Ralf Gold

Fumaric acid esters exert neuroprotective effects in neuroinflammation via activation of the Nrf2 antioxidant pathway

Inflammation and oxidative stress are thought to promote tissue damage in multiple sclerosis. Thus, novel therapeutics enhancing cellular resistance to free radicals could prove useful for multiple sclerosis treatment. BG00012 is an oral formulation of dimethylfumarate. In a phase II multiple sclerosis trial, BG00012 demonstrated beneficial effects on relapse rate and magnetic resonance imaging markers indicative of inflammation as well as axonal destruction. First we have studied effects of dimethylfumarate on the disease course, central nervous system, tissue integrity and the molecular mechanism of action in an animal model of chronic multiple sclerosis: myelin oligodendrocyte glycoprotein induced experimental autoimmune encephalomyelitis in C57BL/6 mice. In the chronic phase of experimental autoimmune encephalomyelitis, preventive or therapeutic application of dimethylfumarate ameliorated the disease course and improved preservation of myelin, axons and neurons. In vitro, the application of fumarates increased murine neuronal survival and protected human or rodent astrocytes against oxidative stress. Application of dimethylfumarate led to stabilization of the transcription factor nuclear factor (erythroid-derived 2)-related factor 2, activation of nuclear factor (erythroid-derived 2)-related factor 2-dependent transcriptional activity and accumulation of NADP(H) quinoline oxidoreductase-1 as a prototypical target gene. Furthermore, the immediate metabolite of dimethylfumarate, monomethylfumarate, leads to direct modification of the inhibitor of nuclear factor (erythroid-derived 2)-related factor 2, Kelch-like ECH-associated protein 1, at cysteine residue 151. In turn, increased levels of nuclear factor (erythroid-derived 2)-related factor 2 and reduced protein nitrosylation were detected in the central nervous sytem of dimethylfumarate-treated mice. Nuclear factor (erythroid-derived 2)-related factor 2 was also upregulated in the spinal cord of autopsy specimens from untreated patients with multiple sclerosis. In dimethylfumarate-treated mice suffering from experimental autoimmune encephalomyelitis, increased immunoreactivity for nuclear factor (erythroid-derived 2)-related factor 2 was detected by confocal microscopy in neurons of the motor cortex and the brainstem as well as in oligodendrocytes and astrocytes. In mice deficient for nuclear factor (erythroid-derived 2)-related factor 2 on the same genetic background, the dimethylfumarate mediated beneficial effects on clinical course, axon preservation and astrocyte activation were almost completely abolished thus proving the functional relevance of this transcription factor for the neuroprotective mechanism of action. We conclude that the ability of dimethylfumarate to activate nuclear factor (erythroid-derived 2)-related factor 2 may offer a novel cytoprotective modality that further augments the natural antioxidant responses in multiple sclerosis tissue and is not yet targeted by other multiple sclerosis therapies.

Efficacy and safety of oral fumarate in patients with relapsing-remitting multiple sclerosis: a multicentre, randomised, double-blind, placebo-controlled phase IIb study

BACKGROUND Oral fumarate (BG00012) might have dual anti-inflammatory and neuroprotective effects. Our aim was to assess the efficacy and safety of BG00012 in patients with relapsing-remitting multiple sclerosis. METHODS 257 patients, aged 18-55 years, with relapsing-remitting multiple sclerosis were randomly assigned to receive 120 mg once daily (n=64), 120 mg three times daily (n=64), or 240 mg three times daily (n=64) BG00012, or placebo (n=65) for 24 weeks. During an extension period of 24 weeks for safety assessment, patients treated with placebo received BG00012 240 mg three times daily. The primary endpoint was total number of new gadolinium enhancing (GdE) lesions on brain MRI scans at weeks 12, 16, 20, and 24. Additional endpoints included cumulative number of new GdE lesions (weeks 4-24), new or enlarging T2-hyperintense lesions, new T1-hypointense lesions at week 24, and annualised relapse rate. Analysis was done on the efficacy-evaluable population. Safety and tolerability were also assessed. This study is registered with ClinicalTrials.gov, number NCT00168701. FINDINGS Treatment with BG00012 240 mg three times daily reduced by 69% the mean total number of new GdE lesions from week 12 to 24 compared with placebo (1.4 vs 4.5, p<0.0001). It also reduced number of new or enlarging T2-hyperintense (p=0.0006) and new T1-hypointense (p=0.014) lesions compared with placebo. BG00012 reduced annualised relapse rate by 32% (0.44 vs 0.65 for placebo; p=0.272). Adverse events more common in patients given BG00012 than in those given placebo included abdominal pain, flushing, and hot flush. Dose-related adverse events in patients on BG00012 were headache, fatigue, and feeling hot. INTERPRETATION The anti-inflammatory effects and favourable safety profile of BG00012 warrant further long-term phase III studies in large patient groups.

Natalizumab treatment for multiple sclerosis: updated recommendations for patient selection and monitoring.

Natalizumab, a highly specific α4-integrin antagonist, is approved for treatment of patients with active relapsing-remitting multiple sclerosis (RRMS). It is generally recommended for individuals who have not responded to a currently available first-line disease-modifying therapy or who have very active disease. The expected benefits of natalizumab treatment have to be weighed against risks, especially the rare but serious adverse event of progressive multifocal leukoencephalopathy. In this Review, we revisit and update previous recommendations on natalizumab for treatment of patients with RRMS, based on additional long-term follow-up of clinical studies and post-marketing observations, including appropriate patient selection and management recommendations.

CNTF is a major protective factor in demyelinating CNS disease: A neurotrophic cytokine as modulator in neuroinflammation

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). So far, immunological mechanisms responsible for demyelination have been the focus of interest. However, mechanisms regulating axon maintenance as well as glial precursor-cell proliferation and oligodendrocyte survival might also influence disease outcome. The cytokine ciliary neurotrophic factor (CNTF), which was originally identified as a survival factor for isolated neurons, promotes differentiation, maturation and survival of oligodendrocytes. To investigate the role of endogenous CNTF in inflammatory demyelinating disease, we studied myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) in CNTF-deficient and wild-type C57BL/6 mice. Disease was more severe in CNTF-deficient mice and recovery was poor, with a 60% decrease in the number of proliferating oligodendrocyte precursor cells (OPCs) and a more than 50% increase in the rate of oligodendrocyte apoptosis. In addition, vacuolar dystrophy of myelin and axonal damage were more severe in CNTF-deficient mice. These specific pathological features could be prevented by treatment with an antiserum against tumor necrosis factor-α, suggesting that endogenous CNTF may counterbalance this effect of TNF-α (ref. 7). Here we identify a factor that modulates, in an inflammatory environment, glial cell survival and is an outcome determinant of EAE.

Distinct and nonredundant in vivo functions of IFNAR on myeloid cells limit autoimmunity in the central nervous system

The action of type I interferons in the central nervous system (CNS) during autoimmunity is largely unknown. Here, we demonstrate elevated interferon beta concentrations in the CNS, but not blood, of mice with experimental autoimmune encephalomyelitis (EAE), a model for CNS autoimmunity. Furthermore, mice devoid of the broadly expressed type I IFN receptor (IFNAR) developed exacerbated clinical disease accompanied by a markedly higher inflammation, demyelination, and lethality without shifting the T helper 17 (Th17) or Th1 cell immune response. Whereas adoptive transfer of encephalitogenic T cells led to enhanced disease in Ifnar1(-/-) mice, newly created conditional mice with B or T lymphocyte-specific IFNAR ablation showed normal EAE. The engagement of IFNAR on neuroectodermal CNS cells had no protective effect. In contrast, absence of IFNAR on myeloid cells led to severe disease with an enhanced effector phase and increased lethality, indicating a distinct protective function of type I IFNs during autoimmune inflammation of the CNS.

Animal models for autoimmune demyelinating disorders of the nervous system

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) that takes a relapsing-remitting or a progressive course (reviewed in Refs 1,2). Its counterpart in the peripheral nervous system (PNS) is chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) (reviewed in Ref. 3). In addition, there are acute, monophasic disorders, such as the inflammatory demyelinating polyradiculoneuropathy termed Guillain-Barré syndrome (GBS) in the PNS, and acute disseminated encephalomyelitis (ADEM) in the CNS. Both MS and GBS are heterogeneous syndromes. In MS different exogenous assaults together with genetic factors can result in a disease course that finally fulfils the diagnostic criteria. In both diseases, axonal damage can add to a primarily demyelinating lesion and cause permanent neurological deficits. No single animal model exists that mimics all the features of human demyelinating diseases; rather, the available models reflect specific facets. Here, we focus on experimental autoimmune encephalomyelitis (EAE) and neuritis (EAN) as models in rat and mouse strains, and discuss their distinct histopathology and the roles played by different autoantigens.

Detection of DNA Fragmentation in Apoptosis: Application of In Situ Nick Translation to Cell Culture Systems and Tissue Sections'

Since DNA fragmentation is a key feature of programmed cell death (PCD) and also occurs in certain stages of necrosis, we have adapted the methodology of in situ nick-translation (ISNT) to detect DNA fragmentation on a single-cell level. We first established the technique for cell preparations. Apoptosis was induced by gamma-irradiation on freshly isolated rat thymocytes. After fixation procedures, ISNT was performed by overnight incubation either with fluorescein-12-dUTP or with digoxigenin-labeled 11-dUTP and DNA polymerase I. The enzymatic incorporation of labeled nucleotides at sites of DNA fragmentation was detected by flow cytometry either directly or indirectly with fluorescein-conjugated anti-digoxigenin. The quantitative results demonstrated close correlation with morphological essays for apoptosis, DNA gel electrophoresis, and ISNT. Proliferating cells determined by bromodeoxyuridine immunofluorescence were not labeled by ISNT. Immunocytochemistry for cell surface antigens in combination with ISNT allowed the identification of specific cell types undergoing PCD. Furthermore, the simultaneous application of photolabeling techniques with ethidium monoazide and ISNT led to the identification of DNA fragmentation in cells with still intact membranes. Extending ISNT to tissue sections of paraformaldehyde-fixed, paraffin-embedded material reliably revealed labeling of cells with typical morphological features of apoptosis. However, this technique was not useful in detecting early stages of necrotic cell death.

Potassium Channel KIR4.1 as an Immune Target in Multiple Sclerosis

BACKGROUND Multiple sclerosis is a chronic inflammatory demyelinating disease of the central nervous system. Many findings suggest that the disease has an autoimmune pathogenesis; the target of the immune response is not yet known. METHODS We screened serum IgG from persons with multiple sclerosis to identify antibodies that are capable of binding to brain tissue and observed specific binding of IgG to glial cells in a subgroup of patients. Using a proteomic approach focusing on membrane proteins, we identified the ATP-sensitive inward rectifying potassium channel KIR4.1 as the target of the IgG antibodies. We used a multifaceted validation strategy to confirm KIR4.1 as a target of the autoantibody response in multiple sclerosis and to show its potential pathogenicity in vivo. RESULTS Serum levels of antibodies to KIR4.1 were higher in persons with multiple sclerosis than in persons with other neurologic diseases and healthy donors (P<0.001 for both comparisons). We replicated this finding in two independent groups of persons with multiple sclerosis or other neurologic diseases (P<0.001 for both comparisons). Analysis of the combined data sets indicated the presence of serum antibodies to KIR4.1 in 186 of 397 persons with multiple sclerosis (46.9%), in 3 of 329 persons with other neurologic diseases (0.9%), and in none of the 59 healthy donors. These antibodies bound to the first extracellular loop of KIR4.1. Injection of KIR4.1 serum IgG into the cisternae magnae of mice led to a profound loss of KIR4.1 expression, altered expression of glial fibrillary acidic protein in astrocytes, and activation of the complement cascade at sites of KIR4.1 expression in the cerebellum. CONCLUSIONS KIR4.1 is a target of the autoantibody response in a subgroup of persons with multiple sclerosis. (Funded by the German Ministry for Education and Research and Deutsche Forschungsgemeinschaft.).

Effect of laquinimod on MRI-monitored disease activity in patients with relapsing-remitting multiple sclerosis: a multicentre, randomised, double-blind, placebo-controlled phase IIb study

BACKGROUND A 24-week phase II trial has shown that 0.3 mg of laquinimod given daily to patients with relapsing-remitting multiple sclerosis was well tolerated and reduced the formation of active lesions. We assessed the effect of oral daily 0.3 and 0.6 mg laquinimod on MRI-monitored disease activity in a 36-week double-blind, placebo-controlled phase IIb study. METHODS The study was done in 51 centres in nine countries. Inclusion criteria were one or more relapses in the year before entry and at least one gadolinium enhancing (GdE) lesion on screening MRI. Of 720 patients screened, 306 eligible patients were enrolled. Patients, aged 18-50 years, were randomly assigned to placebo (n=102), laquinimod 0.3 mg a day (n=98), or 0.6 mg a day (n=106). Brain MRI scans and clinical assessments were done at week -4, baseline, and monthly from week 12 to week 36. The primary outcome was the cumulative number of GdE lesions at weeks 24, 28, 32, and 36. The principal analysis of the primary endpoint was done on the intention-to-treat cohort. This study is registered with ClinicalTrials.gov, number NCT00349193. FINDINGS Compared with placebo, treatment with laquinimod 0.6 mg per day showed a 40.4% reduction of the baseline adjusted mean cumulative number of GdE lesions per scan on the last four scans (simple means 4.2 [SD 9.2] vs 2.6 [5.3], p=0.0048); treatment with 0.3 mg per day showed no significant effects (3.9 [5.5] vs placebo, p=0.6740). Both doses of laquinimod were well tolerated, with some transient and dose-dependent increases in liver enzymes. A case of Budd-Chiari syndrome-ie, a thrombotic venous outflow obstruction of the liver-occurred after 1 month of exposure in a patient with underlying hypercoagulability who received 0.6 mg laquinimod. Anticoagulant treatment resulted in a decline of liver enzymes to normal without any clinical signs of hepatic decompensation. INTERPRETATION In patients with relapsing-remitting multiple sclerosis, 0.6 mg per day laquinimod significantly reduced MRI-measured disease activity and was well tolerated.

Fumaric acid esters are effective in chronic experimental autoimmune encephalomyelitis and suppress macrophage infiltration

Fumaric acid esters (FAE) have proven their therapeutic efficacy in psoriasis, a Th1 mediated skin disease. More recently, preliminary data have suggested an activity in multiple sclerosis (MS) as well. To investigate further possible mechanisms of action of these compounds in inflammatory diseases, we studied the FAE methyl hydrogen fumarate (MHF) and dimethyl fumarate (DMF) in chronic experimental autoimmune encephalomyelitis (EAE) induced by immunization of C57BL/6 mice with MOG peptide aa 35–55. Preventive treatment with these FAE was delivered twice a day by oral gavage. Both esters had a significant therapeutic effect on the disease course and histology showed a strongly reduced macrophage inflammation in the spinal cord. Multiparameter cytokine analysis from blood detected an increase of IL‐10 in the treated animals. We conclude that the underlying biological activity of FAE in EAE is complex and, to elucidate the molecular mechanisms, further investigation is needed.