Glucocorticoids and central nervous system inflammation

Glucocorticoids (GCs) are well known for their anti-inflammatory and immunosuppressive properties in the periphery and are therefore widely and successfully used in the treatment of autoimmune diseases, chronic inflammation, or transplant rejection. This led to the assumption that GCs are uniformly anti-inflammatory in the periphery and the central nervous system (CNS). As a consequence, GCs are also used in the treatment of CNS inflammation. There is abundant evidence that an inflammatory reaction is mounted within the CNS following trauma, stroke, infection, and seizure, which can augment the brain damage. However an increasing number of studies indicate that the concept of GCs being universally immunosuppressive might be oversimplified. This article provides a review of the current literature, showing that under certain circumstances GCs might fail to have anti-inflammatory effects and sometimes even enhance inflammation.     

Dynamic expression of the Slit‐Robo GTPase activating protein genes during development of the murine nervous system

We investigated the expression of the three known Slit‐Robo GTPase activating protein (srGAP) genes in the developing murine nervous system using in situ hybridization. The three genes are expressed during embryonic and early postnatal development in the murine nervous system, showing a distinct pattern of expression in the olfactory system, the eye, forebrain and midbrain structures, the cerebellum, the spinal cord, and dorsal root ganglia, which we discuss in relation to Slit‐Robo expression patterns and signaling pathways. We also report srGAP2 expression in zones of neuronal differentiation and srGAP3 in ventricular zones of neurogenesis in many different tissues of the central nervous system (CNS). Compared to srGAP2 and srGAP3, the onset of srGAP1 expression is later in most CNS tissues. We propose that these differences in expression point to functional differences between these three genes in the development of neural tissues. J. Comp. Neurol. 513:224–236, 2009. © 2009 Wiley‐Liss, Inc.     

Selection of novel reference genes for use in the human central nervous system: a BrainNet Europe Study

The use of an appropriate reference gene to ensure accurate normalisation is crucial for the correct quantification of gene expression using qPCR assays and RNA arrays. The main criterion for a gene to qualify as a reference gene is a stable expression across various cell types and experimental settings. Several reference genes are commonly in use but more and more evidence reveals variations in their expression due to the presence of on-going neuropathological disease processes, raising doubts concerning their use. We conducted an analysis of genome-wide changes of gene expression in the human central nervous system (CNS) covering several neurological disorders and regions, including the spinal cord, and were able to identify a number of novel stable reference genes. We tested the stability of expression of eight novel (ATP5E, AARS, GAPVD1, CSNK2B, XPNPEP1, OSBP, NAT5 and DCTN2) and four more commonly used (BECN1, GAPDH, QARS and TUBB) reference genes in a smaller cohort using RT-qPCR. The most stable genes out of the 12 reference genes were tested as normaliser to validate increased levels of a target gene in CNS disease. We found that in human post-mortem tissue the novel reference genes, XPNPEP1 and AARS, were efficient in replicating microarray target gene expression levels and that XPNPEP1 was more efficient as a normaliser than BECN1, which has been shown to change in expression as a consequence of neuronal cell loss. We provide herein one more suitable novel reference gene, XPNPEP1, with no current neuroinflammatory or neurodegenerative associations that can be used for gene quantitative gene expression studies with human CNS post-mortem tissue and also suggest a list of potential other candidates. These data also emphasise the importance of organ/tissue-specific stably expressed genes as reference genes for RNA studies.     

Genetic dissection of neurodegeneration and CNS inflammation

Inflammation and neurodegeneration characterize multiple sclerosis, as well as many other diseases of the central nervous system (CNS). The understanding of the molecular pathways that regulate these processes is of fundamental importance for the development of new therapies. Nerve lesions paradigms in animals can serve as important tools to dissect central features of human CNS disease and by using these models certain key regulators have also been identified. However, our knowledge of how aspects of neurodegeneration and CNS inflammation are regulated on a genomic level is very limited. Such knowledge may help to unravel disease mechanisms. By using a standardized nerve trauma model, ventral root avulsion (VRA), in a series of inbred rat strains we here demonstrate a potent genetic regulation of the degree of neuron death and glial activation. Genome wide mapping of these phenotypes in experimental rat strain crosses identifies several quantitative trait loci (QTLs) controlling nerve lesion-induced nerve cell death, local T cell accumulation and expression of MHC class II on microglia. This approach may lead to the identification of evolutionary conserved genetic polymorphisms in key controlling genes, which can serve as prime candidates for association studies in several human CNS diseases.     

Definition of an extracellular matrix protein in rostral portions of the human central nervous system

We have identified and characterized an extracellular matrix (ECM) glycoprotein of cultured astrocytomas, NEC1, that is expressed in normal human brain parenchyma. Detailed immunohistochemical analysis reveals a region-specific NEC1 pattern along the rostrocaudal axis of the central nervous system (CNS), with strong expression throughout the white matter of telencephalon and diencephalon, scant expression in some areas of mesencephalon, and no expression in pons, cerebellum, medulla, spinal cord, and peripheral nervous system. NEC1 is not co-distributed with any known neural cell type, suggesting that expression of specific ECM proteins in the CNS is segmentally controlled.     

Toll-like receptors in central nervous system glial inflammation and homeostasis

Toll-like receptors (TLRs) are a family of pattern-recognition receptors expressed on cells of the innate immune system that allow for the recognition of conserved structural motifs on a wide array of pathogens, referred to as pathogen-associated molecular patterns, as well as some endogenous molecules. The recent emergence of studies examining TLRs in the central nervous system (CNS) indicates that these receptors not only play a role in innate immunity in response to infectious diseases but may also participate in CNS autoimmunity, neurodegeneration, and tissue injury. This review summarizes the experimental evidence demonstrating a role for TLRs in the context of CNS inflammation in both infectious and noninfectious conditions.     

Distribution of the novel developmentally-regulated protein EAP-300 in the embryonic chick nervous system.

In a previous study we described a 300 kDa, developmentally regulated protein identified in embryonic chick neural retina with a monoclonal antibody. Because this protein has been shown to be undetectable in the adult nervous system, and the monoclonal antibody is species-specific, the protein has been named embryonal avian polypeptide of 300 kDa (EAP-300). In the present study we have analyzed the histological expression of EAP-300 during chick embryogenesis. In the developing nervous system, EAP-300 expression was detected as early as Stage 5 (19 h), and was subsequently down-regulated to undetectable levels in the adult. Of particular interest was the association of EAP-300 with putative barriers of neuronal growth, such as the telencephalon/diencephalon glial knot, the dorsal midline in the mesencephalon and the midline in myelencephalon, and the spinal cord roof plate. EAP-300 was also shown to be expressed by Bergmann glia during the period of granule cell migration in the cerebellum. The expression of EAP-300 by radial astrocytes was confirmed in culture by immunofluorescent co-labeling with a MAb to EAP-300 and the R5 MAb, which is a radial astrocyte-specific marker. It has also been shown that EAP-300, when immunopurified from embryonic brain under non-dissociating conditions, co-purifies with a neural keratan sulfate proteoglycan that is also associated with CNS barrier structures during brain development. The restricted expression of EAP-300 in nervous tissue, particularly in CNS barrier structures, suggests that EAP-300 may play an important, but transient, role in the development of the chick nervous system.     

Basic principles of immunological surveillance of the normal central nervous system

Unlike most bodily organs, the central nervous system (CNS) exists behind a blood-tissue barrier designed to minimize the passage of cells and macromolecules into the neural parenchyma. Yet, the CNS is routinely and effectively surveyed by the immune system. This review examines the mechanisms and participants in this immunological surveillance mechanism. The nature of the healthy blood-brain barrier, factors modifying it, and its central position in determining the number and nature of leukocytes permitted to enter, are considered. In addition the role in surveillance played by lymphatic drainage, migrating T and B lymphocytes, and elements of the monocyte/macrophage/microglia family are considered. While all these participants are known to be important in responding to a CNS antigen and/or establishing a site of inflammation in the nervous system, they also are major elements in maintaining the homeostasis of the CNS and permitting the necessary immunological surveillance of that organ.     

Selective and antigen-dependent effects of myelin degeneration on central nervous system inflammation

Damage to myelin sheath or oligodendrocytes may precede or even provoke inflammation of the central nervous system (CNS), but the extent to which these degenerative changes affect inflammation remains largely undefined. To study these processes in more detail, we used CNS antigen-specific T cells in the presence or absence of anti-myelin antibodies to induce experimental autoimmune encephalomyelitis (EAE) in transgenic Lewis rats with low-grade subclinical myelin degeneration and associated microglia cell activation, and in wild-type Lewis rats with an intact CNS. We found that myelin degeneration affects the localization of inflammatory lesions, the numbers of T cells recruited to these lesions, and the severity of the resulting clinical disease. In addition, myelin degeneration and associated microglia cell activation jointly enhance the susceptibility of the CNS to the action of anti-myelin antibodies. Our data show that even subtle alterations of myelin and oligodendrocytes may massively amplify the extent of demyelination and tissue damage, involving different immune effector mechanisms. A similar causal relationship might also operate in human patients with multiple sclerosis, where T cell-mediated inflammation and antibody-mediated demyelination have been documented, and where genetic factors might determine the susceptibility of the target tissue for immune-mediated injury.     

Vasculitis of the nervous system

Vasculitis is inflammation of the blood vessels, which may involve either the central nervous system (CNS), or the peripheral nervous system (PNS), or both. This involvement may be primary and restricted to the CNS, and rarely to the PNS. Vasculitis is inflammation of the blood vessels, which may involve either the central nervous system (CNS), or the peripheral nervous system (PMS), or both. This involvement may be primary and restricted to the CNS, and rarely to the PNS. “Primary angiitis of the CNS” is the term used to describe isolated CNS involvement by vasculitis, in which neither the clinical presentation and behaviour of the disease, nor the histopathology is uniform. This heterogeneity indicates a spectrum, depending on the type and extent of the vascular involvement seen within the CNS, covering a group of disorders, rather than a single disease. This may explain the different prognosis and response to treatments.. In clinical practice vasculitis of the nervous system, secondary to a known cause or underlying disease is more commonly seen than as a primary disorder. Primary systemic vasculitides and connective-tissue disorders, Behçet's Disease, lymphoproliferative diseases and other malignancies, some infections and related conditions, drugs and substance abuse are some of the conditions known to cause vasculitis in the nervous system. There is a broad variety of pathogenetic mechanisms. Both the CNS and the PNS may be involved, either separately or together.     

Cerebrospinal fluid neopterin in paediatric neurology: a marker of active central nervous system inflammation

Aim  Cerebrospinal fluid (CSF) neopterin production is increased by interferon-gamma stimulation and appears to act as a marker of intrathecal immune activation. We aimed to test the usefulness of elevated CSF neopterin as a biological marker of central nervous system (CNS) inflammation.
Method  We retrospectively reviewed CSF neopterin in 158 children (89 males, 69 females, mean age 4y 1mo, SD 3y 11mo, range 1mo–15y).
Results  CSF neopterin levels in children with chronic static CNS disorders ( n =105) were predominantly low, suggesting that inflammation is rare in these patients. We created an upper value of normal (chronic static group 95th centile 27.4nmol/l). CSF neopterin was elevated in all 10 patients with acute encephalitis and in 10 of 12 patients with other acute inflammatory CNS disorders (demyelination, post-infectious ataxia, myelitis). CSF neopterin was also significantly elevated in patients with chronic progressive disorders of inflammatory origin. Interestingly, CSF neopterin was elevated in four of six patients with chronic static disorders who were tested during a febrile exacerbation of seizures or dystonia, suggesting that intrathecal immune activation may be important in this setting.
Interpretation  Neopterin has a short half-life and was useful for monitoring inflammation activity in a patient with relapsing–remitting encephalitis. CSF neopterin is a useful marker of inflammation in a broad range of acute and chronic CNS disorders, and is a significantly more sensitive marker of inflammation than CSF pleocytosis.     

Up-regulation of fatty acid metabolizing-enzymes mRNA in rat spinal cord during persistent peripheral local inflammation

Persistent peripheral inflammation is associated with repetitive painful inputs into the spinal cord, leading to a chronic pain state. Related dramatic changes occur in the central nervous system (CNS) including central sensitization, which results in hyperalgesia. This neural plasticity involves in part fatty acids as functional and structural compounds. We hypothesized that central modification of fatty acids metabolism might occur after prolonged peripheral noxious stimulation. In the present study, the regulation of genes involved in fatty acids metabolism in the rat CNS was investigated during a chronic pain state. Using semiquantitative RT-PCR, we explored in the neuraxis the mRNA expression of brain acyl-CoA synthetases (ACS) and acyl-CoA oxidase (ACO), which are major fatty acid-metabolizing enzymes, following complete Freund's adjuvant (CFA) injection into a hind paw. Similar spinal up-regulation of the isoforms ACS2, ACS3, ACS4, and of ACO was detected early after 30 min, reaching a maximal after 6 h post-injection. Other peaks were also observed after 4 and 21 days post-inoculation, corresponding to the acute and chronic inflammation, respectively. Induction occurred only in the lumbar spinal cord ipsilaterally to the inflamed paw and was completely inhibited by a local anaesthesia of the sciatic nerve, suggesting a neural transmission of the inducing signal. Moreover, intrathecal injection of MK801, a noncompetitive NMDA antagonist, partially prevented these inductions, highlighting the involvement of the neurotransmitter glutamate in the central ACS and ACO up-regulation. These findings suggest that the fatty metabolism is stimulated in the CNS during a chronic pain state.     

Effect of inflammation on central nervous system development and vulnerability

PURPOSE OF REVIEW: Preterm infants are at high risk for neurological sequelae and cognitive dysfunction. These problems have been attributed to a high occurrence of central nervous system (CNS) lesions, but suboptimal brain development appears to be just as important. In this brief review we present the hypothesis that systemic infection/inflammation can severely interfere with normal CNS function and development. RECENT FINDINGS: We focus on the effects of lipopolysaccharide because it is often used to model the systemic inflammatory response induced by infections. The inflammatory signals are propagated across the intact or ruptured blood-brain barrier to the CNS by proinflammatory cytokines, prostaglandins, or lipopolysaccharide. Subsequently, microglia are triggered to release cytokines, oxygen free radicals and trophic factors, which will influence the CNS in various ways. Cognition, dendritic length and spine density, dopaminergic cells, neurogenesis and glial proliferation will be affected. Furthermore, CNS vulnerability and, in some instances, cerebral anomalies and white matter damage are produced. SUMMARY: Hypothetically, all of these effects on the CNS triggered by inflammation may have severe consequences for the individual's ability to cope with environmental exposures during childhood and adulthood.     

A synthetic heparin-mimicking polyanionic compound inhibits central nervous system inflammation

The immunomodulating capacity of heparin led us to test the effect of the synthetic heparin-mimicking and low anticoagulant compound RG-13577 on the course of experimental autoimmune encephalomyelitis (EAE) and central nervous system (CNS) inflammation. EAE was induced in SJL mice by inoculation with whole mouse spinal cord homogenate. RG-13577, delivered intraperitoneally, inhibited the clinical signs of acute EAE and markedly ameliorated inflammation in the spinal cord, primarily by inhibiting heparanase activity in lymphocytes and astrocytes and thus impairing lymphocyte traffic. RG-13577 treatment was effective when started on day of disease induction or day 7 after induction. The low molecular weight heparin, enoxaparin, tested under the same conditions, exerted only a minor insignificant inhibitory effect. RG-13577 also inhibited the tyrosine phosphorylation of several proteins, particularly Erk1 and Erk2 of the MAP kinase signaling pathways associated with inflammation and cell proliferation. RG-13577 blocked the activity of sPLA(2) and inhibited CNS PGE(2) production both in vivo and in vitro.     

Chemokines and the inflammatory response to viral infection in the central nervous system with a focus on lymphocytic choriomeningitis virus

Leukocyte migration to the central nervous system (CNS) is a common process with often devastating consequences that follows infection of this tissue compartment with a variety of viruses. The mechanisms underlying this process are poorly defined but, it is hypothesized that chemokines may be important regulatory signals for the cerebral recruitment and extravasation of leukocytes. Here we discuss this hypothesis in the context of different viral infections of the CNS with emphasis on lymphocytic choriomeningitis virus (LCMV). In general, the pattern of chemokine gene expression in these CNS viral infections is dynamic and complex with often overlapping expression of a number of different subclasses of chemokine genes. In the case of CNS infection with LCMV, cerebral chemokine gene expression was observed in euthymic and to a lesser extent athymic mice and preceded increases in cytokine gene expression and in euthymic mice, CNS leukocyte recruitment. These observations together with the finding that CRG-2/IP-10, a prominently expressed chemokine gene in many different CNS viral infections, was expressed by cells intrinsic to the CNS e.g. astrocytes, suggest that activation of chemokine gene expression may be a direct, early and localized host response to viral infection. These findings are consistent with the proposed involvement of chemokines as key signaling molecules for the migration of leukocytes to the CNS following virus infection.     

The role of integrins in immune-mediated diseases of the nervous system

Immune-mediated diseases of the CNS and PNS, such as multiple sclerosis and Guillain-Barré syndrome, respectively, constitute a major cause of transient and permanent neurological disability in the adult.The aetiology and pathogenesis of these disorders are only partially understood. On a cellular level, focal mononuclear-cell infiltration with demyelination and eventual axonal loss is a crucial pathogenetic event that leads to inflammation and subsequent dysfunction. Here, the evidence that integrins, a family of cell adhesion molecules, expressed on neural and immune cells might play a central role in immune cell recruitment to the CNS and PNS, and probably in tissue repair is reviewed. Distinct integrin expression patterns are observed in multiple sclerosis and Guillain-Barré syndrome. Therapeutic targeting of integrins has been very successful in the corresponding animal models and holds promise as a novel treatment strategy to combat human immune-mediated disorders of the nervous system.     

Gene transfer into the central nervous system in vivo using a recombinanat lentivirus vector

Gene transfer vectors derived from human immunodeficiency virus (HIV-1) efficiently transduce nondividing cells and may provide for the delivery of their gene products to discrete regions of the brain. We investigated whether stable gene transduction can be achieved in cells of the central nervous system (CNS) in vivo by a potent lentivirus vector. The herpes simplex virus type 1 protein VP22 has been known to facilitate intercellular protein transport and thereby provides an opportunity to increase the effectiveness of therapeutic genes by enhancing the delivery of their protein products. We developed a lentiviral vector construct expressing enhanced green fluorescent protein (EGFP) fused at its N-terminus to the herpes simplex virus VP22. In order to determine expression of the fusion protein in specific cells such as neurons in the CNS, a neuron-specific promoter was also placed into the construct. The viral vectors were injected directly into the striatum and hippocampus of mouse brains. We found that the lentivirus vector efficiently and stably transduced nondividing cells in the CNS with transgene expression for over 3 months. We also show that the delivery of VP22-EGFP fusion protein encoded by the lentivirus was effectively transported between neuronal cells via axons in vivo. Doubly labeled experiments revealed that our lentiviral vector is capable of delivering gene products to neurons and astrocytes in CNS. The data also demonstrate that up to 90% of the CNS cells transduced by our lentiviral vector under the control of the neuronal promoter are neurons.