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Sepsis, Immunity and Memory
Tomás Huerta
Mentors: Betty Diamond, Bruce T. Volpe
Affiliations:Feinstein Medical Research Institute,
Weill Medical College of Cornell University
Tomás Huerta
Mentors: Betty Diamond, Bruce T. Volpe
Affiliations:Feinstein Medical Research Institute,
Weill Medical College of Cornell University
Title slide
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What is Sepsis?
Baby is attacked by aggressive bacteria
Infection triggers a mix of: pro-inflammatory responses anti-inflammatory responses
Sepsis happens when there is too much pro-inflammatory responses
If unchecked rapid death
Introduction/Background
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What is Sepsis?
Introduction/Background
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How big of a problem is Sepsis?
Serious problem in all emergency rooms in hospitals
Very frequent in babies and people over 70 years old
Common in already sick people (diabetic, heart attack, etc.)
In USA: 751,000 cases per year 215,000 deaths (29%)
In the world (estimate): 10-100 million cases 28-50% death
Introduction/Background
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Sepsis occurs in Stages
① “systemic inflammatory response syndrome” (pro-inflammatory response)
② severe sepsis
③ septic shock
④ multiple organ failure
Introduction/Background
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What causes Sepsis? Exaggerated inflammatory response of the
MACROPHAGES of the “innate” immune system to microbes (bacteria, virus)
INFECTION triggers inflammation:
Introduction/Background
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Immune System Innate immunity: always present (ready to attack); many
pathogenic microbes have evolved to resist innate immunity
Adaptive immunity: stimulated by exposure to microbe; more potent
Introduction/Background
Macrophages are phagocytes
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The main players in Sepsis
Introduction/Background
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The main players in Sepsis
Introduction/Background
innateIS
Cell death
nervoussystem
adaptive IS
microbes
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Order of events in Sepsis
Introduction/Background
microbial infection
DEATH of immune cells – hypo-inflammation
hyper-inflammatory response (macrophages)
CYTOKINE STORM (too much cytokines)
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Therapy for Sepsis
Introduction/Background
microbial infection
DEATH of immune cells – hypo-inflammation
hyper-inflammatory response (macrophages)
CYTOKINE STORM (too much cytokines)
Anti-inflammatory drugs
Anti-apoptotic drugs
Anti-microbial drugs
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Post-Sepsis and Cognition
Up to 70% of post-sepsis survivors have problems with cognition:
memory loss (amnesia)
attention deficit
lack of executive control
anxiety disorder
It is not known why the cognitive deficits happen
Introduction/Background
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High Cytokines enter the Brain
Cytokines in the brain may alter the well-being of the CNS
Introduction/Background
During the cytokine storm, elevated
cytokines enter the brain
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High Cytokines and Memory Loss
The Problem
cytokines accumulate in brain areas that encode memory
high level of cytokines cause memory loss
elevated cytokines enter the brain
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How to Study Memory?
The Problem
Use “animal model” mouse
Study the HIPPOCAMPUS (brain region that encodes memory)
Study SYNAPTIC PLASTICITY (basic cellular process for memory)
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Memory Centers in the Brain
hippocampus
parahippocampal /perirhinal cortex
The Problem
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Stating The Problem
The Problem
It is likely that the high level of cytokines that enter the brain during sepsis cause an
impairment of synaptic plasticity, the cellular basis for memory
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Our Hypothesis
Hypothesis
2) We propose that hippocampal slices prepared from mice that had suffered sepsis (a few weeks before) will show
impaired synaptic plasticity
1) We propose that adding high levels of cytokines to hippocampal slices will cause
an impairment of synaptic plasticity
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Methods
Methods
Extract hippocampal slices from the brain of a mouse (male, 2-4 weeks of age)
Keep slices alive (up to 24 hours) by incubating them in special medium
Place hippocampal slice in the recording chamber
Record excitatory post-synaptic potentials
Induce SYNAPTIC PLASTICITY
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Excitatory Post-Synaptic Potential
Stim 1Rec
DG
CA1
Stim 2
SUBCA3
Methods
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Methods
Stim 1
Stim 2
Rec
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Synaptic potential AFTER synaptic plasticity
Synaptic potential before synaptic plasticity
*
*
Methods
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Experimental Plan
Methods
Aim 1: high levels of cytokines will impair synaptic plasticity
Study 3 groups of slices = 15 slices per group
Experimental Group #1 (“High Cytokine” Group): synaptic plasticity in the presence of high cytokines (~100 micromolar)
Experimental Group #2 (“Low Cytokine” Group): synaptic plasticity in the presence of low cytokines (~10 micromolar)
Control Group (“No Cytokine” Group): Try to induce synaptic plasticity in the absence of cytokines
Statistical Analysis: compare the results from each experimental group against the control group, by using Student’s t test. A probability of less then 0.05 will be considered significant
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Experimental Plan
Methods
Aim 2: post-sepsis slices will have impaired synaptic plasticity
Study 2 groups of mice:
Post-Sepsis Group: Try to induce synaptic plasticity in slices from mice that underwent sepsis
No-Sepsis Control: Try to induce synaptic plasticity in in slices from mice that did not suffer sepsis
Sample Number:
Study 3 mice per group, 5 slices per mouse, for a total of 15 slices per group
Statistical Analysis: compare whether the results from both groups are significantly different by using Student’s t test. A probability of less then 0.05 will be considered significant
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Expected Results
Results
Aim 1: high levels of cytokines will impair synaptic plasticity
Experimental Group #1 (“High Cytokine” Group): synaptic plasticity will be absent or highly reduced (significantly lower than control group)
Experimental Group #2 (“Low Cytokine” Group): synaptic plasticity will be marginal or, perhaps, unaffected
Control Group (“No Cytokine” Group): synaptic plasticity will be strong
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Expected Results
Results
Post-Sepsis Group: synaptic plasticity will be absent or highly reduced (significantly lower than control group)
No Sepsis Group: synaptic plasticity will be strong
Aim 2: post-sepsis slices will have impaired synaptic plasticity
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Significance of this research
Discussion
It would be useful to know whether synaptic plasticity is abolished by high levels of cytokines (applied directly to the brain)
It would be useful to know whether synaptic plasticity is absent in the post-sepsis brain
Therapies can be designed to stop the cytokines from entering the brain and affecting synaptic plasticity
Therapies can be designed to recover the deficient synaptic plasticity in post-sepsis patients that exhibit memory problems
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References
Citation slide
Tracey K.J. (2002) The inflammatory reflex. Nature 420: 853-859.
Tracey K.J. (2005) “Fatal sequence: The killer within”. Washington DC: Dana Press.
Murphy KM., Travers P. and Walport M. (2007) “Janeway’s Immunology”. New York: Garland Science.
Diamond B., et al (2009) Losing your nerves? Maybe it’s the antibodies. Nature Reviews Immunology May 5. [Epub ahead of print]