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Neuro Science

Seminars

LH
by Linda H.

Neuroglia - Introduction

How can we subdivise the cells of the CNS?

  • neurons

  • glial cells

    • microglia

    • macroglia

      • astrocytes

      • oligodendrocytes

      • OPCs = NG2 cells = Polydendrocytes

      • ependymal cells


Neuroglia - Introduction

What are the most important cells in the CNS and why?

neurons

  • 1x10^12

  • specific network of synapses which governs all brain function

  • only cell that performs the nervous system's actual function: information processing


Neuroglia - Introduction

How can we influence neurogenesis?

  • sports

  • activity


Neuroglia - Introduction

Which glial cells perform blood-brain-barrier-function?

all of them!

Neuroglia - Introduction

What happens with the blood brain barrier during neuroinflammation?

compromised —> some cells can flow through


Neuroglia - Introduction

What are ependymal cells?

= like “epithelial cells” between central canal and the ventricles

—> regulate composition and flux of the CSF


Neuroglia - Introduction

What is the function of microglia?

= immune cells

  • first responder within minutes

  • guardeners

  • fast and proliferative


Neuroglia - Introduction

What is the function of astrocytes?

  • second cells to respond —> creating a glial scar

  • synaptic formation, stimulate axonal formation

  • myelin debris clearance

  • neurotransmitter recycling


Neuroglia - Introduction

What is the main function of oligodendrocytes and what is special about that?

—> myelinating of cells in CNS

<-> Schwann cells in PNS


special:

myelination of axons = 50:1 oligodendrocytes:Schwann cell

Neuroglia - Introduction

How does a NG2 cell look like?

LNS and PDZ domain


Neuroglia - Introduction

What is the main function of OPCs? How can we call them too? What are specialties?


= NG2 cells

functions:

  • before birth: give rise to astrocytes and oligodendrocytes

  • after birth: only give rise to oligodendrocytes

specialties:

  • very proliferative

  • can synapse with neurons and maintain synaptic contacts while proliferating (divide in halfs)

  • act to damage

  • in white and gray matter

  • express transcription factor Olig2 and Sox10

  • DO NOT express transcription factor GFAP

  • binds to cytoskeleton via PDZ domain, Syntenin and ERM proteins


Neuroglia I

How many types of astrocytes do we have and why are they built? What is there function?

A1

= harmful

induced by neuroinflammation

destructive to synapses and neurons

—> loss of function and gain of neurotoxicity

A2

= protective

induced by ischemia

neuronal survival and tissue repair

Neuroglia I

Which cells and cytokines are essential for the induction of A1 astrocytes?

activated microglia

  • IL-1 alpha

  • TNF

  • C1q

Neuroglia I

Which normal functions are lost when developing into A1 astrocytes? What kind of function do they have additionally?

loss of normal function

  • Synapse Regulation: inability to promote formation and function of synapses

    —> existing synapses are reduced and the formation of new synapses is inhibited

  • Phagocytosis: inability to clear synaptosomes and toxic myelin debris

additionally

  • Gain of Neurotoxicity

Neuroglia I

Which cytokine can lead to a reversion of A1 astrocytes?

TGF beta

Neuroglia I

What can we use as a therapeutic target strategy against A1?

  • inhibit A1

  • block Il1 alpha, TNF, C1q

  • reversion through TGF beta

Neuroglia I

How do activated microglia specifically induce the A1 astrocyte phenotype and why is the combination of all three identified cytokines (IL-1α, TNF, and C1q) necessary for this transformation?

Induction through activated microglia secreting IL-1α, TNF, and C1q

= combination necessary and sufficient

—> individual cytokines only trigger a partial phenotype

—> synergistic effect is essential to achieve the full functional transition and gene expression profile

Neuroglia I

What specific homeostatic functions are lost when an astrocyte transitions to the A1 state and how do these losses contribute to neurodegeneration beyond the direct effects of the secreted neurotoxin?


Loss of function

  • synapse regulation

    • existing synapses are reduced

    • formation of new synapses inhibited

  • phagocytosis

    • synaptosomes and toxic myelin debris isn´t cleared out

—> inhibition of tissue repair and remyelination


Neuroglia I

Given that A1 astrocytes are abundant in many human neurodegenerative diseases, what are the ethical considerations and potential clinical challenges of using drugs to broadly inhibitor revert these cells?

  • A primary challenge: selectively targeting the neurotoxic A1 phenotype

  • A1 cells may serve good functions, such as fighting infections

Neuroglia II

Do A1 astrocytes play a role in MS?

yes

—> clusterin expression increased

—> inhibits differentiation of Oligodendrocytes and OPCs by inhibiting PI3K-AKT-mTOR pathway

—> loss of myelin production in CNS


Neuroglia II

How can we target MS therapies?

  • activating AKT (reduces damage of OPC´s)

  • KO of astrocytic Clusterin (can restore OPC differentiation)


Neuroglia II

Using the knowledge we have acquired in immunology; which role does the immune system play in MS and the initial demyelination?

  • B cells

    • autoantibodies against NG2 are targeting the surface of OPCs

  • CD8 T cells

    • INF-gamma exposure induces MHC I expression on OPCs

    • direct cell damage through CD8

  • reactive astrocytes express Clusterin

    • inhibition of the PI3K-AKT-mTOR pathway

    • changes in OPCs and Oligodendrocytes


Neuroglia II

What does the PI3K-AKT-mTOR pathway do and how does its inhibition by Clusterin lead to the effects on glial cells seen in this paper?

  • functions of the pathway

    • OPC proliferation, differentiation and cell survival

  • inhibition by Clusterin

    • secreted Clusterin binds to (VLDLR) expressed on the surface of OPCs

    • reduction in the phosphorylation of PI3K, AKT, and mTOR

    • signals for survival and maturation of OPCs are turned off

    • + CLU prevents astrocytes from clearing myelin cell debris

—> cell death, no remyelination


Neuroglia II

Which receptors does Clusterin bind to (OPCs, oligodendrocytes)?

  • VLDLR (OPCs and mature oligodendrocytes)

  • ApoER2 (astrocytes)


Parkinson´s Disease - Introduction

What is PD?

= most prevalent motor disease

—> affects the basal ganglia circuity

—> Striatum —> substantia nigra —> dopaminergic neurons


Parkinson´s Disease - Introduction

What´s special about dopaminergic neurons?

  • no resting like heart —> need lots of energy, ATP

  • full of iron


Parkinson´s Disease - Introduction

What are the three main symptoms?

  • resting tremor

  • rigidity (“Zahnradphänomen” e.g. stern expression)

  • bradykinesia (slow movements)


PD is

Parkinson´s Disease - Introduction

What is the onset of PD?

motor symptoms

BUT: begins before e.g. constipation, depression, bad sleep, neck/back pain

Parkinson´s Disease - Introduction

How can we treat PD?

  • L-Dopa —> symptomatic relief

    • works as a neurotransmitter

    • NO healing

  • inserting brain pace maker in Nuc. subthalamicus

    • electric pulse

    • less able to judgements (go to prostitute, …)

    • Hinweis: Dopaminmangel führt dazu, dass N. subthalamicus dauerhaft überaktiv ist


Parkinson´s Disease - Introduction

What seems to prevent PD?

  • smoking

  • coffee


Parkinson´s Disease - Introduction

What are Lewy bodies?

= accumulation of alpha-Synucleine

= marker of cell death

Parkinson´s Disease - Introduction

What can be differential diagnosis? How can we exclude them?

Lewy body dementia

more symmetrical

progressive supranuclear palsy (PSP)

more symmetrical,

expression with wide eyes, fall very often

childhood-onset Huntington´s Disease

hyperkinesis/dyskinesis

Parkinson´s Disease I

What can cause Parkinson´s Disease? Which neurons are concerned?

  • genetic mutations

  • environmental toxins

  • breakdown in cellular quality control

—> loss of dopaminergic neurons in the substantia nigra (pars compacta u. pars reticulata)


Parkinson´s Disease I

Which role plays mitochondrial dysfunction?

physiologically

mitochondria —> ATP production —> Neurons have a high demand on ATP

in Parkinson´s

—> impaired mitochondrial quality control

—> accumulation of dysfunctional mitochondria + increased oxidative stress

—> neuronal damage

Parkinson´s Disease I

Which mechanisms lead to an impaired mitochondrial quality control? Which type of Parkinson´s is concerned?

mutations in

  • PINK1 (PARK6)

  • Parkin (PARK2)

= autosomal recessive juvenile Parkinson´s disease

Parkinson´s Disease I

Which role play PINK1 (PARK 6) and Parkin (PARK2) usually in mitochondria?

PINK1 (PARK 6)

  • senses mitochondrial damage

Parkin (PARK 2)

  • labels damaged mitochondria for degradation

—> Mitophagy

Parkinson´s Disease I

How is Mitophagy defined and how is the process?

= selective autophagic removal of damaged mitochondria

  • damaged mitochondria: inability to import PINK1

  • PINK1 accumulates on mitochondrial membrane

  • PINK1 phosphorylates ubiquitin and activates Parkin

  • Parkin ubiquitinates outer membrane proteins

  • damaged mitochondria are degraded


Parkinson´s Disease I

Do you think mitochondrial dysfunction is a cause or a consequence of Parkinson’s disease?

mitochondrial dysfunction

  • in autosomal recessive juvenile Parkinson´s disease

    • cause (PINK1 and Parkin mutations)

  • in other forms of Parkinson´s disease

    • consequence of protein aggregation (α-Synuclein = Lewy-Körperchen)


Parkinson´s Disease I

Could increasing mitophagy also have negative effects for neurons?


  • could promote apoptosis

  • Parkin may degradade the survival protein Mcl-1, which accelerates the death of the nerve cell rather than protecting it


Parkinson´s Disease I

Why do animal models often fail to reproduce human Parkinson’s disease accurately?

  • compensatory mechanisms or the short lifespan

    • prevents mitochondrial damage from reaching the critical threshold for cell death

  • different species respond very differently to the loss of PINK1 or Parkin

    • demonstrated by comparisons between resistant mice and more susceptible rats or fruit flies

Parkinson´s Disease II

What can be side effects of an accumulation of damaged mitochondria?

—> release of mitochondrial DNA (mtDNA)

—> activation of innate immune pathways

Parkinson´s Disease II

Which pathway of the innate immune system may be concerned?

cGAS-STING-pathway

  • cytosolic DNA activates cGAS

  • cGAS activates STING

  • STING induces type I INF and inflammatory CKs


Parkinson´s Disease II

Which CKs are released when cGAS-STING pathway is activated?

INF type 1 signaling increased

  • Il-6

  • TNF

  • Il-1 beta

  • INF beta


Parkinson´s Disease II

To what extent could targeting STING signaling be a viable therapeutic strategy in Parkinson’s disease, and would complete inhibition be beneficial or could partial modulation be more effective?  


  • promising strategy

    • complete loss in mouse models prevents the neurodegeneration

  • complete blockade carries immunological risks

    • STING = key regulator of the innate immune response

    • results under germ-free laboratory conditions

    + it does not correct the original mitophagy defect


Parkinson´s Disease II

Why do mutator mice show stronger inflammation when Parkin is absent compared to when Parkin is present?  


Parkin = responsible for clearing damaged mitochondria (Mitophagy)


Without Parkin

—> mitochondrial DNA (mtDNA) accumulates

—> triggers an immune response


MS - Introduction

How is MS defined? Which part of the neurosystem is cocncerned?


motor function associated

demyelinating disease that concerns

  • white AND grey matter

  • cortical demyelination


MS - Introduction

What is the onset of MS? Which symptoms do patients acquire?

periphery

—> Autoantigen not known

  • sensory and visual disturbances

  • motor impairments

  • fatigue

  • pain

  • cognitive deficits

MS - Introduction

What can influence MS?

  • gender

  • age

  • genetics (HLA)

  • environment

  • hygiene (more hygiene —> amount of prevalence)

  • microbiome (dysbiotic?)


MS - Introduction

Which special animal experiments are performed in MS research?

RR mice

—> develop EAE

  • immunize with myelin antigen (autoantigen)

  • transient autoimmune disease = EAE

  • Experimental Autoimmune Encephalomyelitis


MS - Introduction

What is the pathophysiology?

pathophysiology:

  • CD4 pos T cells (autoantigen - MOG?) cross the blood brain barrier

  • inflammation through microglia and macrophages


MS - Introduction

What do we know about the incidence in the world?


  • northern hemisphere is more affected


MS - Introduction

What caused an increase of the incidence in Japan?

  • influence of the western diet

  • (when McD came to Japan)


MS - Introduction

What do we know about gut-brain axis?


—> dysbiosis can lead to an increase of Th17 cells and an imbalance between Th17 and Treg —> blood with immune cells can flow through sinuses in the dura mater of the brain and get in touch with antigens of the CSF

MS I

How is MS characterized?

  • demyelination and axonal damage

    → progressive disability


MS I

Which subtypes of MS can we distuinigsh?

  • relapse-remitting (RRMS)

  • progressive (PMS)


MS I

How could the gut microbiome influence MS?

  • gut-brain axis

  • gut dysbiosis —> neuroinflammation and MS progression?


MS I

Which species are reduced? Which are increased in MS?

↓

  • SCFA producing bacteria

  • Faecalibacterium saccharivorans

  • F. prausnitzii

↑

  • Akkermansia —> phytate degradation is higher

  • Ruthenibacterium lactatiformans

  • H. hathewayi

  • Eisenbergiella taya

shift away from SCFA-producing taxa

MS I

Which consequences does the shift from SCFA-producing taxa have?

lower concentration of short-chain fatty acids (acetate, propionate)

—> can influence the T reg/Th17 ratio

—> can trigger inflammation

MS I

How may Akkermansia muciniphila MS influence?

higher phytate degradation

  • higher concentration of iron and zinc (usually binded by phytate) ↑

  • higher concentration of myo-Inositol ↑

—> modulation of availability of minerals

MS I

Which drugs can influence the gut microbiome and trigger MS during therapy?

DMT (Disease modifying therapy)

  • e.g. Fingolimod (—> INF-beta)

MS I

How is the gut microbiome associated with MS

pathophysiology?


  • imbalance in bacterial species

    • decline in protective microbes e.g. Faecalibacterium prausnitzii (SCFA producing)

      • deficiency in immunoregulatory short-chain fatty acids and pyruvate

  • functional metabolic changes promote inflammatory processes

  • molecular mimicry of microbial peptides activates potentially autoreactive T cells.


MS I

Why is a household-controlled study design important

in this study?


  • minimizes confounding factors such as

    • diet

    • lifestyle

    • geographic location

—> The study effectively reduces environmental variance while increasing statistical power to detect true MS-associated microbial and functional changes.


MS I

How could gut microbiome findings be relevant

for future MS research and clinical applications?

  • basis for MS biomarkers

  • future preventive or therapeutic strategies

    • development of “designer probiotics”

    • personalized therapy


MS II

Why is it a good possibilty to compare twins in MS research?

—> genetic MS risk is the same

—> mostly same lifestyle and microbiome since they grew up in the same houshold

MS II

Why could bacteria influence the pathology of MS?

  • T cell activation (ileal bacteria)

  • molecular mimicry

    • bacterial antigens may cross-react with CNS autoantigen MOG triggeren T cell activation

  • Treg suppression (ileal bacteria)


MS II

Which T cells play a role in MS (ileal bacteria)?

Th17 activation in CD4 before migration to CNS

MS II

Why is it interesting to sample the microbes from the ileum?

  • highest concentration of pro-inflammatory Th17 cells.

  • disease-promoting bacteria could stay undetected in conventional stool samples

    • all enteroscopically collected samples differed from those in the fecal samples.


MS II

What is the difference between alpha and beta diversity regarding the gut microbiom?

  • alpha diversity = diversity within a single sample  

  • beta diversity = comparison of microbial profiles between different samples

  • no significant differences in either alpha or beta diversity

  • BUT mice that developed MS-like disease showed distinct alpha and beta diversity compared to healthy recipients


MS II

What was observed in the diseased mice at the endpoint regarding the composition of their gut microbiota?

  • selective outgrowth of two Lachnospiraceae taxa

    • Lachnoclostridium

    • Eisenbergiella tayi

  • reduction in alpha diversity and displaced other genera, such as Akkermansia (reduced)

    <-> gegensätzliche Erkenntnisse in den beiden papers

Lymphatic drainage of the CNS - Introduction

Which structure is mostly important for the blood-brain-barrier?

  • Pia mater

  • Arachnoidea mater


Lymphatic drainage of the CNS - Introduction

Which are the 2 big sinuses? Where do we find them? What is special about them?

  • superior sagittal sinus

  • transverse sinus

—> in Dura mater

—> fenestrated, no blood-brain-barrier

—> antigens accumulate in immune hubs = neuroimmunological interfaces —> APCs meet antigens from CSF in dura mater —> efflux through lymphatic vessels into the dCLN


Lymphatic drainage of the CNS - Introduction

What is the way of antigens in the brain beginning with antigens or waste in brain parenchyma?

brain parenchyma —> soluble antigens can diffundate into CSF —> subarachnoid space —> cribiform plate —> afferent olfactory nerve rootlets —> nasal mucosa —> dCLN

BUT cells can´t actively leave through this way!


new research findings:

Brain parenchyma → Interstitial fluid/waste → Glymphatic system → CSF (generated in ventricles by choroid plexus) → Dural meninges → lymphatic vessels in Dura mater → deep Cervical lymph nodes (dCLN)


Lymphatic drainage of the CNS - Introduction

Where are T cells primed? How do they get into the brain?

primed in the deep cervical lymph nodes

—> vascular system —> cerebral venous sinuses —> T cells and APCs can flow into the Dura mater and meet antigens from the CSF —> drainage through lymphatic vessels back into the cervical lymph nodes

Lymphatic drainage of the CNS I

Perisinusal dura uses adhesion (VCAM1, ICAM1, P-selectin) and chemokine (CXCL12) cues loosely analogous to lymph node HEVs. Does this qualify as a tertiary lymphoid structure under homeostasis, and what would that mean for CNS immune privilege?

  • specialized immune centers or neuroimmunological interfaces

  • NOT tertiary lymphoid structures

  • the presence of organized stromal and immune elements is confirmed —> contribute to the maintenance of homeostasis

  • The immune system is not “blind” to brain antigens but actively monitors them

    • through direct antigen presentation at the dural veins

Lymphatic drainage of the CNS I

Lymphatic ablation and dCLN ligation both leave CSF antigen influx into perisinusal dura intact. If lymphatic exit were blocked, would T-cell priming shift from the dCLN to the perisinusal sites, and what would that imply for tolerance versus autoreactivity?

  • New T cells are not activated at the sinus hubs because there are hardly any naive T cells there

  • only reactivate T cells that have already been activated

  • Blocking lymphatic drainage therefore suppresses initial activation in the dCLNs rather than redirecting it

    —> imbalance between tolerance and autoimmunity

Lymphatic drainage of the CNS I

Could cerebral venous sinus thrombosis or chronic dural inflammation serve as natural experiments to test the sinus interface concept in Alzheimer's or MS, and which clinical readouts would matter?

Thrombosis or inflammation could impair immune surveillance

evidenced by

  • T-cell activation

  • antigen accumulation (specfically e.g. amyloid-beta or MOG)

  • cytokine release


Lymphatic drainage of the CNS II

How does impaired CNS lymphatic drainage contribute to neurodegenerative disease?


  • waste products from the brain are no longer properly removed

  • toxic, misfolded proteins accumulate

  • damaged or dead nerve cells

    —> may be a major cause of Alzheimer’s disease and other neurodegenerative disorders


Lymphatic drainage of the CNS II

What is the glymphatic system and how does it interact with meningeal lymphatic network?


= network along the blood vessels

  • moves CSF through the brain tissue and flushes out cellular waste products

  • waste products enter the CSF

  • transported via the meningeal lymphatic network to the cervical lymph nodes


Lymphatic drainage of the CNS II

What is meningeal immunity and why are dural sinuses considered immunological hubs?


  • Immune cells in the dura form a network

    • surveils the brain and maintains CNS homeostasis via cytokines

  • dural sinuses are key hubs

    • they control T‑cell migration and allow CSF to enter the meningeal lymphatics for waste removal


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