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Molecular Neuroscience II > 9 - Multiple Sclerosis > Flashcards

9 - Multiple Sclerosis Flashcards

1
Q

How can gadolinium based agents be used for diagnosis of brain disease (like Multiple Sclerosis)?

A

Can only cross the blood brain barrier where it has been pathologically affected

Reveals scattered lesions

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2
Q

True or false? Multiple sclerosis can be transmitted genetically as shown by parents increasing heredity and increased heredity in twins.

A

True

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3
Q

Why are Na channels redistributed in early stage of MS?

A

Demyelination at nodes of ranvier

Redistribution is a ‘rescue attempt’

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4
Q

What are the four stages of oligodendrocyte life?

A
  • Migration
  • Proliferation
  • Differentiation
  • Myelination
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5
Q

What is the key signalling molecule between oligodendrocytes and axons?

A

Fyn kinases

A non-receptor Src-family tyrosine kinase

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6
Q

How do miRNA influence the development of oligodendrocytes?

A
  • High miRNA expression leads to differentiation into mature myelinated oligodendrocytes
  • Low miRNA expression leads to proliferation
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7
Q

How can monoclonal antibodies treat MS?

A
  • Blocking the migration of lymphocytes across the blood brain barrier
  • 45% reduction of relapses
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8
Q

What is multiple sclerosis? LInked to what? Where is pathology localized to?

A
  • Immune mediated demyelinating disease of the human central nervous system
  • Linked to major histocompatibility complex (MHC) class II
  • Pathology is localized to white matter, where inflammation causes local demyelination, degeneration of myelin forming cells (oligodendrocytes) and axonal degeneration
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9
Q

How many people have MS in North America and Europe?

A

2.5 million in North America and Europe

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10
Q

How many lifespan years does MS reduce?

A

Approximately 10

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11
Q

Magnetic resonance imaging after injecting ____ is one of the methods used for the diagnostics of disease progress and also to evaluate effects of MS treatment

A

gadolinium (Gd)-based contrast agents

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12
Q

What are the two main groups of symptoms in multiple sclerosis patients?

A
  • Motor, sensory and cognitive impairment (easily detected)
  • Cardiovascular system, sexual impairment, dysphagia (difficulty swallowing), respiratory problems and pain are often overlooked
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13
Q

What makes the detection of MS difficult?

A

Scattered lesions resulting in a variety of symptoms

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14
Q

What is often the initial symptom of MS?

A
  • Blurred or double vision
  • Red-green colour distortion (or colour blindness)
  • Abnormal sensory feelings (numbness, prickling or pins and needles)
  • Muscle weakness and difficulty with coordination and balance
  • Partial or complete paralysis
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15
Q

What are the four forms of multiple sclerosis that progress over time?

A
  1. Clinically silent MS
  2. Relapsing-remitting MS (RRMS) - 85% of cases, early onset (29 yo), 2x more females and 1-2 episodes a year
    or
  3. Primary progressive MS (PPMS) - 15% of cases, late onset (around 39 years), males:females, sometimes observed is progressive relapsing MS (PRMS)
  4. Secondary progressive MS (SPMS), occurs after 8-20 years of RRMS
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16
Q

True or false? Multiple sclerosis is heritable. What do children of MS affected parents show?

A

False, not heritable.

Children of MS affected parents have 20-30x higher risk to develop MS

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17
Q

What two vitamin deficiencies are risk factors for MS?

A
  • Vitamin D

- Vitamin A

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18
Q

Is tobacco smoking a risk factor for MS?

A

Yes

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19
Q

What two things evidence a possible viral connection to MS?

A
  • The Epstein-Barr Virus (EBV), also called human herpesvirus 4 (HHV-4) infection is a risk factor in developing MS. Not known if it is cause or result of disease. 90-95% are infected worldwide, mostly asymptomatic.
  • An MS animal model (experimental allergic encephalomyelitis (EAE)) uses attenuated rabies virus, which triggers T cell-mediated destruction of myelin
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20
Q

Why might MS pathology be induced by endogenous retroviruses?

A
  • Approximately 8 percent of the human genome is comprised of retrovirus-like sequences.
  • Polymorphism of x-linked viral locus HERV-Gc1 (human endogenous retrovirus) was found to be associated with remitting/relapsing and secondary progressive form of MS
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21
Q

What is a axonal retraction bulb?

A

A swelling that forms at proximal end of transected neurons, this can survive for some time without myelin, but eventually degenerates

Seen in multiple sclerosis, caused by transection during cortical demyelination

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22
Q

What is the estimated total axonal loss in chronic MS lesions?

A

70%

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23
Q

How do most demyelinated axons react at the beginning of MS?

A
  • Survive
  • Recover
  • Redistribute Na channels
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24
Q

What does reduced myelin trophic support from MS cause intracellularly?

A

disorganization of the cytoskeleton and eventual axon degeneration

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25
Q

What are the three types of demyelination lesions in the cortex caused by multiple sclerosis?

A
  • Type I lesions (white and grey matter)
  • Type II lesions (small perivascular areas)
  • Type III lesions (pial surface into the cortex, often demyelinating multiple gyri)
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26
Q

What are the four stages of an oligodendrocytes life? What are they called at each stage (5)

A
  • Migration (precursor)
  • Proliferation (progenitor)
  • Differentiation (pro-oligodendrocyte and immature oligodendrocyte)
  • Myelination (mature oligodendrocyte)

These steps are critical for remyelination of MS affected axons. All transcription factors and cytoplasmic regulatory proteins and receptor must be present for this to occur successfully.

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27
Q

What does myelination in CNS mostly occur?

A

During postnatal development, but continues into adulthood

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28
Q

What is the key mediator between neurons and oligodendrocytes? What is the consequence of knockout of this protein?

A

Src-family tyrosine kinase Fyn

Knockout of Fyn kinase causes abnormal oligodendrocyte development and hypomyelination

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29
Q

What are the 3 things that Fyn does intracellularly in oligodendrocytes upon binding to axonal cell adhesion molecule L1?

A
  • Morphological differentiation
  • Cytoskeleton recruitment
  • Local protein synthesis
  1. Fyn signalling regulates Rho GTPase (RhoA), which is involved in oligodendrocyte differentiation
  2. Fyn mediates binding of tubulin and the microtubule associated protein Tau (regulates assembly and stabilization of microtubules)
  3. Fyn activation in response to binding of axonal cell adhesion molecule L1 facilitates the site specific translation of myelin basic protein (MBP) by phosphorylation of transacting factor heterogeneous nuclear ribonucleoprotein A2 (hnRNP A2)
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30
Q

Explain Fyn tyrosine kinase binding to axonal cell adhesion molecule L1 causes cytoskeleton recruitment

A

Fyn mediates binding of tubulin and the microtubule associated protein Tau (regulates assembly and stabilization of microtubules)

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31
Q

Explain Fyn tyrosine kinase binding to axonal cell adhesion molecule L1 causes morphological differentiation

A

Fyn signalling regulates Rho GTPase (RhoA), which is involved in oligodendrocyte differentiation

32
Q

Explain Fyn tyrosine kinase binding to axonal cell adhesion molecule L1 causes local protein synthesis

A

Fyn activation in response to binding of axonal cell adhesion molecule L1 facilitates the site specific translation of myelin basic protein (MBP) by phosphorylation of transacting factor heterogeneous nuclear ribonucleoprotein A2 (hnRNP A2)

33
Q

What are the two main areas of the adult brain where neural stem/progenitor cells (NSPCs) are found?

A
  • Ventricular-subventricular zone

- Hippocampal subgranular zone

34
Q

What do stem/progenitor cells (NSPCs) do in the brain? What happens in multiple sclerosis?

A

Differentiate mostly into neurons, some become astrocytes and oligodendrocytes.

After demyelination, the fate of NSPCs changes to favor oligodendrogenesis and migration of oligodendrocytes towards the corpus callosum

  • in MS, as the disease progresses, the NSPC-OPC-oligodendrocyte transition becomes disrupted
  • Some labs researching possibilities to counteract the progress of MS by stimulating and controlling the oligodendrocyte generation from NSPCs
35
Q

What are four ways for creating animal models of demyelination (MS models)?

A
  • Toxin-induced demyelination
  • Inflammation-induced demyelination
  • Viral-induced demyelination
  • Genetic myelin mutants
36
Q

What are three types of toxin induced demyelination models?

A
  • Lysolecithin injection
  • Ethidium bromide injection
  • Cuprizone (copper chelator) feeding induces demyelination in young adult mice within 5-6 weeks
37
Q

How is inflammation-induced demyelination done?

A

Injection of CNS tissue or antigen into susceptible species

38
Q

What are some examples of viral induced demyelination models?

A
  • Theiler’s murine encephalomyelitis virus (TMEV) injected into SJL mice. C57BL/6 mice are resistant to TMEV
  • Rabies virus
  • Mouse hepatitis virus (MHV)
  • Semliki Forest Virus (SFV), does not need to be injected intracranially and therefore is useful to study blood brain barrier in the MS pathogenesis
39
Q

What is an example of genetically induced demyelination? What is a disadvantage of this method for MS modeling?

A

Myelin deficient (md) rat and mouse mutants (jimpy) have a mutation in the gene encoding for proteolipid protein (PLP) that results in central myelination deficits.

There is lack of inflammation in the demyelinated areas of the mutant brains, which is a disadvantage because the mutants pathology does not exactly reflect MS.

40
Q

How many of the total cells in the CNS are microglia?

A

15%

41
Q

Why does neuroinflammation occur?

A

It is mediated mostly by microglia and astroglia and is a protective response of the CNS in an attempt to remove harmful stimuli and to initiate a healing process.

Controlled inflammation results in destroying pathogens, removal of cellular debris and elimination of toxic substances.

42
Q

What can excessive neuroinflammation cause?

A
  • Restricted cell renewal regenerative capacity
  • Neuronal damage and uncontrolled inflammation amplify each other, inducing a self propagating cycle, which results in fast progression of virtually all neurodegenerative disorders.
43
Q

How is experimental autoimmune encephalomyelitis induced? Why?

A

Immunization with one of a myelin antigen or by transfer of activated myelin-specific CD4+ T cells (T helper cells) from mice with EAE (autoimmune encephalomyelitis)

  • EAE is mediated by myelin specific T cells, which are activated in the periphery and translocate into the CNS. The following permeabilization of the blood-brain barrier allows more inflammatory mediators to enter the brain
44
Q

What do T cells in the brain do in mice with experimental autoimmune encephalomyelitis?

A

Interact with the antigen (myelin) releasing mediators that recruit other immune cells and activate microglia. Activation of the immune cells and microglia results in production of proteases, glutamate, reactive oxygen species and other cytotoxic agents which promote myelin breakdown

45
Q

What two types of T cells are involved in MS pathogenesis?

A
  • CD4+ T lymphocytes (CD4+ helper T cells) that receive signals from MHC class II molecules
  • CD8+ cytotoxic T cells that recognize MHC class I antigens (especially in CSF)
46
Q

Which T cell involved in MS pathogenesis is found to outnumber the other by 3-10 fold?

A

CD8+

The opposite is true in healthy people without MS

47
Q

True or false? Inhibiting CD4+ pathway with antibodies is an effective treatment for MS?

A

False

Antibody treatment against CD8+ shows promising effects, best results are observed when both T cells are inhibited

48
Q

What is a disadvantage of inhibiting CD8+ T cells?

A

Opportunistic viral infections, such as John Cunningham virus, which induces progressive multifocal leukoencephalopathy (PML), a rare demyelination disease.

49
Q

How is differentiation of oligodendrocytes dependent on miRNA?

A

miR-219 and miR-338 act as brakes that defer the proliferation of oligodendrocyte lineage cells and trigger myelination this way.

  • miR-219 and miR-338 silence expression of the PDGFRa, Sox6, FoxJ3 and ZFP238 transcription factors, which have inhibtory effects on differentiation of oligodendrocyte precursor cells
50
Q

Does dicer expression increase or decrease during oligodendrocyte differentiation? Why? What happens when dicer is blocked or deleted?

A

Increases,

differentiation is dependent on miRNAs, which inhibit transcription factors which might trigger proliferation.

Blockade of dicer induces disturbance in myelination process and deletion results in demyelination, oxidative damage, lipid accumulation, inflammation, astrocytosis microgliosis and neuronal degeneration and axonal damage.

51
Q

What is toll-like receptor (TLR) signalling?

A
  • Class of receptors which are important in immune response signalling
  • Astrocytes express many TLRs and their miRNA levels change in response to different inflammatory stimuli
52
Q

What are two miR regulators of TLR signalling, important in MS?

A

miR-146a - represents a negative regulator of TLR signalling

miR-326 - Upregulated in relapses patients and is one of the most upregulated miRNAs in active MS lesions, especially in aggressive forms of the disease called the Marburg variant of MS. These results indicate that modifying miRNAs can be a novel approach to treat MS.

53
Q

What were semaphorins originally identified as?

A

Semaphorins were originally identified as axonal guidance factors in neuronal development

54
Q

What two processes do semaphorins modulate immune response in?

A

Mediate immune response especially in cell-cell contacts (1) and cell migration (2).

55
Q

What are the two families of semaphorin receptors that have been identified?

A
  • Neuropilins

- Plexins

56
Q

How do semaphorins and their receptors modulate immune response in multiple sclerosis?

A
  • Antigen presentation induces Sema4A expression on T cells, this is maintained on Th1-differentiating T cells.
  • Semaphorins seem to be important novel targets for therapy of inflammation (knocking down or blocking may be therapy for MS)
57
Q

How are dendritic cells involved in MS?

A

Dendritic cells are a key immune regulator involved in the pathogenesis of MS (especially in terms of cell-cell interaction with semaphorins)

They are antigen presenting cells that can present semaphorin Sem4A to T cells to induce inflammation and pathogenesis of MS

58
Q

What can viral semaphorins be used for?

A

Suppression of host immune system resposne

59
Q

Where are myelin specific T cells generated?

A

In the periphery

60
Q

What semaphorin can promote the transmigration and subsequent invasion of immune cells, including dendritic cells, into the CNS?

A

Sema3A

61
Q

What semaphorins interact with plexin-B1 (receptors for semaphorin) or VLA-1 (late antigen A-1) expressed on microglia/macrophages? What is the consequence of this?

A
  • Sema4D
  • Sema7A

Increase production of inflammatory molecules, including nitric oxide (NO) and cytokines that are toxic to oligodendrocytes.

62
Q

What is Npc 1 knockout used for?

A

A model for demyelination

  • Npc1 protein is involved in intracellular transport of cholesterol
  • Mutation of this gene causes Newman-Pick type C disease (fatal and involves abnormal myelin formation)
  • Npc1 transgenic mice expressing Cre recombinase under the control of the Synapsin1 promoter leads to blockade of oligodendrocyte maturation (normal density of NG2-positive oligodendrocytes) and demyelination
63
Q

What percent of myelin is lipids? What percent of these lipids are cholesterol?

A

70% lipid

78% of lipids is cholesterol

64
Q

Mutation in the Npc1 gene can cause blockade of oligodendrocyte maturation and demyelination. These changes were correlated with what?

A

Decrease of expression of active FYN kinase

65
Q

How does conditional deletion of Npc1 gene differ from Npc1 knockout with Cre recombinase under the control of Synapsin1 promoter?

A

Conditional deletion of Npc1 expressed in the oligodendrocytes induced significantly delayed demyelination compared to the one that was driven by Cre recombinase and synapsin1 neuronal promoter

66
Q

What do Histamine receptor 1 (H1R) antagonists due to pathogenesis of MS?

A

Inhibit progress of MS in animal models and lower incidence of MS in humans .

67
Q

what do histamine receptor 2 (H2R) agonists and antagonists do with animal models of MS?

A

Agonists: showed neuroprotective properties

Antagonists: accelerated neuronal loss

68
Q

What do histamine 3 autoreceptors (H3R) do with MS? What does this suggest for H3 agonists?

A

Inhibit pro-inflammatory release of histamine, therefore specific H3 agonists may be useful in treatment of MS

69
Q

What do histamine 4 receptors (H4R) do?

A
  • Inflammatory mediators
  • Regulate eosinophil migration and selective chemotaxy of mast cells that lead to augmentation of histamine-mediated immune responses and eventually to chronic inflammation
  • H4R are involved in dendritic cell activation and T cell differentiation
70
Q

What is interferon β (IFNβ)? Is there a connection to MS?

A

An anti-inflammatory mediator

  • Can treat MS, but the mechanism is unclear
71
Q

Name two injection treatments of MS. What are two disadvantages for these treatments?

A
  • Interferon β (IFβ)
  • Glatiramer acetate (GA - a polymer of amino acids that mimics myelin basic protein (MBP) a major component of CNS myelin. GA rescued antigen presentation and stimulates secretion of cytokines associated with anti-inflammatory actions.

Disadvantage is need of frequent injections and side effects (mostly allergic reactions)

72
Q

What is Mitoxantrone? How can it treat MS?

A

It is an anti-cancer drug what has immunosuppressant and antineoplastic properties

  • Does not cure MS, but significantly slows progress of disease in any stage. It is administered once every 3 months and generally is well tolerated but poses a risk of cardiotoxicity and hepatotoxicity
73
Q

Name for new approaches to treating MS

A
  • Blocking lymphocyte migration
  • Targeting T cells
  • Targeting B cells
  • Mixed mechanism (eg. monoclonal antibody against lymphocytes or ATP analogies that selectively affect immune cells resulting in DNA damage and apoptosis)
74
Q

When are off-label therapies used for MS patients? Name 3.

A

When they cannot tolerate approved therapies.

  • Immunosuppressants approved for preventing rejection of transplants
  • Chemotherapeutic which interferes with DNA synthesis by inhibiting dihydrofolate reductase
  • High doses of corticosteroids to prevent inflammation
75
Q

How can histone deacetylase inhibitors be used to treat MS?

A
  • Histone acetyl transerases (HATs) and histone deacetylases (HDACs) target not only histones, but also numerous proteins with key roles in cell metabolism, signalling and death.
  • HDAC inhibitor sodium phenylbutyrate and its metabolite sodium phenylacetate blocked or slowed neurodegeneration in mouse model
  • Trichostatin (another HDAC inhibitor) slowed the progress of axonal loss and demyelination in C57BL/6 mice immunized with the myelin oligodendrocyte glycoprotein peptide MOG35-55, an experimental model of chronic MS
  • Large doses of HDAC inhibitors induce T cell apoptosis, whereas low doses reduce T cell proliferation and function
76
Q

What are three methods to target re-myelination processes after the ravaging effects of MS?

A
  • Enhancement of endogenous repair mechanisms
  • An antibody against LINGO-1 (inhibits oligodendrocyte differentiation) successfully promoted re-myelination in different animal models and is in the clinical phase I
  • Transplantation of myelin-forming cells (OPCs, Schwann cells, olfactory ensheathing cells, stem cells). Research indicates that transplantations create, rather than repair, supporting microenvironment. They are not very effective in re-myelination

Molecular Neuroscience II (7 decks)

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