that selective brain regions, some of which are associated with sympathetic function, process or modulate immune function through pathways that are partially dependent on C-fibres. Together with previous studies demonstrating the motor control pathways from brain to immune targets, these findings indicate a central neuroimmune system to monitor host status and coordinate appropriate host responses.

Neuronal α1/2-adrenergic stimulation of IFN-γ, IL-6, and CXCL-1 in murine spleen in late experimental arthritis.

OBJECTIVE: Functional cross-talk exists between sympathetic nerve fibers and cytokine-producing splenic cells in early collagen type II-induced arthritis (CIA) (day 32). These earlier experiments demonstrated exclusively neuronal sympathetic regulation of IFN-γ, CXCL1, IL-6, and TGF-ß. However, in late arthritis, the sympathetic influence might change due to loss of sympathetic nerve fibers and appearance of neurotransmitter-producing cells. We aimed to investigate neurotransmitter-dependent regulation of IFN-γ, CXCL1, IL-6, and TGF-ß in murine spleen in late CIA. METHODS: Spleens were removed when animals reached day 58 (46-68) after immunization to generate 0.35 mm-thick spleen slices, which were transferred to superfusion microchambers to electrically induce release of neurotransmitters. Using respective neurotransmitter antagonists, effects of released neurotransmitters on cytokine secretion were investigated. RESULTS: There was electrically induced inhibition of IFN-γ, CXCL1, and IL-6, and stimulation of TGF-ß, which was much less pronounced than in early CIA. There existed ß adrenergic inhibition of IFN-γ, IL-6, and TGF-ß (and stimulation of CXCL1) independent of electrical stimulation (interpreted as non-neuronal). However, there was a neuronal α1/2 adrenergic stimulation of IFN-γ, CXCL1, and IL-6 and, we observed neuronal A1-adenosinergic stimulation of TGF-ß. CONCLUSIONS: In the late phase of CIA, non-neuronal modulation of cytokine secretion increases while neuronal regulation strikingly decreases. Particularly, ß-adrenergic effects are non-neuronal while α1/2-adrenergic effects are clearly neuronal. We suggest that alterations in sympathetic innervation of the spleen fundamentally change the functional neuroimmune interplay in the spleen of arthritic mice.

Ventral tegmental area-basolateral amygdala-nucleus accumbens shell neurocircuitry controls the expression of heroin-conditioned immunomodulation.

The present investigations sought to determine whether the ventral tegmental area (VTA), basolateral amygdala (BLA), and nucleus accumbens shell (NAC) comprise a circuitry that mediates heroin-induced conditioned immunomodulation. Rats were given conditioning trials in which they received an injection of heroin upon placement into a distinctive environment. Prior to testing, rats received unilateral intra-BLA microinfusion of a D(1) antagonist concomitantly with unilateral intra-NAC shell microinfusion of an NMDA antagonist. Disconnection of the VTA-BLA-NAC circuit impaired the ability of the heroin-paired environment to suppress lipopolysaccharide-induced immune responses, defining for the first time a specific neural circuit involved in conditioned neural-immune interactions.

Ascending caudal medullary catecholamine pathways drive sickness-induced deficits in exploratory behavior: brain substrates for fatigue?

Immune challenges can lead to marked behavioral changes, including fatigue, reduced social interest, anorexia, and somnolence, but the precise neuronal mechanisms that underlie sickness behavior remain elusive. Part of the neurocircuitry influencing behavior associated with illness likely includes viscerosensory nuclei located in the caudal brainstem, based on findings that inactivation of the dorsal vagal complex (DVC) can prevent social withdrawal. These brainstem nuclei contribute multiple neuronal projections that target different components of autonomic and stress-related neurocircuitry. In particular, catecholaminergic neurons in the ventrolateral medulla (VLM) and DVC target the hypothalamus and drive neuroendocrine responses to immune challenge, but their particular role in sickness behavior is not known. To test whether this catecholamine pathway also mediates sickness behavior, we compared effects of DVC inactivation with targeted lesion of the catecholamine pathway on exploratory behavior, which provides an index of motivation and fatigue, and associated patterns of brain activation assessed by immunohistochemical detection of c-Fos protein. LPS treatment dramatically reduced exploratory behavior, and produced a pattern of increased c-Fos expression in brain regions associated with stress and autonomic adjustments paraventricular hypothalamus (PVN), bed nucleus of the stria terminalis (BST), central amygdala (CEA), whereas activation was reduced in regions involved in exploratory behavior (hippocampus, dorsal striatum, ventral tuberomammillary nucleus, and ventral tegmental area). Both DVC inactivation and catecholamine lesion prevented reductions in exploratory behavior and completely blocked the inhibitory LPS effects on c-Fos expression in the behavior-associated regions. In contrast, LPS-induced activation in the CEA and BST was inhibited by DVC inactivation but not by catecholamine lesion. The findings support the idea that parallel pathways from immune-sensory caudal brainstem sources target distinct populations of forebrain neurons that likely mediate different aspects of sickness. The caudal medullary catecholaminergic projections to the hypothalamus may significantly contribute to brain mechanisms that induce behavioral "fatigue" in the context of physiological stressors.

Neuron-immune interactions in the sensitized thalamus induced by mustard oil application to rat molar pulp.

We have reported that mustard oil application to the rat dental pulp induces neuronal activation in the thalamus. To address the mechanisms involved in the thalamic changes, we performed neuronal responsiveness recording, immunohistochemistry, and molecular biological analysis. After mustard oil application, neuronal responsiveness was increased in the mediodorsal nucleus. When MK801 (an N-methyl-D-aspartate receptor antagonist) was applied to the mediodorsal nucleus, the enhanced responsiveness was decreased. N-methyl-D-aspartate receptor 2D, glial fibrillary acidic protein, and antigen-presenting cell-related gene mRNAs in the contralateral thalamus were up-regulated at 10 minutes after mustard oil application, but were down-regulated within 10 minutes after the antagonist application. OX6-expressing microglia and glial fibrillary acidic protein-expressing astrocytes did not increase until 60 minutes after mustard oil application. These results suggested that the thalamic neurons play some roles in regulating the glial cell activation in the mediodorsal nucleus via N-methyl-D-aspartate receptor 2D during pulp inflammation-induced central sensitization.

Nigral neurodegeneration triggered by striatal AdIL-1 administration can be exacerbated by systemic IL-1 expression.

Neuroinflammation has been proposed as an important component of Parkinson's Disease (PD) aetiology and/or progression. However, the inflammatory components and the mechanisms underlying their effects are only partially known. By injecting an adenovirus expressing IL-1 in the striatum, we provoked progressive neurodegeneration of dopaminergic cells in the substantia nigra, motor symptoms and microglial activation. All these effects were attenuated by an anti-inflammatory treatment. Interestingly, peripheral inflammatory stimuli exacerbated IL-1beta induced neurodegeneration and the central inflammatory reaction. These data provide evidence that central, chronic IL-1beta expression can trigger and systemic IL-1beta exacerbate nigral neurodegeneration and highlight the functional relevance of this cytokine in PD.

Immune challenge and satiety-related activation of both distinct and overlapping neuronal populations in the brainstem indicate parallel pathways for viscerosensory signaling.

Caudal brainstem viscerosensory nuclei convey information about the body's internal state to forebrain regions implicated in feeding behavior and responses to immune challenge, and may modulate ingestive behavior following immune activation. Illness-induced appetite loss might be attributed to accentuated "satiety" pathways, activation of a distinct "danger channel" separate from satiety pathways, or both. To evaluate neural substrates that could mediate the effects of illness on ingestive behavior, we analyzed the pattern and phenotypes of medullary neurons responsive to consumption of a preferred food, sweetened milk, and to intraperitoneal lipopolysaccharide challenge that reduced sweetened milk intake. Brainstem sections were stained for c-Fos, dopamine beta-hydroxylase, phenylethanolamine-N-methyltransferase, and glucagon-like peptide-1 (GLP-1) immunoreactivity. Sweetened milk intake activated many neurons throughout the nucleus of the solitary tract (NTS), including A2 noradrenergic neurons in the caudal half of the NTS. LPS challenge activated a similar population of neurons in the NTS, in addition to rostral C2 adrenergic and mid-level A2 noradrenergic neurons in the NTS, many C1 and A1 neurons in the ventrolateral medulla, and in GLP-1 neurons in the dorsal medullary reticular nucleus. Increased numbers of activated GLP-1 neurons in the NTS were only associated with sweetened milk ingestion. Evidence for parallel processing was reflected in the parabrachial nucleus, where sweetened milk intake resulted in activation of the inner external lateral, ventrolateral and central medial portions, whereas LPS challenge induced c-Fos expression in the outer external lateral portions. Thus, signals generated in response to potentially dangerous physiological conditions seem to be propagated via specific populations of catecholaminergic neurons in the NTS and VLM, and likely include a pathway through the external lateral PBN. The data indicate that immune challenge engages multiple ascending neural pathways including both a distinct catecholaminergic "danger" pathway, and a possibly multimodal pathway derived from the NTS.

Repeated administration of mirtazapine inhibits development of hyperalgesia/allodynia and activation of NF-kappaB in a rat model of neuropathic pain.

Antidepressants have been widely used to treat neuropathic pain for many years. However, the mechanisms of their analgesic actions are little known and remain controvertible. Recent studies indicate that cytokines in central nervous system (CNS) play a critical role in the pathological states of pain. The present study was designed to explore the effects and most appropriate dosage of mirtazapine in treating neuropathic pain and its possible neuroimmune mechanisms. L5 spinal nerve transection was done to produce hyperalgesia in rats. Mirtazapine (10, 20 and 30 mg/kg, respectively) was orally administered daily for 14 days, beginning from the 5th day after nerve transection. Mechanical and thermal hyperalgesia was measured using Von-Frey filament and Hargreaves tests before and after the surgery. Rats were then sacrificed on days 3, 7, 14, 21 post-administration. The inflammatory cytokines production such as TNFalpha, IL-1beta, IL-10 and nuclear factor kappa B (NF-kappaB) activity in brain was quantified using enzyme-linked immunosorbent assay (ELISA) and electrophoretic mobility shift assay (EMSA). We found that mirtazapine (20 and 30 mg/kg) can markedly attenuate mechanical and thermal hyperalgesia produced by nerve transection, most significantly on the 14th day. The elevated TNFalpha, IL-1beta and NF-kappaB in brain were accordingly reduced, while the expression of increased IL-10 were even stimulated after repeated mirtazapine administration. Our data could conclude that mirtazapine suppressed neuropathic pain partially through inhibiting cerebral proinflammatory cytokines production and NF-kappaB activation in CNS.

[Involvement of cerebellohypothalamic projections in the modulation of lymphocyte function by cerebellar fastigial nuclei].

AIM: To explore the effect of cerebellar fastigial nuclei (FN)on lymphocyte function and the pathway mediating the effect. METHODS: Kainic acid (KA) was microinjected into bilateral FN of rats to destroy neuronal bodies in the FN. On the eighth day after the surgery, lymphocyte percentage in the peripheral blood and level of sheep red blood cell(SRBC)-specific IgM antibody in the serum were measured by using blood corpuscle counter and enzyme-linked immunosorbent assay (ELISA), respectively.A technology of electrolytic lesion was used to destroy the projections of cerebellar FN neurons to hypothalamus in decussation of superior cerebellar peduncle(xscp). RESULTS: On the eighth day after the microinjection of KA into the bilateral FN of rats, the Nissl-stained neuronal bodies in the FN disappeared and glia could proliferated within the damaged FN. In the nuclei close to FN, the interposed nuclei and the dentate nuclei, Nissl-stained neurons still could be seen. On the control cerebellar sections, in which FN was infused with saline, we could see the normal Nissl-stained neurons in the FN and the other two nuclei.On day 8 following the effective FN lesions, both the lymphocyte percentage in the peripheral blood and the level of anti-SRBC IgM antibody in the serum were significantly increased in comparison with those of control rats infused with saline in the FN. On the eighth day after electrolytic lesion of the fibres in xscp, the FN-hypothalamic projections were damaged and there were no visible BDA-positive endings in hypothalamus. Meanwhile, both the lymphocyte percentage in the peripheral blood and the level of anti-SRBC IgM antibody in the serum were remarkably enhanced relative to those of control rats with sham lesion of xscp. CONCLUSION: The electrolytic lesion of the FN-hypothalamic projections in xscp causes an enhancement of lymphocyte function similar to that of KA lesions of neuronal soma in the FN. These findings suggest that the cerebellohypothalamic projections participate in mediating the modulation of lymphocyte function by the cerebellum.

Role of IFN-gamma in an experimental murine model of West Nile virus-induced seizures.

Seizures are a major complication of viral encephalitis. However, the mechanisms of seizure-associated neuronal dysfunction remain poorly understood. We report that intranasal inoculation with West Nile virus (WNV) (Sarafend) causes limbic seizures in C57BL/6 mice, but not in interferon (IFN)-gamma-deficient (IFN-gamma-/-) mice. Both strains showed similar levels of virus in the brain, as well as similar concentrations of the cytokines, tumor necrosis factor and interleukin-6, both of which can alter neuronal excitability. Experiments in chimeric IFN-gamma-/- mice reconstituted with IFN-gamma-producing leukocytes showed that IFN-gamma is not required during central nervous system infection for limbic seizure development, suggesting a role for IFN-gamma in the developing brain. This was supported responses to pentylenetetrazole, kainic acid (KA), and N-methyl-d-aspartate (NMDA). Both strains of mice exhibited similar behavior after pentylenetetrazole challenge. However, while NMDA and KA treatment resulted in characteristic seizures in C57BL/6 mice, these responses were diminished (NMDA treatment) or absent (KA treatment) in IFN-gamma-/- mice. Furthermore, NMDA-receptor blockade with MK-801 in WNV-infected C57BL/6 mice abrogated seizures and prolonged survival. Our data show that IFN-gamma plays an important role in the development of the excitatory seizure pathways in the brain and that these cascades become pathogenic in encephalitic WNV infection.

p53 protein, interferon-gamma, and NF-kappaB levels are elevated in the parkinsonian brain.

We and other workers found markedly increased levels of proinflammatory cytokines and apoptosis-related proteins in parkinsonian brain. Although the pathogenesis of Parkinson's disease (PD) remains enigmatic, apoptosis might be involved in the degeneration of dopaminergic neurons in PD. To investigate the possible presence of other inflammatory cytokines and/or apoptosis-related protein, the levels of p53 protein, interferon-gamma, and NF-kappaB were measured for the first time in the brain (substantia nigra, caudate nucleus, putamen, cerebellum, and frontal cortex) from control and parkinsonian patients by a highly sensitive sandwich enzyme-linked immunosorbent assay. The p53 protein level in the caudate nucleus was significantly higher in parkinsonian patients than in controls (P<0.05), whereas this protein in the substantia nigra, putamen, and cerebral cortex showed no significant difference between parkinsonian and control subjects. The interferon-gamma level was significantly higher in the nigrostriatal dopaminergic regions (substantia nigra, caudate nucleus, and putamen) in parkinsonian patients than in the controls (P<0.05), but was not significantly different in the cerebellum or frontal cortex between the two groups. In accordance with previous immunohistochemical analysis, the NF-kappaB level in the nigrostriatal dopaminergic regions was significantly higher in parkinsonian patients than in the controls (P<0.05). These data suggest that the significant increase in the levels of p53 protein, interferon-gamma, and NF-kappaB reflect apoptosis and the inflammatory state in the parkinsonian brain and that their elevation is involved in the degeneration of the nigrostriatal dopaminergic neurons.

Organization of immune-responsive medullary projections to the bed nucleus of the stria terminalis, central amygdala, and paraventricular nucleus of the hypothalamus: evidence for parallel viscerosensory pathways in the rat brain.

Immune-responsive neurons in the brainstem, primarily in the nucleus of the solitary tract (NTS) and ventrolateral medulla (VLM), contribute to a significant drive on forebrain nuclei responsible for brain-mediated host defense responses. The current study investigated the relative contribution of brainstem-derived ascending pathways to forebrain immune-responsive nuclei in the rat by means of retrograde tract tracing and c-Fos immunohistochemistry. Fluorogold was iontophoresed into the bed nucleus of stria terminalis (BST), central nucleus of the amygdala (CEA), paraventricular nucleus of the hypothalamus (PVN), and the pontine lateral parabrachial nucleus (PBL; an important component of ascending viscerosensensory pathways) followed 2 weeks later by intraperitoneal injection of lipopolysaccharide (LPS, 0.1 mg/kg) or saline. The NTS and VLM provide immune-responsive input to all four regions, via direct, predominantly catecholaminergic, projections to the PVN, the lateral BST, and the CEA, and mostly non-catecholaminergic projections to the PBL. The PBL provides a major LPS-activated input to the BST and CEA. The pattern of LPS-activated catecholaminergic projections from the VLM and NTS to the forebrain is characterized by a strong predominance of VLM input to the PVN, whereas the NTS provides a greater contribution to the BST. These findings indicate that direct and indirect pathways originate in the caudal brainstem that propagate immune-related information from the periphery with multiple levels of processing en route to the forebrain nuclei, which may allow for integration of brain responses to infection.

Orchiectomy for suspected microscopic tumor in patients with anti-Ma2-associated encephalitis.

OBJECTIVE: To report the presence of microscopic neoplasms of the testis in men with anti-Ma2-associated encephalitis (Ma2-encephalitis) and to discuss the clinical implications. METHODS: Orchiectomy specimens were examined using immunohistochemistry with Ma2 and Oct4 antibodies. RESULTS: Among 25 patients with Ma2-encephalitis younger than 50 years, 19 had germ-cell tumors, and 6 had no evidence of cancer. These 6 patients underwent orchiectomy because they fulfilled five criteria: 1) demonstration of anti-Ma2 antibodies in association with MRI or clinical features compatible with Ma2-encephalitis, 2) life-threatening or progressive neurologic deficits, 3) age < 50 years, 4) absence of other tumors, and 5) new testicular enlargement or risk factors for germ-cell tumors, mainly cryptorchidism or ultrasound evidence of testicular microcalcifications. All orchiectomy specimens showed intratubular-germ cell neoplasms unclassified type (IGCNU) and other abnormalities including microcalcifications, atrophy, fibrosis, inflammatory infiltrates, or hypospermatogenesis. Ma2 was expressed by neoplastic cells in three of three patients examined. Even though most patients had severe neurologic deficits at the time of orchiectomy (median progression of symptoms, 10 months), 4 had partial improvement and prolonged stabilization (8 to 84 months, median 22.5 months) and two did not improve after the procedure. CONCLUSIONS: In young men with Ma2-encephalitis, 1) the disorder should be attributed to a germ-cell neoplasm of the testis unless another Ma2-expressing tumor is found, 2) negative tumor markers, ultrasound, body CT, or PET do not exclude an intratubular germ-cell neoplasm of the testis, and 3) if no tumor is found, the presence of the five indicated criteria should prompt consideration of orchiectomy.

Neural-endocrine-immune complex in the central modulation of tumorigenesis: facts, assumptions, and hypotheses.

For the precise coordination of systemic functions, the nervous system uses a variety of peripherally and centrally localized receptors, which transmit information from internal and external environments to the central nervous system. Tight interconnections between the immune, nervous, and endocrine systems provide a base for monitoring and consequent modulation of immune system functions by the brain and vice versa. The immune system plays an important role in tumorigenesis. On the basis of rich interconnections between the immune, nervous and endocrine systems, the possibility that the brain may be informed about tumorigenesis is discussed in this review article. Moreover, the eventual modulation of tumorigenesis by central nervous system is also considered. Prospective consequences of the interactions between tumor and brain for diagnosis and therapy of cancer are emphasized.

Attenuated pseudorabies virus-evoked rapid innate immune response in the rat brain.

Ba-DupGreen (BDG) is a highly attenuated, Bartha-derived pseudorabies virus (PRV) expressing green fluorescent protein (GFP) with immediate-early kinetics. Innate immune mechanisms underlying the low infectivity of the virus and the disappearance of infected neurons from the brain were studied at cellular level following injection of BDG into the spleen. The temporal shift in the expression between GFP and viral structural proteins allowed us to discriminate three stages of viral infection in the compromised neurons in correlation with the ongoing local inflammatory response. Iba1/lectin/OX42-positive microglia were recruited to infected neurons within 4-6 h following the initiation of virus replication, incorporated BrdU, isolated the infected cells before the disintegration of their membranes and phagocytosed collapsed neurons. Ex vivo-labeled blood and bone marrow-derived leukocytes, including ED-1-positive macrophages were involved in the immune cell assembly around compromised neurons, which resulted in the complete clearance of infected neurons from the early-infected brain regions.