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

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

What is Sepsis?

Introduction/Background

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

Sepsis occurs in Stages

① “systemic inflammatory response syndrome” (pro-inflammatory response)

② severe sepsis

③ septic shock

④ multiple organ failure

Introduction/Background

What causes Sepsis? Exaggerated inflammatory response of the

MACROPHAGES of the “innate” immune system to microbes (bacteria, virus)

INFECTION triggers inflammation:

Introduction/Background

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

The main players in Sepsis

Introduction/Background

The main players in Sepsis

Introduction/Background

innateIS

Cell death

nervoussystem

adaptive IS

microbes

Order of events in Sepsis

Introduction/Background

microbial infection

DEATH of immune cells – hypo-inflammation

hyper-inflammatory response (macrophages)

CYTOKINE STORM (too much cytokines)

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

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

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

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

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)

Memory Centers in the Brain

hippocampus

parahippocampal /perirhinal cortex

The Problem

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

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

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

Excitatory Post-Synaptic Potential

Stim 1Rec

DG

CA1

Stim 2

SUBCA3

Methods

Methods

Stim 1

Stim 2

Rec

Synaptic potential AFTER synaptic plasticity

Synaptic potential before synaptic plasticity

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*

Methods

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

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

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

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

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

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]