Helena Radbruch

Multiple sclerosis - candidate mechanisms underlying CNS atrophy.

Recently it has become clear that the neuronal compartment plays a more important role than previously thought in the pathology of multiple sclerosis. Apart from demyelination, neuronal pathology is apparently largely responsible for the brain atrophy that can be observed early on and throughout the course of the disease. The loss of axons and their neurons in the course of chronic neuroinflammation is a major factor determining long-term disability in patients. The actual steps leading from immune attack against the myelin sheath to neuronal damage are not yet fully clear. Here we review key findings about direct axonal damage processes, demyelination-related neuronal pathology and cell-body pathology, the major pathologic correlates that underlie brain atrophy in MS.

IL-17 and GM-CSF Expression Are Antagonistically Regulated by Human T Helper Cells

GM-CSF–producing T helper cells in humans follow a distinct regulation program as compared to TH17 cells and are associated with multiple sclerosis. Cytokine Rivalry In patients with autoimmune diseases, cytokines—secreted immune mediators—are a crucial cause of tissue damage. However, the interplay between different cytokines and their individual roles in disease aggravation and resolution remain poorly defined, especially in humans. Noster et al. report that T helper (TH) cell production of granulocyte-macrophage colony-stimulating factor (GM-CSF) may play a pathogenic role in the brain of patients with multiple sclerosis (MS). They found that TH17-related cytokines—thought from mouse studies to be critical for pathogenesis—actually prevented induction of GM-CSF, whereas TH1-type cytokines promoted GM-CSF. These data provide a rationale for decreasing GM-CSF in patients with MS and suggest that, for MS at least, human may know best. Although T helper 17 (TH17) cells have been acknowledged as crucial mediators of autoimmune tissue damage, the effector cytokines responsible for their pathogenicity still remain poorly defined, particularly in humans. In mouse models of autoimmunity, the pathogenicity of TH17 cells has recently been associated with their production of granulocyte-macrophage colony-stimulating factor (GM-CSF). We analyzed the regulation of GM-CSF expression by human TH cell subsets. Surprisingly, the induction of GM-CSF expression by human TH cells is constrained by the interleukin-23 (IL-23)/ROR-γt/TH17 cell axis but promoted by the IL-12/T-bet/TH1 cell axis. IL-2–mediated signal transducer and activator of transcription 5 (STAT5) signaling induced GM-CSF expression in naïve and memory TH cells, whereas STAT3 signaling blocked it. The opposite effect was observed for IL-17 expression. Ex vivo, GM-CSF+ TH cells that coexpress interferon-γ and T-bet could be distinguished by differential chemokine receptor expression from a previously uncharacterized subset of GM-CSF–only–producing TH cells that did not express TH1, TH2, and TH17 signature cytokines or master transcription factors. Our findings demonstrate distinct and counterregulatory pathways for the generation of IL-17– and GM-CSF–producing cells and also suggest a pathogenic role for GM-CSF+ T cells in the inflamed brain of multiple sclerosis (MS) patients. This provides not only a scientific rationale for depleting T cell–derived GM-CSF in MS patients but also multiple new molecular checkpoints for therapeutic GM-CSF suppression, which, unlike in mice, do not associate with the TH17 but instead with the TH1 axis.

Fatigue in multiple sclerosis is closely related to sleep disorders: a polysomnographic cross-sectional study:

Background: Sleep disorders can cause tiredness. The relationship between sleep disorders and fatigue in patients with multiple sclerosis (MS) has not yet been investigated systematically. Objective: To investigate the relationship between fatigue and sleep disorders in patients with MS. Methods: Some 66 MS patients 20 to 66 years old were studied by overnight polysomnography. Using a cut-off point of 45 in the Modified Fatigue Impact Scale (MFIS), the entire cohort was stratified into a fatigued MS subgroup (n = 26) and a non-fatigued MS subgroup (n = 40). Results: Of the fatigued MS patients, 96% (n = 25) were suffering from a relevant sleep disorder, along with 60% of the non-fatigued MS patients (n = 24) (p = 0.001). Sleep-related breathing disorders were more frequent in the fatigued MS patients (27%) than in the non-fatigued MS patients (2.5%). Significantly higher MFIS values were detected in all (fatigued and non-fatigued) patients with relevant sleep disorders (mean MFIS 42.8; SD 18.3) than in patients without relevant sleep disorders (mean MFIS 20.5; SD 17.0) (p < 0.001). Suffering from a sleep disorder was associated with an increased risk of fatigue in MS (odds ratio: 18.5; 95% CI 1.6–208; p = 0.018). Conclusion: Our results demonstrate a clear and significant relationship between fatigue and sleep disorders.

Autoregulation of Th1-mediated inflammation by twist1

The basic helix-loop-helix transcriptional repressor twist1, as an antagonist of nuclear factor κB (NF-κB)–dependent cytokine expression, is involved in the regulation of inflammation-induced immunopathology. We show that twist1 is expressed by activated T helper (Th) 1 effector memory (EM) cells. Induction of twist1 in Th cells depended on NF-κB, nuclear factor of activated T cells (NFAT), and interleukin (IL)-12 signaling via signal transducer and activator of transcription (STAT) 4. Expression of twist1 was transient after T cell receptor engagement, and increased upon repeated stimulation of Th1 cells. Imprinting for enhanced twist1 expression was characteristic of repeatedly restimulated EM Th cells, and thus of the pathogenic memory Th cells characteristic of chronic inflammation. Th lymphocytes from the inflamed joint or gut tissue of patients with rheumatic diseases, Crohns disease or ulcerative colitis expressed high levels of twist1. Expression of twist1 in Th1 lymphocytes limited the expression of the cytokines interferon-γ, IL-2, and tumor necrosis factor-α, and ameliorated Th1-mediated immunopathology in delayed-type hypersensitivity and antigen-induced arthritis.

Patterns of retinal nerve fiber layer loss in multiple sclerosis patients with or without optic neuritis and glaucoma patients

OBJECTIVE Optical coherence tomography (OCT) has gained increasing attention in multiple sclerosis (MS) research and has been suggested as outcome measure for neuroprotective therapies. However, to date it is not clear whether patterns of retinal nerve fiber layer thickness (RNFLT) loss are different in MS compared to other diseases such as glaucoma and data on RNFLT loss in MS patients with or without optic neuritis (ON/NON) have remained inconsistent or even contradictory. METHODS In this large cross-sectional study we analyzed the patterns of axonal loss of retinal ganglion cells in MS eyes (n=262) with and without history of ON (MS/ON: 73 eyes; MS/NON: 189 eyes) and patients eyes with glaucomatous optic disc atrophy (GA: n=22; 39 eyes) in comparison to healthy control eyes (HC: n=406 eyes). RESULTS We found that significant average and quadrant RNFLT loss is detectable by OCT in both MS and GA patients compared to healthy controls (p<0.01). The age- and gender adjusted average and quadrant RNFLT did not differ significantly between MS and GA patients (p>0.05). Average (p<0.0001) and quadrant (p<0.05) RNFL thinning is significantly more severe in MS/ON versus MS/NON eyes, and the extent of RNFL thinning varies across quadrants in MS/ON eyes with the highest degree of RNFLT loss in the temporal quadrant (p<0.001). CONCLUSION RNFLT reduction across all four quadrants in MS patients as a whole as well as in MS/NON eyes argues for a diffuse neurodegenerative process. Superimposed inflammatory attacks to the optic nerve may cause additional axonal damage with a temporal preponderance. Future studies are necessary to further evaluate the capacity of OCT to depict disease specific damage patterns.

Expanding Two-Photon Intravital Microscopy to the Infrared by Means of Optical Parametric Oscillator

Chronic inflammation in various organs, such as the brain, implies that different subpopulations of immune cells interact with the cells of the target organ. To monitor this cellular communication both morphologically and functionally, the ability to visualize more than two colors in deep tissue is indispensable. Here, we demonstrate the pronounced power of optical parametric oscillator (OPO)-based two-photon laser scanning microscopy for dynamic intravital imaging in hardly accessible organs of the central nervous and of the immune system, with particular relevance for long-term investigations of pathological mechanisms (e.g., chronic neuroinflammation) necessitating the use of fluorescent proteins. Expanding the wavelength excitation farther to the infrared overcomes the current limitations of standard Titanium:Sapphire laser excitation, leading to 1), simultaneous imaging of fluorophores with largely different excitation and emission spectra (e.g., GFP-derivatives and RFP-derivatives); and 2), higher penetration depths in tissue (up to 80%) at higher resolution and with reduced photobleaching and phototoxicity. This tool opens up new opportunities for deep-tissue imaging and will have a tremendous impact on the choice of protein fluorophores for intravital applications in bioscience and biomedicine, as we demonstrate in this work.

Differential immune cell dynamics in the CNS cause CD4+ T cell compartmentalization

In the course of autoimmune CNS inflammation, inflammatory infiltrates form characteristic perivascular lymphocyte cuffs by mechanisms that are not yet well understood. Here, intravital two-photon imaging of the brain in anesthetized mice, with experimental autoimmune encephalomyelitis, revealed the highly dynamic nature of perivascular immune cells, refuting suggestions that vessel cuffs are the result of limited lymphocyte motility in the CNS. On the contrary, vessel-associated lymphocyte motility is an actively promoted mechanism which can be blocked by CXCR4 antagonism. In vivo interference with CXCR4 in experimental autoimmune encephalomyelitis disrupted dynamic vessel cuffs and resulted in tissue-invasive migration. CXCR4-mediated perivascular lymphocyte movement along CNS vessels was a key feature of CD4(+) T cell subsets in contrast to random motility of CD8(+) T cells, indicating a dominant role of the perivascular area primarily for CD4(+) T cells. Our results visualize dynamic T cell motility in the CNS and demonstrate differential CXCR4-mediated compartmentalization of CD4(+) T-cell motility within the healthy and diseased CNS.

Attention Network Test reveals alerting network dysfunction in multiple sclerosis

Attention is one of the cognitive domains typically affected in multiple sclerosis. The Attention Network Test was developed to measure the function of the three distinct attentional networks, alerting, orienting, and executive control. The Attention Network Test has been performed in various neuropsychiatric conditions, but not in multiple sclerosis. Our objective was to investigate functions of attentional networks in multiple sclerosis by means of the Attention Network Test. Patients with relapsing—remitting multiple sclerosis (n = 57) and healthy controls (n = 57) matched for age, sex, and education performed the Attention Network Test. Significant differences between patients and controls were detected in the alerting network (p = 0.003), in contrast to the orienting (p = 0.696) and the conflict (p = 0.114) network of visual attention. Mean reaction time in the Attention Network Test was significantly longer in multiple sclerosis patients than in controls (p = 0.032), Multiple sclerosis patients benefited less from alerting cues for conflict resolution compared with healthy controls. The Attention Network Test revealed specific alterations of the attention network in multiple sclerosis patients which were not explained by an overall cognitive slowing.

Encephalopathy, visual disturbance and hearing loss—recognizing the symptoms of Susac syndrome

Background. A 23 year-old female presented to a neurology department with a 3 year history of recurrent episodes involving hearing loss, encephalopathy, focal neurological deficits, and visual field deficits. In the 3 years before presentation, the patient had been treated with methylprednisolone for suspected acute demyelinating encephalomyelitis and peripheral otogenic dysfunction from which she made a complete recovery, and for a visual defect in both eyes caused by bilateral branch retinal arterial occlusion, from which she partially improved and commenced long-term treatment with acetylsalicylic acid.Investigations. Detailed history, clinical examination, extensive laboratory work-up, cerebrospinal fluid analysis, cerebral and spinal MRI, periventricular single-voxel 1H magnetic resonance spectroscopy, retinal fluorescence angiography, optical coherence tomography, audiometry, neurophysiological work-up (EEG, evoked potentials).Diagnosis. Susac syndrome, characterized by a combination of encephalopathy, branch retinal artery occlusions, and hearing loss.Management. Long-term immunosuppressive treatment with azathioprine (150 mg/day) and prednisolone (10 mg/day), and inhibition of thrombocyte function with acetylsalicylic acid (100 mg/day).

In vivo imaging of lymphocytes in the CNS reveals different behaviour of naïve T cells in health and autoimmunity

BackgroundTwo-photon laser scanning microscopy (TPLSM) has become a powerful tool in the visualization of immune cell dynamics and cellular communication within the complex biological networks of the inflamed central nervous system (CNS). Whereas many previous studies mainly focused on the role of effector or effector memory T cells, the role of naïve T cells as possible key players in immune regulation directly in the CNS is still highly debated.MethodsWe applied ex vivo and intravital TPLSM to investigate migratory pathways of naïve T cells in the inflamed and non-inflamed CNS. MACS-sorted naïve CD4+ T cells were either applied on healthy CNS slices or intravenously injected into RAG1 -/- mice, which were affected by experimental autoimmune encephalomyelitis (EAE). We further checked for the generation of second harmonic generation (SHG) signals produced by extracellular matrix (ECM) structures.ResultsBy applying TPLSM on living brain slices we could show that the migratory capacity of activated CD4+ T cells is not strongly influenced by antigen specificity and is independent of regulatory or effector T cell phenotype. Naïve T cells, however, cannot find sufficient migratory signals in healthy, non-inflamed CNS parenchyma since they only showed stationary behaviour in this context. This is in contrast to the high motility of naïve CD4+ T cells in lymphoid organs. We observed a highly motile migration pattern for naïve T cells as compared to effector CD4+ T cells in inflamed brain tissue of living EAE-affected mice. Interestingly, in the inflamed CNS we could detect reticular structures by their SHG signal which partially co-localises with naïve CD4+ T cell tracks.ConclusionsThe activation status rather than antigen specificity or regulatory phenotype is the central requirement for CD4+ T cell migration within healthy CNS tissue. However, under inflammatory conditions naïve CD4+ T cells can get access to CNS parenchyma and partially migrate along inflammation-induced extracellular SHG structures, which are similar to those seen in lymphoid organs. These SHG structures apparently provide essential migratory signals for naïve CD4+ T cells within the diseased CNS.