LINGO-1 antagonists as therapy for multiple sclerosis: in vitro and in vivo evidence

Emerging strategies for the treatment of multiple sclerosis

Despite extraordinary advances in the field of neuroimmunology, ideal treatment for patients with multiple sclerosis remains an unmet need. Existing treatments are only partially effective in preventing multiple sclerosis relapses, have a limited impact on the accrual of disability, have not been effective in progressive forms of the disease, and treatment remains preventive rather than restorative. This review provides an overview of emerging therapies and targets, and incorporates strategies for two different approaches to multiple sclerosis: prevention, through immune modulation; and repair, through neuroprotection and remyelination. Agents at all stages of development, from late-stage clinical trials of BG-12, teriflunomide, alemtuzumab, daclizumab and anti-CD20 agents, to novel approaches in preclinical testing, are discussed.

LINGO-1 and Neurodegeneration: Pathophysiologic Clues for Essential Tremor

Essential tremor (ET), one of the most common adult-onset movement disorders, has been associated with cerebellar Purkinje cell degeneration and formation of brainstem Lewy bodies. Recent findings suggest that genetic variants of the leucine-rich repeat and Ig domain containing 1 (LINGO-1) gene could be risk factors for ET. The LINGO-1 protein contains both leucine-rich repeat (LRR) and immunoglobulin (Ig)-like domains in its extracellular region, as well as a transmembrane domain and a short cytoplasmic tail. LINGO-1 can form a ternary complex with Nogo-66 receptor (NgR1) and p75. Binding of LINGO-1 with NgR1 can activate the NgR1 signaling pathway, leading to inhibition of oligodendrocyte differentiation and myelination in the central nervous system. LINGO-1 has also been found to bind with epidermal growth factor receptor (EGFR) and induce downregulation of the activity of EGFR-PI3K-Akt signaling, which might decrease Purkinje cell survival. Therefore, it is possible that genetic variants of LINGO-1, either alone or in combination with other genetic or environmental factors, act to increase LINGO-1 expression levels in Purkinje cells and confer a risk to Purkinje cell survival in the cerebellum.Here, we provide a concise summary of the link between LINGO-1 and neurodegeneration and discuss various hypotheses as to how this could be potentially relevant to ET pathogenesis.

Neutralization of LINGO-1 during in vitro differentiation of neural stem cells results in proliferation of immature neurons

Identifying external factors that can be used to control neural stem cells division and their differentiation to neurons, astrocytes and oligodendrocytes is of high scientific and clinical interest. Here we show that the Nogo-66 receptor interacting protein LINGO-1 is a potent regulator of neural stem cell maturation to neurons. LINGO-1 is expressed by cortical neural stem cells from E14 mouse embryos and inhibition of LINGO-1 during the first days of neural stem cell differentiation results in decreased neuronal maturation. Compared to neurons in control cultures, which after 6 days of differentiation have long extending neurites, neurons in cultures treated with anti-LINGO-1 antibodies retain an immature, round phenotype with only very short processes. Furthermore, neutralization of LINGO-1 results in a threefold increase in βIII tubulin-positive cells compared to untreated control cultures. By using BrdU incorporation assays we show that the immature neurons in LINGO-1 neutralized cultures are dividing neuroblasts. In contrast to control cultures, in which no cells were double positive for βIII tubulin and BrdU, 36% of the neurons in cultures treated with anti-LINGO-1 antibodies were proliferating after three days of differentiation. TUNEL assays revealed that the amount of cells going through apoptosis during the early phase of differentiation was significantly decreased in cultures treated with anti-LINGO-1 antibodies compared to untreated control cultures. Taken together, our results demonstrate a novel role for LINGO-1 in neural stem cell differentiation to neurons and suggest a possibility to use LINGO-1 inhibitors to compensate for neuronal cell loss in the injured brain.

LINGO1 variants in essential tremor and Parkinson's disease

The leucine-rich repeat and Ig domain containing 1 gene (LINGO1), recently considered to be conferred increased risk of essential tremor (ET), has been also implicated in Parkinson disease (PD). As the two common movement disorders have overlapping clinical and pathological features, it has been postulated that the LINGO1 gene may play a role in the pathogenesis of the two diseases. Here, we review published reports of the LINGO1 variants in ET and PD in an attempt to better understand the molecular and pathogenic relationship of LINGO1 to the two disorders.

Current status of myelin replacement therapies in multiple sclerosis

Multiple sclerosis is an autoimmune disease of the human central nervous system characterized by immune-mediated myelin and axonal damage, and chronic axonal loss attributable to the absence of myelin sheaths. There are two aspects to the treatment of MS-first, the prevention of damage by suppressing the maladaptive immune system, and second, the long-term preservation of axons by the promotion of remyelination, a regenerative process in which new axons are restored to demyelinated axons. Medicine has made significant progress in the first of these in recent years-there is an increasing number of ever more effective disease-modifying immunomodulatory interventions. However, there are currently no widely used regenerative therapies in MS. Conceptually, there are two approaches to remyelination therapy-transplantation of myelinogenic cells and promotion of endogenous remyelination mediated by myelinogenic cells present within the diseased tissue. In this chapter, in addition to describing why remyelination therapies are important, we review both these approaches, outlining their current status and future developments.

Promising treatments of tomorrow for multiple sclerosis

The therapeutic options for multiple sclerosis are rapidly expanding. What was once seen as a disease with little hope for treatment is now a target of rapid drug development. Current therapies have demonstrated efficacy in limiting the impact of the disease, but none is fully effective in all patients. However, promising new treatments are on the horizon. In this review we will discuss potential novel immunomodulating drugs that are in advanced stages of investigation; these drugs include monoclonal antibodies, chimeric molecules, and oral therapies. The use of hematopoietic stem cells will also be discussed and, in addition, we will look farther ahead at possible novel targets for the development of new immunomodulatory or neuroprotective pharmaceuticals.

Monoclonal antibody therapy in multiple sclerosis: Paradigm shifts and emerging challenges

Therapeutic approaches to multiple sclerosis (MS) are based on altering the functions of the immune system, either by using broad immunosuppressive drugs used for transplantation rejection and rheumatology, or by modulating them more discreetly with beta interferon and synthetic amino-acid copolymers. These strategies are only partially successful, have important safety and tolerability limitations, and have shown to be mostly effective in earlier stages of the disease, in which acute relapses dominate the clinical picture. For progressive phenotypes of MS there are currently no effective therapeutic options. As very specific and potent immunosuppressive agents, monoclonal antibodies (mAbs) may offer considerable advantages over other therapies for MS. During the last decade, anti-a4 integrin natalizumab became the first approved mAb for treatment of relapsing MS, after convincingly demonstrating clinically significant effects on two large Phase 3 trials. Moreover, the concept of disease remission was introduced for the first time, to describe patients that show no signs of clinical or imaging markers of disease activity during therapy with natalizumab. Of the mAbs under development for MS, alemtuzumab and rituximab have also shown promising evidence of effectiveness, and potentially expanded the therapeutic horizon to reversal of disease progression in early relapsing patients, and progressive patients who previously had not been studied. However, the appearance of progressive multifocal leukoencephalopathy (PML) in natalizumab-treated MS patients, as well as in patients with lymphoma, lupus and rheumatoid arthritis treated with rituximab, and autoimmune-type complications in alemtuzumab-treated MS patients underlines the fact that extended efficacy comes with significant clinical risks. The challenge is then how best to utilize therapies that have evidently superior efficacy in a chronic disease of young adults, to obtain the best benefit-risk ratio, and how to monitor and prevent emergent safety concerns.

Brain perihematoma genomic profile following spontaneous human intracerebral hemorrhage

Background

Spontaneous intracerebral hemorrhage (ICH) represents about 15% of all strokes and is associated with high mortality rates. Our aim was to identify the gene expression changes and biological pathways altered in the brain following ICH.

Methodology/Principal Findings

Twelve brain samples were obtained from four deceased patients who suffered an ICH including perihematomal tissue (PH) and the corresponding contralateral white (CW) and grey (CG) matter. Affymetrix GeneChip platform for analysis of over 47,000 transcripts was conducted. Microarray Analysis Suite 5.0 was used to process array images and the Ingenuity Pathway Analysis System was used to analyze biological mechanisms and functions of the genes. We identified 468 genes in the PH areas displaying a different expression pattern with a fold change between −3.74 and +5.16 when compared to the contralateral areas (291 overexpressed and 177 underexpressed). The top genes which appeared most significantly overexpressed in the PH areas codify for cytokines, chemokines, coagulation factors, cell growth and proliferation factors while the underexpressed codify for proteins involved in cell cycle or neurotrophins. Validation and replication studies at gene and protein level in brain samples confirmed microarray results.

Conclusions

The genomic responses identified in this study provide valuable information about potential biomarkers and target molecules altered in the perihematomal regions.

Animal models of multiple sclerosis--potentials and limitations

Experimental autoimmune encephalomyelitis (EAE) is still the most widely accepted animal model of multiple sclerosis (MS). Different types of EAE have been developed in order to investigate pathogenetic, clinical and therapeutic aspects of the heterogenic human disease. Generally, investigations in EAE are more suitable for the analysis of immunogenetic elements (major histocompatibility complex restriction and candidate risk genes) and for the study of histopathological features (inflammation, demyelination and degeneration) of the disease than for screening of new treatments. Recent studies in new EAE models, especially in transgenic ones, have in connection with new analytical techniques such as microarray assays provided a deeper insight into the pathogenic cellular and molecular mechanisms of EAE and potentially of MS. For example, it was possible to better delineate the role of soluble pro-inflammatory (tumor necrosis factor-α, interferon-γ and interleukins 1, 12 and 23), anti-inflammatory (transforming growth factor-β and interleukins 4, 10, 27 and 35) and neurotrophic factors (ciliary neurotrophic factor and brain-derived neurotrophic factor). Also, the regulatory and effector functions of distinct immune cell subpopulations such as CD4+ Th1, Th2, Th3 and Th17 cells, CD4+FoxP3+ Treg cells, CD8+ Tc1 and Tc2, B cells and γδ+ T cells have been disclosed in more detail. The new insights may help to identify novel targets for the treatment of MS. However, translation of the experimental results into the clinical practice requires prudence and great caution.

Axon-oligodendrocyte interactions during developmental myelination, demyelination and repair

In multiple sclerosis, CNS demyelination is often followed by spontaneous repair, mostly achieved by adult oligodendrocyte precursor cells. Extent of this myelin repair differs, ranging from very low, limited to the plaque border, to extensive, with remyelination throughout the 'shadow plaques.' In addition to restoring neuronal connectivity, new myelin is neuroprotective. It reduces axonal loss and thus disability progression. Reciprocal communication between neurons and oligodendrocytes is essential for both myelin biogenesis and myelin repair. Hence, deciphering neuron-oligodendrocyte communication is not only important for understanding myelination per se, but also the pathophysiology that underlies demyelinating diseases and the development of innovative therapeutic strategies.

The development of benzimidazoles as selective rho kinase inhibitors

Rho Kinase (ROCK) is a serine/threonine kinase whose inhibition could prove beneficial in numerous therapeutic areas. We have developed a promising class of ATP-competitive inhibitors based upon a benzimidazole scaffold, which show excellent potency toward ROCK (IC(50)<10nM). This report details the optimization of selectivity for ROCK over other related kinases such as Protein kinase A (PKA).

Overcoming remyelination failure in multiple sclerosis and other myelin disorders

Protecting axons from degeneration represents a major unmet need in the treatment of myelin disorders and especially the currently untreatable secondary progressive stages of multiple sclerosis (MS). Several lines of evidence indicate that ensuring myelin sheaths are restored to demyelinated axons, the regenerative process of remyelination, represents one of the most effective means of achieving axonal protection. Remyelination can occur as a highly effective spontaneous regenerative process following demyelination. However, for reasons that have not been fully understood, this process is often incomplete or fails in MS. Recognizing the reasons for remyelination failure and hence identifying therapeutic targets will depend on detailed histopathological studies of myelin disorders and a detailed understanding of the molecular mechanisms regulating remyelination. Pathology studies have revealed that chronically demyelinated lesions in MS often fail to repair because of a failure of differentiation of the precursor cell responsible for remyelination rather than a failure of their recruitment. In this article we review three mechanisms by which differentiation of precursor cells into remyelinating oligodendrocytes are regulated-the Notch pathway, the Wnt pathway and the pathways activated by inhibitor of differentiation in myelin debris-and indicate how these might be pharmacologically targeted to overcome remyelination failure.