imjured brain Flashcards
Define TBI
“a traumatically induced structural injury and/or
physiologic disruption of brain function as a result of
and external force”
• Clinical signs:
• Any period of loss, or a decreased level, of consciousness
• Any loss of memory of events immediately before and after
injury
• Any alteration in mental state and the time of injury
(confusion, slow thinking)
• Neurologic deficits (weakness, balance, visual, speech,
general sensory).
Describe Brain Regions vulnerable to TBI
Dorsolateral PFC - executive function, working memoery, thinking
Orbifrontal cortex-> emotional and social respondong
Tempoeral lobe -> memory and retreival
Amydala- emotional learning fear
Entorhinal hippocampal complex- delctarative memory, attention
Ventral brain stem -> life support (FATAL) (i.e pupillary reflex = damage here and is bad)
Cerebellum -> coordination, working memory
WHat are residual effects of tBI?
- Cognitive impairment
- Seizure disorder
- Mood disorder
- Behavioural problems
- Impaired vision, hearing
- Personality changes
- Language problems
- PTSD
Describe ’Mechanism’ of closed head injuries
Coup/contrecoup injury (top): Damage to the brain caused by initial sudden ‘high velocity’ head movement
(coup), followed by additional injury occurring opposite in the ‘rebound’ (contrecoup)
• Different ‘layers’ of the brain experience different levels of physical stress / rates of movement (r
tell me about brian protection mechanisms?
Dural folds provide protection and restrict
movement of the brain inside the cranium
in arachnoid space it can move a lot so these axons and blood vessels are vulnerable to shearing
Describe Diffuse Axonal Injury
Unresitricted head movement results in pulling, which axons are sensitive too, they cant stretch
so they often break, TBI is usually a mater of diffuse axonal white matter injury
Once axon is broken, it swells up, so does brain, , and immune cells are triggered
Causes structural and functional network disruption
Describe brain Hematomas
blood pooling outside blood vessels
Blood Brain Barrier (BBB) disruption
• Contribution to immune responses
• Infiltration of blood-derived cells into brain parenchyma
small blood vessel can slowly cause swelling and thus issues
an be intra cerebal
or subdural
or epidural
or subarachnoid
Difference between primary and secondary insult
Primary:
Instant cell death from mechanical impact
Immediate
Secondary:
Gradual cell death from molecular and cellular
response to primary injury
Minutes to years after
- Secondary injury causes majority of cell death
- TBI known to negatively impact and to induce long-term cognitive deficits
How do we improve behavioural outcomes
following brain injury
Targeting Neuroinflammation - cellular responses
following brain injury
• Activation of brain’s resident immune cells (microglia)->
Ø 10-20% of cells in the brain
Ø Many different phenotypes ranging from PRO to ANTI
inflammatory
Ø Secrete chemokines, phagocytosis of debris, synaptic pruning
• Infiltration of blood-derived cells (monocytes,
neutrophils, macrophages, T-cells, B-cells)
Whats up with m1/m2 microglia
M2 like meant to be anti inflam
m1 pro inflam
Microglial activation exists on a spectrum
• Microglia become chronically dysfunctional after TBI -> cognitive impairment
straight after injury there is increase in microglia, but then m2 tapers off while m1 keeps on going
Describe Tools to study microglia and how to
differentiate from macrophages
Microglia and macrophages share many functional
and phenotypic characteristic
• Blood-derived monocytes differentiate into
microglia-like cells once in the brain parenchyma
• Macrophages that infiltrate into the brain can adopt
microglia like morphology and also express similar
marker proteins (almost indistinguishable).
• Very difficult to differentiate their phenotype and
functional roles
• Microglia and macrophages share expression of
IBA1, CX3CR1, CSF1R, F4/80, CD45, CD11b
How do you study microglia?
- Pharmacological ablation – CSF1R inhibitor
- Genetic ablation – CSF1R knockout mouse
- Microglia specific genetic ablation – CX3CR1creERT2 x iDTR mouse
Describe Pharmacological ablation – CSF1R inhibitor (PLX5622)
> > CSF1R = colony stimulating factor 1
PLX5622 small molecule inhibitor of CSF1R
Microglia rely on CSF1R signaling for
survival
CSF1R inhibitor results in microglial cell
death
may affect function/induce cell death in
peripheral macrophages which also express
CSF1R
CSF1R IS ON ALL MICROGLIA AND WTHOUT IT THE CELL DIES
THIS DRUG PLX CAN GO THROUGH BBB
ISSUES: NOT THAT SPECIFIC, YOUVE MANIPULATED STUFF IN BLOOD BC THATS HOW YOU GIVE DRUG
describe Genetic targeting of microglia using creERT2
technology and a microglia specific promote
• Microglia specific promoter: CX3CR1
»CX3CR1 promoter drives creERT2 expression in
microglia continuosly but isnt found in nucleus
• When tamoxifen (TAM) administered, creERT2
translocates to nucleus, where it can be effective
>• creERT2 translocates to nucleus and cuts
out the stop codon to initiate
transcription of iDTR
?iDTR (‘the death receptor’) transcribed in
microglia cells
• Inject Diphteria Toxin (human version)
and kill the microglia (only cells that is
expressing iDTR).
SO BASICALLY MAKED MICROGLIA WITH DEATH RECEPTOR
also blood has creet2 receptors, but since blood has high turnover rate, so you wait 4 weeks so the blood doesnt get affected by toxin
How to assess rate of adult neurogenesis?
Doublecortin expressed 0-4 weeks post birth of new neuron
• Number of doublecortin positive cells = number of newborn neurons
• Newborn neurons are sensitive to injury
• Brain injury results in an overall reduction in newborn neurons
BRDU as well, use it to tag neurons
BrdU can be incorporated into the newly synthesized DNA of replicating cells (during the S phase of
the cell cycle during which DNA is replicated), substituting for thymidine during DNA replication
