Late Brain Involvement after Neonatal Immune Activation.

The neonatal immune system is still immature, which makes it more susceptible to the infectious agents. Neonatal immune activation is associated with increased permeability of the blood-brain barrier, causing an inflammatory cascade in the CNS and altering behavioral and neurochemical parameters. One of the hypotheses that has been studied is that neuroinflammation may be involved in neurodegenerative processes, such as Alzheimer's disease (AD). We evaluate visuospatial memory, cytokines levels, and the expression of tau and GSK-3ß proteins in hippocampus and cortex of animals exposed to neonatal endotoxemia. C57BL/6 mice aging two days received a single injection of subcutaneous lipopolysaccharide (LPS). At 60,120, and 180 days of age, visual-spatial memory was evaluated and the hippocampus and cortex were dissected to evaluate the cytokines levels and expression of tau and GSK-3ß proteins. The animals exposed to LPS in the neonatal period present with visuospatial memory impairment at 120 and 180 days of age. Here there was an increase of TNF-α and IL-1ß levels in the hippocampus and cortex only at 60 days of age. Here there was an increase in the expression of GSK-3ß in hippocampus of the animals at 60, 120, and 180 days of age. In the cortex, this increase occurred in the 120 and 180 days of age. Tau protein expression was high in hippocampus and cortex at 120 days of age and in hippocampus at 180 days of age. The data observed show that neonatal immune activation may be associated with visuospatial memory impairment, neuroinflammation, and increased expression of GSK-3ß and Tau proteins in the long term.

Inflammation-induced reversible switch of the neuron-specific enolase promoter from Purkinje neurons to Bergmann glia.

Neuron-specific enolase (NSE) is a glycolytic isoenzyme found in mature neurons and cells of neuronal origin. Injecting adeno-associated virus serotype 9 (AAV9) vectors carrying the NSE promoter into the cerebellar cortex is likely to cause the specific transduction of neuronal cells, such as Purkinje cells (PCs) and interneurons, but not Bergmann glia (BG). However, we found BG-predominant transduction without PC transduction along a traumatic needle tract for viral injection. The enhancement of neuroinflammation by the co-application of lipopolysaccharide (LPS) with AAV9 significantly expanded the BG-predominant area concurrently with the potentiated microglial activation. The BG-predominant transduction was gradually replaced by the PC-predominant transduction as the neuroinflammation dissipated. Experiments using glioma cell cultures revealed significant activation of the NSE promoter due to glucose deprivation, suggesting that intracellularly stored glycogen is metabolized through the glycolytic pathway for energy. Activation of the glycolytic enzyme promoter in BG concurrently with inactivation in PC may have pathophysiological significance for the production of lactate in activated BG and the utilization of lactate, which is provided by the BG-PC lactate shuttle, as a primary energy resource in injured PCs.

Detection of IL-20R1 and IL-20R2 mRNA in C57BL/6 mice astroglial cells and brain cortex following LPS stimulation.

BACKGROUND: Astrocytes, which comprise ~90% of overall brain mass, are involved in brain immunity. These cells represent the non-professional class of CNS-resident APCs and may promote or inhibit CNS inflammation depending on the cytokines they secrete. IL-10 family of cytokines and their receptors, IL-20R1 and IL-20R2, may have a role in shifting astrocytes to a neuroprotective or neurodegenerative function. OBJECTIVE: To address the expression of IL-20R1 and IL-20R2 cytokine receptors in astrocytes and brain cortex of C57BL/6 mice. METHODS: We investigated the expression of IL-20R1 and IL-20R2 in C57BL/6 mice astroglial cells and brain cortex in response to lipopolysaccharide (LPS), using reverse-transcription polymerase chain reaction (RT-PCR) method. RESULTS: Astrocytes were able to express IL-20R1 and IL-20R2 mRNA not only in response to LPS stimulation but also in the absence of LPS. Furthermore, we found the expression of IL-20R1 and IL-20R2 mRNA in the cortex of adult C57BL/6 mice. CONCLUSIONS: IL-20R1 and IL-20R2 are constitutively express in the brain. Since most neuropathological processes involve astrocytes and inflammatory cytokines, these findings have important implications for future therapeutic strategies.

Antigenic compartmentation of the cerebellar cortex in an Australian marsupial, the tammar wallaby Macropus eugenii.

The mammalian cerebellar cortex is apparently uniform in composition, but a complex heterogeneous pattern can be revealed by using biochemical markers such as zebrin II/aldolase C, which is expressed by a subset of Purkinje cells that form a highly reproducible array of transverse zones and parasagittal stripes. The architecture revealed by zebrin II expression is conserved among many taxa of birds and mammals. In this report zebrin II immunohistochemistry has been used in both section and whole-mount preparations to analyze the cerebellar architecture of the Australian tammar wallaby (Macropus eugenii). The gross appearance of the wallaby cerebellum is remarkable, with unusually elaborate cerebellar lobules with multiple sublobules and fissures. However, despite the morphological complexity, the underlying zone and stripe architecture is conserved and the typical mammalian organization is present.

Effect of Cerebellohypothalamic Glutamatergic Projections on Immune Function.

Our previous work has shown that lesions of the cerebellar interposed nuclei (IN) suppress immune cell functions. Since there is no direct structural connection between the cerebellum and immune system, we explored the pathway mediating the cerebellar immunomodulation at the profile of cerebellohypothalamic projections to understand this modulation. Anterograde tracing of nerve tracts from the cerebellar IN to the hypothalamus was conducted by injection of anterograde tracer dextran-texas red (dextran-TR) in the cerebellar IN. We observed that dextran-TR-labeled nerve fibers, which were sent by cerebellar IN neurons, traveled in the superior cerebellar peduncle (SCP), crossed in SCP decussation, and entered the hypothalamus. In the hypothalamus, the fibers mostly terminated in the lateral hypothalamic area (LHA). Retrograde tracing by injection of retrograde tracer fluoro-ruby (FR) in the LHA found that FR-labeled neurons appeared in contralateral cerebellar IN. Fluorescent immunohistochemistry for glutamate revealed that many of the FR-labeled neurons were glutamatergic. These results demonstrate a direct glutamatergic projection from the cerebellar IN to the LHA. Reduction of the cerebellohypothalamic glutamatergic projections by microinjection of 6-diazo-5-oxo- L-norleucine (DON), an inhibitor of glutaminase for glutamate synthesis, in bilateral cerebellar IN led to suppression of peripheral lymphocyte number, T lymphocyte proliferation, and serum anti-sheep red blood cell IgM level. But the DON injection in the cerebellar cortex that does not send axons to the hypothalamus did not significantly alter all the immune parameters. These findings suggest that cerebellohypothalamic glutamatergic projection modulates immune function, and that via the pathway, the cerebellum implements its immunoregulatory effect.

Familial hemophagocytic lymphohistiocytosis in a pediatric patient diagnosed by brain magnetic resonance imaging.

Familial hemophagocytic lymphohistiocytosis (fHLH) is an autosomal recessive disorder characterized by proliferation and infiltration of several organs by activated lymphocytes and macrophages. Without allogeneic stem cell transplantation, fHLH is fatal. We describe a previously healthy 11-month-old boy with a rapidly progressive encephalopathy. An older brother died at 8 months following a subacute encephalopathy diagnosed as meningoencephalitis. The family history led to the suspicion of a metabolic disease, but metabolic studies were unrevealing. MRI showed multiple inhomogeneous signal abnormalities in the cortex and white matter, most prominent in the cerebral hemispheres and around the dentate nucleus. Gadolinium-enhanced T1-weighted images showed a multitude of enhancing foci, suggestive of perivascular enhancement. Based on MRI pattern with multiple lesions, perivascular enhancement and family history, fHLH was suspected. DNA analysis showed that the patient was compound-heterozygous for the c.445 G>A (p.Gly149Ser) mutation in exon 1 and the c.757 G>A (p.Glu253Lys) mutation in exon 2 of the perforin 1 gene. The patient was treated according to the international HLH-2004 protocol (dexamethasone, etoposide, cyclosporine, intrathecal methotrexate and prednisolone) followed by allogeneic cord blood transplantation. He showed a significant neurological and radiological improvement. The reported case demonstrates that MRI pattern recognition can lead to early diagnosis of fHLH, with subsequent adequate treatment.

Neuroadaptive changes in cerebellar neurons induced by chronic exposure to IL-6.

IL-6 is an important signaling molecule in the CNS. CNS neurons express IL-6 receptors and their signal transduction molecules, consistent with a role for IL-6 in neuronal physiology. Research indicates that IL-6 levels are low in the normal brain but can be significantly elevated in CNS injury and disease. Relatively little is known about how the elevated levels of IL-6 affect neurons. In the current study we show that under conditions of chronic exposure, IL-6 induces alterations in the level of protein expression in developing CNS cells. Such changes may play a role in the altered CNS function observed in CNS conditions associated with elevated levels of IL-6 in the CNS.

Clonazepam responsive opsoclonus myoclonus syndrome: additional evidence in favour of fastigial nucleus disinhibition hypothesis?

Opsoclonus myoclonus syndrome is a rare paraneoplastic syndrome seen in 50% of children with neuroblastoma. Neural generator of opsoclonus and myoclonus is not known but evidences suggest the role of fastigial nucleus disinhibition from the loss of function of inhibitory (GABAergic) Purkinje cells in the cerebellum. We present a child with paraneoplastic opsoclonus myoclonus syndrome who responded well to clonazepam. Response to clonazepam is an evidence for the involvement of GABAergic neural circuits in the genesis of opsoclonus myoclonus syndrome and is in agreement with fastigial nucleus disinhibition hypothesis.

IgM anti-GQ1b monoclonal antibody inhibits voltage-dependent calcium current in cerebellar granule cells.

Miller-Fisher syndrome (MFS), which is known to be associated with anti-GQ1b antibodies and to cause ataxia, is a variant of an acute inflammatory neuropathy. However, the pathogenic role of anti-GQ1b antibodies remains unclear. In this study, we investigated the effects of mouse IgM anti-GQ1b monoclonal antibody (IgM anti-GQ1b mAb) on the spontaneous muscle action potential of a rat spinal cord-muscle co-culture system and on the voltage-dependent calcium channel (VDCC) current in cerebellar granule cells and Purkinje cells using the whole-cell patch clamp technique. The frequency of spontaneous muscle action potential of the innervated muscle cells was transiently increased by IgM anti-GQ1b mAb and then was blocked completely, which was the same finding as reported previously. Moreover, the cerebellar granule cell VDCC current was decreased by 30.76+/-7.60% by 5 microg/mL IgM anti-GQ1b mAb, whereas IgM anti-GQ1b mAb did not affect the VDCC current in cerebellar Purkinje cells. In immunocytochemistry, IgM anti-GQ1b mAb stained the whole cell surface of cerebellar granule cells, but not that of Purkinje cells. Therefore, the clinical symptoms of Miller-Fisher syndrome, such as cerebellar-like ataxia, may be explained by the inhibitory effects of anti-GQ1b antibodies on VDCC current in cerebellar granule cells.

CD8 positive T-cell infiltration in the dentate nucleus of paraneoplastic cerebellar degeneration.

Recent reports have discussed the presence of cytotoxic T cells in paraneoplastic cerebellar degeneration (PCD). We report an autopsy case of PCD associated with anti-Hu antibody, in which we revealed infiltration of CD8+ T cells in and around the dentate nucleus but not in the cerebellar cortex, in addition to severe Purkinje cell loss. Some infiltrated mononuclear cells expressed cytotoxic cell marker, Granzyme B. Decrease of neurons and reduced presynapses were demonstrated in the dentate nucleus. This is the first report that suggests the possibility of the dentate nucleus being primarily attacked followed by Purkinje cell loss in PCD.

Preservation of ultrastructure and immunoreactivity in cryosections of brain tissue stored in a sucrose-gelatin solution at freezing temperatures.

We evaluated the preservation of ultra-structure and immunoreactivity in cryosections of central nervous system tissue mounted with and stored in a sucrose-gelatin solution for one month at -20 degrees C or -80 degrees C. The ultra-structure of synaptic structure in these sections was well preserved and comparable to that of freshly cut cryosections. Quantitative analysis of mitochondrial ultra-structure demonstrated gradually lower degrees of preservation in sections stored at -20 degrees C and -80 degrees C compared with that in freshly cut sections. We observed distinct metabotropic glutamate receptor 1 (mGluR1)-immunogold labelling at peri-synaptic sites in freshly cut sections and also in those stored at -20 degrees C and -80 degrees C. Quantitative analysis of mGluR1 immunoreactivity revealed that the total number of immunogold particles per synapse and the number of non-specifically bound particles were similar under all three conditions. However, the percentage of gold particles bound to a specific synaptic region was greatest in freshly cut sections (79.0%) and progressively lower in sections stored at -20 degrees C (76.1%), in which sections were not frozen, and in sections stored at -80 degrees C (68.0%). These data indicate that ultra-thin cryosections may be conveniently stored in a sucrose-gelatin solution at -20 degrees C for cryoultramicrotomy-immunolabelling.

Expression of Toll-like receptor 3 in the human cerebellar cortex in rabies, herpes simplex encephalitis, and other neurological diseases.

There is recent in vitro evidence that human neurons express the innate immune response receptor, Toll-like receptor-3 (TLR-3), and that expression is enhanced in viral infections. The authors examined the immunohistochemical expression of TLR-3 in the cerebellar cortex of postmortem human brains. Purkinje cells were found to express TLR-3 in all cases of rabies (4 of 4) and herpes simplex encephalitis (2 of 2) as well as in cases of amyotrophic lateral sclerosis (1 of 2), stroke (1 of 2), and Alzheimer's disease (3 of 3). In cases of viral infection, direct viral infection was not necessary for enhanced neuronal TLR-3 expression, suggesting that soluble factors likely play an important role in inducing TLR-3 expression. In addition to neurons, occasional Bergmann glia expressed TLR-3 in some cases. This study has provided evidence that human brain neurons can express TLR-3 in vivo and suggests that neurons may play an important role in initiating an inflammatory reaction in a variety of neurological diseases.

Targeted gene therapy to antigen-presenting cells in the central nervous system using hematopoietic stem cells.

BACKGROUND: Hematopoietic stem cells (HSC) have been previously used as vectors for gene therapy of systemic disease. The effectiveness of HSC-mediated gene therapy largely depends on efficient gene delivery into long-term repopulating progenitors and targeted transgene expression in an appropriate progeny of the transduced pluripotent HSCs. In the present study, we examined the feasibility of using HSC transduced with self-inactivating (SIN) lentiviral vectors for the delivery of gene therapy to the central nervous system (CNS). MATERIAL AND METHODS: We constructed two SIN lentiviral vectors, EF.GFP and DR.GFP, to express the green fluorescent protein (GFP) gene controlled solely by the promoter of either a housekeeping gene EF-1alpha or the human HLA-DRalpha gene, which is selectively expressed in antigen-presenting cells. RESULTS: We demonstrated that both vectors efficiently transduced human pluripotent CD34+ cells capable of engrafting NOD/SCID mice. Only the DR.GFP vector mediated transgene expression in the murine CNS containing human HLA-DR+ cells. These cells express surface markers characteristic of resident CNS microglia. Furthermore, human dendritic cells derived from transduced and engrafted human cells potently stimulated allogeneic T cell proliferation. CONCLUSIONS: The present study demonstrated successful targeting of transgene expression to CNS microglia after stable gene transduction of pluripotent HSC.

Interleukin-6 produces neuronal loss in developing cerebellar granule neuron cultures.

CNS levels of the cytokine interleukin-6 (IL-6) are elevated during CNS injury and disease, but it is unclear if IL-6 contributes to the pathologic process. Our studies show that in a well-characterized CNS developmental model system, primary cultures of rodent cerebellar granule neurons, chronic exposure to IL-6 during neuronal development can result in cell damage and death in a subpopulation of developing granule neurons. Chronic exposure to IL-6 also increased the susceptibility of the granule neurons to a toxic insult produced by excessive activation of NMDA receptors. These results are consistent with a role for IL-6 in the neuropathology observed in the developing CNS during injury and disease.

Abnormal Purkinje cell activity in vivo in experimental allergic encephalomyelitis.

Cerebellar deficits in multiple sclerosis (MS) tend to persist and can produce significant disability. Although the pathophysiological basis for these deficits is not clear, it was recently reported that the expression of the sensory neuron-specific sodium channel Nav1.8 (which is not normally expressed within the cerebellum) is aberrantly upregulated within Purkinje cells in experimental allergic encephalomyelitis (EAE) and in human MS. The expression of Nav1.8 in cultured Purkinje cells has been shown to alter the activity pattern of these cells in vitro by decreasing the number of spikes per conglomerate action potential and by contributing to the production of sustained, pacemaker-like activity upon depolarization, suggesting the hypothesis that, in pathophysiological situations where Nav1.8 is upregulated within Purkinje cells, the pattern of activity in these cells will be altered. In the present study, we examined this hypothesis in vivo in mice with EAE. Our results demonstrate a reduction in the number of secondary spikes per complex spike and irregularity in the temporal organization of secondary spikes in Purkinje cells from mice with EAE in which Nav1.8 is upregulated. We also observed abnormal bursting activity in Purkinje cells from mice with EAE, which was not observed in control animals. These results demonstrate functional changes in Purkinje cells in vivo within their native cerebellar environment in EAE, a model of MS, and support the hypothesis that misexpression of Nav1.8 can contribute to cerebellar deficits in neuroinflammatory disorders by altering the pattern of electrical activity within the cerebellum.

Increased sensitivity to N-methyl-D-aspartate receptor-induced excitotoxicity in cerebellar granule cells from interleukin-1 receptor type I-deficient mice.

The effects of chronic exposure to excitatory amino acids (EAAs) were examined in cultured cerebellar granule cells (CGCs) from wild type (WT) and interleukin-1 receptor type I (IL-1RI)-deficient mice. After 8 days in culture, the cells were exposed to 100 microM glutamate or 300 microM N-methyl-D-aspartate (NMDA) for 24 h. Analysis of cell viability, as assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay and phase-contrast microscopy revealed that CGCs from IL-1RI-deficient mice were more vulnerable to EAAs as compared to the WT controls. The results indicate that IL-1RI signalling is important for neuronal survival. The effect of glutamate on the CGCs from IL-1RI-deficient mice was decreased by the non-competitive NMDA-receptor antagonist MK-801, supporting the involvement of NMDA receptors in the glutamate-induced excitotoxicity.

[Paraneoplastic cerebellar degeneration associated with ovarian cancer: anti-Yo immunoreactivity in autoptic cerebellum and ovarian carcinoma]. / Paraneoplastische Degeneration des Kleinhirns bei Ovarialkarzinom Anti-Yo-positive Immunreaktivität der Kleinhirn- und Tumorzellen.

Paraneoplastic cerebellar degeneration is a rare disorder caused likely by autoimmune mechanisms in malignant oncologic diseases, and the most common tumors are ovarian, breast, lung cancer, and m. Hodgkin. An immune reaction is supposed to be directed against identical antigens of cerebellum and tumor, and paraneoplastic antibodies called anti-Yo, anti-Hu, anti-Ri, or anti-Tr are often detected in blood and cerebrospinal fluid. The course of paraneoplastic cerebellar degeneration as a complication of ovarian cancer is described. The relationship between the malignancy and pathologic changes in cerebellum was confirmed by positive immunohistochemical and immunofluorescence reaction between a patient's anti-Yo-positive serum and her own Purkinje's and ovarian cancer cells.

Chemokine receptor CXCR2 regulates the functional properties of AMPA-type glutamate receptor GluR1 in HEK cells.

Experiments were conducted in both HEK cells and cerebellar neurons to investigate whether CXC chemokine receptor 2 (CXCR2) is functionally coupled to GluR1. The co-expression of CXCR2 with GluR1 in HEK cells increased (i) the GluR1 "apparent" affinity for the transmitter; (ii) the GluR1 channel open probability; and (iii) GluR1 binding site cooperativity upon CXCR2 stimulation with CXC chemokine ligand 2 (CXCL2). The affinity of C-terminal-deleted GluR1 for glutamate (Glu) remained stable instead. Furthermore, CXCL2 increased the binding site cooperativity of AMPA receptors in rat cerebellar granule cells; and the amplitude of spontaneous excitatory postsynaptic current (sEPSCs) in Purkinje neurons (PNs). Our findings indicate that the coupling of CXCR2 with GluR1 may modulate glutamatergic synaptic transmission.

Microglial cells protect cerebellar granule neurons from apoptosis: evidence for reciprocal signaling.

The microglia are the immune cell population of the nervous system and play important roles both in normal function and in disease. Reciprocal neuron-microglia interactions are not well understood, in particular those concerning the crosstalk between the two cell populations when neuronal damage does occur. We have used a well-established model of apoptosis in cerebellar granule neurons to test the effect of co-culturing microglial cells with them or of exposing them to microglia-conditioned medium. Microglial cells, derived from cortical or cerebellar mixed glial cultures and plated over cerebellar granule neurons, protected these neurons from apoptosis induced by shifting them, at 7 days in vitro, for 24 h from a depolarizing (high-potassium) to a nondepolarizing (low-potassium) medium. The same result was achieved when microglial cells obtained from mixed glial cortical cultures were plated over a membrane well insert in the culture chamber, permitting medium exchange without physical contact with granule neurons. A similar result was obtained when the low-potassium, apoptosis-inducing medium was conditioned by 48-h exposure to microglial cells; 24-h exposure to microglial cells was not enough to confer neuroprotective capability to the conditioned medium. However in double-conditioned medium experiments, in which the medium was first exposed to apoptotic neurons and then to microglial cells, unknown signal(s) released by apoptotic neurons, conferred to the 24-h conditioned medium a strong neuroprotective action, similar to that observed in the co-cultures experiments. This finding, together with the results from co-culture experiments, is explained by admitting that molecules released in the medium by apoptotic neurons potentiate the anti-apoptotic activity of microglia. Our results, therefore, demonstrate not only that normally microglial cells release in the medium molecule(s) able to rescue neurons from apoptotic death, but that unknown diffusible signal(s) from apoptotic neurons enhance(s) microglial neuroprotective properties as well.

Presynaptic impairment of cerebellar inhibitory synapses by an autoantibody to glutamate decarboxylase.

Glutamic acid decarboxylase (GAD), the enzyme responsible for converting glutamate to gamma-aminobutyric acid (GABA), is a target of humoral autoimmunity in stiff-man syndrome and subacute cerebellar ataxia. Recently, we found that an anti-GAD autoantibody in the CSF of an ataxic patient selectively suppressed GABA-mediated transmission on cerebellar Purkinje cells without affecting glutamate-mediated transmission. Here, we examine the mechanism by which the autoantibody impaired the inhibitory transmission, using immunohistochemistry and whole-cell recording in rat cerebellar slices. The present results indicate that CSF immunoglobulins prepared from an ataxic patient acted on the presynaptic terminals of GABAergic interneurons and decreased GABA release onto Purkinje cells.