Exam 3 Flashcards
Multiple Sclerosis
Secondary disorder
Glial cells of the brain: Oligodendrocytes
Multiple Sclerosis (MS)
-Blocks messages being sent to CNS
Epidemiology
- Most common inflammatory neurological disease
- 600,000 live with MS
- no direct genetic link
- More woman have MS than men
- immune disorder,
- If a women becomes pregnant with MS it will lessen the symptoms of MS
MS more common in the northern hemisphere
- More north you move from equator, increased risk of MS
- Possible Vitamin D deficiency
- In the first 15 years, location of living is correlated with MS
MS presentation
- Characterized by lesions in the white matter, can spread to dark matter
- can use MRI to accurately diagnose MS, have to be at least 5mm
- can get lesions in a lot of different places, site of lesions affect symptoms
MS presentation symptoms (video)
big three
-Dysarthria (plaques on brain stem)
difficulty speaking, movements,
-Nystagmus (plaques on nerve of eyes)
Intention Tremor- smaller, limited to one area
Other plague locations and symptoms
-plaques in Sensory Pathways from Skin
Patterns of MS
-Typically progresses in one of four patterns
1- Relapsing-remitting MS (RRMS)
–Symptom flare-ups (relapse) separated by periods of remission where most symptoms resolve spontaneously
SPMS
2- Secondary progressive MS
symptoms worse gradually overtime without remission periods in between
Typical MRI and clinical progression of MS
Relapsing-remitting phase- have symptoms that spike and plateua, lossing ability to repair oligodentrocytes
-secondary progressive phase- brain volume decreases greatly, no more remission, can’t repair oligodentrocytes
MS most likely caused by a mix of genetic and environmental factors
genetics
-Some evidence for genetic cause due to familial MS risk, identical twins (one have MS, 33% other might
might be slight but definitely not
Genetics of MS
- HLA-DRB1*1501 allele increases disease risk up to threefold
- links the disease to T-cell functionality
- adaptive immune system
- strongest genetic risk
Environmental links to MS
-Smoking increases risk of MS twofold in women and threefold in men
-decrease in men’s smoking rate sufficient to explain the increase in female to male ratio of MS
- Vitamin D deficiency- humans can synthesize vitamin D in the skin (requires light)
Lower level of vitamin D correlate with increased risk of MS
-Fish can provide vitamin D
Myelination
oligodendrocytes in CNS wrap around dendrocytes, donating lipids,
Myelin organization
flatten sheets that wrap around axon, there is cytoplasmic reigon but as it flattens some cytoplasm is squeezed out so it’s mostly lipids.
MBP holds membranes together
PLP is transmembrane and spanes the membrane,
membrane aids in electrcal signaling
Myelination
-everytime there is an action potential, you change the membrane potential, this changes the charge of the membrane which triggers membrane voltage gated channels
- the nodes: helps to ancor the voltage gated channels in that region
if you lose myelin sheet, you lose the localization at those channels, you’d have to keep it going instead of it having little breaks(or skipping)
Demyelination is a hallmark of MS
Overall losing myelination
Cellular hallmarks of MS
-Inflammation, glial activation and axonal damage are also histopathological makers of the disease
What causes demyelination?
-The bodies immune system attacks the myelin proteins leading to their degradation
Immune system review
-Adaptive immunity
Adaptive immunity is dependent on lymphocytes
different B cell to recognize one specific antigen
same with T cells
Lymphocytes are activated by helper T cells
CD4+
Activated B cells become antibody secreting plasma cells
Cytotoxic T cells: Cell-mediated response
recognize infection inside of cell, causes cell’s to lyse
What causes demyelination?
1) An autoreactive (attacking something from body) CD4+ cell is reactive to myelin (oligodendrocyte)
-might occur becomes of trauma, or an antigen that is very similar. Another theory is that during the formation of the CD4+ cell, something went wrong
2) Activation of CD4+ and CD8+ (lyse bad cells) cells which move into the brain (very difficult for them to do, why there might be trauma) , also reactive to myelin. CD4+ cells activate microglia which release cytokines(inflammatory signals which further damage oligodendrocytes)
Both cells start to act to destroy oligodendrocytes
T cells are thought to be the biggest part of this
B cells come in later to target and cause phagocytosis
Remyelination
Periods of remission can be accounted for by phases or remyelination
Oligodendrocyte precursor cells
precursor cells move to areas where
Regenerated myelin is thinner but effective
- fully allows for saltatory conduction to occur once more
- provides tropic factors to the axon to promote survival (growth factors that are pro survival, more they have, stronger they become) if you lose these factors, causes degeneration and makes it harder to remyelinate
Repair mechanisms diminish as the disease progresses
decline of time between symptoms
loss of myelin can result in axonal damage
Axons themselves start to break, macorphages take apart axons, and you lose brain volume, gray matter
The myelin provides tropic factors promoting axonal health
-Toxic signals released from activated microglia and macrophages (cytokines, NO, glutamate) can also damage axons
Current treatment options
supportive care- just making life easier
disease modifying drugs-
experimental therapeutics- drugs that have made it too drug trails
Supportive care
Different for all patients
-depends on where dyemylination has occurred
Glucocorticoids
- steroids that dampen immune response
- Anti-inflammatory
- Decrease cytokines production (less overall inflammation)
- inhibits T cell activation(some early response is dampened so less early on)
- Cannot be taken long term
Spasticity
- GABA agonist (Baciofen)
- Inhibits acetylcholine release to decrease muscle contraction
- muscle spasms, increase GABA to decrease acetylcholine
Depression (decrease in serotonin)
- SSRI-serotonin reuptake inhibitors
- Keeps serotonin in the synapse longer
- doesnt let it go back in the cell to be reused
Sexual Dysfunction
-viagra
-acts as vasodilator
-
Disease-modifying drugs
-Chronic treatments that attempt to change the course of the disease
Interferons
- IFNB is a naturally occurring cytokine which down-regulates immune response
- is an anti-inflammatory (dampens the immune system)
- can decrease T-cell activation
- Helps prevent passage into the Blood Brain Barrier
- decreases B cell response
- Are essential just small polypeptides (should be cheap bc they are easy to make
Disease modifying drugs
Glatiramer acetate (GA)
- it competes for the binding site, so it will prevent but not lead to activation
- Suppresses T-cell activation
- Competitvely binds
Natalizumab
- Blocks a4b1 integrin on T-cell that is required for entry into the brain
- inhibits movement of t-cells into the cns
- lymphocytes have receptor (a4b1 integrin
- it prevents protein-protein interaction, prevents T-cells from being able to move outside the PNS
Experiemental approaches: Na+ blockers
-dosage is finicky
-can’t stop all Na+ channels as that can be very deadly
There is a persistent Na+ influx
(if you can selectively inhibit the Na+ channels on affected oligodendroyctes you could decrease excitotoxitity
Vitamin D (experiemental)
Semi-mature DC make naive CD4+ cells that have anti-inflammatory, this is what vitamin D helps to do
Stem Cells (Experimental approaches
research in general is very difficult to do
Experimental approaches: HSCT
-Stem cells present in spine or bone marrow?
Lymphoid progenitor
-Hematopoietic stem cells
used through transplantation, you have autoactivated T cells(which have memory), so if you get rid of them you get rid of that memory
So what they do it do low doses of chemotherapy that causes stem cells to leave bone marrow and enter blood stream, separate stem cells from blood then wreck the immune system and put stem cells back in body
Experimental approaches: NPC transplantation
- Introduction of induced neuroprogenitor cells
- can differentiate into oligodendrocytes, neurons and astrocytes
- Replace damaged cells in brain to relieve symptoms
Metastatic (secondary) brain tumors
-Lung and breast cancer most likely to metastasis
Don’t tend to metastasis further in the brain as a secondary tumor
If you have multiple secondary tumors, they are all independent from primary tumor
Primary CNS tumors
-Cancers originating and typically remaining in the brain
Named based on cell type of tissue they are affecting
Medulloblastoma- most common in childern
Distribution of primary brain tumors
Glioblastoma
Astrocytoma
Oligodendroglioma
make up 1/3 of all brain tumors
Gliomas (focus of our lectures)
-caused by multiple gene mutations
not inherited