[Neuroprotection in the treatment of multiple sclerosis]. / Neuroprotektion in der Therapie der Multiplen Sklerose.

Atrophy, the wasting or shrinkage of tissue, of the nervous system is the main feature of neurodegeneration, i.e. the umbrella term for the progressive loss of structure or function of neurons. Loss of neurons due to cell death and axonal degeneration characterize neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease or amyotrophic lateral sclerosis. In these illnesses, it still has to be elucidated to which extent inflammation is part of the pathology. Conversely, in chronic inflammation of the central nervous system (CNS), atrophy has previously also been described and neurodegeneration is discussed as a pathologic feature. The most frequent chronic inflammatory disease of the CNS is multiple sclerosis (MS), which leads to devastating relapsing-remitting symptoms and disability during the relapses, increasingly during the course of disease in patients. Meanwhile it became clear that axons already reveal pathology early in the disease and neurons are affected in the cortex and the spinal cord, albeit to a different extent. The broadening of understanding neurodegenerative aspects of MS pathology demands and creates new therapeutic strategies. Current medication used in MS treatment as well as medications about to be approved are primarily anti-inflammatory therapies. By modulating the immune system and thereby blocking key steps of the pathology, the immunomodulation therapies in MS have a slight impact on disability progression. There is, however, clinical and experimental data concerning the potential neuroprotective properties of novel therapies. Combining anti-inflammatory and direct neuroprotective or even neuroregenerative therapy strategies would be a step forward in the treatment of multiple sclerosis.

G-protein-coupled receptor screen reveals a role for chemokine receptor CCR5 in suppressing microglial neurotoxicity.

G-protein-coupled receptors (GPCRs) form the largest superfamily of membrane proteins, and several GPCRs have been implicated in signaling between neurons and glia to protect neurons from pathological stresses. Here, we have used a screening strategy to investigate GPCRs that are involved in neuronal protection. The real-time PCR was performed using 274 primers targeting nonsensory GPCR mRNAs, which were listed on the database. The cDNAs from control and nerve-injured hypoglossal nuclei of mouse brain were used, and the alterations of PCR products were compared. This screen and the subsequent in situ hybridization screen exhibited six GPCR mRNAs which were prominently and convincingly induced in nerve-injured hypoglossal nuclei. Among these candidates, the chemokine receptor CCR5 was selected, based on the marked induction in CCR5 mRNA in microglia after nerve injury. The mRNA expression of ligands for CCR5, such as regulated on activation normal T-cell expressed and secreted (RANTES/CCL5), MIP-1alpha, and MIP-1beta, were induced in injured motor neurons, indicating that CCR5 and its ligands were expressed in microglia and neurons, respectively, in response to nerve injury. In vitro, lipopolysaccharide (LPS)-induced expression of mRNAs for inflammatory cytokines (IL-1beta, IL-6, and tumor necrosis factor-alpha) and inducible nitric oxide synthase (iNOS) in microglia were all suppressed by RANTES. Those suppressions were not observed in microglia from CCR5 null mice. In addition, nerve injury-induced motor neuron death seen in wild type C56BL/6J mice was accelerated in CCR5 knock-out C57BL/6J. These results may suggest that CCR5-mediated neuron-glia signaling functions to protect neurons by suppressing microglia toxicity.

Influence of injury severity on the rate and magnitude of the T lymphocyte and neuronal response to facial nerve axotomy.

The temporal relationship between severity of peripheral axonal injury and T lymphocyte trafficking to the neuronal cell bodies of origin in the brain has been unclear. We sought to test the hypothesis that greater neuronal death induced by disparate forms of peripheral nerve injury would result in differential patterns of T cell infiltration and duration at the cell bodies of origin in the brain and that these measures would correlate with the magnitude of neuronal death over time and cumulative neuronal loss. To test this hypothesis, we compared the time course of CD3(+) T cell infiltration and neuronal death (assessed by CD11b(+) perineuronal microglial phagocytic clusters) following axonal crush versus axonal resection injuries, two extreme variations of facial nerve axotomy that result in mild versus severe neuronal loss, respectively, in the facial motor nucleus. We also quantified the number of facial motor neurons present at 49 days post-injury to determine whether differences in the levels of neuronal death between nerve crush and resection correlated with differences in cumulative neuronal loss. Between 1 and 7 days post-injury when levels of neuronal death were minimal, we found that the rate of accumulation and magnitude of the T cell response was similar following nerve crush and resection. Differences in the T cell response were apparent by 14 days post-injury when the level of neuronal death following resection was substantially greater than that seen in crush injury. For nerve resection, the peak of neuronal death at 14 days post-resection was followed by a maximal T cell response one week later at 21 days. Differences in the level of neuronal death between the two injuries across the time course tested reflected differences in cumulative neuronal loss at 49 days post-injury. Altogether, these data suggest that the trafficking of T cells to the injured FMN is dependent upon the severity of peripheral nerve injury and associated neuronal death.

IL-2 gene knockout affects T lymphocyte trafficking and the microglial response to regenerating facial motor neurons.

Following facial nerve axotomy in mice, T cells cross the intact blood-brain barrier (BBB), home to nerve cell bodies in the facial motor nucleus (FMN), and augment neuroregenerative processes. The pivotal T cell immunoregulatory cytokine, IL-2, appears to have bidirectional effects on neuronal and microglial cell function, suggesting rival hypotheses that IL-2 could either enhance or disrupt processes associated with regeneration of axotomized facial motor neurons. We tested these competing hypotheses by comparing the effect of facial nerve axotomy on C57BL/6-IL-2(-/-) knockout and C57BL/6-IL-2(+/+) wild-type littermates. Since IL-2 may also be produced endogenously in the brain, we also sought to determine whether differences between the knockout and wild-type mice were attributable to loss of IL-2 gene expression in the CNS, loss of peripheral sources of IL-2 and the associated effects on T cell function, or a combination of these factors. To address this question, we bred novel congenic mice with the SCID mutation (mice lacking T cell derived IL-2) that were homozygous for either the IL-2 knockout or wild-type gene alleles (C57BL/6scid-IL-2(-/-) and C57BL/6scid-IL-2(+/+) littermates, respectively). Groups were assessed for differences in (1) T lymphocytes entering the axotomized FMN; (2) perineuronal CD11b(+) microglial phagocytic clusters, a measure of motor neuron death; and (3) activated microglial cells as measured by MHC-II positivity. C57BL/6-IL-2(-/-) knockout mice had significantly higher numbers of T cells and lower numbers of activated MHC-II-positive microglial cells in the regenerating FMN than wild-type littermates, although the number of CD11b(+) phagocytic microglia clusters did not differ. Thus, despite the significant impairment of T cell function known to be associated with loss of peripheral IL-2, the increased number of T cells entering the axotomized FMN appears to have sufficient activity to support neuroregenerative processes. Congenic C57BL/6scid-IL-2(-/-) knockout mice had lower numbers of CD11b(+) microglial phagocytic clusters than congenic C57BL/6scid-IL-2(+/+) wild-type littermates, suggesting that loss of the IL-2 gene in the CNS (and possibly the loss of other unknown sources of the gene) enhanced neuronal regeneration. Further study of IL-2's complex actions in neuronal injury may provide greater understanding of key variables that determine whether or not immunological processes in the brain are proregenerative.

The role of excitotoxicity in secondary mechanisms of spinal cord injury: a review with an emphasis on the implications for white matter degeneration.

Following an initial impact after spinal cord injury (SCI), there is a cascade of downstream events termed 'secondary injury', which culminate in progressive degenerative events in the spinal cord. These secondary injury mechanisms include, but are not limited to, ischemia, inflammation, free radical-induced cell death, glutamate excitotoxicity, cytoskeletal degradation and induction of extrinsic and intrinsic apoptotic pathways. There is emerging evidence that glutamate excitotoxicity plays a key role not only in neuronal cell death but also in delayed posttraumatic spinal cord white matter degeneration. Importantly however, the differences in cellular composition and expression of specific types of glutamate receptors in grey versus white matter require a compartmentalized approach to understand the mechanisms of secondary injury after SCI. This review examines mechanisms of secondary white matter injury with particular emphasis on glutamate excitotoxicity and the potential link of this mechanism to apoptosis. Recent studies have provided new insights into the mechanisms of glutamate release and its potential targets, as well as the downstream pathways associated with glutamate receptor activation in specific types of cells. Evidence from molecular and functional expression of glutamatergic AMPA receptors in white matter glia (and possibly axons), the protective effects of AMPA/kainate antagonists in posttraumatic white matter axonal function, and the vulnerability of oligodendrocytes to excitotoxic cell death suggest that glutamate excitotoxicity is associated with oligodendrocyte apoptosis. The latter mechanism appears key to glutamatergic white matter degeneration after SCI and may represent an attractive therapeutic target.

Facial nerve lesion response; strain differences but no involvement of IFN-gamma, STAT4 or STAT6.

Facial nerve lesions lead to a retrograde response characterized by activation of glia surrounding axotomized motoneurons and up-regulation of immunological cell surface molecules such as major histocompatibility complex (MHC) antigens. Cytokines, in particular interferon-gamma, are potent inducers of MHC expression and glial activation. We have here tested whether axotomy-induced activation is changed in transgenic mouse strains lacking components of the IFN-gamma signaling pathway, STAT4 or STAT6. No differences regarding astrocyte activation, ss2-microglobulin or MHC class I expression were discernible as compared to wild type controls. In contrast, there were conspicuous differences in the reaction between the examined wild type strains (C57BL/6J, BALB/c and 129/SvJ), suggesting considerable polymorphisms in the genetic regulation of these events, however, not involving IFN-gamma, STAT4 or STAT6.

Mycoplasma pneumoniae causing nervous system lesion and SIADH in the absence of pneumonia.

A patient was admitted for fever and acute respiratory failure (ARF), rapidly progressive tetraparesis, delirium, behavioral abnormalities, and diplopia. Leukocytosis and a rise in C-reactive protein were present. A syndrome of inappropriate anti-diuretic hormone secretion (SIADH) was also diagnosed. Lumbar puncture yielded colorless CFS with mononuclear pleocytosis and protein rise. Electrodiagnosis revealed demyelinating polyneuropathy and axonal degeneration. Serum IgG and IgM for mycoplasma pneumoniae (MP) was consistent with acute infection, and erythromycin was started with rapid resolution of symptoms. Contrarily to most reports, an associated respiratory disease was not present and SIADH in association with MP has been reported only once, in a patient without direct central nervous system (CNS) involvement. Differential diagnosis and possible pathogenic mechanisms are discussed.

Axonal degeneration induced by intraneural injection of Campylobacter jejuni antiserum containing high titer anti-GM1 antibody.

Ganglioside-like structures in CAMPYLOBACTER JEJUNI ( C. JEJUNI) lipooligosaccharide (LOS) can induce antiganglioside antibodies, which might cause nerve damage. In this study, we injected the following three antisera directly into the sciatic nerve of guinea pigs, to investigate the role of anti-glycolipids antibody in inducing neural injury: (i) the wild strain antiserum, a mixture of the sera obtained from the guinea pigs immunized with C. JEJUNI wild-type strain (HS:19) that had a high titer anti-GM1 IgG antibody (range: 800-6,400; median: 2,400) and a high titer anti-LOS IgG antibody; (ii) the GALE mutant antiserum, a mixture of the sera obtained from the guinea pigs immunized with the GALE mutant strain that had only a high titer anti-LOS IgG antibody but no anti-GM1 antibody; and (iii) the control antiserum, a mixture of the sera obtained from the guinea pigs immunized with Freund's complete adjuvant alone which had no anti-GM1 or anti-LOS IgG antibody. Pathological examinations showed that the wild strain C. JEJUNI antiserum produced axonal degeneration in sciatic nerves. Demyelination was rare, and no inflammatory cells were present. The pathological features are consistent with those seen in human patients with axonal GBS. No such changes were observed in nerves injected with the GALE mutant antiserum. The experiment showed that passive transfer of serum containing high titer GM1 antibody caused axonal degeneration of peripheral nerves. The result, which reproduced our previous findings in an active immunization study, therefore further confirmed the critical role of the anti-glycolipid antibody in the induction of neuropathy.

[Update on pathophysiologic and immunotherapeutic approaches for the treatment of multiple sclerosis]. / Multiple-Sklerose-Update zur Pathophysiologie und neuen immuntherapeutischen Ansätzen.

Multiple sclerosis (MS) is a chronic disabling disease with significant implications for patients and society. The individual disease course is difficult to predict due to the heterogeneity of clinical presentation and of radiologic and pathologic findings. Although its etiology still remains unknown, the last decade has brought considerable understanding of the underlying pathophysiology of MS. In addition to its acceptance as a prototypic inflammatory autoimmune disorder, recent data reveal the importance of primary and secondary neurodegenerative mechanisms such as oligodendrocyte death, axonal loss, and ion channel dysfunction. The deepened understanding of its immunopathogenesis and the limited effectiveness of currently approved disease-modifying therapies have led to a tremendous number of trials investigating potential new drugs. Emerging treatments take into account the different immunopathological mechanisms and strategies, to protect against axonal damage and promote remyelination. This review provides a compilation of novel immunotherapeutic strategies and recently uncovered aspects of known immunotherapeutic agents. The pathogenetic rationale of these novel drugs for the treatment of MS and accompanying preclinical and clinical data are highlighted.

Progressive systemic sclerosis associated with multiple mononeuropathy.

BACKGROUND: Progressive systemic sclerosis (PSS) is a chronic connective tissue inflammatory disease which commonly attacks the skin and the visceral organs, but rarely the peripheral nervous system. OBJECTIVE: The aim of this study was to investigate PSS accompanied by peripheral neuropathy clinically, electrophysiologically and pathologically from a sural nerve biopsy. METHODS: Two women suffering from PSS but without any other collagen disease were studied. Both patients developed peripheral neuropathy with multiple mononeuropathy of the limbs, and in one woman, in the trunk as well. RESULTS: A biopsy of the sural nerve revealed axonal and myelin segmental degeneration, loss of large myelinated fibers and an increase of collagen fibers, but there was no evidence of vasculitis. An electron microscopic examination revealed degenerated axons, disrupted myelin sheaths and multilayered basal lamina in the capillaries. CONCLUSION: Mononeuropathy in PSS suggests that ischemic neuropathy may be related to the immune-mediated vasculopathy.

Lymphocyte regulation of neuropeptide gene expression after neuronal injury.

The neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylyl cyclase-activating peptide (PACAP) are induced strongly in neurons after several types of injury, and exhibit neuroprotective actions in vitro and in vivo. It is thought that changes in expression of neuropeptides and other molecules in injured neurons are mediated by new factors produced in Schwann and immune cells at the injury site, a loss of target-derived factors, or a combination of mediators. To begin to determine the role of the inflammatory mediators, we investigated axotomy-induced changes in VIP and PACAP gene expression in the facial motor nucleus in severe combined immunodeficient (SCID) mice, and in mice with targeted mutations in specific cytokine genes. In normal mice, VIP and PACAP mRNA was induced strongly in facial motor neurons 4 days after axotomy. The increase in PACAP mRNA was blocked selectively in SCID mice, indicating that mechanisms responsible for VIP and PACAP gene induction are not identical. The loss of PACAP gene expression in SCID mice after axotomy was fully reversed by an infusion of normal splenocytes, suggesting that PACAP mRNA induction requires inflammatory mediators. PACAP and VIP mRNA inductions, however, were maintained in mice lacking leukemia inhibitory factor (LIF) and interleukin-6 (IL-6), and in mice lacking both receptors for tumor necrosis factor alpha (TNFalpha). The data suggest that an inflammatory response, most likely involving T lymphocytes, is necessary for the axotomy-induced increase in PACAP but not in VIP. LIF, IL-6, and TNFalpha, however, are not required for this response to injury.

Interleukin-6 (IL6) and cellular response to facial nerve injury: effects on lymphocyte recruitment, early microglial activation and axonal outgrowth in IL6-deficient mice.

Nerve injury triggers numerous changes in the injured neurons and surrounding non-neuronal cells. Of particular interest are molecular signals that play a role in the overall orchestration of this multifaceted cellular response. Here we investigated the function of interleukin-6 (IL6), a multifunctional neurotrophin and cytokine rapidly expressed in the injured nervous system, using the facial axotomy model in IL6-deficient mice and wild-type controls. Transgenic deletion of IL6 caused a massive decrease in the recruitment of CD3-positive T-lymphocytes and early microglial activation during the first 4 days after injury in the axotomized facial nucleus. This was accompanied by a more moderate reduction in peripheral regeneration at day 4, lymphocyte recruitment (day 14) and enhanced perikaryal sprouting (day 14). Motoneuron cell death, phagocytosis by microglial cells and recruitment of granulocytes and macrophages into injured peripheral nerve were not affected. In summary, IL6 lead to a variety of effects on the cellular response to neural trauma. However, the particularly strong actions on lymphocytes and microglia suggest that this cytokine plays a central role in the initiation of immune surveillance in the injured central nervous system.