Effector pathways in immune mediated central nervous system demyelination

Effects of natalizumab on oligoclonal bands in the cerebrospinal fluid of patients with multiple sclerosis: a systematic review and meta-analysis

INTRODUCTION

Oligoclonal bands (OCBs) in cerebrospinal fluid (CSF) are utilized for diagnosing multiple sclerosis (MS), as they are found in 95% of patients. Additionally, OCBs are linked to disease prognosis. The primary contributors to OCB production are long-lived plasma cells. This study aims to quantify the impact of natalizumab (NTZ) on OCB levels in the CSF of MS patients.

METHODS

A systematic search on MEDLINE, SCOPUS and Web of Science for English-written and peer-reviewed longitudinal studies on adults was performed. Methodological quality was assessed with the Newcastle-Ottawa Scale. Proportional meta-analysis was performed in R using a generalized linear mixed-effects model. We investigated heterogeneity with influence diagnostics, sensitivity analysis and meta-regression.

RESULTS

Eight eligible studies of adequate quality with a total sample of 326 relapsing-remitting MS patients were included. A summary rate of 14.07% [95% CI, 4.48%-36.36%] for complete loss of OCBs and 42.02% [95% CI, 15.23%-74.51%] for reduction in OCB number or intensity was observed, both with considerable heterogeneity. Pooled estimates dropped (11% [95% CI, 0.04%-0.29%] and 34% [95% CI, 0.11%-0.68%] respectively) after the identification of an influential study. Multivariable meta-regression identified IgG index as a factor contributing to heterogeneity (adj. p = 0.0279), regarding reduction of OCB number or intensity.

DISCUSSION

In conclusion, our systematic review and meta-analysis showed that NTZ can lead to reduction of intrathecal OCBs in MS patients, indicating a possible effect of NTZ on memory plasma cells, which are the main source of OCBs in MS.

Ceramide and Sphingosine Regulation of Myelinogenesis: Targeting Serine Palmitoyltransferase Using microRNA in Multiple Sclerosis

Ceramide and sphingosine display a unique profile during brain development, indicating their critical role in myelinogenesis. Employing advanced technology such as gas chromatography-mass spectrometry, high performance liquid chromatography, and immunocytochemistry, along with cell culture and molecular biology, we have found an accumulation of sphingosine in brain tissues of patients with multiple sclerosis (MS) and in the spinal cord of rats induced with experimental autoimmune encephalomyelitis. The elevated sphingosine leads to oligodendrocyte death and fosters demyelination. Ceramide elevation by serine palmitoyltransferse (SPT) activation was the primary source of the sphingosine elevation as myriocin, an inhibitor of SPT, prevented sphingosine elevation and protected oligodendrocytes. Supporting this view, fingolimod, a drug used for MS therapy, reduced ceramide generation, thus offering partial protection to oligodendrocytes. Sphingolipid synthesis and degradation in normal development is regulated by a series of microRNAs (miRNAs), and hence, accumulation of sphingosine in MS may be prevented by employing miRNA technology. This review will discuss the current knowledge of ceramide and sphingosine metabolism (synthesis and breakdown), and how their biosynthesis can be regulated by miRNA, which can be used as a therapeutic approach for MS.

Sphingosine Toxicity in EAE and MS: Evidence for Ceramide Generation via Serine-Palmitoyltransferase Activation

Multiple sclerosis (MS) is a demyelinating disorder characterized by massive neurodegeneration and profound axonal loss. Since myelin is enriched with sphingolipids and some of them display toxicity, biological function of sphingolipids in demyelination has been investigated in MS brain tissues. An elevation of sphingosine with a decrease in monoglycosylceramide and psychosine (myelin markers) was observed in MS white matter and plaque compared to normal brain tissue. This indicated that sphingosine toxicity might mediate oligodendrocyte degeneration. To explain the source of sphingosine accumulation, total sphingolipid profile was investigated in Lewis rats after inducing experimental autoimmune encephalomyelitis (EAE) and also in human oligodendrocytes in culture. An intermittent increase in ceramide followed by sphingosine accumulation in EAE spinal cord along with a stimulation of serine-palmitoyltransferase (SPT) activity was observed. Apoptosis was identified in the lumbar spinal cord, the most prominent demyelinating area, in the EAE rats. TNFα and IFNγ stimulation of oligodendrocytes in culture also led to an accumulation of ceramide with an elevation of sphingosine. Ceramide elevation was drastically blocked by myriocin, an inhibitor of SPT, and also by FTY720. Myriocin treatment also protected oligodendrocytes from cytokine mediated apoptosis or programmed cell death. Hence, we propose that sphingosine toxicity may contribute to demyelination in both EAE and MS, and the intermittent ceramide accumulation in EAE may, at least partly, be mediated via SPT activation, which is a novel observation that has not been previously reported.

On the horizon: possible neuroprotective role for glatiramer acetate

Inflammation and neurodegeneration characterize the pathogenesis of multiple sclerosis (MS). Slow axonal degeneration, rather than acute inflammation, is considered the cause of chronic disability in MS. The signs of acute axonal damage and loss have been shown to occur early in the lesion development of patients with chronic MS and often correlate with demyelination and inflammation. While immune activity in the central nervous system has traditionally been considered to be a detrimental event in MS, recent studies have found that autoimmune T cells may play an important role in protecting neurons from the ongoing spreading damage. Neuroprotectio n in MS is a new and evolving concept, and many questions remain with regard to potential targets for therapeutic intervention. Preliminary studies, both in animals and in humans, have suggested that glatiramer acetate (GA) may confer neuroprotective activity in addition to bystander suppression. Additional research is needed to determine if these promising neuroprotective effects correlate with the long-term effect of G A in MS.

Heparanase upregulates Th2 cytokines, ameliorating experimental autoimmune encephalitis

Heparanase is an endo-beta-d-glucuronidase that cleaves heparan sulfate (HS) saccharide chains. The enzyme promotes cell adhesion, migration and invasion and plays a significant role in cancer metastasis, angiogenesis and inflammation. The present study focuses on the involvement of heparanase in autoimmunity, applying the murine experimental autoimmune encephalitis (EAE) model, a T-cell dependent disease often used to investigate the pathophysiology of multiple sclerosis (MS). Intraperitoneal administration of recombinant heparanase ameliorated, in a dose dependent manner, the clinical signs of the disease. In vitro and in vivo studies revealed that heparanase inhibited mitogen induced splenocyte proliferation and mixed lymphocyte reaction (MLR) through modulation of their repertoire of cytokines indicated by a marked increase in the levels of IL-4, IL-6 and IL-10, and a parallel decrease in IL-12 and TNF-alpha. Similar results were obtained with active, latent, or point mutated inactive heparanase, indicating that the observed inhibitory effect is attributed to a non-enzymatic activity of the heparanase protein. We suggest that heparanase induces upregulation of Th2 cytokines, resulting in inhibition of the inflammatory lesion of EAE.

Early blood-brain barrier permeability in cerebella of PLSJL mice immunized with myelin basic protein

The blood-brain barrier (BBB) is dramatically but transiently compromised in the cerebella of myelin basic protein immunized mice at least 1 week prior to the development of the paralytic phase of experimental allergic encephalomyelitis (EAE). Treatment of mice with the peroxynitrite-dependent radical scavenger uric acid (UA) during the first week after immunization blocks the early increase in cerebellar BBB permeability and the subsequent development of clinical signs of EAE. These results indicate that the early loss of BBB integrity in the cerebellum is likely to be a necessary step in the development of paralytic EAE.

Combination therapy in multiple sclerosis

Multiple sclerosis is an inflammatory/demyelinating and neurodegenerative disease. Treatment of MS is currently based on various different therapeutic algorithms of a sequential or escalating therapy with immunomodulators or immunosuppressants, generated partly from evidence based medicine and partly from expert's consensus. However, these therapies are not always effective as monotherapies. An alternative would be the combination of agents which already have some proven efficacy in MS therapy, are directed against different mechanisms of the pathogenic chain, and ideally result in synergic effects and a profile of reduced toxicity. Combination therapy in multiple sclerosis can be: Combination of two or more anti-inflammatory agents or combination of anti-inflammatory agents plus neuroprotective agents. Many combinations of drugs have been or are being tested in multiple sclerosis. Clinical trials have included a low number of patients for short periods of time. Preliminary studies on safety suggest that some combination therapies might be safe and efficacious. Ongoing and new phase III clinical trials involving a greater number of patients for longer periods of time are needed to verify this hypothesis. A wise balance between efficacy and safety and extremely clear information to patients should drive clinical decisions.

Differential effects of Th1, monocyte/macrophage and Th2 cytokine mixtures on early gene expression for immune-related molecules by central nervous system mixed glial cell cultures

Cytokines secreted within the central nervous system (CNS) are important in the development of multiple sclerosis (MS) lesions. The balance between Th1, monocyte/macrophage (M/M) and Th2 cytokines in the CNS may be pivotal in determining the outcome of lesion development. We examined the effects of mixtures of cytokines on gene expression by CNS glial cells, as mixtures of cytokines are present in MS lesions, which in turn contain mixtures of glial cells. In this initial analysis by gene array, we examined changes at 6 hours to identify early changes in gene expression that represent primary responses to the cytokines. Rat glial cells were incubated with mixtures of Th1, M/M and Th2 cytokines for 6 hours and examined for changes in early gene expression employing microarray gene chip technology. A minimum of 814 genes were differentially regulated by one or more of the cytokine mixtures in comparison to controls, including changes in expression in a large number of genes for immune system-related proteins. Expression of the proteins for these genes likely influences development and inhibition of MS lesions as well as protective and regenerative processes. Analysing gene expression for the effects of various combinations of exogenous cytokines on glial cells in the absence of the confounding effects of inflammatory cells themselves should increase our understanding of cytokine-induced pathways in the CNS.

Abnormal endothelial tight junctions in active lesions and normal-appearing white matter in multiple sclerosis

Blood-brain barrier (BBB) breakdown, demonstrable in vivo by enhanced MRI is characteristic of new and expanding inflammatory lesions in relapsing-remitting and chronic progressive multiple sclerosis (MS). Subtle leakage may also occur in primary progressive MS. However, the anatomical route(s) of BBB leakage have not been demonstrated. We investigated the possible involvement of interendothelial tight junctions (TJ) by examining the expression of TJ proteins (occludin and ZO-1 ) in blood vessels in active MS lesions from 8 cases of MS and in normal-appearing white (NAWM) matter from 6 cases. Blood vessels (10-50 per frozen section) were scanned using confocal laser scanning microscopy to acquire datasets for analysis. TJ abnormalities manifested as beading, interruption, absence or diffuse cytoplasmic localization of fluorescence, or separation of junctions (putative opening) were frequent (affecting 40% of vessels) in oil-red-O-positive active plaques but less frequent in NAWM (15%), and in normal (< 2%) and neurological controls (6%). Putatively "open" junctions were seen in vessels in active lesions and in microscopically inflamed vessels in NAWM. Dual fluorescence revealed abnormal TJs in vessels with pre-mortem serum protein leakage. Abnormal or open TJs, associated with inflammation may contribute to BBB leakage in enhancing MRI lesions and may also be involved in subtle leakage in non-enhancing focal and diffuse lesions in NAWM. BBB disruption due to tight junctional pathology should be regarded as a significant form of tissue injury in MS, alongside demyelination and axonopathy.

Transdifferentiation of mesenchymal stem cells into Schwann cell-like myelinating cells

Bone marrow stromal cells (MSC) are multipotent stem cells that differentiate into cells of the mesodermal lineage. Although adult, their differentiation potential is remarkable, and they are able to transdifferentiate. Transdifferentiated cultivated rat MSC (tMSC) changed morphologically into cells resembling typical spindle-shaped Schwann cells (SC) with enhanced expression of LNGF receptor, Krox-20, CD104 and S100beta protein and decreased expression of bone morphogenetic protein receptor-1A compared to untreated rat MSC (rMSC). Transdifferentiation was reversible and repeatable. To evaluate the myelinating capacity, rMSC, tMSC, or SC cultured from male rats were grafted into an autologous muscle conduit bridging a 2-cm gap in the female rat sciatic nerve. The presence of the male-specific SRY gene (as revealed by PCR analysis) and S100 immunoreactivity of pre-labeled tMSC confirmed the presence of the implanted cells in the grafts. Three weeks after grafting, an appropriate regeneration was noted in the SC and in the tMSC groups, while regeneration in the rMSC group and in the control group without any cells was impaired. In contrast to SC, in some cases, single tMSC were able to myelinate more than one axon. Our findings demonstrate that it may be possible to differentiate MSC into therapeutically useful cells for clinical applications.

Human bone marrow stromal cell treatment improves neurological functional recovery in EAE mice

We investigated the treatment of remitting-relapsing experimental autoimmune encephalomyelitis (EAE) in mice with human bone marrow stromal cells (hBMSCs). hBMSCs were injected intravenously into EAE mice upon onset of paresis. Neurological functional tests were scored daily by grading clinical signs (score 0-5). Immunohistochemistry was performed to measure the transplanted hBMSCs, cell proliferation (bromodeoxyuridine, BrdU), oligodendrocyte progenitor cells (NG2), oligodendrocytes (RIP), and brain-derived neurotrophic factor (BDNF). The maximum clinical score and the average clinical scores were significantly decreased in the hBMSC-transplanted mice compared to the phosphate-buffered-saline-treated EAE controls, indicating a significant improvement in function. Demyelination significantly decreased, and BrdU(+) and BDNF(+) cells significantly increased in the hBMSC-treated mice compared to controls. Some BrdU(+) cells were colocalized with NG2(+) and RIP(+) immunostaining. hBMSCs also significantly reduced the numbers of vessels containing inflammatory cell infiltration. These data indicate that hBMSC treatment improved functional recovery after EAE in mice, possibly, via reducing inflammatory infiltrates and demyelination areas, stimulating oligodendrogenesis, and by elevating BDNF expression.

Erythropoietin treatment improves neurological functional recovery in EAE mice

Erythropoietin (EPO), originally recognized for its central role in erythropoiesis, has been shown to improve neurological outcome after stroke. Here, we investigated the treatment of experimental autoimmune encephalomyelitis (EAE) in mice with EPO. Mice were treated with recombinant human EPO (rhEPO) upon onset of paresis. Neurological functional tests were scored daily by grading of clinical signs (score 0-5). Hematoxylin and eosin (HE) staining of cerebral tissue was performed to detect inflammatory infiltrates. Double staining for Luxol fast blue and Bielshowsky was used to demonstrate myelin and axons, respectively. Immunohistochemistry was performed to measure the expression of bromodeoxyuridine (BrdU, a marker for cell proliferation), NG2 (a marker for oligodendrocyte progenitor cells) and brain-derived neurotrophic factor (BDNF). Treatment with rhEPO significantly improved neurological functional recovery, reduced inflammatory infiltrates and demyelination, and increased oligodendrocyte progenitor cell proliferation and BDNF+ cells compared to the EAE controls. These data indicate that rhEPO treatment improved functional recovery after EAE in mice, possibly, via stimulating oligodendrogenesis, downregulating proinflammatory infiltrates and by elevating BDNF expression.

Immunotherapy in autoimmune neuromuscular disorders

Important progress has been made in our understanding of the cellular and molecular processes underlying autoimmune neuromuscular diseases that has led us to identify targets for rational therapeutic intervention. Although antigen-specific immunotherapy is not yet available, old and new immunomodulatory treatments, alone or in combination, provide effective immunotherapy for most autoimmune disorders. In parallel, the achievements of molecular medicine provide more specific yet largely experimental therapeutic tools that need to be tested in the human diseases. Here we review the principles and targets of immunotherapy for autoimmune neuromuscular disorders, address applications and practical guidelines, and give an outlook on future developments.

Inflammation in multiple sclerosis: the good, the bad, and the complex

Inflammation has always been thought of as detrimental in the pathophysiology of multiple sclerosis (MS). However, emerging genetic data, magnetic-resonance-imaging studies, and immunopathological evidence challenge this simplistic view. The evidence leads to the conclusion that inflammation is tightly regulated, and that its net effect may be beneficial in MS, thus explaining some of the results from recent trials of anti-inflammatory agents. We argue that the use of anti-inflammatory drugs to treat MS may not be appropriate in all cases. Precise identification of the inflammatory pathways to be targeted in the different phases of the disease and the timing of such interventions are therefore crucial.

Matrix metalloproteinases in inflammatory myopathies: enhanced immunoreactivity near atrophic myofibers

OBJECTIVES

To further examine the role of proteolytic enzyme expression of matrix metalloproteinases (MMP) and T-cell markers in inflammatory myopathies and controls.

MATERIAL AND METHODS

We studied the expression of MMP-2, MMP-7, and MMP-9 in 19 cases of inflammatory myopathies and controls using immunocytochemistry.

RESULTS

Inflammatory myopathies showed distinct patterns of up-regulation of MMP. MMP-9 was strongly expressed in atrophic myofibers in all inflammatory myopathies. MMP-2 immunoreactivity was similar in its distribution, however, to a weaker intensity. In dermatomyositis the perifascicular atrophy showed pronounced MMP-9 immunoreactivity, probably reflecting denervated patterns of myofibers. Moreover, MMP-7 strongly immunolabeled invaded myofibers in polymyositis cases only.

CONCLUSION

These patterns confirm, that MMP-7 up-regulation is prominent in PM, while MMP-2 immunoreactivity is only slightly elevated in inflamed muscle. In general, MMP-9 up-regulation appears to be an important additional molecular event in the multistep process of all inflammatory myopathies.

Chemokines and chemokine receptors in inflammatory demyelinating neuropathies: a central role for IP-10

Inflammatory cell recruitment is an important step in the pathogenesis of autoimmune demyelinating diseases of the PNS. Chemokines might play a critical role in promoting leucocyte entry into the nervous system during immune-mediated inflammation. Here, we report the expression pattern of the chemokine receptors CCR-1, CCR-2, CCR-4, CCR-5 and CXCR-3 in sural nerve biopsies obtained from patients with classical Guillain-Barré syndrome (acute inflammatory demyelinating polyradiculoneuropathy), chronic inflammatory demyelinating polyradiculoneuropathy and various non-inflammatory neuropathies. A consistent chemokine receptor expression pattern was immunohistochemically detected in inflammatory demyelinating neuropathies and quantitation of labelled mononuclear cells revealed significantly elevated cell counts compared with controls. CCR-1 and CCR-5 were primarily expressed by endoneurial macrophages, whereas CCR-2, CCR-4 and CXCR-3 could be localized to invading T lymphocytes. Quantitative analysis revealed that CXCR-3 was expressed at highest numbers by infiltrating T cells compared with the other receptors. Thus, expression and distribution of CXCR-3 suggest a specific role of this receptor in chemokine-mediated lymphocyte traffic into the inflamed PNS tissue. Therefore, we further analysed the expression of its ligands interferon-gamma-inducible protein of 10 kDa (IP-10) and monokine induced by interferon-gamma (Mig). Significantly increased levels of IP-10 could be measured in the CSF of patients with inflammatory neuropathies, whereas no differences were observable for Mig. In situ hybridization for IP-10 mRNA mirrored the distribution of the cognate receptor within the inflamed PNS, and delineated endothelial cells as the primary cellular source of IP-10. Our results imply a pathogenic role for specific chemokine receptors and IP-10 in the genesis of inflammatory demyelinating neuropathies.

Human MBP-specific T cells regulate IL-6 gene expression in astrocytes through cell-cell contacts and soluble factors

One of the distinctive features of multiple sclerosis (MS) attacks is homing to the CNS of activated T cells able to orchestrate humoral and cell-based events, resulting in immune-mediated injury to myelin and oligodendrocytes. Of the complex interplay occurring between T cells and CNS constituents, we have examined some aspects of T-cell interactions with astrocytes, the major components of the glial cells. Specifically, we focused on the ability of T cells to regulate the gene expression of interleukin-6 (IL-6) in astrocytes, based on previous evidence showing the involvement of this cytokine in CNS disorders. We found that T-cell adhesion and T-cell soluble factors induce IL-6 gene expression in U251 astrocytes through distinct signaling pathways, respectively, resulting in the activation of NF-kappaB and IRF-1 transcription factors. In a search for effector molecules at the astrocyte surface, we found that alpha3beta1 integrins play a role in NF-kappaB activation induced by T-cell contact, whereas interferon-gamma (IFN-gamma) receptors dominate in IRF-1 induction brought about by T-cell-derived soluble factors. Similar phenomena were observed also in normal fetal astrocyte cultures. We therefore propose that through astrocyte induction, T cells may indirectly regulate the availability of a cytokine which is crucial in modulating fate and behavior of cell populations involved in the pathogenesis of MS inflammatory lesions.

Fibroblast growth factor-II gene therapy reverts the clinical course and the pathological signs of chronic experimental autoimmune encephalomyelitis in C57BL/6 mice

The development of therapies aimed to promote remyelination is a major issue in chronic inflammatory demyelinating disorders of the central nervous system (CNS) such as multiple sclerosis (MS), where the permanent neurological impairment is due to the axonal loss resulting from recurrent episodes of immune-mediated demyelination. Here, we show that the intrathecal injection of a herpes simplex virus (HSV) type-1 replication-defective multigene vector, engineered with the human fibroblast growth factor (FGF)-II gene (TH:bFGF vector), was able to significantly revert in C57BL/6 mice the clinicopathological signs of chronic experimental autoimmune encephalomyelitis (EAE), the animal model of MS. The treatment with the TH:bFGF vector was initiated within 1 week after the clinical onset of EAE and was effective throughout the whole follow-up period (ie 60 days). The disease-ameliorating effect in FGF-II-treated mice was associated with: (1) CNS production of FGF-II from vector-infected cells which were exclusively located around the CSF space (ependymal, choroidal and leptomeningeal cells); (2) significant decrease (P < 0.01) of the number of myelinotoxic cells (T cells and macrophages) both in the CNS parenchyma and in the leptomeningeal space; and (3) significant increase (P < 0.01) of the number of oligodendrocyte precursors and of myelin-forming oligodendrocytes in areas of demyelination and axonal loss. Our results indicate that CNS gene therapy using HSV-1-derived vector coding for neurotrophic factors (ie FGF-II) is a safe and non-toxic approach that might represent a potential useful 'alternative' tool for the future treatment of immune-mediated demyelinating diseases.

Intrathecal delivery of IFN-gamma protects C57BL/6 mice from chronic-progressive experimental autoimmune encephalomyelitis by increasing apoptosis of central nervous system-infiltrating lymphocytes

The exclusive detrimental role of proinflammatory cytokines in demyelinating diseases of the CNS, such as multiple sclerosis, is controversial. Here we show that the intrathecal delivery of an HSV-1-derived vector engineered with the mouse IFN-gamma gene leads to persistent (up to 4 wk) CNS production of IFN-gamma and inhibits the course of a chronic-progressive form of experimental autoimmune encephalomyelitis (EAE) induced in C57BL/6 mice by myelin oligodendrocyte glycoprotein (MOG)(35-55). Mice treated with the IFN-gamma-containing vector before EAE onset showed an earlier onset but a milder course of the disease compared with control mice treated with the empty vector. In addition, 83% of IFN-gamma-treated mice completely recovered within 25 days post immunization, whereas control mice did not recover up to 60 days post immunization. Mice treated with the IFN-gamma-containing vector within 1 wk after EAE onset partially recovered from the disease within 25 days after vector injection, whereas control mice worsened. Recovery from EAE in mice treated with IFN-gamma was associated with a significant increase of CNS-infiltrating lymphocytes undergoing apoptosis. During the recovery phase, the mRNA level of TNFR1 was also significantly increased in CNS-infiltrating cells from IFN-gamma-treated mice compared with controls. Our results further challenge the exclusive detrimental role of IFN-gamma in the CNS during EAE/multiple sclerosis, and indicate that CNS-confined inflammation may induce protective immunological countermechanisms leading to a faster clearance of encephalitogenic T cells by apoptosis, thus restoring the immune privilege of the CNS.

Delivery to the central nervous system of a nonreplicative herpes simplex type 1 vector engineered with the interleukin 4 gene protects rhesus monkeys from hyperacute autoimmune encephalomyelitis

Systemic administration of antiinflammatory molecules to patients affected by immune-mediated inflammatory demyelinating diseases of the central nervous system (CNS) has limited therapeutic efficacy due to the presence of the blood-brain barrier (BBB). We found that three of five rhesus monkeys injected intrathecally with a replication-defective herpes simplex virus (HSV) type 1-derived vector engineered with the human interleukin 4 (IL-4) gene were protected from an hyperacute and lethal form of experimental autoimmune encephalomyelitis induced by whole myelin. The intrathecally injected vector consistently diffused within the CNS via the cerebrospinal fluid and infected ependymal cells, which in turn sustained in situ production of IL-4 without overt immunological or toxic side effects. In EAE-protected monkeys, IL-4-gene therapy significantly decreased the number of brain as well as spinal cord inflammatory perivenular infiltrates and the extent of demyelination, necrosis, and axonal loss. The protective effect was associated with in situ downregulation of inflammatory mediators such as tumor necrosis factor alpha (TNF-alpha) and monocyte chemoattractant protein 1 (MCP-1), upregulation of transforming growth factor beta (TGF-beta), and preservation of BBB integrity. Our results indicate that intrathecal delivery of HSV-1-derived vectors containing antiinflammatory cytokine genes may play a major role in the future therapeutic armamentarium of inflammatory CNS-confined demyelinating diseases and, in particular, in the most fulminant forms where conventional therapeutic approaches have, so far, failed to achieve a satisfactory control of the disease evolution.

Spectrum and classification of inflammatory demyelinating diseases of the central nervous system

The aim of this review is to highlight recent observations concerning the pathogenesis of acute and chronic inflammatory demyelinating diseases in the central nervous system. Without attempting to provide a didactic classification or a complete survey, we emphasize the discriminative nature of new clinical, imaging, and immunopathologic data, which, even in the absence of specific molecular markers, modify our views about the nosologic relations among these overlapping clinicopathologic entities. In the light of new findings, multiple sclerosis may represent a spectrum of demyelinating diseases rather than a single entity.

Therapeutic relevance of altered cytokine expression

Cytokines and their receptors have numerous physiological functions. Altered concentrations of these mediators are associated with various afflictions. For example, over-expression of cytokines has been associated with altered drug concentrations and activity. Greater concentrations of cardiovascular drugs have been observed in humans and laboratory animals with various types of inflammatory disorders compared to healthy controls. Interestingly, the observed higher concentrations of drugs such as propranolol and verapamil have not been associated with increased effects. Indeed, reduced response to these cardiovascular drugs is observed, suggestive of cytokine-mediated downregulation of receptors. Increased cytokine concentrations have also been associated with decreased response to drugs used in treatment of other disorders such as AIDS, asthma and psychiatric diseases. This reduced response to drug in the presence of altered cytokine concentrations is especially relevant to the elderly population which has a greater incidence of multiple diseases and elevated concentrations of various cytokines compared to younger individuals. Furthermore, inflammatory conditions and their accompanied increased over-expression of cytokines are suggested to be the main determinants of therapeutic failure in myocardial infarction and angina. Therefore, altered cytokine concentrations may influence therapeutic outcomes of pharmacotherapy and result in treatment failure.

The effect of myelinating Schwann cells on axons

Myelinating Schwann cells control the number of neurofilaments and elevate the phosphorylation state of neurofilaments in the axon, eventually leading to the typical large axon caliber. Conversely, absence of myelin leads to lower amounts of neurofilaments, reduced phosphorylation levels, and smaller axon diameters. In addition, myelinating Schwann cells mediate the spacing of Na(+) channel clusters during development of the node of Ranvier. When axons are associated with mutant Schwann cells in inherited neuropathies, their calibers are reduced and their neurofilaments are less phosphorylated and more closely spaced. Also, axonal transport is reduced and axons degenerate at the distal ends of long nerves. Myelin-associated glycoprotein may mediate some aspects of Schwann cell-axon communication, but much remains to be learned about the molecular bases of Schwann cell-axon communication.

Multiple sclerosis: current pathophysiological concepts

Multiple sclerosis (MS) is an often disabling disease primarily affecting young adults that exhibits extraordinary clinical, radiological, and pathological heterogeneity. We review the following: (a) known environmental and genetic factors that contribute to MS susceptibility; (b) current knowledge regarding fundamental pathophysiological processes in MS, including immune cell recruitment and entry into the central nervous system (CNS), formation of the plaque, and orchestration of the immune response; (c) descriptive and qualitative distinct pathological patterns in MS and their implications; (d) the evidence supporting the causative role of direct toxins, cell-mediated and humorally mediated immune mechanisms, and the concept of a "primary oligodendrogliopathy" in demyelination and axonal injury; (e) the potential benefits of inflammation; (f) the prospects for remyelination; and (g) therapeutic implications and approaches suggested by putative pathophysiological mechanisms.

Central nervous system gene therapy with interleukin-4 inhibits progression of ongoing relapsing-remitting autoimmune encephalomyelitis in Biozzi AB/H mice

Multiple sclerosis (MS) is an immune-mediated inflammatory disease of the central nervous system (CNS) that might benefit from anti-inflammatory therapies. However, systemic delivery of anti-inflammatory drugs in MS patients has so far been disappointing, mostly due to the limited capacity of these molecules to enter the CNS. We injected into the cisterna magna (i.c.) of Biozzi AB/H mice affected by a relapsing-remitting form of experimental autoimmune encephalomyelitis (EAE), the animal model of MS, a non-replicative herpes simplex virus (HSV) type-1-derived vector containing the interleukin (IL)-4 gene (d120:LacZ:IL-4). CNS delivery of the d120:LacZ:IL-4 vector, after EAE onset, induced the in situ production of IL-4 by CNS-resident cells facing the cerebrospinal fluid (CSF) spaces and reduced by 47% (P < 0.02) the disease-related deaths. Compared with mice treated with the control d120:lacZ vector, IL-4-treated mice also showed a shorter duration of the first EAE attack, a longer inter-relapse period, and a reduction in the severity and duration of the first relapse. Protection from EAE progression in IL-4-treated mice was associated with activation of microglia in spinal cord areas where mRNA content of the pro-inflammatory chemokines, macrophage chemoattractant protein-1 (MCP-1) and Rantes, was reduced and that of the anti-inflammatory cytokine IL-4 was increased. Finally, CNS-infiltrating mononuclear cells from IL-4-treated mice produced lower levels of MCP-1 mRNA compared with control mice. Our results, showing that IL-4 gene delivery using HSV-1 vectors induces protection from EAE by in situ modulating the cytokine/chemokine-mediated circuits sustaining effector cell functions, indicate that the intrathecal 'therapeutic' use of nonreplicative HSV-1-derived vectors containing anti-inflammatory molecules might represent an alternative strategy in inflammatory diseases of the CNS.

Cytokine therapy in immune-mediated demyelinating diseases of the central nervous system: a novel gene therapy approach

Pro-inflammatory cytokines play a crucial role in the regulatory and effector phase of the immune-mediated mechanism sustaining multiple sclerosis pathogenesis (MS) thus supporting the use of anti-inflammatory cytokines as a therapeutic option. Systemic administration of cytokines shows, however, limited therapeutic efficacy and undesirable/unpredictable side-effects. We have developed a non-toxic system to deliver cytokines within the central nervous system (CNS) based on the intrathecal (i.c.) administration of non-replicative herpes simplex (HSV) type-1-derived viral vectors engineered with heterologous cytokine genes. Compared to controls, mice affected by experimental autoimmune encephalomyelitis (EAE) and i.c. injected with an HSV-1-derived vector containing the gene of the anti-inflammatory cytokine IL-4 showed a significant amelioration of clinical and pathological EAE signs. A decreased mRNA expression of the monocyte chemoattractant protein-1 (MCP-1) by mononuclear CNS-infiltrating cells was also observed. Peripheral T cells from IL-4-treated mice were not affected both in their antigen-specific proliferative response and in the cytokine secretion pattern. Our results indicate that CNS cytokine delivery with HSV-1-derived vectors is a feasible therapeutic strategy and might represent an alternative approach for the treatment of immune-mediated demyelinating diseases. Advantages of this approach over systemic cytokine administration are the high cytokine level reached within the CNS and the absence of side-effects on the peripheral immune system. The short-lasting cytokine production in the CNS after a single vector administration (4 weeks) is the limiting factor of this novel technology which, although promising, has to be improved.

Cytokine gene therapy of autoimmune demyelination revisited using herpes simplex virus type-1-derived vectors

The peripheral delivery of drugs in patients affected by central nervous system (CNS)-confined diseases is therapeutically ineffective due to the presence of the blood-brain barrier which forms an inaccessible wall to the majority of CNS targeting molecules. When molecules with an anti-inflammatory profile have been systemically administered to patients affected by a chronic inflammatory demyelinating disease of the CNS, such as multiple sclerosis (MS), results have been disappointing. A successful therapeutic approach in MS should therefore consider the delivery of anti-inflammatory molecules directly into the CNS in order to inhibit blood-borne CNS-confined mononuclear cells which act as ultimate effector cells directly destroying oligodendrocytes and/or releasing myelinotoxic substances. Biological and physical vectors engineered with heterologous genes coding for immunomodulatory cytokines with an anti-inflammatory profile might represent the appropriate tool to deliver therapeutic genes into the CNS of patients with MS. So far, cytokine gene therapy has never been attempted in MS, but encouraging results have been obtained in the animal model of MS, experimental autoimmune encephalomyelitis (EAE), using viral vectors or plasmids engineered with cytokine genes and then injected systemically, either in the blood stream or circulating encephalitogenic T cells, or into the CNS. Here, we critically discuss the various attempts made in EAE using gene therapy protocols based on the delivery of immunomodulatory cytokine genes. Special emphasis is put on the use of non-replicative herpes simplex type-1 (HSV)-derived vectors engineered with the gene of the immunomodulatory cytokine interleukin (IL)-4.

Chemokine receptor antagonism as a new therapy for multiple sclerosis

New information about the role of tissue inflammation in the pathogenesis of multiple sclerosis (MS) has driven a search for effective and specific therapeutics that address leukocyte trafficking. These developments in understanding MS are complemented by advances in clarifying the molecular mechanisms of leukocyte extravasation and providing the knowledge base needed to modulate tissue inflammation. Of particular interest are the chemokines and their receptors. Chemokines constitute a large family of chemoattractant peptides that regulate the vast spectrum of leukocyte migration events. This review discusses MS and proposes that identifying the chemokines and receptors involved in the inflammation associated with this disorder may lead to therapeutic intervention.