Structural and Clinical Correlates of a Periventricular Gradient of Neuroinflammation in Multiple Sclerosis.

OBJECTIVES: To explore in vivo innate immune cell activation as a function of the distance from ventricular CSF in patients with multiple sclerosis (MS) using [18F]-DPA714 PET and to investigate its relationship with periventricular microstructural damage, evaluated by magnetization transfer ratio (MTR), and with trajectories of disability worsening. METHODS: Thirty-seven patients with MS and 19 healthy controls underwent MRI and [18F]-DPA714 TSPO dynamic PET, from which individual maps of voxels characterized by innate immune cell activation (DPA+) were generated. White matter (WM) was divided in 3-mm-thick concentric rings radiating from the ventricular surface toward the cortex, and the percentage of DPA+ voxels and mean MTR were extracted from each ring. Two-year trajectories of disability worsening were collected to identify patients with and without recent disability worsening. RESULTS: The percentage of DPA+ voxels was higher in patients compared to controls in the periventricular WM (p = 6.10e-6) and declined with increasing distance from ventricular surface, with a steeper gradient in patients compared to controls (p = 0.001). This gradient was found in both periventricular lesions and normal-appearing WM. In the total WM, it correlated with a gradient of microstructural tissue damage measured by MTR (r s = -0.65, p = 1.0e-3). Compared to clinically stable patients, patients with disability worsening were characterized by a higher percentage of DPA+ voxels in the periventricular normal-appearing WM (p = 0.025). CONCLUSIONS: Our results demonstrate that in MS the innate immune cell activation predominates in periventricular regions and is associated with microstructural damage and disability worsening. This could result from the diffusion of proinflammatory CSF-derived factors into surrounding tissues.

MicroRNA-152 attenuates neuroinflammation in intracerebral hemorrhage by inhibiting thioredoxin interacting protein (TXNIP)-mediated NLRP3 inflammasome activation.

Neuroinflammation significantly contributes to brain injury and neurological deterioration following intracerebral hemorrhage (ICH). MicroRNA-152(miR-152) was reported to be downregulated in ICH patients and to possess anti-inflammatory properties in other diseases. In this study, we aimed to explore the role of miR-152 in ICH, and the underlying mechanisms, using a collagenase-induced rat ICH model and hemin-exposure as a cell model. We first confirmed that miR-152 was consistently downregulated in both models. Overexpression of miR-152 in microglial BV2 cells reduced hemin-induced inflammatory response and reactive oxygen species (ROS) generation, thus protecting co-cultured neuronal HT22 cells. Moreover, overexpression of miR-152 by intracerebroventricular lentivirus injection in ICH rats significantly alleviated neurodecifits, brain edema, and hematoma. These changes were associated with a marked reduction in ICH-induced neuronal death, as detected by co-staining of NeuN and TUNEL, and ICH-induced neuroinflammation, as revealed by inflammatory cytokine levels as well as by the number of Iba1 positive-stained cells in the perihematomal region. Mechanistically, miR-152 significantly inhibited ICH-induced TXNIP expression, and its overexpression blocked the interaction between TXNIP and NOD-like receptor pyrin domain containing 3(NLRP3), thus inhibiting NLRP3-driven inflammasome activation to attenuate neuroinflammation in vivo and in vitro. Moreover, the results of si-TXNIP transfection further confirmed that TXNIP inhibition was involved in the reduction of NLRP3 inflammasome activation by the overexpression of miR-152. Collectively, the present study demonstrates that miR-152 confers protection against ICH-induced neuroinflammation and brain injury by inhibiting TXNIP-mediated NLRP3 inflammasome activation, indicating a potential strategy for ICH treatment.

Orexin-A enhances feeding in male rats by activating hindbrain catecholamine neurons.

Both lateral hypothalamic orexinergic neurons and hindbrain catecholaminergic neurons contribute to control of feeding behavior. Orexin fibers and terminals are present in close proximity to hindbrain catecholaminergic neurons, and fourth ventricular (4V) orexin injections that increase food intake also increase c-Fos expression in hindbrain catecholamine neurons, suggesting that orexin neurons may stimulate feeding by activating catecholamine neurons. Here we examine that hypothesis in more detail. We found that 4V injection of orexin-A (0.5 nmol/rat) produced widespread activation of c-Fos in hindbrain catecholamine cell groups. In the A1 and C1 cell groups in the ventrolateral medulla, where most c-Fos-positive neurons were also dopamine ß hydroxylase (DBH) positive, direct injections of a lower dose (67 pmol/200 nl) of orexin-A also increased food intake in intact rats. Then, with the use of the retrogradely transported immunotoxin, anti-DBH conjugated to saporin (DSAP), which targets and destroys DBH-expressing catecholamine neurons, we examined the hypothesis that catecholamine neurons are required for orexin-induced feeding. Rats given paraventricular hypothalamic injections of DSAP, or unconjugated saporin (SAP) as control, were implanted with 4V or lateral ventricular (LV) cannulas and tested for feeding in response to ventricular injection of orexin-A (0.5 nmol/rat). Both LV and 4V orexin-A stimulated feeding in SAP controls, but DSAP abolished these responses. These results reveal for the first time that catecholamine neurons are required for feeding induced by injection of orexin-A into either LV or 4V.

Signaling through three chemokine receptors triggers the migration of transplanted neural precursor cells in a model of multiple sclerosis.

Multiple sclerosis (MS) is a multifocal disease, and precursor cells need to migrate into the multiple lesions in order to exert their therapeutic effects. Therefore, cell migration is a crucial element in regenerative processes in MS, dictating the route of delivery, when cell transplantation is considered. We have previously shown that inflammation triggers migration of multi-potential neural precursor cells (NPCs) into the white matter of experimental autoimmune encephalomyelitis (EAE) rodents, a widely used model of MS. Here we investigated the molecular basis of this attraction. NPCs were grown from E13 embryonic mouse brains and transplanted into the lateral cerebral ventricles of EAE mice. Transplanted NPC migration was directed by three tissue-derived chemokines. Stromal cell-derived factor-1α, monocyte chemo-attractant protein-1 and hepatocyte growth factor were expressed in the EAE brain and specifically in microglia and astrocytes. Their cognate receptors, CXCR4, CCR2 or c-Met were constitutively expressed on NPCs. Selective blockage of CXCR4, CCR2 or c-Met partially inhibited NPC migration in EAE brains. Blocking all three receptors had an additive effect and resulted in profound inhibition of NPC migration, as compared to extensive migration of control NPCs. The inflammation-triggered NPC migration into white matter tracts was dependent on a motile NPC phenotype. Specifically, depriving NPCs from epidermal growth factor (EGF) prevented the induction of glial commitment and a motile phenotype (as indicated by an in vitro motility assay), hampering their response to neuroinflammation. In conclusion, signaling via three chemokine systems accounts for most of the inflammation-induced, tissue-derived attraction of transplanted NPCs into white matter tracts during EAE.

Neuro-immune interactions in the postnatal ventricular-subventricular zone.

As described in this book, the interaction between the immune system and the brain can affect multiple cerebral functions, such as: neural remodeling, synaptic plasticity or neurotransmitter releasing. Neurogenic niches are not the exception, in fact, pro-inflammatory cytokines and chemokines exert a strong regulation in neural stem cells (NSCs) of the ventricular-subventricular zone (V-SVZ) by interacting with cell membrane receptors and activating multiple downstream pathways. These neuro-immune interactions modulate quiescence, cell adhesion, migration, self-renewal, differentiation, cytoskeletal rearrangement, and cell survival. In this chapter, we describe the cellular composition and cytoarchitecture of the main neurogenic niche in the adult mammalian brain: the V-SVZ. We also discuss the current evidence indicating that many immunological molecules can control the function of this neurogenic niche in the adult brain under both physiological and pathological conditions.

Potential roles of HDAC inhibitors in mitigating ischemia-induced brain damage and facilitating endogenous regeneration and recovery.

Ischemic stroke is a leading cause of death and disability worldwide, with few available treatment options. The pathophysiology of cerebral ischemia involves both early phase tissue damage, characterized by neuronal death, inflammation, and blood-brain barrier breakdown, followed by late phase neurovascular recovery. It is becoming clear that any promising treatment strategy must target multiple points in the evolution of ischemic injury to provide substantial therapeutic benefit. Histone deacetylase (HDAC) inhibitors are a class of drugs that increase the acetylation of histone and non-histone proteins to activate transcription, enhance gene expression, and modify the function of target proteins. Acetylation homeostasis is often disrupted in neurological conditions, and accumulating evidence suggests that HDAC inhibitors have robust protective properties in many preclinical models of these disorders, including ischemic stroke. Specifically, HDAC inhibitors such as trichostatin A, valproic acid, sodium butyrate, sodium 4-phenylbutyrate, and suberoylanilide hydroxamic acid have been shown to provide robust protection against excitotoxicity, oxidative stress, ER stress, apoptosis, inflammation, and bloodbrain barrier breakdown. Concurrently, these agents can also promote angiogenesis, neurogenesis and stem cell migration to dramatically reduce infarct volume and improve functional recovery after experimental cerebral ischemia. In the following review, we discuss the mechanisms by which HDAC inhibitors exert these protective effects and provide evidence for their strong potential to ultimately improve stroke outcome in patients.

Japanese encephalitis virus induce immuno-competency in neural stem/progenitor cells.

BACKGROUND: The low immunogenicity of neural stem/progenitor cells (NSPCs) coupled with negligible expression of MHC antigens has popularized their use in transplantation medicine. However, in an inflammatory environment, the NSPCs express costimulatory molecules and MHC antigens, and also exhibit certain immunomodulatory functions. Since NSPCs are the cellular targets in a number of virus infections both during postnatal and adult stages, we wanted to investigate the immunological properties of these stem cells in response to viral pathogen. METHODOLOGY/PRINCIPAL FINDINGS: We utilized both in vivo mouse model and in vitro neurosphere model of Japanese encephalitis virus (JEV) infection for the study. The NSPCs residing in the subventricular zone of the infected brains showed prominent expression of MHC-I and costimulatory molecules CD40, CD80, and CD86. Using Flow cytometry and fluorescence microscopy, we observed increased surface expression of co-stimulatory molecule and MHC class I antigen in NSPCs upon progressive JEV infection in vitro. Moreover, significant production of pro-inflammatory cyto/chemokines was detected in JEV infected NSPCs by Cytokine Bead Array analysis. Interestingly, NSPCs were capable of providing functional costimulation to allogenic T cells and JEV infection resulted in increased proliferation of allogenic T cells, as detected by Mixed Lymphocyte reaction and CFSE experiments. We also report IL-2 production by NSPCs upon JEV infection, which possibly provides mitogenic signals to T cells and trigger their proliferation. CONCLUSION/SIGNIFICANCE: The in vivo and in vitro findings clearly indicate the development of immunogenicity in NSPCs following progressive JEV infection, in our case, JEV infection. Following a neurotropic virus infection, NSPCs possibly behave as immunogenic cells and contribute to both the innate and adaptive immune axes. The newly discovered immunological properties of NSPCs may have implications in assigning a new role of these cells as non-professional antigen presenting cells in the central nervous system.

Anti-P ribosomal antibodies induce defect in smell capability in a model of CNS -SLE (depression).

UNLABELLED: Systemic lupus erythematosus (SLE) is an autoimmune disease associated with more than 100 different autoantibodies, some of which may be associated with specific neuropsychiatric (NPSLE) manifestations. Injection of anti-P ribosomal antibodies (anti-P) directly to the brain ventricles of mice induces depression manifested by increased immobility time in the forced swim test (FST). METHODS: Mice were injected intracerebroventricularily (ICV) with affinity-purified human anti-P antibodies or normal commercial IgG as control. Mice were examined for depression by the forced swimming test (FST) and for olfactory function by the smell threshold test. Treatments included the antidepressant drug fluoxetine or aroma therapy by exposure to lemon or cinnamon odor. RESULTS: Mice injected with anti-P developed depression-like behavior, which improved significantly upon treatment with fluoxetine. Depressed mice had a significant deficit in olfactory function which was not reversed by fluoxetine. Exposure of anti-P-injected mice to lemon odor was associated with some improvement of the immobility time, a measure of depression. CONCLUSIONS: ICV injection of anti-P induces both depression-like behavior and impaired olfactory function in mice. Fluoxetine and possibly lemon odor exposure improve depressive behavior in these mice.

A new EAE model of brain demyelination induced by intracerebroventricular pertussis toxin.

Experimental autoimmune encephalomyelitis (EAE) is a primary animal model of multiple sclerosis (MS). MS predominantly presents with evidence of lesions in the subcortical periventricular white matter regions of the brain. Research into the pathogenesis of the demyelinating lesions in the brain has been hampered by the fact that conventional models of EAE present with progressive ascending paralysis which recapitulates mainly the spinal cord lesions of multiple sclerosis. There is little evidence of brain involvement. Systemic administration of pertussis toxin (PTx) has been shown to induce the proinflammatory cascade of TGF-beta, IL-6, and Th17 in the central nervous system, which recently has been identified as essential in the development of EAE. To determine whether intracerebroventricular (icv) administration of PTx would result in subcortical periventricular demyelinating lesions in the brain, we examined the effect in a MOG induced EAE model. We found that icv PTx induced subcortical periventricular brain lesions that resemble the pathologic demyelinating lesions of MS. Moreover, icv PTx induced Th17 infiltration and increased expression of cytokines IL-6 and TGF-beta. We thus generated a highly reproducible model with remarkable histological similarities to the predominant demyelinating brain lesions seen in MS.

Exaggerated sickness behavior and brain proinflammatory cytokine expression in aged mice in response to intracerebroventricular lipopolysaccharide.

Age-associated changes in glial reactivity may predispose individuals to exacerbated neuroinflammatory cytokine responses that are permissive to cognitive and behavioral complications. The purpose of this study was to determine if aging is associated with an exaggerated sickness response to central innate immune activation. Our results show that intracerebroventricular (i.c.v.) administration of lipopolysaccharide (LPS) caused a heightened proinflammatory cytokine response (IL-1beta, IL-6, and TNFalpha) in the cerebellum 2h post i.c.v. injection in aged mice compared to adults. This amplified inflammatory profile was consistent with a brain region-dependent increase in reactive glial markers (MHC class II, TLR2 and TLR4). Moreover, LPS caused a prolonged sickness behavior response in aged mice that was paralleled by a protracted expression of brain cytokines in the cerebellum and hippocampus. Finally, central LPS injection caused amplified and prolonged IL-6 levels at the periphery of aged mice. Collectively, these data establish that activation of the central innate immune system leads to exacerbated neuroinflammation and prolonged sickness behavior in aged as compared to adult mice.

Brain-immune communication pathways.

Communication between the central nervous and immune systems lies at the heart of the neuroimmune axis. We trace here some of the major conceptual hurdles which were raised, first against the acceptance of a neuroimmune axis and later in understanding it. We review the major concepts formulated and established during the last two decades and focus on four pathways that have been proposed as important in communication: the neural route, circumventricular organs, blood-brain barrier transport of cytokines, and secretions from BBB cells. These and other pathways have established the existence of a neuroimmune axis, but raise new questions on how they act and interact with one another.

Severe necrotizing encephalitis in a Yorkshire terrier: topographic and immunohistochemical study.

Necrotizing encephalitis of the Yorkshire terrier is a chronic non-suppurative encephalitis that was reported in approximately 15 cases worldwide. We report the case of a 10-year-old female Yorkshire terrier with gross evidence of severe cortical degeneration and necrosis. Microscopically, affected areas were mainly located in the cortical white matter and in the mesencephalon without implication of the cerebellum. Cavitation necrosis, demyelination, gemistocytic astrocytosis, marked perivascular lymphocytic cuffing with a diffuse lymphocytic/histiocytic/gitter cell infiltration characterized the lesions. Immunohistochemical analysis identified the major infiltration of T lymphocytes and macrophages with implication of some cytotoxic lymphocytes and IgG-producing plasma cells; depositions of IgG in the affected white matter were also observed. Specific stains did not reveal fungal, protozoal or bacterial organisms and reverse transcriptase-polymerase chain reaction analysis for distemper virus was also negative. The lympho-histiocytic inflammation suggests a T-cell-mediated and a delayed-type immune reaction as a possible pathogenic mechanism for this brain disorder.

Immunohistochemical changes related to ageing in the mouse hippocampus and subventricular zone.

We investigated mainly immunohistochemical changes of nestin (a marker of neuroepithelial stem cells) and Ki-67 (a marker of proliferating cells) proteins related to ageing in the mouse hippocampus and subventricular zone (SVZ) using young adult (8 weeks old) and middle-aged (40 weeks old) mice. In the present study, no significant changes in neurons and astrocytes of the hippocampal CA1 sector were found in a middle-aged male ICR mice without severe senile weakness, as compared with young adult animals. In contrast, a significant change in the number of microglia was found in the hippocampal CA1 sector of the middle-aged mice. Furthermore, no significant changes in the number of nestin- and Ki-67-positive cells were observed in the hippocampal CA1 sector of the middle-aged mice. On the other hand, decreases in the number of nestin- and Ki-67-immunopositive cells were observed in the SVZ of the middle-aged mice. Furthermore, a migration of nestin- and Ki-67-immunoreactive cells in the corpus callosum was not observed in the SVZ of the middle-aged mice. In the dentate gyrus, significant decreases in the number of Ki-67-immunopositive cells were observed in the middle-aged mice. Our study also showed that nestin immunoreactivity was observed in both Ki-67-postive cells and astrocytes in the SVZ of young adult mice. These findings emphasize the need to recognize ageing as important factors in studies of microglia, which may help to clarify the role of glial cell structure and function during ageing processes. Furthermore, the present findings suggest that ageing processes may decrease neurogenesis in the corpus callosum, SVZ and dentate gyrus. Thus our present findings provide valuable information for the neurogenesis during ageing processes.

Molecular aspects of fever and hyperthermia.

A rise in core temperature during fever usually results from change in the thermocontroller characteristics, resulting in an elevation of the set point of body temperature. Time course and extent of natural fevers are variable, but an upper limit (41 degrees C in humans), at which core temperature is maintained for some time and reduced when the set point of body temperature returns to its normal level, rarely is exceeded. Although any rise in body temperature may result from fever, those rises that are not accompanied by supportive changes in thermoeffector activities are termed hyperthermia.

Subarachnoidal and intraventricular human neurocysticercosis: application of an antigen detection assay for the diagnosis and follow-up.

BACKGROUND: Neurocysticercosis (NC) is a parasitic disease of the central nervous system caused by the larval stage of Taenia solium. Although imaging studies are recommended for diagnosis and follow-up of patients, their high cost and restricted availability limit their use. Among various immunological tests, the detection of HP10 antigen in cerebral spinal fluid (CSF) has proved to be a useful tool for the diagnosis of NC in the case of viable but not dead parasites. OBJECTIVES: This study was designed to evaluate the usefulness of the detection of HP10 antigen for the diagnosis and follow-up of NC patients. METHODS: The effectiveness of this HP10 assay was analysed for the CSF of 46 confirmed NC cases (21 men, 25 women) who had been clinically and radiologically described. RESULTS: In 21 of 24 NC patients (87.5%) with viable parasites localized in the SA space at the base of the brain or in the ventricles these were detected by means of the HP10 assay, whilst none of the three patients with viable parasites in the parenchyma or sulci had these detected. Used for the follow-up of patients after cysticidal treatment, it was showed that levels of HP10 dropped significantly only among those patients whose cysticerci were clearly damaged. CONCLUSIONS: HP10 antigen assay is recommended as a support for diagnosis and follow-up in NC patients with viable parasites localized in the SA space at the base of the brain or in the ventricles, thereby potentially reducing the number of imaging studies required.

Nuclear STAT3 translocation in guinea pig and rat brain endothelium during systemic challenge with lipopolysaccharide and interleukin-6.

During systemic inflammation, cytokines are released by immune-competent cells into the circulation, which in turn signal the brain to mediate brain-controlled signs of illness. Cytokine-responsive brain cells can be mapped by histological analysis of cytokine-induced transcription factors or transcription factor-associated molecules revealing different cell phenotypes that respond to activation of the immune system. Critical sites mediating cytokine-dependent immuneffector functions can be divided into two groups, one group of responding cells situated along a tight blood-brain barrier (BBB), and a second cell group in structures with an open BBB, e.g., the sensory circumventricular organs (CVOs). Previous reports from our group suggest that activation of the signal transducer and activator of transcription factor 3 (STAT3) during lipopolysaccharide (LPS)-induced systemic inflammation is mediated by interleukin-6 (IL-6) and occurs in astrocytes of the rat CVOs. Here we show in the guinea pig a time-dependent marked LPS-induced STAT3 activation within astrocytes and endothelial cells of the CVOs, within astrocytes located in brain structures with a functional BBB and within the brain endothelium of the entire brain. In addition, systemic treatment of rats with either rat recombinant IL-6 or LPS induced STAT3 activation in brain endothelial cells in a similar way as observed in the guinea pig brain, stressing the involvement of IL-6 in this phenomenon in a more generalized way. The STAT3-activated brain cells are located in critical target structures mediating cytokine action during LPS-induced inflammation. STAT3-controlled transcriptional activation with yet unknown cell-specific functional consequences seems to be involved in this process.

Comparison of ventricular and lumbar cerebrospinal fluid T cells in non-inflammatory neurological disorder (NIND) patients.

The aim of the present study was to define the cellular composition of ventricular, as compared with lumbar, cerebrospinal fluid (CSF) in patients with non-inflammatory neurological disorders (NIND). We addressed this issue by determining the cellular composition of lumbar CSF from patients with normal pressure hydrocephalus (NPH) who were undergoing lumbar CSF drainage during evaluation for shunting procedures, and evaluating ventricular CSF from a subset of these who underwent subsequent placement of ventriculoperitoneal shunts. We determined the cellular composition of lumbar CSF from 18 patients with NPH, and found that the leukocyte differentials, and relative proportions of CD4+ and CD8+ central memory (TCM), effector memory (TEM) and naive cell (TNaive) populations, were equivalent to those found previously in studies of CSF from patients with NIND. We further evaluated cells in the ventricular CSF of five patients who had previously undergone lumbar drainage. Leukocyte differential counts, as well as CD4+ and CD8+ TCM, TEM, and TNaive proportions, were equivalent in matched ventricular and lumbar CSF samples. These observations support the hypothesis that leukocytes enter the CSF in a selective fashion, at its site of formation in the choroid plexus. The results implicate CSF T cells in the immune surveillance of the central nervous system.

Modulation of Alzheimer's pathology by cerebro-ventricular grafting of hybridoma cells expressing antibodies against Abeta in vivo.

Accumulation in brain of the beta-amyloid peptide (Abeta) is considered as crucial pathogenic event causing Alzheimer's disease (AD). Anti-Abeta immune therapy is a powerful means for Abeta clearance from the brain. We recently showed that intravenous injections of anti-Abeta antibodies led to reduction, elevation or no change in brain Abeta42 concentrations of an AD mouse model. We report here, in a second passive immunization protocol, a different bioactivity of same antibodies to alter brain Abeta42 concentrations. Comparing the bioactivity of anti-Abeta antibodies in these two passive immunization paradigms underscores the potential of immune therapy for AD treatment and suggests that both the epitope recognized by the antibody and the mode of antibody administration are crucial for its biological activity.