Thomas Zeis

Molecular Changes in White Matter Adjacent to an Active Demyelinating Lesion in Early Multiple Sclerosis

A stereotactic biopsy of a 17‐year‐old woman revealed an active inflammatory demyelinating lesion compatible with pattern III multiple sclerosis (MS) according to Lucchinetti et al. The biopsy included a white matter region distant from the active inflammatory demyelinating lesion with abnormal MRI signal, lacking histopathological signs of demyelination and/or oligodendrocyte apoptosis. Expression analysis of this area revealed a strong up‐regulation of neuronal nitric oxide synthase (nNOS). Furthermore, detection of nitrotyrosine provided evidence for reactive nitrogen species (RNS)‐mediated damage to oligodendrocytes. Concomitantly, genes involved in neuroprotection against oxidative stress such as heme oxygenase 1 were up‐regulated. Even though a single case report, this study shows earliest molecular changes in white matter surrounding an actively demyelinating lesion during the first manifestation of MS, pointing toward a more widespread pathological process. Therapeutic targeting of the identified mechanisms of tissue injury might be crucial to prevent further lesion formation or secondary tissue damage.

The immunomodulatory oligodendrocyte

Oligodendrocytes, the myelinating glial cells of the central nervous system (CNS), are due to their high specialization and metabolic needs highly vulnerable to various insults. This led to a general view that oligodendrocytes are defenseless victims during brain damage such as occurs in acute and chronic CNS inflammation. However, this view is challenged by increasing evidence that oligodendrocytes are capable of expressing a wide range of immunomodulatory molecules. They express various cytokines and chemokines (e.g. Il-1β, Il17A, CCL2, CXCL10), antigen presenting molecules (MHC class I and II) and co-stimulatory molecules (e.g. CD9, CD81), complement and complement receptor molecules (e.g. C1s, C2 and C3, C1R), complement regulatory molecules (e.g. CD46, CD55, CD59), tetraspanins (e.g. TSPAN2), neuroimmune regulatory proteins (e.g. CD200, CD47) as well as extracellular matrix proteins (e.g. VCAN) and many others. Their potential immunomodulatory properties can, at specific times and locations, influence ongoing immune processes as shown by numerous publications. Therefore, oligodendrocytes are well capable of immunomodulation, especially during the initiation or resolution of immune processes in which subtle signaling might tip the scale. A better understanding of the immunomodulatory oligodendrocyte can help to invent new, innovative therapeutic interventions in various diseases such as Multiple Sclerosis. This article is part of a Special Issue entitled SI: Myelin Evolution.

Fullerenols and glucosamine fullerenes reduce infarct volume and cerebral inflammation after ischemic stroke in normotensive and hypertensive rats

Cerebral inflammation plays a crucial role in the pathophysiology of ischemic stroke and is involved in all stages of the ischemic cascade. Fullerene derivatives, such as fullerenol (OH-F) are radical scavengers acting as neuroprotective agents while glucosamine (GlcN) attenuates cerebral inflammation after stroke. We created novel glucosamine-fullerene conjugates (GlcN-F) to combine their protective effects and compared them to OH-F regarding stroke-induced cerebral inflammation and cellular damage. Fullerene derivatives or vehicle was administered intravenously in normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) immediately after transient middle cerebral artery occlusion (tMCAO). Infarct size was determined at day 5 and neurological outcome at days 1 and 5 after tMCAO. CD68- and NeuN-staining were performed to determine immunoreactivity and neuronal survival respectively. Cytokine and toll like receptor 4 (TLR-4) expression was assessed using quantitative real-time PCR. Magnetic resonance imaging revealed a significant reduction of infarct volume in both, WKY and SHR that were treated with fullerene derivatives. Treated rats showed an amelioration of neurological symptoms as both OH-F and GlcN-F prevented neuronal loss in the perilesional area. Cerebral immunoreactivity was reduced in treated WKY and SHR. Expression of IL-1β and TLR-4 was attenuated in OH-F-treated WKY rats. In conclusion, OH-F and GlcN-F lead to a reduction of cellular damage and inflammation after stroke, rendering these compounds attractive therapeutics for stroke.

An essential role of MAG in mediating axon–myelin attachment in Charcot–Marie–Tooth 1A disease

Charcot-Marie-Tooth disease type 1A (CMT1A) is a hereditary demyelinating peripheral neuropathy caused by the duplication of the PMP22 gene. Demyelination precedes the occurrence of clinical symptoms that correlate with axonal degeneration. It was postulated that a disturbed axon-glia interface contributes to altered myelination consequently leading to axonal degeneration. In this study, we examined the expression of MAG and Necl4, two critical adhesion molecules that are present at the axon-glia interface, in sural nerve biopsies of CMT1A patients and in peripheral nerves of mice overexpressing human PMP22, an animal model for CMT1A. We show an increase in the expression of MAG and a strong decrease of Necl4 in biopsies of CMT1A patients as well as in CMT1A mice. Expression analysis revealed that MAG is strongly upregulated during peripheral nerve maturation, whereas Necl4 expression remains very low. Ablating MAG in CMT1A mice results in separation of axons from their myelin sheath. Our data show that MAG is important for axon-glia contact in a model for CMT1A, and suggest that its increased expression in CMT1A disease has a compensatory role in the pathology of the disease. Thus, we demonstrate that MAG together with other adhesion molecules such as Necl4 is important in sustaining axonal integrity.

Coronin 1-Mediated Naive T Cell Survival Is Essential for the Development of Autoimmune Encephalomyelitis

Autoimmune encephalomyelitis is a disease of the CNS that can develop when an initial peripheral inflammatory stimulus is followed by infiltration and reactivation of T lymphocytes in the CNS. We report a crucial role for coronin 1, which is essential for maintenance of the naive T cell pool, for the development of murine experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis. In the absence of coronin 1, immunization with myelin oligoglycoprotein (MOG35–55) peptide largely failed to induce EAE symptoms, despite normal mobilization of leukocyte subsets in the blood, as well as effector cytokine expression comparable with wild-type T cells on polyclonal stimulation. Susceptibility of coronin 1-deficient mice to EAE induction was restored by transfer of wild-type CD4+ T cells, suggesting that the observed resistance of coronin 1-deficient mice to EAE development is T cell intrinsic. Importantly, although coronin 1-deficient regulatory T cells (Tregs) showed a suppressor activity comparable with wild-type Tregs, Treg depletion failed to restore EAE development in coronin 1-deficient animals. These results suggest a hitherto unrecognized role of naive T cells in the development of autoimmune encephalomyelitis and reveal coronin 1 as a crucial modulator of EAE induction.

ALCAM (CD166) is involved in extravasation of monocytes rather than T cells across the blood–brain barrier:

Activated leukocyte cell adhesion molecule (ALCAM) has been proposed to mediate leukocyte migration across the blood–brain barrier (BBB) in multiple sclerosis or experimental autoimmune encephalomyelitis (EAE). Here, we confirmed vascular ALCAM expression in human brain tissue samples in situ and on two different human in vitro BBB models. Antibody-mediated inhibition of ALCAM reduced diapedesis of human CD4+ Th1 but not of Th17 cells across the human BBB in vitro. In accordance to human Th1 cells, mouse Th1 cells showed reduced diapedesis across an ALCAM−/− in vitro BBB model under static but no longer under flow conditions. In contrast to the limited role of ALCAM in T cell extravasation across the BBB, we found a contribution of ALCAM to rolling, adhesion, and diapedesis of human CD14+ monocytes across the human BBB under flow and static conditions. Taken together, our study highlights the potential differences in the CNS expression of ALCAM in mouse and human and supports a prominent role for ALCAM in the multi-step extravasation of monocytes across the BBB.

Transcriptional regulation induced by cAMP elevation in mouse Schwann cells.

In peripheral nerves, Schwann cell development is regulated by a variety of signals. Some of the aspects of Schwann cell differentiation can be reproduced in vitro in response to forskolin, an adenylyl cyclase activator elevating intracellular cAMP levels. Herein, the effect of forskolin treatment was investigated by a comprehensive genome-wide expression study on primary mouse Schwann cell cultures. Additional to myelin-related genes, many so far unconsidered genes were ascertained to be modulated by forskolin. One of the strongest differentially regulated gene transcripts was the transcription factor Olig1 (oligodendrocyte transcription factor 1), whose mRNA expression levels were reduced in treated Schwann cells. Olig1 protein was localized in myelinating and nonmyelinating Schwann cells within the sciatic nerve as well as in primary Schwann cells, proposing it as a novel transcription factor of the Schwann cell lineage. Data analysis further revealed that a number of differentially expressed genes in forskolin-treated Schwann cells were associated with the ECM (extracellular matrix), underlining its importance during Schwann cell differentiation in vitro. Comparison of samples derived from postnatal sciatic nerves and from both treated and untreated Schwann cell cultures showed considerable differences in gene expression between in vivo and in vitro, allowing us to separate Schwann cell autonomous from tissue-related changes. The whole data set of the cell culture microarray study is provided to offer an interactive search tool for genes of interest.

Identification of Inflammatory, Metabolic, and Cell Survival Pathways Contributing to Cerebral Small Vessel Disease by Postmortem Gene Expression Microarray

Cerebral small-vessel disease (SVD) is characterized by periventricular white matter (WM) changes and general brain atrophy. SVD is prevalent in elderly individuals and is frequently associated with the development of vascular dementia (VaD). Studies of the molecular basis of SVD are sparse. We have to gain further insight into the pathogenic mechanisms of SVD. Therefore, we compared gene expression patterns in the brains of SVD and control patients, in order to identify cellular pathways changed in diseased brains. We compared the expression of mRNA transcripts in postmortem, macroscopically normal-appearing human brain tissues isolated from frontal, temporal and occipital cortical and subcortical regions in 5 SVD and 5 non-SVD control patients. Significant expression changes were determined by fold change F>1.2 in either direction, and p<0.05. We identified 228 genes differentially expressed in cortex (89 up-, 139 down-regulated) and 555 genes in WM (223 up-, 332 down-regulated) in SVD patients. Pathway analyses revealed that upregulated genes were associated with inflammation and apoptosis in WM, suggesting active cell death. Downregulated genes were associated with coagulation and fatty and amino acids metabolisms. In the cortex, down-regulated genes were principally associated with neuronal functions. Our data revealed widespread changes in the transcriptome profiles in the cortex and WM of human SVD brains, with a predominance of changes in WM. We provide for the first time a comprehensive view of the molecular alterations in human SVD brains that seem to contribute to the neuropathogenesis of SVD.

A Chronic Relapsing Animal Model for Multiple Sclerosis

Multiple Sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). One of the mostly used animal models for MS is experimental autoimmune encephalomyelitis (EAE). Until now several different EAE models have been developed, differing in the immunological reaction, inflammatory processes and the neuropathophysiology in the CNS. Here, we present a model induced in Dark Agouti rats by immunization with the N-terminal fragment of myelin oligodendrocyte glycoprotein. This specific model shows several similarities to MS, such as a relapsing-remitting disease course, demyelination and axonal degeneration. By immunohistochemical characterization, lesions could be detected mostly in the spinal cord, but also in the optic nerve, brainstem, cerebellum and in different areas of the forebrain. The mimicking of particular features of MS and the occurrence of special disease entities like optic neuritis, Devic’s disease and the acute MS form of Marburg’s type makes this EAE type an excellent model for investigating certain aspects of the pathophysiology seen in MS.

Molecular pathology of Multiple Sclerosis lesions reveals a heterogeneous expression pattern of genes involved in oligodendrogliogenesis

ABSTRACT Little is known about the decisive molecular factors that regulate lesion remyelination in Multiple Sclerosis. To identify such factors, we performed a differential gene expression analysis of normal appearing white matter (NAWM), active, remyelinating, and inactive demyelinated lesions. As expected, many genes involved in inflammatory processes were detected to be differentially regulated between these tissue types. Among them, we found an increased expression of members of the STAT6 pathway such as STAT6, IL4 and IL4R in active, remyelinated and inactive demyelinated lesions. This suggests that a protective, anti‐inflammatory reaction, as already reported to be present in MS NAWM, is further enhanced in lesion tissues. Focusing on genes influencing oligodendrogliogenesis, we found a decreased expression of NKX2–2 in active, remyelinated and inactive demyelinated lesions, whereas SOX10 was downregulated in inactive demyelinated lesions, when compared to NAWM. Simultaneously, CXCL12 (SDF1) expression was strongly increased in active, remyelinated and inactive demyelinated lesions, but increased expression of the IGF1 and IGF2 genes was found in inactive demyelinated lesions. This demonstrates that, in principle, expression of genes promoting oligodendrogliogenesis occurs in MS lesion tissue ‐ even in inactive demyelinated lesions. In contrast, oligodendrogenesis inhibiting genes such as JAG1 were also expressed at higher levels in inactive demyelinated lesions. Both, oligodendrogliogenesis promoting as well as inhibiting genes are expressed in all lesion tissues. However, no clear promoting or inhibiting expression pattern could be detected in any of the different types of lesioned tissues. This might reflect the heterogeneity of lesion development in MS patients, both in terms of mechanisms and temporal differences. HIGHLIGHTSLesion tissues express both, oligodendrogliogenesis promoting and inhibiting genes.Gene expression patterns vary significantly in single lesion tissue types.Gene expression heterogeneity might be causative for non‐uniform remyelination.